JP2003314412A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injector which reduces the rate of change of a fuel injection amount even if the contact part of a valve member is worn, in a structure where the contact part of the valve member is seated on the conical surface of a valve body in a protruded curved shape. <P>SOLUTION: The valve body 12 comprises, on an inner peripheral wall, the conical surface 13 reduced in diameter toward an injection hole 14 side in fuel flow direction. The valve member 20 comprises, at the injection hole 14 side end part, the contact part 21 seated on the conical surface 13. The contact surface of the contact part 21 seated on the conical surface 13 is formed in the protruded curved shape 22 forming a part of a spherical surface. The center O of the radius r of the protruded curved shape 22 is positioned on the side of the valve member 20 apart from the center axis 100 thereof as viewed from the contact position of the protruded curved shape 22 coming into contact with the conical surface 13. The radius of the protruded curved shape 22 of the contact part 21 is not determined by a seat diameter ds and the seat angle θ of the conical surface 13, and the radius center is set larger than the spherical surface on the center axis 100. A cylindrical surface 23 is extended from the end of the protruded curved shape on the upstream side of fuel to an anti-injection hole side along the center axis 100 of the valve member 20. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device (hereinafter referred to as "fuel injection device") that reduces the rate of change of the fuel injection amount even if the contact portion of the valve member seated on the conical surface of the valve body is worn.
Is called an injector).

[0002]

2. Description of the Related Art A conical surface having a diameter reduced in a fuel flow direction toward an injection hole is provided on an inner peripheral wall of a valve body, and a contact portion of a valve member is seated on the conical surface to interrupt fuel injection from the injection hole. Then
An injector that injects fuel from an injection hole by separating from a conical surface is known. As the shape of the abutting portion seated on the conical surface of the valve body, for example, a corner formed by the tapered surfaces (hereinafter, a “corner formed by the tapered surfaces” is simply called a corner), A spherical shape is known as disclosed in JP-A 8-218973.

In FIGS. 4A and 4B, the conical surface 20
2 shows the injector seated on the convex curved surface 214. The tip of the valve member disclosed in Japanese Patent Laid-Open No. 8-218973 is spherical and the entire tip is spherical, but the entire tip of the valve member 210 is not spherical. However, the convex curved surface 214 forms a part when the entire tip of the valve member 210 is spherical. Since the spherical center of the spherical surface of the valve member tip portion formed in a spherical shape is on the central axis of the valve member, the radial center O of the convex curved surface 214 is also on the central axis 220 of the valve member 210. Since the convex curved surface 214 constitutes a part of the spherical surface, the convex curved surface 214
The radius r of is determined by the seat diameter ds and the seat angle θ of the conical surface 202.

When the valve member is separated from the conical surface, the throttle position of the opening flow path formed between the conical surface and the contact portion is the seat position where the distance between the contact portion and the conical surface is the minimum. However, the flow passage area of the opening flow passage formed annularly in the circumferential direction is determined at the minimum. As shown in FIG.
Convex curved surface 214 formed on the contact portion 212 of the valve member 210
In the injector that abuts on the conical surface 202 formed on the inner peripheral wall of the valve body 200, the conical surface 202 and the abutting part 212 when the abutting part 212 separates from the conical surface 202.
When the seat diameter is the same, the throttling position of the open flow passage formed between and depends on the angle of the corner, but compared to the injector that abuts the conical surface at the corner, the fuel upstream side, that is, the valve member 210. It is generally separated from the central axis 220 of the. Therefore, if the lift amount is the same, the contact area of the valve member having a spherical surface has a larger flow passage area at the throttle position than the corner portion.

Further, the increasing rate of the flow passage area from the throttle position toward the upstream side and the downstream side is larger when the contact portion is spherical than at the corner portion. The flow path resistance of the opening flow path formed between the surface and the contact portion is smaller when the contact portion is spherical than at the corner portion.
If the lift amount and the seat diameter are the same, the pressure loss of the opening flow path is smaller than that of the contact portion having a spherical shape having a corner portion, and the fuel injection pressure injected from the injection hole increases. Therefore, the fuel can be atomized and injected.

