JP2006280174A - Stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient stepping motor which can utilize effective magnetic flux efficiently by reducing ineffective magnetic flux. <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) whose two or more polar teeth set circumferentially being 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 stators 9 and 10 which are arranged with their inner yokes 3 and 4 coupled together. The circumferential gap RG between polar teeth between the polar tooth 3a(4a) of the inner yoke 3(4) and the polar tooth 7a(8a) of the outer yoke 7(8) is set narrower at the center C1 between the tip of the polar tooth 3a(4a) of the inner yoke 3(4) and the polar tooth 7a(8a) of the outer yoke 7(8). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  In the conventional stepping motor, the inner yoke and the outer yoke are arranged mutually so that the gap between the pole teeth in the circumferential direction of the first pole tooth of the outer yoke and the second pole tooth of the inner yoke is equal. (See Patent Document 1).

In addition, it is disclosed that the gap between the pole tooth tip of the inner yoke and the pole tooth root of the outer yoke is narrowed (see Patent Document 2).
JP-A-8-205510 Japanese Patent Laid-Open No. 10-127024

  However, the conventional stepping motor has the following problems.

  (1) Since the gap between the pole teeth is set to be equal, or the gap between the pole tooth tip of the inner yoke and the pole tooth root of the outer yoke is set narrow, it becomes weaker on the pole tooth tip side. The magnetic force of the rotor magnet and the exciting force of the exciting coil that becomes stronger at the center of the pole teeth cannot be used effectively.

  (2) The magnetic flux generated from the tip or root of the pole teeth becomes an ineffective flux that does not contribute to the rotational torque, but the gap between the pole teeth is set at an equal interval, or the pole tooth tip of the inner yoke and the pole teeth of the outer yoke When the gap between the two is set narrow, the reactive magnetic flux generated from the tip of the pole tooth and the root of the pole tooth tends to increase.

  The object of the present invention is to provide a highly efficient stepping motor that can reduce the reactive magnetic flux and efficiently use the effective magnetic flux.

  In order to achieve the above object, a stepping motor according to claim 1 includes an inner yoke and an outer yoke having a plurality of pole teeth arranged alternately facing each other in the circumferential direction, and an exciting coil sandwiched between the yokes. And a plurality of stator teeth arranged to be joined to the inner yoke so as to be rotatable with a predetermined gap from the plurality of pole teeth, and different magnetic poles are alternately arranged on the outer peripheral surface. In a stepping motor having a magnetized rotor, a gap between the pole teeth in the circumferential direction between the pole teeth of the inner yoke and the pole teeth of the outer yoke is determined by the tip of the pole teeth of the inner yoke and the outer yoke. It is characterized in that it is set narrow in the central part between the pole tooth tips.

  In the said structure, a magnetic flux can be concentrated on the center part between pole tooth tips.

  The stepping motor according to claim 2 is the stepping motor according to claim 1, wherein the length of the central portion is the length in the axial direction between the pole tooth tip of the inner yoke and the pole tooth tip of the outer yoke. It is characterized in that it is set to approximately 1/3.

  In the above configuration, it is possible to prevent the reactive magnetic flux from increasing at the tip and root of the pole teeth.

  According to a third aspect of the present invention, there is provided the stepping motor according to the first or second aspect, wherein the gap between the pole teeth at the central portion is set to be substantially uniform.

  In the above configuration, it is possible to prevent the magnetic flux from concentrating extremely and to diffuse the magnetic flux in the central portion.

  According to the present invention, the gap between the pole teeth of the inner yoke and the pole teeth of the outer yoke in the circumferential direction is the central portion between the pole tooth tip of the inner yoke and the pole tooth tip of the outer yoke. Since it is set narrowly, the reactive magnetic flux can be reduced and the effective magnetic flux can be used efficiently, and a highly efficient stepping motor suitable for miniaturization can be provided.

  Hereinafter, embodiments of the present invention will be described 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. 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).

  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.

