JPH11289740A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor for stepping motor for which a bush can be formed with high accuracy as well as inexpensively. SOLUTION: A stepping motor incorporates a rotor 20 composed of a rotor magnet 21, a supporting member 22 having an attaching hole 22a near the center of the magnet 21, a bush 23 which is fixed and held in the attaching hole 22a of the supporting member 22, and a rotating shaft 23 which is inserted into a center hole 23b of the bush 23 by press-fitting, etc., and a stator includes two bearings which rotatably support both ends of a rotary shaft 24 of the rotor 20 and coils arranged in such a way that the coils face opposite to the magnet 21. In the stepping motor, the bush 23 constitutes the rotor 20 of the motor so that the bush 23 is formed through sintering and pressing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor, and more particularly to a bush for fixing and holding a rotating shaft of a rotor.

[0002]

2. Description of the Related Art Conventionally, a stepping motor is configured as shown in FIG. That is, in FIG.
The stepping motor 1 includes a stator 2 and a rotor 5 rotatably supported by bearings 3 and 4 provided on the stator 2.

[0003] The stator 2 includes a stator substrate 2a, a coil 2b connected to the stator substrate 2a, a flange 2c for supporting the bearings 3 and 4, and a case 2d surrounding the whole. I have.

On the other hand, as shown in FIG. 4, a rotor 5 has a hollow cylindrical rotor magnet 5a, a cup 5b mounted in the rotor magnet 5a, and a bush fixed and held at the center of the cup 5b. 5c, a rotating shaft 5d attached to the bush 5c, and a yoke 5g disposed outside the rotor magnet 5a.

The rotor magnet 5a is open at both ends and is appropriately magnetized in the circumferential direction of the permanent magnet. The cup 5b is formed in a hollow cylindrical shape whose one end is open. The cylindrical side surface is in contact with the inner wall surface of the hollow portion of the rotor magnet 5a and is fixed by bonding or the like. And a mounting hole 5e for fixing and holding the bush 5c.

The bush 5c is formed in a substantially cylindrical shape in the drawing, and has a step 5f at one end. The bush 5c is fixedly held by, for example, press-fitting the step 5f into the mounting hole 5e of the cup 5b. The rotating shaft 5d is inserted into the center hole of the bush 5c by press fitting or the like, is fixed and held, and has a driving gear 6 at one end.

Further, when the rotating shaft 5d is mounted on the bearings 3 and 4 supported on the flange 2c of the stator 2,
A resin washer 7 is inserted on the bearing 3 side, and two resin washers 8a and 8b and a spring washer 8c between them are inserted on the bearing 4 side so as not to move along the axial direction. . The yoke 5g is formed so as to extend outward in the axial direction so as to face the coil 2b on the stator 2 side so as to sandwich the coil 2b from both sides in the axial direction.

According to the stepping motor 1 configured as described above, by controlling the driving of the coil 2 b of the stator 2, the magnetic field generated in the coil 2 b is transmitted to the magnetic field of the rotor magnet 5 a via the yoke 5 g of the rotor 5. And the rotor 5 is rotationally driven.

[0009]

However, in the stepping motor 1 having such a structure, the bush 5c is formed by cutting Al, Bs or the like to reduce costs. For this reason, the rotating shaft 5
The center hole of the bush 5c for press-fitting and holding d may have reduced processing accuracy due to setting of the processing machine or the like.

On the other hand, as shown in FIG. 5, a configuration is known in which the diameter of the bush 5c is increased and the cup 5b is omitted. In this case, there is a problem that the cost of the bush 5c increases. Further, there is also a method of resin-molding the bush 5c integrally with the rotating shaft 5d. However, in this case, since it is necessary to provide a rotation stopper on the rotating shaft 5d, there is a problem that the cost is increased.

In view of the above, an object of the present invention is to provide a stepping motor in which a bush can be formed with high accuracy and at low cost.

