JP2010145486A - Optical scanning device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanning device which effectively shields the majority of stray light without exerting bad influence on optical performance and restrains, to a minimum, bad influence on a printing image due to the projection of the stray light onto the surface of a photoreceptor; and to provide an image forming apparatus equipped with the same. <P>SOLUTION: The optical scanning device includes; a polygon mirror 74 which deflects and scans laser light from a laser diode; reflection mirrors 76 which reflect the laser light which is reflected by the reflection plane of the polygon mirror 74 and scanned in the main scanning direction; and second fθ lenses 77 which transmit the laser light reflected by the reflection mirrors 76 to make it incident onto the surface of a photoreceptor drum 3. In the reflection mirrors 76k, 76c, 76m and 76y, main optical path reflection-used areas 76A, which are used for the reflection of the main optical path G of the laser light scanned in the main scanning direction, and main optical path reflection-unused areas 76B, which are adjacent to the main optical path reflection-used areas 76A, are masked by nonreflection members 61 which restrain the reflection of the laser light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical scanning device including a reflection mirror that reflects a laser beam and is incident on the surface of a photosensitive member, and an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile including the same. The present invention relates to a measure for suppressing reflection of laser light in a main light path reflection non-use region that is not used for reflection of the main light path of laser light in a reflection mirror.

  In this type of electrophotographic image forming apparatus, the surface of the photoconductor is scanned with laser light, the intensity of the laser light is controlled, and a latent image such as an image or text is scanned on the surface of the photoconductor. Writing is performed line by line, the latent image on the surface of the photoreceptor is developed with toner, a toner image is formed on the surface of the photoreceptor, and the toner image on the surface of the photoreceptor is transferred to a recording sheet.

  An optical scanning device is used for such laser light projection. The optical scanning device includes a semiconductor laser that emits laser light, a rotating polygon mirror that reflects and scans the laser light from the semiconductor laser, and a plurality of lenses that refract the laser light deflected and scanned by the rotating polygon mirror. The laser beam deflected and scanned is condensed and projected onto the surface of the photosensitive member through each lens. Then, while the laser beam is repeatedly scanned in the main scanning direction on the surface of the photoconductor, the surface of the photoconductor is moved in the sub-scanning direction, and a latent image is formed on the surface of the photoconductor.

  In general, a plurality of lenses are provided in the main optical path of laser light from the semiconductor laser to the surface of the photoreceptor, and among these, an fθ lens, a toroidal lens, and the like are included. The fθ lens corrects the laser light reflected by the rotary polygon mirror and moving at a constant angular velocity so as to move at a constant velocity on the surface of the photosensitive member. The toroidal lens corrects the light beam of the laser light in the sub-scanning direction.

  In the optical scanning device having such a configuration, the laser light reflected by one reflecting surface (mirror surface) of the rotary polygon mirror is condensed and projected onto the surface of the photoconductor via a plurality of lenses. There has been a problem that the laser light reflected by the corners of the reflecting surfaces adjacent to each other of the rotating polygon mirror is incident on the rotating polygon mirror again. This is because the laser beam reflected by hitting the corner of the rotating polygon mirror deviates from the main optical path, so the laser beam reflected by the holding unit for holding the reflecting mirror located on the main optical path of the laser beam is again rotated polyhedral This is because the light enters the mirror.

Therefore, the laser beam (laser beam deviating from the main optical path) reflected by the end of the holding unit that holds the reflecting mirror located on the main optical path of the laser beam and hits the corner of the rotating polygon mirror is outside the incident area with respect to the rotating polygon mirror. By forming an inclined surface or the like that reflects the laser beam, the laser beam reflected by the holding unit for holding the reflecting mirror located on the main optical path of the laser beam is prevented from entering the rotary polygon mirror again. Those are known (for example, see Patent Document 1).
JP-A-6-109996

  By the way, the stray light deviating from the main optical path of the laser light is not only the laser light reflected by the corners of the rotary polygon mirror and reflected, but a part of the main optical path of the laser light trying to pass through the fθ lens is stray light. And may enter the rotating polygon mirror again. As shown in FIG. 7, since the fθ lens 81 has a convex surface 81a on the laser light incident side (lower side in FIG. 7), the main optical path of the laser light to be incident on the fθ lens 81 A part of the light G1 is reflected and spreads on the convex surface 81a of the fθ lens 81, and the reflected and spread light becomes stray light G2 (shown by a two-dot chain line in FIG. 7) and enters the rotating polygon mirror again. Because it is done. In FIG. 7, reference numeral 82 denotes a photoconductor.

  In that case, the stray light reflected by the fθ lens is placed outside the incident area with respect to the rotating polygon mirror by arranging the fθ lens so as to be inclined with respect to the optical path of the stray light so that the stray light reflected by the fθ lens does not enter the rotating polygon mirror again. It is possible to make it turn.

  However, if the fθ lens is disposed at an inclination, the main optical path of the laser light that passes through the fθ lens is also affected, which may adversely affect the optical performance.

  On the other hand, coupled with the increase in the number of reflecting surfaces of the rotary polygon mirror accompanying the recent demand for higher speed, the stray light re-reflected by these reflecting surfaces also tends to increase. Therefore, although stray light (laser light) reflected by hitting the corner of the rotating polygon mirror or stray light reflected by the fθ lens is directed outside the incident area with respect to the rotating polygon mirror, these stray light is Along with the stray light re-reflected by the reflecting surface of the rotary polygon mirror, there is a possibility that it will be re-reflected by a reflecting mirror or lens located on the optical path of other laser light and projected onto the surface of the photoreceptor.

