JPH0973209A - Color electrophotographic printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten adjusting time by a reduction in the number of exposure devices requiring positional adjustments and also to reduce visible color slippage. SOLUTION: Electrophotographic process stations 61-64 for yellow, magenta, cyan, and black form electrostatic latent images by exposing photosensitive drums 71-74 charged by chargers 81-84 to laser beams from laser scanners 91-94, and render the electrostatic latent images visible by developing them with toners from developing devices 101-104. The stations 61-64 are arranged serially on the transfer-paper carrying path of a printer main body. The laser scanner 94 for black situated furthest downstream is used as a fiducial one, the laser scanner 91 for yellow situated furthest upstream requires no adjustments, and the remaining laser scanners 92 and 93 for magenta and cyan are positionally adjusted in relation to the fiducial laser scanner 94.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic printer in which three or four electrophotographic process stations are arranged in series and arranged on a transfer material conveying path of a printer body.

[0002]

2. Description of the Related Art Conventionally, a color electrophotographic printer of this type is known from Japanese Patent Application Laid-Open No. 1-126881. This is formed by, for example, four photosensitive drums arranged at a predetermined interval and each photosensitive drum,
Transfer material: detection means for detecting each registration mark image sequentially transferred to the transfer paper, and transfer material among the plurality of registration mark images for each photosensitive drum transferred on the transfer material sequentially detected by the detection means. The irradiation of the light beam to each remaining photosensitive drum is started based on the relative difference between the detection timing of the registration mark image formed on the most downstream photosensitive drum in the transport direction and transferred to the transfer material and the detection timing of each remaining registration mark image. A correction unit is provided to individually correct the position, the irradiation angle of the light beam to each remaining photosensitive drum, and the optical path length of the light beam to each remaining photosensitive drum.

As a result, the position of the optical scanning device and the writing position with respect to the remaining three photosensitive drums among the four photosensitive drums are adjusted with respect to the reference optical scanning device.

[0004]

However, in this prior art example, when the most downstream reference is largely deviated, the remaining three are adjusted to this, and therefore the color misregistration is scanned even if it is reduced by the adjustment. There was a possibility that it would be adjusted to something that deviated from the specified values such as width and skew. Further, there is a problem in that all the remaining three optical scanning devices with respect to the reference optical scanning device have to be adjusted in position, and it takes a long time to perform the adjustment.

Therefore, according to the first and second aspects of the present invention, the number of exposure devices for position adjustment can be reduced, the adjustment time can be shortened, and the appearance of color misregistration can be reduced, and good color image printing can be achieved. Provide a color electrophotographic printer capable of According to the third aspect of the present invention, the number of exposure devices for position adjustment can be reduced, the adjustment time can be shortened, and the visual color misregistration can be minimized to achieve better color image printing. Provide a color electrophotographic printer.

[0006]

According to the first aspect of the present invention,
Electrostatic latent image carrier, charging device for charging the electrostatic latent image carrier, exposure device for exposing the electrostatic latent image carrier charged by the charging device with a light beam to record an image as an electrostatic latent image And an electrophotographic process station equipped with a developing device for developing an electrostatic latent image recorded by this exposure device with toner so as to make it visible, corresponding to three colors of yellow, magenta and cyan or four colors including black. In a color electrophotographic printer in which three or four units are arranged in series on the transfer material transport path of the printer body, the remaining electrophotography of the exposure device of each electrophotographic process station except the exposure device of the yellow electrophotographic process station One of the exposure devices of the process station is fixed as a reference exposure device, and the other is adjustable in position with respect to the corresponding electrostatic latent image carrier. . As a result, the reference exposure device and the exposure device of the yellow electrophotographic process station do not require adjustment, and the number of exposure devices to be adjusted can be reduced.

According to a second aspect of the present invention, in the color electrophotographic printer according to the first aspect, a laser beam scanning device is used as an exposure device, and the beam diameter is the largest or the scanning is performed among the laser beam scanning devices used. The laser light scanning device having the largest variation is used for the exposure device of the yellow electrophotographic process station. As a result, the exposure device with the worst beam diameter characteristics or large variation is used as the exposure device for the electrophotographic process station of yellow, which has a light appearance color. do not become.

