JPS60136614A - Rotating device - Google Patents

Abstract

PURPOSE:To improve productivity by constituting a dynamic pressure shaft part having a shaft symmetrical curved surface form, on the bottom end part of a spindle, a dynamic pressure bearing part which receives this dynamic pressure shaft, and a dynamic pressure groove carved on either of the two. CONSTITUTION:The shaft diameter of the lower part of a spindle 4 is made smaller, and a spherical shaped dynamic pressure shaft 17 is formed on the bottom end face in an integrated form with the spindle 4. Spiral dynamic pressure grooves 18 having a depth of scores of mum are carved on the surface of this dynamic pressure shaft 17. The dynamic pressure shaft 17 is supported by a dynamic pressure bearing 19 provided under the shaft 17, and this supporting part is formed into a semi-spherical recess part 20 having nearly the same shaped spherical surface as the spherical surface form of the dynamic pressure shaft 17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a rotating device used in a rotating optical deflector for a line laser printer, and more particularly to a device in which a rotating rotor is supported by a hydrodynamic gas bearing.

[Technical background of the invention and its problems]

Recently, laser printers using semiconductor lasers have been developed. In this laser printer, an optical deflector using a polyhedral mirror is used to convert information such as a document into an electrical signal. This polyhedral mirror generally has the shape of a thin regular polygon.

Each side has a mirror-finished reflective surface. The polyhedral mirror is provided coaxially with a rotatable spindle, and is rotated by the spindle to reflect incident light in different directions. At this time, in order to obtain high resolution in the above-mentioned electrical signal conversion, it is necessary for K to increase the rotation speed of the spindle (1Q'rpm or more) and increase the light deflection speed. moreover.

Since an optical system is used as the conversion means, it is necessary to maintain the positional accuracy of the polyhedral mirror with very high precision, and for this purpose, the rotational precision of the spindle must be made highly precise.

That is, in a rotating device for rotationally driving such a polyhedral mirror, the spindle must be rotated at high speed and must have a highly accurate rotation precision. For this reason.

Conventionally, a herringbone type or tilting pad type dynamic pressure gas is used for spindle bearings for radial support, and magnetic bearings using permanent magnets are used for axial support. There is. (For example, Japanese Patent Application No. 57-107529) By using these two bearings together, the above conditions are satisfied, and other advantages such as low frictional torque loss and no need for lubricating oil can be obtained.

Conventionally, when using the above-mentioned hydrodynamic gas bearings and magnetic bearings, the hydrodynamic gas bearings are provided at both ends of the spindle, and between the bearings there is a motor for rotating the spindle, and a rotary optical deflector. Many are equipped with polyhedral mirrors. Note that the magnetic bearing that supports the radial force of the spindle is generally provided at the end of the spindle along with one of the hydrodynamic gas journal bearings.

However, the structure of a magnetic bearing is somewhat complicated, and it is necessary to incorporate several layers of ring-shaped permanent magnets on the bearing side and the shaft side, respectively. This has the disadvantage of low productivity and high manufacturing costs due to the large number of parts.
It may be oL, but this magnetic bearing only has a magnetic coupling of permanent magnets.
Therefore, since it is supported in the axial direction, if sudden or large vertical vibration occurs, the magnetic coupling may be broken, and there is a risk that axial support may become impossible.

[Purpose of the invention]

The present invention has been made in view of the above points, and its purpose is to provide a rotating device that can improve productivity without impairing performance and is less affected by vibrations.

[Summary of the invention]

The present invention provides a rotating device in which a spindle is supported by a hydrodynamic gas bearing and is rotated by a drive device, wherein at least one hydrodynamic gas bearing is provided at the lower end of the spindle and has an axisymmetric curved surface shaped hydrodynamic shaft portion. and a hydrodynamic pressure bearing section having four parts having an axisymmetric curved surface shape for receiving the hydrodynamic pressure shaft sections, and a hydrodynamic groove carved in either one of the hydrodynamic pressure bearing section or the hydrodynamic pressure shaft section. It is characterized by supporting both the radial direction and the axial direction by the hydrodynamic gas bearing.

[Embodiments of the invention]

A case where an embodiment of the present invention is applied to a rotating optical deflector for a laser printer will be described with reference to the drawings. The drawing is a sectional front view of this embodiment.

A support rod (3) fixed with a nut (2) is provided on the upper surface of the upper housing (1). Spindle (
4) is hollow at its upper end, and the support rod (3) is inserted into this hollow portion. Support rod (3)
A hemispherical protrusion (5) is provided on the lower end surface of the lever.
The force between the hollow bottom of the spindle (4) and the lower end of the support rod (3) prevents them from coming into contact with each other during rotation of the spindle (4). A plurality of dynamic pressure grooves (6) engraved in the axial direction of 10 μm are arranged.

A cylindrical dynamic pressure bearing (7) is press-fitted into the hollow inner surface of the spindle (4) facing the dynamic pressure groove (6). This cylindrical dynamic pressure bearing (force includes support rods (3
) Cera is used as the material to prevent wear. In addition, these support rods (3) and cylindrical hydrodynamic bearings (7)
The gap between the two is several tens of μm. Spindo.

A polygonal mirror (9) having a plurality of reflective mirror surfaces (8) on the side surface is installed coaxially with the spindle (4) on the upper part of the spindle (4). )
It is placed on a pedestal that protrudes in the shape of an empty shell, and is fixed by a holding plate I and a fixture Q. In addition, a polyhedral mirror (9
) is generally a soft metal such as aluminum or copper that can easily be processed into a mirror surface. Moreover, the spindle (4) and the polyhedral mirror (9) may be formed integrally.

On the other hand, a motor rotor (2), which is a part of a motor that is a drive device that provides rotational motion to the spindle (4), is fixed to the intermediate portion of the spindle (4). Also.

Coil part I faces this motor rotor shaft, and the upper housing (1), this upper part 7), the housing (1), and the bolt (
15) is fixed to the inner circumference of the lower housing (10).

The lower part of the spindle (4) has a small shaft diameter, and a spherical dynamic pressure shaft part is formed integrally with the spindle (4) at the lower end. The surface of this dynamic pressure axis (I7) has a depth of several tens of μm.
A spiral dynamic pressure groove α frame of m is engraved.

The dynamic pressure shaft (Lη) is supported by the dynamic pressure shaft (to) provided below, but this supported part is connected to the dynamic pressure shaft (17
) is a concave part of a hemisphere with a spherical surface that is almost the same as the spherical shape of -
It's so hot. In this embodiment, the dynamic pressure bearing frame is formed by cold forging.

Note that the hydrodynamic bearing α-yu is housed in the bearing casing I21J, and is fixed by a ring-shaped fixing plate C4. Note that the inner diameter of this fixing plate @ is larger than the diameter of the dynamic pressure shaft (17). On the other hand, the bearing casing Qυ is inserted from the bottom of the lower housing (1[9) to the lower housing αe with the KO ring (c) interposed, and then,
Insert the bottom cover (A) into the lower housing df via the O-ring @.
9 by tightening them with bolts (c).

In this way, the spindle (4) is connected to the support rod (3), the dynamic pressure groove (
6).

It is supported by a hydrodynamic gas bearing consisting of a cylindrical hydrodynamic bearing (7) and a hydrodynamic gas bearing consisting of a hydrodynamic shaft a7), a hydrodynamic groove α, and a hydrodynamic bearing canopy.

Next, the operation of the apparatus configured as described above will be explained. A drive device consisting of a motor rotor α and a coil portion (14) is driven to rotate the spindle (4).

At this time, the number of revolutions of the spindle (4) reaches tens of thousands of revolutions, but the spindle /I/(4) has dynamic pressure grooves (6), (11G
Due to the effect of The spindle (4) supports against radial forces, but the hydrodynamic gas bearing with the spherical dynamic pressure shaft (Q7) provided at the lower end supports the main spindle (4) against not only radial but also axial forces. ). The reason for this is that the dynamic pressure effect of the spiral dynamic pressure grooves (α) carved in the dynamic pressure axis (I7) acts perpendicularly to the spherical concave wing surface, so the spindle supporting force generated by this K is axially This is because it occurs in a direction with a certain angle.

Therefore, the spindle (4) can rotate together with the polyhedral mirror (9) at high speed and with high precision. Therefore, the polyhedral mirror (9) has an entrance window (
A laser beam incident from a mirror surface (not shown) is reflected by a reflecting mirror surface (8), and the laser beam can be scanned in a predetermined area.

In this way, in this embodiment, the spindle (4) is supported in both the radial and axial directions by the hydrodynamic gas bearing having the spherical hydrodynamic axis ←η provided at the lower end of the spindle (4). I decided to do so. For this reason, the spindle (4)
The length of the device itself can be shortened, making it possible to downsize the entire device. In addition, the hydrodynamic shaft (1η) can be formed integrally with the spindle (4), and the hydrodynamic bearing H can be manufactured by cold forging, so the number of parts can be reduced compared to when conventional magnetic bearings are used. This has greatly reduced the number of assemblies and makes production extremely easy.In addition, since the spindle (4) rotates without contact, there is no deterioration in rotational performance compared to the conventional method.In addition, the spindle (4) rotates without contact. 4) When the spindle (4) is stopped, etc., the spindle (4) is supported in contact with the hydrodynamic bearing αl, so the influence of vertical vibration is very small.

In addition, although the above-mentioned example described the case where it was used as a rotary optical deflector for a laser printer, it is not limited to this, but it can also be used as a disk rotary table for various audio equipment.

It may also be used in equipment that requires high speed or high precision rotation, such as a 4-bi disc drive device.

〔Effect of the invention〕

As explained above, the rotating device of the present invention can reduce the number of parts and is extremely easy to assemble and produce. Therefore, productivity can be improved without impairing rotational performance, and an inexpensive device can be provided.

[Brief explanation of the drawing]

The drawing is a sectional front view showing one embodiment of the present invention. 3...Support rod, 4...Spindle. 6.18...Dynamic pressure groove, 7...Cylindrical dynamic pressure bearing. 13...Motor rotor, 14...Coil part. 17...Dynamic pressure shaft, 19...Dynamic pressure bearing. 20...Concave part.

Claims (2)

[Claims] (1) In a rotating device in which a spindle is supported by a hydrodynamic gas bearing and rotated by a drive device, a hydrodynamic bearing portion has a recessed portion having an axisymmetric curved surface shape. 1. A rotating device comprising: a dynamic pressure groove carved in either one of a dynamic pressure bearing part or a dynamic pressure shaft part. (2) The rotating device according to claim 1, wherein the hydrodynamic shaft portion and the recessed portion of the hydrodynamic bearing portion each have a spherical shape among axisymmetric curved surfaces.