JP5995547B2 - Paper feeding device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a sheet feeding device that pulls out and conveys a sheet from a sheet bundle loaded on a sheet loading table, and an image forming apparatus including the sheet feeding device.

  This type of paper feeding device includes a paper stacking table on which a stack of sheets is stacked, a paper transporting belt disposed above the paper stacking base, and a fan that sucks air through the vent holes of the paper transporting belt. In some cases, the uppermost sheet of the sheet bundle is attracted to and conveyed by the sheet conveying belt by suction of air through the ventilation holes of the conveying belt.

  In such a sheet feeding device, when the uppermost sheet of the sheet bundle and the next sheet that overlaps with the uppermost sheet are adhering to each other while being adhered to the sheet conveying belt, multiple feeding of the sheets occurs. For this reason, air is blown onto the end face of the sheet bundle, air is allowed to enter between the sheets, each sheet is dispersed, and it is easy to suck and pull out the sheets one by one from the sheet bundle. Double feeding is prevented.

  For example, in Patent Document 1, air is blown to the front end surface and side end surfaces of a sheet bundle, the uppermost sheet of the sheet bundle is levitated to the sheet conveyance belt, and the sheet is adsorbed to the sheet conveyance belt and conveyed. . Further, when the sheet is floating, the actuator for detecting the position of the upper surface of the sheet bundle is retracted so that the actuator does not affect the sheet floating.

JP 2011-46457 A

  By the way, when the paper is thick paper, the paper becomes heavier and the rigidity thereof becomes higher, so that it is difficult to attract the paper by the paper transport belt. For this reason, it is necessary to make the upper surface of the sheet bundle closer to the sheet conveying belt to facilitate the adsorption of the sheet by the sheet conveying belt.

  However, when the upper surface of the sheet bundle is brought closer to the sheet conveying belt, not only the uppermost sheet of the sheet bundle but also the next sheet overlapping the uppermost sheet is easily attracted to the sheet conveying belt. Cause double feed. In particular, when the paper is curled or the size of the paper is small, the next paper is easily attracted by the paper transport belt, and the frequency of occurrence of double feeding of paper increases.

  Therefore, the present invention has been made in view of the above-described conventional problems, and even for thick paper, it is possible to satisfactorily adsorb the paper by the paper transport belt, and effectively prevent double feeding of paper. An object of the present invention is to provide a sheet feeding device capable of performing the above and an image forming apparatus including the same.

  In order to solve the above-described problems, a paper feeding device according to the present invention is configured to adsorb a sheet stacking unit by stacking a sheet stacking unit, a lifting unit that lifts and lowers the sheet stacking unit, and sucking the sheets of the sheet stacking by air suction. A sheet feeding device including a sheet conveying member that conveys the sheet stacking base by controlling the lifting unit during an adsorption period in which the sheet is adsorbed to the sheet conveying member by suction of the air. A control unit is provided that lowers the specified amount and starts the conveyance of the sheet by the sheet conveying member during or after the specified amount of the sheet stacking table is lowered.

  In such a paper feeding device of the present invention, the paper stacking base is lowered by a specified amount during the suction period in which the paper is sucked by the paper transport member. At this time, if the uppermost sheet of the sheet bundle and the next sheet overlapping the uppermost sheet are in the state of being adsorbed by the sheet conveying member, the uppermost sheet is favorably adsorbed by the sheet conveying member. However, a part of the next sheet is only attracted to the sheet conveying member, and the next sheet does not completely float from the upper surface of the sheet bundle. For this reason, when the sheet stacking table is lowered by a specified amount and the upper surface of the sheet bundle is lowered by a specified amount, the next sheet follows the upper surface of the sheet bundle and follows the upper surface of the sheet bundle. It is separated from the paper and shaken off. In this state, when the conveyance of the sheet by the sheet conveying member is started, only the uppermost sheet is conveyed, and the double feeding of the sheets does not occur.

  In the paper feeding device of the present invention, the control unit transports the paper by the paper transport member after a predetermined time has elapsed since starting the control of the lifting unit for lowering the paper stacking base by a specified amount. Has started.

  In this case, after the next sheet is shaken off from the sheet conveying member, only the uppermost sheet is reliably conveyed by the sheet conveying member.

  Furthermore, the paper feeding device of the present invention includes a position detection unit that detects the upper surface position of the sheet bundle that has reached the first suction position, and the control unit detects the upper surface position of the sheet bundle by the position detection unit. When detected, the upper surface position of the sheet bundle is raised to a second suction position higher than the first suction position by controlling the elevating unit to start the suction period. In the suction period, The sheet stacking table is lowered by a specified amount by controlling the elevating unit, and the upper surface position of the sheet bundle is lowered to a separation position lower than the first suction position.

  Here, the second suction position is the highest, the first suction position is the next highest, and the separation position is the lowest. Therefore, when the upper surface position of the sheet bundle is raised to the second suction position, even if the sheets in the sheet bundle are thick sheets, the sheets are favorably attracted to the sheet conveying member. Even if the uppermost sheet of the sheet bundle and the next sheet overlapping the uppermost sheet are attracted to the sheet conveying member, if the upper surface position of the sheet bundle is lowered to the separated position, the next sheet Following the upper surface of the bundle, it is separated from the paper conveying member and reliably shaken off.

  The paper feeding device of the present invention further includes a paper detection unit that detects the paper conveyed to a predetermined position by the paper conveyance member, and the control unit detects when the paper is detected by the paper detection unit. , The suction of the paper to the paper transport member by the suction of the air and the transport of the paper by the paper transport member are stopped, and the elevation unit is moved until the upper surface position of the paper bundle is detected by the position detection unit. The sheet loading table is raised by the control.

  Thereby, the upper surface position of the sheet bundle is returned to the first suction position, and the suction of the second sheet can be started.

Furthermore, the paper feeding device of the present invention further includes a paper input unit for inputting that the paper stored in the paper feeding device is a second paper thicker than the first paper , and the control unit includes the paper input unit. When the second sheet is input, the sheet stacking table is lowered by a specified amount by controlling the elevating unit during the suction period, so that the specified amount of the sheet stacking table is lowered or ended. When the sheet conveyance member starts to convey the sheet later and the sheet input unit inputs that the sheet is not the second sheet, the position of the sheet stacking table is maintained.

For example, the paper input unit is an input operation unit, and the input operation unit receives the second operation when the input operation unit inputs that the second paper is stored in the paper feeding device . The fact that it is a sheet is output to the control unit.

Alternatively, the paper input unit is a sensor provided in the paper feeding device, and the sensor detects that the paper contained in the paper feeding device is the second paper and outputs the second paper to the control unit. doing.

  On the other hand, an image forming apparatus of the present invention includes the paper feeding device of the present invention and a printing unit that records an image on a sheet supplied from the paper feeding device.

  Such an image forming apparatus of the present invention also has the same operational effects as the sheet feeding apparatus of the present invention.

  As described above, according to the present invention, the sheet stacking table is lowered by a specified amount during the adsorption period in which the sheet is adsorbed by the sheet conveying member. At this time, if the uppermost sheet of the sheet bundle and the next sheet overlapping the uppermost sheet are in the state of being adsorbed by the sheet conveying member, the uppermost sheet is favorably adsorbed by the sheet conveying member. However, a part of the next sheet is only attracted to the sheet conveying member, and the next sheet does not completely float from the upper surface of the sheet bundle. For this reason, when the sheet stacking table is lowered by a specified amount and the upper surface of the sheet bundle is lowered by a specified amount, the next sheet follows the upper surface of the sheet bundle and follows the upper surface of the sheet bundle. It is separated from the paper and shaken off. In this state, when the conveyance of the sheet by the sheet conveying member is started, only the uppermost sheet is conveyed, and the double feeding of the sheets does not occur.

