JPH0698524A - Stepping motor - Google Patents

Abstract

PURPOSE:To enable a joint part from being engaged securely with a simple structure without increasing the load for rotation of a shaft. CONSTITUTION:In this motor where a joint part 40 traveling in an axial direction on a lead screw 38a formed at the extension side of a shaft has gear parts 40d and 40e which are engaged to the lead screw 38a and at the same time it has an energizing means 40g the gear parts 40d and 40c to the lead screw 38a, a sub-gear part 40h for assisting engagement with the lead screw 38a is formed at the joint part 40.

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 shock resistant structure of a connecting portion which moves on a lead screw formed on a shaft of 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. 8 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 cylindrical shape is formed at 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. . Further, a spring material 11c for maintaining a good meshing state of the lead screw 38a is attached to a portion of the connecting portion 11 which faces the gear portions 11a and 11b. Further, a sub-guide shaft 12 is stretched over the frame 2 along the shaft 6 so as to guide the movement of the connecting portion 11, and the insertion portion is adhesively fixed to the frame 2. The connecting portion 11 is a portion that is connected to a movable portion that is driven by the stepping motor 1. For example, when the video camera is equipped with the stepping motor 1, a lens holder is connected to the connecting portion 11. This is to move the zoom lens and focus lens.

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, the spring member 11c is formed on the connecting portion 11, and the connecting portion 1 is urged by the spring force.
The gear parts 11a, 11b of No. 1 and the lead screw 38a are kept in good meshing condition.

However, when an impact is applied to the stepping motor 1, the gear portions 11a and 11b of the connecting portion 11 may cause tooth skipping. Therefore, for example, when the video camera is equipped with the stepping motor 1, there is a problem that the zoom lens and the focus lens are out of focus.

As a measure to prevent the tooth jumping of the connecting portion 11, the biasing force of the spring member 11c is set to be strong so that the gear portions 11a and 11b and the lead screw 38 can be applied with a larger force.
It is conceivable to engage with a. However, this measure increases the load on the rotation of the shaft 6. As a result, there have been problems that power consumption increases and large acoustic noise occurs.

In view of the above problems, an object of the present invention is to provide a stepping motor capable of preventing tooth jumping of a connecting portion with a simple structure without increasing a load on rotation of a shaft.

[0013]

According to the stepping motor of the present invention, the above-mentioned object is achieved by rotating a rotor arranged in a stator so as to rotate a shaft on a lead screw formed on the extension side of the shaft. A stepping device that includes a connecting portion that moves along the direction, the connecting portion includes a gear portion that meshes with the lead screw, and an urging means that urges the gear portion toward the lead screw. In the motor, this is achieved by forming a sub-gear portion for assisting the engagement with the lead screw in the connecting portion.

In the above structure, preferably, the sub gear portion is formed in a portion of the coupling portion which is not subjected to the urging force of the urging means.

Further, it is preferable that the sub-gear portion engages with the lead screw only at the time of impact.

Furthermore, preferably, the sub gear portion is
It is formed in at least one place of the connecting portion.

[0017]

According to the above construction, the rotation of the rotor causes
The connecting portion moves along the axial direction on the lead screw formed on the extension side of the shaft. The connecting portion has a gear portion that meshes with the lead screw. Further, the connecting portion has a biasing means for biasing the gear portion to the lead screw. Further, a sub gear portion is formed in this connecting portion so as to assist the engagement with the lead screw. Therefore, even if the gear part jumps at the time of impact, as long as the sub gear part meshes with the lead screw, the connecting part as a whole does not jump.

Further, when the sub gear portion is formed in a portion of the coupling portion that is not subjected to the urging force of the urging means, even if the sub gear portion is increased, the load on the rotation of the shaft is not increased. Is.

Further, if the sub-gear portion is meshed with the lead screw only at the time of impact, it is not always meshed with the lead screw, so that the feed accuracy of the connecting portion is not adversely affected.

If the sub gear portion is formed in at least one place of the connecting portion, the tooth jump of the connecting portion can be effectively prevented.

[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
A metal bearing 34a is mounted in the mounting hole 32c formed in a. In this metal bearing 34a, for example,
The one that is sintered and molded into a cylindrical shape by the powder metallurgy method is used. The metal bearing 34a is welded and fixed W to the frame 32 as shown in FIG. 1 (a). Specifically, the outer peripheral portion of the metal bearing 34a and the inner peripheral portion of the mounting hole 32c are weld-fixed W by laser welding,
Welding is applied to three locations on the outer periphery of the metal bearing 34a.

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. As the thrust bearing 34b, as shown in FIG. 1B, for example, a resin bearing formed in a concave shape is used. A flange portion 34c having a diameter outwardly expanded is provided on a peripheral portion of the thrust bearing 34b, and the flange portion 34c prevents the thrust bearing 34b from coming out of the mounting hole 32d. There is.

