JP2002350762A - Optical writing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical writing device capable of reducing the deviation of a synchronism detecting plate caused by temperature rise and the positional deviation of respective colors written on a photoreceptor in a main scanning direction. SOLUTION: This optical writing device 5 is arranged on the obliquely upper side of an image forming part provided with a photoreceptor drum, and positioned and fixed on the main body frame 29 of an image forming device by a master reference pin A and a slave reference pin B on the housing side of an image forming device main body. The frame 29 is provided with a positioning hole (round hole) 29A on the pin A side and an oblong hole 29B on the pin B side. The pin A is positioned and fit in the positioning hole 29A of the main body frame 29, while the pin B side is fit in the oblong hole 29B of the main body frame 29. The pin A and the synchronism detecting plate S on which a synchronism detector is mounted are positioned on the same line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing apparatus for writing a latent image by irradiating a light beam on a surface to be scanned of a plurality of image carriers arranged in parallel, and to provide the optical writing apparatus. The present invention relates to an image forming apparatus that forms a multicolor image, such as a copying machine, a printer, a facsimile, and a plotter.

[0002]

2. Description of the Related Art Conventionally, light beams emitted from a plurality of light sources are applied to four image bearing members (for example, photosensitive drums) arranged side by side to write a latent image thereon, and each image bearing member is subjected to writing. After the latent images formed on the sheet are developed with respective developers of different colors (for example, yellow, magenta, cyan, and black toners) to be visualized, the transfer of a recording sheet or the like carried on a transfer conveyance belt or the like is performed. The material is sequentially conveyed to the transfer section of each image carrier, and the visible images of each color formed on each image carrier are superimposed and transferred on the transfer material, and then the image transferred on the transfer material is fixed. A tandem type color image forming apparatus that obtains a multicolor image by using a tandem type is known.

In such a tandem type color image forming apparatus, there has been conventionally known a type in which a latent image is written on each image carrier separately by an optical writing device provided separately for each image carrier. However, an optical writing device using an optical deflector including a polygon mirror and a motor for driving the polygon mirror is relatively expensive, and providing an individual optical writing device for each image carrier reduces component costs and manufacturing costs. There is a problem in point.

In addition, a large installation space is required to install a plurality of optical writing devices each having an optical deflector in correspondence with the number of image carriers, and there is also a problem that the entire image forming apparatus becomes large. .

In order to reduce the cost and size of the tandem type color image forming apparatus, an optical deflector is shared by a plurality of light sources as a means for performing optical writing on a plurality of image carriers. 2. Description of the Related Art An optical writing apparatus has been proposed in which light beams from a plurality of light sources are simultaneously deflected and scanned by an optical deflector to irradiate a plurality of image carriers to perform optical writing.

[0006]

As described above, an optical writing apparatus for simultaneously deflecting and scanning light beams from a plurality of light sources and irradiating a plurality of image carriers with one optical deflector to perform optical writing is described below. A plurality of light source units, one optical deflector, and a plurality of light beams which are arranged symmetrically in two directions about the optical deflector and which are deflected and scanned by the optical deflector are respectively guided on the corresponding surfaces to be scanned. And a configuration in which these optical members are housed in one housing, so that the number of parts can be reduced compared to a configuration having a plurality of conventional optical writing devices, and installation is possible. Since the space can be reduced, the cost and size of the image forming apparatus can be reduced.

[0007] In the case of an image forming apparatus provided with the optical writing device configured as described above and forming a full-color image, usually, as a plurality of light source units, a light source unit for black and three light source units for color ( For example, light source units for cyan, magenta, and yellow are provided. In the black and white mode for forming a black and white image, only the light source unit for black is used. In the color mode for forming a color image, the above four light source units are used. used.

In the color mode, four light source units for black and color are used, and light beams from the four light source units are simultaneously deflected and scanned by one optical deflector, and each of the light beams passes through an optical system. To irradiate the four image carriers with light. When a latent image is formed by irradiating light to the four image carriers, a synchronization sensor is provided for adjusting the writing position of the light from each of the four light sources in the main scanning direction. Adjust the color writing timing.

