JPH11351101A - Fuel injection valve for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection nozzle capable of reducing influence of eccentricity of a nozzle needle from a nozzle body, by disposing near to a seat portion of the nozzle needle a recess portion which controls axial dislocation of the nozzle needle from the nozzle body. SOLUTION: At upstream side of a seat portion 9 of a nozzle needle 3, a stepped-shape and substantially cylindrical recess portion 8 is formed by external surface cutting machining or the like, so that eccentricity of the nozzle needle 3 from a nozzle body 2 can be corrected. Thus, influence of the eccentricity of the nozzle needle 3 from the nozzle body 2 can be reduced, resulting in uniforming spray pattern of two or more nozzle holes 6, respectively. Providing the nozzle needle 3 with the recess portion 8 facilitates machining of a fuel injection nozzle 1. Accordingly, the high-quality and accurate fuel injection nozzle 1 can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve for an internal combustion engine for injecting fuel into a combustion chamber of an internal combustion engine such as a direct injection diesel engine.

[0002]

2. Description of the Related Art In general, a direct injection type diesel engine uses a hall type fuel injection nozzle. However, in this Hall-type fuel injection nozzle, the fuel in the sack volume formed at the tip of the nozzle body reaches the combustion chamber from the valve seat after the fuel is injected, that is, after the nozzle needle is seated on the valve seat of the nozzle body. Fuel accumulated in the passage is ejected due to high temperature and pressure fluctuations in the combustion chamber, and is discharged as unburned gas particularly when the diesel engine rotates at a high speed, thereby increasing HC in the exhaust gas of the diesel engine. There is.

[0003]

Therefore, for example, in Japanese Utility Model Laid-Open No. 5-83369, a dead volume (a volume of a suck volume) is provided between a valve seat of a nozzle body and an injection hole.
There is described a valve covered orifice (VCO) type fuel injection nozzle having a structure in which the inlet of the injection hole is closed at the tip of the nozzle needle. This fuel injection nozzle uses HC
Although there is a reduction effect, there is a problem that the influence of the eccentricity between the nozzle body and the nozzle needle is large, and the spray shape of each injection hole varies greatly.

As a method for suppressing the variation of the spray shape for each injection hole, Japanese Patent Application Laid-Open No.
There is a Hall type fuel injection nozzle described in Japanese Patent Application Laid-Open No. 9-14091. These are separate from normal sliding parts,
By providing another sliding portion directly above or directly below the valve seat portion of the nozzle body, axial misalignment of the nozzle needle can be prevented, and variation in the spray shape of each injection hole can be greatly reduced.

However, in the conventional hole type fuel injection nozzle, in order to achieve the above-described effects, another valve seat portion in which the tip of the nozzle needle is seated is additionally provided.
It is necessary that the two sliding parts are formed coaxially and precisely, but the valve seat part is formed at the bottom of the small diameter (about 4 mm) and deep hole (about 40 mm) of the nozzle body after the fuel reservoir. I have. Therefore, there is a problem that it is very difficult to secure another precision by additionally configuring another sliding portion directly above or directly below the valve seat portion of the nozzle body.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fuel injection for an internal combustion engine in which the effect of eccentricity between a nozzle body and a nozzle needle can be suppressed by providing a centering mechanism near a valve seat or a seat. It is to provide a valve. Another object of the present invention is to provide a fuel injection valve for an internal combustion engine that is easy to process and the like and that can easily ensure accuracy by providing an alignment mechanism near a seat portion of a nozzle needle.

[0007]

According to the first aspect of the present invention, the centering mechanism is provided near the valve seat of the nozzle body or near the seat of the nozzle needle.
When the nozzle needle rises from the valve seat, the axial displacement between the nozzle body and the nozzle needle is suppressed. Thereby, the influence of the eccentricity between the nozzle body and the nozzle needle can be suppressed, so that the spray shapes sprayed from two or more injection holes can be made uniform.

