JPH03264767A - Fuel injector - Google Patents

Abstract

PURPOSE:To make it possible to promptly draw out fuel by forming a negative pressure generating part, for generating a negative pressure during injection of fuel, between a nozzle plate, secured to the point end face of an injection nozzle and provided with a plurality of injection holes, and a protector mounted for protecting this nozzle plate. CONSTITUTION:In a fuel injector, a nozzle plate 21 of almost disk shape, provided in its central part with a plurality of injection holes 21A connected to an injection port 6B is secured to the lower end face 6D of an injection nozzle 6 in which a needle valve 9, opened and closed by actuation of an electromagnetic actuator, is fitted. A protector 22 for protecting this nozzle plate 21 is mounted. Here, a tapered part 22B serving as a negative pressure generating part, whose diameter is gradually reduced downward from an end face 22A, is formed on the internal peripheral side of the protector 22. In this way, when fuel is injected from the injection hole 21A, the fuel is drawn outward by generating a negative pressure between the protector 22 and the nozzle plate 21.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a fuel injector suitable for use in an electronically controlled fuel injection device such as an automobile engine, and in particular, the present invention relates to a fuel injector suitable for use in an electronically controlled fuel injection device such as an automobile engine. This invention relates to a fuel injector that can prevent fuel from remaining in the fuel injector.

[Prior Art] A fuel injector according to the prior art is shown in FIGS. 3 to 5.

In the figure, 1 is an injector body formed into a stepped cylindrical shape, 2 is a casing constituting the injector body 1, and the casing 2 has a hollow outer part 2A in which a fuel flow port 3 is formed in the radial direction. It consists of a lid part 2B formed on the upper end side in the axial direction of the outer cylinder part 2A, and a hollow cylindrical core part 2C formed to protrude and penetrate through the center of the lid part 2B. Reference numeral 4 designates a stepped cylindrical holder that constitutes the injector body 1 together with the casing 2. The upper end of the holder 4 is fitted and fixed to the lower end of the casing 2, and a needle valve 9, which will be described later, is attached to the inner periphery of the lower end. A substantially U-shaped or C-shaped plate stopper 5 for regulating the valve opening position is fitted and fixed together with an injection nozzle 6, which will be described later.

Reference numeral 6 designates an injection nozzle formed into a hollow cylindrical body whose upper end side in the axial direction is fitted and fixed to the holder 4 with the plate stopper 5 sandwiched therebetween, and the injection nozzle 6 has a large diameter extending in the axial direction. A guide hole 6A, an injection port 6B opening on the lower side of the injection nozzle 6, and a concave conical valve seat 6C located between the injection port 6B and the guide hole 6A are formed. A nozzle plate 7, which will be described later, is fixed to the lower end surface 6D.

Reference numeral 7 indicates a substantially disk-shaped nozzle plate, and in the center of the nozzle plate 7, for example, four injection holes 7A, 7A, . . . (see FIG. 5) communicating with the injection port 6B are arranged at predetermined intervals. Each of the injection holes 7A is configured to inject fuel in different directions. As shown in FIGS. 4 and 5, the upper surface 7C of the nozzle plate 7 is fixed to the lower end surface 6D of the injection nozzle 6 at an annular welded portion 7B using means such as laser welding.

Reference numeral 8 denotes a protector formed of a synthetic resin material or the like in a substantially cylindrical shape, and the protector 8 is attached to the lower end side of the injection nozzle 6 so as to cover the nozzle plate 7.

The inner end surface 8A of the protector 8 abuts the lower surface 7D of the nozzle plate 7, and an annular chamber A is formed between the protector 8 and the nozzle plate 7.

