Rotating polygon mirror, optical deflection device, scanning optical device, and image forming device

Abstract

To prevent an accuracy surface affecting the assembly accuracy of a rotary polygon mirror from being deposited in a step of deposition on the rotary polygon mirror.SOLUTION: A rotary polygon mirror 3 comprises: a first surface 31 that is connected with a plurality of reflection surfaces 33; and a second surface 32 that is connected with the plurality of reflection surfaces 33 and opposite to the first surface 31. The first surface 31 has an annular projection part 35 that projects in a rotation axis direction and centered on a rotation axis. The second surface 32 has an annular pedestal part 36 that projects in the rotation axis direction opposite to the direction of the projection part 35 and centered on the rotation axis. When the rotary polygon mirrors 3 are stacked in the rotation axis direction, a wall on an inner peripheral side of the projection part 35 and a wall on an outer peripheral side of the pedestal part 36 are fitted to each other.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a rotating polygon mirror, an optical deflection device including a rotating polygon mirror, a scanning optical device including an optical deflection device, and an image forming apparatus including a scanning optical device. [Background technology]

[0002] Conventionally, a scanning optical device used in an image forming device such as a laser printer optically modulates a laser beam emitted from a light source in response to an image signal, and the optically modulated laser beam is deflected by a rotating polygon mirror of an optical deflection device. The laser beam deflected by the rotating polygon mirror is focused on a photosensitive drum by a scanning lens such as an fθ lens, and an electrostatic latent image is formed on the photosensitive drum. Then, toner is attached to the electrostatic latent image formed on the photosensitive drum by a developing device to form a toner image, and the formed toner image is transferred to a recording material such as recording paper. Thereafter, the recording material to which the toner image has been transferred is conveyed to a fixing device, where the toner image on the recording material is fixed to the recording material by heating and pressurizing it, thereby completing the printing process.

[0003] For example, Patent Document 1 proposes a film-forming process for a rotating polygon mirror used in the optical deflection device of the above-mentioned scanning optical device. For example, aluminum, glass, etc. are used for the rotating polygon mirror. In the film-forming process for the rotating polygon mirror, a deposition film or an anodized film is applied to the reflecting surface of the rotating polygon mirror to increase the reflectance, eliminate the angle dependency, and prevent oxidation. FIG. 8 is a diagram explaining the process of applying a coating liquid to the reflecting surface of the rotating polygon mirror described in Patent Document 1. In order to form a reflective film on the rotating polygon mirror, the rotating polygon mirror is set on the coating liquid so as not to come into contact with the coating liquid. At this time, as shown in FIG. 8, the rotating polygon mirror is set in a state where it is separated from the coating liquid by more than the shortest distance between the rotation axis of the rotating polygon mirror and the reflecting surface. Next, the rotating polygon mirror is rotated to apply the coating liquid to the corners of the rotating polygon mirror (the part indicated by 10 in the figure). By rotating the rotating polygon mirror, the coating liquid spreads over the reflecting surface, and the coating liquid is finally applied to the entire reflecting surface 4a. In this way, even if the reflecting surface of the rotary polygon mirror is not completely immersed in the surface of the coating liquid, the coating liquid can be completely spread over the reflecting surface.

[0004] Also, for example, Patent Document 2 proposes a rotating polygon mirror molded from resin. FIG. 9 is a diagram for explaining the configuration of the rotating polygon mirror proposed in Patent Document 2. In FIG. 9, rotating polygon mirror 45A is a rotating polygon mirror having four mirror surfaces M1 to M4 arranged so as to surround a predetermined rotation axis SL. Substrate 100 is formed from, for example, resin, and has four side surfaces 110 corresponding to mirror surfaces M1 to M4. In rotating polygon mirror 45A, a reflective film RC is formed on each side surface 110, so that the surface of reflective film RC becomes mirror surfaces M1 to M4. In this way, in recent years, manufacturing costs of rotating polygon mirrors have been reduced by molding them from resin material instead of metal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP2010-191470 Public Relations [Patent Document 2] JP2017-126008 Public Relations Summary of the Invention [Problem to be solved by the invention]

[0006] In order to suppress the dependency of reflectance on the angle of incidence of light incident on the reflecting surface of the rotating polygon mirror proposed in the above-mentioned Patent Documents 1 and 2, for example, a monolayer film of a substance having a desired refractive index is formed on the reflecting surface. The monolayer film is formed by a vacuum film formation method represented by deposition or sputtering, or a wet film formation method using a solution. In this case, for example, Patent Documents 1 and 2 disclose a method in which the target rotating polygon mirror is passed through a shaft supporting the rotating polygon mirror and the mirrors are stacked and then the film is formed in a connected state.

