JPH07122424B2 - Fuel injection valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection valve used for metering fuel and supplying it to an internal combustion engine.

[Conventional technology]

Among the conventional fuel injection valves, the type in which the needle valve penetrating the valve case body moves axially outward and its end is separated from the opening edge of the valve case body to inject fuel to the outside,
The amount of fuel injected to reach the gap between the needle valve and the inner wall of the valve case is adjusted by adjusting the gap area and the moving amount of the needle valve.

Here, the movement amount of the needle valve is carried out by selecting the thickness of the inset type shim forming a part of the valve case body and changing the length of the valve case body (for example, the actual opening number 54-16).
9619).

[Problems to be solved by the invention]

However, as shown in FIG. 5, for example, the cross section of the gap 20 between the body 1 having the inner diameter d ₁ = 4 mm and the needle valve 2 having the diameter d ₂ which constitutes the valve case body is annular, and the flow passage area S ₁ = 0.
To make it 2 mm ² , the needle valve 2 must be machined so that d ₁ −d ₂ ≈ 32 μm. Therefore, even if an error of 1% is expected in the amount of fuel metered by the cross-sectional area S ₁ , the diameter error is 0.32 μm, and extremely difficult precision machining is required for the body 1 and needle valve 2. Therefore, it was not possible to fully cope with the accuracy of metering.

In order to eliminate such a problem, the present invention does not give a metering function to the gap between the needle valve having a large diameter and the valve case body, and has a diameter which does not require so much precision machining for fuel metering. An object of the present invention is to provide a fuel injection valve having a structure having small metering holes.

[Means for solving problems]

For this reason, in the present invention, the hollow portion of the valve case body is bypassed and bored in this valve case body, and flows into the gap between the wall surface of the hollow portion after completion of this bypass and the needle valve penetrated into this hollow portion. The fuel injection valve has a metering hole having a diameter smaller than that of the hollow portion for metering the fuel to be used.

[Action]

As a result, the fuel reaching the gap between the needle valve and the inner wall of the valve case is metered by the metering hole, and when the needle valve moves to the outside, the flow rate is further reduced by the amount of movement and is injected to the outside. .

Since the diameter of the metering hole is small and the error range of its cross-sectional area is small without performing extremely precise machining, accurate machining can be realized by easy machining.

〔Example〕

FIG. 1 shows a first embodiment according to the present invention. The fuel injection valve as a whole is mainly composed of a substantially hollow cylindrical case portion, which is made of a soft magnetic material in a hollow body 1. The first case 61 tightly coupled and the second, third, and fourth cases 62, 63, and 64 made of a non-magnetic material, and the first, second, and third cases 61, 62, and 63. The spaces are joined by welding, and the third and fourth cases 63, 64 are joined by brazing. First case 61 having an L-shaped cross section
A ring-shaped coil 7 wound around a ring-shaped bobbin 7a is fitted in the outer peripheral portion of the, and a cover 8 is provided on the outer side of the coil 7, which is connected to the first case 61 by tightening. There is. A connector 9 having a connector pin 9a for covering the fourth case 64 and a part of the cover 8 and connecting to the power source of the coil 7 is formed by injection molding of resin.

A cylindrical movable core 10 is slidably inserted in the hollow portion of the case portion. The movable core 10 can smoothly reciprocate in the axial direction in the second and third cases 62 and 63. A through hole 10a is formed in the movable core 10 in the axial direction, and a pressing piece 10b made of a non-magnetic metal material is press-fit into the through hole 10a.

The cross section of the pressing piece 10b and the movable core 10 has four fuel passages formed in the gap between the pressing piece 10b and the movable core 10 by utilizing the through holes 10a as shown in FIG. 2, and the pressing piece 10b and the movable core 10 are integrated. It is in contact with the needle valve 2 of FIG.

A hollow cylindrical magnet 11 is fixed inside the first case 61 so as to face the movable core 10, and the needle valve 2 is inserted from the opening edge 1a at the tip of the body 1 into the center of the magnet 11. The rear end portion of the needle valve 2 projects rearward from the rear end surface of the magnet 11 by the moving amount h of the needle valve 2. Therefore, the shim 12 having an appropriate thickness so that the movement amount h becomes a predetermined amount is selected and is interposed between the magnet 11 and the body 1. The body 1, the shim 12, and the magnet 11 constitute a valve case body of the fuel injection valve, and the fuel flows into the gap between the wall surface of these hollow portions and the needle valve 2.

A large diameter portion 2b is formed in the vicinity of the rear end portion of the needle valve 2, and a spring 3 is provided between the ring 4 fitted in the circumferential groove formed in the large diameter portion 2b and the rear end of the body 1. It is attached and presses the needle valve 2 backward. As a result, the tapered surface of the end portion 2a at the tip of the needle valve 2 is seated from the outside on the opening edge 1a of the body 1 formed in a corresponding tapered shape.

The first intermediate portion 2c of the needle valve 2 is formed by a cylindrical surface that slides on the inner wall of the body 1 while keeping the fuel-tightness,
The second intermediate portion 2d also slides on the inner wall of the body 1, but four chamfered portions are formed to allow the fuel to flow.

A fuel filter 15 and an adjustment pipe 14 through which fuel flows are provided in the fourth case 64.
The auxiliary spring 13 that contacts the front end of the movable core 10 presses the rear end of the movable core 10. The pressing force of this auxiliary spring 13 is
Smaller than the opposite direction, the force adjustment changes the position of the adjust pipe with respect to the fourth case 64 back and forth,
The dynamic injection amount of this valve is determined to be the specified value, and the fourth
It is fixed to the fourth case 64 by crushing the case 64 from the outside.

