JP2011072054A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor excellent in operability in attaching a magnet to a frame. <P>SOLUTION: The motor 10 includes a cylindrical magnet structure 11, a lidded cylindrical frame 41 for holding the magnet structure 11 in the inner circumferential surface and serving as a yoke, a core 51 disposed on the inner circumferential surface side of the magnet structure 11, and a rotary shaft 61 fixed on the center of the core 51 and rotatably supported by a pair of bearings 79, 80. The magnet structure 11 includes an uneven-thickness magnet 21 formed by repeating thick portions 26 and thin portions 27 in the circumferential direction, and a sub-yoke 31 disposed on the outer circumferential direction side of the magnet 21. The sub-yoke 31 is formed integrally with the magnet 21 by an insertion molding method. The magnet structure 11 is pressed into the inside of the frame 41, thereby disposing the magnet 21 at a predetermined position of the frame 41. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a motor, and more particularly to a motor in which a magnet is fixedly arranged inside a frame as a housing.

  2. Description of the Related Art Motors configured to function as a yoke of a magnet by disposing a magnet inside a cylindrical or covered cylindrical (cup-shaped) frame made of a magnetic material are widely used.

  In recent years, a DC motor (hereinafter, referred to as a “square cylinder motor” for convenience) has been developed as a motor used in laser printers, audio loading mechanisms, and the like. It has been put into practical use. The rectangular cylinder motor has a magnet with an uneven thickness whose thickness (diameter thickness) changes periodically with respect to the circumferential direction. Therefore, increase the starting torque and decrease the cogging torque. Can do. Also in this square cylinder type motor, a magnet is disposed inside a frame formed of a magnetic material. (For example, refer to Patent Document 1).

JP 2007-6688 A

  As described above, when the magnet is disposed inside the frame, it is necessary to make the gap between the frame and the magnet as small as possible from the viewpoint of reducing the magnetic resistance. For this reason, the dimensional accuracy of the frame and magnet must be strictly controlled. In addition, when the magnet is pushed into the frame, the magnet is likely to be chipped or cracked, so the operator needs to pay close attention. In particular, the square cylindrical motor needs to be more careful because the circumferential angle of the magnet with respect to the frame is restricted and there is no degree of freedom of rotation in the circumferential direction. For this reason, a method excellent in assembling workability when a magnet is pushed into and fixed to the frame is required.

  As a means for suppressing breakage and cracking of the magnet, a method of integrally forming the magnet on the frame is conceivable. However, when a covered cylindrical frame is employed as the frame, it is physically difficult to integrally form the magnet so that the magnet is arranged at a certain distance from the lid.

  Moreover, since the cylinder part and a cover part are generally shape | molded as an integrated object by a drawing process with a covered cylinder frame, the thickness (thickness) of a cylinder part and the thickness of a cover part must be substantially equal. That is, the thickness of the lid cannot be arbitrarily changed with respect to the thickness of the cylinder. In this respect, the cylindrical portion also functions as a yoke, so a certain thickness or more is required. On the other hand, the lid portion is added to the axial length of the motor. There is a demand to make it as thin as possible from the viewpoint of miniaturization. Therefore, a method for realizing this conflicting demand is also required.

  The present invention has been made in view of such circumstances, and a main object of the present invention is to provide a motor excellent in assembling workability.

  In order to solve the above problems, a motor according to one aspect of the present invention includes a cylindrical magnet as a whole, and a frame having a cylindrical cylindrical portion that is formed using a magnetic material and has the magnet disposed inside. A cylindrical sub yoke made of a magnetic material is interposed between the frame and the magnet, and the sub yoke is integrated with the magnet when the magnet is formed. To do.

  In another aspect of the present invention, the outer peripheral surface of the frame has a polyhedral shape.

  Moreover, in another one aspect | mode of this invention, the said flame | frame is formed in the cup shape which has a cover part which covers one open end of the said cylinder part.

  According to still another aspect of the present invention, at least one through hole is formed in the sub yoke, and a part of the magnet is formed in the through hole.

  In this case, the through hole preferably has a smaller cross-sectional diameter on the inner peripheral surface side than a cross-sectional diameter on the outer peripheral surface side.

  According to still another aspect of the present invention, the sub yoke is formed with at least one protrusion protruding from the inner peripheral surface of the sub yoke toward the axial center.

