JPH0759907B2 - Deceleration control device for internal combustion engine - Google Patents

Description

The present invention relates to a deceleration control device for an internal combustion engine.

<Prior Art> In order to maintain the idle speed of the internal combustion engine at an optimum value and improve the fuel consumption, in recent years, as shown in FIG. 6, an auxiliary air passage 2 that bypass-connects the upstream and downstream of the intake throttle valve 1 An idle control valve 3 as an air flow control valve is installed in the valve, and the opening degree of the idle control valve 3 is a pulse signal from the control unit 4 according to the engine operating state based on the engine speed, the engine cooling water temperature, and the like. There is provided an idle speed control device for controlling the idle speed by increasing / decreasing the duty ratio by controlling the idle speed. 5
Is an engine body, 6 is an air flow meter, and 7 is an air cleaner.

By the way, such an idle speed control device has an anti-afterburn valve (AB
V) function is provided for deceleration air-fuel ratio correction.

This is because when the fuel in the intake manifold flows into the combustion chamber immediately after deceleration when the intake throttle valve 1 is fully closed, the air-fuel ratio becomes overrich, and it is discharged to the exhaust system as it is without igniting secondary air and exhaust gas. Afterburning is caused by heat and adversely affects the exhaust system. To prevent this, air is introduced into the intake manifold during deceleration, and this air amount is controlled by adjusting the opening of the idle control valve 3. It is something that is done.

<Problems to be Solved by the Invention> In the conventional deceleration air-fuel ratio correction control, the idle control valve 3 immediately before deceleration is based on the engine cooling water temperature and the intake air flow rate.
The initial opening control amount, that is, the initial duty ratio of the pulse signal for the air-fuel ratio correction is determined, and thereafter, during deceleration, the duty ratio for the air-fuel ratio correction is reduced to zero at a constant rate. (Shown by the solid line in FIG. 5).

However, in the conventional setting of the initial duty ratio and the reduction ratio, the deceleration response of the engine is poor and the vehicle is in a decelerated state with a feeling of acceleration, which is dangerous when driving in urban areas.

Therefore, in order to improve such a problem, measures such as lowering the set level of the initial duty ratio or increasing the reduction ratio can be considered (indicated by the chain line in FIG. 5). Although the deceleration state accompanied by the can be solved, the problem that the deceleration shock becomes large occurs.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a deceleration control device having a deceleration-time air-fuel ratio correction function that allows a pleasant deceleration feeling to be obtained without increasing deceleration shock.

<Means for Solving Problems> Therefore, in the present invention, as shown in FIG. 1, the auxiliary air passage bypassing the intake throttle valve is driven by a pulse signal to adjust the opening degree according to the duty ratio. In an internal combustion engine having a deceleration-time air-fuel ratio correction means for controlling an opening degree of the air-flow rate control valve during deceleration to prevent an air-fuel ratio overrich during deceleration, Means, an engine cooling water temperature detection means, and an engine speed detection means, and the deceleration-time air-fuel ratio correction means is configured to open the air flow control valve based on the intake air flow rate and the cooling water temperature at the start of deceleration. The initial control amount setting means for setting the initial value of the control amount, the initial value set by the initial control amount setting means, while increasing the reduction rate according to the elapsed time from the start of deceleration The higher the reduction ratio, the larger the increase in the decrease ratio, and the correction means for correcting the decrease.

<Operation> In the above configuration, by detecting deceleration, the initial valve opening control amount for air-fuel ratio correction of the air flow control valve is set based on the intake air flow rate and cooling water temperature at the time of detection, and the air-fuel ratio at deceleration is set. The correction initial air flow rate is determined. After that, the initial set values of the air-fuel ratio and the correction amount are increased in accordance with the elapsed time from the start of deceleration, and the increase in the reduction ratio is increased as the engine speed increases, and the air-fuel ratio correction amount becomes zero. Since the decrease correction is performed until that time, in the initial stage of deceleration, enough air can be supplied to prevent overrich, and the deceleration shock due to misfire etc. will not increase, and with the passage of time, deceleration start The higher the engine speed at this time, the larger the gradient of decrease in the amount of air, so that the engine can be smoothly decelerated and a good feeling of deceleration can be obtained.

<Example> Hereinafter, an example of the present invention is described based on a drawing. still,
The hardware configuration is the same as that of the conventional one shown in FIG. 6, and only the software configuration relating to the deceleration air-fuel ratio correction control is different. Therefore, only this software configuration will be described below.