[0006]

In the injector shown in FIG. 4, when the abutting portion 212 is repeatedly seated on and away from the conical surface 202, the abutting portion 212 abuts as shown by the chain double-dashed line in FIG. 4B. The part 212 wears. Then, with respect to the wear amount δ, the throttle position of the opening flow path formed between the conical surface 202 and the contact portion 212 moves toward the fuel downstream side, that is, the central shaft 220 side, and the maximum lift amount of the valve member 210 increases. growing. When the wear amount δ of the contact portion 212 increases, the fuel flow rate flowing between the contact portion 212 and the conical surface 202, that is, the fuel injection amount injected from the injection hole 204 changes compared to before the wear. An object of the present invention is to provide an injector in which the contact portion of the valve member is seated on the conical surface of the valve body with a convex curved surface and the rate of change in fuel injection amount is small even if the contact portion wears. .

[0007]

According to the injector of the first aspect of the present invention, the contact surface of the contact portion of the valve member seated on the conical surface of the valve body is a convex curved surface. Since the fuel injection pressure is higher than that of the injector with the corner seated on the conical surface, the fuel injected from the injection hole can be atomized.

Further, the radius center of the convex curved surface at the contact position with the conical surface is located on the far side from the center axis of the valve member when viewed from the contact position. That is, when the seat diameter when the convex surface is seated on the conical surface and the seat angle formed by the conical surface are the same, the convex surface is more convex than the spherical surface whose radial center is located on the central axis of the valve member. Has a large radius. The radius of the convex curved surface is set regardless of the seat diameter and the seat angle.

When the radius of the convex curved surface that abuts the conical surface becomes large, even if the abutting portion wears due to the valve member repeatedly sitting on and leaving the conical surface, the amount of change in the lift amount of the valve member is small. Become. In addition, when the abutting portion moves away from the conical surface when the throttle position of the opening channel formed between the abutting portion and the conical surface moves due to abrasion of the abutting portion, the radius of the convex curved surface Becomes larger, the movement amount of the diaphragm position becomes smaller. Therefore, if the wear amount of the abutting portion is the same, the larger the radius of the convex curved surface is, the lower the flow rate of the fuel flowing through the opening channel, that is, the change rate of the fuel injection amount can be reduced. Here, the rate of change of the fuel flow rate or the fuel injection amount represents the ratio of the amount of increase or decrease of the fuel flow rate or the fuel injection amount that has changed due to wear to the fuel flow rate or the fuel injection amount before wear. Further, by increasing the radius of the convex curved surface, the gap formed between the convex curved surface and the conical surface becomes smaller, so that it becomes difficult for foreign matter to be caught between the convex curved surface and the conical surface. Therefore, it is possible to prevent the fuel from leaking between the valve member and the valve body due to the foreign matter being caught.

According to the injector of claim 2 of the present invention, the rate of change of the fuel flow rate flowing through the opening flow path formed between the contact portion and the conical surface before and after wear is 3%.
The radius of the convex curved surface is set as follows. Therefore, the change rate of the fuel injection amount is small even after wear.

If the radius of the convex curved surface of the contact portion is increased, the lift amount and the change amount of the throttle position in the opening flow path due to wear are reduced, and the change rate of the fuel injection amount can be reduced. However, if the radius of the convex curved surface of the contact portion is increased and the rate of change of the fuel injection amount is reduced too much, the flow resistance of the opening flow path increases and the pressure loss increases. Then, the fuel injection pressure is lowered, and atomization of the injected fuel is impaired. According to the injector of claim 3 of the present invention, the radius of the convex curved surface is set so that the rate of change of the fuel flow rate flowing through the opening channel before and after wear is 1% or more and 3% or less. In addition, the rate of change of the fuel injection amount is reduced and the decrease of the fuel injection pressure is prevented. Therefore, the injected fuel can be atomized.

According to the injector of claim 4 of the present invention, the valve member has a cylindrical surface extending from the fuel upstream end of the convex curved surface toward the non-injection hole side along the central axis direction of the valve member. When the outer diameter is D and the radius of the convex curved surface is r, 0.53D ≦
r. By increasing the radius of the convex curved surface, the change rate of the fuel injection amount can be reduced even if the contact portion is worn.

