Sheet feeding device, image forming device, method and program

Abstract

To enable air spraying in accordance with an overlapped state of multi-fed sheets.SOLUTION: A sheet feeder for feeding sheets to a conveyance path from a tray comprises: a fan provided so as to be able to spray air toward ends of sheets of a sheet bundle placed on the tray; a multi-feeding detection unit for detecting multi-feeding of the conveyed sheets; and an overlapping determination unit for determining the overlapped state of the multi-fed sheets. A fan control unit of the sheet feeder controls the fan in accordance with the overlapped state determined by the overlapping determination unit when the sheets are multi-fed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a sheet feeding device, an image forming device, a method, and a program, and more particularly to a sheet feeding device, an image forming device, a method, and a program that use an air blowing system. [Background technology]

[0002] In image forming devices such as copiers and printers, the air feeding method is known as one of the configurations for feeding paper to the image forming section. In the air feeding method, air is blown onto the stacked paper, causing the paper to float and be placed on a conveyor belt, which is then driven to feed the paper to the image forming section.

[0003] In the air paper feed system, it is desirable for the user to thoroughly separate the stacked sheets in advance, but if the sheets are not properly separated, they will overlap and float up. In this case, a double feed occurs in which the sheets are transported overlapping each other, resulting in a jam. As a technology to prevent such double feed, for example, Japanese Patent Application Laid-Open No. 2007-308207 (Patent Document 1) discloses a technology in which "when a double feed is detected, the device executes an adjustment mode and adjusts the air blowing means so that an air pressure sufficient to separate the sheets is obtained" (see [Abstract]). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-308207 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the adjustment of the air blowing means is merely a change in the air volume by adjusting the rotation speed of the fan, so for example, in the case of a multi-feed in which the sheets are tightly packed together, the sheets may not be separated sufficiently, and multi-feeding may not be prevented. Therefore, when separating sheets in a multi-feed, a mechanism for blowing air according to the state of overlap of the sheets is desired.

[0006] The present disclosure has been made in view of the above-described background. According to one aspect, a technique is disclosed that enables air blowing depending on the overlapping state of sheets in multi-feeding. [Means for solving the problem]

[0007] The sheet supply device disclosed herein, which supplies sheets from a tray to a conveying path, includes a fan that is capable of blowing air toward the edges of sheets in a stack of sheets placed on the tray, a fan control unit that controls the fan, a multi-feed detection unit that detects whether the sheets being conveyed are being multi-fed, and an overlap determination unit that determines the overlap state of the sheets in the multi-feed, and when a multi-feed is detected, the fan control unit controls the fan in accordance with the overlap state determined by the overlap determination unit.

[0008] In the above disclosure, the overlap determining unit determines the overlap state based on the amount of misalignment of the leading edges of the overlapping sheets.

[0009] In the above disclosure, the overlap determination unit compares the amount of deviation of the leading edge with a threshold value, and the overlap state indicates the result of the comparison.

[0010] In the above disclosure, the fan control unit controls the fan to operate when the overlap state indicates that the leading edge deviation is equal to or less than a threshold value.

[0011] In the above disclosure, the fan control unit controls the fan to stop when the overlap condition indicates that the leading edge deviation is greater than a threshold value.

[0012] In the above disclosure, the fan control unit controls the fan to repeat a separation operation consisting of operation and stop when the overlap state indicates that the deviation amount of the leading edge is equal to or less than a threshold value.

[0013] In the above disclosure, the fan control unit determines the number of times to repeat the separating operation according to the amount of deviation of the tip.

[0014] In the above disclosure, the fans include a fan that blows air in a direction to lift sheets from the sheet stack, and a fan that blows air in a direction to separate the sheets of the sheet stack.

[0015] In the above disclosure, the fan control unit controls the fan so that the amount of air blown varies based on the amount of deviation of the tip.

[0016] In the above disclosure, the fan control unit controls the fan to repeat the sorting operation, and thereafter, when a double feed is detected, outputs a predetermined notification.

[0017] In the above disclosure, when a double feed is detected by the double feed detection unit, the fan control unit does not control the fan for the sorting operation if the number of remaining sheets to be supplied to the conveying path is less than or equal to a predetermined number.

[0018] In the above disclosure, the fan control unit stops the sheet supply to the conveying path and controls the fan for the separating operation.

[0019] In the above disclosure, the fan control unit adjusts at least one of the number of times the separating operation is repeated and the amount of air blown by the fan based on the size of the sheets in controlling the fan.

[0020] In the above disclosure, when starting to supply sheets to the conveying path, the fan control unit controls the fan to blow air toward the edge of the sheets in the sheet stack placed on the tray.

[0021] An image forming apparatus according to the present disclosure includes the sheet feeding device described above, and an image forming section that forms an image on a sheet fed from the sheet feeding device to a conveying path.

[0022] The control method disclosed herein is a method for controlling an apparatus that supplies sheets from a tray to a conveying path, the apparatus having a fan that is capable of blowing air toward the edges of sheets in a stack of sheets placed on the tray, and the method includes a step of detecting that the sheets being conveyed are being double-fed, a step of determining the overlapping state of the sheets in the double-fed state, and a step of controlling the fan according to the overlapping state determined in the determining step when the double-fed state is detected.

[0023] A program according to the present disclosure is a program for causing a computer to execute a control method. The control method is a method for controlling an apparatus that supplies sheets from a tray to a conveyance path, the apparatus having a fan that is configured to blow air toward an edge of a sheet of a sheet stack placed on the tray. The control method includes the steps of detecting a multi-feed of conveyed sheets, determining an overlap state of the sheets in the multi-feed, and, when the multi-feed is detected, controlling the fan in accordance with the overlap state determined in the determining step. [Effects of the Invention]

[0024] According to the present disclosure, it is possible to blow air according to the overlapping state of sheets during multi-feeding.

[0025] The above and other objects, features, aspects and advantages of the present disclosure will become apparent from the following detailed description of the disclosure taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a diagram showing the appearance of an image forming apparatus 100. FIG. [Figure 2] FIG. 2 is a diagram showing a configuration of an image forming unit 110 of the image forming apparatus 100. [Figure 3] FIG. 2 is a diagram illustrating a paper feeding device included in the image forming apparatus 100 of FIG. [Figure 4] 4 is a cross-sectional view showing a cross section taken along the arrow BB in FIG. 3. [Figure 5] 2 is a block diagram showing an example of a hardware configuration related to a control unit 200 of the image forming apparatus 100. FIG. [Figure 6] FIG. 2 is a diagram schematically illustrating components of control according to the present embodiment. [Figure 7] 10 is a diagram illustrating a control procedure for the fan of the first pre-separating section 311. FIG. [Figure 8] 10 is a diagram illustrating a control procedure for the fan of the first pre-separating section 311. FIG. [Figure 9] 10 is a diagram illustrating a control procedure for the fan of the first pre-separating section 311. FIG. [Figure 10] 10 is a diagram illustrating a control procedure for the fan of the second pre-separating section 312. FIG. [Figure 11] 10 is a diagram illustrating a control procedure for the fan of the second pre-separating section 312. FIG. [Figure 12] 2 is a diagram schematically illustrating a double feed sensor 40 and its surrounding area according to the present embodiment. FIG. [Figure 13] 10A and 10B are diagrams illustrating a mechanism for determining a state of multifeed according to the present embodiment. [Figure 14] 10 is a timing chart of fan control by the first pre-separation unit 311. [Figure 15] 10 is a timing chart of fan control by the second pre-separation unit 312. [Figure 16] 3A and 3B are diagrams illustrating a fan control method according to the present embodiment. [Figure 17] FIG. 10 is a diagram illustrating an application example of the fan control procedure according to the present embodiment. [Figure 18] 10A and 10B are diagrams for explaining an example of fan control based on paper size according to the present embodiment. [Figure 19] 4 is a flowchart of a fan control process according to the present embodiment. [Figure 20]4 is a flowchart of a fan control process according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. Their names are also the same. Therefore, detailed descriptions thereof will not be repeated. When referring to numbers or quantities, the scope of the present disclosure is not necessarily limited to those numbers or quantities unless otherwise specified.

