JPH05232396A - Rotary polygonal mirror - Google Patents

Abstract

PURPOSE:To obtain the rotary polygonal mirror which maintains practicable accuracy while its weight and size are reduced and its assembly is facilitated as the rotary polygonal mirror for an optical device having a laser beam scanning system, etc. CONSTITUTION:A symbol 1 is the reflection surface of the rotary polygonal mirror constituted by coating the surface of a polygonal base body 3 with a metallic reflection film and a transparent protective film. The polygonal base body 3 is constituted by combining a first member 31 made of a rigid material-reinforced resin to be joined to a revolving shaft 2 and a second member 32 made of a resin covering the outer peripheral surface of this member, by which the rotary polygonal mirror eliminating the change in the accuracy of the reflection surfaces by the centrifugal force at the time of high-speed rotation and the moisture absorption at the time of a high temp. and high humidity and having a high reflectivity is obtd. The revolving shaft 2 made of metal is integrally formed with the first member 31 in such a manner that the resin infiltrates to the groove 2a at its front end. The second member 32 is formed on the surface thereof with the revolving shaft as a reference axis and, therefore, the parallelism of the revolving shaft and the respective reflection surfaces 1 is provided with the high accuracy. The connection to a motor is facilitated by the tapered part 2c at the other end of the revolving shaft and a good plane tilt is attained.

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 used in an optical device having a laser beam scanning system.

[0002]

2. Description of the Related Art A rotary polygon mirror is used in an optical device having a laser beam scanning system, such as a laser beam printer or a digital copying machine, and has a function of scanning a laser beam onto a printing drum at a high speed.

Conventionally, optical glass or aluminum alloy has been mainly used as a material for the rotary polygon mirror.
In general, these are formed into regular polygons by grinding or cutting, and then, in the former case, a polishing process is performed, and in the latter case, a reflecting mirror surface is formed by a cutting process with a diamond bite.

[0004] To form a mirror surface of a glass material by polishing, it required a great deal of skill and a huge amount of processing time. In addition, when cutting aluminum alloy with a diamond bite, it is possible to shorten the processing time by cutting 5 to 10 layers, but it is difficult to automate the processing and scratches on the mirror surface due to cutting chips. Were likely to occur and productivity was extremely poor. This rotating polygon mirror occupies the weight of the laser beam scanning system having a high cost.

Typical examples of conventional rotary polygon mirrors are shown in FIG. 7 and FIG. 7 is optical glass or aluminum alloy, and the reflecting mirror surface 8 is mirror-finished by the above-mentioned means,
Thereafter, in the former case, the metal reflection film and the transparent protective film 10
However, in the latter case, the transparent protective film 10 is deposited by means such as vacuum deposition or sputtering. Transparent protective film 1
For 0, a relatively hard transparent film such as SiO 2 is deposited to about 2000 angstroms.

Further, it has a hole 9 in the center, is inserted into the rotor portion of a motor (not shown) with the lower end portion of the rotating polygon mirror as a reference, and is pressed and fixed from above by a spring member. Since the accuracy of the rotary polygon mirror is closely related to the printing quality, for example, the flatness of each mirror surface is λ / 4 and the surface roughness of each mirror surface is 0.02μ.
mRmax and relative tilting require about 50 seconds.

[0007]

Conventionally, in order to achieve the above-mentioned accuracy by the above-mentioned machining, an extremely large number of steps and man-hours have been required, which has been a factor of high cost.

In order to solve such a conventional problem, a resin or a composite resin material mainly containing a resin is molded by a mold to obtain a polygonal substrate, and then a metal reflection film and a transparent protective film are provided on each side surface. Several methods have already been proposed for attaching and obtaining a rotary polygon mirror.

