JPH0517392B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel control device for an internal combustion engine that performs fuel control based on the pressure in the intake pipe of the internal combustion engine and the rotational speed of the engine.

One method of electrically controlling the amount of fuel supplied to an internal combustion engine is to drive an electromagnetic injection valve in synchronization with the rotational speed of the internal combustion engine. A method of calculation is used based on the pressure, rotation speed, etc.

When calculating the valve opening time using a microcomputer, the pressure is converted to voltage using a semiconductor pressure sensor, and then this voltage is converted to a digital value using an AD converter and input into the microcomputer.

When detecting pressure with a microcomputer,
AD above at certain time intervals or synchronized with rotation
It is conceivable to perform conversion. In the case of a four-stroke internal combustion engine for automobiles, ripples occur in the pressure due to each cycle of suction, compression, etc.

Therefore, the detected pressure may change each time depending on which value of the pressure ripple is taken depending on the timing of the AD conversion, and it is necessary to average the detected pressure. Furthermore, since the frequency of the ripple is proportional to the rotational speed of the internal combustion engine, the higher the rotational speed, the higher the frequency.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional technology, and the ripples are removed to some extent from the output of the pressure sensor using a filter configured with an electric circuit.
After that, the output of the filter is converted into a digital value by an AD converter at predetermined time intervals, and this digital value is averaged a predetermined number of times by a microcomputer, and the rotation speed is changed during acceleration/deceleration to improve controllability of valve opening time. An object of the present invention is to provide a fuel control device for an internal combustion engine that can control the fuel consumption of an internal combustion engine.

Embodiments of the fuel control device for an internal combustion engine according to the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of one embodiment. In FIG. 1, an internal combustion engine 3 is a known four-stroke spark ignition internal combustion engine installed in an automobile, and combustion air is supplied to an air cleaner 2, an intake pipe 33, and a throttle valve 3.
Inhale after step 2.

Further, fuel is supplied to the intake pipe 33 from a fuel system (not shown).
The fuel is supplied through an electromagnetic injection valve 31 provided upstream of a throttle valve 32. A pressure sensor 1 for detecting the pressure in an intake pipe 33 is connected downstream of the throttle valve 32. The pressure sensor 1 is, for example, a known semiconductor pressure sensor that converts the absolute pressure of the intake pipe 33 into voltage and outputs it.

The water temperature sensor 34 detects the temperature of the cooling water of the internal combustion engine 3, and is like a thermistor whose resistance decreases as the temperature increases.

The opening sensor 35 is like a potentiometer whose output voltage changes depending on the opening of the throttle valve 32.

The ignition coil 36 supplies high voltage to spark plugs (not shown) provided in each cylinder of the internal combustion engine 3.
The output signals of the pressure sensor 1, the water temperature sensor 34, the opening sensor 35, the primary voltage of the ignition coil 36, etc. are input to the control device 4, and the control device 4 calculates the opening time of the electromagnetic injection valve 31. , to drive the electromagnetic injection valve 31.

FIG. 2 is a block diagram showing the detailed internal configuration of the control device 4. In FIG. 2, 100 is a microcomputer incorporating a ROM 200 for storing programs and a RAM 201 for temporarily storing data.

101 is a low-pass filter that smoothes the output of the pressure sensor 1, and here the cutoff frequency is set to 33Hz. Therefore, the higher the rotational speed of the internal combustion engine 3, the smoother it is.

The interface 104 converts the output of the water temperature sensor 34 into voltage, and the interface 105 converts the output of the opening sensor 35 into voltage.

Low pass filter 101, interface 10
The three outputs of 4,105 are multiplexer 102
The multiplexer 102 selects one of the three outputs according to a signal from the microcomputer 100 and outputs it to the AD converter 103.

The AD converter 103 converts the input voltage into a digital value (hereinafter referred to as AD conversion), this conversion operation is started by the output signal of the microcomputer 100, and after the conversion is completed, the conversion completion signal and the conversion result are sent to the microcomputer 100. It is now output to .

On the other hand, the comparator 106 converts the voltage of the primary coil of the ignition coil 36 into a signal at a theoretical level,
D-type flip-flop 107 (hereinafter referred to as FF)
It is designed to be output to the clock terminal of. The output of this FF 107 becomes "L" in synchronization with the generation of high voltage by the ignition coil 36, and becomes "H" in response to the output signal of the microcomputer 100.

The output signal of the FF 107 is transferred to the gate terminal of the counter 108 and the first interrupt terminal of the microcomputer 100. The clock terminal of the counter 108 is connected to the output terminal of the oscillator 114, and the output signal of the FF 107 is "H".
The period counter 108 is adapted to count the output of the oscillator 114.

When the first interrupt becomes "L", the microcomputer 100 reads the count value of the counter 108, clears the counter 108, and then sets the FF 107 to make its output "H". Therefore, the count value of the counter 108 corresponds to the ignition cycle of the internal combustion engine 3.

