JP2004352438A - Sheet feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To favorably separate sheets, and securely feed them one by one in accordance with the kinds of the sheets. <P>SOLUTION: Air is blown to a prescribed position of a sheet stacking unit 32, and the uppermost sheet on the sheet stacking unit is separated. Above the uppermost sheet, a carrying unit 31 is disposed, and the uppermost sheet is sucked by the carrying unit to be carried to a carrying passage. The carrying unit is controlled to move in a separating direction or approaching direction to the uppermost sheet in accordance with the sheet kind indicating the size and thickness of the sheet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sheet feeding apparatus used in an image forming apparatus such as a copying machine, a facsimile, or a printer, and more particularly to a sheet feeding apparatus that feeds a sheet-shaped recording medium using air.
[0002]
[Prior art]
Generally, in an image forming apparatus, a toner image formed on an image carrier such as a photosensitive drum is transferred to a sheet-like recording medium (hereinafter simply referred to as a sheet) at a transfer position to form an image. Is fed from a sheet feeding device to a transfer position via a sheet conveying path.
[0003]
As a sheet feeding device, for example, air is blown on sheets stacked on a sheet mounting table such as a paper feed tray, so that the sheets on the sheet mounting table are lifted, and the sheets are separated one by one, and then moved to the top. There is a type in which a positioned sheet is sucked (sucked) to a feeding belt (conveying belt) and fed. In such a sheet feeding apparatus, if the sheet is sucked and transported under the same conditions regardless of the size and / or thickness of the sheet, the suction force is too strong depending on the sheet, and the sheet may be damaged. Sometimes. On the other hand, depending on the sheet, the suction force may be too weak to be fed.
[0004]
In order to cope with such a problem, for example, the sheet stored in the supply tray is raised by driving the elevator motor until the uppermost layer thereof once contacts the contact sensor, and then the supply tray is lowered by a predetermined distance to initialize the sheet. After making settings, air suction is performed by a vacuum motor in this state, and the uppermost sheet is adsorbed on the conveyance belt and conveyed in a predetermined direction. At this time, the elevator motor is driven according to the time required until the sheet is adsorbed. Then, there is a device in which the distance between the contact sensor and the uppermost sheet is adjusted to a value appropriate for suction (see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-6-40579 (paragraphs (0017) to (0025), FIGS. 1 to 5)
[0006]
[Problems to be solved by the invention]
By the way, in the sheet feeding device described in Patent Literature 1, an elevator motor is driven in accordance with a required time until sheet adsorption, and an interval between the contact sensor and the uppermost sheet is adjusted to an appropriate value for suction. I am trying to do it.
[0007]
In other words, in the sheet feeding apparatus described in Patent Document 1, the sheets stored in the supply tray are moved in the vertical direction, and are moved according to the sheet type (sheet type) such as the size and / or thickness of the sheet. The distance between the conveyor belt and the uppermost sheet (that is, the supply tray) is adjusted. When the supply tray is moved in the vertical direction in this way, when the uppermost sheet is separated, the air blown to the supply tray is reduced. The spray position may be slightly changed, and the uppermost sheet may not be properly separated.
[0008]
Then, if the separation of the sheets is not performed properly, the suction to the conveyor belt is not performed well, and there is a problem that a problem such as a double feed of the sheets occurs.
[0009]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet feeding apparatus capable of improving sheet separation and feeding sheets one by one according to a sheet type.
[0010]
[Means for Solving the Problems]
According to the present invention, there is provided a sheet feeding device for sending out a top sheet from a sheet stacking unit on which a plurality of sheets are stacked to a conveyance path, wherein air is blown to a predetermined position of the sheet stacking unit. A separation unit that separates the top sheet on the sheet stacking unit, a conveyance unit that is disposed above the top sheet, and suctions the top sheet and conveys the top sheet to the conveyance path; A movement control unit for controlling movement in a direction away from or approaching the uppermost sheet, thereby obtaining a sheet feeding apparatus.
[0011]
In this way, air is blown to a predetermined position of the sheet stacking unit to separate the uppermost sheet on the sheet stacking unit, and the conveying unit sucks the uppermost sheet and conveys the sheet to the conveying path. If the movement is controlled in the direction away from or approaching the upper sheet, the position of the air blown to the sheet on the sheet stacking unit can be kept constant, and no failure occurs in the separation of the sheet. In addition, the sheet can be suctioned favorably. Further, since the suction force of the sheet changes with the movement of the transport unit, it is not necessary to control the air volume of the suction fan.
