JPH06108943A - Fuel injection device - Google Patents

Abstract

PURPOSE:To eliminate uncontrollable leakage fuel leaking out from injectors during the stop of an engine so as to prevent an air-fuel ratio at the engine starting time from becoming overrich, thereby improving emission. CONSTITUTION:A high pressure pipeline 19 is connected to a fuel tank 9 through a branch pipe 31, a by-pass valve 35 and a return pipeline 33. An ECU 1 opens the by-pass valve 35 when an ignition switch is turned off and closes the by-pass valve 35 when the ignition switch is turned on. As a result, during the stop of an engine, the pressure in the high pressure pipeline parts 15, 19, 21, 31, 41 escapes through the return pipeline 33 so as to prevent fuel from leaking into an intake pipe 5 from a main injector 7 and a start injector 43.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device,
In particular, the present invention relates to a fuel injection device capable of reducing HC at engine start.

[0002]

2. Description of the Related Art Since a fuel supply system to an engine is usually at a high pressure, some fuel leaks from the injector into the intake pipe even after the engine is stopped. The amount of this leaked fuel cannot be controlled. Therefore, when the engine is started, combustion is performed in a state where such unmanageable leaked fuel is added, the air-fuel ratio is likely to be overrich, and the emission is deteriorated.

In recent years, it has become necessary to reduce the emission at the time of starting, as seen in the stricter emission regulation values in the United States. So, from the past,
Studies have been conducted to improve the valve tightness of the injector.

[0004]

However, even if the valve tightness is improved, it is difficult to make the amount of fuel leaked from the injector "0". Therefore, the fuel injection device of the present invention was completed for the purpose of preventing the air-fuel ratio at the time of engine starting from becoming excessively rich due to such unmanageable leaked fuel, and improving the emission.

[0005]

The fuel injection device of the present invention, which has been made to achieve this object, has a stop determination means for determining that the engine is stopped, and the engine is stopped by the stop determination means. If it is determined that the amount of staying fuel is reduced, the amount of staying fuel in the intake pipe that leaks from the fuel injection system into the intake pipe is reduced.

According to this fuel injection device, when the stop determination means determines that the engine is stopped, the staying fuel reduction means determines the amount of fuel leaking from the fuel injection system into the intake pipe. Reduce. As a result, fuel does not stay in the intake pipe while the engine is stopped, and when starting the engine, the engine can be started with the expected air-fuel ratio without excess staying fuel.

The staying fuel reducing means can be a pressure reducing means for reducing the pressure of the fuel injection system as described in claim 2. According to the fuel injection device of the second aspect, the pressure reducing means reduces the pressure of the fuel injection system while the engine is stopped, and the fuel does not leak from the injector into the intake pipe. As a result, the air-fuel ratio does not become overrich when the engine is started.

As described in claim 3, further,
If a pressure increasing means for increasing the pressure of the fuel injection system at the time of engine start is also provided, not only emission improvement at engine start but also startability improvement can be achieved. Further, the staying fuel reducing means may be suction means for sucking air in the intake pipe as described in claim 4. According to the apparatus of the fourth aspect, the air in the intake pipe is sucked while the engine is stopped. Therefore, even if there is fuel leaking from the injector, it is sucked together with the air and stays in the intake pipe. Absent. As a result,
The air-fuel ratio does not become overrich when the engine is started.

Further, in the fuel injection device according to the present invention, further, if a return means for returning the air sucked by the suction means to the inside of the intake pipe during engine operation is provided, the fuel is sucked while the engine is stopped. Fuel can be used for combustion without having to discharge it to the outside.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows the configuration of a fuel injection system as a first embodiment to which the present invention is applied. In the system according to the first embodiment, the electronic control circuit (ECU) 1 controls the valve opening of the main injector 7 provided in the intake pipe 5 of the engine 3 to inject the fuel from the fuel tank 9. It is configured.

A fuel tank 9 is connected to the main injector 7.
From the side, the low-pressure pipe 11, the fuel injection pump 13, the first high-pressure pipe 15, the fuel filter 17, and the second high-pressure pipe 19
Fuel is supplied via the. Here, the second high-pressure pipe 1
9, branch pipes 21, 31, 41 are provided at three locations.

