JPH10184433A - Thermostat trouble detecting device for engine cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely detect a failure in operation of a thermostat by a comparatively low-cost means. SOLUTION: When an opening trouble wherein a thermostat 13 is not closed but left opened occurs, in a temperature range where if the thermostat 13 is normal, it is closed, behavior at a cooling water temperature on the engine side is widely different from behavior of that during normal operation, whereby in the temperature area, based on a cooling water temperature on the engine side detected by a cooling water temperature sensor 20, the presence of an opening trouble of the thermostat 13 is diagnosed. When a release trouble where the thermostat 13 is not opened and left closed occurs, behavior at a cooling water temperature on the engine side is widely differed from that of normal operation in a temperature region where the thermostat 13 is opened normally, whereby at the temperature region, based on a cooling water temperature on the engine side detected by the cooling water temperature sensor 20, the presence of the closing trouble of a thermostat 13 is diagnosed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermostat fault detecting device for an engine cooling system for detecting the presence or absence of a fault in a thermostat for adjusting the temperature of engine cooling water.

[0002]

2. Description of the Related Art Generally, in a water-cooled engine, a thermostat that automatically opens and closes according to the temperature of a cooling water is provided in a cooling water circulation path for circulating the cooling water between a cooling water passage (water jacket) in the engine and a radiator. Until the warm-up operation is completed after the engine is started, the thermostat is closed to stop the circulation of cooling water, and the temperature of the cooling water on the engine side is quickly raised to an appropriate temperature range to improve fuel efficiency and reduce emissions. Automatically opens the thermostat when the engine coolant temperature exceeds the appropriate temperature range.
The cooling water on the radiator side is circulated to the engine side to lower the cooling water temperature on the engine side to an appropriate temperature range.

[0003]

The failure modes of the thermostat include an open failure in which the thermostat is left open and a closed failure in which the thermostat is left closed. When an open failure occurs, even during a cold start, in which the engine is started in a cold state, the cooling water in the radiator is circulated through the engine from the beginning of the start, so the temperature of the cooling water on the engine side after starting increases. , The warm-up of the engine is delayed, leading to deterioration of fuel efficiency and increase in emissions. Also, when a closed failure occurs, even when the temperature of the cooling water on the engine side exceeds the proper temperature range, the cooling water on the radiator side is not circulated to the engine side. There is a risk of overheating.

[0004] Therefore, when a failure of the thermostat occurs, it is desirable to immediately detect the failure and warn the driver. However, to date, no technology has been developed to detect the failure of the thermostat. However, there is a risk that the vehicle may be operated without knowing it for a long period of time, or may continue to operate until the engine overheats in the event of a closed failure.

As a known technique for detecting a failure in the engine cooling system, as shown in Japanese Patent Laid-Open No. 19329/1992, water temperature sensors are provided at the inlet and outlet of a radiator, respectively, so that the inlet and outlet water temperatures of the radiator can be measured. There is one that evaluates the heat radiation performance of a radiator based on the radiator and detects deterioration of the radiator. Since the thermostat automatically opens and closes according to the temperature of the cooling water on the engine side, even if the temperature of the cooling water on the radiator side, which is unrelated to the opening and closing operation of the thermostat, is detected at two points as in the above-described known technology. No thermostat failure can be detected. In addition, two new temperature sensors have to be provided on the radiator side, which has the disadvantage of increasing the cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to detect a thermostat failure in an internal combustion engine cooling system capable of detecting a failure of the thermostat accurately with relatively inexpensive means. It is to provide a device.

[0007]

First, in order to facilitate understanding of the present invention, the behavior of the cooling water temperature when a thermostat fails will be described with reference to FIGS. 2, 4, 7, and 9. FIG.

FIGS. 2, 4, 7, and 9 all show the behavior of the engine-side cooling water temperature after startup when an open failure occurs in which the thermostat is left open, as compared with the normal state. Things. During cold start, when the engine is cold, since the thermostat is closed if the thermostat is normal, the circulation of cooling water is stopped, and the engine-side cooling water temperature starts to rise immediately immediately after starting, When an open failure occurs, even during a cold start, the cooling water in the radiator circulates through the engine from the beginning of the start. The temperature temporarily drops due to the inflow of water, and thereafter, the engine-side cooling water temperature gradually rises.

Focusing on such behavior of the engine-side cooling water temperature, the thermostat failure detecting device according to claim 1 of the present invention determines the cooling water temperature (engine-side cooling water temperature) of the cooling water circulation path on the engine side of the thermostat. If the thermostat is normal, it is detected by the detection means, and if the thermostat is normal, the presence or absence of an open failure of the thermostat is diagnosed by the open failure diagnosis means based on the engine-side cooling water temperature detected by the cooling water temperature detection means. . If the thermostat is normal, the behavior of the engine-side cooling water temperature differs greatly between the normal state and the time of the open failure in the closed temperature range. A good diagnosis can be made. In addition, since the cooling water temperature detecting means may use an engine controlling water temperature sensor that is also provided in the conventional engine, there is no need to add a new cooling water temperature detecting means to the conventional engine control system, and the cost is reduced. There are also significant advantages in terms of aspects.

In this case, the amount or rate of decrease in the engine-side cooling water temperature immediately after the start of the engine is determined, and the presence or absence of an open failure is determined based on the amount or rate of the decrease in the engine-side cooling water temperature. The diagnosis may be made. Even when the engine is stopped, the radiator is exposed to the outside air, so the radiator-side cooling water temperature is lower than the engine-side cooling water temperature. Therefore, when an open failure occurs, the engine-side cooling water temperature is temporarily reduced immediately after the start due to the inflow of the cooled cooling water on the radiator side. Diagnosis can be made with high accuracy.

Alternatively, the amount of increase in the temperature of the engine-side cooling water until one of the elapsed time after the start of the engine, the number of ignitions, and the integrated value of the heat generated by the engine reaches a predetermined value is determined. The presence or absence of an open failure may be diagnosed based on the amount of increase in the engine-side cooling water temperature. Here, the period for determining the amount of increase in the engine-side cooling water temperature may be determined by the elapsed time after the start of the engine, or may be determined by the number of ignitions or the integrated value of the amount of heat generated by the engine. If it is determined by the number of ignitions or the integrated value of the calorific value of the engine, it is possible to eliminate the influence of the fluctuation of the increase amount of the engine-side cooling water temperature due to the fluctuation of the engine operating state, and to improve the accuracy of diagnosis of the open failure.

[0014] Further, after the engine is started, the engine-side cooling water temperature may be increased until the temperature rises to a predetermined amount.
Alternatively, one of the elapsed time until the engine-side cooling water temperature reaches the predetermined water temperature, the number of ignitions, and the integrated value of the heat generated by the engine may be determined, and the presence or absence of the open failure may be diagnosed based on the determined value. Even in this case, the above claim 3
In the same manner as described above, an open fault can be diagnosed with high accuracy.

