JPH1077882A - Internal combustion engine deceleration control device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the fuel cut area by lowering the recovery rotation speed of deceleration fuel cut. Kind Code: A1 In an internal combustion engine in which a throttle valve is driven to open and close by an actuator, it is determined whether or not a decrease rate ΔNe of an engine rotation speed Ne exceeds a predetermined value during deceleration fuel cut (S1). S2). When the decrease rate ΔNe exceeds a predetermined value, the target opening of the throttle valve is increased by a constant opening (S3), and a drop in the rotational speed is suppressed due to a decrease in pumping loss.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deceleration control device for an internal combustion engine, and more particularly, to a device capable of reducing a recovery rotation speed of a fuel cut during deceleration.

[0002]

2. Description of the Related Art Conventionally, as one of measures for improving fuel efficiency in a vehicle internal combustion engine, fuel supply to the engine is stopped during a deceleration operation in which the throttle valve is fully closed and the engine speed is higher than a predetermined speed. A so-called deceleration fuel cut is performed.

[0003]

In the deceleration fuel cut, fuel supply is restarted when the engine speed becomes equal to or lower than a predetermined speed (recovery speed). However, the recovery speed is set as low as possible. As a result, the fuel cut area is expanded, and the effect of improving fuel efficiency by the fuel cut is increased.

However, there is a response delay in the rise of the engine torque in response to the restart of the fuel supply, and when the rate of decrease in the rotational speed during the deceleration fuel cut is greater, the fuel supply must be restarted at a higher rotational speed unless the engine stops. There is fear. That is, in FIG. 5, when the recovery rotation speed is set to a relatively high value (1), even if the response delay occurs, engine stall does not occur, but the recovery rotation speed is relatively low (2). ), The engine will stall without increasing the rotation speed due to the response delay.

Therefore, conventionally, the recovery rotation speed is set to be relatively high so that engine stall does not occur even when the rotation speed is most rapidly reduced. When the fuel cut is gradual, the fuel supply is restarted even though the fuel cut can be continued, and there is a problem that the fuel efficiency improvement effect by the deceleration fuel cut cannot be maximized.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to improve the fuel efficiency by reducing the deceleration fuel by enabling the recovery rotational speed to be set sufficiently low while avoiding the occurrence of engine stall. And

[0007]

The invention according to claim 1 is configured as shown in FIG. In FIG.
The deceleration fuel cut means is provided for decelerating operation of the engine.
Stop fuel supply to the engine. On the other hand, the rotation decrease rate detecting means detects a decrease rate of the engine rotation speed in a state where the fuel supply to the engine is stopped by the deceleration fuel cut means.

The throttle opening drive means forcibly opens and drives the throttle valve interposed in the intake system of the engine based on the reduction rate detected by the rotation reduction rate detection means.
The deceleration fuel cut is performed when the throttle valve is fully closed. However, if the throttle valve is opened during such fuel cut, pumping loss (suction resistance) decreases,
It is possible to suppress the drop in rotation. Here, when the rotation speed is rapidly decreased during the deceleration fuel cut and the rate of decrease of the rotation speed is large, it is necessary to restart the fuel supply at a higher rotation speed. Since it is possible to suppress a decrease in the speed, it is possible to continue the fuel cut to a lower rotation speed than when the throttle valve is not driven to open.

According to the second aspect of the present invention, the throttle opening driving means forcibly opens the throttle valve only when the reduction rate detected by the rotation reduction rate detecting means is larger than a predetermined value. And According to such a configuration,
Even when the throttle valve is not forcibly driven to open, when the rotation speed drops relatively slowly and the rotation speed at which fuel supply is to be resumed is sufficiently low, the throttle valve is kept fully closed.

According to a third aspect of the present invention, the throttle opening drive means variably sets an opening for forcibly opening the throttle valve in accordance with the reduction rate detected by the rotation reduction rate detection means. The configuration was adopted. According to this configuration, it is possible to open the throttle valve more largely as the rotation speed at which the rotation speed decreases and the fuel supply to be restarted is higher, so that it is possible to increase the effect of suppressing rotation drop due to a reduction in pumping loss. is there.

