PUMP

Abstract

In a cylinder, a plunger is reciprocated in a plunger receiving hole to pressurize fluid in a pump chamber. A delivery passage hole extends in a direction generally perpendicular to an axis of the plunger receiving hole from the pump chamber to a radial intermediate location of the cylinder, which is located between the pump chamber and an outer peripheral surface of the cylinder in a radial direction of the cylinder. A tilted delivery passage hole is tilted relative to the axis of the plunger receiving hole and extends from a portion of the delivery passage hole, which is radially spaced from the pump chamber, toward the outside of the cylinder.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2008-17269 filed on Jan. 29, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pump.

2. Description of Related Art

A fuel injection apparatus, which injects fuel in a compression ignition internal combustion engine, has a supply pump that pumps fuel to supply high pressure fuel to a common rail. In the supply pump, a pump chamber is defined in a cylinder. When a plunger received in a plunger receiving hole of the cylinder is reciprocated, fuel in the pump chamber is pressurized and is discharged toward the common rail through a delivery passage formed in the cylinder. The delivery passage is tilted relative to an axis of the plunger receiving hole (see, for example, Japanese Unexamined Patent Publication No. JP2006-170169A).

In the case of the supply pump recited in Japanese Unexamined Patent Publication No. JP2006-170169A, when the fuel in the pump chamber is pressurized, the cylinder is expanded outwardly by the fuel pressure to generate the stress at a pump chamber side opening (hereinafter, referred to as a delivery passage opening) of the delivery passage. The stress is concentrated at the portion of the delivery passage opening where the angle, which is defined between the axis of the plunger receiving hole and the axis of the delivery passage, is an acute angle. Cracking of the cylinder may start at the portion of the delivery passage opening where the stress is concentrated.

SUMMARY OF THE INVENTION

The present invention addresses the above disadvantage. Thus, it is an objective of the present invention to limit cracking of a cylinder of a pump, in which a delivery passage is tilted relative to an axis of a plunger receiving hole.

According to the present invention, there is provided a pump that includes a cylinder and a plunger. The cylinder defines a pump chamber, a plunger receiving hole, an intake passage and a delivery passage. The plunger receiving hole is continuous from the pump chamber and is coaxial with the pump chamber. The intake passage is communicated with the pump chamber to supply fluid from an external fluid supply source to the pump chamber. The delivery passage is communicated with the pump chamber to output the fluid from the pump chamber to an outside of the cylinder. The plunger is received in the plunger receiving hole in a reciprocable manner to pressurize the fluid in the pump chamber and to deliver the pressurized fluid out of the pump chamber through the delivery passage. The delivery passage includes a lateral delivery passage hole and a tilted delivery passage hole. The lateral delivery passage hole extends through the pump chamber in a direction generally perpendicular to an axis of the plunger receiving hole and includes a first hole section and a second hole section. The first hole section extends from the pump chamber to an outer peripheral surface of the cylinder and is closed with a closing member. The second hole section extends from the pump chamber to a radial intermediate location of the cylinder, which is located between the pump chamber and the outer peripheral surface of the cylinder in a radial direction of the cylinder. The tilted delivery passage hole is tilted relative to the axis of the plunger receiving hole and extends from a portion of the second hole section, which is radially spaced from the pump chamber, toward the outside of the cylinder.

According to the present invention, there is also provided a pump, which includes a cylinder and a plunger. The cylinder defines a pump chamber, a plunger receiving hole, an intake passage and a delivery passage. The plunger receiving hole continuous from the pump chamber and is coaxial with the pump chamber. The intake passage is communicated with the pump chamber to supply fluid from an external fluid supply source to the pump chamber. The delivery passage is communicated with the pump chamber to output the fluid from the pump chamber to an outside of the cylinder. The plunger is received in the plunger receiving hole in a reciprocable manner to pressurize the fluid in the pump chamber and to deliver the pressurized fluid out of the pump chamber through the delivery passage. The delivery passage includes a delivery passage hole and a tilted delivery passage hole. The delivery passage hole extends in a direction generally perpendicular to an axis of the plunger receiving hole from the pump chamber to a radial intermediate location of the cylinder, which is located between the pump chamber and an outer peripheral surface of the cylinder in a radial direction of the cylinder. The tilted delivery passage hole is tilted relative to the axis of the plunger receiving hole and extends from a portion of the delivery passage hole, which is radially spaced from the pump chamber, toward the outside of the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a longitudinal schematic cross sectional view of a pump according to a first embodiment of the present invention;