Reference numeral 9 indicates a needle valve provided in the injection nozzle 6 so as to be slidable in the axial direction, and the needle valve 9 is connected to the guide hole 6A.
A valve shaft 9A that slides inside the valve shaft 9A, a large diameter portion 9B that is formed on the upper end side of the valve shaft 9A and that fits into an anchor 11, which will be described later, and a valve shaft 9A that is located below the large diameter portion 9B. A stopper portion 9C is formed in a flange shape in the middle and comes into contact with the plate stopper 5, and a stopper portion 9C is formed on the lower end side of the valve shaft 9A and is formed in the valve seat 6C.
It is composed of a convex conical valve portion 9D that is seated and separated from the valve portion 9D. A fuel flow path 10 is formed between the needle valve 9 and the injection nozzle 6.

Numeral 11 is an anchor fixed to the large diameter portion 9B of the needle valve 9 by means such as laser welding while facing the end face of the core portion 2C of the casing 2. Numeral 12 is an anchor fixed to the large diameter portion 9B of the needle valve 9 by means such as laser welding while facing the end surface of the core portion 2C of the casing 2. The adjustment rod 12 and the anchor 11 are shown as a spring receiving member inserted into the adjustment rod 12 and the anchor 11.
A valve spring 13 is disposed between the valve spring 13 and
constantly urges the needle valve 9 in the valve closing direction.

Reference numeral 14 denotes a solenoid as an electromagnetic actuator fitted between the outer cylindrical portion 2A and the core portion 2C of the casing 2. The solenoid 14 is energized when an injection signal is input via the terminal bin 15, and the valve is activated. By attracting the anchor 11 against the spring force of the spring 13, the needle valve 9 is opened.

16 is a connector provided on the outside of the lid portion 2B of the casing 2, and 17 is a filter fitted to the outer cylinder portion 2A of the casing 2 so as to cover the fuel flow port 3.

The conventional fuel injector has the above-mentioned configuration, and its operation will be explained next.

First, the fuel from the fuel pump is supplied to the fuel pipe (not shown).
The fuel is supplied into the casing 2 from the fuel flow port 3 via the filter 17 and flows from the outer periphery of the anchor 11 through the plate stopper 5 and into the fuel flow path 10 between the injection nozzle 6 and the needle valve 9. Then, when power is supplied to the solenoid 14 via the terminal pin 15 in response to an injection signal from a control unit (not shown), the anchor 11 is attached to the lower end surface of the core portion 2C of the casing body 2 together with the needle valve 9. It is attracted against the spring force. As a result, the needle valve 9 is separated from the valve seat 6C and opened, and fuel is injected to the outside from the injection port 6B of the injection nozzle 6 through each injection hole 7A.

On the other hand, when the power supply is stopped, the solenoid 14 is demagnetized and the needle valve 9 is seated on the valve seat 6C by the spring force of the valve spring 13, thereby stopping fuel injection.

[Problem to be solved by the invention]

By the way, in the above-mentioned conventional technology, since the upper surface 7C of the nozzle plate 7 is fixed to the lower end surface 6D of the injection nozzle 6 at the welded part 7B by laser welding, the welded part 7B becomes rough or dense. This may cause the following problems.

That is, if the welded part 7B is rough, welding defects occur in several places in the circumferential direction of the welded part 7B, creating gaps, which reduces the strength of the nozzle plate 7 to the injection nozzle 6, and also causes the upper surface of the nozzle plate 7 to deteriorate. 7C and the lower end surface 6D of the injection nozzle 6
A gap is formed between the injection port 6B and the injection port 6B through this gap.
A part of the fuel injected from the chamber may leak into the chamber A. In addition, if the welding part 7B is made dense, the welding beams during welding may overlap each other, so the welding part 7B
So-called cracks tend to occur in several places in the circumferential direction, and the injected fuel may leak into the chamber A through these cracks. Furthermore, even if the welding part 7B is properly welded, due to "variations" in the processing accuracy of the nozzle plate 7, thermal deformation of the nozzle plate due to heat during welding, etc., the upper surface 7C of the nozzle plate 7 A gap is generated between the end face 6D and the fuel injected from the injection port 6B may leak into the chamber A through this gap.

