JP2006280052A - Electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the efficiency of an electric motor having a split core. <P>SOLUTION: A core 20 split with a foundation portion 32 split and an erect portion 34 are fastened with bolts 36. This brings a joint surface 46 of the foundation portion 32 to the erect portion 34 into close contact with each other, thus reducing magnetic resistance and improving efficiency. The bolt 36, made of non-magnetic material, reduces the number of magnetic fluxes passing through the bolt, thus reducing an eddy current developed in the bolt. Moreover, a ratio (H/D) of a distance H between a teeth front end face 48 and a bolt head top face 50 to a diameter D of a bolt hole is set at ≤0.3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric motor, and relates to a core structure serving as a magnetic path.

  The electric motor has magnetic poles arranged to form a moving magnetic field. The magnetic pole generally includes a tooth standing on a common yoke and a coil wound around the tooth. A moving magnetic field is formed by supplying electric power to the coils of the magnetic poles in a predetermined phase according to the arrangement order. It is preferable that the teeth tips of adjacent magnetic poles are close to each other. This is because the magnetic field fluctuation on the side facing the magnetic pole and receiving the magnetic field formed by the magnetic pole can be reduced, and loss can be reduced. On the other hand, the space between the teeth is a space in which the coil is arranged. If this space is small, the coil cross-sectional area becomes small, which is disadvantageous for generating a strong magnetic field. In view of this, the tip portion of the teeth is provided with bevel portions projecting on both sides toward the adjacent teeth, while the portion around which the coil is wound is made thinner than the tip portion to increase the coil cross-sectional area.

  However, the coil needs to be inserted into a so-called slot between the teeth from the gap between the tips of the narrow teeth, and the workability is poor, and the ratio of the total cross-sectional area of the conducting wire forming the coil to the slot cross-sectional area (space factor) ) Cannot be large enough. In order to solve this problem, the following patent document describes a technique in which a core is divided, a coil is first attached to one of the divided pieces, and then the divided pieces are joined.

JP-A-6-327208 JP 2000-253635 A

  In the above-mentioned patent document, the divided cores are abutted together and molded by resin and bonded. For this reason, there is a problem that the divided pieces that are abutted do not sufficiently adhere to each other at the joint surfaces, and a gap is generated as a magnetic circuit, resulting in an increase in magnetic resistance. In addition, in order to mold with resin, dedicated equipment is required, which causes a problem of increasing costs.

  It is an object of the present invention to reduce the gap by bonding the divided cores with a simple configuration.

  In the present invention, the divided cores are fastened with bolts to reduce the gap of the joint surface between the divided pieces. Specifically, in the electric motor of the present invention, teeth are erected on the yoke to form a core, and coils are provided on the teeth to serve as magnetic poles. It has an overhanging portion. The core is divided into a base part including a yoke and a standing part at the base of the tooth or the trunk of the tooth, and the coil is held between the base part and the umbrella part. The base part and the standing part which are the divided pieces of the core are fixed by using bolts arranged extending in the standing direction of the teeth.

  The bolt that joins the base portion and the standing portion is preferably made of a nonmagnetic material. When a magnetic flux flows through the bolt, an eddy current is generated due to a change in the magnetic flux density of the magnetic flux, leading to an increase in iron loss. For this reason, it is preferable that the bolt is made of a non-magnetic material in which magnetic flux does not easily flow.

  In addition, when inserting the bolt that joins the foundation part and the standing part from the tip end surface of the tooth, if the head part of the bolt is close to the tip end surface of the tooth and the part where the fluctuation of the magnetic flux density is large, the nonmagnetic material is used. Therefore, an eddy current is generated in the bolt and a loss occurs. In order to reduce this loss, by making the top face of the bolt head deeper than the tip face of the teeth, the bolt is prevented from being located in a portion where the magnetic flux fluctuation is large. Specifically, the ratio of the distance from the tip end surface of the tooth to the top surface of the bolt head and the diameter of the bolt hole in the tip end surface of the tooth is set to 0.3 or more.

  Moreover, you may provide an unevenness | corrugation in the joint surface of a base part and an upright part so that it may mutually mesh when these are fixed.

  The core can be a powder magnetic core in which powder or particles of a magnetic material are pressed into a predetermined shape. Further, the standing portion of the core can be configured to increase the mechanical strength with respect to the base portion, and the base portion can have a higher specific resistance than the standing portion. For example, the strength can be increased by applying heat to a magnetic powder or the like and then heat-treating, and such a material can be used for the standing portion, while the base portion is not subjected to heat treatment. Use in a pressure-molded state.

