Ranging device

Abstract

To provide a ranging device capable of regulating movement of a rotor magnet.SOLUTION: A ranging device 1 measures a distance between itself and an object by scanning an outside with light to detect the light reflected by the object, the device comprising a mirror 18, a spindle 13, and a swing motor 20. The mirror 18 is swingingly driven to thus scan the outside with the light. The spindle 13 has the mirror 18 fixed thereon. The swing motor 20 has a tubular rotor magnet 22 inserted into the spindle 13 and a rotor fixing part 31 fixing the rotor magnet 22 to the spindle 13, and causes the spindle 13 to be swingingly driven by energization. The rotor fixing part 31 regulates movements of the rotor magnet 22 in an axial direction, a radial direction, and a rotational direction of the spindle 13.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a distance measuring device. [Background technology]

[0002] Conventionally, there is known a distance measuring device that detects the distance to an object by emitting a transmission wave and detecting the reflected wave from the object of the irradiated transmission wave. For example, the rotary reciprocating actuator disclosed in Patent Document 1 is used in a LiDAR (Light Detection and Ranging) device, and is reciprocated by the magnetic flux generated by a magnet fixed to a rotating shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-43027 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the movement of the rotating shaft and magnet in the thrust direction is restricted by a spacer and a preload spring, but no restriction is provided for the movement in the rotational or radial directions.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a distance measuring device capable of restricting the movement of a rotor magnet. [Means for solving the problem]

[0006] The distance measuring device of the present invention measures the distance to an object by scanning light to the outside and detecting light reflected by the object, and includes a mirror (18), an oscillating shaft (13), and an actuator (20). The mirror scans light to the outside by being driven to oscillate. The mirror is fixed to the oscillating shaft. The actuator has a cylindrical rotor magnet (22) inserted into the oscillating shaft, and a rotor fixing portion (31, 41, 48) that fixes the rotor magnet to the oscillating shaft, and drives the oscillating shaft by passing electricity. The rotor magnet is restricted in movement in the axial direction, radial direction, and rotational direction relative to the oscillating shaft by the rotor fixing portion. This makes it possible to appropriately restrict the movement of the rotor magnet. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing a distance measuring device according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing a swing actuator of the distance measuring device according to the first embodiment. [Diagram 3] FIG. 2 is a cross-sectional view showing a rotor fixing part according to the first embodiment. [Figure 4] FIG. 11 is a cross-sectional view showing a rotor fixing part according to a second embodiment. [Diagram 5] FIG. 11 is a cross-sectional view showing a rotor fixing part according to a third embodiment. [Figure 6] 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] FIG. 7 is a view taken in the direction of an arrow VII in FIG. 6. [Figure 8] FIG. 11 is a cross-sectional view showing a rotor fixing part according to a fourth embodiment. [Figure 9] FIG. 13 is a cross-sectional view showing a protrusion and a groove according to a fifth embodiment. [Figure 10] FIG. 13 is a cross-sectional view showing a rotor fixing part according to a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A distance measuring device according to the present invention will now be described with reference to the drawings. In the following, in a number of embodiments, substantially the same components are designated by the same reference numerals, and description thereof will be omitted.

[0009] (First embodiment) The first embodiment is shown in Fig. 1 to Fig. 3. As shown in Fig. 1, the distance measuring device 1 is a LiDAR (Light Detection and Ranging) device that measures the distance to an object by irradiating light and detecting reflected light from the object onto which the light is irradiated. The distance measuring device 1 is mounted on, for example, a vehicle and used to detect an object present in front of the vehicle.

[0010] The distance measuring device 1 includes a light emitting unit 91, a light receiving unit 92, and a swing actuator 5, and is housed in a housing 93. The light emitting unit 91 intermittently outputs a light beam B. The output light beam B is reflected by a mirror 18 that is driven to swing, and is emitted to the outside through an optical window 94. The light receiving unit 92 receives the reflected light from an object irradiated with the light beam B. The light detected by the light receiving unit 92 is converted into an electrical signal, and is used to calculate the distance to the object.