  Specifically, as shown in FIG. 8, the laser light from each laser diode corresponding to each color of black (K), cyan (C), magenta (M), and yellow (Y) is reflected by a mirror, A rotating polygon mirror 91 that reflects each laser beam reflected by the mirror, a first fθ lens 92 that refracts each laser beam from the rotating polygon mirror 91, and each laser beam that passes through the first fθ lens 92 is individually reflected. A plurality of reflecting mirrors 93k, 93c, 93m, and 93y, and four second fθ lenses 94k, 94c, 94m, and 94y that individually refract the laser beams from the reflecting mirrors 93k, 93c, 93m, and 93y, respectively. In the optical scanning device 9 having the above, the main optical path of the laser beam from the laser diode corresponding to black (indicated by a one-dot chain line in FIG. 8) Then, the light is reflected by the rotary polygon mirror 91 and scanned in the main scanning direction (the front and rear direction in FIG. 8), further passes through the first fθ lens 92 and is reflected by the reflection mirror 93k, and then passes through the second fθ lens 94k. And projected onto the surface of the photoconductor 95k corresponding to black. At this time, a part of the main optical path of the laser light projected through the second fθ lens 94k to the surface of the photoconductor 95k corresponding to black is reflected by the convex surface of the second fθ lens 94k and spreads to stray light ( This stray light is re-reflected at the upper end of the reflecting mirror 93m that reflects the laser light from the laser diode corresponding to magenta, passes through the second fθ lens 94m, and is black. The light is projected onto the surface of the photoreceptor 95m corresponding to different magenta.

  Further, as shown in FIG. 9, the main optical path of the laser light from the laser diode corresponding to magenta (indicated by the alternate long and short dash line in FIG. 9) is reflected by the rotary polygon mirror 91 and scanned in the main scanning direction X. The light passes through the first fθ lens 92 and is reflected by the reflection mirror 93m, then passes through the second fθ lens 94m and is projected onto the surface of the photoconductor 95m corresponding to magenta. At this time, a part of the main optical path of the laser beam projected through the second fθ lens 94m to the surface of the photoconductor 95m corresponding to magenta is reflected by the convex surface of the second fθ lens 94m and spreads to stray light ( This stray light is re-reflected at the lower end of the reflection mirror 93m, passes through the second fθ lens 94m, and is projected onto the surface of the photoconductor 95m corresponding to magenta. Furthermore, the stray light reflected by the convex surface of the second fθ lens 94m (indicated by a two-dot chain line in FIG. 9) is reflected again at the upper end of the reflecting mirror 93m, passes through the first fθ lens 92, and is incident again on the rotary polygon mirror 91. The The configuration in FIG. 9 is the same as the configuration in FIG. 8, and the same portions are denoted by the same reference numerals and detailed description thereof is omitted.

  Thus, when stray light re-reflected by a reflecting mirror or lens located on the optical path of another laser beam is projected onto the surface of the photoconductor, the exposure intensity on the surface of the photoconductor is extremely reduced, There is a concern that print images will be adversely affected.

  The present invention has been made in view of the above points, and the object of the present invention is to effectively block most of stray light without adversely affecting the optical performance and project stray light on the surface of the photoreceptor. It is an object of the present invention to provide an optical scanning apparatus and an image forming apparatus provided with the optical scanning apparatus that can suppress the adverse effect on the printed image due to the above.

  In order to achieve the above object, in the present invention, a light source that emits laser light, a rotary polygon mirror that deflects and scans the laser light from the light source, and a reflection surface of the rotary polygon mirror that reflects and scans in the main scanning direction. As an optical scanning device comprising a reflection mirror that reflects the laser beam that is reflected and an fθ lens that transmits the laser beam reflected by the reflection mirror and is incident on the surface of the photoreceptor, the reflection mirror is arranged in the main scanning direction. The main optical path reflection non-use area adjacent to the main optical path reflection use area used for reflection of the main light path of the scanned laser light is masked by a non-reflective member that suppresses reflection of the laser light.

  Due to this specific matter, the main optical path of the laser light from the light source is reflected in the main optical path reflection use region of the reflection mirror, passes through the fθ lens, and is incident on the surface of the photoconductor.

  In that case, even if stray light that is re-reflected by a reflection mirror or lens located on the optical path of another laser beam is about to enter the reflection mirror, the reflection of the main optical path that is used to reflect the main optical path of the laser beam by the reflection mirror The non-reflective member masking the main optical path reflection non-use area adjacent to the use area suppresses re-reflection of stray light on the reflection mirror. For this reason, most of the stray light entering the reflection mirror is shielded, and a reduction in exposure intensity due to the projection of the stray light onto the surface of the photoconductor can be suppressed, thereby preventing adverse effects on the printed image.

  In particular, the following configurations are listed as specifying the reflecting mirror masked by the non-reflecting member. That is, as the reflection mirror that is masked by the non-reflective member, a reflection mirror at a position where the re-reflection distance of stray light from the fθ lens is long and the re-reflection distance of stray light to the rotary polygon mirror is short is applied.

  Due to this specific matter, stray light that is reflected and spreads on the convex surface of the fθ lens and becomes wider as it approaches the rotating polygon mirror is reflected at a position where the re-reflection distance from the fθ lens is far and the re-reflection distance to the rotating polygon mirror is short. Most of the light is efficiently shielded by the non-reflective member masking the main light path reflection non-use area adjacent to the main light path reflection use area in the mirror. In addition, since the non-reflecting member masks the main optical path reflection non-use area in the reflecting mirror, most of the stray light re-reflected by reflecting mirrors and lenses located on the optical path of other laser beams is also efficient. It will be well shaded.

  In particular, the following configurations are listed as specifying the main optical path reflection non-use area. That is, the main optical path reflection non-use area is provided adjacent to a direction orthogonal to the main scanning direction of the main optical path reflection use area on the reflection mirror.

  By this specific matter, the main light path of the laser light that scans the main light path reflection use area on the reflection mirror during the scanning of the laser light is not shielded by the non-reflecting member. As a result, it is possible to smoothly reflect the main optical path of the laser light while blocking stray light by the non-reflective member that masks the main optical path reflection non-use area in the direction orthogonal to the main scanning direction of the main optical path reflection use area. Become.

