CN218472868U - Electric machine - Google Patents

Abstract

The utility model discloses a motor, include: a housing assembly; a stator coupled to the housing assembly; the rotor is arranged in the stator in a penetrating mode and comprises a rotating shaft which is rotatably connected with the shell component, a rotor frame which is connected to the rotating shaft and a plurality of magnets which are connected to the rotor frame; the rotor frame outer peripheral face is seted up a plurality of recesses, the recess includes first bottom surface and relative the second bottom surface that first bottom surface slope set up, every be provided with one in the recess magnet. The utility model discloses a set up the recess that holds magnet at the rotor frame surface, can be so that magnet part imbeds in the rotor frame to can use the magnet that thickness is thicker, improve the magnetic field intensity of magnet, and then increase motor torque.

Description

Electric machine

Technical Field

The utility model relates to a motor.

Background

An electric machine is a power plant that is common in the art and typically includes a stator and a rotor. In a brushless motor, a rotor generally includes a rotating shaft, a rotor frame connected to the rotating shaft, and a plurality of magnets connected to the rotor frame, and a stator includes a plurality of windings surrounding the rotor, and when the windings are energized, the windings can generate a changing magnetic field, so as to generate a driving force with the magnets to drive the rotor to rotate.

In the prior art, the outer peripheral surface of the rotor frame is generally in a circular arc shape, the magnet is generally in a tile shape, and the magnet is attached to the outer peripheral surface of the rotor frame in an adhesive connection mode; on the other hand, the existing magnet is tile-shaped and uniform in overall thickness, and the thickness of the magnet is limited by the space inside the motor, so that the magnetic field formed by the magnet is difficult to strengthen, and the torque of the motor is difficult to increase.

Accordingly, there is a need for improvements in the art that overcome the deficiencies in the prior art.

Disclosure of Invention

To the weak point that exists among the above-mentioned technique, the utility model provides a motor, it can use the magnet that thickness is bigger to increase the torque.

In order to solve the technical problem, the utility model provides a motor, include:

a housing assembly;

a stator coupled to the housing assembly; and the number of the first and second groups,

the rotor is arranged in the stator in a penetrating mode and comprises a rotating shaft rotatably connected with the shell component, a rotor frame connected to the rotating shaft and a plurality of magnets connected to the rotor frame;

the rotor frame is characterized in that a plurality of grooves are formed in the outer peripheral surface of the rotor frame, each groove comprises a first bottom surface and a second bottom surface which is obliquely arranged relative to the first bottom surface, and one magnet is arranged in each groove.

Furthermore, the grooves are uniformly distributed on the periphery of the rotor frame by taking the axis of the rotor frame as a center, and the grooves and the magnets arranged in the grooves are symmetrical by a symmetrical plane passing through the axis of the rotor frame.

Further, the magnet comprises a first surface attached to the first bottom surface and a second surface attached to the second bottom surface.

Furthermore, a tip part is formed between the first surface and the second surface, and an avoiding groove for accommodating the tip part is arranged between the first bottom surface and the second bottom surface.

Further, the shell assembly comprises a shell, a front end cover and a rear end cover, the front end cover and the rear end cover are respectively connected to two ends of the shell, and the stator comprises a stator core fixed inside the shell, a stator frame connected with the stator core and a plurality of windings connected to the stator frame.

Furthermore, the stator core comprises an outer sleeve and a plurality of stator teeth connected with the outer sleeve and extending into the outer sleeve, the stator frame comprises an outer framework connected with the outer sleeve and stator tooth sleeves sleeved outside the stator teeth, and the winding is wound on the stator tooth sleeves.

Further, the exoskeleton includes with the surface of the interior surface laminating of outer tube, the surface is provided with the sand grip, the internal surface be equipped with the spacing groove of sand grip adaptation.

Furthermore, the stator tooth includes the limiting plate portion and connect in limiting plate portion with the extension between the outer tube, limiting plate portion orientation the inner end face of rotor exposes in the stator tooth cover, the inner end face personally submits the arc surface with the rotor axis is the center.

