Patent Publication Number: US-2021167676-A1

Title: Axial gap motor

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-215078, filed Nov. 28, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an axial gap motor. 
     2. Related Art 
     An axial gap motor described in JP-A-2009-296701 (Patent Literature 1) includes a rotor provided to be rotatable around a rotation axis and stators disposed to be opposed to hold the rotor therebetween. The rotor includes a rotor support and a magnet. The rotor support includes an annular rim section and a shaft section, a magnet held between the rim section and the shaft section, and an annular disc-like connecting section extending from the shaft section to the rotation axis side. The connecting section connects, for example, a driving shaft such as an input shaft of a transmission of a vehicle and an intermediate portion of a rib or the like. 
     In the rotor support described in Patent Literature 1, the shaft section, which holds the magnet, and the driving shaft are connected by the connecting section. Therefore, when torque is applied to the rotor, a bending moment concentrates on the connecting section and deformation easily occurs in the connecting section. As a result, vibration, noise, and the like involved in the deformation of the connecting section occur. 
     SUMMARY 
     An axial gap motor according to an application example of the present disclosure includes: a shaft extending along a rotation axis; a rotor including a hub, an annular rim, a coupling section coupling the hub and the rim, and a magnet held by the rim, the rotor rotating around the rotation axis together with the shaft; and a stator disposed to be separated from the rotor with a gap in an axial direction parallel to the rotation axis. A reinforcing member is provided in the coupling section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view showing a schematic configuration of an axial gap motor according to a first embodiment. 
         FIG. 2  is an exploded perspective view showing a rotor and a shaft shown in  FIG. 1 . 
         FIG. 3  is a plan view showing only a part of the rotor shown in  FIG. 2 . 
         FIG. 4  is a X 1 -X 1  line sectional view of  FIG. 3 . 
         FIG. 5  is a sectional view showing a first modification of the rotor shown in  FIG. 4 . 
         FIG. 6  is a sectional view showing a second modification of the rotor shown in  FIG. 4 . 
         FIG. 7  is a sectional view showing a third modification of the rotor shown in  FIG. 4 . 
         FIG. 8  is a longitudinal sectional view showing a schematic configuration of an axial gap motor according to a second embodiment. 
         FIG. 9  is an exploded perspective view showing a rotor, which is a conventional example, and the shaft. 
         FIG. 10  is an exploded perspective view showing a rotor, which is a conventional example, and the shaft. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     An axial gap motor according to the present disclosure is explained in detail below based on embodiments shown in the accompanying drawings. 
     1. First Embodiment 
       FIG. 1  is a longitudinal sectional view showing a schematic configuration of an axial gap motor according to a first embodiment.  FIG. 2  is an exploded perspective view showing a rotor and a shaft shown in  FIG. 1 .  FIG. 3  is a plan view showing only a part of the rotor shown in  FIG. 2 .  FIG. 4  is a X 1  -X 1  line sectional view of  FIG. 3 . Note that  FIG. 1  is a X 2 -X 2  line sectional view of  FIG. 3 . 
     An axial gap motor  1  shown in  FIG. 1  adopts a double stator structure including a shaft  2  that rotates around a rotation axis J, a rotor  3  that is fixed to the shaft  2  and rotates around the rotation axis J together with the shaft  2 , and a pair of stators  4  and  5  disposed on both sides in an axial direction A of the rotor  3  along the rotation axis J. Such an axial gap motor  1  rotates the rotor  3  and the shaft  2  around the rotation axis J and transmits a rotational force to a driving target member coupled to the shaft  2 . In this specification, for convenience of explanation, a direction along the rotation axis J is referred to as “axial direction A” as well, a direction orthogonal to the axial direction A is referred to as “radial direction R” as well, and the circumferential direction of the rotor  3  and the stators  4  and  5  is referred to as “circumferential direction C”. An arrow distal end side of the axial direction A is referred to as “upper” as well and the opposite side of the arrow distal end side is referred to as “lower” as well. Further, a plan view of viewing from above along the axial direction A is simply referred to as “plan view” as well. An arrow distal end side of the radial direction R is referred to as “outside” as well and an arrow proximal end side of the radial direction R is referred to as “center” as well. 
     The shaft  2  has a substantially columnar shape partially having a different outer diameter and is solid. Consequently, mechanical strength of the shaft  2  is improved. However, the shaft  2  may be hollow. In this case, a wire for the axial gap motor  1  can be inserted through the inside of the shaft  2 . 
