JPS62247148A - Abnormality detector for air-fuel ratio sensor - Google Patents

Abstract

PURPOSE:To suppress the deterioration in the quality of exhaust gas, by judging an air-fuel ratio sensor to be abnormal, to urge the replacement thereof, when the width of fluctuation in a corrected value in the feedback control of the air-fuel ratio has been larger than a prescribed magnitude for over a prescribed time. CONSTITUTION:Detection signals from a pressure sensor 6, a rotation sensor 7, a water temperature sensor 8 and so forth, which correspond to the operating parameters of an engine 1, are read in the microprocessor 113 of a controller 11 so that a basic fuel injection quantity is calculated. The result of the calculation is corrected on the basis of the output from an O2 sensor 9 serving as an air-fuel ratio sensor. An injector 4 is driven depending on the result of the correction to feed a prescribed quantity of fuel to the engine 1. When the width of fluctuation in the corrected value has been larger than a prescribed magnitude for over a prescribed time, the O2 sensor 9 is judged to be abnormal, and a warning signal is generated by the controller 11 to urge the replacement of the O2 sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an abnormality detection device for an air-fuel ratio sensor that detects abnormalities such as deterioration in responsiveness of the air-fuel ratio sensor.

[Conventional technology]

FIG. 1 is a diagram showing the configuration of a general control device for an internal combustion engine. In this first factor, 1 is the engine, 2 and 3
4 is the intake pipe that introduces the air-fuel mixture into the engine 1, and 4 is the intake pipe 2.
5 is located between the intake pipes 2 and 30 and is opened or closed according to the will of the driver; 6 detects the pressure inside the intake pipe 3 downstream of the throttle valve 5; Pressure sensor %7 is a rotation sensor that generates a pulse in proportion to the rotation of the engine 1, 8 is a water temperature sensor that detects the cooling water temperature Kt of the engine 1, and 9 is the exhaust pipe 1 of the engine 1.
A 02 sensor is disposed at 0 and serves as an air-fuel ratio sensor for detecting the air-fuel ratio from exhaust gas components, and 11 is a control device that performs arithmetic processing based on the outputs of the above-mentioned sensors and controls the injector 4t.

The t*111id A/D converter inputs the detection output of the pressure sensor 6 and the detection output of the water temperature sensor 8, converts the analog signal into a digital value, and then sends it to the microprocessor 113. Reference numeral 112 denotes an input circuit that receives the on/off signal of the rotation sensor 7 and the detection signal of the 02 sensor 9, and sends these signals to the microprocessor 113. Microprocessor 113 includes A/D converter 111 and input circuit 1
Based on the information input from 12, injector 4
The microprocessor 113 has a ROMI 15 that stores the calculation processing procedures and data (setting values), and a ROMI 15 that temporarily stores the data during calculation processing. It is connected to RAMI 16 for storage. The output of the microprocessor 113 is sent to an output circuit 114 to drive the injector 4'ft.

In the internal combustion engine control device configured as described above, first, the microprocessor 113 reads the detection signals of the pressure sensor 61, rotation sensor 7, water temperature sensor 8, etc., that is, the operating parameters of the engine 1, and performs a basic fuel injection calculation. Then, the calculation result is further corrected based on the output of the OX sensor 9 to calculate the fuel injection amount, and the injector 4 is driven with the determined drive pulse width to supply a predetermined amount of fuel to the engine 1. .

FIG. 2 is a diagram showing air-fuel ratio feedback control between the output of the 02 sensor 9 and the actual air-fuel ratio of the engine 1.

That is, when the output a of the 0-ttV sensor changes from rich to 1, the correction value C is subjected to a corresponding increase integral correction, and when it changes from full to rich, a decrease integral correction is performed. The actual air-fuel ratio varies within a range of ±1 to 2% around the stoichiometric air-fuel ratio, and control is performed close to the stoichiometric air-fuel ratio.

Hikoo, t4 is 02 after the actual air-fuel ratio crosses the stoichiometric air-fuel ratio.
This is the time it takes for the output of the sensor 9 to reverse, and this is caused by the time it takes for the gas exhausted from the engine 1 to reach the Oz sensor 9, the response time of the zero-limit sensor 9, and the like.

[Problem that the invention seeks to solve]

Although the conventional air-fuel ratio control device is constructed as described above, the responsiveness of the 02 sensor 9 may deteriorate due to clogging caused by carbon in the exhaust gas caused by long-term use or adhesion of foreign matter due to the use of poor quality gasoline. There is a problem that is getting worse. The waveform diagram in FIG. 3 shows the air-fuel ratio feedback control in such a case. In other words, if the time td until the output of the air-fuel ratio sensor is reversed while the actual air-fuel ratio crosses the stoichiometric air-fuel ratio is longer than normal, the slope of the waveform of the correction value C is determined by control and will be different from normal. Since they are the same, their amplitude increases. Therefore, the actual air-fuel ratio varies greatly depending on the amplitude of the correction value C. For this reason, there were problems such as the purification efficiency of the three-way catalyst deteriorated and the exhaust gas deteriorated.

