Patent Application
20170174455
The present invention relates to a sheet feeding apparatus and an image forming apparatus, and more particularly, to a sheet feeding apparatus and an image forming apparatus that are configured to feed a sheet with use of an electrostatic attracting force.
There have been proposed a large number of image forming apparatus, such as a copying machine and a printer, employing a friction separating system as a system for conveying sheets from a cassette having the sheets stacked thereon. In the friction separating system, a sheet feeding roller made of a rubber material is rotated while being pressed against the sheets stacked on the cassette, to thereby convey the uppermost sheet among the sheets stacked on a middle plate. In this case, in order to prevent double feeding in which a sheet arranged in contact under the uppermost sheet is simultaneously conveyed, there is known a configuration of conveying the sheet while pressing the sheet against a separation pad, or a configuration of applying a force in a direction opposite to the conveyance direction to the sheets other than the uppermost sheet by a retard roller. In such a friction separating configuration, the sheet is conveyed while being applied with a large normal force, and hence noise due to the feeding operation becomes a problem.
In order to solve this problem, there has been proposed an apparatus having a configuration employing an electrostatic attraction separating system (see PTL 1). In this apparatus, when the sheet is to be attracted, an endless belt is caused to sag to increase the attraction area for attraction and separation. After the sheet is attracted and separated, a tension is provided to the belt to obtain a flat-surface state, and the sheet is conveyed in this state. Therefore, noise at a sheet feeding unit can be significantly reduced.
Further, there has also been proposed an apparatus having a configuration in which power is fed to an endless electrostatic attraction belt including electrodes (see PTL 2 and PTL 3). In the apparatus disclosed in PTL 2, positive power and negative power are fed to integrated electrodes arranged on the endless electrostatic attraction belt from two rollers configured to stretch the electrostatic attraction belt. Further, the apparatus disclosed in PTL 3 has a configuration in which power feeding brushes are arranged, which are each brought into contact with only electrodes in an attracting range among electrodes arranged on the endless electrostatic attraction belt and divided in the peripheral direction. Further, there has also been proposed an apparatus having a configuration in which the position of the power feeding unit and the position of the sheet attracting surface are offset in the peripheral direction of the electrostatic attraction belt (see PTL 4).
PTL 1: Japanese Patent Application Laid-Open No. 2012-140224
PTL 2: Japanese Patent Application Laid-Open No. H06-255823
PTL 3: Japanese Patent Application Laid-Open No. 2001-48370
PTL 4: Japanese Patent Application Laid-Open No. 2000-247474
In the apparatus disclosed in PTL 2, each of the positive power and the negative power is fed at one position, and hence during power feeding, the voltage is applied to the entire region of the electrostatic attraction belt. Therefore, the sheet is separated from the electrostatic attraction belt under a state in which the voltage is applied during sheet conveyance, and hence charges remain on the electrostatic attraction belt due to separating discharge. The residual charges deteriorate the attracting force of the electrostatic attraction belt, and hence the residual charges are required to be removed.
In the related art described above, the voltage is applied to the entire region of the electrostatic attraction belt during the operation of attracting the sheet, and hence even if a neutralization unit is brought into contact with the electrostatic attraction belt in this state, a sufficient neutralization effect cannot be obtained. Therefore, after the conveyance of the preceding sheet is completed, the endless electrostatic attraction belt is rotated one lap under a state in which the power feeding is stopped so that the entire region is brought into contact with the neutralization unit for neutralization. Then, the power feeding is restarted to carry out the operation of conveying the next sheet. Therefore, the productivity may be remarkably reduced.
When the power feeding configuration disclosed in PTL 3 is attempted to be applied to the apparatus disclosed in PTL 1, the attracting range is vertically moved. Therefore, it is difficult to feed power while reliably bringing the power feeding brushes into contact with the electrodes arranged on the electrostatic attraction belt.
Further, in PTL 4, there is disclosed an electrostatic attraction conveyance belt configured to convey the sheet while attracting the sheet by an electrostatic force, in which opposite-polarity electrodes are sequentially arrayed on a flexible base member. In this electrostatic attraction conveyance belt, the electrodes are arranged on the inner peripheral side of the base member and are arranged so as to be inclined by a predetermined angle with respect to a belt rotating direction. A power feeder is arranged on the inner peripheral side of the base member, and power feeding terminals of the electrodes are made of a metal. Further, the electrodes are not protected by a protective layer, and a joining member of the endless belt is mounted on the outer peripheral side of the base member. With this configuration, the conveyance speed of the electrostatic attraction conveyance belt can be set stable. However, even when the power feeding position and the attracting position are offset on the same plane of the electrostatic attraction belt as in PTL 4, it has been difficult to solve the above-mentioned problems.
