JP2007181264A - Stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat stepping motor which is constituted so that it can output relatively high torque, being flat. <P>SOLUTION: This figure is a schema which shows the arrangement of the magnetic poles of magnets 10a and 10b that constitute the rotor 7 of a stepping motor. For the topside magnet 10a and the downside magnet 10b of the rotor 7, alternate magnetic poles are magnetized in heteropolarity in its circumferential direction, and for the topside magnet 10a and the downside magnet 10b, their opposed magnetic poles are magnetized in homopolarity. The first stator assembly 12 is arranged at a specified gap from the topside magnet 10a of the rotor 7, and the second stator assembly 13 is arranged at a specified gap from the downside magnet 10b. The first stator assembly 12 and the second stator assembly 13 are slid for π/2 each in electric angle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stepping motor that is driven to rotate stepwise by a pulse signal, and more particularly to a PM type stepping motor that uses a permanent magnet as a rotor.

  Conventionally, a PM type stepping motor using a magnet as a rotor has a strong torque and high positioning accuracy, and is therefore preferably used for precision equipment such as a facsimile, a video camera, and a flexible disk drive. Such a PM type stepping motor includes a claw pole type stepping motor in which a permanent magnet is formed by a long rotor, and a flat type stepping motor in which a permanent magnet is formed by a thin disk rotor. are categorized. The former claw pole type stepping motor is disclosed in, for example, Patent Document 1, and the latter flat type stepping motor is disclosed in, for example, Patent Document 2. A claw pole type stepping motor can obtain a relatively large torque, but a flat type stepping motor is suitable for a thin shape in terms of structure. Further, Patent Document 3 proposes a flat type stepping motor having a structure using a silicon copper plate punched into the core portion, and this flat type stepping motor can be constructed at low cost from the structure. There is.

  The structure of a general flat type stepping motor is also disclosed in Patent Document 3 and the like, and is not particularly shown. However, a disc that is magnetized at equal intervals so as to have different magnetic poles alternately on both sides of the outer peripheral surface. A rotor having a magnet of a type, and having a gap on one surface of the magnet and coaxially arranged, radially extending outwardly and externally extending radially outwardly toward the center, the internal teeth And a first stator assembly having coils for exciting the external teeth, and a second stator assembly having the same configuration as described above and having a gap on the other surface of the magnet. It has become.

  FIG. 11 is a perspective view showing magnetic poles of a magnet formed on a disk-type rotor of a conventional flat type stepping motor. As shown in FIG. 11, a resin core 32 is fitted in the central portion of the rotor 31 formed in an annular shape, and a through hole 33 for press-fitting a rotating shaft (shaft) (not shown) is provided in the central portion. It has been. On the circumference of the upper surface side (front surface side) of the rotor 31, a magnet 34 magnetized in multiple poles is arranged so that S poles and N poles are alternately arranged. Further, although not shown in FIG. 11, the magnet 34 has N-pole and S-pole magnetic poles alternately on the circumference on the lower surface side (back surface side) with opposite polarities to the opposing magnetic poles on the upper surface side. Has been placed. The rotor 31 formed in this way is configured to be able to rotate stepwise by a pulse magnetic flux from a stator assembly (not shown).

FIG. 12 is a schematic diagram showing the magnetic pole arrangement and the stator arrangement of the upper surface side and lower surface side magnets in the rotor of FIG. As shown in FIG. 12, the magnet 34a on the upper surface side of the rotor 31 has S poles and N poles arranged alternately, but the magnet 34b on the lower surface side of the rotor 31 faces the S pole of the magnet 34a on the upper surface side. Thus, the N pole is arranged, and the S pole is arranged opposite to the N pole of the upper surface side magnet 34a. The poles of the poles are arranged alternately. That is, the magnet 34a on the upper surface side and the magnet 34b on the lower surface side of the rotor 31 are magnetized with opposite polarities of different polarities. The first stator assembly 35 and the second stator assembly 36 arranged with gaps on both surfaces of the magnets 34a and 34b in the rotor 31 are arranged at positions where the π / 2 phase is shifted in electrical angle. ing.
JP-A-8-88965 JP-A-62-268353 Japanese Patent Laying-Open No. 2005-110376

