JPH0698523A - Stepping motor - Google Patents

Abstract

PURPOSE:To apply a proper pressure to a shaft and at the same time to maintain the spring performance of a thrust spring properly by welding and fixing an intermediate bearing to a frame. CONSTITUTION:A resin bearing 34b is lightly press-fitted into a fitting hole 32b provided at a frame 32 and a metal bearing 34a is fitted into a fitting hole 32c. Then, a yoke assembly is laid out at the base edge part side in the axial direction and the metal bearing 34a is inserted into a diameter-reduced part but the opening side of a case body 33 is laid out so that it faces the frame 32 and does not contact a bent piece 32a. Then, the total length from a reference surface to the bent piece 32b is determined with the reception surface of a thrust spring 42 as a reference. Also, aligning with the inner diameter of the innermost periphery surface of a yoke assembly is performed following the inner diameter of a metal bearing 34a and a resin bearing 34b and then the metal bearing 34a is welded and fixed W to the frame 32 in three directions by laser welding positioning it on the aligned axis.

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 stepping motor having an improved thrust preloading structure for a shaft extending from a rotor.

[0002]

2. Description of the Related Art For example, a stepping motor is used as a driving means for a zoom lens and a focus lens of OA equipment and a video camera. This is because the stepping motor has the characteristics that position control and speed control can be easily performed by digital signals, and that it is inexpensive and easy to miniaturize.

FIG. 9 shows an example of a conventional PM type stepping motor. As shown in the figure, the frame 2 of the stepping motor 1 extends in the axial direction of the motor, and its axial cross section is U-shaped. A case body 3 having a bottomed tubular shape is attached to one axial end of the frame 2.

A cylindrical yoke assembly 4 (stator) is accommodated in the case body 3. The yoke assembly 4 is formed, for example, by integrally molding four pairs of pole tooth yokes with resin. The yoke assembly 4 is provided with, for example, two coils 5a and 5b, the outer circumference of which is covered by the case body 3.

Further, in the yoke assembly 4,
A rotor 8 formed by attaching a magnet 7 is arranged on the outer periphery of the shaft 6 on the base end side. Magnet 7
A predetermined gap G is provided around the inner periphery of the yoke assembly 4. Therefore, the shaft 6 is rotated by the rotating magnetic field generated by sequentially switching the currents flowing through the coils 5a and 5b. The shaft 6 extends from the rotor 8 to the frame 2, and a lead screw 6a is formed on the outer peripheral portion of the shaft 6 on the extension side. The shaft 6 is rotatably supported by bearings 9a and 9b at both ends of the lead screw 6a.

The bearings 9a and 9b are the same as the frame 2 described above.
It is attached to both axial ends. The bearing 9a that supports the base end side of the shaft 6 is formed by a metal bearing having a cylindrical shape. That is, the shaft 6
Is rotatably inserted in the metal bearing 9a. On the other hand, the bearing 9b that supports the extended end of the shaft 6 is
It is formed by a pivot bearing.

The lead screw 6a of the shaft 6 is meshed with the gear portions 11a and 11b of the connecting portion 11, and the rotation of the shaft 6 causes the connecting portion 11 to move in the axial direction. . Then, a sub-guide shaft 12 is stretched over the frame 2 along the shaft 6 to guide the movement of the connecting portion 11, and the insertion portion is adhesively fixed to the frame 2.

A thrust receiver 13 is brought into contact with the base end portion of the shaft 6, and a thrust plate 14 is used to close the opening of the case body 3 by means of a thrust spring 14. Loaded within 3.

[0009]

By the way, in the conventional stepping motor 1, in order to apply an appropriate thrust preload to the shaft 6, the frame 2 and the bearing 9 are used.
It is necessary to strictly set the dimensional accuracy of each component such as a, 9b, the case body 3, the yoke assembly 4, the rotor 8 and the like, and there is a problem that the manufacturing / assembling cost thereof increases.

