JPH0677108B2 - Polygon mirror - Google Patents

Description

The present invention relates to a laser scanning optical system used in a laser printer, a bar code reader, a laser copying machine, or the like, which reflects laser light to irradiate the surface of a photoconductor. It relates to a polygon mirror for doing.

[Conventional technology]

As shown in FIG. 9, a conventional polygon mirror is a polygon that rotates a laser beam from a laser unit such as a semiconductor laser or a gas laser in a laser printer known as an example of a hermetic 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 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, the groove portion for generating dynamic pressure is functionally generated by the lower groove portion f _{1 having a} herringbone shape, the middle groove portion f ₂ and the upper groove portion f ₃ which form a herringbone shape, and a radial load is generated. Air is sent to the upper surface of the fixed shaft d by the support and the middle groove portion f _2, and
The thrust load is supported by increasing the air pressure between the upper end of the thrust bearing g and the thrust bearing g.

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 surface run-out of the reflecting surface must be reduced, so that the gap between the fixed shaft and the rotary sleeve is extremely narrow.

[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 it is manufactured by cutting a flat plate of aluminum alloy with high reflectance with diamond, but its thickness was 10 mm or more to maintain the shape. However, when the polygon mirror rotates at high speed, most of the load is air resistance at the outer edge of the polygon, and considering that the area for reflecting the laser light is 1 mm or less, the width is narrow. The power loss due to the disturbance of the surrounding air becomes extremely large.

For these reasons, the sliding portion between the fixed shaft and the rotary sleeve is extremely precisely processed so that the dynamic pressure by air is effectively generated, and the rotary sleeve, the polygon rotor,
The rotating parts such as the mirror part and the rotor magnet must be precisely processed, and at the same time, the mass balance must 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 it with an air film, the balance adjustment is very complicated, and moreover, in the case of a burnout accident that accidentally rotates the polygon rotor in the opposite direction. There was a security problem due to the connection.

The present invention intends to properly eliminate this conventional drawback, and to provide a compact polygon mirror capable of high-speed rotation with significantly improved verticality and parallelism of the polygon rotor, and less air resistance during rotation. Furthermore, it is an object of the present invention to provide a polygon mirror which has a small tilt of the reflecting surface, is capable of stable high-speed rotation, and can reflect a laser beam or the like with high accuracy in a simple configuration, easy manufacture and inexpensive form.

[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 polygon mirror characterized in that magnets are held on both surfaces of the rotating body through magnetic attraction plates inserted in fitting holes formed in the rotating body, and stator coils are arranged corresponding to these magnets, respectively. Is.

[Embodiment] An embodiment of the present invention will be described with reference to FIGS. 1 to 4. In FIG. 1, a flat plate having a plurality of mirror surfaces 2 having a through hole 1 formed at the center and an outer peripheral edge of a regular polygon. The rotating body 3 in the shape of a ring is rotatably attached to the bush 5 ₁ which penetrates the through hole 1 and is located on the outer periphery of the fixed shaft 5 provided on the support body 4, and in which the dynamic pressure generating groove 11 ₁ is formed on the outer periphery. Provided as a polygon rotor, the stator coil 6 which is fixed in parallel with the flat plate rotating body 3 and rotates the polygon rotor is provided on the support body 4 or the cover body 12, and the permanent magnet or the secondary magnet provided on the rotating body 3 is provided. A motor unit for rotating the rotating body 3 is constituted by the conductor magnet 7 and the stator coil 6, and the dynamic pressure generating grooves 11 or spiral grooves are formed on both side surfaces of the rotating body 3 and are opposed thereto. With the receiving member 10 serving as a thrust receiving plate interposed, Are so as to form a thrust dynamic pressure bearing is pressed sandwich from both ends of the Mesh 5 _1. That is, the rotating body 3
The magnets 7 and 7 are held on both sides of the rotating body through the magnetic attraction plate 18 inserted into the fitting hole 8 formed in the above, and the stator coils 6 and 6 are respectively provided corresponding to these magnets 7 to form polygons. As a mirror.

