JP2012007529A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To atomize fuel well in an initial stage of the fuel injection.SOLUTION: A fuel injection valve 10 includes: a needle 1; a nozzle body 2 in which the needle 1 is freely and slidably arranged; an upstream-side sheet part 3 in which the needle 1 comes in contact with the nozzle body 2 on the upstream side of the fuel flow in the nozzle body 2; a downstream-side sheet part 4 in which the needle 1 comes in contact with the nozzle body 2 on the downstream side of the fuel flow in the nozzle body 2; a sheet recessed part 6 which is formed between the upstream-side sheet part 3 and the downstream-side sheet part 4. When the needle 1 is seated on the upstream-side sheet part 3 and the downstream-side sheet part 4, the sheet recessed part 6 is sealed by the upstream-side sheet part 3 and the downstream-side sheet part 4, and the fuel containing cavitation bubble is retained.

Description

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

  In a direct injection internal combustion engine, it is known that atomization of fuel injected from a fuel injection valve affects exhaust gas components and engine output. Conventionally, by making the channel cross-sectional area of the bubble holding channel larger than the channel cross-sectional area of the cavitation generating channel and making the outlet of the cavitation generating channel a rapidly expanding flow, a vertical vortex is generated in the bubble holding channel. There has been a proposal to form and retain cavitation bubbles (for example, Patent Document 1). The atomization of fuel is promoted by the collapse of the cavitation bubbles.

JP 2006-177174 A

  However, in order to generate cavitation bubbles in the proposal disclosed in Patent Document 1, fuel injection starts when the needle lifts, and generation of negative pressure due to high-speed fuel flow is necessary. For this reason, when the flow of the fuel is slow, such as when the needle is in a low lift state, there is a problem that cavitation bubbles are not easily generated and atomization of the fuel is difficult to be promoted.

  Therefore, the fuel injection valve disclosed in the present specification has an object to obtain good atomization of fuel in the initial stage of fuel injection.

  In order to solve this problem, a fuel injection valve disclosed in the present specification includes a needle, a nozzle body in which the needle is slidably disposed, and the needle upstream of the fuel flow in the nozzle body. Is provided upstream of the downstream seat portion, the upstream seat portion in contact with the nozzle body, the downstream seat portion in contact with the nozzle body on the downstream side of the fuel flow in the nozzle body, and the downstream seat portion. And when the needle is seated on the upstream seat portion and the downstream seat portion, the cavitation bubble generating portion is sealed by the upstream seat portion and the downstream seat portion, and the cavitation bubble generating portion A fuel holding unit for holding the fuel containing the generated cavitation bubbles is provided.

  The fuel containing the cavitation bubbles generated by the cavitation bubble generation unit during the fuel injection is confined in the fuel holding unit when the fuel injection is completed. At the next fuel injection, this trapped fuel containing cavitation bubbles is injected first. For this reason, fuel containing cavitation bubbles can be injected even in a state where the flow of fuel is slow and new cavitation bubbles are difficult to be generated, such as in a low lift state at the beginning of injection. As a result, fuel atomization can be promoted.

  The cavitation bubble generation part in such a fuel injection valve can be a sheet recess formed between the upstream seat part and the downstream seat part.

  The seat recess can generate cavitation bubbles when the fuel that has passed through the upstream seat portion flows in. In addition, when the needle is seated on the nozzle body, the upstream side seat portion and the downstream side seat portion are sealed to form a fuel holding portion that holds fuel.

  In such a fuel injection valve, the first outer surface that contacts the upstream seat portion of the needle has a first angle formed with the central axis of the needle, and the second outer periphery that contacts the downstream seat portion of the needle. The second angle formed by the surface with the central axis of the needle can be made the same.

  As a result, the needle is seated simultaneously on the upstream seat portion and the downstream seat portion, and the fuel containing cavitation bubbles can be confined in the fuel holding portion without leakage.

  Such a fuel injection valve can be configured to have an air intake hole that communicates the outside of the nozzle body and the fuel holding portion.

  The needle is not lifted, the air is taken into the fuel holding portion in a state where the fuel is trapped in the fuel holding portion, and the bubbles generated by taking in the air are utilized for atomizing the fuel immediately after the start of injection. .