[0012]
In the present invention, the movement control unit controls the movement of the transport unit to a detection position in a separated state that differs depending on a sheet type indicating the size and thickness of the sheet, and determines a positional relationship between the transport unit and the uppermost sheet. A position detector that measures a distance between the transport unit and the uppermost sheet and obtains the position of the transport unit as a detection position. The driving of the transport unit is controlled based on an optimal position set for each sheet type and indicating the optimal position of the transport unit.
[0013]
As described above, the transport unit is controlled to move based on the detection position in consideration of the difference in the separation state according to the sheet type indicating the size and thickness of the sheet, and the positional relationship between the transport unit and the top sheet is determined. By doing so, it is possible to always perform good sheet conveyance according to the sheet type.
[0014]
The movement control unit may move the conveyance unit while maintaining the substantially horizontal state with respect to the sheet stacking unit to change the position of the conveyance unit. The position of the transport unit may be changed by changing an angle with respect to the sheet stacking unit.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention to them unless otherwise specified, and are merely mere descriptions. This is just an example.
[0016]
First, an image forming apparatus using a sheet feeding apparatus according to the present invention will be described with reference to FIG. The illustrated image forming apparatus includes first to third sheet feeding devices 3 to 5, and here, the first to third sheet feeding devices 3 to 5 are so-called air sheet feeding devices. Sheets are selectively fed from the first to third sheet feeding devices 3 to 5, and are fed to the conveyance path 7 by feed rollers 10. Various types of sheets are set in the sheet cassettes corresponding to the first to third sheet feeding apparatuses 3 to 5 as needed.
[0017]
The conveyance path 7 is provided with a registration roller 11, and the toner image is transferred to the sheet conveyed on the conveyance path 7 by the image forming unit 13 at the transfer position. Thereafter, the sheet is sent to the fixing unit 14, where the toner image on the sheet is fixed on the sheet.
[0018]
Then, the sheet is discharged outside by the discharge roller 15. In the illustrated example, the image forming unit 13 includes a photosensitive drum 18, a charger 20, an exposure device 21, a developing device 22, a transfer belt 23, a cleaning device 24, and the like.
[0019]
Here, an example of the air feeding apparatus according to the present invention will be described with reference to FIG. The illustrated air feeding device includes a transport unit 31, and the transport unit 31 is disposed above a sheet stacking table (sheet stacking unit) 32 such as a sheet feed tray on which a plurality of sheets S are stacked. ing. The bottom surface (not shown) of the sheet stacking table 32 moves upward each time the sheet S is fed, and positions the uppermost sheet S at a predetermined position.
[0020]
The transport unit 31 includes a unit frame 33, and a transport belt portion (suction belt portion) 34 is supported on the unit frame 33. The transport belt section 34 includes a drive roller 35 and a driven roller 36, and a transport belt 37 is stretched between the drive roller 35 and the driven roller 36. Then, a driving force is applied to the driving roller 35 from a driving source such as a motor. When the driving roller 35 rotates in a direction indicated by a solid arrow, the transport belt 37 rotates.
[0021]
Although not shown, the sheet is sucked by the conveyor belt section 34 by driving a suction fan (not shown) as described later. The transport belt is divided into, for example, two parts along the sheet feeding direction (the direction indicated by the dashed arrow in FIG. 2). As a result, the transport belt has a cutout portion extending in the sheet feeding direction. In other words, the notch is used as an air suction port.
[0022]
From the downstream side in the sheet feeding direction, air for separating sheets (hereinafter referred to as separation air) is blown toward the sheet stacking table 32, and the separation air is blown to a predetermined position on the sheet stacking table 32. The sheets S sprayed and stacked on the sheet stacking table 32 are separated one by one.
[0023]
As shown in FIG. 2, a position detector 38 is disposed in the transport belt unit 34, and the distance between the top sheet of the sheet stacking table 32 and the position detector 38 is measured by the position detector 38. Is done. The position detector 38 includes, for example, a light-emitting unit and a light-receiving unit, emits light from the light-emitting unit, receives the reflected light reflected by the uppermost sheet at the light-receiving unit, and detects the time from light emission to light reception. The above distance will be measured accordingly.
