JP2014172700A - Sheet feeding device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeding device capable of feeding separately each sheet surely by a simple constitution, and to provide an image forming device.SOLUTION: A sheet feeding device controls an air spray part 30 and an adsorption conveyance part 20 as follows: when a sheet supported on a tray 12 is adsorbed and conveyed, air spray speed is heightened; when the air spray speed reaches a first prescribed value or higher, an adsorption operation of the sheet is performed, and after finish of the adsorption operation of the sheet, the air spray speed is lowered; and when the air spray speed reaches a second prescribed value or lower, conveyance of the sheet is started.

Description

  The present invention relates to a sheet feeding apparatus and an image forming apparatus, and more particularly to an apparatus that sucks and conveys a sheet after the air is blown and floated on the sheet.

  2. Description of the Related Art Conventionally, image forming apparatuses such as color copiers and color printers are provided with a sheet feeding device that feeds a sheet to a transfer unit in order to transfer a toner image formed on a photoreceptor onto the sheet. ing. As such a sheet feeding device, a plurality of sheets are floated by blowing air to the end of a sheet bundle supported by a tray, and then sucked by an adsorption feeding belt disposed above, one by one. There are air feed types that feed.

  In such a sheet feeding apparatus, when the user pulls out the storage, sets the sheet and stores the storage, the tray 12 starts to rise in the direction of arrow A as shown in FIG. Stop at the position where the distance becomes B. Thereafter, when the feeding signal is detected, the separation fan 31 is operated, and air is sucked in the direction of arrow C shown in FIG. This air is blown out in the directions of arrows D and E from the firing nozzle 33 and the separation nozzle 34 through the separation duct 32, and the several sheets at the top of the sheet bundle SA are floated. Further, the suction fan 36 is operated to discharge air in the arrow F direction. At this time, the suction shutter 37 is closed.

  Further, when a predetermined time elapses after the feeding signal is detected and the floating of several sheets is stabilized, the suction shutter 37 is rotated in the G direction. As a result, an upward suction force is generated from a suction hole (not shown) formed in the suction conveyance belt 21, and the uppermost sheet is attracted to the suction conveyance belt 21. Thereafter, when the belt driving roller 41 is rotated in the J direction, the uppermost sheet adsorbed by the adsorption conveyance belt 21 is conveyed integrally with the adsorption conveyance belt 21 and is moved to the next conveyance path by the drawing roller pair 42. Sent.

  In FIG. 16, reference numerals 101 and 102 denote sensors that detect the floating position of the uppermost sheet that is floated by air. A control unit (not shown) determines whether the uppermost sheet floating position is within a predetermined range in which suction conveyance by the suction conveyance belt 21 is possible by the sensors 101 and 102.

  When the control unit determines that the uppermost sheet is outside the predetermined range based on the signals from the sensors 101 and 102, the control unit moves the tray 12 up and down so that the floating position of the uppermost sheet is within the predetermined range. Control. For example, during the air blowing operation, the tray 12 is raised when it is determined that the floating position of the uppermost sheet is below a predetermined range, and the tray 12 is lowered when it is determined that it is above the predetermined range. .

  By the way, depending on the type and environment of the sheet, the sheets may be adsorbed, and in this case, the sheet may not be separated even if air is blown. Therefore, in the conventional sheet feeding apparatus, for example, the air flow path is provided so as to be movable in the vertical direction, and the air flow path is moved in the vertical direction to increase or decrease the air blowing speed (amount). It makes it easier to release the adsorption (see Patent Document 1).

JP 2002-128300 A

  By the way, in the conventional sheet feeding apparatus in which the air blowing speed is increased or decreased, an air flow path moving means for moving the air flow path in the vertical direction is required. However, when the air flow path moving means is provided in this way, the apparatus is increased in size and cost, and control is complicated.

  Accordingly, the present invention has been made in view of such a situation, and an object thereof is to provide a sheet feeding apparatus and an image forming apparatus that can reliably separate and feed sheets with a simple configuration. It is.

  In the sheet feeding apparatus, the present invention is capable of changing the air blowing speed in which air is blown to the end portion of the sheet in order to float the sheet supported by the tray and the sheet supported by the tray. An air blowing unit, a suction feeding unit that sucks and feeds a sheet that has floated by the air blown by the air blowing unit, and an air blowing speed is increased when the sheet is sucked and conveyed. A state in which the sheet suction operation is performed in a state where the spraying speed is equal to or higher than the first predetermined speed, and after the sheet suction operation is completed, the air spraying speed is reduced, and the air spraying speed is equal to or lower than the second predetermined speed. And a control means for controlling the air blowing unit and the suction feeding unit so as to start the conveyance of the sheet.

