JPS6221972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine rotation speed control device.

Conventionally, there has been a tendency to lower the idling speed of automobile engines in order to improve fuel efficiency or reduce exhaust gas. However, considering variations in engine performance and changes over time, there is a limit to how much the idling speed can be reduced.
Therefore, in recent years, electronic control devices that can accurately and stably control the idling speed over a long period of time have come into use as a new technical means.

A conventional device for controlling the idling speed of an engine will be explained below with reference to FIGS. 1 to 4.

FIG. 1 is a block diagram showing an example of a conventional device for controlling the idling speed of an engine by changing the stopper position of a throttle valve using a DC motor.

In FIG. 1, 1 is an ignition coil, 2 is an ignition coil control device, 3 is a period measuring circuit connected to the ignition coil 1 and measures the time interval between ignition signals, and 4 is a period measurement circuit that measures the time interval between the ignition signals. A rotation speed calculation circuit that converts into a rotation speed signal having a weight of the actual engine rotation speed N, 5 a target rotation speed calculation circuit that calculates a target idling rotation speed No. 6, the rotation speed calculation circuit 4 and the target rotation speed calculation circuit. A deviation detection circuit 7 compares the output signals from each of the circuits 5 and outputs a signal indicating the magnitude relationship between the two output signals and a signal indicating the difference, that is, a rotation speed deviation signal. Input two types of output signals,
A control pulse width calculation circuit that calculates the optimum driving time of the DC motor 121; 8 is the DC motor 121;
9 is a pulse width counter, which has a preset counter inside, and outputs an output signal from the control period counter 8. At the same time, the output value of the control pulse width calculation circuit 7 is preset, and at the same time, subtraction is started at fixed time intervals, and until the contents of the preset counter reach zero, an output signal is sent along with this subtraction counting operation. Continue. 10 is a control signal generation circuit;
Inputting the output signal from the deviation detection circuit 6,
A forward rotation signal or a reverse rotation signal for driving the DC motor 121 in forward rotation or reverse rotation is output. 1
1 is the output terminal 10 of the control signal generation circuit 10
A drive circuit inputs an output signal from 1 and 102 to drive the DC motor 121 in forward or reverse rotation; 12 is a throttle valve drive device that converts the rotational motion of the DC motor 121 into linear motion; The reduction mechanism 122 converts into
a switch 123 that detects the fully closed state of the accelerator pedal 14 in the state of
25. 13 is a throttle valve.

Based on the above configuration, the operation of the conventional example will be explained with reference to the drawings.

Figure 2 shows the target idling speed of the engine.
FIG. 3 is a relationship diagram showing the relationship between the rotation speed deviation of No., the actual engine rotation speed N, and the drive time of the DC motor. Figures 3 and 4 show changes in the actual engine speed N,
3 is a time chart showing the operation of a forward rotation signal and a reverse rotation signal output from a control signal generation circuit. Note that the intermittent control period _T1 in FIG. 4 is shown as being shorter than the same period T in FIG.

First, the time interval between ignition signals measured by the period measuring circuit 3 is converted into an actual engine rotation speed signal weighted by the rotation speed in the rotation speed calculation circuit 4 and inputted to the deviation detection circuit 6. Further, an output signal of the target idling rotation speed No. calculated by the target rotation speed calculation circuit 5 is also input to the deviation detection circuit 6. As a result, the deviation detection circuit 6 detects the actual engine speed N and the target idling speed.
The difference between the two output signals of No. is output as a rotation speed deviation signal to the control pulse width calculation circuit 7, and a comparison signal indicating the magnitude relationship between the two output signals is output to the control signal generation circuit 10 and the control pulse width calculation circuit 7. Output to. Therefore, the control pulse width calculation circuit 7 calculates the optimum driving time of the DC motor 121 according to the above-mentioned two types of signals, the rotation speed deviation signal and the comparison signal, and outputs this driving time to the pulse width counter 9. .

In FIG. 2, the horizontal axis shows the rotational speed deviation, that is, the difference No-N between the target idling rotational speed No. and the actual engine rotational speed N, and the vertical axis shows the driving time Tp. Here, forward rotation and reverse rotation mean forward rotation drive and reverse rotation drive of the DC motor 121, respectively, and the throttle valve 1
3 indicates the open and closed states, respectively. Now, if the rotational speed deviation No-N falls within the dead zone rotational speed Nd, the driving time Tp becomes zero and the DC motor 121 is not driven.

