JP2006288065A - Stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a small stepping motor which can be processed and assembled easily and producing a large output torque. <P>SOLUTION: The stepping motor comprises a rotor 13 having a permanent magnet 12 magnetized with multi-poles in the thrust direction and secured to a rotating shaft 11, bearings 14 and 15 for supporting the rotor 13 rotatably, a housing 16 for securing the bearings 14 and 15 while keeping at predetermined positions and formed to surround the rotor, and stators 17-20 having a U-shaped core wound with a coil and fixed to the bearings 14 and 15. The stators are provided, respectively, with a protrusion at the distal end of the core and arranged to be inserted with the rotor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stepping motor.

The configuration of a conventional stepping motor is shown in FIG.
FIG. 10 is a perspective view showing a conventional claw-pole PM type stepping motor with a part broken away.

  The stepping motor 50 includes a permanent magnet 54, an A-phase stack 51, and a B-phase stack 52. The permanent magnet 54 is composed of a plurality of magnetic bodies 53 in which N poles and S poles are alternately arranged outward in the radial direction of the rotor.

  The A-phase stack 51 is composed of an upper pole 51a, a lower pole 51b, and a coil 51c. Similarly, the B-phase stack 52 is formed of an upper pole, a lower pole 52b, and a coil 52c which are not shown. The A-phase stack and the B-phase stack are arranged with a ¼ pole pitch shifted.

  In the stepping motor configured as described above, the winding length of the coil is longer than the number of turns. Along with this, the resistance of the coil increases and the flowing current decreases. Moreover, since a coil is arrange | positioned on the outer side of a permanent magnet, a radius will become large with respect to the number of turns. In reducing the size, the number of turns decreases as the radius decreases. Since the magnetomotive force of the coil is expressed by the product of the current flowing through the coil and the number of turns, if the size is reduced, a sufficient magnetomotive force cannot be obtained and the output is also reduced.

  In addition, the A-phase stack 51 and the B-phase stack 52 are formed by a sheet metal press, but a complicated mold is required to form a complicated pole shape.

  Patent Document 1 discloses a description of a conventional stepping motor and an example of a stepping motor in which the radial direction is further reduced.

  Non-Patent Document 1 discloses various types of stepping motors.

JP 2002-34227 A Naoshi Mijo, Atsushi Sugawara “Stepping Motor and Microcomputer Control” General Electronic Publishing 2000 3rd Edition

  In the conventional stepping motor, since the coil is concentrically arranged with respect to the rotation axis outside the permanent magnet, the length of the coil becomes longer with respect to the number of turns. Accordingly, the resistance of the coil increases, the current does not flow easily, and a sufficient magnetomotive force cannot be obtained when the size is reduced.

  In addition, a complicated mold is required to form each stack. In order to further reduce the size, it is important to reduce the leakage flux and concentrate the flux on the surface of the permanent magnet efficiently and intensively.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a stepping motor that is small in size, high in output, and easy to process and assemble.

  A rotor having at least a permanent magnet magnetized in the direction of the rotation axis fixed to the rotation axis, a bearing supporting the rotor, and fixing the bearing in a predetermined position, and surrounding the rotor A stepping motor having a housing with a coil wound around a U-shaped core, the stator being arranged so as to sandwich the permanent magnet, at the tip of the U-shaped core The stepping motor is provided with a convex portion.

  A stator pair is formed by the two stators, and a U-shaped core tip portion of the stator pair is disposed on one magnetic pole area of the permanent magnet.

  The stepping motor is provided with another pair of stators that are opposed to the leading ends of the U-shaped cores of the stator pair and are arranged symmetrically with respect to a straight line passing through the rotation axis center on the plane of the permanent magnet.

  In the stepping motor of the present invention, since the coil length can be reduced with respect to the number of turns by winding the coil around the core, the resistance value is reduced. Therefore, the magnitude of the current that can be flowed can be increased, and a large magnetomotive force can be obtained. Further, by providing a convex portion at the tip of the stator, magnetic flux flows intensively from the convex portion, so that high output can be obtained. Since the core is U-shaped, it can be formed without using a complicated mold.

  Further, by arranging the stator pair on one magnetic pole area, the magnetic flux generated by the magnetomotive force generated by the coil is concentrated on one magnetic pole area, and the leakage magnetic flux is reduced. Furthermore, since the magnetic flux concentrates on the above-described convex portion at the front end of the stator, the generated magnetic flux is more efficiently converted into a rotational force.

  Step angle accuracy is improved by providing another pair of stators facing the U-shaped core tip of the stator pair and arranged symmetrically with the straight line passing through the rotation axis center on the plane of the permanent magnet. To do.

1 is an exploded perspective view showing a first embodiment of the stepping motor of the present invention, FIG. 2 is a perspective view showing the first embodiment of the stepping motor of the present invention, and FIG. 3 is a first embodiment of the stepping motor of the present invention. 4 is a front sectional view taken along the line AA shown in FIG. 3, FIG. 5 is a top view showing the positional relationship between the permanent magnet and the stator of the stepping motor of the present invention, and FIG. It is a front view of a core in the first embodiment of the stepping motor.
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

First, the configuration of the stepping motor 10 will be described.
The rotating shaft 11 is formed with spherical portions 11a and 11b whose both ends are processed into a hemispherical shape. In addition, a flange portion 11c for fixing the permanent magnet 12 to be described later while maintaining a predetermined position, and an end surface portion 11d for positioning the thrust direction with a predetermined gap are formed. The material is a non-magnetic material (SUS303).

  The cylindrical permanent magnet 12 has a hole 12a formed in the central axis and is magnetized with four poles at equal angular intervals in the thrust direction. The number of magnetization is not limited to 4 poles, and may be increased within a possible range of magnetization. The material is a rare earth magnet (for example, neodymium).

  The shaft on the spherical surface portion 11b side of the rotating shaft 11 is inserted into the hole 12a of the permanent magnet 12, and abuts against the flange portion 11c to perform positioning in the thrust direction. In the case of a bonded magnet, the fixing is performed by slightly pressing the shaft diameter of the rotating shaft engaged with the hole 12a and lightly press-fitting and then fixing. In the case of a sintered magnet, since it is easy to break, the diameter of the hole 12a is formed to be slightly larger than that of the rotating shaft 11, and after being positioned in the radial direction with a jig or the like, it is bonded and fixed. A permanent magnet 12 is attached to the rotating shaft 11 to form a rotor 13.

  The rotor 13 is supported by bearings 14 and 15 that support the thrust direction and the radial direction. The two bearings 14 and 15 are positioned by the housing 16 at predetermined positions in the thrust direction and the radial direction.

  The bearing 14 is provided with four slits 14a, 14b, 14c, and 14d. The slits 14a and 14d and the slits 14b and 14c are formed in a substantially letter C shape and form a pair. Furthermore, the slits 14a and 14d and the slits 14b and 14c are each arranged on one magnetic pole area (1/4 circle) of the permanent magnet 12 (FIG. 5). The bearing recess 14e includes an end surface portion 14g that supports the rotor 13 in the thrust direction and a side surface portion 14f that supports the rotor 13 in the radial direction (FIG. 4). A radial direction positioning portion 14h and a thrust direction positioning flange portion 14i are provided so as to maintain a predetermined position with the housing 16.

  The bearing 15 is provided with slits 15 a, 15 b, 15 c, 15 d at the same angular positions as the bearing 14. The slits 15a and 15d and the slits 15b and 15c are formed in a substantially C shape and make a pair. The bearing portion 15e includes an end face portion 15g that pivotally supports the rotor 13 in the thrust direction and a through hole 15f that pivotally supports the rotor 13 in the radial direction (FIG. 4). A radial direction positioning portion 15h and a thrust direction positioning flange portion 15i are provided so as to maintain a predetermined position with the housing 16. The bearings 14 and 15 are made of a non-magnetic bearing material (brass or resin).

  The housing 16 has a hollow cylindrical shape, and slits 16a to 16d are provided at positions corresponding to the bearings 14 and 15 on both end faces. A stator, which will be described later, is inserted into and fixed to the slits of the housing 16 and the bearings 14 and 15. The rotor 13 is housed inside the hollow cylinder and is protected from the outside. The inner diameter of the hollow cylinder is formed so as to fit closely with the outer diameter of the radial positioning portions 14h and 15h of the bearing. The material is a non-magnetic material (aluminum).

  The stator 17 is formed by winding a coil 17b around a core 17a. The substantially U-shaped core 17a is provided with two convex portions 17c at the tip. Since the coil 17b is wound to a length between the two convex portions 17c, the slope portion 17d is provided in a portion where the coil is not wound so that the cross-sectional area of the core is increased and the magnetic flux is not easily saturated. (Fig. 6). A soft magnetic material is generally used for the core material (for example, permalloy, pure iron). In order to bring out a predetermined performance, a post-processing heat treatment is performed.

  In general, a coil wound around a bobbin is generally attached to a core. However, in order to further reduce the size, the coil is wound without using a bobbin in the embodiment of the present invention. If a coil is wound directly around the core, there is a possibility that disconnection or a short circuit due to disconnection may occur. To prevent this, it is better to wind a thin insulating tape around the core, or wind a coil after applying varnish.