     The rotor  3  having a disc shape is fixed to the shaft  2  concentrically with the shaft  2 . As shown in  FIGS. 1 to 3 , the rotor  3  includes a hub  31  located in the center of the rotor  3 , an annular rim  32  located further on the outer side than the hub  31 , and a coupling section  33  coupling the hub  31  and the rim  32 . A plurality of permanent magnets  6  are held by the rim  32 . The rotor  3  is explained in detail below. 
     The stators  4  and  5  are attached to the shaft  2  via bearings  71  and  72 . The shaft  2  and the rotor  3  are rotatably supported with respect to a motor case  10  configured by combining the stators  4  and  5  using a side surface case  8 . In this embodiment, a radial ball bearing is used as the bearings  71  and  72 . However, the bearings  71  and  72  are not limited to the radial ball bearing. Various bearings such as an axial ball bearing, an angular ball bearing, and a taper roller bearing can be used. 
     As shown in  FIG. 1 , the stators  4  and  5  are disposed to hold the rotor  3  from above and below. Specifically, the stator  4  is disposed on the lower side of the rotor  3  via a gap and the stator  5  is disposed on the upper side of the rotor  3  via a gap. The stators  4  and  5  are disposed vertically symmetrically with respect to the rotor  3 . 
     The stator  4  includes an annular back yoke  41  disposed concentrically with the shaft  2 , a plurality of stator cores  42  supported on the upper surface of the back yoke  41  and disposed to be opposed to the permanent magnets  6 , and a plurality of coils  43  disposed in the stator cores  42 . Similarly, the stator  5  includes an annular back yoke  51  disposed concentrically with the shaft  2 , a plurality of stator cores  52  supported on the lower surface of the back yoke  51  and disposed to be opposed to the permanent magnets  6 , and a plurality of coils  53  disposed in the stator cores  52 . The pluralities of stator cores  42  and  45  are disposed in the stators  4  and  5  in this way. Consequently, the shaft  2  rotates smoothly and the axial gap motor  1  has excellent driving efficiency. 
     The configuration of the stators  4  and  5  is explained in detail below. However, since the stators  4  and  5  have the same configuration, the stator  4  is representatively explained below. Explanation about the stator  5  is omitted. 
     The back yoke  41  is made of any one of various magnetic materials such as a stacked body of electromagnetic steel plates and a pressurized powder body of magnetic powder, in particular, a soft magnetic material. The back yoke  41  may be configured by an aggregate of a plurality of parts. 
     The stator cores  42  are disposed on the upper surface of the back yoke  41 . The stator  4  includes a plurality of stator cores  42 . The plurality of stator cores  42  are arranged side by side at equal intervals along the circumferential direction C. The stator corers  42  are made of any one of various magnetic materials such as a stacked body of electromagnetic steel plates and a pressurized powder body of magnetic powder, in particular, a soft magnetic material. 
     The stator cores  42  may be firmly fixed to the back yoke  41  by, for example, melting, an adhesive, or welding or may be engaged with the back yoke  41  by any one of various engaging means. 
     The coils  43  disposed on the stator cores  42  are wound on the outer circumferences of the stator cores  42 . Electromagnets are configured by the stator cores  42  and the coils  43 . The coils  43  may be individually wound on the stator cores  42  or may be wound up in a bobbin shape in advance and fit in the outer circumferences of the stator cores  42 . 
     The axial gap motor  1  includes a not-shown energization circuit. The coils  43  are coupled to the energization circuit. The coils  43  are energized at a predetermined period or in a predetermined pattern. When the coils  43  are energized by, for example, a three-phase alternating current, magnetic fluxes are generated from the electromagnets and an electromagnetic force acts on the permanent magnets  6  opposed to the electromagnets. This state is periodically repeated, whereby the rotor  3  rotates around the rotation axis J. 
     The stator  4  is explained above. The entire stator  4  may be molded by resin. By molding the stator  4  with the resin in this way, it is possible to fix the back yoke  41  and the stator cores  42  to each other and obtain a more stable stator  4 . 
     The configuration of the rotor  3  is explained in detail. 
     As explained above, the rotor  3  includes the rotor support  30  including the hub  31  located in the center of the rotor  3 , the annular rim  32  located further on the outer side than the hub  31 , and the coupling section  33  coupling the hub  31  and the rim  32 . 
