JP2004300540A - Partial plastic working method for component made of high-hardness magnetic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a partial plastic working method for a component made of a high-hardness magnetic material which easily enables partial plastic working of the component made of the high-hardness magnetic material without deteriorating the original high hardness and magnetic properties in the surrounding area. <P>SOLUTION: When performing the partial plastic working on the components 4 and 12 made of the high-hardness magnetic material, parts 4a and 12b to be subjected to plastic working are heated and converted into a softened area A showing a hardness of ≤HRC20 and a drawing degree of ≥60%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of partially plastic working of a high-hardness magnetic material part used for an electromagnetic fuel injection valve or the like.
[0002]
[Prior art]
It is already known that a magnetic component of an electromagnetic fuel injection valve is made of a ferrite-based high-hardness magnetic material containing 2.5% of Ni, 1% of Al, and 0.1% of Ti, as disclosed in Patent Document 1, for example. ing.
[0003]
[Patent Document 1]
JP-A-2002-4013
[Problems to be solved by the invention]
The ferrite-based high hardness magnetic material is subjected to precipitation hardening heat hardening heat treatment (550 °, 3 h), thereby dispersing and precipitating extremely fine compounds of Ni, Al, and Ti in the crystal. Increases hardness.
[0005]
By the way, such a high-hardness magnetic material has extremely low plastic workability, and an external force is applied to cause plastic deformation, and fracture starts from a compound in a crystal as a starting point. Therefore, conventionally, it has been extremely difficult to join a component made of a high-hardness magnetic material to another component by plastic working such as caulking.
[0006]
The present invention has been made in view of such circumstances, and has been made to facilitate the partial plastic working of a component made of a high-hardness magnetic material without impairing the original high-hardness magnetic properties around it. An object of the present invention is to provide a method of partial plastic working of a part made of a high hardness magnetic material, which is made possible.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method for partially plasticizing a part made of a high-hardness magnetic material, wherein a part to be plastically worked is made into a softened region in which the hardness becomes 20 or less by heating. The feature.
[0008]
The high hardness magnetic material part corresponds to a magnetic cylinder 4 and a movable core 12 of the present invention described later.
[0009]
According to the first feature, it is possible to impart a drawing degree of approximately 60% or more to a part of the high-hardness magnetic material part that requires plastic working, so that the plastic working of the part can be performed easily and reliably. And the surroundings can maintain the original high hardness magnetic properties.
[0010]
According to a second feature of the present invention, in addition to the first feature, the heating is high-frequency heating.
[0011]
According to the second feature, it is possible to clarify the boundary between the original high hardness region and the softened region of the high hardness magnetic material part, and therefore, only the predetermined portion where the plastic working is performed is formed in the softened region. Thus, the original high-hardness magnetic properties can be maintained in portions other than the plastic working portion.
[0012]
Further, according to the present invention, in addition to the first feature, a third feature is that the heating is laser beam heating.
[0013]
This third feature also makes it possible to clarify the boundary between the original hardened region and the softened region of the high-hardness magnetic material part, and therefore, it is possible to form only a predetermined portion where plastic working is performed in the softened region. It is possible to maintain the original high-hardness magnetic properties in portions other than the plastic working portion.
[0014]
Still further, according to the present invention, in addition to the first feature, the high-hardness magnetic material comprises 10 to 20% by weight of Cr, 0.1% by weight of Si, 1% by weight or more of at least one of Al and Ni, and a balance of ferrite. A fourth feature is that the alloy contains Fe, Mn, C, P, and S, and the total of Al and Ni is 1.15 to 6 wt%.
[0015]
According to the fourth feature, it is possible to provide an inexpensive high-hardness magnetic material having good magnetic properties, a high hardness of 20 to 40 HRC without surface hardening, and excellent wear resistance.
[0016]
Still further, according to the present invention, in addition to any one of the first to fourth features, the high-hardness magnetic material is a magnetic cylinder of a valve housing in an electromagnetic fuel injection valve, and a part of the magnetic cylinder includes the magnetic cylinder. A fifth feature is that a softened region is formed and the valve seat member is fixed to the magnetic cylinder by caulking the softened region.
[0017]
According to the fifth feature, in the electromagnetic fuel injection valve, the magnetic cylinder made of a high-hardness magnetic material can be partially caulked, and the valve seat member can be easily and reliably fixed thereto.