Further, at the time of an open failure, the rate of increase in the temperature of the engine-side cooling water is smaller than that in the normal state, so that the rate of increase in the temperature of the engine-side cooling water is periodically determined after the engine is started. The presence / absence of an open failure may be diagnosed based on the number of times that the rate of rise of the engine-side cooling water temperature has become equal to or less than a predetermined value. This makes it possible to repeat the diagnosis of the open failure based on the rate of increase in the temperature of the engine-side cooling water, thereby making it possible to diagnose the open failure with high reliability.

In this case, the rate of rise of the engine-side cooling water temperature is determined according to claim 6, wherein the water temperature rise per predetermined time, the water temperature rise per predetermined number of ignitions, and the water temperature rise per predetermined heat generated by the engine. The determination may be made by either of the above. Here, when the rate of increase of the engine-side cooling water temperature is determined from the amount of water temperature rise per predetermined number of ignitions or the amount of water temperature rise per predetermined amount of heat generated by the engine, the effect of the fluctuation of the rate of increase of the engine-side cooling water temperature due to the fluctuation of the engine operating state Can be eliminated, and the accuracy of diagnosis of an open fault can be improved.

Further, the vehicle speed, the outside air temperature, the intake air temperature, and the operating state of the air conditioner all affect the heat radiation amount of the cooling water and fluctuate the behavior of the engine-side cooling water temperature. The data used for the open failure diagnosis processing is at least one of vehicle speed, outside air temperature, intake air temperature, and operating state of the air conditioner.
The correction may be based on the With this configuration, it is possible to diagnose an open failure in consideration of the amount of heat dissipated in the cooling water, and accordingly, it is possible to improve the accuracy of diagnosis of the open failure.

Next, a method of diagnosing a closed failure in which the thermostat is closed without opening the thermostat will be described. FIG. 12 shows the behavior of the engine-side cooling water temperature at the time of occurrence of the closing failure in comparison with the normal operation. When the engine coolant temperature exceeds the thermostat valve opening temperature, the valve opens if the thermostat is normal, and the cooling water on the radiator side is circulated to the engine side, and the engine coolant temperature drops. At times, the thermostat does not open, the cooling water is not circulated, and the engine-side cooling water temperature continues to rise.

Attention is paid to this point. In the eighth and ninth aspects, if the thermostat is normal, it is determined whether or not the thermostat is closed based on the engine-side cooling water temperature detected by the cooling water temperature detecting means in the open temperature range. Diagnosis is made by the closed failure diagnosis means. If the thermostat is normal, the behavior of the engine-side cooling water temperature in the open temperature range is significantly different from that of the normal state and the time of the closed failure. A good diagnosis can be made.

In this case, the change rate of the engine-side cooling water temperature after reaching the temperature range in which the thermostat opens after the engine is started is determined, and based on the change rate of the engine-side cooling water temperature. The presence or absence of the thermostat closing failure may be diagnosed. That is, as shown in FIG. 12, the rate of change of the engine-side cooling water temperature after reaching the temperature range in which the thermostat opens is greatly different between the normal state and the closed state. Thus, the presence or absence of a closed failure can be diagnosed with high accuracy.

Here, the rate of change of the engine-side cooling water temperature is:
As in the eleventh aspect, the determination may be made based on any of the water temperature change amount per predetermined time, the water temperature change amount per predetermined number of ignitions, and the water temperature change amount per predetermined engine generated heat. Judging from the change in water temperature per predetermined number of ignitions and the change in water temperature per predetermined heat generated by the engine, it is possible to eliminate the effect of fluctuations in the rate of change in engine-side cooling water temperature due to fluctuations in engine operating conditions, and to improve the accuracy of diagnosis of open failures. it can.

Further, a diagnosis of a closed failure may be made when the integrated value of the heat generated by the engine after starting the engine reaches a predetermined amount. With this configuration, it is determined whether or not the time for performing the diagnosis of the closing failure (that is, within a predetermined period after the temperature reaches the temperature range in which the thermostat opens) without being affected by the fluctuation of the engine operating state. The determination can be made with high accuracy.

Alternatively, the diagnosis of the closing failure may be made when the engine-side cooling water temperature becomes higher than the thermostat valve opening temperature by a predetermined temperature. That is, as shown in FIG. 12, at the time of the closing failure, the engine-side cooling water temperature continues to rise above the thermostat valve opening temperature, so that the engine-side cooling water temperature becomes higher than the thermostat valve opening temperature by a predetermined temperature. If the failure diagnosis is performed, the close failure diagnosis can be accurately performed at the time when the behavior of the engine-side cooling water temperature is most greatly different between the normal time and the closed failure time.

Further, the vehicle speed, the outside air temperature, the intake air temperature, and the operating state of the air conditioner all affect the amount of heat radiated from the cooling water and fluctuate the behavior of the temperature of the engine side cooling water.
As described above, the data used for the closing failure diagnosis processing may be corrected based on at least one of the vehicle speed, the outside air temperature, the intake air temperature, and the operating state of the air conditioner. With this configuration, it is possible to diagnose a closed failure in consideration of the amount of heat dissipated in the cooling water, and the diagnostic accuracy of the closed failure can be improved accordingly.

When the radiator fan for cooling the radiator is constituted by an electric fan, a diagnosis of a closed failure may be made during a period in which the radiator fan is stopped. . If you do this,
It is possible to prevent the temperature of the engine-side cooling water from lowering due to the operation of the radiator fan, and accordingly, it is possible to improve the diagnosis accuracy of the closing failure.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, based on FIG.
A schematic configuration of the entire cooling system 1 will be described. A water jacket 12 is provided inside the cylinder block and the cylinder head of the engine 11.
Cooling water is injected into 2. A thermostat 13 is provided at an outlet of the water jacket 12, and high-temperature cooling water passing through the thermostat 13 is sent to a radiator 15 via a cooling water circulation path 14. The cooling water whose temperature is lowered by radiating the heat in the radiator 15 is returned into the water jacket 12 through the cooling water circulation path 16. Therefore, when the thermostat 13 is opened, the cooling water circulates along the route of the water jacket 12, the thermostat 13, the cooling water circulation passage 14, the radiator 15, the cooling water circulation passage 16, and the water jacket 12.
Cool 1 to a suitable temperature.

A water pump 17 is provided at the inlet of the water jacket 12, and the water pump 17 is driven to rotate by engine power transmitted through a belt 19, and the rotation of the water pump 17 causes the cooling water to circulate. The cooling water in the path is forcibly circulated. On the other hand, behind the radiator 15, a radiator fan 18 composed of an electric fan is installed, and the rotation of the radiator fan 18 enhances the heat radiation effect of the radiator 15, thereby promoting the cooling of the cooling water in the radiator 15. You.

In the cylinder block of the engine 11, a cooling water temperature sensor 20 (cooling water temperature detecting means) for detecting a cooling water temperature (cooling water temperature on the engine side) in the water jacket 12, which is a cooling water circulation path closer to the engine 11 than the thermostat 13 is. Is provided. The mounting position of the engine-side cooling water temperature sensor 20 may be a cooling water circulation path on the engine 11 side of the thermostat 13, and may be mounted on a portion of the water jacket 12 on the cylinder head side, for example.

