JPH09324745A - Axial plunger pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge the air of the inside of a cylinder room without inviting the leak of an operation liquid. SOLUTION: Plural plungers 19 are arranged facing to a swash plate 16 integrated with a drive shaft 13. A pump is operated after push-pressing the plunger 19 in order by the swash plate 16. An air bleeding passage 51 opened/ closed by the plunger 19 is formed near the largest projected stroke position of the plunger end of a cylinder room 50. The air bleeding passage 51 is opened only when the plunger 19 stays near the largest projected stroke and the air in the cylinder room 50 is discharged. When the operation liquid is pressurized by the plunger 19, the air bleeding passage 51 is blocked by the plunger 19. Therefore, the operation liquid is not leaked from the air bleeding passage 51.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial plunger pump used as a fuel pressurizing pump for a fuel injection device of an automobile, and more particularly to an axial plunger pump improved so that the air that has entered the pump can be efficiently discharged. Regarding

[0002]

2. Description of the Related Art As a pump device of this type, an axial plunger pump as disclosed in, for example, Japanese Utility Model Publication No. 2-92073 has been devised. In this axial plunger pump, a swash plate is integrally provided at the end of the drive shaft, while a plurality of plungers are arranged in the housing at positions facing the swash plate so that the plunger can move forward and backward. When the swash plate oscillates and rotates, a plurality of plungers are sequentially pressed by the swash plate to repeat protrusion and retreat.When each plunger protrudes, the hydraulic fluid sucked into the cylinder chamber is continued and the plunger retracts. It is designed to discharge.

[0003]

However, in such an axial plunger pump, if air stays inside the pump, the pump performance may deteriorate. In particular, if air stays inside the cylinder chamber, the discharge flow rate may decrease. It is likely to cause variations and generation of pulse pressure. On the other hand, it is conceivable to form an air vent passage in the cylinder chamber, but if a simple air vent passage is formed in the cylinder chamber, a large amount of hydraulic fluid will leak from the air vent passage along with air during the plunger discharge process. However, this causes another problem that the pump efficiency is reduced.

Therefore, the present invention is intended to provide a pump device capable of reliably discharging the air flowing into the inside of the cylinder chamber without causing the leakage of the hydraulic fluid to obtain stable pump performance. is there.

[0005]

As a means for solving the above-mentioned problems, the present invention is provided with a plurality of plungers which can be moved back and forth facing a swash plate which rotates integrally with a drive shaft. In the axial plunger pump in which the plunger is sequentially pressed by the swash plate and repeatedly projects and retracts in the cylinder chamber, an air vent passage opened and closed by the plunger is formed in the cylinder chamber near the maximum projecting stroke position of the plunger end. . When the plunger reaches the vicinity of the maximum stroke position during the projecting operation of the plunger, the air vent passage that was closed by the plunger until now is opened, and the accumulated air in the cylinder chamber is discharged to the outside of the pump from this air vent passage. Then, when the plunger shifts to the backward movement, the air vent passage is closed again by the plunger, and the pressurized hydraulic fluid does not leak from the air vent passage.

The air bleed passage may be formed upward from the vicinity of the uppermost portion of each cylinder chamber in the vertical direction. In this case, the air in the cylinder chamber gathers in the vicinity of the uppermost portion in the vertical direction, and then is quickly discharged to the outside of the pump through the air vent passage.

Furthermore, the inner wall of the plunger may be formed in a tapered shape so that the inner diameter on the open end side becomes large. In this case, the air inside the plunger moves to the outside of the plunger along the tapered inner wall and is quickly discharged to the outside of the pump from the air vent passage.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

In this embodiment, an axial plunger pump 1 according to the present invention is applied to a fuel pressurizing pump of a fuel injection system for an automobile, and as shown in FIG. Fuel (working fluid) such as gasoline, which has been supplied in a low pressure state via the, is pressurized to a predetermined pressure by the axial plunger pump 1 and supplied to the injector 4, and the fuel is injected into the injector 4.
The fuel is injected into the cylinder (not shown) of the engine and the excess fuel is returned from the injector 4 to the suction passage 5 of the pump 1.

In this axial plunger pump 1, the pump housing 6 has a housing body 8 having a recess 7.
And a front cover 9 attached to the front end thereof, and a pump function block 60, which will be described later, is fixed in the recess 7 of the housing body 8. A drive shaft 13 is supported by the front cover 9 via radial bearings 14 and 15 composed of needle bearings and metal bearings. The drive shaft 13 has an end portion on the side facing the inside of the housing 6. A swash plate 16 having an end surface inclined at a predetermined angle with respect to the axis is integrally formed, and a cup for coupling with a camshaft (not shown) of the engine is provided at an end portion of the housing 6 on the side projecting to the outside. A ring 17 is provided.

