JP5127615B2 - Optical scanning device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an optical scanning device provided in an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer.

  An optical scanning device provided in a conventional image forming apparatus is shown in FIG. This optical scanning device includes a light source (not shown) that emits laser light based on image information, and a deflector 100 (hereinafter, polygon mirror) that performs deflection scanning. The polygon mirror 100 is rotationally driven by a motor (not shown) (hereinafter, polygon motor). In addition, the first lens 101, the second lens 102 (102a, 102b) for spotting the laser beam at a constant speed and on the drum, and a plurality of folding mirrors 103 (103a-103d) for reflecting the beam in a predetermined direction. ), A dust-proof glass 104 is provided. The optical scanning device is provided with an upper lid 106 for shielding the inside and the outside of the optical box 105 for storing the above-described components.

  In a color image forming apparatus as shown in FIG. 10, a plurality of image stations 110 (110Y, 110M, 110C, 110K) are provided. Each image station 110 includes a photosensitive drum 111 (111Y, 111M, 111C, 111K) and a developing device 112 (112Y, 112M, 112C, 112K).

  The process of forming an electrostatic latent image will be described by taking as an example the case of forming an electrostatic latent image on the photosensitive drum 111C. The laser light emitted from the light source is deflected and scanned by the polygon mirror 100. The laser beam subjected to the deflection scan forms an electrostatic latent image on the photosensitive drum 111C through the first lens 101, the folding mirror 103a, the second lens 102a, the folding mirror 103b, the folding mirror 103d, and the dustproof glass 104. The electrostatic latent image formed on the photosensitive drum 111C is visualized by the developing device 112C, and transferred to the recording material P via the recording material P or the intermediate transfer belt 113 by a transfer device (not shown). The toner image transferred to the recording material P is fixed by a fixing device (not shown), and image formation is completed.

  The conventional electrophotographic image forming apparatus has a problem that the optical box is thermally deformed by heat generated by the rotation of the polygon mirror 100, and is shifted to the scanning line, bent, or tilted. The exposure position of the laser beam on the photosensitive drum 111 fluctuates due to the thermal deformation of the optical box or the refractive index change due to the thermal deformation of the lens arranged in the optical scanning device, and various characteristics such as the irradiation position and tilt change. . In particular, in the case of a color image forming apparatus, a so-called color misregistration phenomenon occurs in which lines that should overlap each other color do not overlap due to scanning line misalignment, bending, and inclination. When color misregistration occurs, image quality deteriorates.

  Here, the color shift due to thermal deformation of the optical scanning device will be described in detail. When an electrostatic latent image is formed by an optical scanning device, heat is generated by a current flowing in a motor coil or IC when the polygon mirror 100 is rotated. These heats are diffused in the optical scanning device by the air flow generated by the rotation of the polygon mirror 100, and each part of the scanning device including the optical box is thermally expanded. Laser light from an optical scanning device provided in a copying machine or a printer is irradiated on the photosensitive drum 111 through the folding mirror 103 and various optical lenses. For this reason, when the optical component itself or the optical component undergoes thermal deformation due to slight thermal fluctuation in the optical box, the scanning line is displaced, bent, or tilted as a result.

  FIG. 11 is a diagram schematically showing the color misregistration caused by the above-described temperature rise caused by the shift, bend, and tilt of the scanning line in the color image forming apparatus. The amount of color misregistration in the figure is greatly shown for easy understanding. A solid line portion at a substantially central portion on the scanning line in FIG. 11 indicates an optical center position in each color.

  The scanning line fluctuates due to thermal expansion of each element of the image forming apparatus, and a magnification and a writing position are generated in the main scanning direction, and an irradiation position, inclination, and bending are generated in the sub-scanning direction. Further, in the main scanning direction, the amount of expansion and contraction of the image near each image height varies as the optical center position varies.

