JP2012246138A - Sheet feeder and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeder capable of preventing the double feeding of sheets without causing an increase in cost, and to provide an image forming apparatus.SOLUTION: Air is blown by a draining nozzle 33 to side surfaces of the sheets supported by a tray 12 to float the sheets, and also, air is blown by a separation nozzle 34 to the floated sheets to separate the sheet Sa placed at the uppermost position among the floated sheets. Then, the separated uppermost sheet Sa is sucked and conveyed by a sucking/conveying belt 21, and then, conveyed by a pair of conveying rollers 42 provided at the downstream side of the sucking/conveying belt 21 in the sheet feeding direction. Then, after the uppermost sheet Sa reaches the pair of conveying rollers 42, a loop is formed in the uppermost sheet Sa between the sucking/conveying belt 21 and the pair of conveying rollers 42, and then, air is blown from the separation nozzle 34 to the loop SL of the uppermost sheet Sa.

Description

  The present invention relates to a sheet feeding apparatus and an image forming apparatus, and more particularly to a sheet feeding and separating sheet by blowing air onto the sheet.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a printer or a copying machine includes a sheet feeding device that feeds sheets one by one from a sheet storage unit in which a plurality of sheets are stored. As such a sheet feeding device, air is blown to the end of a sheet bundle stored in the sheet storage unit to float a plurality of sheets, and the sheet is adsorbed to an adsorption conveyance belt disposed above. There is an air feed type that feeds.

  Such an air feeding type sheet feeding apparatus blows air to the end portion of a sheet bundle to float a plurality of sheets and separates the sheets one by one, and sucks and conveys the sheets. And a suction conveyance unit having a tension belt for feeding.

  By the way, in such a sheet feeding apparatus, in order to reliably separate and feed the sheets, that is, in order to prevent double feeding of the sheets, for example, in the vertical direction between the tension belt for feeding and the uppermost sheet. There is one provided with a movable pressing member (see Patent Document 1). The uppermost sheet is pressed by this pressing member, thereby preventing the flow of air blown between the uppermost sheet and the sheet immediately below. Here, by blocking the flow of air in this way, the uppermost sheet swells upward, and the uppermost sheet and the sheet immediately below are reliably separated.

JP 2007-223700 A

  By the way, in the conventional sheet feeding apparatus, if the sheet is separated and fed while the uppermost sheet is pressed by the pressing member, the following problems occur. In some cases, the uppermost sheet and the sheet directly below the sheet are shifted and overlapped at the same time due to a cutting burr generated when cutting the sheet or an increase in frictional force. That is, there is a problem that the sheets cannot be reliably separated and are sent out in a state where the sheets are overlapped.

  Accordingly, the present invention has been made in view of such a current situation, and an object thereof is to provide a sheet feeding apparatus and an image forming apparatus that can prevent double feeding of sheets without causing an increase in cost. It is what.

The present invention relates to a tray that can be moved up and down to support a sheet, and the sheet supported by the tray is floated and air is blown to an end portion of the sheet in order to separate the uppermost sheet among the sheets that have been rolled. An air blowing unit, an adsorption conveyance unit that adsorbs and conveys the separated uppermost sheet, and an uppermost sheet that is provided downstream of the adsorption conveyance unit in the sheet conveyance direction and conveys the uppermost sheet. A sheet conveyance unit; and a controller that controls the suction conveyance unit and the sheet conveyance unit, and the control unit is configured such that the uppermost sheet reaches the uppermost sheet after the uppermost sheet reaches the sheet conveyance unit. The suction conveyance unit and the sheet conveyance unit are controlled so as to form a loop between the sheet conveyance unit and the sheet conveyance unit.
Is.

  As in the present invention, after the uppermost sheet reaches the sheet conveying section, a loop is formed between the suction conveying section and the sheet conveying section, and the uppermost sheet and the sheet immediately below are separated, thereby increasing the cost. The sheet can be prevented from being fed multiple times without incurring.

1 is a diagram illustrating a schematic configuration of an image forming apparatus including a sheet feeding device according to an embodiment of the present invention. The figure which shows the structure of the said sheet feeding apparatus. FIG. 6 is a first diagram illustrating a sheet feeding operation of the sheet feeding apparatus. FIG. 9 is a second diagram illustrating a sheet feeding operation of the sheet feeding apparatus. FIG. 10 is a third diagram illustrating the sheet feeding operation of the sheet feeding apparatus. The control block diagram of the said sheet feeding apparatus. 6 is a timing chart for explaining a sheet feeding operation of the sheet feeding apparatus. 6 is a flowchart for explaining a sheet feeding operation of the sheet feeding apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus including a sheet feeding device according to an embodiment of the present invention.

  In FIG. 1, reference numeral 1000 denotes an image forming apparatus, 1001 denotes an image forming apparatus main body constituting the image forming apparatus 1000, and a sheet feeding unit 700 is connected to one side of the image forming apparatus main body 1001. Further, a sheet processing apparatus 800 that performs a folding process, a stapling process, a punching process, a bookbinding process, and the like is connected to the other side of the image forming apparatus main body 1001 with respect to a sheet output from the image forming apparatus main body 1001. Further, an image reading device 200 including a document feeding device 100 for feeding a document to a platen glass (not shown) is provided on the upper part of the image forming apparatus main body 1001.

  Further, inside the image forming apparatus main body 1001, an image forming unit 101 including a cylindrical photosensitive drum 111, a developing device 113, and the like, a fixing unit 177 disposed on the downstream side of the image forming unit 101, and A discharge roller pair 180 and the like are provided. Further, a sheet feeding device 120 that feeds sheets S such as paper and OHT stored in the paper feeding cassettes 114 and 115 is provided at the lower part of the image forming apparatus main body 1001. A control unit 300 that controls the operation of the image reading apparatus 200, the image forming unit 101, the sheet feeding unit 700, the sheet processing apparatus 800, and the like with a predetermined program is provided at a predetermined position of the image forming apparatus main body 1001. Yes.

  The sheet feeding unit 700 includes sheet storage decks 701 and 702 that are detachably provided in the unit main body 700A, and a sheet feeding device 120 that feeds out the sheets S stored in the sheet storage decks 701 and 702. Yes.

  When an image is formed by the image forming apparatus 1000 configured as described above, first, an original (not shown) is automatically sent to the platen glass by the original feeder 100, and an image including the scanner unit 104, the image sensor 109, and the like. Image information is read by the reading unit. The read image information is processed by the control unit 300 and sent to the exposure control unit 110.

  Then, the exposure control unit 110 outputs a laser beam based on the processing result, and the surface of the photosensitive drum 111 is exposed by the laser beam, whereby an electrostatic latent image is formed on the photosensitive drum 111. Thereafter, the electrostatic latent image on the photosensitive drum 111 is developed by the developing unit 113, and as a result, a toner image is formed on the photosensitive drum 111.

  On the other hand, the sheets S stored in the sheet feeding cassettes 114 and 115 in parallel with the toner image forming operation or the sheets stored in the sheet storage decks 701 and 702 of the sheet feeding unit 700 are transferred to the sheet feeding device. 120 is fed to the image forming unit 101. Then, the toner image on the photosensitive drum 111 is transferred to the sheet in the transfer unit 116, and the sheet on which the toner image is transferred in this manner is conveyed to the fixing unit 177, and the toner image is fixed in the fixing unit 177. Thereafter, the sheet is conveyed to the sheet processing apparatus 800.

  FIG. 2 is a diagram illustrating a configuration of the sheet storage deck 702 and the sheet feeding device 120 of the sheet feeding unit 700. The sheet feeding device 120 provided in the image forming apparatus main body 1001 and the sheet storage deck 701 has the same configuration.

  The sheet storage deck 702 includes a sheet storage 11 that can be pulled out by the slide rail 15. The sheet storage 11 includes an elevating tray 12 on which a plurality of sheets S are placed and supported. When the sheet storage 11 is pulled out, the tray 12 is lowered to a predetermined position and the sheet is stored. Can be replenished or replaced.

