JP2003328894A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent exfoliation of a surface layer due to difference in hardness relative to a base material, and improve durability by providing the surface layer on the base material via an inner face layer and a gradient layer. <P>SOLUTION: A core cylinder 5, a valve seat member 6, a valve element 8, and the like are installed in a valve casing 1, and when an electromagnetic coil 15 is energized, an anchor part 9 is attracted by the core cylinder 5 to open the valve element 8. An inner face layer 19 composed of chromium, a gradient layer 20 gradually changing from chromium to chromium nitride via chromium dinitride; and a core protective film 18 having a surface layer 21 composed of chromium nitride. An anchor protection film 22 is similarly formed on a contact end face 9C of the anchor part 9. Thereby, the contact end faces 5C, 9C can be protected by the surface layers 21, 25, and exfoliation of the surface layers 21, 25 can be prevented by the inner face layers 19, 23 and the gradient layers 20, 24. <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 valve preferably used for injecting fuel into an automobile engine or the like.

[0002]

2. Description of the Related Art Generally, a fuel injection valve used in, for example, an automobile engine injects fuel supplied to a fuel passage toward the inside of an intake pipe of the engine by opening a valve body by an electromagnetic coil or the like. To do. A conventional fuel injection valve having such a configuration is known, for example, from Japanese Patent Laid-Open No. 2000-8990.

The above-mentioned conventional fuel injection valve has a valve casing having a fuel passage inside, a core cylinder formed of a magnetic material in a cylindrical shape and provided in the valve casing, and the valve casing. A valve seat member provided with a valve seat surrounding the injection port and a displaceable member provided in the fuel passage of the valve casing are attracted to the core cylinder by energizing the electromagnetic coil to be attracted to the core seat. It is generally constituted by a valve body that is separated from the valve seat.

Here, when the fuel injection valve is closed, the end face of the anchor portion forming a part of the valve body and the end face of the core cylinder face each other with an axial gap. Then, when the injection valve is opened, the anchor portion of the valve body is adsorbed to the core cylinder, so that the end surface of the valve body collides with the end surface of the core cylinder, and these are in contact with each other. In this case, since the anchor portion of the valve body repeatedly collides with the core cylinder every time the injection valve opens, deterioration such as wear and damage easily occurs on these end faces.

Therefore, in the prior art, a hard coating made of, for example, chrome nitride (chromium mononitride = CrN) or the like is formed on the end portion of the core portion and the anchor portion formed of a magnetic material such as electromagnetic stainless steel. Is provided, the wear resistance is further enhanced.

[0006]

By the way, in the above-mentioned prior art, by providing a hard coating such as chrome nitride on the end face of the anchor portion and the core cylinder, these end faces are protected and wear resistance is improved. It is configured to increase.

However, the anchor portion and the core tube, which are the base material when forming the film, are formed by using a magnetic metal material such as electromagnetic stainless steel, which has a Vickers hardness of about 100 to 300 Hv. It is a relatively soft material. On the other hand, since the chromium nitride coating has a high hardness of, for example, about 1000 to 2500 Hv, there is a large hardness difference between the base material and the coating.

For this reason, in the prior art, it is difficult to improve the adhesion of the coating to the anchor portion and the core cylinder, and when the injection valve is used, while the anchor portion and the core cylinder repeatedly collide, these The coating may peel off from the end faces. As a result, in the injection valve, the core cylinder and the valve body are easily worn and damaged at the peeled portion of the coating, and the peeled coating may be clogged in the injection valve as foreign matter. There is a problem that it is difficult to improve sex.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to stably adhere a hard coating to a relatively soft material such as a core cylinder or a valve body. The present invention provides a fuel injection valve capable of reliably protecting the contact portion between the core cylinder and the valve element for a long period of time, and improving durability and reliability.

[0010]

In order to solve the above-mentioned problems, the invention of claim 1 is arranged in the valve casing so as to be displaceable, and the electromagnetic coil is energized to be attracted to the core cylinder so that the valve seat member In a fuel injection valve having a valve body that is separated from a valve seat, the valve body and the core cylinder have contact portions that contact each other when the valve body is adsorbed by the core cylinder, and the valve body and the core cylinder contact each other. An inner surface layer formed of chrome (Cr) to cover the surface of the contact portion at the contact portion between the contact portion and the core tube, and chromium to chromium dinitride (C) provided to cover the inner surface layer.
A structure is provided in which a graded layer that gradually changes to chromium mononitride (CrN) via rN ₂ ) and a surface layer that is formed using the chromium mononitride and covers the graded layer are provided. .

With this structure, the composition of the components contained between the relatively soft inner surface layer made of chromium and the hard surface layer made of chromium mononitride is changed from chromium to chromium dinitride. It is possible to dispose a graded layer that gradually changes to chromium nitride and to gradually change the hardness thereof. As a result, the inner surface layer made of metal can be stably adhered to the abutting portion of the core cylinder or the valve body, and the surface side of the inner surface layer is provided with the surface through the inclined layer. The layers can be joined stably.

Therefore, even when the abutting portion of the valve body repeatedly collides with the abutting portion of the core cylinder, these abutting portions can be protected by the surface layer for a long period of time, and the durability thereof can be improved. At the same time, the inner surface layer and the inclined layer can surely prevent the surface layer from peeling off from the core cylinder or the valve body having the different hardness.

According to the second aspect of the present invention, the valve body and the core cylinder have an abutment portion that abuts each other when the valve body is adsorbed to the core cylinder. At the contact portion of the core cylinder, an inner surface layer formed of titanium (Ti) and covering the surface of the contact portion, and a titanium dinitride (TiN ₂ ) layer covering the inner surface layer are provided. It is configured such that a graded layer that gradually changes to titanium mononitride (TiN) through it and a surface layer that is formed using the titanium mononitride and covers the graded layer are provided.

As a result, even if titanium, titanium dinitride or titanium mononitride is used, the inner surface layer, the graded layer and the surface layer can be successively formed with high hardness.

[0015]

DETAILED DESCRIPTION OF THE INVENTION A fuel injection valve according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

1 to 7 show a first embodiment, and in this embodiment, a fuel injection valve used in an automobile engine or the like will be described as an example.

Reference numeral 1 denotes a valve casing which forms an outer shell of a fuel injection valve. The valve casing 1 includes a magnetic cylinder 2 and a yoke 1 which will be described later.
3, a resin cover 16 and the like are included.

Reference numeral 2 denotes a stepped cylindrical magnetic cylinder which constitutes the main body of the valve casing 1. The magnetic cylinder 2 is shown in FIGS.
As shown in FIG. 3, it is made of a magnetic stainless material or the like, and is formed as a stepped thin metal pipe. The magnetic cylindrical body 2 has a large diameter portion 2A located on one side in the axial direction, a medium diameter portion 2B formed by reducing the diameter on the other side in the axial direction of the large diameter portion 2A, and the medium diameter. A small diameter portion 2C formed by reducing the diameter on the other side in the axial direction of the portion 2B, and the small diameter portion 2C.
And a thin annular magnetic resistance increasing portion 2D formed in the axially intermediate portion thereof. In this case, the magnetic resistance increasing portion 2D is arranged so as to surround the gap S between the valve body 8 and the core cylinder 5 described later, and the closed magnetic path H described later is short-circuited by the small diameter portion 2C at the position of the gap S. To prevent it.

Reference numeral 3 denotes a fuel passage provided in the magnetic cylindrical body 2. In the fuel passage 3, one end side of the large diameter portion 2A of the magnetic cylindrical body 2 serves as a fuel inlet, and from this inlet, a core cylinder described later is formed. 5, it extends in the axial direction to the position of the valve seat member 6 through the inside of the valve body 8 and the like. A fuel filter 4 for cleaning the fuel is attached to the large diameter portion 2A on the inlet side.

Reference numeral 5 denotes a core cylinder provided inside the magnetic cylinder 2 by means such as press fitting. The core cylinder 5 is made of a magnetic metal material such as electromagnetic stainless steel as shown in FIGS. 2 and 3. It is formed in a tubular shape and has a hardness (Vickers hardness) of, for example, about 100 to 300 Hv. The core cylinder 5 has a large-diameter press-fitting portion 5A that is press-fitted into the medium-diameter portion 2B of the magnetic cylinder 2, and a reduced-diameter extension from the large-diameter press-fitting portion 5A toward the small-diameter portion 2C of the magnetic cylinder 2. It is configured to include a small-diameter sleeve portion 5B that defines the valve opening position of the valve body 8.

Here, the tip surface of the small-diameter sleeve portion 5B (the end surface located on the downstream side of the fuel passage 3) is in contact with the anchor portion 9 when the valve body 8 is closed as shown in FIG. 9C
And an abutting end surface 5C on the core cylinder 5 side facing each other with a gap S in the axial direction sandwiched therebetween.
Are contact portions that come into contact with each other when they are attracted to the core cylinder 5. For this reason, a core protection film 18 described later is provided on the contact end surface 5C of the core cylinder 5, and an anchor protection film 22 is provided on the contact end surface 9C of the anchor portion 9.

Reference numeral 6 denotes a cylindrical valve seat member which is located on the downstream side of the core cylinder 5 and provided in the small-diameter portion 2C of the magnetic cylindrical body 2. The valve seat member 6 has a valve seat member 6 as shown in FIG. An injection port 6A for injecting the fuel in the fuel passage 3 to the outside and a substantially conical valve seat 6B formed so as to surround the injection port 6A are provided. Further, a nozzle plate 7 having a plurality of nozzle holes 7A formed therein is fixed to the tip end surface of the valve seat member 6 at a position covering the injection port 6A.

Reference numeral 8 denotes a valve body which is located between the core cylinder 5 and the valve seat member 6 and is accommodated in the small-diameter portion 2C of the magnetic cylinder body 2 so as to be displaceable in the axial direction. As shown in FIG. 6, for example, a stepped tubular anchor portion 9 made of a magnetic metal material or the like is formed to extend in the axial direction, and is fixed to the tip end portion of the anchor portion 9 and seated on the valve seat 6B of the valve seat member 6. It is constituted by a spherical valve portion 10 that performs

Here, the anchor portion 9 is a cylinder having an adsorbing portion 9A located on the upstream side of the fuel passage 3, a diameter reduced from the adsorbing portion 9A and extending to the downstream side, and a valve portion 10 fixed to the tip portion. And a shaft portion 9B having a shape. And
The end surface of the adsorption portion 9A located on the upstream side of the fuel passage 3 becomes the contact end surface 9C on the side of the anchor portion 9 that contacts the contact end surface 5C of the core cylinder 5 when the valve body 8 opens, and the corresponding contact surface 9C.
Are covered with an anchor protection film 22. Also, the shaft portion 9
In B, an oil passage hole 9D forming a part of the fuel passage 3 is formed in the radial direction.

The valve body 8 has an electromagnetic coil 15 which will be described later.
The valve portion 10 is held in a state of being seated on the valve seat 6B of the valve seat member 6 by the spring force of the valve spring 11 when power is not supplied to the valve seat member 6. Further, when power is supplied to the electromagnetic coil 15, the attraction portion 9A of the anchor portion 9 is magnetically attracted to the core cylinder 5 against the spring force of the valve spring 11, and the valve portion 10 of the valve seat member 6 has a valve seat 6B. The valve opens after being separated from.

Reference numeral 11 denotes a valve spring provided in the magnetic cylindrical body 2. The valve spring 11 has a cylindrical spring bearing 12 press-fitted and fixed in the core cylinder 5, and a valve body 8 (anchor portion 9). ) Adsorption part 9
It is arranged in a compressed state between A and A and always urges the valve element 8 in the valve closing direction.

Reference numeral 13 denotes a stepped tubular yoke provided on the outer peripheral side of the magnetic tubular body 2. The yoke 13 is made of, for example, a magnetic metal material or the like, and has a radially enlarged tubular portion that covers the electromagnetic coil 15 from the outside in the radial direction. 13A and a diameter-reduced cylinder portion 13B that is formed on the other end side of the diameter-enlarged cylinder portion 13A with a reduced diameter and is fixed to the outer peripheral side of the small-diameter portion 2C of the magnetic cylinder 2. Further, a substantially C-shaped connecting core 14 that magnetically connects the enlarged diameter cylindrical portion 13A and the medium diameter portion 2B of the magnetic cylindrical body 2 is provided.

Reference numeral 15 denotes a medium diameter portion 2B of the magnetic cylinder 2 and the yoke 1.
An electromagnetic coil provided between the expanded diameter cylindrical portion 3A of 3 and
The electromagnetic coil 15 forms a closed magnetic circuit H by being supplied with power from the outside, and opens the valve body 8 magnetically.

Reference numeral 16 denotes a resin cover provided on the outer peripheral side of the large-diameter portion 2A of the magnetic cylinder 2, and the resin cover 16 has the yoke 13, the connecting core 14, the electromagnetic coil 15 and the like attached to the magnetic cylinder 2. In this state, it is formed by means of injection molding or the like. Further, the resin cover 16 is integrally formed with a connector 17 for supplying power to the electromagnetic coil 15.

When electric power is supplied to the electromagnetic coil 15 by using the connector 17, a closed magnetic circuit H (shown by a dotted line in FIG. 2) is formed by the core cylinder 5, the anchor portion 9, the yoke 13, etc. When the anchor portion 9 is adsorbed to the core cylinder 5, the valve body 8 opens. At this time, the contact end surface 9C of the anchor portion 9 is configured to contact the contact end surface 5C of the core cylinder 5 via the protective films 18 and 22 described later.

Reference numeral 18 denotes an annular core protective film provided on the abutting end surface 5C of the core cylinder 5. The core protective film 18 is a multi-layered film having at least three layers as shown in FIGS. It is formed and includes an inner surface layer 19, a gradient layer 20 and a surface layer 21, which will be described later.

The inner surface layer 19 is the innermost layer of the three layers of the core protective film 18, and the inner surface layer 19 is made of chromium (C).
r) or other metallic material, for example 400 to 500 Hv
It has a degree of hardness. Then, the inner surface layer 19 is directly fixed to the abutting end surface 5C of the core cylinder 5 by means of, for example, a sputtering method, a plating treatment or the like, and almost covers the surface thereof. In this case, the inner surface layer 19 is made of metal and the core cylinder 5, and has a hardness relatively close to that of the core cylinder 5. Therefore, the inner surface layer 19 stably adheres to the surface of the abutting end surface 5C, and these have high adhesion.

Reference numeral 20 denotes an inclined layer disposed between the inner surface layer 19 and the surface layer 21, and the inclined layer 20 is formed so that the composition of the contained components changes in an inclined manner with respect to the thickness direction. , Its main component is chromium to chromium dinitride (CrN ₂ ).
The structure is such that it changes in a gradual manner to chromium mononitride (CrN) via

Then, the graded layer 20 is fixed to the surface of the inner surface layer 19 by means of, for example, a sputtering method or the like, and almost covers the surface. As shown in FIG. 5, the two layers including the inner surface layer 19 and the inclined layer 20 are formed to have a thickness t1 of, for example, about 1 to 15 μm. Also,
The hardness of the gradient layer 20 is in the range of, for example, about 500 to 1000 Hv, and gradually increases from the inner surface layer 19 toward the surface layer 21.

In this case, the portion of the inclined layer 20 located on the inner surface layer 19 side is formed relatively soft with, for example, chromium as a main component, and the portion at the middle layer position is formed with, for example, chromium dinitride as a main component. For example, chromium mononitride or the like is the main component, and the portion located on the surface layer 21 side is formed to be harder. That is, the graded layer 20 changes from the inside to the outside as shown in the following chemical formula 1.

[0036]

[Chemical formula 1] Cr → CrN ₂ → CrN

As a result, the gradient layer 20 has a structure in which the inner surface layer 19 and the surface layer 21 are bonded to each other with high strength and the adhesion between them is enhanced.

Reference numeral 21 denotes a surface layer disposed on the outermost side of the three layers of the core protective film 18. The surface layer 21 is made of chromium mononitride (chromium nitride) which is harder than chromium dinitride and the like. It has a hardness of about 1000 to 2500 Hv. The surface layer 21 is fixed to the surface of the gradient layer 20 by a method such as a sputtering method, and is, for example, 1-10.
The surface of the graded layer 20 is almost covered with a thickness t2 of about .mu.m, preferably about 3 .mu.m.

As a result, the core protective film 18 becomes the inner surface layer 1
The hardness gradually increases in the order of 9, the graded layer 20, and the surface layer 21. Therefore, in the present embodiment, the surface layer 21
Through the inner surface layer 19 and the inclined layer 20 through the soft core tube 5
Can be stably fixed to the contact end surface 5C of the contact end surface 5C.
The surface layer 21 and the like can protect the from the collision with the anchor portion 9.

On the other hand, 22 is an annular anchor protection film provided on the abutting end surface 9C of the anchor portion 9 of the valve body 8. The anchor protection film 22 is, as shown in FIGS. Almost similarly to the above, the inner layer 23, the gradient layer 24, and the surface layer 25, which will be described later, are included.

Reference numeral 23 is an inner surface layer of the anchor protection film 22, and the inner surface layer 23 is made of a metal material such as chrome having a hardness of about 400 to 500 Hv, and is fixed directly to the contact end surface 9C of the anchor portion 9. There is. Further, the inner surface layer 23, which is made of metal and the anchor portion 9, is in stable contact with the surface of the contact end surface 9C.

Reference numeral 24 denotes a gradient layer which is disposed in close contact between the inner surface layer 23 and the surface layer 25. The gradient layer 24 has a composition similar to that of the gradient layer 20 of the core protective film 18, for example, the composition of contained components. Is formed so as to change in an inclined manner with respect to the thickness direction, and the main component thereof changes in an inclination from chromium to chromium mononitride via chromium dinitride. The gradient layer 24 is fixed to the surface of the inner surface layer 23, and the thickness of the two layers including the inner surface layer 23 and the gradient layer 24 is, for example, about 1 to 15 μm.

The graded layer 24 is, for example, 500 to 10
The hardness is about 00 Hv, and the hardness gradually increases from the inner surface layer 23 to the surface layer 25. Thereby, the gradient layer 24 joins the inner surface layer 23 and the surface layer 25 with high strength and enhances the adhesiveness between them.

Reference numeral 25 is a surface layer of the anchor protection film 22, and the surface layer 25 is made of chromium mononitride or the like, for example, 1000
It has a hardness of about 2500 Hv. The surface layer 25 is fixed to the surface of the inclined layer 24 and has a thickness of 1 to 10 μm, for example.
It has a thickness t2 of about m, preferably about 3 μm.

As a result, the hardness of the anchor protection film 22 gradually increases in the order of the inner surface layer 23, the inclined layer 24, and the surface layer 25, so that the surface layer 25 becomes the contact end surface 9C of the soft anchor portion 9. It can be stably fixed, and the contact end surface 9C can be protected by the surface layer 25 and the like from collision with the core cylinder 5.

The fuel injection valve according to the present embodiment has the above-mentioned structure, and its operation will be described below.

First, when power is supplied to the electromagnetic coil 15, the small diameter portion 2C of the magnetic cylinder 2 is magnetically cut off at the position of the magnetic resistance increasing portion 2D. The closed magnetic circuit H is passed through the cylinder 5, the suction portion 9A of the valve body 8 (anchor portion 9), the yoke 13, the connecting core 14, and the like.
Can be stably formed, and the closed magnetic path H passes through the gap S between the anchor portion 9 and the core tube 5. As a result, the valve body 8 is
The anchor portion 9 is magnetically attracted by the core cylinder 5 and is axially displaced against the valve spring 11, whereby the valve portion 10 opens. As a result, the fuel supplied into the fuel passage 3 is injected from the injection port 6A of the valve seat member 6 toward the intake pipe of the engine or the like.

On the other hand, when the power supply to the electromagnetic coil 15 is stopped, the valve portion 10 is caused by the spring force of the valve spring 11 to cause the valve seat member 6 to move.
6A, the injection port 6A is closed (valve closed).

Here, when the valve body 8 opens, since the anchor portion 9 of the valve body 8 is adsorbed by the core cylinder 5, its abutting end surface 9C collides with the abutting end surface 5C of the core cylinder 5. Then, these collisions are repeated every time the valve body 8 is opened.

However, the surface layer 21 of the core protective film 18 is stably adhered to the abutting end surface 5C of the core tube 5 via the inner surface layer 19 and the inclined layer 20, and the abutting end surface 9C of the anchor portion 9 is formed. Since the surface layer 25 of the anchor protection film 22 is in close contact with the inner surface layer 23 and the inclined layer 24 in a stable manner, the contact end surfaces 5C and 9C can be protected from collision and the surface layer 21 , 25 can be prevented from peeling from the contact end surfaces 5C, 9C.

Thus, according to the present embodiment, the core end surface 5C of the core tube 5 is provided with the core protective film 18 including the inner surface layer 19, the inclined layer 20 and the surface layer 21, and the anchor portion 9 abuts. An anchor protection film 22 including an inner surface layer 23, an inclined layer 24, and a surface layer 25 is provided on the end surface 9C.

As a result, the inner surface layer 19 made of metal can be stably adhered to the abutting end surface 5C of the core cylinder 5, and the surface side thereof is changed from chromium to chromium mononitride via chromium dinitride. The graded layer 20 that changes in a grade can be closely attached. As a result, the surface layer 21 made of chromium mononitride can be stably fixed to the abutting end surface 5C of the core cylinder 5 through the inner surface layer 19 and the inclined layer 20. A strong bond can be formed between the layer 21 and
The adhesiveness of these can be enhanced.

Further, the surface layer 25 is surely fixed to the abutting end surface 9C of the anchor portion 9 through the inner surface layer 23 of the anchor protection film 22 and the inclined layer 24, similarly to the case of the core cylinder 5. be able to.

Therefore, even when the abutting end surface 9C of the anchor portion 9 repeatedly collides with the abutting end surface 5C of the core cylinder 5, the abutting end surfaces 5C and 9C are formed by the surface layers 21 and 25 for a long period of time. It is possible to protect and prevent the core cylinder 5 and the anchor portion 9 from being worn early.

Then, the surface layers 21 and 25 are peeled off from the core cylinder 5 and the anchor portion 9 having different hardnesses from each other.
3 and the inclined layers 20 and 24 can surely prevent the foreign matter such as the peeled protective films 18 and 22 from clogging the injection valve, so that durability and reliability can be improved.

Next, FIG. 8 shows a second embodiment according to the present invention, and the feature of this embodiment is that titanium and its nitride are used instead of chromium and its nitride. . In addition, in the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

Reference numeral 31 denotes an annular core protection film provided on the abutting end surface 5C of the core cylinder 5. The core protection film 31 has a multi-layer structure having at least three layers as in the first embodiment. An inner layer 32 and a gradient layer 3 which will be described later and are formed as a film
3 and the surface layer 34.

Reference numeral 32 denotes an inner surface layer of the core protective film 31, which is made of a metal material such as titanium (Ti) and has a hardness of, for example, about 400 to 500 Hv. Then, the inner surface layer 32 is directly fixed to the abutting end surface 5C of the core cylinder 5 by means such as sputtering or plating.
It almost covers the surface. In this case, the inner surface layer 32 is
As in the case of the inner surface layer 19 according to the first embodiment, since the core tube 5 and the metal are metal, the contact end surface 5C thereof is
It is in close contact with.

Reference numeral 33 denotes a graded layer which is disposed in close contact with the inner surface layer 32 and the surface layer 34, and the graded layer 33 has, for example, a composition of contained components that changes in a gradient with respect to the thickness direction. Formed from titanium to titanium dinitride (T
It has a configuration in which it is inclined to titanium mononitride (TiN) via iN ₂ ).

The gradient layer 33 is fixed to the surface of the inner surface layer 32 by means of, for example, the sputtering method, and almost covers the surface. Further, the thickness dimension of the two layers including the inner surface layer 32 and the inclined layer 33 is formed to be, for example, about 1 to 15 μm. The hardness of the graded layer 33 is in the range of, for example, about 500 to 1000 Hv, and the inner surface layer 32 is
To the surface layer 34 gradually increases.

In this case, the portion of the inclined layer 33 located on the inner surface layer 32 side is formed relatively soft with titanium or the like as the main component, and the portion at the middle layer position is formed with titanium dinitride or the like as the main component. The part formed on the surface layer 34 side is slightly harder, and for example, titanium mononitride or the like is the main component, and the part is further hardened. That is, the graded layer 33 changes from the inner side to the outer side as in the following formula (2).

[0062]

[Chemical formula 2] Ti → TiN ₂ → TiN

As a result, the gradient layer 33 joins the inner surface layer 32 and the surface layer 34 with high strength and enhances the adhesion between them.

Reference numeral 34 is a surface layer which constitutes an outer portion of the core protective film 31, and the surface layer 34 is made of titanium mononitride (TiN) or the like which is harder than titanium dinitride.
It has a hardness of about 2500 Hv. The surface layer 34 is fixed to the surface of the gradient layer 33 by a method such as a sputtering method and is, for example, about 1 to 10 μm, preferably 3 μm.
The surface of the gradient layer 33 is covered with a thickness of about m. As a result, the hardness of the core protective film 31 gradually increases in the order of the inner surface layer 32, the inclined layer 33, and the surface layer 34.

On the other hand, in the present embodiment, the contact surface 9C of the anchor portion 9 of the valve body 8 is also made of titanium and its nitride, and is used in the same manner as the core protection film 31. (Not shown).

Thus, in this embodiment having such a configuration, it is possible to obtain substantially the same operational effects as those of the first embodiment. That is, the surface layer 34 of the core protective film 31 can be stably fixed to the abutting end surface 5C of the soft core tube 5 via the inner surface layer 32 and the inclined layer 33, and the abutting end surface 5C is formed by the surface layer 34 and the like. It can be protected from a collision with the anchor portion 9. Moreover, the contact end surface 9C of the anchor portion 9 can be protected by the anchor protection film.

Further, by using titanium and its nitride as the core protective film 31, the material of the protective film 31 and the like can be appropriately selected according to the material of the core cylinder 5 and the anchor portion 9, and the degree of freedom in design can be increased. You can

[Brief description of drawings]

FIG. 1 is a sectional view showing a fuel injection valve according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing an enlarged tip side of a fuel injection valve.

FIG. 3 is an enlarged cross-sectional view showing a core cylinder alone.

FIG. 4 is an enlarged cross-sectional view of a main part of a core protective film and the like showing an enlarged part a in FIG.

5 is an enlarged cross-sectional view of a main part in FIG. 4 showing an inner surface layer, a gradient layer and a surface layer of a core protective film in an enlarged manner.

FIG. 6 is an enlarged sectional view showing the valve body alone.

FIG. 7 is an enlarged cross-sectional view of a main part of an anchor protection film and the like showing an enlarged part b in FIG.

FIG. 8 is an enlarged sectional view of an essential part of the core protection film of the fuel injection valve according to the second embodiment of the present invention, viewed from the same position as in FIG.

[Explanation of symbols]

1 valve casing 2 Magnetic cylinder 3 fuel passage 5 core tube 5C, 9C Contact end face (contact part) 6 valve seat member 6A injection port 6B valve seat 8 valve 11 valve spring 15 Electromagnetic coil 18,31 Core protective film 19,23,32 inner layer 20, 24, 33 graded layer 21,25,34 surface layer 22 Anchor protective film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomokazu Misawa             1370 Onna, Atsugi, Kanagawa             Nissia Jex (72) Inventor Nobutake Ishii             1370 Onna, Atsugi, Kanagawa             Nissia Jex F term (reference) 3G066 AD07 BA47 BA48 BA49 CC06U                       CC15 CD21 CE22 CE34

Claims (2)

[Claims] 1. A valve casing having an internal fuel passage, a core cylinder formed of a magnetic material in a cylindrical shape and provided in the valve casing, and a valve seat provided in the valve casing and surrounding an injection port. A valve seat member formed and a valve element displaceably provided in the fuel passage of the valve casing and attracted to the core cylinder by energizing an electromagnetic coil to separate from the valve seat of the valve seat member. In the fuel injection valve provided, the valve body and the core cylinder have contact portions that contact each other when the valve body is adsorbed to the core cylinder, and the contact portion of the valve body and the core cylinder contact each other. An inner surface layer formed of chromium (Cr) at the contact portion and covering the surface of the contact portion, and an inner surface layer provided over the inner surface layer and containing chromium dinitride (CrN ₂ ) and chromium mononitride. A graded layer that gradually changes to (CrN), and the mononitride A fuel injection valve comprising a surface layer formed of chrome and covering the inclined layer. 2. A valve casing having a fuel passage inside, a core cylinder formed of a magnetic material in a tubular shape and provided in the valve casing, and a valve seat provided in the valve casing and surrounding an injection port. A valve seat member formed and a valve element displaceably provided in the fuel passage of the valve casing and attracted to the core cylinder by energizing an electromagnetic coil to separate from the valve seat of the valve seat member. In the fuel injection valve provided, the valve body and the core cylinder have contact portions that contact each other when the valve body is adsorbed to the core cylinder, and the contact portion of the valve body and the core cylinder contact each other. An inner surface layer formed of titanium (Ti) at the contact portion and covering the surface of the contact portion, and titanium mononitride provided from the titanium through titanium dinitride (TiN ₂ ) to cover the inner surface layer. A graded layer that gradually changes to (TiN), and the mononitride A fuel injection valve comprising a surface layer formed of titanium and covering the inclined layer.