JPH11148420A - Equipment for detecting abnormality in thermostat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect abnormality in the operation of a thermostat exactly and promptly. SOLUTION: After starting an engine 1, an electronic control unit(ECU) 51 calculates with elapse of time each estimated cooling water temperature obtained by assuming the normal or the abnormal operation of a thermostat based on various operation state parameters, including water temperature at the time of starting the engine 1, intake-air temperature, engine speed, intake-air quantity, etc. The abnormal operation state of the thermostat 16 is determined when the cooling water temperature measured with a water temperature sensor 14 reached no reference value, and the estimated cooling water temperature assuming the normal operation of the thermostat 16 has reached the given value or more after elapsing given time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermostat abnormality detecting device for detecting an abnormality in a thermostat that opens and closes a part of a circulation path of cooling water in order to adjust a heat radiation effect of a heat generating engine by cooling water.

[0002]

2. Description of the Related Art A thermostat is a passage opening / closing valve whose opening / closing state switches at a specific temperature, and is used for a cooling water passage of a water-cooled cooling device.

For example, a cooling device widely used in an automobile engine is configured such that cooling water circulates between a cooling water passage inside the engine and a radiator by the action of a water pump. With this configuration, the cooling water absorbs heat generated from inside the engine, and further dissipates to the outside via the radiator.

Here, the thermostat opens and closes a circulation path of cooling water in order to adjust the temperature of the engine to an appropriate temperature. That is, when the cooling water temperature is lower than a predetermined value (usually, about 80 ° C.), such as during warm-up operation immediately after the start of the engine, the valve is closed, and when the cooling water temperature is higher than the predetermined value, the valve is opened. And circulates cooling water between the inside of the engine and the radiator.

[0005] By the way, the thermostat closes in a natural state where the cooling water is at room temperature, but the valve may not be closed in a fully open state or a half open state due to deterioration of members. In such a case, not only is the engine in a supercooled state, the efficiency of the heater is reduced, but also the so-called low-temperature increase, in which the fuel injection amount is increased when the engine is at a low temperature, is constantly executed. It was supposed to make it worse.

To solve such a problem, see, for example,
In the "insulating device for cooling water in an automobile or the like" described in JP-A-213117, a detection device that determines that there is an abnormality in a thermostat when a water temperature detected by a water temperature sensor during a normal operation is not within a reference range is disclosed. Provided.

Further, in the technique disclosed in this publication, if the cooling water temperature actually measured by a water temperature sensor or the like is lower than a predetermined value after a predetermined time has elapsed after the start of the engine, it is determined that there is an abnormality in the operation state of the thermostat. The composition is also taken.

[0008]

However, in the former device, no means is provided for discriminating the state of the engine and various operating conditions, and it is not possible to obtain sufficient reliability for the abnormality judgment.

Also, apart from the operation state of the thermostat, the manner of change of the cooling water temperature after the engine starts greatly differs depending on the operation state of the engine and external environmental conditions. There is a possibility of erroneous determination such as
There is a problem that sufficient reliability in abnormality detection cannot be obtained. Further, there is a drawback in that when the operation state of the thermostat is normal, it is necessary to wait for a predetermined time to elapse in any case.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a thermostat abnormality detecting device capable of accurately and quickly detecting a thermostat operation abnormality.

[0011]

According to a first aspect of the present invention, there is provided a cooling water circulation passage for an engine, wherein when the cooling water temperature is lower than a predetermined value, the passage is closed. And a cooling water temperature detecting means for detecting a cooling water temperature of the engine to detect an operation abnormality of the thermostat for opening the cooling passage when the cooling water temperature is equal to or higher than a predetermined value. If the detected cooling water temperature is lower than the predetermined reference water temperature, it is determined that there is an abnormality in the operation of the thermostat.If the detected cooling water temperature is equal to or higher than the predetermined reference water temperature, the thermostat normally operates. In a thermostat abnormality detection device that determines that the thermostat is operating, a first method for estimating a cooling water temperature under conditions assuming an abnormal operation of the thermostat. Recirculating water temperature estimating means, second cooling water temperature estimating means for estimating the cooling water temperature under conditions assuming normal operation of the thermostat, and estimated by the first cooling water temperature estimating means when the thermostat is determined to be normal. A normal judgment permitting means for permitting a normal judgment only when the cooling water temperature is lower than a predetermined water temperature, and a cooling water temperature estimated by the second cooling water temperature estimating means at the time of abnormality judgment of the thermostat is equal to or higher than a predetermined water temperature. And a normality determination permitting means for permitting the abnormality determination only when.