  The sheet storage 11 is provided with a rear end regulating plate 13 that is a rear end regulating member that abuts the rear end, which is the upstream end of the sheet S in the sheet feeding direction, and regulates the rear end position of the sheet S. ing. The sheet storage 11 includes a front end restricting plate 17 that restricts the front end of the sheet that is the downstream end in the sheet feeding direction, and a restriction that restricts the position of the sheet S in the width direction that is orthogonal to the sheet feeding direction. A side end regulating plate 14 and a slide rail 15 which are members are provided. The rear end regulating plate 13 and the side end regulating plate 14 are configured such that the positions can be arbitrarily changed depending on the size of the sheet S to be stored.

  Further, an air feeding type sheet feeding mechanism (hereinafter referred to as an air feeding mechanism) 150 for separating and feeding the sheets one by one is disposed on the upper portion of the sheet storage case 11. The air sheet feeding mechanism 150 floats and separates the upper portion of the sheet bundle on the tray, and separates the sheets S one by one while sucking and conveying the sheets S stacked on the tray 12. The air spraying part 152 is provided.

  Here, the suction conveyance unit 151 is stretched over the belt driving roller 41 and rotates in the direction of the arrow P, so that the suction conveyance belt 21 that adsorbs and conveys the sheet S, and the adsorption conveyance belt 21 adsorbs the sheet S. The suction fan 36 that generates the negative pressure is provided. Here, a plurality of the suction conveyance belts 21 are arranged at a predetermined interval in the width direction, and the belt drive roller 41 is rotated by an adsorption conveyance belt drive motor 21M shown in FIG. Rotate in P direction.

  Further, the suction duct 51 is provided inside the suction conveyance belt 21 and sucks air through a suction hole (not shown) formed in the suction conveyance belt 21. The suction duct 51 is provided with a suction shutter 37 for turning ON / OFF the suction operation of the suction conveyance belt 21 and a suction fan 36 as a negative pressure generating unit.

  The air blowing unit 152 is configured to blow the air from the side surface on the front end side to the upper portion of the sheet bundle, the separation nozzle 34, the separation fan 31, and the air from the separation fan 31 to the nozzles 33 and 34. Is provided with a separation duct 32. A part of the air sucked by the separation fan 31 passes through the separation duct 32 and is blown in the direction of the arrow C by the firing nozzle 33, and several sheets of the upper part of the sheet S stacked on the tray 12 are floated. Let

  The other air is blown in the direction of arrow D by the separation nozzle 34 that constitutes the separation part that blows air to the edge of the sheet that has been blown, and the sheet that has been blown and floated by the separation nozzle 33 that constitutes the separation part 1 The sheets are separated one by one and adsorbed onto the adsorption conveyance belt 21. Reference numeral 52 denotes a sheet surface detection sensor that detects that the sheet has reached the feedable position, and reference numeral 56 denotes an adsorption completion sensor that indicates that the uppermost sheet Sa has been adsorbed by the adsorption conveyance belt 21.

  Next, a sheet feeding operation of the sheet feeding device 120 (air feeding mechanism 150) configured as described above will be described. First, when the user pulls out the sheet storage case 11 to set the sheet S and then stores the sheet storage case 11, the tray 12 starts to rise in the direction of arrow A as shown in FIG. Eventually, when reaching the feedable position where the distance between the uppermost sheet Sa stacked on the tray 12 and the suction conveyance belt 21 becomes B, the sheet surface detection sensor 52 detects this and outputs a detection signal to the control unit. To do. Then, the CPU 301 shown in FIG. 6 to be described later stops the tray 12 at this feedable position based on this detection signal, and then prepares for a sheet feed signal for starting feeding.

  Next, when the sheet feeding signal is detected, the CPU 301 operates the separation fan 31 and sucks air in the direction indicated by the arrow E. The air is blown onto the sheet bundle from the directions of arrows C and D by the firing nozzle 33 and the separation nozzle 34 through the separation duct 32, respectively. As a result, as shown in FIG. 3B, several sheets S1 to S3 including the uppermost sheet Sa of the sheet bundle and the second sheet from the top (hereinafter referred to as a sheet immediately below) Sb float. To do. Further, the CPU 301 operates the suction fan 36 and discharges air in the arrow F direction.