  As in the present invention, when the sheet is sucked, the air blowing speed is increased, and after the sheet sucking operation is finished, the air blowing speed is reduced when the sheet is sucked and conveyed. Thus, the sheet can be reliably separated and fed.

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 a first embodiment of the invention. The figure explaining the structure of the said sheet feeding apparatus. The figure explaining the sheet feeding operation | movement of the said sheet feeding apparatus. The figure explaining the raising / lowering mechanism of the tray of the said sheet feeding apparatus. The figure which shows the detectable lower limit of the sheet floating upper limit sensor and sheet floating upper limit sensor of the said sheet feeding apparatus. The figure showing the change of the wind speed of the separation and separation fan of the said sheet feeding apparatus. The figure showing the frequency | count of the rolling operation | movement before the rolling operation | movement according to the thickness of the said sheet | seat feeding apparatus, the kind, and environment. The figure explaining the logic of the sheet floating lower limit sensor and sheet floating upper limit sensor of the said sheet feeding apparatus. The figure which shows the operation screen of the operation part of the said printer. The control block diagram of the said sheet feeding apparatus. 6 is a flowchart illustrating suction feeding operation control of the sheet feeding device. 6 is a timing chart for explaining suction feeding operation control of the sheet feeding device. 9 is a timing chart for explaining suction feeding operation control of a sheet feeding device according to a second embodiment of the present invention. 6 is a flowchart illustrating suction feeding operation control of the sheet feeding device. The figure explaining the structure of the conventional sheet feeding apparatus. The figure explaining the structure of the conventional 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 that is an example of an image forming apparatus including a sheet feeding device according to a first 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 placement 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, a transfer unit 118 composed of the photosensitive drum 112 and a transfer charger, a fixing unit 114, and the like. . The sheet feeding device 103 stores a sheet S such as an OHT, and a plurality of sheet storage units 115 that are detachable from the printer main body 101, and a suction conveyance belt 21 that sends out the sheets S stored in the sheet storage unit 115, and the like. I have. In FIG. 1, a CPU 301 is a control unit that controls an image forming operation of the printer main body 101 and a sheet feeding operation of the sheet feeding apparatus 103.

  Next, an image forming operation of the printer 100 having such a configuration will be described. When an image reading signal is output from the CPU 301 provided in the printer main body 101 to the image reading unit 130, the image reading unit 130 reads an image of the document D. Thereafter, a laser beam corresponding to the electric 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 irradiation with light. Then, the electrostatic latent image is developed by the developing device 113, whereby toner is formed on the photosensitive drum. An image is formed.

  On the other hand, when a paper feed signal is output from the CPU 301 to the sheet feeding device 103, the sheet S is fed from the sheet storage unit 115. Thereafter, the fed sheet S is sent to the transfer unit 118 in synchronization with the toner image on the photosensitive drum by the registration roller 117. Next, the toner image is transferred to the sheet sent to the transfer unit 118 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 printer 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 unit 115 supports the sheet S and can be moved up and down, a rear end regulating plate 13 that regulates the position of the rear end that is the upstream end of the sheet S in the sheet feeding direction, a front end regulating plate 17, A side end regulating plate 14 for regulating the position of the sheet S in the width direction orthogonal to the sheet feeding direction is provided. The rear end restricting plate 13 and the side end restricting plate 14 which are restricting portions that restrict the movement of the sheets stacked and supported on the tray 12 are configured so that the positions can be arbitrarily changed according to the size of the stored sheets. Yes.

  The sheet storage unit 115 can be pulled out from the printer main body 101 by the slide rail 15, and when the sheet storage unit 115 is pulled out from the printer main body, the tray 12 is lowered to a predetermined position to replenish or replace sheets. It can be performed. The tray 12 is moved up and down by an elevating mechanism shown in FIG. 4 to be described later provided with a tray elevating motor such as a stepping motor or a DC servo motor.

