JP2010193568A - Integral assembly composed of motor case and magnet in electric motor, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an integral assembly composed of a motor case for an electric motor and a magnet, capable of reducing the number of manufacturing processes compared with a conventional method, reducing time and labor necessary for manufacturing, and also solving various problems resulting from the adhesion of a magnet material to the motor case and lowering manufacturing cost, thereby facilitating manufacture of the integral assembly. <P>SOLUTION: The motor case 12 for the electric motor is injection-molded by using a composite material composed of soft magnetic powder and thermoplastic resin. The magnet 14 is injection-molded by using the composite material composed of the soft magnetic powder and thermoplastic resin. Then, the motor case 12 and the magnet 14 are integrally molded by two-color injection-molding, and the integral assembly 15 composed of the motor case 12 and the magnet 14 is manufactured. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor case / magnet integrated assembly in an electric motor and a method of manufacturing the same.

Conventionally, inner rotor type permanent magnet servo motors (electric motors) have been widely used for automobile electrical equipment, semiconductor manufacturing equipment, and the like.
In this electric motor, as shown in FIG. 7, on the inner surface of a motor case 200 as an outer case that functions as a back yoke, a ring-shaped segment continuous in the circumferential direction or a segment-type magnet (permanent magnet) separated in the circumferential direction. ) 202 is fixed, and a rotating rotor (not shown) is arranged at the center thereof.

In this type of electric motor (DC motor), a cylindrical metal case, generally a structural steel material such as JIS SS400 or SPC, has been used as the motor case 200.
However, in the case of the metal motor case 200, it is difficult to process and form it with high accuracy, and a lot of man-hours are required for its manufacture.

Specifically, conventionally, in order to seamlessly form and form the metal motor case 200, a deep drawing process of a metal material has been performed as the processing method. In this case, in order to prevent the occurrence of cracks or the like during the processing, It is necessary to make the motor case 200 of the final desired depth through such a processing step, which requires a lot of man-hours for the processing, and accordingly, the processing cost increases.
In addition, the metal motor case 200 is heavy in addition to high material cost, and particularly when used for automobiles, it is difficult to meet such demands while reducing the weight of parts. There is a problem.

  In addition, when a metal case is used for the motor case 200, as shown in FIG. 8 (a), after the motor case 200 is processed and formed, the inner surface of the motor case 200 has a ring shape or a segment type (hereinafter referred to as a ring shape). It is necessary to bond and fix the magnet material (which becomes magnet 202 by magnetization) using an adhesive 204 (see FIG. 7). It was happening.

  When adhering the magnet material to the motor case 200, in order to position the magnet material in an accurately corresponding position with respect to the rotor, the magnet material must be adhered in a state of being accurately positioned. The magnet material was positioned using a jig for positioning, and the adhesive was fixed.

  In addition, it is necessary to perform adhesive application processing, adhesion of the magnet material to the motor case 200, and further curing of the adhesive by heating and ultraviolet irradiation. In order to bond and fix the motor case 200, much labor and time are required.

  FIG. 8 (b) shows a conventional motor manufacturing process. As shown in FIG. 8 (b), steel material processing is performed to manufacture a metal motor case 200 and to fix and fix a magnet material. Many processes such as motor case dimension inspection, adhesive bonding of magnet material, curing of adhesive, inspection of adhesion position were required.

In addition, when the magnet material is bonded to the motor case 200, variations in the application of the adhesive occur, and as a result, variations in the adhesive strength occur, and in the worst case, between the magnet material and the motor case 200. Will cause adhesion peeling.
Furthermore, there is a large difference in thermal expansion and contraction between the metal motor case 200 and the magnet material, which causes stress concentration in the adhesive layer and subsequently adversely affects the adhesive strength.

In addition, there exist some which were described in the following patent document 1, patent document 2, and patent document 3 with respect to this invention.
Patent Document 1 discloses that a motor case and a blocking member on the inner surface thereof are integrally formed by injection molding. However, in the one described in Patent Document 1, the motor case is simply a resin, and The blocking member is simply an elastomer, and is different from the present invention which is intended for a motor case having a function as a back yoke and a magnet (permanent magnet) on the inner surface thereof.

Patent Document 2 discloses an invention relating to a “spindle motor for information equipment”, in which a metal housing of a hydrodynamic bearing device is formed by metal injection molding.
However, the one described in Patent Document 2 relates to a bearing housing, and the object of injection molding is a housing alone, which is different from the present invention.

