JPH0444846Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to the improvement of a fuel injection nozzle for a diesel engine, and involves dividing a nozzle holder that accommodates a needle valve into a metal holder part and a nozzle part having an injection hole. is made of silicon nitride-based ceramic material, and the valve seat provided at the tip of the holder part and the tapered surface provided on the inner surface of the nozzle part are formed into a continuous valve seat, thereby improving durability. The present invention provides a fuel injection nozzle rich in fuel injection nozzles.

A fuel injection nozzle is normally fixed to the cylinder head into a combustion chamber formed between the cylinder head and the top of the piston.

Therefore, since the nozzle hole of the fuel injection nozzle faces into the combustion chamber, this nozzle hole is always exposed to high temperatures, and the fuel is likely to seize at this nozzle hole, causing fuel injection. This has the disadvantage of causing problems in the engine's condition, reducing engine output and deteriorating the quality of exhaust gas.

The conditions that the fuel injection nozzle must meet are as follows: (1) No seizure occurs in the nozzle hole. (2) Good fuel consumption; (3) It has excellent durability.

In order to meet this condition, in recent years ceramic materials have been used for fuel injection nozzles, for example,
The invention of Publication No. 161417 relates to a fuel injection nozzle in which a nozzle part in which a nozzle hole and a valve seat are integrally formed with a ceramic body is fitted to the tip of a nozzle body. , the valve seat is formed into a tapered shape, and the valve seat is fitted so that the periphery of the nozzle portion is supported by the inner wall of the nozzle body, and the needle valve has a shape in which a tapered valve surface and its tip extend into the nozzle hole. A fuel injection nozzle having a fuel injection nozzle is disclosed.

However, although ceramic materials have significantly higher heat resistance than metal materials, they are highly brittle and have poor workability, so it is necessary to avoid applying impact force to ceramic materials during use.

If the strength of the ceramic nozzle part, which has high heat resistance but poor brittleness, is increased and a valve seat is installed in the nozzle part, the wasted volume from the valve seat to the tip of the nozzle hole can be gradually reduced. Combustion conditions can be improved, such as by reducing hydrocarbon components. However, as in the embodiment described in the above publication, a valve seat is provided in the ceramic nozzle part,
If the surrounding area is supported, there is a risk that the nozzle portion will be damaged by impact, and it has been difficult to obtain an optimal ceramic fuel injection nozzle structure.

The present invention has been developed by focusing on the above-mentioned problems, and improves the impact resistance of the nozzle part made of highly heat-resistant ceramic material, making it possible to provide a valve seat in the nozzle part. It is an object of the present invention to provide a fuel injection nozzle for a diesel engine that can gradually reduce waste volume by bringing the nozzle hole outlet and the nozzle hole close to each other.

To achieve the above object, the fuel injection nozzle for a diesel engine of the present invention has a configuration including a needle valve having a tapered tip, and a metal holder of a nozzle holder that slidably accommodates the needle valve. Department and
It has a ceramic nozzle part that is joined to the tip of the metal holder part, and a fastening fitting that covers the ceramic nozzle part and tightens and fixes the nozzle part to the metal holder part. The present invention is characterized in that a metal layer is formed on the inner peripheral portion, and a valve seat portion having the same tapered surface is formed on the inner peripheral portion of the tip of the holder portion and the inner peripheral portion of the nozzle portion.

The metal layer formed on the inner surface of the nozzle may be formed by attaching a thin metal plate to a metallized layer provided on the surface of the ceramic material using adhesive means or the like.

Since the valve seat of the nozzle part of the above structure is formed of a metal layer, impact resistance is enhanced, and furthermore, it can be tightened from the outside with a tightening fitting to prevent damage due to internal pressure and impact.

Next, embodiments of the present invention will be described with reference to the drawings.

The figure is a sectional view showing the main parts of a fuel injection nozzle, in which a nozzle part 3 made of ceramic material is attached to the tip of a metal holder part 1 with a valve seat part 2 formed at the tip.
The nozzle part 3 and the holder part 1 are housed in a bag-shaped tightening fitting 4, and the tightening fitting 5 is screwed onto a threaded part 6 provided on the outer periphery of the holder part 1 to secure the holder. The nozzle part 3 is pressed and fixed to the tip of the part 1. A needle valve 7 is inserted into the holder portion 1 so as to be movable up and down.

The nozzle portion 3 is made of a silicon nitride ceramic material, and its inner surface is formed into a tapered surface 8 that matches the tapered surface 7A forming the valve portion at the tip of the needle valve 7. This tapered surface 8 needs to withstand the pressing force of the tapered surface 7A provided at the tip of the needle valve 7, so a thin metal plate 11 (metal layer) is fixed thereto.
A nozzle hole 9 is formed perpendicularly to this tapered surface 8. A hole 10 that is wide enough to prevent the fuel spray injected from the nozzle hole 9 from colliding is provided in a portion of the fastening fitting 4 located in front of the nozzle hole 9.

