JPS63266420A - Polygonal mirror - Google Patents

Abstract

PURPOSE:To reflect laser light with good accuracy under high speed rotation with high accuracy and to facilitate manufacture and assembly by shrinkage- fitting a metallic member onto a ceramic cylindrical body, grasping both side faces thereof by means of receiving members and providing dynamic pressure generating grooves to the opposite surfaces. CONSTITUTION:A bushing 51 is fitted onto a polygonal mirror rotor formed by shrinkage fitting of the outside circumferential member 32 onto the cylindrical body 31 consisting of ceramic nd both of the body 31 are grasped by the thrust receiving members 10 and the fitted together with the bushing by a stationary shaft 5. The dynamic pressure generating grooves 11 are provided to the sliding surface opposite to the members 10. Since the ceramic member is enclosed by the metallic member, the high-speed rotation can be executed while the breakage of said member is prevented. The perpendicular ity and parallelism of the polygonal rotor are greatly improved and the rotation is stabilized. The manufacture and assembly are facilitated and the cost is reduced.

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 9, a conventional polygon mirror is a 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 dynamic pressure generating groove section functionally generates dynamic pressure by the lower groove section f having a herringbone shape, and the middle groove section f2 and the upper groove section f forming the herringbone shape, thereby applying a radial load. Air is sent to the upper surface of the fixed shaft d through the support and central groove rt, 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.
A stator coil Ct for driving the rotor magnet C1 is fixed so as to surround the rotor magnet C3, forming a driving morph C, and a laser beam is irradiated from the outside onto the mirror b of the polygon rotor a; A laser entrance/exit window is formed on a part of the upper peripheral surface of the outer tube i, and a polygon rotor rotates at high speed by a drive motor C. The gap between the fixed shaft and the rotating sleeve is made extremely narrow because it is not only necessary to maintain high accuracy but also to reduce the surface runout of the reflecting surface.

[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 diamond-cutting a flat plate of aluminum alloy, which is easy to cut and has a high reflectance, but in order to maintain its shape, the thickness was over 10 meters. However, when a 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
Considering that the polygon mirror has a narrow width which is sufficient even if it is less than fl, the power loss due to 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, the fixed shaft with a length of 50 f1 or more must be precisely machined and the distance between it and the rotating sleeve must be 3 μm or less, which makes mass production difficult, and requires even higher speed image processing. When performing this, it is desirable to increase the rotation speed of the polygon mirror to 30,000 rpm or more, but in the case of such high-speed rotation, the radial load on the fixed shaft increases, and support by an air film is extremely difficult. It is difficult, balance adjustment is very complicated, and the assembly configuration and manufacturing process are troublesome.If the rotating body is made of ceramics, the ductility is extremely low, so cranks are likely to form on the surface. If a crack occurs on the surface during rotation, the tension caused by the centrifugal force of high-speed rotation will immediately spread to the crank, causing it to break and cause an accident.Furthermore, in the event of a breakage, it may escape from the window hole and fly out of the case, creating a dangerous situation. In addition, there were many problems such as safety concerns due to accidents that damaged expensive equipment.

The present invention aims to accurately eliminate these conventional drawbacks by creating a compact polygon mirror that significantly improves the perpendicularity and parallelism of the polygon rotor, has less air resistance during rotation, and is capable of high-speed rotation. In addition, the polygon mirror is easy to construct, easy to assemble, and inexpensive because the reflecting surface is less likely to fall, making it highly accurate, suitable for mass production, and good for safety.Also, stable high-speed rotation is possible, and the polygon mirror can accurately reflect laser beams, etc. It is intended to be provided in a suitable format.

[Means for solving problems]

The present invention comprises a polygon mirror rotor including a ceramic cylinder and a metal outer peripheral member that is shrink-fitted to the outer periphery of the cylinder, and a magnet and a mirror surface on the outer peripheral surface of the outer peripheral member. Further, a stator coil is provided corresponding to the magnet, a bushing is fitted to the ceramic cylinder body, and a movable part is attached to either the outer circumferential surface of the bushing or the sliding surface of the ceramic cylinder body facing the bushing. A groove for generating pressure is formed, and the ceramic cylinder is held between thrust bearing members from both sides and fitted with a fixed shaft together with a bushing, and a groove for generating dynamic pressure is formed on the sliding surface facing the bearing member. This is a polygon mirror characterized by the following.