  And the following structure is hung up as what specifies the said main optical path reflection non-use area | region more concretely. That is, the main optical path reflection non-use area is provided adjacent to both sides of the main optical path reflection use area, which are positioned substantially at the center in the direction orthogonal to the main scanning direction, on the reflection mirror. Yes.

  Due to this specific matter, it is designed so that the main optical path of the laser beam that scans the main optical path reflection use area on the reflection mirror when scanning the laser beam is reflected at the approximate center in the direction orthogonal to the main scanning direction of the reflection mirror. However, the main optical path reflections on both sides orthogonal to the main scanning direction of the main optical path reflection use area by the non-reflective members masking the main optical path reflection non-use areas on both sides orthogonal to the main scanning direction of the main optical path reflection use area. It is possible to smoothly reflect the main optical path of the laser light in the main optical path reflection use area at the substantially center in the direction orthogonal to the main scanning direction of the reflection mirror while blocking stray light to be re-reflected in the non-use area.

  On the other hand, the main optical path reflection non-use area is provided adjacent to the other side perpendicular to the main scanning direction of the main optical path reflection use area located on one side orthogonal to the main scanning direction on the reflection mirror. When the laser beam is scanned, the main optical path of the laser beam that scans the main optical path reflection use area on the reflection mirror is reflected on one side orthogonal to the main scanning direction of the main optical path reflection use area of the reflection mirror. Even if designed, the non-reflective member masking the main optical path reflection non-use area on the other side orthogonal to the main scan direction of the main optical path reflection use area is orthogonal to the main scan direction of the main optical path reflection use area. Smooth the main optical path of the laser beam in the main optical path reflection use area on one side orthogonal to the main scanning direction of the reflection mirror while blocking stray light to be re-reflected in the other main optical path reflection non-use area It is possible to reflection.

  In addition, when the main optical path reflection use area is curved with respect to the main scanning direction on the reflection mirror, the main optical path reflection use area is arranged on both sides orthogonal to the main scan direction of the main optical path reflection use area. Are provided adjacent to each other.

  Due to this particular matter, even when a bow is generated in the main optical path of the laser beam that is scanned on the reflection mirror on the main optical path reflection use area when the laser beam is scanned, the bow is generated even if the main optical path of the laser beam is curved. Non-reflective masking adjacent main optical path reflection non-use areas on both sides orthogonal to the main scanning direction of the main optical path reflection use area curved so as to be used for reflection of the main optical path along the main optical path reflection use area. The member blocks stray light to be re-reflected in the main optical path reflection non-use areas on both sides orthogonal to the main scanning direction of the main optical path reflection use area, and the main part of the laser beam generated with bow in the curved main optical path reflection use area. It is possible to smoothly reflect the optical path.

  In particular, the following configurations are listed as specifying the non-reflective member. That is, the non-reflective member is formed of a sheet member having a surface roughness for diffusing the laser light or a material having a color with low reflectance.

  With this specific matter, stray light can be diffused or reflected with a low reflectance even if it enters the non-reflective member, and the stray light can be effectively blocked.

  On the other hand, when the coating agent applied to the reflecting mirror is applied as the non-reflecting member, the non-reflecting member can be easily and inexpensively installed on the reflecting mirror, and the degree of freedom in installing the non-reflecting member Will improve dramatically and will be very advantageous to implement.

  In addition, when such an optical scanning device is used in an image forming apparatus, printing is performed by projecting stray light onto the surface of the photoreceptor effectively shielding most of the stray light without adversely affecting the optical performance. It is possible to provide an image forming apparatus that can minimize adverse effects on images.

  In short, the main part of the stray light is suppressed by re-reflecting the stray light incident on the reflection mirror by masking the non-reflecting member on the main light path reflection non-use area that is not used for the reflection of the main light path of the laser light in the reflection mirror. Can be shielded, and a decrease in exposure intensity due to the projection of stray light onto the surface of the photoreceptor can be suppressed, thereby suppressing adverse effects on the printed image.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic sectional view showing an image forming apparatus to which an optical scanning device according to an embodiment of the present invention is applied. The image forming apparatus A includes a document reading device B that reads an image of a document, and records and forms an image of the document read by the document reading device B or an image received from the outside in color or single color on a recording sheet. ing.

  In the document reading device B, when the document is set on the document set tray 40, the pickup roller 41 is pressed against the surface of the document and rotates, whereby the document is pulled out from the document set tray 40, and the next roller roller 42 and separation pad are separated. 43 is separated into one by one after passing between the two and then conveyed to the conveyance path 44.

  In the conveyance path 44, the leading edge of the document abuts on the registration roller 45, so that the leading edge of the document is aligned parallel to the registration roller 45, and then the document is conveyed by the registration roller 45, the document guide 46 and the reading glass 47. Pass between. At this time, the light from the light source of the first scanning unit 48 is applied to the surface of the document through the reading glass 47, and the reflected light is incident on the first scanning unit 48 through the reading glass 47. The image is reflected by the mirrors of the second scanning units 48 and 49 and guided to the imaging lens 50, and an image of the original is formed on a CCD (Charge Coupled Device) 51 by the imaging lens 50. The CCD 51 reads an image of a document and outputs image data indicating the image of the document. Further, the document is transported by a transport roller 52 and discharged to a document discharge tray 54 via a discharge roller 53.

