JP5479008B2 - Brushless motor - Google Patents

Description

  The present invention relates to a so-called inner rotor type brushless motor in which a rotor is rotatably provided on a radially inner side of a stator.

  2. Description of the Related Art Conventionally, there is known a brushless motor that includes a stator having teeth around which a coil is wound and a rotor that is rotatably provided in the radial direction of the stator, and that drives the rotor by controlling energization of the coil. It has been. The rotor of this type of brushless motor has a rotating shaft, a substantially cylindrical rotor core that is fitted and fixed to the rotating shaft, and a magnet that is provided on the outer peripheral surface of the rotor core. As the magnet, a segment type magnet formed in a tile shape is often used. In this case, a plurality of magnets are arranged in parallel on the outer peripheral surface of the rotor core so that the magnetic poles change in order in the circumferential direction.

Here, when the rotor is rotated, each magnet repeatedly approaches and separates from the teeth of the stator, so that a change in magnetic flux with respect to each of the teeth is large, and this becomes a cogging torque and causes vibration and noise. For this reason, various techniques have been proposed to reduce the cogging torque.
For example, there is a segment type magnet that is divided into two in the axial direction and each is shifted in the circumferential direction (see, for example, Patent Document 1). With this configuration, when the rotor is rotated, the change in magnetic flux with respect to each tooth can be reduced, and the cogging torque can be reduced.

JP 2004-208341 A

However, in the above-described prior art, since each magnet is fixed to the rotor core using an adhesive or the like, it is difficult to position each magnet, and it is difficult to reduce the desired cogging torque. There is a problem that the work is troublesome.
Moreover, when it fixes with an adhesive agent, there exists a subject that a magnet may drop | omit by aging degradation.

  Accordingly, the present invention has been made in view of the above-described circumstances, and is capable of easily assembling the rotor while reducing the cogging torque and preventing the magnet from falling off due to aging. A motor is provided.

In order to solve the above-described problems, the invention described in claim 1 includes a stator and a rotor that is rotatably provided on a radially inner side of the stator, and the rotor is fixed around a rotating shaft. The magnet units are provided in a plurality of stages along the axial direction, and the magnet units of each stage are brushless motors arranged at a predetermined angle in the circumferential direction. A cylindrical rotor core that is externally fitted and fixed to a shaft, a plurality of magnets arranged in parallel along the circumferential direction on the outer circumferential surface of the rotor core, and a magnet holder for positioning the plurality of magnets in the circumferential direction The magnet holder is provided on a plurality of arm portions interposed between the plurality of magnets and one end side of the plurality of arm portions, and the arm portions are connected to each other. And a ring-shaped base portion which, in the end face of the base portion, the projections interposed between a plurality of magnets disposed on the adjacent magnet unit provided, on the basis of the position of the projection, adjacent The relative positions of the magnet units to be determined are determined.

By comprising in this way, a magnet can be positioned easily using a magnet holder and a magnet unit can be assembled easily.
Further, the magnet units at each stage can be arranged in a state of being shifted by a desired angle by simply overlapping the magnet units in the axial direction using the protrusions provided on the base portion of the magnet holder. For this reason, a cogging torque can be reduced reliably and assembly workability | operativity can be improved.
Furthermore, since each magnet is positioned and fixed using a magnet holder, it is not necessary to use an adhesive as in the prior art, and it is possible to prevent the magnet from falling off due to deterioration over time.

The invention described in claim 2 is characterized in that the rotor is provided with a magnet cover that integrally covers the periphery of the magnet unit in a state where the plurality of magnet units are provided on the rotating shaft. And
By comprising in this way, while being able to prevent damage to a magnet reliably, each magnet unit can be integrated reliably. For this reason, a highly reliable brushless motor can be provided.

