JP2007181314A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily form the rotor core in a complicated shape of an electric motor to reduce the manufacturing cost of the motor. <P>SOLUTION: In the motor 1, the covered cylindrical rotor core 22 is installed to an end of a shaft 21, and a rotor 2 is supported by a so-called cantilever structure. On the outer circumferential surface of the rotor core 22, there is provided an abutting portion for determining the installation positions of a field magnet 230 and a sensor magnet 24 for rotation position detection. The rotor core 22 is formed with a process including pressure molding and sintering of metal powder material. This makes it possible to form the rotor core in a complicated shape with ease, and to reduce the number of parts of the rotor 2 and the manufacturing cost of the motor 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric motor.

  Conventionally, a brushless motor that indirectly detects the position of the magnetic pole of a field magnet by detecting a change in the magnetic field by a sensor magnet provided separately from the field magnet by a sensor such as a hall element. Are known.

  For example, in Patent Document 1, in a brushless motor used as a power source for an open / close valve of an exhaust gas recirculation device, a Hall element is mounted on a circuit board disposed on a current supply side, and an end of a rotor having a field magnet A technique is disclosed in which a driving magnet is appropriately controlled by detecting a rotational position of a rotor in which a sensor magnet is attached to a portion and a Hall element faces the sensor magnet in a thrust direction.

On the other hand, a rotor core used in an electric motor is usually formed by laminating electromagnetic steel sheets or by cutting a magnetic material. As another forming method, for example, in Patent Document 2, induction is performed. In a rotor of an electric motor and a synchronous motor, by combining a material obtained by mixing a highly magnetic metal material and a highly conductive metal material by sintering, the ratio of the highly conductive metal composition increases as the outer surface of the rotor is closer. Techniques to do this are disclosed.
US Pat. No. 6,737,771 JP 2002-34182 A

  By the way, when the field magnet and the sensor magnet are respectively attached to different members of the rotor as in the motor of Patent Document 1, it is complicated to align the circumferential direction positions of the field magnet and the sensor magnet. Requires a lot of work, and the number of parts constituting the rotor increases, resulting in an increase in motor manufacturing costs and man-hours.

  If an attempt is made to arrange the sensor magnets on the rotor core, the shape of the rotor core becomes complicated, and the shape of the cross section perpendicular to the axial direction in the rotor core changes in a complicated manner along the axial direction. Further, even when the motor is further downsized, it is desired to make the shape of the rotor core complicated. However, the lamination of electromagnetic steel sheets requires a large number of dies to form a complicated shape, and it takes time to form the magnetic material, and the manufacturing cost increases.

  The present invention has been made in view of the above problems, and has as its main purpose to easily form a rotor core having a complicated shape in an electric motor.

  The invention according to claim 1 is an electric motor, which is a shaft and a magnetic body formed by a process including pressure molding and sintering of a powder material, and the central axis is the central axis of the shaft. A rotor core having a matching cylindrical portion and attached to the shaft, a field magnet attached to the outer peripheral surface of the rotor core, a housing having a cylindrical portion surrounding the central axis, and an inner surface of the cylindrical portion An armature that is fixed to the outer peripheral surface of the rotor core and generates a torque about the central axis with the field magnet, and the shaft with respect to the housing. And a bearing mechanism that rotatably supports the shaft.

  Invention of Claim 2 is the motor of Claim 1, Comprising: The said rotor core is provided with the cover part which obstruct | occludes one edge part of the said cylindrical part, The said cover part is attached to the said shaft, The other end of the cylindrical portion is a free end, and at least a part of the bearing mechanism is located in the cylindrical portion.

  The invention according to claim 3 is the motor according to claim 1 or 2, wherein the field magnet is a set of a plurality of field magnet elements, and the rotor core is the plurality of field magnets. A first magnet contact portion that determines a position in the central axis direction by contacting with each of the magnet elements for use, and a second magnet contact portion that determines a position in the circumferential direction.

  Invention of Claim 4 is a motor of Claim 3, Comprising: From the surface on the said rotor core in which a said 1st magnet contact part is in contact with the surface by the side of the said central axis of the said field magnet element A protrusion is provided that protrudes toward the one end face of the field magnet element while being spaced apart and abuts against the one end face.

  According to a fifth aspect of the present invention, there is provided the motor according to any one of the first to fourth aspects, wherein the sensor magnet has an annular shape centered on the central axis and is mounted on an outer peripheral surface of the rotor core. A sensor that is disposed outside the sensor magnet with respect to the central axis and that detects a magnetic field from the sensor magnet to detect a direction of the rotor core, the rotor core including the sensor magnet A sensor magnet contact portion that contacts and determines the position of the sensor magnet in the central axis direction is provided.

