Reciprocating rotary motor with elastic limiting structure

Abstract

The utility model discloses a reciprocating rotation motor with elastic limiting structure, and the motor includes the stator and rotor that cooperate with each other, the stator makes the rotor along clockwise and counterclockwise direction make the alternate reciprocating rotation through magnetic force effect, and the limiting piece is arranged on the path of the reciprocating rotation of the rotor, and the material quality of limiting piece is non -metallic elastic material, when the rotor clockwise rotates to the first limit position, the rotor is blocked by limiting piece, when the rotor counterclockwise rotates to the second limit position, the rotor is blocked by limiting piece. The utility model because limiting piece adopts non -metallic elastic material to make, when the rotor rotates to reach clockwise or counterclockwise limit position, is blocked by the limiting piece of non -metallic elastic material, makes that the self -positioning torque increases, avoids the swing of rotor to be too big, and the noise problem that the rotor and stator collide simultaneously is avoided.

Description

Technical Field

[0001] This utility model relates to the field of motor technology, specifically to a reciprocating motor with an elastic limiting structure. Background Technology

[0002] Electric toothbrushes are becoming increasingly popular, and more and more people are using them. To meet market demands, electric toothbrush manufacturers have introduced a wider variety of operating modes. For example, there are vibrating electric toothbrushes, which use a DC motor to drive an eccentric block to rotate, thereby generating vibration and causing the brush head to vibrate. There are also reciprocating electric toothbrushes, which use a motor output shaft to rotate back and forth at a certain frequency / angle, causing the brush head to oscillate back and forth. The newest type is a sweeping and vibration integrated type, which adjusts the speed and angle of the motor's oscillation and vibration by controlling (inputting composite signals at both ends of the motor, with different frequencies / duty cycles). For example, inputting a low-frequency oscillation signal of about 0.5Hz-4Hz allows the brush head to oscillate back and forth relatively slowly within an angle range of ±15°-±30°, while simultaneously superimposing a relatively high-frequency vibration signal of about 150Hz-290Hz allows the brush head to oscillate back and forth relatively quickly within an angle range of ±1°-±8°. As a controlled reciprocating motor, the self-positioning force of the motor is usually designed to be relatively small. However, when the user uses it (while brushing their teeth), there will be a certain deflection force (the magnitude of which is also related to the user's habits). When the deflection force is greater than the motor's self-positioning force, the rotor will deflect to one side. Excessive rotor deflection will cause the motor output to decrease. Therefore, physical limits are often set inside the motor to limit the motor output swing angle within a safe range. Since the rotor is also vibrating at a high frequency, when the rotor deflects and hits the physical limit, a high-frequency impact occurs, resulting in noise. This noise brings a bad user experience. To avoid impact, the limit angle needs to be further increased. However, some users have excessive deflection force when brushing their teeth, which will cause the rotor to deflect too much. After excessive deflection, the vibration force of brushing teeth will decrease significantly, which contradicts the user's needs. Utility Model Content

[0003] In view of this, the present invention provides a reciprocating motor with an elastic limiting structure. When the rotor rotates to the physical limit and is expected to collide, the elasticity of the physical limit effectively avoids the noise problem caused by high-frequency impact while ensuring vibration force.

[0004] The technical solution is as follows: a reciprocating motor with an elastic limiting structure, wherein the motor includes a stator and a rotor that cooperate with each other. The stator causes the rotor to reciprocate alternately in clockwise and counterclockwise directions through magnetic force. A limiting member is provided on the reciprocating rotation path of the rotor. The limiting member is made of a non-metallic elastic material. When the rotor rotates clockwise to the first limit position, the rotor is blocked by the limiting member. When the rotor rotates counterclockwise to the second limit position, the rotor is blocked by the limiting member.

[0005] Using the above technical solution, the limiting component is made of non-metallic elastic material. There are no special requirements for the specific material of the non-metallic elastic material. Any existing non-metallic elastic material can be used, such as rubber, polyurethane, nylon, polytetrafluoroethylene, etc. When the rotor rotates to the limit position of clockwise or counterclockwise, it is blocked by the limiting component made of non-metallic elastic material. Even if there is a collision between the two, due to the special properties of the limiting component material, the noise that may be generated between them is extremely small. Therefore, it is no longer necessary to increase the limiting angle as in the existing technology, and the problem of high-frequency noise is also effectively avoided.