Among these, a fuel pressure regulating valve 23 is attached to the first branch pipe 21. This fuel pressure regulating valve 23
Is connected to the surge tank 27 of the intake pipe 5 by the negative pressure pipe 25, the open / closed state is changed by the negative pressure from the negative pressure pipe 25, and excess fuel is supplied to the fuel tank 9 via the return pipe 29.
The fuel pressure in the high-pressure pipe 19 is maintained at a predetermined value by returning to the above. In addition, the second branch pipe 31 is connected to a second return pipe 33 connected to the fuel tank 9 via a bypass valve 35. And the third
A start injector 43 for injecting fuel into the intake pipe 5 when the engine is started is attached to the branch pipe 41 of the above.

As a result of being constructed in this way, of the piping,
The portions indicated by reference numerals 15, 17, 21, 31, and 41 are +2.9 kg / c in intake pipe pressure during engine startup.
It has a high pressure of m ² . The ECU 1 receives various detection signals such as vehicle speed, accelerator opening, cooling water temperature, air conditioner switch status, and ignition switch status.
Various calculations are executed based on these detection signals, and as described above, the main injector 7 is controlled to be opened, and the control signals are also output to the fuel injection pump 13 and the bypass valve 35.

A feature of the control processing of the ECU 1 is control of the bypass valve 35. As shown in FIG. 2, when the ignition switch is off, the bypass valve 35 is opened (S101,
S102), the bypass valve 35 is closed when the ignition switch is on (S101, S10).
The control content is 3).

As a result of such control, while the engine is stopped, the pressure in the high-pressure pipe portions 15, 19, 21, 31, 41 is released via the second return pipe 33, and the main injector 7 and the starter are started. High pressure is not applied to the injector 43, and fuel does not leak into the intake pipe 5 from here. Therefore, when the engine is started thereafter, it is possible to realize a good emission state without causing an overrich state due to leaked fuel as in the conventional case.

Next, a second embodiment will be described. As shown in FIG. 3, the system of the second embodiment is generally the same as that of the first embodiment, except that an electric damper 50 is attached instead of the second branch pipe 31 from the high-pressure pipe 19. The difference is that there is no bypass valve 35 or second return pipe 33.

This electric damper 50, as shown in FIG.
A cylinder 51 opening to the high-pressure pipe 19 and a piston 53 fitted in the cylinder 51 via a seal material 52.
And a stepping motor 54 for moving the piston 53 forward and backward. The stepping motor 54 is composed of a rotor 55 at the center and a stator coil 56 on the outer periphery of the rotor 55. The rotor 55 is provided with a central hole 57 with a thread groove. A thread groove 59 provided at the end of the shaft 58 fixed to the piston 53 is screwed into the center hole 57 of the rotor 55. In addition, a coil spring 61 that gives a force to push the piston 53 back in the forward direction is attached to the inside of the cylinder 51, and a step portion (hereinafter referred to as a step portion) that regulates the rearward movement position of the damper 53 by restricting the backward movement of the piston 53. , A full-open stopper) 63, and a stepped portion (hereinafter, referred to as a full-close stopper) 65 that defines the fully closed position of the damper by limiting the movement of the piston 53 in the forward direction. The coil spring 61 serves to prevent rattling when the piston 53 operates.

The electric damper 50 is drive-controlled in the procedure shown in FIG. First, it is determined whether or not the ignition switch is off (S200). When the ignition switch is off, after the fuel injection pump 13 is stopped,
It is determined whether a predetermined time T (for example, 5 seconds) has passed (S201). This is the electric damper 5 by the following processing.
This is because the fuel pressure on the high-pressure pipe side cannot be reduced to a low pressure unless the fuel supply is completely stopped when 0 is controlled to the fully open state.

If the determination in S201 is "YES", the stepping motor 54 is driven to move the piston 53 backward until it collides with the full-open stopper 63, and the damper chamber is fully opened (S202). Then, the main relay is turned off, and thereafter the electric damper 50 is maintained in this state (S203).

On the other hand, when the ignition switch is not turned off, the main relay is turned on (S204), the stepping motor 54 is driven to move the piston 53 forward until it collides with the fully closed stopper 65, and the damper chamber is fully closed. Yes (S205). As a result of executing the above control, when the engine is stopped, the internal volume of the high-pressure pipe 19 increases,
The pressure drops accordingly. As a result, the pressure in the high-pressure pipe portions 15, 19, 21, 41 is released, the high pressure is not applied to the main injector 7 and the start injector 43, and the fuel does not leak into the intake pipe 5 from here. . Therefore, when starting the engine after this,
A good emission state can be realized without inducing an overrich state due to leaked fuel as in the conventional case. The volume change of the high-pressure pipe 19 due to the movement of the piston 53 from the position of the fully closed stopper 65 to the position of the fully opened stopper 63 is sufficient to be several cc to 10 cc.

When the engine is started, the electric damper 50 is driven in the fully closed direction, so that the pressure in the high pressure pipes 15, 19, 21 can be instantly increased. As a result, even if the pressure in the high-pressure pipe is reduced while the engine is stopped, the fuel injection at the time of starting will not be adversely affected.

Next, a third embodiment will be described. The system of the third embodiment is generally similar to the first and second embodiments, but as shown in FIG. 6, does not include the bypass valve 35 or the electric damper 50. The feature is that the fuel pressure regulating valve 70 having the configuration shown in FIG. 7 is provided.

The fuel pressure regulating valve 70 includes a main body 71, a diaphragm 72 for partitioning the main body 71 into an upper chamber 71a and a lower chamber 71b, a return spring 73 for urging the diaphragm 72 downward in the drawing, and a center of the diaphragm 71. A fuel outlet 76 connected to the return pipe 29, including a valve body 74 attached to the lower surface and a valve seat 75 with which the valve body 74 contacts, and a high pressure pipe 19 in the lower chamber 71b.
Fuel inlet 77 for supplying fuel from the upper chamber 7
1a is provided with a negative pressure introducing port 78 for introducing a negative pressure from the surge tank 27, and a fuel bypass hole 79 is further formed in the side wall of the fuel outlet 76.

During engine operation, the fuel pressure regulating valve 70 is
Negative pressure from surge tank 27 and return spring 7
The diaphragm position is changed according to the balance between the urging force of No. 3 and the pressure of the fuel introduced into the lower chamber 71b, thereby controlling the gap between the valve body 74 and the valve seat 75 to adjust the fuel return amount. , And acts to keep the fuel pressure in the high-pressure pipe 19 at a predetermined value (for example, intake pipe pressure +2.9 kg / cm ² ).

On the other hand, when the engine is stopped, the valve element 74 and the valve seat 75 are in contact with each other, and the mouth of the fuel outlet 76 is closed. However, since the fuel outlet 76 is provided with the fuel bypass hole 79, the high-pressure fuel in the lower chamber 71 b is returned through the fuel bypass hole 79. Therefore, the fuel in the high-pressure pipe 19 is the fuel tank 9
It is returned until the pressure difference with the pressure (atmospheric pressure) disappears. As a result, the internal pressure of the high-pressure pipe is reduced while the engine is stopped, and the main injector 7 and the start injector 4 are
No high pressure is applied to the fuel cell 3, and fuel does not leak into the intake pipe 5 from here. Therefore, when the engine is started thereafter, it is possible to realize a good emission state without causing an overrich state due to leaked fuel as in the conventional case.

The size of the fuel bypass hole 79 is, for example, φ0. So that the fuel pressure in the high-pressure pipe 19 can be maintained at a predetermined value until the clearance between the valve element 74 and the valve seat 75 during engine operation. It is desirable to reduce the size to about 1 mm. In the present embodiment, the fuel bypass hole 79 is provided on the side wall of the fuel outlet 76.
A small hole is opened in the valve body 74 or the valve seat 75, or the valve body 7
A groove may be provided on the contact surface between the valve 4 and the valve seat 75.

Next, a fourth embodiment will be described. In the system of the fourth embodiment, as shown in FIG. 8, the fuel injection system is the same as the conventional one, and the canister 80 is provided near the main injector.
It is characterized by the arrangement of. This canister 80 contains activated carbon inside, and has one opening pipe 81 connected to the intake pipe 5 and another opening pipe 82 connected to a 6-way solenoid valve 83. The atmosphere opening 84, the pressure accumulator 85, and the second intake pipe communication passage 86 are connected to the 6-way solenoid valve 83.

As shown in FIG. 9, the six-way solenoid valve 83 connects the canister 80 to the atmosphere opening 84 and the second intake pipe communication passage 86 to the pressure accumulator 85 in a first state (( A)) and the atmosphere opening 84 and the second intake pipe communication path 86 are both blocked, and the canister 80 is switchable between a second state (the illustrated state (B)) in which the canister 80 is connected to the pressure accumulator 85. ing. Then, the ECU 1 operates as shown in FIG.
As shown in, when the ignition switch is off,
The 6-way solenoid valve 83 is switched to the second state (S4).
01, S402). On the other hand, when the ignition switch is on, the 6-way solenoid valve 83 is switched to the first state (S401, S403).

