WO2016009259A1

WO2016009259A1 - Fluid temperature control system

Info

Publication number: WO2016009259A1
Application number: PCT/IB2015/001071
Authority: WO
Inventors: Daisuke Tokozakura; Kazuya Arakawa; Takahiro Shiina
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2014-07-18
Filing date: 2015-06-29
Publication date: 2016-01-21
Also published as: JP6142852B2; JP2016023588A

Abstract

A fluid temperature control system has a first channel (21) through which engine oil can flow, a second channel (22) through which transmission oil can flow, and a third channel (23) through which engine coolant can flow, and includes a heat exchanger (1) in which the second channel (22) is interposed between the first channel (21) and the third channel (23) so that heat is exchanged between the engine oil and the transmission oil and between the transmission oil and the engine coolant, a first flow control device (30) configured to control the flow rate of the engine coolant in the third channel (23), based on the liquid temperature of the engine coolant, and a second flow control device (40) configured to control the flow rate of the engine oil in the first channel (21), based on the oil temperature of the transmission oil.

Description

FLUID TEMPERATURE CONTROL SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a fluid temperature control system capable of regulating the temperature of fluid used in an engine or a transmission.

2. Description of Related Art

[0002] Various systems are known as the above type of fluid temperature control system. For example, a heat exchanger capable of exchanging heat between one of three different fluids (transmission oil, engine oil, and engine coolant) with two other fluids is disclosed in Japanese Patent Application Publication No. 2013-120054 (JP 2013-120054 A). The heat exchanger is configured such that the above-indicated one of the three fluids can bypass a heat dissipating portion, based on the temperature of this fluid.

[0003] The heat exchanger of JP 2013-120054 A may increase or reduce the temperature of the selected one fluid. Since the heat exchanger can control the temperature of this fluid, by causing the fluid to bypass the heat dissipating portion, based on the temperature of the fluid, it is possible to reduce losses (friction loss, heat loss, etc.) of a region or part to which the fluid is supplied. However, heat is inevitably exchanged between the remaining two fluids. Therefore, the temperatures of the remaining two fluids are naturally determined without being controlled, and may end up in increasing losses in regions or parts to which the remaining two fluids are supplied. For example, when the fluid whose temperature is to be controlled is transmission oil, losses in the engine may be increased. When the fluid whose temperature is to be controlled is one other than the transmission oil, losses in the engine or transmission may be increased. Then, the losses may result in reduction of fuel economy.

SUMMARY OF THE INVENTION

[0004] In view of the above-described disadvantages encountered in the related art, the invention provides a fluid temperature control system capable of reducing the disadvantages, and curbing reduction of fuel economy.

[0005] According to one aspect of the invention, a fluid temperature control system including a heat exchanger, a first flow control device and a second flow control device is provided. The heat exchanger is connected to a first channel, a second channel, and a third channel. The first channel is configured to permit engine oil to flow through the first channel, and the second channel is configured to permit transmission oil to flow through the second channel, while the third channel is configured to permit engine coolant to flow through the third channel. The heat exchanger includes the second channel between the first channel and the third channel, so as to exchange (i) heat between the engine oil and the transmission oil and (ii) heat between the transmission oil and the engine coolant. The first flow control device is configured to control a flow rate of the engine coolant in the third channel, based on a liquid temperature of the engine coolant. The second flow control device is configured to control a flow rate of the engine oil in the first channel, based on an oil temperature of the transmission oil.

[0006] In the fluid temperature control system as described above, the flow rate of the engine oil in the first channel and the flow rate of the engine coolant in the third channel may be set as reference flow rates respectively, after warm-up of the engine is completed and when the oil temperature of the transmission oil is lower than a predetermined oil temperature. The first flow control device may be configured to reduce the flow rate of the engine coolant in the third channel to a level that is lower than the reference flow rate of the engine coolant, before warm-up of the engine is completed. The second flow control device may be configured to reduce the flow rate of the engine oil in the first channel to a level that is lower than the reference flow rate of the engine oil, when the oil temperature of the transmission oil is equal to or higher than the predetermined oil temperature. Here, each of the first flow control device and the second flow control device may include a flow regulating valve.

[0007] In the fluid temperature control system as described above, the first flow control device may be configured to shut off the third channel before warm-up of the engine is completed. The second flow control device may be configured to shut off the first channel when the oil temperature of the transmission oil is equal to or higher than a predetermined oil temperature.

[0008] In the fluid temperature control system as described above, when the oil temperature of the transmission oil is lower than a predetermined oil temperature, and the liquid temperature of the engine coolant is equal to or higher than a predetermined temperature, after warm-up of the engine is completed, the first flow control device may be configured to open the third channel, and the second flow control device may be configured to open the first channel. Here, each of the first flow control device and the second flow control device may include a channel switching valve.

[0009] In the fluid temperature control system as described above, an amount of change of loss torque of the transmission with respect to an amount of change of the oil temperature of the transmission oil may be larger than an amount of change of loss torque of the engine with respect to an amount of change of the oil temperature of the engine oil.