This synchronous sensor is attached to the housing, but since the housing is provided with the deflector as described above, a short while after the deflector starts to rotate,
The housing itself is heated by the heat generated from the deflector, and the heat expands the housing to cause a state in which the position of the synchronous detection plate shifts.

[0010] The positional shift of the synchronization detecting plate causes a positional shift of the light beam scanning of each color, causing a color shift in a color image formed on the transfer material, which causes a deterioration in image quality.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended to reduce the displacement of the synchronization detection plate when the temperature of the housing rises and the displacement of each color written on the photoreceptor in the main scanning direction. It is an object of the present invention to provide an optical writing device capable of reducing occurrence of a shift, and further to provide an image forming apparatus including the optical writing device and capable of improving image quality. And

[0012]

According to a first aspect of the present invention, there is provided an optical writing apparatus for achieving the above object.
A plurality of light sources, an optical deflector for deflecting and scanning light beams from the plurality of light sources in two directions, and symmetrically disposed in the two directions with respect to the optical deflector, An optical system for guiding a plurality of light beams to be deflected and scanned on the corresponding surfaces to be scanned, respectively, and forming the plurality of light sources, the optical deflector, and the optical system in a single housing; In the optical writing apparatus provided with a synchronization detecting means at the leading end in the scanning direction, the beam synchronization detecting means serving as a reference for positioning the plurality of light beams in the main scanning direction is used for positioning with the image forming apparatus main body. Is arranged on the side of the projection serving as a main reference.

According to a second aspect of the present invention, in order to achieve the above object, in the optical writing apparatus according to the first aspect, the optical writing apparatus is used for positioning the position of the synchronization detecting means and the image forming apparatus main body. The position of the projection serving as a main reference is arranged on the same line.

According to a third aspect of the present invention, there is provided an image forming apparatus including the optical writing device according to the first aspect, in order to achieve the above object.

According to a fourth aspect of the present invention, there is provided an optical writing apparatus according to the second aspect, in order to achieve the above object.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an optical writing apparatus and an image forming apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of the optical writing apparatus according to the present invention. FIG. 2 is an enlarged view of the left side of the optical deflector of the optical writing apparatus shown in FIG. It is a fragmentary sectional view. FIG. 3 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention including the optical writing device shown in FIG. FIG. 4 is a plan view showing the configuration of the upper surface side of the substrate of the optical writing device shown in FIG. FIG. 1 shows a cross-sectional configuration along the line II in FIG. 5 shows the arrangement of the optical deflector and the optical system extracted from the configuration of the optical writing device shown in FIG. 1. FIG. 6 shows the arrangement of the light source from the configuration on the upper surface side of the substrate shown in FIG. FIG. 2 shows an arrangement configuration of a unit, an optical deflector, and an optical system.

The image forming apparatus shown in FIG. 3 is a full-color image forming apparatus in which a plurality of drum-shaped photoconductive photosensitive members (hereinafter, photosensitive drums) 1, 2, 3, and 4 are arranged as a plurality of image carriers. And these four photosensitive drums 1 to 4
For example, images corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (Bk) are formed in order from the right in the drawing. The order of the colors is not limited to this and can be set arbitrarily.

Around each of these four photosensitive drums 1 to 4, charging units (charging rollers, charging brushes, charging chargers, etc.) 6, 7, 8, 9 are formed in order to form an image by an electrophotographic process. , The light beam L from the optical writing device 5
1, L2, L3, and L4 exposed portions and developing portions (Y, M,
C, Bk developing devices) 10, 11, 12, 13
And transfer means (transfer rollers, transfer brushes, etc.) 14, 15, 1
Transfer / conveyance device 22 provided with 6, 17 and cleaning unit (cleaning blade, cleaning brush, etc.) 1
8, 19, 20, 21 and the like are provided, and it is possible to form an image of each color on each of the photosensitive drums 1 to 4.

