JP2000078824A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stepping motor where a rotary shaft can be attached easily and with high accuracy to a rotor magnet by simple constitution. SOLUTION: A stepping motor 10, which contains a rotor 20 comprising a hollow cylindrical rotor magnet 21 and a rotary shaft 24 fixed and retained in the vicinity of the center of this rotor magnet 21 by a bush, a stator 11 comprising bearings 12 and 13 supporting the rotary shaft of the rotor 20 rotatably, and a coil 15 arranged to oppose the rotor magnet 21, is constituted so that the bush may be constituted of one sheet at least of discs 22 and 23 equipped with center attachment holes 22b and 23b where the rotary shaft is press-fitted and peripheral edges 22a and 23a bonded to the inwall of the rotor magnet.

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.

[0002]

2. Description of the Related Art Conventionally, a stepping motor is configured, for example, 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.

The stator 2 includes a yoke 5g and a coil 2b, a flange 2c for supporting the bearings 3 and 4, and a case 2d surrounding the whole.

On the other hand, as shown in FIG. 6, 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, and a rotating shaft 5d attached to the bush 5c.

[0005] The rotor magnet 5a is open at both ends, is constituted by a permanent magnet, or is appropriately magnetized in the circumferential direction. 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 fixed by, for example, press-fitting the step 5f into the mounting hole 5e of the cup 5b, and then caulking the step 5f of the bush 5c to the cup 5b at a plurality of surrounding locations. Will be retained. The rotating shaft 5
d 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 so as to sandwich the coil 2b from both sides in the axial direction.

According to the stepping motor 1 configured as described above, when a current flows through the coil 2 b of the stator 2, the magnetic field generated in the coil 2 b mutually interacts with the magnetic field of the rotor magnet 5 a via the yoke 5 g. As a result, the rotor 5 is driven to rotate.

[0009]

However, in the stepping motor 1 having such a configuration, the rotor 5
At the time of assembling, the rotating shaft 5d is first press-fitted into the bush 5c, and the step 5f of the bush 5c is fixed by caulking to the mounting hole 5e of the cup 5b, and then the cup 5b is inserted into the rotor magnet 5a. The rotor magnet 5 is attached by an adhesive applied to the outer peripheral surface of the cup 5b.
The cup 5b is adhered and fixed in a.
Therefore, since the bush 5c and the cup 5b are required to attach the rotating shaft 5d to the center of the rotor magnet 5a, the number of parts is increased and the bush 5c is increased.
Since a is provided with a step 5f for attaching to the cup 5b, the shape becomes complicated, and there is a problem that these parts costs and assembly costs increase.

Further, when the rotor magnet 5a has a small thickness, such as a neodymium magnet, the bonding surface is increased, and the rotor magnet 5a and the cup 5 are formed.
The adhesive strength is increased by pouring an adhesive between b. At this time, there is a problem that it is difficult to control the dimension between the rotor magnet 5a and the cup 5b because the dimension control greatly affects the adhesive strength.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a stepping motor in which a rotating shaft can be easily and accurately attached to a rotor magnet with a simple structure.

[0012]

According to the present invention, there is provided a rotor comprising: a hollow cylindrical rotor magnet; a rotating shaft fixedly held by a bush near the center of the rotor magnet; A stepper motor including: a bearing that rotatably supports a rotating shaft of a rotor; and a stator that is disposed so as to face the rotor magnet. This is achieved by a stepping motor characterized in that the stepping motor comprises at least one disk having a center mounting hole and an outer peripheral edge bonded to the inner wall surface of the rotor magnet.

In the stepping motor according to the present invention, preferably, the bush has a rising portion extending in an axial direction from an inner edge of the center hole.

In the stepping motor according to the present invention, preferably, the bush has a step on the outer peripheral edge.

In the stepping motor according to the present invention, preferably, the bush is provided with a thermal expansion absorbing hole.

