JP4488862B2 - Optical deflector, optical scanning device, and image forming apparatus - Google Patents

Description

  The present invention relates to an optical deflector used in an optical writing device of an electrophotographic copying machine, a printer, a facsimile machine, or a composite machine of these, an optical scanning device using the optical deflector, and an image forming apparatus.

  In recent years, an electrophotographic recording apparatus using a laser writing apparatus such as a digital copying machine or a laser printer has been developed to have an optical deflector of 20000 revolutions / minute or more as the printing speed increases and the pixel density increases. In order to satisfy the required quality of long life, high durability and low noise, high-speed rotation is required, and an optical deflector using a dynamic pressure bearing as a support portion of the rotating body has been put into practical use.

  As such an optical deflector, a rotating polygon mirror as a deflection reflecting surface is integrally formed on a high-speed rotating body outside the ceramic fixed shaft and constituting a gas dynamic pressure bearing together with the fixed shaft. It has been. And what comprised the high-speed rotary body with the ceramic sleeve which has fixed thickness in a radial direction, and the metal outer periphery cylinder member fixed to the outer periphery by shrink fitting is known (for example, refer patent document 1). ). The thermal expansion coefficient of the outer peripheral cylindrical member is larger than the thermal expansion coefficient of the ceramic sleeve. In this optical deflector, after the ceramic sleeve is shrink-fitted and fixed, the inner diameter of the ceramic sleeve is processed into a predetermined shape. The gap between the ceramic fixed shaft and the ceramic sleeve is made uniform according to the radial centrifugal stress acting on the rotational speed of the high-speed rotating body and the shrinkage compression stress relieved by thermal expansion due to friction. The stitch shape of the inner diameter of the ceramic sleeve is determined.

  However, in this conventional example, when a mirror-finished polygon mirror (rotating polygonal mirror) is shrink-fitted, the reflecting surface is distorted due to the compressive stress at the time of shrink-fitting, the flatness is deteriorated, and a highly accurate reflecting surface is maintained. I can't. As a result, there is a problem that a good image output cannot be obtained.

  Even when the reflective surface of the polygon mirror is processed after shrink fitting, if the temperature of the rotating body rises due to high-speed rotation, the linear expansion coefficient of the ceramic sleeve is smaller than the linear expansion coefficient of the metal outer cylindrical member. The compressive stress is removed, the deflecting reflecting surface of the polygon mirror is distorted, the flatness is deteriorated, and a highly accurate reflecting surface cannot be maintained. As a result, there is a problem that a good image output cannot be obtained.

  In addition to the above conventional example, the method of fixing the rotary polygon mirror to the rotating body includes a method of fixing with a screw, a method of fixing through a leaf spring, a method of press-fitting, adhesion, etc. Stress is generated due to the negative effect on the reflective surface. Further, since the two parts are overlapped, the angle variation (surface tilt) of the reflection surface of the polygon mirror increases. Furthermore, the weight balance changes, the balance of the rotating body is lost, and the vibration tends to increase. The vibration generated by the optical deflector vibrates the periphery of the optical deflector and causes noise and image degradation. The noise level tends to be particularly high at a high speed of 20000 rpm.

  In order to solve such a problem, the present applicant has filed a patent application regarding the optical deflector described below. That is, a cylindrical protrusion protruding in the axial direction is formed on a metal outer member that is shrink-fitted or press-fitted into a ceramic sleeve supported by a hydrodynamic bearing, and the coefficient of thermal expansion is substantially the same as that of the metal outer member. A boss-like protrusion that protrudes in the axial direction on the inner side in the radial direction of the reflecting surface is formed on the polygon mirror to be fixed, and the outer peripheral surface of the boss-like protrusion is fixedly fitted to the inner peripheral surface of the cylindrical protrusion. It was set as the structure to do. By adopting such a configuration, even when distortion occurs in the fitting portion between the sleeve having a different coefficient of thermal expansion and the metal outer peripheral member when the temperature rises, the influence of the distortion acting on the reflection surface of the polygon mirror is ignored. It is made as small as possible, and the light beam deflection function is maintained with high accuracy.

  However, in the above conventional example, the polygon mirror is provided with a boss-like protrusion protruding in the axial direction and fixed to the cylindrical protrusion protruding in the axial direction of the metal outer peripheral member. Due to the bias toward the polygon mirror and the balance of the rotating body was corrected, the unbalance of the rotating body could not be made sufficiently small, and the unbalanced vibration was large. In addition, since the polygon mirror was fixed on the mirror finishing reference surface provided on the polygon mirror and the reflecting surface was mirror finished, the angle variation of the reflecting surface with respect to the rotation center axis of the hydrodynamic bearing was large.

Japanese Patent Laid-Open No. 7-190047 JP 2000-206439 A

An object of the present invention is to maintain a highly accurate deflecting / reflecting surface, to have a small angle variation (surface tilt) of the deflecting / reflecting surface, to obtain a favorable image output, and to obtain the center of gravity of the rotating body of the hydrodynamic bearing. It is an object of the present invention to provide an optical deflector that can adjust the balance of a rotating body with high accuracy and has low vibration and low noise by adopting a configuration that can be arranged near the middle.
Another object of the present invention is to provide a high-precision, low-vibration, low-noise optical scanning device by using the optical deflector according to the present invention, and to provide a high-quality, low-noise image forming apparatus. .

More specific objects corresponding to the inventions described in the claims of the present invention are as follows.
When a polygon mirror is press-fitted into a flange, an elastic member is interposed between the flange and the polygon mirror, so that when the polygon mirror is press-fitted into the flange, the polygon mirror is elastically fixed, causing temperature changes and vibration shocks. Accordingly, there is provided an optical deflector in which there is no displacement of the polygon mirror due to the above, and therefore the change with time of the contact state with the flange is small, and the change with time of the deflection reflection surface accuracy of the polygon mirror is small. Furthermore, there is provided an optical deflector for high-speed rotation in which the unevenness of the contact surfaces of the flange and the polygon mirror does not affect the accuracy of the deflection reflection surface of the polygon mirror.

Provided is an optical deflector with improved sealing performance against entry of processing oil during polygon mirror processing and cleaning liquid during cleaning.
Provided is an optical deflector that prevents the elastic member from being deformed by centrifugal force when the rotating body is rotated after the assembly, and thus the balance of the rotating body corrected with high accuracy is not lost.
Provided is a low-cost optical deflector that is easy to process an elastic member.
An optical deflector including a ring-shaped spacer capable of absorbing excessive stress when a polygon mirror is press-fitted into a flange by deformation is provided.

