JP3480281B2 - Thermostat abnormality detection device - Google Patents

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 abnormality of a thermostat which opens and closes a part of a circulation passage of cooling water in order to adjust a heat radiation effect of a heat generating engine by the cooling water.

[0002]

2. Description of the Related Art A thermostat is a passage opening / closing valve that opens and closes at a specific temperature and is used in a cooling water passage of a water-cooling type cooling device.

For example, in a cooling device widely used for automobile engines, cooling water is constructed to circulate 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 the heat generated from the inside of the engine and further dissipates it to the outside through the radiator.

Here, the thermostat opens and closes the circulation path of the 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.) during warm-up immediately after the engine is started, the valve is closed, and when the cooling water temperature is higher than the predetermined value, the valve is open. The cooling water is circulated between the inside of the engine and the radiator.

By the way, the thermostat closes in a natural state where the cooling water is at room temperature, but it often fails to close in a fully open state or a half open state due to deterioration of members or the like. In such a case, not only the engine becomes supercooled and the efficiency of the heater decreases, but also when the engine is at a low temperature, the fuel injection amount is increased, that is, so-called low temperature increase is always executed, which in turn reduces fuel consumption and exhaust gas. It was supposed to make it worse.

[0006] With respect to such a problem, for example, Japanese Patent Laid-Open No.
In the "cooling water warming / injecting device for automobiles etc." described in JP-A-213117, a detection device for determining that the thermostat is abnormal when the water temperature detected by the water temperature sensor during steady operation is not within a reference range is disclosed. It is provided.

Further, in the technique of this publication, it is determined that the operating state of the thermostat is abnormal when the cooling water temperature measured by a water temperature sensor or the like is below a predetermined value after a predetermined time has elapsed after the engine was started. The composition is also taken.

[0008]

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

In addition to the operating state of the thermostat, the mode of change of the cooling water temperature after the engine is started greatly differs depending on the operating state of the engine and external environmental conditions. Therefore, according to the latter configuration, the normal thermostat becomes abnormal. There is a possibility of erroneous determination, such as deciding that
There has been a problem that sufficient reliability in abnormality detection cannot be obtained. Further, there is a drawback that the confirmation of the normal operating state of the thermostat must wait for a predetermined time set in advance in any case.

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

[0011]

In order to achieve the above object, the invention according to claim 1 is provided in a cooling water circulation passage of an engine, and when the cooling water temperature is below a predetermined value, the passage is closed. The cooling water temperature detecting means for detecting the cooling water temperature of the engine is provided in order to detect the operation abnormality of the thermostat which opens the cooling passage when the cooling water temperature is equal to or higher than a predetermined value. If the measured 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, and if the detected cooling water temperature is equal to or higher than the predetermined reference water temperature, the thermostat operates normally. In a thermostat abnormality detection device that determines that the thermostat is operating, a first method for estimating the cooling water temperature under a condition in which the thermostat operation abnormality is assumed. The cooling water temperature estimating means, the second cooling water temperature estimating means for estimating the cooling water temperature under the condition that the thermostat is normally operated, and the first cooling water temperature estimating means for estimating the normality of the thermostat Normality determination permission means for permitting normality determination only when the cooling water temperature is lower than a predetermined water temperature, and the cooling water temperature estimated by the second cooling water temperature estimation means at the time of abnormality determination of the thermostat is equal to or higher than a predetermined water temperature. and summarized in that with only a abnormal determination permission means for permitting abnormality determination when it is.

According to the above construction, two estimated cooling water temperatures are calculated on the basis of the engine operating state and the like under the assumed conditions that the operating state of the thermostat is normal and the operating state is abnormal. By comparing the water temperature and the respective estimated cooling water temperatures and limiting the permission conditions for the abnormality determination or the normal determination, it is possible to improve the reliability in the abnormality or normal determination of the thermostat. Further, when the thermostat is normal under operating conditions or environmental conditions where the temperature rise of the engine is relatively fast, the confirmation can be performed quickly.

