JP2007268840A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which secures a positional accuracy against the revolving polyhedron of a returning mirror in a usual-using environment without being affected by an irreversible deformation in the high- or low temperature environment of an optical housing wherein different species of components with different thermal expansion coefficients are mounted. <P>SOLUTION: The image forming apparatus is equipped: with an optical housing 12 for supporting the returning mirror 18 for reflecting a laser beam which is radiated inside from a laser beam emitter 14; and a mounting plate 13 composed of a different material having a thermal expansion coefficient different from that of the optical housing 12 and supporting the revolving polyhedron 19 for receiving the laser beam reflected by the returning mirror 18 while being fastened to the optical housing 12 at plural positions through fastening means 27. All the plural fastening means 27 are separated from the straight line for connecting the laser beam emitter 14 to the returning mirror 18 in the optical housing 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a rotating polyhedron by irreversible deformation of an optical housing in which parts made of different materials having different coefficients of thermal expansion (hereinafter referred to as different parts) are assembled. The present invention relates to a technique for preventing the occurrence of a position error of a folding mirror with respect to.

  For example, as described in Patent Document 1 described later, an image forming apparatus includes an optical housing that houses an optical system. In this optical system, a laser beam emitted from a laser emitter is provided on a photosensitive drum. An optical device such as a rotating polyhedron (polygon mirror) that reflects so as to scan the surface of the lens in the axial direction is provided.

  In order to reduce the size of the image forming apparatus, the optical housing also houses a motor composed of a flat motor for driving the rotating polyhedron and an integrated circuit for controlling the motor.

  In order to prevent the heat generated by the motor and the integrated circuit from affecting the thermal expansion of the optical housing and the position error of the optical system (hereinafter referred to as an optical device) due to this, the motor and the integrated circuit can conduct heat. A heat dissipating part that is attached to a rectangular mounting plate made of, for example, an aluminum alloy, is formed integrally with the mounting plate, or is assembled with the mounting plate so as to be able to conduct heat, and is exposed to the outside of the optical housing. A means for forcibly air-cooling the heat dissipating part is further provided.

  Here, the mounting plate is fastened to the optical housing at a plurality of locations by fastening means such as screws.

  On the other hand, in the prior art, the laser emitter and the folding mirror are arranged on both sides of the rotating polyhedron in the long side direction of the mounting plate, and the laser beam emitted from the laser emitter is coaxial with the motor by the folding mirror. In some cases, a technique for making the light incident on a rotating polyhedron supported on the surface is used.

In this case, in order to reduce the size, the optical path from the laser emitter to the folding mirror is made close to the rotating polyhedron, and fastening means such as screws for fixing the mounting plate to the optical housing between the laser emitter and the folding mirror It is not uncommon for multiple to be lined up.
Japanese Patent No. 3075497

  By the way, for example, in a high temperature environment or a low temperature environment in use, for example, in a high temperature environment exceeding 35 ° C., the optical housing and the mounting plate are thermally expanded, but the mounting plate is a dissimilar material having a coefficient of thermal expansion different from that of the optical housing, Due to the difference in thermal expansion between the optical housing and the mounting plate, the optical housing is deformed irreversibly between its multiple fastening means to be larger than its natural thermal expansion due to the dissimilar parts made of aluminum alloy. This irreversible deformation remains even when the ambient temperature is restored.

  In particular, when this irreversible deformation remains on the straight line connecting the laser emitter and the folding mirror, a position error of the folding mirror with respect to the rotating polyhedron occurs, and the laser beam reflected by the folding mirror is correct. The light beam scanning position on the surface of the photosensitive drum is shifted without being directed to the rotating polyhedron at an angle, and in some cases, an image defect occurs.

  In consideration of such circumstances, the present invention is not affected by irreversible deformations in a high temperature environment or a low temperature environment of an optical housing in which different parts having different thermal expansion coefficients are assembled. An object of the present invention is to provide an image forming apparatus capable of ensuring the positional accuracy of a mirror with respect to a rotating polyhedron.

  In order to achieve this object, the present invention comprises an optical housing that houses a folding mirror that reflects a laser beam emitted from a laser emitter, and a dissimilar material having a coefficient of thermal expansion different from that of the optical housing. An image forming apparatus that includes a mounting plate that supports a rotating polyhedron that receives a laser beam reflected by a mirror and is fastened to the optical housing at a plurality of locations via fastening means. The technical means is characterized in that it is separated from a straight line connecting the laser emitter and the folding mirror in the housing.

  For example, when a plurality of fastening means are arranged in parallel with a straight line connecting the laser emitter and the folding mirror in the optical housing, irreversible deformation of the optical housing between the fastening means and the laser emitter These fastening means may be separated from the straight line connecting the laser emitter and the folding mirror so as not to affect the straight line connecting the folding mirror.