[0028] Although the sheet feeding device will be described as a configuration provided in an image forming apparatus, the target equipment in which the sheet feeding device is provided is not limited to an image forming apparatus.

[0029] [Terminology] The main terms used in this disclosure are explained below.

[0030] "Sheet" refers to any medium on which an image can be formed by an image forming device. For example, this includes paper, resin film sheets, etc., but here we will use "paper" as a representative example. Therefore, a paper stack, which will be described later, is an example of a sheet stack.

[0031] A "job" refers to a unit of processing that an image forming apparatus executes to form an image on paper. Jobs include, for example, print jobs and copy jobs. In the following embodiments, a case where a print job is executed will be mainly described, but the job is not limited to a print job as long as it involves paper feeding.

[0032] The "edges of a sheet of paper" refer to the sides of the sheet of paper, and include the leading edge, trailing edge, left edge, and right edge in the direction in which the sheet is transported by the image forming apparatus.

[0033] "Width of sheet" refers to the length of the sheet extending across the edges of the sheet. "Double feeding" refers to the phenomenon in which two or more sheets of paper are fed overlapping each other.

[0034] The hardware configuration of an image forming apparatus 100 to which a paper feeder according to this embodiment is applied will be described below.

[0035] The image forming apparatus 100 includes an image reading unit 105 , an image forming unit 110 , an operation panel 115 , a paper feed unit 120 , and a paper discharge tray 125 .

[0036] In this embodiment, the image forming apparatus 100 is realized as an MFP (Multifunction Peripheral) having, for example, a scanner function, a copy function, a facsimile function, a network function, a box function, and other functions.

[0037] The image reading unit 105 optically reads a sheet of paper on which an original image has been formed, thereby obtaining the read image. The image forming unit 110 forms an image on the sheet of paper based on the read image obtained by the image reading unit 105.

[0038] Operation panel 115 accepts operation input from the user to image forming apparatus 100. Furthermore, operation panel 115 displays screens such as setting screens. A more detailed hardware configuration of operation panel 115 will be described with reference to FIG.

[0039] Paper feed unit 120 has multiple trays, each of which stores a type of paper that differs in size, basis weight, etc. from the paper stored in the other trays. Paper of the type specified by a job is removed one sheet at a time from the tray by a paper feed device (not shown in FIG. 1) provided in association with paper feed unit 120 and transported to image forming unit 110. The trays are configured to be manually openable and closable, and to allow stacks of paper to be manually set (stored) in them. Each tray has an open / close sensor 50 that detects when the tray is opened or closed, a set sensor 55 that detects when a stack of paper has been set, and a sensor 45 that detects the paper size. Paper output tray 125 receives paper that has been formed with an image by image forming unit 110 and is then output.

[0040] 2 is a diagram showing the configuration of the image forming unit 110 of the image forming apparatus 100. The image forming unit 110 includes an intermediate transfer belt 11, a drive roller 18, a driven roller 13, imaging units 14Y, 14M, 14C, and 14K, a secondary transfer roller 13A, and a fixing unit 17.

[0041] The intermediate transfer belt 11 is configured as an endless belt, and is driven to rotate in the direction of arrow A in the figure (counterclockwise direction) by a drive roller 18 and a driven roller 13.

[0042] Imaging units 14Y, 14M, 14C, and 14K are arranged sequentially along the lower surface of intermediate transfer belt 11 in the direction of rotation of intermediate transfer belt 11, and generate toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively.

[0043] Each of the imaging units 14Y, 14M, 14C, and 14K includes a photosensitive drum 1 (image carrier), a charger 2, an exposure unit 3, a developer 4, a primary transfer roller 5, and a cleaner 6. Each imaging unit forms an electrostatic latent image in accordance with the information of the original image based on the job, and develops the formed electrostatic latent image with toner. As a result, four-color toner images are formed on the four photosensitive drums 1 of the imaging units 14C, 14M, 14Y, and 14K. The processing of the imaging units is well known, so detailed description will not be repeated.

[0044] The four color toner images formed on the four photosensitive drums 1 of the imaging units 14C, 14M, 14Y, and 14K are sequentially transferred and superimposed on the surface of the intermediate transfer belt 11 to form a full-color toner image.

[0045] In the rotation direction of the intermediate transfer belt 11, while the paper P is inserted in the nip between the secondary transfer roller 13A and the intermediate transfer belt 11, the toner image on the surface of the intermediate transfer belt 11 is transferred to the paper P. The fixing device 17 fixes the toner image to the paper P.

[0046] Paper feed unit 120, which supplies paper P to image forming unit 110, has multiple (three in FIG. 1) paper feed trays 21A-21C. Paper feed unit 120 may also include tray 21D, which feeds paper P from outside image forming apparatus 100. Image forming apparatus 100 has a transport mechanism for transporting paper P stored in trays 21A-21D to image forming unit 110. The transport mechanism includes paper feed rollers 23A-23D, transport paths 30A-30E, transport rollers 31A and 32, timing roller 33, paper discharge roller 34, and paper discharge tray 125, which are provided in association with trays 21A-21D.

[0047] Each of the trays 21A to 21D stores a stack of sheets P. The trays 21A to 21D may store the same type of sheets P. Entrances to the transport paths 30A to 30D are provided downstream of the sheet feed rollers 23A to 23D of the trays 21A to 21D, respectively.

[0048] The outlets of conveying paths 30A to 30D are all connected to the inlet of conveying path 30E, and the outlet of conveying path 30E is provided upstream of paper discharge roller 34. Conveying rollers 31A and 32, timing roller 33, secondary transfer roller 13A, and fixing unit 17 are sequentially arranged between the inlet and outlet of conveying path 30E.

[0049] When one of the multiple types of paper P stored in trays 21A to 21D is selected by a user or by a job, the paper feed roller (e.g., 23A) corresponding to the selected type of paper P is rotated, and the paper P is supplied to the conveying roller 31A via the conveying path (in this case, conveying path 30A) and conveying path 30E.

