JP4788277B2 - Control device for internal combustion engine for automobile - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine for an automobile, and in particular, when a fuel supply is resumed (fuel recovery) based on a driver's accelerator operation from a fuel supply stop (fuel cut) state, the vehicle accompanying the resumption of fuel supply The present invention relates to a control device for an automobile internal combustion engine for suppressing vibration (torsional vibration of a drive system).

In an internal combustion engine for automobiles, fuel supply is stopped and fuel consumption is reduced during a predetermined deceleration operation. When a driver's accelerator operation is detected in a fuel supply stop state, the fuel supply is resumed. Yes.
When the fuel supply is resumed, the drive shaft torque of the vehicle increases rapidly, and torsional vibration (cracking vibration) occurs in the drive system.

Therefore, in the technique described in Patent Document 1, the torsional vibration of the drive system is stopped by stopping the fuel supply to the cylinder that burns after a predetermined time or a predetermined number of cycles with reference to the fuel supply restart timing. The peak of is suppressed.
Japanese Patent Laid-Open No. 10-252514

However, in the technique described in Patent Document 1, since the fuel cut timing for torque reduction is determined based on the fuel supply restart timing, it is optimal when an engine misfire occurs after the fuel supply restarts. There was a problem that the fuel cut could not be performed at the right timing.
In view of such a situation, an object of the present invention is to make it possible to accurately suppress vehicle vibration after resumption of fuel supply, with the fuel cut timing after resumption of fuel supply being an optimal timing.

For this reason, in the present invention, when the fuel supply is restarted from the fuel supply stop state based on the accelerator operation of the driver, the timing at which the combustion is actually started is detected so as not to be affected by misfire or the like. The fuel supply to some cylinders is stopped at the vehicle vibration suppression timing determined at the timing when the backlash of the gear in the transmission is filled with reference to the combustion start timing.

  According to the present invention, by performing fuel cut to some cylinders with reference to the actual combustion start timing after resumption of fuel supply, torque can be stabilized at optimum timing against disturbance after resumption of fuel supply. Down can be performed, and vehicle vibration can be reliably reduced.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a system diagram of an automobile internal combustion engine (engine) showing an embodiment of the present invention.
An engine 1 mounted on a vehicle is provided with an electrically controlled throttle valve 3 for intake air amount control in an intake passage 2 thereof. Each cylinder is provided with a fuel injection valve 4 and a spark plug 5.
The output side of the engine 1 is connected to a drive shaft 7 of the vehicle via a transmission 6.

The operations of the electric throttle valve 3, the fuel injection valve 4, and the spark plug 5 are controlled by an engine control unit (ECU) 10.
Signals are input to the ECU 10 from various sensors.
The accelerator pedal sensor 11 detects the depression amount (accelerator opening) APO of the accelerator pedal and outputs a corresponding signal.

The crank angle sensor 12 outputs a signal synchronized with the rotation of the crankshaft of the engine 1, and can detect the engine speed Ne from this signal.
The air flow meter 13 detects the intake air amount Qa of the engine 1 and outputs a corresponding signal.
The vehicle speed sensor 14 detects a vehicle speed (output shaft rotation speed of the transmission 6) VSP and outputs a corresponding signal.

The gear stage sensor 15 detects the gear stage (gear position) of the transmission 6 and outputs a corresponding signal.
Further, if necessary, a combustion pressure sensor 16 is provided for each cylinder so as to face the cylinder, and the combustion pressure (in-cylinder pressure) Pc of each cylinder can be detected.
Here, the ECU 10 controls the opening degree of the electric throttle valve 3 mainly based on the accelerator opening degree APO, so that the fuel injection valve 4 has a desired air-fuel ratio with respect to the intake air amount Qa controlled thereby. The amount of fuel injection is controlled. Then, the air-fuel mixture of the intake air and the injected fuel is ignited by the spark plug 5 and burned to obtain the engine output.

  Further, during a predetermined deceleration operation, fuel cut is performed to stop fuel injection of the fuel injection valve 4 to reduce fuel consumption. Specifically, the fuel is operated under the condition (fuel cut start condition) that the accelerator opening APO = 0 (the foot is released from the accelerator pedal) and the engine speed Ne is equal to or higher than a predetermined fuel cut speed. When the accelerator opening APO> 0 is reached by the driver's accelerator operation or the engine speed Ne is equal to or lower than the predetermined fuel recovery speed, the fuel cut ends and the fuel recovery (fuel recovery (fuel Reinjection).

