JPS603532A - Abnormality discriminating method of temperature sensor - Google Patents

Abstract

PURPOSE:To eliminate an erroneous confirmation of the first stage of starting of an engine, and to always discriminate an abnormality exactly by discriminating whether an output value of a temperature sensor is larger or smaller than a prescribed discriminating value, after a prescribed time in which the engine is capable of warming up enough after starting of the engine has elapsed, and discriminating an abnormality basing on a result of its discrimination. CONSTITUTION:A prescribed temperature TAO is set as a temperature TA of an absorbed air of the inside of a suction pipe 2 by initializing of a controlling circuit 14, and thereafter, whether the first prescribed time t1 has elapsed or not after starting of an engine 3 is discriminated. After the prescribed time t1 has elapsed, an output value VTA of a suction temperature sensor 9 is read, and whether the output value VTA of the suction temperature sensor is larger or smaller than a prescribed discriminating value VTAH is discriminated. In case the output value VTA of the suction temperature sensor 9 is larger than the discriminating value VTAH, whether a state of VTA>VTAH is continued exceeding the second prescribed time t2 or not is discriminated, and when it is continued exceeding the time t2, it is discriminated as an abnormality, it is alarmed and also stored, and thereafter, an F/S (fail safe) action is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for determining abnormality in a temperature sensor used for controlling an internal combustion engine.

Internal combustion engines for automobiles, etc. (hereinafter simply referred to as engines)
One method of controlling the operating state of the engine is to control the fuel injection fAm of the engine. In this device, the absolute pressure P e , A in the intake pipe downstream of the throttle valve is detected by a pressure sensor, and the engine speed is detected by a rotation sensor, and the basic fuel injection time Ti is determined using the detection output of this sensor. Furthermore, the required fuel injection amount is determined by multiplying the basic fuel injection time Ti by an increase or decrease correction coefficient according to other engine operating parameters such as engine cooling water waterfall Tw and intake air temperature TA, or transient changes in the engine. The corresponding fuel injection time Tout is calculated.

The above-mentioned cooling water temperature Tw and intake air temperature TA are detected by a temperature sensor such as a thermistor, and in this temperature sensor, the temperature signal is set to be a high voltage at low temperature, and in the low temperature range where the engine may be placed. A thermistor and a resistor are often combined so that the temperature signal saturates. This is because the temperature signal change rate is required to be largely covered in a region where it is desired to precisely control the engine according to the temperature.

In order to determine whether there is an abnormality in the temperature sensor, conventionally, a predetermined determination value was set to a value slightly larger than the saturated voltage, and the determination was made at the same time as the engine started. There were cases where a temperature signal larger than the discrimination value was output, and it was sometimes mistaken as an abnormality at the beginning of the engine startup.

The present invention has been made to solve these conventional drawbacks, and an object of the present invention is to provide a method for determining an abnormality in a temperature sensor that prevents misidentification at the initial stage of engine startup and accurately determines an abnormality. .

The temperature sensor abnormality determination method according to the present invention is a method of determining the magnitude of the output value of the temperature sensor and a predetermined discrimination value after a predetermined period of time has elapsed from the start of the engine, and determining the abnormality based on the determination result. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In Fig. 1, reference numeral 1 indicates an afterfilter, and the intake air passes through this filter 1, passes through the intake pipe 2, and passes through the engine 3.
The amount of air is regulated by a throttle valve 4 provided in the intake pipe 2. 5 is, for example, a potentiometer, which generates a level according to the opening degree of the throttle valve 4.
6°”@%”2″’otl*401.

7 is the intake absolute pressure sensor that generates an output voltage at a level corresponding to the absolute pressure PEA of the engine 3, 1 is a cooling water temperature sensor that generates an output voltage at a level corresponding to the water temperature, and 8 is the crank of the engine 3. When the rotation angle of the shaft (not shown) is top dead (TDC), it is pulsed
9 is the intake pipe 2.
10 is an oxygen concentration sensor that generates an output voltage at a level corresponding to the oxygen concentration in the exhaust gas; 11 is an exhaust pipe; 12 is an exhaust gas sensor; It is the original catalyst. Reference numeral 13 denotes an injector, which is provided in the intake pipe 2 near an intake valve (not shown) of the engine 3, and is configured to inject and supply fuel to the engine 3 in an amount corresponding to an input pulse period. Throttle opening sensor 5, intake absolute pressure sensor 6, cooling water temperature sensor 7
, crank angle sensor 8, intake temperature sensor 9, and oxygen mi sensor 10 are input to the control circuit 14.

The control circuit 14 is constituted by a so-called microprocessor such as a microcomputer, for example, and calculates the basic fuel injection time Ti and the basic fuel injection time Ti according to a predetermined program. The fuel injection time TO1lt corresponding to the actual fuel injection amount is calculated.

FIG. 2 is a block diagram showing a specific configuration of the control circuit 14. As shown in FIG. In FIG. 2, the control circuit 14 is a CPU (central processing circuit) that performs digital arithmetic processing according to a program.
It has 15. An input/output bus 16 is connected to the CPU 15, and data signals or address signals are input/output to/from the CPU 15 via the input/output bus 16. The input/output bus is connected to an A/D converter 17, an MPX (multiplexer) 18, a counter 19, a ROM (IJ-do-on memory) 201, a RAM (random access memory) 21, and a drive circuit 22 for the injector 11. MP, X18 selectively converts any one of the output signals of sensors 5 to 7.9 and 10 into A/
This is a switch that relays supply to the D converter 17. The counter 1 measures the generation cycle of output pulses from the crank angle sensor 6-8 supplied via the waveform shaping circuit 24.