Provided is an optical deflector in which a ring-shaped spacer is not displaced with respect to a polygon mirror or a flange due to a temperature change, and a balance of a rotating body corrected with high accuracy is not lost.
When the polygon mirror is press-fitted into the flange, the polygon mirror is elastically fixed so that there is no displacement of the mirror due to temperature change or vibration shock, so the change in contact state with the flange over time is small, and the mirror reflection surface accuracy Optical deflector for high-speed rotation that prevents the accuracy of the mirror reflecting surface from being affected by the unevenness of the contact surfaces of the flange and the polygon mirror. The container can be obtained without adding special parts.
An optical deflector capable of absorbing excessive stress when a polygon mirror is press-fitted into a flange is provided.

Provided is an optical scanning device in which noise caused by vibration of the optical deflector is small, the reflecting surface of the optical deflector is maintained with high accuracy, and the scanning beam shape is constant and stable.
Provided is a multi-beam optical scanning device in which noise caused by vibration of the optical deflector is small, the reflecting surface of the optical deflector is maintained with high accuracy, and the scanning beam shape is constant and stable.

  Provided is an image forming apparatus in which noise caused by vibration of an optical deflector is small, a scanning beam of an optical scanning device is constant and stable, and a high-quality image can be obtained.

  According to a first aspect of the present invention, there is provided an optical deflector in which a rotating body having a polygon mirror is supported by a hydrodynamic bearing and is driven to rotate by a motor. The rotating body includes a sleeve having a hydrodynamic bearing surface and the sleeve. A flange fixed to the flange, a polygon mirror press-fitted to the flange, and a permanent magnet for driving. The polygon mirror is hollowed to form a cup shape and a reflection formed on the polygon mirror. Part or all of the surface is overlapped with the hydrodynamic bearing surface formed on the sleeve at a position in the rotational axis direction and coupled to the flange, and an elastic member is interposed between the flange and the polygon mirror. Features.

The elastic member can be constituted by an O-ring as in the invention described in claim 2, or can be constituted by a ring-shaped spacer as in the invention described in claim 4.
When the elastic member is formed of an O-ring, a circumferential groove for holding the outer periphery of the O-ring may be provided on the flange or the polygon mirror as in the third aspect of the invention.
When the elastic member is composed of a ring-shaped spacer, the ring-shaped spacer is preferably formed with a thin intermediate portion between the inner diameter and the outer diameter. Further, as in the invention described in claim 6, it is preferable that the linear expansion coefficient of the ring spacer is substantially the same as the linear expansion coefficient of the polygon mirror or the flange.

According to a seventh aspect of the present invention, a light beam from a semiconductor laser is guided to a surface to be scanned through an optical system including a light deflector to form a light beam spot and deflected by the light deflector. An optical scanning apparatus for scanning a surface with a light beam spot, wherein the optical deflector is the optical deflector according to any one of claims 1 to 6 .

The invention according to claim 8 has a semiconductor laser that emits a plurality of light beams, and guides the plurality of light beams from the semiconductor laser to a surface to be scanned through an optical system including an optical deflector. The optical deflector according to any one of claims 1 to 6 , wherein in the optical scanning device that forms a beam spot and deflects it with an optical deflector, the surface to be scanned is adjacently scanned with the plurality of optical beam spots. It is an optical deflector.

According to a ninth aspect of the present invention, there is provided an image forming apparatus in which a latent image is formed on a photosensitive surface of a photosensitive medium by optical scanning with an optical scanning device, and the latent image is visualized to obtain an image. The optical scanning device according to claim 7 or 8 is used as an optical scanning device that performs optical scanning of a surface.

  According to the first aspect of the present invention, when the polygon mirror is press-fitted into the flange, the polygon mirror is elastically fixed to the flange by the elastic member, and there is no deviation of the mirror due to temperature change or vibration shock. The change in the contact state with time is small, and the change with time in the accuracy of the deflecting reflection surface of the polygon mirror is small. Furthermore, it is possible to provide an optical deflector that can withstand high-speed rotation without degrading the accuracy of the deflecting / reflecting surface of the polygon mirror due to the unevenness of the contact surface between the flange and the polygon mirror.

According to the invention described in claim 2, in the invention described in claim 1, it is possible to provide an optical deflector with improved sealing performance against the ingress of processing oil during mirror processing and cleaning liquid during cleaning.
According to the invention of claim 3, in the invention of claim 2, there is no deformation of the O-ring due to centrifugal force when the rotating body is rotated after assembly, and the balance of the rotating body corrected with high accuracy is achieved. An optical deflector that does not collapse can be provided.

According to the invention described in claim 4, in the invention described in claim 1, it is possible to provide an optical deflector that is easy to process the elastic member and is low in cost.
According to the invention described in claim 5, in the invention described in claim 4, an optical deflector provided with a ring-shaped spacer capable of absorbing excessive stress when the polygon mirror is press-fitted into the flange by deformation is provided. can do.
According to the invention described in claim 6, in the invention described in claim 4, the ring-shaped spacer does not shift with respect to the polygon mirror or the flange due to temperature change, and the balance of the rotating body corrected with high accuracy is lost. It is possible to provide an optical deflector that does not occur.

According to the seventh aspect of the present invention, there is provided an optical scanning device in which noise caused by vibration of the optical deflector is small, the reflection surface of the optical deflector is maintained with high accuracy, and the scanning beam shape is constant and stable. Can do.
According to the eighth aspect of the present invention, there is provided a multi-beam optical scanning device in which the noise caused by the vibration of the optical deflector is small, the reflecting surface of the optical deflector is maintained with high accuracy, and the scanning beam shape is constant and stable. can do.

According to the ninth aspect of the present invention, it is possible to provide a high-quality image forming apparatus in which noise caused by the vibration of the optical deflector is small, the scanning beam of the optical scanning device is constant and stable.

  Embodiments of an optical deflector, an optical scanning device, and an image forming apparatus according to the present invention will be described below with reference to the drawings.

  A first embodiment of an optical deflector using a dynamic pressure air bearing will be described with reference to FIGS. 1, 2, 3, 4, and 5. The dynamic pressure air bearing can also use a gas other than air as a lubricating fluid. 1 to 5, the lower surface of the portion corresponding to the flange of the cover case 21 in which the bottomed cylinder with flange is turned down is finished with high accuracy to serve as an attachment reference surface 21a to the optical housing. The housing 1 is fixed to the lower surface side of the cover case 21. The housing 1 has a shape close to a disk, and a cylindrical bearing mounting portion 1b is integrally formed at the center of the upper surface thereof, and a cylindrical fixed shaft 2 constituting a hydrodynamic bearing is formed on the inner peripheral side of the bearing mounting portion 1b. Is fixed by fitting or the like.