According to the injector of the fifth aspect of the present invention, the valve member has a cylindrical surface extending from the fuel upstream end of the convex curved surface toward the non-injection hole side along the central axis direction of the valve member. When the outer diameter is D and the radius of the convex curved surface is r, 0.53D ≦
r ≦ D. By setting the maximum value of the radius of the convex curved surface, it is possible to prevent the fuel injection pressure from decreasing. Therefore, the injected fuel can be atomized.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. An injector according to one embodiment of the present invention is shown in FIG. The valve body 12 is fixed to the inner wall of the fuel injection side end of the valve housing 16 by welding. The valve body 12 has a conical surface 13 on its inner peripheral wall whose diameter decreases toward the injection hole 14 side in the fuel flow direction. As shown in FIG. 1, the valve member 20 includes an abutting portion 2 that is seated on the conical surface 13.
1 is provided at the end of the injection hole 14 side. When the contact portion 21 is seated on the conical surface 13, the fuel injection from the injection hole 14 is cut off,
When the contact portion 21 is separated from the conical surface 13, the fuel is injected from the injection hole 14.

The contact surface of the contact portion 21 seated on the conical surface 13 is a convex curved surface 22 forming a part of a spherical surface. Therefore, the curvatures of the entire convex curved surface 22 are equal. The center O of the radius r of the convex curved surface 22 is located on the other side of the central axis 100 of the valve member 20 when viewed from the contact position of the convex curved surface 22 that contacts the conical surface 13. The radius of the convex curved surface 22 is larger than that in the case where the tip of the valve member on the injection hole side is spherical. A cylindrical surface 23 extends from the fuel upstream end of the convex curved surface 22 along the central axis 100 of the valve member 20 to the side opposite to the injection hole.

As shown in FIG. 2, the tubular member 30 is inserted into the inner peripheral wall of the valve housing 16 on the side opposite to the injection hole and is fixed to the valve housing 16 by welding. The tubular member 30 has the injection hole 1
From the 4 side, the first magnetic tube portion 32, the non-magnetic tube portion 34, and the second
It is composed of a magnetic tube portion 36. The non-magnetic tubular portion 34 prevents a magnetic short circuit between the first magnetic tubular portion 32 and the second magnetic tubular portion 36.

The movable core 40 is formed of a magnetic material in a cylindrical shape and is fixed to the end portion 24 of the valve member 20 on the side opposite to the injection hole by welding. The movable core 40 reciprocates together with the valve member 20. Outflow hole 4 that penetrates the cylindrical wall of the movable core 40
2 forms a fuel passage that communicates the inside and the outside of the cylinder of the movable core 40.

The fixed core 44 is formed of a magnetic material in a cylindrical shape. The fixed core 44 is inserted into the tubular member 30, and is fixed to the tubular member 30 by welding. The fixed core 44 is installed on the side opposite to the injection hole with respect to the movable core 40 and faces the movable core 40.

The adjusting pipe 46 is the fixed core 4
4 is press-fitted to form a fuel passage therein. The spring 48 is locked to the adjusting pipe 46 at one end and to the movable core 40 at the other end. By adjusting the press-fitting amount of the adjusting pipe 46,
The load of the spring 48 applied to the movable core 40 can be changed. The movable core 40 and the valve member 20 are biased toward the conical surface 13 by the biasing force of the spring 48.

The coil 50 is wound around a spool 52. The terminal 55 is insert-molded to the connector 54 and is electrically connected to the coil 50. When the coil 50 is energized, a magnetic attraction force acts between the movable core 40 and the fixed core 44, and the movable core 40 is attracted to the fixed core 44 side against the biasing force of the spring 48.

The filter 60 is installed on the fuel upstream side of the fixed core 44 and removes foreign matters in the fuel supplied to the injector 10. The fuel that has flowed into the fixed core 44 through the filter 60 has a fuel passage in the adjusting pipe 46, a fuel passage in the movable core 40, and an outflow hole 42.
It passes between the inner peripheral wall of the valve housing 16 and the outer peripheral wall of the valve member 20 sequentially. When the valve member 20 separates from the conical surface 13, the fuel passes through the opening flow path formed between the contact portion 21 and the conical surface 13 and is guided to the injection hole 14.

By energizing the coil 50 intermittently and intermittently injecting the injector 10, the abutting portion 21 repeats sitting on and leaving the conical surface 13. As a result, the contact portion 21 is worn. When the contact portion 21 wears, the valve member 2
As the lift amount of 0 increases, the throttle position of the opening channel moves to the fuel downstream side, so that the flow rate of fuel flowing through the opening channel, that is, the fuel injection amount changes. However, the contact portion 2
The radius r of the convex curved surface 22 of No. 1 is not determined by the seat diameter ds and the seat angle θ of the conical surface 13, and is set larger than the spherical surface having the radius center O on the central axis 100. The rate of change of the flow rate of the fuel flowing through the opening flow path, that is, the rate of change of the fuel injection amount is reduced with respect to the wear amount of

The radius r of the convex curved surface 22 when the sheet diameter ds is 1.4 mm and the outer diameter D of the cylindrical surface 23 is 1.5 mm.
FIG. 3 shows the relationship between the flow rate of the fuel flowing through the opening channel and the rate of change of the fuel flow rate. It can be seen that the change rate of the fuel flow rate decreases as the radius r increases. It is desirable that 0.53D ≦ r so that the rate of change is 3% or less.

When the radius r of the convex curved surface 22 is increased, the rate of change of the fuel flow rate is reduced, but the flow passage resistance of the open flow passage is increased and the fuel injection pressure is reduced. In order to suppress the decrease in the fuel injection pressure while suppressing the decrease in the fuel flow rate change rate, it is desirable that the fuel flow rate change rate be 1% or more and 3% or less.

In the present embodiment, by increasing the radius of the convex curved surface 22, the gap formed between the convex curved surface 22 and the conical surface 13 becomes smaller, so that the convex curved surface 22 and the conical surface 13 are formed.
It becomes difficult for foreign matter to get caught between Therefore, it is possible to prevent the fuel from leaking between the valve member 20 and the valve body 12 due to the foreign matter being caught. In this embodiment,
The convex curved surface 22 forms a part of a spherical surface, and the curvatures of the entire convex curved surface 22 are equal, but may be convex curved surfaces having different curvatures.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the vicinity of a nozzle hole of an injector according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an injector according to the present embodiment.

FIG. 3 is a characteristic diagram showing a relationship between a sheet diameter and a flow rate change rate in the present embodiment.

FIG. 4 is a cross-sectional view showing the vicinity of a nozzle hole of a conventional injector.

[Explanation of symbols]

10 Injector (fuel injection device) 12 valve body 13 conical surface 14 injection holes 20 valve members 21 Contact part 22 Convex curved surface 40 movable cores 44 fixed core

Claims (5)

[Claims] 1. A valve body having a conical surface that reduces in diameter in the direction of fuel flow toward the injection hole, and a valve body that is seated on the conical surface to close the injection hole and separated from the conical surface to cause the injection. A valve member having a contact portion that opens a hole, wherein the contact surface of the contact portion seated on the conical surface is a convex curved surface, and the contact position with the conical surface The fuel injection device is characterized in that the radius center of the convex curved surface in is located at a position beyond the central axis of the valve member when viewed from the contact position. 2. The abutting portion wears due to repeated seating and separation from the conical surface, and changes in the fuel flow rate flowing between the abutting portion and the conical surface before and after the abrasion. The fuel injection device according to claim 1, wherein the radius of the convex curved surface is set so that the ratio is 3% or less. 3. The abutting portion wears due to repeated seating on and away from the conical surface, and changes in the fuel flow rate flowing between the abutting portion and the conical surface before and after abrasion. The fuel injection device according to claim 2, wherein the radius of the convex curved surface is set so that the ratio is 1% or more and 3% or less. 4. The valve member has a cylindrical surface extending from the fuel upstream side end of the convex curved surface toward the non-injection hole side along the central axis direction of the valve member, and the outer diameter of the cylindrical surface is D. The fuel injection device according to claim 1, wherein 0.53D ≦ r, where r is the radius of the convex curved surface. 5. The fuel injection device according to claim 4, wherein 0.53D ≦ r ≦ D.