JPH05176520A - Bearing construction of stepping motor - Google Patents

Abstract

PURPOSE:To obtain a stepping motor having high reliability with low noises at a low price by a pivot bearing having a reduced number of components in the stepping motor equipped with a lead screw shaft. CONSTITUTION:An excellent stepping motor having a reduced number of components and obtained at a low price, having low noises with no rolling sound of a steel ball and having a slight inclination of a shaft is obtained by forming a pivot bearing of resin as a solid bearing having the steel ball receiving section (in a conical-shape or recessed spherical-shape) receiving the steel ball 4 on the front end of a lead screw shaft 1 and a cylinder section 5a wrapping the outer diameter of the front end of the lead screw shaft 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor having a lead screw shaft used in a video camera or the like.

[0002]

2. Description of the Related Art In recent years, stepping motors have been digitized and have been used for new consumer applications such as video camera autofocus. Accordingly, there is a further demand for low noise and low cost. Has been done.

A stepping motor used in a conventional video camera autofocus will be described below. FIG. 4 is a sectional view of a conventional stepping motor. In FIG. 4, 1 is a lead screw shaft provided with a lead screw 1a. A bearing 2 is press-fitted and fixed to a cup-shaped frame 3. A steel ball 4 is attached to the tip of the lead screw shaft 1, and a pivot bearing 5 for receiving the steel ball 4 is attached to the angle 6. At the other end of the lead screw shaft 1, a holding spring 7 that restrains the movement of the lead screw shaft 1 in the axial direction is provided, and the lead screw shaft 1 is rotatably fixed. Also, the lead screw shaft 1
A magnet 8 is provided in the to form a rotor. A stator portion 9 is housed in the cup-shaped frame 3 at a position facing the outer periphery of the magnet 8.

The pivot bearing of the stepping motor constructed as described above will be described in more detail. The pivot bearing 5 includes several steel balls 5c in a cup-shaped case.
The steel balls 4 at the tip of the screw shaft 1 rotate together with the lead screw shaft 1 so that several steel balls 5c in contact with the steel balls 4 roll. A cover 5d is fixed to the flange portion of the cup-shaped case by spot welding in order to prevent the steel balls 5c from falling off during assembly.

[0005]

However, in the above-mentioned conventional structure, the pivot bearing 5 has a large number of parts and the cost is high, and the steel ball 5c is the lead screw shaft 1.
Noise occurs due to the rotation of the lead screw shaft 1, and the lead screw shaft 1 moves in the direction of the pressing spring 7 by the axial thrust by exceeding the force of the pressing spring 7 that restricts the movement of the lead screw shaft 1 in the axial direction due to an impact or the like. The lead screw shaft 1 is tilted from the axial direction, and the lead screw 1
There is a problem that the load mechanism using a is adversely affected.

The present invention solves the above-mentioned conventional problems, and provides an inexpensive, low-noise and highly reliable stepping motor which does not use rolling and has a small number of parts.

[0007]

In order to achieve this object, a pivot bearing of a stepping motor of the present invention is a resin-integrated molded product that encloses a steel ball receiving portion and a lead screw shaft tip outer diameter with a minute clearance. It has a part structure.

[0008]

With this configuration, the number of parts is reduced and the steel balls do not roll so that noise can be reduced, and because the lead screw shaft tip outer shape is wrapped with a minute clearance, the lead screw shaft moves due to impact or the like. It is possible to secure high reliability with less inclination of the lead screw shaft.

[0009]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the structure other than the pivot bearing is the same as the conventional one, and the description thereof is omitted. Further, an enlarged view is shown in FIG. 2 for clarifying the pivot bearing portion of FIG. Reference numeral 5 denotes a pivot bearing, which includes a conical portion having a cone angle θ of 120 ° for receiving the steel ball 4 at the tip of the lead screw shaft 1 and a cylindrical portion 5a enclosing the tip of the lead screw shaft 1 with a gap of about 0.05 mm. It is a resin-integrated molded product that is fixed to the angle 6 by press fitting.

