JP4385492B2 - Thermostat failure diagnosis device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a failure diagnosis device for a thermostat provided in an engine cooling system.
[0002]
[Prior art]
Conventionally, for example, as shown in JP-A-4-339127, a cooling device and a control device that controls the cooling device are provided, and the control device is controlled according to various operating parameters of the engine (internal combustion engine). In a temperature control device for an engine in which different temperature target values are set, a target value generator is provided in the control device, and the target value generator sets different temperature target values for the control device according to various use states. Has been done.
[0003]
The cooling device of the temperature control device includes a thermostat that switches between a state in which cooling water of the engine is circulated to the radiator (cooler) side and cooled and a state in which the cooling water is returned to the engine via a short-circuit pipe without being supplied to the radiator side. A valve (mixing valve) is provided. Then, the temperature target value set according to the operating state of the engine is compared with the actual engine temperature. When the engine temperature is equal to or higher than the temperature target value, the thermostat valve is opened and the cooling water is supplied to the radiator. By circulating the cooling water to the side, when the engine temperature is lower than the temperature target value, by circulating the cooling water to close the thermostat valve and bypass the radiator, The temperature of the cooling water is rapidly increased.
[0004]
Further, in order to diagnose a failure of the thermostat valve, it is detected whether or not an increase in the engine temperature occurs while the thermostat valve is intentionally closed, and when the increase in the engine temperature does not occur, Diagnosing that a failure has occurred in the thermostat valve is performed.
[0005]
[Problems to be solved by the invention]
In the above temperature control apparatus configured to control the temperature target value serving as a reference for executing the opening / closing control of the thermostat valve according to the operating state of the engine, the thermostat valve is intentionally closed. Based on the degree of increase in the engine temperature in the state, when it is configured to detect a failure of the thermostat valve, the engine temperature changes according to the control of the temperature target value. There is a problem that it is difficult to accurately diagnose the failure of the thermostat valve.
[0006]
For example, when the temperature target value is set to a low temperature side and the engine coolant temperature is controlled to be low, the coolant temperature does not change so significantly even if the thermostat valve is closed. Although the valve is normal, there are problems such as being misdiagnosed as being in an open failure state, or being misdiagnosed as being normal even though the thermostat valve is abnormal.
[0007]
The present invention has been made in view of the above points, and an object of the present invention is to provide a thermostat failure diagnosis device capable of accurately diagnosing a failure of a thermostat valve with a simple configuration.
[0012]
[Means for Solving the Problems]
Claim 1 The invention according to the invention is an electric control type that is opened to circulate the cooling water to the radiator when the cooling water temperature of the engine is higher than the target temperature, and is closed when the cooling water temperature is lower than the target temperature. A thermostat valve, target temperature setting means for setting the target temperature in correspondence with the operating state of the engine, and a failure detection means for detecting an open failure of the thermostat valve in a valve closing temperature region, the failure detection The target temperature is set to be higher than the normal time until the open failure detection by the means is completed.
[0013]
According to the above configuration, the target temperature is set higher than the normal time by the target temperature setting means when the failure detection means detects the open failure of the thermostat valve in the valve closing temperature region where the cooling water temperature is lower than the target temperature. Therefore, the occurrence of misdiagnosis due to the fact that there is no difference between the target temperature and the actual cooling water temperature is prevented.
[0014]
Claim 2 The invention according to the invention is an electric control type that is opened to circulate the cooling water to the radiator when the cooling water temperature of the engine is higher than the target temperature, and is closed when the cooling water temperature is lower than the target temperature. A thermostat valve, target temperature setting means for setting the target temperature in correspondence with the operating state of the engine, and failure detection means for detecting a closing failure of the thermostat valve in the valve opening temperature region, and detecting this failure The target temperature is set to be lower than the normal time until the closed failure detection by the means is completed.
[0015]
According to the above configuration, when the failure detection means detects the thermostat valve closing failure in the valve opening temperature range where the cooling water temperature is higher than the target temperature, the target temperature is lower than normal by the target temperature setting means. Therefore, the occurrence of misdiagnosis due to the fact that there is no difference between the target temperature and the actual cooling water temperature is prevented.
[0016]
Claim 3 The invention according to claim 1 Or 2 The thermostat failure diagnosis device according to claim 1, further comprising feedback control means for feedback-controlling the thermostat valve so that the actual cooling water temperature approaches the target temperature, and based on a deviation between the target temperature and the actual cooling water temperature during the feedback control. Thus, the failure detection means detects the failure of the thermostat valve.