[0011] As shown in Fig. 2, the oscillation actuator 5 includes a mirror section 10, an oscillation motor 20, and an encoder 25. The mirror section 10 includes a base 11, a spindle 13, a holder 17, and a mirror 18. The base 11 includes an attachment section 111 and holding walls 112 and 113, and is integrally formed from, for example, a metal. The attachment section 111 is attached to a housing (not shown) by a bolt or the like. The holding walls 112 and 113 are provided substantially vertically on both ends of the attachment section 111.

[0012] The spindle 13 is disposed approximately parallel to the mounting portion 111, and is rotatably supported on the base 11 by bearings 14, 15 provided on the retaining walls 112, 113. The bearings 14, 15 in this embodiment are ball bearings, but bearings other than ball bearings may be used. The spindle 13 is formed extending from the bearing 15 side to the outside of the base 11, to the side of the swing motor 20 and the encoder 25. Hereinafter, the swing axis direction of the spindle 13 will be referred to simply as the "axial direction" as appropriate.

[0013] The E-ring 16 is provided on the axially outer side of the bearing 14, and functions to prevent the spindle 13 from coming off. The preload spring 35 is provided between the rotor magnet 22 and the bearing 15, and biases the spindle 13 toward the encoder 25 (downward in the plane of the paper in FIG. 2).

[0014] The holder 17 is press-fitted and fixed to the spindle 13. The mirror 18 is formed in a flat plate shape and is attached to the holder 17 so as to be symmetrical about the oscillation axis. By forming the holder 17 and the mirror 18 symmetrical about the oscillation axis, the moment of inertia during oscillation can be made equal in both directions.

[0015] The holder 17 and the mirror 18 are disposed inside the base 11 so that the mirror surface 181 faces away from the mounting portion 111, and are driven to swing by the swing motor 20. The mirror 18 reflects the light beam B output from the light emitting portion 91 on the mirror surface 181, and emits the light beam B to the outside in a direction according to the swing position of the mirror 18, thereby scanning the light beam B within a preset scanning range.

[0016] The oscillation motor 20 is provided on one side in the axial direction of the mirror unit 10. The oscillation motor 20 has a stator 21, a rotor magnet 22, a rotor fixing unit 31, etc. The stator 21 is fixed to the holding wall 113 with bolts or the like. The stator 51 is provided with an electromagnetic coil and a fixed magnet (not shown).

[0017] The rotor magnet 22 is a cylindrical two-pole magnet, and the spindle 13 is inserted into an axial hole 221. The rotor magnet 22 is fixed to the spindle 13 by a rotor fixing part 31. Details of the rotor fixing part 31 will be described later. For the sake of simplicity, in explaining the rotor fixing structure, the side of the rotor magnet 22 facing the mirror part 10 in the axial direction will be referred to as the "upper side", and the side opposite the mirror part 10 will be referred to as the "lower side".

[0018] The rotor magnet 22 is a so-called inner rotor that is disposed inside the stator 51, and oscillates around a stationary position when current is applied to the electromagnetic coil. Here, the oscillating motion is a motion that periodically repeats forward and reverse rotations within a predetermined angular range less than 360°. When current is turned off to the electromagnetic coil, the rotor magnet 22 returns to the stationary position and becomes stationary due to the magnetic force of the fixed magnet. The size of the rotor magnet 22 can be designed arbitrarily according to mounting constraints, the required magnetic force, and the like.

[0019] The encoder 25 has a disk 26 and a detection element 27, and is housed in a case 29. The disk 26 is attached to a disk hub (not shown) that is press-fitted and fixed to the spindle 13, and rotates integrally with the spindle 13. The detection element 27 is mounted on a substrate 28, and detects the rotational position of the disk 26. This enables the encoder 25 to detect the oscillation positions of the oscillation motor 20 and the mirror 18. A through hole 281 is formed in the substrate 28, and the spindle 13 is inserted therethrough.

[0020] However, from the standpoint of strength, the rotor magnet 22 cannot be directly fixed to the spindle 13 by press-fitting or the like. Here, for example, if the rotor magnet 22 is positioned in the axial direction by a spacer and a preload spring 35 between two bearings that hold the oscillating shaft, in a high-temperature environment, the spacer and the preload spring 35 will stretch in the axial direction, and an excessive load will be applied to the rotor magnet 22, which may cause the rotor magnet 22 to crack. In addition, the load of the preload spring 35 will become so large that the bearings 15 may be damaged.