[0007] In such a manufacturing process, when the rotary polygon mirrors are stacked, the clearance between the reflecting surfaces of the adjacent rotary polygon mirrors and the rotation phase are not regulated. Therefore, there is a risk of partial unevenness in the film thickness occurring on the inner diameter of the rotary polygon mirror's rotation shaft and on the base of the rotary polygon mirror that is grounded on the rotor part side. For example, if partial unevenness in the film thickness occurs on the base of the rotary polygon mirror, the assembly accuracy when the rotary polygon mirror is installed on the optical deflector is impaired, and unevenness in the pitch of the scanning line may occur due to the surface tilt of the reflecting surface. In addition, if partial unevenness in the film thickness occurs on the inner diameter of the rotary polygon mirror's rotation shaft, the reflecting surface may deform due to the fitting state with the rotary shaft, causing a decrease in optical performance, and thus deteriorating image quality. Therefore, it is an issue to ensure mechanical accuracy in the film formation process by preventing film formation on the precision surface of the rotary polygon mirror that affects the assembly accuracy of the rotary polygon mirror.

[0008] The present invention has been made under these circumstances, and an object of the present invention is to prevent deposition of a film on precision surfaces that affect the assembly precision of a rotary polygon mirror during a deposition process for the rotary polygon mirror. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention has the following configuration.

[0010] (1) A rotating polygonal mirror with multiple reflecting surfaces and , a motor that drives the rotary polygon mirror, and the optical deflection device that deflects laser light by the plurality of reflecting surfaces, the rotating polygon mirror has a first surface connected to the plurality of reflecting surfaces, and a second surface connected to the plurality of reflecting surfaces; In the direction of the rotation axis of the rotating polygon mirror The first aspect On the opposite side of a second surface, the first surface comprising: The above a first protrusion having a ring shape centered on the axis of rotation of the rotating polygon mirror and protruding in the direction of the axis of rotation; the first protrusion has a top surface portion whose height from the first surface is uniform throughout the annular shape; The second surface is opposite to the first protrusion. To a second protruding portion having a ring shape centered on the rotation axis of the rotating polygon mirror; the second protrusion has a top surface portion whose height from the second surface is uniform throughout the annular shape; having The top surface of the second protrusion serves as a mounting surface for the rotary polygon mirror relative to the motor, and a plurality of When the rotary polygon mirrors are stacked in the direction of the rotation axis, an inner wall of the first protrusion and an outer wall of the second protrusion are fitted together. The first protrusion and the second protrusion are configured as described above, and the height of the top surface of the first protrusion from the first surface is greater than the height of the top surface of the second protrusion from the second surface. Characterized by light deflection device . (2) A rotary polygon mirror having a plurality of reflecting surfaces, comprising: a first surface connected to the plurality of reflecting surfaces; and a second surface connected to the plurality of reflecting surfaces and located opposite to the first surface in a direction of a rotation axis of the rotary polygon mirror, the first surface having a first protrusion protruding in the direction of the rotation axis and having a ring shape centered on the rotation axis of the rotary polygon mirror; the second surface having a second protrusion protruding in the opposite direction to the first protrusion and having a ring shape centered on the rotation axis of the rotary polygon mirror; a top surface of the first protrusion having a plurality of recesses arranged at approximately equal intervals in the rotation direction of the rotating polygon mirror, the top surface being a flat surface having steps; and a top surface of the second protrusion having a plurality of convex portions arranged at approximately equal intervals in the rotation direction of the rotating polygon mirror, the top surface being a flat surface having steps. (3) A rotary polygon mirror having a plurality of reflecting surfaces, comprising: a first surface connected to the plurality of reflecting surfaces; and a second surface connected to the plurality of reflecting surfaces and located opposite to the first surface in a direction of a rotation axis of the rotary polygon mirror, wherein the first surface has a first protrusion protruding in the direction of the rotation axis and having a ring shape centered on the rotation axis of the rotary polygon mirror; and the second surface has a second protrusion protruding in the opposite direction to the first protrusion and having a ring shape centered on the rotation axis of the rotary polygon mirror, wherein when a plurality of the rotary polygon mirrors are stacked in the direction of the rotation axis, the first protrusion and the second protrusion are configured so that a wall of the first protrusion fits into an outer peripheral wall of the second protrusion, the first protrusions have the same shape corresponding to each of the reflecting surfaces when the ring shape is divided by a line connecting the center of the rotation axis and both ends of the reflecting surface, the second protrusions have the same shape corresponding to each of the reflecting surfaces when the ring shape is divided by a line connecting the center of the rotation axis and both ends of the reflecting surface, and the shapes corresponding to the reflecting surfaces of the first protrusion and the second protrusion are D-cut shapes. (4) An optical deflection device comprising: a rotating polygon mirror according to (2) having a plurality of reflecting surfaces that reflect laser light; and a motor that drives the rotating polygon mirror. (5) An optical deflection device comprising: a rotating polygon mirror according to (2) having a plurality of reflective surfaces that reflect laser light; and a motor that drives the rotating polygon mirror, wherein the convex portion of the second protrusion is mounted on a base that supports the rotating polygon mirror of the motor. (6) A scanning optical device comprising: a light source that emits laser light; and an optical deflection device according to any one of (1), (4), or (5) having a rotating polygon mirror that deflects the laser light. (7) An image forming apparatus for forming an image on a recording material, comprising: an image forming section having a photosensitive drum for forming an image on the recording material; and a scanning optical device having the light source and for irradiating the photosensitive drum of the image forming section with laser light emitted from the light source to form an electrostatic latent image, as described in (6). Effect of the Invention