[0006] Preferably, the limiting member is made of rubber.

[0007] Preferably, compared to the initial position, the first extreme position is +20° to +40°, and the second extreme position is -20° to -40°.

[0008] Preferably, the stator includes a housing, and two sets of magnet assemblies are disposed inside the housing. The two sets of magnet assemblies are arranged facing each other. Each set of magnet assemblies includes two magnets. The magnetic poles of the two magnets in the same set of magnet assemblies facing the rotor surface are opposite, and the magnetic poles of adjacent magnets in the two sets of magnet assemblies facing the rotor surface are the same.

[0009] The rotor includes a rotating shaft, which is rotatably mounted inside the housing. A rotor core is provided on the rotating shaft, and rotor teeth are provided on the rotor core corresponding to each group of magnet assemblies. Coil windings are wound on the rotor teeth.

[0010] The limiting member is provided between adjacent magnets of the two sets of magnet assemblies. The limiting member is in contact with the inner wall of the housing. The limiting member is elongated and its two ends are respectively close to the first limit position and the second limit position.

[0011] Preferably, the limiting member has mounting grooves at both ends, and the limiting member is clamped between adjacent magnets of the two sets of magnet assemblies through the mounting grooves at both ends, and a portion of the adjacent magnets of the two sets of magnet assemblies is clamped in the corresponding mounting groove.

[0012] Preferably, the limiting member is further provided with a limiting groove, and a limiting post is provided inside the housing, the limiting post being fastened in the limiting groove.

[0013] Preferably, the stator includes a housing, one end of which is fitted with an end cap. Two sets of magnet assemblies are disposed inside the housing, with the two sets of magnet assemblies facing each other. Each set of magnet assemblies includes two magnets. The magnetic poles of the two magnets in the same set of magnet assemblies facing the rotor are opposite, and the magnetic poles of adjacent magnets in the two sets of magnet assemblies facing the rotor are the same.

[0014] The rotor includes a rotating shaft, a first bearing is provided inside the end cover, a second bearing is provided inside the housing opposite the first bearing, the two ends of the rotating shaft are respectively inserted into the first bearing and the second bearing, a rotor core is provided on the rotating shaft, and rotor teeth are installed on the rotor core corresponding to each group of magnet components, and coil windings are wound on the rotor teeth.

[0015] One end of the rotating shaft extends freely out of the end cover to form a limiting part. A limiting rod is installed on the limiting part radially. The limiting member is fixedly installed on the outer side of the end cover, with its two ends close to the first limit position and the second limit position, respectively. When the rotor rotates to the first limit position or the second limit position, the limiting rod touches the limiting member.

[0016] Preferably, the stator includes a housing, and two sets of magnet assemblies are disposed inside the housing. The two sets of magnet assemblies are arranged facing each other. Each set of magnet assemblies includes two magnets. The magnetic poles of the two magnets in the same set of magnet assemblies facing the rotor surface are opposite, and the magnetic poles of adjacent magnets in the two sets of magnet assemblies facing the rotor surface are the same.

[0017] The rotor includes a rotating shaft, which is rotatably mounted inside the housing. A rotor core is provided on the rotating shaft, and rotor teeth are installed on the rotor core corresponding to each group of magnet assemblies. Coil windings are wound on the rotor teeth.

[0018] A limiting member is installed on the same side of the two rotor teeth. The two ends of the limiting member are flush with the tooth top surface of the corresponding rotor teeth. When the rotor rotates to the first limit position or the second limit position, the limiting member touches the inner wall of the housing.

[0019] Preferably, the stator includes a housing, and two sets of magnet assemblies are disposed inside the housing. The two sets of magnet assemblies are arranged facing each other. Each set of magnet assemblies includes two magnets. The magnetic poles of the two magnets in the same set of magnet assemblies facing the rotor surface are opposite, and the magnetic poles of adjacent magnets in the two sets of magnet assemblies facing the rotor surface are the same.

[0020] The rotor includes a rotating shaft, which is rotatably mounted inside the housing. A rotor core is provided on the rotating shaft, and rotor teeth are installed on the rotor core corresponding to each group of magnet assemblies.