  However, the conventional flat type stepping motor uses a disk-type flat magnet because of its structure. As shown in FIG. 12, each of the upper surface side magnet 34a and the lower surface side magnet 34b. When the opposing magnetic poles are magnetized with different polarities, the magnetic paths of the magnets 34a and 34b are in separate directions on the upper surface side and the lower surface side, so the magnetic path becomes shorter. That is, the upper-side magnet 34a has a magnetic path formed by the first stator assembly 35 disposed on the upper surface side, and the lower-side magnet 34b has a magnetic path formed by the second stator assembly 36 disposed on the lower surface side. . For this reason, it is difficult to further increase the magnetic flux generated from the first stator assembly 35 and the second stator assembly 36, and as a result, there is a problem that the torque of the stepping motor cannot be further increased.

  Therefore, a technical problem to be solved in order to obtain a flat stepping motor structure that is thin and capable of outputting a relatively high torque arises, and the present invention solves the problem. It is for the purpose.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 is a stepping in which a predetermined gap is provided on both sides in the rotational axis direction of the rotor magnet, and a pair of stator assemblies are provided respectively. In the rotor magnet, magnetic poles of different polarities are alternately arranged in the circumferential direction of each surface facing the stator assembly, and the opposing magnetic poles on the one surface side and the other surface side on the upper and lower surfaces, respectively. It has a configuration arranged with the same polarity.

  According to such a stepping motor, in a flat type stepping motor using a rotor magnet in which a magnet is formed on a disk-type rotor, one side (for example, the upper surface side or the surface side) and the other surface side of the rotor magnet In each circumferential direction (for example, the lower surface side or the back surface side), each magnetic pole is magnetized so that magnetic poles of different polarities are alternately arranged, and on the upper and lower surfaces in the axial direction of the rotor magnet, The magnetic poles are magnetized so that the opposing magnetic poles on one surface side (for example, the upper surface side or the front surface side) and the other surface side (for example, the lower surface side or the back surface side) have the same polarity.

  The invention according to claim 2 is the invention according to claim 1, wherein the magnetic pole on the one surface side and the magnetic pole on the other surface side are arranged at equal intervals in the circumferential direction.

  According to such a stepping motor, the magnetic poles on both sides of the rotor magnet are arranged at equal intervals in the circumferential direction so as to generate a uniform torque output and step at equal pitch intervals.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the iron core constituting the stator assembly is composed of a silicon steel plate.

  According to such a stepping motor, the iron core of the stator assembly is made of a silicon steel plate so as to generate a large magnetic flux and obtain a strong torque.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the silicon steel plate is formed by punching a plate material and has a laminated structure.

  According to such a stepping motor, in order to suppress the heat generation by reducing the eddy current of the iron core generated by the magnetic flux as much as possible, the silicon steel plates configured as the iron core of the stator assembly are laminated.

  According to the invention of claim 1, by making the opposing magnetic poles on the upper and lower surfaces of the rotor magnet have the same polarity, the magnetic path in the magnet that has conventionally been in a separate direction on the upper and lower surfaces of the rotor magnet, The direction of the magnetic poles on both sides of each magnetic pole can be changed. Thereby, the magnetic path becomes longer than the rotor magnet of the conventional stepping motor, and the magnetic flux generated by the coil can be increased. As a result, it is possible to increase the holding torque (torque that holds the stop position against an external force) and to improve the torque speed characteristic (characteristic capable of obtaining high torque at a high frequency).

  According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the magnetic poles on both sides of the rotor magnet are arranged at equal intervals in the circumferential direction. Output can be generated and stepped at equal pitch intervals.

  According to the invention described in claim 3, in addition to the effects of the invention described in claims 1 and 2, since the iron core of the stator assembly is composed of a silicon steel plate, a large magnetic flux is generated to generate a strong torque. Obtainable.