[0050] Conveying rollers 31A and 32 convey paper P supplied from a paper feed roller (23A in this case) to timing roller 33. Timing roller 33 operates in synchronization with the full-color toner image transferred onto the surface of intermediate transfer belt 11, and supplies paper P conveyed by conveying rollers 31A and 32 to the nip between secondary transfer roller 13A and intermediate transfer belt 11. Paper P that has passed through the nip between secondary transfer roller 13A and intermediate transfer belt 11 passes through fuser 17 and is discharged onto paper discharge tray 125 by paper discharge roller 34.

[0051] A double feed sensor 40 for detecting double feed is provided on the conveying path 30E between the conveying rollers 31A and 32. The mechanism for detecting double feed using the double feed sensor 40 will be described later.

[0052] Fig. 3 is a diagram illustrating a paper feeder included in image forming apparatus 100 in Fig. 1. Fig. 4 is a cross-sectional view taken along arrow BB in Fig. 3. Image forming apparatus 100 has a paper feeder for each of trays 21A to 21D. Since the configuration of the paper feeder is the same for each tray, the trays 21A to 21D will be collectively referred to as tray 21 in the description common to all of them.

[0053] Referring to FIG. 3, sheet feeding device 10, which is an example of a sheet supplying device, has a fan that blows air onto a stack of sheets P stacked on loading tray 111 of tray 21. By controlling the fan, sheet P at the top of the stack is lifted and separated from the stack, and the separated sheet P is transported in transport direction X. Sheet feeding device 10 is equipped with member 12 associated with loading tray 111, side fans 13L and 13R that blow air from the sides onto the stack of sheets, a leading edge fan 14 that blows air onto the leading edge of the stack of sheets, a suction transport unit 15 that transports sheets P while suctioning them, and a transport unit 16 for sheet P (shown only in FIG. 4). Also, sheet position sensors PS1 to PS4 shown in FIG. 4 are provided associated with each tray. Transport unit 16 constitutes transport paths 30A, 30B, 30C, 30D, and 30E shown in FIG. 2.

[0054] The loading tray 111 can be raised and lowered by a lifting mechanism (not shown) as indicated by the outline arrow in the drawing. The loading tray 111 is configured to maintain the height of the stack of sheets of paper loaded on top at an optimum height for floating and separating the sheets of paper P by the air blown from the side fans 13L and 13R and the tip fan 14.

[0055] Member 12 is a member that regulates the placement position of paper P on loading tray 111, and includes members 12A, 12B, 12L, and 12R. Member 12A is arranged on the leading edge side of paper P loaded on loading tray 111, and regulates the leading edge position of paper P. Here, the conveying direction X of paper P is the direction in which suction conveying section 15 conveys paper P. Member 12A is a box-shaped housing that houses leading edge fan 14. In this case, member 12A is provided in a portion facing the loading tray 111 side and a portion facing upward on the loading tray 111 side, and these portions may be connected to each other.

[0056] Member 12B is disposed on the rear end side of the paper sheets P loaded on loading tray 111. Member 12B is a plate-shaped member configured to be movable in the transport direction X of the paper sheets P, and regulates the rear end position of the paper sheets P by lightly pressing the paper sheets P loaded on loading tray 111 from the rear end side.

[0057] The members 12L and 12R are arranged on the left and right edges of the paper P stacked on the loading tray 111 and lightly press the paper P from both sides to regulate the position of the paper P in the width direction Y. The members 12L and 12R are configured as housings that house the side fans 13L and 13R. The members 12L and 12R have openings 122 in their upper parts facing the loading tray 111.

[0058] The side fans 13L, 13R have air ducts 131 with air outlets 132 formed therein. The air outlets 132 are provided to coincide with the openings 122 of the members 12L, 12R. As a result, the side fans 13L, 13R blow air onto the top of the stack of paper sheets from both sides in the width direction Y, which is perpendicular to the conveyance direction X of the paper sheets P, and function as floating fans that float the paper sheets P at the top of the stack of paper sheets.

[0059] The direction in which air is blown out from the outlets 132 of the side fans 13L, 13R is angled toward the conveyance direction X as needed, taking into consideration the balance with the direction in which air is blown out from the front end fan 14. The height direction in which air is blown out from the outlets 132 of the side fans 13L, 13R is also angled vertically as needed, taking into consideration the balance with the direction in which air is blown out from the front end fan 14. In this embodiment, the side fans 13L, 13R are provided on both sides of the sheet P, but a configuration in which side fans are provided on only one side is also possible.

[0060] Tip fan 14 is housed inside member 12A. Tip fan 14 has air duct 141 in which air outlet 142 (shown only in FIG. 4) is formed. Air outlet 142 is provided so as to coincide with opening 121 formed in member 12A.

[0061] The leading edge fan 14 is a function-switching fan that can switch between functions as a separation fan for separating multiple sheets P that have floated up from the stack of sheets, and as a levitation fan for levitating the upper sheets P of the stack of sheets. The leading edge fan 14 has a leading edge shutter 143 and a switching drive unit 144 that drives the leading edge shutter 143. The switching drive unit 144 drives the leading edge shutter 143 based on commands from the control unit 200, thereby controlling the switching and on / off of the functions of the leading edge fan 14 between a separation fan and a levitation fan, and also controlling the number of rotations (rotational speed) of the fan to adjust the airflow volume.

[0062] The suction conveyance unit 15 is disposed above the leading edge of the paper sheet P. The suction conveyance unit 15 includes a drive roller 151, two driven rollers 152A and 152B, an endless belt 153, and a suction fan 154.

[0063] The drive roller 151 is arranged upstream in the transport direction X of the paper P, with its axis facing the width direction Y of the paper P. The driven rollers 152A and 152B are arranged side by side in the stacking direction of the paper P. These driven rollers 152A and 152B are arranged a predetermined distance downstream from the drive roller 151 in the transport direction X of the paper P, with their axes kept parallel to the drive roller 151.

[0064] Belt 153 is wound around drive roller 151 and driven rollers 152A and 152B. Belt 153 has a large number of small diameter through holes (shown in FIGS. 7 to 9).

[0065] The suction fan 154 is disposed between the drive roller 151 and the driven rollers 152A and 152B, on the inner periphery of the belt 153 that is wound around them. When the suction fan 154 rotates, the space on the inner periphery of the belt 153 becomes negative pressure, and air flows toward the inner periphery through holes drilled in the belt 153. As a result, the paper P that has risen from the paper stack is sucked and adsorbed to the surface of the belt 153. That is, the suction conveyance unit 15 uses the suction fan 154 to adsorb the paper P to the belt 153, and conveys the paper P in the conveyance direction X by rotating the belt 153 due to the drive of the drive roller 151. The suction conveyance unit 15 can freely turn on / off the conveyance of the paper P by the drive roller 151 and turn on / off the adsorption of the paper P by the suction fan 154, based on instructions from the control unit 200.