According to the above configuration, two estimated cooling water temperatures are calculated based on the engine operating state and the like under the assumed conditions of normal and abnormal operating states of the thermostat, respectively, and a predetermined standard By comparing the water temperature with the respective estimated cooling water temperatures and limiting the permission conditions for performing the abnormality determination or the normality determination, it is possible to improve the reliability of the thermostat abnormality or normality determination. Further, when the thermostat is normal under an operating condition or an environmental condition in which the temperature rise of the engine is relatively fast, it is possible to quickly confirm the thermostat.

According to a second aspect of the present invention, in the thermostat abnormality detecting device according to the first aspect, after the engine is started,
In a case where the cooling water temperature estimated by the first cooling water temperature estimating means is lower than the predetermined water temperature after a predetermined time has elapsed, the gist of the present invention is to suspend the determination as to whether or not the thermostat has an operation abnormality.

According to the above configuration, even when the slope relating to the rise of the cooling water temperature during the warm-up operation is slow and it is presumed that there is an abnormality in the operation state of the thermostat, the cooling water temperature can be reduced. If the slow rise mode may be caused by other factors such as the operating state of the engine or environmental conditions, the determination that the thermostat is abnormal should be suspended to appropriately prevent erroneous determination. Will be able to

According to a third aspect of the present invention, in the thermostat abnormality detecting device according to the first or second aspect, the first cooling water temperature detected by the cooling water temperature detecting means becomes equal to or higher than a predetermined reference water temperature. When the cooling water temperature estimated by the cooling water temperature estimating means is equal to or higher than a predetermined water temperature, the determination of whether there is an operation abnormality in the thermostat is suspended.

According to a fourth aspect of the present invention, in the thermostat abnormality detecting device according to any one of the first to third aspects, the first cooling water temperature estimating means estimates the predetermined cooling time after the engine is started. When the cooling water temperature becomes equal to or higher than the predetermined water temperature, the gist of the present invention is to suspend the determination as to whether the thermostat has an operation abnormality.

According to the configuration of the third or fourth aspect of the present invention, it is presumed that the slope relating to the rise of the cooling water temperature during the warm-up operation is sufficiently large, and the thermostat appears to be operating normally. Even if this is the case, if the high rise rate of the cooling water temperature may be caused by other factors such as the operating condition of the engine or environmental conditions, the determination that the thermostat is normal should be suspended. Thereby, erroneous determination can be suitably prevented.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a first embodiment in which a thermostat abnormality detecting device according to the present invention is applied to an engine cooling system of an automobile will be described with reference to the drawings.

As shown in FIG. 1, a four-cylinder engine 1
Is a cylinder 3, a piston 4, a crankshaft 5, a connecting rod 6 for connecting the piston 4 and the crankshaft 5, a water jacket 7 surrounding the cylinder 3, and an internal space provided outside the engine body and communicating with the water jacket 7. Radiator 8, cooling fan 9, water pump 10 and the like.

In the combustion chamber 11 of each cylinder 3, the air-fuel mixture explodes and burns, causing the piston 4 to move up and down, and this up-and-down movement is converted into the rotational driving force of the crankshaft 5 via the connecting rod 6. Further, the supply of the air-fuel mixture and the discharge of the combustion gas are performed via an intake / exhaust port (not shown). The water jacket 7 serving as a space for circulating cooling water cools the cylinder head 12 and the cylinder block 13 heated by the explosion and combustion of the air-fuel mixture as necessary, or maintains the cylinder 3 at a constant temperature.
It is configured to surround the outer periphery of.

The radiator 8 and the cooling water circulation path of the water jacket 7 are connected by upper and lower communication passages 14 and 15. A thermostat 16 is provided in the middle of the upper communication passage 14. Thermostat 1
Reference numeral 6 denotes a valve that opens and closes mechanically according to the water temperature. In the present embodiment, when the water temperature is 80 ° C. or less, the valve 6 closes to close the communication passage 14 and the water temperature exceeds 80 ° C. Then, the valve is opened and the passage 14 is opened.

A water temperature sensor 41 provided on the inner wall of the water jacket 7 detects a cooling water temperature THW and sends a detection signal to an electronic control unit (ECU) 51. Next, an electronic control unit (ECU) 51 that controls and diagnoses various parts of the engine including the thermostat 16 based on the operating state of the engine 1 will be described.