The optical writing device 5 has four photosensitive drums 1 to
The reference numeral 4 is disposed obliquely above the image forming unit arranged side by side, and is positioned and fixed to the main body frame 29 of the image forming apparatus by the main reference pin A and the sub reference pin B on the housing side. The upper surface of the frame 29 is shown in FIG. 4. The main reference pin A side is a decision hole (round hole) 29A, and the sub reference pin B side is a long hole 29B.

The optical writing device 5 has four light source units 52, 53, 54, 5 as shown in the configuration examples in FIGS.
5, an optical deflector 62 for deflecting and scanning the light beams L1 to L4 from the respective light source units in two symmetric directions, and symmetrically arranged in the two directions with the optical deflector 62 as a center, An optical system (imaging lenses 63 and 6) for guiding a plurality of light beams L1 to L4, which are deflected and scanned by the unit 62, onto the scanning surfaces of the corresponding photosensitive drums 1 to 4 to form an image.
4, 69, 70, 71, 72, mirrors 65, 66, 67, 68, 73, 74, 75, 76, 7 for turning back the optical path
7, 78, 79, 80, etc.), and these components are housed in one housing 50.

More specifically, the housing 50 includes a base 50A on which the optical deflector 62 and the optical system are provided, and a base 50A.
A having a frame-shaped side wall 50B surrounding the periphery of A.
The base 50A is provided at a substantially central portion of the side wall 50B to partition the housing 50 up and down. The optical members (imaging lenses 63, 64, 69-72, optical path turning mirrors 65-68, 73-80, etc.) which are arranged at the approximate center of the base 50A are on both sides (upper surface side) of the base 50A. And the lower side). Further, covers 87 and 88 are provided on the upper and lower portions of the housing 50, and an opening for passing a light beam is provided on the lower cover 87, and dustproof glasses 83, 84 and 8 are provided in the openings.
5, 86 are attached.

In the optical writing device 5, color-separated image data input from a document reading device (scanner) or an image data output device (personal computer, word processor, facsimile receiving unit, etc.) (not shown) is used for driving a light source. And drives the light source (semiconductor laser (LD)) in each of the light source units 52 to 55 to emit a light beam. Each light source unit 52-5
The light beam emitted from the mirror 5 passes through cylindrical lenses 56 to 59 for correcting surface tilt, and is directly or mirror 6
The two-stage polygon mirror 62 which reaches the optical deflector 62 via 0 and 61 and is rotated at a constant speed by a polygon motor 62c.
Deflected scanning is performed in two directions symmetric at a and 62b. In the configuration shown in FIGS. 1, 2 and 5, the polygon mirror is divided into upper and lower stages for the light beams L2 and L3 and for the light beams L1 and L4. In this case, the configuration may be such that the four light beams are deflected and scanned.

The polygon mirrors 62a, 62 of the optical deflector 62
The light beams deflected and scanned in two directions by two beams in 2b respectively pass through first imaging lenses 63 and 64 composed of, for example, upper and lower two-layer fθ lenses, and are returned by first return mirrors 65 to 68. After passing through the opening of the base 51, for example, a long toroidal lens (WTL)
Pass through the second imaging lenses 69 to 72 made of
Folding mirrors 73, 75, 77, 79, third folding mirrors 74, 76, 78, 80, dustproof glasses 83 to 86
Irradiates the surfaces to be scanned of the photosensitive drums 1 to 4 for the respective colors to write an electrostatic latent image.

In the optical writing device 5, the four light source units 52 to 55 include a semiconductor laser (LD) as a light source.
And a collimating lens for collimating the emitted light beam of the semiconductor laser, and these are integrated into a holder. However, a black light source unit (for example, a light source unit denoted by reference numeral 54) frequently used when forming a black and white image. May have a multi-beam configuration including a set of two or more light sources (LD) and a collimating lens in order to enable high-speed writing. Further, 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. The pixel density (for example, 600 dpi, 1200 dpi, etc.) can be switched.

