JPS58127942A - Copying device - Google Patents

Abstract

PURPOSE:To measure exactly surface potential of a photosensitive drum by obtaining sequential standard signals from rotation of a photosensitive drum, and correcting sequential control timing. CONSTITUTION:A clock pulse generating disc 111 rotating in synchronism with a photosensitive drum 1 crosses a photointerruptor 113 during the rotation, the collector 115 of a transistor Q generates clock pulses, and delivers them through an interface 117 to a microcomputer 119. This microcomputer 119 counts the pulses, and turns on and off each action load at prescribed timings in accordance with the count value. During the second rotation of the drum 1 surface potentials on the drum 1 exposed through a gray scale GS having ten steps are measured with a potential sensor displayed on a display part. Surface potential on the drum 1 can be thus exactly measured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copying apparatus equipped with K so that the potential on the surface of a light body can be measured with high precision.

Normally, the copying operation in a copying machine is as follows: Charging → Exposure → Development →
Each operating device involved in the copying process, such as transfer→cleaning or→fixing, operates according to a predetermined operation sequence. After the process of charging → exposure → development,
An image corresponding to the original is formed on the photosensitive drum. Further, the transfer paper to be copied is fed from a cassette containing the transfer paper at a timing such that the leading edge of the transfer paper matches the leading edge of the image on the photosensitive drum. On this occasion,
Mechanical errors in the paper conveyance system and misalignment of the transfer paper result in misalignment of the image on the transfer paper. however,
Errors in the mechanical system and slight timing deviations in copying machines are not often a major problem. However, especially in color copying machines, in order to obtain a color image by superimposing yellow, magenta, and cyan color images, the transfer paper fed from the cassette is adjusted to prevent skewing and to adjust the feed timing. After passing through the rollers, it is wrapped around a transfer drum for successive transfers of the toner image multiple times. After three cycles of charging, exposure, development, and transfer, the transfer paper is separated from the transfer drum, fixed, and discharged from the apparatus. When winding the transfer paper around the transfer drum, the leading edge of the transfer paper is gripped by a plurality of grippers called grippers, and the leading edge of the transfer paper is held in place. High precision is required for the timing of opening and closing of this gripper and the timing of sending out the transfer paper from the timing roller. In the color copying apparatus, a reference signal generating device is provided on the side surface of the transfer drum, and as the transfer drum rotates, the timing of the sequence operation is corrected at regular intervals to perform the above-described copying operation. Therefore, in a color copying machine,
The transfer paper is fed, gripped by a gripper, and after three transfers, the transfer paper is separated, fixed, and discharged. Based on the timing of the transfer paper conveyance system, the sequence should be performed in order to suppress errors in the transfer paper conveyance system within limits. For this reason, timing correction is performed by matching the sequence operation to a reference signal generated by a device placed on the circumference of the transfer drum as the transfer drum rotates nine times.

On the other hand, as copiers in recent years have become microcomputerized and equipped with surface potential measuring devices that measure and display the surface potential on photosensitive drums, transfer paper is no longer fed for machine maintenance or image quality adjustment. Therefore, it has become necessary to perform a sequence operation different from the normal copying operation.

For example, by installing the above-mentioned surface potential measuring device in a color copying machine, for example, a gray scale GS having reflection densities that differ step by step in 10 steps in consecutive adjacent areas as shown in FIG. As shown in the figure, the document is placed correctly in the scanning direction of the illumination in the area surrounded by the three installation marks ON/~0N4Z written on the document table 3 of the copying device PT. In this way, the latent image surface potential of grayscale GS is
Measure over each stage and display this. This measurement 1
The sequence for displaying is executed by a control device (not shown). Using the surface potential displayed according to this sequence as a guide, the high voltage of the copying machine FT and exposure of the original are adjusted. However, since this sequence was corrected using the reference signal of the transfer drum, sampling of the latent image potential of the gray scale GS was affected due to errors in the mechanical interlock between the transfer drum and photosensitive drum and variations in sensitivity in the circumferential direction of the photosensitive drum. There were drawbacks such as timing shifts and potential errors in areas that were supposed to have the same concentration. According to experiments, variations of up to 30 ("I) to tOcV) have been measured.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, an object of the present invention is to provide a copying apparatus that can accurately measure the surface potential of a photosensitive drum based on a gray scale.

According to the present invention, a sequence reference signal is obtained from the rotation of a photosensitive drum, and sequence control timing is corrected using this photosensitive drum reference signal, thereby reducing mechanical system errors of the copying device and sensitivity variations in the circumferential direction of the photosensitive drum. This eliminates variations in surface potential measurements caused by Therefore, the surface potential at each stage of gray scale GS can be measured accurately.

