JPH1030477A - Fuel cut controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress torque shock and improve fuel consumption by a fuel cut compatibly by delaying a start of the fuel cut after predetermined deceleration drive condition is established and delaying ignition angular timing during the delayed time of the fuel cut. SOLUTION: A control unit 10 for inputting output signals from a crank angle sensor 11, aero-flow meter 12, an idle switch 13, etc., discriminates whether of not a fuel cut is performed, and if NO, further discriminates whether the predetermined deceleration drive condition is performed, namely the idle switch 13 is turned ON, and further discriminates whether the rotational frequency of an engine is over the rotational frequency of the engine in the fuel cut condition. When the deceleration drive condition is established, a first predetermined time(delayed time for fuel cut) T1 and a second predetermined time(delayed time for ignition timing delay) T2 are set according to a level of the current engine rotational frequency. Further, when the value of timer is defined as TM, in the case of TM>=T2, delaying time for ignition is increased gradually, and in the case of TM>=T1, the fuel cut shall be started.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cut control apparatus for an internal combustion engine, and more particularly to a technique for reducing the occurrence of a shock due to a fuel cut.

[0002]

2. Description of the Related Art Generally, in an internal combustion engine, in order to improve fuel efficiency, under a predetermined deceleration operation condition, specifically, it is required that the throttle valve is substantially fully closed and the engine speed is higher than a predetermined fuel cut speed. As a trigger, the fuel supply to the engine is cut, but the fuel cut causes a torque step and a shock.

Therefore, as disclosed in JP-A-54-55237 and JP-A-7-103030,
It has been proposed to reduce the shock by gradually reducing the fuel supply amount and shifting to a fuel cut after a predetermined deceleration operation condition is satisfied. However, if the air-fuel ratio becomes lean and deviates from the ternary range by gradually decreasing the fuel supply amount, the rebound to the exhaust performance increases.

For this reason, in practice, after a predetermined deceleration operation condition is satisfied, the fuel supply amount is not reduced, but is delayed for a predetermined time to shift to fuel cut (fuel cut delay). By shifting to fuel cut after waiting for the torque to decrease with a drop in boost in the fully closed state of the valve, the torque step at the time of fuel cut is minimized.

[0005]

However, in order to further reduce the torque step by the above-mentioned fuel cut delay, the amount of air when the throttle valve is fully closed (the amount of air in the auxiliary air passage) is reduced or the delay time is reduced. It is necessary to wait longer for the torque to decrease sufficiently.However, if the amount of air when the throttle valve is fully closed is reduced, the required torque may not be obtained due to a shortage of absolute air during fuel recovery. In addition, if the delay time is increased, there is a problem that the fuel cut timing is naturally delayed and fuel consumption is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to further improve the fuel cut delay technology so that both a further reduction in torque shock and an improvement in fuel economy due to fuel cut can be achieved. I do.

[0007]

Therefore, according to the present invention, as shown in FIG. 1, in an internal combustion engine provided with fuel cut means for cutting fuel supply to the engine under predetermined deceleration operation conditions. A fuel cut delay means for delaying the start of fuel cut by the fuel cut means from the establishment of the predetermined deceleration operation condition for a predetermined time,
An ignition timing retarding means for retarding the ignition timing during the fuel cut delay time is provided to constitute a fuel cut control device for the internal combustion engine.

That is, due to the delay of the fuel cut, not only does it wait for the torque to decrease when the throttle valve is fully closed, but also the ignition timing is retarded during this delay time to more effectively reduce the torque. By doing so, the torque step at the time of the fuel cut transition is further reduced, and the occurrence of a shock is prevented. The invention according to claim 2 is characterized in that the ignition timing retarding means gradually retards the ignition timing.

This prevents the occurrence of a shock due to the ignition timing retard. In the invention according to claim 3, the fuel cut delay means causes the fuel cut to be performed after a lapse of a first predetermined time from the satisfaction of the predetermined deceleration operation condition, and the ignition timing delay means includes: From the satisfaction of the predetermined deceleration operation condition, a second time shorter than the first predetermined time
The ignition timing is retarded after a predetermined time has elapsed.

That is, after the predetermined deceleration operation condition is satisfied, the ignition timing is retarded after the second predetermined time, and the fuel cut is performed after the first predetermined time (> the second predetermined time). Here, the reason for delaying the ignition timing is
If the ignition timing is retarded at the same time as the throttle valve is fully closed, it is possible that a shock will occur at that point, and immediately after the throttle valve is fully closed, the torque will decrease relatively greatly, and the subsequent torque Since the decrease is relatively gradual, the ignition timing is not retarded while the torque is relatively large, and it is smoother to retard the ignition timing from the time when the torque decreases relatively gently. It is.