The bent piece 32a of the frame 32 is also included.
On the side, as shown in FIGS. 2A, 2B and 2C, the case body 33 is located. This case body 33
Has a cylindrical shape with a bottom. 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, a cylindrical yoke assembly 35 (stator) 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. And this yoke assembly 3
For example, two coils 36a and 36b are formed on the casing 5, and the outer circumference thereof covers the case body 33 described above.
Are glued together. 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 formed to substantially match the outer diameter d2 of the metal bearing 34a. 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 does not abut the bent piece 32a.

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 to substantially match the inner diameter of the thrust 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. This lead screw 38a is 0.6 mm
It is a double pitch screw with a pitch of 0.3 mm. The shaft 38 has the lead screw 38
The metal bearing 34a and the thrust bearing 34 are provided at both ends of a.
It is rotatably supported by b.

A lead screw 38a is formed on the extending side of the shaft 38. The lead screw 38a includes gear parts 40d, 40
e is in mesh. Similar to the lead screw 38a, the gear portions 40d and 40e are double-threaded screws having a pitch of 0.6 mm, and by setting the screw thread interval to a large value of 0.3 mm, rattling is eliminated.

This connecting portion 40 is shown in FIGS. 4 (a) and 4 (b).
As shown in (c) and (d), a plate-shaped connecting portion main body 40a, a nut portion 40b formed on the connecting portion main body 40a, and an L-shape hanging on the connecting portion main body 40a. It mainly consists of a holding portion 40c that presents. The lower surface of the connecting portion body 40a faces the gear portions 40d,
40e is formed. These gear parts 40d, 40e
Are formed at two locations along the axial direction with a predetermined interval.

Further, the holding portion 40c is hung between the gear portions 40d and 40e, and the tip end side thereof is positioned so as to face the gear portions 40d and 40e. A circular concave portion 40f is provided inside the bent portion of the holding portion 40c, and the portion is formed to be thin.
Therefore, by giving flexibility to the thin bent portion,
The tip end side is used as the biasing means 40g and the gear parts 40d, 40
It is configured to urge the lead screw 38a toward the lead screw 38a. That is, the holding portion 40c is formed of a material such as metal or resin that can give flexibility to the bent portion.

Further, at the base end of the holding portion 40c,
A sub gear portion 40h is formed to assist the engagement with the lead screw 38a. This sub gear part 4
0h indicates the lead screw 38a and the gear portion 40
Similar to d and 40e, it is a double thread screw with a pitch of 0.6 mm, and the thread pitch is set to 0.3 mm. Also,
The sub gear portion 40h is formed at the base end portion of the holding portion 40c in order to form the sub gear portion 40h at a portion that is not subjected to the urging force of the urging means 40g. This is because the sub gear portion 40h is formed so as to mesh with the lead screw 38a only when an impact in the thrust direction is applied without receiving the urging force of the urging means 40g. That is, as shown in FIG. 5, the sub gear portion 40h is connected to the lead screw 38
a is provided with a gap S therebetween, and the gear portions 40d, 40
Unlike e, it does not always mesh with the lead screw 38a.

As shown in FIG. 6, the sub gear portion 40h is formed at one place, whereas the gear portions 40d and 40e are formed at two places with a predetermined gap. ing. The holding portion 40c may be formed at two or more locations by improving the shape of the holding portion 40c.
The gear parts 40d and 40e and the sub gear part 40h are
As shown in FIGS. 7A and 7B, the shaft 38 has a relationship of approximately 90 degrees in the radial direction.

The nut portions 40b are provided upright on the connecting portion body 40a, and two pairs are formed so as to face each other. A screw hole is formed at the tip of each nut portion 40b.

Further, insertion holes 40i are formed through the left and right side surface portions of the connecting portion body 40a. A sub guide shaft, which will be described later, is inserted into the insertion hole 40i.

On the other hand, the shaft 32 is attached to the frame 32.
The sub-guide shaft 41 is inserted and bridged in parallel with 8, and 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. The sub-guide shaft 41 has the insertion hole 40 formed in the connecting portion 40 as described above.
It is inserted through i. Therefore, the coupling portion 40 is guided along the sub guide shaft 41 as the shaft 38 rotates by the meshing of the gear portions 40d, 40e and the lead screw 38a, and is slidably moved on the lead screw 38a in the axial direction. Will be.

