JPS63241515A - Polygon mirror - Google Patents

Abstract

PURPOSE:To permit stable high-speed rotation with compact constitution by inserting and disposing a magnet into a magnet rotating body and mounting a back up ring on the rotating body so as to face the magnet. CONSTITUTION:The magnet 7 is fitted and disposed in an insertion hole 8 for fitting formed to the rotating body 3 and the back up ring 9 consisting of a magnetic body is freely attachably and detachably mounted on the rotating body 3 so as to face the magnet 7 and to press and held the magnet 7 so that the magnetic lines of force of the magnet 7 can be connected in a circumferential direction. Balance adjustment of a polygon rotor can, therefore, be made by the back up ring 9 and the magnet 7 provided on the polygon rotor can be exactly retained; in addition, the stable rotational operation is permitted by connecting the magnetic lines of force in the circumferential direction. The reduction of the thickness, size and weight of the mirror is thereby permitted and the higher rotating speed is obtd.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is a laser scanning optical system used in laser printers, barcode leagues, laser copying machines, etc., in which laser light is reflected and irradiated onto the surface of a photoreceptor. This relates to a polygon mirror for

[Conventional technology]

As shown in Figure 6, a conventional polygon mirror is a well-known example of a sealed structure suitable for high-definition image processing.In a laser printer, a polygon mirror is rotated by laser light from a laser unit consisting of a semiconductor laser, gas laser, etc. The light is reflected by a mirror b of the rotor a and irradiated onto the surface of the photoreceptor, and the polygon rotor a is configured to be rotated by a drive motor C on a fixed shaft d via a sleeve e.

A large number of grooves for generating dynamic pressure are formed on the outer peripheral surface of the fixed shaft d, so that dynamic pressure for supporting thrust loads and radial loads is generated by rotation of the rotating sleeve e. That is, this groove for generating dynamic pressure generates dynamic pressure by the lower groove f having a herringbone shape, the middle groove f forming the herringbone shape, and the upper groove f, thereby generating a radial load. Supports the central groove r! This allows air to be sent to the upper surface of the fixed shaft d, thereby increasing the air pressure between the fixed shaft d and the thrust bearing g at the upper end, thereby supporting the thrust load.

A polygon rotor a is screwed to the upper part of the rotating sleeve e, and a rotor magnet CI is fixed to the lower part.
And stator coil C for driving rotor magnet CI! is fixed so as to surround the rotor magnet Cl and serves as a drive motor C, and transmits the laser light irradiated from the outside onto the mirror b of the polygon rotor a, and the laser light reflected to the desired exposure surface. The laser entrance/exit window is formed on a part of the upper circumferential surface of the outer cylinder l, and the polygon rotor, which is rotated at high speed by the drive motor C, not only needs to maintain high rotation accuracy but also has a high reflection The gap between the fixed shaft and the rotating sleeve is made extremely narrow in order to minimize surface runout.

[Problem that the invention seeks to solve]

However, since such laser printers reproduce clear characters and images at high speed, the polygon mirror must be rotated at high speed and with minimal tilting of the reflective surface. It is manufactured by cutting a flat plate of aluminum alloy, which is easy to cut and has a high reflectivity, with diamonds, but in order to maintain its shape, the thickness was over 10 cranes. However, when the polygon mirror rotates at high speed, most of the load is due to air resistance at the outer edge of the polygon, and the area that reflects the laser beam is I
Considering that the polygon mirror has a narrow width which is sufficient even if it is less than N, the power loss caused by the disturbance of the surrounding air by the polygon mirror becomes extremely large.

For these reasons, the sliding part between the fixed shaft and the rotating sleeve is machined with extreme precision to effectively generate dynamic pressure from the air, and the rotating sleeve, polygon rotor,
Rotating parts such as the mirror and rotor magnets must be precisely machined, and at the same time the mass balance must be suitably adjusted.

However, the inclination of the reflective surface of the polygon mirror is ±1.
In order to achieve a diameter of 5 μm or less, a fixed shaft with a length of 50 am or more must be precisely machined and the distance between it and the rotating sleeve must be 3 μm or less, making mass production difficult and requiring even higher speed image processing. When performing this, it is desired that the rotational speed of the polygon mirror be 30.0OOrp- or more, but in the case of such high-speed rotation, the radial load on the fixed shaft increases, and the support by the air film is insufficient. This was extremely difficult, and the balance adjustment was extremely complicated and problematic.

The present invention aims to accurately eliminate these conventional drawbacks by creating a compact polygon rotor that is easy to balance, has little air resistance during rotation, and can rotate at high speed.
Furthermore, it is an object of the present invention to provide a polygon mirror that has a simple structure, is easy to manufacture, and is inexpensive, and is capable of stable high-speed rotation with little tilting of its reflecting surface and that can accurately reflect laser light and the like.

Means for Solving Problem C] The present invention provides a polygon rotor in which a rotating body with a mirror surface is rotatably provided on a fixed shaft provided on a support body, a magnet provided on the rotating body, and a polygon rotor facing the magnet. and a stator coil for rotating the rotating body, the magnet being inserted into the rotating body, and a backup ring corresponding to the magnet being attached to the rotating body. .

〔Example〕

Embodiments of the present invention will be described with reference to FIGS. 1 to 3. The rotating body 3 is formed into a flat plate, has a through hole 1 formed in the center, and has a plurality of mirror surfaces 2 whose outer periphery is a regular polygon. A polygon rotor is formed by penetrating the hole 1 and rotatably mounted on a fixed shaft 5 provided on the support 4. A stator coil 6, which is fixed in parallel with the flat rotating body 3 and rotates the polygon rotor, is attached to the support 4. In preparation for this, a motor unit for rotating the rotating body 3 is configured by a magnet 7, which is a permanent magnet or a secondary conductor provided on the rotating body 3, and the stator coil 6, and the magnet 7 is formed on the rotating body 3. A backup ring 9 made of a magnetic material is removably attached to the rotating body 3 in correspondence with the magnet 7 to press and hold the magnet 7, and the magnetic field lines of the magnet 7 are are connected in the circumferential direction.

The rotating body 3 is disposed facing a sliding member 10 having a groove 11 for generating dynamic pressure on the sliding surface interposed on the supporting body 4. A cylindrical portion 3 into which a backup ring 9 can be fixedly or removably fitted
1, but it is also possible to use a magnet that can be fitted with a yoke that covers a disk-shaped rotor core.The magnet 7 is embedded in the insertion hole 8 of the rotating body 3, and The upper surfaces may be flush with each other, or the magnet 7 may be placed in a recessed state or a protruding state from the upper surface of the insertion hole 8, and the bank up ring 9 may have a corresponding protruding portion inserted into the recess. Or, if it is in a protruding state, use one with four parts that fit into it. Further, the backup ring 9 is made of a magnetic material to facilitate connection of lines of magnetic force in the circumferential direction and also serves as reinforcement, but it may be made of another material with a magnetic material embedded therein as required.

The sliding member 10 is a rectangular or circular plate with a surface for generating dynamic pressure on one or both of the sliding surfaces of the surface facing the rotating body 3 and/or the surface facing the stator coil 6. The groove 11 is made of a hard ceramic material, such as a SIC sintered body, an α-3iC sintered body containing BeO, or a 5iJa sintered body, in which a spiral groove is formed leaving the land portion 101, for example, for a thrust bearing. The rotating body 3 may also be made of a hard ceramic material, and in this case, dynamic pressure generating grooves 11 may be formed on the sliding surface as necessary.

A plurality of insertion holes 8 are formed and arranged in an annular shape in the rotating body 3, and as shown in the example in FIG.
5 fixed shafts connected and arranged in a ring shape so as to be formed alternately 5
It is also possible to have a plurality of magnetic poles annularly magnetized along a plane perpendicular to It is convenient to use a coating layer with a high ratio as part of the mirror.

11 in the figure. A large number of herringbone-shaped grooves for generating dynamic pressure are provided on the outer circumferential surface of the fixed shaft 5 or a corresponding surface thereof. Reference numeral 12 is an integrated cover, which is fitted onto the support 4 to provide a sealed structure for laser printers, etc., and can be omitted when high clarity is not required, such as for bar code leagues. Reference numeral 13 is a light projection window, and reference numeral 14 is a fastening nut that prevents loosening due to temperature expansion and time.

In addition, when the spiral direction of the dynamic pressure generation groove 11 is provided on both sides, it may be carved in the opposite direction as necessary so that it can receive thrust loads in both forward and reverse rotations, making it better for maintenance and safety. Alternatively, the mirror surface 2 on the outer periphery of the rotating body 3 can also be balanced with aluminum foil.

In the specific example shown in FIG. 5, a sleeve-shaped bushing 5 made of ceramic material has a herringbone-shaped groove on the outer periphery on a metal support shaft 5 as a fixed shaft. The means for restricting the flying height of the rotary body 3 may be selected from an upper sliding plate 15, a washer, or other stopper provided on the fixed shaft 5 at a position above the rotary body 3. However, by attaching a coil spring or other reliable member to the sliding plate 15,
The structure may be such that the reliable structure or the like is provided on the fixed shaft 5 at the upper part of the rotating body 3 as a pressing member.

In this embodiment, the upper sliding plate 15 is made of a ceramic material, and is provided with grooves for generating dynamic pressure on the sliding surface side as necessary, and is provided opposite to the rotating body 3. A coil spring 17 is interposed between the washer 16 and the rotating body 3 to serve as a floating height restraining mechanism.

The support body 4 is made of a magnetic material and is designed to constantly exert an attractive force between it and the magnet 7 to prevent the rotating body 3 from falling, and to obtain stable rotation using this attractive force. Furthermore, the fixed shaft 5 is precisely machined for parallelism between the shaft end faces and perpendicularity with the herringbone groove surface, but if necessary, a similarly precision-machined sleeve-shaped bushing 5 may be fitted and provided. In these cases, the fixed shaft 5 or bushing 51 may be used as a stepped shaft to correspond to each member.

Note that the fixed shaft 5 and the support body 4 may also be made of a ceramic material mainly composed of SiC. In addition, a flat stator coil 6 is provided on the support body 4 in relation to the magnet 7 provided on the rotary body 3, and the rotary body 3 of the polygon rotor is rotated as a motor. The end surface of the movable member 1O is processed so that the fixed shaft 5 is perpendicular to the inner peripheral surface of the through hole 1 and perpendicular to the mirror surface 2 formed on the outer peripheral edge thereof.

Therefore, the rotating body 3 with the mirror surface 2 can be rotated smoothly with good mass balance, fluid balance, and magnetic balance on the fixed shaft 5 on the support 4, and can be operated with low air resistance during rotation. be.

In this case, the grooves 11 for generating dynamic pressure are formed on one or both of the corresponding surfaces of the sliding member 10 made of ceramic material interposed between the support body 4 and the rotating body 3, and the groove 11 for generating dynamic pressure is formed on the other surface. The thrust bearing part is a smooth plane, and the radial bearing part is the outer peripheral surface of the fixed shaft 5 or the through hole 1.
A herringbone-shaped groove 11 for generating dynamic pressure is provided on either one of the cylindrical surfaces of the cylindrical surface. , and the other surface is a smooth cylindrical surface. In this embodiment, a dynamic pressure generating groove 11 for supporting a thrust load and a dynamic pressure generating groove 111 for supporting a radial load are formed. Each groove has a depth of about 3 to 10 μm layers. In addition, this dynamic pressure generation groove 11 is connected to the rotating body 3.
It is also good to groove both sides of the sliding member 10 or sliding plate 15 to improve balance and eliminate deformation.
Compared to when forming spiral grooves on only one side, when forming spiral grooves on both sides, it is necessary to select a thickness that will not deform, since ceramic plates that are thinner than the diameter may deform after forming the grooves. .

The sliding plate 15 and/or the sliding member 10 is made into a smooth land surface with an overall waviness of 0.3 .mu.m or less and a maximum surface roughness of 0.1 .mu.m, and is then roughened to 3 to 10 .mu.m by shot blasting. This is a spiral groove with a depth of .

Note that when manufacturing a radial bearing that utilizes the hydrodynamic effect, the above-mentioned shot blasting can be used to form grooves. In any case, the dynamic pressure generating groove 11 can be machined with high precision using a hard ceramic material, and the shape of the sliding part suitable for generating dynamic pressure can be maintained even when dynamic pressure is generated. Furthermore, it can be used effectively and with durability even under a certain amount of load, even against solid friction that occurs when starting and stopping.

〔Effect of the invention〕

The present invention provides a polygon mirror that includes a magnet provided on a rotating body and a stator coil that is opposed to the magnet and rotates the rotating body, in which the magnet is inserted into the rotating body and backed up in response to the magnet. By attaching the ring to the rotating body, the balance of the polygon rotor can be adjusted using the bank up ring, and the magnets provided in the polygon rotor can be properly held down. Furthermore, the magnetic lines of force of the magnets are connected in the circumferential direction, resulting in stable rotation. Even if the thickness of the rotor core made of 6 permanent magnets or secondary conductors and the polygon rotor whose outer peripheral surface is a mirror part is thin, the amount of deformation can be reduced. Compared to conventional polygon mirrors, it can be made significantly thinner, smaller, and lighter, and it can also reduce air resistance, and the same rotational speed as conventional polygon mirrors can be obtained with significantly less power. If you input the same amount of power as the polygon mirror, you will be able to obtain a higher rotation speed, and the function as a polygon mirror that stably scans the light beam will be maintained well at all times. It is a compact polygon mirror that is easy to rotate, has little air resistance during rotation, and can rotate at high speed.
A polygon mirror with a simple structure and low cost that can rotate stably at high speed with little tilting of the reflecting surface and can accurately reflect laser beams and the like can be obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention, FIG.
1 is a plan view taken along line 1, FIG. 3 is a plan view taken along line 1-ff in FIG. FIG. 6 is a longitudinal sectional view of a conventional example. 1... Through hole, 2... Mirror surface, 3... Rotating body, 31
... Cylindrical part, 4... Support body, 5... Fixed shaft, 6...
... Stator coil, 7 ... Magnet, 8 ... Insertion hole, 9 ... Backup ring, 10 ... Sliding member, 11 ... Dynamic pressure generation groove, 14 ... Fastening Nand,
15...Sliding plate, I6...Washer, 17...Spring.

Claims (4)

[Claims] (1) A rotating body with a mirror surface is rotatably mounted on a fixed shaft provided on a support body to form a polygon rotor, and a magnet provided on the rotating body and a stator coil facing the magnet and rotating the rotating body are provided. 1. A polygon mirror comprising: the magnet being inserted into a rotating body; and a backup ring corresponding to the magnet being attached to the rotating body. (2) A patent in which the magnet is a permanent magnet or a secondary conductor fitted into a plurality of annular insertion holes formed in the rotating body, and is held under pressure by the backup ring made of a magnetic material. A polygon mirror according to claim 1. (3) The rotating body is a regular polygonal flat plate with a through hole in the center, and is disposed facing a sliding member having a groove for generating dynamic pressure on the sliding surface interposed on the support. 2. A polygon mirror according to claim 1 or 2. (4) The rotating body has a through hole in the center of a flat rotating plate, and a cylindrical part around the through hole into which the backup ring can be detachably fitted. A polygon mirror according to any one of ranges 1 to 3.