JP2008228367A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless motor in which a rotating shaft can surely be fixed easily and cost effectively and an rotational angle of the rotating shaft can be detected with high precision. <P>SOLUTION: This brushless motor 1 includes a stator 3 fitted inside and fixed on a yoke 2 and a rotor 4 provided rotatably to the stator 3. The other end of the rotating shaft 9 of the rotor 4 is supported rotatably by a rear bearing 14 provided at the other end side of the axial direction of the yoke 2 and an encoder 25 for detecting the rotational angle of the rotating shaft 9 is provided at the other side of the rotating shaft 9. A contracted diameter portion 71, whose diameter is contracted by a step and on which the rear bearing 14 is inserted movably in the axial direction, is formed at the other side of the rotating shaft 9. The inner ring 14a of the rear bearing 14 fitted outside the contracted diameter portion 71 is pinched in the axial direction by a step portion 73 formed on the rotating shaft 9 and the rotary encoder 25. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a brushless motor including a rotation angle detection device that detects a rotation angle of a rotor.

In general, a brushless motor has a stator that is fitted and fixed to a bottomed cylindrical yoke, and a rotor that is rotatably provided to the stator.
The stator has a substantially cylindrical stator core, and a plurality of teeth portions for winding a coil around the stator core are formed protruding inward in the radial direction. Between each tooth part, a dovetail slot extending in the axial direction is formed, and a coil is inserted from this slot so that the coil is wound around each tooth part. On the other hand, the rotor has a rotating shaft that is rotatably supported by the yoke, and a permanent magnet is disposed on the rotating shaft along the circumferential direction.
In the brushless motor configured as described above, when the coil is energized, a magnetic field is formed in the tooth portion, and the rotating shaft is driven by a magnetic attractive force or repulsive force generated between the permanent magnet of the rotor.

This type of brushless motor is sometimes used to link a speed reduction mechanism to a rotating shaft and drive a driven body via the speed reduction mechanism. Further, in order to control the operation of the driven body, a brushless motor may be provided with a rotary encoder. This rotary encoder is a rotation angle detection device for detecting the rotation angle of the rotation shaft of the rotor, and is disposed at one end of the rotation shaft and is arranged with the rotation plate interposed between the rotation plate and the rotation plate. A light emitting element and a light receiving element. The rotary plate is provided with a plurality of slits. And the light irradiated from the light emitting element is received by the light receiving element through the slit, and this becomes a detection signal so that the rotation angle of the rotating shaft can be recognized (see, for example, Patent Document 1).
JP 2006-282101 A

  By the way, for example, when using a harmonic gear mechanism (also referred to as a harmonic drive mechanism (registered trademark), a strain wave gearing mechanism, etc.) as a speed reduction mechanism, the driven body is driven by directly connecting it to a rotating shaft. A thrust is generated in the thrust direction from the harmonic gear mechanism, and the rotation shaft of the brushless motor is pressed or pulled depending on the rotation direction. If the position of the rotating shaft is shifted due to this pressing force or tensile force, the distance between the rotary plate of the rotary encoder provided on the rotating shaft and the light receiving / emitting element changes, and it becomes difficult to detect the rotation angle of the rotating shaft. There are challenges.

  In addition, when the rotation shaft is fixed so that the position of the rotation shaft does not shift and the length of the rotation shaft does not become long, the outer ring of the bearing for rotatably supporting the rotation shaft is press-fitted and fixed to the bearing housing. In addition, it is necessary to press-fit and fix the inner ring on the rotating shaft. For this reason, not only a special assembling device is required, which requires centering accuracy between the bearing and the rotary shaft, but also a special bearing with a wider internal clearance of the bearing in consideration of deformation when the inner and outer rings of the bearing are pressed. Is necessary and costly.

  Accordingly, the present invention has been made in view of the above-described circumstances, and is a brushless capable of reliably and reliably fixing the rotation shaft and detecting the rotation angle of the rotation shaft with high accuracy. A motor is provided.

  In order to solve the above-described problems, the invention described in claim 1 is provided with a yoke having a cylindrical portion, a stator fitted and fixed to the cylindrical portion of the yoke, and rotatably with respect to the stator. A rotation shaft of the rotor, one end side of which is rotatably supported by a first bearing provided on one end side in the axial direction of the yoke, while the other end side is on the other end side in the axial direction of the yoke. A brushless motor that is rotatably supported by a second bearing provided, and provided with a rotation angle detection device for detecting a rotation angle of the rotation shaft on the other end side of the rotation shaft, On the other end side, a reduced diameter portion is formed which is reduced in diameter by a step and into which the second bearing is inserted so as to be movable in the axial direction, and an inner ring of the second bearing which is externally fitted to the reduced diameter portion is A step formed on the rotation shaft and the rotation angle detection device Wherein the sandwiching axially between.