FIG. 2 is a flow chart relating to deceleration air-fuel ratio correction control of one embodiment of the present invention.

In FIG. 1, in S1, data of engine speed, cooling water temperature, intake air flow rate, and data from an idle switch are input from a crank angle sensor, a water temperature sensor, and an air flow meter, respectively. In S2, it is determined whether or not deceleration is being performed depending on whether the idle switch is ON or OFF. And
When it is determined that the vehicle is decelerating, the process proceeds to S3, and it is determined whether the deceleration determination is the first time or the second or later time, that is, whether the deceleration is started or is in the middle of deceleration. .

In S4, based on the initial control amount map for deceleration air-fuel ratio correction shown in FIG. 3, based on the intake air flow rate and cooling water temperature at the start of deceleration, the initial control amount for deceleration air-fuel ratio correction at the time of deceleration start, that is, duty Set the initial value of the ratio (initial control amount setting function). Next, in S5, the decrease rate characteristic of the control amount based on the engine speed at the start of deceleration as shown in FIG. 4 is selected, the decrease rate is searched according to the elapsed time, and the current deceleration air-fuel ratio correction is performed in S6. The reduction rate retrieved in S5 is subtracted from the minute control amount (decrease correction function).

Then, in S7, it is determined whether or not the subtraction calculation value becomes zero in S6, and if it is not zero, the decrease rate is searched again based on the elapsed time, and the previous subtraction calculation value is set as the current control amount, The reduction rate retrieved is subtracted from the control amount. In this manner, the control amount corresponding to the air-fuel ratio correction during gradual deceleration is subtractively corrected to decrease it to zero.

With this configuration, it is possible to secure a sufficient intake air amount in the early stage of deceleration for the purpose of preventing overrich and emission measures, and it is possible to accelerate the decrease in the air-fuel ratio correction amount during deceleration. Therefore, the deceleration shock immediately after deceleration does not increase, and moreover, the engine speed can be smoothly reduced and a pleasant deceleration feeling can be obtained (shown by the broken line in FIG. 5).

<Effects of the Invention> As described above, according to the present invention, the initial value of the air-fuel ratio correction amount control amount at the time of deceleration is set based on the intake air flow rate at the time of deceleration start and the cooling water temperature. As the engine speed is higher and the time after deceleration elapses, the reduction rate of the control amount is increased and the reduction correction is performed.Therefore, the air amount for deceleration air-fuel ratio correction decreases rapidly with the passage of time. In addition, the higher the engine speed during deceleration, the faster the reduction in the latter half of deceleration. Therefore, it is possible to quickly decelerate without increasing the deceleration shock and improve the feeling of deceleration. Further, the accuracy of air-fuel ratio correction during deceleration that matches the amount of wall-flow fuel, which is the main cause of overriching during deceleration, is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a control flowchart of an embodiment of the present invention, FIG. 3 is an initial control amount setting characteristic diagram used in the same embodiment, and FIG. FIG. 5 is a diagram for comparing deceleration characteristics of the present invention with a conventional example, and FIG. 6 is a hardware configuration diagram for explaining the conventional example. 1 ... intake throttle valve, 2 ... auxiliary air passage, 3 ... idle control valve (air flow control valve), 4 ... control unit, 5 ... engine body, 6 ... air flow meter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-57-32035 (JP, A) JP-A-57-2441 (JP, A) JP-A-59-119040 (JP, A) JP-A 58- 155239 (JP, A)

Claims (1)

[Claims] 1. An auxiliary air passage that bypasses an intake throttle valve is provided with an air flow control valve that is driven by a pulse signal and whose opening is adjusted according to its duty ratio, while the opening of the air flow control valve is used during deceleration. In an internal combustion engine equipped with deceleration air-fuel ratio correction means for performing control to prevent air-fuel ratio overrich during deceleration, engine intake air flow rate detection means, engine cooling water temperature detection means, and engine speed detection means are provided. An air-fuel ratio correction means for deceleration, an initial control amount setting means for setting an initial value of an opening control amount of the air flow control valve based on an intake air flow rate and a cooling water temperature at the start of deceleration,
Correcting means for increasing and decreasing the initial value set by the initial control amount setting means in accordance with the elapsed time from the start of deceleration, and increasing the decrease rate as the engine speed increases to correct the decrease. A deceleration control device for an internal combustion engine, which is configured.