Patent Publication Number: US-2022239200-A1

Title: Motor and air compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese patent application No. 2021-012029, filed on Jan. 28, 2021 and Japanese patent application No. 2022-009748, filed on Jan. 25, 2022, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a motor and an air compressor using the motor. 
     BACKGROUND ART 
     A motor controls rotation by including a rotation position detection circuit that detects the rotation position of a rotor. It is important that a substrate on which a rotation position detection circuit is mounted has a constant positional relationship with a stator. It is available that a motor in which a substrate on which a rotation position detection circuit is mounted is fixed to a stator (see PTL 1).
     PTL 1: Japanese Patent No. 5264864   

     When a motor is used in an environment where there is charged dust, etc., a substrate on which a rotation position detection circuit is mounted may be replaced in order to suppress the influence of the environment. When the substrate is fixed to the stator as disclosed in PTL 1, it is necessary to disassemble the motor so that the attachment position of the substrate is exposed when replacing the substrate, which causes a problem that the replacement work is complicated. 
     An object of the invention is to provide a motor in which a substrate can be easily replaced. 
     Another object of the invention is to provide a structure of an air compressor using a motor, in which a substrate can be easily replaced. 
     SUMMARY OF INVENTION 
     According to an aspect of the invention, there is provided a motor including: a central shaft extending in an axial direction; a stator extending in the axial direction around the central shaft; a rotor facing an outer side in a radial direction of the stator and configured to rotate around the central shaft; a substrate which is located on one side in the axial direction with respect to the rotor and on which a rotation position detection circuit configured to detect a rotation position of the rotor is mounted; and a case located on one side in the axial direction with respect to the substrate and configured to support the stator, in which the stator includes a restricting portion configured to restrict a position in a circumferential direction of the substrate, the case includes a fixing portion configured to fix the substrate, and the substrate includes a restricted portion whose position in the circumferential direction is restricted by the restricting portion, and a fixed portion fixed to the fixing portion. 
     According to another aspect of the invention, there is provided an air compressor including: a motor; a compression mechanism configured to be driven by the motor; and a crankcase in which a part of the compression mechanism is incorporated, in which the motor includes: a central shaft extending in an axial direction; a stator extending in the axial direction around the central shaft; a rotor facing an outer side in a radial direction of the stator and configured to rotate around the central shaft; and a substrate which is located on one side in the axial direction with respect to the rotor and on which a rotation position detection circuit configured to detect a rotation position of the rotor is mounted, the crankcase includes a fixing portion configured to fix the substrate, and the substrate includes a fixed portion fixed to the fixing portion. 
     According to an aspect of the invention, it is possible to provide the motor in which the substrate can be easily replaced. 
     According to another aspect of the invention, it is possible to provide the structure of the air compressor using the motor, in which the substrate can be easily replaced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing a motor according to a first embodiment of the invention, in which a winding is not shown. 
         FIG. 2  is a rear perspective view of the motor shown in  FIG. 1 , as viewed from the +Y side. 
         FIG. 3  is a side view of the motor shown in  FIG. 1 , as viewed from the +X side. 
         FIG. 4  is a side sectional view showing the motor shown in  FIG. 3 , taken along a plane orthogonal to the X-axis and passing through a central axis J. 
         FIG. 5  is a perspective view showing a state in which a rotor plate is removed from  FIG. 1 . 
         FIG. 6  is a front view showing a state in which the rotor plate is removed from the motor shown in  FIG. 1 , as viewed from the −Y side. 
         FIG. 7  is a rear view showing a state in which a case, a substrate, and a magnet holder are removed from the motor shown in  FIG. 1 , as viewed from the +Y side. 
         FIG. 8  is a perspective view showing a state in which a rotor core and a rotor magnet are removed from  FIG. 5 . 
         FIG. 9  is a perspective view showing a state in which the magnet holder is removed from  FIG. 6 . 
         FIG. 10  is a front view of the substrate, as viewed from the −Y side. 
         FIG. 11  is a rear perspective view showing a state in which a shaft, the case, and the substrate are removed from  FIG. 2 . 
         FIG. 12  is a rear perspective view of the rotor core. 
         FIG. 13  is a rear perspective view of the rotor plate. 
         FIG. 14  is a plan view of an air compressor from which a cover (not shown) is removed. 
         FIG. 15  is a perspective view of a compression mechanism and the motor. 
         FIG. 16  is a front view of the compression mechanism and the motor shown in  FIG. 15 , as viewed from the −Y side. 
         FIG. 17  is a perspective view showing a state in which the rotor plate is removed from  FIG. 15 . 
         FIG. 18  is a front view showing a state in which the rotor plate is removed from the compression mechanism and the motor shown in  FIG. 15 , as viewed from the −Y side. 
         FIG. 19  is a plan sectional view showing the compression mechanism and the motor shown in  FIG. 15 , taken along a plane orthogonal to the Z-axis and passing through the central axis J. 
         FIG. 20  is an enlarged view of the part “A” shown in  FIG. 19 . 
         FIG. 21  is a rear perspective view of the compression mechanism and the motor shown in  FIG. 15 , as viewed from the +Y side. 
         FIG. 22  is an enlarged view of the part “B” shown in  FIG. 21 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a motor and an air compressor according to an embodiment of the invention will be described with reference to the drawings. Meanwhile, in the following drawings, in order to make each configuration easy to understand, the scale and number and the like in each structure may be different from those in the actual structure. 
     Further, in the drawings, the XYZ coordinate system is shown as a three-dimensional Cartesian coordinate system as appropriate. In the XYZ coordinate system, the Y-axis direction is defined as a direction parallel to an axial direction of a central axis J shown in  FIG. 1 . The Z-axis direction is defined as an upper and lower direction of  FIG. 1  in a radial direction with respect to the central axis J. The X-axis direction is defined as a direction orthogonal to both the Z-axis direction and the Y-axis direction. In any of the X-axis direction, the Y-axis direction, and the Z-axis direction, the side pointed by the arrow shown in the drawing is defined as the + side, and the opposite side is defined as the − side. 
     Further, in the following description, the positive side (+Y side) in the Y-axis direction is referred to as the “front side” or “one side,” and the negative side (−Y side) in the Y-axis direction is referred to as the “rear side” or “the other side.” Meanwhile, the rear side (the other side) and the front side (one side) are names used only for explanation and do not limit the actual positional relationship and direction. Further, unless otherwise noted, the direction (Y-axis direction) parallel to the central axis J is simply referred to as the “axial direction,” the radial direction centered on the central axis J is simply referred to as the “radial direction,” and the circumferential direction centered on the central axis J, that is, the circumference (θ-direction) of the central axis J is simply referred to as the “circumferential direction.” In the radial direction, the side approaching the central axis J is referred to as the “inner side in the radial direction,” and the side away from the central axis J is referred to as the “outer side in the radial direction.” In the circumferential direction, the side pointed by the arrow shown in the drawing is defined as the + side, and the opposite side is defined as the − side. The positive side (+θ side) in the circumferential direction is referred to as “one side,” and the negative side (−θ side) in the circumferential direction is referred to as “the other side.” 