  In addition, a document placed on the document table glass 55 can be read. The registration roller 45, the document guide 46, the document discharge tray 54, and the like and the members above them are integrated into a cover body 56 that is pivotally supported on the back side of the document reader B so as to be opened and closed. Yes. When the cover body 56 is opened, the document table glass 55 is released, and a document can be placed on the document table glass 55. When the document is placed and the cover body 56 is closed, the first and second scanning units 48 and 49 are moved in the sub-scanning direction (left-right direction in FIG. 1) while the first scanning unit 48 moves the document table glass. The document surface on 55 is exposed, and reflected light from the document surface is guided to the imaging lens 50 by the first and second scanning units 48 and 49, and the image of the document is formed on the CCD 51 by the imaging lens 50. Imaged. At this time, the first and second scanning units 48 and 49 are moved while maintaining a predetermined speed relationship with each other, and reflection of the document surface, the first and second scanning units 48 and 49, the imaging lens 50, and the CCD 51 is performed. The positional relationship between the first and second scanning units 48 and 49 is always maintained so that the length of the optical path of the light does not change, so that the focus of the original image on the CCD 51 is always maintained accurately. It has become.

  The entire image of the original read in this way is transmitted and received as image data to the image forming apparatus A, and the image is recorded on the recording paper in the image forming apparatus A.

  On the other hand, the image forming apparatus A includes an optical scanning device 1, a developing device 2, a photosensitive drum 3 (photosensitive member), a charger 4, a cleaner device 5, an intermediate transfer belt device 8, a fixing device 12, a paper conveying device 18, a feeding device. The paper tray 10 and the paper discharge tray 15 are configured.

  The image data handled in the image forming apparatus A uses data corresponding to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color (for example, black). This is in accordance with the monochrome image. Therefore, the developing device 2 (2k, 2c, 2m, 2y), the photosensitive drum 3 (3k, 3c, 3m, 3y), the charger 4 (4k, 4c, 4m, 4y), the cleaner device 5 (5k, 5c, 5m, 5y) are provided to form four types of latent images corresponding to each color, k corresponding to black, c corresponding to cyan, m corresponding to magenta, and y corresponding to yellow. Four image stations Sk, Sc, Sm, and Sy are configured.

  The photoconductor drum 3 is disposed at substantially the center of the image forming apparatus A. The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. In addition to a contact type roller type or brush type charger, a charger type charger is used. .

  The optical scanning device 1 is a laser scanning unit (LSU) provided with a laser diode and a reflection mirror, and exposes the surface of a charged photosensitive drum 3 according to image data and statically responds to the surface according to the image data. An electrostatic latent image is formed.

  The developing device 2 develops the electrostatic latent image formed on the photosensitive drum 3 with (K, C, M, Y) toner. The cleaner device 5 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer belt device 8 disposed above the photosensitive drum 3 includes an intermediate transfer belt 7, an intermediate transfer belt driving roller 21, a driven roller 22, an intermediate transfer roller 6 (6k, 6c, 6m, 6y), and an intermediate A transfer belt cleaning device 9 is provided.

  The intermediate transfer belt drive roller 21, the intermediate transfer roller 6, the driven roller 22, etc. stretch and support the intermediate transfer belt 7, and move the intermediate transfer belt 7 in the direction of arrow C.

  The intermediate transfer roller 6 is rotatably supported in the vicinity of the intermediate transfer belt 7, is pressed against the photosensitive drum 3 via the intermediate transfer belt 7, and transfers the toner image on the photosensitive drum 3 to the intermediate transfer belt 7. A transfer bias is applied.

  The intermediate transfer belt 7 is provided so as to come into contact with the photosensitive drums 3k, 3c, 3m, and 3y, and the toner images on the surfaces of the photosensitive drums 3k, 3c, 3m, and 3y are sequentially superimposed on the intermediate transfer belt 7. Are transferred to form a color toner image (a toner image of each color). This transfer belt is formed in an endless belt shape using a film having a thickness of about 100 μm to 150 μm.

  The transfer of the toner image from the photosensitive drum 3 to the intermediate transfer belt 7 is performed by the intermediate transfer roller 6 that is in pressure contact with the back surface of the intermediate transfer belt 7. A high voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 6 in order to transfer the toner image. The intermediate transfer roller 6 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the recording paper.

  As described above, the toner images on the surfaces of the photosensitive drums 3k, 3c, 3m, and 3y are stacked on the intermediate transfer belt 7 to form a color toner image indicated by the image data. The toner images of the respective colors stacked in this way are transported together with the intermediate transfer belt 7 and transferred onto the recording paper by the secondary transfer device 11 that contacts the intermediate transfer belt 7.

  The intermediate transfer belt 7 and the transfer roller 11a of the secondary transfer device 11 are pressed against each other to form a nip region. Further, the transfer roller 11a of the secondary transfer device 11 has a voltage for transferring the toner image of each color on the intermediate transfer belt 7 onto a recording sheet (high polarity (+) opposite to the toner charge polarity (-)). Voltage) is applied. Further, in order to constantly obtain the nip region, either the transfer roller 11a of the secondary transfer device 11 or the intermediate transfer belt drive roller 21 is made of a hard material (metal or the like), and the other is a soft material such as an elastic roller. (Elastic rubber roller, foaming resin roller, etc.).

  In addition, the toner image on the intermediate transfer belt 7 may not be completely transferred onto the recording paper by the secondary transfer device 11, and the toner may remain on the intermediate transfer belt 7. Causes color mixing. Therefore, the residual toner is removed and collected by the intermediate transfer belt cleaning device 9. The intermediate transfer belt cleaning device 9 includes, for example, a cleaning blade that comes into contact with the intermediate transfer belt 7 as a cleaning member, and the back side of the intermediate transfer belt 7 is supported by a driven roller 22 at a portion where the cleaning blade comes into contact. .

  The paper feed tray 10 is a tray for storing recording paper, and is provided below the image forming unit of the image forming apparatus A. The paper discharge tray 15 provided on the upper side of the image forming unit is a tray for placing printed recording paper face down.