The connecting portion 40 is 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, the lens holder is connected to the nut portion 40b of 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 procedure for assembling the stepping motor of the above embodiment and its operation will be described. First, as shown in FIG. 1 (b), the mounting hole 32 formed in the frame 32.
The thrust bearing 34b is lightly press-fitted into d. Also, FIG.
As shown in (a), 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. 2A, with reference to the receiving surface X of the thrust spring 42, the total length L from the reference surface B to the bent piece 32b of the frame 32 is determined. In addition, with reference to the inner diameters D1 and D2 of the metal bearing 34a and the resin bearing 34b, the yoke assembly 35 is used.
The innermost peripheral surface F2 is centered with the inner diameter D3, and these are set so as to be coaxially located. In this state,
As shown in (a), the metal bearing 34a is welded and fixed to the frame 32 by laser welding from three directions.

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 extended end portion thereof has the thrust bearing 3a.
4b is contacted. Therefore, the metal bearings 34 mounted on the bent pieces 32a and 32b of the frame 32, respectively.
a, the thrust bearing 34b rotatably supports both ends of the lead screw 38a formed on the shaft 38.

Next, 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.
The frame 32 is inserted through the insertion hole 40i formed in the connecting part body 40a, and the insertion part is adhesively fixed to the frame 32. Further, the gear portions 40d and 40e of the connecting portion 40 are meshed with the lead screw 38a of the shaft 38, and the lead screw 38a is biased by the biasing means 40g located on the tip side of the holding portion 40c. At this time, the sub gear portion 40h is not meshed with the lead screw 38a as shown in FIG. Therefore, the connecting portion 40 is guided along the sub-guide shaft 41 as the shaft 38 rotates, and is slid on the lead screw 38a in the axial direction. In this way, the stepping motor 31 is completed. To do.

As described above, the connecting portion 40 includes the sub gear portion 40.
Since h is formed to assist the engagement with the lead screw 38a, even if the gear parts 40d and 40e are tooth-jumped when a shock is applied in the thrust direction, the sub-gear part 40h Will act as a stopper at the time of impact. Therefore, as long as the sub gear portion 40h meshes with the lead screw 38a, the connecting portion 4h
It is possible to prevent tooth jump of zero. The sub gear portion 40h is formed in a portion that is not subjected to the urging force of the urging means 40g, and the lead screw 38h is formed only at the time of impact.
Since it meshes with a, even if this sub gear portion 40h is provided,
The load on the rotation of the shaft 38 does not increase. As described above, the sub gear portion 40h is only subjected to an impact.
Engages with the lead screw 38a, the connecting portion 40
There is no adverse effect on the feed accuracy. If the sub gear portion 40h is provided at at least one location of the connecting portion 40, tooth jumping of the connecting portion 40 can be effectively prevented.

[0047]

As described above, according to the stepping motor of the present invention, it is possible to prevent the jumping of the connecting portion with a simple structure, and the load on the rotation of the shaft is not increased. Therefore, it is possible to prevent an increase in power consumption and acoustic noise.

[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.

2A and 2B are a vertical sectional view and a left side view of the stepping motor of the present embodiment, in which a metal bearing is mounted on a frame and a yoke assembly is arranged.

3A and 3B show a rotor of a stepping motor of the present embodiment, FIG. 3A is a longitudinal sectional view thereof, and FIG.

4A and 4B show a connecting portion of the stepping motor of the present embodiment, FIG. 4A is a left side view thereof, and FIG.
(C) is a right side view thereof, and (d) is a plan view thereof.

FIG. 5 is an explanatory view showing a sub-gear portion and a lead screw formed in a connecting portion of the stepping motor of this embodiment.

FIG. 6 is an explanatory view showing a gear portion and a sub gear portion formed in a connecting portion of the stepping motor of this embodiment.

7A and 7B show a connecting portion meshed with a lead screw of a stepping motor of the present embodiment, FIG. 7A is an enlarged front view of a relevant portion, and FIG. 7B is a right side view thereof.

FIG. 8 is a vertical sectional view showing an example of a conventional stepping motor.

[Explanation of symbols]

 31 stepping motor 32 frame 33 case body 35 yoke assembly (stator) 37 rotor 38 shaft 38a lead screw 40 connecting portion 40d, 40e gear portion 40g biasing means 40h sub gear portion

Claims (4)

[Claims] 1. A connecting portion is provided which is axially moved on a lead screw formed on an extension side of a shaft of the rotor arranged in the stator, when the rotor is rotated.
A stepping motor in which the connecting portion has a gear portion that meshes with the lead screw and also has a biasing means for biasing the gear portion to the lead screw, wherein the connecting portion is connected to the lead screw. A stepping motor, wherein a sub gear part for assisting meshing is formed. 2. The stepping motor according to claim 1, wherein the sub gear portion is formed in a portion of the coupling portion that is not subjected to the biasing force of the biasing means. 3. The sub gear portion is configured to mesh with the lead screw only at the time of impact,
The stepping motor according to claim 1 or 2. 4. The stepping motor according to claim 1, wherein the sub gear portion is formed at at least one location of the connecting portion.