Diagnostic method and diagnostic device for vehicle cooling system

Abstract

According to the present invention, a control unit (31) of a vehicle diagnoses whether a bypass valve (21) is in a state in which first cooling water can be made to flow to a radiator (18), or is in a state in which the first cooling water cannot be made to flow to the radiator (18), on the basis of the temperature of the first cooling water at a first position in a main passage (16), and the temperature of the first cooling water at a second position in the main passage (16). The control unit (31) can accurately determine the state of the bypass valve (21) by using the temperatures of the first cooling water at the first position and the second position in the main passage (16).

Description

[Technical Field]

[0001] The present invention relates to a diagnostic method and a diagnostic device for a vehicle cooling system. [Background technology]

[0002] For example, Patent Document 1 discloses a technique for diagnosing a malfunction of a thermostat incorporated in an engine coolant circuit of a hybrid vehicle.

[0003] In Patent Document 1, a malfunction of the thermostat is diagnosed by comparing an estimated temperature that takes into account the temperature change of the coolant when the thermostat is normal with the actual temperature of the coolant.

[0004] However, in a hybrid vehicle, in addition to an engine coolant circuit that cools the internal combustion engine, there is also a cooling circuit that cools a so-called high-power unit that is made up of units that use electricity as energy, such as a drive motor.

[0005] In the cooling circuit that cools such a high-power unit, the allowable water temperature is lower than that of the engine coolant circuit, so the temperature difference between the outside air temperature and the coolant temperature (the so-called air-water temperature difference) is small.As a result, if the condition of the thermostat is diagnosed using the actual temperature difference and the estimated temperature difference, there is a risk that the diagnostic accuracy will be low.

[0006] In other words, there is room for further improvement in determining the state of a switching valve used in a cooling circuit that cools a high-power unit of a hybrid vehicle. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-1447 Summary of the Invention

[0008] The vehicle cooling system 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 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, and diagnoses whether the bypass valve is in a state that allows the first refrigerant to flow to the radiator or a state that prevents the first refrigerant from flowing to the radiator based on the temperature of the first refrigerant at a first position in the main passage that is downstream of the radiator in the flow direction of the first refrigerant and upstream of the downstream end of the bypass passage, and the temperature of the first refrigerant at a second position in the main passage that is downstream of the downstream end of the bypass passage and upstream of the high-power unit in the flow direction of the first refrigerant.

[0009] According to the present invention, the state of the bypass valve can be accurately diagnosed by using the temperatures of the first refrigerant at a position downstream of the radiator and upstream of the downstream end of the bypass passage, and at a position downstream of the downstream end of the bypass passage and upstream of the high-power unit. [Brief explanation of the drawings]

[0010] [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

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0012] FIG. 1 is an explanatory diagram that shows a schematic overview of a vehicle cooling system to which the present invention is applied.

[0013] A vehicle to which the present invention is applied has an internal combustion engine 1 mounted thereon 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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).

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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 .

[0031] 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.

[0032] 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.

[0033] 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).

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 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.

[0039] Furthermore, in the vehicle cooling system, 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 bypass valve 21 switches the flow of the first coolant in the first cooling system 15 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.

[0040] The control unit 31 of the vehicle corresponds to a diagnostic unit, and diagnoses whether the bypass valve 21 is in a state where it can flow the first coolant to the radiator 18 or is in a state where it cannot flow the first coolant to the radiator 18, based on the temperature of the first coolant at the first position of the main passage 16 and the temperature of the first coolant at the second position of the main passage 16. In other words, the control unit 31 diagnoses whether the bypass valve 21 is in a state where it can flow the first coolant to the radiator 18, based on the temperature difference between the coolant temperature at the first position of the main passage 16 and the coolant temperature at the second position of the main passage 16, and the ratio (proportion) of the coolant temperature at the first position of the main passage 16 to the coolant temperature at the second position of the main passage 16.

[0041] If the first cooling water flows into the radiator 18, the first cooling water at the first position of the main passage 16 and the first cooling water at the second position of the main passage 16 are cooled (heat exchanged) by the radiator 18.

[0042] On the other hand, if the first cooling water does not flow into the radiator 18, the first cooling water at the first position of the main passage 16 will remain stagnant at this position and its temperature will hardly change over time, but the first cooling water at the second position of the main passage 16 will absorb heat and its temperature will rise each time it cools the high-power unit 19.

[0043] Therefore, the control unit 31 can accurately determine the state of the bypass valve 21 by using the temperatures of the first cooling water at the first position of the main passage 16 and the second position of the main passage 16.