[0011]

According to the first aspect of the present invention, a decrease in rotation speed during fuel cut can be suppressed, and a rotation speed at which fuel supply should be resumed can be reduced, so that a fuel cut range is expanded and fuel efficiency is improved. There is an effect that it can be further improved. According to the second aspect of the present invention, it is possible to suppress the rotation drop due to the opening drive of the throttle valve only when the rotation speed is rapidly reduced and the recovery rotation speed needs to be set relatively high. Thus, there is an effect that a reduction in deceleration due to unnecessary opening drive can be avoided.

According to the third aspect of the present invention, in order to keep the recovery rotation speed low, the throttle valve can be driven to open by a necessary and sufficient opening degree, and the rotation speed at which fuel supply is to be resumed is stabilized. In addition, there is an effect that a decrease in deceleration due to the occurrence of unnecessary opening drive can be avoided with high accuracy.

[0013]

Embodiments of the present invention will be described below. In FIG. 2, an internal combustion engine 1 has a throttle valve 2
The air is sucked in through the air and mixed with the fuel injected from the electromagnetic fuel injection valve 3 provided in the intake port of each cylinder to form an air-fuel mixture. Note that the fuel injection valve 3 may be of a type that directly injects fuel into the combustion chamber.

The air-fuel mixture sucked into the cylinder is ignited and burned by spark ignition by the spark plug 4. A control unit 5 for controlling the fuel injection amount by the fuel injection valve 3 receives a rotation signal from a crank angle sensor 6, an intake air flow rate signal from an air flow meter 7, and the like.

The control unit 5 incorporating a microcomputer calculates a fuel injection amount based on signals from the various sensors, and at a predetermined injection timing synchronized with engine rotation, a pulse width corresponding to the fuel injection amount. Is output to the fuel injection valve 3. Here, when the throttle valve 2 is fully closed and the engine rotation speed Ne is equal to or higher than a preset cut rotation speed, a deceleration fuel cut for stopping the fuel supply by the fuel injection valve 3 is started, When the valve 2 is opened or the engine rotation speed Ne falls below a preset recovery rotation speed, the fuel supply is restarted (deceleration fuel cut means).

The throttle valve 2 is configured to be opened and closed by an actuator 8 such as a motor.
Is determined, and the actuator 8 is controlled in accordance with the target opening. Here, it is preferable that a sensor for detecting the throttle opening is provided, and feedback control is performed so that the actual opening matches the target opening.

The control unit 5 receives an accelerator opening signal from an accelerator opening sensor 9 and the like to determine the target opening. The flowchart of FIG. 3 shows the state of the throttle control during the deceleration fuel cut. The control unit 5 has the functions of the rotation reduction rate detecting means and the throttle opening driving means as software as shown in the flowchart of FIG.

First, in step 1 (shown as S1 in the figure, the same applies hereinafter), it is determined whether or not the deceleration fuel cut is being performed. When the deceleration fuel cut is being performed, the routine proceeds to step 2, where the rate of decrease ΔNe (Δ
Ne = Ne _OLD −Ne _NEW ) exceeds a predetermined value.

When the decrease rate .DELTA.Ne exceeds a predetermined value, that is, when the engine rotational speed Ne drops sharply, the routine proceeds to step 3, where the target opening of the throttle valve 2 is set to a predetermined constant value. The throttle valve 2 is forcibly opened by increasing the opening. Since the opening of the throttle valve in step 3 is not considered as a condition for restarting fuel supply, the processing in step 3 does not restart fuel supply.

When the throttle valve 2 is opened in the fuel cut state, the drop in rotation is suppressed due to a decrease in pumping loss (suction resistance). On the other hand, it is necessary to set the recovery rotation speed higher as the rotation speed drops sharply in the fuel cut state (see FIG. 5). However, as described above, the rotation speed is increased by forcibly opening the throttle valve. Is suppressed, the engine stall can be avoided even if a relatively low recovery rotation speed adapted to a state where the rotation is gradually reduced is applied. Therefore, even if a low rotation speed is set as a preset recovery rotation speed that is suitable for a state in which the decrease in rotation is relatively gradual, it is possible to always execute a fuel cut in a wide area without stalling. Becomes possible.

