AND LIQUID HEAT EXCHANGER SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a contact surface-treated product, a liquid circulation system and a liquid heat exchanger system and, more particularly, to a contact surface-treated product applied to a system that uses liquid, a liquid circulation system that is formed to include the contact surface-treated product and a liquid heat exchanger system that is formed to include the contact surface-treated product.

2. Description of the Related Art

[0002] For example, Japanese Patent Application Publication No. 2006-249951 (JP-A-2006-249951) describes a contact surface-treated product applied to an existing system that uses liquid. An engine described in JP-A-2006-249951 is equipped with an oil pan at a lower portion of an engine block. A contact surface-treated product is provided on an engine oil falling surface within a contact surface that contacts oil (liquid) inside the engine. The contact surface-treated product has been subjected to oil repellent film treatment. By so doing, the engine described in JP-A-2006-249951 promptly returns engine oil, supplied from the oil pan to the engine block, and the like, back to the oil pan, and uses a smaller amount of engine oil. Thus, the temperature of engine oil is early increased while preventing inclusion of air by a pump.

[0003] However, the contact surface-treated product provided for the engine described in JP-A-2006-249951 has been desired to be able to regulate the flow of liquid according to the operating state of the system in response to various requests, such as a request for slowly returning engine oil to the oil pan depending on the operating state of the engine. SUMMARY OF THE INVENTION

[0004] The invention provides a contact surface-treated product, liquid circulation system and liquid heat exchanger system that are able to regulate the flow of liquid according to the operating state of a system.

[0005] A first aspect of the invention provides a contact surface-treated product. The contact surface-treated product includes a contact surface that contacts liquid used in a system, wherein a contact angle of the contact surface with the liquid varies with operating temperature of the system, and a predetermined temperature, at which the contact angle of the contact surface becomes 90 degrees, is set to fall within the range of the operating temperature.

[0006] With the above contact surface-treated product, the contact surface-treated product includes a contact surface that contacts liquid used in a system, wherein a contact angle of the contact surface with the liquid varies with operating temperature of the system, and a predetermined temperature, at which the contact angle of the contact surface becomes 90 degrees, is set to fall within the range of the operating temperature. Thus, it is possible to regulate the flow of liquid according to the operating state of the system.

[0007] A second aspect of the invention provides a liquid circulation system. The liquid circulation system includes: a contact surface-treated product; a storage portion in which liquid used in the liquid circulation system is stored; and a liquid return portion that returns the liquid, supplied from the storage portion to a supply target portion, back to the storage portion. The contact surface-treated product has a contact surface that contacts the liquid, wherein a contact angle of the contact surface with the liquid varies with operating temperature of the liquid circulation system, and a predetermined temperature, at which the contact angle of the contact surface becomes 90 degrees, is set to fall within the range of the operating temperature. In addition, the contact surface-treated product is applied to at least part of the liquid return portion.

[0008] In addition, the liquid circulation system may further include: a rotating body that transmits power to a wheel of a vehicle; and a case that accommodates the rotating body inside and inside which the storage portion is provided at a bottom, wherein an inner wall surface of the case may constitute the liquid return portion.

[0Q09] In addition, the liquid circulation system may further include a breather mechanism that separates gas inside the case from the liquid and that discharges the gas to the outside of the case.

[0010] In addition, the liquid circulation system may further include a pumping device that draws the liquid, stored in the storage portion, and that pumps the liquid to the supply target portion.

[0011] In addition, in the liquid circulation system, the predetermined temperature may be set to fall within the range of 40 ⁰ C to 60°C.

[0012] With the above liquid circulation system, the contact surface-treated product includes a contact surface that contacts liquid used in a system, wherein a contact angle of the contact surface with the liquid varies with operating temperature of the system, and a predetermined temperature, at which the contact angle of the contact surface becomes 90 degrees, is set to fall within the range of the operating temperature. Thus, it is possible to regulate the flow of liquid according to the operating state of the system.

[0013] A third aspect of the invention provides a liquid heat exchanger system. The liquid heat exchanger system includes: a contact surface-treated product; and a heat exchange portion that contacts the liquid to exchange heat with the liquid. The contact surface-treated product includes a contact surface that contacts liquid used in the liquid heat exchanger system, wherein a contact angle of the contact surface with the liquid varies with operating temperature of the liquid heat exchanger system, and a predetermined temperature, at which the contact angle of the contact surface becomes 90 degrees, is set to fall within the range of the operating temperature. In addition, the contact surface-treated product is applied to at least part of the heat exchange portion.

[0014] In addition, the liquid heat exchanger system may further include: a motor that has a rotor and a stator that is provided around an outer periphery of the rotor; and a case that accommodates the motor and the liquid, wherein the motor may constitute the heat exchange portion and may be cooled by being brought into contact with the liquid and exchanging heat with the liquid, an inner wall surface of the case may constitute the heat exchange portion and may cool the liquid by contacting the liquid and exchanging heat with the liquid, and the contact surface-treated product may be applied to at least the inner wall surface of the case and the rotor.

[0015] In addition, in the liquid heat exchanger system, the contact surface-treated product may be applied to an inner wall surface of the case at a downstream side in a scooping direction in which the liquid is scooped by rotation of a rotating body that is provided inside the case and that transmits power to a wheel of a vehicle.

[0016] In addition, in the liquid heat exchanger system, the predetermined temperature may be set to fall within the range of 0 ⁰ C to 40 ⁰ C.

[0017] With the above liquid heat exchanger system, the contact surface-treated product includes a contact surface that contacts liquid used in a system, wherein a contact angle of the contact surface with the liquid varies with operating temperature of the system, and a predetermined temperature, at which the contact angle of the contact surface becomes 90 degrees, is set to fall within the range of the operating temperature. Thus, it is possible to regulate the flow of liquid according to the operating state of the system.

BRIEF DESCRIPTION OF THE DRAWINGS [0018] The foregoing and further objects, features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a schematic configuration diagram of a contact surface-treated product according to a first embodiment of the invention;

FIG. 2 is a graph that illustrates the relationship between temperature of the contact surface-treated product according to the first embodiment of the invention and liquid surface tension;

FIG. 3 is a table that shows an example of a surface treatment agent used for a surface film of the contact surface-treated product according to the first embodiment of the invention;

FIG. 4 is a schematic configuration diagram of a vehicle equipped with a transmission to which the contact surface-treated product according to the first embodiment of the invention is applied;

FIG. 5 is a schematic configuration diagram of the transmission to which the contact surface-treated product according to the first embodiment of the invention is applied;

FIG. 6 is a graph that shows the relationship between oil temperature of the transmission, to which the contact surface-treated product according to the first embodiment of the invention is applied, and contact angle;

FIG. 7 is a graph that shows the relationship between oil temperature of the transmission, to which the contact surface-treated product according to the first embodiment of the invention is applied, and oil level;

, FIG. 8 is a schematic configuration diagram of a vehicle equipped with a driving system to which a contact surface-treated product according to a second embodiment of the invention is applied;

FIG. 9 is a schematic configuration diagram of the driving system to which the contact surface-treated product according to the second embodiment of the invention is applied;

FIG. 10 is a graph that shows the relationship between temperature of the driving system, to which the contact surface-treated product according to the second embodiment of the invention is applied, and motor efficiency;

FIG. 11 is a graph that shows the relationship between oil temperature of the driving system, to which the contact surface-treated product according to the second embodiment of the invention is applied, and kinematic viscosity;

FIG. 12 is a graph that shows the relationship between oil temperature of the driving system, to which the contact surface-treated product according to the second embodiment of the invention is applied, and contact angle; and

FIG. 13 is a graph that shows the relationship between oil temperature of the driving system and motor efficiency and the relationship between oil temperature of the driving system and mechanical efficiency when no contact surface-treated product is applied to the driving system.

DETAILED DESCRIPTION OF EMBODIMENTS

[0019] Hereinafter, a contact surface-treated product, a liquid circulation system and a liquid heat exchanger system according to an embodiment of the invention will be described in detail with reference to the accompanying drawings. Note that the embodiment does not limit the scope of the invention. In addition, components described in the following embodiment encompass those that can be easily replaced by a person skilled in the art or substantially equivalent components.

[0020] FIG. 1 is a schematic configuration diagram of a contact surface-treated product according to a first embodiment of the invention. FIG. 2 is a graph that illustrates the relationship between temperature of the contact surface-treated product according to the first embodiment of the invention and liquid surface tension. FIG. 3 is a table that shows an example of a surface treatment agent used for a surface film of the contact surface-treated product according to the first embodiment of the invention. FIG. 4 is a schematic configuration diagram of a vehicle equipped with a transmission to which the contact surface-treated product according to the first embodiment of the invention is applied. FIG. 5 is a schematic configuration diagram of the transmission to which the contact surface-treated product according to the first embodiment of the invention is applied. FIG. 6 is a graph that shows the relationship between oil temperature of the transmission, to which the contact surface-treated product according to the first embodiment of the invention is applied, and contact angle. FIG. 7 is a graph that shows the relationship between oil temperature of the transmission, to which the contact surface-treated product according to the first embodiment of the invention is applied, and oil level. [0021] The contact surface-treated product 1 according to the present embodiment shown in FIG. 1 is applied to a system that uses liquid. The contact surface-treated product 1 has a contact surface 2 , that contacts the liquid used in the system. The contact angle θ of the contact surface 2 with liquid varies with the operating temperature of the system. That is, in the contact surface-treated product 1, the contact angle θ of the contact surface 2 with liquid varies with the operating temperature of the system to which the contact surface-treated product 1 is applied.

[0022] Here, the contact angle θ at which the contact surface 2 of the contact surface-treated product 1 contacts liquid is an angle made between the surface of a solid as viewed from the liquid side, here, the contact surface 2, and liquid. The contact surface 2 of the contact surface-treated product 1 is substantially in point contact with liquid on the contact surface 2 when the contact angle θ approaches 180 degrees and repels liquid more easily. Thus, wettability of the contact surface 2 against liquid relatively decreases, and the contact surface 2 has a high repellency, here, super-water repellency, when the liquid is water (super-oil repellency when the liquid is oil). On the other hand, the contact surface 2 of the contact surface-treated product 1 is in plane contact with liquid on the contact surface 2 when the contact angle θ approaches 0 degrees, and liquid adheres to the contact surface 2 more easily. Thus, wettability of the contact surface 2 against liquid relatively increases, and the contact surface 2 has a high hydrophilicity, here, super-hydrophilicity, when the liquid is water (super-lipophilicity when the liquid is oil).

[0023] The characteristic of the contact surface 2 switches between water repellency (oil repellency) and hydrophilicity (lipophilicity) at the contact angle θ that is substantially equal to 90 degrees. That is, the contact surface-treated product 1 is able to serve as a super-water repellent surface (super-oil repellent surface) when the contact angle θ is larger than 90 degrees, while the contact surface-treated product 1 is able to serve as a super-hydrophilic surface (super-lipophilic surface) when the contact angle θ is smaller than 90 degrees. Then, the contact angle θ of the contact surface 2 with liquid varies with the surface tension of the contact surface 2, the surface tension of the liquid, and the like. The surface tension of liquid varies with the temperature of the liquid, and the like. That is, the contact angle θ of the contact surface 2 with liquid varies as the temperature of liquid varies. In other words, as the operating temperature of the system that uses liquid varies and then the temperature of the liquid varies, the contact angle θ of the contact surface 2 with liquid varies.

[0024] Then, the contact surface 2 of the contact surface-treated product 1 is configured so that a predetermined temperature, at which the contact angle θ of the contact surface 2 becomes 90 degrees, is set to fall within the range of the operating temperature of the system. By so doing, the contact surface-treated product 1 is able to appropriately regulate the flow of liquid that flows in contact with the contact surface 2 according to the operating state of the system to which the contact surface-treated product 1 is applied.

[0025] Specifically, the contact surface-treated product 1 is formed to include a body portion 3, an uneven portion 4 and a surface film 5. The body portion 3 constitutes the base of the contact surface-treated product 1. The uneven portion 4 is provided on the surface of the body portion 3. The uneven portion 4 has a so-called fractal structure formed of microscopic asperities on the surface of the body portion 3. The surface film 5 is a surface-treated film formed on the surface of the body portion 3 adjacent to the uneven portion 4. The surface film 5 is a surface-treated film treated with a low surface tension agent, such as a fluororesin film. The contact surface-treated product 1 has the above contact surface 2 on which the surface of the surface film 5 contacts liquid.

[0026] Here, where the contact angle between the contact surface 2 and liquid on the contact surface 2 is θ, the liquid surface tension, which is the surface tension of liquid on the contact surface 2, is rL, the solid surface tension, which is the surface tension of the surface film 5 of the contact surface 2, is rS, and the fractal dimension of the fractal structure of the uneven portion 4 is A, the contact angle θ may be expressed by the following mathematical expression (1).

[0027] [Mathematical Expression 1]

[0028] In addition, where the temperature of liquid is T, the critical temperature is TC, the density is d, and the molecular weight is M, the temperature dependence equation of the liquid surface tension rL is expressed by the following mathematical i expression (2).

[0029] [Mathematical Expression 2]

[0030] As shown in the mathematical expression (1), the contact angle θ of the contact surface 2 with liquid varies with the solid surface tension rS of the contact surface 2 and the liquid surface tension rL. From the above relationship, in the relationship between the solid surface tension rS and the liquid surface tension rL, for example, when rS is substantially equal to l/4 ^» rL, the contact angle θ becomes 90 degrees at which the characteristic of the contact surface 2 switches between water repellency (oil repellency) and hydrophilicity (lipophilicity); when rS is smaller than l/4 ^# rL, the contact angle θ is larger than 90 degrees at which the contact surface 2 is able to serve as a super-water repellent surface (super-oil repellent surface); and, when rS is larger than l/4*rL, the contact angle θ is smaller than 90 degrees at which the contact surface 2 is able to serve as a super-hydrophilic surface (super-lipophilic surface).

[0031] In addition, as shown in the mathematical expression (2), the liquid surface tension rL varies with the temperature T of liquid. FIG. 2 is a view that shows the relationship between temperature T of liquid and liquid surface tension rL. The liquid surface tension rL becomes relatively small as the temperature T of liquid becomes relatively high, and becomes relatively large as the temperature T of liquid becomes relatively low. Here, the surface film 5 fixedly adheres to the surface of the body portion 3 adjacent to the uneven portion 4, so the solid surface tension rS of the surface film 5 substantially remains unchanged irrespective of the operating temperature of the system. That is, as the temperature T of liquid varies and then the liquid surface tension rL varies, the contact angle θ of the contact surface 2 with liquid varies.

[0032] In other words, a predetermined temperature t of liquid, at which the contact angle θ is substantially equal to 90 degrees, can be set at a desired temperature by setting the solid surface tension rS at an appropriate value so as to satisfy the equation rS « l/4 ^« rL against the liquid surface tension rL at the predetermined temperature t, that is, by appropriately selecting a surface treatment agent used for the surface film 5.

[0033] For example, when, in the contact surface 2 that contacts oil (for example, the liquid surface tension rL is 20 to 30 mN/m) as liquid, the predetermined temperature t at which the characteristic of the contact surface 2 switches between oil repellency and lipophilicity, that is, the predetermined temperature t at which the contact angle θ is substantially equal to 90 degrees, is set at 40 to 60°C, for example, about 50 ⁰ C, it is only necessary to use a surface treatment agent having a solid surface tension rS of about 6 to 7 mN/m, that is, for example, perfluoro laurate, for the surface film 5.

[0034] FIG. 3 is a table that exemplifies an example of a surface treatment agent compound suitable for a desired predetermined temperature t and an approximate solid surface tension rS when the predetermined temperature t at which the contact angle θ is substantially equal to 90 degrees is set for the contact surface 2 that contacts oil. When the predetermined temperature t at which the contact angle θ is substantially equal to 90 degrees is set at -20 to O ⁰ C, for example, perfluoro alkoxy alkane having a solid surface tension rS of about 10 mN/m may be used for the surface film 5. When the predetermined temperature t at which the contact angle θ is substantially equal to 90 degrees is set at 0 to 20 ⁰ C, for example, perfluorooctyl ethyl acrylate having a solid surface tension rS of about 9 mN/m may be used for the surface film 5. When the predetermined temperature t at which the contact angle θ is substantially equal to 90 degrees is set at 20 to 40 ⁰ C, for example, perfluorooctyl ethyl methacrylate having a solid surface tension rS of about 8 mN/m may be used for the surface film 5. When the predetermined temperature t at which the contact angle θ is substantially equal to 90 degrees is set at 40 to 60 ⁰ C, for example, perfluoro laurate having a solid surface tension rS of about 7 mN/m may be used for the surface film 5 as described above. When the predetermined temperature t at which the contact angle θ is substantially equal to 90 degrees is set at 60 to 8O ⁰ C, for example, trifluoroethyl having a solid surface tension rS of about 6 mN/m may be used for the surface film 5.

[0035] With the contact surface-treated product 1, it is possible to appropriately set the predetermined temperature t at which the contact angle θ of the contact surface 2 with liquid becomes 90 degrees. Then, in the contact surface-treated product 1 according to the present embodiment, the predetermined temperature t is set to fall within the range of the operating temperature of the system to which the contact surface-treated product 1 is applied. That is, in the contact surface-treated product 1, the characteristic of the contact surface 2 switches between water repellency (oil repellency) and hydrophilicity (lipophilicity) as the temperature of liquid varies with variation in the operating temperature of the system to which the contact surface-treated product 1 is applied. In the contact surface-treated product 1, as the temperature of liquid becomes lower than the predetermined temperature t at which the contact angle θ becomes 90 degrees, the contact surface 2 serves as a super-water repellent surface (super-oil repellent surface). Thus, the contact surface 2 becomes repellent to liquid, and the flow of liquid that flows in contact with the contact surface 2 becomes relatively fast, that is, liquid flows more easily. On the other hand, in the contact surface-treated product 1, as the temperature of liquid becomes higher than the predetermined temperature t at which the contact angle θ becomes 90 degrees, the contact surface 2 serves as a super-hydrophilic surface (super-lipophilic surface). Thus, the contact surface 2 comes to have a higher affinity for liquid, and the flow of liquid that flows in contact with the contact surface 2 becomes relatively slow, that is, liquid becomes hard to flow. Therefore, the contact surface-treated product 1 is able to appropriately regulate the flow of liquid that flows in contact with the contact surface 2 according to the operating state of the system to which the contact surface-treated product 1 is applied, that is, according to the operating temperature of the system.

[0036] In the following description, the contact surface-treated product 1 according to the present embodiment is applied to a transmission 50 as a liquid circulation system shown in FIG. 4 and FIG. 5 as the system that uses liquid.

[0037] As shown in FIG. 4, the transmission 50 transmits power, that is, output torque, from a power source 101 mounted on a vehicle 5OA, to wheels FL and FR under a suitable condition based on the driving state of the vehicle 5OA. The transmission 50 is provided on an output side of the power source 101, that is, an internal combustion engine, such as a gasoline engine, a diesel engine and an LPG engine. The transmission 50 may be a manual transmission, an automatic transmission, and a continuously variable transmission. Here, it is assumed in the description that the transmission 50 is an automatic transmission.

[0038] The rotation output from the power source 101 is appropriately changed in speed by the transmission 50 and is then transmitted to the wheels FL and FR that are the left front wheel and right front wheel of the vehicle 5OA. The wheels FL and FR are driven as drive wheels. In this way, the vehicle 5OA drives. Note that the power source 101 may be an electric motor such as a motor. In addition, the vehicle 5OA is a so-called FF drive vehicle. In the FF drive vehicle, the power source 101 is mounted at the front of the vehicle 5OA in a forward travelling direction, the wheels FL and FR that are left and right front wheels are provided as drive wheels, and wheels RL and RR that are left and right rear wheels are driven wheels that do not generate driving force. However, the drive type of the vehicle 5OA may be an FR drive type or a four-wheel drive type.

[0039] The transmission 50 is provided on the output side of the power source 101, and changes the speed of rotation output from the power source 101. Then, the transmission 50 according to the present embodiment is a system that uses oil as liquid. The transmission 50 corresponds to the liquid circulation system according to the aspect of the invention and circulates oil through various portions of the system. In addition, the transmission 50 also serves as a lubricating device by circulating oil. That is, the transmission 50 circulates oil as liquid, and the circulated oil lubricates and cools various portions of the transmission 50.

