JPH0518335A - Fuel injection pump of internal combustion engine - Google Patents

Abstract

PURPOSE:To eliminate generation of crack or the like caused by impact at the time of seating and improve durability of a discharge valve and a seat member by arranging the discharge valve and a constant pressure valve on the same axis, and sealing the top end of the discharge valve to the seat of the valve seat member. CONSTITUTION:The bottom end of a discharge valve 10 inserted into an inner valve device 20, namely, the top end corner part on the upstream side is processed in a conical shape, and the conical part is seated on the seat part 9 of a valve seat member 6. A spherical constant pressure valve 21 for shutting the passage is seated on the top end part of the discharge valve 10, and a constant pressure valve return bearing 24 is interposed between a spring 22 brought in contact with the upstream side of the constant pressure valve 21 and a spring 23 in side the concave part 5 of the top end of a plunger barrel 1. Hereat, a fuel injection valve is closed, and pressure wave returning from the fuel injection valve side acts on the constant pressure valve 21 from the concave part 11 of the discharge valve 10 via a throttle part 18 and a daumping volume 19, and thereby pushes and opens the constant pressure valve 21 against the spring 24 so as to return to the side of a pressure-feed chamber 4, consequently, the pressure on the side of a high pressure passage 15 is maintained to the specified pressure with which that of the spring 24 is balanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection pump for an internal combustion engine, and more particularly to a fuel injection pump provided with a discharge valve and a constant pressure valve.

[0002]

2. Description of the Related Art In a diesel engine, it is known that high-pressure fuel injection can improve exhaust color and improve fuel consumption efficiency. However, when high-pressure injection is performed, the pressure pulsation that reciprocates in the high-pressure pipe after the fuel injection valve is closed is not rapidly attenuated, and the fuel injection valve is opened again to cause secondary injection, or immediately after the end of injection. A sudden pressure drop causes a negative pressure to cause cavitation, and the sudden drop causes a problem that the combustion gas flows backward from the combustion chamber side. In order to solve such a problem, a constant pressure valve is conventionally provided. That is, after the fuel injection valve is closed, the pressure wave returning in the high-pressure pipe is returned to the fuel injection pump side by opening the equal pressure valve, and the internal pressure of the pipe is reduced to a certain pressure. It is intended to eliminate. As a structure of a fuel injection pump provided with such an equal pressure valve, the structure shown in FIGS. 3 to 5 is used.

In FIG. 3, a valve seat member 41 and a holding lid 42 of the seat member 41 are arranged at the tip of the plunger barrel 40, and a discharge valve 44 seated on the valve seat member 41 and a seat portion of the holding lid 42 are arranged. Seated equal pressure valve 4
3 and 3 are arranged in parallel, and the passage from the side of the plunger barrel 40 is communicated with these equal pressure valve 43 and the discharge valve 44 through the oblique drilled hole 45, and further, the discharge valve 44 and the equal pressure valve 43. The diagonal side of the hole 4
It is connected to the outlet side through 7. in this case,
The plunger barrel 4 is tightened by the tightening bolts 57 screwed into the pump housing 56 from above via the press fittings 55.
0, the valve seat member 41, and the pressing lid 42 are pressed to maintain oil tightness. Further, a throttle 50 for attenuating the pressure wave is provided in the drill hole 47 on the side of the equal pressure valve 43. FIG. 4 is a cross section of another embodiment in which a plurality of bolts 46 inserted from above the pressing lid 42 are screwed directly into the plunger barrel 40 to tighten the pressing lid 42 and the sheet member 41 to achieve oil tightness.

On the other hand, in FIG. 5, the discharge valve 44 and the equal pressure valve 43.
Are arranged in series on the same axis, and the equal pressure valve 43 is seated on the tip end surface of the discharge valve 44 on the fuel injection pump side.
Is provided with a fuel passage 48 opened by the equal pressure valve 43, and a damping volume 49 and a throttle portion 50 for relaxing a pressure wave from the fuel injection valve side are formed in the fuel passage 48. Further, in the discharge valve 44, a large-diameter seat member 51 provided on the outer peripheral portion of the discharge valve 44 is seated on the seat portion at the tip of the valve housing 52. In this case, the fuel discharged from the fuel injection pump pushes the large-diameter seat member 51 open through the groove 53 provided on the outer circumference of the discharge valve 44 and flows out to the high-pressure pipe side.

