JP3186159B2 - Fuel injection valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage injection type fuel injection valve in which the initial injection is suppressed by suppressing the injection rate at the initial stage of the fuel injection, and the main injection is subsequently performed by increasing the injection rate.

[0002]

2. Description of the Related Art In a fuel injection valve of an internal combustion engine, an injection characteristic is made variable in accordance with an elapsed injection time in order to reduce fuel ignitability, reduce noise, and prevent emission of harmful components. It is known that the injection rate is reduced in the early stage of the injection and the injection rate is increased when the main injection is reached. As such a two-stage injection type fuel injection valve, one disclosed in Japanese Utility Model Publication No. 53-23855 has been proposed.

[0003] In this apparatus, a small amount of initial injection is performed by pressing the lift amount of a needle valve by a first spring at an early stage of injection, and when the fuel pressure continues to increase, the first and second springs are caused to operate. In response, the needle valve is greatly lifted, and a large amount of main injection is performed.

[0004] The conventional two-stage injection type fuel injection valve disclosed in the above publication includes a nozzle portion 91 and a holder portion 92 as shown in FIG. A first spring 921 for controlling the lift of the nozzle needle 911 during the injection, and a second spring 921 for controlling the lift of the nozzle needle 911 during the main injection.
And a spring 922. A gap 925 for setting the initial lift s at the time of the initial injection includes a push rod 923 receiving the urging force of the first spring 921,
Receiving tray 924 receiving the urging force of second spring 922
And between the end surfaces of the two.

[0005]

However, when this kind of fuel injection valve is mounted on an engine, the nozzle holder is often pressed against the engine and fixed.

In this case, since an axial load is applied to the nozzle holder and pressed against the engine, an axial compressive load is applied to the nozzle holder, so that the nozzle holder generates elastic strain due to axial compression. I do. This will be described in more detail with reference to FIG. As shown in the figure, the push rod 92 forming the gap 925
3 and the saucer 924 are respectively the nozzle needle 91
1 and a nozzle holder 920.

When mounting such a fuel injection valve on an engine, the nozzle holder 920 is pressed against the engine and fixed. At this time, a large load is applied to the nozzle holder 920, so that an elastic strain occurs in the nozzle holder 920, and the gap 9
25, that is, the initial lift s decreases.

The initial lift amount s is set to, for example, 0.08 to 0.1 in order to maintain good engine performance such as the ignitability of fuel, reduction of noise, and prevention of emission of harmful components.
The initial lift amount s must be adjusted with high accuracy at the stage of assembling the fuel injection valve. Due to the variation in pressure, the above-described variation in strain occurs. For this reason, the initial lift amount varies, for example, to about 0.08 to 0.03 mm, and there is a problem that characteristics such as fuel ignitability, generation of noise, and emission of harmful components vary from engine to engine.

The present invention has been made in view of such circumstances. It is an object of the present invention to accurately adjust an initial lift amount even when a nozzle holder has a variation due to compression strain.
Tomo to be able to maintain the engine performance good keeping
Another object is to provide a fuel injection valve having excellent durability .

[0010]

Since SUMMARY OF THE INVENTION The present invention to achieve the above object, and the first spring when the first spring and the total injection to regulate the valve opening pressure during initial injection DOO
A stopper wall is provided at an end of a nozzle holder accommodating a second spring for regulating a valve opening pressure, and a nozzle body is connected to the stopper wall. Fuel supplied through a fuel supply passage is connected to the nozzle body. pressure containing a needle valve to open the lift has been injection hole when it reaches over valve opening pressure of, the upper end of the needle valve by attaching the bushing, this
The diameter of the upper end surface of the bush is the diameter of the upper end surface of the needle valve.
Larger and can contact the stopper wall at the time of all injections
And a push rod for transmitting the pressing force of the first spring to the needle valve.
A pressure pin is provided that is pressed against the stopper wall by receiving the pressing force of the second spring, and faces the upper end surface of the bush with a gap corresponding to a predetermined initial lift amount. And

[0011]

According to the structure of the present invention, the initial lift amount is set by the distance between the upper end surface of the bush attached to the upper end of the needle valve and the pressure pin abutted against the stopper wall. As described above, the influence of the dimensional fluctuation of the nozzle holder is eliminated. For this reason, when the fuel injection valve is mounted on the engine, even if an elastic strain is generated in the nozzle holder due to an axial compression load applied to the nozzle holder, there is no concern that the initial lift amount will change. And d
The diameter of the upper end surface of the bush attached to the upper end of the needle valve
Needle diameter is larger than the diameter of the
Set the diameter so that it can contact the wall,
The contact area that comes in contact with and separates from the stopper wall has been increased.
The wear resistance of the part is improved, and the durability can be improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below based on one embodiment shown in the drawings.