Further, the thrust receiver 1 is provided in the case body 3.
There is also a countermeasure to set the spring constant of the thrust spring 14 interposed between the No. 3 and the holding plate 15 to be small and to make the displacement amount large, but this makes the installability (installation) at the time of assembly worse. Further, there is a problem that the spring performance of the thrust spring 14 deteriorates when an impact is applied.

In view of the above-mentioned problems, an object of the present invention is to provide a stepping motor capable of applying an appropriate thrust preload to the shaft by a simple and inexpensive assembly and maintaining good spring performance. Especially.

[0012]

According to the stepping motor of the present invention, a frame extending in the axial direction of the motor and a cylindrical body arranged on one axial end side of the frame are provided. Of the stator, a rotor disposed in the stator, and a shaft extending from the rotor. The shaft is inserted into an intermediate bearing mounted on a side portion of the stator of the frame. Achieved by welding and fixing an intermediate bearing to the above frame in a stepping motor in which one end of the stepping motor is rotatably supported by contacting it with a thrust bearing and the other end is contacted by a thrust spring and a thrust preload is applied. To be done.

In the above structure, preferably, the intermediate bearing is a sintered metal bearing.

Further, preferably, the above-mentioned welding is performed by laser welding.

Furthermore, it is preferable that the stator is not in contact with the frame.

[0016]

According to the above construction, the shaft of the rotor is
It is rotatably supported by a thrust bearing and an intermediate bearing. Further, one end of this shaft is in contact with the thrust bearing, and the other end is in contact with the thrust spring. That is, the thrust preload is applied to the shaft by the thrust spring. Further, the intermediate bearing is mounted on the stator side portion of the frame, and the intermediate bearing is welded and fixed to the frame. Therefore, the displacement of the intermediate bearing from the frame is prevented, and one end of the shaft is brought into contact with the thrust bearing to be positioned, so that the assembly is simplified and the shaft is loaded with an appropriate thrust preload. It is a thing.

If a sintered metal bearing is used as the intermediate bearing, it can be fixed by welding, its sizing can be facilitated, and the assembling can be simplified.

Further, if laser welding is adopted as the above-mentioned welding, it is possible to perform precise welding on a fine portion and to reduce heat influence and material deformation on the welded portion.

The stator is not in contact with the frame, and the stator and the bearing assembly are cut off from each other. Therefore, the assembly dimension error of the stator does not adversely affect the thrust spring, which also simplifies the assembly and loads the shaft with an appropriate thrust preload.

Further, even if a shock is applied, the stator and the bearing assembly are cut off from each other, so that the thrust spring is less likely to be subjected to a shock load and the spring performance is maintained well.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings. The examples described below are
Since it is a preferred specific example of the present invention, various technically preferable limitations are attached, but the scope of the present invention is, unless otherwise stated to limit the present invention, in the following description.
It is not limited to these modes.

1 (a), (b) and (c) show P of this embodiment.
1 shows an M type stepping motor. As shown, the frame 32 of the stepper motor 31
Are extended such that the axial direction of the motor is the longitudinal direction thereof. The frame 32 is made of sheet metal, and its axial cross section has a U-shape as shown in FIG. The bending pieces 32a and 32b located at both axial ends of the frame 32 are provided with mounting holes 32c and 32d centered in the axial direction.

Bending piece 32 located on the base end side in the axial direction
An intermediate bearing 34a is mounted in the mounting hole 32c formed in a. As the intermediate bearing 34a, for example, a metal bearing sintered and formed into a cylindrical shape by a powder metallurgy method is used. The metal bearing 34a is welded and fixed W to the frame 32 as shown in FIGS. 1 (a) and 2. Specifically, the outer peripheral portion of the metal bearing 34a and the inner peripheral portion of the mounting hole 32c are welded and fixed W by laser welding, and as shown in FIG.
Welding is applied to three locations on the outer periphery of a.

On the other hand, a thrust bearing 34b is mounted in a mounting hole 32d formed in the bending piece 32b located on the axially proximal end side. This thrust bearing 34b is
As shown in FIG. 1B, for example, a resin bearing formed in a concave shape is used. A flange portion 34c having a diameter radially outwardly provided is provided on a peripheral portion of the resin bearing 34b.
The flange portion 34c prevents the resin bearing 34b from coming out of the mounting hole 32d.

