JP2004111697A - Ferromagnetic member and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a thinner insulating film in a ferromagnetic member, as compared with before, and to increase magnetic efficiency. <P>SOLUTION: A pore 6c is filled with a thermosetting phenol resin 25 to a yoke 6 made of metal, having the pore 6c on a surface and insulating particles 24, are combined with the phenol resin 25 as a binder, thus forming an insulating film 12 between the yoke 6 and a coil 13. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ferromagnetic member and a method of manufacturing a ferromagnetic member, and more particularly to formation of an insulating film of a yoke member made of a ferromagnetic material and around which a coil is wound.
[0002]
[Prior art]
Conventionally, ferromagnetic members having ferromagnetism have been used for yoke members and plungers of solenoid valves. The solenoid valve includes a yoke member in which a coil is wound in a housing, and a plunger is movable in the yoke member in the axial direction. The solenoid valve having such a configuration generates a magnetic field by energizing the coil to excite the coil, and a magnetic circuit is formed between the housing, the yoke member, and the plunger. For example, in a solenoid valve having such a configuration, the yoke member and the coil are insulated by a bobbin made of resin, and a magnetic circuit is formed (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-2002-206658 (FIG. 1)
[0004]
[Problems to be solved by the invention]
When a bobbin that insulates the yoke member and the coil is made by injection molding with a resin, it is necessary to ensure the required strength of the molded product. For this reason, the bobbin requires a predetermined thickness. For example, the resin used for the above-described bobbin needs to have relatively high heat resistance and high fluidity of the resin and excellent injection moldability, and polybutylene terephthalate and polyphenylene sulfide having this property are required. When using the coil, the radial thickness of the coil needs to be 0.3 mm or more, and the axial thickness needs to be 0.5 mm or more.
[0005]
In this case, if the thickness of the yoke member and the bobbin is reduced, the mounting density of the coil wound around the yoke member is increased by the reduced thickness, and the solenoid valve can be reduced in size. For this reason, it is better to make the thickness of the yoke member and the bobbin as thin as possible. Also, regarding the thickness of the coil in the axial direction of the bobbin, it is possible to increase the mounting density of the coil and to efficiently transmit the magnetic field generated from the coil to the yoke components. Is good.
[0006]
Therefore, the present invention has been made in view of the above problems, and has as its technical object to improve the magnetic efficiency by forming an insulating film thinner than before on a ferromagnetic member.
[0007]
[Means for Solving the Problems]
A technical measure taken to solve the above problem is that in a ferromagnetic member made of a metal having pores opened on the surface, insulating particles are bonded to pores on the surface of the metal ferromagnetic member.
[0008]
According to the above-described means, in the ferromagnetic member made of metal having pores opened to the surface, if the insulating particles are bonded to the pores on the surface of the metal ferromagnetic member, the surface of the metal ferromagnetic member has an insulating property. The particles can be combined to form an insulating film having a size of a particle level on the surface of the ferromagnetic member. Therefore, it is possible to form an insulating film thinner than before on the ferromagnetic member.
[0009]
In this case, the thermosetting resin enters the pores, and after the thermosetting resin is melted and solidified, the insulating particles are bonded to the pores. The insulating particles are bonded to the pores, and a strong insulating film can be formed.
[0010]
In addition, if the ferromagnetic member is a yoke member around which a coil is wound, it is possible to secure insulation between the coil and the yoke member by securing an insulating interval at an extremely small particle level. Thereby, the magnetic field generated by the coil can be efficiently transmitted to the yoke member. In addition, since the space for winding the coil is increased, the number of times of winding the coil is reduced, and in the case of a solenoid valve using a coil, the size of the solenoid valve in the radial direction can be reduced. Alternatively, by increasing the space for winding the coil, the number of times of winding the coil can be increased, whereby the magnetomotive force of the solenoid valve can be increased, and the responsiveness of the plunger can be improved.
[0011]
Further, the technical means taken to solve the above-mentioned problem is a step of evacuating a ferromagnetic member made of a metal having pores, dissolving a phenol resin, and forming insulating particles in the phenol resin. Mixing to form a mixed solution, immersing the evacuated ferromagnetic member in the mixed solution, removing the ferromagnetic member from the mixed solution, solidifying the phenolic resin by elevating the temperature and melting. And bonding the insulating particles adsorbed on the surface of the ferromagnetic member with the phenol resin.
[0012]
According to the above means, the phenol resin is dissolved to form a mixed solution in which the insulating particles are mixed in the phenol resin. Then, the ferromagnetic member made of a metal having pores is evacuated, and the evacuated ferromagnetic member is immersed in the mixed solution. Then, the ferromagnetic member is taken out of the mixed solution, and the phenol resin is heated. By solidifying after melting, the insulating particles adsorbed on the surface of the ferromagnetic member can be bonded to the ferromagnetic member by a phenol resin by a simple method.
