JPH0677110B2 - 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 supplied to the upper surface of the fixed shaft d by the middle groove portion f ₂ , and the air pressure between the upper end of the fixed shaft d and the thrust bearing g 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, most of the load when the polygon mirror is rotating at high speed is due to the air resistance at the outer edge of the polygon, and the area that reflects the laser light is 1 m.
Considering that the width is narrow enough for m or less, the power loss due to the polygon mirror disturbing 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 with an air film, the balance adjustment is very complicated, and the assembly configuration and manufacturing process are troublesome, and the rotating body etc. If it is made of ceramics, its ductility is extremely low, so cracks are likely to occur and if the surface has cracks or cracks occur on the surface during rotation, the cracks immediately propagate due to the tension due to the centrifugal force of high-speed rotation and break. There were many problems such as an accident, and it was dangerous because it would escape from the window hole to the outside of the case in the event of a destruction accident, and it could lead to an accident that damages expensive equipment, etc. .

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. In addition, there is little tilt of the reflecting surface, it is highly accurate and suitable for mass production, it is good in terms of security, stable high speed rotation is possible, and a polygon mirror that can accurately reflect laser light, etc. is configured easily, easy to assemble and manufacture, and cheap It is intended to be provided in various forms.

[Means for solving problems]

According to the present invention, a polygon mirror rotor is constituted by a ceramic cylindrical body and a metal outer peripheral member which is shrink-fitted and fixed to the outer periphery of the cylindrical body. A magnet is provided on the rotor and a mirror surface is provided on the outer peripheral surface of the outer peripheral member. And a stator coil is provided corresponding to the magnet, a bush is fitted to the ceramic cylinder, and the bush is fitted to the outer peripheral surface of the bush or the sliding surface of the ceramic cylinder facing the bush. A groove for pressure generation is formed, and the ceramic cylindrical body is sandwiched from both sides thereof by a thrust receiving member and fitted with a bush by a fixed shaft, and a groove for dynamic pressure generation is formed on a sliding surface facing the receiving member. This is a polygon mirror characterized by being provided.

〔Example〕

The embodiment of the present invention will be described with reference to FIGS. 1 and 2. The through-hole 1 is formed in the center, and the through-hole 1 is formed on a flat plate having a plurality of mirror surfaces 2 having a regular polygonal outer peripheral edge. a ceramic cylindrical body 3 ₁ which is made of a tube body 3 ₁ metal of the outer member which is fixed Me shrink the outer periphery 3 ₂ which comprise a plurality of the outer peripheral edge of the outer peripheral member 3 ₂ regular polygon A polygon mirror rotor 3 is formed on the mirror surface 2, and the rotor 3 penetrates through the through hole 1 and is located on the outer periphery of the fixed shaft 5 provided on the support body 4, and the dynamic pressure generating groove 11 is formed on the outer peripheral surface. ₁ is provided rotatably on the bush 5 ₁ formed with, and the outer peripheral member 3 ₂ fixed parallel to, a stator coil 6 for rotating the rotor 3 to the support 4 or the cover member 12, the rotor 3 the outer peripheral member 3 _second magnet 7 of permanent magnets or secondary conductors provided between said stator coil 6 A motor unit for rotating the rotor 3 is constructed so that a thrust receiving member 10 made of a metal or a ceramic material is interposed between the rotor 3 and the support body 4, and the rotor 3 and the supporting member 4 are opposed to each other. Grooves for dynamic pressure generation on or on any of the formed sliding surfaces
Formed 11,11 ₁ .

The cylindrical body 3 ₁ of the rotor 3 is a cylindrical body or a rectangular cylindrical body having a circular through hole in the center, and is fitted to the fixed shaft 5 or a bush 5 ₁ supported by the fixed shaft 5, and the support body 4 The receiving member 10 is disposed face-to-face with the receiving member 10 interposed above.
As the 10 lies on a surface facing the surface and the stator coil 6 to face the magnet 7 of the rotor 3 in triangular or circular plate body, sandwiching the cylindrical body 3 ₁ is provided on both sides of the axial side of the cylindrical body 3 ₁ I am doing it. Hard The cylindrical body 3 ₁ hydrodynamic grooves 11 on both sides of the sliding surface of the surface corresponding to the receiving member 10, for example twisting direction is the spiral groove of the opposite form, leaving a land portion Ceramic materials such as SiC sintered body, BeO containing α
-It is preferable that the thrust bearing portion is formed by using a SiC sintered body, a Si ₃ N ₄ sintered body or the like, and the receiving member 10 is also a thrust receiving plate using a flat plate of a hard ceramic material. Alternatively, a dynamic pressure generating groove may be formed on the corresponding sliding surface as required. The clearance between the rotor 3 and the receiving member 10 of the thrust receiving plate is 5 to 15 μm. When the rotor 3 starts up, the rotor 3 comes into close contact with the lower receiving member 10 side, and after the dynamic pressure is generated after rotation, the upper receiving member 10 side appears. It is possible to drive close to.

