JP2010116236A - Paper feeder, paper feed unit and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeder capable of reliably separating paper sheets from each other irrespective of the kind of papers, and preventing any damage of paper sheets. <P>SOLUTION: A paper feeder 1A comprises a paper sheet loading stand 2 with paper sheets P being loaded thereon, a sucking and conveying mechanism 3 for sucking and conveying the paper sheets P loaded on the paper sheet loading stand 2, a separation projection 5A which is displaceable in the projecting and accommodating direction with respect to a suction surface 30b, and projected from the suction surface 30b to separate a highest paper sheet from second and subsequent paper sheets when two or more paper sheets P are sucked by the suction surface 30b, and a solenoid 52 which displaces the separation projection 5A to the separation position for projecting the projection from the suction surface 30b and the accommodation position for accommodating the projection to the suction surface 30b side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a paper feeding device that sucks and feeds stacked paper with air, and in particular, when two or more papers are picked up, the uppermost space is used as a trigger for separating the second and subsequent papers. Separation protrusions that can be formed between the first sheet and the second and subsequent sheets are storable.

  Conventionally, an air feeding device has been used as a paper feeding device for an image forming apparatus such as a copying machine. In the air feeding device, air is blown to the side end face of the loaded paper to float it, and the lifted paper is sucked by a suction surface such as a perforated belt in which an air inlet for sucking air is formed. A mechanism for rotating and transporting the sheet is used.

  In such an air sheet feeding device, when two or more sheets are stuck to the suction surface, a separation mechanism is required to separate them.

  As the separation mechanism of the air feeding mechanism, a mechanism that blows air from the edge of the adsorbed paper and blows air between the paper is well known, but especially with thin plain paper or recycled paper Separation was difficult, and there was a problem that paper could not be separated by air blowing alone and doubled.

  In order to assist the separation effect by air blowing, a method of projecting a protrusion from an adsorption surface is known (see, for example, Patent Document 1). In this method, the uppermost sheet that directly acts on the suction force is adsorbed to the idle surface so as to wrap around the protrusion, whereas the sheet adsorbed by the uppermost sheet is sucked by air. Since this force does not act directly, it stops at the point where it touches the protrusion, or it adsorbs to the adsorption surface with a gentle deflection. In this way, more reliable separation can be obtained by utilizing the difference in posture generated between the uppermost sheet and the second and subsequent sheets.

JP-A-61-254438

  In the system in which the sheet adsorbed on the adsorption surface is lifted and separated using a protrusion, the sheet is rubbed while the protrusion is in contact with the sheet when the sheet is conveyed. Image forming apparatuses such as copiers have come to support not only plain paper and recycled paper, but also art paper and coated paper whose surface is coated.

  Since the surface of these papers is easily damaged, there arises a problem that the surface of the paper is damaged by a protrusion for assisting separation when the paper is conveyed. Further, in the case of non-carbon paper, there is a possibility that black streaks may enter a position that has passed through the protrusion, which causes a problem that the quality of the output paper is impaired.

  With coated paper and non-carbon paper, it is relatively easy to blow air into the gaps between the overlapping sheets, so that the protrusion height of the protrusion from the adsorption surface can be reduced. If the protrusion height of the protrusion is lowered, it is possible to suppress the occurrence of scratches on the paper. However, if the protrusion height of the protrusion is lowered, it becomes impossible to reliably separate the plain paper and the recycled paper, and the problem of double feeding occurs. For this reason, conventionally, it has been difficult to cope with various types of paper with one type of paper feeder.

  The present invention has been made in order to solve the above-described problems, and is capable of reliably separating sheets regardless of the type of paper, and also capable of preventing the occurrence of scratches on the sheet, and a sheet feeding apparatus including the sheet feeding apparatus. An object is to provide a unit and an image forming apparatus.

  In order to solve the above-described problems, the invention described in claim 1 is a sheet mounting table on which a plurality of sheets are stacked, a sheet stacked on the sheet mounting table is sucked from the upper surface, and the uppermost sheet is sucked. The suction surface, a transport mechanism for transporting the paper sucked on the suction surface to the paper transport path, and a structure that can be displaced in a direction in which the suction surface protrudes and is stored. A sheet feeding device including a separation protrusion that pushes down a part of the sheet to be sucked, a separation position where the separation protrusion protrudes with respect to the suction surface, and a protrusion driving unit that displaces the separation protrusion to a storage position stored on the suction surface side. .

  In the sheet feeding device according to claim 1, when the separation protrusion is displaced to the separation position and two or more sheets are sucked to the suction surface, the leading edge of the overlapped sheet is pushed down by the separation protrusion, and the second sheet Subsequent sheets are lifted from the uppermost sheet adsorbed on the adsorption surface, and a space is formed between the leading end surface of the uppermost one sheet and the leading end surfaces of the second and subsequent sheets. . By forming a space between the front end surfaces of the overlapped sheets, the sheets are reliably separated.

  In the paper feeding device according to claim 1, the separation protrusion can be displaced to the storage position, and both the plain paper and the recycled paper which are difficult to be separated and the coated paper which is easily damaged are supported. can do.

  According to the second aspect of the present invention, the first operation mode in which the separation protrusion is displaced to the storage position by the protrusion driving unit to perform the paper feeding operation, and the second operation mode in which the separation protrusion is displaced to the separation position to perform the paper feeding operation. The sheet feeding device according to claim 1, further comprising: a control unit configured to switch between the first operation mode and the second operation mode.

  According to a second aspect of the present invention, the sheet feeding operation is performed by displacing the separation protrusion to the separation position for a sheet that requires reliable separation, and the separation protrusion is displaced to the storage position for a sheet that is easily damaged. It is possible to perform a paper feeding operation, and it is possible to reliably handle various types of paper.

  According to a third aspect of the present invention, there is provided the paper feeding device according to the first aspect, further comprising a control unit that causes the projection driving unit to displace the separation protrusion between the separation position and the storage position in accordance with the conveyance of the sheet by the conveyance mechanism. .

  According to another aspect of the present invention, when the paper is separated, the separation protrusion is displaced to the separation position so that the separation is reliably performed. When the paper is conveyed, the separation protrusion is displaced to the storage position, thereby causing a scratch on the paper. Therefore, improvement in separation performance and prevention of scratches can be achieved at the same time.

  According to a fourth aspect of the present invention, the timing at which the separation protrusion is displaced to the separation position by the protrusion driving unit is such that the trailing edge of the preceding sheet conveyed by the conveyance mechanism passes through the separation protrusion and then the next sheet is conveyed. The timing at which the separation protrusion at the separation position is displaced to the retracted position until immediately before the start of the conveyance mechanism is immediately after the separation protrusion is displaced to the separation position. The sheet feeding device according to claim 2, wherein the sheet feeding device is immediately before starting.

  According to a fourth aspect of the present invention, the separation protrusion protrudes to the separation position between the time when the sheet is adsorbed on the adsorption surface and the time when the conveyance is started, the sheet is separated, and the sheet passes through the adsorption surface. By shifting the separation protrusion to the storage position during storage, the sheet separation performance can be improved and the occurrence of scratches can be reliably achieved.

  The invention described in claim 5 includes a suction detection sensor that detects whether or not the paper is sucked to the suction surface, and a paper detection sensor that detects the paper transported by the transport mechanism. The sheet feeding device according to claim 4, wherein the timing at which the separation protrusion is displaced to the separation position and the storage position by the protrusion driving unit and the timing at which the sheet is conveyed by the conveyance mechanism are controlled according to the output of the sheet detection sensor.

  In the paper feeding device according to claim 5, when the suction of the paper to the suction surface is detected to control the timing of the separation projection displacement, and when the paper is continuously sucked to the suction surface, By detecting the conveyed paper, the timing of displacement of the separation protrusion is controlled. Accordingly, the separation protrusion protrudes to the separation position after the sheet is adsorbed on the adsorption surface and starts to be conveyed, and the separation protrusion is displaced to the storage position while the sheet passes the adsorption surface. it can.

  According to a sixth aspect of the present invention, the suction detection sensor detects the presence or absence of the suction of the paper to the suction surface by detecting the displacement of the separation protrusion pressed against the paper sucked to the suction surface. The paper feeding device described.

  According to a sixth aspect of the present invention, the actuator of the suction detection sensor is also used as the separation protrusion, and the separation protrusion has a function of separating the paper and a function of detecting the suction of the paper on the suction surface. And the configuration can be simplified.

  According to the seventh aspect of the present invention, the control unit is configured to perform an operation mode in which the paper type of the paper loaded on the paper placement table is set in advance, and is executed according to the paper type selected from the preset paper types. The paper feeding device according to claim 2, wherein

  In the paper feeding device according to the seventh aspect, the user can select the paper type of the paper loaded on the paper mounting table, so that the separation protrusion can be displaced by an operation suitable for the paper type.

  In the invention according to claim 8, the control unit sets at least one of coated paper and non-carbon paper as a selectable paper type, or both, and applies the paper type of the paper loaded on the paper mounting table. 8. The paper feeding device according to claim 7, wherein when the work paper or the non-carbon paper is selected, the first operation mode is selected.

  In the paper feeding device according to the eighth aspect, it is possible to reliably prevent the generation of scratches on easily scratched paper such as coated paper and non-carbon paper.

  According to the ninth aspect of the invention, one or a plurality of paper trays in which paper is stored, a paper mounting table on which a plurality of papers are stacked in the paper tray, and the paper stacked on the paper mounting table are sucked from the upper surface. A suction surface that sucks the uppermost paper, a transport mechanism that transports the paper sucked by the suction surface to the paper transport path, and a structure that can be displaced in a direction that protrudes and is stored with respect to the suction surface. A separation protrusion that protrudes from the surface and depresses a part of the sheet adsorbed to the adsorption surface; a separation position that projects the separation protrusion relative to the adsorption surface; and a protrusion drive unit that displaces the separation protrusion to a storage position stored on the adsorption surface side Is a paper feed unit.

  In the paper feeding unit according to claim 9, by providing the paper feeding device described above, it is possible to displace the separation protrusion to the storage position. Corresponding to both easy-to-attach coated paper and the like, it is possible to reliably prevent double feeding.

  According to a tenth aspect of the present invention, there is provided an image forming unit that forms an image on a sheet, a sheet feeding device that feeds the sheet to the image forming unit, and a sheet that is fed from the sheet feeding unit to the image forming unit. A sheet feeding device on which a plurality of sheets are stacked, and a sheet loaded on the sheet loading table from a top surface, A suction surface that sucks the paper, a transport mechanism that transports the paper sucked on the suction surface to the paper transport path, and is configured to be displaceable in a direction protruding and stored with respect to the suction surface, protruding from the suction surface, A separation projection that pushes down a portion of the sheet that is attracted to the suction surface; a separation drive that projects the separation projection relative to the suction surface; and a projection drive unit that displaces the separation projection to a storage position stored on the suction surface side. The paper feed operation is performed by displacing the separation protrusion to the storage position by the protrusion drive unit. Separation by the protrusion drive unit according to control executed by switching between the first operation mode and the second operation mode in which the separation protrusion is displaced to the separation position to perform the paper feeding operation, or according to the conveyance of the paper by the conveyance mechanism The image forming apparatus performs control to displace the protrusion between the separation position and the storage position.

  In the image forming apparatus according to the tenth aspect, by providing the above-described paper feeding device, it is possible to displace the separation protrusion to the storage position, and the plain paper, the recycled paper, and the like that are difficult to separate, Corresponding to both easy-to-attach coated paper and the like, it is possible to reliably prevent double feeding and improve image quality.

  According to an eleventh aspect of the present invention, an operation unit that selects a paper type of the paper loaded on the paper mounting table is provided, and the control unit determines an operation mode to be executed according to the paper type selected by the operation unit. An image forming apparatus according to claim 10.

  In the image forming apparatus according to the eleventh aspect, the user can select the paper type of the paper loaded on the paper mounting table, so that the separation protrusion can be displaced by an operation suitable for the paper type.

  According to a twelfth aspect of the present invention, an operation unit that selects the first operation mode or the second operation mode is provided, and the control unit determines an operation mode to be executed according to the operation mode selected by the operation unit. The image forming apparatus according to claim 10.

  In the image forming apparatus according to the twelfth aspect, the displacement operation of the separation protrusion can be switched by a user operation in accordance with the state of occurrence of scratches on the output paper, the state of occurrence of double feed, and the like. It can respond flexibly.

  According to the paper feeding device of the present invention, the separation protrusion is provided in an arrangement in which a space is formed between the front end surfaces of the overlapped sheets, and the separation protrusion is stored in the separation position where the separation protrusion protrudes from the suction surface and the suction surface side. Displacement to the storage position can prevent the paper from being damaged without deteriorating the paper separation performance.

  According to the paper feeding unit of the present invention, it is possible to reliably prevent double feeding by providing the above-described paper feeding device. In addition, according to the image forming apparatus of the present invention, by providing the above-described sheet feeding device, it is possible to reliably prevent double feeding and improve image quality.

  Hereinafter, embodiments of a sheet feeding device, a sheet feeding unit including the sheet feeding device, and an image forming apparatus to which the sheet feeding unit is connected will be described with reference to the drawings.

<Configuration Example of Paper Feeding Device according to First Embodiment>
FIG. 1 is a side view illustrating an example of a sheet feeding device according to the first embodiment, and FIG. 2 is a plan view of a suction conveyance mechanism illustrating an example of a sheet feeding device according to the first embodiment as viewed from below. FIG. 3 is a perspective view of a sheet storage unit showing an example of a sheet feeding device according to the first embodiment. 4 is a side view showing an operation example of the paper feeding device of the first embodiment, FIG. 5 is a front view showing an operation example of the paper feeding device of the first embodiment, and FIG. FIG. 6 is a side view of a main part illustrating an operation example of the sheet feeding device according to the first embodiment.

  The sheet feeding device 1A according to the first embodiment is indicated by an arrow F on the suction conveyance mechanism 3 that sucks and feeds the paper P stacked on the paper placement table 2 and the paper P sucked by the suction conveyance mechanism 3. A separation air blowing mechanism 4 that blows separation air A1 from the front in the conveyance direction of the paper P is provided.

  In addition, when two or more sheets P are sucked by the suction conveyance mechanism 3, the sheet feeding device 1A has a separation air blowing mechanism between the uppermost sheet P1 and the second and subsequent sheets P2. 4 is provided with a separation protrusion 5A that forms a separation air introduction space E into which separation air A1 blown out from 4 is introduced.

  The separation protrusion 5A is configured to protrude and store in accordance with a previously specified paper type, operation mode, etc., and to prevent the occurrence of scratches on the paper P while ensuring separation performance regardless of the paper type of the paper P. Make it possible.

  Details of the sheet feeding device 1A according to the first embodiment will be described below. The sheet feeding device 1A includes a sheet loading table 2 in a sheet storage unit 20 in which a space that can be stored in a form in which a predetermined number of sheets P are stacked is formed.

  The sheet placing table 2 is moved up and down along the stacking direction of the sheets P by a lifting mechanism (not shown). In the paper storage unit 20, a paper front end abutting surface 21 that regulates the front end position of the paper P loaded on the paper placement table 2 is formed along the elevation direction of the paper placement table 2.

  The sheet feeding device 1 </ b> A includes an upper limit detection sensor 22 that detects the uppermost sheet P stacked on the sheet placing table 2. The upper limit detection sensor 22 is composed of, for example, a pair of optical sensors, and is disposed at a position for detecting that the uppermost sheet P stacked on the sheet mounting table 2 is at the height H1 that can be sucked by the suction conveyance mechanism 3. The

  In the sheet feeding device 1 </ b> A, when the stacking height of the sheet P on the sheet mounting table 2 is reduced by feeding the sheet P stacked on the sheet mounting table 2 by the suction conveyance mechanism 3, the uppermost sheet P is limited to the upper limit. The sheet placing table 2 is raised to a position detected by the detection sensor 22, and the position of the uppermost sheet P stacked on the sheet placing table 2 is controlled so as to be the height H 1 that can be sucked by the suction transport mechanism 3. The

  The suction conveyance mechanism 3 includes a conveyance belt 30 at an upper portion of the paper storage unit 20. Further, the suction conveyance mechanism 3 includes a driving roller 31 around which the conveyance belt 30 is wound, a first driven roller 32, and a second driven roller group 33 having two driven rollers.

  The conveyance belt 30 is endless, and the intake ports 30 a penetrating the conveyance belt 30 are arranged in parallel in the width direction of the conveyance belt 30, and a plurality of intake ports 30 a arranged in parallel in the width direction of the conveyance belt 30 are arranged in the conveyance belt 30. It is formed over the entire length direction orthogonal to the width direction.

  The drive roller 31 has an axis in a direction orthogonal to the conveyance direction of the paper P indicated by the arrow F, and is driven to rotate by a motor described later. The first driven roller 32 and the second driven roller group 33 have an axis parallel to the axis of the drive roller 31, and are freely rotatable following the rotation of the conveying belt 30 when the drive roller 31 is driven to rotate. It is a configuration.

  In the suction conveyance mechanism 3, the second driven roller group 33 is disposed in front of the paper leading edge abutting surface 21 in the conveyance direction of the paper P indicated by the arrow F. In addition, a driving roller 31 is arranged on the upper part of the sheet placing table 2. Further, a first driven roller 32 is disposed between the second driven roller group 33 and the driving roller 31 on the upper part of the sheet placing table 2.

  In the suction conveyance mechanism 3, the conveyance belt 30 is stretched along the conveyance direction of the paper P between the driving roller 31 and the second driven roller group 33. Thus, the suction conveyance mechanism 3 has the rear end side wound around the driving roller 31 of the conveyance belt 30 positioned above the paper P stacked on the paper placement table 2, and the second driven roller of the conveyance belt 30. The leading end side wound around the group 33 is positioned in front of the sheet leading end abutting surface 21. Further, in the suction conveyance mechanism 3, the two conveyance belts 30 are arranged side by side with respect to the conveyance direction of the paper P.

  Then, when the driving roller 31 is rotationally driven in the direction indicated by the arrow, each conveying belt 30 rotates, and the side of the conveying belt 30 facing the sheet placing table 2 moves in the conveying direction of the sheet P indicated by the arrow F. .

  The lower end position on the circumferential surface of the drive roller 31 and the lower end position on the circumferential surface of the first driven roller 32 are configured to have substantially the same height. On the other hand, in the second driven roller group 33, the lower end position on the circumferential surface of the lower driven roller is configured to be higher than the lower end position of the first driven roller 32 by a predetermined amount. .

  As a result, the side between the driving roller 31 and the first driven roller 32 on the side of the transport belt 30 facing the paper placement table 2 is substantially parallel to the surface of the paper P stacked on the paper placement table 2. On the other hand, the space between the first driven roller 32 and the second driven roller group 33 is inclined upward along the conveyance direction of the paper P, and the conveyance belt 30 is the first driven roller 32. It becomes a bent form at the part wound around.

  The suction transport mechanism 3 includes a suction chamber 34 into which air that sucks the paper P is sucked onto the transport belt 30. The suction chamber 34 has a space in which air is sucked by a fan (not shown) formed inside the conveyance belt 30, and a lower side facing the conveyance belt 30 located on the side facing the sheet placement table 2 is opened. Air is sucked in from the air inlet 30a of the conveyor belt 30 on the side facing 2.

  In the suction conveyance mechanism 3, when the air in the suction chamber 34 is sucked by a fan (not shown), the suction chamber 34 becomes negative pressure, so that the suction chamber 34 has a negative pressure from the suction port 30 a of the transport belt 30 located on the side facing the sheet placing table 2. Air is sucked in, and a flow of air that adsorbs the paper P to the transport belt 30 on the side facing the paper placement table 2 is generated.

  Accordingly, the suction surface 30b that sucks the paper P is configured by the transport belt 30 facing the paper placement table 2 in which air is sucked into the suction chamber 34 from the suction port 30a.

  The sheet feeding device 1 </ b> A includes a sheet conveyance path 35 through which the sheet P fed out by the suction conveyance mechanism 3 is conveyed. The sheet conveyance path 35 includes a guide member that guides conveyance of the sheet P sucked and fed out by the adsorption conveyance mechanism 3, and includes a conveyance belt 30 on the side facing the sheet placement table 2 and a sheet leading end abutting surface 21. A sheet entrance 36 through which the sheet P enters is formed between the upper end.

  The sheet feeding device 1 </ b> A includes a conveyance roller 37 and a driven roller 38 facing the conveyance roller 37 in the sheet conveyance path 35. The transport roller 37 is rotationally driven by a motor described later, and transports the paper P fed by the suction transport mechanism 3 while being sandwiched between the driven roller 38.

  The sheet feeding device 1 </ b> A includes a sheet feeding detection sensor 39 in the sheet conveyance path 35. The paper feed detection sensor 39 is composed of, for example, a pair of optical sensors, and detects the paper P fed out by the suction conveyance mechanism 3.

  The separation air blowing mechanism 4 includes a separation air outlet 40 through which the separation air A <b> 1 is blown out at the paper entrance 36. The separation air outlet 40 forms an air path in a direction in which the separation air A <b> 1 is blown obliquely toward the paper storage unit 20 with respect to the conveyance belt 30 positioned in front of the paper front end abutting surface 21.

  The separation air blowing mechanism 4 blows out the air sucked by the blowing fan 41 from the separation air outlet 40 as the separation air A1. The separation air A1 blown out from the separation air outlet 40 is oriented along the conveyance belt 30 on the side facing the sheet placement table 2, and the conveyance belt 30 on the side facing the sheet placement table 2 by the suction conveyance mechanism 3. From the front of the sheet P adsorbed to the sheet P in a substantially horizontal orientation with respect to the sheet P.

  The separation protrusion 5A is disposed between the two conveying belts 30 arranged in parallel to the left and right with respect to the conveyance direction of the paper P, in front of the paper front end abutting surface 21 with respect to the conveyance direction of the paper P indicated by the arrow F. Is done. The front end position of the paper P loaded on the paper mounting table 2 is regulated by the paper front end abutting surface 21. Accordingly, the separation protrusion 5A is disposed at a position where the vicinity of the front end of the paper P sucked by the suction conveyance mechanism 3 is separated from the suction surface 30b.

  The separation protrusion 5 </ b> A is formed of, for example, a plate-like member, and is rotatably supported by a shaft 50 that is coaxial with the first driven roller 32. The separation protrusion 5A is formed between the portion facing the sheet front end abutting surface 21 and the portion wound around the first driven roller 32 with respect to the conveyance belt 30 on the side facing the sheet placing table 2. It protrudes from the suction surface 30b along the transport direction.

  The separation protrusion 5A is formed with an inclined surface in which the amount of protrusion from the suction surface 30b gradually increases along the conveyance direction of the paper P from the first driven roller 32 side, and rotates about the shaft 50 as a fulcrum. The amount of protrusion from the suction surface 30b at the portion facing the paper leading edge abutting surface 21 changes. Thereby, the separation protrusion 5A can be displaced in a direction in which the separation protrusion 5A protrudes and is stored with respect to the suction surface 30b.

  The sheet feeding device 1A includes an elastic member 51 that presses the separation protrusion 5A in a direction protruding from the suction surface 30b. The elastic member 51 is configured by, for example, a coil spring, a torsion coil spring, or the like that is elastically deformed with respect to the pressing force. The separation protrusion 5 </ b> A is a separation position that protrudes downward at a predetermined height from the suction surface 30 b while being pressed by the elastic member 51.

  The sheet feeding device 1A includes a solenoid 52 that displaces the separation protrusion 5A. The solenoid 52 is an example of a protrusion driving unit, and the movable element 52 a is connected to the hook portion 54 of the separation protrusion 5 </ b> A via the link 53. When the solenoid 52 is not driven, the separation protrusion 5A is in a separation position that protrudes from the suction surface 30b by the force pressed by the elastic member 51, as shown in FIG.

  When the solenoid 52 is driven, as shown in FIG. 4B, the hook 52 of the separation protrusion 5 </ b> A is pulled by the link 53 by pulling the mover 52 a. The separation protrusion 5A rotates around the shaft 50 while elastically deforming the elastic member 51, and is displaced in the storage direction with respect to the suction surface to be in the storage position. When the solenoid 52 is in a non-driven state, the separation protrusion 5A returns to the separation position by the force pressed by the elastic member 51. The protruding height of the separation protrusion 5A from the suction surface 30b in the retracted position when the solenoid 52 is driven is set lower than the separation protrusion 5A in the separation position.

  The sheet feeding device 1A includes a floating air blowing mechanism 6 that blows floating air A2 from the side onto the paper P loaded on the paper placing table 2. In the floating air blowing mechanism 6, a floating air outlet 60 is formed on the side of the paper storage unit 20. The floating air blowing mechanism 6 blows out the air sucked by the blower fan 61 as the floating air A2 from the floating air outlet 60, and blows the floating air A2 from the side to the paper P loaded on the paper placing table 2. Then, the paper P is floated.

  The sheet feeding device 1 </ b> A includes a suction detection sensor 7 that detects the presence or absence of the paper P sucked by the suction transport mechanism 3. In this example, the suction detection sensor 7 detects whether or not the paper P is attracted to the suction transport mechanism 3 by detecting the displacement of the separation protrusion 5A when the paper P is sucked by the suction transport mechanism 3.

  The suction detection sensor 7 is composed of, for example, a pair of optical sensors, and detects the separation protrusion 5 </ b> A that is pushed up and displaced by the paper P sucked by the suction conveyance mechanism 3. That is, when the sheet P is sucked by the suction conveyance mechanism 3, the vicinity of the center near the leading end of the sheet P is pushed down by the separation protrusion 5A. On the other hand, the separation protrusion 5A is pushed up by the force of adsorbing the paper P.

  When a force for pushing up the separation protrusion 5A is applied, the elastic member 51 is elastically deformed, and the separation protrusion 5A rotates about the shaft 50 as a fulcrum and is displaced in the retracted direction with respect to the suction surface 30b.

  Further, when the sheet P sucked by the suction conveyance mechanism 3 is lost and the force for pushing up the separation protrusion 5A is no longer applied, the separation protrusion 5A is rotated about the shaft 50 by the elastic force of the elastic member 51, and with respect to the suction surface 30b. Displaces in the protruding direction.

  As described above, the separation protrusion 5 </ b> A is displaced by the rotation operation depending on whether or not the sheet P is attracted to the suction conveyance mechanism 3. Thus, when the predetermined displacement of the separation protrusion 5 </ b> A is detected by the suction detection sensor 7, it is determined that the paper P is sucked to the transport belt 30 by the suction transport mechanism 3.

  Further, by making it possible to detect the presence or absence of suction by the operation of the separation protrusion 5A that pushes down the paper P sucked by the suction conveyance mechanism 3, the actuator of the suction detection sensor 7 is also used as the separation protrusion 5A. Note that the actuator of the adsorption detection sensor 7 may be formed of a member independent of the separation protrusion.

  FIG. 7 is a functional block diagram illustrating an example of a control system of the sheet feeding device according to the first embodiment. The sheet feeding device 1A includes a control unit S1 that performs sheet feeding control and an operation unit S2 that selects a sheet type of the sheet P. The control unit S1 stores the paper type in the operation unit S2 based on the selectable paper type and the operation mode corresponding to the paper type stored in the storage unit S3 including a nonvolatile memory. Displays the selection screen.

  The control unit S1 selects an operation mode during the paper feeding operation based on the paper type selected on the paper type selection screen displayed on the operation unit S2. FIG. 8 is an explanatory diagram showing an example of the paper type setting information, showing the relationship between the paper type and the operation mode, and the position of the separation protrusion in each operation mode.

  The control unit S1 causes the separation projection 5A to protrude from the suction surface 30b in mode (1) which is the first operation mode in which the sheet feeding operation is performed at the storage position where the separation protrusion 5A is stored on the suction surface 30b side. The mode (2), which is the second operation mode in which the paper feeding operation is performed at the separation position, is switched based on the paper type selected by the operation unit S2.

  The paper type on which mode (1) is executed is, for example, glossy paper, matte paper, non-carbon paper, or the like, which is easily separated but easily damaged. The paper type on which the mode (2) is executed is paper that is difficult to separate, such as plain paper, high-quality paper, recycled paper, and color paper.

  In accordance with the operation mode selected based on the paper type selected in the operation unit S2, the control unit S1 adsorbs the solenoid 52 that drives the separation protrusion 5A by the adsorption conveyance mechanism 3 detected by the adsorption detection sensor 7. Control is performed according to the presence / absence of the paper P and the presence / absence of the paper P fed out by the suction conveyance mechanism 3 detected by the paper feed detection sensor 39. Note that the operation mode may be directly selected by the operation unit S2.

  Further, the control unit S1 determines whether or not there is a sheet P adsorbed by the adsorption conveyance mechanism 3 detected by the adsorption detection sensor 7 using the motor M1 that rotates the drive roller 31 and the motor M2 that rotates the conveyance roller 37. Control is performed according to the presence or absence of the paper P fed out by the suction conveyance mechanism 3 detected by the paper feed detection sensor 39.

  Further, the control unit S1 uses a suction conveyance mechanism 3 detected by the suction detection sensor 7 to open and close a solenoid S10 that opens and closes a shutter (not shown) that switches whether or not the floating air A2 is blown out by the floating air blowing mechanism 6. Control is performed according to the presence / absence of P and the presence / absence of paper P fed out by the suction conveyance mechanism 3 detected by the paper feed detection sensor 39. The control unit S1 also controls a motor (not shown) that drives each blower fan. Further, the control unit S1 controls the motor M3 that raises and lowers the paper placing table 2 according to the presence or absence of the paper P detected by the upper limit detection sensor 22. Here, the control unit S1 may be configured by a control unit of the image forming apparatus described later. The operation unit S2 may be configured by an operation display unit of the image forming apparatus described later.

<Example of Operation of Paper Feeding Device of First Embodiment>
FIG. 9 is a time chart showing an example of the operation of the sheet feeding device according to the first embodiment. Next, an operation example of the sheet feeding device 1A according to the first embodiment will be described with reference to each drawing. To do.

  The control unit S1 displays a paper type selection screen for selecting the paper type of the paper P loaded on the paper mounting table 2 on the operation unit S2 based on the paper type setting information stored in the storage unit S3.

  When the paper type of the paper P loaded on the paper mounting table 2 is selected on the paper type selection screen, the control unit S1 sets the operation mode of the separation protrusion 5A based on the paper type setting information stored in the storage unit S3. select.

  In the following description, it is assumed that plain paper is selected as the paper type of the paper P, for example. When plain paper is selected, mode (2) is selected as the operation mode of the separation protrusion 5A.

  When the control unit S1 starts the sheet feeding operation, the position of the uppermost sheet P stacked on the sheet placing table 2 is determined based on the output of the upper limit detection sensor 22 as the height H1 that can be sucked by the sucking and conveying mechanism 3. Thus, the motor M3 that raises and lowers the paper placing table 2 is controlled.

  In the paper feeding operation of the paper P, a fan (not shown) of the suction conveyance mechanism 3 is driven, and the blower fan 41 of the separation air blower mechanism 4 and the blower fan 61 of the floating air blower mechanism 6 are driven. The adsorption operation is performed. Further, when mode (2) is selected in the operation mode, the solenoid 52 is not driven, and the separation protrusion 5A is projected from the suction surface 30b by the force pressed by the elastic member 51 to be the separation position.

  When the air in the suction chamber 34 is sucked in by a fan (not shown), the suction chamber 34 becomes negative pressure, so that air is sucked in from the air inlet 30a of the transport belt 30 located on the side facing the paper placing table 2, and the paper The flow of air that adsorbs the paper P is generated on the conveyance belt 30 on the side facing the mounting table 2. Further, by opening a shutter (not shown) of the floating air blowing mechanism 6, the air sucked by the blowing fan 61 is blown out from the floating air outlet 60 and floats from the side of the paper P loaded on the paper placing table 2. Air A2 is blown.

  As a result, the paper P stacked on the upper side of the paper P stacked on the paper mounting table 2 starts to float. A time t <b> 1 shown in FIG. 9 is a time for waiting for the floated paper P to be attracted to the transport belt 30 after the paper feeding operation is started.

  The uppermost sheet P stacked on the sheet placing table 2 is adsorbed by the conveyance belt 30 constituting the adsorption surface 30b at the timing ta shown in FIG. When the paper P is sucked by the transport belt 30, a part of the paper P is pushed down by the separation protrusion 5A that protrudes from the suction surface 30b and is in the separation position in this example.

  The separation protrusion 5 </ b> A protrudes from the suction surface 30 b in front of the paper front end abutting surface 21 with respect to the conveyance direction of the paper P indicated by the arrow F. The front end position of the paper P loaded on the paper mounting table 2 is regulated by the paper front end abutting surface 21.

  The conveyor belt 30 located on the side facing the sheet placing table 2 is bent at a portion wound around the first driven roller 32, and is formed between the first driven roller 32 and the second driven roller group 33. The conveyance belt 30 positioned therebetween is inclined upward along the conveyance direction of the paper P. As a result, the sheet P adsorbed to the conveyance belt 30 is bent at a portion where the conveyance belt 30 is wound around the first driven roller 32.

  As a result, the sheet P sucked by the sucking and conveying mechanism 3 is pushed down by the separation protrusion 5A near the center near the tip, and is lifted from the suction surface 30b near the center of the tip.

  When two or more sheets P are adsorbed by the suction conveyance mechanism 3, a plurality of sheets P are stuck by electrostatic force or the like, and two or more sheets P are adsorbed by the adsorption conveyance mechanism 3. Then, the vicinity of the center of the vicinity of the leading ends of the two or more sheets P is pushed down by the separation protrusion 5A.

  Since the uppermost sheet P1 sucked by the sucking and conveying mechanism 3 is directly subjected to the sucking force by the sucking air, as shown in FIG. 6, except for the vicinity of the center of the front end face pushed down by the separation protrusion 5A. The belt 30 is bent according to the portion wound around the first driven roller 32 and is sucked to the suction surface 30b.

  On the other hand, the second and subsequent sheets P2 attached to the uppermost sheet P and adsorbed by the adsorbing and conveying mechanism 3 do not directly receive the adsorbing force by the adsorbing air. As a result, the second and subsequent sheets of paper P2 do not follow the bent form of the conveyor belt 30 at the portion wound around the first driven roller 32, and the uppermost one sheet P1 and the second and subsequent sheets. Sheet P2 is separated from the front end surface.

  Then, the vicinity of the center of the vicinity of the leading ends of the two or more sheets P is pushed down by the separation protrusion 5A, so that the second and subsequent sheets of the sheet P2 are lifted from the topmost sheet P1 near the center of the leading end surface. As shown in a), a separation air introduction space E is formed between the leading end surfaces of the uppermost sheet P1 and the second and subsequent sheets P2.

  When the blower fan 41 is driven in the separation air blowing mechanism 4, the air sucked by the blower fan 41 is blown out from the separation air outlet 40. The separation air A1 blown out from the separation air outlet 40 is oriented along the conveyance belt 30 on the side facing the sheet placement table 2, and the conveyance belt 30 on the side facing the sheet placement table 2 by the suction conveyance mechanism 3. From the front of the sheet P adsorbed to the sheet P in a substantially horizontal orientation with respect to the sheet P.

  When two or more sheets P are sucked by the suction conveyance mechanism 3, as described above, the center of the vicinity of the front end of the sheet P is pushed down by the separation protrusion 5A, so that the topmost sheets P1 and P2 The second and subsequent sheets of paper P2 are separated from the leading end surface, and a separation air introduction space E is formed. As a result, the separation air A1 blown out from the separation air blowing mechanism 4 in a substantially horizontal direction with respect to the sheet P passes through the separation air introduction space E as shown in FIG. P1 and the second and subsequent sheets of paper P2 are separated.

  In the sheet feeding device 1A, as described above, when the sheet P is adsorbed to the conveyance belt 30 by the adsorption conveyance mechanism 3, the separation protrusion 5A constituting the actuator of the adsorption detection sensor 7 is pushed up by the force that adsorbs the sheet P. It is done. The separation protrusion 5A rotates about the shaft 50 as the elastic member 51 is elastically deformed. Accordingly, when the displacement of the separation protrusion 5A is detected by the suction detection sensor 7 at the timing ta shown in FIG. 9 and the output of the suction detection sensor 7 changes to ON (with suction), the control unit S1 moves to the transport belt 30. It is determined that the first sheet P is sucked.

  At time t2 shown in FIG. 9, the output of the suction detection sensor 7 changes to ON at timing ta, and it is detected that the paper P is sucked on the transport belt 30, and then the separation protrusion 5A, the separation air A1, etc. This is the separation waiting time for separating the paper P by the action of.

  When the output of the suction detection sensor 7 changes to ON at timing ta and detects that the paper P is sucked to the transport belt 30, the control unit S1 drives the solenoid 52 within the separation waiting time t2 to separate the sheet. The protrusion 5A is displaced to the storage position. The operation of storing the separation protrusion 5A may be performed at any timing within the separation waiting time t2, as indicated by a broken line in FIG. However, in order to ensure separation when two or more sheets P are adsorbed, the time for the separation protrusion 5A to protrude to the separation position is as long as possible while the sheet P is stopped. Preferably, the data is stored at the timing indicated by the solid line in FIG.

  In this example, when the mode (2) is selected as the operation mode and the sheet feeding operation is started, the separation protrusion 5A protrudes to the separation position. However, as shown by the one-dot chain line in FIG. When the suction detection sensor 7 detects the suction of the paper P at ta, the separation protrusion 5A may protrude to the separation position, and the storing operation may be performed within the separation standby time t2.

  When the output of the suction detection sensor 7 changes to ON at timing ta and the control unit S1 detects that the paper P is sucked to the transport belt 30, the control unit S1 opens a shutter (not shown) that opens and closes the floating air outlet 60 to the solenoid S10. And the blowing of the floating air A2 from the floating air outlet 60 is stopped. The suction operation of the paper P by the suction transport mechanism 3 continues. It should be noted that the strength of the air flow of the floating air A2 blown out by the floating air blowing mechanism 6 can be switched, and the floating air A2 is blown and sucked out with a strong air flow until the suction detection sensor 7 detects the suction of the paper P. When the detection sensor 7 detects the suction of the paper P, the air flow A2 may be blown out by switching to a weak air volume.

  In the separation operation of the paper P, the fan (not shown) of the suction conveyance mechanism 3 is driven and the suction operation of the paper P is continued. Therefore, the uppermost sheet P1 is held while being sucked by the conveyance belt 30. Is done. On the other hand, since the blowing of the flying air A2 by the floating air blowing mechanism 6 is stopped or the air volume is reduced, the separated second and subsequent sheets P2 are stacked again on the sheet placing table 2.

  The controller S1 rotationally drives the drive roller 31 of the suction conveyance mechanism 3 by the motor M1 at a timing tb when the sheet P is attracted to the conveyance belt 30 by the suction conveyance mechanism 3 and a predetermined separation waiting time t2 has elapsed. The conveyance roller 37 is rotationally driven by the motor M2, and the sheet P feeding operation is started.

  When the driving roller 31 is rotationally driven in the direction indicated by the arrow, the conveying belt 30 rotates, and the side of the conveying belt 30 facing the paper placing table 2 moves in the direction indicated by the arrow F. As a result, the paper P sucked to the transport belt 30 by the suction transport mechanism 3 is fed out in the transport direction indicated by the arrow F. In the paper feeding operation of the paper P, the separation air A1 is continuously blown out by the separation air blowing mechanism 4, so that a force is generated to return the separated second and subsequent papers P toward the paper storage unit 20. Yes. This prevents the second paper P from being transported to the paper entrance 36 by being tied to the first paper P.

  When the paper P sucked by the suction transport mechanism 3 is fed out by the transport belt 30, the leading end of the fed paper P enters the detection position of the paper feed detection sensor 39 at timing tc, and the output of the paper feed detection sensor 39. Changes to ON (paper present), the paper P is detected, and is sandwiched between the transport roller 37 and the driven roller 38.

  When the control unit S1 detects that the output of the paper feed detection sensor 39 changes to ON at timing tc and the leading edge of the first sheet P fed out by the transport belt 30 reaches the transport roller 37, the floating air A shutter (not shown) that opens and closes the air outlet 60 is opened, and the blowing of the floating air A2 from the air floating outlet 60 is resumed.

  The control unit S1 detects that the output of the paper feed detection sensor 39 is turned ON at timing tc and the leading edge of the paper P fed by the transport belt 30 has reached the paper feed detection sensor 39, and then the transport roller 37. When the predetermined waiting time set in consideration of the time until the paper P is nipped by the driven roller 38 elapses, the rotational driving of the driving roller 31 is stopped. On the other hand, the rotation drive of the conveyance roller 37 continues.

  As a result, the sheet P sandwiched between the transport roller 37 and the driven roller 38 is transported at time t3. In the paper feeding operation of the paper P, the suction operation of the paper P by the suction conveyance mechanism 3 is continued, and a force for sucking the paper P to the conveyance belt 30 is working, but the conveyance roller 37 and the driven roller 38 The conveyance force by the clamping is stronger than the adsorption force, and the paper P is pulled out with the conveyance belt 30 stopped.

  When the paper P sandwiched between the transport roller 37 and the driven roller 38 is transported, the rear end of the paper P passes through the suction detection sensor 7. When the trailing edge of the paper P passes through the suction detection sensor 7, the output of the suction detection sensor 7 changes to OFF (no suction) due to the displacement of the separation protrusion 5A constituting the actuator of the suction detection sensor 7.

  When the paper P sandwiched between the transport roller 37 and the driven roller 38 is transported, the rear end of the paper P passes through the paper feed detection sensor 39. When the trailing edge of the paper P passes through the paper feed detection sensor 39, the output of the paper feed detection sensor 39 changes to OFF (no paper). When the mode (2) is selected as the operation mode, the control unit S1 controls the separation protrusion 5A to protrude to the separation position when the output of the paper feed detection sensor 39 changes to OFF. In addition, control for stopping the rotational driving of the conveying roller 37 is performed, and a shutter (not shown) that opens and closes the floating air outlet 60 is closed, and the blowing of the floating air A2 from the floating air outlet 60 is stopped.

  Here, in the paper feeding operation of the paper P, the suction operation of the paper P by the suction transport mechanism 3 continues, and the second belt is applied to the transport belt 30 exposed while the first paper P is transported. The paper P may be adsorbed. However, as described above, when the leading edge of the first paper P is detected by the paper feed detection sensor 39, the driving of the transport belt 30 is stopped at a predetermined timing, so that the first paper P is transported. The second sheet P adsorbed on the conveyance belt 30 in the middle is not conveyed.

  As a result, at the timing td when the trailing edge of the first sheet P passes through the suction detection sensor 7, the second sheet P is adsorbed to the transport belt 30, and the first sheet at timing te. During the time t4 until the rear end of P passes through the paper feed detection sensor 39, the output of the suction detection sensor 7 may remain ON (with suction) and may not change.

  In this way, in consideration of the state in which the output of the suction detection sensor 7 does not change because the succeeding paper P is continuously attracted to the transport belt 30 as the preceding paper P is transported, the controller S1 Using the outputs of the detection sensor 7 and the paper feed detection sensor 39, the separation protrusion 5A is projected and stored.

  That is, when the output of the suction detection sensor 7 changes to OFF because the rear end of the paper P that is nipped and transported between the transport roller 37 and the driven roller 38 passes through the suction detection sensor 7, the control unit S1 When the output of the suction detection sensor 7 is ON and the rear end of the paper P passes through the paper feed detection sensor 39 and the output of the paper feed detection sensor 39 is turned OFF, the separation protrusion 5A is brought to the separation position. Make it protrude.

  Further, after the output of the suction detection sensor 7 is turned off or the output of the paper feed detection sensor 39 is turned off, the separation protrusion 5A is stored in the storage position after a predetermined separation standby time has elapsed.

  Furthermore, after the output of the paper feed detection sensor 39 is turned off or the output of the suction detection sensor 7 is turned on, the rotation of the conveyance belt 30 and the conveyance roller 37 is started after a predetermined separation waiting time has elapsed. Further, during the separation standby time after the output of the paper feed detection sensor 39 is changed to OFF, the rotation driving of the conveyance belt 30 and the conveyance roller 37 is stopped.

  As a result, in the feeding operation of the second and subsequent sheets of paper P, control is performed to project the separation protrusion 5A at the timing when the output of the suction detection sensor 7 or the paper feed detection sensor 39 changes to OFF. After the rear end of P passes through the separation protrusion 5A, the separation protrusion 5A protrudes to the separation position.

  Further, before the paper P attracted to the transport belt 30 is transported by the transport belt 30 and the transport roller 37 being rotated, the control for storing the separation protrusion 5A is performed, and the transported paper P is separated from the separation protrusion 5A. While passing through 5A, the separation protrusion 5A is stored in the storage position.

  In this example, the first sheet P sandwiched between the transport roller 37 and the driven roller 38 is transported, and the trailing edge of the first sheet P passes through the paper feed detection sensor 39 at timing te. When the trailing edge of the first sheet P passes through the sheet feed detection sensor 39 and the output of the sheet feed detection sensor 39 changes to OFF, the process shifts to preparation for feeding the second sheet P. When the output of the paper feed detection sensor 39 changes to OFF, the control unit S1 performs control to cause the separation protrusion 5A to protrude to the separation position. In addition, control for stopping the rotational driving of the conveying roller 37 is performed, and a shutter (not shown) that opens and closes the floating air outlet 60 is closed, and the blowing of the floating air A2 from the floating air outlet 60 is stopped.

  At timing te, since the second sheet P is already attracted to the transport belt 30, at time t5, the output of the paper feed detection sensor 39 changes to OFF at timing te, and the separation protrusion 5A is brought to the separation position. This is a separation waiting time for separating the paper P by the action of the separation protrusion 5A and the separation air A1 after the protrusion.

  The control unit S1 controls the conveyor belt 30 at a timing tf when a predetermined separation waiting time t5 has elapsed after the first sheet P passes through the sheet feed detection sensor 39 and the separation protrusion 5A protrudes to the separation position. The conveyance roller 37 is rotationally driven to start feeding the second sheet P.

  When the second sheet P attracted to the transport belt 30 is fed out, the output of the paper feed detection sensor 39 changes to ON at timing tg, and the sheet P is detected, and the transport roller 37 and the driven roller 38 It is pinched.

  When the control unit S1 detects that the output of the paper feed detection sensor 39 changes to ON at timing tg and the leading edge of the second sheet P fed out by the transport belt 30 has reached the transport roller 37, the floating air A shutter (not shown) that opens and closes the air outlet 60 is opened, and the blowing of the floating air A2 from the air floating outlet 60 is resumed.

  The control unit S1 detects that the output of the paper feed detection sensor 39 is turned ON at timing tg and the leading edge of the paper P fed by the transport belt 30 has reached the paper feed detection sensor 39, and then the transport roller 37. When the predetermined waiting time set in consideration of the time until the paper P is nipped by the driven roller 38 elapses, the rotational driving of the driving roller 31 is stopped. On the other hand, the rotation drive of the conveyance roller 37 continues. As a result, the paper P sandwiched between the transport roller 37 and the driven roller 38 is transported at time t6.

  When the paper P sandwiched between the transport roller 37 and the driven roller 38 is transported, the trailing edge of the second paper P passes through the suction detection sensor 7 at timing th. When the trailing edge of the paper P passes through the suction detection sensor 7, if the third paper P is not continuously sucked by the conveyance belt 30, suction detection is performed by the displacement of the separation protrusion 5 </ b> A constituting the actuator of the suction detection sensor 7. The output of the sensor 7 changes to OFF (no adsorption).

  When the paper P sandwiched between the transport roller 37 and the driven roller 38 is transported, the trailing edge of the second paper P passes through the paper feed detection sensor 39 at the timing ti. When the trailing edge of the paper P passes through the paper feed detection sensor 39, the output of the paper feed detection sensor 39 changes to OFF. When the mode (2) is selected as the operation mode, the control unit S1 outputs three sheets when the second sheet P passes through the sheet feed detection sensor 39 and the output of the sheet feed detection sensor 39 changes to OFF. The process proceeds to preparation for feeding the eye paper P, and control is performed to project the separation protrusion 5A to the separation position.

  When the second sheet P passes through the suction detection sensor 7, the suction operation by the suction transport mechanism 3 is continued, and the floating air A <b> 2 is blown from the floating air outlet 60, so that the third sheet P is adsorbed to the conveyor belt 30. Times t <b> 7 and t <b> 8 are times for waiting for the third sheet P to be attracted to the conveyance belt 30 after the second sheet P passes through the suction detection sensor 7.

  When the third sheet P is attracted to the conveyance belt 30 at timing tj, a part of the sheet P is pushed down by the separation protrusion 5A at the separation position. When two or more sheets P are sucked by the suction conveyance mechanism 3, the separation air introduction space E is formed by pushing down the vicinity of the center of the front end of the sheet P by the separation protrusion 5A as described above. As a result, the separation air A1 blown from the separation air blowing mechanism 4 in a substantially horizontal direction with respect to the paper P passes through the separation air introduction space E, and the uppermost sheet P1 and the second and subsequent sheets. The paper P2 is separated.

  In the paper feeding device 1A, as described above, when the paper P is attracted to the transport belt 30 by the suction transport mechanism 3, the separation protrusion 5A is pushed up by the force of attracting the paper P, and the separation protrusion 5A is displaced at timing tj. Is detected by the adsorption detection sensor 7. When the output of the suction detection sensor 7 changes to ON (with suction), the control unit S1 determines that the third sheet P is sucked onto the transport belt 30.

  At time t9, the output of the suction detection sensor 7 changes to ON at timing tj, and it is detected that the paper P is attracted to the transport belt 30, and then the paper is moved by the action of the separation protrusion 5A and the separation air A1. This is a separation waiting time for separating P.

  When the output of the suction detection sensor 7 changes to ON at timing tj, the control unit S1 drives the solenoid 52 within the separation standby time t9 to displace the separation protrusion 5A to the storage position. The operation of storing the separation protrusion 5A may be performed at any timing within the separation standby time t9.

  The operation of projecting the separation protrusion 5A may be performed during time t7 after the output of the suction detection sensor 7 is turned OFF at timing th. Further, it may be performed during the separation waiting time t9 after the output of the adsorption detection sensor 7 is turned ON at the timing tj. As described above, it is preferable that the separation protrusion 5A protrude longer. Therefore, when the output of the paper feed detection sensor 39 changes to OFF at the timing ti, the separation protrusion 5A is protruded to the separation position.

  When the output of the adsorption detection sensor 7 changes to ON at timing tj, the control unit S1 closes a shutter (not shown) that opens and closes the floating air outlet 60, and stops the blowing air A2 from the floating air outlet 60. .

  The control unit S1 is configured such that at a timing tk when a predetermined separation waiting time 9 has elapsed after the third sheet P is adsorbed to the conveyance belt and the output of the adsorption detection sensor 7 is turned ON, The conveyance roller 37 is rotationally driven to start feeding the third sheet P. The timing at which the feeding of the paper P is started may be based on the timing ti when the second paper P passes through the paper feed detection sensor 39 and the output of the paper feed detection sensor 39 is turned off. Thereafter, the above process is repeated.

  Here, when the sheet of the paper type for which the mode (1) is selected as the operation mode is selected, the above-described processing is performed with the separation protrusion 5A stored in the storage position as shown in FIG. Is executed. The storage position of the separation protrusion 5A may be such that the separation protrusion 5A does not protrude from the suction surface 30b.

<Example of effects of sheet feeding device according to first embodiment>
In the case of plain paper or the like, if two or more sheets are adsorbed on the conveyor belt 30, they are difficult to separate. Therefore, in the mode (2) corresponding to plain paper or the like, as shown in FIGS. 4A and 5A, the separation protrusion 5A protrudes to the separation position at the timing when the sheet P is attracted to the conveyance belt 30. As a result, the stuck paper P is lifted from the suction surface 30b so as to be easily separated, and the separation is promoted. Further, the separation protrusion 5A is stored in the storage position at the timing when the paper P is conveyed, thereby preventing the paper P from being damaged.

  On the other hand, in the mode (1) corresponding to coated paper or the like, as shown in FIGS. 4B and 5B, both the timing at which the paper P is attracted to the transport belt 30 and the timing at which the paper P is transported. The separation protrusion 5A is stored in the storage position. In the case of coated paper or the like, even if two or more sheets are adsorbed to the conveyor belt 30, they are easily separated. However, if the separation protrusion 5A protrudes at a height suitable for separation of plain paper, there is a risk of scratching due to friction during conveyance. Therefore, the separation protrusion 5A is set to the storage position to prevent the paper P from being damaged.

  In this way, by making it possible to select an operation mode for switching the presence / absence of the protrusion of the separation protrusion 5A according to the paper type of the paper P, the separation performance when two or more sheets are attracted to the transport belt 30 is improved. And preventing the occurrence of scratches during paper conveyance.

<Configuration Example of Paper Feed Unit of the Present Embodiment>
FIG. 10 is a configuration diagram illustrating an example of a paper feeding unit including the paper feeding device according to each embodiment. The paper supply unit 90 includes a plurality of paper trays constituting the paper storage unit 20 shown in FIG. 1 and the like, in this example, three paper trays P220, P221, and P222. Further, on each of the paper trays P220, P221, and P222, the suction conveyance mechanism 3 having the conveyance belt 30 and the separation protrusion 5A shown in FIG.

  Further, when two or more sheets P are sucked by the suction conveyance mechanism 3, the separation air blowing mechanism 4 that blows the separation air A1 between the uppermost one sheet and the second and subsequent sheets is provided. It is done. In addition, a floating air outlet 60 is formed on the side of each paper tray P220, P221, P222, and a floating air blowing mechanism 6 that blows floating air from the side of the paper P loaded on the paper trays P220, P221, P222. Is provided.

  The paper trays P220, P221, and P222 are provided so that they can be pulled out in the front-rear direction of the drawing by opening a front door (not shown) provided on the front side of the drawing. In addition, the front surface of the paper tray can be configured as an exterior plate, and a handle or the like that can be put on the exterior plate can be provided, and the paper tray can be pulled out and pushed in using the handle or the like.

  The paper feeding direction of the paper P by the suction conveyance mechanism 3 is a direction (left direction in the drawing) orthogonal to the drawing direction of the paper trays P220, P221, and P222.

  The paper P sucked by the suction conveyance mechanism 3 is separated into one sheet by the action of the separation protrusion 5 and the separation air blowing mechanism 4. The sheet P fed out from the sheet tray P220 by the suction conveyance mechanism 3 has a nip portion at substantially the same height as the lower surface of the conveyance belt 30 wound around the lower driven rollers of the second driven roller group 33 shown in FIG. Is sandwiched between a pair of conveying rollers 37 and a driven roller 38.

  The paper P sandwiched between the transport roller 37 and the driven roller 38 is transported by the transport roller 37 and the transport direction is changed downward by the action of the guide member. Next, the paper is transported downward by transport rollers R223 to R227 constituting the paper transport path in the vertical direction, guided by the guide member in the substantially horizontal direction on the left side of the figure, and then contacted with the transport roller R228 in the rotation stopped state. Stop in contact.

  The conveyance roller R228 functions as a registration roller for taking a timing with an image forming process in the image forming apparatus 10 to be described later. Thereafter, the paper P is fed into the image forming apparatus with the start of rotation of the transport roller 228 and the like.

  Similarly, the sheet P fed from the sheet tray P221 by the suction conveyance mechanism 3 is substantially the same height as the lower surface of the conveyance belt 30 wound around the lower driven rollers of the second driven roller group 33 shown in FIG. Are sandwiched between a pair of conveying rollers 37 and a driven roller 38 having a nip portion.

  The paper P sandwiched between the transport roller 37 and the driven roller 38 is transported by the transport roller 37 and the transport direction is changed downward by the action of the guide member. Next, after being transported downward by the transport rollers R226 and R227 and guided in a substantially horizontal direction on the left side of the drawing by the guide member, the leading end abuts on the transport roller R228 in a rotation stopped state and stopped. It is sent into the image forming apparatus with the start of rotation.

  Further, the sheet P fed out from the sheet tray P222 by the suction conveyance mechanism 3 is substantially the same height as the lower surface of the conveyance belt 30 wound around the lower driven rollers of the second driven roller group 33 shown in FIG. It is sandwiched between a pair of conveying rollers 37 and a driven roller 38 having a nip portion.

  The paper P sandwiched between the transport roller 37 and the driven roller 38 is transported by the transport roller 37 and stopped with the leading end in contact with the transport roller R228 in a rotation stop state, and the rotation of the transport roller R228 is started. It is sent into the image forming apparatus.

<Example of Configuration of Image Forming Apparatus of Embodiment>
FIG. 11 is a configuration diagram illustrating an example of an image forming apparatus to which a paper feeding unit including the paper feeding device of each embodiment is connected. The image forming apparatus 10 is, for example, a digital color copier, and includes an automatic document feeder 11 at the top of the apparatus body, and includes an image reading unit 12, an image forming unit 13, a belt unit 14, a paper feeding unit 15, and a fixing device T. , A reverse paper discharge unit 16 and a refeed unit 17.

  The automatic document feeder 11 feeds the documents one by one and conveys them to the image reading position, and discharges the document after the image reading to the document discharge tray.

  The automatic document feeder 11 includes a document placement tray 101, a document separation unit 103, a document transport unit 105, a document discharge unit 107, a document discharge tray 109, and a document reversing roller 111 for reversing the front and back sides of the document. Prepare.

  A plurality of originals placed on the original placement tray 101 are separated one by one by the original separation unit 103 and conveyed to the image reading position via the original conveyance unit 105.

  The document reading position is provided on the downstream side of the document conveying unit 105, and an image of the document is read through the slit 201 of the image reading unit 12, and the read document is discharged by the document discharge unit 107. The paper is discharged onto the tray 109. In double-sided scanning, a document on which one side is scanned is conveyed by a document reversing roller 111 in a direction indicated by a two-dot chain line arrow.

  Then, after the document is stopped in a state where the trailing edge of the document in the advancing direction is held, the document reversing roller 111 is reversely rotated and conveyed again to the image reading position via the document conveying unit 105. Thereafter, the document is discharged onto the document discharge tray 109 by the document discharge unit 107.

  The above-described process is repeated for a plurality of documents placed on the document placement tray 101.

  The image reading unit 12 includes a first mirror unit 205 that integrates the above-described slit 201, a document irradiation lamp 213, and a first mirror 215 that reflects the reflected light of the document, a second mirror 217, and a third mirror 219. And a second mirror unit 207 integrated with each other.

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

  In a mode in which the document conveyed by the automatic document conveying device 11 is read by the image reading unit 12, the first mirror unit 205 and the second mirror unit 207 are fixed at the positions shown in the drawing.

  The image information read by the image reading unit 12 is subjected to appropriate image processing and then temporarily stored in the memory of the control unit. The image information of each color read by the image reading unit 12 and stored in the memory is sequentially read from the memory and transmitted as an electrical signal to the image forming unit 13 for each color.

  The image forming unit 13 forms four image forming units 130 (130Y, 130M, and 130C) of yellow (Y), magenta (M), cyan (C), and black (BK) that form a toner image corresponding to the color separation image. , 130BK).

  Each image forming unit 130 includes a photosensitive member 310 having a photosensitive layer provided on a drum-shaped metal substrate, a charger 320, an exposure optical system 330 serving as an image writing unit, a developing device 340, a primary transfer unit 350, and a cleaning unit 360. Is the main component. The exposure optical system 330 is an exposure unit configured with a laser optical system.

  In the figure, only members constituting the yellow (Y) image forming unit are denoted by reference numerals, and the other image forming units have the same configuration, and thus the reference numerals are omitted.

  The developing device 340 stores a two-component developer including a carrier and toner. Further, the developing device 340 includes a cylindrical non-magnetic developing sleeve containing a plurality of fixed magnets, a developer accommodating portion, and a toner concentration detection sensor.

  The developer is magnetically supported on the developing sleeve by the action of a plurality of magnets, and is conveyed to the developing area by the rotation of the developing sleeve. Next, the developer after the development processing is applied to the developing sleeve by the action of a repulsive magnetic field. Removed from. In addition, a bias voltage in which a DC voltage having a predetermined polarity (here, negative polarity) and an AC voltage are superimposed is applied to the developing sleeve.

  The primary transfer unit 350 includes a primary transfer roller that faces the circumferential surface of the photoreceptor 310 with the intermediate transfer belt 401 interposed therebetween.

  The cleaning unit 360 removes the toner remaining on the photoreceptor 310 after the primary transfer, and stores the removed toner in a waste toner box DT installed on the side of the paper tray.

  The image forming units 130 of the respective colors have yellow (Y), magenta (M), cyan (C), and black (from the top) along the traveling direction of one plane A of the intermediate transfer belt 401 arranged in the vertical direction. BK).

  The belt unit 14 includes the above-described intermediate transfer belt 401, support rollers 405, 406, and 407 that suspend the intermediate transfer belt, a backup roller 410, and the like.

  Further, the transfer roller 510 is disposed opposite to the intermediate transfer belt 401, and a secondary transfer unit is configured by the backup roller 410 that rotates while being pressed against the transfer roller 510.

  The image forming process in the image forming apparatus 10 is performed as follows. The surface of the photoreceptor 310 that rotates counterclockwise in the drawing is charged to a predetermined polarity (here, negative polarity) by the charger 320.

  Next, the exposure optical system 330 performs exposure corresponding to the first color signal, that is, the yellow (Y) image signal, and a latent image corresponding to the yellow (Y) image is formed on the photoreceptor 310. The

  The latent image on the photoconductor 310 is reversely developed in contact or non-contact with the developer of the developing device 340 to form a yellow (Y) toner image on the photoconductor 310, and then intermediate transfer is performed by the primary transfer unit 350. Primary transfer is performed on the belt 401.

  The image forming process using other color signals sequentially started after a predetermined time from the start of image forming using the first color signal is the same for each color of magenta (M), cyan (C), and black (BK) as in the case of yellow. This is performed by the image forming unit 130.

  The toner images of the respective colors formed on the photoreceptors 310 of the respective colors are secondarily transferred while being superimposed on the intermediate transfer belt 401, and a color toner image is formed on the intermediate transfer belt 401. On the other hand, the surface of the photoreceptor 310 after the completion of the primary transfer process is cleaned by the cleaning unit 360.

  Note that the start timing of each image forming process for the photosensitive member 310 or the intermediate transfer belt 401 is performed as follows. That is, the registration sensor 413 is provided outside the intermediate transfer belt 401 and in a section from the position where the transfer roller 510 is located to the position where the yellow image forming unit is provided as viewed in the rotation direction of the intermediate transfer belt.

  Then, the time is measured starting from the time when the registration sensor 413 detects the reference mark provided on the intermediate transfer belt 401, and sequentially (Y), (M), (C), and (BK) every time a predetermined time elapses. Start the image forming process.

  The control unit S includes a CPU that performs arithmetic control processing, a ROM that stores various programs, a RAM that stores various data, and the like, and performs all controls such as control related to a series of image forming processes.

  The image forming apparatus 10 includes three paper trays P11, P12, and P13 at the lower part of the apparatus main body. Each of the paper trays P11, P12, and P13 may include the above-described transporting bell, the suction transport mechanism 3 having the separation protrusion 5A, the separation air blowing mechanism 4, the floating air blowing mechanism 6, and the like. Each of the paper trays P11, P12, and P13 can be pulled out toward the front of the drawing.

  The paper trays P11, P12, and P13 include paper feed rollers 503, 513, and 523, separation rollers 506, 516, and 526, and transport rollers R1, R2, and R3. The paper P sent out by these rollers is transported by the transport roller R4. It is conveyed by ~ R7.

  The registration roller 59 is provided downstream of the conveyance roller R7 and at a position close to the secondary transfer unit. Further, a fixing device T having a fixing roller T1 having a built-in heating source and a pressure roller T2 rotating in pressure contact with the fixing roller T1 is disposed downstream of the secondary transfer portion on the conveyance path.

  The paper discharge roller 600 discharges the paper P on which an image has been formed. On the paper discharge tray 650, the paper P discharged by the paper discharge roller 600 is stacked.

  The reversing unit paper discharge unit 16 reverses the discharged paper P and discharges it. The paper refeeding unit 17 reversely conveys the paper on which the image is formed on one side, and refeeds the paper to the registration roller 59.

  Next, other configurations of the apparatus will be briefly described in relation to the process from when the color toner image formed on the intermediate transfer belt 401 is transferred onto a sheet and discharged outside the apparatus.

  The paper P is fed by the paper feed rollers 503 (513 and 523) at an appropriate timing corresponding to image formation on the intermediate transfer belt 401. The paper P to be fed is a paper of a size selected on the operation display unit 150 in which the number of sheets, a start button, a magnification, an image density, and the like can be set. The paper trays P11, P12, P13, Alternatively, the paper is fed from the paper trays P220, P221, and P222 of the paper feeding unit 90.

  Next, the sheet P is nipped and conveyed by the separation roller 506 and a plurality of conveyance rollers R1 to R7 provided on the conveyance path, and conveyed to a registration roller 59 provided on the upstream side of the secondary transfer unit. .

  After the leading end of the sheet P comes into contact with the registration roller 59, the sheet P is fed at a timing overlapping with the color toner image area on the intermediate transfer belt 401 by restarting the rotation of the registration roller 59.

Next, the paper P is pressed and nipped together with the intermediate transfer belt 401 by the backup roller 410 and the transfer roller 510 in the secondary transfer portion, and during this time, the color toner image on the intermediate transfer belt 401 is secondarily transferred onto the paper P. The It is desirable to apply a predetermined transfer bias voltage to the transfer roller 510 during the secondary transfer.
The sheet P on which the color toner image has been transferred is separated from the intermediate transfer belt 401, conveyed to the fixing device T by a conveyance belt (not shown), and the color toner is melted and fixed on the sheet P by heating and pressure processing. .

