JP2006070782A - Failure determination device for cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure determination device for a cooling device, performing failure determination in a state of specifing a failure mode. <P>SOLUTION: In this failure determination device for the cooling device cooling an internal combustion engine 10 by cooling water circulating a circuit with a thermostat 12, a water temperature sensor 42 for detecting the temperature of the cooling water is provided, and failure determination of the cooling device is performed based on the change state of the detected temperature when the detected temperature of the water temperature sensor 42 is within a predetermined temperature range. For example, the change state of the temperature detected by the water temperature sensor 42 is time required for the detected temperature of the water temperature sensor 42 to change from a lower limit value to an upper limit value within the predetermined temperature range, and when the change time exceeds predetermined time, closing failure of the thermostat 12 is determined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a failure determination device for a cooling device that cools an internal combustion engine with cooling water that circulates in a circulation path including a thermostat.

Conventionally, an abnormality of the cooling device is detected from the temperature of the engine coolant at the time of starting the engine, and when the rising gradient of the detected temperature of the water temperature sensor does not indicate a predetermined rising gradient, it is determined that the water temperature sensor is abnormal. A technique for determining that the thermostat is abnormal when an upward gradient greater than a predetermined value is shown is known (see, for example, Patent Document 1).
JP-A-11-173149

  However, as disclosed in the above-mentioned prior art, a failure of the engine cooling device may be an abnormality of a thermostat or a water temperature sensor. However, in the above-described conventional technology, the cause of the failure of the cooling device is considered. Even if the location (whether it is a thermostat or a water temperature sensor) can be identified, it is impossible to grasp even the failure mode (failure mode).

  Accordingly, an object of the present invention is to provide a failure determination device for a cooling device that performs failure determination in such a manner that a failure mode can be specified.

In order to solve the above-described problem, according to one aspect of the present invention, in a failure determination device for a cooling device that cools an internal combustion engine with cooling water that circulates a circulation path including a thermostat,
A water temperature sensor for detecting the temperature of the cooling water is provided, and a failure determination of the cooling device is performed based on a change mode of the detected temperature when the temperature detected by the water temperature sensor is within a predetermined temperature range. A failure determination device for a cooling device is provided.

  In this aspect, the change mode of the detection temperature of the water temperature sensor includes a change time required for the detection temperature of the water temperature sensor to change from a lower limit value to an upper limit value of the predetermined temperature range, and the change time is a predetermined time. In the above case, it may be determined that the thermostat is closed.

  Further, the change mode of the detection temperature of the water temperature sensor includes a change time required for the detection temperature of the water temperature sensor to change from the upper limit value to the lower limit value of the predetermined temperature range, and the change time is equal to or longer than the predetermined time. In this case, it may be determined that the thermostat is open.

In addition, a change mode of the detected temperature of the water temperature sensor is such that the rising time required for the detected temperature of the water temperature sensor to change from the lower limit value to the upper limit value of the predetermined temperature range and the detected temperature of the water temperature sensor are A descent change time required to change from the upper limit value to the lower limit value of the predetermined temperature range,
It may be determined that the response of the water temperature sensor is abnormal when the rising change time is a predetermined time or more and the falling change time is a predetermined time or more.

  Further, a means for calculating the engine heat generation amount during the change time may be further provided, and the predetermined time may be changed according to the calculated engine heat generation amount.

  Further, the change mode of the detection temperature of the water temperature sensor includes the number of times the detection temperature of the water temperature sensor repeats the rising process and the lowering process within the predetermined temperature range per predetermined time, and the number of times is less than a predetermined value. The water temperature sensor may be determined to be a failure.

  In any case, the upper limit value of the predetermined temperature range corresponds to the temperature at which the thermostat opening operation occurs, and the lower limit value of the predetermined temperature range corresponds to the temperature at which the thermostat closing operation occurs. May be.

