JPH09177638A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inject fuel in two stages, i.e., the pilot injection and the main injection, with a simple constitution by forming a notch part which is communicated with an injection hole and in which an end part of a needle valve in the lift direction is located forward of an end part of the injection hole on an outer circumferential surface of the needle valve. SOLUTION: When the pressure of the fuel to be force fed to a spring storage hole 2b of an injection nozzle 1 reaches the valve-opening pressure, a needle valve 6 is lifted against a nozzle spring 7 to the degree in which a lower end part of an annular groove 6d (notch part) is exposed from a valve sliding hole 3a. A relatively large amount of fuel is injected (pilot injection) from the lower end part of the annular groove 6d. When the fuel pressure is temporarily dropped by the injection, and the needle valve 6 is seated on a valve seat 3b, the fuel injection is once stopped. Then, the fuel pressure rises, and the needle valve 6 is lifted again, and because the oil feed ratio at the time is set high, the needle valve is lifted by the total lift amount, and the fuel is injected (main injection) from an injection hole 6c.

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 used in an internal combustion engine such as a diesel engine, and more particularly to a poppet type fuel injection nozzle.

[0002]

2. Description of the Related Art Generally, a fuel injection nozzle of this kind is slidable in a valve body and a nozzle body having a valve seat formed at one end opening of the valve slide hole. The needle valve is provided with an injection hole that opens to the outer peripheral surface of the needle valve. The injection hole is blocked by the inner peripheral surface of the valve sliding hole when the valve portion of the needle valve is seated on the valve seat by the nozzle spring, but the needle valve is lifted by the fuel pumped to the nozzle. Then, the fuel is exposed from the valve sliding hole to inject the fuel (see Japanese Patent Laid-Open No. 62-20671).

[0003]

It is desirable that the fuel injection nozzle be capable of injecting fuel in two stages of pilot injection and main injection when the engine rotates at a low speed such as during idling. However, there is no conventional poppet type fuel injection nozzle capable of injecting fuel in two stages of pilot injection and main injection.

In a poppet type fuel injection nozzle having a large injection hole, since the fuel injection amount per unit time is large, the needle valve lifts when the oil feed rate is low such as when the engine runs at a low speed. When the fuel injection is performed, the fuel pressure temporarily decreases, the needle valve is seated on the valve seat, and the fuel injection is interrupted. After that, when the pressure of the fuel rises, the needle valve lifts again and injection is performed again. In such a case, two-stage injection is performed. However, the size of the injection hole is determined according to the engine in which the fuel injection nozzle is used, and cannot be arbitrarily changed. Therefore, enlarging the injection hole cannot be a solution for performing two-stage injection.

[0005]

In order to solve the above problems, the invention according to claim 1 has a nozzle main body having a valve slide hole and a valve seat formed at one end opening of the valve slide hole. And a needle valve slidably provided in the valve slide hole, and provided with a valve portion for seating on the valve seat at an end portion protruding from the valve slide hole. In the fuel injection nozzle, the opening in the outer peripheral surface is shielded by the inner peripheral surface of the valve sliding hole when the needle valve is seated, and the injection hole exposed from the valve sliding hole is formed when the needle valve is lifted. A notch is formed on the outer peripheral surface of the needle valve, the notch being in communication with the injection hole and having an end in the lift direction of the needle valve located in front of the end of the injection hole in the same direction.
In this case, the notch may be formed in an annular shape along the circumferential direction of the needle valve. In addition, a plurality of the injection holes and the cutouts may be formed in the same number, and the cutouts may be respectively communicated with the injection holes and may be arranged apart from each other in the circumferential direction of the needle valve. .

[0006]

In the invention according to claim 1, the needle valve lifts when the pressure of the fuel pumped to the fuel injection nozzle reaches a predetermined pressure. Then, the notch portion is first exposed from the valve sliding hole, and the fuel is injected from there. At this time, the oil feed rate is low at the beginning of the pressure feed of the fuel. Therefore, when the fuel is injected from the cutout portion, the pressure of the fuel is temporarily reduced, and the needle valve once seats or moves toward the valve seat side. After that, when the fuel pressure rises, the needle valve lifts again. Then, the fuel is injected from the cutout portion, but at this time, the fuel feeding rate is high, so the fuel pressure hardly drops, and the needle valve lifts by the full lift amount. When the needle valve is fully lifted, the injection hole is exposed from the valve sliding hole, and the fuel is injected from there. Such an operation is the same in the invention according to claim 2 or 3.

[0007]

Embodiments of the present invention will now be described with reference to FIGS.
This will be described with reference to FIG. 1 and 2 show an embodiment of the present invention. First, the overall configuration of the fuel injection nozzle 1 of this embodiment will be described with reference to FIG.
The nozzle 1 includes a nozzle holder 2. The nozzle holder 2 has a rod shape, and an oil feed hole 2a extending downward from the upper end surface is formed therein, and a spring extending from the lower end portion to the lower end surface of the oil feed hole 2a. A storage hole 2b is formed. Fuel is pumped to the oil feed hole 2a from a fuel injection pump (not shown), and then to the spring housing hole 2b.

