JPH0572847A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent an image from being formed superposed over a surface of paper where another image is formed. CONSTITUTION:The electrophotographic device is provided with a top side sensor 11a and a bottom side sensor 11b to detect whether or not the image is formed on at least one surface of the paper in the paper feeding and carrying path 12, feeding paper to a transfer part 3, and a microcomputer to control feeding of the paper concerned again by forcibly ejecting it when the formation of the image is detected on the paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus such as an electrostatic transfer type copying machine or a laser printer capable of double-sided copying.

[0002]

2. Description of the Related Art An electrophotographic apparatus has a transfer section composed of a photoconductor and a transfer charger. In the transfer section, an image of the photoconductor is transferred onto one side of a sheet contacting the photoconductor. It is like this.

In a copying machine, which is an electrophotographic apparatus capable of double-sided copying, a sheet of paper is reversed after forming an image on one side thereof, and is fed again to a paper feeding and feeding path for being repeatedly fed to a transfer section. It is like this.

[0004]

However, when an image has already been formed on the surface of the paper on which copying is to be performed,
That is, when a so-called backing paper is used, in which an image is formed only on one side and the side on which the image is not formed is used, the one-sided copy is erroneously performed on the side on which the image is already formed. As described above, when a paper is fed or when a backing paper is used when performing double-sided copying, there is a problem in that a copy is performed by directly superimposing it on an already formed image.

[0005]

In order to solve the above-mentioned problems, an electrophotographic apparatus according to the present invention is an electrophotographic apparatus which forms an image on a sheet at a transfer section, in which the sheet is conveyed to the transfer section. A detection unit, such as a detection sensor, provided on the path, and a control unit that discharges the sheet when the detection unit detects that an image is already formed on at least one side of the sheet on which an image is formed. It is characterized by having and.

[0006]

With the above construction, when an image is formed on one side of a sheet, the transfer section is used when the back side is used and the image is formed on the side of the sheet on which the image is formed. The detection unit detects that an image is already formed on the surface of the sheet on which the image is formed, in the conveyance path to. As a result, the control unit ejects the sheet to the outside without forming an image.

On the other hand, in the case of forming an image on both sides of a sheet, if a sheet on which an image is already formed is mistakenly fed, both sides of the sheet are detected by the detecting means in the conveying path to the transfer section. When it is detected that an image is already formed on one side or both sides, the control unit ejects the sheet to the outside without forming an image.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 2, a copying machine, which is an electrophotographic apparatus having a double-sided copying function according to the present embodiment, has a transfer section 3 for forming an image on a sheet and a transfer section 3 for transferring an image. And a fixing unit 6 for fixing the formed image on the sheet.

The transfer section 3 is provided with a photosensitive drum 2 which forms an image in which toner is attached to an electrostatic latent image exposed through the optical system 1, and a lower portion of the photosensitive drum 2 in the drawing. The transfer charger 4 is provided to transfer the image formed on the photosensitive drum 2 onto a sheet.

The fixing unit 6 has a pair of heated upper and lower heat rollers 6a and 6b. These heat rollers 6a and 6b are used to transfer the sheets on which the images are transferred by the transfer unit 3 to each other. The image is fixed on the sheet by pressing the sheet.

A conveyor belt 5 is arranged between the transfer section 3 and the fixing section 6, and the conveyor belt 5 is provided.
Allows the sheet on which the image is transferred by the transfer unit 3 to be fixed on the fixing unit 6
It is designed to be transported to. In the conveyance direction of the fixing unit 6, there is provided a first gate 21 that switches the conveyance direction of the paper between the discharge conveyance path 22 direction and the circulation lower conveyance path 23 direction.

Further, in the copying machine of this embodiment, the paper on which the image has been formed in the transfer section 3 and the fixing section 6 is repeatedly transferred so that double-sided copying in which an image is formed on both sides of the paper is possible. A circulation path is provided for transporting to.

In the circulation path, the transfer section 3, the fixing section 6, the conveyor belt 5, the first gate 21, and the circulation lower conveyance path 23 are arranged, and the sheet is turned upside down. A mechanism 25, a duplex tray 20 for storing the reversed paper, and a paper feeding unit 8 are arranged.

The lower circulation path 23 and the sheet reversing mechanism 2
5, the paper conveyance direction in the circulation lower conveyance path 23 is the direction of the paper reversing mechanism 25 and the duplex tray 2.
A second gate 24 for switching to the 0 direction is provided.

A paper feed roller 19 for sending the paper to the paper feed / transport path 12 is provided in the duplex tray 20 in the transport direction, and the paper feed roller 19 and the paper feed / transport path 1 are provided.
A registration roller 18 that sends the conveyed sheet at a predetermined timing is provided between the sheet and the sheet 2.

As shown in FIGS. 1 and 3, the paper feed unit 8 is provided with a manual paper feed tray 13, an upper cassette 14 for storing paper, a lower cassette 15, and a large capacity tray 16 in this order from the top. There is. A paper feed roller 17 is provided on the paper feed side of the large-capacity tray 16 to convey the accommodated paper to the paper feed conveyance path 12 via a registration roller 18, and the paper feed side of the manual paper feed tray 13 is provided. The apparatus is provided with a take-in roller 9 that conveys a sheet inserted from the outside of the copying machine into the machine, and a sheet feeding roller 10 that feeds the sheet that has been conveyed into a sheet feeding and conveying path 12. The upper cassette 14 and the lower cassette 15 have paper feed sides 1 for feeding paper, respectively.
Paper feed rollers 28 and 29 for feeding paper to the paper 2 are provided.

A registration roller 18 is provided in the paper feed / transport path 12.
Via the duplex tray 20 or the large-capacity tray 16 via the lower conveyance roller 27, the paper conveyed from the manual feed tray 13 and the upper cassette 14, and the lower conveyance roller 27. Upper transport roller 2 that transports the received sheet to the transfer unit 3.
And 6 are provided. Between the upper conveyance roller 26 and the photoconductor drum 2 of the transfer section 3, the conveyed sheet is stopped once if necessary and then is supplied to the photoconductor drum 2 at a predetermined timing. Is provided.

Further, an upper sensor 11a and a lower sensor 11b, which are detection means such as a contact type CCD (Charge Coupled Device) sensor, are provided above and below the conveyance path between the upper conveyance roller 26 and the registration roller 7. ing. The upper sensor 11a and the lower sensor 11b
Is configured to detect whether or not an image is formed on one side / both sides of a sheet passing through the conveyance path.

As shown in FIG. 4, each of the sensors 11a and 11a
The output of b is input to the microcomputer 30 which is a control means. When it is detected by the upper sensor 11a and / or the lower sensor 11b that an image is already formed on the surface of the sheet on which the image is formed, the microcomputer 30 ejects the sheet without forming the image. In this way, the drive motor 31 of each roller for conveying the paper is controlled.

The presence / absence of an image on the paper by the sensors 11a and 11b is detected by the CC obtained from the front surface of the paper.
If the D value is greater than or equal to the predetermined threshold value, it is determined that the image is not formed, and if it is less than the threshold value, it is determined that the image is formed.

The operation of the microcomputer 30 in the case of copying on the paper in the above-mentioned structure will be described with reference to FIG.

When copying is started, first, it is judged whether or not the front end of the paper is detected by a sensor (not shown) or the like, that is, whether or not the paper is fed (S1). When the leading edge of the paper is detected, it is determined whether the one-sided copy mode in which copying is performed on only one side of the paper (S2). In the one-sided copy mode, only the upper sensor 11a is used to copy the upper side of the paper, that is, copy is performed. The detection of the surface to be cut is started (S3). On the other hand, if the one-sided copy mode is not set, it is determined whether the one-sided copy in the two-sided copy is the back side copy (S4).
The process proceeds to the next image transfer process without performing detection by b.
Upper side sensor 1 for copying on the first side in double-sided copying
Detection of both sides of the sheet by the 1a and the lower sensor 11b is started (S5).

Upper sensor 11a or vertical sensor 11a
・ It is judged whether the output value of 11b is less than the threshold value (S
6) If it is equal to or more than the threshold value, it is determined whether or not the trailing edge of the sheet is detected (S7), the threshold value and the sensor output value are compared and determined until the trailing edge is detected, and then the trailing edge is detected. If so, the detection by the sensor ends.

On the other hand, when the output value of the sensor is less than the threshold value, it is determined that an image is formed on the sheet, the drive motor 31 is operated, the sheet is forcibly discharged (S9), and then the sheet is fed. Unit 8 or duplex tray 20
To re-feed the paper (S10). When color paper or the like is used as the paper, the detection by the sensors 11a and 11b is not performed in advance on the operation panel (not shown).

With the above configuration, even when a sheet such as a backing sheet on which an image is already formed is mistakenly mixed with a sheet to be copied by mistake, or when the front and back sides of the backing sheet are reversed and mixed. Since the paper is forcibly discharged and re-fed when the image is formed, there is no inconvenience that the images are overlapped and there is no need to copy again.

In the above embodiment, the CCD sensor is used as the detecting means, but the present invention is not limited thereto.

[0028]

As described above, the electrophotographic apparatus according to the present invention has the detecting means provided on the sheet conveying path to the transfer section, and at least one side of the sheet on which an image is formed by the detecting means. It is configured to include a control unit that discharges the sheet when it is detected that an image has already been formed.

Therefore, when an image has already been formed on the paper on which the image is to be formed, the paper is forcibly ejected when the image is formed, so that there is no inconvenience that the images are overlapped and formed. .. As a result, there is an effect that it is not necessary to perform copying again.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a paper feeding unit in a copying machine of the present invention.

FIG. 2 is a schematic configuration diagram of a copying machine of the present invention.

FIG. 3 is a block diagram showing a flow of sheets in a sheet feeding unit.

FIG. 4 is a block diagram showing configurations of a sensor and a microcomputer of the present invention.

FIG. 5 is a flowchart showing a control operation of the microcomputer of the present invention.

[Explanation of symbols]

 3 Transfer Part 11a Upper Sensor (Detecting Means) 11b Lower Sensor (Detecting Means) 12 Paper Feed Conveying Path 30 Microcomputer (Control Means)

Claims (1)

[Claims] 1. An electrophotographic apparatus for forming an image on a sheet at a transfer section, wherein at least an image on the sheet is formed by the detecting section provided on a sheet conveying path to the transfer section and the detecting section. An electrophotographic apparatus, comprising: a control unit that discharges the sheet when it is detected that an image has already been formed on one side.