  On the surface of the cylindrical fixed shaft 2, a plurality of oblique grooves 2a for forming a hydrodynamic bearing are formed side by side in the circumferential direction. The groove 2a is formed in two places with a predetermined distance from the fixed shaft 2 in the direction of the central axis thereof, and the two grooves 2a are formed with the inclination directions opposite to each other. A cylindrical sleeve 16 is fitted on the outer peripheral side of the fixed shaft 2 with a minute bearing clearance between the outer peripheral surface of the fixed shaft 2 and the inner peripheral surface of the sleeve 16. The sleeve 16 constitutes the rotating body 3 together with a flange 17 fitted so as to be integrated with the outer peripheral side thereof, a polygon mirror 18 fitted so as to be integrated with an upper outer peripheral side of the flange 17, and the like. When the rotating body 3 starts rotating, the air pressure in the bearing clearance formed between the sleeve 16 and the fixed shaft 2 is increased by the two grooves 2a, and the rotating body 3 is not in contact with the fixed shaft 2. Is supported in the radial direction (radial direction).

  A fixed portion 5 of an attraction type magnetic bearing is fixed inside the fixed shaft 2. The fixed portion 5 of the attractive magnetic bearing is fixed by being sandwiched in the axial direction by press-fitting and fixing a flat dish-shaped cap 6 and a ring-shaped stopper 7 to the inner cylinder portion of the fixed shaft 2. A fine hole with a diameter of about 0.2 to 0.5 mm is formed in the center of the cap 6 to attenuate the vertical vibration using the viscous resistance when air passes. As a material for the cap 6 and the stopper 7, a stainless steel plate, which is a nonmagnetic material, is used.

  The fixed portion 5 of the attraction type magnetic bearing is made of a ferromagnetic material in which a ring-shaped permanent magnet 8 magnetized with two poles in the direction of the rotation axis and a central circle smaller than the inner diameter of the ring-shaped permanent magnet 8 are formed. 1 fixed yoke plate 9, and similarly, a second fixed yoke plate 10 made of a ferromagnetic material having a central circle smaller than the inner diameter of the ring-shaped permanent magnet 8. The first fixed yoke plate 9 and the second fixed yoke plate 10 sandwich the ring-shaped permanent magnet 8 in the axial direction, and the center circle of the first fixed yoke plate 9 and the center circle of the second fixed yoke plate 10 are It is arranged so as to be coaxial with the rotation center axis, and is fixed in the fixed shaft 2. As a material of the ring-shaped permanent magnet 8, a rare earth permanent magnet may be used, but other types of magnets may be used. As the material for the fixed yoke plates 9 and 10, a steel plate is used.

  On the upper surface of the housing 1, a printed circuit board 11 having a hole for escaping the bearing mounting portion 1b at the center is disposed and fixed by screwing or the like. A stator 12 is fitted and fixed on the outer peripheral side of the bearing mounting portion 1 b of the housing 1 above the printed circuit board 11. Since the housing 1 is made of a conductive material such as an aluminum alloy, an eddy current flows through the housing 1 due to the influence of an alternating magnetic field caused by the rotation of the rotor magnet 14. The printed circuit board 11 is preferably composed of an iron substrate so that the motor loss is not increased by this eddy current. The printed circuit board 11 is mounted with a hall element 13 which is a position detection element for switching energization to the winding coil 12a.

  The motor unit is mounted on the rotor magnet 14 attached to the rotating body 3, the winding coil 12a, the stator 12 around which the winding coil 12a is wound, the printed board 11 to which the winding coil 12a is connected, and the printed board 11. It is comprised with the Hall element 13 etc. which were made. The stator 12 is formed by stacking silicon steel plates so that an eddy current flows and iron loss does not increase. The rotating body 3 is fixed to a sleeve 16, a flange 17 fixed to the outside of the sleeve 16, a polygon mirror 18 fixed to the flange 17, a rotating portion 19 of a magnetic bearing fixed to the polygon mirror 18, and the flange 17. The rotor magnet 14 is composed of an O-ring 24 disposed between the flange 17 and the polygon mirror 18. The sleeve 16 is made of ceramics, the flange 17 is made of an aluminum alloy, and the sleeve 16 and the flange 17 are fixed by shrink fitting.

  The flange 17 corresponds to a rotor housing of the motor, and the rotor magnet 14 for the motor fixed to the lower side of the flange 17 is fixed to the flange 17 by adhesion or press fitting. The rotor magnet 14 may be a permanent magnet divided in the circumferential direction, but is formed in a ring shape so that adhesion or press-fitting can be easily performed, and N poles and S poles are alternately magnetized in the circumferential direction. If a plastic magnet having a linear expansion coefficient substantially the same as that of the flange 17 is used as the material of the rotor magnet 14 and is fixed to the flange 17 by press-fitting, the change in unbalanced vibration of the rotating body 3 due to temperature change can be reduced. It is more suitable as a motor for high speed rotation.

  As shown in detail in FIG. 3, a step is formed at the upper end of the flange 17 by slightly projecting the entire circumference in the outer diameter direction, and the portion provided with this step is a press-fitted inner diameter portion 17a. . The ceiling part of the upper part of the polygon mirror 18 is formed in a shape recessed inward, and a cylindrical surface is formed into which the press-fitted inner diameter part 17a of the flange 17 is fitted. The cylindrical surface slightly protrudes in the outer peripheral direction over the entire circumference. A press-fit outer diameter portion 18a is formed. This press-fit outer diameter portion 18a is fixed to the press-fit inner diameter portion 17a of the flange 17 by press-fitting. The diameter of the press-fit outer diameter portion 18 a of the polygon mirror 18 is formed to be slightly larger than the diameter of the press-fit inner diameter portion 17 a of the flange 17. The flange 17 and the polygon mirror 18 are both made of an aluminum alloy, but are of different materials with different linear expansion coefficients of several percent or less. The polygon mirror 18 is made of a pure aluminum alloy having a high aluminum content in order to form a mirror surface having a high reflectivity, and the linear expansion coefficient of the material is about 24.6 × 10 −6 / ° C. On the other hand, the flange 17 is made of a structural aluminum alloy, and the material has a linear expansion coefficient of about 23.8 × 10 −6 / ° C., which is about 3% smaller than that of the polygon mirror 18.