The output signal of the cooling water temperature sensor 20 is taken into an electronic control unit 22 (hereinafter abbreviated as "ECU"). The ECU 22 is mainly composed of a microcomputer, and performs engine control and thermostat failure diagnosis. The ECU 22 is an engine control ECU.
And a thermostat failure diagnosis ECU, or one ECU may perform both engine control and thermostat failure diagnosis.

The ECU 22 includes, as information for performing engine control and thermostat failure diagnosis, a cooling water temperature signal from the cooling water temperature sensor 20, an engine speed signal from an engine speed sensor 23, and an intake air sensor 24. , An intake air temperature signal from an intake air temperature sensor 25, a vehicle speed signal from a vehicle speed sensor 26, and a signal indicating an operation state of a blower motor (not shown) of the air conditioner 27 are also read. The ECU 22 includes a warning lamp 28 which is a warning means for warning when a failure of the thermostat 13 is detected, and a thermostat 1.
A backup RAM 29 which is a writable nonvolatile memory for storing the failure information of No. 3 is connected. The backup RAM 29 is supplied with power from a battery (not shown) even when the engine is stopped, retains the memory of the failure information, and can read the failure information at the time of repair / inspection.

The ROM (storage medium) built in the ECU 22 stores programs for diagnosing thermostat failures, which will be described later, and executes these programs to diagnose the presence or absence of an open failure and a closed failure of the thermostat 13. I do. In this case, an open failure in which the thermostat 13 is left open is performed by any one of the following five diagnostic methods.

[Open Fault Diagnosis (1)] First, the outline of the open fault diagnosis (1) will be described with reference to FIG. FIG. 2 shows the behavior of the engine-side cooling water temperature after starting when the thermostat 13 has an open failure in comparison with the normal state. During a cold start in which the engine 11 is started in a cold state, since the thermostat 13 is closed if the thermostat 13 is normal, the circulation of the cooling water is stopped, and the engine-side cooling water temperature starts to rise immediately immediately after the start. However, if an open failure occurs, the radiator
In the event of an open failure, the temperature of the engine-side cooling water temporarily drops due to the inflow of the cooling water on the radiator 15 side, and the engine-side cooling water then immediately cools down. The cooling water temperature gradually rises. The temporary decrease in the engine-side cooling water temperature immediately after the start, which occurs at the time of the opening failure described above, is caused by the fact that the radiator is continuously exposed to the outside air while the engine is stopped.
This is a phenomenon that occurs because the radiator-side cooling water temperature is lower than the engine-side cooling water temperature.

The open-circuit failure diagnosis (1) focuses on a temporary decrease in the engine-side cooling water temperature immediately after the start, which occurs at the time of the open-circuit failure. The open-circuit failure diagnosis program shown in FIG. The amount of reduction is determined, and the amount of reduction is compared with a determination value to diagnose the presence or absence of an open failure. Hereinafter, processing contents of the open failure diagnosis program shown in FIG. 3 will be described.
This program is started at a predetermined time interval or at a predetermined crank angle after the ignition key (IG key) is turned on, and plays a role as an open-failure diagnosis means referred to in the claims.

When this program is started, it is first determined in step 101 whether or not the IG key is on and before the engine is started. If it is before the engine is started, the process proceeds to step 102 in which the engine temperature detected by the coolant temperature sensor 20 is detected. After storing the side cooling water temperature as initial values of the starting water temperature THWS and the minimum water temperature THWmin, in step 103, a starter (not shown) is turned on to start the engine 11.

Thereafter, in step 104, it is determined whether or not the engine is in cold start based on whether or not the starting water temperature THWS is lower than a predetermined temperature (a predetermined temperature equal to or lower than the valve closing temperature of the thermostat 13). If not, the program ends without performing the subsequent diagnostic processing.

On the other hand, in the case of a cold start, the minimum water temperature THWmin is updated every time the engine-side cooling water temperature THW decreases during a period from the start until a predetermined time elapses by the processing of steps 105 to 108. When a predetermined time has elapsed from the start, the routine proceeds to step 109, in which the engine-side cooling water temperature decrease amount ΔTHW after the start is obtained by subtracting the minimum water temperature THWmin up to that point from the start-time water temperature THWS.

Thereafter, in step 110, the engine-side cooling water temperature decrease ΔTHW after starting is compared with a judgment value. If the engine-side cooling water temperature decrease ΔTHW is larger than the judgment value, the routine proceeds to step 111, where the thermostat 13 is turned on. It is determined that an open failure has occurred, and in the next step 112, the information of the open failure is stored in the backup RAM 29, and in step 113, the warning lamp 28 is turned on or blinks to warn the driver and warn the driver. finish. If it is determined in step 110 that the engine-side cooling water temperature decrease amount ΔTHW is equal to or smaller than the determination value, the program is terminated without determining that an open failure has occurred.

In this program, the diagnosis of the open failure is made based on the amount of decrease in the engine-side coolant temperature after starting ΔTHW. However, the rate of decrease in the engine-side coolant temperature after start (water temperature increase per predetermined time, predetermined The diagnosis of the open failure may be made based on the water temperature rise per ignition count or the water temperature rise per predetermined engine generated heat.

[Open Fault Diagnosis (2)] First, the outline of the open fault diagnosis (2) will be described with reference to FIG. FIG. 4 shows the behavior of the engine-side cooling water temperature after the start when the thermostat 13 has an open failure in which the thermostat 13 is left open in comparison with the normal state. When an open failure occurs, even during a cold start, since the cooling water in the radiator 15 is circulated into the engine 11 from the beginning of the start, at the time of the open failure, the temperature of the engine-side cooling water after startup is normal. Will be much slower than that.

Focusing on this characteristic, in the open-circuit failure diagnosis (2), the amount of increase in the engine-side cooling water temperature within a predetermined time after starting the engine is determined by the open-circuit failure diagnosis program shown in FIG. Is compared with a determination value to diagnose the presence or absence of an open failure. Hereinafter, processing contents of the open failure diagnosis program shown in FIG. 5 will be described. This program is started at predetermined time intervals or at predetermined crank angle intervals after the IG key is turned on, and plays a role as an open failure / failure diagnosis means referred to in the claims.

When this program is started, step 1
In the steps 21 to 124, the engine 11 is started after reading the water temperature at the start, similarly to the above-described open failure diagnosis (1), and in the case of the cold start, the processing after the step 125 is executed as follows. First, in steps 125 and 126, the time during which the engine has been idling since the cold start is accumulated by a post-start time timer. When the accumulated time reaches a predetermined time (step 127), the current engine-side cooling water temperature is measured. Then, the engine-side coolant temperature rise ΔTHW within a predetermined time after the cold start is calculated by subtracting the starting coolant temperature from (step 128).

