Motor

Abstract

To provide a motor capable of achieving improved holding torque.SOLUTION: A motor 1 includes a shaft 2, a rotor 3 fixed to the shaft 2, a first magnetic body 3 fixed to the shaft 2, and a stationary portion having a second magnetic body 4. One of the first magnetic body 3 and the second magnetic body 4 has a magnet. The first magnetic body 3 opposes the second magnetic body 4 over the entire circumference.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a motor. [Background technology]

[0002] Conventionally, motors have been used as drive sources for various devices. There are various types of motors, and the motor to be used is selected depending on the purpose and situation. In motors used in information devices, automotive applications, etc., for example, motors used in electric vehicle doors and electric hatch gates, there is a demand to hold the rotating body in a fixed position, such as by suppressing rotation of the motor shaft when the motor is stopped.

[0003] Patent Document 1 describes a technique for increasing holding torque, which is the torque required to hold a rotating body in a fixed position. Patent Document 1 describes a DC motor that includes four field poles and an armature core with five teeth that extend radially from a shaft and face the field poles, with a groove at the center of the angular spacing on the outer circumferential surface of each tooth at the tip of the armature core that increases the air gap between the field poles and the armature core. The presence of this air gap stabilizes the opposing positional relationship between the field poles and the armature core when no drive voltage is applied, increasing the holding torque. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 1-91640 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the technology described in Patent Document 1, if the field poles and teeth move out of their stable positions, for example, when the motor shaft rotates due to an external force, the rotor may continue to rotate, making it impossible to maintain the position of the rotor. Therefore, an object of the present invention is to provide a motor that can achieve an improvement in holding torque. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention employs the following means. That is, a motor according to one aspect of the present invention includes a shaft; a rotating body fixed to the shaft; a first magnetic body fixed to the shaft; a stationary portion having a second magnetic body, one of the first magnetic body and the second magnetic body has a magnet; The first magnetic body faces the second magnetic body over the entire periphery.

[0007] In the present invention, the first magnetic body and the second magnetic body face each other in the radial direction, The distance between the opposing surfaces of the first magnetic body and the second magnetic body may be constant over the entire circumference. In the present invention, the first magnetic body and the second magnetic body face each other in the axial direction, The opposing surfaces of the first magnetic body and the second magnetic body may be flat surfaces. In either case, the opposing surfaces of the first magnetic body and the second magnetic body may have magnetic pole portions.

[0008] In the present invention, the opposing surfaces of the first magnetic body and the second magnetic body have magnetic pole portions, The first magnetic body may be configured to bias the shaft in the axial direction by a magnetic force between the first magnetic body and the second magnetic body. At this time, the first magnetic body has a plane perpendicular to the axial direction, a sliding member having a sliding surface that contacts the flat surface of the first magnetic body; The second magnetic body may be biased toward the sliding member by a magnetic force between the first magnetic body and the second magnetic body.

[0009] On the other hand, in the present invention, a frame is provided, the opposing surfaces of the first magnetic body and the second magnetic body each have a magnetic pole portion; The first magnetic body may be a second magnet fixed to the inner circumferential surface of the frame, and in this case, the second magnet may face the rotor as a member of a stator.

[0010] The first magnetic body may be a first magnet and may contain aluminum, nickel, and cobalt, and the second magnetic body may be a second magnet and may contain iron. The first magnetic body is disposed on one end side of the shaft, A biasing member for biasing the shaft in the axial direction may be provided and disposed on the other end side of the shaft.

[0011] In the present invention, a fixed member fixed to the shaft and having a plane perpendicular to the axial direction; a sliding member having a sliding surface that comes into axial contact with the flat surface of the fixed member, The biasing member may bias the sliding member toward the fixed member, thereby biasing the shaft in the axial direction.

[0012] In the present invention, the first magnetic body is disposed on one end side of the shaft, a third magnetic body fixed to the other end of the shaft; a fourth magnetic body facing the three magnetic bodies; It may have a configuration having the above. In this case, the third magnetic body may be configured to bias the shaft in the axial direction by a magnetic force between the third magnetic body and the fourth magnetic body.

[0013] In the present invention, the strength of the magnetic field that one of the first magnetic body and the second magnetic body applies to the other magnetic body may be greater than the coercive force of the other magnetic body. [Brief explanation of the drawings]

[0014] [Figure 1] 3 is a cross-sectional view of the motor according to the first embodiment of the present invention, taken along the line CC in FIG. 2, and including the axis of the shaft. FIG. [Figure 2] 2 is a cross-sectional view of a motor according to a first embodiment of the present invention, taken along a line perpendicular to the axis of a shaft, and taken along the line AA in FIG. 1. FIG. [Figure 3] 1 is an enlarged cross-sectional view of a first magnet and its vicinity in a motor according to a first embodiment of the present invention, taken along a cross section including the axis of a shaft. [Figure 4] 6 is a cross-sectional view of a motor according to a second embodiment of the present invention, taken along the line DD in FIG. 5, the cross-section including the axis of the shaft. FIG. [Figure 5] 5 is a cross-sectional view of a motor according to a second embodiment of the present invention, taken along a line perpendicular to the axis of the shaft, and taken along the line BB in FIG. 4. FIG. [Figure 6] FIG. 10 is an enlarged cross-sectional view of a section including the axis of the shaft, showing a first magnet and its vicinity in a motor according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view of a motor according to a third embodiment of the present invention, taken along a line including the axis of the shaft. [Figure 8] FIG. 10 is a cross-sectional view of a motor according to a fourth embodiment of the present invention, taken along a line including the axis of the shaft. [Figure 9] FIG. 10 is a cross-sectional view of a motor according to a fifth embodiment of the present invention, taken along a line including the axis of the shaft. [Figure 10] FIG. 10 is a cross-sectional view of a motor according to a sixth embodiment of the present invention, taken along a line including the axis of the shaft. [Figure 11] FIG. 11 is a cross-sectional view of a motor according to a seventh embodiment of the present invention, taken along a line including the axis of the shaft. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, motors according to embodiments that are exemplary aspects of the present invention will be described with reference to the drawings. [First embodiment] Fig. 1 is a cross-sectional view of a motor 1 according to a first embodiment, taken along a line including the axis x of the shaft 2. Fig. 2 is a cross-sectional view of a motor 1 according to this embodiment, taken along a line perpendicular to the axis x of the shaft 2. Fig. 1 corresponds to the CC cross-sectional view in Fig. 2, and Fig. 2 corresponds to the AA cross-sectional view in Fig. 1. Note that in the direction of the axis x (hereinafter also referred to as the "axial direction"), the direction of the arrow a on the left side is defined as one side a, and the direction of the arrow b on the right side is defined as the other side b (this also applies to all subsequent embodiments).

