JPH08247002A - Fuel injection nozzle - Google Patents

Abstract

PURPOSE: To secure the desired fuel flow in a unit time and reduce the capacity of a sack hole at the same time. CONSTITUTION: A protruded conical coupling section 16 is provided at the bottom section of the sack hole 13 of a hole type fuel injection nozzle 1 formed with multiple nozzle holes 15 at the round top section 14 of the tip of a nozzle body 5, and a recessed conical coupled section 26 to be coupled with the coupling section 16 at a prescribed clearance is provided at the tip of a needle 6 slidably stored in the inner hole 11 of the nozzle body 5. When the needle 6 is lifted from the truncated cone seat section 12 of the nozzle body 5, the flow of the fuel flowing from the truncated cone seat section 12 to multiple nozzle holes 15 via the sack hole 13 is made smooth. When the needle 6 is seated on the truncated cone seat section 12 of the nozzle body 5, the coupling section 16 and the coupled section 26 are brought nearby, and the capacity of the sack hole 13 can be 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 attached to an internal combustion engine for injecting fuel into a combustion chamber of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection nozzle of a direct injection type diesel engine, as shown in FIGS.
The Hall-type fuel injection nozzle 100 has been used in which one or more injection holes 103 are provided in the nozzle 2 and the spray can be dispersed in a wide range by directing the spray in a direction suitable for the combustion chamber. A suck hole 104 is formed in the circular top portion 102 of the hole-type fuel injection nozzle 100. Further, in the hole-type fuel injection nozzle 100, when the needle 105 is lifted from the seat portion 106 during fuel injection, the fuel passage 1 from the seat portion 106 to the injection hole 103 via the suck hole 104 is provided.
07 is formed.

[0003]

However, in the case of this hole type fuel injection nozzle 100, the fuel in the suck hole 104 may leak into the combustion chamber through the injection hole 103 after the injection is completed. The fact that the fuel leaked from the suck hole 104 is discharged as an unburned component is one of the factors that generate the soluble organic component (hereinafter referred to as SOF) contained in the particulates present in the exhaust gas. The Hall-type fuel injection nozzle 1 is used to reduce the SOF.
It is known that it is very effective to reduce the volume of the 00 suck hole 104 (hereinafter referred to as suck volume).

Therefore, for example, Japanese Patent Laid-Open No. 1-177449.
Japanese Patent Laid-Open No. 3-294655 and Japanese Patent Laid-Open No. 3-294655 disclose a technique for reducing the suck volume by providing a protrusion at the tip of the needle toward the bottom of the suck hole. However, although these techniques are effective in reducing the suck volume, the protrusion of the tip of the needle narrows the fuel passage from the seat portion through the suck hole to the injection hole, and the fuel flow rate per unit time is reduced. Therefore, there is a problem that a desired fuel flow rate per unit time cannot be secured.

An object of the present invention was made in view of the above circumstances, and it is an object of the present invention to provide a fuel injection nozzle capable of reducing the suck volume while ensuring a desired fuel flow rate per unit time. .

[0006]

According to a first aspect of the present invention, there is provided a reciprocating needle, a seat portion on which the needle is seated, an injection hole for injecting fuel, and a space between the seat portion and the injection hole. A nozzle body having a suck hole formed in the seat portion, and when the needle is lifted from the seat portion, the needle portion and the nozzle body reach the nozzle hole from the seat portion through the suck hole. A fuel injection nozzle in which a fuel passage is formed,
The sack hole, while facing the tip of the needle, has a convex fitting portion protruding toward the tip side of the needle, the needle, when seated on the seat portion,
A technical means having a concave fitting portion that is fitted to the fitting portion is adopted.

According to a second aspect of the present invention, in addition to the fuel injection nozzle according to the first aspect, the fitting portion is formed in a convex conical shape so as to extend along a direction in which the injection hole is formed. The fitted portion is formed in a concave conical shape so as to follow the shape of the fitting portion.

[0008]

According to the invention described in claim 1, when the needle is lifted from the seat portion of the nozzle body, the fuel is provided between the convex fitting portion of the suck hole and the concave fitting portion of the needle. Clearance is formed that does not interfere with the flow of Therefore, the fuel smoothly flows in the fuel passage, so that a desired fuel flow rate per unit time can be obtained. Also,
When the needle sits on the seat of the nozzle body,
Since the convex fitting portion of the sack hole and the concave fitting portion of the needle are fitted together, the volume of the sack hole is reduced.

According to the second aspect of the present invention, since the fitting portion of the suck hole is formed in a convex conical shape along the injection hole forming direction, when the needle is lifted from the seat portion, Fuel smoothly flows from the fitting part of the suck hole to the injection hole.

