ENGINE TEMPERATURES

FIELD OF THE INVENTION

[0001] The present invention relates to an internal combustion engine. More particularly, but not exclusively, the present invention relates to a bearing structure rotatably supporting a crankshaft of the internal combustion engine.

BACKGROUND OF THE INVENTION

[0002] Generally, an internal combustion engine for a two-wheeled vehicle includes a crankcase assembly divided into two crankcase halves, a crank chamber being defined and formed by the crankcase halves, a crankshaft housed in the crank chamber and a cylinder block connected to the crankcase. A crankshaft is rotatably attached on a crankcase through a pair of rotary bearings each disposed on a LH and a RH crankcase, a piston slidable in a cylinder bore is connected to a crank pin of the crankshaft through a connecting rod. The crankcase houses the crankshaft assembly, clutch assembly, starter assembly and gearbox assembly and other ancillary systems, which include lubrication system, cooling system and exhaust system, all housed in the main engine body. The crankcase is made of know metals like aluminium.

[0003] The pair of rotary bearings are made of know metals like steel. The pair of rotary bearings is each disposed on each of the crank case halves. The pair of rotary bearings is press fitted/slide fitted into an insert present in the crank case halves. The insert functions as a holding member for the rotary bearings. The insert is made of a known metal like cast iron.

BRIEF DESCRIPTION OF DRAWINGS

[0004] The above and other features, aspects and advantages of the subject matter will be better understood with regard to the following description, appended claims and accompanying drawings where: [0005] Fig. 1 illustrates a side view of a two-wheeled vehicle.

[0006] Fig. 2 illustrates a side view of an engine assembly for a two wheeled vehicle.

[0007] Fig. 3 illustrates a RH crankcase according to an embodiment of the present invention.

[0008] Fig. 4 illustrates a detailed side view of a crankcase assembly according to an embodiment of the present invention.

[0009] Fig. 5 illustrates a side perspective view of a RH crankcase assembly employing the proposed invention according to an embodiment of the present invention.

[00010] Fig. 6 illustrates a sectional view of an engine assembly taken along XX' plane in Fig. 2.

[00011] Fig. 7 illustrates a detailed view of a sectional view of a crankshaft assembly. [00012] Fig. 8 illustrates a detailed view of the restraining mechanism employed in the inner wall of the insert in the crankcase assembly.

[00013] Fig. 9 illustrates the elements of the restraining mechanism according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION [00014] Typically, an internal combustion engine in a two-wheeled vehicle includes a crankcase assembly divided into two crankcase halves, a crank chamber being defined and formed by the crankcase halves, a crankshaft housed in the crank chamber and a cylinder block connected to the crankcase. A clutch cover is arranged towards the right so that it is adjacent to the crankcase in the vehicle width direction. A counter shaft is arranged in the crankcase halves flanked by transmission cover, the rotation of the crankshaft being transmitted to the counter shaft. A drive shaft is arranged rearward or upward of the counter shaft in the crankcase halves, the driving wheel being attached to the drive shaft through chain and sprocket means. The counter shaft is connected to the drive shaft through a gearbox.

[00015] Typically, an internal combustion engine in a two-wheeled vehicle includes a crankcase assembly including two crankcase halves. The two crankcase halves include a RH crankcase and a LH crankcase. The crankcase assembly defines a crank chamber and the crank chamber is formed by the crankcase halves. A crankshaft is housed in the crank chamber and a cylinder block is connected to the two crankcase halves. A clutch cover is arranged towards the right side of the crankcase assembly, so that the clutch cover remains adjacent to the RH crankcase in the vehicle width direction. Further, a countershaft is arranged in the two crankcase halves flanked by a transmission cover, the rotation of the crankshaft being transmitted to the counter shaft. Furthermore, a drive shaft is arranged rearward or upward of the counter shaft in the two crankcase halves, a driving wheel being attached to the drive shaft through chain and sprocket means. The countershaft is connected to the drive shaft through a gearbox.

[00016] The crankshaft is rotatably mounted inside the crank chamber with the help of a pair of bearing assembly. The pair of bearing assembly includes a RH bearing assembly and a LH bearing assembly, each disposed on the RH crankcase and the LH crankcase respectively. The bearing assembly includes a plurality of ball bearings held by an insert. During assembly of each of the insert loaded with bearing assembly into the two crankcase halves, any minimum clearance between the bearing assembly, the insert, and the crankcase is overcome during assembly inside the engine assembly.

