FUEL INJECTION DEVICE

Abstract

A fuel injection device for smooth discharge of a gas accumulated therein comprising a fuel pump, a solenoid valve for injecting pressurized fuel into the intake passage of an engine, a high-pressure fuel passage extending from the fuel pump to the solenoid valve and has a medially positioned constant-pressure chamber, and a fuel return passage connected to a fuel return pipe, with the fuel return passage extending from the constant-pressure chamber and having a medially positioned priming pump. The constant-pressure chamber is configured with the top wall in the upper space thereof disposed above the opening of the high-pressure fuel passage opposite the solenoid valve, the fuel return passage opens into the upper space at a position above the opening of the high-pressure fuel passage, and the gas accumulating in the constant-pressure chamber is discharged from the upper space toward the fuel tank via the fuel return passage.

Claims

1. A fuel injection device for a carburetor having a body and an air intake passage, comprising: a fuel pump positioned at a bottom surface of the body with a pump diaphragm positioned parallel to the bottom surface, a constant pressure chamber positioned on a side surface of the body with the pressure-adjusting diaphragm positioned parallel to the side surface, a first high-pressure fuel passage extending from the fuel pump to the constant pressure chamber and a second high-pressure fuel passage extending from the constant pressure chamber towards the intake passage; and a fuel return passage that extends from the constant pressure chamber towards a fuel tank, wherein the constant pressure chamber includes first and second openings to the first and second high-pressure fuel passages, and a third opening to the fuel return passage positioned above the first and second openings to the first and second high-pressure fuel passages.

2. The fuel injection device according to claim 1, further comprising a priming pump connected to the fuel return passage.

3. The fuel injection device according to claim 1, further comprising a fuel return pipe connected to the fuel return passage.

4. The fuel injection device according to claim 2, further comprising first and second check valves interconnected to the priming pump and the fuel return passage and positioned at a predetermined interval along the fuel return passage.

5. The fuel injection device according to claim 4, wherein the priming pump includes a cup shape that covers an opening side of the first and second check valves and forms a pump chamber.

6. The fuel injection device according to claim 4, wherein the fuel return passage includes a bypass path formed between the first and second check valves and includes a non-return valve that restricts passage of a fluid in the bypass path to only a fuel return direction.

7. The fuel injection device according to claim 6, wherein the non-return valve is configured to close when the priming pump is activated.

8. The fuel injection device according to claim 1, wherein the pump diaphragm of the fuel pump has a direction of displacement that is parallel to a gravitational direction.

9. The fuel injection device according to claim 8, wherein the pressure-adjusting diaphragm of the constant pressure chamber has a direction of displacement that is orthogonal to the gravitational direction.

10. The fuel injection device according to claim 1, further comprising a solenoid valve interposing the constant pressure chamber and the air intake passage along the second high-pressure fuel passage.

11. A fuel injection device comprising a fuel pump positioned at a bottom surface of the body with a pump diaphragm positioned parallel to the bottom surface, a high-pressure fuel passage that extends from the fuel pump toward an intake passage of an engine and has a medially positioned constant-pressure chamber for adjusting the fuel to a predetermined pressure, wherein the constant pressure chamber is positioned on a side surface of the body and includes a pressure-adjusting diaphragm positioned parallel to the side surface of the body, and a fuel return passage connected to a fuel return pipe, with the fuel return passage extending from the constant-pressure chamber, wherein the constant-pressure chamber includes a first opening that opens into the high-pressure fuel passage and a second opening that opens into the fuel return passage, wherein the second opening to the fuel return passage is positioned above the first opening to the high-pressure fuel passage.

12. The fuel injection device of claim 11, wherein the constant-pressure chamber is configured so that a displacement surface of the pressure-adjusting diaphragm faces a direction orthogonal to a gravitational direction.

13. The fuel injection device according to claim 11, further comprising first and second check valves interconnected to the priming pump and the fuel return passage and positioned at a predetermined interval along the fuel return passage.