[0021] The stator also includes a wire frame, which is fixedly connected to the inner wall of the housing. The rotating shaft rotatably passes through the wire frame. A coil winding is wound around the rotor teeth on the wire frame. The wire frame is provided with limiting members corresponding to the first and second limit positions. When the rotor rotates to the first or second limit position, the rotor teeth touch the corresponding limiting members.

[0022] Compared with the prior art, the beneficial effects of this utility model are as follows: Since the limiting component is made of non-metallic elastic material, when the rotor rotates to the limit position of clockwise or counterclockwise, it is blocked by the limiting component made of non-metallic elastic material, which increases the self-positioning torque, avoids excessive rotor swing, and avoids the noise problem caused by the collision between the rotor and the stator. Attached Figure Description

[0023] Figure 1 An exploded view of a motor according to one embodiment;

[0024] Figure 2 A schematic diagram of the internal structure of a motor according to one embodiment;

[0025] Figure 3 This is a schematic diagram of the planar structure of a motor according to one embodiment;

[0026] Figure 4 for Figure 3 AA section view;

[0027] Figure 5 This is a schematic diagram of the structure of a limiting member according to one embodiment;

[0028] Figure 6 This is a schematic diagram showing the installation position of the limiting member in another embodiment;

[0029] Figure 7 This is a schematic diagram showing another installation position for the limiting component;

[0030] Figure 8 This is a schematic diagram showing other installation positions of the limit component. Detailed Implementation

[0031] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0032] like Figure 1-5 As shown, a reciprocating motor with an elastic limiting structure is provided. The motor includes a stator and a rotor that cooperate with each other. The stator causes the rotor to reciprocate alternately in clockwise and counterclockwise directions by magnetic force. A limiting member 4 is provided on the reciprocating rotation path of the rotor. The limiting member 4 is made of a non-metallic elastic material. When the rotor rotates clockwise to the first limit position, the rotor is blocked by the limiting member 4. When the rotor rotates counterclockwise to the second limit position, the rotor is blocked by the limiting member 4.

[0033] This application does not limit the specific types of non-metallic elastic materials; any existing non-metallic elastic materials can be used, such as rubber, polyurethane, nylon, polytetrafluoroethylene, etc. In this example, the limiting element is made of rubber.

[0034] Compared to the initial position, the first extreme position is +20° to +40°, and the second extreme position is -20° to -40°.

[0035] In some embodiments, the stator includes a housing 2, within which two sets of magnet assemblies 5 are disposed facing each other. Each set of magnet assemblies 5 includes two magnets 5a. The magnetic poles of the two magnets 5a in the same set of magnet assemblies 5 facing the rotor surface are opposite, and the magnetic poles of adjacent magnets 5a in the two sets of magnet assemblies 5 facing the rotor surface are the same. The rotor includes a shaft 6, which is rotatably mounted in the housing 2. A rotor core 9 is disposed on the shaft 6. Rotor teeth are disposed on the rotor core 9 corresponding to each set of magnet assemblies, and coil windings 10 are wound on the rotor teeth.

[0036] Specifically, the rotor teeth include a tooth root 9b and a tooth tip 9a connected thereto. The tooth root 9b is connected to the rotor core 9, and the coil winding is wound on the tooth root 9b. The tooth tip 9a faces the space between the two magnets 5a of the corresponding magnet assembly 5; this position is the initial position. When the coil winding 10 is energized, the magnetic poles generated on the two rotor teeth are opposite, such as... Figure 4 The magnetic pole distribution shown generates a changing magnetic field on the two rotor teeth by passing in alternating currents. Through the magnetic force between the rotor and stator, the rotor is driven to perform alternating clockwise and counterclockwise reciprocating motions.

[0037] The limiting member 4 is provided between adjacent magnets 5a of the two sets of magnet assemblies 5. The limiting member 4 is attached to the inner wall of the housing 2. The limiting member 4 is long and narrow, with its two ends close to the first limit position and the second limit position, respectively.

[0038] In some embodiments, to facilitate fixing the limiting member 4, each of the two ends of the limiting member 4 has a mounting groove 4a. The limiting member 4 is clamped between the adjacent magnets 5a of the two sets of magnet assemblies 5 through the mounting grooves 4a corresponding to its two ends, and a portion of the adjacent magnets 5a of the two sets of magnet assemblies 5 is clamped in the corresponding mounting groove 4a.

