JPH05280394A - Fuel cut control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent hunting while performing fuel cut by increasing a fuel cut rotation number as an inclination of a descending road for a fuel cut device for an internal combustion engine. CONSTITUTION:When an operation is shifted to a speed reducing operation, and if an engine rotation number exceeds an initial value NRT+k3 of a fuel cut rotation number, it is determined that XFCLL becomes 1 for the first time, where fuel cut is performed (step 86). When the rotation number gets under a restoration rotation number NRT after that, it is determined that XFCLL=0, where a fuel supply condition is restored (step 76). When an inclination of a descending road becomes large during speed reduction, and if the engine rotation number exceeds the next cut rotation number NRT+k2 (>NRT+k3), the fuel cut is controlled at a second cut rotation number Ne+k1 (step 98).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention cuts fuel when the engine speed exceeds a first predetermined value in deceleration operation, and a second predetermined value on the engine speed lower side than the first predetermined value. The present invention relates to a fuel cut control device that restarts fuel supply when the value falls below a value.

[0002]

2. Description of the Related Art In an internal combustion engine, fuel is cut to prevent afterfire and the like caused by unburned gas being discharged into an exhaust pipe during deceleration operation. The fuel cut is performed when the engine speed exceeds a first predetermined value, and the fuel supply is restarted when the engine speed falls below a second predetermined value on the low rotation side of the first predetermined value. .. The first predetermined value for fuel cut is somewhat higher than the second predetermined value for fuel return, so-called hysteresis is provided to prevent hunting when the engine speed stays around the predetermined value. I am trying to do it. It is preferable that the number of revolutions of the fuel returning is low from the viewpoint of saving fuel consumption, but if it is lowered too much in relation to the idling, it may stall before returning to the fuel, and there is a lower limit. Therefore, a somewhat higher fuel cut rotation speed is set with respect to this lower limit. However, in deceleration operation on a downhill where the gradient becomes large, the number of revolutions increases significantly when the fuel is restored, and the normal hysteresis value makes the number of return revolutions too small for the fuel cut number of revolutions. The cutting is repeated frequently and hunting occurs. Therefore, in order to prevent this hunting, Japanese Unexamined Patent Publication No. 60-79131 discloses a technique for increasing the fuel cut speed and preventing hunting when steady running with the throttle valve fully closed continues for a long time. There is.

[0003]

In the case where the vehicle is equipped with an automatic transmission, the engine speed between fuel cut and fuel return during operation on a downhill slope where the slope becomes tight becomes large. It changes a lot. That is, when the automatic transmission is provided, the speed ratio in the automatic transmission changes in response to the torque change due to the fuel cut-return. This causes the engine speed to change significantly. On the other hand, in the case of the manual transmission, the drive system is only connected by gears even in deceleration operation where the slope of the downhill becomes large, so the engine speed gradually increases as the vehicle speed increases. However, there is no sudden change in engine speed as in an automatic transmission.
In an automatic transmission, the engine speed changes greatly due to the torque change associated with the fuel cut-return.To prevent hunting from occurring due to such a large engine speed change, the fuel cut after the fuel return occurs. It is necessary to set the rotating speed to a large value. Although hunting can be prevented by increasing the fuel cut rotation speed, it becomes difficult to perform fuel cut, and the fuel consumption efficiency deteriorates.

It is an object of the present invention to prevent hunting, yet to prevent fuel from being cut off in a timely manner and to prevent the fuel consumption rate from deteriorating.

[0005]

According to the present invention, in an internal combustion engine for a vehicle with an automatic transmission, as shown in FIG.
Fuel supply control means A for controlling fuel supply to the internal combustion engine
And a fuel cut signal is generated when the engine speed exceeds a first predetermined value in the deceleration operation state, and the engine speed falls below a second predetermined value on the low rotation side of the first predetermined value. A fuel cut control device for an internal combustion engine, which includes a fuel return signal for restarting fuel supply, performs fuel cut when a fuel cut signal is present, and restores fuel supply by the fuel return signal. In C., means C for detecting a decelerating operation state in which the slope of the downhill changes, and hysteresis changing means for changing the difference between the first predetermined value and the second predetermined value according to the change of the slope are provided. A fuel cut control device for an internal combustion engine is provided.

