JP3719515B2 - Engine cooling system thermostat failure detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermostat failure detection device for an engine cooling system that detects the presence or absence of a failure of a thermostat that adjusts the temperature of cooling water of an engine.
[0002]
[Prior art]
Generally, in a water-cooled engine, a thermostat that automatically opens and closes according to the cooling water temperature is provided in a cooling water circulation path that circulates the cooling water between a cooling water passage (water jacket) in the engine and a radiator, and starts the engine. Until the warm-up operation is completed later, the thermostat is closed and the circulation of the cooling water is stopped, and the engine-side cooling water temperature is quickly raised to an appropriate temperature range to improve fuel consumption and reduce emissions, and to cool the engine side. When the water temperature exceeds the appropriate temperature range, the thermostat is automatically opened, and the cooling water on the radiator side is circulated to the engine side to reduce the cooling water temperature on the engine side to the appropriate temperature range ( For example, JP-A-58-008225).
[0003]
[Patent Document 1]
JP 58-008225 A (2nd page, etc.)
[0004]
[Problems to be solved by the invention]
By the way, the failure modes of the thermostat include an open failure in which the thermostat is opened and a closed failure in which the thermostat is opened. If an open failure occurs, the cooling water in the radiator will be circulated in the engine from the beginning even during a cold start when the engine is cold. This hinders the warming up of the engine, leading to a deterioration in fuel consumption and an increase in emissions. In addition, when a closed failure occurs, even if the coolant temperature on the engine side exceeds the appropriate temperature range, the cooled coolant on the radiator side is not circulated to the engine side, so the engine coolant temperature continues to rise and the engine There is a risk of overheating. Therefore, when a thermostat failure occurs, it is desirable to immediately detect it and alert the driver.
[0005]
As a known technique for detecting a failure in the engine cooling system, as shown in JP-A-4-19329, water temperature sensors are provided at the inlet and the outlet of the radiator, respectively, and the radiator is based on the inlet water temperature and the outlet water temperature of the radiator. There is one that detects the deterioration of the radiator by evaluating the heat dissipation performance of the radiator. Since the thermostat automatically opens and closes according to the coolant temperature on the engine side, even if the coolant temperature on the radiator side that is unrelated to the opening and closing operation of the thermostat is detected at two locations as in the above-described known technology. A thermostat failure cannot be detected. In addition, two temperature sensors must be newly provided on the radiator side, and there is a disadvantage that the cost increases accordingly.
[0006]
The present invention has been made in view of such circumstances. Accordingly, the object of the present invention is to provide a thermostat failure detection device for an internal combustion engine cooling system capable of accurately detecting a failure of a thermostat with a relatively inexpensive means. There is to do.
[0007]
[Means for Solving the Problems]
First, in order to facilitate understanding of the present invention, the behavior of the cooling water temperature when the thermostat fails will be described with reference to FIGS. 5 and 6.
[0008]
FIG. 5 shows the behavior of the engine-side cooling water temperature and the radiator-side cooling water temperature when an open failure occurs in which the thermostat is left open, compared with the normal time. At cold start, if the thermostat is normal, the valve is closed, so the circulation of the cooling water is stopped and the rise of the engine side cooling water temperature is promoted, and the radiator side cooling water temperature hardly rises, but an open failure occurs. If this occurs, the cooling water in the radiator will be circulated in the engine from the beginning even during a cold start, so the increase in the engine-side cooling water temperature after the start is delayed, while the radiator-side cooling water temperature is Begin to rise from.
[0009]
Also, after the warm-up is completed (after opening the thermostat), if the engine-side cooling water temperature falls below the thermostat valve closing temperature, if the thermostat is normal, the engine is closed and circulation of the cooling water is stopped. The side cooling water temperature rises again and the radiator side cooling water temperature decreases, but in the event of an open failure, the cooling water continues to circulate without closing the thermostat and the engine side cooling water temperature continues to decrease, while the radiator side cooling water temperature Will rise.
