JPH03864Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an electric motor using a dynamic pressure air bearing, and more specifically to an electric motor that can be applied as a drive source for a polygon mirror.

(Prior Art) Conventionally, a small electric motor using a dynamic pressure air bearing has been proposed for rotating a polygon mirror for optical scanning. The structure is such that a groove is provided on either the cylindrical outer circumferential surface of a rotating body or the inner circumferential surface of a fixed bearing that rotatably fits and supports the cylindrical outer circumferential surface of the rotating body to form a hydrodynamic bearing. ,
A magnet is fixed to the cylindrical inner peripheral surface of the rotating body, and a driving coil is arranged opposite to the magnet.

In Figure 2, which explains a conventional small electric motor,
The radial direction of the shaft portion 12 and bearing portion 14 is supported by air dynamic pressure during rotation. Then, in order to support the thrust direction by magnetic repulsion force, a holding magnet 1 is installed.
3-1 is located above the shaft magnet 13-2.

(Problems to be Solved by the Invention) In FIG. 2, the arm 16 that supports the holding magnet 13-1 is located outside the polygon mirror 18, which becomes an obstacle when reducing the motor size.

Further, in order to center the holding magnet 13-1, both the bearing portion 14 and the arm 16 are required to have high dimensional accuracy.

(Means for Solving the Problems) Therefore, it is an object of the present invention to provide an electric motor that allows reduction in motor dimensions and allows for easy positioning of the presser magnet.

In order to achieve such an object, in the present invention, a rotating magnet body having a hollow part is fixed at the center of rotation of the rotating body, and a fixed shaft passing through the hollow part of the rotating magnet body is fixed by magnetic action with the rotating magnet body. , characterized in that a floating magnet and a holding magnet that levitate and support the rotating magnet are fixed so as to sandwich the rotating magnet.

(Example) In FIG. 1, an air dynamic pressure groove (not shown) is provided around a rotor 3, which is a rotating body rotatably fitted on the inner periphery of a fixed bearing 4. This results in non-contact in the radial direction.

Rotor magnet 1 which is a rotating magnet body having a hollow part
-2 is fixed to the center of rotation of the rotor 3 by press fitting or adhesive.

A presser magnet 1-2 is placed above the rotor magnet 1-2.
1. Floating magnets 1-3 are located below,
Magnetic poles are set so that a repulsive magnetic force acts on the portion facing the rotor magnet 1-2. Therefore, the rotor 3 is positioned in the thrust direction by the repulsive force exerted on the holding magnet 1-1 and the floating magnet 1-3.

The floating magnet 1-3 is attached to a support 5 which is formed upright integrally with the base 6, and has a reference numeral 5 extending over almost the entire length in the longitudinal direction.
Part b is inserted and fixed. Holder magnet 1-
1 is inserted over the magnet support 10 which is a fixed shaft, and
The magnet support 10 is fixed by adhesive or the like, and the lower end 5a of the magnet support 10 is press-fitted into the support support 5.

It penetrates the hollow part of the magnet support 10 or the rotor magnet 1-2, and has a gap between them such that they do not come into contact, for example, a gap of 0.1 to 0.2 mm.

The yoke 11 is fixed to the magnet support 10 with screws 20, and plays a role in forming a magnetic path A that strengthens the repulsive force while performing the function of preventing the holding magnet 1-1 from floating.

In the illustrated example, the yoke 11 and the threaded portion that holds it protrude from the upper surface of the polygon mirror 2, but a configuration in which they do not protrude may also be used.

Reference numeral 7 denotes a cylindrical drive magnet, which is fixed to the inner circumference of the rotor 3. Reference numeral 9 indicates a yoke having a structure in which many rings are stacked one on top of the other to prevent the generation of eddy currents. A drive coil 8 is wound around the outer periphery of this yoke 9.

In this configuration, the rotor 3 generates dynamic pressure by rotating and is not in contact with the rotor 3 in the radial direction. When the rotor magnet 1-3 approaches the floating magnet 1-3 or the holding magnet 1-1 due to an external force, the repulsive force with the approaching magnet increases,
The repulsive force with the distant magnet decreases, maintaining the required floating position as a hydrodynamic bearing.

The assembly order of the small electric motor according to this example is carried out as follows.

First, the fixed bearing 4 is assembled on the base 6, and the magnet column 10 and the floating magnet 1- are attached to the column 5.
Fix 3.

Next, the rotor 3, on which the rotor magnet 1-2 and polygon mirror 2 have been assembled in advance, is placed into the fixed bearing 4. At this time, the rotor magnets 1-2 are inserted through the magnet columns 10.

Finally, the presser magnet 1-1 is press-fitted into the magnet support 10 and fixed with screws via the yoke 11.

As explained above, in this example, the holding magnet 1-1 is fixed by the magnet support 10, so the arm 16 in the prior art is unnecessary, and the electric motor can therefore be made more compact. In addition, the holding magnet 1 is held by the magnet support 10 with center accuracy.
By fixing -1, the center of the presser magnet 1-1 can be easily brought out, and the imbalance of force in the radial direction of the magnet can be reduced.

In this example, the groove for air dynamic pressure is provided around the rotor 3, but it may also be provided on the inner periphery of the fixed bearing 4.

Other matters omitted from explanation are Utility Model Application No. 61-58853
According to the small electric motor disclosed in No.

(Effects of the invention) In the present invention, the presser magnet is fixed to a fixed shaft and replaced with the conventional overhanging arm, so the dimensions of the electric motor can be reduced, and the position of the presser magnet is performed based on the fixed shaft. It is convenient and easy to carry out.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a small electric motor illustrating an embodiment of the present invention, and FIG. 2 is a sectional view of a small electric motor according to the prior art. 1-1... Holder magnet, 1-2... Rotor magnet (as a rotating magnet body), 1-3... Levitating magnet, 3... Rotor (as a rotating body), 10...
...magnetic column (as a fixed axis).

Claims (1)

[Claims for Utility Model Registration] A dynamic pressure bearing in which a groove is provided on either the cylindrical outer circumferential surface of a rotating body or the inner circumferential surface of a fixed bearing that rotatably fits and supports the cylindrical outer circumferential surface of the rotating body. and a magnet is fixed to the cylindrical inner peripheral surface of the rotating body, and a driving coil is arranged opposite to the magnet, the rotating magnet having a hollow part at the center of rotation of the rotating body. The rotating magnet body is fixed, and a floating magnet and a holding magnet that levitate and support the rotating magnet body by magnetic action with the rotating magnet body are fixed to a fixed shaft penetrating the hollow part of the rotating magnet body so as to sandwich the rotating magnet body. An electric motor featuring: