JP2013169131A - Rotor for brushless motor, and electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor for a brushless motor, which improves the output of a motor while decreasing the weight of end plates attached to both end portions of a rotor core, inertia, and a cost; and an electric power steering device equipped with the rotor for a brushless motor.SOLUTION: On an outer peripheral surface of a rotor core 8, near both sides in circumferential directions of a plurality of opening portions 11 provided in the circumferential direction and in which magnets 9 are inserted and fixed, groove portions 12 are formed so as to divide peripheral edge portions of the opening portions 11 from each other, thereby preventing the short circuit of magnetic fluxes of the magnet 9. At both ends in an axial direction of the rotor core 8, end plates 10 having projections 13 are fixed by press-fitting the projections 13 in the grooves 12, and prevent scattering of the magnets 9 inserted and fixed in the openings 11. The depth of the groove portion 12 is made to be equal to the opening portion 11 or an outer diameter side in a diametrical direction of the rotor core 8, and inner diameter dimensions of the end plate 10 is equal to or slightly smaller than the inscribed circle diameter of the opening portion 11.

Description

  The present invention relates to a structure of a brushless motor rotor in which a permanent magnet is embedded, and an electric power steering apparatus including the same.

  2. Description of the Related Art Conventionally, a brushless motor is known in which a rotor having a permanent magnet is disposed inside a stator having an exciting coil, and the rotor is rotated by supplying electric power to the exciting coil of the stator. The rotor in such a brushless motor is configured such that a rotor core on which electromagnetic steel plates are laminated, a permanent magnet, and a shaft that is an output shaft rotate together. The rotor core is provided with a shaft at the center of rotation and a permanent magnet near the outer peripheral end. The rotor core rotates according to the magnetic field generated by the stator and outputs the power from the shaft. The permanent magnet is inserted into an opening provided in the rotor core and fixed to the rotor core with an adhesive. A pair of end plates made of aluminum alloy are provided so as to sandwich the rotor core from both sides of the rotor in the rotation axis direction, and the permanent magnet is fixed to the rotor core and prevents the permanent magnet from scattering during high-speed rotation. Yes.

  By the way, since the material (linear expansion coefficient) is different between the rotor core and the end plate, the amount of change due to heat of the rotor core and the end plate is different. Therefore, when the permanent magnet and the end plate are fixed to the rotor core using an adhesive, stress in the compression direction or the tensile direction is generated in the rotor core along the radial direction, starting from the portion fixed by the adhesive. Therefore, for example, when the rotor core is formed by laminating a plurality of electromagnetic steel plates, there is a problem that the electromagnetic steel plates at the axial ends are deformed.

  As a prior art for improving this part, Patent Document 1 discloses a stainless plate as an intermediate member having a linear expansion coefficient between the rotor core and the end plate, and between the rotor core and the end plate. A rotor is provided. With the intermediate member of this configuration, the end plate is not bonded to the rotor core. Moreover, since the difference between the linear expansion coefficient of the intermediate member and the linear expansion coefficient of the rotor core is small, the radial stress generated in the rotor core is reduced, and deformation of the electrical steel sheet can be suppressed.

JP 2006-238531 A

  However, in this prior art, an expensive stainless steel plate is used as an intermediate member of the nonmagnetic material in addition to the end plate made of an aluminum alloy which is a nonmagnetic material, so that the material cost increases. In addition, the end plate and the stainless steel plate have a structure that covers the entire surface of the end portion of the rotor core, so that there is a problem that the material cost further increases and the weight and inertia of the rotor increase.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a brushless motor rotor that improves motor output while reducing the weight, inertia, and cost of end plates attached to both ends of a rotor core. Another object is to provide an electric power steering apparatus including the same.

In order to solve the above problems, a brushless motor rotor according to the present invention includes a shaft that is an output shaft of a motor, a cylindrical rotor core that is press-fitted and fixed to the shaft, and a circumferential direction on the outer peripheral side of the rotor core. And a plurality of openings inserted into the plurality of openings, and annular end plates disposed on both end faces of the rotor core.
In particular, in the brushless motor rotor according to the present invention, the rotor core includes a groove portion extending in the axial direction so as to prevent a short circuit of magnetic flux between the magnets, and the end plate is formed by extending in the axial direction. A projection is provided, and the projection is fitted and fixed to the groove.
The electric power steering apparatus according to the present invention includes the brushless motor rotor.

Furthermore, the groove is provided in the vicinity of both sides of the opening in the circumferential direction of the rotor core.
Furthermore, the groove is provided on the same side as the opening or on the outer diameter side in the radial direction of the rotor core.
The inner diameter of the end plate is the same as or slightly smaller than the inscribed circle diameter of the opening.

