JPH05231267A - Fuel injection nozzle and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a fuel injection nozzle which reduces the generation of smoke and manufacture thereof by setting a ratio between the length of the linear part and the sectional size of a sectional shape to a proper value and increasing penetration. CONSTITUTION:In the injection nozzle 23 of a nozzle tip 22, a ratio L/D between the length L of the linear part in a longitudinal direction of the injection nozzle 23 and the diameter D of a sectional shape is set to a value within a range of 2-4. Further, since a peripheral edge part 17 on the injection nozzle inlet side is formed in a curve shape, penetration of fuel is increased, mixture of fuel and air is promoted, and the generation of smoke is reduced.

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 for injecting fuel into a combustion chamber through injection holes and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a molding method for manufacturing a tip of an injection nozzle or the like using a ceramic material containing ceramic particles, an injection molding method or a wax core is used, and then a wax core is used. A method of elution by heating is known. Further, in order to reduce the resistance of the fuel flow to the inner surface side of the injection hole, R (R: radius of curvature;
Radius of curvature or tapering is generally known (for example, Japanese Utility Model Laid-Open No. 63-156463). Further, it has been reported that, in the suckless type nozzle, the wraparound of the fuel near the nozzle hole induces the turbulence of the spray.

Further, Japanese Utility Model Laid-Open No. 60-49262 discloses a fuel injection valve for a diesel engine. The fuel injection valve for a diesel engine has a needle valve seated on a seat surface formed in the valve body and lifted by fuel oil pressure, and an injection hole formed at a position of the seat surface of the valve body. The edge portion of the opening on the inlet side that opens to the seat surface is cut to form a widened portion.

Further, Japanese Utility Model Laid-Open No. 60-75683 discloses a fuel injection nozzle. The fuel injection nozzle has a plurality of injection holes separated in the circumferential direction and arranged in multiple stages.

[0005]

However, in the fuel injection nozzles disclosed in the above-mentioned publications, in which the inner surface of the injection hole is tapered, an accurate and precise shape is required in order to suppress smoke generation. Not specified. Moreover, when the injection hole of the fuel injection nozzle is formed in a tapered shape on the inner surface of the injection hole, drilling,
With a machining method such as laser machining or electric discharge machining, it is extremely difficult to machine an accurate taper, and the manufacturing cost becomes high, which is not preferable in practice.

Therefore, an object of the present invention is to solve the above-mentioned problems, and the injection hole is formed to have a rectangular or circular cross-sectional shape and a taper is formed on the peripheral edge portion on the injection hole inlet side. By forming the minor diameter or diameter D and the length L of the straight portion in the longitudinal direction of the injection hole into an optimized injection hole shape,
It is an object of the present invention to provide a fuel injection nozzle that increases fuel penetration, promotes mixing of fuel and air, and reduces smoke generation, and a manufacturing method thereof.

[0007]

In order to achieve the above object, the present invention is configured as follows. That is,
The present invention relates to a fuel injection nozzle comprising a nozzle body having a hole through which a fuel flow path and a needle valve are inserted, and a nozzle tip which is integrally formed with the nozzle body and has a nozzle hole formed therein. Relationship between the length L of the straight portion of the injection hole and the minor diameter of the rectangle or the diameter D of the circle, the cross-sectional shape of which is rectangular or circular, and the peripheral edge of the injection hole inlet side is rounded or tapered. Is set to L / D> 2-4.

In this fuel injection nozzle, at least the peripheral portion of the injection hole is made of ceramics.

Alternatively, the present invention comprises a step of adding water and a binder to a ceramic powder and mixing them to prepare a slurry,
The shape after firing forms a radius or taper on the peripheral portion on the inlet side of the injection hole, and the relationship between the length L of the straight portion of the injection hole and the minor diameter of the rectangle or the diameter D of the circle is L / D> 2. A step of arranging the injection hole forming pin having a shape corresponding to the injection hole shape set to 4 to 4 and the silicon rubber member having the outer surface of the radius in the cavity of the casting mold in which the porous mold and the mold are combined. A step of manufacturing the molded body by injecting the slurry into the cavity to solidify by water absorption, a step of extracting the injection hole forming pin from the casting mold, and removing the molded body from the mold, and drying the molded body. The present invention relates to a method for manufacturing a fuel injection nozzle, which includes a step of heating to remove the silicon rubber and manufacturing a fired body in which the shape of the silicon rubber is transferred.

