JP3134970B2 - 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 fuel injection valve mounted on an internal combustion engine, and more particularly to a fuel injection valve which does not generate secondary injection at the end of fuel injection.

[0002]

2. Description of the Related Art Conventionally, a technology for increasing the pressure of a fuel injection system has been developed in order to cope with the tightening of exhaust gas regulations of a diesel engine. A sharp cut of the jet is essential. As a method of sharply cutting the fuel injection, a method of increasing the speed of the fuel injection valve in the seating direction of the nozzle needle is known.

[0003]

However, if the speed of the seating direction of the needle of the fuel injection valve is increased, the seating speed of the nozzle needle with respect to the nozzle body is increased immediately before the seating. As the impact at the time of collision increases and the speed at the moment of sitting increases, the bounce of the nozzle needle increases, which causes secondary injection, which makes it difficult to sharply cut the injection Had become.

[0004] It is an object of the present invention to provide a fuel injection valve which ensures both sharp cut at the end of fuel injection and prevention of secondary injection.

[0005]

According to a first aspect of the present invention, there is provided a fuel injection valve, comprising: a reciprocally movable valve member;
A valve having a valve body sliding hole for guiding the valve member slidably in the axial direction, a fuel reservoir chamber adjacent to the valve body sliding hole, a valve seat capable of contacting the valve member, and an injection hole. A main body, a biasing unit that biases the valve member in a valve closing direction, a pressure chamber that houses the biasing unit, and increases a pressure of the valve member in a valve closing direction by increasing a pressure; A communication path is provided that allows the fuel reservoir chamber and the pressure chamber to communicate with each other by elastic deformation accompanying axial contraction of the valve member generated after seating on the valve seat portion and axial expansion of the valve body. And

[0006]

According to the fuel injection valve of the present invention, when the valve member (hereinafter, referred to as "nozzle needle") is seated on the valve seat of the valve body (hereinafter, referred to as "nozzle body") at the end of the fuel injection, An impact load acts between the nozzle needles. At the time of this impact load, if the fuel injector is of the internal valve type, elongation due to tensile impact stress occurs in the axial direction of the nozzle body, and as a reaction, shrinkage due to compressive impact stress occurs in the axial direction of the nozzle needle. Occurs. At this time, the fuel reservoir chamber is temporarily (instantaneously) communicated with the pressure chamber (hereinafter, referred to as "spring chamber") via the communication passage due to the elastic expansion and contraction elastic deformation caused by the impact load. The instantaneous pressure increase in the spring chamber increases the valve closing direction force of the nozzle needle after the end of the injection, thereby preventing bounce of the nozzle needle and reliably preventing the occurrence of the secondary injection.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment in which the present invention is applied to a fuel injection nozzle portion attached to a combustion chamber of a diesel engine.
Shown in In FIG. 1, a casing member 11 of the injector 10 includes a nozzle holder 12, a packing 14, and a nozzle body 16, and the nozzle holder 12, the packing 14, and the nozzle body 16 are integrally connected by a retaining ring 18.

In the nozzle body 16, an injection hole 20, a valve body guide hole 22, a fuel reservoir 24, and a valve body slide hole 26 are formed. Are fitted in a liquid-tight and slidable manner. Injection hole 2
0 is opened and closed by the valve body 3 formed in the nozzle needle 28.
The second valve seat 34 is opened and closed by being seated on and separated from the valve seat 34.
Step 36 formed on the large diameter portion 30 of the nozzle needle 28
When the valve is fully opened, it comes into contact with the packing 14 and plays a role of a stopper so that the valve opening does not become any larger.

The projection 38 protruding from the top of the large diameter portion 30 of the nozzle needle 28 is fitted in a fitting hole 44 of a pressure pin 40. Fitting hole 44 of pressure pin 40
On the opposite side, a projection 48 for guiding the compression coil spring 46 is formed. A compression coil spring 4 is provided inside a spring chamber 50 formed in the nozzle holder 12.
One end 46a is in contact with the pressure pin 42, and the other end 46b is in contact with the bottom surface 50a of the spring chamber 50 via the shim 52. The spring chamber 50 communicates with the low-pressure chamber 54 via an orifice 56.

