JPH0329975B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to idle speed control of an internal combustion engine for an automobile. In the case of internal combustion engines for automobiles, attempts have been made to lower the engine speed during idle to improve fuel efficiency and reduce harmful exhaust emissions, but due to the characteristics of internal combustion engines, if the engine speed is too low, Not only does the rotational fluctuation cause discomfort to the driver, but there are also inconveniences such as the rotation stopping. For this reason, the rotation speed must be set slightly higher than the stability limit, but considering the manufacturing tolerances of the engine, it is necessary to set a considerably high rotation speed as the stability limit. The initial goal of reducing exhaust emissions becomes difficult to achieve.

Conventionally, to solve this problem, the engine speed is detected and the intake air amount is controlled to increase or decrease to bring it to the target speed, and the so-called idle speed is settled at a low speed that tends to be unstable. A control device has been used. According to this type of device, when the engine stalls, the amount of intake air is increased, increasing the output and increasing the rotation speed, and conversely, when the engine speed increases too much, the amount of intake air is reduced and the rotation speed is lowered. Since feedback control is performed, the advantage is that stable idling can be achieved near the desired target rotation speed.

However, when considering the case where the engine is rapidly transitioned from a high-speed operating state to an idle state using a conventional device, firstly, when the engine enters the idle state and idle speed control is started, the engine speed is much higher than the target speed. Since the width exceeds the width, the amount of intake air will be extremely narrowed down by feedback control. After that, due to the gradual decrease in engine rotation,
Although the error with the target rotation speed is reduced, due to response delays existing in various parts of the engine, such as a detection delay in the engine rotation speed or a response delay in the intake air amount control means, the difference between the engine rotation speed and the target rotation speed may be reduced. continues to decrease, and the control is later reversed to increase the rotation speed. At this time, the initial rotational speed error was so large that the amount of intake air was narrowed down to an extreme degree, and the effect of response delay was greater than during normal control, resulting in a significant abnormal drop in rotational speed. Become. If the target rotational speed is set to a low rotational speed that tends to be inherently unstable, this abnormal decrease in the rotational speed may be catastrophic, leading to the engine stopping.

In consideration of the above-mentioned inconveniences, the target rotational speed is set a little higher in conventional devices, but it cannot be denied that this reduces the effect compared to the initial purpose.

The present invention has been made in view of the drawbacks of the conventional devices, and it is an object of the present invention to provide an idle rotation speed control device that does not cause an abnormal decrease in the rotation speed even when decelerating from high speed rotation. A detailed description will be given below with reference to the drawings. FIG. 1 is a drawing showing an embodiment of the present invention, in which 1 is an engine, 2 is an intake pipe, 3 is a throttle valve, 4 is a solenoid valve, and 5 is a diagram showing the throttle valve 3 when the solenoid valve 4 is open. A bypass passage that communicates the upstream and downstream (intake pipe 2), 6 a throttle switch that operates when the throttle 3 is in the closed position, that is, the idle position, and 7 a pressure that operates when the negative pressure in the intake pipe 2 is below a predetermined value. A sensor 8 is a water temperature sensor that detects the cooling water temperature that indicates the operating state of the engine; 9 is a rotation speed sensor 10 that detects the engine rotation speed by a tooth profile arranged around the flywheel 12; 11 is a target rotation speed setting device that receives the output of the water temperature sensor and sets a target engine rotation speed according to the cooling water temperature; 11 is the output a of the throttle switch 6; the output b of the pressure sensor 7;
A computing device receives the output c of the rotation speed sensor 9 and the output d of the target rotation speed setting device 10, and outputs an opening/closing signal e for controlling the duty of the solenoid valve 4. control the amount of air. The arithmetic unit 11 is composed of, for example, a microcomputer, and is composed of functional blocks as shown in FIG. That is, the second
In the figure, 11-1 is an error detector that outputs the error ΔN between the engine speed c and the target rotation speed d;
-2 is the duty pulse D according to the error △N
It is a duty converter that outputs, for example, a function such as duty D=K・△N+D ₀ is given.
In the equation, D ₀ indicates the reference duty when the error ΔN=0, and is set to, for example, 50%. K is a proportionality constant, for example, when △N = ±100 rpm, D = 0% or
K=0.5 is set so as to achieve 100%, which is a factor that determines the responsiveness of this device, and is adjusted to a preferable value. Reference numeral 11-3 is an AND gate which applies logic 1 to the switch 11-4 when the idle signal is ON (throttle switch operating state) and the low negative pressure signal b is ON (pressure sensor 7 operating state). In this state, pulse D passes through switch 11-4 and is applied to output e. Conversely, when the engine is not in an idling state or when the intake pipe negative pressure is high, the pulse D is blocked, and a duty corresponding to, for example, ΔN=0 is generated at the output e.

Next, FIG. 3 shows an example of the characteristics of the target rotation speed setting device 10, and the target rotation speed is determined according to the cooling water temperature.
N _T is output.