  According to a second aspect of the present invention, the inner ring of the first bearing is press-fitted and fixed to one end side of the rotating shaft, and the outer ring of the first bearing is fitted to a first bearing housing provided on one end side in the axial direction of the yoke. Is inserted so as to be movable in the axial direction.

  The invention described in claim 3 is characterized in that an outer ring of the second bearing is press-fitted and fixed to a second bearing housing provided on the other axial end side of the yoke.

  According to a fourth aspect of the present invention, the rotation angle detecting device is a rotary encoder provided with a rotating plate, the rotating plate is attached to the reduced diameter portion of the rotating shaft via a hub, and the hub and the rotating The inner ring of the second bearing is held in the axial direction by the step portion of the shaft.

  According to the present invention, the inner ring of the second bearing inserted into the reduced diameter portion of the rotating shaft is sandwiched between the stepped portion of the rotating shaft and the rotation angle detecting device, so that the inner ring of the second bearing is not press-fitted and fixed to the rotating shaft. The rotating shaft and the second bearing can be securely fixed. For this reason, if only the outer ring of the second bearing is press-fitted and fixed to the second bearing housing, it is possible to prevent displacement of the rotating shaft. Therefore, it is possible to detect the rotation angle of the rotating shaft with high accuracy by securely fixing the rotating shaft, and it is possible to use a general-purpose bearing as the second bearing, thereby reducing the cost. Can do.

Further, since the second bearing may be inserted into the reduced diameter portion of the rotating shaft without being press-fitted, a special assembling device is not required and the rotating shaft can be easily assembled.
Further, since the rotation shaft and the second bearing can be fixed using a rotation angle detection device or the like provided on the other end side of the rotation shaft, a part for holding the second bearing in the axial direction is prepared. There is no need. For this reason, an increase in the number of parts can be prevented.

Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the brushless motor 1 is a so-called inner rotor type having a yoke 2, a stator 3 fitted and fixed to the yoke 2, and a rotor 4 provided rotatably with respect to the stator 3. It is an electric motor.

The yoke 2 is formed in a bottomed cylindrical shape, and has a peripheral wall 5 and an end portion (bottom portion) 6. On the inner peripheral surface side of the peripheral wall 5, a reduced diameter portion 7 that is reduced inward in the radial direction by a step near the end portion 6 is formed. The stator 3 is brought into contact with the stepped portion 8 formed by the reduced diameter portion 7 so that the stator 3 is positioned in the axial direction.
A yoke-side bearing housing 10 is formed on the end portion 6 of the yoke 2 substantially in the center in the radial direction, and a front bearing 11 for rotatably supporting one end side of the rotating shaft 9 is provided. The outer diameter E1 of the peripheral wall 5 is set to about 20 to 30 mm.

  The stator 3 is formed by laminating a metal plate obtained by punching a plate material of a magnetic material with a press or the like in the axial direction, or press-molding a soft magnetic powder, and has a substantially cylindrical stator core 44. have. The stator core 44 is formed by integrally molding a core main body 45 that forms a peripheral wall and a plurality of (in this embodiment, nine) tooth portions 46 that protrude radially inward from the core main body 45.

The teeth portion 46 is a portion around which the coil 48 is wound, and is provided at equal intervals in the circumferential direction. The tooth portion 46 is provided with three U-phase, V-phase, and W-phase air-core coils 52 detachably in the radial direction via insulating sheets (not shown). The air core coil 52 is formed by winding the coil 48 in advance.
A pair of retaining insulators 54 and 55 are set on the stator core 44 so as to be inserted from the outside in the axial direction toward the stator core 44 side.

  These retaining insulators 54 and 55 are for restricting movement of the air-core coil 52 in the withdrawal direction, and have a plurality of interposing portions 58 and 59 interposed between the respective tooth portions 46. ing. Ring portions 56 and 57 having substantially annular shapes are integrally formed on the outer side ends of the interposition portion 58 and the interposition portion 59, respectively. That is, the retaining insulators 54 and 55 are in a state where the interposition portions 58 and 59 are connected by the ring portions 56 and 57, respectively.