     As shown in  FIG. 1 , the hub  31  includes a through-hole  311  piercing through the hub  31  between an upper surface  311   a  and a lower surface  311   b  along the rotation axis J. The shaft  2  is fixed to the through-hole  311  by, for example, press fitting. Consequently, the shaft  2  and the rotor  3  are fixed. The length of the hub  31  along the rotation axis J, that is, the length in the axial direction A of the hub  31  is larger than the lengths in the axial direction A of the rim  32  and the coupling section  33 . Consequently, a larger contact area of the hub  31  with the shaft  2  is secured to increase fixing strength. However, a fixing method for the shaft  2  and the rotor  3  is not particularly limited. The shape and the like of the hub  31  are not limited to the above. 
     As shown in  FIG. 3 , the rim  32  is formed in an annular shape having the center on the rotation axis J and includes a plurality of through-holes  321  provided at equal intervals along the circumferential direction C. The through-holes  321  pierce through the rim  32  between an upper surface  321   a  and a lower surface  321   b  along the rotation axis J. The permanent magnets  6  are respectively inserted into the through-holes  321 . The number of the permanent magnets  6  is decided by the number of phases and the number of poles of the axial gap motor  1 . For example, the number of the permanent magnets  6  is twenty-four in this embodiment. Examples of the permanent magnets  6  include a neodymium magnet, a ferrite magnet, a samarium-cobalt magnet, an alnico magnet, and a bond magnet. However, the permanent magnets  6  are not limited to these magnets. 
     As shown in  FIG. 3 , the coupling section  33  includes a plurality of beams  331  extending along the radial direction R. The plurality of beams  331  radially extend along the radial direction R centering on the rotation axis J and couple the hub  31  and the rim  32 . That is, the coupling section  33  includes the plurality of beams  331  radially extending from the hub  31 . Consequently, the plurality of beams  331  are disposed at equal intervals along the circumferential direction C. Voids  332  are formed among the beams  331 . Since the coupling section  33  includes the beams  331  and the voids  332 , it is possible to achieve a reduction in the weight of the rotor  3  without greatly spoiling the rigidity of the rotor  3 . 
     An extension pattern of the beams  331  is not limited to the radial shape. For example, the beams  331  may cross one another to form a lattice shape or the beams  331  may form a honeycomb structure such that the plan view shape of the voids  332  is formed in a polygonal shape such as a hexagonal shape. 
     The plan view shape of the beams  331  is not particularly limited. In  FIG. 3 , the beams  331  are formed in a linear shape. The beams  331  include portions where the width of the beams  331  extending in the linear shape, that is, the length of the beams  331  in a direction of the beams  331  (the circumferential direction C) orthogonal to both of the rotation axis J and an axis (the radial direction R) on which the beams  331  extend gradually changes. Specifically, the beams  331  include a first portion  3311  and a second portion  3312 , the widths of which are different from each other. The width of the first portion  3311  is large compared with the width of the second portion  3312 . By providing the first portion  3311  in a coupling section to the hub  31  as shown in  FIG. 3 , such beams  331  is much less easily deformed even when stress concentrates on the coupling section. Consequently, it is possible to more surely suppress occurrence of vibration and noise in the rotor  3 . By reducing the width of the second portion  3312  on which stress relatively less easily concentrates, it is possible to achieve a further reduction in the weight of the rotor  3 . The plan view shape of the beams  331  is not limited to the linear shape and may be any shape. 
     As shown in  FIGS. 1, 2, and 4 , the rotor  3  includes a reinforcing member  91  provided on the upper side of the rotor support  30  and a reinforcing member  92  provided on the lower side of the rotor support  30 . 
     The reinforcing members  91  and  92  are respectively plate-like members, plan view shapes of which are formed in annular shapes. The reinforcing member  91  is provided in contact with the upper surface  321   a  of the rim  32  and an upper surface  331   a  of the coupling section  33 . The reinforcing member  92  is provided in contact with the lower surface  321   b  of the rim  32  and a lower surface  331   b  of the coupling section  33 . Consequently, the rotor support  30  is held between the two reinforcing members  91  and  92 . 
     By providing such reinforcing members  91  and  92 , the rotor support  30  is reinforced to suppress bending deformation and torsional deformation from occurring. Examples of the bending deformation include bending deformation along the axial direction A indicated by an arrow T 1  in  FIG. 4  and bending deformation along the circumferential direction C indicated by an arrow T 2  in  FIG. 4 . Examples of the torsional deformation include torsional deformation around an axis extending in the radial direction R indicated by an arrow T 3  in  FIG. 4 . By providing the reinforcing members  91  and  92 , it is possible to suppress these kinds of deformation. 
