JPH11159420A - Fuel injection nozzle and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance fuel injection efficiency, and to easily manufacture a fuel injection nozzle by joining a nozzle tip member composed of an injection molding sintered body and a cylindrical nozzle body to introduce fuel to the nozzle tip member. SOLUTION: A fuel injection nozzle has a structure joined to a nozzle body being another member by forming a nozzle tip member 1 of an injection molding sintered body. In the tip member 1 of the fuel injection nozzle, an injection front chamber 4 to form an injection hole 3 becomes a valve seat. The tip member 1 is a part to control injection by abutting/separating a needle 5 to control injection. A reason of adopting an injection molding method for a nozzle tip part is that a cross section of a hole of the injection hole 3 can be made microscopic by exceeding a limit in machine work. Thus, fuel injection efficiency can be enhanced by the adoption of a joining structure and the adoption of the injection molding method.

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 for a direct injection diesel engine or a gasoline engine, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, a system called a direct injection type for the purpose of improving the combustion efficiency of a diesel engine or a gasoline engine has been put to practical use and has attracted attention. This direct injection type engine does not mix fuel and air in advance and feeds the mixture into the combustion chamber as in the prior art, but directly injects fuel into the combustion chamber.

[0003] The fuel injection nozzle, which is the main component of such a direct injection type engine, has a fine injection hole formed at the tip, and forms a predetermined air-fuel mixture by blowing out the fuel at a high pressure. In particular, setting of the shape, arrangement position, and number of the injection holes at the tip of the nozzle is important, and various ideas have been devised.

[0004]

As described above, the shapes of the holes formed in the fuel injection nozzle are various, and high-precision machining is required. As means for further increasing the fuel injection efficiency, there are fine holes and irregular shapes or multiple arrangements of the injection holes, but when forming the injection holes by drilling or the like at the tip of the nozzle which is a minute component, the cross-sectional area is 2. The limit was a circular hole of about 0.3 × 10 minus square mm 2. In addition, since the injection hole is communicated with the space serving as the pre-injection chamber, processing from the inside of the nozzle is substantially difficult, and processing from the outside is performed. Due to the generated burrs, a difference occurs in the pressure loss of each injection hole, and normal fuel injection may not be performed.

An object of the present invention is to provide a fuel injection nozzle which can increase the fuel injection efficiency and is easy to manufacture, and a method for manufacturing the same.

[0006]

SUMMARY OF THE INVENTION The present inventor has studied the application of the injection molding method and the manufacturability since the degree of freedom of the shape of the injection hole of the fuel injection nozzle and the need for a finer diameter are required. As a result, it has been found that the above object can be achieved by applying an injection molding method to a nozzle tip having an injection hole for ejecting fuel at a high pressure and joining it to a nozzle body which is a separate member.

That is, according to the present invention, there is provided a nozzle tip member made of an injection-molded sintered body provided with one or more injection holes in a pre-injection chamber, which is substantially a sintered surface, Is a fuel injection nozzle that is joined to a cylindrical nozzle body that guides the fuel injection.

Further, in the manufacturing method of the present invention for manufacturing the fuel injection nozzle, a kneaded body of an organic binder and a metal powder is injection-molded in a shape of a nozzle tip having one or a plurality of injection holes provided in a pre-injection chamber. Then, a kneaded body of an organic binder and a metal powder is injection-molded so as to be in contact with the tip body to form a cylindrical body part body, and the tip body and the body are formed. This is a manufacturing method in which the nozzle molded body integrated with the partial molded body is degreased and then sintered.

In another manufacturing method, a kneaded body of an organic binder and a metal powder is injection-molded in a shape of a nozzle tip provided with one or a plurality of injection holes in a pre-injection chamber to form a tip molded body. This is a manufacturing method in which after obtaining, degreasing and sintering to form a nozzle tip member, and then joining the nozzle body made of a molten product which has been previously processed into a cylindrical shape.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION One of the biggest features of the fuel injection nozzle of the present invention is that the nozzle tip member is an injection molded sintered body,
That is, it has a structure joined to a nozzle body which is a separate member. Tip member 1 of fuel injection nozzle applied to the present invention
As shown in FIG. 1 to FIG. 3, a pre-injection chamber 4 in which an injection hole 3 is formed serves as a valve seat, and a part for controlling injection by performing contact and separation of a needle 5 for controlling injection. It is. As shown in FIGS. 1 to 3, the formation of the pre-injection chamber, the formation of the injection holes, and the valve seat surface have a complicated shape, as well as abrasion resistance to needles, cavitation resistance to high-pressure jetted fuel, or corrosion resistance. Is required.

On the other hand, the nozzle body 2 connected to the nozzle tip member 1 may form a cylindrical space in which fuel can be guided and a drive system such as a needle can be installed. There is no requirement for abrasion resistance or the like. The present inventors first attempted to manufacture a fuel injection nozzle by integral molding by an injection molding method.