  Similarly, the stator 18 is formed by winding the coil 18b on the core 18a, the stator 19 is formed by winding the coil 19b on the core 19a, and the stator 20 is formed by winding the coil 20b on the core 20a, and is formed at the tip of the cores 18a, 19a, 20a. Are formed with convex portions 18c, 19c, and 20c. (Both have the same shape as the stator 17) The stator 17 and the stator 20 constitute a pair of stators, and the stator 18 and the stator 19 constitute a pair of stators. Each of them is arranged symmetrically with a straight line passing through the central axis of the permanent magnet 12.

Next, the assembly procedure will be described.
The radial positioning portion 14h of the bearing 14 is inserted into the housing 16 and abuts against the thrust positioning flange 14i. Thereafter, the slits of the housing 16 and the bearing 14 are aligned and fixed at predetermined positions. Fixing uses an adhesive.

  Next, the spherical portion 11b side of the rotor 13 is inserted into the bearing recess 14e. The radial direction positioning portion 15h of the bearing 15 is inserted into the housing 16 while being inserted into the through hole 15e of the bearing 15 on the spherical surface portion 11a side of the rotor 13, and abuts against the thrust direction positioning flange portion 15i. Thereafter, the slits of the housing 16 and the bearing 15 are fixed to a predetermined position. Fixing uses an adhesive.

  The rotor 13 is rotatably supported by the bearings 14 and 15 and the housing 16. The thrust direction is regulated by the end face portions 14g and 15g, and maintains a predetermined clearance from the rotor.

  Next, the stator is inserted and fixed in a slit formed in the bearing. Insert the stator 17 until it hits the slits 14a and 15a. Similarly, the stator 18 is inserted into the slits 14b and 15b, the stator 19 is inserted into the slits 14c and 15c, and the stator 20 is inserted into the slits 14d and 15d until they are in contact with each other. Thereby, positioning in the radial direction is performed. Since the slits 14a (15a) and 14d (15d) and the slits 14b (15b) and 14c (15c) are arranged on one magnetic pole area (1/4 circle), the stator inserted and fixed to the slit is Since the stator 17 and the stator 20 are arranged on one magnetic pole area, and the stator 18 and the stator 19 are arranged on one magnetic pole area, magnetic flux leakage is reduced and magnetic force is efficiently output. Converted to torque. Moreover, since the convex part provided in the front-end | tip of a stator is arrange | positioned so that a permanent magnet may be inserted | pinched, magnetic force is converted into output torque more efficiently. The thrust direction is positioned using a jig (not shown), and fixed with a predetermined gap from the permanent magnet. An adhesive is used for fixing.

  Next, wiring. The wiring is made so that the stators 17 and 19 and 18 and 20 are connected to have the same polarity when further excited. (For example, when the stator 17 is excited to the N pole as viewed from the bearing 15 side, the stator 19 is also wired to have the N pole.) There are two types of wiring, series and parallel. In order to make the magnetic force generated in the coil uniform, a series that can equalize the currents flowing in the coils is preferable.

Subsequently, the operation will be described.
In small stepping motors, excitation methods such as two-phase excitation and 1-2 phase excitation are common. One embodiment of the present invention can also be rotated by these excitation methods. Here, description will be made taking two-phase excitation as an example. FIG. 9 is a view illustrating the rotation principle of the stepping motor according to the present invention as viewed from the bearing 15 side, and illustrates the clockwise rotation. The S pole is displayed in black for easy understanding. Further, the circles on the permanent magnet 12 in the figure are shown for the purpose of recognizing the rotational position for the sake of explanation.

  First, all the stators are excited to the S pole. Then, the permanent magnet 12 stops at the position shown in FIG. ((1))

  Next, the magnetic poles of the stators 18 and 20 are reversed and excited to the N pole. Then, a clockwise rotational moment is generated in the permanent magnet 12 by the generated magnetic force, and the permanent magnet 12 rotates 45 degrees clockwise and stops. ((2))

  Next, the magnetic poles of the stators 17 and 19 are reversed and excited to the N pole. Due to the generated magnetic force, a clockwise rotational moment is generated in the permanent magnet 12, and the permanent magnet 12 rotates 45 ° clockwise and stops. ((3))

  Next, the magnetic poles of the stators 18 and 20 are reversed and excited to the S pole. Then, a clockwise rotational moment is generated in the permanent magnet 12 by the generated magnetic force, and the permanent magnet 12 rotates 45 degrees clockwise and stops. ((4))

Next, the magnetic poles of the stators 17 and 19 are reversed and excited to the S pole. Due to the generated magnetic force, a clockwise rotational moment is generated in the permanent magnet 12, and the permanent magnet 12 rotates 45 ° clockwise and stops. ((5))
Here, the rotor 13 rotates 180 °. If changing the magnetic pole is one step, one rotation is made in eight steps. Needless to say, when rotating counterclockwise, the order in which the magnetic poles are reversed may be reversed.

Subsequently, a second embodiment of the stepping motor of the present invention will be described.
FIG. 7 is a top view of a second embodiment of the stepping motor of the present invention, and FIG. 8 is a front view of the core of the stepping motor of the present invention. In the second embodiment, a different part from the first embodiment will be described. Since the assembly method, wiring, and rotation principle are the same as those in the first embodiment, they are omitted.

  In the second embodiment, a semicircular cutout 21c is provided near the tip of the U-shaped core 21a. As a result, a convex portion is formed at the tip (FIG. 8). A coil (not shown) is wound around the core 21a to form the stator 21. Since the convex portion is formed by providing the semicircular cutout portion 21c, the number of turns of the coil can be increased and the magnetomotive force can be increased.

  As shown in FIG. 7, the four stators 21 are arranged symmetrically about a straight line (X axis, Y axis) that passes through the center of the rotation axis and intersects vertically. This is a configuration in which a pair of stators are arranged on the left and right when the Y axis is viewed as a dividing line. According to this configuration, the accuracy of the rotation angle is further improved.

  The shape and arrangement of the stator are not limited to the above-described embodiments, and the stator 21 may be used in the arrangement as in the first embodiment. Further, the stators 17, 18, 19, and 20 may be arranged as in the second embodiment.

1 is an exploded perspective view showing a first embodiment of a stepping motor according to the present invention. The perspective view which shows 1st Example of the stepping motor of this invention The top view which shows the 1st Example of the stepping motor of this invention Front sectional view cut along A-A shown in FIG. The top view which showed the positional relationship of the permanent magnet and stator of the stepping motor of this invention The front view of a core in the first embodiment of the stepping motor of the present invention Top view in the second embodiment of the stepping motor of the present invention Front view of the core of the stepping motor of the present invention FIG. 6 is a diagram illustrating the rotation in the clockwise direction, as viewed from the bearing side of the stepping motor of the present invention. The perspective view which fractured | ruptured and showed one part with the conventional claw pole type PM type stepping motor

Explanation of symbols

10 Stepping motor 11 Rotating shaft 11a Spherical surface portion 11b Spherical surface portion 11c Flange portion 11d End surface portion 12 Permanent magnet 12a Hole 13 Rotor 14 Bearing 14a Slit 14b Slit 14c Slit 14d Slit 14e Bearing concave portion 14f Side surface portion 14g End surface portion 14h Radial direction positioning portion 14i Thrust direction positioning flange portion 15 Bearing 15a Slit 15b Slit 15c Slit 15d Slit 15e Through hole 15f Bearing portion 15g End surface portion 15h Radial direction positioning portion 15i Thrust direction positioning portion 16 Housing 16a Slit 16b Slit 16c Slit 16d Slit 17 Stator 17a Core 17b Coil 17c Convex part 17d Slope part 18 Stator 18a Core 18b Coil 18c Convex part 19 Stator 19a Core 19b Ile 19c Convex 20 Stator 20a Core 20b Coil 20c Convex 21 Stator 21a Core 21c Notch 50 Stepping motor 51 A phase stack 51a Upper pole 51b Lower pole 51c Coil 52 B phase stack 52b Lower pole 52c Coil 53 Multiple Magnetic body 54 Permanent magnet

Claims (3)

at least,
A rotor in which a multi-pole magnetized permanent magnet is fixed to the rotation axis;
A bearing that pivotally supports the rotor;
A housing formed to hold the bearing in place and to surround the rotor;
And a stator with a coil wound around a U-shaped core,
A stepping motor in which the stator is arranged so as to sandwich the permanent magnet,
A stepping motor characterized in that a convex portion is formed at the tip of the U-shaped core.   2. The stepping motor according to claim 1, wherein a stator pair is constituted by the two stators, and a U-shaped core tip portion of the stator pair is disposed on one magnetic pole area of the permanent magnet.   The stator pair is provided with another pair of stators that are opposed to the leading ends of the U-shaped cores of the stator pair and are arranged in axial symmetry with a straight line passing through the center of the rotation axis on the plane of the permanent magnet. 2. The stepping motor according to 2.

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