[0010]
FIG. 6 shows the behavior of the engine-side cooling water temperature and the radiator-side cooling water temperature when a closed failure occurs in which the thermostat is closed and closed compared with the normal time. When the engine-side coolant temperature exceeds the thermostat valve opening temperature, if the thermostat is normal, the valve is opened and the radiator-side cooled coolant is circulated to the engine side, the engine-side coolant temperature decreases, and the radiator-side coolant is cooled. Although the water temperature rises, at the time of a closed failure, the thermostat does not open, the cooling water circulation is not performed, and the engine side cooling water temperature continues to rise, while the radiator side cooling water temperature does not rise very much.
[0011]
In this way, when the thermostat fails, the behavior of the engine-side cooling water temperature and the radiator-side cooling water temperature is significantly different from the normal state, so the behavior of the engine-side cooling water temperature and the radiator-side cooling water temperature can be determined to determine whether the thermostat is normal or failure. Is possible.
[0015]
there , Claims 1 Then, the presence or absence of a thermostat open failure is diagnosed based on the temperature change rate of each of the engine side cooling water temperature and the radiator side cooling water temperature.
That is, as shown in FIG. 5, the temperature change rate of the cooling water temperature on the engine side / radiator side is different between the open failure time and the normal time, so the thermostat is calculated from the temperature change rate of the cooling water temperature on the engine side / radiator side. It is possible to accurately determine whether it is normally closed or an open failure.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment (1)]
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire cooling system of the engine 11 will be described with reference to FIG. A water jacket 12 is provided inside the cylinder block and the cylinder head of the engine 11, and cooling water is injected into the water jacket 12. A thermostat 13 is provided at the outlet of the water jacket 12, and high-temperature cooling water that passes through the thermostat 13 is sent to the radiator 15 through the cooling water circulation path 14. The cooling water whose temperature has decreased due to heat dissipation by the radiator 15 is returned into the water jacket 12 via the cooling water circulation path 16. Accordingly, when the thermostat 13 is opened, the cooling water circulates through the path of the water jacket 12 → thermostat 13 → cooling water circulation path 14 → radiator 15 → cooling water circulation path 16 → water jacket 12 to cool the engine 11 to an appropriate temperature.
[0023]
In addition, a water pump 17 is provided at the inlet of the water jacket 12, and the water pump 17 is connected to a cooling fan 18 installed behind the radiator 15, and the water pump 17 and the cooling fan 18 connect the belt 19. Rotation is integrally driven by engine power transmitted through the vehicle. The rotation of the water pump 17 promotes the circulation of the cooling water in the cooling water circulation path, and the rotation of the cooling fan 18 enhances the heat dissipation effect of the radiator 15 and promotes the cooling of the cooling water in the radiator 15.
[0024]
The cylinder block of the engine 11 includes an engine-side cooling water temperature sensor 20 (engine-side cooling water temperature detecting means) that detects a cooling water temperature (engine-side cooling water temperature) in the water jacket 12 that is a cooling water circulation path on the engine 11 side of the thermostat 13. ) Is provided. The engine side coolant temperature sensor 20 may be attached to the coolant circulation path on the engine 11 side of the thermostat 13, and may be attached to a cylinder head side portion of the water jacket 12, for example.
[0025]
A radiator side cooling water temperature sensor 21 (radiator side cooling water temperature detecting means) for detecting a cooling water temperature (radiator side cooling water temperature) sent to the radiator 11 side in the middle of the cooling water circulation path 14 on the radiator 15 side of the thermostat 13. Is provided. In addition, the attachment position of the radiator side cooling water temperature sensor 21 should just be the cooling water circulation path | route of the radiator 15 side rather than the thermostat 13, for example, may be attached to the radiator 15.
[0026]
Output signals of both the engine side / radiator side cooling water temperature sensors 20, 21 are taken into an electronic control unit 22 (hereinafter abbreviated as "ECU"). The ECU 22 is mainly composed of a microcomputer, and performs engine control and thermostat failure diagnosis. The ECU 22 may be composed of two ECUs separated into an engine control ECU and a thermostat failure diagnosis ECU, or a single ECU may perform both engine control and thermostat failure diagnosis. .
