Hybrid vehicle cooling system

Abstract

A first cooling system (15) has a main passage (16) through which first cooling water can circulate, a radiator (18) for performing heat exchange with the first cooling water, an intercooler (11) for cooling supercharged intake air of an internal combustion engine (1) by using the first cooling water, a bypass passage (17) connected to the main passage (16) so as to to bypass the radiator (18), and a bypass valve (21) for controlling the flow rate of the first cooling water flowing through the bypass passage (17). The intercooler (11) is positioned on the downstream side of a high-power unit (19) and on the upstream side of the radiator (18) in terms of the direction in which the first cooling water flows. The bypass valve (21) is controlled such that the first cooling water does not flow to the radiator (18) when the temperature of the first cooling water is less than a first prescribed value.

Description

[Technical Field]

[0001] The present invention relates to a cooling system for a hybrid vehicle. [Background technology]

[0002] For example, Patent Document 1 discloses a technology for circulating the cooling water by bypassing the intercooler when the temperature of the cooling water flowing through the intercooler is low and the engine is not in a supercharged state, in order to prevent the condensed water from freezing in the intercooler.

[0003] In Patent Document 1, when the outside air temperature is below zero, the coolant will basically always bypass the intercooler unless supercharging is performed. In this case, the coolant is cooled by the radiator even though the water temperature is low, and the water temperature remains low or drops further.

[0004] Therefore, with the technology disclosed in Patent Document 1, when supercharging is performed when the outside air temperature is below zero, sub-zero cooling water suddenly flows into the intercooler, which may cause the intake air to transiently condense inside the intercooler and freeze the water in the intake air. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-172151 Summary of the Invention

[0006] The cooling system for a hybrid vehicle of the present invention includes a first cooling system that cools an on-board high-power unit with a first refrigerant, the first cooling system having a main passage through which the first refrigerant can circulate, a radiator that exchanges heat with the first refrigerant, a cooler that cools supercharged intake air of an on-board internal combustion engine with the first refrigerant, a bypass passage connected to the main passage so as to bypass the radiator, and a bypass valve that controls the flow rate of the first refrigerant flowing through the bypass passage, the cooler being located downstream of the high-power unit and upstream of the radiator in the flow direction of the first refrigerant, and controlling the bypass valve so that the first refrigerant does not flow to the radiator when the temperature of the first refrigerant is below a first predetermined value.

[0007] According to the present invention, when the first refrigerant is at a low temperature, it bypasses the radiator and is therefore prevented from being overcooled. This prevents intake air from condensing and freezing in the cooler when the outside temperature is low in a hybrid vehicle. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an explanatory diagram schematically illustrating an outline of a vehicle cooling system to which the present invention is applied; [Figure 2] FIG. 10 is an explanatory diagram schematically showing the calculation process of the integrated heat quantity. [Figure 3] 6 is a flowchart showing a procedure for diagnosing the first cooling system. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0010] FIG. 1 is an explanatory diagram that shows a schematic overview of a vehicle cooling system to which the present invention is applied.

[0011] A vehicle to which the present invention is applied is equipped with an internal combustion engine 1 for generating electricity, and drive wheels (not shown) are driven by electric motors 2 and 3. In other words, the vehicle to which the present invention is applied is a series hybrid vehicle in which all of the power of the internal combustion engine 1 is used for generating electricity.

[0012] The internal combustion engine 1 is mounted on the vehicle for generating power and drives the generator 4. In other words, the internal combustion engine 1 is mechanically connected to the generator 4. The electric power generated by the generator 4 is supplied via an inverter 5 to a battery (not shown), the front-wheel drive electric motor 2, and the rear-wheel drive electric motor 3. The battery is capable of charging and discharging electric power.

[0013] The front-wheel drive motor 2 and the rear-wheel drive motor 3 are, for example, synchronous motors that use permanent magnets in their rotors. The front-wheel drive motor 2 and the rear-wheel drive motor 3 are driven by AC power from an inverter 5. The front-wheel drive motor 2 and the rear-wheel drive motor 3 also function as generators when the vehicle decelerates. In other words, the front-wheel drive motor 2 and the rear-wheel drive motor 3 can charge the battery via the inverter 5 with regenerative energy generated when the vehicle decelerates.

