JPH09289767A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stepping motor which can improve productivity by improving workability of a part and improve angular accuracy and generating torque. SOLUTION: Cavities 72A, 72B are formed at both ends in an axial direction of a magnet 70 which is fixed coaxially with a shaft 20. The pole tooth part 51A of a bobbin 27A which includes a flange part 30 and through which a shaft passes is fitted into the cavity 72A and fixed inside a case 71, and the pole tooth part 51B of a bobbin 27B is fitted into the cavity 72B and fixed inside the case 71. Long pole teeth 52A, 52A which are located in rotational symmetry to the shaft 20 from the external edge part of the magnet 70 which is separated from the cavity 72A to the flange part 30 which the bobbin 27A includes, and long pole teeth 52B, 52B which are located in rotational symmetry to the shaft 20 from the external edge part of the magnet 70 which is separated from the cavity 72B to the flange part 30 which the bobbin 27B includes are supported by a pole tooth supporting body 76 which is fixed on the inner surface of the case 71 by shifting them from each other by a prescribed angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor having a small diameter suitable for use in a timepiece, a camera, medical equipment or the like, and more particularly to a stepping motor which can be miniaturized without impairing workability.

[0002]

2. Description of the Related Art FIG. 3 is a perspective view showing the structure of an example of a small diameter stepping motor according to the prior art. In the stepping motor shown in FIG. 3, bobbins 4 and 4 around which a coil 6A or 6B is wound are arranged on both sides of a cylindrical magnet 2 coaxially fixed to a shaft 1 in the axial direction. With such a configuration, the outer diameter can be made smaller than that of a conventional stepping motor in which a coil is arranged on the outer circumference of a magnet, for example.

FIG. 4 is a diagram showing a detailed structure of the stepping motor as shown in FIG. 3, and FIG. 4 (a) is a vertical sectional view. In FIG. 4A, a cylindrical magnet 21 magnetized to have four poles in the circumferential direction is provided at the axial center of the shaft 20.
Are coaxially fixed.

The shaft 20 is fitted in a bearing press-fitting recess 45 formed at the center of each of the supporting members 40A and 40B formed on the inner surfaces of both ends of a cylindrical case 71 forming the outer shell of the stepping motor. It is rotatably supported by a bearing 24.

A pair of bobbins 26A (A phase, FIG. 4) adjacent to both sides of the magnet 21 and having the same hollow shape as each other.
Left side in (a)) and 26B (phase B, right side in FIG. 4A) are arranged, and the shaft 20 penetrates. Further, washers 23, 23 for enhancing the rotary slidability are rotatably inserted into the shaft 20 on both shaft end sides of the magnet 21.

FIG. 4B is a perspective view showing the external configuration of the bobbin 26B described above. Since the bobbin 26A has the same shape as the bobbin 26B, illustration and description thereof will be omitted.

The bobbin 26B has a cylindrical winding portion 36 having an inner diameter larger than the outer diameter of the shaft 20, and a winding portion 3
6 has a flange portion 30 integrally formed at the base end portion (downward in FIG. 4B) and a press-fitting convex portion 28 projecting in the axial direction from the flange portion 30, and is entirely made of a soft material such as pure iron. The magnetic material is integrally formed. A coil 38 is attached to the winding portion 36.
B is wound.

At the tip of the bobbin 26B (upper side in FIG. 4B), a U-shaped yoke 34 is attached. The yoke 34 is made of a soft magnetic material such as pure iron, and is composed of a bottom plate portion 67B and a pair of short pole teeth 50B, 50B standing upright from both ends thereof, and a through hole is formed at the center of the bottom plate portion 67B. ing.

The press-fitting convex portion 28 has a cylindrical shape having a diameter larger than that of the winding portion 36 and being coaxial with the winding portion 36.
It is fitted in a press-fitting recess 42 formed coaxially with the bearing press-fitting recess 45 at 0B.

A pole tooth support 46 is formed on the inner surface of the central portion of the case 71 in the axial direction so as to surround the outer periphery of the magnet 21 in a non-contact and coaxial manner. The pole tooth support 46 is made of a non-magnetic material such as resin and is made up of two sets of long pole teeth 48.
A (not shown) and 48B (see FIG. 4A) are integrally fixed.

FIG. 4 (c) is a sectional view taken along the line AA 'in FIG. 4 (a). As shown in the figure, the pole tooth support 46 has long pole teeth 48B and short pole teeth 50B which are axially symmetrical with respect to the axis of the shaft 20 and which have long pole teeth 48B and short pole teeth 50B. They are offset by 90 ° and supported. Although not shown, the above-mentioned pole tooth support member 46 is configured to support the yokes 34, 34 that face each other in the axial direction by offsetting each other by 45 °.

