JP2004293312A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an opening and closing seating sound, and to enhance the abrasion resistance of a seating surface. <P>SOLUTION: This fuel injection valve is constituted by coating the upper end surface of an anchor (a valve element upper member) 31 of a fuel injection valve of an internal combustion engine with a rubber layer 51, and coating the surface of the rubber layer 51 with a flexible DCL (diamond-like carbon) layer 52, and thereby reduces a sound generated at seating time to the lower end surface of a cylindrical core member 4 of an electromagnetic coil when opening a valve, and high abrasion resistance can be provided, and swelling of the rubber layer can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection valve for an internal combustion engine or the like, and more particularly to a technique for reducing a collision sound at the time of opening and closing a valve body to reduce radiated sound to the outside.
[0002]
[Prior art]
2. Description of the Related Art In general, in a fuel injection valve of an internal combustion engine or the like, a valve element which is urged by a return spring and seated on a valve seat is lifted by an electromagnetic actuator to open the valve (see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Unexamined Patent Publication No. 2002-534638
[Problems to be solved by the invention]
In such a fuel injection valve, a collision sound is generated when the valve body is opened and closed, specifically, a collision sound is generated when the valve is closed and a valve seat (or a connected body thereof) is collided with a stopper. The collision sound and the vibration caused by the collision propagate through the constituent members and are radiated from the hard resin molded to cover the casing, thereby forming a noise source.
[0005]
Further, since the metal valve element and the valve seat come into direct contact with each other when the valve is closed, it is difficult to ensure the sealing performance.
Then, it is common practice to coat the valve body with a rubber layer by molding and baking. However, the valve lift of the fuel injection valve is generally around 100 microns, but when the rubber layer is thick, the rubber swells with fuel, the valve lift changes, and the fuel injection amount changes. . Further, when the rubber layer is made thin, the rubber layer is worn by friction with a valve seat when the valve is closed, and is easily damaged.
[0006]
The present invention has been made in view of such conventional problems, and it is possible to reduce a collision at the time of opening and closing the valve body, effectively reduce the sound radiated to the outside, and maintain a constant valve body lift amount. It is an object of the present invention to provide a fuel injection valve which can maintain such a function for a long period of time without changing the fuel injection amount while maintaining the above-mentioned function by the wear resistance of the collision surface.
[0007]
[Means for Solving the Problems]
Therefore, the present invention provides a fuel injection valve for an internal combustion engine or the like, in which a rubber layer is coated on a seating surface of a valve body when the valve is opened and closed, and the surface of the rubber layer has flexibility such as DLC (diamond-like carbon). It is configured to be coated with a layer.
[0008]
With such a configuration, the rubber layer reduces the collision at the time of seating the valve body and can reduce the collision noise, and the DLC layer has a small friction coefficient and abrasion resistance, so that the abrasion of the seating surface is suppressed, As a result, the inner rubber layer can be made thin, so that the valve lift is kept constant and the fuel injection amount is not changed, and the rubber layer can be prevented from contacting the fuel and swelling of the rubber layer.
[0009]
Further, by adopting a configuration in which the rubber layer and the DLC layer are coated on the seating surface with the valve seat member when the valve body is closed, the smoothness of the surface of the DLC layer having flexibility and the elasticity of the rubber layer are improved. A simple valve closing seal function is obtained.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example used for a fuel injection valve of an internal combustion engine (gasoline engine) according to the first embodiment.
[0011]
An electromagnetic coil 2 is fixed to the outside of a cylindrical casing 1 made of a magnetic material (metal), and a valve body in which a cylindrical anchor 31 and a ball 32 are welded and integrated inside the casing 1. 3 is slidably inserted in the axial direction. The lower peripheral wall of the anchor 31 is provided with a fuel passage hole 31a. The ball 32 has a plurality of flat surfaces 32a cut on the peripheral side.
[0012]
A cylindrical core member 4 is fixed to the inner wall of the casing 1 with a predetermined clearance above the valve body 3 (anchor 31) (it will be described based on the positional relationship in the illustrated state; the same applies hereinafter). A cylindrical spring stopper 5 is inserted and fixed in the core member 4, and a return spring 6 is inserted in a compressed state between a lower end of the spring stopper 5 and a stepped portion of the anchor 31, When the electromagnetic coil 2 is not energized, the valve body 3 is seated on the valve seat member 7 by the elastic compression force of the return spring 6 to close the valve.
[0013]
A ball 32 of the valve body 3 is seated on the inside of the lower end of the casing 1 and a valve seat member 7 having an injection port opened at the center is welded to the lower end of the valve seat 3. A nozzle plate 8 having an opening 8a (see FIG. 3) is welded.
[0014]
A cap member 9 is fixed to the outside of the lower end of the casing 1, and the lower end of a coil cover 10 that covers the outside of the electromagnetic coil 2 is welded to the casing 1.
[0015]
A fuel filter 11 is fitted and fixed to the upper end of the casing 1.
A portion from the upper end of the coil cover 10 to the upper end of the casing 1 and a portion excluding the ends of the leads 2a of the electromagnetic coil 2 are molded by injection molding with a resin to form a resin casing 12, and the resin casing 12 is formed. A seal member 13 is inserted between the upper end surface of the casing 12 and the upper end flange surface of the metal casing 1.
[0016]
The resin casing 12 forms a connector portion 12a around the end of the lead 2a of the electromagnetic coil 2.
In the fuel injection valve having such a basic configuration, in the present invention, the following cushioning mechanism is provided on the seating surface when the valve body is opened and closed.