  In FIG. 12, the diameter φD2 of the press-fit inner diameter portion 17a and the press-fit outer diameter portion 18a is larger than the diameter φD1 of the dynamic pressure bearing. A reference surface 17b for mirror finishing is formed on the flange 17 in a direction perpendicular to the hydrodynamic bearing surface 16a of the sleeve 16. The mirror surface processing reference surface 17b is on the lower surface opposite to the polygon mirror 18 side, and the mirror contact surface 17c is formed on the upper surface side which is the surface opposite to the mirror surface processing reference surface 17b. . A press-fitting guide portion 17d is formed on the flange 17 slightly above the mirror contact surface 17c so that the outer peripheral surface of the flange 17 slightly protrudes. A gap portion 17e is formed on the outer peripheral surface side of the flange 17 so as not to contact the inner diameter of the polygon mirror 18 except for the press-fitting guide portion 17d.

  On the outer peripheral side of the polygon mirror 18, two stages of deflection reflection surfaces 18c and 18d are integrally formed in the axial direction. The polygon mirror 18 is hollowed out in a substantially cup shape, and a dynamic pressure bearing surface 16a (see FIG. 2) formed on the sleeve 16 and a part of the deflection reflection surfaces 18c and 18d formed on the polygon mirror 18 are formed. It overlaps at a position in the rotation axis direction and is fixed to the sleeve 16. A rotary part 19 of a suction type magnetic bearing is fixed by press-fitting in the center of the ceiling part of the polygon mirror 18, and most of the rotary part 19 is located in the polygon mirror 18. As shown in FIG. 1, the rotary part 19 of the attraction type magnetic bearing has an outer portion that forms a magnetic gap between the center circle of the first fixed yoke plate 9 and the center circle of the second fixed yoke plate 10. A cylindrical surface is formed, and the outer cylindrical surface is arranged so as to be coaxial with the rotation center axis. As a material of the rotating part 19 of the attraction type magnetic bearing, a permanent magnet or a steel-based ferromagnetic material is used.

  The lower end of the polygon mirror 18 hollowed out in a substantially cup shape is open, and this open end surface faces the upper surface of the stepped portion of the flange 17. On the inner periphery of the lower end portion of the polygon mirror 18, a press-fitting guide portion 18 e made of an inward protruding ridge facing the press-fitting guide portion 17 d of the flange 17 is formed over the entire circumference. When the polygon mirror 18 is press-fitted into the flange 17, the press-fitting guide portion 18 e of the flange 17 and the polygon mirror 18 is fitted to a slight extent. An O-ring 24 that is an elastic member is disposed between the lower end of the polygon mirror 18 and the flange 17. A groove for accommodating the O-ring 24 is formed around the lower end of the polygon mirror 18, and the outer periphery of the O-ring 24 is held in close contact with the inner periphery of the groove of the polygon mirror 18.

  Since the rotator 3 is rotationally driven at a high speed, as shown in FIG. 2, the balance is corrected by the correction surfaces 18 b and 14 a at two upper and lower portions of the rotator 3. Since the center of gravity 3a of the rotating body is disposed in the vicinity of the middle in the axial direction of the hydrodynamic bearing, the balance of the rotating body can be corrected with high accuracy, and unbalanced vibration can be reduced to a very small level.

  A wiring pattern for electrically connecting the motor winding 12a and the hall element 13 to a predetermined location is formed on the printed circuit board 11, and the drive circuit 20 sequentially controls the hall element 13 according to the position detection signal of the hall element 13. It is configured to switch the energization to the motor winding 12a and rotate the rotating body 3 to perform constant speed control.

The deflecting / reflecting surfaces 18c and 18d of the polygon mirror 18 are integrally formed by ultraprecision cutting according to the following method.
In the first step, the sleeve 16 and the flange 17 are fixed by shrink fitting.
In the second step, the inner diameter of the sleeve 16 that becomes the hydrodynamic bearing surface 16a is finished with high accuracy.
In the third step, the mirror-finishing reference surface 17b used for forming the deflection reflection surfaces 18c and 18d of the polygon mirror 18 on the flange 17 is formed. As shown in FIG. 4, a processing jig (taper bar) 22 is passed through the inner diameter of the sleeve 16 to fix the sleeve 16. The flange 17 is formed with a mirror-finishing reference surface 17b which is cut with the processing blade 23 and is perpendicular to the inner diameter central axis of the sleeve 16, that is, the central axis of the hydrodynamic bearing.
In the fourth step, the polygon mirror 18 is press-fitted into the flange 17.

  When the polygon mirror 18 is press-fitted into the flange 17 as described above, the press-fitting guide portions 17d and 18e that are fitted to a small extent are used as a guide, so that the shaft centers of the flange 17 and the polygon mirror 18 are aligned. I try not to slip. The press-fit portions 17a and 18a of the flange 17 and the polygon mirror 18 are press-fitted over a minute step, and when the press-fit is completed, as shown in FIG. The formed steps are in mesh. In the state where the press-fitting is completed, the O-ring (24) between the lower end of the polygon mirror 18 and the flange 17 is elastically deformed in the axial direction, and the surfaces in contact with the flange 17 and the polygon mirror 18 are brought into close contact and compressed. It is fixed in the state.

  In the fifth step, the flange 17 is fixed by the mirror-finished reference surface 17b, and high-precision deflecting / reflecting surfaces 18c and 18d are formed at a certain angle with respect to the central axis of the inner diameter of the sleeve 16 by ultraprecision cutting. Is done.

  In the first embodiment described above, the rotating body 3 includes the sleeve 16 having the hydrodynamic bearing surface 16a, the flange 17 fixed to the sleeve 16, the polygon mirror 18 press-fitted and fixed to the flange 17, and the drive. The rotor magnet 14 is a permanent magnet for use, and an O-ring 24 disposed between the flange 17 and the polygon mirror 18. The polygon mirror 18 is hollowed in a substantially cup shape and formed on the sleeve 16. Since the hydrodynamic bearing surface 16a and the deflection reflection surfaces 18c and 18d formed on the polygon mirror 18 are partially overlapped and fixed at positions in the rotation axis direction, the deflection reflection surface 18c of the polygon mirror is fixed. 18d, the deformation due to the temperature change is suppressed to a small level, and the center of gravity 3a of the rotating body 3 is arranged substantially at the center of the hydrodynamic bearing. Such as available balance modification, unbalanced change of the rotating body due to temperature change is suppressed, it is possible to obtain a small light deflector vibration.

Since the flange 17 is formed with the mirror processing reference surface 17b orthogonal to the hydrodynamic bearing surface 16a of the sleeve 16, the angle variation of the reflecting surface is small, and the scanning position accuracy of optical scanning can be improved.
The mirror-finishing reference surface 17b is formed on the opposite side of the polygon mirror 18 with the mirror contact surface 17c as a boundary. Therefore, the mirror-finished reference surface 17b having high squareness accuracy with respect to the rotation center axis of the hydrodynamic bearing can be exposed to the outside of the rotating body 3 in a state where the sleeve 16, the flange 17, and the polygon mirror 18 are integrated. In addition, the mirror surface processing reference surface 17b is used when the deflecting / reflecting surfaces 18c and 18d are mirror-finished, so that the mirror-finishing with high accuracy can be performed.

