Brushless motor and servo control system

Abstract

The utility model discloses a brushless motor and a servo control system. The brushless motor comprises a stator assembly; a rotor assembly disposed on an outer side of the stator assembly in a radial direction, the rotor assembly configured to rotate relative to the stator assembly; a torque holding assembly including: a torque holding ring made of a permanent magnet material and fixed to the stator assembly; a torque holding plate made of a magnetically conductive material and fixed to the rotor assembly; wherein the torque retaining ring is provided with an annular first main body and a plurality of magnetic pole units arranged in the circumferential direction, and each magnetic pole unit is composed of an N pole and an S pole; and wherein the torque holding plate has an annular second body arranged on the outside of the first body in the radial direction and a plurality of salient poles spaced apart in the circumferential direction, each salient pole facing a respective magnetic pole unit.

Description

Technical Field

[0001] The utility model relates to a brushless motor and a servo control system, and more particularly to a brushless motor with higher positioning accuracy and a servo control system comprising the brushless motor. Background Art

[0002] When powered, the rotor of a brushless motor rotates relative to the stator, outputting torque and speed. When powered off, the rotor is expected to remain in a fixed position, requiring a holding torque to secure it. Conventional technology, however, suffers from relatively low rotor position accuracy during power-off periods.

[0003] Therefore, it is desired to propose a brushless motor to improve the defects in the above-mentioned prior art. Utility Model Content

[0004] According to a first aspect of the present invention, a brushless motor is proposed, comprising: a stator assembly; a rotor assembly, arranged on the outside of the stator assembly in a radial direction, the rotor assembly being configured to rotate relative to the stator assembly; a torque retaining assembly, comprising: a torque retaining ring, made of a permanent magnetic material and fixed to the stator assembly; a torque retaining plate, made of a magnetic conductive material and fixed to the rotor assembly; wherein the torque retaining ring has an annular first body and a plurality of magnetic pole units arranged in a circumferential direction, the magnetic pole units being composed of an N pole and an S pole; and wherein the torque retaining plate has an annular second body and a plurality of salient poles spaced apart in the circumferential direction, the second body being arranged on the outside of the first body in a radial direction, each salient pole facing a corresponding magnetic pole unit.

[0005] According to this solution, due to the reluctance effect between the magnetic poles of the torque retaining ring and the salient poles of the torque retaining plate, the torque retaining ring applies torque to the torque retaining plate, maintaining the torque retaining plate in a fixed position relative to the torque retaining ring, thereby maintaining the rotor in a fixed position relative to the stator. By providing more magnetic poles and corresponding salient poles, the rotor assembly's positional accuracy can be improved.

[0006] In some embodiments, the stator assembly may include a stator frame, a support frame and a stator core piece, the stator core piece is fixed to the stator frame, the support frame is located radially inside the torque retaining ring, and the torque retaining ring is fixed to the stator frame through the support frame; the rotor assembly may include a rotor yoke and an excitation permanent magnet, the excitation permanent magnet is fixed to the inner surface of the rotor yoke and arranged on the outside of the stator core piece in the radial direction, and the torque retaining plate is fixed to the rotor yoke.

[0007] In some aspects, the salient pole may protrude from the second body in an axial direction, the salient pole facing an N pole or an S pole of the magnetic pole unit in a radial direction.

[0008] According to this solution, the magnetic poles can apply a circumferential holding torque to the salient poles, thereby keeping the rotor assembly stationary in the circumferential direction.

[0009] In some solutions, the salient pole may be provided with a groove extending in the radial direction on a side away from the second body.

[0010] According to this solution, the groove can appropriately reduce the force of the magnetic pole on the salient pole, so that the salient pole will not swing violently under the action of the magnetic pole, thereby making the rotation of the rotor assembly more stable.

