JPH0712029A - High pressure fuel pump - Google Patents

Abstract

PURPOSE:To prevent fuel, leaked from a sliding clearance between a piston and a cylinder, from infiltrating into grease with which a bearing and a needle bearing are charged. CONSTITUTION:A peripheral end part 101a of a diaphragm 101 is interposed by upper/lower part housings 102, 103, and an internal peripheral end part 101b of this diaphragm is inserted to a groove part 104b in the lower part of a piston 104, to seal a sliding part of the piston 104 and a cam chamber 10 in a manner of liquid pressure. In this way, a bearing and a needle bearing are prevented from seizure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high pressure fuel pump used in an in-cylinder injection system for injecting gasoline directly into a cylinder of an engine.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view showing a conventional high-pressure fuel pump, and FIG. 8 is a sectional view taken along the line VIII-VIII in FIG. In the figure, 1 is a housing, 2 is a cylindrical cylinder formed in the housing 1, 3 is a piston slidably arranged in the cylinder 2, 4 is a spring for applying downward force to the piston 3, 5 Is a cam formed on the shaft 6, 7
Is a needle bearing rotatably arranged on the outer periphery of the cam 5 and is in contact with the end of the piston 3. Shaft 6
Are rotatably supported by a pair of bearings 8 and 9 mounted in the housing 1. An oil seal 11 that seals the outside air from the cam chamber 10 is attached to the outside of the bearing 8. A pulley 36 is fixed to the tip of the shaft 6 protruding to the outside of the housing 1, and the pulley 36 is connected to a crankshaft 38 of an engine 35 via a belt 37.
It is connected to a drive pulley 39 mounted above.

Reference numeral 12 is a cover, which comprises a suction valve 13, a discharge valve 18, a suction port 17 and a discharge port 22. The intake valve 13 includes a ball 14 and a valve seat 15
And a spring 16 that constantly urges the ball 14 toward the valve seat 15. On the other hand, the discharge valve 1
8 is a ball 19, a valve seat 20, and a spring 21 for constantly urging the ball 19 toward the valve seat 20.
It has and.

FIG. 9 is a block diagram showing an in-cylinder injector for a 4-cylinder gasoline engine equipped with a conventional high-pressure fuel pump. This fuel system includes a fuel tank 25 and a fuel tank 25.
A low-pressure fuel pump 27 inserted in the fuel filter 26, a high-pressure fuel pump 29 into which fuel discharged from the low-pressure fuel pump 27 is guided, and a suction pipe 28 for the high-pressure fuel pump 29.
Similarly, a discharge pipe 30, a distribution pipe 31 to which high-pressure fuel discharged from the high-pressure fuel pump 29 is guided, and a distribution pipe 3
Four fuel injection valves 32 connected to 1 for injecting fuel into the cylinder of the engine 35, a pressure adjustment valve 33 for adjusting the fuel pressure of the distribution pipe 31 to a constant value (for example, 100 kgf / cm ² ), and a pressure adjustment valve. A return pipe 34 for returning the fuel from the fuel tank 33 to the fuel tank 25.

Next, the operation will be described. Fuel tank 2
The fuel in 5 is filtered by the filter 26, and the low pressure fuel pump 2
7 predetermined pressure (for example, 2.5 kgf /
It is pressurized to cm ² ). The pressurized fuel is the intake pipe 28
Through the suction port 17 of the high-pressure fuel pump 29.
When the piston 3 descends, the intake valve 13 opens and the fuel flows into the pressurizing chamber 23 from the passage 24. When the piston 3 rises, the intake valve 13 closes and the discharge valve 18 opens to release the fuel. It is pressure-fed from the discharge port 22 to the distribution pipe 31 via the discharge pipe 30.

The pressures in the discharge pipe 30 and the distribution pipe 31 are preset by a pressure control valve 33 arranged at the rear end of the distribution pipe 31 (for example, 100 kgf / cm).
² ) be maintained. The fuel leaked from the pressure regulating valve 33 for pressure regulation is returned to the fuel tank 25 via the return pipe 34. The injection valve 32 connected to the distribution pipe 31 and arranged for each cylinder of the engine 35 is controlled by a control circuit (not shown) at an optimum timing of the intake stroke or compression stroke of each cylinder to inject fuel into the cylinder of the engine 35. To do. The injected fuel mixes with air and is ignited and exploded by a spark plug (not shown) at an optimum timing near the end of the compression stroke.

Referring now to FIG. 9, when the engine 35 rotates, the drive pulley 39 mounted on the crankshaft 38 of the engine 35 rotates, and the pulley 36 and the shaft 6 fixed to the pulley 36 via the belt 37 rotate. Rotate.

Thus, in FIG. 7, when the shaft 6 rotates, the cam 5 formed on the shaft 6 also rotates,
The piston 3 descends as the cam 5 rotates. Since the piston 3 is driven by the cam 5 via the needle bearing 7, the frictional force acting between the cam 5 and the piston 3 is reduced. Since a predetermined pressure (for example, 2.5 kgf / cm ² ) is applied to the suction port 17 by the low-pressure fuel pump 27 as described above, the piston 3 descends and the pressure in the pressurizing chamber 23 is reduced to the suction port. When the pressure becomes lower than 17, the intake valve 13 opens and the fuel in the intake pipe 28 flows into the pressurizing chamber 23.

Next, when the piston 3 rises past the bottom dead center, the fuel in the pressurizing chamber 23 is compressed, and when the pressure in the pressurizing chamber 23 becomes higher than the pressure in the intake port 17, the intake valve 1
3 is closed again. When the piston 3 further rises, the fuel in the pressurizing chamber 23 is compressed, and when the pressure in the pressurizing chamber 23 becomes higher than the pressure in the discharge pipe 30 (for example, 100 kgf / cm ² ), the discharge valve 18 opens. Pressurizing chamber 23
The fuel inside is discharged into the discharge pipe 30. Next, when the piston 3 begins to descend past the top dead center, the discharge valve 18
Is closed, the suction valve 13 is opened, and the suction pipe 28 is closed again.
The fuel inside flows into the pressurizing chamber 23. The bearings 8 and 9
The needle bearing 7 is filled with grease so that it can rotate smoothly.

[0010]

Since the conventional high-pressure fuel pump is constructed as described above, the fuel leaks from the clearance between the sliding portions of the piston 3 and the cylinder 2, and the leaked fuel is lost by the bearings 8 and 9. Further, there is a problem that the grease penetrates into the grease-enclosed portion of the needle bearing 7, the grease is diluted, and the bearings 8 and 9 and the needle bearing 7 are seized. Further, since the viscosity of the fuel is low and the pressure in the pressurizing chamber 23 becomes high, the leakage of the fuel becomes large. When the leaked fuel fills the cam chamber 10, the piston 3 reciprocates to move the oil seal 11 from the cam chamber 10. There was a risk that fuel would leak to the outside after passing, and in the worst case, a fire would occur.

The present invention has been made to solve the above problems, and an object thereof is to obtain a high-pressure fuel pump capable of preventing seizure of bearings and needle bearings and preventing fuel from leaking to the outside of the pump. And

[0012]

A high-pressure fuel pump according to the present invention has a piston sliding portion and a cam chamber hydraulically sealed by a diaphragm. In addition, the inner peripheral portion of the diaphragm is fixed to the holding member, a recess is formed in the center of the holding member, and the piston end is inserted into this recess so that the cam drives the piston through the holding member. is there.
Further, the diaphragm chamber formed by the diaphragm and the housing is communicated with the suction port or the return pipe.

[0013]

In the high pressure fuel pump according to the present invention, the piston sliding portion and the cam chamber are hydraulically sealed, so that the fuel is prevented from entering the grease filling portions of the bearing and the needle bearing. Further, since the diaphragm chamber is connected to the suction port or the return pipe, the fuel leaked from the piston sliding portion is not accumulated in the diaphragm chamber and the pressure of the diaphragm chamber is maintained at a low pressure.

[0014]

【Example】

Example 1. An embodiment of the present invention will be described with reference to FIGS. 1 is a sectional view and FIG. 2 is a sectional view taken along the line II-II in FIG. In the figure, 101 is a diaphragm, 102 is an upper housing, and a flange 102a is formed in the lower part. 103 is a lower housing,
A flange 103a is formed on the upper part. The outer peripheral edge portion 101 a of the diaphragm 101 has a flange 102 a of the upper housing 102 and a flange 10 of the lower housing 103.
It is sandwiched and held with 3a. A piston 104 has a hole 104a into which the spring 4 is inserted and a groove 104b into which the inner peripheral end portion 101b of the diaphragm 101 is inserted. Upper housing 102 and diaphragm 10
And 1 form a diaphragm chamber 105, and the diaphragm chamber 105 communicates with the suction port 17 via a passage 106. Reference numeral 107 is a ring that urges the ball 14 toward the valve seat 15.

Next, the operation will be described. Piston 10
4 is lowered and the pressure in the pressurizing chamber 23 becomes lower than the pressure in the intake port 17, the intake valve 13 is opened and the fuel is supplied to the pressurizing chamber 2.
Inflow into 3. At this time, since the inner peripheral end portion 101b of the diaphragm 101 is inserted into the groove 104b of the piston 104, the volume of the diaphragm chamber 105 increases as the piston 104 descends. Fuel is supplied to the increased diaphragm chamber 105 from the suction port 17 through the passage 106. Next, when the piston 104 rises past the bottom dead center, the fuel in the pressurizing chamber 23 is compressed and the pressurizing chamber 2
When the pressure inside 3 becomes higher than the pressure at the suction port 17, the suction valve 13 is closed. When the piston 104 further rises, the pressure inside the pressurizing chamber 23 rises, and when the pressure inside the pressurizing chamber 23 becomes higher than the pressure at the discharge port 22, the discharge valve 18 opens and fuel is discharged.

At this time, fuel leaks from the pressure chamber 23 on the high pressure side to the diaphragm chamber 105 on the low pressure side through the gap of the sliding portion of the piston 104. Since the volume of the diaphragm chamber 105 decreases as the piston 104 rises and the fuel leaks from the pressurizing chamber 23, the excess fuel is discharged to the intake port 17 through the passage 106. In this way, the pressure in the diaphragm chamber 105 becomes equal to the pressure in the suction port 17. The fuel in the diaphragm chamber 105 is composed of the outer peripheral end portion 101a and the inner peripheral end portion 101b of the diaphragm 101.
Since it is sealed with, it will not leak into the cam chamber 10.

Example 2. In the first embodiment, the inner peripheral end portion 101b of the diaphragm 101 is connected to the groove portion 10 of the piston 104.
4b, the inner peripheral end portion 101b of the diaphragm 101 is attached to the holding member 1 as shown in FIGS.
09 and the retainer 110 may be sandwiched, a recess 109a may be formed in the center of the holding member 109, and the lower end 108b of the piston 108 may be inserted into the recess 109a.

According to this embodiment, the diaphragm 101
The seal strength of the inner peripheral end portion 101b is improved. Further, the inner peripheral end portion 101b of the diaphragm 101 is attached to the holding member 109.
Since the outer peripheral end portion 101a of the diaphragm 101 is sandwiched between the lower housing 103 and the upper housing 102, the piston 108 can be inserted from the upper portion of the cylinder 2, so that the parts can be sequentially stacked upward. ,
Workability is improved.

Example 3. In the third embodiment, as shown in FIGS. 5 and 6, a nipple 111 is arranged in the diaphragm chamber 105, and the nipple 111 is connected to the first return pipe 113 via the second return pipe 112. . According to this embodiment, the pressure in the diaphragm chamber 105 is as shown in FIG.
It becomes lower than that shown in Fig. 2, and the force pushing the diaphragm 101 downward by the pressure of the diaphragm chamber 105 becomes small,
The durability of the diaphragm 101 is improved.

In each of the first to third embodiments described above, the case where the high-pressure fuel pump has one cylinder has been described, but the same effect can be obtained when the high-pressure fuel pump has two or more cylinders.

[0021]

As described above, according to the present invention, the piston sliding portion and the cam are hydraulically sealed by the diaphragm, so that the fuel in the pressurizing chamber is filled with grease in the bearing and the needle bearing. Bearings,
The seizure of the needle bearing is prevented. Also, external leakage is prevented. Further, since the diaphragm chamber is configured to communicate with the suction port or the return pipe, the reciprocating motion of the piston maintains the pressure of the diaphragm chamber at a low pressure and improves the durability of the diaphragm.

[Brief description of drawings]

FIG. 1 is a sectional view showing a high-pressure fuel pump according to a first embodiment of the present invention.

2 is a cross-sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view of a high pressure fuel pump according to a second embodiment of the present invention.

FIG. 4 is a sectional view taken along the line III-III in FIG.

FIG. 5 is a sectional view of a high pressure fuel pump according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a cylinder injection device for a four-cylinder gasoline engine to which a third embodiment of the present invention is applied.

FIG. 7 is a sectional view showing a conventional high-pressure fuel pump.

8 is a cross-sectional view taken along the line VIII-VIII of FIG.

FIG. 9 is a configuration diagram of a cylinder injection device for a 4-cylinder gasoline engine to which a conventional high-pressure fuel pump is applied.

[Explanation of symbols]

 2 cylinder 4 spring 5 cam 17 intake port 101 diaphragm 102 housing 103 housing 104 piston 105 diaphragm chamber 109 holding member 109a recess 112 return pipe 113 return pipe

[Procedure amendment]

[Submission date] December 1, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

4 is a cross - sectional view taken along the line IV-IV in FIG.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (4)

[Claims] 1. A high-pressure fuel pump comprising: a cylinder formed in a housing; a piston slidably arranged in the cylinder; and a cam for converting the rotation of a drive shaft into a reciprocating motion of the piston. A high-pressure fuel pump, wherein a sliding portion of the piston and the cam side are hydraulically sealed by a diaphragm. 2. An inner peripheral portion of a diaphragm is fixed to a holding member, a recess is formed in the center of the holding member, and a piston end is inserted into the recess, and a cam drives a piston via the holding member. The high-pressure fuel pump according to claim 1, characterized in that. 3. The high-pressure fuel pump according to claim 1, wherein a diaphragm chamber formed by the diaphragm and the housing is communicated with the suction port. 4. The high pressure fuel pump according to claim 1, wherein a diaphragm chamber formed by the diaphragm and the housing is connected to the return pipe.