JP2000255835A - Paper winding detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect winding of paper around a fixing roller reliably regardless of paper material or presence of foreign matter. SOLUTION: This detector is provided with a first electrode 60 formed so as to come into contact with the paper conveying surface of a fixing roller 40 and is capable of being engaged and disengaged with/from a fixing roller 40 for intermittent engagement/disengagement. A static eliminating brush 50 is used as a second electrode 61, and both electrodes 60, 61 are connected to a detection circuit 62. Voltage is applied to the first electrode 60 and the voltage from the second electrode 61 is detected and to detect a resistor between both electrodes 60, 61. If paper S exists, the resistor value increases, thus it is possible to detect paper winding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-conveying device for conveying a sheet used in an image forming apparatus such as a copying machine, a printer, and a facsimile, for example, a sheet wrap detecting device for detecting wrapping of a sheet in a fixing roller of a fixing device. About.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, in a fixing apparatus in which an image is transferred to a sheet such as a plain paper or an OHP sheet and a fixing process is performed while the sheet is being conveyed, a sheet is caught from a fixing roller by a separation claw after fixing. Has been peeled off. However,
When the toner adheres to the fixing roller, the paper may adhere to the fixing roller and be entangled by the toner, or the paper may be wrapped around the fixing roller if the peeling is not successful due to deformation of a peeling claw or the like. Then, if the paper is continuously used in a wound state without being removed, the paper is heated and, in the worst case, fires.

Therefore, by detecting the winding of the sheet at an early stage, the influence on various image forming operations thereafter is prevented. For example, in Japanese Patent Application Laid-Open No. 3-152581, a detection surface of a color having a light reflection amount different from that of paper is formed on a peripheral surface of at least one fixing roller in a fixing device, and the detection surface is outside the paper conveyance path and detected. A reflection type photo interrupter for detecting a sheet wound around the fixing roller is provided at a position facing the surface. Thus, when the paper is wound around the fixing roller, the surface to be detected is covered with the paper, the light reflected by the paper is incident on the photo interrupter, and the change in the amount of reflected light is detected to detect the winding of the paper, thereby immediately forming an image. The operation can be stopped.

[0004]

In the above-mentioned prior art, the winding of the paper is detected by a change in the reflectance between the fixing roller and the opposing fixing roller using a reflection type photo interrupter. It is necessary to use a material having a high reflectivity as a material to be formed, and accordingly, the apparatus becomes expensive. Further, when unfixed toner adheres to the fixing roller, erroneous detection is likely to occur, and reliability is lacking. In addition, when an image is formed on a transmissive sheet such as an OHP sheet, even if the sheet is wound, light passes through the sheet, and the amount of reflected light does not change, so that the sheet cannot be detected. . As described above, there are various restrictions on the method of optically detecting, and it is not always possible to reliably detect winding of a sheet on any sheet.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a highly reliable sheet winding detection device capable of reliably detecting sheet winding regardless of the material of the sheet.

[0006]

The problem to be solved by the present invention is that a large difference occurs in the resistance on the paper transport surface of a transport body such as a fixing roller for rotating and transporting the paper due to the presence or absence of the paper. Is used to detect winding of the paper. Therefore, at least one electrode may be provided so as to be in contact with the paper transport surface in order to detect the resistance of the conductive transport body on the paper transport surface. An electrode is also provided at a certain location, and the resistance between both electrodes is detected. Since the resistance value between these two points is larger if the paper is wrapped than when it is not wrapped, the presence or absence of the paper can be recognized based on the difference in the resistance value, and the paper can be transferred to the conveyance body regardless of the material of the paper. Winding can be easily detected.

Here, the portion electrically connected to the sheet conveying surface is, for example, a static elimination member provided for static elimination on the sheet conveying surface, or a shaft member of the conveying member. By using the electrode as an electrode, it is not necessary to newly provide an electrode, and the cost of the detection device can be reduced. Further, when the pair of electrodes are integrally held by the holding member, the two electrodes come into contact with different portions at a predetermined interval on the sheet conveying surface, and the detection accuracy can be improved.

The first electrode that comes into contact with the paper transport surface is a sliding member that slides on the paper transport surface or a rolling member that rolls on the paper transport surface. When the first electrode is held by the elastic member, the adverse effect of the first electrode contacting the sheet conveying surface can be reduced. Further, when the first electrode is intermittently separated, the load on the sheet conveying surface can be reduced, and damage such as wear of the first electrode can be prevented.
Further, if a plurality of sheets are arranged along the width direction of the sheet conveyance surface or the rotation direction of the conveyance body, the sheet conveyance surface or the first
It is possible to prevent erroneous detection due to the attachment of foreign matter to the electrode, and it is possible to support paper of different sizes, and it is possible to reliably detect winding.

Alternatively, it is possible to use a peeling claw for peeling the paper from the paper transport surface as the first electrode. Since the peeling nail is arranged at a position where the paper starts to wind around the transport body, the peeling claw can be used. This can be detected immediately when wrapping occurs. Therefore, the amount of wrapping of the sheet is small, so that the sheet removing operation becomes easy.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus provided with a paper wrap detecting device of the present invention will be described with reference to the drawings.
The image forming apparatus according to the present embodiment is a digital image forming apparatus (digital copying machine) having a facsimile function and a printer function.