[0013]
In this case, if Ni-Zn ferrite particles are used as the insulating particles, the permeability is relatively large among the iron oxides and the specific resistance is as high as 10 ⁸ Ωcm or more. It is possible to form a highly insulating insulating film. The insulating particles other ferromagnetic, Ni-Mg-Zn ferrite, Mn-Zn ferrite, Mn-Mg-Zn there is a ferrite or magnetite, 10 than Ni-Zn ferrite in terms of resistivity ² OMEGA. cm, but can be used based on the required insulating properties.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 shows a configuration of a solenoid valve 1 according to one embodiment. The solenoid valve 1 shown in FIG. 1 has a yoke 6 around which a coil 13 is wound in a hollow cylindrical housing 11 made of a magnetic material such as iron. The yoke 6 is made of a ferromagnetic material (for example, pure iron SUYB φ8.9), and has a hollow cylindrical shape with a concave portion at the center in the axial direction. The yoke 6 has a non-magnetic insulating portion (non-magnetic portion) 7 formed at the center in the axial direction for insulating magnetism and electricity, and magnetic insulating portions (magnetic portions) are formed on both sides thereof. The yoke 6 is a circumferential flange whose both ends in the axial direction extend in the radial direction. An insulating film 12 is formed on the surface of a central concave portion formed by the flange. Is wound.
[0016]
In the present embodiment, the yoke member 5 will be described as the yoke alone or the yoke 6 including the coil 13 wound around the yoke 6 via the insulating film 12.
[0017]
A through hole having a small diameter hole and a large diameter hole is formed in the center of the yoke 6 in the axial direction, and a plunger (pure iron SUYB φ8.89) 14 is axially supported by the small diameter hole and the large diameter hole. Is movable.
[0018]
Next, the operation of the solenoid valve 1 having the above configuration will be briefly described. The electromagnetic valve 1 is connected to an external connector (not shown), and the coil 13 is energized from the external connector. When the coil 13 is energized from the external connector, the coil 13 is excited by the energization of the coil 13, and a magnetic field is generated in the coil 13. The generated magnetic field is transmitted from the yoke (for example, the left side in FIG. 1) 1a to the plunger 4 via a gap (air gap) between the yoke 10a and the plunger 4. Then, the plunger 14 passes through a yoke (for example, the right side shown in FIG. 1) 1a and returns to the coil 13, thereby forming a closed-loop magnetic circuit in the housing.
[0019]
According to the above-described configuration, a magnetic flux proportional to the current supplied to the coil 13 is generated in the coil 13, and as a result, an electromagnetic force acts on the plunger 4, and the plunger 4 is moved in the axial direction by a magnetic attractive force (see FIG. 1). (Rightward) and move axially along the inner wall of the large diameter hole in the yoke. In this case, on the sliding surface 9 between the plunger 4 and the yoke member 5, a protective film 8 made of tetrafluoroethylene coating or the like is preferably formed in order to secure insulation and slidability between the two.
[0020]
In the solenoid valve 1 having such a configuration, the yoke 6 which is a feature of the present invention will be described in detail. The yoke 6 shown in FIG. 1 has a rear yoke 6a on the left side and a front yoke 6b on the right side. The rear yoke 6a and the front yoke 6b are integrally formed via a non-magnetic portion 7. The yoke 6 is formed of a porous sintered body obtained by performing pressure molding using ferromagnetic metal particles and sintering a molded product after the pressure molding. In this case, as the metal particles constituting the porous sintered body, reduced iron is used as a general-purpose and inexpensive metal particle in consideration of the relationship between magnetic properties and magnetic permeability or compressibility during pressure molding. Powder is used here. Therefore, a method of manufacturing the yoke 6 will be described with reference to FIG. In the following description of the manufacturing method, the flow (step) of each process is simply described as “S”.
[0021]
As the atomized reduced iron powder for forming the yoke 6, a powder having a particle size of 20 μm or more (preferably, 20 to 150 μm) is prepared (S1), and is filled in a mold for forming a yoke. Then, a pressure of 7 t / cm ² is applied to the mold to perform pressure molding (S2), so that the green density is 7.1 Mg / m ³ or more. Thus, the rear yoke 6a is formed by primary molding (S3).
[0022]
Then, particles for forming the non-magnetic portion 7 are prepared (S4). The particles forming the nonmagnetic portion 7 are used by adding hematite particles having a particle size of about 1 μm to mill-scale reduced iron powder having a particle size of 45 μm or less (preferably 45 to 20 μm). In general, hematite particles are a paramagnetic material that exhibits weak ferromagnetic properties at 260 K or higher, has a relative magnetic permeability close to 1.0 within a normal temperature range, and does not have magnetic hysteresis properties. Then, the prepared hematite particles are put into, for example, a mechanofusion device, and a hematite film is formed on the entire surface of the mill-scale reduced iron powder by a frictional force by a mechanofusion method (S5), and the nonmagnetic portion is formed. Particles for producing 7 are produced through such a process.