Now, when the switch 123 provided in the throttle valve drive circuit 12 is in the ON state, that is, when the accelerator pedal 14 is in the fully closed state, the control signal generation circuit 10 is in a state in which it outputs an output signal from its output terminals 101 and 102. becomes. Therefore, the control signal generation circuit 10 determines the magnitude relationship between the target idling rotation speed No. and the actual engine rotation speed N from the output signal of the deviation detection circuit 6. That is, (No
-N)Nd/2, the control signal generation circuit 10 guides the output signal of the pulse width counter 9 to the output terminal 101 as a normal rotation signal, and (No-
If N)-(Nd/2), the output signal of the pulse width counter 9 is led to the output terminal 102 as a reverse signal. Therefore, while the output signal is being output from the output terminal 101, the DC motor 121 is driven to rotate in the normal direction, the throttle stopper 124 is pushed out, and as a result, the throttle valve 13 is opened and the engine speed is increased. will rise. On the other hand, the output terminal 1
While the output signal is being output from 02, the DC motor 121 is driven in reverse, the throttle stopper 124 is retracted, and as a result, the throttle valve 13 is closed and the engine speed is decreased.

Next, the operation until the engine speed becomes stable will be explained with reference to FIG.

Figure 3 shows that the engine load increases before time t ₁ , and the engine speed N changes to the target idling speed.
Indicates the state below No. The engine speed at time _t1 is N, and the output value of the control pulse width calculation circuit 7 is T _p1 as shown in FIG.
Therefore, the pulse width counter 9 outputs an output signal for a time width T _p1 from time t ₁ . Since the engine speed N is less than the target idling speed No, the control signal generating circuit 10 which receives the output signal of the pulse width counter 9 outputs a normal rotation signal as shown in FIG. 3a from its output terminal 101. output,
The drive circuit 11, which receives this normal rotation signal, drives the DC motor 121 in normal rotation for a time width T _p1 and pushes out the throttle stopper 124 . As a result, the throttle valve 13 opens and the engine speed increases. Next, the engine rotation speed at time t ₂ after a certain period T from time t ₁ is N ₂ .
At this point in time _t2 , the engine speed N is still below the target idling speed No, and as in the case at point in time _t1 , during the time width T _p2 , the DC motor 12
1 in normal rotation. As a result, the engine rotation speed N increases, and before reaching time _t3 , the rotation speed deviation No-N becomes a value within the dead zone rotation speed Nd, and the output signal that drives the DC motor 121 stops outputting. . Even at time _t3 , this output signal is not output, and thereafter, the DC motor 121 will not be driven until the rotation speed deviation No-N exceeds the dead band rotation speed Nd due to some disturbance. . Therefore, by using the intermittent control method as described above, the engine speed N can be adjusted to the target idling speed.
Can be controlled and maintained near No.

In order to improve responsiveness in the above-mentioned intermittent control method, it is necessary to shorten the period T of the intermittent control. However, if the period T is shortened, a problem such as overshoot of the engine rotation speed N occurs.

The above-mentioned problems will be explained below with reference to FIG.

Assume that the accelerator pedal 14 is now in the fully closed position. If the engine speed at time t ₃ is N ₃ , the DC motor 121 is driven in normal rotation during the time width T _p3 as described above, and as a result, the engine speed N increases. However, since the period T ₁ of the intermittent control is shorter than the same period T shown above in Fig. 3,
Assuming that the engine speed N continues to rise at t ₄ and that the control after time t ₄ is stopped, the engine speed N continues to rise at the time t ₄ as shown by the broken line in FIG. After that, it continued to rise for a while and then stabilized.

However, at time _t4 , as mentioned above,
Since the driving time T _p4 of the DC motor 121 is given by the rotational speed deviation No. ₄ , the throttle valve 13 is opened too much, and the time point shown in FIG.
As shown by the solid line after t ₄ , the engine speed N
exceeds the target idling rotational speed No., resulting in so-called overshoot, which is unfavorable in terms of control. Therefore, in order to prevent this overshoot, it is necessary to select an intermittent control period T _NO that does not cause the above-mentioned overshoot of the engine rotation speed N even in the case of the maximum drive time T _PM of the DC motor 121 that is possible in terms of control. . However, in the case of the period T _NO selected in this way, if the drive time Tp of the DC motor 121 is short, the control period Ts is too long.
This means sacrificing responsiveness, and it is technically extremely difficult to achieve both the above-mentioned controllability and responsiveness.

The present invention has been made by focusing on the above points,
It is an object of the present invention to provide an engine rotation speed control device that optimally balances controllability and responsiveness by keeping the time interval Ts at which driving of a DC motor is stopped constant.

An embodiment of the present invention will be described below with reference to FIGS. 5 and 6.

Note that the same configurations as those of the above-described conventional example shown in FIG. 1 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 5 is a block diagram showing an embodiment of the present invention, particularly showing the constituent parts different from the above-mentioned conventional example shown in FIG.

Further, FIG. 6 is a time chart showing the waveform operation of each part in FIG. 5.

In FIG. 5, 15 is a control suspension counter;
6 and 17 are differentiating circuits. Note that 6 is a deviation detection circuit, 7 is a control pulse width calculation circuit, 9 is a pulse width counter, 10 is a control signal generation circuit, and 11 is a drive circuit, each of which shows the same parts as in FIG.