As a countermeasure against heat in the optical scanning device, the following method has been proposed (for example, Patent Document 1). Patent Document 1 discloses a configuration in which a standing wall having an opening through which a light beam passes is provided between a polygon mirror and a scanning imaging optical system in order to suppress the influence of heat of a motor that drives the polygon mirror. ing. According to this, since the heat-generated wind generated by driving the polygon mirror does not directly hit the imaging optical system, distortion of the imaging optical system can be suppressed and image quality deterioration can be suppressed.
JP 2007-79515 A

  However, the optical scanning device of Patent Document 1 reduces thermal expansion of optical components (optical lenses and mirrors). As described above, the cause of the optical scanning device that generates the shift, bend, and tilt of the scanning line due to the temperature rise is not only the optical component but also the deformation of the optical box that supports the optical component. Therefore, it is necessary to take measures not only for measures against temperature rise for optical components but also for deformation of the optical box holding the optical components.

  As shown in FIG. 12, when the polygon mirror 100 rotates, a wind is generated toward the outside of the plane horizontal to the rotation axis of the polygon mirror 100. As described above, since heat is generated from the motor when the polygon mirror 100 is rotated, this wind is heated. As described above, when the wall for blocking the wind hitting the optical component is provided between the polygon mirror 100 and the optical component, the heated wind hits the wall, and the temperature of the wall rises and the wall is deformed. When this wall is deformed, this deformation affects the optical box, and the optical box is thermally deformed. As a result, the scanning line shifts, bends, and tilts due to the deformation of the optical box.

  Further, in an optical scanning device provided in an actual image forming apparatus, a rib-shaped reinforcing member is molded integrally with the optical box in the optical box or the reinforcing member is fixed to the optical box at a plurality of fixing points, and the rigidity of the optical box is increased. And the deformation of the optical box due to heat is suppressed. The optical box is deformed by the deformation of the reinforcing members caused by the heated wind on these reinforcing members. Thereby, the scanning line shifts, bends, and tilts due to the deformation of the optical box.

In view of the above problems, an optical scanning device according to a first aspect of the present invention includes a light source that emits light based on image data, a rotary polygon mirror that deflects light emitted from the light source, and a rotary drive of the rotary polygon mirror. A deflecting unit including a driving unit, an optical box to which the light source and the deflecting unit are attached,
The standing portion that is provided integrally with the optical box and that stands up from a position adjacent to the placement position of the deflection means of the optical box, and the deflection so as to cover at least a part of the standing portion. A wind-shielding member provided between the means and the standing part, the wind-shielding member being extendable with respect to the standing part by being fixed to the optical box at one location. It is characterized by that.

According to the optical scanning device of the first aspect, the wind shielding member that covers the standing portion standing from the position adjacent to the arrangement position where the deflecting means of the optical box is arranged is fixed to the optical box at one location. Therefore, the optical box can be prevented from being deformed.

(First embodiment)
An optical scanning device according to this embodiment will be described with reference to FIGS.

  FIG. 1 is a schematic diagram of an image forming apparatus including an optical scanning device according to the present embodiment. FIG. 2 is an overall perspective view of the optical scanning device according to this embodiment. FIG. 3 is a perspective view around the polygon mirror of the optical scanning device shown in FIG. In FIGS. 2 and 3, a lid member to be described later is not shown for the explanation of the internal components of the optical scanning device.

  First, FIG. 1 will be described. The image forming apparatus in the present embodiment includes an optical scanning device 11, image forming units 12 (12 Y, 12 M, 12 C, and 12 K) corresponding to the respective colors, and an intermediate transfer belt 13. The image forming unit 12 includes a photosensitive drum 14 (scanned body, 14Y, 14M, 14C, and 14K), a charging device 15 (15Y, 15M, 15C, and 15K), and a developing device 16 (16Y, 16M, 16C, and 16K). Is provided. As is apparent from FIG. 1, the image forming apparatus according to the present embodiment employs a method in which the optical scanning device 11 performs exposure from the lower surface side of the image forming unit, and the optical scanning device 11 moves to the upper photosensitive drum 14. Irradiate the beam.

  Based on the input image data, the optical scanning device 11 scans the photosensitive drum 14 uniformly charged by the charging device 15 to form an electrostatic latent image. The electrostatic latent image is visualized by the developing device 16 using toner. The toner image on the photosensitive drum 14 is transferred to the intermediate transfer belt 13 by a transfer device (not shown) at the primary transfer portion T (Ty, Tm, Tc, Tk). The toner image on the intermediate transfer belt 13 is transferred to the recording material P conveyed from the paper supply unit 17 by a transfer device (not shown) at the secondary transfer unit t. The toner image transferred to the recording paper P is heat-fixed on the recording material P by the fixing device 18 and discharged to the paper discharge unit 19.

  Next, the optical scanning device 11 provided in the image forming apparatus shown in FIG. 1 will be described with reference to FIGS. 2 is provided with a plurality of light sources 21 corresponding to the respective colors, and laser light is emitted from the light sources 21 according to image data. Laser light emitted from the light source 21 is deflected and scanned by a deflector 22 (hereinafter referred to as a polygon mirror 22). The polygon mirror 22 is driven by a motor. A lens for guiding the laser beam is arranged on the photosensitive drum so as to face the reflecting surface of the polygon mirror 22. This lens is provided with, for example, an optical lens that performs constant-speed scanning while forming an image. In this embodiment, the optical lens is composed of a plurality of lenses of the first optical lens 23 (23a, 23b) and the second optical lens 24 (24a to 24d). However, the optical lens is an optical element that forms an optical system. The number is not limited to this.

  The two lenses of the first optical lenses 23a and 23b are shared by beams corresponding to yellow and magenta, cyan and black, and the second optical lens is arranged for each color. Further, folding mirrors 25 (25a to 25f) for guiding the laser beam subjected to deflection scanning to each photosensitive drum are disposed on the optical path of each beam. Each of the above components is fixed to each mounting portion of the optical box (positioning means) 26 and positioned.

  As shown in FIG. 2, a wall 27 is provided around the polygon mirror 22 to block hot air generated by the rotation of the polygon mirror 22 from hitting the first optical lens 23. The wall 27 is integrally formed with the wall 27 in order to ensure the rigidity of the optical scanning device 11. The optical scanning device 11 using the method of scanning in the opposite direction with respect to the polygon mirror 22 as in this embodiment is generally an optical scanning device in which an optical path is moved a plurality of times by a folding mirror 25 in order to realize a compact product. 11 is used to fold the light beam. Therefore, there are many optical components arranged in the optical scanning device 11, and the rigidity of the optical box 26 is insufficient. As a countermeasure, a rib-like wall 27 having a height extending from the bottom surface of the optical box 26 to the ceiling (lid member) is integrally formed with the optical box 26 to increase the rigidity of the optical box 26.

  However, in order to secure the optical path of the light deflected by the polygon mirror 22, there are restrictions on the places where ribs having a height can be arranged. Usually, the polygon mirror 22 is provided at the center of the optical scanning device 11. Therefore, in order to effectively increase the rigidity of the optical box 26, it is preferable to provide a rib-shaped wall around the polygon mirror 22. In the optical scanning device 11 of the present embodiment, a wall 27 for ensuring strength is provided around the polygon mirror 22 in a portion excluding the deflection scanning region to ensure rigidity. An opening 28 is provided in the wall 27, and laser light passes from the opening 28 toward the first optical lens 23.

In addition to this, reflected light from the incident surface or the exit surface of the optical lenses 23 and 24 returns to the wall 27 and returns to the polygon mirror 22, and the reflected light enters the opposing optical lenses 23 and 24. The so-called flare light prevention and polygon mirror 22 dust prevention effects are provided.

  However, by providing the wall 27 as described above, heat tends to concentrate around the polygon mirror 22 due to heat generated by the driving device (motor or IC) that rotates the polygon mirror 22. As described above, the airflow in the vicinity of the reflection surface when the polygon mirror 22 rotates is directed to the outside of the rotation axis (see FIG. 12). For this reason, the wall 27 is exposed to the heat-generated wind generated by the rotational drive of the polygon mirror 22. Thereby, the wall 27 is thermally expanded and deformed, and as a result, the optical box 26 in which the wall 27 is integrally formed is deformed. Therefore, in the present embodiment, the windshield member 29 for preventing the wind generated by the rotation of the polygon mirror 22 from directly hitting the wall 27 is arranged along the wall 27 around the polygon mirror 22 and formed around the polygon mirror 22. The temperature rise of the wall 27 is suppressed.

