JPH1030516A - Inner cam type fuel injection pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any fuel leakage at the time of low pressurization so as to practice sufficient fuel pressurization. SOLUTION: The present inner cam type fuel injection pump is provided with a cam ring 1 having cam swells 3 on its inside peripheral surface 2, with a rotor for making rotation in linkage to an engine in radial directionally inside of the cam ring 1 and with a plunger 9 for moving to the inside in radial direction by being pushed by the abovementioned cam swells 3 in the inside of the rotor so as to pressurize and forcibly feed fuel, while the plunger 9 is formed solid in its end part 10 in its radial directional inside and provided with hollow part 12 formed on the radial directional outside from the end part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner-cam type fuel injection pump used for fuel injection of a diesel engine.

[0002]

2. Description of the Related Art An inner cam type fuel injection pump is disclosed in
As disclosed in JP-A-3-85366 and JP-A-5-126008, a cam ring having a cam ridge on the inner peripheral surface is fixed to the pump body, and the rotor is interlocked with the engine at a radial inside thereof. And rotate it. A cylinder is formed inside the rotor along the radial direction thereof, and a plunger is housed in the cylinder so as to be slidable back and forth. Rollers are arranged radially outside the rotor from the plunger via shoes, and these receive centrifugal force generated by rotation of the rotor and fuel pressure charged into the cylinder,
They are brought into contact with each other while being driven radially outward. Then, as the roller rolls on the inner peripheral surface of the cam ring, the shoe and the plunger reciprocate in the radial direction of the rotor according to the shape of the inner peripheral surface of the cam ring. As the rollers ride on the cam ridges, they move radially inward, causing the plunger to pressurize the fuel in the cylinder.

[0003] As described above, the plunger is like a piston for pressurizing fuel in a cylinder, and its structure is entirely formed as a solid shaft so as to sufficiently withstand the compressive force during pressurization. Is common.

[0004]

By the way, when the fuel is pressurized to a very high pressure, the plunger is deformed into a barrel shape by receiving a large compressive force, and the outer diameter is expanded. For this reason, in anticipation of this, the outer diameter of the cylinder is set to be relatively large, and sliding of the plunger is allowed even in the case of maximum deformation.

However, this configuration has a problem that when pressurizing only to a low pressure, the gap between the plunger and the cylinder becomes large and fuel leaks therefrom, and pressurization cannot be performed sufficiently.

[0006]

According to the present invention, there is provided an inner cam type fuel injection pump comprising a cam ring having a cam ridge on an inner peripheral surface, a rotor rotating in conjunction with an engine radially inside the cam ring, and A plunger that is pressed by the cam lobes in the rotor and moves inward in the radial direction to pressurize and feed the fuel, wherein a radially inner end is formed solid, and a hollow is formed radially outward from the end. And a plunger in which a portion is formed.

[0007] According to the above configuration, when the plunger receives a high compressive force, the partition wall of the hollow portion can be bulged radially inward of the plunger, and the bulging can be performed inside the plunger. As a result, the amount of swelling outward in the radial direction of the plunger can be reduced, the inner diameter of the cylinder can be reduced, and fuel leakage can be prevented.

[0008]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a vertical sectional front view of an inner cam type fuel injection pump according to the present invention, and FIG. 2 is a vertical sectional side view of the same. As shown, such a fuel injection pump has a cam ring 1 fixed to a pump body (not shown). The cam ring 1 is formed in an annular shape, and its inner peripheral surface is a cam surface 2, and the cam surface 2 is formed with four cam ridges 3 projecting radially inward at 90 ° circumferential intervals. . A rotor 4 is arranged concentrically on the radially inner side of the cam ring 1, and the rotor 4 receives an engine driving force from a rotating shaft (not shown).
It rotates in the direction of the arrow in conjunction with the engine.

The rotor 4 has a large diameter portion 5 and a small diameter portion 6 integrally, and a cylinder bore 7 is formed inside the large diameter portion 5 along the diameter thereof. The cylinder bore 7 defines two continuous cylinders 8 extending in the radial direction.

In each of the cylinders 8, the same plunger 9 is opposed to each other so as to be reciprocally slidable. Plunger 9
Here, in particular, the solid portion 10 forming the inner or center end portion in the rotor radial direction (hereinafter also simply referred to as the radial direction) is used.
And a hollow shaft portion 11 which is a portion radially outward from the solid portion 10. The solid portion 10 is formed to be solid, and closes a radially inner end of the plunger 9. Further, the hollow shaft portion 11 has a hollow hole 12 as a hollow portion at the shaft center portion thereof, and an outer end of the plunger 9 in the radial direction is opened. Thus, the plunger 9 as a whole
A radially outer end is formed in an open cup shape.

A sliding groove 8a having a rectangular cross section is formed at a radially outer end of the cylinder 8, and a shoe 13 is slidably accommodated in the sliding groove 8a along the radial direction. The shoe 13 has a roller receiving groove 14 having an arc-shaped cross section on a radially outer end surface. In the roller receiving groove 14, a roller 1 long in the rotor axial direction (hereinafter, also simply referred to as the axial direction) is provided.
5 are rollably engaged, and the roller 15 also rolls on the cam surface 2.

A fuel passage 16 is provided in the small diameter portion 6 of the rotor 4 along the center thereof. The fuel passage 16 is opened at a center of the rotor in a cylinder bore 7 and communicates with both cylinders 8. The fuel passage 16 is provided with one filling passage 17 for filling the fuel, and further provided with one distribution passage 18 at a position (phase) different from that of the filling passage 17 in the circumferential direction.

A control sleeve 19 is slidably fitted in the outer peripheral portion of the filling passage 17 in the small diameter portion 6 in the axial direction and the circumferential direction.
A barrel 19a fixed to the pump body is fitted. The control sleeve 19 is provided with a filling port 20 that can communicate with the filling passage 17 by rotation of the rotor 4. The same number of filling ports 20 as the number of cylinders of the engine are provided at regular intervals in the circumferential direction, and each of them sequentially communicates with the filling passage 17 by the rotation of the rotor 4. Also, the same number of distribution ports 21 as the number of cylinders of the engine are provided at equal intervals in the circumferential direction, and each of them sequentially communicates with the distribution passage 18 by the rotation of the rotor 4.

In the above configuration, fuel supplied from a feed pump (not shown) is stored in a radially outer region of the filling port 20. This fuel is always maintained at a constant pressure by the pressure regulating valve.

When the rotor 4 rotates and the filling port 20 and the filling passage 17 communicate with each other, the fuel at a constant pressure enters the cylinder 8, and the plunger 9, the shoe 13 and the roller 15 reduce the centrifugal force and the fuel pressure, respectively. Then, they are pushed radially outward and come to press against each other.
Since the rollers 15 roll on the cam surface 2, they reciprocate integrally along the rotor radial direction according to the shape of the cam surface 2.

In particular, when the roller 15 rides on the cam peak 3, the plungers 9 move (lift) inward in the radial direction and approach each other, and pressurize the fuel in the cylinder 8 from the opposite direction. After the pressurized fuel enters the fuel passage 16, the distribution passage 18 and the distribution port 2
1 through a delivery valve (not shown) and pressure-fed to a fuel injection valve of a predetermined cylinder.

At this time, the filling passage 17 is closed by the inner wall of the control sleeve 19, but when the rotation of the rotor 4 advances, the filling passage 17 will be communicated with the filling port 20. Then, at the moment when the communication is achieved, the pressurized fuel is discharged (spilled) from these passages 17 and ports 20 in the backward flow direction.
As a result, the fuel pressure is reduced and the pumping ends.
Thus, the filling passage 17 and the filling port 20
It is also used for both charging and discharging fuel.

The control sleeve 19 is rotated around the center of the rotor by a governor mechanism (not shown) and slidably moved in the axial direction of the rotor, whereby the communication timing and the communication period of the filling port 20 can be appropriately changed. In this way, it is possible to perform fuel pumping at an optimal timing, an optimal amount, and an optimal pressure in accordance with the operation state of the engine.

When the pressure feeding is completed, the fuel enters the cylinder 8 from the filling port 20 through the filling passage 17 and the fuel passage 16, and the plungers 9 move (unlift) radially outward and separate from each other. At this time, the distribution passage 18 is closed by the inner wall of the barrel 19a.

In this way, the plunger 9 executes fuel filling, discharging (pressure feeding), and discharging (spill) once each time the roller 15 moves up and down one cam peak 3 once.

By the way, as described above, the plunger 9
Receives a compressive force along the rotor radial direction when pressurizing the fuel. Then, as shown in FIG. 3A, in the conventional plunger formed in a solid shaft shape, the entire plunger is deformed into a barrel shape, and the swelling amount s outward in the plunger radial direction is increased. The cylinder inner diameter had to be increased in anticipation.

However, according to the plunger 9 of the present invention shown in FIG. 3B, since the hollow portion, that is, the hollow hole 12 is provided, the inner wall of the hollow hole 12 is bulged radially inward of the plunger, and the bulging is prevented. It can be performed inside the plunger 9. As a result, the amount of swelling s outward in the radial direction of the plunger
Can be reduced, and the gap with the plunger 9 can be reduced by making the cylinder inner diameter smaller than before. Then, fuel leakage at the time of low-pressure feeding can be reduced, and sufficient fuel pressurization can be performed.

In particular, in the plunger 9 of the present invention, the thickness t ₁ of the solid portion 10 along the radial direction of the rotor is set to a relatively large value, and the thickness of the hollow shaft portion 11 along the radial direction of the plunger. t there is a value greater than _2. Thereby, the rigidity of the solid part 10 can be strengthened.

Here, as shown in FIG. 4, when the thickness t ₁ of the solid portion 10 is small, the solid portion 10 is bent and deformed, and the plunger 9 becomes flared (open mouth shape), so that the hollow shaft portion 11 expands. There is a possibility that the amount of protrusion may increase, but such a plunger 9 prevents this, and ensures that only the hollow shaft portion 11 swells and deforms in the plunger radial direction.

Incidentally, referring to FIG.
The outer peripheral wall of the bottom is also formed in a rounded cross section having an optimum R value to prevent the above-described deformation. On the other hand, when the hollow shaft portion 11 expands and deforms, the cylinder 8 expands and deforms in the radially expanding direction due to the oil film rigidity based on the EHL theory, and the reaction force causes the hollow shaft portion 11 to be compressed and contracted in the radially decreasing direction. Can be

By the way, in the plunger 9, since the hollow hole 12 is provided, the weight can be reduced, the inertial weight can be reduced, and the plunger 9 can be prevented from jumping. That is, when the internal pressure of the cylinder 8 decreases at the end of the pressure feeding, if the inertia force of the plunger 9 is large, the plunger 9 separates from the shoe 13 (that is, jumps) and collides with the plunger 9 on the opposite side. So plunger 9
Thus, the inertia weight is reduced by reducing the weight, and the followability to the shoe 13 is improved, so that the collision between the plungers 9 can be prevented.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the plunger 9, the open end on the outer side in the rotor radial direction can be bridged in a bridge shape. Further, a closed hollow portion can be provided inside the plunger, a plurality of hollow portions can be provided, and the shape can be changed. The number of plungers is not limited to the above, and can be increased to four or the like or reduced to one.

[0029]

The present invention exhibits the following excellent effects.

(1) To prevent fuel leakage during low pressure pressurization,
Sufficient pressurization can be performed.

(2) The inertial weight can be reduced and the plunger can be prevented from jumping.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing an inner cam type fuel injection pump according to the present invention.

FIG. 2 is a longitudinal sectional side view showing an inner cam type fuel injection pump according to the present invention.

FIG. 3 is a longitudinal sectional view showing a state of deformation of a plunger,
(A) shows the case of the related art, and (b) shows the case of the present invention.

FIG. 4 is a longitudinal sectional view showing a state of deformation of another plunger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cam ring 2 Cam surface 3 Cam peak 4 Rotor 9 Plunger 10 Solid part 12 Hollow hole

Claims (1)

[Claims] A cam ring having a cam ridge on an inner peripheral surface thereof;
A rotor that rotates in conjunction with an engine radially inside the cam ring, and a plunger that is pressed by the cam ridge inside the rotor and moves radially inward to pressurize and pressurize the fuel; An inner cam type fuel injection pump, comprising: a plunger having a solid inner end portion and a hollow portion formed radially outward from the end portion in the rotor radial direction.