JPS63257717A - Polygon mirror - Google Patents

Abstract

PURPOSE:To make the titled polygon mirror small in size and light in weight, by holding a magnet on both faces of a rotor through a magnetic adsorbing plate which is inserted into a fitting hole formed on the rotor, and also, arranging a stator coil in accordance with these magnets, respectively. CONSTITUTION:A motor unit for rotating a rotor 3 is constituted of a permanent magnet provided on the rotor 3 or a magnet 7 of a secondary conductor, and a stator coil 6, a dynamic pressure generating groove 11 is formed on both side faces of the rotor 3, a receiving member 10 of thrust force is arranged so as to be opposed to said groove, pressed, and inserted and held from both ends, by which a thrust dynamic pressure bearing is formed, and by providing the magnet 7 and the stator coil 6 on both faces of the rotor 3 through a magnetic adsorbing plate 18 which is inserted into a fitting hole 8 formed on the rotor 3, a polygon mirror is formed. Also, plural fitting holes 8 of a circular shape for allowing the rotor 3 to fit in a cylindrical body are arranged and provided annularly on a concentric circle centering around a through-hole 1, allowed to communicate with the fitting hole, respectively, and a recessed groove 17 for fitting in a ring-like plate is formed on both faces of the rotor 3.

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 well-known example of a sealed structure suitable for high-definition image processing.In laser printers, the laser beam from a laser unit consisting of a semiconductor laser, gas laser, etc. is rotated. The light is reflected by mirror b of polygon rotor a and irradiated onto the surface of the photoreceptor, and polygon rotor a is driven by drive motor C.
It is configured to be rotated by a sleeve e on a fixed axis d.

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 is functionally capable of generating dynamic pressure and supporting a radial load by a lower groove section f having a herringbone shape, and a middle groove section f2 and an upper groove section r3 forming a herringbone shape. , and the central groove r2 feeds air 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.
A stator coil Cfi for driving the rotor magnet C is fixed to surround the rotor magnet C1 to form a drive motor C, and a laser beam is irradiated from the outside onto the mirror b of the polygon rotor a. and a polygon rotor which is rotated at high speed by a drive motor C, and a laser entrance/exit window is formed on a part of the upper circumferential surface of the outer tube i, which transmits the laser light reflected to the desired exposure surface. In this case, the gap between the fixed shaft and the rotating sleeve is made extremely narrow because it is necessary not only to maintain high rotational 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 reflectivity, but in order to maintain its shape, its thickness has become over 10W. 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 is narrow enough to be smaller than a crane, the power loss caused by the disturbance of the surrounding air becomes extremely large.

For these reasons, the sliding parts between the fixed shaft and the rotating sleeve are machined with extreme precision to effectively generate dynamic pressure from air, and the rotating sleeve, polygon rotor,
Rotating parts such as the mirror part and rotor magnet 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 wm 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 desirable to set the rotation speed of the polygon mirror to 30.00 rpm 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 extremely difficult. It is difficult, and the balance adjustment is very complicated, and there is also a safety problem because the polygon rotor may be accidentally rotated in the opposite direction, leading to a burnout accident.

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. The purpose of the present invention is to provide a polygon mirror that has a simple configuration, is easy to manufacture, and is inexpensive, with a reflective surface that is less likely to fall, can be rotated stably at high speed, and can accurately reflect laser beams, etc. be.

[Means for solving problems]

The present invention provides a polygon mirror in which a rotating body with a mirror surface is rotatably mounted on a fixed shaft mounted on a support body to form a polygon rotor, a magnet is provided on the rotating body, and a stator coil is provided corresponding to the magnet. ,
A polygon mirror characterized in that magnets are held on both sides of the rotating body through magnetic adsorption plates inserted into fitting holes formed in the rotating body, and stator coils are provided corresponding to each of these magnets. be.

