JP2014178341A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: an image cannot be formed accurately in a desired position on photoreceptor drums 102Y-102Bk due to vibration transmitted to an optical scanner 200 which is mounted between image forming units 101Y-101Bk and a housing unit 109 housing a recording material in a vertical direction.SOLUTION: An image forming apparatus 100 includes: a paper-feed roller 120 and a conveyance roller 121 for conveying a recording material from a housing unit 109 toward a paper discharge unit 110; image forming units 101Y-101Bk arranged between the housing unit 109 and the paper discharge unit 110; and an optical scanner 200 which is arranged between the image forming units 101Y-101Bk and the housing unit 109 and includes an optical box 201 containing light source units 202Y-202Bk, a polygon mirror 203, and a first wall 61 located between the polygon mirror 203 and a conveyance path and having more reinforcing ribs 50 than a second wall 62 located opposite the first wall 61.

Description

  The present invention relates to an image forming apparatus including an optical scanning device that exposes a photoconductor to form an image on the photoconductor.

  An image forming apparatus using an electrophotographic method forms a latent image on a photosensitive member by exposing the photosensitive member with a light beam emitted from an optical scanning device, and develops the latent image with toner. It is visualized as a toner image. The toner image formed on the photosensitive member is transferred to a recording material, fixed on the recording material by heat and pressure of a fixing device, and output as an output product.

  In order to reduce the size of the main body of the image forming apparatus, the image forming apparatus has a configuration in which an optical scanning device is disposed below the photoconductor and the photoconductor is exposed from below (hereinafter referred to as a bottom exposure configuration). is there. In the image forming apparatus having the bottom exposure configuration, while the recording material is conveyed along the conveyance path from the accommodating portion in which the recording material is accommodated to the paper discharge portion disposed above the accommodating portion in the vertical direction, An image is formed on a recording material (Patent Document 1).

  The optical scanning device includes a light source, a rotating polygon mirror that is rotationally driven to polarize the light beam emitted from the light source, and a lens or mirror that guides the light beam deflected by the rotating polygon mirror to the photosensitive member. It becomes the composition accommodated in. Accordingly, the relative positional relationship between the mirror and the lens is fixed in the optical scanning device, so that a latent image can be formed at a desired position on the photosensitive member.

JP-A-2005-004050

  However, since the optical scanning device is disposed in the vicinity of the transport path, there has been a problem that vibration generated by the rotational drive of the transport roller provided in the transport path propagates to the optical box. In particular, when the rotation speed of the conveyance roller and the rotation speed of the rotary polygon mirror are increased in order to increase the printing speed of the image forming apparatus, the vibration propagates to the wall located between the rotary polygon mirror and the conveyance path. May also increase, and the relative positional relationship of optical components such as mirrors and lenses may dynamically change. As a result, the laser beam applied to the photosensitive member to form the electrostatic latent image vibrates, and a striped image defect called banding occurs.

  An object of the present invention is to provide an image forming apparatus capable of suppressing image defects caused by vibration of an optical scanning device.

  In order to solve the above-described problem, the image forming apparatus according to claim 1 performs recording along a conveyance path from a storage unit that stores a recording material to a paper discharge unit that is disposed above the storage unit in the vertical direction. A conveying unit configured to convey a material; and an image forming unit disposed between the storage unit and the paper discharge unit in a vertical direction, wherein a plurality of photoconductors are arranged at different positions in a horizontal direction, Image forming means for developing an electrostatic latent image formed on the photosensitive member with toner, and transferring the toner images on the plurality of photosensitive members to the recording material conveyed by the conveying means; and the image in the vertical direction. An optical scanning device disposed between a forming unit and the housing unit, the light source emitting a plurality of light beams for forming the electrostatic latent image on the plurality of photosensitive members; The light beam is the plurality of photoconductors. A rotary polygon mirror that is rotationally driven to deflect the plurality of light beams so as to scan the optical beam, and an optical box to which the rotary polygon mirror is attached, and the rotary polygon mirror and the A second wall constituting the optical box, located on the opposite side to the first wall with respect to the rotary polygon mirror, located on the first wall constituting the optical box It is characterized in that a larger number of reinforcing ribs than the wall are provided.

  According to the present invention, it is possible to suppress image defects caused by the vibration of the optical scanning device.

