JP2006160484A - Double feed detection method, recording sheet carrying device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect double feed by low-cost and simple control. <P>SOLUTION: In a paper carrying device, loaded sheets on a plurality of paper feed trays 8, 9, and 10 are fed one by one to be carried. Thickness of paper stored in each of the plurality of the paper feed trays 8, 9, and 10 is compared with thickness of paper fed from one of the plurality of paper feed trays 8, 9, and 10 detected by a paper thickness detecting device 101. Based on result of comparison, if double feed of paper has occurred or not is determined. In case where double feed is detected, a message for informing of the fact is given to a liquid crystal operation panel. Images on preceding transfer paper is cleaned once, and the paper determined as double feed is discharged as white paper to a separate discharge destination. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a double feed detection method for detecting double feed of recording sheets, a recording sheet transport apparatus using the double feed detection method, and an image forming apparatus including the recording sheet transport apparatus.

  In an apparatus having a conveyance path for conveying a sheet cut to a predetermined size, for example, an image forming apparatus such as a copying machine or a printer, the sheet is conveyed from a sheet feeding tray one by one and an image is formed on the sheet. In this case, when double feeding is performed with two or more sheets overlapped, binding, editing, etc. are performed with blank paper mixed in the formed paper, image misalignment, etc. End up.

Therefore, for example, in the invention disclosed in Patent Document 1, in the double feed detection method in the apparatus that feeds and transports the sheets one by one from a plurality of stacked sheets, the thickness of the fed sheets Are sequentially detected and stored, and when a new sheet is sent out, an average value of the sheet thicknesses stored in the past is obtained, and the average value is compared with the thickness of the sheet to be sent out to determine the weight of the sheet. It is characterized by detecting the transmission. With this configuration, it is possible to detect double feed from the first sheet that is fed. Note that a transmissive light sensor or a sensor using a swing arm is used as a detecting means for detecting the sheet thickness.
JP-A-11-116101

  By the way, in the invention described in Patent Document 1, the thicknesses of sheets sent out to detect double feeding are sequentially detected and stored, and when a new sheet is sent out, the sheet thickness stored in the past is detected. The average value is obtained, and the average value is compared with the thickness of the sheet to be fed to detect the double feed of the paper. With this configuration, a storage unit is required for detecting the double feed. It is necessary to detect the sheet pressure every time one sheet is fed and compare the detected value stored in the memory. There are various types of paper such as plain paper, thick paper, thin paper, and the second original drawing. Each time the thickness of one sheet is read, it is necessary to compare with each of the various types of paper, which only increases the cost. In addition, the control was complicated.

  The present invention has been made in view of such a state of the art, and an object thereof is to enable detection of double feeding of recording sheets with low-cost and simple control.

  In order to achieve the above object, the first means sends out the recording sheet in an apparatus for feeding and conveying the recording sheets stacked on each of a plurality of paper feed trays one by one, and forms an image. A thickness of the recording sheet sent out at a previous position is detected, and the thickness of the detected recording sheet is compared with a sheet type setting of the paper feed tray information to detect double feeding of recording sheets. And

  When the second means detects double feeding in the first means, a message to that effect is sent to the operation unit, and after the first transfer paper image has been cleaned once, the fed recording sheet is discharged to another state. It is characterized by discharging the blank paper first.

  The third means is a recording sheet transporting apparatus that feeds and transports the recording sheets stacked on each of the plurality of sheet feeding trays one by one, and the recording sheets stored in each sheet feeding tray of the plurality of sheet feeding trays First detecting means for detecting the thickness of the recording sheet, second detecting means for detecting the thickness of the recording sheet fed from one of the plurality of paper feeding trays, and the first and second detecting means. Comparing means for comparing the thicknesses of the recording sheets respectively detected by the means, and determining means for determining whether or not the recording sheets are double-fed from the comparison result are provided.

  According to a fourth means, in the third means, the first detection means detects the recording sheet based on the thickness information set by the means for inputting information relating to the thickness of the stored recording sheet. It is characterized by detecting the thickness.

  The fifth means is characterized in that the image forming apparatus includes the recording sheet conveying apparatus according to the third or fourth means.

  A sixth means is a color image forming apparatus having a function of forming a color image by superimposing a single color image on the image forming apparatus according to the fifth means, and when the determination means determines that double feeding, To that end, it is characterized by comprising display means for displaying and means for discharging the recording sheet to be transferred to another paper discharge destination after once cleaning the front transfer paper image.