In view of this, the present invention has an object to provide a sheet feeding apparatus and an image forming apparatus that are capable of preventing decrease in productivity by enabling both of generation of an electrostatic attracting force and neutralization without control of switching between power feeding and neutralization.
According to one embodiment of the present invention, there is provided a sheet feeding apparatus, including a stacking unit on which a sheet is stacked; a first rotary member arranged on an upside of the stacking unit; a second rotary member arranged on a downstream in a sheet feeding direction with respect to the first rotary member; an endless attracting member configured to rotate in a peripheral direction of the endless attracting member whose inner surface is supported by the first rotary member and the second rotary member and to feed the sheet by attracting the sheet at an attracting position opposed to the sheet stacked on the stacking unit; a first electrode element and a second electrode element that are arranged on the endless attracting member, the first electrode element and the second electrode element each including a plurality of attracting force generation electrodes and a plurality of power feeding electrodes, each of the attracting force generation electrodes connected to each of attracting force generation electrodes to correspond with each other, the plurality of attracting force generation electrodes of the first electrode element and the plurality of attracting force generation electrodes of the second electrode element being alternately arranged to be spaced with each other in the peripheral direction of the endless attracting member; a power feeding unit arranged at a position different from the attracting position and capable of supplying a positive voltage and a negative voltage to the first electrode element and the second electrode element, respectively; and a neutralization unit arranged at a position different from the attracting position and the power feeding unit and configured to be brought into contact with the first electrode element and the second electrode element to remove a residual charge on the endless attracting member, wherein the first electrode element and the second electrode element each comprise connecting lines configured to connect the plurality of attracting force generation electrodes to the power feeding electrodes corresponding to the respective plurality of attracting force generation electrodes so as to lie next to each other in a width direction perpendicular to the peripheral direction at positions different from each other in the peripheral direction, and wherein the plurality of attracting force generation electrodes of each of the first electrode element and the second electrode element are configured to move to the attracting position along with rotation of the endless attracting member by feeding power from the power feeding unit through each of the power feeding electrodes corresponding thereto, so that each of the attracting force generation electrodes generates an electrostatic attracting force.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
According to the one embodiment of the present invention, without the control of switching between the power feeding and the neutralization, the attracting member can constantly maintain the electrostatic attracting force at the attracting position corresponding to the sheet, and the generation of the electrostatic attracting force and the neutralization are both enabled to enable sheet feeding without reducing the productivity.
Now, an embodiment of the present invention is described in detail with reference to the drawings. Note that,
In
Note that, the original from which an image is read is conveyed onto the platen glass by an automatic original feeding apparatus 41a. Further, the apparatus main body 100A includes an image forming unit 55, sheet feeding apparatus 51 and 52 configured to feed sheets S (hereinafter also referred to as “paper (S)”) to the image forming unit 55, and a sheet inverting unit 59 configured to invert the sheet S and convey the inverted sheet S to the image forming unit 55.
The image forming unit 55 includes an exposure unit 42, and four process cartridges 43 (43y, 43m, 43c, and 43k) configured to form toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (Bk). Further, the image forming unit 55 includes an intermediate transfer unit 44, a secondary transfer unit 56, and a fixing unit 57 provided on an upward side of the process cartridges 43.
In this case, the process cartridges 43 include photosensitive drums 21 (21y, 21m, 21c, and 21k), charging rollers 22 (22y, 22m, 22c, and 22k), and developing rollers 23 (23y, 23m, 23c, and 23k). The process cartridges 43 also include drum cleaning blades (24y, 24m, 24c, and 24k).
The intermediate transfer unit 44 includes an intermediate transfer belt 25 stretched by a belt driving roller 26, a secondary transfer inside roller 56a, and the like, and primary transfer rollers 27 (27y, 27m, 27c, and 27k) brought into abutment against the intermediate transfer belt 25 at positions opposed to the photosensitive drums 21. Then, as described later, a positive transfer bias is applied to the intermediate transfer belt 25 by the primary transfer rollers 27 so that the negative-polarity toner images on the photosensitive drums 21 are sequentially transferred onto the intermediate transfer belt 25 in an overlapping manner. With this, a full-color image is formed on the intermediate transfer belt 25.