[0014] The internal combustion engine 1 also has an intake passage 6 and an exhaust passage 7. In the intake passage 6, an air filter 8, an air flow meter 9, a supercharger 10, an intercooler 11, and an intake temperature sensor 12 are arranged in this order from the upstream side.

[0015] The air filter 8 captures and removes foreign matter in the intake air. The air flow meter 9 detects the intake air volume. The air flow meter 9 is capable of detecting the intake air temperature, and the detected value is used to estimate the outside air temperature. The supercharger 10 supercharges the intake air of the internal combustion engine 1. The supercharger 10 may be a compressor of a turbocharger or an electric supercharger. The intercooler 11 corresponds to a cooler and cools the intake air of the internal combustion engine 1 supercharged by the supercharger 10. The intercooler 11 belongs to a first cooling system 15 described later, and is cooled by first cooling water. The intercooler 11 is a so-called charge air cooler. The intake air temperature sensor 12 detects the intake air temperature downstream of the intercooler 11.

[0016] In addition, the internal combustion engine 1 is capable of implementing exhaust gas recirculation (EGR), which introduces (recirculates) a portion of the exhaust gas from the exhaust passage 7 into the intake passage 6 as EGR gas, and has an EGR passage 13 as an exhaust gas recirculation passage that branches off from the exhaust passage 7 and is connected to the intake passage 6.

[0017] One end of the EGR passage 13, which is on the downstream side in the flow direction of the EGR gas, is connected to the intake passage 6, and the other end, which is on the upstream side, is connected to the exhaust passage 7. One end of the EGR passage 13 is connected to the intake passage 6 at a position upstream of the turbocharger 10 and downstream of the air flow meter 9. The EGR passage 13 is provided with an electric EGR valve 14 that adjusts (controls) the flow rate of EGR gas in the EGR passage 13. The EGR valve 14 is controlled using the detection value of the intake air temperature sensor 12. In other words, the EGR is controlled using the detection value of the intake air temperature sensor 12.

[0018] Here, the generator 4, inverter 5, front wheel drive motor 2, rear wheel drive motor 3, and intercooler 11 can be cooled by first cooling water as a first refrigerant.

[0019] The first cooling water can circulate through a main passage 16 in the first cooling system 15. The first cooling system 15 has the main passage 16 and a bypass passage 17 that branches off from the main passage 16 and bypasses a radiator 18, which will be described later. The first cooling water can flow into the bypass passage 17.

[0020] The first cooling water is capable of cooling the generator 4, inverter 5, front wheel drive motor 2, rear wheel drive motor 3 and intercooler 11, and is capable of heat exchange (cooling) in a radiator 18 arranged in the main passage 16.

[0021] In other words, the first cooling system 15 has a main passage 16, a radiator 18, an inverter 5, an intercooler 11, a generator 4, a front-wheel drive motor 2, a rear-wheel drive motor 3, and a bypass passage 17. Furthermore, the first cooling system 15 cools the inverter 5, the generator 4, the front-wheel drive motor 2, and the rear-wheel drive motor 3, which constitute an on-board high-power unit 19. The high-power unit 19 is a collection of units that use electricity as energy, and in this specification, the high-power unit 19 includes the inverter 5, the generator 4, the front-wheel drive motor 2, and the rear-wheel drive motor 3 as components. In this embodiment, the front-wheel drive motor 2 and the rear-wheel drive motor 3 are arranged in parallel within the first cooling system 15.

[0022] The first cooling system 15 also has a reservoir tank 20 for the first cooling water, a bypass valve 21 that controls the flow rate of the first cooling water flowing through the bypass passage 17, a water pump 22 that pumps the first cooling water, and first to third temperature sensors 23, 24, 25 that can detect the temperature of the first cooling water at predetermined positions within the main passage 16 (first cooling system 15).

[0023] The reservoir tank 20 is capable of storing the first cooling water therein. The reservoir tank 20 is located downstream of the intercooler 11 in the first cooling system 15.