  Further, Patent Document 3 discloses an invention about an “electric throttle valve device”, in which a cylindrical stator is formed by injection molding using the same material, and a motor case and a magnet material are formed using the cylindrical stator. Although the point which made it combine is disclosed, this thing is different from this invention by the point by which the motor case and the magnet material are comprised with the same material.

Special table 2003-530808 gazette JP 2005-140339 A JP 2000-8886 A

  The present invention is based on the above circumstances, and can reduce the number of manufacturing steps compared to the conventional method, reduce the labor and time required for manufacturing, and solve the above-mentioned problems caused by the application of the magnet material with an adhesive. An object of the present invention is to provide a motor case / magnet integrated assembly for an electric motor that can be manufactured at low cost and a method for manufacturing the same.

  Thus, claim 1 relates to a motor case / magnet integrated assembly, in which a motor case as an outer case having a function as a back yoke and a magnet fixed to the inner surface of the motor case are integrated. The motor case is composed of an injection-molded composite material obtained by mixing soft magnetic powder and a thermoplastic resin as a binder, and as a hard magnetic powder and binder for a permanent magnet. A composite bonded magnet material injection-molded body mixed with a thermoplastic resin is fixed to the inner surface of the motor case, and the motor case and the bonded magnet material are integrated by injection molding. The magnetic poles of the N pole and the S pole are alternately magnetized in the circumferential direction with respect to the bonded magnet material.

  According to a second aspect of the present invention, in the first aspect of the present invention, the motor case includes both sides in the circumferential direction centered on a portion located at a boundary between the magnetic poles of the N pole and the S pole in the magnet on the inner surface side of the motor case. However, it is characterized in that it is partially thick with respect to the portion located at the center in the circumferential direction of the magnetic pole.

  According to a third aspect of the present invention, in the second aspect, the thickened portion has a maximum thickness at the boundary position of the magnetic pole, and the thickness gradually decreases as the distance from the boundary position increases in the circumferential direction. Features.

  Claim 4 relates to a method of manufacturing an integrated assembly of a motor case and a magnet. First, one of the motor case and the bonded magnet material is first injection-molded, and the other is left in the mold and the other is molded. The motor case and the bonded magnet material are molded and integrated by a two-color molding method in which a mold is used for injection molding, and then the bonded magnet material is magnetized.

Effects and effects of the invention

  As described above, the motor case / magnet integrated assembly according to the present invention is composed of a composite injection molded body in which the motor case is a mixture of soft magnetic powder and a thermoplastic resin as a binder. The magnet material is composed of an injection molding of a composite material (bond magnet material) made by mixing hard magnetic powder for permanent magnets and a thermoplastic resin as a binder, and these are integrated by injection molding. In addition, in the present invention, it is difficult to process when manufacturing a motor case using a metal material as in the prior art. It can solve the problems such as high processing man-hours and high cost. Also, after manufacturing the motor case, the problem of labor for applying and curing the adhesive when fixing the magnet material, and positioning at the time of bonding work Or if adhesive is applied Variation in adhesive strength due to such regard, can solve the problem of bonding exfoliation, the integral assembly body of the motor case magnet by a reduced number of steps can be produced inexpensively, and it is possible that the weight be lighter.

By the way, when the motor case is made of a composite material of a soft magnetic powder and a thermoplastic resin as a binder, that is, a bond material, the motor case is naturally back as compared with the case where the motor case is made of a soft magnetic metal material. Magnetic field lines are less likely to pass through the motor case as a yoke.
Accordingly, if the motor case is thin over the entire circumference, the magnetic lines of force from the magnet on the inner surface side will leak from the motor case to the outside.
If the magnetic field lines leak to the outside as described above, that is, if magnetic leakage occurs, the motor performance is degraded.

In this case, if the thickness of the motor case is increased over the entire circumference, magnetic leakage can be prevented, and deterioration of the motor performance can be prevented. On the other hand, if the thickness of the motor case is increased, the motor case The weight increases, and the effect of configuring a conventional heavy metal motor case with a composite material (bond material) of magnetic powder and thermoplastic resin is diminished.
Further, when the thickness of the motor case is increased over the entire circumference, the amount of material used increases and the material cost increases.

  In this case, the circumferential direction of the magnetic pole covers a predetermined circumferential length at both sides in the circumferential direction centering on a portion located at the boundary between the magnetic poles of the north pole and the south pole of the magnet on the inner surface side in the motor case. It is comprised partially thickly with respect to the site | part located in the center of.