  Of the pair of retaining insulators 54, 55, the retaining insulator 54 attached to the rear bracket 13 side has a ring portion 56 formed with a substantially annular inlay portion 62. The inlay portion 62 is for positioning in a radial direction and an axial direction of a power distribution plate 63 to be described later, and is formed so as to extend outward from the inner peripheral edge of the ring portion 56 in the axial direction. Yes. In addition, the spigot part 62 has a diameter smaller than that of the ring part 56, thereby forming a stepped part 64.

  The power distribution plate 63 is for supplying external power to the air-core coil 52 attached to the tooth portion 46 of the stator 3, and is connected to the terminal portion of the coil 48 that forms the air-core coil 52. . The power distribution plate 63 includes a substantially disk-shaped substrate 65 and lead wires 66 electrically connected to the substrate 65. On the inner periphery of the substrate 65, an inlay portion 62 of a retaining insulator 54 is fitted.

  Further, the surface of the substrate 65 on the side of the stator 3 is in contact with the stepped portion 64 of the retaining insulator 54. Thus, the distribution plate 63 is positioned in the radial direction and the axial direction by the inlay portion 62 of the retaining insulator 54. The lead wire 66 is drawn to the outside through a grommet 67 provided on the peripheral wall 5 of the yoke 2 and is electrically connected to an external power source (not shown). As a result, the power from the external power source can be supplied to the coil 48 of the stator 3 via the power distribution plate 63.

The rotor 4 has an iron rotating shaft 9 and a ring-shaped permanent magnet 12 fitted and fixed to the rotating shaft 9. The permanent magnet 12 is magnetized so that the magnetic poles are changed in order in the circumferential direction (in this embodiment, magnetized to 8 poles).
Here, a yoke-side reduced diameter portion 70 and a rear bracket-side reduced diameter portion 71 that are reduced in diameter by steps are formed on one end side and the other end side of the rotary shaft 9, respectively. An inner ring 11 a of a front bearing 11 provided in the yoke-side bearing housing 10 is press-fitted into a yoke-side reduced diameter portion 70 formed on one end side of the rotating shaft 9.

  Further, the outer ring 11 b of the front bearing 11 is inserted into the yoke-side bearing housing 10 so as to be movable in the axial direction. The front bearing 11 is adapted to determine the position in the axial direction by contacting the stepped portion 72 formed on the proximal end side of the yoke-side reduced diameter portion 70. The press-fitting allowance between the yoke-side reduced diameter portion 70 and the inner ring 11a of the front bearing 11 is preferably about 2 to 10 μm considering that both are made of iron.

  On the other hand, an inner ring 14 a of the rear bracket side bearing 14 is inserted into a rear bracket side reduced diameter portion 71 formed on the other end side of the rotary shaft 9 so as to be movable in the axial direction with respect to the rotary shaft 9. The rear bearing 14 is provided on the rear bracket 13 that closes the opening 2 a of the yoke 2, whereby the rear bracket-side reduced diameter portion 71 is rotatably supported on the rear bracket 13 via the rear bearing 14. It is in the state that was done.

  The rear bracket 13 is formed of an aluminum material in a substantially disk shape, and has an inlay portion 15 that fits inside the yoke 2. On the outer peripheral surface of the spigot portion 15, a plurality of female screw portions 17 are engraved at equal intervals in the circumferential direction. On the peripheral wall 5 of the yoke 2, there is a portion corresponding to the female screw portion 17 of the spigot portion 15. Bolt holes 18 are formed. The bolt 19 is screwed into the female screw portion 17 and the bolt hole 18 so that the rear bracket 13 is not rotatable in the circumferential direction with respect to the yoke 2.

  A rear bracket-side bearing housing 16 that protrudes toward the permanent magnet 12 side (lower side in FIG. 1) of the rotor 4 is formed at a substantially radial center of the inlay portion 15. The rear bracket side bearing housing 16 is formed with an insertion hole 20 through which the rotary shaft 9 can be inserted, and an outer ring 14b of the rear bearing 14 is press-fitted therein.

  The press-fitting allowance between the outer ring 14b of the rear bearing 14 and the insertion hole 20 of the rear bracket side bearing housing 16 is preferably about 20 to 30 μm in consideration of the fact that the rear bracket 13 is made of aluminum. The rear bearing 14 is adapted to be positioned in the axial direction by abutting against a stepped portion 20a formed on the insertion hole 20 side of the rear bracket side bearing housing 16.

