JP6465312B2 - Light source driving circuit board mounted on optical scanning device and optical scanning device - Google Patents

Description

  The present invention relates to a light source driving circuit board mounted on an optical scanning device having a plurality of light sources, and an optical scanning device.

  In general, in an electrophotographic image forming apparatus, light emitted from a light source of an optical scanning device is deflected and scanned by a rotary polygon mirror to irradiate the surface of the image carrier, and this light irradiation irradiates the surface of the image carrier. The formed electrostatic latent image is developed by a developing device, and a toner image obtained by this development is heated and pressed by a fixing device and fixed on a recording sheet.

  Here, the optical scanning device mounted on the color image forming apparatus needs to be provided with the same number of light sources as the reference colors to be used (for example, four colors of black, cyan, magenta, and yellow). The light emitted from the plurality of light sources is deflected and scanned by a rotary polygon mirror, and then enters each image carrier corresponding to each light source (each color). Thus, in order for light emitted from a plurality of light sources to enter different image carriers, it is necessary to separate the optical paths of the light emitted from the light sources.

  Therefore, as shown in FIG. 5, it has been proposed to arrange a plurality of light sources 100 in a staircase pattern. According to this, since the positions of the plurality of light sources in the Y direction (the rotation axis direction of the rotary polygon mirror) are different from each other, it becomes easy to separate the optical paths of the light emitted from each light source. Each light source 100 is constituted by, for example, a laser diode and is attached to the drive circuit board 101. The drive circuit board 101 includes a board body 102 and a driver IC 103 for causing the laser diode 100 to oscillate. The driver IC 103 is disposed as close as possible to the laser diode 100 in order to reduce noise (see, for example, Patent Document 1).

JP 2008-76935 A

  However, in the conventional drive circuit board 101 shown in FIG. 5, since the plurality of light sources 100 are arranged in a staircase pattern, the dimension of the board body 102 in the Y direction becomes large. As a result, there is a problem that the size of the substrate main body 102 increases and the entire optical scanning device increases.

  The present invention has been made in view of this point, and an object of the present invention is to make the substrate body as small as possible.

  The light source driving circuit board according to the present invention is mounted on an optical scanning device that deflects and scans light emitted from a plurality of light sources by a rotating polygon mirror.

  A substrate body to which the plurality of light sources are attached; and a plurality of driving ICs provided corresponding to each of the plurality of light sources and driving the light sources, wherein each of the driving ICs includes the plurality of light sources. The light source group is arranged so as to be located on the opposite side to the light source corresponding to each driving IC with respect to a straight line passing through the centroid position of the light source group and extending in a direction orthogonal to the rotation axis of the rotary polygon mirror. .

  According to the present invention, the substrate body can be made as small as possible.

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus equipped with an optical scanning device having a light source driving circuit board in the embodiment. FIG. 2 is a perspective view showing the internal structure of the optical scanning device. 3 is a cross-sectional view taken along line III of FIG. FIG. 4 is a plan view of the light source driving circuit board as viewed from the light source mounting surface side. FIG. 5 is a view corresponding to FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

<Image forming apparatus>
FIG. 1 is a cross-sectional view illustrating a schematic structure of the image forming apparatus 1. The image forming apparatus 1 is, for example, a tandem color printer. As shown in FIG. 1, the intermediate transfer belt 7, the primary transfer unit 8 and the secondary transfer unit 9, a fixing device 11, and an optical scanning device 15. And a plurality of image forming units 16.

  A paper feed cassette 3 is disposed below the inside of the main body 2 of the image forming apparatus 1. The paper feed cassette 3 stores and accommodates sheets (not shown) such as paper before printing. A first paper transport unit 21 is provided on the side of the paper feed cassette 3. The first paper transport unit 21 receives the paper fed from the paper feed cassette 3 and transports the paper to the upper secondary transfer unit 9.

  A manual paper feed unit 5 is provided on the right side of the paper feed cassette 3. A second paper transport unit 22 is provided on the left side of the manual paper feed unit 5. The second paper transport unit 22 receives the paper sent from the manual paper feed unit 5 and transports it to the first paper transport unit 21.

  The optical scanning device 15 is disposed above the second paper transport unit 22 and irradiates the image forming unit 16 with laser light based on the image data received by the image forming device 1. For example, four image forming units 16 are provided above the optical scanning device 15. An endless intermediate transfer belt 7 is provided above each image forming unit 16. The intermediate transfer belt 7 is wound around a plurality of rollers and is rotationally driven by a driving device (not shown).

  As shown in FIG. 1, the four image forming units 16 are arranged in a line along the intermediate transfer belt 7, and respectively form yellow, magenta, cyan, or black toner images. That is, in each image forming unit 16, an electrostatic latent image of the original image is formed on the photosensitive drum 25 by the laser light irradiated by the optical scanning device 15, and each color toner is developed by developing the electrostatic latent image. An image is formed.