  As will be clarified later, the portion of the motor case located at the boundary between the magnetic poles of the N and S poles is the portion where the density of the magnetic field lines is highest, that is, the portion where the magnetic flux is concentrated. It becomes the portion where magnetic saturation is most likely and magnetic leakage is likely to occur.

  Therefore, in this second aspect, the portion where magnetic leakage is most likely to occur is partially thickened with respect to the other portions. By doing so, the thickness of the motor case is made as thin as possible. However, the magnetic leakage was prevented, and it was possible to achieve both the demand for weight reduction required for the motor case and the maintenance of good motor performance.

  In this case, the partially thick portion can have a maximum thickness at the boundary position of the magnetic pole, and the thickness gradually decreases as the distance from the boundary position increases in the circumferential direction. 3).

  Claim 4 relates to a method for manufacturing a motor case / magnet integrated assembly. In this manufacturing method, one of the motor case and the magnet material is first injection-molded, and then one of the motor case and the magnet is left in the mold. Using the same mold, the other is injection-molded (two-color molding), thereby integrating the motor case and the magnet material, and thereafter magnetizing the magnet material, so that the motor case -Manufactures an integrated assembly of magnets. According to this manufacturing method, an integrated assembly of a motor case and a magnet can be manufactured inexpensively, easily and accurately with a small number of steps.

It is a figure of the motor case and magnet integral assembly and electric motor which are one embodiment of the present invention. It is a manufacturing-process figure of the assembly | attachment body of the same embodiment. It is a flowchart of the manufacturing process of the electric motor of FIG. It is a figure of other embodiment of this invention. It is explanatory drawing of the advantage of embodiment of FIG. It is a figure of other embodiment of this invention. It is a figure which shows an example of the conventional motor case and magnet assembly. It is explanatory drawing of the manufacturing process of the assembly | attachment body of FIG.

Next, embodiments of the present invention will be described in detail below.
In FIG. 1, 10 is an electric motor (DC pulse motor), and 12 is a bottomed cylindrical motor case as an outer case that functions as a back yoke. A cylindrical (permanent magnet) 14 is fixed integrally.
As shown in the drawing, here, the magnet 14 is fixed directly to the inner surface of the motor case 12 without the adhesive 204, unlike the conventional one shown in FIG.
In the present embodiment, the motor case 12 and the magnet 14 constitute an integral assembly 15.
In this embodiment, the magnet 14 and the motor case 12 constitute a stator.

Reference numeral 16 denotes a rotating rotor disposed at the center, 18 denotes a winding in the rotor 16, and 20 denotes a rotating shaft.
The rotary shaft 20 is rotatably supported at the end portions in the axial direction by bearing portions 22 and 24.
As shown in FIG. 4, the rotor 16 has comb teeth 26 extending radially from the center, and a winding 18 is wound around each comb tooth 26.

In this embodiment, the motor case 12 is composed of a composite injection-molded body obtained by mixing soft magnetic powder and a thermoplastic resin as a binder.
As the soft magnetic powder, various powders having excellent magnetic permeability such as iron powder and stainless steel powder can be used.
As the thermoplastic resin, various materials such as polyamide 12, polyamide 6, PPS, PBT, EEA, EVA, polypropylene, polyethylene, PVC, CPVC can be used, but PPS excellent in rigidity, heat resistance, and chemical resistance. Is particularly preferred.

The mixing ratio of the soft magnetic powder and the thermoplastic resin can be various ratios, but it is preferable that the mixing ratio is such that the content ratio of the soft magnetic powder is 50 to 70% by volume.
If the content ratio of the soft magnetic powder is less than 50% by volume, the desired magnetic properties cannot be obtained sufficiently. On the other hand, if the content exceeds 70% by volume, the mixing ratio of the thermoplastic resin is reduced and injection molding can be performed satisfactorily. Absent.
Preferably, soft magnetic powder having an average particle size of 100 to 200 μm is used.

In this embodiment, the magnet 14 is also composed of an injection molded body.
Specifically, the magnet 14 is molded integrally with the motor case 12 as an injection molded body of a composite bonded magnet material obtained by mixing hard magnetic powder for permanent magnets and a thermoplastic resin as a binder.
This bonded magnet material injection molding is then magnetized to form a magnet 14.
Here, the magnetization is performed in a state in which N poles and S poles are alternately positioned in the circumferential direction as shown in FIG.

In this embodiment, various hard magnetic powders for the magnet (permanent magnet) 14 can be used. In this embodiment, magnetic powder of a rare earth iron-based alloy is used as the hard magnetic powder.
Here, as the rare earth iron-based alloy, Nd—Fe—B, Sm—Fe—N based magnetic powder or the like can be suitably used.