The pump function block 60 includes a cylinder block 11 for accommodating a plurality of plungers 19 in the axial direction, a suction check valve 24 and a discharge check valve 2.
A valve block 10 for accommodating 5 is axially divided, and these blocks 10 and 11 are fixed to the bottom portion of the housing 6 in a superposed state by a bolt 12 penetrating the central portion of both blocks 10 and 11. The cylinder block 11 is made of a ferrous metal material having high hardness, and the valve block 10 is made of an aluminum material.

Among them, the cylinder block 11 is provided with a plurality of cylinder holes 18 along the axial direction at equal intervals in the circumferential direction, and a plunger 19 and its plunger 19 are attached to each cylinder hole 18 in the direction of the swash plate 16. The bottom wall of each cylinder hole 18 is closed by the end surface of the valve block 10, and the cylinder hole 50 and the end surface of the valve block 10 form the cylinder chamber 50 in the present invention. It is designed to be configured. Each plunger 19 housed in the cylinder block 11 has a hemispherical recess 20 formed on the top surface thereof, and a shoe 21 described later is slidably fitted in the recess 20.

On the other hand, the valve block 10 is formed with a plurality of suction ports 22 and discharge ports 23 which communicate with the respective cylinder holes 18 of the cylinder block 11, and each suction port 22 has a suction check valve 24. In addition, each discharge port 23 is provided with a discharge check valve 25. Of these, the suction port 22 corresponds to the corresponding cylinder hole 1
8 is formed along the axial direction of the valve block 10,
On the back surface of the valve block 10, the housing body 8
The suction side annular groove 26 formed on the inner surface of the bottom wall of the housing is communicated with the suction passage 5 of the housing body 8 via the annular groove 26. On the other hand, the discharge port 23 is
Discharge from the corresponding cylinder hole 18 radially outward of the valve block 10 and communicates with a discharge side annular groove 27 formed on the outer peripheral surface of the valve block 10, and the discharge of the housing main body 8 through this annular groove 27. It communicates with the passage 28. Therefore, each plunger 19 is
8 (cylinder chamber 50), the working fluid is sucked into each cylinder hole 18 through the suction side annular groove 26, and the working fluid is passed through the discharge side annular groove 27 to the discharge passage 28. Sent out.

Reference numeral 29 in the drawing denotes a low pressure regulator which is provided between the suction pipe connecting port (not shown) of the suction passage 5 and the suction side annular groove 26 to maintain the suction pressure at a constant low pressure. Drain port 3 of low pressure regulator 29
0 communicates with the fuel tank 2 through the return pipe 31.

On the other hand, a disk-shaped auxiliary plate 38 is attached to the end face of the swash plate 16 formed on the drive shaft 13 so as to be relatively rotatable. A boss 39 is provided at the center of the auxiliary plate 38, and the boss 39 is fitted into a support hole 40 formed at the center of the end face of the swash plate 16 so as to be relatively rotatable. A thrust plate 41 having a high hardness and a small friction coefficient is rotatably attached to an end surface of the auxiliary plate 38 on the cylinder block 11 side by a bolt 42, and the thrust plate 41 is fitted and held by each of the plungers 19. The shoe 21 is slidably abutted. Since each plunger 19 is biased by the spring in the direction of the swash plate 16 as described above, each shoe 21 is constantly pressed against the thrust plate 41 by the biasing force of the plunger 19. Further, a load supporting flange 43 is provided at a rear position of the swash plate 16 of the front cover 9, and between the load supporting flange 43 and the swash plate 16 and between the swash plate 16 and the auxiliary plate 38, Thrust bearings 44a and 44b, which are needle bearings, are interposed. In the thrust bearings 44a and 44b, the auxiliary plate 38 has the plunger 19
The axial component of the reaction force received from the front cover 9
Is supported by the load support flange 43 of the auxiliary plate 38, and the radial component of the reaction force received from the plunger 19 is supported by the fitting portion between the boss 39 of the auxiliary plate 38 and the support hole 40 of the drive shaft 13. It has become.