[0006]

The fuel supply control means A controls the fuel supply to the internal combustion engine, and the fuel cut control means B generates a fuel cut signal when the engine speed exceeds the first predetermined value in the deceleration operation state. , A fuel return signal for restarting fuel supply is generated when the engine speed falls below a second predetermined value on the low rotation side of the first predetermined value, and fuel cut is performed when a fuel cut signal is received. The return signal restores fuel supply.

The decelerating operation state detecting means C detects a decelerating operating state in which the slope of the downhill changes, and the hysteresis changing means D detects the first predetermined value and the second value according to the change of the inclination.
The difference from the predetermined value of is changed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 10 is a cylinder block and 12 is a cylinder block.
Is a piston, 14 is a cylinder head, 16 is a combustion chamber, 1
Reference numeral 8 is an intake valve, 20 is an intake port, 22 is an exhaust valve, 24 is an exhaust port, and 26 is a spark plug. The intake port 20 is provided with a throttle valve 32 through an intake pipe 28 and a surge tank 30.
Connected to. The injector 34 is provided for each cylinder. The center electrode of the distributor 36 is the ignition coil 3
8 and the distribution electrodes are respectively connected to the spark plugs 26 of the corresponding cylinders. The control circuit 40 controls the injector 34 and the igniter 42 in order to perform desired fuel injection control and ignition control. The distributor 36 is provided with crank angle sensors 44 and 46. The crank angle sensor 44 is arranged to face the detection member 48 on the distribution shaft 36a of the distributor 36, and generates a pulse signal at every 30 ° crank angle. The second crank angle sensor 46 is arranged to face the detection member 50 on the distribution shaft 36a of the distributor 36, and generates a pulse signal at every 720 ° of crank angle. Further, a slot sensor 54 is connected to the throttle valve 32, a signal corresponding to the opening degree of the throttle valve 32 is generated, and the control circuit 40
Entered in. An air flow meter 56 is arranged in the intake pipe 28 upstream of the throttle valve 32, and a signal indicating the intake air amount is input to the control circuit 40.

FIG. 3 shows a fuel injection routine, which is executed prior to the fuel injection of each cylinder. This timing is incremented by the arrival of the 30 ° CA signal from the crank angle sensor 44, and the timing from the crank angle sensor 46 to 7.
It can be known by the value of the counter that is cleared by the arrival of the 20 ° CA signal. At step 60, it is judged if the fuel cut flag XFCLL = 1. When XFCLL = 0, the routine proceeds to step 62, where the fuel injection amount TAU suitable for the operation is calculated by the engine speed and the engine speed-intake air amount ratio. In step 64, the fuel injection signal to the injector 34 is formed so that the fuel injection amount according to TAU is obtained.

When XFCLL = 1 in step 60, steps 62 and 64 are bypassed and fuel injection is not performed (fuel cut). FIG. 4 shows a fuel cut control routine in which the fuel cut flag XFCLL is controlled. This routine is executed every fixed time (for example, every 4 milliseconds). Step 7
At 0, it is determined whether or not the idle switch (IDLSW) is ON. IDLSW is O when the throttle valve is in the idle position.
N, OFF when opened from the idle position. IDLSW
When it is OFF (when the throttle valve is not in the idle position), the routine proceeds to step 72, where the counter CLLON is cleared. This counter CLLON is a counter for measuring the duration of time after the throttle valve 32 is returned to the idle position. In step 74, the fuel cut speed N _FC = N _RT +
Set to k ₃ . N _RT + k ₃ is the number of revolutions at which fuel cut is performed in a normal deceleration state, and a predetermined value N _{RT of the} number of revolutions at which the fuel supply state is restored from the fuel cut state.
Is a value obtained by adding the hysteresis amount k ₃ during normal operation. Next, in step 76, the fuel cut flag XFCLL
= 0, and fuel cut is not performed (No in step 60 of FIG. 3).

When the throttle valve 32 is returned to the idle position for deceleration operation and the idle switch is turned on, the routine proceeds from step 70 to step 78, and the counter CLLON is incremented. At step 80, it is judged if CLLON> T. Here, T is the maximum value of the deceleration time on a flat road. Since CLLON ≦ T at first, the routine proceeds to step 82, where it is judged if XFCLL = 1 (fuel cut). If the fuel has not been cut (XFCLL = 0), the routine proceeds to step 84, where it is judged if the engine speed is equal to or higher than the fuel cut speed (Ne> N _FC ). When the engine speed is not equal to or higher than the fuel cut speed (Ne ≦ N _FC ), the routine proceeds to step 76, where XFCLL = 0 and fuel cut is not performed.

In step 84, Ne> N_FCWhen is a slot
The engine speed is N when the valve is in the idle position._FC(= N_RT+
k₃) It is determined that the vehicle is decelerating to perform a higher fuel cut, and the
Proceed to step 86, set XFCLL = 1, and cut fuel.
(Yes in step 60 of FIG. 3). Burning in this way
Next time this routine is executed after starting charge cut operation
If the deceleration operation continues, in step 80 CLLON ≤T
Then, since XFCLL = 1 in step 82, step 88
The fuel cut speed is N_FC= N_FC+ K₂Set to
Be done. Where k₂> K₃Is. That is, the idle swim
After the switch is turned on, it is initially N_FC= N_RT+ K₃(Step
74) Fuel is cut, but once fuel is cut
Then the first fuel cut rotation N_RT+ K₃(Step 74)
Than k₂-K₃Only a large fuel cut rotation is set
It At step 90, if the engine speed is less than the fuel return speed.
Lower (Ne <N_RT) Or not. Ne ≧ N_RTWhen is
Proceed to step 86, XFCLL = 1, and the fuel cut state
Maintained. Ne <N in step 90 _RTWhen, that is, d
Engine speed is fuel return speed N_RTIf you fall below
Proceed to step 76, XFCLL = 0, and fuel cut
Then, the fuel supply state is restored.

If the deceleration state is still continuing, the continuous ON time of the idle switch exceeds the predetermined value while the routine of FIG.
It is judged that CLLON> T, the routine proceeds to step 92, where it is judged if the fuel cut flag XFCLL = 1. When the fuel is cut once after the deceleration operation is started, and then after returning to the fuel supply state and step 92 is passed, the routine proceeds to step 94, the flag XFC = 0 is cleared, the routine proceeds to the step 84 and thereafter, and the engine speed Ne. Is fuel cut rotation N
It is determined whether _FC is exceeded, the second fuel cut processing is performed, and the rotational speed is set in step 88 N _FC =
Fuel cut is performed when N _RT + k ₂ is exceeded. Then, in the next routine, the routine proceeds from step 92 to step 96, but since XFC = 0 is cleared in step 94, the routine proceeds from step 96 to step 98, and the next fuel cut rotational speed N _FC is at that time. It is set to a value (= N _e + k ₁ ) obtained by adding a predetermined value to the engine speed, and step 1
At 00, XFC = 1 is set. Therefore, the next fuel cut rotation speed after the fuel supply is restored is N _FC = N _e + k ₁ set in step 98.

FIG. 5 illustrates the fuel cut operation of the embodiment.
There is. Time t since you entered the downhill road₁And the accelerator pedal
When it is returned and the idle switch is turned on (Fig. 5- (b)),
The value of the counter CLLON is cleared (step 72).
If the engine speed is higher than the initial fuel cut speed
(NE> N_RT+ K₃) Is set by the fuel cut flag XFCLL
Then, the fuel cut is executed (FIG. 5- (c)). At the same time
Fuel cut rotation is N _FC= N_RT+ K₂Set to
Step 88).

At time t ₂ , the engine speed becomes equal to or lower than the fuel return speed (Ne <N _RT ), the fuel cut flag XFCLL is reset (FIG. 5- (c)), and the fuel supply is restored. The engine speed is maintained at a value equal to or lower than the fuel cut rotation N _FC (= N _e + k ₁ ) unless the slope of the downhill road changes. When the slope of the downhill becomes steep at the point A, the engine speed starts to increase, and at time t ₃ , the engine speed becomes larger than the update value (N _RT + k ₂ ) of the fuel cut speed and the fuel cut flag XFCLL. Is set again (Fig. 5- (c)), and the fuel cut is executed again. At the same time, the next fuel cut rotation is N _FC = N
It is set to _e + k ₁ (step 98). Then, at time t ₄ , the engine speed is equal to or lower than the fuel return speed (Ne <N _RT ).
Then, the fuel cut flag XFCLL is reset again (Fig. 5- (c)), and the fuel supply is restored. The engine speed is the fuel cut speed N unless the slope of the downhill road changes.
The value is maintained below _FC (= N _e + k ₁ ).

When the slope of the descending road becomes steeper at point B,
The engine speed starts to increase again, and at time t ₄ , the engine speed becomes larger than the updated value of the fuel cut speed (N _e + k ₁ ), and the fuel cut flag XFCLL is set again (Fig. 5- (c)). , The fuel cut is executed again. At the same time, the next fuel cut rotation is set to N _FC = N _e + k ₁ . Then, when the engine speed becomes equal to or lower than the fuel return rotation (Ne <N _RT ) at time t ₅ , the fuel cut flag XFCLL is reset again (FIG. 5- (c)), and the fuel supply is restored.

FIG. 6 illustrates the prior art, in which the fuel cup
The engine speed is the fuel return speed as an initial value before deceleration.
N_RTSomewhat larger N_FCIs set to, once fuel cut
After going, N_FCSet to + k. Automatic transmission of vehicle
In this case, the increase in engine speed after returning the fuel is not significant.
Therefore, when the value of k is appropriately reduced, the fuel cut rotation N
_FC+ K is easily exceeded, and fuel cut and fuel return are frequent
Repeatedly, there is a problem that hunting occurs. Incidentally, hand
In the case of a dynamic transmission vehicle, there is little change in the number of revolutions, so
Fuel cut rotation N even if the value is small_FCEasy to exceed + k
Hunting does not occur because it does not.

FIG. 7 shows the case where the value of k is made larger than that of FIG. 6, but in this case, even if the engine speed increases after the fuel cut, the fuel cut speed N _FC + k is not exceeded and the fuel is not cut. Therefore, there is a problem that the fuel consumption rate is deteriorated.

[0019]

As described above, according to the present invention, the fuel cut speed is gradually increased at every fuel cut to increase the fuel cut speed, and therefore, when the vehicle is traveling on a downhill road, the fuel consumption is changed every time the tilt changes. The cutting can be performed, and the prevention of hunting and the improvement of fuel consumption efficiency can be balanced.

[Brief description of drawings]

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

FIG. 2 is an overall schematic configuration diagram of an internal combustion engine of an embodiment.

FIG. 3 is a flowchart of a fuel injection routine.

FIG. 4 is a flowchart of a fuel cut routine.

FIG. 5 is a timing diagram illustrating the operation of the embodiment.

FIG. 6 is similar to FIG. 5, but shows a case where the hysteresis is set small in the prior art.

FIG. 7 shows a case where the hysteresis is set large in the same manner as in the prior art.

[Explanation of symbols]

 10 ... Cylinder block 12 ... Piston 16 ... Combustion chamber 18 ... Intake valve 32 ... Throttle valve 34 ... Injector 36 ... Distributor 38 ... Ignition coil 40 ... Control circuit 42 ... Igniter 44, 46 ... Crank angle sensor 56 ... Air flow meter

Claims (1)

[Claims] 1. An internal combustion engine for a vehicle with an automatic transmission,
Fuel supply control means for controlling fuel supply to the internal combustion engine,
A fuel cut signal is generated when the engine speed exceeds a first predetermined value in the deceleration operation state, and fuel is output when the engine speed falls below a second predetermined value on the lower rotation side than the first predetermined value. A fuel cut control device for an internal combustion engine, comprising a fuel cut signal for generating a fuel return signal for resuming supply, performing fuel cut when there is a fuel cut signal, and restoring fuel supply by the fuel return signal, Fuel cut of an internal combustion engine provided with means for detecting a decelerating operation state in which the slope of the slope changes and means for changing the difference between the first predetermined value and the second predetermined value according to the change of the slope. Control device.