A REGULAR TEMPERATURE SYSTEM FOR POWERTRAIN OF VEHICLE AND CONTROL METHOD THEREFOR

Technical Field

[1] This invention relates to a regular temperature system for powertrain of vehicle and a control method therefor using cooling water discharged from the vehicle engine. In particular, a temperature regulation system which can efficiently control the temperature of vehicle powertrain at optimal level, with a simple configuration of devices, and the control method for said system. Background Art

[2] Generally, engines of motor vehicles are protected from overheating or overcooling with cooling water which is heated by engine or cooled with heat radiator. Therefore, temperature of vehicle engines can be maintained within desirable range. The cooling water also can be used to control the temperature of power transmission to improve engine output power and fuel economy. In other words, cooling water can be used to optimize the temperature of powertrains of vehicles including engines and transmissions.

[3] The common regular temperature systems for powertrains, when warming up the engine of the vehicle, keep circulate the cooling water discharged from the engine(ENG) in the circulation line(l) through a cooling water valve(TS), as illustrated in the Fig. 1. That is, cooling water is circulated from ® to © in the circulation line(l) and protects the engine from local overheating with the heat capacity of the cooling water.

[4] At this time, the transmission(TM) is in cold condition. However, the oil in the transmission(TM) is heated by the friction heat generated from the friction between the gears when the vehicle runs. The transmission(TM) is heated up rather slowly though the oil becomes hot fast. That is, the engine(ENG) is not locally overheated but warmed up slowly. The transmission(TM) is cooled down by the heat exchanger(EX) which will be described later.

[5] The cooling water is fed to the radiator(RA) through the cooling line(2) controlled by the cooling water valve(TS), then cooled down, and fed to the heat exchanger(EX) through the connection line(3). Therefore, the cooling water keeps cooling the transmission(TM) via the heat exchanger(EX). That is, the transmission(TM) is kept cooled while the cooling water is circulated in the heat exchanger(EX).

[6] The cooling water in such system is fed from the heat exchanger to the circulation line(l) via recirculation line(4) and returns to the eng. Here, the heat exchanger exchanges heat between the cooling water fed through the connection line(3) at lower temperature and the oil of the transmission(TM) fed through the transmission line(9) at higher temperature. That is, the heat exchanger(EX) cools down the transmission(TM) oil using the cooling water to the normal operating condition of the transmission.

[7] However, in this system which represents the common powertrain temperature regulating system can warm up the engine(l) but cannot warm up the transmission. In particular, such system can only cool down but cannot warm up a transmission. Disclosure of Invention Technical Problem

[8] This invention provides a regular temperature system for vehicle powertrain which can optimize and maintain the engine temperature at the most desirable level by bypassing the engine cooling water at the inlet of the engine to heat or cool the oil in transmission(TM) as well as controlling the engine temperature, to solve the problems in the common systems described above.

[9] In addition, this invention provides a regular temperature system for vehicle powertrain by bypassing selectively either the cooling water at high temperature discharged from the engine or the cooling water at lower temperature from the outlet of radiator to heat or cool transmission(TM) oil.

[10] In addition, this invention provides a control method for the regular temperature system for vehicle powertrain. Technical Solution

[11] In order to achieve abovementioned technical objects, the regular temperature system for vehicle powertrain in accordance with this invention, wherein the temperatures of the engine and transmission(TM) is controlled at optimal levels using temperature sensors installed on the engine and transmission(TM) and the cooling water which circulates the engine, radiator, and transmission, comprises; a heating unit which heats the passenger room of the vehicle with the cooling water from the engine; a circulation line which circulates the cooling water using a pump; a cooling line which cools the cooling water with a radiator and returns the cooling water to the engine; a cooling water valve which controls the flow of the cooling water discharged from the engine to the cooling line, circulation line or the heating unit; and a transmission(TM) temperature control unit which regulates the temperature of transmission(TM) at optimal level by heating or cooling the transmission(TM) with the cooling water cooled with the radiator or heated in the engine.