The secondary transfer unit 56 includes the secondary transfer inside roller 56a and a secondary transfer outside roller 56b that is brought into contact with the secondary transfer inside roller 56a across the intermediate transfer belt 25. Then, as described later, a positive secondary transfer bias is applied to the secondary transfer outside roller 56b, to thereby transfer the full four-color image formed on the intermediate transfer belt 25 onto the sheet S.
The fixing unit 57 includes a fixing roller 57a and a fixing backup roller 57b. Then, the sheet S is nipped and conveyed between the fixing roller 57a and the fixing backup roller 57b, to thereby pressurize and heat the toner image on the sheet S and fix the toner image onto the sheet S. The sheet feeding apparatus 51 and 52 respectively include cassettes 51a and 52a configured to receive the sheets S, and sheet attraction and separation feeding units 51b and 52b having a function of feeding the sheets S received in the cassettes 51a and 52a one by one while attracting the sheets S by static electricity.
Note that, in
Next, an image forming operation of the image forming apparatus 100 having the above-mentioned configuration is described. When the image forming operation is started, first, the control unit 70 controls the exposure unit 42 to radiate laser light on the surfaces of the photosensitive drums 21 based on image information from a personal computer (not shown) or the like. At this time, the surfaces of the photosensitive drums 21 are uniformly charged to a predetermined polarity and potential by the charging rollers 22. When the laser light is radiated, charges in a region radiated by the laser light are decayed, to thereby form electrostatic latent images on the surfaces of the photosensitive drums.
After that, the control unit 70 develops the electrostatic latent images by toner of yellow (Y), magenta (M), cyan (C), and black (Bk) supplied respectively from the developing rollers 23, to thereby visualize the electrostatic latent images as toner images. Then, the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 25 by a primary transfer bias applied to each of the primary transfer rollers 27, to thereby form a full-color toner image on the intermediate transfer belt 25.
On the other hand, the control unit 70 actuates the sheet feeding apparatus 51 and 52 in parallel with the above-mentioned toner image forming operation, and controls the sheet attraction and separation feeding units 51b and 52b to separate and feed only one sheet S from each of the cassettes 51a and 52a. When the sheet S is fed from the sheet feeding apparatus 51, the sheet S is detected by a sheet leading edge detection sensor 51c and arrives at a pull-out roller pair 71 including pull-out rollers 51d and 51e. Further, when the sheet S is fed from the sheet feeding apparatus 52, the sheet S is detected by a sheet leading edge detection sensor 52c and arrives at a pull-out roller pair 72 including pull-out rollers 52d and 52e. The sheet S nipped by the pull-out roller pair 71 or 72 is fed through the conveyance path 103 to be brought into abutment against a nip portion of a stopped registration roller pair 62 including registration rollers 62a and 62b, to thereby adjust the position of the leading edge (skew feed correction).
Next, the control unit 70 drives the registration roller pair 62 at a timing at which, in the secondary transfer unit 56, the position of the full-color toner image on the intermediate transfer belt matches with the position of the sheet S. With this, the sheet S is conveyed to the secondary transfer unit 56, and in the secondary transfer unit 56, the full-color toner image is collectively transferred onto the sheet S by the secondary transfer bias applied to the secondary transfer outside roller 56b.
The control unit 70 conveys the sheet S having the full-color toner image transferred thereon to the fixing unit 57 to heat and pressurize the sheet S by the fixing unit 57 and melt and mix the toner of respective colors, to thereby fix the full-color image onto the sheet S. After that, the control unit 70 discharges the sheet S having the image fixed thereon through the discharge unit 58 arranged on the downstream of the fixing unit 57. Note that, when images are formed on both surfaces of the sheet S, the conveyance direction of the sheet S is inverted by the sheet inverting unit 59 to convey the sheet S to the image forming unit 55 again.
Now, the sheet attraction and separation feeding units 51b and 52b in the sheet feeding apparatus 51 and 52 are described in detail with reference to
As described above, the sheet feeding apparatus 51 includes the cassette 51a, and the sheet attraction and separation feeding unit 51b configured to feed the sheets S received in the cassette 51a one by one while attracting the sheets S by static electricity. The sheet feeding apparatus 51 further includes an elevating unit 301 capable of elevating a middle plate 301a serving as a stacking unit on which the sheets are to be stacked and which is arranged to be elevatable on the cassette 51a, and the sheet leading edge detection sensor 51c configured to detect the passage of the sheet fed by the sheet attraction and separation feeding unit 51b.