The operation of the apparatus according to the embodiment of the present invention described above will be explained using FIG. In the figure, a indicates the operation of the throttle switch, and the H level indicates that the throttle valve 3 is closed and the engine is in an idle state. p indicates the negative pressure in the intake pipe, and the negative pressure increases when the throttle valve 3 is closed, and then gradually decreases (approaches atmospheric pressure) as the engine speed decreases. Note that the dashed line indicates the operating pressure of the pressure sensor 7. b represents the output of the pressure sensor 7, which outputs an L level while the pressure p exceeds the operating pressure. c is rotation speed sensor 9
The figure shows the deceleration after the throttle valve 3 is closed at the output of . The broken line c' shows the deceleration pattern when the present invention is not implemented. d represents the target idle rotation speed N _T set at this time.

Therefore, the difference between c and d is ΔN.

This error △N is determined by the error detector 11 in FIG.
-1 to the duty converter 11-2.
given to. Again in FIG. 4, D is the output of the duty converter 11-2, which is a pulse with a duty proportional to the error ΔN.

This figure illustrates the duty of the pulse. e
After entering the idle state, wait until the output b of the pressure sensor 7 becomes H level, that is, after the intake pipe negative pressure falls below the operating pressure, the pulse D passes through the converter 11-4. It shows how the solenoid valve 4 is controlled to open and close.

Now, in FIG. 4, when the engine is operating at high speed, the rotational speed error ΔN becomes abnormally large immediately after the throttle valve 3 is closed and the engine enters the idle state. For this reason, the duty D has also reached a value where the amount of bypass air should be set to the minimum value in order to compensate for the large rotational speed error △N, and when the engine reaches the idle speed, it has become so large that it stalls the engine. There is. Therefore, when the rotation speed control is started at this duty immediately after the throttle switch 6 goes to the H level, the engine is rapidly decelerated due to the above-mentioned circumstances and behaves as indicated by the broken line c'. The target rotational speed d is set at a fairly unstable rotational speed for the initial purpose, and the degree of deceleration is significant, and after the response delay time of the system has passed, the rotational speed will reach a point where it can no longer be recovered. This may cause the engine to stop.

However, in the present invention, sudden deceleration is detected by utilizing the fact that the intake pipe negative pressure greatly exceeds the steady negative pressure during sudden deceleration, and when the negative pressure reaches a value equal to or higher than the operating pressure of the pressure sensor 7, feedback rotation control is performed. This prevents the engine from stalling, since the duty pulse e corresponding to the error is applied to the electromagnetic valve 4 near the time when the rotation speed has settled down to a steady idle, that is, when the error ΔN in the rotational speed has become small to some extent.

As explained above, in the present invention, engine speed control is stopped in a transient state during sudden deceleration, and control is started when the engine reaches near the idle set speed. →It is possible to obtain highly reliable control without causing inconveniences such as stoppages.

In order to obtain the same effect as that of the present invention, it is possible to consider a method of clamping the duty D so that it does not exceed a certain value when the rotational speed error △N is large. If the target rotational speed cannot be achieved unless a large duty is given, the initial purpose will not be achieved due to insufficient control, and a low clamp value cannot be set, so no effect can be expected.

In FIG. 2, △N is simply an error detector 11-
1, but in this case, the engine speed is offset and settled with respect to the target speed.
Of course, if the target rotation speed is set in consideration of this offset, the objective can be achieved, so there is no problem, but in order to ensure accuracy, error detection 11-1
If an integral characteristic is added to , and so-called P-1 control is performed, the offset will disappear. However, the response of the system becomes even slower due to the added integral term, so the effect of the present invention becomes significantly greater in this case.
Further, in FIG. 1, the rotation speed sensor 9 for detecting the engine rotation speed is of an electromagnetic pickup type, but it goes without saying that the same effect can be obtained by using an ignition signal.

As described above, according to the present invention, since the intake pipe negative pressure is detected and the start of feedback of the rotation speed at the time of transition to idle is determined, unstable control of the rotation speed at the time of transition to idle can be prevented, and furthermore, the intake pipe negative pressure is detected. Since the inhibition period at the start of feedback control is determined by the pipe negative pressure, it is possible to detect the transition to steady idling with good responsiveness and accuracy before the rotation speed decreases, and it is possible to more stably control the idling rotation. control.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a block diagram showing a configuration example of the arithmetic device 11 in FIG. 1, FIG. 3 is a characteristic diagram of the target rotation speed setting device 10 in FIG. 1, and FIG. 4 is a timing diagram for explaining the operation of the device in FIG. 1. It's a chat. In the figure, 1 is the engine, 3 is the throttle valve, 4 is the electromagnetic valve, 5 is the bypass passage, 6 is the throttle switch, 7 is the pressure sensor, 9 is the rotation speed sensor, 10 is the target rotation speed setting device, and 11 is the calculation It is a device.

Claims (1)

[Claims] 1. Idle detection means for detecting the idle state of the engine, rotation speed detection means for detecting the engine rotation speed, rotation speed setting means for determining the idle target rotation speed of the engine, and engine When it detects that it is idle,
A calculation means is provided for controlling the intake air amount of the engine according to the error between the idle target rotation speed and the detected actual engine rotation speed, and performs feedback control so that the engine rotation speed becomes the idle target rotation speed. In the engine, negative pressure in the intake pipe of the engine is detected, and when the negative pressure in the intake pipe is equal to or higher than a predetermined value, the start of feedback control of the rotation speed is prohibited regardless of the output of the idle detection means, and the idle detection means detects the engine when the engine is idle. An engine rotation speed control device comprising pressure detection means for starting feedback control of the rotation speed when the negative pressure in the intake pipe reaches a predetermined value during state detection.