JPS62295017A - Optical scanner - Google Patents

Abstract

PURPOSE:To allow an optical scanner to resist rapid rotation, to improve its scanning efficiency and setting up the reflection factor of a non-magnetic phase polygon mirror surface >=eighty and several % by forming different anisotropic structures on the inner and outer peripheral parts of a carbon group alloy magnet rotor by a specific simple process. CONSTITUTION:A required outer peripheral part of the rotor 7 consisting of manganese- aluminium-carbon group alloy magnet is formed as a part 7b obtained by orientating easy magnetization axes in prior on the plane vertical to the rotary shaft direction of the rotor 7. A non-magnetic phase part 7c consisting of alloy is formed on a required surface layer part of the outer peripheral part, its surface is formed as a mirror surface and the easy magnetization axes are orientated in prior on a large part of the portion opposed to an electromagnetic coil 8 out of the part other than the outer peripheral part of the magnet rotor 7 at least in the direction parallel with the rotary shaft direction of the rotor 7. Since the surface is finished as a mirror surface, a polygon mirror surface having a high reflection factor >=eighty and several % can be obtained and extremely excellent picture quality (multigradation) can be obtained. Thus, the optical scanner resisting rapid rotation and having high scanning efficiency can be obtained.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to an optical scanning device used in laser printers, scanners such as copying machines, information recording devices such as videos, and the like.

Conventional technology A polygon mirror is attached to the rotating side of a high-speed motor used in scanners such as laser printers and copying machines, and a signal-modulated laser beam is projected onto the polygon mirror from a light emitter (not shown) and is deflected. As a result, it has already been proposed that, for example, a traveling photoreceptor (an example of a light receiver) having a photoconductive layer is scanned with light to form a latent image, and copies of this are made using known electrophotographic techniques. ing.

In addition, in response to the recent strong demand for thinner information processing equipment, lower cost, reduction in the number of parts, and improved precision due to integration, we have developed a magnet rotor and polygon mirror for the motor in optical scanning equipment. A 114-structure structure is also being used to integrate the structure.

This has a structure as shown in FIG. 4, for example, as shown in Japanese Unexamined Patent Publication No. 59-197010.

In FIG. 4, a cover member 2 is placed on the upper side of the housing member 1, and a bearing sleeve 11 is fixed to the lower part of the housing member 1 to support the magnet rotor and polygon mirror 6. The extension of the shaft 4 is connected to the sleeve 1.
The hydrodynamic bearing is loosely fitted into the shaft 1 with a gap of several microns between the shaft 4 and the shaft 4, and a large number of spiral and herringbone grooves are cut on the outer periphery of the extension of the shaft 4. A rotor receiver 6 is formed at a portion slightly above the middle of the shaft 4, on which a magnet rotor/polygon mirror 6 is placed, and is held down from above by a rotor fixing plate 3. There is.

The magnet rotor/polygon mirror 6 may be a barium ferrite magnet with a copper-plated or electroless nickel-plated mirror surface formed on the surface, an alnico magnet, or a manganese-aluminum-carbon alloy magnet with a mirror-polished surface. is disclosed.

A predetermined number of electromagnetic coils 8 are disposed at the bottom of the inner surface of the housing 1, facing the magnet rotor/polygon mirror 6, via a printed circuit board 9, forming a stator.

Reference numeral 10 denotes a Hall element disposed opposite the magnet as a sensor used for changing the phase of the electromagnetic coil 8 and checking the rotation speed, and is provided on the printed circuit board 9.

Problems to be Solved by the Invention However, the polygon mirror-integrated optical scanning device using the rotor 6 described in the above-mentioned publication has the following problems.

Barium ferrite magnets have very low reflectance, so
A layer of copper, aluminum, nickel, etc. must be formed on the outer circumferential surface of the rotor 6, and then a desired mirror surface must be obtained by precision cutting, polishing, etc., which not only increases the number of processing steps and increases costs, but also prevents the use of barium ferrite. The mechanical strength of the magnet is low, making it unsuitable for high-speed rotation to achieve high scanning efficiency.

In addition to the above problems, alnico magnets also have the iHc of the magnet.
(coercive force) is very small, so if it is made thinner, the generated magnetic flux will decrease and the motor efficiency will be extremely poor.

The manganese-aluminum-carbon alloy magnet is already disclosed in Japanese Patent Application Laid-Open No. 51-89434,
Although it has a high reflectance of 70% or more, a reflectance of 80 or more is desired for use in high image quality (multi-gradation) applications.

In addition, in order to obtain high resolution, the outer diameter of the rotor must be increased, but manganese-aluminum
In order to stably obtain a ferromagnetic phase in a carbon-based alloy magnet and at the same time preferentially orient the axis of easy magnetization in the direction of the rotational axis using a simple process to obtain high magnetic properties, the outer diameter of the rotor must be reduced.