If the idle state does not continue until a predetermined time elapses after the cold start (when the determination in step 125 is "No"), the diagnosis processing in step 126 and subsequent steps is performed without performing the diagnosis processing. Quit the program.
This is because if the idle state does not continue for a predetermined time,
This is because the amount of heat generated by the engine within a predetermined time fluctuates, and the amount of increase in the engine-side cooling water temperature ΔTHW fluctuates.

If the idle state has continued for a predetermined time after the cold start, in step 129, the above-mentioned step 128 is performed.
The engine-side coolant temperature rise ΔTHW calculated in the above is compared with a determination value. If the engine-side coolant temperature rise ΔTHW is larger than the determination value, it means that the rise speed of the engine-side coolant temperature is fast. Then, it is determined that the thermostat 13 is normally closed, and the program ends.

On the other hand, if it is determined in step 129 that the engine-side coolant temperature rise .DELTA.THW is equal to or smaller than the determination value, it means that the engine-side coolant temperature rise speed is slow, so the process proceeds to step 131, and the thermostat 13 Is determined to have an open fault, and in the next step 132, information on the open fault is stored in the backup RAM 29, and
In step 133, the warning lamp 28 is turned on or blinks to warn the driver, and the program ends.

In this program, in consideration of the fact that the engine operating condition affects the behavior of the engine-side cooling water temperature, the open failure is diagnosed during the continuation of the idling. If there is a period in which the operation state is substantially constant, an open failure diagnosis may be performed during that period.

[Open Fault Diagnosis (3)] In the open fault diagnosis (2), since the engine-side coolant temperature rise ΔTHW within a predetermined time after the cold start is calculated, the idle state is switched from the cold start to the predetermined time. By calculating the engine-side cooling water temperature rise ΔTHW when the engine is continuously operated, the influence of the fluctuation of the engine operating state is prevented. Accordingly, in the open failure diagnosis (2), the diagnosis of the open failure cannot be performed unless the idle state continues for a predetermined time from the cold start.

Therefore, in the open failure diagnosis (3), the engine heat generated after the cold start is determined so that the open failure diagnosis can be performed accurately even when the idle state does not continue from the cold start. By integrating and calculating the engine-side coolant temperature rise during the period until the integrated value becomes a predetermined value, it is possible to eliminate the influence of the change in the engine-side coolant temperature rise due to the change in the engine operating state. I have.

The processing contents of the open failure diagnosis program shown in FIG. 6 for performing the processing of the open failure diagnosis (3) will be described below. This program is started at predetermined time intervals or at predetermined crank angle intervals after the IG key is turned on, and plays a role as an open failure / failure diagnosis means referred to in the claims.

This program differs from the program shown in FIG. 5 used in the open failure diagnosis (2) only in the processing of steps 125a to 127a relating to the calculation of the engine-side cooling water temperature rise. Is the same. Therefore, only the processing of steps 125a to 127a will be described.

At the time of cold start, after reading the engine speed NE and the intake air amount G in step 125a,
At 26a, an engine generated heat amount Q corresponding to the current engine speed NE and the load G / NE is calculated from a two-dimensional map of the engine generated heat amount Q which parameters the engine speed NE and the load G / NE. Then, the next step 126b
Then, the accumulated heat value of the engine の Q (i-1) is added to the accumulated heat value of the engine 今 回 Q (i-1) to update the accumulated heat value of the engine 、 Q (i). It is determined whether or not the calorific value ΣQ (i) has reached a predetermined value.

Then, when the integrated value of heat generated by the engine ΣQ (i) after the cold start reaches a predetermined value, step 128
Then, the engine-side coolant temperature rise ΔTHW after the cold start is calculated by subtracting the starting coolant temperature from the current engine-side coolant temperature. Subsequent processing is the same as in the open failure diagnosis (2).

As described above, if the engine-side cooling water temperature increase ΔTHW until the integrated value of the heat generated by the engine 冷 Q (i) after the cold start reaches the predetermined value is calculated and the open failure is diagnosed, the engine operation can be started. The influence of the fluctuation of the amount of increase in the engine-side cooling water temperature due to the fluctuation of the state can be eliminated, and the diagnosis accuracy of the open failure can be improved.

Instead of the heat generated by the engine, the number of ignitions may be integrated, and the engine-side coolant temperature rise until the integrated value reaches a predetermined value may be calculated to diagnose the open failure. Even in this case, the influence of the fluctuation in the amount of increase in the engine-side cooling water temperature due to the fluctuation in the engine operating state can be reduced, and the diagnosis accuracy of the open failure can be improved.

[Open Fault Diagnosis (4)] In the open fault diagnosis (2) and (3) described above, the elapsed time after the cold start or the cumulative value of the calorific value of the engine (or the number of ignitions) reaches a predetermined value. The amount of increase in the engine-side cooling water temperature is determined, and the presence or absence of an open failure is diagnosed based on the amount of increase in the engine-side cooling water temperature. In the open failure diagnosis (4), as shown in FIG. The elapsed time until the engine-side cooling water temperature reaches the predetermined water temperature after the start of the engine is calculated, and the presence or absence of an open failure is diagnosed from the length of the time.

The processing content of the open fault diagnosis program shown in FIG. 8 for performing the open fault diagnosis (4) will be described below. This program is started at predetermined time intervals or at predetermined crank angle intervals after the IG key is turned on, and plays a role as an open failure / failure diagnosis means referred to in the claims.

When this program is started, first, the starting water temperature THWS is read before starting (steps 141 and 1).
42) Then, after the determination value K for the open failure determination according to the starting water temperature THWS is calculated by a preset map or mathematical formula (Step 143), the engine 11 is started (Step 144). And if it is a cold start,
The time during which the idle state continues from the start is integrated by the post-start time timer (steps 145 to 14).
7). The operation of integrating the after-start time timer is continued until the engine side coolant temperature THW detected by the coolant temperature sensor 20 rises to a predetermined coolant temperature (step 148).

If the accelerator is turned on and the engine is not in an idle state before the engine-side cooling water temperature THW rises to a predetermined water temperature (when the determination is "No" in step 146), the following diagnostic processing is performed. This program is terminated without performing. This is because when the engine is no longer in the idle state, the heat generated by the engine fluctuates, and the degree of increase in the engine-side cooling water temperature THW fluctuates.

After the cold start, if the idling state continues until the engine side coolant temperature THW rises to a predetermined water temperature, the accumulated time of the post-start time timer at that time, that is, from the time after the cold start to the time when the engine side The time required for the cooling water temperature THW to rise to the predetermined water temperature is compared with the determination value K calculated in step 143. If this time is shorter than the determination value K, the rate of increase of the engine-side cooling water temperature is reduced. Since it means that it is fast, the process proceeds to step 150, where it is determined that the thermostat 13 is normally closed, and the program is terminated.

On the other hand, if it is determined in step 149 that the time required for the engine-side cooling water temperature THW to rise to the predetermined water temperature is equal to or greater than the determination value K, the engine-side cooling water temperature rising speed is slow. In step 151, it is determined that the thermostat 13 has an open failure, and in the next step 152, the backup RAM 2
In step 153, the information of the open failure is stored in
Then, the warning lamp 28 is turned on or blinks to warn the driver and the program is terminated.