According to the above configuration, since the bush holding the rotating shaft is composed of at least one disk, the manufacturing cost of the bush can be reduced, and the outer peripheral edge of the bush is directly connected to the rotor magnet. Since it is adhesively fixed to the inner wall surface, a cup for attaching the bush in the conventional stepping motor to the rotor magnet becomes unnecessary, and the cost of parts and assembly can be reduced. In addition, since the bonding state between the bush and the rotor magnet can be visually recognized from the outside, quality control can be easily performed.

When the bush has a rising portion extending in the axial direction from the inner edge of the center hole, the rising portion can be easily processed by, for example, burring, and the rising portion allows the rising portion to be formed in the center hole. The holding strength of the press-fitted rotating shaft can be increased.

In the case where the bush has a step on the outer peripheral edge, when the bush is adhered to the inner wall surface of the rotor magnet, the adhesive accumulates on the step, and this adhesive is formed. The hardening of the pool allows the bush to be adhesively fixed to the low magnet. Therefore, the bush can be more securely fixed to the rotor magnet.

When the bush has a thermal expansion absorbing hole, even if each disk constituting the bush thermally expands, the thermal expansion is absorbed by the thermal expansion absorbing hole, and the thermal expansion is absorbed. Deformation due to expansion can be prevented. Therefore, cracking of the rotor magnet due to thermal expansion of the bush can be prevented.

[0020]

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 a configuration of an embodiment of a stepping motor 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 attached to a flange 16 and a case 17.

The stator 11 includes a stator substrate 14, a yoke 25, and a coil 15, and includes the bearing 1
It has a flange 16 for supporting the two and 13 and a case 17 for surrounding the whole.

On the other hand, as shown in FIG. 2, the rotor 20 has a hollow cylindrical rotor magnet 21 and bushes 22, 23 mounted in the rotor magnet 21.
And a rotating shaft 24 attached to the bushes 22 and 23
And is composed of

The rotor magnet 21 is open at both ends, is constituted by a permanent magnet, and is appropriately magnetized in the circumferential direction. The bushes 22 and 23 are formed of two disks, and their outer peripheral edges 22a and 23
a 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 has central holes 22b and 23b for attaching the rotating shaft 24 at the center. The rotating shaft 24 is inserted into the central holes 22b and 23b of the bushes 22 and 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
Bearing 1 supported on flange 16 and case 17
When mounted on the bearings 2, 13, a resin washer 18 is provided on the bearing 12 side, and two resin washers 19a, 19b and a spring washer therebetween are provided on the bearing 13 side so as not to move in the axial direction. 19c are interposed. Further, the yoke 25 is formed so as to extend toward the outside in the axial direction so as to face the coil 15 from both sides in the axial direction.

Here, the bushes 22 and 23 are made of, for example, iron or aluminum. In the case of iron, the cost can be reduced, and in the case of aluminum, since it is not a magnetic material, the magnetic influence can be suppressed.

The bushings 22, 23 have step portions 22c, 23c on their outer peripheral edges 22a, 23a. The steps 22c and 23c are, for example,
When punching 23, it can be formed by press working or the like at the same time. Thereby, when the bushes 22 and 23 are attached to the inner wall surface of the rotary magnet 21 by the adhesive, the adhesive is entirely spread within the space defined by the step portions 22c and 23c and the inner wall surface of the rotary magnet 21. The bushes 22 and 23 can be more securely adhered and fixed to the rotary magnet 21 by the adhesive pool being hardened by the hardening of the adhesive pool.

Further, the bushings 22 and 23 are provided with rising portions 22 extending axially from central holes 22b and 23b.
d and 23d. The rising portions 22d and 23d
Is processed by burring, for example. As a result, the holding strength of the bushes 22 and 23 with respect to the rotating shaft 24 is increased. In addition, bush 2
In the case where the thickness of the disks constituting the disks 2 and 23 is, for example, 1.5 mm or more and the bushes 22 and 23 are relatively thick, the rising portions 22c and 23c may be omitted.

