JP2010035326A - Axial gap motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial gap motor reducing inertia moment of a rotor while deterioration of rigidity of the rotor is prevented and increasing an amount of magnetic flux flowing between magnetic poles of a magnet. <P>SOLUTION: The motor includes an almost disk-like stator, a rotor back yoke 8 formed in the almost disk-like shape and the magnet 9 which is formed in an almost cylindrical shape, in which a plurality of magnetic poles different in polarities are formed in equal pitches in a circumferential direction and which is fitted to one end face of the rotor back yoke 8. The magnet 9 is provided with a rotor 3 in which a prescribed gap is formed with a plurality of salient poles of the stator and which is arranged by facing the stator. The rotor back yoke 8 of the rotor 3 is provided with thick rib parts 10 which are positioned between the adjacent magnetic poles of the magnet 9 by the same number as the magnetic poles of the magnet 9 in the other end face 8b of one end face to which the magnet 9 is fitted and are radially integrated in the rotor back yoke 8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an axial gap type electric motor including a rotor and a stator, and more particularly to a technique for reducing the inertia moment of the rotor.

  The axial gap type electric motor includes a substantially disk-shaped stator and a substantially disk-shaped rotor disposed to face the stator. Examples of such an axial gap type motor include the following. The stator includes a substantially disc-shaped stator body, a plurality of salient poles integrally disposed on an end surface of the stator, and a coil wound around the salient poles, while the rotor is a disc-shaped magnetic material. And a magnet that is integrally formed in a ring shape and attached to the end surface of the rotor back yoke. Here, the outer diameters of the plurality of salient poles provided in the stator are substantially equal to the outer diameters of the rotor back yoke and the magnet provided in the rotor.

  The magnet is formed with a plurality of magnetic poles having different polarities alternately in the circumferential direction. A predetermined gap is formed between the salient pole of the stator and the magnet of the rotor, and the rotor is positioned so as to be rotatable at a position facing the stator.

  As described above, in the axial gap type electric motor, the outer diameter of the rotor is substantially equal to the outer diameter of the stator. On the other hand, in the radial gap type electric motor, the outer diameter of the cylindrical rotor is generally smaller than the inner diameter of the annular stator, and the rotor is rotatably arranged inside the stator.

  As described above, when both motors having different basic configurations of the stator and rotor are designed to have substantially the same output characteristics, the axial length of the rotor of the axial gap type motor is smaller than the axial length of the rotor of the radial gap type motor. Become. On the other hand, the outer diameter of the rotor of the axial gap type electric motor is larger than the outer diameter of the rotor of the radial gap type electric motor. Therefore, the outer shape of the axial gap type motor is a flat shape having a larger diameter and a shorter axial length than the radial gap type motor.

Here, assuming that the rotor is a solid cylinder, when the radius of the rotor is r (m) and the mass of the rotor is M (kg), the inertia moment I of the rotor is I = 2 × Mr ² Become. That is, the moment of inertia I is proportional to the square of the radius r. Therefore, if the masses of the rotors of both motors are the same, the inertia moment I of the rotor of the axial gap type motor can be considerably larger than the inertia moment I of the rotor of the radial gap type motor. .

  As described above, when the inertia moment I of the rotor increases, when the control current for controlling the rotational drive of the rotor is supplied to the coil provided in the stator, the input of the control current is delayed with respect to the rotation of the rotor. Occurs. That is, the response performance of the rotor rotation operation with respect to the control current is degraded. Therefore, in the axial gap type electric motor, it is required to reduce the inertia moment I of the rotor in order to improve the response of the rotational speed of the rotor to the control current.

  In order to reduce the moment of inertia I of the rotor, the invention described in Patent Document 1 employs a technique in which the rotor back yoke is formed from a thin metal plate to reduce the mass of the rotor. Here, the thin metal plate has low rigidity such as bending strength, and the rotor itself may vibrate when the rotor rotates. Therefore, the thin metal plate is pressed, and a plurality of reinforcing ribs are formed at equal circumferential pitches along the radiation from the center of the circular rotor back yoke toward the outer peripheral surface.