In this program, in consideration of the fact that the time required for the engine side coolant temperature THW to rise to the predetermined coolant temperature after the cold start differs depending on the coolant temperature THWS at the time of starting, step 143 is performed according to the coolant temperature THWS at the start. The determination value K for determining the open failure is calculated. This makes it possible to diagnose a highly reliable open failure that is not affected by the starting water temperature THWS.

Instead of integrating the time until the engine-side cooling water temperature THW rises to a predetermined temperature, the time until the amount of increase in the engine-side cooling water temperature THW after starting reaches a predetermined amount is integrated. The diagnosis of the open failure may be performed based on the accumulated time. In this case, the starting water temperature T
There is an advantage that the effect of HWS on the integration time is reduced.

The object to be integrated may be replaced by the heat generated by the engine or the number of ignitions from the elapsed time after the start.
When integrating the heat generated by the engine, the same procedure as in steps 125a to 126b in FIG. 6 may be performed. And
After the cold start, the integrated value of the heat generated by the engine (or the number of times of ignition) until the engine-side cooling water temperature reaches the predetermined water temperature or the amount of increase in the engine-side cooling water temperature reaches the predetermined amount is compared with the judgment value, and an open failure occurs. The diagnosis may be made. With this configuration, the influence of the fluctuation of the engine-side cooling water temperature due to the fluctuation of the engine operating state can be eliminated, and the diagnosis of the open failure can be performed accurately even if the idle state does not continue.

[Open Failure Diagnosis (5)] In the open failure diagnosis (5), as shown in FIG. 9, the amount of increase ΔTHW in the engine-side cooling water temperature is determined every predetermined time after the engine is started, and the engine-side cooling water temperature is determined. The presence or absence of an open failure is diagnosed based on the number of times the amount of rise becomes equal to or less than the determination value.

FIG. 10 showing the processing of the open failure diagnosis (5)
The processing contents of the open failure diagnosis program shown in FIG. 11 will be described. This program is started at predetermined time intervals or at predetermined crank angle intervals after the IG key is turned on, and plays a role as an open failure / failure diagnosis means referred to in the claims.

When this program is started, step 1
In steps 61 to 164, the engine 11 is started after reading the water temperature at startup, similarly to the above-described open failure diagnosis (1). In the case of a cold start, the processing after step 165 is executed as follows. First, at step 165, the provisional fail counter is cleared, and the processing at steps 166 to 171 continues until the engine-side coolant temperature THW reaches the valve opening temperature of the thermostat 13. The process of calculating the water temperature rise ΔTHW within the time is repeated.

That is, if the engine-side cooling water temperature THW is lower than the valve opening temperature of the thermostat 13, a two-dimensional map is obtained from the engine speed NE and the intake air amount G (load G / NE) through the processing of steps 167 to 169. Is calculated, and the accumulated heat generated by the engine Q is added to the accumulated heat generated by the engine ΣQ (i-1) to update the accumulated heat generated by the engine ΣQ (i). This integrated value of the heat generated by the engine ΣQ is calculated in Step 17 described later.
3 is used to calculate a judgment value of the open failure.

Every time a predetermined time elapses, in step 171, the engine-side cooling water temperature THW at that time is stored as the current water temperature THWF (i).
In step 2, the current water temperature THWF (i) is changed to the previous water temperature THWF.
By subtracting (i-1), the amount of water temperature rise per predetermined time Δ
Calculate THW.

Thereafter, in step 173, a judgment value corresponding to the integrated value of the heat generated by the engine ΣQ (i) within the predetermined time calculated in step 169 is calculated by a preset map or mathematical formula. As a result, the determination value is calculated in consideration of the influence of the fluctuation of the increase amount of the engine-side cooling water temperature due to the fluctuation of the engine operating state. After the calculation of the determination value, the engine generated heat amount integrated value ΣQ (i) is cleared. Then, in the next step 174, the water temperature increase amount ΔTHW per predetermined time
Is compared with the determination value obtained in step 173. If the water temperature rise amount ΔTHW is equal to or less than the determination value, there is a suspicion of an open failure, so the process proceeds to step 175, the temporary fail counter is incremented, and the program ends. . If the water temperature increase amount ΔTHW per predetermined time is larger than the determination value, the program is terminated without any operation.

In this way, after the cold start, until the engine-side cooling water temperature THW reaches the valve opening temperature of the thermostat 13, the water temperature increase amount ΔTHW is calculated and compared with the judgment value at predetermined time intervals. When the value is the value, the process of incrementing the temporary fail counter is repeated.
The engine-side cooling water temperature THW is the thermostat 1
At the time when the valve opening temperature reaches 3, the above-described processing is terminated, and the routine proceeds to step 176, where the value of the temporary fail counter is compared with a predetermined value. Proceed to 177 and thermostat 13
Is determined to have an open failure, and in the next step 178, information on the open failure is stored in the backup RAM 29, and in step 179, the warning lamp 28 is turned on or blinks to warn the driver and warn the driver. To end. still,
If it is determined in step 176 that the value of the temporary fail counter is smaller than the predetermined value, the program is terminated without determining that an open failure has occurred.

In this program, the water temperature rise ΔTHW per predetermined time is calculated. The water temperature rise per predetermined engine generated heat or the water temperature rise per predetermined number of ignitions is calculated and compared with the judgment value. You may do it. The point is that after the engine is started, the rate of increase in the engine-side cooling water temperature is periodically determined, and the presence or absence of an open failure is diagnosed based on the number of times that the rate of increase in the engine-side cooling water temperature has fallen below the determination value. good. This makes it possible to repeat the diagnosis of the open failure based on the rate of increase in the temperature of the engine-side cooling water, thereby making it possible to diagnose the open failure with high reliability.

Each open fault diagnosis (1) to (5) described above
In consideration of the fact that the engine operating condition affects the behavior of the engine-side cooling water temperature, diagnosis of an open failure during idling (or a period in which an almost constant operating condition is continued), The behavior of the engine-side cooling water temperature is determined based on the amount of heat or the number of ignitions. However, the factors that affect the behavior of the engine-side cooling water temperature are not only the engine operating conditions, but also the factors that affect the amount of heat dissipated in the cooling water (vehicle speed, outside air temperature, intake air temperature, air conditioner operating conditions). This is a factor that affects the behavior of the side cooling water temperature. Accordingly, data such as a determination value, a predetermined period, and a detected water temperature used in the diagnosis processing of the open failure may be corrected based on at least one of the vehicle speed, the outside air temperature, the intake air temperature, and the operating state of the air conditioner. . If you do this,
Diagnosis of open faults taking into account the amount of heat dissipated in the cooling water becomes possible,
To that extent, the accuracy of diagnosis of an open failure can be improved.

Since the heat generated by the engine is lost during the fuel cut, the accumulation of the elapsed time, the number of ignitions, and the heat generated by the engine may be performed except for the fuel cut period.