[0010]

The fuel injection nozzle and the method for manufacturing the same according to the present invention are configured as described above and operate as follows. That is, according to the present invention, the cross-sectional shape of the injection hole is formed into a rectangular shape or a circular shape, and the peripheral portion of the injection hole inlet side is formed into a rounded shape or a taper shape, and the length L of the injection hole and the short diameter of the rectangular shape or the circular shape. Since the relationship with the diameter D of L / D> 2-4 was set, the fuel penetration can be increased,
Smoke generation can be reduced by promoting the mixing of fuel and air.

Further, according to the present invention, by simply arranging the injection hole forming pin and the silicon rubber member in the casting mold cavity by the above manufacturing process, the radius R is formed on the peripheral portion of the injection hole inlet side.
Alternatively, a taper can be formed, and the relationship between the length L of the injection hole and the short diameter of the rectangle or the diameter D of the circle can be easily and accurately formed into a shape of L / D> 2-4. Therefore, the manufacturing cost can be reduced, and the practical value can be significantly improved.

[0012]

Embodiments of the fuel injection nozzle and the method for manufacturing the same according to the present invention will be described below with reference to the drawings. Figure 1
FIG. 3 is a sectional view showing a main part of an embodiment of a fuel injection nozzle according to the present invention.

The fuel injection nozzle according to the present invention is for injecting fuel into a combustion chamber, and has a nozzle body 31 having a hole for inserting a fuel flow path and a needle valve, and the nozzle body 3.
1 and the nozzle tip 22, which is integrally formed and has a nozzle hole 23 formed therein. In this fuel injection nozzle, the nozzle body 31 is made of a metal material such as an SCM material, and the nozzle body 31 and the nozzle tip 22 are joined at a joining portion 29. The nozzle tip 22 can be formed as a multi-injection hole consisting of a plurality of injection holes 23, but in this embodiment, only two injection holes 23 are shown for the sake of easy understanding of the description.

The nozzle tip 22 is made of ceramics such as zirconia ZrO _{2 having} high heat resistance and high temperature. The outer surface 26 side of the nozzle tip 22 is a surface exposed to the combustion chamber. As shown in FIG. 2, the injection hole 23 formed in the nozzle tip 22 of the fuel injection nozzle is composed of a straight or straight portion 21 having a rectangular or circular cross section. Further, a radius R or a taper T is formed on the peripheral edge portion 17 of the inner surface 25 of the injection hole 23 on the injection hole inlet side. In this fuel injection nozzle, when the length of the injection hole 23 is L and the length of the short diameter of the rectangular section or the diameter of the circular shape is D, L / D> 2 to 4 is set.

In this fuel injection nozzle, when the fuel supplied from the fuel injection pump is injected through the injection hole 23 by opening the needle valve, the radius R or taper T of the injection hole inlet side peripheral edge portion 17 and the injection hole 23. Due to the above relationship of the length of the straight portion in the longitudinal direction with respect to the diameter of the fuel, the penetration of the fuel is increased, and the mixing of the fuel injected from the injection hole 23 and the air is promoted. Therefore, the mixture of fuel and air becomes good, a good combustion state can be secured, and the generation of smoke can be reduced.

With this fuel injection nozzle, the radius R or taper T of the injection hole inlet side peripheral portion 17 of the injection hole 23 is provided, the thickness of the nozzle tip 22 is 1 mm, and the rectangular dimension 0 as the cross-sectional shape of the injection hole 23. .15 × 0.35 mm, the length L of the linear portion in the longitudinal direction was variously changed, that is, the size of the taper T was changed, and the test results were obtained. In FIG. 2, the horizontal axis represents the relationship L / D between the rectangular minor axis D (0.15 mm) and the length L of the straight portion of the injection hole 23, and the vertical axis represents the penetration (m
m) is shown. In addition, 1 mse after the start of fuel injection
As a result of measuring the penetration of c by the submerged spray method, the values shown in FIG. 2 could be obtained. As can be seen from the graph, when L / D ≧ 2 to 4.5, the penetration can be increased to 60 mm or more. If the fuel penetration is increased, the mixing of the fuel and air can be promoted, and the generation of smoke can be reduced.

