JP2008064033A - Fuel injection valve - Google Patents

Abstract

An object of the present invention is to obtain a fuel injection valve capable of further atomizing fuel while suppressing the spread of fuel spray.
A plurality of flow speed increases between a fuel passage 4a and a nozzle hole 5a in a fuel cavity 18 to prevent the fuel from colliding to both sides to prevent the fuel from going straight from the fuel path 4a to the nozzle hole 5a. A part 19 is provided. The flow velocity increasing portion 19 is provided with an inclined surface 19a that continuously decreases the cross-sectional area of the fuel cavity 18 toward the radially outer side of the fuel passage 4a. By reducing the cross-sectional area of the fuel cavity 18 by the inclined surface 19a, the flow velocity of the fuel that has collided with the flow velocity increasing portion 19 is increased.
[Selection] Figure 4

Description

  The present invention relates to a fuel injection valve for an internal combustion engine used in, for example, an automobile engine.

  In the conventional fuel injection valve, a plurality of cylindrical barrier bodies are disposed in the fuel cavity. Then, the fuel is diffused and atomized by the swirl force of the vortex generated when the fuel collides with the barrier body (see, for example, Patent Document 1).

JP 2004-68725 A

  In the conventional fuel injection valve as described above, a vortex is generated when the fuel collides with the barrier body, and the vortex swirls the fuel vigorously inside the nozzle hole, so that the fuel injected from the nozzle hole is effective by centrifugal force. Is diffused and atomized. However, at the same time, the fuel is widely scattered in the circumferential direction of the nozzle hole due to centrifugal force, so the fuel spray spreads greatly, the amount of fuel adhering to the intake pipe and the engine inner wall increases, and at low temperatures such as when starting the engine The amount of unburned fuel cannot be reduced sufficiently. Further, in order to meet stricter exhaust gas regulations, further atomization of fuel is required.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel injection valve capable of further atomizing the fuel while suppressing the spread of the fuel spray. .

  A fuel injection valve according to the present invention is a valve seat having a fuel passage and a facing surface provided around the downstream end of the fuel passage, and a valve that opens and closes the fuel passage by being attached to and detached from the valve seat on the upstream side of the fuel passage. A member, and a cavity forming member disposed opposite to the opposing surface and having a plurality of nozzle holes opposing the opposing surface, and forming a fuel cavity between the opposing surface and a fuel passage in the fuel cavity; Between the nozzle holes, a plurality of flow speeds that prevent the fuel from going straight from the fuel passage to the nozzle holes and increase the fuel flow speed by decreasing the cross-sectional area of the fuel cavity toward the radially outer side of the fuel passage. The increasing portions are provided at intervals in the circumferential direction of the fuel passage.

  The fuel injection valve according to the present invention prevents the fuel from going straight from the fuel passage to the nozzle hole and reduces the cross-sectional area of the fuel cavity toward the radially outer side of the fuel passage to increase the fuel flow velocity. Since the increased portion is provided between the fuel passage in the fuel cavity and the nozzle hole, the fuel is greatly disturbed by causing a difference in the flow velocity of the fuel, thereby further atomizing the fuel. In addition, the generation of turning force can be suppressed, and the spread of fuel spray can be suppressed.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
1 is a cross-sectional view of a fuel injection valve according to Embodiment 1 of the present invention. In the figure, a cylindrical fixed iron core 3 is fixed to an upper end portion of a magnetic pipe 1 via a nonmagnetic pipe 2. The magnetic pipe 1, the nonmagnetic pipe 2 and the fixed iron core 3 are arranged coaxially.

  A valve seat 4 and a plate 5 as a cavity forming member are fixed to the lower end portion in the magnetic pipe 1. The plate 5 is provided with a plurality of injection holes 5a for injecting fuel. Also, in the magnetic pipe 1, a ball 6 as a valve member, a needle pipe 7 welded and fixed to the ball 6, and a movable iron core welded and fixed to the upper end portion of the needle pipe 7 (the end portion opposite to the ball 6). 8 are inserted.

  The ball 6, the needle pipe 7 and the movable iron core 8 are slidable within the magnetic pipe 1. Thereby, the ball 6 is detached from the valve seat 4. Further, the upper end surface of the movable iron core 8 is brought into contact with and separated from the lower end surface of the fixed iron core 3.

  A compression spring 9 that presses the needle pipe 7 in a direction in which the ball 6 is pressed against the valve seat 4 is inserted into the fixed iron core 3. An adjuster 10 for adjusting the load of the compression spring 9 is fixed in the fixed iron core 3. Further, a filter 11 is inserted into the upper end portion of the fixed iron core 3 that serves as a fuel introduction portion.

  An electromagnetic coil 12 is fixed to the outer periphery of the lower end portion (movable iron core 8 side end portion) of the fixed iron core 3. The electromagnetic coil 12 has a resin bobbin 13 and a coil body 14 wound around the outer periphery thereof. Two metal plates 15 constituting a magnetic path are welded and fixed between the magnetic pipe 1 and the fixed iron core 3.

  The magnetic pipe 1, the fixed iron core 3, the electromagnetic coil 12, and the metal plate 15 are integrally formed in a resin housing 16. The resin housing 16 is provided with a connector portion 16a. A terminal 17 that is electrically connected to the coil body 14 is drawn into the connector portion 16a.

  2 is an enlarged cross-sectional view of the tip portion of the fuel injection valve of FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III of FIG. In addition, since the cross section of the front-end | tip part of a fuel injection valve is left-right symmetric, FIG. 2 has shown only the part of the left side from the centerline. The valve seat 4 is provided with a fuel passage 4a. A seat 4b is provided at the peripheral edge of the upstream end of the fuel passage 4a. A guide portion 4 c for guiding the reciprocating motion of the ball 6 is provided in the valve seat 4. The ball 6 is guided by the guide portion 4c and seated / separated from the seat portion 4b. Thereby, the upstream end opening of the fuel passage 4a is opened and closed. The outer periphery of the ball 6 is processed into a pentagon.

  Around the downstream end of the fuel passage 4 a of the valve seat 4, a facing surface 4 d that faces the plate 5 is provided. A fuel cavity 18 is formed between the facing surface 4 d and the plate 5. The nozzle hole 5a faces the facing surface 4d. Further, the nozzle holes 5a are arranged at equal intervals in the circumferential direction on one circumference centered on the center of the fuel passage 4a.

  Between the fuel passage 4a in the fuel cavity 18 and the nozzle hole 5a, a plurality of flow velocity increasing portions 19 are provided that prevent the fuel that has collided from entering the both sides to prevent the fuel from going straight from the fuel passage 4a to the nozzle hole 5a. It has been. The flow velocity increasing portion 19 is provided with an inclined surface 19a that continuously decreases the cross-sectional area of the fuel cavity 18 toward the radially outer side of the fuel passage 4a. By reducing the cross-sectional area of the fuel cavity 18 by the inclined surface 19a, the flow velocity of the fuel that has collided with the flow velocity increasing portion 19 is increased.

  The flow velocity increasing portions 19 are arranged at equal intervals in the circumferential direction on one circumference centered on the center of the fuel passage 4a. The flow velocity increasing portion 19 has an arc shape with the center of the fuel passage 4a as the center. Further, the flow velocity increasing portion 19 is bilaterally symmetric about a straight line connecting the center of the fuel passage 4a and the center of the injection hole 5a. Furthermore, the flow velocity increasing portion 19 is formed integrally with either the valve seat 4 or the plate 5.

  Next, the operation of the fuel injection valve will be described. When the electromagnetic coil 12 is energized from the outside via the terminal 17, magnetic flux is generated in the magnetic path constituted by the fixed iron core 3, the metal plate 15, the magnetic pipe 1 and the movable iron core 8, and the movable iron core 8 is fixed by the magnetic attractive force. It is attracted to the iron core 3. Thereby, the ball 6 is separated from the seat portion 4b, and the fuel passage 4a is opened.

