JP2012063481A - Optical housing, optical scanner, and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical housing that suppresses a color shift due to thermal expansion of the optical housing more than an optical scanner described in claim 1, the optical scanner, and an image formation apparatus.SOLUTION: Top-side ribs 56a as ribs which extend from nearby a polygon scanner 50 to nearby scanning lenses 43 are provided on a top surface on one side with respect to a symmetrical line, and back-side ribs 56b which extend from nearby the polygon scanner 50 to nearby the scanning lenses 43 are provided on a reverse surface on the other side. Consequently, regions of a first housing from the polygon scanner 50 to the scanning lenses are warped convexly to the top surface on the one side with respect to the symmetrical line, and concavely to the top surface on the other side.

Description

  The present invention relates to an optical housing, an optical scanning device, and an image forming apparatus.

  2. Description of the Related Art Conventionally, a so-called tandem type color image forming apparatus is known that forms images of different colors (visible images) on a plurality of latent image carriers and superimposes these images on each other to form a color image. . This image forming apparatus forms a latent image on a latent image carrier by irradiating each latent image carrier with writing light, which is a light beam corresponding to image information, and scanning it. Develop to obtain an image.

  In this tandem type image forming apparatus, a counter scanning type optical scanning apparatus is generally used as an optical scanning apparatus that irradiates each latent image carrier with a writing light, which is a light beam corresponding to image information, and scans it. Used.

In this counter scanning type optical scanning device, a rotary deflector having a rotary polygon mirror is attached at the approximate center of the optical housing of the optical scan device, passes through the center of rotation of the rotary deflector, and with respect to the rotational axis direction of the rotary deflector. A scanning lens (fθ lens), which is an optical element, is attached to the optical housing so as to be line symmetric with respect to one symmetry line drawn so as to be orthogonal to each other.
In recent years, a scanning lens having a function of having power in the sub-scanning direction (condensing light in the sub-scanning direction) has been used for the purpose of reducing the number of parts.

  At the time of image formation, the rotary polygon mirror rotates at a high speed, so that the bearing portion of the rotary deflector generates heat. Due to this heat generation, the vicinity of the rotating deflector of the optical housing is thermally expanded. By such thermal expansion, the vicinity of the rotary deflector expands in a direction orthogonal to the axial direction of the rotary deflector. However, as the distance from the rotary deflector increases, the temperature of the optical housing decreases and the amount of thermal expansion also decreases. As a result, there is no escape space for thermal expansion in the direction orthogonal to the axial direction of the rotary deflector in the vicinity of the rotary deflector, so that the vicinity of the rotary deflector is distorted and deformed. In particular, due to the difference in thermal expansion between the front surface of the optical housing (the mounting surface on which the rotating deflector and the scanning lens are mounted) and the back surface (the surface opposite to the mounting surface), The optical housing warps in a convex shape or a concave shape with respect to the front surface. As a result, the scanning lens mounting portion of the optical housing to which the scanning lens disposed in the vicinity of the rotating deflector is mounted is deformed, and the vertical position of the scanning lens (the axial direction of the rotating deflector) is displaced. If the position of the scanning lens having power in the sub-scanning direction is displaced, the scanning light applied to the latent image carrier is shifted from the ideal position in the sub-scanning direction. In the counter scanning type optical scanning device, the direction of deviation of the scanning light scanned to one side with respect to the symmetry line is opposite to the direction of deviation of the scanning light scanned to the other side, and color deviation is remarkable. become.

  Patent Document 1 describes an optical scanning device in which a hole is provided on a surface of an optical housing facing a rotating polygon mirror. By providing the hole, the vicinity of the rotary polygon mirror of the housing is thermally expanded so as to close the hole. That is, by providing the hole portion, a escape field for thermal expansion in a direction orthogonal to the axial direction of the rotary deflector of the optical housing can be created. Thereby, distortion deformation due to thermal expansion in a direction orthogonal to the axial direction of the rotary deflector in the vicinity of the rotary deflector of the optical housing can be suppressed, and warpage of the optical housing due to thermal expansion can be suppressed. As a result, deformation of the scanning lens mounting portion of the optical housing can be suppressed, and the change in the posture of the scanning lens can be suppressed.

  However, just by providing a hole as described in Patent Document 1, distortion deformation due to thermal expansion cannot be completely removed, and convex warpage or concave warpage occurs on the upper surface. The color shift could not be sufficiently suppressed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical housing and an optical scanning capable of suppressing color shift due to thermal expansion of the optical housing as compared with the optical scanning device described in Patent Document 1. An apparatus and an image forming apparatus are provided.

In order to achieve the above object, the invention of claim 1 is provided in the vicinity of a plurality of light sources, a rotating deflector for deflecting and scanning light emitted from the plurality of light sources in the main scanning direction, and the rotating deflector. A pair of scanning lenses having power in at least the sub-scanning direction arranged symmetrically with respect to a symmetry line drawn in a direction orthogonal to the axial direction of the rotation axis of the rotation deflector through the rotation center of the rotation deflector. The light emitted from at least one of the plurality of light sources is incident on the scanning lens on one side by the rotary deflector, is reflected by one or more reflecting mirrors, is irradiated on the irradiated object, and the remaining light sources The light emitted from the light beam is incident on the other scanning lens by the rotary deflector, is reflected by the same number of reflecting mirrors as the one side, and is used in an opposed scanning optical scanning device that irradiates the irradiated object. ,at least In the optical housing to which the pair of scanning lenses and the rotating deflector are attached, the mounting surface to which the scanning lens and the rotating deflector are attached on at least one side with respect to the symmetry line, or a surface opposite to the attaching surface. A rib extending from the vicinity of the rotary deflector to the vicinity of the scanning lens is provided on the back surface, and the warp direction due to thermal expansion on one side is different from the warp direction due to thermal expansion on the other side with respect to the symmetry line. It is a feature.
According to a second aspect of the present invention, in the optical housing of the first aspect, a rib is provided on the mounting surface on one side with respect to the symmetry line, and a rib is provided on the back surface on the other side with respect to the symmetry line. To do.
According to a third aspect of the present invention, a plurality of light sources, a rotary deflector that deflects and scans light emitted from the plurality of light sources in the main scanning direction, and the rotary deflector are disposed in the vicinity of the rotary deflector. A pair of scanning lenses having power in at least the sub-scanning direction arranged symmetrically with respect to a symmetry line drawn in a direction orthogonal to the axial direction of the rotation axis of the rotary deflector through the rotation center, and having a plurality of light sources The light emitted from at least one of them is incident on the scanning lens on one side by the rotary deflector, is reflected by one or more reflecting mirrors, is irradiated on the irradiated object, and the light emitted from the remaining light sources is , Used in a counter-scanning optical scanning device that is incident on the other scanning lens by the rotary deflector, is reflected by the same number of reflecting mirrors as the one side, and irradiates the irradiated object. Scanning lens And an optical housing to which the rotating deflector is attached, the scanning lens and the rotating deflector are attached to a mounting surface and a back surface opposite to the mounting surface from the vicinity of the rotating deflector to the scanning lens. A rib extending to the vicinity is provided, the rib provided on at least one of the mounting surfaces with respect to the symmetry line and the rib provided on the back surface are asymmetrical, and the warping direction due to thermal expansion on one side with respect to the symmetry line, and the other The warping direction due to thermal expansion on the side is made different.
According to a fourth aspect of the present invention, in the optical housing of the third aspect, on one side with respect to the symmetry line, the width of the rib provided on the attachment surface is made smaller than the width of the rib provided on the back surface. The width of the rib provided on the back surface is narrower than the width of the rib provided on the attachment surface on the other side with respect to the symmetry line.
According to a fifth aspect of the present invention, in the optical housing according to the third or fourth aspect, the number of ribs provided on the mounting surface is greater than the number of ribs provided on the back surface on one side with respect to the symmetry line. The number of ribs provided on the back surface is less than the number of ribs provided on the mounting surface on the other side with respect to the symmetry line.
According to a sixth aspect of the present invention, in the optical housing according to any one of the third to fifth aspects, the length of the rib provided on the mounting surface is set on the back surface on one side with respect to the symmetry line. The length of the rib provided on the back surface is shorter than the length of the rib provided on the mounting surface on the other side with respect to the symmetry line.
According to a seventh aspect of the present invention, in the optical housing according to any one of the third to sixth aspects, the height of the rib provided on the mounting surface on one side with respect to the symmetry line is higher than the height of the rib provided on the back surface. The height of the rib provided on the back surface is lower than the height of the rib provided on the mounting surface on the other side with respect to the symmetry line.
According to an eighth aspect of the present invention, in the optical housing according to any one of the first to seventh aspects, the rib, the mounting surface, and the back surface are integrally formed.
According to a ninth aspect of the present invention, in the optical housing according to any one of the first to seventh aspects, the optical housing is provided in the vicinity of the rotating deflector on the mounting surface and the back surface, and extends across the light scanned by the rotating deflector. A first wall is disposed on one side and the other side of the symmetry line, and is provided in the vicinity of the scanning lens on the mounting surface and the back surface, respectively, and extends so as to cross the light scanned by the rotary deflector. The portions are arranged on one side and the other side of the symmetry line, the rib is constituted by a member separate from the optical housing, and is sandwiched between the first wall portion and the second wall portion. Is.
According to a tenth aspect of the present invention, in the optical housing of the ninth aspect, the linear expansion coefficient of the rib is made larger than the linear expansion coefficient of the surface to which the rib is attached.
According to an eleventh aspect of the present invention, in the optical housing according to any one of the first to tenth aspects, the optical housing is attached to a housing that houses optical system components disposed on an optical path of light after the scanning lens. It is characterized by this.
According to a twelfth aspect of the present invention, a plurality of light sources, a rotary deflector that deflects and scans light emitted from the plurality of light sources in the main scanning direction, and the rotary deflector are disposed in the vicinity of the rotary deflector. A pair of scanning lenses having power in at least the sub-scanning direction arranged symmetrically with respect to a symmetry line drawn in a direction orthogonal to the axial direction of the rotation axis of the rotary deflector through the rotation center, and having a plurality of light sources The light emitted from at least one of them is incident on one scanning lens by the rotary deflector, and the light emitted from the remaining light sources is the light of the counter scanning system that is incident on the other scanning lens by the rotary deflector. In a scanning device, the optical housing according to any one of claims 1 to 11 is used as an optical housing to which at least the pair of scanning lenses and the rotary deflector are attached. The one in which the features.
The invention of claim 13 separately develops a plurality of latent image carriers, optical writing means for writing a latent image on each latent image carrier, and latent images formed on each latent image carrier. In the image forming apparatus comprising a plurality of developing means and a transfer means for transferring the visible image obtained on each latent image carrier by development superimposed on the transfer body, the optical writing means is claimed as the optical writing means. The optical scanning device according to item 12 is used.

