JPS6296755A - Fuel injection controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to repeat the feedback control of an air-fuel ratio by comparing the variation rate of established air-fuel ratio with that of actual air-fuel ratio to judge whether a linear O2 sensor has returned to its normal state or not after the sensor has been judged to be abnormal. CONSTITUTION:A control unit 4 controls a fuel injection valve 3 on an output signal delivered by a linear O2 sensor 6a which outputs the signal in proportion to O2 concentration in exhaust gas to execute the feedback control of air-fuel ratio, and stops the feedback control when the operating means 9 of the control unit 4 judges the sensor 6a to be abnormal. In addition, after the above abnor mality has been judged, the variation rate of the air-fuel ratio operated on a load state is compared with that decided on the output of the sensor 6a every prescribed hour, and when a difference between the both variation rates stays within a fixed range, the sensor 6a is judged to be normal. Thus the feedback control can be repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection control device for an internal combustion engine, and particularly to an air-fuel ratio feedback fuel correction method thereof.

[Conventional technology]

Conventionally, this type of internal combustion engine fuel injection control device includes one shown in Japanese Patent Application Laid-Open No. 60-69241, which controls a fuel injection valve 3 provided in an intake pipe 2 of an engine 1, as shown in FIG. The drive noculus is controlled according to the engine operating state at that time. That is, the engine operating state is detected by the output of an engine intake air amount sensor (not shown), the detection result is input to the control unit 4 to calculate the basic fuel injection amount, and the exhaust pipe 5
detects the residual O3 concentration inside the air-fuel ratio sensor 6 using the air-fuel ratio sensor 6, calculates the air-fuel ratio feedback fuel correction amount, and drives the fuel injection valve according to the result of adding the fuel correction amount to the basic fuel injection amount. and was using A/B feedback control.

In this way, the fuel supply amount is calculated by the hunt roll unit 4.
At this time, the following process is executed to prevent abnormal calculation of the air-fuel ratio feedback fuel correction amount due to a failure of the air-fuel ratio sensor 6 or the like. First, in the control unit 4, after confirming that the engine is warmed up using the cooling water temperature sensor 7, the engine rotation speed determined by the rotation speed sensor (not shown) is determined not to exceed a predetermined value and for a predetermined period of time. After the air-fuel ratio sensor 6 outputs a signal corresponding to the concentration in the exhaust gas, for example,
If a predetermined period of time has elapsed since the fuel was increased (generally speaking, the fuel content is rich), it is determined whether the output of the air-fuel ratio sensor 6 indicates a lean air-fuel ratio. And here, when the air-fuel ratio shows lean even though it is controlled to be rich,
It was determined that the air-fuel ratio sensor was abnormal, and air-fuel ratio feedback fuel correction control was prohibited.

[Problem that the invention seeks to solve]

Since the conventional internal combustion engine fuel injection control device is configured as described above, once the air-fuel ratio sensor 6 is mistakenly determined to be abnormal, the air-fuel ratio feedback fuel correction remains prohibited. However, unless the air-fuel ratio sensor 6 is replaced with a new one, a problem arises in that the engine is often operated at an air-fuel ratio setting that produces a large amount of harmful gas components in the exhaust gas.

This invention was made in order to solve the above-mentioned problems, and it is possible to prevent unnecessary replacement of the air-fuel ratio sensor, and also to reduce the air-fuel ratio at which a large amount of harmful gas components are emitted from the exhaust gas. An object of the present invention is to obtain an internal combustion engine fuel injection control device that can prevent the fuel injection control device from operating with the settings unchanged.

[Means for solving problems]

The internal combustion engine fuel injection control device according to the present invention has zero residual amount in exhaust gas. The concentration is detected by a linear O sensor and air-fuel ratio feedback is performed, and the linear O,
If the sensor is determined to be abnormal, the set air-fuel ratio change rate and IJ calculated based on the engine load condition at predetermined intervals
Near 0. The sensor output is compared with the calculated air-fuel ratio change rate, and if the difference between the two is within a predetermined range, it is determined that the linear O and centimeters are normal, and the air-fuel ratio feedback fuel correction control is re-executed. This is how it was done.

[Effect]

In this invention, it is determined that the linear O sensor is abnormal, and the linear O! Even if fuel correction according to the sensor is prohibited, linear 0. Since it is determined whether the rate of change of the sensor output signal is normal, if it is determined that the rate of change of the sensor output signal is normal, it becomes possible to re-execute the air-fuel ratio feedback fuel correction using the linear O sensor.