[0012]

According to the present invention, a rotor magnet, a support member having a mounting hole near the center of the rotor magnet, and a bush fixed and held in the mounting hole of the support member are provided. And a rotating shaft mounted by press-fitting or the like in the center hole of the bush, two bearings rotatably supporting both ends of the rotating shaft of the rotor, and a rotor magnet. And a stator comprising:
The stepping motor is achieved by a stepping motor, wherein the bush is formed by a sintering press.

Preferably, in the stepping motor according to the present invention, the bush is formed by sintering copper, copper iron or iron powder.

[0014] In the stepping motor according to the present invention, preferably, the bush is arranged such that the bush is provided in a mounting hole of the supporting member.
It is attached by caulking.

In the stepping motor according to the present invention, preferably, the bush has a step, and the step is mounted on the supporting member by caulking the step.

According to the above construction, since the bush holding the rotary shaft is formed by sintering press from, for example, copper, copper iron, or iron powder, the manufacturing cost of the bush can be reduced and the rotary shaft can be used. Since the processing accuracy of the center hole to be press-fitted is determined by the finishing accuracy of the press die for manufacturing the bush, variations in the processing accuracy of the center hole are reduced, and the assembling accuracy of the rotor of the stepping motor is reduced. Will be improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 shows the configuration of a stepping motor incorporating one embodiment of a rotor according to the present invention. In FIG. 1, a stepping motor 10 includes a stator 11 and a rotor 20 rotatably supported by bearings 12 and 13 provided on the stator 11.
And is composed of

The stator 11 includes a stator substrate 14 and a coil 15 connected to the stator substrate 14 and a flange 1 for supporting the bearings 12 and 13.
6, and a case 17 surrounding the whole.

On the other hand, as shown in FIG. 2, the rotor 20 has a hollow cylindrical rotor magnet 21, a cup 22 as a support member mounted in the rotor magnet 21, and fixed to the center of the cup 22. The held bush 23 and the rotating shaft 24 attached to the bush 23
And a yoke 25 attached to the outside of the rotor magnet 21.

The rotor magnet 21 is open at both ends and is appropriately magnetized in the circumferential direction of the permanent magnet. The cup 22 is formed in a hollow cylindrical shape whose one end is open. The cylindrical side surface is in contact with the inner wall surface of the hollow portion of the rotor magnet 21 and is fixed by bonding or the like. And a mounting hole 22a for fixing and holding the bush 23.

The bush 23 is formed to be thin in the axial direction in the drawing, and has a step 23a on one side, that is, on the bearing 12 side. And bush 2
3, the step portion 23a is inserted into the mounting hole 22a of the cup 22, and is fixed and held. The rotating shaft 24 is inserted into the center hole 23b of the bush 23 by press fitting or the like, is fixed and held, and has a driving gear 26 at one end.

Further, the rotating shaft 24 is connected to the stator 11
When the bearings 12 and 13 are mounted on the bearings 12 and 13 supported on the flange 16, a resin washer 18 is provided on the bearing 12 side, and a spring member 19 is provided on the bearing 13 side so as not to move along the axial direction. Are interposed respectively. The yoke 25 extends outward in the axial direction,
The coils 15 on the stator 11 side are formed to face each other so as to sandwich the coil 15 from both sides in the axial direction.

The conventional stepping motor 1 shown in FIGS. 3 and 4 and the stepping motor 10 according to the present invention are different in the following points. That is, in this case, the bush 23 is formed by sintering and pressing copper, copper iron or iron powder. Thus, the center hole 23b of the bush 23 can be formed with high accuracy based on the finishing accuracy of the press die.

The bush 23 has a stepped portion 2
After the bush 23 is pressed or inserted into the mounting hole 22a of the cup 22, the step 23a is crushed by caulking as shown by an arrow A in FIG. 22 is fixedly held. still,
This caulking is performed at a plurality of locations at equal angular intervals with respect to the center axis, for example, at four locations as shown in FIG.