[0023]
Next, after the particles in which the coating of hematite particles is formed on the entire surface of the mill-scale reduced iron powder by S5 are filled in a mold in which the rear yoke 6a already formed in S3 is formed, a predetermined pressure ( For example, by applying 8 t / cm ² ), pressure molding (secondary molding) is performed (S6), and the mill-scale reduced iron powder is compressed to form the nonmagnetic portion 7 (S7).
[0024]
Thereafter, in the steps up to S7, the atomized reduced powder of the same material and the same particle size as the rear yoke 6a is placed in a mold in which the already formed rear yoke 6a and the non-magnetic portion 7 are integrally formed. The yoke 6b is filled for molding (S8). Further, a predetermined pressure similar to that at the time of molding the rear yoke 6a is applied to perform pressure molding (S9), and a portion corresponding to the front yoke 6b is integrally molded (S10).
[0025]
Thereafter, a molded article integrally formed with magnetic parts on both sides of the non-magnetic part 7 produced by the above-described process is sintered at 1073K (= 800 ° C.) in a nitrogen atmosphere (S11), and A porous yoke 6 having pores on the surface on which the nonmagnetic portion 7 is integrated is formed. Thereafter, the surface is polished by sizing in order to obtain the dimensional accuracy of the yoke 6 (S12), and the pores 6c are exposed on the surface of the yoke 6, and thereafter, the process proceeds to insulation treatment of the surface of the yoke 6 (S13). .
[0026]
In the surface insulation treatment shown in FIG. 3, a metal sintered body, that is, a yoke 6 made by firing in the steps up to S13 shown in FIG. 2 is prepared (S21), and the yoke 6 is evacuated by a vacuum device. It is pulled (S22).
[0027]
On the other hand, a solution for forming the insulating film 12 on the yoke 6 is prepared. This solution is made of a thermosetting resin, for example, a phenol resin. When a phenolic resin is used for the solution, the phenolic resin is dissolved using Asenton as a solvent (S23). Next, ferromagnetic insulating fine particles made of ferromagnetic and having an insulating property are mixed with the phenol resin solution. As the ferromagnetic insulating particles 24 used here, for example, various iron oxides made of iron oxide such as soft magnetic ferrite and maghemite are used. Among the above-described iron oxides, Ni-Zn ferrite is a particle having a relatively large magnetic permeability and the largest specific resistance, and is used as the insulating particles 24 in the present embodiment. Hematite particles are paramagnetic particles having a specific resistance (e.g., 10 < ⁸ > [Omega] .cm or more) at the same level as that of Ni-Zn ferrite, but the insulation between the yoke 6 and the coil 13 is prioritized. It is preferable to use hematite particles. In addition, the particle diameter of the Ni—Zn ferrite or hematite particles is used according to the wire diameter of the insulated wire used for the coil 13. For example, when three kinds of AIW wires having a wire diameter of the coil 13 of φ: 0.33 mm are used, the insulating particles 24 may be particles having a particle diameter of 30 μm or less. When the insulating particles 24 having a particle size of 30 μm or less are used, the viscosity of the mixture of the phenolic resin 25 and the insulating particles 24 is adjusted to be 0.8 Pa · s to reduce the sedimentation of the insulating particles. Suppress.
[0028]
Then, the evacuated sintered body is impregnated with a phenol solution in which Ni-Zn ferrite particles serving as the above-mentioned insulating particles are mixed (S25). Thereafter, the temperature is raised to a temperature at which the phenol resin dissolves, and then cooled to solidify the phenol resin impregnated inside the sintered body (S26), and the Ni—Zn adsorbed on the surface of the yoke 6 as the sintered body. When the ferrite particles 24 are bonded using the phenol resin 25 as a binder (S27), the Ni—Zn ferrite particles 24 are bonded to the surface of the yoke 6 by the phenol resin 25 to form the insulating film 12, as shown in FIG. Thus, an insulating layer is formed.
[0029]
When the coil 13 is wound around the yoke 6 formed in this way in a state of being aligned in the circumferential direction, the concave shape of the yoke 6 where the coil 13 is provided is actually changed to the wire diameter of the coil 13. It is preferable to perform knurling according to the size and then perform vacuuming to form the insulating film 12.