[0027]
In the ECU 22, as information for performing engine control and thermostat failure diagnosis, in addition to the cooling water temperature signals from both the cooling water temperature sensors 20, 21, the engine speed signal from the engine speed sensor 23, the intake air amount sensor 24. , An intake air temperature signal from the intake air temperature sensor 25, a vehicle speed signal from the vehicle speed sensor 26, and a signal indicating the operating state of the blower motor of the air conditioner 27 are also read. The ECU 22 is connected with a warning lamp 28 that is a warning means for warning when a malfunction of the thermostat 13 is detected, and a backup RAM 29 that is a writable nonvolatile memory for storing malfunction information of the thermostat 13. . The backup RAM 29 is supplied with power from a battery (not shown) even when the engine is stopped, holds the failure information, and can read the failure information during repair / inspection.
[0028]
The ROM (storage medium) built in the ECU 22 stores each program for thermostat failure diagnosis shown in FIGS. 2 to 4, and by executing these programs, the thermostat 13 is opened or closed. Diagnose. The processing contents of each program will be described below.
[0029]
FIG. 2 is a failure diagnosis main program that supervises the entire thermostat failure diagnosis process. This program serves as a failure diagnosis means in the claims, and is repeatedly activated every predetermined time or every predetermined crank angle after an ignition switch (not shown) is turned on. When this program is started, first, in step 100, an open failure diagnosis program shown in FIG. 3 to be described later is executed to diagnose whether an open failure has occurred in which the thermostat 13 is left open. Thereafter, in step 200, a closed failure diagnosis program shown in FIG. 4 to be described later is executed to diagnose whether or not a closed failure that causes the thermostat 13 to be closed has occurred, and this program ends.
[0030]
Here, an open failure diagnosis method using the open failure diagnosis program of FIG. 3 will be described with reference to the time chart of FIG. FIG. 5 shows the behavior of the engine-side cooling water temperature and the radiator-side cooling water temperature when an open failure occurs in comparison with the normal time. When the engine 11 is started in a cold state, when the thermostat 13 is normal, the valve is closed, so that the circulation of the cooling water is stopped and the rise of the engine-side cooling water temperature is promoted. Since the side cooling water temperature hardly rises, the temperature difference between the engine side cooling water temperature and the radiator side cooling water temperature increases with time. On the other hand, when an open failure occurs, the cold cooling water in the radiator 15 is circulated in the water jacket 12 of the engine 11 from the beginning even during a cold start. The temperature difference from the radiator side cooling water temperature is much smaller than normal.
[0031]
Focusing on this point, in the open failure diagnosis program of FIG. 3, whether the thermostat is normally closed depending on whether the temperature difference between the engine-side cooling water temperature and the radiator-side cooling water temperature in the predetermined period after the cold start is large or small, It is determined whether or not there is an open failure. Specifically, first, in step 101, it is determined whether or not the engine is cold-started based on whether or not the engine-side coolant temperature Te at the time of startup is equal to or lower than the valve closing temperature of the thermostat 13. Exit this program without diagnosing open failure.
[0032]
Here, the reason for performing the open failure diagnosis at the cold start is that the engine side coolant temperature and the radiator side coolant temperature are substantially the same or close to each other at the beginning of the cold start. This is because the period of time until Te reaches the valve opening temperature of the thermostat 13 is largely different from that of the cooling water temperature at the time of the open failure and at the normal time, and it is easy to detect the open failure compared to other operation periods.
[0033]
If it is determined in step 101 that the engine is cold-started, the process proceeds to step 102, where it is determined whether an open failure diagnosis condition is satisfied. Here, the open failure diagnosis conditions are (1) that both the engine-side cooling water temperature sensor 20 and the radiator-side cooling water temperature sensor 21 are normal, and (2) that a predetermined time has elapsed since the cold start (however, The predetermined time is set within the time until the engine side cooling water temperature Te reaches the valve opening temperature of the thermostat 13 after the cold start), and (3) the engine side cooling water temperature Te is lower than the valve opening temperature of the thermostat 13. The open failure diagnosis condition is satisfied when all the conditions (1) to (3) are satisfied.
Here, the condition (1) (both cooling water temperature sensors 20, 21 are normal) is determined by, for example, whether the output voltages of the cooling water temperature sensors 20, 21 are within a predetermined range. The above condition (2) (after a predetermined time has elapsed since the cold start) is a time condition necessary until a clear difference appears in the behavior of the cooling water temperature between the open failure and the normal time. The above condition (3) (the engine-side cooling water temperature Te is lower than the valve opening temperature of the thermostat 13) is that when the engine-side cooling water temperature Te exceeds the valve opening temperature of the thermostat 13, the thermostat 13 opens. This is because it becomes difficult to determine an open failure.