14. The fuel injection device according to claim 13, wherein the priming pump includes a cup shape that covers an opening side of the first and second check valves and forms a pump chamber.

15. The fuel injection device according to claim 13, wherein the fuel return passage includes a bypass path formed between the first and second check valves and includes a non-return valve that restricts passage of a fluid in the bypass path to only a fuel return direction.

16. The fuel injection device according to claim 15, wherein the non-return valve is configured to close when the priming pump is activated.

17. The fuel injection device of claim 12, wherein the fuel pump is configured so that a displacement surface of the pump diaphragm faces a direction parallel to a gravitational direction.

18. The fuel injection device of claim 11, wherein the constant pressure chamber includes a top wall, wherein the fuel return passage opens into an upper space adjacent the top wall at a position above the opening of the high-pressure fuel passage.

19. The fuel injection device of claim 11, further comprising a high-pressure fuel injection passage extending from the constant pressure chamber to an air intake passage.

20. The fuel injection device according to claim 19, further comprising a solenoid valve interposing the constant pressure chamber and the air intake passage along the high-pressure fuel injection passage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a layout diagram of the engine fuel supply system in which the fuel injection device is disposed according to an embodiment of the present invention;

[0016] FIG. 2 is a vertical sectional view depicting the detailed configuration of the fuel injection device of FIG. 1; and

[0017] FIG. 3 is a vertical sectional view of a conventional example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Embodiments of the invention are described below in reference to the drawings. In the present invention, the upward and downward directions indicate directions corresponding to the direction of gravitational force in the typical state of use of the equipment in which the engine is mounted. In addition, the terms upper space and lower space denote upper and lower spaces relative to the vertically middle position in a predetermined space under typical conditions of use.

[0019] FIG. 1 is a layout diagram depicting the configuration of the fuel supply system of an engine 1 in which a fuel injection device 3A is disposed in accordance with this embodiment. A fuel supply pipe 5 that extends from a fuel tank 2 is connected to the fuel injection device 3A disposed so as to constitute a portion of an intake passage 10 of the engine 1. Fuel is injected with a designated timing and supplied to the engine 1 via a solenoid valve 32 in which the injection opening side is exposed to the intake passage 10.

[0020] In reference to FIG. 2, a fuel pump 31 having a fuel pressurization chamber partitioned by a diaphragm is mounted on the fuel injection device 3A, and the fuel is pressurized by the reciprocating displacement of the diaphragm through the introduction of a pulsating pressure from the engine 1 to the back pressure chamber, and is supplied to the solenoid valve 32 via the high-pressure fuel passage 36. In addition, a medially positioned constant-pressure chamber 33A is provided medially along the high-pressure fuel passage 36 and is used to adjust the fuel pressurized to a high pressure by the fuel pump 31 so that the fuel is kept at a constant pressure.

[0021] In addition, a fuel return passage 38 extends from the constant-pressure chamber 33A and connects to a fuel return pipe 6 so that excess fuel is returned to the fuel tank 2. Two check valves 341, 342 are connected at a designated distance medially on the side of the fuel return passage 38, and a cup-shaped member 343 made of an elastic resin is affixed as suction/push-out means so as to cover the space on the side surface to which the valve openings are exposed to form a priming pump 34A.

[0022] In this embodiment, the constant-pressure chamber 33A is formed so that the top wall of the upper space of the chamber is positioned above (higher than) the opening of the high-pressure fuel passage 36 opposite from the solenoid valve 32, and the opening of the fuel return passage 39 is disposed in the upper space at a location that is above (higher than) the opening of the high-pressure fuel passage 36, so that the air, vapor, or other gas accumulated in the constant-pressure chamber 33A is discharged from the upper space towards the fuel tank 2 via the fuel return passage 38.