In FIG. 1, reference numeral 1 denotes a nozzle holder, to which a stopper wall 2 serving as a spacer and a nozzle body 3 are axially connected via a retaining nut 4.

A fuel supply passage 5 is provided at one end of the nozzle holder 1.
The fuel supply passage 5 is connected to a fuel supply pump (not shown), and communicates with the nozzle body 3 from the stopper wall 2 through the inside of the side wall of the nozzle holder 1.

In the nozzle holder 1, a first spring chamber 6 and a second spring chamber 7 are provided, and the first spring chamber 6 and the second spring chamber 7 are rods serving also as partition walls. It is divided in the axial direction by the holder 8. A guide hole 9 is formed in the center of the rod holder 8 also serving as the partition wall.

The first spring chamber 6 accommodates a first spring 10 for setting the valve opening pressure for initial injection, and the second spring chamber 7 cooperates with the first spring 10. A second spring 11 for setting the valve opening pressure for all injections is accommodated. A shim 12 for adjusting the set load of the first spring 10 is provided on the ceiling of the first spring chamber 6, and the ceiling of the second spring chamber 7, that is, the lower surface of the rod holder 8. Is provided with a shim 13 for adjusting the set load of the second spring 11.

A push rod 14 is slidably inserted into a guide hole 9 formed in the rod holder 8, and an upper end of the push rod 14 is introduced into the first spring chamber 6. A spring receiving portion 15 is formed at the upper end of the push rod 14.
Are pressed by the first spring 10.

The lower end of the push rod 14 extends downward through the second spring chamber 7.

As shown in FIG. 2, the stopper wall 2 connected to the nozzle holder 1 has a through hole 16 in the center and a recess 17 in the lower surface. .

A pressure pin 18 also serving as a spring receiver is slidably inserted into the through hole 16. The pressure pin 18 is pressed by the second spring 11, and the flange portion 18 formed on the pressure pin 18 by the pressing of the second spring 11
a comes into contact with the stopper wall 2. A sliding hole 19 is formed in the center of the pressure pin 18, and the lower end of the push rod 14 is slidably inserted into the sliding hole 19.

The nozzle body 3 connected to the stopper wall 2 is provided with a receiving hole 20 at a central portion, and a fuel reservoir 21 communicating with the receiving hole 20 and a fuel reservoir located at a lower end thereof. An injection hole 22 connected to the portion 21 is formed. The fuel reservoir 21 communicates with the fuel supply passage 5, so that fuel is supplied from the fuel supply pump to the fuel reservoir 21 through the fuel supply passage 5.

A needle valve 25 is slidably fitted in the accommodation hole 20. The needle valve 25 is configured such that a valve portion 26 formed at the lower end contacts and separates from a valve seat formed at the lower end of the nozzle body 3 to open and close the injection hole 22. The pressure receiving surface 27 having an inclined shape is provided.

At the upper end of the needle valve 25, a small-diameter pressing rod 28 is integrally projected. This pressing rod 2
The upper end of 8 is slidably inserted into a slide hole 19 formed in the pressure pin 18, and is in contact with the lower end surface of the push rod 14.

Accordingly, the load of the first spring 10 is transmitted to the needle valve 25 via the push rod 14 and the pressing rod 28, and the needle valve 25 is pushed down by the pressing force of the first spring 10, and Are in contact with the valve seat so as to be able to come and go.

At the upper end of the needle valve 25, a bush 30 surrounding the pressing rod 28 and having a lower height than the pressing rod 28 is attached. The bush 30 is accommodated in a concave portion 17 formed on the lower surface of the stopper wall 2. The upper surface 30 a of the bush 30 is connected to the lower surface 18 b of the pressure pin 18 facing the concave portion 17.
Facing. When the valve portion 26 of the needle valve 25 is in a closed state in which the valve portion 26 is in contact with the valve seat and the flange portion 18a of the pressure pin 18 is in contact with the stopper wall 2, the upper surface 30a of the bush 30 and the lower surface of the pressure pin 18 1
8b, and the separation dimension s forms the lift of the initial injection, that is, the initial lift.

When the valve portion 26 of the needle valve 25 is in a closed state in which it contacts the valve seat, the upper surface 30a of the bush 30
Is spaced apart from the ceiling surface of the concave portion 17 of the stopper wall 2 with a dimension L, and the distance L is set so as to be a lift for all the injections.

The operation of the embodiment having such a configuration will be described. Fuel is supplied from a fuel supply pump (not shown) to the fuel reservoir 21 through the fuel supply passage 5, and when the fuel pressure in the fuel reservoir 21 reaches the initial valve opening pressure, the pressure receiving surface 27 formed on the needle valve 25 changes the fuel reservoir. The needle valve 25 is pushed up by receiving the fuel pressure of the portion 21, and thus the first valve 25 is pushed through the pressing rod 28 and the push rod 14.
The needle valve 25 is lifted because the spring 10 is compressed. Therefore, the valve portion 26 separates from the valve seat and the injection hole 22
Is opened, and the fuel in the fuel reservoir 21 is injected from an injection hole 22 to an engine (not shown).

