JPH0389823A - Small-sized motor - Google Patents

Abstract

PURPOSE:To realize a small-sized motor with high reliability at a low cost by adjusting the axial position of a bearing means and also by adjusting the deflection quantity of a pre-load spring to regulate its spring pressure. CONSTITUTION:A bearing holder 17 is thread-engaged with the hole 16A of a holder 6A and fixed in the manner of enabling positioning in the axial direction (longitudinally). Therefore, when the axial position of the bearing holder 17 relative to the holder 6A is adjusted, the position of a pivot bearing 7 built in the bearing holder 17 can be moved axially and the deflection quantity of the spring part 13 of a pre-load spring 12 can be adjusted freely to fix a pre- load spring pressure (biasing force) for energizing (biasing) a screw shaft 8 axially. As a result, the axial energizing force of the screw shaft can be maintained always at the optimum value regardless of the processing accuracy and built-in accuracy of each part.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a preload spring that presses a screw shaft in the axial direction of a lead screw type stepping motor, etc.
The present invention relates to a small motor equipped with bearing means for supporting a screw shaft against the preload spring.

[Conventional technology]

Lead screw type stepping motors are used to move the heads of magnetic disk drives.

This type of small motor generally includes a preload spring that axially presses a screw shaft (output shaft) on which a lead screw is formed, and bearing means that supports the screw shaft against the preload spring.

FIG. 2 is a longitudinal sectional view of a conventional small motor of this type.

In FIG. 2, two cylindrical stator yokes 1, l
The stator unit is constructed by arranging them in the axial direction so as to face each other and fixing them by welding or the like.

An excitation coil 2.2 is installed in the annular hollow portion of each stator yoke 1, (2).

The cross section of each stator yoke 1, (2) is approximately U-shaped as shown, and a plurality of pole teeth (magnetic poles) partially protruding inward are formed on the inner diameter portion thereof.

A plate 4 is fixed to one end of the stator unit 1.1, and a sliding bearing 5 for rotational support is fixed to the center of the plate 4 by caulking or the like.

A substantially U-shaped holder 6 is fixed to the outside of the attachment Fi4 with screws or the like.

Holes 15 and 16 are formed in both side walls of the holder 6, and are concentric with the motor shaft (screw shaft 8 to be described later).
The holder 6 is fixed to the plate 4 by screws or the like, with the slide bearing 5 fitted into the hole 15 on the motor body side.

A pivot bearing (bearing means) 7 is fixed in the hole 16 of the holder 6 on the side opposite to the motor body by light press-fitting or the like.

The screw shaft 8, which is the motor output shaft, is connected to the sliding bearing 5.
and is rotatably supported by the pivot bearing 7.

A spiral groove 9 is formed on the surface of the portion of the screw shaft 8 between the two bearings 5 and 7.

The screw shaft 8 extends into the motor body, and the extended portion thereof includes the inner diameter portion 3 of the stator yoke 1, l.
．． A rotor magnet (cylindrical permanent magnet) 10 (opposed to the comb-shaped magnetic pole portion) 3 is fixed.

Recesses are formed in the center of the end faces of both ends of the screw shaft 8, and balls IIA and 11B are installed in these recesses.

A preload spring 12 is fixed to the rear end of the stator unit facing away from the stator yoke 1.1, and a spring portion 13 formed at the center of the preload spring 12 is connected to the magnet 10.
It is pressed against the ball IIA of the example.

On the other hand, the other end (front end) of the screw shaft 8 is supported by the bearing means (pivot bearing) 7 via the ball IIB.

In this way, the screw shaft 8 is always pressed (biased) toward the vibond bearing 7 by the preload spring 12.

In this state, a predetermined gap is formed between the rotor magnet 10 and the inner diameter portion 3.3 of the stator yoke 1.1, and the coil 2.2 in the stator yoke 1, 1 is excited in a predetermined manner. By doing so, the screw shaft 8 rotates in a stepwise manner clockwise or counterclockwise.

[Technical problem to be solved by the invention] The preload spring 1
The biasing force (hereinafter referred to as preload spring pressure) on the screw shaft 8 due to 2 is generated by slightly bending the spring portion 13 of the preload spring 12 during assembly.

However, in the conventional structure, the preload spring pressure is determined by the dimensional accuracy of various parts, and the preload spring pressure also varies considerably due to variations in the dimensional accuracy of various parts.

For example, the preload spring pressure may vary due to variations in the dimensional accuracy of the preload spring 12, the diameters of the balls IIA and IIB, the screw shaft length, the shape and dimensions of the recesses at both ends of the screw shaft, the dimensions of the holder 6, the yoke dimensions, the pivot bearing, etc. will change considerably.

As described above, in the conventional small motor, there are many factors that cause variations in the preload spring 12, so the variations in preload spring pressure also increase.

As a result, if the preload spring pressure (pressing force) becomes too small, when moving the magnetic head (not shown), the screw shaft 8 will move in the axial direction (toward the preload spring side) due to its inertia. If it gets stuck, it won't move smoothly, or the damping will increase, making the movement noise louder.

On the other hand, if the preload spring pressure becomes too large, the preload spring 12
The durability of the contact portion between the spring portion 13 and the ball IIA decreases, causing wear, or in the worst case, making it impossible to rotate.

Furthermore, when the abrasion of the contact portion increases, stamping accuracy decreases and hysteresis occurs. Furthermore, since the pressure acting on the pivot bearing 7 also increases, the durability of the pivot bearing 7 also decreases.

In order to solve the above-mentioned technical problems, grease is generally applied to the abutment part, but the durability of this depends on variations in the amount of application and the type of grease.
This cannot be a satisfactory solution.

