JPH0610456B2 - Fuel cut system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel cut system mainly applied to an automobile.

[Prior Art] In recent years, many automobile engines are equipped with a fuel cut system that cuts fuel during deceleration in order to improve fuel economy.

As a prior art relating to this type of fuel cut system, as shown in Japanese Patent Application No. 57-189414 filed earlier, a fuel cut valve is provided in the middle of the slow passage and the closing position for the throttle is used for normal idling operation. A carburetor that is set closer to the closing side than the closed position corresponding to the state, an actuator attached to this carburetor that shifts the closed position of the throttle valve to a predetermined idle-up position during operation, and a throttle opening Idle switch that outputs an open signal when the degree is on the open side and a close signal when the degree is on the close side, and a high-speed signal is output when the engine speed exceeds the set speed. If a closing signal is output from the rotation sensor that outputs a low speed signal when it goes down and the idle switch There are those comprising a fuel cut control means for switching the fuel cut valve as a prerequisite that the high-speed signal from the rotation sensor is output to the operating state of the actuator with switching to fuel cut position.

[Problems to be Solved by the Invention] However, in this device, the set rotation speed of the rotation sensor is set to, for example, about 1200 rpm, and the fuel cut is released when the engine is lower than the rotation speed. There is. Therefore, there is a problem that the fuel cut region is relatively narrow and fuel saving is insufficient. That is, in such a system, unless the throttle opening at which the idle switch switches to the closing signal output state is set to the opening side from the idle up position, the vehicle enters a deceleration state and a fuel cut occurs. Immediately after the idle-up is performed, the idle switch is switched to cancel the fuel cut and chattering occurs. The idle switch may also serve as a switch for determining the idle state in the feedback carburetor, and in this case, the switching set value is naturally restricted within a certain range. As described above, since there are many restrictions on the set value of the idle switch, it is difficult to set the return rotation speed of the fuel cut to a low value. Therefore, in such a conventional system, the return rotation for canceling the fuel cut is performed. As described above, the number had to be as high as 1200 rpm.

In order to deal with such a problem, it is conceivable to remove the idle-up function from the fuel cut mechanism and set the return rotation speed for canceling the fuel cut to a value lower than 1200 rpm. By doing so, since the chattering described above is not caused, the fuel cut area can be expanded.
If only this is used, engine stalling is likely to occur when the clutch pedal is depressed, etc., making it unusable for practical use.

The present invention was made in view of such circumstances,
In the carburetor type engine in which the distance from the fuel supply position to the combustion chamber must be relatively long, the operating range in which engine stall easily occurs when the return speed is set to a low value will be described later. The intermediate operating range and the operating range immediately below the return speed are specified, and the specified operating range and other operating ranges are controlled separately, and the fuel to be executed during the control is also specified. By making it possible to quickly replenish the fuel using a piston pump, the fuel cut area can be substantially expanded while preventing engine stalling, and overall fuel economy can be improved without problems. The purpose is to provide a possible fuel cut system.

[Means for Solving the Problems] In order to achieve such an object, the present invention is a fuel cut system applied to a vehicle engine equipped with a carburetor, in which fuel cut is performed during deceleration of the vehicle and the engine is At the same time as the fuel cut, the fuel cut mechanism is configured so that the fuel cut can be released when the rotation speed falls below a predetermined return rotation speed and when the transmission relationship between the engine and the wheel is broken. In addition to eliminating the function to perform idle-up, the engine speed and the engine stall limit rotational speed that exists slightly higher than the engine rotational speed (the engine-wheel transmission relationship is suddenly cut off during fuel cut). It means the minimum value in the rotation speed that does not cause engine stall. The same shall apply hereafter) or When the transmission relationship between the engine and the wheel is broken in the operating range immediately after the speed falls below the return speed, the piston pump is operated to supply the required amount of fuel to the existing fuel supply provided in the carburetor. The engine is supplied from an auxiliary fuel supply path that is different from the path, or the required amount of fuel is supplied to the engine from an auxiliary fuel supply path that is different from the existing fuel supply path provided in the carburetor, and at the same time throttle is applied. A feature is that a mechanism for opening the valve by a required angle is provided. In addition,
The present invention is premised on a carburetor engine in which auxiliary fuel is supplied from an auxiliary fuel supply path to a portion of the carburetor upstream of the throttle valve. That is, in the carburetor type engine, the fuel supply position tends to be relatively far from the combustion chamber, and the engine stall tends to be a problem when the fuel is returned from the fuel cut. Moreover, in order to prevent such engine stalling, connecting the auxiliary fuel supply path downstream from the throttle valve of the carburetor is special in the intake manifold and intake port when supplying auxiliary fuel. It is difficult unless you adopt a simple structure. That is, in the carburetor engine, it is effective to provide the auxiliary fuel supply path upstream of the throttle valve in order to prevent the structure from becoming complicated, and the present invention is based on this structure. There is.

[Operation] With such a configuration, the fuel cut is executed when the vehicle is decelerated. Then, when the number of revolutions of the engine falls below the predetermined return number of revolutions and when the transmission relationship between the engine and the wheels is broken by the depression operation of the clutch pedal or the like, the fuel cut state is released, Fuel begins to be supplied from the slow port of the carburetor.

When the fuel cut is released on condition that the transmission relationship between the engine and the wheels is broken, the auxiliary fuel may be supplied from a special auxiliary fuel supply path. That is, if the transmission relationship is broken in the above-mentioned intermediate operating range or in the operating range immediately after the speed falls below the return rotational speed, the fuel supply mechanism works to supply the required amount of fuel to the engine and the fuel. The cut is released. This refueling is performed through an auxiliary fuel supply path different from the existing fuel supply path provided in the carburetor, so that the auxiliary fuel can be quickly replenished at the moment when the transmission state is cut off. Therefore, even if the return rotational speed is set to a low value, it is possible to eliminate the problem that engine stall occurs immediately after the reverse driving force from the wheels to the engine is cut off due to the fuel return delay. This refueling is performed only in the operating range immediately below the intermediate and return rotational speeds that may cause an engine stall, and in other operating ranges, wasteful refueling is not performed. That is, the intermediate operating range described above is a narrow operating range between the return engine speed and the engine stall avoidance limit engine speed, and the operating range immediately after the return engine speed falls below the return engine speed is limited in time. Area. Therefore, if the auxiliary fuel is supplied only in such a specific operation range, the engine stall can be effectively prevented by the minimum required refueling, and the return speed can be reasonably set to a low value. You can As a result, the fuel cut region can be expanded without any problem, and the fuel economy effect as a whole can be improved by the fuel saving effect resulting from the expansion of the fuel cut region.

Since the auxiliary fuel supply path is communicated with the upstream portion of the carburetor throttle valve as described above, the distance between the auxiliary fuel supply path and the combustion chamber must be relatively large. Absent. However, in the present invention, since the fuel is forcibly supplied to the auxiliary fuel supply path by using the piston pump, for example, in the case where an injector having an invalid time is provided at the same position to supply the fuel. Compared with, the fuel can be replenished more quickly, and the required fuel can be replenished to the combustion chamber as quickly as possible.

Further, in the carburetor type as described above, since the combustion chamber and the point where fuel is supplied are distant from each other, the difference between the engine stall avoidance limit speed and the return speed is relatively large, and the intermediate operation as described above is performed. There will be an area. In the present invention, since the auxiliary fuel is quickly replenished even in this intermediate operation range, engine stall can be reliably prevented.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

The drawings are system explanatory views of a fuel cut system according to the present invention, in which 1 is a carburetor of an automobile engine, 2 is a throttle valve of the carburetor 1, 3 is a float chamber, 4 is a fuel cut mechanism, 5 Is an air-fuel ratio correction mechanism provided in association with the fuel cut mechanism 4.
The carburetor 1 has a normal structure in which a fuel cut valve 6 is provided in the middle of a slow passage (not shown). The carburetor 1 has an idle for automatically adjusting the idling speed. An opening adjustment mechanism 7 is attached. The idle opening adjustment mechanism 7 includes an actuator 8 with a built-in step motor for changing the closed position of the throttle valve 2 and the actuator 8 in the direction in which the operating speed of the engine is detected and the idling speed converges to 650 rpm, for example. Is an ordinary one which is provided with an actuator control mechanism 9 for operating the actuator at a slow speed. Further, the fuel cut mechanism 4 is configured such that the fuel cut valve 6 is controlled to be opened / closed by the fuel cut control means 11, but it does not have a direct interlocking relationship with the idle up means unlike the conventional one. . That is, this fuel cut mechanism 4
Does not have the function of performing idle-up at the same time as the fuel cut. Fuel cut valve 6
Is maintained in the open state when the fuel cut release signal a is input to the input terminal 6a, and when the fuel cut signal b is input, the fuel from the slow passage is completely cut. The state is changed to a state in which only a small amount of fuel is allowed to pass. Further, the fuel cut control means 11 turns on the rotation sensor 125, the neutral switch 13, the clutch switch 14, and the idle switch 15, respectively.
An electrical circuit configured to output the fuel cut signal b to the fuel cut valve 6 only when all of these are in the OFF state as an input information, and the rotation sensor 12, the neutral state. When at least one of the switch 13, the clutch switch 14, and the idle switch 15 is in the ON state,
A fuel cut release signal a is output to the fuel cut valve 6. The rotation sensor 12 detects the number of revolutions of the engine and turns off when the number of revolutions exceeds a set number of revolutions (eg, 900 rpm).
It is configured so that when it goes down, it goes on when it goes down. Further, the neutral switch 13 is set to be OFF when the transmission is other than neutral and ON when the transmission is in neutral. Further, the clutch switch 14 is turned off when the clutch for transmitting the power of the engine to the wheel side is in the connected state, and is turned on when the clutch is in the disconnected state. Further, the idle switch 15 is used for the carburetor 1.
The throttle valve 2 is turned off when the opening of the throttle valve 2 shifts to the closing side from a predetermined set value, and turned on when the opening of the throttle valve 2 shifts to the open side from the predetermined set value.

On the other hand, the air-fuel ratio correction mechanism 5 is a fuel supply mechanism 1 that temporarily supplies a required amount of fuel to the engine at a predetermined time described later.
6 and a valve opening mechanism 17 for opening the throttle valve 2 by a required angle at that time. The refueling mechanism 16 connects an inlet 19 having a check valve 18 to the float chamber 3 via an inlet passage 21 and an outlet 22 having an outlet passage 23 having a check valve 23 which is a special auxiliary fuel supply passage. Intake passage 1 of carburetor 1 via 24
An electromagnetic type piston pump 25 as shown in the drawing opened in a, and a pump drive circuit for outputting an operation command signal d to the pump 25 for a fixed time when an energizing signal c is input to an input terminal 26a. 26 and a drive circuit control means 30 for outputting an energizing signal c to the pump drive circuit 26 only in a predetermined operation pattern. Thus, the outlet passage 24 forms an auxiliary fuel supply passage different from the main passage and the slow passage that are existing fuel supply passages of the carburetor 1. Therefore, this outlet passage 24 is provided in the carburetor 1 as is clear from the drawing.
It is opened upstream of the throttle valve 2. The piston pump 25 is a cylinder 2 that forms a pump chamber 27.
A piston 29 is housed in the pump 8, and the piston 29 can be moved forward and backward by the urging force of a spring 31 and the electromagnetic attraction force of a solenoid 32 to perform a pump function. The pump drive circuit 26 uses the solenoid 3
2, a pulse voltage of, for example, about 20 Hz is applied to move the piston of the pump 25 back and forth. Further, the valve opening mechanism 17 is connected to the actuator 8 of the idle opening adjusting mechanism 7 and the actuator control mechanism 9 of the idle opening adjusting mechanism 7 for a certain time when the energizing signal e is input to the input terminal 33a. An actuator drive circuit 33 that outputs an operation stop signal f to stop the operation of the control mechanism 9 and rapidly drives the actuator 8 to open the throttle valve 2 by a certain angle. The drive circuit control means 30 outputs the energizing signal e only in a predetermined operation pattern shown in the table.

Here, the drive circuit control means 30 uses the rotation sensor 12
ON, O of the neutral switch (N-SW) 13, the clutch switch 14, and the idle switch 15
With the FF state and the fuel cut (F / C) cancellation signal a from the fuel cut control means 11 as input information, the operating state of the vehicle is the operating pattern I shown in the above table,
The urging signals c and e are output only when it is determined to belong to II, III, or IV and it is determined to belong to the second or third operation patterns II or III. That is, in the first operation pattern I shown in this table, the vehicle is decelerated in the fuel cut state, the rotation speed of the engine falls below the return rotation speed (for example, 900 rpm), and the rotation sensor is switched to ON. It is a pattern that cancels the fuel cut at that time, and the transmission relationship between the engine and the wheels is maintained even after canceling the fuel cut. Further, the second operation pattern II is that the fuel cut is released when the engine speed falls below the return speed, and immediately after (for example, within 0 or 5 seconds) the transmission relationship between the engine and the wheels. It is a pattern that is cut off. In the third pattern III, when the engine speed is in the intermediate operation range between the engine stall avoidance limit speed (for example, 1200 rpm) and the return speed, the transmission relationship between the engine and the wheel is broken, and By this, the clutch switch 14 or the neutral switch 13 is turned on to release the fuel cut. Further, the fourth pattern IV is a pattern in which the transmission relationship between the engine and the wheels is broken in an operating range in which the engine speed is kept at or above the engine stall avoidance limit speed, thereby canceling the fuel cut. is there.