A thin metal plate 11 (metal layer) is bonded to the tapered surface 8 of the nozzle part 3 using a metallized layer, and this metal plate 11 forms a part of the valve seat part of the needle valve 7. . This tapered surface 8 and the valve seat part 2
are formed into continuous surfaces, and both constitute a valve seat portion that contacts the tapered surface 7A at the tip of the needle valve 7.

A positioning part 12 is formed by cutting out a part of the circumferential surface of the nozzle part 3 made of ceramic material in a crescent shape, and a groove part 13 is also provided in the holder part 1.
A key 14 is inserted across the groove portion 13 and the positioning portion 12 to determine the positions of the holder portion 1 and the nozzle portion 3.

Further, a groove 15 is provided between the upper inner surface of the fastening fitting 4 and the outer surface of the holder part 1.
A key 16 is inserted into the key 16 to determine the relative position between the holder portion 1 and the fastening fitting 4.

In this embodiment, as described above, the nozzle holder is divided into the metal holder part 1 and the nozzle part 3 made of ceramic material fixed to the tip thereof, and a thin metal plate 11 (metal layer ) is fixed through a metallized layer, and a valve seat part 2 made of a tapered surface is formed on the inner surface of this metal plate 11, and a tapered surface 7 formed at the tip of the needle valve 7 is formed on this valve seat part 2.
It is characterized in that it is constructed so that A is pressed into contact with it to function as a needle valve. Therefore, with this structure and the fastening fitting 4, the volume from the valve seat portion 2 to the tip of the nozzle hole 9 becomes extremely small, thereby reducing wasted volume that increases hydrocarbons in the exhaust gas. It can be helpful.

In the present invention, since the nozzle portion 3 having the nozzle holes 9 is made of ceramic material as described above, it is highly heat resistant, does not cause oil to seize on the nozzle holes 9, and drains fuel easily.

The nozzle holder is constructed by dividing the part exposed to high temperatures into a metal holder part 1 and the part exposed to high temperatures into a nozzle part 3 made of ceramic material, and connecting the two with a fastening fitting 4. Since the valve seat part 2 is formed by the tapered surface 8 that is continuous with the lower end of the inner surface of the part 1 and the inner surface of the nozzle part 3, it is possible to form the valve seat part of a needle valve in the same way as a metal nozzle holder. .

The needle valve 7 comes into impact contact with the tapered surface 8 of the nozzle part 3, but since the inner surface of the nozzle part 3 is made of a metal plate 11, it has sufficient durability against impact force. .

In other words, since the nozzle portion 3 made of ceramic material is protected by the metal layer, it is possible to eliminate the disadvantage of being easily damaged due to the use of ceramic material, which is a brittle material.

Furthermore, since the nozzle portion 3 is small, even if it is damaged, it can be easily replaced, and the cost required for replacement can be reduced.

As explained above, the fuel injection nozzle for a diesel engine of the present invention includes a needle valve having a tapered tip, a metal holder portion of a nozzle holder that slidably accommodates the needle valve, and a metal holder portion of the nozzle holder that slidably accommodates the needle valve. It has a ceramic nozzle part that is joined to the tip of the ceramic holder part, and a fastening fitting that covers the ceramic nozzle part and tightens and fixes the nozzle part to the metal holder part, and the inner periphery of the nozzle part Since a metal layer is formed on the holder portion and a valve seat portion having the same tapered surface is formed on the inner periphery of the tip of the holder portion and the inner periphery of the nozzle portion, the following effects can be obtained.

That is, the heat resistance is improved by forming the nozzle part with the valve seat made of ceramic material, and the nozzle part is reinforced by making the valve seat a thin metal layer and tightening it from the outside with metal fittings. Durability can be improved by increasing mechanical strength and durability. Therefore, since the valve seat and the nozzle injection outlet can be formed close to each other, waste volume can be reduced, combustion conditions can be improved, and hydrocarbon components in the exhaust gas can be reduced. Furthermore, in the present invention, a ceramic nozzle part is joined to the tip of the metal holder part of the nozzle holder, a metal layer is formed on the inner circumference of the nozzle part, and the inner circumference of the tip of the holder part and the nozzle are bonded. Since the valve seat part having the same tapered surface as the inner periphery of the holder part and the nozzle part can be formed by co-machining, manufacturing is easy. There is a certain effect.

[Brief explanation of the drawing]

The figure is a sectional view showing a main part of a fuel injection nozzle for a diesel engine according to an embodiment of the present invention. 1...Holder part, 2...Valve seat part, 3...Nozzle part, 4, 5...Tightening fitting, 7...Needle valve, 8...Tapered surface, 9...Nozzle hole, 11...Metal thin plate, 1
4, 16...key.

Claims (1)

[Scope of utility model registration request] A needle valve having a tapered tip; a metal holder portion of a nozzle holder that slidably accommodates the needle valve; a ceramic nozzle portion joined to the tip of the metal holder portion; a clamping fitting that covers a ceramic nozzle part and tightens and fixes the nozzle part to the metal holder part; a metal layer is formed on the inner circumference of the nozzle part; A fuel injection nozzle for a diesel engine, characterized in that a valve seat portion having the same tapered surface is formed at the inner peripheral portion of the nozzle portion.