  Further, the image forming apparatus A is provided with a paper transport device 18 for sending the recording paper in the paper feed tray 10 to the paper discharge tray 15 via the secondary transfer device 11 and the fixing device 12. The sheet conveying device 18 has an S-shaped sheet conveying path 25, and along this sheet conveying path 25, a pickup roller 16, a pre-registration roller 19, a registration roller 14, a fixing device 12, and each conveying roller 13. , And a discharge roller 17 and the like.

  The pickup roller 16 is a call-in roller that is provided at the end of the paper feed tray 10 and supplies recording paper from the paper feed tray 10 to the paper transport path 25 one by one. Each of the transport rollers 13 and the pre-registration rollers 19 is a small roller for promoting and assisting the transport of the recording paper, and is provided at a plurality of locations along the paper transport path 25.

  The registration roller 14 temporarily stops the recording paper that has been conveyed, aligns the leading edge of the recording paper, and a color toner image on the intermediate transfer belt 7 in the nip area between the intermediate transfer belt 7 and the secondary transfer device 11. Is transferred to the recording paper in a timely manner as the photosensitive drum 3 and the intermediate transfer belt 7 rotate. For example, the registration roller 14 is configured so that the leading edge of the color toner image on the intermediate transfer belt 7 matches the leading edge of the image forming range on the recording sheet in the nip region between the intermediate transfer belt 7 and the secondary transfer device 11. Transport.

  The fixing device 12 receives the recording sheet on which the toner image is transferred, and conveys the recording sheet between the heat roller 31 and the pressure roller 32. The heat roller 31 is controlled so as to have a predetermined fixing temperature, and the recording paper is thermocompression bonded together with the pressure roller 32 to melt, mix, and press the toner image transferred to the recording paper. It has a function of heat fixing.

  The recording paper after fixing the toner images of the respective colors is discharged onto the paper discharge tray 15 by the discharge rollers 17.

  Note that it is also possible to form a monochrome image using only the image forming station Sk and transfer the monochrome image to the intermediate transfer belt 7 of the intermediate transfer belt device 8. Similarly to the color image, this monochrome image is also transferred from the intermediate transfer belt 7 to the recording paper and fixed on the recording paper.

  When printing on both sides of the recording paper as well as on both sides, after fixing the image on the surface of the recording paper by the fixing device 12, the recording paper is being conveyed by the paper discharge roller 17 in the paper conveyance path 25. Then, the paper discharge roller 17 is stopped and then rotated in the reverse direction, the recording paper is passed through the reversing path Sr, the recording paper is turned upside down, and the recording paper is guided to the registration roller 14 and is the same as the surface of the recording paper. Then, an image is recorded and fixed on the back surface of the recording paper, and the recording paper is discharged to the paper discharge tray 15.

  2 and 3A, 3B are a perspective view, a schematic plan view, and a schematic cross-sectional view showing the optical scanning device 1 according to the present embodiment in detail.

  In the optical scanning device 1 of the present embodiment, laser diodes 71 (71k, 71c, 71m, 71y) as respective light sources corresponding to the respective colors of black (K), cyan (C), magenta (M), and yellow (Y). ), Mirrors 72 (72k, 72c, 72m, 72y) for reflecting the laser beams of the laser diodes 71k, 71c, 71m, 71y, and the laser beams from the mirrors 72k, 72c, 72m, 72y. A mirror 73, a rotating polygon mirror (hereinafter referred to as a polygon mirror) 74 that reflects each laser beam from the mirror 73, a first fθ lens 75 that refracts each laser beam from the polygon mirror 74, and the first fθ A plurality of reflecting mirrors 76 (76k, 76c, 76m, 76y) for individually reflecting each laser beam transmitted through the lens 75; Four second fθ lenses 77 (77k, 77c, 77m, 77y) for individually refracting the laser beams from these reflecting mirrors 76k, 76c, 76m, 76y are arranged at predetermined positions in the housing 1a. Has been.

  The polygon mirror 74 has an octahedral regular polygonal column shape, is driven to rotate at high speed, and repeatedly scans in the main scanning direction X while reflecting each laser beam by a mirror (reflection surface) on each peripheral surface thereof. To do. The polygon mirror 74 is rotatably supported and fixed on a mirror mounting table, and the mirror mounting table is supported and fixed by a screw or the like (not shown) on a support member mounted and fixed in the housing 1a. ing.

  The first fθ lens 75, each reflection mirror 76, and each second fθ lens 77 are elongated in the main scanning direction X and reflected in the main scanning direction X in order to reflect and refract each laser beam repeatedly scanned in the main scanning direction X. It is formed in the shape of a bar shortened in a direction orthogonal to the direction X, and both ends thereof are supported and fixed to the housing 1a.

  Laser light emitted from the laser diode 71k corresponding to black is sequentially reflected by the mirror 72k, the mirror 72m, and the mirror 73, reflected by the polygon mirror 74, scanned in the main scanning direction X, and further transmitted through the first fθ lens 75. Then, the light is reflected by the single reflecting mirror 76k, passes through the second fθ lens 77k, and enters the photosensitive drum 3k corresponding to black.

  Laser light emitted from the laser diode 71c corresponding to cyan is sequentially reflected by the mirror 72c, the mirror 72m, and the mirror 73, reflected by the polygon mirror 74, scanned in the main scanning direction X, and further transmitted through the first fθ lens 75. Then, the light is reflected by the two reflecting mirrors 76c and 76c, passes through the second fθ lens 77c, and enters the photosensitive drum 3c corresponding to cyan.

  Laser light emitted from the laser diode 71 y corresponding to yellow is sequentially reflected by the mirrors 72 y and 72 k and the mirror 73, reflected by the polygon mirror 74, scanned in the main scanning direction X, and further transmitted through the first fθ lens 75. Then, the light is reflected by the two reflecting mirrors 76y and 76y, passes through the second fθ lens 77y, and enters the photosensitive drum 3y corresponding to yellow.