  The primary transfer unit 8 is disposed above each image forming unit 16. The primary transfer unit 8 includes a transfer roller that primarily transfers the toner image formed by the image forming unit 16 to the surface of the intermediate transfer belt 7.

  Then, the intermediate transfer belt 7 is driven to rotate, and the toner image of each image forming unit 16 is transferred to the intermediate transfer belt 7 at a predetermined timing, so that the surface of the intermediate transfer belt 7 has yellow, magenta, A color toner image in which toner images of four colors of cyan and black are superimposed on each other is formed.

  As shown in FIG. 1, the secondary transfer unit 9 has a transfer roller 17 disposed on the left side of the intermediate transfer belt 7. The secondary transfer unit 9 applies a transfer bias voltage having a polarity opposite to that of the toner to the sheet sent from the first sheet transport unit 21 so as to transfer the toner image from the intermediate transfer belt 7 to the sheet. It has become.

  The fixing device 11 is provided above the secondary transfer unit 9. Between the secondary transfer unit 9 and the fixing device 11, a third paper transport unit 23 that transports the paper on which the toner image has been secondarily transferred to the fixing device 11 is formed. The fixing device 11 includes a pressure roller 18, a fixing roller 19, and a heating roller 20. The fixing device 11 heats and pressurizes the sheet conveyed from the third sheet conveying unit 23 to fix the toner image on the sheet.

  A branch portion 27 is provided above the fixing device 11. The sheet discharged from the fixing device 11 is discharged from the branching unit 27 to the sheet discharging unit 28 formed on the upper portion of the image forming apparatus 1 when double-sided printing is not performed. When performing duplex printing, the paper is conveyed again from the branching unit 27 to the secondary transfer unit 9 via the fourth paper conveying unit 24.

<Optical scanning device>
As shown in FIG. 2, the optical scanning device 15 includes a plurality of light sources 32, a polygon mirror 36 as a rotating polygon mirror into which light emitted from each of the plurality of light sources 32 is incident, and a box shape that houses the polygon mirror 36. The housing 31 is provided. 2 shows a state in which a lid member (not shown) that closes the casing 31 is removed.

  As shown in FIG. 3, the polygon mirror 36 is provided at the bottom of the casing 31 via a polygon motor 37. The polygon mirror 36 is formed in a regular hexagonal shape, for example, and is driven to rotate by a polygon motor 37.

  In addition, an imaging lens (fθ lens) 38 provided in the optical path of the light reflected by the polygon mirror 36 is accommodated in the housing 31. The imaging lens 38 is installed at the bottom of the casing 31 on the side of the polygon mirror 36.

  The light sources 32 are provided in the same number (that is, four) as the number of reference colors used in the image forming apparatus 1 (four in this embodiment, black, cyan, magenta, and yellow). Each light source 32 is disposed in a through hole 31 a formed in the side wall portion of the housing 31. A light source driving circuit board 33 is fixed to the outer surface of the side wall of the housing, and the plurality of light sources 32 are mounted on the light source driving circuit board 33.

  The four light sources 32 are formed of laser diodes having a plurality of light emitting units 39 (see FIG. 4). In the present embodiment, four light emitting units 39 are provided at the tip of each light source 32. The four light emitting units 39 are arranged such that a straight line connecting the adjacent light emitting units 39 becomes a square shape. Thus, each light source 32 emits a plurality (four in the present embodiment) of laser beams.

  As shown in FIG. 2, a collimator lens 40, an aperture 41, a first mirror 42, a second mirror 43, a third mirror 44, and a cylindrical lens 45 are arranged between each light source 32 and the polygon mirror 36. Has been.

  The collimator lens 40 is a lens for converting a plurality of laser beams emitted from each light source 32 into parallel light. The aperture 41 is for regulating the spread of the laser beam. The cylindrical lens 45 is a lens for condensing the laser beam group and guiding it to the polygon mirror 36.

  Further, as shown in FIG. 3, the light source 32, the collimator lens 40 (not shown), the aperture 41, and the first mirror 42 are arranged so that the height from the bottom surface of the housing 31 is different for each optical path 32. Has been.

  Thus, the plurality of laser beams emitted from the light source 32 are collimated by the collimator lens 40 and then pass through the aperture 41 so that the spread of the beams is regulated and reflected by the first mirror 42. . The laser beam reflected by the first mirror 42 is reflected by the second mirror 43 and the third mirror 44 and enters the cylindrical lens 45. The plurality of laser beams incident on the cylindrical lens 45 are condensed with each other. The condensed laser beam is reflected by the polygon mirror 36 and passes through the imaging lens 38 to form an image on the photosensitive drum 25.