     Meanwhile, as used herein, the phrase “extending in the axial direction” includes not only the case of extending strictly in the axial direction (Z-axis direction), but also the case of extending in a direction inclined in a range of less than 45° with respect to the axial direction. Further, as used herein, the phrase “extending in the radial direction” includes not only the case of extending strictly in the radial direction, that is, in a direction perpendicular to the axial direction (Z-axis direction), but also the case of extending in a direction inclined in a range of less than 45° with respect to the radial direction. Further, the phrase “being parallel” includes not only the case of being strictly parallel, but also the case where the angle formed by each other is inclined in a range of less than 45°. 
     First Embodiment 
     &lt;Overall Configuration&gt; 
       FIG. 1  is a perspective view showing a motor  100  according to a first embodiment of the invention, in which a winding is not shown. 
       FIG. 2  is a rear perspective view of the motor  100  shown in  FIG. 1 , as viewed from the +Y side. 
     The motor  100  includes a shaft  301  extending in the axial direction, a stator  200 , a rotor  300 , a substrate  400 , and a case  500 . The motor  100  is an outer rotor type motor in which the rotor  300  is arranged on the outer side in the radial direction of the stator  200 . 
     The rotor  300  includes a magnet holder  330  on one side in the axial direction. The rotor  300  includes a rotor plate  302  on the other side in the axial direction. The rotor plate  302  is made of a non-magnetic material, and is, for example, an aluminum die-cast part. The rotor plate  302  has a through-hole  305  that penetrates in the axial direction. Ten through-holes  305  are provided at equal intervals in the circumferential direction. 
     Hall ICs  411 ,  412 , and  413  (see  FIG. 9 ) and a connector  402  are mounted on the substrate  400 . The Hall ICs  411 ,  412 , and  413  are examples of rotation position detection circuits that detect the rotation position of the rotor  300 . The connector  402  has a terminal capable of externally outputting the signal detected by the Hall ICs  411 ,  412 , and  413 . The substrate  400  has through-holes  403 ,  404 , and  405  that penetrate in the axial direction. 
     The case  500  is located on one side in the axial direction with respect to the substrate  400 . The case  500  supports the stator  200 . The case  500  may not directly support the stator  200 . The substrate  400  is fixed to the case  500  by being screwed into screw holes  513 ,  514 , and  515  of the case  500  through the through-hole  403 ,  404 , and  405 . The screw holes  513 ,  514 , and  515  of the case  500  extend from one end in the axial direction to the other side in the axial direction. The screw holes  513 ,  514 , and  515  of the case  500  are examples of fixing portions. The through-holes  403 ,  404 , and  405  of the substrate  400  are examples of fixed portions. Three or more fixing portions and fixed portions are provided. Since the substrate  400  is fixed to the case  500  instead of being fixed to the stator  200 , the substrate  400  can be easily retrofitted and replaced. 
     The through-holes  403 ,  404 , and  405  of the substrate  400  are located on the outer side in the radial direction with respect to the rotor  300 . That is, the fixing portions and the fixed portions are located on the outer side in the radial direction with respect to the rotor  300 . In this way, the substrate  400  can be easily fixed and removed. 
       FIG. 3  is a side view of the motor  100  shown in  FIG. 1 , as viewed from the +X side. 
       FIG. 4  is a side sectional view showing the motor  100  shown in  FIG. 3 , taken along a plane orthogonal to the X-axis and passing through the central axis J. 
     In  FIGS. 3 and 4 , the parts mounted on the substrate  400  are not shown. 
     The shaft  301  extends along the central axis J. The stator  200  extends in the axial direction about the central axis J. The rotor  300  faces the stator  200  on the outer side in the radial direction and rotates about the shaft  301 . The rotor  300  includes the magnet holder  330 , a rotor core  310 , and the rotor plate  302  in this order from one side in the axial direction to the other side in the axial direction. The magnet holder  330  has a through-hole  331  that penetrates in the axial direction. Ten through-holes  331  are provided at equal intervals in the circumferential direction. The rotor core  310  has a through-hole  311  that penetrates in the axial direction. Ten through-holes  311  are provided at equal intervals in the circumferential direction. The rotor plate  302 , the rotor core  310 , and the magnet holder  330  are fixed by bolts or the like that penetrate the through-holes  305 ,  311 , and  331 . That is, the rotor core  310  is fitted with the rotor plate  302 . 
     The rotor plate  302  includes a cylindrical portion  304  having a cylindrical hole that penetrates in the axial direction. The center of the cylindrical portion  304  is arranged along the central axis J. The shaft  301  penetrates the cylindrical hole of the cylindrical portion  304 . The motor  100  includes a rotor bush  306  between an outer peripheral surface of the shaft  301  and an inner peripheral surface of the cylindrical portion  304 . The shaft  301  is fixed to the rotor plate  302  via the rotor bush  306 . That is, the rotor plate  302  is fitted with the shaft  301 . 
     The case  500  has a through-hole  501  that penetrates in the axial direction. The case  500  has bearings  502  and  503  in the through-hole  501 . The bearing  502  is arranged on one side in the axial direction with respect to the bearing  503 . Outer peripheral surfaces of inner races of the bearings  502  and  503  are fixed to the case  500  in the through-hole  501 . The shaft  301  is fixed to inner peripheral surfaces of inner races of the bearings  502  and  503 . The shaft  301  is supported to be rotatable about the central axis J by the bearings  502  and  503 . 
       FIG. 5  is a perspective view showing a state in which the rotor plate  302  is removed from  FIG. 1 . 
     The rotor core  310  is an annular member extending in the axial direction. The rotor core  310  is composed of, for example, a laminated steel plate formed by laminating electromagnetic steel plates in the axial direction. The rotor core  310  has, on the inner peripheral surface thereof, a side wall portion  312  protruding inward in the radial direction and extending in the axial direction. Ten side wall portions  312  are provided at equal intervals in the circumferential direction. The rotor  300  includes a rotor magnet  320 . The rotor magnet  320  is a rectangular parallelepiped. The rotor magnet  320  is fixed between the side wall portion  312  and the side wall portion  312  adjacent to the side wall portion  312 . Ten rotor magnets  320  are provided at equal intervals in the circumferential direction. The rotor magnets  320  face the stator  200  on the inner side in the radial direction. 
       FIG. 6  is a front view showing a state in which the rotor plate  302  is removed from the motor  100  shown in  FIG. 1 , as viewed from the −Y side. 