  A sixth aspect of the present invention is the motor according to the fifth aspect, wherein the sensor magnet is provided on an outer peripheral surface of one end of the rotor core, and is attached to one end of the armature and the sensor. A bus bar surrounding the outer periphery of the magnet is further provided, and the sensor is disposed on the inner peripheral portion of the bus bar.

  A seventh aspect of the present invention is the motor according to the fifth or sixth aspect, wherein the rotor core further includes a rotor cover that covers the sensor magnet and at least a part of the field magnet.

  In the present invention, the rotor core having the cylindrical portion can be easily formed, and the manufacturing cost of the motor can be reduced.

  In the invention of claim 2, even if the rotor core is supported by a so-called cantilever structure, the rotor core can be easily formed. In the invention of claim 3, the rotor core is formed in the central axis direction and the circumferential direction. Thus, a contact portion for determining the position of the field magnet element can be easily provided. Further, in the invention of claim 4, the field magnet element can be accurately positioned in the central axis direction, and leakage of magnetic flux from the field magnet element to the rotor core can be suppressed to increase drive efficiency. .

  Furthermore, in the invention of claim 5, a contact portion for determining the mounting position of the sensor magnet can be easily provided. In the invention of claim 6, the bus bar protrudes from the rotor core to the side opposite to the armature. The amount can be reduced. In the invention of claim 7, the number of parts can be reduced by covering at least a part of the sensor magnet and the field magnet with one cover.

  FIG. 1 is a longitudinal sectional view of an electric motor 1 according to an embodiment of the present invention. The motor 1 is a so-called brushless motor and is used as a power steering drive source for assisting the steering of the automobile. Note that some of the parallel diagonal lines in the details of the cross section are omitted. The motor 1 includes a rotor portion 2 that is a rotating assembly, a stator portion 3 that is a fixed assembly, a substantially bottomed cylindrical housing 11 that houses the rotor portion 2 and the stator portion 3, and a bearing mechanism 4.

  When the motor 1 is actually used, an opening on the upper side of the housing 11 in FIG. Control Unit) ") 71 is attached. A pump is attached to the outside of the bottom of the housing 11, and the inside of the pump and the inside of the housing 11 are filled with oil that is a fluid for power steering. In the following description, for the sake of convenience, the opening side of the housing 11 is described as the upper side and the bottom side of the housing 11 is the lower side along the central axis J1, but the central axis J1 does not necessarily coincide with the direction of gravity.

  The housing 11 is formed as a single member by aluminum die casting, and has a substantially cylindrical tubular part 111 surrounding the central axis J1, a bottom part 112 covering the lower end of the tubular part 111 and having an opening 1121 formed in the center, an opening A substantially cylindrical bearing holding portion 113 that protrudes from 1121 along the central axis J1 toward the upper end of the cylindrical portion 111 is provided.

  The rotor portion 2 has a shaft 21 with one end (upper end) projecting from the tip of the bearing holding portion 113 around the center axis J1, and a thick cylindrical portion 222 whose center axis coincides with the center axis J1 of the shaft 21. A rotor core 22 attached to the rotor 21, a field magnet 230 attached on the outer peripheral surface of the rotor core 22, an annular sensor magnet 24 centered on the central axis J 1 and attached to the outer peripheral surface of the upper end of the rotor core 22, and The upper rotor cover 25 a that covers the upper part of the field magnet 230 and the sensor magnet 24 and the lower rotor cover 25 b that covers the lower part of the field magnet 230 are provided.

  The rotor core 22 is a magnetic body (magnetic) formed by a process including pressure molding and sintering of a metal powder material (for example, a mixed powder containing iron powder as a main component and 1 to 2% of copper powder as a whole). A cover portion 221 that closes the upper end of the cylindrical portion 222, and the cover portion 221 is attached to the shaft 21 by press-fitting the shaft 21 into the central opening of the cover portion 221. The lower end of the cylindrical portion 222 is a free end. In this way, by supporting the rotor core 22 with a so-called cantilever structure, the bearing mechanism 4 is positioned in the rotor core 22 and the height (axial length) of the motor 1 is reduced. . The entire bearing mechanism 4 does not need to be located inside the rotor core 22, and at least a part of the bearing mechanism 4 may be located only in the cylindrical portion 222 of the rotor core 22.

  The armature 30 is fixed to the inner peripheral surface of the cylindrical portion 111 of the housing 11 so as to face the outer peripheral surface of the rotor core 22, and the central axis of the armature 30 coincides with the central axis J 1 of the shaft 21. The armature 30 is arranged radially from the inner peripheral surface of the annular portion (so-called core back) of the core 31 made of a magnetic material with the tip toward the central axis J1 and centering on the central axis J1 (that is, the housing 11). A plurality of teeth (see reference numeral 311 in FIG. 2) extending from the inner peripheral surface toward the shaft 21 and the field magnet 230, an insulator 32 covering the plurality of teeth, and a plurality of teeth conducting a conductor from above the insulator 32 in multiple layers The coil 35 provided by winding is provided. The coil 35 is formed by winding a conductive wire on the outer periphery of the teeth and the insulator 32 in the vertical direction (the direction of the central axis J1).

  A bus bar 51 to which a connection for supplying a drive current to the coil 35 of the armature 30 is arranged at the upper end of the armature 30, and the bus bar 51 is also connected to the ECU 71. On the upper surface of the bus bar 51, a circuit board 52 on which Hall elements and the like to be described later are mounted is mounted and attached. The bus bar 51 has a substantially annular shape centered on the central axis J1, and surrounds the outer periphery of the sensor magnet 24 with a gap. The bus bar 51 is not limited to an annular shape as long as it surrounds the outer periphery of the sensor magnet 24, and may be U-shaped or C-shaped.

  In the motor 1, the stator 3 is fixed in the housing 11 with the armature 30, the bus bar 51, the circuit board 52, etc. as main parts, and the bearing mechanism 4 is held inside the bearing holding part 113 of the housing 11. The The bearing mechanism 4 is a pair of bearings 41 and 42 arranged along the central axis J1, and the shaft 21 of the rotor portion 2 is supported by the pair of bearings 41 and 42 in the bearing holding portion 113. Thus, the shaft 21 is supported so as to be rotatable relative to the housing 11 about the central axis J1. Then, a drive current is supplied to the armature 30 via the bus bar 51 to generate a torque centered on the central axis J1 between the field magnet 230 and the armature 30, and the rotor portion 2 rotates. To do.

  On the bus bar 51 side of the circuit board 52, three electronic devices and three hall elements 53 that are sensors for detecting the orientation (that is, the rotational position) of the rotor core 22 are mounted so as to protrude downward. The hall element 53 is held by a sensor holder 54 described later and is disposed on the inner peripheral portion of the bus bar 51. As a result, the Hall element 53 is disposed outside the sensor magnet 24 with respect to the central axis J <b> 1 and faces the sensor magnet 24. The sensor magnet 24 is magnetized in the same manner as the field magnet 230, and the rotational position of the field magnet 230 is indirectly detected by the Hall element 53 detecting the magnetic field from the sensor magnet 24. Detected. Then, the drive current to the armature 30 is controlled based on the detection result.

  FIG. 2 is an exploded perspective view showing main components of the stator unit 3. 2, only the core 31 is shown for the armature 30, but actually, when the bus bar 51 is attached to the upper end of the armature 30, the teeth 311 of the core 31 are covered with the insulator 32, and further the insulator. An armature 30 in which a coil 35 is formed by winding a conductive wire from above 32 is prepared (see FIG. 1).

  The bus bar 51 is an annular resin body 511 formed by resin injection molding, and a plurality (four in this embodiment) arcuately stacked in the resin body 511 at intervals in the direction toward the central axis J1. Wiring board 512 (see FIG. 1) and a plurality of connector pins 513 each of which is a substantially linear metal having rigidity. Each connector pin 513 is J-shaped, and both end portions 513a and 513b are exposed upward from the resin main body 511. The wiring board 512 has a plurality of terminals 5121 for connection with the armature 30 and a flat terminal 5122 for connection with an external current supply unit, and connects between the plurality of terminals 5121 and the flat terminals 5122. The part and a part between both end portions of the connector pin 513 are resin-molded so as to be positioned in the resin main body 511 by insert molding at the time of injection molding.

  On the other hand, one end portion (hereinafter referred to as “substrate-side end portion”) 513a of both end portions of each connector pin 513 connected to the circuit board 52 is formed from the surface of the resin main body 511 facing the circuit board 52. An end portion of the connector pin 513 opposite to the circuit board 52 (hereinafter referred to as “connector side end portion”) 513b that protrudes vertically is detachably connected to an external connector (not shown) that outputs a signal to the ECU 71. Is done.