     A constituent material of the reinforcing members  91  and  92  is not particularly limited. However, a material having a Young&#39;s modulus higher than the Young&#39;s modulus of a constituent material of the rotor support  30  is preferably used. By using such a material, it is possible to, while achieving a reduction in the weight of the rotor  3 , suppress deterioration in mechanical strength involved in the reduction in the weight. As a result, it is possible to realize the rotor  3  that achieves both of a reduction in weight and low deformability. 
     In the axial gap motor  1 , large torque is caused by an interaction of the permanent magnets  6  and the stators  4  and  5 . The torque sometimes periodically fluctuates. In that case, vibration occurs in the rotor  3  and noise also occurs according to the occurrence of the vibration. On the other hand, by providing the reinforcing members  91  and  92 , it is possible to suppress deformation of the rotor support  30 . Since the deformation of the rotor support  30  is suppressed, it is possible to suppress vibration and noise that occur during the rotation of the rotor  3 . 
     Examples of a constituent material of the rotor support  30  include metal materials such as stainless steel, an aluminum alloy, a magnesium alloy, and a titanium alloy. The constituent material of the rotor support  30  is preferably a nonmagnetic material. Consequently, the rotor support  30  less easily affects magnetic fluxes formed by the permanent magnets  6  and the coils  43 . Problems such as a decrease in torque less easily occur. Examples of the nonmagnetic material include austenitic stainless steel. 
     The reinforcing member  91  includes a through-hole  911  in the center thereof and the reinforcing member  92  includes a through-hole  921  in the center thereof. The hub  31  of the rotor support  30  is inserted into each of the through-holes  911  and  921 . 
     Examples of a constituent material of the reinforcing members  91  and  92  include a metal material, a ceramics material, a carbon fiber, a glass fiber, and a resin material and include a composite material of one or two or more kinds of these materials. 
     The reinforcing members  91  and  92  preferably include an electromagnetic steel plate. Since the electromagnetic steel plate has a relatively high Young&#39;s modulus, even when the rigidity of the rotor support  30  is low, the reinforcing members  91  and  92  give rigidity to the rotor support  30 . Consequently, it is possible to particularly suppress deformation of the rotor support  30 . Further, since the electromagnetic steel plate is a soft magnetic material, fluctuation in torque, in particular, cogging torque due to alternate side-by-side arrangement of an N-pole magnet and an S-pole magnet along the circumferential direction C is reduced. Occurrence of vibration of the rotor  3  and noise involved in the vibration is suppressed. 
     The reinforcing members  91  and  92  may include a magnetic material other than the electromagnetic steel plate. In this case, the same effects as the effects explained above are obtained. Examples of the magnetic material other than the electromagnetic steel plate include soft magnetic materials such as an amorphous metal, Permalloy, Sendust, Permendure, and pure iron. 
     An average thickness of the reinforcing members  91  and  92  is not particularly limited. However, the average thickness of the reinforcing members  91  and  92  is preferably 0.10 mm or more and 1.50 mm or less and more preferably 0.20 mm or more and 1.00 mm or less. Such reinforcing members  91  and  92  give a sufficient reinforcing effect to the rotor support  30  while suppressing the thickness of the rotor  3  from increasing. Therefore, it is possible to realize the rotor  3  with less vibration and noise while avoiding an increase in the weight and an increase in the size of the rotor  3 . 
     The reinforcing members  91  and  92  may be fixed to the rotor support  30  by any method. Examples of the fixing method include an adhesive, joining metal, and welding. However, the adhesive is preferably used. By using the adhesive, not only the rotor support  30  and the reinforcing members  91  and  92  but also the permanent magnets  6  and the reinforcing members  91  and  92  can be bonded. As a result, the rotor  3  can be integrated by the reinforcing members  91  and  92 . Deformation of the rotor  3  can be particularly reduced. 