Further, when fuel supply is resumed from the fuel cut state based on the driver's accelerator operation, torque control is performed to prevent vehicle vibration.
The torque control at the time of fuel recovery will be described with reference to the flowchart of FIG.
In S1, it is determined whether or not the fuel is recovered from the fuel cut state. If the fuel is recovered, the process proceeds to S2. However, during the fuel recovery, if the engine speed Ne is less than the predetermined fuel recovery speed and the fuel is recovered, the vehicle vibration will not be a problem, so the fuel recovery will be performed based on the driver's accelerator operation from the fuel cut state. Only in the case that it has been, proceed to S2.

In S2, it is determined whether or not combustion has actually started after fuel recovery.
Specifically, when the combustion pressure sensor 16 is provided, the combustion pressure Pc is detected thereby, and the combustion start timing is detected when the combustion pressure Pc exceeds a predetermined value.
Alternatively, the change amount ΔNe of the engine speed Ne is detected, and the combustion start timing is detected when the change amount ΔNe of the engine speed exceeds a predetermined value.

When the actual combustion start timing is detected in the determination of S2, the process proceeds to S3 to start the torque control with this timing as a reference.
In S3, the time Tc from the actual combustion start timing to the vehicle vibration suppression timing is calculated from the engine speed Ne, the vehicle speed VSP, the gear stage, and the like.
The vehicle vibration suppression timing here refers to FIG. 4, and after the fuel supply is restarted, the drive shaft torque of the vehicle becomes 0 from the negative value during the deceleration fuel cut by the start of combustion, and the gear of the transmission Is the timing when the backlash is filled, in other words, the timing immediately before the drive shaft torque rises rapidly from zero.

When the predetermined time Tc for determining the vehicle vibration suppression timing is set by the engine speed Ne, as shown in FIG. 3A, the higher the engine speed Ne, the shorter the combustion interval. Set.
Further, when the vehicle speed VSP is set, as shown in FIG. 3B, the higher the vehicle speed VSP, the higher the engine speed and the shorter the combustion interval if the gear stage is the same. Set.

When setting by gear stage, as indicated by the solid line in FIG. 3C, the lower the gear stage, the higher the engine speed and the shorter the combustion interval at the same vehicle speed. Set it short. Further, since the backlash is larger as the gear is on the lower speed side, in this case, as indicated by the dotted line in FIG. 3C, the lower the gear stage, the longer Tc may be set.
The time Tc may be set by a combination of two or more parameters among the engine speed Ne, the vehicle speed VSP, and the gear stage.

In next S4, the number n of fuel cut cylinders corresponding to the torque reduction amount is set. Normally, one cylinder (n = 1) may be used, but when the required amount of torque reduction is large, the fuel cut is set for a plurality of cylinders.
Specifically, an accelerator operation amount, for example, a change amount ΔAPO of the accelerator opening APO is detected, and when this is large, the fuel cut cylinder number n is increased. Alternatively, the number n of fuel cut cylinders is increased in order to increase the torque reduction amount at the lower speed side, depending on the gear stage.

In next S5, it is determined whether or not a predetermined time Tc has elapsed from the actual combustion start timing, and the process proceeds to S6 when the predetermined time Tc has elapsed (when the vehicle vibration suppression timing is reached).
In S6, since it is the vehicle vibration suppression timing, the fuel cut is performed for the n cylinders. That is, for example, when n = 1, fuel cut is performed for the fuel injection cylinder at that time, and when n = 2, fuel cut is performed for the next fuel injection cylinder.

FIG. 4 is a time chart for torque control during fuel recovery.
When the accelerator opening APO> 0 is reached by the driver's accelerator operation from the deceleration fuel cut state, the fuel supply is resumed from the time t1.
Here, it is assumed that misfire occurs and the start of combustion is delayed. Then, the start of combustion is detected at the time t2 when the combustion pressure exceeds a predetermined value due to the actual start of combustion (or when the amount of change in the rotational speed exceeds the predetermined value) t2. When the start of combustion is detected, fuel is cut to some cylinders at time t3 when a predetermined time Tc has elapsed with reference to this.