[0014] According to the present invention, it is possible to prevent deposition of a film on precision surfaces that affect the assembly precision of a rotary polygon mirror in a deposition process for the rotary polygon mirror. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus according to first to third embodiments. [Diagram 2] FIG. 1 is a perspective view showing a configuration of a scanning optical device according to first to third embodiments; [Diagram 3] 1 is a cross-sectional view illustrating a configuration of an optical deflection device according to first to third embodiments; [Figure 4] FIG. 1 is a diagram for explaining the configuration of a rotating polygon mirror according to the first embodiment. [Diagram 5]Schematic diagram of the film forming apparatus of Examples 1 to 3 [Figure 6] FIG. 10 is a diagram for explaining the configuration of a rotating polygon mirror according to the second embodiment. [Figure 7] FIG. 11 is a diagram for explaining the configuration of a rotating polygon mirror according to the third embodiment. [Figure 8] Schematic diagram for explaining a conventional film-forming coating process for a rotary polygon mirror. [Figure 9] FIG. 1 is a perspective view illustrating the configuration of a conventional rotating polygon mirror; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. EXAMPLES

[0017] [Configuration of image forming device] FIG. 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus 110 of the first embodiment. In FIG. 1, a process cartridge 102, which is an image forming unit, has a photosensitive drum 103 on which an electrostatic latent image is formed, and a charging roller 111 which charges the photosensitive drum 103 to a predetermined potential. Furthermore, the process cartridge 102 has a developing roller 112 which attaches toner to the electrostatic latent image formed on the photosensitive drum 103 to form a toner image. At a position facing the photosensitive drum 103, which is an image carrier, a transfer roller 107 is disposed which transfers the toner image formed on the photosensitive drum 103 onto a recording material P (on the recording medium) which is a recording medium to be conveyed. In addition, the scanning optical device 101 irradiates the photosensitive drum 103 with a laser beam L according to image data to form an electrostatic latent image.

[0018] When the image forming apparatus 110 starts an image forming operation, the photosensitive drum 103 in the process cartridge 102 is driven to rotate, and the charging roller 111 charges the surface of the photosensitive drum 103 to a uniform potential. The scanning optical device 101 irradiates the surface of the photosensitive drum 103 charged to a uniform potential with a laser beam L according to image data to form an electrostatic latent image. Then, toner is attached to the electrostatic latent image formed on the photosensitive drum 103 (on the image carrier) by the developing roller 112, and a toner image is formed. Meanwhile, the recording material P is fed one by one from the paper feed section 104 on which the recording material P is placed to a conveying path by the feed roller 105. The recording material P fed to the conveying path is further conveyed to the transfer roller 107 by the conveying roller 106. The toner image formed on the photosensitive drum 103 is transferred to the recording material P conveyed to the transfer roller 107 by the transfer roller 107.

[0019] The recording material P onto which the toner image has been transferred is conveyed to a fixing device 108, which heats and pressurizes the toner image on the recording material P to fix it to the recording material P. The recording material P onto which the toner image has been fixed is then discharged by a discharge roller 109 to the outside of the image forming apparatus 110. Note that, in this embodiment, the charging roller 111 and the developing roller 112 are configured to be integrated with the photosensitive drum 103 inside the process cartridge 102, but they may be configured separately from the photosensitive drum 103.

[0020] [Configuration of scanning optical device] The scanning optical device 101 will be described with reference to Fig. 2. Fig. 2 is a perspective view showing the configuration of the scanning optical device 101, and shows a state in which a lid (not shown) for sealing the inside of a housing 203 is removed.

[0021] The laser light L emitted from the light source unit 201 is collected in the sub-scanning direction by the cylindrical lens 202, and limited to a predetermined beam diameter by an optical diaphragm 204 formed in a part of the housing 203. The laser light L that passes through the diaphragm 204 is deflected by a rotary polygon mirror 3 mounted on a motor board 4 of the optical deflection device 1 (see FIG. 3). The laser light L then passes through an fθ lens 205 and scans the photosensitive drum 103 (not shown in FIG. 2), which is the surface to be scanned. The cylindrical lens 202, the optical deflection device 1, and the fθ lens 205 are housed inside the housing 203, and the light source unit 201 is attached to a side wall of the housing 203 from the outside of the housing 203. The rotor 7 and the rotating shaft 8 will be described later.

[0022] [Configuration of the optical deflection device] Next, the optical deflection device 1 will be described with reference to Fig. 3. The optical deflection device 1 has a rotating polygon mirror having a plurality of reflective surfaces that reflect laser light, and a motor that rotates the rotating polygon mirror. The rotating polygon mirror rotated by the motor deflects the laser light L emitted from the light source unit 201.

[0023] 3 is a cross-sectional view of the optical deflection device 1. The optical deflection device 1 has a rotating polygon mirror 3 molded from resin, and the rotating polygon mirror 3 has a reflecting surface 33 that reflects the laser light L. In addition to the rotating polygon mirror 3, the optical deflection device 1 has a motor board 4 made of sheet metal, a bearing sleeve 5 supported by the motor board 4, a stator core 9a fixed to the motor board 4, and a stator coil 9b fixed to the stator core 9a. Furthermore, the optical deflection device 1 has a rotor 7 equipped with a rotor magnet 6, a rotating shaft 8 integrated with the rotor 7, and a base 2 supporting the rotating polygon mirror 3.