     The length of the permanent magnets  6  along the rotation axis J, that is, the thickness of the permanent magnets  6  is substantially equal to the length of the through-holes  321  along the rotation axis J, that is, the thickness of the through-holes  321 . The plan view shape of the permanent magnets  6  is substantially equal to the plan view shape of the through-holes  321 . Consequently, the permanent magnets  6  fill the through-holes  321  almost without gaps. Since the upper surfaces of the permanent magnets  6  can be aligned with the upper surface  321   a  of the rim  32 , it is possible to bond the reinforcing member  91  to both of the rim  32  and the permanent magnets  6 . Similarly, since the lower surfaces of the permanent magnets  6  can be aligned with the lower surface  321   b  of the rim  32 , it is possible to bond the reinforcing member  92  to both of the rim  32  and the permanent magnets  6 . As a result, it is possible to particularly integrate the rotor  3 . 
     The reinforcing member  91  is in contact with the upper surface  331   a  (a first surface) of the coupling section  33 . Similarly, the reinforcing member  92  is in contact with the lower surface  331   b  (a second surface) of the coupling section  33 . That is, the reinforcing members  91  and  92  are provided on both of the upper surface  331   a  facing one end side (the upper end side) of the rotation axis J and the lower surface  331   b  facing the other end side (the lower end side) of the rotation axis J of the coupling section  33 . Consequently, it is possible to suppress deformation of the coupling section  33  including the beams  331 , which are easily deformed, and suppress occurrence of vibration and noise. When the coupling section  33  includes the beams  331 , a windage loss easily occurs according to the rotation of the rotor  3 . However, covering the coupling section  33  with the reinforcing members  91  and  92  contributes to a reduction in such a windage loss. In this specification, “in contact” indicates a state of direct contact or indirect contact via an interposed object such as an adhesive. 
     The reinforcing members  91  and  92  are respectively formed in the plate shapes as explained above and couple the beams  331 . Consequently, the beams  331  can be integrated. Therefore, the coupling section  33  can be sufficiently reinforced even in a state in which the voids  332  are provided among the beams  331 . As a result, it is possible to achieve both of a reduction in weight and low deformability. 
     As explained above, the coupling section  33  includes the voids  332  located among the beams  331 . Since the coupling section  33  includes the beams  331  and the voids  332 , it is possible to achieve a reduction in the weight of the rotor  3 . 
     The voids  332  may be substituted by bottomed recesses. In that case, the recesses may be opened in the upper surface  331   a  or may be opened in the lower surface  331  b. In that case as well, it is possible to achieve a reduction in the weight of the rotor  3 . 
     A filler may be stored in at least a part of the voids  332  according to necessity. Examples of the filler include an adhesive, a resin mold material, a resin foam, and a foaming material. By providing the filler, it is possible to further reinforce the rotor  3  and improve low deformability without greatly spoiling a reduction in weight. 
     The reinforcing members  91  and  92  shown in  FIGS. 1 and 2  are provided not only in the coupling section  33  but also in the rim  32 . That is, the reinforcing members  91  and  92  are provided from the coupling section  33  to the rim  32 . Specifically, the reinforcing member  91  is in contact with the upper surface  321   a  of the rim  32 . Similarly, the reinforcing member  92  is in contact with the lower surface  321   b  of the rim  32 . Consequently, the rim  32 , which is easily deformed by a magnetic force, can be more firmly reinforced. As a result, it is possible to suppress occurrence of vibration and noise of the rotor  3  involved in deformation of the coupling section  33  and the rim  32 . In this embodiment, as explained above, the reinforcing members  91  and  92  are in contact with not only the rim  32  but also the permanent magnets  6 . Consequently, it is possible to particularly reduce the deformation of the rim  32 . 
     In this case, the reinforcing member  91  is provided between the permanent magnets  6  and the stator  5 . Similarly, the reinforcing member  92  is provided between the permanent magnets  6  and the stator  4 . In such disposition of the reinforcing members  91  and  92 , when the reinforcing members  91  and  92  are magnetic bodies, it is possible to reduce cogging torque and suppress occurrence of vibration and noise in the rotor  3 . 
     Further, the reinforcing members  91  and  92  shown in  FIGS. 1 and 2  are provided in the hub  31  as well. Specifically, the reinforcing member  91  is in contact with the upper surface  311   a  of the hub  31 . Similarly, the reinforcing member  92  is in contact with the lower surface  311   b  of the hub  31 . Consequently, the reinforcing members  91  and  92  are disposed to extend from the hub  31  to the rim  32  through the coupling section  33 . As a result, it is possible to integrate substantially the entire rotor  3  and particularly reduce deformation of the rotor  3 . 