On the other hand, if it is determined in step 2 that the decrease rate ΔNe is equal to or less than the predetermined value, the process proceeds to step 4, and
The current throttle valve opening is maintained. Therefore, even if control for forcibly opening the throttle valve is not executed, the throttle valve is kept fully closed by the processing in step 4 when the condition of the decrease in rotation is not rapid, and the throttle valve is opened. When the drop in rotation is suppressed by forcibly opening the throttle valve, the throttle valve is kept open.

In step 5, it is determined whether or not the fuel supply restart condition is satisfied and the fuel cut is completed. If the fuel cut is being performed, the process returns to step 2 to perform throttle control based on the decrease rate ΔNe. . On the other hand, when the fuel cut is completed, the routine proceeds to step 6, where the target opening set for suppressing the drop in rotation is reset to the normal target opening, and the control is ended.

In the above description, the throttle valve is forcibly opened by a certain opening when the decrease rate ΔNe exceeds a predetermined value. May be widely opened, and an embodiment of the configuration according to the flowchart of FIG. 4 will be described. The flowchart of FIG. 4 differs from the flowchart of FIG. 3 only in the step 3A, and thus the description will focus on the step 3A.

In the flow chart of FIG. 4, if it is determined that the decrease rate .DELTA.Ne exceeds a predetermined value during the fuel cut, the routine proceeds to step 3A, in which the throttle valve opening corresponding to the decrease rate .DELTA.Ne is stored in advance. Refer to the map
The throttle valve opening corresponding to the decrease rate ΔNe determined to exceed the predetermined value is obtained, and the throttle valve opening is set to the target opening.

That is, when the drop in the rotational speed is large, it is necessary to open the throttle valve greatly to suppress the drop in the rotation. However, when the drop in the rotational speed is relatively small, the throttle valve is similarly opened. If you open it wide,
The drop in rotation is excessively suppressed, and the deceleration is impaired. Therefore, a configuration in which the throttle valve is opened as the reduction rate ΔNe increases as the reduction rate ΔNe increases does not cause engine stall due to resumption of fuel supply at a preset recovery rotation speed, and the deceleration is impaired due to excessive opening drive. It is not to be done.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of an apparatus according to the first embodiment.

FIG. 2 is a system configuration diagram of an internal combustion engine in the embodiment.

FIG. 3 is a flowchart showing a first embodiment of throttle control during deceleration fuel cut.

FIG. 4 is a flowchart showing a second embodiment of throttle control during deceleration fuel cut.

FIG. 5 is a time chart showing a difference in rotation speed change due to a recovery rotation speed in deceleration fuel cut.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Throttle valve 3 Fuel injection valve 4 Spark plug 5 Control unit 6 Crank angle sensor 7 Air flow meter 8 Actuator 9 Accelerator opening sensor

Claims (3)

[Claims] 1. A deceleration fuel cut means for stopping fuel supply to the engine in a deceleration operation state of the engine, and a decrease in engine speed when the fuel supply to the engine is stopped by the deceleration fuel cut means. A rotation reduction rate detecting means for detecting a rate, and a reduction rate detected by the rotation reduction rate detecting means,
A deceleration control device for an internal combustion engine, comprising: throttle opening drive means for forcibly opening and driving a throttle valve interposed in an intake system of the engine. 2. The throttle opening driving means for forcibly opening the throttle valve only when the reduction rate detected by the rotation reduction rate detecting means is greater than a predetermined value. 2. The deceleration control device for an internal combustion engine according to claim 1. 3. The throttle opening drive means variably sets an opening for forcibly opening and driving a throttle valve according to a reduction rate detected by the rotation reduction rate detection means. Item 3. The deceleration control device for an internal combustion engine according to item 1 or 2.