JPS61192831A - O2 sensor deterioration correcting apparatus - Google Patents

Abstract

PURPOSE:To suppress the deterioration of emission by measuring the cycle of the response performance of an O2 sensor and comparing said cycle with preset feedback control cycle and varying the feedback coefficient when the deterioration of the O2 sensor is judged. CONSTITUTION:In engine operation, the existence of stationary operation is judged from the engine revolution speed detected by a revolution sensor 11 and the load detected by a load sensor 20 in a stationary-state judging circuit 21 of a control unit 13, and when stationary operation is judged, the cycle D1 due to the response performance of an O2 sensor 12 is measured by a cycle measuring circuit 22. Said cycle D1 is compared with a normal cycle D2 in a comparison circuit 24, and if D1=D2, it is judged that the O2 sensor 12 is normal. When D1>D2, it is judged that the O2 sensor 12 is deteriorated, and the (D1-D2) value is input into an alpha-value (feedback coefficient) calculating circuit 17, and the obtained Pi-value is varied so as to form lean shift according to (D1-D2) value, and fuel injection quantity is reduced.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to an Oi sensor deterioration correction device in an air-fuel ratio control device for maintaining the air-fuel ratio of a mixture near the stoichiometric air-fuel ratio through feedback control based on a signal from an OI sensor in a vehicle engine. It is. rBackground of the invention 12 The O sensor in the air-fuel ratio control device is attached to the exhaust system of the engine, detects the oxygen concentration in the exhaust gas, determines whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio, and determines the oxygen concentration. It generates an electromotive force according to the Therefore, the 02 sensor is
They constantly come in contact with exhaust gas and are affected by the temperature and lead in the fuel, so they deteriorate after long-term use. If the sensor deteriorates, the sensor output will go awry, making it impossible to perform proper air-fuel ratio control. Therefore, the sensor may be replaced with a new one, or corrected to ensure proper air-fuel ratio control. This is necessary. By the way, the deterioration of the 0° sensor is
Deterioration cannot be determined simply based on the 9-hour mileage, as it varies depending on the vehicle's driving history, the engine used, etc. [Prior Art] When the Oi sensor deteriorates, the voltage of the sensor output decreases. As shown, a method for correcting the voltage drop in the sensor output has been proposed.

Problem to be Solved by the Invention J However, as shown in the above-mentioned prior art, the voltage drop in the sensor output occurs only at the stage when the deterioration of the 02 sensor has progressed considerably, and therefore, it is necessary to solve the problem after that stage. , there is a problem that the deterioration cannot be corrected. When a general O2 sensor deteriorates, the response delay of the sensor gradually increases in the initial stage, and the cycle of feedback IQ control becomes longer than in the normal case. Furthermore, response deterioration occurs when the air-fuel ratio changes from rich to lean and from lean to rich, and generally the time to change from lean to ridge is longer than the time to change from rich to lean.
The air-fuel ratio shifts to the richer side than the stoichiometric air-fuel ratio. The exhaust gas purification rate of the three-way catalyst deteriorates, and fuel efficiency also deteriorates. For this reason, it is desirable to correct the deterioration of the 01 sensor from the initial stage when it begins to deteriorate. [Means for Solving the Problems] In view of the problems in the prior art described above, the present invention provides an air-fuel ratio feedback control system using an 02 sensor.
Deterioration of the z sensor is accurately determined at an early stage, and corrections are made so that the air-fuel ratio does not deviate from the stoichiometric air-fuel ratio.
The present invention aims to provide a two-sensor deterioration correction device. The means for this are a steady state determination circuit that determines steady operation based on the engine speed and load, a cycle measurement circuit that measures the cycle of O° sensor responsiveness in steady state, and a comparison of the above cycle with a preset feedback control cycle. and a comparison circuit that determines the deterioration of the 0□ sensor, and in the case of deterioration of the 01 sensor, the feedback P,
This is characterized by changing the I constant. ] The above O! Based on the configuration of the sensor deterioration correction device, in a steady state, the period of O1 sensor responsiveness is measured, and by comparing it with the normal case under the same operating conditions, early deterioration of the O1 sensor can be detected. At this time, the feedback P and I constants are changed according to the period time difference, and the air-fuel ratio is changed to shift to the lean side, thereby correcting the rich side deviation of the air-fuel ratio and achieving the stoichiometric air-fuel ratio. It will keep the fuel ratio close to that.

【Example】

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. In the figure, to explain the case where the present invention is applied to an engine with a fuel injection device, reference numeral 1 is an engine body, and as an intake system of the engine body 1, an air 70 immediately downstream of an air cleaner 2 - a meter 3 connects an intake pipe 4. The throttle body 5 communicates with the engine body 1 via an intake manifold 6. Further, a three-way catalytic converter 8 for exhaust gas purification is attached to the exhaust pipe 7 from the engine body 1, and a single injector 10 injects fuel as a single point system on the downstream side of the throttle valve 9 in the throttle body 5. It is set up properly. On the other hand, a signal corresponding to the intake air amount from the air flow meter 3, a signal corresponding to the engine rotation speed from the rotation sensor 11, and a signal corresponding to the engine rotation speed from the rotation sensor 11, and a signal from the 0□ sensor 12 attached to the exhaust system to detect the oxygen concentration in the exhaust gas. Signal and control unit 13
The circuit is configured to input the A control unit 13 determined based on input signals from each of these sensors, etc.
The output signal from the injector 10 determines the amount of fuel to be injected together with the valve opening time of the injector 10. To explain the fuel injection control system in the control unit 13, signals of intake air and IQ from the air flow meter 3 and engine rotation speed N from the rotation sensor 11 are input to the basic injection pulse width calculation circuit 15, and the basic injection pulse width Tp is input to the basic injection pulse width calculation circuit 15.
Calculate. Further, the signal from the 02 sensor 12 is input to the air-fuel ratio determination circuit 16 to determine whether the air-fuel ratio is rich or lean, and based on this, the α value calculation circuit 17
The Pi constant is calculated and the feedback coefficient α is calculated. The basic injection pulse width Tp, α value, and various correction coefficient values are input to the fuel injection pulse width calculation circuit 18 to calculate the injection pulse width Ti, and the signal of this pulse width Ti is sent to the drive circuit. Injector 10 via 19
given to. On the other hand, to explain the 02 sensor deterioration correction system, the engine rotation speed from the rotation sensor 11 and the load signal from the negative pressure sensor 20 are input to the steady state determination circuit 21 to determine whether or not steady operation is occurring. In the case of steady operation, the cycle measurement circuit 22 measures the cycle of the output of the Or sensor 12 from rich to lean or from lean to rich. Here, when the O2 sensor 12 deteriorates and the response delay increases, the feedback control period D1 increases accordingly.On the other hand, the memory circuit 23 stores a table showing the normal period D2 in the steady operating state. This period D2 and the measured period D1 are compared in the comparison circuit 24, and if period '1lJD1>period 'lfJ D t, it is 0.
2 sensor 12 has deteriorated, and the period (Dl-D
z) is input to the α value calculation circuit 17. Therefore, the α value calculation circuit 11 calculates Pilil calculated from the output from the air-fuel ratio determination circuit 16 with a period (DI −D
z) so that it becomes a lean shift according to the value of α
It is designed to reduce the value. Next, the operation of the device configured in this way will be explained. First, in the steady state of operation, the steady state judgment time rH21
Based on the output, the period measuring circuit 22 measures the period D1 associated with the responsiveness of the Ox sensor 12, and the comparison circuit 24 compares it with the normal period Da. Therefore, if there is no response delay of the 02 sensor 12, the period Di
= period D2, and the comparison circuit 24 does not output a change signal. Therefore, the α value calculation circuit 17 calculates the α value only based on the determination result of the air-fuel ratio determination circuit 16. Then, the basic injection pulse width Tp based on the intake air mQ and the engine speed N, the α value of the feedback coefficient, etc. are input to the fuel injection pulse width calculation circuit 18, and the fuel injection pulse width Ti is calculated. By injecting fuel, feedback control is performed to maintain the air-fuel ratio near the stoichiometric air-fuel ratio. On the other hand, when the response delay of the O2 sensor 12 begins to occur, the comparison circuit 24 determines that the O2 sensor 12 has started to deteriorate, and the value of the period (Dr Dx> is calculated by the α value calculation circuit 24.
Enter. Therefore, in the α value extraction circuit 17, the Pi value is changed to lean shift according to the value of the period (DI Dz), the α value becomes smaller, and thereby the fuel injection amount is reduced and shifted to the lean side. Ru. For this reason, the above 02
Due to the response delay of the sensor 12, the cycle of feedback control becomes longer and richer, but this is corrected by decreasing the fuel injection amount, and in this way, the air-fuel ratio is maintained near the stoichiometric air-fuel ratio without deviation. It will be done. Here, as the deterioration of the Ox sensor 12 progresses and the response delay increases, the correction amount also increases to maintain normal air-fuel ratio control. Although one embodiment of the present invention has been described above, it is similarly applicable to an air-fuel ratio Ill m using a carburetor, a multi-point injector, and the like. Furthermore, instead of using the negative pressure sensor 20, it is also possible to use the basic injection pulse width Tp1 or the output of the throttle sensor to determine steady operation.

【Effect of the invention】

As is clear from the above description, according to the present invention, 02
Since deterioration is determined based on the response delay of the sensor, the deterioration can be accurately detected at the initial stage. o
2 sensor begins to deteriorate, the feedback coefficient is corrected according to the length of the feedback control cycle to maintain the air-fuel ratio near the stoichiometric air-fuel ratio, which prevents deterioration of emissions and improves fuel efficiency. It will also give you an advantage.

[Brief explanation of drawings]

The drawing is an overall configuration diagram showing an embodiment of the O2 sensor deterioration correction device according to the present invention. 11... Rotation sensor, 12... 01 sensor, 13.
...Control unit, 17...α value calculation circuit, 20...
- Negative pressure sensor, 21... Steady state determination circuit, 22... Period measurement circuit, 23... Memory circuit, 24... Comparison circuit.

Claims (1)

[Claims] A steady state determination circuit that determines steady operation based on the engine speed and load, a cycle measurement circuit that measures the cycle of O_2 sensor responsiveness in steady state, and a cycle measurement circuit that measures the cycle of O_2 sensor response by comparing the above cycle with a preset feedback control cycle. A comparison circuit for determining deterioration of the O_2 sensor, and in the case of deterioration of the O_2 sensor, a feedback coefficient is changed in accordance with a shift in cycle time.