     As explained above, the axial gap motor  1  according to this embodiment includes the shaft  2 , the rotor  3 , and the stators  4  and  5 . The shaft  2  extends along the rotation axis J. The rotor  3  includes the hub  31 , the annular rim  32 , the coupling section  33  coupling the hub  31  and the rim  32 , and the permanent magnets  6  held by the rim  32  and rotates around the rotation axis J together with the shaft  2 . The stators  4  and  5  are respectively disposed to be separated from the rotor  3  with a gap in the axial direction A parallel to the rotation axis J. The reinforcing members  91  and  92  are provided in the coupling section  33  of the rotor  3 . 
     In such an axial gap motor  1 , by providing the reinforcing members  91  and  92 , it is possible to suppress deformation of the coupling section  33 . As a result, it is possible to suppress deformation of the rotor support  30 . Since deformation of the rotor support  30  is suppressed, it is possible to suppress vibration and noise that occur during the rotation of the rotor  3 . 
     2. First Modification 
       FIG. 5  is a sectional view showing a first modification of the rotor  3  shown in  FIG. 4 . In  FIG. 5 , a cross section of the same part as the part shown in  FIG. 4  is shown. 
     In the rotor  3  shown in  FIG. 4 , a cross section of the beams  331  is solid. On the other hand, a cross section of beams  331 A shown in  FIG. 5  is hollow. That is, the beams  331 A shown in  FIG. 5  include, on the inside of the beams  331 A, hollow sections  333  extending along the radial direction R and not exposed to side surfaces of the beams  331 A. A reduction in the weight of such beams  331 A can be achieved without greatly spoiling bending strength. As a result, it is possible to realize a rotor  3 A further reduced in weight while suppressing occurrence of vibration and noise. 
     In the first modification explained above, the same effects as the effects in the first embodiment are obtained. 
     3. Second modification 
       FIG. 6  is a sectional view showing a second modification of the rotor  3  shown in  FIG. 4 . In  FIG. 6 , a cross section of the same part as the part shown in  FIG. 4  is shown. 
     In a rotor  3 B shown in  FIG. 6 , beams  331  B of a coupling section  33 B include recesses  335   a  opened in upper surfaces  331   a  of the beams  331  B and recesses  334   b  opened in lower surfaces  331   b  of the beams  331  B. A reduction in the weight of the beams  331  B can be achieved without greatly spoiling bending strength. As a result, it is possible to realize the rotor  3 B further reduced in weight while suppressing occurrence of vibration and noise. One of the recesses  335   a  and  334   b  may be omitted. 
     In the second modification explained above, the same effects as the effects in the first embodiment are obtained. 
     4. Third Modification 
       FIG. 7  is a sectional view showing a third modification of the rotor  3  shown in  FIG. 4 . In  FIG. 7 , a cross section of the same part as the part shown in  FIG. 4  is shown. 
     In a rotor  3 C shown in  FIG. 7 , beams  331 C include recesses  335  opened in side surfaces  331   d  of the beams  331 C. A reduction in the weight of the beams  331 C can be achieved without greatly spoiling bending strength. As a result, it is possible to realize the rotor  3 C further reduced in weight while suppressing occurrence of vibration and noise. 
     In the third modification explained above, the same effects as the effects in the first embodiment are obtained. 
     5. Second Embodiment 
       FIG. 8  is a longitudinal sectional view showing a schematic configuration of an axial gap motor according to a second embodiment. 
     The second embodiment is explained below. In the following explanation, differences from the first embodiment are mainly explained. Explanation about similarities to the first embodiment is omitted. In  FIG. 8 , the same components as the components in the first embodiment are denoted by the same reference numerals and signs. 
     The second embodiment is the same as the first embodiment except that the configurations of the rotor  3  and the stator  5  are different. 
     The stator  5  according to the first embodiment explained above includes the stator cores  52  and the coils  53 . On the other hand, in a stator  5 D according to this embodiment, the stator cores  52  and the coils  53  are omitted. Therefore, an axial gap motor  1 D according to this embodiment has a single stator structure. 
     In the rotor  3  according to the first embodiment explained above, the reinforcing members  91  and  92  are provided to hold the rotor support  30  from above and below. On the other hand, in a rotor  3 D according to this embodiment, the reinforcing member  92  is omitted. In this way, in this embodiment, by omitting one of the reinforcing members  91  and  92 , a reduction in the weight of the rotor  3 D can be achieve. The stator cores  42  and the coils  43  are provided in the stator  4  according to this embodiment. However, by providing the reinforcing member  91  located on the surface on the opposite side of the stator cores  42  and the coils  43  in the rotor support  30 , that is, the upper surface of the rotor support  30 , in other words, by omitting only the reinforcing member  92 , it is possible to sufficiently reinforce the rotor  3 D while achieving a reduction in the weight of the rotor  3 D. 