Further, in the optical path of each of the light beams L1 to L4, there is provided a synchronization detecting mirror (not shown) for extracting a light beam at a scanning start position in the main scanning direction, and the light beam reflected by the synchronization detecting mirror is provided. Are received by the synchronization detectors 81 and 82 as indicated by broken lines in FIG. 5, and a synchronization signal for starting scanning is output. Also, as shown in FIG.
Third folding mirror 7 arranged in the optical path of the third light beam
4, 76 and 78 are provided with skew adjustment stepping motors 92, 93 and 94, respectively, and the scanning line positions of the light beams L1 to L3 are shifted (inclined) with respect to the scanning line position of the light beam L1. Has been corrected.

The scanning direction of the light beam deflected by the optical 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 (the moving direction of the photosensitive drum surface). Direction. 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.

As shown in FIG. 3, a transfer / transport belt 22a stretched over a drive roller and a plurality of driven rollers is disposed below the four photosensitive drums 1-4 arranged in parallel.
It is conveyed by a driving roller in the direction indicated by the arrow in the figure. Further, a plurality of paper feed units 23 and 24 containing transfer materials such as recording paper are installed in the lower part of the main body of the image forming apparatus. The transfer materials stored in the paper feed units 23 and 24 The paper is fed to the transfer / conveyance belt 22a via rollers, conveyance rollers, and registration rollers 25, and is carried and conveyed by the transfer / conveyance belt 22a.

The latent images formed on the photoconductors 1 to 4 by the optical writing device 5 correspond to Y, M, C, and B of the developing units 10 to 13, respectively.
The toner images of the respective colors Y, M, C, and Bk are developed and developed with toner of each color of k, and the developed toner images of each color of B, K The image is transferred by being superimposed on the transfer material carried thereon. The transfer material onto which the four color images have been transferred is conveyed to a fixing device 26, where the image is fixed by the fixing device 26, and then discharged onto a discharge tray 28 by a discharge roller 27.

In the optical writing device 5, the housing 50
Is a base 50A on which the optical deflector 62 and the optical system are disposed,
And a frame-shaped side wall 50B surrounding the periphery of the base 50A, and the base 50A is provided at a substantially central portion of the side wall 50B to partition the housing 50 up and down. The four light source units 52 to 55 The optical deflector 62 is disposed on the side wall 50B, and is provided on the base 50A of the housing 50.
The optical members (the imaging lenses 63, 64, 69-72, the mirrors 65-68, 73-80, etc.) for forming the optical system are arranged substantially at the center of the base 50A. And the lower surface side), so that the optical writing device 5 is secured while securing the entire optical path length of the optical system.
The size of the housing 50 is less than half of the optical path length, so that the optical writing device 5 can be made compact.

In the image forming apparatus having the structure shown in FIG. 1, an image forming section having four photosensitive drums 1 to 4 arranged side by side, an optical writing device 5, and a transfer / conveyance device 22 are provided in the image forming apparatus main body. It is stored compactly, and further horizontally (X in the figure)
2), the installation space is smaller than in the conventional horizontal arrangement, and the tandem-type color image forming apparatus can be further miniaturized.

In the optical writing device 5 having the above-described configuration, the optical writing device 5 (housing) thermally expands due to the heat generated from the optical deflector 62 by continuous printing, and a plurality of beams are aligned in the main scanning direction. As described above, a change in the position of the beam synchronization detectors 81 and 82 serving as a reference causes color misregistration in a color image formed on a transfer material and causes a reduction in image quality. is there.

Therefore, in this embodiment, as shown in FIG. 4, the reference pin A is positioned and fitted into the fixing hole 29A of the main body stay 29, while the secondary reference pin B side is connected to the main body stay 2 as shown in FIG.
The reference pin A and the position of the synchronization detection plate S on which the synchronization detectors 81 and 82 are mounted are located on the same line.

