JP7707714B2 - Vehicle Cooling System - Google Patents

Description

The present invention relates to a vehicle cooling system.

Patent Document 1 describes a vehicle cooling device that includes a first cooling system, a second cooling system that circulates cooling water to a second cooling object that is cooler than the first cooling object, a first heat exchanger that exchanges heat between oil in a transmission and the cooling water of the first cooling system, and a second heat exchanger that exchanges heat between the oil and the cooling water of the second cooling system. This vehicle cooling device does not perform heat exchange when the oil temperature is equal to or lower than a predetermined oil temperature, performs heat exchange by the first heat exchanger when the oil temperature is higher than the predetermined oil temperature and the cooling water temperature of the second cooling system is higher than the predetermined water temperature, and performs heat exchange by both heat exchangers when the oil temperature is higher than the predetermined oil temperature and the cooling water temperature of the second cooling system is equal to or lower than the predetermined water temperature.

JP 2016-125629 A

Here, a hybrid vehicle equipped with an engine and an electric motor can be switched between an engine driving mode in which the vehicle runs using at least the engine as a driving force source, and an EV driving mode in which the vehicle runs using the electric motor as a driving force source without using the engine as a driving force source.

However, when the technology described in Patent Document 1 is applied to a hybrid vehicle in which an electric motor is built into the transmission, there is a problem in that the transmission containing the electric motor cannot be properly cooled. In other words, when the inverter for the electric motor and the transmission are cooled by a common low-temperature cooling system, the transmission may be cooled to a temperature lower than the appropriate temperature due to the influence of the inverter's management temperature, or the heat dissipation amount of the radiator may be insufficient when the transmission is at a high temperature. Also, when the transmission is cooled by a high-temperature cooling system, cooling water cannot be supplied to the transmission when the water pump of the high-temperature cooling system is stopped.

The present invention was made in response to the above-mentioned problems, and aims to provide a vehicle cooling system that can properly cool a transmission that incorporates an electric motor.

The present invention is a vehicle cooling system that is mounted on a hybrid vehicle having a transmission with a built-in electric motor and has driving modes including an engine driving mode in which the vehicle runs using at least the engine as a driving force source, and an EV driving mode in which the vehicle runs using the electric motor as a driving force source without using the engine as a driving force source, and that includes a first water pump that operates using the engine as a driving force source, a high-temperature cooling water circulation circuit through which cooling water that at least cools the engine circulates, and a low-temperature cooling water circulation circuit that includes a second water pump that operates electrically, cools at least an inverter electrically connected to the electric motor, and through which cooling water that is lower in temperature than the cooling water circulating in the high-temperature cooling water circulation circuit circulates. The vehicle cooling system is characterized by including a cooling circuit switching unit that switches the supply state of cooling water to an oil cooler that cools transmission oil of the transmission, and a control unit that controls the cooling circuit switching unit based on the driving mode.

In this way, the present invention provides a vehicle cooling system that can properly cool a transmission that incorporates an electric motor.

FIG. 1 is a configuration diagram of a vehicle equipped with a vehicle cooling system according to an embodiment of the present invention. FIG. 2 is a diagram showing the flow of coolant in a first state of the vehicle cooling system according to the embodiment of the present invention. FIG. 3 is a diagram showing the flow of coolant in the vehicle cooling system according to the embodiment of the present invention in a second state. FIG. 4 is a diagram showing the flow of coolant in the vehicle cooling system according to the embodiment of the present invention in a third state. FIG. 5 is a diagram showing the temperature state when no heating is required and the control state of the cooling circuit switching unit with respect to the driving mode in the vehicle cooling system according to one embodiment of the present invention. FIG. 6 is a diagram showing the flow of coolant in the vehicle cooling system according to the embodiment of the present invention in a fourth state. FIG. 7 is a diagram showing the control state of the cooling circuit switching unit with respect to the temperature state and the driving mode when heating is required in the vehicle cooling system according to one embodiment of the present invention.

