JPH0677111B2 - Polygon mirror - Google Patents

Description

The present invention relates to a polygon mirror for reflecting a laser beam and irradiating the surface of a photoconductor in a laser scanning optical system used in a laser printer, a laser copying machine or the like. It is a thing.

[Conventional technology]

As shown in FIG. 8, a conventional polygon mirror is a polygon that rotates a laser beam from a laser unit including a semiconductor laser or a gas laser in a laser printer known as an example of a closed structure suitable for high-definition image processing. It is reflected by the mirror b of the rotor a and irradiates the surface of the photoconductor, and the polygon rotor a is configured to be rotated in the atmosphere by the drive motor c on the fixed shaft d via the sleeve e. .

A large number of dynamic pressure generating grooves are formed on the outer peripheral surface of the fixed shaft d, so that the rotation of the rotary sleeve e generates dynamic pressure for supporting the thrust load and the radial load. That is, groove for dynamic pressure generating is functionally to generate dynamic pressure by a central groove f ₂ and the upper groove f ₃ of the lower groove portion f ₁ and herringbone herringbone shaped support radial load, In addition, air is sent to the upper surface of the fixed shaft d by the middle groove portion f ₂ , and the air pressure between the thrust bearing g at the upper end of the fixed shaft d is increased to support the thrust load.

The polygon rotor a is screwed to the upper part of the rotating sleeve e, the rotor magnet c ₁ is fixed to the lower part, and a stator coil for driving the rotor magnet c ₁ is used.
c ₂ is fixed so as to surround the rotor magnet c ₁ to form a drive motor c, and the laser light emitted from the outside to the mirror b of the polygon rotor a and the laser light reflected to a desired exposure surface The polygonal rotor, which has a laser entrance / exit window h for transmitting light formed on a part of the upper peripheral surface of the outer cylinder i and is rotated at a high speed by the drive motor c, must maintain high rotational accuracy. Not only that, the gap between the fixed shaft and the rotating sleeve is extremely narrow because the surface wobbling of the reflecting surface must be reduced.

[Problems to be solved by the invention]

However, since such a laser printer reproduces clear characters and images at a high speed, the polygon mirror must be rotated at a high speed and with the reflection surface not tilting. It is easy to cut and is manufactured by cutting a flat plate of aluminum alloy with high reflectance with diamond, but in order to maintain the shape,
Its thickness was over 10 mm. However, the load when the polygon mirror is rotating at high speed is mostly due to the air resistance at the outer peripheral edge of the polygon rotor with the mirror, and considering that the area that reflects the laser light is a narrow width of 1 mm or less, the polygon The power loss due to the rotor disturbing the surrounding air becomes extremely large.

For these reasons, the sliding portion between the fixed shaft and the rotating sleeve is extremely precisely processed so that the dynamic pressure by air is effectively generated, and the rotating sleeve, the polygon rotor, the mirror portion, the rotor Rotating parts such as magnets must be precisely processed, and at the same time, the mass balance should be adjusted appropriately.

However, the surface tilt of the reflecting surface of the polygon mirror is ± 1.5.
In order to reduce the size to less than μm, it is necessary to accurately machine a fixed shaft with a length of 50 mm or more, and the distance between it and the rotating sleeve must be less than 3 μm, so mass production of the product is difficult, and high-speed image processing is required. When performing, it is desired to set the rotation speed of the polygon mirror to 30,000 rpm or more.
In the case of such high speed rotation, the radial load on the fixed shaft increases, it is extremely difficult to support with the air film, and the balance adjustment is very complicated, and the air has poor heat conduction and heat dissipation and heat generation due to heat generation phenomenon. There was a problem.

The present invention intends to properly eliminate this conventional drawback. Since the rotating body is driven in a gas lighter than the enclosed air, the verticality and parallelism of the polygon rotor can be greatly improved during rotation operation. Wind loss is greatly reduced, and it is a compact polygon mirror that can rotate at high speed. Furthermore, it does not dissipate heat well and does not corrode, so it is good in terms of safety and can rotate stably at high speed, and it can accurately reflect laser light etc. It is an object of the present invention to provide a polygon mirror in a form that is simple in construction, easy to manufacture, and inexpensive.

