JP7238614B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to a control device for an internal combustion engine.

2. Description of the Related Art As a cooling device for an internal combustion engine, a water-cooling type cooling device that circulates cooling water between an engine body and a radiator is known. Such a cooling device is provided with a thermostat that adjusts the flow rate of cooling water flowing through the radiator. The thermostat is closed when the cooling water temperature is lower than a predetermined value (for example, 75° C.), such as during warm-up immediately after the engine is started, and in this state, circulation of cooling water to the radiator side is stopped. be. Therefore, the internal combustion engine can be quickly warmed up.

However, if an abnormality such as sticking occurs in the thermostat and the valve remains open (sticking open state), the cooling water will circulate through the radiator even during warm-up, causing the internal combustion engine to run. It cannot be warmed up quickly. Therefore, various methods have been proposed to detect thermostat anomalies.

For example, in Patent Document 1, a state in which the temperature of cooling water detected by a water temperature sensor is lower than a threshold value and the absolute value of the amount of change in the temperature of cooling water is smaller than a predetermined value is maintained for a predetermined time. The thermostat abnormality is determined based on whether or not it continues until the

JP 2012-82731 A

When the engine speed increases, the value of the water temperature sensor may temporarily decrease, and the amount of change in the coolant temperature may become smaller. In such a case, the conventional technology may erroneously determine that the thermostat is abnormal (stuck open) because the amount of change in the coolant temperature does not exceed a predetermined value.

Accordingly, an object of the control device for an internal combustion engine disclosed in the present specification is to improve the accuracy of thermostat abnormality detection.

In order to solve this problem, the control device for an internal combustion engine disclosed in this specification supplies a cooling medium that has passed through a cooling passage formed inside an engine body of an internal combustion engine to the engine body via a radiator. a radiator path for recirculation, a pump driven by the internal combustion engine to circulate the cooling medium, and a temperature detecting section provided near an outlet of the cooling passage for detecting the temperature of the cooling medium that has passed through the cooling passage. a thermostat that opens when the temperature of the cooling medium is equal to or higher than a predetermined temperature to allow the cooling medium to flow through the radiator path; a rotation speed detection unit that detects the rotation speed of the internal combustion engine; When the temperature of the cooling medium is lower than the predetermined temperature, the temperature of the thermostat is determined based on whether or not the amount of change in the temperature of the cooling medium detected by the temperature detection unit in a predetermined period is equal to or less than a first threshold. an abnormality detection unit for detecting an abnormality ; a degree of increase in the rotation speed of the internal combustion engine detected by the rotation speed detection unit; When the degree of increase in the rotation speed that affects the amount of change in the temperature of the engine during a predetermined period is equal to or greater than a second threshold value, the first threshold value is set to be smaller than when the degree of increase in the rotation speed is less than the second threshold value. a correction unit that corrects the value to a value that suppresses erroneous detection of the thermostat as being abnormal .

The control device for an internal combustion engine disclosed in the present specification can improve the accuracy of thermostat abnormality detection.

FIG. 1 is a schematic diagram showing the configuration of a cooling system to which a control device for an internal combustion engine according to the first embodiment is applied. FIG. 2 is a flowchart (part 1) showing an example of thermostat abnormality determination processing. FIG. 3 is a flowchart (part 2) showing an example of thermostat abnormality determination processing. FIG. 4 is a flow chart showing details of the water temperature threshold setting process in the first embodiment. FIG. 5 is a time chart showing the relationship between the engine speed and the value output from the water temperature sensor. FIG. 6 is a schematic diagram showing the configuration of a cooling system to which the control device for an internal combustion engine according to the second embodiment is applied. FIG. 7 is a flowchart showing a water temperature threshold setting process when the water pump is an electric water pump in the second embodiment. FIG. 8A is a time chart showing the relationship between the engine speed, the water pump flow rate, and the value output from the water temperature sensor, and FIG. 8B is the time t12 of FIG. It is an enlarged view of the vicinity. FIG. 9 is a flowchart showing the details of the water temperature threshold setting process when the water pump is a mechanical water pump in the second embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, etc. of each part may not be illustrated so as to completely match the actual ones. In some drawings, details may be omitted.