[0023] When, in order to cease high-speed rotation, an accelerator (not illustrated) is released and the throttle lever 7 is returned to the original idle position, the throttle shaft 5 fixed to the throttle lever 7 rotates towards the closed direction due to the urging force of the urging device 6, returning to the original idle position. In this embodiment, a damping member 8 having frictional force is in contact with the throttle shaft 5 in a state of being pressed against the shaft, so that the return to the idle position occurs slowly over time rather than suddenly, as in conventional examples.

[0024] In this embodiment, the constant-pressure chamber 33A is configured so that the displacement surface of the pressure-adjusting diaphragm of the chamber faces to the side; a vertical space is formed so that the width of the space in the vertical direction is greater than the width of the space in the displacement direction; and the disk is placed upright so that the top surface faces sideways. In addition, the fuel return passage 38 extends from a location in the vicinity of the top wall in the upper space; the high-pressure fuel passage 36 that extends from the fuel pump 2 is connected at a location in the vicinity of the bottom wall in the lower space; and the high-pressure fuel passage 36 opens towards the solenoid valve 32 slightly above the passage.

[0025] With this configuration, the air, vapor, or other gas that has low specific gravity and accumulates in the upper space of the vertically elongated constant-pressure chamber 33A, which extends parallel to the direction of gravity, is readily separated in the vertical direction from the liquid fuel, and is smoothly discharged from the fuel return passage 38 that opens in the vicinity of the top wall of the upper space. On the other hand, the high-pressure fuel passage 36 opposite from the solenoid valve 32 opens into the lower space at a position away from the opening of the fuel return passage 38, allowing optimal engine performance to be maintained because the gas does not readily flow towards the solenoid valve 32.

[0026] The fuel return passage 38 is used both to discharge air, vapor, or other gases, and to allow the excess fuel that has been discharged from the fuel pump 31 to be returned to the fuel tank 2. In a conventional fuel injection device, however, the fuel in the fuel tank is pressurized by high temperatures after the engine is stopped. To overcome this shortcoming, the spring pressure of the check valve of the medially disposed priming pump 34A is set high, and considerable resistance is created to the passage of materials through this section, impeding the flow of excess fuel and the discharge of gas.

[0027] In this embodiment, two check valves 341, 342 are connected at a designated distance from each other on the side of the fuel return passage 38; a bypass passage is left between the two check valves 341, 342; and a non-return valve 35 is disposed in this portion to prevent passage of fluid only in the fuel return direction. The discharged fuel will thereby be prevented from flowing backwards while being admitted into the pump in an efficient manner, when the priming pump 34A is used during engine start-up. The excess fuel or air will be caused to bypass the priming pump 34A and to flow via the nonreturn valve 35 in a smooth manner during times other than engine startup.

[0028] In this embodiment, the fuel injection device 3A has a substantially rectangular parallelepiped external shape, the fuel pump 31 is provided with a diaphragm on the inside of the bottom surface parallel to the bottom surface, and the constant-pressure chamber 33A is provided with a diaphragm parallel to the side surf ace and inward of one side surface thereof. Consequently, the respective required functional parts are arranged in the fuel injection device in an efficient manner without being bulky, and overall compactness is achieved.

[0029] As described above, the present invention provides a fuel injection device for injecting and supplying fuel to the intake passage of an engine. Gas that has accumulated in the device can be smoothly discharged, the supplied fuel can be kept at a stable pressure and flow rate during engine operation, and optimal engine performance can be maintained.

KEY

[0030] 1 Engine

[0031] 2 Fuel tank

[0032] 3A Fuel injection device

[0033] 5 Fuel supply pipe

[0034] 6 Fuel return pipe

[0035] 10 Intake passage

[0036] 31 Fuel pump

[0037] 32 Solenoid valve

[0038] 33A Constant-pressure chamber

[0039] 34A Primping pump

[0040] 35 Non-return valve

[0041] 36 High-pressure fuel passage

[0042] 38 Fuel return passage

[0043] 341, 342 Check valves