[0024] In the optical deflection device 1, when the stator core 9a is excited by a driving current supplied from a driving circuit provided on the motor board 4, the rotor 7 mounting the rotating polygon mirror 3 rotates at high speed. Then, the laser light L emitted from the light source unit 201 is deflected by the reflecting surface 33 of the rotating polygon mirror 3 rotating at high speed.

[0025] [Configuration of rotating polygon mirror] Next, the rotating polygon mirror 3 will be described in detail with reference to Fig. 4. Fig. 4(a) is a perspective view of the rotating polygon mirror 3 described in Fig. 3 when viewed obliquely from above, and Fig. 4(b) is a perspective view of the rotating polygon mirror 3 when viewed obliquely from below. Fig. 4(c) shows a cross-sectional view of two overlapping rotating polygon mirrors 3 shown in Fig. 4(a) cut along line AA.

[0026] The rotating polygon mirror 3 is molded from a resin material such as cycloolefin resin, polycarbonate resin, or acrylic resin. The rotating polygon mirror 3 has a prismatic shape with a square bottom surface. The rotating polygon mirror 3 has reflecting surfaces 33 forming the four side surfaces of the square, a first surface 31 which is a top surface perpendicular to the four reflecting surfaces 33, and a second surface 32 which is a bottom surface perpendicular to the four reflecting surfaces 33, faces the first surface 31, and is substantially parallel to the first surface 31. Furthermore, the rotating polygon mirror 3 has a center hole 34 which is fitted onto the rotating shaft 8 shown in FIG. 3 and serves as a rotation center.

[0027] Moreover, a first surface 31 of the rotating polygon mirror 3 is provided with a concentric (coaxial) ring-shaped protrusion 35 (first protrusion) centered on the rotation shaft 8 in the direction of the rotation shaft 8 into which the rotating polygon mirror 3 is fitted. A flat surface of the same height is formed on the top surface of the protrusion 35. Similarly, a second surface 32 of the rotating polygon mirror 3 is provided with a concentric (coaxial) ring-shaped pedestal 36 (second protrusion) centered on the rotation shaft 8 in the opposite direction to the protrusion 35 of the rotation shaft 8 into which the rotating polygon mirror 3 is fitted. The pedestal 36 is a precision surface that abuts against the pedestal 2 in FIG. 3 described above, and a flat surface of the same height is formed on the top surface of the pedestal 36.

[0028] As shown in FIG. 4(c), when two rotating polygon mirrors 3 are stacked, the base 36 of the upper rotating polygon mirror 3 fits inside the protrusion 35 of the lower rotating polygon mirror 3, and the outer periphery (wall on the outer periphery) of the base 36 fits into the inner periphery (wall on the inner periphery) of the protrusion 35. A gap G is formed by the height at which the protrusion 35 of the rotating polygon mirror 3 fits into the base 36. In addition, in the rotating polygon mirror 3, the height of the base 36 from the second surface 32 of the top surface is lower than the height of the protrusion 35 from the first surface 31 of the top surface. Therefore, as shown in FIG. 4(c), when the rotating polygon mirrors 3 are stacked, the top surface of the protrusion 35 of the lower rotating polygon mirror 3 is in contact with the second surface 32 of the upper rotating polygon mirror 3. On the other hand, the top surface of the base portion 36 of the upper rotating polygon mirror 3 is not in contact with the first surface 31 of the lower rotating polygon mirror 3, leaving a gap (clearance).

[0029] [Film forming equipment] The configuration of a film forming apparatus for forming a multilayer film on the rotary polygon mirror 3 of this embodiment will be described with reference to FIG. 5. FIG. 5(a) is a schematic diagram showing the configuration of a vacuum deposition apparatus as an example of the film forming apparatus of this embodiment. The vacuum deposition apparatus 500 includes a film forming chamber 501 whose interior is maintained in a vacuum state, and an exhaust system 502 consisting of a vacuum pump and the like that sets the film forming chamber 501 in a vacuum state. A revolving part 504 that performs a revolving drive around a revolution axis 503 is disposed in the film forming chamber 501, and the revolving part 504 is driven by a drive mechanism 505 via a gear 506 to perform the revolving drive. The rotary polygon mirror 3 has a rotation axis part 507 that passes through the center hole 34, and the rotation axis part 507 with the rotary polygon mirror 3 stacked on the rotation axis part 507 is installed on the revolution part 504 at an angle of Sθ with respect to the horizontal direction, and the rotation axis part 507 is rotated by a mechanism not shown. The rotating polygon mirror 3 is driven to revolve around itself by the revolution drive of the revolution part 504 and by rotation drive around the rotation axis part 507, and a reflective film having desired optical characteristics is formed on the surface of the reflective surface 33 while the rotating polygon mirror 3 is driven to revolve around itself by the revolution drive of the revolution part 504 and by rotation drive around the rotation axis part 507.