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

According to the above configuration, even when it is presumed that the operating state of the thermostat is abnormal due to the gradual slope of the cooling water temperature rise during the warm-up operation, the cooling water temperature When there is a possibility that the slow rising mode is caused by other factors such as engine operating conditions and environmental conditions, it is possible to suitably prevent erroneous judgments by suspending the judgment that the thermostat is abnormal. 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 is detected before the cooling water temperature detected by the cooling water temperature detecting means exceeds a predetermined reference water temperature. When the cooling water temperature estimated by the cooling water temperature estimating means is equal to or higher than the predetermined water temperature, the gist is to suspend the determination as to whether or not the thermostat has an abnormal operation.

According to a fourth aspect of the present invention, in the thermostat abnormality detecting device according to any of the first to third aspects, the first cooling water temperature estimating means estimates the engine before starting a predetermined time after starting the engine. When the temperature of the cooling water is equal to or higher than a predetermined water temperature, the gist is to suspend the determination as to whether or not the thermostat has an abnormal operation.

According to the configuration of the invention described in claim 3 or 4, it is inferred that the inclination of the increase of the cooling water temperature during the warm-up operation is sufficiently large and the thermostat apparently operates normally. However, if there is a possibility that the high rate of increase of the cooling water temperature may be due to other factors such as engine operating conditions and environmental conditions, the judgment that the thermostat is normal should be suspended. As a result, it is possible to preferably prevent erroneous determination.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment, in which the thermostat abnormality detection device according to the present invention is applied to an engine cooling system of an automobile, will be described below 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 connecting the piston 4 and the crankshaft 5, a water jacket 7 surrounding the cylinder 3, an outer space of the engine body, and its internal space communicates with the water jacket 7. A radiator 8, a cooling fan 9, a water pump 10 and the like are provided.

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 motion 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 the intake / exhaust port (not shown). The water jacket 7 as a space for circulating the cooling water cools the cylinder head 12 and the cylinder block 13 heated by the explosion / combustion of the air-fuel mixture as necessary, or maintains a constant temperature.
It is configured to surround the outer periphery of the.

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

The water temperature sensor 41 provided on the inner wall of the water jacket 7 detects the temperature THW of the cooling water and sends the detection signal to the electronic control unit (ECU) 51. Next, an electronic control unit (ECU) 51 that controls and diagnoses each part 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. 2, the ECU 5
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 in which these units are connected to an external input circuit 57 and an external output circuit 58 by a bus 59. Here, the ROM 53 stores in advance programs relating to various operation controls, failure diagnosis, and the like. The RAM 54 temporarily stores the calculation result of the CPU 52 and the like. The backup RAM 55 is a non-volatile memory that stores data even after the engine is stopped. The timer counter 56 can simultaneously perform a plurality of timing operations. The external input circuit 57 includes a buffer, a waveform circuit, a hard filter (a circuit including an electric resistance 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 the throttle valve opening degree TA according to 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 is
Detects oxygen concentration in exhaust gas. The intake pressure sensor 45 detects the intake pressure PM. The vehicle speed sensor 46 detects the 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
U52 reads the detection signals of the various sensors 41 to 47 input via the external input circuit 57 as input values. C
Based on these input values, the PU 52 executes various operation controls such as control of the fuel injection amount and fuel injection timing by the injector 48, failure diagnosis, and the like.

Next, of the various controls executed by the ECU 51, the contents of the control relating to the abnormality detection of the thermostat 16 will be described. 3 and 4 show a "thermostat abnormality detection routine" for detecting the thermostat abnormality of the present embodiment. A program relating to this routine is stored in advance in the ROM 53 of the ECU 51, 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, at step 101, the count values e of the normal product warm-up counter and the abnormal product warm-up counter.
cts and ect f are predetermined values Δects and Δectf, respectively.
Count up one by one. Here, the warm-up counter is an estimation counter for calculating an estimated value of the current cooling water temperature from the engine operating condition which changes every moment and environmental conditions such as cooling water temperature at the time of engine start and outside air temperature. The water temperature THW0 at start, intake air temperature THA, heater ON
The estimated value is calculated with reference to a map (not shown) that is 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 product warm-up counter uses the estimated cooling water temperature (count value e) under the assumption that the thermostat 16 is operating normally.
cts), while the abnormal product warm-up counter calculates the estimated cooling water temperature (count value ectf) under the assumption that the thermostat 16 has an abnormality.