This reinforcing rib has a U-shaped circumferential cross section as viewed from the radial direction, and the upper surface of the rotor back yoke has a convex shape, and on the lower surface of the rotor back yoke, the back side of the convex shape has a concave shape. It has become. On the lower surface of the rotor back yoke, a magnet formed in an annular shape and alternately formed with magnetic poles having different polarities is integrally attached. Here, the number of poles of the magnetic pole of the magnet is the same as the number of reinforcing ribs, and the reinforcing ribs are arranged in the portion between the poles of the magnet. Therefore, the concave shape of the reinforcing rib is arranged in the inter-electrode portion of the magnet, and a gap is formed between the inter-electrode portion of the magnet and the back yoke. As a result, the magnetic flux change in the portion between the magnets is softened, and the cogging torque is reduced.
JP 2004-297902 A

  In the above-described prior art, the uneven rotation of the rotor is certainly reduced by reducing the cogging torque. However, the amount of magnetic flux flowing between the magnetic poles formed in the magnet is reduced due to the gap formed between the inter-pole portion of the magnet and the rotor back yoke. Therefore, the amount of magnetic flux flowing from the magnet to the plurality of salient poles formed on the stator also decreases, and the rotational torque of the rotor decreases. Therefore, it can be said that the axial gap type electric motor of the prior art is not suitable for applications that require high torque.

  Therefore, while keeping in mind that the rigidity of the rotor does not decrease, the inertia moment of the rotor is reduced, thereby improving the responsiveness of the rotational speed of the rotor, increasing the amount of magnetic flux flowing between the magnetic poles of the magnet, and increasing the torque. The present invention provides an axial gap motor that can be realized.

  In order to solve the above problems, the present invention includes a substantially disc-shaped stator body portion, and a plurality of salient poles integrally formed on the end surface of the stator body portion at equal circumferential circumferential pitch positions, A stator having a coil wound around the salient pole, a rotor back yoke formed in a substantially disc shape and having a shaft fitting hole formed in a substantially central portion, a substantially annular shape, a circumferential direction, etc. A plurality of magnetic poles having different polarities alternately in pitch, and a magnet attached to one end face of the rotor back yoke, wherein the magnet has a predetermined gap between the plurality of salient poles of the stator. In an axial gap type electric motor comprising a rotor that forms a gap and is opposed to the stator, and a rotary shaft that is formed in a substantially cylindrical shape and is fitted and fixed to the shaft fitting hole of the rotor. The rotor back yoke of the rotor is positioned between the adjacent magnetic poles of the magnet, on the other end face of the one end face to which the magnet is attached, in the same number as the magnetic poles of the magnet. Thick rib portions are integrally formed radially on the yoke.

  In this way, by providing a plurality of thick rib portions on the rotor back yoke and making the rotor back yoke portion other than the rib portions thin, a reduction in the moment of inertia of the rotor including the rotor back yoke is realized. The In addition, by arranging a thick rib portion between adjacent magnetic poles of the magnet, the amount of magnetic flux flowing between the magnetic poles of the magnet is increased.

  Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a longitudinal sectional view of an axial gap type electric motor (hereinafter simply referred to as “motor”) of the present embodiment.

  The electric motor 1 includes a stator 2 and a rotor 3 disposed to face the stator 2. The stator 2 is a so-called compacted body formed by press molding soft magnetic powder, and has a plurality of protrusions integrally formed on a substantially annular stator body 5 and an end surface 5 a of the stator body 5. And a pole portion 6. In addition, a coil 7 is wound around the salient pole portion 6 by overlapping winding. In the present embodiment, the number of salient pole parts is twelve.

  The rotor 3 includes a substantially disk-shaped rotor back yoke 8 made of a magnetic material, and a magnet 9 formed in a substantially disk shape and attached to one end surface 8 a of the rotor back yoke 8. The magnet 9 is a so-called ring magnet in which metal powder such as neodymium (Nd) is integrally formed by sintering, and magnetic poles having different N and S poles are alternately formed by magnetization, and the number of magnetic poles Is octupole. Further, the magnet 9 is attached to one end surface 8a of the rotor back yoke 8 by an adhesive of a thermosetting resin.