[0005]

The above conventional fuel injection pump provided with a discharge valve and an equal pressure valve is provided with the structure shown in FIGS.
In this case, since the equal pressure valve 43 and the discharge valve 44 are arranged in parallel with each other, an oblique drill for connecting the discharge valve 44 and the equal pressure valve 43 with the fuel injection pump side and the high pressure pipe side is provided. The holes 45 and 47 are required to be machined, and it is very difficult to machine the holes, and it is difficult to ensure the accuracy of the inner surface of the drilled hole. Further, since the throttle portion 50 is provided in this passage, There is a drawback that it causes an edge between the two and causes a problem of stress concentration. Furthermore, when the equal pressure valve 43 and the discharge valve 44 are arranged in parallel in such a manner, the dimensions on both sides in the parallel direction become very small, so that as shown in FIG. 4, a plurality of bolts are arranged in the direction perpendicular to the parallel direction. Since 46 must be arranged separately, the tightening force of the bolt does not act uniformly, and there is a drawback that the sealing of the joint surface is likely to be insufficient.

On the other hand, the structure of FIG. 5 in which the equal pressure valve 43 and the discharge valve 44 are arranged in series does not have the above-mentioned drawbacks, but
A large-diameter seat portion 51 is formed on the outer peripheral portion of the discharge valve 44 and is seated on a seat portion of the valve housing 52. In this way, fuel passes from the seat portion to the tip of the discharge valve 44. Since it is necessary to form the groove 53 for causing this, there is a problem that a small-diameter constricted portion is formed on the upstream side of the seat portion, and a crack may occur in this portion due to an impact when the discharge valve is seated. .
In addition, in this conventional example, the lid 54 that covers the housing 52 is screwed into a pump housing (not shown) to squeeze the housing 52 and keep the oil-tightness.
As the housing 52 is rubbed while rotating, the lid 5
4 has a drawback that the contact surface between the housing 4 and the housing 52 tends to be insufficiently sealed.

The present invention aims to eliminate these conventional drawbacks. That is, the object of the present invention is to improve the durability of the discharge valve itself and the tightening structure that can improve the sealing property in the interior chamber that houses the discharge valve in the fuel injection pump including the discharge valve and the equal pressure valve. An arrangement structure of a discharge valve and an equal pressure valve is provided.

[0008]

In order to solve the above problems, in the present invention, as shown in FIG. 1, a discharge valve 10 and an equal pressure valve 21 are arranged in series in the axial direction, and the discharge valve 10 is internally provided. The seat member 6 and the pressing lid 7 are sequentially arranged on the front end side of the plunger barrel 1, and the discharge valve 10 is surrounded by a plurality of bolts 28 that are equally spaced and fixed. Further, the discharge valve 10 is seated at the front end thereof on the seat 9 of the valve seat member 6, and the equal pressure valve 21 is provided.
Is seated on the upstream end surface of the discharge valve 10.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 showing an embodiment of the present invention, 1
Is a plunger barrel in which the plunger 2 is installed, and is installed in the pump housing 3. The tip of the plunger barrel 1 has a pressure feed chamber 4 at the tip of the plunger 2.
There is formed a spring interior chamber 5 communicating with. Reference numeral 6 denotes a valve seat member, which is installed inside the pump housing 3 so as to come into contact with the tip end surface of the plunger barrel 1 and is further inserted into the pump housing 3 on the outer side thereof. A lid 7 is arranged. A valve interior chamber 20 is formed through the valve seat member 6 so as to communicate with the spring interior chamber 5 in the vertical direction.
The valve seat portion 9 is formed by an inclined step portion formed near the lower end of 0.

Then, the lower end of the discharge valve 10 inserted into the valve interior chamber 20, that is, the upstream end corner portion is processed into a conical shape, and this conical portion is directed to the seat portion 9 of the valve seat member 6. Seated. In this case, a recess 8 is formed on the lower end surface of the pressing lid 7, the spring receiver 13 inserted into the recess 8 and the recess 1 formed on the upper end of the discharge valve 10.
A discharge valve return spring 14 is interposed between the discharge valve 10 and the valve 2, and the discharge valve 10 is pressed against the seat 9. This discharge valve 1
The recess 12 of 0 penetrates the spring receiver 13 and holds the pressing lid 7
It communicates with the high-pressure passage 15 side formed in. A vertical groove 16 is formed on the outer periphery of the discharge valve 10.
The upper end of the is communicated with the inside of the recess 11 through the outlet hole 17.

A passage consisting of a damping volume 19 having a large volume is formed from the bottom of the recess 11 of the discharge valve 10 to the upstream end surface of the recess 11 and the throttle portion 18. A spherical equal pressure valve 21 for closing this passage is seated on the tip of the discharge valve 10, and a spring receiver 22 that is in contact with the upstream side of the pressure valve 21 and a recess 5 at the tip of the plunger barrel 1 are seated. A constant pressure valve return spring 24 is interposed between the spring receiver 23 and the spring receiver 23. A passage 26 is formed in the spring receiver 23 installed inside the recess 5 of the plunger barrel 1 so as to connect the pumping chamber 4 with the inside of the recess 5.