  According to the present invention, the rib extending from the vicinity of the rotating deflector to the scanning lens controls the warping direction of the region between the rotating deflector of the optical housing and the scanning lens, and the thermal expansion on one side with respect to the symmetry line. The warping direction of the region between the rotating deflector and the scanning lens due to the above and the warping direction of the region between the rotating deflector and the scanning lens due to thermal expansion on the other side are made different. More specifically, the surface provided with the rib has a larger volume than the surface not provided with the rib. Since the rib extends from the rotary deflector toward the scanning lens, the amount of thermal expansion that thermally expands toward the scanning lens on the surface on which the rib is provided is larger than that on the surface on which the rib is not provided. Therefore, in this case, the optical housing is curved in an arc shape so that the surface provided with the rib having a large amount of thermal expansion is the outer periphery and the surface side where the rib is not provided is the inner periphery. As a result, one side with respect to the symmetry line is warped so that the surface provided with the rib is convex. Therefore, if the rib is provided on the mounting surface side, the region between the rotation deflector of the optical housing and the scanning lens can be bent convexly with respect to the mounting surface, and if the rib is provided on the back surface, the optical housing is provided. The area between the rotary deflector and the scanning lens can be bent concavely with respect to the mounting surface. As described above, by providing the rib on one of the attachment surface and the back surface, it is possible to control the warping direction of the region between the rotation deflector of the optical housing and the scanning lens. In addition to the above, the warping direction can also be controlled by making the shape (width, height, etc.) and number of ribs different between the attachment surface side and the back surface side.

  If the rib is provided on the attachment surface or the back surface on at least one side with respect to the symmetry line as in the invention according to claim 1, the warp direction due to thermal expansion on one side with respect to the symmetry line, and the other side The warp direction due to thermal expansion can be made different. That is, the rib is provided so that at least one side with respect to the symmetry line is warped in a direction opposite to the warp direction of the original optical housing. For example, if the warp of the original optical housing is convex with respect to the mounting surface, ribs are provided on at least one back surface with respect to the symmetry line, and one side is warped concavely. As a result, one side of the symmetry line warps in the direction opposite to the original warping direction of the optical housing, and the other side not provided with the rib warps in the original warping direction of the optical housing. As a result, the warp directions due to thermal expansion on one side and the other side can be made different from each other with respect to the symmetry line.

  Further, as in the invention according to claim 3, the rib provided on the attachment surface on at least one side with respect to the symmetry line and the rib provided on the back surface are asymmetric, and one side with respect to the symmetry line is You may make it curve in the direction opposite to the curvature direction of the original optical housing.

  According to the present invention, the rib extending from the vicinity of the rotating deflector to the vicinity of the scanning lens causes the warp direction due to the thermal expansion of the region between the rotating deflector on one side and the scanning lens with respect to the symmetry line, and the other side. The following effects can be obtained by making the warpage direction due to thermal expansion different. That is, as shown in FIG. 23, the direction of deviation of the incident position of the scanning light with respect to the scanning lenses 43a and 43b due to the warp of the optical housing 70 is reversed between one side (right side in the figure) and the other side (left side in the figure). can do. On the side where the region between the rotary deflector and the scanning lens warps convexly with respect to the mounting surface (the right side in the figure), the scanning lens mounting part of the optical housing 70 is displaced upward in the figure due to thermal expansion. The position of the scanning lens 43b is displaced upward. Therefore, the incident position of the scanning light on the scanning lens 43b is shifted to the optical housing side (lower side in the figure) with respect to the ideal incident position (center part in the vertical direction in the figure) A. In this case, the scanning lens 43b having power in the sub-scanning direction is bent toward the center side of the scanning lens 43b, thereby moving away from the optical housing 70 with respect to the ideal optical path indicated by the dotted line in the drawing (in the drawing). (Upper side) (Refer to the solid line in the figure). As a result, the scanning light in the irradiated object 10b on the right side in the drawing is shifted to the upstream side in the irradiated object moving direction with respect to the ideal scanning position B.

  On the other hand, since the scanning lens mounting portion of the optical housing 70 is displaced downward in the figure due to thermal expansion, the position of the scanning lens 43a is displaced downward in the figure. Therefore, the ideal incident position A is shifted to the side away from the optical housing 70 (upper side in the figure). In this case, the optical path of the scanning light is shifted to the optical housing side (lower side in the figure) with respect to the ideal optical path (dotted line in the figure) by the scanning lens (see the solid line in the figure). As a result, the scanning light from the irradiated object 10a on the left side in the drawing is also shifted to the upstream side in the irradiation object moving direction with respect to the ideal scanning position B.