  In the stator portion 3, the bus bar 51 is electrically connected to the armature 30 by connecting the lead wire from the coil 35 (not shown) to the outer peripheral terminal 5121 by caulking. At this time, the plurality of leg portions 514 provided on the outer periphery of the bus bar 51 abut on the upper surface of the core 31, and the protrusions formed at the tips of the leg portions 514 are engaged with the vertical grooves on the outer peripheral surface of the core 31. By combining, the position of the bus bar 51 with respect to the core 31 is determined.

  On the inner peripheral surface of the bus bar 51, an arc-shaped concave portion 516 for receiving the arc-shaped sensor holder 54 made of resin is formed. When the Hall element 53 is attached to the circuit board 52, the Hall element 53 Are inserted and held in the respective recesses 541 of the sensor holder 54, and the terminals of the Hall element 53 are inserted into holes formed in lands on the circuit board 52, and then the sensor holder 54 is connected to the bus bar 51 side of the circuit board 52. It is fixed to the surface. The sensor holder 54 is fixed to the circuit board 52 by thermal welding in which the protrusions 542 of the sensor holder 54 are inserted into the holes 521 of the circuit board 52 and the protrusions 542 are heated and melted to be crushed. Thereafter, the terminals of the Hall element 53 are joined to the circuit board 52 by soldering.

  The circuit board 52 is fixed to the bus bar 51 after the sensor holder 54 is attached to the circuit board 52. First, the sensor holder 54 is fitted into the recess 516, and two of the two provided on the upper surface of the resin body 511 are provided. The resin protrusions 5111 are inserted into the holes 522 of the circuit board 52, and the board-side end parts 513 a of the plurality of connector pins 513 are inserted into the holes 523 of the circuit board 52. Then, the circuit board 52 is firmly fixed to the bus bar 51 by heat welding that heat-melts and crushes the protrusion 5111, and the board-side end 513a is joined to the circuit board 52 by soldering.

  FIG. 3 is an exploded perspective view showing the rotor core 22 and its peripheral components. As shown in FIG. 3, the field magnet 230 is a set of a plurality of field magnet elements 23 (so-called segment magnets) each extending in the direction of the central axis J1, and the outer peripheral surface of the rotor core 22 along the circumferential direction. Arranged above. As the field magnet element 23, for example, a sintered body containing neodymium is used.

  The rotor core 22 is in contact with the upper end of each field magnet element 23 to contact the first magnet contact portion 223 that determines the position in the central axis J1 direction, the second magnet contact portion 224 that determines the position in the circumferential direction, and Further, a sensor magnet contact portion 225 that contacts the lower surface of the sensor magnet 24 and determines the position of the sensor magnet 24 in the central axis J1 direction is further provided.

  The upper rotor cover 25a and the lower rotor cover 25b are formed of stainless steel in a substantially cylindrical shape, the upper rotor cover 25a has an edge that extends inward at the upper end, and the lower rotor cover 25b extends inward at the lower end. Has an edge. The upper rotor cover 25a is covered from the upper side of the rotor core 22 to which the plurality of field magnets 230 and the sensor magnets 24 are attached, and is fixed with an adhesive, and the lower rotor cover 25b is the lower side of the rotor core 22 And fixed with an adhesive. Accordingly, the upper rotor cover 25a can cover the field magnet 230 and a part of the sensor magnet 24, and the sensor magnet 24 as well as the field magnet element 23 can be covered by the two rotor covers 25a and 25b. It is possible to cover, and it is possible to reliably prevent these magnets from falling off. Further, since the sensor magnet 24 can be covered with the same structure as when only the field magnet element 23 is covered, the number of parts of the rotor portion 2 can be reduced.

  FIG. 4 is an enlarged view showing a part of the rotor unit 2. In FIG. 4, a part is shown in cross section. The first magnet abutting portion 223 is opposed to the upper end surface (hereinafter referred to as “upper end surface”) 231 with respect to the direction of the central axis J1 of the field magnet element 23, and the field from the opposing surface 2231. A protrusion 2232 that protrudes toward the upper end surface 231 of the magnet element 23 is provided. The protrusion 2232 protrudes from the opposing surface 2231 while being separated from the surface 226 on the rotor core 22 that contacts the surface on the central axis J1 side of the field magnet element 23 (that is, the back surface of the field magnet element 23). It abuts on the upper end surface 231 of the magnet element 23 for use.

