JP2617445B2 - Fuel injection valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection valve, and more particularly, to a structure of a fuel injection valve that introduces assist air to promote atomization of fuel.

[Prior Art] Various fuel injection valve structures for promoting fuel atomization for the purpose of improving fuel efficiency and purifying exhaust gas have been devised. As an example, a fuel injection valve is provided at the tip of a needle valve that opens and closes a fuel injection hole. There is a pintle in which the injection hole is inserted and protruded to protrude, and the tip of the pintle has an umbrella shape whose diameter gradually increases. In recent years, there has been proposed a fuel injection valve having the above-described structure, in which assist air is supplied to the fuel injection valve to further promote atomization.

For example, Japanese Patent Application Laid-Open No. 57-200666 proposes a configuration in which an air flow injection hole for assist air is formed concentrically around a fuel injection port, and in Japanese Patent Application Laid-Open No. 58-77162, A proposal has been made in which assist air is directly supplied to the outer periphery and an airflow injection hole is formed below the pintle.

[Problems to be Solved by the Invention] Japanese Patent Application Laid-Open No. 57-200666 has a problem that the efficiency of atomization is low because assist air is not directly supplied to the injected fuel. On the other hand, the above-mentioned Japanese Patent Application Laid-Open No. 58-77162 does not have such a problem, but according to experiments by the inventors, atomization may not be sufficient depending on conditions.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel injection valve that constantly and efficiently atomizes fuel.

[Means for Solving the Problems] The configuration of the present invention will be described with reference to FIG. 1. A fuel injection hole 1a is provided in a lower end surface 1c of the fuel injection valve 1.
Pintle 3 is inserted through 1a. The tip of the pintle 3 is an umbrella-shaped portion 31 whose diameter gradually increases.

Below the lower end surface 1c, a partition wall 41 is spaced apart from this.
The space between the partition wall 41 and the lower end surface 1c is defined as an assist air supply path 611. Drilled holes 4 in the partition wall 41
1a is provided, through which the tip of the pintle 3 is inserted. Thus, an airflow injection hole F for assist air is formed on the outer periphery of the insertion portion of the pintle 3.

Then, on the upper surface of the partition wall 41, a first portion 411 formed so as to be closest to the lower end surface 1c is formed with the hole 41a.
A second portion 412 is provided on the peripheral edge and is formed to be further away from the lower end surface 1c at an outer peripheral portion surrounding the periphery of the hole 41a.
Assist air is allowed to flow in toward 1.

[Operation and Effect] The fuel injected from the fuel injection hole 1a flows in the distal direction along the outer periphery of the pintle 3. On the other hand, the assist air supply path 61
The air that has reached from 1 flows at high speed through the air jet holes F in the axial direction along the pintle 3. Then, both the fuel and the air collide with the umbrella-shaped portion 31 at the tip of the pintle, and are sent out at an ejection angle proportional to the opening angle θ.

That is, the first portion 411 is provided on the upper surface of the partition wall 41 at the periphery of the hole 41a.
Are the smallest. Therefore, the assist air flowing from the second portion 412 to the first portion 411 after flowing through the supply passage 611 is sufficiently accelerated toward the pintle 3 at the periphery of the hole 41a, and the first assist air approaches the lower end surface 1c. Most of the assist air flowing along the portion 411 is located at the base 32 of the pintle 3 located near the fuel injection hole 1a on the lower end surface 1c.
Collide with Then, from the base portion 32 of the pintle 3 toward the tip of the pintle 3 shaped like an umbrella, it flows over the surface of the pintle at a sufficient speed.

The fuel flowing out of the fuel injection hole 1a flows on the pintle surface, and the assist air accelerates the fuel flowing on the pintle surface within a sufficient approach distance from the base 32 to the tip of the pintle 3, and the fuel advances. After it is sufficiently accelerated, it reaches the umbrella-shaped portion 31 at the tip of the pintle 3 and is sprayed at a sufficient ejection angle according to the opening angle θ. The atomized state at this time is extremely good because the fuel is delivered at a sufficient ejection angle and a sufficient contact area with the assist air is secured.