     The inner surface in the radial direction of the rotor magnet  320  radially faces a claw portion  332  of the magnet holder  330 . The one side surface in the axial direction of the rotor magnet  320  axially faces the claw portion  332  of the magnet holder  330 . In this way, the claw portion  332  restricts the movement of the rotor magnet  320  toward one side in the axial direction and inward in the radial direction. The claw portion  332  is an example of a holder claw portion. 
       FIG. 7  is a rear view showing a state in which the case  500 , the substrate  400 , and the magnet holders  330  are removed from the motor  100  shown in  FIG. 1 , as viewed from the +Y side. 
     The inner surface in the radial direction of the rotor magnet  320  radially faces a claw portion  303  of the rotor plate  302 . In this way, the claw portion  303  restricts the movement of the rotor magnet  320  inward in the radial direction. The claw portion  303  is an example of a plate claw portion. The other side surface in the axial direction of the rotor magnet  320  radially faces the rotor plate  302 . In this way, the rotor plate  302  restricts the movement of the rotor magnet  320  toward the other side in the axial direction. 
       FIG. 8  is a perspective view showing a state in which the rotor core  310  and the rotor magnets  320  are removed from  FIG. 5 . 
     The stator  200  includes a stator core  210 . The stator core  210  has twelve slots for accommodating the windings of the stator  200 . The stator core  210  is composed of, for example, a laminated steel plate formed by laminating electromagnetic steel plates in the axial direction. The stator  200  includes an insulator  220  that covers the stator core  210  from the other side in the axial direction. The stator  200  includes an insulator  230  that covers the stator core  210  from one side in the axial direction. The insulators  220  and  230  are fixed to the stator core  210 . 
     The magnet holder  330  is a member arranged on one side in the axial direction of the rotor core  310  and the rotor magnet  320 . The magnet holder  330  is an annular member having a flat plate surface in the axial direction and making one revolution in the circumferential direction. The magnet holder  330  is made of, for example, a non-magnetic material such as aluminum. Since the magnet holder  330  is made of a non-magnetic material, it does not affect the magnetic field generated by the rotor magnet  320 . The axial thickness of the magnet holder  330  is thicker than the axial thickness of one of the electromagnetic steel plates constituting the rotor core  310 . In this way, the strength of the magnet holder  330  can be secured. 
       FIG. 9  is a perspective view showing a state in which the magnet holder  330  is removed from  FIG. 6 . 
     The insulator  230  has, on the outer peripheral side thereof, thin-walled portions  230   a ,  230   b , and  230   c  having a thin radial thickness. The thin-walled portion  230   a  has a convex portion  231  on the outer surface in the radial direction thereof. The thin-walled portion  230   b  has a convex portion  232  on the outer surface in the radial direction thereof. The thin-walled portion  230   c  has a convex portion  233  the outer surface in the radial direction thereof. The convex portions  231 ,  232 , and  233  protrude outward in the radial direction and extend in the axial direction. 
     The substrate  400  has concave portions  421 ,  422 , and  423  having shapes corresponding to the convex portions  231 ,  232 , and  233  at positions corresponding to the convex portions  231 ,  232 , and  233 . The concave portions  421 ,  422 , and  423  are recessed outward in the radial direction from the inner peripheral surface of the substrate  400 . 
     The convex portions  231 ,  232 , and  233  are fitted into the concave portions  421 ,  422 , and  423  to restrict the position in the circumferential direction of the substrate  400 . The shapes of the convex portions  231 ,  232 , and  233 , and the concave portions  421 ,  422 , and  423  as viewed from the axial direction may be any shape such as a circle or a square as long as it can restrict the position in the circumferential direction of the substrate  400 . The convex portions  231 ,  232 , and  233  are examples of restricting portions. The concave portions  421 ,  422 , and  423  are examples of restricted portions. A concave portion provided on the outer peripheral surface of the insulator  230  may be used as the restricting portion, and a convex portion provided on the substrate  400  may be used as the restricted portion. When the convex portions  231 ,  232 , and  233  provided on the thin-walled portions  230   a ,  230   b , and  230   c  are used as the restricting portions as in the present embodiment, the convex portions  231 ,  232 , and  233  can serve as reinforcing ribs for the thin-walled portions  230   a ,  230   b , and  230   c , and can suppress the deformation in the radial direction of the insulator  230 . The deformation in the radial direction of the insulator  230  causes the position of the substrate  400  to be shifted. 
       FIG. 10  is a front view of the substrate  400 , as viewed from the −Y side. 
     The Hall ICs  411 ,  412 , and  413  are mounted at intervals of 60 degrees in the circumferential direction on the substrate  400 . The substrate  400  has a length of 120 degrees in the circumferential direction. 
     The concave portions  421 ,  422 , and  423  of the substrate  400  have a semicircular shape as viewed from the axial direction. Of the concave portions  421 ,  422 , and  423 , the concave portion  421  is the concave portion on the one end side in the circumferential direction. Of the concave portions  421 ,  422 , and  423 , the concave portion  423  is the concave portion on the other end side in the circumferential direction. A line A, which is a tangent line to one side surface in the circumferential direction of the concave portion  421 , is parallel to a line B, which is a tangent line to the other side surface in the circumferential direction of the concave portion  423 . In this way, when retrofitting the substrate  400 , the convex portions  231 ,  232 , and  233  can be smoothly fitted into the concave portions  421 ,  422 , and  423 , and the substrate  400  can be easily retrofitted. The convex portions  231 ,  232 , and  233  may have a triangular shape as viewed from the axial direction. The convex portions  231 ,  232 , and  233  may have a trapezoidal shape as viewed from the axial direction. 
     The concave portions  421 ,  422 , and  423  are located in a triangle C that is a polygon having the through-holes  403 ,  404 , and  405  of the substrate  400  as vertices. In this way, the positional deviation in the circumferential direction of the substrate  400  can be reduced. The triangle C is an example of a polygon having a fixing portion and a fixed portion as vertices. 
     In the present embodiment, a lead wire from the winding of the stator  200  is not connected to the substrate  400 . Therefore, the substrate  400  does not have a power line for driving the motor  100 . On the substrate  400 , a Hall signal component connected to a motor drive control IC is arranged, and there is no motor drive control IC or the like. Therefore, the substrate  400  can be easily retrofitted and replaced. 
       FIG. 11  is a rear perspective view showing a state in which the shaft  301 , the case  500 , and the substrate  400  are removed from  FIG. 2 . 
     Ten claw portions  332  of the magnet holder  330  are provided at equal intervals in the circumferential direction. 
     The inner surface in the radial direction of the rotor magnet  320  is a flat surface. The claw portion  332  is located at an end portion in the circumferential direction of the rotor magnet  320 . Since the inner surface in the radial direction of the rotor magnet  320  is a flat surface, a gap between the rotor magnet  320  and the stator  200  is larger at the end portion than at the center portion in the circumferential direction of the rotor magnet  320 . When the claw portion  332  is provided at the end portion in the circumferential direction of such a rotor magnet  320 , the claw portion  332  does not interfere with the rotation of the motor  100  and can reliably hold the rotor magnet  320 . 
