JP2006126669A - Optical scanner and image forming apparatus provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner which can cope with high resolution or speed-up of an apparatus and can be changed in both ways at a low cost, without changing the housing for installing an optical element and causing contamination to be produced from dust such as toner, and to provide an image forming apparatus provided with the optical scanner. <P>SOLUTION: The optical scanner comprises a first optical system which couples luminous fluxes emitted from light sources; a holder which fixes the light sources and the first optical system; a second optical system which condenses the luminous flux coupled by the first optical system in a long line shape, in the main scanning direction; an optical deflector which deflects the luminous flux condensed by the second optical system; a third optical system which condenses the luminous flux deflected by the deflector onto the face to be scanned as a light spot; and an optical housing which houses the holder and the optical systems. Four or more holes are bored for inserting the holder into the optical housing, the holder is inserted into only two holes, and holes other than these are hermetically sealed with a plate or a resin member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides optical writing for digital copying machines, facsimiles, laser printers, etc., in which an electrostatic latent image is formed on a photosensitive member by a plurality of beams, and a multicolor image is obtained by superimposing the electrostatic latent images. The present invention relates to an optical scanning device used in the system and an image forming apparatus including the same.

In recent years, optical means for emitting laser beams emitted from a plurality of light sources as scanning beams are integrally formed in one housing, and each scanning beam emitted from the housing is provided corresponding to each scanning beam. There are known multicolor image forming apparatuses that form images of a plurality of colors by forming images on a plurality of photoconductors, and obtain multicolor images by superimposing and transferring them onto recording paper on each photoconductor (for example, patents). Reference 1 and 2).
For example, four photosensitive drums are arranged along the conveyance direction of the recording paper, and a latent image is formed by simultaneously exposing with a scanning beam corresponding to each of the photosensitive drums, and these visible images are formed on the same recording paper. Digital copiers, laser printers, and the like that are sequentially superimposed and transferred to obtain color images have been put into practical use.
A plurality of scanning means are used when performing optical scanning with such an image output machine. However, a large space is required to arrange the scanning means, and the entire apparatus is increased in size. As disclosed in Japanese Patent Application Laid-Open No. 2004-218, there has been proposed a system in which a plurality of light beams are incident on a single deflector and scanned, and imaging lenses are stacked and arranged.
Further, in Patent Document 2, a structure in which a laser diode and a cylindrical lens are integrally combined is attached to a circular opening, and laser beams of four colors can be irradiated to the photosensitive drum by the two structures. A method has been proposed.
JP-A-10-254212 JP 2003-248186 A

However, in Patent Document 1, it is possible to obtain a high resolution, but since a large and expensive part such as a beam splitter is used, the optical scanning device is also increased in size and expensive. In order to avoid this, a method of adjusting the beam to a desired resolution pitch on the photosensitive drum without using a beam splitter has been studied and put into practical use.
However, even if the resolution is lowered, the number of holders for fixing the first optical system is the same, and the cost reduction range is small. Further, if the number of holders is reduced, a new optical housing is required, and a new cost is generated.
Moreover, in patent document 2, since the holder itself becomes quite large because it is a structure in which a laser diode and a cylindrical lens are combined together, it becomes difficult to assemble, and an opening for inserting two structures is provided. There are four, and it is considered that dust such as toner enters from there. Further, it is difficult to reduce the laser beam by fixing the cylindrical lens away from the polygon scanner.
In view of the above, the object of the present invention is to cope with high resolution or high speed of the apparatus without changing the housing for installing the optical element, and can be changed to either one at low cost. It is an object of the present invention to provide an optical scanning device and an image forming apparatus provided with the optical scanning device that prevent contamination from dust and the like from occurring.