[0018]
Still further, according to the present invention, in addition to any one of the first to fourth features, the high-hardness magnetic material is a movable core in an electromagnetic fuel injection valve, and the softened region is formed at an end of the movable core. The sixth feature is that the valve element is fixed to the movable core by caulking the softened region.
[0019]
According to the sixth feature, in the electromagnetic fuel injection valve, the movable core made of a high-hardness magnetic material can be partially caulked, and the valve body can be easily and reliably fixed thereto.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below based on embodiments of the present invention shown in the accompanying drawings.
[0021]
1 is a longitudinal sectional view of an electromagnetic fuel injection valve for an internal combustion engine using a component made of a high hardness magnetic material of the present invention, FIG. 2 is an enlarged view of a part of FIG. 1, and FIG. FIG. 4 is a diagram showing the relationship between the hardness and the degree of drawing and the quality of the caulking connection, and FIG. 4 is a microscopic structure diagram of the periphery of the boundary between the high hardness region and the softened region in the hard magnetic material.
[0022]
First, an electromagnetic fuel injection valve for an internal combustion engine using a component made of a high hardness magnetic material of the present invention will be described with reference to FIGS.
[0023]
A valve housing 2 of an electromagnetic fuel injection valve I for an internal combustion engine includes a cylindrical valve seat member 3 having a valve seat 8 at a front end, and a magnetic cylinder 4 coaxially coupled to a rear end of the valve seat member 3. And a non-magnetic cylinder 6 coaxially coupled to the rear end of the magnetic cylinder 4.
[0024]
The valve seat member 3 has, at its rear end, a connecting cylinder 3a protruding toward the magnetic cylinder 4 with an annular shoulder 3b from the outer peripheral surface thereof, and an annular coupling to the outer peripheral surface of the coupling cylinder 3a. A groove 38 is formed. The connecting cylinder 3a is fitted to the inner peripheral surface of the front end of the magnetic cylinder 4 and is fixed in a liquid-tight manner. The present invention is applied to the fixing method, which will be described later.
[0025]
The magnetic cylinder 4 and the non-magnetic cylinder 6 are coaxially and liquid-tightly joined to each other by laser beam welding over the entire circumference with their facing end faces abutting.
[0026]
The valve seat member 3 has a valve hole 7 opened at the front end surface thereof, a conical valve seat 8 connected to the inner end of the valve hole 7, and a cylindrical guide hole 9 connected to a large diameter portion of the valve seat 8. And An injector plate 10 made of a steel plate having a plurality of fuel injection holes 11 communicating with the valve hole 7 is liquid-tightly welded to the front end surface of the valve seat member 3 in a liquid-tight manner.
[0027]
The fixed core 5 is press-fitted and fixed to the inner peripheral surface of the non-magnetic cylinder 6 from the rear end side in a liquid-tight manner. At this time, a portion that does not fit with the fixed core 5 is left at the front end of the non-magnetic cylinder 6, and the valve assembly V is accommodated in the valve housing 2 extending from the portion to the valve seat member 3.
[0028]
The valve assembly V is connected to a valve body 18 comprising a hemispherical valve part 16 for opening and closing the valve hole 7 in cooperation with the valve seat 8 and a valve rod part 17 for supporting the same, and a valve rod part 17. And a movable core 12 which extends from the magnetic cylinder 4 to the non-magnetic cylinder 6, is inserted therein, and is coaxially opposed to the fixed core 5. The valve rod portion 17 and the movable core 12 are fixed to each other after a stopper element 14 formed coaxially and integrally with the valve rod portion 17 is fitted into a connection hole 36 at the center of the movable core 12. The present invention is also applied to the fixing method, which will be described later.
[0029]
The tip end of the stopper element 14 protrudes from the suction surface 12a of the movable core 12, and is usually opposed to the suction surface 5a of the fixed core 5 with a gap s corresponding to the valve opening stroke of the valve element 18. You. The amount g of protrusion of the stopper element 14 from the suction surface 12a of the movable core 12 is determined by the distance between the suction surfaces 5a and 12a of the fixed core 5 and the movable core 12 when the stopper element 14 contacts the fixed core 5. The air gap g is set so that when the coil 30 is demagnetized from the excited state, the residual magnetic flux between the cores 5 and 12 is quickly eliminated. The end face of the stopper element 14 and the suction surface 12a of the movable core 12 are simultaneously finished by grinding after the stopper element 14 is pressed into the movable core 12. In this manner, the gap s and the air gap g related to each other can be precisely obtained.