  When the field magnet element 23 is fixed to the rotor core 22, as shown in FIG. 4, the upper end surface 231 of the field magnet element 23 comes into contact with the protrusion 2232 of the first magnet contact part 223, As a result, the field magnet element 23 is accurately positioned in the direction of the central axis J1. Furthermore, the protrusion 2232 reduces the contact area of the upper end surface 231 of the field magnet element 23, between the upper end surface 231 and the opposing surface 2231, and the lower end surface of the field magnet element 23 and the rotor core 22. By providing a gap therebetween, leakage of magnetic flux from the upper and lower end surfaces of the field magnet element 23 to the rotor core 22 can be suppressed and drive efficiency can be increased.

  In the rotor portion 2, as shown in FIGS. 3 and 4, one side surface of the field magnet element 23 abuts on the second magnet abutment portion 224, thereby positioning the field magnet element 23 in the circumferential direction. Is done accurately. The width of the recess into which the field magnet element 23 is fitted may be a width into which the field magnet element 23 is fitted with a clearance fit. In this case, both sides of the recess and the field magnet element Therefore, the surfaces on both sides of the recess serve as the second magnet contact portion 224 for positioning the field magnet element 23 in the circumferential direction. The field magnet element 23 is fixed to the rotor core 22 by bonding the back surface to the surface 226.

  As described above, in the motor 1, the bearing mechanism 4 is held in the bearing holding portion 113 of the housing 11 formed as one member, and the rotor core 22 is a so-called cantilever in which the bearing mechanism 4 is disposed. Supported by structure. Therefore, although the cross-sectional shape of the rotor core 22 perpendicular to the central axis in the central axis direction changes in a complicated manner, the rotor core 22 is formed through processes such as pressure molding and sintering of a metal powder material. Even the rotor core 22 having a complicated shape can be easily formed, and the manufacturing cost of the motor can be reduced. Moreover, the shape of the rotor core 22 can also be designed freely.

  The shape of the rotor core 22 is not limited to that shown in FIG. 1, but when the rotor core 22 is connected to the shaft 21 and has at least a cylindrical portion, the cross-sectional shape perpendicular to the central axis changes in a complex manner with respect to the central axis direction. Thus, such a rotor core 22 is difficult to produce by laminating electromagnetic steel sheets or cutting metal, but by manufacturing the rotor core 22 from a powder material, such a problem can be solved.

  Furthermore, by manufacturing the rotor core 22 from a powder material, a first magnet contact portion 223, a second magnet contact portion 224, which determine the mounting position of the field magnet element 23 with respect to the central axis direction and the circumferential direction, And the sensor magnet contact part 225 which determines the attachment position of the sensor magnet 24 can be provided easily. Thus, the sensor magnet 24 can be magnetized in a state where the field magnet element 23 and the sensor magnet 24 are integrally attached to the rotor core 22, and the field magnet 230 and the sensor magnet 24 can be magnetized. The magnetic position can be adjusted with high accuracy.

  Further, the motor 1 does not require special members or jigs for positioning the field magnet element 23 and the sensor magnet 24, and the upper rotor cover 25a and the lower rotor cover 25b are used for the field. Since the magnet element 23 for magnets and the magnet 24 for sensors can be covered, the number of parts of the rotor part 2 can be reduced, and the manufacturing cost and man-hour of the motor 1 can be reduced.

  Furthermore, the sensor magnet 24 is provided on the outer peripheral surface of the upper end of the rotor core 22, and the bus bar 51 is opposite to the armature 30 by arranging the sensor magnet 24 and the hall element 53 so as to face each other in the radial direction. The amount of protrusion from the rotor core 22 to the side can be reduced, and the axial length of the motor 1 can be shortened.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the said embodiment, A various change is possible.

  The shapes of the first magnet contact portion 223, the second magnet contact portion 224, and the sensor magnet contact portion 225 may be variously modified. For example, a convex portion is provided at the upper end of the field magnet element 23. The projecting portion 2232 is omitted from the opposing surface 2231 of the concave portion of the rotor core 22, and the magnetic convex portion of the magnet contacts the opposing surface 2231 (in this case, the first magnet contact portion 223), whereby the field magnet element 23. The mounting position may be determined. The concave portion into which the field magnet element 23 is fitted may be omitted, and the protrusion provided on the outer surface of the rotor core 22 may serve as the first magnet contact portion 223 or the second magnet contact portion 224. For example, a protrusion 2232 that protrudes outward from the outer surface of the rotor core 22 and protrudes further downward and contacts the upper end surface 231 of the field magnet element 23 or a protrusion 2232 that protrudes obliquely downward from the outer surface of the rotor core 22. May be provided. In addition, the sensor magnet 24 may be magnetized before being attached, and in this case, a D-cut for positioning in the circumferential direction can be easily formed in the rotor core 22. As another example, the sensor magnet 24 may be formed by injection molding, and the sensor magnet 24 may be positioned by a protrusion generated in the gate portion and a recess formed in the rotor core 22.