The invention according to claim 4 is characterized in that a means is provided for setting the first predetermined time to be shorter on the high rotation side depending on the engine speed. On the high rotation side, the torque decreases relatively quickly after the throttle valve is fully closed, and thus the torque decreases in a short time. Therefore, on the high rotation speed side, the delay time of the fuel cut is shortened, and the fuel cut is accelerated to improve the fuel efficiency.

In the invention according to claim 5, when the first predetermined time is set to be shorter on the high rotation speed side depending on the engine speed, the second predetermined time depends on the engine speed. A means is provided for setting the rotation speed to be shorter on the high rotation side. Thus, regardless of the change in the delay time of the fuel cut, the time from the start of the ignition timing to the start of the fuel cut, that is, the time during which the ignition is delayed, is secured, and the effect of the retard is secured.

According to a sixth aspect of the present invention, when the ignition timing is gradually retarded, the ignition timing retarding means has means for limiting a maximum retardation amount of the ignition timing. I do. This prevents the torque from dropping due to excessive retardation.

[0014]

According to the first aspect of the present invention, the torque can be more effectively reduced prior to the fuel cut by the ignition timing retard during the fuel cut delay time.
It is possible to prevent the occurrence of a shock by reducing the torque step at the time of the fuel cut transition, and it is not necessary to lengthen the delay time of the fuel cut so much. Can be

According to the second aspect of the invention, by gradually retarding the ignition timing, it is possible to prevent the occurrence of a shock due to the retardation. According to the third aspect of the present invention, by delaying the ignition timing retard during the fuel cut delay time, the ignition timing is set after the torque in the fully closed state of the throttle valve is relatively gradually reduced. By retarding and compensating for the decrease in torque, the torque can be reduced more smoothly.

According to the fourth aspect of the present invention, by setting the first predetermined time (the fuel cut delay time) to be shorter on the high rotation side, the torque is reduced in a short time on the high rotation side. The fuel cut can be accelerated to improve fuel efficiency. According to the fifth aspect of the invention, the second predetermined time (i.e., the delay time of the ignition timing delay) is set to be shorter on the high rotation side in accordance with the first predetermined time (the fuel cut delay time). By doing so, it is possible to secure the time during which the vehicle is retarded.

According to the sixth aspect of the invention, when the ignition timing is gradually retarded, the maximum retardation amount of the ignition timing can be limited to prevent a drop in torque due to excessive retardation.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment (one example) of the present invention will be described below. FIG. 2 shows a system configuration.
The control unit 10 incorporates a microcomputer, performs arithmetic processing based on signals from various sensors, and controls the operation of the fuel injection valve 2 and the ignition coil 3 provided for each cylinder of the engine 1.

The various sensors include a crank angle sensor 11, an air flow meter 12, an idle switch 13, and the like. In the case of a four-cylinder engine, the crank angle sensor 11 outputs a reference signal and a unit crank angle (1
〜2 °), the crank angle can be detected, and the engine speed N can be detected.

The air flow meter 12 is, for example, a hot wire type.
The intake air flow rate Q can be detected. Idle switch 13
Turns ON upon detecting a substantially fully closed position of the throttle valve.
Here, the control unit 10 determines the basic fuel injection amount Tp = based on the intake air flow rate Q and the engine speed N.
K · Q / N (K is a constant) is calculated, and various corrections are performed to obtain a final fuel injection amount Ti = Tp · COEF (COF
F is determined for each correction coefficient), and a drive pulse signal having a pulse width corresponding to Ti is output to the fuel injection valve 2 of each cylinder at a predetermined timing synchronized with the engine rotation to perform fuel injection. However, when the fuel cut command (FC = 1) is issued by the fuel cut control routine of FIG. 3 described later, the output of the drive pulse signal to the fuel injection valve 2 is stopped to perform the fuel cut.

The control unit 10 determines the ignition timing based on the engine speed N and the basic fuel injection amount Tp, and controls the operation of the ignition coil 3 at that timing.
The ignition is performed by a spark plug (not shown). However,
Prior to the start of the fuel cut, the ignition timing is corrected for retard. The retard amount is calculated by a fuel cut control routine of FIG. 3 described later, and the ignition timing is calculated by an ignition timing calculation routine of FIG. 4 described later. The ignition timing is retarded based on the retard amount.