1 is a cross-sectional view illustrating an image forming apparatus to which an embodiment of a paper feeding device of the present invention is applied. FIG. 3 is a perspective view illustrating an appearance of the sheet feeding device according to the present embodiment as viewed obliquely from above. FIG. 3 is a plan view illustrating a main part of a paper feeding device. FIG. 3 is a front view illustrating a main part of a paper feeding device. FIG. 4 is a perspective view showing the sheet feeding device with the sheet drawer portion removed, as viewed obliquely from the rear. It is a perspective view which shows a contact member and a position switching part seeing from the diagonally forward direction, and has shown the state when a paper feeder is pulled out. It is a perspective view which shows a contact member and a position switching part seeing from diagonally forward, and has shown the state when a paper feeder is pushed in. (A), (b), (c) is a side view which shows the positional relationship of the retracting position of a contact member, a standby position, and a 1st suction position, the shielding piece of a contact member, and an optical sensor. . FIG. 3 is a perspective view showing a paper drawer portion of the paper feeding device as viewed obliquely from above and front. It is a perspective view which shows a paper drawer part seeing from back diagonally upward. It is a perspective view which shows a paper drawer part seeing from back diagonally downward. It is a perspective view which shows roughly the opening-and-closing valve provided in the air intake duct of the paper drawer part. 2 is a block diagram schematically showing a control system of the image forming apparatus. FIG. 3 is a plan view showing an operation panel of the image forming apparatus. FIG. It is sectional drawing which shows a paper feeding apparatus roughly. (A), (b) is a figure which shows the procedure for registering the kind of paper accommodated in the paper feeder on the screen of the display part of the operation panel. FIG. 4 is a diagram conceptually illustrating a data table in which types of sheets stored in a sheet feeding device are registered. (A), (b) is a figure which shows the procedure for inputting which recording paper is supplied from which of each paper feed cassette and each paper feeder on the screen of the display part of an operation panel. 3 is a flowchart illustrating a control procedure of a paper feeding device. (A)-(c) is an operation | movement transition diagram of a paper feeder when drawing a recording paper and conveying it. (D)-(f) is the operation | movement transition diagram following FIG. 20A. 6 is a timing chart illustrating a control procedure of the paper feeding device.

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

  FIG. 1 is a cross-sectional view showing an image forming apparatus to which an embodiment of a paper feeding device of the present invention is applied. The image forming apparatus 1 is roughly composed of a printing unit 11, a sheet transport unit 12, a sheet supply unit 13, a large-capacity paper feed cassette (LCC) 14, a document reading device 15, and a document transport device 16. .

  In the printing unit 11, after the residual toner on the surface of the photosensitive drum 21 is removed and collected by the cleaning device 26, the surface of the photosensitive drum 21 is uniformly charged to a predetermined potential by the charging device 22, and then the laser exposure device 23. The surface of the photosensitive drum 21 is exposed to form an electrostatic latent image on the surface, and the developing device 24 develops the electrostatic latent image on the surface of the photosensitive drum 21 to form a toner image on the surface of the photosensitive drum 21. To do.

  The transfer roller 25 is pressed against the photosensitive drum 21 to form a nip area with the photosensitive drum 21, and the recording paper conveyed through the paper conveyance path 33 is sandwiched and conveyed in the nip area. At the same time, the toner image on the surface of the photosensitive drum 21 is transferred onto the recording paper. Then, the recording paper is sandwiched between the heating roller 28 and the pressure roller 29 of the fixing device 27 and heated and pressed to fix the toner image on the recording paper.

  On the other hand, the paper supply unit 13 includes a plurality of paper supply cassettes 38. Each paper feed cassette 38 includes a pickup roller 39 and the like for pulling out and feeding out recording sheets one by one, and sends out the pulled-out recording sheets to the sheet transport path 33 of the sheet transport section 12.

  The large-capacity paper feed cassette (LCC) 14 can store a large amount of recording paper, pulls out the recording paper one by one, and sends it out to the paper transport path 33 of the paper transport section 12.

  The recording sheet is conveyed through a sheet conveying path 33 and is discharged to a sheet discharge tray 37 via a transfer roller 25 and a fixing device 27 and a sheet discharge roller 36. In this paper conveyance path 33, the recording paper is temporarily stopped and the leading edges of the recording paper are aligned, and then the recording paper is fed in accordance with the transfer timing of the toner image in the nip area between the photosensitive drum 21 and the transfer roller 25. A registration roller 32 for starting conveyance, a conveyance roller 31 for urging conveyance of a recording sheet, a sheet discharge roller 36, and the like are arranged.

  Further, when printing not only on the front side of the recording paper but also on the back side, the position of the branch claw 35 is switched, and the recording paper is conveyed in the reverse direction from the paper discharge roller 36 to the reverse path 34, so that the recording paper The front and back sides are reversed, and the recording paper is again guided to the registration roller 32, and an image is recorded and fixed on the back surface of the recording paper in the same manner as the front surface of the recording paper, and the recording paper is discharged to the paper discharge tray 37.

  Next, the document reading device 15 and the document conveying device 16 mounted on the upper part of the main body of the image forming apparatus 1 will be described. The document conveying device 16 is pivotally supported on the back side of the document reading device 15 by a hinge (not shown), and the document conveying device 16 is opened by moving the front portion up and down to open the document reading device. Documents can be placed on the 15 document placement glasses 44.

  In the document reading device 15, the first scanning unit 45 is moved in the sub-scanning direction, and the document on the document placement glass 44 is illuminated by the light source of the first scanning unit 45 while following the second scanning unit 46. The reflected light is reflected by the mirrors of the first and second scanning units 45, 46, and the reflected light is further condensed by the imaging lens 47 and led to a CCD (Charge Coupled Device) 48, and the original image of the original is captured by the CCD 48. Read the image.

  When reading an image on the surface of the document being conveyed by the document conveying device 16, the first scanning unit 45 is moved to a reading position below the document reading glass 55 and the second scanning unit 45 is moved in accordance with the position of the first scanning unit 45. The scanning unit 46 is positioned. In the document transport device 16, the document is drawn from the document tray 57, transported to the document reading glass 55 through the document transport path 58, and the document on the document reading glass 55 is illuminated by the light source of the first scanning unit 45. The reflected light is reflected by the mirrors of the first and second scanning units 45 and 46, and the reflected light is condensed by the imaging lens 47 and guided to the CCD 48. The image of the original is read by the CCD 48, and the original is read. The document is discharged to the document discharge tray 62.

  The original image read by the CCD 48 in this manner is input to the laser exposure device 23 of the image forming apparatus 1, and the image is recorded on the recording paper in the image forming apparatus 1, and this recording paper is output as a copy original.

  Next, the configuration of the paper feeding device 71 of the present embodiment built in the large capacity paper feeding cassette 14 will be described in detail. The large-capacity paper feed cassette 14 contains a plurality of paper feed devices 71, all of the paper feed devices 71 having the same configuration, storing a large amount of recording paper, and drawing out the recording paper one by one. Then, the sheet is sent to the sheet conveyance path 33 of the image forming apparatus 1.

  FIG. 2 is a perspective view showing the external appearance of the paper feeding device 71 of the present embodiment as viewed obliquely from above. The paper feeding device 71 has a drawer housing 71a, and the main part of the paper feeding device 71 is provided inside the drawer housing 71a. The drawer housing 71a is supported by a well-known mechanism combining rollers and rails (not shown), for example, so as to be reciprocally movable in the arrow directions Ma and Mb within the main body of the large-capacity paper feed cassette 14, so The paper feeding device 71 can be taken in and out of the accommodation space inside the main body of the paper cassette 14. A sheet bundle is replenished and set in the sheet feeding device 71 in a state where the sheet feeding device 71 is pulled out from the accommodation space inside the main body of the large capacity sheet feeding cassette 14. In addition, in a state where the paper feeding device 71 is pushed into the housing space inside the main body of the large capacity paper feeding cassette 14, the paper bundle 71 sequentially draws out the sheets of the paper bundle to the paper transport path 33 of the image forming apparatus 1. And fed.

  3 and 4 are a plan view and a front view showing the paper feeding device 71 of the present embodiment. As shown in FIGS. 3 and 4, the sheet feeding device 71 includes an outer frame 72 (the frame of the drawer housing 71 a shown in FIG. 2), a bottom plate 73, and a paper stacking base 74 disposed inside the outer frame 72. , And a paper drawer 75 disposed on one upper side of the outer frame 72.

  The sheet stacking table 74 is used for stacking a large amount of recording sheets (sheet bundle) and is provided inside the outer frame 72 so as to be moved up and down. The paper stacking base 74 is formed with an opening 74 a that is long in the recording paper drawing direction (paper transport direction) E. The paper trailing edge guide 76 is supported on the bottom plate 73 so as to be reciprocally movable along the recording paper drawing direction E, and protrudes upward through the opening 74 a of the paper stacking table 74. The recording paper drawing direction (paper conveyance direction) E is the front, and the direction opposite to the drawing direction E is the rear.

  Recesses 74b are formed on both sides of the sheet stacking table 74, and assist ducts 77 and 78 are disposed in the respective recesses 74b. The assist ducts 77 and 78 are supported on both sides of the outer frame 72 so as to be able to reciprocate in a direction orthogonal to the drawing direction E, and are moved in conjunction with each other so as to approach each other or to be separated from each other. The

  The paper drawing section 75 includes four endless paper conveyance belts 81, a set of rollers 82 and 83 around which each paper conveyance belt 81 is stretched, an intake / exhaust fan 84, an intake duct 85, an exhaust duct 86, and the like. ing. Each paper transport belt 81 is formed with a large number of air holes 81 a, and air is sucked from the air holes 81 a of each paper transport belt 81 to the intake / exhaust fan 84 through the intake duct 85. Further, the air exhausted from the intake / exhaust fan 84 is guided through the exhaust duct 86 and is blown out from the exhaust duct 86 to the inside of the outer frame body 72 in the direction opposite to the extraction direction E (rearward).

  FIG. 5 is a perspective view showing the outer frame body 72, the bottom plate 73, the paper stacking board 74, and the like viewed obliquely from the rear side with the paper drawer portion 75 removed. As shown in FIG. 5, two protruding pieces 74 c are formed on both sides of the paper stacking table 74, and each protruding piece 74 c protrudes from the opening 72 a on both sides of the outer frame body 72. On one side of the outer frame 72, two wires 87 are connected to the protruding pieces 74 c on one side of the paper stacking base 74, and each wire 87 is hooked around a plurality of driven pulleys 88 and drawn around a take-up pulley 89. It is connected. On the other side of the outer frame 72, the other two wires 87 are connected to the protruding pieces 74c on the other side of the sheet stacking table 74, and the other wires 87 are connected to a plurality of other driven pulleys 88. It is drawn around and connected to another take-up pulley 89. Each winding pulley 89 is fixed to both ends of a common shaft 91 that is rotatably supported. The shaft 91 is rotationally driven by a pulse motor 92 to rotate each winding pulley 89, and each wire 87 is wound to each winding 87. It is wound around the pulley 89 and is fed out from each winding pulley 89.

  When the shaft 91 is rotationally driven by the pulse motor 92 and each take-up pulley 89 is rotated in the clockwise direction, each wire 87 is taken up by each take-up pulley 89, the paper stacking table 74 is raised, and each take-up pulley 89 is also turned up. When the take-up pulley 89 is rotated in the counterclockwise direction, each wire 87 is fed out from each take-up pulley 89, and the sheet stacking table 74 is lowered. Further, the rotation angle of the take-up pulley 89 that is rotationally driven by the pulse motor 92 and the height of the paper stacking base 74 are in a corresponding relationship. Therefore, by controlling the rotation direction and rotation angle of the pulse motor 92, the height of the sheet stacking base 74 can be adjusted and set.

  Further, as shown in FIG. 5, assist fans 79 and 80 are provided outside the assist ducts 77 and 78, respectively. Each of the assist ducts 77 and 78 is a hollow body and has a ventilation path therein. Air sucked by each of the assist fans 79 and 80 is sent to the ventilation paths of the respective assist ducts 77 and 78. The air is blown out to the inside of the outer frame 72 from the blowout ports 77a and 78a of the assist ducts 77 and 78.

  Further, as shown in FIGS. 2, 3, and 5, the contact member 101 is supported on the upper portion of the paper rear end guide 76 so as to be reciprocally rotatable in the arrow rotation directions Qa and Qb. The contact member 101 is reciprocally rotated. When the paper feeding device 71 is pulled out from the storage space inside the main body of the large-capacity paper feeding cassette 14, the position switching unit 102 keeps the contact member 101 substantially vertical in conjunction with the drawing operation of the paper feeding device 71. Rotate in the arrow rotation direction Qa and retract. In this state, the sheet bundle can be replenished and set on the sheet stacking board 74 without being caught on the contact member 101. Further, when the paper feeding device 71 is pushed into the storage space inside the main body of the large capacity paper feeding cassette 14, the position switching unit 102 makes the contact member 101 substantially horizontal in conjunction with the pushing operation of the paper feeding device 71. Rotate it in the arrow rotation direction Qb until it falls. In this state, when the paper stacking base 74 is raised and the contact member 101 comes into contact with the rear end portion of the upper surface of the sheet bundle, the contact member 101 prevents the rear end portion of the recording sheets of the paper bundle from being lifted.

  6 is a perspective view showing a state of the contact member 101 and the position switching unit 102 when the paper feeding device 71 is pulled out, and FIG. 7 is a diagram of the contact member 101 when the paper feeding device 71 is pushed in. 3 is a perspective view showing a state of the position switching unit 102. FIG.

  As shown in FIGS. 6 and 7, the abutting member 101 is provided on the upper portion of the front side wall of the paper rear end guide 76 facing the recording paper drawing direction E. The contact member 101 includes a shaft portion 101a, a column portion 101b, two rollers 101e, a fan-shaped shielding piece 101f fixed around the shaft portion 101a, and the like. Thus, the shaft portion 101a and the contact member 101 are urged in the arrow rotation direction Qb.

  Further, an optical sensor 104 is disposed below the shaft portion 101 a and is fixed to the front side wall of the paper trailing edge guide 76. The optical sensor 104 is a light emitting element and a light receiving element that are arranged to face each other with a gap therebetween, and detects the shielding piece 101f when the shielding piece 101f that rotates together with the contact member 101 is between the light emitting element and the light receiving element. .

  The position switching unit 102 includes a rotating member 105, a rod 106, a coil spring 107, and the like. The position switching unit 102 moves the contact member 101 away from the upper surface of the sheet bundle in conjunction with the loading / unloading operation of the sheet feeding device 71. Or abut.

  Here, in the state where the paper feeding device 71 is pulled out as shown in FIG. 6, the rod 106 moves in the arrow direction Ma due to the urging force of the coil spring 107, the rotating member 105 rotates and rises, and the arm of the rotating member 105 The portion 105c comes into contact with the column portion 101b of the contact member 101, and the contact member 101 rises substantially vertically and retreats to the separation retreat position. Further, the shielding piece 101 f of the shaft portion 101 a protrudes in the pull-out direction (forward) E and moves away from the optical sensor 104.

  As shown in FIG. 7, when the paper feeding device 71 is pushed in, the whole paper feeding device 71 is housed in the housing space inside the main body of the large-capacity paper feeding cassette 14, and one end of the rod 106 is fed into the large-capacity paper feeding. Abutting on the main body frame of the cassette 14, the rod 106 moves in the arrow direction Mb, the rod 106 pushes the rotating member 105, and the rotating member 105 rotates against the urging force of the coil spring 107 and tilts. Then, the arm portion 105c of the rotating member 105 moves away from the position of the column portion 101b of the abutting member 101, the abutting member 101 is biased in the arrow rotation direction Qb by the torsion spring 103, and the abutting member 101 is moved. It rotates in the arrow rotation direction Qb and falls to a standby position obliquely below the horizontal. The shielding piece 101f of the shaft portion 101a rotates in the arrow rotation direction Qb and passes between the light emitting element and the light receiving element of the optical sensor 104.

  Thereafter, the sheet stacking table 74 is raised, the rear end of the upper surface of the sheet bundle pushes up the contact member 101, and the contact member 101 is slightly obliquely above the first suction position Bp1 (the sheet bundle). Up to the height at which the uppermost recording sheet is sucked). Further, the shielding piece 101f of the shaft portion 101a rotates in the arrow rotation direction Qa, enters between the light emitting element and the light receiving element of the optical sensor 104, and is detected by the optical sensor 104.

  8A, 8 </ b> B, and 8 </ b> C show the separation and retraction position, the standby position, and the first suction position Bp <b> 1 of the contact member 101, the shielding piece 101 f of the contact member 101, and the optical sensor 104. The positional relationship is shown.

  When the paper feeding device 71 is pulled out, as shown in FIG. 8A, the abutting member 101 rises substantially vertically and is in the separated retreat position, and the shielding piece 101f of the shaft portion 101a is in the pulling direction (front) E. It protrudes toward the center of the optical sensor 104 and is out of the space between the light emitting element 104a and the light receiving element 104b. For this reason, the shielding piece 101 f is not detected by the optical sensor 104.

  Immediately after the sheet feeding device 71 is pushed in, as shown in FIG. 8B, the abutting member 101 falls down below the horizontal position and is in a standby position, and the shielding piece 101f of the shaft portion 101a is an optical sensor. 104 is separated from between the light emitting element 104a and the light receiving element 104b. For this reason, the shielding piece 101 f is not detected by the optical sensor 104.

  Further, when the rear end portion of the upper surface of the sheet bundle pushes up the contact member 101, the contact member 101 is lifted slightly obliquely upward from the horizontal as shown in FIG. 8C to reach the first suction position Bp1. The shielding piece 101f of the shaft portion 101a is between the light emitting element 104a and the light receiving element 104b of the optical sensor 104. For this reason, the shielding piece 101 f is detected by the optical sensor 104.

  Therefore, based on the detection output of the optical sensor 104, it can be determined whether the contact member 101 is in the separation / retraction position, the standby position, or the first suction position Bp1.

  Next, the configuration of the paper drawer 75 will be described in detail. FIG. 9 is a perspective view showing the paper drawer portion 75 as viewed obliquely from the upper front. FIG. 10 is a perspective view showing the paper drawer portion 75 as viewed obliquely from above and rear, and FIG. 11 is a perspective view of the paper drawer portion 75 as seen from diagonally below and rear.

  As shown in FIGS. 9, 10, and 11, the paper drawing unit 75 includes four endless paper conveyance belts 81, a set of rollers 82 and 83 that bridge the paper conveyance belts 81, an intake / exhaust fan 84, An intake duct 85 and an exhaust duct 86 are provided.

  The intake duct 85 is a hollow body, and has an air suction path that is long in a direction orthogonal to the drawing direction (paper conveyance direction) E, and one end 85 a thereof is connected to the intake / exhaust fan 84. Then, as indicated by an arrow F, air is sucked from the air suction path of the intake duct 85 to the intake port (not shown) of the intake / exhaust fan 84 through the one side end 85a.

  In addition, air suction holes 94 (shown in FIG. 15) that overlap with the plurality of air holes 81 a of the paper transport belt 81 are formed on the lower surface 85 g of the intake duct 85 for each paper transport belt 81. Each air suction hole 94 is connected to the air suction path of the intake duct 85. When the air inside the intake duct 85 is sucked by the intake / exhaust fan 84, the outside air passes through the air holes 81a of the paper transport belts 81 and the air suction holes 94 of the lower surface 85g of the air intake duct 85, so Flows into.

  Furthermore, the front end portion 85c and the rear end portion 85d of the intake duct 85 are formed with respective recesses 85h, and the rollers 82 and 83 are disposed in these recesses 85h so as to be rotatably supported. The paper transport belt 81 is bridged between the rollers 82 and 83. The output shaft of the transport motor 93 is connected to the shaft of the front roller 82 via the transport clutch 127. The transport clutch 127 connects or disconnects the output shaft of the transport motor 93 and the shaft of the front roller 82. With both shafts connected by the transport clutch 127, the front motor 82 is rotationally driven in the arrow direction D by the transport motor 93, the rear roller 83 is driven to rotate, and each paper transport belt 81 is moved in the arrow direction D. Move around.

  The exhaust duct 86 is also a hollow body and has a long ventilation path in a direction orthogonal to the drawing direction E. One end 86a of the exhaust duct 86 is connected to the intake / exhaust fan 84, as indicated by an arrow K. Air is sent from the exhaust port (not shown) of the intake / exhaust fan 84 to the ventilation path of the exhaust duct 86 through the one end 86a of the exhaust duct 86.

  A plurality of exhaust ports 96 communicating with the ventilation path of the exhaust duct 86 are formed on the inner wall surface 86 d of the exhaust duct 86. An inner wall surface 86 d of the exhaust duct 86 is provided so as to overlap with an outer surface of a contact plate 72 b (shown in FIG. 5) of the outer frame body 72, and each exhaust port 96 of the exhaust duct 86 is a contact plate of the outer frame body 72. It faces the inside of the outer frame 72 through the notch 72c of 72b. When air is sent from the intake / exhaust fan 84 to the exhaust duct 86, the air is blown out from the exhaust ports 96 toward the inside of the outer frame 72 (rearward).

  Further, an opening / closing valve 111 is provided inside the one side end 85 a of the intake duct 85, and the opening / closing valve 111 opens and closes the air suction path of the intake duct 85. FIG. 12 is a diagram schematically showing the on-off valve 111. As shown in FIG. 12, the on-off valve 111 is rotatably supported by a shaft 112, and an arm 113 is rotatably connected to a part of the on-off valve 111 away from the shaft 112, and this arm 113 is a plunger 115 of a solenoid 114. Is rotatably connected to. When the plunger 115 is retracted or protrudes due to the deactivation or energization of the solenoid 114, the on-off valve 111 reciprocates and the on-off valve 111 opens and closes the air suction path of the intake duct 85.

  If the opening / closing valve 111 of the air suction path of the intake duct 85 is opened during the operation of the intake / exhaust fan 84, the air holes 81a of the paper transport belts 81 pass through the air suction path of the intake duct 85 to the intake / exhaust fan 84. Air is sucked, and at the same time, air is sent from the intake / exhaust fan 84 to the ventilation path of the exhaust duct 86, and the air is blown out from each exhaust port 96 toward the inside (rear) of the outer frame 72. Even when the intake / exhaust fan 84 is in operation, when the on / off valve 111 of the air suction path of the intake duct 85 is closed, almost no air is sucked from each vent hole 81a of each paper transport belt 81, and each exhaust air is exhausted. Almost no air is blown from the mouth 96.

  Next, the configuration of the control system of the image forming apparatus 1 will be described. FIG. 13 is a block diagram schematically showing a control system of the image forming apparatus 1. In FIG. 13, the main control unit 121 includes an image forming apparatus 1 (a printing unit 11, a sheet conveyance unit 12, a sheet supply unit 13, a document reading device 15, a document conveyance device 16, and a sheet feeding device of a large capacity sheet feeding cassette 14. 71, etc.) and is composed of a CPU, a RAM, a ROM, various interfaces and the like.

  The memory 122 is, for example, a hard disk device (HDD), and stores various data and programs. The image processing unit 123 performs various image processes on the image data.