Further, one end of a metal bellows 45 which covers the periphery of the drive shaft supporting portion of the housing 6 to the periphery of the swash plate 16 is joined to the outer peripheral edge portion of the auxiliary plate 38 in a hermetically sealed state. There is. The other end of the bellows 45 is similarly joined to the annular mounting flange 46 in a hermetically sealed state, and the outer peripheral edge portion of the mounting flange 46 is interposed between the joint portion of the housing body 8 and the front cover 9. ,
It is coupled to the housing body 8 together with the front cover 9 by bolts 47. A relatively high-viscosity lubricating liquid is sealed in the space around the drive shaft surrounded by the bellows 45. That is, the bellows 45 divides the interior of the housing 6 into a hydraulic fluid chamber 48 filled with the hydraulic fluid (fuel) leaking from the cylinder block 11 and a lubricating fluid chamber 49 filled with a lubricating fluid.

Further, a return passage 53 is formed in the upper wall portion of the recess 7 of the housing body 8 to connect the hydraulic fluid chamber 48 and the drain port 30 of the low pressure regulator 29. The return passage 53 is provided in the cylinder hole 18
It is for returning the hydraulic fluid leaking into the hydraulic fluid chamber 48 from the sliding gap between the plunger 19 and the plunger 19 to the fuel tank 2, and extends obliquely upward from the upper wall portion of the recess 7 to communicate with the drain port 30. ing.

By the way, each of the cylinder chambers 50 for accommodating the plunger 19 is formed with an air vent passage 51 for discharging the air in the cylinder chamber to the outside of the pump. As shown in FIG. 3, all the air bleed passages 51 are formed in the cylinder block 11 so as to extend obliquely upward from the vicinity of the uppermost portion in the vertical direction of each cylinder hole 18, and the end portion of the cylinder block 11 on the outer peripheral side is formed. The air that opens to the hydraulic fluid chamber 48 of the pump housing 6 and escapes from these air vent passages 51 is further discharged from the hydraulic fluid chamber 48 into the fuel tank 2 through the return passage 53, the drain port 30, and the return pipe 31. It has become so. An orifice 52 is provided in a portion of each air vent passage 51 facing the cylinder hole 18, as shown in an enlarged portion surrounded by a circular broken line in FIG. The orifice 52 opens in the cylinder hole 18 in the vicinity of the maximum projecting stroke position at the end of the plunger 19, and is opened and closed by the outer peripheral surface of the plunger 19. Therefore, the orifice 52 is closed by the plunger 19 in a normal state because of the opening position thereof, and is opened only when the plunger 19 is displaced in the vicinity of the maximum protruding stroke position.

The inner wall 54 of the plunger 19 accommodated in each cylinder hole 18 is tapered so that the inner diameter on the open end side is larger than the inner diameter on the bottom side.
The air inside the plunger 19 is transferred to its tapered inner wall 54.
It can be smoothly discharged to the outside of the plunger 19 along. Furthermore, the end of the return passage 53 on the hydraulic fluid chamber 48 side is opened immediately above the end of the air bleed passage 51 on the outer peripheral surface side of the cylinder block (the same axial position as the end). The air that has escaped from each air vent passage 51 to the hydraulic fluid chamber 48 returns along the inner peripheral surface of the hydraulic fluid chamber 48 to the return passage 5
It is supposed to gather in 3.

In the above structure, when the drive shaft 13 is rotated by starting the engine, the swash plate 16 integrated with the drive shaft 13 is rotated, whereby the auxiliary plate 38 is prevented from rotating by the bellows 45 and the swash plate 16 is rotated. It swings (pivots) integrally with the swash plate 16 while rotating relative to. When the auxiliary plate 38 swings in this way, the plunger 19 on the cylinder block 11 repeats the forward / backward movement in sequence through the thrust plate 41 and the shoe 21 in sliding contact therewith, so that the pump action is continuously performed. At this time, the suction passage 5 from the fuel tank 2 via the supply pump 3
After the working fluid (fuel) supplied to is regulated to a set low pressure by the low pressure regulator 29 in the middle of the suction passage 5,
Suction side annular groove 26, suction port 22, suction check valve 2
4 is sequentially sucked into the cylinder hole 18, where the plunger 19 pressurizes the cylinder hole 18
Is supplied to the injector 4 through the discharge check valve 25, the discharge port 23, the discharge side annular groove 27, and the discharge passage 28 in order, and the surplus of the hydraulic fluid used in the injector 4 is returned to the suction passage 5.

Further, the air mixed in the working fluid (fuel) and the air staying inside the pump are discharged from the cylinder chambers 50 to the outside of the pump in the following manner during the pump operation. In the drawings, air is indicated by a symbol a.