  The press-fitting and fixing portion between the flange 17 and the polygon mirror 18 is configured by press-fitting and fixing a press-fitting inner diameter portion 17 a formed on the flange 17 and a press-fitting outer diameter portion 18 a formed on the polygon mirror 18. The stress due to the press-fitting and fixing of the polygon mirror 18 is difficult to be transmitted to the deflecting reflecting surfaces 18c and 18d, and the deformation of the deflecting reflecting surface is suppressed to be small. Since the press-fitting portion has a diameter larger than the diameter of the dynamic pressure bearing, it is possible to form a mirror-finished reference surface with high squareness accuracy with respect to the rotation center axis of the dynamic pressure bearing.

  Since the rotor magnet 14, which is a driving permanent magnet, is fixed to the flange 17, deformation of the deflection reflection surfaces 18 c and 18 d due to the fixing of the rotor magnet 14 is suppressed to a small level. Since the sleeve 16 is made of ceramic, the dynamic pressure bearing surface has high wear resistance and can have a long life. Since the sleeve 16 and the flange 17 are fixed by shrink fitting, the fastening of the sleeve 16 and the flange 17 having different linear expansion coefficients is firmly fixed without being loosened by a temperature change, and the vibration change is suppressed to a small level. Since the rotating portion 19 of the magnetic bearing is fixed to the polygon mirror 18, the variation in the height position of the deflecting / reflecting surface is small, and the positional accuracy of the deflecting / reflecting surface is high. Since the deflection reflection surfaces 18c and 18d formed on the polygon mirror 18 are formed in a plurality of stages in the axial direction, a plurality of light beams from a plurality of light sources can be scanned. The deflecting / reflecting surfaces 18c and 18d formed on the polygon mirror 18 are formed by mirror processing after integrating the sleeve 16 and the flange 17 and the polygon mirror 18, so that the central axis (rotation) of the hydrodynamic bearing surface 16a of the sleeve 16 is rotated. An angle with respect to the central axis) is constant, and a highly accurate deflection reflection surface can be formed.

  Since the press-fitting guide portions 17d and 18e are formed on the flange 17 and the polygon mirror 18, the center axis is not shifted when the polygon mirror 18 is press-fitted into the flange 17, so that the initial imbalance does not increase. Since the guide portions 17d and 18e for press-fitting are configured such that the guide outer diameter portion 17d formed on the flange 17 and the guide inner diameter portion 18e formed on the polygon mirror 18 are fitted to a slight extent, the flange and the polygon mirror Eighteen press-fitting guide portions 17d and 18e can be easily formed. When the polygon mirror 18 is press-fitted and fixed to the flange 17, the guide outer diameter portion 17 d of the flange 17 is disposed closer to the press-fitting start side than the guide inner diameter portion 18 e of the polygon mirror. It is possible to reduce the deformation of the deflecting reflecting surfaces 18c and 18d by reducing the portion where the mirror press-fitting guide portions 17d and 18e come into contact.

  Since the press-fitting portions 17a and 18a of the flange 17 and the polygon mirror 18 are provided with a slip-off preventing portion, the flange 17 and the polygon mirror 18 are kept in close contact with each other by an axial elastic force acting on the flange 17 and the polygon mirror 18. The press-fitting part of can not come off. Since the slip-off preventing portion is composed of small steps provided in the flange press-fitting inner diameter portion 17a and the mirror press-fitting outer diameter portion 18a, the slip prevention portion can be easily formed.

  A gap 17e is provided between the flange 17 and the polygon mirror 18 so as to overlap at least the deflecting / reflecting surfaces 18c and 18d at a position in the rotation axis direction. Therefore, due to the influence of the contact between the flange outer diameter and the polygon mirror inner diameter, The deflection reflection surfaces 18c and 18d of the polygon mirror are not deformed.

  Since the polygon mirror 18 and the flange 17 are fixed in a state where the O-ring 24 between the lower end of the polygon mirror 18 and the flange 17 is elastically deformed in the axial direction, the polygon mirror 18 is elastically fixed, and temperature changes and vibrations occur. There is no displacement of the polygon mirror 18 due to the impact, so that the change with time of the contact state with the flange 17 is small, and the change with time of the accuracy of the deflecting reflecting surfaces 18c and 18d is small. Further, since the O-ring 24, which is an elastic member, is interposed between the flange 17 and the polygon mirror 18, the accuracy of the mirror reflecting surface does not deteriorate due to the influence of the irregularities on the contact surface between the flange 17 and the polygon mirror 18. .

  Further, since the surfaces of the O-ring 24 that contact the flange 17 and the polygon mirror 18 are fixed in close contact with each other, it is possible to improve the sealing performance against the ingress of processing oil during mirror processing and cleaning liquid during cleaning. An optical deflector can be provided. Since the outer periphery of the O-ring 24 is held in close contact with the inner periphery of the groove of the polygon mirror 18, the O-ring is deformed by centrifugal force when the rotating body is rotated after assembly, and the O-ring 24 is corrected with high accuracy. The balance of the rotating body will not be lost.

  The configuration and operation of the optical deflector according to the second embodiment using the dynamic pressure air bearing will be described with reference to FIGS. Since only the configuration of the rotating body is different from that of the first embodiment, only the configuration of the rotating body will be described, and the same parts as those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted. The rotating body 3 includes a sleeve 16, a flange 17 fixed to the outside of the sleeve 16, a polygon mirror 18 fixed to the flange 17, a rotating portion 19 of a magnetic bearing fixed to the polygon mirror 18, and a rotor fixed to the flange 17. The magnet 14 is composed of a ring-shaped spacer 25 which is an elastic member disposed between the flange 17 and the polygon mirror 18. Since the flange 17 and the polygon mirror 18 are fixed to the ring-shaped spacer 25 which is an elastic member in a deformed state, a material whose Young's modulus is smaller than that of the polygon mirror 18 is suitable as the material. .

  In the example shown in FIG. 7, the ring-shaped spacer 26 has a thin intermediate portion between the inner diameter and the outer diameter. More specifically, the ring-shaped spacer 25 in the example shown in FIG. 6 has a rectangular cross-sectional shape, whereas the ring-shaped spacer 26 in the example shown in FIG. By cutting off the lower surface side leaving the inner peripheral edge, the intermediate portion between the inner diameter and the outer diameter is formed thin. In the ring-shaped spacer 26, the upper surface of the outer peripheral edge is in contact with the bottom surface of the polygon mirror 18, and the lower surface of the inner peripheral edge is in contact with the upper surface of the horizontal step portion of the flange 17. By configuring the ring-shaped spacer 26 in this way, it is possible to use a material equal to or higher than the Young's modulus of the material of the polygon mirror 18.