The elevating unit 301 (see
The sheet attraction and separation feeding unit 51b includes a first nipping and conveying roller pair 202, a second nipping and conveying roller pair 201, a neutralization roller pair 250, and a flexible and endless attracting member 200 to be nipped and conveyed by those nipping and conveying roller pairs 201 and 202.
As illustrated in
In this case, when the upper surface of the uppermost sheet Sa is positioned at a predetermined height, in the sheet surface height detection unit 302, the sensor flag 302a is pivoted to change the shielding state of the photosensor 302b, to thereby detect the upper surface position of the uppermost sheet Sa. The control unit 70 controls the operation of the elevating unit 301 so that the upper surface of the uppermost sheet Sa is always detected by the sheet surface height detection unit 302, and the middle plate 301a is maintained at a position at which the upper surface height of the uppermost sheet Sa becomes substantially constant. As a result, an air gap Lr between the first nipping and conveying roller pair 202 and the upper surface of the uppermost sheet Sa is maintained substantially constant.
The second nipping and conveying roller pair 201 is arranged on the downstream in the sheet feeding direction with respect to the first nipping and conveying roller pair 202, and includes a second nipping and conveying inner roller 201a and a second nipping and conveying outer roller 201b. The second nipping and conveying inner roller 201a is arranged on the inner side of the attracting member 200, and has a rotary shaft 201j rotatably supported by a shaft support member (not shown) whose position is fixed. The drive from a second driving unit 203 is transmitted to the second nipping and conveying inner roller (second rotary member) 201a via a drive transmitting unit (not shown).
The second nipping and conveying outer roller 201b is arranged at a position opposed to the second nipping and conveying inner roller 201a under a state in which the endless belt-like attracting member 200 is nipped between the second nipping and conveying outer roller 201b and the second nipping and conveying inner roller 201a. The shaft of the second nipping and conveying outer roller 201b is supported rotatably by a shaft support member (not shown). The second nipping and conveying outer roller 201b rotate along with (following rotation) the attracting member 200 rotated in the arrow F direction by the second nipping and conveying inner roller 201a rotating in the same direction. Note that, a second pressure spring (not shown) is coupled to the shaft support member (not shown), and the second nipping and conveying outer roller 201b is biased in the axial center direction of the second nipping and conveying inner roller 201a by the second pressure spring to nip the attracting member 200 together with this roller 201a.
The first nipping and conveying roller pair 202 includes a first nipping and conveying inner roller 202a and a first nipping and conveying outer roller 202b. The first nipping and conveying inner roller 202a is arranged on the inner side of the attracting member 200, and has a rotary shaft 202j rotatably supported by a shaft support member (not shown) whose position is fixed. The drive from a first driving unit 204 is transmitted to the first nipping and conveying inner roller (first rotary member) 202a via a drive transmitting unit (not shown).
Note that, the first nipping and conveying inner roller 202a constructs the first rotary member arranged on the upward side of the middle plate 301a serving as the stacking unit. Further, the second nipping and conveying inner roller 201a constructs the second rotary member arranged on the downstream in the feeding direction of the sheet S (arrow J direction in
The first nipping and conveying outer roller 202b is arranged at a position opposed to the first nipping and conveying inner roller 202a under a state in which the attracting member 200 is nipped between the first nipping and conveying outer roller 202b and the first nipping and conveying inner roller 202a. The shaft of the first nipping and conveying outer roller 202b is supported rotatably by a shaft support member (not shown). The first nipping and conveying outer roller 202b is rotated in association with the attracting member 200 rotated in the arrow G direction by the first nipping and conveying inner roller 202a rotating in the same direction. Note that, a first pressure spring (not shown) is coupled to the shaft support member (not shown), and the first nipping and conveying outer roller 202b is biased in the axial center direction of the first nipping and conveying inner roller 202a by the first pressure spring to nip the attracting member 200 together with this roller 202a.
In this embodiment, the endless attracting member 200 is supported by the second nipping and conveying inner roller 201a, the first nipping and conveying inner roller 202a, and a neutralization inner roller 250a that are three rotary members arranged along the sheet feeding direction. Then, the attracting member 200 has a length larger than [sum D1+D2+D3 of distances between rotation centers of the respective rollers 201a, 202a, and 250a]+[sum of wrapping lengths of the attracting member 200 on the respective rollers 201a, 202a, and 250a].
With such a length, the attracting member 200 can sag downward while being rotated (moved) by the rotation of the second nipping and conveying inner roller 201a and the first nipping and conveying inner roller 202a. With this, although the air gap Lr exists between the first nipping and conveying roller pair 202 and the uppermost sheet Sa among the sheets S stacked on the middle plate 301a, the attracting member 200 can be brought into contact with the uppermost sheet Sa.
At positions along the outer peripheries of the attracting member 200 different from the attracting position (position represented by C in
Further, as illustrated in
Next, with reference to
As illustrated in
That is, the above-mentioned electrode elements 205 and 206 on the base layer 200a respectively include the power feeding electrodes 205a and 206a corresponding to power feeding sections B1, the connecting lines 205b and 206b corresponding to offset sections B2, and the attracting force generation electrodes 205c and 206c corresponding to an attraction section B3. The attracting force generation electrodes 205c and 206c in the attraction section B3 are arranged alternately into a pectinate shape (alternately protrude in a pectinate manner).
The connecting lines 205b and 206b are each set to have such a length that the attracting force generation electrodes 205c and 206c moving from the attracting position (C in
The power feeding electrodes 205a and 206a corresponding to the respective power feeding sections B1 at both end portions in the width direction are respectively arranged in a collective manner in the vicinity of both the end portions of the attracting member 200 in the width direction. The connecting lines 205b and 206b corresponding to the offset sections B2 are wired to be oblique to the width direction of the attracting member 200. The respective surfaces of the power feeding electrodes 205a and 206a are exposed on the surface in only parts corresponding to the power feeding sections B1, and other parts are covered with the attraction layer 200b.
As described above, the connecting lines 205b and 206b are extended from the respective attracting force generation electrodes 205c and 206c toward the upstream side in the rotating direction of the attracting member 200. Further, the power feeding brushes 260a and 260b serving as the power feeding units are arranged on the upstream side in the rotating direction of the attracting member 200 with respect to the attracting position (position represented by C in
With the configuration above, when the voltages are applied to the respective power feeding electrodes 205a and 206a, the attracting force generation electrodes 205c and 206c generate electrostatic forces at positions shifted in the peripheral direction of the attracting member 200 (rotating direction: arrow H direction) with respect to the respective corresponding power feeding electrodes 205a and 206a. That is, in the above-mentioned electrode elements 205 and 206, the attracting force generation electrodes 205c and 206c, which have moved to the attracting position along with the rotation of the attracting member 200, generate electrostatic attracting forces by being fed power from the above-mentioned supply units 265a and 265b through the corresponding power feeding electrodes 205a and 206a.
Note that, in this embodiment, the attraction layer 200b is made of polyimide that is a dielectric having a volume resistivity of 108 Ωcm or more, and the layer thickness thereof is set to about 100 μm. Further, the first and second electrode elements 205 and 206 are made of a conductor having a volume resistivity of 106 Ωcm or less, and copper having a layer thickness of about 10 μm is used as this conductor.
In this case, the connecting lines 205b and 206b corresponding to the offset sections B2 of the respective first and second electrode elements 205 and 206 are wired to be inclined with respect to the width direction of the attracting member 200, but the present invention is not limited thereto, and may be wired in a stepped manner, for example. Note that, considering the intervals between the adjacent connecting lines 205b and between the adjacent connecting lines 206b, it is most efficient to wire the elements obliquely.
Further, in this embodiment, as described later, the material and the thickness of the attracting member 200 are adjusted so that the attracting member 200 is shaped to sag downward when the attracting member 200 approaches the sheet S. Thus, the attracting member 200 has an appropriate elasticity (flexibility).
Now, with reference to
As illustrated in
The sheet surface height detection unit 302 illustrated in
The sheet leading edge detection sensors 51c and 52c illustrated in
The elevating unit 301 is actuated through control of the control unit 70 so as to elevate the middle plate 301a on which the sheets S are to be stacked and which is arranged to be elevatable on each of the cassettes 51a and 52a. The elevating unit 301 changes the positions of the middle plate 301a and the uppermost sheet among the sheets S stacked on the middle plate depending on the pivoting angle of the lifter 301b pivotably arranged below the middle plate 301a.
The second driving unit 203 includes a pulse motor or the like, and is controlled by the control unit 70 to rotationally drive the second nipping and conveying inner roller 201a. Further, the first driving unit 204 includes a pulse motor or the like, and is controlled by the control unit 70 to rotationally drive the first nipping and conveying inner roller 202a.