As described above, the rotor and polygon mirror are integrated, thin and flat, the outer diameter of the polygon mirror is large, the motor efficiency is high, and the structure can withstand high speed rotation.
Furthermore, it has been extremely difficult to realize an optical scanning device in which the reflectance of the polygon mirror surface is 8o or more.

Means for Solving the Problems The present invention has been made to solve the above problems, and the desired outer circumference of a rotor made of manganese-aluminum-carbon alloy magnets is aligned with the rotation axis of the rotor. The axis of easy magnetization is preferentially oriented in a plane perpendicular to the direction, and a non-magnetic phase portion of the alloy is provided in a desired surface layer portion of the outer peripheral portion, and the surface of the non-magnetic phase portion is mirror-finished. Further, the axis of easy magnetization is preferentially oriented at least in a direction parallel to the rotational axis direction of the rotor in most of the portion of the magnetic rotor other than the outer peripheral portion facing the electromagnetic coil. This is what I did.

In a manganese-aluminum-carbon alloy magnet rotor, the part facing the electromagnetic coil preferentially aligns the axis of easy magnetization in a direction parallel to the rotational axis direction in order to generate large power for rotational drive. To solve the problem of increasing the outer diameter of the magnet rotor and polygon mirror using a simple process in order to achieve high magnetic properties and high resolution at the same time, we developed a manganese-aluminum-carbon alloy magnet. Focusing on plastic workability, only the desired outer peripheral part of the magnet rotor is pressurized and compressed in a direction parallel to the rotational axis direction, and the axis of easy magnetization is preferentially oriented in a plane perpendicular to the 11111 direction of rotation of the rotor. This is made possible by allowing

In addition, a nonmagnetic phase (mainly composed of AIMn (τ phase)) formed by transformation of a face-centered tetragonal ferromagnetic phase (τ phase) is formed on a desired surface layer portion of the outer peripheral portion, and this surface is mirror-finished. This is based on the fact that a polygon mirror surface with a high reflectance of 8o coefficient or more can be obtained by finishing the polygon mirror, resulting in very good image quality (multi-gradation).

Furthermore, since the rotor has high mechanical strength, it can withstand high-speed rotation, and an optical scanning device with extremely high scanning efficiency can be realized.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings. FIG. 2 shows an external sectional view of the optical scanning device of the present invention. However, it is similar to the conventional example shown in FIG. 4 in that FIG. 2 is a surface-facing flat motor having a magnet rotor and polygon mirror. Therefore, the same reference numerals are given to the parts corresponding to those of the conventional example. However, the major difference is the structure of the magnet rotor and polygon mirror. Specifically, the same magnet (manganese-aluminum-carbon alloy magnet) has different anisotropic structures within the rotor, and at the same time the outer peripheral surface is The point is that it is a mirror surface made of the non-magnetic phase of the alloy.

Therefore, the detailed description of the present invention below will also be described as follows. The details of the secondary non-magnetic phase polygon mirror 7 will be explained mainly with reference to FIG.

Manganese 69.8% by weight, aluminum 29.7% by weight
A regular octagonal prism billet of manganese-aluminum-carbon alloy having a composition of 0.5% by weight of carbon was prepared by melting and casting, heat treated by holding at 1000°C and then cooling, and then molded at a temperature of 700'C. It was extruded into a square shape (extrusion ratio = 6) to produce a regular octagonal prism billet (circumference diameter: 33H). In this state, the axis of easy magnetization was preferentially oriented in a direction parallel to the rotation axis direction (extrusion direction).

The above regular octagonal prism billet is cut to a suitable length in the direction perpendicular to the rotation axis, and the regular octagonal billet is placed in a mold of desired size with a regular octagonal inner surface, and one end of the billet is cut into a suitable length. The height of the outer periphery side is increased by placing the other end face on a flat punch and compressing and upsetting the other end face using a regular octagonal punch with a concave shape of an appropriate size. A polygon with a stepped state in which the height was lower than the internal height (the outer periphery was strongly compressed), the outer diameter was larger than the original regular octagonal prism billet, and the circumscribed circle diameter was 55 mm was obtained.

Regarding samples created using the same process as above,
X-ray diffraction of the internal magnetic anisotropic structure.

As confirmed by torque measurement, the inside facing the electromagnetic coil 8 formed in a flat shape has a groove 7a in which the axis of easy magnetization is preferentially oriented in a direction parallel to the rotational axis direction (hereinafter abbreviated as axially anisotropic part). Until now, only the outer peripheral portion a+ was a portion 7b (hereinafter abbreviated as in-plane anisotropic portion) in which the axis of easy magnetization was preferentially oriented in a plane perpendicular to the direction of the rotation axis.

Furthermore, when the magnetic properties of a portion corresponding to the axially anisotropic portion 7IL in FIG. 1 were measured, they showed a high value of (BH)m,=e,3sMG-Oe in the direction parallel to the rotational axis direction.