Further, with respect to this fuel injection nozzle, the nozzle tip is machined using a drill,
When a nozzle having a circular cross-sectional shape and a diameter D of φ0.24 mm was manufactured and the same test as above was performed, and assuming that the length of the straight portion in the longitudinal direction is L, L / D was 2 to 4. It was confirmed that the range was proper. That is, the penetration value of this fuel injection nozzle was almost the same as the penetration value of the rectangular injection hole.

Next, an embodiment of the method of manufacturing the fuel injection nozzle according to the present invention will be described with reference to FIGS.
FIG. 3 is an explanatory view showing a process of arranging the injection hole forming pin and silicon rubber in the cavity of the ceramic molding apparatus, FIG. 4 is an explanatory view showing a process of injecting the slurry into the cavity, and FIG. FIG. 6 is an explanatory view showing a step of pulling out the pin and the forming pin, FIG. 6 is an explanatory view showing a step of drying and solidifying the inking portion, and FIG. 7 is a ceramic molding apparatus for achieving the method for manufacturing a fuel injection nozzle according to the present invention. It is sectional drawing which shows an example.

As shown in FIG. 7, the ceramics forming apparatus is preferably applied to manufacture a nozzle tip of a fuel injection nozzle used in a diesel engine, for example. In this ceramic forming apparatus, a mold 1 is provided with a slurry injection port, that is, a slurry injection passage 2 and a cavity 3 communicating with the slurry injection passage 2, and a metal-made hole for forming a rectangular shape at the tip. A through hole 4 and a pin insertion hole 18 for detachably attaching the pin insertion / removal rotary jig 6 having the injection hole forming pin 5 which is a pin are formed. The cavity 3 is formed on the lower surface of the mold 1, and the slurry injection passage 2 leads from the upper part of the mold 1 to the cavity 3. The shape of the cavity 3 is the outer shape of the tip of the fuel injection nozzle, that is, the nozzle tip 22. The shape of the injection hole forming pin 5 is formed so as to correspond to the shape of the injection hole 23 formed in the nozzle tip 22, and is formed in a rectangular shape here.

The mold 1 is set on the positioning table 8.
The upper surface 11 of the positioning table 8 is arranged in contact with the lower surface 12 of the mold 1. A hole 13 is formed in the positioning base 8, and a through hole 15 for moving up and down an inner surface forming pin 14 serving as a molding pin and a pin elevating jig 10 to which the inner surface forming pin 14 is attached is formed. ing. The pin raising / lowering jig 10 is provided with an appropriate fixing means such as a screw and the like.
It is detachably fixed to the inner surface forming pin 14 so that the inner surface forming pin 14 can be projected into the cavity 3.

A porous mold 9 made of gypsum or the like is placed in the hole 13 formed in the positioning table 8. This porous type 9
Form the cavity 3 in cooperation with the mold 1 and the inner surface forming pin 14. In other words, a molding die in which a part of the wall surface of the cavity 3 is formed by the porous portion 30 is configured. The porous portion 30 formed of the porous mold 9 absorbs water from the slurry S injected into the cavity 3 from the slurry injecting passage 2 and causes the wall surface of the cavity to be infiltrated.
Has the effect of solidifying. A through hole 16 is formed in the porous mold 9 at a position facing the cavity 3, and the inner surface forming pin 14 can be moved up and down through the through hole 16. The inner surface forming pin 14 can be set in a state in which it can rise in the through hole 16 and project into the cavity 3, and serves as a surface forming the inner surface 25 of the molded body.

The ceramic molding apparatus is constructed as described above, and the molding apparatus can be used to mold the nozzle tip 22 in the fuel injection nozzle according to the present invention. That is, the nozzle tip 22 is manufactured by slip casting, which is one of the ceramic molding methods. A metal part having a cavity 3 partially having a porous portion and having a slurry injection passage 2 communicating with the cavity 3 and a pin insertion hole 18 into which the injection hole forming pin 5 which is a hole forming pin can be inserted. 1 of a ceramic component molding method for molding a ceramic material into a predetermined shape using a mold 1.
Is one.

