JP2011079636A - Paper feeding device and image forming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeding device in a simple configuration, which stably feeds paper by eliminating an adverse effect caused by the stop of the rear end of paper in an air action area of an air separating means. <P>SOLUTION: The paper feeding device includes: a paper suction conveying means sucking and conveying the papers stored in a paper storage means; an air separating means blowing air to the front end of the paper sucked and conveyed by the paper suction conveying means from below a downstream side; a paper conveying passage provided with a plurality of conveying means conveying the paper sent out by the paper suction conveying means; and a control means performing the control for moving the paper downstream while repeating the conveyance and the stop. When the control means determines that the rear end of the paper stops in the air action area from a downstream end position of the air blown by the air separating means to the front end of a paper suction area of the paper suction conveying means in the temporary stop of the paper by the control means, the control means stops the paper after conveying the paper until the rear end of the paper passes through the air action area. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention particularly relates to a paper feeding device used in a copying machine, a printer, or the like that produces an image using electrophotography, and an image forming system including the paper feeding device.

  An image forming apparatus using electrophotography transfers a toner image formed on an image carrier by performing charging, exposure, and development processing directly or once to an intermediate transfer member and then transferred to a sheet (transfer material). Then, a fixing process is performed to fix on the paper.

  The image forming apparatus includes a sheet storage unit that can store sheet-like sheets in a stacked state, and a sheet supply unit that separates and conveys the sheets stored in the sheet storage unit one by one. Is provided.

  As a first form of the paper feeding device, there is known a paper feeding device in which a transport roller and a separating roller in pressure contact with the transport roller are provided in front of the paper fed by the paper feed roller.

  Further, as a second form of the paper feeding device, there is provided paper feeding having a paper adsorbing / conveying means in a form in which the paper stored in the paper storing means is sucked onto the movable belt by using a reduced pressure air flow and sent to a predetermined position. There is a device.

  The paper feeding device according to the present invention belongs to the above-described second form having the paper suction conveying means.

  A sheet feeding device having the following configuration has been proposed as an embodiment of a sheet feeding device configured to use a sheet suction conveyance unit. That is, an endless sheet feeding belt is disposed above the sheet feeding tray. The paper feed belt is provided so as to travel across the suction air flow path. A transport roller for holding and transporting paper fed from the paper feed unit is disposed immediately after the paper feed unit having the paper feed belt. Then, the distance (x1) between the sheet holding line by the conveying roller and the suction end line of the sheet feeding belt is made smaller than the minimum sheet feeding size. In addition, a paper end detector is provided immediately after the downstream side of the transport roller, and the distance (x2) between the detection point of the paper end detector and the suction rear end line is made smaller than the minimum paper feed size.

  In addition, the above configuration prevents the carry-in of the paper that occurs when the distance between the paper holding line by the transport roller and the suction end line of the belt is larger than the minimum paper size in each size paper to be used. As a result, the accompanying paper jamming can be avoided (see, for example, Patent Document 1).

JP-A-5-116783

  The paper feeding device disclosed in Patent Document 1 is considered to be useful to enable prevention of double feeding of paper without requiring a special separating means. However, it is a paper feeding device on the assumption that the distance (x1) is smaller than the minimum paper feeding size, and the degree of freedom in design is limited. Not mentioned.

  The paper feeding device according to the present invention has the same paper suction and conveyance means as the paper feeding belt of Patent Document 1, but there is a possibility that a plurality of papers may be sucked by the paper suction and transportation means during paper feeding. Intentionally, it is assumed that an air separation unit is provided in the vicinity of the downstream position of the sheet storage unit.

  Further, it is assumed that the sheet conveyance control in the sheet conveyance path is performed by the stay control method described later.

  It is a technical problem of the present invention to solve a peculiar problem (described later) that may occur in the sheet feeding device having the two configurations described above.

  By the way, in a normal image forming apparatus, it is general to design the sheet conveying speed on the sheet conveying path from the sheet feeding unit to the registration roller to be faster than the image forming process speed. This is because the timing of the toner image area and the paper can be finally adjusted even if, for example, a paper transport is delayed with respect to the toner image formed on the intermediate transfer member due to the slip of the transport roller or the like. Is intended.

  For this purpose, there is a control method called stay control as one form of paper transport control. For example, a plurality of sheets are sequentially fed onto a sheet conveyance path from the paper feeding unit to the transfer unit, and the conveyance at the conveyance speed as described above and the conveyance pause are repeatedly provided immediately before the transfer unit. This is a method of guiding to a registration roller.

