JPH06249103A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To provide a fuel injection pump which can reduce errosion of a wall surface of a fuel chamber or a spill protector which protects the wall surface. CONSTITUTION:When a plunger 3 is lifted, a plunger lead 31 of the plunger 3 is communicated with a feed hole 22. Fuel inside a plunger chamber 21 showing spill flow is returned to a fuel chamber 11 through the plunger lead 31 and the feed hole 22 with high speed. A volume of a suction chamber 23 below the plunger 3 is increased by lifting the plunger 3. The pressure inside the suction chamber 23 is lowered, and a part of the fuel flowed into the feed hole 22 from the plunger lead 31 is suctioned into the suction chamber 23 through a suction hole 29. As a result, an amount and kinetic energy of the spill fuel injected to an inner wall 11a of the fuel chamber 11 from the feed hole 22 are decreased, and the errosion thereof is decreased.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fuel injection pump for a diesel engine.

[0002]

2. Description of the Related Art A conventional fuel injection pump for a diesel engine has a cylinder fitted in a bore of a housing, a fuel chamber defined by the cylinder and the housing, and a fuel chamber penetrating the cylinder and communicating with the cylinder bore. A feed hole, a plunger that is slidably fitted in the cylinder bore and pumps the fuel sucked into the plunger chamber through the feed hole, and a plunger that is opened at a predetermined position on the outer peripheral surface of the plunger so as to be able to communicate with the feed hole. A plunger lead communicating with the chamber and a delivery valve provided between the pump chamber and the fuel pipe and opened at a predetermined valve opening pressure are provided.

When the plunger is pressure-fed, the plunger interrupts the communication between the feed hole and the pump chamber and then pressurizes the pump chamber. When the pressure exceeds the opening pressure of the delivery valve, the fuel in the pump chamber is delivered. Deliver to fuel line through valve. After that, when the plunger lead further communicates with the feed hole due to the further rise of the plunger, the fuel in the pump chamber returns (spills) to the fuel chamber through the plunger lead and the feed hole in a high-speed jet state.

[0004]

However, there is a problem that the erosion on the wall surface of the fuel chamber becomes serious when the above-mentioned high-speed jet flow at the time of spilling impinges on the wall surface of the fuel chamber.
In particular, this problem may become more serious as the injection pressure increases as a measure against exhaust gas. It is possible to prevent the erosion of the wall surface of the fuel chamber by surrounding the wall surface of the fuel chamber with a halved cylindrical plate called a spill protector, but instead, the erosion of the spill protector itself becomes a problem.

The present invention has been made in view of the above problems, and an object thereof is to provide a fuel injection pump capable of reducing the erosion of a fuel chamber wall surface or a spill protector for protecting the wall surface.

[0006]

A fuel injection pump of the present invention connects a cylinder fitted in a bore of a housing, a fuel chamber defined by the cylinder and the housing, and the fuel chamber and the cylinder bore. A feed hole, a plunger slidably fitted into the cylinder bore and pumping the fuel sucked into the plunger chamber in the cylinder bore through the feed hole through a delivery valve, and the plunger at a predetermined position on the outer peripheral surface of the plunger. In a fuel injection pump including a plunger lead that is opened so as to be able to communicate with a feed hole and that communicates with the plunger chamber, the fuel injection pump is located on the opposite side of the plunger chamber across the plunger, and is partitioned within the cylinder bore. Inhalation in which the volume increases with pumping of the plunger When the suction chamber and the Fi - is characterized by comprising a suction hole communicating the Dohoru.

[0007]

When the plunger rises in the cylinder bore, the volume of the plunger chamber is reduced, and the fuel sucked into the plunger chamber in advance is pressurized after the plunger closes the feed hole and passes through the delivery valve. Pumped. When the plunger further rises, the plunger lead of the plunger communicates with the feed hole, and the fuel (spill flow) in the plunger chamber returns from the plunger lead through the feed hole to the fuel chamber at high speed.

On the other hand, the volume of the suction chamber below the plunger increases as the plunger rises, and the pressure in the suction chamber decreases.
Therefore, a part of the fuel flowing from the plunger lead into the feed hole is sucked into the suction chamber through the suction hole. As a result, the amount and kinetic energy of the spill fuel that strikes the inner wall of the fuel chamber from the feedhole is reduced, and the erosion due to the spill fuel is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the fuel injection pump of the present invention will be described with reference to the drawings. First, the structure of this fuel injection pump will be described with reference to FIG. Bore 1 formed in housing 1
A cylinder 2 is fitted into the cylinder 0, and a plunger 3 is fitted directly into the bore of the cylinder 2 so as to be rotatable. The plunger 3 is urged by the driving cam (not shown) through the rod 30 to move up and down.

After the cylinder 2 and the delivery valve 4 which will be described later are successively fitted into the bore 10, the valve holder 5 is screwed into the upper end of the bore 10 of the housing 1. The lower end surface of the valve holder 5 is urged to the lower side of the cylinder 2 through the valve seat cylinder 41 of the delivery valve 4, and the stepped portion of the outer peripheral surface of the cylinder 2 is pressed against the stepped portion of the bore 10 by this urging, so that the cylinder 2 and the delivery are delivered. The valve seat cylinder 41 of the valve 4 is fixed.

The delivery valve 4 includes a valve seat cylinder 41 having a valve hole, a valve body 42 fitted in the valve seat cylinder 41, and a spring 43 for closing the valve body 42 by pressing the valve body 42 against an upper opening surface of the valve seat cylinder 41. The base end of the spring 43 is locked to the step surface in the central through hole of the valve holder 5. The upper part of the cylinder bore 20 of the cylinder 2 has a plunger chamber 21 defined by the upper end surface of the plunger 3 and the delivery valve 4.
The plunger chamber 21 is connected to a fuel pipe (not shown) through the valve hole of the delivery valve 4 and the central through hole of the valve holder 5. In addition, the plunger chamber 21
Is a through hole (not shown) that opens at the upper end surface of the plunger 3.
Is communicated with the plunger lead 31, and the plunger lead 31 is formed of a groove which is located slightly below the upper end surface of the plunger 3 and is obliquely recessed in the circumferential direction.

On the other hand, a feed hole 22 is provided at a predetermined position of the cylinder 2 in a radial direction, and the feed hole 22 can communicate with the plunger lead 31 at a predetermined stroke position of the plunger 3. . On the other hand, the lower portion of the cylinder bore 20 of the cylinder 2 is defined by the lower end surface of the plunger 3 and the bottom surface of the cylinder bore 20.
It is 3. One end of the suction hole 24 is opened at a predetermined distance above the bottom surface of the suction chamber 23.
The other end of 4 is opened in the radial center of the feed hole 22. The lower end of the suction chamber 23 communicates with one end of the check valve 7 in the housing 1 through the discharge hole 25.
The check valve 7 opens only in the direction in which fuel is discharged from the suction chamber 23 through the discharge hole 25.

A feed hole 2 is provided in the bore of the housing 1.
A fuel chamber 11 is formed in a large-diameter ring shape so as to face 2 and the fuel chamber 11 communicates with the other end of the check valve 7 through a communication hole 13. The spill protector 8 is arranged opposite to the feed hole 22 in order to prevent erosion of the inner wall 11 a of the fuel chamber 11. The basic operation of this fuel injection pump will be described below.

FIG. 2 shows the state where the plunger 3 is at the bottom dead center position, and the plunger chamber 21 is supplied with fuel from the fuel chamber 11 through the feed hole 22. Plunger chamber 21 and feed hole 2 as the plunger 3 moves up
5 is cut off (see FIG. 3), fuel pressurization in the plunger chamber 21 is started, and when a predetermined pressure is reached, the valve body 42 of the delivery valve 4 moves upward against the spring 43 and the valve seat The valve hole of the cylinder 41 is opened. As a result, the fuel is pressure-fed from the valve holder 5 to the injection valve through a fuel pipe (not shown).

After that, when the plunger lead 31 communicates with the feed hole 22 due to the upward movement of the plunger 3, the fuel in the plunger chamber 21 is transferred to the plunger lead 31 and the feeder.
The fuel is spilled into the fuel chamber 11 through the hole 22, whereby the pressure in the fuel chamber 21 is reduced, the delivery valve 4 is closed, and the fuel pressurizing process is completed. It should be noted that the valve body 42 of the delivery valve 4 moves downward by a predetermined stroke to suck back a predetermined amount of fuel even after closing the valve hole, and the fuel in the plunger chamber 21 is extra spilled by that amount. In order to control the fuel discharge amount per time, the plunger 3 is rotated by a sleeve (not shown), and the plunger lead 3
The communication timing between 1 and the feedhole 22 may be changed.

Next, the behavior of the fuel through the suction chamber 23, which is the main part of this embodiment, will be described. The period from the start of the lift of the plunger 3 until the suction chamber 23 communicates with the suction hole 24 is a decompression period, and the pressure in the suction chamber 23 decreases as the volume of the plunger 3 increases due to the upward movement.

Next, the period from when the suction chamber 23 communicates with the suction hole 24 to the top dead center of the plunger 3 is the suction period, and the feed hole 22 increases as the volume of the suction chamber 23 increases.
Fuel is sucked into the suction chamber 23 through the suction hole 24.
What is important here is that the plunger 3 has a suction hole 24 formed so as to communicate the suction chamber 23 with the suction hole 24 at the same time as or immediately before the plunger lead 31 communicates with the feed hole 22. It is in. In this way, when the plunger lead 31 communicates with the feed hole 22 and the large pressure fuel in the plunger chamber 21 is spilled into the feed hole 22 through the plunger lead 31, the feed hole 22 moves to the suction hole 24. Since the fuel is sucked, a part of the spill fuel is bypassed from the suction hole 24 to the suction chamber 23, thereby reducing the amount and energy of the high-speed jet impinging on the inner wall 8a of the spill protector 8 and reducing the inner wall 8a. Erosion can be reduced.