As an example, Japanese Patent Laid-Open No. 19622/1986
The rotating polygon mirror proposed in Japanese Patent No. 0 is shown in FIG. 1
Reference numeral 1 denotes a polygonal base body formed by molding a resin such as PMMA, ABS, polycarbonate or the like, or a composite material of these resins and another material such as glass fiber, carbon fiber or the like, and 12 is a reference surface and a polygonal base body. It is molded to the shape and accuracy required for molding. Thirteen
Is a metal reflective film of, for example, Cu, Al, Ag, or the like having an enhanced reflection function, and 14 is a transparent protective film of, for example, SiO, TiO ₂ or the like whose main purpose is to protect the metal reflective film 13. Further, it has a hole 15 in the central portion, and is inserted into the rotor portion of a motor (not shown) with reference to the lower end portion of the rotating polygon mirror, and is pressed and fixed by a spring member from the upper portion. This proposal is a resin molding of a conventional rotary polygonal mirror of an aluminum base, and has the following problems.

(1) Since each mirror surface is at a right angle to the reference surface 12 and no draft can be provided, the mold becomes a split mold, and each mirror surface and the reference surface can be maintained at the required accuracy at the same time. difficult.

(2) Since the thickness from each mirror surface is not uniform, sink marks are likely to occur during molding, and it is difficult to improve the accuracy of flatness.

(3) Since the thickness from each mirror surface is thick and not uniform, the flatness changes at high speed rotation.

Further, Japanese Patent Application Laid-Open No. 64-3619 discloses that
A method is disclosed in which the central hole is used as a boss, the thickness of each mirror surface is reduced, and injection pressure molding is performed. Problem (2) in the above-mentioned JP-A-61-196220
And (3) are resolved, but issue (1) is not resolved,
At the same time, it is difficult to attach this boss to the motor accurately.

Further, in Japanese Patent Application Laid-Open No. 1-180512, a base material made of a resin in which the center hole is used as a boss and the thickness of each mirror surface is thinned and at the same time, the rigidity is increased by a stiffening material, , A technique of integrally molding a reflecting surface member made of resin with high processing accuracy is disclosed. However, similarly to the above, the problem (1) is not solved, and since the boss portion and the reflecting surface member are made of different materials, it is difficult to maintain the accuracy of surface tilt.

Further, Japanese Unexamined Patent Publication No. 3-24515 discloses a technique in which a rotary polygon mirror based on a polygonal base made of a photocurable resin is fixed to a rotary shaft connected to a motor by photocuring. .. As described above, since the surface tilt of each mirror surface requires extremely strict accuracy, it is generally difficult to maintain accuracy in the method of bonding and fixing the processed rotary polygon mirror to the shaft.

The present invention eliminates the above-mentioned drawbacks of the prior art, and an object thereof is to provide a rotary polygon mirror based on resin molding with high accuracy and at low cost. Especially the rotary polygon mirror based on resin molding,
If the molding is performed with the lower end surface as a reference, it is difficult to maintain the accuracy of the lower end surface and each mirror surface because of the mold structure. Accordingly, it is an object of the present invention to provide a rotary polygon mirror which eliminates such a reference of the lower end surface, has good moldability at the same time, and can be easily and highly accurately connected to a motor.

Further, the rotary polygon mirror based on resin molding has a problem that each mirror surface changes due to centrifugal force during high-speed rotation and moisture absorption during high temperature and high humidity. However, the present invention is practical in such cases as well. The present invention provides a rotary polygon mirror that can be maintained at high accuracy.

[0018]

In order to achieve this object, a rotary polygon mirror of the present invention has a rotary shaft made of metal, a polygonal base made of resin, and an outer peripheral surface of the polygonal base. A second member forming at least an outer peripheral surface of the polygonal substrate, the first substrate being joined to the rotating shaft by a molding means, and the first member being joined to the rotating shaft. The outline is that it is composed of the above-mentioned members.

More preferably, the first member is a resin material reinforced with a stiffening material, and the second member has a substantially uniform thickness of 1 mm or less, and the outer circumference of the first member is small. On the surface and on the end surface on the side opposite to the extending side of the rotation axis, an even more preferable means is such that the polygonal base body has a concave portion such that the cross-section constituting the outer peripheral surface is smaller than the axial thickness, The concave portion has a radial rib so as to connect each corner of the first member to a cylindrical portion that joins the rotation shaft, and an even more preferable means is that the outer surface of the second member is the metal reflection film and the metal reflection film. It includes a structure of being covered with a transparent protective film.

[0020]

When the rotary polygon mirror is made of resin or a composite material mainly made of resin, it is possible to reduce the inertia by reducing the specific gravity as compared with the conventional glass or metal. Further, since it is joined to the rotary shaft by the molding means, there is no need to use the conventional lower end surface as a reference surface, and by so-called insert molding with the rotary shaft as a reference, each mirror surface of the rotary shaft with high accuracy can be obtained. It is possible to realize a rotating polygon mirror having the same.

Further, the polygonal base body is formed by combining a first member joined to the rotating shaft and at least a second member forming an outer peripheral surface, and the first member is a stiffening member. The second member is made of a resin material that is reinforced with a stiffener, and the second member has a substantially uniform thickness of 1 mm or less and is opposite to the outer peripheral surface of the first member and the rotation axis extending side. Since it is configured to be provided on the end face, it is possible to realize a rotary polygon mirror in which the surface accuracy does not change due to centrifugal force during high-speed rotation or moisture absorption during high temperature and high humidity, and the reflectance of each mirror surface is good.

Further, the polygonal base body has a concave portion such that the cross section constituting the outer peripheral surface is smaller than the axial thickness, and the concave portion is a cylindrical portion for joining each corner and the rotary shaft in the first member. By having the radial ribs that connect to each other, it is possible to simultaneously realize a rotary polygonal mirror in which the inertia is further reduced and the surface accuracy does not change due to centrifugal force during high-speed rotation.

Further, since the second member is covered with the metal reflection film and the transparent protective film, even when a material having a high water absorption rate is used as the second member, the surface under high temperature and high humidity conditions is high. A rotary polygon mirror with little change in accuracy can be realized.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a rotary polygon mirror in one embodiment of the present invention, FIG. 2 is an enlarged view of a portion A in FIG. 1, FIG. 3 is a rear view, 1 is a reflecting surface of the rotary polygon mirror, and 2 is a rear view. Is a rotating shaft made of metal such as stainless steel and has grooves 2a and 2b near both ends.
And has a tapered portion 2c at the tip. 3 is a resin-molded polygonal substrate, on the surface of which a metal reflection film 5,
And the transparent protective film 6 is covered. The polygonal base 3 is configured by combining a first member 31 joined to the rotating shaft and a second member 32 forming an outer surface.

The rotating shaft 2 is set in the first mold in advance, and then the resin of the first member 31 is injected to be integrally molded.
Next, the rotary shaft integrated with the first member is set in the second mold and integrally molded with the second member 32. This second mold is precisely finished so that the parallelism of each reflecting surface 1 can be ensured with the required accuracy with respect to the rotation axis 2. It is also possible to mold the first member and the second member at the same time by a so-called two-color molding method.

The first member 31 is made of thermosetting resin such as epoxy type or polyester type, or thermoplastic resin such as polycarbonate, polyarylate, polyether sulfone, liquid crystal polymer, glass fiber, inorganic filler and various whiskers. A material mixed with stiffening material such as is mainly used. In particular, the optimum material is selected according to conditions such as high mechanical rigidity, low creep, low coefficient of thermal expansion, and low water absorption rate. It is molded by a known means. The resin material wraps around the groove 2a of the rotary shaft to be firmly bonded.