Advantageous Effects

[12] The regular temperature system for powertrain of vehicle in accordance with this invention can maintain the engine temperature at optimal level using the cooling water which circulates in the circulation line and also can maintain the temperature of transmission(TM) at optimal level by heating or cooling the transmission(TM) using the cooling water which is fed to cooling line.

Brief Description of the Drawings [13] Fig. 1 is a circuit diagram of the general temperature regulation system for powertrain of vehicle; [14] Fig. 2 is a circuit diagram of an embodiment of the regular temperature system for powertrain of vehicle in accordance with this invention; [15] Fig. 3 is a circuit diagram illustrating the cooling of the transmission by the regular temperature system shown in the Fig. 2;

[16] Fig. 4 is a longitudinal section of the cooling water valve shown in the Fig. 2;

[17] Fig. 5 is a circuit diagram of another embodiment of the regular temperature system for powertrain of vehicle in accordance with this invention; [18] Fig. 6 is a circuit diagram showing the warmingup of the transmission by the regular temperature system presented in the Fig. 5; [19] Fig. 7 is a circuit diagram showing the coolingdown of the transmission by the regular temperature system presented in the Fig. 5;

[20] Fig. 8 is a circuit diagram showing the normal operating status of the regular temperature system presented in the Fig. 5; [21] Fig. 9 is a circuit diagram showing the operating status of the regular temperature system presented in the Fig. 5 when running under heavy load; [22] Fig. 10 is a circuit diagram showing the passengerroom heating state of the regular temperature system presented in the Fig. 5; [23] Fig. 11 is a block diagram showing the valve operation means for the control of the heating valve and cooling valve shown in the Fig. 5;

[24] Fig. 12 is a flowchart showing the control method of warmingup transmission in accordance with an embodiment of the regular temperature system for powertrain of vehicle of this invention; [25] Fig. 13 is a flowchart showing the control method of coolingdown transmission in accordance with an embodiment of the regular temperature system for powertrain of vehicle of this invention; [26] Fig. 14 is a flowchart showing the control method of coolingdown overheated engine in accordance with an embodiment of this invention; and, [27] Fig. 15 is a flowchart showing the control method of heating passenger room of vehicle in accordance with an embodiment of this invention.

Mode for the Invention [28] The regular temperature system for powertrain of vehicle in accordance with this invention is described hearinbelow in detail referring to the annexed drawings. Fig. 2 is a circuit diagram of an embodiment of the regular temperature system for powertrain of vehicle in accordance with this invention. Fig. 3 is a circuit diagram illustrating the cooling of the transmission(TM) by the regular temperature system shown in the Fig. 2. Fig. 4 is a longitudinal section of the cooling water valve shown in the Fig. 2. Fig. 5 is a circuit diagram of another embodiment of the regular temperature system for powertrain of vehicle in accordance with this invention. Fig. 6 is a circuit diagram showing the warmingup of the transmission(TM) by the regular temperature system presented in the Fig. 5. Fig. 7 is a circuit diagram showing the coolingdown of the transmission(TM) by the regular temperature system presented in the Fig. 5. Fig. 8 is a circuit diagram showing the normal operating status of the regular temperature system presented in the Fig. 5. Fig. 9 is a circuit diagram showing the operating status of the regular temperature system presented in the Fig. 5 when running under heavy load. Fig. 10 is a circuit diagram showing the passengerroom heating state of the regular temperature system presented in the Fig. 5. Fig. 11 is a block diagram showing the valve operation for the control of the heating valve and cooling valve shown in the Fig. 5. Fig. 12 is a flowchart showing the control method of warmingup transmission (TM) in accordance with an embodiment of the regular temperature system for powertrain of vehicle of this invention. Fig. 13 is a flowchart showing the control method of coolingdown transmission(TM) in accordance with an embodiment of the regular temperature system for powertrain of vehicle of this invention. Fig. 14 is a flowchart showing the control method of coolingdown overheated engine in accordance with an embodiment of this invention. Fig. 15 is a flowchart showing the control method of heating passenger room of vehicle in accordance with an embodiment of this invention.

