JP4139118B2 - Optical writing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical writing device that irradiates a scanning surface of an image carrier with a light beam and writes a latent image, and a copying machine, printer, facsimile, plotter, and the like that includes the optical writing device to form an image. The present invention relates to an image forming apparatus.
[0002]
[Prior art]
Light beams emitted from a plurality of light sources are applied to four image carriers (for example, photoconductor drums) arranged in parallel to write latent images, and latent images formed on the image carriers are recorded. After developing with different color developers (for example, yellow, magenta, cyan, and black toners) to make visible images, transfer materials such as recording paper carried on a transfer conveyance belt or the like are transferred to each image carrier. Tandem to obtain a multicolor image by sequentially transporting to the transfer unit and transferring each color visible image formed on each image carrier superimposed on the transfer material and fixing the image transferred on the transfer material A color image forming apparatus of the type is known.
[0003]
7 and 8 show an example of an optical writing device used in a tandem color image forming apparatus. The optical writing device 100 includes four light source units 52, 53, 54, 55 and an optical deflector 62 that deflects and scans light beams L1, L2, L3, and L4 from each light source unit in two symmetrical directions. Have. The optical deflector 62 includes motor rotation control electrical components such as a driver IC, a capacitor, and a resistor, and a motor rotation coil.
Further, a plurality of light beams which are arranged symmetrically with respect to the vertical axis passing through the optical deflector 62 and are deflected and scanned by the optical deflector 62 are respectively applied to the scanned surfaces of the corresponding photosensitive drums 1, 2, 3, 4 respectively. An optical system for guiding and imaging is provided. The optical system includes optical elements such as fθ lenses 63 and 64, long lenses 69, 70, 71, and 72, and optical path folding mirrors 65, 66, 67, and 68. These constituent members described above are accommodated in one housing 50.
[0004]
The housing 50 includes a partition member 50A in which the optical deflector 62 and the optical system are disposed, and a frame-shaped side wall 50B surrounding the partition member 50A. The partition member 50A is provided at a substantially central portion of the side wall 50B. It is provided and has a structure that partitions the housing 50 up and down. The four light source units 52, 53, 54, and 55 are disposed on the side wall 50 </ b> B of the housing 50, and the light deflector 62 is disposed at a substantially central portion of the partition member 50 </ b> A of the housing 50.
The partition member 50A is formed with light passage openings 50A-1, 50A-2, 50A-3, and 50A-4 for allowing the beam to reach the mirror in the lower region.
[0005]
In the optical writing device 100, color-separated image data input from a document reading device (scanner) or an image data output device (personal computer, word processor, facsimile receiver, etc.) (not shown) is converted into a light source driving signal. Accordingly, the light source (semiconductor laser (LD)) in each light source unit 52, 53, 54, 55 is driven to emit a light beam. The light beams L1, L2, L3, and L4 emitted from the light source units 52, 53, 54, and 55 pass through the cylindrical lenses 56, 57, 58, and 59 for correcting the surface tilt and directly or via the mirrors 60 and 61, respectively. The light deflector 62 is then deflected and scanned in two symmetrical directions by two-stage polygon mirrors 62a and 62b rotated at a constant speed by a polygon motor.
[0006]
The light beams deflected and scanned in two directions by two beams by the two-stage polygon mirrors 62a and 62b of the optical deflector 62 pass through, for example, fθ lenses 63 and 64 having two upper and lower layers, respectively, to form a long toroidal lens (WTL). Are reflected by the first folding mirrors 65, 66, 67 and 68 through the second imaging lenses 69, 70, 71 and 72. The first folding mirrors 65, 66, 67, and 68 are arranged on the upper side of the partition member 50A.
Thereafter, the light beam passes through the openings 50A-1, 50A-2, 50A-3, and 50A-4, and is then reflected or transmitted by optical elements such as second folding mirrors 73, 75, 77, and 79, for example. Irradiation onto the scanned surface of the body drums 1, 2, 3, and 4 writes an electrostatic latent image.
[0007]
As described above, the optical writing device in such a tandem type color image forming apparatus has the optical deflector 62 composed of a polygon mirror and its driving motor, and the fθ characteristic provided in the vicinity of the optical deflector 62. The fθ lenses 63 and 64 are disposed, and thereafter, the long lenses 69, 70, 71, and 72 are disposed in the same space (on the same surface) (on the scanning surface side).
The optical deflector 62 has a heat source such as a driver IC for driving a driving motor, a capacitor, a resistor, and a coil, and heat is generated by friction caused by high-speed rotation of the rotating shaft of the motor. For this reason, when the polygon mirror is rotated, the driver IC and the like generate heat, and the temperature on the upper surface side of the partition member on which the optical deflector is disposed rises due to the heat generated by the heat from the heat on the lower surface side of the partition member. To do.