[0011] In some embodiments, the torque retaining plate may further include a plurality of additional salient poles spaced apart in the circumferential direction, each additional salient pole being arranged near a corresponding salient pole, the additional salient poles protruding inward from the second body in a radial direction, and the additional salient poles facing the N pole or S pole of the magnetic pole unit in an axial direction.

[0012] According to this solution, the magnetic poles can apply additional circumferential holding torque to the additional salient poles, thereby better keeping the rotor assembly stationary.

[0013] In some embodiments, the torque retaining plate may further include a plurality of additional salient pole pairs spaced apart in the circumferential direction, each additional salient pole pair including two additional salient poles, which respectively face the N pole or S pole of the magnetic pole unit on both sides in the axial direction.

[0014] According to this solution, the magnetic pole can apply additional holding torque to the two additional salient poles of the additional salient pole pair respectively, and the position holding accuracy of the rotor assembly is improved.

[0015] In some aspects, the magnetic pole unit may be magnetized such that the salient pole faces one of the N pole and the S pole of the magnetic pole unit, and the additional salient pole faces the other of the N pole and the S pole of the magnetic pole unit.

[0016] According to this solution, the salient pole and the additional salient pole respectively act on a corresponding one of the N pole and the S pole of the magnetic pole unit, further improving the holding torque applied by the magnetic pole unit to the salient pole, thereby further improving the position holding accuracy of the rotor assembly.

[0017] In some solutions, the salient poles may be formed by punching out of the rotor yoke, with the salient poles facing the north pole or the south pole of the magnetic pole unit in the radial direction.

[0018] According to this solution, there is no need to set up a separate torque retaining plate, so that the structure of the brushless motor is simple and more stable, and the salient poles can be formed only by punching the rotor yoke, which reduces the production cost of the brushless motor.

[0019] In some embodiments, a recess may be provided on the salient pole, the recess extending in the radial direction, the recess forming another salient pole, and the other salient pole facing the N pole or S pole of the magnetic pole unit in the axial direction.

[0020] According to this solution, the magnetic pole can apply an axial holding torque to the other salient pole, thereby keeping the rotor assembly stationary.

[0021] In some aspects, the magnetic pole unit may be magnetized such that a salient pole faces one of the N pole and the S pole of the magnetic pole unit and another salient pole faces the other of the N pole and the S pole of the magnetic pole unit.

[0022] According to this solution, the salient pole and the other salient pole respectively act with a corresponding one of the N pole and the S pole of the magnetic pole unit, further improving the holding torque applied by the magnetic pole unit to the salient pole, thereby further improving the position holding accuracy of the rotor assembly.

[0023] In some aspects, the magnetic pole units may be arranged continuously in the circumferential direction.

[0024] In some aspects, the pole units may be spaced apart in a circumferential direction.

[0025] In some aspects, the magnetic pole unit may be composed of a pair of N poles and S poles arranged in the circumferential direction.

[0026] In some aspects, the magnetic pole unit may be composed of a pair of N poles and S poles arranged in a radial direction.

[0027] In some embodiments, the magnetic pole units may be arranged on an outer surface of the support frame.

[0028] In some embodiments, the pole unit can be embedded inside the support frame.

[0029] In some embodiments, the pole units can be made by sintering, bonding, or plastic magnetic processes.

[0030] According to a second aspect of the present invention, a servo control system is provided, comprising the brushless motor according to the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 FIG1 shows an external schematic diagram of a brushless motor according to an embodiment of the present utility model;

[0032] Figure 2 shows an exploded view of a brushless motor according to an embodiment of the present invention;

[0033] Figure 3 A front cross-sectional view of a brushless motor according to a first embodiment of the present invention is shown;

[0034] Figure 4 A schematic diagram of a torque retaining assembly according to a first embodiment of the present utility model is shown;

[0035] Figure 5 shows a front cross-sectional view of a brushless motor according to a second embodiment of the present invention;