  As shown in FIG. 1, the paper sensor 128 is provided in the vicinity of the transport roller 31 in the paper transport path 33 of the image forming apparatus 1, and is used for recording paper fed from the paper feed device 71 to the transport roller 31. Detect the tip. The open / close detection unit 129 detects the loading / unloading state of the sheet feeding device 71 with respect to the accommodation space inside the main body of the large-capacity sheet feeding cassette 14 and outputs the detection result to the main control unit 121.

  In the sheet feeding device 71, the intake / exhaust fan 84 sucks the air in the intake duct 85 and exhausts the air to the exhaust duct 86. Further, the pulse motor 92 raises and lowers the paper stacking table 74. Furthermore, the optical sensor 104 detects whether the contact member 101 is in the separation / retraction position, the standby position, or the first suction position Bp1. Further, the solenoid 114 is deenergized or energized to cause the plunger 115 to protrude or retract, and the open / close valve 111 opens or closes the air suction path of the intake duct 85. Further, the transport clutch 127 transmits or blocks the rotation of the output shaft of the transport motor 93 to the shaft of the roller 82.

  The operation panel 124 includes a display unit 125 made up of a liquid crystal display device and the like, and an input operation unit 126 made up of a plurality of operation keys and a touch panel superimposed on the screen of the display unit 125. Are displayed on the screen of the display unit 125, and instructions, data, and the like input by the operation of the input operation unit 126 are output to the main control unit 121.

  FIG. 14 is a plan view showing the operation panel 124. As shown in FIG. 14, the operation panel 124 includes a display unit 125 and an input operation unit 126. The input operation unit 126 includes a user setting key 131, a start key 132, a numeric keypad 133, and the like, a touch panel (not shown) superimposed on the screen of the display unit 125, and the like. When any one of the display buttons (display areas) on the screen of the display unit 125 is operated, the touch panel detects the operated display button. The input operation unit 126 notifies the main control unit 121 of an operated key or a display button (display area) detected by the touch panel. For example, by operating each key or each display button, the type of each sheet accommodated in each sheet feeding device 71 of each sheet feeding cassette 38 and large capacity sheet feeding cassette 14 can be input, or each sheet feeding cassette can be input. It is possible to input the recording paper from 38 and each paper feeding device 71. Alternatively, the start of printing by the printing unit 11 or the like of the image forming apparatus 1 can be input by operating the start key 132.

  In such a configuration, for example, the main control unit 121 causes the document reading device 15 to read a document image, stores image data indicating the document image in the memory 122, and the image processing unit 123 stores the image data in the memory 122. The image data is processed, and the image of the document indicated by the image data in the memory 122 is recorded on the recording paper by the printing unit 11.

  Further, when one of the paper feed cassettes 38 of the paper supply unit 13 is instructed as a recording paper supply source by the operation of the input operation unit 126 and the start of printing is instructed by the operation of the start key 132, a response is received. Then, the main control unit 121 controls the paper feed cassette 38 to supply recording paper from the paper feed cassette 38 to the printing unit 11.

  Alternatively, when one of the paper feeding devices 71 of the large capacity paper feeding cassette 14 is instructed as a recording paper supply source by the operation of the input operation unit 126 and the start of printing is instructed by the operation of the start key 132, The control unit 121 controls the paper feeding device 71 to supply recording paper from the paper feeding device 71 to the printing unit 11.

  Further, when the paper feeding device 71 is taken in and out of the storage space inside the main body of the large capacity paper feeding cassette 14 in order to replenish the paper bundle to the paper feeding device 71, the following control is performed, The separation / retraction position, the standby position, and the first suction position Bp1 of the contact member 101 are sequentially set.

  First, when the paper feeding device 71 is pulled out from the storage space inside the main body of the large-capacity paper feeding cassette 14, the drawing state of the paper feeding device 71 is detected by the open / close detection unit 129. In response to this, the main controller 121 starts to rotate the pulse motor 92 and lowers the sheet stacking table 74 to the lower limit position. At this time, the abutting member 101 moves to the separated and retracted position as shown in FIG. 8A in conjunction with the drawing operation of the paper feeding device 71, and the shielding piece 101f is not detected by the optical sensor 104. In this state, the sheet bundle is replenished to the sheet stacking board 74.

  After the sheet bundle is replenished, when the sheet feeding device 71 is pushed into the storage space inside the main body of the large-capacity sheet cassette 14, the open / close detection unit 129 detects the pushing state of the sheet feeding device 71. The When the open / close detection unit 129 detects the pressing state of the paper feeding device 71, the main control unit 121 rotates the pulse motor 92 in the reverse direction to raise the paper stacking table 74.

  Immediately after the sheet feeding device 71 is pushed in, as shown in FIG. 8B, the contact member 101 falls below the horizontal and moves to the standby position, and the shielding piece 101f is not detected by the optical sensor 104. In this state, when the sheet stacking table 74 is raised and the upper surface of the sheet bundle is raised, the rear end portion of the upper surface of the sheet bundle comes into contact with the contact member 101 and pushes up the contact member 101. As the contact member 101 is pushed up, the contact member 101 moves to the first suction position Bp1 as shown in FIG. 8C, and the shielding piece 101f is detected by the optical sensor 104. In response to this, the main controller 121 stops the pulse motor 92 and positions the uppermost recording sheet (upper surface of the sheet bundle) of the sheet bundle at the first suction position Bp1 of the contact member 101. As a result, as shown in the schematic side view of FIG. 15, the upper surface of the sheet bundle is positioned at the first suction position Bp <b> 1 that is optimal for adsorption to the surface of each sheet conveying belt 81. Further, the abutting member 101 abuts on the rear end portion of the upper surface of the sheet bundle to prevent the recording sheets of the sheet bundle from being lifted, and the upper surface of the sheet bundle is stably and accurately positioned at the first suction position Bp1, thereby optically The height position of the upper surface of the sheet bundle is accurately detected by the sensor 104.

  Further, when recording paper is supplied from the paper feeding device 71, the following control is performed. First, the main control unit 121 operates the assist fans 79 and 80 to send air from the assist fans 79 and 80 to the assist ducts 77 and 78, and the air is exhausted from the exhaust ports 77 a of the assist ducts 77 and 78. The air is blown from both sides of the bundle of sheets on the sheet stacking board 74 from 78a to allow air to enter between the recording sheets, thereby causing the recording sheets to vary. Further, the main control unit 121 operates the intake / exhaust fan 84, deenergizes the solenoid 114, opens the open / close valve 111 of the air suction path of the intake duct 85, and supplies air from the intake / exhaust fan 84 to the exhaust duct 86. Then, air is blown from the exhaust ports 96 to the front end surface of the sheet bundle, so that the air enters between the recording sheets and the recording sheets are dispersed. As a result, the adhesion of the recording sheets in the sheet bundle is reduced, the recording sheets can be easily pulled out from the sheet bundle, and the recording sheets can be pulled out one by one.

  At the same time, air is sucked from the intake duct 85 to the intake / exhaust fan 84, and the air is sucked through the air holes 81a of the paper transport belt 81 and the air suction holes 94 of the lower wall portion 85g of the air intake duct 85, and the paper transport belts. The recording paper is sucked and sucked on the surface of 81.