  Specifically, when a sheet (referred to as sheet 1) located downstream on the sheet conveyance path is conveyed and its trailing edge passes through the position of a predetermined sheet detection sensor, the leading edge of the sheet (referred to as sheet 2) located upstream is moved. The paper is conveyed until it is detected by the paper detection sensor. Therefore, when the next predetermined paper detection sensor detects the stay (presence) of the paper 1, the conveyance of the paper 2 is stopped, and otherwise, the paper is detected by the next predetermined paper detection sensor. It is control that it conveys until the front-end | tip of 2 is detected. By such control, the sheets are conveyed so as not to collide with each other, and are stopped.

  In order to facilitate understanding, description will be made with reference to FIG. FIG. 5 is an explanatory diagram showing a schematic configuration on a sheet conveyance path in an image forming system mainly including an image forming apparatus main body and an optional sheet feeding apparatus.

  In the figure, there are a plurality of transport rollers consisting of a pair of transport rollers on a paper transport path from a paper feed section having a paper storage means to a transfer section for transferring an image onto the paper, and a paper for detecting the paper between the respective transport rollers. A detection sensor is provided. For example, when the leading edge of the sheet sent out on the sheet conveyance path is detected by a sheet detection sensor at a predetermined location, the conveyance roller involved in the conveyance is temporarily stopped. In the above aspect, which of the transport rollers is temporarily stopped is controlled based on the paper feed direction size information, the distance information from the front end position of the paper stacking unit of the paper storage means to the installation position of each paper detection sensor, and the like. It is judged for the means.

  For example, the paper 3 that was in the position where the paper 4 is shown on the paper transport path is transported downstream, and after the leading end is detected by a predetermined fourth paper detection sensor, the transport is stopped. It is assumed that there is a space for feeding one sheet at a downstream position in the vicinity of the sheet storage means. Then, the paper 4 in the paper storage means is sucked and transported (paper fed) by the paper suction transport means. Then, the leading edge of the paper is detected by the second paper detection sensor, which is a predetermined paper detection sensor, from the paper size information obtained in advance in the paper conveyance direction. At this time, if the fourth paper detection sensor, which is the next paper detection sensor (predetermined paper detection sensor), detects the stay of the paper 3 (synonymous with the standby state), the first and second transport rollers are inoperative. The paper 4 is temporarily stopped. That is, the sheet 4 is kept in a standby state until the sheet 3 is transported from the current position to make a space. Next, when the sheet 4 can be transported after the sheet 3 is transported from the illustrated position, the sheet 4 is transported until the leading edge is detected by the fourth sheet detection sensor, and the third and fourth transport rollers are inactivated. Thus, the paper 4 is temporarily stopped again. According to this paper transporting operation, there is a space in the vicinity of the paper storage means that enables paper to be fed, so that the next paper 5 is fed by the paper suction transporting means. When the leading edge of the paper transported via the first and second transport rollers is detected by the second paper detection sensor and there is no space downstream from the second paper detection sensor, both transport rollers are inoperative. Thus, the paper 5 is temporarily stopped.

  Through such control (retention control) in which the conveyance state and the pause state are alternately repeated, the sheet is guided to a registration roller disposed close to the transfer unit, and the leading end is sandwiched between the registration rollers. It is made to wait in the state. Thereafter, the sheet is sent out at the timing of overlapping with the image area on the image carrier by the rotation of the registration roller.

  In the above-described aspect, for example, when the paper (paper 3 or paper 4) sent out from the paper storage means is in the initial pause state, the rear end thereof is the opening of the duct (air blowout port) constituting the air separation means Meaning) may stop on top. In other words, it may stop within the action area (synonymous with the blowing area) of the air (air flow) blown out from the opening (see FIG. 4). FIG. 4 is an explanatory diagram schematically showing the air action region.

  As described above, the state in which the trailing edge of the sheet stops in the air acting area is, for example, a sheet having a non-standard size whose feed direction size is slightly longer (for example, about 5 mm) than the standard size. In some cases, there is a high risk of control difficulties.

  In addition, when the dwell control method is used in which the timer is activated based on the paper feeding operation from the paper storage means without using the paper detection sensor, and the predetermined transport roller is driven for the time corresponding to the length in the paper feed direction. There is a possibility that a similar situation occurs. In addition, slipping between the transport roller and the paper, a decrease in the transport roller diameter over time, or a combination of these conditions is likely to cause the same phenomenon.

As described above, when the trailing edge of the sheet is stopped in the air action area functioning as the air separating unit, the next sheet is squeezed when the next sheet is attracted and conveyed on the sheet adsorption conveying unit. The edges are violent (fluttering), generating turbulent flow and hindering paper feeding. For example, there is a problem that the paper that should be normally sucked buckles and causes jamming (paper jam), or the paper that is attracted by the violent paper causes double feeding of the paper. . In particular, the frequency of occurrence was high in thin paper of about 80 g / m ² .