[0034]
If any one of the above conditions (1) to (3) is not satisfied in step 102, the open failure diagnosis condition is not satisfied, and the present program is terminated without performing an open failure diagnosis. The processing of step 102 including the determination of the above condition (1) (both cooling water temperature sensors 20, 21 are normal) serves as failure diagnosis prohibiting means in the claims.
[0035]
On the other hand, if all of the above conditions (1) to (3) are satisfied and the open failure diagnosis condition is satisfied, the process proceeds to step 103 where the temperature difference between the engine side cooling water temperature Te and the radiator side cooling water temperature Tr is reached. (Te−Tr) is calculated, and in the next step 104, the open failure determination reference value α for determining an open failure from this temperature difference (Te−Tr) is used as the heat generation amount of the engine 11 and the heat dissipation amount of the cooling water. As a parameter, at least one of the intake air amount Q, the engine speed Ne, the intake air temperature, the vehicle speed, and the operating state of the blower motor of the air conditioner 27 is calculated using a map or a function equation.
[0036]
Thereafter, in step 105, the temperature difference (Te−Tr) between the engine side cooling water temperature Te and the radiator side cooling water temperature Tr is compared with the open failure determination reference value α, and the temperature difference (Te−Tr) is determined as the open failure determination criterion. When the value is greater than or equal to the value α, the routine proceeds to step 106, where it is determined that the thermostat 13 is normally opened and the program is terminated.
[0037]
On the other hand, when the temperature difference (Te−Tr) between the engine-side cooling water temperature Te and the radiator-side cooling water temperature Tr is smaller than the open failure determination reference value α, the routine proceeds to step 107, where it is determined that the thermostat 13 is an open failure. In the next step 108, the warning lamp 28 is turned on or blinking to warn the driver, and information on open failure is stored in the backup RAM 29, and this program is terminated.
[0038]
The open failure diagnosis program of FIG. 3 described above plays a role as an open failure diagnosis means in the claims.
[0039]
Next, a closed failure diagnosis method using the closed failure diagnosis program of FIG. 4 will be described with reference to the time chart of FIG. FIG. 6 shows the behavior of the engine-side cooling water temperature and the radiator-side cooling water temperature when a closed failure occurs that causes the thermostat 13 to be closed and closed as compared with the normal time. When the engine-side coolant temperature exceeds the thermostat valve opening temperature, if the thermostat 13 is normal, the valve is opened, and the cooled coolant on the radiator side is circulated to the engine 11 side, the engine-side coolant temperature is lowered, and the radiator Since the side cooling water temperature rises, the temperature difference between the engine side cooling water temperature and the radiator side cooling water temperature decreases with time. On the other hand, when a closed failure occurs, even if the engine-side coolant temperature exceeds the thermostat valve opening temperature, the thermostat 13 does not open and the coolant is not circulated, and the engine-side coolant temperature continues to rise. However, since the radiator-side cooling water temperature does not rise so much, the temperature difference between the engine-side cooling water temperature and the radiator-side cooling water temperature increases with time.
[0040]
Focusing on this point, in the closed failure diagnosis program of FIG. 4, the engine side cooling water temperature and the radiator side cooling water temperature are set for a predetermined period after the engine side cooling water temperature reaches the valve opening temperature of the thermostat 13 after the cold start. It is determined whether the thermostat is normally open or a closed failure depending on whether the temperature difference is large or small. Specifically, first, in step 201, it is determined whether or not the engine is cold-started based on whether or not the engine-side coolant temperature Te at the time of startup is equal to or lower than the valve closing temperature of the thermostat 13. This program is terminated without diagnosing a closed fault.
[0041]
On the other hand, if it is determined in step 201 that the engine is cold-started, the process proceeds to step 202, where it is determined whether or not a closed failure diagnosis condition is satisfied. Here, the closed failure diagnosis condition is (1) that both the engine-side cooling water temperature sensor 20 and the radiator-side cooling water temperature sensor 21 are normal, and (2) the engine-side cooling water temperature Te exceeds the valve opening temperature of the thermostat 13. (3) The engine-side cooling water temperature Te is higher than the valve closing temperature of the thermostat 13, and a closed failure occurs when all of the conditions (1) to (3) are satisfied. Diagnostic conditions are met.
