JPS6213751A - Idle rotation speed control device in engine - Google Patents

Abstract

PURPOSE:To make it possible to prevent the rotational speed of an engine from greatly dropping from a desired rotational speed, by setting a feed-back control amount of an idle rotational speed adjusting means to a small value during a predetermined period after the engine returns into the idle running range. CONSTITUTION:An engine control device 9 determines that the operation of an engine is in an idle running range to be subjected to feed-back control if the rotational speed of the engine detected by a rotational speed sensor 21 is below a predetermined value, and calculates a desired rotational speed Ne in accordance with the temperature of cooling water, etc. within a predetermined time set by a timer if the operation of the engine is just after returning into the idle running range. Just after the returning, an actual rotational speed N detected by a rotational speed sensor 21 is such as N>Ne, and therefore, the amount of feed-back is set to a small value, and therefore, the opening degree of a solenoid valve 18 is gradually decreased to lower the rotational speed N down to Ne. Further, after lapse of the timer set time the amount of feed- back control is turned to be large. Thus, it is possible to aim at enhancing the running ability of the engine in the idler running range.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine idle speed control device.

(Prior Art) Recently, in many automobile engines, feedback control is performed to converge the idle rotation speed to a target rotation speed set in consideration of warm-up operation and the like.

For example, as seen in Japanese Unexamined Patent Application Publication No. 55-60636, an intake air amount adjusting means consisting of a proportional solenoid valve or the like is provided in the assist air passage bypassing the throttle valve. It is known that the amount of intake air flowing through the assist air passage is adjusted according to the deviation between the actual engine speed and the target engine speed, thereby adjusting the idle speed to the target engine speed.

In this type of device, when setting the idling operating range where feedback control is performed, in order to prevent engine stalling due to insufficient intake air amount when returning to feedpack control, feedback control is started in the engine It is necessary to provide some margin between the rotation speed and the target rotation speed.

That is, it is necessary to set a certain width for the idling operation range in which feedback control is performed, and therefore, the feed pack control width is set accordingly.

Therefore, after returning to the idle operating range, the amount of intake air flowing through the assist air passage is gradually reduced based on the feedback signal, and after the engine speed is gradually lowered toward the target speed, It is designed to stabilize at the target rotational speed, that is, to transition to a steady state.

(Problems to be Solved by the Invention) However, in the conventional system, the negative limit of the feedback control width is reached during the transition period to the steady state, that is, before the target engine speed is reached, and after that, Even if feedback control on the positive side is performed, there is a problem in that the engine speed drops significantly and drivability deteriorates.

A possible solution to this problem is to stop feedback control for a certain period of time after recovery).
If the engine speed reaches the target speed during the feedback control stop, there is a risk of engine stalling, which is not preferable as a solution to the above problem.

It is also possible to speed up the responsiveness of the feedback control by setting a large control gain value for the feed/<vine control during the transition period, in other words, to prevent the feedback control width from reaching the negative limit. If such a method is used, the speed at which the engine speed falls increases, the drop becomes even larger, and the engine speed rises, resulting in the so-called hunting phenomenon of the engine speed. Undesirable.

The present invention has been made in consideration of the above-mentioned circumstances, and its technical problem is that during the transition period from returning to the idle operating range until reaching the target rotation speed, the subsequent transition to a steady state An object of the present invention is to provide an engine idle speed control device that makes the following more preferable.

(Means 1 for solving the problem) The present invention subdivides feedback control in the idle operation region,
Based on the viewpoint that control should be performed in accordance with the transition period, during this transition period, the feedback control width is set to be small for a predetermined period of time after returning to the idle operation range. This essentially narrows the idle operating range, that is, suppresses the control amount, thereby preventing feedback control from reaching its negative limit when transitioning to a steady state.

Specifically, as shown in FIG. 1, a rotation speed detection means detects the rotation speed of the engine, and upon receiving a feedback signal from the rotation speed detection means, in an idling operation region,
The engine is characterized by comprising a rotation speed adjustment means for adjusting the idle rotation speed to a target rotation speed, and a control weight setting means for setting the feedback control amount to a small value for a predetermined period after returning to the idle operation range. .