[0016] 1, the motor 1 according to this embodiment has a housing 1a as a stationary part and an armature 1b as a rotating body rotatably supported relative to the housing 1a. The motor 1 is a so-called inner rotor type brushed DC motor.

[0017] Here, the "stationary portion" refers to a portion that is stationary relative to the rotating body, and does not have to be completely stationary. In this embodiment, the stationary portion includes the frame 10 and end plates 13 that constitute the housing 1a, as well as the second magnet 4, first bearing 21, second bearing 22, circuit board 14, bracket 15, etc., which will be described later.

[0018] The motor 1 includes a shaft (rotating shaft) 2 that supports an armature 1b rotatably relative to a housing 1a. The armature 1b includes a rotor (rotating body) 6, a commutator 5, and the like. The rotor 6 is fixed to the shaft 2. The rotor 6 includes a rotor core 61 having a plurality of salient poles (magnetic pole portions) protruding in the radial direction, and windings (not shown) wound around each salient pole.

[0019] The housing 1a is formed by a frame 10 and an end plate 13. A drive magnet (hereinafter referred to as a "second magnet" or "frame magnet") 4 that faces the outer peripheral surface of the rotor 6 in the radial direction, a substrate (circuit board) 14, a bracket 15 that supports the brushes 12, etc. are attached to the frame 10. The frame magnet 4 is attached to the inner peripheral surface of the frame 10. The salient poles of the rotor core 61 of the rotor 6 face the frame magnet 4.

[0020] The frame 10 has a cylindrical shape with one end 10x (near the end on one side a in FIG. 1) closed when the shaft 2 protrudes. The opening of the other end 10y (near the end on the other side b in FIG. 1) of the frame 10 is closed by an end plate 13.

[0021] An armature 1b is housed inside the frame 10, and the other end 10y of the frame 10 is closed by an end plate 13, thereby forming a housing 1a that houses the rotor 6. An end 10b (hereinafter sometimes referred to as the "bottom") on one end 10x side of the frame 10 has a portion (hereinafter referred to as the "protruding portion") 10a that protrudes toward the end of one end side a of the shaft 2 (toward the one side a), and a first bearing 21, which will be described later, is fixed inside this protruding portion 10a. The power of the motor 2 can be extracted to the outside from the protruding portion of the shaft 2.

[0022] The first bearing portion 21 is held in the center of one end portion 10x of the frame 10 as viewed from the direction of the axis x. Furthermore, the second bearing portion 22 is held in the center of the end plate 13 as viewed from the direction of the axis x. That is, the first bearing portion 21 is located on one side of the rotor 6 in the axial direction, and the second bearing portion 22 is located on the other side of the rotor 6 in the axial direction. The shaft 2 is journaled at two locations by the first bearing portion 21 and the second bearing portion 22 (sometimes collectively referred to as "bearings 21, 22"). The armature 1b is held rotatably relative to the frame 10 by the bearings 21, 22.

[0023] A commutator 5 is provided on a part of the shaft 2 on the end plate 13 side of the rotor 6 (a part of the other side b of the shaft 2). The commutator 5 has commutator segments 52 on the outer peripheral surface of a support portion 51 that supports the commutator, and the commutator segments 52 are connected to windings wound around a rotor core 61.

[0024] The power supply unit 20 is made up of the end plate 13, the circuit board 14, the bracket 15, the second bearing 22, the power supply connection part 11, the brush 12, etc. The circuit board 14 is attached to the outside of the end plate 13 via the bracket 15. The power supply connection part 11 includes a power supply terminal 16, and an electric current is supplied from the outside by a power supply line connected to the power supply terminal 16.

[0025] Brushes 12 are electrically connected to the power supply connection portion 11, and are arranged so that the tips of the brushes 12 contact the outer circumferential surface of the commutator 5. Electric power is supplied to the commutator segments 52 of the commutator 5 via the brushes 12, thereby driving the motor 1.

[0026] An encoder including a disk 23 formed of, for example, a magnet, and a sensor 17 such as a Hall sensor is fixed to the end of the other side b of the shaft 2. The sensor 17 is also mounted on the circuit board 14 at a position facing the disk 23. For example, the magnetic information of the disk 23 can be detected by the sensor 17, and the rotational state of the shaft 2 (number of rotations, rotation angle, etc.) can be read.

[0027] In this embodiment, a first magnetic body 3 is attached to one side a of the shaft 2, and a holding torque is generated between the first magnetic body 3 and a frame magnet (second magnetic body, second magnet) 4. The first magnetic body 3 faces the frame magnet 4, which serves as the second magnetic body, over the entire circumference. Specifically, as shown in FIG. 2, the outer peripheral surface of the first magnetic body 3 is a curved surface with a constant outer diameter over the entire circumference. The first magnetic body 3 is, for example, a disk-shaped magnet.

[0028] The frame magnet 4 and the first magnetic body 3 face each other in the radial direction. The facing surfaces of the frame magnet 4 and the first magnetic body 3 facing each other have a constant diameter over the entire circumference. In particular, the facing surface of the first magnetic body 3 is the outer peripheral surface, and the facing surface of the frame magnet 4 is the inner peripheral surface. The first magnetic body 3 rotates together with the shaft 2 around the axis x, which is the axis of the shaft 2, as the central axis.

[0029] FIG. 3 is an enlarged cross-sectional view of the first magnetic body 3 and its vicinity in the motor 1 according to this embodiment, taken along a plane including the axis of the shaft 2. As shown in FIG. As shown in FIGS. 1 to 3, the outer peripheral surface of the first magnetic body 3 faces the inner peripheral surface of the frame magnet 4 in the radial direction with a predetermined gap (magnetic gap) therebetween.

[0030] The inner peripheral surface of a portion of the frame magnet 4 in many regions in the direction of the axis x (region E in FIG. 1) faces radially the outer peripheral surface of the rotor core 61. Moreover, the inner peripheral surface of the other portion of the frame magnet 4 in a region extending to one side a in the direction of the axis x (region F in FIG. 1) faces radially the outer peripheral surface of the first magnetic body 3.