[00017] The further clearance between the bearing assembly and the insert may occur only during the operation of the engine assembly under high operating temperatures. During the engine operation under high operating temperatures, the bearing assembly, the insert, and the two crankcase halves tend to expand. The expansion rate is not uniform for the bearing assembly, the insert, and the two crankshaft halves. This is because, the crankcase is made of aluminium, the bearing assembly includes balls made of steel, and the insert is made of cast iron. The cast iron insert and the aluminium crankcase tend to expand more than the expansion of the steel balls in the bearing assembly. Hence, an undesired clearance is created between the insert and the bearing assembly. The steel balls in the bearing assembly have clearance more than required. Therefore, due to lose fitting, the steel balls tend to move freely in the expanded space available and an undesired noise is generated. The bearing assembly tends to move up and down in the radial direction inside the crankcase. Due to this, during cranking of the engine, the crank noise is higher at higher engine operating temperature. The rider, during cranking of the engine, gets a feel of lose parts being present inside the engine assembly.

[00018] Hence, it is an objective of the present invention to reduce crank noise by arresting the movement of the bearing assembly in the radial direction during higher engine operating temperatures.

[00019] According to an embodiment of the present invention, a restraining mechanism is provided in the crankcase assembly of the engine assembly to reduce radial movement of the bearing assembly.

[00020] Each of the RH insert and the LH insert includes a slot capable of accommodating a restraining mechanism.

[00021] According to an embodiment of the present invention, the restraining mechanism includes a preloaded elastic member pressed against a restraining member in assembled condition. Further, the elastic member and the restraining member are held in position inside the slot by a locking member. The locking member is detachably attached to a wall of the crankcase.

[00022] At normal engine operating temperatures, the restraining member and the preloaded elastic member are tightly held inside the slot by the locking member. However, during higher engine operating temperatures, due to thermal expansion of the cast iron insert, a clearance is generated between the bearing assembly outer race and the inner diameter of the insert. The restraining member is now free to move inside the expanded slot disposed in the outer race of the bearing. The restraining member is pushed inside the slot by the preloaded elastic member held tightly by the locking member, the restraining member is pushed until there exists clearance, and therefore, any upward movement in the radial direction of the bearing assembly is restrained by the restraining mechanism.

[00023] Therefore, any clearance between the insert and the bearing assembly is completely occupied by the restraining mechanism and the undesired movement and noise created due to radial movement of the bearing assembly is prevented.

[00024] Further, according to an embodiment of the present invention, the restraining member is not allowed to fall out of the slot by the locking member and instead the restraining member is allowed to move inside the slot due to force exerted by the preloaded compression member. The restraining member is pushed inside the slot until the clearance is available inside the slot, which is created due to expansion of the insert and the crankcase. Hence, the radial movement of the bearing assembly is successfully prevented through the disclosed restraining mechanism. Further, the crank noise is substantially reduced by arresting the movement of the bearing assembly in the radial direction.

[00025] Hence, according to an embodiment of the present invention, a more stable functioning of the crankshaft is provided.

[00026] According to an embodiment of the present invention, the restraining mechanism includes an elastic member, a restraining member and, a locking member. The elastic member is a preloaded spring, the restraining member is a spherical object, for example, the spherical object is a steel ball, and the locking member is attached to the wall of the crankcase through a bolt.

[00027] The present subject matter and its embodiments would now be described in greater detail in conjunction with the figures in the following description.The following description provides a convenient illustration for implementing exemplary embodiments of the invention. However, the description and the appended drawings are only used by those skilled in the art to understand the objects, features, and characteristics of the present invention and not to be used to confine the scope and spirit of the present invention. [00028] Fig. 1 illustrates a side view of a two-wheeled vehicle, for example, a motorcycle (100) according to an embodiment. The motorcycle (100) according to an embodiment includes a front wheel (101) steered by a handlebar (102) and a rear wheel (103) supported by a swing arm (104). Steering assembly parts including the handlebar (102) and the front wheel (101 are supported for pivotal steering operation on a head pipe (105) at the front end of the vehicle body frame (106). A seat (110) for a driver and a pillion is placed rearward to a fuel tank (114). An engine assembly (113) is disposed below the fuel tank. A front fender (111) is provided above the front wheel (101) to avoid the said vehicle and its occupants from being splashed with mud. Likewise, a rear fender (112) is placed above the rear wheel (103), and to the outer side in the radial direction of rear wheel (103). Rear fender (112) inhibits rainwater or the like from being thrown up by rear wheel (103). The swing arm (104) along with a shock absorber (109) is supported at a front portion thereof for pivotal motion and upward and downward rocking motion on the rear side of a lower portion of the vehicle body frame (106).