[0024] One downstream end of the bypass passage 17 is connected to the main passage 16 downstream of the radiator 18 in the flow direction of the first cooling water, and the other upstream end is connected to the main passage 16 upstream of the radiator 18. The first cooling water circulates in the main passage 16 clockwise in FIG. 1. In other words, the first cooling water flows into the water pump 22 via the intercooler 11 and is discharged from the water pump 22 to the radiator 18 side.

[0025] The bypass valve 21 is an electromagnetic three-way valve disposed at a connection portion between one end of the bypass passage 17 and the main passage 16. The bypass valve 21 can prevent the first cooling water from flowing through the bypass passage 17 and allow the first cooling water that has passed through the radiator 18 to circulate through the main passage 16, or can prevent the first cooling water from flowing through the radiator 18 and allow the first cooling water that has passed through the bypass passage 17 to circulate through the main passage 16. That is, at the connection portion between one end of the bypass passage 17 and the main passage 16, the bypass valve 21 can open the main passage 16 so that the first cooling water that has passed through the radiator 18 can flow downstream, and can close the bypass passage 17 so that the first cooling water that has passed through the bypass passage 17 does not flow downstream. In addition, the bypass valve 21 is capable of closing the main passage 16 at the connection between one end of the bypass passage 17 and the main passage 16 so that the first cooling water that has passed through the radiator 18 does not flow downstream, and opening the bypass passage 17 so that the first cooling water that has passed through the bypass passage 17 flows downstream.

[0026] The bypass valve 21 is opened and closed in response to a command from the control unit 31. The opening and closing control of the bypass valve 21 is performed based on output signals (detected temperatures) from the first temperature sensor 23, the second temperature sensor 24, the third temperature sensor 25, etc., which are input to the control unit 31.

[0027] Basically, the bypass valve 21 is controlled so that when the temperature of the first cooling water becomes high (for example, 40°C or higher), the first cooling water flows into the radiator 18. Also, basically, when the temperature of the first cooling water becomes low (for example, less than 40°C), the bypass valve 21 is controlled so that the first cooling water flows into the bypass passage 17 and does not flow into the radiator 18.

[0028] That is, the bypass valve 21 controls the flow rate of the first cooling water flowing through the radiator 18 and the flow rate of the first cooling water flowing through the bypass passage 17 .

[0029] The water pump 22 applies pressure to the first cooling water and discharges it so that the first cooling water circulates (flows) through the first cooling system 15.

[0030] The first temperature sensor 23 is located in the main passage 16, upstream of the water pump 22 and downstream of the reservoir tank 20, in the flow direction of the first coolant. The first temperature sensor 23 detects the temperature of the first coolant in the main passage 16, at a position downstream of the intercooler 11 and upstream of the radiator 18, in the flow direction of the first coolant. In other words, the first temperature sensor 23 detects the temperature of the first coolant at a third position in the main passage 16, which is downstream of the high-power unit 19 and upstream of the radiator 18, in the flow direction of the first coolant.

[0031] The second temperature sensor 24 is located in the main passage 16, upstream of the bypass valve 21 and downstream of the radiator 18 in the flow direction of the first coolant. The second temperature sensor 24 detects the temperature of the first coolant in the main passage 16 at a position downstream of the radiator 18 in the flow direction of the first coolant and upstream of the bypass valve 21. In other words, the second temperature sensor 24 detects the temperature of the first coolant at a first position in the main passage 16, which is downstream of the radiator 18 in the flow direction of the first coolant and upstream of the downstream end of the bypass passage 17 (upstream of the bypass valve 21).

[0032] The third temperature sensor 25 is located in the main passage 16, upstream of the inverter 5 and downstream of the bypass valve 21, in the flow direction of the first cooling water. The third temperature sensor 25 detects the temperature of the first cooling water in the main passage 16, at a position downstream of the downstream end of the bypass passage 17 and upstream of the high-power unit 19, in the flow direction of the first cooling water. In other words, the third temperature sensor 25 detects the temperature of the first cooling water at a second position in the main passage 16, which is downstream of the downstream end of the bypass passage 17 and upstream of the high-power unit 19 (upstream of the inverter 5) in the flow direction of the first cooling water.

[0033] The intercooler 11 is located downstream of the high-power unit 19 in the flow direction of the first cooling water within the first cooling system 15. The high-power unit 19 is located downstream of the bypass valve 21 in the flow direction of the first cooling water within the first cooling system 15.