  As described above, according to the present invention, it is possible to obtain a failure determination device for a cooling device that performs failure determination in a manner in which a failure mode can be specified.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

FIG. 1 is a system configuration diagram showing an embodiment of a cooling apparatus failure determination apparatus according to the present invention. The failure determination device for a cooling device according to the present embodiment is configured around an electronic control unit 40 (hereinafter referred to as “ECU 40”). The ECU 40 is configured as a microcomputer including a CPU, a ROM, a RAM, and the like connected to each other via a bus (not shown). The ECU 40 may be embodied by an EFI / ECU that controls the engine (internal combustion engine) 10. The ECU 40 has a CAN (controller area)
Various electronic components in the vehicle (for example, a vehicle speed sensor and a meter ECU) are connected via an appropriate bus such as a network.

  The engine 10 includes a thermostat 12 that opens and closes depending on the temperature of engine cooling water. The thermostat 12 is a kind of automatic valve, and closes when the temperature of the engine cooling water is low, suppresses heat dissipation of the engine cooling water, opens when the temperature of the engine cooling water is high, and promotes heat dissipation of the engine cooling water. Thus, it has a function of maintaining the engine cooling water within a desired temperature range. The present invention does not particularly specify the configuration or type (such as a bellows type or wax type) of the thermostat 12 in detail, and can be applied to any thermostat that can be opened and closed depending on the temperature of the engine cooling water. is there.

  In the example of the cooling device schematically shown in FIG. 2, the thermostat 12 is provided integrally with, for example, a water inlet housing. In a state where the thermostat 12 is opened, the engine coolant from the cylinder head is circulated by the water pump through the thermostat 12 to the cylinder block and the cylinder head after being radiated by the radiator. The present invention does not particularly specify the configuration of the cooling device such as the engine cooling water circulation method and the arrangement of the thermostat 12, but can be applied to any cooling device including a thermostat.

  The ECU 40 is connected to a water temperature sensor 42 that detects the temperature of engine cooling water. The water temperature sensor 42 is disposed, for example, in a water jacket in the intake manifold of the engine 10 and supplies an electric signal corresponding to the temperature of the engine cooling water to the ECU 40.

  FIG. 3 shows the relationship between the opening / closing timing of the thermostat 12 and the detected temperature of the water temperature sensor 42 with time on the horizontal axis. FIG. 3A shows that both the thermostat 12 and the water temperature sensor 42 are normal. The graph in the case is shown.

As shown in FIG. 3A, when the engine is started, the temperature of the engine cooling water rises with an increase in the amount of heat generated by the engine, and eventually reaches the valve opening temperature T _OPEN of the thermostat 12 so that the thermostat 12 Open operation. When the thermostat 12 is opened, the temperature of the engine coolant begins to drop accordingly, and eventually reaches the valve closing temperature T _CLOSE of the thermostat 12, and the thermostat 12 is closed. When the thermostat 12 is closed, the temperature of the engine cooling water starts to rise accordingly, and eventually reaches the valve opening temperature T _OPEN of the thermostat 12, and the thermostat 12 is opened. Thereafter, similarly, the opening / closing operation of the thermostat 12 is repeated under the precondition that the engine heat generation amount is within a certain appropriate range.

  FIG. 3B shows the same graph when the thermostat 12 has a closed failure. The failure of closing of the thermostat 12 means that the movement of the thermostat 12 in the closing direction becomes defective due to the deterioration of the movement of the wax part or the inclusion of foreign matter, and the thermostat 12 does not completely close (does not return to the closed state). Refers to failure mode. When the thermostat 12 is closed, the thermostat 12 is not completely closed. Therefore, as shown in FIG. 3B, the temperature rise of the engine cooling water becomes slow.

  FIG. 3C shows the same graph when the thermostat 12 has an open failure. The opening failure of the thermostat 12 refers to a failure mode in which the movement of the thermostat 12 in the opening direction becomes defective due to a foreign object biting in the spring portion and the thermostat 12 does not fully open (does not return to the open state). Say. When the opening of the thermostat 12 fails, the thermostat 12 does not open completely, and as shown in FIG. 3C, the temperature drop of the engine cooling water becomes slow.