FIG. 2 is partial cross sectional view of a cylinder of the pump shown in FIG. 1;

FIG. 3 is an enlarged partial cross sectional view of a section indicated by III in FIG. 2;

FIG. 4 is a partial cross sectional view of the cylinder of a first modification of the first embodiment;

FIG. 5 is a partial cross sectional view of the cylinder of a second modification of the first embodiment;

FIG. 6 is a partial cross sectional view of the cylinder of a third modification of the first embodiment;

FIG. 7 is a partial cross sectional view of the cylinder of a fourth modification of the first embodiment;

FIG. 8 is a partial cross sectional view of the cylinder of a fifth modification of the first embodiment; and

FIG. 9 is a partial cross sectional view of a cylinder of a pump according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

A first embodiment of the present invention will be described with reference to the accompanying drawings. In a fuel injection apparatus, which injects fuel to a combustion chamber of a compression ignition internal combustion engine, a pump 1 according to the present embodiment is used as a supply pump that supplies the high pressure fuel to a common rail that stores the high pressure fuel.

FIG. 1 shows the structure of the pump 1 of the present embodiment. A pump housing 10 of the pump 1 includes a cam chamber 10a, a slider receiving hole 10b and a cylinder receiving hole 10c. The cam chamber 10a is located at a lower end of the pump housing 10. The slider receiving hole 10b is generally cylindrical and extends upwardly from the cam chamber 10a. The cylinder receiving hole 10c is generally cylindrical and extends from the slider receiving hole 10b to an upper end surface of the pump housing 10.

The cam chamber 10a receives a camshaft 11, which is driven by the undepicted compression ignition internal combustion engine (hereinafter, referred to as the internal combustion engine). The camshaft 11 is rotatably supported by the pump housing 10. Furthermore, a cam 12 is formed in the camshaft 11.

A cylinder 13 is installed in the cylinder receiving hole 10c such that the cylinder 13 closes the opening of the cylinder receiving hole 10c. A generally cylindrical plunger receiving hole 13a is formed in the cylinder 13, and a generally cylindrical plunger 14 is received in the plunger receiving hole 13a in a reciprocable manner. A pump chamber 15 is continuous from the plunger receiving hole 13a in a coaxial manner and is defined by an upper end surface of the plunger 14 and an inner peripheral surface of the cylinder 13.

A seat 14a is connected to a lower end of the plunger 14, and the seat 14a is urged against a slider 17 by a spring 16. The slider 17 is configured into a generally cylindrical shape and is reciprocably received in the slider receiving hole 10b. A cam roller 18 is rotatably installed to the slider 17 and is engaged with the cam 12. When the cam 12 is rotated through the rotation of the camshaft 11, the plunger 14 is reciprocated together with the seat 14a, the slider 17 and the cam roller 18.

A fuel well 19 is formed between the cylinder 13 and the pump housing 10. The low pressure fuel, which is outputted from an undepicted feed pump (an external fluid supply source), is supplied to the fuel well 19 through an undepicted low pressure pipe. Also, the fuel well 19 is communicated with the pump chamber 15 through an intake passage 13b of the cylinder 13 and an intake passage 31a of a solenoid valve 30.

A delivery passage 13c, which is always communicated with the pump chamber 15, opens to the inner peripheral surface of the cylinder 13. The pump chamber 15 is connected to an undepicted common rail through the delivery passage 13c, a delivery valve 20 and an undepicted high pressure fuel pipe.

The delivery valve 20 is installed to the cylinder 13 on the downstream side of the delivery passage 13c. The delivery valve 20 include a valve element 20a and a spring 20b. The valve element 20a is driven to open or close the delivery passage 13c. The spring 20b urges the valve element 20a against a valve seat in a valve closing direction. The fuel, which is pressurized in the pump chamber 15, drives the valve element 20a against the urging force of the spring 20b in a valve opening direction away from the valve seat, so that the pressurized fuel is sent to the common rail.