Schematic sectional view of the image forming apparatus The perspective view which shows the structure of an optical scanning device, and sectional drawing of an optical scanning device Schematic showing how the optical scanning device is inserted into the image forming apparatus The figure which shows the analysis result of the vibration which arises in the optical scanning device which does not provide the reinforcing rib Schematic diagram of reinforcing ribs provided in optical scanning device The figure which shows the result of having measured the vibration acceleration transmitted to an optical scanning device

(Configuration of image forming apparatus)
FIG. 1 is a schematic cross-sectional view of an electrophotographic image forming apparatus 100. An image forming apparatus 100 illustrated in FIG. 1 includes four image forming units 101Y, 101M, 101C, and 101Bk that form toner images of yellow, magenta, cyan, and black. The image forming units 101Y, 101M, 101C, and 101Bk respectively include photosensitive drums 102Y, 102M, 102C, and 102Bk that are photosensitive members. These photosensitive drums 102Y, 102M, 102C, and 102Bk are arranged at different positions in the horizontal direction. Each image forming unit includes charging devices 103Y, 103M, 103C, and 103Bk that charge the photosensitive drums 102Y, 102M, 102C, and 102Bk, and developing devices 104Y, 104M, and 104C that develop the electrostatic latent image on the photosensitive drum with toner. , 104Bk. Further, each image forming unit includes cleaning devices 111Y, 111M, 111C, and 111Bk that remove residual toner on the photosensitive drum from the photosensitive drum.

  The image forming apparatus 100 includes an optical scanning device 200, transfer rollers 105Y, 105M, 105C, and 105Bk, an intermediate transfer belt 106, a cleaning device 112, a storage unit 109 that stores a recording material, a paper discharge unit 110, a transfer roller 107, a fixing unit. A device 108 is provided. The optical scanning device 200 is disposed between the image forming units 101Y, 101M, 101C, and 101Bk in the vertical direction and the storage unit 109 that stores the recording material.

  Next, the image forming process will be described. The optical scanning device 200 emits light beams (laser beams) LY, LM, LC, and LBk that expose the photosensitive drums 102Y, 102M, 102C, and 102Bk charged by the charging devices 103Y, 103M, 103C, and 103Bk, respectively. Exposure to light beams forms electrostatic latent images on the photosensitive drums 102Y, 102M, 102C, and 102Bk.

  The developing device 104Y develops the electrostatic latent image formed on the photosensitive drum 102Y with yellow toner. The developing device 104M develops the electrostatic latent image formed on the photosensitive drum 102M with magenta toner. The developing device 104C develops the electrostatic latent image formed on the photosensitive drum 102C with cyan toner. The developing device 104Bk develops the electrostatic latent image formed on the photosensitive drum 102Bk with black toner.

  The yellow toner image formed on the photosensitive drum 102Y is transferred to the intermediate transfer belt 106, which is an intermediate transfer body, by the transfer roller 105Y in the transfer portion Ty. The cleaning device 111Y collects toner remaining on the photosensitive drum 102Y without being transferred to the intermediate transfer belt 106, between the transfer portion Ty in the rotation direction of the photosensitive drum 102Y and the charging portion of the charging device 103Y.

  The magenta toner image formed on the photosensitive drum 102M is transferred to the intermediate transfer belt 106 by the transfer roller 105M at the transfer portion Tm. The cleaning device 111M collects the toner remaining on the photosensitive drum 102M without being transferred to the intermediate transfer belt 106 between the transfer portion Tm in the rotation direction of the photosensitive drum 102M and the charging portion of the charging device 103M.

  The cyan toner image formed on the photosensitive drum 102C is transferred to the intermediate transfer belt 106 by the transfer roller 105C at the transfer portion Tc. The cleaning device 111C collects the toner remaining on the photosensitive drum 102C without being transferred to the intermediate transfer belt 106 between the transfer portion Tc in the rotation direction of the photosensitive drum 102C and the charging portion of the charging device 103C.

  The black toner image formed on the photosensitive drum 102Bk is transferred to the intermediate transfer belt 106 by the transfer roller 105Bk at the transfer portion TBk. The cleaning device 111Bk collects the toner remaining on the photosensitive drum 102Bk without being transferred to the intermediate transfer belt 106 between the transfer portion TBk in the rotation direction of the photosensitive drum 102Bk and the charging portion of the charging device 103Bk.