[29] Referring to the Fig. 2, an embodiment of the regular temperature system for powertrain of vehicle in accordance with this invention comprises a heating unit(50), circulation line(62), cooling line(64), cooling water valve(70) and the transmission(TM) temperature control unit which will be described later. The functions and effects of the said members are described hereinbelow referring to the related drawings.

[30] The heating unit(50) heats the passenger room of the vehicle using the heat of the cooling water discharged from the engine(ENG). The heating unit(50), as illustrated for an example, can be constituted with; a heater line(52) connecting the cooling water valve(70) at the outlet of the engine(ENG) and the outlet side of the circulation line(62) which will be described later; and the room heater(52a) which is installed in the said heater line(52) to provide heat to the room. That is, the heater line(52) installed with the room heater(52a) and connected with the cooling water valve(70) and circulation line(62).

[31] The heating unit(50) receives cooling water in high temperature from the engine(ENG) via the cooling water valve(70) and circulates it in the heater line(52). The heater line(52) also bypasses the cooling water to the circulation line(62). At this time, the heater line(52) heats the passenger room of the vehicle with the room heater(52a).

[32] The circulation line(62), as illustrated, circulates the cooling water discharged from the engine(ENG) to return it to the engine(ENG) using a pump(P). The circulation line(62) described above forms a closed loop as illustrated with the dotted line.

[33] The cooling line(64), as illustrated, cools down the cooling water discharged from the engine(ENG) by circulating through the radiator(RA), and returns it to the engine(ENG) through the circulation line(62). The cooling line(64) in this system forms a closed loop as illustrated.

[34] The cooling water valve(70) distributes the cooling water from the engine(ENG) to the cooling line(64), circulation line(62), and heating unit(50). The cooling water valve(70), as illustrated, is installed at the outlet side (or also can be called 'inlet side') of the engine(ENG). The operation of the cooling water valve(70) in this system can be executed with a thermostat which opens or closes the flow path according to the temperature of the cooling water, or with a variablecontrol type thermostat or a mo- tordriven valve.

[35] The transmission temperature control unit maintains the temperature of the transmission(TM) at optimal level by heating or cooling it with the cooling water heated up in the engine(ENG) or cooleddown in the radiator(RA).

[36] The transmission temperature control unit in this system, as illustrated for an example, can be implemented by being comprised of; the bypass line(81) which receives cooling water from the outlet(62b) of the circulation line(62) which is connected with the inlet side of the engine(ENG) and feeds it to the cooling water valve(70); a heat exchanger(83) which exchanges heat between the cooling water bypassed by said bypass line(81) and the oil of the transmission (TM); and the transmission line(85) in which said oil of the transmission(TM) is circulated. That is, the transmission temperature control unit can be constituted with the bypass line(81); heat exchanger(83), and; transmission line(85). Here, said outlet(62b) can be formed as the meeting point of the circulation line(62) and bypass line(81), as illustrated.

[37] The engine(ENG) and transmission(TM) are provided with temperature sensors.

Therefore, the temperatures of the engine(ENG) and transmission(TM) are monitored by the temperature sensors, respectively.

[38] In the regular temperature system for powertrain of vehicle in accordance with an exemplary embodiment of the present invention, as described above, the cooling water is circulated through the circulation line(62) in the earlier phase of the engine(ENG) operation. In this phase, the engine(ENG) heats up the cooling water and discharges it through the cooling water valve(70) which feeds the cooling water to the circulation line(62) only. Therefore, the cooling water warmsup the engine(ENG) by circulating through the circulation line(62) in the path depicted with ® and © in the figure.

