JP2007124851A - Stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stepping motor having less vibration that reduces cogging only without deteriorating torque characteristics. <P>SOLUTION: This stepping motor is made up of a freely rotatable rotor comprising a cylindrical permanent magnet, supported by a rotating shaft, in which N poles and S poles are alternately magnetized at predetermined pitches in the radial direction on the circumferential surface, a stator 2 structured by stacking a set of annular stator yokes 4, 5 in two layers, in which a plurality of pole teeth 15 arrayed in a comb shape are engaged with each other and combined having the predetermined pitches corresponding to the pitches of the magnetic poles of the rotor, and exciting coils that excite the pole teeth 15 of the stator yokes 4, 5 to different poles from each other. A cutout is provided from the tip end portion side toward the base portion side on each pole tooth 15 so as to scatter the concentration of magnetic force at the tip end portion side of the pole teeth 15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stepping motor, and more particularly to a stepping motor including a stator having a pair of annular yokes in which pole teeth arranged in a comb shape are alternately meshed.

  In recent years, the permanent magnet type stepping motor has been increasingly used as various actuator parts because of its good controllability.

  Most permanent magnet type stepping motors are combined with two-phase exciting coils and pole teeth arranged in a comb-like pattern for each phase alternately arranged in correspondence with each other. Two-phase annular yokes, and magnetic poles (N poles, S poles) rotatably supported in the hollow portions of these annular yokes via a rotating shaft and corresponding to the pole teeth of the annular yoke And a rotating permanent magnet (rotor) that is alternately magnetized with different polarities at a constant pitch. Then, the rotor is rotated by a certain rotation angle by the magnetic attraction force or magnetic repulsion force between the excitation pole formed on the pole teeth of the annular yoke and the magnetic pole of the rotor by inputting a pulse signal shifted in phase to each excitation coil. It is to be moved (for example, see Patent Document 1).

In recent years, permanent magnet type stepping motors are used not only for actuator parts but also for various types of equipment. With the improvement in performance of various types of equipment, high torque, low cogging, low vibration, Quality stepping motors are in demand.
JP-A-10-94236.

  However, in a stepping motor, the demands for high torque, low cogging and low vibration are contradictory, and it is difficult to satisfy both. That is, in this type of stepping motor, the entire surface of one pole tooth corresponds to one pole of the rotating permanent magnet, so that the detent torque is likely to increase, and the static angle error, vibration characteristics, and damping characteristics tend to deteriorate. Therefore, if the surface magnetic flux of the permanent magnet is dropped in order to reduce the detent torque, there is a problem that the torque characteristics are also lowered.

  Therefore, there is a technical problem to be solved in order to provide a low-vibration stepping motor by reducing only cogging without reducing the torque characteristics, and the present invention aims to solve this problem. To do.

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 is a cylindrical permanent magnet in which N poles and S poles are alternately magnetized at a predetermined pitch on a radial circumferential surface. A rotatable rotor that is supported by a rotating shaft, and a plurality of pole teeth arranged in a comb shape having a predetermined pitch corresponding to the pitch of the magnetic poles of the rotor are alternately meshed and combined. A stator composed of an annular yoke and an exciting coil for exciting the pole teeth of the annular yoke to different polarities, so that the magnetic force concentration on the tip side of the pole teeth is distributed to each of the pole teeth. Provided is a stepping motor characterized in that a notch is provided from the tip side toward the root side.

According to this configuration, when a cut is made in the tip portion of the pole tooth, the magnetic field at the tip portion is dispersed and the detent torque is reduced. In addition, since the magnetic field has the property of being easily collected at the tip of the pole tooth, even if the pole tooth area is reduced by cutting, the same torque characteristics can be obtained. Therefore, even if the pole tooth width and the surface magnetic flux of the permanent magnet are the same as the conventional one, the detent torque is smaller than that of the conventional stepping motor, and a stepping motor having the same magnitude in torque characteristics can be obtained.

  A second aspect of the present invention provides a stepping motor according to the first aspect, wherein the stator is formed by stacking a plurality of the annular yokes.

  According to this configuration, a stepping motor having a larger number of step stages can be obtained.

  A third aspect of the present invention provides a stepping motor according to the first aspect, wherein the cut is formed in a slit shape.

  According to this configuration, a stepping motor having a slit-like cut from the tip can be obtained.

  According to a fourth aspect of the present invention, there is provided a stepping motor according to the first aspect, wherein the notch is formed into a trapezoidal shape that gradually becomes narrower as it advances toward the base portion.

