JP2019028382A - Optical scanner and image forming apparatus - Google Patents

Abstract

To provide an optical scanner that can reduce, compared with a prior art, the amount of air entering the inside of the optical scanner from an opening for a deflected and scanned light beam to pass through in association with rotation of deflection and scanning means.SOLUTION: An optical scanner 50 comprises: a semiconductor laser 1; a polygon mirror 4 that deflects and scans a laser beam L emitted from the semiconductor laser 1; and an optical box 9 and a cover 10 that accommodates the polygon mirror 4, the optical box 9 and cover 10 including an opening 11 for the laser beam L deflected and scanned by the polygon mirror 4 to pass through. In the opening 11, a width in a direction orthogonal to a scanning direction of the polygon mirror 4 changes according to a position in the scanning direction.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an optical scanning apparatus suitable for an image forming apparatus such as an electrophotographic copying machine or a laser beam printer that forms an image on a recording medium using an electrophotographic process, and an image forming apparatus including the optical scanning apparatus.

  An image forming apparatus having an electrophotographic process is equipped with an optical scanning device that performs optical writing by scanning a light beam on the surface of a photoreceptor. In many of these optical scanning devices, a plurality of optical members such as a polygon mirror (deflection scanning means) for deflecting and scanning a light beam emitted from a light source such as a semiconductor laser and an fθ lens as a scanning lens are accommodated in an optical box. Yes.

  Further, as in the configuration described in Patent Document 1, the optical box of the optical scanning device is provided with an opening through which the light beam passes when the light beam is irradiated onto the photosensitive member.

JP 2014-134711 A

  However, in the configuration described in Patent Document 1, when the polygon mirror rotates at high speed, air containing dust enters the optical scanning device from the opening of the optical box. In this case, for example, if dust in the air adheres to the reflection surface of the polygon mirror, the reflectance of the reflection surface decreases, and if it adheres to the fθ lens, the light transmittance decreases. As a result, the light amount of the light beam applied to the photoconductor is reduced, which may cause image defects such as uneven density of the image.

  Therefore, the present invention has been made in view of such a current situation, and the amount of air that enters the optical scanning device from the opening through which the deflected and scanned light beam passes with the rotation of the deflection scanning means. An object of the present invention is to provide an optical scanning device that can be reduced as compared with the prior art.

  In order to achieve the above object, a typical configuration of an optical scanning device according to the present invention includes a light source, a deflection scanning unit that deflects and scans a light beam emitted from the light source, and a housing member that houses the deflection scanning unit. A receiving member having an opening through which the light beam deflected and scanned by the deflection scanning unit passes, wherein the width of the opening in a direction perpendicular to the scanning direction of the deflection scanning unit is It changes depending on the position in the scanning direction.

  According to the above configuration, in the optical scanning device, the amount of air that enters the optical scanning device from the opening through which the deflected and scanned light beam passes is reduced as compared with the prior art as the deflection scanning unit rotates. be able to.

1 is a schematic cross-sectional view of an image forming apparatus. It is a perspective view of an optical scanning device. It is a schematic diagram which shows the tool which adjusts the position of a semiconductor laser. It is a schematic diagram for demonstrating the inclination of the scanning line of a polygon mirror. It is a front view of an optical scanning device. It is sectional drawing of an optical scanning device.

(First embodiment)
<Image forming apparatus>
First, the overall configuration of the image forming apparatus A including the optical scanning device according to the first embodiment of the present invention will be described with reference to the drawings together with the operation during image formation.

  As shown in FIG. 1, the image forming apparatus A includes an image forming unit that transfers a toner image onto a sheet, a sheet feeding unit that supplies the sheet toward the image forming unit, and a fixing unit that fixes the toner image on the sheet. .

  The image forming unit includes a process cartridge P that can be attached to and detached from the image forming apparatus A main body, an optical scanning device 50, and a transfer roller 85. The process cartridge P includes a rotatable photosensitive drum 81 (photosensitive member), a charging roller 82, a developing device 84, and the like. In addition, an optical bench 83 is provided as a part of the casing of the image forming apparatus A at the opposed portion of the process cartridge P, and the optical scanning device 50 is installed on the optical bench 83.

  At the time of image formation, when a control unit (not shown) receives an image forming job signal, the sheet S stacked and stored in the sheet stacking unit 86 by the feeding roller 87 and the conveying roller 88 is sent out to the image forming unit.

  On the other hand, in the image forming unit, a bias is applied to the charging roller 82, whereby the surface of the photosensitive drum 81 in contact with the charging roller 82 is charged. Thereafter, a laser beam L is emitted from a semiconductor laser 1 (see FIG. 3) provided in the optical scanning device 50, and the photosensitive drum 81 is irradiated with the laser beam L according to image information. As a result, the potential of the photosensitive drum 81 is partially reduced, and an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 81.

  Thereafter, a bias is applied to the developing sleeve 92 provided in the developing device 84, whereby toner is attached to the electrostatic latent image formed on the surface of the photosensitive drum 81 from the developing sleeve 92, thereby forming a toner image.

  Next, the toner image formed on the surface of the photosensitive drum 81 is sent to a transfer nip portion formed between the photosensitive drum 81 and the transfer roller 85. When the toner image arrives at the transfer nip portion, a bias having a polarity opposite to the toner charging polarity is applied to the transfer roller 85, and the toner image is transferred to the sheet S.

  Thereafter, the sheet S to which the toner image has been transferred is sent to the fixing device 89, where it is heated and pressurized at the fixing nip formed between the heating portion and the pressure portion of the fixing device 89, and the toner image is transferred to the sheet S. To be established. Thereafter, the sheet S is discharged to the discharge tray 91 by the discharge roller 90.

<Optical scanning device>
Next, the configuration of the optical scanning device 50 will be described.

  FIG. 2 is a perspective view of the optical scanning device 50 with the cover 10 removed. As shown in FIG. 2, the optical scanning device 50 includes a semiconductor laser 1 (see FIG. 3), a laser support 12 that supports the semiconductor laser 1, and an anamorphic lens 2 in which a collimator lens and a cylindrical lens are integrally formed. Further, it has an aperture stop 3, a polygon mirror 4 (deflection scanning means), a deflector 5 for rotationally driving the polygon mirror 4, a BD sensor 6 (synchronization signal detection means), and an fθ lens 7.

  These optical members are accommodated in the optical box 9. A cover 10 is attached to the upper surface of the optical box 9 from the viewpoint of dust prevention and the like. That is, the optical box 9 and the cover 10 are storage members that store the optical members described above. Further, the optical box 9 and the cover 10 form an opening 11 through which the laser beam L passes when the photosensitive drum 81 is irradiated. The opening 11 may be formed in either the optical box 9 or the cover 10.

  Next, the basic operation of the optical scanning device 50 will be described. First, when the semiconductor laser 1 emits a laser beam L, the laser beam L is converted into substantially parallel light or convergent light in the main scanning direction, which is the rotational axis direction of the photosensitive drum 81, by the anamorphic lens 2, and the sub beam orthogonal to the main scanning direction. In the scanning direction, the light is converged light.

  Next, the laser beam L passes through the aperture stop 3 and is limited in its beam width, and forms an image on the reflecting surface 4a of the polygon mirror 4 in a focal line shape extending in the main scanning direction. Next, when the polygon mirror 4 is rotated by the deflector 5, the laser beam L is deflected and scanned while being reflected by the reflecting surface 4a.

  The laser beam L deflected and scanned by the polygon mirror 4 first enters the BD sensor 6. At this time, the image writing timing to the photosensitive drum 81 is determined based on the signal output from the BD sensor 6.

  Next, the deflection-scanned laser beam L enters the fθ lens 7. The fθ lens 7 is a lens for forming an image of the laser beam L on the photosensitive drum 81, condenses the laser beam L so as to form a spot on the photosensitive drum 81, and scans the spot. Is designed to be kept at a constant speed. In order to obtain such characteristics, the fθ lens 7 is formed of an aspheric lens. The laser beam L that has passed through the fθ lens 7 passes through the opening 11 formed by the optical box 9 and the cover 10 and is imaged and scanned on the photosensitive drum 81.

  Next, when the polygon mirror 4 is further rotated, the laser beam L is scanned on the photosensitive drum 81 in the main scanning direction. Further, the photosensitive drum 81 is rotationally driven, whereby the laser beam L is scanned in the sub-scanning direction. In this way, an electrostatic latent image is formed on the surface of the photosensitive drum 81.

<Position adjustment method of semiconductor laser>
Next, a method for adjusting the position of the semiconductor laser 1 will be described.