  The cleaning devices 111Y, 111M, 111C, and 111Bk of this embodiment include a blade that contacts the photosensitive drum, and collects the residual toner by scraping the toner remaining on the photosensitive drum by the blade.

  The image forming units 101 </ b> Y, 101 </ b> M, 101 </ b> C, and 101 </ b> Bk sequentially transfer the toner images corresponding to the respective color components onto the intermediate transfer belt 106 so that a full-color toner image is formed on the intermediate transfer belt 106.

  The toner image transferred onto the intermediate transfer belt 106 is conveyed to the transfer portion T2 as the intermediate transfer belt 106 rotates in the arrow direction. At this time, the recording material in the storage unit 109 is fed one by one by the sheet feeding roller 120 and conveyed to the transfer unit T2 by the conveying roller 121. The recording material conveyed by the paper feeding roller 120 is supplied to the transfer unit T <b> 2 so as to be in contact with the toner image on the intermediate transfer belt 106 after adjusting the paper position and feeding timing by the conveying roller 121. That is, the paper feed roller 120 and the transport roller 121 function as a transport unit that transports the recording material from the storage unit 109 toward the paper discharge unit 110. Further, a path through which the recording material is transported from the storage unit 109 to the paper discharge unit 110 corresponds to a transport path.

  When the toner image transferred onto the intermediate transfer belt 106 and the recording material fed from the conveying roller 121 enter the transfer portion T2, a transfer voltage is applied to the transfer roller 107, and the toner image on the intermediate transfer belt 106 is recorded. It is transferred to the material. The recording material onto which the toner image has been transferred in the transfer portion T2 is conveyed to the fixing device 108. The fixing device 108 fixes the toner image on the recording material by heating the recording material while conveying the recording material. Thereafter, the recording material P on which the toner image is fixed is discharged to the paper discharge unit 110.

  That is, the image forming units 101Y, 101M, 101C, and 101Bk, the intermediate transfer belt 106, and the transfer roller 107 function as image forming units that are disposed between the storage unit 109 and the paper discharge unit 110 in the vertical direction.

  The image forming apparatus 100 includes a cleaning device 112 between the transfer unit T2 and the transfer unit Ty in the rotation direction of the intermediate transfer belt 106. The cleaning device 112 includes a blade that comes into contact with the intermediate transfer belt 106, and scrapes residual toner on the intermediate transfer belt 106 with the blade, thereby removing toner remaining on the intermediate transfer belt 106 without being transferred to the recording medium. to clean up.

(Configuration of optical scanning device)
Next, the optical scanning device 200 will be described. FIG. 2A is a perspective view showing the configuration of the optical scanning device 200, and FIG. 2B is a cross-sectional view of the optical scanning device 200.

  As shown in FIG. 2A, the optical scanning device 200 includes an optical component in an optical box 201 configured by a first wall 61, a second wall 62, a third wall 63, and a fourth wall 64. Contained. In the optical box 201, the longitudinal direction of the first wall 61 and the longitudinal direction of the second wall 62 are parallel, and the longitudinal direction of the first wall 61 and the longitudinal direction of the second wall 62 are respectively The third wall 63 and the fourth wall 64 are orthogonal to the longitudinal direction. Light source units 202Y, 202M, 202C, and 202Bk are attached to the third wall 63 of the optical box 201. The light source unit 202Y emits laser light LY that exposes the photosensitive drum 102Y, and the light source unit 202M emits laser light LM that exposes the photosensitive drum 102M. The light source unit 202C emits laser light that exposes the photosensitive drum 102C, and the light source unit 202Bk emits laser light LBk that exposes the photosensitive drum 102Bk. The light source units 202Y, 202M, 202C, 202Bk are arranged close to each other.

  As shown in FIG. 2A, a polygon mirror (rotating polygonal mirror) 203 having four reflecting surfaces is installed at the center of the optical box 201. At the time of image formation, the polygon mirror 203 rotates the rotation axis indicated by the dotted line in FIG. 2A in the R1 direction.