The fuel supplied from the fuel filter 15 side of the fuel injection valve passes through the adjust pipe 14 into the fourth and third cases 64 and 63, and then through the through hole 10a of the movable core 10 to the magnet 11 and the shim 12.
And the needle valve 2 and the rear end of the body 1, and the path up to this point is the first fuel passage 21a.

From the rear end of the body 1 to the first intermediate portion 2c of the needle valve 2.
A circular metering hole 16 is formed in the body 1 by bypassing, and the metering fuel is supplied to the second fuel passage 21b downstream of the intermediate portion 2c, that is, the gap between the needle valve 2 and the body 1 after the bypass is completed. The needle valve 2 is fed into the injection port 17 which is closed by the seating of the end 2a of the needle valve 2 against the opening edge 1a of the body 1. The cross-sectional area of the metering hole 16 is smaller than the minimum flow cross-sectional area of the second fuel passage 21b.

Now, when an exciting current is passed through the coil 7, the movable core 10 and the magnet 11
An attractive force due to the electromagnetic force of the coil 7 acts between them, and when this attractive force exceeds the combined force between the spring 3 and the auxiliary spring 13, the movable core 10 is attracted and moved to the magnet 11, and the pressing piece 10a moves the needle valve 2 The rear end is pushed to overcome the movement amount h and come into contact with the magnet 11. Therefore, the needle valve 2 opens the injection port 17 and the metering fuel is injected to the outside.

The injection amount of this fuel injection valve is determined by the cross-sectional area of the metering hole 16 and the area of the gap when the injection port 17 is opened. It can be moved by adjusting the selection. For the former,
As shown in FIG. 3 showing the AA cross section in the metering hole 16 of FIG. 1, when it is desired to process the sectional area S ₂ of the metering hole 16 to 0.4 mm ² , its diameter d ₃ = 0.5 mm. You can do it. Therefore, the error of the metering hole 16 when the error of 1% is expected in the injection amount corresponds to 5 μm. Therefore, compared to the conventional configuration shown in FIG. 5, the injection amount can be adjusted more easily by machining a circular metering hole with a smaller diameter.
16 can be performed with high accuracy.

Although the first intermediate portion 2c of the needle valve 2 was kept in a hermetically sealed state with the inner wall of the body 1, even if there was a gap for fuel to flow in this portion, the flow passage cross-sectional area could be adjusted. If the sum of the sectional area of the metering hole 16 is smaller than the minimum channel sectional area of the second fuel passage 21b, the metering by the metering hole 16 can be sufficiently realized.

Further, the number of the metering holes 16 is not limited to one, and a plurality of holes may be formed.

FIG. 4 shows a second embodiment according to the present invention, in which the needle valve 2 is shorter and thinner than the first embodiment. The spring 3, one end of which abuts on the ring 4 of the needle valve 2,
It is provided on the outer periphery of the needle valve 2 and is fitted into a stopper 18 that constitutes the valve case body together with the body 1, shim 12, and magnet 11, and the other end is indicated by the protrusion of the stopper 18.
The stopper 18 is provided between the hollow magnet 11 and the first fuel passage.
21a is in contact with a shim 12 that adjusts the distance between the body 1 and the magnet 11, and the fuel in the fuel passage 21a flows into the notch 12a of the shim 12. The needle valve 2 slides on the stopper 18 and the inner wall of the body 1, and a chamfered portion 2d into which fuel flows and a tapered end portion 2a are formed at the tip thereof. A circular metering hole 16 connecting the cutout 2a and the chamfered portion 2d is provided in the body 1.

As in the second embodiment, the fuel metering hole 16 may be guided to the vicinity of the injection port portion 17.

In addition, the electromagnetic force of the coil 7 is not used to drive the needle valve 2,
Hydraulic pressure or the like may be used.

〔The invention's effect〕

As described above, according to the present invention, the gap between the needle valve and the valve case body has no fuel metering function, and the fuel metering is performed by the metering hole formed in the valve case body.
Since this metering hole has a smaller diameter than the hollow portion of the valve case body, it is possible to improve the metering accuracy without precision processing, and accurate fuel metering is realized.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a fuel injection valve of a first embodiment according to the present invention, and FIG. 2 is a movable core 10 and a pressing piece in FIG.
10b is a transverse sectional view, FIG. 3 is an enlarged transverse sectional view taken along the line AA of FIG. 1, and FIG. 4 is a longitudinal sectional view of the fuel injection valve of the second embodiment according to the present invention. FIG. 6 is a cross-sectional view of a fuel metering portion of a conventional fuel injection valve. 1, 11, 12, 18 ... Body forming valve case body, magnet, shim, stopper, 1a ... Opening edge, 2 ... Needle valve, 2a ... End, 16
… Metering holes.

Claims (1)

[Claims] 1. A needle valve, which is penetrated into a hollow portion of a valve case body, and in which fuel is flowing into a gap between the hollow portion and a wall surface of the valve case body, is moved in an axial direction, and an end portion of the needle valve is formed into the valve case body. In a fuel injection valve that injects the fuel to the outside by separating from the opening edge of the valve, the hollow portion of the valve case body is bypassed, and the hole is formed in the valve case. A fuel injection valve having a metering hole having a diameter smaller than that of the hollow portion for metering the fuel flowing into the gap with the needle valve.