[0031] That is, the frame magnet 4 is a component that constitutes the stator, and generates a driving force for the motor 1 by opposing the rotor 6 and acting magnetically. The frame magnet 4 also opposes the first magnetic body 3 and acts magnetically to generate a holding torque. The frame magnet 4 corresponds to the "second magnetic body" in this invention.

[0032] The frame magnet 4 is, for example, a ferrite magnet or a ferromagnetic rare earth magnet, and is a permanent magnet with a predetermined magnetic flux density. On the other hand, the first magnet 3 is, for example, formed of a non-oriented steel plate. The frame magnet 4, which serves as a second magnet that generates the driving force of the motor 1, exerts a magnetic field on the first magnetic body 3, and the coercive force of the first magnetic body 3 is smaller than the strength of the magnetic field.

[0033] As shown in FIG. 2, the inner peripheral surface of the frame magnet 4 is magnetized at equal intervals of 90° central angle so that two different magnetic poles (N and S poles) alternate in the circumferential direction. Furthermore, the magnetic poles of the frame magnet 4 generate two different magnetic poles in the circumferential direction on the outer peripheral surface of the first magnetic body 3, and the magnetic poles of the first magnetic body 3 and the frame magnet 4 facing each other are opposite. Meanwhile, the outer peripheral portion of the first magnetic body 3, which has a small coercive force, is affected by the magnetic force generated by the frame magnet 4, and each portion facing the frame magnet 4 exhibits a magnetic pole (e.g., S pole at position d) opposite to the magnetic pole of the frame magnet 4 (e.g., N pole at position c). In other words, the facing surfaces of the first magnetic body 4 and the second magnetic body facing each other in the radial direction have multiple magnetic pole portions. Therefore, an attractive force (both arrows G in FIG. 3) is generated between the frame magnet 4 and the first magnetic body 3, suppressing the first magnetic body 3 from rotating with the shaft 2.

[0034] Increasing the holding torque of a motor generally involves increasing the cogging. Increasing the cogging causes pulsation in the rotation of the motor shaft. The presence of peaks in the torque (holding torque) in this pulsation suppresses and holds the rotation of the motor shaft. However, if the pulsation is large, once a force that exceeds the torque peak is applied to the shaft by some external force, the torque peak may be gradually overcome due to inertia, causing the shaft to rotate.

[0035] In this embodiment, holding torque is generated by the magnetic force (attractive force) generated between the first magnetic body 3, which does not contribute to the driving force of the motor 1, and the frame magnet 4, which corresponds to the second magnet. By providing the motor 1 with the first magnetic body 3 that generates holding torque, the peak of the holding torque can be increased. If the coercive force of the first magnetic body 3 is relatively large, the rotation of the second magnet 4 together with the shaft 2 may result in increased torque pulsation (cogging).

[0036] In this embodiment, a magnet with small coercive force is used for the first magnetic body 3. Therefore, even if the shaft 2 is rotated by an external force or the like, the first magnetic body 3 is affected by the magnetic force generated by the frame magnet 4 at the rotation position, and each portion of the first magnetic body 3 facing the frame magnet 4 exhibits a magnetic pole opposite to that of the frame magnet 4. In other words, the relative positional relationship between the magnetic pole of the frame magnet 4 and the magnetic pole of the first magnetic body 3 does not change, and an attractive force due to the magnetic force is generated between the frame magnet 4 and the first magnetic body 3.

[0037] By using the first magnetic body 3 with a small coercive force, it is possible to increase the holding torque while avoiding large pulsations (cogging), thereby suppressing the generation of relatively large noise and vibrations when driving the motor 1. Furthermore, even when an external force is applied, it is possible to prevent the rotor (rotating body) 6 from rotating due to inertia.

[0038] Examples of magnetic materials with low coercive force suitable for the first magnetic body 3 include so-called electromagnetic steel sheets such as silicon steel sheets and non-oriented steel sheets, and so-called alnico magnets, which are magnets containing aluminum, nickel, and cobalt. On the other hand, examples of magnets with high coercive force suitable for the second magnet (second magnetic body) include various permanent magnets containing iron.

[0039] In the configuration of this embodiment, the magnitude of the holding torque can be adjusted not only by adjusting the strength of the magnetic force of the frame magnet 4, which corresponds to the second magnet, but also by adjusting the thickness of the first magnetic body 3 (i.e., the area of ​​the outer circumferential surface of the first magnetic body 3 facing the second magnet), as indicated by the double-headed arrow H in FIG. 3 . That is, to further improve the holding torque, the thickness of the first magnetic body 3 can be increased. For example, in the direction of the axis x of the motor 1, the thickness of the first magnetic body 3 may be greater than the thickness of each of the steel plates forming the rotor 6, greater than the length from the inner surface (bottom surface) of the bottom portion 10b of the frame 10 facing the first magnetic body 3 to the end of the second magnet 4 on the arrow a side, or less than the thickness of the commutator 5.

[0040] [Second embodiment] Next, a motor according to a second embodiment, which is another example of the present invention, will be described with reference to the drawings. Fig. 4 is a cross-sectional view of a motor 201 according to a second embodiment, taken along a line including the axis x of the shaft 2. Fig. 5 is a cross-sectional view of a motor 201 according to this embodiment, taken along a line perpendicular to the axis x of the shaft 2. Fig. 4 corresponds to the cross-sectional view taken along line DD in Fig. 5, and Fig. 5 corresponds to the cross-sectional view taken along line BB in Fig. 4. Furthermore, FIG. 6 is an enlarged cross-sectional view of the first magnetic body 203 and its vicinity in the motor 201 according to this embodiment, taken along a line including the axis of the shaft 2. As shown in FIG.

[0041] The motor 201 according to the second embodiment has the same configuration as the motor 1 according to the first embodiment, except that the first magnetic body 203 arranged on one side a of the shaft 2 and the structure in the vicinity thereof are different. Therefore, in this embodiment, the same reference numerals are used to designate members having the same configuration as those in the first embodiment, and detailed descriptions thereof will be omitted.

[0042] In this embodiment, the motor 201 has a first magnetic body 203 for generating holding torque attached to one side a of the shaft 2. The outer peripheral surface of the first magnetic body 203 is a disk-shaped magnet having a constant outer diameter and curved all around, as shown in Fig. 5. The first magnetic body 203 rotates together with the shaft 2 around an axis line x, which is the axis of the shaft 2, as its central axis.