Furthermore, the outer sleeve comprises a fixing cover for accommodating the limiting plate part, the fixing cover comprises a first end face superposed with the inner end face, and the first end face is provided with a concave groove communicated with the matching hole.

Further, the motor further comprises a circuit assembly arranged in the shell assembly and a magnetic ring connected to the rotating shaft, the circuit assembly comprises a circuit board and a Hall sensor arranged on the circuit board, and the Hall sensor is arranged outside the peripheral surface of the magnetic ring.

Compared with the prior art, the utility model, its beneficial effect is: the utility model can embed the magnet part into the rotor frame by arranging the groove for accommodating the magnet on the outer surface of the rotor frame, thereby using the magnet with thicker thickness, improving the magnetic field intensity of the magnet and further increasing the torque of the motor; in addition, the groove comprises a first bottom surface and a second bottom surface which are obliquely arranged with each other, so that the contact area between the groove and the magnet can be increased, the connection between the groove and the magnet is firmer, and the guiding and the positioning during the magnet installation are convenient.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Wherein:

fig. 1 is a schematic structural diagram of the motor of the present invention.

Fig. 2 is a cross-sectional view of the motor of the present invention.

Fig. 3 is a schematic structural view of the rotor of the present invention.

Fig. 4 is a schematic view of the connection between the rotor frame and the magnet according to the present invention.

Fig. 5 is a schematic structural diagram of the stator of the present invention.

Fig. 6 is a schematic structural view of a stator core according to the present invention.

Fig. 7 is a schematic structural diagram of the middle stator frame according to the present invention.

Fig. 8 is a sectional view of the stator of the present invention.

Fig. 9 is a schematic structural diagram of the circuit module according to the present invention.

Fig. 10 is a schematic structural view of another viewing direction of the motor in the present invention.

Fig. 11 is a schematic structural view of the wire seat and the wire pressing member of the present invention.

Fig. 12 is a schematic structural view of the wire holder of the present invention when separated from the wire pressing member.

Fig. 13 is a schematic view of the middle magnetic ring of the present invention installed on the rotating shaft.

Detailed Description

In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

The terms "comprising" and "having," as well as any variations thereof, in the present application are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

As shown in fig. 1 to 13, a motor according to a preferred embodiment of the present invention includes a housing assembly 1, a rotor 2, a stator 3, and a circuit assembly 4.

As shown in fig. 1 and 2, the housing assembly 1 includes a case 10, a front cover 11 connected to one end of the case 10, and a rear cover 12 connected to the other end of the case 10. The housing 10 is hollow and tubular, and has a cavity 100 therein, and a front end cap 11 and a rear end cap 12 respectively seal two ends of the cavity 100.

As shown in fig. 3, the rotor 2 includes a rotating shaft 20, a rotor frame 21 fixedly coupled to the rotating shaft 20, and a plurality of magnets 22 fixedly coupled to the rotor frame 21.

The shaft 20 has one end rotatably connected to the rear cover 12 and the other end extending out of the front cover 11 for connection to a load. Bearings 23 are provided between the rotation shaft 20 and the front cover 11 and between the rotation shaft 20 and the rear cover 12 to make the rotation of the rotation shaft 20 smoother.

The rotor frame 21 and the magnet 22 are located inside the cavity 100. As shown in fig. 4, the rotor frame 21 is substantially in the shape of a gear, and the outer peripheral surface thereof is provided with a plurality of grooves 210 for accommodating the magnets 22, the magnets 22 can be fixedly mounted in the grooves 210 by gluing or the like, the number of the grooves 210 can be selected as appropriate, and in this embodiment, the number of the grooves 210 is 8.

Obviously, by providing the groove 210 on the outer circumferential surface of the rotor frame 21, the magnet 22 is partially embedded inside the rotor frame 21, so that the thickness of the magnet 22 can be increased without affecting the occupation of the magnet 22 on the external space, the magnetic field strength of the magnet 22 is increased, and the torque of the motor is increased.