In order to solve the above-mentioned problem, the invention according to claim 1 includes a first optical system for coupling a light beam emitted from a light source, a holder for fixing the light source and the first optical system, A second optical system for condensing the light beam coupled by the first optical system into a line that is long in the main scanning direction, an optical deflector for deflecting the light beam collected by the second optical system, An optical scanning device comprising: a third optical system that condenses the light beam deflected by the deflector as a light spot on a surface to be scanned; and an optical housing that houses the holder and the optical system. The optical scanning device is characterized in that four or more holes for inserting the holder are opened, the holder is inserted into only two of these holes, and the other holes are sealed with a sheet metal or a resin member. .
The invention according to claim 2 is characterized in that the hole is arranged substantially symmetrically with respect to a line passing through the center of the deflector and parallel to the scanned surface. To do.
According to a third aspect of the present invention, there is provided the optical scanning device according to the first or second aspect, wherein the hole exists in a range of 60 ° or 60 ° ± 10 ° with respect to a perpendicular standing on the surface to be scanned. To do.
The invention according to claim 4 is characterized in that the holder has two light sources and two first optical systems, and the optical scanning device according to any one of claims 1 to 3.
According to a fifth aspect of the present invention, the reflective surface of the deflector is divided into two upper and lower stages in the axial direction, or has a height corresponding to the reflective point. Features the described optical scanning device.
According to a sixth aspect of the present invention, there is provided an image forming apparatus including the optical scanning device according to any one of the first to fifth aspects.

  According to the present invention, since the structure is simple and no large parts are used, it is possible to mount four or more holders in four or more holes. It is possible to cope with the resolution or the high speed (printing speed) of the apparatus, and it is possible to change at a low cost because the housing is not changed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a front view illustrating the overall configuration of the main part of the image forming apparatus. Here, a general tandem type image forming apparatus will be described.
An endless belt 70 having a holding function for holding transfer paper is stretched between two rollers 71 and 72 serving as support members arranged facing each other in the horizontal direction. A photosensitive member (photosensitive member) carrying toner images of BK (black), Y (yellow), C (cyan), and M (magenta) from the downstream side in the rotational direction indicated by the arrows along the upper belt of the belt 70. Drum) 1BK, 1Y, 1C, 1M are arranged in contact with belt 70.
Around these photosensitive drums 1BK, 1Y, 1C, and 1M, charging rollers 72BK, 72Y, 72C, and 72M, developing devices 73BK, 73Y, 73C, and 73M, and cleaning units 74BK, 74Y, and 74C, in order of the respective rotational directions. 74M etc. are arranged. The developing rollers 75 provided in the developing devices 73BK, 73Y, 73C, and 73M are disposed in proximity to the corresponding photosensitive members.
An image forming unit is constituted by a charging device, a developing device, a cleaning unit, and the like disposed around each of the photosensitive drums. In other words, the image forming units 76BK, 76Y, 76C, and 76M are disposed so as to face the belt 70 as a unit for forming an image with each color of BK, Y, M, and C.
Transfer devices 77BK, 77Y, 77C, and 77M are disposed through the belt 70 so as to face the photosensitive drums 1BK, 1Y, 1C, and 1M in the image forming units 76BK, 76Y, 76C, and 76M.
Further, an optical writing means 10 is disposed above each photosensitive drum 1BK, 1Y, 1C, 1M, and a laser beam Lb modulated according to a color image signal is emitted, and each photosensitive drum 1BK, 1Y is emitted. The exposure unit between the charging roller and the developing device in 1C and 1M is irradiated.
Here, there is no problem even if the order of the photosensitive drums 1BK, 1Y, 1C, and 1M is not the same. The same applies to the charging devices, developing devices, cleaning means, and the like around the photosensitive drums 1BK, 1Y, 1C, and 1M. Further, there is no problem even if the optical writing means 10 is disposed below each of the photosensitive drums 1BK, 1Y, 1C, and 1M.