[0043] The first magnetic body 203 is disposed at a position closer to the one side a than the first magnetic body 3 in the first embodiment, more specifically, at a position closer to the inner surface of the bottom portion 10b of the frame 10. That is, the first magnetic body 203 and the inner surface of the bottom portion 10b face each other in the axial direction. The first magnetic body 203 and the bottom 10b of the frame 10 face each other in the axial direction over the entire circumference of the end face on one side a of the first magnetic body. The opposing surfaces of the first magnetic body 203 and the bottom 10b of the frame 10 are flat surfaces.

[0044] The frame 10 is formed of a steel plate, which is a magnetic body, and a magnetic force acts between the first magnetic body 203 and the bottom part 10b of the frame 10, generating a holding torque. Therefore, in this embodiment, the bottom part 10b of the frame 10 corresponds to the "second magnetic body" in the present invention.

[0045] The first magnetic body 203 is a permanent magnet with a relatively high magnetic flux density, such as a ferrite magnet or a rare earth magnet. On the other hand, the frame 10 made of a steel plate has a coercive force that is smaller than the strength of the magnetic field that the first magnetic body 203 applies to the bottom part 10b of the frame 10.

[0046] 6, the first magnetic body 203 is magnetized to have two different magnetic poles (S pole and N pole) in the thickness direction (the same as the axis x direction.) Therefore, the opposing surfaces of the first magnetic body 203 and the second magnetic body (bottom 10b of frame 10) have multiple magnetic pole portions in the axial direction.

[0047] As shown in Fig. 5, the surface of the first magnetic body 203 facing the inner surface of the bottom portion 10b of the frame 10 is magnetized at equal intervals of 90° central angle so that two different magnetic poles (N pole and S pole) alternate in the circumferential direction. On the other hand, the inner surface of the bottom portion 10b of the frame 10 facing the first magnetic body 203 has a magnetic pole opposite to that of the first magnetic body 203. In other words, the inner surfaces of the first magnetic body 203 and the bottom portion 10b of the frame 10, which face each other in the axial direction, have multiple magnetic pole portions. Therefore, an attractive force (indicated by a double-headed arrow P in Fig. 6) due to a magnetic force is generated between the first magnetic body 203 and the inner surface of the bottom portion 10a of the frame 10, suppressing the movement of the first magnetic body 203 in the rotational direction.

[0048] In this embodiment, the holding torque is generated by a magnetic force (attractive force) generated between the first magnetic body 203, which does not contribute to the driving force of the motor 201, and the inner surface of the bottom 10b of the frame 10. By providing the motor 201 with the first magnetic body 203 that generates the holding torque, the peak of the holding torque can be increased.

[0049] In this embodiment, the strength of the magnetic field of the first magnetic body 203 is greater than the coercive force of the bottom portion 10b of the frame 10 formed from a steel plate. Therefore, the inner surface of the bottom 10b of the frame 10 facing the first magnetic body 203 has a magnetic pole of opposite polarity to that of the first magnetic body 203, and a magnetic force (attractive force) is generated between the first magnetic body 203 and the inner surface of the bottom 10b of the frame 10. This suppresses the rotation of the first magnetic body 203 together with the shaft 2. This suppresses the generation of relatively large pulsation (cogging), suppresses the generation of noise and vibration when the motor 201 is driven, and prevents the rotor (rotating body) 6 from rotating due to inertia even when an external force is applied.

[0050] [Third embodiment] Next, a motor according to a third embodiment, which is another example of the present invention, will be described with reference to the drawings. 7 is a cross-sectional view of a motor 301 according to the third embodiment, taken along a plane including the axis x of the shaft 2 (similar to the first embodiment, this is a sectorial cut-out cross-section, corresponding to the CC cross-section shown in FIG. 2). Note that in this embodiment, a cross-sectional view of a cross-section perpendicular to the axis x of the shaft 2 is omitted, but since it is actually similar to FIG. 5 in the second embodiment, please refer to that figure.

[0051] The motor 301 according to the third embodiment has the same configuration as the motor 1 according to the first embodiment, except for the difference in the structure near the first magnetic body 203 arranged on one side a of the shaft 2. Therefore, in this embodiment, members having the same configuration as those in the first embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted. Furthermore, since the first magnetic body 203 also has the same configuration as that in the second embodiment, it is given the same reference numeral 203 as that in the second embodiment, and detailed descriptions thereof will be omitted.

[0052] In this embodiment, the motor 301 has a ring-shaped magnetic member 304 attached to the inner surface of the bottom 10b of the frame 10. The magnetic member 304 is disposed opposite the first magnetic body 203 and acts magnetically on the first magnetic body 203 to generate a holding torque. Therefore, in this embodiment, the magnetic member 304 corresponds to the "second magnetic body" of the present invention.

[0053] The first magnetic body 203 and the magnetic member 304 face each other in the axial direction. The first magnetic body 203 and the magnetic member 304 face each other over the entire circumference in the axial direction. The facing surfaces of the first magnetic body 203 and the magnetic member 304 facing each other are flat surfaces. The first magnetic body 203 is a permanent magnet with a relatively high magnetic flux density, such as a ferrite magnet, a rare earth magnet, etc. The coercive force of the magnetic member 304 is smaller than the strength of the magnetic field that the first magnetic body 203 applies to the magnetic member 304.

[0054] As in the second embodiment, as shown in Fig. 5, the surface of the first magnetic body 203 facing the magnetic member 304 is magnetized at equal intervals of 90° central angle so that two different magnetic poles (north and south poles) alternate in the circumferential direction. On the other hand, the magnetic member 304 has a magnetic pole opposite to that of the first magnetic body 203. In other words, the opposing surfaces of the first magnetic body 203 and the magnetic member 304 facing each other in the axial direction have a plurality of magnetic pole portions. Therefore, an attractive force (indicated by a double-headed arrow L in Fig. 7) due to a magnetic force is generated between the first magnetic body 203 and the magnetic member 304, suppressing the movement of the first magnetic body 203 in the rotational direction.

[0055] In this embodiment, a holding torque is generated by a magnetic force (attractive force) generated between the first magnetic body 203, which does not contribute to the driving force of the motor 301, and the magnetic member 304. By including the first magnetic body 203 and the magnetic member 304, which generate a holding torque, in the motor 301, the peak of the holding torque can be increased.