[0024]
Here, referring to FIG. 3, the transport unit 31 is attached to an image forming apparatus housing (hereinafter simply referred to as a housing) so as to be movable up and down with respect to the sheet mounting table 32 (that is, in a direction of coming and going). I have. In the example shown in FIG. 3, racks 39a and 39b extending vertically are formed on both side surfaces (right side surface and left side surface in the figure) of the unit frame 33, and pinions 40a and 40b mesh with these racks 39a and 39b, respectively. ing.
[0025]
The rotation shaft 41a of the pinion 40a is coupled to the rotation shaft of a drive motor 42 mounted on the housing, while the pinion 40b is rotatably mounted on the housing. Further, on the side surface facing the pinion 40a, a pinion 40c is rotatably held by the unit frame 33, and the pinion 40c is engaged with the pinion 40b. A pulley (not shown) is provided on the rotation shaft 41b of the pinion 40c. Similarly, a pulley is also provided on the rotation shaft 41a of the pinion 40a, and these pulleys are connected by a timing belt 43. .
[0026]
As a result, when the pinion 40a is rotationally driven by the rotational drive (forward or reverse) of the drive motor 42, the pinion 40b is also rotationally driven via the timing belt 43 and the pinion 40c, and is transmitted via the racks 39a and 39b. The transport unit 31 moves up and down. The drive motor 42 is controlled by the control device as described later.
[0027]
Referring to FIG. 4 as well, when a sheet size and type are selected on operation panel 51 and a print start button (not shown) is pressed, control device 52 executes a paper feed start operation. In the control device 52, the distance between the position detector 38 (that is, the transport unit 31) and the top sheet S on the sheet stacking table 32 is set in advance as the optimum distance in accordance with the sheet size and the thickness. In the sheet feeding start operation, the control device 52 controls the position of the transport unit 31 in accordance with the optimum distance corresponding to the selected sheet size and thickness (hereinafter simply referred to as the selected sheet).
[0028]
At this time, as described above, in the position detector 38, the distance between the transport unit 31 and the top sheet S is given to the control device 52 as a detection distance, and the control device 52 calculates the optimum distance and the detection distance. In comparison, the drive of the drive motor 42 is controlled in accordance with the deviation.
[0029]
For example, when the optimum distance is greater than the detection distance, the control device 52 determines that the transport unit 31 is located below the optimal position, controls the drive of the drive motor 42, and moves the transport unit 31 upward. Will do.
[0030]
On the other hand, when the optimum distance <the detection distance, the control device 52 determines that the transport unit 31 is located above the optimal position, controls the drive of the drive motor 42, and moves the transport unit 31 downward. Will be.
[0031]
After adjusting the position of the transport unit 31 according to the type of sheet in this way, the control device 52 controls the drive of the transport unit motor 53 to rotate the drive roller 35 and rotate the transport belt 37. At the same time, the suction fan 54 is operated. In addition, the separation air is blown to a predetermined position of the sheet stacking table 32 to separate the sheets. Suction is performed by the driving of the suction fan, and the uppermost sheet S on the sheet stacking table 32 is sucked by the transport unit 31, fed by the transport belt 37 in the feeding direction, and sent out to the transport path.
[0032]
As described above, if the transport unit 31 is moved in accordance with the type of sheet while maintaining a substantially horizontal state in the up-down direction, the blowing position of the separation air blown to the sheet on the sheet stacking table 32 is different. In other words, since the sheet is always constant, no failure occurs in the separation of the sheet, and the suction can be favorably performed according to the type of the sheet. Moreover, since the suction force of the sheet changes depending on the movement of the transport unit 31, it is not necessary to control the air volume of the suction fan.
[0033]
The detection of the detection distance by the position detector may be performed only when the sheet type is selected, or may be performed each time a sheet is fed. Further, in the above-described example, the case where the separation air is blown to the predetermined position of the sheet stacking table 32 after the position of the transport unit 31 is adjusted according to the sheet type has been described. The sheet may be raised, the position of the sheet may be detected by a position detector in the raised state, and the conveyance unit 31 may be driven and controlled to the optimum position according to the detected position. Furthermore, in the above-described example, the transport unit 31 is driven and controlled to the optimum position in accordance with the detection of the sheet position by the position detector, but the optimum position defined by the sheet size and type input from the operation panel 51 is controlled. Alternatively, the transport unit 31 may be driven and controlled. In this case, no position detector is required.