On the other hand, a closed failure in which the thermostat 13 is left closed is performed by one of the following two diagnostic methods.

[Closed Fault Diagnosis (1)] First, the outline of the closed fault diagnosis (1) will be described with reference to FIG. FIG.
FIG. 9 shows the behavior of the engine-side cooling water temperature when a closed failure occurs, in comparison with the normal operation. When the engine-side cooling water temperature exceeds the thermostat valve opening temperature, if the thermostat 13 is normal, the valve is opened, and the cooled cooling water on the radiator 15 side is circulated to the engine 11 side, and the engine-side cooling water temperature decreases. In the case of a closing failure, the thermostat 13 does not open, the cooling water does not circulate, and the engine-side cooling water temperature continues to rise.

Focusing on this point, in the closed fault diagnosis (1),
After the engine-side cooling water temperature reaches the thermostat valve opening temperature, the change rate of the engine-side cooling water temperature is compared with a determination value to diagnose the presence or absence of a closing failure. Here, the rate of change of the engine-side cooling water temperature may be determined based on any of a water temperature change per predetermined time, a water temperature change per predetermined number of ignitions, and a water temperature change per predetermined engine generated heat.

The processing content of the closed fault diagnosis program shown in FIG. 13 for performing the closed fault diagnosis (1) will be described below. This program is started every predetermined time (for example, every 200 ms) after the IG key is turned on, and plays a role as a closed-failure diagnosis means referred to in the claims.

When this program is started, first, at step 201, the engine-side cooling water temperature THW detected by the cooling water temperature sensor 20 is read, and at the next step 202, a sensor (cooling water temperature sensor 20, It is determined whether the intake air amount sensor 24, the intake air temperature sensor 25, and the vehicle speed sensor 26) are normal. Here, whether the sensor is normal or not is determined by whether or not the output voltage of the sensor is within a predetermined voltage range. If it is determined that the sensor is abnormal, a normal failure diagnosis cannot be performed, so that the program is terminated without performing the subsequent processing.

If the sensor is normal, the routine proceeds to step 203, where it is determined whether or not a misfire has occurred. When a misfire occurs, the amount of heat generated by the engine decreases and the behavior of the engine-side cooling water temperature fluctuates. This program is terminated without performing the processing of.

If no misfire has occurred, step 20
4 to determine whether or not the engine is a cold start, the engine-side cooling water temperature THWS at the time of the start is, for example, 60 ° C. (the thermostat 13).
(The predetermined temperature equal to or lower than the valve closing temperature), the program is terminated without performing the subsequent diagnostic processing unless the engine is cold-started.

If it is a cold start, the routine proceeds to step 205, where it is determined whether or not the integrated value of engine generated heat amount SQENG integrated by the engine generated heat amount integration program of FIG. Here, the determination calorie is the calorie generated by the engine required until the normal thermostat 13 opens reliably after the cold start. Therefore,
If the engine-generated heat amount integrated value SQENG has not reached the determination heat amount, the program ends without performing the subsequent diagnostic processing.

On the other hand, the integrated value of the heat generated by the engine SQ
If ENG has reached the determination calorific value, the routine proceeds to step 206, where it is determined whether or not a closed failure flag XDTHWCL set by a closed failure flag setting program of FIG. 16 to be described later is “0” meaning a closed failure. . Note that the closing failure flag XDTHWCL is set to “1” which means normal at the time of initialization.

If the closed failure flag XDTHWCL is “0” indicating a closed failure, the process proceeds to step 207, and
It is determined that the thermostat 13 has a closed failure, and in the next step 208, information on the closed failure (engine speed, intake air amount, engine-side cooling water temperature, vehicle speed and failure code at the time of the closed failure) is stored in the backup RAM 29. At the same time, in step 209, the warning lamp 28 is turned on or blinks to warn the driver and the program is terminated.

Next, the processing content of the engine generated heat amount integration program shown in FIG. 14 will be described. This program, I
It is started every predetermined time (for example, every 100 ms) after the G key is turned on, and the heat generated by the engine after the start is integrated as follows. First, in step 221, the intake air amount GA and the intake air temperature T
The HA, the vehicle speed SPD, and the operating state ELB of the blower fan of the air conditioner 27 are read, and in the next step 222, it is determined whether or not the fuel is being cut. During the fuel cut, the heat generated by the engine becomes zero, and the temperature of the engine-side cooling water decreases due to heat radiation. Therefore, if the fuel is being cut, the routine proceeds to step 226, where the integrated value of the heat generated by the engine up to the previous time S
A predetermined value (for example, 10) is subtracted from QENG (i-1) to cancel the effect of the fuel cut.

On the other hand, if the fuel is not being cut, the routine proceeds to step 223, where the amount of heat generated by the engine QENG is reduced as shown in FIG.
It is calculated according to the intake air amount GA from the map of FIG. still,
As a parameter for calculating the engine generated heat amount QENG, an intake pipe pressure or a fuel injection amount may be used instead of the intake air amount GA.

After calculating the engine generated heat quantity QENG, the routine proceeds to step 224, where the current engine generated heat quantity QENG is added to the previous engine generated heat quantity integrated value SQENG (i-1), and the engine generated heat quantity integrated value SQENG (i ) Is updated. Thereafter, at step 225, the engine-generated heat amount integrated value SQENG (i) is corrected by multiplying the correction coefficients KQTHA, KQSPD, and KQELB according to the intake air temperature THA, the vehicle speed SPD, and the blower fan operating state ELB.

Here, the correction coefficient K corresponding to the intake air temperature THA
QTHA is calculated according to the intake air amount GA from the map of FIG. Note that the outside air temperature may be used instead of the intake air temperature THA. Also, a correction coefficient KQS corresponding to the vehicle speed SPD
The PD is calculated according to the vehicle speed SPD from the map of FIG. The correction coefficient KQELB according to the blower fan operating state ELB is calculated according to the ON / OFF of the blower fan from the map of FIG.

As described above, the intake air temperature THA, the vehicle speed SPD,
The reason why the engine-generated heat amount integrated value SQENG (i) is corrected according to the blower fan operating state ELB is that the intake air temperature TH
A, the vehicle speed SPD, and the blower fan operating state ELB all affect the amount of heat released from the cooling water and change the behavior of the engine-side cooling water temperature. Since the amount of heat dissipated in the cooling water of the blower fan changes depending on the operation mode (strong / weak air blowing, introduction of outside air / circulation of the vehicle interior), the correction coefficient KQELB may be changed depending on the operation mode.

Next, the processing contents of the closed failure flag setting program shown in FIG. 16 will be described. This program is IG
It is started every predetermined time (for example, every 100 ms) after the key is turned on, and the closing failure flag XDTHWCL is set as follows. First, in step 231, the change amount DT of the engine-side cooling water temperature every predetermined time (for example, every 100 ms)
HW is obtained by subtracting the current engine-side cooling water temperature THW (i) from the previous engine-side cooling water temperature THW (i-1).