[0040] As shown in FIG. 5, the transmission 50 has a storage portion 51 and an oil return portion 52 that serves as a liquid return portion. The storage portion 51 stores oil. The oil return portion 52 returns oil, supplied from the storage portion 51 to a supply target portion 53, back to the storage portion 51. The supply target portion 53 is formed to include at least a lubricated portion 53a. The lubricated portion 53a includes, for example, not only gears 55, which will be described later, but also portions that need supply of oil for lubrication in the transmission 50. Note that the lubricated portion 53a includes, for example, portions between a belt and pulleys when the transmission 50 is a belt-type continuously variable transmission.

[0041] More specifically, the transmission 50 is formed to include a supply portion 54, the gears 55 and a case 56.

[0042] The supply portion 54 supplies oil, stored in the storage portion 51, to the supply target portion 53. The supply portion 54 is formed to include an oil passage 54a and a pump 54b that serves as a pumping device. The oil passage 54a allows oil in the storage portion 51 to flow therethrough. The oil passage 54a is connected to the supply target portion 53. The pump 54b is provided in the oil passage 54a. The pump 54b draws oil, stored in the storage portion 51, into the oil passage 54a through a strainer 54d, which is an oil inlet port, or the like, and then pumps the oil to the supply target portion 53.

[0043] Note that the supply target portion 53 may be formed to include a control target portion 53b in addition to the lubricated portion 53a. The control target portion 53b is, for example, frictional engagement portions (clutches and brakes) for appropriately switching the transmission path of power in the gears 55, which will be described later, or pulleys, or the like, if the transmission 50 is, for example, a belt-type continuously variable transmission. That is, the supply portion 54 may be configured to not only supply the lubricated portion 53a with oil stored in the storage portion 51 but also supply the control target portion 53b with the oil. In this case, in the supply portion 54, for example, a hydraulic control circuit portion 54c is provided in the oil passage 54a between the pump 54b and the control target portion 53b. The hydraulic control circuit portion 54c, for example, controls the pressure of oil supplied to the lubricated portion 53a and the control target portion 53b by the pump 54b.

[0044] In addition, it is applicable that the supply portion 54 has no pump 54b that serves as the pumping device and, for example, various gears 55a, 55b, 55c and 55d immersed in oil in the storage portion 51 among the gears 55, which will be described later, scoop oil, stored in the storage portion 51, to splash the oil on the lubricated portion 53a of the supply target portion 53, thus supplying the lubricated portion 53a with oil.

[0045] The gears 55 transmit power from the power source 101 to the wheels FL and FR of the vehicle 5OA. The gears 55 include a plurality of the gears 55a, 55b, 55c and 55d that serve as rotating bodies that rotate with power transmitted. That is, the gears 55 are formed to include the plurality of gears 55a, 55b, 55c and 55d as rotating bodies for appropriately changing the speed of rotation output from the power source 101. For example, the gears 55 are rotatable so that a rotary shaft (main shaft) 55g is inserted through the gears 55a and 55b. The rotary shaft 55g is rotatably supported by bearings 55e and 55f, and the like. In addition, the gears 55 are rotatable so that a rotary shaft (counter shaft) 55j is inserted through the gears 55c and 55d. The gears 55c and 55d are rotatably supported by bearings 55h and 55i, and the like, while the gears 55c and 55d are in mesh with the gears 55a and 55b, respectively. The gears 55 are configured so that, as any one of the gears 55a, 55b, 55c and 55d rotates, the other gears also rotate. When the power transmission path is appropriately changed, the gears 55 are able to change the speed of rotation output from the power source 101 and then output the rotation. Then, the gears 55 constitute the above supply target portion 53. Furthermore, the gears 55 constitute the lubricated portion 53a of the above supply target portion 53.

[0046] Note that, for example, when the transmission 50 is a belt-type continuously variable transmission, pulleys, and the like, around which a belt is wound function as rotating bodies that transmits power to wheels of the vehicle according to the invention, and, when the transmission 50 is a toroidal continuously variable transmission, an input disk, an output disk, and the like, that hold a power roller in between function as the rotating bodies.

[0047] The case 56 accommodates the gears 55 inside, and the storage portion 51 is provided at the bottom inside the case 56. The case 56 is formed to include a transmission case 57 and an oil pan 58. The oil pan 58 is fixed to the transmission case 57 so as to close an opening of the transmission case 57 to thereby form accommodating space inside the case 56. The case 56 accommodates the supply portion 54, the gears 55, and the like, in the accommodating space. In addition, when the transmission 50 is mounted on the vehicle 5OA, the case 56 is arranged so that the oil pan 58 is located at the lower side of the transmission case 57 in the vertical direction. Thus, oil accommodated in the case 56 is stored at the bottom at the lower side inside the case 56 in the vertical direction, that is, at the bottom of the oil pan 58. Therefore, the storage portion 51 that stores oil is located at the bottom of the oil pan 58. The case 56 is, for example, formed of steel sheet; however, the material for the case 56 is not limited to it. The case 56 may be formed of resin, or the like.

[0048] Then, an inner wall surface 56a of the case 56 serves as the above-described oil return portion 52. Then, the inner wall surface 56a of the case 56, which serves as the oil return portion 52, is formed to include an inner wall surface 57a of the transmission case 57 and an inner wall surface 58a of the oil pan 58. For example, part of oil supplied to the gears 55, which are the supply target portion 53, flies off due to the rotation of the gears 55 and then adheres to the inner wall surface 56a of the case 56, which is the oil return portion 52, that is, the inner wall surface 57a of the transmission case 57 and the inner wall surface 58a of the oil pan 58. After that, the oil flows along the inner wall surface 57a and the inner wall surface 58a under jits own weight and returns to the storage portion 51. Note that the oil return portion 52 may be formed to include not only the inner wall surface 56a of the case 56 but also an oil return passage (not shown), a return pipe (not shown), or the like, that returns oil to the storage portion 51.

[0049] Note that the transmission 50 may include a breather mechanism 59. The breather mechanism 59 separates gas from oil inside the case 56 and discharges the gas outside the case 56. The breather mechanism 59 extends through the transmission case 57 to provide fluid communication between the inside and outside of the case 56. As oil in the storage portion 51 inside the case 56 is agitated by the gears 55, or the like, during operation of the transmission 50, the pressure inside the case 56 may become higher than the pressure outside the case 56. At this time, the breather mechanism 59 discharges gas inside the case 56 to the outside of the case 56 to eliminate a pressure difference between the inside and outside of the case 56. Then, when the breather mechanism 59 discharges gas to the outside of the case 56, the breather mechanism 59 separates oil (for example, oil atomized by agitation) from the gas to prevent oil in the case 56 from being blown out to the outside of the case 56 along with the discharged gas.

[0050] In the thus configured transmission 50, oil stored in the storage portion 51 is supplied to the lubricated portion 53a, the control target portion 53, and the like, that serve as the supply target portion 53 via the oil passage 54a, the pump 54b, the hydraulic control circuit portion 54c, and the like of the supply portion 54. Then, oil supplied to the lubricated portion 53a, the control target portion 53b, and the like, that serve as the supply target portion 53 is returned to the storage portion 51 via the inner wall surface 56a of the case 56, which is the oil return portion 52, that is, the inner wall surface 57a of the transmission case 57, the inner wall surface 58a of the oil pan 58, and the like. That is, oil stored in the storage portion 51 circulates through the supply portion 54, the supply target portion 53 and the oil return portion 52. During then, the oil lubricates and cools the lubricated portion 53a of the transmission 50, and also functions as working fluid in the control target portion 53b.

[0051] Incidentally, such oil used to lubricate the transmission 50 relatively decreases its viscosity to tend to flow more easily as the temperature increases, while the oil relatively increases its viscosity to tend to be hard to flow as the temperature decreases. Thus, in the existing transmission of this type, when the amount of oil supplied to the supply target portion is constant, the amount of oil that flows along the oil return portion back to the storage portion tends to increase with an increase in oil temperature, and the amount of oil tends to reduce with a decrease in oil temperature. Then, the oil level of oil in the storage portion tends to be relatively high because the amount of oil that flows along the oil return portion back to the storage portion increases with an increase in oil temperature. On the other hand, the oil level tends to be relatively low because the amount of oil that flows along the oil return portion back to the storage portion reduces with a decrease in oil temperature.

[0052] As a result, in the existing transmission, the oil level of oil in the storage portion becomes higher than a predetermined level with an increase in oil temperature to, for example, increase portions of gears immersed in oil. This increases the oil agitation resistance of the gears. Therefore, there is a possibility that a power loss of the transmission increases to influence fuel economy or the pressure inside the case excessively increases to cause a breather blow in which a small amount of oil is blown out from the breather mechanism. On the other hand, in the existing transmission, the oil level of oil in the storage portion becomes lower than a predetermined level with a decrease in oil temperature, and, for example, the oil level becomes lower than the oil inlet port for the pump. This may cause the pump to draw air inside. Therefore, there is a possibility that the lubrication of the lubricated portion and the controllability of the control target portion deteriorate. Then, for example, when the total amount of oil used for the transmission is reduced to suppress an increase in the agitation resistance of the gears and suppress a breather blow when the temperature of the transmission is high, air inclusion of the pump occurs more easily when the temperature of the transmission is low. On the other hand, when the total amount of oil used for the transmission is increased to suppress air inclusion of the pump when the temperature of the transmission is low, an increase in the agitation resistance of the gears or a breather blow occurs more easily when the temperature of the transmission is high. In addition, because the total heat capacity of oil increases, there is a possibility that warm-up performance consequently decreases. In addition, for example, even when air inclusion of the pump is prevented under a situation that oil repellent film treatment is applied to the oil return portion to cause oil, supplied to the supply target portion, to be promptly returned to the storage portion and, by so doing, the total amount of oil used for the transmission is reduced to improve warm-up performance, there is a possibility that an increase in agitation resistance of the gears or a breather blow consequently occurs more easily when the temperature of the transmission is high. Therefore, in the existing transmission, it is desired to appropriately regulate the oil level of oil stored in the storage portion according to the operating state of the transmission.

[0053] Then, in the transmission 50 according to the present embodiment, as shown in FIG. 5, the above described contact surface-treated product 1 is applied to the oil return portion 52 to appropriately regulate the flow of oil that flows in contact with the contact surface 2 of the oil return portion 52 according to the operating state of the transmission 50, that is, according to the operating temperature of the transmission 50, to thereby adjust the oil level of oil in the storage portion 51 to an appropriate level according to the operating state of the transmission 50.

