JP2000175432A - Stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent noise due to rotary backlash as well as suppress axial loss and reduce power consumption, when a stepping motor is used for the lens drive device or the like of a video camera. SOLUTION: A centering part 16c is provided at a screw shaft 16 via a falling-off protection part 16a, and at the same time a shaft protective large hole 12b and a shaft support small hole 12c are formed at a first thrust bearing 12. The falling-off protection part 16a is inserted freely into the shaft protection large hole 12b, by providing a gap with a specific interval in a radial direction, and at the same time the centering part 16c is engaged to the shaft support small hole 12c for supporting the screw shaft 16 in the form of line contact, thus enabling the axial center of the screw shaft 16 to coincide with the center of the first thrust bearing 12 at all times and preventing backlash from occurring in the radial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor used for a lens driving device of a video camera and a head driving device of a CD-ROM drive or a floppy disk drive.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing an example of a conventional stepping motor.

Conventionally, as a stepping motor of this type, as shown in FIG.
0 is a metal bearing 21, a thrust bearing 22, and a leaf spring 2
There is known a stepping motor 1 which is rotatably supported via a rotor 3 and is rotated by a current supplied to a first coil 26 and a second coil 27 of a stator section 25 when a screw shaft 20 fixed to a rotor 29 is rotated. As the material of the thrust bearing 22, a resin mainly made of polyacetal has been widely used because of its low cost, low frictional loss during sliding and low sliding noise. .

[0004]

However, the resin, which is the material of the thrust bearing 22, has a linear expansion coefficient of about ^10.sup.-4 / .degree. C., and is about one order of magnitude larger than the metal, which is the material of the screw shaft 20. In addition, in general, the molding accuracy of the resin material is not so high, and the size is likely to vary. Therefore, if the gap between the screw shaft 20 is too small, the rotational load of the screw shaft 20 increases,
In severe cases, there is a risk of causing the rotation of the screw shaft 20 to be locked. For this reason, a gap of a predetermined interval (for example, 30 μm) must be provided in the radial direction between the thrust bearing 22 and the screw shaft 20.
As a result, the screw shaft 20 rattles in the radial direction at the time of the rotation, and not only noise is generated, but also the shaft loss of the screw shaft 20 increases, and there is a disadvantage that the driving power is wasted.

[0005] In view of such circumstances, an object of the present invention is to provide a stepping motor capable of preventing noise caused by rotation play of a screw shaft, and at the same time, suppressing shaft loss and reducing power consumption. And

[0006]

That is, the present invention has an annular stator portion (2), a frame (10) is attached to one of the stator portions, and a leaf spring (13) is attached to the other. A first thrust bearing (12) is provided on the frame, and a second thrust bearing (1) is provided on the leaf spring.
5) is provided so as to face the first thrust bearing.
In a stepping motor (1) in which a screw shaft (16) is rotatably supported between a thrust bearing and a second thrust bearing, and a rotor (17) is mounted on the screw shaft so as to be located in the internal space of the stator portion. , A centering portion (16c, 16c) at at least one end of the screw shaft via a fall-off protection portion (16a, 16b).
16d), and at least one of the first thrust bearing and the second thrust bearing has a large shaft protection hole (12b, 15b) and a small shaft support hole (12b).
c, 15c), and the fall-off protection portion is loosely inserted with a predetermined gap in the radial direction with respect to the large shaft protection hole, and at the same time, the centering portion engages with the small shaft support hole. The screw shaft is configured to be supported in line contact.

[0007] By adopting such a configuration, the axis of the screw shaft always coincides with the center of the first thrust bearing or the second thrust bearing during rotation, so that there is no occurrence of a rattling in the radial direction.

[0008] Incidentally, reference numerals in parentheses are for convenience showing corresponding elements in the drawings, and therefore, the present invention is not limited to the description on the drawings. The same applies to the column of “Claims”.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the stepping motor according to the present invention, and FIG. 2 is an enlarged view of a main part of the stepping motor shown in FIG.

As shown in FIG. 1, the stepping motor 1 has an annular stator portion 2. The stator portion 2 is an annular first coil 5 surrounded by two stator yokes 3. And an annular second coil 7 surrounded by two stator yokes 6.

A frame 10 is mounted in front of the stator portion 2 (left side in FIG. 1) via a flange 9. A first resin-made thrust bearing formed in a hat shape is provided at the end of the frame 10. 12 are fitted. on the other hand,
A cover 14 is attached to the rear of the stator portion 2 (right side in FIG. 1) via a leaf spring 13, and a resin-made second thrust bearing 15 formed in a hat shape is provided in a center hole of the leaf spring 13. The first thrust bearing 12 is attached to the first thrust bearing 12 in such a manner as to be fitted in the center hole of the cover 14 and restrained from moving in the radial direction.