[0030]
In the present embodiment, the yoke 6 and the coil 13 are insulated by adsorbing and bonding the Ni-Zn ferrite particles 24, which are insulating particles, to the surface of the yoke 6. Actually, in the embodiment, when a wire having a wire diameter of φ: 0.33 mm is used, and when a particle having an insulating particle diameter of 30 μm or less is used, the yoke 6 and the coil are formed by a bobbin made of a conventional resin. 13, the thickness of the insulating layer can be reduced to the level of the insulating particles (about several μm), and in practice, the thickness of the insulating film 12 is 90% or more. Reduction becomes possible. Thereby, when the same yoke 6 having the same size is used in the space where the coil 13 is wound, the coil 13 can be wound extra by the thickness of the insulating film 12. An extra coil 13 can be wound. For example, when winding the coil 13 composed of seven layers, the coil of the eighth layer can be mounted in the same mounting space. That is, the magnetomotive force for moving the plunger 4 of the solenoid valve 1 can be increased by several percent (for example, about 14%) without increasing the size of the solenoid valve 1 in the radial direction.
[0031]
Regarding the thickness of the coil 13 in the axial direction, the effect of reducing the thickness of the insulating film 12 is increased, and a slight gap of 30 μm is formed by the ferromagnetic insulating Ni—Zn ferrite particles 24. Formed. Therefore, most of the magnetic field generated from the coil 13 is transmitted from the coil 13 to the yoke 6 without being attenuated even by the insulating film 12 formed in the axial direction, so that the magnetic efficiency of the solenoid valve 1 is greatly increased. . Therefore, the magnetic efficiency of the solenoid valve 1 is improved, and the performance improvement of the solenoid valve 1 can be expected.
[0032]
【effect】
According to the present invention, with respect to a ferromagnetic member made of a metal having pores, insulating particles are bonded to the pores, and an insulating film having a particle level can be formed on the ferromagnetic member. A thin insulating film can be formed on the ferromagnetic member.
[0033]
In this case, the thermosetting resin enters the pores, solidifies after the thermosetting resin is melted, and if the insulating particles are bonded to the pores, the thermosetting resin that has entered the pores is cured, The insulating particles are bonded to the pores on the surface of the ferromagnetic member, and a strong insulating film can be formed.
[0034]
In addition, if the ferromagnetic member is a yoke member around which the coil is wound, it is possible to secure insulation between the coil and the yoke member by securing an insulating interval at an extremely fine particle level, and the coil is generated by the coil. The magnetic flux can be efficiently transmitted to the yoke member. Therefore, a solenoid valve with good magnetic efficiency can be obtained.
[0035]
Further, according to the present invention, the ferromagnetic member made of a metal having pores is evacuated to dissolve the phenol resin, thereby producing a mixed solution in which insulating particles are mixed in the phenol resin. Then, after immersing the evacuated ferromagnetic member in the mixed solution, the ferromagnetic member is taken out of the mixed solution, and the phenol resin is melted and solidified, thereby adsorbing on the surface of the pores by a simple method. The insulating particles thus obtained can be bonded to the ferromagnetic member with a phenolic resin at a particle-level thickness.
[0036]
In this case, if Ni-Zn ferrite particles are used as the insulating particles, the permeability is relatively large among iron oxides and the specific resistance is as high as 10 ⁸ Ωcm or more. , A highly insulating insulating film can be formed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of a solenoid valve according to an embodiment of the present invention.
FIG. 2 shows a manufacturing process of the yoke shown in FIG.
FIG. 3 is a flow chart showing a process of insulating the surface of the yoke shown in FIG. 1;
FIG. 4 is a schematic view of a surface of a yoke subjected to an insulating process.
[Explanation of symbols]
1 solenoid valve 5 yoke member 6 yoke (ferromagnetic member)
6c Pores 7 Non-magnetic portion 12 Insulating film 13 Coil 24 Insulating particles (Ni-Zn ferrite particles, hematite particles)
25 Phenolic resin (thermosetting resin)

Claims (5)

A ferromagnetic member made of a metal having pores opened on the surface, wherein insulating particles are bonded to the pores. 2. The ferromagnetic member according to claim 1, wherein the pores are filled with a thermosetting resin, and the thermosetting resin is melted and solidified to bond the insulating particles to the pores. 3. The ferromagnetic member according to claim 1, wherein the ferromagnetic member is a yoke member around which a coil is wound. Evacuation of a ferromagnetic member made of a metal having pores,
Dissolving the phenolic resin, mixing the insulating particles in the phenolic resin to form a mixed solution, and immersing the mixed solution in a vacuum-drawn ferromagnetic member;
Removing the ferromagnetic member from the mixed solution, heating and melting the phenol resin, solidifying the resin, and bonding the insulating particles adsorbed on the surface of the pores with the phenol resin. A method for producing a ferromagnetic member, comprising: The method according to claim 4, wherein Ni-Zn ferrite particles are used as the insulating particles.

Images