[0010] The fluid temperature control system according to the invention includes the first flow control device and the second flow control device, as well as the heat exchanger. In the heat exchanger, the second channel is interposed between the first channel and the third channel, so that heat is directly exchanged (i) between the engine oil and the transmission oil, and (ii) between the transmission oil and the engine coolant. The first flow control device controls the flow rate of the engine coolant in the third channel, based on the liquid temperature of the engine coolant. The second flow control device controls the flow rate of the engine oil in the first channel, based on the oil temperature of the transmission oil. Therefore, the fluid temperature control system can optimally control transfer of thermal energy between the fluids, according to operating conditions of the engine and the transmission. Accordingly, the fluid temperature control system is able to suppress increase of losses in the engine and the transmission, and improve fuel economy, under various operating conditions.

BRIEF DESCRIPTION OF THE DRAWINGS [0011] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a view showing the overall configuration of a fluid temperature control system according to one embodiment of the invention;

FIG. 2 is a view useful for explaining a heat exchanger included in the fuel temperature control system;

FIG. 3 is a view useful for explaining the structures and one example of operation of a first flow control device and a second flow control device included in the fluid temperature control system;

FIG. 4 is a view useful for explaining the structures and one example of operation of the first flow control device and the second flow control device;

FIG. 5 is a view useful for explaining the structures and one example of operation of the first flow control device and the second flow control device;

FIG. 6 is a flowchart useful for explaining the operation of the first flow control device and the second flow control device;

FIG. 7 is a view showing changes in the temperatures of respective fluids after cold start of an engine connected to the fluid temperature control system;

FIG. 8 is a view showing changes in the temperatures of respective fluids after cold start of the engine, as compared with those of a conventional system; and

FIG. 9 is a view showing loss torque lines indicating loss torque with respect to the kinetic viscosity of oil in the engine and a transmission connected to the fluid temperature control system.

DETAILED DESCRIPTION OF EMBODIMENTS

[0012] A fluid temperature control system according to one embodiment of the invention will be described in detail with reference to the drawings. It is to be understood that this invention is not limited by this embodiment.

[0013] The fluid temperature control system according to the embodiment of the invention will be described with reference to FIG. 1 through FIG. 9.

[0014] The fluid temperature control system of this embodiment is configured to control the temperature of fluid used in a drive system of a vehicle. As shown in FIG. 1 , the drive system includes an engine (such as an internal combustion engine) 110 as a driving power source of the vehicle, and a transmission (a stepwise variable automatic transmission or a continuously variable transmission) 120 that transmits power of the engine 110 toward drive wheels.

[0015] The engine 110 includes an engine oil circuit (ENG oil circuit) 111 through which engine oil as a fluid circulates, and a coolant circuit (ENG coolant circuit) 112 through which engine coolant as a fluid circulates. Also, the transmission 120 includes a transmission oil circuit (T/M oil circuit) 121 through which transmission oil as a fluid circulates.

[0016] During cold operation of the engine 110, the fluid temperature control system curbs or restricts transfer of thermal energy of the engine coolant, so as to reduce delay of warm-up of the engine 110, and also raises the oil temperature Ttm of the transmission oil using thermal energy of the engine oil, so as to achieve early warm-up of the transmission 120. After warm-up operation of the engine 110 is completed, the fluid temperature control system raises the oil temperature Ttm of the transmission oil using thermal energy of the engine oil or engine coolant, so as to achieve early warm-up of the transmission 120. Also, the fluid temperature control system transfers thermal energy of the transmission oil to the engine coolant, so as to suppress excessive temperature rise of the transmission oil caused by overload operation of the transmission 120, for example. Therefore, the fluid temperature control system includes a heat exchanger 1 capable of regulating the temperature of each fluid according to operating conditions of the engine 110 and the transmission 120.

[0017] The heat exchanger 1 is connected to the engine oil circuit 111, transmission oil circuit 121, and the coolant circuit 112. The fluid temperature control system has an oil delivery channel 11 through which the engine oil is fed from the engine oil circuit 111 to the heat exchanger 1, and an oil return channel 12 through which the engine oil is retumed from the heat exchanger 1 to the engine oil circuit 111. The fluid temperature control system also has an oil delivery channel 13 through which the transmission oil is fed from the transmission oil circuit 121 to the heat exchanger 1, and an oil return channel 14 through which the transmission oil is returned from the heat exchanger 1 to the transmission oil circuit 121. The fluid temperature control system has a coolant delivery channel 15 through which the engine coolant is fed from the coolant circuit 112 to the heat exchanger 1 , and a coolant return channel 16 through which the engine coolant is returned from the heat exchanger 1 to the coolant circuit 112.