Therefore, in the prior art, when fuel leaks from the injection port 6B into the chamber A formed between the nozzle plate 7 and the protector 8, this fuel gradually drips from the chamber A into the external intake pipe. When the engine is running, the fuel easily vaporizes due to heat, so it mixes with the intake air and burns.However, when the engine is stopped, it remains in the intake pipe as a wall film flow, so when the engine is started again, the fuel is The air becomes too rich and the air-fuel ratio drops (over-rich condition).
, there are problems in that engine startability deteriorates and incomplete combustion occurs.

The present invention has been made in view of the problems of the prior art described above, and the present invention allows fuel that has entered between the upper surface of the nozzle plate and the lower surface of the injection nozzle to be quickly led out to the outside, and when the engine is restarted. To provide a fuel injector which can effectively improve engine startability by preventing fuel from becoming rich, and can significantly improve reliability.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the feature of the configuration adopted by the present invention is that the nozzle plate is located radially outward from each injection hole, and the nozzle plate and the injection nozzle A plurality of fuel outlet holes are provided on the inner periphery of the tip side of the protector to allow the fuel that has entered between the nozzle plate and the nozzle plate to be discharged to the outside. A negative pressure generating section is provided which generates a negative pressure in the engine and causes the fuel to be led out from the respective fuel outlet holes using the negative pressure.

[Operation J] With the above configuration, during fuel injection, negative pressure is generated between the negative pressure generating part of the protector and the nozzle plate, and this negative pressure removes the fuel that has entered between the nozzle plate and the tip surface of the injection nozzle. The fuel can be quickly led out from each fuel outlet hole.

[Example] Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2. Note that the same reference numerals are given to the same components as those of the prior art described above, and the explanation thereof will be omitted.

In the figure, 21 indicates a nozzle plate, and although the nozzle plate 21 is formed almost the same as the nozzle plate 7 described in the prior art, each injection hole 21A is provided on the inner circumferential side of the nozzle plate 21.
For example, four fuel outlet holes 21B, 21B, . . . (see FIG. 2) are located radially outward from each injection hole
They are drilled at a diameter smaller than 1A and spaced apart by 90 degrees.

Further, the nozzle plate 21 is formed by welding the annular welded portion 2IC all around by laser welding, so that the upper surface 2
1D is fixed to the lower end surface 6D of the injection nozzle 6. The fuel outlet holes 21B are arranged so that even if fuel enters the gap formed between the upper surface 21D of the nozzle plate 21 and the lower end surface 6D of the injection nozzle 6, the fuel can be guided to the outside. It has become. Further, on the lower surface 21E of the nozzle plate 21, a protector 22, which will be described later, is provided.
The inner peripheral end surface 22A of is in contact with the inner peripheral end surface 22A.

Reference numeral 22 denotes a protector, and although the protector 22 is formed almost in the same way as the protector 8 described in the prior art, the inner peripheral side thereof has a tapered portion as a negative pressure generating portion whose diameter gradually decreases downward from the end surface 22A. 22B is formed. When fuel is injected from each injection hole 21A of the nozzle plate 21, the tapered portion 22B generates a negative pressure between the nozzle plate 21 and the nozzle plate 21 due to the jet flow, and this negative pressure causes the fuel to flow from each fuel outlet hole 21B. The fuel is drawn out (suctioned) to the outside in the direction of the arrow.

The fuel injector according to this embodiment has the configuration described above, and its basic operation is not particularly different from that of the prior art.

However, in this embodiment, the nozzle plate 21 is provided with each small-diameter fuel outlet hole 21B located radially outward from each injection hole 21A, and the end surface 22 is provided on the inner peripheral side of the protector 22.
Since the tapered part 22B is provided whose diameter gradually decreases downward from A, cracks occurring in the welded part 21C of the nozzle plate 21, machining accuracy of the nozzle plate 21, thermal deformation, etc.
Even if a gap is created between the upper surface 21D of the nozzle plate 21 and the lower end surface 6D of the injection nozzle 6, and fuel enters this gap, when fuel is injected to the outside from each injection hole 21A,
This jet flow causes the taper part 22B and the nozzle plate 21 to
It is possible to generate negative pressure between the
Therefore, the fuel that has entered between the upper surface 21D of the nozzle plate 21 and the lower end surface 6D of the injection nozzle 6 can be quickly led out from each fuel outlet hole 21B together with the injection flow.