[00029] The vehicle body frame (106) includes the head pipe (105), a pair of left and right main frames (107). The head pipe (105) is positioned at a front end portion of the vehicle body frame (106). The main frames (107) extend in a leftwardly and rightwardly branching state obliquely downwardly rearwardly from a lower portion of the head pipe (105).

[00030] Fig. 2 illustrates a side view of an engine assembly for a two wheeled vehicle (100) in accordance with an embodiment of the subject matter. A combustion chamber is covered by a cylinder body (12) and a cylinder head (11). The engine assembly comprises of a carburettor, which supplies the air fuel mixture to the combustion chamber. In another embodiment, a fuel injection system may be used. A crankshaft is rotatably supported inside the crankcase assembly. The crankcase assembly includes a RH crankcase (not shown) and a LH crankcase (13). [00031] Fig. 3 illustrates a RH crankcase according to an embodiment of the present invention. The RH crankcase (201) is preloaded with a bearing assembly (not shown). The bearing assembly includes a plurality of ball bearings. The bearing assembly is held by an RH insert (202a) disposed on the RH crankcase (201. According to an embodiment of the present invention, in order to prevent any clearance occurring between the RH insert (202a) and the crankcase (201), a restraining mechanism is provided in the RH insert (202a). To accommodate the restraining mechanism in the RH insert (202a), a slot (204) is provided on the outer periphery of the RH insert (202a). In order to retain the restraining mechanism inside the slot (204), a locking member (203) is provided on an inside wall (205) of the RH crankcase (201). The locking member (203) is detachably attached to the inside wall (205) of the RH crankcase (201). The proposed mechanism provides more stable crankshaft operation.

[00032] Fig. 4illustrates a detailed side view of a crankcase assembly according to an embodiment of the present invention. The figure illustrates a detailed view of an RH insert (202a) according to the present invention. The RH insert (202a) is configured to include a slot (204). The slot (204) by virtue of its wedge shape, allows easy movement of parts disposed in it. The slot (204) ensures axial movement of the restraining member inside the slot (204), which also results in restraining of the radial motion of the bearing assembly. Hence, the slot (204) allows easy movement of the restraining member (201) whenever there is expansion of the RH insert (202a) at higher engine operation temperatures. The slot (204) is easily machined into the wall of the RH insert (202a). Hence, a more simpler method is employed to prevent radial movement of the bearing assembly at higher engine operation temperatures

[00033] Fig. 5 illustrates a side perspective view of a RH crankcase assembly employing the proposed invention according to an embodiment of the present invention. The RH crankcase (201) includes the RH insert (202a) capable of holding the bearing assembly (not shown).The restraining member (301) along with a preloaded elastic member (302) is disposed in the slot (204). The arrangement of the restraining member (301) and the preloaded elastic member (302) inside the slot (204) is kept in place by the locking member (203). The restraining mechanism prevents radial movement of the bearing assembly under high engine operations. [00034] During high engine operating temperatures, the RH crankcase (201) and the RH insert (202a) tend to expand creating more clearance between the bearing outer race required space around the ball bearings and the RH insert (202a). Hence, during engine operation, the plurality of ball bearings inside the bearing assembly tends to move freely, which is undesirable. Hence, the free moving plurality of ball bearing tends to make undesired noise. The free movement of the plurality of ball bearings is prevented according to the proposed invention.

[00035] Whenever, there is expansion in the RH crankcase (201) and the RH insert (202a), the restraining member (301) tends to move further into the slot (204). The wedge-shape of the slot and the preloaded elastic member (302) aid the forward movement of the restraining member (301) into the slot (204). Hence, the restraining member (301) occupies any clearance created in the RH insert (202a) and bearing outer race. Therefore, the radial movement of the plurality of ball bearings and the bearing assembly is prevented.

