JP2007270207A - Soft magnetic material for magnetic circuit and actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft magnetic material for a magnetic circuit whose magnetic properties such as magnetic flux density and magnetic permeability can be further improved, and to provide an actuator. <P>SOLUTION: The soft magnetic material for a magnetic circuit is formed of an iron-based solidified metal provided with a matrix structure essentially consisting of ferrite and an iron-carbon compound dispersed into the matrix structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a soft magnetic material for a magnetic circuit and an actuator.

Conventionally, Patent Document 1 discloses an actuator in which an upper core and a lower core are formed by laminating steel plates. Patent Document 2 provides a magnetic material having an interior and a surface portion covering the interior. According to this, the inside of the magnetic material is formed by sintering a green compact obtained by hardening an aggregate of soft magnetic particles coated with an electrical insulating coating. The surface is hardened by carburizing or vacuum quenching. Patent Document 3 discloses a magnetic circuit member formed by casting a cast iron melt and solidifying it to form a solidified body in which spheroidal graphite or worm-like graphite is produced, and heat-treating the solidified body.
JP 2003-318025 A JP 2003-272910 A JP 2002-322532 A

  According to the technique according to Patent Document 1, by laminating steel plates, the electric resistance at the boundary between the steel plates is increased. Therefore, even if eddy current is generated, the loop of eddy current is limited, and eddy current loss is reduced. The However, there is a limit to increasing the magnetic flux density. Furthermore, according to the technique according to Patent Document 1, since a method of laminating a number of steel plates punched with a press die in the thickness direction is employed, the cost tends to increase. In particular, since a steel plate containing silicon is hard, there is a limit to punching with a press die, which tends to increase costs. Furthermore, there is a possibility that the degree of freedom in designing the three-dimensional shape of the upper core and the lower core on which the steel plates are laminated may be limited.

  Further, according to the technology according to Patent Document 2, since the electrical insulating coating coated with the soft magnetic particles has a high electrical resistance, even if an eddy current is generated, the eddy current loop is limited and the eddy current loss is reduced. Is reduced. Furthermore, since the inside of the soft magnetic particles coated with the electrical insulating film is hardened, the interior is formed. Compared to the method of stacking a number of punched steel sheets in the thickness direction, the three-dimensional shape of the magnetic material A degree of freedom in design is easily secured. However, since the soft magnetic particles are coated with an electrical insulating coating, there is a limit to increasing the magnetic flux density and permeability.

  Further, according to the technology according to Patent Document 3, a cast iron melt is cast to form a magnetic circuit member having spheroidal graphite or worm-like graphite, so that the degree of freedom in designing the three-dimensional shape of the magnetic circuit member is ensured. easy. Furthermore, since spheroidal graphite or worm-like graphite has a higher electrical resistance than that of the matrix structure, even if eddy current is generated, the loop of eddy current is limited and eddy current loss is reduced. However, since graphite has a low magnetic flux density and magnetic permeability, if a large number of spherical graphite or worm-like graphite is produced, there is a limit to increasing the magnetic flux density and magnetic permeability.

  As described above, according to the technology according to each of the above patent documents, there is a limit to increase the magnetic flux density and the magnetic permeability, and there is a limit to the miniaturization of the actuator on which the soft magnetic material for the magnetic circuit is mounted.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a soft magnetic material for a magnetic circuit and an actuator that can further improve magnetic characteristics such as magnetic flux density and magnetic permeability.

  A soft magnetic material for a magnetic circuit according to aspect 1 is characterized by being formed of an iron-based solidified metal including a base structure mainly composed of ferrite and an iron-carbon compound dispersed in the base structure.

  An actuator according to aspect 2 is an actuator including a mover, a stator disposed so as to face the mover, and a case member having an inner wall surface surrounding and holding the outer wall surface of the stator. Is formed of a soft magnetic material for a magnetic circuit according to aspect 1.

  According to the aspects 1 and 2, the iron-based solidified metal includes a base structure mainly composed of ferrite and an iron-carbon compound dispersed in the base structure. Since the matrix structure is mainly composed of ferrite, it has a composition close to that of pure iron and can improve magnetic properties such as magnetic flux density and magnetic permeability. For this reason, magnetic characteristics such as magnetic flux density and magnetic permeability in the soft magnetic material for magnetic circuit can be further improved.