Thus, according to this embodiment, fuel can be prevented from leaking and remaining in the chamber A between the nozzle plate 21 and the protector 22, and the air-fuel ratio can be prevented from becoming excessively rich when the engine is restarted. This not only improves the restartability of the engine, but also allows the fuel injected from the injection port 6B to be mixed with intake air and sent into the engine, and furthermore, the reliability of the fuel injector is greatly improved. Various effects can be achieved, such as the ability to achieve

In the above embodiment, it has been described that, for example, four fuel outlet holes 21B are formed on the outside of each injection hole 21A in the radial direction, spaced apart by 90 degrees. Two, three, or five or more holes 21B may be provided at predetermined intervals in the circumferential direction on the radially outer side of each injection hole 21A.

Further, in the embodiment, the tapered portion 22 of the protector 22
Although B is described as being formed by gradually decreasing the diameter downward, the tapered part 22B as a negative pressure generating part may be formed as a convex curved or concave curved taper, for example, and the tapered part 22B is Any shape is sufficient as long as it can generate a negative pressure between it and the nozzle plate 21 during fuel injection and allow the negative pressure to lead the fuel to the outside from each fuel outlet hole 21B.

〔Effect of the invention〕

As described in detail above, according to the present invention, the nozzle plate has a plurality of holes located radially outward from each injection hole, and which guides the fuel that has entered between the nozzle plate and the tip surface of the injection nozzle to the outside. A fuel outlet hole is bored on the inner periphery of the tip side of the protector, and when fuel is injected from each injection hole of the nozzle plate, a negative pressure is generated between the nozzle plate and the fuel outlet hole. Since a negative pressure generating part is provided to lead the fuel to the outside, the fuel that has entered between the nozzle plate and the tip surface of the injection nozzle can be quickly led out from each fuel outlet hole, and when the engine is stopped, the air is removed. Prevents the fuel ratio from decreasing and becoming overrich,
This not only greatly improves the restartability of the engine, but also provides various effects such as improving the reliability of the fuel injector.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, in which FIG. 1 is a longitudinal sectional view showing an enlarged main part of the fuel injector along the direction of arrow II in FIG. 2, and FIG. is a plan view of the nozzle plate showing the state in which the protector of Fig. 1 is removed;
3 to 5 show the prior art, FIG. 3 is a vertical sectional view of a fuel injector, FIG. 4 is a vertical sectional view showing an enlarged main part in FIG. 3, and FIG. FIG. 3 is a plan view of the nozzle plate with the protector shown in the figure removed. 1... Injector body, 6... Injection nozzle, 6B
...Injection port, 9...Needle valve, 14...Solenoid (electromagnetic actuator), 21...Nozzle plate, 21A...Injection hole, 21B...Fuel outlet hole, 2
2...Protector, 22B...Tapered part (negative pressure generation part).

Claims (1)

[Claims] An injector body, an injection nozzle provided on one end side of the injector body and having an injection port formed on the tip side, and a plurality of injection holes fixed to the tip surface of the injection nozzle and communicating with the injection port of the injection nozzle. a nozzle plate with a hole formed therein, a protector attached from the outside to the tip side of the injection nozzle to protect the nozzle plate, and a protector that can be slid into the injection nozzle to open and close the injection port of the injection nozzle. In the fuel injector, the nozzle plate has a diameter larger than that of each injection hole, and an electromagnetic actuator that is provided in the injector body and opens the needle valve by being supplied with power from the outside. A plurality of fuel outlet holes are provided on the outer side of the nozzle plate and allow the fuel that has entered between the nozzle plate and the tip surface of the injection nozzle to flow out to the outside. A fuel injector characterized by being provided with a negative pressure generating section that generates a negative pressure between the nozzle plate and the nozzle plate when fuel is injected from the injection hole, and causes the negative pressure to lead the fuel to the outside from the fuel outlet holes. .