[0066] 4, conveying section 16 is disposed downstream of suction conveying section 15 in conveying direction X of paper P. Conveying section 16 includes a lower guide member 161, an upper guide member 162, a lower conveying roller 163, and an upper conveying roller 164. Lower guide member 161 and upper guide member 162 are disposed to sandwich, at an interval from each other, the path of paper P conveyed from suction conveying section 15. Lower guide member 161 rotatably supports lower conveying roller 163, and upper guide member 162 rotatably supports upper conveying roller 164.

[0067] The lower transport roller 163 and the upper transport roller 164 supported as described above form a nip portion that holds the paper sheet P therebetween, and transports the paper sheet P nipped in the nip portion in the transport direction X.

[0068] Fig. 5 is a block diagram showing an example of a hardware configuration related to control unit 200 of image forming apparatus 100. In Fig. 4, image forming apparatus 100 includes, in addition to image reading unit 105, image forming unit 110, and operation panel 115 shown in Fig. 1, control unit 200, communication I / F (Interface) 215, data reader / writer 222, conveyance motor I / F (Interface) 70, fan I / F (Interface) 60, sensor I / F (Interface) 80, and bus 230 connecting these. The units in Fig. 5 exchange data via bus 230.

[0069] The control unit 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a timer 203, a RAM (Random Access Memory) 205, and an HDD (Hard Disk Drive) 210. The control unit 200 corresponds to a computer that controls the entire image forming apparatus 100.

[0070] CPU 200 executes a control program for controlling image forming apparatus 100. As an example, CPU 200 executes programs for displaying information and forming images. ROM 202 stores programs such as an operating system (OS) executed by CPU 200. RAM 205 stores application programs and data executed by CPU 200. In some aspects, RAM 205 may be a static random access memory (SRAM) or a dynamic random access memory (DRAM).

[0071] HDD 210 stores various programs and data used in image forming apparatus 100. In another aspect, HDD 210 may be replaced with an auxiliary storage device such as an SSD (Solid State Drive).

[0072] Communication I / F 215 transmits and receives data to and from other devices. Image forming apparatus 100 may include multiple communication I / Fs 215. In one aspect, communication I / F 215 may include any or all of a LAN (Local Area Network) port and a Wi-Fi (Wireless Fidelity) (registered trademark) transceiver.

[0073] When an external storage medium 223 such as an external HDD is detachably attached, the data reader / writer 222 writes data or programs including images to the attached storage medium 223 or reads data or programs from the storage medium 223 based on instructions from the CPU 201. The storage medium 223 stores information such as recorded programs or data by electrical, magnetic, optical, mechanical or chemical action so that a computer or other device can read the information.

[0074] In one aspect, operation panel 115 includes input unit 220 and display unit 225. Operation panel 115 can be configured as a touch screen that combines input unit 220 such as a plurality of touch sensors with display unit 225 such as a liquid crystal display. Operation panel 115 may further include a plurality of physical keys as input unit 220.

[0075] The sensor I / F 80 receives the detection signal 41 from the double feed sensor 40, the detection signal 51 from the open / close sensor 50, the detection signal 551 from the set sensor 55, and the detection signal 451 from the sensor 45, converts the received signals into digital data, and outputs the converted data to the control unit 200. Here, for simplicity of explanation, the sensor I / F 80 outputs the detection signals 41, 51, 551, and 451 representing digital data to the control unit 200.

[0076] The transport motor I / F 70 includes a transmission circuit that transmits motor control commands to motors provided in connection with the transport of paper P. The fan I / F 60 includes a transmission circuit that transmits commands to control fans provided in the paper feeder 10. The fan I / F 60 has a front fan I / F (Interface) 61, a suction fan I / F (Interface) 62, and a side fan I / F (Interface) 63 that transmit commands to the front fan 14, the suction fan 154, and the side fans 13L and 13R, respectively. The motors of each fan are driven according to the commands. For example, the commands include PWM (Pulse Width Modulation) commands that adjust the airflow, i.e., that determine the motor rotation speed (which may include the rotation direction). The commands for the front fan 14 include a command to control the switching drive unit 144.

[0077] 6 is a diagram schematically illustrating the components of the control according to this embodiment. These components of control unit 200 are realized by CPU 201 reading out a program stored in ROM 202, HDD 210, etc., and executing it while expanding it in RAM 205. In another aspect, some or all of the components in FIG. 6 may be realized using a dedicated integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0078] Referring to FIG. 6, the control unit 200 includes a fan control unit 300, a double feed detection unit 350 having an overlap determination unit 351, a recovery detection unit 360, a notification unit 370 that outputs a notification regarding the status of the image forming device 100, and a paper size detection unit 380.

[0079] The recovery detection unit 360 detects a user's recovery operation on the image forming apparatus 100. The recovery operation refers to an operation to resolve a multifeed when a multifeed is detected. More specifically, when a multifeed is detected, the control unit 200 controls the notification unit 370 to output a notification on the display unit 225 indicating that a multifeed has occurred, stops the feeding of the paper P to the conveyance path and the image formation process, and then waits for a start instruction based on a user operation received from the operation panel 115. Based on the notification from the notification unit 370, the user performs a recovery operation on the image forming apparatus 100 to resolve the multifeed. The recovery operation in this embodiment includes, for example, a user operation of opening the tray 21 and pulling out the multifeed paper, a user operation of removing a stack of paper stored in the tray 21, manually separating the paper, and then resetting the separated stack of paper in the tray 21, or a combination of these user operations. Note that the recovery operation is not limited to these. The recovery detection unit 360 monitors the detection signals 51, 551 from the open / close sensor 50 and the set sensor 55, detects a user operation such as a recovery operation or a reset operation based on the detection signals 51, 551, and outputs the detection result.

[0080] The paper size detection unit 380 detects the size of the paper P fed from the tray 21 based on the detection signal 41 from the multi-feed sensor 40. The overlap determination unit 351 has a leading edge misalignment calculation unit 352 that calculates the amount of misalignment at the leading edges of the overlapping paper sheets P. The multi-feed detection unit 350 detects that a multi-feed has occurred based on the detection signal 41 from the multi-feed sensor 40.

[0081] The fan control unit 300 includes a separation unit 310 that controls the fan to separate the stack of sheets in the tray 21, and an air volume change unit 320 that generates a command to control the fan according to a PWM method to change the air volume from the fan when separation is performed. The separation unit 310 includes a first pre-separation unit 311 that controls the fan to separate the stack of sheets in the tray 21 each time a sheet P is fed from the tray 21 to the conveyance path, and a second pre-separation unit 312 that controls the fan to separate the stack of sheets in the tray 21 each time a double feed is detected. The fan control unit 300 outputs commands 61a, 62a, and 63a for controlling the fans in this manner to the leading edge fan 14, the side fan 13L, and the side fan 13R, respectively, via the fan I / F 60. The fan control procedure of the first pre-separation unit 311 and the second pre-separation unit 312 will be described later with reference to FIGS. 7 to 11.