After that, when the plunger 3 starts to move downward, the volume of the suction chamber 23 decreases, and the fuel in the suction chamber 23 flows back to the feed hole 22 through the suction hole 24 at the initial stage, and the suction chamber 23 and the suction hole 23. After the valve 24 is shut off, the check valve 7 is opened to return to the fuel chamber 11. In this embodiment, as shown in FIG. 1, a notched portion 33 is formed to open and close the opening of the suction hole 24 on the outer periphery of the lower end of the plunger 3. The notch shape of the notch portion 33 is a diagonally oblique line shape that substantially matches the upper edge shape of the plunger lead 31, whereby the plunger 3 rotates and the plunger lead 31 and the feed hole. When the communication timing with the suction port 22 changes, the suction chamber 23 and the suction hole 2
The communication timing with 4 also changes, and the suction chamber 23 and the suction hole 24 communicate with each other at the same time as or immediately before the communication between the plunger lead 31 and the feed hole 22, and the spill fuel suction effect by the suction chamber 23. Is not lowered by the rotation of the plunger 3.

It is also possible to use an orifice instead of the check valve 7. (Embodiment 2) Another embodiment will be described with reference to FIG.
However, components having the same functions as those of the first embodiment are designated by the same reference numerals. In this embodiment, the suction chamber 23 and the filler are
The suction holes 24a and 24b communicate with the dohole 22, and the discharge hole 25, the check valve 7, and the communication hole 24 are omitted.

The suction hole 24a is formed obliquely upward from the lower outer circumference of the cylinder 2 to the radial center of the feed hole 22, and the suction hole 24b extends from the outer circumferential opening of the suction hole 24a to the lower end of the inner circumferential surface of the suction chamber 23. It is opened diagonally downward. As the volume of the suction chamber 23 increases due to the upward movement of the plunger 3,
First, a flow is formed in which fuel flows from the fuel chamber 11 into the suction chamber 23 through the feed hole 22.

Next, when the plunger lead 31 and the feed hole 22 are communicated with each other, the spill flow from the plunger chamber 21 to the feed hole 22 through the plunger lead 31 causes the fuel in the feed hole 22 and the fuel in the feed hole 22. Since the flow is opposite to the flow in the vicinity of the opening on the chamber 11 side, the kinetic energy of the spill flow into the fuel chamber 11 is reduced. Further, due to the fuel suction from the feed hole 22 through the suction holes 24a and 24b, a part of the spill flow is bypassed to the suction chamber 23, whereby the amount and kinetic energy of the spill flow into the fuel chamber 11 is reduced, and the spill flow is reduced. Erosion of the inner wall 8a of the protector 8 is reduced.

Particularly, in this embodiment, since the opening of the suction hole 24a on the side of the feed hole 22 communicates obliquely toward the opening of the feed hole 22 on the plunger side, the spill flow flowing into the feed hole 22 is generated. It is easy to flow into the suction hole 24a, which is more effective in reducing the spill flow to the fuel chamber 11. On the other hand, when the plunger 3 descends, the fuel in the suction chamber 23 is returned to the feed hole 22 through the suction holes 24a and 24b.

Like the suction holes 24a and 24b of the second embodiment, the suction hole 24 of the first embodiment can also be formed by two oblique holes that are obliquely formed in the cylinder 2, or
It is also possible to form one swash hole and a radiating hole that is pierced from the opening of the swash hole on the outer peripheral surface side of the cylinder 2 to the suction chamber 23 in the radial direction. In this case, the suction hole 24 is manufactured. The process becomes easier.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a fuel injection pump to which an embodiment of the present invention is applied, particularly a main-part cross-sectional view at a time point when a plunger lead of a plunger communicates with a feed hole and a spill is started. is there.

FIG. 2 is a cross-sectional view of the main parts of the fuel injection pump when the plunger of FIG. 1 is at a position near bottom dead center.

FIG. 3 is a cross-sectional view of essential parts of the fuel injection pump when the plunger of FIG. 1 starts a pressurizing stroke.

FIG. 4 is a cross-sectional view of essential parts of a fuel injection pump of another embodiment.

[Explanation of symbols]

 1 housing, 2 cylinders, 3 plunger, 4 delivery valve 11 fuel chamber, 20 cylinder bore, 21 plunger chamber, 22 feed hole, 23 suction chamber, 31 plunger lead, 24 suction hole.

Claims (1)

[Claims] 1. A cylinder fitted in a bore of a housing, a fuel chamber defined by the cylinder and the housing, a feed hole communicating with the fuel chamber and the cylinder bore, and slidably in the cylinder bore. A plunger that is inserted into the plunger chamber in the cylinder bore through the feed hole and pressure-feeds the fuel through a delivery valve, and is opened at a predetermined position on the outer peripheral surface of the plunger so as to communicate with the feed hole. In a fuel injection pump including a plunger lead communicating with the plunger chamber, a suction chamber that is located on the opposite side of the plunger chamber across the plunger and is partitioned and formed in the cylinder bore, the volume of which increases with the pressure feeding of the plunger. , The suction chamber and the feed hole Fuel injection pump, characterized in that it comprises a passage to the suction hole.