As shown in the block diagram of FIG.
1 is a central processing unit (CPU) 52, a read-only memory (ROM) 53, a random access memory (RAM) 5
4, a backup RAM 55, a timer counter 56, and the like. The ECU 51 constitutes a logical operation circuit formed by connecting these components to the external input circuit 57 and the external output circuit 58 via a bus 59. Here, the ROM 53 stores in advance programs related to various operation controls, failure diagnosis, and the like. The RAM 54 temporarily stores the calculation results of the CPU 52 and the like. The backup RAM 55 is a nonvolatile memory that stores data even after the engine stops. The timer counter 56 can perform a plurality of timing operations simultaneously. The external input circuit 57 includes a buffer, a waveform circuit, a hard filter (a circuit including an electric resistor and a capacitor), an A / D converter, and the like. The external input circuit 57 includes a drive circuit and the like. As described above, the water temperature sensor 41 detects the cooling water temperature THW in the water jacket 7. The throttle sensor 42 detects a throttle valve opening TA in accordance with the depression amount of an accelerator pedal (not shown). The rotation speed sensor 43 detects the rotation speed of the crankshaft 5, that is, the engine rotation speed NE. The oxygen sensor 44
Detect the oxygen concentration in the exhaust. The intake pressure sensor 45 detects the intake pressure PM. Vehicle speed sensor 46 detects vehicle speed SPD. The intake air temperature sensor 47 detects the temperature (intake air temperature) THA of the intake air introduced into the air cleaner. These various sensors 41 to 47 are connected to external inputs. CP
U <b> 52 reads detection signals of various sensors 41 to 47 input via the external input circuit 57 as input values. C
Based on these input values, the PU 52 performs various operation controls, failure diagnosis, and the like, for example, control of the fuel injection amount and fuel injection timing by the injector 48.

Next, among the various controls executed by the ECU 51, the contents of the control relating to the detection of an abnormality of the thermostat 16 will be described. FIGS. 3 and 4 show a “thermostat abnormality detection routine” according to the thermostat abnormality detection of the present embodiment. A program relating to this routine is stored in the ROM 53 of the ECU 51 in advance, and is executed every predetermined time after the main power supply of the vehicle is turned “ON”.

In this thermostat abnormality detection routine, the ECU 51 first determines in step 101 the count value e of the normal product warm-up counter and the abnormal product warm-up counter.
cts and ects are respectively set to predetermined values Δects and Δectf.
Count up by one. Here, the warm-up counter is an estimating counter for calculating an estimated value of the current cooling water temperature from an ever-changing operating state of the engine and environmental conditions such as a cooling water temperature and an outside air temperature at the time of starting the engine. The starting water temperature THW0, the intake air temperature THA, and the heater ON
An estimated value is calculated by referring to a map (not shown) created and stored in advance based on various operating state parameters such as OFF, engine speed NE, intake air amount Q, and the like. The normal warm-up counter calculates the estimated cooling water temperature (count value e) on the assumption that the thermostat 16 is operating normally.
cts), while the abnormal warm-up counter calculates the estimated cooling water temperature (count value ectf) on the assumption that the thermostat 16 is abnormal.

As shown in FIG. 5, the estimated cooling water temperature of the normal product warm-up counter (hereinafter, simply referred to as a normal product counter) is
Normally, a mode is shown in which the temperature rises monotonously for a while after the start of the engine (time t0), and when the temperature reaches a predetermined temperature (for example, 80 ° C.), the temperature is kept constant. Cooling water temperature is 80 ℃
Thermostat 16 maintains the valve closed state until
This is because if the temperature is 80 ° C. or more, the valve is repeatedly opened, and if the temperature is lower than 80 ° C., the valve returns to the closed state. On the other hand, in the case of the estimated cooling water temperature ectf by the abnormal product warm-up counter (hereinafter simply referred to as abnormal product warm-up counter) ectf, its rising speed is slower than that of the estimated cooling water temperature ects of the normal product warm-up counter, and in the time chart, , Will show a slower slope. Since the thermostat 16 remains open, the radiator 8 and the engine 1
This is because the cooling water circulates between the two, and when the temperature of the cooling water is low at the time of starting the engine or immediately after the start of the engine, the cooling water enters a supercooled state.

In the following step 102, the abnormal coolant warm-up counter ectf sets the predetermined cooling water temperature (ET
HW + α) is determined. If the determination is affirmative, the process proceeds to step 103a,
If the determination is negative, the process moves to step 103b.

In step 103a, the normality determination permission flag XMTS is set to "0" (no setting), while in step 103b, the normality determination permission flag XMTS is set to "1". In any case, the process proceeds to step 104.

