JP5839021B2 - Cooling device for internal combustion engine - Google Patents

Description

  The present invention relates to a cooling device for an internal combustion engine, and more particularly to a technique for diagnosing a failure of a thermostat valve provided in the cooling device for an internal combustion engine.

  Japanese Patent Laid-Open No. 2010-196587 (Patent Document 1) discloses an abnormality detecting an abnormality of a thermostat valve provided in an engine cooling system in a hybrid vehicle capable of EV traveling that travels by a driving force of a motor with an engine stopped. A detection device is disclosed. When the EV travel increases, the opportunity for detecting the abnormality of the thermostat valve decreases due to a decrease in the opportunity for operating the engine. In this abnormality detection device, the engine coolant is heated by the heater during the EV travel, and the engine coolant is If the temperature rises above the determination temperature, it is determined that the thermostat valve is operating normally (see Patent Document 1).

JP 2010-196587 A JP 2007-270661 A JP 2007-56722 A

  The amount of heat of the cooling water heated by the exhaust heat of the engine can be used for heating the air conditioner, etc. Even when the engine is stopped, the electric pump is operated according to the heating request of the air conditioner, etc. It can happen to circulate. In this case, since the engine is stopped, the thermostat valve is closed, and the cooling water circulates without passing through the radiator. As a result, there may occur a situation in which the temperature of the circulating cooling water is lower than the temperature of the cooling water remaining in the radiator circulation passage for flowing the cooling water to the radiator.

  When the engine starts in this situation and the failure diagnosis of the thermostat valve is executed, the relationship between the temperature of the circulating cooling water and the temperature of the cooling water in the radiator circulation passage is reversed. There is a possibility that an erroneous determination is made in the failure diagnosis.

  The present invention has been made to solve such a problem, and an object thereof is to suppress erroneous determination in failure diagnosis of a thermostat valve provided in a cooling device for an internal combustion engine.

  An internal combustion engine cooling device according to the present invention includes a cooling water passage formed inside the internal combustion engine, a radiator for cooling the cooling water, a radiator circulation passage, a bypass passage, a heat exchanger, a thermostat valve, An electric pump, first and second temperature sensors, and a control device are provided. The radiator circulation passage is a passage for returning the cooling water discharged from the cooling water passage to the cooling water passage through the radiator. The bypass passage is a passage for returning the cooling water discharged from the cooling water channel to the cooling water channel without passing through the radiator. The heat exchanger is provided in the bypass passage and uses the amount of heat that the cooling water has. The thermostat valve is connected to the radiator circulation passage and the bypass passage, and according to the temperature of the cooling water flowing through the thermostat valve, the cooling water from the radiator circulation passage is shut off and the cooling water from the bypass passage is made into the cooling water passage. It can be switched to either a closed state for outputting or an open state for outputting the cooling water from the radiator circulation passage and the cooling water from the bypass passage to the cooling water passage. The electric pump circulates cooling water. The first temperature sensor detects the temperature of the cooling water in the cooling water channel. The second temperature sensor detects the temperature of the cooling water in the radiator circulation passage. The control device performs failure diagnosis of the thermostat valve after starting the internal combustion engine based on the output of the first temperature sensor and the output of the second temperature sensor. When the electric pump is operated in response to the operation request of the heat exchanger while the internal combustion engine is stopped, the thermostat valve is closed. When the electric pump is activated while the internal combustion engine is stopped, the control device starts the failure diagnosis that is performed after the internal combustion engine is started more than when the electric pump is not activated while the internal combustion engine is stopped. Delay.

  In this cooling device for an internal combustion engine, when the electric pump is operated in response to the operation request of the heat exchanger while the internal combustion engine is stopped, than when the electric pump is not operated while the internal combustion engine is stopped, Since the start of failure diagnosis performed after starting the internal combustion engine is delayed, the failure diagnosis of the thermostat valve is performed in a state where the relationship between the temperature of the cooling water in the cooling water passage and the temperature of the cooling water in the radiator circulation passage is reversed. It can be avoided to start. Therefore, according to the cooling apparatus for an internal combustion engine, erroneous determination can be suppressed in failure diagnosis of the thermostat valve.

  Preferably, the control device starts a failure diagnosis when an increase amount (ΔECT) of the coolant temperature detected by the first temperature sensor after the internal combustion engine is started exceeds a predetermined value. The first value indicating the predetermined value when the electric pump is operated while the internal combustion engine is stopped is more than the second value indicating the predetermined value when the electric pump is not operated while the internal combustion engine is stopped. large.

  The failure diagnosis of the thermostat valve is performed based on the temperature of the cooling water. According to the cooling device for the internal combustion engine, the start of the failure diagnosis is adjusted based on the cooling water temperature. It can be adjusted with high accuracy.

  Preferably, the control device integrates the intake air amount to the internal combustion engine after the internal combustion engine is started, and starts the failure diagnosis when the integrated value of the intake air amount exceeds a predetermined value. The first value indicating the predetermined value when the electric pump is operated while the internal combustion engine is stopped is more than the second value indicating the predetermined value when the electric pump is not operated while the internal combustion engine is stopped. large.