     Such an effect is obtained because of a reason explained below. Since the stator cores  42  and the coils  43  attract the permanent magnets  6  of the rotor  3 D with a magnetic force, the rotor support  30  is easily bent downward in  FIG. 8 . On the other hand, by providing the reinforcing member  91  on the upper surface of the rotor support  30 , tension of pulling in a surface of the reinforcing member  91  is applied to the reinforcing member  91 . The reinforcing member  91  has sufficient yield strength against the tension. Accordingly, it is possible to sufficiently suppress deformation of the rotor support  30 . 
     Therefore, based on both of the first embodiment and this embodiment, the reinforcing members  91  and  92  are provided on at least one of the upper surface  331   a  (the first surface) facing one end side of the rotation axis J and the lower surface  331   b  (the second surface) facing the other end side of the rotation axis J of the coupling section  33 . Consequently, deformation of the coupling section  33  including the beams  331 , which are easily deformed, is suppressed and occurrence of vibration and noise is suppressed. 
     In the rotor  3 D according to this embodiment, the outer diameter of the reinforcing member  91  is reduced. The reinforcing member  91  is provided further on the shaft  2  side than the permanent magnets  6 . Consequently, the area of the reinforcing member  91  can be reduced and a reduction in weight and a reduction in cost can be achieved. The permanent magnets  6  themselves have sufficient rigidity and function as reinforcing bodies that suppress deformation of the rotor support  30 . Accordingly, even if the permanent magnets  6  are not covered by the reinforcing member  91 , it is possible to sufficiently suppress deformation of the rotor  3 D. 
     The size of the reinforcing member  91  is not limited to the size described above and may be size for covering all or a part of the permanent magnets  6 . The reinforcing member  92  may be provided without being omitted. In that case as well, the reinforcing member  92  may be provided to avoid the permanent magnets  6  or may be provided to cover the permanent magnets  6 . 
     In the second embodiment explained above, the same effects as the effects in the first embodiment are obtained. 
     6. Structure Analysis 
     In order to evaluate a difference in a deformation amount due to a difference in the configuration of a rotor, a simulation result by a structure analysis is explained. 
     In a simulation, about the rotor  3  shown in  FIG. 2 , a rotor  3 Y shown in  FIG. 9 , and a rotor  3 Z shown in  FIG. 10 , displacement amounts at the time when a translational force and a rotational force (torque) were applied were compared. The simulation result is shown in Table 1 below. 
       FIG. 9  is an exploded perspective view showing the rotor  3 Y, which is a conventional example, and the shaft  2 .  FIG. 10  is an exploded perspective view showing the rotor  3 Z, which is the conventional example, and the shaft  2 . 
     In the rotor  3 Y shown in  FIG. 9 , the plan view shape of voids  332 Y included in a coupling section  33 Y is different from the plan view shape of the voids  332  included in the coupling section  33  of the rotor  3  shown in  FIG. 2 . Reinforcing members  91 Y and  92 Y shown in  FIG. 9  are respectively provided in only a rim  32 Y of the rotor  3 Y. 
     In the rotor  3 Z shown in  FIG. 10 , the plan view shape of voids  332 Z included in a coupling section  33 Z is the same as the plan view shape of the voids  332  included in the coupling section  33  of the rotor  3  shown in  FIG. 2 . On the other hand, the thickness of the coupling section  33 Z is larger than the thickness of the coupling section  33  of the rotor  3  shown in  FIG. 2 . 
     Reinforcing members  91 Z and  92 Z shown in  FIG. 10  are respectively provided in only a rim  32 Z of the rotor  3 Z. 
     “Weight” in Table 1 indicates the weights of the rotors  3 ,  3 Y, and  3 Z. “Displacement amount (1)” in Table 1 indicates a displacement amount along the axial direction A of the permanent magnets  6  at the time when a translational force of 100 N is applied to the entire permanent magnets  6  along the axial direction A. Further, “displacement amount (2)” in Table 1 indicates a displacement amount along the circumferential direction C of the permanent magnets  6  at the time when a rotational force of 6 N·m is applied to the entire permanent magnets  6  along the circumferential direction C. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Simulation result 
               
            
           
           
               
               
               
            
               
                   
                 Displacement 
                 Displacement 
               
               
                   
                 amount (1) at 
                 amount (2) at 
               
               
                   
                 the time when 
                 the time when a 
               
            
           
           
               
               
               
            
               
                 Structure condition 
                 a translational 
                 rotational force is 
               
            
           
           
               
               
               
               
               
               
            
               
                 FIG. 
                 Difference 
                   
                   
                 force is applied 
                 applied along the 
               
               
                 showing 
                 in structure 
                   
                   
                 along the axial 
                 circumferential 
               
            
           
           
               
               
               
               
               
            
               
                 structure 
                 from FIG. 2 
                 Weight 
                 direction A 
                 direction C 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 FIG. 2 
                 — 
                 93.0 
                 g 
                 16 μm 
                 2.5 
                 μm 
               
               
                 (embodiment) 
               
               
                 FIG. 9 
                 The reinforcing 
                 118.0 
                 g 
                 18 μm 
                 19.0 
                 μm 
               
               
                 (comparative 
                 members 91Y and 
               
               
                 example) 
                 92Y are provided in 
               
               
                   
                 only the rim 32Y 
               
               
                 FIG. 10 
                 1: The reinforcing 
                 108.5 
                 g 
                 19 μm 
                 48.0 
                 μm 
               
               
                 (Comparative 
                 members 91Z and 
               
               
                 example) 
                 92Z are provided in 
               
               
                   
                 only the rim 32Z 
               
               
                   
                 2: The thickness of 
               
               
                   
                 the coupling section 
               
               
                   
                 33Z is large 
               
               
                   
               
            
           
         
       
     
     As shown in Table 1, a reduction in the weight of the rotor  3  shown in  FIG. 2  equivalent to the embodiment is achieved compared with the rotor  3 Y shown in  FIG. 9  and the rotor  3 Z shown in  FIG. 10  equivalent to the comparative example. 
     On the other hand, as a result of the simulation, the displacement amount (1) of the rotor  3  is sufficiently reduced compared with the displacement amount (1) of the rotor  3 Y heavier than the rotor  3  and the displacement amount (1) of the rotor  3 Z heavier than the rotor  3 . The displacement amount (2) of the rotor  3  is also reduced compared with the replacement amount (2) of the rotor  3 Y and the displacement amount (2) of the rotor  3 Z. 
     From this result, it has been made clear that, by providing the reinforcing members  91  and  92  in the coupling section  33 , it is possible to sufficiently reduce the displacement amount (1) and the displacement amount (2) while achieving a reduction in weight. 
     In particular, in the rotor  3 Y shown in  FIG. 9 , since an area ratio of the voids  332 Y in the coupling section  33 Y is small, it is expected that the coupling section  33 Y alone has higher rigidity than the rigidity of the coupling section  33  shown in  FIG. 2 . However, it has been recognized that the coupling section  33  is sufficiently benefited by the reinforcing action by the reinforcing members  91  and  92 , whereby the rotor  3  shown in  FIG. 2  has rigidity equal to or larger than the rigidity of the rotor  3 Y. 
     Similarly, in the rotor  3 Z shown in  FIG. 10 , since the thickness of the coupling section  33 Z is large, it is expected that the coupling section  33 Z alone has rigidity higher than the rigidity of the coupling section  33  shown in  FIG. 2 . However, it has been recognized that the coupling section  33  is sufficiently benefited by the reinforcing action by the reinforcing members  91  and  92 , whereby the rotor  3  shown in  FIG. 2  has rigidity equal to or larger than the rigidity of the rotor  3 Z. 
     Therefore, it has been recognized that it is effective to provide the reinforcing members  91  and  92  at least in the coupling section  33 . As long as the reinforcing members  91  and  92  are provided in the coupling section  33 , circular voids  332 Y in the coupling section  33 Y may be provided in the coupling section  33  or the coupling section  33  may be formed in a thicker shape than the rim  32 Z in the coupling section  33 Z. 
     Although not shown in Table 1, about the rotor  3 D shown in  FIG. 8  as well, it has been recognized that the displacement amount (1) and the displacement amount (2) can be reduced compared with the comparative example. 
     The axial gap motor according to the present disclosure is explained above based on the illustrated embodiments. However, the present disclosure is not limited to this. The components of the sections can be replaced with any components having the same functions. Any other components may be added to the present disclosure. The modifications and the embodiments explained above may be combined as appropriate. It is also possible to adopt a form in which a shaft is fixed, disposition of a rotor and stators is reversed, and the rotor rotates around the shaft.