[0021] In addition, in a low-temperature environment, the spacer and preload spring 35 shrink in the axial direction, which may cause rattling of the rotor magnet 22. In addition, if the load of the preload spring 35 decreases and the internal rattle of the bearing 15 increases, the spindle 13 may tilt more, which may result in a decrease in distance measurement accuracy.

[0022] Furthermore, even if the rotor magnet 22 is positioned axially by sandwiching it between the preload spring 35 and the spacer, there are no restrictions on the rotational and radial directions, and there is a risk that the rotor magnet 22 will move radially and collide with other components or spin freely relative to the spindle 13.

[0023] Therefore, in this embodiment, movement is restricted to prevent misalignment in the axial, radial, and rotational directions, and the rotor magnet 22 is fixed to the spindle 13 by the rotor fixing portion 31, taking into account axial positional misalignment and load changes due to linear expansion.

[0024] 3, the rotor fixing part 31 has a hub 32, a washer 34, and a preload spring 35. The hub 32 is made of, for example, a metal and has a generally circular disk shape having roughly the same diameter as the rotor magnet 22. The spindle 13 is press-fitted and fixed in a press-fit hole 329.

[0025] In the axial direction, a lower end of the rotor magnet 22 is fixed to the hub 32 by an adhesive 33. By flatly fixing one side of the rotor magnet 22 in the axial direction to the hub 32, movement of the rotor magnet 22 in the radial and rotational directions due to vibrations or the like is restricted.

[0026] A washer 34 is provided on the upper side of the rotor magnet 22. One end of the preload spring 35 abuts against the washer 34, and the other end abuts against the bearing 15. This positions the rotor magnet 22 in the axial direction. By providing the washer 34, one end of the preload spring 35 can be appropriately held on a flat surface.

[0027] In this embodiment, one axial side of the rotor magnet 22 is fixed to the hub 32 with adhesive 33 outside the two bearings 14, 15, and the other side is held in an elastic state by a preload spring 35. This makes it possible to prevent damage to the rotor magnet 22 even if the rotor magnet 22 undergoes linear expansion due to temperature changes.

[0028] As described above, the distance measuring device 1 measures the distance to an object by scanning light to the outside and detecting the light reflected by the object, and includes a mirror 18, a spindle 13, and an oscillating motor 20. The mirror 18 scans light to the outside by being driven to oscillate. The mirror 18 is fixed to the spindle 13. The oscillating motor 20 has a cylindrical rotor magnet 22 inserted into the spindle 13, and a rotor fixing part 31 that fixes the rotor magnet 22 to the spindle 13, and drives the spindle 13 to oscillate when electricity is applied.

[0029] The rotor magnet 22 is restricted in its axial, radial, and rotational directions by the rotor fixing portion 31. This makes it possible to suppress variations in motor performance. In addition, it is possible to prevent the rotor magnet 22 from colliding with other components due to its movement, thereby improving durability.

[0030] The rotor fixing portion 31 has a hub 32 fixed to the spindle 13. One axial end face of the rotor magnet 22 is fixed to the hub 32 with an adhesive 33. This makes it possible to prevent the rotor magnet 22 from moving in the radial direction and from rotating freely with respect to the spindle 13. Furthermore, by fixing the rotor magnet 22 to the hub 32 by flat adhesion, processing can be performed relatively easily.

[0031] The rotor fixing part 31 has a preload spring 35 provided on the opposite side of the hub 32 with the rotor magnet 22 in between. The preload spring 35 presses the rotor magnet 22 towards the hub 32, thereby restricting the axial position. Furthermore, by holding the axial position of the rotor magnet 22 outside the bearings 14, 15 with the preload spring 35, it is possible to absorb stress due to vibration and heat.

[0032] Second embodiment The second to sixth embodiments are different from the above-mentioned embodiments mainly in the rotor fixing structure, and this point will be mainly described. As shown in Fig. 4, the rotor fixing part 37 has a hub 38 with a different shape from the first embodiment.