〔Example〕

Embodiments of the present invention will be explained with reference to the examples of FIGS. 1 to 4. In the example of FIG. 3 is passed through the through hole 1 and attached to the support body 4 (JN), and is rotatably provided on a push 51 having a dynamic pressure generating groove 11+ formed on the outer periphery of the fixed shaft 5. year,
A stator coil 6 fixed in parallel with the flat rotary body 3 and rotating the polygon rotor is provided on the support body 4 or the cover integral 12, and a permanent magnet or a secondary conductor magnet 7 provided on the rotary body 3 and the The stator coil 6 constitutes a motor unit that rotates the rotating body 3, and a dynamic pressure generating /1IIL, that is, a spiral groove is formed on the ii4 side surface of the rotating body 3, and a receiving plate is provided opposite to the spiral groove to serve as a thrust receiving plate. The push 5 with the member 10 interposed therebetween. It is pressed and clamped from both ends to form a thrust dynamic pressure bearing. That is, the magnet 7 is attached to both sides of the rotary body 3 through the magnetic adsorption plate inserted into the fitting hole 8 formed in the rotary body 3.
．． 7, and stator coils 6.6 are provided corresponding to these magnets 7 to form a polygon mirror.

The rotating body 3 has a sliding surface with dynamic pressure generating grooves 11 facing the receiving member IO, and has dynamic pressure generating grooves 11 on both surfaces of the opposing sliding surface, for example. A hard ceramic material in which spiral grooves with opposite twisting directions are formed leaving a land portion, such as a SiC sintered body, an α-5iC sintered body containing BeO, or a 5iJ4 sintered body, is used for thrusting. It is best formed as a bearing part,
The receiving member 10 may also be a thrust receiving plate using a flat plate made of a hard ceramic material. The clearance between the rotating body 3 and the receiving member 10 of the thrust receiving plate is 5 to 15
When the rotating body 3 is started, it comes into close contact with the lower receiving member IO side, dynamic pressure is generated after rotation, and after floating, it can operate close to the upper receiving member 10 side.

Further, the rotating body 3 has a plurality of circular fitting holes 8 for fitting the cylindrical body arranged in an annular manner on a concentric circle centered on the through hole 1, and communicates with each of the fitting holes 8, and rotates. A groove 17 is formed on both sides of the body 3 to fit a ring-shaped flat plate.

That is, a cylindrical magnetic adsorption plate 18 is embedded in the fitting hole 8,
The magnet 7 made of a ring plate material is fitted into the ring-shaped groove 17 formed on both sides of the magnetic adsorption plate 18.
The magnet 7 may be provided in the cylindrical fitting hole 8, and ring-shaped backup plates may be fitted into the ring-shaped recesses tl17 formed on both sides of the magnet 7.

In this case, the magnet 7 or the backup ring is a ring-shaped plate, and has one or more anti-rotation recesses 27 into which the cylindrical magnetic adsorbent 18 or magnet is fitted, allowing for a robust assembly. The magnet 7 may be embedded in the recess m11 of the rotary body 3 or the fitting hole 8, and the upper surface may be flush with each other, or the magnet 7 may be placed against the fitting hole 8. It may be arranged and held in a state where it is thicker or protrudes from the upper surface. In the example shown in FIG. 1, the magnets 7.7 are held on both sides of the rotating body 3 in order to increase the power.

Note that the mirror surface 2 is made of aluminum foil (0.1-0.5m)
Alternatively, it is convenient to form part of the mirror with a vapor deposited film or other coating layer with high reflectance.

In the figure, reference numeral 11+ denotes a dynamic pressure generating groove formed in a herringbone shape, and the pusher 5. is fitted into the fixed shaft 5. A large number of bearings are provided on the outer circumferential surface of the rotating body or on the corresponding side surface of the rotating body to form a radial bearing. The cover I2 is integrated with the cover and is fitted onto the support body 4 to form a sealed structure for laser printers and the like, and can be omitted when high clarity is not required, such as in bar code leagues. 13 is a window for light projection, 14 is a fastener 1-
This prevents loosening due to temperature expansion and time.

Note that when the spiral direction of the dynamic pressure generation groove 11 is provided on both sides, it will not burn out even if it is provided in the opposite direction (same direction on the projection plane) and accidentally rotated in the opposite direction when rotating the polygon rotor. In other words, the dynamic pressure effect is generated during both forward and reverse rotation, and the thrust load is applied to ensure safety. Alternatively, one side may be provided with a clutch action. In this case, it is considered that an intermediate member is interposed and utilized, and furthermore, the mirror surface 2 on the outer periphery of the rotating body 3 can also be balanced with aluminum foil.

In this specific example, a sleeve-shaped pusher 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 the rotating body 3
As a means for restraining the flying height of the rotating body 3, an upper receiving member 10 provided on the fixed shaft 5 is fixed to a washer 15 and a fixing nut 16 or other stopper. A coil spring 16 is attached to the member 10. Alternatively, a spring washer or other elastic member may be attached, or another elastic structure may be provided on the fixed shaft 5 above the rotary body 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 solid/electric ring 5 and the support body 4 are also made of a ceramic material mainly composed of SiC. Furthermore, the support 4 is made of a magnetic material to constantly exert an attractive force between it and the magnet 7 to prevent the rotating body 3 from falling, and this attractive force provides a stable structure. Further, the fixed shaft 5 may be fitted with a sleeve-shaped push 51 that is precisely machined to ensure parallelism between the shaft end surfaces and perpendicularity to the herringbone groove surface. may be used as a stepped shaft to correspond to each member. In addition, a flat stator coil 6 is provided on the support body 4 and the cover 12, respectively, in response to the magnet 7 provided on the rotating body 3, and serves as a motor to rotate the rotating body 3 of the polygon rotor.

Therefore, the rotating body 3 with the mirror surface 2 is rotated smoothly with good maintenance of mass balance, fluid balance, and magnetic balance on the push 51 of the fixed shaft 5 on the support 4, and the air resistance during rotation is also small. It is possible.

In this case, a dynamic pressure generating groove 11 is provided on the corresponding surface of the receiving member 10 interposed between the support body 4 and the rotating body 3, and the opposite side thereof is a smooth plane serving as a thrust bearing portion. Further, the radial bearing portion has a herringbone-shaped dynamic pressure generation groove 11 on either the outer peripheral surface of the pusher 51 on the fixed shaft 5 or the cylindrical surface of the through hole 1. , and the other surface is configured as a smooth cylindrical surface. In this embodiment, there are grooves 11 for generating dynamic pressure to support thrust loads, and grooves 11 for generating dynamic pressure to support radial loads. ez is a groove depth of about 3 to 50 urn, respectively. The dynamic pressure generating grooves 11 may be formed on both sides of the rotating body 3 to improve balance and eliminate deformation.

The rotating body 3 and/or the receiving member 10 have zero waviness over the entire surface.
．． After making the land surface a smooth plane with a maximum surface roughness of 0.1 μm and less than 3 μm, it was
It is preferable to use a material with a spiral groove machined to a depth of ~50 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 groove 11 for generating dynamic pressure can be machined with high precision in the bearing part, and the shape of the sliding part suitable for generating dynamic pressure can be maintained even when the dynamic pressure has stopped. 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.

In the examples shown in FIGS. 5 to 7, a ring-shaped magnetic adsorption plate 18 is embedded and a plurality of circular fitting holes that come into contact with the magnetic adsorption plate are arranged in a ring shape, and a cylindrical magnet is placed in the fitting hole 8. 7 on both sides of the rotating body.

In the example shown in FIG. 8, the push 51 is sandwiched between the receiving members 10 and 10, and a fixing Nand 16 and a spring 16 are provided on the fixed shaft 5.
．． The stator coil 6 is mounted on the cover 12. Note that the support member 4 may also serve as the receiving member 10 between the rotating body 3 and the support member 4, and in this case, the support member 4 may be formed of a ceramic material.