[39] The bypass line(81), as illustrated, is branched off from the outlet(62b) of the circulation line(62), passing through the heat exchanger(83), connected with the thermostat(70) and connected to the inletside of the circulation line(62). The bypass line(81) receives the cooling water that warms up the engine(ENG) from the outlet(62b) of the circulation line(62). The cooling water supplied to the bypass line(81) flows in the exchanger(83) to exchange heat with the oil in the transmission(TM), as depicted in the drawing by © and ®. At this time, the transmission(TM) circulates the oil in the heat exchanger(83) to exchange heat with the cooling water through the transmission line(85). As the result, the transmission(TM) is warmed up at the same time as the engine(ENG).

[40] Referring to the Fig. 3, when the engine(ENG) has been warmed up, the cooling water valve(70) isolates the circulation line(62) and directs the cooling water to the cooling line(64). Then, the cooling line(64) cools the cooling water in the radiator(RA) by circulating the cooling water through the path depicted by ® to © in the drawing.

[41] The bypass line(81), as illustrated, receives cooling water at low temperature from the outlet(62b) of the circulation line(62) and feeds it to the heat exchanger(83). Here, the cooling water exchanges heat with the transmission(TM) oil which is circulated through the transmission line(85) and heat exchanger(83). Consequently, the transmission(TM) is cooled by the transmission oil which is cooled by the cooling water.

[42] On the other hand, the cooling water valve(70) supplies heated cooling water to the heater line(52) selectively as required. Here, the cooling water radiates heat into the passenger room of the vehicle through the room heater(52a), and returned to the engine(ENG) through the heater line(52) and circulation line(62). Consequently, the passenger room is heated by the heat of the cooling water.

[43] The heating unit(50), as illustrated, can further include the heater valve(54) which is installed in the heater line(52) to cutoff allow the flow of the cooling water to the heater line(52) .heater valve(54) turns the room heater(52a) on or off by controlling the flow of the cooling water. If the heating unit(50) opens the heater valve(54) to supply cooling water into the heater line(52), the cooling water can radiate heat through the room heater(52a), or closes the heater valve(54) to cutoff the supply of the cooling water, then the cooling water can be returned to the engine(ENG) through the circulation line(62) and the time required for the warmingup of the engine(ENG) can be shortened.

[44] Referring to the Fig. 4, the cooling water valve(70), as illustrated for an example, can be constituted with; a housing(HU); a wax chamber(71) filled with wax(71a); a valve device(77) and; a elastomeric member(79), or; further include a rod(73); an actuator(AC) and; a piston member(75). That is, the cooling water valve(70) comprises; a housing(HU); a wax chamber(71) filled with wax (7 Ia); a valve device(77) and; an elastomeric member(79), or further include; a housing(HU); a wax chamber(71) filled with wax(71a); a valve device(77); an elastomeric member(79); a rod(73); and actuator(AC) and; a piston member(75).

[45] In other words, the cooling water valve(70) can be implemented to be operated by wax, or by the wax and the device(73, AC, 75) which expands or compresses the wax. Here, the detail description of the said cooling water valve(70) operated with wax is omitted as the description can be substituted with the description of the cooling water valve(70) operated with the device(73, AC, 75) which expands or compresses the wax, presented hereinbelow.

[46] The housing(HU), as illustrated, id formed with multiple flow paths which distribute the cooling water discharged from the engine(ENG) to cooling line(64), circulation line(62), or heating unit(50). These flow paths are opened or closed by the valve device(77) which will be described later. Consequently, cooling water is distributed to cooling line(64), circulation line(62), or heating unit(50) by the valve device(77).

[47] The wax chamber(71), as illustrated, is filled with wax(71a) and installed in the housing(HU). The wax chamber(71) is sealed with packing to prevent the wax(71a) from leaking out. The wax(71a) changes its volume according to the temperature of the cooling water flowing through the flow path of the housing(HU), or by the pressure of the rod(73) which will be described later.

[48] The rod(73), as illustrated, compresses the wax(71a) while being inserted in the wax chamber(71). The rod(73) is so assembled with the wax chamber(71) as to being able to slide and maintain watertightness.

[49] The actuator(AC), as illustrated, is connected to an end of the rod(73). Therefore, the actuator(AC) moves the rod(73) to change the stroke of the rod(73). Consequently, the rod(73) changes the volume of the wax(71a) in the wax chamber(71) by variable stroke.

