JPH0727287U - Stepping motor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a stepping motor capable of reducing manufacturing cost such as shaft processing cost. A rotor having a magnet 1 coaxially fixed to a shaft 1 and a stator having a yoke 5 and a coil 6 arranged on the outer circumference of the magnet 2 are provided. Both ends of the shaft 1 are rotatably supported by the thrust bearings 40 and 50 provided on the stator in a state in which the axial center positions are regulated, and one thrust bearing 50 has the thrust bearing 50 facing the shaft 1. Leaf spring 5 for urging
2 is fixed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a small stepping motor used, for example, for driving a lens of a video camera, and more particularly to an improvement for reducing the manufacturing cost of the motor.

[0002]

[Prior art]

 Video cameras that are commercially available in recent years often have a structure in which a small stepping motor is built in the lens barrel, and the motor moves the lens back and forth to focus.

Known examples of this type of stepping motor are those shown in FIG. 6 or FIG. Describing from the motor of FIG. 6, reference numeral 1 is a metal shaft, a screw portion 1A is formed on the tip end side thereof, and a cylindrical magnet 2 is fixed on the base end side thereof. 2 constitutes a rotor. The outer peripheral surface of the magnet 2 is magnetized so that a plurality of magnetic poles are arranged in the circumferential direction, and a pair of yokes 5 are arranged so as to surround the outer periphery thereof. An unillustrated female screw member is screwed into the screw portion 1A, and the female screw member advances and retracts an article such as a lens.

The yoke 5 is composed of an inner yoke member 4 and an outer yoke member 3 made of a soft magnetic material, and a coil 6 is housed between the pair of yoke members 3 and 4. The inner yoke member 4 has pole teeth (not shown) facing the magnetic poles of the magnet 2, and the pole teeth of each inner yoke member 4 are out of phase with each other. As a result, when positive and negative currents are alternately applied to the pair of coils 6, the magnet 2 rotates stepwise in a predetermined direction.

A leaf spring 7 is fixed to the end surface of one of the yokes 5, and a free end 8 thereof urges the base end of the shaft 1. The base end of a bracket 10 having a U-shape is fixed to the end face of the other yoke 5, and the outer peripheral surface of the shaft 1 is rotated by a radial bearing 9 made of sintered metal fitted in the base end. It is supported freely. The yoke 5, the coil 6, the bracket 10 and the portions fixed to these constitute a stator.

The tip of the bracket 10 is extended to a position facing the tip of the shaft 1, and a thrust bearing 11 such as a pivot bearing is fixed, and the tip of the shaft 1 is rotatably supported by the thrust bearing 11. Has been done. The thrust bearing 11 of this example has a plurality of metal balls 22 rollably housed in a disk-shaped case 21, and is fitted in the recess 26 at the tip of the shaft 1 at the center of the metal balls 22. The metal ball 24 is abutted by the biasing force of the leaf spring 7.

On the other hand, the stepping motor shown in FIG. 7 does not use the pivot bearing 11 as described above, but the metal ball 24 fitted in the tip recess 26 of the shaft 1 is recessed in the bracket 10. By directly abutting the inside of the shaft 32, the front end of the shaft 1 is supported so that the axial center position can be changed. Instead, the outer circumference of the base end portion of the shaft 1 is supported by a radial bearing 30 to ensure the axial center accuracy of the shaft 1.

As described above, in the conventional stepping motor, one or two radial bearings that support the outer peripheral surface of the shaft, a thrust bearing that supports one end of the shaft, and a thrust bearing that presses the other end of the shaft are provided. A structure in which a shaft is supported by a biasing means is generally used.

[0009]

[Problems to be solved by the device]

 However, in the conventional stepping motor, since at least a part of the shaft is supported by the radial bearing, the outer peripheral surface of the shaft 1 is highly accurate in order to improve the slidability between the shaft and the radial bearing and the clearance accuracy. It must be mirror-finished. Therefore, it is necessary to perform centerless polishing and / or barrel polishing on the metal rod as a material, which has a drawback of high manufacturing cost.

Further, since high accuracy is required as described above, there is a problem that a defective product is apt to occur in the shaft or the radial bearing, and the yield is low.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a stepping motor capable of reducing manufacturing costs such as shaft processing costs.

[0012]

[Means for Solving the Problems]

 A stepping motor according to the present invention is a stepping motor having a rotor having a shaft on which a magnet is coaxially fixed, and a stator having a yoke and a coil arranged on the outer circumference of the magnet. The thrust bearing provided on the stator is rotatably supported in a state where the axial center position is restricted, and at least one thrust bearing urges the thrust bearing toward the shaft. Is provided.

[0013]

[Action]

 In this stepping motor, since both ends of the shaft are supported by the thrust bearings, it is only necessary to improve the shape accuracy of the both ends of the shaft that contacts the thrust bearing. Since both ends of the shaft can be processed more easily and at a lower cost than polishing the outer circumference of the shaft, the motor manufacturing cost can be reduced. For the same reason, the incidence of defective products can be reduced and the yield can be improved.

[0014]

【Example】

 FIG. 1 is a vertical sectional view showing an embodiment of a stepping motor according to the present invention. In FIG. 1, the same elements as those of the conventional example of FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted.

The main feature of this embodiment is that both ends of the shaft 1 are supported by the thrust bearings 40 and 50 in a state where the axial center position is restricted, and no radial bearing is used. Therefore, the hole 10A at the base end of the bracket 10 is a simple insertion hole.

The thrust bearing 40 is fitted and fixed in a hole formed in the bracket 10 so as to face the tip of the shaft 1. A conical recess 42 is formed on the surface of the thrust bearing 40 facing the shaft 1, and the tip of the shaft 1 is rotatably supported in the recess 42 via a metal ball 24. As a result, the metal ball 24 is rotatable with respect to both the shaft 1 and the thrust bearing 40.