[0017]
According to the above configuration, for example, when the open-circuit failure of the thermostat valve is detected by the failure detection means in the valve closing temperature region where the cooling water temperature is lower than the target temperature, the target temperature and the actual temperature obtained by the feedback control means are detected. By determining whether or not the state in which the deviation from the cooling water temperature is larger than the predetermined value has continued for a predetermined time, it is accurately diagnosed whether or not the open failure has occurred.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates the present invention. Reference form 1 shows a cooling system for a vehicle engine having the thermostat failure diagnosis apparatus according to FIG. The cooling system includes a first pipe 3 that supplies cooling water derived from the engine body 1 to the radiator 2 and a second pipe 4 that supplies cooling water cooled by the radiator 2 to the engine body 1. The second pipe 4 is provided with a cooling water pump 5 that supplies cooling water to the engine body 1 and a temperature sensor 6 that detects the temperature of the cooling water.
[0019]
The first pipe 3 and the second pipe 4 are connected at two locations by a first bypass pipe 7 and a second bypass pipe 8. Of the two bypass pipes 7 and 8, the first bypass pipe 7 on the engine body 1 side is provided with a heater core 9 of the heating device, and the second bypass pipe 8 and the second pipe 4 on the radiator 2 side are arranged. An electrically controlled thermostat valve 10 is disposed at the connection portion. The first bypass Piping 7 is the first bypass when room heating is not performed. Piping An on-off valve (not shown) is provided to prevent the cooling water from flowing into 7.
[0020]
The thermostat valve 10 is electrically opened when the coolant temperature of the engine is higher than the target temperature, and allows the upstream side portion 4a and the downstream side portion 4b of the second pipe 4 to communicate with each other. Second bypass piping 8 And the second pipe 4 are shut off to supply high-temperature cooling water led out from the engine body 1 to the radiator 2 to be cooled, and then supplied to the engine body 1 through the second pipe 4. It is configured as follows.
[0021]
Further, when the coolant temperature of the engine is lower than the target temperature, the thermostat valve 10 is electrically closed to shut off the upstream side portion 4a and the downstream side portion 4b of the second pipe 4. , Second bypass piping 8 The second bypass pipe is connected to the radiator 2 without supplying the high-temperature cooling water derived from the engine body 1 to the radiator 2 by communicating with the second pipe 4. 8 To the engine main body 1 via the downstream side portion 4b of the second pipe 4.
[0022]
The thermostat failure diagnosis device includes a target temperature setting means 11 for setting the target temperature in accordance with the operating state of the engine, and the thermostat valve 10 based on the target temperature set by the target temperature setting means 11. Feedback control means 12 for feedback control, failure detection means 13 for detecting open and closed faults of the thermostat valve 10, failure detection prohibiting means 14 for prohibiting failure detection by the failure detection means 13 as necessary, Alarm means 15 for notifying that a failure has occurred in the thermostat valve 10 in accordance with a failure detection signal output from the failure detection means 13 is provided.
[0023]
The target temperature setting means 11 sets the target temperature to, for example, 80 ° in order to set the cooling water temperature to an optimum value during normal operation of the engine, for example, at the time of warm except for extremely low load or extremely high load. The target temperature is set to, for example, about 90 ° C. in order to quickly raise the coolant temperature during low-load operation of the engine and the engine body 1 during high-load operation of the engine. The target temperature is set to be lower than 80 ° C. in order to prevent the temperature from rising excessively.
[0024]
The feedback control means 12 obtains a deviation between the target temperature set by the target temperature setting means 11 and the actual cooling water temperature detected by the temperature sensor 6, and sends an open / close signal corresponding to this deviation to the thermostat valve 10. By outputting, feedback control is performed to match the actual cooling water temperature with the target temperature.
[0025]
The failure detecting means 13 detects whether an open failure or a closed failure has occurred in the thermostat valve 10 based on the deviation between the target temperature obtained by the feedback control means 12 and the actual cooling water temperature, and this detection signal Is output to the alarm means 15.
[0026]
That is, in the valve closing temperature region where the actual cooling water temperature is lower than the target temperature, it is confirmed that the state where the absolute value of the deviation is equal to or greater than a predetermined value continues for a certain period of time and the cooling water temperature does not rise. In such a case, an open failure detection signal indicating that an open failure has occurred in the thermostat valve 10 is output to the alarm means 15.
[0027]
In addition, in the valve opening temperature region where the actual cooling water temperature is higher than the target temperature, it is confirmed that the state where the absolute value of the deviation is equal to or greater than a predetermined value continues for a certain period of time and the cooling water temperature does not decrease. In this case, a closed failure detection signal indicating that a closed failure has occurred in the thermostat valve 10 is output to the alarm means 15.
