JP2003148300A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection nozzle 1 capable of preventing unevenness in fuel injection forms Fi, Fj injected from injection holes 5 and 6 even if a needle 7 is displaced when opening a valve, obtaining the stabilized output performance of a diesel engine, preventing fuel in a passage from a needle seat 8 to the projection holes 5 and 6 from staying therein, and preventing an influence to an HC component in exhaust gas. SOLUTION: A nozzle body 2 is formed with a flat valve seat 4 in an inner bottom part, and the needle 7 is arranged in the nozzle body 2 freely to reciprocate, and the needle 7 has the flat needle seat 8 corresponding to the valve seat 4. By this structure, even if the needle 7 is displaced (Ec) when opening the valve, a passage area Pc between the needle seat part 8 and the valve seat 4 can be maintained nearly constant. As a result, the unevenness in the fuel injection forms Fi and Fj injected from the injection holes 5 and 6 is prevented. Furthermore, when closing the valve, the needle seat part 8 and the valve seat 4 are tightly brought in contact with each other to liquid-tightly seal the injection holes 5 and 6, and the fuel in the passage from the needle seat 8 to the injection holes 5 and 6 is prevented from staying therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection nozzle for injecting fuel from an injection hole by separating a valve body from a valve seat by a needle provided in a nozzle body so as to be capable of reciprocating.

[0002]

2. Description of the Related Art In a multi-cylinder internal combustion engine, for example, a diesel engine, a suck holeless nozzle 30 as shown in FIG. 4A is used as a fuel injection nozzle. In this suck holeless nozzle 30, since the tapered valve body (needle seat portion) 31 of the needle 34 comes into contact with the valve seat 33 and closes the left and right injection holes 32a and 32b when the valve is closed, V
It is also called a CO nozzle (valve covered orifice).

When the valve is opened, the needle 34 moves upward and the valve body 31 causes the injection hole 3 to move, as shown in FIG.
2a, 32b away from the injection holes 32a, 32b,
The fuel pumped into the nozzle body 35 is injected into the injection holes 32a, 3
The fuel is injected into the cylinder from 2b.

In this fuel injection nozzle, when the needle 34 is moved upward and opened, the needle 34 may be slightly eccentric (Em) from the center due to the working tolerance of the nozzle body 35 and the needle 34. In this case, the valve body 3
The passage areas A and B between 1 and the valve seat 33 are uneven on the left and right, and for example, the passage area B on the right side is narrower than the passage area A on the left side.

Therefore, the spray shapes 36 and 37 from the left and right injection holes 32a and 32b vary, and the left injection hole 3 is formed.
The spray shape 36 from 2a becomes larger than the spray shape 37 from the right injection hole 32b, and the output performance of the diesel engine may become unstable. In order to prevent this, as shown in FIG. 5, when the valve is closed, the valve body 31 of the needle 34 is attached to the injection hole 32.
It is conceivable that the nozzle holes 32a and 32b are separated from the nozzles a and 32b to be MS nozzles (minisack nozzles) that are not directly blocked.

However, in the MS nozzle, when the valve is closed after fuel injection, the injection hole 32a is passed from the valve body 31 through the sack portion 38,
The fuel accumulated in the passage leading to 32b enters into the combustion chamber as a rear drip due to high temperature and pressure fluctuation in the combustion chamber, and this rear drip incompletely burns and affects the HC component in the exhaust gas. There is a risk.

[0007]

As described above, in the VCO nozzle, when the needle 34 is eccentric (Em) when the valve is opened, due to the nonuniformity of the passage areas A and B, the left and right injection holes 32a,
There is a problem that the output performance of the diesel engine becomes unstable due to variations in the spray shapes 36 and 37 from 32b. Further, in the MS nozzle, the valve body 31 to the sack portion 3 are closed when the valve is closed.
There is a possibility that the fuel accumulated in the passage extending from 8 to the injection holes 32a and 32b may enter the combustion chamber and affect the HC component in the exhaust gas.

The present invention has been made in view of the above circumstances, and an object thereof is to apply to a diesel engine because even if the needle is eccentric when the valve is opened, the spray shape of the fuel injected from the injection hole does not vary. In this case, a stable output performance is obtained, fuel is not accumulated in the passage from the valve element to the injection hole, and a fuel injection nozzle that does not affect the HC component in the exhaust gas is provided.

[0009]

A nozzle body of a fuel injection nozzle has a guide hole extending in a longitudinal direction, forms a flat valve seat on an inner bottom portion, and extends outward from the valve seat. Equipped with communicating holes. A needle having a flat valve body corresponding to the valve seat is axially reciprocally movable in a guide hole of the nozzle body. Due to the forward movement of the needle, the valve element comes into close contact with the valve seat and closes the injection hole.
The return movement of the needle moves the valve body away from the valve seat, opens the injection hole, and injects the fuel pumped into the nozzle body from the injection hole.

In this way, since the valve body and the valve seat of the needle are formed flat, even if the needle is eccentric when the valve is opened, the passage area between the valve body and the valve seat is not uniform. Instead, it is kept almost constant. Therefore, when the fuel is injected from the injection hole through the space between the valve body and the valve seat, the spray shape of the fuel does not vary, and when applied to a diesel engine, stable output performance should be maintained. You can

Moreover, when the valve is closed, the flat valve body and the valve seat are in close contact with each other to seal the injection hole liquid-tightly. Therefore, unlike the case of the MS nozzle (minisack nozzle), the valve body and the valve seat are separated from each other. There is no space between them and fuel does not accumulate in the passage extending from the valve element to the injection hole. As a result, when the valve is closed, due to high temperature and pressure fluctuations in the combustion chamber, the fuel does not drip into the combustion chamber from the passage extending from the valve body to the injection hole, and affects the HC component in the exhaust gas. There is no danger of

(Claim 2) The outer peripheral edge portion of the valve body is
An annular ridge is formed, and the ridge comes into close contact with the valve seat when the needle moves forward.

Since the annular ridge is formed on the valve body, the valve seat and the ridge contact with each other in a small area, the adhesion of the valve body to the valve seat is improved, and the surface pressure is increased to improve the sealing property. Further improve.

(Claim 3) The raised portion of the valve body is formed by recessing the valve body. Therefore, the raised portion can be formed integrally with the valve body, which simplifies the structure and is advantageous in terms of cost. Moreover, by making the valve body recessed to a shallow depth, it is possible to prevent a space from being formed between the valve body and the valve seat when the valve is closed. Therefore, when the valve is closed, the fuel does not invade into the combustion chamber from the passage extending from the valve body to the injection hole as a trailing drop, and the same effect as that of claim 1 is obtained.

The ridge of the valve body is formed on the outer peripheral portion of the conical recess of the valve body, and the valve seat is provided with a conical projection. When the valve element comes into close contact with the valve seat due to the forward movement of the needle, the recess is guided by the protrusion. Therefore, the concave portion and the protruding portion act as positioning of the needle, and the adhesion of the valve body to the valve seat is further improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings based on each embodiment in which a multi-cylinder internal combustion engine such as a diesel engine is applied. FIG. 1 shows a first embodiment of the present invention. In a fuel injection nozzle 1 of a diesel engine or the like, a tubular nozzle body 2 has a stepped guide hole 3 inside. The inner bottom portion 2 a of the guide hole 3 forms a flat valve seat 4 in the vertical direction of the guide hole 3. A plurality of injection holes 5, 6 communicating with the outside of the nozzle body 2 are formed in the valve seat 4 in a downwardly inclined state, and fuel is supplied from the injection holes 5, 6 to each cylinder (not shown) such as a diesel engine. I am trying to make it jet.

Further, a stepped needle 7 is disposed in the guide hole 3 of the nozzle body 2 so as to be reciprocally movable in the axial direction. The needle 7 has a flat needle seat portion 8 corresponding to the valve seat 4 formed as a valve body on the lower end surface portion via the large diameter portion 7a, the tapered portion 7b and the small diameter portion 7c.

In the above structure, the needle 7 moves forward to the closed position (closed valve) shown by the solid line in FIG. 1 and then returns upward, so that the needle seat portion 8 separates from the valve seat 4 and the injection hole 5,
When 6 is opened (valve opened), the fuel pressure-fed from the high-pressure pump of the diesel engine into the guide hole 3 is injected from the injection holes 5 and 6 into each cylinder of the diesel engine.

When the needle 7 is opened to return to the upper direction, the needle 7 may be slightly eccentric (Ec) due to the axis deviation from the center C, as shown by the chain double-dashed line in FIG. However, since the valve seat 4 and the needle seat portion 8 are formed flat, even if the needle 7 is eccentric (Ec), the passage area Pc between the valve seat 4 and the needle seat portion 8 does not become uneven. It is kept almost constant.

Therefore, the injection hole 5, through the passage area Pc,
The spray shapes Fi and Fj of the fuel injected from No. 6 do not vary, and the stable output performance of the diesel engine can be maintained. Due to the clearance between the needle 7 and the nozzle body 2, the eccentricity of the needle 7 (E
c) does not become so large that the needle seat portion 8 separates from the injection holes 5 and 6 when the valve is closed and the injection holes 5 and 6 cannot be completely closed.

Since the valve seat 4 and the needle seat portion 8 are formed flat, the flat valve seat 4 and the needle seat portion 8 are in close contact with each other when the valve is closed, and the injection holes 5 and 6 are liquid-tightly sealed. To do. Therefore, unlike the case of the MS nozzle (minisack nozzle), fuel does not accumulate in the passage extending from the needle seat portion 8 to the injection holes 5 and 6. As a result, when the valve is closed, due to high temperature and pressure fluctuations in the combustion chamber, fuel does not drip into the combustion chamber from the passage extending from the needle seat portion 8 to the injection holes 5 and 6 and enters the combustion chamber. H
There is no risk of affecting the C component.

2A and 2B show a second embodiment of the present invention. The difference of the second embodiment from the first embodiment is that in the second embodiment, an annular raised portion 9 is formed on the outer peripheral edge of the needle seat portion 8. The raised portion 9 is formed by making the central region of the needle seat portion 8 extremely shallow.

In the second embodiment, when the needle 7 moves forward to close the injection holes 5 and 6 and reaches the closed position (closed valve), the raised portion 9 comes into close contact with the valve seat 4. At this time, the valve seat 4
Since the raised portion 9 and the raised portion 9 contact each other in a small area, the adhesion of the needle seat portion 8 to the valve seat 4 is improved, and the surface pressure thereof is increased, so that the sealing performance is further improved. In addition, the raised portion 9
Is formed by denting the needle seat portion 8, the raised portion 9 can be formed integrally with the needle seat portion 8, and the structure is simple, which is advantageous in terms of cost. Moreover, since the needle seat portion 8 is recessed very shallowly,
It is possible to prevent as much as possible from creating a space between the needle seat portion 8 and the valve seat 4 when the valve is closed. Therefore, when the valve is closed, the fuel does not enter the combustion chamber as a trailing drip from the passage extending from the needle seat portion 8 to the injection holes 5 and 6.
The same effect as the first embodiment can be obtained.

FIG. 3 shows a third embodiment of the present invention. The difference of the third embodiment from the second embodiment is that in the third embodiment, the central portion of the needle seat portion 8 is recessed into a conical shape as a concave portion 10 and the outer peripheral portion thereof is a raised portion 9. . Further, a protrusion 11 corresponding to the recess 10 is formed in the center of the valve seat 4.

In the third embodiment, when the needle 7 moves forward to close the injection holes 5 and 6 and reaches the closed position (closed valve), the raised portion 9 comes into close contact with the valve seat 4. At this time, the concave portion 10 of the needle seat portion 8 is guided by the protruding portion 11, and the concave portion 1
0 and the protrusion 11 act as positioning of the needle 7,
The adhesion of the needle seat portion 8 to the valve seat 4 is further improved.

The number of the injection holes 5 and 6 formed in the valve seat 4 can be set as desired according to the model and output of the diesel engine. Also, the angle of the downward inclination of the injection holes 5 and 6 can be set as desired according to the model and output of the diesel engine. Instead of integrally forming the raised portion 9 with the needle seat portion 8, a separate raised portion may be attached to the needle seat portion 8 by brazing or welding.

In addition, various modifications can be made without departing from the gist of the invention in implementing the invention.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a fuel injection nozzle of a multi-cylinder internal combustion engine such as a diesel engine according to the present invention (first embodiment).

FIG. 2A is a vertical sectional view of a fuel injection nozzle according to the present invention, and FIG. 2B is a partial perspective view of a needle (second embodiment).

FIG. 3 is a vertical sectional view of a fuel injection nozzle of the present invention (third embodiment).

4 (a) and (b) are conventional fuel injection nozzles (VC).
It is a longitudinal cross-sectional view showing an (O nozzle).

FIG. 5 is a vertical cross-sectional view showing a conventional MS nozzle.

[Explanation of symbols]

1 Fuel injection nozzle 2 nozzle body 3 guide holes 4 seat 5, 6 injection holes 7 needles 8 Needle seat part (valve body) 9 ridge 10 recess 11 Projection

Claims (4)

[Claims] 1. A hollow nozzle body having a guide hole extending in the longitudinal direction, a flat valve seat formed on an inner bottom portion, and a nozzle hole communicating with the valve seat to the outside, and a hollow nozzle body of the nozzle body. A needle having a valve body which is arranged so as to be reciprocally movable in the axial direction in the guide hole and which is formed flat so as to correspond to the valve seat, and the forward movement of the needle causes the valve body to move to the valve seat. While closely contacting and closing the injection hole, the return movement of the needle causes the valve element to separate from the valve seat, open the injection hole, and inject the fuel pumped into the nozzle body from the injection hole. A fuel injection nozzle characterized by the above. 2. The fuel according to claim 1, wherein the outer peripheral edge portion of the valve element forms an annular ridge so that the ridge comes into close contact with the valve seat when the needle moves forward. Injection nozzle. 3. The raised portion of the valve body is formed by recessing the valve body.
The fuel injection nozzle according to. 4. The raised portion of the valve body is formed on an outer peripheral portion of a recessed portion of the valve body which is formed into a conical shape, and a conical projection is formed on the valve seat, and The fuel injection nozzle according to claim 2, wherein the concave portion is guided to the protrusion when the valve element is brought into close contact with the valve seat by the forward movement.