  According to this configuration, it is possible to obtain a stepping motor having a slit-like cut formed in a trapezoidal shape that gradually becomes narrower as it goes from the tip to the base.

  According to a fifth aspect of the present invention, there is provided a stepping motor according to the first aspect, wherein the notch is formed in a triangular shape so as to gradually become narrower as it advances toward the root portion.

  According to this configuration, it is possible to obtain a stepping motor having slit-like cuts formed in a triangular shape that gradually becomes narrower as it goes from the tip portion toward the root portion.

  According to the first aspect of the present invention, even if the pole tooth width and the surface magnetic flux of the permanent magnet are the same as the conventional one, the detent torque can be reduced and the torque characteristic can be made equal to the conventional one. Without dropping, it is possible to obtain a low vibration stepping motor by reducing only cogging.

  According to the second aspect of the present invention, in addition to the effect of the first aspect of the invention, a high-function stepping motor having a larger number of step stages can be provided by stacking a plurality of the annular yokes.

  According to the third aspect of the invention, since the cut can be easily made by making the cut into a slit shape, the manufacturing is simplified in addition to the effect of the invention of the first aspect.

  In the invention according to claim 4, the notch can be easily made by making the slit into a trapezoidal slit shape gradually becoming narrower as it advances from the tip portion toward the root portion side. In addition to the effects of the first invention, the manufacturing is simplified.

  In the invention according to claim 5, since the slit can be easily made by making the slit into a triangular shape that gradually becomes narrower as it advances from the tip portion toward the root portion side, In addition to the effect of the invention of Item 1, the manufacturing is simplified.

  Hereinafter, the stepping motor of the present invention will be described with reference to preferred embodiments. A cylindrical permanent magnet in which N poles and S poles are alternately magnetized at a predetermined pitch on the circumferential surface in the radial direction in order to achieve the purpose of reducing only cogging and reducing vibration without reducing torque characteristics. A rotatable rotor that is supported by a rotating shaft, and a plurality of pole teeth arranged in a comb shape having a predetermined pitch corresponding to the pitch of the magnetic poles of the rotor are alternately meshed and combined. And a pair of annular yokes stacked in at least two phases, and an exciting coil that excites the pole teeth of the annular yoke to different polarities. This was realized by providing a cut from the tip side toward the root side so as to disperse the magnetic force concentration.

  FIG. 1 is a longitudinal sectional view of a permanent magnet type stepping motor according to the present invention. As shown in FIG. 1, the stepping motor 1 is mainly composed of two sets of stators 2 and 2 and one rotor 3.

  Each stator 2 is formed by three-dimensionally punching a steel plate, and a part of the inner periphery of the main body punched out in a donut shape is bent at a substantially right angle, and the bent inner periphery is shown in FIG. Thus, a plurality of pole teeth 15 are provided in a comb shape, and a set of annular stator yokes 4 and 5 are provided. Then, the stator yoke 4 and the stator yoke are arranged so that the tooth pole 15 on one side (stator yoke 4) of the stator yokes 4 and 5 meshes with the pole tooth 15 on the other side (stator yoke 5) at equal intervals. 5 is combined with each other, and an excitation coil 7 formed by winding a magnet wire around an annular bobbin 6 is interposed between the pair of stator yokes 4 and 5, and the excitation coil 7 is It is formed as an encased stator 2.

  The two sets of stators 2, 2 made in this way are stacked back to back and integrated as a two-phase annular yoke, and flanges 8, 9 made by punching steel plates on the upper and lower surfaces respectively. It is fixed by a method such as welding. Further, as shown in FIGS. 2 and 3, each tooth pole 15 of each stator yoke 4, 5 is provided with an elongated slit-shaped notch 16 from the tip side toward the root side. In addition, in this example, each pole tooth 15 shows what was formed in the trapezoid shape where a width | variety becomes narrow as it goes to the front-end | tip part side from a base part, but the rectangular shape which has the same width from a base part to a front-end | tip part. The pole teeth formed by may be used.

  On the other hand, the rotor 3 is press-fitted and fixed to a rotation shaft 11 having a resin holder 10 as a rotation center, and a cylindrical permanent magnet 12 is coaxially fixed to the outer peripheral surface of the holder 10. The method of fixing the permanent magnet 12 may be a method of insert molding the permanent magnet 12 or a method of press-fitting the holder 10 into the permanent magnet 12. Note that N and S poles are alternately magnetized on the circumferential surface of the permanent magnet 12 in the circumferential direction of the permanent magnet 12 using a magnetizer (not shown). In this magnetization, one pole is provided at an interval corresponding to the entire surface of one pole tooth 15 of the stator yokes 4 and 5.