The vehicle cooling system according to one embodiment of the present invention is equipped with a transmission incorporating an electric motor, and is mounted on a hybrid vehicle having driving modes including an engine driving mode in which the vehicle runs using at least the engine as a driving force source, and an EV driving mode in which the vehicle runs using the electric motor as a driving force source without using the engine as a driving force source. The vehicle cooling system includes a first water pump that operates using the engine as a driving force source, a high-temperature cooling water circulation circuit in which cooling water that at least cools the engine circulates, and a low-temperature cooling water circulation circuit in which cooling water that is lower in temperature than the cooling water circulating in the high-temperature cooling water circulation circuit is circulated, the low-temperature cooling water circulation circuit includes a second water pump that operates electrically, at least cools an inverter electrically connected to the electric motor, and is characterized by including a cooling circuit switching unit that switches the supply state of cooling water to an oil cooler that cools the transmission oil of the transmission, and a control unit that controls the cooling circuit switching unit based on the driving mode. As a result, the vehicle cooling system according to one embodiment of the present invention can appropriately cool the transmission incorporating the electric motor.

Below, a vehicle cooling system according to one embodiment of the present invention will be described with reference to the drawings. Figures 1 to 7 are diagrams showing a vehicle cooling system according to one embodiment of the present invention.

First, the configuration will be described. In FIG. 1, a vehicle 1 is equipped with an engine (referred to as ENG in the drawing) 2, a transmission (referred to as T/M in the drawing) 3, and an electric motor (referred to as MGU in the drawing) 4.

Engine 2 is an internal combustion engine that uses gasoline or diesel fuel and generates driving force (engine torque) for traveling. Inside engine 2, a water jacket (not shown) is provided through which cooling water flows.

The transmission 3 is connected to the engine 2 and transmits the driving force (engine torque) generated by the engine 2. The transmission 3 is equipped with a speed change mechanism (not shown), and the rotation transmitted from the engine 2 is changed in speed by the speed change mechanism and transmitted to the driving wheels (not shown).

The electric motor 4 is electrically connected to a battery (not shown) via an inverter 5. The electric motor 4 is built into the rear part of the speed change mechanism in the transmission 3. The driving force (motor torque) generated by the electric motor 4 for running is transmitted to the drive wheels without passing through the speed change mechanism of the transmission 3.

The electric motor 4 is provided with an oil cooler (indicated as O/C in the figure) 4A, which cools the transmission oil flowing inside the electric motor 4 by exchanging heat with the cooling water.

The vehicle 1 is equipped with one radiator 50. The radiator 50 cools the coolant by exchanging heat with the airflow while the vehicle is running. The radiator 50 is equipped with a high-temperature section 50H that cools the relatively high-temperature coolant taken in from the engine 2, and a low-temperature section 50L that cools the relatively low-temperature coolant taken in from the oil cooler 4A.

The vehicle 1 is equipped with an engine coolant circulation circuit 21. The engine coolant circulation circuit 21 connects the engine 2 and the radiator 50, and circulates the coolant between the engine 2 and the radiator 50. The radiator 50 cools the coolant circulating through the engine coolant circulation circuit 21.

The engine coolant circulation circuit 21 has a feed passage 21A that sends coolant from the engine 2 to the radiator 50, and the feed passage 21A is connected to the radiator 50.

The engine coolant circulation circuit 21 has a return passage 21B that returns the coolant cooled by the radiator 50 to the engine 2, and the return passage 21B is connected to the radiator 50.

The vehicle 1 is equipped with a mechanical water pump (indicated as WP in the figure) 32 that operates using the engine 2 as a driving force source. A pulley (not shown) of the water pump 32 is connected to a crank pulley (not shown) of the engine 2 via a fan belt (not shown), and the water pump 32 forcibly circulates the cooling water using power obtained from the rotation of the engine 2. The water pump 32 constitutes the first water pump in the present invention. The water pump 32 is provided at the end of the return passage 21B on the engine 2 side, and is driven by the engine 2 to send the cooling water sucked from the return passage 21B to the engine 2.