As shown in FIG. 5, the estimated cooling water temperature of the normal product warm-up counter (hereinafter referred to simply as the normal product counter) is
A mode is shown in which, after the normal engine start (time t0), the temperature continues to increase monotonously for a while, and when a predetermined temperature (for example, 80 ° C.) is reached, the constant temperature is maintained. Cooling water temperature is 80 ℃
Thermostat 16 remains closed until
This is because the operation of opening the valve at 80 ° C or higher and returning to the closed state at 80 ° C is repeated. On the other hand, in the case of the estimated cooling water temperature (hereinafter, simply referred to as abnormal product warming counter) ectf by the abnormal product warming counter, its rising speed is slower than the estimated cooling water temperature ects of the normal product warming counter, and on the time chart, , Will show a slower slope. Since the thermostat 16 remains open, the radiator 8 and the engine 1 are always
This is because the cooling water circulates between them and becomes supercooled when the cooling water temperature is low at the time of starting the engine or immediately after the starting.

In the following step 102, the judgment cooling water temperature (ET) preset by the abnormal product warm-up counter ectf is set.
HW + α) or more is determined. If the determination is affirmative, the process proceeds to step 103a,
If the determination is negative, the process proceeds to step 103b.

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

In step 104, the determination cooling water temperature (ETHW) preset by the normal product warm-up counter ects is set.
+ Α) or more is determined. Then, if the determination is negative, the process proceeds to step 105a, and if the determination is positive, 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 either case, the process proceeds to step 106.

In step 106 (FIG. 4), it is judged whether or not the 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 judgment water temperature (ETHW + α), that is, the reference water temperature ETHW or more. . 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, the normal determination permission flag XMTS is "0" (no setting), the routine processing of this time is once ended. On the other hand, if the determination is affirmative, the process proceeds to step 108 and step 10
In 8, it is judged that "the thermostat 16 is normal" and the routine processing of this time is ended. Step 1
If the routine processing is terminated after the determination in 08, EC
U51 prohibits execution of another interrupt of the routine process.

On the other hand, if a negative determination is made in step 106, the process proceeds to step 109, and in step 109, a predetermined time (5 minutes in this embodiment) has elapsed after the engine was started. Determine whether or not. If the determination is affirmative, the ECU 51 shifts the process to step 110, and if the determination is negative, the process is temporarily terminated.

In step 110, it is determined whether or not the abnormality determination permission flag XMTF is set to "1". Then, if the determination is negative, the routine processing of this time is once ended. On the other hand if the determination is affirmative, the flow goes to step 11 1, the step 111
In, it is judged that "the thermostat 16 is abnormal". Then, the processing of this time is ended, and the execution of another interrupt to this routine is prohibited.

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

The ECU 51 executes the thermostat 16 based on the "thermostat abnormality detection routine" described above.
The abnormal condition, that is, the malfunction in the fully opened or half opened state is detected. Further, when the operating state of the thermostat 16 is normal, it is confirmed. As is clear from this routine, the ECU 51 determines that the thermostat 1
Assuming that 6 is normal and that the thermostat 16 is abnormal, the estimated values of the cooling water temperature under both conditions are used as normal product warming counter ects and abnormal product warming counter ectf in various operating states. Calculate based on the parameters.

Then, after the engine is started, the abnormal item warm-up counter ectf being less than the judgment water temperature value (ETHW + α) is a permission condition for judging that the thermostat 16 is operating normally ( Step 103
b). Further, inevitably, the abnormal item warm-up counter ectf being equal to or higher than the determination water temperature value (ETHW + α) is a prohibition condition that the determination that the thermostat 16 is normally operating should not be made (step 103a).