  Here, a plane in which the rotation axis of the polygon mirror 203 is a perpendicular is defined as a virtual plane. The laser beam LY emitted from the light source unit 202Y and the laser beam LBk emitted from the light source unit 202Bk are incident on the reflection surface of the polygon mirror 203 through an optical path obliquely incident on the virtual plane from the upper side in the vertical direction. On the other hand, the laser light LC emitted from the light source unit 202C and the laser light LM emitted from the light source unit 202M take an optical path obliquely incident from the lower side in the vertical direction with respect to the virtual plane, and the reflecting surface of the polygon mirror 203 Is incident on.

  The laser beam LY emitted from the light source unit 202Y enters the reflection surface of the polygon mirror 203. The laser beam LY is deflected (reflected) to the A side shown in FIG. The laser beam LM emitted from the light source unit 202M is incident on the same reflecting surface as the reflecting surface of the polygon mirror 203 on which the laser beam LY is incident. The laser beam LM is deflected to the same side (A side) as the laser beam LY by the reflection surface of the polygon mirror 203. Here, the A side corresponds to the first direction.

  On the other hand, the laser beam LBk emitted from the light source unit 202Bk is incident on a reflection surface different from the reflection surface on which the laser beams LY and LM are incident. The laser beam LBk is deflected by the reflection surface of the polygon mirror 203 toward the B side shown in FIG. The laser beam LC emitted from the light source unit 202C is incident on the same reflecting surface as the reflecting surface of the polygon mirror 203 on which the laser beam LBk is incident. The laser beam LC is deflected to the same side (B side) as the laser beam LBk by the reflection surface of the polygon mirror 203. Here, the B side corresponds to the second direction.

  The laser beams LY and LM deflected by the polygon mirror 203 become laser beams that move in the + X direction. That is, by being deflected by the rotating polygon mirror 203, the laser beam LY becomes a laser beam that scans the photosensitive drum 102Y in the + X direction, and the laser beam LM becomes a laser beam that scans the photosensitive drum 102M in the + X direction.

  On the other hand, the laser beams LBk and LC deflected by the polygon mirror 203 become laser beams that move in the −X direction. That is, by being deflected by the rotating polygon mirror 203, the laser beam LBk becomes a laser beam that scans the photosensitive drum 102Bk in the −X direction, and the laser beam LC becomes a laser beam that scans the photosensitive drum 102C in the −X direction. .

  That is, the optical scanning device 200 polarizes the laser light emitted from the light source units 202Y, 202M, 202C, and 202Bk by the polygon mirror 203 to the A side and the B side, respectively, to thereby change the photosensitive drums 102Y, 102M, 102C, and 102Bk. This is a counter scanning type optical scanning device for exposure.

  Next, the optical paths of the laser beams LY, LM, LC, and LBk deflected by the polygon mirror 203 will be described with reference to FIG. As shown in FIG. 2B, the optical box 201 includes a polygon mirror 203, lenses 206, 207, 208, 209, 210, 211, reflection mirrors 212, 213, 214, 215, 216, 217, and the like. Optical components are attached. The optical box 201 is further provided with a cover 218 for dust-proofing the polygon mirror 203, each lens, and each reflection mirror.

  The laser beam LY deflected by the polygon mirror 203 is incident on the reflection mirror 212 after passing through the lenses 206 and 207. The reflection mirror 212 reflects the incident laser beam LY toward the photosensitive drum 102Y. The cover 218 has an opening 219 through which the laser light LY reflected by the reflection mirror 212 passes. The opening 219 is closed by a transparent dustproof window 223 that allows the laser light LY to pass therethrough. The laser beam LY that has passed through the dustproof window 223 forms an image on the photosensitive drum 102Y.

  The laser beam LM deflected by the polygon mirror 203 passes through the lens 206 and then enters the reflection mirror 213. The reflection mirror 213 reflects the incident laser light LM toward the lens 208. The laser beam LM reflected by the reflection mirror 213 passes through the lens 208 and enters the reflection mirror 214. The reflection mirror 214 reflects the incident laser light LM toward the photosensitive drum 102M. The cover 218 has an opening 220 through which the laser light LM reflected by the reflection mirror 214 passes. The opening 220 is closed by a transparent dustproof window 224 that allows the laser light LM to pass therethrough. The laser beam LM that has passed through the dustproof window 224 forms an image on the photosensitive drum 102M.