According to the second and third aspects of the present invention, by providing the recessed portion having the concave shape, the misalignment between the nozzle body and the nozzle needle is corrected. Thereby, the influence of the eccentricity between the nozzle body and the nozzle needle can be suppressed, so that the spray shapes sprayed from two or more injection holes can be made uniform. Further, by providing the recess portion in a substantially cylindrical shape on the outer peripheral surface of the nozzle needle, the processing of the internal combustion engine fuel injection valve is facilitated, and a high quality internal combustion engine fuel injection valve can be manufactured.

According to the fourth aspect of the present invention,
By making the angle difference between the inlet of the recess of the nozzle needle and the outer peripheral surface of the seat part a predetermined value or more, the separation of the fuel flow can be sufficiently generated and the axial deviation between the nozzle body and the nozzle needle is suppressed. it can. Thereby, the influence of the eccentricity between the nozzle body and the nozzle needle can be suppressed, so that the spray shapes sprayed from two or more injection holes can be made uniform.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings. FIGS. 1 and 2 show a first embodiment of the present invention. FIG. 1 is a view showing a tip shape of a hole type fuel injection nozzle for a direct injection diesel engine. FIG. 2 is a diagram showing a state in which fuel flows in the Hall-type fuel injection nozzle.

A hall-type fuel injection nozzle (hereinafter abbreviated as fuel injection nozzle) 1 for a direct injection type diesel engine according to the present embodiment is a cylinder head (not shown) of a direct injection type diesel engine (hereinafter referred to as an internal combustion engine). So that the fuel pressurized to a high pressure by a fuel injection pump (not shown) can be better ignited and burned,
This is a fuel injection valve for an internal combustion engine that sprays into a combustion chamber (not shown) formed between a cylinder head and a piston (not shown).

The fuel injection nozzle 1 is provided at a tip end of a nozzle holder (not shown) with a nozzle body 2 fastened and fixed using a fastening member such as a retaining nut, and is reciprocally accommodated in the nozzle body 2, and is loaded with a spring. The nozzle needle 3 is closed by the valve.

The nozzle body 2 is formed in a substantially cylindrical shape. Inside the nozzle body 2, an inner hole 4 drilled in the axial direction of the nozzle body 2 and a valve seat portion provided continuously at the tip of the inner hole 4 to form a frusto-conical hollow portion inside the nozzle body 2 5 and two pieces provided near the valve seat 5.
Four injection holes 6 are arranged. Each injection hole 6 has an injection passage (having a hole diameter of, for example, φ) for spraying fuel into the combustion chamber of the internal combustion engine.
(0.2 mm to 0.3 mm), an inlet is provided in the valve seat 5, and an outlet is provided on the outer peripheral surface of the tip of the nozzle body 2.

On the other hand, the nozzle needle 3 is formed in a substantially round bar shape, and is closed in a direction in which two or more injection holes 6 are closed by a coil spring (not shown) as an urging means housed in the nozzle holder. Always energized. The nozzle needle 3 includes a cylindrical shaft portion 7 and a substantially conical seat portion 9 provided on the distal end side with respect to the shaft portion 7.
A predetermined clearance (nozzle chamber) 10 is maintained between the inner hole 4 of the nozzle body 2 and the shaft portion 7 so as to be reciprocally movable. Although not shown, the rear end of the nozzle needle 2 is slidably supported in the nozzle body 2.

Here, as is well known, the clearance 10
Functions as a fuel passage for passing high-pressure fuel supplied from the fuel injection pump through a fuel supply path (not shown). Further, when the seat portion 9 is separated (lifted and lifted) from the valve seat portion 5 of the nozzle body 2, the nozzle needle 3 and the outer peripheral surface of the seat portion 9 (hereinafter referred to as a seat surface) are in contact with each other. A fuel passage (for example, a clearance of 0.25 mm to 0.30 mm) 11 is formed between the fuel passage and the inner peripheral surface.

When the fuel injection into the combustion chamber of the internal combustion engine is completed, the seat 9 of the nozzle needle 3 is seated (seat) on the valve seat 5 of the nozzle body 2. A stepped recess 8 is provided therebetween. The recessed portion 8 is a portion corresponding to the centering mechanism of the present invention, and is recessed from a truncated conical imaginary line (two-dot chain line in FIG. 1) extending the rear end edge of the seat portion 9.
It is a substantially cylindrical groove portion. The inlet of the recess 8 is set to have a sufficiently large angle difference (for example, 45 °) θ or more with respect to the inclination angle of the inner peripheral surface of the valve seat 5. When the fuel injection nozzle 1 is closed, the distance between the concave recess 8 and each injection hole 6 is such that the seal length necessary for closing each injection hole 6 with the seat 9 of the nozzle needle 3 is secured. Have been.

The tapered edge portion 13 which is the upstream edge of the recess portion 8 (the entrance of the recess portion 8) and the downstream edge of the tapered portion 12 having a truncated conical shape on the tip side of the shaft portion 7 is formed by the nozzle body 2 In line contact with the valve seat portion 5. Also, the recess 8
At the downstream edge (exit of the recess 8) and the sheet 9
The seat edge 14, which is the upstream edge of the nozzle body, is in line contact with the valve seat 5 of the nozzle body 2 to form a seat diameter. Since the inclination angle of the outer peripheral surface of the tapered portion 12 is smaller than the inclination angle of the outer peripheral surface of the seat portion 9, even when the valve is closed, most of the tapered portion 12 has the valve seat 5 of the nozzle body 2.
Never sit down.

[Operation of First Embodiment] Next, the operation of the fuel injection nozzle 1 of this embodiment will be briefly described with reference to FIGS.

When the fuel is pumped from the fuel injection pump into the nozzle body 2 via the fuel supply path, the chamber pressure in the clearance (nozzle chamber) 10 increases. When the chamber pressure of the clearance 10 becomes higher than the set load (valve opening pressure) of the coil spring, the nozzle needle 3 moves (lifts) from the valve seat 5 of the nozzle body 2 to the side where each injection hole 6 is opened, The fuel passage 11 is opened (see FIG. 1).

As a result, the fuel in the clearance 10 flows into the recess 8 through the passage between the inner hole 4 of the nozzle body 2 and the tapered portion 12 of the nozzle needle 3.
When the fuel flows into the recess 8, the flow cannot flow along the shape of the recess 8 at the entrance of the recess 8, and the flow is separated. As described above, when the separation of the flow occurs, the injection pressure of the recess portion 8 is not changed to the flow velocity, and the injection pressure is maintained as it is. For this reason, a force in the centripetal direction is generated on the outer peripheral surface of the recess 8 by the injection pressure.

Therefore, since the nozzle needle 3 always operates while receiving a force coaxial with the outer peripheral surface (seat surface) of the valve seat portion 5 of the nozzle body 2, the misalignment between the nozzle needle 3 and the nozzle body 2 is reduced. Be corrected. Thereby, the fuel in the clearance 10 flows into each of the two or more injection holes 6 through the fuel passage 11. And each injection hole 6
Is sprayed into the combustion chamber of the internal combustion engine in the form of mist from the outlet.

[Effects of the First Embodiment] As described above, the fuel injection nozzle 1 of the present embodiment has the shaft portion 7 of the nozzle needle 3.
By providing the concave recessed portion 8 on the outer peripheral surface between the nozzle body 2 and the seat portion 9, the nozzle body 2 and the nozzle needle 3 can be automatically aligned with each other. The nozzle body 2 and the nozzle needle 3 when the nozzle needle 3 is lifted from the valve seat 5
Can be suppressed.

Therefore, the influence of the eccentricity between the nozzle body 2 and the nozzle needle 3 can be suppressed, so that the eccentricity of the clearance between the outer peripheral surface of the seat portion 9 and the inner peripheral surface of the valve seat portion 5 can be reduced. In addition, since the flow rate of the fuel flowing into each of the two or more injection holes 6 is made uniform, the spray shape of the fuel injected from each of the injection holes 6 can be made uniform.
Further, by forming the recessed portion 8 on the outer peripheral surface of the nozzle needle 3 by, for example, an outer surface cutting process, the machining becomes easier as compared with the case where the recessed portion 8 is provided in the nozzle body 2, so that high quality and high precision can be achieved. A simple fuel injection nozzle 1 can be manufactured.

[Second Embodiment] FIG. 3 shows a second embodiment of the present invention, and is a diagram showing a tip shape of a hall type fuel injection nozzle for a direct injection diesel engine.

In this embodiment, the shaft 7 of the nozzle needle 3
A tapered portion 15 having a truncated cone shape having a steeper inclination angle than the tapered portion 12 is provided between the tapered portion 12 and the tapered portion 12. Then, when the nozzle needle 3 is seated on the valve seat 5, the recess portion 8 as a centering mechanism between the nozzle body 2 and the nozzle needle 3 is provided with two or more of the seat edge portion 14 of the nozzle needle 3 and the nozzle body 2. It is configured to be located at a position separated from the injection hole 6 by a predetermined dimension (for example, 0.3 mm).

Then, the sheet edge portion 14 and the recess portion 8
Is secured by an amount necessary for reducing the seat pressure when the nozzle needle 3 is seated on the valve seat portion 5 to an allowable value or less. When the fuel injection nozzle 1 is closed, the distance between the concave recess 8 and each injection hole 6 is such that the seal length necessary for closing each injection hole 6 with the seat 9 of the nozzle needle 3 is secured. Have been.

[Modification] In this embodiment, the nozzle body 2
The recess 8 is provided near the upstream side of the seat portion 9 of the nozzle needle 3 as a centering mechanism for suppressing the axial deviation between the nozzle needle 3 and the nozzle needle 3, but the recess 8 is provided near the valve seat 5 of the nozzle body 2. Is also good. Although the recess 8 has a substantially cylindrical groove, the groove 8 may be an R-shaped groove, a V-shaped groove, a U-shaped groove, or the like.
The recess 8 needs to be provided on the outer peripheral surface of the nozzle needle 3.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a tip shape of a Hall-type fuel injection nozzle (first embodiment).

FIG. 2 is an explanatory view showing a state in which fuel flows through a Hall-type fuel injection nozzle (first embodiment).

FIG. 3 is a cross-sectional view showing a tip shape of a Hall-type fuel injection nozzle (second embodiment).

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fuel injection nozzle (fuel injection valve for internal combustion engine) 2 nozzle body 3 nozzle needle 5 valve seat 6 injection hole 8 recess (alignment mechanism) 9 seat

Claims (4)

[Claims] (A) a nozzle body having two or more injection holes from which fuel is injected, and a valve seat provided near these injection holes; and (b) contacting the valve seat when the valve is closed. It has a sheet part that touches,
A nozzle needle that closes the injection hole with the seat portion; and (c) a centering mechanism that is provided near the valve seat portion or near the seat portion and that suppresses axial misalignment between the nozzle body and the nozzle needle. A fuel injection valve for an internal combustion engine comprising: 2. The fuel injection valve for an internal combustion engine according to claim 1, wherein the alignment mechanism has a concave recessed portion in the nozzle needle for separating a flow of fuel, near the seat portion. A fuel injection valve for an internal combustion engine. 3. The fuel injection valve for an internal combustion engine according to claim 2, wherein the recess portion is provided in a substantially cylindrical shape on the outer peripheral surface of the nozzle needle. . 4. The fuel injection valve for an internal combustion engine according to claim 2, wherein the nozzle needle has an angle difference between an inlet of the recess portion and an outer peripheral surface of the seat portion equal to or more than a predetermined value. A fuel injection valve for an internal combustion engine.