  The scanning light imaged on the surface of the photosensitive drum 25 scans the surface of the photosensitive drum 25 in the main scanning direction by the rotation of the polygon mirror 36, and scans in the sub-scanning direction by the rotation of the photosensitive drum 25. An electrostatic latent image is formed on the surface of the body drum 25.

  As shown in FIG. 4, the light source drive circuit board 33 includes a board body 34 to which the four light sources 32 are attached, and a plurality of drive ICs 35 for driving the light sources 32.

  The substrate body 34 is formed in a rectangular plate shape. The longitudinal direction of the substrate body 34 coincides with the direction orthogonal to the rotation axis of the polygon mirror 36 (defined as the X direction), and the short direction of the substrate body 34 is the rotation axis direction of the polygon mirror 36 (sub-scanning direction). In the following, it is defined as the Y direction). An attachment hole 34a and an attachment hole 34b are formed at both ends in the X direction at one end of the substrate body 34 in the Y direction. One attachment hole 34a is formed in a long hole shape long in the X direction, and the other attachment hole 34b is formed in a circular hole shape.

  The four light sources 32 are mounted on one side surface of the substrate body 34 in the thickness direction. The four light sources 32 are arranged so that the positions in the Y direction are shifted stepwise from one side of the X direction to the other side. The four light sources 32 are arranged at equal intervals in the X direction, and are also arranged at equal intervals in the Y direction.

  The driving IC 35 is a package of circuits for driving the light sources 32. The driving IC 35 is mounted on the same surface as the surface on which the light source 32 is attached in the substrate body 34. A total of four drive ICs 35 are provided for each of the four light sources 32. Each of the four driving ICs 35 is disposed adjacent to each driving IC 35 in the Y direction.

  Here, when the centroid position of the light source group including the four light sources 32 is C, a straight line passing through the centroid position C and extending in the X direction (a direction orthogonal to the rotation axis of the polygon mirror 36) is L1. When a straight line passing through the center position C and extending in the Y direction is L2, each driving IC 35 is arranged to be located on the opposite side of the light source 32 corresponding to each driving IC 35 across the straight line L1. Yes. The distances d1 between the driving ICs 35 and the corresponding light sources 32 are equal to each other.

  Of the four driving ICs 35, the two driving ICs 35 located on one side in the X direction from the straight line L2 and the two driving ICs 35 located on the other side in the X direction are opposite to each other across the straight line L1. Is located. Thus, the four driving ICs 35 are arranged point-symmetrically with respect to the centroid position C.

  As described above, according to the light source driving circuit board 33 of the present embodiment, each driving IC 35 passes through the centroid position C of the light source group composed of the four light sources 32 and is orthogonal to the rotation axis of the polygon mirror 36. It arrange | positions so that it may be located in the opposite side to the light source 32 corresponding to each said drive IC35 with respect to the straight line L1 extended in a direction. Therefore, the light source 32 and the driving IC 35 can be efficiently arranged on the substrate body 34 while reducing the dimension of the substrate body 34 in the Y direction as compared with the conventional example of FIG. Thus, the overall size of the optical scanning device 15 can be reduced by reducing the size of the substrate body 34.

  In the present embodiment, an even number of four driving ICs 35 are provided and are arranged point-symmetrically with respect to the centroid position C of the light source group. Since the driving IC 35 generates heat during operation, the thermal deformation characteristics of the substrate body 34 can be made symmetric with respect to the centroid position C by arranging the driving IC 35 with respect to the centroid position C. it can. Therefore, the optical scanning control considering the thermal deformation of the substrate body 34 can be easily performed.

  As described above, the present invention is useful for the light source driving circuit board mounted on the optical scanning device.

C Centroid position L1 Line 1 Image forming device 32 Light source 33 Light source driving circuit board 35 Driving IC
36 polygon mirror 45 cylindrical lens

Claims (3)

A light source drive circuit board mounted on an optical scanning device that deflects and scans light emitted from a plurality of light sources by a rotating polygon mirror,
A substrate body to which the plurality of light sources are attached;
A plurality of driving ICs provided corresponding to each of the plurality of light sources and driving the light sources;
Each of the driving ICs is a light source corresponding to each of the driving ICs with respect to a straight line passing through the centroid position of the light source group including the plurality of light sources and extending in a direction perpendicular to the rotation axis of the rotary polygon mirror. A light source drive circuit board, which is arranged to be located on the opposite side. The light source driving circuit board according to claim 1,
An even number of the plurality of driving ICs is provided, and the light source driving circuit board is arranged point-symmetrically with respect to the centroid position of the light source group.   An optical scanning device comprising the light source drive circuit board according to claim 1.

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