The pivot bearing constructed as described above will be described in more detail with reference to FIGS. 1 and 2. Since the pivot bearing is received by the resin molded product instead of the conventional rolling bearing, friction with the steel ball 4 at the tip of the lead screw shaft 1 occurs and the axial loss increases, but the lead screw shaft 1 at the other end of the lead screw shaft is axially moved. Since the pressure of the presser spring 7 that restrains the movement of the product is as small as 40 to 120 gf for video camera autofocus etc., the shaft loss increase is 0.1 gf · cm when the pivot bearing material is greased with polyacetal resin. And it's small and practical. Further, in order to further reduce the friction, it is effective to use a resin material such as a fluororesin-filled grade or an oil-impregnated grade polyacetal. Further, the conical angle is θ, but if it is small, it will be wedge-shaped and the frictional load will increase, so it is desirable to make it as large as 100 ° or more. ° is appropriate. Further, even if the lead screw shaft 1 exceeds the force of the pressing spring 7 that restrains the axial movement of the lead screw shaft 1 due to an impact or the like and the lead screw shaft 1 moves in the pressing spring direction by the axial thrust, the outer diameter of the tip end of the lead screw shaft 1 is reduced to 0. Since it has the cylindrical portion 5a which encloses the gap of about 05 mm, the lead screw shaft 1 does not tilt beyond the gap, and the load mechanism using the lead screw 1a is not adversely affected.

As described above, according to the present embodiment, the pivot bearing has a conical steel ball receiving portion having a conical angle θ of 120 ° and a cylinder that encloses the lead screw shaft tip outer diameter with a gap of about 0.05 mm. It is possible to realize a stepping motor with a bearing structure that has a small number of parts, no rolling noise of steel balls, and a small tilt of the lead screw shaft due to impact etc. ..

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, the portion of the tip of the lead screw shaft 1 that receives the steel ball 4 is a concave spherical surface 5b.
The above is the same as the configuration of FIGS. The difference from the configuration of FIG. 2 is that the receiving portion of the steel ball 4 has a conical shape to a concave spherical surface 5b.
That is the point. Since the receiving portion of the steel ball 4 is the concave spherical surface 5b, the steel ball receiving portion of the pivot bearing 5 comes into point contact with the steel ball 4 as compared with the first embodiment, so the speed at the contact surface is small,
The shaft loss can be further suppressed and a highly efficient stepping motor can be realized.

[0015]

As described above, the pivot bearing of the present invention is
It is made of a resin-integral molded product that has a steel ball receiving part and a cylindrical part that encloses the outer diameter of the tip of the lead screw shaft, so it is low cost, high in noise, and small in tilting of the shaft due to impact etc. A stepping motor can be realized.

[Brief description of drawings]

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

FIG. 2 is an enlarged sectional view of a pivot bearing portion according to the first embodiment of the present invention.

FIG. 3 is an enlarged sectional view of a pivot bearing portion according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a conventional stepping motor.

[Explanation of symbols]

 1 Lead Screw Shaft 2 Bearing 4 Steel Ball 5 Pivot Bearing 5a Pivot Bearing Cylindrical Part 5b Pivot Bearing Concave Spherical Part 7 Presser Spring

Claims (3)

[Claims] 1. A bearing comprising a lead screw shaft which is rotatably held, a pivot bearing which has a steel ball mounted at its tip to receive the steel ball, and a holding spring which restrains the axial direction at the other end. In the stepping motor that constitutes the holding mechanism, the pivot bearing is made of resin integrated molding,
A bearing structure for a stepping motor having a steel ball receiving portion and a cylindrical portion that encloses a tip screw outer diameter of the lead screw shaft with a minute clearance. 2. The bearing structure for a stepping motor according to claim 1, wherein the steel ball receiving portion of the pivot bearing has a conical shape and the conical angle is 100 ° to 140 °. 3. The bearing structure for a stepping motor according to claim 1, wherein the steel ball receiving portion of the pivot bearing is a concave spherical surface.