The lift of the needle valve 25 rises to a position where the bush 30 provided at the upper end of the needle valve 25 contacts the pressure pin 18, and the upper surface 3 of the bush 30 is lifted.
When 0a contacts the lower surface 18b of the pressure pin 18,
Since the pressure pin 18 is pressed by the second spring 11, the elevation of the needle valve 25 temporarily stops.

This state is the pre-lift, and the initial injection is performed. The lift amount of the initial injection depends on the upper surface 30a of the bush 30 and the lower surface 18 of the pressure pin 18.
This corresponds to the initial separation dimension s from b.

After the initial injection as described above, when the fuel pressure in the fuel reservoir 21 further rises and exceeds the valve opening pressure of all injections, the pressing rod 28 pushes the first spring 10 through the push rod 14. Push, and at the same time, bush 30
Pushes up the pressure pin 18, so that the pressure pin 18 pushes the second spring 11. Therefore, the needle valve 25 rises against the pressing force of the first and second springs 10 and 11, whereby the injection hole 22 is further opened, and the fuel in the fuel reservoir 21 is discharged.
Injected from 2. This state is the full injection.

In this full injection, the bush 3
The needle valve 25 rises until the upper surface 30a of the needle valve 25 contacts the ceiling surface of the concave portion 17 of the stopper wall 2, that is, the total lift L
, The needle valve 25 stops.

In the above configuration, the members for setting the initial lift s are the bush 30 and the pressure pin 18.
The bush 30 is provided on the upper end of the needle valve 25, and the bush 30 is
Has been positioned and stopped. Therefore, the initial lift s is not affected by a change in the dimension of the nozzle holder 1 in the axial direction.

That is, when the fuel injection valve of the present embodiment is mounted on an engine (not shown), the nozzle holder 1 is pressed against the engine, so that an axial compressive load is applied to the nozzle holder 1 and an axial compression load is applied. Elastic strain due to compression may occur, but such compressive strain of the nozzle holder 1 does not affect the stopper wall 2. Therefore, the support position of the pressure pin 18 does not change, and as a result, the upper surface 30a of the bush 30 and the pressure pin 18
The initial lift amount s can be maintained with high accuracy without deviation of the distance from the lower surface 18b.

For this reason, the initial lift amount s does not vary for each engine, and a high-precision dimension of, for example, about 0.08 to 0.1 mm can be maintained. Characteristics such as noise reduction and prevention of emission of harmful components can be maintained in a uniform and favorable state.

Since the bush 30 attached to the upper end of the needle valve 25 is used, the diameter d2 of the upper end surface of the bush 30 is set to be larger than the diameter d1 of the upper end surface of the needle valve 25. And the lower surface 1 of the pressure pin 18
The contact area of the recess 8b and the recess 17 of the stopper wall 2 with respect to the ceiling surface can be increased, so that the abrasion resistance of the contact portion is improved and the life characteristics are improved. This is more advantageous when applied to a small fuel injection valve in which the diameter of the needle valve 25 is small.

Furthermore, the initial lift amount s is set to, for example, 0.
The means shown in FIGS. 3 and 4 can be adopted to adjust the dimensions to a high precision of about 08 to 0.1 mm. That is, when the distance between the lower surface 18b of the pressure pin 18 and the upper surface 30a of the bush 30 does not reach the predetermined initial lift when the flange portion 18a of the pressure pin 18 is in contact with the stopper wall 2, As shown in FIG.
Flange 18a of pressure pin 18 and stopper wall 2
If the shim 40 is interposed between the bush 30, the distance between the lower surface 18b of the pressure pin 18 and the upper surface 30a of the bush 30 can be adjusted to a predetermined initial lift s.

In this case, adjustment can be made by adopting a method as shown in FIG. 4, for example.

That is, first, the valve opening pressure of the initial injection is measured. In this case, the first spring chamber 6 of the nozzle holder 1
The push rod 14, the stopper wall 2, and the nozzle body 3 are assembled with the shim 12 and the first spring 10, and fastened by the retaining nut 4. In this state, the valve opening pressure of the initial injection is measured by a commercially available nozzle tester (not shown). If the valve opening pressure of the initial injection is not the predetermined value, the shim 12 is replaced to adjust the valve opening pressure to the predetermined value.

