JPS5857048A - Fuel cut control device of vehicle engine with automatic speed change gear - Google Patents

Abstract

PURPOSE:To improve the fuel consumption saving effect remarkably by making the fuel cut feasible again at a fuel recover engine speed lower than a fuel cut engine speed when an automatic speed change gear is down shifted in response to a braking operation. CONSTITUTION:A fuel cut control circuit interrupting the fuel feed while an engine speed is equal to or more than a fuel recover engine speed when an accelerator pedal is released is provided in a fuel injection control circuit 100 which is fed with individual signals from a fuel injection time sensor 1, cooling water temperature sensor 2, engine load sensor 3, and accelerator pedal sensor 4. A pseudo-idle signal generator circuit 300 is also provided. Then, when an idle signal S1 from the above-mentioned sensor 4 and a braking signal SB from a brake sensor 6 are input, a down shift solenoid 8 is actuated and also a pseudo-idle signal is generated corresponding to that occurring if the accelerator pedal is depressed at a predetermined time lag and is again released.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle that is equipped with a fuel cut device in the fuel supply system and can be driven by rotating drive wheels from an engine through an automatic transmission, and particularly relates to a fuel cut control device for the vehicle. It is something.

With the fuel cut device, the power from the engine is actually unnecessary during coasting (coasting) when the accelerator pedal is released, and the engine does not burn as much! Therefore, the fuel supply to the engine is interrupted (hereinafter referred to as fuel cut) for the purpose of improving fuel efficiency and suppressing the emission of unburned harmful substances. Various types of fuel cut devices have been proposed in the past, one example of which is shown in FIG.

In this figure, l is the engine crank angle sensor, ignition timing sensor, fuel injection timing sensor, c is the engine cooling water temperature sensor, and 3 is the engine such as the throttle opening sensor, engine intake negative pressure sensor, engine intake air amount sensor, etc. The load sensor is the accelerator pedal sensor, and the fuel injection timing signal 8t1 from these sensors is the engine cooling water temperature signal Sw1.
The engine load signal SI and the idle signal S□ are the fuel injection control circuit 1 including the fuel cut control circuit -〇〇
00.

10/ is an injection pulse determining circuit, and this circuit receives signals 8,
, ay, and SL are input, and the injection pulse width corresponding to the optimum fuel supply for the operating condition is calculated from the signals sw and sL, and the fuel injection pulse Sp having the pulse width is inputted to the signal St.
Based on this, the output is synchronized with the rotation of the engine. Through this fuel injection pulse S, +2 dry/(102), the injector j in the intake system of the engine combustion chamber is opened, and an appropriate amount of fuel commensurate with the operating state of the engine is injected from this injector into the engine. It is possible to supply the fuel to the engine combustion chamber at a predetermined time synchronized with the cloud, and to operate the engine efficiently as usual.

Since the injection timing signal St is a pulse signal with a frequency corresponding to the engine speed, the F/v converter 201 converts the frequency of the signal into a voltage and performs a fuel cut on the engine speed signal Nv. Supplied to the judgment circuit O-. The reference voltage generation circuit OJ receives the signal SW, and from this signal, it sends the reference voltages N, , N, corresponding to the engine rotation speed cloud for fuel cut control judgment to the fuel cut judgment circuit -〇- according to the engine cooling water temperature. supply The reference voltage category is the lower limit of the engine speed at which fuel can be cut, which varies depending on the engine cooling water temperature, as shown in Figure 1. In other words, if the engine speed is below this, the fuel supply will be restarted (hereinafter referred to as fuel recovery). This voltage corresponds to the limit value of the engine speed (fuel recovery speed) at which the engine stalls even if the engine is stopped, and is the fuel recovery speed signal. Also, as shown in Figure 2, the reference voltage N0 is a voltage corresponding to the engine rotation speed (fuel cut rotation speed), which is set on the higher rotation side than the fuel recovery @ number for the purpose of preventing hunting. This is the rotation speed signal. Fuel cut judgment circuit-O
In addition, during coasting driving when the accelerator pedal is released, the engine speed signal N is input.
If v is the fuel recovery rotational speed signal MN, if it is thicker, H
A level fuel cut signal S0 is supplied to the injection pulse determining circuit 10/f. At this time, the cough circuit 10/ stops outputting the fuel injection pulse Sp, does not open the injector j, interrupts the fuel supply, and executes the fuel cut as specified. During the same coasting run, the engine speed signal N■ is the fuel recovery speed signal N.
If the cloud becomes cloudy, the fuel cut determination circuit Oλ sets the fuel cut signal S0 to a low (L) level to cause the injection pulse determination circuit 10/ to resume the normal fuel injection control action, thereby recovering the fuel and causing an engine stall. can be prevented. After fuel recovery, even if the engine speed rises while coasting, due to cloudy weather or driving down the board, and the corresponding signal N becomes higher than the fuel recovery speed signal Nf, the fuel The cut determination circuit 02 sets the determination reference voltage to No.
Therefore, unless the engine speed signal Ny exceeds the fuel cut speed signal N0, the fuel cut signal S0 cannot be raised to the H level, fuel supply to the engine continues, and the engine speed signal Nv changes to the fuel cut signal N0. When the cut rotation speed signal N0 or higher, the fuel cut signal S0 is set to H level again to execute the fuel cut again, and the judgment reference voltage is changed from 7i-No to Nfl again, and the engine rotation speed signal Nv becomes the fuel recovery rotation speed. Maintain the signal N until it becomes below.