A flange portion 21 is formed on the outer peripheral edge of the inlay portion 15 on the side opposite to the rear bracket side bearing housing 16 (upper side in FIG. 1). When the flange portion 21 abuts against the opening end of the yoke 2, the axial position of the rear bracket 13 is determined.
In addition, a stepped recess 22 is formed at a substantially central portion in the radial direction on the opposite side of the inlay portion 15 from the rear bracket side bearing housing 16, and the rotary 23 is accommodated therein.

  The rotary 23 constitutes a rotary encoder 25 which is a rotation angle detection device for detecting the rotation angle of the rotation shaft 9, and is fastened and fixed to the other end of the rotation shaft 9 by a bolt 26. The rotary 23 has a hub 27 formed in a stepped cylindrical shape. The hub 27 includes a first cylinder portion 27a fitted on the rotary shaft 9, and a second cylinder that is provided on the opposite side of the first cylinder portion 27a from the rotor 4 and has a larger diameter than the first cylinder portion 27a. Part 27b.

A bolt hole 30 is formed near the second cylinder portion 27b on the inner peripheral surface side of the first cylinder portion 27a, and the bolt 26 is screwed therein.
Here, the axial length L1 of the first cylindrical portion 27a is set such that the front end of the first cylindrical portion 27a can slightly press the rear bearing 14 when the bolt 26 is tightened. Further, the outer diameter E2 of the first cylindrical portion 27a is set to a size that can contact only the inner ring 14a of the rear bearing 14.

  Therefore, the inner ring 14 a of the rear bearing 14 is held in the axial direction by the stepped portion 73 formed on the proximal end side of the rear bracket side reduced diameter portion 71 on the rotating shaft 9 and the hub 27 of the rotary 23. For this reason, the rotating shaft 9, the rotary 23, and the inner ring 14a of the rear bearing 14 are integrated. Moreover, since the outer ring 14b of the rear bearing 14 is press-fitted and fixed to the rear bracket-side bearing housing 16, the rotary shaft 9 and the rotary 23 are rotatably supported by the rear bracket 13 via the rear bearing 14. Become.

A substantially annular sensor magnet 28 is externally fitted and fixed to the outer peripheral surface of the second cylindrical portion 27 b of the hub 27. Moreover, the outer flange part 29 is formed in the opposite end to the 1st cylinder part 27a of the 2nd cylinder part 27b.
When the sensor magnet 28 comes into contact with the outer flange portion 29, the sensor magnet 28 is positioned in the axial direction. A rotary scale 31 is provided substantially at the center in the radial direction of the outer flange portion 29. An insertion hole 32 that allows a tool (not shown) used when fastening and fixing the rotary 23 to be inserted is formed substantially at the center in the radial direction of the rotary scale 31.

  A bottomed cylindrical holder 33 is provided outside the rotary 23 to cover it. The holder 33 is for positioning the rotary detection unit 24 constituting the rotary encoder 25, and the rotary detection unit 24 is attached so as to cover the outer surface of the holder 33. The rotary detection unit 24 is obtained by mounting various devices on a flexible substrate 34 having a substantially U-shaped cross section.

Specifically, a sensor module 35 is mounted on the flexible substrate 34 at a portion corresponding to the end portion (bottom wall) 33a of the holder 33, and a Hall IC (Integrated Circuit) 36 is provided at a portion corresponding to the peripheral wall 33b of the holder 33. Has been implemented.
The holder 33 is formed with a hole 37 and a notch 38 at portions corresponding to the sensor module 35 and the Hall IC 36, respectively. Further, an outer flange portion 39 is formed on the peripheral edge of the opening 33 on the peripheral wall 33b of the holder 33, and a storage groove 40 capable of storing the end portion of the flexible substrate 34 is formed in a portion corresponding to the Hall IC 36 here. .

  A cover 41 is provided outside the rotary detection unit 24 to cover it. The cover 41 is formed in a bottomed cylindrical shape, and has an end portion (bottom wall) 41a and a peripheral wall 41b. The cover 41 is attached to the rear bracket 13 that closes the opening of the peripheral wall 41b. The peripheral wall 41b is formed with a notch 42 for pulling out the flexible substrate 34 of the rotary detection unit 24 to the outside. The flexible substrate 34 drawn out from the notch 42 is connected to a control device (not shown).

Next, the procedure for assembling the rotor 4 to the yoke 2 will be described.
As shown in FIGS. 1 to 3, first, the permanent magnet 12 is externally fitted and fixed slightly closer to the rear bracket 13 (rightward in FIG. 2) than the approximate center in the axial direction of the rotating shaft 9. Next, the inner ring 11 a of the front bearing 11 is press-fitted into one end side of the rotating shaft 9, that is, the yoke-side reduced diameter portion 70. At this time, the inner ring 11a of the front bearing 11 is press-fitted until it comes into contact with a stepped portion 72 formed on the proximal end side of the yoke-side reduced diameter portion 70 (see FIG. 1).

Subsequently, as shown in FIG. 3, the outer ring 14 b of the rear bearing 14 is press-fitted into the insertion hole 20 of the rear bracket side bearing housing 16 formed in the rear bracket 13. At this time, the outer ring 14b of the rear bearing 14 is press-fitted until it comes into contact with a stepped portion 20a formed on the insertion hole 20 side of the rear bracket side bearing housing 16 (see FIG. 1).
Then, the rotor 4 having the front bearing 11 press-fitted and fixed to the rotary shaft 9 is inserted with the front bearing 11 facing the yoke 2 from the opening 2 a side of the yoke 2. Then, the outer ring 11 b of the front bearing 11 is inserted into the yoke-side bearing housing 10.

  Subsequently, the rear bracket 13 to which the rear bearing 14 is press-fitted and fixed is inserted with the rear bearing 14 facing the yoke 2 from the opening 2a side of the yoke 2. Then, the inner ring 14 a of the rear bearing 14 is inserted into the rear bracket side reduced diameter portion 71 of the rotating shaft 9. Thereafter, the rear bracket 13 is fastened and fixed to the yoke 2 with bolts 19.

  Next, the rotary 23 is set on the rear bracket reduced diameter portion 71 of the rotary shaft 9. At this time, the first cylindrical portion 27a of the rotary 23 is set toward the rotating shaft 9 side. Then, the rotary 23 is fastened and fixed to the rotary shaft 9 with a bolt 26. Then, when the rotary 23 is tightened, the hub 27 is displaced toward the rear bearing 14, and the inner ring 14 a of the rear bearing 14 is sandwiched between the hub 27 and the stepped portion 73 formed on the rotating shaft 9. Since the outer ring 14b of the rear bearing 14 is press-fitted and fixed to the rear bracket 13, this ensures that the rotor 4 is rotatably supported by the rear bracket 13 without shifting in the axial direction.

  On the other hand, the front bearing 11 that is press-fitted and fixed to the yoke-side reduced diameter portion 70 of the rotating shaft 9 is in a state in which the outer ring 11b is inserted into the yoke-side bearing housing 10 so as to be movable in the axial direction. An axial error during assembly of 4 can be allowed here. Thereby, the assembly of the rotor 4 to the yoke 2 is completed.

  Therefore, according to the above-described embodiment, the inner ring 14 a of the rear bearing 14 inserted into the reduced diameter portion 71 on the rear bracket side of the rotating shaft 9 is connected to the stepped portion 73 of the rotating shaft 9 and the hub 27 of the rotary 23 constituting the rotary encoder 25. Therefore, the rotary shaft 9 and the rear bearing 14 can be securely fixed without press-fitting and fixing the inner ring 14a of the rear bearing 14 to the rear bracket-side reduced diameter portion 71. For this reason, if only the outer ring 14 b of the rear bearing 14 is press-fitted and fixed to the rear bracket side bearing housing 16, it is possible to prevent the displacement of the rotary shaft 9. Therefore, it is possible to reduce the cost by using a general-purpose bearing without using a special bearing with a wider internal clearance of the bearing as in the prior art. In addition, the rotation shaft 9 can be securely fixed, and the rotation angle of the rotation shaft 9 by the rotary encoder 25 can be detected with high accuracy.

Further, since the rear bearing 14 has only to be inserted into the reduced diameter portion 71 on the rear bracket side of the rotating shaft 9 without press-fitting, no special assembling device is required, and the rotating shaft 9 can be easily assembled.
Further, since the rotary shaft 9 and the rear bearing 14 can be fixed using the hub 27 of the rotary 23 attached to the reduced diameter portion 71 on the rear bracket side of the rotary shaft 9, the rear bearing 14 is clamped in the axial direction. There is no need to prepare parts for For this reason, an increase in the number of parts can be prevented.