[0034] The internal combustion engine 1 is also capable of cooling the cylinder block and the cylinder head with second cooling water as a second refrigerant. The second cooling water can circulate within a second cooling system 41.

[0035] Although not shown, the second cooling system 41 is equipped with an EGR cooler, an oil cooler for the internal combustion engine 1, a heater core for the vehicle air conditioner, a throttle chamber, etc. The second cooling water cools the EGR cooler, oil cooler, throttle chamber, etc. in the second cooling system 41. The second cooling water also serves as a heat source for the heater core, etc. in the second cooling system 41.

[0036] In such a vehicle cooling system, when the temperature of the first coolant detected by the first temperature sensor 23 is lower than a first predetermined value (e.g., 40°C), the bypass valve 21 controls (switches) the flow of the first coolant in the first cooling system 15 so that the first coolant does not flow to the radiator 18. More specifically, when the temperature of the first coolant detected by the first temperature sensor 23 is lower than the first predetermined value (e.g., 40°C), the bypass valve 21 closes the main passage 16 and opens the bypass passage 17.

[0037] Furthermore, when the temperature of the first coolant detected by the first temperature sensor 23 is equal to or higher than a first predetermined value (e.g., 40°C), the vehicle cooling system controls (switches) the flow of the first coolant in the first cooling system 15 using the bypass valve 21 so that the first coolant flows into the radiator 18. More specifically, when the temperature of the first coolant detected by the first temperature sensor 23 is equal to or higher than the first predetermined value (e.g., 40°C), the bypass valve 21 opens the main passage 16 and closes the bypass passage 17.

[0038] For example, in a situation where the outside air temperature is below zero, it is conceivable that the first cooling water will bypass the intercooler 11 unless supercharging is performed. In this case, if the first cooling water flows into the radiator 18, it will be cooled by the radiator 18, and its temperature will remain low or will decrease further.

[0039] Furthermore, if the first cooling water is made to flow through the intercooler 11 during supercharging, a delay in response to the accelerator operation by the driver will occur, taking into consideration the responsiveness of the bypass valve 21, and the intake air will not be sufficiently cooled by the intercooler 11 at the beginning of supercharging, which may result in the driver not being able to obtain the output that he or she intends.

[0040] However, in the vehicle cooling system of the above-described embodiment, when the temperature of the first coolant is low, the first coolant bypasses the radiator 18 and is therefore prevented from being overcooled. Therefore, the vehicle can prevent intake air from condensing and freezing in the intercooler 11 when the outside air temperature is low.

[0041] Furthermore, in the vehicle cooling system of the above-described embodiment, the intercooler 11 is configured to be constantly cooled by the first cooling water, so that even when the driver requests sudden acceleration, the intake air can be cooled from the very beginning (at the beginning of supercharging), and the output intended by the driver can be generated with good responsiveness.

[0042] When the temperature of the first coolant detected by the first temperature sensor 23 is lower than a first predetermined value (e.g., 40°C) that has been set in advance, the vehicle control unit 31 diagnoses that the bypass valve 21 is closed and the first coolant is not flowing into the radiator 18. When the temperature of the first coolant detected by the first temperature sensor 23 is equal to or higher than the first predetermined value (e.g., 40°C), the control unit 31 diagnoses that the bypass valve 21 is open and the first coolant is flowing into the radiator 18.

[0043] In other words, when the temperature of the first cooling water detected by the first temperature sensor 23 is lower than a first predetermined value (for example, 40°C) set in advance, the control unit 31 diagnoses that the bypass valve 21 is in a closed state, i.e., the bypass valve 21 closes the main passage 16 and opens the bypass passage 17. On the other hand, when the temperature of the first cooling water detected by the first temperature sensor 23 is equal to or higher than a first predetermined value (for example, 40°C), the control unit 31 diagnoses that the bypass valve 21 is in an open state, i.e., the bypass valve 21 opens the main passage 16 and closes the bypass passage 17.

[0044] In other words, the control unit 31 corresponds to a first diagnosis unit that diagnoses the state of the bypass valve 21.