The timer 109 outputs an interrupt signal to the second interrupt terminal of the microcomputer 100 every 5 msec. A digital interface 110 converts, for example, a starting switch (not shown) of the internal combustion engine 3 into a logic level signal and outputs it to the microcomputer 100.

The counter 112 counts the output of the oscillator 111, is preset by the microcomputer 100, starts counting down in response to a trigger signal output from the microcomputer 100, and counts down from the input of the trigger signal until the count value becomes zero. It is designed to output an "H" signal during the period. The driver 113 drives the electromagnetic injection valve 31 while the output of the counter 112 is "H".

The microcomputer 100 receives the smoothed voltage of the pressure sensor 1 and the converted voltage of the water temperature sensor 34, which are input to the multiplexer 102 every time an interrupt signal is input to the second interrupt terminal every 5 msec. , the converted voltages of the opening sensor 35 are sequentially converted and stored in the RAM 201.

Further, when an interrupt signal is input to the first interrupt terminal, that is, when the ignition coil 36 generates a high voltage, the microcomputer 100 controls the pressure sensor 1, the water temperature sensor 34, and the internal combustion engine. The time for driving the electromagnetic injection valve 31 is calculated according to the rotation speed of the engine 3, and a value corresponding to the time is set in the counter 112.

Next, the processing of the program of the microcomputer 100 will be explained. Figure 3 shows part of the data stored in the RAM 201, with the rotation speed at address 80, the data obtained by AD converting the output of the water temperature sensor 34 at address 81, and the output of the opening sensor 35 at addresses 82 and 83.
The AD-converted data is stored, and address 82 is the data from 5 msec ago, and address 83 is the current data.

The 16 pieces of data from address 84 to address 99 are the output of pressure sensor 1 AD converted every 5 msec.
Address 100 is the average of the above 16 pieces of data.

Figure 4 shows the microcomputer 1 when an interrupt signal is input to the second interrupt terminal every 5 msec.
It is a flowchart showing the processing of 00. In step 300, the multiplexer 102 selects the output signal of the interface 104, the AD converter 103 performs AD conversion on the data of the water temperature sensor 34,
Store in address 81 of RAM 201.

Next, in step 301, the data at address 83 of RAM 201 is moved to address 82. In step 302, the output signal of the interface 105 is selected by the multiplexer 102, and the information of the opening sensor 35 is AD converted.
Store in address 83 of RAM201.

In step 303, data at address 98 of RAM201 is converted to 99.
data from address 97 to address 98, and data from address 84 to address 98 from address 85 to address 99.

In step 304, the output signal of the low-pass filter 101 is selected by the multiplexer 102, and the signal obtained by smoothing the output of the pressure sensor 1 is AD-converted.
Store in address. Therefore, in steps 303 and 304, the smoothed data of pressure sensor 1 every 5 msec is
They will be stored in order from address 84 to address 99.

In step 305, if the value obtained by subtracting the data at address 82 from the data at address 83 is greater than the predetermined value A, that is, if the throttle valve 32 is moving in the opening direction, proceed to step 306; otherwise, proceed to step 307. move on.

In step 306, all data at address 84 from address 85 to address 99 are stored. In other words, from address 85
All data at address 99 will be equal to data at address 84.

In step 307, 16 pieces of data from address 84 to address 99 are added, divided by 16, and the output signal of low-pass filter 101 is sampled every 5 msec.
Perform a 16-time moving average.

Therefore, during acceleration when the opening degree of the throttle valve 32 increases, all data from address 88 to address 99 will be equal to the data at address 84, and the result of the moving average will be equal to the instantaneous value of pressure. In effect, the moving average is not performed or the number of moving averages is reduced.

At step 308, the result of step 307 is stored at address 100. As described above, the smoothed data of the water temperature sensor 34, opening sensor 35, and pressure sensor 1 is converted into digital values every 5 msec, and the RAM 201
and then take a 16-time moving average of the smoothed data.

FIG. 5 is a flowchart showing processing when an interrupt signal is input to the first interrupt terminal. In FIG. 5, in step 401, the value of the counter 108, that is, the ignition cycle of the ignition coil 36, is read and stored in a register R1 (not shown) built in the microcomputer 100.

In step 402, the counter 108 is set to 0.

At step 403, FF107 is set and its output is set to "H".

In step 404, the numerical value N is divided by the value stored in the register R1, the ignition period is converted into a rotational speed, and the result is stored in address 80 of the RAM 201. Step 405
The output signal of pressure sensor 1 stored at address 100 of RAM 201 is smoothed, sampled every 5 msec, and moving averaged 16 times.
Multiply the average value of the pressures in step 3 by the constant K, and set the above register.
Store in R1.

In step 406, as shown in FIG. 6, the rotation speed of the internal combustion engine 3 and the pressure of the intake pipe 33 are set,
Select the above constant kij according to the data at addresses 80 and 100 from the table of settings stored in the ROM200 (an example of its storage contents is shown in Figure 6), and combine it with the data in register _R1 above. Perform multiplication.

In step 407, set the result of step 406 to counter 1.
Set to 12. Counter 112 at step 408
is triggered, the counter 112 starts counting down, and the electromagnetic injection valve 31 is driven during the count value calculated in step 406.