  According to the present invention, magnetic properties such as magnetic flux density and magnetic permeability in the soft magnetic material for a magnetic circuit can be further improved. Therefore, applying this soft magnetic material for a magnetic circuit to an actuator is advantageous in reducing the size of the actuator. Furthermore, since the iron-carbon compound dispersed in the matrix structure is a higher strength phase than ferrite, it is advantageous for increasing the strength of the soft magnetic material for magnetic circuits.

  Furthermore, since it is formed of an iron-based solidified metal, it is formed through a process of pouring molten metal into a mold cavity and solidifying it. Therefore, the degree of freedom in selecting the three-dimensional shape of the soft magnetic material for a magnetic circuit can be increased as compared with the method of laminating steel plates in the thickness direction.

  The soft magnetic material for a magnetic circuit according to the present invention is formed of an iron-based solidified metal. It may be used in an as-cast black skin state, or may be subjected to cutting as appropriate. The mold for forming the iron-based solidified metal may be a sand mold, a mold, or a ceramic mold. The iron-based solidified metal includes a base structure mainly composed of ferrite and an iron-carbon compound dispersed in the base structure. The base organization is mainly ferrite. Ferrite is an α phase in which carbon is dissolved in iron and has a composition close to that of pure iron. Since ferrite is excellent in magnetic properties, the permeability and magnetic flux density can be increased.

  Here, “mainly composed of ferrite” means that, for example, in a microscope field of magnification of 100 times or 200 times, when the field of view is 100%, ferrite accounts for 50% or more by area ratio. Preferably, when the field of view is 100%, it is preferable that ferrite accounts for 60% or more and 70% or more, particularly 80% or more and 90% or more in terms of area ratio. The ferrite is preferably silicon ferrite containing silicon.

  The iron-carbon compound is preferably dispersed in the base tissue in an island shape. Thereby, the area of a ferrite is ensured. Generally, the magnetic flux density and permeability of iron-carbon compounds are lower than the magnetic flux density and permeability of ferrite having a composition close to that of pure iron. For this reason, when the aspect ratio (length / width) of the iron-carbon compound is large, the iron-carbon compound extends into a long fiber shape, so that the detour distance of the magnetic flux tends to be excessive, and a satisfactory magnetic flux density and magnetic permeability can be obtained. There is a risk of not. Furthermore, when the aspect ratio of the iron-carbon compound is large, the anisotropy of the strength is increased, which tends to be disadvantageous in terms of ensuring uniform strength in the soft magnetic material for a magnetic circuit. Therefore, the average aspect ratio of the iron-carbon compound is preferably 7 or less, 5 or less, or 4 or less on average. Therefore, the average aspect ratio is preferably about 1.5 to 7 and about 2 to 5 on average. For this reason, the iron-carbon compound is generally dispersed in the matrix structure in the form of particles or pieces. Examples of the iron-carbon compound include pearlite and / or cementite. The pearlite may be layered pearlite or granular pearlite.

  The size of the iron-carbon compound varies depending on the required magnetic properties, the cooling rate of the iron-based solidified metal, the carbon content, etc., but can be exemplified by about 3 to 400 μm, about 10 to 200 μm, about 10 to 100 μm, Furthermore, about 20-50 micrometers can be illustrated. However, it is not limited to these. Since the iron-carbon compound has a lower magnetic permeability than ferrite, it is considered that when the size of the iron-carbon compound is excessively large, the detour ratio of the magnetic flux increases. If the size of the iron-carbon compound is excessively small, the strength improving effect on the soft magnetic material for a magnetic circuit is reduced.

  Note that a relatively large iron-carbon compound of 40 μm or more and a small iron-carbon compound of 10 μm or less may coexist.

  Carbon is effective for lowering the solidification start temperature of the iron-based solidified metal and enhancing castability, and is effective for producing an iron-carbon compound. However, if the carbon content is excessive, the amount of graphite produced increases. Since graphite functions as a notch, it becomes a factor of reducing strength and has a property of reducing magnetic flux density and permeability. Therefore, according to the aspects 1 and 2, it is preferable that the carbon contained in the iron-based solidified metal is produced as an iron-carbon compound and is produced in a small proportion or not substantially as graphite. If the carbon content is too small, the area ratio of the iron-carbon compound may be too small. Considering the above points, examples of the carbon content of the iron-based solidified metal include 2% or less, 1.8% or less, 1.5% or less, and 1.3% or less in terms of mass ratio. Examples are 0% or less, 0.5% or less, 0.2% or less, and 0.1% or less.