[0045] If the difference between the temperature of the first coolant detected by the second temperature sensor 24 and the temperature of the first coolant detected by the third temperature sensor 25 is greater than a preset second predetermined value (e.g., 15°C), the control unit 31 closes the bypass valve 21 and diagnoses that the first coolant is not flowing into the radiator 18. Furthermore, if the difference between the temperature of the first coolant detected by the second temperature sensor 24 and the temperature of the first coolant detected by the third temperature sensor 25 is equal to or less than a preset second predetermined value (e.g., 15°C), the control unit 31 opens the bypass valve 21 and diagnoses that the first coolant is flowing into the radiator 18.

[0046] In other words, if the difference between the temperature of the first cooling water detected by the second temperature sensor 24 and the temperature of the first cooling water detected by the third temperature sensor 25 is greater than a second predetermined value (e.g., 15°C) set in advance, the control unit 31 diagnoses that the bypass valve 21 is in a closed state, i.e., that the bypass valve 21 closes the main passage 16 and opens the bypass passage 17. Furthermore, if the temperature of the first cooling water detected by the first temperature sensor 23 is equal to or greater than a first predetermined value (e.g., 40°C) set in advance, the control unit 31 diagnoses that the bypass valve 21 is in an open state, i.e., that the bypass valve 21 opens the main passage 16 and closes the bypass passage 17.

[0047] In other words, the control unit 31 corresponds to a second diagnosis unit that diagnoses the state of the bypass valve 21.

[0048] Since the vehicle can grasp the temperature of each part in the main passage 16, it is possible to grasp the state of the bypass valve 21.

[0049] Furthermore, the control unit 31 diagnoses that the bypass valve 21 is faulty when the diagnosis of the bypass valve 21 using the temperature of the first cooling water detected by the first temperature sensor 23 (diagnosis by the first diagnostic section) contradicts the diagnosis of the bypass valve 21 using the temperatures of the first cooling water detected by the second temperature sensor 24 and the third temperature sensor 25 (diagnosis by the second diagnostic section). In other words, the control unit 31 corresponds to a fault diagnosis section that diagnoses whether or not the bypass valve 21 is faulty.

[0050] This allows the vehicle to know whether or not the bypass valve 21 has failed.

[0051] Furthermore, after the system is started (after the vehicle starts running), the control unit 31 diagnoses whether or not the bypass valve 21 has failed after the high-power unit 19 gives a predetermined amount of heat to the first coolant.

[0052] The vehicle can prevent erroneous diagnosis by not performing a fault diagnosis on the bypass valve 21 when there is no temperature difference in the first coolant temperature detected by each temperature sensor 23, 24, 25, such as during a cold start.

[0053] Here, the integrated heat quantity Q, which is the amount of heat given to the first cooling water from the high-power unit 19 after the system is started, is calculated, for example, as follows.

[0054] FIG. 2 is an explanatory diagram that schematically shows the process of calculating the cumulative heat quantity Q that is performed in the control unit 31.

[0055] In step S1, the generator loss, which is the amount of loss (power) in the generator 4, is calculated using the rotation speed and torque of the generator 4. The generator loss is calculated, for example, using a map that associates the rotation speed of the generator 4, the torque of the generator 4, and the generator loss. The generator loss is the amount of heat dissipated from the generator 4 to the first cooling system 15. The generator loss increases as the rotation speed of the generator 4 increases, and as the torque of the generator 4 increases.

[0056] In step S2, the rotation speed and torque of the front-wheel drive electric motor 2 are used to calculate the FrMTR loss, which is the amount of loss (power) in the front-wheel drive electric motor 2. The FrMTR loss is calculated, for example, using a map that associates the rotation speed of the front-wheel drive electric motor 2, the torque of the front-wheel drive electric motor 2, and the FrMTR loss. The FrMTR loss is the amount of heat dissipated from the front-wheel drive electric motor 2 to the first cooling system 15. The FrMTR loss increases as the rotation speed of the front-wheel drive electric motor 2 increases, and as the torque of the front-wheel drive electric motor 2 increases.