According to a third aspect of the present invention, in the color electrophotographic printer according to the first aspect, the exposure device of the electrophotographic process station, which is arranged at the most downstream side or the most downstream side in the conveying direction of the transfer material, is used as a reference exposure. Fixed as a device,
The yellow electrophotographic process station is the electrophotographic process station located on the most upstream side in the transfer material conveyance direction, and the exposure device of this yellow electrophotographic process station is positioned without adjustment with respect to the corresponding electrostatic latent image carrier. It was done. As a result, the distance of the exposure device to be adjusted with respect to the reference exposure device can be reduced, and the color misregistration can be minimized.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the main body case 1
An endless belt-shaped sheet conveying belt 2 is arranged around the drive roller 3, the driven roller 4, and the tension rollers 5a and 5b in the central portion of the above. Further, four electrophotographic process stations 61, 62, 63, and 64 are arranged at predetermined positions at an upper position facing the paper transport belt 2. Each of the electrophotographic process stations 6
1, 62, and 63 are yellow, magenta, and cyan electrophotographic process stations required for color printing, the electrophotographic process station 64 is a black electrophotographic process station for black printing, and the paper transport belt 2 is used. Yellow, magenta, cyan, and black are arranged in this order from upstream to downstream in the conveyance direction.

Each of the electrophotographic process stations 61
˜64 are photosensitive drums 71, 72 as electrostatic latent image holders
, 73, 74 are provided, and the photosensitive drums 71, 72, 73 are provided.
, 74 around the charging devices 81, 82, 83, 84, and laser scanning devices 91, 92, 93, 94 as exposure devices.
, Developing devices 101, 102, 103, 104, transfer rollers 111, 112, 113, 114, and cleaning devices 121, 122, 123, 124 are arranged.

The transfer rollers 111, 112, 113,
114 is arranged to face the photosensitive drums 71, 72, 73 and 74 with the sheet conveying belt 2 interposed therebetween. The laser scanning devices 91, 92, 93, 94 are vertically arranged adjacent to the toner boxes 131, 132, 133, 134 for replenishing the toner of the developing devices 101, 102, 103, 104.

At the bottom of the main body case 1, paper feed cassettes 14 and 15 are provided in upper and lower two stages. Then, the transfer paper, which is the transfer material, is fed from the upper paper feed cassette 14 to the paper feed roller 16
Thus, the sheet is picked up one by one and sent out, and is sent out onto the sheet carrying belt 2 via the carrying roller 17, the guide 18, and the registration roller 19. Also,
The transfer paper is picked up one by one by the paper feed roller 20 from the lower paper feed cassette 15 and sent out.
The sheet is conveyed onto the sheet conveying belt 2 via the 1, guide 22, the conveying roller 17, the guide 18, and the registration roller 19.

A suction device 23 for electrostatically attracting the transfer paper on the paper transport belt 2 so that the transfer paper on the paper transport belt 2 is not displaced is provided at the tip of the paper transport belt 2, and the transfer paper sent from the paper feed cassettes 14 and 15 is used as a paper. It is configured to be charged together with the transport belt 2 and to be in close contact with the paper transport belt 2. The image transferred onto the transfer paper at each of the electrophotographic process stations 61 to 64 is finally heat-fixed by the heat fixing device 24 and then discharged.

When a signal for forming an image is input from the outside such as a host computer, this apparatus will
The transfer paper is picked up from the paper feed cassette 14 by the paper feed roller 16, and the transfer roller 17 and the registration roller 1
It is sent out onto the sheet conveying belt 2 with the timing adjusted by 9. Then, the transfer sheet is electrostatically adsorbed on the sheet conveyance belt 2 by the adsorption device 23 and moves together with the sheet conveyance belt 2 without causing a positional shift during conveyance.

On the other hand, the image signal is supplied to each of the laser scanning devices 91 to 94 as a signal corresponding to each color.
For example, a yellow image signal is supplied to the laser scanning device 91, the laser scanning device 91 emits a laser beam according to the image signal, and the photosensitive drum 71 uniformly charged by the charging device 81 is exposed to light. Form a latent image. Then, the electrostatic latent image on the photosensitive drum 71 is developed with a yellow toner by the developing device 101 to be visualized, and the yellow toner image is transferred onto the transfer paper on the paper transport belt 2 by the transfer roller 111. After the transfer, the photosensitive drum 71 is cleaned of residual toner by the cleaning device 121, and then discharged by a discharging lamp (not shown) to prepare for the next electrophotographic process.

Similarly, the magenta, cyan, and black image signals are supplied to laser scanning devices 92 to 94, respectively, and the magenta, cyan, and black electrophotographic process stations 62, 63, and 64 transfer the paper onto the transfer belt 2. The toner images of magenta, cyan, and black are sequentially transferred to. In this way, a color image is formed on the transfer paper, and the transfer paper is heated and fixed by the heat fixing device 24 and then discharged.

By the way, in this apparatus, the electrophotographic process stations 61 to 64 for yellow, magenta, cyan and black are arranged from the paper feed side to the paper discharge side, that is, from the upstream side to the downstream side in the conveyance direction of the paper conveyance belt 2. The laser scanning devices 91 to 9 are arranged at equal pitches, but are mounted at the same time.
Mount 4 as follows. For each of the laser scanning devices 91 to 94, the main scanning width, the sub scanning direction position, and the main scanning direction writing position are adjusted in advance with respect to the mounting reference of the housing.