  According to the iron-based solidified metal according to the present invention, in order to increase the strength, magnetic flux density, and magnetic permeability, for example, the area of the iron-carbon compound is S1 in a microscope field of magnification of 100 times or 200 times, and the graphite When the area is S2, it is preferable to compare the two to increase S1 and decrease S2. Therefore, it is preferable that S1 / S2 is 0.5 or more. For this reason, in consideration of suppressing the formation of graphite, S1 / S2 is exemplified by 1 or more, 2 or more, 3 or more, 4 or more, 6 or more, and more.

  Furthermore, according to the iron-based solidified metal according to the present invention, since the matrix structure is rich in ferrite, for example, when the field of view is 100% in a microscope field of magnification of 100 times or 200 times, the area ratio of iron- The area of the carbon compound is preferably 25% or less and 20% or less.

  An iron-carbon solidified alloy having a mass ratio of 2% or less of carbon is generally called cast steel. Therefore, the iron-based solidified metal according to the present invention is preferably a cast steel system. Silicon improves soft magnetic properties. Therefore, the silicon content of the iron-based solidified metal is exemplified by a mass ratio of 0.3 to 10%. However, if the amount of silicon is large, the strength and hardness increase, but the machinability may decrease. Considering the above points, the upper limit value of the silicon content of the iron-based solidified metal is exemplified by mass ratios of 10%, 8%, 5%, 4%, 3%, and the lower limit value of the silicon content is 0.3%, 0.5%, 0.8%, and 1.0%. Accordingly, the silicon content of the iron-based solidified metal is exemplified by mass ratios of 0.3 to 10%, 0.3 to 8%, and further 0.5 to 4%. However, it is not limited to the above content.

  Manganese contributes to the formation of iron-carbon compounds such as pearlite and cementite. Manganese is contained in common dissolved materials. Examples of the manganese content in the iron-based solidified metal include a mass ratio of 2% or less, 1% or less, 0.6% or less, or 0.4% or less. Since aluminum generates aluminum oxide, it mainly functions as a deoxidizer for molten metal and remains in the iron-based solidified metal. The aluminum content in the iron-based solidified metal can be 0.2% or less, 0.1% or less, and may be substantially 0%. In addition, as an unavoidable impurity, 1 type, or 2 or more types of the impurity element contained in steel systems, such as phosphorus, sulfur, and calcium, are mentioned.

  The iron-based solidified metal may or may not be heat-treated. The heat treatment can be performed by heating in a temperature range from the A1 transformation point to the A3 transformation point or from the A3 transformation point to the melting point. Or it can carry out by heating in the temperature range just under A1 transformation point. Alternatively, when cementite is generated, expecting cementite spheroidization, the temperature is just below the A1 transformation point (temperature range lower by 50 ° C. than the A1 transformation point) and just above (above 50 ° C. higher than the A1 transformation point). It can be performed by repeating the heating in the temperature region of the temperature region a plurality of times.

  The use of the soft magnetic material for magnetic circuits is not particularly limited, and can be used as a yoke for actuators, industrial equipment, household equipment, and the like.

  The actuator according to aspect 2 includes a mover, a stator disposed so as to face the mover, and a case member having an inner wall surface that surrounds and holds the outer wall surface of the stator. The mover may be any one that can move relative to the stator, and may be a rotating type or a type that reciprocates linearly. The case member is formed of the above-described soft magnetic material for a magnetic circuit. The above-described soft magnetic material for a magnetic circuit can improve magnetic properties such as magnetic flux density and magnetic permeability. Therefore, applying this soft magnetic material for a magnetic circuit to an actuator is advantageous in reducing the size of the actuator.

  A motor is illustrated as an actuator. The motor includes a rotatable inner rotor (movable element), a cross-section ring-shaped stator disposed so as to face the inner rotor, and a cross-section ring-shape having an inner wall surface surrounding and holding the outer wall surface of the stator. The case member can be provided. The case member is formed of the above-described soft magnetic material for a magnetic circuit. The shapes of the mover, the stator, and the case member are not particularly limited, but if the stator is cylindrical, the outer wall surface of the stator becomes the outer peripheral wall surface. If the case member is cylindrical, the inner wall surface of the case member is an inner peripheral wall surface.