[0018] As shown in FIG. 2, the heat exchanger 1 has a first channel 21 through which the engine oil can flow, a second channel 22 through which the transmission oil can flow, and a third channel 23 through which the engine coolant can flow. The first channel

21 has an oil inlet to which the oil delivery channel 11 of the engine oil is connected, and an oil outlet to which the oil return channel 12 of the engine oil is connected. The second channel 22 has an oil inlet to which the oil delivery channel 13 of the transmission oil is connected, and an oil outlet to which the oil return channel 14 of the transmission oil is connected. The third channel 23 has a coolant inlet to which the coolant delivery channel 15 of the engine coolant is connected, and a coolant outlet to which the coolant return channel 16 of the engine coolant is connected.

[0019] In the heat exchanger 1, heat is directly exchanged between the engine oil and the transmission oil, and heat is directly exchanged between the transmission oil and the engine coolant. On the other hand, in the heat exchanger 1, heat is not directly exchanged between the engine oil and the engine coolant. To this end, in the heat exchanger 1, the first through third channels 21, 22, 23 are arranged so that heat can be exchanged between the engine oil and the transmission oil and between the transmission oil and the engine coolant. More specifically, in the heat exchanger 1 , the second channel

22 is interposed between the first channel 21 and the third channel 23.

[0020] For example, in the heat exchanger 1, the first through third channels 21, 22, 23 are arranged or oriented so that directions in which the respective fluids flow through these channels 21, 22, 23 are parallel to each other, and the second channel 22, which is located in the middle, is interposed between the first channel 21 and the third channel 23, as shown in FIG. 2.

[0021] Parts of walls of the channels for the fluids to be subjected to heat exchange contact with each other, or are shared with each other. In the heat exchanger 1 , a part of a wall of the first channel 21 and a part of a wall of the second channel 22 may contact with each other, or a part of a wall of the first channel 21 and a part of a wall of the second channel 22 may be shared, so that heat can be directly exchanged between the engine oil and the transmission oil. Further, in the heat exchanger 1, a part of a wall of the second channel 22 and a part of a wall of the third channel 23 may contact with each other, or a part of a wall of the second channel 22 and a part of a wall of the third channel 23 may be shared, so that heat can be directly exchanged between the transmission oil and the engine coolant. It is desirable to make the areas of the walls that contact with each other or are shared as large as possible, so as to increase the efficiency of heat exchange between the fluids. On the other hand, in the heat exchanger 1, the walls of the first channel 21 and the third channel 23 do not contact with each other; therefore, heat is not directly exchanged between the engine oil and the engine coolant.

[0022] Further, in the heat exchanger 1, the engine oil and the transmission oil flow in opposite directions, and the transmission oil and the engine coolant flow in opposite directions, namely, countercurrent is created, so as to enhance the efficiency of heat exchange between the engine oil and the transmission oil and the efficiency of heat exchange between the transmission oil and the engine coolant. To this end, the direction of flow of the transmission oil (T/M oil) is opposite to the directions of flow of the engine oil (ENG oil) and the engine coolant (ENG coolant), as shown in FIG 2.

[0023] The fluid temperature control system is provided with a first flow control device 30 that regulates the flow rate of the engine coolant in the third channel 23, based on the liquid temperature of the engine coolant, and a second flow control device 40 that regulates the flow rate of the engine oil in the first channel 21, based on the oil temperature of the transmission oil.

[0024] In this embodiment, the flow rate of the engine oil in the first channel 21 and the flow rate of the engine coolant in the third channel 23 after warm-up of the engine 110 is completed and when the oil temperature Ttm of the transmission oil is lower than a given oil temperature Ttml are respectively defined as reference flow rates. In this embodiment, it is determined that warm-up of the engine 110 is completed when the liquid temperature Tw of the engine coolant is raised to a given liquid temperature Twl . In the heat exchanger 1 , when the flow rates of the engine oil and engine coolant are the above-mentioned reference flow rates, thermal energy is supplied and received as needed between the engine oil and the transmission oil and between the transmission oil and the engine coolant. Therefore, in this case, if warm-up of the transmission 120 has not been completed, the oil temperature Ttm of the transmission oil can be raised with thermal energy of the engine oil and the engine coolant. Thus, in this case, the transmission 120 can be promptly warmed up, and a torque converter can be promptly locked up. Namely, in the transmission 120, it is possible to promptly terminate a condition where losses (friction loss, stirring loss, etc.) are large before completion of warm-up. Accordingly, the fluid temperature control system can improve fuel economy.

[0025] In the case where the engine 110 has not been warmed up (Tw < Twl), the first flow control device 30 reduces the flow rate of the engine coolant in the third channel 23 to a level that is lower than the reference flow rate of the engine coolant. In this case, the second flow control device 40 makes the flow rate of the engine oil in the first channel 21 equal to the reference flow rate. In this manner, in the heat exchanger 1, the amount of transfer of thermal energy of the engine coolant to the transmission oil can be reduced as compared with when the flow rate of the engine coolant is equal to the reference flow rate. Namely, before completion of warm-up of the engine 110, the quantity of heat of the engine coolant removed or taken by the transmission oil in the heat exchanger 1 can be reduced. Thus, the engine 110, which has not been warmed up, can be promptly warmed up with thermal energy of the engine coolant. Thus, in the engine 110, it is possible to promptly terminate a condition where losses (such as friction loss and stirring loss) are large before completion of warm-up, for improvement of fuel economy, as compared with the case where the engine coolant is caused to flow into the heat exchanger 1. [0026] For example, the flow rate of the engine coolant is reduced so that the amount of thermal energy transferred from the engine oil to the transmission oil becomes larger than that transferred from the engine coolant to the transmission oil. Therefore, before warm-up of the engine 110 is completed, the transmission 120 can be promptly warmed up, with the oil temperature Ttm of the transmission oil raised due to heat of the engine oil, and it is possible for the transmission 120 to promptly terminate the condition where losses (such as friction loss and stirring loss) are large before completion of its warm-up, for improvement of fuel economy.

[0027] Before completion of warm-up of the engine 110, it is desirable for the first flow control device 30 to shut off the third channel 23 so as to inhibit the engine coolant from flowing into the heat exchanger 1. In this manner, in the heat exchanger 1 , transfer of thermal energy of the engine coolant to the transmission oil can be cut off or inhibited. Thus, when the third channel 23 is shut off, the engine 110 can be more promptly warmed up, and the fuel economy can be further improved, as compared with the case where the flow rate of the engine coolant is reduced.

[0028] In the meantime, in the transmission 120, the oil temperature Ttm of the transmission oil may excessively rise due to overload operation, or the like, as described above. The excessive temperature rise of the oil temperature Ttm of the transmission oil may increase heat loss of the transmission 120, and reduce the quality (noise, wear, shift controllability, etc.) of each element of the transmission 120. Thus, when the oil temperature Ttm of the transmission oil is equal to or higher than a given temperature Ttml, the second flow control device 40 reduces the flow rate of the engine oil in the first channel 21 to a level that is lower than the reference flow rate of the engine oil. The given oil temperature Ttml may be set to the lower limit of the oil temperature Ttm of the transmission oil when the transmission 120 is in overload operation, for example. In this case, the first flow control device 30 sets the flow rate of the engine coolant in the third channel 23 to the reference flow rate.

[0029] Through the operation of the second flow control device 40 as described above, the flow rate of the engine oil in the first channel 21 is reduced so that the amount of transfer of thermal energy of the transmission oil to the engine coolant becomes larger than that to the engine oil. Therefore, in the heat exchanger 1 in which the flow rate of the engine oil is thus reduced, excessive temperature rise of the oil temperature Ttm of the transmission oil can be suppressed mainly by the engine coolant. Thus, the fluid temperature control system curbs or restricts increase of losses (such as heat loss) in the transmission 120, and thus improves fuel economy. The fluid temperature control system can also curb reduction of the quality of each element in the transmission 120.

[0030] When the oil temperature Ttm of the transmission oil is equal to or higher than the given oil temperature Ttml, it is desirable for the second flow control device 40 to shut off the first channel 21, and inhibit the engine oil from flowing into the heat exchanger 1. In this manner, in the heat exchanger 1 , excessive temperature rise of the oil temperature Ttm of the transmission oil can be suppressed only by the engine coolant.

[0031] The first flow control device 30 and the second flow control device 40 may be operated by an electronic control unit (ECU), and may operate according to the temperature of each fluid. FIG. 3 through FIG. 5 schematically illustrate the structures of the first flow control device 30 and the second flow control device 40 in simplified forms. The first flow control device 30 and the second flow control device 40 shown in these figures are channel switching valves that open or shut off the third channel 23 and the first channel 21, respectively.

[0032] The first flow control device 30 is disposed on the coolant delivery channel 15. The first flow control device 30 includes a valve body 31, a return spring 32, and a heat-sensitive operating member 33. The valve body 31 includes a communication path 31a that permits the engine coolant in the coolant delivery channel 15 to be fed to the heat exchanger 1, and a shut-off path 31b that inhibits the engine coolant in the coolant delivery channel 15 from flowing into the heat exchanger 1. The operating member 33 is formed of a shape memory alloy, for example. The operating member 33 is immersed in the engine coolant in the coolant delivery channel 15. Namely, the operating member 33 expands and contracts based on the liquid temperature Tw of the engine coolant, so as to operate the valve body 31. In FIG. 3 to FIG. 5, the operating member 33 is not immersed in the engine coolant, for the sake of simplicity in illustration.

[0033] In the first flow control device 30, in the case where warm-up of the engine 110 has not been completed (Tw < Twl), the valve body 31 is pushed and moved under elastic force of the return spring 32, as shown in FIG. 3, so that the operating member 33 is pressed and contracted along with movement of the valve body 31, and the coolant delivery channel 15 is connected to the shut-off path 31b. Therefore, in this case, the first flow control device 30 shuts off the coolant delivery channel 15, and thus shuts off the third channel 23, so as to stop flow of the engine coolant into the heat exchanger 1.