The belt 70 is driven to rotate counterclockwise as indicated by an arrow. A pair of registration rollers 78 are provided at a position further upstream of the upper belt of the belt 70. The transfer paper P is sent out from the paper feed roller 79 toward the registration roller 78.
A fixing device 85 is disposed at a further downstream position of the belt 70 on the downstream side of the upper belt. At the upstream end of the upper belt of the belt 70, above the roller 72 supporting the belt 70, a corona discharge wire as a transfer paper adsorbing means is provided so that the transfer paper P is electrostatically adsorbed to the belt 70. The used charger 80 is provided.
A neutralization means 81 is provided at the downstream end of the upper belt of the belt 70 and opposite to the roller 71 to neutralize the transfer paper P and easily remove it from the belt 70.
The lower belt of the belt 70 is provided with a static elimination means 82 using a corona discharge wire for eliminating the static electricity of the belt 70, and the roller 72 has a cleaning brake which can contact and separate from the roller 72 via the belt 70. 83 is provided.
These image forming means 76BK, 76Y, 76C, 76M provided around the belt 70, the optical writing means 10, the transfer devices 77BK, 77Y, 77C, 77M, the charger 80, the cleaning blade 83, and the charge eliminating means 81, 82. Are process means for image formation.
In this image forming apparatus, when the photosensitive drums 1BK, 1Y, 1C, and 1M start to rotate, the photosensitive members are uniformly charged by the charging rollers 72BK, 72Y, 72C, and 72M during the rotation.
A latent image corresponding to an image to be created is formed by irradiating and scanning the exposure portion of the photosensitive drum with the laser light Lb so that the writing timing is shifted so as to be transferred onto the same transfer paper P, and each developing device A toner image is formed by 73BK, 73Y, 73C, and 73M.
On the other hand, the transfer paper P stored in the paper feed unit is fed out by the paper feed roller 79, and temporarily stops at the position of the pair of registration rollers 78 through a conveyance path indicated by a broken line, and the photosensitive drums 1BK, 1Y, 1C, The transfer paper P that has been stopped by the registration roller 78 is sent out from the registration roller 78 and is attracted to the belt 70 by the charger 80. Then transported.

The respective toner images of the photosensitive drums 1BK, 1Y, 1C, and 1M are sequentially transferred onto the transfer paper P at the transfer portion that is in contact with the photosensitive drums, and the colors are superimposed to form a full-color toner image. It is formed.
The portions where the photosensitive drums 1BK, 1Y, 1C, and 1M are in contact with the belt 70 constitute transfer portions, and the transfer devices 77BK, 77Y, 77C, and 77M are positioned in these transfer portions.
The transfer sheet P on which the full color toner image has been transferred is discharged by the discharging unit 81 and then separated from the belt 70, conveyed as it is to the fixing device 85, fixed, and discharged to the discharge tray 84.
On the other hand, residual toner remaining on the photosensitive drums 1BK, 1Y, 1C, and 1M reaches the cleaning means 74BK, 74Y, 74C, and 74M along with the rotation of the photosensitive drums 1BK, 1Y, 1C, and 1M. To be prepared for the next image formation.
Also, the belt 70 after separating the transfer paper P is discharged by the discharging means 82 and then reaches the cleaning blades 83 of the cleaning means 74BK, 74Y, 74C, and 74M, and is cleaned to prepare for the next transfer sheet conveyance. It is done.
The reason why the belt 70 is cleaned by the cleaning blade 83 is that a part of the toner image may be transferred onto the belt 70 from the photosensitive drums 1BK, 1Y, 1C, and 1M.
This is also to prevent transfer of paper dust from the transfer paper, and transfer toner, paper dust and the like from the back of the next transfer paper. Then, the cleaning blade 83 is separated immediately before the joint of the belt 70 reaches the cleaning blade 83 and is brought into contact again as soon as it passes.
FIG. 2 is a schematic diagram illustrating the optical path of the optical scanning device. The optical scanning device 10 'is housed in a sealed optical housing 20 having a flat box shape. A polygon scanner 3 is provided at a substantially central position of the optical housing 20.
Four photosensitive drums that are a part of the image forming apparatus are arranged in parallel so as to face the optical scanning device 10 ′. Here, the photosensitive drums 1BK, 1Y, 1C, and 1M carrying the toner images of BK (black), Y (yellow), C (cyan), and M (magenta) are set.
In order to irradiate and scan the four photosensitive drums 1BK, 1Y, 1C, and 1M with laser light, a large number of optical elements are arranged around the polygon scanner 3 in the optical housing 20. A group of optical elements on the left side of the polygon scanner 3 is an optical element group for irradiating the photosensitive drum 1BK and the photosensitive drum 1Y.