As shown in FIGS. 2 and 3, two positioning pins 32 are respectively inserted from the outside into the left and right main frames 31a and 31b of the printer main body so as to correspond to yellow, magenta, cyan, and black, respectively. Total of 8
Sheet side mounting reference plates 33Y, 33M, 33C, 33
Fix K. Then, in this state, the yellow, magenta, cyan, and black laser scanning devices 91 to 94 are inserted and attached along the guides 34Y, 34M, 34C, and 34K of the side attachment reference plates 33Y, 33M, 33C, and 33K, and the paper is attached. Scanning width, skew, CCD line sensor, PIN photo sensor, etc. arranged on the conveyor belt 2,
Measure the sub-scanning pitch and the main-scanning writing position. In this case, the position of the yellow laser scanning device 91 is not adjusted, so that the measurement need not be performed.

In this state, a positional deviation evaluation jig is set on the main frames 31a and 31b of the printer main body in place of the other laser scanning devices except the yellow laser scanning device 91, and the positions of the laser scanning devices 92 to 94 are set. The deviation is measured and the laser scanning device with a relatively small error or the smallest absolute error amount is used as a reference, and the remaining 2
Remove the positioning pin 32 from the side mounting reference plate to which the two laser scanning devices are attached, and position and adjust the side mounting reference plate to the best position with respect to the reference while measuring the optical characteristics with a jig (two-dimensional adjustment). It is fixed to the main frames 31a and 31b with screws 34. The yellow laser scanning device 91 is not positioned and is not adjusted.

Then, the magenta, cyan and black laser scanning devices 92 to 94 are again attached to the side reference plate 33.
Each of the laser scanning devices 91 to 33 is inserted along the guides 34M, 34C and 34K of the M, 33C and 33K and is screwed by the screws 35.
Fix 94. As described above, since the two laser scanning devices, the reference laser scanning device and the yellow laser scanning device 91, are not adjusted, only the remaining two are position-adjusted. Therefore, the adjustment work is simplified and the time is shortened. by the way,
When adjusting each of the laser scanning devices 91 to 94 independently, the one with the largest variation in beam diameter or the one with a large difference in optical characteristics such as skew and scanning speed error (fθ error) compared to the other ones will cause color misregistration. Used as a yellow laser scanning device that is the most difficult to see.

FIG. 4 shows an optical system evaluation jig for independently measuring the optical characteristics of the laser scanning device. The CCD line sensors 53, 54, 55 are arranged in the direction perpendicular to the main scanning direction, and the sub-scanning position, skew (judged by the relative difference between the CCD line sensors 53, 54, 55), and face tilt (each CCD line sensor 53). , 54, 5
5) and the sub-scanning beam diameter (determined by the output waveforms of the CCD line sensors 53, 54, 55) are evaluated. In addition, CCD line sensors 54 and 55 on both sides
PIN photosensors 56 and 57 are arranged inside the to measure the scanning speed between two points. PIN photo sensor 56,5
If the width of 7 in the main scanning direction is made sufficiently smaller than the main scanning beam diameter, the main scanning beam diameter can also be measured. Here, the measurement is performed in a state where the sensor part is replaced with a beam scan and scanning is not performed. Note that instead of these sensors, CCD
Area sensors may be used.

Based on the result of the measurement thus performed,
The one having the largest variation in beam diameter or the one having a large difference in optical characteristics such as skew and scanning speed error (f.theta.
Use as 1. That is, an image having a light color such as yellow, for which it is difficult to visually determine the color misregistration, can be used in such a manner even if there is some color misregistration. This simplifies the adjustment work without the need to match the accuracy of the laser scanning device 91 with that of another laser scanning device. Other laser scanning devices 9 except the yellow laser scanning device 91
When one of 2 to 94 is used as a standard laser scanning device,
The laser scanning device 94 of the black electrophotographic process station 64 located at the most downstream side is used as a reference. That is, it is desirable that the color of the image that is gradually transferred from upstream to downstream be dark in consideration of the effect of transfer deviation on the paper transport belt 2 and dust, and to achieve this, from upstream to downstream, yellow is used. , Magenta, cyan, and black are arranged in this order.

Then, as shown in FIG. 5, the laser scanning device 94 of the black electrophotographic process station 64 is used.
Side mounting reference plates 33M and 3 for mounting the intermediate magenta and cyan laser scanning devices 92 and 93, respectively.
When the 3C is fixed to the main frame 31a, two-dimensional adjustment is performed in the optical axis direction (height direction) and the paper feeding direction, the scanning width,
Adjust the sub-scanning pitch mechanically. The writing position in the main scanning direction is electrically adjusted, and the time from the output of the writing position detection sensor to the data transfer is set for each color laser scanning device. In this way, the most upstream yellow laser scanning device 91 and the most downstream black laser scanning device 94 are located.
No adjustment is made, position adjustment (pitch in the sub-scanning direction, skew, main scanning width) is mechanically performed for the intermediate magenta and cyan laser scanning devices 92, 93, and the writing position in the main scanning direction is electrically adjusted. Therefore, color misregistration can be prevented as much as possible. The two laser scanning devices 92 and 93 need only be adjusted, which simplifies the adjustment work.