  Further, an air feeding type sheet feeding unit (hereinafter referred to as an air feeding unit 150) for separating and feeding the sheets one by one is disposed on the upper part of the sheet storage unit 115. The air sheet feeding unit 150 floats the upper portion of the sheet bundle SA on the tray, and sucks and conveys the sheet S stacked on the tray 12 by suction. And an air blowing part 30 for separating the sheets one by one.

  Here, the suction conveyance unit 20 is stretched over the belt driving roller 41 and sucks the sheet S and feeds the sheet S in the right direction in the figure, and the suction conveyance belt 21 sucks the sheet S to the suction conveyance belt 21. An adsorption fan 36 that generates negative pressure is provided. Further, the suction duct 51 is provided inside the suction conveyance belt 21 and sucks air through a suction hole (not shown) formed in the suction conveyance belt 21. Further, an adsorption shutter 37 is provided between the adsorption fan 36 and the adsorption duct 51 and turns on / off the adsorption operation of the adsorption conveyance belt 21. In the present embodiment, a plurality of suction conveyance belts 21 are arranged with a predetermined interval in the width direction.

  Further, the air blowing unit 30 is used to blow the air on the front front end portion of the stored sheet bundle SA and the separation nozzle 34 and the separation nozzle 34, the separation / separation fan 31, and the nozzles 33 and 34. A separation duct 32 for sending air from the separation fan 31 is provided. As shown in FIG. 3, a part of the air sucked in the direction of arrow C by the blowing / separation fan 31 passes through the separation duct 32 and is blown in the direction of arrow D by the blowing nozzle 33 to be loaded on the tray 12. Several sheets of the upper part of the sheet bundle SA are lifted. Further, the other air is blown in the direction of arrow E by the separation nozzle 34, and the sheets floated by the separation nozzle 33 are separated one by one and adsorbed to the adsorption conveyance belt 21.

  Next, a sheet feeding operation of the sheet feeding apparatus 103 (air feeding unit 150) configured as described above will be described. First, when the user pulls out the sheet storage unit 115 and sets the sheet S on the tray, and then stores the sheet storage unit 11, the tray 12 rises. When the distance between the stacked and supported sheets and the suction conveyance belt 21 reaches a position where the distance can be fed, the CPU 301 stops the tray 12 at this position. Thereafter, the sheet feeding signal for starting feeding is prepared.

  Next, when the sheet feeding signal is detected, the CPU 301 activates the separation / separation fan 31 and sucks air in the direction of arrow C. The air is blown onto the sheet from the direction of arrows D and E from the firing nozzle 33 and the separation nozzle 34 via the separation duct 32. As a result, the upper several sheets of the sheet bundle SA float up. Further, the CPU 301 operates the suction fan 36 and discharges air in the direction F in the drawing. At this time, the suction shutter 37 is closed.

  Next, when a predetermined time elapses after the sheet feeding signal is detected and the upper sheet has stabilized, the CPU 301 drives a suction solenoid 311 shown in FIG. Rotate to As a result, air is sucked from the suction holes provided in the suction conveyance belt 21 and a suction force is generated. Only the uppermost sheet Sa is sucked to the suction conveyance belt 21 by this suction force and the separation air from the separation nozzle 34. Next, the CPU 301 drives a suction conveyance motor 309 shown in FIG. 10 described later to rotate the belt driving roller 41 in the arrow J direction. As a result, the uppermost sheet is conveyed while being adsorbed by the adsorbing and conveying belt 21, and thereafter, sent to the image forming unit by the drawing roller pair 42.

  By the way, the tray 12 is moved up and down by the lifting mechanism shown in FIG. The lifting mechanism as the lifting means moves up and down by unwinding or winding the wire W, one end of which is fixed to the tray 12, via the pulley lifting motor 604 via the pulley 603. As shown in FIG. 4, the sheet storage unit 115 is provided with a tray lower position detection sensor 605 for detecting the lower position of the tray 12, and the sheet is conveyed downstream of the suction conveyance belt 21 in the sheet conveyance direction. A pull-out sensor 620 for detecting that this has been done is disposed.

  As shown in FIG. 4, a sheet presence / absence detection sensor 606 is disposed above the tray 12, and a sheet floating lower limit sensor 607 and a sheet floating upper limit sensor 608 are disposed above the suction conveyance belt 21. A sheet presence / absence detection sensor 606 detects the presence / absence of a sheet on the tray by a flag. The sheet presence / absence detection sensor 606 is disposed below the sheet lifting lower limit sensor 607 and the sheet lifting upper limit sensor 608.