The cooling water temperature sensor 7 consists of a thermistor 7a that is supplied with power from the power supply +Vcc, and is connected in series with the resistor R1 between the power supply +Vcc and ground so that the temperature signal is saturated in the low temperature range in which the engine 3 is operated. A temperature signal is output from the connection point between the thermistor 7a and the resistor R1. Similarly, the intake temperature sensor 9 includes a thermistor 9a and a resistor R2 connected in series between the power supply Vcc and ground. The thermistors 7a and 9a are resistive elements (PTC: POSISTOR) having positive temperature coefficients, but may have negative temperature coefficients if the connection with the resistors is reversed.

Next, the procedure of the method for determining an abnormality in a drought sensor according to the present invention will be explained, for example, in the case of the intake air temperature sensor 9, according to the flowchart of FIG.

First, in the initialization (step 1) of the control circuit 14, a predetermined temperature TAO is set as the Wa If T A of the intake air in the intake pipe 2, and after that, when the first predetermined time t1 has elapsed since the engine 3 was started, It is determined whether or not (step 2). If the predetermined time 11 has elapsed, the output value VTA of the intake air temperature sensor 9 is read (step 3), and the output value VTA of the intake air temperature sensor 9 is determined to be larger than the predetermined judgment value VTAI-1 (step 4). . Here, during the first predetermined time tI, the output value VTA of the intake temperature sensor v9 is the discrimination value V
The warm-up time for the engine 3 is set to 10 minutes, for example, less than TA I-1.

When the output value VTA of the intake air temperature sensor 9 is larger than the determination value VTAH, it is determined whether the state of VTA>TT8 continues beyond the second predetermined time t2 (step 5), and the time 12 is determined. The IIF/S determines that the abnormality has continued beyond the above period, issues an alarm, and memorizes it in step 6).
(Fail Safe) Action is taken (Step 7). On the other hand, if the duration of the state of VTA>TTAI-1 is within the second predetermined time t2, the intake temperature sensor 9
The value read last time is set as the output value VTA.
(''''''-y7'8)・1 After the output value VTA of the intake air temperature sensor 9 is determined to be less than or equal to the determination value VTAI-1 in step 4, or in step 8
After completion of step 9, the process returns to step 3 through step 9 in which all other tasks such as abnormality determination of other sensors are performed, and the above series of operations is repeated in synchronization with the TDC signal.

In the above embodiment, the abnormality determination of the intake air temperature sensor 9 has been described, but the abnormality determination of the cooling water temperature sensor 7 is also performed in exactly the same manner. Further, the temperature sensor is not limited to the cooling water temperature sensor 7 and the intake temperature sensor 9, but any sensor that detects the temperature related to the engine 3 may be used.

As explained above, according to the present invention, after a predetermined period of time has elapsed since the start of the engine to allow the engine to warm up sufficiently, the output value of the temperature sensor and the predetermined judgment value are judged in magnitude, and based on the judgment result, Since abnormalities are determined, there is no misidentification at the initial stage of engine startup, and abnormalities can always be accurately determined.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an electronically controlled fuel supply system to which the temperature sensor abnormality determination method according to the present invention is applied, and FIG. 2 shows a specific configuration of the control circuit shown in FIG. 1. The block diagram and FIG. 3 are flowcharts showing the steps of the method for determining abnormality in a temperature sensor according to the present invention. Explanation of symbols of main parts 2...Intake pipe 3...Engine 5...Throttle opening sensor 6...Intake absolute pressure sensor 7... ... Cooling water temperature sensor 8 ... Crank angle sensor 9 ... Intake temperature sensor Applicant Honda Motor Co., Ltd. Agent Patent attorney Motohiko Makimura 10-

Claims (1)

[Scope of Claims] (1) A method for determining an abnormality in a temperature sensor used to control an internal combustion engine, which comprises determining an output value of the temperature sensor and a predetermined determination value after a first predetermined time has elapsed since the start of the internal combustion engine. A method for determining an abnormality in a temperature sensor, the method comprising: determining the size of a temperature sensor, and determining an abnormality based on the determination result. (2) Claim 1, characterized in that when the time during which the output value of the temperature sensor continues to be on one side with respect to the predetermined determination value exceeds a second predetermined time, it is determined to be abnormal. Method for determining abnormality of temperature sensor described in section. (3) The temperature sensor abnormality determination method according to claim 1 or 2, characterized in that the temperature sensor has a characteristic that its output is saturated in a low temperature range in which the internal combustion engine is operated. 4) The temperature sensor according to claim 1, 2, or 3, characterized in that the value of the temperature signal is a predetermined value within the first predetermined time from the start of the internal combustion engine. (5) If the time during which the output value of the temperature sensor continues to be on one side with respect to the predetermined judgment value is within the second predetermined time, the value of the temperature signal is read in the previous time. 5. The method for determining an abnormality in a temperature sensor according to claim 2, 3, or 4, wherein the output value of the temperature sensor is used as an output value.