[0036] Figure 6 Shown Figure 5 A partial enlarged view of

[0037] Figure 7 A schematic diagram of a torque retaining plate according to a second embodiment of the present invention is shown;

[0038] Figure 8 shows a front cross-sectional view of a brushless motor according to a third embodiment of the present utility model;

[0039] Figure 9 FIG2 shows a schematic diagram of a torque retaining assembly according to a third embodiment of the present invention;

[0040] Figure 10 A schematic diagram showing a torque retaining ring according to another embodiment of the present invention is shown;

[0041] Figure 11 A schematic diagram showing a torque retaining ring according to another embodiment of the present invention is shown;

[0042] Figure 12 A schematic diagram showing a torque retaining ring according to another embodiment of the present invention is shown;

[0043] Figure 13 A schematic diagram of a torque retaining ring according to other embodiments of the present invention is shown.

[0044] Reference numerals:

[0045] 100 brushless motor

[0046] 110 stator assembly

[0047] 112 stator frame

[0048] 114 stator core

[0049] 116 bearings

[0050] 118 support frame

[0051] 120 rotor assembly

[0052] 122 rotor yoke

[0053] 124 Excitation permanent magnet

[0054] 126 rotor shaft

[0055] 128 rotor frame

[0056] 130 Torque retaining ring

[0057] 132 First Subject

[0058] 134 magnetic pole units

[0059] 140 Torque Retention Plate

[0060] 142 Second Subject

[0061] 144 salient pole

[0062] 145 grooves

[0063] 146 Additional salient pole

[0064] 148 Another salient pole DETAILED DESCRIPTION

[0065] In order to make the purpose, scheme and advantages of the technical solution of the present invention more clear, the following will be combined with the drawings of specific embodiments of the present invention to clearly and completely describe the technical solution of the present invention. Unless otherwise specified, the terms used herein have the common meanings in the art. The same reference numerals in the drawings represent the same components.

[0066] For clearer description, unless otherwise specified, the directional terms appearing in this document have the following meanings: the axial direction refers to the direction in which the rotor shaft extends, and the rotor rotates around the axial direction; the radial direction is perpendicular to the axial direction and points toward / away from the rotor shaft; the circumferential direction is perpendicular to both the axial and radial directions.

[0067] Figure 1 Figure 1 shows an external schematic diagram of a brushless motor 100 according to an embodiment of the present invention. Brushless motor 100 primarily includes a stator assembly 110 and a rotor assembly 120. Rotor assembly 120 is rotatable relative to stator assembly 110 to output torque and speed externally. Brushless motor 100 can be used in a servo control system, where servo control is achieved through the torque and speed output by rotor assembly 120.

[0068] Figure 2 and Figure 3The figures show an exploded view and a front cross-sectional view of a brushless motor 100 according to an embodiment of the present invention. The stator assembly 110 mainly includes a stator frame 112, a stator core 114, a bearing 116, and a support frame 118. The stator core 114 is formed of an iron core and a winding wound around it and is fixed to the stator frame 112. The bearing 116 is fixed to the radial inner side of the stator frame 112. The rotor assembly 120 mainly includes a rotor yoke 122, an excitation permanent magnet 124, a rotor shaft 126, and a rotor frame 128. The excitation permanent magnet 124 is fixed to the inner surface of the rotor yoke 122. The rotor yoke 122 and the rotor shaft 126 are fixed to the rotor frame 128. The stator core 114 is radially opposed to the excitation permanent magnets 124. Specifically, the excitation permanent magnets 124 are radially located outside the stator core 114. When the brushless motor 100 is energized, the magnetic field force between the excitation permanent magnets 124 and the stator core 114 provides rotational torque to the rotor assembly 120, causing the rotor assembly 120 to rotate relative to the stator assembly 110. The rotor shaft 126 passes through the inner hole of the bearing 116 to achieve an assembled connection between the stator assembly 110 and the rotor assembly 120. The torque and speed of the rotor assembly 120 are transmitted to external components via the rotor shaft 126.