The solenoid valve 30 is threadably fixed to the cylinder 13 to close the opening of the pump chamber 15 at the location where the solenoid valve 30 is opposed to the upper end surface of the plunger 14. Specifically, the solenoid valve 30 and the plunger 14 are coaxially placed in such a manner that the pump chamber 15 is placed between the solenoid valve 30 and the plunger 14. The intake passage 31a of the solenoid valve 30 and a seat (not shown) are formed in a body 31 of the solenoid valve 30. One end of the intake passage 31a is communicated with the pump chamber 15, and the other end of the intake passage 31a is communicated with the intake passage 13b of the cylinder 13. The seat is formed in the intake passage 31a of the solenoid valve 30.

The solenoid valve 30 includes a solenoid 32, an armature 33, a spring 34, a valve element 35 and a stopper 36. The solenoid 32 generates an attractive force upon energization thereof. The armature 33 is attracted to the solenoid 32 in an attracting direction upon energization of the solenoid 32. The spring 34 urges the armature 33 in an opposite direction, which is opposite from the attracting direction of the armature 33. The valve element 35 is moved integrally with the armature 33 toward and away from the seat to open or close the intake passage 31a of the solenoid valve 30. The stopper 36 limits the position of the valve element 35 at the time of the valve opening. The stopper 36 is clamped between the solenoid valve 30 and the cylinder 13, and a plurality of communication holes (not shown) is formed in the stopper 36 to communicate between the intake passage 31a and the pump chamber 15.

Next, a main feature of the pump 1 of the present embodiment will be described in detail. FIG. 2 shows a partial cross sectional view indicating the main feature of the cylinder 13 of the pump 1 shown in FIG. 1. FIG. 3 is an enlarged cross sectional view of a circled portion III in FIG. 2.

As shown in FIG. 2, the delivery passage 13c includes a lateral delivery passage hole 130 and a tilted delivery passage hole 131. The lateral delivery passage hole 130 extends through the pump chamber 15 in a direction generally perpendicular to an axis 31 of the plunger receiving hole 13a. The tilted delivery passage hole 131 is tilted relative to the axis J1 of the plunger receiving hole 13a and extends from the lateral delivery passage hole 130 toward the outside of the cylinder 13.

Specifically, the lateral delivery passage hole 130 includes a first hole section 1301 and a second hole section 1302. The first hole section 1301 extends from the pump chamber 15 to an outer peripheral surface of the cylinder 13. The second hole section 1302 extends from the pump chamber 15 to a radial intermediate location of the cylinder 13, which is located between the pump chamber 15 and the outer peripheral surface of the cylinder 13 in the radial direction of the cylinder 13.

The tilted delivery passage hole 131 is connected to the second hole section 1302 at a location that is spaced from the pump chamber 15. The tilted delivery passage hole 131 is tilted such that a radial distance between the axis J1 of the plunger receiving hole 13a and the tilted delivery passage hole 131 increased from the plunger 14 (see FIG. 1) side toward the solenoid valve 30 (see FIG. 1) side in the axial direction.

As shown in FIG. 3, the first hole section 1301 includes a generally cylindrical large diameter hole portion 1301a, a generally cylindrical small diameter hole portion 1301b and a tapered step portion 1301c. The large diameter hole portion 1301a opens to the pump chamber 15. The small diameter hole portion 1301b has an inner diameter smaller than that of the large diameter hole portion 1301a and opens to the outer peripheral surface of the cylinder 13. The step portion 1301c is formed between the large diameter hole portion 1301a and the small diameter hole portion 1301b to connect therebetween.

The small diameter hole portion 1301b and the second hole section 1302 (see FIG. 2) are formed by drilling using a common drill from the outside of the cylinder 13. The small diameter hole portion 1301b and the second hole section 1302 are coaxial and have the common inner diameter. The large diameter hole portion 1301a and the step portion 1301c are created through an electrochemical machining process or a cutting process.

The first hole section 1301 is provided to process the second hole section 1302 and is not required for achieving the pumping function of the pump 1. Therefore, the first hole section 1301 is closed by a closing member 40. Specifically, the closing member 40, which is configured into a generally spherical shape, is press fitted into the large diameter hole portion 1301a. The closing member 40 is urged against the step portion 1301c, and the first hole section 1301 is closed through the engagement between the closing member 40 and the step portion 1301c.

The operation of the pump having the above structure will be described. First, when the solenoid 32 of the solenoid valve 30 is not energized, the valve element 35 is placed in the valve opening position by the urging force of the spring 34. That is, the valve element 35 is lifted away from the seat portion of the body 31, so that the intake passage 31a is opened.

In this open state of the intake passage 31a, when the plunger 14 is moved downward, the low pressure fuel, which is discharged from the feed pump, is supplied to the pump chamber 15 through the fuel well 19, the intake passage 13b and the intake passage 31a.

Next, when the plunger 14 begins to move upward, the plunger 14 begins to compress the fuel in the pump chamber 15. However, at the begging of the upward movement of the plunger 14, the solenoid valve 30 is not energized, and thereby the intake valve passage 31a is opened. Therefore, the fuel in the pump chamber 15 spills toward the fuel well 19 side through the intake passage 31a and the intake passage 13b, so that the fuel in the pump chamber 15 is not substantially compressed, i.e., is not substantially pressurized.

When the solenoid valve 30 is energized during the spilling of the fuel from the pump chamber 15, the armature 33 and the valve element 35 are attracted toward the solenoid 32 against the urging force of the spring 34. Thus, the valve element 35 is seated against the seat portion of the body 31, and thereby the intake passage 31a is closed. In this way, the spill flow of the fuel toward the fuel well 19 side is stopped, and the pressurization of the fuel in the pump chamber 15 by the plunger 14 starts. Then, the delivery valve 20 is opened by the fuel pressure developed in the pump chamber 15, so that the fuel is pumped to the common rail, i.e., is delivered out of the pump chamber 15 through the delivery passage 13c.

When the pressurization of the fuel in the pump chamber 15 by the plunger 14 starts, the stress is generated in the pump chamber 15 side opening of the first hole section 1301 and the pump chamber 15 side opening of the second hole section 1302.

However, in the pump 1 of the present embodiment, the first hole section 1301 and the second hole section 1302 extend generally perpendicular to the axis J1 of the plunger receiving hole 13a. Therefore, the stress is uniformly generated in the pump chamber 15 side opening of the first hole section 1301 and the pump chamber side opening of the second hole section 1302, so that the cracking of the cylinder 13 caused by the stress concentration is limited.

Furthermore, the closing member 40 is urged against the step portion 1301c by the pressure of the fuel in the pump chamber 15, so that the degree of sealing between the closing member 40 and the step portion 1301c is improved. Also, the closing member 40, which is configured into the generally spherical shape, can be more easily manufactured in comparison to a closing member having any other shape.

In the above embodiment, the closing member 40, which is configured into the generally spherical shape, is used to close the first hole section 1301. However, the means for closing the first hole section 1301 may modified as follows.

FIG. 4 is a partial cross sectional view of the cylinder 13 in a first modification of the above embodiment. As shown in FIG. 4, the closing member 40 has a large diameter cylindrical portion 401, a small diameter cylindrical portion 402 and a tapered step portion 403. The small diameter cylindrical portion 402 has the outer diameter smaller than that of the large diameter cylindrical portion 401. The tapered step portion 403 is formed between the large diameter cylindrical portion 401 and the small diameter cylindrical portion 402 to connect therebetween.

The large diameter cylindrical portion 401 is press fitted into the large diameter hole portion 1301a of the first hole section 1301, and the small diameter cylindrical portion 402 is press fitted into the small diameter hole portion 1301b of the first hole section 1301. Furthermore, the step portion 403 of the closing member 40 is urged against the step portion 1301c of the first hole section 1301. The first hole section 1301 is closed through the engagement between the step portion 403 and the step portion 1301c. Even in this modification, the closing member 40 is urged against the step portion 1301c by the pressure of the fuel in the pump chamber 15, so that the degree of sealing between the closing member 40 and the step portion 1301c is improved.

