JPH05263685A - Fuel control device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To continue the feedback control of the air-fuel ratio and thereby maintain its control accuracy by providing a plurality of air-fuel ratio sensing means, and regulating the air-fuel ratio in conformity to the sensing signal given by a whole these means when any of them goes in failure. CONSTITUTION:The exhaust pipe of an internal combustion engine is provided with at least two air-fuel ratio sensing means 1, 2. The air-fuel ratio is regulated by an regulating means 4 in conformity to the sensing signal given by either of these means 1, 2. A failure sensing means 3 senses whether any of them 1, 2 goes in failure, and if failed, the ratio is regulated by the means 4 in conformity to the sensing signal given by the whole one of them 1, 2. This permits continuing the feedback control of the air-fuel ratio with the whole air-fuel ratio sensing means even in case any of them 1, 2 is failed, and thereby the control accuracy of the air-fuel ratio can be maintained at good level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control system for an internal combustion engine.

[0002]

2. Description of the Related Art As a conventional technique having a plurality of air-fuel ratio detecting means, for example, as disclosed in JP-A-62-157254,
When it is determined that the air-fuel ratio detecting means on the upstream side of the exhaust pipe is abnormal by using two air-fuel ratio detecting means, there is a case in which the feedback control of fuel by the air-fuel ratio detection is stopped.

[0003]

In the above-mentioned prior art, when one of the air-fuel ratio detecting means is determined to be abnormal, the feedback control of the air-fuel ratio is stopped, so that the control accuracy of the air-fuel ratio deteriorates. is there.

[0004]

In order to solve the above problems, in the present invention, a plurality of air-fuel ratio detecting means and a fuel control device for detecting an abnormality of the air-fuel ratio detecting means are provided. Is provided with an abnormality detection means for determining whether or not is an abnormal state and an air-fuel ratio adjustment means for adjusting the air-fuel ratio.

[0005]

The abnormality detecting means determines from the output signal of the air-fuel ratio detecting means whether or not the air-fuel ratio detecting means is in an abnormal state. The air-fuel ratio adjusting means performs feedback control of the air-fuel ratio based on the output signal of the air-fuel ratio detecting means which is determined to be normal according to the determination result of the abnormality detecting means.

[0006]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a diagram showing a basic configuration of the present invention. Reference numerals 1 and 2 denote air-fuel ratio detecting means, which are attached to the exhaust pipes, respectively. here,
As the air-fuel ratio detecting means, an O ₂ sensor type device whose output is inverted at a certain air-fuel ratio, or a device which outputs a signal of a level corresponding to the air-fuel ratio may be used. Reference numeral 3 denotes an abnormality detecting means, which determines whether or not each sensor is normal by monitoring the level of the output signal of each air-fuel ratio sensor. Reference numeral 4 is an air-fuel ratio adjusting means, which performs feedback control of the fuel supply amount so that a predetermined air-fuel ratio is achieved by the output signal of the air-fuel ratio sensor. Here, when one air-fuel ratio sensor is determined to be abnormal by 3, the other normal sensor adjusts the air-fuel ratio. As a result, even if one of the air-fuel ratio sensors becomes abnormal, the other normal sensor performs feedback control of the air-fuel ratio, so that it is possible to prevent pollution of exhaust gas due to deterioration of air-fuel ratio control accuracy.

FIG. 2 is a system configuration diagram of the present invention. The intake air of the engine is taken in through the intake manifold 5 and the throttle valve 6. The intake air amount is measured by the hot wire sensor 7. A water temperature sensor 9 is attached to the cylinder block 8. The engine speed is detected by the crank angle sensor 10.
The exhaust pipe 11 includes an air-fuel ratio sensor 13 before and after the catalyst 12,
14 are attached respectively. The control unit 15 includes a hot wire sensor, a crank angle sensor,
Output signals of the water temperature sensor and the air-fuel ratio sensor are input, the fuel injection amount and the ignition timing are calculated from these signals, and output to the injector 16 and the ignition coil 17, respectively.

The processing procedure of the control unit 15 will be described with reference to FIG. At 100, it is determined whether or not it is in an operating state in which feedback control of the air-fuel ratio is performed. When it is determined that the feedback control is performed, at 101, the signals of the O ₂ sensors on the upstream side and the downstream side of the exhaust pipe are captured. In 102, O
₂ Determines whether each sensor is in an abnormal state based on the signal level of the sensor. As an example, when the signal level of the sensor is below a certain level for a predetermined time or above a certain level, it is determined that the sensor is abnormal. Here, if the upstream O ₂ sensor is determined to be normal, it selects the upstream O ₂ sensor for an air-fuel ratio control 103. When the upstream O ₂ sensor is determined to be abnormal and the downstream O ₂ sensor is normal, 104 selects the downstream O ₂ sensor. If any of the sensors is abnormal, the air-fuel ratio adjustment gain α is fixed to a predetermined value at 105, and thereafter, the air-fuel ratio feedback control is not performed until any of the sensors becomes normal again.

At 106, it is determined whether the signal level of the O ₂ sensor selected at 103 or 104 is inverted from the lean side to the rich side or from the rich side to the lean side.
If there is an inversion, the signal level of the O ₂ sensor is compared with a predetermined value L at 107, and if it is less than the predetermined value, that is, if the signal is inverted from the rich side to the lean side, at 108, α is changed to PR _{i by the} rich side. to correct. Further, when the signal level of the O ₂ sensor is L or more, that is, when the lean side is inverted to the rich side, α is corrected by PL _{i to the} lean side in 109. Here, the values of PR _i and PL _i may be changed for each of the upstream O ₂ sensor and the downstream O ₂ sensor.