[0030]
The valve rod portion 17 is formed to have a diameter sufficiently smaller than the guide hole 9, and its outer peripheral surface protrudes radially outward and is slidably supported on the inner peripheral surface of the guide hole 9. The first guide projection 25a is integrally formed in the vicinity of the valve portion 16.
[0031]
On the outer peripheral surface of the movable core 12, an annular second guide convex portion 25b slidably supported on the inner peripheral surface of the magnetic cylinder 4 is integrally formed. Thus, a gap 37 is provided between the movable core 12 and the magnetic cylinder 4 before and after the second guide projection 25b.
[0032]
The valve assembly V has a vertical hole 19 starting from the end face of the stopper element 14 and reaching a dead end beyond the spherical center O of the hemispherical valve portion 16, and this vertical hole 19 is connected to the valve portion by the first guide convex portion 25a. The first horizontal hole 20a and the vertical hole 19 communicating with the outer peripheral surface of the valve rod portion 17 closer to 16 are connected to the second horizontal hole 20b and the vertical hole 19 communicating with the outer peripheral surface of the second guide projection 25b. A third lateral hole 20c communicating with the outer peripheral surface of the valve rod portion 17 at the center between the movable core 12 and the first guide convex portion 25a is provided. At this time, the first horizontal hole 20 a is formed in the valve rod portion 17, and the number thereof is at least two orthogonal to the vertical hole 19. The second horizontal hole 20b is formed from the movable core 12 to the stopper element 14, and the number of the second horizontal hole 20b is at least two orthogonal to the vertical hole 19. The diameter d of the second lateral hole 20b is set to be larger than the axial width w of the second guide projection 25b.
[0033]
In the middle of the vertical hole 19, an annular spring seat 24 facing the fixed core 5 side is formed.
[0034]
The fixed core 5 has a vertical hole 21 communicating with the vertical hole 19 of the movable core 12, and a fuel inlet tube 26 internally communicating with the vertical hole 21 is integrally connected to the rear end of the fixed core 5. The fuel inlet tube 26 is composed of a reduced diameter portion 26a connected to the rear end of the fixed core 5 and a subsequent enlarged diameter portion 26b. The pipe shape is inserted or lightly pressed into the vertical hole 21 from the reduced diameter portion 26a. A valve spring 22 for urging the movable core 12 toward the valve closing side of the valve body 18 is contracted between the retainer 23 and the spring seat 24. At this time, the set load of the valve spring 22 is adjusted by the fitting depth of the retainer 23 into the vertical hole 21, and after the adjustment, the outer peripheral wall of the reduced diameter portion 26 a is partially crimped inward to thereby retain the retainer 23. Is fixed to the reduced diameter portion 26a. A fuel filter 27 is mounted on the enlarged diameter portion 26b.
[0035]
The fixed core 5, the movable core 12, and the magnetic cylinder 4 are all made of a ferrite-based high-hardness magnetic material, and are specifically formed by cutting an alloy having the following composition.
[0036]
Cr: 10-20 wt%
Si ・ ・ ・ 0.1wt%
Al and Ni: both of them are contained, at least one of them is 1 wt% or more, and the total of both is 1.15 to 6 wt%
Remaining part: ferritic Fe, impurities Mn, C, P, S
The fact that the total of Al and Ni in the above alloys is 1.15 to 6% by weight, in particular, greatly improves the wear resistance, magnetic force and response of the fixed core 5, the movable core 12 and the magnetic cylinder 4. Involved. That is, about 95% of the total content of Al and Ni becomes precipitates, which greatly affects the hardness, magnetic flux density and volume resistance of the fixed core 5, the movable core 12 and the magnetic cylinder 4. The hardness is desirably large for obtaining abrasion resistance, the magnetic flux density is desirably large for enhancing magnetic force, and the volume resistance is desirably small for enhancing responsiveness.
[0037]
As long as the total content of Al and Ni is 1.15-6 wt%, the hardness of the alloy is HRC20-40. The hardness in this range is sufficient to impart sufficient wear resistance to the fixed core 5, the movable core 12, and the magnetic cylinder 4 without performing any special wear treatment such as plating after cutting the alloy. is there.
[0038]
If the total content of Al and Ni exceeds 6 wt%, the magnetic flux densities of the fixed core 5, the movable core 12, and the magnetic cylinder 4 decrease, so that not only a sufficient magnetic force cannot be obtained but also the volume resistance decreases. As a result, the flow of the magnetic flux is delayed, and the responsiveness of the fixed core 5, the movable core 12, and the magnetic cylinder 4 is reduced.