[0044] When the temperature of the first coolant at the third position of the main passage 16 (the temperature of the first coolant detected by the first temperature sensor 23) is less than a preset first predetermined value (e.g., 40°C), the control unit 31 diagnoses that the bypass valve 21 is in a state where the first coolant cannot flow to the radiator 18, i.e., the main passage 16 is closed by the bypass valve 21 and the first coolant is not flowing into the radiator 18. When the temperature of the first coolant at the third position of the main passage 16 (the temperature of the first coolant detected by the first temperature sensor 23) is less than a preset first predetermined value (e.g., 40°C), the control unit 31 diagnoses that the bypass valve 21 is in a state where the first coolant can flow to the radiator 18, i.e., the bypass passage 17 is closed by the bypass valve 21 and the first coolant is flowing into the radiator 18.

[0045] Then, if the state of the bypass valve 21 diagnosed from the temperature of the first cooling water at the first position of the main passage 16 and the second position of the main passage 16 differs from the state of the bypass valve 21 diagnosed from the temperature of the first cooling water at the third position of the main passage 16, the control unit 31 diagnoses that the bypass valve 21 is faulty.

[0046] Specifically, the control unit 31 diagnoses that the bypass valve 21 is faulty if the temperature of the first coolant at the third position of the main passage 16 (the temperature of the first coolant detected by the first temperature sensor 23) is equal to or higher than a predetermined first predetermined value (e.g., 40°C) and the difference between the temperature of the first coolant at the first position of the main passage 16 (the temperature of the first coolant detected by the second temperature sensor 24) and the temperature of the first coolant at the second position of the main passage 16 (the temperature of the first coolant detected by the third temperature sensor 25) is greater than a predetermined second predetermined value (e.g., 15°C).

[0047] This is a state in which, although the bypass valve 21 should normally open and allow the coolant to flow to the radiator 18, the coolant is not actually flowing to the radiator 18, resulting in a difference between the readings of the second temperature sensor 24 and the third temperature sensor 25. In other words, this is a state in which the bypass valve 21 is diagnosed as having a malfunction on the closing side of the flow of coolant to the radiator 18 (closed valve malfunction).

[0048] In addition, the control unit 31 diagnoses that the bypass valve 21 is faulty if the temperature of the first coolant at the third position of the main passage 16 (the temperature of the first coolant detected by the first temperature sensor 23) is below a predetermined third predetermined value (e.g., 10°C) and the difference between the temperature of the first coolant at the first position of the main passage 16 (the temperature of the first coolant detected by the second temperature sensor 24) and the temperature of the first coolant at the second position of the main passage 16 (the temperature of the first coolant detected by the third temperature sensor 25) is less than a predetermined second predetermined value (e.g., 15°C).

[0049] This is a state in which, although the bypass valve 21 is closed and cooling water should not flow to the radiator 18, cooling water actually flows to the radiator 18, and as a result, there is no difference between the readings of the second temperature sensor 24 and the third temperature sensor 25. In other words, this is a state in which the bypass valve 21 is diagnosed as having a malfunction on the opening side relative to the flow of cooling water to the radiator 18 (open valve malfunction).

[0050] In this way, the control unit 31 can diagnose (diagnose faults in) the bypass valve 21 using the temperature of the first cooling water in each part of the first cooling system 15.

[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 temperatures detected by the temperature sensors 23, 24, and 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 the work performed by the high-power unit 19 on the outside (other than the 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 the first temperature sensor 23 and the outside air temperature, and the surface area of ​​the 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. In other words, the high-power unit 19 cooled by the first cooling system 15 may include at least one of the front-wheel drive motor 2 and the rear-wheel drive motor 3.

[0089] After the system is started (after the vehicle starts running), the vehicle control unit 31 performs the following operation after the high-power unit 19 gives a predetermined amount of heat to the first cooling water: It may be possible to diagnose whether the bypass valve 21 is in a state where the first cooling water can flow to the radiator 18 based on the temperature of the first cooling water at the first position of the main passage 16 and the temperature of the first cooling water calculated (estimated) from the above heat quantity.

[0090] Specifically, for example, when the temperature difference between the temperature of the first coolant at the first position of the main passage 16 and the temperature of the first coolant calculated (estimated) from the heat quantity becomes equal to or greater than a predetermined value, the control unit 31 may diagnose that the bypass valve 21 is in a state where it is possible to flow the first coolant to the radiator 18. Furthermore, for example, when the temperature difference between the temperature of the first coolant at the first position of the main passage 16 and the temperature of the first coolant calculated (estimated) from the heat quantity becomes less than a predetermined value, the control unit 31 may diagnose that the bypass valve 21 is in a state where it is not possible to flow the first coolant to the radiator 18.

[0091] The temperature of the first coolant can be estimated from the amount of heat provided by the high-power unit 19. Therefore, if the first coolant flows into the radiator 18, the temperature of the first coolant at a position (first position) downstream of the radiator 18 and upstream of the downstream end of the bypass passage 17 (upstream of the bypass valve 21) will have a temperature difference from the temperature of the first coolant calculated (estimated) from the amount of heat. This temperature difference is the temperature drop in the radiator 18.