(Overall Configuration of Digital Copying Machine) As shown in FIG. 3, the mechanism of the digital copying machine is roughly divided into a scanner unit 1 as a document reading device and a laser recording unit 2.
It is composed of

The scanner section 1 includes a document table 3 made of transparent glass, a double-sided automatic document feeder (RADF) 4 for automatically feeding and conveying the document onto the document table 3, and a document table 3 on the document table 3. A document image reading unit for scanning and reading an image of a placed document, that is, a scanner unit 5.

The RADF 4 sets a plurality of documents at a time on a predetermined document tray, and automatically feeds the set documents one by one onto the document table 3 of the scanner unit 5. Device. And this RADF4
Comprises a transport path for a one-sided document, a transport path for a two-sided document, and a transport path switching means so that the scanner unit 5 reads one or both sides of the document in accordance with an operator's selection.

The scanner unit 5 includes a lamp reflector assembly 6 for exposing the surface of the original, and a photoelectric conversion device (CCD) for converting a reflected light image from the original to an electric image signal.
7, a first scanning unit 5a equipped with a first reflecting mirror 8a and a second scanning unit 5b equipped with second and third reflecting mirrors 8b, 8c for forming a reflected light image on the CCD 7. It comprises an optical lens body 9. First
The scanning unit 5a travels along the document table 3 from left to right at a constant speed V, and the second scanning unit 5b is controlled so as to travel in the same direction at a speed of V / 2.

As a result, in the scanner unit 1, the RADF
With the operation related to the scanner unit 4 and the scanner unit 5, while the originals to be read are sequentially placed on the original placing table 3,
The scanner unit 5 is moved along the lower surface of the document placing table 3 to sequentially form images of the document placed on the document placing table 3 on the CCD 7 line by line to read the document image.

The image data obtained by reading the original image by the scanner unit 5 is sent to an image processing unit described later, and after being subjected to various processes, is temporarily stored in a memory, and is temporarily stored in the memory in response to an output instruction. The image data is output to the laser recording unit 2, reproduced in the electrophotographic processing unit 10 as a visible image on the photosensitive drum 11, and then transferred to a sheet to form a toner image.

The laser recording section 2 includes a paper storage section 12,
The image forming apparatus includes a sheet feeding / conveying unit 13, a laser writing unit 14, and an electrophotographic processing unit 10 for forming an image. The laser writing unit 14 includes a semiconductor laser that emits a laser beam in accordance with image data read from a memory or image data transferred from an external device such as a personal computer, a polygon mirror that deflects a laser beam at an equal angular velocity, The point at which the applied laser beam irradiates the photoconductor drum 11 of the electrophotographic process unit 10 is corrected so that the laser beam scans the photoconductor drum 11 at a constant speed.
A −θ lens and the like. Electrophotographic process unit 10
According to a known mode, a charging device 15, a developing device 16, a transfer device 17, and a peeling device 1 are provided around the photosensitive drum 11.
8, a cleaning device 19, a static eliminator, and a fixing device 20 downstream of the photosensitive drum 11.

The paper storage unit 12 has a first cassette 21, a second cassette 22, and a multi-manual tray 23. Further, an image is sent from the paper storage unit 12 and an image is printed on the back side of the paper on which the image is recorded. A double-sided copying unit 24 for recording is provided. Paper feed transport unit 13
Indicates that the photosensitive drum 11 and the transfer device 1
In order to convey the sheet to the transfer position between the transfer roller 7 and the transfer roller 7, a paper feed roller, a conveyance roller, and a registration roller are provided.

Each of the cassettes in the paper storage section 12 stores a bundle of papers for each size. When an operator selects a cassette containing papers of a desired size, the bundle of papers in the cassette is stored. The sheets are sent out one by one from the top and sequentially passed through the transport path 25 to the electrophotographic process unit 1.
It is transported toward zero.

A sheet discharge path 26 is provided downstream of the fixing device 20 in the sheet conveyance direction.
Is branched into a transport path 28 leading to the post-processing device 27 and a transport path 29 leading to the duplex copying unit 24.

In the laser writing unit 14 and the electrophotographic processing unit 10, the image data read from the memory is scanned by a laser beam by the laser writing unit 14 to form an electrostatic latent image on the surface of the photosensitive drum 11. The toner image formed and visualized by the toner of the developing device 16 is electrostatically transferred by the transfer device 17 onto the surface of the paper conveyed from the paper storage unit 12 and fixed by the fixing device 20.

The paper on which the image has been formed in this manner is sent from the fixing device 20 to the post-processing device 27 via the transport path 28, or is selectively transported to the duplex copying unit 24 via the transport path 29. Is done. The sheets sent to the post-processing device 27 are subjected to predetermined processing such as sorting or stapling as necessary, and are stacked on the first discharge tray 30 or the second discharge tray 31. Further, the sheet sent to the duplex copying unit 24 is turned over here and is again conveyed to the electrophotographic processing unit 10, where an image is formed on the back surface of the sheet, and discharged after fixing.

(System Configuration of Digital Copier) In this digital copier, the mechanical units such as the above-described various units and the image processing unit that performs image processing on read document image information are controlled by a main central processing unit (CPU). Sub central processing unit (CPU) mounted for each unit
The operation is managed while cooperating with.

As shown in FIG. 4, this system mainly includes an operation panel board 100 for managing and controlling an operation panel, a machine control board 200 for managing and controlling each unit and the like, an original image which is electrically read, and electronic data is read. And a main image processing board 400 for performing predetermined image processing on a document image converted into electronic data by the CCD board 300, and image information processed by the main image processing board 400. Image processing board 5 for further performing predetermined image processing
00 and other expansion boards 600 connected to the sub-image processing board 500 via an interface.
(A printer board, a FAX board, and a function expansion board).