     One claw portion  332  of the plurality of claw portions  332  holds ends in the circumferential direction of both of two adjacent rotor magnets  320  of the plurality of rotor magnets  320 . Since one claw portion  332  holds both of the adjacent rotor magnets  320 , the length in the circumferential direction of the claw portion  332  can be increased, and the strength of the claw portion  332  can be increased. The rotor magnets  320  adjacent to each other in the circumferential direction have different poles from each other. Therefore, when the rotor magnets  320  face the stator  200 , a force outward in the radial direction acts on the other of the rotor magnets  320  when a force inward in the radial direction acts on one of the rotor magnets  320 . Therefore, one claw portion  332  that holds the ends in the circumferential direction of both of the adjacent rotor magnets  320  needs only be able to support one of the rotor magnets  320 . 
     One claw portion  332  of the plurality of claw portions  332  is located at one end in the circumferential direction of the rotor magnet  320 , and another claw portion  332  adjacent to the one claw portion  332  is located at the other end in the circumferential direction of the same rotor magnet  320 . Since one claw portion  332  and another claw portion  332  adjacent to the one claw portion  332  hold both ends in the circumferential direction of the rotor magnet  320 , it is possible to further prevent the rotor magnet  320  from falling off inward in the radial direction. 
     The claw portion  332  has a first claw portion  332   a  extending inward in the radial direction from an inner peripheral portion of the magnet holder  330 , and a second claw portion  332   c  extending toward the other side in the axial direction from the first claw portion  332   a . In the claw portion  332 , a bent portion  332   b  is formed when the first claw portion  332   a  is bent to the second claw portion  332   c . The first claw portion  332   a  faces one side in the axial direction of the rotor magnet  320 . In this way, the first claw portion  332   a  restricts the movement of the rotor magnet  320  toward one side in the axial direction. The second claw portion  332   c  faces the inner side in the radial direction of the rotor magnet  320 . In this way, the second claw portion  332   c  restricts the movement of the rotor magnet  320  inward in the radial direction of the rotor magnet  320 . The radial thickness of the second claw portion  332   c  is thicker than the axial thickness of one of the electromagnetic steel plates constituting the rotor core  310 . In this way, the strength of the second claw portion  332   c  can be secured. 
     The magnet holder  330  holds the rotor magnets  320  via an adhesive. In this way, the adhesive can absorb the dimensional tolerance between the magnet holder  330  and the rotor magnet  320 . In particular, the laminated steel plates constituting the rotor core  310  have a large dimensional tolerance, and a structure for absorbing the dimensional differences is required. 
     The second claw portion  332   c  holds the rotor magnets  320  via an adhesive. In this way, the distance between the second claw portion  332   c  and the rotor magnet  320  can be adjusted with the adhesive. Therefore, even when the curvature of the bent portion  332   b  between the first claw portion  332   a  and the second claw portion  332   c  of the claw portion  332  is small (R is gentle), the rotor magnet can be held without the interference between the claw portion  332  and the rotor magnet  320  (while the rotor magnet  320  is not affected by the curved surface of the bent portion  332   b ). 
       FIG. 12  is a rear perspective view of the rotor core  310 . 
     The rotor core  310  has a flat surface portion  313  between the side wall portion  312  and the side wall portion  312  adjacent to the side wall portion  312 . The flat surface portion  313  is the inner surface in the radial direction of the rotor core  310 . The outer surface in the radial direction of the rotor magnet  320  is fixed to the flat surface portion  313  via an adhesive. That is, the rotor core  310  has an accommodating portion  314  formed by the side wall portion  312 , the side wall portion  312  adjacent to the side wall portion  312 , and the flat surface portion  313  between the side wall portions  312 . The accommodating portion  314  is recessed outward in the radial direction on the inner side in the radial direction of the rotor core  310 . The accommodating portion  314  accommodates the rotor magnet  320 . 
       FIG. 13  is a rear perspective view of the rotor plate  302 . 
     On the inner peripheral side of the rotor core  310 , the rotor plate  302  has the claw portion  303  extending to one side in the axial direction from the other end in the axial direction of the rotor core  310 . Ten claw portions  303  of the rotor plate  302  are provided at equal intervals in the circumferential direction. The claw portion  303  is provided at a position corresponding to the position in the circumferential direction of the claw portion  332  of the magnet holder  330 . The claw portion  303  holds the rotor magnet  320  via an adhesive. 
     The length in the circumferential direction of the claw portion  332  facing the inner surface in the radial direction of the rotor magnet  320  is shorter than the length in the circumferential direction of the claw portion  303  facing the inner surface in the radial direction of the rotor magnet  320 . In the facing surface between the claw portion  303  and the rotor magnet  320 , the length in the circumferential direction is longer than the length in the axial direction. In the facing surface between the claw portion  332  and the rotor magnet  320 , the length in the circumferential direction is shorter than the length in the axial direction. 
     The claw portion  303  holds the inner surface in the radial direction of the rotor magnet  320  mainly over the length in the circumferential direction. When the rotor plate  302  is an aluminum die-cast part, the rotor plate is easily bent when the claw portion  303  is long in the axial direction. Therefore, when the claw portion  303  is short in the axial direction and long in the circumferential direction, a large contact area between the claw portion  303  and the rotor magnet  320  can be secured, and the holding force can be increased. The claw portion  332  holds the inner surface in the radial direction of the rotor magnet  320  mainly over the length in the axial direction. When the magnet holder  330  is an aluminum plate, the magnet holder is easily bent in the axial direction when the claw portion  332  is long in the axial direction and short in the circumferential direction at the time of forming the claw portion  332 . Further, when the claw portion  332  is long in the axial direction and short in the circumferential direction, a large contact area between the claw portion  332  and the rotor magnet  320  can be secured, and the holding force can be increased. 
     &lt;Operation and Effect of Motor  100 &gt; 
     Next, the operation and effect of the motor  100  will be described. 
     The invention according to the above-described embodiment provides a motor including a central shaft extending in an axial direction; a stator extending in the axial direction around the central shaft; a rotor facing the outer side in a radial direction of the stator and configured to rotate around the central shaft; a substrate which is located on one side in the axial direction with respect to the rotor and on which a rotation position detection circuit that detects the rotation position of the rotor is mounted; and a case located on one side in the axial direction with respect to the substrate and configured to support the stator. The stator has a restricting portion configured to restrict the position in a circumferential direction of the substrate, the case has a fixing portion configured to fix the substrate, and the substrate has a restricted portion whose position in the circumferential direction is restricted by the restricting portion, and a fixed portion fixed to the fixing portion. 
     Since the substrate is fixed to the case, the substrate can be easily retrofitted and replaced. 