  The paper P after the fixing process by the fixing device T is conveyed by a paper discharge roller 600 provided downstream, and is discharged onto a paper discharge tray 650 outside the apparatus main body. On the other hand, the surface of the intermediate transfer belt 401 after the secondary transfer is cleaned by the cleaning unit 360, and the next color toner image transfer process is performed.

  In the figure, the position of the switching member 601 is a position when the paper P is discharged without being reversed after the fixing process. When reversely discharging the paper P, the switching member 601 is rotated by a predetermined amount, and the paper P after the fixing process is guided downward along the right side of the switching member 601.

  Next, after the paper is stopped with the rear end being nipped by the reverse roller 602, the paper P is raised along the left side of the switching member 601 by the reverse rotation of the reverse roller 602, and the paper discharge roller 600 is moved. The paper is discharged.

  Further, in the double-sided copy mode using the refeed unit 17, the paper P after the fixing process on which an image is formed on one side is guided downward along the right side of the switching member 601, and the trailing edge of the paper P is It is stopped in a state where it is nipped by the reverse roller 605.

  Next, the reverse roller 605 is reversely rotated and raised along a guide plate (not shown), and is conveyed to a plurality of rollers 701, 702, and 703 and reversely conveys the paper P.

  The image forming process for the second surface of the paper P is the same as described above, and any of the discharge paths after being sent out from the fixing device T is selected.

  On the other hand, the toner removed from the photoreceptor by the cleaning unit 360 is sent to and stored in the waste toner box DT. Although the above is an image forming apparatus that forms a color image, an image forming apparatus that forms a monochrome image may be used.

  The control unit S selects the above-described mode (1) or mode (2) based on the paper type selected on the operation display unit 150 by the user's operation, and the displacement of the separation protrusion 5A in the paper feeding unit 90 and the paper P transport is controlled. In the configuration in which the paper feeding device of the present invention is applied to the paper trays P11, P12, and P13 in the apparatus, the displacement of the separation protrusion 5A and the conveyance of the paper P are controlled in each paper tray.

  Here, the operation mode may be directly selected on the operation display unit 150. Accordingly, the mode (1) or the mode (2) is selected by the user operation regardless of the paper type, depending on the state of occurrence of scratches, the state of occurrence of double feeding, or the like of the paper P that is formed and output after image formation. The operation of the displacement of the separation protrusion 5A can be switched, and it is possible to flexibly cope with the occurrence of a problem.

  The present invention is applied to an image forming apparatus including a sheet feeding device that sucks and feeds stacked sheets with air.

FIG. 3 is a side view illustrating an example of a sheet feeding device according to the first embodiment. It is the top view which looked at the adsorption conveyance mechanism which shows an example of the paper feeder of 1st Embodiment from the lower side. FIG. 3 is a perspective view of a sheet storage unit illustrating an example of a sheet feeding device according to the first embodiment. FIG. 6 is a side view illustrating an operation example of the sheet feeding device according to the first embodiment. FIG. 6 is a front view illustrating an operation example of the sheet feeding device according to the first embodiment. FIG. 6 is a side view of a main part illustrating an operation example of the sheet feeding device according to the first embodiment. 3 is a functional block diagram illustrating an example of a control system of the sheet feeding device according to the first embodiment. FIG. It is explanatory drawing which shows an example of paper type setting information. 6 is a time chart illustrating an operation example of the sheet feeding device according to the first embodiment. It is a block diagram which shows an example of the paper feed unit provided with the paper feeder of each embodiment. 1 is a configuration diagram illustrating an example of an image forming apparatus to which a paper feeding unit including a paper feeding device of each embodiment is connected.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1A ... Paper feeder, 2 ... Paper mounting stand, 20 ... Paper storage part, 21 ... Paper front-end | tip abutting surface, 22 ... Upper limit detection sensor, 3 ... Adsorption conveyance mechanism, DESCRIPTION OF SYMBOLS 30 ... Conveyance belt, 30a ... Air inlet, 30b ... Adsorption surface, 31 ... Drive roller, 32 ... 1st driven roller, 33 ... 2nd driven roller group, 34・ ・ ・ Suction chamber, 39 ... Paper feed detection sensor, 4 ... Separation air blowing mechanism, 5A ... Separation protrusion, 50 ... Shaft, 51 ... Elastic member, 52 ... Solenoid, 6 ... Floating air blowing mechanism, 60 ... Floating air outlet, 61 ... Blower fan, 7 ... Adsorption detection sensor, S1 ... Control unit, S2 ... Operation unit

Claims (12)

A paper table on which a plurality of paper sheets are stacked;
A suction surface for sucking the paper stacked on the paper mounting table from the upper surface and sucking the uppermost paper;
A transport mechanism for transporting the paper adsorbed on the suction surface to a paper transport path;
Separating protrusions configured to be able to project and retract in the suction direction with respect to the suction surface, protrude from the suction surface, and push down a part of the paper sucked to the suction surface;
A sheet feeding device comprising: a separation position where the separation protrusion protrudes with respect to the suction surface; and a protrusion driving unit which displaces the separation protrusion to a storage position stored on the suction surface side. The projection driving unit has a first operation mode in which the separation projection is displaced to a storage position and a paper feeding operation is performed, and a second operation mode in which the separation projection is displaced to a separation position and a paper feeding operation is performed. ,
The sheet feeding device according to claim 1, further comprising a control unit that performs switching between the first operation mode and the second operation mode. The paper feeding device according to claim 1, further comprising a control unit that causes the projection driving unit to displace the separation protrusion between a separation position and a storage position in accordance with the conveyance of the sheet by the conveyance mechanism. The timing of displacing the separation protrusion to the separation position by the protrusion driving unit is such that the conveyance mechanism moves the next sheet after the trailing edge of the preceding sheet conveyed by the conveyance mechanism passes through the separation protrusion. Until just before starting,
The timing at which the separation protrusion at the separation position is displaced to the storage position is from immediately after the separation protrusion is displaced to the separation position to immediately before the next paper conveyance is started by the conveyance mechanism. The sheet feeding device according to claim 2 or 3, A suction detection sensor for detecting whether or not the paper is sucked to the suction surface;
A paper detection sensor for detecting paper transported by the transport mechanism;
The control unit is configured to set a timing at which the projection driving unit displaces the separation protrusion to a separation position and a storage position according to outputs of the suction detection sensor and the paper detection sensor, and a timing at which the transport mechanism transports the paper. The sheet feeding device according to claim 4, wherein the sheet feeding device is controlled. The said adsorption | suction detection sensor detects the displacement of the said separation protrusion pressed by the paper attracted | sucked to the said suction surface, and detects the presence or absence of the suction of the paper to the said suction surface. Paper feeder. The control unit is configured to determine in advance an operation mode to be executed in accordance with a paper type selected from preset paper types, with the paper type of the paper loaded on the paper mounting table being preset. The paper feeding device according to claim 2. The control unit sets at least one of coated paper and non-carbon paper as a selectable paper type, or both, and sets the coated paper or non-carbon paper as the paper type of the paper loaded on the paper mounting table. The sheet feeding device according to claim 7, wherein when selected, the first operation mode is selected. One or more paper trays in which paper is stored;
A paper mounting table on which a plurality of sheets are stacked in the paper tray;
A suction surface for sucking the paper stacked on the paper mounting table from the upper surface and sucking the uppermost paper;
A transport mechanism for transporting the paper adsorbed on the suction surface to a paper transport path;
Separating protrusions configured to be able to project and retract in the suction direction with respect to the suction surface, protrude from the suction surface, and push down a part of the paper sucked to the suction surface;
A sheet feeding unit comprising: a separation position where the separation protrusion protrudes with respect to the suction surface; and a protrusion driving unit which displaces the separation protrusion to a storage position stored on the suction surface side. An image forming unit for forming an image on paper;
A paper feeding device for feeding paper to the image forming unit;
A control unit that performs control to feed a sheet from the sheet feeding device to the image forming unit and form an image in the image forming unit;
The paper feeder is
A paper table on which a plurality of paper sheets are stacked;
A suction surface for sucking the paper stacked on the paper mounting table from the upper surface and sucking the uppermost paper;
A transport mechanism for transporting the paper adsorbed on the suction surface to a paper transport path;
Separating protrusions configured to be able to project and retract in the suction direction with respect to the suction surface, protrude from the suction surface, and push down a part of the paper sucked to the suction surface;
A separation drive position where the separation protrusion protrudes with respect to the suction surface and a protrusion drive unit that displaces the separation protrusion to a storage position stored on the suction surface side;
The control unit has a first operation mode in which the protrusion driving unit displaces the separation protrusion to a storage position to perform a paper feeding operation, and a second operation mode in which the separation protrusion is displaced to a separation position to perform a paper feeding operation. An image forming apparatus characterized in that control is performed by switching operation modes, or control is performed to displace the separation protrusion between a separation position and a storage position by the protrusion driving unit in accordance with sheet conveyance by the conveyance mechanism. . An operation unit for selecting a paper type of the paper loaded on the paper placement table;
The image forming apparatus according to claim 10, wherein the control unit determines an operation mode to be executed according to a paper type selected by the operation unit. An operation unit for selecting the first operation mode or the second operation mode;
The image forming apparatus according to claim 10, wherein the control unit determines an operation mode to be executed according to an operation mode selected by the operation unit.

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