[0008]
Due to this temperature rise, the fθ lenses 63 and 64 and the long lenses 69, 70, 71, and 72 are thermally affected to cause changes in writing magnification and writing positions (beam spot position and beam diameter). There is a problem of causing deterioration of the image.
In order to prevent these problems, glass lenses having a relatively small linear expansion coefficient are used for the fθ lenses 63 and 64 and the long lenses 69, 70, 71 and 72.
[0009]
In addition, the periphery of the optical deflector 62 is hermetically sealed to reduce the thermal influence on the fθ lenses 63 and 64. That is, as shown in FIG. 8, the vicinity of the optical deflector 62 is hermetically sealed by the housing wall 600 shown by hatching and the sealing glass 601 (used for the optical path passage location).
[0010]
[Problems to be solved by the invention]
However, when glass is used for the lens, there is a problem that an increase in cost cannot be avoided.
In the configuration in which the periphery of the optical deflector is sealed, although the temperature influence on the fθ lens and WTL is reduced, the temperature rise of the optical deflector itself is increased and the driver IC is used beyond the operating temperature range. Therefore, a member (fan, heat sink, etc.) for cooling it is necessary, and the cost has been increased. Furthermore, there is a problem that an extra cost for the glass for sealing the space is generated.
[0011]
SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide an optical writing apparatus that can suppress thermal influence on an optical system and can reduce costs, and an image forming apparatus including the optical writing apparatus.
[0012]
[Means for Solving the Problems]
To achieve the above object, according to the first aspect of the present invention, a light source, a light deflector for deflecting and scanning a light beam from the light source, and a scanned object corresponding to the light beam deflected and scanned by the light deflector are provided. An optical writing device comprising an optical system that guides and forms an image on a surface, wherein the light source, the optical deflector, and the optical system are housed in a single housing, wherein the housing is partitioned by a partition member, and the partition member The optical deflector is disposed on one surface side of the optical system, and the optical system is separately disposed with the partition member interposed therebetween, and the partition member is formed of a material having a lower thermal conductivity than the main body of the housing. The optical element disposed on the same side as the optical deflector is formed of glass, and the optical element disposed on the opposite side of the optical deflector is formed of plastic .
[0013]
According to a second aspect of the present invention, in the optical writing device according to the first aspect, the partition member is formed of a material having a smaller linear expansion coefficient than the main body of the housing .
[0014]
According to a third aspect of the present invention, in the optical writing device according to the first aspect, the volume of the optical element disposed on the same side as the optical deflector is an optical disposed on the side opposite to the optical deflector. The configuration is smaller than the volume of the element .
[0015]
According to a fourth aspect of the present invention, in the optical writing device according to the first aspect , a part of the optical deflector protrudes to the opposite side, and the periphery of the protruding part is sealed with the same material as the partition member. The structure is covered .
[0016]
According to a fifth aspect of the present invention, in the optical writing device according to the first aspect , a part of the optical deflector protrudes to the opposite side, and an encircling part surrounding the projecting part is formed. It is formed of the same material as the partition member and opens to the outside of the housing .
[0017]
According to a sixth aspect of the present invention, an image carrier, an optical writing unit that writes a latent image by irradiating a scanning surface of the image carrier with a light beam, and a developing unit that visualizes the latent image. And an image forming apparatus comprising: a transfer unit that transfers the visible image onto a transfer material; and a fixing unit that fixes the image transferred onto the transfer material . The optical writing device according to one of the above is provided.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In addition, only the code | symbol common to the part which is common in a conventional structure is attached | subjected, and the overlapping description is abbreviate | omitted.
1 is a cross-sectional view of the optical writing device, FIG. 2 is a plan view of the optical writing device, FIG. 3 is a diagram showing a scanning state in FIG. 2, and FIG. 4 is a schematic configuration of an image forming apparatus provided with the optical writing device FIG.
First, an outline of the configuration and operation of the image forming apparatus will be described with reference to FIG.
The image forming apparatus having the configuration shown in FIG. 4 is a full-color image forming apparatus in which a plurality of drum-shaped photoconductive photosensitive members (photosensitive drums) 1, 2, 3, and 4 are juxtaposed as a plurality of image carriers. The four photosensitive drums 1 to 4 form, for example, images corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk) sequentially from the right in the drawing. is there. The order of colors is not limited to this, and can be set arbitrarily.