[0057] In step S3, the RrMTR loss, which is the amount of loss (power) in the rear-wheel drive motor 3, is calculated using the rotation speed and torque of the rear-wheel drive motor 3. The RrMTR loss is calculated, for example, using a map that associates the rotation speed and torque of the rear-wheel drive motor 3 with the RrMTR loss. The RrMTR loss is the amount of heat dissipated from the rear-wheel drive motor 3 to the first cooling system 15. The FrMTR loss increases as the rotation speed of the rear-wheel drive motor 3 increases and as the torque of the rear-wheel drive motor 3 increases.

[0058] In step S4, the amount of loss (power) of the high-power unit 19 is calculated, which is the sum of the GEN loss, the FrMTR loss, and the FrMTR loss. The unit of the amount of loss is watt.

[0059] In step S5, the intake air temperature and intake air flow rate at the outlet side of the supercharger 10 are used to calculate the WCAC loss (power), which is the amount of heat exchanged in the intercooler 11. The intake air temperature and intake air flow rate are calculated, for example, according to the intake air temperature detected by the air flow meter 9 and the engine speed and load of the internal combustion engine 1. The WCAC loss increases as the intake air temperature increases and as the intake air flow rate increases. The unit of the WCAC loss is watts.

[0060] In step S6, a correction coefficient is calculated using the outside air temperature and the vehicle speed. The correction coefficient is calculated using a map that associates the outside air temperature estimated from the value detected by the air flow meter 9, the vehicle speed of the vehicle equipped with the vehicle cooling system (detected by a vehicle speed sensor, for example), and the correction coefficient.

[0061] In step S7, the heat transfer coefficient of the amount of heat dissipated from the high-power unit 19 to the outside (other than the first cooling system 15) is calculated using the vehicle speed. The heat transfer coefficient is calculated using, for example, an approximation formula using the vehicle speed, and increases as the vehicle speed increases.

[0062] In step S8, the temperature difference between the temperature T1 of the first coolant detected by the first temperature sensor 23 and the outside air temperature estimated from the value detected by the air flow meter 9 is calculated.

[0063] In step S9, the power of work performed by high-power unit 19 on the outside (other than first cooling system 15) is calculated by multiplying the correction coefficient, the heat transfer coefficient, the temperature difference between the temperature T1 of the first cooling water detected by first temperature sensor 23 and the outside air temperature, and the surface area of ​​high-power unit 19. The unit of the power calculated in step S9 is watts.

[0064] The power calculated in step S9 is the power output from the high-power unit 19 to a location other than the first cooling system 15 (for example, the inside of the engine compartment of a hybrid vehicle).

[0065] In step S10, a value is calculated by subtracting the power from the high power unit 19 to the outside (other than the first cooling system 15) from the amount of loss in the high power unit 19. That is, in step S10, the power applied from the high power unit 19 to the first cooling water of the first cooling system 15 is calculated.

[0066] In step S11, the power calculated in step S10 is multiplied by the interval time to calculate the amount of heat transferred from the high-power unit 19 to the first cooling water in the current cycle. The unit of the amount of heat calculated in step S11 is joule. The amount of heat calculated in step S11 is the difference between the amount of heat generated by the high-power unit 19 per unit time (per cycle) and the amount of heat dissipated per unit time (per cycle) from the high-power unit 19 to a location other than the first cooling system 15 (for example, the engine compartment of the vehicle).

[0067] In step S12, the amount of heat transferred from the high-power unit 19 to the first cooling water in the current cycle is added to the previous value (the amount of heat transferred from the high-power unit 19 to the first cooling water up to the previous time since the system was started) to calculate the cumulative amount of heat Q added by the high-power unit 19 to the first cooling water in the first cooling system 15.

[0068] The integrated heat quantity Q calculated by the control unit 31 is an integrated value of the difference between the heat quantity per unit time (per cycle) of the high power unit 19 and the heat radiation quantity per unit time (per cycle) transferred from the high power unit 19 to a part other than the first cooling system 15 (for example, the engine compartment of a hybrid vehicle). The heat radiation quantity per unit time (per cycle) transferred from the high power unit 19 to a part other than the first cooling system 15 (for example, the engine compartment of a hybrid vehicle) is calculated using the vehicle speed, the outside air temperature, and the temperature of the first coolant detected by the first temperature sensor 23.