  According to the present invention, since the straight line connecting the plurality of fastening means does not coincide with the straight line connecting the laser emitter and the folding mirror, irreversible deformation of the optical housing due to the difference in thermal expansion between the optical housing and the dissimilar parts. Does not occur in the direction of the straight line connecting the laser emitter and the folding mirror on the straight line connecting the laser emitter and the folding mirror.

  As a result, the position accuracy of the folding mirror relative to the rotating polyhedron can be ensured in the normal use environment without being affected by the irreversible deformation of the optical housing remaining after the environmental temperature returns to the normal use environment. In addition, it is possible to prevent the deviation of the light beam scanning range on the surface of the photosensitive drum and the image loss due to this.

  As described above, the present invention comprises an optical housing that houses a folding mirror that reflects a laser beam emitted from a laser emitter, and a dissimilar material having a coefficient of thermal expansion different from that of the optical housing. In an image forming apparatus that supports a rotating polyhedron that receives a laser beam reflected by a folding mirror and includes a mounting plate that is fastened to the optical housing via fastening means at a plurality of locations, all of the plurality of fastening means are The technical means is characterized in that it is separated from a straight line connecting the laser emitter and the folding mirror in the optical housing.

  For example, when a plurality of fastening means are arranged in parallel with a straight line connecting the laser emitter and the folding mirror in the optical housing, irreversible deformation of the optical housing between the fastening means and the laser emitter These fastening means may be separated from the straight line connecting the laser emitter and the folding mirror so as not to affect the straight line connecting the folding mirror, for example, larger than the width range of the folding mirror.

  As a result, according to the present invention, the straight line connecting the plurality of fastening means does not overlap with the straight line connecting the laser emitter and the folding mirror, and the thermal expansion is performed in the linear direction on the straight line connecting the laser emitter and the folding mirror. It is possible to obtain an effect that there is no possibility that irreversible deformation of the optical housing due to the rate difference remains.

  Due to this action, even if irreversible deformation occurs due to the difference in thermal expansion coefficient between the dissimilar parts and the optical housing, it is possible to ensure the positional accuracy of the folding mirror relative to the rotating polyhedron without being affected by this, It is possible to obtain an effect of preventing occurrence of an image defect due to an error in position accuracy.

  Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.

  In the drawings, FIG. 1 is a plan view of an optical unit in an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic view showing an overall configuration of the image forming apparatus.

  The front and rear and up and down directions of the image forming apparatus in FIG.

  As shown in FIG. 2, the image forming apparatus includes a main body housing 1, a paper tray 2 disposed in the main body housing 1, a photosensitive drum 3, a charger 4, an optical unit 5, and a toner supply. And a transfer roller 7. The photosensitive drum 3 is rotated in one direction (clockwise in the figure) at a constant speed, and its surface is uniformly charged by the charger 4. By exposing the laser beam emitted from the unit 5 to a latent image, a latent image is formed. Thereafter, the toner image is developed on the surface of the photosensitive drum 3 by adsorbing toner from the toner supply unit 6 to the latent image. The

  The transfer roller 7 is disposed opposite to the photosensitive drum 3 on which the toner image is formed, is taken out from the paper tray 2 by the pick roller 8, and is fed from the paper tray 2 to the photosensitive drum 3 by the paper conveying means 9. The toner image on the photosensitive drum 3 is transferred onto the sheet fed between the transfer rollers 7 by the action of the transfer roller 7.

  The sheet on which the toner image has been transferred is sent to a fixing device 10 provided in the main body housing 1. The fixing device 10 fixes the toner image on the paper, and the paper is opened on the upper surface of the main body housing 1. To the paper discharge unit 11.

  The front and rear and left and right directions of the optical unit in FIG. The vertical direction in the figure is the direction of the front and back of the paper.

  As shown in FIGS. 1 and 2, the optical unit 5 includes an optical housing 12 made of synthetic resin, a mounting plate 13 made of an aluminum alloy having a different coefficient of thermal expansion, and a right outer surface of the optical housing 12. A laser emitter 14 disposed, a collimator lens 15, an aperture 16, a cylinder lens 17, and a folding mirror 18 disposed in the optical housing 12, are disposed in the optical housing 12, and are attached to the mounting plate 13. A supported rotating polyhedron 19, a motor 20 that drives the rotating polyhedron 19, and an integrated circuit that controls the motor 20 are provided.