The contents managed and controlled for each board will be described below. Operation panel board 100
Are basically controlled by a sub-central processing unit (CPU) 101, a display screen of an LCD display unit 104 arranged on an operation panel 103, and an operation from an operation key group 105 for inputting instructions regarding various modes. It manages input, etc. A memory 102 is provided for storing various control information on the operation panel, such as data input from the operation key group 105 and information to be displayed on the LCD screen.

At this time, the sub CPU 101 performs control data communication with the main central processing unit (CPU) 401 to instruct the operation of the digital copying machine. Further, by transmitting a control signal indicating the operation state of the digital copying machine from the main CPU 401 to the sub CPU 101, the operation state such as the current state of the device is displayed through the LCD display unit 104 of the operation panel 103. It has become.

The machine control board 200 is controlled by a sub CPU 201, and includes ADF, RADF
Automatic document feeder 4, a scanner unit (reading scanner unit) 5, an electrophotographic process unit 10 for reproducing image information as an image, and a paper storage unit 1 for storing a sheet on which the image is recorded.
2, a sheet feeding / conveying unit 13 that sequentially conveys the sheet to the electrophotographic process unit 10; a duplex copying unit 24 that inverts the sheet on which the image is recorded so as to form the image on both sides of the sheet; It manages a post-processing device (finisher) 27 that performs post-processing such as stapling on paper on which images are recorded.

The CCD board 300 includes a CCD 7 and a CCD.
7 drive circuit (CCD gate array) 302, CCD7
An analog circuit 303 for adjusting the gain of analog data output from the A / D converter 304 for converting an analog output of the CCD 7 into a digital signal and outputting it as electronic data.
01.

The main image processing board 400 includes a main C
Controlled by the PU 401, based on the electronic data of the original image sent from the CCD board 300, shading correction, density correction, area separation, filter processing, MTF correction,
A multi-valued image processing unit 402 that performs processing in the state of multi-valued image data such as resolution conversion, electronic zoom (magnification processing), and gamma correction, and various control information such as processed image data or processing procedure management. Memory 40 for storing
3. A laser control unit 404 for controlling the transfer of data to the laser writing unit (LSU) 14 in order to reproduce an image with the processed image information.

The sub-image processing board 500 is connected to the main image processing board 400 through a connector, and has a binary image processing section 501 controlled by the main CPU 401 on the main image processing board 400; Alternatively, a gate array 502 for controlling a memory 502a for storing and managing control information and the like in processing, storing and managing a plurality of document image information, and repeatedly reading a plurality of document images by a desired number of copies, Hard disk 503a for generating a copy of the same, a gate array 503 for controlling the hard disk 503a, a SCSI 504 as an external interface, and a SCSI 5
And a gate array for controlling the IC 04.

A binary image processing unit 501 includes a processing unit for converting multi-valued image information into a binary image, a processing unit for rotating the image, and a binary magnification (zoom) for performing a scaling process on the binary image. It is composed of a processing unit and the like, and further has a fax interface so that a fax image can be transmitted and received via communication means.

The extension board 600 includes a printer board 601 for outputting data transmitted from a personal computer or the like in a printer mode.
A function expansion board 602 for extending the editing function of the digital copier to effectively utilize the features of the digital copier, and transmitting the original image read from the reading scanner unit 5 of the digital copier to the other party, There is a facsimile board 603 and the like which enable image information sent from the destination to be output as a facsimile mode.

Hereinafter, image processing of a digital copying machine will be described.
The processing of image data and the flow of image data in each mode of copy, fax, and printer will be described in further detail.

(Copy Mode) Originals set at predetermined positions of the RADF 4 are sequentially supplied one by one onto the original mounting table 3 of the scanner unit 5, and original images are sequentially read by the scanner unit 5 to form 8-bit images. The data is transferred to the main image processing board 400 as electronic data. The 8-bit electronic data transferred to the main image processing board 400 is subjected to predetermined processing on the multi-value image processing unit 402 as 8-bit electronic image data. Then, processing such as gamma correction is performed on the 8-bit electronic image data, and is sent to the laser writing unit 14 via the laser control unit 404. As a result, the document image read by the reading scanner unit 5 is output by the laser recording unit 2 as a toned copy image.

(Electronic RDH Function in Copy Mode)
As described above, the originals set at the predetermined positions of the RADF 4 are supplied one by one, and the original images are sequentially read.
Main image processing board 400 as electronic data of bits
Is forwarded to. This electronic data is subjected to predetermined processing on the multi-valued image processing unit 402 as 8-bit electronic image data, and thereafter, from the connector 405 on the main image processing board 400 to the connector 505 on the sub-image processing board 500 side. To the sub-image processing board 500 side, and is converted from 8-bit electronic image data to 1-bit electronic image data along with processing such as error diffusion in the multi-level binary conversion unit of the binary image processing unit 501. . The 1-bit electronic image data converted in this manner is transferred to a disk memory such as the hard disk 503a for each document and temporarily stored and managed.

The reason that 8-bit electronic image data is converted into 1-bit electronic image data, including processing such as error diffusion, is that simply performing multi-level binary conversion causes a problem in image quality. This is because there is a reduction in the image quality. Also, the storage capacity of the image is taken into consideration.