[Means for solving problems]

The present invention relates to a polygon mirror in which a rotating body having a mirror surface is rotatably provided on a fixed shaft provided on a support body to form a polygon rotor, and a magnet is provided on the rotating body, and a stator coil is provided corresponding to the magnet. A sliding member made of a ceramic material in which a spiral groove for generating a dynamic pressure is formed is interposed between the rotating body and the support, and a hollow chamber capable of accommodating the polygon rotor is the support. A polygon mirror, characterized in that it has a closed structure with a cover body fitted to the support body, and has a configuration in which the hollow chamber is filled and filled with a gas having a low density with respect to air.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 to 3 in which a rotating body 3 having a flat plate shape, a through hole 1 formed in the center, and a plurality of mirror surfaces 2 having an outer peripheral edge of a regular polygon is penetrated. A polygonal rotor rotatably provided on a fixed shaft 5 provided in a support body 4 through the hole 1 is fixed to the support body 4 in parallel with the flat plate rotary body 3, and a stator coil 6 for rotating the polygon rotor is provided on the support body 4. A motor unit for rotating the rotating body 3 is constituted by a permanent magnet or a secondary conductor magnet 7 provided on the rotating body 3 and the stator coil 6, and is provided between the rotating body 3 and the support body 4. A sliding member 10 made of a ceramic material in which a dynamic pressure generating groove 11, that is, a spiral groove is formed is provided in the inside, and a hollow chamber 20 capable of accommodating the polygon rotor is fitted to the support 4 and the support 4. O with the cover body 12 to wear The sealing member 23 hermetically sealed and is the density to air is less gas in the hollow chamber such as a filled encapsulated structure ring are also available operating at reduced pressure.

In this case, a light gas such as helium gas or hydrogen, that is, a gas having a low density with respect to air is used as the enclosed gas, and the support body 4 of the case constituting the closed hollow chamber 20 or the cover body fitted to the support body 4 is used. The gas supply port 22 may be formed in any one or any of the 12 so that the gas supply port 22 can be replenished in a hatch form or the gas supply source 21 can be connected to continuously supply air. In this circulation system, it is preferable to provide a cooling mechanism to utilize the gas to enhance the heat dissipation effect.

The rotating body 3 is a disc-shaped or square-plate-shaped sliding member 10 having a dynamic pressure generating groove 11 on a sliding surface interposed on the support 4.
The sliding member 10 is used to generate a dynamic pressure on either or both of the sliding surface of the surface of the rotating body 3 facing the magnet 7 and the surface of the rotating body 3 facing the stator coil 6. A hard ceramic material such as a groove 11, for example, a spiral groove whose twist direction is opposite to that of the land, leaving a land portion, such as a SiC sintered body, a BeO-containing α-SiC sintered body, or Si ₃
It is preferable that the thrust bearing portion is formed by using an N ₄ sintered body or the like, and the rotating body 3 may also be a flat plate made of a hard ceramic material, and if necessary, a corresponding sliding surface. A groove for generating dynamic pressure may be formed in.

The magnet 7 may be embedded in the insertion hole 8 of the rotating body 3 so that the upper surface is flatly faced, or the magnet 7 may be arranged in a recessed state or a protruding state with respect to the insertion hole 8 for backup. A plate (not shown) may be applied and held.

A plurality of the insertion holes 8 are formed in the rotating body 3 in an annular shape, and are arranged in a ring shape so as to form a disc-shaped rotor core, and are formed in an annular shape along a plane orthogonal to the fixed shaft 5. A plurality of magnetic poles may be magnetized, and the mirror surface 2 is made of aluminum foil (0.1 to 0.5 mm).
Alternatively, it is convenient to use a vapor-deposited film or other coating layer having high reflectance as the mirror portion.

In the figure, 11 ₁ is a herringbone-shaped groove for dynamic pressure generation, and a large number of grooves are provided on the outer peripheral surface of the fixed shaft 5 or the surface corresponding thereto. 12 ₁ 13 that a sealed structure with a sealing material 23 is fitted to the support 4 in the recessed groove formed in the cover body is light projecting window.

The dynamic pressure generating groove 11 is provided in the opposite direction (the same direction on the projection surface) when the spiral direction is provided on both sides, and even if the polygon rotor is rotationally driven by mistake, it is burned out. That is, the dynamic pressure effect is generated in both forward and reverse rotations and the thrust load is applied to make it effective for security, but if necessary, install it in the same direction (opposite direction on the projection surface). One of them may be provided with a clutch action. In this case, it is considered that the intermediate member is used to intervene, and the mirror surface 2 on the outer periphery of the rotating body 3 can also be adjusted in balance with an aluminum foil.