  According to the present invention, the thickness of the paper stored in the paper feed tray and the thickness of the paper fed from the paper feed tray are compared to determine whether or not the double feed is performed. This makes it possible to determine whether or not double feeding, and it is possible to detect double feeding with low cost and simple control.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. First Embodiment FIG. 1 is a diagram schematically showing the overall configuration of an image forming apparatus composed of a digital multi-function peripheral (MFP) according to a first embodiment of the present invention, and FIG. 2 is an operation in the image forming apparatus of FIG. It is a figure which shows schematic structure of a part.

  As shown in FIG. 1, the image forming apparatus according to the present embodiment is roughly divided into an automatic document feeder (hereinafter referred to as ADF) 1 that automatically feeds a document to a reading unit 50 positioned below, and this ADF 1. A reading unit 50 for reading image information of a document sent out from the writing unit, a writing unit 57 for writing image information from the reading unit 50 or from the outside to an image carrier, a drum-like photoconductor 15 as an image carrier, and a developing unit. 27, etc., a paper feed system that feeds transfer paper as a transfer material to the image image creation system, and a double-sided paper feed unit that feeds the transfer paper in an inverted manner to form images on both sides of the transfer paper 81 or the like.

  The ADF 1 includes a document table 2 on which documents are placed, a sheet feed roller 3 that pulls out documents one by one from the document table 2, a sheet feed belt 4 that conveys the drawn document to a predetermined position, a discharge roller 5, and a document set detection sensor. 7 etc. Then, a document bundle (not shown) placed on the document table 2 with the image surface of the document facing up is fed from the bottom document when the print key 34 on the operation unit 30 shown in FIG. 2 is pressed. The paper is fed to a predetermined position on the contact glass 6 of the reading unit 50 by the feeding roller 3 and the feeding belt 4, and the image data of the original is read by the reading unit 50. The document that has been read is discharged by the feeding belt 4 and the discharge roller 5. Further, when the document set detection sensor 7 detects that the next document is on the document table 2, it is fed onto the contact glass 6 in the same manner as the previous document. The paper feed roller 3, the paper feed belt 4, and the discharge roller 5 are driven by a transport motor 26 shown in FIG.

  The reading unit 50 includes a contact glass 6 on which an original is placed and an optical scanning system. The optical scanning system condenses light from the exposure lamp 51 that illuminates the original, the first, second, and third mirrors 52, 55, and 56, and the third mirror 56 that receive and reflect the reflected light from the original. A lens 53 for forming an image on the image forming surface of the CCD image sensor 54, a CCD image sensor 54 for picking up an image formed on the image forming surface by the lens 53, and the like. The exposure lamp 51 and the first mirror 52 are fixed on a first carriage (not shown), and the second mirror 55 and the third mirror 56 are also fixed on a second carriage (not shown). When reading a document image, the first carriage and the second carriage are mechanically scanned at a relative speed of 2: 1 so that the optical path length does not change.

  This optical scanning system is driven by a scanner drive motor (not shown). The document image is read by the CCD image sensor 54, converted into an electrical signal, and processed. The image magnification is changed by moving the lens 53 and the CCD image sensor 54 in the left-right direction in FIG. That is, the positions of the lens 53 and the CCD image sensor 54 are set in the left-right direction corresponding to the designated magnification.

  After the original is read by the reading unit 50, the original that has been read is discharged by the feeding belt 4 and the discharge roller 5. Further, when the document set detection sensor 7 detects that the next document is on the document table 2, it is fed onto the contact glass 6 in the same manner as the previous document.

  The paper feeding system includes first, second, and third trays 8, 9, and 10 on which transfer papers are stacked, respectively, and a first paper for feeding the transfer paper from these trays 8, 9, and 10 to the image forming system. 1, second and third paper feed units 11, 12, 13, a vertical transport unit 14, and the like. The transfer sheets loaded on the first tray 8, the second tray 9, and the third tray 10 are fed by the first sheet feeding unit 11, the second sheet feeding unit 12, and the third sheet feeding unit 13, respectively. It is conveyed to a position where it abuts on the photoreceptor 15 by the conveyance unit 14.