According to the present invention, a rotor for a brushless motor that improves the output of a motor while reducing the weight, inertia, and cost of end plates attached to both ends of a rotor core, and an electric power steering apparatus including the rotor. There is an effect that it can be provided.
That is, the magnetic flux density generated by the rotor is reduced by the structure in which the groove portion extending in the axial direction is provided in the vicinity of the opening portion provided on the outer peripheral side of the rotor core to insert and fix the magnet so as to prevent short-circuiting of the magnetic flux of the magnet. The motor can be increased in output. In addition, by fitting multiple protrusions on the end plate into the groove and fixing the end plate to the rotor core, an expensive stainless steel plate is not required, reducing weight, reducing inertia, and reducing costs. It becomes.
Further, by providing the groove portions in the vicinity of both sides of the opening portion in the circumferential direction of the rotor core, it is possible to further prevent the magnetic flux from being short-circuited and to further increase the output of the motor. Furthermore, by making the depth of the groove the same or outer diameter side as the opening in the radial direction of the rotor core, and making the inner diameter of the end plate the same as or slightly smaller than the inscribed circle diameter of the opening, The end plate can be made to have the minimum necessary radial dimension, which makes it possible to reduce the weight, reduce inertia and reduce the cost of the end plate.

It is sectional drawing which shows the brushless motor concerning embodiment of this invention. It is a perspective view which shows the structure of a rotor. It is an exploded view which shows the structure of a rotor. It is a side view which shows the structure of a rotor core.

Hereinafter, a brushless motor rotor according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view illustrating a configuration of a brushless motor according to the present embodiment, FIG. 2 is a perspective view illustrating a configuration of a rotor, and FIG. 3 is an exploded view illustrating a method of assembling the rotor. As shown in FIG. 1, the brushless motor 1 includes a substantially cylindrical housing 3 and a substantially disc-shaped front bracket 4 that closes one open end of the housing 3. As a magnetic material forming the housing 3, for example, a general steel material such as SPCC, electromagnetic soft iron, or the like can be applied. The front bracket 4 plays a role of a flange when the brushless motor 1 is attached to a desired device.

Inside the housing 3, a bearing 5 is provided at a substantially central portion of the front bracket 4, and a bearing 6 is provided at a substantially central portion of the bottom portion of the housing 3. The bearing 5 rotatably supports one end of the shaft 2 disposed inside the housing 3, and the bearing 6 rotatably supports the other end of the shaft 2.
A cylindrical rotor core 8 is disposed around the shaft 2. The rotor core 8 is manufactured by being fixed by means of adhesion, boss, caulking or the like in a state where thin plates such as electromagnetic steel plates and cold rolled steel plates are laminated. The shaft 2 is press-fitted and fixed at the center of the rotor core 8 and is configured integrally with the rotor core 8.

  A plurality (2 × n, n is an integer) of magnets 9 for driving the motor are provided on the outer peripheral side of the rotor core 8. The magnet 9 is a rectangular parallelepiped permanent magnet in which the axial direction of the rotor core 8 is the longitudinal direction, and is inserted into a plurality of openings 11 provided at equal intervals on the outer peripheral side of the rotor core 8 and fixed with an adhesive. ing. In the case of the present embodiment, six neodymium magnets are arranged so that the S poles and the N poles are alternately arranged at equal intervals in the circumferential direction of the rotor core 8 to constitute the six pole rotor core 8.

  A stator core 16 is fixed to the inner peripheral surface of the housing 3 so as to be entirely surrounded. An excitation coil 17 is concentrated around the status core 16 via an insulator 18 so as to surround the outer peripheral surface of the rotor core 8. The stator core 16 and the exciting coil 17 constitute a stator 15 of the brushless motor 1. The stator 15 is annularly arranged on the outer peripheral side of the rotor (brushless motor rotor) 7 with a predetermined interval.

  The outer end of the front bracket 4 of the shaft 2 protrudes to the outside, and an output shaft from which the rotational output of the brushless motor 1 can be taken out by connecting a desired shaft or the like to the end protruding to the outside. ing. A resolver 20 that detects the rotational position of the rotor 7 is provided inside the front bracket 4 of the shaft 2. The resolver 20 is attached to the outer peripheral surface of the shaft 2 by press-fitting or the like. The resolver rotor 21 is attached to the front bracket 4 in a state of being opposed to the resolver rotor 21 with a predetermined gap. And.