  At this time, the suction shutter 37, which is a suction switching unit that can be switched to a suction position that sucks the sheet with negative pressure and a blocking position that blocks the negative pressure, is closed, that is, in the blocking position. Sa is not adsorbed by the adsorbing and conveying belt 21.

  Next, when a predetermined time elapses after the sheet feeding signal is detected and the floating of the upper several sheets is stabilized, the CPU 301 drives a suction shutter solenoid 37SL shown in FIG. (A), the suction shutter 37 is rotated in the direction of arrow G. As a result, the suction shutter 37 is switched to the suction position where the sheet is sucked by the negative pressure, the suction duct 51 is opened, and air is sucked in the direction of the arrow H from the suction hole provided in the suction conveyance belt 21, and the suction force is increased. appear. Only the uppermost sheet Sa is adsorbed to the adsorbing and conveying belt 21 by the adsorbing force and the separation air from the separation nozzle 33b.

  Next, when the suction completion detection sensor 56 detects that the uppermost sheet Sa has been sucked by the suction conveyance belt 21, the CPU 301 drives the suction conveyance belt drive motor 21M, and the belt as shown in FIG. The drive roller 41 is rotated in the arrow J direction. As a result, the suction conveyance belt 21 rotates in the direction of the arrow P, and the uppermost sheet Sa is fed in the direction of the arrow K while being sucked by the suction conveyance belt 21, and thereafter, the conveyance rotates in the directions of the arrows L and M. A pair of rollers (drawing roller pair) 42 is conveyed toward the image forming unit. A detection sensor 54 is provided downstream of the conveyance roller pair 42 which is a sheet conveyance unit provided on the downstream side of the suction conveyance unit 151 in the sheet feeding direction, and the CPU 301 causes the CPU 301 to detect the sheet Sa. Monitor the passage.

  By the way, when the uppermost sheet Sa is adsorbed to the adsorbing and conveying belt 21 and conveyed, it is fed in a state in which the sheet Sb directly below adheres to the uppermost sheet Sa due to an increase in sheet cutting burr or frictional force. May be. Therefore, in the present embodiment, as shown in FIG. 5, the uppermost sheet Sa is conveyed while forming a loop upward in the conveyance path between the suction conveyance belt 21 and the conveyance roller pair 42. .

  Then, by conveying the uppermost sheet Sa while forming a loop in this way, the air sent from the separation nozzle 34 is interposed between the loop portion of the uppermost sheet Sa and the front end of the sheet Sb immediately below. You can get in. Furthermore, even when the uppermost sheet Sa and the immediately lower sheet Sb are sent out with a small amount of deviation, the amount of loop formed between the uppermost sheet Sa and the immediately lower sheet Sb is different. Therefore, the adhesion between the sheets is released due to the difference in the loop amount. Therefore, the separation performance of the sheet feeding device can be improved.

  FIG. 6 is a control block diagram of the sheet feeding apparatus 120 according to the present embodiment. As illustrated in FIG. 6, the control unit 300 includes a CPU 301, a ROM 302 that stores a sequence and the like necessary for control, a RAM 303 that stores setting values and the like necessary for control, a timer 304, and an ASIC 310.

  The ASIC 310 includes a motor control unit 311, a solenoid control unit 312 that controls the suction shutter solenoid 37SL, a sheet surface detection sensor 52, a detection sensor 54, and an I / O control unit 313 to which signals from the suction completion detection sensor 56 are input. ing. Then, signals from each sensor are notified to the CPU 301 via the I / O control unit 313. Further, the ASIC 310 includes a high pressure control unit 314 that controls high pressure such as development, charging, and transfer, and a fan control unit 315 that drives the separation fan 31 and the suction fan 36.

