JPH0438330Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rotation support device for a polygon mirror used in, for example, a laser printer, a barcode reader, a laser copying machine, and the like.

[Prior Art] Conventionally, many technologies related to such polygon mirrors are known. In general, the faster the rotation speed of a polygon mirror, the better the efficiency, so for example, 30,
It rotates at high speed like 000rpm. When the polygon mirror is rotated at such high speed, centrifugal force deforms the polygon mirror, that is, a rotating body having a mirror surface. If the deformation is uneven, the mirror surface becomes uneven and the image is distorted. Furthermore, when rotating at high speed, so-called wobbling motion or shaking tends to occur, and such wobbling motion naturally distorts the image. To this end, various support devices for polygon mirrors have been proposed.

For example, in the technique disclosed in Japanese Patent Application Laid-Open No. 59-28757, metal is used for the sliding surface of the rotating body, and the structure is such that no thrust load is applied. However, when the radial load increases during high-speed rotation, it becomes difficult to support the air film using the conventional herringbone-shaped dynamic pressure generating grooves.
Adjusting the balance can also be tricky.

Therefore, the applicant filed a patent application for a device that can rotate stably at high speed and reflect laser light with high accuracy.
Proposed as No. 74496.

In order to better understand the present invention, the prior art disclosed in Japanese Patent Application No. 1982-74496 will first be explained with reference to FIG.

For example, in a laser printer, a laser beam from a laser unit consisting of a semiconductor laser, a gas laser, etc. is reflected from a window 13 onto a mirror 2 formed on the outer peripheral surface of a rotating body 3, and is irradiated onto the surface of a photoreceptor. A magnet 7 is integrally attached to the rotating body 3 with a back-up spring 9. This rotating body 3 receives radial thrust through a fixed shaft 5 provided at its center, and its own weight is received by a thrust plate 10. Although not shown in the drawings, a device in which a thrust plate is provided on the upper part of the rotating body 3 is also known. A herringbone-shaped groove 11 is formed on the sliding surfaces of the fixed shaft 5 and the thrust plate 10, so that dynamic pressure is generated by an air film to support thrust force.

The fixed shaft 5 is fixed to a motor casing 4, and the motor casing is provided with a stator coil 6 and a magnet 7.

[Problems to be solved by the invention] In this prior art, the mirror 2 is made of vapor-deposited aluminum, so it is relatively difficult to achieve precision (on the order of several microns), and multiple circular magnets are used as magnets. Since I was using it, the magnet tended to deform when rotating at high speed. This deforms the mirror surface of the rotating body, causing disturbances in the movement of the reflected light.

It is also known to use polygonal aluminum alloy (herein simply referred to as "aluminum") to form a mirror surface.However, aluminum alloy is relatively weak and deforms. It's easy to do.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a rotation support device for a polygon mirror that does not cause non-uniform deformation due to high speed rotation.

[Findings of the present inventor] As a result of various studies, the present inventor has found that, as mentioned above, non-uniform deformation is undesirable, but if the rotating body is uniformly deformed by centrifugal force, no problem will occur. It has been found that uneven deformation of the rotating body can be prevented by changing the transmission path of the torque of the rotational force applied to the magnet.

[Means for Solving the Problems] The polygon mirror rotation support device of the present invention includes a fixed shaft provided with a shaft sleeve on its outer periphery, and a polygonal rotating body with a mirror surface formed on its outer periphery. is supported by the fixed shaft and upper and lower thrust plates, and in a polygon mirror rotation support device in which a magnet for generating torque is provided integrally with the rotating body, the rotating body is attached to the outer periphery of the shaft sleeve. A rotatable ceramic rotor, an intermediate ring shrink-fitted to the outer periphery of the ceramic rotor, and an aluminum member shrink-fitted to the outer periphery of the intermediate ring and having the mirror surface machined on its radial outer circumferential surface. and a yoke to which the ring-shaped magnet is bonded and shrink-fitted to the outer periphery of the ceramic rotor, and the intermediate ring has an elastic deformation amount equal to that of the ceramic rotor. It is larger than the rotor and smaller than the aluminum rotor.

[Operation] According to the present invention having the above-described structure, the rotational torque applied to the ring-shaped magnet is transmitted to the yoke to which the magnet is bonded. Since the yoke is shrink-fitted to the ceramic rotor, the torque transmitted to the yoke is transmitted to the ceramic rotor. This ceramic rotor rotates at high speed with its radial load supported by the shaft sleeve and its axial thrust load supported by the upper and lower thrust plates. The rotational torque of this ceramic rotor is transmitted to the aluminum rotor, which is shrink-fitted to the outer periphery of the intermediate ring, via the intermediate ring which is shrink-fitted to the outer periphery of the ceramic rotor.

Therefore, the aluminum rotor, which has a mirror surface on its outer periphery, has no unbalanced elements, and if the rotor itself is properly machined, it will not undergo uneven deformation due to rotation.

Here, there is a problem that the aluminum rotor has a larger amount of elastic deformation than the ceramic rotor, and is easily deformed by centrifugal force. However, according to the present invention, an intermediate ring whose elastic deformation is larger than that of a ceramic rotor and smaller than an aluminum rotor is interposed between the rotors, so the shrink fit force of the aluminum rotor is small. Also, the intermediate ring alleviates the difference in deformation between the aluminum rotor and the ceramic rotor. Therefore, even during high-speed rotation, a predetermined fastening force is maintained, the amount of deformation of the aluminum rotor is reduced, and the accuracy of the polygon mirror is improved.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG.