Further, the bushes 22, 23 are
Some of them are provided with thermal expansion absorption holes 22e and 23e. Although only one thermal expansion absorption hole 22d, 23d is shown, its position and number can be arbitrarily selected as long as the strength of the disk is not reduced. 23 rotor magnets 21
The adhesive is attached to the inner wall surface of the bushing, or the inertia with respect to the center of the bushes 22 and 23 may be changed.

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 attached to the center holes 22b and 23b of the bushes 22 and 23 by press fitting or the like. Thereafter, the outer peripheral edges 22a, 23a of the bushes 22, 23 are fixed to the inner wall surface of the rotor magnet 21 by bonding or the like. At this time, the stepped portion 2 provided on the outer peripheral edges 22a, 23a of the bushes 22, 23
The adhesive 27 accumulates in an annular space defined by the inner walls 2c and 23c and the inner wall surface of the rotor magnet 21. Therefore, when the adhesive 27 is cured, the bushes 22 and 23 can be securely bonded and fixed to the rotor magnet 21. The rotor 20 thus assembled is pivotally supported at both ends of the rotating shaft 24 by the bearings 12 and 13 of the stator 11, and the stepping motor 10 is completed.

Thus, the stepping motor 10 is driven by the current flowing through the coil 15 of the stator 11.
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 bushes 22 and 23 are composed of two disks, the bush 2
Since the manufacturing costs of the stepping motors 1 and 2 can be reduced and the outer peripheral edges 22a and 23a of the bushes 22 and 23 are directly bonded and fixed to the inner wall surface of the rotor magnet 21, the conventional stepping motor 1 shown in FIG. The cup 5b as in the case is not required. As a result, the number of parts is reduced, and assembling can be easily performed, so that parts costs and assembling costs can be reduced. Further, since the bonding state between the bushes 22, 23 and the rotor magnet 21 can be easily visually recognized from the outside, quality control can be easily performed.

When the temperature rises during operation of the stepping motor 10 or the like, even if the bushes 22 and 23 themselves thermally expand, the thermal expansion absorption holes 22e and 2
Due to the presence of 3e, deformation due to thermal expansion can be prevented, and cracks and the like of the rotor magnet 21 can be prevented.

FIG. 3 shows a rotor in a second embodiment of the stepping motor according to the present invention. 3, the rotor 30 is different from the rotor 20 shown in FIG. 2 only in that the outer peripheral edges of the bushes 22 and 23 are not provided with a stepped portion. Has substantially the same configuration as the rotor 20 shown in FIG. In this case, the adhesives 27 are accumulated at the corners defined between the outer peripheral edges 22a, 23a and the inner wall surface of the rotor magnet 21 so that the bushes 22, 23 are attached to the rotor magnet 21. It will be adhesively fixed.
Accordingly, although the adhesive strength of the bushes 22 and 23 to the rotor magnet 21 is slightly reduced, the manufacturing costs of the bushes 22 and 23 are reduced because it is not necessary to process the step portions 22c and 23c on the bushes 22 and 23. Can be done.

FIG. 4 shows a rotor in a third embodiment of the stepping motor according to the present invention. 4, the rotor 40 is different from the rotor 30 shown in FIG. 3 in that the center holes 22b and 23b of the bushes 22 and 23 are further provided.
Is different only in that it does not include the rising portions 22d and 23d, and the other configuration is almost the same as the rotor 30 shown in FIG. In this case, the bush 22,
The rotary shaft 24 is press-fitted into the inner peripheral edge of the center hole 22b, 23b. Such a configuration is required when the inner peripheral edge has a strength that can withstand the press-fitting of the rotating shaft 24, and when the thickness of the disks constituting the bushes 22 and 23 is 1.5 mm or more. . In this case, the holding strength of the bushes 22 and 23 to the rotating shaft 24 can be maintained, and the processing of the rising portions 22d and 23d by burring or the like becomes unnecessary, so that the manufacturing cost of the bushes 22 and 23 is further reduced. Can be done.