A thermostat 33 is provided between the engine 2 and the feed passage 21A. When the temperature of the cooling water is lower than a predetermined temperature, the thermostat 33 closes and prevents the circulation of the cooling water in the engine cooling water circulation circuit 21. When the temperature of the cooling water is higher than a predetermined temperature, the thermostat 33 opens and allows the circulation of the cooling water in the engine cooling water circulation circuit 21. That is, when the thermostat 33 is open, the cooling water sent to the engine 2 by the water pump 32 is discharged from the engine 2 after cooling the engine 2. The cooling water is then introduced into the radiator 50 through the feed passage 21A, and after being cooled in the radiator 50, is returned to the water pump 32 through the return passage 21B.

The vehicle 1 is equipped with a high-temperature cooling water circulation circuit 22. Cooling water that at least cools the engine 2 circulates through the high-temperature cooling water circulation circuit 22. A heater core 31 and an EGR cooler 30 are connected to the engine 2 via the high-temperature cooling water circulation circuit 22. The heater core 31 heats the vehicle interior (not shown) by heat exchange with high-temperature cooling water introduced from the engine 2. The EGR cooler 30 cools the exhaust gas discharged from the engine 2 by heat exchange with the cooling water. The exhaust gas cooled by the EGR cooler 30 is sent to the intake path of the engine 2.

The high-temperature cooling water circulation circuit 22 has a feed passage 22A that sends cooling water from the engine 2 to the heater core 31, a feed passage 22B that sends cooling water from the engine 2 to the EGR cooler 30, and a return passage 22C that returns the cooling water from the heater core 31 and the EGR cooler 30 to the engine 2.

The return passage 22C is configured to merge the cooling water from the heater core 31 and the cooling water from the EGR cooler 30. The upstream ends of the feed passages 22A and 22B are connected to the engine 2 without passing through the thermostat 33. The downstream end of the return passage 22C is connected to the suction side of the water pump 32. Therefore, while the engine 2 is operating, the cooling water always circulates through the high-temperature cooling water circulation circuit 22, regardless of whether the thermostat 33 is open or closed.

The vehicle 1 is equipped with a low-temperature cooling water circulation circuit 23. The low-temperature cooling water circulation circuit 23 circulates cooling water that is lower in temperature than the cooling water circulating through the high-temperature cooling water circulation circuit 22. The oil cooler 4A is connected to a radiator 50 via the low-temperature cooling water circulation circuit 23. The radiator 50 cools the cooling water circulating through the low-temperature cooling water circulation circuit 23.

The low-temperature cooling water circulation circuit 23 has a feed passage 23A that sends cooling water from the oil cooler 4A to the radiator 50, and a return passage 23B that returns cooling water from the radiator 50 to the oil cooler 4A. The return passage 23B is provided with an electrically operated electric water pump (referred to as EWP in the figure) 37 and an inverter (referred to as INV in the figure) 5. The electric water pump 37 constitutes the second water pump in the present invention. The cooling water circulating through the low-temperature cooling water circulation circuit 23 cools the oil in the oil cooler 4A and the inverter 5.

Therefore, in the low-temperature cooling water circulation circuit 23, cooling water circulates between the oil cooler 4A and the inverter 5 and the radiator 50. The cooling water circulating in the low-temperature cooling water circulation circuit 23 is at a lower temperature than the cooling water circulating in the high-temperature cooling water circulation circuit 22.

The radiator 50 is provided with an inlet 51A for the engine cooling water circulation circuit 21 and an inlet 51B for the low-temperature cooling water circulation circuit 23.

The radiator 50 is provided with an outlet 52A for the engine cooling water circulation circuit 21 and an outlet 52B for the low-temperature cooling water circulation circuit 23.

The vehicle 1 is equipped with a control unit 10. The control unit 10 is configured as an ECU (Electronic Control Unit) that is made up of a computer unit that includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, etc., an input port, and an output port.

The ROM of the control unit 10 stores various constants, maps, and the like, as well as programs for causing the computer unit to function as the control unit 10. The control unit 10 achieves the intended operation by having the CPU execute the programs stored in the ROM using the RAM as a working area.

The control unit 10 switches the driving mode between an engine driving mode in which the vehicle runs using at least the engine 2 as a driving force source, and an EV driving mode in which the vehicle runs using the electric motor 4 as a driving force source without using the engine 2 as a driving force source. The engine driving mode includes a state in which the vehicle runs using the engine 2 as a driving force source, and a state in which the vehicle runs using both the engine 2 and the electric motor 4 as driving force sources.

The vehicle 1 is equipped with a cooling circuit switching unit 40. The cooling circuit switching unit 40 switches the supply state of cooling water to the oil cooler 4A under the control of the control unit 10. The cooling circuit switching unit 40 is provided between the oil cooler 4A and the low-temperature cooling water circulation circuit 23.

The cooling circuit switching unit 40 is connected to the feed passage 22A to the heater core 31 of the high-temperature cooling water circulation circuit 22 by the communication passage 24A. The cooling circuit switching unit 40 is connected to the return passage 22C from the heater core 31 of the high-temperature cooling water circulation circuit 22 by the communication passage 24B.

More specifically, the cooling circuit switching unit 40 is provided with valves 41 and 42 that switch the cooling water path, and passages 43, 44, and 45 through which the cooling water passes. Passage 43 connects the cooling water outlet of the oil cooler 4A to the valve 42. Passage 44 connects the inverter 5 to the valves 41 and 42 via the return passage 23B. Passage 45 connects the cooling water inlet of the oil cooler 4A to the valve 41.

The cooling circuit switching unit 40 has a first state in which the cooling water of the low-temperature cooling water circulation circuit 23 is supplied to the oil cooler 4A, a second state in which the cooling water of the high-temperature cooling water circulation circuit 22 and the cooling water of the low-temperature cooling water circulation circuit 23 are not supplied to the oil cooler 4A, and a third state in which the cooling water of the high-temperature cooling water circulation circuit 22 is supplied to the oil cooler 4A.

The cooling circuit switching unit 40 also has a fourth state in which the cooling water in the low-temperature cooling water circulation circuit 23 is supplied to the oil cooler 4A and the heater core 31. The cooling circuit switching unit 40 can be switched to any one of the supply states: the first state, the second state, the third state, or the fourth state.

In this way, the cooling circuit switching unit 40 has a first state, a third state, and a fourth state, in which cooling water is supplied to the oil cooler 4A from at least one of the high-temperature cooling water circulation circuit 22 and the low-temperature cooling water circulation circuit 23. The cooling circuit switching unit 40 has a second state, in which cooling water is not supplied to the oil cooler 4A.

As shown in FIG. 2, when the cooling circuit switching unit 40 is in the first state, the feed passage 23A and the return passage 23B of the low-temperature cooling water circulation circuit 23 are connected to the oil cooler 4A via the cooling circuit switching unit 40. Therefore, in the first state, the cooling water of the low-temperature cooling water circulation circuit 23 is supplied to the oil cooler 4A side.

As shown in FIG. 3, when the cooling circuit switching unit 40 is in the second state, the cooling circuit switching unit 40 separates the oil cooler 4A from the low-temperature cooling water circulation circuit 23. In the second state, the low-temperature cooling water circulation circuit 23 circulates through the inverter 5, the electric water pump 37, and the low-temperature section 50L of the radiator 50.

Therefore, in the second state, the cooling water in the low-temperature cooling water circulation circuit 23 is not supplied to the oil cooler 4A. Also, in the second state, the communication passages 24A and 24B are closed by the valves 41 and 42, so the cooling water in the high-temperature cooling water circulation circuit 22 is not supplied to the oil cooler 4A.

As shown in FIG. 4, when the cooling circuit switching unit 40 is in the third state, the cooling circuit switching unit 40 separates the oil cooler 4A from the low-temperature cooling water circulation circuit 23. In the third state, the low-temperature cooling water circulation circuit 23 circulates through the inverter 5, the electric water pump 37, and the low-temperature section 50L of the radiator 50.

Therefore, in the third state, the cooling water of the low-temperature cooling water circulation circuit 23 is not supplied to the oil cooler 4A. Also, in the third state, the passage 45 of the cooling circuit switching unit 40 and the feed passage 22A of the high-temperature cooling water circulation circuit 22 communicate with each other via the communication passage 24A, and the passage 43 of the cooling circuit switching unit 40 and the return passage 22C of the high-temperature cooling water circulation circuit 22 communicate with each other via the communication passage 24B. Therefore, the cooling water of the high-temperature cooling water circulation circuit 22 is supplied to the oil cooler 4A.