  According to the fuel injection valve disclosed in the present specification, good atomization of fuel can be obtained in the initial stage of fuel injection.

FIG. 1 is a cross-sectional view showing the tip of the fuel injection valve of the first embodiment. FIG. 2 is an explanatory diagram illustrating the operation of the fuel injection valve according to the first embodiment. FIG. 3 is an explanatory view showing the operation of the fuel injection valve of the comparative example. FIG. 4 is a graph showing changes in the needle lift amount, the cavitation bubble amount, and the spray particle size of the fuel injection valves of Example 1 and Comparative Example. FIG. 5 is a cross-sectional view showing the tip of another fuel injection valve. FIG. 6 is a cross-sectional view of the tip portion of the fuel injection valve of the second embodiment. FIG. 7 is an explanatory diagram illustrating the operation of the fuel injection valve according to the second embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. However, in the drawings, the dimensions, ratios, and the like of each part may not be shown so as to completely match the actual ones. Further, details may be omitted depending on the drawings.

  FIG. 1 is a cross-sectional view illustrating a tip portion of a fuel injection valve 10 according to the first embodiment. The fuel injection valve 10 includes a nozzle body 2 in which a needle 1 is slidably disposed and a nozzle hole 2a is provided at a tip portion. The fuel injection valve 10 also includes an upstream seat portion 3 where the needle 1 contacts the nozzle body 2 on the upstream side of the fuel flow 5 in the nozzle body 2. Further, the fuel injection valve 10 includes a downstream seat portion 4 where the needle 1 contacts the nozzle body 2 on the downstream side of the fuel flow 5 in the nozzle body 2. The fuel injection valve 10 includes a seat recess 6 formed between the upstream seat portion 3 and the downstream seat portion 4. The sheet recess 6 functions as a cavitation bubble generation unit provided on the upstream side of the downstream sheet unit 4. The seat recess 6 is sealed by the upstream seat portion 3 and the downstream seat portion 4 when the needle 1 is seated on the upstream seat portion 3 and the downstream seat portion 4, and the fuel is retained. Also functions as a holding unit. The seat recess 6 can generate cavitation bubbles in the fuel because the fuel flow path rapidly expands.

  The needle 1 is seated on the upstream seat portion 3 and the downstream seat portion 4 and seals fuel at these two locations (two surfaces). Therefore, the needle 1 has the following external shape. A first angle formed by the first outer peripheral surface 1a1 in contact with the upstream seat portion 3 of the needle 1 and the central axis AX of the needle 1 is defined as θ1. The second angle formed by the second outer peripheral surface 1a2 contacting the downstream seat portion 4 of the needle 1 and the central axis AX of the needle 1 is also set to θ1. That is, the part where the needle 1 is in contact with the upstream sheet part 3 and the part where the needle 1 is in contact with the downstream sheet part 4 are provided on the same tapered surface 1 a having no step. In accordance with this, the angle between the surface on the inner peripheral wall of the nozzle body 2 where the upstream sheet portion 3 is provided and the central axis AX, and the angle between the surface where the downstream sheet portion 4 is provided and the central axis AX. Is also set to θ1. Thereby, it is possible to achieve good sealing performance in the upstream seat portion 3 and the downstream seat portion 4 by the needle 1, and fuel can be confined in the seat recess 6.

  The operation of the fuel injection valve 10 will be described in comparison with the operation of the fuel injection valve 150 of the comparative example shown in FIG. The nozzle body 152 of the fuel injection valve 150 is common to the nozzle body 2 of the fuel injection valve 10. The nozzle body 152 is also common to the nozzle body 2 in that the nozzle body 152 is provided with an injection hole 152a at the tip and a sheet recess 156 is provided. The shape of the needle 151 of the fuel injection valve 150 is different from that of the needle 1 of the fuel injection valve 10. For this reason, the needle 151 and the nozzle body 152 in the fuel injection valve 150 are in contact with each other only at one (one side) seat portion 153.

  As shown in FIG. 2 (A), when the needle 1 of the fuel injection valve 10 is in a large lift state, the fuel that has flowed into the seat recess 6 from the proximal end side of the nozzle body 2 causes cavitation and generates cavitation bubbles 8. To do. The fuel containing the cavitation bubbles 8 is injected from the injection hole 2a.

  The same applies when the needle 151 of the fuel injection valve 150 is in a large lift state as shown in FIG. That is, the fuel that has flowed into the sheet recess 156 from the base end side of the nozzle body 152 causes cavitation and generates cavitation bubbles 8. The fuel containing the cavitation bubbles 8 is injected from the injection hole 152a.

  FIG. 2B shows the fuel injection valve 10 in a closed state. As described above, when the needle 1 is seated on the upstream seat portion 3 and the downstream seat portion 4, the seat recess 6 is sealed by the needle 1 in a state where the fuel containing the cavitation bubbles 8 is confined. .

  FIG. 3B shows the fuel injection valve 150 in the closed state. As described above, even when the needle 151 is seated on the seat portion 153, the fuel existing on the downstream side of the seat portion 153 is discharged from the injection hole 152a.

  FIG. 2C shows the fuel injection valve 10 in a small lift state. Thus, in the small lift state, it is difficult to generate sufficient cavitation bubbles 8 in the seat recess 6 because the flow rate of the fuel flowing into the seat recess 6 is also slow. However, in the case of the present embodiment, the fuel containing the cavitation bubbles 8 generated before that is held in the seat recess 6 and the fuel containing the cavitation bubbles 8 is injected. As a result, fuel atomization is promoted.

  FIG. 3C shows the fuel injection valve 150 in a small lift state. Thus, in the small lift state, it is difficult to generate sufficient cavitation bubbles 8 in the seat recess 6 because the flow rate of the fuel flowing into the seat recess 6 is also slow. Further, unlike the fuel injection valve 10, the fuel injection valve 150 does not hold the fuel containing the cavitation bubbles 8, so that the fuel flowing from the base end side of the nozzle body 152 is only injected as it is.

  FIG. 4 shows changes in the needle lift amount, cavitation bubble amount, and spray particle size of the fuel injection valve 10 of the example and the fuel injection valve 150 of the comparative example. The horizontal axis in FIG. 4 is the crank angle (CA).

  At the time of the small lift in the initial stage of the injection stroke, the amount of cavitation bubbles is small in both the comparative example and the present example. However, in the case of the present embodiment, there are cavitation bubbles 8 held in advance. For this reason, in the case of a comparative example, the spray particle diameter at the time of a small lift is large, but in this embodiment, the spray particle diameter can be atomized.

  In the case of a large lift, equivalent cavitation bubbles can be generated in both the comparative example and this example. For this reason, the spray particle diameter at the time of a large lift can be made equivalent.

  At the end of the injection stroke, the cavitation bubbles flow out rapidly in the comparative example when the small lift state is reached again and the valve is closed. On the other hand, in this embodiment, when the valve is closed, a predetermined amount of cavitation bubbles are held in the sheet recess 6. The held cavitation bubbles are injected at the beginning of the next injection stroke, and the spray particle diameter can be atomized.

  Thus, the fuel injection valve 10 of the present embodiment can atomize the spray particle diameter throughout the fuel injection period.

  In addition, as shown in FIG. 5, it can also be set as the structure provided with the air intake hole 9 which connects the exterior of the nozzle body 2 and the sheet | seat recessed part 6. As shown in FIG. When the valve is closed, air can be taken in from the air intake hole 9 to fill the seat recess 6 with bubbles, and these bubbles can be used for atomization of fuel at the beginning of injection. The air intake hole 9 allows the seat recess 6 to communicate with the combustion chamber (inside the cylinder) that is outside the nozzle body 2. Thereby, exhaust gas and air can be taken in from the combustion chamber. After the needle 1 is lifted and the fuel is injected, the pressure in the nozzle body 2 becomes lower than the pressure outside the nozzle body 2 (combustion chamber side). Due to the pressure difference after fuel injection, the air in the combustion chamber flows into the nozzle body 2 (seat recess 6). Further, the cavitation bubble 8 is also prevented from flowing out of the air intake hole 9 due to the pressure difference between the inside and outside of the nozzle body 2. In addition, the diameter of the air intake hole 9 is set to a diameter through which fuel cannot pass, for example, about 0.02 mm to 0.08 mm. Thereby, it is suppressed that fuel is injected from the air intake hole 9.

