JP2012101935A - Sheet feeder and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeder and an image forming apparatus, which are able to release negative pressure in an adhering duct at the same time when sucking operation of the sheet is finished with a simple configuration.SOLUTION: A suction shutter 37 is provided between the adhesion opening 34a of the adhering duct 34 and a suction fan 36. A communication opening 18 by which the inside and outside of the adhering duct 34 communicate is formed between this suction shutter 37 and the adhesion opening 34a. Additionally, a shield member 19 movable to an open position for opening the communication opening 18 and a shield position for shielding the communication opening 18 is provided in the suction shutter 37. When the suction shutter 37 is moved to the shield position, the shield member 19 is moved to the shield position for shielding the communication opening 18. When the suction shutter 37 is moved to the communicating position, the shield member 19 is moved to the open position for opening the communication opening 18.

Description

  The present invention relates to a sheet feeding apparatus and an image forming apparatus, and more particularly to an apparatus that blows air on a sheet to separate and feed the sheet.

  2. Description of the Related Art Conventionally, image forming apparatuses such as printers and copiers include a sheet feeding device that feeds sheets one by one from a sheet storage unit that stores a plurality of sheets. As such a sheet feeding device, air is blown to the end of the sheet bundle stored in the sheet storage unit to float a plurality of sheets, and only one sheet is sucked to the suction feeding belt disposed above. There is an air paper feed type that feeds the paper (see Patent Document 1).

  In this air sheet feeding type sheet feeding device, an adsorption duct is arranged inside an endless suction conveyance belt, and the inside of this adsorption duct is made into a negative pressure state by a fan or the like. The sheet is sucked through the suction hole. And the sheet | seat is conveyed because the adsorb | sucking conveyance belt rotates.

  In the air feeding type sheet feeding apparatus, a suction shutter for placing the suction duct in a negative pressure state or releasing the negative pressure in the suction duct is disposed in the suction duct. When the sheet is adsorbed on the suction conveyance belt, the suction shutter is opened to make the inside of the adsorption duct in a negative pressure state, and the sheet is adsorbed on the adsorption conveyance belt. In addition, when the leading edge of the sheet conveyed by the suction conveyance belt reaches the drawing roller arranged on the downstream side, the suction shutter is closed to prevent the next sheet from being attracted to the suction conveyance belt. The pressure is released and the rotation of the suction conveyance belt is stopped.

  However, when the suction and conveyance operations of the suction conveyance belt are stopped in this way, the rear end portion of the sheet may be in a state of being sucked by the suction surface of the suction conveyance belt. In this case, since the inside of the suction duct is still in a negative pressure state even when the suction shutter is closed, when the sheet is transported by the drawing roller, a braking force in the direction opposite to the transport direction is applied from the suction transport belt to the sheet. Will be given. Such a braking force causes the sheet to be pulled between the pulling roller and the suction conveyance belt, and causes wrinkles when the sheet is jammed or the sheet is thin paper with low rigidity.

  In order to prevent such sheet tension, for example, a suction duct provided with an opening that communicates the inside and the outside of the suction duct and an opening / closing member that opens and closes the opening has been proposed. In this configuration, when the leading edge of the sheet reaches the drawing roller, the suction shutter is closed, and at the same time, the opening that has been blocked by the opening / closing member is opened so that the inside and the outside of the suction duct communicate with each other. The negative pressure is released to atmospheric pressure (see Patent Document 2). As a result, the above-described problems such as the occurrence of wrinkles in the sheet jam and the sheet are solved.

JP-A-7-196187 JP 2008-001458 A

  However, in the conventional sheet feeding apparatus and image forming apparatus configured to release the negative pressure inside the suction duct by such a configuration, for example, when the opening / closing member is driven by a link mechanism, the structure becomes complicated. At the same time, the parts cost is increased. Further, when the opening / closing member is driven by a drive mechanism such as a solenoid to open / close the suction shutter, the load applied to the drive mechanism increases, and as a result, a drive mechanism having a large operating force is required, resulting in an increase in cost. Will be invited.

  Therefore, the present invention has been made in view of such a current situation, and with a simple configuration, a sheet feeding device and an image that can release the negative pressure inside the suction duct simultaneously with the end of the sheet suction operation. An object of the present invention is to provide a forming apparatus.

  The present invention includes a tray that can be moved up and down to support a sheet, an air blowing unit that blows air toward an upper portion of the sheet supported by the tray, and a sheet that is lifted by the suction conveyance unit In the sheet feeding apparatus, the suction transport mechanism includes a suction duct having a suction opening formed on the suction transport unit side, and a negative pressure that causes the suction transport unit to suck the sheet. Is generated between the suction opening and the negative pressure generation unit in the suction duct, and is disposed between the suction opening and the negative pressure generation unit. A shutter that opens and closes, a communication opening that is formed in a side wall between the suction opening and the shutter in the suction duct, and that communicates the inside and outside of the suction duct, and is movable together with the shutter. The suction opening of the shutter and the negative pressure generation unit are moved to a shielding position that shields the communication opening in accordance with the movement of opening the suction opening and the negative pressure generation unit of the shutter. And a shielding member that moves to an open position that opens the communication opening in accordance with the movement of closing the space.

  As in the present invention, by providing a shutter with a shielding member that opens and closes a communication opening that communicates the inside and outside of the suction duct, the negative pressure inside the suction duct can be reduced simultaneously with the end of the sheet suction operation. Can be released.

1 is a diagram illustrating a schematic configuration of a printer that is an example of an image forming apparatus including a sheet feeding device according to an embodiment of the present invention. The figure which shows the structure of the said sheet feeding apparatus. FIG. 4 is a first diagram illustrating an operation of an upper air blowing unit provided in the sheet feeding apparatus. FIG. 10 is a second diagram illustrating the operation of the upper air blowing unit provided in the sheet feeding apparatus. The control block diagram of the said sheet feeding apparatus. 6 is a flowchart for explaining a sheet feeding operation of the sheet feeding apparatus. 6 is a timing chart for explaining a sheet feeding operation of the sheet feeding apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of a printer which is an example of an image forming apparatus including a sheet feeding device according to an embodiment of the present invention.

  In FIG. 1, 100 is a printer, and 101 is a printer body. An image reading unit 130 for reading a document D placed on a platen glass 120a as a document placing table by an automatic document feeder 120 is provided on the upper portion of the printer main body 101. Below the image reading unit 130, an image forming unit 102 and a sheet feeding device 103 that feeds the sheet S to the image forming unit 102 are provided.

  Here, the image forming unit 102 is provided with a photosensitive drum 112, a developing unit 113, a laser scanner unit 111, and the like. The sheet feeding device 103 is an example of a plurality of sheet storage units 11 that store sheets S such as OHT and are detachable from the apparatus main body 101 and a sheet feeding unit that sends out the sheets S stored in the sheet storage unit 11. And a suction conveyance belt 22 as a feeding belt.

  Next, an image forming operation of the printer 100 having such a configuration will be described. When an image reading signal is output to the image reading unit 130 from a CPU (control device) shown in FIG. 5 (described later) provided in the apparatus main body 101, the image reading unit 130 reads an image. Thereafter, a laser beam corresponding to the electrical signal is emitted from the laser scanner unit 111 onto the photosensitive drum 112. At this time, the photosensitive drum 112 is charged in advance, and an electrostatic latent image is formed by irradiating light, and then the electrostatic latent image is developed by the developing device 113, thereby forming a toner image on the photosensitive drum. Is done.

  On the other hand, when a paper feed signal is output from the CPU to the sheet feeding device 103, the sheet S is fed from the sheet storage case 11. Thereafter, the fed sheet S is sent by a registration roller 117 to a transfer unit constituted by the photosensitive drum 112 and the transfer charger 118 in synchronization with the toner image on the photosensitive drum. Next, the toner image is transferred to the sheet sent to the transfer unit in this way, and then conveyed to the fixing unit 114. Thereafter, the unfixed transfer image is permanently fixed on the sheet S by being heated and pressed by the fixing unit 114. Then, the sheet on which the image is fixed in this manner is discharged from the apparatus main body 101 to the discharge tray 119 by the discharge roller 116.

