JPH0535123A - Electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To provide an electrophotographic copying machine where retransfer or the omission of a character is prevented from occurring. CONSTITUTION:By turning on a switch for starting copying at ST1, a latent image is formed on a photosensitive body and the image is transferred on a transfer intermediate body after developing. Whether or not the retransfer occurs is detected by a photosensor at ST3. In the case that the retransfer does not occur, the machine proceeds to ST4 so as to continue copying as usual. In the case that the retransfer occurs, the machine proceeds to ST5, a primary transfer output value is increased, and the machine proceeds to ST6, the image is transferred on the transfer intermediate body again, then the machine proceeds to ST7, whether or not the retransfer occurs is detected in the same way as the ST3. In the case that the retransfer does not occur, the copying is continued by allowing the machine to proceed to STY. In the case that the retransfer occurs, the machine proceeds to ST5 and the processes of ST5, ST6 and ST7 are repeated until the retransfer is not detected.

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 suitable for full color copying.

[0002]

2. Description of the Related Art In this specification, retransfer means that a toner image transferred to a transfer intermediate returns to a photosensitive member.

In a conventional electrophotographic copying machine equipped with a transfer intermediate, in order to copy an image such as characters written on a document onto a recording medium (final recording medium such as paper), first, a light source lamp or the like is used. The original is irradiated, and the light reflected from the original is applied to the 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 converted into 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 the conventional electrophotographic copying machine, the transfer output (voltage) value of the transfer intermediate, which is involved in the transfer of the toner image formed on the surface of the photoreceptor to the transfer intermediate, is fixed, In the conventional electrophotographic copying machine, due to the margin of the transfer latitude, the optimum transfer is performed in response to the change in the thickness of the toner layer and the change in the static electricity amount (charge amount) of the toner due to the usage of the developer. Is configured.

Next, this latitude will be described.

FIG. 5 is an explanatory view showing an example of the latitude of transfer in a conventional electrophotographic copying machine, and the horizontal axis of the figure shows transfer output.

As shown in the figure, in the conventional electrophotographic copying machine, the transfer output is fixed at 500 V (volt),
The latitude width is 450 V to 550 V, which is an overlapping region 63 of the black solid portion retransfer region 61 and the image density stable region 62 where the toner transfer efficiency is 80% or more.

The conventional electrophotographic copying machine is constructed such that the variation of the toner image due to the variation of the toner charge amount, the thickness of the toner layer and the environment is absorbed by the width of the latitude of 100V.

[0010]

In such a conventional electrophotographic copying machine, the width of the latitude may become narrow depending on the difference between the copying machines used and the environment in which the copying machine is used. In addition, in single color copying and full color copying,
Since the fatigue due to the use of a plurality of developers is different, the optimum transfer output changes every moment. Furthermore, the optimum transfer output changes depending on the environment in which the copier is used.

As a result, in the conventional electrophotographic copying machine using the transfer intermediate, when the toner image is transferred from the photoconductor to the transfer intermediate, when the static electricity of the toner is shaken, or full-color copying is performed. For example, when the toner image is multi-layered, the optimum transfer output may be out of the latitude range, so re-transfer of the solid part (inside the image outline) of the image such as characters and line drawings. Characters are likely to be missing due to retransfer.

Therefore, there is a problem that a part of the image copied on the recording medium does not match the image of the original.

Therefore, the present invention provides an electrophotographic copying machine capable of preventing retransfer and character loss.

[0014]

A photosensitive member, an exposing unit for exposing the photosensitive member, a charging unit for charging the photosensitive member, a predetermined transfer of a charged image formed on the photosensitive member by the exposing unit and the charging unit. Intermediate transfer means for transferring to a transfer body to which a voltage is applied, image forming means for forming a transfer image transferred to the transfer body by the intermediate transfer means on a sheet, and retransfer to the transfer image transferred to the transfer body Is detected and whether the transfer voltage is set to increase when the detection means detects that retransfer is occurring, and retransfer is not occurring. And a setting unit for setting the value of the transfer voltage to be held when it is detected.