  As shown in FIG. 3, a plurality of grooves 12 extending in the axial direction are provided on the outer peripheral surface of the rotor core 8 constituting the brushless motor 1 of the present embodiment. As shown in FIG. 4, the groove portions 12 are formed so that the peripheral portions of the openings 11 are arranged in the vicinity of both sides in the circumferential direction of the plurality of openings 11 provided to insert and fix the magnet 9 along the circumferential direction. It is formed so as to be divided, and the magnetic flux of the magnet 9 is prevented from being shorted. By arranging the groove 12 in the vicinity of both sides in the circumferential direction of the opening 11, the magnetic flux of the magnet 9 is reliably prevented from being short-circuited, and the magnetic flux density generated by the rotor 7 is increased. Enables output.

  A pair of end plates 10 having projections 13 are fixed to both ends of the rotor core 8 in the axial direction by press-fitting the projections 13 into the grooves 12. The end plate 10 is made of an aluminum alloy that is a non-magnetic material, and is disposed so as to cover the opening 11 at both ends in the axial direction of the rotor core 8 so that the magnet is inserted and fixed in the opening 11. 9 is prevented from scattering. Further, the depth of the groove 12 is the same as or outside the opening 11 in the radial direction of the rotor core 8, and the inner diameter of the end plate 10 is the same as or slightly smaller than the inscribed circle diameter of the opening 11. Yes. In this way, the end plate 10 is formed into an annular shape and covers only the vicinity of the opening 11 at both axial end portions of the rotor core 8, thereby achieving weight reduction, low inertia, and low cost.

With the above configuration, the rotor 7 for the brushless motor according to the present embodiment has the output of the brushless motor 1 while reducing the weight, the inertia, and the cost of the end plate 10 attached to both axial ends of the rotor core 8. Can be improved.
That is, by forming the groove portion 12 in the vicinity of both sides in the circumferential direction of the magnet 9, it is possible to further prevent short-circuiting of the magnetic flux of the magnet 9, so that the output of the motor can be increased. Furthermore, by forming the radial position of the groove 12 on the same side as the opening 11 (magnet 9) or on the outer diameter side, the end plate 10 for preventing the magnet 9 from scattering is made the minimum necessary size. ing. The end plate 10 has an inner diameter that is the same as or slightly smaller than the inscribed circle diameter of the opening 11, and by removing portions other than the portions covering both ends of the opening 11, weight reduction, low inertia, and cost reduction are achieved. It becomes possible.

The brushless motor rotor of the present invention is not limited to the above-described embodiments, and various modifications are possible.
Although the example of the aluminum alloy was shown as a material of the end plate 10, it is not limited to this, and other materials may be used as long as they are non-magnetic. For example, the same effect can be obtained with stainless steel or synthetic resin. Moreover, although the example which fixes the end plate 10 to the rotor core 8 by press-fitting fitting was shown, it is not limited to this, It is also possible to fix to the rotor core 8 using an adhesive agent or the like.
Although the example of the neodymium magnet was shown as the magnet 9, it is not limited to this, Even if it uses a ferrite magnet etc., the same effect can be acquired.
Although the example of the 6-pole motor core 8 is shown as the brushless motor 1, it is not limited to this, and can be changed as appropriate. For example, the same effect can be obtained with 8 poles or 10 poles. .
Further, the brushless motor rotor can be applied to an electric power steering device that assists the steering force of an automobile with a motor.

  As described above, the brushless motor rotor according to the present invention is suitably used for a brushless motor in which a magnet is embedded in a rotor core and an electric power steering apparatus including the brushless motor.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Shaft 3 Housing 4 Front bracket 5, 6 Bearing 7 Rotor 8 Rotor core 9 Magnet 10 End plate 11 Opening part (magnet insertion part)
12 Groove 13 Protrusion 15 Stator 16 Stator Core 17 Excitation Coil 18 Insulator 20 Resolver 21 Resolver Rotor 22 Resolver Stator

Claims (5)

A shaft that is an output shaft of the motor, a cylindrical rotor core that is press-fitted and fixed to the shaft, a magnet that is inserted into a plurality of openings formed in the circumferential direction on the outer peripheral side of the rotor core, and the rotor core An annular end plate disposed on both end faces, and
The rotor core includes a groove portion extending in the axial direction so as to prevent a magnetic flux from being short-circuited between the magnets, the end plate includes a plurality of protrusion portions formed extending in the axial direction, and the protrusion portion is formed into the groove portion. A rotor for a brushless motor, which is fitted and fixed to the rotor.   The rotor for a brushless motor according to claim 1, wherein the groove is provided in the vicinity of both sides of the opening in the circumferential direction of the rotor core.   3. The brushless motor rotor according to claim 1, wherein the groove is provided on the outer diameter side or the same as the opening in the radial direction of the rotor core.   The rotor for a brushless motor according to any one of claims 1 to 3, wherein an inner diameter of the end plate is the same as or slightly smaller than an inscribed circle diameter of the opening.   An electric power steering apparatus comprising the brushless motor rotor according to any one of claims 1 to 4.

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