The deflecting and reflecting surfaces 18c and 18d of the polygon mirror 18 are integrally formed by ultraprecision cutting according to the following method.
In the first step, the sleeve 16 and the flange 17 are fixed by shrink fitting.
In the second step, the inner diameter of the sleeve 16 that becomes the hydrodynamic bearing surface 16a is finished with high accuracy by cutting or the like.
In the third step, the mirror-finishing reference surface 17b used for forming the deflection reflection surfaces 18c and 18d of the polygon mirror 18 on the flange 17 is formed. As shown in FIG. 4, a processing jig (tapered rod 22 is passed through the sleeve 16 to fix the sleeve 16 to the inner diameter of the sleeve 16. A reference surface 17b for mirror finishing that is orthogonal to the central axis of the pressure bearing) with high accuracy is formed on the flange 17.

In the fourth step, the polygon mirror 18 is press-fitted into the flange 17. At this time, press fitting is performed by using the press fitting guide portions 17d and 18e fitted as small as possible so that the shaft centers of the flange 17 and the polygon mirror 18 do not shift. The press-fit portions 17a and 18a of the flange 17 and the polygon mirror 18 are press-fitted over a minute step, and in the state where the press-fit is completed, as shown in FIG. The formed steps are in mesh. In the state where the press-fitting is completed, the ring-shaped spacer 25 or 26 between the lower end of the polygon mirror 18 and the flange 17 is elastically deformed in the axial direction, and the surfaces in contact with the flange 17 and the polygon mirror 18 are brought into close contact and compressed. In this state, the flange 17 and the polygon mirror 18 are fixed.
In the fifth step, the flange 17 is positioned with reference to the mirror-finished reference surface 17b, and the highly accurate deflecting / reflecting surfaces 18c and 18d at a certain angle with respect to the central axis of the inner diameter of the sleeve 16 by ultra-precision cutting. Is formed.

  According to the optical deflector according to the second embodiment, since the elastic member is a ring spacer, the processing is easy and the cost is low. Further, if the intermediate portion between the inner diameter and the outer diameter is formed thin like the ring-shaped spacer 26 in the example shown in FIG. 7, the excessive stress when the flange 17 and the polygon mirror 18 are press-fitted is absorbed by plastic deformation. Can do. If the linear expansion coefficient of the ring-shaped spacer 26 in the example shown in FIG. 7 is substantially the same as the linear expansion coefficient of the polygon mirror 18 or the flange 17, the ring-shaped spacer 26 moves relative to the polygon mirror 18 or the flange 17 due to temperature change. There is no deviation and the balance of the rotating body corrected with high accuracy is not lost.

  With reference to FIG. 8, the configuration and operation of the optical deflector according to the third embodiment using a dynamic pressure air bearing will be described. Since only the configuration of the rotating body is different from the first embodiment, only the configuration of the rotating body will be described, and the same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted. In FIG. 8, the rotating body 3 includes a sleeve 16, a flange 17 fixed to the outside of the sleeve 16, a polygon mirror 18 fixed to the flange 17, a rotating portion 19 of a magnetic bearing fixed to the polygon mirror 18, and the flange 17. The rotor magnet 14 is fixed.

The flange 17 is formed with a thin connecting portion 17f that connects the outer periphery of the flange and the mirror mounting surface at a portion in contact with the lower end of the polygon mirror 18, and the thin connecting portion 17f constitutes an elastic deformation portion. The deflecting and reflecting surfaces 18c and 18d of the polygon mirror 18 are integrally formed by ultraprecision cutting according to the following method.
In the first step, the sleeve 16 and the flange 17 are fixed by shrinkage fitting.
In the second step, the inner diameter of the sleeve 16 that becomes the hydrodynamic bearing surface 16a is finished with high accuracy.
In the third step, the mirror-finishing reference surface 17b used for forming the deflection reflection surfaces 18c and 18d of the polygon mirror 18 on the flange 17 is formed. As shown in FIG. 4, a processing jig (taper bar) 22 is passed through the inner diameter of the sleeve 16 to fix the sleeve 16. The flange 17 is formed with a mirror-finishing reference surface 17b which is cut by the processing blade 23 and is orthogonal to the inner diameter central axis of the sleeve 16 (the central axis of the dynamic pressure bearing) with high accuracy.

In the fourth step, the polygon mirror 18 is press-fitted into the flange 17. At this time, press fitting is performed by using the press fitting guide portions 17d and 18e fitted as small as possible so that the shaft centers of the flange 17 and the polygon mirror 18 do not shift. The press-fit portions 17a and 18a of the flange 17 and the polygon mirror 18 are press-fitted over a minute step, and in the state where the press-fit is completed, as shown in FIG. The formed steps are in mesh. Further, when the press-fitting is completed, the lower end of the polygon mirror 18 and the connecting portion 17f formed on the flange 17 are fixed in a state of being elastically deformed in the axial direction.
In the fifth step, the flange 17 is positioned with reference to the mirror-finished reference surface 17b, and the highly accurate deflecting / reflecting surfaces 18c and 18d at a certain angle with respect to the central axis of the inner diameter of the sleeve 16 by ultra-precision cutting. Is formed.

  According to the optical deflector according to the third embodiment, since the connecting portion 17f, which is an elastically deforming portion, is formed on the flange 17, the polygon mirror 18 is elastically fixed when the polygon mirror 18 and the flange 17 are press-fitted. There is no displacement of the polygon mirror due to temperature change or vibration shock. Therefore, the change with time of the contact state with the flange 17 is small, and the change with time of the deflection reflection surface accuracy of the polygon mirror 18 is small. Further, the accuracy of the deflecting / reflecting surfaces 18c and 18d is not lowered by the unevenness of the contact surfaces of the flange 17 and the polygon mirror 18, respectively. The above effects can be obtained without adding special parts. Further, since the connecting portion 17f is partially plastically deformed, excessive stress during press-fitting can be absorbed by the deformation.

  FIG. 9 shows a main part of an embodiment of an optical scanning device provided with the optical deflector according to the present invention. The optical scanning device according to this embodiment is a single beam type device. 9 includes a light source 101, a coupling lens 102, an aperture 103, a cylindrical lens 104, a polygon mirror 105, lenses 106 and 107 constituting a scanning optical system, a mirror 108, a photoconductor 109, a mirror 110, and a lens. 111 and a light receiving element 112.