[0034] On the other hand, in the first flow control device 30, when warm-up of the engine 110 is completed (Tw > Twl), the operating member 33 expands against the elastic force of the return spring 32, as shown in FIG 4 and FIG. 5, so that the valve body 31 is pushed and moved, and the coolant delivery channel 15 is connected to the communication path 31a. Therefore, in this case, the first flow control device 30 opens the coolant delivery channel 15, and permits the engine coolant to flow into the heat exchanger 1. Accordingly, the first flow control device 30 opens the third channel 23.

[0035] The second flow control device 40 is disposed on the oil delivery channel 11 and the oil return channel 14. The second flow control device 40 includes a valve body 41, a return spring 42, and a heat-sensitive operating member 43. The valve body 41 includes a communication path 41a that permits the engine oil in the oil delivery channel 11 to be fed to the heat exchanger 1, and a shut-off path 41b that inhibits the engine oil in the oil delivery channel 11 from flowing into the heat exchanger 1. Like the operating member 33 of the first flow control device 30, the operating member 43 is formed of a shape memory alloy, for example. The operating member 43 is immersed in the transmission oil in the oil return channel 14. Namely, the operating member 43 expands and contracts based on the oil temperature Ttm of the transmission oil, so as to operate the valve body 41.

[0036] In the second flow control device 40, when the oil temperature Ttm of the transmission oil is lower than the given oil temperature Tml, the valve body 41 is pushed and moved under elastic force of the return spring 42, as shown in FIG 3 and FIG 4, so that the operating member 43 is pressed and contracted along with movement of the valve body 41, and the oil delivery channel 11 is connected to the communication path 41a. Therefore, in this case, the second flow control device 40 opens the oil delivery channel 11 , and permits the engine oil to flow into the heat exchanger 1. Accordingly, the second flow control device 40 opens the first channel 21.

[0037] On the other hand, in the second flow control device 40, when the oil temperature Ttm of the transmission oil becomes equal to or higher than the given temperature Ttml, the operating member 43 expands against elastic force of the return spring 42, as shown in FIG. 5, so that the valve body 41 is pushed and moved, and the oil delivery channel 11 is connected to the shut-off path 41b. Therefore, in this case, the second flow control device 40 shuts off the oil delivery channel 11 , and shuts off the first channel 21, so as to inhibit flow of the engine oil into the heat exchanger 1.

[0038] FIG 6 is a flowchart useful for explaining a series of operations of the first flow control device 30 and the second flow control device 40, based on the relationship between the liquid temperature Tw of the engine coolant and the oil temperature Ttm of the transmission oil.

[0039] In the fluid temperature control system, when the oil temperature Ttm of the transmission oil is lower than the given oil temperature Ttml (YES in step ST1), and the liquid temperature Tw of the engine coolant is lower than the given liquid temperature Twl (YES in step ST2), the second flow control device 40 opens the first channel 21, and the first flow control device 30 shuts off the third channel 23 (step ST3).

[0040] The control system proceeds from step ST1 to step ST3 via step ST2 when the engine 110 is in a condition before completion of warm-up thereof, and the engine 110 is in a cold operating region (region A of FIG 7 and FIG. 8). In this region, the temperature of the engine oil is higher than that of the transmission oil, and the temperature of the engine coolant is higher than that of the engine oil (FIG 7). In the cold operating region, the engine coolant does not flow into the heat exchanger 1 , and the engine oil flows into the heat exchanger 1. Therefore, the engine coolant in the cold operation region does not go through reduction of the liquid temperature Tw in the heat exchanger 1 ; therefore, the liquid temperature Tw is substantially equal to that of a conventional system that does not have the heat exchanger 1 (FIG. 8). Consequently, warm-up of the engine 110 is less likely or unlikely to be delayed. On the other hand, in the cold operating region, heat of the engine oil is removed or taken by the transmission oil, so that the oil temperature Teng of the engine oil is reduced to be lower than that of the conventional system, and the oil temperature Ttm of the transmission oil is more rapidly raised than that of the conventional system. Therefore, the transmission 120 can be promptly warmed up. In FIG. 8, the liquid temperature Tw of the engine coolant is reduced to be slightly lower than that of the conventional system after being increased. This phenomenon is caused by reduction of the oil temperature Teng of the engine oil.

[0041] In the fluid temperature control system, when the oil temperature Ttm of the transmission oil is lower than the given oil temperature (YES in step STl), and the liquid temperature Tw of the engine coolant is equal to or higher than the given liquid temperature Twl (NO in step ST2), the second flow control device 40 opens the first channel 21, and the first flow control device 30 opens the third channel 23 (step ST4).

[0042] The control system proceeds from step STl to step ST4 via step ST2, after warm-up of the engine 110 is completed, and when the vehicle is in a normal operating region (region B of FIG. 7 and FIG. 8) in which the oil temperature Ttm of the transmission oil is lower than the given oil temperature Ttml . In the normal operating region, both the engine coolant and the engine oil flow into the heat exchanger 1. Therefore, in the normal operating region, the transmission oil takes heat of the engine coolant as well as that of the engine oil, so that the oil temperature Ttm of the transmission oil is more promptly raised than that of the conventional system. Therefore, the transmission 120 can be promptly warmed up.