That is, continuous paper passing is performed and the writing device 5
When the temperature rises, the housing 50 thermally expands. However, if the elongated hole 29B is arranged on the main reference side which is the writing start side as shown in FIG. 7A, the main reference side extends (see FIG. 7A). The dotted line portion indicates elongation.) Synchronization is shifted, but in the case of the above-described embodiment of the present invention, the sub-reference pin B is deformed, so that the main reference pin A is deformed.
The position fluctuations of the synchronization detectors 81 and 82 arranged on the side are reduced. Further, since the positions of the reference pin A and the synchronization detection plates 81 and 82 are on the same line, the above-described position fluctuation is eliminated.
For this reason, the synchronous detection of the colors serving as the reference for the alignment of the four colors in the main scanning direction does not change the position with respect to the photoreceptor, and the factor of the color shift can be suppressed.

[0034]

As described above, in the optical writing apparatus and the image forming apparatus according to the present invention, in the optical system, the beam synchronization detecting means serving as a reference for alignment of a plurality of beams in the main scanning direction is used as an image. Since it is arranged on the projection side which is a main reference for use in positioning the forming apparatus main body and the optical writing device, even if the housing of the optical writing device is elongated due to a temperature change, the reference for alignment is required. Therefore, there is an effect that the fluctuation of the position between the beam synchronization detecting means and the photoreceptor is reduced, and the factor of color shift can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an optical writing device according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the left side of the optical deflector of the optical writing device shown in FIG. 1 in the figure.

FIG. 3 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention including the optical writing device illustrated in FIG.

FIG. 4 is a plan view showing a configuration of a top surface side of a base of the optical writing device shown in FIG. 1;

FIG. 5 is a diagram illustrating an arrangement configuration of an optical deflector and an optical system extracted from the configuration of the optical writing device illustrated in FIG. 1;

FIG. 6 is a diagram showing an arrangement configuration of a light source unit, an optical deflector, and an optical system extracted from the configuration on the upper surface side of the substrate shown in FIG.

FIG. 7 is a diagram showing an operation of the embodiment of the present invention together with a comparative example.

[Explanation of symbols]

 1, 2, 3, 4 Photoconductor drum 5 Optical writing device 6, 7, 8, 9 Charging unit 10, 11, 12, 13 Developing unit 14, 15, 16, 17 Transfer unit 18, 19, 20, 21 Cleaning Unit 22 Transfer / Conveying Device 22a Transfer / Conveying Belt 23, 24 Paper Feeding Unit 25 Registration Roller 26 Fixing Device 27 Discharge Roller 28 Discharge Tray 29 Body Frame 29A Fixed Hole (Round Hole) 29B Slotted Hole 50 Housing 50A Base 50B Sidewall 52, 53, 54, 55 Light source unit 56-59 Cylindrical lens 60, 61 Mirror 62 Optical deflector 62a, 62b Polygon mirror 62c Polygon motor 63, 64, 69-72 Imaging lens 65-68, 73-80 For turning back optical path Mirrors 81, 82 Synchronous detectors 83-86 Dustproof glass stepping motors 92-94 87, 88 Cover A Main reference pin B Secondary reference pin L1, L2, L3, L4 Light beam

Claims (4)

[Claims] 1. A plurality of light sources, an optical deflector for deflecting and scanning light beams from the plurality of light sources in two directions, and symmetrically arranged in the two directions about the optical deflector, An optical system for guiding a plurality of light beams deflected and scanned by the optical deflector onto respective corresponding scanned surfaces and forming an image, and the plurality of light sources, the optical deflector, and the optical system are housed in one housing. In the optical writing apparatus having a synchronization detector at the leading end of the polarizer in the scanning direction, the beam synchronization detector serving as a reference for alignment of the plurality of light beams in the main scanning direction includes an image forming apparatus main body. An optical writing device, wherein the optical writing device is disposed on a projection side serving as a main reference for use in positioning of the optical writing device. 2. The optical writing apparatus according to claim 1, wherein the position of the synchronization detecting means and the position of the projection serving as a main reference used for positioning the image forming apparatus main body are arranged on the same line. An optical writing device, comprising: 3. An image forming apparatus comprising the optical writing device according to claim 1. 4. An image forming apparatus comprising the optical writing device according to claim 2.