  The present invention has been made in view of the peculiar problems in the sheet feeding device having the above-described configuration, and the main object is that the trailing edge of the sheet is stopped in the air working area of the air separating means with a simple configuration. It is an object of the present invention to provide a paper feeding device that can eliminate adverse effects and can stably feed paper.

  The object of the present application can be achieved by the following constitutional requirements.

1. Paper storage means for stacking and storing paper;
A sheet adsorbing / conveying means that is provided above the sheet accommodating means and adsorbs and conveys the sheet stored in the sheet accommodating means;
An air separating means for blowing air from the downstream side lower side to the leading end portion of the paper that is adsorbed and conveyed by the paper adsorbing and conveying means;
A paper transport path comprising a plurality of transport means for transporting the paper sent out by the paper suction transport means downstream;
Control means for performing control to advance the paper downstream while repeating conveyance and stop in the paper conveyance path,
When the paper is temporarily stopped by the control means, the control means has a trailing edge of the paper in an air action area from a downstream end position of air blowing by the air separating means to a front edge of the paper suction area of the paper suction conveyance means. When it is determined that the paper is stopped, the paper is transported to the downstream side through the predetermined transport means until the trailing edge of the paper passes through the air action area, and then stopped.
A paper feeder characterized by that.

2. Paper storage means for stacking and storing paper;
A sheet adsorbing / conveying means that is provided above the sheet accommodating means and adsorbs and conveys the sheet stored in the sheet accommodating means;
An air separating means for blowing air from the downstream side lower side to the leading end portion of the paper that is adsorbed and conveyed by the paper adsorbing and conveying means;
A paper transport path comprising a plurality of transport means for transporting the paper sent out by the paper suction transport means downstream;
Control means for performing control to advance the paper downstream while repeating conveyance and stop in the paper conveyance path,
When the control unit is temporarily stopped, the control unit controls the rear side of the sheet in an air action area from the leading end position of the sheet stacked in the sheet storage unit to the front end of the sheet adsorption area in the sheet adsorption transport unit. When it is determined that the end is stopped, control is performed to stop the paper after the paper is transported downstream until the trailing edge of the paper passes through the air action region via the predetermined transport means.
A paper feeder characterized by that.

3. The plurality of transport means provided in the paper transport path are transport rollers, and the paper transport path is provided with a plurality of paper detection sensors.
The control means calculates a rear end position of the paper from distance information from the paper stacking portion front end position of the paper detection sensor and paper length information inputted in advance.
Among the sheet detection sensors, when a predetermined sheet detection sensor detects the leading edge of the second sheet fed by the sheet suction and conveyance means, the sheet detection sensor downstream thereof detects the second sheet detection sensor. When it is determined that the trailing edge of the second sheet is not in the air operating area when the first sheet is detected immediately before the sheet is fed, a predetermined transport roller is The second sheet is immediately stopped, and when it is determined that the trailing edge of the second sheet is in the air acting area, the trailing edge of the second sheet passes through the air acting area. Control to stop the transport after transporting until
3. The sheet feeding device according to 1 or 2 above, wherein

  4). 4. An image forming system comprising: the sheet feeding device according to any one of 1 to 3; and an image forming unit that forms a toner image on an image carrier.

  5. 5. The image forming system as described in 4 above, wherein the paper feeding device is used externally to the image forming device.

  According to the paper feeding device according to the present invention, the trailing edge of the paper can be positioned outside the air acting area where the air of the air separating means acts by a simple configuration (control), and as a result, the succeeding paper is stabilized. Enable paper feeding.

  Further, according to the image forming system of the present invention, it is possible to stably feed paper and maintain high productivity of image formation by efficient paper feeding.

1 is a schematic diagram illustrating a configuration of an image forming apparatus main body including a digital color copying machine. FIG. 3 is a schematic diagram for explaining a configuration in a sheet feeding device 9. It is an explanatory view showing the air action area divided into two. It is explanatory drawing which shows an air action area | region typically. FIG. 2 is an explanatory diagram illustrating a schematic configuration on a sheet conveyance path in an image forming system including an image forming apparatus main body and an optional sheet feeding device as main elements.

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

  FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus main body including a digital color copying machine.

  The image forming apparatus main body H shown in the figure has an automatic document feeder 1 at the top, and an image reading unit 2, an image forming unit 3, a belt setting unit for the belt unit 4, a paper feeding unit 5, and a fixing device. T, reverse paper discharge / refeed unit 6, and ADU 7 which is reverse transport means.