  Since the integrated amount of the intake air amount to the internal combustion engine may indicate a tendency of the temperature of the internal combustion engine and the cooling water to rise, in the cooling device for this internal combustion engine, the failure diagnosis starts based on the integrated amount of the intake air amount Adjusted. Therefore, this internal combustion engine cooling device can also suppress erroneous determination in thermostat valve failure diagnosis.

  Preferably, the control device starts a failure diagnosis when an elapsed time from the start of the internal combustion engine exceeds a predetermined value. The first value indicating the predetermined value when the electric pump is operated while the internal combustion engine is stopped is more than the second value indicating the predetermined value when the electric pump is not operated while the internal combustion engine is stopped. large.

  In this internal combustion engine cooling device, since the start of failure diagnosis is adjusted based on the elapsed time from the start of the internal combustion engine, it is not necessary to take in the detection signal of the sensor or the arithmetic processing. Therefore, according to the cooling device for the internal combustion engine, the processing of the control device can be simplified. In addition, the start of failure diagnosis can be adjusted without being affected by sensor abnormality or measurement accuracy.

  Preferably, the control device calculates an estimated value of the cooling water temperature in the radiator circulation passage based on the leakage flow rate flowing through the radiator circulation passage and the output of the first temperature sensor when the thermostat valve is closed. When the output value of the second temperature sensor is larger than the estimated value, it is diagnosed that the thermostat valve is malfunctioning.

  According to the cooling apparatus for an internal combustion engine, the failure diagnosis of the thermostat valve is performed in consideration of the leakage flow rate flowing through the radiator circulation passage when the thermostat valve is closed, so that a highly accurate failure diagnosis can be performed.

  According to the present invention, erroneous determination can be suppressed in failure diagnosis of a thermostat valve provided in a cooling device for an internal combustion engine.

1 is a schematic configuration diagram of a vehicle including a cooling device for an internal combustion engine according to an embodiment of the present invention. It is the figure which showed an example of the change of the engine cooling water temperature before and behind engine starting. It is a flowchart for demonstrating the procedure of the thermostat valve failure diagnostic process performed by ECU shown in FIG. It is a flowchart which shows the process sequence of diagnostic precondition determination shown in FIG. 10 is a flowchart showing a processing procedure for diagnosis precondition determination in Modification 1; 10 is a flowchart showing a processing procedure for diagnosis precondition determination in Modification 2.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic configuration diagram of a vehicle including a cooling device for an internal combustion engine according to an embodiment of the present invention. Referring to FIG. 1, vehicle 100 includes an engine 20, an engine cooling device 10 for cooling engine 20, and a thermal device 300.

  The engine cooling apparatus 10 includes an electric water pump (hereinafter referred to as “electric pump”) 30, a radiator 40, a radiator circulation passage 50, a bypass passage 60, and a thermostat valve 70. Engine cooling device 10 further includes an engine-side cooling water temperature sensor 80, a radiator-side cooling water temperature sensor 90, and a control device (hereinafter also referred to as “ECU (Electronic Control Unit)”) 200.

  The engine 20 has a water jacket 24 for cooling the engine 20 with cooling water. The water jacket 24 is formed around the cylinder of the engine 20 and constitutes a cooling water passage 25 through which the cooling water flows. The cooling water passage 25 is provided between the inlet portion 27 and the outlet portion 26, and sends out the cooling water from the inlet portion 27 from the outlet portion 26. The cooling water flowing in the cooling water passage 25 exchanges heat with the engine 20 to cool the engine 20. Thereby, the engine 20 is maintained at a temperature suitable for combustion.

  The electric pump 30 is a pump that is driven by an electric motor to circulate cooling water of the engine 20. The electric pump 30 is attached to the mounting side surface portion 22 of the engine body. The electric pump 30 delivers cooling water from the inlet 27 into the cooling water channel 25.

  The electric pump 30 is controlled to be driven and stopped by a control signal received from the ECU 200. Further, the electric pump 30 controls the discharge amount of the cooling water discharged from the electric pump 30 by a control signal received from the ECU 200.

  The outlet part 26 constitutes the branch part 120. The branch portion 120 is connected to the radiator circulation passage 50 and the bypass passage 60. By the branch portion 120, the cooling water from the cooling water passage 25 is divided into cooling water to the radiator circulation passage 50 and cooling water to the bypass passage 60.

  The radiator circulation passage 50 is a passage for circulating cooling water between the engine 20, the electric pump 30, and the radiator 40. The radiator circulation passage 50 is constituted by pipes 50 a and 50 b and a radiator 40. The pipe 50 a is provided between the branch part 120 and the inlet part 42 of the radiator 40. The pipe 50 b is provided between the outlet portion 44 of the radiator 40 and the thermostat valve 70. The cooling water warmed by the engine 20 is cooled by passing through the radiator 40.

  The radiator 40 radiates the heat of the cooling water by exchanging heat between the cooling water flowing inside the radiator 40 and the outside air. The radiator 40 is provided with a cooling fan 46. The cooling fan 46 promotes heat exchange by blowing air and improves the heat dissipation efficiency of the cooling water in the radiator 40. The cooling water cooled by the radiator 40 is sent out from the outlet 44.