[0043] In the fluid temperature control system, when the oil temperature Ttm of the transmission oil is equal to or higher than the given oil temperature Ttml (NO in step STl), the second flow control device 40 shuts off the first channel 21, and the first flow control device 30 opens the third channel 23 (step ST5).

[0044] The control system proceeds from step STl to step ST5 when the transmission 120 is in the overload operating region (region C of FIG. 7) as described above. In the overload operating region, the engine coolant flows into the heat exchanger 1 , and the engine oil does not flow into the heat exchanger 1. Therefore, in the overload operating region, the engine coolant takes heat from the transmission oil, so that excessive temperature rise of the oil temperature Ttm of the transmission oil can be suppressed.

[0045] As described above, in the heat exchanger 1 of this embodiment, heat can be directly exchanged between the engine oil and the transmission oil and between the transmission oil and the engine coolant. However, heat is not directly exchanged between the engine oil and the engine coolant. Therefore, when warm-up of the engine 110 is not completed, the fluid temperature control system of this embodiment makes the flow rate of the engine coolant in the third channel 23 lower than the reference flow rate of the engine coolant, or shuts off the third channel 23, so that the engine 110 can be promptly warmed up with thermal energy of the engine coolant, and fuel economy can be improved. In the meantime, in the heat exchanger 1, when warm-up of the engine 110 is not completed, thermal energy of the engine oil can be transferred to the transmission oil. Therefore, the fluid temperature control system can promptly warm up the transmission 120, and improve fuel economy.

[0046] Also, in the heat exchanger 1, when warm-up of the engine 110 is completed, and the oil temperature Ttm of the transmission oil is lower than the given oil temperature Ttml, the flow rate of the engine oil in the first channel 21 and the flow rate of the engine coolant in the third channel 23 are adjusted to the respective reference flow rates, and heat energy is supplied and received as needed between the engine oil and the transmission oil and between the transmission oil and the engine coolant. At this time, in the heat exchanger 1, if the transmission 120 has not been warmed up, thermal energy of the engine oil or engine coolant is transferred to the transmission oil, so as to raise the oil temperature Ttm of the transmission oil. Therefore, the fluid temperature control system can promptly warm up the transmission 120, and improve fuel economy.

[0047] Also, in the heat exchanger 1, when the oil temperature Ttm of the transmission oil is about to rise excessively (when it becomes equal to or higher than the given oil temperature Ttml), the flow rate of the engine oil in the first channel 21 is reduced to be lower than the reference flow rate of the engine oil, or the first channel 21 is shut off, so that increase of the oil temperature Ttm of the transmission oil can be suppressed using the engine coolant. Thus, the fluid temperature control system can curb or restrict increase of losses (such as heat loss) in the transmission 120, and thus improve fuel economy. Furthermore, in the fluid temperature control system, thermal energy that is not needed for the transmission oil is released via the engine coolant; therefore, the quality (noise, wear, shift control characteristics, etc.) of each element of the transmission 120 can be improved.

[0048] Thus, the fluid temperature control system of this embodiment includes the heat exchanger 1 capable of exchanging heat between the engine oil and the transmission oil and between the transmission oil and the engine coolant, the first flow control device 30 that regulates the flow rate of the engine coolant in the third channel 23 based on the liquid temperature of the engine coolant, and the second flow control device 40 that regulates the flow rate of the engine oil in the first channel 21 based on the oil temperature of the transmission oil. Therefore, the fluid temperature control system optimally controls transfer of thermal energy between the fluids, according to operating conditions of the engine 110 and the transmission 120 (e.g., during cold operation of the engine 110, after completion of warm-up of the engine 110, or during overload operation of the transmission 120). Accordingly, the fluid temperature control system can curb or prevent increase of losses in the engine 110 and the transmission 120, and improve fuel economy, in various operating conditions.

[0049] Also, the fluid temperature control system of this embodiment can perform heat exchange between the engine oil and the transmission oil and heat exchange between the transmission oil and the engine coolant, using the single heat exchanger 1. Therefore, the fluid temperature control system can reduce the quantity of heat dissipated from the heat exchanger 1 , as compared with the arrangement in which one heat exchanger is provided for each heat exchange, so as to improve the efficiency of heat exchange between the respective fluids. Also, the use of the single heat exchanger 1 capable of exchanging heat in the two systems leads to reduction of the number of pipes between the heat exchanger 1 and the engine 110 and between the heat exchanger 1 and the transmission 120, and also achieves reduction of the channel lengths of the respective pipes. Therefore, the fluid temperature control system makes it possible to reduce the quantity of heat dissipated from the pipes, and is thus able to improve the efficiency of heat exchange between the respective fluids. Thus, the fluid temperature control system can further enhance the effect of improving fuel economy as described above, by using the heat exchanger 1 and a set of pipes having high heat-exchange efficiencies. Also, the single heat exchanger 1 is installed on the vehicle with an improved degree of freedom, as compared with the arrangement in which one heat exchanger is provided for each heat exchange.

[0050] FIG. 9 shows a loss torque line TLENG indicating loss torque with respect to the kinetic viscosity (temperature) of the engine oil in the engine 110, and a loss torque line TLT/M indicating loss torque with respect to the kinetic viscosity (temperature) of the transmission oil in the transmission 120. In FIG 9, "a" is the slope of the loss torque line TLENG, and "β" is the slope of the loss torque line TLT/M. In FIG 9, "AVENG" is the amount of change of the kinetic viscosity of the engine oil (namely, the amount of change of the oil temperature of the engine oil), and "AVT/M" is the amount of change of the kinetic viscosity of the transmission oil (namely, the amount of change of the oil temperature of the transmission oil). In FIG. 9, "ATLENG" is the amount of change of the loss torque of the engine 110, and "ATLT/ " is the amount of change of the loss torque of the transmission 120. According to FIG. 9, it is understood that the transmission 120 has a higher loss sensitivity to change of the oil temperature than the engine 110. Namely, when the transmission 120 is warmed up after completion of warm-up of the engine 110, the fluid temperature control system of this embodiment raises the oil temperature Ttm of the transmission oil, mainly using thermal energy of the engine coolant, as indicated in the region B of FIG 8; therefore, the loss torque of the engine 110 can be reduced, and fuel economy can be improved.

[0051] As specific examples of the first flow control device 30 and the second flow control device 40 of this embodiment, the channel switching valves that open or shut off the third channel 23 and the first channel 21, respectively, have been illustrated by way of example. Here, specific examples of the first flow control device 30 and the second flow control device 40 operated by the electronic control unit as described above will be described. For example, the first flow control device 30 and the second flow control device 40 are flow regulating valves (such as electromagnetic valves) that can regulate the flow rate of the engine coolant in the third channel 23 and the flow rate of the engine oil in the first channel 21 as needed, under control of the electronic control unit. Therefore, the first flow control device 30 and the second flow control device 40 can be fixed at given valve openings, respectively, under control of the electronic control unit.

[0052] When the flow regulating valves as described above are used as the first flow control device 30 and the second flow control device 40, the electronic control unit performs the following control, in steps ST3 to ST5 shown in FIG. 6. In step ST3, the valve opening of the second flow control device 40 is adjusted so that the flow rate of the engine oil in the first channel 21 becomes equal to the reference flow rate, and the flow rate of the engine coolant in the third channel 23 becomes lower than the reference flow rate. In step ST4, the valve openings of the second flow control device 40 and the first flow control device 30 are adjusted so that the flow rate of the engine oil in the first channel 21 and the flow rate of the engine coolant in the third channel 23 become equal to the respective reference flow rates. In step ST5, the valve opening of the second flow control device 40 is adjusted so that the flow rate of the engine oil in the first channel 21 becomes lower than the reference flow rate, and the valve opening of the first flow control device 30 is adjusted so that the flow rate of the engine coolant in the third channel 23 becomes equal to the reference flow rate.

[0053] Even when the flow temperature control system of this embodiment employs the above-described arrangement and control, substantially the same effects as those of the fluid temperature control system as explained above can be obtained.

[0054] Next, a modified example of the illustrated embodiment will be described. In this modified example, the flow regulating valves are used as the first flow control device 30 and the second flow control device 40, and a control scheme different from that of the illustrated embodiment is employed.

[0055] Before warm-up of the engine 110 is completed, the flow rate of the engine coolant in the third channel 23 is reduced, to be lower than that after warm-up of the engine 110 is completed. Also, the engine oil is caused to flow through the first channel 21 if the oil temperature Ttm of the transmission oil is not equal to or higher than a given temperature Ttml . In these points, the modified example is identical with the illustrated embodiment. However, in some cases, it may be preferable to make the reference flow rates of the engine coolant and the engine oil variable according to the operating point of the engine 110, rather than making these reference flow rates equal to certain fixed values irrespective of conditions of the engine 110, for improvement of the warm-up performance and cooling performance in the engine 110 and the transmission 120.

[0056] Thus, in the modified example, the reference flow rate of the engine coolant in the third channel 23 is changed according to the operating point (e.g., the engine speed) of the engine 110, and its value for each operating point is stored in advance in a storage device (not shown), or the like.

[0057] In the case where the engine 110 has not been warmed up, the electronic control unit of this modified example reads the reference flow rate of the engine coolant according to the operating point of the engine 110, from the storage device, or the like, and controls the first flow control device 30 to a valve opening that is smaller than that corresponding to the reference flow rate. On the other hand, in the case where the engine 110 has been warmed up, the electronic control unit similarly reads the reference flow rate of the engine coolant according to the operating point of the engine 110, and controls the first flow control device 30 to a valve opening (e.g., the maximum valve opening at which the valve is fully opened) that is larger than the valve opening corresponding to the reference flow rate. The valve opening after completion of warm-up is selected according to the required cooling performance of the engine 110. Thus, before completion of warm-up of the engine 110, the flow rate corresponding to the valve opening becomes the maximum flow rate of the engine coolant in the third channel 23, and the engine coolant does not flow through the third channel 23 at a flow rate larger than the reference flow rate; therefore, the flow rate of the engine coolant in the third channel 23 is reduced as compared with that after warm-up of the engine 110 is completed.