<<First embodiment>>
FIG. 1 is a schematic diagram showing the configuration of a cooling system 500 to which a control device for an internal combustion engine according to the first embodiment is applied. The control device for an internal combustion engine according to the present embodiment can be applied to a vehicle equipped with a gasoline engine, an engine using alcohol fuel or gas fuel, and a vehicle equipped with a diesel engine. It can also be applied to a hybrid vehicle equipped with an electric motor for In the following description, the cooling medium is assumed to be cooling water, but the cooling medium may be liquid or gas, and is not particularly limited to this.

As shown in FIG. 1, in the present embodiment, a cooling system 500 returns cooling water that has passed through a water jacket 12 formed inside an engine body 10 of an internal combustion engine to the engine body 10 via a radiator 14. It comprises a radiator path 20, a bypass path 25 that returns water to the engine body 10 without passing through the radiator 14, and a water pump 16 that is driven by a crankshaft (not shown) of the engine body 10 and circulates cooling water. Water jacket 12 is an example of a cooling passage.

A heating heat exchanger (heater core) 15 installed in the vehicle compartment is installed in the bypass route 25 . Incidentally, in the bypass route 25, in addition to the route passing through the heater core 15, for example, a route for cooling the throttle valve may be formed.

A water temperature sensor 51 is provided in the vicinity of the cooling water outlet 12 a of the water jacket 12 . A water temperature sensor 51 detects the temperature of cooling water that has passed through the water jacket 12 (hereinafter referred to as engine outlet water temperature). The water temperature sensor 51 is an example of a temperature detector.

A thermostat 17 is provided downstream of the radiator 14 in the radiator path 20 . The thermostat 17 opens when the engine outlet water temperature is equal to or higher than a predetermined temperature (75° C. in this embodiment) to allow cooling water to flow through the radiator path 20 . On the other hand, when the engine outlet water temperature is lower than the predetermined temperature, the valve is closed to cut off the flow of cooling water through the radiator path 20 .

The cooling system 500 also includes an ECU (Electronic Control Unit) 100 . The ECU 100 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a storage device, and the like. The ECU 100 executes a thermostat abnormality determination process and a water temperature threshold value setting process, which will be described later, by executing programs stored in the ROM or storage device. The ECU 100 is an example of an abnormality detection section and a correction section.

In addition to the water temperature sensor 51 described above, the ECU 100 is connected to a crank position sensor 52, an intake air temperature sensor 53, a vehicle speed sensor 54, a battery 59, and the like. The crank position sensor 52 detects the number of revolutions of a crankshaft (not shown), that is, the number of engine revolutions. The crank position sensor 52 is an example of a rotational speed detector. An intake air temperature sensor 53 detects the temperature of intake air introduced into an air cleaner (not shown) (intake air temperature). A vehicle speed sensor 54 detects the vehicle speed. The ECU 100 executes thermostat abnormality determination processing and water temperature threshold setting processing based on signals input from each sensor.

Next, the thermostat abnormality determination process executed by the ECU 100 will be described based on the flowcharts of FIGS. 2 and 3. FIG. The processes in FIGS. 2 and 3 are executed at predetermined time intervals (every predetermined determination period (for example, every 20 seconds)).

In FIG. 2, the ECU 100 first determines whether or not a condition for executing the abnormality determination process for the thermostat 17 (determination process execution condition) is satisfied (step S11). For example, the ECU 100 determines that the engine outlet water temperature at the engine start is a predetermined value (eg, -10°C) or more, the intake air temperature at the engine start is a predetermined value (eg, -10°C) or more, and the engine speed is within a predetermined range ( For example, within the range of 0 rpm to 4500 rpm), the vehicle speed is within a predetermined range (for example, within the range of 65 km/h to 128 km/h), and the battery voltage is equal to or higher than a predetermined voltage, the determination process execution condition is satisfied. determined to be

If the determination process execution condition is not satisfied (step S11/NO), the ECU 100 terminates the processes of FIGS. On the other hand, if the determination processing execution condition is satisfied (step S11/YES), the ECU 100 executes water temperature threshold setting processing for setting a water temperature threshold used for determining abnormality of the thermostat 17 (step S13). Details of the water temperature threshold setting process will be described later.

Next, the ECU 100 determines whether it is time to acquire the engine outlet water temperature (step S20). In this step, it is determined whether or not it is time to start counting the predetermined period in order to obtain the amount of change in the engine outlet water temperature during the predetermined period (for example, 10 seconds). For example, the ECU 100 determines that the timing at which a predetermined period of time (for example, 10 seconds) has elapsed since the start of the thermostat abnormality determination process is the timing to acquire the engine outlet water temperature.

If it is time to acquire the engine outlet water temperature (step S20/YES), the ECU 100 acquires the engine outlet water temperature (engine outlet water temperature at the start of the predetermined period) (step S21), and proceeds to step S23.

On the other hand, if it is not the time to acquire the engine outlet water temperature (step S20/NO), the ECU 100 determines whether or not the engine outlet water temperature at the start of the predetermined period has been acquired (step S22). If the engine outlet water temperature at the start of the predetermined period has not been acquired (step S22/NO), the process returns to step S11, but if the engine outlet water temperature at the start of the predetermined period has been acquired (step S22/YES), the process proceeds to step S23. .

The ECU 100 determines whether or not a predetermined period of time (for example, 10 seconds) has elapsed after obtaining the engine outlet water temperature at the start of the predetermined period of time (step S23). If the predetermined period has not elapsed (step S23/NO), the process returns to step S11, but if the predetermined period has elapsed (step S23/YES), the ECU 100 sets the engine outlet water temperature (engine outlet water temperature after the predetermined period has elapsed). acquire (step S25).

Next, the ECU 100 calculates the water temperature change amount ( FIG. 3 : step S26). Specifically, the ECU 100 subtracts the engine outlet water temperature at the start of the predetermined period from the engine outlet water temperature after the predetermined period.

The ECU 100 determines whether or not the amount of change in water temperature calculated in step S26 is less than the water temperature threshold (step S27). If the amount of water temperature change is equal to or greater than the water temperature threshold (step S27/NO), the ECU 100 determines that the thermostat 17 is normal and increments the normal counter (step S31).

On the other hand, if the amount of water temperature change is less than the water temperature threshold (step S27/YES), the ECU 100 determines that the engine outlet water temperature is less than 75° C. during the current determination period (for example, from the start of the thermostat abnormality determination process to step S28). (period until start of judgment) It is judged whether or not it has continued (step S28).

If the engine outlet water temperature has remained below 75° C. for the current determination period (step S28/YES), the ECU 100 increments an abnormality counter that counts abnormalities in the thermostat 17 (step S29). This is because, theoretically, when the engine outlet water temperature is less than 75° C., the thermostat 17 is closed and the cooling water does not pass through the radiator 14, so the water temperature change should be equal to or greater than the water temperature threshold. In the present embodiment, the engine outlet water temperature at which the thermostat 17 closes is set to 75° C., but it is not limited to this. The engine outlet water temperature at which the thermostat 17 closes may be, for example, a temperature higher than 75°C, such as 80°C or 85°C, or a temperature lower than 75°C, such as 70°C.

On the other hand, if the determination in step S28 is negative, the process proceeds to step S33.

Next, the ECU 100 determines whether or not the abnormality counter is equal to or greater than a predetermined value (eg, 3) (step S33). If the abnormality counter is greater than or equal to the predetermined value (step S33/YES), the ECU 100 determines that the thermostat 17 is abnormal (step S43), and terminates the processing of FIGS.

On the other hand, if the abnormality counter is less than the predetermined value (step S33/NO), the ECU 100 determines whether the normal counter is equal to or greater than a predetermined value (eg, 3) (step S35).

If the normality counter is less than the predetermined value (step S35/NO), the ECU 100 does not perform the process of step S37 and ends the processes of FIGS. 2 and 3 . On the other hand, if the normality counter is greater than or equal to a predetermined value (eg, 3) (step S35/YES), the ECU 100 turns on the provisional normality determination flag (step S37).

The ECU 100 determines whether or not the temporary normality determination flag is ON and the engine outlet water temperature is 75° C. or higher (step S39). When the temporary normality determination flag is ON and the engine outlet water temperature is 75° C. or higher, the ECU 100 determines that the thermostat 17 is normal (step S41), and terminates the processing of FIGS.