In FIG. 1, the polygon mirror rotation support device according to the present invention includes a motor casing 20, and a coil board 21 is mounted on the upper surface of the motor casing 20, and a fixing bolt 2 is mounted on the upper surface of the motor casing 20.
2, and an iron core 23 and a coil 24 constituting the motor are installed inside the motor. A fixed shaft 25 is fixed to the center of the motor casing 20 with a lower stopper nut 26.
A shaft sleeve 27 has a herringbone-shaped dynamic pressure generating groove 27a on the outer periphery of the fixed shaft 25.
is provided. A ring-shaped ceramic rotor 28 constituting the rotating body R is rotatably provided on the outer periphery of the shaft sleeve 27. An upper thrust plate 29 and a lower thrust plate 30 made of ceramic are provided above and below the rotor 28, which is made of ceramic, and are adapted to receive the thrust load in the axial direction of the rotating body R. The ceramic rotor 28 side surfaces of the upper and lower thrust plates 29 and 30 each have spiral grooves 29.
a, 30a are formed. A ring-shaped yoke 31 is shrink-fitted to the lower outer periphery of the ceramic rotor 28. This yoke 31 is made of steel, for example, and a ring portion 32 extending below the yoke 31 is made of steel.
A ring-shaped magnet 33a is attached to the inside of the ring by adhesive. Above the yoke 31 is an aluminum rotor 3 which has a polygonal planar shape when viewed from the outer circumferential surface and has a mirror surface M formed on the outer circumferential surface.
3 is located. An intermediate ring 34 is arranged between the ceramic rotor 28 and the aluminum rotor 33, and the intermediate ring 34 is fixed to the outer peripheral surface of the ceramic rotor 28 by shrink fit, and is fixed to the aluminum rotor 28 by shrink fitting. A rotor 33 made of aluminum is fixed to the outer peripheral surface of an intermediate ring 34 by shrink fitting. The intermediate ring 34 is made of a material that has a larger amount of elastic deformation than ceramic and a smaller amount of elastic deformation than aluminum alloy, and is made of stainless steel, for example.

Note that the reference numeral 35 in FIG. 1 indicates an upper locking nut that fixes the shaft sleeve 27 and the upper and lower thrust plates 29, 30.

By controlling the current flowing through the motor coil 24 at the coil base 21, rotational torque is applied to the magnet 33a in a known manner. The torque applied to the magnet 33a is transmitted to the aluminum rotor 33 via the yoke 31, the ceramic rotor 28, and the intermediate ring 34, so that the mirror surface M rotates at high speed. The ceramic rotor 28 is supported by a shaft sleeve 27, and its axial thrust is supported by upper and lower thrust plates 29, 30.

Here, when the rotating body R rotates at high speed, centrifugal force is generated, and the amount of elastic deformation caused by the centrifugal force is different between the ceramic rotor 28 and the aluminum rotor 33. However, the presence of the stainless steel intermediate ring 34 alleviates the difference in the amount of deformation.

Note that since the ceramic rotor 28 is held from three directions by the shaft sleeve 27 and the upper and lower thrust plates 29 and 30, the rotating body R will not wobble in the vertical or radial direction.

[Effects of the invention] According to the polygon mirror rotation support device of the invention described above, there is no unbalanced element in the aluminum rotor forming a mirror surface on the outer periphery.
By properly mirror-finishing the aluminum rotor itself, the mirror surface will not deform even when rotating at high speeds. Mirror-finishing the aluminum rotor itself is easier than vapor deposition, and the processing accuracy is higher. Moreover, an intermediate ring was provided between the ceramic rotor and the aluminum rotor, so
Differences in deformation due to high-speed rotation are alleviated, and there is no need to increase the shrinkage fit.

[Brief explanation of the drawing]

FIG. 1 is a sectional front view showing one embodiment of the polygon mirror rotation support device of the present invention, and FIG. 2 is a sectional front view showing a prior art. 25... fixed shaft, 27... shaft sleeve, 28...
...ceramic rotor, 29...upper thrust plate, 30...lower thrust plate, 31...yoke,
33a... Magnet, 33... Aluminum rotor, 34... Intermediate ring, M... Mirror surface, R... Rotating body.

Claims (1)

[Scope of utility model registration request] A fixed shaft with a shaft sleeve provided on the outer periphery and a polygonal rotating body with a mirror surface formed on the outer circumferential surface are provided, and the rotating body is supported by the fixed shaft and upper and lower thrust plates, and is used for generating torque. In the rotation support device for a polygon mirror, the magnet is integrally provided with the rotating body, and the rotating body includes a ceramic rotor rotatably provided on the outer periphery of the shaft sleeve, and a ceramic rotor that is heated on the outer periphery of the ceramic rotor. A fitted intermediate ring, an aluminum rotor which is shrink-fitted to the outer periphery of the intermediate ring and whose radially outer circumferential surface is machined with the mirror surface, and the ring-shaped magnet are bonded, and a yoke shrink-fitted to the outer periphery of the ceramic rotor, and the intermediate ring has an elastic deformation amount greater than that of the ceramic rotor and smaller than that of the aluminum rotor. rotation support device.