  As a result, when the sheet bundle SA stacked on the tray 12 rises to the sheet feeding start position, the sheet presence / absence detection sensor 606 is placed on the upper surface of the sheet bundle SA before the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608. Can be detected. Note that the on-edge of the sheet presence / absence detection sensor 606 is disposed below the air outlet of the stray fan duct 610.

  The sheet levitation lower limit sensor 607 and the sheet levitation upper limit sensor 608 are sensors that detect the position of the sheet that has been levitated by the wind pressure generated by the separation / separation fan 31 and optically detect the sheet. The sheet floating lower limit sensor 607 is adjusted in sensitivity so that a floating sheet positioned below the sheet floating upper limit sensor 608 can be detected.

  Here, the detectable lower limits at which the sheets can be detected by the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608 are set as shown in FIG. In this way, by setting the detectable lower limit of the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608, it is detected whether the floated sheet is located within an appropriate range in which suction by the suction conveyance unit 20 is possible. 4 and 5, the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608 are arranged along the sheet feeding direction. However, by arranging them in the direction perpendicular to the sheet feeding direction, Accurate detection is possible.

  By the way, as an initial operation before performing the sheet feeding operation, a pre-blowing operation is performed in which air is blown to the vicinity of the upper sheet of the sheet bundle by the separation / separation fan 31 in order to prevent double feeding of the sheets. In the present embodiment, the air wind speed, which is the blowing speed of the air blown out by the blowing / separation fan 31 during the pre-blowing operation, is set at a constant cycle, for example, as shown in FIG. It is changed to a trapezoidal shape, and air is blown onto the seat with strength. Note that if the strength is applied, the air wind speed may be changed to a triangular shape as shown in FIG.

  Here, by changing the air wind speed at a constant cycle in this way, in other words, by repeatedly increasing and decreasing the air wind speed a predetermined number of times, even if the sheet is likely to stick, the sheet is reliably rolled up. be able to. As shown in FIG. 7, the number of whirling operations performed by the whirling / separation fan 31 includes the sheet type (thin paper, plain paper, thick paper), the surface property of the sheet (coated paper, uncoated paper), and the operating environment (temperature) of the apparatus. , Humidity) and the like. For example, when the temperature is 25 ° C. or higher and the humidity is 65% or higher, the sheet is more likely to be in close contact than when the temperature is 25 ° C. or lower and the humidity is 65% or lower. Further, the cycle of the air wind speed, in other words, the control waveform of the separation / separation fan 31 may be arbitrarily changed according to the productivity of the apparatus.

  On the other hand, when a sheet feeding operation is performed after the pre-rolling operation, the suction shutter 37 is opened when the winding / separation fan 31 exceeds a predetermined wind speed, that is, the solid line A or more shown in FIG. Is controlled to adsorb. That is, in the present embodiment, the timing at which the sheet is adsorbed to the adsorbing and conveying belt 21 is such that the air blowing speed by the separation / separation fan 31 is equal to or higher than the predetermined wind speed (first predetermined speed) indicated by the solid line A. It is time to become.

The value of the solid line A is about 1.0 m ³ / min. When such a wind speed is reached, the sheet is well-rolled, and an appropriate position where the uppermost sheet approaches the suction conveyance belt 21. It becomes. It can be detected from the rotation speed of the whirling / separation fan 31 that the wind speed has become A or more. Generally, the fan / separation fan 31 is equipped with an FG (frequency generator) circuit, and it is determined that the wind speed is A or more based on a frequency proportional to the rotational speed output from the FG circuit. To do.

  Further, as described above, after the sheet is adsorbed, the adsorbing and conveying belt 21 is rotated to convey the sheet to the drawing roller 42 side, and the drawing sensor 620 detects that the sheet has been conveyed. Here, in the present embodiment, the rotation of the suction conveyance belt 21 is performed at a speed equal to or lower than a predetermined wind speed suitable for separating the sheet sucked by the separation / separation fan 31 and the sheet below it, that is, in FIG. Control is performed so as to be performed when the value is equal to or less than the solid line B shown.

In other words, in the present embodiment, the timing at which the suction conveyance of the sheet by the suction conveyance belt 21 is started is when the periodically changing air wind speed is equal to or lower than a predetermined wind speed (second predetermined speed). . The value of the solid line B is about 0.3 m ³ / min. When such a wind speed is reached, the sheet adsorbed on the adsorbing and conveying belt 21 is separated from the sheet below it.