  Here, the motor control unit 311 controls the speed and rotation direction of various motors such as the lifter drive motor 12M that raises and lowers the tray 12, the suction conveyance belt drive motor 21M, and the conveyance roller drive motor 42M. In the present embodiment, when the lifter is lowered, the stepper motor or DC is used as the lifter drive motor 12M so that the stepping operation of stopping the tray 12 for a predetermined time after being lowered for a predetermined time can be repeatedly lowered. Servo motor is used.

  By the way, in the present embodiment, the CPU 301 (control unit 300) shifts the timing of driving the conveyance roller drive motor 42M and the adsorption conveyance belt drive motor 21M via the motor control unit 311 when conveying the sheet by adsorption. . That is, as shown in FIG. 7, the timing for starting the driving of the conveying roller driving motor 42M is set later than the timing for starting the driving of the suction conveying belt driving motor 21M. That is, the driving of the conveying roller driving motor 42M is started after the driving of the suction conveying belt driving motor 21M is started and the uppermost sheet Sa reaches the conveying roller pair 42. Thus, by delaying the timing for starting the driving of the conveying roller driving motor 42M, the uppermost sheet Sa is looped upward between the suction conveying belt 21 and the conveying roller pair 42 as shown in FIG. Can be formed.

  Further, when the uppermost sheet Sa reaches the conveyance roller pair 42 and the detection sensor 54 detects this, the suction shutter solenoid 37SL is turned OFF and the suction shutter 37 is closed after a predetermined time (Ymsec) has passed. When the suction shutter 37 is closed in this manner, the suction conveyance belt 21 loses the suction conveyance force, and thereafter, the uppermost sheet Sa is conveyed only by the conveyance roller pair 42, so that the formed loop is eliminated. The

  Next, the sheet feeding operation of the sheet feeding apparatus 120 according to the present embodiment will be described with reference to the flowchart shown in FIG.

  First, before starting sheet feeding, the sheet loop amount is determined from various conditions (sheet loop amount determining means) (S401). When the stiffness of the sheet is low, a loop at the leading end of the sheet is easily formed, and by increasing the amount of the loop, the shape of the loop of the uppermost sheet Sa and the sheet Sb immediately below is different. On the other hand, when the stiffness of the sheet is high, even if the loop at the leading end of the sheet is small, the top sheet Sa and the sheet Sb directly below are different in shape.

For this reason, for example, when the surface property of the sheet is low such as coated paper or small basis weight (60 g / mm ² or less), the sheet loop amount is controlled to be large. In addition, since the rigidity of the sheet increases as the basis weight of the sheet increases, in the case of thick paper having a large basis weight (100 g / mm ² or more), the sheet loop amount is decreased. Thus, sheet separation performance can be further enhanced by determining the loop formation amount in accordance with various conditions such as sheet shape, surface properties, basis weight and the like.

Next, after the sheet loop amount is determined, the suction conveyance belt drive motor 21M is activated at the timing to be fed (S402). Thereafter, when a predetermined time Xmsec shown in FIG. 7 has elapsed (Y in S403), the conveyance is performed. The roller drive motor 42M is activated (S404). Here, Xmsec, which is the timing for starting the driving of the conveying roller pair 42, is set so as to satisfy the following conditions.
Xmsec> (conveying time from the tip regulating plate 17 to the nip portion of the conveying roller pair 42)
-(Acceleration time of transport roller drive motor) (1)

  That is, the uppermost sheet Sa reaches the nip portion of the pair of transport rollers 42 when the transport roller driving motor 42M is in a stopped state or in a state where the rotation speed has not reached a constant rotational speed from the start of driving. The conveyance roller drive motor 42M is activated at the timing. When the predetermined time Xmsec is set under the above conditions, a difference in sheet conveyance speed between the suction conveyance belt drive motor 21M and the conveyance roller drive motor 42M occurs when the sheet reaches the conveyance roller pair 42.

  The difference in sheet conveyance speed at this time includes the case where the sheet conveyance speed by the conveyance roller drive motor 42M is zero. The size of the loop amount formed on the uppermost sheet Sa is determined by the set predetermined time Xmsec, and the loop amount formed increases as the predetermined time Xmsec is set longer. Therefore, the predetermined time Xmsec is appropriately set according to the basis weight (rigidity) of the sheet in the condition of the above formula (1).