  FIG. 3 is a schematic diagram showing a tool for adjusting the position of the semiconductor laser 1. Here, FIG. 3A is a diagram of the semiconductor laser 1 viewed from the direction of the arrow y, and FIG. 3B is a diagram of the semiconductor laser 1 viewed from the direction of the arrow z.

  As shown in FIG. 3, as a tool for adjusting the position of the semiconductor laser 1, a spot observation system 13, such as a CCD camera, a chuck 14, and a light guide 15 are used.

  The chuck 14 holds the laser support 12 into which the semiconductor laser 1 is press-fitted. The chuck 14 is configured to be displaceable in three directions indicated by arrows x, y, and z by a three-axis stage (not shown). That is, the chuck 14 can move the position of the semiconductor laser 1 by moving the laser support 12 by the three-axis stage.

  The light guide 15 is connected to an illumination light source (not shown), and emits ultraviolet rays UV for curing the photocurable adhesive.

  Next, a method for adjusting the position of the semiconductor laser 1 using the above-described position adjusting tool will be described.

  First, the semiconductor laser 1 is set at a predetermined position by the three-axis stage of the chuck 14. Next, a laser beam L is emitted from the semiconductor laser 1 by a semiconductor laser light emitting circuit (not shown).

  The laser beam L emitted from the semiconductor laser 1 passes through an optical member such as the anamorphic lens 2, is deflected and scanned by the polygon mirror 4, and forms an image on the spot observation system 13. While observing the image formation state of the laser spot on the spot observation system 13, the semiconductor laser 1 is moved by moving the three-axis stage of the chuck 14, so that the laser beam L on the spot observation system 13 in the sub-scanning direction. Adjust the irradiation position.

  After adjustment of the irradiation position, a photo-curing adhesive (not shown) is applied, and the light guide 15 is irradiated with ultraviolet rays UV to cure the photo-curing adhesive, and the laser support 12 is fixed to the optical box 9. . In this way, the position of the semiconductor laser 1 is adjusted.

  By adjusting the position of the semiconductor laser 1 in a state where each optical member is mounted on the optical box 9 in this manner, the position at the time of position adjustment is taken into account in consideration of manufacturing errors and the like of each optical member including the optical box 9. The irradiation position of the laser light beam L in the sub-scanning direction can be adjusted.

<Inclination of polygon mirror scanning line>
Next, the inclination of the scanning line of the polygon mirror 4 caused by the fθ lens 7 and the optical box 9 being inclined in the sub-scanning direction will be described.

  FIG. 4 is a schematic diagram for explaining the inclination of the scanning line of the polygon mirror 4. Here, in FIG. 4, a scanning line having no inclination with reference to the irradiation position in the sub-scanning direction of the laser beam L at the position C (0 mm image height) where the position adjustment of the semiconductor laser 1 is performed is defined as L2, and the sub-scanning direction. Let L2 ′ be a scanning line with a slope.

  In the present embodiment, in the scanning direction (main scanning direction) of the polygon mirror 4, the position C where the position adjustment of the semiconductor laser 1 described above is performed corresponds to the central portion of the image area on the photosensitive drum 81. And a position corresponding to the central portion of the opening 11.

  As shown in FIG. 4, at the position C (0 mm image height) where the position of the semiconductor laser 1 is adjusted, the position in the sub-scanning direction is between the scan line L2 having no tilt and the scan line L2 ′ having the tilt. Are the same. On the other hand, at positions z1 and z2 (+100 mm image height, −100 mm image height) shifted by ± 100 mm in the main scanning direction from the position C where the position of the semiconductor laser 1 is adjusted, there is an inclination with the scan line L2 having no inclination. A difference (x1, x2) occurs in the position in the sub-scanning direction between the scanning lines L2 ′.

  That is, at positions other than the position C (0 mm image height) at which the position of the semiconductor laser 1 is adjusted in the main scanning direction, the position in the sub-scanning direction of the scanning line L2 ′ with inclination is the sub-scanning of the scanning line L2 with no inclination. Deviation occurs with respect to the position in the direction. Further, the amount of deviation increases as the distance from the position C where the position of the semiconductor laser 1 is adjusted increases.