[50] The actuator(AC) according to the present invention, for example, can be implemented with an electric motor or solenoid. If the rod(73), as illustrated, is constructed so be moved by screwfeeding mechanism by being screw jointed with the wax chamber(71), the actuator(AC) is preferably an electric motor so that the rod(73) can rotate easily. In this configuration, the actuator(AC) can control the stroke of the rod(73) more precisely as the rod(73) is moved by screwfeeding mechanism. [51] The piston member(75) operates the valve device(77) by moving up or down according to the expansion or shrinkage of the wax(71a). Consequently, the valve device(77) closes or opens the flow path in the housing(HU) with the piston member(75). The valve device(77) and piston member(75), as illustrated, are supported by the elastomeric member(79). The valve device(77) and piston member(75) returns to their original positions by the elastic force of the elastomeric member(79).

[52] Referring to the Fig. 5, the second exemplary embodiment of the regular temperature system for powertrain of vehicle in accordance with the present invention, as illustrated, has the same configuration of the circulation line(62) and heating unit(50) as that of the first exemplary embodiment of the present invention which was described hereinabove. However, as illustrated, the configuration of the cooling line(64) and the cooling water feeding lines(87, 89) to the heat exchanger(83) differ from those of the first exemplary embodiment of the present invention. These differences are described in detail hereinbelow.

[53] The cooling line(64), as illustrated, receives cooling water from the cooling water valve(70) and then returns the cooling water to the cooling water valve(70) through the radiator(RA). Of course, the cooling water fed to the cooling water valve(70) returns to the engine(ENG) through the circulation line(62).

[54] From the cooling line(64), as illustrated, the high temperature line(87) equipped with a heating valve(87a) is branched off at the inlet(64a), and the low temperature line(89) installed with a cooling valve(89a) is branched at the outlet(64b).

[55] Consequently, when the heating valve(87a) is open, the cooling line(64) feeds high temperature cooling water to the high temperature line(87), and when the cooling valve(89a) is open, it feeds cooling water to the low temperature line(89).

[56] The high temperature line(87) receives high temperature cooling water from the inlet(64a) of the cooling line(64) and feeds it to the heat exchanger(83). The high temperature line(87) heats the transmission(TM) with the heat exchanger(83) to which high temperature cooling water is supplied, in the aforementioned way. The operation of the high temperature line(87) is controlled by the heating valve(87a).

[57] The low temperature line(89) receives low temperature cooling water from the outlet(64b) of the cooling line(64) which is connected with the outlet side of the radiator(RA) and feeds it to the heat exchanger(83). Here, the low temperature line(89) cools the transmission(TM) through the heat exchanger(83) to which the low temperature cooling water is supplied, in the aforementioned method. The operation of the low temperature line(89) is controlled by the cooling valve(89a).

[58] The heating valve(87a) and cooling valve(89a) are operated by a valve operation means which operates the heating valve(87a) or cooling valve(89a) according to the temperature measured with the temperature sensors installed on the transmission(TM) and engine(ENG). The valve operation means will be described later.

[59] In the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention, as described hereinabove, the cooling water is circulated through the circulation line(62), as illustrated, when the engine(ENG) is being warmed up. At this time, the thermostat(70) closes all the lines except the circulation line(62). That is, the thermostat(70) cuts off cooling water supply to all other lines than the circulation line(62). Consequently, the cooling water in the circulation line(62) flows in the order depicted by ® and © in the drawing.

[60] Referring to the Fig. 6, in the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention, when the engine(ENG) warming up has been completed and it is turn to warm p the transmission (TM), the high temperature cooling water heated in the engine(ENG) is fed to the cooling line(64). Therefore, the cooling water valve(70) directs the flow of the high temperature cooling water to the cooling line(64). At this time, the high temperature line(87) is opened by the heating valve(87a). As the result, the high temperature cooling water flows through the high temperature line(87) and heat exchanger(83), heats the transmission(TM) oil, and returns to the engine(ENG) through the return line(83a). That is, the high temperature cooling water flows in the sequence of ® through © in the drawing.