[0028]
The failure detection prohibiting means 14 detects the open failure of the thermostat valve 10 by the failure detecting means 13 when the target temperature is set to less than 80 ° C. by the target temperature setting means 11 during high engine operation. And when the target temperature is set to about 90 ° C. by the target temperature setting means 11 during low load operation of the engine or the like, the failure detection means 13 prohibits the detection of the closed failure of the thermostat valve 10. It is configured as follows.
[0029]
A basic control operation executed in the failure diagnosis apparatus having the above configuration will be described with reference to a flowchart shown in FIG. When the control operation starts, it is determined whether or not the target temperature TT set by the target temperature setting means 11 is higher than the actual cooling water temperature TS detected by the temperature sensor 6 (step S1).
[0030]
If it is determined YES in step S1 and the target temperature TT is higher than the actual cooling water temperature TS, that is, it is confirmed that the temperature is in the closed temperature region of the thermostat valve 10, the target temperature setting means 11 It is determined whether or not the set target temperature TT is set to a lower temperature than the normal time (step S2).
[0031]
When it is determined NO in step S2 and it is confirmed that the target temperature TT is set to a normal temperature of about 80 ° C or a high temperature side of about 90 ° C, failure detection control described later is executed. After that (step S3), the opening / closing control of the thermostat valve 10 based on the deviation between the target temperature TT and the actual cooling water temperature TS is executed (step S4).
[0032]
On the other hand, when it is determined as YES in step S2 and it is confirmed that the target temperature TT is set to a low temperature side less than 80 ° C, for example, about 70 ° C, the failure detection control is prohibited. After (step S5), the process proceeds to step S4 and the opening / closing control of the thermostat valve 10 is executed.
[0033]
If it is determined NO in step S1 and it is confirmed that the target temperature TT is lower than the actual cooling water temperature TS, that is, in the valve opening temperature region of the thermostat valve 10, the target temperature setting means Whether or not the target temperature TT set in 11 is set to a higher temperature than the normal time is determined (step S6). When it is determined NO in step S6 and it is confirmed that the target temperature TT is set to a normal temperature of about 80 ° C or a low temperature side of less than 80 ° C, the process proceeds to step S3. The failure detection control of the thermostat valve 10 is executed.
[0034]
On the other hand, if it is determined as YES in step S2 and it is confirmed that the target temperature TT is set to a high temperature side of about 90 ° C., the process proceeds to step S5 to detect the failure of the thermostat valve 10. Prohibit control.
[0035]
Next, the failure detection control executed in step S3 of the basic control will be described based on the flowchart shown in FIG. When the control operation starts, it is determined whether or not the cooling water temperature has risen to some extent after a predetermined time, for example, about 300 seconds has elapsed after the engine is started (step S11). Determines whether the failure diagnosis of the thermostat valve 10 is in an incomplete state (step S12).
[0036]
If YES is determined in step S12, after obtaining a deviation ΔT between the target temperature TT set in the target temperature setting means 11 and the actual cooling water temperature TS detected by the temperature sensor 6 ( Step S13), it is determined whether or not the absolute value | ΔT | of the deviation is larger than a preset reference deviation α (Step S14). If YES is determined in step S14, the count value C of the failure determination counter is incremented by 1 (step S15), and then the count value C is compared with a preset reference time β. Thus, it is determined whether or not a predetermined time has elapsed (step S16).
[0037]
If it is determined YES in step S16 and it is confirmed that the absolute value | ΔT | of the deviation is larger than the reference deviation α for a predetermined time or longer, the thermostat valve 10 is turned on. A detection signal indicating that an open failure or a closed failure has occurred is output to the alarm means 15 to notify that a failure has occurred (step S17).
[0038]
For example, when detecting an open failure of the thermostat valve 10 that is executed in a valve closing temperature range in which the target temperature TT is higher than the actual cooling water temperature TS, a state in which the actual cooling water temperature TS is lower than the target temperature TT by a predetermined value or more is a predetermined time If it is confirmed that the engine coolant temperature has not risen close to the target temperature, it is determined that an open failure has occurred in which the thermostat valve 10 is stuck open for some reason. An open failure detection signal is output to the alarm means 15.
