JP2006280040A - Stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stepping motor which is high in torque efficiency and is fit for downsizing. <P>SOLUTION: This stepping motor 100 is equipped with a stator 9(10) where an exciting coil 5(6) is caught between an inner yoke 3(4) and an outer yoke 7(8) where two or more polar teeth in its circumferential direction are arranged to engage with each other, and a rotor magnet 1 which is arranged rotatably, leaving a gap G from the two or more polar teeth, in the center hole piercing the plurality of stators 9 and 10 which are arranged with their inner yokes 3 and 4 joined together. The axial gaps TP1 off the tips of the polar teeth of the rotor magnet 1 between the tips of the polar teeth of the inner yoke 3(4) and the bases of the polar teeth of the outer yoke 7(8) are set to be roughly the same each as the gap G between polar teeth 3a, 4a, 7a and 8a and the rotor magnet 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stepping motor having a rotor magnet that rotates in a stator.

Conventional stepping motors include at least a pole tip gap in the axial direction between the pole tooth tip of the inner yoke and the pole tooth root of the outer yoke or between the pole tooth tip of the outer yoke and the pole tooth root of the inner yoke. One is configured to be larger than the gap provided between the pole teeth and the rotor magnet (see Patent Document 1).
Japanese Patent Laid-Open No. 4-109836

  However, the conventional stepping motor has the following problems.

  (1) If the pole tooth tip gap described above is set larger than the gap provided between the pole tooth and the rotor magnet, a useless space that does not contribute to torque increases between the inner yoke and the outer yoke, The magnetic force of the rotor magnet or coil cannot be used effectively, and the torque decreases.

  (2) On the other hand, if the pole tooth tip gap is set to be smaller than the gap provided between the pole tooth and the rotor magnet, the reactive magnetic flux between the pole tooth tip gaps will increase, causing problems such as yoke saturation. As a result, the magnetic flux to the gap of the rotor magnet is reduced, so that the torque efficiency is reduced.

  An object of the present invention is made in view of the above problems, and is to provide a stepping motor suitable for downsizing with high torque efficiency.

  In order to achieve the above object, a stepping motor according to claim 1 is a stator in which an excitation coil is sandwiched between an inner yoke and an outer yoke arranged so that a plurality of circumferentially arranged pole teeth mesh with each other. And a central hole that penetrates the plurality of stators arranged by joining the inner yokes and is rotatably arranged with a predetermined gap from the plurality of pole teeth, and different magnetic poles are alternately magnetized on the outer peripheral surface. In the stepping motor comprising the rotor, the axial pole tip gap between the pole tooth tip of the inner yoke and the pole tooth base of the outer yoke is the gap between the plurality of pole teeth and the rotor. It is characterized by being set substantially the same as the predetermined gap.

  In the said structure, the magnetic force of a rotor or an exciting coil can be utilized effectively, and the increase in the invalid magnetic flux between pole tooth tip gaps can be prevented.

  A stepping motor according to a second aspect is the stepping motor according to the first aspect, wherein the pole tooth tip gap in the axial direction between the pole tooth tip of the outer yoke and the pole tooth root of the inner yoke is the plurality of poles. The predetermined gap between the teeth and the rotor is set to be approximately the same.

  In the said structure, the magnetic force of a rotor or an exciting coil can be utilized effectively, and the increase in the invalid magnetic flux between pole tooth tip gaps can be prevented.

  The stepping motor according to claim 3 is the stepping motor according to claim 1 or 2, wherein the length between the pole tooth tips of the inner yoke and the length in the axial direction of the rotor in the plurality of stators arranged in a joint are: It is set so that it may substantially correspond.

  In the above configuration, the magnetic force of the rotor or exciting coil can be used effectively, and an increase in the reactive magnetic flux between the pole tooth tip gaps and the reactive magnetic flux in the rotor can be prevented.

  A stepping motor according to a fourth aspect is the stepping motor according to the first or second aspect, wherein both ends of the rotor in the axial direction are arranged so as to be located in the respective pole tooth tip gaps. .

  In the above configuration, the reactive magnetic flux in the pole tooth tip gap can be supplied to the rotor for effective use.