  A shaft fitting hole 8c is formed at a substantially central portion of the rotor back yoke 8, and the substantially cylindrical rotary shaft 4 is fitted and fixed to the shaft fitting hole 8c. The stator 2 and the rotor 3 are opposed to each other with a predetermined distance, and a predetermined gap 11 is formed between the magnet 9 of the rotor 3 and the plurality of salient pole portions 6 of the stator 3. .

  The stator 2 and the rotor 3 are contained in a front bracket 21 and an end bracket 22. The front bracket 21 is formed in a substantially bottomed cylindrical shape, the stator body 5 of the stator 2 is attached, and the end bracket 22 is also formed in a substantially bottomed cylindrical shape, and is fitted into the front bracket 21 by press fitting. . The rotating shaft 4 is rotatably supported by the front bracket 21 and the end bracket 22 via bearings 23 and 24.

  Next, power supply to the coil 7 from a control device (not shown) will be described. A substrate 25 for supplying power to the coil 7 is attached to the stator body 5. In the substrate 25, insertion holes (not shown) through which the plurality of salient pole parts 6 are inserted correspond to the positions of the salient pole parts 6, and the same number as the number of salient pole parts 6 is formed. The substrate 25 is attached to the stator body 5 while inserting the plurality of salient poles 6. Further, a part 25 a of the substrate 25 protrudes from the outlet 41 of the substrate 25 formed by the front bracket 21 and the end bracket 22 toward the outside of the electric motor 1.

  A lead wire 7 a from the coil 7 is connected to the substrate 25, and a motor coupler 26 is attached to a part 25 a of the substrate 25. A lead wire coupler 27 is attached to the lead wire 28 connected to a control device (not shown), and the motor coupler 26 and the lead wire coupler 27 are connected to each other. Then, electric power is supplied to the coil 7 from a control device (not shown) via the lead wire 28, the substrate 25, and the lead wire 7a.

  An encoder ring 51 having a plurality of reflection slits is attached to one end 4a of the rotating shaft 4. On the other hand, an encoder board 53 is attached to the end bracket 22, and an optical sensor 52 is attached to the encoder board 53 at a position facing the reflection slit. An encoder cover 54 is attached to the end bracket so as to cover the encoder board 53.

  The encoder ring 51 rotates together with the rotating shaft 4, the rotation angle is detected by the optical sensor 52, and a control device (not shown) supplies controlled electric power to the coil 7 based on the detected rotation angle.

  Next, the rotor 3 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a perspective view of the rotor, and FIG. 3 is a perspective view of the rotor as viewed from the direction A in FIG. FIG. 4 is a front view of the rotor, and FIG. 5 is an enlarged view of a main part of the rotor as seen from the direction B in FIG. 3, 5, and 6, although it cannot actually be recognized from the appearance, for the sake of convenience of explanation, the boundaries of alternately different magnetic poles of the magnet 9 are shown by solid lines.

  As described above, the rotor 3 includes the substantially disk-shaped rotor back yoke 8 and the magnet 9 that is formed in a substantially disk shape and is attached to one end face 8 a of the rotor back yoke 8. φ is set to about 40 mm. The other end surface 8b located on the back surface of the one end surface 8a of the rotor back yoke 8 to which the magnet 9 is attached is provided with a plurality of thick rib portions 10 formed integrally with the rotor back yoke 8 itself. .

  The rib portions 10 are formed radially from the shaft fitting hole 8 c toward the outer peripheral surface 8 d, and the number of rib portions 10 is eight, which is the same as the number of magnetic poles of the magnet 9. 9a and 9a.

  With the rotor back yoke 8 having such a structure, the portion 12 where the rib portion 10 is formed can be thick, while the portion 13 where the rib portion 10 is not formed can be thin. In the present embodiment, the circumferential length L of the rib portion 10 is about 5 mm, the thickness H1 of the portion 12 where the rib portion 10 is formed is 2 mm, and the thickness of the portion 13 where the rib portion 10 is not formed. H2 is set to 1 mm, respectively.