  FIG. 2 is a diagram illustrating a configuration of the sheet feeding apparatus 103. The sheet storage 11 includes a tray 12 that can be moved up and down on which a plurality of sheets S are placed and supported. In addition, an air feeding type sheet feeding mechanism (hereinafter referred to as an air feeding mechanism) 150 for separating and feeding the sheets one by one is disposed on the upper portion of the sheet storage case 11. The air feeding mechanism 150 lifts and lifts the upper portion of the sheet bundle on the tray, and separates the sheets S one by one. The air spraying part 152 is provided.

  Here, the suction conveyance unit 134 includes a suction conveyance belt 22 that is rotatably spanned between the driving roller 41 a and the driven roller 41 b, and a negative pressure generation unit that generates a negative pressure for causing the sheet S to be attracted to the adsorption conveyance belt 22. The suction fan 36 is provided. Further, an end portion of a suction duct 34 having a suction opening 34a formed on the lower surface is inserted inside the suction transport belt 22 which is an endless suction transport portion. Note that FIG. 2 schematically illustrates the suction duct 34 so as to extend upward for easy understanding of the configuration, but in reality, the end of the suction duct 34 is in a direction perpendicular to the paper surface in the drawing. It extends to.

  In addition, a number of suction holes 22h are formed in the suction surface of the suction conveyance belt 22, and the suction duct 34 is operated via the suction holes 22h and the suction opening 34a on the suction conveyance belt side (suction conveyance section side). By sucking the sheet, the sheet is sucked. A suction shutter 37 is provided inside the suction duct 34 to rotate about a shaft 37a as a fulcrum and open and close the duct 34 between the suction fan 36 and the suction opening 34a.

  The air blowing unit 152 is for blowing air toward the upstream side in the sheet feeding direction toward the downstream end in the sheet feeding direction of the sheet supported by the tray 12 to float the sheet. The air blowing section 152 is a separation nozzle 425 and a separation nozzle 435 for blowing air from the leading end side to the upper portion of the sheet bundle, a separation fan 450, and separation for sending air from the separation fan 450 to the nozzles 425 and 435. A duct 440 is provided. A part of the air sucked by the separation fan 450 passes through the separation duct 440 and is blown in the direction of the arrow C by the firing nozzle 425, and several of the sheets S stacked on the tray 12 are floated. Let Further, the other air is blown in the direction of arrow D by the separation nozzle 435, and the sheets floated by the separation nozzle 425 are separated one by one and adsorbed to the adsorption conveyance belt 22.

  Next, the sheet feeding operation of the sheet feeding apparatus 103 (air feeding mechanism 150) configured as described above will be described. When the sheet feeding signal is detected, the CPU operates the separation fan 450 to suck in air. The air is blown onto the sheet bundle from the directions of arrows C and D by the firing nozzle 425 and the separation nozzle 435 through the separation duct 440, respectively. As a result, the upper several sheets of the sheet bundle rise. Further, the CPU activates the suction fan 36 and discharges air in the direction F in the drawing. At this time, since the suction shutter 37 is closed as shown in FIG. 1, the uppermost sheet Sa is not adsorbed to the adsorbing and conveying belt 22.

  Next, when a predetermined time elapses after the sheet feeding signal is detected and the floating of the upper several sheets is stabilized, the CPU turns on a suction solenoid, which will be described later, and moves the suction shutter 37 in the direction of arrow G. Rotate. As a result, air is sucked from the suction holes 22h provided in the suction conveyance belt 22 and the suction opening 34a of the suction duct 34, and the suction duct 34 is brought into a negative pressure state, and suction force is generated. Only the uppermost sheet Sa is adsorbed to the adsorbing and conveying belt 22 by the adsorbing force and the separation air from the separation nozzle 435. The suction duct 34 is provided with a suction completion sensor (not shown) for detecting that the sheet has been sucked by the suction conveyance belt 22.

  Subsequently, the CPU drives a belt drive motor, which will be described later, and rotates the belt drive roller 41a in the arrow J direction. As a result, the uppermost sheet Sa is conveyed in the arrow K direction while being adsorbed by the adsorption conveyance belt 22. Thereafter, the uppermost sheet Sa is arranged on the downstream side in the sheet conveying direction, and is pulled out by the drawing roller 42 that is a drawing portion that rotates in the directions of arrows P and M, and is conveyed toward the image forming unit. A path sensor 43, which is a reflection type photosensor, is provided downstream of the drawing roller 42, and the CPU monitors the passage of the sheet Sa by the path sensor 43.

