JPH06272632A - Check valve for fuel pump - Google Patents

Abstract

PURPOSE:To keep a residual pressure at a low value inside a fuel passage after an engine is stopped, and restrain leakage from a fuel injection valve. CONSTITUTION:A check valve 1 for restricting a reverse flow of fuel at the time of inoperation is disposed in a discharge port of a fuel pump. A spiral strip 25 is projected on the inner circumference of a fuel discharge hole 24 of the valve body 21. A pair of projecting pieces 26 to be loosely engaged with the spiral stripe 25 are formed in a part in the circumferential direction in the middle portion of a shaft portion 22a of a valve member 22. When the valve member 22 at the time of inoperation of the pump is to be moved in the closing direction from the (a) state to the (b) state, the movement is temporarily restricted by the engagement of the spiral stripe 25 with the projecting pieces 26, thus releasing a residual pressure. Thereafter, the valve member 22 is seated in the (c) state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved check valve for a fuel pump used in a fuel injection type internal combustion engine.

[0002]

2. Description of the Related Art In a fuel injection type internal combustion engine using an electromagnetic fuel injection valve, fuel is pressure-fed to a fuel pipe equipped with a fuel injection valve by an electric fuel pump arranged in a fuel tank or the like. At the same time, excess fuel is returned through a pressure regulator that is opened at a predetermined pressure provided on the outlet side of the fuel pipe. It is always kept at a predetermined pressure. In general, the intake pipe pressure is introduced to the pressure regulator, and a pressure adjusting action is performed so that the differential pressure between the intake pipe pressure and the fuel pressure becomes constant.

In order to retain the fuel in the fuel pipe after the engine is stopped, that is, after the pump is stopped, a check valve has been conventionally provided in the discharge port of the fuel pump to prevent the reverse flow of the fuel ( For example, JP-A-57
-184470 gazette etc.).

[0004]

In the structure in which the check port is provided in the discharge port of the fuel pump as in the above-mentioned conventional case, the check valve is closed instantly when the pump is stopped, and a relatively high residual pressure is maintained in the fuel pipe. It Therefore, there is a drawback that fuel easily leaks from the fuel injection valve into the intake manifold while the engine is stopped, and when the engine is restarted, it becomes a rich mixture and the startability is deteriorated.

[0005]

Therefore, in the present invention, the closing operation of the check valve when the pump is stopped is slightly delayed to reduce the residual pressure. That is, the present invention, in the discharge port of the fuel pump that pressure-feeds the fuel to the fuel injection valve,
In a check valve in which a valve element is slidably inserted, a seat surface is formed around the fuel discharge hole of the discharge port, and a screw is projected on the inner circumference of the fuel discharge hole, and the fuel is At the intermediate portion of the shaft portion of the valve body inserted through the discharge hole, a projection piece that engages with the thread is formed in a part in the circumferential direction, and the seal portion at one end of the shaft portion is located at a position away from the seat surface. It is characterized in that respective forming positions are set so that the screw thread and the protruding piece are engaged with each other.

[0006]

When the pump stops as the engine stops, the residual pressure in the fuel pipe pushes the valve element in the closing direction. When the valve body moves part way, the projection piece in the middle part of the shaft portion engages with the thread, and the movement in the closing direction is temporarily restricted. At this time,
Since the projection piece is formed in a part in the circumferential direction, the fuel can flow through the fuel discharge hole, and the residual pressure is continuously released. Further, the valve body pressed by the residual pressure advances in the closing direction while rotating along the thread, and eventually the seal portion seats on the seat surface to close the fuel discharge hole.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a check valve 1 according to the present invention.
FIG. 2 is a sectional view showing the overall configuration of the fuel pump 2 including the check valve 1. Also, FIG.
FIG. 3 is an explanatory view showing an outline of a fuel supply system including this fuel pump 2, in which the fuel pump 2 is housed in a fuel tank 3 and a plurality of electromagnetic fuel injection valves 4
Fuel is pressure-fed through the fuel passage 6 to the fuel gallery 5 connected to. A diaphragm type pressure regulator 7 is provided at the outlet of the fuel gallery 5, and the surplus fuel exiting from the pressure regulator 7 is returned to the fuel tank 3 via a return passage 8.

The structure of the fuel pump 2 as a whole will be described. In FIG. 2, 11 is a substantially cylindrical casing,
The suction port 1 is provided on each end surface of the casing 11.
2, the discharge port 13 is provided. Further, a pump chamber 14 is formed at an end portion of the casing 11 on the suction port 12 side, and a disk-shaped turbine vane 1 is formed therein.
5 are accommodated. The turbine vane 15 has a large number of vanes radially formed at an outer peripheral edge thereof at an equal pitch. When the turbine vane 15 rotates, the fuel sucked from the suction port 12 is pressurized and the casing 11 is rotated. It is designed to be sent inside. A motor section 16 for driving the turbine vane 15 is formed inside the casing 11 through which the pressurized fuel flows. The motor unit 16 includes an armature 18 attached to a drive shaft 17 and a magnet 19 fixed to the inner circumference of the casing 11, and a brush (not shown) is in sliding contact with a commutator 20 at the end of the armature 18.

The discharge port 13 is formed in a substantially cylindrical shape along the axial direction of the casing 11, and is connected to the above-mentioned fuel passage 6. And
A check valve 1 for preventing backflow of fuel while the pump is stopped is incorporated in the discharge port 13.