  Also, various types of thermoplastic resins such as polyamide 12, polyamide 6, PPS, PBT, EVA, polypropylene, polyethylene, PVC, and CPVC can be used as the thermoplastic resin for magnet composites (bond magnet materials). PPS having excellent chemical resistance is particularly suitable.

  In the present embodiment in which the motor case 12 and the magnet 14 (strictly, the magnet material before magnetization) are integrally formed by injection molding, a composite material for the motor case 12 and a composite material for the magnet 14 are used. It is preferable to use the same kind of thermoplastic resin. Specifically, it is preferable to use the above PPS.

In the composite material (bonded magnet material) for the magnet 14, the mixing ratio of the magnetic powder and the thermoplastic resin is preferably determined so that the magnetic powder is 50 to 70% by volume.
If the content of the magnetic powder is less than 50% by volume, the desired magnetic properties cannot be obtained. Conversely, if the content of the magnetic powder exceeds 70% by volume, the resin content is relatively low and injection molding cannot be performed satisfactorily.
In addition, the suitable particle size of magnetic powder is 100-200 micrometers by an average particle diameter.

FIG. 3 shows a process of manufacturing the electric motor 10 in the present embodiment.
As shown in the figure, in this embodiment, a bonded magnet material is first formed by injection molding.
Specifically, a magnet molded body 14A is molded by injecting a composite material (bonded magnet material) for the magnet 14 into the cavity 30 of the molding die 28 having the split dies 28A and 28B shown in FIG. FIG. 2 (I)). Subsequently, the motor case 12 is injection molded by a two-color molding method.

Specifically, the split mold 28A is used as a common mold, and the split mold 28B and the split mold 28C are replaced with the previously formed magnet molded body 14A, and the cavity 32 is formed there. A composite material for the motor case 12 is injected into the cavity 32 by an injection machine to form the motor case 12, and at the same time, the motor case 12 and the magnet molded body 14A are integrated (FIG. 2 (II)).
Then, as shown in FIG. 3, the magnet molded body 14A is magnetized through an inspection of the position of the magnet molded body 14A to form a magnet 14 (FIG. 2 (IV)).

Thereafter, the rotor 16 is assembled through a magnetic force inspection of the magnet 14 to constitute the electric motor 10.
In this case, the magnet molded body 14A is first molded and then the motor case 12 is molded. Conversely, the motor case 12 is molded first, and then the magnet molded body 14 is molded into two colors. May be integrally molded and fixed.

  In the motor case / magnet integrated assembly 15 of the present embodiment as described above, it is difficult to process the motor case 12 using a metal material as in the conventional case, and the number of processing steps is large. In addition, it can solve the problems such as high cost, and the problem of labor for applying and curing the adhesive when the magnet material is bonded and fixed after the manufacture of the motor case 12, as well as positioning and adhesive during the bonding operation. It is possible to solve the problems of adhesive strength variation and adhesive peeling due to variations in coating, etc., the motor case / magnet integrated assembly 15 can be manufactured at low cost with less man-hours, and the weight can be reduced. It becomes possible.

  Furthermore, according to the manufacturing method of the present embodiment, the motor case / magnet integrated assembly 15 can be manufactured inexpensively, easily and with high accuracy with a small number of steps.

FIG. 4 (a) shows another embodiment of the present invention (in FIG. 4, the winding 18 of the rotor 16 is omitted).
This embodiment of the motor case 12, the position of the boundary of the magnetic poles of the N and S poles in the magnet 14 a predetermined circumferential length both sides of the circumferential direction about the site located (position of figure P ₁₎ over the (entire circumference 4 circumferential length of one minute), with respect to site located at the position of the center in the circumferential direction of the pole (position of figure P _2), the thick portion forming a partially thick This is an example of 34.

In this example, the thick portion 34 becomes maximum thickness at the position P ₁ of the boundary of the magnetic poles, it has a shape which thickness is gradually reduced as the distance from the position P ₁ of the boundary in the circumferential direction. In this example, the thick portion 34 has a curved shape with a continuous outer peripheral shape.