[0082] Fig. 12 is a diagram schematically illustrating a multi-feed sensor 40 and its surrounding area according to this embodiment. Referring to Fig. 12, at a position where the conveying sections 16 of each tray 21 (tray 21A, tray 21B, and tray 21C are shown in Fig. 12), registration rollers 44 that correct misalignment of paper P in the width direction Y and the multi-feed sensor 40 are provided in order in the conveying direction. The registration rollers 44 temporarily stop rotating for each sheet P being conveyed to correct the misalignment, and then restart. This misalignment correction operation is repeated for each sheet P being conveyed.

[0083] The double feed sensor 40 is configured to be able to detect that multiple sheets of paper P have passed through the conveyance path each time the registration rollers 44 are activated.

[0084] More specifically, the multi-feed sensor 40 has an ultrasonic wave transmission circuit 40a and an ultrasonic wave reception circuit 40b shown in FIG. Of the ultrasonic waves transmitted from the ultrasonic wave transmission circuit 40a toward the paper P, only the ultrasonic wave components that pass through the paper P are received by the ultrasonic wave reception circuit 40b. The multi-feed sensor 40 outputs the received signal of the ultrasonic wave reception circuit 40b as a detection signal 41. Upon receiving the detection signal 41 from the multi-feed sensor 40, the multi-feed detection unit 350 compares the degree of attenuation of the detection signal 41 with a threshold value and detects multi-feed based on the comparison result. More specifically, when there is no multi-feed and only one sheet of paper P is being transported, the degree of attenuation of the ultrasonic waves due to the paper P is low. However, when a multi-feed occurs in which two or more sheets of paper P are transported overlapping each other, the degree of attenuation of the ultrasonic waves due to the paper P is high. Therefore, when the reception level of the ultrasonic waves indicated by the detection signal 41 decreases, multi-feed is detected.

[0085] FIG. 13 is a diagram schematically illustrating a mechanism for determining the state of multifeed according to the present embodiment. When multifeed is detected, overlap determination unit 351 determines the overlap state of sheet P1 and sheet P2. Control unit 200 starts timing using timer 203 each time registration roller 44 is activated. Time R1 in FIG. 13 indicates the time from registration roller 44 activation to detection of multifeed by multifeed sensor 40, and arrows T1 and T2 indicate the length of time required from registration roller 44 activation time ST until multifeed is detected at time R1; these times and times are calculated based on the output of timer 203.

[0086] In the upper part of FIG. 13, the multi-feed sensor 40 detects a multi-feed when the leading edges of two sheets P1 and P2 conveyed from the registration rollers 44 after activation are aligned (hereinafter referred to as a perfect multi-feed). In contrast, in the lower part of FIG. 13, the multi-feed sensor 40 detects a multi-feed when the leading edges of two sheets P1 and P2 conveyed from the registration rollers 44 after activation are misaligned (hereinafter referred to as a fast-forwarding multi-feed). In the case of the fast-forwarding multi-feed shown at the bottom, the time T2 required for the multi-feed to be detected is longer than the time T1 required for the perfect multi-feed shown at the top. The overlap determination unit 351 detects the length of time elapsed from the activation of the registration rollers 44 until the multi-feed is detected, compares the detected length of time with a threshold value TH, and determines (detects) the overlap state of the sheets P during the multi-feed based on the comparison result. For example, the threshold value TH is a time calculated by experiment or the like, and indicates the above-mentioned required time when the detected multi-feed is a perfect multi-feed.

[0087] When the detected multifeed is determined to be early multifeed, the deviation amount calculation unit 352 calculates the time difference according to (T2-T1) and outputs the calculated time difference as the deviation amount G of the leading edges of the sheets P1 and P2.

[0088] 7 to 9 are diagrams illustrating the control procedure for the fan of the first pre-separator 311. In the diagrams, the thick arrows indicate the direction of airflow (airflow direction) generated by the fan, and the thickness of the arrow indicates the amount of airflow. Referring to FIGS. 7 to 9, the first pre-separator 311 performs a floating step when starting to execute a job. In the floating step, the first pre-separator 311 controls the side fans 13L and 13R of the tray 21 designated by a user operation or a job to float the sheet P from the stack of sheets in the tray 21, controls the leading edge fan 14 to operate as a floating fan, and controls the suction fan 154 (FIG. 7). As a result, the sheet floats from the stack of sheets in the tray 21, and the first sheet P on the suction fan 154 side of the stack of sheets is attracted to the belt 153. The suction conveyor 15 has a sensor (not shown) that detects the attraction of the sheet P to the belt 153.

[0089] When the sensor detects that the sheet P has been adsorbed to the belt 153, the first pre-separating unit 311 performs a separation step. In the separation step, in order to separate the second sheet P from the first sheet P, the first pre-separating unit 311 controls the side fans 13L and 13R to stop, and controls the front end fan 14 to change its airflow direction so that it operates as a separation fan (FIG. 8). The front end fan 14 switches its airflow direction so that air is blown between the first sheet P and the second sheet P.

[0090] After the sorting step has been performed for a predetermined time, the first pre-sorting unit 311 performs the paper feeding step. In the paper feeding step, the first pre-sorting unit 311 controls the motor to rotate the belt 153 in order to transport the paper P attracted to the belt 153 in the transport direction X. This causes the first paper P of the paper stack to be sent to the transport unit 16 (FIG. 9).

[0091] The first pre-separating unit 311 repeatedly executes the floating step, the separating step, and the paper feeding step for each sheet of paper P until the execution of the job is completed.

[0092] 10 and 11 are diagrams illustrating the fan control procedure of the second pre-separator 312. Unlike the first pre-separator 311, which controls the fan for each sheet of paper P sent to the transport section 16, the second pre-separator 312 controls the fan while stopping the supply of sheets P to the transport path, i.e., while stopping the rotation of the belt 153, when a double feed is detected. At this time, the second pre-separator 312 controls the fan to perform a separating operation to separate the stack of sheets of paper P so as to eliminate any tight contact between sheets of paper P before feeding the sheets from the tray 21 to the transport section. This makes it possible to reduce the occurrence of paper jams when a double feed is detected.

[0093] More specifically, the second pre-handling unit 312 performs a floating step shown in Fig. 10, followed by a handling step shown in Fig. 11. The floating step and the handling step are similar to the control of the fan shown in Figs. 7 and 8, and therefore description thereof will not be repeated.

[0094] In fan control by the first pre-separating unit 311, the time required to perform the floating step and the separating step depends on the productivity of continuous printing, but fan control by the second pre-separating unit 312 ensures sufficient time to perform the floating step and the separating step. More specifically, fan control by the second pre-separating unit 312 is performed after a multi-feed is detected and a recovery operation by the user is detected, but before continuous printing starts (before resuming), so that the time required to perform the floating step and the separating step can be ensured without being limited by the productivity of continuous printing.

[0095] Fig. 14 is a timing chart of fan control by first pre-sorting unit 311. Fig. 15 is a timing chart of fan control by second pre-sorting unit 312. First pre-sorting unit 311 and second pre-sorting unit 312 output commands 61a, 62a, and 63a for fan control. Tip fan 14, suction fan 154, and side fans (side fans 13L, 13R) are controlled to change either or both of the airflow direction and air volume in accordance with commands 61a, 62a, and 63a, respectively.