Next, the fuel cut control routine of FIG. 3 will be described. This routine is executed every predetermined time. Step 1 (shown as S1 in the figure; the same applies hereinafter)
Then, it is determined whether or not the fuel is being cut (fuel cut flag FC = 1). If the fuel cut is not being performed (FC = 0), the idling switch 13 is turned on (throttle valve is almost fully closed) in step 2 to determine whether or not a predetermined deceleration operation condition is satisfied. It is determined whether or not the engine speed N is equal to or higher than a predetermined fuel cut speed Nfc. In addition,
Usually, the condition is that the water temperature is equal to or higher than a predetermined value, but this is omitted in this flow.

If these conditions are not satisfied, fuel cut is not performed, so the routine proceeds to step 4 where the timer TM
Is set to 0, and this routine ends. When these conditions are satisfied, that is, when the idle switch 13 is turned on
When the throttle valve is substantially fully closed and the engine speed N is equal to or higher than the predetermined fuel cut speed Nfc, the deceleration operation condition for fuel cut is satisfied, and the process proceeds to step 5 and subsequent steps.

In step 5, a first predetermined time (fuel cut delay time) T1 and a second predetermined time (ignition timing delay time) T2 are set according to the current engine speed N. (T1> T2). However, this setting is performed only for the first time immediately after the deceleration operation condition is satisfied. Specifically, the engine speed N is compared with a predetermined threshold value to determine whether the engine speed is low or high, and on the low engine speed, the first predetermined time T1 = T1L and the second The predetermined time T2 = T2L, the first predetermined time T1 = T1H (<T1L) is set on the high rotation side so that each is shorter than the low rotation side, and the second predetermined time T2 = T1H ( <T2L).

More specifically, as shown in Table 1, on the low rotational speed side, a first predetermined time (fuel cut delay time) T
1 = T0, second predetermined time (ignition timing delay delay time)
T2 = T0-a, and on the high rotation side, a first predetermined time (fuel cut delay time) T1 = T0 / n, a second predetermined time (ignition timing delay time) T2 = T0 / na
Set to. Here, T1−T2 = a on both the low rotation side and the high rotation side, and the retard time of the ignition timing is constant.

[0026]

[Table 1]

In step 6, the value of the timer TM is increased by the time interval ΔT during execution of this routine (TM = TM + ΔT) in order to measure the delay time after the deceleration operation condition is satisfied. In step 7, the value of the timer TM is compared with the second predetermined time T2, and this routine is terminated while TM <T2. Then, when TM ≧ T2, the process proceeds to step 8 and thereafter to start retarding the ignition timing.

In step 8, in order to gradually retard the ignition timing, the retard amount R is increased by a small amount ΔR (R = R
+ ΔR). Then, in step 9, a limiter process for the retard amount R is performed. That is, the retardation amount R is compared with a predetermined maximum retardation amount, and when R> the maximum retardation amount, R is limited to the maximum retardation amount.

In step 10, the value of the timer TM is compared with the first predetermined time T1, and this routine is terminated while TM <T1. During this time, the ignition timing is gradually retarded.
Then, when TM ≧ T1, the process proceeds to step 11 and thereafter to start the fuel cut. In step 11, the fuel cut flag F is set to 1 to perform the fuel cut.

Then, in step 12, the timer TM is set to 0, and this routine ends. After starting the fuel cut,
Since FC = 1 in the determination in step 1, the process proceeds to steps 13 and 14 to determine whether or not the fuel cut release condition is satisfied. That is, in step 13, the idle switch 13 is turned off.
F (throttle valve opened), step 14
It is determined whether or not the engine speed N is equal to or greater than a predetermined recover speed Nre.

If none of these conditions is satisfied, the fuel cut is continued, and this routine ends. When any of these conditions is satisfied, the process proceeds to step 15 and thereafter to cancel the fuel cut. Steps
At 15, the fuel cut flag FC is set to 0, and the fuel supply is restarted (fuel recovery).

Then, in step 16, the retard amount R is returned to 0, and this routine is terminated. It should be noted that if the retard amount R is gradually returned, the shock at the time of recovery can be reduced. Next, the ignition timing calculation routine of FIG. 4 will be described. This routine is executed in synchronization with the ignition cycle.

In step 21, based on the engine speed N and the basic fuel injection amount Tp, the basic ignition timing (ignition advance) MA
Set the DV. In step 22, the retard amount R set by the fuel cut control routine of FIG. 3 is read. In step 23, the final ignition timing ADV = MADV-R is obtained by subtracting the retardation amount R from the basic ignition timing MADV.

In this embodiment, steps 2 and
Steps 3 and 11 correspond to fuel cut means, and step 10 corresponds to fuel cut delay means. Steps 7, 8, and 23 correspond to ignition timing retarding means.
Step 5 corresponds to the first predetermined time and second predetermined time setting means, and step 8 corresponds to the maximum retard amount limiting means.