  FIG. 3D shows the same graph when the water temperature sensor 42 has a response abnormality. The response abnormality of the water temperature sensor 42 is a failure mode in which the detected temperature of the water temperature sensor 42 follows the temperature change of the engine cooling water for a while, but the followability is poor. Therefore, when the response of the water temperature sensor 42 is abnormal, as shown in FIG. 3 (D), the manner of raising and lowering the detected temperature of the water temperature sensor 42 is generally slow.

In the present embodiment, paying attention to the manner of change in the detected temperature of the water temperature sensor 42 that varies depending on such a difference in failure mode, the detected temperature of the water temperature sensor 42 is within a predetermined temperature range (T _{CLOSE to} T _OPEN ). One feature is that a failure determination of the cooling device is performed based on the detected temperature change mode.

  The characteristic configuration of the present invention will be described below with reference to FIG. FIG. 4 is a flowchart illustrating an example of a flow of processing executed by the ECU 40.

First, when the ignition switch is turned on and the engine 10 is started, the ECU 40 determines whether or not the temperature detected by the water temperature sensor 42 is _{equal to} or higher than the valve closing temperature T _CLOSE (step 100). When the detected temperature of the water temperature sensor 42 is equal to or higher than the valve closing temperature T _CLOSE, it is determined that the thermostat 12 has shifted to the opening / closing operation state, and the process proceeds to an abnormality determination process in step 200 and subsequent steps.

On the other hand, when the detected temperature of the water temperature sensor 42 is not equal to or higher than the valve closing temperature T _CLOSE , the ECU 40 estimates the temperature rise of the engine cooling water (step 110), and the estimated water temperature of the engine cooling water is a predetermined value (for example, the valve closing temperature). If it is equal to or greater than (T _CLOSE ) (YES determination at step 120), similarly, it is determined that the thermostat 12 has shifted to the opening / closing operation state, and the routine proceeds to an abnormality determination process at step 200 and thereafter. On the other hand, if the estimated value is not greater than or equal to the predetermined value (NO determination at step 120), it is determined that the thermostat 12 has not yet shifted to the opening / closing operation state, and the current processing routine is terminated.

  Here, the estimated water temperature of the engine cooling water in step 110 may be any appropriate method. For example, the integrated value of the heat generated by the engine (supplied heat amount) accumulated after the engine is started and the vehicle speed (vehicle speed sensor). It may be calculated on the basis of the integrated value (heat radiation amount) of the cooling amount that changes depending on the detection). The estimated water temperature may be corrected in consideration of the intake air temperature of the engine 10 and the atmospheric pressure. The calculation method of the engine heat generation amount may be any appropriate method, and may be calculated based on, for example, an integrated value of the intake air amount of the engine 10.

According to the processing in steps 100 to 120 described above, when the temperature of the engine cooling water enters the operating temperature range (T _{CLOSE to} T _OPEN ) of the thermostat 12, the process proceeds to the abnormality determination processing in step 200 and subsequent steps. Thus, it is possible to make an abnormality determination by paying attention only to the manner of change in the detected temperature of the water temperature sensor 42 within the operating temperature range of the thermostat 12. That is, it is possible to make an abnormality determination based on the change mode of the temperature detected by the water temperature sensor 42 from around the time t0 shown in FIG.

If the estimated value is equal to or greater than the predetermined value, the process proceeds to an abnormality determination process in step 200 and _subsequent steps while the detected temperature of the water temperature sensor 42 remains below the valve closing temperature _TCLOSE . In this case, the engine cooling water is estimated. Unless the estimation error of the water temperature is large, a failure of the water temperature sensor 42 will be determined in an abnormality determination process in step 210 or 220 described later.