Thus, the fuel and air delivered at a sufficient ejection angle are well mixed with each other, and the atomization of the fuel is ensured.

[Embodiment] In FIG. 2, a lower end of the fuel injection valve 1 is fitted to an opening provided in a side wall of the engine intake pipe P via an adapter 4 for assisting air supply. The injection valve 1 has a well-known structure used for electronic fuel injection control. The injection valve 1 has a needle valve 2 in a cylindrical main body. Open and close the hole 1a. The operation of the needle valve 2 is controlled by an electromagnetic coil 11 built in the main body. Fuel is supplied from the tank 51 to the connector 1b at the upper end of the valve body by the pump 52. The supplied fuel pressure is controlled by a known pressure regulating valve 53 provided in the piping system.

The adapter 4 is a cylindrical body having a bottom and is airtightly fitted into a side wall opening of the intake pipe P. In the side wall,
Azisto air supply passage 61 opening upstream of throttle valve S
Is formed, which reaches the outer periphery of the adapter 4 and communicates with an opening 4a provided therein. The supply path 61 further extends in the side wall of the intake pipe P, and reaches a reference pressure chamber (not shown) of the pressure regulating valve via a joint 62.

The bottom wall 41 of the adapter 4, which is a partition wall, is gradually thinned from the outer periphery toward the center, and is inclined upward to communicate with the assist air supply passage 61 between the bottom wall 41 and the lower end surface 1c of the fuel injection valve 1. A road 611 is formed. And the bottom wall 4
A cutout hole is provided at the center of 1 and the pintle 3 at the tip of the needle valve 2 is inserted through the hole. The detailed structure is shown in FIG.

In the figure, the pintle 3 protrudes downward through the fuel injection hole 1a, and the tip of the pintle 3 further passes through a hole 41a provided at the center of the bottom wall 41. The distal end of the pintle 3 is once reduced in diameter and then gradually increased in diameter toward the distal end to form an umbrella-shaped portion 31. Around the portion where the pintle 3 is inserted through the cutout hole 41a is an airflow injection hole F from which assist air is jetted into the intake pipe P at a high speed.

The upper surface of the bottom wall 41 extending from the outer second portion 412 is closest to the lower end surface 1c at the periphery of the hole 41a, and the first portion 4
The supply path 611 gradually decreases in the area of the supply passage 611 toward the first portion 411, and becomes minimum at this portion 411.

Here, the distance between the lower end surface 1c of the injection valve 1 and the upper end of the bottom wall 41 is H, the distance between the lower end surface 1c and the minimum diameter portion of the pintle 3, that is, the base of the umbrella-shaped portion 31, is A, The length is B, the diameter of the pintle insertion portion is d, and the diameter of the hole 41a is D. Area of the airflow nozzle hole F is ^{(D 2 -d 2) · π} / 4, in order to increase the flow rate of the assist air at該噴hole F is, πDH> (D ² -
d ² ) · π / 4, that is, H> (D ² −d ² ) / 4D.

Further, according to the experiments by the inventors, the interval H is H ≦ H.
A + (1/3) · B is recommended. FIG. 3 shows (D ²
−d ² ) /4D=0.47 (mm), A + (1/3) · B = 0.92 (mm)
Shows the change in the fuel spray state when the interval H is changed. As is known from the figure, when the interval H is set to H = 0.5 (mm) which satisfies the above condition, the atomization of the fuel can be clearly performed without changing the spray angle as compared with the case where the supply of the assist air is stopped. Has been improved. However, when H = 1.0 (mm) and H = 1.5 (mm) that do not satisfy the above conditions,
The spray angle is extremely small as compared with the case where no assist air is supplied, and coarsening due to the recombination of the fuel fine particles at the center of the spray is recognized.