[0039] In some embodiments, the limiting member 4 is further provided with a limiting groove 4b, and a limiting post 2a is provided inside the housing 2. The limiting post 2a is fixedly connected to the housing 2, and the limiting post 2a is clamped in the limiting groove 4b.

[0040] like Figure 2 As shown, the housing 2 is waist-shaped, with two opposite side walls being flat and the other two opposite side walls being arc-shaped. The two sets of magnet assemblies 5 are respectively installed on the two arc-shaped side walls of the housing 2. To facilitate the fixing of the magnets 5a, a magnet frame 3 is fixedly installed on the inner wall of the housing 2. The magnet frame 3 has mounting slots corresponding to each magnet 5a, and the magnets 5a are respectively installed in the corresponding mounting slots.

[0041] An end cap 15 is installed at one end of the housing 2. A first bearing 14 is installed inside the end cap 15. A second bearing 1 is installed inside the housing 2, directly opposite the first bearing 14. Both ends of the rotating shaft 2 are respectively inserted into the first bearing 14 and the second bearing 1. One end of the rotating shaft 2 extends out of the second bearing 1 to form an output end. Other functional components, such as a toothbrush, can be further connected to this output end.

[0042] like Figure 1 As shown, a commutator 11 and a brush 13 are installed on the shaft 1 near the end cover 15. A first adjusting washer 12 is installed between the brush 13 and the first bearing 14. A copper sleeve 8 is installed between the rotor core 9 and the second bearing 1. A second adjusting washer 7 is also installed between the copper sleeve 8 and the second bearing.

[0043] In some embodiments, such as Figure 6As shown, another installation method for the limiting component is provided. The stator includes a housing 2, one end of which is fitted with an end cap 15. Two sets of magnet assemblies 5 are arranged inside the housing 2, facing each other. Each set of magnet assemblies 5 includes two magnets 5a. The magnetic poles of the two magnets 5a in the same set of magnet assemblies 5 are opposite to those facing the rotor surface, and the magnetic poles of adjacent magnets 5a in the two sets of magnet assemblies 5 are the same facing the rotor surface. The rotor includes a shaft 6. A first bearing 14 is arranged inside the end cap 15. A second bearing 1 is arranged inside the housing 2, facing the first bearing 15. The two ends of the shaft 6 are respectively inserted into the first bearing 15 and the second bearing 1. A rotor core 6 is arranged on the shaft 6. Rotor teeth are installed on the rotor core 6 corresponding to each set of magnet assemblies 5. Coil windings 10 are wound on the rotor teeth.

[0044] Specifically, the rotor teeth include a tooth root 9b and a tooth tip 9a connected thereto. The tooth root 9b is connected to the rotor core 9, and the coil winding is wound on the tooth root 9b. The tooth tip 9a faces the space between the two magnets 5a of the corresponding magnet assembly 5; this position is the initial position. When the coil winding 10 is energized, the magnetic poles generated on the two rotor teeth are opposite, such as... Figure 4 The magnetic pole distribution shown generates a changing magnetic field on the two rotor teeth by passing in alternating currents. Through the magnetic force between the rotor and stator, the rotor is driven to perform alternating clockwise and counterclockwise reciprocating motions.

[0045] One end of the rotating shaft 6 extends freely out of the end cover 15 to form a limiting part 16. A limiting rod 17 is installed on the limiting part 16 radially. The limiting member 4 is fixedly installed on the outer side of the end cover 15, with its two ends close to the first limit position and the second limit position, respectively. When the rotor rotates to the first limit position or the second limit position, the corresponding end of the limiting rod 17 touches the limiting member 4.

[0046] In this structural form, the structure of the other parts of the motor is the same as described above, and will not be repeated here.

[0047] In some embodiments, such as Figure 7As shown, another installation method for the limiting component is provided. The stator includes a housing 2, in which two sets of magnet assemblies 5 are arranged. The two sets of magnet assemblies 5 are arranged facing each other. Each set of magnet assemblies 5 includes two magnets 5a. The magnetic poles of the two magnets 5a in the same set of magnet assemblies 5 facing the rotor surface are opposite, and the magnetic poles of adjacent magnets 5a in the two sets of magnet assemblies 5 facing the rotor surface are the same. The rotor includes a rotating shaft 6, which is rotatably installed in the housing 2. A rotor core 9 is provided on the rotating shaft 6. Rotor teeth are installed on the rotor core 9 corresponding to each set of magnet assemblies 5. A coil winding 10 is wound on the rotor teeth.