[0034]
In the above-described example, an example in which the transport unit 31 is moved with respect to the uppermost sheet S while maintaining a substantially horizontal state has been described. However, as illustrated in FIG. The distance between the transport unit 31 and the uppermost sheet S may be changed according to the type of sheet.
[0035]
That is, as the sheet size and the thickness increase, the rotation angle of the transport unit 31 may be controlled to be smaller. In this case, the rotation angle of the transport unit 31 from the horizontal position is set in advance as an optimal rotation angle in the control device according to the sheet type, and the control device rotates the transport unit 31 in accordance with the optimal rotation angle. You control the angle, that is, the position.
[0036]
As described above, when the rotation angle of the transport unit 31 is controlled, an angle detector is used as a position detector, and a rotation mechanism that rotates the transport unit 31 around a fulcrum is required. . This rotation mechanism may be configured such that, for example, a shaft gear is mounted on the rotation shaft of the drive roller 35, and a driving force is applied to the shaft gear by a stepping motor to rotate the transport unit 31 about the fulcrum.
[0037]
【The invention's effect】
As described above, according to the present invention, air is blown to a predetermined position of the sheet stacking unit to separate the uppermost sheet on the sheet stacking unit, and the conveying unit sucks the uppermost sheet and conveys the sheet to the conveying path. In doing so, the transport unit is controlled to move in the direction away from or approaching the uppermost sheet, so that the blowing position of the air blown to the sheets on the sheet stacking unit can be kept constant, and the sheets can be separated. There is an effect that the sheet can be satisfactorily suctioned without causing a defect, and the suction force of the sheet changes according to the movement of the transport unit. Therefore, it is not necessary to control the air volume of the suction fan.
[0038]
In the present invention, the transport unit is controlled to move in accordance with the sheet detection position based on the separation state that changes depending on the sheet type indicating the size and thickness of the sheet, and the positional relationship between the transport unit and the top sheet is determined. Therefore, there is an effect that good sheet conveyance can always be performed according to the sheet type.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of an image forming apparatus using a sheet feeding apparatus according to the present invention.
FIG. 2 is a diagram schematically showing an example of a sheet feeding apparatus according to the present invention from the side.
FIG. 3 is a diagram illustrating an example of a drive system used in an example of a sheet feeding apparatus according to the present invention.
FIG. 4 is a block diagram showing a control system used in an example of the sheet feeding apparatus according to the present invention.
FIG. 5 is a diagram schematically showing another example of the sheet feeding apparatus according to the present invention from the side.
[Explanation of symbols]
31 transport unit 32 sheet loading table (sheet loading unit)
33 Unit frame 34 Conveyor belt unit 35 Drive roller 36 Driven roller 37 Conveyor belt 38 Position detectors 39a, 39b Racks 40a to 40c Pinion 42 Drive motor 43 Timing belt 51 Operation panel 52 Control device

Claims (5)

A sheet feeding device for sending a top sheet from a sheet stacking unit on which a plurality of sheets are stacked to a conveyance path,
Separating means for blowing air to a predetermined position of the sheet stacking unit to separate the top sheet on the sheet stacking unit by the air;
A transport unit that is disposed above the uppermost sheet and sucks the uppermost sheet and transports the uppermost sheet to the transport path.
A sheet feeding device, comprising: movement control means for controlling the movement of the conveyance unit in a direction away from or approaching the uppermost sheet. The movement control means controls the movement of the transport unit according to a sheet type indicating the size and thickness of the sheet, and determines a positional relationship between the transport unit and the uppermost sheet. The sheet feeding device according to claim 1, wherein: A position detector that measures a distance between the transport unit and the top sheet and obtains a position of the transport unit as a detection position,
The movement control means drives and controls the transport unit based on the detection position and an optimal position indicating an optimal position of the transport unit preset according to the sheet type. The sheet feeding device according to claim 2. 4. The apparatus according to claim 1, wherein the movement control unit moves the transport unit while keeping the transport unit substantially horizontal with respect to the sheet stacking unit to change the position of the transport unit. A sheet feeding device according to any one of the above. The sheet feeding device according to any one of claims 1 to 3, wherein the movement control unit changes an angle of the transport unit with respect to the sheet stacking unit to change a position of the transport unit. Feeder.

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