In the present embodiment, the bottom wall 41 is formed in the area around the hole 41a.
Has a lower end surface 1c from the second portion 412 toward the first portion 411.
At the first portion 411 around the periphery of the hole 41a. Therefore, the flow passage area of the supply passage 611 gradually decreases from the outer peripheral portion, and becomes the smallest at the periphery of the hole 41a. As a result, the assist air is applied to the pintle 3 inserted through the hole 41a.
Accelerate enough towards. The assist air flowing along the upper surface of the bottom wall 41 is throttled by a small-area flow passage close to the lower end surface 1c, and most of the assist air is located near the base 32 of the pintle 3 located near the fuel injection hole 1a on the lower end surface 1c. (Fig. 1).

In particular, in this embodiment, the upper surface of the bottom wall 41 is
Since the air is upwardly inclined so as to gradually approach 1c, the accelerated assist air is guided in the extension direction along the inclined surface, and is supplied to the pintle base 32 more efficiently. Then, from this pintle base portion 32, it flows on the surface of the pintle 3 at a sufficient speed toward the tip of the pintle 3 shaped like an umbrella.

On the other hand, the fuel flowing out of the fuel injection hole 1a flows on the surface of the pintle 3, and the assist air accelerates the fuel flowing on the surface of the pintle during a sufficient approach distance from the base 32 to the tip of the pintle 3, and Is accelerated to reach the umbrella-shaped portion 31 at the tip of the pintle 3 and sprayed at a sufficient ejection angle according to the opening angle θ. The atomization state at this time is very good because the fuel is delivered at a sufficient ejection angle and the contact area with the assist air is large, and the two are sufficiently mixed.

Further, in the present embodiment, since the pressure of the assist air supply passage 61 in which the fuel injection hole 1a is opened is introduced into the reference pressure chamber of the pressure regulating valve 53, the differential pressure before and after the injection hole 1a is always constant. And the fuel can be metered accurately.

4 and 5 show another embodiment of the present invention. In the figure, the lower wall 41 of the adapter 4 has a periphery 4 around a hole 41a.
A casting spacer body 42 is protruded at some places. As a result, when the fuel injection valve 1 is fitted to the adapter 4, the end face 1c thereof is accurately positioned by contacting the upper surface of the spacer body 42, and the interval H with the bottom wall 41 can be reduced without assembling time. Is properly set and maintained.

[Brief description of the drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is an enlarged sectional view of a lower end portion of a fuel injection valve, FIG. 2 is an enlarged sectional view of a lower end portion of a fuel injection valve, and FIG. FIG. 3 is a diagram showing a fuel spray state, FIGS. 4 and 5 show another embodiment of the present invention, FIG. 4 is an enlarged sectional view of a lower end portion of the fuel injection valve, FIG. 5 is a sectional view taken along line VV in FIG. DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve 1a ... Fuel injection hole 2 ... Needle valve 3 ... Pintle 4 ... Assist air supply adapter 4a ... Opening 41 ... Bottom wall (partition wall) 41a ... Drilled hole 411 First part 412 Second part 53 Pressure regulating valve 61, 611 Assist air supply path F Air jet hole P Engine supply pipe S Throttle valve

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masahiro Takeda 1-1-1 Showa-cho, Kariya-shi Nippondenso Co., Ltd. (56) References JP-A-57-200666 (JP, A) JP-A-59-96476 JP-A-58-77162 (JP, A) JP-A-57-164252 (JP, U) JP-A-59-123661 (JP, U)

Claims (1)

(57) [Claims] 1. A fuel injection valve for opening and closing a fuel injection hole opened on a lower end surface of a main body by an internally provided needle valve, wherein a pintle provided at a tip of the needle valve is inserted through the fuel injection hole and protrudes. At the same time, in a fuel injection valve formed by forming the tip of the pintle into an umbrella shape having an gradually increasing diameter without an umbrella, and supplying assist air to the tip of the pintle, an interval is provided below the lower end face. A partition wall is provided, and a space between the partition wall and the lower end surface is used as a supply path for the assist air. A cutout hole is provided in the partition wall, and the end of the pintle is inserted into the hole, and the outer periphery of the insertion portion is formed. And a first portion formed on the upper surface of the partition wall so as to be closest to the lower end surface, and surrounds the periphery of the hole. On the outer part A fuel injection valve, comprising: a second portion formed so as to be further away from the lower end surface, and assist air is allowed to flow from the second portion to the first portion.