The right optical element group is an optical element group for irradiating the photosensitive drum 1C and the photosensitive drum 1M. The group of optical elements on the left side includes an optical element group for guiding laser light to the photosensitive drum 1BK and an optical element group for guiding laser light to the photosensitive drum 1Y.
The optical element group for guiding the laser beam to the photosensitive drum 1BK includes an fθ lens 4-BK, a first mirror 5-1BK, a toroidal lens 6-BK, a second mirror 5-2BK, and a third mirror 5-3BK. Etc., and in this order, reaches the photosensitive drum 1BK through the dust-proof glass 7-BK.
The optical element group for guiding the laser beam to the photosensitive drum 1Y includes an fθ lens 4-Y, a first mirror 5-1Y, a toroidal lens 6-Y, a second mirror 5-2Y, and a third mirror 5-3Y. And the like, proceeding in this order to reach the photosensitive drum 1Y through the dust-proof glass 7-BK.
Photosensitive drums 1BK, 1Y, fθ lenses 4-BK, 4-Y, first mirror 5-1BK, second mirror 5-2BK, first mirror 5-1Y, first mirror 5-2Y, etc. and dustproof glass 7- BK, 7-Y is composed of a long mirror that is long in the depth direction of the paper surface. Since the fθ lens 4-BK and the fθ lens 4-Y are integrally formed, they are handled as the fθ lens 4.
In order to determine the writing start timing for each photosensitive drum, a detection sensor 9-1 is disposed on the scanning start end side. The detection sensor 9-1 is commonly used to detect both the laser beams Lb directed to the photosensitive drums 1BK and 1Y, and the light beam Lb reflected on one end side of the second mirror 5-2BK is reflected on the mirror 5. -2'BK and mirror 8-1BK are reflected in this order and led to the detection sensor 9-1.
Similarly, the light beam Lb reflected on one end side of the second mirror 5-2Y is reflected in the order of the mirror 8-1Y and guided to the detection sensor 9-1. These mirrors 5-2′BK, 8-1BK, 8-1Y, etc. are mirrors for guiding the laser light Lb to the detection sensor 9-1, and small mirrors are used.

The optical element group on the right side is configured symmetrically with the optical element group on the left side, the optical element group for guiding the laser beam to the photosensitive drum 1M, and the laser beam to the photosensitive drum 1C. And an optical element group.
The optical element group for guiding the laser beam to the photosensitive drum 1M includes an fθ lens 4-M, a first mirror 5-1M, a toroidal lens 6-M, a second mirror 5-2M, and a third mirror 5-3M. And the like, proceeding in this order to reach the photosensitive drum 1M through the dust-proof glass 7-M.
The optical element group for guiding the laser beam to the photosensitive drum 1C includes an fθ lens 4-C, a first mirror 5-1C, a toroidal lens 6-C, a second mirror 5-2C, and a third mirror 5-3C. And the like, proceeding in this order to reach the photosensitive drum 1C through the dust-proof glass 7-C.
Photosensitive drums 1M and 1C, fθ lenses 4-M and 4-C, a first mirror 5-1M, a second mirror 5-2M, a first mirror 5-1C, a second mirror 5-2C, etc., and a dustproof glass 7- M and 7-C are long mirrors that are long in the depth direction of the paper surface. Since the fθ lens 4-M and the fθ lens 4-C are integrally formed, they are handled as the fθ lens 4 ′.
In order to determine the writing start timing for the photosensitive drum, a detection sensor 9-2 is disposed on the scanning start end side. The detection sensor 9-2 is commonly used to detect both the laser beams Lb directed to the photosensitive drums 1M and 1C, and the mirror 5 reflects the light beam Lb reflected from one end side of the second mirror 5-2M. -2'M and 8-1M are sequentially reflected and led to the detection sensor 9-2.
Similarly, the light beam Lb reflected on one end side of the second mirror 5-2C is reflected in the order of the mirror 8-1M and guided to the detection sensor 9-2. These mirrors 5-2′M, 8-1M, 8-1C and the like are mirrors for guiding the laser light Lb to the detection sensor 9-2, and small mirrors are used.

FIG. 3 is a perspective view showing the above-mentioned optical element in a three-dimensional manner together with the yellow (Y) side optical scanning means. FIG. 4 is a perspective view showing the entire optical element in three dimensions. 3 and 4, laser light sources 30-Y and 30-BK, collimating lenses 11-Y and 11-BK, and a cylindrical lens 40- that emit laser light to the polygon scanner 3 to be guided to the left optical element group. Y, 40-BK is shown.
Also shown are laser light sources 30-C, 30-M and cylindrical lenses 40-C, 40-M that emit laser light to the polygon scanner 3 for guiding to the right optical element group. 3 and 4, the same members as those in FIGS. 1 and 2 are denoted by the same reference numerals, and redundant description is omitted.
FIG. 5 is a perspective view showing an optical housing according to the present invention. FIG. 6 is a plan view showing the relationship between the LD holder and the polygon scanner according to the present invention. FIG. 7 is a front view of FIG. FIG. 8 is a plan view showing the relationship between the LD holder and the polygon scanner when the number of LD holders is four. FIG. 9 is a front view of FIG.
5 to 9 showing the embodiment of the present invention for the optical scanning device, the shape of the cylindrical lens 40-Y, 40-BK, 40-C, 40-M installed in the optical housing 20 is the cylindrical lens. It is the same form as the conventional example except that it is different from the installation of 40'-Y, 40'-BK, 40'-C, 40'-M.
1 and 5 to 9, the holders 100 and 100 ′ are inserted into two holes 41 a and 41 d of the four holes 41 a, 41 b, 41 c and 41 d provided in the optical housing 20 to close them. To do. The other holes 41b and 41c are closed by cover members 101 and 101 'made of sheet metal or a resin member, so that dust does not enter from the outside.
Although it is arbitrary in which hole the holders 100 and 100 ′ are inserted, it is desirable that the holders 100 and 100 ′ be installed approximately symmetrically across the polygon scanner 3. The holders 100 and 100 ′ fixed in the holes fixedly support the two collimating lenses 11 and the two laser diodes 30 on the inner surface thereof.

As shown in FIGS. 6 and 7, the collimating lens 11 and the laser diode 30 are fixed at a certain distance on the Z direction and the XY plane shown in FIG. Here, the intersections of the respective optical axes (Y and BK, C and M) are set so as to substantially coincide with each other on the polygon scanner 3, and there are 60 lines perpendicular to the scanning line and 60 lines passing through the center of each optical axis. Keep the angle ± 10 °.
In this manner, the holder 100 of FIG. 6 is placed at the position 30-Y or 30-BK in FIGS. 8 and 9, and the holder 100 ′ of FIG. 6 is placed at the position 30-C or 30-M in FIG. However, the laser beam can reach the photosensitive drum, and the design is facilitated.
Here, the cylindrical lens 40-Y, 40-BK, 40-C, 40-M is a method of fixing the optical housing 20, but the two collimating lenses 11 and the two laser diodes 30 in FIG. 6 can be fixed in advance. Design as follows.
As shown in FIGS. 3 and 4, the polygon scanner 3 is divided into two parts 3u and 3d in the vertical direction, and laser light is applied to the mirror surface from the left and right to the upper or lower stage, or the shape is elongated in the Z-axis direction without being divided. . Even if the position of the optical axis changes slightly, the polygon scanner 3 can be used as it is without being changed, and if it is divided, the rotational load of the polygon scanner 3 can be reduced and the optical characteristics can be more stable. Each has its merit.