  Hereinafter, the windshield member 29 will be described in more detail. FIG. 3 is a view when the windshield member 29 is installed in the optical scanning device 11. The windshield member 29 is installed along the surface of the wall 27 on the side facing the polygon mirror 22. As shown in FIG. 4, the windshield member 29 is configured to contact the wall 27 with a substantially linear contact portion 291. By adopting such a configuration, an air layer A (gap) can be formed in a large portion between the wall 27 and the windshield member 29. Thereby, even if the temperature of the windshield member 29 rises, the heat conduction to the wall 27 can be suppressed to a small extent, so that the thermal deformation of the wall 27 can be suppressed.

  Further, when the contact surface between the windshield member 29 and the wall 27 is increased, the heat of the windshield member 29 is transmitted to the wall 27 due to heat conduction, leading to thermal deformation of the optical box 26. On the other hand, in the optical scanning device 11 of the present embodiment, the windshield member 29 is fixed to the optical box 26 at one place, and the windshield member 29 is not fixed to the optical box 26 or the wall 27 at other places. . In other words, the windshield member 29 is provided in the optical box 26 so as to be extendable and contractable from one fixed place independently of the optical box 26 (including the wall 27). Thereby, even if the windshield member 29 is thermally expanded, the force generated in the windshield member 29 during expansion can be prevented from acting on the wall 27 as much as possible.

  As another support method, a non-contact state away from the wall 27 may be used, and the same effect can be obtained even if a substantially point-like contact is provided instead of a substantially linear shape. Further, the windshield member 29 has a height substantially equal to or higher than the wall 27 in order to prevent wind from hitting the wall 27 of the optical box 26.

  Further, as shown in FIG. 5, the windshield member 29 is configured to face one surface of the lid member 51. A gap B is formed between the windshield member 29 and the lid member 51. This gap is a gap for diffusing the wind that has been directed upward after the air current from the polygon mirror 22 hits the windshield member 29 to the surroundings. By providing this gap, the heat circulates in the optical scanning device 11 without spreading around the polygon mirror 22, the temperature increase amount is made uniform, and local deformation due to heat concentration can be suppressed. it can.

  The left figure of FIG. 6 shows the temperature of the wall 27 depending on the presence or absence of the windshield member 29, and the right figure shows the temporal change amount (deviation from the ideal scan line) of the scanning line depending on the presence or absence of the windshield member 29. As can be seen from FIG. 6, by providing the windshield member 29, the temperature rise of the wall 27 is suppressed, and as a result, the amount of change in the scanning line is suppressed.

  The windshield member 29 is also provided on the back side of the surface of the wall 27 that faces the reflecting surface of the polygon mirror. As shown in FIG. 7, the wind generated by the rotation of the polygon mirror 22 flows from the upstream side to the downstream side in the scanning direction. Therefore, on the downstream side in the scanning direction, the wind that flows out from the gap with the lid member 51 and the opening 28 flows to the wall surface on the back side of the wall surface facing the polygon mirror 22 as indicated by the arrow in FIG. Therefore, on the downstream side in the scanning direction, it is not possible to suppress the temperature rise of the wall simply by shielding the wall surface facing the polygon mirror 22. Therefore, as shown in FIG. 7, a second windshield member 72 that shields the back surface of the wall 27 that faces the reflecting surface of the polygon mirror 22 is provided. Thereby, the thermal expansion of the wall 27 can be suppressed, and a further effect can be expected. In particular, since hot air having a high temperature hits the vicinity of the opening that is close to the polygon mirror 22, the deformation of the wall 27 can be suppressed by providing the hot air. The windshield member 29 and the second windshield member 72 may be formed of the same member, or may be formed of different members.

  Further, in the wall 27 formed around the polygon mirror 22, there are a portion that greatly affects the deformation of the optical box 26 and a portion that does not. This is due to differences in the strength of each part of the wall 27, heat distribution (difference in temperature rise), and the like. Therefore, as shown in FIG. 8, the windshield member 29 may not be configured to cover the entire surrounding wall surface covering the polygon mirror 22 but may be configured to cover only a part. As an example, FIG. 8 illustrates a configuration that covers the surface of the wall 27 in the vicinity of the IC 81, the capacitor 82, and the like mounted on the polygon mirror drive circuit board. In this case, there is an effect of shielding not only the motor coil but also the portion where the heat from the IC 81 and the capacitor 82 hits the wall surface by the air flow.