If the determination in step S39 is negative, the ECU 100 terminates the processing of FIGS. 2 and 3 without making a normal determination. This is because when the thermostat 17 is functioning normally, the engine outlet water temperature eventually reaches 75° C. or higher, so by confirming the normality determination after the engine outlet water temperature reaches 75° C. or higher, the thermostat 17 This is to prevent erroneous determination of normality.

(Water temperature threshold setting process: S13)
Next, details of the water temperature threshold value setting process ( FIG. 2 : step S13) executed by the ECU 100 will be described based on the flowchart of FIG. 4 .

In the process of FIG. 4, first, the ECU 100 uses a preset map and/or calculation formula based on the difference between the engine outlet water temperature and the intake air temperature, the amount of intake air, the vehicle speed, and whether or not the fuel is being cut. to calculate the water temperature threshold (step S131). In step S131, the ECU 100 calculates the water temperature threshold when the degree of engine speed increase is less than the speed increase threshold.

Next, the ECU 100 calculates the degree of increase in engine speed (step S133). Specifically, the ECU 100 calculates the difference between the current engine speed and the smoothed value of the engine speed.

Next, the ECU 100 determines whether or not the degree of increase in the engine speed is equal to or greater than the speed increase threshold (step S135). When the degree of increase in the engine speed is less than the speed increase threshold (step S135/NO), the process proceeds to step S20 in FIG. Accordingly, the ECU 100 determines whether or not the thermostat 17 is abnormal using the water temperature threshold calculated in step S131.

On the other hand, if the degree of increase in engine speed is greater than or equal to the speed increase threshold (step S135/YES), the ECU 100 corrects the water temperature threshold (step S137). Specifically, the water temperature threshold is corrected to a value smaller than the water temperature threshold calculated in step S131. That is, when the degree of increase in engine speed is greater than or equal to the speed increase threshold, ECU 100 corrects the water temperature threshold to a value smaller than the water temperature threshold when the degree of increase in engine speed is less than the speed increase threshold. For example, when the water temperature threshold calculated in step S131 is 0.5°C, the ECU 100 corrects the water temperature threshold to 0.3°C when the degree of increase in engine speed is greater than or equal to the speed increase threshold.

Here, the reason why the water temperature threshold is set to a value smaller than the water temperature threshold calculated in step S131 when the degree of increase in the engine speed is equal to or greater than the speed increase threshold will be described.

FIG. 5 is a time chart showing the relationship between the engine speed and the value output from the water temperature sensor 51 (water temperature sensor value) when the heater is in use. As shown in FIG. 5, when the engine speed starts to increase at time t1, the sensor value of the water temperature sensor 51 provided near the outlet 12a of the water jacket 12 starts to decrease at time t2 and then increases again.

This is for the following reasons. When the heater is used in the passenger compartment, the temperature of the cooling water drops in the heater core 15 and rises when the engine main body 10 passes. Here, the faster the cooling water flow rate (the higher the engine speed), the smaller the cooling water temperature drop in the heater core 15 and the cooling water temperature rise in the engine body 10, and the water temperature deviation in the entire cooling system 500. becomes smaller. When the engine speed increases (when the water pump 16 speed increases), the cooling water flow speed increases, so the water temperature difference in the cooling system 500 as a whole changes from "large" to "small". Therefore, the sensor value of the water temperature sensor 51 mounted upstream of the heater core 15 (near the outlet 12a of the water jacket 12) decreases.

At this time, for example, when the engine outlet water temperature at the start of the predetermined period is obtained at time t3, and the engine outlet water temperature after the predetermined period has elapsed is obtained at time t4, the amount of change in water temperature becomes smaller due to the decrease in the water temperature sensor value. Therefore, if the abnormality of the thermostat 17 is detected using the water temperature threshold when the degree of increase in the engine speed is smaller than the engine speed increase threshold (for example, during normal operation), it is possible to erroneously detect the abnormality of the thermostat 17 (stuck open). have a nature.

Therefore, the ECU 100 according to the present embodiment sets the water temperature threshold to a value smaller than the water temperature threshold calculated in step S131 when the degree of increase in the engine speed is equal to or greater than the speed increase threshold. As a result, erroneous detection of an abnormality (stuck open) of the thermostat 17 is suppressed, and the accuracy of detecting an abnormality of the thermostat 17 is improved.

As described above in detail, according to the first embodiment, the cooling water that has passed through the water jacket 12 formed inside the engine body 10 of the internal combustion engine is supplied to the engine body 10 via the radiator 14 . a radiator path 20 that circulates to the water, a water pump 16 that is driven by the engine body 10 and circulates the cooling water, and a water temperature that is provided near the outlet 12a of the water jacket 12 and detects the temperature of the cooling water that has passed through the water jacket 12. A sensor 51, a thermostat 17 that opens when the temperature of the cooling water is equal to or higher than a predetermined temperature (75° C.) to allow the cooling water to flow through the radiator path 20, and a crank that detects the rotation speed of the internal combustion engine. The thermostat 17 is controlled based on the position sensor 52 and whether the amount of change in the temperature of the cooling water detected by the water temperature sensor 51 in a predetermined period is equal to or less than the water temperature threshold when the temperature of the cooling water is below a predetermined temperature. An ECU 100 that detects an abnormality and corrects the water temperature threshold to a lower value than when the degree of increase is less than a predetermined value when the degree of increase in the number of revolutions of the engine body 10 detected by the crank position sensor 52 is equal to or greater than the upper revolution threshold. And prepare. As a result, even if the value of the water temperature sensor 51 temporarily decreases when the engine speed increases and the amount of change in the engine outlet water temperature becomes small, it is possible to prevent erroneous detection of an abnormality (stuck open) of the thermostat 17. can be suppressed. Therefore, the abnormality detection accuracy of the thermostat 17 is improved.

In the first embodiment, the water pump 16 is a water pump (mechanical water pump) driven by the crankshaft of the engine body 10, but the water pump 16 may be an electric water pump. In this case, the water temperature threshold may be corrected based on the degree of increase in the water pump speed instead of the degree of increase in the engine speed.

<<Second Embodiment>>
Especially in a hybrid vehicle, the sensor value of the water temperature sensor 51 described above may drop significantly when the water pump 16 returns from a stopped state. More specifically, when the water pump 16 is a mechanical water pump, the sensor value of the water temperature sensor 51 may drop significantly when the engine recovers from an intermittent stop. Further, when the water pump 16 is an electric water pump, the engine is intermittently stopped and the heater is not used, so that the water pump 16 is stopped. When the water pump 16 starts operating, the sensor value of the water temperature sensor 51 may drop significantly. Therefore, in the second embodiment, when the vehicle is a hybrid vehicle, processing for further correcting the water temperature threshold is performed based on whether or not the water pump 16 has recovered from the stopped state.

FIG. 6 is a schematic diagram showing the configuration of a cooling system 500A to which the control device for an internal combustion engine according to the second embodiment is applied. In the second embodiment, cooling system 500A is mounted on a hybrid vehicle. It is also assumed that the water pump 16 is an electric water pump. Since other configurations are the same as those of the cooling system 500 according to the first embodiment, detailed description thereof will be omitted.

FIG. 7 is a flowchart showing the details of the water temperature threshold setting process executed by the ECU 100 according to the second embodiment.

In the process of FIG. 7, first, the ECU 100 uses a preset map and/or calculation formula based on the difference between the engine outlet water temperature and the intake air temperature, the amount of intake air, the vehicle speed, and whether or not the fuel is being cut. to calculate the water temperature threshold Torg (step S501). In step S501, the ECU 100 calculates a water temperature threshold when the degree of increase in water pump rotation speed (W/P rotation speed) is less than the threshold.

Next, the ECU 100 calculates the degree of increase in the W/P rotation speed (step S503). Specifically, the ECU 100 calculates the difference between the current W/P rotation speed and the smoothed value of the W/P rotation speed.

Next, the ECU 100 determines whether or not the degree of increase in the W/P rotation speed is equal to or greater than a threshold (step S505). If the degree of increase in the W/P rotation speed is less than the threshold (step S505/NO), the process proceeds to step S20 in FIG. Accordingly, the ECU 100 uses the water temperature threshold value Torg calculated in step S501 to determine whether or not the thermostat 17 is abnormal.

On the other hand, if the degree of increase in the W/P rotation speed is equal to or greater than the threshold (step S505/YES), the ECU 100 sets the water temperature threshold correction amount to ΔT (eg, 0.2° C.) (step S507).

Next, the ECU 100 determines whether or not the vehicle has traveled a predetermined distance or longer with the water pump 16 stopped (after W/P stop running) (step S509). Specifically, when the distance traveled by the vehicle with the water pump 16 stopped is greater than or equal to a predetermined threshold value, the ECU 100 determines that the W/P stop running has been performed.

Here, an example method of obtaining the distance traveled by the vehicle while the water pump 16 is stopped will be described. For example, the ECU 100 uses the variable Espdsum to obtain the distance traveled by the vehicle while the water pump 16 is stopped.

The ECU 100 stops the water pump 16 when the processes shown in FIGS. 2 and 3 are completed, when the operating time of the water pump 16 is equal to or greater than a predetermined value, or when the integrated flow rate of the water pump 16 is equal to or greater than a predetermined value. The variable Espdsum representing the distance traveled by the vehicle is reset to zero. The integrated flow rate of the water pump 16 can be calculated by multiplying the target flow rate of the water pump 16 by time. For example, the ECU 100 starts integrating the flow rate of the water pump 16 at the timing when the target flow rate of the water pump 16 becomes equal to or greater than a predetermined value.

After resetting the variable Espdsum, the ECU 100 determines whether the target flow rate of the water pump 16 is less than a predetermined value (eg, 1.5 L/min) at predetermined time intervals. When the target flow rate is less than the predetermined value, the ECU 100 adds a constant Espdcon representing the distance traveled by the vehicle during the predetermined time to the variable Espdsum (Espdsum←Espdsum+Espdcon). Then, when the value of the variable Espdsum obtained after resetting the variable Espdsum to 0 and before the determination in step S509 is equal to or greater than a predetermined threshold value, the ECU 100 determines that the W/P stop running has been performed. to decide.

If the W/P stop running is not executed (step S509/NO), the ECU 100 uses the water temperature threshold correction amount ΔT to calculate the water temperature threshold Tc (step S515). More specifically, the water temperature threshold Tc is calculated by subtracting the water temperature threshold correction amount ΔT from the water temperature threshold Torg calculated in step S501. That is, water temperature threshold Tc=Torg-ΔT.

On the other hand, if the W/P stop running has been performed (step S509/YES), the ECU 100 corrects the water temperature threshold correction amount ΔT to calculate the water temperature threshold Tc (step S513). More specifically, the water temperature threshold value Tc is calculated by multiplying the correction amount ΔT of the water temperature threshold value by a coefficient K larger than 1 and subtracting it from the water temperature threshold value Torg calculated in step S501. That is, water temperature threshold Tc=Torg-ΔT×K. Therefore, the water temperature threshold Tc after W/P stop running is lower than the water temperature threshold Tc when W/P stop running is not performed.

Here, the reason why the ECU 100 corrects the correction amount ΔT of the water temperature threshold when the W/P stop running has been executed will be described.

FIG. 8A is a time chart showing an example of the relationship between the engine speed, the water pump flow rate, and the value output from the water temperature sensor 51 (water temperature sensor value) in a hybrid vehicle. FIG. 8B is an enlarged view of the vicinity of time t12 in FIG. 8A.

In FIG. 8A, during period D1 between time t11 and time t12, the engine is intermittently stopped (engine speed=0 [rpm]) and the heater is not used (heater off). 16 is stopped (water pump flow rate = 0 [L/min]). During the period D1, the cooling water in the cooling water pipe around the radiator 14 is cooled by running wind, but the cooling water remaining in the water jacket 12 inside the engine body 10 is not cooled. Here, as shown in FIG. 8(A), at time t12, when the engine is restored from the intermittent stop, the engine speed increases, and when the water pump 16 is restored from the stopped state, the dotted line in FIG. 8(A) , the water temperature sensor value (engine water temperature) rises sharply and then falls sharply. This is presumably because the cooling water around the radiator 14 cooled by the running wind during the period D1 is mixed with the warm cooling water inside the engine body 10 .

At this time, for example, as shown in FIG. 8B, when the engine outlet water temperature at the start of the predetermined period is obtained at time t13, and the engine outlet water temperature after the predetermined period has elapsed is obtained at time t14, the effect of the decrease in the water temperature sensor value is , the amount of change in water temperature becomes smaller. Moreover, the amount of change in water temperature is smaller than the amount of change in water temperature when the W/P stop running is not performed. Therefore, if abnormality of the thermostat 17 is detected using the water temperature threshold value (Tc=Torg-ΔT) when the W/P stop running is not performed, there is a possibility that the abnormality of the thermostat 17 is erroneously detected.

Therefore, in the second embodiment, when the vehicle is a hybrid vehicle, the ECU 100 sets the water temperature threshold value to the rotational speed is set to a smaller value than when the degree of increase in is less than the threshold, and furthermore, when the W/P stop running has been implemented, the water temperature threshold is set to a smaller value. In other words, the ECU 100 sets the water temperature threshold value to a value smaller than the water temperature threshold value when the W/P stop running is not performed after the W/P stop running. As a result, erroneous detection of an abnormality (stuck open) of the thermostat 17 is suppressed, and the accuracy of detecting an abnormality of the thermostat 17 is improved.

Although FIG. 7 described the processing when the water pump 16 is an electric water pump, the water pump 16 may be a mechanical water pump. In this case, as shown in FIG. 9, the ECU 100 calculates the degree of increase in the engine speed in step S503A corresponding to step S503 in FIG. Further, in step S505A corresponding to step S505 in FIG. 7, it is determined whether or not the degree of increase in the engine speed is equal to or greater than the speed increase threshold.

In step S509A corresponding to step S509 in FIG. 7, the ECU 100 determines that the distance traveled by the vehicle with the engine stopped (that is, the vehicle travels only by the electric motor with the engine stopped intermittently) is equal to or greater than a predetermined threshold. (whether or not the engine has been intermittently stopped). This is because, in the case of the mechanical water pump, if the engine is stopped, the water pump 16 is also stopped. Whether or not the engine is intermittently stopped may be determined by, for example, whether or not the engine speed is equal to or lower than a predetermined speed.

If the engine is intermittently stopped (step S509A/YES), the ECU 100 sets the water temperature threshold value Tc to Tc=Torg-ΔT×K (step S513). On the other hand, if the engine is not intermittently stopped (step S509A/NO), the ECU 100 sets the water temperature threshold Tc to Tc=Torg-ΔT (step S515).

As described above, the process shown in FIG. 9 can appropriately correct the water temperature threshold even in a hybrid vehicle equipped with a mechanical water pump. Abnormality detection accuracy can be improved.

The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited to these, and various modifications of these examples are within the scope of the present invention, and furthermore, It is self-evident from the above description that many other embodiments are possible within the scope.

10 engine body 12 water jacket 12a outlet 14 radiator 16 water pump 17 thermostat 20 radiator path 25 bypass path 51 water temperature sensor 52 crank position sensor 100 ECU
500,500A cooling system

Claims (1)

a radiator path for recirculating a cooling medium that has passed through a cooling passage formed inside an engine body of an internal combustion engine to the engine body via a radiator;
a pump driven by the internal combustion engine for circulating the cooling medium;
a temperature detection unit provided near an outlet of the cooling passage for detecting the temperature of the cooling medium that has passed through the cooling passage;
a thermostat that opens when the temperature of the cooling medium is equal to or higher than a predetermined temperature to allow the cooling medium to flow through the radiator path;
a rotation speed detection unit that detects the rotation speed of the internal combustion engine;
When the temperature of the cooling medium is lower than the predetermined temperature, the temperature of the thermostat is determined based on whether or not the amount of change in the temperature of the cooling medium detected by the temperature detection unit in a predetermined period is equal to or less than a first threshold. an anomaly detection unit that detects an anomaly;
The degree of increase in the rotational speed of the internal combustion engine detected by the rotational speed detection unit corresponds to the amount of change in the temperature of the cooling medium over a predetermined period of time when the change in the flow velocity of the cooling medium accompanying the increase in the rotational speed of the internal combustion engine. If it is equal to or greater than a second threshold value indicating the degree of increase in the rotational speed that affects the thermostat , the first threshold value is set to a smaller value than when the degree of increase in the rotational speed is less than the second threshold value, and the thermostat is determined to be abnormal. a correction unit that corrects to a value that suppresses erroneous detection ;
A control device for an internal combustion engine.

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