  In this way, both the one side (right side in the figure) and the other side (left side in the figure) of the symmetry line are shifted to the upstream side in the object movement direction with respect to the ideal irradiation position B. That is, by changing the warping direction due to thermal expansion on one side (right side in the figure) and the warping direction due to thermal expansion on the other side (left side in the figure) with respect to the symmetry line, the irradiation position is relative to the symmetry line. The one side (right side in the figure) and the other side (left side in the figure) can be shifted in the same direction. Accordingly, as in the optical scanning device described in Patent Document 1, the optical housing is compared with the one in which the warp direction due to thermal expansion is the same on one side (right side in the figure) and the other side (left side in the figure) with respect to the symmetry line. The color shift due to the thermal expansion of can be suppressed.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating an image forming station for Y in the printer. FIG. 2 is a schematic configuration diagram showing an optical scanning device in the printer together with four photosensitive members. FIG. 2 is a schematic top view showing a configuration of the optical scanning device. The schematic block diagram of the 1st housing | casing of the same optical scanning device. The figure explaining a mode that a 1st housing | casing is attached to a 2nd housing | casing. (A) is AA sectional drawing of FIG. 5 before a 1st housing | casing deformation | transformation. (B) is AA sectional drawing of FIG. 5 after a 1st housing | casing deformation | transformation. FIG. 6 is a diagram for explaining a shift in a scanning position on a photosensitive member due to a displacement of a scanning lens. (A) is a figure explaining the scanning position shift of C color by the attitude | position change of 43 C of scanning lenses of C color. FIG. 6B is a diagram for explaining a M-color scanning position shift due to a change in posture of the M-color scanning lens 43M. FIG. 2 is a schematic configuration diagram illustrating a first housing according to the first embodiment. Sectional drawing after the heat deformation of the 1st housing | casing of Example 1. FIG. The figure explaining deformation | transformation of the 1st housing | casing before heat deformation and after heat deformation. FIG. 6 is a schematic configuration diagram of a first housing according to a second embodiment. BB sectional drawing of FIG. FIG. 10 is a schematic configuration diagram of a first housing of a modification of the second embodiment. CC sectional drawing of FIG. FIG. 6 is a schematic configuration diagram of a first housing of Example 3. (A) is DD sectional drawing of FIG. (B) is EE sectional drawing of FIG. FIG. 6 is a schematic configuration diagram of a first housing of Example 4. (A) is FF sectional drawing of FIG. (B) is GG sectional drawing of FIG. FIG. 10 is a schematic configuration diagram of a first housing according to a fifth embodiment. HH sectional drawing of FIG. 22B is a cross-sectional view taken along the line II of FIG. The figure explaining the effect of this invention.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color laser printer (hereinafter simply referred to as a printer) will be described.
FIG. 1 is a schematic configuration diagram illustrating a printer according to the present embodiment. The printer includes a housing 1 and a paper feed cassette 2 that can be pulled out from the housing 1. Image forming stations 3Y, 3C, and 3C for forming toner images (visible images) of each color of yellow (Y), cyan (C), magenta (M), and black (K) are provided at the center of the housing 1. 3M, 3K. Hereinafter, the subscripts Y, C, M, and K of the respective symbols indicate members for yellow, cyan, magenta, and black, respectively.

FIG. 2 is a schematic configuration diagram showing an image forming station for yellow (Y). The other image forming stations have the same configuration.
As shown in FIGS. 1 and 1, the image forming stations 3Y, 3C, 3M, and 3K include drum-shaped photoconductors 10Y, 10C, 10M, and 10K as latent image carriers that rotate in the direction of arrow A in the drawing. ing. Each of the photoreceptors 10Y, 10C, 10M, and 10K includes an aluminum cylindrical substrate having a diameter of 40 [mm] and an OPC (organic photo semiconductor) photosensitive layer that covers the surface of the photoreceptor. Each of the image forming stations 3Y, 3C, 3M, and 3K includes charging devices 11Y, 11C, 11M, and 11K that charge the photoconductors around the photoconductors 10Y, 10C, 10M, and 10K, respectively. Further, developing devices 12Y, 12C, 12M, and 12K as developing means for developing the latent image formed on the photosensitive member, and cleaning devices 13Y, 13C, 13M, and 13K for cleaning residual toner on the photosensitive member are also provided around the photosensitive member. In preparation.

  Below each of the image forming stations 3Y, 3C, 3M, and 3K, an optical writing unit 4 that performs optical scanning with the writing light L on the photoconductors 10Y, 10C, 10M, and 10K is provided. Further, an intermediate transfer unit 5 including an intermediate transfer belt 20 to which toner images formed by the image forming stations 3Y, 3C, 3M, and 3K are transferred above the image forming stations 3Y, 3C, 3M, and 3K. It has. Further, a fixing unit 6 is provided for fixing the toner image transferred to the intermediate transfer belt 20 onto a recording paper P as a transfer member. In addition, toner bottles 7Y, 7C, 7M, and 7K that contain toner of each color of yellow (Y), cyan (C), magenta (M), and black (K) are loaded on the top of the casing 1. . The toner bottles 7 </ b> Y, 7 </ b> C, 7 </ b> M, and 7 </ b> K can be detached from the housing 1 by opening a paper discharge tray 8 formed on the top of the housing 1.

  The optical writing unit 4 as an optical scanning device has a laser diode as a light source, and writing light L as a light beam is directed from this laser diode toward a polygon mirror having a regular polygonal column structure that is rotationally driven. Fire. The emitted writing light L is reflected while being deflected in the main scanning direction by the mirror surface of the rotating polygon mirror. Then, after being folded by a plurality of reflecting mirrors, the peripheral surfaces of the photoreceptors 10Y, 10C, 10M, and 10K that are uniformly charged by the charging devices 11Y, 11C, 11M, and 11K are scanned. Thereby, electrostatic latent images for Y, C, M, and K are formed on the peripheral surfaces of the photoreceptors 10Y, 10C, 10M, and 10K as latent image carriers. The detailed description of the optical writing unit 4 will be described later.

  The intermediate transfer belt 20 of the intermediate transfer unit 5 serving as transfer means is driven to rotate counterclockwise in the figure at a predetermined timing while being wound around a drive roller 21, a tension roller 22 and a driven roller 23. In addition, the intermediate transfer unit 5 includes primary transfer rollers 24Y, 24C, 24M, and 24K that primarily transfer the toner images formed on the photoreceptors 10Y, 10C, 10M, and 10K to the intermediate transfer belt 20. Further, a secondary transfer roller 25 that transfers the toner image primarily transferred onto the intermediate transfer belt 20 to the recording paper P, and a belt that cleans residual toner on the intermediate transfer belt 20 that has not been transferred onto the recording paper P. A cleaning device 26 is also provided.

Next, a process for obtaining a color image in this printer will be described.
First, in the image forming stations 3Y, 3C, 3M, and 3K, the photoreceptors 10Y, 10C, 10M, and 10K are uniformly charged by the charging devices 11Y, 11C, 11M, and 11K. Thereafter, scanning exposure is performed with the writing light L generated based on the image information, and electrostatic latent images are formed on the surfaces of the photoreceptors 10Y, 10C, 10M, and 10K. These electrostatic latent images are developed with toners of the respective colors carried on the developing rollers 15Y, 15C, 15M, and 15K of the developing devices 12Y, 12C, 12M, and 12K, and are converted into Y, C, M, and K toner images. Become. The Y, C, M, and K toner images on the photoreceptors 10Y, 10C, 10M, and 10K are formed on the intermediate transfer belt 20 that is rotated counterclockwise by the action of the primary transfer rollers 24Y, 24C, 24M, and 24K. The primary transfer is carried out in order. The image forming operation of each color at this time is shifted in timing from the upstream side in the moving direction of the intermediate transfer belt 20 toward the downstream side so that the toner image is transferred to the same position on the intermediate transfer belt 20. Executed.

  The surfaces of the photoconductors 10Y, 10C, 10M, and 10K after the completion of the primary transfer are cleaned by the cleaning blades 13a of the cleaning devices 13Y, 13C, 13M, and 13K to prepare for the next image formation.

  The toner filled in the toner bottles 7Y, 7C, 7M, and 7K is placed in the developing devices 12Y, 12C, 12M, and 12K of the image forming stations 3Y, 3C, 3M, and 3K by a conveyance path (not shown) as necessary. A fixed amount is supplied.

  On the other hand, the recording paper P in the paper feed cassette 2 is transported into the housing 1 by a paper feed roller 27 disposed in the vicinity of the paper feed cassette 2 and is secondary by a registration roller pair 28 at a predetermined timing. It is conveyed to the transfer unit. Then, the toner image formed on the intermediate transfer belt 20 is transferred to the recording paper P in the secondary transfer portion. The recording paper P onto which the toner image has been transferred passes through the fixing unit 6 to fix the toner image, and is then discharged to the paper discharge tray 8 by the discharge roller 29. Similar to the photoconductor 10, the transfer residual toner remaining on the intermediate transfer belt 20 is cleaned by a belt cleaning device 26 that contacts the intermediate transfer belt 20.