[0048] Specifically, the rotor teeth include a tooth root 9b and a tooth tip 9a connected thereto. The tooth root 9b is connected to the rotor core 9, and the coil winding 10 is wound on the tooth root 9b. The tooth tip 9a faces the space between the two magnets 5a of the corresponding magnet assembly 5; this position is the initial position. When the coil winding 10 is energized, the magnetic poles generated on the two rotor teeth are opposite, such as... Figure 4 The magnetic pole distribution shown generates a changing magnetic field on the two rotor teeth by passing in alternating currents. Through the magnetic force between the rotor and stator, the rotor is driven to perform alternating clockwise and counterclockwise reciprocating motions.

[0049] A limiting member 4 is installed on the same side of the two rotor teeth. The two ends of the limiting member 4 are flush with the tooth top surface of the corresponding rotor teeth. When the rotor rotates to the first limit position or the second limit position, the limiting member 4 touches the inner wall of the housing 2. In order to facilitate better contact between the limiting member 4 and the housing 2, a thickening part 18 can also be installed on the inner wall of the housing 2. The surface of the thickening part 18 is basically flush with the surface of the magnets 5a at both ends.

[0050] The limiting member 4 can also be installed on both sides of the rotor teeth to better perform the limiting function.

[0051] In this structural form, the structure of the other parts of the motor is the same as described above, and will not be repeated here.

[0052] In some embodiments, such as Figure 8As shown, another installation method for the limiting component is provided. The stator includes a housing 2, in which two sets of magnet assemblies 5 are arranged facing each other. Each set of magnet assemblies 5 includes two magnets 5a. The magnetic poles of the two magnets 5a in the same set of magnet assemblies 5 facing the rotor surface are opposite, and the magnetic poles of adjacent magnets 5a in the two sets of magnet assemblies 5 facing the rotor surface are the same. The rotor includes a rotating shaft 6, which is rotatably mounted in the housing 2. A rotor core 9 is provided on the rotating shaft 6, and rotor teeth are installed on the rotor core 9 corresponding to each set of magnet assemblies 5.

[0053] The stator also includes a wire frame 19, which is fixedly connected to the inner wall of the housing 2. The rotating shaft 6 rotatably passes through the wire frame 19, and a coil winding 10 is wound around the rotor teeth on the wire frame 19. Specifically, the rotor teeth include a tooth root 9b and a tooth tip 9a connected thereto. The tooth root 9b is connected to the rotor core 9, and the tooth tip 9a faces between the two magnets 5a of the corresponding magnet assembly 5. This position is the initial position. The coil winding 10 is wound around the tooth root 9b on the wire frame 19. When the coil winding 10 is energized, the magnetic poles generated on the two rotor teeth are opposite, such as... Figure 4 The magnetic pole distribution shown generates a changing magnetic field on the two rotor teeth by passing in alternating currents. Through the magnetic force between the rotor and stator, the rotor is driven to perform alternating clockwise and counterclockwise reciprocating motions.

[0054] The wire frame 19 is provided with limiting members 4 corresponding to the first limit position and the second limit position respectively. When the rotor rotates to the first limit position or the second limit position, the top 9a of the rotor teeth touches the corresponding limiting member 4.

[0055] In this structural form, the structure of the other parts of the motor is the same as described above, and will not be repeated here.

[0056] Finally, it should be noted that the above description is merely a preferred embodiment of the present utility model. Those skilled in the art, under the guidance of the present utility model, can make various similar representations without departing from the spirit and claims of the present utility model, and such modifications all fall within the protection scope of the present utility model.

Claims

1. A reciprocating motor with an elastic limiting structure, characterized in that, The motor includes a stator and a rotor that cooperate with each other. The stator causes the rotor to rotate alternately in clockwise and counterclockwise directions by magnetic force. A limit member is provided on the path of the rotor's reciprocating rotation. The limit member is made of a non-metallic elastic material. When the rotor rotates clockwise to the first limit position, the rotor is blocked by the limit member. When the rotor rotates counterclockwise to the second limit position, the rotor is blocked by the limit member.

2. The motor according to claim 1, characterized in that, The limiting component is made of rubber.

3. The motor according to claim 1 or 2, characterized in that, Compared to the initial position, the first extreme position is +20° to +40°, and the second extreme position is -20° to -40°.

4. The motor according to claim 3, characterized in that, The stator includes a housing, inside which two sets of magnet assemblies are arranged. The two sets of magnet assemblies are arranged facing each other. Each set of magnet assemblies includes two magnets. The magnetic poles of the two magnets in the same set of magnet assemblies facing the rotor surface are opposite, and the magnetic poles of adjacent magnets in the two sets of magnet assemblies facing the rotor surface are the same. The rotor includes a rotating shaft, which is rotatably mounted inside the housing. A rotor core is provided on the rotating shaft, and rotor teeth are provided on the rotor core corresponding to each group of magnet assemblies. Coil windings are wound on the rotor teeth. The limiting member is provided between adjacent magnets of the two sets of magnet assemblies. The limiting member is in contact with the inner wall of the housing. The limiting member is elongated and its two ends are respectively close to the first limit position and the second limit position.

5. The motor according to claim 4, characterized in that, The limiting member has mounting grooves at both ends. The limiting member is clamped between adjacent magnets of the two sets of magnet assemblies through the mounting grooves at both ends, and a portion of the adjacent magnets of the two sets of magnet assemblies is clamped in the corresponding mounting groove.

6. The motor according to claim 5, characterized in that, The limiting member is also provided with a limiting groove, and a limiting post is provided inside the housing, the limiting post being locked in the limiting groove.

7. The motor according to claim 3, characterized in that, The stator includes a housing, one end of which is fitted with an end cap. Two sets of magnet assemblies are arranged inside the housing, with the two sets of magnet assemblies facing each other. Each set of magnet assemblies includes two magnets. The magnetic poles of the two magnets in the same set of magnet assemblies facing the rotor are opposite, and the magnetic poles of adjacent magnets in the two sets of magnet assemblies facing the rotor are the same. The rotor includes a rotating shaft, a first bearing is provided inside the end cover, a second bearing is provided inside the housing opposite the first bearing, the two ends of the rotating shaft are respectively inserted into the first bearing and the second bearing, a rotor core is provided on the rotating shaft, and rotor teeth are installed on the rotor core corresponding to each group of magnet components, and coil windings are wound on the rotor teeth. One end of the rotating shaft extends freely out of the end cover to form a limiting part. A limiting rod is installed on the limiting part radially. The limiting member is fixedly installed on the outer side of the end cover, with its two ends close to the first limit position and the second limit position, respectively. When the rotor rotates to the first limit position or the second limit position, the limiting rod touches the limiting member.

8. The motor according to claim 3, characterized in that, The stator includes a housing, inside which two sets of magnet assemblies are arranged. The two sets of magnet assemblies are arranged facing each other. Each set of magnet assemblies includes two magnets. The magnetic poles of the two magnets in the same set of magnet assemblies facing the rotor surface are opposite, and the magnetic poles of adjacent magnets in the two sets of magnet assemblies facing the rotor surface are the same. The rotor includes a rotating shaft, which is rotatably mounted inside the housing. A rotor core is provided on the rotating shaft, and rotor teeth are installed on the rotor core corresponding to each group of magnet assemblies. Coil windings are wound on the rotor teeth. A limiting member is installed on the same side of the two rotor teeth. The two ends of the limiting member are flush with the tooth top surface of the corresponding rotor teeth. When the rotor rotates to the first limit position or the second limit position, the limiting member touches the inner wall of the housing.

9. The motor according to claim 3, characterized in that, The stator includes a housing, inside which two sets of magnet assemblies are arranged. The two sets of magnet assemblies are arranged facing each other. Each set of magnet assemblies includes two magnets. The magnetic poles of the two magnets in the same set of magnet assemblies facing the rotor surface are opposite, and the magnetic poles of adjacent magnets in the two sets of magnet assemblies facing the rotor surface are the same. The rotor includes a rotating shaft, which is rotatably mounted inside the housing. A rotor core is provided on the rotating shaft, and rotor teeth are installed on the rotor core corresponding to each group of magnet assemblies. The stator also includes a wire frame, which is fixedly connected to the inner wall of the housing. The rotating shaft rotatably passes through the wire frame. A coil winding is wound around the rotor teeth on the wire frame. The wire frame is provided with limiting members corresponding to the first and second limit positions. When the rotor rotates to the first or second limit position, the rotor teeth touch the corresponding limiting members.

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