JPH0223699B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to an air-fuel ratio control device that controls fuel based on a signal from an oxygen sensor (O ₂ sensor) disposed in an exhaust pipe.

Conventionally, proportional control and integral control have been used in combination to control the air-fuel ratio using an O ₂ sensor.

As for these control devices, Japanese Patent Application Laid-open No. 1983
As stated in Publication No. 81434, the control signal is controlled by the rotation speed and air amount.

However, such devices have disadvantages in that they cannot perform accurate control over a wide operating range and in that they cannot easily correct control signals.

That is, in feedback control using an O ₂ sensor, if the feedback control gain of the control signal is too large, hunting will occur in the control, and if the feedback control gain is small, the response will be slow and it will not be possible to clear the exhaust regulations. Furthermore, since internal combustion engines are used in a wide range of operating ranges from idling to high speeds, the feedback control gain of the control signal needs to be optimal for each operating range.

However, with the above-mentioned techniques, such fine-grained control is almost impossible.

Furthermore, as disclosed in JP-A-51-106828, a method has been proposed in which the proportionality constant or integral constant is changed according to the operating conditions, but this method had the following problems. .

First, the resistors, operational amplifiers, capacitors, etc. that make up the integral circuit or proportional circuit are affected by heat, which causes the feedback control signal to become curved, resulting in longer convergence times and hunting. .

That is, there is a phenomenon in which the feedback control gain determined by the time constant changes because the resistors, operational amplifiers, capacitors, etc. that constitute the integral circuit or the proportional circuit are thermally affected by temperature fluctuations. As a result, the feedback control gain is no longer constant with respect to temperature changes, and even in the same operating state, the feedback control gain will vary if the temperature differs.

In other words, for example, if we set the temperature on the horizontal axis and the feedback control gain on the vertical axis and look at the magnitude, the magnitude of the feedback control gain will differ if the temperature differs even under the same operating condition, and if you connect them, the feedback control gain will change. The gain becomes curvilinear, and reliability with respect to temperature deteriorates.

Therefore, the feedback control gain of the feedback control signal is no longer constant depending on the temperature, and even under the same operating condition, the feedback control gain of the feedback control signal becomes curved and converges as described above when viewed from the temperature situation. There were problems in that it took a long time and hunting occurred. Particular care must be taken when the control device is placed in the engine room.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for an internal combustion engine that can perform accurate control over a wide operating range and can also easily correct control signals.

The features of the present invention include: (a) a first memory element that stores an arithmetic processing program; (b) a second memory element that stores a predetermined feedback control gain corresponding to the operating state of the internal combustion engine. (c) A third storage area where data associated with calculation processing is temporarily stored.
(d) a memory element provided in the exhaust pipe of the internal combustion engine according to the arithmetic processing program stored in the first memory element;
A feedback control calculation is executed based on the output signal of the O ₂ sensor, and the feedback control calculation is performed using a feedback control gain selected from the second storage element corresponding to the operating state of the internal combustion engine. a microprocessing unit that executes an operation that generates a signal; (e) an air-fuel mixture concentration adjusting means that adjusts the air-fuel mixture concentration supplied to the internal combustion engine based on a feedback control signal from the microprocessing unit; The air-fuel ratio control device is constructed from the following.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an example of the configuration of an electronic fuel control system for an internal combustion engine according to the present invention.

To explain the basic configuration of the present invention with reference to FIG. 1, this system uses a known microprocessing unit (hereinafter referred to as
(abbreviated as MPU) 100, a readable and rewritable memory element (hereinafter abbreviated as RAM) 101,
a memory element (hereinafter abbreviated as ROM) 102 in which an arithmetic processing program is stored; a memory element (hereinafter abbreviated as ROM) 103 in which fixed data such as basic fuel characteristics of the carburetor and feedback control gain are stored;
and an element (hereinafter abbreviated as I/O) that has the function of translating the engine operating state into a signal that can be transmitted to the MPU 100 and outputting a signal for operating the on-off solenoids 104 and 105 based on the arithmetic processing results of the MPU 100. ) 108, each of which is connected in parallel.

To describe the I/O 108 in more detail, there are analog information and digital information as information representing the engine operating state. The means for transmitting analog information to the MPU 100 is a multiplexer (hereinafter abbreviated as MPX) 106 that selects any one input from a plurality of analog inputs;
and an analog/digital converter (hereinafter abbreviated as AD) that has a circuit that converts an analog quantity into a digital quantity and a register that stores the conversion result.
107 and operates as follows.