The bent piece 32a of the frame 32 is also included.
The case body 33 is located on the side. As shown in FIGS. 4A, 4B, and 4B, the case body 33 has a bottomed cylindrical shape. A mounting hole 33b is provided in the bottom portion 33a of the case body 33. The mounting hole 33b has a size that allows a rotor, which will be described later, to pass therethrough, and a pressing plate, which will be described later, is attached to this.

Further, as shown in FIG. 5, a yoke assembly 35 (stator) having a cylindrical shape is housed in the case body 33. The yoke assembly 35 is formed, for example, by integrally molding the insulator portions of four pairs of pole tooth yokes with resin. Then, for example, two coils 36a and 36b are formed in the yoke assembly 35, and the case body 33 described above is adhered so as to cover the outer circumference thereof.

Specifically, the yoke assembly 35 is shown in FIG.
It is molded as shown in. First, for four sets of pole tooth yokes 35a as shown in FIG.
As shown in FIG. 6B, the molds K1 and K2 are used for holding. The mold K1 opens and closes in the direction of arrow A, and the mold K2 slides in the direction of arrow B. Here, the molds K1 and K2 are wound with a coil 36
The resin injection space S is formed in the portions to be a and 36b and the inner peripheral surface portion where the rotor 37 described later is inserted.
1 and S2 are obtained. Then, in this state, outsert molding is performed. That is, from the resin injection gate provided at the predetermined position to the resin injection space S
Resin is injected into 1, S2. As a result, FIG.
As shown in (c) and FIG. 6D which is an enlarged vertical sectional view thereof, the resin layer formed in the resin injection space S1 is formed as an insulating layer F1 for the coil winding. On the other hand, the resin layer formed in the resin injection space S2 is formed as the innermost peripheral surface F2 of the yoke assembly 35. After the outsert molding is performed in this manner, FIG.
As shown in the plan view and the sectional view in (e) and (f), the terminal pin PT is press-fitted to complete the yoke assembly 35.

After that, winding is applied to form the coils 36a and 36b as shown in FIG. A diameter-reduced portion 35b is formed of resin on one inner peripheral edge portion of the yoke assembly 35 in the axial direction.
The inner diameter d1 of the reduced diameter portion 35b is the same as the metal bearing 34a.
Is formed so as to substantially match the outer diameter d2. As shown in FIG. 1A, the yoke assembly 35 is arranged such that the opening side of the case body 33 faces the frame 32, and the yoke assembly 35 is formed by the bending piece 32.
It is arranged so as not to contact a.

A rotor 37 is arranged in the yoke assembly 35. This rotor 37
A plurality of magnets 3 are provided on the outer circumference of the shaft 38 on the base end side.
It is formed by attaching 9. Specifically, FIG.
As shown in (a) and (b), two cylindrical magnets 39 are attached and fixed to the base end side of the shaft 38 after two cylindrical magnets 39 have been axially centered and height-determined at predetermined intervals. Is
It has 12 poles. On the other hand, the extended end portion of the shaft 38 has a curvature surface R such as a spherical surface formed by cutting or the like.
Is formed. Also, this shaft 3
The outer diameter of the extended end portion of No. 8 is formed so as to substantially match the inner diameter of the resin bearing 34b.

A predetermined gap G is provided around the magnet 39 and the inner peripheral surface of the yoke assembly 35. Therefore, the shaft 38 is rotated by the rotating magnetic field generated by sequentially switching the currents flowing through the coils 36a and 36b.

The shaft 38 extends from the rotor 37 to the frame 32, and the shaft 3
A lead screw 38a is formed on the outer peripheral portion of the extension side of 8. The shaft 38 is provided with the metal bearing 34a and the resin bearing 3 at both ends of the lead screw 38a.
It is rotatably supported by 4b.