  The automatic document feeder 1 includes a document placing table 101, a document separating unit 103, a document conveying unit 105, a document discharging unit 107, a document discharging table 109, and a pair of rollers for reversing the front and back surfaces of the document. Inversion means 111 is provided.

  A plurality of documents (not shown) placed on the document placing table 101 are separated one by one by the document separating unit 103 and conveyed toward the image reading position via the document conveying unit 105.

  The document reading position is provided at a lower portion of the document conveying unit 105, where an image of the document is read through the slit 201 constituting the image reading unit 2, and the read document is read by the document discharge unit 107. The document is discharged onto the document discharge table 109.

  In the double-sided copy mode, an original document that has been read and transported on one side is conveyed by the document reversing unit 111 in the direction indicated by a two-dot chain line arrow.

  Then, after the document reversing means 111 rotates in the reverse direction after being stopped while biting the trailing edge of the document in the advancing direction, it is again guided to the image reading position via the document conveying unit 105, and then the document The paper is discharged onto the document discharge table 109 by the paper discharge means 107.

  The image reading unit 2 includes a slit 201, a first mirror unit 205 in which a document irradiation lamp 213 and a first mirror 215 are integrated, and a second mirror unit 207 in which a second mirror 217 and a third mirror 219 are integrated. Have

  Further, an imaging lens 209 that forms an image of reflected light from the third mirror 219 on the imaging device, and a linear imaging device that obtains image information by photoelectrically converting a light image formed by the imaging lens 209 (Hereinafter referred to as CCD) 211.

  The image information is subjected to appropriate image processing and then temporarily stored in a memory in the control means S described later.

  In the aspect in which the document fed by the automatic document feeder 1 is read by the image reading unit 2, the first mirror unit 205 and the second mirror unit 207 are fixed at positions as shown in the figure.

  The image information for each color read by the image reading unit 2 is sequentially extracted from the memory, and is input as an electrical signal to the exposure optical system for each color, which is a latent image forming unit.

  The image forming unit 3 forms four sets of image forming means 30 (30Y, 30M, 30C, yellow (Y), magenta (M), cyan (C), and black (BK) that form a toner image corresponding to the color separation image. 30BK: hereinafter referred to as an image forming unit).

  Each image forming unit 30 includes a photosensitive drum 310, a charger 320, an exposure optical system 330 as an image writing unit, a developing device 340, a transfer unit 350, a cleaning unit 360, and the like.

  In the drawing, only the members constituting the yellow image forming unit are provided with reference numerals, and the reference numerals are omitted for the other image forming units.

  The developing device 340 includes a developer carrying member (hereinafter referred to as a developing sleeve or a sleeve) having a rotatable and nonmagnetic cylindrical shape, a magnetic carrier (hereinafter simply referred to as a carrier), and a nonmagnetic toner (hereinafter referred to as a carrier). Hereinafter, the developer containing the toner is stored.

  The transfer unit 350 is composed of a roller facing a part of the peripheral surface of the photosensitive drum 310 via an intermediate transfer belt 401 described later, but may be a discharge wire electrode. The cleaning unit 360 removes the toner remaining on the photosensitive drum 310 after the transfer, and the removed toner is stored in the waste toner box DT.

  Each of the image forming units 30 is yellow from above along the traveling direction of one flat surface (stretching surface) A of the loop-shaped intermediate transfer belt 401 constituting the belt unit 4 that is long in the vertical direction. (Y), magenta (M), cyan (C), and black (BK) are arranged in this order.

  The intermediate transfer belt 401, support rollers 405, 406, 407, a backup roller 410, and the like that rotatably suspend the intermediate transfer belt constitute the belt unit 4.

  Image formation by the configuration of the image forming unit 30 and the belt unit 4 is performed as follows.

  As the image forming process starts, the surface of the photosensitive drum 310 that rotates counterclockwise is charged to a predetermined polarity by the charger 320. Next, the exposure optical system 330 performs exposure corresponding to the first color signal, that is, the yellow (Y) image signal, and a latent image corresponding to the yellow (Y) image is formed on the photosensitive drum 310. It is formed.

  The latent image is reversely developed by the developing device 340 and converted into a yellow (Y) toner image, and then transferred onto the intermediate transfer belt 401 by the action of the transfer unit 350.

  Image formation with other color signals that is sequentially started after a predetermined time from the start of image formation with the first color signal is performed for each of magenta (M), cyan (C), and black (BK) by the same process as described above. This is done by the image forming unit 30.

  Each toner image on the photosensitive drum formed by each image forming unit is sequentially transferred so as to overlap with an image area where a yellow (Y) toner image is present, and is superimposed on the intermediate transfer belt 401. An image is formed.