  The laser light emitted from the laser diode 71m corresponding to magenta is reflected by the mirror 73, reflected by the polygon mirror 74, scanned in the main scanning direction X, and further transmitted through the first fθ lens 75 to be reflected by two pieces. The light is reflected by the mirrors 76m and 76m, passes through the second fθ lens 77m, and enters the photosensitive drum 3m corresponding to magenta.

  Each of the photoconductor drums 3k, 3c, 3m, and 3y is driven to rotate in the arrow direction shown in FIG. 3B, and each photoconductor is irradiated with each laser beam that is repeatedly scanned in the main scanning direction X. Respective electrostatic latent images are formed on the surfaces of the drums 3k, 3c, 3m, and 3y. The electrostatic latent images on the surfaces of the photosensitive drums 3k, 3c, 3m, and 3y are respectively developed to become toner images, and these toner images are transferred onto the recording paper via the intermediate transfer belt 7 and transferred onto the recording paper. A color toner image is obtained.

  In the above configuration, as shown in FIG. 4, the laser beam emitted from the laser diode 71k corresponding to black is reflected and transmitted through the second fθ lens 77k, and the laser diode 71c corresponding to cyan is emitted. Of the two reflection mirrors 76c and 76c arranged to reflect the laser light and transmit it to the second fθ lens 77c, the re-reflection distance of the stray light from the second fθ lens 77c is long and the stray light is re-reflected to the polygon mirror 74. The reflection mirror 76c at the position where the reflection distance is short (the right reflection mirror 76c in FIG. 3B) reflects the laser light emitted from the laser diode 71y corresponding to yellow and transmits it to the second fθ lens 77y. Stray light from the second fθ lens 77y of the two reflecting mirrors 76y, 76y arranged Is emitted from the reflection mirror 76y (the right reflection mirror 76y in FIG. 3B) and the laser diode 71m corresponding to magenta at a position where the re-reflection distance is long and the re-reflection distance of stray light to the polygon mirror 74 is short. Of the stray light from the second fθ lens 77m out of the two reflection mirrors 76m, 76m arranged to reflect the transmitted laser light and transmit it to the second fθ lens 77m, and stray light to the polygon mirror 74 The reflection mirror 76m (the right reflection mirror 76m in FIG. 3B) at a position where the re-reflection distance is near is provided with a non-reflection member 61 that suppresses reflection of laser light. The non-reflective member 61 is formed of a sheet member having a surface roughness for diffusing laser light. The non-reflective member 61 is a main optical path reflection use region 76A (FIG. 5) used for reflection of the main optical path G of the laser light scanned in the main scanning direction X by the target reflection mirrors 76k, 76c, 76y, and 76m. (A) to (c), a region adjacent to the white portion), that is, a main light path reflection non-use region 76B (in FIG. 5) that is not used for reflection of the main light path G of the laser light scanned in the main scanning direction X. (A) to (c) are attached so as to mask the hatched portion). In this case, the main optical path G of the laser light extends linearly on the reflection mirror 76 substantially in parallel with the main scanning direction.

  The main optical path reflection non-use area 76B is provided in the Y direction (shown in FIG. 5) perpendicular to the main scanning direction X of the main optical path reflection use area 76A on the reflection mirror 76 (76k, 76c, 76y, 76m). ing. More specifically, as shown in FIG. 5A, the reflecting mirror 76k that reflects the laser beam emitted from the laser diode 71k corresponding to black and transmits the reflected laser beam to the second fθ lens 77k, and cyan. The reflection mirror 76c that reflects the laser light emitted from the laser diode 71c that transmits and transmits the reflected light to the second fθ lens 77c (the rereflection distance of stray light from the second fθ lens 77c is long and the rereflection distance of stray light to the polygon mirror 74 is long). The main optical path reflection use area 76A of the reflection mirror 76c at a close position is located at substantially the center in the Y direction orthogonal to the main scanning direction X (left-right direction in FIG. 5A) on the reflection mirrors 76k and 76c. The main light path reflection non-use area 76B is set in the main light path reflection use area 76A on the reflection mirrors 76k and 76c. They are respectively provided in the Y direction sides perpendicular to the main scanning direction X (in Fig. 5 both upper and lower sides). Further, as shown in FIG. 5B, the reflection mirror 76m (the stray light from the second fθ lens 77m) that reflects the laser beam emitted from the laser diode 71m corresponding to magenta and transmits the reflected laser beam to the second fθ lens 77m is reproduced. The main optical path reflection use region 76A of the reflection mirror 76m at a position where the reflection distance is long and the re-reflection distance of stray light to the polygon mirror 74 is short is left and right in the main scanning direction X on the reflection mirror 76m (FIG. 5B). The main optical path reflection non-use area 76B is set in the main scanning direction X of the main optical path reflection use area 76A on the reflection mirror 76m. Is provided on the other side (lower side in FIG. 5) in the Y direction perpendicular to the line. Further, as shown in FIG. 5C, the reflection mirror 76y that reflects the laser light emitted from the laser diode 71y corresponding to yellow and transmits the reflected light to the second fθ lens 77y (reproduction of stray light from the second fθ lens 77y). The main light path reflection use region 76A of the reflection mirror 76y) at a position where the reflection distance is long and the stray light re-reflection distance to the polygon mirror 74 is short is left and right in the main scanning direction X on the reflection mirror 76y (FIG. 5C). The main optical path reflection non-use area 76B is set to be on the other side in the Y direction (lower side in FIG. 5C) perpendicular to the direction), and the main optical path reflection use area 76A on the reflection mirror 76y. Is provided on one side in the Y direction orthogonal to the main scanning direction X (upper side in FIG. 5C).