  The laser beam LBk deflected by the polygon mirror 203 passes through the lenses 209 and 210 and then enters the reflection mirror 215. The reflection mirror 215 reflects the incident laser beam LBk toward the photosensitive drum 102Bk. The cover 218 has an opening 222 through which the laser beam LBk reflected by the reflection mirror 215 passes. The opening 222 is closed by a transparent dustproof window 226 that allows the laser beam LBk to pass therethrough. The laser beam LBk that has passed through the dustproof window 226 forms an image on the photosensitive drum 102Bk.

  The laser beam LC deflected by the polygon mirror 203 passes through the lens 209 and then enters the reflection mirror 216. The reflection mirror 216 reflects the incident laser light LC toward the lens 211. The laser beam LC reflected by the reflection mirror 216 passes through the lens 211 and enters the reflection mirror 217. The reflection mirror 217 reflects the incident laser beam LC toward the photosensitive drum 102C. The cover 218 has an opening 221 through which the laser light LC reflected by the reflection mirror 217 passes. The opening 221 is closed by a transparent dustproof window 225 that allows the laser light LC to pass therethrough. The laser beam LC that has passed through the dustproof window 225 forms an image on the photosensitive drum 102C.

(Installation of optical scanning device)
Next, a method for mounting the optical scanning device 200 on the image forming apparatus 100 will be described with reference to FIG. In the image forming apparatus 100, an insertion port is provided on the side surface of the image forming apparatus main body opposite to the side on which the conveyance path is provided with respect to the image forming units 101Y, 101M, 101C, and 101Bk. When the image forming apparatus 100 is assembled or the optical scanning apparatus 200 is replaced, the optical scanning apparatus 200 is inserted into the mounting area of the image forming apparatus main body from the insertion opening.

  When the optical scanning device 200 is attached to the image forming apparatus 100, the optical scanning device 200 is inserted into the insertion port of the image forming apparatus main body 100 in an inclined state as shown in FIG. Here, the bottom of the optical box 201 is obliquely cut out so that the height in the vertical direction of the optical box 201 decreases from the predetermined position of the bottom of the optical box 201 toward the back in the insertion direction. . Thereby, even when the optical box 201 is inserted obliquely when the image forming apparatus 100 is assembled or the optical scanning apparatus 200 is replaced, the possibility that the optical box 201 collides with the insertion opening can be suppressed. This improves operability when the optical scanning device 200 is inserted into the insertion slot.

  Further, in the optical scanning device 200, the bottom of the optical box 201 on the back side in the insertion direction is cut obliquely, so that the height of the first wall 61 positioned between the polygon mirror 203 and the conveyance path is high. The height of the second wall 62 located on the opposite side of the polygon mirror 203 from the first wall 61 is lower. Here, the height of the first wall 61 is, for example, 23 [mm], and the height of the second wall 62 is, for example, 40 [mm]. That is, the rigidity of the first wall 61 is lower than the rigidity of the second wall 62. Therefore, the first wall 61 is more susceptible to vibrations caused by rotation of the polygon mirror 203 and driving of the paper feed roller 120 and the transport roller 121 than the second wall 62.

  After the optical box 201 is inserted into the insertion slot in a tilted state, the optical box 201 has a height in the vertical direction of the mounting area from the positioning boss 601a to the second wall 62 as shown in FIG. Since it is higher than the height dimension up to, it is inserted in the insertion direction while being inclined at an angle α [°]. This is because the positioning boss 601a gets over the frame portion 602a located on the front side of the positioning hole 601b in the insertion direction.

  As shown in FIG. 3C, the optical scanning device 200 is disposed at a predetermined position of the image forming apparatus 100 by fitting the positioning boss 601 a into the positioning hole 601 b provided in the frame 602. That is, the positioning boss 601a corresponds to a positioning member for positioning the optical box 201 of the optical scanning device 200 at a predetermined position of the image forming apparatus 100, and the positioning hole 601b corresponds to a regulating member that engages with the positioning boss 601a. To do. The positioning boss 601a and the positioning hole 601b are provided on the near side in the insertion direction so that they can be seen when the optical scanning device 200 is assembled.

  After the optical scanning device 200 is inserted into the mounting area of the image forming apparatus main body, a cover that closes the insertion port is screwed to the image forming apparatus main body.