The second member 32 is mainly made of a natural material having good moldability such as PMMA, polycarbonate, polyarylate, etc., and is integrally molded so as to cover the first member as described above. The cross-sectional thickness t of the second member 32 is set to be approximately 1 mm or less over the entire circumference, and is preferably set to be about 0.5 mm which is thin within a range that allows molding. The mold for forming each mirror surface has sufficient flatness and surface roughness, and is molded by a means such as pressure compression molding so as to have the best transferability to the mold, thereby obtaining a flatness λ / 4. , Surface roughness 0.1 μm
Rmax or less can be realized.

For the first member and the second member, it is preferable to select materials of essentially the same system. This is because there is no fear of peeling due to the difference in the coefficient of thermal expansion, and the adhesion is good. For example, 30 glass fibers are used as the first member.
Very good results can be obtained by selecting a polycarbonate resin reinforced by mixing up to 50 wt% and a natural material of a polycarbonate resin as the second member.

On the surface of the second member 32, Ni, Cu,
A metal reflection film 5 of Al, Ag or the like is deposited by a known means such as vacuum deposition or sputtering to a thickness of about 1000 Å. Although not shown preferably, an oxide such as SiO ₂ is interposed between the second member 32 and the metal reflection film 5 as a base treatment.

Further, on the surface of the metal reflection film 5, for example, S
The transparent protective film 6 such as iO, TiO ₂ or MgF ₂ is vacuum deposited,
By a known means such as sputtering, the film thickness d = λ / 2n
Will be put on. Here, λ is the wavelength and n is the refractive index.

As described above, the surface roughness of the polygonal substrate 3 is 0.1 μmRmax or less and the metal reflection film 5 is obtained by sufficiently polishing the molding die so that the transferability to the die is good. By applying the transparent protective film 6, the reflectance of the reflecting surface 1 is secured at about 85%. More preferably, the transparent protective film 6 can have a reflectance of 90% or more by using a dielectric film having a different refractive index as a multilayer film structure of two layers or four layers.

Next, a second embodiment of the present invention will be described with reference to FIGS.
Shown in. 4 is a sectional view of the rotary polygon mirror of the present invention, FIG. 5 is an enlarged view of a portion B in FIG. 4, and FIG. 6 is a rear view. The same members as those in the first embodiment are designated by the same reference numerals, and the following description will be omitted.

The first member 31 forming the polygonal base 3 has a recess 4 on the extending side of the rotary shaft 2, and each corner is connected to a cylindrical part 31b by a radial rib 31a. The cross-sectional thickness a of each mirror surface portion is set to be substantially uniform over the entire circumference and smaller than the height b. Further, the sectional thickness a is the sectional thickness t1 of the first member 31.
And a sectional thickness t2 of the second member 32,
It is set as 1 ≧ t2. That is, the polygonal base body 3 has a thin two-layered structure and has a first member 31 integrally formed with the rotating shaft and a second member 32 configured to cover the surface thereof.
And are integrally molded. Therefore, as compared with the first embodiment, a further reduction in weight can be achieved and a rotary polygon mirror with improved surface accuracy can be realized by making the wall thickness uniform.

The rotary polygon mirror thus integrated with the rotary shaft is connected to a motor unit (not shown). The rotary shaft 2 is inserted into the bearing of the motor unit, and the retaining ring is inserted into the groove 2b to be fixed. Since the rotary shaft 2 has the tapered portion 2c at the tip thereof, it can be smoothly inserted. Of course, in order to rotate the rotary polygon mirror, a multi-pole magnet for generating a driving force is joined to the rotary polygon mirror by means of, for example, bonding, heat welding, or integral molding. Become a part.

The present invention illustrates the case where the shape of the polygonal base body is a regular hexagon, but the shape is not limited to this, and various regular polygons and, for example, a cylindrical side surface is partially cut into a flat surface to form a reflecting surface. The shape as described above is also included.

[0037]

As described above, according to the present invention, since the rotary polygon mirror is made of resin or a composite material mainly composed of resin, it is possible to lower the inertia by reducing the specific gravity as compared with the conventional glass or metal. Become. Further, since it is joined to the rotary shaft by the molding means, there is no need to use the conventional lower end surface as the reference surface, and so-called insert molding is performed with the rotary shaft as a reference, so that each mirror surface of the rotary shaft reference with high accuracy can be obtained. It is possible to realize a rotating polygon mirror having the same.

Further, since the polygonal base body is constructed by combining the first member joined to the rotary shaft and at least the second member constituting the outer peripheral surface, centrifugal force and high temperature during high-speed rotation are high. It is possible to realize a rotary polygon mirror in which the surface accuracy does not change due to moisture absorption at high humidity and the reflectance of each mirror surface is good.

Further, the polygonal base body has recesses such that the cross section constituting the outer peripheral surface is smaller than the axial thickness, and the recesses are cylinders for joining the respective corners and the rotary shaft by the first member. By providing the radial ribs so as to connect the parts to each other, it is possible to realize a rotary polygonal mirror at the same time in which the inertia is further reduced and the surface precision does not change due to centrifugal force during high-speed rotation.

Further, since the second member is covered with the metal reflection film and the transparent protective film, even if a material having a high water absorption rate is used as the second member, the change of the surface accuracy at the time of high temperature and high humidity is changed. It is possible to realize a rotating polygon mirror with less power consumption.

Further, by integrating the rotary polygon mirror with the rotary shaft, the joining to the motor becomes easy, and the deterioration of the surface collapse due to the joining to the motor can be prevented.

In summary, since a rotary polygon mirror can be obtained that is light weight, small in size, and easy to assemble, while maintaining practical accuracy, it is very effective in reducing the cost of the laser beam scanning system.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotary polygon mirror according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of part A in FIG.

FIG. 3 is a rear view of the rotary polygon mirror in the first embodiment of the present invention.

FIG. 4 is a sectional view of a rotary polygon mirror in a second embodiment of the present invention.

5 is an enlarged view of part B in FIG.

FIG. 6 is a rear view of the rotary polygon mirror in the second embodiment of the present invention.

FIG. 7 is a shape diagram showing an example of a conventional rotary polygon mirror (in the case of aluminum).

8 is a cross-sectional view of the mirror surface portion in FIG.

FIG. 9 is a sectional view of another example of a conventional rotary polygon mirror (in the case of resin).

[Explanation of symbols]

 1 Reflective Surface 2 Rotational Axis 2a, 2b Groove 2c Tapered Part 3,11 Polygonal Substrate 4 Recessed 5,13 Metal Reflective Film 6,10,14 Transparent Protective Film 7 Aluminum Alloy 8 Reflective Mirror Surface 9 Center Hole 12 Reference Surface 15 Center Part hole 31 First member 31a Rib 31b Cylindrical part 32 Second member

Claims (5)

[Claims] 1. A rotating shaft made of metal, a polygonal base made of resin, and a metal reflection film and a transparent protective film deposited on the outer peripheral surface of the polygonal base, the polygonal base being the rotating body. A rotary polygon mirror comprising a first member joined to a shaft by a molding means and joined to the rotary shaft, and a second member constituting at least an outer peripheral surface. 2. The rotary polygon mirror according to claim 1, wherein the first member is a resin material reinforced with a stiffening material. 3. The second member has a substantially uniform thickness of 1 mm or less on the outer peripheral surface of the first member and on the end surface opposite to the rotary shaft extending side. The rotating polygon mirror described in 1. 4. The polygonal base body is formed with a concave portion such that a cross-section forming an outer peripheral surface is smaller than an axial thickness, and the concave portion joins each corner and the rotary shaft with the first member. The rotary polygon mirror according to claim 1, wherein the rotary polygon mirror has radial ribs so as to connect to the cylindrical portion. 5. The second member is covered with the metal reflective film and the transparent protective film.
The described rotating polygon mirror.