  Note that FIG. 4 described above shows a state in which the uppermost sheet Sa is sucked by the suction fan 36, but when detecting the floating position of the sheet, the suction fan 36 is not operated and the separation / separation fan 31 is operated. Make it work. As a result, the raising / lowering of the tray 12 can be controlled based on on / off of the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608 shown in FIG. The sheet can be reliably positioned within a predetermined range.

  Further, in the present embodiment, when the air wind speed control shown in FIG. 6 is performed, the tray is based on the sheet lift lower limit sensor 607 and the sheet lift upper limit sensor 608 when the air wind speed is a predetermined value (solid line A or higher). The raising / lowering of the tray 12 is controlled, and otherwise the raising / lowering of the tray 12 is not performed. Thus, in the present embodiment, when the air wind speed is equal to or higher than the solid line A shown in FIG. Thereafter, as described above, when the air wind speed is equal to or lower than the solid line B shown in FIG. 6, that is, when the air wind speed becomes weak, the suction conveyance belt 21 is controlled to operate.

  In this way, by operating the suction conveyance belt 21 when the air wind speed becomes weak, it is not necessary to perform the raising / lowering control of the tray 12 when the air wind speed is weak, and thus the control becomes simple. Further, since wasteful operations can be reduced, the tray lifting motor 604 can be made highly durable.

  FIG. 8 is a diagram for explaining the logic of the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608. In the present embodiment, the standby position of the sheet bundle when the suction fan 36 and the separation / separation fan 31 are not operating is the on-edge of the sheet floating lower limit sensor 607, and as shown in FIG. A state where the sensor 607 is turned on is a standby state of the sheet bundle.

  Further, when the sheet bundle is in a standby state, when the rolling / separation fan 31 is driven, the upper part of the sheet bundle is rolled up, and the uppermost sheet of the sheet bundle is floated. Then, as shown in FIG. 8B, the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608 are turned on so that the uppermost sheet that has floated falls within an appropriate range in which suction by the suction conveyance unit 20 is possible. The raising / lowering of the tray 12 is controlled.

  That is, when the uppermost sheet of the sheet bundle is lifted, the raising / lowering of the tray 12 is controlled so that the uppermost sheet is positioned at the appropriate sheet control position where the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608 are turned on. When the sheet floating lower limit sensor 607 is turned off after the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608 are turned on, it is determined that the uppermost sheet surface has risen from the appropriate position for controlling the paper surface, and the tray 12 is lowered. .

  FIG. 9 is a diagram illustrating an operation screen of the operation unit 320 which is a setting unit illustrated in FIG. Rotation that optimizes the maximum wind speed and the minimum wind speed of the separation / separation fan 31 by inputting sheet information such as the material, basis weight, and surface smoothness of the sheet surface loaded on the tray 12 from this operation screen. The number of rotations of the separation / separation fan 31 is set to be a number. When the separation / separation fan 31 operates based on the input sheet information, the uppermost sheet is located between the sheet floating lower limit sensor 607 and the sheet floating upper limit sensor 608 without performing the lifting / lowering operation of the tray 12. Alternatively, the sheet moves upward from the sheet floating upper limit sensor 608.

  FIG. 10 is a control block diagram of the sheet feeding apparatus 103 according to the present embodiment. A CPU 301 that controls the sheet feeding apparatus 103 is connected to a dedicated ASIC 302 that drives various loads such as a suction fan 36, a separation / separation fan 31, a suction conveyance motor 309, and a suction solenoid 311, and a memory 303. The memory 303 stores information such as the control table for the separation / separation fan 31 shown in FIG.

  The ASIC 302 is connected to the suction fan 36, the separation / separation fan 31, the suction conveyance motor 309, and the suction solenoid 311 via a driver 304. The ASIC 302 is connected with a temperature detection sensor 332 and a humidity detection sensor 333, which are environmental sensors, a sheet lift lower limit sensor 607, and a sheet lift upper limit sensor 608. The ASIC 302 is connected to a suction completion sensor 331 that is a suction detection unit that detects that a sheet has been sucked onto the suction conveyance belt 21 and an operation unit 320 that inputs a sheet size and the like. In this embodiment, the CPU 301 controls the sheet feeding apparatus 103 via the ASIC 302, but the sheet feeding apparatus 103 may be directly controlled.