  The image data read by the reading unit 50 is written by the writing unit 57 on the photoconductor 15 of the image forming system. The writing unit 57 emits a laser beam modulated based on the image data, and converts the laser beam emitted from the laser output unit 58 and deflected at a constant angular velocity into a constant linear velocity deflection, thereby converting the photoconductor 15. An image forming lens 59 for forming an image on the top, a mirror 60 for passing the image forming lens 59 and returning the laser light to the photoconductor 15 side, and the like. Inside the laser output unit 58, a laser diode that is a laser light source and a rotating polygon mirror that is rotated at a constant high speed by a motor are provided. The laser light emitted from the laser output unit 58 is deflected by the polygon mirror rotating at a constant speed as described above, passes through the imaging lens 59, is folded back by the mirror 60, and is focused on the surface of the photoreceptor 15. To do.

  The deflected laser light is exposed and scanned in the direction (main scanning direction) perpendicular to the direction in which the photosensitive member 15 rotates, and the line-by-line recording of the image signal output from the selector 64 of the image processing unit described later is performed. An image (electrostatic latent image) is formed on the surface of the photoconductor 15 by repeating main scanning at a predetermined cycle corresponding to the rotational speed and recording density of the photoconductor 15.

  The image forming system includes a photosensitive member 15 that forms a latent image by laser light from a laser output unit 58, a developing unit 27 that develops the latent image on the photosensitive member 15, and a conveying belt 16 that conveys transfer paper from a paper feeding system. The image forming apparatus includes a fixing unit 17 that fixes an image transferred onto the transfer paper, a paper discharge unit 18 that discharges the fixed transfer paper, and the like. The photoreceptor 15 on which the latent image is formed by the laser light passes through the developing unit 27 to form a toner image. Then, the toner image on the photoconductor 15 is transferred while the transfer paper is conveyed by the conveyance belt 16 at the same speed as the rotation of the photoconductor 15. Thereafter, the image is fixed by the fixing unit 17 and discharged to the paper discharge tray 19 by the paper discharge unit 18.

  The double-sided paper feed unit 81 is used when images are formed on both sides of the transfer paper. The double-sided paper feed conveyance path 83 for carrying the transfer paper drawn from the middle of the paper discharge unit 18 and the transfer paper are conveyed. A reversing unit 82 for reversing the direction, a reversing paper discharge conveyance path 84 for sending the reversed transfer paper to the paper discharge unit 18 again, and the like. With this configuration, if a branching claw (not shown) provided in the paper discharge unit 18 for switching the conveyance path is set upward, the transfer is performed by transferring the image fed from each of the paper feed trays 8 to 10. The paper is once stored in the reversing unit 82 of the double-sided paper feeding unit 81 without guiding the paper to the paper discharge tray 19 side. After that, the transfer paper stocked in the duplex feeding unit 81 is transported again in the middle of the vertical transport unit 14 with the top and bottom reversed, and an image is formed on the back surface of the transfer paper by the photoconductor 15 and discharged. By setting the branching claw in the unit 18 downward, it is guided to the paper discharge tray 19.

  Note that the photoconductor 15, the transport belt 16, the fixing unit 17, the paper discharge unit 18, and the development unit 27 are driven by the main motor 25 in FIG. It is transmitted and driven by the paper feed clutches 22-24. The vertical conveyance unit 14 is driven by the driving force of the main motor 25 being transmitted by the intermediate clutch 21.

  As shown in FIG. 2, the operation unit 30 includes a liquid crystal touch panel 31, a numeric keypad 32, a clear / stop key 33, a print key 34, a mode clear key 35, an initial setting key 38, and the like. The liquid crystal touch panel 31 is provided with function keys 37 for setting various functions, and displays a message indicating the number of copies and the state of the image forming apparatus.

  An example of the display on the liquid crystal touch panel 31 of the operation unit 30 is shown in detail in FIG. In the liquid crystal touch panel 31, when the operator touches the displayed key, the key portion indicating the selected function is inverted in black. In addition, when it is necessary to specify the details of the function (for example, when the magnification is changed, the variable value is displayed), the detailed function setting screen is displayed by touching the key. Since the liquid crystal touch panel 31 uses a dot display, it is possible to graphically perform an optimal display at that time.

  The message area in the upper left displays whether copying is possible. The message “Ready to copy” displays a message “Please wait” until you can copy after turning on the power. . On the right side of this message area, a copy number display section for displaying the set number of copies is displayed. Under these message area and copy number display area, an automatic density key that automatically adjusts the image density, an automatic paper selection key that automatically selects the transfer paper, a magnification key that sets the enlargement / reduction ratio, Format document key for selecting whether the document is a standard document (format document), a manual density adjustment key for manually adjusting the image density, and a paper feed unit 11 to 11 for manually selecting the size of the transfer paper A paper display key for displaying the size and setting direction of the transfer paper set in 13, a sort key for designating a process for arranging copies in order of pages, a staple key for designating a process for binding the sorted papers in part, A duplex key for setting a duplex mode and an aggregation key for setting an aggregation mode for printing a plurality of document images on one transfer sheet are displayed. The sort key and the staple key are displayed when a post-processing device (not shown) having a built-in stapler or sorter is provided.

  FIG. 4 is a block diagram showing a schematic configuration of a control unit in the image forming apparatus of FIG. 1, and each unit is connected with a main controller as a center. The main controller 20 controls the entire image forming apparatus. The main controller 20 includes a main motor 25, an intermediate clutch 21 and first to third paper feeding clutches 22, 23, 24 necessary for transporting transfer paper. The operation unit 30, the image processing unit 49, and the ADF 1 are connected to each other. The operation unit 30 performs display for an operator and function setting input control from the operator, and an image processing unit (hereinafter also referred to as IPU) 49 executes control of each unit related to image output from image input. These units 30, 49, the motor 25, the first to fourth paper feed clutches 21 to 24, and the main controller 20 exchange machine status and operation commands as necessary. Each of these units functions as a distributed control device for the main controller 20.

  A connection I / F 48 is further connected to the main controller 20, and information on the image forming apparatus connected via the connection I / F 48 is acquired, and the operation is controlled by setting the operation. Alternatively, a request from another connected image forming apparatus is acquired and the operation of the own apparatus is controlled. A document set detection sensor 7 and a conveyance motor 26 for conveying the document are connected to the ADF 1, and a liquid crystal display 31 and various input keys 32 to 35 are connected to the operation unit 30.

  FIG. 5 is a block diagram showing details of the IPU 49 of FIG. In this embodiment, the IPU 49 includes an image data input / output system, an image processing system, and an output system. The input system optically reads an image such as a document image, a CCD image sensor 54, an A / D converter 61 that converts an image signal from the CCD image sensor 54 into a digital signal, and an image signal from the A / D converter 61. A shading correction circuit 62 that performs shading correction, an MTF correction / γ correction circuit 63 that further performs MTF correction, γ correction, and the like on the image signal, and enlarges / reduces the image signal from the MTF correction / γ correction circuit 63 in accordance with the magnification. The zoom processing circuit 72 includes a selector 64 that sets the image data from the zoom processing circuit 72 to be sent to the image memory controller 65 or the writing γ correction unit 71. On the output side, a writing γ correction unit 71 that performs γ correction on the writing side with respect to the image data selected by the selector 64, and a writing unit that writes (prints) an image based on the correction data from the writing γ correction unit 71 57.

  When such an input / output system is configured, the reflected light irradiated from the exposure lamp 51 and reflected by the document surface is photoelectrically converted by the CCD image sensor 54 and converted into a digital signal by the A / D converter 61. The image signal converted into the digital signal is subjected to shading correction by the shading correction circuit 62, and then subjected to MTF correction and γ correction in the MTF correction / γ correction circuit 63, and the magnification processing circuit 72 converts the image signal into an image signal. After enlarging or reducing in accordance with the magnification, the selector 64 selects the destination of the image signal to the writing γ correction unit 71 or the image memory controller 65, and if the writing γ correction unit 71 side is selected, the magnification is changed. The processed image signal is input to the writing γ correction unit 71 as it is, and after the γ correction is performed, the writing unit 57 performs writing on the photoconductor 15.

  The image processing system includes an image memory controller 65, an image memory 66, a CPU 68, a ROM 69, a RAM 70, and an I / O port 67. Between the image memory controller 65 and the selector 64, an image signal can be input and output bidirectionally. The CPU 68 controls the setting to the image memory controller 65 and the control of the reading unit 50 and the writing unit 57, the ROM 69 stores a program processed by the CPU 68, the RAM 70 stores data processed by the CPU 68, and a work area of the CPU 68 Also works. The I / O port 67 is connected to the operation unit 30 and transmits / receives image data.

  FIG. 6 is a timing chart for explaining an image signal for one page in the selector 64. In FIG. 6, / FGATE, which is a frame gate signal, represents a valid period in the sub-scanning direction of one page of image data. / LSYNC is a main scanning synchronization signal for each line, and the image signal becomes valid at a predetermined clock after this signal rises. A signal indicating that the image signal in the main scanning direction is valid is a line gate signal / LGATE. These signals are synchronized with a pixel clock VCLK which is a vertical synchronizing signal, and data of 8 bits per pixel (256 gradations) is transmitted for one cycle of VCLK. In this embodiment, it is assumed that the closer the image data is to 255, the more white the image is.

  FIG. 7 is a flowchart showing the main operation of the image forming apparatus described above. When the power is turned on, an initialization process is first performed (step S701). The main contents of initialization are resetting various flags, clearing various counters, clearing the image memory, resetting the image formation mode (magnification, division, etc.), etc. (the processing contents of the initialization subroutine are omitted). . After completion of initialization, the process waits for an event (any change factor) from the key input or the image forming engine (step S702). When the user performs any key operation, the operation unit 30 notifies the user of a key input event. Similarly, when an image forming engine changes, for example, when a document is set on the ADF 1, a signal change of the document setting detection sensor 7 is notified as an engine event. When one of the key and engine events occurs, it is determined whether the generated event is a key input or an engine (step S703). In the case of an engine, engine event processing is called (step S704). In the case of key input, key input event processing is called (step S705). After these processings are performed, the process waits for an event in step S702 again. .

  FIG. 8 is a flowchart showing the processing content of the key input event processing subroutine of step S705 of FIG. In the key input event process, first, a key press event of the print start key 34 is checked (step S801). If it is the print start key 34, copy processing is executed (step S808). If the print start key 34 has not been pressed, it is checked whether or not the numeric key 32 has been entered (step S802). If the key event is the numeric keypad 34, numeric keypad processing is performed (step S809). If the key event is not the numeric keypad 34, it is checked whether or not the clear stop key 33 is pressed (step S803). If the event is the clear stop key 33, the clear stop process is executed (step S810). If it is not an event of the clear stop key 33, it is checked whether or not it is a press event of a print setting key displayed in the liquid crystal touch panel 31 (step S804). When a setting key for various printing functions represented by an automatic density key or a manual density adjustment key in FIG. 3 is pressed, a print setting process is executed (step S811).

  If the print setting key has not been pressed, a determination is made of a duplex setting key event displayed on the liquid crystal touch panel 31 (step S805). When the duplex function shown in FIG. 3 is selected or released from the selected state, duplex setting processing is executed (step S812). If the duplex function is not selected, it is determined whether or not the format document setting key event is displayed on the liquid crystal touch panel 31 (step S806). When the format document function shown in FIG. 3 is selected or released from the selected state, the format document setting process is executed (step S813). If it is not the format original function, it is determined whether there has been a key event other than steps S801 to S806 (step 807). If it is another key event, other key processing is executed (step S814). If each key event process is executed, the process is terminated (step S518).

  FIG. 9 is a diagram illustrating a configuration of the paper thickness detection device 101 provided at a position immediately upstream of the registration rollers 14a of the vertical conveyance unit 14 in FIG. The paper thickness detection device 101 includes a D / A control unit constant current circuit 102, an LED 103, and a phototransistor 104. The transfer paper fed from each of the paper feed trays 8, 9, 10 is adjusted in thickness by the paper thickness detection device 101 at a position where the leading edge of the transfer paper bites the registration roller 14 a from the feed roller through the transport roller of the vertical transport unit. The detected paper thickness information is compared with the paper thickness information obtained by setting the paper type of the tray fed from the paper feed tray. The paper type setting for each tray can be switched according to the user's set paper as shown in FIG. When the double feed is detected, the transfer paper is kept waiting at the registration roller 14a, the image data that is scheduled to be transferred to the transfer paper is cleaned as it is, and the paper is conveyed without the image data on the intermediate belt. The paper is transported to a different location from the set paper output destination. However, if only one paper discharge destination can be selected, it cannot be switched, so that a warning is displayed on the operation unit 30 (liquid crystal touch panel 31), and the continuous job is stopped.

  Double feed detection is performed by switching the resistance value on the phototransistor 104 side. That is, when the paper type of the transfer paper is displayed on the liquid crystal touch panel 31 of the operation unit 30 as shown in FIG. 10 and the paper feed tray storing the transfer paper of the paper type is designated, the output resistance value of the phototransistor 104 is displayed. Is set to a resistance corresponding to the thickness of the designated transfer paper. Here, resistance values of three types of resistances, a normal resistance, a resistance for plain paper, and a resistance for the second original drawing, are set, respectively, and stored in a paper feed stage selected from the liquid crystal touch panel 31 at the time of image formation. The CPU 68 determines whether or not to double-feed based on the output of the phototransistor 104 based on the switched output resistance.

  With this configuration, the first detection means in the present embodiment is the CPU 68 that detects the relationship between the paper feed stage and the paper type input from the liquid crystal touch panel 31, and the second detection means is the paper thickness detection apparatus 101. In addition, when the comparison means and the determination means determine that the CPU 68 is a means for inputting information related to the thickness of the stored paper and the double feed, the display means for displaying the fact is displayed on the liquid crystal touch panel 31. The CPU 68 corresponds to each of the CPUs 68 for once cleaning the transfer paper image and discharging the paper to be transferred to a different paper discharge destination.

  As described above, according to the present embodiment, it is possible to detect double feeding by detecting the paper thickness with the paper thickness detection device (optical system sensor) 10 before image formation on the transfer paper. In addition, when double feeding is detected, the paper is not sent to the image transfer position, so that unnecessary image formation is eliminated and the occurrence of paper jam can be prevented.

2. Second Embodiment FIG. 11 is a diagram showing a second embodiment of the present invention. The second embodiment is an example in which the present invention is applied to a tandem-type indirect color copying machine.

  In FIG. 11, reference numeral 100 is a copying machine main body, 200 is a paper feed table on which it is placed, 300 is a scanner mounted on the copying apparatus main body 100, and 400 is an automatic document feeder (ADF) mounted thereon.

  The copying machine main body 100 is provided with an endless belt-shaped intermediate transfer member 110 at the center. The intermediate transfer member 110 includes, for example, a base layer made of a material that hardly stretches, such as a fluorine resin with a small stretch or a rubber material with a large stretch, such as a canvas, an elastic layer provided on the base layer, It is composed of a smooth coat layer coated on the surface. The elastic layer is made of, for example, fluorine rubber or acrylonitrile-butadiene copolymer rubber, and the coat layer is made of, for example, fluorine resin.

  As shown in FIG. 11, the intermediate transfer member 110 configured as described above is wound around the first, second, and third support rollers 114, 115, and 116, and rotates clockwise in FIG. To do. In this embodiment, an intermediate transfer body cleaning device 117 for removing residual toner remaining on the intermediate transfer body 110 after image transfer is provided to the left of the second support roller 115 among the three support rollers. Yes.

  In addition, on the intermediate transfer member 110 stretched between the first support roller 114 and the second support roller 115, yellow (Y), cyan (C), magenta (M), The tandem image forming unit 120 is configured by horizontally arranging four image forming units 118Y, 118C, 118M, and 118K for forming a black (K) monochrome image. An exposure device 121 is further provided on the tandem image forming unit 120 as shown in FIG. The alphabet after the reference number represents the color and is distinguished by adding Y for yellow, C for cyan, M for magenta, and K for black.

  On the other hand, a secondary transfer device 122 is provided on the opposite side of the intermediate transfer body 110 from the tandem image forming unit 120. In the illustrated example, the secondary transfer device 122 is configured by spanning a secondary transfer belt 124 that is an endless belt between two rollers 123, and a third support roller 116 via an intermediate transfer body 110. The image on the intermediate transfer body 110 is transferred to a transfer sheet.

  Next to the secondary transfer device 122, a fixing device 125 for fixing the transfer image on the transfer paper is provided. The fixing device 125 is configured to press the pressure roller 127 against the fixing belt 126 which is an endless belt. The secondary transfer device 122 described above is also provided with a transfer paper transport function for transporting the transfer paper after image transfer to the fixing device 125. Of course, a transfer roller or a non-contact charger may be disposed as the secondary transfer device 122. In such a case, it is difficult to provide this transfer paper conveyance function together.

  Under the secondary transfer device 122 and the fixing device 125, a transfer paper reversing device 128 for reversing the transfer paper to record images on both sides of the transfer paper is provided in parallel with the tandem image forming unit 120. .