  As shown in FIGS. 2 to 4, the inner yoke 3 (4) having a plurality of pole teeth 3 a (4 a) and the outer yoke 7 (8) having a plurality of pole teeth 7 a (8 a) face each other and mesh with each other. It is arranged. C1 is the pole teeth 3a (4a) tip of the inner yoke 3 (4) and the pole teeth 7a (8a) of the outer yoke 7 (8) arranged so that the pole teeth 3a (4a) and the pole teeth 7a (8a) mesh with each other. ) It is the central part of the pole tooth tip S1 between the tips.

  As shown in FIG. 4, in the inner yoke 3 (4) and the outer yoke 7 (8) arranged so as to face each other and mesh with each other, the circumference between the pole teeth 3a (4a) and the pole teeth 7a (8a) The interpolar gap RG in the direction is preferably set to be the narrowest in the central portion C1 of the interpolar tooth tip S1. Thereby, a magnetic flux can be concentrated on the center part C1 of S1 between the said pole tooth front-end | tips.

  Moreover, it is preferable that the length of the central portion C1 of the pole tooth tip S1 is set to be approximately 1/3 of the pole tooth tip S1. Thereby, it is possible to prevent the reactive magnetic flux at the tip and root of the pole tooth from being increased.

  On the other hand, it is preferable that the gap RG between the pole teeth of the center portion C1 is set substantially uniformly. Thereby, it can prevent that magnetic flux concentrates on one point extremely, and can diffuse magnetic flux in center part C1.

  In FIG. 2, B1 is the length of the exciting coil 5 (6) in the axial direction, and L1 is the length of the parallel portion in the axial direction of the rotor magnet 1 divided by the groove 1a.

  The center of the central portion C1 between the tip ends of the pole teeth S1 is preferably arranged substantially coincident with the center of B1 because the exciting force of the exciting coil 5 (6) can be used efficiently. Moreover, it is preferable that the center of the center portion C1 between the pole tooth tips S1 substantially coincides with the center of L1. Thereby, the magnetic force of the rotor magnet 1 can be utilized efficiently.

  According to the above embodiment, the gap RG in the circumferential direction between the pole teeth 3a (4a) of the inner yoke 3 (4) and the pole teeth 7a (8a) of the outer yoke 7 (8) is Since the central portion C1 between the tip of the pole tooth 3a (4a) of the yoke 3 (4) and the tip of the pole tooth 7a (8a) of the outer yoke 7 (8) is set narrow, the effective magnetic flux is reduced by reducing the reactive magnetic flux. Can be efficiently used, and a high-efficiency stepping motor suitable for miniaturization with high torque can be provided.

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 yoke 3 (4), 7 (8) of FIG. It is an expanded view of the pole tooth part of yoke 3 (4), 7 (8).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor magnet 1a Groove parts 3 and 4 Inner yokes 3a and 4a Inner yoke pole teeth 7a and 8a Outer yoke pole teeth 5 and 6 Excitation coils 7 and 8 Outer yokes 9 and 10 Stator 13 Inner yoke joint S1 Inner pole Tooth and outer yoke pole tooth length G gap RG Circumferential tooth gap B1 Excitation coil axial length L1 Rotor magnet 1 axial parallel length

Claims (3)

A stator composed of an inner yoke and an outer yoke having a plurality of pole teeth arranged alternately facing each other in the circumferential direction, and an excitation coil sandwiched between the yokes, and a plurality of members disposed by joining the inner yokes In a stepping motor provided with a rotor that is rotatably arranged with a predetermined gap from the plurality of pole teeth in a central hole that penetrates the stator, and different magnetic poles are alternately magnetized on the outer peripheral surface,
The gap between the pole teeth of the inner yoke and the pole teeth of the outer yoke in the circumferential direction is set narrow at the center between the pole tooth tip of the inner yoke and the pole tooth tip of the outer yoke. Stepping motor characterized by being made.   2. The length of the central portion is set to approximately 1/3 of the axial length between the pole tooth tip of the inner yoke and the pole tooth tip of the outer yoke. Stepper motor.   The stepping motor according to claim 1, wherein the gap between the pole teeth at the center is set to be substantially uniform.

Images