  Here, although the windshield member 29 is fixed to the optical box 26, the windshield member 29 is fixed to the optical box 26 at one location. In FIG. 8, fastening is performed with one screw 83. In this case, when the two or more points are fixed, deformation of the windshield member 29 between the two points deforms the optical box 26. Therefore, the windshield member 29 is fixed to the optical box 26 at one point, and the other support portions are only in contact with the wall 27, so that even if the windshield member 29 is deformed, the deformation can be released. Yes.

  There are other fixing methods besides screw fixing. For example, screws may be inserted between the optical box 26 and the elastic member with an elastic member, or inserted into a protrusion, groove, hole, or the like. In the case of a fastening method that is not used, it is not counted as a fastening part.

  The windshield member 29 of the present embodiment is preferably made of a resin member or a metal member. In general, the resin member has a lower heat absorption effect than the metal member, but has a higher heat insulation effect. In addition, the metal member has a lower heat insulation effect than the resin member, but has a higher endothermic effect. In the case of using a resin member, by utilizing this heat insulating effect, the speed at which the scanning line is displaced, bent, or tilted can be made more gradual. In the case of using a metal member, by utilizing this endothermic effect, the speed at which the scanning line shifts, bends, and tilts can be made gentler.

  In the present embodiment, the above-described configuration is formed by performing a drawing process on a part of the metal member, and an air layer A is formed between the windshield member 29 and the wall 27, thereby ensuring a heat insulation effect and an endothermic effect. Is secured. As a matter of course, the effect increases as the thickness of the metal member increases in order to secure the heat capacity.

  As another method, as shown in FIG. 9, the windshield member 29 may be configured by combining a metal member 91 and a resin member 92. 9 has a configuration in which a metal member 91 such as aluminum is provided on the front side, and a resin member 92 is used on the back side (surface facing the wall 27). By using this configuration, it is possible to achieve both the heat absorption effect by the metal member 91 and the heat insulation effect by the resin member 92.

  Although the windshield member 29 shown in FIG. 9 is configured so as not to come off by fitting the metal member 91 to the resin member 92 with the protrusions, the windshield member 29 may be fixed using screws. In that case, since there is no problem that the windshield member 29 is deformed, the number of fastening screws is not necessarily one. However, the location fixed to the optical box 26 needs to be one location.

  Note that the shape of the windshield member 29 is not necessarily the illustrated shape, and may be any shape as long as the same effect can be obtained. Further, the windshield member 29 need not be a single component even when only a resin material or a metal material is used, and may be configured by a plurality of components. Moreover, when comprised in such a some component, if the location attached to the optical box 26 is one location, members may be fixed in multiple locations.

  Further, although the optical scanning device 11 exemplified in the present embodiment uses a method of scanning in the opposite direction with respect to the polygon mirror 22, it does not need to be a method of scanning in the opposite direction. For example, the optical scanning device 11 may be a system in which a polygon mirror 22 is provided for each color photosensitive drum 14 and exposure is performed independently.

  In the present embodiment, the configuration in which the wall 27 is covered with the windshield member 29 has been described. However, the polygon mirror 22 and the optical lenses 23 and 24 may be separated by the windshield member 29 without providing the wall 27. In this case, the windshield member 29 covers the polygon mirror 22 by providing a surface facing the polygon mirror 22. It has an opening 28 through which the laser light passes. Thereby, since it is possible to prevent the heated wind from directly hitting the optical lens disposed in the vicinity of the polygon mirror 22, it is possible to suppress the shift, bend, and inclination of the scanning line due to the thermal deformation of the optical lens.

  Further, the windshield member 29 at this time is fixed to the optical box 26 at one place, and is held in the housing by making point contact or line contact with the optical box 26 at a position other than the fixed position. Thereby, even if the windshield member 29 is thermally deformed, the amount of deformation can be released.