[0058] Also, in this modified example, the reference flow rate of the engine oil in the first channel 21 also changes according to the operating point (e.g., the engine speed) of the engine 110, and its value for each operating point is stored in advance in a storage device, or the like. Further, in this modified example, the required flow rate of the engine oil in the first channel 21 after completion of warm-up of the engine 110 is set. The required flow rate changes according to the operating point (e.g., the engine speed) of the engine 110 and the oil temperature Ttm of the transmission oil. When the oil temperature Ttm of the transmission oil is lower than a given oil temperature Ttml, the required flow rate is set to a value that is equal to or larger than the reference flow rate of the engine oil according to the operating point of the engine 110. When the oil temperature Ttm is equal to or higher than the given oil temperature Ttml, the required flow rate is set to a value that is smaller than the reference flow rate of the engine oil according to the operating point of the engine 110. Values of the required flow rate corresponding to the operating point of the engine 110 and the oil temperature Ttm of the transmission oil are stored in advance in a storage device, or the like.

[0059] In the case where the engine 110 has not been warmed up, the electronic control unit of the modified example reads the reference flow rate of the engine oil corresponding to the operating point of the engine 110 from the storage device, or the like, and controls the second flow control device 40 to the valve opening corresponding to the reference flow rate. On the other hand, in the case where the engine 110 has been warmed up, the electronic control unit reads the required flow rate of the engine oil corresponding to the operating point of the engine 110 and the oil temperature Ttm of the transmission oil, from the storage device, or the like, and controls the second flow control device 40 to the valve opening corresponding to the required flow rate. Thus, when the oil temperature Ttm of the transmission oil becomes equal to or higher than the given oil temperature Itml, the engine oil does not tlow through the first channel 21 at the How rate equal to or higher than the reference flow rate; therefore, the flow rate of the engine oil in the first channel 21 is reduced, as compared with the case where the oil temperature Ttm is lower than the given oil temperature Ttml .

[0060] The fluid temperature control system of the modified example employs the above-described arrangement and control, so that substantially the same effects as those of the fluid temperature control system of the illustrated embodiment can be obtained. In addition, the warm-up performance and cooling performance of the engine 110 and the transmission 120 can be more effectively improved.

Claims

CLAIMS:

1. A fluid temperature control system, comprising:

a heat exchanger connected to a first channel, a second channel, and a third channel, the first channel being configured to permit engine oil to flow through the first channel, the second channel being configured to permit transmission oil to flow through the second channel, the third channel being configured to permit engine coolant to flow through the third channel, and the heat exchanger including the second channel between the first channel and the third channel, so as to exchange (i) heat between the engine oil and the transmission oil and (ii) heat between the transmission oil and the engine coolant;

a first flow control device configured to control a flow rate of the engine coolant in the third channel, based on a liquid temperature of the engine coolant; and

a second flow control device configured to control a flow rate of the engine oil in the first channel, based on an oil temperature of the transmission oil.

2. The fluid temperature control system according to claim 1, wherein:

the flow rate of the engine oil in the first channel and the flow rate of the engine coolant in the third channel are set as reference flow rates respectively, after warm-up of the engine is completed and when the oil temperature of the transmission oil is lower than a predetermined oil temperature;

the first flow control device is configured to reduce the flow rate of the engine coolant in the third channel to a level that is lower than the reference flow rate of the engine coolant, before warm-up of the engine is completed; and

the second flow control device is configured to reduce the flow rate of the engine oil in the first channel to a level that is lower than the reference flow rate of the engine oil, when the oil temperature of the transmission oil is equal to or higher than the predetermined oil temperature.

3. The fluid temperature control system according to claim 2, wherein each of the first flow control device and the second flow control device includes a flow regulating valve.

4. The fluid temperature control system according to claim 1, wherein:

the first flow control device is configured to shut off the third channel before warm-up of the engine is completed; and

the second flow control device is configured to shut off the first channel when the oil temperature of the transmission oil is equal to or higher than a predetermined oil temperature.

5. The fluid temperature control system according to claim 1, wherein

when the oil temperature of the transmission oil is lower than a predetermined oil temperature and the liquid temperature of the engine coolant is equal to or higher than a predetermined temperature, after warm-up of the engine is completed, the first flow control device is configured to open the third channel, and the second flow control device is configured to open the first channel.

6. The fluid temperature control system according to claim 5, wherein

each of the first flow control device and the second flow control device includes a channel switching valve.

7. The fluid temperature control system according to any one of claims 1 through 6, wherein

an amount of change of loss torque of the transmission with respect to an amount of change of the oil temperature of the transmission oil is larger than an amount of change of loss torque of the engine with respect to an amount of change of the oil temperature of the engine oil.