  According to the invention described in claim 4, in addition to the effect of the invention described in claim 3, the silicon steel plate configured as the iron core of the stator assembly has a laminated structure. By reducing the current as much as possible, the heat generation of the stepping motor can be suppressed.

  The present invention is directed to a stepping motor in which a pair of stator assemblies are provided on both sides of the rotor magnet in the direction of the rotation axis of the rotor magnet for the purpose of increasing the holding torque and improving the motor characteristics, on the surface facing the stator assembly of the rotor magnet. This is realized by arranging different polarities alternately and arranging the same polarities on the upper and lower surfaces.

  A preferred embodiment of the present invention will be described below with reference to FIGS. In the claims, a configuration in which a magnet is formed on the rotor is expressed as a rotor magnet. However, in the following embodiments, the rotor and the magnet will be described separately for easy understanding. That is, the stepping motor according to the present invention is magnetized at equal intervals so as to be magnetic poles of different polarities alternately in the circumferential direction on the upper surface side and the lower surface side of the disk-shaped rotor, and the upper and lower surfaces of the rotor And a rotor having a disk-type magnet in which each magnetic pole is magnetized so that the opposite magnetic poles have the same polarity and a gap on the same axis of one side of the magnet are arranged with a gap extending radially outward A first stator assembly having an inner tooth and an outer tooth extending radially opposite to the center, and having a coil for exciting the inner tooth and the outer tooth; and a first starter disposed with a gap on the other surface of the magnet. The second stator assembly has the same configuration as the assembly. Further, the first stator assembly and the second stator assembly arranged on both surfaces of the magnet are respectively arranged at positions where the π / 2 phase is shifted in electrical angle.

  With such a configuration, the magnetic path in the magnet can be changed to the magnetic pole directions on both the upper and lower surfaces of each magnetic pole, so that the magnetic path becomes longer, and as a result, is generated by the first and second stator assemblies. Magnetic flux increases. As a result, it is possible to increase the holding torque that can hold the stop position against an external force, and it is possible to improve torque speed characteristics and obtain a large torque even with a high frequency pulse.

  Hereinafter, specific embodiments of a stepping motor according to the present invention will be described in detail with reference to the drawings. In the drawings used in each embodiment described below, the same components are denoted by the same reference numerals, and redundant description will be omitted as much as possible.

  First, a basic configuration of a stepping motor according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing a stepping motor 1 according to an embodiment of the present invention, and FIG. 2 is a plan view showing a rotor 7 of the stepping motor shown in FIG. FIG. 3 is a plan view for explaining a magnetized portion of the magnet 10 shown in FIG. 4 is a plan view showing the first stator assembly 12 of the stepping motor 1 shown in FIG. 1, and FIG. 5 is a plan view showing the second stator assembly 13 of the stepping motor 1 shown in FIG. FIG. 6 is an exploded perspective view of the stepping motor 1 shown in FIG.

  In FIG. 1, a circular flange 3 is fixed to one end face of a flat and short cylindrical casing 2. A shaft 6 is rotatably mounted at the center of the casing 2 via bearings 4 and 5. The bearings 4 and 5 are made of an iron-based material, and the axial lengths of the bearings 4 and 5 are slightly longer. In addition, the coil terminal part entrance / exit which is not shown in figure is formed in the suitable place of the casing 2. As shown in FIG.

  Further, a rotor 7 formed in a flat disk shape is attached to an axially intermediate portion of the shaft 6. As shown in FIG. 2, the rotor 7 includes a rotor housing 9 having a shaft penetrating hole 8 and a magnet 10 integrally provided on the outer peripheral side of the rotor housing 9. Are integrally penetrated and fixed.

  As shown in FIG. 3, there are a large number of magnetized portions 11 in which N poles and S poles are alternately formed on the outer peripheral portions on both sides of the magnet 10, for example, 48 pieces (48 poles) in the illustrated example. Are provided at equal pitches (equal intervals) along the circumferential direction of the magnet 10. In FIG. 3, the N pole and S pole magnetized portions on the back side (back side of the paper) of the magnet 10 are not displayed. The magnet 10 is formed by punching a metal plate material. Further, the magnetized portion 11 of the magnet 10 can be provided by being formed in comb-shaped pole teeth.

  A pair of stator assemblies of a first stator assembly 12 and a second stator assembly 13 are fixed inside the casing 2 of FIG. 1, and these first and second stator assemblies 12 and 13 are arranged in the axial direction of the shaft 6. They are arranged at predetermined intervals (in the vertical direction in FIG. 1). That is, the first stator assembly 12 for A-phase excitation and the second stator assembly 13 for B-phase excitation are arranged with a predetermined gap on both sides of the magnet 10 in the axial direction of the rotor 7.

In FIG. 1, the first and second stator assemblies 12, 13 include a coil 14 wound around a resin bobbin (not shown) and a cylindrical iron core 15 provided on the inner diameter side of the coil 14. ing. The iron core 15 can be formed of a magnetic material such as a laminated material of silicon copper plate, a laminated material of SECC, an iron-based sintered material, or a copper-based sintered material, and by changing the material of these magnetic materials It is possible to cope with a change in required magnetic properties. When the iron core 15 is laminated with a silicon copper plate or the like, the laminating direction is made to coincide with the radial direction of the coil 14 so as to reduce the magnetic resistance in the example of FIG. 1, but the present invention is not limited to this. It is also possible to stack 14 axial directions.

  As shown in FIG. 4, the end surface of the coil 14 facing the rotor 7 has a stator body 16 formed in an annular shape in plan view, and a disk type provided on the inner peripheral side of the stator body 16. A yoke 17 is attached, and a hole 18 corresponding to the inner diameter of the casing 2 is formed at the center of the disk-type yoke 17. The outer stator body 16 and the inner disk type yoke 17 are formed by punching one flat metal plate material and shaping the material into an annular or disk shape having pole teeth.

  4 and 5 show the planar shapes of the first stator assembly 12 and the second stator assembly 13, respectively. As shown in FIGS. 4 and 5, a plurality of external teeth 19 are formed on the inner peripheral portion of the stator body 16 of the first and second stator assemblies 12, 13, and the outer teeth 19 on the inner peripheral edge side are the stator teeth. 48 are provided at equal pitches along the circumferential direction of the main body 16. Further, the outer peripheral teeth 19 on the inner peripheral edge side are arranged so as to face each other with a predetermined gap in the axial direction of the shaft 6 with respect to the magnetized portion 11 on the magnet 10 side.

  Further, the outer peripheral shape of the inner disk-type yoke 17 is formed in a tooth profile that matches the inner peripheral tooth profile of the stator body 16. In other words, 48 outer teeth 20 are formed on the outer periphery of the disk-shaped yoke 17 so as to correspond to the outer teeth 19 on the inner periphery of the stator body 16, and the outer teeth 19 and the inner teeth 20 are mutually connected. It is arranged to be inserted.

  4 and 5, the outer air gap G1 in the radial direction between the inner teeth 20 on the outer peripheral edge side and the stator body 16 is in the radial direction between the outer teeth 19 on the inner peripheral edge side and the disk-type yoke 17. Although it is larger than the inner air gap G2, the size of the inner air gap G2 can be equal to or smaller than the outer air gap Gl if necessary.

  The stepping motor 1 configured in this way can be disassembled into parts as shown in FIG. That is, the rotor 7 is mainly composed of the shaft 6, the rotor housing 9, and the magnet 10, and the first stator assembly 12 and the second stator assembly 13 are mainly the casing 2, the bearing 4 (or 5), and the coil, respectively. 14, outer teeth 19, and inner teeth 20.

  In the stepping motor of the present invention, in the basic configuration as described above, the magnet 10 is magnetized so that magnetic poles of different polarities are alternately arranged in the circumferential directions of the upper surface and the lower surface of the rotor 7. In addition, on the upper and lower surfaces in the axial direction of the rotor 7, the magnet 10 is magnetized so that the magnetic poles facing each other on the upper surface side and the lower surface side have the same polarity.

  FIG. 7 is a schematic diagram showing the polarities of the magnetic poles of the magnetized portion 11 on both sides of the magnet 10 in FIG. 7 shows a part of the 48 magnetic poles of the magnet 10 in FIG. That is, as shown in FIG. 7, the magnet 10a on the upper surface side of the rotor 7 is magnetized so that the N-pole and S-pole magnetic poles are alternately different in polarity. In addition, the magnet 10b on the lower surface side of the rotor 7 is alternately magnetized with N and S poles having different polarities so that the magnetic poles facing the magnetic poles of the magnet 10a on the upper surface side have the same polarity. That is, the upper surface side magnet 10a and the lower surface side magnet 10b of the rotor 7 are magnetized with different polarities in the circumferential direction, and the upper surface side magnet 10a and the lower surface side magnet 10b face each other. The magnetic poles are magnetized with the same polarity.

  A first stator assembly 12 is disposed on the upper surface of the rotor 7 with a predetermined gap from the upper surface side magnet 10a, and a second stator assembly 13 is disposed on the lower surface with a predetermined gap from the lower surface side magnet 10b. Has been placed. The first stator assembly 12 and the second stator assembly 13 are arranged at positions where the π / 2 phase is shifted in electrical angle.

  By arranging the magnetic poles of the magnet 10 as shown in FIG. 7, the magnetic paths in the magnet 10 of FIG. 1 (magnets 10a and 10b in FIG. 7) are changed to the magnetic pole directions on the upper and lower surfaces of each magnetic pole. Therefore, the magnetic path becomes longer than that of the conventional magnetic pole configuration shown in FIG. For example, in FIG. 7, the magnetic pole direction can be changed to the magnetic path of the route of N pole of the magnet 10a → first stator assembly 12 → second stator assembly 13 → S pole of the magnet 10b. The length of the magnetic path is about twice as long as that of the conventional magnetic pole configuration. As a result, the magnetic flux generated by the coil increases, and as a result, the holding torque that holds the stop position against the external force can be increased, and the torque speed characteristics can be obtained even with a high frequency pulse. Can be improved.

  That is, in the conventional stepping motor, as shown in FIG. 12, since the opposing magnetic poles of the upper and lower magnets 34a and 34b have different polarities, the S pole of the magnet 34a → the first stator assembly 35 → N of the magnet 34a. Since the magnetic paths of the magnets 34a and 34b are separate magnetic paths, such as the magnetic path of the poles and the magnetic path of the N pole of the magnet 34b → the second stator assembly 36 → the S pole of the magnet 34b, Since the magnetic path is short, the magnetic flux of the coil cannot be increased. However, as shown in FIG. 7, the opposing magnetic poles on the upper and lower surfaces of the magnets 10a and 10b are made to have the same polarity, so that the magnetic paths in the magnets 10a and 10b are changed to the first stator assemblies 12 on both upper and lower surfaces of each magnetic pole. And the second stator assembly 13 can be changed so that the magnetic path becomes longer, resulting in an increase in the generated magnetic flux, thereby realizing an increase in holding torque and an improvement in torque speed characteristics. It becomes possible.

  FIG. 8 is a diagram showing experimental results of the holding torque in the conventional and stepping motors of the present invention. That is, the holding torque of the conventional stepping motor in which the magnetic poles on the upper and lower surfaces of the magnet are different magnetic poles was 13.7 mNm (millinewton meter), whereas the magnetic poles on the upper and lower surfaces of the magnet are the same magnetic pole. The holding torque of the stepping motor is 20.6 mNm, and the holding torque of the stepping motor according to the present invention is 150% (1.5 times) that of the prior art.

  FIG. 9 is a diagram showing experimental results of torque speed characteristics in the conventional and stepping motors of the present invention. As shown in FIG. 9, when the frequency of the driving pulse of the stepping motor is 400 PPS (Pulses Per Second), the pull-out torque of the conventional stepping motor (torque that can continue to rotate even when a load is applied) is 11. Whereas it is 85 mNm, the pull-out torque of the stepping motor of the present invention is 12.935 mNm, and the torque speed characteristic is improved by 109%.

  In general, the torque speed characteristic of a stepping motor decreases as the pulse frequency increases. However, even when the driving pulse frequency is 1200 PPS, the pullout torque of the conventional stepping motor is 8.26 mNm. The pull-out torque of the stepping motor is 8.73 mNm, and the torque speed characteristic is improved by 106%. That is, as can be seen from FIG. 9, when the frequency of the driving pulse is 800 PPS, the torque speed characteristic of the stepping motor of the present invention is improved by 110% (1.1 times) at the maximum.

  FIG. 10 is a graph showing torque speed characteristics in the conventional and stepping motors of the present invention, where the horizontal axis represents pulse frequency (PPS) and the vertical axis represents pullout torque (mNm). As can be seen from FIG. 10, the pull-out torque of the stepping motor of the present invention is improved over the pull-out torque of the conventional stepping motor in all pulse frequency ranges.

  The above embodiment shows an example in which a normal magnetic iron core is used for the core portion. However, the flat type stepping motor using the iron core having a structure using a silicon copper plate punched for the core portion is also described above. The same effect as in the embodiment can be obtained. Furthermore, even if the silicon copper plate is laminated to reduce the eddy current in the iron core, the same effect as in the above-described embodiment can be obtained.

  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.

It is sectional drawing which shows the stepping motor 1 which concerns on one Example of this invention. It is a top view which shows the rotor 7 of the stepping motor shown in FIG. It is a top view explaining the magnetization part of the magnet 10 shown in FIG. FIG. 2 is a plan view showing a first stator assembly 12 of the stepping motor 1 shown in FIG. 1. It is a top view which shows the 2nd stator assembly 13 of the stepping motor 1 shown in FIG. It is a disassembled perspective view of the stepping motor 1 shown in FIG. It is a schematic diagram which shows the polarity of the magnetic pole of the magnetized part 11 in the both surfaces side of the magnet 10 in FIG. It is a figure which shows the experimental result of the holding torque in the stepping motor of the past and this invention. It is a figure which shows the experimental result of the torque speed characteristic in the conventional stepping motor of this invention. It is a figure which shows the graph of the torque speed characteristic in the conventional stepping motor of this invention. It is a perspective view which shows the magnetic pole of the magnet formed in the disc shaped rotor of the conventional flat type stepping motor. FIG. 12 is a schematic diagram illustrating a magnetic pole arrangement and a stator arrangement on the upper surface side and the lower surface side of the rotor of FIG. 11.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stepping motor 2 Casing 3 Flange 4, 5 Bearing 6 Shaft 7 Rotor 8 Hole 9 Rotor housing 10, 10a, 10b Magnet 11 Magnetized part 12 1st stator assembly 13 2nd stator assembly 14 Coil 15 Iron core 16 Stator body 17 Disc type Yoke 18 Hole 19 External tooth 20 Internal tooth 31 Rotor 32 Resin core 33 Through hole 34, 34a, 34b Magnet 35 First stator assembly 36 Second stator assembly

Claims (4)

A stepping motor in which a predetermined gap is provided on both sides of the rotation axis direction of the rotor magnet, and a pair of stator assemblies are provided,
In the rotor magnet, magnetic poles of different polarities are alternately arranged in the circumferential direction of the respective surfaces facing the stator assembly, and the opposing magnetic poles on the one surface side and the other surface side have the same polarity on the upper and lower surfaces, respectively. A stepping motor characterized by being arranged.   2. The stepping motor according to claim 1, wherein the magnetic pole on the one surface side and the magnetic pole on the other surface side are arranged at equal intervals in the circumferential direction.   3. The stepping motor according to claim 1, wherein the iron core constituting the stator assembly is a silicon steel plate. 4. The stepping motor according to claim 3, wherein the silicon steel plate is formed by punching a plate material and is laminated.

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