[0039]
In addition, when detecting a closed failure of the thermostat valve 10 that is executed in a valve opening temperature region in which the target temperature TT is lower than the actual cooling water temperature TS, a state in which the actual cooling water temperature TS is larger than the target temperature TT by a predetermined value or more is a predetermined time. If it is confirmed that the engine coolant temperature has not decreased to near the target temperature, it is determined that a closed failure has occurred in which the thermostat valve 10 is stuck in the closed state for some reason. A closed failure detection signal is output to the alarm means 15.
[0040]
If NO is determined in step S14 and it is confirmed that the absolute value | ΔT | of the deviation is equal to or smaller than a reference deviation α set in advance to a predetermined value, the count value C is set to 0. After resetting (step S18), the process returns. On the other hand, if it is determined as NO in step S16 and it is confirmed that the count value C of the failure determination counter is equal to or less than the reference value β, the process returns as it is and the above control operation is repeated.
[0041]
As described above, the valve is opened to circulate the cooling water to the radiator 2 when the engine cooling water temperature is higher than the target temperature, and is closed when the cooling water temperature is lower than the target temperature. The thermostat valve 10, the target temperature setting means 11 for setting the target temperature according to the operating state of the engine, the failure detection means 13 for detecting an open failure of the thermostat valve 10 in the valve closing temperature region, and the target There is provided a failure detection prohibiting means for prohibiting the detection of an open failure by the failure detecting means when the target temperature is set to a lower temperature than the normal time by the temperature setting means. According to the thermostat failure diagnosis apparatus according to the above reference embodiment The failure of the thermostat valve 10 can be accurately diagnosed with a simple configuration.
[0042]
That is, since the presence or absence of the open failure is detected in a region excluding the operation state where the target temperature TT is set to the low temperature side as described above, for example, in the high temperature region where the target temperature TT is set to about 90 ° C, If the thermostat valve 10 is normal, feedback control is performed to bring the actual cooling water temperature TS closer to the target temperature TT as shown by the solid line in FIG. When an open failure has occurred in the thermostat valve 10, the actual cooling water temperature TS is maintained at a considerably lower state than the target temperature TT as shown by the broken line in FIG. The deviation between the temperature TT and the actual cooling water temperature TS increases.
[0043]
On the other hand, in the low temperature region where the target temperature TT is set to about 70 ° C., the target temperature TT and the actual cooling water temperature TS substantially coincide with each other even when the thermostat valve 10 has an open failure. Thus, there is a possibility that the thermostat valve 10 is erroneously diagnosed as being normal, or conversely, the thermostat valve 10 is normal but being erroneously diagnosed as being abnormal.
[0044]
Therefore, when the target temperature is set to a lower temperature than the normal time by the target temperature setting unit 11 as described above, the detection of the open failure by the failure detection unit 13 is prohibited, whereby the target temperature TT and the It is possible to prevent an erroneous diagnosis due to a small deviation from the actual cooling water temperature TS, and to accurately detect an open failure of the thermostat valve 10 based on the deviation.
[0045]
Further, when the target temperature is set to a lower temperature than the normal time by the target temperature setting means 11 as described above, the failure detection prohibiting means 14 detects the closing failure of the thermostat valve 10 by the failure detecting means 13. In this case, the closed failure detection is performed in a region excluding the operating state where the target temperature TT is set to the high temperature side, for example, in a low temperature region where the target temperature TT is set to about 70 ° C. Will be. For this reason, by determining whether or not feedback control for bringing the actual cooling water temperature TS close to the low target temperature TT is properly executed based on the deviation, the target temperature TT and the actual cooling water temperature TS are determined. It is possible to accurately detect a closed failure of the thermostat valve 10 without causing a misdiagnosis due to a small deviation of the thermostat valve 10.
[0046]
FIG. The above-described failure detection prohibiting means 14 is provided to prevent erroneous detection when a failure of the thermostat valve 10 is detected. Reference form Instead, when the open failure of the thermostat valve 10 is executed in the valve closing temperature region, the target temperature is set higher than the normal time by the target temperature setting unit 11 until the failure detection by the failure detection unit 13 is completed. In addition, when the failure of the thermostat valve 10 is executed in the valve opening temperature region, the target temperature TT is set from the normal time by the target temperature setting unit 11 until the failure detection by the failure detection unit 13 is completed. By setting the low temperature side as well, it is possible to accurately detect open and closed failures of the thermostat valve 10. 1 shows a configured thermostat failure diagnosis apparatus according to an embodiment of the present invention. .
[0047]
That is, it is determined whether or not the target temperature TT set in the target temperature setting means 11 is larger than the actual cooling water temperature TS detected by the temperature sensor 6 (step S21), and YES is determined in step S21. When it is confirmed that the target temperature TT is higher than the actual cooling water temperature TS, that is, in the valve closing temperature region of the thermostat valve 10, the target temperature setting means 11 sets the target temperature TT from the normal time. Is also set to the high temperature side (step S22).