When all the originals set on the RADF 4 have been read, the hard disk 50 is temporarily
The 1-bit electronic image data stored in 3a is repeatedly read by the number of copies specified by the control of the gate array 503, and the read 1-bit electronic image data is again transmitted through the connectors 405 and 505. To the main image processing board 400 to perform processing such as gamma correction, and then to the laser writing unit 14 via the laser control unit 404. Thereby, the scanner unit 1
Is output from the laser recording unit 2 as a copy image with gradation.

As described above, it has been described that the image group is repeatedly read out by the desired number of copies after all the original images have been read. However, the image output of the first copy is ready for a predetermined number of images. It is also possible to configure so as to output sequentially in stages.

(Printer Mode) An image sent from an external device connected to a network such as a personal computer is developed as an image in a page unit on a printer board 601 and then an SCS as an interface.
The data is temporarily transferred from the I504 to the sub-image processing board 500 side and stored in a memory such as the hard disk 503a.

The image developed as a page image on the printer board 601 is stored in the sub-image processing board 50.
Although the page image is sent to the 0 side, the page image is not subjected to the binary image processing and is only temporarily stored in the hard disk 503a. Also, when the stored page image is read from the hard disk 503a, the 2
No value image processing is performed.

The image information temporarily stored in the hard disk 503a is sent to the main image processing board 400 while being read from the hard disk 503a in a predetermined page order, and is subjected to gamma correction. To laser writing unit 14
The writing of the image is controlled to reproduce the image.

(Fax Mode) In the fax mode, there are processes for transmitting a document to a destination and receiving a document from the destination. First, transmission of a document to a destination will be described. Transmission documents set at a predetermined position of the RADF 4 are sequentially supplied one by one onto the document table 3, and images of the transmission documents are sequentially read by the scanner unit 5. The data is transferred to the main image processing board 400 as bit electronic data.

The 8-bit electronic data transferred to the main image processing board 400 is subjected to predetermined processing on the multi-value image processing section 402 as 8-bit electronic image data.
The 8-bit electronic image data is then sent from the connector 405 on the main image processing board 400 to the sub-image processing board 500 via the connector 505 on the sub-image processing board 500, and the binary image processing unit In the multi-value binary conversion unit 501, 8-bit electronic image data is converted into 1-bit electronic image data together with processing such as error diffusion.

The transmission document thus formed into a binary image is compressed in a predetermined format and stored in a memory. Then, a transmission procedure with the destination is performed, and when a state where transmission is possible is secured, the transmission original image compressed in a predetermined format read from the memory is transferred to the fax board 603 side, and the fax board 603 is transmitted. After performing necessary processing such as changing the compression format, the data is sequentially transmitted to the other party via the communication line.

Next, processing of a document image transmitted from the other party will be described. When the original image is transmitted from the other party via the communication line, the fax board 603
While receiving the original image transmitted from the other party while performing the communication procedure in the above, the received image compressed in a predetermined format is provided in the binary image processing unit 501 of the sub-image processing board 500. The document image is sent from the facsimile interface to the binary image processing unit 501 and subjected to compression / decompression processing to reproduce the document image transmitted as a page image.

The original image reproduced as an image in page units is transferred to the main image processing board 400 side, performs gamma correction, and performs laser control.
The writing of the image is controlled by the laser writing unit 14 so that the image is reproduced.

As can be seen from the above configuration, the image processing section for performing predetermined processing on image information is mainly composed of the scanner section 1.
A main image processing board 400 that processes the original image read and input from the MFP as multi-valued image information, and a predetermined process such as binarization processing on the original image information processed as multi-valued image information by the main image processing board 400 After performing a predetermined process on image information sent from a device connected via an external interface, the multi-value image processing unit 4 of the main image processing board 400
And a sub-image processing board 500 for transferring data to the 02 side.

The laser control unit 404 of the main image processing board 400 controls writing of image information by the laser writing unit 14 so that the image is reproduced on the photosensitive drum 11 by the laser writing unit 14.

Then, C of the main image processing board 400
Since the PU 401 also manages and controls the sub-image processing board 500, the flow of the entire image continuously processed in each processing unit can be managed, the flow of data and processing becomes smooth, and image data is lost. Not even.

With this configuration, a document image read and input from the scanner unit 1 can be reproduced as a copy image from the laser recording unit 2 without impairing the characteristics of the image of the document as a multi-valued image. When high-speed output processing is performed using an electronic RDH function or the like, it becomes possible by using the sub-image processing board 500, the hard disk 503a, and the like.

Further, processing and output of image information from an external device such as a facsimile or a printer, and binarization of a transmission original which is further subjected to multi-value image processing only for a facsimile, that is, a document in which the characteristics of the original image are maintained. It is configured so that appropriate processing can be performed on image information in accordance with digital characteristic functions provided as a digital copying machine, such as processing. Furthermore, by dispersing the image processing unit, it is possible to prepare a wide variety of digital copying machine variations (lineup), and it is possible to install a digital copying machine that meets the needs of the user.
Further, even after the installation, the system can be easily expanded according to the user's request.