The magnet 7 are embedded deployed into the insertion hole 8 of the round hole provided on the outer peripheral member 3 ₂ of the rotor 3, may be flat surfaces combined a top, the top surface of the magnet 7 relative to the insertion hole 8 It is very good that it is arranged in a recessed state or a projected state, and a backup plate (not shown) is applied and held. In the example of Fig. 1,
The magnets 7, 7 are held on both sides of the rotor 3 so that the power can be increased.

Wherein at insertion holes 8 is formed deployed in several annularly cylindrical body 3 ₁ or the outer peripheral member 3 ₂ of the rotor 3, the fixed shaft 5 and connected deployed in a ring shape so as to form a disk-shaped rotor core A plurality of magnetic poles may be magnetized in a ring shape along a plane orthogonal to the mirror surface 2, and the mirror surface 2 may be an aluminum foil (0.1 to 0.5 mm) or a vapor-deposited film or other material having a high reflectance. It is convenient to use the coating layer as the mirror part.

In the figure, reference numeral 11 ₁ denotes a dynamic pressure generating groove formed in a herringbone shape, and a large number of radial bearings are provided on the outer peripheral surface of the bush 5 ₁ fitted to the fixed shaft 5 or on the corresponding side surface of the rotating body. Is forming. 12 is a cover body, which is a support body 4.
It has a sealed 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.

Although the cylindrical body 3 ₁ are those having the dynamic pressure generating grooves 11 on its upper and lower surfaces, opposite direction (projection plane when the dynamic pressure generating grooves 11 are spiral direction provided on both sides Same direction)
In order to prevent the burning of the polygon rotor even if it is mistakenly rotated in the opposite direction when the polygon rotor is rotationally driven, that is, the dynamic pressure effect is generated and the thrust load is received in both forward and reverse rotations. Although it is effective in terms of security, it may be provided in the same direction (opposite direction on the projection plane) if necessary, and one of them may serve as a clutch action. In this case, taking advantage of the receiving member 10 serving as the intermediate member is considered, it is possible to balance a mirror 2 also aluminum foil or an aluminum vapor deposition in addition to the outer periphery of the outer member 3 ₂ of the rotor 3. As the outer peripheral member 3 _2, a ring-shaped, flat body has regular polygon outer peripheral edge, but is obtained by a mirror 2 by fixing the aluminum foil to the outer peripheral surface, a truncated cone the upper and lower surfaces The outer peripheral surface may be formed into a mirror surface by gradually reducing the thickness outward.

Incidentally, there is provided a sleeve-like bush 5 ₁ of ceramic material having a herringbone-like grooves on the metal securing shaft 5 as a fixed shaft 5 is in this embodiment the outer periphery, but the rotor 3
As a means for restraining the floating amount of the above, the upper receiving member 10 provided on the fixed shaft 5 above the rotor 3 is configured to be fixed by selecting the washer 15 and the fixing nut 16 or other stoppers. Alternatively, an elastic member such as a coil spring, a spring washer, or the like may be additionally provided, or another elastic structure may be provided as a pressing member on the fixed shaft 5 above the rotor 3.

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. The support 4 is made of a magnetic material so that the rotor 3 is prevented from crashing by constantly exerting an attractive force between the support 4 and the magnet 7, and a stable rotation is obtained by this attractive force. May be considered. 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.

Thus the rotor 3 with a mirror surface 2 is smooth rotating sleeve-like bush 5 ₁ mass balance on the fixed shaft 5 in the supporting body 4, fluid balance and the magnetic balance is well maintained, air resistance during rotation Can be driven 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 4 and the rotor 3, and the opposing surface thereof is a smooth flat surface to form a thrust bearing portion.
In the radial bearing portion, a herringbone-shaped groove 11 ₁ for dynamic pressure generation is formed on either _one of the outer peripheral surface of the sleeve-shaped bush 5 ₁ on the fixed shaft 5 or the cylindrical surface of the through hole 1,
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 10 μm. The dynamic pressure generating groove 11 may be grooved on both sides of the rotor 3 to improve balance and prevent deformation.

The entire surface of the rotor 3 and / or the receiving member 10 has a waviness of 0.3.
The land surface is a smooth flat surface with a maximum surface roughness of 0.1 μm or less at μm or less, and then 3 to 10 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 the shot plast described above can be similarly performed. In any case, the dynamic pressure generating grooves 11 and 11 ₁ can be machined in the bearing portion with high accuracy, and the shape of the sliding portion suitable for generating the operation can be used even when dynamic pressure is generated. It is maintained and is effectively used with durability against solid rubbing generated at the time of starting and stopping as long as it has a certain load.

3 in the illustrated example is provided on the bush 5 cover 12 to the stator coil 6 with those held ₁ at a receiving member fixing nut 16 clamped to provided the fixed shaft 5 between 10 and 10 and coil spring 17. Incidentally, Yes and the magnet 7 provided in the cylindrical body 3 ₁ of the rotor 3 may also be combined to the receiving member 10 between the tubular body 3 ₁ and the support 4 with the support 4, in this case the support 4 May be made of a ceramic material.

In the concrete example shown in FIGS. 4 to 6, the fixed shaft 5 made of metal is used as the rotary shaft.
For example, a herringbone-shaped groove 11 for generating dynamic pressure on a bolt.
Sandwiched ₁ but provided with a sleeve-like bush 5 ₁ of metal or ceramic material having the outer periphery, and the rotating cylinder 3 ₁ from both sides in the thrust receiving member 10, 10, the fixed shaft 5 together with the bush 5 ₁ The dynamic pressure generating grooves 11 and 11 are provided on the sliding surface facing the receiving members 10 and 10 so as to be easily assembled.

Further, in this embodiment, the outside air easily flows from the through hole 20 formed in the receiving member 10 to the dynamic pressure bearing portion between the bush 5 ₁ and the cylindrical body 3 ₁ . The backup ring of the ring-shaped iron piece 18, fixes and for better magnetic circuit of the magnet 7, there is for taking mass balance, the balance without impairing the strength of the cylindrical body 3 ₁ made of ceramic can do. in this case,
The bolt of the fixed shaft 5 is screwed into the screw hole 21, and the washer 15 is packed.
19 is used together so that the receiving members 10 and 10 can be easily clamped, and the support body 4 is provided with a guide air passage 22 communicating with the through hole 20 provided in the lower receiving member 10. There is. Further, when the magnet 7 is embedded in the insertion hole 8 of the rotor 3, it is possible to cover it with a synthetic resin coating agent.

In a 7-9 FIG example instead a tubular body 3 ₁ of a metal hollow cylinder that is secured by a shrink fit on the outer periphery 3 ₂ a flange-like plate members, so-called abacus spherical body upper and lower surfaces as a truncated cone and the safety thereof a large-diameter outer peripheral surface and a mirror surface 2 of a polygon, a strong protection and the window portion 13 of the rotation at that remove the edge portions reducing the windage loss balance, as well as the cylindrical body 3 ₁ as a form covered with a metal member Is raised. In this case, an upper and lower surfaces are conical shape of the outer peripheral member 3 _2, to have the small short windage length of the outer periphery near the mirror 2 contour so gradually decreases outward thick, cylindrical body 3 ₁
You can enhance the safety by enclosing the outer circumference of.

〔The invention's effect〕

According to the present invention, a polygon mirror rotor is constituted by a ceramic cylindrical body rotatably fitted to a fixed shaft, and a metal peripheral member which is shrink-fitted and fixed to the outer periphery of the cylindrical body. And a mirror surface is formed on 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 cylindrical body, and the bush outer peripheral surface or a ceramic cylinder facing this. A groove for generating dynamic pressure is formed on one of the body-side sliding surfaces, and the cylindrical body is sandwiched by thrust receiving members from both sides thereof and fitted with a bush by a fixed shaft, and a sliding surface facing the receiving member. By providing a groove for dynamic pressure generation on the outer circumference of the cylindrical body made of ceramics with low ductility is surrounded by a metal outer peripheral member with high ductility, it is possible to prevent the cylindrical body from being broken by cracks, and Be destroyed box member have been blocked by a metal member, danger fewer jumping outside of the case,
Moreover, a large initial compression pressure remains on the outer peripheral surface of the cylindrical body due to the shrinkage fit, and the radial and circumferential tensions due to the centrifugal force are offset to suppress the occurrence or propagation of cracks, limiting the rotational speed. It is possible to raise it, and it is possible to greatly improve the verticality and parallelism of the polygon rotor by being sandwiched by the receiving members, and to reduce the core runout of the rotor as much as possible. Adjustment is easy and stable rotation operation is possible, and even if the thickness of the rotor core that consists of permanent magnets or secondary conductors for rotating the polygon rotor and the outer peripheral surface of the polygon rotor is thin, its deformation The amount can be reduced,
Compared with the conventional polygon mirror, the dimension in the direction of the rotation axis with the polygon mirror attached becomes shorter, and it is possible to make it extremely thin and compact and its air resistance can be significantly reduced, and with a smaller power. The same rotation speed as the conventional one can be obtained, and if the same amount of electric power as the conventional one is input, the polygon mirror can obtain a higher rotation speed, and the thrust is generated by producing a dynamic pressure effect on the polygon rotor. The load is satisfactorily received, so maintenance and safety are easy, and even if there is solid contact at the time of starting and stopping, it does not wear, and it is easy to manufacture and dimensional accuracy is easy to obtain, and highly accurate processing is possible. In addition, it is suitable for mass production and has a good function as a polygon mirror that constantly scans light rays, and the ceramic member is interposed by the case and the metal member of the outer peripheral member. Since it is sandwiched by the bar and the receiving member, there is no obstacle due to breakage, safety and reliability are increased, and a polygon mirror that can accurately reflect laser light etc. is configured Simple and easy to manufacture It can be obtained in an inexpensive form is there.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention, and FIG. 2 is FIG.
A cross-sectional view taken along the line I, FIG. 3 is a sectional side view of another embodiment,
FIG. 4 is a longitudinal cross-sectional view of a part of still another embodiment, FIG. 5 is a bottom view taken along line II-II in FIG. 4, FIG. 6 is a plan view taken along line III-III in FIG. 4, and FIG. FIG. 8 is a longitudinal sectional view of a part of another embodiment, FIG. 8 is a perspective view of the rotor, and FIG. 9 is a longitudinal sectional view of a conventional example. 1 ... Through hole, 2 ... Mirror surface, 3 ... Rotor, 3 ₁ ... Cylindrical body, 3 ₂ ... Outer peripheral member, 4 ... Support body, 5 ... Fixed shaft, 5 ₁ ... Bush, 6 ...
Stator coil, 7 ... Magnet, 8 ... Insertion hole, 10 ... Receiving member, 11,111 ₁ ... Dynamic pressure generating groove, 12 ... Cover body, 15 ... Washer, 16 ... Fixing nut, 17 ... Spring.

Claims (5)

[Claims] 1. A polygon mirror rotor comprising a ceramic cylindrical body and a metal outer peripheral member which is shrink-fitted and fixed to the outer periphery of the cylindrical body, wherein a magnet and a mirror surface are formed on the outer peripheral surface of the outer peripheral member. And a stator coil is provided corresponding to the magnet, a bush is fitted to the ceramic cylinder, and either the outer peripheral surface of the bush or the sliding surface of the ceramic cylinder facing the bush is formed. A groove for dynamic pressure generation is formed, and the ceramic cylindrical body is sandwiched by thrust receiving members from both sides thereof and fitted with a bush by a fixed shaft, and a groove for dynamic pressure generation is formed on a sliding surface facing the receiving member. A polygon mirror characterized by being provided with. 2. The ceramic cylindrical body is a cylindrical body having a through hole in the center, and spiral grooves for dynamic pressure generation are formed on both upper and lower surfaces of the cylindrical body. Polygon mirror. 3. The magnet according to claim 1, wherein the magnet is arranged in a circular hole provided in a plurality of annular shapes in a ceramic cylinder of the polygon mirror rotor.
The polygon mirror described in the item. 4. The magnet according to claim 1 or 2, wherein the magnets are provided on both sides of a flat plate-shaped outer peripheral member of the polygon mirror rotor, and are opposed to the respective stator coils. Polygon mirror. 5. The outer peripheral member is one in which the upper and lower surfaces are frustoconical surfaces, and the thickness is gradually reduced outward, and the outer peripheral member is arranged at the center of the horizontal surface of the ceramic cylindrical body. The polygon mirror according to claim 2 or 3.