[0042]
Here, the above condition (2) (after a predetermined time has elapsed after the valve opening temperature of the thermostat 13 is exceeded) is necessary until a clear difference appears in the behavior of the cooling water temperatures Te and Tr between the time of closing failure and the time of normal operation. It is a time condition. The above condition (3) (the engine-side cooling water temperature Te is higher than the valve closing temperature of the thermostat 13) is that the thermostat 13 is closed when the engine-side cooling water temperature Te becomes equal to or lower than the valve closing temperature of the thermostat 13. This is because it becomes difficult to determine a closed failure.
[0043]
If any one of the above conditions (1) to (3) is not satisfied in step 202, the closed failure diagnosis condition is not satisfied, and the program is terminated without performing the diagnosis of the closed failure.
[0044]
On the other hand, if all of the above conditions (1) to (3) are satisfied and the closed failure diagnosis condition is satisfied, the process proceeds to step 203 and the temperature difference between the engine side cooling water temperature Te and the radiator side cooling water temperature Tr. (Te−Tr) is calculated, and in the next step 204, the closed failure determination reference value β for determining the closed failure from this temperature difference (Te−Tr) is used as the heat generation amount of the engine 11 or the heat dissipation amount of the cooling water. As a parameter, at least one of the intake air amount Q, the engine speed Ne, the intake air temperature, the vehicle speed, and the operating state of the blower motor of the air conditioner 27 is calculated by a map or a function equation.
[0045]
Thereafter, in step 205, the temperature difference (Te−Tr) between the engine side cooling water temperature Te and the radiator side cooling water temperature Tr is compared with the closed failure determination reference value β, and the temperature difference (Te−Tr) is determined as the closed failure determination criterion. When it is equal to or less than the value β, the routine proceeds to step 206, where it is determined that the thermostat 13 is normally closed and the program is terminated.
[0046]
On the other hand, when the temperature difference (Te−Tr) between the engine-side cooling water temperature Te and the radiator-side cooling water temperature Tr is larger than the closing failure determination reference value β, the process proceeds to step 207, where it is determined that the thermostat 13 is a closing failure. In the next step 208, the warning lamp 28 is turned on or blinking to warn the driver, and information on the closing failure is stored in the backup RAM 29 and the program is terminated. In addition, this program plays a role as a closed fault diagnosis means in the claims.
[0047]
According to the embodiment (1) described above, based on the engine-side cooling water temperature and the radiator-side cooling water temperature detected by the engine-side cooling water temperature sensor 20 and the radiator-side cooling water temperature sensor 21, the thermostat 13 that could not be detected conventionally. Therefore, it is possible to prevent deterioration in fuel consumption, increase in emissions, and overheating due to the failure of the thermostat 13. In addition, the engine-side cooling water temperature sensor 20 may be an engine control water temperature sensor that is also provided in a conventional engine. Therefore, a radiator-side cooling water temperature sensor 21 is newly added to the conventional engine control system. The structure is relatively simple, the cost increase is small, and the demand for cost reduction can be satisfied.
[0048]
Furthermore, in this embodiment (1), when setting the failure determination reference value, parameters that affect the heat generation amount of the engine 11 and the heat dissipation amount of the cooling water are the intake air amount Q, the engine speed Ne, the intake air temperature, Since the failure determination reference value is calculated using at least one of the vehicle speed and the operating state of the blower motor of the air conditioner 27 as a parameter, it is possible to determine the failure in consideration of the heat generation amount of the engine 11 and the heat dissipation amount of the cooling water. Therefore, the failure diagnosis accuracy can be improved accordingly.
[0049]
[Embodiment (2)]
In the embodiment (1), the diagnosis of the open failure and the close failure of the thermostat 13 is performed based on the temperature difference between the engine-side cooling water temperature and the radiator-side cooling water temperature. However, the embodiment shown in FIGS. In 2), the opening failure and the closing failure of the thermostat 13 are diagnosed as follows based on the respective temperature change rates of the engine side cooling water temperature and the radiator side cooling water temperature.