  Reference numeral S denotes a control means (control unit) including a computer, which has a built-in machine operation program and controls a series of image forming processes, including paper feeding and conveyance related to a paper feeding device 9 to be described later. All controls such as control are performed. In other words, the control means S includes a CPU that performs calculation control processing, a ROM that stores various operation programs, a RAM that stores calculation result data, and the like. And while taking in the output of various sensors to said CPU via an interface, it has the structure which controls drive of a motor or a display means etc. based on the information.

  P1, P2, and P3 are paper trays as paper storage means installed in the lower part of the apparatus main body. The feeding sections of the paper trays P1 to P3 are provided with paper feed rollers 503, 513, and 523, separation rollers 506, 516, and 526, and transport rollers R1, R2, and R3. The paper is transported along a paper transport path YH1 in which transport rollers R5 to R7 are disposed.

  Reference numeral 59 denotes a registration roller, which is provided downstream of the conveying roller R7 and close to the secondary transfer portion. At a position downstream of the secondary transfer portion (position where the transfer roller 510 is located), there are a first fixing roller T1 having a built-in heating source and a second fixing roller T2 that rotates while being in pressure contact with the first fixing roller. A fixing device T is provided.

  Reference numeral 600 denotes a paper discharge roller, and reference numeral 650 denotes a paper discharge tray for stacking and storing the discharged paper.

  The sheet conveyance path configuration and conveyance control relating to the reverse sheet discharge / refeed unit 6 and the ADU 7 are well known and are not directly related to the present invention, so the description is omitted.

  Next, a process until the color toner image formed on the intermediate transfer belt 401 is transferred onto the paper P and discharged outside the apparatus will be briefly described.

  Corresponding to the image formation on the intermediate transfer belt 401, the paper P is fed by the paper feed rollers 503 (513, 523) and is directed to the registration rollers 59 via the paper transport path YH1.

  The paper P to be fed is designated on the operation display board 150 in which the number of recorded sheets, a recording start button, a recording magnification, etc. can be set, or automatically according to image data transmitted from a document or an external communication device. It is a sheet material of a size selected for. Further, the paper feed direction size and the like can be taken into the control means S as needed and used for paper feed control.

  The aforementioned paper P is stopped when the leading edge of the paper P comes into contact with the registration roller 59, and the paper P is re-feeded at a timing overlapping with the color toner image area on the intermediate transfer belt 401 by the rotation of the registration roller 59 restarting.

  Next, the sheet P is pressed and nipped together with the intermediate transfer belt by the backup roller 410 and the transfer roller 510 in the secondary transfer unit, and the color toner image on the intermediate transfer belt 401 is transferred onto the sheet P during this time.

  Next, the paper P is separated from the intermediate transfer belt 401 and subjected to a heating / pressurizing process by the fixing device T. As a result, the toner (image) is melted and fixed on the paper P.

  The paper P after the fixing process is discharged by a paper discharge roller 600 onto a paper discharge tray 650 provided outside the apparatus main body.

  In the figure, reference numeral 9 denotes an optional sheet feeding device which is used by being externally coupled to the image forming apparatus main body H (details of the configuration of the sheet feeding device will be described later). An example image forming system according to the present invention is constructed with the image forming apparatus main body H and the paper feeding device 9 as main elements.

  A sheet fed from a sheet storage unit in the sheet feeding device 9 by a sheet feeding unit (referring to a sheet suction / conveying unit to be described later) is sent into the apparatus main body H through a communication port, and the image formation described above is performed. After being processed according to the process, it is discharged onto a discharge tray 650.

  FIG. 2 is a schematic diagram for explaining a configuration in the sheet feeding device 9 according to the present invention.

  In FIG. 2, box-shaped paper storage means (paper storage units) P <b> 20, P <b> 21, P <b> 22 are provided in the paper feeding device 9 in the vertical direction.

  Further, above each paper storage means and at a position near the front including the front end of the paper, paper suction conveyance means VT20, VT21 including endless suction belts SB20, SB21, SB22 which are paper feeding means, A VT 22 is provided. The sheet storage means P20 to P22 have elevating plates 960, 961, and 962 that have a capacity capable of stacking and storing a large amount of sheets P and that can move the stacked sheets in the vertical direction while maintaining a horizontal state. The paper storage means is provided on the front side of the drawing so that it can be pulled out.

  The elevating plates 960 to 962 are driven up as the stacked sheets are used in the image forming process and are sequentially reduced so as to maintain the position of the uppermost sheet at a position where it can be sucked and conveyed within a certain range. It is regulated (controlled).