The inner ring 11a of the front bearing 11 is press-fitted and fixed to the yoke-side reduced diameter portion 70 of the rotary shaft 9, and the outer ring 11b of the front bearing 11 is inserted into the yoke-side bearing housing 10 so as to be movable in the axial direction. For this reason, even if an assembly error occurs when the rotor 4 is assembled to the yoke 2, the position of the front bearing 11 with respect to the yoke 2 is smoothly shifted, and an unreasonable force acts on the rotary shaft 9. There is no. Moreover, since the radial displacement of the front bearing 11 is regulated by the yoke-side bearing housing 10, the front bearing 11 has no risk of impairing its function. Therefore, the rotor 4 can be reliably assembled.
Further, the front bearing 11 also has an inner ring 11a that is press-fitted into the yoke-side reduced diameter portion 70, whereas an outer ring 11b that is inserted into the yoke-side bearing housing 10, so that it is necessary to use a special bearing. Therefore, the cost of the front bearing 11 can be reduced.

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.
Moreover, although the above-mentioned embodiment demonstrated the case where the brushless motor 1 was 8 pole 9 slot, it is not restricted to this.

  Furthermore, in the above-described embodiment, the case where the rotary encoder 25 is provided as the rotation angle detection device and the rotary 23 of the rotary encoder 25 is used as the clamping means of the rear bearing 14 has been described. However, the present invention is not limited to this, and instead of the rotary encoder 25, another rotational angle detection device such as a resolver may be used. For example, when a resolver is used, the rear bearing 14 may be clamped using a resolver rotor (rotor) of the resolver.

  And although the above-mentioned embodiment demonstrated the case where the yoke 2 was a bottomed cylinder shape, it is not restricted to this, The cylinder which the yoke 2 has only the surrounding wall 5 may be sufficient. In this case, a bracket that closes the opening of the yoke 2 may be provided in place of the end portion 6 of the yoke 2, and the yoke-side bearing housing 10 and the front bearing 11 may be provided on the bracket.

It is sectional drawing which shows the structure of the brushless motor in embodiment of this invention. It is a perspective view of a rotor in an embodiment of the present invention. It is a perspective view of the rear bracket in the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Yoke 3 Stator 4 Rotor 5 Perimeter wall (cylinder part)
9 Rotating shaft 10 Yoke side bearing housing (first bearing housing)
11 Front bearing (first bearing)
11a, 14a Inner ring 11b, 14b Outer ring 14 Rear bearing (second bearing)
16 Rear bracket side bearing housing (second bearing housing)
23 Rotary 25 Rotary encoder 27 Hub 31 Rotary scale 71 Rear bracket reduced diameter part (reduced diameter part)
73 steps

Claims (4)

A yoke having a cylindrical portion;
A stator internally fitted and fixed to the cylindrical portion of the yoke;
A rotor provided rotatably with respect to the stator,
The rotating shaft of the rotor is rotatably supported by a first bearing provided at one end side in the axial direction of the yoke, and the second end provided at the other end side in the axial direction of the yoke. It is supported rotatably by a bearing,
A brushless motor provided with a rotation angle detection device for detecting the rotation angle of the rotation shaft on the other end side of the rotation shaft,
On the other end side of the rotating shaft, a reduced diameter portion is formed which is reduced in diameter by a step and into which the second bearing is inserted so as to be movable in the axial direction,
A brushless motor, wherein an inner ring of the second bearing that is externally fitted to the reduced diameter portion is clamped in an axial direction by a step portion formed on the rotating shaft and the rotation angle detecting device.   The inner ring of the first bearing is press-fitted and fixed to one end side of the rotating shaft, and the outer ring of the first bearing is inserted in a first bearing housing provided on the one axial end side of the yoke so as to be movable in the axial direction. The brushless motor according to claim 1.   The brushless motor according to claim 1 or 2, wherein an outer ring of the second bearing is press-fitted and fixed to a second bearing housing provided on the other axial end of the yoke. The rotation angle detection device is a rotary encoder provided with a rotating plate,
The rotating plate is attached to the reduced diameter portion of the rotating shaft via a hub,
The brushless motor according to any one of claims 1 to 3, wherein an inner ring of the second bearing is sandwiched in an axial direction between the hub and the step portion of the rotating shaft.

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