In the rotating body 3, the sliding surface having the dynamic pressure generating groove 11 is a receiving member.
A hard ceramics material that is arranged facing each other in 10 and has grooves 11 for dynamic pressure generation, for example, spiral grooves with opposite twist directions formed on both surfaces of the sliding surfaces facing each other, leaving the land portion. For example, a SiC sintered body, an α-SiC sintered body containing BeO, or a Si ₃ N ₄ sintered body is preferably used as the thrust bearing portion, and the receiving member 10 is also made of hard ceramics. A flat plate of material may be used as the thrust receiving plate. The clearance between the rotating body 3 and the receiving member 10 of the thrust receiving plate is set to 5 to 15 μm, and when the rotating body 3 starts up, the lower receiving member 10 side is brought into close contact with the upper receiving member 10 after the dynamic pressure is generated after the rotation. You can drive close to your side.

Further, the rotary body 3 is provided with circular fitting holes 8 into which the cylindrical body is fitted, which are arranged in a ring shape on a concentric circle centered on the plurality of through-holes 1. A concave groove 17 for inserting a ring-shaped flat plate is formed on both surfaces of the body 3.

That is, a cylindrical magnetic attraction plate 18 is embedded in the fitting hole 8, and the ring-shaped recesses 17 formed on both sides of the magnetic attraction plate 18 are fitted with the magnet 7 of the ring plate material. The magnet 7 is provided in the fitting hole 8 of the
Alternatively, ring-shaped backup plates may be fitted and disposed in the ring-shaped recessed grooves 17 formed on both sides of each.

In this case, the magnet 7 or the backup ring is a ring-shaped plate, and the cylindrical magnetic attraction plate.
18 or one or more anti-rotation recesses 27 for fitting a magnet may be provided to enable robust assembly. The magnet 7 is embedded in the recessed groove 17 or the fitting hole 8 of the rotating body 3,
The upper surface may be flatly faced, or the magnet 7 may be arranged in the recessed state or the protruding state with respect to the fitting hole 8 and held. In the example of FIG. 1, the rotating body 3
It is considered that the power can be increased by holding the magnets 7, 7 on both sides.

The mirror surface 2 is conveniently made of aluminum foil (0.1 to 0.5 mm) or a vapor-deposited film or other coating layer having a high reflectance to form the mirror portion.

In the drawing, 11 ₁ is a herringbone-shaped groove for dynamic pressure generation, and a large number of radial bearings are formed on the outer peripheral surface of the bush 5 ₁ fitted to the fixed shaft 5 or on the side surface of the rotating body corresponding thereto. . Reference numeral 12 is a cover body, which is fitted to the support body 4 and has a closed structure such as a laser printer, and can be omitted when sharpness is not required as in a bar code reader. Reference numeral 13 is a light projecting window portion, and 14 is a retaining nut for preventing loosening due to temperature expansion.

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.

As means although this embodiment are provided with a sleeve-like bush 5 ₁ of ceramic material having the outer periphery of the herringbone-like grooves on the metal securing shaft 5 as a fixed shaft 5 to restrain the floating amount of the rotating body 3 Is a washer 15 and a nut for fixing the upper receiving member 10 provided on the fixed shaft 5 above the rotating body 3.
Although 16 or other stoppers are selected and fixed, a coil spring 16 ₁ or a spring washer or other elastic member is attached to the receiving member 10 or other elastic structure or the like is used as a pressing member to fix the fixed shaft above the rotating body 3. 5 may be provided.