  Now, when making a copy using this color copying machine, set the document on the document table 430 of the automatic document feeder 400 or open the automatic document feeder 400 and place the document on the contact glass 332 of the scanner 300. Then, the automatic document feeder 400 is closed and pressed by it. When a start switch (not shown) is pressed, when a document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 332 and then set on the contact glass 332. Immediately drives the scanner 300 and travels through the first traveling body 333 and the second traveling body 334. Then, the first traveling body 333 emits light from the light source, and the reflected light from the document surface is further reflected toward the second traveling body 334, reflected by the mirror of the second traveling body 334, and passed through the imaging lens 335. The document is placed in the reading sensor 336 and the original content is read.

  When the start switch is pressed, the drive motor rotates the first support roller 114, which is a drive roller, and the second and third support rollers 115, 116, which are the remaining two driven rollers, are driven to rotate. Then, the intermediate transfer member 110 is rotated and conveyed. At the same time, the individual image forming units 118 rotate the photoconductors 140 to form black, yellow, magenta, and cyan single color images on the photoconductors 140, respectively. Then, along with the conveyance of the intermediate transfer body 110, these single color images are sequentially transferred to form a composite color image on the intermediate transfer body 110.

  On the other hand, when the start switch is pressed, one of the paper feed rollers 242 of the paper feed table 200 is selectively rotated, the transfer paper is fed out from one of the paper cassettes 244 provided in multiple stages in the paper bank 243, and the separation roller 245. Are separated one by one into the paper feed path 246, transported by the transport roller 247, guided to the paper feed path 148 in the copying machine main body 100, and abutted against the registration roller 149 to stop. In addition to this, the paper feeding roller 150 is rotated to feed the transfer paper on the manual feed tray 151, separated one by one by the separation roller 152, put into the manual paper feed path 153, and abutted against the registration roller 149. You may make it stop.

  Then, the registration roller 149 is rotated in synchronization with the composite color image on the intermediate transfer body 110, the transfer paper is fed between the intermediate transfer body 110 and the secondary transfer device 122, and transferred by the secondary transfer device 122. To record a color image on the transfer paper.

  The transfer paper after the image transfer is sent to the fixing device 125 by the secondary transfer device 122, and the transfer image is fixed by applying heat and pressure by the fixing device 125, and then switched by the switching claw 155 and discharged by the discharge roller 156. And stacked on the paper discharge tray 57. At this time, it is switched by the switching claw 155 and put into the transfer paper reversing device 128, where it is reversed and led again to the transfer position, an image is recorded also on the back surface, and then discharged onto the paper discharge tray 157 by the discharge roller 156. You can also

  On the other hand, the intermediate transfer body 110 after the image transfer is removed by the intermediate transfer body cleaning device 117 to remove residual toner remaining on the intermediate transfer body 110 after the image transfer, so that the tandem image forming unit 120 can prepare for another image formation. In general, the registration roller 149 is often used while being grounded, but it is also possible to apply a bias for removing paper dust from the transfer paper.

  In the tandem image forming unit 120 described above, each image forming unit 118 includes a charging device 160, a developing device 161, a primary transfer device 162, a photoconductor cleaning device 163, a static elimination device around the drum-shaped photoconductor 140. Equipment.

  Also in this embodiment, the paper thickness detector 101 having the circuit configuration as shown in FIG. 10 is attached, the light emitted from the LED 103 is received by the phototransistor 104, and the paper thickness is determined by the light transmittance of the paper passing between the two. To detect.

  FIG. 12 is a diagram showing a layout of main conveyance parts in which the configurations of the secondary transfer unit 122, the fixing device 125, and the paper feed stage in FIG. 11 are slightly modified. In the example of FIG. 12, a conveyance belt 124 is separately provided at the subsequent stage of the secondary transfer device 122, and the fixing device 125 is replaced with a belt-type fixing device, and the paper feeding stages are four stages. . In both the example of FIG. 11 and the example of FIG. 12, as shown in the enlarged view of the paper thickness detection portion in FIG. 13, the transfer paper fed from each paper feed tray passes through the relay roller to the registration sensor 147 and the leading edge of the transfer paper. The image data on the intermediate transfer belt 110 is aligned with the pre-conveyance transfer paper at the place where the image is bitten. At this time, the paper thickness detection device 101 shown in FIG. 9 detects the paper thickness and compares it with the paper thickness information based on the paper type setting of the previously fed tray. The paper type setting for each tray can be switched according to the user's set paper as shown in FIG. When the double feed is detected, the transfer paper is kept waiting at the registration roller 149, the image data that is scheduled to be transferred to the transfer paper is cleaned as it is, and the paper is conveyed without the image data on the intermediate belt. Transports to a location different from the set paper discharge destination. However, if only one paper discharge destination can be selected, it cannot be switched, so that a warning is displayed on the operation unit 30 (liquid crystal touch panel 31) and continued. The job is to be stopped.