On the other hand, the fact that the normal product warm-up counter ects becomes equal to or higher than the judgment water temperature value (ETHW + α) after the engine is started is a permission condition for judging that the operating state of the thermostat 16 is abnormal. Also, inevitably, the normal product warm-up counter ects determines the determination water temperature value (ETHW +
If it is less than α), it is a prohibition condition that it is not possible to determine that the operating state of the thermostat 16 is abnormal.

In this way, after the permission and prohibition conditions relating to the normal or abnormal determination THW of the thermostat 16 are set, the actual measured value THW of the cooling water temperature by the water temperature sensor 41 is
5 minutes before the engine starts, or 5 minutes before
Even after the lapse of minutes, under the prohibition condition of abnormality determination, the reference water temperature is equal to or higher than ETHW, and the normal determination permission flag X
Thermostat 1 if MTS is set to "1"
It is determined that the operating state of 6 is normal.

On the other hand, even after 5 minutes, the water temperature sensor 4
If the measured value THW of the cooling water temperature according to 1 is less than the reference value ETHW and is under the abnormality determination permission condition (XMTF = “1”), it is determined that the operating state of the thermostat 16 is abnormal.

Here, the actual cooling water temperature T in the engine cooling system equipped with the abnormality detecting device according to this embodiment is used.
The relationship between the HW and the change between the normal product warm-up counter ects and the abnormal product warm-up counter ectf over time,
This will be described with reference to FIGS. 6 and 7. In addition, e shown in the figure
Reference numerals such as cts, ectf, ETHW, and XMTF are the same as those shown in the flowcharts of FIGS. 3 and 4.

In the engine cooling system equipped with the abnormality detecting device according to the present embodiment, FIG. 6 shows a change with time of the cooling water temperature THW or the like when an abnormal operation of the thermostat 16 occurs (inoperable with the valve open). An example is shown. In the figure, the normal product warm-up counter ects is point A (time t
In a), the judgment water temperature (ETHW + α) is reached, and the abnormal product counter ectf has reached the judgment water temperature (ETHW + α) at point B (time tb). Here, for example, like the transition pattern shown by the curve (1),
In the period in which the normality determination permission flag XMTS is set to "1", before 5 minutes have elapsed from the engine start,
When the cooling water temperature THW is equal to or higher than the reference value ETHW, or when the normal determination permission flag XMTS is set to "1", the abnormality determination permission flag XMTF is "1" even after 5 minutes have elapsed. When the cooling water temperature THW becomes equal to or higher than the reference value ETHW within the period set to, it is determined that the thermostat 16 is operating normally.

On the other hand, as shown by the transition pattern indicated by the curve (2) or (3), after 5 minutes, the cooling water temperature is increased even though the normal product counter ectf is equal to or higher than the judgment water temperature (ETHW + α). If THW does not reach the reference water temperature ETHW, it is determined that the operating 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, which assume both normal and abnormal conditions relating to the operating state of the thermostat, are calculated and used as criteria for determination. This improves the accuracy and reliability of thermostat abnormality detection.

Further, as shown in FIG. 7, the normal product warm-up counter ec is maintained even after a predetermined time (5 minutes) has elapsed after the engine was started.
If ts is below the judgment water temperature (ETHW + α),
Regardless of the operating state of the thermostat 16, it is determined that the cooling water temperature is in a condition where it is difficult to increase due to the operating state of the engine, the environment, etc., and the determination of normality or abnormality related to the thermostat 16 is suspended. Become.

Here, in the conventional thermostat abnormality detection device, the thermostat 1 according to the same judgment standard with respect to the difference in the operating state of the engine and the external environmental condition.
6 abnormalities were detected.

In this respect, according to the thermostat abnormality detection apparatus of the present embodiment, even if the cooling water temperature is difficult to rise, erroneous detection can be preferably prevented by considering the conditions. .