A lead screw 38a is formed on the extending side of the shaft 38, and gear parts 40a and 40b of a connecting portion 40 mesh with the lead screw 38a. Then, a sub-guide shaft 41 is inserted and stretched over the frame 32 in parallel with the shaft 38. The sub-guide shaft 41 is lightly press-fitted into the holes 32e and 32f provided in the frame 32 and fixed by an adhesive. Also, this sub guide shaft 41
Is inserted into the connecting portion 40. Therefore, as the shaft 38 rotates, the connecting portion 40 moves to the sub guide shaft 41.
And is slid on the lead screw 38a in the axial direction. Incidentally, 40c in FIG.
Is a spring material attached to keep the gear portions 40a, 40b and the lead screw 38a in a good meshing state.

The connecting portion 40 is used for the stepping motor 3
It is a part connected to the movable part driven by 1.
For example, when the video camera is equipped with the stepping motor 31 of this embodiment, a lens holder is connected to the connecting portion 40 to move the zoom lens and the focus lens.

Further, at the base end of the shaft 36,
As shown in FIG. 1A, the thrust spring 42 is abutted, and the thrust plate 43 closes the mounting hole 33 b of the case body 33 via the thrust receiver 43, whereby the thrust preload is applied to the inside of the case body 33. Is loaded with.

Next, the operation will be described while explaining the assembling procedure of the stepping motor of the above embodiment. First, as shown in FIG. 1B, the resin bearing 34b is lightly press-fitted into the mounting hole 32d formed in the frame 32. Further, as shown in FIG. 2, the metal bearing 34a is mounted in the mounting hole 32c formed in the frame 32.

Next, the yoke assembly 35 is arranged on the axially proximal end side of the frame 32, and the metal bearing 34a is inserted into the reduced diameter portion 35b of the yoke assembly 35. At this time, in the yoke assembly 35, as shown in FIG. 1A, the opening side of the case body 33 is located on the frame 3 side.
2 so that the yoke assembly 35 does not come into contact with the bent piece 32a. A case body 33 is bonded to the yoke assembly 35 in advance, and the outer peripheral portion of the case body 33 is covered with the case body 33.

Then, as shown in FIG. 5, the total length L from the reference surface B to the bent piece 32b of the frame 32 is determined with reference to the receiving surface X of the thrust spring 42. Also, the inner diameter D of the metal bearing 34a and the resin bearing 34b
The inner diameter D3 of the innermost peripheral surface F2 of the yoke assembly 35 is centered on the basis of 1 and D2, and these are set so as to be coaxially located. In this state, as shown in FIGS. 1A and 3, the metal bearing 3 is attached to the frame 32.
4a is welded and fixed W by laser welding from three directions. By using laser welding as described above, it is possible to perform precise welding on a fine portion, and to reduce heat influence and material deformation on the welded portion. Further, in this embodiment, since the sintered metal bearing is used as the intermediate bearing 34a, welding and fixing can be performed, the sizing is easy, and the assembling can be performed more easily.

After that, the rotor 37 is arranged in the yoke assembly 35 through the mounting hole 33b of the case body 33. The shaft 38 of the rotor 37 is inserted into the metal bearing 34a, and the extending end portion thereof is the resin bearing 34b.
Abutted against. Therefore, the bent piece 3 of the frame 32 is
Metal bearings 34a mounted on 2a and 32b,
The resin bearing 34b rotatably supports both ends of the lead screw 38a formed on the shaft 38. Since the extending end of the shaft 38 is formed to have a curved surface R such as a spherical surface, the curved surface R
Comes into contact with the thrust spring 43, so that the shaft rotates smoothly.

Next, at the base end of the shaft 36, as shown in FIG.
As shown in (a), the thrust spring 42 is contacted,
The case body 3 is held by the pressing plate 44 through the thrust receiver 43.
The mounting hole 33b of No. 3 is closed. That is, the thrust preload is applied to the shaft 38 in the case body 33 by the thrust spring 42.

The sub guide shaft 41 is connected to the connecting portion 40.
While being inserted into the frame 32, the frame 32 is inserted, and the inserted portion is adhesively fixed to the frame 32. In addition, the connecting portion 40
Of the stepping motor 3 by engaging the gear portions 40a and 40b of the stepping motor 38 with the lead screw 38a of the shaft 38.
1 is completed. Grease is applied to the lead screw 38a.