  Next, the fuel injection valve 20 of the second embodiment will be described with reference to FIGS. The fuel injection valve 20 includes a nozzle body 22 in which a first needle 21a and a second needle 21b are slidably disposed, and an injection hole 22a is provided at a tip portion. The first needle 21a and the second needle 21b are driven by separate solenoid actuators. The second needle 21b is an outer valve opening needle. The fuel injection valve 20 enters an injection state when the first needle 21a moves to the proximal end side and the second needle 21b moves to the distal end side. The fuel injection valve 20 includes an upstream seat portion 23 in which the first needle 21 a contacts the nozzle body 22 on the upstream side of the fuel flow 25 in the nozzle body 22. Further, the fuel injection valve 20 includes a downstream seat portion 24 where the second needle 21 b contacts the nozzle body 2 on the downstream side of the fuel flow 5 in the nozzle body 22. The fuel injection valve 20 includes a seat recess 26 formed between the upstream seat portion 23 and the downstream seat portion 24. The sheet recess 26 functions as a cavitation bubble generating unit provided on the upstream side of the downstream sheet unit 24. Further, the seat recess 26 is configured such that when the first needle 21 a is seated on the upstream seat portion 23 and the second needle 21 b is seated on the downstream seat portion 24, the upstream seat portion 23, the downstream seat portion 24, It also functions as a fuel holding portion that is sealed by and holds fuel. In the seat recess 26, the fuel flow path expands rapidly, so that cavitation bubbles can be generated in the fuel.

  The operation of the fuel injection valve 20 will be described with reference to FIG. As shown in FIG. 7A, when the first needle 21a and the second needle 21b of the fuel injection valve 20 are in a large lift state, the fuel flowing into the seat recess 26 from the base end side of the nozzle body 22 causes cavitation. Wake up to generate cavitation bubbles 8. The fuel containing the cavitation bubbles 8 is injected from the injection hole 22a.

  FIG. 7B shows the fuel injection valve 20 in a closed state. Thus, when the first needle 21 a is seated on the upstream seat portion 23 and the second needle 21 b is seated on the downstream seat portion 24, the seat recess 26 traps the fuel containing the cavitation bubbles 8. In this state, the first needle 21a and the second needle 21b are sealed.

  FIG. 7C shows the fuel injection valve 20 in a small lift state. Thus, when in the small lift state, the flow rate of the fuel flowing into the seat recess 26 is also slow, so that it is difficult to generate sufficient cavitation bubbles 8 in the seat recess 26. However, the fuel containing the cavitation bubbles generated before is held in the seat recess 26, and the fuel containing the cavitation bubbles 8 is injected. As a result, fuel atomization is promoted.

  Thus, the fuel injection valve 20 can atomize the spray particle diameter throughout the fuel injection period.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

DESCRIPTION OF SYMBOLS 1 ... Needle 2 ... Nozzle body 3, 23 ... Upstream seat part 4, 24 ... Downstream seat part 6, 26 ... Sheet recessed part 8 ... Cavitation bubble 9 ... Air intake hole 10, 20, 150 ... Fuel injection valve 21a ... No. 1 needle 21b ... 2nd needle

Claims (4)

Needle,
A nozzle body in which the needle is slidably disposed;
An upstream seat portion where the needle contacts the nozzle body upstream of the fuel flow in the nozzle body;
A downstream seat portion where the needle contacts the nozzle body at a downstream side of the fuel flow in the nozzle body;
A cavitation bubble generating part provided on the upstream side of the downstream sheet part,
When the needle is seated on the upstream seat portion and the downstream seat portion, the fuel is sealed by the upstream seat portion and the downstream seat portion and includes cavitation bubbles generated by the cavitation bubble generating portion. A fuel injection valve comprising a fuel holding portion for holding the fuel.   2. The fuel injection valve according to claim 1, wherein the cavitation bubble generation unit is a sheet recess formed between the upstream sheet unit and the downstream sheet unit. A first angle formed by a first outer peripheral surface that contacts the upstream seat portion of the needle and a central axis of the needle;
3. The fuel injection valve according to claim 1, wherein the second outer peripheral surface contacting the downstream seat portion of the needle has the same second angle formed by the central axis of the needle.   The fuel injection valve according to any one of claims 1 to 3, further comprising an air intake hole that communicates the outside of the nozzle body and the fuel holding portion.

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