In these cases, the magnet is periodically repeated in the circumferential direction with a thick part that is thick and the central part of the magnetic pole and a thin part that is thin and the boundary part of the magnetic pole,
It is preferable that the through hole or the protrusion is formed on a side surface corresponding to the thick portion of the magnet.

In the motor according to the present invention, the sub yoke integrally formed with the magnet on the outer peripheral side of the magnet is fixedly arranged on the inner peripheral surface side of the frame having the function of the yoke. With this configuration, it is possible to suppress the breakage and breakage of the magnet, which has been a problem in the conventional process of arranging the magnet inside the frame, and to improve the assembly workability. In particular, the effect is effectively exhibited in a motor having a polyhedral shape in cross section, such as a square tube motor.
In addition, when a cup-shaped frame having a lid is used, the thickness of the lid can be reduced according to the thickness of the sub-yoke, so that the motor body can be shortened in the axial direction.

It is a longitudinal section showing the whole motor composition concerning an embodiment of the present invention. It is a cross-sectional view which shows the internal structure of the motor. It is a perspective view which shows the magnet structure of the motor. It is a top view which shows the magnet structure which concerns on the modification of this invention. (A) is a perspective view which shows the sub yoke which concerns on the modification of this invention, (b) is a figure which shows typically the cross-sectional shape of the through-hole formed in the same sub-yoke. (A) (b) is a figure which shows typically the cross-sectional shape of the processus | protrusion formed in the sub yoke which concerns on the modification of this invention.

  Hereinafter, as an example of a preferred embodiment of the present invention, a motor 10 as a square tube DC motor will be described with reference to the drawings.

  As shown in FIG. 1, the motor 10 includes a cylindrical magnet structure 11 that generates a magnetic field, a covered cylindrical (cup-shaped) frame 41 that also functions as a yoke of the magnet structure 11, and a magnet structure. 11 is provided with an iron core 51 that functions as an armature and is arranged at a predetermined interval on the inner peripheral surface side, and a rotary shaft 61 that is fixedly arranged at the center of the iron core 51.

  The motor 10 is a so-called brushed DC motor, which holds a terminal 71 electrically connected to an external power source (not shown) and a brush 73 electrically connected to the terminal 71 and opens the frame 11. A bracket 75 disposed so as to close the end, a commutator 77 that is slidably contacted with the brush 73 and fixed to the rotating shaft 61, supports the rotating shaft 61 rotatably, one is fixed to the frame 41, and the other is the bracket 75. And a pair of bearings 79 and 80 fixed to each other.

  Below, it demonstrates focusing on the magnet structure 11, the frame 41, and the iron core 51. FIG.

  The magnet structure 11 includes a magnet 21 having an uneven thickness and a sub yoke 31 that is integrally formed with the magnet 21 on the outer peripheral surface side of the magnet 21 and has a function as a yoke.

  In this embodiment, the magnet 21 is a bonded magnet formed by injection molding a kneaded material made of magnetic powder (for example, Sm-Fe-N powder) and a binder resin (for example, nylon 6). As shown in FIGS. 2 and 3, the magnet 21 has a cylindrical shape as a whole, and has an inner peripheral surface 22 formed of a circumferential surface and an outer peripheral surface 23 formed of multiple surfaces. The outer peripheral surface 23 is formed by alternately repeating four curved surfaces 24 having an arcuate cross section and four flat surfaces 25 having a rectangular plane shape in the circumferential direction alternately four times.

  Accordingly, when the magnet 21 is observed paying attention to its thickness, the thick portion 26 having a large thickness and the thin portion 27 having a small thickness are set as one set, and four sets are rotated 90 degrees (4-turn rotational symmetry). It is arranged and configured. The thick portion 26 is a portion corresponding to the curved surface 24, and the thin portion 27 is a portion corresponding to the flat surface 25.

  Further, the magnet 21 has four poles of radial magnetization (two N poles and two poles) so that the central part of the thick part 26 is the central part of the magnetic pole and the central part of the thin part 27 is the boundary part of the magnetic pole. 2 poles S pole) are given.

  On the other hand, the sub yoke 31 is formed in a cylindrical shape having a constant circumferential thickness using a magnetic material (in this embodiment, iron). Further, the sub yoke 31 is integrated with the magnet 21 at the time of injection molding of the magnet 21 by an insert molding method. Therefore, the inner peripheral surface 32 and the outer peripheral surface 33 of the sub yoke 31 have a polyhedral shape, and the cross-sectional shape of the inner peripheral surface 32 is the same as the cross-sectional shape of the outer peripheral surface 23 of the magnet 21.