  Accordingly, at the position C where the position of the semiconductor laser 1 is adjusted, the width in the sub-scanning direction of the opening 11 through which the laser beam L passes satisfies the irradiation position standard in the sub-scanning direction including variations at the time of position adjustment. What is necessary is just to set it as the opening width to do. On the other hand, the width in the sub-scanning direction of the opening 11 at a position other than the position C where the position of the semiconductor laser 1 is adjusted in the main scanning direction is determined in consideration of the shift due to the inclination of the scanning line of the polygon mirror 4. It is necessary to make the opening width larger than the position C where the position of the laser 1 is adjusted.

<Opening>
Therefore, in this embodiment, the width in the sub-scanning direction of the opening 11 formed by the optical box 9 and the cover 10 is set as follows.

  FIG. 5 is a front view of the optical scanning device 50. As shown in FIG. 5, in this embodiment, the width of the opening 11 in the sub-scanning direction is set so that the central portion in the main scanning direction corresponding to the position C where the position of the semiconductor laser 1 has been adjusted is small, and from the central portion to the end. Set to increase toward the part. In other words, the width of the opening 11 in the direction orthogonal to the scanning direction of the polygon mirror 4 is changed according to the position in the scanning direction so as to increase from the center to the end in the scanning direction. That is, the width W1 in the sub-scanning direction at the center of the opening 11 in the main scanning direction is smaller than the width W2 in the sub-scanning direction at the end in the main scanning direction.

  As a result, the opening area of the opening 11 is set to be smaller than that of the conventional configuration in which the opening width of the opening 11 in the sub-scanning direction is constant in the main scanning direction. It is possible to approach the minimum area required for L to pass.

<About dust>
Next, dust that enters the optical scanning device 50 as the polygon mirror 4 rotates will be described.

  FIG. 6 is a cross-sectional view of the optical scanning device 50 taken along the line GG shown in FIG. As shown in FIG. 6, when the polygon mirror 4 rotates at high speed, air containing dust enters the optical scanning device 50 through the opening 11 and reaches each optical member through the path indicated by the arrow V. When dust contained in the air adheres to the polygon mirror 4 or the fθ lens 7, as described above, the amount of the laser beam L irradiated to the photosensitive drum 81 may decrease, and density unevenness may occur in the image.

  Here, in the present embodiment, as described above, the width of the opening 11 in the sub-scanning direction is changed according to the position in the main scanning direction, and the opening area of the opening 11 is changed to a laser beam compared to the conventional configuration. It is close to the minimum area required for L to pass. Thereby, when the polygon mirror 4 is rotated, the amount of air entering the optical scanning device 50 through the opening 11 is reduced. Accordingly, the air containing dust is prevented from reaching the optical members such as the polygon mirror 4 and the fθ lens 7, and the dust is less likely to adhere to these optical members. For this reason, it is possible to suppress the occurrence of image defects due to a decrease in the amount of the laser beam L irradiated onto the photosensitive drum 81.

  Further, since the opening area of the opening 11 can be reduced as compared with the conventional configuration, it is known that the motor sound generated with the rotation of the polygon mirror 4 leaks to the outside of the optical scanning device 50 through the opening 11. Than can be suppressed. Accordingly, it is possible to reduce the noise of the entire optical scanning device 50 and the image forming apparatus A.

1. Semiconductor laser (light source)
4. Polygon mirror (deflection scanning means)
9 ... Optical box (collection member)
10 ... Cover (collection member)
DESCRIPTION OF SYMBOLS 11 ... Opening part 50 ... Optical scanning device 81 ... Photosensitive drum (photosensitive body)
A: Image forming apparatus

Claims (3)

A light source;
Deflection scanning means for deflecting and scanning a light beam emitted from the light source;
A housing member for housing the deflection scanning means, and a housing member provided with an opening through which a light beam deflected and scanned by the deflection scanning means passes;
With
The optical scanning device according to claim 1, wherein the width of the opening in a direction perpendicular to the scanning direction of the deflection scanning unit changes according to the position in the scanning direction.   2. The optical scanning device according to claim 1, wherein a width of the opening in a direction orthogonal to the scanning direction increases from a central portion to an end in the scanning direction. In an image forming apparatus that forms a latent image by scanning a photosensitive member with a light beam, and develops the latent image to form an image.
An image forming apparatus comprising the optical scanning device according to claim 1 or 2 as a device for scanning the photosensitive member with a light beam.

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