[0054] That is, in the transmission 50 according to the present embodiment, the inner wall surface 56a of the case 56 that serves as the oil return portion 52, more specifically, the inner wall surface 57a of the transmission case 57 and the inner wall surface 58a of the oil pan 58 are formed of the contact surface-treated product 1. The inner wall surface 57a of the transmission case 57 and the inner wall surface 58a of the oil pan 58 are formed so that the contact surface 2 of the contact surface-treated product 1 is located at a side adjacent to the inner space of the case 56, that is, the contact surface 2 is located at a side that can contact oil. Note that, when the transmission 50 is configured so that the oil return portion 52 is formed to include not only the inner wall surface 56a of the case 56 but also an oil return passage (not shown), a return pipe (not shown), and the like, the contact surface-treated product 1 should also be applied to the inner wall surface of the oil return passage (not shown) and return pipe (not shown).

[0055] Then, in the transmission 50 according to the present embodiment, the predetermined temperature t at which the contact angle θ of the contact surface 2 with oil is 90 degrees is set to fall within the range of the operating temperature of the transmission 50. The range of the operating temperature of the transmission 50 is, for example, about -30 to 200°C. In the contact surface-treated product 1 according to the present embodiment, the predetermined temperature t is set at 40 to 60 ⁰ C, for example, about 50 ⁰ C. Thus, the contact surface-treated product 1 according to the present embodiment, for example, uses perfluoro laurate as the surface treatment agent for the surface film 5 (see FIG. 3).

[0056] In the thus configured transmission 50, as shown in FIG. 6, the oil temperature varies with variation in the operating temperature of the transmission 50. This varies the contact angle θ at which the contact surface 2 of the contact surface-treated product 1 applied to the oil return portion 52 contacts oil. Then, in the transmission 50, the contact angle θ is larger than 90 degrees when the oil temperature is lower than 50°C at the time of engine start, or the like, and the contact surface 2 is able to operate as a super-oil repellent surface. The contact angle θ is smaller than 90 degrees when the oil temperature is higher than 50 ⁰ C, and the contact surface 2 is able to operate as a super-lipophilic surface. On the other hand, the contact angle θ is substantially equal to 90 degrees when the oil temperature is about 50 ⁰ C, and the characteristic of the contact surface 2 switches between oil repellency and lipophilicity.

[0057] As a result, in the transmission 50, when the oil temperature is lower than 50 ⁰ C at the time of engine start, or the like, the contact surface 2 operates as a super-oil repellent surface. Thus, the contact surface 2 of the oil return portion 52 becomes repellent to oil, and the flow of oil that flows toward the storage portion 51 in contact with the contact surface 2 becomes relatively fast, that is, oil flows more easily. By so doing, in the transmission 50, as indicated by the solid line in FIG. 7, in comparison with the case where no contact surface-treated product 1 is applied to the oil return portion 52 (indicated by the alternate long and short dashed lines in FIG. 7), for example, even in a state where the oil temperature is at a low temperature of about 30 ⁰ C and the oil viscosity is relatively high and, therefore, oil is hard to flow, the contact surface 2 operates as a super-oil repellent surface to cause oil to flow more easily. Thus, the transmission 50 is able to relatively increase the amount of oil that returns to the storage portion 51 via the oil return portion 52, and is able to suppress a decrease in the oil level of oil in the storage portion 51, that is, a decrease in oil level. Therefore, the transmission 50 is able to suppress a decrease in oil level when the oil temperature is low, so it is possible to prevent a situation that the oil level in the storage portion 51 becomes lower than the oil inlet port for the pump 54b. This can prevent the pump 54b from drawing air inside. Hence, it is possible to prevent deterioration in the lubrication of the lubricated portion 53a and the controllability of the control target portion 53b. In this case, the transmission 50 is able to prevent a situation that the oil level in the storage portion 51 becomes lower than the oil inlet port for the pump 54b without relatively increasing the total amount of oil used for the transmission 50. Thus, it is possible to prevent an increase in the total heat capacity of oil, and it is possible to suppress a decrease in warm-up performance. That is, the transmission 50 is able to prevent the pump 54b from drawing air and suppress a decrease in warm-up performance when the oil temperature is low.

[0058] On the other hand, in the transmission 50, the contact surface 2 operates as a super-lipophilic surface when the oil temperature is higher than 50°C after completion of warm-up, or the like. Thus, oil more easily adheres to the contact surface 2 of the oil return portion 52, and the flow of oil that flows toward the storage portion 51 in contact with the contact surface 2 becomes relatively slow, that is, oil becomes hard to flow. By so doing, as indicated by the solid line in FIG. 7, in comparison with the case where no contact surface-treated product 1 is applied to the oil return portion 52 (indicated by the alternate long and short dashed lines in FIG. 7), for example, even in a state where the oil temperature is at a high temperature of about 80°C and the oil viscosity is relatively low and, therefore, oil flows more easily, the contact surface 2 operates as a super-lipophilic surface to cause oil to be hard to flow. Thus, the transmission 50 is able to relatively reduce the amount of oil that returns to the storage portion 51 via the oil return portion 52, and is able to suppress an increase in the oil level of oil in the storage portion 51, that is, an increase in oil level. Therefore, the transmission 50 is able to suppress an increase in oil level when the oil temperature is high, so it is possible to prevent an increase in portions of the gears 55 immersed in oil. This can suppress an increase in the oil agitation resistance of the gears 55. Thus, the transmission 50 is able to suppress an increase in power loss of the transmission 50 to suppress deterioration in fuel economy. In addition, the transmission 50 is able to suppress an excessive increase in pressure inside the case 56 and is therefore able to suppress occurrence of a breather blow in which a small amount of oil is blown out from the breather mechanism 59.

[0059] Therefore, by applying the contact surface-treated product 1 to the oil return portion 52, the transmission 50 is able to appropriately regulate the flow of oil that flows in contact with the contact surface 2 along the oil return portion 52 according to the operating state of the transmission 50, that is, the operating temperature of the transmission 50, and the transmission 50 is able to adjust the oil level of oil in the storage portion 51 to an appropriate level according to the operating state of the transmission 50. Thus, the transmission 50 is able to not only prevent the pump 54b from drawing air inside and suppress a decrease in warm-up performance when the temperature of the transmission 50 is low, that is, when the oil temperature is low, but also suppress an increase in the oil agitation resistance of the gears 55 and suppress occurrence of a breather blow in the breather mechanism 59 when the oil temperature is high.

[0060] The above-described contact surface-treated product 1 has the contact surface 2 at which the system (here, transmission 50) using liquid (here, oil) contacts liquid. The contact surface 2 is such that the contact angle θ thereof with liquid varies with the operating temperature of the system and the predetermined temperature t at which the contact angle θ becomes 90 degrees is set to fall within the range of the operating temperature. Thus, the characteristic of the contact surface 2 of the contact surface-treated product 1 switches between water repellency (here, oil repellency) and hydrophilicity (here, lipophilicity) depending on the operating state, that is, the operating temperature, of the system to which the contact surface-treated product 1 is applied. Therefore, it is possible to appropriately regulate the flow of liquid that flows in contact with the contact surface 2 according to the operating state of the system.

[0061] The above described transmission 50 includes the contact surface-treated product 1, the storage portion 51 in which oil is stored, and the oil return portion 52 that returns oil, supplied from the storage portion 51 to the supply target portion 53, back to the storage portion 51. The contact surface-treated product 1 is applied to at least part of the oil return portion 52. Therefore, by applying the contact surface-treated product 1 to the oil return portion 52, the transmission 50 is able to appropriately regulate the flow of oil that flows in contact with the contact surface 2 of the oil return portion 52 according to the operating state of the transmission 50, that is, according to the operating temperature of the transmission 50. Thus, it is possible to adjust the oil level of oil in the storage portion 51 to an appropriate level according to the operating state of the transmission 50.

[0062] In addition, the transmission 50 may include the gears 55a, 55b, 55c and 55d that transmit power to the wheels FL and FR of the vehicle 5OA and the case 56 that accommodates the gears 55a, 55b, 55c and 55d inside and that is provided with the storage portion 51 at the bottom inside the case 56, and the inner wall surface 56a of the case 56 may constitute the oil return portion 52. In this case, by applying the contact surface-treated product 1 to the inner wall surface 56a of the case 56 that constitutes the oil return portion 52, the transmission 50 is able to appropriately regulate the flow of oil that flows along the inner wall surface 56a according to the operating temperature of the transmission 50, and is able to adjust the oil level of oil in the storage portion 51 to an appropriate level according to the operating state of the transmission 50. Then, when the oil temperature is relatively high and the oil viscosity is relatively low, the contact surface 2 of the oil return portion 52 functions as a super-lipophilic surface and therefore, the transmission 50 is able to reduce the amount of oil that returns to the storage portion 51 to thereby suppress an increase in the oil level of oil in the storage portion 51. Thus, it is possible to suppress an increase in the oil agitation resistance of the gears 55a, 55b, 55c and 55d when the oil temperature is high.

[0063] In addition, the transmission 50 may include the breather mechanism 59 that separates gas inside the case 56 from oil and that discharges the gas to the outside of the case 56. In this case, when the oil temperature is relatively high and the oil viscosity is relatively low, the contact surface 2 of the oil return portion 52 functions as a super-lipophilic surface and therefore, the transmission 50 is able to reduce the amount of oil that returns to the storage portion 51 to thereby suppress an increase in the oil level of oil in the storage portion 51. Thus, it is possible to suppress occurrence of a breather blow in the breather mechanism 59 when the oil temperature is high.

[0064] In addition, the transmission 50 may include the pump 54b that draws oil, stored in the storage portion 51, to pump the oil to the supply target portion 53. In this case, when the oil temperature is relatively low and the oil viscosity is relatively high, the contact surface 2 of the oil return portion 52 functions as a super-oil repellent surface and therefore, the transmission 50 is able to increase the amount of oil that returns to the storage portion 51 to thereby suppress a decrease in the oil level of oil in the storage portion 51. Thus, it is possible to prevent the pump 54b from drawing air inside, and it is possible to suppress a decrease in warm-up performance.

[0065] With the transmission 50 according to the above-described embodiment of the invention, the predetermined temperature t, at which the contact angle θ of the contact surface 2 becomes 90 degrees, is desirably set to fall within the range of 40 ⁰ C to 60°C. Therefore, in the transmission 50, when the oil temperature falls within the range of 40 ⁰ C to 60 ⁰ C, the contact angle of the contact surface 2 in the oil return portion 52 becomes 90 degrees. Thus, it is possible to switch the characteristic of the contact surface 2 between oil repellency and lipophilicity. As a result, the transmission 50 is able to, for example, not only prevent the pump 54b from drawing air inside and suppress a decrease in warm-up performance when the oil temperature is low, but also suppress an increase in the oil agitation resistance of the gears 55 and suppress occurrence of a breather blow in the breather mechanism 59 when the oil temperature is high, appropriately.

[0066] Note that the contact surface-treated product and the liquid circulation system according to the above embodiment of the invention are not limited to the above described embodiment; they may be modified in various forms within the scope of the invention recited in the appended claims.

[0067] In the above description, the liquid is oil; however, the liquid is not limited to oil. That is, the contact surface-treated product according to the invention may be applied to a system that uses water as liquid. In this case, the contact surface-treated product is able to appropriately regulate the flow of water according to the operating state of the system. In addition, the contact surface-treated product is applied to the liquid circulation system in the above description; however, the application of the contact surface-treated product is not limited to the liquid circulation system.

[0068] In the above description, the liquid circulation system is applied to the transmission; however, the application of the liquid circulation system is not limited to the transmission. It is applicable as long as the system returns and circulates liquid, supplied from the storage portion to the supply target portion, to the storage portion by the liquid return portion, and it is applicable as long as the liquid circulation system is applied to a system in which the liquid level in the storage portion varies depending on the operating state. The liquid circulation system may be applied not only to an automatic transmission as the transmission but also to a manual transmission or a continuously variable transmission. In addition, the liquid circulation system may be applied not only to the transmission but also to a so-called wet sump machine, such as an engine, a power shovel and a machining robot.

[0069] In the above description, the contact surface-treated product is applied to the liquid return portion (oil return portion 52); however, the application of the contact surface-treated product is not limited to the liquid return portion. Instead, the contact surface-treated product may be applied to a portion other than the liquid return portion (oil return portion 52), for example, the inner wall surface of the oil passage 54a of the supply portion 54, or the like. By so doing, it is possible to regulate the flow of oil supplied to the supply target portion 53 according to the operating state of the transmission 50. In addition, the contact surface-treated product may be applied to a bottom surface of the storage portion 51, that is, a bottom surface of the oil pan 58, or the like. Note that, when the contact surface-treated product is applied only to the liquid return portion (oil return portion 52) as described above, it is possible to, for example, suppress the manufacturing cost of the transmission 50. In addition, the contact surface-treated product is not necessarily applied to the entire liquid return portion (oil return portion 52). It is applicable as long as the contact surface-treated product is applied to at least part of the liquid return portion (oil return portion 52). [0070] FIG. 8 is a schematic configuration diagram of a vehicle equipped with a driving system to which a contact surface-treated product according to a second embodiment of the invention is applied. FIG. 9 is a schematic configuration diagram of the driving system to which the contact surface-treated product according to the second embodiment of the invention is applied. FIG. 10 is a graph that shows the relationship between motor efficiency and temperature of the driving system, to which the contact surface-treated product according to the second embodiment of the invention is applied. FIG. 11 is a graph that shows the relationship between temperature and kinetic viscosity of oil of the driving system, to which the contact surface-treated product according to the second embodiment of the invention is applied. FIG. 12 is a graph that shows the relationship between contact angle and oil temperature of the driving system, to which the contact surface-treated product according to the second embodiment of the invention is applied. FIG. 13 is a graph that shows the relationship between oil temperature and motor efficiency of the driving system and the relationship between oil temperature and mechanical efficiency of the driving system when no contact surface-treated product is applied to the driving system.

[0071] The contact surface-treated product according to the second embodiment has a substantially similar configuration to that of the contact surface-treated product according to the first embodiment. However, the contact surface-treated product according to the second embodiment differs from the contact surface-treated product according to the first embodiment in that the contact surface-treated product according to the above-described first embodiment is applied to the liquid circulation system, whereas the contact surface-treated product according to the second embodiment is applied to a liquid heat exchanger system. Other than the above, with regard to similar configuration, functions and advantageous effects to those of the above first embodiment, the redundant description is omitted as much as possible and like reference numerals are used.

[0072] In the following description, the contact surface-treated product 1 according to the second embodiment is applied to a driving system 200 that serves as the liquid heat exchanger system shown in FIG. 8 and FIG. 9 as the system that uses liquid.

[0073] As shown in FIG. 8, the driving system 200 is applied to and mounted on a so-called hybrid vehicle 200A. The hybrid vehicle 200A uses a power source having a combination of an internal combustion engine ENG (gasoline engine, diesel engine, LNG engine, or the like) that generates engine torque and motors MGl and MG2 that generate motor torque.

[0074] The driving system 200 is a system that uses oil as liquid. The driving system 200 functions as the liquid heat exchanger system according to the invention. The liquid heat exchanger system exchanges heat between the oil, which serves as liquid, and predetermined portions. That is, the driving system 200 causes oil, which serves as liquid, to contact portions of the system, and the oil cools portions of the driving system 200 that have to be cooled.

[0075] The hybrid vehicle 200A includes, as motive power generators, the driving system 200 and the internal combustion engine ENG. The driving system 200 is formed to include the first motor generator MGl and the second motor generator MG2 as motors. Power generated by the internal combustion engine ENG, the first motor generator MGl and the second motor generator MG2 is transmitted to wheels 201. The hybrid vehicle 200A drives as the wheels 201 are driven as drive wheels.

[0076] That is, the hybrid vehicle 200A includes not only the internal combustion engine ENG but also the first motor generator MGl and the second motor generator MG2 as the power source. The hybrid vehicle 200A operates the internal combustion engine ENG efficiently as much as possible while compensating for excess and deficiency of driving force or engine braking force using the first motor generator MGl and the second motor generator MG2, and further regenerates energy during deceleration. By so doing, the hybrid vehicle 200A reduces exhaust gas from the internal combustion engine ENG and, at the same time, improves fuel economy.

[0077] The internal combustion engine ENG, the first motor generator MGl and the second motor generator MG2 are connected to one another by a power distribution and integration mechanism 210, which will be described later. The power distribution and integration mechanism 210 distributes the output from the internal combustion engine ENG between the wheels 201 and one of the first motor generator MGl and the second motor generator MG2, and transmits the output from the other one of the first motor generator MGl and the second motor generator MG2 to the wheels 201. The power distribution and integration mechanism 210 also functions as a transmission for driving force transmitted to the wheels 201 via a gear train 220 and axles 203.

[0078] In short, the internal combustion engine ENG is a heat engine that outputs heat energy, generated by burning fuel, in the form of mechanical energy, such as torque. A gasoline engine, a diesel engine, an LPG engine, or the like, is an example of the internal combustion engine ENG.

[0079] The driving system 200 is formed to include the above-described first motor generator MGl and second motor generator MG2, the power distribution and integration mechanism 210, the gear train 220 and a case 230.

[0080] The first motor generator MGl and the second motor generator MG2 are configured to not only rotate with supplied electric power to output mechanical energy, such as torque, but also be forcibly rotated by external force to generate electromotive force. A permanent magnet synchronous electric motor is an example of the first motor generator MGl or the second motor generator MG2. The first motor generator MGl is formed to include a rotor Rl and a stator Sl that is provided around the outer periphery of the rotor Rl. The second motor generator MG2 is formed to include a rotor R2 and a stator S2 that is provided around the outer periphery of the rotor R2. Each of the stators Sl and S2 is, for example, supplied with three-phase alternating-current electric power to form rotating magnetic field. Each of the stators Sl and S2 is, for example, fixed to the inner wall surface 230a of the case 230, which will be described later. Each of the rotors Rl and R2 is a rotor that is attracted to rotate by the rotating magnetic field formed by a corresponding one of the stators Sl and S2. The rotors Rl and R2 respectively have rotary shafts AxI and Ax2 that integrally rotate with the rotors Rl and R2 along the respective concentric circles. The rotary shafts AxI and Ax2 are coupled to the rotors Rl and R2. [0081] The power distribution and integration mechanism 210 distributes the power, output from the internal combustion engine ENQ between an output side and any one of the first motor generator MGl and the second motor generator MG2. The power distribution and integration mechanism 210 may be, for example, formed of a differential mechanism that includes at least three rotating elements that differentially rotate with respect to one another.

[0082] Here, the power distribution and integration mechanism 210 is formed to include a planetary gear mechanism that distributes or integrates the power of the internal combustion engine ENG, the power of the first motor generator MGl and the power of the second motor generator MG2. The internal combustion engine ENG, the first motor generator MGl and the second motor generator MG2 are respectively connected to the three rotating elements of the planetary gear mechanism. That is, in the power distribution and integration mechanism 210, the internal combustion engine ENG is connected to a planetary gear (or a carrier) 211 of the planetary gear mechanism via a damper 202, or the like, the rotor Rl of the first motor generator MGl is connected to a sun gear 212 of the planetary gear mechanism via the rotary shaft AxI and the rotor R2 of the second motor generator MG2 is connected to a ring gear 213 of the planetary gear mechanism via the rotary shaft Ax2. That is, the internal combustion engine ENG is coupled to the power distribution and integration mechanism 210, and the first motor generator MGl and the second motor generator MG2 transmit torque to the power distribution and integration mechanism 210 so as to apply reaction torque to the power distribution and integration mechanism 210 or assist output torque.

[0083] In addition, in the power distribution and integration mechanism 210, the ring gear 213 is also connected to the gear train 220. The gear train 220 is connected to the wheels 201 via the axles 203.

[0084] The gear train 220 transmits power by a plurality of gears. The gear train 220 is formed to include rotating bodies that rotate with power transmitted. That is, the gear train 220 is, for example, formed to include a counter drive gear 221, a counter driven gear 222, a final drive gear 223, a final driven gear 224 and a differential mechanism 225 as the plurality of gears that serve as the rotating bodies. The counter drive gear 221 is coupled to the ring gear 213 of the power distribution and integration mechanism 210 as described above. The counter driven gear 222 is in mesh with the counter drive gear 221. The final drive gear 223 is coupled to the counter driven gear 222. The final driven gear 224 is in mesh with the final drive gear 223. The differential mechanism 225 is coupled to the final driven gear 224. The wheels 201 are connected to the differential mechanism 225 via the axles 203. The differential mechanism 225 absorbs a difference in rotation between the left and right wheels 201.