On the other hand, when the accelerator pedal is pressed once and then released again, and the idle signal SI goes to the L level, then changes to the H level again, the engine speed signal N■ is equal to or higher than the fuel cut speed signal N0. The fuel cut judgment circuit λO, which depends on whether or not it is reset, changes the judgment reference voltage from N to N.

switch again and repeat the fuel cut described above.

By the way, if the vehicle is capable of driving by transmitting the power from the engine with such a fuel cut*t+ to the driving wheels via the automatic transmission, the automatic transmission will not be able to transfer the power. Since the transmission system is equipped with a torque converter, it is difficult to transmit the reverse drive force from the drive wheels to the engine during coasting, so when the accelerator pedal is released and the transition is made to coasting, the engine speed drops. This is more rapid than in a car equipped with a manual transmission, and the fuel recovery rotation speed must be set to a relatively high rotation speed to prevent engine stalling. When you release the accelerator pedal after revving during warm-up, a fuel cut is performed and then fuel recovery is performed, but if the fuel is cut again after that, the engine will stall, so this is to prevent this. Due to the fact that the fuel cut rotation speed, which is the criterion for refueling, needs to be set higher than the engine rotation speed during warm-up operation, the conventional fuel cut method performs the same control both when the vehicle is stopped and when the vehicle is running. In the control mode, the fuel cut time is short, and it is a pity that we cannot expect sufficient fuel-saving effects.

In the present invention, when braking is to be applied by operating the brakes while coasting, it is more convenient to forcibly downshift the automatic transmission so that the engine brake can be used for this downshift. From the viewpoint that shifting causes an increase in engine speed and tends to lengthen the fuel cut time, it is convenient to use the automatic transmission under such driving conditions. In a coasting driving condition where the driver downshifts and then applies the brakes near the fuel recovery speed,
It has been found that even if the engine rotation speed is below the normal fuel recovery rotation speed, it will still exceed the fuel recovery rotation speed from the town shift number even if it falls below the fuel recovery rotation speed due to the delay in hydraulic operation during downshift. In addition, in this driving condition, the engine is being driven in reverse, so even if the accelerator pedal is released, the engine will not stall even if the fuel is cut again at the fuel recovery speed. A pseudo-idle signal is supplied to the fuel cut device, which indicates that the idle signal is released again after the engine has been pressed, and this is reset as described above. It is an object of the present invention to provide a fuel cut control device that can execute a refuel cut at a low fuel recovery rotation speed, thereby significantly extending the fuel cut time and improving the fuel efficiency effect of the fuel cut.

The present invention will be described in detail below with reference to the illustrated embodiments.

FIG. 3 shows an embodiment of the present invention, in which the same parts as in FIG. The idle signal from V is sent directly to the fuel injection control circuit.

(For details, refer to the fuel cut determination circuit 20 of the fuel cut control circuit QO in FIG. 1).

This circuit is delay circuit 3011 mono multivibrator J
Consists of Oco and AND gate 303, AND gate J
One input terminal of OJ is supplied with a cloudy idle signal S. In the present invention, a brake sensor t such as a brake fluid pressure sensor or a brake pedal switch is separately provided, and this sensor outputs a braking signal SB at H level when the brake is activated. This braking signal SB is supplied via a driver 7 to a downshift solenoid r+ of a homemade transmission on the one hand, and to a delay circuit 30/l on the other hand. delay circuit 3oi
immediately sets the level of the output signal S to L when the brake signal SB goes to L level due to non-operation of the brake, and the brake signal 5
As long as it is at the BfJSL level, the L level output signal 8D is continued to be output, and when the braking signal 8B switches to the H level due to brake operation, the level of the output signal SD is changed to HK after a delay of a predetermined time (details will be described later). , then the braking signal SB
As long as the output signal SD remains at the H level, the output signal SD at the H level continues to be output. The output signal SD of the delay circuit JO/ is supplied to the mono multivibrator 102, and this vibrator synchronizes with the rise of the output signal SD from the delay circuit JO/ and outputs the output signal SG at the L level for a certain period of time to the AND gate JO.
The remaining input terminals of J and the output signal S in the otherwise normal state. is kept at H level.

Downshift solenoid r G2 This is a conventional hydraulically controlled automatic transmission number, and although a detailed explanation will be omitted here, it functions as follows. That is, when the accelerator pedal is depressed to its limit position, the normally open kickdown switch provided in the middle of the accelerator link is closed, and then the downshift solenoid 1 is energized to operate the town shift valve. At this time, the automatic transmission normally automatically selects the immediately lower gear (or lower depending on the vehicle speed), and uses a large reduction ratio to transmit the large output torque that corresponds to the high load to the vehicle drive wheels to provide sufficient acceleration. You can gain power. Therefore, the automatic transmission can be forced to downshift by energizing the town shift solenoid t, and in this example, the downshift solenoid t is used for downshifting the automatic transmission.

By the way, there is a slight time lag until the downshift solenoid t is energized and the town shift of the self-made transmission is actually completed, due to the hydraulic activation delay of the automatic transmission, and the delay circuit JO/ The time delay is set as a time corresponding to this time lag, so that the signal SD is set after the downshift of the automatic transmission is completed, and the output signal SG of the negative polarity pulse is generated. Also, instead of keeping the time delay of the delay circuit JO/ constant as described above, the time delay of the brake signal S
It is also possible to change the timing to be different depending on the number of engine revolutions at the start of B (when the brake is applied).

Note that downshifts in electronically controlled automatic transmissions are performed by directly operating the base shift valve using a combination of electrical signals corresponding to each gear stage, without using the downshift solenoid l. It goes without saying that in the present invention, the automatic transmission can be forcibly downshifted by a signal sent to the downshift solenoid 1. The operation of the fuel cut control device of the present invention having the above-described structure will now be described.

When the accelerator pedal is released and the vehicle starts coasting, the accelerator pedal sensor outputs a high-level idle signal S as shown in the figure.
This idle signal is kept at H level as long as the vehicle is coasting with the accelerator pedal released. However, as long as the brake is not activated and the braking signal is at SB or L level, the 30 mono multivibrators keep the output signal SG at H level as described above, so the signal S and SG are removed. 30J continues to supply the H level signal to the fuel injection control circuit ioo, and this circuit 100
During coasting driving without applying the brakes, the system executes fuel cut control similar to the conventional system described above.

On the other hand, since the braking signal SB is kept at the L level in this way, it is impossible for this to energize the downshift solenoid l. The information can be transmitted to drive the vehicle.

When the brake is actuated here, the brake sensor t detecting this changes the braking signal SB to H level φ at the moment of brake actuation tw i as shown in Figure V.

On the other hand, this H-level braking signal SB becomes an energizing signal for the downshift solenoid 1 as shown in Fig. 1, and is supplied to the downshift solenoid t via the driver 7, which downshifts in synchronization with the rise of the braking signal SB. Solenoid l is energized.

As a result, the automatic transmission performs a downshift, but due to the response delay of the hydraulic operation of the downshift μ automatic transmission, the downshift is completed with a slight time delay from the instant t2. Such a downshift enables the use of a large engine brake that activates the brakes during coasting, providing sufficient braking force to enable rapid deceleration. The downshift causes an increase in engine speed, which makes it possible to extend the fuel cut time in a region where the engine speed is high.

On the other hand, the braking signal SB is supplied to a delay circuit 101, and the scissor delay circuit is configured to detect the rising instant t of the braking signal 8B as shown in FIG.
2, outputs a reserve position Sp that rises at an instant tS + t which is delayed by a time t corresponding to the response delay of the automatic transmission. Mono multivibrator 3 to which this signal SD is input
0 outputs an L level output signal SG for a certain period of time as shown in FIG. 1 in synchronization with the rise of the signal SD. At this time, JOJ calculates the product of the output signal SG and the idle signal S, as shown in Figure 1, the output signal that is kept at H level after the idle signal S rises. The L level is maintained at 1 for a certain period of time t3'lk at instant t3'lk, and a pseudo idle signal is generated in which the accelerator pedal is depressed and then released again, and this is supplied to the fuel injection control circuit 100.

When the fuel injection control circuit ioo, specifically the fuel cut determination circuit λ02 shown in FIG. 1, receives the above-mentioned pseudo-idle signal, the signal rises (instant 1 in FIG. 1).
+ synchronously, set the judgment reference voltage to N. Switch from to N (see Figure 1 for both). Therefore, in a coasting driving state in which the brake is operated near the fuel recovery rotation speed (reference voltage N, equivalent), the engine rotation speed is 1 or more than the fuel recovery rotation speed, or the hydraulic operation of town shift occurs. Due to the delay, the rotation speed is temporarily lower than the fuel recovery speed, so even if the fuel is recovered, the judgment reference voltage is changed from Nf at the time of coasting transition to N. The fuel cut judgment circuit JOJ (see Figure 1) changes the judgment reference voltage from N to Nf again.
Rather than switching to , it is reset by the pseudo idle signal.

On the other hand, the downshift of the own wJgIL speed machine increases the engine rotation speed during such coasting and makes it higher than the fuel recovery rotation speed, and also the fuel cut judgment circuit -〇- (see 1st all). Since the determination reference voltage is switched to N, even if the engine rotation speed does not exceed the fuel recovery rotation speed, re-fuel cut is executed when the engine rotation speed exceeds the fuel recovery rotation speed.

(For example, when the fuel cut control device of the present invention is configured as described above, and during coasting driving where the brakes are not activated, the automatic transmission is downshifted to reduce the engine speed to below the recovery speed of 7 units. Even after the engine speed drops to 6 degrees, the fuel cut judgment reference voltage is returned to the one equivalent to the fuel recovery speed using a pseudo idle signal.Thus, at the point when the engine speed exceeds the fuel recovery speed, Since the fuel was set to be re-cut, under such driving conditions, the fuel-recovery rotation speed and the fuel cut-off rotation speed will also be re-cut. Even if the number of vehicles equipped with an automatic transmission is unavoidable, the fuel cut time can be extended and the fuel efficiency improvement effect of the fuel cut can be improved. FIG. 3 shows another example of the present invention, In this example, braking signal 8B
is supplied to a set terminal S of a flip-flop circuit serving as a brake storage circuit, and an idle signal SI is supplied to a reset terminal R of the flip-flop circuit. The flip-flop circuit is triggered by the rise of the braking signal SB (brake activation).
It is set at
, and an L level signal is output from the output terminal Q, and this output signal is passed through the driver 7 to the downshift solenoid L on one side, and the delay circuit JO/( of the pseudo idle signal generation circuit JOO) on the other hand. @Refer to Figure 3).

In this example device in hot weather, once the brake is activated during coasting, even if the brake is not activated, the output signal from the flip-flop circuit remains at H level unless the accelerator pedal is pressed to accelerate. In order to maintain this, even if the brake is activated once and then deactivated, the H level output signal continues to energize the downshift solenoid l via the driver 7. Therefore,
Even when the brake is not activated, the automatic transmission maintains a downshift state and increases the engine speed to continue the arc length effect of the fuel cut time, and effectively decelerates the vehicle by engine braking. -I can do this. By the way, is this a flip-flop circuit? A signal opposite to the pseudo idle signal generating circuit 300 causes this circuit JOO to have a clouding effect in the same manner as described above, and the object of the present invention can be achieved in the same manner as in the previously described embodiment.

Figure 5 shows another example of the present invention, and in this example, the structure M of Figure 5 is shown.
, the pseudo idle signal generation circuit JOO
An OR gate 3011 is added in the fuel injection control circuit 100, and one input terminal is connected to the signal S(,) from the multivibrator 302, and the other input terminal is connected to the fuel cut circuit in the fuel injection control circuit 100. The fuel cut signal (ts (when this is at H level, the fuel cut) is supplied completely from the fuel cut signal (see Figure 7), and the output of the OR gate 30≠ is supplied to the All gate 303. During the fuel cut when the fuel cut signal S0 goes to H level, the pulse signal SG of negative polarity goes to O during the time period t3 to t4 in Figure 1.
R game) Even if the OR gate is supplied to 30μ, the signal S. , SG and continues to output an H level signal, the AND game 1303 cannot output the pseudo idle signal. Therefore, even if the fuel gets cloudy during the fuel cut, the fuel cut is temporarily interrupted by a pseudo idle signal, reducing the fuel efficiency improvement effect due to the fuel cut, and the engine output torque fluctuates, causing the vehicle body to vibrate. This inconvenience can be avoided. Note that while the fuel cut signal S0 is at L level and not during fuel cut, the OR gate JO4c is set to the signal S. The device of this example functions to supply the data as it is to the MND game (MUND game), and the device of this example can achieve the same operation and effect as the configuration shown in FIG.

FIG. 7 shows still another example of the present invention. In this example, the configuration shown in FIG. In the low rotation range where the recovery rotation speed cannot be exceeded, the effect of extending the fuel cut time on each side can be desired. Conversely, if a downshift is performed at this time, the resulting increase in engine rotation speed will worsen fuel efficiency. (For this reason, the above control is not performed at all.

For this purpose, the comparator circuit 101 receives the engine speed signal Ny from the fuel injection control circuit ioo, the engine speed signal Ny from the converter 01 (see FIG. 1), and the reference voltage generation circuit also in the fuel injection control circuit ioo. Ko OJ (
The fuel recovery rotational speed signal N from the engine (see Fig. 1) is input. Comparison circuit io is signal wing, from N, X I
H/I, (where □ is the deceleration Jk of the high gear position, and IL is the reduction ratio of the low gear position immediately below the gear position with the reduction specific gravity H) and compare this calculation result with the signal NV, or or signal Nv
From this, calculate N■×Work L/H and send this calculation result to the signal N
, the engine speed (signal Ny
) is the fuel recovery rotation speed during downshift (signal N,
), and if so, the AND gate//i high level signal, and if not, the AND gate
It is assumed that gate l1 outputs an L level signal.

Thus, in the configuration of this example, if the engine speed can exceed the fuel recovery speed due to downshifting, the AND gate // receives an H level signal from the comparator circuit IO. Therefore, only the braking signal SB determines the signal level opposite the set terminal S# of the flip-flop circuit. In the low rotation range where the fuel recovery rotation speed is not exceeded even if
/ continues to supply the L level signal to the set terminal of the flip-flop circuit t, and the control described above in FIG. 2 can be prevented from being performed at all. Therefore, the example device operates in a region where the engine speed does not exceed the fuel recovery speed even if the number of downshifts increases, that is, in a low speed range where re-fuel cut is not performed even when the engine speed increases due to a downshift. It is possible to prevent the automatic transmission from being needlessly downshifted and resulting in a decrease in fuel efficiency due to the increase in engine speed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional fuel cut device, Fig. 1 is a diagram showing the fuel cut rotation speed and fuel recovery rotation speed of the same device, and Fig. 3 is a diagram showing a fuel cut control device equipped with the fuel cut control device of the present invention. A block diagram of the cutting device, FIG. 1 is a time chart of various signals in the device, and FIGS.
FIG. 4 is a block diagram similar to FIG. 3 illustrating an example; I... Fuel injection timing sensor, -... Engine cooling water temperature sensor, 3... Engine load sensor, Reference... Accelerator pedal 7t LASA,!・Injector, 6. Brake sensor, 7. Driver, L. Downshift solenoid, Na.
...Brake storage circuit, lO...comparison circuit, ll...A
ND game'F, 100...Fuel injection control circuit, 300
...pseudo idle signal generation circuit, JO/...delay circuit, 30 pieces...mono multivibrator, 301...A
ND gate, 304c...OR gate. Patent applicant Nissan Jitaita Co., Ltd. Figure 2 Figure 4 Figure 7 = 248

Claims (1)

[Claims] L: 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 is below the fuel recovery speed. In this case, the engine is equipped with a fuel cut device that restarts the fuel supply, and then interrupts the fuel supply again when the fuel cut rotation speed exceeds the fuel recovery rotation speed, through an automatic transmission with a downshift mechanism. In a vehicle capable of running at a speed, a brake sensor is provided to detect the operation of the brake, and the automatic transmission is downshifted by a braking signal from the sensor, and a sufficient time delay is caused from the output of the brake m*. For a vehicle equipped with an automatic transmission, the fuel cut device is configured to supply a pseudo idle signal corresponding to when the accelerator pedal is depressed and then released again even if the accelerator pedal is released. Engine fuel cut control device. 2. The engine for a vehicle equipped with an automatic transmission according to claim 1, wherein the downshift of the automatic transmission and the output of the pseudo idle signal are executed as long as the idle signal does not disappear even after the brake is deactivated. Fuel control device. A fuel cut control device for an engine for a vehicle equipped with an automatic transmission according to claim 1 or 2, wherein the pseudo idle signal is arranged not to be supplied to the fuel cut device while fuel supply is interrupted. The downshift of the automatic transmission and the output of the pseudo-idle signal are prevented from being performed in a low engine speed range where the fuel recovery speed cannot be reached even after downshifting the automatic transmission. A fuel cut control device for an engine for a vehicle equipped with an automatic transmission as set forth in any one of items 1 to 143.