Abstract: An optical deflector includes a rotary body including a polygon mirror; a rotation shaft fixed to the rotary body; a bearing unit rotatably supporting the rotation shaft; and a board to which the bearing unit is fixed. Where P [rpm] is the number of revolutions of the rotary body, l [m] is a distance between a center of gravity of the rotary body and the board, m [kg] is mass of the rotary body, r [m] is a radius of the rotation shaft, E [Pa] is Young's modulus of the rotation shaft, and t [mm] is a thickness of the board, the following inequalities are satisfied: 1 2 ? ? ? 3 ? ? ? ? Er 4 4 ? ml 3 ? 2 × P 60 and 0.8 ? t ? 1.8 .

Abstract: An optical writing head includes light-emitting element array chips; a circuit board on which the light-emitting element array chips are mounted; and an imaging element array that focuses light beams emitted from the light-emitting element array chips to form optical spots. The following inequality is satisfied: L 1 < 25.4 × N ? where L1 is an arrangement pitch [mm] between any adjacent light-emitting element array chips at normal temperature, ? is resolution [dpi] in a main scanning direction, and N is the number of light-emitting points of each of the light-emitting element array chips.

Abstract: A light deflector is disclosed that includes a bearing, a motor, a rotary body supported by the bearing and rotated by the motor, and a polygon mirror fixed to the rotary body. The motor includes an annular permanent magnet circumferentially magnetized with six poles and fixed to the rotary body, a rotational position detector part configured to detect the rotational position of the permanent magnet, and a stator assembly including a stator core and nine coils fixed to the stator core.

Abstract: A hydrodynamic bearing unit using oil includes a shaft to be driven, a bearing member configured to support the shaft in a non-contact manner through a bearing gap by a hydrodynamic pressure of the oil, which is generated in the bearing gap while the shaft relatively rotate with respect to the bearing member, a housing configured to house the bearing member and having an opening at one end thereof, another end thereof being enclosed, a sealing member configured to seal a part of the opening of the housing, a channel configured to communicate a space formed between the shaft, the bearing member and the housing with an outside air, and a pressing member configured to press and fix the bearing member on the housing. At least one open part configured to release an air bubble contained in the housing is provided between the bearing member and the sealing member.

Abstract: An optical deflector is disclosed that includes a rotary shaft; plural rotary polygon mirrors laminated in an axis direction of the rotary shaft, the rotary polygon mirrors having reflection surfaces and the reflection surfaces of one rotary polygon mirror and those of another rotary polygon mirror facing in different directions; and a joining section provided between the rotary polygon mirrors. In the optical deflector, the joining section is integrally formed with at least one of the rotary polygon mirrors.

Abstract: An optical deflector, a method of producing the optical deflector, an optical scanning device, and an image forming apparatus are disclosed that are able to save resources, provide high reliability at low cost, and enable stacked and relatively-offset polygon mirrors to be arranged precisely. The optical deflector includes a rotary member supported by a bearing with plural polygon mirrors fixed thereon. The polygon mirrors are stacked along a rotation axis of the rotary member, the polygon mirrors are relatively offset by a predetermined angle in a rotation plane of the rotary member, and an effective deflection area of each of the reflection surfaces of any one of the polygon mirrors is positioned away from a center of the corresponding reflection surfaces of the other one of the polygon mirrors in the direction of the rotation axis.

Abstract: A rotary drive apparatus includes a rotary body with a support portion, a rotor magnet supported by the support portion of the rotary body, a fixation section facing the rotor magnet and rotatably supporting the rotary body, and a winding coil provided in the fixation section, in which an expression E1/E2?0.75 is satisfied where Young's modulus of the rotor magnet is E1 [GPa], and Young's modulus of the support portion is E2 [GPa].

Abstract: In the optical deflector, the mean width of profile elements of a cross section of the deflection surface in the sub scan direction is set to be less than to spacing between spots of the light beams formed in the sub scan direction of the deflection surface. This makes it possible to prevent a variation in the size and shape of the spots of the light beams deflected by the deflection surface due to the undulation (unevenness) of the deflection surface. As a result, it is able to suppress a decrease of the granularity of images and form images with high quality.

Abstract: An optical deflector, a method of producing the optical deflector, an optical scanning device, and an image forming apparatus are disclosed that are able to save resources, provide high reliability at low cost, and enable stacked and relatively-offset polygon mirrors to be arranged precisely. The optical deflector includes a rotary member supported by a bearing with plural polygon mirrors fixed thereon. The polygon mirrors are stacked along a rotation axis of the rotary member, the polygon mirrors are relatively offset by a predetermined angle in a rotation plane of the rotary member, and an effective deflection area of each of the reflection surfaces of any one of the polygon mirrors is positioned away from a center of the corresponding reflection surfaces of the other one of the polygon mirrors in the direction of the rotation axis.

Abstract: An optical deflector including a rotary member supported by a bearing shaft and rotatively driven by a motor for deflecting a plurality of laser beams separated from each other in a rotational axis direction of the rotary member is disclosed. The optical deflector includes a polygon mirror having four sides arranged about the rotational axis direction. Each of the four sides is a continuous plane having a plurality of effective reflection areas separated from each other in the rotational axis direction.

Abstract: An optical scanning apparatus includes a light source that emits a light beam, optical systems through which the light beam travels including one that forms a line image, a polygon mirror that rotates and deflects the light beam with a deflective reflection surface, and a scanning optical system that converges the light beam to scan a target surface with a light beam spot. The optical system closer to the light source than the polygon mirror is configured so as to correct a change in an image-forming position of the light beam spot caused by deformation of the deflective reflection surface originating from the rotation of the polygon mirror.