[0048]
Next, the failure detection control by the failure detection means 13 is executed to detect the open failure of the thermostat valve 10 (step S23), and then the thermostat valve is opened and closed based on the deviation between the target temperature TT and the actual cooling water temperature TS. Control is executed (step S24).
[0049]
If it is determined NO in step S21 and the target temperature TT is lower than the actual cooling water temperature, that is, it is confirmed that the temperature is in the valve opening temperature region of the thermostat valve 10, the target temperature setting means 11 In step S25, the process goes to step S23, and the failure detection control by the failure detection means 13 is executed to detect a closed failure of the thermostat valve 10.
[0050]
When detecting the open failure of the thermostat valve 10 as described above, when the target temperature TT is forcibly set to the high temperature side, the actual cooling water temperature TS is set to a high temperature based on the deviation. By determining whether or not the feedback control approaching the target temperature TT is properly executed, the thermostat valve does not cause a misdiagnosis due to a small deviation between the target temperature TT and the actual cooling water temperature TS. Ten open faults can be accurately detected.
[0051]
In addition, when detecting the closed failure of the thermostat valve 10 as described above, when the target temperature TT is forcibly set to the low temperature side, the actual cooling water temperature TS is set based on the deviation. By determining whether or not the feedback control approaching the low target temperature TT is properly executed, a misdiagnosis caused by a small deviation between the target temperature TT and the actual cooling water temperature TS does not occur. A close failure of the thermostat valve 10 can be accurately detected.
[0052]
In the above embodiment, as shown in FIG. 3, the failure detecting means 13 detects an open failure or a closed failure of the thermostat valve 10 based on the deviation ΔT between the target temperature TT and the actual cooling water temperature TS during the feedback control. Since it comprised in this way, the failure of the thermostat valve 10 can be diagnosed correctly with a simple structure.
[0053]
The determination in step S21 is omitted, and the open failure diagnostic control in a state where the target temperature TT is set to the high temperature side and the closed failure diagnostic control in the state where the target temperature TT is set to the low temperature side are continuously performed. By doing so, an open failure or a closed failure of the thermostat valve 10 may be detected.
[0054]
Further, instead of the above embodiment, as shown in FIG. 6, when a high load and a high vehicle speed state are continued for a predetermined time or more, it is determined whether or not the actual cooling water temperature is increased, etc. An open failure of the thermostat valve 10 may be detected.
[0055]
That is, after the engine is started, the count value C of the failure diagnosis counter is reset to 0 (step Q1), and then it is determined whether or not the engine load is in a high load operating state larger than a predetermined value (step Q2). . If it is determined YES in step Q2, it is determined whether or not the vehicle speed is in a driving state at a high vehicle speed greater than a predetermined value (step Q3). If YES is determined, the count value is determined. C is incremented by 1 (step Q4). If it is determined NO in either of the steps Q2 and Q3, the count value C is reset to 0 (step Q12), and the process proceeds to the following step Q5.
[0056]
Next, a reference time CH for executing failure diagnosis based on the count value C is set based on the coolant temperature at the time of engine start (step Q5). That is, even if the engine and vehicle operating conditions are the same, the reference time CH is set to an appropriate value in order to compensate for changes in the temperature rise gradient of the coolant depending on the coolant temperature at that time.
[0057]
Then, it is determined whether or not the count value C of the counter is larger than the reference time CH (step Q6). If NO is determined, the process returns to step Q2. Further, when it is determined as YES in Step Q6 and it is confirmed that the count value C is larger than the reference time CH, the predicted temperature of the cooling water predicted from the operating state of the engine is a predetermined first value. It is determined whether or not the temperature is higher than the reference temperature t1 (step Q7).
[0058]
The predicted temperature of the cooling water is calculated, for example, by calculating the temperature rise in a predetermined short time using the engine load corresponding to the intake air amount, the vehicle speed, and the intake air temperature as parameters, and this temperature rise is used as the previous predicted temperature. Calculated by adding. The initial value of the predicted temperature is the actual cooling water temperature detected when the engine is started. Further, the first reference temperature t1 is set to a temperature equal to or lower than a target temperature that is a reference for opening and closing the thermostat valve 10.