  Therefore, in the above embodiment, the main optical path G of the laser light emitted from the laser diode 71 (71k, 71c, 71y, 71m) is sequentially reflected by the mirror 72 (72k, 72c, 72y, 72m) and the mirror 73, Reflected by the polygon mirror 74, scanned in the main scanning direction X, further transmitted through the first fθ lens 75, reflected by the reflecting mirror 76 (76k, 76c, 76y, 76m), and second fθ lens 77 (77k, 77c, 77y). , 77m) and is incident on the respective photosensitive drums 3 (3k, 3c, 3y, 3m) corresponding to the respective colors of black (K), cyan (C), magenta (M), and yellow (Y). The

  In that case, the reflection mirror 76c (the right reflection mirror 76c in FIG. 4) at a position where the re-reflection distance of the stray light from the reflection mirror 76k and the second fθ lens 77c is long and the re-reflection distance of the stray light to the polygon mirror 74 is short. The reflection mirror 76y (the right reflection mirror 76y in FIG. 4) at a position where the re-reflection distance of the stray light from the 2fθ lens 77y is long and the re-reflection distance of the stray light to the polygon mirror 74 is short, and the stray light from the second fθ lens 77m. The reflection mirror 76m (the right reflection mirror 76m in FIG. 4) at a position where the re-reflection distance is long and the re-reflection distance of stray light to the polygon mirror 74 is short is provided with a non-reflective member 61 that suppresses reflection of laser light. It has been. As a result, even if stray light re-reflected by the reflection mirror 76 or the second fθ lens 77 located on the optical path of the other laser light attempts to enter the reflection mirror 76 (76k, 76c, 76y, 76m), these reflections are reflected. The reflection mirrors 76k, 76c, 76y, and 76m are formed by the non-reflective member 61 that masks the main optical path reflection non-use area 76B adjacent to the main optical path reflection use area 76A that is used to reflect the main optical path G of the laser light in the mirror 76. Re-reflection of stray light is suppressed. For this reason, most of the stray light entering the reflection mirrors 76k, 76c, 76y, and 76m is shielded, and a reduction in exposure intensity due to the projection of stray light onto the surfaces of the photosensitive drums 3k, 3c, 3y, and 3m is suppressed. Thus, adverse effects on the printed image can be suppressed.

  In addition, the reflection mirror 76 (76k, 76c, 76y, 76m) masked by the non-reflecting member 61 has a long re-reflection distance of stray light from the second fθ lens 77 (77k, 77c, 77y, 77m), and the polygon mirror 74. By applying the reflection mirrors 76k, 76c, 76y, 76m at positions where the re-reflection distance of the stray light to the near is reflected, it is reflected and spreads on the convex surface of the second fθ lenses 77k, 77c, 77y, 77m, and becomes a polygon mirror 74. The stray light, which becomes wider as it approaches, is mainly reflected at the reflection mirrors 76k, 76c, 76y, and 76m where the re-reflection distance from the second fθ lenses 77k, 77c, 77y, and 77m is long and the re-reflection distance to the polygon mirror 74 is short. Non-reflective masking the main optical path reflection non-use area 76B adjacent to the optical path reflection use area 76A The member 61, can be efficiently shielded. Further, the main optical path reflection non-use area 76B in the reflection mirrors 76k, 76c, 76y, and 76m is masked by the non-reflection member 61, so that the reflection mirror 76 (76k, 76c) positioned on the optical path of the other laser light. , 76y, 76m) and most of the stray light re-reflected by the second fθ lenses 77k, 77c, 77y, 77m, etc., can be shielded efficiently.

  Further, the main optical path G of the laser light that scans the main optical path reflection use region 76A on the reflection mirrors 76k and 76c during the scanning of the laser light emitted from the laser diodes 71k and 71c corresponding to black and cyan is the reflection mirror 76k. , 76c is set so as to be reflected at substantially the center in the Y direction orthogonal to the main scanning direction X, the main optical path is reflected on the reflecting mirror 76m during scanning of the laser light emitted from the laser diode 71m corresponding to magenta. When the main optical path G of the laser beam scanned in the use area 76A is set to reflect on one side in the Y direction orthogonal to the main scanning direction X of the reflecting mirror 76m, and from the laser diode 71y corresponding to yellow When scanning the emitted laser light, the main optical path reflection use region 76A is set on the reflection mirror 76y. When the main optical path G of the laser beam to be inspected is set to reflect on the other side in the Y direction perpendicular to the main scanning direction X of the reflecting mirror 76y, the main optical path reflection use area 76A The non-reflecting members 61, 61,... Mask the main optical path reflection non-use areas 76B, 76B on both sides in the Y direction orthogonal to each other, or on the other side or one side in the Y direction, respectively, so as to re-reflect in the main optical path reflection non-use area 76B. The main optical path G of the laser light is reflected in the main optical path reflection use region 76A on the Y-direction approximately center of the reflection mirrors 76k, 76c, 76y, 76m orthogonal to the main scanning direction, or one side or the other side of the Y-direction. It can be reflected smoothly.

  Further, since the non-reflective member 61 is formed of a sheet member having a surface roughness for diffusing laser light, stray light is diffused even if it is incident on the non-reflective member 61, and the stray light can be effectively shielded. it can.

  By using such an optical scanning device 1 for the image forming apparatus A, most of the stray light is effectively shielded without adversely affecting the optical performance, and the photosensitive drum 3 (3k, 3c, 3y, It is possible to provide the image forming apparatus A that can minimize the adverse effect on the printed image due to the projection of the stray light on the surface of 3m).

