JP2013061392A - Optical scanner and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner that is adapted to a plurality of excitation frequencies irrespective of a material of an optical box, and prevents image degradation such as banding.SOLUTION: The optical scanner includes a light source, a light deflector that scans a light beam emitted from the light source, and a folding mirror that reflects the light beam deflection-scanned by the light deflector toward a surface to be scanned. The light source, the light deflector and the folding mirror are disposed in the optical box 11. The optical box 11 is supported by a support part 101 at a plurality of points. The support part 101 includes a leaf spring 102, and a leaf spring support jig 103 for supporting the leaf spring 102 so as to freely move in arrow directions 201a, 201b. The rigidity of the optical box 11 is variable.

Description

  The present invention relates to an optical scanning device and an image forming apparatus equipped with the optical scanning device.

  In a conventional image forming apparatus, an optical scanning apparatus that forms an image by irradiating a photosensitive member with a laser beam may place an optical component such as a reflection mirror (folding mirror) for folding an optical path on an optical box. Many. Optical boxes are mainly made of metal made of aluminum die casting or the like and made of resin.

  If there is an excitation source that excites at the natural frequency of the housing (housing) of this optical box, the housing may vibrate and spot position fluctuations may occur at that natural frequency. In this case, a striped pattern called banding appears, which causes image deterioration. The natural frequency of the housing is determined by the rigidity of the housing itself and the rigidity of the stay fixing the housing. In other words, banding may change depending on the rigidity.

  Therefore, the natural frequency of the housing is changed by changing the fastening force of the screw that fixes the optical box, or fixing the fixed leg of the optical box with the clamp, and changing the contact area between the fixed leg and the clamp. What has been made is proposed (see Patent Document 1).

  There are also proposed ones in which a plurality of fixing portions for fixing the optical box to the main body frame are provided and the natural frequency is changed by changing the fixing portion for each model (see Patent Document 2 and Patent Document 3). ).

  Furthermore, in order to shift the natural frequency of the optical box to a high frequency region, there has been proposed one in which the thickness of the mounting portion of the optical box is set within a certain range (see Patent Document 4).

  However, among the above-described conventional techniques, in the technique of Patent Document 1, a sufficient change in rigidity cannot be expected only by changing the fastening force of the screw, and there is a concern about the occurrence of play when the fastening force is reduced. There is a similar concern in clamp fixing.

  In the techniques of Patent Document 2 and Patent Document 3, it is common that there are a plurality of excitation sources, and it is conceivable that not only the fundamental frequency but also a multiple frequency can be the excitation frequency. It is difficult to optimize the natural frequency of the optical box.

  Furthermore, the technique of Patent Document 4 does not support a plurality of excitation frequencies, and even when the natural frequency of the optical box is shifted to a high frequency range for speeding up of recent image forming apparatuses, If there is an excitation force at that frequency, there is a concern about image degradation such as banding.

  An object of the present invention is to provide an optical scanning device capable of dealing with a plurality of excitation frequencies irrespective of the material of the optical box and preventing image deterioration such as banding, and an image forming apparatus equipped with the optical scanning device. Is to provide.

  To achieve the above object, the present invention provides a light source, a light deflector that scans a light beam emitted from the light source, and a light beam deflected and scanned by the light deflector toward a surface to be scanned. An optical scanning device having the light source, the optical deflector, and the folding mirror mounted in an optical box, wherein the optical box is supported by a plurality of support portions. The support portion has a structure in which the rigidity of the optical box is variable.

  According to the above configuration, the optical box is supported by a support portion at a plurality of locations, and the support portion has a structure in which the rigidity of the optical box is variable.By adjusting the support portion individually for each optical box, Regardless of the material of the optical box, a plurality of excitation frequencies can be supported.

  According to the present invention, an optical scanning device capable of supporting a plurality of excitation frequencies regardless of the material of the optical box and preventing image deterioration such as banding, and an image forming apparatus equipped with the optical scanning device Can be realized.