[61] Referring to the Fig. 7, in the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention, when the transmission(TM) is overheated, the cooling water discharged from the engine(ENG) is fed to the cooling line(64) and cooled in the radiator(RA). Here, the cooling water valve(70) directs the flow of the cooling water to the cooling line(64). At this time, the low temperature line(89) is opened by the cooling valve(89a). Consequently, the low temperature cooling water discharged from the radiator(RA) flows through the low temperature line(89) and heat exchanger(83), cools the oil of the transmission(TM), then flows through the return line(83a) to return to the engine(ENG). That is, the high temperature cooling water flows in the sequence of ® through © in the drawing.

[62] Referring to the Fig. 8, in the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention, when the temperature of the transmission(TM) is maintained at optimal level by the heat exchanger(83), only the cooling line(64) and circulation line(62) are in operation. That is, in the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention, the cooling water is circulated in the flow paths depicted with ® through ® in the drawing so that the engine(ENG) in running mode can be cooled down. The circuit diagram in the Fig. 8 is a view showing the operation in normal running condition.

[63] Referring the Fig. 9, in the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention, when the engine(ENG) is under heavy load, that is, when the vehicle is running with heavy load, the actuator of the thermostat(70) is operated to secure the flow rate of the cooling water at maximum level to increase the quantity of heat radiation to cool the engine(ENG), and at the same time, as illustrated, the transmission(TM) is cooled by the low temperature line(89). At this time, the cooling water flows in the flow paths depicted with ® through © in the drawing. Of course, the cooling water is diverted at the path ® or ©, passes through the heat exchanger(83) via ®, joins with the path © via the path ©, and returns to the engine(ENG). Consequently, the engine(ENG) and transmission™ are cooled at the same time.

[64] Referring to the Fig. 10, in the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention, as illustrated, feeds high temperature cooling water to the heater line(52) via the cooling water valve(70) when heating the passenger room. At this time, as the heater valve(54) is open, the heater line(52) feeds high temperature cooling water to the room heater(52a), and returns cooling water to the engine(ENG) via the circulation line(62). As the result, the passenger room is heated with the room heater(52a).

[65] Here, if the engine(ENG) needs to be heated up, the said heater valve(54) cuts the heater line(52) off to prevent the cooling water from entering the room heater(52a), so that the engine(ENG) can be heated up faster.

[66] Referring to the Fig. 11, the aforementioned valve operation means which operates the heating valve(87a) and cooling valve(89a) in the high temperature line(87) and low temperature line(89), respectively, can be implemented, illustrated for an example, with a comparator, a signaler, and an actuator.

[67] The comparator compares the measured value of the temperature sensors with the set temperature. The signaler provides open or close signals to the heating valve(87a) and cooling valve(89a) according to the result of the comparison performed in said comparator. The actuator drives the heating valve(87a) and cooling valve(89a) according to the signals from the signaler. The actuator is preferably powered by a solenoid to drive the heating valve(87a) and cooling valve(89a) electronically. That is, the heating valve(87a) and cooling valve(89a) are preferably implemented with solenoid valves.

[68] Referring to the Fig. 13, the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention can heat the transmission(TM) with method shown in Fig. 13. This method for heating the transmission(TM) is described in detail hereinbelow. [69] In order to heat the transmission (TM), the temperature of the transmission(TM) has to be measured (Sl). If the temperature of the transmission oil is same or lower than the set value for the heating valve to be opened, the transmission oil is too cold. In this case, check if the temperature of the transmission oil is same or lower than the temperature of the cooling water to confirm that the temperature of the cooling water discharged from the engine(ENG) is high enough to heat the transmission(TM) (S2).

[70] Here, if it is judged that the transmission oil is not too cold, then check if the temperature of the oil is too high to close the heating valve (Sl' and S5).