  On the other hand, when the uppermost sheet Sa reaches the drawing roller 42, the suction solenoid is turned off, the suction shutter 37 is rotated in the direction opposite to the arrow G direction, and the negative pressure state in the suction duct 34 is eliminated. Thereby, the adsorption of the sheet to the adsorption conveyance belt 22 is released. Further, the driving of the belt driving motor is stopped, and the driving of the suction conveyance belt 22 is stopped.

  By the way, when the suction shutter 37 is shielded on the side wall between the suction opening 34a of the suction duct 34 and the suction shutter 37, as shown in FIGS. A communication opening 18 is formed to communicate the inside and the outside on the opening 34a side. A shielding member 19 for closing the communication opening 18 is fixed to the suction shutter 37. The shielding member 19 may be a separate member from the suction shutter 37. However, the shielding member 19 may be formed integrally with the suction shutter 37 manufactured by, for example, sheet metal bending, synthetic resin injection molding, or the like as a part of the suction shutter 37. good. Further, as shown in FIG. 3B, the shielding member 19 is provided on the rear side of the suction shutter 37 in the drawing so as to block the communication opening 18 formed on the side wall of the suction duct 34. It is fixed at the end.

  Here, one end of a link member 24 is connected to the suction shutter 37, and a plunger 23 a of a solenoid 23 is connected to the other end of the link member 24. Reference numeral 28 denotes a spring whose one end is locked to the plunger 23a of the solenoid 23. The spring 28 biases the plunger 23a of the solenoid 23 in a direction to close the suction shutter 37.

  Thereby, when the solenoid 23 is turned ON, the plunger 23a of the solenoid 23 is pulled and the link member 24 is rotated. Accordingly, the suction opening 37a and the suction fan 36 are separated from the blocking position where the suction shutter 37 blocks the suction duct 34 integrally with the shielding member 19, that is, the communication between the suction opening 34a and the suction fan 36 is blocked. Move to the communication position that communicates with the. When the solenoid 23 is turned OFF, the plunger 23a is pulled out by the spring 28 and the link member 24 is rotated in the reverse direction. Accordingly, the suction shutter 37 that can move to the communication position and the blocking position is integrated with the shielding member 19. Move from the communication position to the blocking position. Thus, in the present embodiment, the suction shutter 37 and the shielding member 19 are opened and closed by the single solenoid 23.

  FIG. 3 shows a state in which the suction shutter 37 is in a blocking position where communication between the suction opening 34 a of the suction duct 34 and the suction fan 36 is blocked. In this state, the communication opening 18 is opened without being closed by the shielding member 19, and in this state, the inside of the suction duct (the inside of the suction opening) and the outside communicate with each other. Thus, when the suction shutter 37 is in the blocking position, the generation of negative pressure in the region between the suction shutter 37 and the suction opening 34a in the suction duct 34 can be stopped. Further, as in the present embodiment, when the suction shutter 37 rotates to the blocking position, the shielding member 19 moves to the open position where the communication opening 18 is opened, so that the negative pressure remaining in the suction duct 34 remains. Can be released instantly.

  FIG. 4 shows a state in which the suction shutter 37 rotates and is in a communication position where the suction opening 34 a of the suction duct 34 and the suction fan 36 are communicated. In this state, the shielding member 19 moves to a shielding position that shields the communication opening 18. Therefore, when the suction shutter 37 is in the communication position in this way, the suction fan 36 is in a negative pressure state by the suction fan 36. Can be maintained.

  FIG. 5 is a control block diagram of the sheet feeding apparatus 103 according to the present embodiment. In FIG. 5, a CPU 150 is a control unit that controls the sheet feeding apparatus 103. The CPU 150 issues a drive start command to each drive circuit of the sheet feeding apparatus 103 and detects a conveyed sheet. The output signal from the pulling sensor 43 is received. Further, the CPU 150 is arranged in the suction duct 34 as described above, and receives an output signal from a suction completion sensor (not shown) that detects completion of suction of the uppermost sheet.