(Results of vibration analysis of optical scanning device)
FIG. 4 shows a vibration analysis result when the rotational speed of the polygon mirror is increased in the conventional optical scanning device. In FIG. 4, the portion with a low density indicates that the vibration is larger than the portion with a high density. FIG. 4 shows a state in which the optical scanning device 200 is mounted on the mounting region of the image forming apparatus main body 100. The optical box 201 is supported by the frame 602. The protrusion provided on the first wall 61 of the optical box 201 is inserted into the positioning hole 603 of the image forming apparatus main body 100, whereby the position of the optical scanning device 200 in the insertion direction is determined.

  The vibration generated in the first wall 61 of the optical box 201 is different from the vibration generated in the second wall 62. This is because the height of the first wall 61 is lower than the height of the second wall 62 by notching the bottom part on the back side in the insertion direction of the optical scanning device 200. That is, the rigidity of the first wall is lower than the rigidity of the second wall. Further, the first wall 61 is positioned between the polygon mirror 203 and the paper feed roller 120 and the transport roller 121 in a state where the optical scanning device 200 is mounted on the image forming apparatus main body. Closer to the vibration source than the wall. Therefore, the vibration generated in the first wall by driving the polygon mirror 203, the paper feed roller 120, and the transport roller 121 dynamically changes the relative positional relationship of the optical components housed in the optical box 201. .

  Therefore, in this embodiment, as shown in FIG. 5, reinforcing ribs 51 a, 51 b, 51 c, 51 d, 51 e, 51 f, 51 g, 51 h, 51 i, 51 j are provided on the first wall 61. The reinforcing ribs 51 a, 51 b, 51 c, 51 d, 51 e, 51 f, 51 g, 51 h, 51 i, 51 j are connected to the bottom surface of the optical box 201. The height from the bottom surface of the reinforcing ribs 51a, 51b, 51c, 51d, 51e, 51f, 51g, 51h, 51i, 51j is, for example, 15.5 [mm]. The surface directions of the reinforcing ribs 51 a, 51 b, 51 c, 51 d, 51 e, 51 f, 51 g, 51 h, 51 i, 51 j are the direction perpendicular to the bottom surface of the optical box 201 and the direction perpendicular to the first wall 61. Yes. The reinforcing ribs 51 a, 51 b, 51 c, 51 d, 51 e, 51 f, 51 g, 51 h, 51 i, 51 j suppress the vibration generated in the first wall 61 of the optical box 201, and the relative optical components accommodated in the optical box 201 This contributes to the suppression of dynamic fluctuations in the positional relationship.

  Here, the thickness of the reinforcing ribs 51 a, 51 b, 51 c, 51 d, 51 e, 51 f, 51 g, 51 h, 51 i, 51 j is set to be equal to or less than the thickness of the first wall 61 of the optical box 201. Further, the thickness of the optical box 201 is set to a dimension that does not cause the optical box 201 to shrink in the process in which the temperature of the injection-molded optical box 201 reaches room temperature. If the optical box 201 is contracted, an error occurs in the dimensions of the optical box 201, and the optical scanning device 200 forms an electrostatic latent image at a desired position on the photosensitive drums 102Y, 102M, 102C, and 102Bk. It is not possible. For example, the thickness of the reinforcing ribs 51a, 51b, 51c, 51d, 51e, 51f, 51g, 51h, 51i, 51j is 2.0 [mm], and the thickness of the optical box 201 is 2.5 [mm]. That's fine. Note that the thickness of the reinforcing rib and the thickness of the optical box are not limited to these values, and may be determined to values that do not cause the shrinkage obtained in advance through experiments or the like.

  Here, as shown in FIG. 4, in the first wall 61, the central portion of the first wall 61 in the longitudinal direction (X direction) is an antinode of vibration. Therefore, as shown in FIG. 5, the optical box 201 has a connection portion where the third wall 63 and the first wall 61 are connected in order to suppress the vibration of the center portion of the first wall 61. Reinforcing ribs 51a, 51b, 51c, 51h, 51i, and 51j are provided in the vicinity and in the vicinity of the connection portion where the fourth wall 64 and the first wall 61 are connected. Note that the third wall 63 and the fourth wall 64 are walls that are symmetrical with respect to the polygon mirror 203.