  Next, the frame 41 is formed using a magnetic material (in this embodiment, the same material as the sub-yoke 31), and has a cylindrical cylindrical portion 42 and a flat lid portion that covers one open end of the cylindrical portion 42. 45. One bearing 79 is fixed to the center of the lid 45. The cylindrical portion 42 and the lid portion 45 are formed by drawing as in the conventional technique, but are formed thinner by the thickness of the sub yoke 31 than the conventional frame. .

  The magnet structure 11 is fixedly disposed on the inner peripheral surface 43 of the cylindrical portion 42 in a state where the outer peripheral surface 33 of the sub yoke 31 is substantially in close contact (the magnet 21 is thereby disposed inside the cylindrical portion 42. ) Therefore, the cross-sectional shape of the inner peripheral surface 43 of the frame 41 is substantially the same as the cross-sectional shape of the outer peripheral surface 33 of the sub yoke 31. In other words, the cross-sectional shape of the frame 41 is also a polyhedron shape. Further, the magnet structure 11 is arranged at a certain distance D (see FIG. 1) from the inner surface of the lid portion 45 of the frame 41. The magnet structure 11 may be fixed to the frame 41 by a press-fitting method or a method using a fixing means such as an adhesive.

  Next, in this embodiment, the iron core 51 is formed by laminating a plurality of electromagnetic steel sheets punched into a predetermined shape. The iron core 51 has an annular portion 52 disposed in the center portion, and a plurality (six in this embodiment) of salient poles 53 protruding in the radial direction from the annular portion 52. One salient pole 53 is constituted by a salient pole arm portion 54 extending in the radial direction and a tooth portion 55 at the tip thereof. An exciting coil (not shown) is wound around the salient pole arm portion 54.

  The motor 10 configured as described above can be operated in the same manner as a conventional brushed DC motor. Below, the operation effect peculiar to motor 10 concerning the present invention is explained.

  First, in the motor 10, the magnet structure 11 in which the sub yoke 31 is integrated with the outer peripheral surface 23 of the magnet 21 is disposed on the inner peripheral surface 43 side of the frame 41. Therefore, when the magnet structure 11 is disposed inside the frame 41, the magnet 21 does not contact the frame 41, but the sub yoke 31 made of metal contacts the frame 41 (that is, the frame The sub yoke 31 is interposed between the magnet 41 and the magnet 21). As a result, it is possible to reliably suppress the chipping or cracking of the magnet when the magnet is placed inside the frame, which has occurred in the prior art. In addition, workability in the process of arranging the magnet inside the frame is improved. In particular, in the case of a square cylindrical motor having no degree of freedom of rotation in the circumferential direction, the effect is effectively exhibited.

  In addition, since the magnet 21 and the sub yoke 31 are integrally formed, the magnetic resistance at the contact interface between the magnet 21 and the sub yoke 31 can be minimized. Thereby, the magnetic efficiency of the motor 10 is improved.

  Further, since the sub yoke 31 functions as a yoke together with the frame 41, the thickness of the frame 41 can be reduced. For this reason, when the frame 41 is formed by drawing, the thickness of the lid portion 45 is reduced according to the thickness of the cylindrical portion 42. Thereby, compared with a prior art, the axial direction length of a motor main-body part (part except the shaft 61 from the motor 10) can be shortened. Or when the axial direction length of a motor main-body part is made the same with the conventional structure, the axial direction length of the magnet 21 and the iron core 51 can be lengthened, and the magnetic efficiency of the motor 10 can be improved. Further, the motor 10 can be reduced in weight and cost.

  Although an example of a preferred embodiment of the present invention has been described above, the embodiment is not limited to the above, and various modifications can be made without departing from the gist of the present invention.

  For example, in the above embodiment, the magnet 21 has been described as a cylindrical shape that is continuous in the circumferential direction, but the present invention is not limited to this. For example, like the magnet structure 11A shown in FIG. 4, a plurality (four) of magnet pieces 21a to 21d may be arranged on the inner peripheral surface side of the sub-yoke 31 so as to be cylindrical as a whole. When the magnet pieces 21a to 21d are used, the problem of chipping or cracking of the magnet does not occur originally, but the work of sticking each of the magnet pieces 21a to 21d to the inner peripheral surface of the conventional frame becomes unnecessary. The improvement of sex can be expected.