  When the process proceeds to the abnormality determination process after step 200, first, the ECU 40 observes and monitors the change mode of the detected temperature of the water temperature sensor 42 over a predetermined monitoring time Tmn (step 200). During this time, the ECU 40 determines the engine heat generation amount Wup per unit time while the temperature detected by the water temperature sensor 42 is rising, and the engine heat generation amount Wdn per unit time while the temperature detected by the water temperature sensor 42 is decreasing. Is calculated in each ascending process and each descending process.

Further, ECU 40 may detect the temperature closing temperature T _CLOSE from opening temperature T _OPEN until rising time variation time required to raise the water temperature sensor 42 Tup, and the detected temperature is opening temperature T _OPEN of the water temperature sensor 42 the falling time change time Tdn taken to descend until closing temperature T _CLOSE from calculated at each rising process and the falling process.

  When the predetermined monitoring time Tmn elapses, the ECU 40 performs the processing from step 300 onward based on the information (information obtained in step 200) acquired during that time.

In step 300, it is determined as a first failure determination whether or not the water temperature sensor 42 is in failure (function failure). This determination is, for example,
(A) The integrated value of the engine heat generation amount during the monitoring time Tmn is within an appropriate range, and
(B) When the number of inversions between the ascending process and the descending process during the monitoring time Tmn is equal to or less than a predetermined threshold Th1.
It is assumed that the water temperature sensor 42 is out of order. This is because, after it has been estimated that the temperature of the engine cooling water has reached a certain level, while the appropriate engine heat generation amount continues to be generated, the water temperature sensor has the number of inversions (> predetermined threshold Th1) corresponding thereto. This is because it can be determined that there is a failure in the water temperature sensor 42 if only the number of times of reversal that is contrary to the prediction can be obtained. The number of inversions is the number of times that the temperature detected by the water temperature sensor 42 has shifted from the rising process to the falling process and vice versa. As shown in FIG. It may be counted as the number of times of crossing the intermediate value Th2 within the operating temperature range (T _{CLOSE to} T _OPEN ) of the thermostat 12. The condition (a) is for ensuring the failure determination under the condition that the thermostat 12 is appropriately opened and closed as described above, and the thermostat 12 is caused by an abnormally high engine heat generation amount. This is for eliminating the failure determination under the condition that the valve is kept open or the condition where the thermostat 12 is kept closed due to a small engine heat generation amount. From this point of view, when the time not satisfying the condition (a) is occupied in the monitoring time Tmn, the process of step 300 may be performed again.

  In this step 300, the predetermined threshold value Th1 for the number of inversions is variable according to the integrated value of the engine heat generation amount, considering that the number of inversions changes depending on the magnitude of the integrated value of the engine heat generation amount. May be. When the ECU 40 determines that the water temperature sensor 42 is out of order, the ECU 40 generates and outputs a warning signal and a predetermined diagnosis code requesting the lighting of a predetermined warning lamp (step 400), and this processing routine is terminated. In this case, of course, the abnormality determination after step 320 on the precondition that the water temperature sensor 42 is normal is not executed.

In the subsequent step 310, it is determined whether or not the water temperature sensor 42 is abnormal in response as the second failure determination. As described with reference to FIG. 3D, this determination is performed based on whether or not the rising / lowering mode of the temperature detected by the water temperature sensor 42 is generally slow. In this example,
(D) The rising change time Tup is larger than the threshold value Tju, and
(E) When the descending change time Tdn is larger than the threshold value Tjd,
It is determined that the water temperature sensor 42 is abnormal in response. In this case, from the same viewpoint as the first failure determination described above, the condition (a) may be added.

  In step 310, the threshold value Tju for the rising change time Tup is preferably changed according to the engine heat generation amount Wup in the rising change time Tup, as shown in FIG. This is to take into account that the appropriate change time Tup during the increase decreases as the engine heat generation amount Wup increases. Similarly, the threshold value Tjd for the descending change time Tdn is preferably changed according to the engine heat generation amount Wdn during the descending change time Tdn, as shown in FIG. This is to take into account that the appropriate descending change time Tdn decreases as the engine heat generation amount Wdn increases.

