JPH06335227A - Stepping motor - Google Patents

Abstract

PURPOSE:To provide a high-performance stepping motor with less clearance noise and vibration. CONSTITUTION:A bearing containing oil is divided into two portions (2a and 2b) in circumferential direction, one of them (2b) is magnetized to support a shaft (1b) using a magnetic material, thus pulling the magnetic material shaft 1b with the magnetized bearing 2b containing oil and suppressing the vibration of the shaft inside a clearance.

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 in a lens driving device used in a video camera or the like, a floppy disk head driving device, various OA equipment driving devices and the like.

[0002]

2. Description of the Related Art In recent years, as the equipment has become lighter, thinner, shorter, and smaller, the driving stepping motor has also become smaller, and not only is the motor highly efficient and highly accurate, but it also has low vibration and noise when mounted on the equipment. Is required.

A conventional PM type stepping motor will be described below with reference to the drawings. Figure 3 shows a conventional PM
FIG. 3 is a cross-sectional view of the mold stepping motor, in which the outer diameter of the shaft 1 is held by an oil-impregnated bearing 2. A clearance is provided between the outer diameter of the shaft 1 and the inner diameter of the oil-impregnated bearing 2 so that the oil in the bearing exudes and rotates smoothly. The rotor is composed of a shaft 1 and a magnet 10, and the magnet 10 is fixed to the shaft 1 by press fitting and adhesion.

After the frame 4 and the mounting plate 3 are welded to the stator of the motor, the oil-impregnated bearing 2 is fixed by press-fitting and caulking, and then the outer yoke 4, the coil 7 and the inner yoke 6 are stacked and inserted, and the rotor is fixed and then the spring 8 is attached. The spring retainer 9 is fixed by caulking or welding.

[0005]

SUMMARY OF THE INVENTION Such a conventional PM
In the mold stepping motor, as shown in FIG. 3, the cylindrical oil-impregnated bearing 2 has a larger inner diameter than the outer diameter of the shaft 1 and has a clearance, so that the shaft 1 can freely move by the clearance. In addition, since the stepping motor rotates while repeatedly stopping, it is easy to vibrate. Since there is a clearance between the shaft and the oil-impregnated bearing in this manner, noise is likely to occur even in the motor alone, and its vibration may be amplified when mounted on a device, which may cause a problem.

However, if the clearance is eliminated or extremely reduced in order to solve these problems, the load on the shaft increases, which causes deterioration of other characteristics and seizure of the shaft.

The present invention solves the above problems, and an object of the present invention is to provide a high performance PM type stepping motor in which noise generation is suppressed.

[0008]

In order to achieve the above object, the present invention uses a shaft made of a magnetic material, in which a cylindrical oil-impregnated bearing is circumferentially divided and one of them is magnetized. .

[0009]

According to the present invention, a part of the bearing of the PM type stepping motor attracts the shaft made of a magnetic material to suppress the vibration of the shaft within the clearance, and the noise can be reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. FIG. 1 is a plan sectional view of an embodiment of the present invention, in which a magnetic material shaft 1b is press-fitted into a non-magnetic material shaft 1a. The oil-impregnated bearings 2a and 2b are divided into two, and one of the oil-impregnated bearings 2b is magnetized. FIG. 2 is an enlarged view of a contact portion between the shaft and the oil-impregnated bearing.

With the above structure, the magnetized oil-impregnated bearing 2b can suppress the vibration of the magnetic material shaft 1b within the drawing clearance. However, it goes without saying that the oil-impregnated bearing 2a must not be magnetized. Further, since the magnetic material shaft 1b has the non-magnetic shaft 1a press-fitted into the tip thereof, it is possible to meet the non-magnetic requirement required by the type of equipment.

[0012]

As is apparent from the above embodiments, according to the present invention, it is possible to easily produce a high-performance stepping motor that is inexpensive and does not easily generate noise.

[Brief description of drawings]

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

FIG. 2 is an enlarged perspective view of an oil-impregnated bearing portion of a stepping motor according to an embodiment of the present invention.

FIG. 3 is a plan sectional view of a conventional PM type stepping motor.

[Explanation of symbols]

 1 Shaft 1a Non-magnetic material shaft 1b Magnetic material shaft 2 Oil-impregnated bearing 2a Oil-impregnated bearing that is divided and not magnetized 2b Oil-impregnated bearing that is divided and magnetized 10 Magnet

Claims (1)

[Claims] 1. A stepping motor in which a magnetic material shaft is supported by oil-impregnated bearings that are divided in the circumferential direction and one of which is magnetized.