[0033] The hub 38 is formed of, for example, a metal or the like in a generally circular disk shape having roughly the same diameter as the rotor magnet 22, and the spindle 13 is press-fitted and fixed in a press-fit hole 389. A magnet abutment portion 381 and a groove portion 382 are formed on an adhesive surface 385, which is the surface of the hub 38 facing the rotor magnet 22.

[0034] The magnet abutment portion 381 is formed to protrude from the adhesive surface 385 toward the rotor magnet 22, and its tip surface abuts against the rotor magnet 22 without the adhesive 33. In this embodiment, the magnet abutment portion 381 is formed in an annular shape along the outer edge of the press-fit hole 389. That is, in this embodiment, the rotor magnet 22 and the hub 38 are adhered to the radial outside of the magnet abutment portion 381. The groove portion 382 is formed in an annular shape along the outer edge of the magnet abutment portion 381.

[0035] By providing a protruding magnet contact portion 381 on the adhesive surface 385 of the hub 38 and abutting the hub 38 and the rotor magnet 22 at the magnet contact portion 381, the thickness of the adhesive 33 can be made constant, thereby ensuring the adhesive strength.

[0036] Furthermore, if the adhesive 33 runs up onto the magnet abutment portion 381, the thickness of the adhesive 33 may vary, and the adhesive strength may decrease. Therefore, in this embodiment, a groove portion 382 is provided as a reservoir groove for the adhesive 33. This makes it difficult for the adhesive 33 to run up onto the magnet abutment portion 381, and it is possible to reduce variation in the amount of adhesive 33 applied.

[0037] By providing magnet abutment portion 381 on the radially inner side along press-fit hole 389, it is possible to ensure the press-fit length and to check the adhesion state from the outside. In addition, by forming groove portion 382 along magnet abutment portion 381, it is possible to more appropriately prevent adhesive from running up onto magnet abutment portion 381.

[0038] In this embodiment, a magnet abutment portion 381 that abuts against the rotor magnet 22 without the adhesive 33 is formed protruding from an adhesive surface 385, which is the surface of the hub 38 facing the rotor magnet 22. This allows the thickness of the adhesive 33 to be uniform.

[0039] A groove 382 is formed on the adhesive surface 385. This allows the adhesive 33 to escape into the groove 382, ​​thereby preventing the adhesive 33 from running up onto the magnet abutment portion 381. This also provides the same effects as the above embodiment.

[0040] Third embodiment As shown in FIGS. 5 to 7, a rotor fixing portion 41 of the third embodiment has a hub 42, a spring fixing member 43, a wave washer 44, and a preload spring 35.

[0041] The hub 42 is provided above the rotor magnet 22, and is press-fitted and fixed to the spindle 13. The hub 42 has a base 421 and a protruding portion 422 that are integrally formed of metal or the like. The base 421 is formed in a substantially circular plate shape, and the spindle 13 is press-fitted into a press-fit hole 429 that penetrates in the plate thickness direction. One end of the preload spring 35 abuts against the surface of the base 421 opposite the rotor magnet 22. In this embodiment, the preload spring 35 is received on the flat surface of the hub 42 opposite the rotor magnet 22, so that a washer can be omitted.

[0042] As shown in Figs. 6 and 7, the protrusions 422 are formed to protrude from the surface of the base 421 facing the rotor magnet 22. In this embodiment, four protrusions 422 are formed along the radial direction outside the press-fit hole 429, and are arranged in a cross shape as a whole in a plan view. The protrusions 422 are inserted into grooves 222 formed in the upper surface of the rotor magnet 22. The grooves 222 are formed to extend to the outer circumferential wall of the rotor magnet 22 and open radially outward. The radially outer surface of the protrusions 422 is exposed from the rotor magnet 22.

[0043] By inserting the protrusions 422 formed in a cross key shape into the grooves 222 of the rotor magnet 22, the radial movement of the rotor magnet 22 is restricted and they function as a rotation stopper for the rotor magnet 22 relative to the spindle 13. Note that the shape and number of the protrusions 422 need not be limited to a cross key-shaped arrangement as long as they are capable of restricting radial and circumferential movement, and for example, the four protrusions 422 do not have to be orthogonal to each other.