By the way, when the black laser scanning device 94 at the most downstream side is used as a reference in this way, the cumulative position error in the adjacent cyan laser scanning device 93 is small, but the cumulative position error in the magenta laser scanning device 92 is small. Becomes larger because they are separated by distance. To solve this, assuming that magenta, cyan, and black are of equal importance,
As shown in FIG. 6, the cyan laser scanning device 93 which is located immediately before the most downstream is used as a reference. In this case, the magenta and black laser scanning devices 92 and 94 are adjusted and mounted, but these are cyan laser scanning device 93.
Since they are adjacent to each other, the cumulative position error of both is small.

In the above-described embodiment, as the electrophotographic process station, four stations of yellow, magenta, cyan and black are used, but the electrophotographic process station is not limited to this, and for example, a black electrophotographic process station is used. The present invention can also be applied to a printer for color printing by arranging three electrophotographic process stations other than the stations.

[0026]

As described above, according to the first and second aspects of the present invention, the number of exposure devices for position adjustment can be reduced, adjustment time can be shortened, and the lightest yellow electrophotographic image can be obtained. Since the exposure device of the process station is not adjusted, the color misregistration can be reduced and good color image printing can be performed.

According to the third aspect of the present invention, the number of exposure devices for position adjustment can be reduced, adjustment time can be shortened, and exposure of the lightest yellow electrophotographic process station can be achieved. By arranging the device at the uppermost stream and making no adjustment, it is possible to minimize the appearance of color misregistration and to perform better color image printing.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a mounting configuration of the laser scanning device to the main body frame in the same embodiment.

FIG. 3 is a partial side view showing the configuration of a side attachment reference plate used when attaching the laser scanning device to the main body frame in the same embodiment.

FIG. 4 is a perspective view showing an optical system evaluation jig for independently measuring the optical characteristics of the laser scanning device in the same embodiment.

FIG. 5 is a diagram for explaining position adjustment of the laser scanning device when the most downstream laser scanning device is used as a reference in the embodiment.

FIG. 6 is a view for explaining position adjustment of the laser scanning device when the laser scanning device immediately before the most downstream one is used as a reference in the embodiment.

[Explanation of symbols]

2 ... Paper transport belt 61, 62, 63, 64 ... Electrophotographic process station 71, 72, 73, 74 ... Photosensitive drum (electrostatic latent image carrier) 81, 82, 83, 84 ... Charging device 91, 92, 93 , 94 ... Laser scanning device (exposure device) 101, 102, 103, 104 ... Developing device 33Y, 33M, 33C, 33K ... Side mounting reference plate

Front page continuation (72) Inventor Shoji Iketani 570 Ohito, Ohito-cho, Takata-gun, Shizuoka, Ltd. Inside Tech Ohitoshi Co., Ltd.

Claims (3)

[Claims] 1. An electrostatic latent image carrier, a charging device for charging the electrostatic latent image carrier, and the electrostatic latent image carrier charged by the charging device is exposed to a light beam to form an electrostatic latent image. An electrophotographic process station equipped with an exposure device for recording as an image and a developing device for developing the electrostatic latent image recorded by the exposure device with toner to visualize the image is added with three colors of yellow, magenta, cyan, or black. A color electrophotographic printer in which three or four units corresponding to four colors are arranged in series and arranged on a transfer material conveying path of a printer body, wherein an exposure device of a yellow electrophotographic process station among exposure devices of each of the electrophotographic process stations is used. One of the exposure devices of the rest of the electrophotographic process station except the device is fixed as the reference exposure device, and the other is positioned with respect to the corresponding electrostatic latent image carrier. Color electrophotographic printer, characterized in that it was possible integer. 2. A laser beam scanning device is used as an exposure device, and among the laser beam scanning devices used, the laser beam scanning device having the largest beam diameter or the largest variation in scanning is used as a yellow electrophotographic process station. The color electrophotographic printer according to claim 1, which is used in an exposure device. 3. An electron arranged at the uppermost stream of the transfer material in the transport direction, with the exposure device of the electrophotographic process station arranged at the most downstream side in the transport direction of the transfer material or at the frontmost side of the downstream side being fixed as a reference exposure device. 2. The color according to claim 1, wherein the photographic process station is a yellow electrophotographic process station, and the exposure device of the yellow electrophotographic process station is positioned without adjustment with respect to the corresponding electrostatic latent image carrier. Electrophotographic printer.