[0096] 14, first pre-sorting unit 311 controls side fans 13L, 13R to repeatedly execute a control cycle consisting of a period in which side fans 13L, 13R are operated (period of level H in FIG. 14) and a period in which they are stopped (period of level L in FIG. 14). First pre-sorting unit 311 also controls front end fan 14 to repeatedly execute a cycle consisting of a period in which front end fan 14 is operated as a levitation fan and a period in which front end fan 14 is operated as a sorting fan. As shown in FIG. 14, first pre-sorting unit 311 controls each fan to synchronize the control cycle of front end fan 14 with control cycle 66 of side fans 13L, 13R.

[0097] Referring to FIG. 15, the second pre-separator 312 performs a separation operation on the sheets P of the sheet stack. More specifically, the second pre-separator 312 controls the side fans 13L, 13R to repeatedly execute a control cycle consisting of a period during which the side fans 13L, 13R are operated (the period of level H in FIG. 15) and a period during which the side fans 13L, 13R are stopped (the period of level L in FIG. 15). The second pre-separator 312 also controls the front end fan 14 to repeatedly execute a cycle consisting of a period during which the front end fan 14 is operated as a levitation fan and a period during which the front end fan 14 is operated as a separation fan. As shown in FIG. 15, the second pre-separator 312 controls each fan so that the control cycle 67 of the side fans 13L, 13R is synchronized with the control cycle 66 of the front end fan 14. The control cycle 67 of the second pre-separator 312 is set to be longer than the control cycle 66 of the first pre-separator 311.

[0098] The first pre-separating unit 311 and the second pre-separating unit 312 control the side fans 13L, 13R and the front end fan 14 so that the floating and separating operations of the sheets P are repeated, thereby enabling the stack of sheets to be separated in a manner equivalent to manual separation. In Figures 14 and 15, the lengths of the operating and stopped periods of the side fans 13L, 13R in the control cycle 66 are approximately equal to the lengths of the periods in which the front end fan 14 operates as a floating fan and a separating fan, respectively, but the lengths of both periods do not have to be equal. Also, in Figures 14 and 15, the length of the control cycle 66 (control cycle 67) of the side fans 13L, 13R is equal to the length of the control cycle of the corresponding front end fan 14, but the lengths of both control cycles do not have to be equal.

[0099] Also, in FIG. 15, the second pre-separation unit 312 operates the tip fan 14 as a levitation fan in a control cycle such that the length of the period during which the tip fan 14 operates as a separation fan matches the length of the period during which the tip fan 14 operates as a separation fan, but the lengths of these operating periods may be different.

[0100] Furthermore, since the first pre-separator 311 controls the fan during continuous printing, as shown in FIG. 14, when the floating of the sheet P is completed, i.e., when the adsorption of the sheet P to the belt 153 is detected based on the output of the adsorption sensor, the function of the leading edge fan 14 is switched from the floating fan to the separation fan. FIG. 14 shows the timing T when the adsorption of the sheet P is detected. In contrast, the second pre-separator 312 performs fan control when a multifeed is detected and a recovery operation is detected, i.e., before continuous printing (or after continuous printing), so that sufficient time can be provided to separate the stack of sheets, regardless of the degree of floating of the sheet P. As shown in FIG. 15, the second pre-separator 312 can operate the leading edge fan 14 as a floating fan for a certain period of time during the control cycle to fully separate the stack of sheets.

[0101] Fig. 16 is a diagram illustrating a fan control method according to the present embodiment. Referring to Fig. 16, the procedure by which the second pre-separating unit 312 controls the fan based on the determination result of the overlap determination unit 351 will be described. Fig. 16 shows the leading edge deviation amount G output from the deviation amount calculation unit 352 for each of the cases of early double feeding and exact double feeding determined based on the threshold value TH, and which of the first pre-separating unit 311 and the second pre-separating unit 312 will perform fan control in that case.

[0102] 16, when a double feed is detected and overlap determination unit 351 determines that the double feed is exact, fan control unit 300 activates second pre-separation unit 312 out of first pre-separation unit 311 and second pre-separation unit 312. As a result, when exact double feed is detected, second pre-separation unit 312 controls the fan to provide sufficient time for separating the stack of sheets, thereby enabling the stack of sheets in tray 21 to be separated sufficiently. As a result, it is possible to avoid the occurrence of a double feed when a job is subsequently executed (continuous printing is performed).

[0103] In contrast, when the overlap determining unit 351 determines that the first feeding is a double feeding, the fan control unit 300 does not start the second pre-sorting unit 312 but starts the first pre-sorting unit 311 instead.

[0104] In this way, when the leading edge deviation amount G when a double feed occurs is small, i.e., when the adhesion between sheets P in the sheet stack in tray 21 is strong, second pre-separator 312 is activated to control the fans to provide sufficient time for separating the sheet stack. In this case, to improve the sheet stack separation effect, second pre-separator 312 may control at least one of side fans 13L, 13R and leading edge fan 14 to operate more frequently per unit time, in other words, to repeat short control cycle 67 more times. Alternatively, at least one of side fans 13L, 13R and leading edge fan 14 may be controlled to increase the airflow during operation, i.e., to increase the fan rotation speed.

[0105] In contrast, when the leading edge deviation G is large when a multifeed occurs, i.e., when the adhesion between the sheets P in the stack of sheets in the tray 21 is weak, the number of times the fan operated by the second pre-separating unit 312 operates per unit time is reduced compared to when the leading edge deviation G is small. This reduces the time required to resume a printing operation that was stopped due to the detection of a multifeed, thereby maintaining user convenience. Also, in this case, the number of rotations (air volume) of the fan operated by the second pre-separating unit 312 is reduced compared to when the leading edge deviation G is small. This prevents the sheets P from adhering to each other more closely due to strong air pressure. Therefore, when the printing operation is resumed, the possibility of early multifeed occurring can be reduced.

[0106] FIG. 17 is a diagram showing an application example of the fan control procedure according to this embodiment. (A), (B), and (C) of FIG. 17 show sheets (1) to (5) on which images are formed as sheets P fed when a print job is executed. (A) of FIG. 17 shows a case in which sheets (1) to (5) are fed one by one from tray 21 to conveyance section 16, and no multi-feeding occurs. In (A) of FIG. 17, fan control for pre-sorting by first pre-sorting section 311 is performed for each sheet feed. In (B) of FIG. 17, multi-feeding is detected when the third sheet (3) is fed from tray 21 to conveyance section 16. Therefore, before printing of the third sheet of paper (3) is resumed, the second pre-handling section 312 performs fan control for the second pre-handling, and then, when printing is resumed, the first pre-handling section 311 performs fan control for the first pre-handling, and image formation (printing) on ​​the sheet of paper (3) is resumed.