(Example) In Fig. 2, l is the engine body, and intake air passes through an air cleaner 2, an air flow chamber 3, a throttle valve body 4, an intake manifold 6, an intake port 8 opened and closed by an intake valve 7, and then enters a combustion chamber. The path from the air cleaner 2 to the intake port 8 constitutes an intake passage 10. The amount of intake air flowing through this intake passage IO is controlled by the throttle valve 11, while
The intake air is measured by an air flow meter 12, and fuel injected from a fuel injection valve 13 is mixed with this intake air. Further, exhaust gas from the combustion chamber 9 is discharged to the atmosphere through an exhaust port 15 opened and closed by an exhaust valve 14, an exhaust manifold 16, and the like.

A bypass air passage 17 is attached to the intake passage 10, and the bypass air passage 17 has an upstream end 17.
a is connected to the intake passage 10 on the upstream side of the throttle valve 11, and its downstream end 17b is connected on the downstream side of the throttle valve 11, respectively. and,
A solenoid valve 18, which is a proportional solenoid valve, is connected to the /HaPassF passage 17 as an intake air amount adjusting means.

Reference numeral 19 in FIG. 2 is a control unit consisting of a microcomputer, and the control unit 19 receives a cooling water temperature signal as the engine temperature from the water temperature sensor 20, an engine rotation speed signal from the rotation speed sensor 21, and an idle switch. An ON/OFF signal indicating whether or not the throttle valve 1 is fully closed is input from the control unit 19, and an intake air amount signal from the air flow meter 12 is inputted from the control unit 19.
3 and the solenoid valve 18.

Next, the details of control by the control unit 19 will be explained based on a rough flowchart, but explanations of parts that are not directly related to the present invention, such as fuel injection, will be omitted. still,
The intake air amount, that is, the engine speed, is adjusted by adjusting the opening degree of the solenoid valve 18, and the opening degree of the solenoid valve 18 is adjusted according to the duty ratio of the pulse output from the control unit 19. (The larger the duty ratio, the larger the opening degree of the solenoid valve 18.)
.

Embodiment 3 FIG. 3 shows a flowchart as an example of control in the first embodiment. In this embodiment, after returning to the idle operating range, the control gain value (ΔD FB ) is the normal control gain value (A)
It is set to a smaller value (α<A) (steps S5 to S7), thereby forming a control amount setting means for suppressing the feedback control amount.

First, at the start, after setting the upper and lower limits DL of the control duty in step S1, the cooling water temperature, engine speed, and ON-OFF signal from the idle switch 22 are input as data in step S2.

Thereafter, in step S3, it is determined whether or not the engine is in an idle operating range, that is, whether or not it is an operating range that is subject to feedback control. This determination is made based on whether or not the idle switch 22 is ON, that is, the throttle valve 11 is fully closed, and the engine speed is below a predetermined set speed. If it is within the idling range that requires feedback control, the process moves to step S4, where it is determined whether or not it was also within the idling range last time, that is, whether or not it has just returned to the idling range. If it is immediately after, the control gain value △ is set after the timer (TM) is set (TM+TseC) in step S5.
DFB is set to ΔDFB=α (step S6).

Then, until a predetermined time t sec has elapsed after the return, the process proceeds from step S7 to step S8. In step S8, the target rotation speed Ne for idling operation is calculated based on the cooling water temperature, etc., and in the first step S9, the target rotation speed Ne After the basic duty ratio DB corresponding to is calculated, step SIO
Move to.

In step SIO, the actual engine rotation speed N detected by the rotation speed sensor 21 is compared with the target rotation speed Ne. Since N>Ne immediately after returning to the idle operating region, the process moves to step 311 to subtract the control gain value by ΔDFB=-α from the feedback correction term DFB, and then the control limit is set in step S12. It is determined whether the limit value DL has been reached, and if it has been reached, DFB is set to the limit value DL in step S13; if it has not been reached, the final duty ratio DT is calculated by adding the feedback correction DFE to the basic duty ratio DB (step 514). ),
The final duty ratio DT is output (step 5
15).

Therefore, the opening degree of the solenoid valve 18 is narrowed down little by little, and the engine speed (N) gradually decreases toward the target speed (Ne).

After the set time after recovery (t sec ) has elapsed, the process proceeds from step S7 to step S16, and in step 316, the control gain value (ΔD FB) is set to ΔD FB=
A, that is, the control gain value (ΔD FB) is switched to a large value, and feedback correction is performed based on this value (A) (step S L 4).