  In addition, this invention is not limited to the said embodiment, The other various modifications are included. For example, in the above-described embodiment, the case where the main optical path G of the laser beam extends linearly on the reflection mirror 76 substantially in parallel with the main scanning direction has been described. However, as shown in FIG. When the reflection use area 76A is curved with respect to the main scanning direction X, the main optical path reflection non-use area along both sides (upper and lower sides in FIG. 6) orthogonal to the main scanning direction X of the main optical path reflection use area 76A. 76B may be provided. In that case, even if a bow is generated in the main optical path G ′ of the laser beam scanned on the main optical path reflection use region 76A on the reflection mirror 76 during the scanning of the laser beam, and the main optical path G ′ of the laser beam is curved, Non-reflective masking along the main optical path reflection use area 76A on both sides orthogonal to the main scanning direction X of the main optical path reflection use area 76A curved so as to be used for reflection of the main optical path G 'where the bow has occurred. The member 61 blocks stray light to be re-reflected in the main optical path reflection non-use areas 76B and 76B on both sides orthogonal to the main scanning direction X of the main optical path reflection use area 76A, and bows in the curved main optical path reflection use area 76A. Thus, it is possible to smoothly reflect the main optical path G ′ of the generated laser beam.

  Moreover, in the said embodiment, although the non-reflective member 61 was formed with the sheet | seat member provided with the surface roughness which diffuses a laser beam, the non-reflective member is formed with the material (for example, black etc.) with a low reflectance. In this case as well, when stray light is incident on the non-reflective member, it is reflected with a low reflectance, and the stray light can be effectively shielded. Further, a coating agent applied to the reflecting mirror may be applied as the non-reflecting member. In this case, the non-reflecting member can be easily and inexpensively installed on the reflecting mirror, and the non-reflecting member can be installed freely. The degree of improvement is drastically improved, which is very advantageous for implementation.

1 is a schematic cross-sectional view illustrating an image forming apparatus to which an optical scanning device according to an embodiment of the present invention is applied. It is a perspective view which shows an optical scanning device in detail. (A) is a schematic plan view of an optical scanning device, (b) is the schematic sectional drawing. It is a schematic sectional drawing of the optical scanning device which shows the non-reflective member which shields the stray light from a 2nd f (theta) lens. (A) is a front view of a reflecting mirror corresponding to black and cyan of the optical scanning device, (b) is a front view of a reflecting mirror corresponding to magenta of the optical scanning device, and (c) corresponds to yellow of the optical scanning device. It is a front view of a reflective mirror. It is a front view of a reflective mirror in case the main optical path of a laser beam is curving in the optical scanning device concerning the modification of this embodiment. It is explanatory drawing explaining generation | occurrence | production of the stray light in a 2nd f (theta) lens in the optical scanning device which concerns on a prior art example. It is a schematic sectional drawing of the optical scanning device concerning other conventional examples, and shows whereabouts of the stray light when the laser beam from the laser diode corresponding to black is reflected on the 2nd ftheta lens. It is a schematic sectional drawing of the optical scanning device concerning other conventional examples, and shows whereabouts of the stray light when the laser beam from the laser diode corresponding to magenta is reflected on the 2nd ftheta lens.

Explanation of symbols

1 Optical scanning device 3 (3k, 3c, 3m, 3y)
Photoconductor drum (photoconductor)
61 Non-reflective member 71 (71k, 71c, 71m, 71y)
Laser diode (light source)
74 Polygon mirror (rotating polygon mirror)
76 (76k, 76c, 76m, 76y)
Reflection mirror 76A Main optical path reflection use area 76B Main optical path reflection nonuse area 77 (77k, 77c, 77m, 77y)
Second fθ lens (fθ lens)
A Image forming apparatus G, G ′ Main optical path X Main scanning direction Y Direction orthogonal to main scanning direction

Claims (10)

A light source that emits laser light;
A rotary polygon mirror that deflects and scans laser light from the light source;
A reflecting mirror that reflects the laser beam reflected by the reflecting surface of the rotating polygon mirror and scanned in the main scanning direction;
An fθ lens that transmits the laser light reflected by the reflection mirror and enters the surface of the photoreceptor, and
The main optical path reflection non-use area adjacent to the main optical path reflection use area used for reflection of the main optical path of the laser light scanned in the main scanning direction in the reflection mirror is provided by a non-reflective member that suppresses reflection of the laser light An optical scanning device which is masked. The optical scanning device according to claim 1.
As the reflection mirror masked by the non-reflective member, a reflection mirror at a position where the re-reflection distance of stray light from the fθ lens is long and the re-reflection distance of stray light to the rotary polygon mirror is short is applied. An optical scanning device. The optical scanning device according to claim 1 or 2,
The optical scanning apparatus according to claim 1, wherein the main optical path reflection non-use area is provided adjacent to a direction perpendicular to the main scanning direction of the main optical path reflection use area on the reflection mirror. In the optical scanning device according to any one of claims 1 to 3,
The main optical path reflection use area is located at the approximate center of the direction perpendicular to the main scanning direction on the reflection mirror,
2. The optical scanning device according to claim 1, wherein the main optical path reflection non-use area is provided adjacent to both sides of the main optical path reflection use area perpendicular to the main scanning direction on the reflection mirror. In the optical scanning device according to any one of claims 1 to 3,
The main optical path reflection use area is located on one side orthogonal to the main scanning direction on the reflection mirror,
The optical scanning apparatus, wherein the main optical path reflection non-use area is provided adjacent to the other side orthogonal to the main scanning direction of the main optical path reflection use area on the reflection mirror. In the optical scanning device according to any one of claims 1 to 3,
The main optical path reflection use area is curved with respect to the main scanning direction on the reflection mirror,
The optical scanning device, wherein the main optical path reflection non-use area is provided adjacent to each other along both sides orthogonal to the main scanning direction of the main optical path reflection use area on the reflection mirror. In the optical scanning device according to any one of claims 1 to 6,
The non-reflective member is formed of a sheet member having a surface roughness for diffusing the laser light. In the optical scanning device according to any one of claims 1 to 6,
The non-reflective member is formed of a material having a color with low reflectivity. In the optical scanning device according to any one of claims 1 to 6,
The optical scanning device, wherein the non-reflective member is a coating agent to be coated on the reflection mirror.   An image forming apparatus comprising the optical scanning device according to claim 1.

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