The stepping motor 10 according to the embodiment of the present invention is configured as described above.
It is assembled as follows. First, the rotating shaft 24 is mounted in the center hole 23b of the bush 23 by press fitting or the like, and the bush 23 is pressed or inserted into the mounting hole 22a of the cup 22 as described above, and is fixed and held by crimping. Thereafter, the cylindrical side surface of the cup 22 is fixed to the inner wall surface of the rotor magnet 21 by bonding or the like. The rotor 20 assembled in this manner has both ends of the rotating shaft 24 mounted on the bearings 12 and 13 of the stator 11.
And the stepping motor 10 is completed.

Thus, the stepping motor 10 drives and controls the coil 15 of the stator 11 so that
The magnetic field generated in the coil 15 is applied to the yoke 25 of the rotor 20.
, Interact with the magnetic field of the rotor magnet 21 to rotate the rotor 20.

In this case, since the bush 23 is formed by a sintering press, the dimensional accuracy of the center hole is determined by the finishing accuracy of a mold for manufacturing the bush 23, and thus the variability is varied. , The quality of the bush 23 is stabilized, and the assembling accuracy of the rotor 20 is improved. Further, the bush 23
By being formed by powder sintering of copper, copper iron or iron, the manufacturing cost can be reduced.

In the above embodiment, the bush 2
3 is supported on the rotor magnet 21 via a cup 22 as a support member, but is not limited thereto.
Obviously, the peripheral surface of the bush 23 having a large diameter may be directly attached to the inner wall surface of the rotor magnet 21. In this case, the bush 23
Is formed by a sintering press, so that it can be manufactured at a relatively low cost even if the diameter is increased.

[0029]

As described above, according to the present invention, since the bush for holding the rotating shaft is formed by sintering press from, for example, copper, copper iron or iron powder, the manufacturing cost of the bush is reduced. Since the machining accuracy of the center hole into which the rotating shaft is to be press-fitted is determined by the finishing accuracy of the press die for manufacturing the bush, the variation in the machining accuracy of the center hole is reduced, The assembling accuracy of the rotor of the stepping motor is improved. Thus, according to the present invention, it is possible to provide an extremely excellent rotor of a stepping motor in which a bush can be formed with high accuracy and at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a stepping motor incorporating one embodiment of a rotor according to the present invention.

FIGS. 2A and 2B show a rotor in the stepping motor of FIG. 1, wherein FIG. 2A is a schematic front view and FIG.

FIG. 3 is a schematic sectional view showing a configuration of an example of a conventional stepping motor.

FIG. 4 is a schematic sectional view of a rotor in the stepping motor of FIG.

FIG. 5 is a schematic sectional view showing a modified example of the rotor of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Stepping motor 11 Stator 12, 13 Bearing 14 Stator board 15 Coil 16 Flange 17 Case 18 Resin washer 19 Spring member 20 Rotor 21 Rotor magnet 22 Cup 22a Mounting hole 23 Bush 23a Step 23b Center hole 24 Rotary shaft 25 Yoke

Claims (4)

[Claims] 1. A rotor magnet, a support member having a mounting hole near the center of the rotor magnet, a bush fixed and held in the mounting hole of the support member, and a rotation mounted by press-fitting into the center hole of the bush. A rotor comprising: a shaft; a rotor comprising: two bearings rotatably supporting both ends of a rotating shaft of the rotor; and a stator comprising: a coil disposed so as to face the rotor magnet. A stepping motor, wherein the bush is formed by a sintering press. 2. The stepping motor according to claim 1, wherein the bush is formed by sintering copper, copper iron or iron powder. 3. The stepping motor according to claim 1, wherein the bush is attached to an attachment hole of the support member by caulking. 4. The stepping motor according to claim 3, wherein the bush has a step, and is attached to the support member by caulking the step.