JP2001090628A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform heat treatment effectively in a state that a needle valve and a movable iron core of a fuel injection valve are integrated. SOLUTION: A needle valve 16 and a movable iron core 24 of a fuel injection valve are integrally formed of different sintered metal material and simultaneously sintered. The needle valve 16 is formed of sintered metal material (i.e., SUS440C, SUS420J2) capable of providing predetermined hardness by heat treatment, and the movable iron core 24 is formed of sintered metal material (i.e., SUS410L, SUS430L) capable of maintaining predetermine magnetic properties even when exposed to a temperature of heat treatment for the needle valve. Thus, even when the intergraded sintered product of the needle valve 16 and the movable iron core 24 is heat-treated, the magnetic properties of the movable iron core 24 are not degraded and wear-resistance can be improved by improving surface strength of the needle valve 16 by heat treatment.

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 in which a valve element and a movable iron core are integrated and heat-treated.

[0002]

2. Description of the Related Art In a conventional fuel injection valve, a movable iron core of an electromagnet for driving a valve body (needle valve) is formed of a magnetic material, and the valve body is made of a metal material such as stainless steel having high wear resistance. It was formed by machining, and the valve body and the movable iron core were integrated by welding. However, precision machining of the valve body and welding where high positioning accuracy is required,
It requires a complicated and complicated processing / welding technique, has a disadvantage of low production efficiency and high cost.

Therefore, in recent years, the productivity of fuel injection valves has been improved.
For the purpose of cost reduction, as disclosed in Japanese Patent Application Laid-Open No. H10-115381, it has been proposed to integrally mold a valve body and a movable iron core with raw materials of different sintered metal materials and simultaneously sinter them. .

[0004]

By the way, during operation of the engine, the valve body of the fuel injection valve needs to have high hardness (abrasion resistance) because it repeatedly collides with the valve seat. on the other hand,
Since the movable iron core forms a magnetic circuit, good magnetic properties are required. For this reason, in the above-mentioned publication, a material whose hardness is increased by heat treatment is used for the sintered metal material forming the valve body, and a magnetic material is used for the sintered metal material forming the movable core, and both are integrally formed. In the heat treatment step after forming and simultaneous sintering, only the valve element is partially heat-treated so as not to deteriorate the magnetic characteristics of the movable iron core.

Generally, in a heat treatment step, a metal part is placed in a furnace for heat treatment and heated to perform heat treatment. Therefore, as described in the above-mentioned publication, the valve body of the integrally sintered product of the valve body and the movable iron core is used. If only the heat treatment is partially performed, separate work is required to enclose the movable core with heat insulating material to prevent the movable core from being exposed to the heat treatment temperature, and to remove the heat insulating material from the movable core after the heat treatment. Required
There is a disadvantage that the efficiency of the heat treatment is reduced, the productivity is reduced and the cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and accordingly, it is an object of the present invention to provide a fuel injection valve capable of efficiently performing heat treatment in a state where a valve element and a movable iron core are integrated. Is to do.

[0007]

According to a first aspect of the present invention, there is provided a fuel injection valve, wherein a valve body is formed of a metal material having a predetermined hardness by heat treatment;
The movable core is formed of a metal material capable of maintaining predetermined magnetic characteristics even when exposed to a heat treatment temperature, and heat treatment is performed in a state where the two are integrated. In this case, since the movable core is formed of a metal material capable of maintaining predetermined magnetic characteristics even when exposed to a heat treatment temperature, even if the entire movable core is heat-treated in a state where the movable core and the valve element are integrated, the movable core is movable. The magnetic properties of the iron core do not deteriorate. This eliminates the need to wrap the movable iron core with heat insulating material in the heat treatment process, and allows the integrated body of the movable iron core and the valve element to be placed in a heat treatment furnace as it is and heat-treated efficiently to improve productivity. It can be improved and cost can be reduced. In addition, the surface hardness of the valve body can be increased by the heat treatment to improve the wear resistance, and the magnetic characteristics of the movable iron core can be maintained well after the heat treatment.

The present invention is also applicable to a structure in which the movable iron core and the valve element are separately formed and integrated by welding or the like. It may be possible to integrally mold the raw material of the binding metal material and simultaneously sinter it. In this way, the valve element and the movable iron core can be integrally and efficiently manufactured by molding and sintering the sintered metal material, so that it is necessary to perform precision machining of the valve element and welding that requires high positioning accuracy. Therefore, the effects of improving productivity and reducing costs can be enhanced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. Main body 10 of fuel injection valve
Is a pipe-shaped fixed core 11 made of a magnetic material.
And a non-magnetic pipe portion 12 formed of a non-magnetic material;
The valve body 13 formed of a magnetic material is connected by welding or the like. A fuel filter 14 for filtering fuel sent from a delivery pipe (not shown) is mounted on the inner peripheral side of the upper part of the fixed iron core 11. Furthermore,
A pipe-shaped adjuster 15 is provided on the inner peripheral side of the fixed iron core 11.
Is press-fitted, and a needle valve 1
A spring 17 for urging the valve 6 (valve element) in the valve closing direction (downward) is mounted.

A valve seat 19 is fixed to a lower portion of the valve body 13 that accommodates the needle valve 16 by welding or the like. An injection port 20 formed at the center of the valve seat 19 is provided at the lower end of the needle valve 16. It is opened and closed by the formed seal part 21. Outside the valve seat 19, a seat holder 18 is fixed by welding or the like, and an injection hole plate 22 is provided between the valve seat 19 and the seat holder 18.
Is sandwiched. The injection holes formed in the injection hole plate 22 are exposed downward from the opening 23 on the bottom surface of the sheet holder 18. The valve seat 19 also functions as a valve holder that slidably supports sliding protrusions 32 formed at a plurality of locations on the outer periphery of the lower portion of the needle valve 16.

A cylindrical movable iron core 24 is integrally formed on the upper end of the needle valve 16 as described later, and this movable iron core 24 is urged in a valve closing direction by a spring 17 in the fixed iron core 11. Have been. A plurality of fuel passages 50 (see FIG. 2B) penetrating vertically are formed on the inner peripheral side of the movable core 24. When the collision portion 34 of the needle valve 16 comes into contact with the lower surface of the stopper 33 fixed in the valve body 13, the upper limit position of the needle valve 16 (the upper limit position of the movable iron core 24) is regulated. The fuel that has passed through the fuel filter 14 flows from the inner diameter of the adjuster 15 and the spring 17 into the valve body 13 through the fuel passage 50 of the movable iron core 24, and from the inside of the valve body 13 to the through hole 33 a of the stopper 33 and the needle valve 16 flows into the injection port 20 side through the gap between the sliding projections 32.

On the other hand, on the outer peripheral portion of the main body housing 10,
A molded coil 25 is fitted and mounted so as to cover the non-magnetic pipe portion 12 and its peripheral portion. The molded coil 25 is obtained by winding a coil 27 around a spool 26 made of resin and molding the coil 27 into a cylindrical shape with an insulating resin 28. An upper end and a lower end of the magnetic housing 29 covering the molded coil 25 are fixed to the fixed iron core 11 and the valve body 13 by welding, caulking or the like, respectively. A connector housing 30 is integrally formed with the molded coil 25, and a terminal 31 connected to the coil 27 is insert-molded inside the connector housing 30.

In this case, when the power to the coil 27 is turned off, the movable iron core 24 is moved in the valve closing direction by the spring 17, and the seal portion 2 of the needle valve 16 is moved.
1 is kept in a state in which the injection port 20 is closed by contacting the valve seat 19.

Thereafter, when energization of the coil 27 is started, the magnetic circuit is switched to the magnetic housing 29, the fixed core 11, and so on.
Movable iron core 24: Valve body 13: Magnetic housing 29
When a magnetic flux flows through this magnetic circuit, a magnetic attraction force is generated between the fixed iron core 11 and the movable iron core 24, and the movable iron core 24 is sucked upward, and the needle valve 1
6 seal part 21 is separated from the valve seat 19 to open the injection port 20. Thereby, the fuel in the valve body 13 is injected from the injection holes of the injection hole plate 22.

The above-described needle valve 16 and movable iron core 2
No. 4 is integrally molded with raw materials (mixture of metal powder and binder) of different sintered metal materials and is simultaneously sintered. In this case, the needle valve 16 is made of a nonmagnetic sintered metal material (for example, S
US440C, SUS420J2).
On the other hand, the movable iron core 24 has magnetic characteristics (relatively high magnetic permeability) necessary for forming a magnetic circuit, and can maintain predetermined magnetic characteristics even when exposed to the heat treatment temperature of the needle valve 16. Bonding metal material (for example, SUS410L, S
US430L). In addition, since the needle valve 16 and the movable iron core 24 are simultaneously sintered, it is necessary to select a sintered metal material that can be sintered at substantially the same sintering temperature. If the sintering temperatures of the two are close to each other, the sintering state of the two becomes good even if they are simultaneously sintered, and a stable joining strength can be obtained.

In the molding step, first, the needle valve 16
And one of the movable iron cores 24 is formed from the raw material of the sintered metal material, and then the remaining portion is formed integrally with the previously formed portion using the raw material of the different sintered metal material, and in the next degreasing step, After the molded body is heated and degreased (debindered) at, for example, 500 to 600 ° C., the process proceeds to a sintering process, and is performed, for example, at 130 ° C.
Simultaneous sintering at about 0 ° C and integration.

In the heat treatment step after the simultaneous sintering, the integrally sintered product of the needle valve 16 and the movable core 24 is placed in a furnace for heat treatment, heated at, for example, 1000 ° C., and then rapidly cooled.
Thereby, the needle valve 16 is heat-treated, the hardness and strength of the needle valve 16 are increased, and the wear resistance is improved.

In this case, since the movable core 24 is formed of a metal material capable of maintaining predetermined magnetic characteristics even when exposed to the heat treatment temperature of the needle valve 16, the needle valve 16 and the movable core 24 are integrally sintered. Even if the entire product is heat-treated, the magnetic characteristics of the movable iron core 24 do not deteriorate. For this reason,
In the heat treatment step, an integrally sintered product of the needle valve 16 and the movable iron core 24 can be put into a heat treatment furnace as it is, and heat treatment can be performed efficiently, and productivity can be improved.
Cost can be reduced. In addition, the heat treatment can increase the surface hardness of the needle valve 16 to improve the wear resistance, and can maintain the magnetic characteristics of the movable core 24 well even after the heat treatment, which is required for the needle valve 16 and the movable core 24. Both characteristics can be satisfied.

Further, in this embodiment, the needle valve 1
6 and the movable iron core 24 are integrally molded from raw materials of different sintered metal materials and are simultaneously sintered. Therefore, the needle valve 16 and the movable iron core 24 are formed by molding and sintering the sintered metal material. Can be manufactured efficiently, and there is no need to perform precision machining of the needle valve 16 or welding that requires high positioning accuracy, and the effects of improving productivity and reducing costs can be enhanced. However, the present invention is also applicable to a case where the needle valve 16 and the movable iron core 24 are separately formed and integrated by welding or the like.

In order to improve the responsiveness of the valve opening operation of the fuel injection valve, it is better to increase the rise of the magnetic attraction force immediately after the coil 27 is energized.
After the magnetic core 4 is attracted to the fixed core 11, if the magnetic attraction force is large, the timing at which the movable core 24 separates from the fixed core 11 during the valve closing operation (during demagnetization) is delayed, and the responsiveness of the valve closing operation is reduced. become worse. Therefore, in order to improve the responsiveness of the valve closing operation, the movable iron core 24 is magnetically saturated after the movable iron core 24 is attracted to the fixed iron core 11 so that the magnetic attractive force (saturated attractive force) is obtained.
Need to be suppressed.

In the conventional fuel injection valve, the movable iron core is formed of a magnetic material having high magnetic permeability (such as PB permalloy).
In order to suppress the saturated suction force, it is necessary to form a magnetic throttle portion on the movable iron core, which complicates the shape of the movable iron core and increases the manufacturing cost.

In this regard, in the present embodiment, the movable iron core 24
Is formed of a sintered metal material (SUS410L, SUS430L) having a lower magnetic permeability than that of the conventional PB permalloy, so that the saturation attraction force can be suppressed without forming a magnetic throttle portion on the movable iron core 24. As a matter of course, the magnetic attraction required at the time of opening the valve can be secured. This makes it possible to simplify the shape of the movable iron core 24 and reduce the manufacturing cost while ensuring the responsiveness of the valve opening / closing operation.

However, the movable iron core 24 may be formed of a magnetic material having a higher magnetic permeability than SUS410L and SUS430L as long as the magnetic characteristics do not deteriorate at the heat treatment temperature of the needle valve 16. The intended purpose of the invention can be sufficiently achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a fuel injection valve showing one embodiment of the present invention.

FIG. 2A is a cross-sectional view taken along the line BB of FIG. 2B, in which the needle valve and the movable iron core are partially cut away, and FIG.
AA sectional view of

[Explanation of symbols]

11: fixed iron core, 16: needle valve (valve element), 19
... Valve seat, 20 ... Injection port, 21 ... Seal part, 24
… Movable iron core, 25… mold coil, 27… coil.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F16K 31/06 385 F16K 31/06 385A (72) Inventor Isao Makino 1-1-1, Showa-cho, Kariya-shi, Aichi Co., Ltd. Inside DENSO (72) Inventor Hideo Kiuchi 1-1-1 Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 3G066 BA19 BA46 BA49 BA54 BA61 CC06U CC14 CC24 CC26 CD21 CE24 CE26 CE31 3H106 DA13 DA23 DB02 DB12 DB23 DB32 DC02 DD02 EE35 GA16 GB11 JJ02 JJ03 JJ05 KK18

Claims (2)

[Claims] 1. A fuel injection valve provided with a valve element for opening and closing an injection port and a movable iron core for driving the valve element, wherein the valve element is formed of a metal material capable of obtaining a predetermined hardness by heat treatment. The movable iron core is formed of a metal material capable of maintaining predetermined magnetic characteristics even when exposed to the heat treatment temperature of the valve element, and both are heat-treated in an integrated state. Fuel injection valve. 2. The fuel injection valve according to claim 1, wherein the valve element and the movable iron core are integrally formed of raw materials of different sintered metal materials and are simultaneously sintered.