First, water and a binder are added to zirconia ceramic powder, and the mixture is thoroughly mixed by a ball mill to prepare a slurry S. Furthermore, the injection hole forming pin 5 was formed so that the injection hole 23 had a rectangular cross-sectional shape after firing and a size of 0.15 × 0.35 mm. Also,
Regarding the radius of curvature R of the radius of the injection hole inlet side peripheral portion 17, the silicon having the radius R or the taper T on the outer peripheral surface 24 is formed so that the radius R of the injection hole inlet side peripheral portion 17 or the taper T is formed after firing. The rubber member 20 was used. Next, as shown in FIG. 4, the silicon rubber member 20 is placed in the cavity 3 on the wall surface 27 of the inner surface forming pin 14, and the injection hole forming pin 5 is inserted into the pin insertion hole 18 to form the injection hole. The silicon rubber member 20 is attached to the tip 19 of the working pin 5. At this time, the injection hole forming pin 5 was set in the cavity 3 so that the injection hole 23 had a long side formed from the upstream side 28 of the fuel flow toward the nozzle tip 21.

Then, as shown in FIG.
The injection hole forming pin 5 and the tapered silicon rubber member 2 are provided therein.
Slurry S is injected into the cavity 3 through the slurry injection passage 2 in a state where 0 and 0 are arranged. When the slurry S is injected into the cavity 3, the slurry S infiltrates into the cavity 3 excluding the silicon rubber member 20 and the injection hole forming pin 5 while maintaining the shape of the silicon rubber member 20, and there, The water content of the slurry S is absorbed by the porous portion 30 of the porous mold 9, and the slurry S contains the wall surface 27 of the cavity 3.
And is solidified to form the incarnation portion 7. The inlaid portion 7 is not present in the portion where the silicon rubber member 20 and the injection hole forming pin 5 are present. The inlaid portion 7 has a tapered surface of the silicon rubber member 20 and a cross section of the injection hole forming pin 5. The shape of the straight peripheral surface having a rectangular shape, that is, the shape of the straight portion 21 is transferred.

Therefore, in the state where the shape retaining property is developed in the inlaid portion 7, as shown in FIG. 5, the injection hole forming pin 5 is extracted from the inlaid portion 7 and the injected portion 7 has a straight injection hole. 23 is formed. Further, the forming pin 14 is pulled out from the inlaid portion 7, but at this time, the silicon rubber member 20 is in a state of being attached to the inlaid portion 7. With the solidified state of the inking part 7 further advanced,
As shown in FIG. 6, the inlaid portion 7 is taken out from the mold 1 and the porous die 9, and the inlaid portion 7 is sufficiently dried and degreased. The dried inlaid portion 7 was put into a firing furnace and heated to heat and remove, or burn, the silicon rubber member 20, and the inlaid portion 7 was fired to obtain a fired body. This fired body constitutes the nozzle tip 22 shown in FIG.

Several types of nozzle tips 22 were produced in which the ratio of the length L of the straight portion in the longitudinal direction of the injection hole 23 to the length D of the minor axis of the rectangular section, that is, L / D was changed. Then, the joint portion 29 on the end face of the nozzle tip 22 was joined to the nozzle body 31 made of SCM material by using a solder material to complete the fuel injection nozzle.

[0027]

The fuel injection nozzle and the method for manufacturing the same according to the present invention are configured as described above and have the following effects. That is, according to the present invention, the cross-sectional shape of the straight portion of the injection hole is formed in a rectangular shape or a circular shape, and the peripheral portion of the injection hole inlet side is formed in a rounded shape or a tapered shape, and the length L of the straight portion of the injection hole and the rectangular shape. Can be increased by setting L / D> 2 to 4 to the relationship with the minor diameter of the circle or the diameter D of the circle, and the mixture of fuel injected from the injection hole and air can be increased. Is promoted, combustion is performed well, and smoke generation can be reduced.