On the lower end surface of the nozzle holder 2, a nozzle body 3 is positioned by a knock pin 4 and fixed by a nut 5. The nozzle main body 3 is formed with a valve sliding hole 3a penetrating from the upper end surface to the lower end surface of the nozzle main body 3, and a tapered valve seat having a downwardly expanding diameter is formed at the lower end opening of the valve sliding hole 3a. 3b is formed.

A needle valve 6 is provided in the valve sliding hole 3a of the nozzle body 3.
Is slidably provided. The upper end of this needle valve 6 is
It penetrates through the valve sliding hole 3a and projects into the spring housing hole 2b, and is urged upward through a spring receiver 8 by a nozzle spring 7 arranged in the spring housing hole 2b. on the other hand,
The lower end portion of the needle valve 6 projects downward from the valve sliding hole 3a, and the valve portion 6a is formed therein. This valve 6a
Is seated on the valve seat 3b by the nozzle spring 7. On the other hand, when the pressure of the fuel sent to the spring housing hole 2b reaches a predetermined valve opening pressure, the needle valve 6 lifts against the biasing force of the nozzle spring 7. The total lift amount of the needle valve 6 is defined by the spring receiver 8 hitting the lift restricting member 9.

The needle valve 6 has a fuel hole 6b extending downward from the upper end surface thereof to the upper portion of the valve portion 6a. The fuel pressure-fed to the spring accommodating hole 2b has entered the fuel hole 6b. In addition, an injection hole 6c is formed in the lower end portion of the needle valve 6 adjacent to the upper side of the valve portion 6a. As shown in FIG. 1, the inner end of the injection hole 6c communicates with the fuel hole 6b, and the outer end opens to the outer peripheral surface of the needle valve 6. The opening of the injection hole 6c on the outer peripheral surface of the needle valve 6 is arranged so as to be blocked by the valve sliding hole 3a when the needle valve 6 is seated and exposed from the valve sliding hole 3a when the needle valve 6 is fully lifted. There is.

Although four injection holes 6c are formed in this embodiment, one or a plurality of injection holes 6c other than four may be formed. When a plurality of injection holes 6c are formed, the injection holes 6c are normally arranged at equal intervals in the circumferential direction of the needle valve 6 and arranged at the same position in the axial direction of the needle valve 6. Further, the injection hole 6c of this embodiment is formed so as to be orthogonal to the axis of the needle valve 6, but is inclined by an angle similar to that of the valve seat 3b so as to form an acute angle or an obtuse angle. May be formed.

An annular groove (notch) 6d extending in the circumferential direction of the needle valve 6 is formed on the outer peripheral surface of the needle valve 6 where the injection hole 6c is opened.
Are formed. The annular groove 6d has a groove width (width in the axial direction of the needle valve 6) larger than the diameter of the injection hole 6c, an upper end edge of which is located above the injection hole 6c, and a lower end edge of the annular groove 6d. It is arranged so as to be located below 6c. As is clear from this, the annular groove 6d
An injection hole 6c is opened on the bottom surface of the fuel cell, and fuel is pumped to the annular groove 6d through the injection hole 6c.

In this embodiment, the annular groove 6d
The lower end edge of the valve slide hole 3a is located below the lower end edge of the valve slide hole 3a when the needle valve 6 is seated.
You may arrange | position so that it may be located in the same position as the lower end edge of, or a little above.

In the fuel injection nozzle 1 having the above structure, when the pressure of the fuel pumped to the spring accommodating hole 2b reaches the valve opening pressure defined by the nozzle spring 7, the needle valve 6 resists the biasing force of the nozzle spring 7. And lift. In this case, the needle valve 6
For the following reason, the annular groove 6 is not lifted at the time of low speed rotation of the engine, as shown in FIG.
Lift only to the extent that the lower end of d is exposed from the valve sliding hole 3a. Then, fuel is injected from the lower end of the annular groove 6d.

Here, the oil feed rate of the needle valve 6 at the beginning of the lift is low. In particular, the oil feed rate at the beginning of the lift is low at low speeds such as idling. On the other hand, the exposed area of the annular groove 6d is large. Particularly, in this embodiment, since the lower end edge of the annular groove 6d is located at substantially the same position as the lower end edge of the sliding hole 3a, the annular groove 6d is largely exposed even with a slight lift amount of the needle valve. Therefore, while a small amount of fuel is pumped, a relatively large amount of fuel is injected from the annular groove 6d. As a result, when the needle valve 6 is lifted until the lower end of the annular groove 6d is exposed, the fuel pressure is temporarily reduced by the injection from the annular groove 6d, and the needle valve 6 is seated on or moved toward the valve seat 3b. . As a result, fuel injection is temporarily stopped.
The injection performed during this period is pilot injection.

After that, when the fuel pressure rises, the needle valve 6
Will lift again. At this time as well, fuel is first injected from the annular groove 6d, but the oil transfer rate at this point is high. Therefore, the fuel pressure is hardly reduced by the injection from the annular groove 6d, and the needle valve 6 is lifted by the entire lift amount as shown in FIG. 3 (B). And
Fuel is injected from the injection hole 6c. The injection at this time is the main injection. When the pressure feed of fuel from the fuel injection pump is interrupted, the needle valve 6 is seated by the nozzle spring 7.