  The reinforcing rib will be described with reference to FIG. In the following description, the first wall 61 is divided into three equal parts in the longitudinal direction, and the respective areas are referred to as a first area, a second area, and a third area. The first region is a region in the first wall 61 from the corner of the first wall 61 and the third wall 63 to a length of one third in the longitudinal direction of the first wall 61. That is, the first region is a region at the end portion on the third wall 63 side in the longitudinal direction of the first wall 61. The third region is a region in the first wall 61 from the corner of the first wall 61 and the fourth wall 64 to a length of one third in the longitudinal direction of the first wall 61. That is, the third region is a region at an end portion on the fourth wall 64 side in the longitudinal direction of the first wall 61. The second region is a region sandwiched between the first region and the third region on the first wall 61.

  The number of reinforcing ribs 51a, 51b, 51c, 51d, 51e in the first region is larger than the number of reinforcing ribs 51f in the second region. Further, the number of the reinforcing ribs 51g, 51h, 51i, 51j in the third region is larger than the number of the reinforcing ribs 51f in the second region. This is because the first wall 61 is provided with the reinforcing ribs in the first region and the third region corresponding to the vibration nodes, rather than the reinforcing ribs provided in the second region corresponding to the vibration antinode. It is because the effect which suppresses the vibration which arises in is large. That is, by increasing the number of reinforcing ribs provided in the first region and the third region than the number of reinforcing ribs provided in the second region, the total number of reinforcing ribs provided on the first wall 61 is reduced. Vibration generated in the first wall 61 can be suppressed. If the total number of reinforcing ribs provided on the first wall 61 is reduced, the optical box 201 can be easily molded by injection molding.

  Further, the optical scanning device 200 has a double wall structure in which the first inner wall 71 is provided inside the first wall 61 of the optical box 201 in order to increase the strength of the optical box 201. The reinforcing ribs 51a, 51b, 51c, 51d, 51e, 51f, 51g, 51h, 51i, 51j are provided so as to connect the first wall 61 and the first inner wall 71 of the optical box 201.

  In addition, in the optical box 201 of the present embodiment, reinforcing ribs 52a, 52b, 52c, 52d, and 52e are also provided on the second wall 62 in order to suppress vibration transmitted to the second wall 62. . The reinforcing ribs 52 a, 52 b, 52 c, 52 d, 52 e provided on the second wall 62 are connected to the bottom surface of the optical box 201. Further, a second inner wall 72 is also provided inside the second wall 62, and the reinforcing ribs 52 a, 52 b, 52 c, 52 d, 52 e are connected to the second wall 62 and the second inner wall 72 of the optical box 201. Are connected.

  Here, the number of reinforcing ribs 51 a, 51 b, 51 c, 51 d, 51 e, 51 f, 51 g, 51 h, 51 i, 51 j provided on the first wall 61 is the number of reinforcing ribs 52 a, 52 b, 52 c provided on the second wall 62. , 52d, 52e. This is because the first wall 61 is located between the polygon mirror 203 and the conveyance path provided with the paper feed roller 120 and the conveyance roller 121. That is, the second wall 62 is hardly affected by the vibration generated by driving the paper feed roller 120 and the transport roller 121. Therefore, even if the number of reinforcing ribs provided on the second wall 62 is smaller than the number of reinforcing ribs provided on the first wall 61, vibration transmitted to the second wall 62 can be sufficiently suppressed. . Furthermore, by reducing the number of reinforcing ribs of the second wall 62, the optical box 201 can be easily molded by injection molding.

  FIG. 6 shows the result of measuring the magnitude of vibration transmitted to the longitudinal central portion of the first wall when vibration was applied to each of the optical box provided with the reinforcing rib and the optical box not provided with the reinforcing rib. It is. The horizontal axis indicates the vibration frequency, and the vertical axis indicates the vibration acceleration. The greater the vibration acceleration (vertical axis), the greater the vibration. The broken line is the measurement result of the optical box provided with the reinforcing ribs 51a, 51b, 51c, 51d, 51e, 51f, 51g, 51h, 51i, 51j, 52a, 52b, 52c, 52d, 52e, and the solid line is the reinforcing rib. It is a measurement result of the optical box which is not provided.