Then, if the engine rotation speed (N) is lower than the target rotation speed (Ne), step SIO to step S1 is performed.
7, positive feedback correction, that is, control to widen the opening of the solenoid valve 18, is performed, and in this way, the engine speed (N) is converged to the target speed (N e), and the feedback control is performed. stabilizes.

Figure 4 shows the control details in the transition period from returning to the idle operating range to stabilizing the feedback control in Example X.
This figure shows a comparison between the conventional Y and the conventional Y, and this figure shows a situation during deceleration when the engine speed decreases quickly.

As is clear from Figure 4, in the conventional system (Y), the control gain value was always one foot (ΔDFB=A), which led to the negative limit (-20%) of feedback correction. , in this embodiment (X), since the control gain value was kept small (ΔDFB=α) for t sec after recovery, the fee was 4.7.7. Control, ) F + 7 side.

Limitation (-2°%) This will prevent the temperature from reaching 4°.

Second Embodiment FIG. 5 shows a flowchart of control contents in the second embodiment. In this embodiment, after returning to the idle operating range, the limit DL of the feedback control width can be held for a predetermined time (tsec), that is, minus The value is set to a value (-α>-20) higher than the limit (-20%) on the side (steps S23 to 525), thereby forming a controlled variable setting means.

In addition, in this embodiment, the final duty ratio is calculated and output by basically the same program as in the first embodiment described above, so the flowchart shown in FIG. 5 is a characteristic part of this embodiment. First, data is input in step S20, and it is determined whether or not it has just returned to the idle operating range (step S2).
1. Step 522) is performed. If it is immediately after the return, the process moves to step S23, and step S
In step 23, the foot pull control width DL is set to DL = -α%, and then the timer TM is set (step 524), and it is determined whether t seconds have elapsed since the return (step 52).
5) is carried out.

Therefore, for one second after recovery, the final duty ratio DT is calculated based on the feedback control width DL=-α%, and the opening degree of the solenoid valve 18 is controlled in accordance with this duty ratio DT.

Then, after t seconds have passed since the return, the process proceeds to step S26, and in step S26, the feedback control width DL is increased by 1 α%.
Switching from 1 to 20% is performed. Therefore, subsequent feedback control will be performed based on DL=-20%. In addition, in FIG. 5, step S
27 and subsequent steps are the same as those shown in FIG. 3 described above, so the explanation thereof will be omitted. FIG. 6 is a diagram corresponding to FIG. 4 in the first embodiment described above, and shows the control contents (
This is shown in comparison between the conventional method (Y) and the conventional method (Y).

As is clear from Fig. 6, the feedback control width DFB is narrow (-α〉-
20%), the correction amount DL=-α%
It will become saturated once.

Therefore, during the transition period when the feedback control is stable, it is prevented from reaching -20%, which is the negative limit.

Although the present invention has been described in detail above, when the control unit 19 is constituted by a microcomputer, it goes without saying that it may be of either a digital type or an analog type.

Further, in the above embodiment, the period is set by a timer, but it may be set to, for example, until the target value is passed after recovery.

(Effects of the Invention) As is clear from the above description, according to the present invention, during the transition period from returning to the idle operating range to the steady state where feedback control is stabilized, when transitioning to the steady state, Since the feedback control is prevented from reaching the negative limit, the engine speed is prevented from dropping significantly below the target speed, and the drivability of the idling operation can be improved.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the present invention. FIG. 2 is an overall system diagram of an embodiment. FIG. 3 is a flowchart showing an example of control in the first embodiment. FIG. 4 is an explanatory diagram showing the operation of the first embodiment, FIG. 5 is a flow chart showing an example of control in the second embodiment, and FIG. 6 is an explanatory diagram showing the operation of the second embodiment. 1: Engine body 19: Control unit 21: Rotation speed sensor 22: Idle switch

Claims (1)

[Claims] (1) A rotation speed detection means for detecting the rotation speed of the engine; a rotation speed adjustment means for receiving a feedback signal from the rotation speed detection means and adjusting the idle rotation speed to a target rotation speed in an idle operation region; An engine idle speed control device comprising: control amount setting means for setting a feedback control amount to a small value for a predetermined period after returning to an operating range.