  The bypass passage 60 is a passage for circulating the cooling water without passing through the radiator 40. The bypass passage 60 includes pipes 60 a and 60 b and a heat device 300. The pipe 60 a is provided between the branch part 120 and the thermal device 300. The pipe 60 b is provided between the thermal device 300 and the thermostat valve 70.

  The thermal apparatus 300 includes an EGR (Exhaust Gas Recirculation) cooler 28, a pipe 29, an exhaust heat recovery device 32, a heater core 36, a throttle body 35, and an EGR valve 34.

  The EGR cooler 28 cools the EGR gas with cooling water. The throttle body 35 is prevented from sticking by being warmed by the cooling water. The EGR valve 34 is cooled by cooling water. The exhaust heat recovery device 32 enhances engine startability at low temperatures by warming the cooling water with the heat of the exhaust gas.

  The heater core 36 is used as a heater of the air conditioner, and heats the blown air by exchanging heat between the cooling water and the blown air of the air conditioner. The air conditioner can operate even when the engine 20 is stopped. When there is a heating request from the air conditioner while the engine 20 is stopped, the electric pump 30 is activated and the cooling water circulates in the bypass passage 60. The heater core 36 exchanges heat between the cooling water and the air blown from the air conditioner. Thereby, the temperature of the cooling water flowing through the bypass passage 60 decreases.

  The thermostat valve 70 is disposed in the junction 110 that joins the cooling water that has passed through the radiator circulation passage 50 and the cooling water that has passed through the bypass passage 60. The junction 110 is connected to the radiator 40 via the pipe 50b and to the pipe 60b. Cooling water from the junction 110 is returned to the suction port of the electric pump 30. The thermostat valve 70 is configured to be switched between a closed state and an open state in accordance with the temperature of the cooling water flowing inside the thermostat valve 70 (near the valve body).

  When the temperature of the cooling water in the vicinity of the valve body of the thermostat valve 70 is lower than a predetermined valve opening temperature (for example, about 70 ° C.), the thermostat valve 70 is closed. In this case, the cooling water on the bypass passage 60 side passes through the thermostat valve 70 and is output to the water jacket 24, but the cooling water on the radiator circulation passage 50 side is shut off by the thermostat valve 70 and enters the water jacket 24. Not output. Thus, the cooling water that has taken away the heat of the engine 20 is returned to the engine 20 (water jacket 24) without being cooled by the radiator 40, and the engine 20 is warmed up.

  On the other hand, when the temperature of the cooling water in the vicinity of the valve body of the thermostat valve 70 is equal to or higher than the valve opening temperature, the thermostat valve 70 is opened. In this case, the cooling water from the radiator circulation passage 50 and the cooling water from the bypass passage 60 pass through the thermostat valve 70 and are output to the water jacket 24. Further, the opening degree of the thermostat valve 70 is adjusted according to the temperature of the cooling water. Thereby, the mixing ratio of the cooling water from the radiator circulation passage 50 and the cooling water from the bypass passage 60 is adjusted, and the temperature of the cooling water passed through the water jacket 24 is kept at an appropriate temperature of the engine 20. It is.

  The engine-side cooling water temperature sensor 80 is provided in the branch part 120. The engine-side cooling water temperature sensor 80 detects the temperature of the cooling water delivered from the outlet 26 (hereinafter referred to as “engine outlet water temperature ECT” or simply “ECT”), and the detection result (ECT detection value) to the ECU 200. Output. The engine-side cooling water temperature sensor 80 only needs to be provided in a path through which the cooling water is constantly circulated. For example, the engine-side cooling water temperature sensor 80 may be provided in the cooling water path 25.

  The radiator side cooling water temperature sensor 90 is provided in the pipe 50a. The radiator side cooling water temperature sensor 90 detects the temperature of the cooling water flowing in the pipe 50a of the radiator circulation passage 50 (hereinafter referred to as “radiator inlet water temperature RCT” or simply “RCT”), and the detection result (RCT detection value). Output to ECU 200. The radiator-side cooling water temperature sensor 90 only needs to be provided in the radiator circulation passage 50, and may be provided, for example, in the pipe 50b.

  In the vehicle 100 having the above-described configuration, if the thermostat valve 70 has failed, the valve body will not open even if the coolant temperature near the valve body rises above the valve opening temperature, Even if the cooling water temperature falls below the valve opening temperature, an abnormality such as an open failure that does not close the valve body occurs. In a state where such a failure has occurred, cooling water having an appropriate water temperature cannot be supplied to the cooling water passage 25 of the engine 20, and the operating efficiency of the engine 20 is reduced. For this reason, it is preferable to continuously perform failure diagnosis whether or not the thermostat valve 70 is functioning normally during operation of the engine 20 and find the failure early.

  Therefore, ECU 200 performs failure diagnosis of thermostat valve 70 based on the ECT detection value received from engine-side cooling water temperature sensor 80 and the RCT detection value received from radiator-side cooling water temperature sensor 90. The ECU 200 includes a CPU (Central Processing Unit), a storage device, an input / output buffer, and the like (all not shown).