[0069] When the brushless motor 100 is powered on, the rotor assembly 120 rotates relative to the stator assembly 110 due to the magnetic field force between the excitation permanent magnets 124 of the rotor assembly 120 and the stator core 114 of the stator assembly 110. When the brushless motor 100 is powered off, the magnetic field force between the excitation permanent magnets 124 and the stator core 114 no longer drives the rotor assembly 120 to rotate relative to the stator assembly 110. In this case, it may be desirable for the rotor assembly 120 to remain stationary. For example, when the brushless motor 100 is used to drive and control the louvers of an air conditioning unit, the louvers need to be oriented to a specific open or closed position and maintained in that state when the brushless motor 100 is powered off. This requires that the rotor assembly 120 of the brushless motor 100 remain stationary. For example, when the brushless motor 100 is used to drive and control the flow control component of a valve, when the brushless motor 100 is powered off, the flow control component needs to be located in a specific position to maintain a stable flow through the valve, which also requires the rotor assembly 120 of the brushless motor 100 to remain fixed.

[0070] For this reason, Figure 4As shown, the brushless motor 100 proposed in the present invention also includes a torque retention assembly for maintaining the rotor assembly 120 in a fixed position during power-off of the brushless motor 100. The torque retention assembly includes a torque retention ring 130 and a torque retention plate 140. The torque retention ring 130 is made of a permanent magnetic material and fixed to the stator assembly 110. The torque retention ring 130 has an annular first body 132 and a plurality of magnetic pole units 134 arranged in the circumferential direction. The magnetic pole units 134 are composed of north poles and south poles. The torque retention plate 140 is made of a magnetically conductive material and fixed to the rotor assembly 120. The torque retention plate 140 has an annular second body 142 and a plurality of salient poles 144 spaced apart in the circumferential direction. The second body 142 is arranged radially outside the first body 132, and each salient pole 144 faces a corresponding magnetic pole unit 134. Due to the reluctance effect, the salient poles 144 of the torque retaining plate 140 are acted upon by the magnetic field force of the magnetic pole units 134 of the torque retaining ring 130, thereby maintaining the torque retaining plate 140 stationary relative to the torque retaining ring 130, and further maintaining the rotor assembly 120 stationary relative to the stator assembly 110. The holding torque between the magnetic pole units 134 of the torque retaining ring 130 and the salient poles of the torque retaining plate 140 can be designed by varying the number of poles in the magnetic pole units 134 and the number of salient poles 144 to meet different application requirements.

[0071] According to the above arrangement, two primary magnetic field forces exist within brushless motor 100. The first magnetic field force is exerted by the stator core 114 of stator assembly 110 on the excitation permanent magnets 124 of rotor assembly 120. This first magnetic field force provides the driving force for the rotation of rotor assembly 120. The second magnetic field force is exerted by the magnetic pole units 134 of torque retaining ring 130 on the salient poles 144 of torque retaining plate 140. This second magnetic field force provides the holding torque for securing rotor assembly 120. By setting appropriate parameters, the magnitude of the first magnetic field force can be greater than that of the second magnetic field force. For example, the magnitude of the first magnetic field force can be approximately ten times the magnitude of the second magnetic field force. When brushless motor 100 is powered on, both the first and second magnetic field forces exist. However, because the first magnetic field force is greater than the second, rotor assembly 120 can rotate under the action of the first magnetic field force, overcoming the second magnetic field force, thereby outputting torque and speed. When the brushless motor 100 is powered off, the first magnetic field force disappears and the rotor assembly 120 is maintained in a fixed position under the action of the second magnetic field force, thereby maintaining external components associated with the rotor assembly 120 (e.g., louvers connected to the rotor shaft 126, flow control components, etc.) in a fixed position.

[0072] Preferably, the torque retaining ring 130 can be fixed to the stator frame 112 via the support frame 118, thereby achieving fixation between the torque retaining ring 130 and the stator assembly 110. The torque retaining plate 140 can be fixed to the inner surface of the rotor yoke 122, thereby achieving fixation between the torque retaining plate 140 and the rotor assembly 120.

[0073] Alternatively, as Figure 7 As shown, the salient poles 144 of the torque retaining plate 140 may protrude from the second body 142 in the axial direction, and the salient poles 144 may face the north pole or south pole of the magnetic pole unit 134 of the torque retaining ring 130 in the radial direction. Due to the magnetoresistance effect, the north pole or south pole of the magnetic pole unit 134 can apply a circumferential retaining torque to the salient poles 144, so that the salient poles 144 remain facing the north pole or south pole of the magnetic pole unit 134 in the circumferential direction, thereby keeping the rotor assembly 120 stationary.

[0074] Preferably, if Figure 4 As shown, the salient pole 144 can be provided with a groove 145 extending in the radial direction on a side away from the second body 142. The groove 145 can appropriately reduce the peak force of the magnetic pole of the magnetic pole unit 134 on the salient pole 144, so that the salient pole 144 does not swing violently under the action of the magnetic pole, thereby making the rotation of the rotor assembly 120 more stable. For example, when the brushless motor 100 switches from the power-on state to the power-off state, the rotor assembly 120 continues to rotate under the action of inertia and then stops at a fixed position under the action of the magnetic field force applied by the magnetic pole unit 134 to the salient pole 144. However, if the peak value of the magnetic field force applied by the magnetic pole unit 134 to the salient pole 144 is too large, the salient pole 144 may have a large rotational inertia and may continue to rotate beyond the alignment position of the salient pole 144 and the magnetic pole unit 134, or even move to the next magnetic pole unit 134, thereby causing unstable movement of the rotor assembly. Therefore, by providing the salient pole 144 with a groove 145, the above-mentioned unstable movement of the rotor assembly can be improved.

[0075] In another embodiment, if Figures 5 to 7 As shown, the torque retention plate 140 may further include a plurality of additional salient poles 146 spaced apart in the circumferential direction. Each additional salient pole 146 is arranged adjacent to a corresponding salient pole 144. The additional salient poles 146 protrude radially inward from the second body 142, and the additional salient poles 146 face the north pole or south pole of the magnetic pole unit 134 in the axial direction. Due to the magnetoresistance effect, the north pole or south pole of the magnetic pole unit 134 can apply a circumferential holding torque to the additional salient poles 146, causing the additional salient poles 146 to remain facing the north pole or south pole of the magnetic pole unit 134 in the axial direction, thereby keeping the rotor assembly 120 stationary.

[0076] More preferably, the torque retaining plate 140 may further include a plurality of additional salient pole pairs spaced apart in the circumferential direction, each additional salient pole pair including two additional salient poles 146, and the two additional salient poles 146 respectively face the N pole or S pole of the magnetic pole unit 134 on both sides in the axial direction. The magnetic poles of the magnetic pole unit 134 can apply a circumferential retaining torque to the two additional salient poles 146 of the additional salient pole pair, further improving the retaining torque of the rotor assembly 120, making the rotor assembly 120 more reliably fixed (i.e., still able to remain stationary under the action of a large disturbing external force). It should be understood that the additional salient poles 146 can be provided only on one side of the corresponding magnetic pole unit 134 in the axial direction, or can be provided on both sides of the corresponding magnetic pole unit 134 in the axial direction.

[0077] Preferably, if Figure 6 The magnetic pole unit 134 of the torque retaining ring 130 can be magnetized so that the salient pole 144 faces one of the north and south poles of the magnetic pole unit 134, and the additional salient pole 146 faces the other of the north and south poles of the magnetic pole unit 134. This magnetization process can be performed in a curved magnetic field. The salient pole 144 interacts with one of the north and south poles of the magnetic pole unit 134, and the additional salient pole 146 interacts with the other of the north and south poles of the magnetic pole unit 134. This further enhances the holding torque applied by the torque retaining ring 130 to the torque retaining plate 140, thereby further improving the position-holding accuracy of the rotor assembly 120. For example, some fluid machinery valves require a certain degree of opening and closing to achieve the required flow rate and pressure. When fluid flows through the valve, the flow pressure on the valve components is always present and subject to shock fluctuations. This requires the rotor assembly 120 to be subjected to a greater holding torque to ensure that the valve components remain in a fixed position despite shock fluctuations, thereby maintaining a stable opening and closing degree of the valve.

[0078] In another embodiment, if Figure 8 and Figure 9 As shown, the salient poles 144 can be formed by punching out the rotor yoke 122, with the salient poles 144 radially facing the north pole or south pole of the magnetic pole unit 134. Compared to the previous embodiment, this embodiment does not require a separate torque retaining plate 140, making the structure of the brushless motor 100 simpler and more stable. The salient poles 144 can be formed simply by punching out the rotor yoke 122, reducing the production cost of the brushless motor 100.

[0079] Preferably, if Figure 9As shown, a recess may be provided on the salient pole 144, extending in the radial direction. The recess forms another salient pole 148 (equivalent to the additional salient pole 146 in the above embodiment). The other salient pole 148 faces the north pole or the south pole of the magnetic pole unit 134 in the axial direction. The magnetic pole of the magnetic pole unit 134 can apply an axial holding torque to the other salient pole 148, thereby keeping the rotor assembly 120 stationary.

[0080] Preferably, the magnetic pole unit 134 may be magnetized such that the salient pole 144 faces one of the north pole and the south pole of the magnetic pole unit 134, and the other salient pole 148 faces the other of the north pole and the south pole of the magnetic pole unit 134. The salient pole 144 and the other salient pole 148 respectively interact with the corresponding one of the north pole and the south pole of the magnetic pole unit 134, further improving the holding torque applied by the magnetic pole unit 134 to the salient pole 144, thereby further improving the position holding accuracy of the rotor assembly 120.

[0081] Although Figure 4 As shown, the magnetic pole units 134 of the torque retaining ring 130 may be arranged continuously in the circumferential direction. Figure 10 In the illustrated embodiment, the magnetic pole units 134 may also be spaced apart in the circumferential direction. The magnetic pole units 134 may be composed of a pair of north poles and south poles arranged in the radial direction. The magnetic pole units 134 are arranged on the outer surface of the support frame 118 (e.g., attached to the outer surface of the support frame 118). The magnetic pole units 134 may be manufactured, for example, by sintering, bonding, or plastic magnet processes.

[0082] exist Figure 11 In the illustrated embodiment, the magnetic pole units 134 may be spaced apart in the circumferential direction, and the magnetic pole units 134 may be composed of a pair of N poles and S poles arranged in the circumferential direction, and the magnetic pole units 134 may be arranged on the outer surface of the support frame 118 (for example, adhered to the outer surface of the support frame 118).

[0083] exist Figure 12 In the illustrated embodiment, the magnetic pole units 134 may be spaced apart in the circumferential direction. The magnetic pole units 134 may be composed of a pair of N poles and S poles arranged in the radial direction. The magnetic pole units 134 are embedded in the interior of the support frame 118 .

[0084] exist Figure 13 In the illustrated embodiment, the magnetic pole units 134 may be spaced apart in the circumferential direction. The magnetic pole units 134 may be composed of a pair of N poles and S poles arranged in the circumferential direction. The magnetic pole units 134 are embedded in the interior of the support frame 118 .

[0085] This document describes in detail several exemplary embodiments of the present invention with reference to preferred embodiments. However, it will be understood by those skilled in the art that, without departing from the concept of the present invention, various modifications and variations may be made to the above-mentioned specific embodiments, and the various technical features and structures proposed in the present invention may also be combined without exceeding the scope of protection of the present invention, which is determined by the appended claims.

Claims

1. A brushless motor, characterized in that: include: a stator assembly comprising a stator frame and a stator core member, wherein the stator core member is fixed to the stator frame; a rotor assembly including a rotor yoke and an excitation permanent magnet fixed to an inner surface of the rotor yoke and arranged radially outside the stator core member; Torque holding assembly, comprising: a plurality of magnetic pole units made of permanent magnetic material and fixed to the stator frame; a plurality of salient poles made of a magnetically conductive material and fixed to the rotor yoke; Wherein, the plurality of magnetic pole units are arranged along the circumferential direction, and the magnetic pole units are composed of N poles and S poles; And wherein the plurality of salient poles are arranged at intervals in the circumferential direction, and each of the salient poles faces a corresponding magnetic pole unit.

2. The brushless motor according to claim 1, wherein: The torque holding assembly comprises: a torque retaining ring having an annular first body and fixed to the stator frame, the magnetic pole unit being formed on the torque retaining ring; A torque retaining plate has an annular second body and is fixed to the rotor yoke. The second body is arranged outside the first body in the radial direction. The salient poles are formed on the torque retaining plate.

3. The brushless motor according to claim 2, characterized in that The salient pole protrudes from the second body in an axial direction, and the salient pole faces an N pole or an S pole of the magnetic pole unit in the radial direction.

4. The brushless motor according to claim 3, characterized in that The salient pole is provided with a groove extending along the radial direction on a side away from the second body.

5. The brushless motor according to claim 4, characterized in that: The torque retaining plate further includes a plurality of additional salient poles spaced apart in the circumferential direction, each of the additional salient poles being arranged adjacent to a corresponding salient pole, the additional salient poles protruding inwardly from the second body along the radial direction, the additional salient poles facing the N pole or the S pole of the magnetic pole unit in the axial direction.

6. The brushless motor according to claim 5, characterized in that The torque retaining plate further includes a plurality of additional salient pole pairs spaced apart in the circumferential direction, each of the additional salient pole pairs including two additional salient poles facing the N pole or the S pole of the magnetic pole unit on both sides in the axial direction.

7. The brushless motor according to claim 5, characterized in that The magnetic pole unit is magnetized so that the salient pole faces one of the N pole and the S pole of the magnetic pole unit, and the additional salient pole faces the other of the N pole and the S pole of the magnetic pole unit.

8. The brushless motor according to claim 3, characterized in that The salient poles are formed by punching out the rotor yoke, and the salient poles face the north pole or the south pole of the magnetic pole unit in the radial direction.

9. The brushless motor according to claim 8, characterized in that A recess is provided on the salient pole, the recess extending in a radial direction, and forming another salient pole. The other salient pole faces the N pole or the S pole of the magnetic pole unit in the axial direction.

10. The brushless motor according to claim 9, characterized in that The magnetic pole unit is magnetized such that the salient pole faces one of an N pole and an S pole of the magnetic pole unit, and the other salient pole faces the other of the N pole and the S pole of the magnetic pole unit.

11. The brushless motor according to claim 1, wherein The magnetic pole units are arranged continuously in the circumferential direction.

12. The brushless motor according to claim 1, wherein The magnetic pole units are spaced apart in the circumferential direction.

13. The brushless motor according to claim 12, wherein: The magnetic pole unit is composed of a pair of an N pole and an S pole arranged in the circumferential direction.

14. The brushless motor according to claim 12, wherein: The magnetic pole unit is composed of a pair of an N pole and an S pole arranged in the radial direction.

15. The brushless motor according to any one of claims 1 to 14, characterized in that The magnetic pole unit is made by sintering, bonding or plastic magnet technology.

16. A servo control system, characterized in that: Comprising a brushless motor according to any one of claims 1 to 15.

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