It is a top view of the optical scanning device concerning the present invention. It is a perspective view of the folding mirror mounted in the optical scanning device of FIG. It is a figure which shows the vibration mode of an optical box. It is a figure which shows the other vibration mode of an optical box. It is sectional drawing of the support structure of an optical box. It is a disassembled perspective view of the support part which supports an optical box in case an optical box is standard rigidity. It is a disassembled perspective view of the support part which supports an optical box in case an optical box is low-rigidity. It is a disassembled perspective view of the support part which supports an optical box in case an optical box is highly rigid. It is a figure explaining that the vibration amplitude of an optical box changes. 1 is a schematic configuration diagram of an image forming apparatus equipped with an optical scanning device of the present invention.

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

Example 1
FIG. 1 is a plan view of an optical scanning device according to the present invention. In FIG. 1, reference numeral 11 denotes an optical box. The optical box 11 includes light source units 12a and 12b that emit laser beams, and a cylinder lens 13a that condenses the laser beam L1 from the light source units 12a and 12b in the sub-scanning direction. 13b, a deflection scanning unit 14 that deflects and scans the laser beam L1, scanning lenses 15a and 15b including fθ lenses and surface tilt correction lenses, and a light detection mirror 16a that reflects the laser beam L2 before irradiating the photosensitive drum. 16b, photodetection units 17a and 17b for detecting the laser beam L2 from the photodetection mirrors 16a and 16b, and folding mirrors 18a and 18b for reflecting the laser beam L1 and irradiating the photosensitive drum. The deflection scanning unit 14 is provided with a polygon mirror 14a that reflects a laser beam and a drive motor 14b that rotationally drives the polygon mirror 14a.

  In this embodiment, fixed legs 19a to 19d are attached to four corners of the optical box 11, and support parts 101a to 101d are provided on the fixed legs 19a to 19d, respectively. The support portions 101a to 101d fix the optical box 11 to a main body frame (not shown) with variable rigidity (variable rigidity of the optical box 11).

  FIG. 2 is a perspective view of the folding mirrors 18a and 18b mounted on the optical scanning device. Both ends 201 and 201 of the folding mirrors 18a and 18b are supported by seats 202 and 202, respectively. The seats 202 and 202 have inclined surfaces, and the folding mirrors 18a and 18b are placed on the inclined surfaces. For this reason, the reflecting mirrors 18a and 18b are arranged with their reflecting surfaces inclined.

  Further, leaf springs 203, 203 are attached to the upper surfaces of the seats 202, 202, and the folding mirrors 18a, 18b are firmly fixed to the seats 202, 202 by the leaf springs 203, 203.

  3 and 4 show typical natural vibration modes of the optical box 11, FIG. 3 shows the primary torsional vibration of the optical box 11, and FIG. 4 shows the primary bending vibration of the optical box 11, respectively. . Since the optical box 11 is excited by these vibrations and the positional relationship of the optical system parts group is also shifted, a positional shift occurs when the laser beam L1 is irradiated to a photosensitive member (not shown), which causes banding. It may become.

  FIG. 5 is a cross-sectional view of the support portion 101 (101a to 101d) that supports the fixed legs 19 (19a to 19d) at the corners of the optical box 11. FIG. The fixed leg 19 is fixed to the lower portion of the side wall of the optical box 11, and a leaf spring 102 is fixed to the fixed leg 19 with a screw 20. The leaf spring 102 has a strip shape and is arranged such that its longitudinal direction is parallel to the side surface of the optical box 11. A screw 20 is screwed into the leaf spring 102 at the center.

  A body frame 21 is disposed below the leaf spring 102, and both ends of the leaf spring 102 are supported on the body frame 21 by leaf spring support jigs 103 and 103. The leaf spring support jigs 103 and 103 are fixed on the main body frame 21 by screws 104 and 104. In this case, in the drawing, the right leaf spring support jig 103 is moved in the direction of the arrow 201a, and the left leaf spring support jig 103 is moved in the direction of the arrow 201b. The jigs 103 and 103 are fixed on the main body frame 21. That is, by moving the leaf spring support jigs 103 and 103 in the directions of the arrows 201a and 201b, respectively, the support range of the leaf spring 102 can be changed, and the support rigidity of the support portion 101 with respect to the optical box 11 can be changed. Can do. The detailed configuration of the leaf spring support jigs 103 and 103 will be described later.