[0056] In this embodiment, the strength of the magnetic field of the first magnetic body 203 is greater than the coercive force of the magnetic member 304 . Therefore, the magnetic member 304 facing the first magnetic body 203 has a magnetic pole of opposite polarity to that of the first magnetic body 203, and a magnetic force (attractive force) is generated between the first magnetic body 203 and the magnetic member 304. This suppresses the rotation of the first magnetic body 203 together with the shaft 2. This suppresses the occurrence of pulsation (cogging), suppresses the occurrence of noise and vibration when the motor 301 is driven, and prevents the rotor (rotating body) 6 from rotating due to inertia even when an external force is applied.

[0057] The magnetic field strength of the magnetic member 304 may be greater than the coercive force of the first magnetic body 203. In this case, one surface of the magnetic member 304 facing the inner surface of the bottom 10b of the frame 10 and the other surface of the magnetic member 304 facing the first magnetic body 203 (the surface on one side a and the surface on the other side b) are magnetized with two mutually different magnetic poles (N pole and S pole). In this case, the magnetic member 304 becomes a permanent magnet with a large coercive force, such as a ferrite magnet or a rare earth magnet, and the coercive force of the first magnetic member 203 is smaller than the strength of the magnetic field that the magnetic member 304 applies to the first magnetic member 203.

[0058] [Fourth embodiment] Next, a motor according to a fourth embodiment, which is another example of the present invention, will be described with reference to the drawings. FIG. 8 is a cross-sectional view of a motor 401 according to the fourth embodiment, taken along a plane including the axis x of the shaft 2 (similar to the first embodiment, this is a sectorially cut-out cross-section, equivalent to the CC cross-section shown in FIG. 2).

[0059] The motor 401 according to the fourth embodiment has the same configuration as the motor 1 according to the first embodiment, except that the first magnetic body 403 arranged on one side a of the shaft 2 and the structure in the vicinity thereof are different. Therefore, in this embodiment, the same reference numerals are used to designate members having the same configuration as those in the first embodiment, and detailed descriptions thereof will be omitted.

[0060] In this embodiment, a motor 401 has a first magnetic body 403 for generating holding torque attached to one side a of a shaft 2. The first magnetic body 403 is a disk-shaped magnet having an outer diameter smaller than that of the first magnetic body 203 in the second embodiment, and rotates together with the shaft 2 around an axis x that is the axis of the shaft 2 as its central axis.

[0061] The first magnetic body 403 is disposed in a position close to the inner surface of the bottom portion 10b of the frame 10, similar to the first magnetic body 203 in the second embodiment. However, in this embodiment, the outer diameter of the first magnetic body 403 is small, and the first magnetic body 403 faces the first bearing portion 21 supported by the protrusion portion 10a of the frame 10. The first bearing portion 21 is formed of a sintered material containing iron as a magnetic material. The first magnetic body 403 and the first bearing portion 21 interact magnetically to generate a holding torque. Therefore, in this embodiment, the first bearing portion 21 corresponds to the "second magnetic body" in the present invention.

[0062] The first magnetic body 403 and the first bearing portion 21 face each other in the axial direction. The first magnetic body 403 and the first bearing portion 21 face each other over the entire circumference in the axial direction. The facing surfaces of the first magnetic body 403 and the first bearing portion 21 that face each other are flat surfaces. The first magnetic body 403 is a permanent magnet with a relatively high magnetic flux density, such as a ferrite magnet, a rare earth magnet, etc. The first bearing portion 21 has a small coercive force relative to the strength of the magnetic field applied by the first magnetic body 403.

[0063] The first magnetic body 403 is magnetized with two different magnetic poles (S pole and N pole) in the thickness direction (the same as the axis x direction) similarly to the first magnetic body 203 in the second embodiment. Furthermore, the first magnetic body 403 has a different outer diameter from the first magnetic body 203 in the second embodiment.

[0064] The surface of the other side b of the first bearing unit 21 facing the first magnetic body 403 (hereinafter referred to as the "facing surface") has a magnetic polarity opposite to that of the first magnetic body 403. The facing surfaces of the first magnetic body 403 and the first bearing unit 21, which face each other in the axial direction, have a plurality of magnetic pole portions. Therefore, an attractive force (indicated by a double-headed arrow J in FIG. 8) is generated by a magnetic force between the facing surfaces of the first magnetic body 403 and the first bearing unit 21, suppressing movement of the first magnetic body 403 in the rotational direction.

[0065] In this embodiment, the holding torque is generated by the magnetic force (attractive force) generated between the first bearing 21 and the first magnetic body 403, which does not contribute to driving the motor 401. By including the first magnetic body 403 that generates the holding torque, the peak of the holding torque can be increased.

[0066] In this embodiment, the strength of the magnetic field that the first magnetic body 403 applies to the first bearing portion 21 is greater than the coercive force of the first bearing portion 21. Therefore, the first bearing portion 21 facing the first magnetic body 403 has magnetic poles of opposite polarity, and a magnetic force (attractive force) is generated between the first magnetic body 403 and the first bearing portion 21. This suppresses the rotation of the first magnetic body 403 together with the shaft 2. This suppresses the occurrence of pulsation (cogging), suppresses the occurrence of noise and vibration when the motor 401 is driven, and prevents the rotor (rotating body) 6 from rotating due to inertia even when an external force is applied.

[0067] [Fifth embodiment] Next, a motor according to a fifth embodiment, which is another example of the present invention, will be described with reference to the drawings. 9 is a cross-sectional view of a motor 501 according to the fifth embodiment, taken along a plane including the axis x of the shaft 2 (similar to the first embodiment, this is a sector-shaped cross-section, corresponding to the CC cross-section shown in FIG. 2). Note that in this embodiment, a cross-sectional view of a cross-section perpendicular to the axis x of the shaft 2 is omitted, but the magnetized state of the first magnetic body 503 is similar to that of the first magnetic body 203 in the second embodiment, so please refer to FIG. 5.

[0068] The motor 501 according to the fifth embodiment has the same configuration as the motor 1 according to the first embodiment, except that the first magnetic body 503 arranged on one side a of the shaft 2 and the structure in the vicinity thereof are different. Therefore, in this embodiment, the same reference numerals are used to designate members having the same configuration as those in the first embodiment, and detailed descriptions thereof will be omitted.

[0069] In this embodiment, the motor 501 has a first magnetic body 503 for generating holding torque attached to one side a of the shaft 2. The first magnetic body 503 is a disk-shaped magnet having a constant outer diameter that is smaller than the thickness of the first magnetic body 203 in the second embodiment, and rotates together with the shaft 2 around the axis line x that is the axis of the shaft 2 as its central axis.