  According to the present invention, the axial pole tip gap between the pole tip of the inner yoke and the pole root of the outer yoke is set to be substantially the same as the predetermined gap between the plurality of pole teeth and the rotor. Therefore, a stepping motor suitable for downsizing with high torque efficiency can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an exploded perspective view of a stepping motor according to an embodiment of the present invention. In the figure, since the stators 9 and 10 have the same structure, the configuration of the stator 9 will be mainly described, and the components corresponding to the stator 10 will be described in parentheses.

  In FIG. 1, a stepping motor 100 is formed integrally with a cylindrical rotor magnet 1 made of a plastic magnet or the like in which 10 different magnetic poles are alternately magnetized on the outer peripheral surface, and penetrating in the axial direction of the rotor magnet 1. A shaft 2 made of a nonmagnetic material such as stainless steel, an inner yoke 3 (4) made of a soft magnetic material having a plurality (five) of pole teeth 3a (4a) arranged in the circumferential direction, and a circumferential direction The outer yoke 7 (8) made of a soft magnetic material having a plurality of (five) pole teeth 7a (8a) arranged, and is sandwiched between the inner yoke 3 (4) and the outer yoke 7 (8). The exciting coil 5 (6) for exciting these yokes and the sintered oil-impregnated bearing 11 (12) for rotatably supporting the shaft 2 are provided. The stator 9 (10) includes an inner yoke 3 (4) and an outer yoke 7 (8) arranged so that the pole teeth 3a (4a) and 7a (8a) mesh with each other, and an excitation coil 5 (6). Is done.

  The rotor magnet 1 is rotatably disposed with a gap G from the pole teeth 3a, 4a, 7a, 8a in a central hole that penetrates the stators 9, 10 to which the inner yokes 3, 4 are joined. The rotor magnet 1 has a groove portion 1a having a predetermined width and depth in the circumferential direction of its peripheral surface. The rotor magnet 1 is made of a plastic magnet, but is not limited to this as long as the shape processing of the groove 1a is easy. For example, the rotor magnet 1 is formed by cutting a sintered magnet. It may be.

  In the above configuration, when the exciting coils 5 and 6 are energized, the inner yokes 3 and 4 and the outer yokes 7 and 8 are excited and magnetized by the pole teeth 3a, 4a, 7a, and 8a. As a result, rotational torque is generated by repelling / attracting the magnetic poles of the rotor magnet 1, the rotor magnet 1 is rotationally driven according to the energization of the exciting coils 5, 6, and the driving force is transmitted from the shaft 2 to the outside.

  FIG. 2 is a longitudinal sectional view of the stepping motor 100 of FIG.

  In FIG. 2, the inner yokes 3 and 4 have a joint portion 13 having a thickness C formed by joining the bent portions on the side where the pole teeth 3a and 4a are not disposed. Inside the inner yokes 3 and 4 where the joint portion 13 is formed, the rotor magnet 1 is disposed so as to be rotatable coaxially with the inner yokes 3 and 4 with a gap G from the pole teeth 3a and 4a. The rotor magnet 1 is preferably arranged so that the groove 1 a faces the joint 13.

  FIG. 3 is a side view of the yokes 3 (4) and 7 (8) of FIG. FIG. 4 is a development view of the pole tooth portions of the inner yoke 3 (4) and the outer yoke 7 (8).

  As shown in FIGS. 3 and 4, the inner yoke having the plurality of pole teeth 3a (4a) and the outer yoke having the plurality of pole teeth 7a (8a) are arranged to face each other and mesh with each other.

  TP1 is a rotor magnet between the tip of the pole teeth 3a (4a) of the inner yoke 3 (4) and the root of the pole teeth 7a (8a) of the outer yoke 7 (8), that is, the valley portion between the pole teeth 7a (8a). TP2 is the tip of the pole teeth 7a (8a) of the outer yoke 7 (8) and the root of the pole teeth 3a (4a) of the inner yoke 3 (4), that is, the pole teeth 3a ( 4a) is a pole tooth tip gap in the axial direction of the rotor magnet 1 between the valley portions.

  When the pole tooth tip gaps TP1 and TP2 are smaller than the gap G, the reactive magnetic flux increases, the effective magnetic flux to the gap G decreases, and the torque decreases. On the other hand, if the pole tooth tip gaps TP1 and TP2 are larger than the gap G, useless space that does not contribute to torque increases and torque decreases.