[0069] In the vehicle, since the internal combustion engine 1 has a portion of the exhaust gas introduced upstream of the intercooler 11, it is possible to recirculate a portion of the exhaust gas to the internal combustion engine 1 even at lower outside temperatures, thereby improving fuel efficiency.

[0070] FIG. 3 is a flowchart showing the flow of diagnosis of the first cooling system 15 performed in the control unit 31.

[0071] In step S21, it is determined whether the cumulative heat quantity Q is equal to or greater than a preset first threshold. Here, the first threshold is a value that causes a temperature difference between the temperatures detected by the temperature sensors 23, 24, and 25, such as the temperature of the first coolant detected by the first temperature sensor 23 and the temperature of the first coolant detected by the second temperature sensor 24, or the temperature of the first coolant detected by the first temperature sensor 23 and the temperature of the first coolant detected by the third temperature sensor 25. More specifically, the first threshold is a value that increases the temperature of the first coolant by, for example, 15°C. In step S21, if the cumulative heat quantity Q is equal to or greater than the first threshold, the routine proceeds to step S22. In step S21, if the cumulative heat quantity Q is less than the first threshold, the routine ends.

[0072] In step S22, it is determined whether the temperature T1 of the first coolant detected by the first temperature sensor 23 is equal to or higher than a first predetermined value (e.g., 40°C). In step S22, if the temperature T1 detected by the first temperature sensor 23 is equal to or higher than the first predetermined value (e.g., 40°C), the process proceeds to step S25. In step S22, if the temperature T1 detected by the first temperature sensor 23 is lower than the first predetermined value (e.g., 40°C), the process proceeds to step S23.

[0073] In step S23, it is determined whether the temperature T1 of the first coolant detected by the first temperature sensor 23 is equal to or lower than a third predetermined value (e.g., 10°C). In step S23, if the temperature T1 detected by the first temperature sensor 23 is equal to or lower than the third predetermined value (e.g., 10°C), the process proceeds to step S28. In step S23, if the temperature T1 detected by the first temperature sensor 23 is higher than the third predetermined value (e.g., 10°C), the process proceeds to step S24.

[0074] In step S24, the failure determination of the bypass valve 21 is not performed and is left pending.

[0075] In step S25, it is determined whether the difference between the temperature T3 of the first cooling water detected by the third temperature sensor 25 and the temperature T2 of the first cooling water detected by the second temperature sensor 24 is equal to or less than a second predetermined value (for example, 15°C).

[0076] In step S25, if the difference between the temperature T3 detected by the third temperature sensor 25 and the temperature T2 detected by the second temperature sensor 24 is equal to or less than the second predetermined value, the process proceeds to step S26. In step S25, if the difference between the temperature T3 detected by the third temperature sensor 25 and the temperature T2 detected by the second temperature sensor 24 is greater than the second predetermined value, the process proceeds to step S27.

[0077] In step S26, it is determined that the bypass valve 21 is operating normally.

[0078] In step S27, it is determined that the bypass valve 21 has an abnormality.

[0079] In step S28, it is determined whether the difference between the temperature T3 of the first cooling water detected by the third temperature sensor 25 and the temperature T2 of the first cooling water detected by the second temperature sensor 24 is equal to or greater than a second predetermined value (e.g., 15°C).

[0080] In step S28, if the difference between the temperature T3 detected by the third temperature sensor 25 and the temperature T2 detected by the second temperature sensor 24 is equal to or greater than the second predetermined value, the process proceeds to step S29. In step S28, if the difference between the temperature T3 detected by the third temperature sensor 25 and the temperature T2 detected by the second temperature sensor 24 is less than the second predetermined value, the process proceeds to step S30.

[0081] In step S29, it is determined that the bypass valve 21 is operating normally.

[0082] In step S30, it is determined that the bypass valve 21 has an abnormality.

[0083] The temperature T1 used in steps S22 and S23 may be the average temperature from the previous routine to the present, and the difference between the temperature T3 and the temperature T2 used in steps S25 and S28 may be the average value of the differences from the previous routine to the present.

[0084] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0085] For example, the front wheel drive motor 2 and the rear wheel drive motor 3 may be arranged in series within the first cooling system 15.