[0059]
If YES is determined in step Q7, it is determined whether or not the actual cooling water temperature detected by the temperature sensor 6 is lower than a predetermined second reference temperature t2 (step Q8). The second reference temperature t2 is set below the target temperature of the thermostat valve 10 and corresponding to the first reference temperature t1. The second reference temperature t2 may be set to a temperature slightly lower than the first reference temperature t1, or the first reference temperature t1 and the second reference temperature t2 may be set to the same temperature.
[0060]
If it is determined NO in step Q8 and it is confirmed that the actual cooling water temperature is sufficiently high, that is, cooling by the radiator 2 is not executed, the thermostat valve 10 is closed. Therefore, it is determined to be normal (step Q9).
[0061]
If YES is determined in step Q8 and it is confirmed that the thermostat valve 10 is opened at a temperature considerably lower than the target temperature, it is determined that an open failure has occurred in the thermostat valve 10 (step Q10). ), An operation signal for operating the alarm means 15 is output (step Q11).
[0062]
As described above, when the high load and the high vehicle speed state are continued for a predetermined time or longer, an open failure of the thermostat valve 10 is detected. Due to the fact that a special operation such as running on a steep uphill in an accelerated state is performed, it is erroneously detected that the thermostat valve 10 is open even though the thermostat valve 10 is not open. This can be effectively prevented, and the failure of the thermostat valve 10 can be accurately diagnosed.
[0063]
Next, still another specific example of the failure detection control will be described based on the flowcharts shown in FIGS. When the control operation starts, the actual coolant temperature detected by the temperature sensor 6 is set as the initial value of the predicted coolant temperature (step Q21), and then the engine load, the vehicle speed, and the intake air temperature are calculated as parameters. The value of the predicted coolant temperature is updated based on the coolant temperature thus set (step Q22).
[0064]
Then, it is determined whether or not the actual cooling water temperature at the time of starting the engine is lower than a relatively low predetermined temperature set to about 35 ° C. (step Q23). The control operation is terminated without performing failure determination.
[0065]
If YES in step Q23, a temperature deviation obtained by subtracting the intake air temperature from the actual cooling water temperature at the time of starting the engine is obtained (step Q24), and this temperature deviation is, for example, about 10 ° C. It is determined whether or not the value is smaller than a sufficiently low value (step Q25), and if it is determined as NO, the control operation is terminated without performing the failure determination.
[0066]
If it is determined as YES in step Q25 and the actual cooling water temperature is at a low value, and it is confirmed that a failure diagnosis using an increase in the cooling water temperature is possible from the cold state, it is predicted cooling water. For example, it is determined whether or not the temperature is higher than a predetermined temperature set in an intermediate temperature range of about 40 ° C. (step Q26). If NO is determined, the process returns to step Q22.
[0067]
If it is determined YES in step Q26, the heat dissipation amount Qorh from the radiator 2 is calculated as described later, and the heat receiving amount Qig from the cooling water engine is calculated (steps Q27 and Q28). A heat quantity ratio R comprising the ratio of the heat radiation quantity Qorh to the heat reception quantity Qig is calculated (step Q29). The larger the heat quantity ratio R, the higher the possibility that the cooling water is cooled by the radiator 2.
[0068]
Next, it is determined whether or not the predicted coolant temperature is higher than a predetermined temperature (for example, 76 ° C.) that is equal to or lower than a target temperature that is a reference for opening / closing control of the thermostat valve 10 (step Q30). Returns to step Q22.
[0069]
If YES in step Q30, after setting a failure determination threshold value α1 based on the actual coolant temperature at the time of engine start (step Q41), the heat ratio R is It is determined whether or not it is larger than the threshold value α1 (step Q42). If YES is determined in step Q42, it is determined that an open failure has occurred in the thermostat valve 10 (step Q43), and a control signal for operating the alarm means 15 is output (step Q44).
[0070]
On the other hand, if NO is determined in step Q42, a normal determination threshold value α2 is set based on the actual cooling water temperature when the engine is started (step Q45), and then the heat quantity ratio R is set to the above value. It is determined whether or not it is smaller than threshold value α2 (step Q46). If it is determined as YES in step Q46, it is determined that the thermostat valve 10 is in a normal state where no open failure has occurred (step Q47).
[0071]
If NO is determined in step Q47, it is determined that the thermostat valve 10 is in a gray zone where it cannot be accurately determined whether the thermostat valve 10 is normal (step Q48). The threshold values α1 and α2 are set in order to compensate for the increase in the cooling water temperature depending on the cooling water temperature at the start of control, as in step Q5 in FIG. It is.
[0072]
The heat release amount Qorh is calculated based on the predicted cooling water temperature θcp and the cooling water temperature θea as described below, and the heat reception amount Qig is calculated based on an operating parameter indicating the operating state of the engine.