In step 104, the normal cooling-up counter ects sets a predetermined cooling water temperature (ETHW).
+ Α) is determined. If the determination is negative, the process proceeds to step 105a, and if the determination is affirmative, the process proceeds to step 105b.

In step 105a, the abnormality determination permission flag XMTF is set to "0" (no setting), while in step 105b, the abnormality determination permission flag XMTF is set to "1". Then, in any case, the process proceeds to step 106.

In step 106 (FIG. 4), it is determined whether or not the actual measured value THW of the cooling water temperature by the water temperature sensor 41 is a value obtained by subtracting a constant α from the determination water temperature (ETHW + α), that is, is equal to or higher than the reference water temperature ETHW. . If the determination is affirmative, the process proceeds to step 107, and if the determination is negative, the process proceeds to step 109.

In step 107, it is determined whether or not the normality determination permission flag XMTS is set to "1". If the determination is negative, that is, if the normality determination permission flag XMTS is “0” (not set), the current routine processing is temporarily terminated. On the other hand, if the judgment is affirmative, the processing shifts to step 108, where
In step 8, it is determined that "the thermostat 16 is normal", and the current routine processing ends. Step 1
When the post-judgment routine processing in step 08 is completed, EC
U51 prohibits the interrupt execution of the routine processing again.

On the other hand, if a negative determination is made in step 106, the process proceeds to step 109. In step 109, a predetermined time (five minutes in this embodiment) has elapsed after the start of the engine. It is determined whether or not. If the determination is affirmative, the ECU 51 shifts the processing to step 110, and if the determination is negative, temporarily ends the processing.

In step 110, it is determined whether or not the abnormality determination permission flag XMTF is set to "1". If the determination is negative, the current routine processing is temporarily terminated. On the other hand, if the judgment is affirmative, the process shifts to step 113 to execute step 111
It is determined that "there is an abnormality in the thermostat 16". Then, the current process is terminated, and the execution of the interrupt to this routine again is prohibited.

After the processing in steps 108 and 111, if the current processing is terminated and the execution of the interrupt is prohibited again, the ECU 51 continues to operate until the next engine start.
This routine process is not executed.

The ECU 51 executes the operation of the thermostat 16 based on the "thermostat abnormality detection routine" described above.
, That is, a malfunction in the fully open or half open state. Further, if the operation state of the thermostat 16 is normal, it is confirmed. Then, as is apparent from this routine, the ECU 51 sets the thermostat 1
Assuming that the temperature of the cooling water 6 is normal and the temperature of the thermostat 16 is abnormal, the estimated values of the cooling water temperature under both conditions are defined as a normal product warm-up counter ects and an abnormal product warm-up counter ectf, respectively. Calculate based on parameters.

Then, after the engine is started, the condition that the abnormal product warm-up counter ectf is less than the determination water temperature value (ETHW + α) is a permission condition for determining that the thermostat 16 is operating normally ( Step 103
b). Inevitably, the condition that the abnormal product warm-up counter ectf becomes equal to or higher than the determination water temperature value (ETHW + α) is set as a prohibition condition in which it is not necessary to determine that the thermostat 16 is operating normally (step 103a).

On the other hand, the fact that the normal product warm-up counter ects becomes equal to or higher than the determination water temperature value (ETHW + α) after the engine is started is a permitting condition for determining that the operation state of the thermostat 16 is abnormal. Also, inevitably, the normal product warm-up counter ects determines the determination water temperature value (ETHW +
The condition that α is not satisfied is a prohibition condition in which it is not necessary to determine that the operation state of the thermostat 16 is abnormal.

After the permission and prohibition conditions concerning the normal or abnormal judgment THW of the thermostat 16 are set in this way, the actual measured value THW of the cooling water temperature by the water temperature sensor 41 is
Before a predetermined time (5 minutes) has elapsed since the engine started, or
Even after a lapse of minutes, under the condition where the abnormality determination is prohibited, the temperature becomes equal to or higher than the reference water temperature ETHW and the normal determination permission flag X
If MTS is set to “1”, thermostat 1
It is determined that the operation state of No. 6 is normal.

On the other hand, the water temperature sensor 4
If the actual measured value THW of the cooling water temperature according to 1 is less than the reference value ETHW and is under the condition for permitting abnormality determination (XMTF = “1”), it is determined that the operation state of the thermostat 16 is abnormal.