Then, the rotating body 3 having the mirror surface 2 has the support body 4 and the cover body 12
The fixed shaft 5 and the dynamic pressure generating groove 11 in the hollow chamber 20 in which a gas having a closed structure and having a low density with respect to air is sealed with
The mass balance, the fluid balance, and the magnetic balance are well maintained on the sliding member 10 made of a ceramic material having the above-described structure, and the ceramic member is smoothly rotated, and the air resistance during rotation is small and the operation can be performed.

In the example shown in FIG. 4, a notched step portion into which the sealing material 23 can be fitted is formed on the support body 4 side, and the cover body 12 has a closed structure in which the hollow chamber 20 is filled with helium gas, which corresponds to the stator coil 6. The sliding member 10 is attached to the boss of the rotating body with the magnet 7.
Are fitted.

In the concrete example of FIG. 5, a ceramic sleeve-shaped bush 9 having a herringbone-shaped groove on the outer periphery is provided on a metal fixed shaft 5 as a rotating shaft, and means for restraining the floating amount of the rotating body 3 is used. The fixed shaft 5 is located above the rotating body 3.
The upper sliding plate 15 or the washer 16 or other stopper provided on the above is selected and applied, but the coil spring 17 or other elastic member is attached to the sliding plate 15 or other elastic structure is rotated as a pressing member. The structure may be provided on the fixed shaft 5 in the upper part of the body 3.

In the embodiment, the upper sliding plate 15 is made of a ceramic material and is provided with a dynamic pressure generating groove 11 on the sliding surface side so as to oppose to the rotating body 3. A coil spring 17 is interposed between the washer 16 and the washer 16 to serve as a mechanism for restraining the flying height of the rotating body 3.

Further, the support 4 is made of an aluminum material and has a helium gas-sealed hermetic structure with the cover 12 and is used as a rotation stopper for the sliding member. It is also possible to select 4 as a sintered body of a ceramic material mainly composed of SiC. Further, the support body 4 is made of a magnetic body so that the attracting force is constantly exerted between the support body 4 and the magnet 7 so that the rotating body 3 May be prevented from falling, and it may be considered to obtain stable rotation by this suction force. Further, the fixed shaft 5 is fixed to the support body 4 by the fastening nut 14, and the parallelism between the shaft end faces and the perpendicularity to the herringbone groove face are precisely machined. The bush 9 may be fitted and arranged, and in these cases, the fixed shaft 5 or the bush 9 may be used as a stepped shaft to correspond to each member. Further, the stator coil 6 having a flat plate shape with respect to the magnet 7 provided on the rotating body 3
Is provided on the support body 4 to rotate the rotating body 3 of the polygon rotor as a motor.
The end surface of the sliding member 10 facing the is processed so that the fixed shaft 5 is at a right angle, that is, at a right angle to the inner peripheral surface of the through hole 1 and at a right angle to the mirror surface 2 formed on the outer peripheral edge thereof.

In this case, there is a dynamic pressure generating groove 11 on the corresponding surface of the sliding member 10 interposed between the support 4 and the rotating body 3 to form a thrust bearing portion, and the radial bearing portion is fixed. It is formed by a herringbone-shaped dynamic pressure generating groove 11 ₁ for dynamic pressure generation provided on either one of the outer peripheral surface of the shaft 5 and the circumferential surface of the through hole 1. In this embodiment, Is a dynamic pressure generating groove 11 for supporting a thrust load, and a dynamic pressure generating groove 11 ₁ for supporting a radial load is 3 to 10 respectively.
The groove depth is about μm. The dynamic pressure generating grooves 11 may be formed on both sides of the rotating body 3 by groove processing to improve balance and eliminate the formation, or the sliding member 10 or the sliding plate.
As for 15, it is possible to select a thickness that does not deform because a ceramic plate that is thinner than the diameter may be deformed after groove processing when it is formed on both sides compared to when spiral grooves are processed on only one side. Be considered.

The waviness of the entire surface of the sliding plate 15 and / or the sliding member 10 is 0.
The land surface is a smooth flat surface with a maximum surface roughness of 0.1 μm at 3 μm or less, and then 3 to 10 μm by shot blasting.
It is a spiral groove having a depth of m.

In the case of manufacturing a radial bearing utilizing the effect of dynamic pressure, the groove machining by shot blasting can be performed similarly. In any case, it is possible to process the dynamic pressure generating groove 11 with high accuracy using a hard ceramic material, and the shape of the sliding portion suitable for generating the dynamic pressure is maintained even when the dynamic pressure is generated. In addition, even with respect to solid rubbing that occurs at the time of starting and stopping, it can be effectively used with durability under a certain load.