Further, the plurality of grooves 210 are uniformly distributed on the periphery of the rotor frame 21 with the axis of the rotor frame 21 as the center, the cross sections of the grooves 210 are axisymmetric, and the symmetry plane 24 of each groove 210 passes through the axis of the rotor frame 21, and accordingly, the magnet 22 is also symmetric, and is also symmetric with the symmetry plane 24 after being installed in the groove 210. The angles between the symmetry planes 24 of two adjacent grooves 210 are the same, so that the magnetic poles of the magnets 22 are uniformly distributed.

The groove 210 includes a first bottom surface 2100 and a second bottom surface 2101, the first bottom surface 2100 and the second bottom surface 2101 are symmetrically disposed, and an included angle a is formed between the two bottom surfaces, the included angle a is preferably an obtuse angle, so that the magnet 22 has a larger width B, the space between two adjacent magnets is smaller, and the continuity between the magnetic poles is better. In a preferred embodiment, the included angle A is 135 degrees, such that the included angle C between the first bottom surface 2100 and the second bottom surface 2101 of the adjacent groove 210 is 90 degrees.

Accordingly, the magnet 22 includes a first surface 220 corresponding to the first bottom surface 2100 and a second surface 221 corresponding to the second bottom surface 2101, and an included angle D formed between the first surface 220 and the second surface 221 is the same as the included angle a, so that the first surface 220 and the second surface 221 can respectively fit with the first bottom surface 2100 and the second bottom surface 2101 when being mounted. Obviously, by arranging the first bottom surface 2100 and the second bottom surface 2101, the attachment area of the magnet 22 and the rotor frame 21 can be increased, so that the magnet 22 is more firmly attached to the rotor frame 21 and is not easy to loosen, and the reliability and stability of the operation of the motor are ensured; meanwhile, the conical part of the magnet 22 can be guided by the two bottom surfaces when being installed in the groove 210, so that the magnet can be conveniently positioned in the groove 210 to complete installation.

The magnet 22 further includes an arc 223 connected between the first surface 220 and the second surface 221, the arc 223 being convex in a direction away from the first surface 220 and the second surface 221, so that the thickness of the magnet 22 can be further increased, and by controlling the curvature of the arc 223, the maximum thickness of the magnet 22 can be controlled, thereby controlling the magnetic force of the magnet 22. Since the magnet 22 is embedded in the rotor frame 21, the magnet 22 can be made thicker without or without affecting the size of the rotor 2, and the thickness of the magnet 22 and thus the magnetic force thereof can be increased in a limited space, so that the rotational torque of the motor is larger.

In order to prevent interference when the magnet 22 is installed, a concave avoiding groove 2102 is formed between the first bottom surface 2100 and the second bottom surface 2101, and when the magnet 22 is installed, a tip portion 222 formed between the first surface 220 and the second surface 221 is accommodated in the avoiding groove 2102, so that the requirement on machining precision can be reduced, and the magnet 22 and the groove 210 can be further ensured to be reliably attached; in addition, the escape groove 2102 can accommodate more glue, thereby improving the firmness of the connection of the magnet 22 and the rotor frame 21.

With reference to fig. 4, the rotor frame 21 is provided with a plurality of heat dissipation holes 212 extending along the axial direction of the rotor frame, and the heat dissipation holes 212 penetrate through the front and rear end surfaces of the rotor frame 21, so as to dissipate heat through the airflow flowing through the heat dissipation holes 212 when the rotor frame 21 rotates, thereby improving the heat dissipation effect. In this embodiment, the cross section of the heat dissipation holes 212 is circular, and two of the heat dissipation holes are used as one set, and there are four sets of heat dissipation holes 212, and the four sets of heat dissipation holes 212 are uniformly distributed around the axis of the rotor frame 21.

Rotor frame 21 adopts the silicon steel sheet to fold and presses and forms, set up the same locating hole 213 in a plurality of positions on every silicon steel sheet, when folding, fix a position through locating hole 213 and the reference column on the mould, thereby guarantee the position accuracy of silicon steel sheet, the rotor frame 21 of making is of high quality, in the embodiment, locating hole 213's cross-section is the rectangle, its quantity is four, use rotor frame 21's axis as central evenly distributed, and every locating hole 213 all is located between two sets of adjacent louvres 212, can understand, locating hole 213 also has the thermolysis.