Here, the actual cooling water temperature T in the engine cooling system provided with the abnormality detecting device according to the present embodiment.
HW, and the relationship between changes over time between the normal warm-up counter ects and the abnormal warm-up counter ectf,
This will be described with reference to FIGS. Note that e shown in FIG.
Symbols such as cts, ectf, ETHW, and XMTF are the same as the symbols shown in the flowcharts of FIGS.

FIG. 6 shows a time-dependent change in the cooling water temperature THW, etc., when the thermostat 16 is operated abnormally (inoperable while the valve is open) in the engine cooling system provided with the abnormality detecting device according to the present embodiment. An example is shown below. In the figure, the normal warm-up counter ects is at point A (time t).
In a), the determination water temperature (ETHW + α) has been reached, and the abnormal product counter ectf has reached the determination water temperature (ETHW + α) at point B (time tb). Here, for example, as in a transition pattern indicated by a curve (1),
During a period in which the normality determination permission flag XMTS is set to “1”, before 5 minutes have elapsed since the engine was started,
When the cooling water temperature THW becomes equal to or higher than the reference value ETHW, or in a period in which the normality determination permission flag XMTS is set to “1”, the abnormality determination permission flag XMTF is set to “1” even after 5 minutes have elapsed. If the cooling water temperature THW becomes equal to or higher than the reference value ETHW within the period set in the above, it is determined that the thermostat 16 is operating normally.

On the other hand, as shown in the transition pattern shown by the curve (2) or (3), even after the normal product counter ectf has become equal to or higher than the judgment water temperature (ETHW + α) after 5 minutes, the cooling water temperature If the THW does not reach the reference water temperature ETHW, it is determined that the operation state of the thermostat 16 is abnormal.

As described above, in the thermostat abnormality detecting device of the present embodiment, two estimated cooling water temperatures are calculated assuming both normal and abnormal conditions related to the operating state of the thermostat, and are used as criteria for determination. As a result, the accuracy and reliability of the thermostat abnormality detection are improved.

As shown in FIG. 7, even if a predetermined time (5 minutes) elapses after the engine is started, a normal warm-up counter ec.
When ts is lower than the determination water temperature (ETHW + α),
Regardless of the operation state of the thermostat 16, it is determined that the cooling water temperature is under a condition that is unlikely to rise due to the operating state of the engine, the environment, and the like, and the determination of normality or abnormality related to the thermostat 16 is to be suspended. Become.

Here, in the conventional thermostat abnormality detecting device, the thermostat 1 according to the same criterion for the difference in the operating state of the engine and the external environmental condition.
No. 6 abnormality was detected.

In this regard, according to the thermostat abnormality detecting device of the present embodiment, even if the condition is such that the cooling water temperature does not easily rise, erroneous detection can be suitably prevented by considering the condition. .

According to the embodiment in which the abnormality of the thermostat 16 is detected in the manner described above, the following effects can be obtained. -By adopting two estimated cooling water temperatures assuming that the operation state of the thermostat is normal and abnormal, as criteria for detecting thermostat abnormality, and providing permission conditions for normal determination and abnormality determination of the thermostat, The precision and reliability of normal / abnormal detection have been improved.

Even if a predetermined time has elapsed since the engine was started,
In addition, when the cooling water temperature assuming normality of the thermostat is lower than the reference water temperature, the determination is temporarily suspended, so that the erroneous determination of the thermostat can be suitably prevented.

(Second Embodiment) Next, a second embodiment of the thermostat abnormality detecting device according to the present invention will be described, focusing on the differences from the first embodiment.

The device of the second embodiment is also applied to an engine cooling system of a car, and after the engine is started,
This is for determining whether the thermostat is normal or abnormal with respect to the operating state.

Also in the apparatus of the second embodiment, the configuration of the engine cooling system of the automobile to be applied (FIG. 1) and the circuit configuration of the ECU (electronic control unit) 51 are the same as those of the second embodiment. It is the same as the device of the first embodiment, and the duplicate description thereof is omitted here.

FIG. 8 shows a part of the apparatus according to the second embodiment corresponding to the routine shown in FIG. 4 among the "thermostat abnormality detection routine" shown in FIGS. Replaced by a routine,
In the steps denoted by the same reference numerals, the processing contents are the same.

That is, in the thermostat abnormality detection routine of the second embodiment, if the judgment in step 106 (FIG. 8) is negative, that is, the water temperature sensor 41
If the cooling water temperature THW detected by the above is lower than the reference water temperature ETHW, the process proceeds to step 106b.