〔Example〕

Embodiments of the present invention will be described with reference to FIGS. 1 and 2. A through hole 1 is formed in the center, and the through hole 1 forms a flat rotating body having a plurality of mirror surfaces 2 whose outer periphery is a regular polygon. 3. Ceramic cylindrical body. and a metal outer circumferential member 3□ which is shrink-fitted and fixed to the outer periphery of the cylindrical body 3I, and the outer circumferential member 3!
A polygon mirror rotor 3 is formed by forming a plurality of mirror surfaces 2 whose outer peripheral edges are regular polygons, and this rotor 3 is passed through the through hole 1 and placed on the outer periphery of a fixed shaft 5 provided on a support 4. A bushing 5. has a groove 111 for generating dynamic pressure formed on its outer circumferential surface. A stator coil 6 is provided on the support body 4 or the cover integral 12, and is provided on the support body 4 or the cover integral 12, and is fixed in parallel with the outer circumferential member 3□ and rotates the rotor 3, and is provided on the outer circumference member 3□ of the rotor 3. A motor unit for rotating the rotor 3 is constituted by a permanent magnet or a secondary conductor magnet 7 and the stator coil 6, and a thrust receiving member 10 made of metal or ceramic material is provided between the rotor 3 and the support body 4. This rotor 3
Dynamic pressure generating grooves 11.degree. 11 are formed on either or either of the sliding surfaces formed opposite to the sliding surfaces.

The cylindrical body 3I of the rotor 3 is a cylindrical body or a rectangular cylindrical body with a circular through hole in the center, and the fixed shaft 5 or a bush 5 that is fitted and supported on the fixed shaft 5. The receiving member 10 is a rectangular or circular plate that has a surface facing the magnet 7 of the rotor 3 and the stator. On the surface facing the coil 6, the cylindrical body 3. It is provided on both sides of the axial direction side surface and holds the cylindrical body 3I therebetween. Also, this receiving member 1 is attached to the cylindrical body 3I.
Dynamic pressure generation grooves 11 on both sliding surfaces of the surface corresponding to 0
For example, a hard ceramic material, such as St.
C sintered body, α-5iC sintered body containing BeO, or 5iJ
4. It is preferable to form the thrust bearing part by using a sintered body or the like, and the receiving member 10 may also be a thrust receiving plate by using a flat plate of hard ceramic material. A groove for generating dynamic pressure may be formed on the sliding surface.The clearance between the rotor 3 and the receiving member 10 of the thrust receiving plate is 5 to 15 μm, and the rotor 3 is in close contact with the lower receiving member 10 side when starting. After rotation, dynamic pressure is generated, and after floating, it can be operated close to the upper receiving member 10 side.

The magnet 7 may be embedded in a circular insertion hole 8 provided in the outer peripheral member 3□ of the rotor 3, and the upper surfaces may be flush with each other, or the magnet 7 may be inserted into the insertion hole 8 from the upper surface. It may be arranged in a recessed state or in a protruding state and held by a back-up plate (not shown). In the example shown in FIG. 1, the power can be increased by holding magnets 7 and 7 on both sides of the rotor 3. This is taken into consideration.

The insertion hole 8 is inserted into the cylindrical body 31 of the rotor 3 or the outer peripheral member 3.
A plurality of fixed shafts 5 are formed and arranged in a ring shape on the t, and a fixed shaft 5 is arranged in a ring shape so as to form a disc-shaped rotor core.
It is also possible to have a plurality of magnetic scrapers annularly magnetized along a plane orthogonal to It is convenient to use a coating layer with high reflectance as part of the mirror.

In the figure, reference numeral 111 denotes a dynamic pressure generating groove formed in a herringbone shape, and the bushing 5. is fitted into the fixed shaft 5. A large number of bearings are provided on either the outer circumferential surface of the rotor or the corresponding side surface of the rotating body to form a radial bearing.

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 indicates a light projection window, and reference numeral 14 indicates a tight napht, which prevents loosening due to temperature expansion and time.

The cylindrical body 3I is provided with dynamic pressure generating grooves 411 on both its upper and lower surfaces, but the spiral direction of the dynamic pressure generating grooves 11 is opposite when provided on both surfaces (the same direction on the projection plane). ) to prevent burnout even if the polygon rotor is rotated in the opposite direction by mistake.
In other words, it produces a dynamic pressure effect during both forward and reverse rotations and receives thrust loads, making it effective for safety purposes, but if necessary, one can be installed in the same direction (opposite in the projection plane) to provide a clutch action. In this case, the use of the receiving member 10 as an intermediate member is considered, and the mirror surface 2 on the outer periphery of the outer peripheral member 3□ of the rotor 3 is also covered with aluminum foil or thin aluminum to adjust the balance. be able to. The outer circumferential member 3□ is a ring-shaped flat plate whose outer circumferential edge is a regular polygon, and aluminum foil is fixed to the outer circumferential surface to form a mirror surface 2, and both upper and lower surfaces are truncated conical. It is also possible to have a shape in which the thickness gradually decreases toward the outside to form a part of the outer circumferential surface into a mirror surface.

In this specific example, a sleeve-shaped bushing 5I made of a ceramic material having a herringbone-shaped groove on the outer periphery is provided on the metal fixed shaft 5 as the fixed shaft 5, but as a means for restraining the flying height of the rotor 3, The upper receiving member 10 provided on the fixed shaft 5 at a position above the rotor 3 is fixed by selecting a washer 15 and a fixing nut 16 or other stopper. Alternatively, an elastic structure or the like may be attached to the fixed shaft 5 at the upper part of the rotor 3 as a pressing member.

Further, the support body 4 is made of an aluminum material and is used to prevent the sliding member from rotating, but the fixed shaft 5 and the support body 4 are also made of a ceramic material mainly composed of SiC. Furthermore, the support body 4 is made of a magnetic material to constantly exert an attractive force between it and the magnet 7 to prevent the rotor 3 from falling, and to obtain stable rotation with this attractive force. In addition, the fixed shaft 5 may be fitted with a sleeve-shaped bushing 5I that is precisely machined to ensure parallelism between the shaft end faces and perpendicularity to the herringbone groove surface, and step the bushing 51. The shaft may correspond to each member.

The rotor 3 with the mirror surface 2 is thus mounted on the sleeve-like bushing 5 of the fixed shaft 5 on the support 4. In addition, the mass balance, fluid balance, and magnetic balance are well maintained, the rotor rotates smoothly, and the air resistance during rotation is small.

In this case, there is a dynamic pressure generating groove 11 on the corresponding surface of the receiving member 10 interposed between the support body 4 and the rotor 3, and the opposite side thereof is a smooth flat surface, which is used as a thrust bearing part. The radial bearing portion has a herringbone-shaped dynamic pressure generating groove 11 on either the outer circumferential surface of the sleeve-shaped bushing 51 on the fixed shaft 5 or the cylindrical surface of the through hole l. , and the other surface is configured as a smooth cylindrical surface. In this embodiment, a dynamic pressure generating groove 11 for supporting a thrust load and a dynamic pressure generating groove 11 for supporting a radial load are used. ．． are groove depths of about 3 to 10 μm, respectively. The dynamic pressure generating grooves 11 may be formed on both sides of the rotor 3 to improve balance and eliminate deformation.

The rotor 3 and/or the receiving member 10 have zero waviness over the entire surface.
．． After making the land surface a smooth plane with a surface roughness of 3 μm or less and a maximum surface roughness of 0.1 μm, it was
It is preferable to use a material with a spiral groove machined to a depth of ~10 μm.