[71] Next, if the temperature of the cooling water is found out to be high enough to heat the transmission(TM) up, the cooling water which has been fed from the engine(ENG) to the cooling line(64) is directed to the heat exchanger(83) via the high temperature line by opening the heating valve in the high temperature line to bypass the high temperature cooling water (S3). At this time, the cooling water valve is opened to feed the high temperature cooling water to the cooling line(64).

[72] Next, check if the temperature of the transmission oil is same or higher than the set closing temperature of the heating valve in order to confirm that the transmission(TM) has been heated up to the set temperature (S4) by the high temperature supplied in the cooling water feed step (S3).

[73] If the transmission oil is heated up to the set temperature, the high temperature cooling water supply to the heat exchanger(83) is stopped by closing the heating valve for the high temperature line to prevent overheating of the transmission(TM) (S5). At this time, the cooling water valve is closed to stop the supply of cooling water.

[74] Referring to the Fig. 13, the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention can cool the transmission with the method shown in the Fig. 13. This method of cooling the transmission is described in detail below.

[75] In order to cool the transmission, measure the temperature of the transmission(TM) oil and compare it with the set opening temperature of the cooling valve to see if it is overheated (SI l).

[76] If the temperature of the transmission(TM) oil is same or higher than the set opening temperature of the cooling valve, check whether the temperature of the cooling water discharged from the radiator(RA) is low enough to cool the transmission(TM) (S 12) by comparing the temperatures of the cooling water and the transmission oil.

[77] If the temperature of the cooling is same or lower than that of the transmission oil, the low temperature cooling water discharged from the cooling line(64) through the radiator(RA) is supplied to the heat exchanger(83) by opening the low temperature line(89) which feeds the low temperature cooling water to the heat exchanger(83). Here, the low temperature line(89) is opened by opening both the cooling valve and the cooling water valve (S 13, S 14). When cooling water is supplied to the radiator(RA) by opening the cooling valve and the cooling water valve, the radiator(RA) is started up to cool the cooling water in the radiator(RA) (S15).

[78] At this time, the temperature of the transmission is measured, and if it is not overheated, then check if the temperature is too low, and if it is too low, the cooling valve is closed (SH' and S 17).

[79] Next, when the radiator(RA) was operated and the cooling water in the radiator(RA) has been cooled down, check that the transmission(TM) has been cooled down to the set temperature by the low temperature cooling water fed via the low temperature line (S 16). An then, the supply of high temperature cooling water to the heat exchanger(83) is stopped to prevent overcooling of the transmission(TM) by closing the cooling valve to close the low temperature line(89) (S 17). In addition, the cooling water valve(70) is closed to stop the supply of the cooling water from the engine(ENG) to the radiator(RA) via the cooling water valve(70) (S 18). In addition, the radiator(RA) fan is stopped to prevent further cooling of the cooling water in the radiator(RA).

[80] In addition, the regular temperature system for powertrain of vehicle according to the present invention can be so configured as to stop the supply of cooling water to the heat exchanger(83) by closing the cooling valve when the temperature of the transmission(TM) is in the optimal range by being cooled down or heated up with the aforementioned methods. In this configuration, the optimal temperature condition of the transmission(TM) can be maintained for a certain time as cooling water is not supplied to the heat exchanger(83).

[81] Referring to the Fig. 14, the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention can cool the engine (ENG), if it is overheated, with the cooling water discharged from the engine(ENG) with method presented in the Fig. 14. That is, the cooling method shown in Fig. 14 is for coolingdown an overheated engine when the vehicle is running upward a slope, or at high speed, or is overloaded.

[82] To cool an overheated engine, first, measure the temperature of the cooling water discharged from the engine(ENG) to check if it is overheated (S21) by comparing the temperature of the cooling water with the set temperature of the cooling water valve (S211). If it is found out to be overheated, then check if the temperature is same or higher than the highest set temperature to see if the temperature of the cooling water is approaching the maxim allowable limit (S212).

