JP2973616B2 - Rotating polygon mirror - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary polygon mirror, and more particularly to a rotary polygon mirror used as a beam deflecting means of a laser beam scanning optical system incorporated in an image forming apparatus such as a laser printer or a facsimile or an image reading apparatus.

[0002]

2. Description of the Related Art A polygonal rotary polygon mirror used as a beam deflecting means is required to have a high level of surface accuracy (flatness), surface inclination accuracy, and division accuracy of each reflecting surface. Conventionally, these various polygon mirrors are made of aluminum alloy,
It was manufactured using optical glass as a material through a molding process, a cutting process, and a polishing process. However, it is difficult to process metal materials and glass materials with high precision, mass productivity is low, and costs are considerably high.

Therefore, recently, various attempts have been made to manufacture a rotary polygon mirror by injection molding using a resin as a raw material. If resin is used as a material, a high-precision molded product can be mass-produced using a high-precision mold. In fact, we have developed a rotating polygon mirror with the required accuracy. However, in the case of a rotating polygonal mirror made of resin, sufficient characteristics (jitter value, image quality) are not obtained when the polygonal mirror is attached to a rotating shaft of a motor, even if the required accuracy is satisfied by itself.

[0004]

Object, structure and operation of the present invention
It is an object of the present invention to provide a rotary polygon mirror made of a resin, which, of course, satisfies the required accuracy as a single product and which suppresses deformation even when mounted on a rotary drive shaft and has good optical performance. In order to achieve the above object, a rotary polygon mirror according to the present invention is made of a resin material, and has a mounting surface which is pressed against a mounting seat surface of a rotary drive shaft with a center line roughness of about 0.1 μm or less and a maximum roughness of about 0.1 μm or less. Finished to a mirror surface of 1.0 μm or less.

In a rotary polygon mirror, usually, a hole at the center is loosely fitted to a rotary shaft of a motor, and a bottom surface (mounting surface) is pressed against a mounting seat surface fixed to the rotary shaft by screwing in an axial direction. Assembled. Even if the rotating polygonal mirror made of resin satisfies the required accuracy as a single product, it does not exhibit sufficient performance after it is mounted on the rotary drive shaft because the material itself has a low longitudinal elastic modulus and the elastic deformation in the mounted state is low. This is because surface accuracy, surface inclination accuracy, and division accuracy of each reflection surface are reduced. By the way, the longitudinal elastic modulus of the resin is 2-10 ×
10 ⁴ kg / cm ² , that of aluminum and glass is 6
８8 × 10 ⁵ kg / cm ² and 5 to 10 × 10 ⁵ kg / c
m ² .

Therefore, in the present invention, the mounting surface of the rotary polygon mirror is finished to a mirror surface, so that the mounting surface and the seat surface have good adhesion when mounted on the rotary drive shaft, and the rotary polygon mirror itself is deformed. And there is very little deformation over time, and sufficient optical performance can be obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the rotary polygon mirror according to the present invention will be described below with reference to the accompanying drawings. 1 and 2, reference numeral 1 denotes a rotary polygon mirror as a first embodiment, and reference numeral 10 denotes a stepping motor for rotational driving.

The rotary polygon mirror 1 is integrally formed by injection molding using polycarbonate as a material, has a mounting hole 2 in the center, and has four flat reflecting surfaces (mirror surfaces) 3a, 3b, 3 The mounting surface 4, which has 3c and 3d and is a bottom surface, is mirror-finished as described in detail below.
The stepping motor 10 includes a stator 11, a rotor 12, and a drive shaft 13 and a mounting seat 14 integrally fixed to the rotor 12, and the configuration and operation of the motor 10 itself are well known.

The rotary polygon mirror 1 has the mounting hole 2 loosely fitted on the drive shaft 13, and a leaf spring 15 and a washer 1
By tightening the screw 17 through the
0 is attached. In this mounting state, the mounting surface 4 of the rotary polygon mirror 1 is not the mounting hole 2 fitted to the drive shaft 13 but the mounting surface 4 is formed by the elastic force of the leaf spring 15 compressed by the screw 17. 14a. The drive shaft 13, the mounting seat 14, and the rotor 12 are in a fitted state, and the three members and the rotary polygon mirror 1 rotate integrally.

Incidentally, the bottom surface of the cavity (the surface corresponding to the mounting surface 4) of the mold for molding the rotary polygon mirror 1 was polished and then polished to a mirror surface. By using such a mold, it is possible to obtain the rotary polygon mirror 1 whose mounting surface 4 is mirror-finished. Of course, the inner surfaces of the molds corresponding to the reflecting surfaces 3a to 3d are also mirror-finished.

As described above, the rotating polygon mirror 1 having the mounting surface 4 mirror-finished is mounted on the mounting seat 14 as described above.
By elastically attaching in a press-contact state in step 5, deformation of the reflecting surfaces 3a to 3d (reduction of reflecting surface accuracy, surface falling accuracy, division accuracy) is almost eliminated, and the mounting surface 4 is polished (the bottom surface of the mold is polished). The image quality when forming an image by scanning with a laser beam is remarkably improved as compared with the case where only finishing is performed. This is because the mounting surface 4 of the rotary polygon mirror 1 is mirror-finished, so that the contact area with the seat surface 14a is increased and the adhesion is improved.