  When the ECU 40 determines that the water temperature sensor 42 is abnormal in response, the ECU 40 generates and outputs a warning signal and a predetermined diagnosis code for requesting lighting of a predetermined warning lamp (step 400), and this processing routine is terminated. In this case, of course, the abnormality determination after step 320 on the precondition that the water temperature sensor 42 is normal is not executed.

In the following step 320, it is determined whether or not the thermostat 12 is an open failure as a third failure determination. As described with reference to FIG. 3C, this determination is performed based on whether or not the manner in which the detected temperature of the water temperature sensor 42 decreases is slow. In this example,
(F) The rising change time Tup is smaller than the threshold value Tju, and
(G) When the descending change time Tdn is larger than the threshold value Tjd,
It is determined that the thermostat 12 is open and has a failure. In this case, from the same viewpoint as the first failure determination described above, the condition (a) may be added.

  Similarly, in step 320, the threshold value Tju and threshold value Tjd for the rising change time Tup and the falling change time Tdn are preferably set as shown in FIGS. 5 (A) and 5 (B). It changes according to engine heat generation amount Wup, Tdn. Note that the threshold Tju and the threshold Tjd may be the same as or different from the threshold used in step 310.

  If the ECU 40 determines that the thermostat 12 is open and malfunctioning, the ECU 40 generates and outputs a warning signal and a predetermined diagnosis code requesting lighting of a predetermined warning lamp (step 400), and the processing routine is terminated. If it is determined that the thermostat 12 is not open and malfunctioning, the process proceeds to step 330.

In the following step 330, it is determined whether or not the thermostat 12 is a closed failure as a fourth failure determination. As described with reference to FIG. 3B, this determination is performed based on whether or not the rising mode of the detected temperature of the water temperature sensor 42 is slow. In this example,
(H) The rising change time Tup is larger than the threshold value Tju, and
(I) When the descending change time Tdn is smaller than the threshold value Tjd,
It is determined that the thermostat 12 is closed and has a failure. In this case, from the same viewpoint as the first failure determination described above, the condition (a) may be added.

  Similarly in step 330, the threshold value Tju and the threshold value Tjd for the rising change time Tup and the falling change time Tdn are preferably set as shown in FIGS. 5 (A) and 5 (B). It changes according to engine heat generation amount Wup, Tdn. Note that the threshold value Tju and the threshold value Tjd may be the same as or different from the threshold values used in step 310 and step 320 described above.

  If the ECU 40 determines that the thermostat 12 is closed and malfunctioned, the ECU 40 generates and outputs a warning signal and a predetermined diagnosis code requesting lighting of a predetermined warning lamp (step 400), and the processing routine is terminated. If the determination in step 320 is negative, it is determined that the cooling device is normal (step 410), and the processing routine ends.

  As described above, according to the present embodiment, four types of failure modes are performed through the first to fourth failure determinations, that is, (1) failure of the water temperature sensor 42 (failure), and (2) water temperature. An abnormal response of the sensor 42, (3) a closing failure of the thermostat 12, and (4) an opening failure of the thermostat 12 can be identified.

  Further, according to the present embodiment, it is possible to cope with a warning or the like according to the difference in the abnormal mode even during traveling. For example, when an open failure of the thermostat 12 is determined, the engine 10 is likely to be in an overheated state, and it is effective to immediately output a warning prompting stoppage of travel, whereas a close failure of the thermostat 12 is determined. In this case, although it is likely to be overcooled, there is no hindrance to traveling to a repair shop such as a dealer. Therefore, it is effective to mainly provide navigation guidance to the repair shop with a warning.