(Structure of Fixing Device) Next, in the present invention, the fixing device 20 that heats and fixes the sheet while transporting the sheet will be described.
A paper wrap detecting device is provided so that the wrap of the paper can be detected. Here, as shown in FIG. 1, the fixing device 20 has a pair of upper and lower fixing rollers 40 abutted against each other at a predetermined pressure, and the peeling claw 41 abutting on the surface of each fixing roller 40 swings. It is provided swingably around the shaft 42 (see FIG. 11). A front paper guide 43 is disposed upstream of the fixing roller 40 in the paper transport direction, and a pair of upper and lower rear paper guides 44 are disposed downstream of the fixing roller 40.

As shown in FIG. 2, the fixing roller 40 comprises a metal cylinder 45 made of aluminum or the like, and a protruding shaft 46 integrally protruded or attached to both ends of the cylinder 45 via a bearing 48 on a frame 47. The fixing roller 40 is rotatably driven by transmitting a driving force from a motor controlled by the CPU 201 of the machine control board 200. A heating element 49 such as a heater and a lamp is housed inside the cylinder 45, and the heating element 49 is inserted into the through hole 46a of the protruding shaft 46 and supported by the heating element support member 49a.

The width of the fixing roller 40 in the axial direction (width direction) is set to be larger than the maximum size of the paper used.
A part of the outer peripheral surface is used as a sheet conveying surface, and its width is the same as the sheet width of the maximum size. Further, since the fixing roller 40 has conductivity, the outer peripheral surface may be charged by the sheet S that has passed through the photosensitive drum 11 and has been charged. Therefore, a static elimination member 50 such as a static elimination brush or a roller is provided over substantially the entire area in the axial direction in order to eliminate static on the outer peripheral surface, and is grounded.

(Structure of the paper wrap detecting device) The paper wrap detecting device is provided with a first paper contacting surface of each fixing roller 40.
An electrode 60, a second electrode 61 that contacts another portion of the fixing roller 40 that is electrically connected to the sheet transport surface, and a detection circuit 62 that detects the presence or absence of the sheet S from the resistance between the electrodes 60 and 61. And

Here, the charge removing member 50 is used as the second electrode 61.
Since the charge removing member 50 is in contact with the sheet conveying surface of the fixing roller 40, the second electrode 61 is electrically connected to the sheet conveying surface. Also, the first electrode 60
The conductive contact 63 is swingably supported around a fulcrum 64, and can be separated from and connected to the fixing roller 40 by being rocked by a separating means such as a motor and a solenoid. Then, the static elimination member 50 that is the second electrode 61
The first electrode 60 is connected to the detection circuit 62 by a lead such as a lead wire, and an electric circuit is formed by interposing the sheet conveying surface of the fixing roller 40 between the first electrode 60 and the second electrode 61. Is done. It is preferable that the first electrode 60 be installed at an upstream side in the rotation direction, that is, at a position close to the peeling claw 41 from the viewpoint of early detection.

The detecting circuit 62 detects a resistance between the two electrodes 60 and 61 by applying a constant voltage (5 to 12 V) to the first electrode 60 and measuring the voltage from the second electrode 61. The presence or absence of the sheet S is detected based on the resistance value. The detection circuit 62 is connected to the CPU 201 of the machine control board 200, and controls an image forming operation based on an output signal from the detection circuit 62. That is, the paper wrap detecting device is managed by the machine control board 200.

In the above-described fixing device 20, the sheet S on which the electrostatic latent image is transferred by the photosensitive drum 11 is conveyed on the front sheet guide 43, and then the upper and lower fixing rollers 4 are moved.
0, the toner image on the paper S is fixed. The sheet S is separated from the fixing rollers 40 by the peeling claws 41.
The sheet is peeled from above and conveyed between the paper guides 44 to complete the fixing process. In the above processing procedure, the paper S to be separated from each fixing roller 40 by the separation claw 41 after fixing may be wound around any one of the fixing rollers 40 without being separated.

The detection circuit 62 applies a constant voltage to the first electrode 60 and detects a change in the voltage through the second electrode 61. This detection may be performed at all times, but may be performed in accordance with the timing at which the sheet S passes through the fixing roller 40 in accordance with the image forming operation, thereby suppressing power consumption.

Then, the resistance between the first electrode 60 and the second electrode 61 is calculated based on the voltage detected by the detection circuit 62. When the sheet S is not wound around the fixing roller 40, the resistance value is small because only the conductive sheet conveying surface exists between the electrodes 60 and 61. However, when the paper S is wound, the detected voltage is very low because the paper S has no conductivity, and the resistance value between the electrodes 60 and 61 becomes very large. As described above, since a large difference occurs in the resistance depending on the presence or absence of the sheet S on the sheet transport surface, it is possible to easily detect that the sheet S has been wound around the fixing roller 40. Moreover, even if the sheet is a transparent OHP sheet, the difference in resistance value can be detected, so that the winding of the sheet S can be reliably detected regardless of the material of the sheet S.

When the winding of the sheet S is detected as described above, an output signal indicating that there is a sheet is output from the detection circuit 62 to the CPU.
201, and the image forming operation is immediately stopped based on the output. Then, when the user removes the wound paper S, the image forming operation can be performed. At this time, before the start of the image forming operation, the detection of the winding of the sheet S may be performed again to confirm that there is no sheet.

Here, since the first electrode 60 is detachable from the fixing roller 40, the first electrode 60 is held at a position away from each fixing roller 40 when the sheet S is not conveyed. The paper S is conveyed and the fixing rollers 40
Is performed by the CPU 201 of the machine control board 200 so as to intermittently contact the fixing rollers 40 a plurality of times during the fixing process. The timing of the separation and contact of the first electrode 60 is such that the sheet S is separated and contacted a plurality of times during the time when the sheet S passes through the fixing roller 40, and varies depending on the length of the sheet S. No leakage.

Thus, the fixing roller 40 and the first electrode 6
0, so that damage to the paper transport surface of the fixing roller 40 and damage due to abrasion of the first electrode 60 can be prevented.
Adhesion to the electrode 60 can be prevented. Further, since the first electrode 60 contacts the fixing roller 40 a plurality of times regardless of the length of the sheet S being conveyed, erroneous detection can be prevented. Therefore, the winding state of the sheet S can be accurately recognized over a long period of time, and the reliability of the detection device can be improved.

Next, a specific structure of the first electrode 60 will be described. As shown in FIG. 5A, in the first electrode 60, a sliding member 63a made of a conductive material such as a metal or a plastic, which is in sliding contact with the sheet conveying surface, is used as a contact 63, which is formed in a spherical shape. . The contact 63 is fixed to the tip of a spring 66 connected to the solenoid 65 of the separation / contact means so as not to rotate. This spring 66
By using a conductive material and electrically connecting the solenoid 65 to the detection circuit 62, an electrical connection with the fixing roller 40 can be obtained from the detection circuit 62 via the solenoid 65, the spring 66, and the contact 63. . The solenoid 65 is attached to a cover or a frame that covers the fixing roller 40. Further, an elastic member such as a conductive rubber may be used instead of the spring 66.

By turning the solenoid 65 on and off, the spring 66 held by the solenoid 65 is turned on and off.
Makes a vertical movement, and the contact 63 fixed to the spring 66 also moves up and down, and comes into contact with and separates from the fixing roller 40. By holding the contact 63 by the spring 66, the contact 63 collides with the fixing roller 40 when the apparatus itself vibrates. The impact on the fixing roller 40 can be reduced by the spring 66, 40 can be prevented from being damaged. Also, during maintenance of the fixing device 20, by pushing up the spring 66, the first electrode 60 can be prevented from hindering the work, and the work can be performed easily.

When the contact 63 of the first electrode 60 is formed into a spherical shape, the contact 63 slides on the sheet conveying surface of the fixing roller 40 without rolling while being pressed by the spring 66. Therefore, a stable contact state can be obtained at all times, the fluctuation of the applied voltage is suppressed, and it is possible to prevent the detection signal from fluctuating due to noise on the detection signal, and to prevent the detection error from occurring, and to eliminate the detection failure and to obtain a stable paper. Winding can be detected.

Here, as the contact 63, instead of the spherical sliding member 63a, as shown in FIG. 5B, a roller-shaped rolling member 63b made of a conductive material may be used. In this case, the contact 63 is held by a spring 66, but is rotatably supported by a conductive arm 67 fixed to the tip of the spring 66 so as to be rotatable.
The contact 63 is connected to the spring 6 via the arm 67.
6 and an electrical conduction state is obtained. The other configuration is the same as the above, and the same effects can be obtained.

As described above, the contact 63 is connected to the rolling member 63b.
As a result, the contact 63 also rolls on the sheet conveying surface as the fixing roller 40 rotates, reducing the load on the fixing roller 40 and preventing the sheet conveying surface from being damaged.
The life of the fixing roller 40 can be extended.

The paper S has various sizes.
The fixing roller 40 has a width larger than the sheet size in the axial direction (width direction) so that the fixing process can be performed on the sheet S. Therefore, there is no case where one sheet of the first electrode 60 cannot cover the entire sheet conveyance surface, but a detection error may occur. Therefore, the arrangement of the first electrode 60 becomes important. As shown in FIG. 6, a plurality of, for example, four, are arranged in a row in the width direction of the sheet conveying surface. At this time, the interval between the first electrodes 60 is set to be smaller than the minimum sheet width Wmin so that the sheet S having the minimum sheet width Wmin allowed by the fixing device 20 can be handled. Each first electrode 60 is connected in parallel to the detection circuit 62, and performs detection by applying a voltage one by one.

With this arrangement, it is possible to efficiently perform the winding detection on all the sheets S irrespective of the size of the sheets S by arranging the minimum first electrodes 60 without unnecessarily providing the first electrodes 60. it can.

As shown in FIG. 7, the first electrode 60 is disposed at a plurality of positions, for example, three positions on the same circumference along the rotation direction of the fixing roller 40 with respect to the rotation direction of the fixing roller 40. . Note that a plurality of pieces may be arranged in the width direction as shown in FIG. By arranging in this manner, erroneous detection due to fatigue and wear of the first electrode 60 can be prevented, and long-term reliable detection of paper wrapping can be performed. That is, toner may adhere to the fixing roller 40. If the toner adheres to the first electrode 60, the resistance value recognized by the detection circuit 62 includes the resistance value of the adhered toner component. It causes detection. Therefore, if the toner is attached at a plurality of locations, the resistance value detected by the first electrode 60 to which the toner is attached is different from the resistance value of the one to which the toner is not attached. By not referring to the resistance value, the subsequent detection of paper wrapping can be performed normally.

To reliably detect the winding, it is desirable to dispose the first electrodes 60 as described above, but the number of first electrodes 60 increases. Therefore, as shown in FIG.
The electrodes 60 are placed on different circumferences of the fixing roller 40 respectively.
Four pieces are placed one by one and at each position of the ABCD in order at a constant interval along the rotation direction. This is for the case where the fixing reference position of the sheet S is on the left side in the width direction.
When the fixing reference position is located at the center in the width direction, the fixing reference position is as shown in FIG.

That is, the first electrodes 60 are arranged in order from the upstream side in the rotation direction with reference to the passing position where the sheet S passes through the fixing roller 40. First, the first electrodes 60 at the position A near the passing position are used. Detects the winding of the paper S,
Subsequently, detection is sequentially performed by the first electrodes 60 at the B position, the C position, and the D position. By arranging such a small number of the first electrodes 60, it is possible to detect the sheet wrapping quickly and reliably, and it is possible to realize the detecting device at low cost.

In the above-described embodiment, the discharging brush 50 is used as the second electrode 61. Instead, as shown in FIG. 9, the discharging brush 50 is integrally provided at the end of the cylinder 45 of the fixing roller 40. The protruding shaft 46 is used. The protruding shaft 46 is formed of the same member as the cylinder 45 or is formed of a conductive material, so that the protruding shaft 46 is electrically connected to the sheet conveying surface. The first electrode 60 is the same as described above.

Then, by electrically connecting the protruding shaft 46 and the detection circuit 62, an electric circuit is formed from the first electrode 60 to the detection circuit 62 via the sheet conveying surface of the fixing roller 40 and the protruding shaft 46. . Since the protruding shaft 46 rotates,
By sliding the brush, voltage can be taken out to the outside. Further, the bearing 48 that supports the protruding shaft 46 may be made conductive and connected to the detection circuit 62.

By forming the second electrode 61 as a shaft member such as the protruding shaft 46 or the bearing 48, the number of members that come into contact with the sheet conveying surface of the fixing roller 40 can be reduced, and the surface of the fixing roller 40 is damaged. It is difficult to stick, and the life can be extended. In addition, the control of the discharging brush 50 when detecting paper wrapping is unnecessary, and the detection device can be realized with a simple configuration. Further, when the shaft member is grounded, there is no difference in the resistance value at each position when a plurality of first electrodes 60 are installed, so that the detection accuracy is increased.

Next, FIG. 10 shows a sheet wrap detecting device according to another embodiment. In this detection device, the peeling claw 41 is used as the first electrode 60. That is, as shown in FIG. 11, a conductive film 70 is formed on the tip that comes into contact with the fixing roller 40, which is a part of the peeling claw 41, and the conductive film 70 is attached to the conductive swing shaft 42 by a lead wire or pattern wiring. Are connected by a conducting wire 71. Alternatively, the peeling claw 41 itself is formed of a conductive material. Then, the swing shaft 42 is connected to the detection circuit 62. The configuration other than the first electrode 60 is the same as the above embodiment.

When a part or all of the peeling claw 41 is configured as the first electrode 60, the original peeling claw 41
Can be detected without interfering with the operation of (1), there is no need to separately provide the first electrode 60, and an inexpensive and space-saving detection device can be realized.
In addition, since the peeling claw 41 is disposed immediately downstream of the position where the sheet S passes with respect to the fixing roller 40, if this is used, this is immediately detected at a place where the sheet is wrapped around the fixing roller 40. be able to. Therefore, the rotation of the fixing roller 40 can be stopped when the sheet S is slightly wound around the fixing roller 40, and the sheet S can be easily removed.

FIG. 12 shows a sheet wrap detecting apparatus according to another embodiment. In this detection device, the first electrode 60 and the second
The electrode 61 is integrally held by a holding member 72 at an interval to form an electrode unit 73. And the first
The structure of the electrode 60 and the second electrode 61 is the same as that shown in FIG. 5. If a solenoid is used as the holding member 72, the two electrodes 60 and 61 are integrated with the fixing roller 40 by one solenoid. Can be separated.
The other configuration is the same as the above embodiment.

The second electrode 61 comes into contact with another portion of the sheet conveying surface different from the contact portion of the first electrode 60,
The distance between the two contact points is always kept constant. Therefore, when a predetermined voltage is applied from the first electrode 60 and the second electrode 61 is set to the ground, there is no variation in the resistance value between these two points, and the detection accuracy is improved. In addition, both electrodes 60 and 61
By integrating them into a unit, the number of members is reduced, the mounting work is easy, and the detection device can be realized at low cost. Since such installation is easy, it may be installed not only in one place but also in a plurality of places.

Note that the present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention. For example, as shown in FIG. 13, when the first electrode 60 is bent using a leaf spring so as to come into contact with the sheet conveying surface of the fixing roller 40, the first electrode 60 is pressed against the fixing roller 40 by its own elastic force. If the tip contacting the fixing roller 40 has an arcuate curvature, the contact state is stable and the detection accuracy is improved. Further, it may be vertically movable so as to be separated from and connected to each other.

Further, the combination of the first electrode and the second electrode is not limited to each of the above embodiments, but may be a combination of a neutralization brush, a shaft member,
Alternatively, if an existing member such as a peeling claw and a shaft member is used, only wiring is required, and the cost can be reduced.

In some fixing devices, one of the fixing rollers is a heat roller having a built-in heater, and the other is a pressure roller that presses against the heat roller. In this case, the paper is wound around the heat roller. Therefore, a sheet wrap detecting device is provided for this heat roller. If the pressure roller is a conductive rubber, a paper winding detection device may be provided for this roller.

The paper wrap detecting device is not limited to the detection of the wrapping of the paper in the fixing device, but may be applied to a transport body for transporting the paper. It may be.