  Further, the electric motor according to another aspect of the present invention is an electric motor in which a tooth is provided on a yoke to form a core, and a coil is provided on the tooth to form a magnetic pole. The core has a protruding overhang on both sides of the tip, and the core is divided into a base including the yoke and a standing part at the base of the teeth or the trunk of the teeth. The foundation portion and the standing portion are held between the portions, and the concavities and convexities provided on the joint surfaces thereof are engaged and fixed. At the meshing portion, the gap between the base portion which is a divided piece and the standing portion can be reduced.

  Also in this aspect, the core material can be a dust core. Further, the characteristics of the core base portion and the standing portion can be increased in the magnetic permeability in the base portion, and the standing portion can be increased in mechanical strength.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of an electric motor 10 according to the present embodiment, and FIG. 2 is a cross-sectional view of one magnetic pole of a stator of the electric motor 10. FIG. 3 is an exploded perspective view of the stator.

  The electric motor 10 is a so-called axial type electric motor in which the poles of the stator 12 and the rotor 14 face each other in the axial direction of the output shaft 16 of the electric motor 10. Stator 12 includes a core 20 fixed to case 18. The core 20 includes a substantially ring-shaped yoke 22 (see FIG. 2), and teeth 24 (see FIG. 2) that are erected from the yoke 22 toward the rotor and arranged in the circumferential direction. FIG. 2 is a cross-section of the core 20 on a cylindrical surface with the axis of the electric motor 10 as an axis, and is a view focusing on one magnetic pole. The yoke 22 is the range shown in FIG. 2 of the core 20, and the adjacent magnetic poles are connected to each other at this portion. The teeth 24 are the range of the core 20 shown in FIG. A tip 26 (upper end in FIG. 2) of the tooth 24 is provided with a bevel portion 26 that extends and protrudes toward the adjacent tooth side. A coil 30 is wound around a trunk portion 28 that is a portion of the teeth between the bevel portion 26 and the yoke 22.

  The rotor 14 includes a disk 31 fixed to the output shaft 16 and permanent magnets 33 arranged in a circumferential direction on a surface of the disk 31 facing the stator 12. When electric power is supplied to the coils 30 in which the stator 12 is arranged at a predetermined phase to form a rotating magnetic field, the rotor 14 is rotated by the interaction between the permanent magnet 33 of the rotor 14 and the rotating magnetic field, and the output shaft 16 is rotated. Rotate.

  As described above, when the bevel portion 26 is provided at the tip of the tooth, it is impossible to adopt a method of forming a magnetic pole by fitting a coil, which has been formed in a predetermined shape, into the tooth in advance. Therefore, in the present embodiment, the core 20 is divided at the trunk portion 28 of the tooth into a base portion 32 and a standing portion 34 arranged so as to stand on the core portion 32. The division position may be a boundary portion between the yoke 22 and the tooth 24, or may be a position where a part of the base side of the yoke 22 and the tooth 24 is integrated as shown in FIG. As long as the standing portion 34 can be fixed by a bolt 36, which will be described later, the division position may be further on the tooth tip side than the position shown in FIG.

  The base portion 32 and the standing portion 34 are provided with bolt holes 38 and 40 that extend perpendicularly to the surface from the tip end surface of the teeth, and the bolt 36 passes therethrough. The threaded tip of the bolt 36 reaches the screw hole of the case 18 where it is screwed. A head 42 of the bolt 36 (hereinafter referred to as a bolt head 42) abuts against a shoulder portion 44 which is a portion where the diameter of the bolt hole 40 changes, and the base portion 32 and the standing portion 34 are attached to the case by tightening the bolt 36. Fixed. At this time, as the reaction force of the bolt tension, the base portion 32 and the standing portion 34 are subjected to a force for bringing them close to each other, and the joint surfaces 46 of the both are brought into close contact with each other. The joint surface 46 is a divided surface obtained by dividing the core described above into a base portion and a standing portion.

  The aforementioned dividing or joining surface 46 must be provided at a position where the shoulder 44 of the bolt hole is formed. That is, in FIG. 2, if it is provided at the position of the shoulder portion 44 or above, the portion above the division surface of the teeth cannot be fixed to the bolt, so it cannot be provided at such a position. Even if the lower portion of the shoulder portion 44 is too thin, there is no strength and the portion on the tip side of the tooth cannot be fixed. Therefore, the dividing surface should be provided at a lower position to obtain the required strength. become.