  Further, the main control unit 121 rotationally drives the conveyance motor 93, connects the conveyance clutch 127, rotates the rollers 82, and moves the respective sheet conveyance belts 81 so that the recording sheets are fed by the respective sheet conveyance belts 81. The paper is drawn in the drawing direction E and is conveyed to the conveyance roller 31 of the image forming apparatus 1. When the leading edge of the recording sheet is detected by the sheet sensor 128 provided in the vicinity of the conveyance roller 31, that is, when the leading edge of the recording sheet reaches the predetermined position Ps, the main control unit 121 biases the solenoid 114. Then, the on-off valve 111 of the air suction path of the intake duct 85 is closed to stop the suction of air from each vent hole 81a of each paper transport belt 81, and the transport clutch 127 is shut off, so that each paper transport belt 81 is Stop. As a result, the recording paper can be easily pulled out from each paper transport belt 81 by the transport roller 31, and the recording paper is quickly pulled out and transported through the transport path 33 of the image forming apparatus 1. After the recording paper has been pulled out in this way, the solenoid 114 is de-energized, the open / close valve 111 of the air suction path of the intake duct 85 is opened, the air suction by the intake / exhaust fan 84 is resumed, and the transport clutch 127 is connected. Then, the rotation of the rollers 82 and 83 by the conveyance motor 93 is restarted, the next recording sheet is attracted to the surface of each sheet conveyance belt 81, and the recording sheet is pulled out in the drawing direction E by each sheet conveyance belt 81. Then, the recording paper is conveyed to the conveying roller 31 of the image forming apparatus 1, and thereafter the recording paper is repeatedly adsorbed on the surface of each paper conveying belt 81, and the recording paper is pulled out in the drawing direction E by each paper conveying belt 81 and conveyed. go.

  When the upper surface of the sheet bundle is lowered due to repeated drawing of the recording sheets, the pulse motor 92 is rotated until the shielding piece 101f is detected by the optical sensor 104, and the upper surface of the sheet bundle is positioned at the first suction position Bp1. To do.

  By the way, when the recording sheet is a thick sheet, the recording sheet becomes heavier and the rigidity thereof is increased, so that it is difficult to adsorb the recording sheet by each sheet conveying belt 81. For this reason, the position of the upper surface of the sheet bundle is changed to the second suction position Bp2 (shown in FIG. 15) closer to each paper transport belt 81 than the first suction position Bp1, and the recording paper is adsorbed by each paper transport belt 81. Need to be easy. That is, when the recording paper is plain paper, the upper surface of the paper bundle is positioned at the first suction position Bp1, the recording paper is sucked by each paper transport belt 81, and when the recording paper is thick paper, The upper surface of the bundle is positioned at the second suction position Bp2, and the recording paper is sucked by each paper transport belt 81.

  However, in a state where the upper surface of the sheet bundle is closer to each sheet conveying belt 81, not only the uppermost recording sheet of the sheet bundle but also the next recording sheet that overlaps the uppermost recording sheet is placed on each sheet conveying belt 81. Adsorption is likely to occur, which causes double feeding of recording paper. In particular, when the recording paper is curled or the size of the recording paper is small, the next recording paper that overlaps the uppermost recording paper is easily adsorbed to each paper transport belt 81, so that the recording paper Double feed is likely to occur.

  Therefore, in the present embodiment, when the recording paper stored in the paper feeding device 71 is a thick paper, the top surface of the paper bundle is positioned at the second suction position Bp2, and the top of the paper bundle is conveyed by each paper transport belt 81. After adsorbing the upper layer recording paper, during the adsorbing period in which the uppermost recording paper is adsorbed, the paper stacking base 74 is lowered by a predetermined amount, and the upper surface of the paper bundle is also lowered to overlap the uppermost recording paper. After the next recording sheet is shaken off, the recording sheet is pulled out and conveyed by each sheet conveying belt 81 to prevent double feeding of the recording sheet.

  Next, the raising / lowering control of the paper stacking table 74 will be described in detail. First, a procedure for registering thick paper when it is stored in the paper feeding device 71 will be described. The user presses the user setting key 131 on the operation panel 124 shown in FIG. In response to this, the main control unit 121 displays a system setting screen 141 as shown in FIG. 16A on the display unit 125 of the operation panel 124. When the user operates the “paper tray setting” display button 142 on the system setting screen 141, a paper tray setting screen 143 as shown in FIG. 16B is displayed under the control of the main control unit 121. When the user operates the “plain paper / postcard” display button 144 corresponding to the paper feeding device 71 on the paper feeding tray setting screen 143, a pop-up screen 145 is displayed under the control of the main control unit 121. . Further, when the user operates the “thick paper” display button 146 on the pop-up screen 145, the thick paper is registered in the registration data table in the memory 122 corresponding to the paper feeding device 71 by the control of the main control unit 121. Then, “thick paper” is displayed on the display button 144 in the paper feed tray setting screen 143. FIG. 17 illustrates a registration data table. As shown in FIG. 17, in the registration data table DT, the types and sizes of the sheets accommodated in the respective sheet feeding cassettes 38 and the large capacity sheet feeding cassettes 14 are registered. ing.

  The paper size is detected by a sensor (not shown) built in each paper feed cassette 38 and each paper feed device 71 and automatically registered in the registration data table DT. Alternatively, when the “paper tray setting” display button 142 in FIG. 16A is selected and the paper tray setting screen 143 or the pop-up screen 145 in FIG. A screen may also be displayed, and the size of the recording paper may be set on this other screen and registered in the registration data table DT. Also, the thickness of the recording paper can be detected by a known ultrasonic sensor and automatically registered in the registration data table DT.

  Next, a procedure for inputting which of the paper feeding devices 71 of the paper feeding cassettes 38 and the large capacity paper feeding cassettes 14 is to be supplied will be described. First, the user operates the display area 162 on the standby screen 161 displayed on the display unit 125 of the operation panel 124 as shown in FIG. In response to this, the main control unit 121 displays a paper selection screen 163 as shown in FIG. 18B on the display unit 125 of the operation panel 124. Each display area 165 in the paper selection screen 163 corresponds to each paper feed cassette 38 and each paper feed device 71, and each display area 165 is accommodated in each paper feed cassette 38 and each paper feed device 71. Each paper type is displayed. When the display area 165 in which the desired paper type is displayed is selected from each display area 165 and operated, and the OK button 166 is designated, in response to this, the main control unit 111 selects the selected display. The paper feed cassette 38 or the paper feed device 71 corresponding to the area 165 is selected. When the start of printing is input by operating the start key 132 on the operation panel 124, in response to this, the main control unit 121 controls the selected paper feeding cassette 38 or the paper feeding device 71 to select the selected one. The recording paper of the type displayed in the selected display area 165 is supplied from the paper supply cassette 38 or the paper supply device 71 to the printing unit 11, and the printing unit 11 is controlled to supply the image. Print on recording paper.

  Next, the control procedure of the sheet feeding device 71 will be described with reference to the flowchart of FIG. 19 and the operation transition diagrams of FIGS. 20A (a) to 20 (c) and 20B (d) to (f). This control procedure is performed for each paper feeding device 71 of the large capacity paper feeding cassette 14.

  First, when the sheet feeding device 71 is selected by operating the operation panel 124 as shown in FIGS. 18A and 18B and a job start (image printing start) is instructed, in response to this, The main control unit 121 operates the intake / exhaust fan 84 and the conveyance motor 93 of the selected sheet feeding device 71. However, the solenoid 114 is de-energized, the open / close valve 111 of the air suction path of the intake duct 85 is closed, the transport clutch 127 is shut off, and the recording paper is not attracted and transported by each paper transport belt 81. maintain.

The main control unit 121 refers to the registration data table DT to determine whether the recording paper stored in the paper feeding device 71 is plain paper (first paper) or thick paper (second paper). Determination is made (step S201 in FIG. 19). For example, if the recording paper is plain paper (“plain paper” in step S201 in FIG. 19), the air suction path of the intake duct 85 is opened and closed while the upper surface of the sheet bundle is maintained at the first suction position Bp1. The valve 111 is opened and closed, and the conveying clutch 127 is connected and disconnected, and the recording sheet is sucked and drawn out from the surface of each sheet conveying belt 81 (step S202 in FIG. 19).

  If the recording sheet is a thick sheet (“thick sheet” in step S201 in FIG. 19), the main control unit 121 applies a lowering drive signal to the pulse motor 92 to temporarily lower the sheet stacking board 74. Then, as shown in FIG. 8 (b), when the contact member 101 falls below the horizontal position and moves to the standby position, and the shielding piece 101f is no longer detected by the optical sensor 104, the main control unit responds accordingly. 121 stops the pulse motor 92. Further, the main control unit 121 applies a rising drive signal to the pulse motor 92 to raise the sheet stacking board 74. At this time, when the contact member 101 is pushed up by the upper surface of the sheet bundle on the sheet stacking table 74 and the contact member 101 moves to the first suction position Bp1 as shown in FIG. The piece 101f is detected, and the upper surface of the sheet bundle on the sheet stacking table 74 rises to the first suction position Bp1 (step S204 in FIG. 19, FIG. 20A (a)).

  Subsequently, the main control unit 121 applies a rising drive signal for 15 pulses to the pulse motor 92 from the time point when the shielding piece 101f is detected by the optical sensor 104, and further raises the paper stacking base 74, thereby the paper stacking base 74. The upper surface of the upper sheet bundle is raised from the first suction position Bp1 to the second suction position Bp2 (step S205 in FIG. 19, FIG. 20A (b)). For example, the second suction position Bp2 is a position that is higher by about 2 mm than the first suction position Bp1.

  Thereafter, the main control unit 121 energizes the solenoid 114 to open the on-off valve 111 of the air suction path of the intake duct 85 and suck air from each vent hole 81a of each paper transport belt 81 so that each paper sheet. The recording sheets of the sheet bundle are sucked by the conveyance belt 81 (step S206 in FIG. 19, FIG. 20A (c)).

  Then, in a state where the recording paper is adsorbed by each paper transport belt 81, the main control unit 121 applies a downward drive signal for 45 pulses to the pulse motor 92, and lowers the paper stacking base 74 by a specified amount. The upper surface of the sheet bundle on the stacking table 74 is lowered from the second suction position Bp2 to the separation position Bp3 below the first suction position Bp1 (step S207 in FIG. 19, FIG. 20B (d)). For example, the specified amount by which the paper stacking table 74 is lowered is 6 mm. Therefore, the separation position Bp3 is a position that is about 6 mm lower than the second suction position Bp2 and about 4 mm lower than the first suction position Bp1.

  Here, as shown in FIG. 20A (c), the uppermost recording sheet P1 of the sheet bundle and the next recording sheet P2 that overlaps the uppermost sheet P1 are overlapped and adsorbed to each sheet conveying belt 81. Then, even if the uppermost recording sheet P1 is satisfactorily attracted to each sheet conveying belt 81, for example, only the leading end of the next recording sheet P2 is attracted to each sheet conveying belt 81, and the trailing end The portion is in contact with the upper surface of the sheet bundle, and the next recording sheet P2 is not completely lifted from the upper surface of the sheet bundle. Therefore, as shown in FIG. 20B (d), when the sheet stacking table 74 is lowered by a specified amount and the upper surface of the sheet bundle is lowered to the separation position Bp3, the next recording sheet P2 follows the upper surface of the sheet bundle. It is separated from the uppermost recording sheet P1 and shaken off.

  After the next recording paper P2 is shaken off in this way, the main control unit 121 connects the transport clutch 127, moves each paper transport belt 81 around, and pulls out the recording paper by each paper transport belt 81 to form an image. It conveys to the conveyance roller 31 of the apparatus 1 (step S208 of FIG. 19, FIG. 20B (e)). When the leading edge of the recording sheet is detected by the sheet sensor 128 provided in the vicinity of the conveyance roller 31, that is, when the leading edge of the recording sheet reaches the predetermined position Ps, the main control unit 121 deenergizes the solenoid 114. Then, the on-off valve 111 of the air suction path of the intake duct 85 is closed, the suction of air from each vent hole 81a of each paper transport belt 81 is stopped, the transport clutch 127 is shut off, and each paper transport belt 81 is Stop. As a result, the recording sheet is quickly pulled out and conveyed by the conveying roller 31 (step S209 in FIG. 19, FIG. 20B (f)).

  Thereafter, similarly, the upper surface of the sheet bundle is raised to the first suction position Bp1 (step S204 in FIG. 19, FIG. 20A (a)), and then the upper surface of the sheet bundle is further raised to the second suction position Bp2 ( 19 (step S205 in FIG. 19 and FIG. 20A (b)), the recording paper of the uppermost layer of the sheet bundle is adsorbed by each paper transport belt 81 (step S206 in FIG. 19, FIG. 20A (c)), and by each paper transport belt 81 The upper surface of the sheet bundle is lowered to the separation position Bp3 while maintaining the suction state of the recording sheet (step S207 in FIG. 19, FIG. 20B (d)), the next recording sheet P2 is shaken off, and each sheet is conveyed. The recording paper is pulled out by the belt 81 and conveyed to the conveyance roller 31 of the image forming apparatus 1 (steps S208 and S209 in FIG. 19, and FIGS. 20B (e) and (f)).

  FIG. 21 is a timing chart showing a control procedure of the paper feeding device 71. In the timing chart of FIG. 21, when the start of the job is instructed at time t0, the operation of the intake / exhaust fan 84 and the conveyance motor 93 is started. However, the solenoid 114 is de-energized, the open / close valve 111 of the air suction path of the intake duct 85 is closed, and the transport clutch 127 is shut off, so that the recording paper is adsorbed and transported by each paper transport belt 81. There is nothing. Further, the lowering drive signal is applied to the pulse motor 92, the paper stacking table 74 is once lowered, and the shielding piece 101f is not detected by the optical sensor 104.

  Next, at time t1, an ascending drive signal is applied to the pulse motor 92, the sheet stacking board 74 is raised, the upper surface of the sheet bundle is raised to the first suction position Bp1, and the shielding piece 101f is detected by the optical sensor 104. Then, at the subsequent time t2, a rising drive signal for 15 pulses is applied to the pulse motor 92, the paper stacking table 74 is further raised, and the upper surface of the paper bundle is raised to the second suction position Bp2.

  Next, at time t3, the solenoid 114 is energized to open the on-off valve 111 of the air suction path of the intake duct 85, and air is sucked from each vent hole 81a of each paper transport belt 81, and each paper transport belt. By 81, the recording sheets of the sheet bundle are sucked.

  At a subsequent time t4, with the uppermost recording paper adsorbed on each paper transport belt 81, a lowering drive signal is applied to the pulse motor 92, the paper stacking table 74 is lowered, and the sheet bundle The upper surface is lowered to the separation position Bp3, and the next recording sheet overlapping the uppermost recording sheet is shaken off.

  Further, at time t5, that is, at time t5 after a certain time Δt from the time t4 when the lowering of the paper stacking base 74 is started, the transport clutch 127 is connected, and each paper transport belt 81 moves in a circular manner, so that each paper transport is performed. The recording paper is pulled out by the belt 81 and conveyed to the conveyance roller 31 of the image forming apparatus 1.

When the leading edge of the recording sheet is detected by the sheet sensor 128 provided in the vicinity of the conveying roller 31 at time t6, that is, when the leading edge of the recording sheet reaches the predetermined position Ps, the solenoid 114 is de-energized and the intake air is sucked. The opening / closing valve 111 of the air suction path of the duct 85 is closed, the recording paper suction by each paper transport belt 81 is stopped, and the transport clutch 127 is shut off, so that the recording paper is pulled out and transported by each paper transport belt 81. Stopped. As a result, the recording sheet is quickly pulled out and conveyed by the conveying roller 31.
Accordingly, when the recording time of the sheet bundle of the sheet bundle by the sheet conveying belts 81 is defined as the adsorption period Tb, the upper surface of the sheet bundle is lowered to the separation position Bp3 during the adsorption period Tb, and the uppermost layer. The next recording sheet that overlaps the other recording sheet is shaken off, and drawing and conveyance of the recording sheet by each sheet conveying belt 81 are started.