  Reference numeral 154 denotes a drive circuit for turning on / off the suction fan 36, and reference numeral 155 denotes a drive circuit for the solenoid 23 for moving the suction shutter 37 and the shielding member 19 in the suction duct 34 integrally. Reference numeral 156 denotes a driving circuit for the belt driving motor 140 that drives the suction conveyance belt 22, and 157 denotes a driving circuit for the drawing roller motor 141 that drives the drawing roller 42.

  Next, the sheet feeding operation of the sheet feeding apparatus 103 according to the present embodiment will be described using the flowchart shown in FIG. 6 and the timing chart shown in FIG. When feeding a sheet, the user first pulls out the sheet storage case 11 and sets the sheet S. When the sheet storage case 11 is stored, the tray 12 rises and stops at a position where the suction conveyance belt 21 can adsorb and convey the sheet.

  Here, in the initial state before the sheet feeding is started, as shown in FIG. 3, the suction shutter 37 is in the blocking position, and the shielding member 19 installed on the suction shutter opens the communication opening 18. Since it is in the open position where it opens, the atmospheric pressure in the suction duct 34 is the same as the atmospheric pressure.

  Next, when a feed start signal is input to the CPU 150, the CPU 150 inputs a control signal to the drive circuit 154 of the suction fan 36 to activate (ON) the suction fan 36 as shown in FIG. (S1). Similarly, the separation fan 450 is driven to start air blowing. After that, when a plurality of sheets are floated by air blowing and the paper surface position of the uppermost sheet Sa reaches a distance that can be sucked by the suction conveyance belt 22, a control signal is input to the drive circuit 155 of the solenoid 23 to input the control signal. 7 (b), the suction solenoid 38 is turned on.

  When the suction solenoid 38 is turned on in this way, the suction shutter 37 moves to the communication position (opening operation) as shown in FIG. 4, and at the same time, the shielding member 19 closes the communication opening 18 (closing operation) (S2). . As a result, the inside of the suction duct 34 is in a negative pressure state. As a result, among the sheets S stored in the storage 11, the uppermost sheet is sucked from the suction hole 22 h of the suction transport belt 22 to the suction transport belt 22. Adsorbed.

  Next, when the suction completion sensor (not shown) detects that the uppermost sheet has been sucked (Y in S3), a control signal is sent to the drive circuit 156 of the belt drive motor 140 as shown in FIG. The belt drive motor 140 is turned on by inputting. When the belt driving motor 140 is turned on in this way, the suction conveyance belt 22 to which the sheet is adsorbed starts to be driven (S4), and conveys the sheet. At the same time, as shown in FIG. 7 (d), a control signal is input to the drive circuit 157 of the drawing roller motor 141 to turn on the drawing roller motor 141, and the driving of the drawing roller 42 is started (S5). . Thereafter, the output of the drawing sensor 43 that determines that the sheet has reached the drawing roller 42 is monitored.

  Next, as shown in FIG. 7E, when the leading edge of the sheet reaches the pulling roller 42 and the pulling sensor 43 is turned on (Y in S6), the control signal of the drive circuit 155 of the solenoid 23 is stopped. Then, the solenoid 23 is turned off as shown in FIG. When the solenoid 23 is turned off in this way, as shown in FIG. 3, the suction shutter 37 is closed and moved to the blocking position, and at the same time, the shielding member 19 is opened to release the communication opening 18 (S7). ).

  As a result, the inside of the suction opening 34a side of the suction duct 34 that was in the negative pressure state communicates with the outside, and the inside of the suction opening 34a side becomes atmospheric pressure. As a result, the suction force of the suction conveyance belt 22 is reduced. The sheet suction to the suction conveyance belt 22 is released. Here, the negative pressure remaining in the suction duct 34 is removed by releasing the shielding of the communication opening 18 by the shielding member 19 simultaneously with the movement of the suction shutter 37 to the blocking position as in the present embodiment. It can be released instantly.