  As an example, the ECU 200 performs the following fault diagnosis with high diagnostic accuracy. That is, in the water temperature region where the thermostat valve 70 is not originally opened (the water temperature region below the valve opening temperature), since the thermostat valve 70 is in a closed state, in theory, cooling water flows through the bypass passage 60 and the radiator circulation passage. 50 does not flow cooling water. Therefore, a difference of a predetermined value or more occurs between the ECT detection value and the RCT detection value. Therefore, when the difference between the ECT detection value and the RCT detection value is less than a predetermined value in the water temperature range where the thermostat valve 70 is not originally opened, the thermostat valve 70 is open, that is, the thermostat valve 70 is in an open failure state. Judgment can be made.

  However, actually, even if the thermostat valve 70 is normally closed, if the water pressure in the radiator circulation passage 50 is increased by driving the electric pump 30, the cooling water in the radiator circulation passage 50 is transferred from the thermostat valve 70 to the cooling water passage 25. Leak out. In this case, although the thermostat valve 70 is in the closed state, an amount of cooling water corresponding to the leakage flow rate of the thermostat valve 70 flows into the radiator circulation passage 50 from the cooling water passage 25 and is cooled in the radiator circulation passage 50. Since it is mixed with water, the radiator inlet water temperature RCT approaches the engine outlet water temperature ECT. Thereby, since the temperature difference between the ECT detection value and the RCT detection value becomes small, there is a possibility that the accuracy of the failure diagnosis is lowered.

  Therefore, the ECU 200 performs a failure diagnosis of the thermostat valve 70 in consideration of leakage of cooling water from the thermostat valve 70 even when the thermostat valve 70 is normal. Specifically, the ECU 200 calculates an estimated value of the radiator inlet water temperature RCT based on the ECT detection value and the leakage flow rate of the thermostat valve 70, and based on the comparison result between the calculated RCT estimated value and the RCT detection value, A process of diagnosing whether or not the thermostat valve 70 is faulty (hereinafter referred to as “thermostat valve fault diagnosis process”) is performed. The thermostat valve failure diagnosis process will be described in detail later using a flowchart.

  By the way, as described above, the amount of heat of the cooling water heated by the exhaust heat of the engine 20 can be used for heating of the air conditioner. In this embodiment, for example, the heater core 36 provided in the bypass passage 60 is used. It is used when heating the air conditioner. Here, the amount of heat of the heated cooling water can be used even when the engine 20 is stopped. Even when the engine 20 is stopped, the electric pump 30 is operated to cool the engine 20 according to a heating request or the like. Circulating water can occur. In this case, since the engine 20 is stopped, the thermostat valve 70 is closed, and the cooling water does not flow into the radiator circulation passage 50 but circulates through the cooling water passage 25 and the bypass passage 60 of the engine 20. Then, while the cooling water circulating through the cooling water passage 25 and the bypass passage 60 is deprived of heat by the heater core 36, the cooling water staying in the radiator circulation passage 50 is only natural heat radiation. There may occur a situation in which the temperature of the circulating cooling water is lower than the temperature of the cooling water in the radiator circulation passage 50. As a result, if the engine outlet water temperature ECT is higher than the radiator inlet water temperature RCT, the relationship between the engine outlet water temperature ECT and the radiator inlet water temperature RCT is reversed, so that an erroneous determination can be made in failure diagnosis.

  FIG. 2 is a diagram illustrating an example of a change in engine coolant temperature before and after the engine 20 is started. Referring to FIG. 2, it is assumed that engine 20 is stopped before time t1, and the condition of ECT detection value <RCT detection value is generated due to heating use or the like while the engine is stopped. It should be noted that failure diagnosis of the thermostat valve 70 is not performed while the engine 20 is stopped.

  It is assumed that the engine 20 is started at time t1. If it does so, engine cooling water will be heated by the exhaust heat of the engine 20, and the ECT detection value which shows the temperature of the cooling water of an engine exit will begin to raise. Note that immediately after the start of the engine 20, the temperature of the cooling water is lower than the opening temperature of the thermostat valve 70, and the thermostat valve 70 is closed, so no increase in the RCT detection value is observed. The state of ECT detection value <RCT detection value continues until time t2, and ECT detection value> RCT detection value after time t2.

  Thus, even if the engine 20 is started at time t1, the ECT detection value <RCT detection value until time t2, and if failure diagnosis is started before time t2, the ECT detection value that should be originally obtained> The fault diagnosis is erroneously determined due to the reverse relationship of the RCT detection values. Therefore, in this embodiment, in consideration of such an erroneous determination region between time t1 and time t2, the ECU 200 requests the heating of the air conditioner while the engine 20 is stopped (the thermostat valve 70 is closed). When the electric pump 30 is activated, the start of the failure diagnosis process of the thermostat valve 70 performed after the engine 20 is started is delayed as compared with the case where the electric pump 30 is not activated while the engine 20 is stopped. Thereby, it is avoided that the failure diagnosis is performed in a state where the magnitude relationship between the ECT detection value and the RCT detection value is reversed, and erroneous determination in the failure diagnosis is suppressed.