According to this 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 normal and abnormal thermostat operating conditions as criteria for thermostat abnormality detection, and by establishing permission conditions for normal and abnormal thermostat determination, Precision and reliability in normal / abnormal detection are improved.

・ Even if a predetermined time has elapsed after the engine was started,
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 appropriately prevented.

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

The device of the second embodiment is also applied to the engine cooling system of an automobile, and after the engine is started,
This is to determine whether the thermostat is operating normally or abnormally.

Further, also in the apparatus of the second embodiment, the configuration of the engine cooling system of the automobile to which the invention is applied (FIG. 1) and the circuit configuration of the ECU (electronic control unit) 51 are the same as those of the above It is similar to the device of one embodiment, and redundant description thereof is omitted here.

In the apparatus of the second embodiment, of the "thermostat abnormality detection routine" shown in FIGS. 3 and 4, the portion corresponding to the routine shown in FIG. 4 is shown in FIG. To be replaced in a routine,
The processing contents of the steps having the same reference numerals are the same.

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

In step 106b, step 1
02, 103a and 103b (FIG. 3), it is determined whether the normal determination permission flag XMTS is set to "1". And if the decision is positive,
The process proceeds to step 109.

On the other hand, if the determination is negative, the ECU 51
Does not interrupt the routine again until the engine is started next time. 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 by the water temperature sensor 41 reaches the reference water temperature ETHW, until the next engine operation. Will prevent the thermostat 16 from being judged to be abnormal or normal.

With the above-described structure, 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 detection device according to the present invention will be described, focusing on the points different from the first embodiment.

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

Also in the device of the third embodiment, as in the second embodiment, the configuration of the engine cooling system of the automobile to which the invention is applied (FIG. 1) and the circuit configuration of the ECU (electronic control unit) 51. Is similar to the device of the first embodiment described above, and redundant description of them here will be omitted.

Now, the device of the third embodiment is similar to that of FIG.
In the "thermostat abnormality detection routine" shown in FIG. 4 and FIG. 4, a portion corresponding to the routine shown in FIG. 4 is replaced with the routine shown in FIG. The processing content is also the same.

That is, in the thermostat abnormality detection routine of the third embodiment, as shown in FIG. 9, after the processing of step 106a having the same processing content as that of step 109 in the first embodiment described above, the judgment is made. The process proceeds to step 106 or step 106b depending on the. If the determination in step 106b is affirmative, the process proceeds to step 106, but if the determination is negative, the process ends, and the routine is interrupted again until the next engine start. Will not be performed. Further, in the processing in step 106, E
When the determination of the CU 51 is negative, the process corresponding to step 109 in the first embodiment is not performed, and the process directly proceeds to step 110.

As described above, if it is determined that 5 minutes have not elapsed since the engine was started (step 106a) and 5 minutes have not elapsed, the normal determination permission flag XMTS is set to "1". Whether or not (step 1
06b). If the decision is negative, EC
U51 ends the process and does not interrupt the routine again until the next engine start.

If the processing routine is configured as in this embodiment, as shown in FIG. 10, for example, the abnormal product warm-up counter ectf reaches the judgment water temperature (ETHW + α) before a predetermined time (5 minutes) has elapsed after the engine was started. In this case, regardless of the operating state of the thermostat 16, it is determined that the cooling water temperature THW is easily increased due to the operating state of the engine, the environment, etc., and it is determined whether the thermostat 16 is normal or abnormal. Will not be done. Therefore, erroneous detection of whether the thermostat 16 is normal or abnormal is suitably prevented.

As described above, according to the third embodiment as well, the same effect as that of the first embodiment relating to the abnormality detection of the thermostat 16 can be obtained. Moreover, as in the second embodiment, it is possible to more appropriately avoid the erroneous detection when the operating state of the engine or the environmental conditions do not meet the highly reliable determination conditions.