[0073]
First, the algebraic sum of the amount of heat per unit time transferred to the cooling water is proportional to the product of the heat capacity of the cooling water and the rate of temperature increase per unit time. By applying this relationship to the cooling system model shown in FIG. 1, a differential equation such as the following equation (1) is obtained.
[0074]
CM · dθe / dt = qig−qe−qor−qoh (1)
However,
C: Specific heat of cooling water [kcal / kg · ° K]
M: Mass of cooling water [kg]
θe: Cooling water temperature [° K]
qig: Heat quantity per unit time [kcal / s] transferred from the combustion gas to the cooling water
qoe: Heat quantity per unit time [kcal / s] transferred from the engine surface to the atmosphere
qor: heat quantity per unit time [kcal / s] transferred from the radiator surface to the atmosphere
qoh: Heat quantity per unit time [kcal / s] transferred from the heater core surface to the atmosphere
The amount of heat per unit time and the total amount of heat transferred from the combustion gas of the engine body 1 to the cooling water are determined according to the following equation (2) based on the amount of heat generated by the fuel that has contributed to combustion in the injected fuel.
[0075]
qig = Rcηg (γ) Huγgf (2)
However,
Rc: Ratio of the amount of heat transferred to the cooling water in the supply amount of combustion gas
ηg: Ratio of the calorific value of the combustion gas that contributes to an increase in the combustion gas temperature
γ: γ = λ when λ ≧ 1, and γ = 1 when λ <1
λ: Excess air ratio of combustion gas
gf: Fuel supply amount per unit time [kg / s]
Hu: Low calorific value of fuel [kcal / kg]
The amount of heat per unit time and total heat transferred from the engine surface, radiator surface, and heater core surface to the atmosphere is expressed by the following equation (3) for the engine surface, the following equation (4) for the radiator surface, and the following for the heater core surface: It can be expressed as shown in equation (4).
[0076]
qoe = koe (Vs) (θe−θae) (3)
However,
koe: Thermal conductivity from the engine surface to the atmosphere
Vs: Vehicle speed [km / h]
θae: Engine surface ambient temperature [° K]
qor = kor (Vs) (θe−θar) (4)
However,
kor: thermal conductivity from the radiator surface to the atmosphere
θar: Radiator surface ambient temperature [° K]
qoh = koh (Voh) (θe−θah) (5)
However,
koh: Thermal conductivity from the heater core surface into the atmosphere
Voh: Flow velocity of the atmosphere passing through the heater core surface [km / h]
θah: Ambient temperature on the heater core surface [° K]
By substituting the above formulas (3) to (5) into the formula (1), a differential formula of the following formula (6) can be obtained.
[0077]
CM · dθe / dt = qig−koe (Vs) (θe−θae) −kor (Vs) (θe−θar) −koh (Voh) (θe−θah) (6)
Here, at the time of practical use, the cooling system model is limited to detecting the open failure in the valve opening region of the thermostat valve 10, and the cooling system model targets below the valve opening temperature of the thermostat valve 10 for simplification. Also, θae, θar, θah, and Voh are respectively replaced with the intake air temperature θia. Further, when koh (Voh) is divided into a constant term at Voh = 0 and an increment from the constant term as shown in the following equation (7), qoe, qor and qoh are expressed by the following equations (8) to (10). become that way.
[0078]
koh (Voh) = Δkoh (Voh) + koh0 (7)
However, Δkoh (0) = 0
qoe = koe (Vs) (θe−θia) (8)
qor = kor (Vs) (θe−θia) (9)
qoh = [Δkoh (Voh) + koh0] (θe−θia) (10)
Therefore, the following equation (11) is obtained from the above equation (6).
[0079]
CM · dθe / dt = qig−k (Vs) (θe−θia) −qorh (11)
However,
qorh = qor + Δkoh (Voh) (θe−θia)
k (Vs) = koe (Vs) + koh0
If it is currently unknown whether the thermostat valve 10 is operating normally, that is, the qorh is unknown, the cooling water temperature at this time is set as the actual cooling water temperature detected by the temperature sensor 6 (θe = θea). ), The following equation (12) is obtained from the above equation (11).
[0080]
CM · dθea / dt = qig−k (Vs) (θea−θia) −qorh (12)
Next, θe = θep is defined as the unknown cooling water temperature when it is assumed that the thermostat valve 10 operates normally and the blower fan for heating does not operate. Also in this case, since it is considered that the path to the radiator 2 is disconnected and qorh = Qorh = 0, the following equation (13) is obtained from the above equation (11).