In step 106b, step 1
It is determined whether the normality determination permission flag XMTS described in 02, 103a, and 103b (FIG. 3) is set to "1". And if the judgment is affirmative,
The process moves to step 109.

On the other hand, if the determination is negative, the ECU 51
Terminates the processing and does not interrupt the routine again until the next engine start. By providing such a step 106b, if the abnormal product warm-up counter ectf becomes equal to or higher than the determined cooling water temperature before the cooling water temperature THW detected by the water temperature sensor 41 reaches the reference water temperature ETHW, until the next operation of the engine. Means that the thermostat 16 is not judged to be abnormal or normal.

With the above-described configuration, the same effect as that of the first embodiment relating to the abnormality detection of the thermostat 16 can be obtained. Moreover, erroneous detection when the operating state of the engine or the environmental condition does not meet the highly reliable determination condition can be more preferably avoided.

(Third Embodiment) Next, a third embodiment of the thermostat abnormality detecting device according to the present invention will be described, focusing on the differences from the first embodiment.

The device of the third embodiment is also applied to an engine cooling system of an automobile, and determines whether the thermostat is normal or abnormal after the engine is started.

Also in the device of the third embodiment, similarly to the second embodiment, the configuration of the engine cooling system of the automobile to be applied (FIG. 1) and the circuit configuration of the ECU (electronic control unit) 51. Are the same as those in the first embodiment, and a duplicate description thereof will be omitted here.

The device of the third embodiment is similar to that of FIG.
In the “thermostat abnormality detection routine” shown in FIG. 4, a part corresponding to the routine shown in FIG. 4 is replaced with the routine shown in FIG. 9, and in steps denoted by the same reference numerals, The processing contents are the same.

That is, in the thermostat abnormality detection routine of the third embodiment, as shown in FIG. 9, after performing the processing of step 106a having the same processing contents as step 109 in the first embodiment, the determination is made. Shifts the processing to step 106 or step 106b in accordance with. If the determination in step 106b is affirmative, the process proceeds to step 106. If the determination is negative, the process ends, and until the next engine start, the routine is again interrupted. Shall not be performed. Further, in the processing in step 106, E
If the determination by the CU 51 is negative, the process directly proceeds to step 110 without performing the process corresponding to step 109 in the first embodiment.

After determining whether five minutes have elapsed since the start of the engine (step 106a), if five minutes have not elapsed, the normality determination permission flag XMTS is set to "1". (Step 1)
06b). And if the judgment is negative, EC
U51 terminates the process and does not interrupt the routine again until the next engine start.

If the processing routine is configured as in the present embodiment, for example, as shown in FIG. 10, the abnormal product warm-up counter ectf reaches the determination water temperature (ETHW + α) before a predetermined time (5 minutes) has elapsed since the engine was started. In this case, regardless of the operation state of the thermostat 16, it is determined that the cooling water temperature THW is likely to easily rise due to the operating state of the engine, the environment, and the like, and a determination is made as to whether the thermostat 16 is normal or abnormal. Will not be performed. For this reason, erroneous detection of normality or abnormality of the thermostat 16 is suitably prevented.

As described above, according to the third embodiment, the same effects as those of the first embodiment relating to the abnormality detection of the thermostat 16 can be obtained. Moreover, similarly to the second embodiment, erroneous detection when the operating state of the engine or the environmental condition does not meet the highly reliable determination condition can be more preferably avoided.

In each of the above embodiments, the cooling water temperature estimating means (warm-up counter) is provided on the assumption that the thermostat 16 is in two operating states related to abnormality and normal operation. Inoperable,
Three or more estimating means may be provided assuming an abnormality or the like in which the thermostat becomes inoperable in the fully opened state.

Further, a means for estimating the cooling water temperature may be added, assuming that the thermostat 16 is inoperable in the closed state. In this case, it is sufficient to assume a state in which the cooling water temperature continues to rise even after it exceeds a predetermined water temperature (80 ° C.). Then, for example, when the cooling water temperature by the estimating means reaches a predetermined value, an abnormality determination permission flag is set, and when the cooling water temperature by the water temperature sensor 41 exceeds the determination value, an abnormality determination is made based on logic. May be configured.

In each of the embodiments, the predetermined elapsed time after the start of the engine is set to 5 minutes as one criterion for detecting an abnormality of the thermostat 16. It depends on Therefore, an algorithm may be configured to appropriately determine the predetermined elapsed time based on the cooling water temperature at the time of starting.