In each of the above-mentioned embodiments, the cooling water temperature estimating means (warm-up counter) is provided assuming two kinds of operating states relating to abnormality and normality of the thermostat 16, but the thermostat 16 is in a half-open state, for example. Inoperable,
Three or more estimating means may be provided on the assumption that the thermostat is inoperable when it is fully opened.

Further, it is possible to add a cooling water temperature estimating means which assumes an abnormality in which the thermostat 16 is inoperable when the thermostat 16 is closed. In this case, it may be assumed that 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 estimation 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 performed based on an algorithm based on a logic. Should be configured.

Further, in each of the embodiments, the predetermined elapsed time after the engine is started is set to 5 minutes as one standard for detecting the abnormality of the thermostat 16. However, this value depends on the characteristics of the engine and the external environment. It depends on Therefore, the algorithm may be configured to appropriately determine the predetermined elapsed time based on the cooling water temperature at the time of starting.

Further, after a lapse of a predetermined time after the engine is started, the deviation between the measured cooling water temperature by the water temperature sensor 41 and the normal product warming counter is within a predetermined range, and the measured cooling water temperature and the abnormal product warming counter are the same. The algorithm may be configured so that the condition for normality determination of the thermostat 16 is that the deviation between and is outside the predetermined range.

Further, as in each of the present embodiments, by comparing the estimated water temperature by the plurality of cooling water temperature estimation means with the detection value of the water temperature sensor 41 after a lapse of a predetermined time after the engine is started,
The configuration for detecting the abnormality of the cooling system can also be applied to the abnormality detection of the water temperature sensor 41.

Although the respective embodiments of the present invention have been described above, technical ideas other than the claims which can be understood from the embodiments will be described below together with their effects. -To detect an abnormal operation of a thermostat, which is provided in the cooling water circulation passage of the engine, closes the passage when the cooling water temperature is lower than a predetermined value and opens the cooling passage when the cooling water temperature is equal to or higher than the predetermined value. Equipped with cooling water temperature detection means for detecting the cooling water temperature of the engine, and when the detected cooling water temperature is lower than a predetermined reference water temperature after a predetermined time elapses after the engine is started, it is determined that the operation of the thermostat is abnormal. If the detected cooling water temperature is equal to or higher than a predetermined reference water temperature, in the thermostat abnormality detection device for determining that the thermostat is operating normally, a condition assuming an abnormal operation of the thermostat. Cooling water temperature estimating means for estimating the cooling water temperature below, 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 is provided, and 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 are based on the deviation of the thermostat operation abnormality. A thermostat abnormality detection device that limits the determination conditions for detection.

According to this structure, it is possible to improve the reliability in determining whether the thermostat is abnormal or normal. Provided in an engine cooling device having a cooling water circulation passage, cooling water filled in the passage, and cooling water temperature detecting means for detecting the cooling water temperature in order to cool the engine,
When the detected cooling water temperature is lower than the predetermined reference water temperature after a predetermined time has elapsed after the engine is started, it is determined that the engine cooling device has an abnormality, and the detected cooling water temperature is the predetermined reference water temperature. In the above case, in the cooling device abnormality detection device that determines that the cooling device is operating normally, the cooling water temperature estimation means that estimates the cooling water temperature under the condition that the cooling device operation abnormality is assumed. 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, the cooling water temperature estimated by the plurality of cooling water temperatures, and the cooling An abnormality detecting device for an engine cooling device, which determines that there is an abnormality in any of the members constituting the cooling device based on the deviation from the cooling water temperature detected by the water temperature detecting means.

According to this structure, when there is an abnormality in any member such as the cooling circulation passage or the cooling water temperature detecting device that constitutes the cooling device, the abnormality can be grasped quickly and accurately.

In this specification, means and concepts relating to the constitution of the invention are defined as follows. -The term "engine" generally 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 not only a device that detects an abnormality of the thermostat but also a device that can determine the normal and abnormal operating states. -Holding a judgment (judgment) includes a broad concept from temporary interruption to cancellation, such as not only canceling the judgment in the processing routine of that time but also canceling the judgment until the next engine start.