As described above, by fixing the metal bearing 34a to the frame 32 by welding W, the metal bearing 34a
Since the displacement of a from the frame 32 is prevented, and one end of the shaft 32 is brought into contact with and positioned by the resin bearing 34b, the assembly is simplified and the shaft 3
8 is loaded with an appropriate thrust preload.

Further, the yoke assembly 35 is not in contact with the bent piece 32a of the frame 32, and the yoke assembly 35 and the bearing assembly are cut off from each other.
Therefore, the assembly dimension error of the yoke assembly 35 does not adversely affect the thrust spring 42, and the assembly can be made simpler. Therefore, an appropriate thrust preload can be applied to the shaft, there is no variation in thrust preload, and stable rotation can be obtained with low loss. Further, even if a shock is applied, since the yoke assembly 35 and the bearing assembly are cut off from each other, it is difficult to apply a shock load to the thrust spring 42, so that the spring performance of the thrust spring can be maintained well. .

[0043]

As described above, the stepping motor according to the present invention is simple and inexpensive to assemble, and it is possible to easily apply an appropriate thrust preload to the shaft, which results in low loss. With this, stable rotation can be obtained. Further, the spring performance of the thrust spring can be maintained well.

[Brief description of drawings]

1A and 1B show an embodiment of a stepping motor according to the present invention, in which FIG. 1A is a partially cutaway plan view, FIG. 1B is a longitudinal sectional view of an essential part thereof, and FIG.

FIG. 2 is a vertical cross-sectional view showing a state in which an intermediate bearing is mounted on the frame of the stepping motor of this embodiment.

FIG. 3 is an explanatory view showing a welding state of the intermediate bearing and the frame of the stepping motor of the present embodiment.

4A and 4B show a case of a stepping motor of the present embodiment, FIG. 4A is a left side view of the case, and FIG.
(C) is the right side view.

FIG. 5 is a vertical cross-sectional view showing a component positioning state of the stepping motor of this embodiment.

6A and 6B show a forming method and a structure of a yoke assembly of a stepping motor of the present embodiment, FIG. 6A is an exploded perspective view of four pairs of pole tooth yokes, and FIG. 6B is a vertical cross-sectional view of a holding state by a mold; (C) is a perspective view of a resin layer molding state, (d) is an enlarged vertical sectional view of the resin layer molding state, (e) is a plan view of the completed yoke assembly, and (f) is a longitudinal sectional view of the completed yoke assembly.

FIG. 7 is a vertical cross-sectional view showing a coil mounting state of the yoke assembly of the stepping motor of the present embodiment.

8A and 8B show a rotor of a stepping motor of the present embodiment, FIG. 8A is a vertical sectional view thereof, and FIG. 8B is a perspective view thereof.

FIG. 9 is a vertical sectional view showing an example of a conventional stepping motor.

[Explanation of symbols]

 31 Stepping Motor 32 Frame 33 Case Body 34a Intermediate Bearing (Metal Bearing) 34b Thrust Bearing (Resin Bearing) 35 Yoke Assembly (Stator) 37 Rotor 38 Shaft 42 Thrust Spring W Welding Fixing

Claims (4)

[Claims] 1. A frame extending in the axial direction of a motor, a tubular stator disposed on one axial end of the frame, a rotor disposed in the stator, and the rotor. And an extended shaft, the shaft being inserted into an intermediate bearing mounted on the stator side portion of the frame, and one end of which is abutted against the thrust bearing and rotatably supported. A stepping motor in which an end portion is in contact with a thrust spring and a thrust preload is applied thereto, wherein an intermediate bearing is welded and fixed to the frame. 2. The stepping motor according to claim 1, wherein the intermediate bearing is a sintered metal bearing. 3. The stepping motor according to claim 1, wherein the welding is laser welding. 4. The stepping motor according to claim 1, wherein the stator does not contact the frame.