[0107] 17(C), fan control for the second pre-separation is performed, and then a multi-feed is detected again. More specifically, a multi-feed occurs when the third sheet (3) is fed from tray 21 to conveyance section 16, and fan control for the second pre-separation is performed by second pre-separation section 312. Then, printing of sheet (3) is resumed, and a multi-feed is detected again.

[0108] In this case, even if fan control for the second pre-separation is performed again, the stack of sheets may not be separated sufficiently, and multiple feeding may occur again. In step DS1, fan control unit 300 controls notification unit 370 to display a message on operation panel 115 urging the user to reload the sheets. This prompts the user to check the state of the stack of sheets in tray 21, and the user performs a recovery operation. When the recovery operation is detected, control unit 200 first activates first pre-separation unit 311 to resume printing, and controls fan control for the first pre-separation. As a result, in FIG. 17(C), printing of sheets (3) and onward is performed normally after the recovery operation (after the notification).

[0109] In this embodiment, when a multifeed is detected during continuous printing, the second pre-separating unit 312 performs fan control for the second pre-separating. However, if the number of remaining prints is equal to or less than a predetermined value, the fan control for the second pre-separating may be omitted (not performed) and the printing operation may continue. For example, in (B) of FIG. 17, when the number of remaining prints after detecting a multifeed, which is three sheets, is equal to or less than the predetermined value, the fan control by the second pre-separating is not performed and the image forming apparatus 100 continues the printing operation. This allows productivity related to continuous printing to be maintained.

[0110] 18 is a diagram illustrating an example of fan control based on paper size according to the present embodiment. Paper size detection unit 380 detects the size of paper P sent from tray 21 to transport unit 16. More specifically, sensor 45 provided on tray 21 is composed of a push-type sensor and a mechanism that moves in conjunction with the movement of regulating plate member 12 that regulates the position of the paper stack held by tray 21, and paper size detection unit 380 detects the size of paper stored in tray 21 based on the output of sensor 45.

[0111] The second pre-separator 312 controls the fan based on the sheet size detected by the sheet size detector 380. The sheets PS in the lower tier in FIG. 18 are shorter than the sheets PL in the lower tier by a length LN. When a stack of long sheets PL is set in the tray 21, the sheet size is larger than when short sheets PS are set, and the time required for fan control to separate the sheets increases. In this embodiment, when a double feed is detected or when a large sheet PL is detected by the sheet size detector 380, the second pre-separator 312 controls the fan to increase the number of repetitions of the second pre-separator control cycle 67 or to increase the fan airflow, similar to the fan control procedure shown in FIG. 16. This allows the fan control of the second pre-separator 312 to maintain the sheet separation performance regardless of the size of the sheets P. Note that in FIG. 18, the width parallel to the conveyance direction of the sheets P is used as the sheet size, but the width extending in a direction intersecting (perpendicular to) the conveyance direction may also be used, or a combination of these may be used.

[0112] 19 and 20 are flowcharts of the fan control process according to this embodiment. In this process, a flag F stored in RAM 205 is used as a control variable. Flag F is set to "ON" when second pre-separation fan control is performed by second pre-separation unit 312 during job execution. The fan controlled here is the fan of the tray 21 specified by the job or the tray 21 in which paper of the size specified by the job is set.

[0113] First, when a job is started, the CPU 201 sets "OFF" to the flag F. The CPU 201 controls the fan of the tray 21 as the first pre-separating unit 311 (step S1), and controls the suction conveying unit 15 to feed the paper P that has floated from the tray 21, i.e., to send it to the conveying unit 16 (step S3).

[0114] CPU 201, functioning as multi-feed detection unit 350, determines whether or not multi-feeding has been detected (step S5). If it is determined that multi-feeding has not been detected (NO in step S5), CPU 201 determines whether or not it is necessary to form an image on the next sheet P based on the job, i.e., whether or not to end execution of the job (step S7). If it is determined that it is necessary to form an image on the next sheet P, i.e., to continue execution of the job (YES in step S7), the process returns to step S1. On the other hand, if it is determined that it is not necessary to form an image on the next sheet P, i.e., to end execution of the job (NO in step S7), the process ends.

[0115] If it is determined that a double feed has been detected (YES in step S5), CPU 201, as misalignment amount calculation unit 352, calculates the leading edge misalignment amount G (step S11) and performs a process to remove the double-fed sheets P (step S13). This process may be performed automatically or manually. In the manual process, CPU 201, as notification unit 370, outputs a notification that a double feed has occurred.

[0116] When the CPU 102 detects a user's recovery operation as the recovery detection unit 360, it determines whether the flag F is "ON" (step S15). When the CPU 102 determines that the flag F indicates "ON" (YES in step S15), it causes the notification unit 370 to display a notification urging the user to reset (step S17). The CPU 201 detects the user's reset operation based on the detection signals 51, 551 from the open / close sensor 50 and the set sensor 55 (step S19), and returns to step S1.

[0117] When CPU 102 determines that flag F indicates "OFF" (NO in step S15), CPU 201, functioning as overlap determination unit 351, determines whether leading edge deviation amount G and threshold value TH satisfy the condition (leading edge deviation amount G≦TH) (step S21). When CPU 201 determines that this condition is not satisfied (NO in step S21), that is, when it determines that the detected multifeed is early multifeed, it returns to step S1 without performing the second pre-sorting.

[0118] On the other hand, if the CPU 201 determines that the above conditions are met (YES in step S21), that is, if the detected multi-feed is exact multi-feed, the CPU 201 controls the fan for second pre-sorting as the second pre-sorting unit 312 (step S23). When performing second pre-sorting, the CPU 201 sets flag F to "ON". Then, the process returns to step S1.

[0119] The second pre-sorting process of step S23 will be described in detail with reference to FIG. 20. The CPU 201, as the second pre-sorting unit 312, determines the number of times the control cycle 67 is to be repeated based on the leading edge deviation amount G (step S25). The CPU 201 performs the second pre-sorting as shown in FIG. 15. More specifically, the CPU 201, as the second pre-sorting unit 312, switches the leading edge fan 14 between the floating fan and the sorting fan in each control cycle 67 the number of times determined in step S21 (step S27). This periodically switches the airflow direction of the leading edge fan 14 relative to the stack of sheets in the tray 21. The CPU 201, as the second pre-sorting unit 312, also switches the side fans 13L and 13R on and off (operated and stopped) in each control cycle 67 the number of times determined in step S21 (step S29).

[0120] The above-described fan control methods by the second pre-separating unit 312 can be implemented in any suitable combination. According to the embodiment, when a double feed is detected, the fan can be controlled according to the overlap state (the result of the determination in step S21), that is, based on the leading edge deviation amount G. Furthermore, when a double feed is detected, the second pre-separating unit 312 repeatedly performs a floating step for floating the sheets P and a separating step for separating the sheets P on the stack of sheets in the tray 21, thereby preventing the occurrence of a double feed when the printing operation is subsequently resumed.