[0085] Therefore, in the thus configured gear train 220, the power of the internal combustion engine ENQ the power of the first motor generator MGl and the power of the second motor generator MG2 are integrated by the power distribution and integration mechanism 210, and the integrated power is transmitted to the differential mechanism 225 via the counter drive gear 221, the counter driven gear 222, the final drive gear 223 and the final driven gear 224 while the rotational speed thereof is varied, and, in addition, the powers distributed to the left and right by the differential mechanism 225 are transmitted to the wheels 201 via the axles 203.

[0086] The case 230 accommodates the first motor generator MGl, the second motor generator MG2, the power distribution and integration mechanism 210, the gear train 220 and oil that serves as liquid.

[0087] When the power train of the hybrid vehicle 200A is thus configured, the power of the internal combustion engine ENG, the first motor generator MGl and/or the second motor generator MG2 is transmitted to the wheels 201 via the axles 203, and the like, and the wheels 201 are driven as the drive wheels, whereby the hybrid vehicle 200A is able to drive.

[0088] Then, the hybrid vehicle 200A controls the outputs from the internal combustion engine ENG, the first motor generator MGl and the second motor generator MG2 based on the driving state to make it possible to cause the hybrid vehicle 200A to drive in various modes. The modes, for example, include a mode in which the hybrid vehicle 200A drives by any one of the internal combustion engine ENG and the second motor generator MG2, a mode in which the hybrid vehicle 200A drives by coordination between the internal combustion engine ENG and the second motor generator MG2, and a mode in which the first motor generator MGl generates electric power using part of the output from the internal combustion engine ENG. Furthermore, the modes also include a mode that allows the second motor generator MG2 to regenerate electric power from kinematic energy of the hybrid vehicle 200A input from the wheels 201 during deceleration.

[0089] Here, the first motor generator MGl and the second motor generator MG2 are accommodated in the case 230 together with the power distribution and integration mechanism 210 and the gear train 220 as described above. When the first motor generator MGl, the second motor generator MG2, the power distribution and integration mechanism 210 and the gear train 220 rotate inside the case 230 in the driving system 200, heat generated from these mechanisms increases the temperature inside the case 230. Hereinafter, a cooling system 204 that cools the case 230 in order to prevent such increase in temperature will be described with reference to FIG. 8.

[0090] The cooling system 204 is formed to include a cooling jacket 205, a radiator 206, a pump 207 and a circulation passage 208.

[0091] The circulation passage 208 is a path through which a cooling medium (for example, coolant) circulates. In the circulation passage 208, the cooling jacket 205, the radiator 206 and the pump 207 are provided in the stated order in the direction in which the cooling medium circulates.

[0092] The cooling jacket 205 is, for example, provided in contact with a side face on the outer side of the case 230. The cooling jacket 205 cools the case 230 with the cooling medium supplied through the circulation passage 208.

[0093] The radiator 206 cools the cooling medium that circulates through the circulation passage 208 by heat exchange with outside air. The radiator 206 is, for example, formed to include a radiator fan (not shown) that forcibly feeds outside air to the body portion of the radiator 206.

[0094] The pump 207 feeds the cooling medium through the circulation passage 208 in a predetermined circulation direction.

[0095] Here, in the driving system 200, oil is accommodated inside the case 230 as described above. The driving system 200 supplies oil to the first motor generator MGl and the second motor generator MG2 that are accommodated in the case 230 and that produce a relatively large amount of heat. The first motor generator MGl and the second motor generator MG2 contact oil to exchange heat to thereby cool the first motor generator MGl and the second motor generator MG2. Note that the driving system 200 supplies the oil not only to the first motor generator MGl and the second motor generator MG2 but also to the power distribution and integration mechanism 210, the gear train 220, and the like, for lubrication, and the power distribution and integration mechanism 210 and the gear train 220 contact oil to exchange heat to thereby cool the power distribution and integration mechanism 210 and the gear train 220. In this way, the driving system 200 uses oil to cool the portions inside the case 230.

[0096] Then, in the cooling system 204, the cooling medium flows through the circulation passage 208 by the operation of the pump 207. Thus, for example, the cooling medium is fed from the radiator 206 to the cooling jacket 205, and the cooling medium exchanges heat with the case 230 of the driving system 200 to thereby cool the case 230. Then, in the driving system 200, on the inner wall surface 230a side of the cooled case 230, gas and oil inside the case 230 contact the inner wall surface 230a and exchange heat with the inner wall surface 230a to thereby cool the gas and the oil inside the case 230. In this way, in the cooling system 204, the cooling medium that circulates through the circulation passage 208 removes heat of the case 230 itself of the driving system 200 to make it possible to cool the case 230. By so doing, the driving system 200 is able to cool gas or oil that contacts the inner wall surface 230a of the case 230, and, as a result, the driving system 200 is able to cool the first motor generator MGl, the second motor generator MG2, the power distribution and integration mechanism 210, the gear train 220, and the like, that contact the oil.

[0097] Here, FIG. 9 is a cross-sectional view showing the schematic configuration of the driving system 200, taken along the line IX-IX in FIG. 8. As shown in FIG. 9, in the driving system 200, the cooling jacket 205 is provided in contact with the side face on the outer side of the case 230. In the driving system 200, a cooling wall surface 230b is provided on the inner wall surface 230a of the case 230, and the cooling wall surface 230b corresponds to the back side of an outer face portion of the case 230, with which the cooling jacket 205 contacts. The cooling wall surface 230b is cooled by the cooling jacket 205 most.

[0098] In the driving system 200 according to the present embodiment, as shown in FIG. 9, the first motor generator MGl is arranged at substantially the center inside the case 230, the counter driven gear 222 is arranged on the right upper side of the first motor generator MGl, and the final driven gear 224 is arranged on the lower side of the counter driven gear 222. The bottom of the case 230 at the lower side in the vertical direction functions as the storage portion 251 that stores oil. The storage portion 251 stores oil so that parts of the first motor generator MGl and final driven gear 224 are immersed. The final driven gear 224 that serves as the rotating body rotates to scoop oil stored in the storage portion 251.

[0099] In addition, the case 230 has a guide passage 252 inside. The guide passage 252 receives oil, scooped by rotating the final driven gear 224, and guides the oil to the above described cooling wall surface 230b. The guide passage 252 has a receiving portion 252a at one end thereof. The receiving portion 252a receives scooped oil. Then, the guide passage 252 is formed as an oil passage inside the case 230. The oil passage extends from the receiving portion 252a toward the bottom of the case 230 through the vicinity of the cooling wall surface 230b. By so doing, in the driving system 200, for example, oil scooped in the direction indicated by the arrows shown in FIG. 9 (in the counterclockwise direction with respect to the rotation center of the final driven gear 224 in FIG. 9) is guided by the guide passage 252. That is, scooped oil is received by the receiving portion 252a. The received oil is guided by the guide passage 252 to the cooling wall surface 230b and is then returned to the storage portion 51 at the bottom of the case 230.

[0100] In the thus configured driving system 200, the power of the internal combustion engine ENG, the first motor generator MGl and/or the second motor generator MG2 is transmitted to the gear train 220 via the power distribution and integration mechanism 210, and various gears that constitute the gear train 220 rotate. Here, in the driving system 200, as the final driven gear 224 included in the gear train 220 rotates, oil stored in the storage portion 51 at the bottom of the case 230 is scooped. Scooped oil flies off toward the first motor generator MGl, the second motor generator MG2, the power distribution and integration mechanism 210 and the gear train 220 inside the case 230 to lubricate various operations and remove heat generated from the operations, that is, cool various portions. In addition, part of scooped oil contacts the inner wall surface 230a of the case 230, adheres thereto and then exchanges heat with the inner wall surface 230a to be cooled, and is then returned to the storage portion 51 under its own weight. In addition, oil received by the receiving portion 252a when scooped is guided by the guide passage 252 to the cooling wall surface 230b. The guided oil contacts the cooling wall surface 230b, which constitutes part of the inner wall surface 230a of the case 230, and exchanges heat with the cooling wall surface 230b to be cooled, and is returned to the storage portion 51 at the bottom of the case 230 through the guide passage 252. In the driving system 200, the inner wall surface 230a of the case 230 contacts oil to exchange heat to thereby cool the oil. At this time, within the inner wall surface 230a, the cooling efficiency is highest at the cooling wall surface 230b. Thus, the guide passage 252 is used to guide oil to the cooling wall surface 230b to make it possible to effectively cool oil.

[0101] Incidentally, the first motor generator MGl and the second motor generator MG2 used for the above driving system 200 are, for example, such that the motor efficiency tends to decrease as the temperature increases, while the motor efficiency tends to increase as the temperature decreases, as shown in FIG. 10. Therefore, in the driving system 200 of this type, the first motor generator MGl and the second motor generator MG2 are cooled to a relatively low temperature to thereby make it possible to improve the motor efficiency of each of the first motor generator MGl and the second motor generator MG2. On the other hand, oil used in the above driving system 200 is, for example, such that the kinematic viscosity tends to decrease to allow oil to flow more easily as the temperature increases, while the kinematic viscosity tends to increase to have oil hard to flow as the temperature decreases, as shown in FIG. 11. For example, the kinematic viscosity of oil tends to steeply increase at 0 ⁰ C or below. Therefore, in the driving system 200 of this type, in a state where the oil temperature is relatively low, the kinematic viscosity of oil is high, so the drag resistance (rotational resistance) of oil attended with rotation of each of the rotors Rl and R2 of the first motor generator MGl and second motor generator MG2 relatively increases. This may decrease the rotation efficiency of each of the first motor generator MGl and the second motor generator MG2 to thereby decrease the mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2. That is, in the above driving system 200, for example, if the first motor generator MGl and the second motor generator MG2 are just simply cooled in order to improve the motor efficiency of each of the first motor generator MGl and the second motor generator MG2, it may lead to a decrease in the rotation efficiency, that is, the mechanical efficiency, of each of the first motor generator MGl and the second motor generator MG2, resulting in a decrease in the efficiency of each of the first motor generator MGl and the second motor generator MG2 as a whole. Therefore, in the existing driving system of this type, it is desired to appropriately regulate the heat exchange state between oil and predetermined portions according to the operating state of the driving system.

[0102] Then, as shown in FIG. 8 and FIG. 9, by applying the contact surface-treated product 1 to at least part of the heat exchange portion 253 that exchanges heat with oil when the oil contacts the heat exchange portion 253, the driving system 200 according to the present embodiment appropriately regulates the flow of oil that flows in contact with the contact surface 2 of the heat exchange portion 253 according to the operating state of the driving system 200, that is, according to the operating temperature of the driving system 200, and regulates the heat exchange state between oil and the heat exchange portion 253, that is, the cooling state, according to the operating state of the driving system 200. [0103] The heat exchange portion 253 is a portion that contacts oil to exchange heat with the oil in the driving system 200. In the present embodiment, the heat exchange portion 253 is formed to include the first motor generator MGl, the second motor generator MG2 and the inner wall surface 230a of the case 230, including at least the cooling wall surface 230b. That is, the first motor generator MGl and the second motor generator MG2 constitute the heat exchange portion 253, and contacts oil to exchange heat with the oil to be cooled as described above. The inner wall surface 230a of the case 230 constitutes the heat exchange portion 253, and contacts oil to exchange heat with the oil to cool the oil as described above. Here, the heat exchange portion 253 is formed to further include the power distribution and integration mechanism 210 and the gear train 220.

[0104] Then, in the driving system 200, the contact surface-treated product 1 is applied to at least part of the heat exchange portion 253, here, the first motor generator MGl, the second motor generator MG2 and the inner wall surface 230a of the case 230, including the cooling wall surface 230b. Specifically, the inner wall surface 230a of the case 230 is formed so that the entire contact surface 2 of the contact surface-treated product 1 is located at a side adjacent to the inner space of the case 230, that is, the contact surface 2 is located at a side that can contact oil. In addition, the first motor generator MGl and the second motor generator MG2 are formed so that the contact surface 2 of the contact surface-treated product 1 is located on the surfaces of the rotors Rl and R2 adjacent to the stators Sl and S2, that is, the contact surface 2 is located at a side that can contact oil. More specifically, in the first motor generator MGl and the second motor generator MG2, the contact surface 2 of the contact surface-treated product 1 is provided on the surfaces of the rotors Rl and R2 facing the stators Sl and S2 with respect to a direction perpendicular to the rotary shafts AxI and Ax2.

[0105] Then, in the driving system 200, the predetermined temperature t, at which the contact angle θ of the contact surface 2 with oil becomes 90 degrees, is set to fall within the range of the operating temperature of the driving system 200. Here, the operating temperature of the driving system 200, for example, ranges from about -30 to 120°C. For example, FIG. 13 is a graph that shows the relationship between oil temperature and motor efficiency of the driving system and the relationship between oil temperature and mechanical efficiency of the driving system when no contact surface-treated product is applied to the driving system. For example, as shown in FIG. 13, with an increase in oil temperature, the motor efficiency of each of the first motor generator MGl and the second motor generator MG2 decreases (indicated by the line A in FIG. 13), while the kinematic viscosity of oil decreases. Thus, the drag resistance (rotational resistance) of oil attended with rotation of each of the rotors Rl and R2 of the first motor generator MGl and second motor generator MG2 decreases to thereby improve the mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2 (indicated by the line B in FIG. 13). The motor efficiency of each of the first motor generator MGl and the second motor generator MG2 is, for example, substantially 100% when the oil temperature is about -30 ⁰ C. The mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2 is, for example, substantially 100% when the oil temperature is about 120°C. Then, in the example shown in FIG. 13, the oil temperature at which the lines of the motor efficiency and mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2 intersect with each other ranges from about 0 to 40 ⁰ C, for example, about 20 ⁰ C. That is, when no contact surface-treated product 1 is applied to the driving system, for example, the mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2 tends to be lower than the motor efficiency thereof in a state where the oil temperature is lower than 20 ⁰ C, and the motor efficiency of each of the first motor generator MGl and the second motor generator MG2 tends to be lower than the mechanical efficiency thereof in a state where the oil temperature is higher than 20 ⁰ C.

[0106] Then, the contact surface-treated product 1 is configured so that the predetermined temperature t, at which the contact angle θ of the contact surface 2 with oil is 90 degrees, is set to fall within the range of 0 to 40 ⁰ C, for example, about 20 ⁰ C. In the contact surface-treated product 1 according to the present embodiment, perfluorooctyl ethyl acrylate is, for example, used as a surface treatment agent for the surface film 5 (see FIG. 3).

[0107] In the thus configured driving system 200, as shown in FIG. 12, when the oil temperature varies with variation in the operating temperature of the driving system 200, the contact angle θ of the contact surface 2 of the contact surface-treated product 1 with oil varies, the contact surface-treated product 1 being applied to at least part of the heat exchange portion 253, here, the inner wall surface 230a of the case 230 and the surfaces of the rotors Rl and R2 of the first motor generator MGl and the second motor generator MG2. Then, in the driving system 200, when the oil temperature is lower than 20 ⁰ C at the time of engine start, or the like, the contact angle θ is larger than 90 degrees and, therefore, the contact surface 2 is able to operate as a super-oil repellent surface. When the oil temperature is higher than 20 ⁰ C, the contact angle θ is smaller than 90 degrees and, therefore, the contact surface 2 is able to operate as a super-lipophilic surface. When the oil temperature is about 20 ⁰ C, the contact angle θ is substantially equal to 90 degrees and, therefore, the characteristic of the contact surface 2 switches between oil repellency and lipophilicity.

[0108] As a result, in the driving system 200, when the oil temperature is lower than 20 ⁰ C at the time of engine start, or the like, the contact surface 2 operates as a super-oil repellent surface and therefore, the contact surface 2 on the surfaces of the rotors Rl and R2 of the first motor generator MGl and the second motor generator MG2 becomes repellent to oil, and the flow of oil that flows in contact with the contact surface 2 becomes relatively fast, that is, oil flows more easily. By so doing, for example, even when the oil temperature is at a low temperature of about O ⁰ C and the kinematic viscosity of oil is relatively high, the contact surface 2 on the surfaces of the rotors Rl and R2 of the first motor generator MGl and the second motor generator MG2 operates as a super-oil repellent surface to allow oil to flow more easily, that is, to repel oil more easily. Thus, the driving system 200 is able to suppress the drag resistance (rotational resistance) of oil attended with rotation of each of the rotors Rl and R2 of the first motor generator MGl and the second motor generator MG2, and is able to suppress a decrease in the rotation efficiency of each of the first motor generator MGl and the second motor generator MG2. Hence, it is possible to suppress a decrease in the mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2. In this case, the oil cooling efficiency for the first motor generator MGl and the second motor generator MG2 slightly decreases to slightly decrease the motor efficiency of each of the first motor generator MGl and the second motor generator MG2. However, the amount by which a decrease in the mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2 is suppressed is relatively large. Therefore, consequently, the driving system 200 is able to improve the efficiency resulting from the motor efficiency and mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2 in total. That is, the driving system 200 is able to achieve both the motor efficiency and mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2 when the oil temperature is low. At this time, in the driving system 200, the contact surface 2 of the inner wall surface 230a of the case 230 operates as a super-oil repellent surface to allow oil to flow more easily, that is, becomes repellent to oil. Thus, the cooling efficiency of the inner wall surface 230a of the case 230 for oil decreases, and the oil temperature inside the case 230 rapidly increases to a predetermined temperature at which the kinematic viscosity is relatively small.

[0109] Then, in the driving system 200, when the temperature of oil inside the case 230 increases to a predetermined temperature and is, for example, higher than 20°C, the contact surface 2 operates as a super-lipophilic surface. Thus, oil adheres more easily to the contact surface 2 on the inner wall surface 230a of the case 230 and the surfaces of the rotors Rl and R2 of the first motor generator MGl and the second motor generator MG2, and the flow of oil that flows in contact with the contact surface 2 becomes relatively slow, that is, oil becomes hard to flow. By so doing, oil adheres to the contact surface 2 of the inner wall surface 230a of the case 230 more easily, so the driving system 200 is able to improve the cooling efficiency of the inner wall surface 230a of the case 230 for oil. In addition, oil adheres to the contact surface 2 on the surfaces of the rotors Rl and R2 of the first motor generator MGl and the second motor generator MG2 more easily, so the driving system 200 is also able to improve the efficiency of cooling the first motor generator MGl and the second motor generator MG2 with oil. As a result, the cooling efficiency for the first motor generator MGl and the second motor generator MG2 improves, so the driving system 200 is able to improve the motor efficiency of each of the first motor generator MGl and the second motor generator MG2. At this time, because the kinematic viscosity of oil has been sufficiently decreased, there is almost no decrease in the mechanical efficiency due to the drag resistance (rotational resistance) of oil attended with rotation of each of the rotors Rl and R2 of the first motor generator MGl and the second motor generator MG2. Thus, the driving system 200 is consequently able to improve the efficiency resulting from the motor efficiency and mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2 in total.

[0110] Therefore, by applying the contact surface-treated product 1 to at least part of the heat exchange portion 253, the driving system 200 is able to appropriately regulate the flow of oil that flows in contact with the contact surface 2 of the heat exchange portion 253 according to the operating state of the driving system 200, that is, according to the operating temperature of the driving system 200. Thus, the driving system 200 is able to regulate the heat exchange state between oil and the heat exchange portion 253, that is, the cooling state, according to the operating state of the driving system 200. Then, by applying the contact surface-treated product 1 to the inner wall surface 230a of the case 230 and the surfaces of the rotors Rl and R2 of the first motor generator MGl and the second motor generator MG2 as part of the heat exchange portion 253, the driving system 200 is able to achieve both a high motor efficiency and a high mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2.

[0111] The contact surface-treated product 1 according to the second embodiment has the contact surface 2 at which the system (here, driving system 200) using liquid (here, oil) contacts liquid. The contact surface 2 is such that the contact angle θ thereof with liquid varies with the operating temperature of the system and the predetermined temperature t, at which the contact angle θ becomes 90 degrees, is set to fall within the range of the operating temperature. Thus, the characteristic of the contact surface 2 of the contact surface-treated product 1 switches between water repellency (oil repellency) and hydrophilicity (lipophilicity) depending on the operating state of the system to which the contact surface-treated product 1 is applied, that is, depending on the operating temperature of the system to which the contact surface-treated product 1 is applied. Therefore, it is possible to appropriately regulate the flow of liquid that flows in contact with the contact surface 2 according to the operating state of the system.

[0112] The driving system 200 according to the second embodiment includes the contact surface-treated product 1 and the heat exchange portion 253 that contacts oil to exchange heat with the oil. The contact surface-treated product 1 is applied to at least part of the heat exchange portion 253. Therefore, by applying the contact surface-treated product 1 to at least part of the heat exchange portion 253, the driving system 200 is able to appropriately regulate the flow of oil that flows in contact with the contact surface 2 of the heat exchange portion 253 according to the operating state of the driving system 200, that is, according to the operating temperature of the driving system 200. Thus, the driving system 200 is able to appropriately regulate the heat exchange state between oil and the heat exchange portion 253, that is, the cooling state, according to the operating state of the driving system 200.

[0113] In addition, the driving system 200 according to the second embodiment includes the first motor generator MGl, the second motor generator MG2 and the case 230. The first motor generator MGl has the rotor Rl and the stator Sl that is provided around the outer periphery of the rotor Rl. The second motor generator MG2 has the rotor R2 and the stator S2 that is provided around the outer periphery of the rotor R2. The case 230 accommodates the first motor generator MGl, the second motor generator MG2 and oil. The first motor generator MGl and the second motor generator MG2 constitute the heat exchange portion 253, and contact oil to exchange heat with the oil to be cooled. The inner wall surface 230a of the case 230 constitutes the heat exchange portion 253, and contacts oil to exchange heat with the oil to cool the oil. The contact surface-treated product 1 may be applied to at least the inner wall surface 230a of the case 230 and the rotors Rl and R2. In this case, by applying the contact surface-treated product 1 to the inner wall surface 230a of the case 230 and the rotors Rl and R2, which constitute part of the heat exchange portion 253, the driving system 200 is able to appropriately regulate the flow of oil that flows around the inner wall surface 230a of the case 230 and the rotors Rl and R2 according to the operating temperature of the driving system 200. Thus, the driving system 200 is able to appropriately regulate the heat exchange state, that is, the cooling state, between oil and the inner wall surface 230a of the case 230 and between oil and the rotors Rl and R2 according to the operating state of the driving system 200. Then, in a state where the oil temperature is relatively low, the contact surface 2 on the inner wall surface 230a of the case 230 and the surfaces of the rotors Rl and R2 operate as a super-oil repellent surface. Thus, the driving system 200 is able to suppress the drag resistance (rotational resistance) of oil attended with rotation of each of the rotors Rl and R2, and is able to suppress a decrease in the mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2. In addition, in a state where the oil temperature is relatively high, the contact surface 2 on the inner wall surface 230a of the case 230 and the surfaces of the rotors Rl and R2 operate as a super-lipophilic surface. Thus, the driving system 200 is able to improve the cooling efficiency of each of the first motor generator MGl and the second motor generator MG2, and is able to improve the motor efficiency of each of the first motor generator MGl and the second motor generator MG2. As a result, the driving system 200 is able to achieve both a high motor efficiency and a high mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2.

[0114] In addition, with the driving system 200 according to the second embodiment, the predetermined temperature t, at which the contact angle θ of the contact surface 2 becomes 90 degrees, is desirably set to fall within the range of 0°C to 40 ⁰ C. Therefore, when the oil temperature falls within the range of 0 ⁰ C to 40°C, the contact angle of the contact surface 2 provided for at least part of the heat exchange portion 253 becomes 90 degrees, and the driving system 200 is able to switch the characteristic of the contact surface 2 between oil repellency and lipophilicity. As a result, the driving system 200 is, for example, able to appropriately achieve both a high motor efficiency and a high mechanical efficiency of each of the first motor generator MGl and the second motor generator MG2.

[0115] Note that the above described contact surface-treated product and liquid heat exchanger system are not limited to the above described embodiment; they may be modified in various forms within the scope of the invention recited in the appended claims.

[0116] In the above description, the contact surface-treated product 1 is applied to the entire inner wall surface 230a of the case 230. Instead, the contact surface-treated product 1 may be applied to at least a rotating body that is provided inside the case 230 and that transmits power to the wheels 201 of the hybrid vehicle 200A. In the above description, the contact surface-treated product 1 may be applied to the inner wall surface 230a of the case 230 at the downstream side in a scooping direction in which oil is scooped by rotation of the final driven gear 224. That is, in the driving system 200, as shown in FIG. 9, the contact surface-treated product 1 may be applied to at least a downstream-side wall surface 230c, which is a wall surface at the downstream side in the scooping direction of oil, on the inner wall surface 230a of the case 230. The downstream-side wall surface 230c is, for example, a wall surface, which includes the cooling wall surface 230b, on the inner wall surface 230a of the case 230, and is a wall surface at a portion facing the above described guide passage 252. Even when the contact surface-treated product 1 is applied only to the downstream-side wall surface 230c on the inner wall surface 230a of the case 230, the contact surface 2 of the downstream-side wall surface 230c, to which scooped oil easily adheres, operates as a super-lipophilic surface in a state where the oil temperature is relatively high. Thus, the driving system 200 is able to improve the cooling efficiency of oil adhering to the downstream-side wall surface 230c, and is able to improve the cooing efficiency for each of the first motor generator MGl and the second motor generator MG2. Hence, the driving system 200 is able to improve the motor efficiency of each of the first motor generator MGl and the second motor generator MG2. In this case, a region to which the contact surface-treated product 1 is applied on the inner wall surface 230a of the case 230 may be relatively reduced, and, for example, it is possible to suppress the manufacturing cost of the driving system 200.

[0117] Furthermore, in the driving system 200, a configuration may be employed in which the contact surface-treated product 1 is applied only to the cooling wall surface 230b on the inner wall surface 230a of the case 230. In this case as well, the contact surface 2 of the cooling wall surface 230b, which is cooled by the cooling jacket 205 most, operates as a super-lipophilic surface. Thus, the driving system 200 is able to improve the cooling efficiency of the cooling wall surface 230b for oil, and is able to improve the cooling efficiency for each of the first motor generator MGl and the second motor generator MG2. Hence, the driving system 200 is able to improve the motor efficiency of each of the first motor generator MGl and the second motor generator MG2. In this case, a region to which the contact surface-treated product 1 is applied on the inner wall surface 230a of the case 230 may be further reduced, and, for example, it is possible to further suppress the manufacturing cost of the driving system 200.

[0118] In the driving system 200 that serves as the liquid heat exchanger system, the case 230 is cooled by the cooling system 204 in the above description; however, the cooling structure is not limited to this. Instead, the cooling structure may be of so-called air-cooled type.

[0119] In the driving system 200 that serves as the liquid heat exchanger system, the final driven gear 224 that serves as the rotating body rotates to scoop oil to thereby supply oil to portions of the case 230 in the above description. Instead, another rotating body may rotate to scoop oil to thereby supply oil or a pump and an oil passage may supply oil.

[0120] In the above description, the contact surface-treated product 1 is applied to at least the inner wall surface 230a of the case 230, including the cooling wall surface 230b, and the rotors Rl and R2 of the first motor generator MGl and the second motor generator MG2 as part of the heat exchange portion 253; however, the application of the contact surface-treated product 1 is not limited to this. Instead, the contact surface-treated product 1 may be applied to the entire heat exchange portion 253, that is, may be applied also to the power distribution and integration mechanism 210 and the gear train 220. In this case as well, it is possible to appropriately regulate the flow of oil that flows in contact with the contact surface 2 of the heat exchange portion 253 according to the operating state of the driving system 200, that is, according to the operating temperature of the driving system 200. Thus, it is possible to appropriately regulate the heat exchange state, that is, the cooling state, between oil and the heat exchange portion 253 according to the operating state of the driving system 200.

[0121] The liquid is oil in the above description; however, the liquid is not limited to oil. That is, the contact surface-treated product according to the aspect of the invention may be applied to a system that uses water as liquid. In this case, the contact surface-treated product is able to appropriately regulate the flow of water according to the operating state of the system. In addition, the contact surface-treated product is applied to the liquid heat exchanger system in the above description; however, the application of the contact surface-treated product is not limited to this.

[0122] The liquid heat exchanger system is applied to the driving system in the above description; however, the application of the liquid heat exchanger system is not limited to this. Instead, it is applicable as long as a system contacts liquid to exchange heat with the liquid. The liquid heat exchanger system may be, for example, applied to the above-described cooling system 204. That is, the contact surface-treated product may be applied to a portion that contacts coolant of the cooling system 204. Note that the liquid circulation system described in the first embodiment may also be similarly applied to the cooling system 204.

[0123] The driving system 200 functions as the liquid heat exchanger system according to the invention in the above description. Instead, by appropriately setting the predetermined temperature t at which the contact angle θ of the contact surface 2 becomes 90 degrees, the driving system 200 may be used as the liquid circulation system according to the invention. In this case, in the driving system 200, the storage portion

251 functions as the storage portion according to the invention, and the guide passage

252 and the inner wall surface 230a of the case 230 function as the liquid return portion according to the invention. Then, for example, by applying the contact surface-treated product 1 to these guide passage 252 and inner wall surface 230a of the case 230, the driving system 200 is able to appropriately regulate the flow of oil that flows in contact with the contact surface of the guide passage 252 and the inner wall surface 230a of the case 230, which constitutes the liquid return portion, according to the operating state of the driving system 200, that is, according to the operating temperature of the driving system 200. Thus, the driving system 200 is able to adjust the oil level of oil in the storage portion 251 to an appropriate level according to the operating state of the driving system 200. Similarly, the transmission 50 functions as the liquid circulation system according to the invention in the above description. Instead, by appropriately setting the predetermined temperature t at which the contact angle θ of the contact surface 2 becomes 90 degrees, the transmission 50 may also be used as the liquid heat exchanger system according to the invention.

[0124] As described above, the contact surface-treated product, the liquid circulation system and the liquid heat exchanger system according to the invention are able to regulate the flow of liquid according to the operating state of a system, and are desirably applied to various contact surface-treated product, liquid circulation system and liquid heat exchanger system.

IDS

JP-2001-191657A

This document describes a printing material that is formed to have a surface of which a receding contact angle decreases when the surface is brought into contact with liquid while being heated.

JP-2007-315424A

Lipophilic treatment is applied to a position to which an inlet port is projected on an oil receiving surface of an oil pan, and oil repellent treatment is applied to a position adjacent to the projected position.