After a lapse of a predetermined time from the start of the engine, the deviation between the measured cooling water temperature by the water temperature sensor 41 and the normal product warm-up counter is within a predetermined range, and the measured cooling water temperature and the abnormal product warm-up counter The algorithm may be configured such that a deviation from the predetermined value is out of a predetermined range as a condition for determining whether the thermostat 16 is normal.

Further, as in each embodiment, after a predetermined time has elapsed after the engine is started, the estimated water temperature by the plurality of cooling water temperature estimating means is compared with the value detected by the water temperature sensor 41,
The configuration for detecting the abnormality of the cooling system can be applied to the abnormality detection of the water temperature sensor 41.

Although the embodiments of the present invention have been described above, technical ideas other than the claims that can be grasped from the embodiments will be described below together with their effects. The cooling water circulation passage of the engine, when the cooling water temperature is lower than a predetermined value, to close the passage, when the cooling water temperature is equal to or higher than a predetermined value, to open the cooling passage to detect an abnormal operation of the thermostat, A cooling water temperature detecting means for detecting a cooling water temperature of the engine; if the detected cooling water temperature is lower than a predetermined reference water temperature after a lapse of a predetermined time after starting the engine, it is determined that the operation of the thermostat is abnormal; When the detected cooling water temperature is equal to or higher than a predetermined reference water temperature, in a thermostat abnormality detecting device that determines that the thermostat is operating normally, a condition assuming an abnormal operation of the thermostat is assumed. A cooling water temperature estimating means for estimating a cooling water temperature under the condition, and estimating the cooling water temperature under conditions assuming normal operation of the thermostat. A plurality of cooling water temperature estimating means including a cooling water temperature estimating means, wherein a thermostat operation abnormality is detected based on a difference between the cooling water temperature estimated by the plurality of cooling water temperatures and the cooling water temperature detected by the cooling water temperature detecting means. An abnormality detection device for a thermostat that limits a determination condition for detection.

With this configuration, it is possible to improve the reliability in determining whether the thermostat is abnormal or normal. An engine cooling device including a cooling water circulation passage, cooling water filled in the passage, and cooling water temperature detecting means for detecting a cooling water temperature for cooling the engine;
If the detected cooling water temperature is lower than a predetermined reference water temperature after a predetermined time has elapsed after starting the engine, it is determined that the engine cooling device is abnormal, and the detected cooling water temperature is determined to be the predetermined reference water temperature. In the above case, in the abnormality detecting device for the cooling device which determines that the cooling device is operating normally, the cooling water temperature estimating means for estimating the cooling water temperature under the condition assuming the abnormal operation of the cooling device. And a plurality of cooling water temperature estimating means including a cooling water temperature estimating means for estimating a cooling water temperature under conditions assuming normal operation of the cooling device, wherein the cooling water temperature estimated based on the plurality of cooling water temperatures; An abnormality detection device for an engine cooling device that determines that any of the members constituting the cooling device has an abnormality based on a deviation from the cooling water temperature detected by the water temperature detection means.

According to this configuration, when any member such as the cooling circulation passage or the cooling water temperature detecting device constituting the cooling device has an abnormality, the abnormality can be quickly and accurately grasped.

In this specification, the means and the concept according to the constitution of the invention are defined as follows. -The engine widely means a drive device, and includes an internal combustion engine, an external combustion engine, an electric motor, and the like.

The thermostat abnormality detecting device includes a device capable of not only detecting an abnormality of the thermostat, but also determining a normal or abnormal operation state. The suspension of the judgment (judgment) includes a broad concept from suspension to suspension, such as stopping the judgment in the current processing routine, as well as stopping the judgment until the next engine start.

[0076]

According to the first aspect of the present invention, two estimated cooling water temperatures are determined based on the engine operating state and the like under the assumed conditions of normal and abnormal operation of the thermostat. By calculating and comparing the predetermined reference water temperature with the respective estimated cooling water temperatures, and limiting the permission conditions for performing the abnormality determination or the normality determination, it is possible to improve the reliability of the thermostat abnormality or normality determination. it can. Further, when the thermostat is normal under an operating condition or an environmental condition in which the temperature rise of the engine is relatively fast, it is possible to quickly confirm the thermostat.

According to the second aspect of the present invention, even in the case where the slope relating to the rise of the cooling water temperature during the warm-up operation is gentle and the operating state of the thermostat is assumed to be abnormal, it can be analogized. If there is a possibility that the slow rise in the cooling water temperature may be caused by other factors such as the operating state of the engine or environmental conditions, the determination that the thermostat is abnormal is suspended, thereby making an erroneous determination. It is possible to suitably prevent such a situation.