As a result of this fuel cut, the torque is reduced at the time point t4 when the drive shaft torque rises rapidly from zero (at the time when the gear backlash is filled), and fluctuations in the drive shaft torque (torsional vibration of the drive system) are shown in the dotted line To the level of the solid line in the figure.
As described above, when the fuel supply is resumed from the deceleration fuel cut state based on the accelerator operation of the driver, the means (S2) for detecting the timing at which actual combustion is started and the actual combustion start timing as a reference By providing the means (S3 to S6) for stopping the fuel supply to some cylinders at the vehicle vibration suppression timing determined as described above, the optimum timing can be obtained regardless of disturbance (misfire etc.) after the fuel supply is resumed. Thus, the torque can be reduced and the vehicle vibration can be reliably reduced.

In addition, according to the present embodiment, the combustion start timing is detected when the combustion pressure exceeds a predetermined value or when the amount of change in the engine speed exceeds a predetermined value. Can be detected.
In addition, according to the present embodiment, the vehicle vibration suppression timing (fuel cut timing) is determined as the time when the predetermined time Tc has elapsed from the actual combustion start timing, thereby simplifying the control.

Further, according to the present embodiment, the predetermined time Tc is variably set according to the engine speed, the vehicle speed, the gear stage of the transmission, and the like, so that it is possible to cope with various driving conditions.
Further, according to the present embodiment, the number of cylinders n at which fuel supply is stopped at the vehicle vibration suppression timing is variably set according to the accelerator operation amount, the gear stage of the transmission, etc. Even when the amount is large, it is possible to cope.

  In the above embodiment, the vehicle vibration suppression timing (fuel cut timing) is determined as a time when a predetermined time has elapsed from the actual combustion start timing, but is determined as a time when a predetermined number of combustion cycles has elapsed from the actual combustion start timing. You may do it. Also in this case, the predetermined number of combustion cycles can be variably set according to the engine speed, the vehicle speed, the gear stage, and the like.

  Further, when the actual combustion start timing is detected by the amount of change in the engine speed, the engine speed is based on the time required to rotate the predetermined rotation angle or the rotation angle rotated at the predetermined time. Therefore, when detecting the combustion start timing, the combustion start is started by increasing the calculation frequency of the engine speed more than usual (decreasing the predetermined rotation angle or shortening the predetermined time). The timing can be accurately captured.

Engine system diagram showing an embodiment of the present invention Flow chart of torque control during fuel recovery Characteristic diagram of time Tc for determining vehicle vibration suppression timing Time chart for torque control during fuel recovery

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 3 Electric throttle valve 4 Fuel injection valve 5 Spark plug 6 Transmission 7 Vehicle drive shaft 10 ECU
11 Accelerator pedal sensor 12 Crank angle sensor 13 Air flow meter 14 Vehicle speed sensor 15 Gear stage sensor 16 Combustion pressure sensor

Claims (9)

In a control device for an internal combustion engine for automobiles that stops fuel supply during a predetermined deceleration operation,
Means for detecting the timing of actual combustion when fuel supply is restarted based on the driver's accelerator operation from the fuel supply stop state;
Means for starting to stop fuel supply to some cylinders at a vehicle vibration suppression timing determined at a timing when the gear backlash in the transmission is filled with reference to an actual combustion start timing;
A control apparatus for an internal combustion engine for automobiles. 2. The control apparatus for an internal combustion engine for an automobile according to claim 1, wherein the combustion start timing is detected when the combustion pressure exceeds a predetermined value. 2. The control apparatus for an internal combustion engine for an automobile according to claim 1, wherein the combustion start timing is detected when an amount of change in engine speed exceeds a predetermined value. The control apparatus for an internal combustion engine for an automobile according to any one of claims 1 to 3, wherein the vehicle vibration suppression timing is determined as a time when a predetermined time has elapsed from an actual combustion start timing. 5. The control apparatus for an automotive internal combustion engine according to claim 4, wherein the predetermined time is variably set according to at least the engine speed. 5. The control apparatus for an internal combustion engine for an automobile according to claim 4, wherein the predetermined time is variably set according to at least the vehicle speed. 5. The control apparatus for an internal combustion engine for an automobile according to claim 4, wherein the predetermined time is variably set according to at least a gear stage of the transmission. 8. The internal combustion engine for an automobile according to claim 1, wherein the number of cylinders at which fuel supply is stopped at the vehicle vibration suppression timing is variably set according to at least an accelerator operation amount. 9. Control device. The number of cylinders for which fuel supply is stopped at the vehicle vibration suppression timing is variably set according to at least the gear stage of the transmission. Control device for internal combustion engine.

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