The rotor frame 21 includes a central hole 214 for passing the rotating shaft 20, in order to facilitate the rotating shaft 20 to pass through the central hole 214 and improve the fastening force between the rotating shaft 20 and the rotor frame 21, protrusions 2140 protruding towards the inside are provided at both ends of the central hole 214, the number of the protrusions 2140 is not limited, and the number of the protrusions 2140 shown in fig. 4 is three, and the protrusions are uniformly distributed around the axis of the central hole 214 (the axis of the central hole 214 is the axis of the rotor frame 21) and are tightly fitted to the rotating shaft 20. Because the contact area between the rotating shaft 20 and the inner surface of the central hole 214 is reduced by the arrangement of the protruding portion 2140, the rotating shaft 20 can be more conveniently inserted, the requirement on the matching precision between the rotating shaft 20 and the rotor frame 21 is lower, and meanwhile, the protruding portion 2140 is tightly matched with the rotating shaft 20, so that the fastening force can be effectively improved, and the connection reliability is improved.

As shown in fig. 5, the stator 3 includes a stator core 30, a stator frame 31 connected to the stator core 30 by injection molding, and a plurality of windings 32 wound on the stator frame 31.

As shown in fig. 6 to 8, the stator core 30 includes an outer sleeve 300 attached to an inner wall of the housing 10, and a plurality of stator teeth 301 attached to the outer sleeve 300 and extending to an inside of the outer sleeve 300. The outer sleeve 300 is substantially circular, the stator teeth 301 include an extending portion 3010 connected to the outer sleeve 300 and a limiting plate portion 3011 disposed on one end of the extending portion 3010 near the center of the outer sleeve 300, two sides of the limiting plate portion 3011 extend to beyond two sides of the stator teeth 301, the width of the limiting plate portion 3011 is greater than that of the stator teeth 301, an inner end face 3012 of the limiting plate portion 3011 facing the center of the outer sleeve 300 is an arc face, and the arc face is centered at the center of the outer sleeve 300, that is, disposed coaxially with the rotor 2, so that the shortest distance between the limiting plate portion and the magnet 22 is always the same, and the magnetic force is more balanced.

The stator core 30 is preferably formed by laminating silicon steel sheets, and heat dissipation holes or positioning holes may be formed therein for heat dissipation or positioning.

The stator frame 31 is used for connecting the stator core 30 and the winding 32, and includes an outer frame 310 connected to the outer sleeve 300 and a stator tooth sleeve 311 connected to the outer frame 310, and the winding 32 is wound on the stator tooth sleeve 311.

The outer frame 310 includes an outer surface 3100 to be attached to an inner surface 3000 of the outer tube 300, and in order to improve a connection strength between the outer frame and the outer frame, the outer surface 3100 of the outer frame 310 is provided with a protrusion 3101 extending in an axial direction of the outer frame 310, and accordingly, the inner surface 3000 of the outer tube 300 has a stopper groove 3001 to be fitted to the protrusion 3101, and circumferential looseness between the both can be prevented by fitting the stopper groove 3001 to the protrusion 3101.

Stator frame 31 is provided with a mating hole 312 extending from outer surface 3100 to stator teeth sleeve 311, stator teeth 301 are accommodated inside mating hole 312, and inner end surface 3012 of limiting plate portion 3011 is exposed to stator teeth sleeve 311 to reliably transmit magnetic force. As shown in fig. 7 and 8, stator teeth sleeve 311 has a fixing cover 3110 for accommodating limiting plate portion 3011, fixing cover 3110 has a first end face 3111 facing the center of stator frame 31, preferably, first end face 3111 is an arc face having the same diameter as inner end face 3012 so that the two faces are flush with each other, and first end face 3111 is provided with a recessed groove 3112 communicating with mating hole 312, so that stator frame 31 can be prevented from shielding the outer edge of inner end face 3012 during injection molding, and inner end face 3012 can be more reliably exposed to first end face 3111. Preferably, the recess 3112 is formed along the axial direction of the stator frame 31 and penetrates both ends of the fixed cover 3110.

As shown in fig. 9, the circuit assembly 4 includes a circuit board 40, and a cable 41 and a plug 42 both connected to the circuit board 40.

As shown in fig. 7 and 9, a plurality of sockets 313 are provided in stator frame 31, and plug members 42 are positioned corresponding to sockets 313, so that circuit board 40 and stator frame 31 can be fixed relative to each other by inserting plug members 42 into sockets 313.

The cable 41 is connected to an external device (e.g., a motor driver) for supplying power and transmitting signals to control the start, stop, and rotation of the motor. The cable 41 generally includes a power supply cable for supplying power to the winding 32 and a control cable for transmitting a signal for control. As shown in fig. 10 and 11, a wire base 14 and a wire pressing member 15 connected to the wire base 14 are disposed on the rear end cover 12, a wire guiding hole 140 communicating the cavity 100 with the outside of the motor is formed between the wire base 14 and the wire pressing member 15, and the wire base 14 further includes a partition 141 extending into the cavity 100, the partition 141 separating the control cables from the power supply cables, so as to arrange the cables 41 of different types more neatly and facilitate the differentiation and wiring.

Preferably, the position between the wire pressing member 15 and the wire housing 14 is adjustable, so that the cable 41 can be compressed by reducing the height of the wire routing hole 140. As shown in fig. 12, as a preferred embodiment, the wire routing seat 14 is provided with two first tooth surfaces 142 oppositely arranged at two sides of the wire routing hole 140, the first tooth surfaces 142 are provided with inverted teeth, and two second tooth surfaces 150 matched with the first tooth surfaces 142 are arranged at two sides of the wire pressing member 15, the first tooth surfaces 142 allow the second tooth surfaces 150 to move towards the direction of reducing the height of the wire routing hole 140, but prevent the second tooth surfaces 150 from moving towards the opposite direction, so that the wire pressing member 15 can move on the wire routing seat 14 in a single direction.

As shown in fig. 2, 3 and 9, the circuit assembly 4 further includes a hall sensor 43 disposed on the circuit board 40 to detect the rotation of the rotating shaft 20. Specifically, the circuit board 40 includes a ring portion 400 sleeved on the rotating shaft 20, the ring portion 400 is provided with at least one hall sensor 43 (3 in this embodiment), a magnetic ring 5 is disposed at a position on the rotating shaft 20 corresponding to the ring portion 400, and can rotate along with the rotating shaft 20, so as to be sensed by the hall sensor 43, and information such as a rotating speed, a rotating angle, and a number of rotating turns of the rotating shaft 20 can be calculated according to a sensing signal. In a preferred embodiment, the hall sensor 43 is exposed on the inner surface of the ring part 400, so that it is closer to the magnetic ring 5, and there is less interference between the two, and the measured result is more accurate. The hall sensor 43 is electrically connected to the cable 41, and can transmit a signal through the cable.

Further preferably, as shown in fig. 3, a mounting sleeve 6 is connected in an inner hole of the magnetic ring 5, the mounting sleeve 6 is sleeved on the rotating shaft 20, and the mounting sleeve 6 is connected with the rotating shaft 20, so that the position of the magnetic ring 5 on the rotating shaft 20 can be adjusted by pushing the mounting sleeve 6 in the mounting process, and the magnetic ring 5 is prevented from being damaged due to direct contact with the magnetic ring 5 in the mounting process. The material of the mounting sleeve 6 is not limited, and as a preferred embodiment, the mounting sleeve 6 is a copper sleeve.

As shown in fig. 13, knurling 60 may be provided on the outer surface of the mounting sleeve 6, so as to provide a larger friction force between the magnetic ring 5 and the mounting sleeve 6, thereby preventing the magnetic ring 5 and the mounting sleeve 6 from loosening, and ensuring a more reliable connection.

The utility model can embed the magnet part into the rotor frame by arranging the groove for accommodating the magnet on the outer surface of the rotor frame, thereby using the magnet with thicker thickness, improving the magnetic field intensity of the magnet and further increasing the torque of the motor; in addition, the groove comprises a first bottom surface and a second bottom surface which are obliquely arranged with each other, so that the contact area between the groove and the magnet can be increased, the connection between the groove and the magnet is firmer, and the guiding and the positioning during the magnet installation are convenient.

The above only is the embodiment of the present invention, not limiting the patent scope of the present invention, all the equivalent structures or equivalent processes that are used in the specification and the attached drawings or directly or indirectly applied to other related technical fields are included in the patent protection scope of the present invention.

Claims (10)

1. An electric machine, comprising:

a housing assembly (1);

a stator (3) connected to the housing assembly (1); and the number of the first and second groups,

the rotor (2) penetrates through the stator (3), and the rotor (2) comprises a rotating shaft (20) rotatably connected with the shell component (1), a rotor frame (21) connected to the rotating shaft (20) and a plurality of magnets (22) connected to the rotor frame (21);

the rotor frame (21) is provided with a plurality of grooves (210) on the outer peripheral surface, each groove (210) comprises a first bottom surface (2100) and a second bottom surface (2101) which is obliquely arranged relative to the first bottom surface (2100), and each groove (210) is internally provided with one magnet (22).

2. The machine according to claim 1, characterized in that a plurality of said grooves (210) are evenly distributed around the periphery of the rotor frame (21) centered on the axis of the rotor frame (21), and that the grooves (210) and the magnets (22) arranged in the grooves (210) are symmetrical with respect to a plane of symmetry (24) passing through the axis of the rotor frame (21).

3. The machine according to claim 1, characterized in that said magnet (22) comprises a first surface (220) abutting said first bottom surface (2100) and a second surface (221) abutting said second bottom surface (2101).

4. A machine according to claim 3, characterized in that a tip portion (222) is formed between said first surface (220) and said second surface (221), and that an escape groove (2102) is provided between said first bottom surface (2100) and said second bottom surface (2101) for accommodating said tip portion (222).

5. The electrical machine according to any of claims 1 to 4, wherein the housing assembly (1) comprises a housing (10) and a front end cap (11) and a rear end cap (12) connected to both ends of the housing (10), respectively, and the stator (3) comprises a stator core (30) fixed inside the housing (10), a stator frame (31) connected to the stator core (30), and a plurality of windings (32) connected to the stator frame (31).

6. The electric machine according to claim 5, wherein the stator core (30) comprises an outer sleeve (300), a plurality of stator teeth (301) connected to the outer sleeve (300) and extending into the outer sleeve (300), the stator frame (31) comprises an outer frame (310) connected to the outer sleeve (300) and a stator teeth sleeve (311) sleeved outside the stator teeth (301), and the winding (32) is wound on the stator teeth sleeve (311).

7. The electric machine according to claim 6, characterized in that the outer frame (310) comprises an outer surface (3100) adapted to an inner surface (3000) of the outer sleeve (300), the outer surface (3100) being provided with a rib (3101), the inner surface (3000) being provided with a limiting groove (3001) adapted to the rib (3101).

8. The electric machine according to claim 6, wherein the stator teeth (301) comprise a limiting plate portion (3011) and an extending portion (3010) connected between the limiting plate portion (3011) and the outer sleeve (300), the limiting plate portion (3011) is exposed to the stator teeth sleeve (311) towards an inner end surface (3012) of the rotor (2), and the inner end surface (3012) is a circular arc surface centered on the axis of the rotor (2).

9. The electric machine according to claim 8, characterized in that the outer sleeve (300) comprises a fixed cover (3110) for housing the stop plate portion (3011), the fixed cover (3110) comprising a first end face (3111) coinciding with the inner end face (3012), the first end face (3111) being provided with a recessed groove (3112) communicating with the mating hole (312).

10. The machine according to any of the claims 1 to 4, characterized in that it further comprises a circuit assembly (4) disposed in the housing assembly (1) and a magnetic ring (5) connected to the rotating shaft (20), the circuit assembly (4) comprising a circuit board (40) and Hall sensors (43) disposed on the circuit board (40), the Hall sensors (43) being disposed opposite to the outer circumferential surface of the magnetic ring (5).

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