Next, another embodiment of the present invention will be described. In the embodiment shown in FIG. 4, the annular groove 6d of the above embodiment overlaps the entire opening of the injection hole 6c, whereas the annular groove 6d overlaps only a part of the lower side of the injection hole 6c. It was done like this. In this embodiment, since the annular groove 6d communicates only with a part of the lower side of the injection hole 6c, the depth of the annular groove 6d is temporarily set to the annular groove 6d of the above embodiment.
When the depth is the same as the above, the communication area becomes small, and there is a possibility that the above-mentioned effects cannot be obtained. In such a case, the communication area between the annular groove 6d and the injection hole 6c can be increased by increasing the depth of the annular groove 6d. The depth of the annular groove 6d is experimentally determined.

In the embodiment shown in FIGS. 5A and 5B, four flattened portions (cutout portions) 6e are formed instead of the annular groove 6d of the embodiment shown in FIG. The respective flattening portions 6e are arranged so as to communicate with the respective injection holes 6c at their central portions. In this embodiment, since the four flattened portions 6e are separated from each other, the exposed area of the needle valve 6 for a certain lift amount is smaller than that of the annular groove 6d formed over the entire circumference of the needle valve 6. Therefore, the injection amount injected from the flattening portion 6e is also the annular groove 6d.
The fuel injection amount is smaller than that of the fuel injection amount, and the fuel pressure drop caused thereby is small. Therefore, this embodiment is suitable for obtaining pilot injection when the oil feed rate is very small.
In other words, the above embodiment having the annular groove 6d is suitable for obtaining pilot injection when the oil feed rate is relatively large.

Further, in the embodiment shown in FIGS. 6A and 6B, the flattened portion 6e of the embodiment shown in FIG. 5 is arranged so as to communicate with the injection hole 6c at one end. is there. By doing so, the injection direction can be changed between the pilot injection and the main injection, and the air in the combustion chamber of the engine can be effectively used.

[0020]

As described above, according to the first aspect of the invention, the effect that the fuel can be injected in two stages of pilot injection and main injection can be obtained. According to the second aspect of the invention, it is possible to obtain the effect that the two-stage injection can be performed even when the oil feed rate is high. According to the invention of claim 3, there is an effect that the two-stage injection can be reliably performed even when the oil feeding rate is low.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention and is shown in FIG.
Is an enlarged cross-sectional view of a main part thereof, FIG. 1B is an enlarged side view of the needle valve, and FIG. 1C is a CC cross-sectional view of FIG. 1B.

FIG. 2 is a cross-sectional view showing the overall configuration of the same embodiment.

FIG. 3 is a cross-sectional view similar to FIG. 1 (A) for explaining the operation of the same embodiment, and FIG. 3 (A) shows a state when the needle valve is initially lifted, and FIG. ) Indicates the condition when the needle valve is fully lifted.

FIG. 4 is an enlarged side view showing a needle valve according to another embodiment of the present invention with a part thereof omitted.

5 is a view showing a needle valve according to still another embodiment of the present invention, FIG. 5 (A) is an enlarged side view with a part thereof omitted, FIG.
FIG. 5B is a sectional view taken along line BB of FIG.

FIG. 6 is a view showing a needle valve according to another embodiment of the present invention, FIG. 6 (A) is an enlarged side view with a part thereof omitted, and FIG. 6 (B).
FIG. 7B is a sectional view taken along line BB in FIG.

[Explanation of symbols]

 1 Fuel Injection Nozzle 3 Nozzle Main Body 3a Valve Sliding Hole 3b Valve Seat 6 Needle Valve 6a Valve 6c Injection Hole 6d Annular Groove (Notch) 6e Flat Face (Notch)

Claims (3)

[Claims] 1. A nozzle main body having a valve sliding hole and a valve seat formed at one end opening of the valve sliding hole, and a nozzle body slidably provided in the valve sliding hole and protruding from the valve sliding hole. A needle valve having a valve portion for seating on the valve seat is provided at the end of the valve seat, and the needle valve has an opening on the outer peripheral surface thereof, and the inner peripheral surface of the valve sliding hole when the needle valve is seated. In the fuel injection nozzle in which the injection hole that is shielded by the needle valve and that is exposed from the valve sliding hole when the needle valve is lifted is formed, the outer peripheral surface of the needle valve communicates with the injection hole and A fuel injection nozzle, characterized in that a notch is formed whose end is located in front of the end of the injection hole in the same direction. 2. The fuel injection nozzle according to claim 1, wherein the cutout portion is formed in an annular shape along the circumferential direction of the needle valve. 3. The injection holes and the cutouts are formed in the same number and in a plurality, and the cutouts are respectively communicated with the injection holes, and are arranged apart from each other in the circumferential direction of the needle valve. The fuel injection nozzle according to claim 1, wherein the fuel injection nozzle is a fuel injection nozzle.