  By reducing the thickness of the portion 13 where the rib portion 10 is not formed, the mass of the rotor back yoke 8 that is a constituent member of the rotor 3 can be reduced, and the inertia moment of the rotor 3 can be reduced. Accordingly, a delay in the rotational speed of the rotor 3 with respect to the control power supplied from the control device (not shown) to the coil 7 of the electric motor 1 can be reduced, and the responsiveness of the rotational speed of the rotor can be improved.

  In addition, the plurality of rib portions 10 formed on the rotor back yoke 8 radially at equal pitches in the circumferential direction increase the rigidity of the rotor 3 and reduce the vibration of the rotor 3 that may occur when the rotor 3 rotates. can do. Therefore, the noise of the electric motor 1 generated by the vibration of the rotor 3 can be suppressed.

  FIG. 6 is an enlarged view of the portion indicated by the cross section BB in FIG. 4 and shows the magnetic flux flowing through the rotor back yoke 8. The rotor back yoke 8 serves as a flow path of magnetic lines of force Φ that flow between the adjacent magnetic poles 9a, 9a. If the area of the cross section perpendicular to the magnetic field lines Φ of the flow path is small, the magnetic flux density increases. If a magnetic flux of a predetermined level or more is caused to flow, the magnetic flux becomes saturated and the magnetic flux of a predetermined level or more cannot be supplied. As a result, a magnetic flux exceeding a predetermined value cannot flow through the salient pole portion 6 of the stator 2, and the output torque of the electric motor 1 cannot be increased.

  Here, in the embodiment of the present invention, the portion 12 where the rib portion 10 is formed is thicker than the portion 13 where the rib portion 10 is not formed. The rib portion 10 is formed between adjacent magnetic poles 9a and 9a. Therefore, a large area of a cross section perpendicular to the magnetic force lines Φ is secured at the location 12 where the rib portion 10 is formed, and the amount of magnetic flux can be increased. Therefore, a large amount of magnetic flux can flow through the salient pole portion 6 of the stator 2, and the output torque of the electric motor 1 can be increased.

It is a longitudinal section of the electric motor in the embodiment of the present invention. It is a perspective view of the rotor in the embodiment of the present invention. FIG. 3 is a perspective view of the rotor in the embodiment of the present invention as viewed from the direction A in FIG. 2. It is a front view of the rotor in the embodiment of the present invention. FIG. 5 is an enlarged view of a main part of the rotor as viewed from the B direction in FIG. 4. FIG. 5 is an enlarged view of a portion indicated by a cross section CC in FIG. 4 and shows a magnetic flux flowing through a rotor back yoke.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Axial gap type electric motor 2 Stator 3 Rotor 4 Rotating shaft 5 Stator main body 6 Salient pole 7 Coil 8 Rotor back yoke 9 Magnet 10 Rib 12 Position where rib is formed 13 Location where no rib is formed

Claims (2)

A stator having a substantially disc-shaped stator body, a plurality of salient poles integrally formed on the end surface of the stator body at equal circumferential pitches, and a coil wound around the salient poles When,
A rotor back yoke formed in a substantially disc shape and having a shaft fitting hole formed in a substantially central portion, and formed in a substantially annular shape, and a plurality of magnetic poles having different polarities alternately in the circumferential direction and the like are formed, A rotor mounted on one end surface of the rotor back yoke, and the magnet forms a predetermined gap between the plurality of salient poles of the stator and is disposed to face the stator. When,
In an axial gap type electric motor that is formed in a substantially cylindrical shape and includes a rotation shaft that is fitted and fixed to the shaft fitting hole of the rotor.
The rotor back yoke of the rotor is located between the adjacent magnetic poles of the magnet, on the other end face of the one end face to which the magnet is attached, in the same number as the magnetic poles of the magnet. An axial gap type electric motor comprising a thick rib portion integrally formed radially with a back yoke. 2. The axial gap type electric motor according to claim 1, wherein the thickness of the portion of the rotor back yoke where the rib member is formed is H <b> 1 (mm), and the portion of the rotor back yoke where the rib portion is not formed. When the thickness is H2 (mm), the relationship between H1 and H2 is 1.5 × H2 ≦ H1 ≦ 3 × H2.

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