In the above embodiment, the bush 2
2 and 23 are composed of two disks, but are not limited thereto, and may be composed of one disk. In order to increase the holding strength, three or more disks are used. Obviously, it may be configured.

In the above embodiment, the bushes 22, 23 are made of, for example, iron. However, the present invention is not limited to this, and the bushes 22 and 23 may be made of other materials. In this case, for example, when reducing the inertia, or when reducing the inertia, the inertia adjustment of the bushes 22, 23 and the rotor 20 can be performed by selecting aluminum or the like or appropriately selecting the plate thickness. .

[0037]

As described above, according to the present invention, since the bush for holding the rotating shaft is composed of two disks, the manufacturing cost of the bush can be reduced and the bush outside the bush can be reduced. Since the peripheral edge is directly adhered and fixed to the inner wall surface of the rotary magnet, a cup for attaching the bush in the conventional stepping motor to the rotary magnet becomes unnecessary, and the cost of parts and assembly can be reduced. Further, since the state of adhesion between the bush and the rotary magnet can be visually recognized from the outside, quality control can be easily performed.

In the case where the bush has a rising portion extending in the axial direction from the inner edge of the center hole, the rising portion can be easily formed by, for example, burring, and the rising portion allows the center hole to be formed in the center hole. The holding strength of the press-fitted rotating shaft can be increased.

In the case where the bush has a step on the outer peripheral edge, when the bush is bonded to the inner wall surface of the rotary magnet, the adhesive accumulates on the step so that the adhesive is removed. The hardening of the pool allows the bush to be adhesively fixed to the rotary magnet.
Therefore, the bush can be more securely fixed to the rotary magnet.

When the bush is provided with a thermal expansion absorbing hole, even if each disk constituting the bush is thermally expanded, the thermal expansion is absorbed by the thermal expansion absorbing hole. Deformation due to expansion can be prevented, and cracks and the like of the magnet can be prevented.

Thus, according to the present invention, it is possible to provide an extremely excellent stepping motor in which the rotating shaft can be easily and accurately attached to the rotor magnet with a simple structure.

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view showing a configuration of a rotor in the stepping motor of FIG.

FIG. 3 is a schematic sectional view of a rotor in a second embodiment of the stepping motor according to the present invention.

FIG. 4 is a schematic sectional view of a rotor in a third embodiment of the stepping motor according to the present invention.

FIG. 5 is a schematic sectional view showing a configuration of an example of a conventional stepping motor.

FIG. 6 is a schematic sectional view of a rotor in the stepping motor of FIG.

[Explanation of symbols]

 Reference Signs List 10 stepping motor 11 stator 12, 13 bearing 14 stator substrate 15 coil 16 flange 17 case 18 resin washer 19a, 19b, 19c washer 20, 30, 40 rotor 21 rotor magnet 22, 23 bush 22a, 23a outer peripheral edge 22b, 23b center Holes 22c, 23c Stepped portions 22d, 23d Rising portions 22e, 23e Thermal expansion absorption holes 24 Rotation shaft 25 Yoke 26 Drive gear 27 Adhesive

Claims (4)

[Claims] 1. A rotor comprising: a hollow cylindrical rotor magnet; and a rotating shaft fixed and held near a center of the rotor magnet by a bush; a bearing rotatably supporting the rotating shaft of the rotor; and a rotor. A stepped motor including: a coil disposed so as to face the magnet; and a stepping motor, wherein the bush has a center mounting hole into which the rotating shaft is press-fitted,
A stepping motor comprising at least one disk having an outer peripheral edge bonded to an inner wall surface of a rotor magnet. 2. The stepping motor according to claim 1, wherein the bush has a rising portion extending in an axial direction from an inner edge of the center hole. 3. The stepping motor according to claim 1, wherein the bush has a step on an outer peripheral edge. 4. The stepping motor according to claim 1, wherein the bush has a thermal expansion absorbing hole.