     Further, the rotation position detection circuit has a Hall IC, and a connector configured to connect the Hall IC and the outside is mounted on the substrate. 
     The rotation position of the rotor can be detected by the Hall IC. 
     A lead wire from the winding of the stator is not connected to the substrate. Therefore, the substrate does not have a power line for driving the motor. On the substrate, a Hall signal component connected to a motor drive control IC is arranged, and there is no motor drive control IC or the like. Therefore, the substrate can be easily retrofitted and replaced. 
     Further, the fixing portion and the fixed portion are located on the outer side in the radial direction with respect to the rotor. 
     Since the fixing portions and the fixed portions are located on the outer side in the radial direction with respect to the rotor, the substrate can be easily fixed and removed. 
     Further, the fixing portion has a screw hole extending in the axial direction, the fixed portion has a hole facing the screw hole in the axial direction and penetrating in the axial direction, and the substrate is fixed to the case by a screw penetrating the hole being screwed into the screw hole. 
     Since the substrate and the case are fixed with the hole of the substrate and the screw hole of the case, the substrate can be easily fixed and removed. 
     Further, three or more fixing portions and fixed portions are provided, and the restricting portion and the restricted portion are located in a polygon having the three or more fixing portions and fixed portions as vertices. 
     Since the restricting portion and the restricted portion are located in the polygon having the three or more fixing portions and fixed portions as vertices, the positional deviation in the circumferential direction of the substrate can be reduced. 
     Further, the stator has a stator core and an insulator fixed to the stator core, the restricting portion has a plurality of convex portions protruding outward in the radial direction on the outer surface side of the insulator, the restricted portion has a plurality of concave portions recessed outward in the radial direction on the inner surface side of the substrate, and the plurality of convex portions are fitted into the plurality of concave portions to restrict the position in the circumferential direction of the substrate. 
     Since the convex portions are fitted into the concave portions, the substrate can be accurately positioned. 
     Since the convex portions are provided on the thin-walled portions on the outer side in the radial direction of the insulator, the convex portions can serve as reinforcing ribs for the thin-walled portions, and can suppress the deformation in the radial direction of the insulator. The deformation in the radial direction of the insulator causes the position of the substrate to be shifted. 
     Further, a tangent line to one side surface in the circumferential direction of the concave portion on one end side in the circumferential direction among the plurality of concave portions is parallel to a tangent line to the other side surface in the circumferential direction of the concave portion on the other end side in the circumferential direction among the plurality of concave portions. 
     Therefore, when retrofitting the substrate, the convex portions can be smoothly fitted into the concave portions, and the substrate can be easily retrofitted. 
     The convex portions have a semicircular shape as viewed from the axial direction. The convex portions may have a triangular shape as viewed from the axial direction. The convex portions may have a trapezoidal shape as viewed from the axial direction. 
     The invention according to the above-described embodiment provides a motor including a central shaft extending in an axial direction; a stator extending in the axial direction around the central shaft; and a rotor facing the outer side in a radial direction of the stator and configured to rotate around the central shaft. The rotor includes a rotor plate fitted with the central shaft, a rotor core fitted with the rotor plate and having an accommodating portion recessed outward in the radial direction on the inner side in the radial direction, a rotor magnet accommodated in the accommodating portion and facing the stator on the inner side in the radial direction, and a magnet holder having a holder claw portion that restricts the movement of the rotor magnet toward one side in the axial direction and inward in the radial direction. 
     Therefore, the magnet holder can prevent the rotor magnet from falling off inward in the radial direction. 
     Further, the holder claw portion has a first claw portion extending inward in the radial direction from the inner peripheral portion and a second claw portion extending toward the other side in the axial direction from the first claw portion. The first claw portion faces one side in the axial direction of the rotor magnet, and the second claw portion faces the inner side in the radial direction of the rotor magnet. 
     Therefore, the rotor core, the rotor plate, and the magnet holder can hold the rotor magnet from six directions, so that it is possible to further prevent the rotor magnet from falling off. 
     Further, the inner surface in the radial direction of the rotor magnet is a flat surface, and the holder claw portion is located at an end portion in the circumferential direction of the rotor magnet. 
     Since the inner surface in the radial direction of the rotor magnet is a flat surface, the gap between the rotor magnet and the stator is larger at the end portion than at the center portion in the circumferential direction of the rotor magnet. When the holder claw portion is provided at the end portion in the circumferential direction of such a rotor magnet, the holder claw portion does not interfere with the rotation of the motor and can reliably hold the rotor magnet. 
     Further, the rotor has a plurality of rotor magnets adjacent to each other in the circumferential direction, and the holder claw portion holds the ends in the circumferential direction of both of the adjacent rotor magnets. 
     Since the holder claw portion holds both of the adjacent rotor magnets, the length in the circumferential direction of the holder claw portion can be increased, and the strength of the holder claw portion can be increased. 
     The adjacent rotor magnets have different poles from each other. Therefore, when the rotor magnets face the stator, a force outward in the radial direction acts on the other of the rotor magnets when a force inward in the radial direction acts on one of the rotor magnets. Therefore, one holder claw portion that holds the ends in the circumferential direction of both of the adjacent rotor magnets needs only be able to support one of the rotor magnets. 
     Further, the magnet holder has a plurality of holder claw portions adjacent to each other in the circumferential direction, one of the plurality of holder claw portions is located at one end in the circumferential direction of the rotor magnet, and another one adjacent to the holder claw portion is located at the other end in the circumferential direction of the rotor magnet. 
     Since both ends in the circumferential direction of the rotor magnet are held, it is possible to further prevent the rotor magnet from falling off inward in the radial direction. 
     Further, the magnet holder is made of a non-magnetic material. 
     Since the magnet holder is made of a non-magnetic material, it does not affect the poles of the rotor magnet. Further, even when the poles of adjacent rotor magnets are different, the magnetic force will not be short-circuited. Moreover, there is no influence on the magnetic force toward the Hall IC. 
     Further, the rotor core is composed of a laminated steel plate formed by laminating a plurality of electromagnetic steel plates in the axial direction, and the axial thickness of the magnet holder is thicker than the axial thickness of one electromagnetic steel plate. 
     Therefore, the strength of the magnet holder can be secured. 
     Further, the radial thickness of the second claw portion is thicker than the axial thickness of one electromagnetic steel plate. 
     Further, the magnet holder holds the rotor magnet via an adhesive. 
     Therefore, the adhesive can absorb the dimensional tolerance between the magnet holder and the rotor magnet. In particular, the laminated steel plates have a large dimensional tolerance, and a structure for absorbing the dimensional differences is required. 
     Moreover, even when the curvature of the bent portion between the first claw portion and the second claw portion of the holder claw portion is small (R is gentle), the rotor magnet can be held without the interference between the holder claw portion and the rotor magnet (while the rotor magnet is not affected by the curved surface of the bent portion). 