  Accordingly, as shown in FIG. 5 described above, a loop is formed on the uppermost sheet Sa between the lower end 41A of the belt driving roller 41 and the nip portion 42A of the conveying roller pair 42. Then, by forming a loop in the uppermost sheet Sa in this way, the air sent from the separation nozzle 34 enters between the loop portion SL of the uppermost sheet Sa and the front end of the immediately lower sheet Sb. Thus, the separation performance is improved.

  The loop portion SL of the uppermost sheet Sa is a sheet transport indicated by an arrow N in FIG. 5 from a lower end (lowermost) 41A of the belt driving roller 41 that is downstream of the sheet suction area of the suction transport belt 21 in the sheet feeding direction. It is formed downstream in the direction. Here, in the present embodiment, the lower end 41 </ b> A of the belt driving roller 41 is disposed on the upstream side in the sheet feeding direction with respect to the front end regulating plate 17. In other words, the front end regulating plate 17 is arranged downstream of the sheet suction area of the suction conveyance belt 21 in the sheet feeding direction.

  By arranging the lower end 41A of the belt driving roller 41 at such a position, when a loop is formed on the uppermost sheet Sa, the leading edge of the immediately lower sheet Sb is more sheet than the loop portion SL of the uppermost sheet Sa. It comes to be located downstream in the transport direction. As a result, the air sent from the separation nozzle 34 efficiently enters between the loop portion SL of the uppermost sheet Sa and the immediately lower sheet Sb, and the separation performance can be improved.

  Next, the control timing time of the suction shutter solenoid 37SL is controlled according to the determined sheet loop amount (sheet loop amount control means). That is, when a predetermined time (Ymsec) has elapsed after the leading edge of the sheet reaches the nip portion 42A of the conveying roller pair 42 (Y in S405), the suction shutter solenoid 37SL is turned off (S406). As a result, the suction shutter 37 rotates in the direction of arrow G in FIG. 5 and closes the suction duct 51.

  When the suction duct 51 is closed in this way, the suction operation is turned off, and the suction conveyance belt 21 loses the conveyance force. In other words, the loop amount of the sheet changes according to the conveyance time during which the sheet is conveyed by the adsorption conveyance belt 21, that is, the timing at which the adsorption shutter solenoid 37SL is turned off. Therefore, in the present embodiment, the CPU 301 (control unit 300) controls the closing timing of the suction shutter 37 in order to control the loop amount of the sheet.

  Subsequently, when a predetermined time (Zmsec) from when the suction shutter 37 is closed until the suction force is lost (Y in S407), the drive of the suction conveyance belt drive motor 21M is stopped (S408). As a result, the uppermost sheet Sa is conveyed by the conveying roller pair 42 while releasing the loop formed at the leading edge of the sheet. Thereafter, when the trailing edge of the uppermost sheet Sa is detected and the detection sensor 54 is turned OFF (Y in S409), the conveyance roller drive motor 42M is stopped (S410), and the paper feeding operation is completed. This paper feed control is an explanation for feeding one sheet, but if this control is repeated, a plurality of sheets can be fed continuously.

  As described above, in this embodiment, after the uppermost sheet Sa reaches the conveyance roller pair 42, a loop is formed between the adsorption conveyance unit 151 (the adsorption conveyance belt 21) and the conveyance roller pair 42. Like to do. Then, by blowing air from the separation nozzle 34 to the loop portion SL of the uppermost sheet Sa, it is possible to prevent double feeding of sheets without causing an increase in cost.

In the description so far, the case where the loop is formed on the sheet by delaying the timing of driving the conveyance roller driving motor 42M rather than the suction conveyance belt driving motor 21M has been described. Not exclusively. For example, by setting the target speeds of the suction conveyance belt drive motor 21M and the conveyance roller drive motor 42M to different speeds and satisfying the following conditions, a difference in speed is generated between the suction conveyance belt 21 and the conveyance roller pair 42, whereby the sheet A loop can be formed at the tip.
Speed of suction conveyance belt 21> Speed of conveyance roller pair 42

  Here, when the speed difference is generated between the suction conveyance belt 21 and the conveyance roller pair 42 as described above, the sheet loop amount can be controlled by controlling the timing of closing the suction shutter 37. it can. In other words, the loop amount of the sheet changes according to the conveyance time for conveying the sheet by the suction conveyance belt 21.