[0030] FIG. 5(b) is an enlarged cross-sectional view showing the state where the rotating polygon mirror 3 is stacked on the rotation shaft part 507. The rotating polygon mirrors 3 are stacked in the axial direction of the rotating shaft part 507, which is the rotation shaft, so that the first surface 31 faces upward. At this time, as shown in FIG. 4(c), the inner peripheral part (inner peripheral wall) of the protrusion 35 of the rotating polygon mirror 3 and the outer peripheral part (outer peripheral wall) of the base part 36 are fitted together, resulting in a structure in which the inner diameter of the central hole 34 of the rotating polygon mirror 3 and the base part 36 are sealed (sealed). When the rotating polygon mirror 3 is stacked on the rotation shaft part 507, the positions of the topmost and bottommost parts of the rotating polygon mirror 3 in the axial direction of the rotation shaft part 507 are restricted by a restricting member (not shown).

[0031] With the above-described configuration of the rotating polygon mirror 3, the central hole 34 of the rotating polygon mirror 3 and the top surface of the base 36, which are the joint surfaces with the rotor 7 when assembling the optical deflection device 1, do not rub against each other when the rotating polygon mirrors 3 are stacked in the deposition process by the vacuum deposition device 500. As a result, it is possible to prevent a decrease in the precision of the rotating polygon mirror 3 due to scratches and rubbing. In addition, by configuring the central hole 34 and the base 36, which are precision surfaces that affect the assembly precision of the rotating polygon mirror, so that the base 36 is inside the protrusion 35, the top surface of the base 36, which is the contact surface with the base 2 of the rotor 7 that supports the rotating polygon mirror 3, is not vapor-deposited. Therefore, the top surface of the base 36 can be accurately assembled to the optical deflection device 1 in a state where the mechanical precision is guaranteed. As a result, a decrease in optical performance due to the surface tilt (tilting of the reflecting surface 33) and surface deformation (deformation of the reflecting surface 33) caused by the rotating polygon mirror 3 is prevented, and the reliability of the scanning optical device 101 can be improved.

[0032] Moreover, the multilayer film on which the reflective surface 33 is formed is formed across the first surface 31 and the second surface 32 in the deposition process by the vacuum deposition apparatus 500. As shown in FIG. 5(b), a gap G is formed so that the ridges of the reflective surfaces 33 of the vertically adjacent rotatable polygon mirrors 3 do not come into contact with each other depending on the height at which the protrusions 35 and the base 36 of the rotatable polygon mirror 3 are fitted together. As a result, the reflective surfaces 33 of the vertically adjacent rotatable polygon mirrors 3 can reliably secure an appropriate clearance (gap) for stable film formation. Furthermore, since no intermediate parts such as spacers are required to provide a gap between the vertically adjacent rotatable polygon mirrors 3, the equipment can be minimized, and the method of forming the film on the rotatable polygon mirror 3 can be made inexpensive and highly productive.

[0033] Furthermore, when multiple rotating polygon mirrors 3 are stacked on the rotation axis part 507, shear stress is applied to the rotating polygon mirrors 3 due to weight and positional restrictions, and there is a particular concern about surface deformation of the reflecting surface 33 of the rotating polygon mirror 3. However, because the structure holds the opposing portions of the protrusions 35 of the rotating polygon mirror 3 to which shear stress is applied, it is possible to suppress surface deformation of the reflecting surface 33. This ensures the mechanical precision of the reflecting surface 33 during film formation and improves reliability.

[0034] The shapes of the protrusions 35 and base 36 in this embodiment may have any dimensions that protrude further in the direction of the rotation axis of the rotating polygon mirror 3 than the reflecting surface 33 and that allow at least a portion of the inner periphery of the protrusions 35 to fit into the outer periphery of the base 36. For example, the shapes of the protrusions 35 and base 36 shown in Fig. 4 are not required as long as the base 36 fits inside the protrusions 35 of the rotating polygon mirror 3, even if there is a small gap or wobble.

[0035] As described above, according to this embodiment, it is possible to prevent deposition of a film on a precision surface that affects the assembly precision of the rotary polygon mirror in the deposition process for the rotary polygon mirror. EXAMPLES

[0036] The shapes of the protrusions and base of the rotating polygon mirror in Example 1 were concentric ring shapes centered on the rotation axis of the rotating polygon mirror. In Example 2, a rotating polygon mirror in which the shapes of the protrusions and base are different from those in Example 1 will be described.

[0037] [Configuration of rotating polygon mirror] Fig. 6 is a schematic diagram for explaining the shape of the rotating polygon mirror 30 of this embodiment. Fig. 6(a) is a perspective view of the rotating polygon mirror 30 when viewed obliquely from above, and Fig. 6(b) is a perspective view of the rotating polygon mirror 30 when viewed obliquely from below. Fig. 6(c) shows a cross-sectional view of two overlapping rotating polygon mirrors 30 shown in Fig. 6(a) cut along line BB.

[0038] The rotating polygon mirror 30 of this embodiment is molded from a resin material, similar to the rotating polygon mirror 3 of the first embodiment. Similarly to the rotating polygon mirror 3 of the first embodiment, the rotating polygon mirror 30 has a prismatic shape with a square bottom surface. The rotating polygon mirror 30 has reflecting surfaces 33 forming four side surfaces of the square, a first surface 31 which is a top surface perpendicular to the four reflecting surfaces 33, and a second surface 32 which is a bottom surface perpendicular to the four reflecting surfaces 33, faces the first surface, and is substantially parallel to the first surface. Furthermore, the rotating polygon mirror 30 has a center hole 34 which is fitted into the rotating shaft 8 of the rotor 7 of the optical deflection device 1 and serves as a rotation center.