[0010]

【Example】

[Structure of Embodiment] Next, a fuel injection nozzle of the present invention will be described based on an embodiment shown in the drawings. 1 to 3 are cross-sectional views showing the tip of the Hall-type fuel injection nozzle.
The other parts of the hole-type fuel injection nozzle have a well-known structure, and therefore illustration and description thereof will be omitted.

The Hall-type fuel injection nozzle 1 is attached to each cylinder head 2 of a direct injection type diesel engine, and the fuel pressurized to a high pressure by a fuel injection pump (not shown) can be better ignited and burned. The combustion chamber 4 formed between the cylinder head 2 and the piston 3.
It is a fuel injection nozzle for an internal combustion engine that sprays inside. The Hall-type fuel injection nozzle 1 includes a nozzle body 5 and a needle 6 slidably accommodated in the nozzle body 5.

The nozzle body 5 is formed in a substantially cylindrical shape. A nozzle holder (not shown) is connected to the rear end of the nozzle body 5 by using a retaining nut (not shown) or the like. Inside the nozzle body 5, an inner hole 11 bored in the axial direction of the nozzle body 5 and a truncated cone seat portion 12 formed so as to be connected to the tip of the inner hole 11 are formed.
And the sack hole 1 communicating with the truncated cone seat portion 12
3 and 3 are provided. The inner hole 11, the truncated cone seat portion 12 and the suck hole 13 are substantially coaxial.

Two to four injection holes 15 are alternately bored on the same circumference in the hemispherical circular top portion 14 in which the suck hole 13 is formed. The plurality of injection holes 15 are injection passages (opening diameters of, for example, φ0.2 to φ0.3) for spraying fuel into the combustion chamber 4 of the diesel engine. On the inner wall side of the circular top portion 14, that is, on the bottom portion of the suck hole 13, a convex conical fitting portion 16 that fits with the needle 6 is formed. The conical inner wall surface of the fitting portion 16 is formed so as to be in the same direction as the formation direction of the plurality of injection holes 15, and is flush with the bottom portions of the plurality of injection holes 15. Has been done.

On the other hand, the needle 6 is formed in a substantially round bar shape, and is constantly urged in the direction of closing the plurality of injection holes 15 by a coil spring (urging means) (not shown) housed in the nozzle holder. The needle 6 includes a columnar shaft portion 21 and a substantially conical tip portion 22, and reciprocates while maintaining a predetermined clearance (nozzle chamber) 23 between the inner hole 11 of the nozzle body 5 and the shaft portion 21. It is movably housed. Although not shown, the rear end of the needle 6 is slidably held in the nozzle body 5.

As is well known, the clearance 23 is a passage for passing fuel supplied through a route (not shown). Further, when the tip end portion 22 is detached (lifted) from the truncated cone seat portion 12, the needle 6 has a fuel passage (for example, a clearance) from the truncated cone seat portion 12 to the plurality of injection holes 15 through the suck hole 13. 0.25 mm
.About.0.30 mm) 24 is formed. On the outer periphery of the tip portion 22 of the needle 6, the truncated cone seat portion 12 of the nozzle body 5 is provided.
A conical seat portion 25 that is seated on is formed.

The conical seat portion 25 constitutes a valve seat together with the truncated cone seat portion 12 of the nozzle body 5, and the conical seat portion 2
5 and the truncated cone seat portion 12 can be liquid-tightly contacted (seated) to shut off the fuel passage 24. Further, the conical seat portion 25 is moved by the movement (lift) of the needle 6 in the valve opening direction.
Is removed from the truncated cone seat portion 12, the fuel passage 2
4 is in an open state, and the fuel supplied from the clearance 23 side is passed to the plurality of injection holes 15 side.

At the most tip of the tip portion 22 of the needle 6,
A fitted portion 26 that fits into the fitting portion 16 in a state of facing the fitting portion 16 of the sack hole 13 with a predetermined clearance is formed. The fitted portion 26 has a concave conical shape so as not to interfere with the fitting portion 16 when the conical seat portion 25 of the needle 6 is seated on the truncated cone seat portion 12. As shown in FIG. 2, the clearance is set in consideration of the amount of reduction due to wear of the truncated cone seat portion 12 of the nozzle body 5 and the conical seat portion 25 of the needle 6.

[Operation of Embodiment] Next, the operation of the Hall-type fuel injection nozzle 1 of this embodiment will be briefly described with reference to FIGS. 1 to 3.