A metal screw shaft 16 is provided between the first thrust bearing 12 and the second thrust bearing 15.
Moves the feed screw portion 16e from the stator portion 2 to the frame 1
It is rotatably supported so as to protrude toward the 0 side (left side in FIG. 1) and to be loosely inserted into the flange 9. The screw shaft 16 is in linear contact with the first thrust bearing 12 and the second thrust bearing 15 while keeping the axis of the screw shaft aligned with the centers of the first thrust bearing 12 and the second thrust bearing 15 at all times.

That is, a small-diameter cylindrical drop-off protection portion 16a is formed at the front end portion (left end portion in FIG. 1) of the screw shaft 16, and a conical centering portion 16c is provided at the front side of the drop-off protection portion 16a. It is installed continuously. Similarly, a small-diameter cylindrical fall-off protection portion 16b is formed at the rear end (the right end in FIG. 1) of the screw shaft 16, and a hemispherical centering portion 16d is provided on the rear side of the fall-off protection portion 16b. It is installed continuously. On the other hand, as shown in FIG. 2, the first thrust bearing 12 has a main body 12a, and a large-diameter cylindrical shaft protection large hole 12b is formed in the center of the main body 12a. Further, a small-diameter cylindrical shaft support small hole 12c is formed concentrically at the center of the bottom surface of the shaft protection large hole 12b. Similarly, the second thrust bearing 15 corresponds to FIG.
As shown in FIG. 5, a main body 15a is provided, and a large-diameter cylindrical shaft protection large hole 15b is formed at the center of the main body 15a. Furthermore, a small-diameter cylindrical shaft support small hole 15c is formed concentrically at the center of the bottom surface of the shaft protection large hole 15b. At the front end of the screw shaft 16, the falling-off protection portion 16a is connected to the first thrust bearing 12a.
The shaft protection large hole 12b is loosely inserted with a predetermined clearance in the radial direction, and the centering portion 16
c engages with the shaft support small hole 12c of the first thrust bearing 12 and is in line contact therewith, and at the rear end of the screw shaft 16, the falling-off protection portion 16b is in contact with the shaft protection large hole 15b of the second thrust bearing 15. It is loosely inserted with a predetermined gap in the radial direction, and the centering portion 16 d
Are engaged with the small shaft support holes 15c of the second thrust bearing 15 and are in line contact with each other. Therefore, the axis of the screw shaft 16 always coincides with the center of the first thrust bearing 12 and the center of the second thrust bearing 15. The line is in line contact with the first thrust bearing 12 and the second thrust bearing 15 while maintaining the state.

Further, lubricating oil is held in the large shaft protection hole 12b of the first thrust bearing 12 and the large shaft protection hole 15b of the second thrust bearing 15, and the periphery of the shaft body 16f of the screw shaft 16 is shown in FIG. 1
As shown in (2), the rotor 17 is fixed so as to be located in the internal space of the stator section 2.

Since the stepping motor 1 has the above configuration, the first coil 5 and the second coil 7 of the stator section 2 are energized to drive the stepping motor 1. Then, the first coil 5 and the second coil 7
Interaction between the rotor 17 and the rotor 17
Rotates, and the screw shaft 16 rotates accordingly.

At this time, the axial center of the screw shaft 16 is always in contact with the first thrust bearing 12 and the second thrust bearing 12 even during rotation.
Since the screw shaft 16 matches the center of the thrust bearing 15, the screw shaft 16 does not rattle in the radial direction.
Therefore, not only does noise caused by the rotation of the screw shaft 16 not occur, but also the shaft loss associated with the rotation of the screw shaft 16 decreases, and the power consumption required to drive the stepping motor 1 decreases. In addition, the falling-off protection part 16a of the screw shaft 16 and the first
A predetermined gap is provided in the radial direction between the large shaft protection hole 12b of the thrust bearing 12 and a gap between the falling protection portion 16b of the screw shaft 16 and the large shaft protection hole 15b of the second thrust bearing 15. Since a predetermined gap is provided in the radial direction, the rotational load of the screw shaft 16 may be increased due to a difference in linear expansion coefficient between the screw shaft 16 and the first thrust bearing 12 or the second thrust bearing 15. There is no danger of causing a rotation lock.