The present invention was made to solve the above problems, and an object of the present invention is to provide an abnormality detection device for an air-fuel ratio sensor that can suppress deterioration of exhaust gas.

[Means for solving problems]

An abnormality detection device for an air-fuel ratio sensor according to the present invention includes an air-fuel ratio sensor that detects an air-fuel ratio from exhaust gas components of an internal combustion engine, and corrects the amount of supplied fuel according to the output of the air-fuel ratio sensor, and corrects the amount of fuel supplied according to the output of the air-fuel ratio sensor. A control device that determines that the air-fuel ratio sensor is abnormal if the fluctuation range is greater than a predetermined value and for a predetermined time.

[For production]

In this invention, if the amplitude of the correction value of the air-fuel ratio feedback control exceeds a predetermined value and this continues for a predetermined time or more, the control device can determine that the air-fuel ratio sensor is abnormal and prompt the air-fuel ratio sensor to be replaced. .

〔Example〕 An embodiment of the present invention will be described below with reference to the drawings.

The configuration of this invention in the drawings is the same as the device shown in FIG. 1, and the difference is the content of control by the control device 11. FIG. 4 is a flowchart showing this control procedure. First, in step 201, Engine operating parameters such as intake pipe internal pressure, engine speed, and water temperature are read from the detection outputs of the pressure sensor 61, rotation sensor 7, and water temperature sensor 8. Next, in step 202, a basic fuel injection amount is calculated. That is, the rotation-synchronized injection nozzle width τ1 in which the injector 4 is driven in synchronization with the crank angle signal obtained from the rotation sensor 7 is determined. And then step 2
In step 03, the output of the air-fuel ratio sensor is determined, and if the output is rich, a fuel decrease integral correction CFBI is performed (step 204), and if the output is lean, a fuel increase i integral correction CFB2 is performed (step 204). 205). Further, in step 206, it is determined whether the output changes from rich to rich to t, and if the output changes to t, then in step 207, the correction value Crn is set.
zt is stored and the process proceeds to step 210, and if it has not changed, the process proceeds to step 208. In step 208, it is determined whether or not the output has changed from I) to rich. If it has changed, the correction value Crnxk is stored in step 209, and the process proceeds to step 210. In step 210, it is determined whether the variation range CFB2-CFBI of the correction value is greater than or equal to a predetermined value α1, for example, ±3% of the stoichiometric air-fuel ratio, as shown in FIG. 3(c), and whether this continues for a predetermined time or longer. However, if it exceeds a predetermined value, the failure determination result is stored in step 211, an alarm signal is generated to notify an abnormality of the air-fuel ratio sensor in step 212, and the basic fuel injection amount calculation result is converted to a correction value in step 213. The fuel injection amount, that is, the injection pulse width τ2 is calculated by correcting it using CFB. Also step 208
If the output does not change from lean to rich in step 210, and if the fluctuation range of the correction value does not exceed a predetermined value in step 210, the process proceeds to step 213, where the fuel injection amount is calculated. In addition,
The reason why a failure is determined when Cr2-CFBI > α continues for a predetermined period of time is to prevent malfunction by setting a % time limit, since it is possible that the fluctuation range becomes large transiently, such as during acceleration/deceleration. .

Further, in the above embodiment, the air-fuel ratio feedback control fuel injection device was explained as an example of the abnormality detection device of the air-fuel ratio sensor, but the above embodiment is not limited to this, and even if a feedback control carburetor is used. It has the same effect as the example.

〔Effect of the invention〕

As described above, according to the present invention, the air-fuel ratio sensor is determined to be abnormal if the fluctuation range of the correction value of the air-fuel ratio feedback control exceeds a predetermined value and continues for a predetermined time or more. This has the effect of encouraging replacement and therefore suppressing deterioration of exhaust gas.

[Brief explanation of drawings]

Fig. fa1 is a configuration diagram of the control device for an internal combustion engine according to the present invention, Fig. 2 is an operation waveform diagram showing air-fuel ratio feedback control under normal conditions, and Fig. 3 shows the air-fuel ratio when the responsiveness of the air-fuel ratio sensor deteriorates. Operation waveform diagram showing feedback control, 4th
The figure is a flowchart showing the operation of an abnormality detection device for an air-fuel ratio sensor according to an embodiment of the present invention. 1... Engine, 9... Air-fuel ratio sensor, 11...
Control device.

Claims (3)

[Claims] (1) An air-fuel ratio sensor that generates an output according to lean or rich air-fuel ratio from the exhaust gas components of the internal combustion engine, and an air-fuel ratio sensor that corrects the amount of fuel supplied to the internal combustion engine according to the output of this air-fuel ratio sensor, and In addition to feedback control of the fuel ratio,
and a control device that determines that the air-fuel ratio sensor is abnormal if the fluctuation range of the correction value exceeds a predetermined value and exceeds a predetermined time. Detection device. (2) The abnormality detection device for an air-fuel ratio sensor according to claim 1, wherein the control device generates an alarm signal when determining an abnormality in the air-fuel ratio sensor. (3) The preset value is ±3% of the stoichiometric air-fuel ratio.
An abnormality detection device for an air-fuel ratio sensor according to claim 1 or 2, characterized in that: