JPH0572872A - Electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To provide an electrophotographic copying machine forming a stable copied image. CONSTITUTION:When the power switch of a copying machine is turned on in the step ST1, the charge output VG of a photosensitive body is waved and a toner patch image is formed on the photosensitive body in the step ST2, to transfer the toner image on a transfer intermediate body. In the step ST3, the toner sticking quantity of the toner patch image is detected by a photosensor, and the relational expression (f) of the charge output VG and the toner sticking quantity is obtained. In the step ST4, the toner patch image of the same peripheral length as that of the photosensitive body is formed on the transfer intermediate body in reference charge output VGO, to detect the toner sticking quantity of this image. When it is decided that the detected toner sticking quantity is uneven in the step ST5, a difference AD in the toner sticking quantity detected in the step ST4, is calculated based on a prescribed toner sticking quantity as a reference in the step ST6. In the step ST7 the correction quantity of the charge output corresponding to the difference D is obtained based on the relational expression (f) and a charge output control part controls the electrification of the photosensitive body. based on the data of the correction quantity through a main control part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine, and more particularly to an electrophotographic copying machine suitable for full-color electrophotographic copying.

[0002]

2. Description of the Related Art In a conventional electrophotographic copying machine equipped with a transfer intermediate, in order to transfer an image such as characters written on a document onto a recording medium (final recording medium such as paper), a light source lamp is first used. The original is illuminated by the light source and the like, and the light reflected from the original is applied to the uniformly charged photoconductor through a reflecting mirror or the like. The photoconductor is exposed by receiving the reflected light from the document, and an electrostatic latent image having a pattern corresponding to the document image is formed on the surface of the photoconductor.

Then, the electrostatic latent image is visualized as a toner image by toner, and the toner image is transferred to a transfer intermediate. The toner image transferred to the transfer intermediate is transferred to the recording medium. Thereafter, the toner image on the recording medium is fused, and the copying is completed.

In a conventional full-color electrophotographic copying machine, an original image is developed as a toner image in the order of yellow, magenta, and cyan on a belt-shaped photosensitive member, and the developed toner image is transferred to a belt-shaped transfer intermediate. Transferred to the body,
A combined image in which the yellow, magenta, and cyan toner images are combined is formed on this transfer intermediate.

As described above, since it is necessary to align the yellow, magenta, and cyan toner images on the transfer intermediate, the conventional electrophotographic copying machine has a peripheral length of the photosensitive member (a belt-shaped photosensitive member The length in the rotating direction) is an integral multiple of the circumferential length of the transfer intermediate (the length in the rotating direction of the belt-shaped transfer intermediate). In general,
Since the size of the entire copier and the sensitivity of the photoconductor are limited,
The circumference of this photoconductor is set to twice the circumference of the transfer intermediate.

[0006]

In such a conventional electrophotographic copying machine, when the peripheral length of the photoconductor is long, the film is formed on the surface of the photoconductor uniformly over the entire surface area of the photoconductor. Since it is technically difficult to form such a film, a slight unevenness in charging, unevenness in sensitivity and the like occur on the photoconductor during copying. Therefore, when a photoreceptor long in the circumferential direction is used in an electrophotographic copying machine, there is a problem that a uniform toner image cannot be obtained on the entire photoreceptor in the circumferential direction.

Particularly, in a full-color electrophotographic copying machine, the occurrence of unevenness in the toner image due to the uneven charging, uneven sensitivity, etc. described above adversely affects the full-color image formed on the recording medium. There is a problem.

This effect will be described below.

FIG. 6 is a graph showing the relationship between the circumferential position of the photosensitive member and the toner adhesion amount. In the figure, the horizontal axis represents the position in the circumferential direction of the photoconductor, and the vertical axis represents the toner adhesion amount of the toner image formed on the photoconductor.

For example, in an electrophotographic copying machine configured to develop a toner image on a photoconductor in the order of yellow, magenta, and cyan, as shown in FIG. When the toner adhesion amount of No. 1 is non-uniform, yellow development and cyan development are performed in the range indicated by the symbol A, and magenta development is performed in the range indicated by the symbol B to form a full-color image. On the contrary, when the full-color image is formed by performing magenta development in the range indicated by the symbol A and performing yellow development and cyan development in the range indicated by the symbol B, Since the balance of the toner adhesion amounts of yellow, cyan, and magenta is different between the two, if a full-color image with different colors is formed on the recording medium. Cormorants there is a problem.

The influence on the formed image when such an imbalance of the toner adhesion amounts of yellow, cyan and magenta occurs is generally more prominent in the halftone area than in the solid area (that is, in the color tone). It is known that changes are noticeable).

Therefore, the present invention provides an electrophotographic copying machine capable of forming a stable copy image by making the toner adhesion amount of the toner image in the circumferential direction of the photosensitive member uniform.

[0013]

A photosensitive member, a charging unit for charging the photosensitive member, a transfer unit for transferring a toner image formed on the photosensitive member to a transfer member according to an original image, and a transfer member by the transfer unit. Image forming means for forming the toner image transferred onto the sheet on the sheet, detecting means for detecting the toner amount of the toner image formed on the transfer body along the circumferential direction of the transfer body, and toner detected by the detecting means. And a charging output control unit that controls the charging output of the charging unit so that the toner amount of the toner image formed on the photosensitive member becomes uniform along the circumferential direction of the photosensitive member based on the amount.

[0014]

The toner image formed on the photoconductor charged by the charging means is transferred to the transfer body by the transfer means.
The toner amount of the toner image formed on the transfer body is detected by the detection unit along the circumferential direction of the transfer body, and the charging output control unit determines the charging output of the charging unit based on the detected toner amount in the circumferential direction of the photoconductor. It is controlled so that the toner amount of the toner image is uniform. Therefore, the toner amount of the toner image in the circumferential direction of the photoconductor becomes uniform, whereby the toner amount of the toner image transferred to the transfer intermediate is stable, and a stable copy image can be formed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view showing the arrangement of a full-color copying machine which is an embodiment of the electrophotographic copying machine according to the present invention. FIG. 3 is an enlarged view of an essential part showing an enlarged portion including a transfer intermediate body provided in the full-color copying machine of FIG.

As shown in FIG. 2, the full-color copying machine 10 of this embodiment is provided with an original table 11 made of transparent glass on the upper surface of the machine frame. An exposure optical system 12 is arranged below the document table 11.

The exposure optical system 12 is a light source lamp 12a for irradiating the original 13 placed on the original table 11 with light, and a reflected light from the original 13 on the photoconductor 14 along an optical path indicated by a chain line. It includes a plurality of reflecting mirrors 12b for guiding, an imaging lens 12c arranged on the optical path, and a color separation filter 12d having color filters of three primary colors of red, green and blue.

On the optical axis of the exposure optical system 12, there is arranged a belt-shaped photosensitive member 14 made of an organic photosensitive member (OPC) to which a light image subjected to exposure scanning is irradiated.

Below the photoconductor 14, a paper 15 is accommodated.
Two paper feed cassettes 16 and 17 are provided. Paper feed rollers 18 and 19 are provided on the upper surfaces of the paper feed cassettes 16 and 17, respectively.

The paper feed rollers 18 and 19 are configured to eject the paper 15 from the paper feed cassettes 16 and 17, respectively, and send it toward the transfer intermediate 20.

A timing roller 21 is provided on the delivery side of the paper 15 from the paper feed rollers 18 and 19 toward the transfer intermediate 20, and the timing roller 21 rotates in synchronization with the transfer intermediate 20. Is configured.

The transfer intermediate 20 is obtained by adding a conductive material such as carbon black in an amount of 1% to several tens% by weight to a binder resin, for example, a polycarbonate resin heated to a melting temperature, and then adding the conductive material into a film or It is manufactured by forming it into a tubular shape. The electrical resistance value of the transfer intermediate 20 manufactured in this way is 1 × 10 ⁷ Ω /
It is contained within the range of □ to 1 × 10 ⁹ Ω / □.

The transfer intermediate body 20 is constituted so as to be rotationally driven in the clockwise direction (arrow shown in the figure) by the first, second and third rollers 22a, 22b and 22c, so that the photosensitive body 14 is driven. It is pressed against a driving roller 23 that is rotationally driven.

A primary transfer charger 24 is provided on the back surface side of the transfer intermediate 20 in the portion where the drive roller 23 is pressed against the transfer intermediate 20.

A secondary transfer roller 26 is disposed in contact with the transfer intermediate body 20 on the surface side of the transfer intermediate body 20 in the portion where the third roller 22c is disposed.

On the side of the secondary transfer roller 26 where the paper 15 is delivered,
The peeling plate 27, the transport belt 28, and the fixing device 29 are
They are arranged in this order.

As shown in FIG. 3, on the surface side of the transfer intermediate 20 stretched between the third roller 22c and the first roller 22a, the toner adhesion amount on the transfer intermediate 20 is detected. A photo sensor 51 for doing so is provided.

The arrangement of the photo sensor 51 is the transfer intermediate.
The position is not limited to the position shown in FIG. 3 as long as the toner adhesion amount on 20 can be detected.

As shown in FIG. 2 again, the photoconductor 14 irradiated with the reflected light from the exposure optical system 12 is driven to rotate counterclockwise (arrow shown in the figure) by the driving roller 23 and the driven roller 30. Is configured to.

In the vicinity of the outer periphery of the driven roller 30, a cleaning device 31 for removing the toner remaining on the photoconductor 14,
A discharging lamp 32 for discharging the photoconductor 14 and a charging charger 33 for charging the photoconductor 14 are arranged in this order along the rotation direction of the photoconductor 14.

The cleaning device 31 is provided with cleaning blades 31a made of, for example, urethane. These cleaning blades 31a are pressed against the photoconductor 14 so as to scrape off, for example, toner remaining on the photoconductor 14. It is configured.

Above the photoconductor 14, a black and white developing tank 43 and color developing tanks 44, 45 and 46 are arranged in a non-contact state with the photoconductor 14. Color developing tanks 44, 45 and
The yellow, magenta, and cyan color developers are contained in 46, respectively.

Next, the operation of the full-color copying machine 10 of this embodiment will be described.

When a copy start switch (not shown) provided in the full-color copying machine 10 is pressed, the copy mode is executed. This copy mode has a copy cycle in which yellow, magenta, and cyan are developed and transferred to the transfer intermediate 20, and when the copy mode is executed, the yellow copy cycle is executed first.

That is, the original 13 placed on the original table 11
On the other hand, light is emitted from the light source lamp 12a to perform exposure scanning. The reflected light from the original 13 is separated into color components by a color separation filter 12d via a reflecting mirror 12b and an imaging lens 12c.

The color separation filter 12 is obtained by the above-described exposure scanning.
The light for each color component transmitted through each color filter of d is irradiated onto the photoconductor 14 that is uniformly charged by the charging charger 33, and the photoconductor 14 is exposed at the P portion.

As a result, a yellow electrostatic latent image corresponding to the image of the original 13 is formed on the photoconductor 14. This electrostatic latent image is developed by a developing magnet roller at a portion facing a developing tank 44 having a yellow developer which is a complementary color of the color separation filter 12d.
The toner image is developed and visualized by the developer supplied by 44a to form a toner image. This toner image is transferred to the transfer intermediate 20 by the primary transfer charger 24.

When this yellow copying cycle ends,
The photoconductor 14 is cleaned by the cleaning device 31 and discharged by the discharge lamp 32.

Thereafter, the magenta and cyan toner images are transferred to the transfer intermediate 20 in the same copying cycle as the yellow copying cycle described above.

Therefore, when the yellow, magenta, and cyan copying cycles are executed, the toner image for each color component is transferred to the same position on the transfer intermediate 20 by the primary transfer charger 24, and the toner for each color component is transferred. The toner images are completed by superimposing the images.

On the other hand, the sheets 15 stored in the sheet feeding cassettes 16 and 17 are fed one by one to the timing roller 21 by the sheet feeding rollers 18 and 19, and the timing roller 21 is synchronized with the rotational driving of the transfer intermediate 20. Then, the paper 15 is conveyed between the transfer intermediate 20 and the secondary transfer roller 26.

After the toner image formed on the transfer intermediate 20 is transferred by the secondary transfer roller 26 to the conveyed paper 15, the paper 15 is separated from the transfer intermediate 20 by the peeling plate 27 and is fixed by the conveying belt 28. Introduced to 29.

After the toner image is fixed on the paper 15 by the fixing device 29, the paper 15 is discharged to the outside, whereby the one-time copying mode is completed.

Next, consider the case where the photoconductor 14 is replaced with a new photoconductor.

The characteristics of the film on the surface of the new photoconductor that has been replaced are not exactly the same as the characteristics of the film on the surface of the photoconductor that has been used so far, but they are generally different. Further, when the photosensitive member is long in the circumferential direction, it is technically difficult to form a uniform film over the entire surface area of the photosensitive member when forming a film on the surface of the photosensitive member. For this reason, some uneven charging, uneven sensitivity, and the like occur on the photoconductor.

A control device included in the full-color copying machine 10 shown in FIG. 2 for preventing such charging unevenness and sensitivity unevenness and for uniformly controlling the toner adhesion amount on the photosensitive member will be described. To do.

FIG. 4 is a block diagram showing an embodiment of the configuration of this control device.

As shown in the figure, the control device 60 of this embodiment comprises an output amplification section 61, a main control section 62 and a charging output control section 63.

The output amplifying section 61 is connected to the photo sensor 51 for detecting the toner adhesion amount of the toner image formed on the transfer intermediate body 20 shown in FIGS. 2 and 3, and amplifies the output signal from the photo sensor 51. Is configured to.

The main control unit 62 receives the amplified output signal of the photo sensor 51 sent from the output amplifying unit 61, and the toner adhesion amount of the toner image formed on the photoconductor 14 based on this output signal is detected. The correction amount of the charging output of the photoconductor 14 is obtained so as to be uniform.

The charging output control unit 63 is connected to the charging charger 33, and controls the charging charger 33 that charges the photoconductor 14 based on a signal corresponding to the correction amount of the charging output sent from the main control unit 62. Is configured.

The photoconductor 14 is an example of the photoconductor of the present invention. The transfer intermediate 20 is an example of the transfer body of the present invention.
The primary transfer charger 24 is an embodiment of the transfer means of the present invention. Secondary transfer roller 26, peeling plate 27, conveyor belt
28 and the fixing device 29 are examples of the image forming means of the present invention. The charging charger 33 is an embodiment of the charging means of the present invention. The photo sensor 51 is an embodiment of the detecting means of the present invention. The main controller 62 and the charging output controller 63 are examples of the charging output controller of the present invention.

Next, the operation of the control device 60 will be described.

FIG. 1 shows a control device 60, in particular a control device.
6 is a flowchart showing the operation of a main control unit 62 included in 60.

For example, when the photoconductor 14 in FIG. 2 is replaced with a new photoconductor, as shown in FIG.
1, the power switch of the copying machine (not shown) provided in the full-color copying machine 10 in FIG. 2 is pressed (ON).
It is determined whether it has been done. If it is determined that the power switch is turned on, the process proceeds to step ST2, and if it is determined that it is not turned on, the operation ends.

Next, in step ST2, the charging output V _G of the replaced new photoconductor is shaken to form a toner patch image on the photoconductor. This toner patch image is a transfer intermediate 20
Is transcribed to.

The charging output V _G shaken at this time is
For example, 400 V may be used as the reference charging output V _G0 and shaken in steps of ± 30 V.

Next, in step ST3, the charging output V _G
The density of the toner patch image transferred to the transfer intermediate body 20 when shaken is detected by the photosensor 51 as the toner adhesion amount, and the relational expression f between the charging output V _G and the detected toner adhesion amount is obtained.

Next, at step ST4, a toner patch image having the same circumference as the photoconductor 14 (one circumference) is formed on the transfer intermediate 20 in the state of the reference charging output V _G0 , and the formed toner patch image is formed. The amount of toner adhered to is detected by the photo sensor 51 along the circumferential direction of the transfer intermediate 20.

The position in the circumferential direction may be searched based on the distance from the index hole or the like by providing an index hole in the photoconductor or the transfer intermediate.

Next, in step ST5, the photo sensor
It is determined by 51 whether the toner adhesion amount detected along the circumferential direction of the transfer intermediate 20 is uneven. If it is determined that the detected toner adhesion amount is uneven, step ST
Proceed to step 6, and if it is determined that the toner adhesion amount is uniform,
The operation is terminated without correcting the charging output.

To determine whether or not there is unevenness in the toner adhesion amount, for example, a plurality of detection values regarding the toner adhesion amount along the circumferential direction of the transfer intermediate 20 are averaged, and this average value and each detection value are determined. The comparison may be performed, and determination may be made based on whether or not the comparison result is within a predetermined range.

Then, in step ST6, step ST4
At the reference charging output V _G0 , the difference (toner density difference) ΔD in the toner adhesion amount detected from the toner patch image of the same circumferential length as that of the photoconductor 14 formed on the transfer intermediate 20 is set to the predetermined toner. Calculate based on the amount of adhesion. The predetermined toner adhesion amount serving as the reference may be, for example, the toner adhesion amount along the circumferential direction of the transfer intermediate 20 detected by the photo sensor 51 at the initial stage of installation of the copying machine.

Next, at step ST7, the charging output V _G obtained at step ST3 so that the toner adhesion amount becomes uniform.
Based on the relational expression f between the detected toner adhesion amount and the detected toner adhesion amount, the correction amount of the charging output corresponding to the difference ΔD of the toner adhesion amount obtained in step ST6 is obtained.

The data of the correction amount of the charging output thus obtained is sent from the main control unit 62 to the charging output control unit 63, and the charging output control unit 63 sets the photosensitive member 14 on the basis of the correction amount data. The charging charger 33 that is charged is controlled.

Therefore, the toner adhesion amount of the toner image formed on the replaced photoconductor can be made uniform. As a result, the toner adhesion amount of the toner image transferred to the transfer intermediate 20 is stable, and a stable copy image can be formed.

In this embodiment, the operation of the control device 60 is executed when the power switch of the copying machine is pressed, but the copying machine is controlled so that the user can execute this operation at a desired timing. A dedicated switch or the like for starting the operation of the device 60 may be provided, and the operation may be started when the switch is pressed.

Next, a method in which the main control section 62 makes the toner adhesion amount of the toner image formed on the photosensitive member uniform will be described.

FIG. 5 is a graph showing the relationship between the circumferential position of the photosensitive member, the toner adhesion amount and the charging output. Figure 5
(A) is a graph showing the relationship between the circumferential position of the photoconductor and the toner adhesion amount when no correction is made by the control device 60, and FIG. 5 (B) is the circumferential position of the photoconductor and the main position. The graph showing the relationship with the charging output output from the charging charger 33 controlled by the charging output control unit 63 based on the correction amount obtained by the control unit 62, and FIG. 7 is a graph showing the relationship between the circumferential position of the photoconductor and the toner adhesion amount that is uniformly controlled by the control device 60, when performed.

The horizontal axes of FIGS. 5A, 5B and 5C indicate the positions in the circumferential direction of the photosensitive member, which are represented by the same scaling. The vertical axis in each of FIGS. 5A and 5C represents the toner adhesion amount of the toner image formed on the photoconductor, and the vertical axis in FIG. 5B represents the charging output.

As shown in FIG. 5A, for example, it is assumed that the toner adhesion amount in the circumferential direction of the newly replaced photosensitive member is non-uniform.

At this time, the control device 60 is corrected in accordance with the operation shown in FIG. 1 so that the charging output shown in FIG. 5B is output, that is, the toner adhesion amount at the circumferential position of the photoconductor is changed. If the amount is small, increase the charging output, and if the amount of toner attached is large, decrease the charging output.
The charging output control unit 63 controls the charging charger 33 based on the correction value from the main control unit 62.

As a result, as shown in FIG. 5C, there is an effect that a stable (constant) toner adhesion amount can be obtained in the circumferential direction of the photoconductor and a stable full color image can be obtained.

The control device 60 included in the full-color copying machine 10 is provided with a ROM (read only memory) (not shown), and uniformly controls the toner adhesion amount on the photosensitive member shown in FIG. The operation based on the flowchart for is programmed in advance, and its program is stored in this ROM. The program stored in the ROM is read by the main control unit 62,
It is feasible.

According to the above-described embodiment, the toner adhesion amount of the toner image formed on the transfer intermediate is detected by the photo sensor 51 along the circumferential direction of the transfer intermediate, and the main controller 62 is detected according to the detection result. A correction amount of the charging output of the photoconductor is obtained, and the charging output of the charging charger that charges the photoconductor is controlled based on the correction amount. Therefore, the toner adhesion amount of the toner image in the circumferential direction of the photoconductor can be made uniform, and a stable copy image can be formed.

[0077]

As described above, according to the present invention, the photoconductor, the charging means for charging the photoconductor, and the transfer means for transferring the toner image formed on the photoconductor to the transfer body according to the original image. An image forming means for forming a toner image transferred onto a transfer body by a transfer means on a sheet; a detecting means for detecting the toner amount of the toner image formed on the transfer body along the circumferential direction of the transfer body; A charging output control means for controlling the charging output of the charging means so that the toner amount of the toner image formed on the photoconductor becomes uniform along the circumferential direction of the photoconductor based on the toner amount detected by the means. Therefore, it is possible to form a stable copy image by making the toner adhesion amount of the toner image uniform in the circumferential direction of the photoconductor.

[Brief description of drawings]

FIG. 1 is a flowchart showing an operation of a main control unit included in a control device.

FIG. 2 is a sectional view showing the configuration of a full-color copying machine which is an embodiment of the electrophotographic copying machine according to the present invention.

FIG. 3 is an enlarged view of a main part showing a portion including a transfer intermediate body provided in the full-color copying machine of FIG. 2 in an enlarged manner.

FIG. 4 is a block configuration diagram showing an example of a configuration of a control device.

FIG. 5 is a graph showing the relationship between the circumferential position of the photoconductor, the toner adhesion amount, and the charging output.

FIG. 6 is a graph showing the relationship between the circumferential position of the photoconductor and the toner adhesion amount.

[Explanation of symbols]

 10 Full Color Copier 14 Photoreceptor 20 Transfer Intermediate 24 Primary Transfer Charger 26 Secondary Transfer Roller 27 Separation Plate 28 Conveyor Belt 29 Fixing Device 33 Charging Charger 51 Photo Sensor 62 Main Control Section 63 Charge Output Control Section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyuki Onishi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation

Claims (1)

[Claims] 1. A photoconductor, a charging means for charging the photoconductor, a transfer means for transferring a toner image formed on the photoconductor to a transfer body according to an original image, and the transfer body by the transfer means. Image forming means for forming a toner image transferred onto a sheet on a sheet, detecting means for detecting the toner amount of the toner image formed on the transfer body along the circumferential direction of the transfer body, and detecting means for detecting the toner quantity. And a charging output control unit that controls the charging output of the charging unit so that the toner amount of the toner image formed on the photoconductor becomes uniform along the circumferential direction of the photoconductor based on the generated toner amount. An electrophotographic copying machine characterized by that.