That is, during pump operation, the displacement of the plunger 19 changes from the backward direction to the protruding direction, and the plunger 1
When 9 reaches the vicinity of the maximum stroke position as shown in FIG. 1, the end portion of the plunger 19 opens the orifice 52 of the air vent passage 51, and the air a existing in the cylinder chamber 50 is removed by the orifice 52 (air The liquid is discharged into the hydraulic fluid chamber 48 through the drain passage 51). When the orifice 52 opens, not only the air a but also the working fluid in the cylinder chamber 50 may flow out through the orifice 52 into the working fluid chamber 48. At this time, the pressure in the cylinder chamber 50 is extremely high. Since it is low, even if it flows out from the cylinder chamber 50, the amount thereof becomes very small. In addition, as described above, the hydraulic fluid chamber 4
The air a that has flowed into 8 is sequentially discharged through the return passage 53, the drain port 30, and the return pipe 31 to the fuel tongue 2 outside the pump.

Then, when the displacement of the plunger 19 changes again in the backward direction from the above state and the plunger 19 is slightly displaced in the backward direction, the plunger 19 closes the orifice 52 again as shown in FIG. During the subsequent pressurization of the hydraulic fluid, a large amount of hydraulic fluid does not flow out of the cylinder chamber 50 into the hydraulic fluid chamber 48 through the orifice 52.

Since the axial plunger pump 1 opens the air vent passage 51 only when the plunger 19 is in the vicinity of the maximum protruding stroke as described above, a large amount of the plunger 19 moves backward (during the discharging process). It is possible to reliably discharge the air a in the cylinder chamber 50 without causing the leakage of the hydraulic fluid. For this reason, the discharge of the air a from the cylinder chamber 50 can be reliably prevented from reducing the discharge flow rate, causing variations, and generating pulsating pressure, without causing a decrease in pump efficiency due to leakage of the hydraulic fluid. . In particular, when a low-viscosity hydraulic fluid such as fuel is pressurized to a high pressure as in this embodiment, the hydraulic fluid leaks often become a problem even with a small number of holes. In the above, the problem of this leak can be reliably solved as described above.

The embodiment of the present invention is not limited to the one described above. For example, as shown in FIG. 4, the air vent passage 51a may be formed radially from each cylinder hole 18, As shown in FIG. 5, all the air vent passages 51b may be formed from the uppermost position of the cylinder hole 18 toward the upper side in the vertical direction. In the former case, all the passages 51a can be drilled toward the center of the cylinder block 11, and the length of the passages 51a itself is the shortest, so that the passages 51a can be easily formed. It is possible to manufacture at low cost. Also,
In the latter case, the air a in the cylinder hole 18 can be most efficiently discharged to the outside of the pump due to the characteristic that the air a goes upward.

[0026]

As described above, according to the present invention, the cylinder chamber
An air bleed passage opened and closed by the plunger is formed near the maximum projecting stroke position at the end of the plunger, and the air bleed passage is opened only when the plunger is near the maximum projecting stroke position. The air that has flowed in can be reliably discharged without causing a leak of the hydraulic fluid, and as a result, stable pump performance can be obtained without lowering pump efficiency or generating pulse pressure.

When the air vent passage is formed upward from the vicinity of the uppermost portion in the vertical direction of each cylinder chamber, the air in each cylinder chamber can be discharged to the outside of the pump more quickly.

Further, when the inner wall of the plunger is formed in a tapered shape so that the inner diameter on the open end side becomes large, the air inside the plunger can be quickly discharged along the inner wall.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the same embodiment.

FIG. 3 is a sectional view of a cylinder block showing the same embodiment.

FIG. 4 is a sectional view of a cylinder block showing another embodiment of the present invention.

FIG. 5 is a sectional view of a cylinder block showing still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Axial plunger pump, 13 ... Drive shaft, 16 ... Swash plate, 19 ... Plunger, 50 ... Cylinder chamber, 51 ... Air vent passage, 54 ... Inner wall.

Claims (3)

[Claims] 1. A plurality of plungers are arranged so as to be able to move forward and backward so as to face a swash plate that rotates integrally with a drive shaft, and the plungers are sequentially pressed by the swash plate to repeatedly project and retract in the cylinder chamber. In the plunger pump, an air bleed passage opened and closed by the plunger is formed in the cylinder chamber in the vicinity of the maximum protruding stroke position at the end of the plunger. 2. The axial plunger pump according to claim 1, wherein the air bleed passage is formed upward from the vicinity of the uppermost portion in the vertical direction of each cylinder chamber. 3. The axial plunger pump according to claim 1, wherein the inner wall of the plunger is formed in a tapered shape so that the inner diameter on the open end side becomes large.