  Further, according to the present embodiment, the failure mode can be easily specified from the diagnosis code (four types of diagnosis codes in this example) extracted by a dealer or the like, so that the repair of the failure is facilitated.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above-described embodiment, assuming the situation where it is not certain that “the water temperature sensor 42 is normal”, which is a precondition for the abnormality determination of the thermostat 12, The estimation process and the failure / response abnormality determination process of the water temperature sensor 42 in the above steps 300 and 310 are executed. If, for example, the normality of the thermostat 12 is determined by another determination method, the above step 110 is performed. 120 and the above steps 300 and 310 may be omitted. In this case, if there is at least one step of raising and lowering the temperature detected by the water temperature sensor 42, the abnormality determination in steps 320 and 330 can be performed, and the determination in a shorter time is possible.

In the above-described embodiment, the number of inversions evaluated in step 300 may be the number of inversions in any section as long as the thermostat 12 is in the open / close operation state, for example, the valve opening temperature T _{OPEN of the} thermostat 12. The counting may be started from the stage of reaching.

Further, the operating temperature range (T _{CLOSE to} T _OPEN ) of the thermostat 12 may be determined based on the design value of the thermostat 12 or determined based on the relationship with the actual detected temperature of the water temperature sensor 42. Also good.

1 is a system configuration diagram showing an embodiment of a cooling device failure determination device according to the present invention. 2 is a diagram illustrating an example of a schematic configuration of a cooling device including a thermostat 12. FIG. It is a graph which shows the relationship between the opening-and-closing timing of the thermostat 12, and the detection temperature of the water temperature sensor 42 taking time on a horizontal axis. 3 is a flowchart illustrating an example of a flow of processing executed by an ECU 40. It is a figure which shows the change aspect of threshold value Tju and threshold value Tjd according to engine calorific value Wup and Tdn.

Explanation of symbols

10 Engine 12 Thermostat 40 ECU
42 Water temperature sensor

Claims (7)

In a failure determination device for a cooling device that cools an internal combustion engine with cooling water that circulates in a circulation path including a thermostat,
A water temperature sensor for detecting the temperature of the cooling water is provided, and a failure determination of the cooling device is performed based on a change mode of the detected temperature when the temperature detected by the water temperature sensor is within a predetermined temperature range. Failure determination device for cooling device.   The change mode of the detection temperature of the water temperature sensor includes a change time required for the detection temperature of the water temperature sensor to change from a lower limit value to an upper limit value of the predetermined temperature range, and when the change time is a predetermined time or more The failure determination device for a cooling device according to claim 1, wherein the failure determination device determines that the failure is a thermostat closing failure.   The change mode of the detected temperature of the water temperature sensor includes a change time required for the detected temperature of the water temperature sensor to change from the upper limit value to the lower limit value of the predetermined temperature range, and when the change time is equal to or longer than the predetermined time. The failure determination device for a cooling device according to claim 1, wherein the failure determination device determines that the opening failure of the thermostat. The change mode of the detected temperature of the water temperature sensor is such that the rising time required for the detected temperature of the water temperature sensor to change from the lower limit value to the upper limit value of the predetermined temperature range and the detected temperature of the water temperature sensor are the predetermined temperature. Including the descent time required to change from the upper limit to the lower limit of the temperature range,
The failure of the cooling device according to claim 1, wherein when the rising change time is a predetermined time or more and the falling change time is a predetermined time or more, it is determined that the response of the water temperature sensor is abnormal. Judgment device. Means for calculating an engine heat generation amount during the change time;
The failure determination device for a cooling device according to any one of claims 2 to 4, wherein the predetermined time is changed in accordance with the calculated engine heat generation amount.   The change mode of the detection temperature of the water temperature sensor includes the number of times that the detection temperature of the water temperature sensor repeats the rising step and the falling step within the predetermined temperature range per predetermined time, and when the number of times is equal to or less than a predetermined value, The cooling device failure determination device according to claim 1, wherein the failure determination device determines that the water temperature sensor has failed.   The upper limit value of the predetermined temperature range corresponds to a temperature at which the thermostat opening operation occurs, and the lower limit value of the predetermined temperature range corresponds to a temperature at which the thermostat closing operation occurs. The failure determination device for a cooling device according to claim 1.

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