  Further, as in the sub-yoke 31A shown in FIG. 5A, one or more (two in the illustrated example) through-holes 34 (in the illustrated example, circular in the side surface corresponding to the thick part of the magnet). (Opening) may be provided. Since the shrinkage rate is different between the magnet and the sub yoke, a gap or crack may be generated between the magnet and the sub yoke during cooling in the injection molding process. Therefore, by providing a through hole in the sub yoke and forming a part of the magnet in the through hole, the bonding strength between the magnet and the sub yoke is improved. Thereby, it can be expected that gaps and cracks that may occur between the magnet and the sub yoke are suppressed. In this case, as shown in FIG. 5B, by making the cross-sectional diameter of the through hole 34 on the inner peripheral surface 32 side smaller than the cross-sectional diameter on the outer peripheral surface 33 side, the above-described effects can be exhibited more effectively. Can be expected.

  Further, as shown in FIGS. 6A and 6B, the projections 35 and 36 protruding inward (axial center side) from the inner peripheral surface 32 of the sub-yokes 31B and 31C are replaced with the through holes 34 or penetrated. You may provide with the hole 34. FIG. FIG. 6A shows a form in which a through hole is formed in the protrusion 35, and FIG. 6B shows a form in which a through hole is not formed in the protrusion 36. By providing the projections 35 and 36, the same effect as the case where the through hole 34 is provided can be expected. In the case of the protrusions 35 and 36, it can be expected that the above-described effects can be more effectively exhibited by increasing the inner cross-sectional diameter than the cross-sectional diameter on the inner peripheral surface 32 side.

  The through hole 34 and the protrusions 35 and 36 may be provided on the side surface corresponding to the thin portion of the magnet, but it is preferable that the through hole 34 and the projections 35 and 36 be provided on the side surface corresponding to the thick portion that is the center of the magnetic pole. It is preferable mainly from the viewpoint of starting torque. This is considered to be because the internal stress generated by the difference in contraction rate can be concentrated on the thin wall portion that is the boundary portion of the magnetic poles that does not affect the starting torque.

  Moreover, in the said embodiment, although the uneven-shaped magnet was used, it is not limited to this. For example, the present invention can also be applied when using a magnet having a constant thickness in the circumferential direction.

  Moreover, in the said embodiment, although the flame | frame 41 was made into cup shape, it is not limited to this. If the frame has a cylindrical portion, a certain effect is exhibited.

  Moreover, although the said embodiment demonstrated as a DC motor with a brush, it is not limited to this. If it is the structure which arrange | positions a magnet inside a flame | frame, the effect of this invention can be exhibited.

DESCRIPTION OF SYMBOLS 10 Motor 11, 11A Magnet structure 21 Magnet 21a-21d Magnet piece 22 Inner peripheral surface 23 Outer peripheral surface 24 Curved surface 25 Flat surface 26 Thick part 27 Thin part 31, 31A, 31B, 31C Sub yoke 34 Through-hole 35, 36 Protrusion 41 frame (yoke)
42 cylinder 45 lid 51 iron core 61 rotating shaft 71 terminal 73 brush 75 bracket 77 commutator
79,80 A pair of bearings

Claims (7)

A cylindrical magnet as a whole,
In a motor comprising a frame having a cylindrical tube portion that is formed using a magnetic material and has the magnet disposed inside,
A cylindrical sub yoke made of a magnetic material is interposed between the frame and the magnet,
The sub-yoke is integrated with the magnet when the magnet is molded.   The motor according to claim 1, wherein an outer peripheral surface of the sub yoke has a polyhedral shape.   The motor according to claim 1, wherein the frame has a cup shape having a lid portion that covers one open end of the cylindrical portion. At least one through hole is formed in the sub yoke,
The motor according to claim 1, wherein a part of the magnet is formed in the through hole.   The motor according to claim 4, wherein the through hole has a smaller cross-sectional diameter on the inner peripheral surface side than a cross-sectional diameter on the outer peripheral surface side.   The motor according to any one of claims 1 to 5, wherein the sub yoke is formed with at least one protrusion protruding from an inner peripheral surface thereof toward an axial center side. The magnet has a thick portion that is thick and becomes the center of the magnetic pole, and a thin portion that is thin and thin that becomes the boundary portion of the magnetic pole.
The motor according to any one of claims 4 to 6, wherein the through hole or the protrusion is formed on a side surface portion corresponding to the thick portion of the magnet.

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