As a result of such control, the pressure accumulator 85 is in a state of accumulating a negative pressure due to the negative pressure of the intake pipe during engine operation, and when the engine is stopped, the negative pressure is transferred to the canister 80. The air in the intake pipe 5 is sucked. Therefore, when the engine is stopped, the fuel that has leaked into the intake pipe 5 is adsorbed by the canister 80, and when the engine is started, an overrich state due to the leaked fuel as in the past does not occur, and a good emission state is obtained. Can be realized.

The fuel gas adsorbed in the canister 80 is purged into the intake pipe 5 due to the differential pressure between the atmospheric pressure and the intake pipe negative pressure during engine operation. Therefore, the canister 80 will not be saturated even if it is used for a long time. In this embodiment, the fuel is adsorbed to the canister using the pressure accumulator that stores a negative pressure during engine operation, but the suction pump may be used to adsorb the fuel. Absent.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention. For example, although the piston type electric damper is used in the second embodiment, the internal pressure of the high pressure pipe while the engine is stopped can be sufficiently reduced by simply providing a volume chamber and controlling the opening / closing of the volume chamber. Is. However, the second
When the piston system is used as in the embodiment, the internal pressure of the high-pressure pipe can be immediately increased when the engine is started, which is more desirable in terms of improving the startability. Therefore, also in the first and third embodiments, the internal pressure of the high-pressure pipe, which has become low when the engine is stopped, can be increased earlier by adjusting the fuel injection pump drive condition at the engine start. Is more preferable.

Further, in the fourth embodiment, a dedicated canister for adsorbing leaked fuel while the engine is stopped is provided, but this can also be used for normal canister purging, or conversely for normal canister purging. Those may be used according to the gist of the present invention.

[0033]

As described above, according to the fuel injection device of the present invention, unmanageable leaked fuel leaking from the injector when the engine is stopped is eliminated, and the air-fuel ratio at the engine start becomes overrich. It can prevent and improve emission.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a fuel injection device of a first embodiment.

FIG. 2 is a flowchart of control processing in the first embodiment.

FIG. 3 is a configuration diagram showing a fuel injection device of a second embodiment.

FIG. 4 is a sectional view showing a structure of an electric damper of a fuel injection device according to a second embodiment.

FIG. 5 is a flowchart of control processing in the second embodiment.

FIG. 6 is a configuration diagram showing a fuel injection device of a third embodiment.

FIG. 7 is a sectional view showing a structure of a fuel pressure regulating valve of a fuel injection device of a third embodiment.

FIG. 8 is a configuration diagram showing a fuel injection device of a fourth embodiment.

FIG. 9 is an explanatory diagram showing a switching state of a 6-way solenoid valve of a fuel injection device according to a fourth embodiment.

FIG. 10 is a flowchart of control processing in the fourth embodiment.

[Explanation of symbols]

1 ... Electronic control circuit (ECU), 3 ... Engine,
5 ... intake pipe, 7 ... main injector, 9 ...
・ Fuel tank, 11 ... Low-pressure pipe, 13 ... Fuel injection pump, 15, 19 ... High-pressure pipe, 21, 31, 4
1 ... High pressure branch pipe, 29, 33 ... Return pipe, 35 ... Bypass valve, 43 ... Start injector, 50 ... Electric damper, 53 ... Piston, 54 ... Stepping Motor, 63 ... Fully open stopper, 65 ... Fully closed stopper, 70 ... Fuel pressure regulating valve, 79 ... Fuel bypass hole, 80 ... Canister, 83 ... 6-way solenoid valve, 84 ... ..Air opening, 8
5 ... Accumulator, 86 ... Intake pipe communication passage.

Claims (5)

[Claims] 1. A stop determination means for determining that the engine is stopped, and an intake pipe for fuel leaking from the fuel injection system into the intake pipe when the stop determination means determines that the engine is stopped. A fuel injection device comprising: a staying fuel reducing means for reducing a staying amount. 2. The fuel injection device according to claim 1, wherein the staying fuel reducing means is a pressure reducing means for reducing the pressure of the fuel injection system. 3. The fuel injection device according to claim 2,
Further, the fuel injection device is also provided with a pressure increasing means for increasing the pressure of the fuel injection system when the engine is started. 4. The fuel injection device according to claim 1, wherein the staying fuel reducing means is suction means for sucking air in the intake pipe. 5. The fuel injection device according to claim 4,
Further, the fuel injection device is provided with a returning means for returning the air sucked by the suction means into the intake pipe during engine operation.