The fuel supply system passes through fuel supply holes 60 and 62 formed in the nozzle holder 12, a fuel supply hole 64 formed in the packing 14, and a fuel supply hole 66 formed in the nozzle body 16. Is in communication with The fuel reservoir 24 communicates with the injection hole 20 via the valve body guide hole 22 around the nozzle needle 28. The fuel passage that allows the fuel reservoir 24 and the spring chamber 50 to communicate with each other is constituted by the annular groove 70, the communication hole 72, the communication hole 74, and the communication hole 76. That is, the annular groove (hereinafter referred to as “oil collecting groove”) 70 is formed in an annular concave shape at the lower part of the outer peripheral wall of the large diameter portion 30, and the communication hole 72 is formed in the large diameter portion 30.
And connects the oil collecting groove 70 to the communication hole 74. The communication hole 74 is formed by the large diameter portion 30 and the protrusion 3.
8 is formed in the axial direction, and is opened at the end on the protrusion side.
The communication hole 76 is penetrated in the axial direction of the pressure pin 40, the nozzle needle side end communicates with the communication hole 74, and the opposite end communicates with the spring chamber 50.

As shown in FIG. 2, in a steady state when the valve is fully closed, the oil collecting groove 70 and the fuel storage chamber 24 are separated from each other. The closest distance in the direction is the distance L. Here, in the steady state when the valve is fully closed, the closest axial direction distance between the seating position P of the valve body 32 on the valve seat 34 and the oil collecting groove 70 is Ln, and the seating position P and the fuel reservoir Assuming that the most remote axial distance from the upper surface of L.24 is Lb, the difference between the closest axial distance Ln and the most remote axial distance Lb is the distance L (L = Ln-Lb).
This distance L is between the nozzle needle 28 and the nozzle body 16.
Is set to be larger than the amount of elastic deformation caused by the set load by the compression coil spring 46, and the nozzle needle 28
Is set smaller than the amount of elastic deformation due to the seating impact force. This is because the fuel reservoir chamber 24 and the oil collecting groove 70 communicate with each other only when the seating impact of the nozzle needle 28 occurs due to the contraction of the nozzle needle 28 and the extension of the nozzle body 16.

When the nozzle needle 28 is in the valve open state and in the steady state when fully closed, the oil collecting groove 70 faces the inner wall of the valve body sliding hole 26, so that the fuel sump chamber 24 and the oil collecting groove 70 are shut off. (Ln> Lb). However, the nozzle needle 28
Immediately after seating, as shown in FIG. 2, the portion corresponding to the distance Ln of the nozzle needle 28 contracts due to the impact load, and the portion corresponding to the distance Lb of the nozzle body 16 expands, so that Ln ′ <Lb ′. The oil collecting groove 70 and the fuel reservoir 24 communicate with each other. Here, Ln ′: an axial distance of a portion corresponding to the distance Ln of the nozzle needle 28 after the elastic deformation Lb ′: an axial distance of a portion corresponding to the distance Lb of the nozzle body 16 after the elastic deformation. As a result, immediately after the needle is seated, the high-pressure fuel in the fuel reservoir 24 instantaneously flows into the oil collecting groove 70, and the oil collecting groove 70, the communication holes 72, 74,
It flows into the spring chamber 50 via 76.

The orifice 56 formed in the nozzle holder 12 has a passage area smaller than the minimum passage cross-sectional area of the communication holes 72, 74, 76. This is because when the needle is seated, the high-pressure fuel in the fuel sump chamber 24 instantaneously flows into the oil collecting groove 70 and flows into the spring chamber 50 via the communication holes 72, 74, and 76. At this time, the low-pressure chamber 54 side This is to prevent the fuel from flowing instantaneously.

When fuel flows from the communication hole 76 into the spring chamber 50, the fuel gradually flows out through the orifice 56 to the low-pressure chamber 54 with the passage of time. Next, the operation will be described. When the fuel is pumped by a pump (not shown), the fuel supply holes 60, 62, 64, 66
When the fuel flows into the fuel reservoir chamber 24 via the nozzle, and the balance between the set pressure of the compression coil spring 46 and the pressure received by the high-pressure fuel of the nozzle needle 28 is lost, the nozzle needle 28 rises and fuel is injected from the injection hole 20. It is injected.

At the end of fuel injection, the valve body 32 of the nozzle needle 28 is seated on the valve seat 34 of the nozzle body 16.
After the valve is seated, the nozzle needle 28 is moved to the nozzle body 16.
Is about 10 times the urging force of the compression coil spring 46, for example. The impact force causes the nozzle needle 28 to contract and the nozzle body 16 to expand. At this time, as described above, the distance Ln ′ <
Lb ′, the fuel reservoir 24 communicates with the oil collecting groove 70, and the fuel in the fuel reservoir 24 flows into the spring chamber 50 through the oil collecting groove 70, through the communication holes 72, 74, 76. Then, the pressure in the fuel chamber 24 decreases and the pressure in the spring chamber 50 increases, so that the valve closing direction force acting on the nozzle needle 28 increases, and the bounce of the nozzle needle 28 is suppressed. This prevents secondary injection immediately after fuel injection.