  Next, sheet suction and feeding operation control of the sheet feeding apparatus 103 according to the present embodiment will be described with reference to a flowchart shown in FIG. 11 and a timing chart shown in FIG. When the ASIC 302 receives the paper feed start signal from the operation unit 320, the suction fan 36 and the separation / separation fan 31 are turned on (S201), and the suction fan 36 and the separation / separation fan 31 are rotated. Next, the tray lifting / lowering motor 604 is turned on and pre-rolling is performed based on setting information from the operation unit 320, environmental information from the temperature detection sensor 332 and the humidity detection sensor 333, and a wind speed variable table stored in the Memory 303. Set the number of times to perform.

  Next, the ASIC 302 performs pre-blowing a predetermined number of times (S202). When the air wind speed becomes greater than a predetermined value after the sheet is rolled by a predetermined number of pre-rollings (Y in S203), that is, the air wind speed exceeds the solid line A (first predetermined speed) shown in FIG. Then, the ASIC 302 turns on the adsorption solenoid (S204). Thereby, the suction operation of the sheet by the suction fan 36 is performed. Next, when it is determined by the suction completion sensor 331 that the sheet suction operation has been completed (Y in S205), the blowing / separation fan 31 is controlled so as to reduce the air wind speed (S206).

  Next, when the air wind speed becomes lower than a predetermined value (Y in S207), that is, when the air wind speed becomes equal to or lower than the solid line B (second predetermined speed) shown in FIG. To start the sheet suction conveyance operation (S208). Thereafter, when it is detected that the sheet has been conveyed by the pull-out sensor 620, it is determined whether the job is completed (S209). If the job is continued (N in S209), the fan / separation fan control is performed ( (S210), the control of S203 to S208 is performed again. Thereafter, control of S203 to S208 is performed until the job is completed (Y in S209).

  As described above, in the present embodiment, when the sheet is sucked and conveyed, the air blowing speed is increased, and the sheet sucking operation is performed when the air blowing speed is equal to or higher than the first predetermined speed. In addition, after the sheet suction operation is completed, the air blowing speed is reduced, and when the air blowing speed is equal to or lower than the second predetermined speed, the conveyance of the sheet is started. In other words, in this embodiment, when the sheet is sucked, the air blowing speed is increased, and after the sheet sucking operation is finished, the air blowing speed is reduced when the sheet is sucked and conveyed. Yes. When the sheet is sucked and conveyed in this way, the sheet can be reliably separated and fed with a simple configuration by changing the air blowing speed.

  Next, a second embodiment of the present invention will be described. FIG. 13 is a timing chart for explaining suction feeding operation control of the sheet feeding apparatus according to the present embodiment, and FIG. 14 is a flowchart thereof.

  Sheet suction and feeding operation control of the sheet feeding apparatus 103 according to the present embodiment will be described with reference to FIGS. 13 and 14. When the ASIC 302 receives a paper feed start signal from the operation unit 320, the suction fan 36 and the separation / separation fan 31 are turned on (S301), and the suction fan 36 and the separation / separation fan 31 are rotated. Next, the tray lifting / lowering motor 604 is turned on, and pre-setting is performed based on the setting information from the operation unit 320, the environmental information from the temperature detection sensor 332 and the humidity detection sensor 333, and the wind speed variable table stored in the Memory 303. Set the number of times to whisper.

  Next, the ASIC 302 performs the pre-rolling a predetermined number of times (S302), and after rolling the sheet by the predetermined number of times of pre-rolling, controls the blowing / separation fan 31 so as to reduce the air wind speed. After that, when an adsorption permission signal is received from the CPU 301 and the adsorption permission signal is received (S303), the fan / separation fan 31 is controlled to increase the air wind speed (S304). When the air wind speed is greater than a predetermined value (Y in S305), that is, when the air speed is equal to or higher than the solid line A shown in FIG. 6, the suction solenoid is turned on (S306). Thereby, the suction operation of the sheet by the suction fan 36 is performed. Next, when the suction completion sensor 331 determines that the sheet suction operation has been completed (Y in S307), the fan / separation fan 31 is controlled so as to reduce the air velocity (S308).