  In addition, positioning pins 105 and 105 are provided on both end sides of the leaf spring 102 (on the end portion side relative to the position where the leaf spring support jigs 103 and 103 are disposed). An absolute position 102 is fixed with respect to the main body frame 21. Thereby, the positional relationship between the optical box 11 and a photosensitive drum (not shown) is constant. The detailed configuration of the positioning pins 105 and 105 will also be described later.

  6 to 8 show the structure of the support portion 101 in detail, FIG. 6 is an exploded perspective view when the leaf spring support jigs 103 and 103 are arranged at the standard position, and FIG. 7 shows the rigidity of the support portion 101. FIG. 8 is an exploded perspective view when the leaf spring support jigs 103 and 103 are moved in the direction of decreasing, and FIG. 8 is an exploded view when the leaf spring support jigs 103 and 103 are moved in the direction of increasing the rigidity of the support portion 101. It is a perspective view.

  The leaf spring support jigs 103 and 103 are composed of a rectangular parallelepiped upper member 103a and a lower member 103b, and the upper member 103a and the lower member 103b are arranged with the leaf spring 102 interposed therebetween. Long holes 106 (106a, 106b) are formed in the upper member 103a along the longitudinal direction, and long holes 107 (107a, 107b) are formed in the lower member 103b along the longitudinal direction. By forming these long holes 106 and 107, the support range of the leaf spring 102 can be changed.

  The plate spring 102 is formed with screw through holes 108 (108a, 108b), and the main body frame 21 is formed with screw holes 109 (109a, 109b). Then, the screws 104 (104a, 104b) are inserted into the elongated holes 106 (106a, 106b) of the upper member 103a, the screw through holes 108 (108a, 108b) of the leaf spring 102, and the elongated holes 107 (107a, 107b) of the lower member 103b. The leaf spring 102 can be firmly fixed to the main body frame 21 by being inserted into the main body frame 21 and screwed into the screw holes 109 (109a, 109b) of the main body frame 21 and tightening.

  Further, pin leaf holes 110 (110a, 110b) are formed in the leaf spring 102, and positioning holes 111 (111a, 111b) are formed in the main body frame 21. Then, the positioning pin 105 (105a, 10b) is inserted into the pin through hole 110 (110a, 110b) of the leaf spring 102 and fitted into the positioning hole 111 (111a, 111b) of the main body frame 21, thereby the plate. The position of the spring 102 can be set to a predetermined position.

  In FIG. 6, the screw 104 (104b, 104b) has a substantially central portion of the elongated hole 106 (106a, 106b) of the upper member 103a and a substantially central portion of the elongated hole 107 (107a, 107b) of the lower member 103b. It is inserted.

  In FIG. 7, the screws 104 (104b, 104b) are located to the left of the elongated holes 106 (106a, 106b) of the upper member 103a (the side closer to the center of the optical box 11), and further, the elongated holes 107 (107a) of the lower member 103b. 107b) on the left side (side closer to the center of the optical box 11).

  In FIG. 8, the screws 104 (104b, 104b) are located on the right side (the side away from the center of the optical box 11) of the long holes 106 (106a, 106b) of the upper member 103a and further on the long holes 107 ( 107a, 107b) on the right side (the side away from the center of the optical box 11).

  As shown in FIGS. 6 to 8, the rigidity of the optical box 11 as shown in FIGS. 3 and 4 can be changed by changing the positions of the leaf spring support jigs 103 and 103. That is, the natural frequency of the optical box 11 can be changed.

  FIG. 9 is a graph showing the amplitude of a certain vibration mode of the optical box 11. When the leaf spring supporting jigs 103 and 103 are in the standard position as shown in FIG. 6, the amplitude is as indicated by a solid line 301. In this case, there is a frequency of the excitation force in the vicinity of the amplitude peak, and the natural frequency of the optical box 11 is easily excited.

  Therefore, as shown in FIG. 7, the positions of the leaf spring support jigs 103, 103 are shifted to lower the rigidity of the support portion 101 and lower the natural frequency of the optical box 11. In this way, the peak frequency of the amplitude can be moved away from the frequency of the excitation force in the direction of lower frequency as indicated by the dotted line 302 in FIG.

  Further, as shown in FIG. 8, the positions of the leaf spring support jigs 103 and 103 are shifted to increase the rigidity of the support portion 101 and increase the natural frequency of the optical box 11. In this way, the peak of amplitude can be moved away from the frequency of the excitation force in the direction of higher frequency as indicated by the dotted line 303 in FIG.

  The position when the leaf spring supporting jigs 103 and 103 are shifted is not limited to the position shown in FIGS. 6 to 8 but may be an arbitrary intermediate position between the position in FIG. 6 and the position in FIG. Alternatively, an arbitrary intermediate position between the position in FIG. 7 and the position in FIG. 8 may be used.

  According to the present embodiment, the natural frequency of the optical box 11 can be changed even after the configuration and design values of the optical box 11 are determined and assembled, so that the natural frequency of the optical box 11 is excited after the assembly. Even when the excitation source and the excitation frequency are found, it is possible to provide a support structure that realizes an optical box with a small vibration amplitude. If the optical scanning device of this embodiment is mounted on an image forming apparatus, an image forming apparatus with little image deterioration such as banding caused by vibration of the optical box can be realized.

Example 2
Next, an image forming apparatus equipped with the optical scanning device of Embodiment 1 will be described. FIG. 10 shows a schematic configuration of an image forming apparatus according to the present invention.

  Reference numeral 400 denotes an image forming apparatus. In the image forming apparatus 400, image forming units 403, 404, 405, and 406 for each color are arranged in the running direction of the intermediate transfer belt 401. Four types of image forming units 403, 404, 405, and 406 are provided, and each includes a K developing unit having black toner, a C developing unit having cyan toner, an M developing unit having magenta toner, and a Y having yellow toner. Development unit.

  The image forming unit 403 charges a toner hopper that stores toner, a developing device 408 that forms a toner layer and supplies toner to the photosensitive drum 407, a drum cleaner 409 that cleans the photosensitive drum 407, and a photosensitive drum 407. And an optical scanning device 411 that writes an electrostatic latent image on the photosensitive drum 407.

  A toner hopper, a developing roller, a drum cleaner 409, a charger 410, and the like included in the image forming unit 403 are attached to the main body frame 21 (see FIG. 5) and configured to be able to be pulled out from the main body of the image forming apparatus 400. As the optical scanning device 411, the one shown in the first embodiment is used. The other image forming units 404, 405, and 406 have substantially the same configuration.

  The intermediate transfer belt 401 is stretched around a plurality of rollers and passes through the secondary transfer roller 402. A belt cleaner 412 removes residual toner on the intermediate transfer belt 401. The primary transfer roller 413 is disposed on the inner side of the intermediate transfer belt 401 so as to face the photosensitive drum 407 and the like, facing the photosensitive drum 407 and the like.

  The sheet 414 is pulled out from the sheet feeding device 415 by the pickup roller 416, passes through a separation roller, etc., and is held between the secondary transfer roller 402 and the counter roller 402A, and is brought into contact with the intermediate transfer belt 401 to transfer an image. The toner is fed toward the fixing device 418 via the conveyance belt 417.

  The fixing device 418 includes a backup roller 419, an elastic roller 420, a heating roller 421, a fixing belt 422, and the like. The fixing belt 422 is stretched between the elastic roller 420 and the heating roller 421, and is driven by the rotation of the heating roller 421 or other rollers. The sheet 414 is pressed against the elastic roller 420 side by a backup roller 419.

  The heating roller 421 has heating means such as a halogen heater in a metal hollow shaft, and heats the fixing belt 422. The surface of the elastic roller 420 is formed of an elastic body such as silicon rubber, and the pressing force of the backup roller 419 makes the nip portion convex toward the elastic roller 420 to prevent the paper 414 from being wound around the fixing belt 422. Yes.

  When an image is formed, the photosensitive drum 407 is charged by the charger 410, and the photosensitive drum 407 is exposed by a laser beam corresponding to the image by the optical scanning device 411, and the potential on the photosensitive drum 407 is lowered. The exposed portion reaches the developing device 408 by the rotation of the photosensitive drum 407, the charged toner of the developing device 408 adheres to the image forming position, and a toner image is formed on the photosensitive drum 407.

  The toner image formed on the photosensitive drum 407 is transferred to the intermediate transfer belt 401 when the primary transfer roller 413 presses the intermediate transfer belt 401 against the photosensitive drum 407. The toner images on the photosensitive drums 407 of the image forming units 403, 404, 405, and 406 are similarly transferred to the intermediate transfer belt 401, thereby forming a color toner image.

  By the conveyance of the intermediate transfer belt 401, the toner image is transferred to the paper 414 conveyed at the site of the secondary transfer roller 402. The sheet 414 on which the toner image is transferred is conveyed to the fixing device 418 by the conveying belt 417, and the toner is melted and fixed by heat and pressure to form a color image.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, each of the above embodiments is only an example of the present invention, and the present invention is not limited only to the configuration of each of the above embodiments. . Needless to say, changes in design and the like within the scope of the present invention are included in the present invention.

  For example, even if the plate thickness of the plate spring 102 is changed, the rigidity of the optical box 11 can be made variable. Even if the material of the leaf spring 102 is changed, the rigidity of the optical box 11 can be made variable.

  By using the optical scanning device of the present invention, it is possible to realize an image forming apparatus with little difference in banding and color misregistration.

DESCRIPTION OF SYMBOLS 11 Optical box 12a, 12b Light source unit 13a, 13b Cylinder lens 14 Deflection scanning unit 14a Polygon mirror 14b Drive motor 15a, 15b Scanning lens 16a, 16b Photodetection mirror 17a, 17b Photodetection unit 18a, 18b Folding mirror 19 (19a-19d ) Fixed leg 20 Screw 21 Body frame 101 (101a to 101d) Support portion 102 Leaf spring 103 Leaf spring support jig 103a Upper member 103b Lower member 104 (104a, 104b) Screw 105 (105a, 105b) Positioning pin 106 (106a, 106b) Long hole 107 (107a, 107b) Long hole 108 (108a, 108b) Screw through hole 109 (109a, 109b) Screw hole 110 (110a, 110b) Pin through hole 111 (111a, 111b) Positioning hole 400 image Forming device 411 the optical scanning device

JP 2001-215435 A JP 2007-034167 A JP 2000-292730 A JP 2004-029585 A

Claims (6)

A light source; an optical deflector that scans the light beam emitted from the light source; and a single or a plurality of folding mirrors that reflect the light beam deflected and scanned by the optical deflector toward a scanned surface. An optical scanning device in which the light source, the optical deflector, and the folding mirror are placed in an optical box,
The optical scanning device is characterized in that a plurality of portions of the optical box are supported by a support portion, and the support portion has a structure in which the rigidity of the optical box is variable.   The said support part has a leaf | plate spring, The rigidity of the said optical box is made variable by changing the area of the leaf | plate spring of the part which supports the said optical box among this leaf | plate spring. The optical scanning device according to 1. A main body frame for storing the optical box is provided,
The leaf spring supports the optical box at the center thereof, and both ends are fixed to the main body frame via a supporting jig, and the optical jig is supported by moving the supporting jig. The optical scanning device according to claim 2, wherein an area of the leaf spring is changed.   The optical scanning device according to claim 3, wherein the plate spring is fixed to the main body frame by a positioning member.   The optical scanning device according to claim 1, wherein the support portion is disposed corresponding to a vicinity of a corner portion of the optical box.   An image forming apparatus comprising the optical scanning device according to claim 1.