Next, the operation of this embodiment will be described.

First, when the vehicle is in a driving state other than deceleration, at least one of the rotation sensor 12, the neutral switch 13, the clutch switch 14, and the idle switch 15 is O.
Since it is in the N state, the fuel cut release signal a from the fuel cut control means 11 of the fuel cut mechanism 4
The fuel cut valve 6 is held in the open state. On the other hand, at the time of deceleration of the vehicle, all of the rotation sensor 12, the neutral switch 13, the clutch switch 14, and the idle switch 15 are turned off. Therefore, the fuel cut signal b is output from the fuel cut control means 11, and the fuel cut signal is output. The valve 6 is fully closed, or only a minute amount of fuel is allowed to pass. That is, the fuel cut state is set.
Then, from this state, the fuel cut release state is restored through any of the operation patterns I, II, III, IV described above. First, in the case of the first operation pattern I, the rotation sensor 12 is switched to ON when the engine speed falls below a predetermined return speed, and the fuel cut is released. The actuator 8 and the pump 15 of the fuel supply mechanism 16 do not operate. This is because, in this case, the engine and the wheels are maintained in the transmission relationship even after the return, so that there is no risk of engine stalling. On the other hand, in the case of the second operation pattern II, the engine speed falls below the return speed, the fuel cut is released, and the transmission relationship between the engine and the wheels is interrupted while the fuel is about to return. Therefore, if it is left as it is, the engine may be stopped, but at that moment, the actuator 8 and the pump 25 are actuated to shift the closed position of the throttle valve 2 to the opening side by a required angle, and at the same time, the carburetor 1 To reinforce a certain amount of fuel. for that reason,
The engine stall is effectively avoided. Also, the third pattern II
In the case of I, the fuel cut is canceled because the transmission relationship between the engine and the wheels is broken when the engine speed falls below the engine stall avoidance limit speed, so the fuel recovery will be delayed as it is. However, at that moment, the actuator 8 and the pump 25 are actuated to move the closed position of the throttle valve 2 to the opening side by a required angle and replenish the carburetor 1 with a certain amount of fuel. . Therefore, the engine stall is effectively avoided. Further, in the case of the fourth pattern IV, the actuator 8 and the pump 25 do not operate at all, but at this time, the fuel cut is released while the engine speed exceeds the engine stall avoidance limit speed. Therefore, even if the transmission relationship between the engine and the wheels is interrupted and the biasing force from the wheels is not transmitted to the engine, there is no possibility that the engine will stop.

In this way, the fuel cut and its cancellation can be performed. In this system, when the fuel cut is canceled, the closed position of the throttle valve 2 is shifted to the open side and the carburetor 1 is connected to the piston side as needed. Since a constant amount of fuel is replenished by using the piston pump 25 that can forcibly discharge the fuel immediately when 29 operates, the fuel cut is performed in the operating region where the engine speed is relatively low. Even if is released, there is no inconvenience that the engine will stop due to the delay in the return of fuel, or breathing will occur. Moreover, since the fuel cut mechanism 4 does not have a function of performing idle-up at the same time as the fuel cut,
There is no restriction that the switching set value of the idle switch must be set to a high value in order to prevent chattering and the like. Therefore, in the present fuel cut system, it is possible to set the return rotational speed at which the fuel cut should be canceled to a low value of about 900 rpm, for example. Therefore, it is possible to expand the operating range in which the fuel cut is performed as compared with the conventional one, and it is possible to effectively improve the fuel economy. Moreover, in this system, the operation patterns when the fuel cut is released are classified in detail,
Only in an actually required operation pattern, the closed position of the throttle valve 2 is moved to the open side, and the carburetor 1 is replenished with a constant amount of fuel. It is possible to effectively eliminate the inconvenience.