[0121] <Programs and storage media> In this embodiment, the program may be stored in storage medium 223 instead of ROM 202 or HDD 210. Storage medium 223 may be implemented by a non-volatile storage medium such as a CD-ROM (Compact Disc - Read Only Memory), a DVD-ROM (Digital Versatile Disk - Read Only Memory), a USB (Universal Serial Bus) memory, a memory card, a Flexible Disk (FD), a magnetic tape, a tray tape, a Magnetic Optical Disc (MO), a Mini Disc (MD), an IC (Integrated Circuit) card (excluding memory cards), an optical card, a mask ROM, an EPROM, or an EEPROM (Electronically Erasable Programmable Read-Only Memory). Image forming apparatus 100 may also acquire the program by downloading it via a communication line (not shown) and communication I / F 215, for example.

[0122] Furthermore, the program may be provided not as a standalone program but as part of an arbitrary program. In this case, the processing according to each embodiment is realized in cooperation with the arbitrary program. Even if the program does not include some of the modules, it does not deviate from the spirit of the program according to each embodiment. Furthermore, the image forming apparatus 100 may be configured in the form of a so-called cloud service in which at least one server executes part of the processing of the program.

[0123] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0124] 14 Front fan, 13L, 13R Side fans, 100 Image forming device, 105 Image reading unit, 110 Image forming unit, 154 Suction fan, 200 Control unit, 202 ROM, 205 RAM, 300 Fan control unit, 311 First pre-separating unit, 312 Second pre-separating unit, 320 Air volume change unit, 350 Double feed detection unit, 351 Overlap determination unit, 352 Misalignment amount calculation unit, 360 Recovery detection unit, 370 Notification unit, 380 Paper size detection unit.

Claims

1. A sheet feeding device that feeds sheets from a tray to a conveying path, a fan that is provided so as to be able to blow air toward the edge of the sheet of the sheet stack placed on the tray; a fan control unit that controls the fan; a double feed detection unit that detects double feeding of conveyed sheets, the fan includes a first fan and a second fan that blows air in a direction to lift the sheets from the sheet stack; the first fan is configured to be able to switch between a function as a separating fan that blows air in a direction to separate the sheets that have floated from the sheet stack, and a function as a floating fan that blows air in a direction to float the sheets of the sheet stack, The fan control unit In order to supply the sheet from the tray to the conveying path, the second fan is switched from operation to stop, and this switching is set as one cycle, and in this cycle, in synchronization with the switching, the function of the first fan is switched from the floating fan to the separating fan, and switching control of the fan is performed; When a double feed of sheets supplied to the conveying path and conveyed is detected, the fan control unit sets the period to a value indicating that the amount of misalignment of the leading edges of the overlapping sheets in the double feed is equal to or less than a threshold value, and sets a period longer than the other period set when the amount of misalignment of the leading edges of the overlapping sheets is greater than the threshold value.

2. The sheet feeding device according to claim 1 , wherein, when the multi-feeding is detected, the fan control unit determines the number of times to repeat the cycle in accordance with the amount of misalignment of leading edges of the overlapping sheets in the multi-feeding.

3. The sheet supply device according to claim 1 or 2, wherein when the double feed is detected, the fan control unit controls the fans so that the amount of air blown by at least one of the first fan and the second fan changes based on the amount of misalignment of the leading edges of the overlapping sheets in the double feed when performing fan switching control.

4. The fan control unit The sheet feeding device according to claim 1 , further comprising: a predetermined notification output when the multi-feed is detected.

5. 5. The sheet supply device according to claim 1, wherein when the double feed is detected, the fan control unit stops supplying sheets to the conveying path and performs switching control of the fan when the amount of misalignment of the leading edges of the overlapping sheets in the double feed is less than a threshold value.

6. When the fan control unit detects that the amount of deviation of the leading edges of the overlapping sheets in the multi-feed is equal to or less than a threshold, the fan control unit performs the fan switching control, The sheet feeding device according to claim 1 , wherein at least one of the number of times the cycle is repeated and the amount of air blown by the fan is adjusted based on the size of the sheet.

7. The fan control unit 7. The sheet supply device according to claim 1, wherein when starting to supply sheets from the tray to the conveying path, the first fan and the second fan are controlled to blow air toward the edge of the sheet of the sheet stack placed on the tray in a direction that causes the sheet to float.

8. 8. An image forming apparatus comprising: the sheet supplying device according to claim 1; and an image forming section that forms an image on the sheet supplied from the sheet supplying device to the conveying path.

9. A method for controlling an apparatus for feeding sheets from a tray to a conveying path, comprising: the device has a fan that is provided so as to be able to blow air toward the edge of the sheet of the sheet stack placed on the tray, the fan includes a first fan and a second fan that blows air in a direction to lift the sheets from the sheet stack; the first fan is configured to be able to switch between a function as a separating fan that blows air in a direction to separate the sheets that have floated from the sheet stack, and a function as a floating fan that blows air in a direction to float the sheets of the sheet stack, The method comprises: detecting that a double feed of sheets being conveyed has occurred; a step of switching the second fan from operation to stop in order to supply the sheet from the tray to the conveying path, setting the switching as one cycle, and performing switching control of the fan so that the function of the first fan is switched from the floating fan to the separation fan in synchronization with the switching in the cycle, The step of performing the switching control includes, when a double feed of sheets supplied to the conveying path and conveyed is detected, setting the period as the period when it indicates that the amount of misalignment of the leading edges of the overlapping sheets in the double feed is equal to or less than a threshold value, and setting a period longer than other periods set when it indicates that the amount of misalignment of the leading edges is greater than the threshold value.

10. The method according to claim 9 , wherein the step of performing the switching control includes a step of determining, when the multi-feed is detected, the number of times to repeat the cycle according to the amount of misalignment of leading edges of overlapping sheets in the multi-feed.

11. A program causing a computer to execute a method for controlling a device for feeding sheets from a tray to a conveying path, comprising: the device has a fan that is provided so as to be able to blow air toward the edge of the sheet of the sheet stack placed on the tray, the fan includes a first fan and a second fan that blows air in a direction to lift the sheets from the sheet stack; the first fan is configured to be able to switch between a function as a separating fan that blows air in a direction to separate the sheets that have floated from the sheet stack, and a function as a floating fan that blows air in a direction to float the sheets of the sheet stack, The method comprises: detecting that a double feed of sheets being conveyed has occurred; a step of switching the second fan from operation to stop in order to supply the sheet from the tray to the conveying path, setting the switching as one cycle, and performing switching control of the fan so that the function of the first fan is switched from the floating fan to the separation fan in synchronization with the switching in the cycle, The step of performing the switching control includes a step of, when a double feed of sheets supplied to the conveying path and conveyed is detected, setting the period as the period when it indicates that the amount of misalignment of the leading edges of the overlapping sheets in the double feed is equal to or less than a threshold value, and setting a period longer than other periods set when it indicates that the amount of misalignment of the leading edges is greater than the threshold value, in the program.

12. The program according to claim 11 , wherein the step of performing the switching control includes a step of determining, when the multifeed is detected, the number of times to repeat the cycle in accordance with the amount of misalignment of leading edges of the overlapping sheets in the multifeed.

Images