The operation of one embodiment of the present invention will be explained below with reference to FIGS. 5 and 6.

The pulse width counter 9 is in a subtraction counting operation until just before time _t1 shown in FIG. At time _t1 , the internal counter value becomes zero and the counting operation is stopped. As a result, the output terminal 91 of the pulse width counter 9 becomes "L" at time _t1 , as shown in FIG. 6a.
An output signal that changes from level to "H" level is output. The differentiating circuit 16 inputs the output signal outputted from the output terminal 91, and outputs the pulse _p1 as shown in FIG.
Send to 1. At this time _t1 , the control pause counter 15 is reset, and the control pause counter 1
The output terminal 152 of 5 is set to "L" as shown in FIG. 6c.
At the same time, the subtraction counting operation is started at fixed time intervals, and after the time Ts shown in FIG. 6, that is, at time _t2 , the output terminal 152 becomes "H".
become the level. As a result, the differentiating circuit 17 receives the output signal from the output terminal 152 and applies a pulse _p3 as shown in FIG. 6d to the input terminal 92 of the pulse width counter 9. At this time point _t2 , the pulse width counter 9 presets the output of the control pulse width calculation circuit 7 to its internal preset counter, sets the output terminal 91 to "L" level, and at the same time Start subtraction counting operation. Therefore, the output value of the control pulse width calculation circuit 7 is now
Tp, then after the time Tp, i.e. the point in time
At _t3 , the output terminal 91 becomes "H" level. At the same time, the pulse width counter 9 measures the time Tp
During this period, the output signal is output to the control signal generation circuit 10.

Therefore, in one embodiment of the present invention, like the conventional device described above, the time period corresponding to the rotational speed deviation No−N between the target idling rotational speed No. and the actual engine rotational speed N is
The drive signal Tp is generated to drive the DC motor 121, but after that, the above-mentioned control pause counter 1
5 and the operations of the differentiating circuits 16 and 17 are repeated. That is, after the drive signal stops being generated, the drive signal is not generated for the time Ts set by the control pause counter 15, and the drive signal is not generated for the time Ts set by the control pause counter 15.
It will occur again after.

In one embodiment of the present invention, the time Ts is selected to be equal to the sum of dead time and delay time of the engine near the target idling speed No, so that it is constant regardless of the driving time width of the DC motor 121. As a result, the above-mentioned engine rotation overshoot as shown in FIG. 4 does not occur, and controllability is improved. Further, even if the drive time of the DC motor 121 changes, the minimum control time interval is always obtained, so responsiveness is improved.

The control device described above in one embodiment of the present invention can also be constructed using an analog circuit or a microcomputer, and the drive device provided in the control device is not limited to the above-mentioned DC motor, but can be driven in a wide variety of ways. It can be easily inferred that the present invention can be implemented in any actuator drive system. Furthermore, although a method of controlling the idling speed is used in this embodiment, the present invention can be practiced at any engine speed. Furthermore, in order to vary the engine speed,
Although the throttle valve is controlled, it goes without saying that other engine parameters may also be controlled.

As explained above, the present invention is a control device that intermittently controls the fuel amount and intake air amount and automatically controls the engine speed using the deviation from the target rotation speed. By keeping the variable drive device pause time Ts constant, the controllability and responsiveness of the engine speed control device can be greatly improved, and as a result, the actual engine speed can be controlled accurately over a long period of time. It can be controlled stably and has a remarkable effect on improving engine fuel efficiency and reducing exhaust gas.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram showing a conventional example, Fig. 2 is a relationship diagram showing the relationship between engine speed deviation and DC motor drive time, and Figs. 3 and 4 show changes in actual engine speed. 5 is a block diagram showing an embodiment of the present invention, and FIG. 6 is a waveform operation of each part in FIG. 5. This is a time chart showing. 4... Rotation speed calculation circuit, 5... Target rotation speed calculation circuit, 6... Deviation detection circuit, 7... Control pulse width calculation circuit, 8... Control period counter, 9... Pulse width counter, 10... Control signal generation circuit, 11... drive circuit,
12... Throttle valve drive device, 13... Throttle valve, 15... Control stop counter, 16,1
7... Differential circuit. In addition, in the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1: an actuator that changes the intake air amount or fuel amount of the engine; a deviation detection circuit that calculates a rotation speed deviation between a desired target engine rotation speed and an actual engine rotation speed; A control pulse width calculation circuit that calculates the target drive time of the actuator, and a drive circuit that drives and realizes the target drive time of the actuator by the output of the control pulse width calculation circuit, and the engine rotation speed that drives the drive circuit intermittently. 1. An engine rotational speed control device, characterized in that the control device is provided with a control pause counter to keep the control pause time constant when driving the drive circuit intermittently.