The support 4 is made of an aluminum material and is used as a rotation stopper for the sliding member. The fixed shaft 5 and the support 4 are also made of a ceramic material mainly composed of SiC. You can also choose to do this, and further, if the support is made of a magnetic material, the magnet 7
It may be considered that a suction force is constantly exerted between and to prevent the rotating body 3 from falling, and that a stable rotation is obtained by this suction force. Further, the fixed shaft 5 is fitted with a sleeve-shaped bush 5 ₁ which is precisely machined in terms of parallelism between the shaft end surfaces and perpendicularity to the herringbone groove surface, and the bush 5 ₁ is used as a stepped shaft to correspond to each member. May be. Further, a flat plate-shaped stator coil 6 is provided on the support body 4 and the cover 12 with respect to the magnet 7 provided on the rotating body 3 to rotate the rotating body 3 of the polygon rotor as a motor.

Therefore, the rotating body 3 having the mirror surface 2 is smoothly rotated on the bush 5 ₁ of the fixed shaft 5 on the support 4 while maintaining good mass balance, fluid balance and magnetic balance, and the air resistance during rotation is also small. You can drive.

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 rotating body 3, and the opposing surface is a smooth flat surface to form a thrust bearing portion. Further, in the radial bearing portion, a herringbone-shaped dynamic pressure generating groove 11 ₁ for dynamic pressure generation is formed on either the outer peripheral surface of the bush 5 ₁ on the fixed shaft 5 or the cylindrical surface of the through hole 1. Then
The other surface is configured as a smooth cylindrical surface, and in this embodiment, a dynamic pressure generating groove 11 for supporting a thrust load and a dynamic pressure generating groove for supporting a radial load.
11 ₁ is a groove depth of about 3 to 50 μm. The dynamic pressure generating grooves 11 may be grooved on both sides of the rotating body 3 to improve balance and eliminate deformation.

The waviness of the entire surface of the rotating body 3 and / or the receiving member 10 is 0.3.
If the surface roughness is less than μm and the maximum surface roughness is 0.1 μm, the land surface should be flat and then 3-50 μm by shot blasting.
It is preferable to use 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, the dynamic pressure generating groove 11 can be machined in the bearing portion with high accuracy, and the shape of the sliding portion suitable for generating the dynamic pressure is maintained even when the dynamic pressure is generated. Moreover, even with respect to solid rubbing generated at the time of starting and stopping, it can be effectively used with durability under a certain load.

In the example of FIGS. 5 to 7, a ring-shaped magnetic attraction plate 18 is embedded and provided, and a plurality of circular fitting holes abutting on the magnetic attraction plate are arranged in a ring shape, and a cylindrical magnet is fitted in the fitting hole 8. 7 is provided on both sides of the rotating body.

In the example of FIG. 8, the bush 5 ₁ is sandwiched between the receiving members 10 and 10 and is held by a fixing nut 16 and a spring 16 ₁ provided on the fixed shaft 5, and the stator coil 6 is provided on the cover body 12. .
The receiving member 10 between the rotating body 3 and the supporting body 4 may also be used as the supporting body 4. In this case, the supporting body 4 may be made of a ceramic material.

〔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 magnetic attraction plate inserted into a fitting hole formed in the rotating body. By holding magnets on both sides of the rotating body via stator coils and arranging stator coils corresponding to these magnets respectively, the perpendicularity and parallelism of the polygon rotor can be greatly improved, and the rotor runout can be minimized. In addition, the assembly and deployment are simple and robust, the balance adjustment is easy, and stable rotational movement is possible.The rotor core is made of permanent magnets or secondary conductors for rotating the polygon rotor, and the outer peripheral surface is the mirror part. Even if the polygon rotor is considered to be thin, the amount of deformation can be reduced, and compared with conventional polygon mirrors, the polygon The size in the direction of the rotating shaft equipped with the rail is shortened, it is possible to make it extremely thin and compact and lightweight, and its air resistance can also be significantly reduced, and with a smaller power, the same rotation speed as the conventional one can be achieved. It is possible to properly press the magnet provided on the rotor, and to connect the magnetic lines of force of the magnet in the circumferential direction for stable rotation, and to easily assemble and hold the magnet on the rotor easily. In addition, if the same level of power as before is applied, 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 safety are improved. Even if there is solid contact at the time of start / stop, it does not wear, and the dynamic pressure generation effect at the time of dynamic pressure generation is maintained well, and high thrust load Since it can be supported, the function as a polygon mirror that stably scans a light beam is always good, and a polygon mirror that can accurately reflect a laser beam or the like can be configured by the interposition of a ceramic sliding member. Simple and easy to manufacture. It is obtained in the form.

[Brief description of drawings]

1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a perspective view of a rotor, FIG. 3 is a perspective view showing a separated state thereof, and FIG. 4 is an enlarged cutaway side view of line II in FIG. FIG. 5 is a perspective view of another embodiment of the rotor, and FIG. 6 is a perspective view showing its separated state.
FIG. 7 is an enlarged sectional side view taken along the line II-II in FIG.
FIG. 9 is a sectional side view of yet another embodiment, and FIG. 9 is a longitudinal sectional view of a conventional example. 1 ... Through hole, 2 ... Mirror surface, 3 ... Rotating body, 4 ... Support body, 5 ...
Fixed shaft, 5 ₁ ... Bushing, 6 ... Stator coil, 7 ... Magnet, 8 ... Fitting hole, 10 ... Receiving member, 11, 11 ₁ ... Dynamic pressure generating groove, 15 ... Washer, 16 ... Fixing nut, 17 … Concave groove, 18… Magnetic adsorption plate.

Claims (9)

[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 polygon, the magnets are held on both sides of the rotating body through the magnetic attraction plates inserted into the fitting holes formed in the rotating body, and the stator coils are arranged corresponding to these magnets. mirror. 2. The rotating body is rotatably fitted to an outer peripheral surface of a bush fitted and arranged on the fixed shaft, and the outer peripheral surface of the bush or a sliding surface of the rotating body facing the outer peripheral surface. The polygon mirror according to claim 1, wherein one of the surfaces has a groove for generating a dynamic pressure. 3. The rotating body is a plate body made of a ceramic material having spiral grooves for generating dynamic pressure formed on both side surfaces thereof, and is sandwiched by thrust receiving plates provided facing both side surfaces, The polygon mirror according to claim 2, wherein a fixed member is fitted to the fixed shaft together with the bush. 4. The rotary body is provided with a plurality of circular fitting holes arranged in an annular shape for inserting a cylindrical body, and the circular fitting holes communicate with the fitting holes, and ring-shaped flat plates are provided on both sides of the rotary body. Claim 2 which is one in which a concave groove for inserting the
The polygon mirror according to item 3 or 3. 5. The rotating body is provided with cylindrical magnetic attraction plates in circular fitting holes arranged in a plurality of annular shapes, and the magnets are fitted into ring-shaped concave grooves formed on both sides of the magnetic attraction plates. The polygon mirror according to any one of claims 2 to 4, wherein the polygon mirror is jointly arranged. 6. The rotating body is provided with a ring-shaped magnetic attraction plate, a plurality of circular fitting holes abutting against the magnetic attraction plate are arranged in a ring shape, and a cylindrical magnet is provided in the fitting hole of the rotating body. The polygon mirror according to claim 2 or 3, which is provided on both sides. 7. The rotating body is provided with the magnets in cylindrical fitting holes arranged in a plurality of annular shapes, and ring-shaped backup plates are fitted into ring-shaped recessed grooves formed on both sides of the magnets, respectively. The polygon mirror according to any one of claims 2 to 4, which is provided. 8. The magnet or the backup ring is a ring-shaped plate body, and is provided with one or more detent recesses for fitting the cylindrical magnetic attraction plate or magnet. The polygon mirror according to any one of items 2 to 7. 9. The rotating body has a flat plate having a through hole in the center, an outer peripheral edge of a regular polygonal shape, and a fitting hole for annularly arranging a magnet concentrically with the through hole and having an outer peripheral surface. The polygon mirror according to any one of claims 4 to 8, which is a polygon rotor having a mirror surface formed by fixing aluminum foil to the.