  The fuel is introduced into the fuel injection valve from the upper part of FIG. 1 via a derivative pipe (not shown), and between the filter 11, adjuster 10, compression spring 9, needle pipe 7, guide portion 4 c and the outer periphery of the ball 6. And the fuel passage 18 through the fuel passage 4a.

  The fuel supplied to the fuel cavity 18 flows from the center of the fuel cavity 18 toward the radially outer side of the fuel cavity 18 and is distributed to the plurality of injection holes 5a. At this time, as shown in FIG. 4, part of the fuel flows through the main flow path 20 formed between the flow velocity increasing portions 19 adjacent to each other, but the other fuel collides with the flow velocity increasing portion 19, It flows along the flow velocity increasing part 19.

  The flow velocity of the fuel flowing along the flow velocity increasing portion 19 is increased by decreasing the flow path cross-sectional area toward the radially outer side of the fuel cavity 18. The fuel that has been accelerated flows from both sides of the flow velocity increasing portion 19 into the main flow path 20. At this time, since there is a large difference between the flow velocity of the fuel flowing from the flow velocity increasing portion 19 into the main flow channel 20 and the flow velocity of the fuel flowing directly into the main flow channel 20 without passing through the flow velocity increasing portion 19, the shear force due to the viscosity of the fuel The effect can be greatly obtained, and the fuel is greatly disturbed.

  Further, since the fuel accelerated by the flow velocity increasing portion 19 flows into the main flow path 20 vigorously, as shown in FIG. 4, it collides violently with the fuel that similarly flows from the adjacent flow velocity increasing portion 19 and uses collision turbulence. Further disturbance amplification can be achieved. In addition, since this disturbed fuel collides again with the similarly disturbed fuel flowing from the other main flow path 20 on the nozzle hole 5a, it is possible to obtain a larger disturbance.

  Such greatly disturbed fuel is effectively atomized because droplet breakup is greatly promoted by the disturbance when injected from the injection hole 5a. Further, since the swirl force hardly occurs in the fuel flowing into the nozzle hole 5a, the fuel injected from the nozzle hole 5a does not greatly scatter in the circumferential direction, and the spread of fuel spray can be suppressed.

  FIG. 5 shows the result of comparison of the particle size of the fuel droplets injected from the fuel injection valve and the spread of the fuel spray between the case where the known barrier body is used and the case where the flow velocity increasing portion 19 of the first embodiment is used. It is explanatory drawing which shows. In FIG. 5, normalization is performed based on a case where a known barrier body having no inclined surface 19 a (slope) is used. As a result, when the flow velocity increasing unit 19 of the first embodiment was used, the particle size of the fuel droplets was reduced to 0.8, and the spread of the fuel spray was suppressed to 0.85.

Further, since the flow velocity increasing portion 19 is symmetrical with respect to a straight line connecting the center of the fuel passage 4a and the center of the nozzle hole 5a, it is possible to effectively cause fuel collision disturbance on each nozzle hole 5a. Further atomization of the fuel becomes possible.
Furthermore, since the flow velocity increasing portion 19 is formed integrally with either the valve seat 4 or the plate 5, the flow velocity increasing portion 19 can be easily formed by pressing or cutting.

Embodiment 2. FIG.
Next, FIG. 6 is a cross-sectional view of the fuel cavity of the fuel injection valve according to Embodiment 2 of the present invention, and corresponds to a cross section taken along line III-III in FIG. In the first embodiment, the same number of flow velocity increasing portions 19 as the nozzle holes 5a are arranged. However, in the second embodiment, one flow velocity increasing portion 19 is provided upstream of a plurality of (here, two) adjacent nozzle holes 5a. Has been placed. That is, in the first embodiment, the nozzle hole 5a and the flow velocity increasing portion 19 correspond 1: 1, but in the second embodiment, they correspond 2: 1. Other configurations are the same as those in the first embodiment.