According to the third or fourth aspect of the present invention,
Even when the slope relating to the rise of the cooling water temperature during the warm-up operation is sufficiently large and the thermostat is assumed to be operating normally, the high rise rate of the cooling water temperature indicates the operating state of the engine. If there is a possibility that the thermostat is caused by other factors such as environmental conditions or the like, by suspending the determination that the thermostat is normal, erroneous determination can be suitably prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of an engine cooling system to which a thermostat abnormality detection device according to the present invention is applied.

FIG. 2 is a block diagram showing an electrical configuration of an ECU.

FIG. 3 is a flowchart illustrating a thermostat abnormality detection procedure according to the first embodiment;

FIG. 4 is a flowchart illustrating a thermostat abnormality detection procedure according to the first embodiment;

FIG. 5 is a time chart comparing changes in normal and abnormal warm-up counters.

FIG. 6 is a time chart showing an example of a change mode of the cooling water temperature after starting the engine.

FIG. 7 is a time chart showing an example of a change mode of the cooling water temperature after starting the engine.

FIG. 8 is a flowchart illustrating a thermostat abnormality detection procedure according to the second embodiment.

FIG. 9 is a flowchart illustrating a thermostat abnormality detection procedure according to the third embodiment.

FIG. 10 is a time chart showing an example of a mode of change of the cooling water temperature after the engine is started.

[Explanation of symbols]

1 ... Engine, 2 ... Cooling system, 3 ... Cylinder, 4 ...
Piston, 5 ... crankshaft, 6 ... connecting rod, 7
... water jacket, 8 ... radiator, 9 ... cooling fan, 10 ... water pump, 11 ... combustion chamber, 12 ... cylinder head, 13 ... cylinder block, 16 ... thermostat, 41 ... water temperature sensor, 42 ... throttle sensor,
43: rotation speed sensor, 44: intake pressure sensor, 45: oxygen sensor, 46: vehicle speed sensor, 47: intake temperature sensor, 51
... ECU, 52 ... CPU, 53 ... ROM, 54 ... RA
M, 55: backup RAM, 56: timer counter, 57: external input circuit, 58: external output circuit, 59:
bus.

Claims (4)

[Claims] 1. A cooling water circulation passage for an engine,
A cooling water temperature detecting means for detecting a cooling water temperature of the engine to detect an operation abnormality of a thermostat for closing the passage when the cooling water temperature is lower than a predetermined value and opening a cooling passage when the cooling water temperature is higher than the predetermined value; If the detected cooling water temperature is lower than a predetermined reference water temperature after a predetermined time has elapsed after starting the engine, it is determined that there is an abnormality in the operation of the thermostat, and the detected cooling water temperature is predetermined. When the temperature is equal to or higher than the reference water temperature, in the thermostat abnormality detecting device that determines that the thermostat is operating normally, the first cooling for estimating the cooling water temperature under conditions assuming the thermostat operation abnormality is performed. Water temperature estimating means; second cooling water temperature estimating means for estimating a cooling water temperature under conditions assuming normal operation of the thermostat; A normal determination permission means for permitting a normal determination only when the cooling water temperature estimated by the first cooling water temperature estimating means is lower than a predetermined water temperature during a normal determination of the thermostat; and A thermostat abnormality detection device comprising: normal determination permission means for permitting abnormality determination only when the cooling water temperature estimated by the second cooling water temperature estimation means is equal to or higher than a predetermined water temperature. 2. After a predetermined period of time has elapsed since the start of the engine, if the cooling water temperature estimated by the second cooling water temperature estimating means is lower than the predetermined water temperature, it is determined whether or not the thermostat has a malfunction. The thermostat abnormality detection device according to claim 1 or 2, wherein the thermostat abnormality detection device is put on hold. 3. When the cooling water temperature estimated by the first cooling water temperature estimating means becomes equal to or higher than a predetermined water temperature before the cooling water temperature detected by the cooling water temperature detecting means becomes equal to or higher than a predetermined reference water temperature. 3. The thermostat abnormality detecting device according to claim 1, wherein the determination of whether there is an operation abnormality in the thermostat is suspended. 4. If the cooling water temperature estimated by the first cooling water temperature estimating means becomes equal to or higher than a predetermined water temperature before a predetermined time has elapsed after the start of the engine, the thermostat has an abnormal operation. The thermostat abnormality detection device according to any one of claims 1 to 3, wherein determination of whether or not the thermostat is abnormal is held.