As shown in FIG. 6, when the cooling circuit switching unit 40 is in the fourth state, the feed passage 23A and the return passage 23B of the low-temperature cooling water circulation circuit 23 are connected to the oil cooler 4A via the cooling circuit switching unit 40.

Therefore, in the fourth state, the cooling water of the low-temperature cooling water circulation circuit 23 is supplied to the oil cooler 4A side. Also, in this fourth state, the cooling water of the low-temperature cooling water circulation circuit 23 is supplied to the heater core 31 by the communication passage 24A and returned from the heater core 31 by the communication passage 24B. Therefore, the cooling water of the low-temperature cooling water circulation circuit 23 is supplied to the oil cooler 4A and the heater core 31.

Here, the water pump 32 cannot circulate the cooling water when the engine 2 is stopped. Therefore, in the EV driving mode, the engine 2 is stopped and the cooling water does not circulate through the high-temperature cooling water circulation circuit 22, so the transmission oil cannot be cooled by the cooling water in the high-temperature cooling water circulation circuit 22. On the other hand, the electric water pump 37 is operated by electricity, so it can be driven even in the EV driving mode. In other words, even in the EV driving mode, it is possible to cool the transmission oil using the cooling water circulating in the low-temperature cooling water circulation circuit 23.

The control unit 10 controls the cooling circuit switching unit 40 based on the driving mode. In more detail, the control unit 10 controls the cooling circuit switching unit 40 based on the driving mode, the oil temperature of the transmission oil (hereinafter also referred to as the oil temperature), and the water temperature of the engine.

Figures 5 and 7 show the control state of the cooling circuit switching unit 40 with respect to the temperature state and the driving mode. Figure 5 shows the control state when there is no heating request, and Figure 7 shows the control state when there is a heating request. A heating request is a request to heat the passenger compartment with hot water passing through the heater core 31.

In Figures 5 and 7, TWc is a threshold value related to the engine water temperature, and is the lower limit water temperature at which waste heat from the engine 2 may be used to warm up the transmission 3. TOc1 is the upper limit oil temperature that is acceptable for cooling the electric motor 4 and is the upper limit oil temperature when attempting to further increase the oil temperature of the transmission 3. TOc2 is the lower limit oil temperature of the transmission 3 at which a temperature difference with the temperature of the cooling water in the low-temperature cooling water circulation circuit 23 is unacceptable.

Based on FIG. 5, we will first explain the case where the engine water temperature < TWc. When the transmission oil temperature (referred to as transmission oil temperature in the figure) is oil temperature < TOc1, the second state is selected in both the engine driving mode and the EV driving mode. When the oil temperature ≧ TOc1 and oil temperature < TOc2, the third state is selected in the engine driving mode, and the first state is selected in the EV driving mode. When the oil temperature ≧ TOc2, the third state is selected in the engine driving mode, and in the EV driving mode, a transition to engine driving and the third state are selected.

Next, the difference between the case where engine water temperature ≧ TWc and the above case where engine water temperature < TWc will be explained. When oil temperature < TOc1, the third state is selected in the engine driving mode. In other cases, it is the same as the case where engine water temperature < TWc in Figure 5.

First, the case where engine water temperature < TWc will be described with reference to FIG. 7. When the transmission oil temperature (referred to as transmission oil temperature in the figure) is oil temperature < TOc1, the second state is selected in both engine driving mode and EV driving mode. When oil temperature ≧ TOc1 and oil temperature < TOc2, the third state is selected in engine driving mode, and the fourth state is selected in EV driving mode. When oil temperature ≧ TOc2, the third state is selected in engine driving mode, and a transition to engine driving and the third state is selected in EV driving mode.

Next, the difference between the case where engine water temperature ≧ TWc and the above case where engine water temperature < TWc will be explained. When oil temperature < TOc1, the third state is selected in the engine driving mode. In other cases, it is the same as the case where engine water temperature < TWc in Figure 7.