  As shown in FIG. 6, when comparing the vibration acceleration generated in the optical box when the rotation speed of the polygon mirror is changed, the optical box provided with the reinforcing rib is compared with the optical box provided with no reinforcing rib. Is about 88% lower than the maximum. This is because the rigidity of the first wall 61 is increased by providing the optical box 201 with the reinforcing rib. Furthermore, even at a frequency of a frequency other than 800 [Hz] at which the vibration acceleration is the lowest, the optical acceleration of the optical box 201 provided with the reinforcing rib is lower than that of the optical box 201 provided with no reinforcing rib.

  According to the present invention, vibration that causes an error in the relative positional relationship of the optical components housed in the optical box 201 can be suppressed, and image defects such as banding can be suppressed.

  In the present embodiment, the first wall 61 is provided with ten reinforcing ribs 51 a, 51 b, 51 c, 51 d, 51 e, 51 f, 51 g, 51 h, 51 i, 51 j, and the second wall 62 is provided with five reinforcements. The ribs 52a, 52b, 52c, 52d, and 52e are provided. However, the number of reinforcing ribs is not limited to the number of this embodiment. For example, two reinforcing ribs 51 a and 51 i may be provided on the first wall 61 and a reinforcing rib 52 c may be provided on the second wall 62. In the state where the optical scanning device 200 is mounted on the image forming apparatus 100, the optical scanning device 200 is provided on the first wall 61 according to the strength of vibration generated on the first wall 61 positioned between the polygon mirror 203 and the conveyance path. What is necessary is just to determine the number of reinforcement ribs suitably.

101Y Image forming unit 101M Image forming unit 101C Image forming unit 101Bk Image forming unit 106 Intermediate transfer belt 107 Transfer roller 109 Storage unit 110 Paper discharge unit 121 Transport roller 200 Optical scanning device 201 Optical box 202Y Light source unit 202M Light source unit 202C Light source unit 202Bk Light source unit 203 Polygon mirror 50 Reinforcing rib 61 First wall 62 Second wall

Claims (8)

Transport means for transporting the recording material along a transport path from a housing section for housing the recording material to a paper discharge section disposed above the housing section in the vertical direction;
An image forming unit disposed between the storage unit and the paper discharge unit in the vertical direction, wherein a plurality of photoconductors are arranged at different positions in the horizontal direction and formed on the plurality of photoconductors. An image forming unit that develops an electrostatic latent image with toner and transfers the toner images on the plurality of photosensitive members to the recording material conveyed by the conveying unit;
An optical scanning device disposed between the image forming unit and the housing portion in a vertical direction, the light source emitting a plurality of light beams for forming the electrostatic latent image on the plurality of photosensitive members A rotating polygon mirror that is rotationally driven to deflect the plurality of light beams so that the plurality of light beams scan on the plurality of photoconductors, and an optical box to which the rotating polygon mirror is attached. An optical scanning device,
The optical box is located between the rotary polygon mirror and the transport path, on the first wall constituting the optical box, on the side opposite to the first wall with respect to the rotary polygon mirror, An image forming apparatus characterized in that a larger number of reinforcing ribs are provided than the second wall constituting the. The optical box is attached to the image forming apparatus by being inserted from a side surface of the image forming apparatus opposite to the conveyance path,
The bottom of the optical box is cut so that the height in the vertical direction of the optical box decreases from the predetermined position of the bottom of the optical box toward the back in the direction in which the optical box is inserted. Is missing,
The image forming apparatus according to claim 1, wherein a height of the first wall is lower than a height of the second wall.   The first region at the end of the first wall in the longitudinal direction of the first wall is more than the second region at the center of the first wall in the longitudinal direction of the first wall. The image forming apparatus according to claim 1, wherein the number of the reinforcing ribs is provided.   The image forming apparatus according to claim 1, wherein the first wall is a double wall, and the reinforcing rib connects the double wall.   The second wall is a double wall, and the reinforcing rib provided on the second wall connects the double wall of the second wall. The image forming apparatus described.   The reinforcing rib is connected to a bottom surface of the optical box, and a surface direction of the reinforcing rib is a direction perpendicular to the bottom surface and a direction perpendicular to the first wall and the second wall. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein a thickness of the reinforcing rib is equal to or less than a thickness of a wall of the optical box. The rotating polygon mirror polarizes each of the plurality of light beams in a first direction and a second direction different from the first direction in order to scan the plurality of photosensitive members. The image forming apparatus according to claim 1.