  FIG. 3 is a flowchart for explaining the procedure of the thermostat valve failure diagnosis process executed by ECU 200 shown in FIG. The processing shown in this flowchart is performed when the engine 20 is started, for example, when the engine is started after idling is stopped, or when the vehicle 100 is a hybrid vehicle, and the engine 20 is further stopped to drive by the driving force of the motor. This is executed when the engine is started when switching from EV running to HV running by operating the engine 20. This flowchart is realized by executing a program stored in advance in the ECU 200 at a predetermined cycle, and for some steps, it is also possible to implement processing by constructing dedicated hardware (electronic circuit). .

  Referring to FIG. 3, ECU 200 determines the radiator inlet water temperature RCT based on the ECT detection value received from engine-side cooling water temperature sensor 80 and the leakage flow rate flowing through radiator circulation passage 50 when thermostat valve 70 is closed. An estimated value (RCT estimated value) is calculated (step S10). Specifically, ECU 200 can calculate the RCT estimated value using the following equation as an example.

RCT estimated value = (ECT detection value × leakage flow rate + RCT estimated value (previous value) × (pipe volume−leakage flow rate)) / pipe volume (1)
In equation (1), the RCT estimated value is calculated on the assumption that the cooling water of the ECT detection value and the cooling water of the RCT estimated value (previous value) are uniformly mixed according to the ratio of the leakage flow rate to the pipe volume. The

  Here, the leakage flow rate may be a fixed value determined in advance by an experimental result or the like, or may be a fluctuation value set to a larger value as the flow rate of the electric pump 30 increases, for example. The pipe volume is the volume of the pipe through which the cooling water from the engine side cooling water temperature sensor 80 to the radiator side cooling water temperature sensor 90 flows. Note that the calculation accuracy can be improved by dividing the pipeline into an arbitrary number of regions and applying the above equation (1) for each of the divided regions.

  Next, ECU 200 performs a process of determining whether or not a precondition for performing an open failure diagnosis process for thermostat valve 70 (hereinafter also simply referred to as “diagnosis precondition”) is satisfied (step S20). The details of this processing will be described in detail later with reference to FIG.

  Then, ECU 200 determines whether or not to perform thermostat open failure diagnosis processing based on the processing result of step S20 (step S30). When it is determined that the diagnosis precondition is not satisfied (NO in step S30), ECU 200 ends the process without performing the thermostat open failure diagnosis process (the processes in steps S40 to S60). That is, the ECU 200 prohibits the thermostat open failure diagnosis process when the diagnosis precondition is not satisfied.

  On the other hand, when it is determined in step S30 that the diagnosis precondition is satisfied (YES in step S30), ECU 200 performs thermostat open failure diagnosis processing (steps S40 to S60).

  That is, ECU 200 determines whether or not the RCT detection value received from radiator-side cooling water temperature sensor 90 is higher than the RCT estimated value calculated in step S10 (step S40). When the detected RCT value is higher than the estimated RCT value (YES in step S40), ECU 200 determines that thermostat valve 70 is in an open failure state (step S50). If the thermostat valve 70 is in an open failure state, a larger amount of heated cooling water than the assumed leakage flow rate flows into the radiator circulation passage 50, and a situation occurs in which the RCT detection value is higher than the RCT estimated value. is there. On the other hand, when the RCT detection value is equal to or less than the RCT estimated value (NO in step S40), ECU 200 determines that thermostat valve 70 is normal (step S60).

  FIG. 4 is a flowchart showing a diagnostic precondition determination process executed in step S20 of FIG. Referring to FIG. 4, ECU 200 determines whether or not the monitor precondition is satisfied. The monitor precondition is a condition set as a premise for monitoring (monitoring) a water temperature increase amount ΔECT indicating an increase in cooling water temperature after engine start in steps S130 and S160 described later. As an example, the ECU 200 determines that the monitor precondition is satisfied when all of the following conditions (a) to (f) are satisfied.

(A) The thermostat failure diagnosis is not completed after the current engine start.
(B) The ECT detection value is lower than the valve opening temperature of the thermostat valve 70 (for example, 70 ° C.).

(C) The ECT detection value at the time of engine start is included in the range of −10 ° C. to + 56 ° C.
(D) The engine is starting.

(E) The amount of time change of the ECT detection value is a predetermined value (for example, 0.1 ° C./second) or more.
(F) The engine-side cooling water temperature sensor 80 and the radiator-side cooling water temperature sensor 90 are normal.

  Condition (a) is based on the premise that the thermostat failure diagnosis is performed once during the period from when the engine 20 is started to when it is stopped. Condition (b) is a condition for ensuring that the thermostat valve 70 is closed (if normal). Conditions (c) and (d) are conditions for ensuring that the ECT detection value increases in such a manner that a thermostat failure can be diagnosed after the engine is started. Condition (e) is a condition for guaranteeing an increase in the engine water temperature after the engine is started. The condition (f) is a condition for ensuring the reliability of the ECT detection value or the RCT detection value. Note that the above conditions (a) to (f) may be appropriately selected as monitor preconditions.