  The rotor 3 configured in this manner is arranged in the stators 2 and 2 with the permanent magnets 12 spaced apart from the pole teeth 15 of the stator 2 by a small distance, and the rotating shaft 11 is connected to the center part of the flanges 8 and 9. By being rotatably attached to the bearing 13 and the bearing 14 that are respectively fixed to each other, the stator 2 is rotatably arranged.

  Since the stepping motor 1 configured in this manner rotates due to the interaction of the rotor 3 with the magnetic flux excited in the stator 2, an annular pulse signal is input to the excitation coil 7 of each stator 2. An exciting pole is formed on the pole teeth 15 of the yoke (stator yokes 4 and 5), and the rotor 3 is moved at a certain rotation angle by the magnetic attractive force or magnetic repulsive force between the exciting pole and the magnetic pole of the rotor 3 (permanent magnet 12). Rotate and move. This is sequentially repeated every time a pulsed drive voltage (pulse signal) is input, and stepping rotation is performed.

  Therefore, according to the structure of this embodiment, the pole teeth 15 of the stator yoke 4 and the stator yoke 5 are provided with slits 16 in the form of elongated slits from the tip side toward the root side. Since the magnetic field at the tip portion of the pole tooth 15 is dispersed by the notch 16, the detent torque is reduced. Further, since the magnetic field tends to gather at the tip of the pole tooth 15, even if the pole tooth area is reduced by cutting, an equivalent torque characteristic can be obtained. Therefore, even if the width of the pole teeth 15 and the surface magnetic flux of the permanent magnet 12 are the same as those of the conventional stepping motor, the detent torque is smaller than that of the conventional stepping motor and the torque characteristics are the same as those of the conventional stepping motor. Become. As a result, even if the width of the pole teeth 15 and the surface magnetic flux of the permanent magnet 12 are the same as the conventional one, the detent torque is smaller than that of the conventional stepping motor, and the torque characteristic is the same as the conventional stepping motor. Simply by making incisions, it can be easily obtained without significantly changing the structure.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

  For example, in the structure of the above-described embodiment, the notch 16 provided in the pole tooth 15 is disclosed as a long and narrow slit shape from the distal end side toward the root portion side. For example, as shown in FIG. The notch 17 is formed in a trapezoidal shape that becomes gradually narrower as it goes to the part side, or it is formed in a triangular shape so that it gradually becomes narrower as it goes to the root part side as shown in FIG. An incision 18 may be provided. Moreover, although the structure of the two-phase stepping motor has been disclosed, it can be applied in the same manner even if it is other than two-phase.

1 is a longitudinal sectional view of a stepping motor according to the present invention. Sectional drawing which shows the structure of the stator in a stepping motor same as the above. The enlarged top view of the pole tooth in a stator same as the above. The top view which shows the modification of a pole tooth same as the above. The top view which shows the other modification of a pole tooth same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stepping motor 2 Stator 3 Rotor 4 Stator yoke 5 Stator yoke 6 Bobbin 7 Excitation coil 8 Flange 9 Flange 10 Holder 11 Rotating shaft 12 Permanent magnet 13 Bearing 14 Bearing 15 Polar teeth 16 Notch 17 Notch 18 Notch 18

Claims (5)

  A rotatable rotor formed by supporting a cylindrical permanent magnet having N poles and S poles alternately magnetized on a circumferential surface in a radial direction with a rotating shaft, and a predetermined value corresponding to the pitch of the magnetic poles of the rotor A stator composed of an annular yoke in which a plurality of pole teeth arranged in a comb-teeth shape are alternately meshed and combined, and an exciting coil for exciting the pole teeth of the annular yoke to different polarities. The stepping motor is characterized in that a cut is provided in each of the pole teeth from the tip side toward the root side so as to disperse the magnetic force concentration on the tip side of the pole tooth.   2. The stepping motor according to claim 1, wherein the stator is formed by stacking a plurality of the annular yokes.   The stepping motor according to claim 1, wherein the cut is formed in a slit shape.   The stepping motor according to claim 1, wherein the notch is formed in a trapezoidal shape that gradually becomes narrower as it advances toward the base portion. The stepping motor according to claim 1, wherein the stepping motor is formed in a triangular shape so as to gradually become narrower as it advances toward the root portion.

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