[0039] In addition, a first surface 31 of the rotary polygon mirror 30 is provided with a concentric (coaxial) ring-shaped protrusion 35 centered on the rotary shaft 8 in the direction of the rotary shaft 8 into which the rotary polygon mirror 30 is fitted. The protrusion 35 is provided with four recesses 35' at approximately equal intervals, which are formed by cutting out the protrusion 35, for example, to serve as a gate escape when molding the rotary polygon mirror 30. Therefore, the top surface of the protrusion 35 is not at the same height as in the first embodiment, but is a flat surface with a step at the recesses 35'. In addition, a second surface 32 of the rotary polygon mirror 30 is provided with a concentric (coaxial) ring-shaped base 36 centered on the rotary shaft 8 in the opposite direction to the protrusion 35 of the rotary shaft 8 into which the rotary polygon mirror 30 is fitted. In order to stably assemble the rotary polygon mirror 30 to the base 2 on the rotor 7 side, the precision surfaces of the base 36 that come into contact with the base 2 of the rotor 7 of the optical deflection device 1 are limited to only three protrusions 36' protruding from the top surface of the base 36. In this embodiment, the protrusions 36' protruding from the top surface of the base 36 are provided at approximately equal intervals, so that the top surface of the base 36 is a flat surface with steps at the protrusions 36'. The rotary polygon mirror 30 of this embodiment is configured so that when a plurality of rotary polygon mirrors 30 are stacked around the central hole 34 through which the rotation axis passes, at least a part of the inner peripheral wall of the inner peripheral part of the protrusions 35 and the outer peripheral wall of the outer peripheral part of the base 36 fit together.

[0040] FIG. 6(c) is a cross-sectional view of two overlapping rotating polygon mirrors 30 shown in FIG. 6(a) cut along line BB, but is also an enlarged schematic view of the cross-section of the rotating polygon mirrors 30 stacked on the rotation shaft part 507 of the vacuum deposition apparatus 500 of the first embodiment. The rotating polygon mirrors 30 are stacked in the axial direction of the rotation shaft part 507 so that the first faces 31 face upward. At this time, a gap G is formed by the height at which the protrusions 35 and the base parts 36 of the rotating polygon mirrors 30 fit together. When the rotating polygon mirrors 30 are stacked on the rotation shaft part 507, the positions of the topmost and bottommost axial positions of the rotating polygon mirrors 30 on the rotation shaft part 507 are restricted by restricting members (not shown).

[0041] At least a part of the inner peripheral wall of the inner peripheral part of the protrusion 35 of the rotary polygon mirror 30 and the outer peripheral wall of the outer peripheral part of the base part 36 are fitted together, so that the inner diameter of the central hole 34 of the rotary polygon mirror 30 and the base part 36 are sealed (closed). This seals the inner diameter of the central hole 34 of the rotary polygon mirror 30 and the protrusion 36' of the base part 36. As a result, when a plurality of rotary polygon mirrors 30 are stacked during film formation, it is possible to prevent the stacked rotary polygon mirrors 30 and the protrusion 36', which is the contact surface of the base part 36, from coming into contact with each other and being scratched, which would result in a decrease in accuracy. In addition, since the inner diameter of the central hole 34 and the protrusion 36' of the base part 36 can be sealed by the protrusion 35 and the base part 36, no film is formed on the precision surface during assembly, which would affect the assembly accuracy of the rotary polygon mirror, and mechanical accuracy can be maintained. Furthermore, since a constant distance can be maintained between adjacent rotating polygon mirrors 30 without applying stress to the reflecting surface 33 during film formation, film formation on the reflecting surface 33 is stable, and a highly accurate and reliable optical deflection device 1 can be realized.

[0042] Furthermore, by providing the protrusions 35 and base 36 of the rotating polygon mirror 30 with a concave or convex shape, the degree of freedom in designing the protrusions 35 and base 36 can be increased. For example, the rotating polygon mirror 30 may vibrate due to imbalance during rotation due to an error in precision of the reflecting surface 33 of the laser light or due to the center of rotation not completely coinciding with the fitting portion between the center hole 34 and the rotating shaft. In order to prevent vibration due to imbalance, it is possible to provide an adhesive portion on the protrusions 35 of the rotating polygon mirror 30, which is applied with a photocurable adhesive or the like to correct the balance and prevent vibration.

[0043] As described above, according to this embodiment, it is possible to prevent deposition of a film on a precision surface that affects the assembly precision of the rotary polygon mirror in the deposition process for the rotary polygon mirror. EXAMPLES

[0044] The shapes of the protrusions and base of the rotating polygon mirror in Examples 1 and 2 were concentric ring shapes centered on the rotation axis of the rotating polygon mirror. In Example 3, a rotating polygon mirror having protrusions and bases with shapes different from those in Examples 1 and 2 will be described.