[0012] Integrally forming the nozzle tip having a complicated shape and the nozzle body having a simple shape larger than that of the nozzle tip member by injection molding requires a flow during molding to uniformly fill the entire body. Considering the difficulty of control design,
The present invention has a joint structure. Also,
Since the portion requiring the above-mentioned abrasion resistance and the like is limited to the nozzle tip portion, it is not necessary to apply an expensive material to the nozzle body, and the joining structure allows a combination of different materials. .

The reason for adopting the injection molding method at the tip of the nozzle in the present invention is as follows. First, it is possible to reduce the cross section of the injection hole beyond the limit in machining. For example, as shown in FIG. 4, in injection molding, a mold 10 having an outer surface shape at the nozzle tip and a core pin 11 representing an inner surface shape at the nozzle tip are arranged, and a slide pin 12 provided on the mold 10 is further provided. By performing injection molding while moving and abutting the core pin 11,
A nozzle tip member can be formed.

As described above, the method of using the slide pin 12 only needs to have a rigidity enough to withstand the pressure at the time of injection molding, and a small-diameter injection hole can be formed by using a small-diameter slide pin. Further, in the injection molding method, the injection holes formed in the state of the molded body with the metal powder and the organic binder can be contracted at the time of degreasing and sintering so that the injection holes have a smaller cross section.

According to the study of the present inventors, it was possible to form an injection hole having a cross section of not more than 2 × 10 minus square mm by this method. In the present invention, the one or more injection holes which are substantially sintered surfaces are not holes formed by machining after sintering, but holes formed as a sintered body. It means that. Although the above-described molding of the injection hole with the slide pin is most desirable in terms of removing the generation of burrs,
In order to obtain the effect of opening a hole having a small diameter due to shrinkage during sintering, a hole may be formed by machining in a state of a molded body which is easily processed, and the hole may be sintered and shrunk. In the present invention, electrolytic polishing, ultrasonic deburring, or the like may be applied to the injection hole as a post-treatment of the sintered body as a surface treatment that is usually performed. Of course, only cleaning such as ultrasonic cleaning may be used.

Another reason is that the shape of the injection hole can be easily changed. According to the above-described method using the slide pin 12, as long as the cross-sectional shape of the slide pin is changed, the shape of the irregular cross section can be easily manufactured. As the irregular cross section, for example, a cross shape, a slit shape, an ellipse, a rectangle, a star shape, and the like can be used. In addition, as shown in FIG. 4, a counterbore shape can be formed outside the injection hole depending on the shape of the slide pin 12. Of course, it is not necessary to form the slide pins in a simple radial direction, and it is possible to design the slide pins in accordance with the required fuel ejection direction and shape.

The use of a slide pin also has the advantage that meandering and burrs due to drilling or the like can be easily prevented. The occurrence of meandering or burrs is not preferable because it causes a difference in the pressure loss of each injection hole and makes normal injection of fuel impossible. The application of the injection molding method, which can use molding by a pin, can significantly reduce the occurrence of meandering and burrs as compared with the formation of holes by machining.

In the present invention, the material of the nozzle tip member is not particularly specified. However, when abrasion resistance and erosion resistance are particularly required, it is desirable to use SUS440C or the like. Normally, chromium molybdenum steel or nickel chromium molybdenum steel (SCM / SNCM class) is used, and quenched or carburized and quenched. Further, it is better that the density is as high as possible, and it is desirable that the sintered density be 95% or more.

The nozzle body can be manufactured from an injection-molded sintered body, or a molten product can be used. The nozzle tip member and the nozzle body are manufactured as separate members in advance, and when joining them, use diffusion bonding, welding, a method using a brazing material, a friction joining method, a shrink fitting method, and a combination thereof. Can be.

When the nozzle body is made of an injection-molded sintered body, it can be joined after being sintered as a separate member in advance as described above. It is preferable to perform degreasing and sintering after forming a molded body, since metallurgically reliable joining is possible.

In this case, a tip molded body obtained by injection molding an organic binder having a nozzle tip shape provided with one or a plurality of injection holes in a pre-ejection chamber and metal powder is manufactured, and then another metal is formed. A tip molded body is set in a mold, and an organic binder and metal powder are injection-molded so as to be in contact with the tip molded body to form a cylindrical body molded body. It is possible to

Also, the cylindrical nozzle body can be formed by machining a molten product, and can be manufactured at low cost if the joining property with the tip member does not matter. The material of the nozzle body is chrome molybdenum steel, nickel chrome molybdenum steel (SCM / S
NCM class) or stainless steel can be used.

[0023]

Embodiments of the present invention will be described below. (Example 1) 42 vol% of organic piner is kneaded with 58 vol% of SUS440C water atomized powder having an average particle diameter of 9 µm, and a tip molded body having a shape shown in Fig. 2 is formed using an injection mold shown in Fig. 4. Was injection molded. In the mold shown in FIG. 4, a mold 13 having an outer shape at the nozzle tip and a core pin 11 showing an inner shape at the nozzle tip are arranged to obtain a cavity 13 shape. Slide pin 1 provided on mold 10
2 is moved to contact the core pin 11 with the inlet 14.
Inject more. The conditions are molding temperature 165 ° C, molding pressure 4
0 to 80 MPa. An injection hole having a shape is formed by the slide pin 12. Extrusion pin 15 after molding
The molded product was released from the mold to obtain a tip molded product.

