JPS6328217B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential calculation circuit for an intake air amount control device for an internal combustion engine.

In internal combustion engines, particularly in-vehicle internal combustion engines, it is necessary to control the engine speed during idling in order to suppress harmful components in exhaust gas or improve fuel efficiency. For this reason, there is an intake air amount control device that supplementally controls the intake air amount so that the engine speed becomes a predetermined target rotation speed depending on the operating state of the engine.

The intake air amount control device detects the actual rotation speed of the engine, and performs feedback control to control the amount of intake air that passes through the auxiliary intake air passage that bypasses the throttle valve according to the actual rotation speed. It is. Generally, in feedback control, a proportional operation (P
action), an integral action proportional to the time integral of that deviation (I action), and the rate of change of that deviation (differential).
There is a differential operation (D operation) proportional to , and each operation can be used alone or in a composite operation such as PI operation.

Incidentally, the D operation is an operation that corrects the control amount when it is likely to become large with respect to the target rotation speed, and the responsiveness and stability of control are improved by performing a combined operation with other operations. Therefore, the intake air amount control device is provided with a differential calculation circuit for the D operation.

FIG. 1 shows a conventional digital differential calculation circuit. In FIG. 1, an output pulse A from a crank angle sensor (not shown) is supplied to an input terminal IN, and a counter 1 and a timing pulse generator 2 are also connected thereto. counter 1
A divider 3 is connected to the output end of the divider 3, and a subtracter 4 and a latch 5 are connected to the output end of the divider 3. The output of latch 5 is connected to the other input of subtracter 4. A divider 6 is connected to the output end of the subtracter 4, and the divider 6 is connected to the output end of the counter 1. Also, the timing pulse B is sent to the divider 3, and the timing pulse C is sent to the subtracter 4.
However, the timing pulse D is supplied to the latch 5, and the timing pulse E is supplied to the divider 6 from the timing pulse generator 2.

2A to 2E show respective pulse signals A to E in the circuit of FIG. 1, respectively. input terminal
The timing pulse generator 2 generates timing pulses B, C, D, and E in the order according to the output pulse A of the crank angle sensor supplied to IN. When the output pulse A is supplied to the divider 3, the generation period Tt of the output pulse A is counted by the counter 1. The crank angle sensor is located on the engine's crankshaft (hereinafter referred to as "crankshaft").
Since the counter 1 generates an output pulse every time the engine rotates one revolution, the output signal of the counter 1 has a period Tt per one revolution of the engine. The engine rotation speed Nt is calculated by the divider 3 from this period Tt. The engine speed Nt is Nt=K/Tt...(1) (K is a constant). Then, from the rotational speed Nt and the rotational speed Nt-1 of the engine one revolution before, which is stored in the latch 5, the subtracter 4 calculates the rotational speed change ΔN during one rotation of the engine. The rotational speed change ΔN is determined by ΔN=Nt−Nt−1 (2). Next, a speed change Dt per engine rotation is calculated by a divider 6 from the rotational speed change ΔN and the period Tt. The speed change Dt is obtained from Dt=ΔN/Tt (3). A digital signal representing this speed change Dt is output from the divider 6.

For example, when an output pulse from a crank angle sensor as shown in FIG.
Nt changes as shown in Figure 3b. The speed change Dt output as a digital signal from the divider 6 has a characteristic as shown in FIG. 3c. Note that Ns in FIG. 3b is the target rotational speed, and broken line A is an analog change in the engine rotational speed.

However, in such a conventional differential calculation circuit, the output change of the speed change Dt becomes rough as shown in FIG. The disadvantage was that the feedback control of the intake air amount was not good.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a digital differential calculation circuit that can improve the control of the amount of intake air through the D operation.

Embodiments of the present invention will be described below with reference to FIGS. 4 to 6.

In FIG. 4, parts equivalent to those in FIG.
An adder 10 is connected to each output terminal of 8 and 9. Further, the latch 7 is supplied with a timing pulse F, the latch 8 with a timing pulse G, and the latch 9 with a timing pulse H from the timing pulse generator 2. The output signal of the adder 10 becomes the control amount for the D operation. Other configurations of the differential calculation circuit according to the present invention are as follows.
Since it is the same as the conventional example shown in the figure, the explanation will be omitted here.

5A to 5H show respective pulse signals A to H in the circuit of FIG. 4, respectively. The timing pulse generator 2 first responds to the output pulse A of the crank angle sensor supplied to the input terminal IN.
Each pulse is generated in the order of timing pulses B, C, D, and E, and one of the timing pulses F, G, and H is generated after the timing pulse E is generated in the order of timing pulses F, G, and H. The output terminal of the divider 6 outputs a digital signal representing the speed change Dt per engine revolution. For example, when the output pulses of the crank angle sensor are generated as shown in FIG. 6a, the engine speed Nt output as a digital signal from the divider 3 is as shown in FIG. 6b.
The speed change Dt output as a digital signal from the divider 6 is determined by timing pulses F, G,
The latches 7, 8, 9, 7, 8, . . . are stored in the order according to H. The latches 7, 8, 9 hold and output digital signals representing the same speed change Dt until a timing pulse is applied to each again. Therefore, the output digital signal levels of the latches 7, 8, and 9 are as shown in FIG. become that way. The output signal of this adder 10 becomes the control amount for the D operation.

As described above, according to the differential calculation circuit according to the present invention, the calculated speed change (differential) per engine rotation is added to at least the previously calculated speed change, and the value is output as the control amount for the D operation. Therefore, the feedback control of the intake air amount by the D operation becomes good.

Note that the differential calculation circuit of the present invention is not limited to the above-described embodiment, and a microcomputer may be used to process the same arithmetic operation as the circuit of the above-described embodiment by a program.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional example of a differential calculation circuit, Figures 2 and 3 are operational waveform diagrams of the circuit in Figure 1, and Figure 4 shows an embodiment of the differential calculation circuit of the present invention. The block diagrams of FIGS. 5 and 6 are operational waveform diagrams of the circuit of FIG. 4. Explanation of symbols of main parts, 1... Counter, 2...
...timing pulse generator, 3,6...divider,
4...Subtractor, 5,7,8,9...Latch, 10
...Adder.

Claims (1)

[Claims] 1. Differentiation of the deviation between the actual rotation speed and the target rotation speed to be used as a control signal in an intake air amount control device that supplementarily controls the intake air amount according to the actual rotation speed so that the engine rotation speed becomes the target rotation speed. A differential calculation circuit that generates a differential signal having a level representing the magnitude of the differential signal every predetermined rotation of a crankshaft of an engine, the circuit including a plurality of holding means, and a differential signal that is stored in a predetermined order each time the differential signal is generated. A differential calculation circuit comprising: switching means for causing one of the plurality of holding means to hold; and addition means for adding the holding output levels of the plurality of holding means.