Thereafter, in step 232, it is determined whether or not the electric radiator fan 18 is off. If the radiator fan 18 is off, the process proceeds to step 233, where the radiator fan 18 is switched from on to off. It is determined whether or not a predetermined time (for example, 5 seconds) has elapsed since then, and if this time has elapsed, the process proceeds to step 234 to determine a closed failure. Step 232 described above
233 is “No”, that is, when the radiator fan 18 is on, or when the radiator fan 1
If a predetermined time (for example, 5 seconds) has not elapsed since the switching of the switch 8 from the on state to the off state, the program is terminated without determining the closing failure. This is to prevent the cooling water from being radiated by the radiator fan 18.

If a predetermined time (for example, 5 seconds) has elapsed since the radiator fan 18 was switched from on to off, in step 234, the water temperature change amount DTHW is compared with a determination value (for example, 0 ° C.). If the water temperature change amount DTHW is smaller than the determination value, it can be estimated that the thermostat 13 is normally opened.
The closing failure flag XDTHWCL is set to “1” meaning normal, and the program ends.

On the other hand, if the water temperature change amount DTHW is equal to or larger than the determination value, it means that the engine-side cooling water temperature THW has continued to rise abnormally, so the routine proceeds to step 236, where the closed failure flag XDTHWCL is set to the closed failure. Is set to "0", which means that the program ends. Note that the determination value to be compared with the water temperature change amount DTHW in step 234 is not limited to 0 ° C., and may be a plus temperature.

In the above-described closed-failure diagnosis (1), the water temperature change amount DTHW for each predetermined time is calculated. In the closed-failure diagnosis (2), the water-temperature change amount for each predetermined engine-generated heat amount is used. Calculate the quantity DTHWSQ. Further, in the above-described closed-failure diagnosis (1), the closed-failure diagnosis is performed when the integrated value of the calorific value of the engine after starting reaches a predetermined amount. However, in the closed-failure diagnosis (2), the engine-side cooling is performed. When the water temperature becomes higher than the valve opening temperature of the thermostat 13 by a predetermined temperature, a diagnosis of a closing failure is made.

The processing contents of the closed fault diagnosis program shown in FIG. 18 for performing the closed fault diagnosis (2) will be described below. This program is started every predetermined time (for example, every 200 ms) after the IG key is turned on, and plays a role as a closed-failure diagnosis means referred to in the claims.

When this program is started, first, in step 241, the engine side coolant temperature THW detected by the coolant temperature sensor 20 is read, and the predetermined engine generated heat quantity calculated by the coolant temperature change amount calculation program shown in FIG. The water temperature change amount DTHWSQ for each is read. Thereafter, in Steps 242 and 243, when it is determined that the sensors such as the cooling water temperature sensor 20 used for the closing failure diagnosis are normal and no misfire has occurred, the process proceeds to Step 244, and the engine-side cooling water temperature THW is set. A predetermined temperature (for example, 5 ° C.) from the valve opening temperature of the thermostat 13 (for example, 90 ° C.)
Compare with a higher temperature, eg, 95 ° C. This temperature is
If the thermostat 13 is normal, it is the temperature at which the valve is reliably opened. Therefore, the engine-side cooling water temperature THW is 95
If the temperature is not more than ℃, the program is terminated without performing the subsequent diagnostic processing.

On the other hand, when the engine-side cooling water temperature THW is 95 ° C.
If the water temperature change amount DTHWSQ is equal to or less than the judgment value (eg, 0 ° C.), the process proceeds to step 245, and if the water temperature change amount DTHWSQ is equal to or less than the judgment value, the thermostat 13 normally operates. Since it can be estimated that the valve is open, the program is terminated without performing the subsequent processing.

If the water temperature change amount DTHW is larger than the determination value, it means that the engine-side cooling water temperature THW has continued to rise abnormally. Therefore, the process proceeds to step 246, and it is determined that the thermostat 13 has a closed failure. In step 247, the information of the closing failure is stored in the backup RAM 29, and in step 248, the warning lamp 28 is turned on or blinks to warn the driver, and the program ends.

Next, the processing contents of the water temperature change amount calculation program shown in FIG. 19 will be described. This program is started every predetermined time (for example, every 100 ms) after the IG key is turned on, and calculates a water temperature change amount DTHWSQ for each predetermined engine generated heat amount as follows. First, in step 251,
The engine-generated heat amount integrated value SQENG and the engine-side cooling water temperature THW integrated by the engine-generated heat amount integration program of FIG. 14 described above are read.

Thereafter, at step 252, it is determined whether or not the integrated value of engine generated heat amount SQENG has exceeded a predetermined value (see FIG. 17). Every time the integrated value of engine generated heat amount SQENG exceeds the predetermined value, the process proceeds to step 253. , The change amount DTHWSQ of the engine-side cooling water temperature is calculated by subtracting the current water temperature THW from the previous water temperature THWO. Thereafter, in step 254, THWO is updated with the current water temperature THW, the accumulated engine calorific value SQENG is cleared, and the program ends.

In this program, the water temperature change amount DTHWSQ is calculated for each predetermined amount of heat generated by the engine, but the water temperature change amount may be calculated for each predetermined number of ignitions. In addition, the water temperature change amount for each predetermined time may be calculated during the period in which the idle state is continued or the period in which the substantially constant operation state is continued.

In the example of the system configuration shown in FIG. 1, the radiator fan 18 is constituted by an electric fan. However, the radiator fan is connected to the water pump 17, and the radiator fan and the water pump 17 are integrally rotated by the engine power. You may do it. Radiator 1
The mounting position of 5 is not limited to the outlet portion of the water jacket 12, but may be another portion such as the inlet portion of the water jacket 12.

In addition, the present invention can be implemented with various modifications without departing from the gist, such as execution of only one of the open failure diagnosis program and the closed failure diagnosis program.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an entire engine cooling system according to an embodiment of the present invention.

FIG. 2 is a time chart for explaining a method of open fault diagnosis (1).

FIG. 3 is a flowchart showing a processing flow of an open failure diagnosis program of the open failure diagnosis (1).

FIG. 4 is a time chart for explaining a method of open fault diagnosis (2).

FIG. 5 is a flowchart showing a processing flow of an open failure diagnosis program of the open failure diagnosis (2).

FIG. 6 is a flowchart showing a processing flow of an open failure diagnosis program of the open failure diagnosis (3).

FIG. 7 is a time chart for explaining a method of open fault diagnosis (4).

FIG. 8 is a flowchart showing a flow of processing of an open failure diagnosis program of the open failure diagnosis (4).

FIG. 9 is a time chart for explaining a method of the open fault diagnosis (5).

FIG. 10 is a flowchart showing the flow of processing in the first half of the open failure diagnosis program of the open failure diagnosis (5).

FIG. 11 is a flowchart showing the processing flow of the second half of the open failure diagnosis program of the open failure diagnosis (5).

FIG. 12 is a time chart for explaining a method of closing fault diagnosis (1).

FIG. 13 is a flowchart showing a processing flow of an open failure diagnosis program of the closed failure diagnosis (1).