  If it is determined in step S110 that the monitor precondition is not satisfied (NO in step S110), ECU 200 shifts the process to step S180, and the diagnosis precondition is not satisfied (step S180).

  If it is determined in step S110 that the monitor precondition is satisfied (YES in step S110), ECU 200 causes electric pump 30 to operate during the previous engine stop (from the previous engine stop to the current engine start). It is determined whether or not (step S120).

  If electric pump 30 is operating while the engine is stopped (YES in step S120), ECU 200 determines that water temperature increase ΔECT indicating the amount of increase in the ECT detection value after engine 20 is started is a predetermined value A ( > It is determined whether or not it is larger than the predetermined value B) (step S130). This predetermined value A is a determination value of a diagnostic precondition when the electric pump 30 is operating while the engine is stopped, and a determination value B of the diagnostic precondition when the electric pump 30 is not operating while the engine is stopped. Greater than (default value). As an example, the predetermined value B is 1 ° C., and the predetermined value A is 3 ° C. Thereby, the start of the failure diagnosis when the electric pump 30 is operating while the engine is stopped can be delayed as compared with the case where the electric pump 30 is not operated while the engine is stopped.

  If it is determined in step S130 that the water temperature increase amount ΔECT is larger than predetermined value A (YES in step S130), ECU 200 assumes that the diagnostic precondition is satisfied (step S140). When it is determined in step S130 that the water temperature increase amount ΔECT is equal to or smaller than predetermined value A (NO in step S130), ECU 200 does not satisfy the diagnosis precondition (step S150).

  On the other hand, when it is determined in step S120 that electric pump 30 is not operating during the previous engine stop (NO in step S120), ECU 200 determines whether or not water temperature increase amount ΔECT is greater than predetermined value B. Is determined (step S160). If it is determined in step S160 that the water temperature increase amount ΔECT is larger than the predetermined value B (YES in step S160), ECU 200 assumes that the diagnostic precondition is satisfied (step S170). If it is determined in step S160 that the water temperature increase amount ΔECT is equal to or smaller than the predetermined value B (NO in step S160), ECU 200 does not satisfy the diagnosis precondition (step S180).

  As described above, in the engine cooling device 10, when the electric pump 30 is operated in response to a heating request of the air conditioner while the engine 20 is stopped, the electric pump 30 is operated while the engine 20 is stopped. Since the start of the failure diagnosis performed after the start of the engine 20 is delayed as compared with the case where there is not, the failure diagnosis of the thermostat valve 70 is started in a state where the relationship between the engine outlet water temperature ECT and the radiator inlet water temperature RCT is reversed. Can be avoided. Therefore, according to the engine cooling device 10, it is possible to suppress erroneous determination in the failure diagnosis of the thermostat valve 70.

  Further, the failure diagnosis of the thermostat valve 70 is performed based on the temperature of the cooling water. According to the engine cooling device 10, the start of the failure diagnosis is adjusted based on the cooling water temperature. The time can be adjusted accurately.

  Further, according to the engine cooling device 10, since the failure diagnosis of the thermostat valve 70 is performed in consideration of the leakage flow rate flowing through the radiator circulation passage 50 when the thermostat valve 70 is closed, the failure diagnosis with high accuracy can be performed. .

[Modification 1]
In the above-described embodiment, the start of the thermostat valve failure diagnosis process after the engine is started based on the amount of increase (ΔECT) in the engine coolant temperature (ECT detection value) after the engine 20 is started (the diagnosis precondition is satisfied) However, instead of the water temperature increase amount ΔECT, an integrated amount of the intake air amount to the engine 20 after the engine 20 is started may be used. This is because the integrated intake air amount after the engine 20 has started can show a tendency of the temperature of the engine 20 and the cooling water to rise.

  The overall configuration of the vehicle in the first modification is the same as that of the vehicle 100 shown in FIG. Further, the overall processing procedure of the thermostat valve failure diagnosis executed by the ECU 200 in the first modification is the same as the processing procedure shown in FIG.

  FIG. 5 is a flowchart showing a processing procedure for diagnosis precondition determination (processing executed in step S20 of FIG. 3) in the first modification. Referring to FIG. 5, this flowchart includes steps S132 and S162 in place of steps S130 and S160 in the flowchart shown in FIG.

  That is, if it is determined in step S120 that the electric pump 30 has been operated during the previous engine stop (YES in step S120), the ECU 200 determines the amount of intake air to the engine 20 after the engine 20 is started. It is determined whether or not the integrated intake air amount indicating the integrated amount is greater than a predetermined value C (> predetermined value D) (step S132). The predetermined value C is a diagnosis precondition determination value when the electric pump 30 is operating while the engine is stopped, and a diagnosis precondition determination value when the electric pump 30 is not operating while the engine is stopped. Greater than D (default value). As an example, the predetermined value C is 50 g, and the predetermined value D is 20 g. The intake air amount to the engine 20 can be detected by an air flow meter (not shown). By setting the predetermined value C> the predetermined value D, the start of the failure diagnosis when the electric pump 30 is operating while the engine is stopped can be delayed more than when the electric pump 30 is not operating while the engine is stopped. it can.

  If it is determined in step S132 that the integrated intake air amount is greater than the predetermined value C (YES in step S132), the process proceeds to step S140, and the diagnosis precondition is satisfied. If it is determined in step S132 that the integrated intake air amount is equal to or smaller than predetermined value C (NO in step S132), the process proceeds to step S150, and the diagnosis precondition is not satisfied.

  On the other hand, when it is determined in step S120 that the electric pump 30 is not operating during the previous engine stop (NO in step S120), the ECU 200 determines whether or not the integrated intake air amount is greater than the predetermined value D. Is determined (step S162). If it is determined that the integrated intake air amount is greater than predetermined value D (YES in step S162), the process proceeds to step S170, and the diagnosis precondition is satisfied. If it is determined in step S162 that the integrated intake air amount is equal to or smaller than predetermined value D (NO in step S162), the process proceeds to step S180, and the diagnosis precondition is not satisfied.

  Also according to the first modification, when the electric pump 30 is operated in response to a heating request of the air conditioner while the engine 20 is stopped, than when the electric pump 30 is not operated while the engine 20 is stopped, Since the start of the failure diagnosis performed after the engine 20 is started can be delayed, erroneous determination can be suppressed in the failure diagnosis of the thermostat valve 70 as in the above embodiment.

[Modification 2]
In the first modification, the start of the thermostat valve failure diagnosis process after the engine is started (establishment of the diagnostic precondition) is delayed based on the integrated intake air amount after the engine 20 is started. Alternatively, the elapsed time after starting the engine may be used instead. As a result, the sensor detection signal capturing process and the arithmetic process are not required, and the process of the ECU 200 is simplified. In addition, the start of failure diagnosis can be adjusted without being affected by sensor abnormality or measurement accuracy.

  The overall configuration of the vehicle in Modification 2 is the same as that of vehicle 100 shown in FIG. Further, the overall processing procedure of the thermostat valve failure diagnosis executed by the ECU 200 in the second modification is the same as the processing procedure shown in FIG.

  FIG. 6 is a flowchart showing a processing procedure for diagnosis precondition determination (processing executed in step S20 of FIG. 3) in the second modification. Referring to FIG. 6, this flowchart includes steps S134 and S164 in place of steps S130 and S160 in the flowchart shown in FIG.

  That is, when it is determined in step S120 that the electric pump 30 has been operated during the previous engine stop (YES in step S120), the ECU 200 determines that the elapsed time from the start of the engine 20 is a predetermined value T1 (> It is determined whether or not a predetermined value T2) has been exceeded (step S134). The predetermined value T1 is a determination value for the diagnostic precondition when the electric pump 30 is operating while the engine is stopped, and is a determination value for the diagnostic precondition when the electric pump 30 is not operating while the engine is stopped. It is larger than T2 (default value). As an example, the predetermined value T1 is 5 seconds, and the predetermined value T2 is 2 seconds. Note that the elapsed time from the start of the engine 20 can be measured by a timer or the like (not shown). By setting the predetermined value T1> predetermined value T2, the start of the failure diagnosis when the electric pump 30 is operating while the engine is stopped can be delayed more than when the electric pump 30 is not operating while the engine is stopped. it can.

  If it is determined in step S134 that the elapsed time has exceeded the predetermined value T1 (YES in step S134), the process proceeds to step S140, and the diagnosis precondition is satisfied. If it is determined in step S134 that the elapsed time is equal to or less than predetermined value T1 (NO in step S134), the process proceeds to step S150, and the diagnosis precondition is not satisfied.

  On the other hand, when it is determined in step S120 that electric pump 30 is not operating during the previous engine stop (NO in step S120), ECU 200 determines whether or not the elapsed time exceeds predetermined value T2. (Step S164). If it is determined that the elapsed time has exceeded predetermined value T2 (YES in step S164), the process proceeds to step S170, and the diagnosis precondition is satisfied. If it is determined in step S164 that the elapsed time is equal to or less than predetermined value T2 (NO in step S164), the process proceeds to step S180, and the diagnosis precondition is not satisfied.

  Also in the second modification, when the electric pump 30 is operated in response to a heating request of the air conditioner while the engine 20 is stopped, than when the electric pump 30 is not operated while the engine 20 is stopped, Since the start of the failure diagnosis performed after the engine 20 is started can be delayed, erroneous determination can be suppressed in the failure diagnosis of the thermostat valve 70 as in the above embodiment.

  Further, in the second modification, since the start of the failure diagnosis is adjusted based on the elapsed time after the engine 20 is started, the process for acquiring the detection signal of the sensor and the calculation process become unnecessary. Therefore, according to the second modification, the processing of the ECU 200 can be simplified. In addition, the start of failure diagnosis can be adjusted without being affected by sensor abnormality or measurement accuracy.

  In the above-described embodiment and the first and second modifications, the failure diagnosis of the thermostat valve 70 is performed in consideration of the leakage flow rate flowing through the radiator circulation passage 50 when the thermostat valve 70 is closed. The method is not limited to such a method. For example, the present invention can also be applied to a case where failure diagnosis is performed based on a comparison between the ECT detection value and the RCT detection value more simply.

  The present invention can be applied to a hybrid vehicle equipped with a traveling motor in addition to the engine 20 and a vehicle not equipped with a traveling motor. The present invention can be applied to engine starting after idling stop or after IG ON operation by a user in a vehicle not equipped with a traveling motor. In a hybrid vehicle, the engine when switching from EV traveling to HV traveling is further applied. The present invention can also be applied to starting.

  In the above description, engine 20 corresponds to an embodiment of “internal combustion engine” in the present invention, and heater core 36 corresponds to an embodiment of “heat exchanger” in the present invention. The engine-side cooling water temperature sensor 80 corresponds to one embodiment of the “first temperature sensor” in the present invention, and the radiator-side cooling water temperature sensor 90 corresponds to one embodiment of the “second temperature sensor” in the present invention. Corresponding to

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  DESCRIPTION OF SYMBOLS 10 Engine cooling device, 20 Engine, 22 Mounting side surface part, 24 Water jacket, 25 Cooling water channel, 26, 44 Outlet part, 27, 42 Inlet part, 28 Cooler, 29, 50a, 50b, 60a, 60b Piping, 30 Electric pump , 32 Exhaust heat recovery device, 34 EGR valve, 35 Throttle body, 36 Heater core, 40 Radiator, 46 Cooling fan, 50 Radiator circulation passage, 60 Bypass passage, 70 Thermostat valve, 80 Engine side cooling water temperature sensor, 90 Radiator side cooling water temperature Sensor, 100 vehicle, 110 junction, 120 branch, 200 ECU, 300 thermal equipment.

Claims (5)

A cooling device for an internal combustion engine,
A cooling water channel formed inside the internal combustion engine;
A radiator for cooling the cooling water;
A radiator circulation passage for returning the cooling water discharged from the cooling water passage to the cooling water passage via the radiator;
A bypass passage for returning the cooling water discharged from the cooling water channel to the cooling water channel without passing through the radiator;
A heat exchanger that is provided in the bypass passage and uses the amount of heat of the cooling water;
A thermostat valve connected to the radiator circulation passage and the bypass passage;
The thermostat valve is in a closed state in which the cooling water from the radiator circulation passage is shut off and the cooling water from the bypass passage is output to the cooling water passage according to the temperature of the cooling water flowing through the thermostat valve. An electric pump for switching the cooling water from the radiator circulation path and the cooling water from the bypass path to an open state for outputting to the cooling water path, and further circulating the cooling water;
A first temperature sensor for detecting a temperature of the cooling water in the cooling water channel;
A second temperature sensor for detecting a temperature of the cooling water in the radiator circulation passage;
A controller for diagnosing the failure of the thermostat valve after the internal combustion engine is started based on the output of the first temperature sensor and the output of the second temperature sensor;
When the electric pump is operated in response to the operation request of the heat exchanger while the internal combustion engine is stopped, the thermostat valve is closed,
When the electric pump is operated while the internal combustion engine is stopped, the control device is performed after the internal combustion engine is started more than when the electric pump is not operated while the internal combustion engine is stopped. A cooling device for an internal combustion engine that delays the start of failure diagnosis. The controller starts the failure diagnosis when an increase in the coolant temperature detected by the first temperature sensor after the internal combustion engine is started exceeds a predetermined value,
The first value indicating the predetermined value when the electric pump is operated while the internal combustion engine is stopped is a second value indicating the predetermined value when the electric pump is not operated while the internal combustion engine is stopped. The cooling device for an internal combustion engine according to claim 1, wherein the cooling device is larger than the value of. The control device integrates the intake air amount to the internal combustion engine after the internal combustion engine is started, and when the integrated value of the intake air amount exceeds a predetermined value, starts the failure diagnosis,
The first value indicating the predetermined value when the electric pump is operated while the internal combustion engine is stopped is a second value indicating the predetermined value when the electric pump is not operated while the internal combustion engine is stopped. The cooling device for an internal combustion engine according to claim 1, wherein the cooling device is larger than the value of. The controller starts the failure diagnosis when an elapsed time from the start of the internal combustion engine exceeds a predetermined value,
The first value indicating the predetermined value when the electric pump is operated while the internal combustion engine is stopped is a second value indicating the predetermined value when the electric pump is not operated while the internal combustion engine is stopped. The cooling device for an internal combustion engine according to claim 1, wherein the cooling device is larger than the value of.   The control device calculates an estimated value of a coolant temperature in the radiator circulation passage based on a leakage flow rate flowing through the radiator circulation passage and an output of the first temperature sensor when the thermostat valve is closed. The cooling of the internal combustion engine according to any one of claims 2 to 4, wherein when the output value of the second temperature sensor is larger than the estimated value, the thermostat valve is diagnosed as malfunctioning. apparatus.

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