According to the present invention, since the optical elements can be arranged facing each other with the polygon scanner 3 interposed therebetween, the design can be made in a space-saving manner, and the optical characteristics are substantially symmetrical, so that the optical and physical confirmations are halved. Is efficient.
According to the present invention, the holes 41a, 41b, 41c, 41d for inserting the holders 100, 100 ′ are present in the range of 60 ° or 60 ° ± 10 ° with respect to the vertical line standing on the surface to be scanned. Since two to four holders can be mounted, it is easy to increase the number of laser diodes in order to increase the resolution or increase the printing speed.
According to the present invention, since the holders 100 and 100 ′ have the two light sources 30 and the two first optical systems 11, the holders 100 and 100 ′ can be manufactured in a compact manner, and the cylindrical lens 40 is not mounted on the holders 100 and 100 ′. Thus, the laser beam can be adjusted to be small, and optical writing of two colors out of the four colors can be realized.
According to the present invention, since the reflecting surface of the deflector is divided into two upper and lower stages 3u and 3d in the axial direction or has a height corresponding to the reflecting point, the same polygon scanner 3 can be used even if the number of holders changes. Is easy to change.
According to the present invention, since the image forming apparatus has the above-described optical writing device, it is possible to cope with higher resolution or higher speed of the device, and it is possible to change at low cost because it does not involve changing the housing. .

1 is a front view illustrating an overall configuration of a main part of an image forming apparatus. Schematic explaining the optical path of an optical scanning device. The perspective view which shows the above-mentioned optical element three-dimensionally with the optical scanning means of the yellow (Y) side. The perspective view which shows the whole optical element in three dimensions. The perspective view which shows the optical housing by this invention. The top view which shows the relationship between LD holder and polygon scanner by this invention. The front view of FIG. The top view which shows the relationship between the LD holder and polygon scanner when there are four LD holders. The front view of FIG.

Explanation of symbols

1Y photoconductor (photosensitive drum), 3 optical deflector (polygon scanner), 4th optical system (fθ lens), 5-1Y second optical system (first mirror), 5-2Y second optical System (second mirror), 6-Y second optical system (toroidal lens), 5-3Y third optical system (third mirror), 7-Y third optical system (dust-proof glass), 8-1Y Third optical system (mirror), 10 optical writing means, 10 'optical scanning device, 11 first optical system (collimating lens), 20 optical housing, 30-Y light source (laser diode), 40-Y first Optical system (cylindrical lens), 41a hole, 41b hole, 41c hole, 41d hole, 100 LD holder (laser diode holder), 100 'LD holder (laser diode holder), 101 cover member, 101' cover member

Claims (6)

  A first optical system for coupling a light beam emitted from a light source, a holder for fixing the light source and the first optical system, and a light beam coupled by the first optical system are long in the main scanning direction. A second optical system that collects light in a linear form, an optical deflector that deflects the light beam collected by the second optical system, and the light beam deflected by the deflector is collected as a light spot on the surface to be scanned. In an optical scanning device including a third optical system that emits light and an optical housing that houses the holder and the optical system, the optical housing includes four or more holes into which the holder is inserted. The optical scanning device is characterized in that the holder is inserted into only two of them, and the other holes are sealed with a sheet metal or a resin member.   2. The optical scanning device according to claim 1, wherein the holes are arranged substantially symmetrically with respect to a line passing through the center of the deflector and parallel to the scanned surface.   3. The optical scanning device according to claim 1, wherein the hole exists in a range of 60 [deg.] Or 60 [deg.] ± 10 [deg.] With respect to a vertical line formed on the surface to be scanned.   The optical scanning device according to claim 1, wherein the holder includes two light sources and two first optical systems.   5. The optical scanning device according to claim 1, wherein the reflecting surface of the deflector is divided into two upper and lower stages in the axial direction or has a height corresponding to a reflecting point. 6. An image forming apparatus comprising the optical scanning device according to claim 1.

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