On the other hand, the thrust bearing 50 is arranged so as to face the base end of the shaft 1 and is supported by a metal leaf spring 52 fixed to the end surface of the yoke 5. The leaf spring 52 has an annular plate portion and an elastically deformable free end 54 projecting inward from the annular plate portion, and the thrust bearing 50 is fitted and fixed in a hole formed in the free end 54. There is.

A conical recess 48 is formed on the surface of the thrust bearing 50 facing the shaft 1, and a metal ball 44 fitted in a recess 46 formed at the rear end of the shaft 1 is formed in the recess 48. Is rotatably supported. This metal ball 44 is also rotatable with respect to both the shaft 1 and the thrust bearing 50.

The material of the thrust bearings 40 and 50 is not limited, but, for example, a metal-sintered body of iron-copper system, iron system, copper system, etc., resin such as polyacetal, nylon, etc., ceramics, etc. can be used. In particular, the resin thrust bearing is preferable in that the sliding noise with the shaft is small and the noise of the stepping motor is reduced.

In the stepping motor configured as described above, since both ends of the shaft 1 are supported by the thrust bearings 40 and 50, it is only necessary to improve the shape accuracy of both ends of the shaft that abut the thrust bearings 40 and 50. Since both ends of the shaft can be processed more easily and at a lower cost than polishing the outer circumference of the shaft, the manufacturing cost can be reduced as compared with the conventional product, the defective product rate can be reduced, and the yield can be improved.

The present invention is not limited to the above embodiment, and a bearing structure as shown in FIG. 2 may be adopted. The illustrated thrust bearing 62 has a cylindrical shape and has a conical receiving surface 64 on one end side. The metal ball 44 fitted in the recess 46 at the base end of the shaft 1 is supported by the receiving surface 64 of the thrust bearing 62. The thrust bearing 62 is axially movably inserted through a central hole of an annular support plate 60 fixed to the end of the yoke 5, and a flange 62A is formed on the outer periphery of the end on the recess 64 side. .

A coil spring (biasing means) 66 is interposed between the flange portion 62 A and the support plate 60, and the thrust bearing 62 is biased toward the shaft 1. According to the structure in which the thrust bearing 62 is biased by the coil spring 66 as described above, there is also an advantage that the thrust bearing is less likely to tilt as compared with the case where the leaf spring 52 is used.

As the biasing means of the thrust bearing, a double annular leaf spring 70 as shown in FIG. 3 can also be used. The leaf spring 70 is formed by connecting an outer ring portion 72 and an inner ring portion 74, which are concentric to each other, with a plurality of bridging portions 76 in a centrally symmetric manner, and the bridging portions 76 in this example are spiral. The thrust bearing is fixed in the inner ring portion 74 while the outer ring portion 72 is fixed to a yoke or the like for use. According to such a double annular leaf spring 70, the effect of preventing the thrust bearing from tilting is further enhanced.

As the thrust bearing, those shown in FIGS. 4 and 5 can also be used. In the center of the recess 82 of the thrust bearing 80, a plurality of receiving surfaces 84 having a conical shape as a whole and a groove 86 for dividing the receiving surfaces 84 are radially formed. , Metal balls 24 are supported.

According to such a thrust bearing 80, since the contact area between the receiving surface 84 and the metal ball 24 is small due to the existence of the groove 86, the sliding resistance can be reduced. Further, even when the thrust bearing 80 is made of a soft resin, the groove 86 does not cause the receiving surface 84 to stick to the metal ball 24 like a suction cup, which prevents an increase in sliding resistance due to the sticking. it can. This effect is remarkable in the present invention in which the pair of thrust bearings are pressed toward the shaft.

As the thrust bearing, a pivot bearing as shown by reference numeral 11 in FIG. 6 can be used, and any other known thrust bearing can be used in the present invention. Furthermore, it goes without saying that the structure and shape of the motor may be changed as appropriate. For example, a shaft having no threaded portion 1A may be used, and the application of the motor of the present invention is not limited to driving a lens.

[0027]

[Effect of device]

 As described above, according to the stepping motor of the present invention, since both ends of the shaft are supported by the thrust bearings, it is only necessary to improve the shape accuracy of the both ends of the shaft in contact with the thrust bearing. Since both ends of the shaft can be processed more easily and at lower cost than polishing the outer circumference of the shaft, the motor manufacturing cost can be reduced. In addition, the incidence of defective products can be reduced, and the yield can be improved.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view showing a thrust bearing used in another embodiment of the present invention.

FIG. 3 is a front view of a thrust bearing used in another embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view showing a thrust bearing used in another embodiment of the present invention.

FIG. 5 is a front view of the thrust bearing.

FIG. 6 is a vertical cross-sectional view showing a conventional stepping motor.

FIG. 7 is a vertical sectional view showing another conventional stepping motor.

[Explanation of symbols]

 1 Shaft (Part of Rotor) 2 Magnet (Part of Rotor) 5 Yoke (Part of Stator) 6 Coil (Part of Stator) 10 Bracket (Part of Stator) 24,44 Metal Ball 40, 50, 62 , 80 Thrust bearing 52, 70 Leaf spring (biasing means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03B 13/36 H02K 37/14 535 M 9180-5H 8411-2K G03B 3/00 A

Claims (1)

[Scope of utility model registration request] 1. A stepping motor comprising a rotor having a shaft on which a magnet is coaxially fixed, and a stator having a yoke and a coil arranged on the outer periphery of the magnet, wherein both ends of the shaft are provided on the stator. The thrust bearing is rotatably supported in a state where the axial center position is restricted, and at least one thrust bearing is provided with a biasing means for biasing the thrust bearing toward the shaft. A characteristic stepping motor.