That is, a plurality of analog inputs, for example, the output voltage from the pressure sensor 109 that detects intake pipe negative pressure,
Sensors 110 and 111 that detect cooling water temperature or intake air temperature, output voltage from _O2 sensor 300, etc. are connected to MPX106.
MPX106 selects one of the analog inputs mentioned above according to instructions from MPU100 and outputs it to ADC100.
Connect to 7. Then, the ADC 107 is activated and the analog quantity is converted into a digital quantity. The conversion result is stored in the conversion result storage register mentioned above.
The MPU 100 takes in the memory contents of this register at an appropriate timing, and stores it in the RAM 100 as necessary.
Access a certain address and memorize this information. When the import is completed, MPU100 becomes MPX1
06, and connect another analog input to ADC 107. Thereafter, a plurality of pieces of analog information are converted into digital quantities and taken in in the same manner. The O ₂ sensor 300 is attached to the exhaust manifold, and its output end is connected to the MPX 106. Therefore, the output voltage of the O ₂ sensor 300 as shown in FIG. 2b is captured at an appropriate sampling period.

Reference number 112 is the rotation speed detection sensor I/O1
08 is directly input.

In the above, the present invention detects the operating state of the engine, corrects the return control gain (integral component I, proportional component P) accordingly, and improves controllability such as improving transient response or keeping the supplied air-fuel ratio constant. The purpose is to improve. Therefore, the operation will be explained using FIG. 2. As shown in FIG. 2a, the supplied air-fuel ratio becomes rich as the on-duty ratio of the solenoid gradually decreases, and gradually approaches the ternary point and exceeds it at a certain point. From this point on, the supplied air-fuel ratio becomes rich, but this air-fuel mixture is taken into the cylinder via the intake manifold, passes through the compression, explosion, and exhaust strokes, and by the time it reaches the O ₂ sensor 300, it is always in the operating state. There is a fixed delay time.
That is, after time b, the output voltage of the O ₂ sensor 300 is reversed as shown in FIG. 2b. This means that the O ₂ sensor 300, which is captured at an appropriate sampling period,
It is known from the information. If this voltage value is larger than a predetermined value, the supplied air-fuel ratio exceeds the ternary point and has become rich. That is, since it is richer by C than the ternary point, at this point the on-duty ratio of the solenoid is increased by a certain value P so as to make the supplied air-fuel ratio lean. this is,
When it is determined that the load is too high, the time data set in the duty register is set to the above-mentioned constant value P.
This can be realized by adding time data corresponding to , and storing it in the duty register again. Thereafter, when the on-duty ratio of the solenoid is gradually increased at a predetermined rate, the air twist ratio in the cylinder gradually becomes leaner after a certain point, as shown in FIG. 2a. If the on-duty ratio of the solenoid is increased enough to exceed the three-dimensional point and become lean, after the delay time as described above, the O ₂ sensor 3
00 output voltage is below the comparison level. At this time, it is known that the supplied air-fuel ratio has become leaner than the ternary point. Therefore, in order to make the supplied air-fuel ratio rich, the on-duty ratio of the solenoid is suddenly decreased by the above-mentioned constant value P. This can be realized by subtracting the time data corresponding to the constant value P from the time data stored in the duty register at the time when it is determined that the duty register is rich, and resetting the result in the duty register.

However, even if the on-duty ratio of the solenoid is suddenly changed, the air-fuel ratio in the cylinder does not become rich immediately; it remains lean until a certain point, and then gradually becomes richer. Thereafter, the on-duty ratio of the solenoid is gradually reduced at a predetermined rate. During this time, a timing occurs when the output voltage of the O ₂ sensor 300 is reversed and exceeds the ternary point.

As described above, by constantly monitoring the output voltage of the O ₂ sensor 300 and controlling the on-duty ratio of the solenoid, it is possible to prevent the supplied air-fuel ratio from deviating significantly from the ternary point. For this purpose, the above-mentioned constant value P (this is called the proportional component P) is required.
and the increase/decrease in the on-duty ratio (this is defined as the integral component I
It is necessary to accurately control the engine operating conditions, such as engine speed, load, cooling water temperature, throttle valve opening, etc., or a combination of these. This will be explained in more detail with reference to FIG.