[0086] Furthermore, the arrangement order of the components of the high-power unit 19 (such as the generator 4) within the first cooling system 15 is not limited to the arrangement in the above-described embodiment; for example, the drive motors 2 and 3 may be arranged upstream of the generator 4, or the generator 4 and the drive motors 2 and 3 may be arranged upstream of the inverter 5.

[0087] In the above-described embodiment, the bypass valve 21 is a solenoid valve. However, the bypass valve 21 may be a thermostat, and the main passage 16 and the bypass passage 17 may be opened and closed at a connection portion between one end of the bypass passage 17 and the main passage 16 according to the temperature of the first cooling water.

[0088] The present invention is also applicable to hybrid vehicles in which only the front wheels of the vehicle are driven, or hybrid vehicles in which only the rear wheels of the vehicle are driven. That is, the high-power unit 19 cooled by the first cooling system 15 includes at least one of the front-wheel drive motor 2 and the rear-wheel drive motor 3.

Claims

1. a first cooling system that cools an on-board high-power unit with a first refrigerant; the first cooling system includes a main passage through which the first refrigerant can circulate, a radiator that exchanges heat with the first refrigerant, a cooler that cools supercharged intake air of an internal combustion engine mounted on a vehicle with the first refrigerant, a bypass passage connected to the main passage so as to bypass the radiator, and a bypass valve that controls the flow rate of the first refrigerant flowing through the bypass passage; the cooler is located downstream of the high-power unit and upstream of the radiator in a flow direction of the first refrigerant, a cooling system for a hybrid vehicle, the cooling system controlling the bypass valve so that the first refrigerant does not flow to the radiator when the temperature of the first refrigerant is lower than a first predetermined value, a first temperature sensor that detects the temperature of the first refrigerant at a position downstream of the cooler and upstream of the radiator in a flow direction of the first refrigerant; A cooling system for a hybrid vehicle having a first diagnostic unit that diagnoses that the first refrigerant is not flowing into the radiator if the temperature of the first refrigerant detected by the first temperature sensor is less than the first predetermined value, and diagnoses that the first refrigerant is flowing into the radiator if the temperature of the first refrigerant detected by the first temperature sensor is equal to or greater than the first predetermined value.

2. a second temperature sensor that detects the temperature of the first refrigerant in the main passage at a position downstream of the radiator in a flow direction of the first refrigerant and upstream of a downstream end of the bypass passage; a third temperature sensor that detects the temperature of the first refrigerant in the main passage at a position downstream of the downstream end of the bypass passage and upstream of the high-power unit in the flow direction of the first refrigerant; 2. The cooling system for a hybrid vehicle according to claim 1, further comprising: a second diagnostic unit that diagnoses that the first refrigerant is not flowing into the radiator if a difference between the temperature of the first refrigerant detected by the second temperature sensor and the temperature of the first refrigerant detected by the third temperature sensor is greater than a second predetermined value, and that diagnoses that the first refrigerant is flowing into the radiator if a difference between the temperature of the first refrigerant detected by the second temperature sensor and the temperature of the first refrigerant detected by the third temperature sensor is equal to or less than the second predetermined value.

3. 3. The cooling system for a hybrid vehicle according to claim 2, further comprising a fault diagnosis unit that diagnoses that the bypass valve is faulty when the diagnosis by the first diagnosis unit and the diagnosis by the second diagnosis unit contradict each other.

4. 4. The cooling system for a hybrid vehicle according to claim 3, wherein the fault diagnosis unit performs fault diagnosis of the bypass valve after the system is started and a predetermined amount of heat is applied to the first refrigerant from the high-power unit.

5. the heat quantity is a difference between the heat quantity of the high-power unit and the heat quantity radiated from the high-power unit to a part other than the first cooling system, 5. The cooling system for a hybrid vehicle according to claim 4, wherein the amount of heat radiation is calculated using a vehicle speed of the hybrid vehicle, an outside air temperature, and a temperature of the first refrigerant.

6. 6. The cooling system for a hybrid vehicle according to claim 1, wherein a part of the exhaust gas from the internal combustion engine is introduced upstream of the cooler.

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