  Next, the ASIC 302 drives the suction conveyance motor when the air wind speed is lower than a predetermined value (Y in S309), that is, when the air wind speed is equal to or lower than the solid line B shown in FIG. The sheet suction conveyance operation is started (S310). Thereafter, when it is detected by the pull-out sensor 620 that the sheet has been conveyed, it is next determined whether or not the job has been completed (S311). If the job is to be continued (N in S311), again in S303 to S310. Take control. Thereafter, the control in S303 to S210 is performed until the job is completed (Y in S311).

  As described above, in the present embodiment, the wind speed of the blowing / separation fan 31 is moderately suppressed until an adsorption permission signal is received. Thereby, energy saving of the printer itself can be achieved, and the noise of the printer can be reduced. In addition, it is possible to minimize problems caused by a decrease in the moisture content of the sheet, which is caused by air blowing by the separation / separation fan 31.

  In the description so far, the case where the cycle of changing the air blowing speed is made to coincide with the cycle of the sheet feeding operation has been described, but the present invention is not limited to this. For example, the spraying speed change period may be set to an integral multiple of the sheet feeding operation period, and the spraying speed may be changed even during the sheet feeding operation. Thereby, a sheet can be rolled more reliably.

DESCRIPTION OF SYMBOLS 12 ... Tray, 20 ... Adsorption conveyance part, 21 ... Adsorption conveyance belt, 30 ... Air blowing part, 31 ... Separation / separation fan, 36 ... Adsorption fan, 37 ... Adsorption shutter, 100 ... Printer, 101 ... Printer main body, 102 ... Image forming unit 103 ... Sheet feeding device 150 ... Air feeding unit 301 ... CPU 302 ... ASIC 303 ... Memory 311 ... Adsorption solenoid 607 ... Sheet floating lower limit sensor 608 ... Sheet floating upper limit sensor 620 ... Pullout sensor, S ... Sheet, Sa ... Top sheet

Claims (8)

A tray that can move up and down while supporting the sheet;
An air blowing section that blows air to an end of the sheet to float the sheet supported by the tray, and the air blowing speed can be changed;
An adsorbing and feeding unit that adsorbs and feeds a sheet levitated by the air blown by the air blowing unit;
When the sheet is sucked and conveyed, the air blowing speed is increased, the sheet blowing operation is performed in a state where the air blowing speed is equal to or higher than the first predetermined speed, and after the sheet sucking operation is completed, Control means for controlling the air spraying unit and the suction feeding unit so as to reduce the spraying speed and start conveying the sheet in a state where the air spraying speed is equal to or lower than a second predetermined speed;
A sheet feeding apparatus comprising: Elevating means for elevating the tray;
Detecting means for detecting whether the uppermost sheet of the sheets supported by the tray is located within an appropriate range capable of being sucked by the suction feeding unit;
When the air blowing speed is equal to or higher than the first predetermined speed, the control means determines that the uppermost sheet is within the appropriate range based on a signal from the detection means before performing the sheet suction operation. 2. The sheet feeding apparatus according to claim 1, wherein the elevating means is controlled as described above, and the elevating means is not controlled when the air blowing speed becomes equal to or lower than the second predetermined speed.   In the initial operation before starting the suction feeding operation of the sheet, the control unit sprays the air to the end portion of the sheet while repeatedly increasing and decreasing the air spray speed a predetermined number of times. The sheet feeding apparatus according to claim 1, wherein the sheet feeding device is controlled. Setting means for setting sheet information;
An environmental sensor for detecting the operating environment,
4. The sheet feeding apparatus according to claim 3, wherein the control unit sets the predetermined number of times based on setting information from the setting unit and environmental information from the environmental sensor.   After the initial operation is completed, the control means sets the air blowing speed to a second predetermined speed or less, and increases the air blowing speed when starting the sheet suction and feeding operation. 5. The sheet feeding apparatus according to claim 3, wherein the air blowing unit is controlled. Comprising a suction detection means for detecting that the sheet has been sucked by the suction feeding section;
The said control means controls the said air blowing part so that the blowing speed of the said air may be decelerated based on the signal from the said adsorption | suction detection means, The any one of Claim 1 thru | or 5 characterized by the above-mentioned. Sheet feeding device.   7. The cycle of increasing and decelerating the air blowing speed in the sheet sucking and feeding operation is set to an integral multiple of the cycle of the sheet sucking and feeding operation. The sheet feeding apparatus described in 1.   An image forming apparatus comprising: the sheet feeding device according to claim 1; and an image forming unit that forms an image on a sheet fed from the sheet feeding device. .

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