  As shown in FIG. 2, the optical unit 5 includes a group of scanning lenses 21 for causing the laser beam reflected from the rotating polyhedron 19 to scan at a constant speed on the photosensitive drum 3, and the converged laser beam. A final mirror 22 that reflects toward the photosensitive drum 3 is provided, and the opened surface of the optical housing 12 is closed with a lid 23.

  As shown in FIG. 1, the mounting plate 13 is formed in a rectangular shape, and the mounting plate 13 is fitted into the lower surface of the front portion of the optical housing 12 from the lower side (the back side in FIG. 1). A rectangular opening 24 is formed.

  The laser emitter 14, the collimator lens 15, the aperture 16, and the cylinder lens 17 are as close as possible to the opening 24 behind the right end of the rear long side of the opening 24 and parallel to the long side of the opening 24. The folding mirror 18 is fixed behind the opening 24 and to the left of the opening 24 so as to cross the optical path of the laser beam at a predetermined angle. Is fixed.

  An integrated circuit is supported on the upper surface of the right half portion of the mounting plate 13 exposed in the optical housing 12, the motor 20 is fixed to the upper surface of the left half portion, and the rotating polyhedron 19 is the rotating shaft of the motor 20. Fixed to.

  In this way, the laser emitter 14, the collimator lens 15, the aperture 16, the cylinder lens 17, the folding mirror 18, and the rotating polyhedron 19 are arranged, and the rotating polyhedron 19 is unidirectionally (clockwise in FIG. 1) at a constant speed. The laser beam emitted from the laser emitter 14 is reflected on the rotating polyhedron 19 by the folding mirror 18 and further reflected by the rotating polyhedron 19 by rotating the laser beam from the laser emitter 14. A laser beam is deflected in one direction within a predetermined angle range on a plane parallel to the paper surface.

  From the four sides of the mounting plate 13, along the back surface of the optical housing 12, a total of six flanges 25, two each from the front and rear long sides and one each from the left and right short sides, are extended. Each of the portions 25 is formed with one screw insertion hole 26.

  The mounting plate 13 is fastened to the optical housing 12 by screwing fastening means 27 made of, for example, screws inserted into the screw insertion holes 26 into the optical housing 12.

  The latter two flanges 25 are continuously extended so that the two screw insertion holes 26 formed in these flanges 25 are separated rearward from the straight line connecting the laser emitter 14 and the folding mirror 18.

  The extent to which these two screw insertion holes 26 and the fastening means 27 inserted through them are separated from the straight line connecting the laser emitter 14 and the folding mirror 18 is the deformation remaining in the optical housing 12 between the fastening means 27. What is necessary is just to make it the extent which does not affect the straight line which connects the said laser emitter 14 and the folding mirror 18, for example, should just be larger than the width range (projection range to the front-back direction of the folding mirror 18) of the folding mirror 18.

  As a result, all the fastening means 27 are arranged apart from the straight line connecting the laser emitter 14 and the folding mirror 18 in the optical housing 12, and the deformation occurs in a high temperature environment exceeding 35 ° C., for example. When the temperature is returned to the use temperature environment (generally 10 ° C. to 35 ° C.), the position error of the folding mirror 18 with respect to the rotating polyhedron 19 does not remain.

  Although not shown in the figure, a heat radiating portion integrated with these is provided on the lower surface of the left flange 25.

  In one embodiment of the present invention, the flange 25 is continuously extended from the mounting plate 13 along the back surface of the optical housing 12, and the fastening means 27 is disposed in a range occupied by the optical housing 12 in plan view. It is also possible to arrange a part or all of the fastening means 27 in the opening 24.

  In this case, for example, the optical housing 12 is provided with a flange extending from the peripheral edge of the opening 24 into the opening 24, and the fastening means 27 inserted through the flange is screwed to the mounting plate 13. Is done.

  The present invention is applied to an image forming apparatus such as a printer, a copying machine, a facsimile, or a complex machine using electrophotographic technology.

It is a top view of the present invention. It is the schematic of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Optical housing 13 Mounting plate 14 Laser emitter 18 Folding mirror 19 Rotating polyhedron 20 Motor 27 Fastening means

Claims (2)

An optical housing that supports a folding mirror that reflects a laser beam emitted from a laser emitter, and a rotating polyhedron that is made of a different material having a coefficient of thermal expansion different from that of the optical housing and receives the laser beam reflected by the folding mirror. In an image forming apparatus comprising a mounting plate that is fastened to the optical housing via fastening means at a plurality of locations,
An image forming apparatus characterized in that all of the plurality of fastening means are separated from a straight line connecting the laser emitter and the folding mirror in the optical housing. 2. The image forming apparatus according to claim 1, wherein all of the plurality of fastening units are separated from the straight line farther than a width range of the folding mirror.

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