  Embodiment 1 of the present invention will be described below with reference to FIGS. Example 1 satisfies the conditions described in each claim. A low carbon iron scrap material and silicon were melted at 1650 to 1700 ° C. in a high frequency furnace to obtain a cast steel base hot water. 0.2 parts by mass of ferrosilicon (silicon content: 75% by mass) and 0.05 parts by mass of an aluminum lump were accommodated in a crucible with respect to 100 parts by mass of the original hot water. After the main hot water was poured into the crucible and the slag was removed, the molten metal was poured into a cavity of a mold (sand mold) and solidified to form a test piece. The pouring temperature was 1600 ° C. In the molten metal, the aluminum powder functions as a deoxidizer that removes the oxygen content of the molten iron. Thereafter, the test piece was taken out from the mold. In accordance with this, test pieces according to Examples 1 to 3 and test pieces having cast steel compositions according to Comparative Examples 1 to 3 were formed. The cavity of the mold was a Y block shape (JIS G O307).

  Thereafter, heat treatment was performed for 1 hour by heating and holding the test piece at 1000 ° C. in a vacuum. Ferritization proceeds by heat treatment. Magnetic property evaluation and component analysis were performed after heat treatment. Table 1 shows the components and magnetic properties of the test pieces after heat treatment. The magnetic characteristics were measured with a DC BH analyzer.

  As shown in Table 1, according to Examples 1 to 3, the magnetic flux density is 1.65 T (tesla) or higher, and the maximum magnetic permeability is as high as 2650 or higher. Thus, according to Examples 1 to 3, both the magnetic flux density and the maximum magnetic permeability are high in balance. On the other hand, according to Comparative Example 1, both the magnetic flux density and the maximum magnetic permeability are low. According to Comparative Example 2, although the maximum magnetic permeability is good, the magnetic flux density is low. According to Comparative Example 3, although the maximum magnetic permeability is good, the magnetic flux density is low.

  FIG. 1 shows hysteresis curves of Example 1 and Comparative Example 3. For the hysteresis curve, a test piece having an outer diameter of 26 mm, an inner diameter of 19 mm, and a thickness of 2 mm was used, and the DC BH characteristics were measured with an excitation coil of 200 turns and a detection coil of 50 turns. In FIG. 1, the characteristic line A <b> 1 indicates Example 1 and the characteristic line A <b> 2 indicates Comparative Example 3. As can be seen from FIG. 1, since both Example 1 and Comparative Example 3 are soft magnetic materials, there is little hysteresis but there is a difference in magnetic characteristics.

  FIG. 2 shows an optical micrograph of the metal structure of Example 1 (prior to heat treatment, night corrosion) (photographed site is a site about 2 mm deep from the outermost wall surface of the cast product). In FIG. 2, the lead lines indicate grain boundaries, island-like pearlite, and ferrite matrix, respectively. As shown in FIG. 2, the base structure is a ferrite structure. The crystal grain size of ferrite is considerably large, and is about 2 to 3 millimeters on average. Magnetic properties such as magnetic flux density and magnetic permeability are improved when the crystal grain size of ferrite is larger. As is clear from FIG. 2, iron-carbon compounds are generated in an island shape in this base organization. The iron-carbon compound is considered to be pearlite (black particles in the photograph) and / or cementite (free cementite). Here, flaky or granular pearlite (black particles in the photograph) having a length of about 30 to 60 μm is generated. As shown in FIG. 2, the average aspect ratio (length / width) of the iron-carbon compound is about 2 to 7. According to FIG. 2, since the base structure is rich in ferrite, the ferrite occupies 70% or more in the area ratio when the field of view is 100% in the microscope field of magnification of 100 times. When the field of view is 100%, the area of the island-like iron-carbon compound is 25% or less in terms of area ratio.

  FIG. 3 shows an optical micrograph of the metal structure of Example 1 (after heat treatment, night corrosion) (photographed site is a site about 2 mm deep from the outermost wall surface of the cast product). In FIG. 3, a part different from the part shown in FIG. 2 is photographed. Also in FIG. 3, the base structure is a ferrite structure, and island-like pearlite is dispersed in the base structure. The crystal grain size of ferrite is considerably large and is about 2 to 3 millimeters.

  According to the structure shown in FIG. 3 (magnification 200 times), when the area of the iron-carbon compound is S1 and the area of graphite is S2 in the optical microscope field of view, S1 / S2 = 0.5 or more.