[0050]
In the open failure diagnosis program shown in FIG. 7, as in FIG. 3, the open failure diagnosis process after step 103a is executed at the time of cold start and when the open failure diagnosis condition is satisfied (steps 101 and 102). ). The open failure diagnosis condition is the same as that of the embodiment (1). When diagnosing an open failure, first, in step 103a, the engine-side cooling water temperature change rate ΔTe is set to the difference between the previous engine-side cooling water temperature Te (i-1) and the current engine-side cooling water temperature Te (i). And the radiator-side cooling water temperature change rate ΔTr 1 is obtained as the absolute value of the difference between the previous radiator-side cooling water temperature Tr (i−1) and the current radiator-side cooling water temperature Tr (i).
[0051]
Thereafter, in step 104a, an open failure determination reference value γ for determining an open failure from the engine side cooling water temperature change rate ΔTe and an open failure determination reference value for determining an open failure from the radiator side cooling water temperature change rate ΔTr. δ is a parameter that determines the heat generation amount of the engine 11 or the heat dissipation amount of the cooling water, and is at least one of the intake air amount Q, the engine speed Ne, the intake air temperature, the vehicle speed, and the operating state of the blower motor of the air conditioner 27. It is calculated by a map or a function formula as a parameter.
[0052]
Thereafter, in step 105a, it is determined whether or not the engine-side cooling water temperature change rate ΔTe is equal to or greater than the open failure determination reference value γ, and the radiator-side cooling water temperature change rate ΔTr is equal to or less than the open failure determination reference value δ. If both the conditions of ≧ γ and ΔTr ≦ δ are satisfied, the routine proceeds to step 106, where it is determined that the thermostat 13 is normally opened and the program is terminated.
[0053]
On the other hand, when either ΔTe ≧ γ or ΔTr ≦ δ does not satisfy the condition, the routine proceeds to step 107 where it is determined that the thermostat 13 is an open failure, and the warning lamp 28 is turned on or blinked at the next step 108. The driver is warned and information on the open failure is stored in the backup RAM 29 and the program is terminated.
[0054]
On the other hand, in the closed fault diagnostic program shown in FIG. 8, as in FIG. 4, when the cold fault is started and the closed fault diagnostic condition is satisfied, the closed fault diagnostic process after step 203a is executed (step 201). 202). The closed fault diagnosis condition is the same as in the first embodiment (1). When making a diagnosis of a closed failure, first, in step 203a, the engine-side cooling water temperature change rate ΔTe is set to the difference between the previous engine-side cooling water temperature Te (i-1) and the current engine-side cooling water temperature Te (i). And the radiator-side cooling water temperature change rate ΔTr is obtained as the absolute value of the difference between the previous radiator-side cooling water temperature Tr (i−1) and the current radiator-side cooling water temperature Tr (i).
[0055]
Thereafter, in step 204a, the closed failure determination reference value ε for determining the closed failure from the ratio ΔTe / ΔTr of the engine-side cooling water temperature change rate ΔTe and the radiator-side cooling water temperature change rate ΔTr, It is calculated by a map or a function equation using at least one of parameters that influence the heat dissipation amount of the cooling water, that is, the intake air amount Q, the engine speed Ne, the intake air temperature, the vehicle speed, and the operating state of the blower motor of the air conditioner 27 as parameters. .
[0056]
Thereafter, in step 205a, the ratio ΔTe / ΔTr of the engine-side cooling water temperature change rate ΔTe and the radiator-side cooling water temperature change rate ΔTr is compared with the closed failure determination reference value ε. If ΔTe / ΔTr ≦ ε, step 206 is performed. Then, it is determined that the thermostat 13 is normally closed, and this program is terminated.
[0057]
On the other hand, if ΔTe / ΔTr> ε, the routine proceeds to step 207, where it is determined that the thermostat 13 is a closed failure, and in the next step 208, the warning lamp 28 is lit or blinked to warn the driver. Then, the closed RAM information is stored in the backup RAM 29 and the program is terminated.
[0058]
[Other Embodiments]
In the embodiments (1) and (2), the diagnosis of the open failure of the thermostat 13 is performed after a predetermined time has elapsed since the cold start, but after the opened thermostat 13 is closed (see FIG. 5). An open failure may be diagnosed after a predetermined time elapses after T2. In short, if the thermostat 12 is normal, the open failure may be diagnosed in the closed temperature range. Further, as a parameter used when calculating the failure determination reference value, the intake pipe pressure may be used instead of the intake air amount, and the outside air temperature may be used instead of the intake air temperature.
[0059]
In the system configuration example of FIG. 1, the cooling fan 18 that cools the radiator 15 is rotationally driven by the power of the engine 11, but an electric fan that uses an electric motor as a drive source may be used. Further, the attachment position of the radiator 15 is not limited to the outlet portion of the water jacket 12, and may be another portion such as an inlet portion of the water jacket 12.
[0060]
The behavior of the engine-side cooling water temperature and the radiator-side cooling water temperature is also affected by the failure of the blower motor of the water pump 17, the cooling fan 18, and the air conditioner 27. Therefore, the water pump 17 is determined from the engine-side cooling water temperature and the radiator-side cooling water temperature. The failure of the cooling fan 18 and the blower motor of the air conditioner 27 may be diagnosed. Further, when the engine-side cooling water temperature sensor 20 fails, the output signal of the radiator-side cooling water temperature sensor 21 may be used as engine control information.
[0061]
In addition, the present invention can be implemented with various modifications within a range not departing from the gist, such as executing only one of the open failure diagnosis program and the closed failure diagnosis program.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an entire engine cooling system in an embodiment (1) of the present invention.
FIG. 2 is a flowchart showing a flow of processing of a thermostat failure diagnosis main program.
FIG. 3 is a flowchart showing a process flow of an open fault diagnosis program according to the embodiment (1).
FIG. 4 is a flowchart showing a processing flow of a closed fault diagnosis program according to the embodiment (1).
FIG. 5 is a time chart showing the behavior of the engine-side cooling water temperature and the radiator-side cooling water temperature when an open failure occurs in which the thermostat is left open, compared with normal time.
FIG. 6 is a time chart showing the behavior of the engine-side cooling water temperature and the radiator-side cooling water temperature when a closed failure occurs in which the thermostat is closed and closed compared with normal time.
FIG. 7 is a flowchart showing a process flow of an open fault diagnosis program according to the embodiment (2).
FIG. 8 is a flowchart showing a processing flow of a closed fault diagnosis program according to the embodiment (2).
[Explanation of symbols]
11 ... Engine
12 ... Water jacket
13 ... Thermostat
14 ... Cooling water circuit
15 ... Radiator
16 ... Cooling water circuit
18 ... Cooling fan
20 ... Engine-side cooling water temperature sensor (engine-side cooling water temperature detection means)
21 ... Radiator side cooling water temperature sensor (radiator side cooling water temperature detecting means)
22 ... ECU (failure diagnosis means, open failure diagnosis means, closed failure diagnosis means, failure diagnosis prohibition means)
23. Engine speed sensor
24. Intake amount sensor
25 ... Intake air temperature sensor
26 ... Vehicle speed sensor
27 ... Air conditioner
28 ... Warning lamp (Warning means)
29 ... Backup RAM

Claims (1)

A thermostat failure detection device for an internal combustion engine cooling system for detecting a failure of a thermostat provided between the engine and a radiator in a circulation path of cooling water for cooling the engine,
Engine-side cooling water temperature detecting means for detecting a cooling water temperature in the cooling water circulation path on the engine side from the thermostat (hereinafter referred to as “engine-side cooling water temperature”);
A radiator side cooling water temperature detecting means for detecting a cooling water temperature of the cooling water circulation path on the radiator side of the thermostat (hereinafter referred to as “radiator side cooling water temperature”);
Failure diagnosis means for diagnosing the presence or absence of a failure of the thermostat based on the engine side cooling water temperature detected by both the engine side and radiator side cooling water temperature detection means and the radiator side cooling water temperature;
The failure diagnosing means is an open failure diagnosing means for diagnosing the presence or absence of a failure (hereinafter referred to as “open failure”) that the thermostat is not closed and opens in a closed temperature range if the thermostat is normal. The open failure diagnosing means determines whether the thermostat is open or not based on the temperature change rates of the engine-side cooling water temperature and the radiator-side cooling water temperature detected by both the engine-side and radiator-side cooling water temperature detecting means. An engine cooling system thermostat failure detection device characterized by diagnosing.

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