[83] Next, the degree of the overheat of the cooling water, which was found out to be overheated in the cooling water judgment step (S21), is diagnosed (S22). In this step, whether the temperature of the cooling water discharged from the radiator rises too rapidly by comparing it with the set temperature change rate (S221). If it judged that the temperature is rising too rapidly, the cooling water valve is opened to feed the cooling water discharged from the engine(ENG) to the radiator(RA) (S23).

[84] On the other hand, if it is judged that the temperature of the cooling water is not rising too rapidly, then it is checked if the radiation capacity of the radiator is decreased (S222). If it is judged that the radiation capacity of the radiator(RA) is decreased, the temperature of the cooling water is checked to see if it is at dangerous level (S223). And if it is, the cooling discharged from the engine(ENG) is fed to the radiator(RA) by opening the cooling water valve to cool the cooling water rapidly (S23). And then, the radiator fan is turned on to blow wind to the radiator(RA) to which the cooling water is being fed through the cooling water valve (S24).

[85] Next, check if the temperature of the cooling water is same or lower than the set temperature to confirm that the temperature of the rapidlycooled cooling water has reached safe level (S25).

[86] Then, if it is judged that the temperature of the cooling water is at safe level, the radiator fan is slowed down for slower cooling of the cooling water (S26).

[87] Next, check if the temperature of the cooling water is same or lower than the set optimal temperature to confirm that the temperature of the slowlycooled cooling water has reached set normal temperature level (S27).

[88] If the cooling water is at normal temperature level, the radiator fan is turned off to stop forced cooling of the cooling water (S28) to prevent overcooling.

[89] When the forced cooling is stopped, it can be judged whether the temperature of the cooling water has reached the set optimal level by confirming that the temperature is same or lower than the set offtemperature of the cooling water valve (S29). When the temperature of the cooling water is at the set optimal level, the cooling water valve can be closed to stop the supply of the cooling water to the radiator(RA) (S30).

[90] In addition, the regular temperature system for powertrain of vehicle according to the present invention can warmup or heat the engine(ENG) to the optimal temperature level, when the engine(ENG) is cooler than optimal temperature, with the cooling in the circulation line(62) which was described earlier.

[91] In order to warmup or heat the engine(ENG) to the optimal temperature level with the cooling in the circulation line(62), the cooling water has to be circulated in the circulation line(62). That is, cooling water valve(70) is operated so that the cooling water is circulated only in the circulation line(62). And then, when the engine(ENG) has reached the set temperature, the cooling water circulation in the circulation line(62) is stopped to prevent overheating of the engine(ENG). Consequently, the engine(ENG) can reach the set optimal temperature level by being warmedup or heated with the cooling water.

[92] Referring to the Fig. 15, the regular temperature system for powertrain of vehicle of the secondary embodiment according to the present invention can heat passenger room in accordance with the method illustrated in the drawing using the cooling water discharged from the engine(ENG).

[93] To heat the passenger room, first, check that heater switch is turned on (S41). If it is not turned on, then turn it on. Next, make sure that the room airconditioner which is driven by the engine is turned off (S42).

[94] Next, judge (S43) that the temperature of the cooling water has been warmedup to room heating temperature by the engine(ENG), and if it has, then open the heater valve to supply cooling water to the room heater(52a) (S44).

[95] When the passenger room has been heatedup by the heat of the cooling water through the room heater, the temperature of the cooling water is checked to see if it has been cooleddown too much (S45). If it has, the heater valve is closed to stop the cooling water supply to the room heater(52a) (S46).

[96]

[97] The regular temperature system for powertrain of vehicle according to the present invention, as set forth and described hereinabove, can control the temperature of the engine(ENG) with the cooling water in the circulation line(62), and can heatup or cooldown the transmission(TM) with the cooling water in the cooling line(64). Therefore, the system according to the present invention can maintain the temperatures of the engine(ENG) and transmission(TM) at desired level.

[98]

[99] While it is apparent that the illustrative embodiments of the invention herein disclose fulfills the objective stated above, it will be appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments which come within the spirit and scope of the present invention.