  The sheet position restriction in the height direction can be executed by an appropriate sensor and the control means S. In addition, about the structure which raises / lowers a raising / lowering board, the well-known technique containing a wire and a pulley can be used.

  Since these position restrictions and the lifting mechanism of the lifting plate do not directly characterize the present invention, a detailed description is omitted, but for example, Japanese Patent Laid-Open No. 2006-027797 can be referred to.

  The lowermost surface of the suction belt (the surface of the lower side of the parallel plane, the surface that is the paper suction conveyance surface and that faces the uppermost paper of the stored paper) and the stacked paper P A gap is formed between the uppermost paper. In the present embodiment, the gap is about 15 mm, but this value can be changed according to various conditions and does not restrict the present invention.

  In this embodiment, the leading edge of the sheet is used to float at least the uppermost sheet in the paper feeding operation for sucking the sheet through the suction belt (SB) and sucking the sheet on the suction belt. A sheet floating means for blowing air to the side surface is provided. In FIG. 2, 986 is an air blowing port of one duct that constitutes a sheet floating means together with a sirocco fan or the like, and is formed on a side regulating member 920 that regulates the side of the sheet. The tip regulation position to be performed is shown.

  R20 to R29 are paper conveyance means (hereinafter referred to as conveyance rollers) composed of conveyance rollers, and the conveyance rollers R23 to R29 are arranged on the paper conveyance path YH2. The transport rollers R20 to R22 are provided corresponding to the paper storage means P20 to P22, and play a role of feeding the paper sucked and transported by the paper suction transport means VT20 to VT22 into the downstream paper transport path YH2.

  The distance between the rollers that are adjacent to each other during the conveyance of the sheet is constant, and is the distance that can relay the smallest size sheet in the feeding direction among the sheets to be used. Specifically, the distance is smaller than the long side dimension of the postcard size (100 mm × 148 mm).

  Although not shown in the figure, each transport roller is connected via a clutch to a power transmission means that is rotated by a motor built in the paper feeding device, and is also released from rotation to stop and rotate. It is configured to be controlled. The transport rollers on the paper transport path YH1 in FIG. 1 have the same configuration.

  Reference numerals 810 to 816 denote paper detection sensors (hereinafter referred to as sensors), which are provided one by one between the transport rollers R23 to R29 on the paper transport path YH2. The sheet conveyance path YH1 in the image forming apparatus main body H shown in FIG. 1 has the same configuration, but is omitted in FIG.

  The sheet detection sensors 810 to 816 may be configured with a combination of them evenly or unequally, but in this embodiment, they are equally spaced. Further, the distance information from the front end position of the paper stacking unit of each paper storage means (P20 to P22) related to paper conveyance to each paper detection sensor (810 to 816), along with the feed direction length information of the paper to be used, It is used for conveyance control via the control means S shown in FIG. The leading edge position of the paper stacking unit refers to a leading edge contact portion (tip regulation guide surface) provided on the downstream side (left side in the drawing) in the paper transport direction in the paper storage unit.

  The installation positions and intervals of the sensors (810 to 816) are not provided in correspondence with the size of each standard sheet in the feeding direction. For example, the conveyance control of the standard minimum size sheet is used as a reference. Position and spacing are provided. In other words, the conveyance roller related to the conveyance of the paper is stopped via the control means S based on the detection output information each time the sensor detects the leading edge of the minimum size paper. At this time, for example, when the front end of the fed paper is detected by the sensor 810 and driving of the transport rollers R20 and R23 related to transport is stopped, the rear end of the paper has passed through the above-described air action region. It is set to become. Further, when the same sensor 810 detects the trailing edge of the same sheet, the subsequent sheet can be fed or fed based on the detected output information. In the initial state where no sheet exists on the sheet conveyance path YH2 to the registration roller 59 in FIG. 1 and YH1 in FIG. 1, sheet conveyance control by the stay control method is ignored. In other words, the paper fed by the paper suction transport means (VT) is transported downstream as long as the downstream sensor outputs that the paper is not present. Stopped while being pinched. When the second and subsequent sheets are fed one after another, the sheets are controlled to stop without colliding with the preceding sheets. The sheet conveyance control in such an initial state is basically performed by the same control regardless of the sheet size in the feeding direction.