     Further, the rotor plate includes a rotor plate having a plate claw portion that restricts the movement of the rotor magnet toward the other side in the axial direction and inward in the radial direction. 
     The rotor plate can further prevent the rotor magnet from falling off inward in the radial direction. 
     Further, the plate claw portion extends to one side in the axial direction from the inner peripheral portion of the rotor plate, and the plate claw portion faces the inner side in the radial direction of the rotor magnet. 
     The rotor core, the rotor plate, and the magnet holder can hold the rotor magnet from six directions, so that it is possible to further prevent the rotor magnet from falling off. 
     Further, the length in the circumferential direction of the holder claw portion facing the inner surface of the rotor magnet is shorter than the length in the circumferential direction of the plate claw portion facing the inner surface of the rotor magnet. 
     The plate claw portion holds the inner surface of the rotor magnet mainly over the length in the circumferential direction. The rotor plate is an aluminum die-cast part and is easily bent when it is long in the axial direction. Therefore, when the plate claw portion is short in the axial direction and long in the circumferential direction, a large contact area between the plate claw portion and the rotor magnet can be secured, and the holding force can be increased. 
     The holder claw portion holds the inner surface of the rotor magnet mainly over the length in the axial direction. The magnet holder is an aluminum plate and is easily bent when the holder claw portion is long in the axial direction and short in the circumferential direction. Further, when the holder claw portion is long in the axial direction and short in the circumferential direction, a large contact area between the holder claw portion and the rotor magnet can be secured, and the holding force can be increased. 
     Further, in the facing surface between the plate claw portion and the rotor magnet, the length in the circumferential direction is longer than the length in the axial direction. Moreover, in the facing surface between the holder claw portion and the rotor magnet, the length in the circumferential direction is longer than the length in the axial direction. 
     Second Embodiment 
     Next, a second embodiment of the invention will be described. Since a basic configuration of the motor  100  in the present embodiment is not different from that in the first embodiment, a duplicate description will be omitted, and only the different parts will be described. In other words, unless otherwise noted in the present embodiment, the configuration of the motor  100  is the same as that in the first embodiment. 
     &lt;Overall Configuration&gt; 
       FIG. 14  shows an air compressor  600  according to a second embodiment of the invention.  FIG. 14  is a plan view showing a state in which a cover (not shown) covering an upper surface of the air compressor  600  is removed. The air compressor  600  is a portable compressor, and is used in a state of being mounted on the ground with the +Z direction as the upward direction and the −Z direction as the downward direction. 
     As shown in  FIG. 14 , the air compressor  600  according to the present embodiment includes two tanks  615  and a mechanism part arranged above the tanks  615 . The mechanism part includes the motor  100 , a fan  601 , a compression mechanism, a control board, and the like. 
     The fan  601  is provided for introducing cooling air into the mechanism part to cool heat-generating parts such as the motor  100  and the control board. The fan  601  is fixed to the shaft  301  of the motor  100 , and is configured to integrally rotate when the motor  100  is driven. 
     The compression mechanism is driven by the motor  100  to generate compressed air, and compresses the air introduced into a cylinder by reciprocating a piston. The air compressor  600  according to the present embodiment is a multi-stage compressor having two compression mechanisms of a primary compression mechanism  610  and a secondary compression mechanism  611 . 
     As shown in  FIG. 19 , the primary compression mechanism  610  includes a primary cylinder  610   a  and a primary piston  610   b  reciprocally arranged in the primary cylinder  610   a , and the air in the primary cylinder  610   a  can be compressed by reciprocating the primary piston  610   b  with the driving force of the motor  100 . Further, the secondary compression mechanism  611  includes a secondary cylinder  611   a  and a secondary piston  611   b  reciprocally arranged in the secondary cylinder  611   a , and the air in the secondary cylinder  611   a  can be compressed by reciprocating the secondary piston  611   b  with the driving force of the motor  100 . The air supplied form the outside is first compressed by the primary compression mechanism  610 . The air compressed by the primary compression mechanism  610  is introduced into the secondary compression mechanism  611  and further compressed by the secondary compression mechanism  611 . The air compressed in two stages in this way is sent and stored in the tank  615 . 
     The tank  615  is provided for storing the compressed air generated by the compression mechanism. The air compressor  600  according to the present embodiment includes two tanks  615 . The two tanks  615  are arranged parallel to each other along the longitudinal direction of the air compressor  600 . 
     The compressed air stored in the tank  615  is depressurized to an arbitrary pressure by passing through a pressure reducing valve  616 , and can be taken out from an air outlet to the outside. In the present embodiment, an air coupler  617  is provided at the air outlet, and an air hose can be attached and detached with one touch. By connecting the air hose to the air outlet in this way, the compressed air in the tank  615  can be taken out and used. 
     Meanwhile, although not particularly shown, a control board that controls the entire operation of the air compressor  600  is provided between the compression mechanism and the tank  615 . This control board is arranged on the lower surface side of the compression mechanism so as to be substantially horizontal to the ground. This control board is mainly composed of a CPU, and includes a ROM, a RAM, and an I/O, and the like. Further, the CPU is configured to control various input devices and output devices by reading a program stored in the ROM. 
     Examples of the input device of this control board include various operation switches, pressure sensors, Hall ICs (rotation position detection circuit), thermistors, and the like. Meanwhile, the input device is not limited to these input devices, and other input devices may be provided. 
     The operation switch refers to various switches that can be operated by a user. Although not described in detail herein, for example, a plurality types of operation switches such as a switch for turning the power on and off and a switch for switching the operation mode may be provided. This operation switch is arranged on an operation panel provided on the surface of a cover (not shown). 
     The pressure sensor is provided for measuring the internal pressure of the tank  615 . The control board controls the start or stop of the driving of the motor  100  based on the pressure value detected by the pressure sensor. Specifically, the ON pressure, which is a pressure value for starting the driving of the compression mechanism, and the OFF pressure, which is a pressure value for stopping the driving of the compression mechanism, are preset. For example, when the internal pressure of the tank  615  drops due to the use of compressed air and the internal pressure of the tank  615  drops to the preset ON pressure, the motor  100  is driven to fill the compressed air. Further, when the internal pressure of the tank  615  reaches the preset OFF pressure while the motor  100  is being driven, the driving of the motor  100  is stopped. 
     As already described in the first embodiment, the Hall IC (rotation position detection circuit) is provided for detecting the rotation position of the motor  100 . The control board can calculate the rotation speed (rpm) of the motor  100  by analyzing the signal from the Hall IC. 
     The thermistor is provided for detecting the temperature of the motor  100 . The temperature detected by this thermistor is used to correct the control of the motor  100 . 
     Further, as the output device of this control board, the motor  100  is provided. That is, the control board is configured to control the rotation of the motor  100  based on the input signal from the input device described above. 