In the above description, the fuel pushed out from the pumping chamber 4 by the plunger 2 is the passage 2 of the spring receiver 23.
6 into the recess 5 and further acts on the tip surface of the discharge valve 10 in the interior chamber 20 in the valve seat member 6 downstream thereof to push up the discharge valve 10 against the spring 14, It flows out from the groove 16 through the outlet 17 to the high-pressure passage 15 side. On the other hand, when the fuel injection valve is closed and the pressure wave returning from the fuel injection valve side returns from the recess 11 of the discharge valve 10 through the throttle portion 18 and the damping volume 19, the equal pressure valve 2
1 against the spring 24, pushes the equal pressure valve 21 open against the spring 24, and returns to the pressure feeding chamber 4 side.
The pressure on the 5 side is held at a specific pressure that balances with the spring 25.

In the above description, the valve seat member 6 and the pressing lid 7 at the upper end of the plunger barrel 1 are provided with the fastening bolts 28 which are inserted from above into a plurality of vertically extending bolt holes. The sheet member 6 and the pressing lid 7 are tightened and fixed by screwing them into the front end surface of the discharge valve 10, and the tightening bolt 28 surrounds the discharge valve 10 in a circular shape as shown in FIG.
A plurality of valve seat members 6 are arranged at equal intervals so that the valve seat member 6 can be tightened with a uniform tightening force. In this embodiment, eight tightening bolts 28 are used, but the number can be increased or decreased as necessary.

Reference numeral 29 denotes a pressing ring arranged outside the pressing lid 7. The tip of the bolt 30 inserted through the upper end surface of the pressing ring is screwed into the front end surface of the pump housing 3 to further push the pressing lid 7 from above. Supports pressing.

[0015]

According to the present invention, the following effects can be obtained.

First, the discharge valve and the equal pressure valve are arranged coaxially, and the tip of the discharge valve is seated on the seat of the valve seat member. Therefore, the seat portion of the discharge valve is formed to have a large diameter. Unlike the conventional one, no constriction is formed on the upstream side of the seat, there is no problem such as cracking due to impact at the time of seating, and the durability of the discharge valve and the durability of the seat member can be improved.

Since the sheet member and the pressing lid are fastened and fixed to the plunger barrel side by the bolts inserted through the pressing lid and the sheet member,
Unlike the conventional method of tightening by screwing into a pump housing or the like, the sealing performance can be improved, and there is less risk of problems such as fuel leakage from the mating portion.

At this time, the tightening bolts are arranged so that the equal pressure valve and the discharge valve are arranged on the same axis as described above, and are arranged at equal intervals so as to surround the discharge valve internal chamber. Force can be applied, and the sealing performance of the mating surfaces is also improved.

Further, by arranging them on the same axis and tightening them with bolts as described above, it is not necessary to provide an oblique drilling hole, the processing is easy, and it is necessary to provide a narrowed portion in the oblique processing part. Since there is no step, no step is formed in the drilled hole portion, and the accuracy of drilling is improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a discharge valve and an equal pressure valve internal portion showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the main part of FIG.

FIG. 3 is a vertical cross-sectional view of a discharge valve internal portion showing a conventional example.

FIG. 4 is a cross-sectional view of a main part showing another conventional example.

FIG. 5 is a vertical cross-sectional view of a main part showing another conventional example.

[Explanation of symbols]

1 Plunger barrel 6 sheet members 7 Holding lid 9 valve seat 10 discharge valve 18 aperture 19 damping volume 21 Isobaric valve 28 Tightening bolt

Claims (2)

[Claims] 1. A fuel injection pump including a discharge valve and a constant pressure valve, wherein the discharge valve and the constant pressure valve are arranged on the same axis so that the constant pressure valve is located upstream in the fuel discharge direction, and the discharge valve The upstream end of the discharge valve is seated on the seat portion of the discharge valve seat member in which the valve is mounted, and the equal pressure valve seat portion also formed on the upstream end surface of the discharge valve is biased by a spring, etc. A fuel injection pump for an internal combustion engine, wherein a pressure valve is seated, and a discharge valve is provided with a fuel return passage having a damping volume and a throttle portion which is opened and closed by the equal pressure valve. 2. A fuel injection pump having a discharge valve and a constant pressure valve, wherein the discharge valve and the constant pressure valve are arranged on the same axis so that the constant pressure valve is upstream in the fuel discharge direction, and the discharge valve A valve seat member for mounting the valve and a pressing lid are sequentially arranged on the tip end surface of the plunger barrel, and a plurality of bolts are arranged at equal intervals so as to surround the circumference of the discharge valve. And a fuel injection pump for an internal combustion engine, characterized in that the valve seat member is penetrated through and tightened.