Figure 3 shows the basic flow of this control.
The _O2 sensor output is converted into a digital value by A/D conversion in step 10. The value is compared with the reference value slice level S/L in step 20, and
Perform lean judgment. However, even in the case of rich, when moving from lean to rich, the proportional component P must be taken into consideration as described above, and a determination is required, which is performed in step 30. Step 30 results
If YES, process the proportional component P in step 50, if NO, process the duty cycle in step 40.
In order to gradually reduce DS, a duty value Δd corresponding to integral component I is subtracted from the duty cycle DS value. Then, in step 90, the value of the duty cycle DS is output to the pulse output PO (outputs P ₀₁ and P ₀₂ corresponding to the two solenoids), and the solenoid
Move SOL1 and SOL2. After that, return to step 10 and repeat the same process again. The above is a case where it is determined to be rich, but if it is determined to be lean, it passes through steps 60, 70, and 80, and the only difference is the sign of the duty value Δd corresponding to the proportional component P and the integral component I. Perform the same process with .

In the present invention, the proportional component P and integral component I, which are control signals, are determined as follows.

That is, the proportional component P and the integral component I are stored in the ROM 103 in advance as one piece of information regarding the engine operating state. MPU100
When this routine is entered based on the arithmetic processing program shown in FIG. 4 stored in the ROM 102, various operating conditions are acquired in step 15, and the corresponding proportional component P and integral component I are calculated in step 25. demand. Here, the integral components I _R and I _L are determined.

Next, regarding integral component I, step 35
Based on the determination result of the output voltage of the O ₂ sensor 300, it is determined whether the current attempt is to make it rich or lean.

When the discrimination result is obtained in step 35, step 45
55, the correction time ΔT _po is obtained from the integral components I _R and I _L .

Next, in step 65, the correction time previously determined is
The correction time T _po ( _t ) is determined by increasing or decreasing T _po (t-1), and based on this result, the on-duty ratio is set in the duty register in step 75.

Further, the proportional component P is set using a value already determined according to each operating state at the time when the output voltage of the O ₂ sensor 300 is reversed from a predetermined value.

As described above, according to the present invention, the feedback control gain is stored in the memory element, and when performing feedback control, the appropriate feedback control gain is read out and the feedback control signal is determined. This provides a feedback control gain that allows for fine-grained control.

Furthermore, the feedback control gain does not change even with temperature fluctuations, and as a result, the feedback control gain remains constant regardless of temperature changes.

In other words, as mentioned above, if you look at the magnitude by setting the temperature on the horizontal axis and the feedback control gain on the vertical axis, the magnitude of the feedback control gain will be the same even if the temperature is different under the same operating condition. By connecting them, the feedback control gain becomes linear, improving reliability over temperature.

Therefore, even if the temperature state changes, the feedback control gain remains constant, and the feedback control signal becomes linear, eliminating problems such as a long convergence time and hunting.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of the present invention, FIG. 2 is a characteristic diagram of a control signal with respect to a sensor characteristic diagram, and FIGS. 3 and 4 are flowcharts of the present invention. 102...First memory element, 103...Second memory element, 101...Third memory element, 300...
... _O2 sensor, 100...microprocessing unit, 104, 105...air mixture concentration adjustment means.

Claims (1)

[Claims] 1 (a) A first memory element 102 in which an arithmetic processing program is stored; (b) A second memory element 102 in which a predetermined feedback control gain is stored in accordance with the operating state of the internal combustion engine. Memory element 103; (c) third storage element in which data associated with arithmetic processing is temporarily stored;
(d) A memory element 101 provided in the exhaust pipe of the internal combustion engine according to the arithmetic processing program stored in the first memory element.
A feedback control calculation is executed based on the output signal of the O ₂ sensor 300, and the feedback control calculation is performed using a feedback control gain selected from the second storage element 103 in accordance with the operating state of the internal combustion engine. a microprocessing unit 100 that executes an operation for generating a feedback control signal; (e) the microprocessing unit 100;
An air-fuel ratio control device comprising air-fuel mixture concentration adjusting means 104, 105 for adjusting the air-fuel mixture concentration supplied to the internal combustion engine based on a feedback control signal from the internal combustion engine.