     Subsequently, a specific aspect of the compression mechanism and the motor  100  according to the present embodiment will be described. 
       FIG. 15  is a perspective view of the compression mechanism and the motor  100 . 
       FIG. 16  is a front view of the compression mechanism and the motor  100  shown in  FIG. 15 , as viewed from the −Y side. 
       FIG. 17  is a perspective view showing a state in which the rotor plate  302  is removed from  FIG. 15 . 
       FIG. 18  is a front view showing a state in which the rotor plate  302  is removed from the compression mechanism and the motor  100  shown in  FIG. 15 , as viewed from the −Y side. 
     The compression mechanism and the motor  100  according to the present embodiment include the shaft  301  extending in the axial direction, the stator  200 , the rotor  300 , a substrate  650 , and a case  680 . 
     The motor  100  is an outer rotor type motor in which the rotor  300  is arranged on the outer side in the radial direction of the stator  200 . Basic aspects of the stator  200  and the rotor  300  are the same as those in the first embodiment. 
     In the present embodiment, as shown in  FIGS. 15 and 16 , the motor  100  is arranged on the front side (−Y side) of the compression mechanism. As shown in  FIG. 19 , the shaft  301  of the motor  100  penetrates the inside of the compression mechanism, and cylinders of the compression mechanism protrude on both the left and right sides of the shaft  301 . Specifically, the primary compression mechanism  610  is arranged on the −X side of the shaft  301 , and the secondary compression mechanism  611  is arranged on the +X side of the shaft  301 . The shaft  301  of the motor  100  serves as a crankshaft of the compression mechanism. The crankshaft and crank mechanism are well known structures. That is, a crank arm is attached to the shaft  301  (crankshaft), and a connecting rod is attached to the crank arm via a crank pin. A piston is attached to the tip of the connecting rod. When the shaft  301  rotates, the crank arm attached to the shaft  301  (crankshaft) rotates, and thus, the connecting rod reciprocates while swinging. With such an action, the rotation motion of the shaft  301  is converted into the reciprocating motion of the piston, and the compression mechanisms arranged on both sides of the shaft  301  are activated. 
     As shown in  FIGS. 17 and 18 , the substrate  650  has an arcuate shape with a central angle of about 120 degrees and has a length of 120 degrees in the circumferential direction. Similar to the first embodiment, on this substrate  650 , the Hall ICs (not shown) are mounted at intervals of 60 degrees in the circumferential direction. The Hall IC is an example of a rotation position detection circuit that detects the rotation position of the rotor  300 . Meanwhile, although not particularly shown, the Hall IC according to the present embodiment is a Hall IC for surface mounting and is surface-mounted on the substrate  650 . When the Hall IC for surface mounting is used, the thickness in the axial direction can be suppressed. 
     This substrate  650  includes a connector arrangement portion  660  in which a connector to which an electric wire  670  can be connected is arranged. As shown in  FIG. 18  and the like, this connector arrangement portion  660  is provided to protrude outward in the radial direction and located on the outer side in the radial direction with respect to the rotor  300 . In the present embodiment, a plurality of connectors are arranged on either the front or back surface of this connector arrangement portion  660 . Specifically, as shown in  FIGS. 21 and 22 , a control board connector  661  for connecting the control board and a thermistor connector  662  are arranged on the surface of the connector arrangement portion  660  on the side of the compression mechanism. A lead type thermistor is connected to the thermistor connector  662 . The control board connector  661  has a terminal capable of externally outputting the signal detected by the Hall IC and the signal of the thermistor inputted to the substrate  650  via the thermistor connector  662 . As the substrate  650  and the control board are connected by the electric wire  670  via these connectors, a signal can be outputted from the substrate  650  to the control board and used for feedback control. 
     Meanwhile, in the present embodiment, an axis of the motor  100  is arranged in a horizontal direction, and a control board having a control circuit for the motor  100  is arranged below the motor  100 . Further, as shown in  FIG. 18  and the like, the connector arrangement portion  660  described above is arranged below the rotor  300 . Therefore, the electric wire  670  connected to the connector of the substrate  650  can be routed downward as it is and connected to the control board. In this way, the structure is such that the electric wire  670  can be easily handled. Further, since the connector arrangement portion  660  is not exposed on the upper surface, the structure is such that the substrate  650  is not easily damaged. 
     Further, this substrate  650  has protrusions  656 ,  657 , and  658  protruding outward in the radial direction. These protrusions  656 ,  657 , and  658  are provided at intervals of 60 degrees in the circumferential direction. Through-holes  653 ,  654 , and  655  penetrating in the axial direction are formed in the protrusions  656 ,  657 , and  658 , respectively. 
     The case  680  is a crankcase in which a part of the compression mechanism is incorporated. The case  680  according to the present embodiment incorporates a crank part that is a part of the compression mechanism. The crank part is a part of the compression mechanism and is a mechanism part around the crankshaft including the crank arm described above. This case  680  is located on one side in the axial direction with respect to the substrate  650 . This case  680  has four leg portions  686  protruding downward and is secured above the tank  615  by the four leg portions  686 . Meanwhile, of the four leg portions  686 , the pair of leg portions  686  arranged on the front side (−Y side) are arranged on the outer side in the radial direction of the substrate  650 . 
     The case  680  supports the stator  200 . The case  680  may not directly support the stator  200 . The substrate  650  is fixed to the case  680  by being screwed into screw holes  683 ,  684 , and  685  of the case  680  through the through-holes  653 ,  654 , and  655 . The screw holes  683 ,  684 , and  685  of the case  680  extend from one end in the axial direction to the other side in the axial direction. The screw holes  683 ,  684 , and  685  of the case  680  are examples of the fixing portions. The through-holes  653 ,  654 , and  655  of the substrate  650  are examples of the fixed portions. Three or more fixing portions and fixed portions are provided. Since the substrate  650  is fixed to the case  680  instead of being fixed to the stator  200 , the substrate  650  can be easily retrofitted and replaced. 
     Further, this case  680  rotatably supports the crankshaft (the shaft  301 ) of the compression mechanism. The case  680  may not directly support the crankshaft. 
     The through-holes  653 ,  654 , and  655  of the substrate  650  are located on the outer side in the radial direction with respect to the rotor  300 . That is, the fixing portions and the fixed portions are located on the outer side in the radial direction with respect to the rotor  300 . In this way, the substrate  650  can be easily fixed and removed. 
     The case  680  described above has a support portion protruding outward in the radial direction from the substrate  650 . Specifically, as shown in  FIGS. 15 and 16 , the case  680  has a first support portion  681  protruding downward (−Z side) from the protrusion  656  of the substrate  650 , and a second support portion  682  protruding downward (−Z side) from the connector arrangement portion  660  of the substrate  650 . Since the support portion protruding outward in the radial direction from the substrate  650  in this way, the substrate  650  does not hit against the floor surface when the case  680  is placed on the floor surface. 
     By the way, the insulator  230  according to the present embodiment does not have the convex portions  231 ,  232 , and  233  described in the first embodiment, and the substrate  650  according to the present embodiment does not have the concave portions  421 ,  422 , and  423  described in the first embodiment. Therefore, the present embodiment is not configured such that the position in the circumferential direction of the substrate  400  is restricted by fitting the convex portions  231 ,  232 , and  233  into the concave portions  421 ,  422 , and  423 . The substrate  650  according to the present embodiment is attached to the case  680  so as not to come into contact with the insulator  230 . 
     Further, as shown in  FIG. 20 , as viewed in the axial direction, a gap G larger than a thickness T of the substrate  650  is provided between the insulator  230  and the fixing portion of the case  680 . Therefore, even when the substrate  650  is slid horizontally in the X-axis direction or the Y-axis direction, the substrate  650  does not come into contact with the insulator  230 . By setting in this manner, the substrate  650  can be moved inward to overlap the insulator  230 , so that the substrate  650  can be moved relatively freely. 
     Here, in the present embodiment, as shown in  FIG. 15 , the leg portions  686  are arranged on the outer side in the radial direction of the substrate  650 . Therefore, the substrate  650  cannot be slid outward in the radial direction as it is. Further, the leg portion  686  is arranged between the protrusions  653 ,  654  of the substrate  650 . Therefore, when the substrate  650  is slid in the circumferential direction as it is, the protrusions  653 ,  654  interfere with the leg portion  686 . In such an arrangement, when the convex portions  231 ,  232 , and  233  are fitted into the concave portions  421 ,  422 , and  423  as in the first embodiment, the leg portions  686  may become an obstacle and the substrate  650  may not be replaced. In this regard, in the present embodiment, the gap G larger than the thickness T of the substrate  650  is provided between the insulator  230  and the fixing portion of the case  680 . Therefore, the substrate  650  can be rotated in the circumferential direction, and the substrate  650  can be replaced while avoiding the leg portions  686 . Meanwhile, in the present embodiment, the fixing portion of the case  680  is formed to protrude toward the motor  100  as viewed in the axial direction. Therefore, a recessed portion  687  that is recessed to the side opposite to the motor  100  from the fixing portion as viewed in the axial direction is provided on the inner side in the radial direction of the fixing portion (see  FIG. 19 ). This recessed portion  687  extends in the circumferential direction so as to face the stator  200 . Therefore, when the substrate  650  is rotated in the circumferential direction at the time of replacement, the substrate  650  can be rotated using the recessed portion  687  of the case  680 , making it difficult for the substrate  650  to come into contact with the insulator  230 . 
     Meanwhile, the inner corner of the substrate  650  according to the present embodiment has a chamfered shape  663  (C surface in the present embodiment). Therefore, even when the inner corner of the substrate  650  comes into contact with the insulator  230  and the like at the time of sliding and replacing the substrate  650 , breakage or damage is less likely to occur. 
     &lt;Operation and Effect of Air Compressor  600 &gt; 
     Next, the operation and effect of the air compressor  600  will be described. 
     The invention according to the above-described embodiment provides an air compressor including a motor; a compression mechanism configured to be driven by the motor; and a crankcase in which a part of the compression mechanism is incorporated. The motor includes a central shaft extending in an axial direction; a stator extending in the axial direction around the central shaft; a rotor facing the outer side in a radial direction of the stator and configured to rotate around the central shaft; and a substrate which is located on one side in the axial direction with respect to the rotor and on which a rotation position detection circuit that detects the rotation position of the rotor is mounted. The crankcase has a fixing portion configured to fix the substrate, and the substrate has a fixed portion fixed to the fixing portion. 
     Since the substrate is fixed to the crankcase, the substrate can be easily retrofitted and replaced. 
     Further, the fixing portion and the fixed portion are located on the outer side in the radial direction with respect to the rotor. 
     Since the fixing portions and the fixed portions are located on the outer side in the radial direction with respect to the rotor, the substrate can be easily fixed and removed. 
     Further. the stator has a stator core and an insulator fixed to the stator core, and as viewed in the axial direction, a gap larger than the thickness of the substrate is provided between the insulator and the fixing portion. 
     Since the gap larger than the thickness of the substrate is provided between the insulator and the fixing portion, the substrate and the insulator are less likely to interfere with each other, and thus, the substrate can be easily retrofitted and replaced. 
     Further, the rotation position detection circuit is surface-mounted on the substrate. 
     When the rotation position detection circuit is surface-mounted on the substrate, the axial thickness can be reduced. Therefore, the substrate and the insulator are less likely to interfere with each other, and thus, the substrate can be easily retrofitted and replaced. 
     Further, the substrate has a connector arrangement portion in which a connector to which an electric wire can be connected is arranged, and the connector arrangement portion is located on the outer side in the radial direction with respect to the rotor. 
     Since the connector arrangement portion is located on the outer side in the radial direction with respect to the rotor, the electric wire can be easily attached to and detached from the connector, and thus, the substrate can be easily retrofitted and replaced. 
     Further, a plurality of connectors are arranged in the connector arrangement portion. Since a plurality of connectors are arranged in one connector arrangement portion in this way, the electric wire can be easily attached to and detached from the connector, and thus, the substrate can be easily retrofitted and replaced. 
     Further, an axis of the motor is arranged in a horizontal direction, a control board having a control circuit for the motor is arranged below the motor, and the connector arrangement portion is arranged below the rotor. 
     Since the control board is arranged below the motor and the connector arrangement portion is arranged below the rotor, the control board and the connector arrangement portion are close to each other. Therefore, the electric wire connecting both members can be easily handled, and thus, the substrate can be easily retrofitted and replaced. 
     Further, the crankcase has a support portion that protrudes outward in the radial direction from the substrate. 
     Since the support portion that protrudes outward in the radial direction from the substrate is provided, the substrate does not hit against the floor when the motor  100  and the compression mechanism are placed on the floor, and the damage of the substrate can be prevented. 
     Meanwhile, in the second embodiment described above, the aspect in which the insulator  230  does not have the convex portions  231 ,  232 , and  233 , and the substrate  650  does not have the concave portions  421 ,  422 , and  423  has been described. However, the invention is not limited thereto. The same convex portions  231 ,  232 , and  233  as those in the first embodiment may be provided on the insulator  230 , and the same concave portions  421 ,  422 , and  423  as those in the first embodiment may be provided on the substrate  650 . Further, the position in the circumferential direction of the substrate  400  may be restricted by fitting the convex portions  231 ,  232 , and  233  into the concave portions  421 ,  422 , and  423 . That is, the stator may have a restricting portion that restricts the position in the circumferential direction of the substrate, and the substrate may have a restricted portion whose position in the circumferential direction is restricted by the restricting portion. 
     Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist thereof. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and the equivalent scope thereof.