[0017]
FIG. 2 is an enlarged view of part A of FIG.
A rubber layer 51 is coated on the upper end surface of the anchor 31 constituting the upper part of the valve body 3, that is, the seating surface with the lower end surface of the core member 4, and the surface of the rubber layer 51 is coated with a flexible DLC layer ( (Hereinafter referred to as a flexible DLC layer) 52.
[0018]
With this configuration, at the time of opening the valve, the collision when the anchor 31 is seated on the lower end surface of the core member 4 is mitigated by the rubber layer 51, so that the collision noise and, consequently, the radiation noise from the resin casing 12 to the outside can be reduced.
[0019]
In addition, the flexible DLC layer has a small coefficient of friction and abrasion resistance, so that the abrasion of the seating surface is suppressed, and as a result, the inner rubber layer can be made thin, so that the lift amount of the valve body 3 is kept constant. It is not necessary to change the fuel injection amount.
[0020]
FIG. 4 shows an abrasion test of the coated PTFE substrate coated with the flexible DLC layer under a predetermined condition (a SUJ2 ball base material is slid on the PTFE substrate for a predetermined distance at a predetermined speed by applying a predetermined pressure). The results obtained are shown in comparison with the uncoated material.
[0021]
Further, since the rubber layer 51 can be prevented from coming into contact with the fuel to prevent swelling of the rubber layer 51, the above-mentioned buffer function can be maintained for a long period of time while ensuring durability.
The flexible DLC layer can be flexibly deformed integrally with the rubber layer when the rubber layer is elastically deformed. Incidentally, the conventional DLC layer has poor flexibility, and when the rubber layer is elastically deformed, it is cracked and has no durability.
[0022]
Further, the rubber layer can be formed of any of fluorine rubber, fluorosilicone rubber, ethylene propylene rubber and the like.
FIG. 5 shows a comparison of the coefficient of friction between a rubber material coated with the flexible DLC layer and an untreated material. As shown in the figure, it is apparent that even if the rubber material alone has a large friction coefficient, the friction coefficient can be significantly reduced by coating the surface with the flexible DLC, and high wear resistance can be obtained.
[0023]
FIG. 3 is an enlarged view of part B of FIG.
That is, the surface of the ball 32 constituting the valve body 3, at least the portion including the seating surface with the valve seat member 7, is covered with the rubber layer 61, and the surface of the rubber layer 61 is covered with the flexible DLC layer 62. .
[0024]
Thereby, at the time of closing the valve, the collision when the ball 32 is seated on the valve seat member 7 is mitigated by the rubber layer 61, so that the collision noise and the radiation noise to the outside can be reduced. The flexible DLC layer 62 keeps the valve lift constant, does not change the fuel injection amount, prevents swelling of the rubber layer 61, and maintains the buffer function for a long period of time while ensuring durability. The same can be done.
[0025]
In addition, due to the smoothness of the flexible DLC layer 62 having flexibility and the elasticity of the rubber layer 61, a good valve-sealing function can be obtained.
In this embodiment, since the rubber layer and the flexible DLC layer are provided on both the seating surface when the valve is opened and the seating surface when the valve is closed, the seating sound between when the valve is opened and when the valve is closed is reduced. Although the noise reduction effect can be greatly reduced, a configuration in which a rubber layer and a flexible DLC layer are simply applied to only one of them may be used.
[0026]
Further, in the present embodiment, the rubber layer and the flexible DLC layer are formed on the seating surface on the valve body side as a seating surface when the valve body is opened and closed, but the mating seating surface on which the valve body is seated, specifically, The rubber layer and the flexible DLC layer may be provided on the lower end surface of the core member 4 or the seating surface of the valve seat member 7.
[0027]
Further, technical ideas other than the claims that can be grasped from the embodiment will be described below together with their effects.
(A) In the fuel injection valve according to any one of claims 1 to 3, a cylindrical part end face of the valve body abutting on a cylindrical core member end face magnetized by an electromagnetic coil when the valve body is opened, It is characterized by being coated with the rubber layer and the DLC layer.
[0028]
With this configuration, the seating noise at the time of opening the valve can be reduced without changing the valve lift amount and therefore the fuel injection amount, and while suppressing the wear of the seating surface.
(B) In the fuel injection valve according to any one of claims 1 to 3 and (a), the rubber layer is formed of any one of fluoro rubber, fluoro silicone rubber, and ethylene propylene rubber. It is characterized by the following.
[0029]
Thereby, the rubber layer can be formed of any of fluoro rubber, fluorosilicone rubber and ethylene propylene rubber, and the surface of the rubber layer alone is coated with DLC having flexibility even if the friction coefficient is large. , The friction coefficient can be significantly reduced, and high wear resistance can be obtained.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a configuration of a fuel injection valve of an internal combustion engine according to a first embodiment of the present invention.
FIG. 2 is an enlarged view of a portion A in FIG.
FIG. 3 is an enlarged view of a portion B in FIG. 1;
FIG. 4 is a view showing a wear characteristic test result of a flexible DLC.
FIG. 5 is a view showing a coefficient of friction of various rubber materials coated with flexible DLC.
[Explanation of symbols]
2 ... Electromagnetic coil 3 ... Valve 4 ... Core member 6 ... Return spring 7 ... Valve seat member 31 ... Anchor 32 ... Ball 51,61 ... Rubber layer 52,62 ... Flexible DLC layer

Claims (2)

A fuel injection valve characterized in that a rubber layer is coated on a seating surface of a valve body when the valve is opened and closed, and the surface of the rubber layer is coated with a DLC (diamond-like carbon) layer having flexibility. The fuel injection valve according to claim 1, wherein the rubber layer and the DLC layer are coated on a seating surface of the valve body with the valve seat member when the valve body is closed.

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