  On the other hand, in the paper feeding / conveying control of the standard size paper larger than the minimum size in the feeding direction, it is assumed that there is a space for one sheet at the most upstream part (pointing to the vicinity of the downstream of the paper storing means) on the paper conveying path. The paper feed control at that time is performed as follows. First, based on the size information of the paper to be fed, the distance from the front end position of the paper stacking unit of the paper storage means is close to the target paper size and at a distance position smaller (shorter) than that size, for example, Tip detection output information is obtained from a predetermined sensor 811. After that, while the time until the trailing edge of the sheet passes through the air acting area is counted by a timer, the related conveying rollers R20, R23, R24 are continuously driven to reach the set time (count up). If S determines, the conveyance roller is stopped. The relationship between the stop of the transport roller based on the timer count described above and the trailing edge position of the paper with respect to the air action area at that time, or the relation with the paper at the immediately downstream position, etc. is confirmed through experiments. Therefore, accurate control can be performed.

  As described above, since the trailing edge of the paper does not exist in the air acting area when the paper is temporarily stopped by the staying control method, it is possible to avoid problems such as jamming at the time of feeding the subsequent paper, and to be stable. Can be fed.

  When a non-standard size paper that is slightly larger than a standard size paper is used, the paper size is manually input using the operation display board 150 (see FIG. 1) and used as a factor for paper feed control. It will be. However, unlike the case of standard size paper, it may not be possible to control with high accuracy. In this case, the trailing edge of the paper may stop in the air acting area at the time of temporary stop immediately after paper feeding. For such irregular-size paper, a sensor associated with a standard-size paper close to that is used for leading edge detection, and control is performed to delay the stop time of the transport roller by a sufficient time, Similar problems can be avoided. Alternatively, if there is not enough time until the above-described conveyance roller stops, the sheet immediately before the sheet is conveyed by a small amount at the same time as the sheet is conveyed until the trailing edge of the sheet exits the air acting area. As a result, the above-mentioned problems can be avoided.

  Instead of the timer control, a single sheet detection sensor (hereinafter referred to as a unit sensor) 850 is provided in the vicinity of the downstream side of the air action area, and is conveyed based on the trailing edge detection output information of the sheet by the sensor 850. Control to stop the related conveying roller is also possible. In such a configuration, regardless of the standard size or the irregular size, the trailing edge of the paper can be completely out of the air acting area when the paper is temporarily stopped after feeding.

  Next, the paper feeding or transport control in a state where the downstream area of the paper transport path is filled with a standard size paper larger than the minimum size and there is a predetermined space in the most upstream part will be described.

  For example, a case where a new sheet (not shown, but referred to as sheet 7 for convenience) is fed in a state where the rear end of a predetermined sheet is detected by the sensor 812 will be described. When the leading edge of the sheet 7 is detected by the sensor 810 and then detected by the vacant downstream sensor 811, the downstream sensor 812 detects the preceding sheet (not illustrated, sheet 6). When the control means determines that the trailing edge of the sheet 7 is not in the air action area, the conveyance of the sheet 7 is immediately stopped. On the other hand, when the control means determines that the trailing edge of the sheet 7 is in the air acting area, the sheet is transported until the trailing edge of the sheet 7 passes the air acting area and then stopped. Also in this case, if the sensor 850 is attached, the control is easy, and if there is not much room between the opposing edges of the paper 6 and the paper 7, the case of an irregular size is used. As described above, the paper 6 may be conveyed by a predetermined amount at the same time. In the above description, the space when the paper 7 is fed is a space that approximates the size of the used paper in the feed direction. However, there may be a case where the space is smaller. In such a case, the feeding of the sheet 7 is interrupted until a predetermined space is formed, or the sheet 7 is put on standby in a state where the leading end of the sheet 7 is held between the transport rollers R24 and the like. Then, after the sheet 6 is re-conveyed and passes through the conveyance roller R25, the sheet 7 is re-conveyed, and the leading end of the sheet 7 is sandwiched between the conveyance roller R25 and the like that are driven and stopped based on information detected by the sensor 812 Can be controlled to stop. In this way, in the present invention, by controlling so that the trailing edge of the fed paper does not stop in the air action area, the occurrence of problems such as jamming that is a concern during the feeding of the next paper is generated. Can be prevented.

  In addition, the air action area | region is divided and shown in two areas in FIG. One is the entire area (A) from the downstream end position of air blowing (air blowing) by the air separating means in the paper transport direction to the front edge of the paper suction area of the paper suction transport means. One is the area (a), which is an area (from the front end position (front end regulating member G surface) of the paper stacked in the paper storage means to the front end of the paper suction area in the paper suction conveyance means ( (B) This is a section for explaining that the degree of damage is large when the trailing edge of the sheet stops in the air action area, particularly in the area (b).