[0022]
Around each of the four photosensitive drums 1 to 4, charging units (charging roller, charging brush, charging charger, etc.) 6, 7, 8, 9 for forming an image by an electrophotographic process, optical writing Are disposed on the exposure unit of the light beams L1 to L4 from the image forming device 5, development units (development units of each color of Y, M, C, and Bk) 10, 11, 12, 13, and the transfer conveyance belt 22a and the back surface thereof. Transfer means 22 having transfer means (transfer rollers, transfer brushes, etc.) 14, 15, 16, 17 and cleaning units (cleaning blades, cleaning brushes, etc.) 18, 19, 20, 21 etc. are provided. Thus, it is possible to form images of the respective colors on the respective photosensitive drums 1 to 4.
[0023]
Under the four photosensitive drums 1 to 4 arranged side by side, a transfer conveyance belt 22a stretched between a driving roller and a plurality of driven rollers is disposed, and is driven by the driving roller in a direction indicated by an arrow in the figure. Being transported. In addition, a plurality of paper feeding units 23 and 24 that store transfer materials such as recording paper are installed at the lower part of the main body of the image forming apparatus, and the transfer materials stored in the paper feeding units 23 and 24 feed paper. The paper is fed to the transfer conveyance belt 22a through the roller, the conveyance roller pair, and the registration roller pair 25, and is carried and conveyed by the transfer conveyance belt 22a.
[0024]
The latent images formed on the photoconductors 1 to 4 by the optical writing device 5 are developed with toners of colors Y, M, C, and Bk of the developing units 10 to 13 to be visualized. The imaged toner images of each color of Y, M, C, and Bk are sequentially superimposed and transferred onto the transfer material carried on the transfer conveyance belt 22 a by the transfer units 14 to 17 of the transfer conveyance device 22.
The transfer material onto which the four color images have been transferred is conveyed to the fixing device 26, where the image is fixed by the fixing device 26, and then discharged onto the paper discharge tray 28 by the paper discharge roller pair 27.
[0025]
As shown in FIG. 2, in the optical writing device 5, the four light source units 52, 53, 54, and 55 are arranged symmetrically in substantially opposite directions with respect to the axis passing through the optical deflector 62. As shown in FIG. 1, the optical writing device 5 guides the plurality of light beams L1 to L4 deflected and scanned by the optical deflector 62 onto the scanned surfaces of the corresponding photosensitive drums 1 to 4, respectively. An optical system for imaging (comprising optical members (optical elements) such as imaging lenses 63, 64, 69 to 72, and optical path folding mirrors 65 to 68, 73 to 80) is provided. Housed in one housing 50.
In the housing 50, fθ lenses 63 and 64 (first imaging lens) which are optical elements constituting the optical system, long toroidal lenses (WTL) 69 to 72 (second imaging lens), optical path The folding mirrors 65-68, 73-80, etc. are arranged separately on both surfaces (upper surface side and lower surface side) of the partition member 50C.
Covers 87 and 88 are provided at the upper and lower portions of the housing 50, and an opening through which the light beam passes is provided in the lower cover 87, and the dustproof glasses 83, 84, 85, and 86 are provided in the openings. Is attached.
[0026]
In the optical writing device 5, color-separated image data input from an unillustrated document reading device or the like is converted into a light source driving signal as in the conventional example, and the light sources in the light source units 52 to 55 are accordingly converted. A semiconductor laser (LD) is driven to emit a light beam, passed through cylindrical lenses 56 to 59 for surface tilt correction, and led to an optical deflector 62 directly or via mirrors 60 and 61, and a polygon motor 62c. Are deflected and scanned in two symmetrical directions by two-stage polygon mirrors 62a and 62b rotated at a constant speed.
The polygon mirrors 62a and 62b are divided into two upper and lower stages for the light beams L2 and L3 and for the light beams L1 and L4. However, a thick polygon mirror may be used to deflect and scan four light beams. Good.
[0027]
The light beams deflected and scanned in two directions by the polygon mirrors 62a and 62b of the optical deflector 62 pass through the fθ lens lenses 63 and 64, respectively, and are folded by the first folding mirrors 65 to 68 to be separated into the partition member 50C. After passing through the openings 50C-1, 50C-2, 50C-3, and 50C-4, long toroidal lens (WTL) lenses 69 to 72 disposed on the lower surface side of the partition member 50C are passed through, Two scanning mirrors 73, 75, 77, and 79, third folding mirrors 74, 76, 78, and 80, and dust-proof glasses 83 to 86 on the scanned surfaces of the photosensitive drums 1, 2, 3, and 4 for each color. Irradiate and write an electrostatic latent image.