Next, the configuration of the optical writing unit 4 will be described.
FIG. 3 is a schematic configuration diagram showing the optical writing unit 4 in the printer according to this embodiment together with four photosensitive members.
FIG. 4 is a schematic top view illustrating the configuration of the scanning device, and FIG. 5 is a schematic configuration diagram of the first housing 70.
As shown in FIG. 3, the writing unit 4 includes optical system components such as a polygon scanner 50 as a rotary deflector, various reflection mirrors, and various lenses. Optical system components such as the polygon scanner 50, various reflection mirrors, and various lenses are housed in an optical housing 131. Dustproof glass 48Y, 48C, 48M, and 48K are provided on the housing cover 107 that covers the opening above the optical housing 131.
As shown in FIG. 4, the housing 131 is a first housing 70 as an optical housing made of resin that houses optical system components provided on the optical path between the light source and the scanning lenses 43Y, 43C, 43M, and 43K. And a second housing 60 made of resin or the like for housing an optical element provided on the optical path from the scanning lenses 43Y, 43C, 43M, and 43K to the photosensitive member.

  As shown in FIG. 5, the first housing 70 includes laser diodes 46Y, 46C, 46M, and 46K as light sources, collimating lenses 52Y, 52C, 52M, and 52K, cylindrical lenses 53Y, 53M, 53C, and 53K, and rotational deflection. The polygon scanner 50 and polygon mirrors 41a and 41b, which change the laser scanning equiangular motion to constant velocity linear motion, have power in the sub-scanning direction (condensed light in the sub-scanning direction), and are troublesome for the polygon mirror. The scanning lenses 43Y, 43M, 43C, and 43K, which are optical elements that perform the correction, are housed.

  As shown in FIG. 5, the polygon scanner 50 includes polygon mirrors 41a and 41b, which are two rotating polygon mirrors having a regular polygonal prism shape, a polygon motor (not shown), and electronic components for controlling the driving of the polygon motor. The circuit board 150 is mounted. These polygon mirrors 41a and 41b have reflecting mirrors on their six side surfaces, and are connected in the vertical direction so that the centers of the regular polygonal columns overlap each other (see FIG. 3). The polygon scanner 50 is fastened with screws to a polygon scanner mounting portion surrounded by a soundproof wall 54 of the first housing 70. Cutouts are provided at two locations on the soundproof wall 54, and soundproof glasses 42a and 42b are attached to the cutouts.

  Laser diodes 46 </ b> Y, 46 </ b> C, 46 </ b> M, and 46 </ b> K that are light sources are attached to the side surface of the first housing 70. The K-color laser diode 46K is mounted directly above the M-color laser diode 46M, and the Y-color laser diode 46Y is mounted directly above the C-color laser diode 46C. The K-color optical system components (scanning lens 43K, collimating lens 52K, and cylindrical lens 53K) are arranged directly above the M-color optical system components, and the Y-color optical system components (scanning lens 43Y, collimating lens 52Y). The cylindrical lens 53Y) is mounted immediately above the C-color optical system component. Specifically, the optical components (collimator lens 52 and cylindrical lens 53) before deflection of K color and Y color are arranged on the front surface which is the mounting surface of the first housing 70 to which the scanning lens and the polygon scanner are mounted. The optical components that are attached and are not deflected in the M color or the C color are attached to the back surface that is the surface opposite to the attachment surface of the first housing 70 (see FIG. 10B). The K-color scanning lens 43K is attached to the M-color scanning lens 43M in an overlapping manner, and the Y-color scanning lens 43Y is attached to the C-color scanning lens 43M in an overlapping manner.

  As shown in FIG. 3, an M optical system and a K optical system are disposed on the right side of the polygon scanner 50 in the drawing. On the left side of the polygon scanner 50 in the drawing, an optical system for Y and an optical system for C are arranged. Further, as shown in FIG. 5, the writing unit 4 passes through the rotation centers of the polygon mirrors 41a and 41b and the symmetry line drawn in the direction orthogonal to the axial direction of the rotation axes of the polygon mirrors 41a and 41b. This is a counter scanning type optical scanning device in which an optical system component and a laser diode as a light source are arranged in a line-symmetrical position to form a pair. Specifically, the scanning lenses 43Y, 43M, 43K, which are optical elements, the laser diodes 46Y, 46M, C, K which are light sources, the collimating lenses 52Y, 52M, 52C, 52K, the cylindrical lenses 53Y, 53M, 53C, Each of K is arranged at a line symmetrical position. In the following description, the right side (the side on which the optical system components for K and M are arranged) with respect to the symmetry line of the first housing 70 is referred to as the right optical system. The left side (the side on which the optical system components for Y and C are arranged) with respect to the symmetry line is referred to as the left side optical system.

  As shown in FIGS. 4 and 6, the first casing 70 is attached to the approximate center of the second casing 60 so that the polygon scanner 50 is positioned approximately in the center of the writing unit 4. Specifically, as shown in FIG. 5, screws (not shown) are inserted into through holes 71 provided at four corners of the first housing 70, and screws are inserted into screw holes (not shown) of the second housing 70. By stopping, the first casing 70 is fixed to the second casing 60. Further, as shown in FIG. 3, the central portion of the housing cover 107 as a lid member is opened, extends from the opening to the polygon scanner 50 side, and the lower ends are the upper surfaces of the soundproof glasses 42a and 42b and the soundproofing. An inner wall portion 106 that contacts the upper surface of the wall 54 is formed. And the deflector cover 105 which is a cover member is attached so that the opening part of this housing | casing cover 107 may be covered. As a result, the polygon scanner 50 is hermetically sealed by the bottom surface of the housing 131, the soundproof glasses 42a and 42b, the soundproof wall 54, the inner wall portion 106, and the deflector cover 105.

  The writing lights Ly, Lc, Lm, and Lk emitted from the laser diodes 46Y, 46C, 46M, 46K are converted into parallel light beams by the collimating lenses 52Y, 52M, 52C, 52K, and then the cylindrical lens 53Y. , M, C, and K, the light is condensed in the sub-scanning direction (the direction corresponding to the photosensitive member surface moving direction on the photosensitive member surface). Next, the main scanning direction (axis line on the surface of the photoconductor is reflected while being reflected by any one of the mirror surfaces formed on each of the six side surfaces of the polygon mirrors 41a and 41b having a regular hexahedron structure rotated at high speed by a polygon motor (not shown). In a direction corresponding to the direction). Then, the scanning lenses 43Y, M, C, and K convert the moving speed in the deflection direction of the light deflected in the main scanning direction at a constant angular velocity by the polygon mirrors 41a and 41b to the constant speed and in the sub scanning direction. The light is condensed and so-called surface tilt, which is the mirror surface tilt of the polygon mirrors 41a and 41b, is corrected.

  The Y, C, M, and K writing lights Ly, Lc, Lm, and Lk that have passed through the scanning lenses 43Y, M, C, and K are reflected on the reflecting mirrors of the Y, C, M, and K reflecting optical systems. Head. For example, the Y writing light Ly that has passed through the scanning lens 43Y is reflected to the first reflecting mirror 44Y and the second reflecting mirror 45Y, and is guided to the surface of the Y photoconductor 10Y. Similarly, the laser beams Lc, Lm, and Lk for C, M, and K are reflected by the first reflecting mirror and the second reflecting mirror, respectively, so that the C, M, and K photoconductors 10C, M, and K are output. Guided to the surface. Note that the Y, C, M, and K writing lights Ly, Lc, Lm, and Lk reflected by the mirror surfaces of the second reflecting mirrors 45Y, 45C, 45M, 45K are dust-proof glass 48Y provided on the housing cover 107. , 48C, 48M, and 48K, and then reaches the surface of the photoreceptors 10Y, 10M, 10C, and 10K.

Due to the high speed rotation of the polygon mirrors 41a and 41b, a bearing portion (not shown) that supports the rotation shafts of the polygon mirrors 41a and 41b generates heat. This heat propagates to the first casing 70 directly below the bearing portion, and the vicinity of the polygon mirror of the first casing 70 is heated. As a result, the vicinity of the polygon mirror of the first housing 70 is thermally expanded and deformed.
7A is a cross-sectional view taken along the line AA in FIG. 5 before the first casing 70 is deformed, and FIG. 7B is a cross-sectional view taken along the line AA in FIG.
As shown in FIG. 7B, when the first casing 70 is thermally expanded, the entire first casing 70 is warped in a concave shape with respect to the front surface 70a of the first casing. As a result, the polygon scanner and the scanning lenses 43Y, 43M, 43C, and 43K disposed in the vicinity of the polygon scanner sink downward in the drawing. Even if the polygon scanner sinks downward in the figure and the incident position of light on the polygon mirror changes, the polygon mirror only reflects the light, so there is almost no influence of such sinking. On the other hand, since the scanning lens has power in the sub-scanning direction, a shift occurs in the scanning position on the photosensitive member.

FIG. 8 is a diagram for explaining a shift in the scanning position on the photosensitive member due to the displacement of the scanning lens.
As shown in FIG. 8A, before displacement, scanning light is incident on the center of the scanning lens, and light is irradiated to an ideal scanning position X on the photosensitive member. On the other hand, as shown in FIG. 8B, when the first housing 70 warps in a concave shape and the scanning lens is displaced downward in the drawing, the scanning light is incident on the upper portion in the drawing from the center of the scanning lens. Since the scanning lens has power in the sub-scanning direction, it bends toward the focal point within the scanning lens. Similarly, since the focal point of the scanning lens is displaced downward, the light emitted from the scanning lens is inclined downward and emitted. As a result, light is irradiated to a position shifted in the sub-scanning direction with respect to the ideal scanning position on the photosensitive member. In particular, in the case of the counter scanning type optical scanning apparatus as in the present embodiment, the color shift is remarkably deteriorated when the posture of the scanning lens is changed for the following reason.

FIG. 9A is a diagram for explaining a C-color scanning position shift due to a change in the posture of the C-color scanning lens 43C, and FIG. 9B is a diagram illustrating the M-color due to a change in the posture of the M-color scanning lens 43M. It is a figure explaining scanning position shift.
As shown in FIG. 8B, when the first housing 70 is deformed into a concave shape and the scanning lens 43C and the M-color scanning lens are displaced downward, the light emitted from the scanning lens is tilted downward. Are emitted. When the light is tilted downward and irradiated by the scanning lens 43C, as shown in FIG. 8A, the photoconductor 10C disposed on one side (left side shown in FIG. 3) with the polygon mirrors 41a and 41b interposed therebetween. The scanning position is shifted to the downstream side in the photosensitive member moving direction with respect to the scanning position before the housing is deformed (before the posture of the optical system component or the light source is changed). On the other hand, when light is tilted downward and irradiated by the scanning lens 43M, the scanning position to the photoconductor 10M disposed on the other side (right side shown in FIG. 3) with the polygon mirrors 41a and 41b interposed therebetween is changed to the housing deformation. With respect to the previous scanning position (before the change in the posture of the optical system component), it shifts to the upstream side in the photosensitive member moving direction. The photoconductor 10Y arranged on one side (left side shown in FIG. 3) across the polygon mirrors 41a and 41b is shifted to the downstream side in the photoconductor moving direction with respect to the scanning position before the housing deformation, as in the case of the C color. The photoconductor 10K disposed on the other side (the right side shown in FIG. 3) with the mirrors 41a and 41b interposed therebetween is shifted upstream in the photoconductor moving direction with respect to the scanning position before deformation of the housing, similarly to the M color. As a result, after the housing is deformed, the C-color and Y-color images formed on the photoconductors 10C and 10Y arranged on one side with the polygon mirrors 41a and 41b interposed therebetween are arranged on the other side with the polygon mirrors 41a and 41b interposed therebetween. The positions of the M-color and K-color images formed on the photoconductors 10M and 10K arranged in the above are greatly shifted. Therefore, in the case of the counter scanning type optical scanning device, the color misregistration is remarkably deteriorated.

  In the above description, the example in which the concave warpage occurs with respect to the front surface 70a of the first housing 70 has been described. However, the structure of the first housing 70 and the front side and the back side of the first housing Depending on various conditions such as a temperature difference from the case, it may warp in a convex shape. When warped in a convex shape, the scanning lens is displaced upward. As a result, in this case, contrary to the previous FIG. 9, in the left optical system, the scanning position is shifted to the upstream side in the photosensitive member moving direction with respect to the ideal scanning line, and the right optical system is scanned. The position is shifted downstream of the ideal scanning line in the photosensitive member moving direction.

  In order to deal with such a problem, the right optical system has an odd number of reflecting mirrors and the left optical system has an even number of reflecting mirrors, so that the right optical system and the left optical system are displaced in the scanning position. The color shift can be suppressed. However, if the number of reflecting mirrors is different between the right optical system and the left optical system, it becomes difficult to make the optical path length the same between the right optical system and the left optical system. For this reason, when the same scanning lens is used for the right optical system and the left optical system, the beam spot diameter irradiated to the right optical system photoconductor (10M, 10K) and the left optical system photoconductor (10C, 10Y). There is a high possibility that a problem such as a difference in the diameter of the beam spot to be irradiated will occur, and a good image may not be obtained.

  Therefore, in the present embodiment, as shown in FIG. 5, the warp direction due to heat of the first casing 70 on one side (right optical system) across the symmetry line is changed to the first casing on the other side (left optical system). The 1st housing | casing which is an optical housing was comprised so that the curvature direction by the heat | fever of the body 70 might differ, respectively. Below, it demonstrates concretely using an Example.

[Example 1]
FIG. 10 is a schematic configuration diagram illustrating the first housing 70 of the first embodiment.
As shown in FIG. 10 (a), the soundproof wall 54, which is the first wall portion of the left optical system on the front surface 70a of the first housing 70 (more precisely, for attaching the soundproof glass of the soundproof wall 54). Between the sound-insulating wall 54 and the front-side transverse rib 56a that is provided in the vicinity of the scanning lens 43Y and is provided so as to cross the scanning light. A plurality of front side control ribs 57a extending to the transverse ribs 56b and controlling the amount of thermal expansion of the front surface are provided. On the other hand, the front side control rib is not provided between the soundproof wall 54 of the right optical system on the front surface 70a and the front side transverse rib 56a, and is asymmetric.

  A polygon scanner mounting portion (a portion surrounded by the soundproof wall 54 shown in FIG. 10A) is recessed on the back surface of the first housing 70 from the surface on which the scanning lens 43 is mounted. As shown in (b), the peripheral part of the polygon scanner 50 on the back surface of the first housing 70 protrudes. The rear side as the second wall portion formed directly behind the portion where the front side transverse rib 56a is formed from the side wall 58 (corresponding to the first wall portion) of the right optical system in the figure of the protruding portion. A plurality of back side control ribs 57b for controlling the amount of thermal expansion of the back surface extending to the transverse rib 56b is provided. On the other hand, the back side control rib 57b is not provided between the side wall 58 of the left optical system on the back surface of the first housing and the back side transverse rib 56b, and is asymmetric.

  The front side control rib 57a and the back side control rib 57b are integrally formed with the first housing 70 by injection molding or the like.

FIG. 11 is a cross-sectional view of the first housing 70 according to the first embodiment after thermal deformation, and FIG. 12 is a diagram illustrating the deformation of the first housing 70 before and after thermal deformation. The dotted line in FIG. 12 is before deformation, and the solid line in the figure indicates after deformation.
As shown in FIG. 11, in the embodiment, in the left optical system of the first housing 70, the front side control rib 57a is provided, but the back side control rib 57b is not provided. The front surface of the first housing 70 has a larger volume than the back surface due to the presence of the front side control rib 57a. As a result, in the left optical system of the first housing 70, the amount of thermal expansion in the optical axis direction on the front surface side is larger than the amount of thermal expansion in the optical axis direction on the back surface side. Therefore, as shown in FIG. 12, the left optical system warps in a convex shape in the figure. By warping in a convex shape, the scanning lens mounting portion of the left optical system of the first housing 70 is displaced upward in the drawing. By displacing upward, the scanning light is incident on the lower side in the figure from the center of the scanning lenses 43Y and 43M. As a result, in the left optical system, the scanning line is shifted upward in the figure, contrary to the previous FIG. 9, and in the left optical system, it shifts to the upstream side in the photosensitive member moving direction with respect to the ideal scanning position.

  On the other hand, as shown in FIG. 11, the right optical system is provided with only the back side control rib 57b without providing the front side control rib 57a, contrary to the left side optical system. Thereby, the back surface of the first housing 70 has a larger volume than the front surface due to the presence of the back side control rib 57a. As a result, the amount of thermal expansion in the optical axis direction on the back surface side is larger than the amount of thermal expansion in the optical axis direction on the front surface side. Therefore, as shown in FIG. 12, the right optical system warps in a concave shape in the figure. By warping in a concave shape, the scanning lens mounting portion of the right optical system of the first housing 70 is displaced downward in the drawing. By being displaced downward, the scanning light is incident on the upper side in the figure from the center of the scanning lenses 43K and 43M. Therefore, in the right optical system, the scanning line is shifted downward in the figure with respect to the scanning line before the deformation, as in FIG. As a result, the right optical system is also shifted upstream in the photoconductor movement direction with respect to the ideal scanning position.

  As described above, in the first embodiment, the right optical system and the left optical system can have the same scanning direction shift direction when the first housing 70 is thermally expanded. Thereby, color shift due to thermal deformation of the first housing 70 can be suppressed.

  In Example 1, the back side control rib 57b is provided in the right optical system, but the back side control rib 57b may not be provided. As shown in FIG. 7B, the entire first housing 70 warps in a concave shape in the drawing, and therefore the right optical system is shown in FIG. 9 without providing the back side control rib 57b. Thus, the scanning position is shifted to the upstream side in the photosensitive member moving direction. Therefore, the front side control rib 57a is provided only on the front surface of the left optical system in which the direction of deviation from the ideal position of the scanning position to the photosensitive member during thermal expansion is to be upstream of the photosensitive member moving direction. The left optical system of the first housing 70 is bent in a convex shape in the drawing to displace the mounting position of the scanning lens upward, and the left optical system is also shifted to the upstream side in the photosensitive member moving direction with respect to the ideal scanning position. .

[Example 2]
Next, Example 2 will be described.
FIG. 13 is a schematic configuration diagram of the first housing 170 according to the second embodiment, and FIG. 14 is a cross-sectional view taken along the line BB of FIG.
Front side control ribs 57a are symmetrically arranged on the right optical system and the left optical system of the front surface 170a of the first housing 170, respectively. Further, the back side transverse rib 56b of the left optical system on the back surface 170b is formed directly behind the front side transverse rib 56a. As a result, as shown in FIG. 14, in the left optical system, the length of the front side control rib 57a is equal to the length of the back side control rib 57b. On the other hand, the back side transverse rib 56b of the right optical system is provided closer to the polygon scanner than the front side transverse rib 56a. As a result, as shown in FIG. 14, the back side control rib 57b provided from the side wall 58 of the right optical system to the back side transverse rib 56b is shorter than the front side control rib 57a.

  In the left optical system, since the control ribs having the same length are provided on both the front surface and the back surface, the volumes of the front surface and the back surface are the same. Therefore, in the left optical system, there is no difference in the amount of thermal expansion between the front surface and the back surface due to the control rib, so the first optical system warps in a concave shape in FIG. As a result, in the left optical system, as shown in FIG. 9, the scanning position is shifted from the ideal scanning position to the downstream side in the photosensitive member moving direction. On the other hand, in the right optical system, since the back side control rib 57b is short, the amount of thermal expansion of the front surface is larger than that of the back surface. As a result, the right optical system of the first housing 170 warps in a convex shape. Therefore, the scanning lenses 43K and 43M of the right optical system are displaced upward in the drawing. As a result, in the right optical system, contrary to the previous FIG. 9, the ideal scanning position is shifted downstream in the photosensitive member moving direction.

  As described above, the length of the back side control rib 57b of either the right side optical system or the left side optical system is made shorter than the length of the front side control rib 57a. The right side optical system and the left side optical system can have the same scanning direction shift direction.

  In the second embodiment, front side control ribs 57a are provided on the front surfaces of the right optical system and the left optical system, respectively, and back side control ribs 57b are provided on the back surfaces of the right optical system and the left optical system. Therefore, the rigidity of the first housing 170 can also be ensured.

  15 and 16, in the left optical system, the length of the back side control rib 57b is shorter than the length of the front side control rib 57a, and in the right side optical system, the length of the front side control rib 57b is shorter. The length of the control rib 57a may be shorter than the length of the back side control rib 57b. In this case, the left optical system warps in a convex shape in the figure, and the right optical system warps in a concave shape. Thereby, in both the left optical system and the right optical system, the scanning position can be shifted to the upstream side in the photosensitive member moving direction with respect to the ideal position. Further, the length of the shorter control rib can be set so that the deviation amount with respect to the ideal scanning position after thermal deformation is the same in the left and right optical systems.

[Example 3]
Next, Example 3 will be described.
FIG. 17 is a schematic configuration diagram of the first housing 270 of the third embodiment, FIG. 18A is a cross-sectional view taken along the line DD in FIG. 17, and FIG. 18B is a cross-sectional view taken along the line E- in FIG. It is E sectional drawing.
In Example 3, in the right side optical system, as shown in FIG. 18B, the height of the back side control rib 57b is set higher than the height of the front side control rib 57a, and in the left side optical system. As shown in FIG. 18A, the height of the front side control rib 57a is made higher than the height of the back side control rib 57b.

  In the right optical system, the back side control rib 57b is made higher than the front side control rib 57a, so that the volume of the back side can be made larger than the front side. As a result, in the right optical system, the first housing 270 warps in a concave shape. On the other hand, in the left side optical system, the front side control rib 57a is higher than the back side control rib 57b, so the volume of the front side is larger than the back side. The housing 270 warps in a convex shape. As described above, also in the configuration of the third embodiment, the warp of the first housing 270 can be made different on the left and right, so that the shift direction of the scanning position after thermal deformation can be made the same in the left and right optical systems. Color misregistration can be suppressed.

  Further, in the third embodiment, control ribs are provided on each of the back surface and the front surface, and these control ribs are provided from the first wall portion (the soundproof wall 54 on the front surface side and the side wall 58 on the back surface side). Since it extends to the second wall (the front side is the front crossing rib 56a and the back side is the back crossing rib 56b), the strength of the first housing 270 can be further increased even in the second embodiment. .

[Example 4]
Next, Example 4 will be described.
FIG. 19 is a schematic configuration diagram of the first housing 370 according to the fourth embodiment, FIG. 20A is a cross-sectional view taken along line FF in FIG. 19, and FIG. 20B is a cross-sectional view along line G- in FIG. It is G sectional drawing.
In Example 4, in the right optical system, as shown in FIG. 20B, the width of the back side control rib 57b is made larger than the width of the front side control rib 57a, and in the left side optical system, As shown in FIG. 20A, the width of the front side control rib 57a is made larger than the width of the back side control rib.

  In the right optical system, the back side control rib 57b is wider than the front side control rib 57a to increase the volume, so that the back side has a larger amount of thermal expansion than the front side. As a result, in the right optical system, the first housing 270 warps in a concave shape. On the other hand, in the left optical system, the front side control rib 57a has a larger width and a larger volume than the back side control rib 57b. Therefore, in the left optical system, the first housing 270 has a convex shape. Warp. As described above, also in the configuration of the fourth embodiment, the warp of the first housing 370 can be made different on the left and right, so that the shift direction of the scanning position after thermal deformation can be made the same between the left and right optical systems. Color misregistration can be suppressed.

  When the height of the control rib is increased and the volume of the control rib is increased as in the third embodiment, if the control rib is too high, the front side control rib may block light, and the back side In the control rib, the control rib may interfere when attached to the second housing 60. On the other hand, when the width of the control rib is increased by increasing the width as in the fourth embodiment, the volume of the control rib is increased without blocking light or interfering with the second housing 60. Can do.

  In addition, as the resin used for the first casing, a resin to which a glass material is added is used to increase the rigidity, so that the fluidity of the resin when the first casing is molded is deteriorated. When the control rib having a high height is molded as in the third embodiment, the resin is difficult to flow into this portion, and the accuracy of the first housing cannot be sufficiently obtained. As in Example 3, by increasing the width of the control rib and increasing the volume of the control rib, the height of each rib of the first housing can be made uniform, and the resin fluidity at the time of molding the first housing can be increased. It is possible to improve the accuracy of the first housing.

[Example 5]
Next, Example 5 will be described.
FIG. 21 is a schematic configuration diagram of the first housing 470 according to the fifth embodiment, FIG. 22A is a cross-sectional view taken along the line H-H in FIG. 22, and FIG. It is I sectional drawing.
In the fifth embodiment, in the right optical system, the number of back side control ribs 57b is larger than the number of front side control ribs 57a, and in the left side optical system, the number of front side control ribs 57a is increased. This is larger than the number of back side control ribs.

  In the right optical system, by increasing the number of back side control ribs 57b as compared with the front side control ribs 57a, the volume of the back side becomes larger than that of the front side, and the amount of thermal expansion of the back side becomes the front side. More than. As a result, the right optical system warps in a concave shape. On the other hand, the left optical system has more front side control ribs 57a than back side control ribs 57b, so that the amount of thermal expansion of the front surface is greater than the thermal expansion of the back surface, and the convex shape is reversed. The As described above, also in the configuration of the fifth embodiment, the warp of the first housing 370 can be made different between the left and right, so that the shift direction of the scanning position after thermal deformation can be made the same by the left and right optical systems. Color misregistration can be suppressed.

  Also, the warpage of the first housing may be controlled by combining the configurations of Examples 2 to 5, for example, the height of the control rib on the long side is made higher than the height of the control rib on the short side, Widen the width or increase the number. As described above, by appropriately combining the configurations of the second to fifth embodiments, it is possible to finely control the amount of warpage of the first housing.

  In the present embodiment, the control rib is integrally formed with the first housing, but the control rib may be formed of a separate member. In this case, on the front surface, the control rib is sandwiched and fixed by the soundproof wall 54 as the first wall portion and the front side transverse rib 56a as the second wall portion. In the case of the back surface, the control rib is sandwiched and fixed by the side wall 58 as the first wall portion and the back side transverse rib 56b as the second wall portion. As a method for fixing the control rib, a known method such as fastening with a screw, bonding with an adhesive, and fitting and fixing can be used.

  As the control rib, a material having a material higher than the linear expansion coefficient of the first housing is used. For example, when it is desired to warp the left optical system in a convex shape, the control rib is fitted into the soundproof wall on the front surface and the front side transverse rib 56a. Since the control rib has a higher linear expansion coefficient than that of the first housing, the front-side transverse rib 56a is expanded at the time of thermal expansion. In this way, by expanding the front crossing rib, the amount of extension of the front side toward the scanning lens on the back side is larger than that on the back side, and can be warped convexly. On the other hand, when the right optical system is warped concavely, the right side can be warped concavely by fitting the back side wall 58 and the back side transverse rib 56b with the control rib. Further, the warpage may be controlled by changing the thermal expansion coefficients of the front side control rib 57a and the back side control rib 57b. That is, in the left optical system, the linear expansion coefficient of the front side control rib 57a is made larger than the linear expansion coefficient of the back side control rib 57b, and in the right optical system, the linear expansion coefficient of the back side control rib 57b is The coefficient of linear expansion of the front side control rib 57a is made larger. Thereby, the direction of curvature can be made different between the left optical system and the right optical system, and color misregistration can be suppressed. In addition to the shape of the control rib, the amount of warpage can be controlled with a higher system by selecting the control rib in consideration of the linear expansion coefficient. As a result, by grasping the timing at which the warpage of the first housing starts, the amount of warpage, the direction of warpage, etc., and determining the shape of the control rib and the linear expansion coefficient, the warpage of the first housing is offset and the warpage It is also possible not to generate itself.

  Further, by making the control rib a separate member, the first housing can be used for various optical scanning devices. That is, depending on the device, the rotation speed of the polygon scanner is different, and the amount of heat generated by the polygon scanner is also different. As a result, the amount of warpage of the first housing varies from device to device. Therefore, in a certain device, when the first housing is thermally deformed, the warpage of the left and right optical systems can be controlled by the control rib so that the scanning line shift amount is the same in the left and right optical systems. If this first housing is used in the apparatus, color misregistration may not be sufficiently suppressed. By using a separate member, the optimal material and shape of the control rib can be selected according to the amount of heat generated by the polygon scanner of the apparatus and attached to the first housing. The optimal amount of warping of the housing can be controlled.

  As described above, according to the first housing 70 as the optical housing of the present embodiment, at least the pair of scanning lenses and the polygon scanner 50 as the rotary deflector are attached. A control rib, which is a rib extending from the vicinity of the polygon scanner to the vicinity of the scanning lens, is provided on at least one of the front and back surfaces of the left and right optical systems, and a warping direction due to thermal expansion on one side with respect to the symmetry line. The warping direction due to thermal expansion on the other side was made different. Specifically, when the warp of the first housing is convex, a control rib is provided on one back surface of the left and right optical systems. Thereby, the side provided with the control rib warps in a concave shape, and the side not provided with the control rib warps in a convex shape. Thereby, the shift direction with respect to the ideal scanning position after thermal deformation of the first casing can be made the same on the left and right, and color shift after the first casing thermal deformation can be suppressed.

  Further, as shown in the first embodiment, the front side control rib 57a may be provided on the front surface of the right optical system, and the back side control rib 57b may be provided on the back surface of the left optical system. Even if comprised in this way, the 1st housing | casing one side will warp in convex shape, and the other side will warp in concave shape, and it can suppress a color shift.

  In addition, as shown in the second to fifth embodiments, control ribs are provided on the front and back surfaces of the left and right optical systems, and the control ribs on the front surface and the back control ribs of at least one of the left and right optical systems are provided. And the warp direction due to thermal expansion on one side with respect to the symmetry line may be different from the warp direction due to thermal expansion on the other side. Specifically, as in the second embodiment, warpage can be controlled by making the lengths of the control ribs different between the front surface and the back surface. If it is desired to warp in a concave shape, the control rib on the back side may be lengthened. If it is desired to warp in a convex shape, the control rib on the front side may be lengthened. For example, when the first casing warps in a concave shape, the length of the control rib on the one side is made longer than the length of the control rib on the back side. Thereby, the curvature of a 1st housing | casing can be varied by the one side and the other side.

  The length of the control rib on the front surface is shorter than the length of the control rib on the back surface on one side with respect to the symmetry line, and the control rib on the back surface is on the other side with respect to the symmetry line. By making the length shorter than the length of the rib on the front surface, one side can be warped in a concave shape and the other side can be warped in a convex shape. The warpage on one side is different from the warpage on the other side. Can be made.

  Further, as in the third embodiment, the warp can be controlled by making the height different between the control rib provided on the front surface and the control rib provided on the back surface. For example, if you want to warp in a convex shape, the height of the front side control rib should be higher than the height of the back side control rib. If you want to warp in a concave shape, set the height of the back side control rib. What is necessary is just to make it higher than the height of a side control rib. Therefore, the height of the front control rib on one side with respect to the symmetry line is set lower than the height of the back control rib, and the height of the back control rib is set on the other side with respect to the symmetry line. By making it lower than the height of the side control rib, one side can be warped in a concave shape, the other side can be warped in a concave shape, and the warpage on one side can be made different from the warp on the other side.

  Further, as in the fourth embodiment, the warpage can be controlled by making the width of the control rib different between the front surface and the back surface. For example, if you want to warp in a convex shape, the width of the front side control rib should be wider than the width of the back side control rib. If you want to warp in a concave shape, control the width of the back side control rib. What is necessary is just to make it wider than the width of a rib. Therefore, the width of the front side control rib is narrower than the width of the back side control rib on one side with respect to the symmetry line, and the width of the back side control rib is made smaller than the width of the front side control rib on the other side with respect to the symmetry line. Further, by narrowing, one side can be warped in a concave shape, the other side can be warped in a concave shape, and the warping on one side can be made different from the warping on the other side.

  Further, as in the fifth embodiment, warpage can be controlled by making the number of control ribs different between the front surface and the back surface. For example, if you want to warp in a convex shape, the number of front side control ribs should be larger than the number of back side control ribs. If you want to warp in a concave shape, control the number of back side control ribs on the front side. What is necessary is just to increase more than the number of ribs. Therefore, on one side of the symmetry line, the number of front side control ribs is less than the number of back side control ribs, and on the other side of the symmetry line, the number of back side control ribs is greater than the number of front side control ribs. By reducing the number, the one side can be warped in a concave shape, the other side can be warped in a concave shape, and the warpage on one side can be made different from the warp on the other side.

  Further, by configuring the control rib as a member separate from the first casing, the control rib suitable for the characteristics of the optical scanning device to which the first casing is attached can be attached to the first casing. The body can be used for a wide variety of models.

  Further, the warpage can be controlled by making the linear expansion coefficient of the control rib different between the front side control rib and the back side control rib. For example, if you want to warp in a convex shape, the linear expansion coefficient of the front side control rib should be higher than the linear expansion coefficient of the back side control rib. If you want to warp in a concave shape, the linear expansion coefficient of the back side control rib May be made higher than the linear expansion coefficient of the front control rib. Therefore, on one side of the symmetry line, the width linear expansion coefficient of the front side control rib is made lower than the linear expansion coefficient of the back side control rib, and on the other side of the symmetry line, the linear expansion coefficient of the back side control rib. By making the lower than the linear expansion coefficient of the front side control rib, one side can be warped in a concave shape, the other side can be warped in a concave shape, and the warpage on one side can be made different from the warpage on the other side. Can do.

  The first housing is attached to a second housing that houses optical elements subsequent to the scanning lens. Thereby, it becomes possible to attach a common 1st housing | casing with respect to the 2nd housing | casing from which the attachment angle and attachment position of a reflective mirror differ according to the layout of an image forming apparatus. Thereby, management of the polygon scanner and the scanning lens can be performed in common among the plurality of optical scanning devices.

  In addition, since the writing unit 4 that is the optical scanning device of the present embodiment includes the first housing, it is possible to suppress the deviation of the scanning lines. Further, by using a writing unit equipped with the first housing as the image forming apparatus, it is possible to obtain a good image in which color misregistration is suppressed.

4: Optical writing unit 10: Photoconductor (irradiated object)
41a, 41b: Polygon mirrors 42a, 42b: Soundproof glass 43: Scanning lens 44: First reflection mirror 45: Second reflection mirror 46: Laser diode 50: Polygon scanner 54: Soundproof wall 56a: Front side transverse rib 56b: Back side transverse rib 57a: Front side control rib 57b: Back side control rib 58: Side wall 60: Second housing 70, 170, 270, 370, 470: First housing 70a, 170a: Front surface 70b, 170b : Back side

JP 2009-198888 A

Claims (13)

Multiple light sources;
A rotating deflector that deflects and scans light emitted from a plurality of light sources in the main scanning direction;
Arranged in the vicinity of the rotary deflector, passing through the rotational center of the rotary deflector, and symmetrically arranged with respect to a symmetry line drawn in a direction perpendicular to the axial direction of the rotational axis of the rotary deflector, at least in the sub-scanning direction A pair of scanning lenses with power,
The light emitted from at least one of the plurality of light sources is incident on the scanning lens on one side by the rotary deflector, is reflected by one or more reflecting mirrors, is irradiated on the irradiated object, and is emitted from the remaining light sources. The incident light is incident on the other scanning lens by the rotary deflector, is reflected by the same number of reflecting mirrors as the one side, and is used in an opposed scanning optical scanning device that irradiates the irradiated object. In the optical housing to which the pair of scanning lenses and the rotary deflector are attached,
A rib that extends from the vicinity of the rotating deflector to the vicinity of the scanning lens is provided on the mounting surface to which the scanning lens and the rotating deflector are mounted on at least one side with respect to the symmetry line, or on the back surface that is the surface opposite to the mounting surface. The warp direction due to thermal expansion on one side and the warp direction due to thermal expansion on the other side are different from each other with respect to the symmetry line. The optical housing of claim 1.
A rib is provided on the mounting surface on one side with respect to the symmetry line,
An optical housing comprising a rib on the back surface on the other side with respect to the symmetry line. Multiple light sources;
A rotating deflector that deflects and scans light emitted from a plurality of light sources in the main scanning direction;
Arranged in the vicinity of the rotary deflector, passing through the rotational center of the rotary deflector, and symmetrically arranged with respect to a symmetry line drawn in a direction perpendicular to the axial direction of the rotational axis of the rotary deflector, at least in the sub-scanning direction A pair of scanning lenses with power,
The light emitted from at least one of the plurality of light sources is incident on the scanning lens on one side by the rotary deflector, is reflected by one or more reflecting mirrors, is irradiated on the irradiated object, and is emitted from the remaining light sources. The incident light is incident on the other scanning lens by the rotary deflector, is reflected by the same number of reflecting mirrors as the one side, and is used in an opposed scanning optical scanning device that irradiates the irradiated object. In the optical housing to which the pair of scanning lenses and the rotary deflector are attached,
A rib that extends from the vicinity of the rotating deflector to the vicinity of the scanning lens is provided on the mounting surface to which the scanning lens and the rotating deflector are attached and the back surface that is the surface opposite to the attaching surface.
With respect to the symmetry line, the rib provided on at least one side of the mounting surface and the rib provided on the back surface are asymmetric, and the warping direction due to thermal expansion on one side and the warping direction due to thermal expansion on the other side with respect to the symmetry line. An optical housing characterized by different from the above. The optical housing of claim 3.
On one side with respect to the symmetry line, the width of the rib provided on the attachment surface is made narrower than the width of the rib provided on the back surface,
An optical housing characterized in that, on the other side of the symmetry line, the width of the rib provided on the back surface is narrower than the width of the rib provided on the mounting surface. The optical housing of claim 3 or 4,
On one side with respect to the symmetry line, the number of ribs provided on the attachment surface is less than the number of ribs provided on the back surface,
An optical housing characterized in that, on the other side with respect to the symmetry line, the number of ribs provided on the back surface is smaller than the number of ribs provided on the mounting surface. The optical housing according to any one of claims 3 to 5,
On one side with respect to the symmetry line, the length of the rib provided on the attachment surface is shorter than the length of the rib provided on the back surface,
An optical housing characterized in that, on the other side with respect to the symmetry line, the length of the rib provided on the back surface is shorter than the length of the rib provided on the mounting surface. The optical housing according to any one of claims 3 to 6,
The height of the rib provided on the mounting surface on one side with respect to the symmetry line is lower than the height of the rib provided on the back surface,
An optical housing characterized in that, on the other side with respect to the symmetry line, the height of the rib provided on the back surface is lower than the height of the rib provided on the mounting surface. The optical housing according to any one of claims 1 to 7,
The optical housing, wherein the rib, the mounting surface, and the back surface are integrally formed. The optical housing according to any one of claims 1 to 7,
First wall portions provided near the rotary deflector on the attachment surface and the back surface, respectively, and extending so as to cross the light scanned by the rotary deflector are disposed on one side and the other side of the symmetry line,
Second wall portions that are respectively provided in the vicinity of the scanning lens on the attachment surface and the back surface and extend across the light scanned by the rotary deflector are disposed on one side and the other side of the symmetry line,
An optical housing, wherein the rib is formed of a member different from the optical housing, and is sandwiched between the first wall portion and the second wall portion. The optical housing of claim 9,
An optical housing characterized in that a linear expansion coefficient of the rib is set larger than a linear expansion coefficient of a surface to which the rib is attached. The optical housing according to any one of claims 1 to 10,
The optical housing, wherein the optical housing is attached to a housing for storing optical system components disposed on an optical path of light after the scanning lens. Multiple light sources;
A rotating deflector that deflects and scans light emitted from a plurality of light sources in the main scanning direction;
Arranged in the vicinity of the rotary deflector, passing through the rotational center of the rotary deflector, and symmetrically arranged with respect to a symmetry line drawn in a direction perpendicular to the axial direction of the rotational axis of the rotary deflector, at least in the sub-scanning direction A pair of scanning lenses with power,
The light emitted from at least one of the plurality of light sources is incident on one scanning lens by the rotary deflector, and the light emitted from the remaining light sources is opposed to the other scanning lens by the rotary deflector. In a scanning optical scanning device,
An optical scanning device using the optical housing according to claim 1 as an optical housing to which at least the pair of scanning lenses and the rotary deflector are attached. A plurality of latent image carriers;
Optical writing means for writing a latent image on each latent image carrier;
A plurality of developing means for individually developing the latent image formed on each latent image carrier, and a transfer means for transferring the visible image obtained on each latent image carrier by development onto the transfer body, respectively. In an image forming apparatus comprising:
An image forming apparatus using the optical scanning device according to claim 12 as the optical writing means.

Images