JPH03214116A - Rotary polygon mirror - Google Patents

Abstract

PURPOSE:To form the rotary polygon mirror which has excellent surface accuracy and durability by using synthetic resin by molding the rotary polygon mirror by using a ring-shaped gate which is provided with a hole part. CONSTITUTION:Molten resin which is pressed in a metallic mold for molding from the nozzle of a molder is charged in a runner 32 through a spool 31 and pressed and then injected radially into the cavity part 10A of the rotary polygon mirror 10 after passing through the thin ring-shaped gate 33. The gate 33 is sheared and separated and after the cavity part 10A is sealed, compression molding is carried out by mold clamping. Therefore, such trouble that the resin in the cavity 10A flows backward toward the gate through the compressing operation of the metallic mold after the injection is eliminated. Consequently, the rotary polygon mirror 10 can be molded out of the resin by the injection and compression molding method, and the rotary polygon mirror which has high surface accuracy as compared with a rotary polygon mirror made of a metallic material, glass, etc., and is made of the synthetic resin is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotating polygon mirror used in an optical device having a laser scanning system.

[Background of the invention]

A rotating polygon mirror included in an optical device that functions as a laser scanning system is generally a regular polygonal prism member such as a regular octagon whose side surfaces are reflective mirrors. It is used for purposes such as converting and scanning the light receiving surface.

Traditionally, aluminum alloy or optical glass is used as the material for such rotating polygon mirrors, and after forming them into regular polygons by cutting or grinding, the former is processed with a carbide cutting tool, while the latter is polished. The method used was to form a reflective mirror surface through processing.

Grinding glass materials requires a huge number of machining processes to achieve flatness accuracy, and compared to metal cutting, it requires a huge number of machining processes.
The cost is more than 0 times higher, and even in metal cutting, the curvature of the machining mark due to the cutting tool or the A of the material itself
There were small drops due to difficulties in processing such as scattering during light scanning due to holes in the Q material, and the cost was high compared to the material cost and processing cost, not compared to the processed teaching molded product.

[Problem that the invention seeks to solve]

Rotating polygon mirrors made of metal or glass are heavy, so the drive system and control system are complicated and expensive to rotate at high speeds, and the rotating polygon itself also forms a highly accurate reflective mirror surface. In order to do so, there are problems that need to be solved, such as the manufacturing process requires a great deal of labor and time and increases manufacturing costs.

Under these circumstances, attempts are being made to mold rotating polygon mirrors using synthetic resin materials instead of metal materials or glass, but injection molding of resin materials does not allow for the complicated shape of rotating polygon mirrors. Therefore, the molding pressure of the resin material becomes uneven, which tends to cause warping and sink marks due to internal stress, and as a result, it is extremely difficult to obtain a reflective mirror surface with sufficient mechanical strength and high surface precision.

The present invention solves and improves this point, and by improving the structure of the gate of the molding die, the surface accuracy and durability are comparable to those made of conventional metal materials or glass. The object of the present invention is to provide a rotating polygon mirror made of synthetic resin.

[Means for Solving the Problems] The above object is to provide a rotating polygon mirror whose surface is a mirror surface of a polygon with a hole in the center, in which the rotating polygon mirror is shaped by a ring-shaped gate provided in the hole. This is achieved by a rotating polygon mirror, which is characterized by the following characteristics:

〔Example〕

An embodiment of the present invention is shown in FIGS. 1-3.

Figure 1 shows the shape of a rotating polygon mirror according to the present invention, Figure 2 shows the type of gate for injection molding the rotating polygon mirror, and Figure 3 shows the structure of a mold for injection molding. It is something that

The rotating polygon mirror IO is a regular polygonal member with eight flat surfaces on its outer circumferential surface, and is made of thermoplastic or thermoplastic material that is injection-molded radially around the hole 11 into which the driving rotation shaft is inserted. It is a plate-shaped molded member made of curable resin.

For example, polycarbonate resin is preferably used as the resin material forming the rotating polygon mirror 10 because it has excellent mechanical strength and has good transferability after molding, so that a high-quality finished surface can be obtained. A metal coating of aluminum is deposited on each of the flat parts to form 8 mirror-finished parts 1.
2 is formed, and its surface is further coated with SiO□ or the like as a protective film.

The rotating polygon mirror 10 is attached to a driving rotating shaft by fitting the hole 11 and rotates as a unit, and the laser beam irradiated to each mirror surface 12 is sequentially changed in its traveling direction. The light is scanned onto the light receiving surface.

Each of the mirror parts 12 requires a surface precision of 0.2 μm or more, and therefore, it is preferable to use injection compression molding to obtain a high degree of flatness through the injection molding of the rotating polygon mirror 10 with a precise surface finish. However, if the gate is structured such that the injection direction of the resin matches the compression direction of the mold, there is a problem in which the resin inside the cavity flows back toward the gate due to the compression action of the mold after injection. I couldn't make it happen.

Therefore, in the present invention, we propose a disk gate type in which resin is injected radially from the inside of the hole 11 into the cavity of the mold, thereby making it possible to mold a rotating polygon mirror by the injection compression molding method described above. That is.

FIG. 2(A) shows the setting side of the disk gate described above with respect to the rotating polygon mirror 10 with a dashed line, and FIG. 2(B) is a sectional view taken along the arrow BB.

Molten resin is press-fitted into the mold from the nozzle of the molding machine, passes through the sprue 31, fills the runner 32, is pressurized, and then passes through the thin ring-shaped gate 33 to the rotating polygon mirror 1.
0 is radially injected into the cavity 10A. Thereafter, the gate 33 is sheared and separated to bring the cavity 10A into a sealed state, thereby enabling compression molding by clamping the mold.

The specific structure and molding action of the mold used in such injection compression molding will be explained with reference to FIG.

The mold includes a fixed side mold plate IA and a mounting plate I that supports this.
The movable mold 2 consists of a fixed side mold 1 consisting of a movable side mold plate 2A, a receiving plate 2B, and a mounting plate 2C that supports these. As shown in the upper part of , the movable template 2A is connected to the fixed template IA.
The first stage of mold clamping maintains a gap of 0.2 to 0.3 mm from It is operated by switching to the second stage of mold clamping.

That is, the sprue bush 3 provided on the stationary mold l
When a nozzle (not shown) of a molding machine is pressed against the sprue bushing 3, the sprue bush 3 slides to the right within the stationary mold plate IA and stops at the position shown.

Next, the movable mold 2 is moved to the left and the molten resin is press-fitted while it is set at the first stage position. In this case, the movable member 4 built in the movable template 2A slides to the left under the force of the compression spring 5, and abuts the abutment surface 4A bored on the left end surface against the end surface of the sprue bush 3. and held in the position shown.

As shown in FIG. 2(A), the abutment surfaces 4A are provided at four equal intervals, and the gaps between the abutment surfaces 4A form the gates 33 of the disk gate described above.

In this state, molten resin is press-fitted, and the resin passes through the sprue 3L runner 32 and is radially injected from the gate 33 into the cavity portion 10A.

After injection is completed, the pressure contact of the nozzle is released and the movable member 4 further slides to the left under the bias of the compression spring 5, whereby the gate 33 is sheared and separated, and at the same time, the movable member 4 is moved to the movable template IA. Said cavity part by engagement of! The OA is brought into a sealed state, and the movable mold 2 is subsequently moved to the left to proceed to the second stage, and as a result, the rotary polygon mirror IO in the cavity portion lOA is compressed and molded.

〔Effect of the invention〕

According to the present invention, it has become possible to mold a rotating polygon mirror using resin by injection compression molding, and a rotating polygon mirror made of synthetic resin has a high surface precision that is comparable to those made of metal or glass. It was realized.

As a result, it has become possible to provide a rotating polygon mirror that is extremely useful in practice and has a reduced weight that does not place a burden on the drive system or control system, and also allows for mass production, resulting in a significant reduction in manufacturing costs.

[Brief explanation of drawings]

FIG. 1 is a plan view and a side view of a rotating polygon mirror according to the present invention. FIG. 2 is an explanatory diagram showing the configuration of a disk gate for the rotating polygon mirror. FIG. 3 is a sectional view of an injection compression mold.

Claims (2)

[Claims] (1) A rotating polygon mirror whose surface is a mirror surface of a polygon with a hole in the center, characterized in that the rotating polygon mirror is formed by a ring-shaped gate provided in the hole. mirror. (2) The rotating polygon mirror according to claim 1, wherein the rotating polygon mirror is resin-molded by injection compression molding.