[0085]

As is apparent from the above description, according to the present invention, the presence or absence of a sheet can be determined by detecting the resistance on the conductive sheet conveying surface such as a fixing roller using a pair of electrodes. In addition, it is possible to reliably detect even a transparent sheet that cannot be detected by an optical detection method, and it is possible to increase the detection accuracy of sheet wrapping without erroneously detecting an attached foreign substance as a sheet.

When the electrode in contact with the paper transporting body is brought into sliding contact with the paper transporting surface, a stable contact state is obtained, and detection errors due to detection errors are eliminated. Alternatively, when the electrodes are rolled on the paper transport surface, the load on the paper transport surface is reduced, the surface is not damaged, the electrodes are not worn, and the life of each electrode can be extended.

By bringing the electrodes into and out of contact with the paper transport surface, the contact time between them can be reduced, the damage to the paper transport surface can be prevented, and the chance of foreign matter adhering to the electrodes can be reduced. Can be eliminated. Further, when the electrodes are held by a conductive elastic member, the impact on the transporting body when the electrodes are brought into contact with each other can be reduced, and damage to the paper transporting surface can be prevented.

Further, if a plurality of electrodes are arranged along the width direction of the sheet conveying surface or the rotating direction of the conveying member, even if foreign matter adheres to one of the electrodes and erroneous detection occurs, the other electrodes can surely detect the foreign matter. Paper wrapping can be detected. Moreover, if you set the placement location in consideration of the paper size,
It can handle various sizes of paper with a small number.

By using a member associated with the carrier such as a peeling claw, a charge removing member, and a shaft member as such an electrode, an installation space is not required, and an inexpensive detector can be provided. In addition, if a plurality of electrodes are integrated into one unit, the mounting operation becomes easy, and the distance between two points for detecting the resistance can be kept constant, so that the detection accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a sheet winding detection device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a fixing roller.

FIG. 3 is an overall configuration diagram of a digital copying machine.

FIG. 4 is a system configuration diagram of the same.

5A and 5B show configuration diagrams of a first electrode, wherein FIG. 5A shows a case of a sliding member, and FIG. 5B shows a case of a rolling member.

FIG. 6 is a diagram showing an arrangement of a first electrode in a width direction.

FIG. 7 is a diagram showing an arrangement of a first electrode in a rotation direction.

FIG. 8 is a diagram showing another arrangement example of the first electrode.

FIG. 9 is a configuration diagram of a sheet winding detection device in which a second electrode is changed.

FIG. 10 is a configuration diagram of a sheet winding detection device according to another embodiment.

FIG. 11 is a view showing a peeling nail;

FIG. 12 is a configuration diagram of a sheet winding detection device according to another embodiment.

FIG. 13 is a view showing another embodiment of the first electrode.

[Explanation of symbols]

 REFERENCE SIGNS LIST 40 fixing roller 41 peeling claw 46 projecting shaft 50 static elimination brush 60 first electrode 61 second electrode 62 detection circuit 63 contact 66 solenoid 67 spring

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H033 AA37 BA11 CA22 CA34 2H072 AA02 AA22 AB21 CA01 CB05 3F048 AA02 AA04 AA05 AB01 BA05 BA15 CC01 DB06 DB07 DC17 EA01 3F049 AA06 AA07 CA13 DA12 LA02 LA05 LA07 LB01

Claims (11)

[Claims] 1. A sheet wrap detecting device for detecting wrapping of a sheet around a transport body that rotates and transports a sheet,
A first electrode in contact with the paper transport surface of the transport body, and a second electrode in contact with a location different from the contact location of the first electrode of the transport body in electrical conduction with the paper transport surface; A detection circuit for detecting the presence or absence of a sheet from the resistance between the two electrodes. 2. The paper wrap detecting device according to claim 1, wherein the transporting member is a conductive fixing roller for fixing the toner image transferred to the paper. 3. The sheet winding detecting device according to claim 1, wherein the first electrode is a sliding member that slides on the sheet conveying surface or a rolling member that rolls on the sheet conveying surface. 4. The paper wrap detecting device according to claim 3, wherein the first electrode is held by a conductive elastic member. 5. A sheet according to claim 1, further comprising a separating means for separating and contacting the first electrode with respect to the sheet conveying surface, wherein the first electrode is intermittently separated. Winding detection device. 6. The sheet winding detecting device according to claim 1, wherein a plurality of the first electrodes are arranged along a width direction of the sheet conveying surface or a rotation direction of the conveying member. 7. The sheet winding detecting device according to claim 1, wherein the first electrode uses a peeling claw for peeling the sheet from the sheet conveying surface. 8. The method according to claim 1, wherein the conductive film formed on the surface of the peeling nail is used as a first electrode, and the first electrode is electrically connected to a detection circuit via a swing shaft of the peeling nail. The paper wrapping detection device according to claim 7. 9. The paper wrap detecting device according to claim 1, wherein the second electrode uses a neutralizing member provided for neutralizing the paper conveying surface. 10. The paper winding according to claim 1, wherein a shaft member of the conveying body is electrically connected to the sheet conveying surface, and the second electrode uses the shaft member. Detection device. 11. A first electrode and a second electrode are integrally held by a holding member at an interval, and the second electrode contacts another portion of the sheet conveying surface different from the contact portion of the first electrode. 3. The paper wrapping detecting device according to claim 1, wherein: