JPH0571391A - Fuel control device of engine - Google Patents

Abstract

PURPOSE:To realize compatibility between the expansion of a fuel feed stop region during operation of a brake and prevention of the occurrence of hunting when a brake is intermittently operated after return of fuel, in an engine to effect cut of fuel during deceleration. CONSTITUTION:During deceleration wherein the number of revolutions of an engine Ne exceeds a first threshold N1, fuel is cut at S3. Meanwhile, in case of Ne<=N1, provided Ne is below a second threshold N2 (N1>N2), return of fuel is effected unconditionally at S8. Even in case of Ne<=N1, provided Ne is higher than N2, it is decided at S6 whether a brake switch is turned ON or not. When the switch is turned ON, it is watched at S7 whether or not fuel cut was carried out at a preceding time. On a condition that fuel cut was executed at a preceding time (F=1), fuel cut is continued. When fuel cut was not carried out at a preceding time, the feed of fuel is returned and ordinary injection is carried out at S8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control system for an engine which cuts fuel during deceleration.

[0002]

2. Description of the Related Art For example, in a fuel injection type gasoline engine that is electronically controlled, it has been known to cut off fuel when the engine is decelerating to a predetermined value or more with a throttle valve fully closed in order to improve fuel consumption and emission. Has been done. By the way, in such an engine that performs fuel cut during deceleration, it is desirable to perform fuel cut in the widest possible rotational speed range from the viewpoint of fuel saving, etc. However, since the combustion state may worsen and an engine stall may occur at the time of recovery, torque fluctuations due to misfire will adversely affect the drivability and drivability of the vehicle, so the recovery speed is usually set too low. It is not possible. However, when the driver is stepping on the brake, a large torque is applied to the deceleration side. Therefore, even if the fuel is returned at a lower rotation speed, hunting that is a practical problem is unlikely to occur. Therefore, it has been conventionally performed to change the fuel return rotation speed depending on whether or not the brake is depressed. Japanese Patent Laid-Open No. 3-111644 discloses an example thereof. That is, according to the publication, the fuel cut start rotational speed is set high when the brake is not operated, and the fuel cut start rotational speed is set low when the brake is operated.

[0003]

However, in the case where the number of revolutions of the fuel return is reduced when the conditions such as the brake operation are satisfied, when the braking operation is intermittently performed after returning from the deceleration fuel cut, etc. To
There has been a problem that a hunting phenomenon occurs in which fuel cut and fuel return are repeatedly repeated, causing a shock, and impairing the driving feeling.

The present invention has been made in view of the above problems, and in an engine for performing fuel cut during deceleration,
An object of the present invention is to provide an engine fuel control device that can achieve both expansion of the fuel cut area during braking, etc., and prevention of shock due to hunting when braking is intermittently performed after fuel recovery, etc. To do.

[0005]

According to the present invention, the control for decreasing the number of revolutions for starting the recovery from the fuel cut is executed only when the fuel cut is executed in the previous calculation cycle. The configuration is as shown in FIG. That is, the engine fuel control device according to the present invention detects the deceleration state from the output of the operating state detecting means and the operating state detecting means for detecting the operating state of the engine, and when the engine speed is high in the decelerating state. It receives the output of the fuel supply stop means during deceleration for stopping the fuel supply to the engine by the fuel supply device and returning the fuel supply when the engine speed drops to a predetermined speed, and the condition detection means for detecting the predetermined condition. A fuel control device for an engine, comprising: a fuel return rotational speed reduction means for decreasing the predetermined rotational speed of fuel supply recovery when a predetermined condition is satisfied, wherein the predetermined control is performed while the fuel supply is stopped by the fuel supply stop means during deceleration. It is characterized by further comprising fuel return rotational speed reduction execution means for executing the reduction of the predetermined rotational speed by the fuel return rotational speed reduction means only when a condition is detected.

The condition detecting means may detect that the brake is operating.

[0007]

When the engine speed is high in the deceleration state, the fuel supply stop means during deceleration is activated to stop the fuel supply to the engine by the fuel supply device, and the engine speed is lowered to the predetermined speed. If detected, fuel return is performed. Here, the rotation speed, which is the threshold value for fuel recovery, is lowered when a predetermined condition such as during brake operation is satisfied, but such a threshold change is performed only when the above condition is satisfied while the fuel supply is stopped, That is, it is executed only when the fuel supply is stopped in the previous calculation cycle, whereby the fuel consumption is improved by expanding the fuel supply stop region during the braking operation and the braking operation is intermittently performed after the fuel is returned. At the same time, it is possible to prevent the occurrence of shock due to the occurrence of hunting.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below with reference to the drawings.

FIG. 2 is an overall system diagram of an embodiment of the present invention. In this embodiment, the intake passage 2 of the engine 1
An air cleaner 3 is connected to the upstream end of the air cleaner 3, and an air flow meter 4 for detecting the intake air amount is disposed downstream of the air cleaner 3. A throttle valve 5 is provided downstream thereof, and the downstream side of the throttle valve 5 is branched via a surge tank 6 and communicated with an intake port 7 of each cylinder. The electromagnetic fuel injection valve 8 is arranged toward the intake port 7 at a position downstream of the intake passage 2. The exhaust port 9 communicates with an exhaust passage 10, and an O ₂ sensor 11 for detecting the oxygen concentration in the exhaust gas is arranged in the exhaust passage 10.