[0045] [Configuration of rotating polygon mirror] Fig. 7 is a schematic diagram for explaining the shape of the rotating polygon mirror 300 of this embodiment. Fig. 7(a) is a perspective view of the rotating polygon mirror 300 when viewed obliquely from above, and Fig. 7(b) is a perspective view of the rotating polygon mirror 300 when viewed obliquely from below. Fig. 7(c) shows a cross-sectional view of two overlapping rotating polygon mirrors 300 shown in Fig. 7(a) cut along line CC.

[0046] The rotating polygon mirror 300 of this embodiment is molded from a resin material, similar to the rotating polygon mirror 3 of the first embodiment and the rotating polygon mirror 30 of the second embodiment. The rotating polygon mirror 300 is in the shape of a prism having a square bottom surface, similar to the rotating polygon mirror 3 of the first embodiment and the rotating polygon mirror 30 of the second embodiment. The rotating polygon mirror 300 has reflecting surfaces 33 forming four side surfaces of the square, a first surface 31 which is a top surface perpendicular to the four reflecting surfaces 33, and a second surface 32 which is a bottom surface perpendicular to the four reflecting surfaces 33, faces the first surface 31, and is substantially parallel to the first surface. The rotating polygon mirror 300 has a center hole 34 which is fitted into the rotating shaft 8 of the rotor 7 of the optical deflection device 1 and serves as a rotation center.

[0047] In addition, a ring-shaped protrusion 350 is provided on the first surface 31 of the rotating polygon mirror 300, which is configured by connecting D-cut portions 351, 352, 353, and 354 provided corresponding to each of the reflecting surfaces 33. Similarly, a ring-shaped base portion 360 is provided on the second surface 32 of the rotating polygon mirror 300, which is configured by connecting D-cut portions 361, 362, 363, and 364 provided corresponding to each of the reflecting surfaces 33. When the protrusion 350 and base portion 360 are divided by a line connecting the center of the central hole 34, which is the rotation axis of the rotating polygon mirror 300, and the vertices at both ends of each of the reflecting surfaces 33, the shapes of the divided regions of the protrusion 350 and base portion 360 are the same and have rotationally symmetric shapes around the rotation axis.

[0048] D-cut portions 351, 352, 353, 354 of protrusion 350 formed on first surface 31 and D-cut portions 361, 362, 363, 364 of base 360 ​​formed on second surface 32 correspond to reflecting surface 33. As shown in FIG. 7(c), the corresponding D-cut portions of protrusion 350 and base 360 ​​are determined for every 90° phase of reflecting surface 33, and the inner peripheral wall of the corresponding D-cut portion of protrusion 350 and the outer peripheral wall of base 360 ​​are fitted together. As shown in FIG. 7(c), in rotating polygon mirror 300, the height of base 360 ​​from second surface 32 is lower than the height of protrusion 350 from first surface 31. 7(c), when the rotating polygon mirrors 300 are stacked, the top surface of the protrusion 350 of the lower rotating polygon mirror 300 is in contact with the second surface 32 of the upper rotating polygon mirror 300. On the other hand, the top surface of the base 360 ​​of the upper rotating polygon mirror 300 is not in contact with the first surface 31 of the lower rotating polygon mirror 300, leaving a gap (clearance). Also, a gap G is formed by the height at which the protrusion 350 and base 360 ​​of the rotating polygon mirror 300 fit together.

[0049] 7(c) is a cross-sectional view taken along line CC of two overlapping rotating polygon mirrors 300 shown in FIG. 7(a), but is also a schematic view showing an enlarged cross-sectional view of rotating polygon mirrors 300 stacked on rotation shaft part 507 of vacuum deposition apparatus 500 of Example 1. Rotating polygon mirrors 300 are stacked in the axial direction of rotation shaft part 507 so that first surface 31 faces upward. When rotating polygon mirrors 300 are stacked on rotation shaft part 507, the positions of the topmost and bottommost parts of rotating polygon mirror 300 in the axial direction of rotation shaft part 507 are restricted by restricting members (not shown).

[0050] The D-cut shape of the protrusions 350 and base 360 ​​of the rotating polygon mirror 300 described above can reliably align the rotational phases of the reflective surfaces 33 of the rotating polygon mirrors 300 on which films are formed during deposition using the vacuum deposition apparatus 500. As a result, it is possible to prevent overlapping reflective surfaces 33 from being shaded or to prevent variations in the film formation state between vertically adjacent reflective surfaces 33 due to shifts in the rotational phases of the multiple rotating polygon mirrors 300, thereby ensuring high quality and stable mass productivity of the rotating polygon mirrors 300.

[0051] As described above, the rotating polygon mirror 300 of this embodiment can achieve the same effects as the above-mentioned embodiments, and in addition, can reliably align the rotational phase of the reflecting surface 33, thereby suppressing variations in the film formation state of the reflecting surface 33.

[0052] As described above, according to this embodiment, it is possible to prevent deposition of a film on a precision surface that affects the assembly precision of the rotary polygon mirror in the deposition process for the rotary polygon mirror. [Explanation of symbols]

[0053] 3 Rotating polygon mirror 31 First Side 32 The Second Side 33 Reflective surface 35 Protrusion 36 Pedestal

Claims

1. 1. An optical deflection device comprising: a rotary polygon mirror having a plurality of reflecting surfaces; and a motor for driving the rotary polygon mirror, the optical deflection device deflecting a laser beam by the plurality of reflecting surfaces, The rotating polygon mirror is a first surface connected to the plurality of reflecting surfaces; a second surface connected to the plurality of reflecting surfaces and located on the opposite side to the first surface in a direction of a rotation axis of the rotary polygon mirror; Equipped with the first surface includes a ring-shaped first protrusion protruding in the rotation axis direction and centered on the rotation axis of the rotary polygon mirror, the first protrusion having a top surface portion whose height from the first surface is uniform throughout the ring shape, the second surface includes a ring-shaped second protrusion that protrudes in a direction opposite to the first protrusion and is centered on the rotation axis of the rotary polygon mirror, the second protrusion having a top surface portion whose height from the second surface is constant throughout the ring shape, the top surface of the second protrusion serves as a mounting surface for the rotary polygon mirror relative to the motor, the first protrusion and the second protrusion are configured such that, when a plurality of the rotary polygon mirrors are stacked in the rotation axis direction, an inner peripheral wall of the first protrusion and an outer peripheral wall of the second protrusion are fitted together; 13. An optical deflection device, comprising: a top surface of the first protrusion having a height from the first surface that is greater than a top surface of the second protrusion having a height from the second surface that is greater than a height from the second surface of the first protrusion.

2. A rotating polygonal mirror having a plurality of reflecting surfaces, a first surface connected to the plurality of reflecting surfaces; a second surface connected to the plurality of reflecting surfaces and located on the opposite side to the first surface in a direction of a rotation axis of the rotary polygon mirror; Equipped with the first surface has a first protrusion that protrudes in the rotation axis direction and has a ring shape centered on the rotation axis of the rotary polygon mirror, the second surface has a ring-shaped second protrusion that protrudes in a direction opposite to the first protrusion and has a center on the rotation axis of the rotating polygon mirror; the first protrusion and the second protrusion are configured such that, when a plurality of the rotary polygon mirrors are stacked in the rotation axis direction, an inner peripheral wall of the first protrusion and an outer peripheral wall of the second protrusion are fitted together; a top surface of the first protrusion has a plurality of recesses provided at substantially equal intervals in a rotation direction of the rotary polygon mirror, and the top surface is a flat surface having steps; A rotating polygon mirror characterized in that a top surface of the second protrusion has a plurality of convex portions arranged at approximately equal intervals in the rotation direction of the rotating polygon mirror, and the top surface is a flat surface having steps.

3. The top surface of the first protrusion has four recesses, 3. The rotary polygon mirror according to claim 2, wherein the top surface of the second protrusion has three of the convex portions.

4. A rotating polygonal mirror having a plurality of reflecting surfaces, a first surface connected to the plurality of reflecting surfaces; a second surface connected to the plurality of reflecting surfaces and located on the opposite side to the first surface in a direction of a rotation axis of the rotary polygon mirror; Equipped with the first surface has a first protrusion that protrudes in the rotation axis direction and has a ring shape centered on the rotation axis of the rotary polygon mirror, the second surface has a ring-shaped second protrusion that protrudes in a direction opposite to the first protrusion and has a center on the rotation axis of the rotating polygon mirror; the first protrusion and the second protrusion are configured such that, when a plurality of the rotary polygon mirrors are stacked in the rotation axis direction, an inner peripheral wall of the first protrusion and an outer peripheral wall of the second protrusion are fitted together; the first protrusion has the same shape corresponding to each of the reflecting surfaces when the ring shape is divided by a line connecting a center of the rotation axis and both ends of the reflecting surface, the second protrusion has the same shape corresponding to each of the reflecting surfaces when the ring shape is divided by a line connecting a center of the rotation axis and both ends of the reflecting surface, A rotating polygon mirror, wherein the shape corresponding to the reflecting surface of each of the first protrusion and the second protrusion is a D-cut shape.

5. 5. The rotating polygon mirror according to claim 4, wherein a height of a top surface portion of the first protrusion from the first surface is greater than a height of a top surface portion of the second protrusion from the second surface.

6. a rotating polygon mirror according to claim 2, 3, or 5, the rotating polygon mirror having a plurality of reflecting surfaces that reflect laser light; A motor for driving the rotating polygon mirror; An optical deflection device comprising:

7. An optical deflection device as described in Claim 6, characterized in that the top surface portion of the second protrusion is mounted on a base that supports the rotating polygonal mirror of the motor.

8. a rotating polygon mirror according to claim 2 or 3, the rotating polygon mirror having a plurality of reflecting surfaces that reflect laser light; A motor for driving the rotating polygon mirror; Equipped with 4. An optical deflection device according to claim 1, wherein the convex portion of the second protrusion is mounted on a base that supports the rotary polygon mirror of the motor.

9. A light source that emits laser light; a rotating polygon mirror for deflecting the laser beam; and A scanning optical device comprising:

10. An image forming apparatus for forming an image on a recording material, an image forming section having a photosensitive drum and performing image formation on a recording material; 10. The scanning optical device according to claim 9, further comprising the light source, the light source being arranged to irradiate the photosensitive drum of the image forming unit with a laser beam emitted from the light source to form an electrostatic latent image; An image forming apparatus comprising:

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