When the fuel is pumped into the nozzle body 5 from the fuel injection pump, the chamber pressure in the clearance 23 rises.
When the chamber pressure in the clearance 23 becomes higher than the set load (valve opening pressure) of the coil spring, the truncated cone seat portion 12 of the needle 6 moves from the truncated cone seat portion 12 of the nozzle body 5 to the side where the plurality of injection holes 15 are opened. (Lift) and fuel passage 2
Open 4 (see Figure 1). As a result, the fuel in the clearance 23 passes through the fuel passage 24 and the plurality of injection holes 1
Inflow to 5. Then, fuel is injected in the form of mist from the outlets of the plurality of injection holes 15 into the combustion chamber 4 to perform fuel injection.

During such fuel injection, the flow of fuel from the frustoconical seat portion 12 through the suck holes 13 to the inlets of the plurality of injection holes 15 is as shown by arrows in FIG. It is the same as the Hall-type fuel injection valve 100 (see FIG. 5), and the fuel flow rate per unit time is also the same as the conventional one.

When the supply of fuel into the nozzle body 5 is cut off and the chamber pressure in the clearance 23 becomes lower than the set load (valve closing pressure) of the coil spring, the needle 6 closes the plurality of injection holes 15. To descend. Then, the truncated cone seat portion 12 of the needle 6 is seated on the truncated cone seat portion 12 of the nozzle body 5, whereby the fuel passage 24 is closed. Therefore, at the end of injection, as shown in FIG. 2, the volume of the suck hole 13 can be significantly reduced as compared with the conventional Hall-type fuel injection valve 100.

[Effects of the Embodiment] As described above, in the Hall-type fuel injection nozzle 1, since the fitted portion 26 at the tip of the needle 6 does not interfere with the smooth passage of fuel during fuel injection, the desired unit time Since the fuel flow rate per hit can be secured, it is possible to prevent the output of the diesel engine from decreasing.

At the end of injection, the fitted portion 26 of the needle 6 and the fitting portion 16 at the bottom of the sack hole 13 approach each other with a predetermined clearance so as to face each other, whereby the volume of the sack hole 13 is increased. Can be reduced. Therefore, it is possible to prevent the fuel in the suck hole 13 from leaking into the combustion chamber 4 of the diesel engine through the plurality of injection holes 15 after the injection is completed. Therefore, it is possible to suppress the generation of SOF contained in the particulates existing in the exhaust gas generated by the operation of the diesel engine.

[Modification] In this embodiment, the opening shape of the plurality of injection holes 15 is circular, but the opening shape of the plurality of injection holes 15 may be polygonal, elliptical, or elliptical. . Further, the number of injection holes 15 may be any number as long as it is 1 or more. A step may be provided between the injection hole 15 and the fitting portion 16.

[0025]

According to the first aspect of the present invention, since a desired fuel flow rate per unit time can be obtained at the time of fuel injection, it is possible to suppress the output reduction of the internal combustion engine. Further, since the volume of the suck hole can be reduced at the end of injection, it is possible to prevent the fuel in the suck hole from leaking into the internal combustion engine through the injection hole after the end of injection. In the invention according to claim 2, the fuel smoothly flows from the suck hole to the injection hole, so that a desired fuel flow rate per unit time can be secured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a tip portion of a Hall-type fuel injection nozzle during fuel injection (Example).

FIG. 2 is a cross-sectional view showing the tip of the Hall-type fuel injection nozzle at the end of injection (example).

FIG. 3 is a cross-sectional view showing how the fuel flows at the time of fuel injection (Example).

FIG. 4 is a sectional view showing a tip portion of a Hall-type fuel injection nozzle during fuel injection (prior art).

FIG. 5 is a cross-sectional view showing the flow of fuel during fuel injection (prior art).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hall type fuel injection nozzle 5 Nozzle body 6 Needle 12 Frustum seat part 13 Suck hole 15 Injection hole 16 Fitting part 24 Fuel passage 26 Fitting part

Claims (2)

[Claims] 1. A reciprocating needle, a seat portion on which the needle is seated, a nozzle hole for injecting fuel, and a nozzle body having a suck hole formed between the seat portion and the nozzle hole. A fuel injection nozzle in which, when the needle is lifted from the seat portion, a fuel passage extending from the seat portion to the injection hole through the suck hole is formed between the needle and the nozzle body, The sack hole has a convex fitting portion that faces the tip of the needle and projects toward the tip of the needle, and the needle fits into the fitting portion when seated on the seat portion. A fuel injection nozzle having a recessed fitted portion to be fitted. 2. The fuel injection nozzle according to claim 1, wherein the fitting portion is formed in a convex conical shape along the forming direction of the injection hole, and the fitted portion is the fitting portion. A fuel injection nozzle, wherein the fuel injection nozzle is formed in a concave conical shape so as to follow the shape of the portion.