FIG. 5 is a partial cross sectional view of the cylinder 13 in a second modification of the above embodiment. As shown in FIG. 5, the closing member 40 has a bolt 41 and a gasket 42. The large diameter hole portion 1301a of the first hole section 1301 opens to the outer peripheral surface of the cylinder 13, and the small diameter hole portion 1301b of the first hole section 1301 opens to the pump chamber 15 of the cylinder 13. The step portion 1301c between the large diameter hole portion 1301a and the small diameter hole portion 1301b has a generally flat surface, which is generally perpendicular to the axis of the large diameter hole portion 1301a and of the small diameter hole portion 1301b. A female screw thread 1301d is formed in the small diameter hole portion 1301b. When the bolt 41 is screwed into the female screw thread 1301d, the gasket 42 is urged against the step portion 1301c to close the first hole section 1301.

In the second modification, the installation of the bolt 41 and the gasket 42 into the cylinder 13 can be performed from the outside of the cylinder 13. Therefore, the installation of the bolt 41 and the gasket 42 into the cylinder 13 can be easily performed. In the second modification, it is possible to eliminate the gasket 42, if desired. In such a case, a head of the bolt 41 may be urged against the step portion 1301c to close the first hole section 1301.

FIG. 6 is a partial cross sectional view of the cylinder 13 in a third modification of the above embodiment. As shown in FIG. 6, the step portion 1301c, which is located between the large diameter hole portion 1301a and the small diameter hole portion 1301b in the first hole section 1301, has a generally flat surface, which is generally perpendicular to the axis of the large diameter hole portion 1301a and of the small diameter hole portion 1301b.

The closing member 40 is initially configured into a generally cylindrical rod, which has a generally constant diameter along the entire length thereof. Then, the cylindrical closing member 40 is installed in the first hole section 1301. Thereafter, the opposed ends of the cylindrical rod-shaped closing member 40 are compressed toward each other to deform the cylindrical rod-shaped closing member 40, so that the length of the cylindrical closing member 40 is shortened and is radially outwardly expanded into the stepped shape of FIG. 6 having an expanded head 43 and a small diameter cylindrical portion 44.

The head 43 limits removal of the closing member 40 from its installed position. Furthermore, the small diameter cylindrical portion 44 is radially outwardly urged against the inner peripheral surface of the first hole section 1301 to close the first hole section 1301. In the third modification, the cylindrical rod, which can be easily manufactured, is used, so that it is advantageous in terms of the costs.

FIG. 7 is a partial cross sectional view of the cylinder 13 in a fourth modification of the above embodiment. As shown in FIG. 7, the step portion 1301c, which is located between the large diameter hole portion 1301a and the small diameter hole portion 1301b in the first hole section 1301, has a generally flat surface, which is generally perpendicular to the axis of the large diameter hole portion 1301a and of the small diameter hole portion 1301b. The closing member 40 is configured into a generally cylindrical shape. The closing member 40 is press fitted into the large diameter hole portion 1301a. Thereafter, the closing member 40 and the cylinder 13 are welded together at a location B in FIG. 7 to close the first hole section 1301.

FIG. 8 is a partial cross sectional view of the cylinder 13 in a fifth modification of the above embodiment. As shown in FIG. 8, the large diameter hole portion 1301a of the first hole section 1301 opens to the outer peripheral surface of the cylinder 13, and the small diameter hole portion 1301b of the first hole section 1301 opens to the pump chamber 15 of the cylinder 13. The step portion 1301c between the large diameter hole portion 1301a and the small diameter hole portion 1301b has a generally flat surface, which is generally perpendicular to the axis of the large diameter hole portion 1301a and of the small diameter hole portion 1301b.

The closing member 40 includes the large diameter cylindrical portion 401 and the small diameter cylindrical portion 402. The outer diameter of the small diameter cylindrical portion 402 is smaller than that of the large diameter cylindrical portion 401. The large diameter cylindrical portion 401 is inserted into the large diameter hole portion 1301a of the first hole section 1301, and the small diameter cylindrical portion 402 is press fitted into the small diameter hole portion 1301b. Thereafter, the large diameter cylindrical portion 401 and the cylinder 13 are securely welded together at the location B in FIG. 8 to close the first hole section 1301.

Second Embodiment

A second embodiment of the present invention will be described with reference to FIG. 9. FIG. 9 is a cross sectional view showing the cylinder 13 of the pump according to the second embodiment. The present embodiment differs from the first embodiment with respect to the structure of the lateral delivery passage hole 130. In the following description, components, which are similar to those of the first embodiment, will be indicated by the same reference numerals and will not be described further.

As shown in FIG. 9, the lateral delivery passage hole 130 is made only of a hole that extends generally perpendicular to the axis J1 of the plunger receiving hole 13a from the pump chamber 15 to the radial intermediate location of the cylinder 13. In other words, the lateral delivery passage hole 130 is made of the hole, which corresponds to the second hole section 1302 of the first embodiment. This lateral delivery passage hole 130 is formed by the electro-discharge machining.

The tilted delivery passage hole 131 is tilted relative to the axis J1 of the plunger receiving hole 13a and extends from the portion of the lateral delivery passage hole 130, which is spaced from the pump chamber 15, toward the outside of the cylinder 13.

According to the present embodiment, the first hole section 1301 and the closing member 40 of the first embodiment can be eliminated.

In the above embodiments, the present invention is applied to the supply pump of the fuel injection apparatus of the internal combustion engine. However, the present invention is not limited to this and can be applied to various types of pumps that draw and pump fluid.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.

Claims

1. A pump comprising:

a cylinder that defines: a pump chamber; a plunger receiving hole that is continuous from the pump chamber and is coaxial with the pump chamber; an intake passage that is communicated with the pump chamber to supply fluid from an external fluid supply source to the pump chamber; and a delivery passage that is communicated with the pump chamber to output the fluid from the pump chamber to an outside of the cylinder; and

a plunger that is received in the plunger receiving hole in a reciprocable manner to pressurize the fluid in the pump chamber and to deliver the pressurized fluid out of the pump chamber through the delivery passage, wherein the delivery passage includes: a lateral delivery passage hole that extends through the pump chamber in a direction generally perpendicular to an axis of the plunger receiving hole and includes: a first hole section that extends from the pump chamber to an outer peripheral surface of the cylinder and is closed with a closing member; and a second hole section that extends from the pump chamber to a radial intermediate location of the cylinder, which is located between the pump chamber and the outer peripheral surface of the cylinder in a radial direction of the cylinder; and a tilted delivery passage hole that is tilted relative to the axis of the plunger receiving hole and extends from a portion of the second hole section, which is radially spaced from the pump chamber, toward the outside of the cylinder.

2. The pump according to claim 1, wherein:

the first hole section includes: a large diameter hole portion that opens to the pump chamber; a small diameter hole portion that has an inner diameter smaller than that of the large diameter hole portion and opens to the outer peripheral surface of the cylinder; and a step portion that is located between the large diameter hole portion and the small diameter hole portion; and

the closing member is urged against the step portion to close the first hole section though engagement between the closing member and the step portion.

3. The pump according to claim 2, wherein the step portion is tapered.

4. The pump according to claim 2, wherein the closing member is generally spherical.

5. The pump according to claim 1, wherein the closing member is threadably fixed to the first hole section from the outer peripheral surface side of the cylinder.

6. The pump according to claim 1, wherein the closing member is press fitted into the first hole section.

7. The pump according to claim 1, wherein the closing member is securely welded to the cylinder.

8. A pump comprising:

a cylinder that defines: a pump chamber; a plunger receiving hole that is continuous from the pump chamber and is coaxial with the pump chamber; an intake passage that is communicated with the pump chamber to supply fluid from an external fluid supply source to the pump chamber; and a delivery passage that is communicated with the pump chamber to output the fluid from the pump chamber to an outside of the cylinder; and

a plunger that is received in the plunger receiving hole in a reciprocable manner to pressurize the fluid in the pump chamber and to deliver the pressurized fluid out of the pump chamber through the delivery passage, wherein the delivery passage includes: a delivery passage hole that extends in a direction generally perpendicular to an axis of the plunger receiving hole from the pump chamber to a radial intermediate location of the cylinder, which is located between the pump chamber and an outer peripheral surface of the cylinder in a radial direction of the cylinder; and a tilted delivery passage hole that is tilted relative to the axis of the plunger receiving hole and extends from a portion of the delivery passage hole, which is radially spaced from the pump chamber, toward the outside of the cylinder.