  As shown in FIGS. 2 and 3, a large number of fine granular compounds are dispersed in the base. According to EPMA, this compound is considered to be a Fe-Si-Al-based compound. Although this compound itself has a magnetic property lower than that of ferrite, it does not substantially increase the detour distance of magnetic flux because it is dispersed as fine particles (average particle size: 10 μm or less or 5 μm or less) in the form of scattered dots. It is estimated to be. Therefore, a decrease in magnetic flux density and magnetic permeability is suppressed.

  The amount of carbon solid solution in the base structure of the cast specimen was 0.05% by mass before the heat treatment. After the heat treatment, it was 0.02% by mass. Thus, the base becomes close to pure iron by heat treatment. Presumably, the graphitization of the carbide progressed by the heat treatment, and the amount of carbon solid solution in the base structure decreased. The amount of solid solution of carbon was calculated from the remaining amount obtained by calculating the total amount of carbon by the combustion infrared absorption method and subtracting the amount of crystallized or precipitated graphite. Fe-Si-Al compounds were not so much observed in the as-cast state, but were produced by heat treatment.

  As can be understood from Table 1, the present invention material has a low carbon content, and the base structure is a structure rich in ferrite. Furthermore, while the amount of carbon in the base structure is generated as an iron-carbon compound (particularly, an island-like iron-carbon compound), the carbon in the base structure is kept low, and the magnetic properties are improved. In the material of the present invention, since silicon is dissolved in the ferrite in the base structure, the specific resistance is 55 to 65 Ωcm (60 Ωcm), which is about four times that of the pure iron material. Therefore, when used as a magnetic circuit member of an actuator such as a motor, a large amount of magnetic flux can be transmitted through the magnetic circuit cross section, iron loss can be reduced, and the actuator can be downsized.

  The material of the present invention can be used as a magnetic path forming member of an actuator. Examples of the actuator include a motor and an electromagnetic valve. For motors, it can be used for rotor cores, stator cores, and the like. Examples of the motor include various motors such as an ABS system motor, a power steering motor, a wiper motor, a window regulator motor, a door lock motor, and a sunroof motor.

  Since the material of the present invention is formed by solidifying the molten metal, there is little change in strength and magnetic properties even in a high temperature environment or an environment with temperature change, so it can be used in an environment at or above the operating environment temperature in a vehicle. Is possible.

  4 to 6 show application examples applied to a motor as an actuator. The motor is mounted on a vehicle or an industrial device, and as shown in FIGS. 4 and 5, as shown in FIGS. 4 and 5, an inner rotor 100 as a mover and a cylindrical iron arranged to face the inner rotor 100. And a ferrous case member 300 having an inner peripheral wall surface 301 that surrounds and holds the outer peripheral wall surface 201 of the stator 200. A permanent magnet 110 is attached to the outer peripheral wall surface of the inner rotor 100. Stator 200 is formed by laminating a plurality of silicon steel plates 210 in the thickness direction (centerline PA direction of stator 200).

  As shown in FIG. 5, the stator 200 includes a plurality of teeth 220 that protrude in the radially inward direction. A coil winding 400 is wound around the tooth portion 220. Along with the power supply to the coil winding 400, a rotating magnetic field that rotates around the center line PA of the stator 200 is generated, and the inner rotor 100 rotates in the stator 200.

  The case member 300 is formed in a cylindrical shape from the soft magnetic material for a magnetic circuit of any one of the first to third embodiments. As shown in FIG. 5, the peripheral wall portion 305 of the case member 300 includes the inner peripheral wall surface 301. And an outer peripheral wall surface 303.

  The case member 300 is formed by loading a cast steel melt into a mold cavity and solidifying it. The mold may be a sand mold, a mold, or a ceramic mold. The outer peripheral wall surface 303 of the case member 300 is used in an as-cast state. The inner peripheral wall surface 301 of the case member 300 is a cut surface obtained by cutting, and the fitting property to the stator 200 is ensured. A cylindrical stator 200 is fitted and held in a cylindrical space formed by a cut inner circumferential wall surface 301 of the case member 300 by press-fitting or caulking.

  As described above, the case member 300 is formed of the soft magnetic material for a magnetic circuit according to any one of the first to third embodiments. The base structure mainly composed of ferrite and the iron-carbon dispersed in the base structure. And a compound. This soft magnetic material for a magnetic circuit may be an as-cast state in which heat treatment is not performed, or may be heat-treated for a predetermined time (for example, 30 to 5 hours) before cutting. The heat treatment can be performed by heating for 30 minutes to 2 hours in a temperature range (1000 ° C.) above the A3 transformation point.