[0092] If this temperature difference is equal to or greater than a predetermined value, it is determined that the first coolant is flowing into the radiator 18. If this temperature difference is less than a predetermined value, it is determined that the first coolant is not flowing into the radiator 18.

[0093] If the first cooling water flows into the radiator 18, the first cooling water at the first position of the main passage 16 will have been cooled (heat exchanged) by the radiator 18. Therefore, if the first cooling water flows into the radiator 18, the temperature of the first cooling water at the first position of the main passage 16 will have a temperature difference with respect to the temperature of the first cooling water at the third position of the main passage 16.

[0094] The above-described embodiments relate to a diagnostic method and a diagnostic device for a vehicle cooling system.

Claims

1. a first cooling system that cools an on-board high-power unit with a first refrigerant; a first cooling system including a main passage through which the first refrigerant can circulate, a radiator that exchanges heat with the first refrigerant, a bypass passage connected to the main passage so as to bypass the radiator, and a bypass valve that controls a flow rate of the first refrigerant flowing through the bypass passage, This diagnostic method for a vehicle cooling system diagnoses whether the bypass valve is in a state that allows the first refrigerant to flow to the radiator or a state that prevents the first refrigerant from flowing to the radiator, based on a temperature of the first refrigerant at a first position in the main passage that is a position downstream of the radiator in a flow direction of the first refrigerant and upstream of a downstream end of the bypass passage, and a temperature of the first refrigerant at a second position in the main passage that is 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. when a temperature of the first refrigerant at a third position of the main passage, which is a position downstream of the high-power unit and upstream of the radiator in a flow direction of the first refrigerant, is less than a first predetermined value, a diagnosis is made that the bypass valve is in a state where the first refrigerant cannot flow to the radiator; When the temperature of the first refrigerant at the third position is equal to or higher than the first predetermined value, the bypass valve is diagnosed as being in a state in which the first refrigerant can flow to the radiator; 2. The diagnostic method for a vehicle cooling system according to claim 1, wherein the bypass valve is diagnosed as faulty if the state of the bypass valve diagnosed from the temperature of the first refrigerant at the first position and the second position differs from the state of the bypass valve diagnosed from the temperature of the first refrigerant at the third position.

3. 3. The diagnostic method for a vehicle cooling system according to claim 2, wherein if the temperature of the first refrigerant at the third position is equal to or higher than the first predetermined value and the difference between the temperature of the first refrigerant at the first position and the temperature of the first refrigerant at the second position is greater than a second predetermined value, the bypass valve is diagnosed as faulty.

4. 4. A diagnostic method for a vehicle cooling system according to claim 2, wherein if the temperature of the first refrigerant at the third position is equal to or lower than a third predetermined value and the difference between the temperature of the first refrigerant at the first position and the temperature of the first refrigerant at the second position is less than a second predetermined value, the bypass valve is diagnosed as faulty.

5. 5. A diagnostic method for a vehicle cooling system according to claim 1, wherein, after the system is started, a diagnosis of the bypass valve is carried out after a predetermined heat quantity set in advance is given to the first refrigerant from the high-power unit.

6. 6. A diagnostic method for a vehicle cooling system as described in claim 5, wherein the heat quantity is calculated by subtracting the heat quantity radiated from the high-power unit into the engine compartment of the hybrid vehicle from the heat quantity due to losses in the high-power unit, and the heat quantity is calculated using the vehicle speed of the hybrid vehicle, the outside air temperature, and the temperature of the first refrigerant.

7. the first cooling system has a cooler that cools supercharged intake air of an internal combustion engine mounted on a vehicle, 7. The diagnostic method for a vehicle cooling system according to claim 5, wherein the heat quantity is calculated taking into consideration the amount of heat radiated from the cooler.

8. a first cooling system in which a first refrigerant for cooling an on-board high-power unit can circulate through a main passage; a first cooling system including a radiator that exchanges heat with the first refrigerant, a bypass passage connected to the main passage so as to bypass the radiator, and a bypass valve that controls a flow rate of the first refrigerant flowing through the bypass passage, After the system is started, a predetermined amount of heat is given to the first refrigerant from the high-power unit, A diagnostic method for a vehicle cooling system that diagnoses whether the bypass valve is in a state that allows the first refrigerant to flow to the radiator or a state that prevents the first refrigerant from flowing to the radiator, based on the temperature of the first refrigerant at a position downstream of the radiator in the flow direction of the first refrigerant and upstream of the downstream end of the bypass passage, and the temperature of the first refrigerant calculated from the heat quantity.

9. 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 performs heat exchange 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; a diagnostic unit that diagnoses whether the bypass valve is in a state that allows the first refrigerant to flow to the radiator or a state that prevents the first refrigerant from flowing to the radiator, based on a temperature of the first refrigerant at a first position in the main passage that is a position downstream of the radiator in a flow direction of the first refrigerant and upstream of a downstream end of the bypass passage, and a temperature of the first refrigerant at a second position in the main passage that is 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.

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