[0081]
CM · dθep / dt = qig−k (Vs) (θep−θia) (13)
By subtracting equation (12) from equation (13) and arranging qorh, the following equation (14) is obtained.
[0082]
qorh = CM · d (θep−θea) / dt + k (Vs) (θep−θea) (14)
When both sides of the above equation (14) are integrated, the following equation (15) is obtained.
[0083]
Qorh = CM (θep−θea) + ∫k (Vs) (θep−θea) dt (15)
Therefore, the calorie ratio R of Qorh to Qig is expressed by the following equation (16) from the above equations (15) and (2).
[0084]
R = Qorh / Qig = [CM (θep−θea) + ∫k (Vs) (θep−θea) dt] / ∫qigdt
In the above equation (16), the left side in the numerator is a term relating to a deviation between the current predicted cooling water temperature and the actual cooling water temperature, and the right side in the numerator is a term relating to an integral value of the deviation between the two temperatures (multiplying the vehicle speed). Integrated value). In this way, the heat dissipation amount Qorh can be lost based on the predicted cooling water temperature and the actual cooling water temperature. And since it is thought that the heat dissipation amount Qorh is so large that the said calorie | heat amount ratio R is large, it is assumed that the thermostat valve 10 exists in an open state.
[0085]
Radiator as above 2 In the case where the open failure of the thermostat valve 10 is detected based on the heat quantity ratio R, which is the ratio of the heat dissipation quantity Qorh of the cooling water in the engine and the heat receiving quantity Qig applied to the cooling water from the engine body 1 There is an advantage that an accurate failure diagnosis suitable for the operation state can be executed.
[0087]
【The invention's effect】
As explained above The present invention is an electric control type that is opened to circulate cooling water to the radiator when the cooling water temperature of the engine is higher than the target temperature, and is closed when the cooling water temperature is lower than the target temperature. Thermostat valve, target temperature setting means for setting the target temperature corresponding to the operating state of the engine, and failure detection for detecting an open or closed failure of the thermostat valve in the valve closing temperature region or the valve opening temperature region Since the target temperature is set to be higher or lower than normal until failure detection by the failure detection means is completed, the deviation between the target temperature and the actual cooling water temperature is small. There is an advantage that an open failure or a closed failure of the thermostat valve can be accurately detected without causing erroneous detection due to the above.
[Brief description of the drawings]
FIG. 1 of the present invention Reference form It is explanatory drawing which shows an example of the cooling system provided with the failure diagnosis apparatus of the thermostat concerning.
FIG. 2 is a flowchart showing a basic control operation for failure diagnosis.
FIG. 3 is a flowchart showing a specific example of failure detection control.
FIG. 4 is a graph showing a change state of cooling water temperature.
[Figure 5] By the thermostat failure diagnosis apparatus according to the embodiment of the present invention Basic control operations for fault diagnosis Work It is a flowchart to show.
FIG. 6 is a flowchart showing another specific example of the failure detection control.
FIG. 7 is a flowchart showing the first half of yet another specific example of failure detection control.
FIG. 8 is a flowchart showing the latter half of the failure detection control.

Claims (3)

An electrically controlled thermostat valve that is opened to circulate the cooling water to the radiator when the engine cooling water temperature is higher than the target temperature, and is closed when the cooling water is lower than the target temperature. and the target temperature setting means for setting the temperature in correspondence to the operating state of the engine, the open failure of the thermostatic valve, and a failure detecting means for detecting at its closing temperature region, the open failure detection by the failure detection means A thermostat failure diagnosing device, wherein the target temperature is set to a higher temperature side than the normal time until the end . An electrically controlled thermostat valve that is opened to circulate the cooling water to the radiator when the engine cooling water temperature is higher than the target temperature, and is closed when the cooling water is lower than the target temperature. Target temperature setting means for setting the temperature in accordance with the operating state of the engine, and failure detection means for detecting a closing failure of the thermostat valve in the valve opening temperature region, and the closed failure detection by this failure detection means A thermostat failure diagnosis apparatus, characterized in that the target temperature is set to a lower temperature side than the normal time until the end . 3. The thermostat failure diagnosis device according to claim 1, further comprising feedback control means for feedback-controlling the thermostat valve so that the actual cooling water temperature approaches the target temperature, and the target temperature and the actual cooling water temperature during the feedback control are provided. A thermostat failure diagnosis device characterized in that a failure of the thermostat valve is detected by a failure detection means based on a deviation from the above.

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