JPH0524033Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a device for diagnosing failure of a plurality of temperature sensors provided in a vehicle engine.

(Prior Art) In recent years, various diagnostic devices have been proposed for diagnosing failures in components within products. For example, in Japanese Patent Application Laid-open No. 57-13520, a self-diagnosis program is run separately from the normal program using signals from a test switch installed outside the product, and this allows for quick and accurate load operation and input signal monitoring. A device that allows inspection to be performed is disclosed.

By the way, conventionally, when detecting a failure in a temperature sensor installed in an engine, especially when detecting a failure that cannot be determined only by detecting a disconnection (for example, a deviation in characteristics), it is necessary to (1) remove the temperature sensor from the engine. The temperature sensor is removed and placed in an environment where the temperature is known, such as in ice water, and the sensor output (voltage, resistance value, etc.) at this time is measured and compared with the actual temperature.

(2) Object to be measured by the temperature sensor (e.g. cooling water temperature)
is measured with another instrument, and this measured value is compared with the output value of the sensor.

Measures such as these are being taken.

However, in case (1), it is difficult to remove the sensor from the engine, and in case (2), it is theoretically necessary to install the above-mentioned instrument in the exact same location as the sensor, but in reality it is difficult to remove the sensor from the engine. However, such mounting is not possible, and the instrument must be mounted near the sensor, which has the disadvantage that accurate failure diagnosis cannot be performed.

(Purpose of the invention) In view of the above circumstances, the present invention is a failure diagnosis device for a vehicle control device that does not require the work of removing the temperature sensor from the engine and can diagnose the failure of the temperature sensor without using other instruments. The purpose is to provide

(Structure of the invention) The present invention provides a vehicle equipped with a plurality of temperature sensors disposed in different parts of a vehicle engine, and in which the engine is controlled according to detection signals output from these temperature sensors. A failure diagnosis device for diagnosing a failure of a control device, the device comprising: sampling means for sequentially sampling the output of each temperature sensor at a plurality of predetermined times when the engine is not in operation; The temperature sensor includes a calculation means for calculating a convergence value of the output of the sensor, and a determination means for determining a failure of the temperature sensor by comparing these convergence values.

According to such a configuration, the output of each temperature sensor is sampled when the engine is not operating, the convergence value is determined, and the failure of the temperature sensor is determined by comparing the convergence values. There is no need to remove the sensor from the engine or attach other instruments to the engine.

(Example) Embodiments of the present invention will be described based on the drawings.

In FIG. 1, reference numeral 1 denotes an engine. A piston 2 is provided in a cylinder of the engine 1, and a combustion chamber 3 is formed above the piston 2. An intake valve 4, an exhaust valve 5, and a spark plug 6 are arranged to face the combustion chamber 3, and an ignition control section 9 consisting of an igniter 7 and a distributor 8 is connected to the spark plug 6. There is.

An intake passage 10 and an exhaust passage 11 communicate with the combustion chamber 3 via the intake valve 4 and exhaust valve 5. The intake passage 10 is provided with an intake air temperature sensor (temperature sensor) 12, an air flow meter 13, a throttle valve 14, a combustion injection valve 15, and an air cleaner 16, and the exhaust passage 11 is provided with an exhaust purifier 17 and an air cleaner 16. An O ₂ sensor 18 is provided to detect the air-fuel ratio of exhaust gas. Furthermore, this engine 1 includes a water temperature sensor (temperature sensor) 2 that detects the temperature of cooling water in the radiator 19.
0, and a control unit 21 for controlling the ignition timing and fuel injection amount of the engine 1.

The control unit 21 includes the intake air temperature sensor 12, the air flow meter 13, and the water temperature sensor 2.
0, a detection signal output from a throttle sensor provided on the throttle valve 14, and a crank angle signal output from a crank angle sensor provided on the distributor 8, and in response to these signals, the ignition control section Normal engine control is performed by outputting control signals to the fuel injection valve 9 and the fuel injection valve 15.

Furthermore, this control unit 21 includes
When diagnosing a failure of the intake air temperature sensor 12 and water temperature sensor 20, a failure diagnosis device 22 as shown in FIGS. 1 and 2 is connected. As shown in FIG.
5, output section 26, input section 27, and CPU 28
It is equipped with The ROM 24 is an element that stores a control program, and the RAM 25 is an element that stores various data. The input unit 27 is designed to allow instructions to be input by key operation.
The output unit 26 displays the contents of the failure diagnosis.

As shown in FIG. 2, this failure diagnosis device 22 includes a sampling section (sampling means) 2.
9, a convergence value calculation section (calculation means) 30, and a failure determination section (judgment means) 31. The sampling section 29 detects the intake air temperature sensor 12 when the engine 1 is not operating.
The output of the water temperature sensor 20 is sequentially sampled at predetermined intervals within a certain period of time, and the convergence value calculation unit 3 calculates the values for each sensor when the elapsed time approaches infinity, based on the values sampled by the sampling unit 29. The convergence value of the outputs of 12 and 20 is calculated. The failure determination unit 31
The two convergence values calculated by the convergence value calculation unit 30 are compared to determine whether the temperature sensors 12, 20 are faulty.