[0012]

FIG. 5 is a diagram showing a magnetic circuit in the stepping motor shown in FIG. 4, FIG. 5 (a) being a cross sectional view, and FIG. 5 (b) being FIG. 5 (a). It is a longitudinal cross-sectional view of A surface and B surface. The arrow F indicates the magnetic current in this stepping motor.

As can be seen from FIG. 5 (b), the conventional stepping motor requires the length of the bottom plate portion 67A (67B) in the entire length. Therefore, there are problems that the total length becomes long, the number of turns of the coil is limited, and the magnetic current becomes complicated.

Further, in the stepping motor as described above, the yoke 34 is composed of a combination of short pole teeth having a partially cylindrical shape and a bottom plate portion having a flat plate shape, so that the productivity is low and it is difficult to obtain high machining accuracy. .

The pole teeth are fixed so as to face the outer circumference of the magnet 21. Therefore, the facing area between the yoke and the magnet is limited to the outer peripheral length of the magnet 21 in the circumferential direction.

On the other hand, in general, the torque generated by the stepping motor is proportional to the area where the yoke and the magnet face each other. Therefore, this torque also depends on the outer peripheral length of the magnet 21, and when the outer diameter of the stepping motor is reduced, the torque also decreases. Resulting in.

Further, in the stepping motor, the positioning accuracy of each pole tooth on the outer circumference of the magnet is an important factor. For this reason, in the past, it has been difficult to increase productivity by requiring careful attention when assembling the stepping motor.

There is also a problem that the positional error between the pole teeth causes an error in the stop position of the rotor (magnet or shaft) of the stepping motor. The present invention has been made under such a background, and an object of the present invention is to provide a stepping motor which improves the workability of parts to enhance the productivity and also improves the angular accuracy and the generated torque.

[0019]

In order to solve the above-mentioned problems, in the invention described in claim 1, the first shaft is fixed to one end in the axial direction, which is fixed coaxially with the shaft for outputting the rotational driving force. A cylindrical magnet having a cylindrical portion and a second cylindrical portion at the other end and magnetized in multiple poles in the circumferential direction, a case for rotatably supporting the shaft therein, and a case fixed inside the case A non-winding portion and a flange portion sandwiching the winding portion and the winding portion in the axial direction, the non-winding portion is loosely inserted into the first cylindrical portion, and the shaft rotatably passes through the axial center. First
Of the bobbin, a non-winding part fixed in the case and a non-winding part sandwiching the winding part in the axial direction, and a flange part. A second bobbin through which the shaft rotatably passes, and a second bobbin that is fixed in the case and abuts the flange portion of the first bobbin at a position rotationally symmetrical with respect to the shaft and has one end of the first bobbin. A number of first pole tooth sets that are proportional to the number of magnetized magnets that reach the outer edge portion that is separated from the cylindrical portion, and the second bobbin that is fixed in the case and is rotationally symmetrical with respect to the shaft. A second pole tooth set, the number of which is in proportion to the number of magnetizations of the magnet that comes into contact with the flange portion of the magnet and one end of which reaches an outer edge portion separated from the second cylindrical portion, The pole tooth set and the second pole tooth set with respect to the shaft Characterized in that it is supported with a phase angle corresponding to the deposition 磁数 the serial magnet.

According to the second aspect of the invention,
2. The stepping motor according to claim 1, wherein the case has a phase angle corresponding to a magnetizing number of the magnet with respect to the shaft, the first pole tooth set and the second pole tooth set being provided on an inner surface of the case. It is characterized by comprising a pole tooth support body which has and supports.

According to the present invention, the first cylindrical portion is formed at one end in the axial direction and the second cylindrical portion is formed at the other end of the magnet which is fixed coaxially with the shaft and is magnetized in multiple poles in the circumferential direction. The first bobbin, which has a flange portion and through which the shaft rotatably passes through the shaft, is provided with a winding except a part thereof so that the non-winding portion is loosely inserted into the first cylindrical portion of the magnet. The second bobbin, which is fixed inside and has a flange portion and through which the shaft rotatably penetrates the shaft center, is wound except for a portion, and the non-winding portion is placed inside the second cylindrical portion of the magnet. It is loosely inserted and fixed inside the case, and the number is proportional to the number of magnetized magnets that are rotationally symmetrical to the shaft from the outer edge of the first cylindrical portion to the flange of the first bobbin. An outer edge portion separated from the first pole tooth set and the second cylindrical portion The second bobbin and the second pole tooth set whose number is proportional to the magnetizing number of the magnet located rotationally symmetrically with respect to the shaft over the flange portion of the second bobbin. With respect to each other, they are supported by being offset from each other by a phase angle corresponding to the magnetizing number of the magnet.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION A stepping motor according to an embodiment of the present invention will be described below. FIG. 1 is a diagram showing a configuration of a stepping motor according to the present embodiment, and FIG. 1A is a vertical sectional view. In FIG. 1, parts corresponding to the parts shown in FIG. 4 are designated by the same reference numerals, and description thereof will be omitted.

In FIG. 1 (a), a magnet 7 magnetized to have four poles in the circumferential direction is provided at the center of the shaft 20 in the axial direction.
0 is fixed coaxially. Both axial ends of the magnet 70 are formed into a cylindrical shape having cavities 72A and 72B coaxially with the shaft 20. This cavity 72A, 72
The inner diameter of B is larger than the pole tooth portions 51A or 51B of the bobbins 27A and 27B described later, respectively.

A pair of bobbins 27A (A phase, FIG. 1) adjacent to both sides of the magnet 70 and having the same hollow shape as each other.
Left side in (a)) and 27B (phase B, right side in FIG. 1A) are arranged, respectively, and the shaft 20 penetrates them. Further, washers 65, 65 for improving the rotary slidability are rotatably inserted into the shaft 20 on both shaft end sides of the magnet 70.

FIG. 1B is a perspective view showing the external structure of the bobbin 27B described above. Since the bobbin 27A has the same shape as the bobbin 27B, illustration and description thereof will be omitted.

The bobbin 27B has a cylindrical winding portion 37 having an inner diameter larger than the outer diameter of the shaft 20, and a winding portion 3
7 has a flange portion 30 integrally formed at the base end portion (downward in FIG. 1B) and a press-fitting convex portion 28 protruding axially from the flange portion 30, and is entirely made of a soft material such as pure iron. The magnetic material is integrally formed. A coil 38 is attached to the winding portion 37.
B is wound.

The tip of the above-mentioned winding portion 37 has a pole tooth portion 51B.
(The bobbin 27A has a pole tooth portion 51A). When the stepping motor is assembled, the magnet 7 described above is used.
0 is loosely inserted inside the cavity 72B (the pole tooth portion 51A is the cavity 72A).

A pole tooth support 76 is formed on the inner surface of the central portion of the case 71 in the axial direction so as to surround the outer periphery of the magnet 70 in a non-contact and coaxial manner. This pole tooth support 76 is made of a non-magnetic material such as resin and is made up of two sets of long pole teeth 52.
A (not shown) and 52B (see FIG. 1A) are integrally fixed.

FIG. 1C is a sectional view taken along the line BB 'in FIG. As shown in the figure, the pole tooth supporter 76 supports the long pole teeth 52B to each other in axial symmetry with respect to the axis of the shaft 20.

Although not shown, the above-mentioned polar tooth support 76 is also provided.
Supports the long pole teeth 52A symmetrically with respect to the axis of the shaft 20, and shifts the long pole teeth 52A, 52A and the long pole teeth 52B, 52B by 45 ° in the outer peripheral direction so as to face each other in the axial direction. To support.

FIG. 2 is a diagram showing a magnetic circuit in the stepping motor shown in FIG. 1. FIG. 2 (a) is a cross-sectional view, and FIG. 2 (b) is a plane A and a plane B in FIG. 2 (a). FIG. The arrow F indicates the magnetic current in this stepping motor.

As described above, according to the present embodiment, it is not necessary to form a yoke having a complicated shape at the tip of the bobbin 27A or 27B. Further, the long pole teeth 52A, 52A and 52B, 52B are supported by the pole tooth support 76 with a deviation of 45 ° in the outer peripheral direction and facing each other in the axial direction. Therefore, processing and positioning are easy, and the productivity of the stepping motor can be improved.

Further, the facing area between the outer peripheral surface of the pole tooth portion 51A or 51B and the inner peripheral surface of the cavity 72A or 72B of the magnet 70 corresponding thereto can be made large, and the generated torque can be increased. it can.

In this embodiment, an example in which the magnet is magnetized to have four poles has been described, but the present invention is not limited to this number of poles. Therefore, the number of long pole teeth and the shift angle between the long pole teeth facing each other in the axial direction with respect to the outer circumferential direction are determined corresponding to the number of phases and the number of poles of the stepping motor.

Further, in the present embodiment, the flange and the winding portion are integrally formed in the bobbin, but the present invention is not limited to this, and the flange portion and the pole tooth may be integrally formed. is there.