Next, the operation of this embodiment will be described with reference to the time charts of FIGS. As shown in FIG. 5, during a fuel cut delay time T2 after the idle switch 13 is turned from OFF to ON and a predetermined deceleration operation condition is satisfied, the boost is reduced in the fully closed state of the throttle valve in accordance with the boost. And the torque decreases.

From the satisfaction of the predetermined deceleration operation condition,
After a second predetermined time T2, the ignition timing is started to be retarded,
The retard amount is gradually increased with the passage of time. Here, if the ignition timing is retarded at the same time when the throttle valve is fully closed, it is considered that a shock occurs at that time, and immediately after the throttle valve is fully closed, the torque decreases relatively greatly, and thereafter, Since the decrease of the torque is relatively slow, the ignition timing is not retarded while the torque is relatively largely reduced, and the ignition timing is retarded from the time when the torque decreases relatively slowly, Reduce the torque smoothly and sufficiently.

Then, from the satisfaction of the predetermined deceleration operation condition,
After a first predetermined time T1, the process shifts to fuel cut. As shown in the figure, the torque step at the time of the fuel cut transition is smaller than that in the case where the ignition timing is not retarded, so that the torque shock due to the fuel cut can be reduced.

As shown in FIG. 6, when the engine speed is low and when the engine speed is high, the torque decreases rapidly after the throttle valve is fully closed during the high speed operation. Therefore, the first delay time (delay time of fuel cut) is set at the time of low rotation.
If T1 = T1L and the second predetermined time (ignition timing delay time) T2 = T2L are uniformly set, as shown in the dotted line in FIG. The fuel consumption deteriorates due to unnecessary fuel injection.

Therefore, on the high rotation speed side, the first predetermined time (fuel cut delay time) T1 is shortened (T1 = T1).
H) To speed up fuel cut and improve fuel economy. Also, the second predetermined time (ignition timing retardation delay time) T2 is set to be shorter on the high rotation side (T2 = T2).
H) The time from the start of the ignition timing retard to the start of the fuel cut (T2-
T1), that is, the time during which the angle is retarded is secured, and the effect of the retard is secured.

Incidentally, by setting as shown in Table 1 above,
Irrespective of the engine speed, the ignition timing retard time (T1-
If T2) becomes constant (a), the retard amount until the transition to the fuel cut is constant as long as the change rate of the retard amount during that period is constant. In this case, the retard amount limiter process is performed. (Step 8) can be made unnecessary. Further, in addition to the control in two stages of the low rotation speed side and the high rotation speed side, a multi-stage or continuous variable control may be performed.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

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

FIG. 3 is a flowchart of a fuel cut control routine.

FIG. 4 is a flowchart of an ignition timing calculation routine.

FIG. 5 is a timing chart at the time of shifting to a fuel cut.

FIG. 6 is a timing chart showing a difference between a low rotation speed and a high rotation speed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Fuel injection valve 3 Ignition coil 10 Control unit 11 Crank angle sensor 12 Air flow meter 13 Idle switch

Claims (6)

[Claims] An internal combustion engine provided with fuel cut means for cutting fuel supply to the engine under predetermined deceleration operation conditions, wherein the start of fuel cut by the fuel cut means is started for a predetermined time after the predetermined deceleration operation conditions are satisfied. A fuel cut control device for an internal combustion engine, comprising: fuel cut delay means for delaying the ignition; and ignition timing delay means for delaying the ignition timing during a fuel cut delay time. 2. The fuel cut control device for an internal combustion engine according to claim 1, wherein said ignition timing retarding means gradually retards the ignition timing. 3. The fuel cut delay means causes the fuel cut to be performed after a first predetermined time has elapsed from the satisfaction of the predetermined deceleration operation condition. 3. The fuel cut of an internal combustion engine according to claim 1, wherein the ignition timing is retarded after a second predetermined time shorter than the first predetermined time has elapsed from the establishment of the operating condition. Control device. 4. A fuel cut control apparatus for an internal combustion engine according to claim 3, further comprising means for setting said first predetermined time to be shorter on a high rotation speed side depending on an engine speed. . 5. A fuel cut control apparatus for an internal combustion engine according to claim 4, further comprising means for setting said second predetermined time to be shorter on a high rotation speed side depending on an engine speed. . 6. The fuel cut control device for an internal combustion engine according to claim 2, wherein said ignition timing retarding means has means for limiting a maximum retardation amount of the ignition timing.