[0076]

According to the first aspect of the present invention, two estimated cooling water temperatures are calculated on the basis of the engine operating state and the like under the assumed conditions that the thermostat is operating normally and abnormally, respectively. By calculating and comparing the predetermined reference water temperature with each estimated cooling water temperature and limiting the permission conditions for making an abnormality judgment or a normal judgment, it is possible to improve the reliability in the abnormality or normal judgment of the thermostat. it can. Further, when the thermostat is normal under operating conditions or environmental conditions where the temperature rise of the engine is relatively fast, the confirmation can be performed quickly.

According to the second aspect of the present invention, even when it is presumed that the operating state of the thermostat is apparently abnormal because the slope of the rise of the cooling water temperature during the warm-up operation is slow. , If there is a possibility that the mode of slowly increasing the cooling water temperature is due to other factors such as engine operating conditions and environmental conditions, the judgment that the thermostat is abnormal is suspended to make a false judgment. It becomes possible to prevent it suitably.

According to the invention described in claim 3 or 4,
Even if the slope of the cooling water temperature rise during warm-up operation is sufficiently large and it seems that the thermostat is apparently operating normally, the high rate of increase of the cooling water temperature is the operating state of the engine. When there is a possibility that it is caused by other factors such as the environmental conditions, environmental conditions, etc., it is possible to preferably prevent the erroneous determination by suspending the determination that the thermostat is normal.

[Brief description of 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 showing a thermostat abnormality detection procedure according to the first embodiment.

FIG. 4 is a flowchart showing a thermostat abnormality detection procedure of the first embodiment.

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

FIG. 6 is a time chart showing an example of how the cooling water temperature changes after the engine is started.

FIG. 7 is a time chart showing an example of how the cooling water temperature changes after the engine is started.

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

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

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

[Explanation of symbols]

1 ... Engine, 2 ... Cooling system, 3 ... Cylinder, 4 ...
Piston, 5 ... Crank shaft, 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 ... Revolution 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.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02D 45/00 F01P 3/20 F01P 7/16 F02B 77/08

Claims (4)

(57) [Claims] 1. A cooling water circulation passage for an engine,
Cooling water temperature detecting means for detecting the cooling water temperature of the engine so as to detect an abnormal operation of a thermostat that closes the passage when the cooling water temperature is below a predetermined value and opens the cooling passage when the cooling water temperature is above a predetermined value. When 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, and the detected cooling water temperature is predetermined. In the abnormality detection device of the thermostat that determines that the thermostat is operating normally when the temperature is equal to or higher than the reference water temperature of No. 1, the first cooling that estimates the cooling water temperature under the condition assuming the operation abnormality of the thermostat Water temperature estimating means, a second cooling water temperature estimating means for estimating the cooling water temperature under conditions assuming normal operation of the thermostat, and At the time of normal determination of the thermostat, a normal determination permission unit that permits the normal determination only when the cooling water temperature estimated by the first cooling water temperature estimation unit is below a predetermined water temperature, and at the time of abnormality determination of the thermostat, thermostat device for detecting abnormality coolant temperature estimated by the second coolant temperature estimating means and a abnormal determination permission means for permitting only abnormality determination when at least a predetermined temperature. 2. If a cooling water temperature estimated by the second cooling water temperature estimating means is lower than a predetermined water temperature after a lapse of a predetermined time after the engine is started, it is determined whether or not the thermostat has an abnormal operation. The thermostat abnormality detection device according to claim 1 or 2, which is held. 3. The cooling water temperature estimated by the first cooling water temperature estimating means is equal to or higher than a predetermined water temperature before the cooling water temperature detected by the cooling water temperature detecting means is equal to or higher than a predetermined reference water temperature. 3. The thermostat abnormality detection device according to claim 1, wherein the determination of whether or not the thermostat has an operation abnormality 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 elapses after the engine is started, the thermostat has an abnormal operation. The thermostat abnormality detection device according to any one of claims 1 to 3, characterized in that the determination as to whether or not it is suspended.