Next, the valve opening pressure for all injections is measured. In this case, the retaining nut 4 is removed to disassemble the assembly, the first spring chamber 6 of the nozzle holder 1 accommodates the shim 12 and the first spring 10, and the second spring chamber 7 includes the rod 12. The holder 8, the shim 13 and the second spring 11 are set, and the pressure pin 1
8 and the bush 30 are additionally assembled and fastened with the retaining nut 4 again. In this state, the valve opening pressure of all injections is measured by the nozzle tester. If the valve opening pressure for all injections is not the predetermined value, the shim 13 is replaced to adjust the valve opening pressure to the predetermined value. Next, the initial lift s is adjusted. In this case, the stopper wall 2 and the nozzle body 3 which are disassembled from the nozzle holder 1 are used, and the pressure pin 18 is attached to the stopper wall 2 and the bush 30 is attached to the needle valve 21. The body 3 is assembled on the dedicated jig 50.

In this state, as shown in FIG.
The pressure pin 18 is brought into direct contact with the bush 30 to
A point alignment is performed, thereby measuring the initial lift. If this measurement does not match the predetermined initial lift s,
As shown in FIG. 4B, the initial lift s can be set by interposing the shim 40 between the flange portion 18a of the pressure pin 18 and the stopper wall 2.

Instead of using the shim 40 as described above, the initial lift s can be adjusted by replacing the pressure pin 18 or the bush 30 with one having a different size.

In the case of the above embodiment, the needle valve 25
Although the pressing rod 28 is formed integrally with the upper end of the push rod 14, if the upper end surface of the needle valve 25 is directly pressed by the lower end of the push rod 14, the pressing rod 28 as a special member can be omitted.

[0043]

The stopper wall 2 may be formed integrally with the end of the nozzle holder 1. In this case, the first spring 10 and the second spring 11 are inserted from the upper end of the nozzle holder 1. What should I do?

[0045]

As described above, according to the present invention, the initial lift s is determined by the amount of the bush attached to the upper end of the needle valve .
Since the distance is set by the distance between the upper end surface and the pressure pin which is brought into contact with the stopper wall, the nozzle holder is not affected by the dimensional fluctuation of the nozzle holder as in the related art. For this reason, even when an elastic strain is generated in the nozzle holder by applying a compressive load to the nozzle holder when the fuel injection valve is mounted on the engine, the initial lift amount s does not change. Therefore, the initial lift amount can be maintained with high accuracy, and characteristics such as fuel ignitability, noise reduction, and emission of harmful components can be kept uniform and favorable for each engine. In addition, adjust the diameter of the upper end surface of the bush above the needle valve.
Larger than the diameter of the end face and can contact the stopper wall during all injections
The upper end face, the stopper wall and the pressure
The contact area with the pin can be increased, so
Wear resistance is suppressed and durability can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fuel injection valve showing one embodiment of the present invention.

FIG. 2 is an exploded cross-sectional view showing a relationship between the needle valve of the embodiment and a pressure pin which is stopped by a stopper wall.

FIG. 3 is a sectional view showing a main part when an initial lift amount is adjusted.

FIGS. 4A and 4B are explanatory diagrams showing a procedure for adjusting an initial lift amount. FIGS.

FIG. 5 is a sectional view showing a conventional fuel injection valve.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Nozzle holder, 2 ... Stopper wall, 3 ... Nozzle body, 5 ... Fuel supply passage, 6 ... First spring chamber, 7 ...
Second spring chamber, 8 rod holder, 10 first spring, 11 second spring, 14 push rod, 18 pressure pin, 21 fuel reservoir, 2
2 ... injection hole, 25 ... needle valve, 28 ... pressing rod, 3
0 ... bush.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-30975 (JP, A) JP-A-59-87272 (JP, A) JP-A-3-119568 (JP, U) JP-A-4-119568 109467 (JP, U) 2-2-64 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 45/08 F02M 61/10

Claims (1)

(57) [Claims] And 1. A nozzle holder, the first spring to regulate the valve opening pressure during housed initial injection into the nozzle holder, the valve opening pressure with the first spring accommodated in the nozzle holder at full injection A second spring for regulating, a stopper wall provided at an end of the nozzle holder, a nozzle body provided with an injection hole connected to the stopper wall and connected to a fuel supply passage, A needle valve which is lifted to open the injection hole when the pressure of the fuel supplied through the fuel supply passage reaches or exceeds each of the valve opening pressures, and an upper end surface of which is larger than and larger than a diameter of an upper end surface of the needle valve.
It has a diameter that can contact the stopper wall during all injections.
And a needle attached to the upper end of the needle valve.
A push rod provided on the nozzle holder for transmitting the pressing force of the first spring to the needle valve; and a slidably supported by the stopper wall and receiving the pressing force of the second spring. A pressure pin which is stopped against the stopper wall and faces the upper end surface of the bush with a gap corresponding to a predetermined initial lift amount.