  The light source 101 is a semiconductor laser element that emits light for optical scanning. The coupling lens 102 is a lens for adapting the light emitted from the light source 101 to the subsequent optical system. The aperture 103 makes the beam light for optical scanning a predetermined shape. The cylindrical lens 104 condenses incident beam light in the sub-scanning direction. The polygon mirror 105 is an optical deflector and corresponds to the polygon mirror 18 in the above-described embodiment. When the polygon mirror 105 is rotationally driven by a motor, incident light is reflected on the deflecting reflection surface. The lenses 106 and 107 are lenses for forming an image of the beam light on the photoconductor 109 as a surface to be scanned. The mirror 108 bends the optical path of the beam light and guides it to the photoconductor 109. The photoconductor 109 forms an electrostatic latent image in accordance with the irradiated beam light. The mirror 110 and the lens 111 collect the beam light on the light receiving element 112. The light receiving element 112 is a light detection element such as a photodiode.

  A beam emitted from the light source 101 which is a semiconductor laser element is a divergent light beam and is coupled to a subsequent optical system by a coupling lens 102. The form of the coupled beam depends on the optical characteristics of the subsequent optical system, and may be a weak divergent light beam, a weak converging light beam, or a parallel light beam. When the beam that has passed through the coupling lens 102 passes through the opening of the aperture 103, a portion having a low light intensity at the periphery of the light beam is blocked and “beam shaped”, and a cylindrical lens that is a “linear imaging optical system” 104 is incident. The cylindrical lens 104 has an approximately semi-cylindrical shape, and a direction without power (a direction in which light is not refracted) is directed to the main scanning direction, and a positive power (power for focusing light) is incident in the sub-scanning direction. The incoming beam is focused in the sub-scanning direction and condensed near the deflection reflection surface of the polygon mirror 105 which is an “optical deflector”.

  The beam reflected by the deflecting and reflecting surface of the polygon mirror 105 passes through the two lenses 106 and 107 forming the “scanning optical system” while being deflected at a constant angular velocity as the polygon mirror 105 rotates at a constant speed. The optical path is bent by the bending mirror 8 and condensed as a light spot on the photoconductive photoconductor 109 forming the substance of the “scanned surface”, and the scanned surface is scanned. Prior to scanning, the beam enters the mirror 110 and is focused on the light receiving element 112 by the lens 111. The timing of writing to the photoconductor 109 is determined by a control unit (not shown) based on the output of the light receiving element 112.

  Thus, the optical deflector according to the present invention is applicable to a single beam type optical scanning device. The single beam type optical scanning device to which the optical deflector according to the present invention is applied has low noise caused by the vibration of the optical deflector, and the deflection reflection surface of the polygon mirror 105 as the optical deflector is maintained with high accuracy. Therefore, the scanning beam shape is constant, and stable optical scanning can be performed.

  FIG. 10 shows a main part of another embodiment of the optical scanning device including the optical deflector according to the present invention. This optical scanning device is a multi-beam type device. In addition, about the same component and member as the Example shown in FIG. 9, it attaches | subjects and shows the same code | symbol. In FIG. 10, a light source 101A is a semiconductor laser array in which four light emitting sources ch1 to ch4 are arranged in a line at equal intervals. In this embodiment, the light emitting sources ch1 to ch4 are arranged in the sub-scanning direction, but the semiconductor laser array 101A may be tilted so that the arrangement direction of the light emitting sources is tilted with respect to the main scanning direction.

  The four beams emitted from the four light emission sources ch1 to ch4 are divergent light beams whose major axis direction of the “elliptical far field pattern” is directed to the main scanning direction as shown in FIG. It is coupled to the subsequent optical system by a coupling lens 102 common to the two beams. The form of each coupled beam depends on the optical characteristics of the subsequent optical system, and may be a weak divergent light beam, a weak convergent light beam, or a parallel light beam. The four beams transmitted through the coupling lens are “beam shaped” by the aperture 3 and converged in the sub-scanning direction by the action of the cylindrical lens 104 which is a “common line imaging optical system”. The four beams converged in the sub-scanning direction are separated from each other in the sub-scanning direction as line images that are long in the main scanning direction in the vicinity of the deflection reflection surface of the polygon mirror 105 that is an “optical deflector”. To do. The polygon mirror 105 corresponds to the polygon mirror 18 in each embodiment of the optical deflector.

  The four beams deflected at a constant angular velocity by the deflecting / reflecting surface of the polygon mirror 105 are transmitted through the two lenses 106 and 107 forming the “scanning optical system”, and the optical path is bent by the bending mirror 108. The four beams whose optical paths are bent are condensed as four light spots separated in the sub-scanning direction on the photoconductor 109 forming the substance of the “scanned surface”, and four scanning lines on the scanned surface are obtained. Are simultaneously scanned. Prior to optical scanning, one of the beams enters the mirror 110 and is focused on the light receiving element 112 by the lens 111. The timing of writing to the photoconductor 109 by the four beams is determined by a control means (not shown) based on the output of the light receiving element 112.

  The “scanning optical system” in this embodiment is an optical system that condenses the four beams simultaneously deflected by the optical deflector (polygon mirror 105) as four light spots on the surface to be scanned of the photoconductor 109. This system is composed of two lenses 106 and 107.

  As described above, the optical deflection apparatus according to the present invention can be applied to a multi-beam optical scanning apparatus. The multi-beam type optical scanning apparatus to which the optical deflector according to the present invention is applied has low noise due to the vibration of the optical deflector, and the deflection reflection surface of the polygon mirror 105 constituting the optical deflector is maintained with high accuracy. Therefore, the scanning beam shape is constant, and stable optical scanning can be performed.

  FIG. 11 shows a configuration of a tandem full-color laser printer as an embodiment of an image forming apparatus provided with the light deflecting device according to the present invention. In FIG. 11, a conveying belt 202 is provided on the lower side of the apparatus so as to convey a transfer sheet (not shown) that is disposed in the horizontal direction and is fed from a sheet feeding cassette 201. On the conveyor belt 202, a yellow (Y) photosensitive member 203Y, a magenta (M) photosensitive member 203M, a cyan (C) photosensitive member 203C, and a black (K) photosensitive member 203K are transferred paper. They are arranged at equal intervals in the above order from the upstream side in the transport direction. Hereinafter, subscripts Y, M, C, and K are appropriately added to the reference numerals to distinguish each color.