  Ferrite is silicon ferrite containing silicon. The iron-carbon compound is pearlite and / or cementite, and a compound having an aspect ratio of 2 to 5 is dispersed in an island shape without growing into a large lump. As described above, the case member 300 is formed of the soft magnetic material for a magnetic circuit in any one of the first to third embodiments, and can improve magnetic characteristics such as magnetic flux density and magnetic permeability. Furthermore, since the iron-carbon compound dispersed in the soft magnetic material for a magnetic circuit is a phase having a strength higher than that of ferrite, it also plays a role of strengthening a base structure mainly composed of ferrite. Therefore, the case member 300 has a function of transmitting a magnetic path loop generated based on the coil winding 400, and also has a function of a restraining member and a strength member for holding and restraining the outer peripheral wall surface 201 of the stator 200. .

  Further, since the case member 300 is formed of a cast steel system as an iron-based solidified metal, the case member 300 is formed through an operation of pouring a molten metal into a cavity of a mold and solidifying it. Therefore, the degree of freedom in selecting the three-dimensional shape of the soft magnetic material for magnetic circuit formed by the case member 300 can be increased.

  Along with the power supply to the coil winding 400, a rotating magnetic field that rotates around the center line PA of the stator 200 is generated, and the inner rotor 100 rotates around the center line PA of the stator 200 in the stator 200. At this time, since the inner rotor 100 is rotated by a magnetic attractive force based on the rotating magnetic field, a force acts on the stator 200 in the circumferential direction based on the magnetic attractive force. As a result, force also acts in the circumferential direction of the peripheral wall portion 305 of the case member 300. In this respect, according to the present example, the iron-carbon compound is a phase having higher strength and hardness than the ferrite base structure, which is advantageous in increasing the strength of the peripheral wall portion 305 of the case member 300. Further, since it is a silicon ferrite matrix having a high silicon content, it has higher strength and hardness than a normal ferrite matrix having a low silicon content. For this reason, it is more advantageous to ensure the strength of the peripheral wall portion 305 of the case member 300. Therefore, it is advantageous for reducing the thickness and weight of the peripheral wall portion 305. It is advantageous for use in an environment where vibration and impact are frequently applied, such as a vehicle, while requiring weight reduction.

  In solidifying the case member 300, it can be said that the central region in the thickness direction of the thickness t in FIGS. The thickness t is appropriately set, but is set to 3 to 10 millimeters. Further, it can be said that the outer peripheral wall surface 303 side and the inner peripheral wall surface 301 side of the case member 300 have a relatively high solidification rate as compared with the central region of the thickness of the peripheral wall portion 305 of the case member 300. Therefore, the outer peripheral wall surface 303 side and the inner peripheral wall surface 301 side of the peripheral wall portion 305 of the case member 300 are close to the mold surface of the mold, and the solidification rate is relatively faster than the central region of the thickness. Even if the compound is formed, it is considered that the growth of the iron-carbon compound is suppressed, and consequently the size of the iron-carbon compound is suppressed.

  On the other hand, in the central region of the thickness of the peripheral wall portion 305 of the case member 300, the solidification rate is slower than the outer peripheral wall surface 303 side and the inner peripheral wall surface 301 side. Is done. Here, the iron-carbon compound has a relatively low magnetic flux density, magnetic permeability, and the like than the ferrite base structure close to pure iron. For this reason, it is expected that the magnetic flux leaks in a radially outward direction from the outer peripheral wall surface 303 of the case member 300 while allowing the magnetic flux to pass through the peripheral wall portion 305 of the case member 300.

  According to the present embodiment, when the silicon content of the soft magnetic material for magnetic circuit constituting the case member 300 is W1, and the silicon content of the silicon steel plate 210 constituting the stator 200 is W2, W1 = Any of W2, W1≈W2, W1> W2, and W1 <W2 may be used.

  FIG. 7 shows another application example applied to a motor as an actuator. The motor basically has the same configuration as that of the second embodiment. A common code | symbol is attached | subjected to a common site | part. In the following, different parts will be mainly described. That is, the stator 200 is formed by laminating a plurality of silicon steel plates 210 containing silicon in the thickness direction, that is, in the center line PA direction of the stator 200. The case member 300 </ b> B is formed by casting a cast steel melt on the outer peripheral side of the stator 200 and solidifying it. Therefore, the gap between the inner peripheral wall surface 301 of the case member 300B and the stator 200 is eliminated, and the connectivity is improved. In particular, since the stator 200 has a laminated structure in which a plurality of silicon steel plates 210 are laminated, the connectivity between the inner peripheral wall surface 301 of the case member 300B and the stator 200 is improved.