The fuel injection valve 8 is operated by a control signal from a control unit 12 composed of a microcomputer. The control unit 12 has, as information for calculating the control signal, a rotation signal from a rotation sensor attached to the distributor 13, an intake air amount signal from the air flow meter 4, an oxygen concentration signal from the O ₂ sensor 11, A water temperature signal from a water temperature sensor 14 for detecting the engine water temperature, an idle signal from an idle switch 15 attached to the throttle valve 5, a brake switch signal for detecting that a brake has been actuated, etc. are input.

In the control unit 12, the engine speed calculated from the rotation signal and the air flow meter 4
The basic fuel injection amount is set based on the intake air amount detected by, the water temperature correction and the like are added to the basic fuel injection amount, and the feedback correction is performed based on the output of the O ₂ sensor 11 to determine the fuel injection amount. It is determined. When the throttle valve is fully closed and the engine speed decelerates higher than a predetermined value, fuel is cut off, and when it is detected that the deceleration state has ended and the predetermined fuel return speed has been reached, the fuel supply state is restored. It

The above-described fuel return rotational speed is normally moved to the lower side when the brake operation is continued, whereby the fuel supply stop (fuel cut) region is expanded to improve the fuel consumption and to strengthen the engine brake. The operation is realized.
FIG. 3 is an explanatory view of such a fuel cut zone. In the figure, the area on the high rotation side indicated by the diagonal lines rising to the right is the fuel cut zone during normal deceleration without brake operation, and the area indicated by the diagonal lines descending to the right on the low rotation side is the fuel that is applied only during continuous braking It is an enlarged part of the cut zone. In addition,
The vertical axis represents the charging efficiency Ce, and the horizontal axis represents the engine speed Ne.

In this embodiment, when the brake is not operated, the fuel is restored when the engine speed Ne drops to N ₁ (first threshold value), and when the brake operation is continued, N ₂ (second
Fuel is restored when the threshold value is reached. Further, after the fuel is once returned at N ₁ , the state of fuel return is maintained and normal injection is executed even if the brake is depressed. By doing so, it is possible to prevent the occurrence of a shock due to the occurrence of hunting when the brake operation is intermittently performed after the fuel is returned.

FIG. 4 is a flow chart for executing the above control. This will be described below. Note that S1 to S9 indicate each step.

In this flow, when starting, first, in S1, it is checked whether or not the idle switch 15 is in the ON state, and if it is in the ON state, then in S2, the engine speed Ne is the first threshold value. See if it is greater than N ₁ . If Ne> N ₁ , it means that the vehicle is in the fuel cut zone during deceleration, so the fuel cut is executed in S3, and then the flag F indicating that the fuel is being cut is set in S4 (F = 1) and the routine returns.

On the other hand, if the determination in S2 is NO, the process proceeds to S5, and it is checked whether Ne is larger than a _second threshold value N ₂ (N ₁ > N ₂ ) during braking. And Ne
In the case of> N ₂ , it is checked in S6 whether the brake switch is in the ON state. If it is in the ON state, next in S7, it is checked whether the flag F is set. When standing, that is, when the fuel cut was performed last time, the process proceeds to S3, and the fuel cut is continued. On the other hand, if the flag F is not set, the process goes to S8 to restore the fuel and execute the normal injection, then reset the flag F in S9 and return.

If the determination in S1 is NO, it means that the vehicle is not decelerating, so that the routine proceeds to S8 and the normal injection is executed.
Further, if NO in S5, that is, if Ne is equal to or less than N ₂ , the process unconditionally proceeds to S8 to return the fuel, and even if Ne is higher than N ₂ , if the determination in S6 is NO, that is, the brake is not activated, S8 is also applied. Proceed to and return the fuel.

In the above embodiment, the fuel return speed is moved to the lower side when the brake is operated. However, the fuel return speed can be changed by turning on / off an external load such as an air conditioner. It is also possible to have an embodiment in which

[0019]

Since the present invention is configured as described above, in an engine that performs fuel cut during deceleration, when a condition such as brake operation is satisfied, the fuel supply stop region is expanded to improve fuel efficiency. In addition, it is possible to prevent the occurrence of a shock due to the occurrence of hunting when the brake operation is intermittently performed after the fuel is returned.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of the present invention.

FIG. 2 is an overall system diagram of an embodiment of the present invention.

FIG. 3 is an explanatory view showing a fuel cut zone in the same embodiment.

FIG. 4 is a flowchart for executing the control of the same embodiment.

[Explanation of symbols]

 1 Engine 8 Fuel Injection Valve 12 Control Unit 13 Distributor 15 Idle Switch

Claims (2)

[Claims] 1. A driving state detection means for detecting a driving state of an engine, and a deceleration state is detected from an output of the driving state detection means. Receiving the outputs of the fuel supply stop means during deceleration for stopping the fuel supply and returning the fuel supply when the engine speed drops to the predetermined speed and the condition detecting means for detecting the predetermined condition, and returning the fuel supply when the predetermined condition is satisfied. A fuel control device for an engine, comprising: a fuel return rotation speed reduction means for decreasing the predetermined rotation speed, wherein the predetermined condition is detected only when the fuel supply is stopped by the fuel supply stop means during deceleration. A fuel control device for an engine, comprising: a fuel-return-rotation-speed-lowering executing means for executing a reduction of a predetermined speed by the fuel-return-rotation-speed lowering means. 2. The fuel control device for an engine according to claim 1, wherein the condition detecting means detects that the brake is operating.