  In the motor 1, the upper rotor cover 25a and the lower rotor cover 25b are made of stainless steel in a substantially cylindrical shape, but are made of a non-magnetic material other than stainless steel (for example, resin). May be.

  The bearing mechanism 4 may have a bearing other than the pair of bearings 41 and 42, for example, the shaft 21 may be supported by an oil-impregnated sleeve. Moreover, the shaft 21 does not need to be supported by a cantilever structure, and may be supported by a both-end support structure. That is, the bearing mechanism that rotatably supports the shaft 21 with respect to the housing 11 may be separated from the rotor core 22 in the vertical direction. The upper rotor cover 25a and the lower rotor cover 25b may be provided integrally, and the entire field magnet 230 and sensor magnet 24 may be covered by one rotor cover.

  The motor 1 may be used for an electric brake system, an electromagnetic suspension, and a transmission system in addition to the electric power steering of an automobile, and may be used for various systems in which a motor having a rotor core having a complicated shape is used.

1 is a longitudinal sectional view of an electric motor according to an embodiment of the present invention. It is a perspective view which decomposes | disassembles and shows the main components of a stator part. It is a perspective view which decomposes | disassembles and shows the rotor core and its surrounding component. It is a figure which expands and shows a part of rotor part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 4 Bearing mechanism 11 Housing 21 Shaft 22 Rotor core 23 Magnet element for field 24 Sensor magnet 25a Upper rotor cover 30 Armature 51 Bus bar 53 Hall element 111 Cylindrical part 221 Lid part 222 Cylindrical part 223 1st magnet contact part 224 Second magnet contact portion 225 Sensor magnet contact portion 226 Surface 230 Field magnet 231 Upper end surface 2232 Projection portion J1 Central axis

Claims (7)

An electric motor,
A shaft,
A magnetic body formed by a process including pressure molding and sintering of a powder material, a rotor core having a cylindrical portion whose central axis coincides with the central axis of the shaft and attached to the shaft;
A field magnet mounted on the outer peripheral surface of the rotor core;
A housing having a cylindrical portion surrounding the central axis;
An armature that is fixed to the inner surface of the cylindrical portion, and that faces the outer peripheral surface of the rotor core and generates torque about the central axis with the field magnet;
A bearing mechanism that rotatably supports the shaft about the central axis with respect to the housing;
A motor comprising: The motor according to claim 1,
The rotor core includes a lid portion that closes one end portion of the cylindrical portion, the lid portion is attached to the shaft, the other end portion of the cylindrical portion is a free end, and at least one of the bearing mechanisms. The motor is characterized in that the part is located in the cylindrical part. The motor according to claim 1 or 2,
The field magnet is a set of a plurality of field magnet elements;
The rotor core includes a first magnet contact portion that determines a position in the central axis direction by contacting each of the field magnet elements and a second magnet contact portion that determines a position in the circumferential direction. A motor characterized by that. The motor according to claim 3,
The first magnet contact portion protrudes toward the one end surface of the field magnet element while being separated from a surface on the rotor core that is in contact with the surface on the central axis side of the field magnet element. A motor comprising a projecting portion that comes into contact with one end face. The motor according to any one of claims 1 to 4,
A sensor magnet mounted on the outer peripheral surface of the rotor core, the ring being centered on the central axis;
A sensor that is disposed outside the sensor magnet with respect to the central axis, detects a magnetic field from the sensor magnet, and detects the orientation of the rotor core;
Further comprising
The motor according to claim 1, wherein the rotor core includes a sensor magnet contact portion that contacts the sensor magnet and determines a position of the sensor magnet in the central axis direction. The motor according to claim 5,
The sensor magnet is provided on an outer peripheral surface of one end of the rotor core;
A bus bar attached to one end of the armature and surrounding an outer periphery of the sensor magnet;
The motor according to claim 1, wherein the sensor is disposed on an inner peripheral portion of the bus bar. The motor according to claim 5 or 6,
The motor according to claim 1, wherein the rotor core further includes a rotor cover that covers the sensor magnet and at least a part of the field magnet.

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