[0044] 5, the spring fixing member 43 is formed, for example, from a metal or the like in a substantially circular disk shape, and is press-fitted and fixed to the spindle 13 below the rotor magnet 22. The spindle 13 is provided with a stepped portion 131 formed so that the lower side of the rotor magnet 22 has a smaller diameter. The spring fixing member 43 is inserted from the lower side of the rotor magnet 22, and press-fitted and fixed to the small diameter portion of the spindle 13 in a state of contact with the stepped portion 131. This determines the axial position of the spring fixing member 43.

[0045] The spring fixing member 43 has a recess 431 formed on a surface facing the rotor magnet 22. A wave washer 44 is provided in the recess 431. The wave washer 44 abuts against the rotor magnet 22 and the spring fixing member 43 in the axial direction. This fixes the axial position of the rotor magnet 22.

[0046] For example, if the wave washer 44 is not provided and the rotor magnet 22 is fixed by sandwiching it between two hubs, there is a risk that the rotor magnet 22 may be damaged if linear expansion occurs due to temperature changes or the like. In this embodiment, the axial position of the rotor magnet 22 is maintained via the wave washer 44, which has elasticity in the axial direction, thereby preventing damage to the rotor magnet 22. Note that, as long as it is elastically deformable in the axial direction, materials other than the wave washer 44, such as rubber, may be used as the elastic member.

[0047] In this embodiment, the rotor fixing part 41 has a hub 42 fixed to the spindle 13 at a base part 421, and a protrusion part 422 formed protruding from the base part 421 fits into a groove part 222 provided on one end face in the axial direction of the rotor magnet 22. A plurality of protrusion parts 422 and groove parts 222 are formed on the radial outer side of the spindle 13 along a straight line extending in the radial direction.

[0048] This makes it possible to prevent the rotor magnet 22 from moving in the radial direction and from rotating freely relative to the spindle 13. Furthermore, in this embodiment, by regulating the position of the rotor magnet 22 without using adhesive, the adhesive does not peel off due to deterioration over time, etc., and the fixed state of the rotor magnet 22 can be stably maintained.

[0049] The rotor fixing portion 41 has a wave washer 44 provided on the opposite side of the hub 42 with the rotor magnet 22 in between. That is, in this embodiment, the wave washer 44 corresponds to the "elastic member". In detail, a spring fixing member 43, which is a receiving member for the wave washer 44, is fixed to the spindle 13 on the opposite side of the hub 42 with the rotor magnet 22 in between, and the wave washer 44 is sandwiched between the rotor magnet 22 and the spring fixing member 43. The wave washer 44 presses the rotor magnet 22 toward the hub 42, thereby restricting the axial position. In addition, it is possible to absorb stress due to vibration and heat. In addition, the same effects as those of the above embodiment are achieved.

[0050] (Fourth embodiment) The fourth embodiment is shown in Fig. 8. The rotor fixing portion 46 of the fourth embodiment has a hub 47, a washer 34, and a preload spring 35. The shape of the hub 47 of this embodiment is similar to that of the hub 42 of the second embodiment, and is provided on the lower side of the rotor magnet 22. The protruding portion of the hub 47 fits into a groove portion formed on the lower side of the rotor magnet 22. The fixing structure on the upper side of the rotor magnet 22 is the same as in the first embodiment. This configuration is similar to the above embodiments.

[0051] (Fifth and Sixth Embodiments) The fifth embodiment is shown in Fig. 9, and the sixth embodiment is shown in Fig. 10. Fig. 9 is a cross-sectional view corresponding to Fig. 6, and in the fifth embodiment, the protrusion 423 is formed in a cylindrical shape and is inserted into the groove 223 formed in a shape corresponding to the upper side surface of the rotor magnet 22.

[0052] 10, a rotor fixing portion 48 of the sixth embodiment has a hub 49 provided below the rotor magnet 22. The hub 49 has a cylindrical protrusion 492 protruding from a base 491, and the protrusion 492 fits into a groove 224 formed on the lower surface of the rotor magnet 22. The shape of the protrusions 423, 492 is not limited to a cylinder, and may be a polygonal prism shape, etc.