Here, if the heat dissipation performance of the low-temperature section 50L of the radiator 50, which is the heat sink of the low-temperature cooling water circulation circuit 23, is reduced, when the transmission oil temperature is TOc2 or higher, cooling the transmission oil with the low-temperature cooling water circulation circuit 23 will exceed the management temperature of the inverter 5. The allowable temperature of the high-temperature cooling water circulation circuit 22 is higher than the allowable temperature of the low-temperature cooling water circulation circuit 23. Therefore, when the transmission oil temperature is TOc2 or higher, it is desirable to be able to cool the transmission oil with the high-temperature cooling water circulation circuit 22.

Therefore, when the current driving mode is the EV driving mode and the oil temperature of the transmission oil is equal to or higher than TOc2 as the first threshold value, the control unit 10 controls the cooling circuit switching unit 40 to transition to the engine driving mode and switch to the third state.

When there is a heating request, the current driving mode is the EV driving mode, and the oil temperature is less than TOc2 and is equal to or greater than TOc1, which is a second threshold lower than TOc2, the control unit 10 controls the cooling circuit switching unit 40 to switch to the fourth state.

As described above, the vehicle cooling system of this embodiment includes a cooling circuit switching unit 40 that switches the supply state of cooling water to the oil cooler 4A that cools the transmission oil of the transmission 3, and a control unit 10 that controls the cooling circuit switching unit 40 based on the driving mode.

As a result, the cooling circuit switching unit 40 is controlled based on the driving mode, so that cooling water can be supplied to the oil cooler 4A from at least one of the low-temperature cooling water circulation circuit 23 or the high-temperature cooling water circulation circuit 22 depending on the driving mode. This allows the transmission 3, which has the electric motor 4 built in, to be appropriately cooled.

In addition, in the vehicle cooling system of this embodiment, the control unit 10 controls the cooling circuit switching unit 40 based on the driving mode, the oil temperature of the transmission oil, and the water temperature of the engine.

This allows the cooling circuit switching unit 40, which switches the cooling circuit that cools the transmission oil based on the driving mode, the oil temperature of the transmission oil, and the engine water temperature, to be controlled so that the transmission 3, which has a built-in electric motor, can be appropriately cooled.

In addition, in the vehicle cooling system of this embodiment, the cooling circuit switching unit 40 can be switched to one of the supply states: a first state in which the cooling water of the low-temperature cooling water circulation circuit 23 is supplied to the oil cooler 4A; a second state in which the cooling water of the high-temperature cooling water circulation circuit 22 and the cooling water of the low-temperature cooling water circulation circuit 23 are not supplied to the oil cooler 4A; and a third state in which the cooling water of the high-temperature cooling water circulation circuit 22 is supplied to the oil cooler 4A.

As a result, when the temperature of the transmission oil is low in the EV driving mode, the cooling circuit switching unit 40 is set to the second state, and the supply of cooling water that cools the transmission oil from the low-temperature cooling water circulation circuit 23 is stopped, thereby avoiding the influence of the managed temperature of the inverter 5 and preventing the transmission 3 from being excessively cooled. This makes it possible to suppress deterioration of the transmission efficiency of the transmission 3.

In addition, even when the engine 2 water temperature is low and the transmission oil temperature is low in the engine driving mode, the cooling circuit switching unit 40 is set to the second state and the supply of cooling water that cools the transmission oil from the low-temperature cooling water circulation circuit 23 is stopped, so that the transmission 3 is not cooled. This makes it possible to suppress deterioration in the transmission efficiency of the transmission 3.

In addition, in the vehicle cooling system of this embodiment, when the current driving mode is the EV driving mode and the oil temperature of the transmission oil is equal to or higher than TOc2 as the first threshold, the control unit 10 controls the cooling circuit switching unit 40 to transition to the engine driving mode and switch to the third state.

As a result, even if the heat dissipation performance of the low-temperature section 50L of the radiator 50, which is the heat dissipator of the low-temperature cooling water circulation circuit 23, is reduced, the inverter management temperature can be met when the transmission oil temperature is high.

In addition, in the vehicle cooling system of this embodiment, the high-temperature cooling water circulation circuit 22 is equipped with a heater core 31 that heats the vehicle interior by heat exchange with the cooling water. The cooling circuit switching unit 40 has a fourth state in which the cooling water of the low-temperature cooling water circulation circuit 23 is supplied to the oil cooler 4A and the heater core 31. The control unit 10 controls the cooling circuit switching unit 40 to switch to the fourth state when there is a heating request, the current driving mode is the EV driving mode, and the oil temperature is less than TOc2 as a first threshold value and is equal to or greater than TOc1 as a second threshold value lower than TOc2.

As a result, even in the EV driving mode in which the engine 2 cannot be used as a heat source, hot water heated by the oil cooler 4A can be supplied to the heater core 31 to heat the vehicle interior, provided that the oil temperature is less than TOc2 as a first threshold value and is equal to or greater than TOc1 as a second threshold value lower than TOc2. This makes it unnecessary to provide an electric heater such as a PTC heater or to operate the engine 2 to heat the vehicle interior, thereby improving fuel efficiency.

Although an embodiment of the present invention has been disclosed, it is apparent that modifications may be made by one of ordinary skill in the art without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1...vehicle 2...engine 3...transmission 4...electric motor 4A...oil cooler 5...inverter 10...control unit 22...high-temperature cooling water circulation circuit 23...low-temperature cooling water circulation circuit 31...heater core 32...water pump (first water pump)
37...Electric water pump (second water pump)
40...Cooling circuit switching unit TOc1...Second threshold value TOc2...First threshold value

Claims (5)

Equipped with a transmission with a built-in electric motor,
The hybrid vehicle is equipped with a hybrid vehicle having, as driving modes, an engine driving mode in which the vehicle runs using at least an engine as a driving force source, and an EV driving mode in which the vehicle runs using the electric motor as a driving force source without using the engine as a driving force source,
a high-temperature cooling water circulation circuit including a first water pump that is operated using the engine as a driving force source, and through which cooling water for at least cooling the engine circulates;
A vehicle cooling system including: a low-temperature cooling water circulation circuit in which a cooling water having a lower temperature than the cooling water circulating in the high-temperature cooling water circulation circuit is circulated; the low-temperature cooling water circulation circuit circulates a cooling water having a lower temperature than the cooling water circulating in the high-temperature cooling water circulation circuit;
a cooling circuit switching unit that switches a supply state of cooling water to an oil cooler that cools transmission oil of the transmission;
a control unit that controls the cooling circuit switching unit based on the driving mode. The vehicle cooling system according to claim 1, characterized in that the control unit controls the cooling circuit switching unit based on the driving mode, the oil temperature of the transmission oil, and the water temperature of the engine. The cooling circuit switching unit is
a first state in which the cooling water of the low-temperature cooling water circulation circuit is supplied to the oil cooler;
a second state in which the cooling water of the high-temperature cooling water circulation circuit and the cooling water of the low-temperature cooling water circulation circuit are not supplied to the oil cooler;
a first state in which the cooling water in the high-temperature cooling water circulation circuit is supplied to the oil cooler, and a third state in which the cooling water in the high-temperature cooling water circulation circuit is supplied to the oil cooler. The vehicle cooling system according to claim 3, characterized in that the control unit controls the cooling circuit switching unit to transition to the engine driving mode and switch to the third state when the current driving mode is the EV driving mode and the oil temperature of the transmission oil is equal to or higher than a first threshold value. the high-temperature coolant circulation circuit includes a heater core that heats the vehicle interior by heat exchange with the coolant,
the cooling circuit switching unit has a fourth state in which the cooling water of the low-temperature cooling water circulation circuit is supplied to the oil cooler and the heater core,
5. The vehicle cooling system according to claim 4, wherein the control unit controls the cooling circuit switching unit to switch to the fourth state when there is a heating request, the current driving mode is the EV driving mode, and the oil temperature is lower than the first threshold value and equal to or higher than a second threshold value that is lower than the first threshold value.