That is, in synchronization with the ignition of the internal combustion engine 3, the driving time of the electromagnetic injection valve 31 is calculated based on the rotational speed of the internal combustion engine and the average pressure of the intake pipe 33, and the electromagnetic injection valve 31 is driven.

Here, the amount of air _Ga taken in by the internal combustion engine 3 is proportional to the pressure P _b of the intake pipe 33, and _Ga = K _R · 1 / T · P _b , η. However, K _R is a constant, T is the intake air temperature,
η is the filling efficiency. Since this charging efficiency η changes depending on the load represented by the rotational speed of the internal combustion engine 3 and the pressure of the intake pipe 33, by setting the charging efficiency in advance in a table such as that shown in FIG. _a can be calculated. Also, as described above, the rotational speed is stored at address 80 in step 404, and the average value of pressure is stored at address 100 in step 308. In steps 405 and 406, the driving pulse width P _w of the electromagnetic injection valve 31 is calculated. P _w is calculated from the air amount G _a by P _w =G _a・1/K _A/F・1/σ _f・1/K _I. However, K _A/F is the set air-fuel ratio (14.7 constant), σ _f is the gasoline density, and K _I is the flow rate gain of the electromagnetic injection valve 31. Therefore, P _w =K _R・1/T・1/K _A/F・1/σ _f・1/K _I・P _b・η. Here, assuming that the intake air temperature T and gasoline temperature are constant, K _R , T, K _A/F , σ _f , and K _I are all constants, and P _b and η are shown in Fig. 5.
100, K _ij , so P _w = K・P _R・η=K・100・K _ij (K is a constant), and step 405 in Figure 5
At 406, the pulse width of the electromagnetic injection valve 31 is calculated.

Note that in the above example, the number of moving averages is 16.
Although the number of times is specified, a different number may be used. Also, due to the deviation of the low-pass filter 101 at each predetermined time,
All data from addresses 84 to 99 of RAM 201 may be made equal.

In addition, even if the deviation between the data at addresses 83 and 82 is less than a predetermined value, that is, when the internal combustion engine 3 is decelerating, data from 84 to 99
All address data may be made equal.

As is clear from the above explanation, according to the fuel control device for an internal combustion engine of the present invention, a voltage proportional to the pressure in the intake pipe of the internal combustion engine is smoothed by a low-pass filter, and the output of the low-pass filter is changed to AD at predetermined intervals.
The converter converts the output into a digital value, and the fuel supply amount is controlled based on the moving average of the output and the internal combustion engine's rotational speed, so the high rotational speed region of the internal combustion engine is sufficiently smoothed by the low-pass filter. Therefore, even a microcomputer can average the pressure in the intake pipe. Therefore, it is possible to improve controllability by changing the number of times of averaging when accelerating or decelerating the internal combustion engine. Further, the number of times of the above-mentioned moving average is changed according to changes in the opening degree of the throttle valve, so that a transient state of the internal combustion engine can be detected quickly and responsiveness of control can be improved.

Furthermore, since the cut-off frequency of the low-pass filter can be increased, the capacitance of the capacitor used in the low-pass filter can be reduced, resulting in cost reduction.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the fuel control device for an internal combustion engine according to the present invention, FIG. 2 is a block diagram showing the configuration of the control device in the fuel control device for the internal combustion engine shown in FIG. 1, and FIG. is a diagram showing the contents of the RAM in the control device of FIG. 2, FIGS. 4 and 5 are flowcharts showing the processing of the microcomputer in the control device of FIG. 2, and FIG. 6 is a diagram showing the contents of the RAM in the control device of FIG. 2. FIG. 2 is a diagram showing the contents of a ROM in FIG. 1...Pressure sensor, 2...Air cleaner, 3
... Internal combustion engine, 4 ... Control device, 31 ... Electromagnetic injection valve, 32 ... Throttle valve, 33 ... Intake pipe, 34 ... Water temperature sensor, 35 ... Opening sensor, 100 ... Microcomputer , 101...
...Low pass filter, 102...Multiplexer, 103...AD converter, 104, 105...
Interface, 106... Comparator, 10
7...D flip-flop, 108, 112...
Counter, 109...Timer, 111, 114...
...Oscillator, 113...Driver, 110...Digital interface, 200...ROM, 2
01...RAM. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A pressure sensor that detects the pressure in the intake pipe of an internal combustion engine and generates a voltage proportional to this pressure, a low-pass filter that smoothes the output of this pressure sensor, and converts the output of this low-pass filter into a digital value at predetermined intervals. An AD converter, a means for moving a predetermined number of outputs of this AD converter, a throttle valve installed in the intake pipe to adjust the amount of intake air, and a means for calculating the number of moving averages when the opening degree of the throttle valve changes. A fuel control device for an internal combustion engine, comprising: means for changing the moving average; and means for controlling the amount of fuel supplied to the internal combustion engine based on the moving average result and the rotational speed of the internal combustion engine.