  The core 20, that is, the foundation portion 32 and the standing portion 34 are configured by a dust core. The dust core is formed by pressing powder or particles of a magnetic material such as iron into a predetermined shape by pressing and insulating an insulating material such as resin. Preferably, a material obtained by coating a magnetic material powder or the like with a resin is press-molded into a predetermined shape. In the dust core, since the conductor is powder and particles, eddy currents are hardly generated and the iron loss is effective. Further, when the bolt 36 is made of a magnetic material, the magnetic flux penetrates the bolt, and an eddy current is generated due to the fluctuation of the magnetic flux density of the penetrating magnetic flux, thereby increasing the loss. In order to prevent or suppress this, in the present embodiment, the bolt 36 is made of a nonmagnetic material such as titanium or nonmagnetic stainless steel.

  Further, in the vicinity of the tooth tip surface 48 of the bolt hole 40, the magnetic flux density fluctuation is large. If there is a bolt head 42 here, even if the bolt is a non-magnetic material, the magnetic flux penetrates and loss occurs due to the generation of eddy current. In the present embodiment, the top surface 50 of the bolt head is lowered from the tooth tip surface 48 so that the bolt is not located in a region where the magnetic flux density fluctuation is large.

  FIG. 4 is a diagram showing the relationship between the ratio (H / D) of the distance H from the tooth tip surface 48 to the bolt head top surface 50 and the diameter D of the bolt hole 40 at the teeth tip surface 48 and the magnetic flux density fluctuation. From the figure, when the ratio H / D is smaller than 0.3, the magnetic flux density fluctuation increases rapidly, and it is considered that the loss increases in this region. Therefore, the ratio H / D is preferably set to 0.3 or more.

  In the present embodiment, since the core is divided and formed as another part, the material, the manufacturing method, and the like can be changed for each part according to the characteristics required for each part. Specifically, the standing portion 34 has a bevel portion 26, a bolt hole 40, and the like, and has a relatively complicated shape, so that strength, particularly bending strength, is required. On the other hand, in the base portion 32, it is more important to reduce the loss than the strength. For this reason, it is required to increase the specific resistance. If the specific resistance is large, the generation of eddy current is reduced and the eddy current loss is reduced, so that the loss can be reduced. In order to give the above-mentioned characteristics to the foundation part 32 and the standing part 34, in this embodiment, the manufacturing method of the dust core is different between the two. As the base portion 32, a powder magnetic core obtained by pressure-molding magnetic powder is used, and the standing portion 34 performs a heating process after pressure-molding the magnetic powder. 5 and 6 are graphs showing differences in strength and specific resistance with and without heat treatment. FIG. 5 is a graph showing the bending strength, and it is understood that the bending strength is higher when heat treatment is performed regardless of the density of the magnetic powder. FIG. 6 is a graph showing the specific resistance, which is higher in the case where the heat treatment was not performed regardless of the density. Therefore, after press molding, heat treatment increases the strength, the specific resistance decreases, heat treatment is performed on the standing portion 34, while the base portion 32 is not heat treated, thereby obtaining the above-described characteristics. be able to.

  In the above embodiment, the base part 32 and the standing part 34 which are the division | segmentation pieces of a core are couple | bonded by tightening a volt | bolt. For this reason, the gap between the two can be reduced, the magnetic resistance due to the gap is reduced, and the efficiency of the electric motor is improved. In addition, since the gap is small, the thermal conductivity of this portion is also improved, and heat can easily flow from the standing portion 34 to the base portion 32 and then to the case 18 to improve heat dissipation.

  Further, since the bolt is made of a nonmagnetic material and the bolt head top surface 50 is positioned deeper than the tooth tip surface 48, the loss generated by the bolt is also reduced. By making the core a dust core and changing the manufacturing method depending on the core part, it is possible to match the characteristics required for that part.

  7 and 8 are diagrams showing a modification of the above-described embodiment. In the example shown in FIG. 7, an uneven shape that meshes with each other is provided on the joint surface 56 of the foundation portion 52 and the standing portion 54 corresponding to the above-described foundation portion 32 and the standing portion 34. When the base portion 52 and the standing portion 54 are coupled, pressure is applied and fixed in the direction in which they are engaged (the vertical direction in the figure). As a result, the degree of adhesion is improved, the magnetic resistance and the thermal resistance are reduced, and the efficiency of the electric motor and the heat dissipation are improved. FIG. 8 is a view showing a modification in which the bolt 36 is removed from the modification of FIG. Concavities and convexities are formed on the joint surface 66 of the base portion 62 and the standing portion 64 as in FIG. If a sufficient bonding force can be obtained by this unevenness, the bolt can be eliminated as in this modification.