  According to such a configuration, the number of flow velocity increasing portions 19 arranged in the fuel cavity 18 can be reduced and the fuel can be atomized.

Embodiment 3 FIG.
Next, FIG. 7 is an enlarged cross-sectional view of the tip portion of the fuel injection valve according to Embodiment 3 of the present invention. In the first embodiment, when the front end portion of the fuel injection valve (the end portion on the injection hole 5a side) is set downward, the inclined surface 19a in which the bottom surface of the fuel cavity 18 gradually increases outward in the radial direction is provided on the flow velocity increasing portion 19. However, in the second embodiment, the flow velocity increasing portion 19 is formed with the inclined surface 19a in which the upper surface of the fuel cavity 18 gradually decreases toward the outside in the radial direction. Other configurations are the same as those in the first embodiment.

  Even with such a configuration, the flow path cross-sectional area of the fuel decreases toward the radially outer side of the fuel cavity 18, so that the flow rate of the fuel flowing along the flow rate increasing portion 19 is increased, which is the same as in the first embodiment. An effect is obtained.

In the flow velocity increasing portion 19, the valve seat 4 and the plate 5 may be configured as separate members and fixed to either the valve seat 4 or the plate 5.
In the above example, the inclined surface 19a that continuously decreases the cross-sectional area of the fuel cavity 18 is provided in the flow velocity increasing portion 19, but a stepped step portion that gradually decreases the cross-sectional area of the fuel cavity 18 is provided. You may provide in the flow velocity increase part 19. FIG.
Furthermore, the shape, position, and number of the nozzle holes 5a and the flow velocity increasing portion 19 are not limited to the above example.

1 is a cross-sectional view of a fuel injection valve according to Embodiment 1 of the present invention. It is an expanded sectional view of the front-end | tip part of the fuel injection valve of FIG. It is sectional drawing which follows the III-III line of FIG. FIG. 4 is an explanatory diagram showing the flow of fuel in the fuel cavity of FIG. 3. Explanatory drawing which shows the result compared with the case where the particle size of the fuel droplet injected from the fuel injection valve and the spread of the fuel spray are the case where the known barrier body is used and the flow velocity increasing portion of the first embodiment is used. It is. It is sectional drawing of the fuel cavity of the fuel injection valve by Embodiment 2 of this invention. It is an expanded sectional view of the front-end | tip part of the fuel injection valve by Embodiment 3 of this invention.

Explanation of symbols

  4 valve seat, 4a fuel passage, 4d facing surface, 5 plate (cavity forming member), 5a injection hole, 6 ball (valve member), 18 fuel cavity, 19 flow velocity increasing portion, 19a inclined surface.

Claims (4)

A valve seat having a fuel passage and an opposing surface provided around the downstream end of the fuel passage;
A valve member that is attached to and detached from the valve seat on the upstream side of the fuel passage and opens and closes the fuel passage; and a plurality of injection holes that are disposed to face the facing surface and face the facing surface, A cavity forming member for forming a fuel cavity between the opposing surfaces;
Between the fuel passage and the injection hole in the fuel cavity, the fuel passage is prevented from going straight from the fuel passage to the injection hole, and the fuel cavity is cut off radially outward of the fuel passage. A fuel injection valve characterized in that a plurality of flow velocity increasing portions for decreasing the area and increasing the fuel flow velocity are provided at intervals in the circumferential direction of the fuel passage.   2. The fuel injection valve according to claim 1, wherein the flow velocity increasing portion is provided with an inclined surface that continuously decreases the cross-sectional area of the fuel cavity toward the radially outer side of the fuel passage.   3. The fuel injection valve according to claim 1, wherein the flow velocity increasing portion is bilaterally symmetric about a straight line connecting the center of the fuel passage and the center of the nozzle hole. 4.   The fuel injection valve according to any one of claims 1 to 3, wherein the flow velocity increasing portion is integrally formed with one of the valve seat and the cavity forming member.

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