FIG. 14 is a flowchart showing the flow of processing of an engine-generated calorie integration program;

FIG. 15 (a) is a graph showing the relationship between an intake air amount GA and an engine generated heat amount Q;
A diagram conceptually showing a map for calculating ENG, (b) a diagram conceptually showing a map for calculating a correction coefficient KQTHA from the intake air temperature THA, and (c) a correction coefficient KQ from the vehicle speed SPD.
FIG. 4D is a diagram conceptually showing a map for calculating SPD, and FIG. 5D is a diagram conceptually showing a map for calculating a correction coefficient KQELB from a blower fan operating state ELB.

FIG. 16 is a flowchart showing a processing flow of a closed failure flag setting program;

FIG. 17 is a time chart for explaining a method of closing fault diagnosis (2).

FIG. 18 is a flowchart showing a processing flow of an open failure diagnosis program of the closed failure diagnosis (2).

FIG. 19 is a flowchart showing the processing flow of a water temperature change amount calculation program.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Engine, 12 ... Water jacket, 13 ... Thermostat, 14 ... Cooling water circulation path, 15 ... Radiator, 16 ... Cooling water circulation path, 18 ... Radiator fan, 2
0: cooling water temperature sensor (water temperature detecting means), 22: ECU
(Open failure diagnosis means, closed failure diagnosis means), 23 ... engine speed sensor, 24 ... intake air amount sensor, 25 ... intake air temperature sensor, 26 ... vehicle speed sensor, 27 ... air conditioner, 28 ... warning lamp (warning means), 29: Backup RAM.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16K 31/68 F16K 31/68 Q G01M 15/00 G01M 15/00 Z

Claims (15)

[Claims] 1. A thermostat failure detection device for an internal combustion engine cooling system for detecting a failure of a thermostat provided in a cooling water circulation path of an engine, the cooling water temperature of a cooling water circulation path closer to the engine than the thermostat (hereinafter referred to as “engine”). A cooling water temperature detecting means for detecting the temperature of the cooling water based on the temperature of the engine-side cooling water detected by the cooling water temperature detecting means in a closed temperature range if the thermostat is normal. A thermostat failure detection device for an engine cooling system, comprising: an open failure diagnosis means for diagnosing the presence or absence of a failure that is left open (hereinafter referred to as “open failure”). 2. The open failure diagnosis means determines an amount or rate of decrease in engine-side cooling water temperature immediately after starting the engine,
The thermostat failure detecting device for an engine cooling system according to claim 1, wherein the presence or absence of an open failure is diagnosed based on the amount or rate of decrease in the engine-side cooling water temperature. 3. The open failure diagnosis means determines the amount of increase in the engine-side cooling water temperature until any one of an elapsed time after starting the engine, the number of ignitions, and an integrated value of the heat generated by the engine reaches a predetermined value. 2. The system according to claim 1, wherein an open failure is diagnosed based on an increase in the engine-side cooling water temperature.
4. A thermostat failure detection device for an engine cooling system according to claim 1. 4. The open failure diagnosis means according to claim 1, wherein: after the engine is started, the engine-side coolant temperature rises until a predetermined amount is reached.
Alternatively, any one of an elapsed time until the engine-side cooling water temperature reaches a predetermined water temperature, the number of ignitions, and an integrated value of the heat generated by the engine is determined, and the presence or absence of an open failure is diagnosed based on the determined value. Item 2. An apparatus for detecting a thermostat failure in an engine cooling system according to Item 1. 5. The open failure diagnosis means periodically determines an increase rate of the engine-side cooling water temperature after the engine is started, and determines an open failure based on the number of times that the increase rate of the engine-side cooling water temperature becomes a predetermined value or less. 2. The apparatus for detecting a thermostat failure in an engine cooling system according to claim 1, wherein the presence or absence of the abnormality is diagnosed. 6. The open-failure diagnosing means determines the rate of increase of the engine-side cooling water temperature by using one of a water temperature rise amount per predetermined time, a water temperature rise amount per a predetermined number of ignitions, and a water temperature rise amount per a predetermined engine generated heat amount. The thermostat failure detection device for an engine cooling system according to claim 5, wherein the determination is made by: 7. The open-failure diagnosis unit corrects data used for the open-failure diagnosis processing based on at least one of a vehicle speed, an outside air temperature, an intake air temperature, and an operation state of an air conditioner. An apparatus for detecting a thermostat failure in an engine cooling system according to any one of claims 1 to 6. 8. In a temperature range in which the thermostat is normal if the thermostat is open, it is determined whether or not there is a closed failure in which the thermostat is not opened but is closed based on the engine-side cooling water temperature detected by the cooling water temperature detecting means. 8. The thermostat fault detecting device for an engine cooling system according to claim 1, further comprising a closed fault diagnosing means for diagnosing the fault. 9. A thermostat failure detection device for an internal combustion engine cooling system for detecting a failure of a thermostat provided in a cooling water circulation path of an engine, wherein a temperature of a cooling water in a cooling water circulation path on an engine side of the thermostat (hereinafter referred to as “engine”) A cooling water temperature detecting means for detecting the temperature of the cooling water based on the temperature of the engine-side cooling water detected by the cooling water temperature detecting means if the thermostat is normal. And a closing failure diagnosing means for diagnosing the presence or absence of a closing failure to be left open. 10. The closing failure diagnosing means determines a rate of change of the engine-side coolant temperature after reaching a temperature range in which the thermostat opens after the engine is started, and based on the rate of change of the engine-side coolant temperature. The thermostat failure detecting device for an engine cooling system according to claim 9, wherein it is diagnosed whether or not the thermostat has a closed failure. 11. The closed-failure diagnosing means may determine the rate of change of the engine-side cooling water temperature by any one of a water temperature change per predetermined time, a water temperature change per predetermined number of ignitions, and a water temperature change per predetermined engine generated heat. The thermostat failure detecting device for an engine cooling system according to claim 10, wherein the determination is made according to the following. 12. The engine cooling system according to claim 11, wherein the closed-failure diagnosis means diagnoses the closed-failure when the integrated value of the heat generated by the engine after starting the engine reaches a predetermined amount. Thermostat failure detection device. 13. The engine cooling system according to claim 11, wherein the closing failure diagnosis unit diagnoses the closing failure when the engine-side cooling water temperature becomes higher than a valve opening temperature of the thermostat by a predetermined temperature. System thermostat failure detection device. 14. The closed-failure diagnosis means corrects data used for a closed-failure diagnosis process based on at least one of a vehicle speed, an outside air temperature, an intake air temperature, and an operating state of an air conditioner. A thermostat failure detecting device for an engine cooling system according to any one of claims 9 to 13. 15. A radiator fan that cools a radiator provided in the cooling water circulation path is configured by an electric fan, and the closing failure diagnosis unit diagnoses a closing failure during a period in which the radiator fan is stopped. The thermostat failure detecting device for an engine cooling system according to any one of claims 9 to 14, wherein the detection is performed.