[0028]
The four light source units 52 to 55 are composed of a semiconductor laser (LD) that is a light source and a collimating lens that collimates the emitted light beam of the semiconductor laser, and these are integrally incorporated in a holder. A light source unit for black (for example, a light source unit denoted by reference numeral 54) that is frequently used at the time of formation has a multi-beam configuration including a pair of two or more light sources (LD) and a collimating lens in order to enable high-speed writing. Also good.
In the case of a multi-beam configuration, if the light source unit is configured to be rotatable about the optical axis with respect to the side wall 50B of the housing 50, the beam pitch in the sub-scanning direction can be adjusted, and the pixel density during monochrome image formation (For example, 600 dpi, 1200 dpi, etc.) can be switched.
[0029]
The optical path of each of the light beams L1 to L4 is provided with a synchronization detection mirror (not shown) for taking out the light beam at the scanning start position in the main scanning direction, and the light beam reflected by the synchronization detection mirror is synchronized with the synchronization detector. The light is received at 81 and 82 and a scanning start synchronization signal is output.
As shown in FIG. 3, the scanning direction of the light beam deflected and scanned by the light deflector 62 is the main scanning direction, which is the axial direction of each of the photosensitive drums 1 to 4. The direction orthogonal to the main scanning direction is the sub-scanning direction, which is the rotation direction of the photosensitive drums 1 to 4 (moving direction of the photosensitive drum surface), and further in the conveyance direction of the transfer conveyance belt 22a described later. is there. That is, the width direction of the transfer conveyance belt 22a is the main scanning direction, and the conveyance direction is the sub-scanning direction.
[0030]
As described above, the optical system installation space of the housing 50 is partitioned vertically by the partition member 50C having low thermal conductivity, that is, heat insulation, and the optical deflector 62 that generates heat is disposed on the upper surface side. Yes. In the present embodiment, the main body of the housing 50 is integrally formed of resin, and the partition member 50C is formed of a highly heat insulating member. As a member having high heat insulation, for example, a resin mixed with glass fiber, a member having a low thermal conductivity itself, or a member having a configuration in which a member having a low thermal conductivity is sandwiched between resins can be employed.
In the optical system, the fθ lenses 63 and 64 disposed on the same side (upper surface side) as the optical deflector 62 are made of glass, and the opposite side, that is, the lower surface that is not easily affected by the heat of the polarizer 62. The long toroidal lenses (WTL) 69 to 72 arranged on the side are made of plastic (for example, polycarbonate or acrylic) which is a material having a linear expansion coefficient larger than that of glass.
The polygon motor 62c of the optical deflector 62 protrudes to the lower surface region, but the periphery of the polygon motor 62c is sealed by a side wall integrally formed with the partition member 50C over the range of the lower cover 87. For this reason, the heat emitted from the optical deflector 62 is restrained from moving to the lower surface side by the heat insulating property of the partition member 50C, and stays almost only on the upper surface side.
[0031]
Since the temperature rise on the lower surface side is suppressed, even if the long toroidal lenses (WTL) 69 to 72 are made of plastic, they are hardly affected by heat. When the optical element arranged on the lower surface side is made of inexpensive plastic, the characteristic deterioration or change due to heat of the optical element can be prevented and the performance can be improved, and the optical element arranged on the lower surface side is also formed of glass As a result, the cost can be reduced.
In the present embodiment, in particular, long toroidal lenses (WTL) 69 to 72, which are optical elements having a large volume, in other words, a large projected area from the top (large size) are disposed on the lower surface side and are made of plastic. Since it is formed, the cost reduction rate is high.
[0032]
The partition member 50C may be formed of a material (for example, aluminum) having a smaller linear expansion coefficient than the main body (plastic) of the housing 50. In this case, the thermal influence on the position of the optical element can be suppressed with high accuracy.
[0033]
Next, a second embodiment will be described based on FIG. In addition, the same part as the said embodiment is shown with the same code | symbol, The description on the structure and function which were already demonstrated is abbreviate | omitted unless there is particular need, and only a principal part is demonstrated (same in other following embodiment).
In the present embodiment, the openings 50C-1, 50C-2, 50C-3, and 50C-4 that allow light to pass from the upper surface side to the lower surface side are blocked with glass 90A, 90B, 90C, and 90D as light transmissive materials. It is characterized by being.
The heat generated on the upper surface side convects to the lower surface side through the openings 50C-1, 50C-2, 50C-3, 50C-4, and the characteristics of the optical element which is easily affected by heat formed of plastic or the like. The purpose is to prevent the decrease.
Although the cost reduction can not be expected by newly providing the glass 90A, 90B, 90C, 90D, it is possible to prevent the deterioration of the characteristics of the optical element made of plastic or the like with high accuracy.
[0034]
Next, a third embodiment will be described based on FIG.
In each of the above embodiments, the periphery of the polygon motor 62c, which is a part of the optical deflector 62 protruding to the lower surface side, is sealed with the same material as the partition member 50C in the region on the lower surface side. There is a possibility that the temperature of the lower surface side is raised and the purpose is to prevent this.
The circumference of the polygon motor 62c is surrounded by a surrounding portion 91 formed of the same material as that of the partition member 50C. The lower end of the surrounding portion 91 passes through the lower cover 87 and opens to the outside of the housing 50. That is, the polygon motor 62 c is exposed to the air outside the housing 50.
The heat of the polygon motor 62c is diffused to the outside of the housing 50 and is cooled by the air outside the housing 50, so that the temperature rise in the lower surface region can be suppressed with high accuracy and the light deflector 62 can be air-cooled. .
[0035]
【The invention's effect】
According to the invention of claim 1 or 6, wherein, as compared to some of the light studies based on glass for example, can be formed by an inexpensive plastic, it is possible to reduce the cost, adverse effects of heat of the light deflector Can be suppressed.
Further, the writing performance can be improved, and the cost can be reduced by using a glass optical element only on one side of the partition member.
Further, the adverse effect of the optical deflector due to heat can be further suppressed.
[0038]
According to the invention of claim 2 or 6, wherein it is possible to suppress the adverse effect of heat of the optical deflector relative to the position of the light optical element with high precision.
[0039]
According to the invention of claim 3 or 6, wherein it is possible to increase the cost reduction rate.
[0041]
According to the invention of claim 4 or 6, wherein it is possible to suppress the adverse effect of heat of the optical deflector in opposition side with high accuracy.
[0042]
According to the invention of claim 5 or 6, wherein it is possible to suppress more accurately the adverse effect of heat of the optical deflector in opposition side.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of the optical writing device according to the first embodiment of the present invention, taken along line AA in FIG.
FIG. 2 is a plan view of the optical writing device.
FIG. 3 is a diagram illustrating a scanning state in FIG. 2;
FIG. 4 is a schematic front view of the image forming apparatus.
FIG. 5 is a cross-sectional view of an optical writing device according to a second embodiment.
FIG. 6 is a cross-sectional view of an optical writing device according to a third embodiment.
FIG. 7 is a cross-sectional view of a conventional optical writing device.
FIG. 8 is a plan view of a conventional optical writing device.
[Explanation of symbols]
50 Housing 50C Partition member 50C-1, 50C-2, 50C-3, 50C-4 Opening 52, 53, 54, 55 Light source unit 62 Optical deflector 63, 64 fθ lenses 69, 70, 71 as optical elements 72 Long Toroidal Lens 91 as an Optical Element

Claims (6)

A light source, an optical deflector that deflects and scans the light beam from the light source, and an optical system that guides and images the light beam deflected and scanned by the optical deflector onto a corresponding scanned surface. In an optical writing device in which an optical deflector and the optical system are housed in one housing,
The housing is partitioned by a partition member, the optical deflector is disposed on one surface side of the partition member, the optical system is separately disposed with the partition member interposed therebetween, and the partition member is disposed on the housing. The optical element is made of a material having a lower thermal conductivity than the main body, and the optical element disposed on the same side as the optical deflector is formed of glass, and the optical element disposed on the opposite side of the optical deflector is plastic. optical writing apparatus characterized by being formed. The optical writing device according to claim 1,
An optical writing apparatus, wherein the partition member is formed of a material having a smaller linear expansion coefficient than the main body of the housing . The optical writing device according to claim 1,
An optical writing apparatus , wherein a volume of an optical element arranged on the same side as the optical deflector is smaller than a volume of an optical element arranged on the opposite side to the optical deflector . The optical writing device according to claim 1,
A part of the optical deflector protrudes on the opposite side, and the periphery of the protruding part is covered with the same material as the partition member in a sealed state . The optical writing device according to claim 1,
A part of the optical deflector protrudes to the opposite side, and an encircling part surrounding the projecting part is formed. The encircling part is formed of the same material as the partition member and opens to the outside of the housing. optical writing apparatus characterized by there. An image carrier, an optical writing unit that irradiates a scanning surface of the image carrier with a light beam to write a latent image, a developing unit that visualizes the latent image, and the visible image is transferred. In an image forming apparatus having a transfer means for transferring to a material and a fixing means for fixing an image transferred on the transfer material ,
An image forming apparatus comprising the optical writing device according to claim 1 as the optical writing unit .

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