The check valve 1 has a discharge port 13
It is composed of a cylindrical valve body 21 press-fitted and fixed therein, and a valve body 22 slidably inserted into the valve body 21.

As shown in detail in FIG. 1, a seat portion 23 is formed on the valve body 21 so as to project inward, and a fuel discharge hole 24 penetrates through the seat portion 23. A tapered seat surface 23a is formed around the fuel discharge hole 24.

The valve body 22 has a shaft portion 22a loosely fitted in the fuel discharge hole 24 and the seat surface 23a.
It has a hemispherical seal portion 22b formed at one end of the shaft portion 22a so as to be seated on. The valve body 22 is held by a stopper 27 provided at the opening of the valve body 21 so as not to come off from the fuel discharge hole 24.

The inner circumference of the fuel discharge hole 24 is
The thread 25 is provided so as to project. In addition, this thread 25 is
It is formed with a relatively small number of turns, such as about two turns. On the other hand, a pair of protrusions 26 that can be loosely engaged with the thread 25 is provided in the intermediate portion of the shaft portion 22a of the valve body 22. As shown in FIG. 4, the protruding piece 26 is circumferentially separated by 9
They are formed in angular ranges of 90 ° with intervals of 0 °. Further, they are inclined with a predetermined twist angle so as to be along the thread 25. An appropriate distance is provided between the projection piece 26 and the seal portion 22b, and the seal portion 22b is separated from the seat surface 23a when they are engaged with each other.

Next, the operation of the configuration of the above embodiment will be described with reference to FIG.
~ It demonstrates with reference to FIG.

During operation of the engine, that is, during operation of the fuel pump 2, the fuel pressurized by the turbine vane 15 is sent from the discharge port 13 to the fuel gallery 5 through the fuel passage 6 and supplied to each fuel injection valve 4. It At this time, the valve body 22 of the check valve 1 is pushed toward the outlet side of the discharge port 13 by the flow of fuel, as shown in FIG. The fuel pressure in the fuel gallery 5 and the fuel passage 6 is kept at a predetermined pressure by the action of the pressure regulator 7.

When the internal combustion engine stops, the fuel pump 2 also stops accordingly. Therefore, the fuel pressure on the fuel passage 6 side becomes relatively higher than the pressure inside the casing 11 of the fuel pump 2, and the fuel tends to flow backward. At this time, the valve body 22 of the check valve 1 is pushed in the closing direction by the backflow of fuel, but as shown in FIG. 5B, the screw 25 on the valve body 21 side and the valve body 22 side are halfway in the middle. Since the projection piece 26 is engaged, the movement of the valve body 22 in the closing direction is temporarily restricted. Since the projection piece 26 is provided only in a part in the circumferential direction, the fuel can flow through the fuel discharge hole 24 even when the projection piece 26 is engaged with the thread 25.
Therefore, the fuel continues to flow back from the fuel passage 6, and the residual pressure in the fuel passage 6 decreases as shown in FIG.

Even when the projection piece 26 of the valve body 22 is engaged with the thread 25 as described above, the valve body 22 receives a pressing force due to the reverse flow of the fuel, and eventually the valve body 22 rotates and moves in the closing direction. Then, as shown in FIG. 5C, the seal portion 22b
Seats on the seat surface 23a. Therefore, the fuel can be retained in the fuel passage 6. That is, the residual pressure can be low and the passage can be filled with fuel.

By keeping the residual pressure in the fuel passage 6 low while the engine is stopped in this way, as shown in FIG. 7, the leakage of fuel from the fuel injection valve 4 is greatly reduced compared to the conventional one. . Therefore, a rich mixture will not be formed at the next start, and deterioration of startability can be prevented.

[0020]

As is apparent from the above description, according to the check valve of the fuel pump according to the present invention, when the operation of the pump is stopped due to the stop of the engine, its closing operation is slightly delayed. Since it is performed, the residual pressure remaining in the fuel passage can be kept lower than before. Therefore, leakage from the fuel injection valve while the engine is stopped can be suppressed, and the startability at the next start is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a check valve according to the present invention.

FIG. 2 is a sectional view of the entire fuel pump provided with this check valve.

FIG. 3 is an explanatory diagram showing an outline of a fuel supply system.

4 is a sectional view of the valve body taken along the line AA of FIG.

FIG. 5 is an explanatory view showing the operation of the valve body.

FIG. 6 is a characteristic diagram showing a change in residual pressure after the engine is stopped in comparison with a conventional one.

FIG. 7 is a characteristic diagram showing a change in the amount of leakage from a fuel injection valve in comparison with a conventional one.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Check valve 13 ... Discharge port 21 ... Valve body 22 ... Valve body 23a ... Seat surface 24 ... Fuel discharge hole 25 ... Thread 26 ... Projection piece

Claims (1)

[Claims] 1. A check valve having a valve body slidably inserted into a discharge port of a fuel pump for feeding fuel to a fuel injection valve, wherein a seat surface is formed around a fuel discharge hole of the discharge port. At the same time, a thread is provided so as to project from the inner circumference of the fuel discharge hole, and a projection piece that engages with the thread is circumferentially provided at an intermediate portion of the shaft portion of the valve body inserted through the fuel discharge hole. And the respective forming positions are set such that the screw and the protruding piece engage with each other at a position where the seal portion at one end of the shaft portion is separated from the seat surface. Check valve.