Next, the control operation of the above device will be explained with reference to the flowchart of FIG. First, the failure diagnosis device 22 is connected to the control unit 21 while the engine 1 is stopped. In this state, the detection signals of the intake air temperature sensor 12 and the water temperature sensor 20 are input to the control unit 21, and further, the detected values are input to the failure diagnosis device 22.

The detected values are read by the sampling section 29 in the failure diagnosis device 22 at regular time intervals (step S ₁ ) and sequentially stored (step S ₂ ).
When sampling is performed for a predetermined period of time in this manner (step S ₃ ), the convergence value calculating section 30 calculates the convergence value of each output as follows based on these sampled values.

The relationship between the detected value T and the elapsed time t is given by the following approximate expression.

T(t)=A・e×p(−αt)+B …(1) (α, A, B: constant) However, the constant A in this formula (1) increases the output value as time passes. It takes a positive value if it is falling, and it takes a negative value if it goes down.

The convergence value calculation unit 30 calculates each constant of equation (1) based on the plurality of detected values (step S ₄ ), and
Each sensor 12, 2 at t→∞ based on equation (1)
Calculate the convergence values β ₁ and β ₂ of the detected value of 0 (step
_S5 ).

If the sensors 12 and 20 are normal, their respective outputs should converge to approximately the same value (ambient temperature) after the engine is stopped. Therefore,
The failure determination unit 31 uses the calculated convergence values β ₁ and β ₂
It is determined whether the difference between the two is less than the minimum value δ (step S ₆ ), and if it is less than the minimum value δ, a determination signal indicating that there is no abnormality is transmitted to the control unit 21. Upon receiving this signal, the control unit 21 displays to the outside that both sensors 12 and 20 are normal (step S ₈ ).
If the difference between both convergence values β ₁ and β ₂ is larger than the minimal value δ, the failure determination unit 31 issues a signal indicating that there is an abnormality. Upon receiving this signal, the control unit 21 displays a message indicating that a failure or characteristic deviation has occurred in at least one of the sensors 12, 20 (step _S7 ).

As described above, according to this device, when the engine 1 is not operating, the outputs of the intake air temperature sensor 12 and the water temperature sensor 20 disposed in the engine 1 are sequentially sampled at a predetermined time, and the output is determined based on these values. Fault diagnosis is performed by calculating the convergence value of the outputs of both sensors at t→∞ and comparing the two, so both sensors 1
Failure diagnosis can be easily performed without removing the 2, 20 from the engine 1 or attaching other instruments to the engine 1.

Note that this embodiment shows a case where there are two temperature sensors. Similar effects can be obtained even when there are three or more temperature sensors. For example, if there are 3 temperature sensors
In this case, as shown in Figure 4a, if the mutual differences between the convergence values calculated based on the detected values of each sensor (the hollow points in the figure) are all within minute values, then , displays that each sensor is normal, and if any one value is far from the other values as shown in Figure b, the sensor corresponding to that value is faulty. The same effect as above can be obtained by displaying a message to that effect.

Furthermore, the present invention can be applied to rotary engines, etc., regardless of the type of engine to which it is applied. Further, in the above embodiment, the fault diagnosis device 22 and the control unit 21 are configured separately and are connected to each other during fault diagnosis, but the fault diagnosis device 22 is integrated into the control unit 21. I don't mind.

(Effects of the invention) As described above, the present invention sequentially samples the detection values at predetermined times of a plurality of temperature sensors placed in different parts of the engine when the engine is not operating, and Since the convergence value of each sensor is calculated based on the value and the failure diagnosis is performed by comparing these calculated values, there is no need to remove the temperature sensor from the engine or attach other instruments to the engine. This has the effect of being able to perform fault diagnosis.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of an engine to which the fault diagnosis device of the present invention is connected, FIG. 2 is a block diagram showing the configuration of the fault diagnosis device, FIG. 3 is a flowchart showing the control operation of the device, and FIG. Figures 4a and 4b are graphs showing the relationship between the output of each sensor and time when the engine is not operating in an engine provided with three temperature sensors. 1...Engine, 12...Intake air temperature sensor (temperature sensor), 20...Water temperature sensor (temperature sensor),
22... Failure diagnosis device, 29... Sampling section (sampling means), 30... Convergence value calculation section (calculation means), 31... Failure determination section (judgment means).

Claims (1)

[Scope of utility model claims] A fault diagnosis for a vehicle control device that includes a plurality of temperature sensors arranged in different parts of a vehicle engine and controls the engine according to detection signals output from these temperature sensors. The apparatus includes sampling means for sequentially sampling the output of each temperature sensor at a plurality of predetermined times when the engine is not operating, and calculating a convergence value of the output of each temperature sensor based on the sampling value by the sampling means. A failure diagnosis device for a vehicle control device, comprising a calculation means and a determination means for determining a failure of the temperature sensor by comparing these convergence values.