[00036] Further, the locking member (203) holds the preloaded elastic member 302 and the restraining member (301) in place during assembly. The locking member (203) is detachable attached to the inside wall of the RH crankcase (201). A provision (203a) is created on the inside wall of the RH crankcase (201). The locking member (203) is attached through locking means (203b), for example, a bolt. [00037] Fig. 6 illustrates a sectional view of an engine assembly taken along XX" plane in Fig.2. From the figure; it is observed that a plurality of ball bearings (501) is disposed on either side of the crankshaft (502). The plurality of ball bearings (501) aid easy movement of the crankshaft (502). The RH insert (202a) is provided with a restraining mechanism (500) according to an embodiment of the present invention. The restraining mechanism (500) includes the locking member (203) bolted to the inside wall of the RH crankcase through a locking means (203b).

[00038] Fig. 7 illustrates a detailed view of a sectional view of a crankshaft assembly. The pluralities of ball bearings (501) are inserted in the RH insert (202a) disposed on either side of the crankshaft (502). The RH insert (202a) is fitted in the two halves of the crankcase assembly. At higher engine operating temperatures, to prevent the radial movement of the plurality of ball bearings inside the RH insert (202a), a restraining mechanism is pre-assembled into the crankcase inside wall. The restraining mechanism includes an elastic member (302) pressed against a restraining member (301). The locking member (203) tightly holds the preloaded elastic member (302) and the restraining member (301) in place inside the slot created in the inside wall of the RH crankcase. The restraining mechanism is disposed on each of the RH insert and the LH insert. [00039] Fig. 8 illustrates a detailed view of the restraining mechanism employed in the inner wall of the insert in the crankcase assembly. The figure illustrates a restraining mechanism disposed in the RH insert (202a). The restraining member (301) is disposed in the slot (204). The restraining member (301) is at a first position (301-1) at a predetermined temperature during normal working condition of the engine assembly, wherein a first end of the preloaded elastic member (302) is pressed against the restraining member (301). Under higher engine operating temperatures greater than the predetermined temperature, the crankcase assembly expands and the slot (204) in the RH insert (202a) tends to expand. One of the sides (204c) of the RH insert (202a) expands from position A to position B with an expansion angle (Θ) there within. The restraining member (301), by virtue of the shape of the slot (204) including a varying cross section and tension exerted by the preloaded elastic member (302), tends to slide inwards into the slot (204) and attains the second position (301-2) from the first position (301-1). Therefore, the restraining member (301) fills the clearance created due to expansion of the crankcase assembly, and the RH insert (202a). Therefore, the second position allow the RH bearing assembly (503) to move in the radial direction and therefore, free movement of the plurality of ball bearings (501) is also restricted. Therefore further, any noise emanating due to movement of the plurality of ball bearings and the RH bearing assembly (503) is prevented. Furthermore, a more reliable and stable operation of the crankshaft assembly is achieved, which results in better engine assembly operation.

[00040] According to an embodiment of the present invention, the at least a slot (204) includes a varying cross-section with a wider cross-section on a side closer (204a) to the locking member (203) compared to another side (204a) away from the locking member (203).

[00041] According to an embodiment of the present invention, the expansion angle Θ is approximately 3 degrees.

[00042] At higher engine operating temperatures greater than the predetermined temperature a similar movement of the restraining member (301) from the first position (301-1) to the second position (301-2) occurs in the LH insert (202b) as well.

[00043] According to an embodiment of the present invention, the temperature ranges from 0-60 degree centigrade and the predetermined temperature above the temperature is approximately 60-100 degree centigrade.

[00044] Fig. 9 illustrates the elements of the restraining mechanism according to an embodiment of the present invention. The radial movement of the plurality of ball bearings and the bearing assembly inside the crankcase assembly is prevented by the restraining mechanism (500). The restraining mechanism (500) inserted in the crankcase includes the restraining member (301) and the preloaded elastic member (302). The preloaded elastic member (302) is preloaded during assembly into the slot (204). The locking member (203) enables locking of the restraining member (301) and the preloaded elastic member (302) inside the slot (204). The slot (204) includes varying dimensions. The slot (204) tapers from the inner wall of the RH crankcase (201) towards the RH insert (202a).

[00045] According to an embodiment of the present invention, the restraining member (301) is a spherical object including a steel ball. The preloaded elastic member (302) is a preloaded spring member. Furthermore, the locking member (203) comprises the provision (203a) enabling the mounting of the locking member (203) onto the inner wall of the crankcase. Further, the locking member (203) includes a hole203c adapted to receive at least a part of the preloaded elastic member (302) during assembly of the restraining mechanism (500).

[00046] Although the subject matter has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. It is to be understood that the aspects of the embodiments are not necessarily limited to the features described herein.