Abstract: An optical scanning apparatus includes a light source that emits a light beam, optical systems through which the light beam travels including one that forms a line image, a polygon mirror that rotates and deflects the light beam with a deflective reflection surface, and a scanning optical system that converges the light beam to scan a target surface with a light beam spot. The optical system closer to the light source than the polygon mirror is configured so as to correct a change in an image-forming position of the light beam spot caused by deformation of the deflective reflection surface originating from the rotation of the polygon mirror.

Abstract: A light deflector is disclosed that includes a bearing, a motor, a rotary body supported by the bearing and rotated by the motor, and a polygon mirror fixed to the rotary body. The motor includes an annular permanent magnet circumferentially magnetized with six poles and fixed to the rotary body, a rotational position detector part configured to detect the rotational position of the permanent magnet, and a stator assembly including a stator core and nine coils fixed to the stator core.

Abstract: A light deflector is disclosed that includes a rotary body supported by a dynamic pressure bearing and rotated by a motor. The rotary body includes a sleeve having a dynamic pressure bearing surface formed on the interior circumferential surface thereof; a flange fixed to the exterior circumferential surface of the sleeve; a polygon mirror press-fitted and fixed to the flange; and a permanent magnet for driving. A substantially cup-like hollow is formed inside the polygon mirror. The polygon mirror is fixed to the flange with the pressure bearing surface formed on the sleeve overlapping at least part of a reflection surface formed on the polygon mirror at a position in a direction of a rotation axis.

Abstract: A high speed rotating apparatus including a shaft, a rotary body, and a motor. The rotary body driven by the motor has a hollow into which the shaft is inserted and forms a dynamic pressure air bearing between the rotary body and the shaft. The rotary body includes first and second rotary members. The first rotary member has an inner circumferential surface held for rotation by the dynamic pressure air bearing. The second rotary member has an inner circumferential surface fixed to the outer circumferential surface of the first rotary member through a hardening insertion process. The hardening insertion process is performed such that a tensile strength of the first rotary member is greater than an axial tensile stress to be produced in the inner circumferential surface of the first rotary member.

Abstract: A polygonal scanner of the present invention includes a rotary body including a ceramic rotary sleeve and a metallic cylindrical member shrinkage-fitted on the rotary sleeve. The cylindrical member is formed with mirror surfaces constituting a polygonal mirror. A dynamic pressure, air bearing supports the rotary body. The mirror surfaces overlap the rotary sleeve in the axial direction of the rotary sleeve. A hole greater in diameter than the dynamic pressure, air bearing is formed in the top wall of the cylindrical member. The cylindrical member includes a stress removing portion positioned between the mirror surfaces and the rotary sleeve for removing a stress ascribable to shrinkage-fitting.

Abstract: A high speed rotating apparatus including a shaft, a rotary body, and a motor. The rotary body driven by the motor has a hollow into which the shaft is inserted and forms a dynamic pressure air bearing between the rotary body and the shaft. The rotary body includes first and second rotary members. The first rotary member has an inner circumferential surface held for rotation by the dynamic pressure air bearing. The second rotary member has an inner circumferential surface fixed to the outer circumferential surface of the first rotary member through a hardening insertion process. The hardening insertion process is performed such that a tensile strength of the first rotary member is greater than an axial tensile stress to be produced in the inner circumferential surface of the first rotary member.

Abstract: A balance correcting method, a dynamic pressure bearing, and an optical scanning apparatus. For balance correction a method of attaching weight to the rotatable body and another method of partly removing the rotatable body are jointly used. At the time of a first balance correcting process step, a balance correction is performed by applying adhesive agent to a recess portion formed on a circular circumference of a polygon mirror or a recess portion constructed with a rotor flange. At the time of a second balance correcting process step, the polygon mirror is partly removed or the rotor flange is partly removed. The method can be applied to a dynamic pressure bearing capable of stabilizing a rotation balance and an optical scanning apparatus having a structure capable of not changing the direction of the reflection surface of the rotatable polygon mirror. The rotating shaft is supported in the radial direction by sucking air existing between the fixing shaft and the rotating shaft.

Abstract: An image forming apparatus with a DC brushless motor including a permanent magnet having n magnetized poles, where n is an even number, a rotatably held rotor on which the permanent magnet is fixed, a stator core having T-shaped pole shoes corresponding to the magnetic poles of the permanent magnet, windings fixed on the stator core and including a plurality of phases for selectively generating magnetic polarities in sequence, a driver circuit for switching conduction to the windings, and a rotating position detector for detecting a rotating position of the permanent magnet. The windings are divided into a plurality of winding groups for generating magnetic polarities in a plurality of the windings so as to produce a magnetic repellent force or a magnetic attractive force between all the magnetic poles of the permanent magnet and T-shaped pole shoes of the stator core associated with selected phases by the driver circuit based on a rotating position detected by the rotating position detector.

Abstract: A polygonal scanner of the present invention includes a rotary body including a ceramic rotary sleeve and a metallic cylindrical member shrinkage-fitted on the rotary sleeve. The cylindrical member is formed with mirror surfaces constituting a polygonal mirror. A dynamic pressure, air bearing supports the rotary body. The mirror surfaces overlap the rotary sleeve in the axial direction of the rotary sleeve. A hole greater in diameter than the dynamic pressure, air bearing is formed in the top wall of the cylindrical member. The cylindrical member includes a stress removing portion positioned between the mirror surfaces and the rotary sleeve for removing a stress ascribable to shrinkage-fitting.