[0053] In the fifth and sixth embodiments, the protrusions 423, 492 are formed in a columnar shape. When the columnar protrusions 423, 492 are inserted into the grooves 223, 224 of the rotor magnet 22, the entire circumference of the columnar protrusions 423, 492 is surrounded by the rotor magnet 22. Even with this configuration, the same effects as the above embodiments can be achieved.

[0054] In the embodiment, the spindle 13 corresponds to the "oscillating shaft", the oscillating motor 20 corresponds to the "actuator", the hubs 32, 38, 42, 47, and 49 correspond to the "retaining plate", the adhesive 33 corresponds to the "interposition", the preload spring 35 and the wave washer 44 correspond to the "elastic member", and the grooves 222 to 224 correspond to the "engagement groove".

[0055] (Other embodiments) In the first and second embodiments, the hubs 32, 38 are provided below the rotor magnet 22. In other embodiments, the hubs may be provided above the rotor magnet, and the upper surface of the rotor magnet may be fixed with an adhesive.

[0056] In the second embodiment, a magnet contact portion is formed along the shaft hole, and a groove portion is formed on the outside of the magnet contact portion. In other embodiments, one of the magnet contact portion and the groove portion may be omitted. In addition, the magnet contact portion and the groove portion may be provided in a different position and shape on the bonding surface from that in the second embodiment.

[0057] In the third to sixth embodiments, the protrusion of the holding plate fits into the groove of the rotor magnet. In other embodiments, an adhesive, rubber, or the like may be provided as a cushioning material to fill the gap between the protrusion and the groove. By providing a cushioning material, collisions between members due to vibrations or the like are mitigated, improving durability. In other embodiments, the actuator and mirror section may have configurations and arrangements different from those of the above embodiments, as long as they can oscillate the mirror.

[0058] As described above, the present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. [Explanation of symbols]

[0059] 1... Distance measuring device 13 Spindle (oscillating shaft) 18 Mirror 20.... Swing motor (actuator) 22 Rotor magnet 222~224 Groove (fitting groove) 31, 37, 41, 46, 48...Rotor fixing part 32, 38, 42, 47, 49...Hub (retaining plate) 33... Adhesive (inclusion) 35...Preload spring (elastic member) 44 Wave washer (elastic member) 422, 423, 492...Protrusion

Claims

1. A distance measuring device that measures a distance to an object by scanning light externally and detecting light reflected by the object, A mirror (18) that is driven to oscillate to scan light to the outside; A swing shaft (13) to which the mirror is fixed; an actuator (20) having a cylindrical rotor magnet (22) inserted into the oscillating shaft and a rotor fixing portion (31, 37, 41, 46, 48) that fixes the rotor magnet to the oscillating shaft, and driving the oscillating shaft to oscillate when energized; Equipped with A distance measuring device in which the rotor magnet is regulated in its axial, radial and rotational movements relative to the oscillation shaft by the rotor fixing portion.

2. The rotor fixing portion (31) has a holding plate (32, 38) fixed to the swing shaft, 2. A distance measuring device according to claim 1, wherein one axial end face of the rotor magnet is fixed to the holding plate by an inclusion (33).

3. A distance measuring device as described in claim 2, wherein a magnet abutment portion (381) that abuts against the rotor magnet without the intervening object is formed protrudingly on an adhesive surface (385) of the retaining plate (38) that faces the rotor magnet.

4. 4. The distance measuring device according to claim 3, wherein a groove (382) is formed in the adhesive surface.

5. The rotor fixing portion (41, 46, 48) has a holding plate (42, 47, 49) fixed to the swing shaft at a base portion (421), 2. A distance measuring device according to claim 1, wherein a protrusion (422, 423, 492) formed to protrude from the base is fitted into a fitting groove (222-224) provided on one end face of the rotor magnet in the axial direction.

6. 6. The distance measuring device according to claim 5, wherein the protrusions (422) and the fitting grooves (222) are formed in a plurality of positions along straight lines extending in the radial direction on the radially outer side of the pivot shaft.

7. 6. The distance measuring device according to claim 5, wherein the protrusion (423, 492) is formed in a columnar shape.

8. 8. The distance measuring device according to claim 2, wherein the rotor fixing portion has an elastic member (35, 44) provided on the opposite side of the rotor magnet to the holding plate.

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