Table 1 below shows this embodiment and a comparative example (conventional example).
The results of the experiment are shown below. The image quality was objectively measured as a jitter value. Here, the mounting seat surface 14a is also mirror-finished.

[0013]

[Table 1]

To explain the surface roughness, Ra
Means the center line average roughness, and Rmax means the maximum roughness. Both are well known as surface measuring methods. As shown in Table 1, Ra = Ra =
If the mirror surface finish is 0.05 μm and Rmax = 0.8 μm, the roughness of the mounting surface of the rotary polygon mirror formed using the mold is, according to actual measurement, Ra <0.1 μm, Rmax
x is smaller than 1.0 μm. With such a rotary polygon mirror, an image with much improved quality was obtained as compared with the comparative example in which the mold bottom was polished and formed.

The jitter value for evaluating the image quality is obtained by actually measuring the times T ₁ , T ₂ , T ₃ , and T ₄ from the start to the end of scanning of each of the four reflecting surfaces of the rotary polygon mirror, and calculates the following equation (1). Was used to calculate. Jitter value ppm = (Tmax−Tmin) / T (1) where Tmax: max (T ₁ , T ₂ , T ₃ , T ₄ ) Tmin: min (T ₁ , T ₂ , T ₃ , T ₄ ) T: Design value In addition, since the surface of the mold is mirror-finished in order to mirror-finish the mounting surface of the rotating polygon mirror, the releasability of the rotating polygon mirror from the mold is improved, and the manufacturing time of the rotating polygon mirror is improved. Yield has improved.

FIGS. 3 and 4 show a second embodiment and a third embodiment of the rotary polygon mirror according to the present invention. In each of these, the reflection surface portions 22 to 25 and 32 to 35 and the other core portions 21 and 31 are integrally formed of different types of resin materials. The difference between the two is that the reflection surface portions 22 to 25,
It is only the form of connection between 32-35 and core portions 21 and 31.

The rotating polygon mirror 2 is provided on the core portions 21 and 31.
A material which is less deformed due to resin deformation or environmental temperature and humidity when 0, 30 rotates at high speed, for example, glass fiber is made of 4
0% by weight of polyphenylene sulfide (PP
S), a liquid crystal polymer (LDP) mixed with 30 wt% of glass fiber is used. Also, the reflection surface portion 22-
25, 32 to 35, materials having good specularity and flatness,
For example, polycarbonate and acrylic are used.

Of course, the mounting surfaces (bottom surfaces) 26 and 36 of these rotary polygon mirrors 20 and 30 are mirror-finished as in the first embodiment, and have the same effects as shown in Table 1 above. Obtained. It should be noted that the rotary polygon mirror according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the gist.

For example, in addition to a four-sided polygon, two faces, six
Plane or eight planes. The reflecting surface is not limited to a flat surface, but may be a curved surface, a spherical surface, a cylindrical surface, or an aspherical surface. Further, the form of attachment of the rotary polygon mirror to the drive shaft is also arbitrary. Further, the resin used is not limited to those described above. For example, polystyrene, acrylonitrile styrene copolymer resin, tetrapolymethylpentene, methyl methacrylate styrene copolymer resin, polyarylate, polysulfone, polyether sulfone, polyphenylene ether, diethylene glycol bisallyl carbonate, and those obtained by aroylating these resins. You may.

[0020]

As is apparent from the above description, according to the present invention, since the rotary polygon mirror is formed of a resin material and its mounting surface is finished to a mirror surface, the adhesion to the mounting seat surface is good. Thus, the image quality can be remarkably improved without being substantially deformed even in the state of being attached to the drive shaft, and without reducing the reflection surface accuracy, the surface inclination accuracy, and the division accuracy. Further, there was no deformation over time in long-term use. Further, the assembling force (holding force) of the rotating polygonal mirror on the drive shaft can be set relatively large, the reliability as a laser beam optical system is improved, and the assembling / adjusting time can be greatly reduced. Since the yield is improved, a significant cost reduction can be expected.

[Brief description of the drawings]

FIG. 1 is a front view showing a state in which a rotary polygon mirror as a first embodiment is assembled to a motor.

FIG. 2 is a sectional view of FIG.

FIG. 3 is a perspective view showing a rotary polygon mirror as a second embodiment.

FIG. 4 is a perspective view showing a rotary polygon mirror as a third embodiment.

[Explanation of symbols]

 1,20,30 ... Rotating polygon mirror 4,26,36 ... Mounting surface 10 ... Motor 12 ... Rotor 13 ... Drive shaft 14 ... Mounting seat 14a ... Seat surface

Claims (1)

(57) [Claims] 1. A rotary polygonal mirror which is made of a polygonal body and rotates and deflects and scans light on each surface by rotating, wherein a mounting surface formed from a resin material into a predetermined shape and pressed against a mounting seat surface of a rotary drive shaft. , The center line average roughness is about 0.1 μm or less, and the maximum roughness is about 1.0
A rotating polygon mirror characterized in that it is finished to a mirror surface of μm or less.