[0039]
Therefore, by setting the total content of Al and Ni to 1.15 to 6 wt%, the wear resistance, magnetic force, and responsiveness of the fixed core 5, the movable core 12, and the magnetic cylinder 4 can be practically satisfied. it can.
[0040]
Incidentally, 10 to 20 wt% of Cr, 0.1 wt% of Si, and the balance of ferrite-based Fe and impurities Mn, C, P and S in the alloy are generally contained in conventional magnetic materials.
[0041]
On the other hand, the valve element 18 integrally formed with the stopper element 14 is made of a material that is nonmagnetic or less magnetic than the movable core 12, for example, JIS SUS304 or SUS440C.
[0042]
Referring again to FIG. 1, a coil assembly 28 is fitted around the outer periphery of the valve housing 2 in correspondence with the fixed core 5 and the movable core 12. The coil assembly 28 includes a bobbin 29 fitted on the outer peripheral surface of the magnetic cylinder 4 from the rear end to the entire non-magnetic cylinder 6, and a coil 30 wound around the bobbin 29. The front end of the coil housing 31 surrounding the coil assembly 28 is welded to the outer peripheral surface of the magnetic cylinder 4, and the rear end is welded to the outer peripheral surface of the yoke 5 b projecting in a flange shape from the outer periphery of the rear end of the fixed core 5. Is done. The coil housing 31 has a cylindrical shape, and has a slit 31a formed on one side and extending in the axial direction.
[0043]
The coil housing 31, the coil assembly 28, the fixed core 5, and the first half of the fuel inlet tube 26 are embedded in a synthetic resin covering 32 formed by injection molding. At this time, the covering 32 is filled into the coil housing 31 through the slit 31a. A coupler 34 for accommodating a connection terminal 33 connected to the coil 30 is integrally connected to an intermediate portion of the cover 32.
[0044]
In a state where the coil 30 is demagnetized, the valve assembly V is pressed forward by the urging force of the valve spring 22, and the valve body 18 is seated on the valve seat 8. Therefore, fuel pumped from a fuel pump (not shown) to the fuel inlet cylinder 26 enters the valve housing 2 through the inside of the pipe-shaped retainer 23, the vertical hole 19 of the valve assembly V, and the first to third horizontal holes 20a to 20c. It is made to stand by and provided for lubrication and cooling around the first and second guide projections 25a and 25b.
[0045]
Now, a method for connecting the magnetic cylinder 4 made of a high-hardness magnetic material and the valve seat member 3 will be described.
[0046]
As shown in FIG. 2, first, an annular connecting groove 38 is formed on the outer peripheral surface of the connecting cylindrical portion 3a of the valve seat member 3, and a portion 4a of the peripheral wall of the magnetic cylindrical body 4 corresponding to the connecting groove 38 is heated. An annular softened region A is formed. In the softened region A, the hardness is reduced due to the thermal decomposition of the precipitated compound in the crystal. The connecting cylinder 3a is fitted to the inner peripheral surface of the front end of the magnetic cylinder 4, and the front end of the magnetic cylinder 4 is brought into contact with the annular shoulder 3b. By applying an inward caulking force, the inner peripheral surface of the softened region A is made to bite into the connection groove 38 over the entire circumference. Thus, the magnetic cylinder 4 and the valve seat member 3 are caulked.
[0047]
In this case, when the relationship between the hardness and the degree of drawing of the softened region A and the quality of the caulking connection was examined, the result shown in FIG. 3 was obtained. That is, if the hardness of the softened region A is less than or equal to HRC20, it is possible to obtain the degree of drawing of 50% or more and to perform the caulking connection reliably, but if the hardness exceeds HRC20, the softened region A is cracked by the caulking force. Occurs, resulting in poor connection. Therefore, in order to obtain good crimping, the hardness of the softened region A needs to be HRC20 or less.
[0048]
When forming the softened region A, high-frequency heating or laser beam heating is appropriate. According to the high-frequency heating or the laser beam heating, as shown in FIG. 4, the boundary between the original high hardness region and the softened region A of the magnetic cylinder 4 can be clarified. Therefore, caulking, that is, only a predetermined portion where plastic working is performed is formed in the softened region A, and the characteristic of the original high-hardness magnetic material in a portion other than the plastic working portion can be prevented from being impaired.
[0049]
Next, a method of connecting the movable core 12 made of a high hardness magnetic material and the valve body 18 will be described.