  Other parts that are not particularly described are configured in the same manner as the first embodiment and function in the same manner.

  As described above, according to the present embodiment, double feed can be detected by detecting the paper thickness with the optical system sensor before image formation on the transfer paper.

  In addition, after detecting double feed, the image formed on the belt is cleaned and discharged to another discharge destination, so that image misalignment or white paper can be avoided during bookbinding and other processing, and abnormal images such as image misalignment can be avoided. Since no output is created, the confidentiality of the data can be maintained.

1 is a diagram schematically illustrating a configuration of an entire image forming apparatus including a digital multifunction peripheral (MFP) according to a first embodiment of the present invention. It is a figure which shows the operation part of the digital multi-functional peripheral of FIG. It is a figure which shows the display state of the message area of the operation part of FIG. FIG. 2 is a block diagram illustrating a schematic configuration of a control unit in the image forming apparatus of FIG. 1. It is a block diagram which shows the detail of IPU of FIG. 6 is a timing chart for explaining an image signal for one page in the selector of FIG. 5. 3 is a flowchart illustrating a main operation of the image forming apparatus according to the first embodiment. It is a flowchart which shows the processing content of the subroutine of the key input event process of step S705 of FIG. FIG. 2 is a diagram illustrating a configuration of a paper thickness detection device provided at a position immediately upstream of a registration roller of the vertical conveyance unit in FIG. 1 on the upstream side in the paper conveyance direction. It is a figure which shows an example of the display state of the liquid crystal operation panel of paper type selection. It is a figure which shows schematic structure of the color copying machine of a tandem type indirect system which concerns on 2nd Embodiment. It is a figure which shows the layout of the conveyance main components of FIG. It is an enlarged view which adds the position of a paper thickness detection apparatus to FIG.

Explanation of symbols

8, 9, 10, 244 Paper feed tray 11, 12, 13 Paper feed unit 14 Vertical transport unit 14a, 149 Registration roller 68 CPU
101 Paper Thickness Detection Device 102 D / A Control Unit Constant Current Circuit 103 LED
104 Phototransistor 242 Feed roller 245 Separation roller 246 Feed path 247 Transport roller

Claims (6)

In a multifeed detection method in an apparatus for sending and conveying recording sheets stacked on each of a plurality of paper feed trays one by one,
Sending out the recording sheet,
Detecting the thickness of the fed recording sheet at a position before image formation,
A double feed detection method comprising: detecting the double feed of recording sheets by comparing the thickness of the detected recording sheet with a sheet type setting of the paper feed tray information.   When a double feed is detected, a message to that effect is output, and a first transfer paper image is once cleaned, and then the fed recording sheet is discharged to another discharge destination. The multifeed detection method according to 1. In a recording sheet conveying apparatus that sends out and conveys recording sheets stacked on each of a plurality of paper feed trays one by one,
First detection means for detecting a thickness of a recording sheet stored in each of the plurality of paper supply trays;
Second detection means for detecting the thickness of a recording sheet fed from one of the plurality of paper feed trays;
Comparison means for comparing the thicknesses of the recording sheets respectively detected by the first and second detection means;
Determination means for determining whether or not the recording sheet is double-fed from the result of comparison;
A recording sheet conveying apparatus comprising:   The first detection means detects the thickness of the recording sheet based on thickness information set by means for inputting information related to the thickness of the stored recording sheet. 4. A recording sheet conveying apparatus according to item 3.   An image forming apparatus comprising the recording sheet conveying apparatus according to claim 3. The image forming apparatus is a color image forming apparatus having a function of forming a color image by superimposing a single color image,
When it is determined by the determination means that double feeding, a display means for displaying that effect,
Means for discharging the recording sheet to be transferred to a separate paper discharge destination after once cleaning the front transfer paper image;
The image forming apparatus according to claim 5, further comprising:

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