JP2008025468A - Temperature sensor failure determination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a temperature sensor failure determination device performing an accurate failure diagnosis. <P>SOLUTION: The temperature failure determination device detecting a temperature changing according to the operation state of the engine is provided with a failure diagnosis control means provided with a diagnosis function diagnosing whether a temperature sensor fails or not, and restarting the diagnosis function and diagnosing a failure when a fixed time passes after an engine stop if an engine is stopped after operation and a temperature sensor failure determination condition is satisfied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor failure determination device, and more particularly to a temperature sensor failure determination device that performs high-precision failure diagnosis of a temperature sensor that detects a temperature that changes according to the operating state of an engine.

As a failure diagnosis method for a temperature sensor such as a water temperature sensor, there are those disclosed in Patent Documents 1 to 4 below.
And what is indicated by patent documents 2 sets judgment temperature according to engine stop time, and judges that a temperature sensor is out of order when the temperature at the time of restart is higher than judgment temperature.

JP-A-11-201834 JP 2000-230453 A Japanese Patent Laid-Open No. 2003-27999 JP 2003-293842 A

By the way, in the conventional temperature sensor failure determination device, since the failure determination as described above is performed, even when the temperature sensor is normal, the engine warm-up operation is insufficient and the engine temperature is low before the engine stops. In addition, there is a disadvantage that the temperature at the next start becomes higher than the determination temperature, and the temperature sensor may be erroneously diagnosed as having a failure.
Further, when the time from the engine stop to the restart is short, the temperature change of the temperature sensor is small, so the diagnostic accuracy is not high.

  An object of the present invention is to realize a temperature sensor failure determination device that performs highly accurate failure diagnosis.

  Accordingly, in order to eliminate the above-described disadvantages, the present invention provides a diagnostic function for diagnosing whether or not the temperature sensor has failed in a temperature sensor failure determination device that detects a temperature that changes according to the operating state of the engine. And a failure diagnosis control means for restarting the diagnosis function and diagnosing the failure after a certain period of time has elapsed after the engine is stopped when the engine is stopped after being operated and the temperature sensor failure determination condition is satisfied. It is characterized by having.

As described above in detail, according to the present invention, the temperature sensor failure determination device that detects the temperature that changes according to the operating state of the engine includes a diagnostic function for diagnosing whether or not the temperature sensor has failed. And a failure diagnosis control means for restarting the diagnosis function and diagnosing the failure after a certain period of time has elapsed after the engine is stopped when the engine is stopped after being operated and the temperature sensor failure determination condition is satisfied. .
Therefore, since the failure diagnosis of the temperature sensor is performed after a certain time has elapsed after the engine is stopped, a highly accurate failure diagnosis can be realized.

  As a result of the invention as described above, the failure diagnosis control means restarts the diagnosis function after a certain period of time has elapsed after the engine is stopped when the engine is operated and then stopped and the temperature sensor failure determination condition is satisfied. Fault diagnosis is performed to achieve highly accurate fault diagnosis.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

1 to 3 show an embodiment of the present invention.
In FIG. 2, 1 is an engine, 2 is an intake passage, and 3 is an exhaust passage.
As shown in FIG. 2, the engine 1 includes a cylinder block 4, a cylinder head 5 mounted on the upper surface of the cylinder block 4, and a piston 6 that slides inside the cylinder block 4.
The cylinder block 4, the cylinder head 5 and the top of the piston 6 form a number of combustion chambers 7 corresponding to the number of cylinders.
The combustion chamber 7 is in communication with the downstream end of the intake passage 2 and with the upstream end of the exhaust passage 3.
At this time, an intake valve 8 for opening and closing the downstream end of the intake passage 2 is provided, and an exhaust valve 9 for opening and closing the upstream end of the exhaust passage 3 is provided.
Further, a spark plug 10 is disposed at the top of the combustion chamber 7.

An air cleaner 11 is provided at the upstream end of the intake passage 2.
In the intake passage 2 downstream of the air cleaner 11, the intake air temperature sensor 12 that detects the intake air temperature, the air flow meter 13, and the throttle opening (“throttle angle”) of the throttle valve 14 are sequentially detected from the upstream side. And a throttle angle sensor 15 for detecting.
Further, an injector 16 is disposed in the intake passage 2 downstream of the throttle angle sensor 15 so as to be directed toward the combustion chamber 7.
Further, a catalyst 17 is provided in the exhaust passage 3, and an oxygen signal in the exhaust gas is detected in the exhaust passage 3 upstream of the catalyst 17, and a rich signal and a lean signal that are inverted as output voltages are output. An oxygen sensor 18 is disposed.

And the control means (it is also called "ECM") 19 which connects the said intake temperature sensor 12, the air flow meter 13, the throttle angle sensor 15, and the oxygen sensor 18 to the input side is provided.
At this time, on the input side of the control means 19, in addition to the above, a crank angle sensor 21 that detects the crank angle of the crankshaft 20, a temperature sensor that detects a temperature that changes according to the operating state of the engine 1, For example, a water temperature sensor 22 that detects the coolant temperature, a knock sensor 23 that detects knock, a cam angle sensor 25 that detects the cam angle of the intake camshaft 24, and a vehicle speed sensor 26 that detects the vehicle speed are connected to each other.
Further, an ignition coil 27 for causing the injector 16 and the spark plug 10 to ignite is connected to the output side of the control means 19.

The control means 19 inputs detection signals from various sensors and the like, and outputs control signals to various components, and constitutes a failure determination device 28 for the water temperature sensor 22 that is the temperature sensor.
At this time, the control means 19 has a diagnostic function for diagnosing whether or not the water temperature sensor 22 as the temperature sensor has failed, is stopped after the engine 1 is operated, and the temperature sensor has failed. When the determination condition is satisfied, a failure diagnosis control means 29 is provided for restarting the diagnosis function and diagnosing the failure after a lapse of a certain time after the engine is stopped.
More specifically, in the failure determination device 28, the diagnosis function of the failure diagnosis control means 29 determines that the water temperature sensor 22 is normal when the engine starting water temperature Tws is lower than the second predetermined temperature Twref2.
Twref2: A determination value for determining whether the engine is started from a cold state (or a semi-warm state).
Further, when the engine start water temperature Tws is equal to or higher than the second predetermined temperature Twref2, the engine stop water temperature Tw1 and the engine stop intake temperature Ta1 after engine operation are measured.
When the engine stop water temperature Tw1 is equal to or higher than the first predetermined temperature Twref1, which is the set stop temperature, the engine stop water temperature Tw1 and the engine stop intake temperature Ta1 after engine operation are stored, and a rediagnosis function timer (simply (Also called “timer”) 30 is started, and the main arithmetic processing section (also called “main CPU”) 31 of the control means 19 is turned off.
Twref1: A determination value for determining whether the engine has been sufficiently warmed up.
Further, when the engine stop water temperature Tw1 is lower than the first predetermined temperature Twref1, the power of the control means 19 is turned off (end of diagnosis).

Then, the failure diagnosis control means 29 includes the temperature when the engine is stopped, for example, the water temperature Tw1 when the engine is stopped, the intake temperature Ta1 when the engine is stopped, and the temperature when restarted, for example, the water temperature Tw2 when restarted, and the intake temperature Ta2 when restarted. When the engine stop temperature, for example, the engine stop water temperature Tw1, the restart temperature, for example, the restart water temperature Tw2 is less than or equal to the set failure determination value, it is a temperature sensor. It has an additional diagnostic function of determining that the water temperature sensor 22 is malfunctioning.
That is, the failure diagnosis control means 29 measures the temperature at the time of engine stop, for example, the water temperature Tw1 at the time of engine stop and the intake air temperature Ta1 at the time of engine stop, and after a predetermined time t1 which is a fixed time after the engine stops, the timer 30 The diagnostic function is restarted, and the water temperature Tw2 at restart and the intake air temperature Ta2 at restart are measured.
Further, a value obtained by subtracting the restart water temperature Tw2 from the engine stop water temperature Tw1, for example, a water temperature decrease amount Td,
Td = Tw1-Tw2
Calculate by
At this time, the correction coefficient Ktw of the failure reference value Twmc, which is a fixed value, is obtained from the intake temperature Ta1 when the engine is stopped and the intake temperature Ta2 when the engine is restarted.
The intake air temperature is used as a substitute for the outside air temperature.
Hereinafter, the relationship among the intake air temperature Ta1 at the time of engine stop, the intake air temperature Ta2 at the time of restart, and the correction coefficient Ktw will be disclosed.
Ta1 <Ta2 → Ktw <1
Ta1> Ta2 → Ktw> 1
The set failure determination value is a value obtained by the product of the failure reference value Twmc and the correction coefficient Ktw.
Then, the water temperature decrease amount Td, which is a value obtained by subtracting the restart water temperature Tw2 from the engine stop water temperature Tw1, and the set failure determination value, that is, the product of the failure reference value Twmc and the correction coefficient Ktw, are compared.
Td ≦ Twmc × Ktw
In this case, it is determined that the high temperature side stack of the water temperature sensor 22 is in failure,
Td> Twmc × Ktw
In this case, it is determined that there is no high temperature side stack failure of the water temperature sensor 22.
3 shows a time chart of the failure determination device 28 of the water temperature sensor 22 which is a temperature sensor. In FIG. 3C, the solid line indicates the water temperature Tw of the normal water temperature sensor 22 and a two-dot chain line. Indicates the water temperature Tw ′ when it is determined that the high temperature side stack of the water temperature sensor 22 is malfunctioning, and the broken line indicates the intake air temperature Ta of the intake air temperature sensor 12.

The failure determination device 28 includes an outside air equivalent temperature detection means, for example, the intake air temperature sensor 12, for detecting an outside air temperature or a temperature linked to the outside air temperature, and the failure determination value is the outside air equivalent temperature detection means. It is a value that varies depending on the outside air equivalent temperature detected by the intake air temperature sensor 12 when the engine is stopped and restarted, that is, the intake air temperature Ta1 when the engine is stopped and the intake air temperature Ta2 when the engine is restarted.
That is, as described above, when the set failure determination value is a value obtained by the product of the failure reference value Twmc and the correction coefficient Ktw, the correction coefficient Ktw is set to the engine stop intake temperature Ta1 and the restart intake temperature. Since it is set according to the magnitude relationship with Ta2, this change in the correction coefficient Ktw affects the failure determination value.

The temperature sensor failure determination condition is an engine stop temperature, for example, an engine stop water temperature Tw1 is equal to or higher than a first predetermined temperature Twref1, which is a set stop temperature.
That is, when the engine stop water temperature Tw1 is equal to or higher than the first predetermined temperature Twref1, which is the set stop temperature, and the temperature sensor failure determination condition is satisfied, the diagnostic function is restarted by the timer 30 after the predetermined time t1 has elapsed, The failure diagnosis by the failure diagnosis control means 29 is started.

In other words, the failure diagnosis control means 29 of the failure determination device 28 has only a diagnostic function related to water temperature sensor failure diagnosis after the passage of a predetermined time t1 from the engine stop when the engine stop water temperature Tw1 is equal to or higher than the first predetermined temperature Twref1. Is restarted, the water temperature Tw2 at the time of restart is measured, and the water temperature decrease amount Td from the engine stop water temperature Tw1 is obtained. This water temperature decrease amount Td is equal to or less than the product of the failure reference value Twmc and the correction coefficient Ktw, that is, Td ≦ Twmc x Ktw
In this case, it is determined that the high temperature side stack of the water temperature sensor 22 is in failure.
At this time, the timing of restarting the diagnostic function after the elapse of the predetermined time t1 from the engine stop is set to be the same as the start timing of the known evaporative diagnosis.
The failure determination device 28 adds the timer 29 to the conventional engine control system so that the diagnosis function can be restarted after a lapse of a predetermined time t1 from the engine stop, and the water temperature decreased to a sufficiently stable temperature after the engine stop. In addition to measuring, taking into account the water temperature conditions when the engine is stopped, the possibility of misdiagnosis when warm-up is insufficient is eliminated.

  The operation will be described along the control flowchart of the temperature sensor failure determination device 28 of FIG.

When the control program of the failure determination device 28 starts (A01), the process proceeds to a process (A02) for measuring the engine start water temperature Tws, and the engine start water temperature Tws is equal to or higher than the second predetermined temperature Twref2, that is,
Tws ≧ Twref2
It shifts to judgment (A03) of whether it is.
Then, this determination (A03) is YES, that is, the engine starting water temperature Tws is equal to or higher than the second predetermined temperature Twref2. Tws ≧ Twref2
In this case, the process proceeds to determination (A04) as to whether or not the engine 1 is in the operation end state.
Further, the determination (A03) is NO, that is, the engine starting water temperature Tws is lower than the second predetermined temperature Twref2. Tws <Twref2
In this case, the process proceeds to a process (A16) for determining that there is no high temperature side stack failure of the water temperature sensor 22 described later, that is, normal.

In the determination (A04) of whether or not the engine 1 is in the operation end state, if this determination (A04) is NO, the determination (A04) is repeated until the determination (A04) becomes YES.
If the determination (A04) is YES, the process proceeds to a process (A05) of measuring the engine stop time water temperature Tw1 and the engine stop time intake temperature Ta1.
After the measurement of the engine stop water temperature Tw1 and the engine stop intake air temperature Ta1, the engine stop water temperature Tw1 is equal to or higher than a first predetermined temperature Twref1, which is a set stop temperature, that is, Tw1 ≧ Twref1.
It shifts to judgment (A06) of whether it is.

In the determination (A06) of whether or not the engine stop water temperature Tw1 is equal to or higher than the first predetermined temperature Twref1 that is the set stop temperature, the determination (A06) is NO, that is, the engine stop water temperature Tw1 is the set stop temperature. It is less than the first predetermined temperature Twref1 that is Tw1 <Twref1
In this case, the process proceeds to a process (A17) for terminating the control program described later.
Further, the determination (A06) is YES, that is, the engine stop time water temperature Tw1 is equal to or higher than the first predetermined temperature Twref1 that is the set stop time temperature. Tw1 ≧ Twref1
In this case, the process proceeds to a process (A07) for storing the engine stop water temperature Tw1 and the engine stop intake temperature Ta1.

Then, after storing the engine stop water temperature Tw1 and the engine stop intake air temperature Ta1 in the process (A07), the diagnosis function is restarted after the predetermined time t1 has elapsed since the engine stop. The process proceeds to a process (A08) for starting the timer 30 so that it can be performed.
In addition, after the timer 30 is started, the process shifts to a process (A09) for turning off the main arithmetic processing unit 31 of the control means 19 (refer to the change part from the on to the off of the engine 1 in FIG. 3A). ).

Thereafter, the system waits for a predetermined time t1 to elapse after the engine is stopped, and proceeds to a process (A10) for restarting the diagnostic function of the failure diagnosis control means 29 after the predetermined time t1 has passed (the diagnostic function of FIG. 3B). (Refer to the change portion of the restart from OFF to ON and the elapsed portion of the predetermined time t1 in FIG. 3C.)
In the process (A10), when the diagnosis function of the failure diagnosis control means 29 is restarted, the process proceeds to a process (A11) for measuring the restart water temperature Tw2 and the restart intake air temperature Ta2.

Further, after the process (A11) of measuring the restart water temperature Tw2 and the restart intake air temperature Ta2, the process of calculating the water temperature decrease amount Td from the measured engine stop water temperature Tw1 and restart water temperature Tw2. Move to (A12).
In this process (A12), the formula Td = Tw1-Tw2
Is used to calculate the water temperature decrease amount Td.

Further, after the process (A12) of calculating the water temperature decrease amount Td based on the engine stop water temperature Tw1 and the restart water temperature Tw2, the failure reference value Twmc is calculated from the engine stop intake temperature Ta1 and the restart intake air temperature Ta2. The process proceeds to processing (A13) for calculating the correction coefficient Ktw.
At this time, the correction coefficient Ktw is calculated according to the relationship between the engine stop intake temperature (Ta1), the restart intake temperature (Ta2), and the correction coefficient (Ktw) as follows.
Ta1 <Ta2 → Ktw <1
Ta1> Ta2 → Ktw> 1

After the correction coefficient Ktw is calculated in the process (A13), the failure determination value in which the water temperature decrease Td calculated in the process (A12) is set, that is, the product of the failure reference value Twmc and the correction coefficient Ktw. The process proceeds to determination (A14) of whether or not the following is true.
This determination (A14) is YES, that is, the water temperature decrease amount Td is equal to or less than the product of the failure reference value Twmc and the correction coefficient Ktw. Td ≦ Twmc × Ktw
In this case, the process proceeds to a process (A15) for determining that the high temperature side stack of the water temperature sensor 22 is in failure.
Further, the determination (A14) is NO, that is, the water temperature decrease amount Td exceeds the product of the failure reference value Twmc and the correction coefficient Ktw. Td> Twmc × Ktw
In this case, the process proceeds to a process (A16) for determining that there is no high temperature side stack failure of the water temperature sensor 22.
Then, after each of the processes (A15) and (A16), the process proceeds to a process (A17) for ending the control program.

Thereby, in the failure determination device 28 for the temperature sensor, the failure determination device 28 has a diagnosis function for diagnosing whether or not the water temperature sensor 22 as the temperature sensor has failed, and the engine 1 is operated. After that, when the temperature sensor failure determination condition is satisfied, the failure diagnosis control means 29 is provided for restarting the diagnosis function and diagnosing the failure after a predetermined time t1, which is a fixed time after the engine is stopped. .
Therefore, since the failure diagnosis of the water temperature sensor 22 that is a temperature sensor is performed after a predetermined time t1 that is a fixed time has elapsed after the engine is stopped, a highly accurate failure diagnosis can be realized.

Further, the failure diagnosis control means 29 is provided with a temperature when the engine is stopped, for example, a water temperature Tw1 when the engine is stopped, an intake temperature Ta1 when the engine is stopped, and a temperature when the engine is restarted, such as a water temperature Tw2 at the time of restart. When the value obtained by subtracting the restart water temperature Tw2 from the engine stop water temperature Tw1 is equal to or less than the set failure determination value, the diagnosis is that the water temperature sensor 22 as a temperature sensor is determined to be in failure. It has a function.
Therefore, since the temperature at the time of restart at which the temperature change rate is stable and is in a stable state is used for failure determination, it is possible to perform failure diagnosis with high accuracy.

Further, the failure determination device 28 includes an outside air equivalent temperature detecting means for detecting an outside air temperature or a temperature linked to the outside air temperature, for example, the intake air temperature sensor 12, and the failure determination value is used as the outside air equivalent temperature detecting means. The temperature corresponding to the outside air equivalent temperature detected when the engine is stopped and restarted, that is, the intake air temperature Ta1 when the engine is stopped and the intake air temperature Ta2 when the engine is restarted is detected.
Therefore, since the failure determination value linked to the outside air equivalent temperature that affects the temperature at which failure diagnosis is performed is used, there is no possibility that the failure determination accuracy is lowered due to a change in the outside air temperature, and usability can be improved.

Furthermore, the temperature sensor failure determination condition is an engine stop temperature, for example, an engine stop water temperature Tw1 is equal to or higher than a first predetermined temperature Twref1 that is a set stop temperature.
Therefore, since the temperature condition for performing the failure determination is set in advance, when the water temperature sensor 22 that is a temperature sensor determines a failure that remains fixed in a high temperature state, a useless diagnosis can be performed. And practically advantageous.

It is a flowchart for control of the failure determination apparatus of the temperature sensor which shows the Example of this invention. It is a system diagram of a failure determination device for a temperature sensor. FIG. 4 is a time chart of a temperature sensor failure determination device, where (a) is an engine time chart, (b) is a time chart indicating restart of a diagnostic function, and (c) is a time chart indicating a change in temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 3 Exhaust passage 4 Cylinder block 5 Cylinder head 6 Piston 7 Combustion chamber 8 Intake valve 9 Exhaust valve 10 Spark plug 11 Air cleaner 12 Intake temperature sensor 13 Air flow meter 14 Throttle valve 15 Throttle angle sensor 16 Injector 17 Catalyst 18 Oxygen Sensor 19 Control means (also referred to as “ECM”)
20 Crankshaft 21 Crank Angle Sensor 22 Water Temperature Sensor 23 Knock Sensor 24 Intake Side Camshaft 25 Cam Angle Sensor 26 Vehicle Speed Sensor 27 Ignition Coil 28 Failure Determination Device 29 Failure Diagnosis Control Unit 30 Rediagnosis Function Timer (also simply referred to as “timer”) )
31 Main arithmetic processing unit (also referred to as “main CPU”)

Claims (4)

  In a failure determination device for a temperature sensor that detects a temperature that changes according to the operating state of the engine, the device has a diagnostic function for diagnosing whether or not the temperature sensor has failed, and is stopped after the engine is operated And a failure diagnosis control means for restarting the diagnosis function and diagnosing the failure after a certain period of time has elapsed after the engine is stopped when the temperature sensor failure determination condition is satisfied. apparatus.   The failure diagnosis control means detects the temperature at the time of engine stop and the temperature at the time of restart, and when the value obtained by subtracting the temperature at the time of restart from the temperature at the time of engine stop is equal to or less than a set failure judgment value. The temperature sensor failure determination device according to claim 1, wherein the temperature sensor is determined to be defective.   An outside air equivalent temperature detecting means for detecting the outside air temperature or a temperature linked to the outside air temperature is provided, and the failure determination value changes depending on the outside air equivalent temperature at the time of engine stop and restart detected by the outside air equivalent temperature detecting means. The temperature sensor failure determination device according to claim 2, wherein   2. The temperature sensor failure determination device according to claim 1, wherein the temperature sensor failure determination condition is that an engine stop temperature is equal to or higher than a set stop temperature.

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