When there is no signal inversion of the O ₂ sensor in 106, the signal level of the O ₂ sensor is compared with a predetermined value L in 110, and when it is less than a predetermined value (lean state), α is further increased by a predetermined amount in 111. Only IR _i is corrected to the rich side. If it is equal to or greater than the predetermined value (rich state), 112 is further corrected to the lean side by a predetermined amount IL _i . IR _i , IL
The value of _i is, PR _i, similarly to the value of PL _i, may be changed in response to the sensor. These setting methods will be described later. By the above processing, even when one of the O ₂ sensors becomes abnormal, the other normal sensor continues the feedback control of the air-fuel ratio to suppress the fluctuation of the air-fuel ratio and increase the harmful components of the exhaust gas. Can be prevented.

A method of setting the above α correction parameters: PR _i , PL _i , IR _i , and IL _i according to the mounting position of the sensor will be described with reference to FIG. (a) is an output signal of the O ₂ sensor, which has a level corresponding to the air-fuel ratio (lean / rich). (b) is the movement of the air-fuel ratio adjustment gain α when the air-fuel ratio is adjusted by the upstream O ₂ sensor, and when the air-fuel ratio is reversed from lean to rich, immediately after the reversal,
The lean correction is performed only for PL ₁ , and thereafter, the lean correction is performed for each IL _{1 in} a predetermined cycle until it is reversed from rich to lean. Similarly, when switching from rich to lean, PR
Rich correction is performed with ₁ and IR ₁ . On the other hand, (C) shows the movement of the air-fuel ratio adjustment gain α when adjusting the air-fuel ratio by the downstream O ₂ sensor, and the response of the air-fuel ratio is delayed on the downstream side with respect to the upstream side. At the time of reversing, the correction amounts when the downstream O ₂ sensor is selected: the values of PL ₂ and PR ₂ are larger than the values of PL ₁ and PR ₁ when the upstream O ₂ sensor is selected, respectively. Thereby, the response delay of the air-fuel ratio adjustment can be improved.

Further, in order to prevent deterioration of controllability due to excessive correction of the air-fuel ratio due to the change of the α correction amount at the time of reversal, the correction amount until the next reversal is corrected when the downstream O ₂ sensor is selected. Amount: The values of IL ₂ and IR ₂ are smaller than the values of IL ₁ and IR ₁ when the upstream O ₂ sensor is selected.

As described above, by changing the adjustment gain of the air-fuel ratio according to the mounting position of the air-fuel ratio sensor,
Fluctuations in the air-fuel ratio can be suppressed.

[0014]

As described above, according to the present invention, even if one of the O ₂ sensors becomes abnormal, the other normal sensor continues the feedback control of the air-fuel ratio to suppress the fluctuation of the air-fuel ratio. It is possible to prevent an increase in harmful components of exhaust gas.

Further, by changing the adjustment gain of the air-fuel ratio depending on the mounting position of the air-fuel ratio sensor, it is possible to suppress the deterioration of the air-fuel ratio controllability due to the difference in the response of the air-fuel ratio detection.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is a system configuration diagram.

FIG. 3 is a diagram showing a processing procedure of air-fuel ratio control.

FIG. 4 is an explanatory diagram of a method of setting an air-fuel ratio adjustment gain.

[Explanation of symbols]

1, 2 ... Air-fuel ratio detecting means, 3 ... Abnormality detecting means, 4 ... Air-fuel ratio adjusting means, 13 ... Air-fuel ratio sensor (upstream side), 14 ... Air-fuel ratio sensor (downstream side), 15 ... Control unit.

Claims (5)

[Claims] 1. A fuel control device comprising at least two air-fuel ratio detecting means in an exhaust pipe of an internal combustion engine, and air-fuel ratio adjusting means for adjusting an air-fuel ratio by any one of these air-fuel ratio detecting means. The air-fuel ratio detecting means determines whether or not it is in an abnormal state, the abnormality detecting means, and the determination result of the abnormality detecting means, based on the detection signal of the air-fuel ratio detecting means determined to be normal, A fuel control device for an internal combustion engine, comprising an air-fuel ratio adjusting means for adjusting a fuel ratio. 2. The air-fuel ratio adjusting means adjusts the air-fuel ratio using the air-fuel ratio detecting means (1) and the air-fuel ratio adjusting means which is located downstream of the exhaust pipe with respect to the air-fuel ratio detecting means (1). 2. The fuel control device for an internal combustion engine according to claim 1, wherein the adjustment gain is set to a value different from that when the fuel ratio detection means (2) is used. 3. The air-fuel ratio adjusting means adjusts the air-fuel ratio with a predetermined adjustment gain 1 immediately after the level of the air-fuel ratio detection signal reverses from lean to rich or from rich to lean, and then again the air-fuel ratio. The fuel control device for an internal combustion engine according to claim 2, wherein the air-fuel ratio is changed at a predetermined adjustment gain 2 ratio until the level of the detection signal is inverted. 4. The air-fuel ratio adjusting means compares with the value of the adjustment gain 1 when the air-fuel ratio is adjusted by using the air-fuel ratio detecting means (1). 3. The fuel control device for an internal combustion engine according to claim 2, wherein the value of the adjustment gain 1 is increased when the air-fuel ratio detecting means (2) located downstream of the exhaust pipe is used. 5. The air-fuel ratio adjusting means exhausts air from the air-fuel ratio detecting means (1) as compared with the value of the adjustment gain 2 when the air-fuel ratio is adjusted using the air-fuel ratio detecting means (1). 3. The fuel control device for an internal combustion engine according to claim 2, wherein the value of the adjustment gain 2 when using the air-fuel ratio detection means (2) located on the downstream side of the pipe is a small value.