FIG. 3 shows the result of comparing the fuel injection characteristics of the injector of the comparative example with the injector of the present embodiment of the same type. As shown in FIG. 3, a conventional comparative example (dotted line) can be understood by comparing changes in the fuel injection rate, the needle lift of the nozzle needle 28, the pressure in the fuel reservoir 24, and the pressure in the spring chamber 50. It was found that the secondary injection occurred, whereas the secondary injection did not occur in the present embodiment (solid line) of the present invention.

Next, a second embodiment of the present invention is shown in FIGS. In the injector according to the second embodiment, a nozzle body inclined surface 82 is formed in a communicating portion between the valve element sliding hole 26 and the spring chamber 50. And nozzle needle 2
Notch planes 80 and 81 are formed on the outer peripheral wall surface of the large diameter portion 30 of FIG. The oil collecting groove 70 and the spring chamber 50 are always in communication with each other via the cutout planes 80 and 81. The other components are the same as those in the first embodiment, so that substantially the same components are denoted by the same reference numerals, and description of the same components will be omitted.

In the second embodiment, in addition to the effect of preventing the occurrence of the secondary injection according to the first embodiment, the pressure pin 40
Since the communication hole formed in the first embodiment is not required, there is an effect that the number of processing steps is simplified as compared with the first embodiment. In addition, the first
In the embodiment, the passage connecting the oil collecting groove 70 and the spring chamber 50 is provided with the oil collecting groove 70 and the communication holes 72, 74, 76.
In the second embodiment, the oil collecting groove 70 and the cutout planes 80 and 81 shown in FIG. 4 are employed. However, instead of these, a communication passage that can communicate the fuel reservoir chamber and the pressure chamber of the present invention is provided. May be constituted by any groove, hole, notch or the like in addition to the V groove and U groove, and the number of these grooves, holes, notches and the like is not limited.

[0019]

As described above, according to the fuel injection valve of the present invention, the fuel reservoir is formed by the expansion and contraction deformation caused by the impact force between the nozzle body and the nozzle needle generated when the nozzle needle is seated at the end of the injection. Is instantaneously communicated with the spring chamber, so that the pressure in the spring chamber at the moment of closing the valve increases the closing direction force of the nozzle needle immediately after the end of injection, so that secondary injection can be reliably prevented. effective.

Therefore, by increasing the speed of the moment when the nozzle needle is seated on the nozzle body at the end of the injection, a sharp cut at the end of the fuel injection is realized, and at the same time, the occurrence of the secondary injection due to the bounce of the nozzle needle is achieved. There is an effect of doing.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of a portion A shown in FIG.

FIG. 3 is a characteristic diagram comparing a fuel injection characteristic according to a first embodiment of the present invention with a fuel injection characteristic of a conventional comparative example.

FIG. 4 is a partial sectional view of a second embodiment of the present invention.

FIG. 5 is a view as seen in the direction of the arrow V shown in FIG. 4;

[Explanation of symbols]

 11 Injector (Fuel Injection Valve) 16 Nozzle Body (Valve Body) 20 Injection Hole 24 Fuel Reservoir 26 Valve Sliding Hole 28 Nozzle Needle (Valve Member) 34 Valve Seat 40 Pressure Pin 46 Compression Coil Spring (biasing means) Reference Signs List 50 spring chamber (pressure chamber) 56 orifice 70 oil collecting groove (communication passage) 72 communication hole (communication passage) 74 communication hole (communication passage) 76 communication hole (communication passage)

Claims (1)

(57) [Claims] 1. A reciprocating valve member, a valve body sliding hole for guiding the valve member slidably in an axial direction, a fuel chamber adjacent to the valve body sliding hole, and a contact between the valve member and the fuel chamber. A valve body having a contactable valve seat portion and an injection hole; a biasing means for biasing the valve member in a valve closing direction; A pressure chamber that increases the pressure of the fuel chamber and the pressure chamber by elastic deformation accompanying axial contraction of the valve member and axial expansion of the valve body that occur after the valve member is seated on the valve seat. And a communication passage through which the fuel can be communicated.