  That is, as the timing of closing the suction shutter 37 is delayed, the loop amount formed on the uppermost sheet Sa increases, and the CPU 301 (control unit 300) closes the suction shutter 37 according to the basis weight (rigidity) of the sheet. Adjust the timing appropriately.

DESCRIPTION OF SYMBOLS 11 ... Sheet storage, 12 ... Tray, 17 ... Front end regulation board, 21 ... Adsorption conveyance belt, 33 ... Separation nozzle, 34 ... Separation nozzle, 37 ... Adsorption shutter, 42 ... Conveyance roller pair, 120 ... Sheet feeding apparatus, DESCRIPTION OF SYMBOLS 150 ... Sheet feeding mechanism, 151 ... Adsorption conveyance part, 152 ... Air spraying part, 300 ... Control part, 700 ... Sheet feeding unit, 1000 ... Image forming apparatus, 1001 ... Image forming apparatus main body, S ... Sheet

Claims (8)

A tray that can be raised and lowered to support the sheet;
An air blowing unit that floats and supports the sheet supported by the tray, and blows air to the end of the sheet to separate the uppermost sheet of the rolled sheets;
An adsorbing and conveying unit that adsorbs and conveys the separated uppermost sheet;
A sheet conveyance unit that is provided on the downstream side of the suction conveyance unit in the sheet conveyance direction and conveys the uppermost sheet conveyed by the adsorption conveyance unit;
A controller that controls the suction conveyance unit and the sheet conveyance unit;
The controller is configured to form a loop between the suction conveyance unit and the sheet conveyance unit on the uppermost sheet after the uppermost sheet reaches the sheet conveyance unit. A sheet feeding apparatus that controls the sheet feeding.   The control unit controls the timing at which driving of the sheet conveying unit is started so that a loop is formed between the suction conveying unit and the sheet conveying unit after the uppermost sheet reaches the sheet conveying unit. The sheet feeding apparatus according to claim 1, wherein The suction conveyance unit is
An adsorbing and conveying belt that adsorbs and conveys a sheet that has been lifted by blowing air;
A negative pressure generating section that generates a negative pressure for adsorbing the sheet to the adsorption conveyance belt;
An adsorption switching unit that can be switched to an adsorption position that adsorbs a sheet by the negative pressure generated by the negative pressure generation unit and a blocking position that blocks negative pressure, and
The control unit starts driving the sheet conveying unit when the sheet conveying speed of the sheet conveying unit when the uppermost sheet reaches the sheet conveying unit is lower than the sheet conveying speed of the suction conveying belt. The sheet feeding apparatus according to claim 2, wherein the sheet feeding apparatus is a sheet feeding apparatus.   4. The sheet feeding device according to claim 3, wherein a loop amount of the uppermost sheet is controlled according to a switching timing of the suction switching unit from the suction position to the blocking position.   5. The sheet feeding apparatus according to claim 4, wherein the loop amount of the uppermost sheet is determined based on at least one of the surface property of the sheet, the basis weight of the sheet, and the shape of the sheet. A regulation member that regulates the position of the downstream end of the sheet supported in the tray in the sheet feeding direction;
4. The control member according to claim 3, wherein the restriction member is disposed downstream of the sheet feeding direction of the suction conveyance belt so as to form a loop in the sheet from the upstream side of the sheet feeding direction. The sheet feeding device according to any one of claims 5 to 5.   2. The sheet feeding apparatus according to claim 1, wherein a loop is formed on the uppermost sheet by setting a sheet conveying speed of the sheet conveying unit to be slower than a sheet conveying speed of the suction conveying unit. .   An image forming apparatus comprising: the sheet feeding device according to claim 1; and an image forming unit that forms an image on a sheet fed from the sheet feeding device. apparatus.

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