In the examples of FIGS. 6 and 7, the stator coil 6 is open to the atmosphere for heat dissipation, and the cover body 12 or the support body 4 is provided outside the support body 4 as a closed structure. The gas supply port 22 is connected to the pump of FIG. In this case, a check valve may be attached to the connecting portion as needed to make it a gas-filled type.

〔The invention's effect〕

According to the present invention, in a polygon mirror including a magnet provided on a rotating body and a stator coil facing the magnet and rotating the rotating body, a spiral for generating dynamic pressure is provided between the rotating body and a support body. A hollow chamber that can accommodate the polygon rotor is provided with a sliding member made of a ceramic material having a groove interposed therebetween, and
The cover body fitted to the support body is hermetically sealed, and the hollow chamber is filled with a gas having a low density with respect to air, so that the rotating body on the ceramic sliding member operates in a gas lighter than air. As a result, the verticality and parallelism of the polygon rotor can be greatly improved, the rotor runout can be reduced as much as possible, and the wind loss during operation can be greatly reduced, enabling stable rotation operation and heat generation. There is no stable operation of the rotor at ultra-high speed, and the durability can be greatly improved, and if helium is used as the enclosed gas,
The thermal conductivity is greater than that of air, the heat dissipation is excellent, the corrosion is small, the angle of deviation of the mirror is small, the windage is significantly small, and the rotor core is composed of a permanent magnet or a secondary conductor for rotating the polygon rotor. Even if the polygon rotor whose outer peripheral surface is a mirror portion is thin, the amount of deformation can be reduced, and compared to the conventional polygon mirror, the dimension in the rotation axis direction in which the polygon mirror is mounted becomes shorter, and it is extremely thin. It can be made smaller and lighter, its air resistance can be significantly reduced, and it will be possible to obtain the same rotation speed as before with a smaller amount of power, and the same amount of power as before will be applied. if,
It becomes a polygon mirror that can obtain a higher rotation speed, and because it produces a dynamic pressure effect on the polygon rotor and receives a good thrust load, maintenance and security is easy and even if there is solid contact at the time of start / stop Since it does not wear, and the dynamic pressure generation effect at the time of dynamic pressure generation is maintained well and can support a high thrust load, it always functions as a polygon mirror that stably scans light rays. In addition, a polygon mirror capable of accurately reflecting a laser beam or the like with the interposition of a ceramic sliding member can be obtained in a simple configuration, easy manufacture, and inexpensive form.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention, and FIG.
Fig. 3 is a plan view taken along line I, Fig. 3 is a plan view taken along line II-II of Fig. 1, Fig. 4 is a sectional side view of another embodiment, and Figs. 5 to 7 are views of yet another embodiment. Partial cut side view,
FIG. 8 is a vertical sectional view of a conventional example. 1 ... Through hole, 2 ... Mirror surface, 3 ... Rotating body, 3 ₁ ... Cylindrical part, 4 ...
Support body, 5 ... Fixed shaft, 6 ... Stator coil, 7 ... Magnet, 8 ... Insertion hole, 10 ... Sliding member, 11, 11 ₁ ... Dynamic pressure generating groove, 12 ... Cover body, 13 ... Light projecting window Part, 15 ... Sliding plate, 16 ...
Washer, 17 ... Spring, 20 ... Hollow chamber, 21 ... Gas supply source, 22 ... Gas supply port.

Claims (4)

[Claims] 1. A polygon mirror in which a rotating body having 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. In the above, a sliding member made of a ceramic material in which a spiral groove for generating dynamic pressure is formed is interposed between the rotating body and the support, and a hollow chamber capable of accommodating the polygon rotor is provided as the support. A polygon mirror, characterized in that it has a closed structure with a cover body fitted to the support body, and that the hollow chamber is filled with a gas having a low density with respect to air. 2. The polygon mirror according to claim 1, wherein the enclosed gas is helium gas. 3. The method according to claim 1, wherein the case comprises a support body and a cover body fitted to the support body, and the case is provided with a helium gas supply port. The polygon mirror according to item 2. 4. The method according to claim 1 or 2, wherein the hollow chamber is filled with helium gas and is connected to a circulation path equipped with a cooling mechanism. Polygon mirror.