[0070] The first magnetic body 503 is disposed in a position close to the bottom 10b of the frame 10, similar to the first magnetic body 203 in the second embodiment. That is, the first magnetic body 503 faces the inner surface of the bottom 10b of the frame 10. The frame 10 is formed of a steel plate, which is a magnetic body. Furthermore, the first magnetic body 503 and the bottom 10b of the frame 10 interact magnetically with each other to generate a holding torque. Therefore, in this embodiment, the bottom 10a of the frame 10 corresponds to the "second magnetic body" in the present invention.

[0071] In the axial direction, the first magnetic body 503 and the inner surface of the bottom 10b of the frame 10 face each other. In addition, the first magnetic body 503 and the inner surface of the bottom 10b of the frame 10 face each other over the entire circumference in the axial direction. The opposing inner surfaces of the first magnetic body 503 and the bottom 10b of the frame 10 are flat surfaces. The first magnetic body 503 is a permanent magnet with a relatively high magnetic flux density, such as a ferrite magnet or a rare earth magnet. On the other hand, the frame 10 made of a steel plate has a coercive force smaller than the strength of the magnetic field that the first magnetic body 503 applies to the bottom part 10b of the frame 10.

[0072] As in the second embodiment, as shown in FIG. 5, the surface of the first magnetic body 503 that faces the inner surface of the bottom 10b of the frame 10 is magnetized at equal intervals of 90° central angles so that two different magnetic poles (N pole and S pole) alternate in the circumferential direction. On the other hand, the inner surface of the bottom 10b of the frame 10 that faces the first magnetic body 503 has a magnetic pole opposite to that of the first magnetic body 503. In other words, the first magnetic body 503 and the inner surface of the bottom 10b of the frame 10 that face each other in the axial direction have multiple magnetic pole portions. Therefore, an attractive force (indicated by a double-headed arrow K in FIG. 9) due to a magnetic force is generated between the first magnetic body 503 and the inner surface of the bottom 10b of the frame 10, suppressing the movement of the first magnetic body 503 in the rotational direction.

[0073] In this embodiment, a washer (hereinafter referred to as a "loose washer") 581 is further provided as a sliding member between the first bearing portion 21 and the first magnetic body 503. The loose washer 581 is made up of a plurality of washers stacked together and is passed through by the shaft 2. One side a of the loose washer 581 is in contact with the first bearing portion 21.

[0074] In this embodiment, the first bearing portion 21 is a sintered impregnated bearing, but it may be made of any material containing a magnetic substance such as iron, and bearings with other structures, such as rolling bearings or other sliding bearings, may also be used. If a rolling bearing having an inner ring and an outer ring is used as the first bearing portion 21, the surface of one side a of the loose washer 581 comes into contact with the outer ring, which is fixed to the bottom portion 10b of the frame 10 and does not rotate with the shaft 2. On the other hand, the surface on the other side b of the loose washer 581 contacts with the surface 503a on one side a of the first magnetic body 503 (surface perpendicular to the direction of the axis x) as a sliding surface 581a.

[0075] The inner surface of the bottom 10b of the frame 10 facing the first magnetic body 503 is a magnetic body (second magnetic body), and therefore an attractive force due to a magnetic force is generated between the first magnetic body 503 and the inner surface of the bottom 10a of the frame 10. Therefore, the first magnetic body 503 is attracted by the magnetic force (attractive force) between it and the inner surface of the bottom 10b of the frame 10, and the first magnetic body 503 is urged against the loose washer 581 (both arrows Q in FIG. 9).

[0076] Therefore, when the first magnetic body 503 tries to rotate together with the shaft 2, a biasing force generated between the surface 503a on one side a of the first magnetic body 503 and the sliding surface 581a of the loose washer 581 generates friction between the sliding surface 581a and the surface 503a on one side a, generating a holding torque. This prevents the shaft 2 from rotating together with the first magnetic body 503. This configuration does not increase pulsation (cogging), and can suppress the generation of noise and vibration when the motor 501 is driven, and can prevent the rotor (rotating body) 6 from rotating due to inertia even when an external force is applied.

[0077] Therefore, in this embodiment, the holding torque due to the attractive force (double arrow K in Figure 9) caused by the magnetic force generated between the first magnetic body 503 and the inner surface of the bottom 10b of the frame 10, and the holding torque due to the frictional force generated by this biasing force (double arrow Q in Figure 9) between the sliding surface 581a of the loose washer 581 and the surface 503a on one side a of the first magnetic body 503 combine to further improve the holding torque of the motor 501.

[0078] In this embodiment, since a large holding torque can be obtained due to the frictional force between the first magnetic body 503 and the loose washer 581, it does not matter if the attractive force due to the magnetic force generated between the first magnetic body 503 and the inner surface of the bottom 10b of the frame 10 (both arrows K in Figure 9) is small.

[0079] That is, in this embodiment, the first magnetic body 503 does not have to be magnetized so that two different magnetic poles (N pole and S pole) alternate in the circumferential direction, as in the first magnetic body 203 shown in Fig. 5. Therefore, even if the surface on one side a (i.e., the flat surface 503a) and the surface on the other side b of the first magnetic body 503 each have a uniform magnetic pole in the thickness direction (the same as the direction of the axis x), a frictional force is generated between the flat surface 503a of the first magnetic body 503 and the sliding surface 581a of the loose washer 581, and a holding torque can be obtained by this frictional force.

[0080] [Sixth embodiment] Next, a motor according to a sixth embodiment, which is another example of the present invention, will be described with reference to the drawings. 10 is a cross-sectional view of a motor 601 according to the sixth embodiment, taken along a plane including the axis x of the shaft 2 (similar to the first embodiment, this is a sectorial cut-out cross-section, corresponding to the CC cross-section shown in FIG. 2). Note that in this embodiment, a cross-sectional view of a cross-section perpendicular to the axis x of the shaft 2 is omitted, but since it is actually the same as FIG. 2 in the first embodiment, please refer to that figure.

[0081] The motor 601 according to the sixth embodiment has the same configuration as the motor 1 according to the first embodiment, except for the different structure in the vicinity of the second bearing portion 22 arranged on the other side b of the shaft 2. Therefore, in this embodiment, the same reference numerals are used to designate members having the same configuration as those in the first embodiment, and detailed description thereof will be omitted.

[0082] In this embodiment, the motor 601 is provided with a loose washer 681 as a sliding member and a coil spring (hereinafter referred to as "coil spring") 682 as a biasing member between the second bearing portion 22 arranged on the other side b of the shaft 2 and the commutator 5. The loose washer 681 is made up of a plurality of washers stacked together and is inserted through the shaft 2.