The screw shaft 16 contacts only the first thrust bearing 12 and the second thrust bearing 15 by linear contact, and the contact portion (sliding portion) has large shaft protection holes 12b, 15b. Since the internal lubricating oil is supplied, the rotation of the screw shaft 16 is performed smoothly without receiving a large frictional load. Further, the falling-off protection portions 16a and 16b of the screw shaft 16 are respectively provided with a shaft protection large hole 12b of the first thrust bearing 12 and a second
Since the screw shaft 16 is fitted into the large shaft protection hole 15b of the thrust bearing 15, there is no possibility that the screw shaft 16 will fall off the first thrust bearing 12 and the second thrust bearing 15 even if an external impact is applied.

In the above embodiment, conical centering portions 16c are provided at both ends of the screw shaft 16.
16d, the stepping motor 1 in which the screw shaft 16 is held in line contact between the first thrust bearing 12 and the second thrust bearing 15 has been described. Either one of them may be provided with a conical centering portion 16c or 16d and held in line contact.

In the above-described embodiment, the small-diameter cylindrical falling-off protection portions 1 are provided at both ends of the screw shaft 16.
Although the stepping motor 1 in which the concentric centering portions 16c and 16d and the concentric centering portions 16c and 16d are provided has been described, in the present invention, the shape of the falling-off protection portions 16a and 16b is not limited to a small-diameter cylindrical shape. The shape of 16d is not limited to a conical shape. For example, the falling-off protection portions 16a and 16b may be formed in a polygonal column shape (such as a hexagonal column shape), or the centering portions 16c and 16b may be formed.
6d can also be formed in a hemispherical shape.

Further, in the above-described embodiment, the stepping motor 1 using the metal screw shaft 16 has been described. However, in the present invention, the material of the screw shaft 16 is not limited to this. It is also possible to employ a screw shaft 16 made of ceramics or resin).

[0022]

As described above, according to the present invention, the annular stator portion 2 is provided, and the frame 10 is attached to one of the stator portions 2 and the leaf spring 13 is attached to the other.
And the first thrust bearing 12 is attached to the frame 10.
And the second thrust bearing 15 is attached to the leaf spring 13 by the first
A screw shaft 16 is rotatably supported between the first thrust bearing 12 and the second thrust bearing 15, and a rotor 17 is mounted on the screw shaft 16 in the internal space of the stator portion 2. In the stepping motor 1 mounted so as to be positioned, at least one end of the screw shaft 16 is provided with centering portions 16c and 16d via drop-off protection portions 16a and 16b, and the first thrust bearing 12 and the second
At least one of the thrust bearings 15 has a large shaft protection hole 12b, 15b and a small shaft support hole 12c, 15c.
Are formed, and the fall-off protection portions 16a, 16b are loosely inserted into the large shaft protection holes 12b, 15b with a predetermined radial gap therebetween, and at the same time, the centering portions 16c, 16d are attached to the shaft support small holes. 12c, 15c
The screw shaft 16 is engaged with the
, So that the axis of the screw shaft 16 always coincides with the center of the first thrust bearing 12 or the second thrust bearing 15 during rotation, so that the rattling in the radial direction does not occur. In addition, it is possible to prevent noise caused by the backlash of the screw shaft 16, and at the same time, reduce shaft loss and reduce power consumption.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a main part of the stepping motor shown in FIG.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Stepping motor 2 ... Stator part 10 ... Frame 12 ... 1st thrust bearing 13 ... Leaf spring 15 ... 2nd thrust bearing 12b, 15b ... Shaft protection large hole 12c, 15c ... Shaft support small hole 16 ... Screw shafts 16a, 16b Fall-out protection parts 16c, 16d Centering part 17 ... Rotor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Uchiyama 5-36-11 Shimbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd. F-term (reference) 5H605 AA05 BB05 CC01 CC02 CC04 CC05 DD03 DD05 EA11 EB02 EB06 FF06 5H607 AA04 BB10 BB14 CC01 DD01 DD02 DD03 DD09 DD16 DD19 GG02 JJ02 KK07

Claims (1)

[Claims] 1. A stator (2) having an annular shape, a frame (10) is mounted on one of the stators, and a leaf spring (13) is mounted on the other, and a first thrust bearing (12) is mounted on the frame. ), A second thrust bearing (15) is provided on the leaf spring so as to face the first thrust bearing, and a screw shaft (16) is rotatably supported between the first and second thrust bearings. In a stepping motor (1) in which a rotor (17) is mounted on the screw shaft so as to be positioned in the internal space of the stator section, at least one end of the screw shaft has a core via a fall-off protection section (16a, 16b). Outer (16c, 16
d), a large shaft protection hole (12b, 15b) and a small shaft support hole (12c, 15c) are formed in at least one of the first thrust bearing and the second thrust bearing. At the same time as being loosely inserted with a predetermined gap in the radial direction with respect to the large hole,
A stepping motor, wherein the centering portion supports the screw shaft such that the centering portion engages with the small shaft support hole and makes line contact.