In this example, the ring-shaped magnet 14 has an inner diameter of 28 mm, an outer diameter of 34 mm, and an axial length of 50 mm. The motor case 12 has an inner diameter of 35 mm and is located from the center O to the center position P ₂ of the magnetic pole. the distance to the periphery of the site is 19 mm, the distance from the center O to the outer periphery of the site located at the position _{P 1} of the boundary of the pole at 21 mm, the thickness of the drawing _{t 2} is 2 mm, the thickness of _{t 1} is 4mm It is.
The thickness of the thick portion 34 gradually decreases from the portion having the maximum thickness t _{1 to} the portion having the minimum thickness t ₂ .
The axial length of the motor case 12 is 70 mm.

As shown in FIG. 5, a portion located at a position P ₁ of the boundaries of the magnetic poles of the magnet 14 is a portion where the magnetic flux density is the highest, the portion prone most magnetic saturation to facilitate, hence magnetic leakage Part.
In this embodiment, the most for about a portion located at a position P ₁ of the boundary of the magnetic leakage is likely part undergo magnetic pole circumferential sides of portion is partially thick, the magnetic flux is most concentrated It is possible to effectively prevent the occurrence of magnetic leakage in the portion that performs.

On the other hand, since the thickness of the motor case 12 in a portion located at a position P ₂ of the central pole is thinner in, as compared with the case of thicker over the motor case 12 to the entire circumference, the motor case 12 The increase in weight can be minimized.
As a result, it is possible to achieve both the demand for weight reduction required for the motor case 12 and the maintenance of good performance of the electric motor 10.

Incidentally in FIG. 4 (b), in equal thickness over the thickness of the motor case 12 to the entire circumference, specifically shows those of the same thickness as the portion located P ₂ in FIG. 4 (b) .
To be as shown FIG. 5 (b), the case is accidentally magnetic saturation at the site of position P ₁ of the boundary of the pole is a portion to concentrate most flux, magnetic leakage field lines from leaking to the outside It will happen. As a result, the magnetic flux density in the motor case 12 decreases, which leads to a decrease in motor performance.

The shape of the thick portion 34 shown in FIG. 4 is merely an example, and the thick portion 34 can be formed in various other shapes.
FIG. 6 shows a specific example.
Of these, the example of FIG. 6A is an example in which the shape (cross-sectional shape) of the thick portion 34 is an angular shape that is the thickest at the boundary position P ₁ of the magnetic pole, and FIG. In this example, the circumferential length of the thick portion 34 is shortened.

Further, the example of FIG. 6C is an example in which the thick portion 34 is formed so that the outer shape is a straight shape in the tangential direction.
In the above example, the magnet 14 is magnetized so that the N pole and the S pole are positioned every 90 ° in the circumferential direction, and the thick portion 34 is formed accordingly. The magnet 14 is magnetized so that the N pole and the S pole are switched at 45 ° intervals in the circumferential direction as shown in FIG. It is also possible to form a part or a part.
In addition, this invention can be comprised and implemented with the form and aspect which added the various change in the range which does not deviate from the meaning.

DESCRIPTION OF SYMBOLS 10 Electric motor 12 Motor case 14 Magnet 15 Motor case and magnet integrated assembly 28 Molding die 34 Thick part

Claims (4)

A motor case as an outer case having a function as a back yoke and a magnet that is fixed to the inner surface of the motor case, the motor case comprising soft magnetic powder and a thermoplastic resin as a binder And a composite bonded magnet material injection molded body obtained by mixing a hard magnetic powder for a permanent magnet and a thermoplastic resin as a binder. Fixed to the inner surface of the motor case,
The motor case and the bonded magnet material are integrated by injection molding, and the N and S poles are alternately magnetized in the circumferential direction of the bonded magnet material. An integrated assembly of a motor case and a magnet in an electric motor.   2. The motor case according to claim 1, wherein both sides of a circumferential direction centering on a portion of the magnet on the inner surface side of the motor case located at the boundary between the magnetic poles of the N pole and the S pole are in the circumferential direction of the magnetic pole. A motor case / magnet integrated assembly in an electric motor, wherein the motor case is partially thick with respect to a portion located in the center of the motor.   3. A motor in an electric motor according to claim 2, wherein the thickened portion has a maximum thickness at a boundary position of the magnetic pole, and the thickness gradually decreases as it moves away from the boundary position in the circumferential direction. Integrated body of case and magnet. It is a manufacturing method of the motor case and magnet integrated assembly in any one of Claims 1-3, Comprising: After injection-molding one of the said motor case and a bond magnet material first, leaving this one in a shaping | molding die The motor case and the bonded magnet material are molded and integrated by a two-color molding method in which the other is injection-molded using the molding die, and then the bonded magnet material is magnetized. To manufacture a motor case / magnet integrated assembly.

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