It is also possible to improve the accuracy of parts in order to minimize variations in the preload spring pressure, but this would lead to an increase in costs.

The present invention was made in view of these technical issues, and it is possible to easily maintain the preload spring pressure at a predetermined value without unnecessarily increasing component precision, and to provide an inexpensive, highly reliable, compact design. The purpose is to provide motors.

[Means for solving problems]

The present invention provides a small motor equipped with a preload spring that presses a screw shaft in the axial direction and a bearing means that supports the screw shaft against the preload spring, in which the axial position of the bearing means is adjusted. To provide a small motor in which the preload spring pressure can be easily maintained at a predetermined value without unnecessarily increasing component accuracy by adjusting the amount of deflection of the preload spring to adjust the spring pressure. It is.

〔Example〕

The present invention will be specifically explained below with reference to FIG.

FIG. 1 is a longitudinal cross-sectional view of the central portion of an embodiment of a small motor according to the present invention.

In FIG. 1, two cylindrical stator yokes 1, l
are lined up in the axial direction facing each other, and are fixed by welding or the like to form a stator unit, and an excitation coil 2.2 is built into the annular hollow part of each stator yoke 1, l. It is.

The cross section of each stator yoke 1.1 is approximately U-shaped as shown in the figure, and a plurality of pole teeth (magnets 8i) partially protruding inward are formed on the inner diameter portion thereof.

A mounting plate 4 is fixed to one end of the stator unit 1.1, and a sliding bearing 5 for rotatably supporting a screw shaft (motor output shaft) 8 is crimped at the center of the plate 4. etc. is fixed.

For the above-mentioned attachment, a substantially U-shaped holder 6A is fixed to the outside of the plate 4 with screws or the like.

Holes 15 and 16A concentric with the screw shaft 8 are formed in both side walls of the holder 6, and the holder 6A has the slide bearing 5 fitted into the hole 15 on the motor body side. The mounting is fixed to the plate 4 by screws or the like.

A hole 16A of the holder 6A on the side opposite to the motor body is a threaded hole, and a cylindrical bearing holder 17 having threads on its outer peripheral surface is screwed into this threaded hole 16A.

A pivot bearing (bearing means) 7 is attached to the inner diameter portion 18 of the bearing holder 17 by light press-fitting or the like.

The screw shaft 8, which is a motor output shaft, is rotatably supported by the sliding bearing 5 and the bearing means (pivot bearing) 7.

A spiral groove 9 is formed on the surface of the screw shaft 8 between the slide bearing 5 and the pivot bearing 7.

The screw shaft 8 extends into the stator unit 1.1, and in its extension there are respective stator yokes l,
A rotor magnet 10, which is a cylindrical permanent magnet, is fixed to the inner diameter portion 3.3 (comb tooth-shaped magnetic pole portion) of the magnet.

Recesses are formed in the center of the end faces of both ends of the screw shaft 8, and balls IIA and 11B are installed in these recesses.

A preload spring 12 is fixed to the rear end of the stator unit facing away from the stator yoke l, 1, and a spring portion 13 formed at the center of the preload spring 12 is connected to the magnet lO.
It is pressed against the ball IIA on the side.

On the other hand, the other end (front end) of the screw shaft 8 is supported by the pivot bearing 7 attached to the bearing holder 17 via the ball 11B.

In this way, the screw shaft 8 is always pressed toward the bearing means (pivot bearing) 7 by the preload spring 12.
energized).

In this state, a predetermined gap is formed between the rotor magnet 10 and the inner diameter portion 3.3 of the stator yoke LL, and the coil 2.2 in the stator yoke 1,
By exciting the screw shaft 8 in a predetermined manner, the screw shaft 8 rotates in a stepwise manner clockwise or counterclockwise.

The bearing holder 17 has a hole 16A in the holder 6A.
It is threadedly engaged with and fixed so that its position can be adjusted in the axial direction (front-back direction).

Therefore, by adjusting the axial position of the bearing holder 17 with respect to the holder 6A, the position of the pivot bearing 7 incorporated in the bearing holder 17 can be moved in the axial direction. 13
By freely adjusting the amount of deflection, the preload spring pressure (pressing force) that urges (presses) the screw shaft 8 in the axial direction can be made constant.

In this way, the processing accuracy and assembly of each part is independent of accuracy.
A small motor such as a lead screw type stepping motor that can always maintain the axial biasing force of the screw shaft 8 at an appropriate value was obtained.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a small motor equipped with a preload spring that presses a screw shaft in the axial direction and a bearing means that supports the screw shaft against the preload spring, By adjusting the axial position of the bearing means, the amount of deflection of the preload spring is adjusted and the spring pressure is adjusted. Therefore, the accuracy of parts and assembly can be adjusted without increasing the accuracy of the screws. The preload spring pressure that presses the shaft in the axial direction can be easily maintained at a constant set value, and a highly reliable small motor can be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the center of an embodiment of a small motor according to the present invention, and FIG. 2 is a longitudinal sectional view of the center of a conventional small motor. 1--Stator yoke, 2-- Coil, 6A-- Holder, 7-- Bearing means (
pivot bearing), 8----screw shaft, 10---
---1 rotor magneto, 12-...-preload spring, 13
--- Spring part, hole --- 1--16A, 17--
--Bearing holder (axial position adjustment means).

Claims (1)

[Claims] (1) In a small motor equipped with a preload spring that presses the screw shaft in the axial direction and a bearing means that supports the screw shaft against the preload spring, by adjusting the axial position of the bearing means. A small motor, characterized in that the spring pressure is adjusted by adjusting the amount of deflection of the preload spring.