JPS6011218B2 - Air-fuel ratio feedback mixture control device - Google Patents

Description

Detailed Description of the Invention The present invention detects the air-fuel ratio of the mixture represented by the oxygen concentration in the exhaust gas of an internal combustion engine in the exhaust system, and controls the air-fuel ratio of the mixture that is returned to the intake system and supplied. The present invention relates to an air-fuel ratio feedback type mixture control device, and particularly to one having a function of detecting a high engine load and stopping engine control to prevent burnout of an exhaust purification catalyst.

Conventional air-fuel ratio engine-type mixture control systems constantly control the engine, so when the amount of intake air increases, the reaction heat of the exhaust purification catalyst increases, creating the risk of catalyst burnout. Ta.

The present invention solves the above-mentioned problem, and uses an air-fuel ratio feedback type mixing system that can stably prevent burnout and deterioration of the exhaust purification catalyst even at high speeds and high loads where the amount of air intake into the internal combustion engine is large. The purpose of this invention is to provide an air control device.

Therefore, in the present invention, an intake air amount meter that directly detects the amount of air taken into the internal combustion engine, and an air-fuel ratio sensor that uses the intake air amount signal from this intake air amount meter as the main parameter and corresponds to the air-fuel characteristics set in advance according to the engine condition. It is equipped with an air-fuel mixture supply device that supplies Nami Aiki, an air-fuel ratio detector that is installed in the exhaust system of an internal combustion engine to detect the air-fuel ratio of the air-fuel mixture, and an exhaust purification catalyst, and integrates and processes the detection signal of this air-fuel ratio detector. In the air-fuel ratio feedback type air-fuel mixture control device configured to obtain a feedback correction amount of the air-fuel ratio and control the air-fuel mixture supply device using feedback control stopping means for stopping the feedback control operation based on the detection signal of the air-fuel ratio detector and fixing the feedback correction amount when the value exceeds the value; The present invention is characterized in that a quantity increase control means configured to suppress the exothermic action of the exhaust purification catalyst by increasing the quantity thereof is provided, and a hysteresis characteristic is provided to the predetermined value of the feedback control stopping means.

The present invention will be specifically described below with reference to embodiments shown in the drawings. FIG. 1 is a block diagram showing the overall configuration of the device of the present invention.
1 is a well-known oxygen concentration detector that generates a detection signal with a step characteristic corresponding to the oxygen concentration in exhaust gas; 2 and 3 constitute a feedback control circuit; An integrator increase/decrease signal is formed, and this signal is used to perform feedback correction on the time width of the output pulse of the electronic fuel injection device 4, which is a fuel supplying device. In general, this feedback control circuit includes a discrimination circuit 2 that compares the detection signal of the oxygen concentration detector 1 with a target setting value, and an integration circuit that integrates the discrimination signal from this discrimination circuit to generate an integral signal with increase/decrease characteristics according to the discrimination signal. It is composed of circuit 3. Reference numeral 5 denotes an intake air amount meter for detecting the intake air amount of the engine, which measures the intake air amount in an analog manner using a resistance division ratio value (Us/UB) as shown in FIG.

As the amount of intake air increases, the voltage value Vs approaches the voltage value Vc. Therefore, when the voltage value Vs exceeds the voltage set by the voltage between the voltages VB and Ez, that is, the value indicating the permissible overheating state of the exhaust purification catalyst, this is determined by the discrimination circuit 6 and the feedback control stop circuit 7 is activated. drive to stop feedback control. Furthermore, this discrimination signal is input to the fuel injection device 4 to increase the amount of fuel supplied from the fuel injection valve 8, and as a result, the mixture supplied to the engine is enriched. Next, a partial detailed circuit of the block diagram shown in FIG. 1 is shown in FIG. 2, and the apparatus of the present invention will be specifically explained based on this circuit.