It is sectional drawing of an image forming apparatus provided with the optical scanning device concerning this embodiment. It is a perspective view of the optical scanning device concerning this embodiment. It is an enlarged view of the optical scanning device concerning this embodiment. It is a figure which shows the positional relationship of the wall and windshield member of the optical scanning device concerning this embodiment. It is sectional drawing of the optical scanning device concerning this embodiment. It is a figure explaining the effect of this embodiment. It is a figure when the 2nd windshield member is provided in the optical scanning device concerning this embodiment. It is a figure which shows the fixing method of the windshield member of the optical scanning device concerning this embodiment. It is a figure when a metal member and a resin member are used for the windshield member of the optical scanning device concerning this embodiment. It is sectional drawing of an image forming apparatus provided with the conventional optical scanning device. FIG. 10 is a diagram illustrating color misregistration in a conventional image forming apparatus. It is a figure explaining the airflow near the polygon mirror of the conventional optical scanning device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Optical scanning device 12 Developing device 13 Intermediate transfer belt 14 Photosensitive drum 21 Light source 22 Deflector (polygon mirror)
23 first optical lens 24 second optical lens 25 folding mirror 26 optical box 27 wall 28 opening 29 windshield member 51 lid member 72 second windshield member 81 IC
82 Capacitor 83 Screw A Air layer B Gap Ty, Tm, Tc, Tk Primary transfer part t Secondary transfer part

Claims (10)

A light source that emits light based on image data;
A deflecting means comprising a rotating polygon mirror for deflecting light emitted from the light source, and a driving means for rotationally driving the rotating polygon mirror ;
An optical box to which the light source and the deflecting means are attached;
An erected portion that is provided integrally with the optical box and is erected from a position adjacent to a position where the deflecting means of the optical box is disposed;
A wind-shielding member provided between the deflecting means and the standing part so as to cover at least a part of the standing part, and fixed by being fixed to the optical box at one place. An optical scanning device comprising: a wind-shielding member that can expand and contract with respect to the portion . The optical scanning device according to claim 1, wherein the standing portion is a reinforcing member that stands up from the bottom of the optical box so as to surround the deflecting unit and reinforces the periphery of the deflecting unit . Optical means for guiding the light deflected by the deflecting means to a scanned object;
The standing portion is a wall provided with an opening that stands from between a position where the deflecting means is disposed and a position where the optical means is disposed in the optical box and allows the light deflected by the deflecting means to pass therethrough. the optical scanning device according to claim 1 or 2, characterized in that. 4. The optical scanning device according to claim 1, wherein a gap is formed between the standing portion and the wind shielding member . 5. The light source includes a first light source that emits a first light beam and a second light source that emits a second light beam,
The rotating polygon mirror deflects the first light beam and the second light beam in opposite directions with the rotating polygon mirror interposed therebetween,
The optical means includes a first lens that guides the first light beam deflected by the rotating polygon mirror to a first object to be scanned, and a second light beam deflected by the rotating polygon mirror. A second lens that leads to the object to be scanned,
The upright portion is reflected by the first lens and is reflected by the second lens and is reflected by the second lens, and the first wall that shields the reflected light of the first light beam toward the second lens. 4. The optical scanning device according to claim 3 , further comprising: the second wall that shields the reflected light of the second light beam toward the first lens . A lid member for closing the optical box;
The wind-shielding member includes a first surface facing the rotary polygon mirror, and a second surface provided by bending from the first surface to a side different from the side where the deflecting means is disposed. With
3. The optical scanning device according to claim 2, wherein an air flow path through which an air flow generated by the rotation of the rotary polygon mirror passes is formed by the second surface and the lid member . The optical scanning device according to claim 3 , wherein the wind shield member covers at least a part of a surface of the standing portion on the optical means side . The air shield member may be made of a resin member, the optical scanning apparatus according to any one of claims 1 to 7. 4. The light according to claim 3 , wherein the wind- shielding member is a metal member on a side where the wind generated by the rotation of the rotary polygon mirror strikes, and a side facing the wall is a resin member. Scanning device. An electrophotographic image forming apparatus comprising an optical scanning device according to any one of claims 1 to 9.

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