  Next, the control signal of the drive circuit 156 of the belt drive motor 140 is stopped, the drive of the belt drive motor 140 is stopped as shown in FIG. 7C, and the drive of the suction conveyance belt 22 is stopped (S8). . At this time, since the suction force due to the negative pressure is not generated, when the suction conveyance belt 22 is stopped in this manner, the sheet is completely separated from the suction conveyance belt 22, and the suction conveyance belt 22, the drawing roller 42, There is no tension caused by the speed difference generated between the two. As a result, the load applied to the drawing roller motor 141 via the drawing roller 42 is reduced, and stable conveyance by the drawing roller 42 is possible without causing skewing of the sheet, jamming, or damage to the sheet.

  Then, as shown in FIG. 7E, when the drawing sensor 43 is turned OFF (Y in S9) and it is detected that the trailing edge of the sheet has passed the drawing roller 42, the control of the drive circuit 157 of the drawing roller motor 141 is performed. Stop the signal. As a result, as shown in FIG. 7D, the drawing roller motor 141 is turned OFF, and the driving of the drawing roller 42 is stopped (S10). Thereafter, the control signal of the drive circuit 154 of the suction fan 36 is stopped, and the suction fan 36 is turned off as shown in FIG. 7A (S11), and the feeding of the sheet S is completed.

  As described above, the communication opening 18 is opened by the shielding member 19 provided on the suction shutter 37 simultaneously with the end of the sheet suction operation by the suction conveyance belt 22. As a result, the negative pressure state inside the duct can be released as soon as possible, the occurrence of a delay jam due to the sheet pulling between the suction conveyance belt 22 and the drawing roller 42 on the downstream side, the sheet has a low rigidity thin paper, etc. Generation of wrinkles and a decrease in productivity can be prevented.

  Furthermore, by providing the suction shutter 37 with the shielding member 19 that opens and closes the communication opening 18, it is possible to prevent the sheet jam from occurring with a simple configuration. As a result, the number of parts can be reduced and not only the cost can be reduced, but also an increase in cost due to an increase in the size of the opening / closing means (solenoid or the like) of the suction shutter 37 can be prevented.

DESCRIPTION OF SYMBOLS 12 ... Tray, 18 ... Communication opening, 19 ... Shielding member, 22 ... Suction conveyance belt, 34 ... Suction duct, 34a ... Suction opening, 36 ... Suction fan, 37 ... Suction shutter, 38 ... Suction solenoid, 42 ... Extraction Roller, 100 ... Printer, 101 ... Printer main body, 102 ... Image forming unit, 134 ... Suction conveyance mechanism, 150 ... Sheet feeding mechanism, 152 ... Air spraying unit, S ... Sheet

Claims (4)

A tray that can be moved up and down to support the sheet, an air blowing unit that blows air toward the upper portion of the sheet supported by the tray, and a sheet that floats is sucked and conveyed by the suction conveyance unit In a sheet feeding device comprising a suction conveyance mechanism,
The suction conveyance mechanism is
A suction duct having a suction opening formed on the suction conveyance unit side;
A negative pressure generating unit that generates a negative pressure in the suction duct that causes the suction conveyance unit to suck the sheet;
A shutter that is disposed between the suction opening and the negative pressure generator in the suction duct, and opens and closes between the suction opening and the negative pressure generator;
A communication opening formed in a side wall between the suction opening and the shutter in the suction duct, and communicating the inside and the outside of the suction duct;
It is provided so as to be movable integrally with the shutter, and moves to a shielding position that shields the communication opening in accordance with the movement of opening the suction opening and the negative pressure generating part of the shutter, and the suction of the shutter A sheet feeding apparatus comprising: a shielding member that moves to an open position that opens the communication opening in accordance with a movement of closing between the opening and the negative pressure generation unit. Arranged on the downstream side of the suction conveyance unit in the sheet conveyance direction, and includes a drawing unit for pulling out the sheet conveyed by the suction conveyance unit;
After the sheet reaches the drawing portion, the shutter is moved so as to close between the suction opening and the negative pressure generating portion, and the communication opening is opened by the shielding member. Item 1. A sheet feeding apparatus according to Item 1.   The sheet feeding apparatus according to claim 1, wherein the shielding member and the shutter are integrally formed.   An image forming apparatus comprising: an image forming unit; and the sheet feeding device according to claim 1 for feeding a sheet to the image forming unit.

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