[0036]

As described above, according to the present invention, the first cylindrical portion is provided at one end in the axial direction and the first cylindrical portion is provided at the other end of the magnet which is fixed coaxially with the shaft and is magnetized in the circumferential direction with a large number of poles. The first bobbin that forms the second cylindrical portion and has the flange portion and through which the shaft rotatably penetrates the shaft center is wound except for a part thereof, and the non-winding portion is formed by the first coil of the magnet. The second bobbin, which is loosely inserted into the cylindrical portion and fixed inside the case, has a flange portion and through which the shaft rotatably passes through the shaft center, is partially wound to form a non-winding portion. The magnet is loosely inserted into the second cylinder portion and fixed inside the case, and the first edge portion is separated from the outer edge portion separated from the first cylinder portion.
The bobbin has a first bobbin and a second bobbin from the outer edge part separated from the second pole part by a number proportional to the number of magnetized magnets positioned rotationally symmetrically with respect to the shaft over the flange part. The number of second magnets proportional to the number of magnetized magnets positioned rotationally symmetrically with respect to the shaft over the flange part
Since the pole teeth set of and the pole teeth support fixed to the inner surface of the case are supported relative to the shaft by a phase angle shift corresponding to the magnetizing number of the magnet, the workability of the parts is improved and the productivity is improved. It is possible to obtain the effect that it is possible to realize a stepping motor that is improved in angle accuracy and generated torque while being increased.

That is, according to the present invention, a yoke having a complicated shape is not required, the manufacturing cost is reduced, the processing accuracy is improved, the coil space is increased, or the stepping motor itself can be shortened. Further, the facing area between the magnet and the pole teeth is increased, and the generated torque is increased accordingly.

Further, it is not necessary to position the pole teeth relative to each other during assembly, and as a result, the rotation accuracy of the rotor is improved, and the assembly accuracy is improved, so that variations in performance among products are reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a stepping motor according to an embodiment of the present invention.

FIG. 2 is a diagram showing a magnetic circuit in the stepping motor of the same embodiment.

FIG. 3 is a perspective view showing the configuration of an example of a small-diameter stepping motor according to a conventional technique.

FIG. 4 is a diagram showing a detailed configuration of a stepping motor as shown in FIG.

5 is a diagram showing a magnetic circuit in the stepping motor shown in FIG.

[Explanation of reference numerals] 20 shafts 27A, 27B bobbins (first and second bobbins) 30 flanges (flange portions) 37 winding portions 51A, 51B pole tooth portions (non-winding portions) 52A, 52A, 52B, 52B long Polar teeth (first and second polar tooth groups) 70 Magnet 71 Cases 72A, 72B Cavities (first and second cylindrical portions) 76 Polar tooth support

Claims (2)

[Claims] 1. A shaft (20) for outputting a rotational driving force.
Is fixed coaxially with the first cylindrical portion (72
(A) and a cylindrical magnet (70) having a second cylindrical portion (72B) at the other end and magnetized in multiple poles in the circumferential direction, and a case (in which the shaft is rotatably supported). 7
1), a non-winding portion (51A, 51B) fixed in the case, a winding portion (37) sandwiching the winding portion (37) in the axial direction, and a flange portion (3).
0) and a first bobbin (27A) in which the non-winding portion is loosely inserted in the first cylindrical portion and the shaft rotatably passes through the shaft center, and the first bobbin is fixed in the case and wound. A second winding part formed of a wire part and a non-winding part and a flange part sandwiching the line part in the axial direction; the non-winding part is loosely inserted into the second cylindrical part, and the shaft rotatably passes through the axial center; Of the bobbin (27B) and an outer edge portion fixed to the case and abutting against the flange portion of the first bobbin at a position rotationally symmetrical with respect to the shaft and having one end separated from the first cylindrical portion. The number of first pole tooth sets (52A, 52A) proportional to the number of magnetized magnets that reach, and the second bobbin that is fixed in the case and is rotationally symmetrical with respect to the shaft. Abutting on the flange portion and one end from the second cylindrical portion A second pole tooth set (52B, 52B) in a number proportional to the number of magnetized magnets reaching the outer edge portion, and the first pole tooth set and the second pole tooth set. Is supported with respect to the shaft with a phase angle corresponding to the magnetizing number of the magnet. 2. The case supports, on its inner surface, the first pole tooth set and the second pole tooth set with a phase angle corresponding to the magnetizing number of the magnet with respect to the shaft. The stepping motor according to claim 1, further comprising a pole tooth support.