  Therefore, the pole tooth tip gap TP1 is preferably set to be substantially the same as the gap G between the pole teeth 3a, 4a, 7a, 8a and the rotor magnet 1. Similarly, the pole tooth tip gap TP2 is preferably set to be substantially the same as the gap G. Thereby, the magnetic force of the rotor magnet 1 and the exciting coils 5 and 6 can be used effectively, and the increase of the invalid magnetic flux in the pole tooth tip gaps TP1 and TP2 can be prevented.

  FIG. 5 is a side view of a portion where the inner yokes 3 and 4 and the rotor magnet 1 are combined.

  In FIG. 5, in the inner yokes 3 and 4 in which the joint portion 13 is formed, the length Y1 between the tips of the pole teeth 3a to the tips of the pole teeth 4a in the axial direction and the length of the rotor magnet 1 in the axial direction. It is preferable that the length L1 is set so as to be substantially coincident with the length L1. As a result, the magnetic force generated from the rotor magnet 1 and the magnetic force induced in the pole teeth by the exciting coils 5 and 6 can be effectively used. The increase in reactive magnetic flux can be prevented.

  On the other hand, you may arrange | position so that the both ends of the axial direction of the rotor magnet 1 may be located in pole tooth tip gap TP1 and TP2, respectively. Thereby, the reactive magnetic flux of the pole tooth tip gaps TP1 and TP2 can be supplied to the rotor magnet 1 for effective use.

  According to the above embodiment, the pole tooth tip gaps TP1 and TP2 are set to be substantially the same as the gap G between the pole teeth 3a, 4a, 7a and 8a and the rotor magnet 1, respectively. The magnetic force of the exciting coils 5 and 6 can be used effectively, and an increase in reactive magnetic flux in the pole tooth tip gaps TP1 and TP2 can be prevented. Further, there is an effect that the torque efficiency can be optimized without increasing the reactive magnetic flux, and further, there is an effect that the reactive magnetic flux is made an effective magnetic flux.

It is a disassembled perspective view of the stepping motor which concerns on embodiment of this invention. It is a longitudinal cross-sectional view of the stepping motor 100 of FIG. It is a side view of the inner yoke 3 (4) and the outer yoke 7 (8) of FIG. It is an expanded view of the pole tooth part of the inner yoke 3 (4) and the outer yoke 7 (8). FIG. 3 is a side view of a portion in which inner yokes 3 and 4 and a rotor magnet 1 are combined.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor magnet 1a Groove parts 3, 4 Inner yoke 3a, 4a Inner yoke pole teeth 7a, 8a Outer yoke pole teeth 5, 6 Excitation coil 7, 8 Outer yoke 9, 10 Stator 13 Inner yoke joint Y1 Length G between the pole tooth tips in the axial direction of the yoke Gap TP1 A pole tip gap TP2 in the axial direction between the pole tooth tip of the inner yoke and the pole tooth root of the outer yoke The pole of the pole tooth of the outer yoke and the pole of the inner yoke Axial pole tooth tip gap L1 between the tooth root and the axial length of the rotor magnet 1

Claims (4)

A stator in which an exciting coil is sandwiched between an inner yoke and an outer yoke arranged so that a plurality of pole teeth arranged in the circumferential direction mesh with each other, and a plurality of stators arranged by joining the inner yoke are passed through In a stepping motor comprising a rotor that is rotatably arranged with a predetermined gap from the plurality of pole teeth in a center hole, and different magnetic poles are alternately magnetized on the outer peripheral surface,
The axial pole tip gap between the pole tooth tip of the inner yoke and the pole tooth root of the outer yoke is set to be substantially the same as the predetermined gap between the plurality of pole teeth and the rotor. Stepping motor characterized by that.   An axial pole tip gap between the pole tooth tip of the outer yoke and the pole tooth root of the inner yoke is set to be substantially the same as the predetermined gap between the plurality of pole teeth and the rotor. The stepping motor according to claim 1.   3. The length between the pole tooth tips of the inner yoke and the length in the axial direction of the rotor in the plurality of stators arranged to be joined are set so as to be substantially coincident with each other. Stepping motor.   3. The stepping motor according to claim 1, wherein both ends of the rotor in the axial direction are disposed so as to be positioned in the pole tooth tip gaps, respectively.

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