[0083] With the shaft 2 passing through the hole of the coil spring 682, a part of the coil spring 682 on one side a is in contact with the support part 51 of the commutator 5, and another part of the coil spring 682 on the other side b is in contact with the one side a of the loose washer 681. The coil spring 682 attempts to expand due to a restoring force from a compressed state between the commutator 5 and the loose washer 681. This restoring force acts to increase the gap between the commutator 5 and the loose washer 681. In other words, the coil spring 682 urges the loose washer 681 from one side a toward the other side b due to its restoring force.

[0084] In the loose washer 681, the surface on the other side b serves as a sliding surface 681a, which is in contact with the surface 22a on the one side a of the second bearing portion 22 (the surface perpendicular to the direction of the axis x). Furthermore, although the second bearing portion 22 in this embodiment is a sintered impregnated bearing, it may be made of any material containing a magnetic substance such as iron, and may be a rolling bearing, other plain bearing, or other bearing having a different structure. If a rolling bearing having an inner ring and an outer ring is used for the second bearing portion 22, the sliding surface 681a comes into contact with the outer ring, which is fixed to the end plate 13 and does not rotate with the shaft 2.

[0085] The coil spring 682 biases the loose washer 681 toward the other side b (toward the second bearing portion 22), thereby biasing the loose washer 681 toward the second bearing portion 22 (both arrows M in FIG. 10). Therefore, when the commutator 5 tries to rotate together with the shaft 2, the sliding surface 681a of the loose washer 681 is urged against the surface 22a of the second bearing portion 22, generating a frictional force between the sliding surface 681a and the flat surface 22a, thereby suppressing the rotation of the shaft 2. With this configuration, the generation of noise and vibration when the motor 601 is driven can be suppressed without increasing pulsation (cogging), and the rotor (rotating body) 6 can be prevented from rotating due to inertia even when an external force is applied.

[0086] Therefore, in this embodiment, the holding torque due to the magnetic force (attractive force, double-headed arrow G in FIG. 10) generated between the magnetic body 3 and the frame magnet 4 and the holding torque due to the frictional force between the sliding surface 681a of the loose washer 681 and the flat surface 22a of the second bearing portion 22 work together to further improve the holding torque. That is, the motor 601 of this embodiment is configured to generate holding torque on both one side a and the other side b of the shaft 2. Therefore, the force that suppresses the rotation of the shaft 2 acts only on one side in the direction of the rotation axis, thereby suppressing the force acting in a twisting direction on the shaft 2.

[0087] [Seventh embodiment] Next, a motor according to a seventh embodiment, which is another example of the present invention, will be described with reference to the drawings. 11 is a cross-sectional view of a motor 701 according to the seventh embodiment, taken along a plane including the axis x of the shaft 2 (similar to the first embodiment, this is a sector-shaped cross-section, corresponding to the CC cross-section shown in FIG. 2). Note that in this embodiment, a cross-sectional view of a cross-section perpendicular to the axis x of the shaft 2 is omitted, but since it is actually the same as FIG. 2 in the first embodiment, please refer to that figure.

[0088] The motor 701 according to the seventh embodiment has the same configuration as the motor 1 according to the first embodiment, except for the different structure in the vicinity of the second bearing portion 22 arranged on the other side b of the shaft 2. Therefore, in this embodiment, the same reference numerals are used to designate members having the same configuration as those in the first embodiment, and detailed description thereof will be omitted.

[0089] In the present embodiment, the length of a support portion 751 of a commutator 5 in the direction of the axis x of the motor 701 is shorter than that of the support portion 51 in the first embodiment, and a third magnetic body 703 for generating holding torque is attached to the other side b of the support portion 751. As shown in Fig. 11 , the third magnetic body 703 is a disk-shaped magnet that has a relatively large thickness and a constant outer diameter in the direction of the axis x, and rotates together with the shaft 2 around the axis x that is the axis of the shaft 2 as its central axis.

[0090] The third magnetic body 703 is disposed with its surface on the other side b in close proximity to the second bearing portion 22. That is, the surface on the other side b of the third magnetic body 703 faces the surface on one side a of the second bearing portion 22 and a partial region of the end plate 13. The first bearing portion 21 is formed of a sintered material containing iron, which is a magnetic material. The end plate 13 is also formed of a steel plate, which is a magnetic material. Therefore, the third magnetic body 703 and the partial region of the second bearing portion 22 and the end plate 13 (hereinafter referred to as the "second bearing portion 22, etc.") interact magnetically with each other to generate a holding torque. Therefore, in this embodiment, the second bearing portion 22, etc. correspond to the "fourth magnetic body" in the present invention.

[0091] The third magnetic body 703 and the second bearing portion 22, etc. face each other in the axial direction. The third magnetic body 703 and the second bearing portion 22, etc. face each other over the entire circumference in the axial direction. The opposing surfaces of the third magnetic body 703 and the second bearing portion 22, etc., which face each other, are flat surfaces. The third magnetic body 703 is a permanent magnet with a relatively high magnetic flux density, such as a ferrite magnet, a rare earth magnet, etc. On the other hand, the second bearing portion 22 etc. have a small coercive force relative to the strength of the magnetic field that the third magnetic body 703 applies to the second bearing portion 22.

[0092] The third magnetic body 703 is magnetized with two different magnetic poles (S pole and N pole) in the thickness direction (the same as the axis x direction) like the first magnetic body 203 in the second embodiment. The third magnetic body 703 has a different outer diameter and thickness from the first magnetic body 203 in the second embodiment.

[0093] The surface (hereinafter referred to as the "opposing surface") on one side a of the second bearing portion 22 etc., which has a small coercive force, has a magnetic polarity opposite to that of the third magnetic body 703. The opposing surfaces of the third magnetic body 703 and the second bearing portion 22 etc., which face each other in the axial direction, have a plurality of magnetic pole portions. Therefore, an attractive force (both arrows N in FIG. 11 ) is generated by a magnetic force between the third magnetic body 703 and the opposing surfaces of the second bearing portion 22 etc., which fixes the movement of the third magnetic body 703 in the rotational direction and prevents the third magnetic body 703 from rotating together with the shaft 2.

[0094] Similar to the first magnetic body 403 in the fourth embodiment, the third magnetic body 703 generates a holding torque on the other side b of the shaft 2 due to a magnetic force (attractive force) generated between the third magnetic body 703, which does not contribute to driving the motor 701, and the second bearing 22, etc. By providing the motor 701 with the third magnetic body 703 that generates a holding torque, the peak of the holding torque can be increased.

[0095] In this embodiment, the strength of the magnetic field that the third magnetic body 703 applies to the second bearing portion 22 and the like is greater than the coercive force of the second bearing portion 22 and the like. Therefore, the second bearing portion 22 etc. that faces the third magnetic body 703 has a magnetic pole of opposite polarity to that of the third magnetic body 703. This makes it possible to prevent the third magnetic body 703 from rotating. In addition, it is possible to prevent pulsation (cogging) from increasing, which makes it possible to suppress the generation of noise and vibration when the motor 701 is driven, and also to prevent the rotor (rotating body) 6 from rotating due to inertia even when an external force is applied.

[0096] Therefore, in this embodiment, in addition to the attractive force (double-headed arrow G in FIG. 11) due to the magnetic force generated between the first magnetic body 3 and the frame magnet 4, the attractive force (double-headed arrow M in FIG. 11) due to the magnetic force generated between the third magnetic body 703 and the second bearing portion 22, etc., combines to further improve the holding torque. That is, the motor 701 according to this embodiment is configured so that holding torque is generated on both the one side a and the other side b of the shaft 2. Therefore, the force that suppresses the rotation of the shaft 2 acts only in one direction along the axis x, and it is possible to suppress the force acting in a twisting direction on the shaft 2.

[0097] The motor of the present invention has been described above with reference to preferred embodiments. As in each of the above embodiments, a structure in which multiple magnetic bodies face each other, for example, a first magnetic body and a second magnetic body, in which at least one of the magnetic bodies has a magnet, is used, whereby the magnetic force of the magnet possessed by one magnetic body attracts the other magnetic body, making it possible to generate a holding torque.

[0098] In this case, if the other magnetic body is formed from a material, such as an electromagnetic steel plate or an Alnico magnet, whose coercive force is smaller than the strength of the magnetic field that one magnetic body exerts on the other magnetic body, in other words, if the strength of the magnetic field that one of the first and second magnetic bodies exerts on the other magnetic body is greater than the coercive force of the other magnetic body, it becomes possible to reduce the cogging torque while improving the coercive force.

[0099] Furthermore, at this time, the first magnetic body and the third magnetic body fixed to the shaft have a shape that has a constant diameter around the entire circumference in the circumferential direction, in other words, a shape that is circular around the entire circumference in a cross section perpendicular to the axial direction, which makes it possible to improve the holding torque without increasing torque ripple, and does not increase noise, vibration, etc.

[0100] Similarly, since the distance between the opposing surfaces of the first and second magnetic bodies is constant around the entire circumference, it is possible to improve the holding torque without increasing torque ripple, and there is no increase in noise, vibration, etc.

[0101] Furthermore, the motor of the present invention is not limited to the configuration of the above embodiment. For example, in each of the above embodiments, the configurations presented as mechanisms for generating holding torque may be appropriately selected and combined arbitrarily on one side and the other side to form a structure, or may be applied to only one side or the other side.

[0102] As an example, a configuration including the first magnetic body 203 and the second magnetic body 304 in the third embodiment may be selected for one side a of the shaft 2, and a configuration including the third magnetic body 703 in the seventh embodiment may be selected for the other side b, and a structure may be formed by combining these.

[0103] As another example, the third magnetic body on the other side b in the seventh embodiment may be the same as the first magnetic body 3 as on the one side a, and the fourth magnetic body facing the third magnetic body may be the frame magnet 4. In this case, the frame magnet 4 is a stator member facing the rotor 6, and also serves as the second magnetic body facing the first magnetic body and the fourth magnetic body facing the third magnetic body.

[0104] Furthermore, in all of the above embodiments, examples have been described in which the invention is applied to an inner rotor type so-called brushed DC motor, but the invention is not limited to motors of this structure, and may be applied to outer rotor type motors or brushless motors.

[0105] In addition, those skilled in the art can appropriately modify the motor of the present invention in accordance with conventionally known knowledge. As long as such modifications still comprise the configuration of the present invention, they are of course included in the scope of the present invention. [Explanation of symbols]

[0106] 1,201,301,401,501,601,701...motor, 1a...housing, 1b...armature (rotating body), 2...shaft, 3,203,403,503...first magnetic body (first magnet), 4...frame magnet (second magnetic body, second magnet), 5...commutator, 6...rotor (rotating body), 10...frame, 10a...protruding portion, 10b...bottom (end on one end 10x side of frame 10), 10x...one end, 10y...other end, 11...power supply connection portion, 12...brush, 13...end plate , 14...circuit board, 15...bracket, 16...power supply terminal, 17...sensor, 20...power supply unit, 21...first bearing portion, 22...second bearing portion, 22a...flat surface, 23...disk, 51...support portion, 52...commutator piece, 53...riser, 54...varistor, 61...rotating body core, 204...drive magnet, 304...magnetic member (first magnetic member), 503a...flat surface, 581, 681...loose washer (sliding member), 581a, 681a...sliding surface, 682...coil spring (urging member), 703...third magnet

Claims

1. A shaft, a rotor fixed to the shaft; a disk-shaped first magnet fixed to the shaft; a stationary portion having a frame and a second magnet fixed to an inner peripheral surface of the frame, the rotor includes a rotor core and a winding wound around the rotor core, The inner peripheral surface of the second magnet is formed in an annular shape, the second magnet faces the rotor in the radial direction, the first magnet faces the second magnet over the entire circumference, the coercive force of the first magnet is smaller than the coercive force of the second magnet, The facing surfaces of the first magnet and the second magnet, which face each other in the radial direction, each have a magnetic pole portion. Motor.

2. The motor according to claim 1 , wherein the distance between the opposing surfaces of the first magnet and the second magnet that face each other in the radial direction is constant over the entire circumference.

3. the first magnet includes aluminum, nickel, and cobalt; The motor of claim 1 , wherein the second magnet comprises iron.

4. A housing having the frame and end plates, The shaft has one end and another end, The motor according to claim 1 , further comprising an encoder provided at the other end of the housing on the other end side of the shaft.

5. the rotor is an armature, 5. The motor according to claim 4, wherein the encoder comprises a disk formed of a magnet and a sensor.

6. the opposing surface of the first magnet is the outer circumferential surface of the first magnet, The motor according to claim 1 , wherein the opposing surface of the second magnet is an inner peripheral surface of the second magnet.

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