  These photoreceptors 203Y, 203M, 203C, and 203K are all formed to have the same diameter, and process members are sequentially arranged around the photoreceptors in accordance with an electrophotographic process. Taking the photoconductor 203Y as an example, a charging charger 204Y, an optical scanning device 205Y, a developing device 206Y, a transfer charger 207Y, a cleaning device 208Y, and the like are arranged in this order in the rotation direction of the photoconductor 203Y. The same applies to the other photoconductors 203M, 203C, and 203K. That is, in this embodiment, the surfaces of the photoconductors 203Y, 203M, 203C, and 203K are irradiated surfaces set for the respective colors, and the optical scanning devices 205Y, 205M, and 205C are applied to the photoconductors. , 205K are provided in a one-to-one correspondence relationship.

  In addition, a registration roller 209 and a belt charging charger 210 are provided around the conveyance belt 202 at the upstream side in the transfer paper conveyance direction with respect to the photoconductor 205Y, and are disposed at a downstream side with respect to the photoconductor 205K. A separation charger 211, a charge removal charger 212, a cleaning device 213, and the like are provided in this order. A fixing device 214 is provided downstream of the belt separation charger 211 in the transport direction, and is connected to a paper discharge tray 215 via a paper discharge roller 216.

  In the above configuration, for example, in the full color mode (multiple color mode), each of the photoconductors 203Y, 203M, 203C, and 203K is based on the image signals of each color for Y, M, C, and K. An electrostatic latent image is formed by optical scanning of a light beam by the optical scanning devices 205Y, 205M, 205C, and 205K. Each of these electrostatic latent images is developed with a corresponding color toner to become a toner image, and is superposed by being sequentially transferred onto a transfer sheet that is electrostatically attracted onto the transport belt 202 and transported. The transfer paper on which the toner images of the respective colors are superimposed is fixed on the transfer paper as a full color image by the fixing device 214, and the transfer paper on which the image is fixed is discharged to the paper discharge tray 215 by the paper discharge roller 216.

  In the black mode (monochrome mode), the photoconductors 203Y, 203M, and 203C and these process members are deactivated, and only the photoconductor 203K is lighted based on the black image signal. An electrostatic latent image is formed by optical scanning of a light beam by a scanning device (one optical scanning device) 205K. This electrostatic latent image is developed with black toner to form a toner image, and is electrostatically attracted onto the conveyance belt 202 and transferred onto a transfer sheet conveyed. The toner image transferred onto the transfer paper is fixed on the transfer paper as a monochrome image by the fixing device 214, and the transfer paper on which the image has been fixed is discharged onto a paper discharge tray 215 by a paper discharge roller 216.

  Thus, the light deflection apparatus according to the present invention can be applied to a tandem full-color laser printer. In the tandem full-color laser printer to which the optical deflector according to the present invention is applied, one optical deflector 300 in which two stages of mirrors are formed in the axial direction is shared by the optical scanning devices 205Y, 205M, 205C, and 205K. Since noise caused by the vibration of the deflector is small and the reflection surface of the optical deflector 300 is maintained with high accuracy, the shape of the scanning beam is constant, and stable optical scanning can be performed.

  Each embodiment described above is an example of a preferred embodiment of the present invention, and the present invention is not limited to this, and various modifications are possible.

1 is a longitudinal sectional view of an optical deflector according to Example 1. FIG. 1 is a longitudinal sectional view of a rotating body of an optical deflector according to Embodiment 1. FIG. FIG. 3 is an enlarged longitudinal sectional view of a polygon mirror press-fitting part of an optical deflector according to Example 1. FIG. 6 is a processing explanatory diagram of a reference surface for mirror processing of the optical deflector according to the first embodiment. 1 is an exploded perspective view of an optical deflector according to Embodiment 1. FIG. 6 is a longitudinal sectional view showing a rotating body of an optical deflector according to Embodiment 2. FIG. FIG. 10 is a longitudinal sectional view showing a modification of the rotating body of the optical deflector according to the second embodiment. FIG. 6 is a longitudinal sectional view showing a rotating body of an optical deflector according to Example 3. FIG. 10 is a perspective view illustrating an optical scanning device according to Example 4; FIG. 10 is a perspective view illustrating a multi-beam optical scanning device according to a fifth embodiment. FIG. 10 is a front view showing a tandem type full-color image forming apparatus according to Example 6;

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Rotating body 14 Driving permanent magnet 16 Sleeve 16a Dynamic pressure bearing surface 17 Flange 18 Polygon mirror 18c Deflection reflection surface 18d Deflection reflection surface 25 O-ring which is an elastic member 26 Elastic member 17f Connecting portion which is an elastic deformation portion

Claims (9)

In an optical deflector in which a rotating body having a polygon mirror is supported by a hydrodynamic bearing and driven to rotate by a motor,
The rotating body includes a sleeve having a hydrodynamic bearing surface, a flange fixed to the sleeve, a polygon mirror press-fitted to the flange, and a driving permanent magnet.
The polygon mirror is hollowed out and formed into a cup shape, and a part or all of the reflective surface formed on the polygon mirror is located at a position in the rotational axis direction with respect to the hydrodynamic bearing surface formed on the sleeve. Superimposed and joined to the flange,
An optical deflector characterized in that an elastic member is interposed between the flange and the polygon mirror. 2. The optical deflector according to claim 1, wherein the elastic member is an O-ring. 3. The optical deflector according to claim 2, wherein a circumferential groove for holding the outer periphery of the O-ring is provided on the flange or the polygon mirror. 2. The optical deflector according to claim 1, wherein the elastic member is a ring spacer. 5. The optical deflector according to claim 4, wherein the ring-shaped spacer has a thin intermediate portion between the inner diameter and the outer diameter. 5. The optical deflector according to claim 4, wherein the linear expansion coefficient of the ring spacer is substantially the same as the linear expansion coefficient of the polygon mirror or the flange. A light beam from a semiconductor laser is guided to a surface to be scanned through an optical system including an optical deflector to form a light beam spot, and deflected by the optical deflector, so that the surface to be scanned is deflected by the light beam spot. The optical scanning device which scans, The said optical deflector is an optical deflector in any one of Claims 1-6 . A semiconductor laser that emits a plurality of light beams, and a plurality of light beams from the semiconductor laser are guided to a scanned surface through an optical system including an optical deflector to form a plurality of light beam spots, The light which is an optical deflector in any one of Claims 1-6 in the optical scanning apparatus which carries out the adjacent scanning of the said to-be-scanned surface by these light beam spots by deflecting with a deflector. Scanning device. An image forming apparatus that forms a latent image on a photosensitive surface of a photosensitive medium by an optical scanning device and obtains an image by visualizing the latent image, and performs optical scanning on the photosensitive surface of the photosensitive medium. as an apparatus, an image forming apparatus using the optical scanning apparatus according to claim 7 or 8.

Images