The tip compact is held at 500 ° C. for 2 hours, followed by degreasing at 1000 ° C. for 1 hour and 1250 ° C.
Sintering at 4 ° C. for 4 hours, tempering in a quenching nitrogen atmosphere, ultrasonic cleaning, and a hardness of 52 HRC.
Was obtained. In this embodiment, the diameter is 0.15
Six injection holes 3 which are substantially sintered skin with a counterbore having an opening angle of 120 degrees on the outlet side with a circular cross section of mm were formed. The sintered density was 97.2% according to the Archimedes method.

The obtained nozzle tip member is provided with S shown in FIG.
A nozzle body obtained by machining a molten product made of CM435 was subjected to electron beam welding to obtain a fuel injection nozzle shown in FIG. 10M for 5 prototype fuel injection nozzles
When a gasoline spray test was conducted at a pressure of Pa, no significant difference was observed in the spray angle and gasoline flow rate obtained in 6 holes, and good results were obtained.

Example 2 SCM43 having an average particle size of 9 μm
5 was kneaded with 58% by volume of water atomized powder and 42% by volume of an organic pinner, and the same injection-molding mold as in Example 1 was used as shown in FIG. did. The obtained tip molded body 16 is placed in the mold 10 having the core pin 11 shown in FIG. 5, and the water atomized powder 57 of SCM435 having an average particle diameter of 9 μm is injected from the injection port 14.
A kneaded body of 43% by volume of the organic piner was injected into the cavity 17 serving as a nozzle body to obtain a composite molded body.

As shown in FIG. 5, the cavity 17 serving as the nozzle body is arranged so as to partially cover the outer peripheral surface of the front end molded body, thereby increasing the joining area and adopting a structure which can easily withstand the internal pressure. I have. Further, the amount of the organic binder is increased in the cavity serving as the nozzle body. This is for increasing the shrinkage rate of the body part molded body more than the contraction rate of the nozzle tip molded body at the time of sintering. In the composite nozzle molded body shape shown in FIG.

The obtained composite molded body is degreased by keeping it at 500 ° C. for 2 hours, and subsequently at 1000 ° C. for 1 hour and 125 ° C.
Sintering at 0 ° C. for 4 hours was performed, followed by quenching, tempering in a nitrogen atmosphere, and ultrasonic cleaning to obtain a fuel injection nozzle having a hardness of 38 HRC. In the present embodiment, six injection holes 3 which are substantially sintered skin with a counterbore having a circular cross section of a diameter of 0.15 mm and an opening angle of 120 ° on the outlet side are formed in the same manner as in the first embodiment. The sintered density is 9 according to the Archimedes method.
6.7%. For the five prototype fuel injection nozzles, there were no significant differences in the spray angles and gasoline flow rates obtained with six holes, and good results were obtained.

[0029]

According to the present invention, it is possible to provide a fuel injection nozzle having an injection hole having a small diameter capable of increasing the fuel injection efficiency by employing the joining structure and the injection molding method. As such, it has great industrial value as a direct injection nozzle for diesel engines and gasoline engines in the future.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a fuel injection nozzle of the present invention.

FIG. 2 is a diagram showing an example of a shape of a nozzle tip member used for a fuel injection nozzle of the present invention.

FIG. 3 is a view showing an example of a shape of a nozzle body used for the fuel injection nozzle of the present invention.

FIG. 4 is a view showing an example of an injection mold used for manufacturing the fuel injection nozzle of the present invention.

FIG. 5 is a diagram showing an example of an injection molding die used when performing composite molding of the fuel injection nozzle of the present invention.

[Explanation of symbols]

1 nozzle tip member, 2 nozzle body, 3 injection holes,
4 Pre-injection chamber, 5 needle, 10 mold, 11 core pin, 12 slide pin, 13 cavity, 14
Injection port, 15 Extrusion pin, 16 Tip molded body, 17
cavity

Claims (5)

[Claims] 1. A nozzle tip member made of an injection-molded sintered body provided in a pre-injection chamber with one or a plurality of injection holes which remain substantially sintered, and a cylinder for guiding fuel to the nozzle tip member. A fuel injection nozzle characterized by being joined to a nozzle body in a shape of a circle. 2. The fuel injection nozzle according to claim 1, wherein the nozzle body is an injection-molded sintered body. 3. The fuel injection nozzle according to claim 1, wherein the nozzle body is a molten product. 4. A molded body of an organic binder and a metal powder is injection-molded into a shape of a nozzle tip provided with one or a plurality of injection holes in a pre-injection chamber to obtain a tip molded body. The kneaded body of the metal powder is injection-molded so as to be in contact with the tip molded body to form a cylindrical body molded body, and the nozzle molded body in which the tip molded body and the body molded body are integrated is degreased. And then sintering the fuel injection nozzle. 5. A molded body of an organic binder and metal powder is injection-molded into a shape of a nozzle tip provided with one or a plurality of injection holes in a pre-ejection chamber to obtain a tip molded body, which is then degreased and fired. A method for manufacturing a fuel injection nozzle, comprising: joining a nozzle tip member to a nozzle body;