This makes it possible to easily and quickly calibrate the high voltage of the apparatus main body and the original lamp lighting voltage. Furthermore, it is therefore possible to realize a copying apparatus that can obtain high-quality images.

The present invention will be described in detail below based on the drawings.

35th! A is a configuration diagram of an embodiment device of the present invention.

In the figure, a photoreceptor consisting of a conductive layer, a CaS light guide layer, and an insulating layer is formed on the surface of nine photoreceptor drums l rotating in the direction a. A document to be copied is placed on the document table 3, and illuminated by an illumination lamp S. Scanning mirrors 7 and 9 scan the original in synchronization with the rotation of the drum l, mirrors 7 and 9 scan the original, respectively.
The illumination lamp 3 also moves to the da position at the same time as it moves to the ql position.

The optical image of the scanned original is transmitted through lens //' and mirror /3.
.

An image is formed on the photoreceptor surface of the photoreceptor drum 1 through the color separator/3 and the mirror 17, and further through the secondary charger 19 for static neutralization at the same time as exposure. A latent image is formed by such exposure means. Here, color separation 1! i/3 is a blue filter tsB and an il filter/jG according to each color separation.

It consists of a red filter/IR filter and a ND' filter/3M, and these filters are rotated to perform color separation of light.

The surface of the photoconductor of the photoconductor drum l is preliminarily cleaned with a blade cleaner 31.
The pre-exposure lamp 33 and the pre-static eliminator 3
S removes the influence of the previous latent image. Next, the photoreceptor surface is uniformly charged with a primary charger n to have a uniform potential. This charged photoconductor surface is neutralized together with the original optical image by a secondary charger 19, and then uniform light is applied to the entire surface by a full-surface exposure lamp n, resulting in a high contrast electrostatic latent on the photoconductor surface. An image is formed. The intensity of the electrostatic latent image, that is, the electrostatic potential, is detected by a potential sensor C placed near the surface of the drum l between the full-surface exposure lamp n and the developer nail.

The developer 16 #/ consists of a yellow developer 1/Y, a magenta developer II/M, a cyan developer nail C, and a black developer 1B, and performs development by supplying each color developer (toner). A nine transfer paper rod or q placed in a cassette S or % is sent to a transfer section SS by a sending roller si or j3. In the transfer section jj, the gripper S7 first grips the leading edge of the transfer paper 1 (or q). Transfer drum! Transfer paper 4I7K held in l.

A transfer corona discharger 59 transfers the developed image on the surface of the photoreceptor of the photoreceptor drum by corona discharge from the back side of the paper. In the case of monochrome copying, immediately after the static electricity is removed by the separation static eliminator 61, the separation claw ≦3 is operated to separate the transfer paper j/ from the transfer section SS. In the case of multicolor copying, the gripper j of the transfer section SS is held until the transfer of the two to three color developed images to be reproduced is completed.
7 and without operating the separation claw 63.
/ is retained.

After the transfer is completed, the transfer section 1 is moved by the operation of the separation tab 3.
The transfer paper j/ is separated from 1 and sent to a heating roller fixing device 67 by a conveyor belt, where the image is fixed. After the fixing is completed, the transfer paper 7 is discharged to the 'tray 69. After the transcription is completed,
The toner remaining on the surface of the photosensitive drum is cleaned by a blade cleaner 31 in preparation for the next copying cycle.

All of the above-mentioned sequences are controlled by a microcomputer, and the clock generator I rotates in synchronization with the photosensitive drum l shown in FIG.
The lock node (rus CP) is generated from the collector l/j of / as shown in FIG. 5 (4).

This clock pulse QP is applied to the interface r-circuit//
7 to an input port of a microcomputer (hereinafter referred to as microcomputer) 119.

The microcomputer //9 counts the clock CP and turns on the operating load at a predetermined timing according to the counted value.
Turn off. Normally, in a copying sequence, a magnetic field generated by a magnet provided on the circumference of a rotating transfer drum srO is
Based on the first reference signal sr, which is generated by detection with a Hall IC (not shown) installed on the main body side, a clock count starts from the time when the falling edge of this first reference signal Sr1 is detected. The desired load is turned on and off according to a predetermined count value. However, when the key switch KS (Fig. 6) is activated, the gray scale GS
When a sequence for measuring the potential of and displaying the potential is selected, the signal that becomes the reference for counting clock pulses CP is
The falling edge Ta2 of the reference signal Sr2 generated by the magnet /7/ and Hall E Q/73 provided on the circumference of the photosensitive drum l shown in FIG. 7 is detected. After that, the clock pulse cp
is counted, and the desired load is turned on and off according to a predetermined count value. The timing of this operation is shown in Figure 1, and the operation procedure is shown in Figure 9. In the timing diagram shown in Figure 1, times t2 and 1° are the times when the microcomputer//9 detects the reference signal Sr2, and the microcomputer//9 detects the falling edge Ta2 of the first reference signal Sr2. Then, the clock pulse CP is re-counted from "O". In the flowchart shown in Figure 9,
In stepta//, ri 31 and 993, the second
Timing correction is performed using the reference signal Sr2.

The numbers shown in parentheses in the figure are clock pulses generated by the rotation of the photosensitive drum l (counted values by the microcomputer l/r on the 3rd floor). Therefore, the clock pulse C
The timing of the sequence operation is controlled based on the count value of P. The process from pressing the copy start button (hours m tl) until the photosensitive drum I rotates once (hours*12) is as follows:
Steps in the flowchart shown in Figure 9? The operations /J to 929 are executed under timing control. During the second rotation of the photosensitive drum l (times t2 to 1.), step 93 is performed.
As shown in 3 to q7, the surface potential of the photosensitive drum 1 based on the gray scale GS is measured in 10 steps using the potential sensor q. After that, step 91 after time t3
The operation indicated by /~de9S is executed and the rotation of the photosensitive drum is stopped (time 14).

The potential measurement sequence using such a gray scale GS is a gray scale at the IO stage, as shown in FIG. At the moment when the portion on the photosensitive drum L that has been exposed at each stage passes the potential sensor R that measures the surface potential,
By sending strobe pulses from the microcomputer to the potential measuring device, the potential measuring device performs measurements at each stage. The measured values are stored in the internal memory of the device, and after reading all the steps, each measured potential is displayed on the display section by switching a switch (not shown). FIG. 70 shows the surface potential of the gray scale latent image on the photosensitive drum l in this sequence. When the microcomputer 11 counts the number of clocks corresponding to the moment when each stage passes the potential sensor q, it sends out a gray scale measurement strobe to display the surface potential, as shown in the timing diagram shown in FIG. According to actual measurements, in such a sequence, there are cases where timing correction is performed using the first reference signal Sr1 from the transfer drum jl, and cases where the timing correction is performed using the first reference signal Sr2 from the photosensitive drum.
When timing correction is performed by
The accuracy improved by approximately J at the above distance. Furthermore, there is almost no error at the leading edge of the image on the photosensitive drum 1, and since the potential is always measured at the same point, variations in surface potential measurements have been greatly reduced.

As described above, the error in the reference signal for timing correction from rounding caused by powder on the photosensitive drum and from exposure to latent image formation in the copying sequence is small. Furthermore, since the latent image is always formed from the same point on the photosensitive drum l, it is less susceptible to variations in sensitivity in the circumferential direction of the drum, making it possible to measure the surface potential with higher accuracy. Note that the second reference signal Sr2 serves as a reference signal for improving accuracy not only in the surface potential measurement sequence but also in other sequences. If it is desired to further improve accuracy, the number of reference signals may be increased.

[Brief explanation of the drawing]

FIG. 7 is an explanatory diagram of the gray school, FIG. 2 is a perspective view showing the arrangement position of the gray scale on the duplicating device, and FIG. 3 is a structural diagram showing an embodiment of the duplicating device according to the present invention.
Figure ψ is a system diagram of the mechanism that generates clock pulses.
Figures (A) to (C) show the clock pulse and the first. A waveform diagram showing the first reference signal, FIG. 6 is a schematic configuration diagram showing the key switch selection section, FIG. 7 is a system diagram showing the reference signal generation mechanism, and FIG. 1 is a timing diagram to explain the control operation. ,
FIG. 9 is a flowchart showing the control operation, and FIG. 1θ is an explanatory diagram showing the surface potential of the photosensitive drum. GS...Gray scale, PT...Copying device, ON
/ -ON da...Installation mark, /...Photosensitive drum, 3...Original table, Q...
- Potential sensor, f7. q...Transfer paper, O...Transfer unit, II...Transfer drum, Otsu3...Separation claw, 67...Heating roller fixing device, lll...Clock pulse generator, l/3 ...Photo-interconnected, /lri...Microcomputer, Q,,Q2...Transistor. Patent applicant Canon Co., Ltd. QS Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1) A photosensitive drum on which an electrostatic latent image based on a document to be copied is formed, a transfer drum around which transfer paper is wound, and a device for developing the electrostatic latent image and transferring the image onto the transfer paper. a control means for executing a sequence different from that of the image transfer means; means for generating a first reference signal serving as a reference for control timing of device operation based on the rotation of the transfer drum; and a control means for executing a sequence different from that of the image transfer means. The copying apparatus is characterized by comprising means for generating a first reference signal serving as a reference for control timing of the sequence, and causing the control means to execute the sequence at the timing of the second reference signal. Copying equipment. 2] The copying apparatus according to claim 1, wherein the second reference signal is generated based on rotation of the photosensitive drum.