JPH0211458B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle that can be driven by having drive wheels rotated by an engine having a fuel cut device in its fuel supply system via an automatic transmission, and particularly to a fuel cut control device thereof.

The fuel cut device is designed to improve fuel efficiency and reduce emissions of unburned harmful substances, since the power from the engine is not actually required during coasting (coasting) with the accelerator pedal released, and engine combustion is not required. , which interrupts the fuel supply to the engine (hereinafter referred to as fuel cut). Various types of fuel cut devices have been proposed in the past, one example of which is shown in FIG.

In this figure, 1 is a fuel injection timing sensor such as an engine crank angle sensor or ignition timing sensor, 2 is an engine cooling water temperature sensor, and 3 is an engine sensor such as a throttle opening sensor, engine intake negative pressure sensor, or engine intake air amount sensor. The load sensor 4 is an accelerator sensor, and the fuel injection timing signal S _t , engine coolant temperature signal S _W , engine load signal S _L and idle signal S _I from these sensors are transmitted to the fuel injection control circuit 100 including the fuel cut control circuit 200 supplied to

Reference numeral 101 denotes an injection pulse determination circuit, which receives signals S _t , S _W , S _L , calculates an injection pulse width corresponding to the optimal fuel supply amount for the operating condition from the signals S _W and S _L , and calculates the injection pulse width corresponding to the optimal fuel supply amount for the operating condition. Signal pulse width fuel injection pulse S _p
Based on S _t , the output is synchronized with the engine rotation. This fuel injection pulse S _p is applied via the driver 102 to open the injector 5 facing the intake system of the engine combustion chamber, and from this injector, an appropriate amount of fuel commensurate with the operating state of the engine is injected into a predetermined amount synchronized with the rotation of the engine. The fuel can be supplied to the engine combustion chamber in time to allow the engine to operate normally and efficiently.

Since the injection timing signal S _t is a pulse signal with a frequency corresponding to the engine rotation speed, the F/V converter 201 converts the frequency of the signal into a voltage and converts the engine rotation speed signal N _V into a fuel cut determination circuit. 202. The reference voltage generation circuit 203 receives the signal _SW , and from this signal supplies reference voltages N _f and N _c corresponding to the engine rotation speed for fuel cut control determination to the fuel cut determination circuit 202 according to the engine cooling water temperature. As shown in Figure 2, the reference voltage N _f is the lower limit of the engine speed at which fuel can be cut, which varies depending on the engine cooling water temperature. This voltage corresponds to the engine speed limit value (fuel recovery speed), which is the fuel recovery speed signal. Further, as shown in FIG. 2, the reference voltage N _c is a voltage corresponding to the engine rotation speed (fuel cut rotation speed) which is set higher than the fuel recovery rotation speed for the purpose of preventing hunting, and is a fuel cut rotation speed signal. In addition, the fuel cut determination circuit 202 receives an idle signal S _I that is at a high (H) level when the accelerator pedal is released, and uses the fuel recovery rotation speed signal N _f as the fuel cut determination criterion while the accelerator pedal is depressed.
When coasting with the accelerator pedal released from the depressed state, the engine speed signal N _V is first compared with the fuel recovery speed signal N _f , and if it is larger than this, the H level fuel cut signal is activated.
S _c is supplied to the injection pulse determination circuit 101 . At this time, the circuit 101 stops outputting the fuel injection pulse S _p , stops opening the injector 5, interrupts the fuel supply, and executes the fuel cut as specified. During the same coasting run, the engine speed signal N _V is the fuel recovery speed signal N _f
If the fuel cut determination circuit 202
The fuel cut signal S _c is set to a low (L) level, causing the injection pulse determining circuit 101 to resume the normal fuel injection control action, and fuel recovery can prevent the occurrence of engine stall. After that, even though coasting is continuing, the engine speed increases due to downhill driving, etc., and the corresponding signal N _V changes to the fuel recovery speed signal N _f
Even if the above occurs, the fuel cut determination circuit 202 does not set the determination reference voltage at the time of fuel recovery.
Since the switch is to N _c , the engine speed signal N _V
Do not set the fuel cut signal S _c to H level unless it exceeds the fuel cut rotation speed signal N _c .
Continuing to supply fuel to the engine, only when the engine rotational speed signal N _V becomes equal to or higher than the fuel cut rotational speed signal N _c , the fuel cut signal S _c is set to the H level again to execute the fuel cut again, and at the same time, the fuel cut judgment circuit 202 is reset, the reference voltage is switched from N _c to N _f again, and the fuel cut described above is performed.

Furthermore, even when the accelerator pedal is depressed once and then released again, and the idle signal S _I changes to the L level and then to the H level again, the fuel cut determination circuit 202 is reset at the same time as the accelerator pedal is depressed, and the determination standard is set. Switch the voltage from N _c to N _f again and repeat the fuel cut described above.

By the way, in a vehicle that can run by transmitting power from an engine equipped with such a fuel cut device to the drive wheels via an automatic transmission, the automatic transmission has a torque converter in its power transmission system. During coasting, the reverse drive force from the drive wheels cannot be directly transmitted to the engine, so when the accelerator pedal is released and the transition is made to coasting, the engine is reversely driven by the drive wheels. The rotation speed drops more rapidly than in cars equipped with a manual transmission, and the fuel recovery rotation speed must be set to a relatively high rotation side to prevent engine stalling, making it easier to perform fuel recovery. This is also the case when the engine is warmed up while the car is stopped, and when the accelerator pedal is released after the engine is idle, the fuel cut is executed and the fuel recovery is performed, but if the fuel is cut again after that, the engine stalls. In order to prevent this, the fuel cut rotation speed, which is the criterion for re-fuel cut, must be set higher than the engine rotation speed during warm-up operation. In the conventional fuel cut control mode, the time required for the fuel cut to be performed while the vehicle is running is short, and the actual situation is that the fuel cut cannot be expected to have a sufficient fuel-saving effect.

In the present invention, when the brakes are applied during coasting, unlike during warm-up operation in a stationary state, the engine is reversely driven by the drive wheels, and the engine is restarted at a fuel recovery rotation speed lower than the fuel cut rotation speed. In order to prevent the engine from stalling even if the fuel cut is performed, when the engine speed once falls below the fuel recovery speed and the fuel is recovered, even if the accelerator pedal is released, if the accelerator pedal is depressed and then released again. supplying a pseudo-idle signal to the fuel cut device and resetting it as described above;
Switching the determination reference voltage from a voltage equivalent to the fuel cut rotation speed (N _c ) to a voltage equivalent to the fuel recovery rotation speed (N _f ), making it possible to perform refueling at a fuel recovery rotation speed lower than the fuel cut rotation speed, This aims to provide a fuel cut control device that significantly extends the fuel cut time and improves the fuel efficiency effect of the fuel cut.

The present invention further provides that when the brakes are applied during coasting, it is more convenient to forcibly downshift the automatic transmission because the engine brake can be used for the braking. Shifting causes an increase in engine speed,
From the viewpoint that the fuel cut time tends to be longer, which is advantageous, under such driving conditions, the square automatic transmission is forcibly downshifted, and in addition, the fuel cut control device using the above-mentioned pseudo idle signal is The present invention also proposes a fuel cut control device that performs a reset operation to make it possible to re-cut the fuel at a fuel recovery rotation speed lower than the fuel cut rotation speed, thereby further extending the fuel cut time significantly and further improving the fuel-saving effect of the fuel cut. It is something.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 3 shows an embodiment of the present invention, in which the same parts as in FIG. 1 are designated by the same reference numerals to avoid redundant explanation thereof.

In the present invention, the idle signal S _I from the accelerator sensor 4 is directly transmitted to the fuel injection control circuit 100 (more specifically, to the fuel cut control circuit 200 in FIG.
The signal is not supplied to the fuel cut determination circuit 202), but is first supplied to the pseudo idle signal generation circuit 300. This circuit 300 has AND gates 301,3
02, consists of an OR gate 303, a mono multivibrator 304, a comparison circuit 305, and a flip-flop circuit 306 as a braking memory circuit,
An idle signal S _I is supplied to one input terminal of the AND gate 301 .

In the present invention, separately, a brake fluid pressure sensor,
A brake sensor 6 such as a brake pedal switch is provided, and this sensor outputs a braking signal S _B of H level when the brake is activated, and outputs this signal when the brake is not activated.
S _B shall be set to L level. A brake signal S _B is applied to the set terminal S of the flip-flop circuit 306, and an idle signal S _I is applied to the reset terminal R of the flip-flop circuit. Flip-flop circuit 9 detects the rise of braking signal S _B (brake operation)
is set and outputs an H level signal from output terminal Q.
It is also assumed that the output terminal Q is reset at the fall of the idle signal S _I (depressing the accelerator pedal) and outputs an L level signal from the output terminal Q.
It is supplied to one input terminal of AND gate 302.

The comparison circuit 305 receives the engine speed signal N _V from the F/V converter 201 (see FIG. 1) of the fuel injection control circuit 100 and the fuel injection control circuit 100.
The fuel recovery rotation speed signal N _f is input from the reference voltage generation circuit 203 (see Fig. 1), and N _V >
When N _f, the high rotation signal S _R of H level is AND gate 3
02, and when N _V <N _f , this signal S _R is turned to L level.

The output signal of the AND gate 302 is supplied to a mono multivibrator 304, and this mono multivibrator normally continues to output an H level signal S _M , but when the output of the AND gate 302 changes to an H level, it synchronizes with the rising edge of the output signal S M. Fixed time output signal
It is assumed that S _M is set to L level and then this output signal S _M is returned to H level.

This signal S _M is ORed with the fuel cut signal S _c output from the fuel cut determination circuit 202 (see FIG. 1) of the fuel injection control circuit 100.
The output signal from the OR gate is supplied to the remaining input terminal of the AND gate 301, and the output signal (pseudo idle signal) S _G from the AND gate 301 is sent to the fuel cut determination circuit of the fuel injection control circuit 100. 202 (see FIG. 1).

The operation of the fuel cut control device of the present invention having the above-described structure will be explained next.

When the accelerator pedal is released and the vehicle starts coasting, the accelerator sensor 4 outputs an idle signal S _I at the H level, and this idle signal is kept at the H level as long as the vehicle is coasting with the accelerator pedal released. If the brake is not operated during coasting, the brake sensor 6 will set the braking signal S _B to L level.
The flip-flop circuit 306 changes the signal from the output terminal Q to L level after the idle signal S _I supplied to its reset terminal R rises. Therefore, upon receiving this signal, the mono multivibrator 304 outputs an H level signal S _M ,
The signal passes through an OR gate 303 and then passes through an AND gate 30.
1. Thus, the AND gate 301 is in H state while coasting without applying the brakes.
The fuel cut determination circuit 20 of the fuel injection control circuit 100 calculates the AND of the high level idle signal S _I and the H level output signal from the OR gate 303.
2 (see FIG. 1) is supplied with an H level output signal S _G. Therefore, during coasting driving without applying the brakes, the same fuel cut as in the conventional device described above is performed.

Here, when the brake is operated, the brake sensor 6 that detects this changes the braking signal S _B to H level, and the flip-flop circuit 306 is set in synchronization with the rise of this signal, and the
The signal going to the AND gate 302 is set to H level, and in this state, even if the brake is deactivated, as long as coasting driving is performed, in other words, when the accelerator pedal is depressed, the vehicle accelerates again and the idle signal goes to the reset terminal R. This will continue unless S _I changes to L level. When the engine rotation speed during braking is equal to or higher than the fuel recovery rotation speed (N _V > N _f ), the comparison circuit 305 outputs an H-level high rotation signal S _R
is supplied to the AND gate 302, which ANDs the output signal of the flip-flop circuit 306 and the high rotation signal S _R , and supplies the mono multivibrator 304 with an H level. At this time, the mono multivibrator 304 outputs an output signal which is normally kept at H level in synchronization with the rising edge of the input signal.
Shifts S _M to L level for a certain period of time. this signal
In S _M , the fuel cut is not being executed at this time, that is, the fuel has already been recovered by the above-mentioned normal fuel cut control during coasting driving without applying the brake, and the fuel cut signal S _c in the fuel injection control circuit 100 is low.
If the fuel cut signal is at the level, the OR gate 303 supplied to one input terminal
Since the output signal level is determined by the signal supplied to the other input terminal, the OR gate 30
3 and is directly supplied to the AND gate 301. Therefore, since the idle signal S _I , which is another input, is kept at H level for coasting driving, the AND gate 301 sends the pseudo idle signal S _G having the same waveform as the signal S _M to the fuel injection control circuit 100. fuel cut determination circuit 202 (first
(see figure). This pseudo idle signal S _G
is at the L level for the above-mentioned period of time from the instant the brake is applied, so it corresponds to a signal that indicates that the accelerator pedal was pressed and then released again even though the driver was coasting with the accelerator pedal released. Then, the determination reference voltage of the fuel cut determination circuit 202 (see FIG. 1) is returned from the fuel cut rotation speed signal N _c to the fuel recovery rotation speed signal N _f .

Therefore, the fuel cut control device of the present invention has the following features:
When the fuel is recovered after the fuel cut during coasting (at this time, the above fuel cut judgment circuit sets the judgment reference voltage to N _f as described above).
When the brake is applied, the pseudo idle signal S _G returns the judgment reference voltage of the fuel cut judgment circuit from N _c to _{the lower N f ,} and the engine speed changes to fuel cut. Even if the number of rotations does not exceed the fuel recovery rotation speed (equivalent to N _f ), the fuel cut can be performed again at a speed equal to or higher than the fuel recovery rotation speed (equivalent to N _f ), and the fuel cut time can be extended to improve the fuel saving effect of the fuel cut. In addition,
This kind of control that enables refueling at a low fuel recovery rotation speed is performed only when braking is applied during coasting, and in this state, the engine is not driving the car with an automatic transmission. Since the engine is reversely driven by the wheels, the engine will not stall even if the fuel is cut off early.

By the way, if the engine speed (N _V ) when the brake is applied during coasting is lower than the fuel recovery speed (N _f ), the AND gate is activated because the comparison circuit 305 sets the high speed signal S _R to L level. 302 does not supply an H level signal to the mono multivibrator 304,
Since the signal S _M is kept at the H level, the above control is not performed, and it is possible to prevent the pseudo idle signal S _G from being generated unnecessarily even in the engine rotation range where there is no possibility of re-fuel cut. Also, when the fuel cut signal S _c is at H level during fuel cut, the OR gate 3
If the output signal level of 03 is kept at H and the above control is not performed, the fuel cut being executed will be temporarily interrupted by the pseudo idle signal S _G , and the fuel cut effect of improving fuel efficiency will be weakened, and the vehicle body will vibrate due to fluctuations in engine output torque. Avoid such inconveniences.

In the above-mentioned example, the flip-flop circuit 306 is provided so that once the brake is activated during coasting, the above effect can be obtained even if the brake is not activated thereafter as long as the vehicle is in the coasting condition. Even if the flip-flop circuit 306 is omitted and the braking signal S _B is directly supplied to the AND gate 302, the same effects as described above can be obtained as long as the brake continues to operate.

Thus, for example, the fuel cut control device of the present invention has the above configuration, and when the brake is activated during coasting, the pseudo idle signal is activated.
S _G returns the fuel cut judgment reference voltage to that corresponding to the fuel recovery rotation speed,
If the engine rotation speed exceeds the fuel recovery rotation speed, which is lower than the fuel cut rotation speed, the fuel cut is executed again after the fuel recovery, so under such driving conditions, the difference between the fuel cut rotation speed and the fuel recovery rotation speed is As mentioned above, even in vehicles equipped with automatic transmissions that have to set both rotational speeds to high values, the fuel cut time can be extended and the fuel efficiency improvement effect of the fuel cut can be improved. .

Note that in the above example, the AND gate 30
2 is directly supplied to the mono multivibrator 304, so that if the condition of N _V > N _f is satisfied when the brake is applied, a pseudo idle signal S _G is generated at the same time as the brake is applied. However, in this case, N _V > N _f and the fuel is immediately re-cut, so if there is a concern that the engine may stall, there is a delay between the AND gate 302 and the mono-multivibrator 304 as shown in FIG. Insert circuit 307 and use this delay circuit.
The L level signal from the AND gate 302 is supplied to the mono multivibrator 304 without any time delay, but the H level signal from the AND gate 302 is supplied to the mono multivibrator 304 with a slight time delay. It is also possible to eliminate the above concerns.

Further, FIG. 5 shows yet another example of the present invention, in which the automatic transmission is forcibly downshifted for the control of the embodiment shown in FIG. 3, and the engine speed is changed by this downshift. In the low rotation range where the rotation speed cannot exceed the fuel recovery rotation speed, the control that should be performed by the device of the present invention is not performed at all.

For this purpose, the downshift solenoid 8 is connected via the driver 7 to the flip-flop circuit 306.
A comparator circuit 9 is provided which is connected to the output terminal Q of the engine and receives the engine speed signal N _V and the fuel recovery speed signal N _f . And comparison circuit 9
is supplied to one input terminal of the AND gate 10 added in this example, and the braking signal S _B from the brake sensor 6 is supplied to the other input terminal of the AND gate 10.
The output terminal of the AND gate 10 is connected to the set terminal S of the flip-flop circuit 306.
Connect to.

The downshift solenoid 8 is already present in ordinary hydraulically controlled automatic transmissions, and although detailed explanation will be omitted here, it functions as outlined below. That is, when the normally open kickdown switch provided in the middle of the accelerator link is closed by pressing the accelerator pedal to its limit position, the downshift solenoid 8 is energized and the downshift valve is actuated. At this time, the automatic transmission automatically selects the immediately lower gear, and uses a large reduction ratio to transmit a large output torque corresponding to the high load to the vehicle drive wheels, making it possible to obtain sufficient acceleration force. Therefore, the automatic transmission can be forcibly downshifted by energizing the downshift solenoid 8, and in this example, the downshift solenoid 8 is used for forcibly downshifting the automatic transmission.

Note that forced downshifts in electronically controlled automatic transmissions are performed by directly operating each shift valve using electrical signals without using the downshift solenoid 8. In this case, too, the downshift solenoid 8 It goes without saying that the automatic transmission can be forced to downshift by a signal directed toward the vehicle.

Also, the comparator circuit 9 converts the input signal N _f to N _f ×I _H /I _L
(However, I _H is the reduction ratio of the high gear, and I _L is the reduction ratio of the low gear selected by downshifting.) and compare this calculation result with the signal N _V , or from the signal N _V. Depending on whether N _V × I _L /I _H is calculated and this calculation result is compared with signal N _f , it is determined whether the engine speed (signal N _V ) can exceed the fuel recovery speed (signal N _f ) during downshift. If so, send an H level signal to the AND gate 10.
Otherwise, it is assumed that an L level signal is output to the AND gate 10.

In the configuration of this example, if the engine speed can exceed the fuel recovery speed due to downshift, the AND gate 10 receives the H level signal from the comparator circuit 9;
The flip-flop circuit 30 is activated only by the braking signal S _B.
The output signal level to be supplied to the set terminal 6 is determined, and the same effect as in the example of FIG. 3 can be achieved. In this example, in addition to this effect, when the brake is applied, the H level signal generated from the output terminal Q of the flip-flop circuit 306 is supplied to the downshift solenoid 8 via the driver 7, and energizes it, so that the automatic transmission is forced to downshifted. This downshift brought the engine speed above the fuel recovery speed even when it was below the fuel recovery speed, and this caused the engine speed to reach the third level even when the engine speed was less than the fuel recovery speed.
The same effects as in the illustrated example can be achieved, the fuel cut time can be further extended, and the fuel efficiency improvement effect of the fuel cut can be further improved. Further, since this downshift occurs in a driving state in which the brake is applied during coasting, the engine braking caused by the downshift can be used for the braking, which is more convenient.

However, in the low engine speed range where the engine speed cannot exceed the fuel recovery speed even by downshifting, the signal level from the comparator circuit 9 to the AND gate 10 is L, so the AND gate 1
0 is an L level signal to the flip-flop circuit 306
The signal continues to be supplied to the set terminal S, and not only the same control as in the example of FIG. 3 is performed, but also no downshift is performed. Therefore, in the low rotation range where there is no possibility of re-cutting the fuel and the effect of extending the fuel cut time by the device of this example cannot be expected, it is possible to prevent the device of this example from operating unnecessarily, and at this time, it is possible to prevent the device from downshifting. If this is done, the fuel cannot be re-cut, and the increase in engine speed due to the downshift will result in poor fuel efficiency, but this inconvenience can be avoided by not performing the downshift.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional fuel cut device, Fig. 2 is a diagram showing the fuel cut rotation speed and fuel recovery rotation speed of the same device,
FIG. 3 is a block diagram of a fuel cut device equipped with the fuel cut control device of the present invention, and FIGS. 4 and 5 are block diagrams similar to FIG. 3 showing two other examples of the present invention, respectively. 1...Fuel injection timing sensor, 2...Engine coolant temperature sensor, 3...Engine load sensor, 4...
...Accelerator sensor, 5...Injector, 6...
Brake sensor, 7... Driver, 8... Downshift solenoid, 9... Comparison circuit, 10...
AND gate, 100...Fuel injection control circuit, 3
00...pseudo idle signal generation circuit, 301,3
02...AND gate, 303...OR gate, 3
04... Mono multivibrator, 305... Comparison circuit, 306... Braking memory circuit, 307... Delay circuit.

Claims (1)

[Scope of Claims] 1. When the accelerator pedal is released, an idle signal corresponding to this interrupts fuel supply to the engine while the engine speed is above the fuel recovery speed, and when the engine speed becomes below the fuel recovery speed, the fuel supply is stopped. If the gas supply is restarted and the accelerator pedal is still released, when the engine speed exceeds the fuel cut speed, which is set higher than the fuel recovery speed, the fuel supply to the engine is interrupted again and the gas pedal is once depressed. If the vehicle is released again after the fuel recovery, the vehicle can be driven via an automatic transmission with an engine equipped with a fuel cut device that interrupts the fuel supply to the engine again under the condition that the engine speed is equal to or higher than the fuel recovery speed. In a vehicle, a brake sensor is provided that detects the operation of the brake and issues a braking signal, and a comparison circuit is provided that detects when the engine rotation speed has become equal to or higher than the fuel recovery rotation speed and issues a high rotation signal, The present invention is characterized in that a pseudo-idle signal generating circuit is provided for supplying a pseudo-idle signal to the fuel cut device from the signal and the high-speed rotation signal, which corresponds to the fact that the accelerator pedal is depressed and then released again even if the accelerator pedal is released. Fuel cut control device for engines for vehicles equipped with automatic transmissions. 2. The fuel cut control device for an engine for a vehicle equipped with an automatic transmission according to claim 1, wherein the braking signal continues to be output as long as the idle signal remains even after the brake is deactivated. 3. Fuel cut control for an engine for a vehicle equipped with an automatic transmission according to claim 1 or 2, wherein the pseudo idle signal is generated with a certain time delay from the braking signal and the high rotation signal. Device. 4. The fuel cut control device for an engine for a vehicle equipped with an automatic transmission according to any one of claims 1 to 3, wherein the pseudo idle signal is not generated during an interruption of fuel supply. 5 When the accelerator pedal is released, the corresponding idle signal interrupts the fuel supply to the engine while the engine speed is above the fuel recovery speed, and when the engine speed falls below the fuel recovery speed, the fuel supply is resumed and the accelerator is released. If the pedal remains released, the fuel supply will be interrupted again when the engine speed exceeds the fuel cut speed, which is set higher than the fuel recovery speed.
If the accelerator pedal is once depressed and then released again, the engine is equipped with a fuel cut device that automatically interrupts the fuel supply to the engine under the condition that the engine speed is equal to or higher than the fuel recovery speed. In a vehicle that can run via a transmission, a brake sensor is provided that detects the operation of the brakes and issues a braking signal, and also detects that the engine rotation speed has exceeded the fuel recovery rotation speed and issues a high rotation signal. A comparison circuit is provided, and the automatic transmission is downshifted by the braking signal, and from the braking signal and the high rotational speed signal, a pseudo-idling signal corresponding to the case where the accelerator pedal is released even after being depressed is released again. A fuel cut control device for an engine for a vehicle equipped with an automatic transmission, characterized in that a pseudo idle signal generation circuit is provided for supplying a signal to the fuel cut device. 6. The fuel cut control device for an engine for a vehicle equipped with an automatic transmission according to claim 5, wherein the braking signal continues to be output as long as the idle signal remains even after the brake is deactivated. 7. The fuel cut control device for an engine for a vehicle equipped with an automatic transmission according to claim 5 or 6, wherein the pseudo idle signal is not generated during interruption of fuel supply. 8. Claims 5 to 7, wherein the transmission path of the braking signal is cut off in a low engine rotation range where the fuel recovery rotation speed cannot be reached even by downshifting the automatic transmission. A fuel cut control device for an engine for a vehicle equipped with an automatic transmission according to any one of the above.