〔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. By holding magnets on both sides of the rotating body through the magnets, and providing stator coils corresponding to each of these magnets, the perpendicularity and parallelism of the polygon rotor can be greatly improved, and the center runout of the rotor can be minimized. In addition to being compact, it is easy to assemble and deploy, and is easy to balance, allowing stable rotational operation. Even if the thickness of the polygon rotor that is part of it is thin, the amount of deformation can be reduced, and compared to conventional polygon mirrors, the dimension in the direction of the rotation axis on which the polygon mirror is attached is shorter, making it significantly thinner, smaller, and lighter. It is possible to significantly reduce the air resistance, obtain the same rotational speed as before with less power, and accurately hold down the magnets installed in the rotor. By connecting the lines of magnetic force in the circumferential direction, stable rotation is possible, and assembly is easy, and the magnet can be easily held on the rotor.
In addition, if the same amount of power is used as before, the polygon mirror can achieve higher rotational speeds, and the polygon rotor generates a dynamic pressure effect to better absorb thrust loads, making maintenance and safety easier. It does not wear out even if it comes into contact with solid objects during startup and shutdown, and the dynamic pressure generation effect is well maintained when generating dynamic pressure and can support high thrust loads, making it possible to stabilize the light beam. The present invention provides a polygon mirror that always functions well as a polygon mirror for scanning, and that can reflect laser beams and the like with high accuracy through the intervention of a ceramic sliding member, with a simple structure, easy manufacture, and low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a slope view of the rotor, FIG. 3 is a slope view showing its separated state, and FIG. 4 is an enlarged cutaway side view taken along line II in FIG. FIG. 5 is a perspective view of another embodiment of the rotor, FIG. 6 is a perspective view showing its separated state,
Figure 7 is an enlarged cutaway side view taken along line 11 of Figure 5 II;
FIG. 8 is a cutaway side view of still another embodiment, and FIG. 9 is a longitudinal sectional view of the conventional example. ■...Through hole, 2...Mirror surface, 3...Rotating body, 4...
...Support, 5...Fixed shaft 1.51...Push,
6... Stator coil, 7... Magnet, 8...
- Fitting hole, 10... Receiving member, 11.11+... Groove for dynamic pressure generation, 15... Washer, 16... Fixing nut, F... Concave groove, 18... Magnetic Adsorption board. Patent Applicant Ebara Corporation Patent Attorney Yakushi Minoru Representative Patent Attorney Yori 1
) Takatsugu Department Patent Attorney Tadashi Takagi
Line Figure 1 Figure 2

Claims (9)

[Claims] (1) A polygon mirror in which a rotating body with a mirror surface is rotatably provided on a fixed shaft provided on a support body to form a polygon rotor, a magnet is provided on the rotating body, and a stator coil is provided corresponding to the magnet, A polygon mirror characterized in that magnets are held on both sides of the rotating body via magnetic adsorption plates inserted into fitting holes formed in the rotating body, and stator coils are provided corresponding to each of these magnets. (2) The rotating body is rotatably fitted to the outer peripheral surface of a pusher fitted and arranged on the fixed shaft,
2. The polygon mirror according to claim 1, wherein a groove for generating dynamic pressure is provided on either the outer peripheral surface of the pusher or the rotating body side sliding surface facing the pusher. (3) The rotating body is a plate made of ceramic material with spiral grooves for generating dynamic pressure formed on both sides thereof, and is held between thrust receiving plates provided facing both sides, and is held together with the push. The polygon mirror according to claim 2, wherein the polygon mirror is fitted onto a fixed shaft with a fixing member. (4) The rotating body is provided with a plurality of circular fitting holes arranged in an annular manner for fitting the cylindrical body, and ring-shaped flat plates are fitted on both sides of the rotating body, communicating with each of the fitting holes. The polygon mirror according to claim 2 or 3, wherein a concave groove is formed to prevent the polygon mirror from forming the polygon mirror. (5) The rotating body has a cylindrical magnetic adsorption plate in a plurality of annularly arranged circular fitting holes, and the magnets are fitted into ring-shaped grooves formed on both sides of the magnetic adsorption plate. A polygon mirror according to any one of claims 2 to 4. (6) The rotating body includes a ring-shaped magnetic adsorption plate, and a plurality of circular fitting holes abutting the magnetic adsorption plate are arranged in a ring shape, and cylindrical magnets are placed in the fitting holes on both sides of the rotating body. A polygon mirror according to claim 2 or 3, which is provided with a polygon mirror. (7) The rotating body includes the magnets in a plurality of annularly arranged cylindrical fitting holes, and ring-shaped backup plates are fitted into ring-shaped grooves formed on both sides of the magnets. A polygon mirror according to any one of claims 2 to 4. (8) Claim 2, wherein the magnet or backup ring is a ring-shaped plate and includes one or more anti-rotation recesses into which the cylindrical magnetic adsorbent or magnet is fitted. The polygon mirror according to any one of items 1 to 7. (9) The rotating body is a flat plate with a through hole in the center, the outer peripheral edge is a regular polygon, and has a fitting hole in which a magnet is arranged in an annular manner concentrically with the through hole, and the outer peripheral surface is made of aluminum. A polygon mirror according to any one of claims 4 to 8, which is a polygon rotor having a mirror surface formed by fixing foil.