  Further, since the case member 300B is formed by casting a cast steel melt from the outer peripheral side of the stator 200 and solidifying it, the inner peripheral wall surface 301 of the case member 300B may not be cut, or The number of man-hours for cutting the inner peripheral wall surface 301 can be greatly reduced. Therefore, it is not necessary to consider much the machinability of the inner peripheral wall surface 301 of the case member 300B. Therefore, the silicon content in the soft magnetic material for a magnetic circuit constituting the case member 300B can be further increased.

  In this case, since the ferrite becomes silicon-rich in the soft magnetic material for the magnetic circuit, the magnetic properties such as the magnetic flux density and the magnetic permeability can be further improved, and further, it is advantageous for increasing the strength and hardness. . The molten metal may be directly cast from the outer peripheral side of the stator 200 and solidified, or the molten metal is applied from the outer peripheral side of the stator 200 via the coating agent in a state where the coating agent is applied to the outer peripheral side of the stator 200. It may be solidified by casting. In addition, since both the silicon steel plate 210 which comprises the stator 200, and the cast steel which comprises the case member 300B are low carbon iron-silicon type | system | group alloys, cast-hole joining property is ensured.

  According to the present embodiment, when the silicon content of the soft magnetic material for magnetic circuit constituting the case member 300B is W1, and the silicon content of the silicon steel plate 210 constituting the stator 200 is W2, W1 = Any of W2, W1≈W2, W1> W2, and W1 <W2 may be used. Since the case member 300B is cast, the man-hours for cutting the case member 300B can be reduced or eliminated. For this reason, it can be set as W1> W2, and magnetic properties, such as the magnetic permeability of case member 300B, and intensity can be raised.

  In the application example described above, the actuator is applied to an inner rotor type motor, but may be applied to an outer rotor type motor. The present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the scope of the invention.

6 is a graph showing hysteresis curves according to Example 1 and Comparative Example 3. It is a photograph which shows the microscopic structure of this invention material. It is a photograph which shows the microscopic structure of this invention material. It is sectional drawing which showed the example of application and followed the axis line of the rotor of an actuator. It is sectional drawing along the direction orthogonal to the axis line of the rotor of an actuator concerning an application example. It is sectional drawing which expands and shows the part of the case member along the direction orthogonal to the axis line of the rotor of an actuator concerning an application example. It is sectional drawing along the direction orthogonal to the axis line of the rotor of an actuator concerning another application example.

Explanation of symbols

  Reference numeral 100 denotes an inner rotor (mover), 200 a stator, 201 an outer peripheral wall surface, 300 a case member, 301 an inner peripheral wall surface, and 400 a coil winding.

Claims (8)

  A soft magnetic material for a magnetic circuit, characterized in that it is made of an iron-based solidified metal comprising a base structure mainly composed of ferrite and an iron-carbon compound dispersed in the base structure.   A soft magnetic material for a magnetic circuit, wherein the ferrite is silicon ferrite containing silicon.   3. The soft magnetic material for a magnetic circuit according to claim 1, wherein the iron-based solidified metal contains 2% or less of carbon by mass ratio.   3. The soft magnetic material for a magnetic circuit according to claim 1, wherein the iron-based solidified metal contains 0.3 to 10% of silicon by mass ratio.   5. The soft magnetic material for a magnetic circuit according to claim 1, wherein the iron-carbon compound is dispersed in the base structure in an island shape. 6.   The soft magnetic material for a magnetic circuit according to any one of claims 1 to 5, wherein the iron-carbon compound is pearlite and / or cementite.   In any one of Claims 1-6, when the area of the said iron-carbon compound is set to S1 and the area of graphite is set to S2 in an optical microscope visual field, S1 / S2 is 0.5 or more. A soft magnetic material for magnetic circuits. In an actuator comprising a mover, a stator disposed so as to face the mover, and a case member having an inner wall surface surrounding and holding an outer wall surface of the stator,
The said case member is formed with the soft-magnetic material for magnetic circuits which concerns on any one of Claims 1-7, The actuator characterized by the above-mentioned.

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