  FIG. 9 is a diagram showing an outline of the assembly process of the stator 12. The core base portion 32 is divided into base portion split pieces 32a (a). This dividing plane is a plane that includes the axis of the electric motor, and is a plane that divides one tooth symmetrically with respect to this plane. The base part 32 may be divided for each tooth or may be divided for several teeth. In the case of illustration, it is the example which provided the division surface for every teeth. The base part divided pieces 32a are combined and arranged in an annular shape (b). Since the base part split piece 32a is provided with a part of the trunk portion 28 of the tooth, when the split pieces are arranged in an annular shape, a part of the stem part 28 protrudes on the annular plate. In this state, they are arranged side by side in the circumferential direction. The coil 30 is attached to the protrusion, and the standing portion 34 is also disposed. In this state, the bolt 36 is inserted into the bolt hole and coupled to the screw hole provided in the case to fix the base portion 32 and the standing portion 34 (c).

  FIG. 10 is a diagram illustrating another example of the assembly process of the stator 12. In this example, the way of dividing the core base portion is different from that shown in FIG. The dividing surface is a plane including the axis of the electric motor, but is divided at a portion between adjacent teeth. The base part divided pieces 32b divided in this way are arranged in an annular shape, and then the stator is assembled in the same manner as in the step of FIG.

  As mentioned above, in this embodiment, although the example which comprises the stator core 20 with a powder magnetic core was shown, the structure of laminating | stacking another structure, for example, an electromagnetic steel plate, etc. can also be taken. In this embodiment, concentrated winding is taken as an example of how to wind the coil, but distributed winding can also be employed. Further, the axial type electric motor has been described as an example. However, the present invention is not limited to this, and the present invention is also applied to a linear motor that is the most common electric motor configuration in which the magnetic poles of the stator and the rotor are opposed to each other in the radial direction. Can be applied.

It is sectional drawing which shows schematic structure of the electric motor 10 of this embodiment. 3 is a cross-sectional view showing a configuration of a magnetic pole of a stator of the electric motor 10. FIG. 2 is an exploded perspective view of the electric motor 10. FIG. It is a figure which shows the relationship between the distance of a bolt head top surface and a teeth front end surface, ratio of a bolt hole diameter, and a magnetic flux density fluctuation | variation. It is a figure which shows the relationship between the presence or absence of the heat processing in a powder magnetic core, and bending strength. It is a figure which shows the relationship between the presence or absence of the heat processing in a powder magnetic core, and a specific resistance. It is a figure which shows the other structural example of the core of a stator. It is a figure which shows the further another structural example of the core of a stator. It is a figure which shows the assembly process of a stator. It is a figure which shows the other assembly process of a stator.

Explanation of symbols

  10 motors, 12 stators, 18 cases, 20 cores, 22 yokes, 24 teeth, 26 bulkheads, 28 trunks, 30 coils, 32 foundations, 34 standing parts, 36 bolts, 38, 40 bolt holes, 42 bolt heads, 46 joint surface, 48 teeth tip surface, 50 bolt top surface.

Claims (8)

An electric motor in which teeth are erected on a yoke to form a core and coils are provided on the teeth to form magnetic poles.
The teeth have a trunk erected from the yoke, and a ridge that projects from both ends of the trunk.
The core is divided into a base portion including a yoke and a standing portion at the base of the teeth or the trunk of the teeth, and the coil is held between the base portion and the bulk portion,
The base portion and the standing portion are fixed by using bolts arranged to extend in the standing direction of the teeth,
Electric motor.   The electric motor according to claim 1, wherein the bolt is made of a nonmagnetic material. The electric motor according to claim 2,
The bolt is inserted from the tip of the tooth into the bolt hole opened in the tooth, and the ratio of the distance from the tip of the tooth to the top surface of the bolt head and the diameter of the bolt hole in the tip of the tooth is 0.3 or more. is there,
Electric motor.   4. The electric motor according to claim 1, wherein the joining surface of the base portion and the standing portion is provided with unevenness that meshes with each other when they are fixed. An electric motor in which teeth are erected on a yoke to form a core and coils are provided on the teeth to form magnetic poles.
The teeth have a trunk erected from the yoke, and a ridge that projects from both ends of the trunk.
The core is divided into a base part including a yoke and a standing part at the base of the tooth or the trunk of the tooth, and the coil is held between the base part and the umbrella part,
The base portion and the upright portion are coupled and fixed by meshing irregularities provided on their joint surfaces,
Electric motor.   6. The electric motor according to claim 1, wherein the core is a powder magnetic core in which powders or particles of a magnetic material are pressed into a predetermined shape. 7.   The electric motor according to claim 6, wherein the standing part of the core has a higher strength than the base part, and the base part has a higher specific resistance than the standing part. 8. The electric motor according to claim 1, wherein the electric motor is an axial motor in which the poles of the interacting stator and the rotor are opposed to each other in the axial direction of the electric motor.

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