Furthermore, since at least the peripheral portion of the injection hole is made of ceramics, the injection hole can be formed into a desired shape with a degree of freedom by molding. Further, ceramics have high heat resistance, and can sufficiently maintain durability and strength even when exposed to high temperatures in the combustion chamber.

Further, the manufacturing method of this fuel injection nozzle is as follows.
In the cavity of the casting mold that combines the plaster mold and the mold,
The injection hole forming pin and the silicon rubber member having a shape corresponding to the shape of the injection hole inlet side peripheral portion attached to the tip of the injection hole forming pin are arranged, and the slurry is injected into the cavity to be solidified by absorbing water and molded. A body was manufactured, the injection hole forming pin was pulled out from the casting mold, the molded body was demolded and dried, the molded body was baked, and the silicon rubber was removed by heating. Therefore, the shape of the silicon rubber was baked. Can be easily and accurately transferred. That is, it is possible to form a complicated extremely small shape with high precision by molding ceramics, and moreover, the corner of the cross-sectional shape of the injection hole can be formed into a sharp rectangle, which can reduce the manufacturing cost and have a large practical effect.

[Brief description of drawings]

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

FIG. 2 is a graph showing penetration with respect to a ratio of a length of a straight portion in a longitudinal direction of a nozzle hole and a minor axis of a rectangle or a diameter of a circle.

FIG. 3 is an explanatory view showing a step of disposing the injection hole forming pin and the silicon rubber in the ceramic molding device in the method for manufacturing the fuel injection nozzle.

FIG. 4 is an explanatory view showing a step of injecting a slurry into a cavity in the method for manufacturing a fuel injection nozzle.

FIG. 5 is an explanatory view showing a step of extracting the injection hole forming pin and the forming pin from the cavity in the method for manufacturing the fuel injection nozzle.

FIG. 6 is an explanatory view showing a step of drying and solidifying the inlaid portion in the method for manufacturing a fuel injection nozzle.

FIG. 7 is a cross-sectional view showing an example of a ceramic molding apparatus for achieving the method for manufacturing a fuel injection nozzle according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Slurry injection passageway 3 Cavity 5 Injection hole forming pin 7 Inking part 9 Porous type (gypsum type) 14 Inner surface forming pin 17 Injection hole inlet side peripheral edge 20 Silicon rubber member 21 Straight part 22 Nozzle tip 23 injection hole 29 joint 31 nozzle body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keio Sekiyama 8 Tsutana, Fujisawa City Kanagawa Prefecture Isuzu Ceramics Research Institute Co., Ltd. (72) Inventor Masahiro Kyuoka 8th Tsutanaka Fujisawa City Kanagawa Prefecture Isuzu Co., Ltd. Ceramics laboratory

Claims (3)

[Claims] 1. A fuel injection nozzle comprising a nozzle body having a hole into which a fuel flow path and a needle valve are inserted, and a nozzle tip which is integrally formed with the nozzle body and has a nozzle hole formed therein. Of the straight line portion is formed in a rectangular shape or a circular shape, and the injection hole inlet side peripheral portion is formed in a rounded shape or a tapered shape, and the length L of the straight line portion of the injection hole and the short diameter of the rectangle or the diameter of the circular shape. A fuel injection nozzle having a relationship with D set to L / D> 2-4. 2. The fuel injection nozzle according to claim 1, wherein at least a peripheral portion of the injection hole is made of ceramics. 3. A step of making a slurry by adding water and a binder to the ceramic powder and mixing them, and the shape after firing forms a rounded or tapered shape on the peripheral portion of the injection hole inlet side, and the length of the straight portion of the injection hole. A silicone rubber having a nozzle hole forming pin having a shape corresponding to the nozzle hole shape in which L and the rectangular minor diameter or the circular diameter D are set to L / D> 2 to 4 and the outer surface of the radius. A step of arranging the member in a cavity of a casting mold which is a combination of a porous mold and a mold; a step of injecting the slurry into the cavity to solidify by water absorption to produce a molded body; Fuel having a step of removing the hole forming pin and demolding and drying the molded body, and a step of heating the molded body to remove the silicon rubber and producing a fired body in which the shape of the silicon rubber is transferred. Of injection nozzle Production method.