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 grooves tt and ti+ can be machined with high accuracy in the bearing part, and the shape of the sliding part suitable for generating dynamic pressure can be maintained even when dynamic pressure is generated. Moreover, it can be used effectively with durability even under a certain degree of load, even against solid friction that occurs when starting and stopping.

In the example shown in FIG. 3, the bush 5I is held between the receiving members 10 and 10 by a fixing nut 16 provided on the fixed shaft 5 and a coil spring 17, and the stator coil 6 is attached to the cover 1.
It is provided in 2. Note that the magnet 7 is provided on the cylindrical body 3I of the rotor 3, and the support 4 may also serve as the receiving member 10 between the cylindrical body 3I and the support 4. In this case, the support 4 may be made of a ceramic material. It is also good to form it with

In the specific example shown in FIGS. 4 to 6, a metal fixed shaft 5 is used as the rotating shaft,
For example, a herringbone-shaped groove for generating dynamic pressure on a bolt 1
1. A sleeve-shaped bushing 51 made of metal or ceramic material having an outer periphery of
I is held between the thrust receiving members 10.10 from both sides,
Dynamic pressure generating grooves 11 and 11 are fitted on the fixed shaft 5 together with the bushing 5, and are provided on the sliding surface facing the receiving member 10°10.
It has a structure that is easy to assemble.

Further, in this embodiment, a through hole 2 is formed in the receiving member 10 for the dynamic pressure bearing portion between the bushing 51 and the cylinder body 31.
This is so that outside air can easily flow from 0. The backup ring 18, which is a ring-shaped piece of iron, is attached to the magnet 7.
This is to improve the magnetic circuit and to maintain mass balance, and the balance can be corrected without damaging the strength of the ceramic cylindrical body 31.

In this case, the bolt of the fixed shaft 5 is screwed into the screw hole 21, and the washer 15 and the packing 19 are used together to easily hold the receiving member 10. A guide air passage 22 communicating with a through hole 20 provided in the receiving member 10 is formed. Furthermore, when the magnet 7 is embedded in the insertion hole 8 of the rotor 3, it can be optionally covered with a synthetic resin coating agent.

In the examples of FIGS. 7 to 9, the cylindrical body 3. A metal outer peripheral member fixed to the outer periphery of 3 by shrink fit. Instead of a brim-shaped flat plate, the top and bottom surfaces are shaped like truncated cones, making it a so-called solopan sphere, and its large-diameter outer peripheral surface is made into a polygonal mirror surface 2 to reduce windage loss and eliminate the edge portion to improve rotational balance. and cylinder body 3
1 and the window portion 13 is covered with a metal member, increasing safety. In this case, both the upper and lower surfaces of the outer circumferential member 3t are conical, and the thickness gradually decreases toward the outside, so the length of the outline of the mirror surface 2 near the outer circumference is short and there is little windage loss, and the cylindrical body 31 Safety can be increased by enclosing the outer periphery of the

〔Effect of the invention〕

In the present invention, a polygon mirror rotor is constructed from a ceramic cylindrical body rotatably fitted to a fixed shaft, and a metal outer peripheral member that is shrink-fitted to the outer periphery of the cylindrical body, and a magnet is attached to this rotor. and a mirror surface on the outer peripheral surface of the outer peripheral member, further disposing a stator coil corresponding to the magnet, fitting a bushing into the ceramic cylinder, and forming a mirror surface on the outer peripheral surface of the bushing or a ceramic cylinder facing the bushing. A groove for generating dynamic pressure is formed on one of the sliding surfaces on the body side, and the cylinder body is held between thrust bearing members from both sides and fitted together with a bushing by a fixed shaft, and the sliding surface faces the bearing member. By providing grooves for generating dynamic pressure, the outer periphery of the ceramic cylinder with low ductility is surrounded by a metal peripheral member with high ductility, which prevents the cylinder from being destroyed by the crank. Even if it breaks, it is blocked by metal parts, so there is little risk of it flying out of the case.
Moreover, due to the shrink fit, a large initial compression pressure remains in the cylinder, especially on the outer peripheral surface, which cancels out the tension in the radial and circumferential directions due to centrifugal force, suppresses the generation or propagation of cranking, and reduces the rotational speed. It is possible to raise the limit, and the perpendicularity and parallelism of the polygon rotor can be greatly improved by being held between the support members, and the center runout of the rotor can be minimized. The rotor core is made of permanent magnets or secondary conductors to rotate the polygon rotor, and the thickness of the polygon rotor is thin, with the outer peripheral surface being a part of the mirror. Compared to conventional polygon mirrors, the size of the polygon mirror in the rotation axis direction is shorter, making it significantly thinner, smaller and lighter, and reducing air resistance. The rotational speed of the mirror can be significantly reduced, and the same rotational speed as before can be obtained with even less power.Also, with the polygon mirror, it is possible to obtain a higher rotational speed with the same amount of power as before. In addition, since the polygon rotor generates a dynamic pressure effect and receives thrust loads well, maintenance and security are easy, there is no wear even if there is solid contact during starting and stopping, and it is easy to manufacture and has a small size. It is easy to achieve precision, and it is suitable for mass production because it can be processed with high precision.Furthermore, it always functions well as a polygon mirror that stably scans the light beam, and the intervening ceramic parts can be removed from the metal of the case and outer peripheral parts. By covering with a member and being held between receiving members, there is no problem due to breakage, increasing safety and reliability, and a polygon mirror that can accurately reflect laser beams, etc. can be obtained in a simple configuration, easy to manufacture, and inexpensive. It is something that can be done.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, and FIG. 2 is a diagram of FIG.
! 3 is a cut side view of another embodiment, FIG. 4 is a longitudinal sectional view of a part of another embodiment, and FIG. 5 is a bottom view of the line in FIG. FIG. 6 is a plan view of the mmNIA shown in FIG. 4, FIG. 7 is a vertical cross-sectional view of a part of another embodiment, FIG. 8 is a slope view of the rotor, and FIG. 9 is a vertical cross-sectional view of a conventional example. be. 1... Through hole, 2... Mirror surface, 3... Rotor, 3.
...Cylinder, 3! ... Outer peripheral member, 4 ... Support body, 5
... Fixed shaft, 51 ... Bush, 6 ... Stator coil, 7 ... Magnet, 8 ... Insertion hole, 10.
...Receiving member, 11.11. ... Groove for dynamic pressure generation, 12.
...Cover integrated, 15...Washer, 16...Fixing nut, 17...Spring.

Claims (5)

[Claims] (1) A polygon mirror rotor is constructed from a ceramic cylinder and a metal outer peripheral member that is shrink-fitted to the outer circumference of the cylinder, and a magnet and a mirror surface are attached to the outer peripheral surface of the outer peripheral member. A stator coil is provided corresponding to the magnet, a bush is fitted to the ceramic cylinder, and a dynamic pressure is applied to either the outer peripheral surface of the bush or the sliding surface of the ceramic cylinder facing the bush. A generating groove is formed, and the ceramic cylinder is held between thrust receiving members on both sides thereof and fitted together with a bush on a fixed shaft, and a dynamic pressure generating groove is provided on the sliding surface facing the receiving member. A polygon mirror that is characterized by (2) The polygon according to claim 1, wherein the ceramic cylinder is a cylindrical body with a through hole in the center, and spiral grooves for generating dynamic pressure are formed on both upper and lower surfaces. mirror. (3) The polygon mirror according to claim 1 or 2, wherein the magnets are arranged in a plurality of annular circular holes provided in the ceramic cylinder of the polygon mirror rotor. (4) The magnets are provided on both sides of the flat outer peripheral member of the polygon mirror rotor, and each magnet is provided opposite to the stator coil.
The polygon mirror according to item 1 or 2. (5) A patent claim in which the outer circumferential member has truncated conical surfaces on both upper and lower surfaces, the thickness gradually decreases outward, and is arranged at the center of the horizontal plane of the ceramic cylindrical body. The polygon mirror according to the range 2 or 3.