First, the discrimination circuit 6 includes dividing resistors 6a and 6b for setting a comparison reference voltage, an input resistor 6c, a comparator 6d, and a resistor 6 for giving hysteresis to the reference setting voltage value.
e, 6g, 6h, transistor 6f, and resistor 6j,
It is composed of a diode 6i, and when the output voltage value Vs of the intake air amount meter 5 exceeds a set value, the comparator 6d outputs a high level. Further, the feedback control stop circuit 7 is composed of a diode 7a, a resistor 7b, and a transistor 7c, and short-circuits the input and output of the integrator 3a of the integration circuit 3 according to the output of the comparator 6d to stop the integration operation. The output of the integrator 3a is held at a predetermined value and the feedback correction is stopped. Further, at the same time as this stop operation, this discrimination signal is inputted as a correction parameter to the fuel injection device 4, and the fuel injection device 4 is operated to increase the amount of fuel supplied. According to the above structure, when the engine is under high load, the amount of intake air increases, and when the output voltage Vs of the intake air amount meter 5 that measures this becomes equal to or higher than the set value, the comparator 6d outputs a high level and the transistor 7c is made conductive to stop the integrating operation of the integrating circuit 3 and stop the feedback control based on the output of the oxygen concentration detector 1. At the same time, the high level output of the comparator 6d is input as a command to the fuel injection device 4, and the fuel This increases the amount of fuel injected from the injection valve 8.

Figure 3 shows the internal circuit of the intake air flow meter 5, and the output is (Us/
The reference point is at Vc, the voltages V8, Vc, and E2 are the division ratio values of fixed resistances, and the intake air amount is extracted as a change in the voltage value Vs.

In addition to the above-mentioned embodiment, as a means for enriching the return air-fuel mixture, the amount of intake air can be set to a certain value (Q in Fig. 4).
) If the feedback control is stopped in the above manner and at the same time the intake air amount characteristics are changed as shown in Fig. 4 to increase the fuel supply amount, it is necessary to send a signal from the discrimination circuit 6 to the electronic fuel injection device 4. There isn't.

That is, even if the resistor 6i and the diode 6i are eliminated, the amount of fuel can be increased by the output of the intake air amount meter 5. This is Q,
Above this point, characteristic A changes to characteristic B, and the intake air amount meter 5 gives a signal to the electronic fuel injection device 4 as if the amount of intake air were large, so the amount of fuel supplied increases and the mixture can be enriched. As described above, in the device of the present invention, the amount of intake air of the internal combustion engine is directly detected, and when the amount of intake air exceeds a predetermined value indicating the allowable overheating state of the exhaust purification catalyst, the detection signal of the air-fuel ratio detector is activated. The feedback control operation is fixed to fix the feedback correction amount, and the amount of fuel supplied to the internal combustion engine is increased by a predetermined amount to suppress the exothermic action of the exhaust purification catalyst. It has the excellent effect of being able to keep the reaction temperature below the allowable temperature without burning out the catalyst even when the engine is running at high speeds and under load, and it also has hysteresis characteristics for the predetermined value that determines the amount of intake air. Therefore, even when the internal combustion engine is operated near this predetermined value, there is an excellent effect that the heat generation effect can be stably suppressed.

[Brief explanation of the drawing]

The attached drawings show an embodiment of the air-fuel ratio feedback type mixture control device according to the present invention. FIG. 1 is a block diagram of the device of the present invention, FIG. 2 is an electrical wiring diagram of the main parts of the device of the present invention, FIG. 3 is a schematic diagram showing an equivalent circuit of the intake air amount meter, and FIG. 4 is a characteristic diagram showing the relationship between the intake air amount and the fixed resistance division ratio in the intake air amount meter. 1... Oxygen concentration detector serving as an air-fuel ratio detector, 2, 3...
...Discrimination circuit/integrator circuit forming the feedback control circuit, 4.
...Electronic fuel injection device, 5...Intake air amount meter, 6...Discrimination circuit, 7...Feedback control stop circuit, 8...Fuel quantity injection valve. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. An intake air amount meter that directly detects the amount of air taken into the internal combustion engine, and uses the intake air amount signal from this intake air amount meter as the main parameter to supply a mixture that corresponds to air-fuel ratio characteristics preset according to the engine condition. The air-fuel mixture supply device is equipped with an air-fuel ratio detector installed in the exhaust system of the internal combustion engine to detect the air-fuel ratio of the air-fuel mixture, and an exhaust purification catalyst, and integrates the detection signal of the air-fuel ratio detector to feed back the air-fuel ratio. In the air-fuel ratio feedback mixture control device configured to determine a correction amount and control the mixture supply device, when the intake air amount of the internal combustion engine exceeds a predetermined value indicating an allowable overheating state of the exhaust purification catalyst, the feedback control stopping means for stopping a feedback control operation based on a detection signal of an air-fuel ratio detector and fixing a feedback correction amount; 1. An air-fuel ratio feedback type mixture control device, comprising: an increase control means configured to suppress the exothermic action of a purification catalyst, and a hysteresis characteristic is given to the predetermined value of the feedback control stop means.