As a result of the above, it has become possible to form polygons with large outer diameters to achieve high resolution using a simple process without degrading the magnetic properties of the portion that generates rotational drive power.

Further, the obtained outer circumferential surface of the polygon was irradiated with a carbon dioxide laser and heated to 780° C. to transform it into a non-magnetic phase, and the surface was again finished to a mirror surface. When we performed X-ray diffraction on this mirror surface, we found that the main diffraction lines were from a non-magnetic phase called IMn (τ phase), with a slight non-magnetic phase called β-Mn phase with a diffraction line intensity of 6% or less. A diffraction line pattern containing a mixture of magnetic phase diffraction lines was obtained, and it was confirmed that the mirror surface portion was a non-magnetic phase. (The strength has also been increased.) Next, the outer circumferential surface of the polygon thus obtained was semi-finished to the desired precision, and finally mirror-finished to the final precision.

Furthermore, the non-magnetic phase mirror surface portion 7C obtained as above
When the spectral reflectance was measured, it was 76.3 to 84.7 inches (λ=400 to 800 nm).

Further aluminum on the outer circumferential surface of these polygons.

It goes without saying that a higher reflectance can be obtained by forming a highly reflective material such as copper, silver, or gold by a method such as vapor deposition to obtain a mirror surface. Furthermore, it is naturally possible to obtain an increased reflection effect by coating with a dielectric material as necessary.

Hole 7 for passing the shaft 4 through the center of the composite anisotropic magnet rotor/non-magnetic phase polygon mirror 7 of the present invention obtained as described above
d, the end surface (magnetic pole forming surface) 76 of the composite anisotropic magnet rotor/non-magnetic phase polygon mirror 7 is magnetized in a predetermined manner so as to face the electromagnetic coil 8 formed in a flat shape. By assembling as shown in Figure 2, a polygon mirror surface with a large outer diameter that achieves high resolution can be integrated with the rotor, making it thin and flat, and can withstand high-speed rotation, resulting in extremely high scanning efficiency. At the same time, since the reflectance of the polygon mirror surface is as high as a coefficient of 80 or more, an optical scanning device with very good image quality (multi-gradation) can be realized.

FIG. 3 shows another embodiment of the present invention, in which the axially anisotropic portion 7a shown in FIG. 1 is cut in order to make the overall structure even thinner in the optical scanning device shown in FIG. , the structure is such that the step with the in-plane anisotropic portion 7b is removed.

Effects of the Invention According to the present invention, the inside of a manganese-aluminum-carbon alloy magnet rotor mainly composed of a face-centered tetragonal ferromagnetic phase,
By forming different anisotropic structures on the outer periphery using a simple process, it is possible to create high magnetic properties that generate power for rotational drive inside, and a large external structure on the outer periphery that achieves high resolution. The polygon mirror surface of the diameter is integrated.

It can be configured with a thin flat structure and can withstand high-speed rotation, resulting in extremely high scanning efficiency.At the same time, the reflectance of the non-magnetic phase polygon mirror surface is high, with a coefficient of over 80, resulting in very good image quality (multi-gradation). ) optical scanning device can be realized.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining the structure of a composite anisotropic magnet rotor/non-magnetic phase polygon mirror of an optical scanning device shown as an embodiment of the present invention, and FIG. 2 is a sectional view showing an embodiment of the present invention. FIG. 3 is a sectional view of an optical scanning device showing another embodiment of the present invention, and FIG. 4 is a sectional view of a conventional optical scanning device. 1...Housing member, 2...Cover member, 3...Rotor fixing plate, 4...Shaft, 5...Rotation Child support, 7... Composite anisotropic magnet rotor and non-magnetic phase polygon mirror, 7a...
... Axial anisotropic part, 7b... In-plane anisotropic part,
7C...Non-magnetic phase mirror surface part, 7d...
Shaft mounting hole, 7e...Magnetic pole forming surface, 8...
・Electromagnetic coil, 9...Printed circuit board, 1o...
... Hall element, 11 ... Bearing sleeve.

Claims (1)

[Claims] A light emitter, a rotor made of a manganese-aluminum-carbon alloy that scans light from the light emitter, an electromagnetic coil that drives the rotor, and a light receiver that receives the light scanned by the rotor. A desired outer circumferential portion of the magnet rotor has an axis of easy magnetization preferentially oriented in a plane substantially perpendicular to the direction of its rotational axis, and a desired surface layer portion of the outer circumferential portion has a non-magnetic layer of the alloy. A magnetic phase portion is provided, and the surface of the non-magnetic phase portion is a mirror surface, and most of the portion of the rotor other than the outer circumferential portion facing the electromagnetic coil is at least parallel to the rotation axis direction of the rotor. An optical scanning device in which the axis of easy magnetization is preferentially oriented in substantially parallel directions.