  Thereafter, similarly, the control procedure from time t1 to time t6 is repeated, and the recording sheets of the sheet bundle are drawn out one by one by each sheet conveying belt 81 and conveyed.

  As described above, in the paper feeding device 71 of this embodiment, when supplying thick paper, the upper surface of the paper bundle is raised to the second suction position Bp2, and the recording paper of the uppermost layer of the paper bundle is fed by each paper transport belt 81. Since it is adsorbed, the thick paper can be adsorbed satisfactorily by each paper conveying belt 81. Further, while maintaining the adsorbing state of the recording paper by each paper transport belt 81, the upper surface of the paper bundle is lowered to the separation position Bp3, and the next recording paper that overlaps the uppermost recording paper is shaken off. Since the recording paper is pulled out and conveyed by the conveying belt 81, the recording paper is not double-fed. In particular, when the recording paper is curled or the recording paper is small in size, the next recording paper that overlaps the uppermost recording paper is easily adsorbed to each paper transport belt 81. The effect of applying is increased.

  In the above embodiment, as is apparent from the timing chart of FIG. 21, the upper surface of the sheet bundle is lowered to the separation position Bp3 during the adsorption period Tb in which the recording sheets of the sheet bundle are adsorbed by the respective sheet conveyance belts 81. Thereafter, drawing and transport of the recording paper by each paper transport belt 81 are started at time t5, but the uppermost recording is performed while the upper surface of the paper bundle is lowered from the second suction position Bp2 to the separation position Bp3. Since the next recording sheet that overlaps the sheet starts to be shaken off, each sheet conveying belt is in the middle of the upper surface of the sheet bundle being lowered to the separation position Bp3, that is, before the upper surface of the sheet bundle reaches the separation position Bp3. The drawing and conveyance of the recording paper by 81 may be started. Accordingly, when the lowering drive signal is applied to the pulse motor 92 and the time when the lowering of the paper stacking base 74 is started, the drawing and transporting of the recording paper by the respective paper transport belts 81 may be started.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Printing part 12 Paper conveyance part 13 Paper supply part 14 Large capacity paper feed cassette (LCC)
15 Document reader 16 Document transport device 33 Paper transport path 71 Paper feed device 72 Outer frame 73 Bottom plate 74 Paper stack 75 Paper drawer unit 76 Paper trailing edge guides 77, 78 Assist ducts 79, 80 Assist fan 81 Paper transport belt ( Paper transport member)
82, 83 Roller 84 Intake / exhaust fan 85 Intake duct 86 Exhaust duct 92 Pulse motor (elevating part)
93 Transport motor 94 Air suction hole 101 Contact member 102 Position switching unit 104 Optical sensor (position detection unit)
105 Rotating member 106 Rod 107 Coil spring 111 On-off valve 114 Solenoid 121 Main control unit (control unit)
122 Memory 123 Image processing unit 124 Operation panel 125 Display unit 126 Input operation unit (paper input unit)
127 Conveying clutch 128 Paper sensor (paper detection unit)
129 Opening / closing detection unit Bp1 First suction position Bp2 Second suction position Bp3 Separation position

Claims (10)

A sheet feeding device comprising a sheet stacking table for stacking a sheet bundle, an elevating unit for moving the sheet stacking table up and down, and a sheet transporting member that sucks and transports the sheets of the sheet bundle by sucking air;
During the adsorption period in which the sheet is adsorbed to the sheet conveying member by the air suction, the sheet stacking table is lowered by a specified amount by controlling the elevating unit, and the defined amount of the sheet stacking table is being lowered. Or a control unit for starting conveyance of the sheet by the sheet conveying member after completion ;
A position detection unit that detects an upper surface position of the sheet bundle that has reached the first suction position;
When the upper surface position of the sheet bundle is detected by the position detection unit, the control unit controls the lifting unit to move the upper surface position of the sheet bundle to a second suction position higher than the first suction position. The suctioning period is started, and during the suctioning period, the sheet stacking table is lowered by a predetermined amount by controlling the elevating unit, so that the upper surface position of the sheet bundle is lower than the first suctioning position. A paper feeding device that is lowered to a separation position . The sheet feeding device according to claim 1 ,
A paper detection unit for detecting the paper transported to a predetermined position by the paper transport member;
When the paper is detected by the paper detection unit, the control unit stops the suction of the paper to the paper transport member by the suction of the air and the transport of the paper by the paper transport member, and detects the position. The sheet stacking device is raised by controlling the elevating unit until the upper surface position of the sheet bundle is detected by the unit. The sheet feeding device according to claim 1 or 2 ,
A paper input unit for inputting that the paper stored in the paper supply device is a second paper thicker than the first paper ;
When the control unit inputs that the second paper is input from the paper input unit, the control unit lowers the paper stacking base by controlling the lifting unit during the suction period, so that the paper stacking is performed. The conveyance of the sheet by the sheet conveying member is started during or after the specified amount of the table is lowered, and the position of the sheet stacking table is maintained when the sheet input unit inputs that the sheet is not the second sheet. A paper feeder characterized by. A sheet feeding device comprising a sheet stacking table for stacking a sheet bundle, an elevating unit for moving the sheet stacking table up and down, and a sheet transporting member that sucks and transports the sheets of the sheet bundle by sucking air
During the adsorption period in which the sheet is adsorbed to the sheet conveying member by the air suction, the sheet stacking table is lowered by a specified amount by controlling the elevating unit, and the defined amount of the sheet stacking table is being lowered. Or a control unit for starting conveyance of the sheet by the sheet conveying member after completion ;
A paper input unit for inputting that the paper stored in the paper supply device is a second paper thicker than the first paper,
When the control unit inputs that the second paper is input from the paper input unit, the control unit lowers the paper stacking base by controlling the lifting unit during the suction period, so that the paper stacking is performed. The conveyance of the sheet by the sheet conveying member is started during or after the specified amount of the table is lowered, and the position of the sheet stacking table is maintained when the sheet input unit inputs that the sheet is not the second sheet. A paper feeder characterized by. The sheet feeding device according to claim 4 ,
A position detection unit that detects an upper surface position of the sheet bundle that has reached the first suction position;
When the upper surface position of the sheet bundle is detected by the position detection unit, the control unit controls the lifting unit to move the upper surface position of the sheet bundle to a second suction position higher than the first suction position. The suctioning period is started, and during the suctioning period, the sheet stacking table is lowered by a predetermined amount by controlling the elevating unit, so that the upper surface position of the sheet bundle is lower than the first suctioning position. A paper feeding device that is lowered to a separation position. The sheet feeding device according to claim 5 ,
A paper detection unit for detecting the paper transported to a predetermined position by the paper transport member;
When the paper is detected by the paper detection unit, the control unit stops the suction of the paper to the paper transport member by the suction of the air and the transport of the paper by the paper transport member, and detects the position. The sheet stacking device is raised by controlling the elevating unit until the upper surface position of the sheet bundle is detected by the unit. A sheet feeding device according to any one of claims 3 to 6 ,
The paper input unit is an input operation unit,
The input operation unit outputs to the control unit that the predetermined sheet is received when the input operation unit inputs that the second sheet is stored in the sheet feeding device. A paper feeder. A sheet feeding device according to any one of claims 3 to 6 ,
The paper input unit is a sensor provided in the paper feeding device,
The sensor detects that a sheet stored in the sheet feeder is the second sheet and outputs the detected sheet to the control unit. A sheet feeding device according to any one of claims 1 to 8 ,
The control unit starts transporting the paper by the paper transport member after a predetermined time from the start of the control of the lift unit for lowering the paper stacking base by a specified amount. . An image forming apparatus comprising: the sheet feeding device according to claim 1; and a printing unit that records an image on a sheet supplied from the sheet feeding device.

Images