[0015]

The charged image from the original is formed on the photoconductor by the exposure means and the charging means, and the charged image formed on the photoconductor is transferred by the intermediate transfer means to the transfer body to which a predetermined transfer voltage is applied. It The detection means detects whether or not retransfer has occurred in the transfer image transferred to the transfer body. The setting means sets so as to hold the value of the transfer voltage when the detection means detects that retransfer is not occurring on the transfer body, and the detection means detects that retransfer is occurring on the transfer body. When the transfer voltage is set, the transfer voltage value is set to increase, and the original is copied in a state where the set transfer voltage value is used. Therefore, it is possible to prevent retransfer and character loss.

[0016]

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

FIG. 2 is a sectional view showing the construction of a color copying machine 10 which is an embodiment of the electrophotographic copying machine according to the present invention.

As shown in FIG. 1, the color copying machine 10 of this embodiment has an original placing table made of transparent glass on the upper surface of the machine frame.
Equipped with 11. Below the document table 11, the exposure optical system
Twelve are arranged.

The exposure optical system 12 is a light source lamp 12a for irradiating the original 13 placed on the original placing 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 photoconductor 14 made of an organic photoconductor (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 constructed so as to eject the paper 15 from the paper feed cassettes 16 and 17, respectively, and feed it toward the transfer intermediate 20.

A timing roller 21 is arranged on the delivery side of the sheet 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 body 20 is configured to be rotationally driven in the clockwise direction (arrow shown in the figure) by the first roller 22a, the second roller 22b and the third roller 22c. It is in pressure contact with a drive roller 23 that rotationally drives 14.

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 predetermined transfer voltage is applied to the transfer intermediate 20 in the vicinity of the surface side of the transfer intermediate 20 in the portion where the first roller 22a is arranged, and is applied to the transfer intermediate 20 as described later. A control setting device 47 for controlling and setting the transfer voltage is provided.

In order to monitor and detect the presence or absence of a toner image on the transfer intermediate 20 transferred from the photoconductor 14 in the vicinity of the surface side of the transfer intermediate 20 in the portion where the second roller 22b is disposed. The reflection type microminiature optical sensor 25 is provided.

The control setting device 47 is connected to the reflective microminiature optical sensor 25, and is configured to control and set the transfer voltage according to the detection signal sent from the reflective microminiature optical sensor 25. ..

A secondary transfer roller 26 is arranged 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 arranged.

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.

The photoconductor 14 irradiated with the reflected light from the exposure optical system 12 is configured to be driven to rotate in the counterclockwise direction (arrow shown in the figure) by the driving roller 23 and the driven roller 30.

In the vicinity of the outer periphery of the driven roller 30, a cleaning device 31 for removing the toner remaining on the photosensitive member 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.

FIG. 3 is a perspective view showing a schematic structure of the color copying machine 10 shown in FIG. In FIG. 2, the constituent elements to which the same reference numerals as those shown in FIG.
Means the same as the component in.

As shown in FIG. 3, inside the front end of the original placing table 11 of the color copying machine 10, for example, a width of 1 mm and a length of 5 to 20 are provided.
A line drawing original 51 of 0 mm is built in, and the line drawing original 51 is provided above the reflecting mirror 52a.

Therefore, in the color copying machine 10, the image of the line drawing original 51 is formed as the line drawing toner patch image 53 on the photoconductor 14 via the reflecting mirrors 52a and 52b, and the line drawing toner patch image 53 is formed.
Is transferred to the transfer intermediate 20 to form a line drawing toner patch image 54.

The photoconductor 14 is an example of the photoconductor of the present invention. The exposure optical system 12 is an embodiment of the exposure means of the present invention. The charging charger 33 is an embodiment of the charging means 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 intermediate transfer means of the present invention. The secondary transfer roller 26 and the fixing device 29 are examples of the image forming means of the present invention. The reflective microminiature optical sensor 25 is an embodiment of the detecting means of the present invention. The control setting device 47 is an embodiment of the setting means of the present invention.

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

FIG. 1 is a flow chart showing the operation for determining the optimum transfer output, that is, the transfer voltage to be applied to the transfer intermediate. FIG. 4 is a graph showing the output state of the reflection type micro optical sensor 25 depending on the presence / absence of retransfer, FIG. 4 (A) shows the output state in the absence of retransfer, and FIG.
Indicates the output state when retransfer occurs. In these figures, the vertical axis represents the output value of the reflective micro optical sensor 25,
The horizontal axis represents the length of the line drawing toner patch image 54 transferred to the transfer intermediate 20.

As shown in FIG. 1, first, in step ST1, when a copy start switch (not shown) provided in the color copying machine 10 is pressed (turned on), step ST1 is entered.
Go to 2.

Next, in step ST2, when the photoconductor 14 and the transfer intermediate body 20 are pre-rotated before the copying of the normal document is started, the line drawing on the photoconductor 14 is performed on the photoconductor 14 by the line drawing document 51 built in the document placing table 11. The toner patch image 53 is formed, and the line drawing toner patch image 53 formed on the photoconductor 14 is
The line image toner patch image 54 is transferred onto the transfer intermediate 20 to which a predetermined voltage (for example, a voltage of 500 V in this embodiment) corresponding to the primary transfer output is applied. Incidentally, in forming the line drawing toner patch image 53 on the photoconductor 14 as described above, the copying machine may be configured to use a blank lamp.

Then, in step ST3, the transfer intermediate 20
The line drawing toner patch image 54 formed above is monitored along the length direction of the line drawing toner patch image 54 by the reflective microminiature optical sensor 25, and there is a partial omission in the solid portion of the line drawing toner patch image 54. Whether or not retransfer occurs is detected depending on whether or not the detection signal is sent to the control setting device 47.

In the control setting device 47, for example, as shown in FIG.
As shown in, if the output state from the reflection type micro light sensor 25 to the control setting device 47 is substantially constant along the length direction of the line drawing toner patch image 54, the occurrence of retransfer is detected. It is determined that there is no. In this state, the primary transfer output value applied first does not change, so the voltage value at this time is set as the primary transfer output value by the control setting device 47, and the process proceeds to step ST4 to copy a normal document. The copy mode is executed.

On the other hand, as shown in FIG. 4B, for example, a state in which the output state from the reflective micro optical sensor 25 to the control setting device 47 is not constant along the length direction of the line drawing toner patch image 54. If so, it is determined that the occurrence of retransfer is detected, and in this state, it is not suitable for copying a normal document, so the process proceeds to step ST5.

In step ST5, the primary transfer output value is increased in the control setting device 47 (in this embodiment, the voltage value is increased by 100 V, for example), and then step ST6.
At, the line drawing toner patch image is formed again on the photoconductor 14, and the line drawing toner patch image is transferred and formed on the transfer intermediate 20.

Then, in step ST7, the transfer intermediate 20
The line drawing toner patch image formed above is monitored along the length direction of the line drawing toner patch image by the reflective microminiature optical sensor 25, and it is determined whether or not there is a partial omission in the solid portion of the line drawing toner patch image. The presence or absence of retransfer is detected,
The detection signal is sent to the control setting device 47.

Similar to step ST3, when the occurrence of retransfer is no longer detected by the reflection type micro optical sensor 25 and the control setting device 47, it is applied in the state where the primary transfer output value is increased. Since the transfer output value does not change, the voltage value at this time is set as the primary transfer output value, and the process proceeds to step ST4 to copy a normal document.

On the other hand, if the occurrence of retransfer is detected even though the primary transfer output value is increased, the step
Returning to ST5, the transfer output value at this time is further increased in the control setting device 47 (in this embodiment, the voltage value is increased by 100 V, for example).

The operations of steps ST5, ST6 and ST6 are repeated until the occurrence of retransfer is not detected. However, when the primary transfer output value becomes equal to or higher than a predetermined voltage value, the transfer intermediate 20 may be damaged (current leaks) due to the relationship of the amount of current flowing through the transfer intermediate 20.
An upper limit is set for the voltage value set as the next transfer output.

The control setting device 47 included in the color copying machine 10 is provided with a ROM (read only memory) and a CPU (central processing unit) not shown, and the optimum transfer shown in FIG. The operation based on the flow chart for defining the output is pre-programmed,
The program is stored in this ROM. ROM
The program stored in is read by the CPU,
Executed.

After the transfer output is set by the above operation, the copy mode executed in step ST4 is yellow,
It has a copy cycle in which magenta and cyan are respectively developed and transferred to the transfer intermediate 20, and when this copy mode is executed, the yellow copy cycle is executed first.

That is, as shown in FIG. 2, the original 13 placed on the original placing table 11 is irradiated with light from the light source lamp 12a to be exposed and scanned. 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 formed 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 uniformly charged by the charging charger 33, and the photoconductor 14 is exposed at the portion A. This allows the photoconductor
On 14, a yellow electrostatic latent image corresponding to the image of the original 13 is formed. This electrostatic latent image is formed in the opposite portion of the developing tank 44 having the yellow developer which is the complementary color of the color separation filter 12d.
The toner is developed and visualized by the developer supplied by the developing magnet roller 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 paper 15 contained in the paper feed cassettes 16 and 17 is fed one by one to the timing roller 21 by the paper feed rollers 18 and 19, and the timing roller 21 is fed to the paper 15 by the timing roller 21.
Is conveyed between the transfer intermediate 20 and the secondary transfer roller 26 in synchronization with the transfer intermediate 20.

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

After the toner image is fixed on the paper 15 by the fixing device 29, the toner image is discharged to the outside, so that one copy mode is completed.

In the color copying machine 10 of this embodiment, when the photoconductor 14 and the transfer intermediate body 20 are pre-rotated before the copying of a normal original document, the line drawing original 61 transferred onto the transfer intermediate body 20 is transferred. The solid part is monitored by the reflective micro light sensor 25,
The detection result of the occurrence of retransfer by monitoring is used as the feedback condition for setting the transfer output, and the transfer output value is changed or held. Therefore, the optimum transfer output value can be set. It is possible to prevent the omission. As a result, it is possible to accurately copy an image such as a character written on a document and its color onto a sheet.

[0062]

As described above, according to the present invention, the photoconductor, the exposing means for exposing the photoconductor, the charging means for charging the photoconductor, and the charging formed on the photoconductor by the exposing means and the charging means. An intermediate transfer means for transferring an image to a transfer body to which a predetermined transfer voltage is applied; an image forming means for forming a transfer image transferred onto the transfer body by the intermediate transfer means on a sheet;
A detection unit that detects whether or not retransfer is occurring in the transfer image transferred to the transfer body, and increases the value of the transfer voltage when the detection unit detects that retransfer is occurring. , And setting means for setting the value of the transfer voltage to be held when it is detected that retransfer is not occurring. Therefore, the occurrence of retransfer or character omission is prevented. be able to.

[Brief description of drawings]

FIG. 1 is a flowchart showing an operation for determining an optimum transfer output.

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

FIG. 3 is a perspective view showing a schematic configuration of the color copying machine shown in FIG.

FIG. 4 is a graph showing an output state of a reflective photosensor depending on whether retransfer occurs.

FIG. 5 is an explanatory diagram showing an example of a latitude of transfer in a conventional electrophotographic copying machine.

[Explanation of symbols]

 10 Color copier 12 Exposure optical system 14 Photoconductor 20 Transfer intermediate 24 Primary transfer charger 25 Reflective ultra-small optical sensor 26 Secondary transfer roller 29 Fixing device 33 Charging charger 47 Control setting device

Claims (1)

Claim: What is claimed is: 1. A photoconductor, an exposure unit that exposes the photoconductor, a charging unit that charges the photoconductor, and an exposure unit and a charging unit that are formed on the photoconductor. An intermediate transfer means for transferring the charged image to a transfer body to which a predetermined transfer voltage is applied, and an image forming means for forming the transfer image transferred to the transfer body by the intermediate transfer means on a sheet,
A detection unit that detects whether retransfer is occurring in the transfer image transferred to the transfer body, and a value of the transfer voltage when the redetection unit detects that retransfer is occurring. An electrophotographic copying machine, comprising: a setting unit that sets the transfer voltage to increase and to hold the value of the transfer voltage when it is detected that retransfer does not occur.