According to a third aspect of the present invention, in the rotor core, a groove into which a part of the plurality of arm portions can be inserted is formed in a portion corresponding to the circumferentially adjacent magnets. A protrusion is inserted.
With this configuration, the magnet can be positioned more easily and reliably, so that the rotor assembly workability can be further improved.
In addition, since each magnet unit can be accurately arranged while being shifted by a desired angle, the cogging torque can be more reliably reduced.
The invention described in claim 4 is characterized in that the protrusion is formed with a tapered portion that gradually tapers toward the tip side.

According to the present invention, the magnet can be easily positioned using the magnet holder, and the magnet unit can be easily assembled.
Further, the magnet units at each stage can be arranged in a state of being shifted by a desired angle by simply overlapping the magnet units in the axial direction using the protrusions provided on the base portion of the magnet holder. For this reason, a cogging torque can be reduced reliably and assembly workability | operativity can be improved.
Furthermore, since each magnet is positioned and fixed using a magnet holder, it is not necessary to use an adhesive as in the prior art, and it is possible to prevent the magnet from falling off due to deterioration over time.

It is a longitudinal cross-sectional view of the brushless motor in embodiment of this invention. It is a perspective view which shows the lamination | stacking state of the magnet unit in embodiment of this invention. It is a disassembled perspective view of the magnet unit in the embodiment of the present invention. It is a perspective view of the magnet holder in the embodiment of the present invention. It is a top view of the magnet holder in the embodiment of the present invention.

(Brushless motor)
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of the brushless motor 1.
As shown in FIG. 1, the brushless motor 1 is used in, for example, an electric power steering device (EPS), and includes a stator 2 and a rotor 3 disposed on the radially inner side of the stator 2. The rotor 3 is rotatably supported by a bracket 4 fixed to one end of the stator 2.

The stator 2 includes a substantially cylindrical stator housing 11 and a substantially cylindrical stator core 12 that is fitted and fixed to the stator housing 11.
One end side (bracket 4 side) of the stator housing 11 is formed with an inlay portion 11 a that is used when the stamper is joined to the bracket 4. Further, a diameter-reduced portion 13 having a diameter reduced by a step is formed on the inner peripheral surface of the stator housing 11, and the stator core 12 is positioned in the axial direction by the step surface 13 a of the diameter-reduced portion 13. .

The stator core 12 has an annular core body 15 that forms an outer peripheral portion, and the outer peripheral surface of the core main body 15 is fixed to the inner peripheral surface of the stator housing 11 by shrink fitting or the like. The core body 15 is a part that forms an annular magnetic path of the stator core 12.
A plurality (9 in this embodiment) of teeth portions 14 are provided on the core body 15 so as to protrude radially inward in the circumferential direction at equal intervals. Each tooth portion 14 is formed in a substantially T shape in an axial plan view, and the coil 7 is wound from the insulator 6 mounted thereon.

  Between teeth portions 14 adjacent in the circumferential direction, dovetail-shaped slots (not shown) are formed extending in the axial direction, and the coil 7 is inserted into these slots. The stator core 12 may be configured by joining a plurality of core units each having a tooth portion 14 divided in the circumferential direction, or may be integrally formed without being divided in the circumferential direction.

The terminal portion 45 of the coil 7 wound around each tooth portion 14 is pulled out toward the other end side (the side opposite to the bracket 4) of the stator housing 11 and connected to the bus bar unit 46 disposed here. Has been.
The bus bar unit 46 is for supplying electric power from the outside to the coil 7, and a plurality of metal bus bars 44 are embedded in a substantially annular resin mold body 43 in the axial direction. . A terminal portion 45 of a predetermined coil 7 is connected to each bus bar 44.

Further, the bus bar unit 46 is connected to a power connector 47 protruding from the outer peripheral portion of the stator housing 11.
A receiving portion 48 is integrally formed at one end of the power connector 47. The receiving portion 48 is formed so that one end of a power cable (not shown) extending from an external power source (not shown) can be fitted and fixed, and can supply electric power from the outside to the bus bar unit 46.

  Further, on the other end side of the power connector 47, a flange portion 49 that extends in close contact with the outer surface of the stator housing 11 is extended. Further, the power connector 47 is integrally formed with a connector terminal 64 penetrating from one end to the other end. The other end (end on the bus bar unit 46 side) of each connector terminal 64 is electrically connected to the bus bar unit 46.

  The bracket 4 fixed to one end side of the stator housing 11 is formed in a substantially cylindrical shape, and is fastened and fixed to the stator housing 11 with bolts (not shown) or the like. At the end of the bracket 4, a joint 4 a that fits into the spigot 11 a when being abutted against the stator housing 11 is integrally formed. A packing 23 such as an O-ring is mounted in a groove carved in the outer periphery of the joint 4a.

The other end of the bracket 4 is opened, for example, so that a rack shaft of an electric power steering device can be inserted. A bearing 25 is press-fitted into the bracket 4 on the opening side. A resolver stator 26 a constituting one of resolvers 26 for detecting the rotational position of the rotor 3 is fixed to the stator 2 side of the bearing 25.
The resolver stator 26a has a core 56 formed by laminating plates made of a magnetic material. The core 56 is provided with a tooth portion 56a projecting radially inward, and a resolver coil 57 is wound around the tooth portion 56a.

The end of the winding of each resolver coil 57 is electrically connected to a sensor connector 27 protruding from the outer periphery of the bracket 4.
The sensor connector 27 has a receiving portion 61 into which a signal cable can be fitted at one end, and the other end is inserted into the bracket 4. In addition, a flange portion 62 that extends in close contact with the outer surface of the bracket 4 is provided on the outer periphery on the other end side. Further, a connector terminal 63 penetrating from one end to the other end is integrally formed in the sensor connector 27, and a resolver coil 57 is electrically connected to the other end (the end on the resolver stator 26a side). ing.

(Rotor)
The rotor 3 has a rotary shaft 22 formed of a hollow shaft, and a rack shaft (not shown) can be inserted into the rotary shaft 22, for example. The rack shaft forms a rack and pinion mechanism in the gear box of the vehicle, and is movable in the axial direction of the brushless motor 1 in accordance with an operation of a steering wheel (not shown). Both ends of the rack shaft are connected to the wheels of the vehicle via a knuckle arm or the like.

One end of the rotary shaft 22 is pivotally supported by a bearing 25 press-fitted into the bracket 4. A resolver rotor 26 b constituting the other of the resolver 26 is fixed to the outer peripheral surface on one end side of the rotating shaft 22. The resolver rotor 26b is configured by a substantially annular permanent magnet in which a plurality of salient poles (not shown) are arranged at equal intervals in the circumferential direction, or a substantially annular laminated steel plate.
As a result, when the resolver rotor 26b rotates together with the rotating shaft 22, the gap permeance between the resolver rotor 26b and the resolver stator 26a varies. The resolver 26 can detect the rotational position of the rotary shaft 22 based on the fluctuation of the gap permeance.

FIG. 2 is a perspective view showing a state in which the magnet unit 31 is overlapped in the axial direction, and FIG. 3 is an exploded perspective view of the magnet unit 31.
As shown in FIGS. 1 to 3, magnet units 31, 31, 31 that are stacked in the axial direction and are configured in three stages are fitted and fixed at positions facing the stator core 12 of the rotating shaft 22.
Here, since each magnet unit 31 is comprised the same, respectively, in the following description, the one magnet unit 31 is demonstrated.

The magnet unit 31 includes a substantially cylindrical rotor core 32 that is externally fitted and fixed to the rotary shaft 22, and a plurality (six in this embodiment) of magnets 33 that are arranged along the circumferential direction on the outer peripheral surface of the rotor core 32. And a magnet holder 34 for positioning the magnet 33.
The rotor core 32 is formed by laminating a plurality of metal plates or press molding a soft magnetic powder body. The inner diameter of the rotor core 32 is set so that the rotary shaft 22 can be press-fitted. Further, the axial length L1 of the rotor core 32 is set to be about 1/3 of the axial length L2 of the stator core 12.

  A plurality (six in this embodiment) of grooves 35 corresponding to the number of magnets 33 are formed on the entire outer surface 32 a of the rotor core 32 along the axial direction. The plurality of grooves 35 are formed at equal intervals in the circumferential direction. The groove 35 is formed in a dovetail shape so that the groove width gradually decreases toward the radially outer side.

  The magnet 33 is a segment-type permanent magnet formed in a tile shape, and is arranged so that the magnetic poles change in order in the circumferential direction. The axial length L3 of the magnet 33 is set so as to substantially match the axial length L1 of the rotor core 32. The circumferential width H1 of the magnet 33 is set so as to substantially coincide with the distance L4 between the grooves 35 adjacent to the circumferential direction of the rotor core 32. That is, it can be said that the groove 35 is formed between the magnets 33 adjacent to each other in the circumferential direction.

  Furthermore, the magnet 33 is formed so as to gradually become thinner from the center in the circumferential direction toward the outer side in the circumferential direction. In other words, the inner peripheral surface 33a of the magnet 33 is formed along the outer peripheral surface 32a of the rotor core 32, while the radius of curvature of the outer peripheral surface 33b of the magnet 33 is set to be smaller than the radius of curvature on the inner surface side. Has been.

4 is a perspective view of the magnet holder 34, and FIG. 5 is a plan view of the magnet holder 34.
As shown in FIGS. 3 to 5, the magnet holder 34 is made of resin, and includes a plurality of arm portions 36 interposed between the magnets 33, and the bracket 4 side end of the arm portion 36 (see FIG. 3). 3, a lower end in FIG. 4, and a ring-shaped base portion 37 that connects each arm portion 36 is integrally formed.

The arm part 36 is formed in a substantially T-shaped cross section, and includes a magnet holding part 38 that extends in the circumferential direction and a ridge part 39 that protrudes radially inward from the circumferential center of the magnet holding part 38. It is configured. The axial length L5 of the arm portion 36 is set to be shorter than the axial length L3 of the magnet 33. That is, the axial length L5 of the arm portion 36 is set to be shorter than the axial length L1 of the rotor core 32.
The convex portion 39 is formed by integrally forming a tapered portion 41 formed so as to be gradually tapered toward the inner side in the radial direction and a fitting convex portion 42 provided on the inner side in the radial direction of the tapered portion 41. It is.

Both side surfaces 41a and 41a of the tapered portion 41 are outer peripheral surfaces 33b of the magnet 33 and are formed so as to correspond to shapes on both sides in the circumferential direction. The fitting ridge 42 is inserted into the groove 35 formed in the rotor core 32, and has a substantially trapezoidal cross section corresponding to the shape of the groove 35.
That is, when the fitting protrusion 42 of the arm portion 36 is inserted in the groove 35 of the rotor core 32 along the axial direction, the outer peripheral surface 32a of the rotor core 32 and the side surface 41a of the tapered portion 41 of the arm portion 36 adjacent in the circumferential direction, Further, the storage recess 51 for storing the magnet 33 is formed by the magnet holding portion 38 (see FIG. 2).

  By storing the magnet 33 in the storage recess 51, the magnet 33 is sandwiched between the arms 36 on both sides in the circumferential direction and is positioned and fixed to the outer peripheral surface 32 a of the rotor core 32. Further, both sides in the circumferential direction of the magnet 33 are restrained radially inward by the magnet restraining portion 38 of the arm portion 36 and the side surface 41 a of the tapered portion 41. For this reason, the magnet 33 can be prevented from rattling or falling off in the radial direction.

Further, the movement of the magnet 33 in the axial direction is more reliably regulated by the base portion 37 formed integrally with the end of the arm portion 36 on the bracket 4 side.
A concave portion 52 is formed in a portion corresponding to the arm portion 36 on the outer peripheral portion of the base portion 37. By forming the recessed portion 52, the magnet holding portion 38 protrudes from the recessed portion 52 toward the outside in the radial direction at the joint portion of the arm portion 36 with the base portion 37.

Furthermore, a plurality (six in this embodiment) of recesses 53 are formed at equal intervals in the circumferential direction on the end surface 37a of the base portion 37 on the bracket 4 side, and protrusions 54 that can be inserted into the grooves 35 of the rotor core 32 here. Is formed.
Each protrusion 54 determines the relative position of the magnet units 31 that overlap in the axial direction, and is formed so that it can be inserted into the groove 35 of the rotor core 32 without rattling. Each projection 54 is formed with a tapered portion 54a that gradually tapers toward the tip side.

  Here, since the axial length L5 of the arm portion 36 is set to be shorter than the axial length L1 of the rotor core 32, when the magnet holder 34 is attached to the rotor core 32, the length of the rotor core 32 is reduced. A part of the groove 35 is exposed. The protrusion 54 of the magnet unit 31 at the other stage is inserted into the exposed portion of the groove 35.

  More specifically, when the third-stage magnet unit 31 is changed to the first-stage magnet unit 31, the second-stage magnet unit 31, and the third-stage magnet unit 31 in order from the bracket 4 side (upper side in FIG. 1), 3 The protrusion 54 of the second stage magnet unit 31 is inserted into the groove 35 of the second stage magnet unit 31. Further, the protrusion 54 of the second stage magnet unit 31 is inserted into the groove 35 of the first stage magnet unit 31. By comprising in this way, positioning of the rotation direction (circumferential direction) of the magnet unit 31 of each step | level is performed.

Here, as shown in FIGS. 2 and 4, each protrusion 54 is arranged at a position shifted by an angle θ1 in the circumferential direction from the position where the arm portion 36 of the base portion 37 is protruded (see FIG. 4). ). In other words, the protrusions 54 are arranged such that the magnet units 31 at the respective stages are displaced from each other in the circumferential direction and have a skew angle θ2 (see FIG. 2).
These angles θ1 and skew angle θ2 are theoretically determined angles. That is, the angle θ1 at which the cogging torque is minimized, and the skew angle θ2 are
θ2 = 360 ° / (the least common multiple of the number of magnetic poles and the number of slots) (1)
θ2 = θ1 × (the number of stages of the magnet unit 31) (2)
It is set to satisfy.

In the present embodiment, since six magnets 33 of each magnet unit 31 are arranged in parallel along the circumferential direction, the number of magnetic poles is six. Further, since six teeth portions 14 project from the stator core 12, the number of slots is nine. Therefore, the least common multiple of the number of magnetic poles and the number of slots is 18, and from equation (1), the skew angle θ2 is
θ2 = 20 °
Set to

Furthermore, in this embodiment, since the number of stages of the magnet unit 31 is 3, the angle θ1 is calculated from the equation (2) as follows:
θ1 ≒ 7 °
Set to
Further, when the three magnet units 31 configured as described above are stacked along the axial direction, the base portion 37 of the magnet holder 34 is interposed between the magnet units 31.

Here, when the magnets 33 adjacent to each other in the axial direction are shifted (skewed) in the circumferential direction, the magnets 33 having different polarities are close to each other. , 33 starts to generate a leakage magnetic flux. As a result, not only the generated torque as the brushless motor 1 is reduced, but also the effect of reducing the cogging torque is reduced.
However, in this embodiment, since the base portion 37 of the magnet holder 34 is interposed between the magnet units 31 adjacent in the axial direction, the base portion 37 restricts the movement of the magnet 33 in the axial direction. In addition, it functions as a shielding plate for reducing the leakage magnetic flux of the magnet 33.

As shown in FIG. 1, each magnet unit 31 fixed to the rotating shaft 22 is covered with a magnet cover 71 around the magnet unit 31.
The magnet cover 71 is formed in a substantially cylindrical shape by a metal plate (for example, stainless steel or the like). Both ends of the magnet cover 71 in the axial direction are crimped radially inward while covering the three-stage magnet unit 31.

(Assembly method of rotor)
Next, a method for assembling the rotor 3 will be described.
First, the arm portion 36 of the magnet holder 34 is inserted into the groove 35 formed in the rotor core 32. Then, the base portion 37 of the magnet holder 34 is brought into contact with the end surface of the rotor core 32. Thereby, the magnet holder 34 is positioned and fixed to the rotor core 32.

  Subsequently, the magnet 33 is attached to the storage recess 51 formed by the outer peripheral surface 32a of the rotor core 32 and the two arm portions 36 and 36 adjacent in the circumferential direction. At this time, the magnet 33 is inserted along the axial direction from the side opposite to the base portion 37 of the magnet holder 34 toward the storage recess 51. Then, the magnet 33 is sandwiched between the arm portions 36 of the magnet holder 34, and is positioned and fixed on the outer peripheral surface 32 a of the rotor core 32. Thereby, the assembly of the magnet unit 31 is completed.

After three magnet units 31 are assembled, the second-stage (middle stage in FIG. 1) magnet unit 31 is superimposed on the first-stage (upper stage in FIG. 1) magnet unit 31. At this time, the protrusion 54 formed on the magnet holder 34 of the second stage magnet unit 31 is inserted into the groove 35 of the first stage magnet unit 31. Since the tapered portion 54 a is formed on the protrusion 54, it can be smoothly inserted into the groove 35 of the first stage magnet unit 31.
Subsequently, the third-stage magnet unit 31 is overlaid on the second-stage magnet unit 31. Also at this time, the protrusion 54 of the third-stage magnet unit 31 is inserted into the groove 35 of the second-stage magnet unit 31.

Next, the three-stage magnet unit 31 is press-fitted into the rotary shaft 22. At this time, the base portion 37 of the first stage magnet holder 34 is directed to the rotating shaft 22 side, and the magnet unit 31 is press-fitted from the other end side (lower end side in FIG. 1) of the rotating shaft 22.
Subsequently, the magnet cover 71 is mounted so as to cover the surface of the three-stage magnet unit 31. Thereafter, the magnet cover 71 is fixed by caulking both ends of the magnet cover 71. Further, the resolver rotor 26 b is press-fitted into the rotating shaft 22 to complete the assembly of the rotor 3. The magnets 33 are magnetized after the assembly of the rotor 3 is completed.

(Function)
Under such a configuration, when the brushless motor 1 is energized, a predetermined current is supplied to the coil 7 wound around the stator core 12 and a magnetic field is generated in each tooth portion 14. Then, an attractive force and a repulsive force are generated between each magnet 33 of the rotor 3 and the rotor 3 rotates.
At this time, the magnet unit 31 is configured in three stages, and each stage of the magnet unit 31 has a skew angle θ2 (see FIG. 2), so that each of the teeth portions 14 when the rotor 3 rotates is supported. The change in magnetic flux is reduced.

  Furthermore, each magnet 33 is formed so as to gradually become thinner from the center in the circumferential direction toward the outer side in the circumferential direction. For this reason, the air gap between each magnet 33 and the teeth part 14 becomes large gradually as it goes to the circumferential direction outer side from the circumferential direction center (refer FIG. 2). That is, the influence of the magnetic force on the teeth portion 14 of each magnet 33 can be gradually weakened from the circumferential center of the magnet 33 toward the circumferential outer side. For this reason, the rapid change of the magnetic flux when the gap | interval of each magnet 33 passes the teeth part 14 can be reduced.

(effect)
Therefore, according to the above-described embodiment, the cogging torque of the brushless motor 1 can be reliably reduced.
Further, when assembling the rotor 3, the magnet holder 31 is attached to each rotor core 32 and then the magnet 33 is inserted between the arm portions 36 to complete the assembly of the magnet unit 31. Furthermore, it is possible to superimpose the magnet units 31 of the respective stages while being shifted by a predetermined angle by simply inserting the protrusions 54 of the magnet units 31 of the respective stages into the grooves 35 of the magnet units 31 of the other stages. For this reason, the rotor 3 can be easily assembled and the assembly workability can be improved.

Since each magnet 33 is positioned and fixed using the magnet holder 34, it is not necessary to use an adhesive as in the conventional case, and the magnet 33 can be prevented from falling off due to deterioration over time.
Further, by inserting the arm portion 36 into the groove 35 formed in the rotor core 32, the arm portion 36 is surely fixed on the outer peripheral surface 32a of the rotor core 32 without rattling, and the positioning of each arm portion 36 is performed. Can be easily performed. For this reason, the assembly workability can be further improved and the magnet 33 can be securely fixed.
Further, by covering the three-stage magnet unit 31 with one magnet cover 71, the magnet 33 can be prevented from being damaged, and each magnet unit 31 can be reliably integrated. For this reason, a highly reliable brushless motor can be provided.

The present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention.
In the above-described embodiment, the case where the magnet units 31, 31, 31 configured in three stages are fitted and fixed to the rotating shaft 22 of the rotor 3 has been described. However, the present invention is not limited to this, and the magnet unit 31 may be configured by a plurality of stages of two or more stages.

  Furthermore, in the above-described embodiment, for example, the six magnets 33 are arranged in one magnet unit 31 in the circumferential direction, and the number of slots of the stator core 12 is set to nine, and the brushless motor 1 has six poles and nine slots. Explained the case. However, the present invention is not limited to this, and the magnet holder 34 can be applied to brushless motors having various numbers of magnetic poles. In this case, the number of arm portions 36 of the magnet holder 34 and the number of grooves 35 of the rotor core 32 may be set according to the number of magnetic poles.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Stator 3 Rotor 4 Bracket 11 Stator housing 12 Stator core 22 Rotating shaft 31 Magnet unit 32 Rotor core 33 Magnet 34 Magnet holder 35 Groove 36 Arm part 37 Base part 54 Protrusion
54a Tapered part 71 Magnet cover

Claims (4)

A stator,
A rotor provided rotatably on the radially inner side of the stator,
The rotor is
A plurality of magnet units fixed around the rotating shaft are provided along the axial direction.
The magnet units at each stage are brushless motors that are arranged at a predetermined angle in the circumferential direction,
Each stage magnet unit
A cylindrical rotor core externally fixed to the rotating shaft;
A plurality of magnets arranged side by side along the circumferential direction on the outer peripheral surface of the rotor core;
A magnet holder for positioning the plurality of magnets in the circumferential direction;
The magnet holder is
A plurality of arm portions interposed between the plurality of magnets;
A ring-shaped base portion that is provided on one end side of the plurality of arm portions and connects the arm portions;
Provided on the end surface of the base portion is a protrusion interposed between a plurality of magnets disposed in adjacent magnet units,
A brushless motor configured to determine a relative position between adjacent magnet units based on a position of the protrusion.   2. The brushless according to claim 1, wherein the rotor is provided with a magnet cover that integrally covers the periphery of the magnet unit in a state where the plurality of stages of magnet units are provided on the rotating shaft. motor. The rotor core is formed with a groove into which a part of the plurality of arm portions can be inserted in a portion corresponding to the gap between the magnets adjacent in the circumferential direction.
The brushless motor according to claim 1, wherein the protrusion is inserted into the groove. The brushless motor according to any one of claims 1 to 3, wherein the protrusion is formed with a tapered portion that gradually tapers toward the tip side.

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