  Briefly explaining the configuration of the main element, the opening (end) of the duct constituting the air separating means is provided on substantially the same plane as the sheet conveyance path plane (horizontal plane indicated by reference numeral 995 as a guide member). ing. Also, the opening of the duct is adjoined by the sheet adsorbing and conveying means and is near the downstream side of the sheet conveying means so that air is blown from the lower downstream side to the leading end portion of the conveyed sheet and has a predetermined inclination. Have Specifically, the extension line on the inner surface on the upstream side of the opening has a relationship of being in contact with the substantially front end of the sheet suction area that is negative pressure for sheet suction. Further, the front end position of the paper suction area is located upstream from the paper front end position in the paper storage means. The above configuration takes into consideration the separation function when a plurality of sheets are sucked by the sheet suction transporting means. In such a configuration, if the rear end of the fed paper is present in the region (b) from the position of the front end regulating member G surface to the front end position of the paper suction region on the paper transport path, it is sucked by the paper suction transport means. For example, the movement of the paper to be blocked is hindered, and for example, the leading end is buckled. On the other hand, if the trailing edge of the paper is present in the area (b) other than the area (b), the damage is less than the above, but stable paper feeding is hindered, for example, by causing turbulent air flow. In the present embodiment, the size of the area (A) is 20 mm, (B) is 5 mm, the air speed of the air separating means is 5 m / sec, the paper conveyance speed is 860 mm / sec, and the image forming process speed is 400 mm. However, these can be appropriately changed according to the specifications.

DESCRIPTION OF SYMBOLS 1 Automatic document feeder 2 Image reading part 3 Image formation part 4 Belt unit 5 Paper feed part 9 Paper feed device 810-816,850 Paper detection sensor (sensor)
G leading edge regulating member P20, 21, 22 Paper storage means SB20, SB21, SB22 Adsorption belt VT20, VT21, VT22 Paper adsorption conveyance means

Claims (5)

Paper storage means for stacking and storing paper;
A sheet adsorbing / conveying means that is provided above the sheet accommodating means and adsorbs and conveys the sheet stored in the sheet accommodating means;
An air separating means for blowing air from the downstream side lower side to the leading end portion of the paper that is adsorbed and conveyed by the paper adsorbing and conveying means;
A paper transport path comprising a plurality of transport means for transporting the paper sent out by the paper suction transport means downstream;
Control means for performing control to advance the paper downstream while repeating conveyance and stop in the paper conveyance path,
When the paper is temporarily stopped by the control means, the control means has a trailing edge of the paper in an air action area from a downstream end position of air blowing by the air separating means to a front edge of the paper suction area of the paper suction conveyance means. When it is determined that the paper is stopped, the paper is transported to the downstream side through the predetermined transport means until the trailing edge of the paper passes through the air action area, and then stopped.
A paper feeder characterized by that. Paper storage means for stacking and storing paper;
A sheet adsorbing / conveying means that is provided above the sheet accommodating means and adsorbs and conveys the sheet stored in the sheet accommodating means;
An air separating means for blowing air from the downstream side lower side to the leading end portion of the paper that is adsorbed and conveyed by the paper adsorbing and conveying means;
A paper transport path comprising a plurality of transport means for transporting the paper sent out by the paper suction transport means downstream;
Control means for performing control to advance the paper downstream while repeating conveyance and stop in the paper conveyance path,
When the control unit is temporarily stopped, the control unit controls the rear side of the sheet in an air action area from the leading end position of the sheet stacked in the sheet storage unit to the front end of the sheet adsorption area in the sheet adsorption transport unit. When it is determined that the end is stopped, control is performed to stop the paper after the paper is transported downstream until the trailing edge of the paper passes through the air action region via the predetermined transport means.
A paper feeder characterized by that. The plurality of transport means provided in the paper transport path are transport rollers, and the paper transport path is provided with a plurality of paper detection sensors.
The control means calculates a rear end position of the paper from distance information from the paper stacking portion front end position of the paper detection sensor and paper length information inputted in advance.
Among the sheet detection sensors, when a predetermined sheet detection sensor detects the leading edge of the second sheet fed by the sheet suction and conveyance means, the sheet detection sensor downstream thereof detects the second sheet detection sensor. When it is determined that the trailing edge of the second sheet is not in the air operating area when the first sheet is detected immediately before the sheet is fed, a predetermined transport roller is The second sheet is immediately stopped, and when it is determined that the trailing edge of the second sheet is in the air acting area, the trailing edge of the second sheet passes through the air acting area. Control to stop the transport after transporting until
The sheet feeding device according to claim 1, wherein the sheet feeding device is provided.   An image forming system comprising: the paper feeding device according to claim 1; and an image forming unit that forms a toner image on an image carrier.   The image forming system according to claim 4, wherein the paper feeding device is used by being externally attached to the image forming device.

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