[0050]
First, a relatively thin caulking tube portion 12b for receiving the flange portion 35 of the valve rod portion 17 is integrally formed at one end of the movable core 12, and the caulking tube portion 12b is heated by high frequency or laser beam to obtain a hardness. The softening region A is HRC 20 or less. Next, after the flange portion 35 of the valve rod portion 17 is fitted into the caulking tube portion 12b, an inward caulking force is applied to the caulking tube portion 12b to give a plastic deformation to the caulking tube portion 12b, and the flange portion 35 is formed. Envelop. In this way, it is possible to obtain a good crimped joint between the movable core 12 and the valve element 18 without substantially impairing the characteristics of the high hardness magnetic material inherent in the movable core 12.
[0051]
In the electromagnetic fuel injection valve I constructed as described above, when the coil 30 is energized by energization, the magnetic flux generated thereby runs sequentially through the fixed core 5, the coil housing 31, the magnetic cylinder 4, and the movable core 12, and The movable core 12 of the valve assembly V is attracted to the fixed core 5 against the set load of the valve spring 22 by the magnetic force, and the valve body 18 separates from the valve seat 8, so that the valve hole 7 is opened and the valve seat 7 is opened. The high-pressure fuel in the member 3 exits the valve hole 7 and is injected from the fuel injection hole 11 toward the intake valve of the engine.
[0052]
At this time, the stopper element 14 fitted and fixed to the movable core 12 of the valve assembly V comes into contact with the suction surface 5a of the fixed core 5, so that the valve opening limit of the valve body 18 is defined, and the suction of the movable core 12 is performed. The surface 12a faces the suction surface 5a of the fixed core 5 with an air gap g therebetween, and direct contact with the fixed core 5 is avoided. In particular, by controlling the dimension of the amount of protrusion of the stopper element 14 from the suction surface 12a of the movable core 12, the air gap g can be obtained accurately and easily, and the stopper element 14 is non-magnetic or weakly magnetic. In addition, the residual magnetism between the cores 5 and 12 when the coil 30 is demagnetized disappears quickly, and the valve closing response of the valve element 18 can be improved.
[0053]
During opening and closing operations of the valve assembly V, the first and second guide projections 25a and 25b slide on the inner peripheral surface of the valve housing 2 so that the valve assembly V is always held in a proper posture without falling down. The fuel injection characteristics can be stabilized.
[0054]
Further, since the second lateral hole 20b having a diameter d larger than the axial width w of the second guide convex portion 25b is opened on the outer peripheral surface of the second guide convex portion 25b formed on the movable core 12, the vertical direction is vertical. Through the plurality of second horizontal holes 20b from the holes 19, the sliding surface of the second guide convex portion 25b and the gap 37 between the movable core 12 and the magnetic cylinder 4 before and after the same are efficiently and simultaneously supplied to the second guide. The movable core 12 and the magnetic cylinder 4 can be effectively cooled as well as the lubrication of the sliding surface of the projection 25b, and the responsiveness and wear resistance of the valve assembly V can be improved. In addition, the movable core 12 and the magnetic cylinder 4 are made of a ferrite-based high hardness magnetic material as described above, and can exhibit good magnetic properties and high wear resistance by themselves. The response and wear resistance of the three-dimensional V can be further improved, and the fuel injection characteristics can be stabilized for a long time. Further, since it is not necessary to perform a special wear-resistant treatment on the movable core 12 and the magnetic cylinder 4 made of a ferrite-based high-hardness magnetic material, the number of manufacturing steps can be reduced, and the cost can be reduced.
[0055]
Further, the second horizontal hole 20b crossing the movable core 12 can suppress generation of an eddy current in the movable core 12 when exciting and demagnetizing the coil 30, and can prevent heating of the movable core 12 due to the eddy current.
[0056]
Further, the vertical hole 19 and the first to third horizontal holes 20a to 20c also serve to remove the extravagance of the valve assembly V in addition to the function of the fuel passage, so that the weight of the valve assembly V can be reduced and the valve assembly V can be further reduced. This contributes to improved responsiveness.
[0057]
The present invention is not limited to the above embodiment, and various design changes can be made without departing from the gist of the present invention.
[0058]
【The invention's effect】
As described above, according to the first aspect of the present invention, when a part made of a high-hardness magnetic material is partially plastically worked, the part to be plastically worked is made into a softened region where the hardness becomes 20 or less by HRC by heating. Approximately 60% or more of the degree of drawing can be imparted to a part of a high-hardness magnetic material part that requires plastic working, and the plastic working of the part can be performed easily and reliably. The original high hardness magnetic properties can be maintained.
[0059]
According to the second aspect of the present invention, in addition to the first aspect, since the heating is performed by high-frequency heating, the boundary between the original high hardness region and the softened region of the high hardness magnetic material part is clearly defined. The original high-hardness magnetic properties can be maintained in portions other than the plastic working portion.
[0060]
Further, according to the third aspect of the present invention, in addition to the first aspect, the heating is performed by laser beam heating, so that the original high-hardness magnetic properties can be maintained in portions other than the plastic working portion. .
[0061]
According to a fourth aspect of the present invention, in addition to the first aspect, the high-hardness magnetic material comprises 10-20 wt% of Cr, 0.1 wt% of Si, and 1 wt% of at least one of Al and Ni. %, The balance being ferrite-based Fe, Mn, C, P, S, and the total of Al and Ni being 1.15 to 6 wt%. Even if it is not applied, it is possible to provide an inexpensive high-hardness magnetic material having a high hardness of HRC 20 to 40 and excellent wear resistance.
[0062]
According to a fifth aspect of the present invention, in addition to any one of the first to fourth aspects, the high-hardness magnetic material is a magnetic cylinder of a valve housing in an electromagnetic fuel injection valve. Since the softened region is formed in a part of the cylinder and the valve seat member is fixed to the magnetic cylinder by caulking the softened region, it is possible to caulk the magnetic cylinder made of a high-hardness magnetic material partially. The valve seat member can be easily and reliably fixed to the valve seat member.
[0063]
According to a sixth aspect of the present invention, in addition to any one of the first to fourth aspects, the high-hardness magnetic material is a movable core in an electromagnetic fuel injection valve, and the movable core has an end portion. The softened region is formed in the movable core, and the valve body is fixed to the movable core by caulking the softened region. Therefore, the movable core made of a high-hardness magnetic material can be partially caulked, and the valve body can be easily formed. It can be securely fixed.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an electromagnetic fuel injection valve for an internal combustion engine using a component made of a high-hardness magnetic material of the present invention. FIG. 2 is an enlarged view of a part of FIG. 1 FIG. FIG. 4 is a diagram showing the relationship between the hardness and the degree of drawing of the steel and the quality of the caulking connection. FIG. 4 is a microscopic structure diagram of the periphery of the boundary between the high hardness region and the softened region in the hard magnetic material.
A: Softening region I: Electromagnetic fuel injection valve 2: Valve housing 3: Valve seat member 4: Magnetic cylinder 4a Plastic working part 12 of magnetic cylinder ···· Movable core 12b ··· Plastic working part of movable core (caulking cylinder part)
18 ··· Valve

Claims (6)

When partially plastically processing high-hardness magnetic parts (4, 12),
A method of partially plasticizing a high-hardness magnetic material part, wherein a part (4a, 12b) to be plastically worked is made into a softened region (A) in which the hardness becomes 20 or less by HRC by heating. The partial plastic working method for a high-hardness magnetic material part according to claim 1,
A partial plastic working method for a component made of a high-hardness magnetic material, wherein the heating is high-frequency heating. The partial plastic working method for a high-hardness magnetic material part according to claim 1,
A partial plastic working method for a component made of a high-hardness magnetic material, wherein the heating is laser beam heating. The partial plastic working method for a high-hardness magnetic material part according to claim 1,
The high-hardness magnetic material contains 10 to 20% by weight of Cr, 0.1% by weight of Si, 1% by weight or more of at least one of Al and Ni, and the balance includes ferrite-based Fe, Mn, C, P, S, and Al. And a Ni alloy having a total content of 1.15 to 6 wt%. A partial plastic working method for a part made of a high-hardness magnetic material according to any one of claims 1 to 4,
The high-hardness magnetic material is a magnetic cylinder (4) of a valve housing (2) in an electromagnetic fuel injection valve (I), and a part (4a) of the magnetic cylinder (4) includes the softened region (A). And forming a valve seat member (3) on the magnetic cylinder (4) by caulking the softened region (A). A partial plastic working method for a part made of a high-hardness magnetic material according to any one of claims 1 to 4,
The high-hardness magnetic material is a movable core (12) in the electromagnetic fuel injection valve (I), and the softened region (A) is formed at an end of the movable core (12). A partial plastic working method for a component made of a high-hardness magnetic material, comprising fixing a valve element (18) to the movable core (12) by caulking.

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