It should be noted that the invention described in the first aspect of the invention includes, as an embodiment thereof, the valve opening mechanism 17 deleted from the illustrated embodiment, and can bring about an effect close to the above-mentioned effect.

[Effects of the Invention] Since the present invention has the above-described configuration, the following effects can be obtained. That is, in the present invention, since the function of performing the idle-up at the same time as the fuel cut is deleted from the fuel cut mechanism, the return speed can be set to a low value without causing the chattering as described above. . Moreover, when canceling the fuel cut on the condition that the reverse driving force from the wheel to the engine is cut off, a special auxiliary fuel supply path different from the slow system passage of the carburetor is used by using the piston pump. Since the fuel can be quickly replenished, the engine stall can be effectively prevented even if the return speed is set to a low value and the fuel cut region is expanded. In addition, the above-mentioned refueling should not be performed unconditionally when the reverse driving force is cut off, but only in the intermediate operating range or the operating range immediately after the return speed is lowered. Therefore, the waste of fuel can be prevented particularly effectively. In other words, the above-mentioned intermediate operating range is a narrow operating range between the return engine speed and the engine stall limit engine speed, and the operating range immediately after the return engine speed falls below is limited in time. It is the driving range. Therefore, if the auxiliary fuel is supplied only in such a specific operating range, the engine stall can be effectively prevented by the minimum required fuel supply, and the return speed should be set to a low value without difficulty. You can

For the above reasons, according to the present invention, without causing chattering of control or engine stall or waste of fuel,
You can comfortably expand the fuel cut area. Therefore, the fuel saving amount by expanding the fuel cut region can be made much larger than the auxiliary fuel supplying amount, and the effect that the fuel economy as a whole can be improved can be obtained.

If the throttle valve is opened at the required angle at the same time as the auxiliary fuel is supplied, the fuel will be replenished from the main system passage of the carburetor, and the reverse driving force from the wheels to the engine will be increased. If fuel is suddenly cut off, fuel can be refilled more quickly, and engine stall can be reliably prevented. Therefore, it is possible to further expand the fuel cut area.

[Brief description of drawings]

 The drawings are system illustrations showing an embodiment of the present invention. 1 ... Vaporizer 2 ... Throttle valve 4 ... Fuel cut mechanism 5 ... Air-fuel ratio correction mechanism 6 ... Fuel cut valve 7 ... Idle opening adjustment mechanism 16 ... Refueling mechanism 17 ... Valve opening mechanism 24 ...... Auxiliary fuel supply route 25 ...... Piston pump

Claims (2)

[Claims] 1. A fuel cut system applied to an engine for a vehicle equipped with a carburetor, wherein the fuel cut is performed when the vehicle is decelerated, and the number of revolutions of the engine falls below a predetermined return number of revolutions. A fuel cut mechanism that is configured to release the fuel cut when the transmission relationship between the engine and the wheel is broken, but does not have the function of performing idle up at the same time as the fuel cut, Between the engine and the wheel in the intermediate operating range between the return rotational speed and the engine stall avoidance limit rotational speed slightly higher than the return rotational speed or in the operating area immediately after the return rotational speed is lowered. When the transmission relationship is broken, the piston pump is activated to supply the required amount of fuel to the carburetor, which is different from the existing fuel supply path. Fuel cut system characterized by comprising; and a fuel supplying mechanism supplying the upstream portion of the throttle valve in the carburetor from auxiliary fuel supply path. 2. A fuel cut system applied to an engine for a vehicle equipped with a carburetor, wherein the fuel cut is performed when the vehicle is decelerated and the number of revolutions of the engine falls below a predetermined return number of revolutions. A fuel cut mechanism that is configured to release the fuel cut when the transmission relationship between the engine and the wheel is broken, but does not have the function of performing idle up at the same time as the fuel cut, Between the engine and the wheel in the intermediate operating range between the return rotational speed and the engine stall avoidance limit rotational speed slightly higher than the return rotational speed or in the operating area immediately after the return rotational speed is lowered. When the transmission relationship is broken, the piston pump is activated to supply the required amount of fuel to the carburetor, which is different from the existing fuel supply path. Fuel cut system characterized by comprising; and a air-fuel ratio correction mechanism for only opening required angle of the throttle valve of the carburetor is supplied to the upstream portion of the throttle valve in the carburetor from auxiliary fuel supply path.