〔Example〕

FIG. 1 is a diagram showing the configuration of an internal combustion engine fuel injection control device according to an embodiment of the present invention. In the figure, 10 is a negative pressure sensor that detects the pressure inside the intake pipe, 11 is a rotational speed sensor that detects the engine rotational speed, and 6a is a residual 0.0% residual in the exhaust gas.
Linear 0 to detect concentration, sen? -t'6 le. Also, 9
is a calculation means in the control unit 4, and this calculation means 9 is composed of an analog/digital converter, a microcomputer, etc. (not shown), and in addition to the output signals of the linear sensor 6a, the negative pressure sensor 10. Rotation speed sensor 11. Signals from the cooling water temperature sensor 7, etc. are input, and based on each signal, the basic fuel supply amount suitable for the engine operating state at that time is calculated, and the linear O sensor is determined to be abnormal due to failure, etc., or to be normal from an abnormal state. The air-fuel ratio feedback fuel correction amount is calculated while determining and calculating whether the air-fuel ratio feedback fuel correction amount and the basic fuel supply amount are added, and the fuel injection valve 3 is controlled with a drive/force corresponding to the result of adding the air-fuel ratio feedback fuel correction amount and the basic fuel supply amount. It is something to do.

FIG. 2 is a flowchart showing the calculation sequence after the IJ near 02 sensor 6a is determined to be faulty in the calculation means 9.The calculation procedure will be explained in detail below using FIG. If it is determined that the linear O sensor 6a is abnormal, interrupt processing is performed at step 100 for the main program processing at predetermined time intervals. First, in step 101, it is determined from the output of the coolant temperature sensor 7 whether the coolant temperature is above a predetermined value and the engine is warmed up. If it is determined that the engine is warmed up, the process proceeds to step 102. In step 102, the engine speed is constant, and a predetermined time T sec after the engine speed becomes constant.
Determine whether the elapsed time has elapsed, and if the condition is met, step 103
Proceed to. In step 103, the rate of change X of the set air-fuel ratio within the calculation means 9 is calculated. and step 104
+7 near 02 sensor 6 determined to be abnormal in
The rate of change in the ate ratio in the exhaust gas, that is, the rate of change in the air-fuel ratio y, is calculated from the output signal of &. Next, in step 105, the difference between the air-fuel ratio change rates X and y is calculated by 9, and if the absolute value of the value
J Near 02sen? It is determined that 6a has returned to the normal state, and it is decided to re-execute the linear O and sensor output feedback air-fuel ratio fuel control, and the process returns to the main grodrum processing. Furthermore, if the conditions are not satisfied in steps 101, 102, and 105, the linear 0. Ends interrupt processing with sensor feedback disabled.

Furthermore, in step 105, the difference in air-fuel ratio change rate X-7
When calculating linear 0. If there is a time Δt required for the air-fuel ratio to be detected by the sensor 6a, the process at time t is calculated as x(t-ΔL)-y(t) in consideration of this.

In the above embodiment, the condition is that the engine speed is constant in step 102, but the same effect as in the above embodiment can be obtained even if the boost pressure is used as a condition parameter in place of the engine speed υ. Further, in the above embodiment, the basic fuel supply amount is calculated based on the output of the negative pressure sensor 10, but this may be the output of an intake air amount sensor that detects the amount of intake air in the intake pipe.

〔Effect of the invention〕

As described above, according to the present invention, even after the linear O sensor is determined to be abnormal, the linear O. Check whether the sensor has returned to normal condition by checking the set air-fuel ratio change rate and lJ near O,
Since the configuration is configured to execute the process by comparing the sensor output with the calculated air-fuel ratio change rate, the air-fuel ratio feedback can be re-executed even after the linear O2 sensor abnormality determination. This makes it possible to create a control device that can respond flexibly to the situation, and the air-fuel ratio control performance is improved because the air-fuel ratio feedback control is not prohibited and the vehicle is not operated at an air-fuel ratio that produces a large amount of harmful gas emissions. Moreover, it has the effect of providing a good driving feeling.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an internal combustion engine fuel injection control device according to an embodiment of the present invention, FIG. 2 is a flow chart showing the operation of the internal combustion engine fuel injection control device, and FIG. 3 is a conventional internal combustion engine fuel injection control device. It is a diagram showing the configuration of an injection control device. 3-ffi8ff injection valve, 4... Control unit, 6&... Linear O, sensor, 7... Cooling water temperature sensor, 9... Calculating means, 10... Negative pressure sensor, 11...
...Rotation speed sensor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (3)

[Claims] (1) An internal combustion engine fuel injection control device that calculates the fuel injection amount based on the load condition of the internal combustion engine and controls the fuel injection valve, and includes a linear O_2 sensor that outputs a signal proportional to the O_2 concentration in exhaust gas. If this linear O_2 sensor is determined to be abnormal, the air-fuel ratio feedback fuel correction control based on the linear O_2 sensor output is stopped, and after the linear O_2 sensor is determined to be malfunctioning, the air-fuel ratio feedback fuel correction control is stopped based on the load condition at predetermined intervals. The air-fuel ratio change rate calculated by An internal combustion engine fuel injection control device comprising: arithmetic means for re-executing control of the fuel injection valve by fuel ratio feedback fuel correction. (2) The internal combustion engine fuel injection control device according to claim 1, wherein the fuel injection amount is controlled based on the output of the intake pipe negative pressure sensor. (3) The internal combustion engine fuel injection control device according to claim 1, wherein the fuel injection amount is controlled based on the output of the intake air amount sensor.