Next, with reference to
As illustrated in
When the sheet S is separated from the attracting member 200 from the state of
Therefore, even when the sheet S is attempted to be attracted to the attracting member 200 again as illustrated in
However, even when the surface of the attracting member 200 is attempted to be neutralized under a state in which the voltages are still applied to the first and second electrode elements 205 and 206, charges are attracted to the first and second electrode elements 205 and 206, and hence the surface of the attracting member 200 cannot be neutralized in this state. When the surface of the attracting member 200 is neutralized, it is necessary to stop the voltage application to the first and second electrode elements 205 and 206.
Next, with reference to
As illustrated in
In this case, the first and second electrode elements 205 and 206 include the offset sections B2 as illustrated in
On the downstream side of the second nipping and conveying roller pair 201, the neutralization roller pair 250 is arranged so as to nip the attracting member 200. The neutralization outer roller 250b is connected to the earth 255. Therefore, the residual charges on the surface of the attracting member 200, which may decrease the electrostatic attracting force for the sheet S, can be removed through the neutralization outer roller 250b.
Further, the neutralization inner roller 250a includes a load torque applying unit 251, which serves as a conveyance resistance against the direction of conveying the attracting member 200. The load torque applying unit 251 constructs a tension providing unit configured to provide a tension to the attracting member 200 so that the contact pressures of the power feeding brushes 260a and 260b to the power feeding electrodes 205a and 206a arranged to be opposed to the power feeding brushes 260a and 260b in the attracting member 200 can be maintained constant.
The neutralization roller pair 250 is rotated in association with the conveyance of the attracting member 200, and hence the neutralization roller pair 250 that is rotated in association with the first nipping and conveying roller pair 202 is continuously pulled by the attracting member 200. Therefore, a tension corresponding to the load torque of the load torque applying unit 251 serving as the tension providing unit is provided to the attracting member 200 between the first nipping and conveying roller pair 202 and the neutralization roller pair 250, and hence the contact between the attracting member 200 and the power feeding brushes 260a and 260b becomes reliable.
Note that, the neutralization roller pair 250 constructs the neutralization unit configured to nip the attracting member 200 in a form of being extended in the width direction (arrow I direction in
Next, with reference to
Now, those steps are described in order. Note that, in this embodiment, in each of the above-mentioned operation steps, as described later, voltages are continuously applied from the positive voltage supply unit 265a and the negative voltage supply unit 265b to the power feeding brushes 260a and 260b, and the attracting force is constantly generated on the attracting member 200. Further, the second driving unit 203 and the first driving unit 204 illustrated in
The initial operation illustrated in
As described above, the neutralization inner roller 250a includes the load torque applying unit 251 as illustrated in
In this case, the first nipping and conveying roller pair 202 may be rotated or stopped. When the initial operation is completed, the distance between the uppermost sheet Sa and the attracting member 200 is in a state of being separated by the air gap Lr between the uppermost sheet Sa and the first nipping and conveying inner roller 202a. The second nipping and conveying roller pair 201 and the first nipping and conveying roller pair 202 may transition to the next operation under a state of being continuously rotated from the initial operation, or may transition to the next operation after stopping the rotation once.
The approaching operation illustrated in
The contact length increasing operation illustrated in
However, when the contact length Mc is smaller than a predetermined length, the force of the attracting member 200 to attract the uppermost sheet Sa is also small, and hence the force cannot overcome the conveyance resistance acting on the uppermost sheet Sa. Therefore, the contact length increasing operation is continued while keeping the uppermost sheet Sa received in the cassette 51a.
The attracting operation illustrated in
The separating operation illustrated in
Further, the load torque applying unit 251 on the shaft of the neutralization inner roller 250a serves as a resistance against the direction of conveying the attracting member 200, and hence the neutralization roller pair 250 rotated in association with the first nipping and conveying roller pair 202 is continuously pulled by the attracting member 200. In other words, a tension is constantly provided to the attracting member 200 between the first nipping and conveying roller pair 202 and the neutralization roller pair 250, and the sag of the attracting member 200 is collected between the second nipping and conveying roller pair 201 and the neutralization roller pair 250.
As a result, the sag of the surface of the attracting member 200 opposed to the uppermost sheet Sa is eliminated and the attracting member 200 is elastically deformed into a substantially linear shape. Thus, the uppermost sheet Sa attracted to the attracting member 200 is raised to be separated from the sheet Sb positioned thereunder. In this case, when the speed difference between the second nipping and conveying roller pair 201 and the first nipping and conveying roller pair 202 is small, the leading edge of the uppermost sheet Sa reaches the downstream side with respect to the attracting position (position of reference symbol C), which causes peeling of the leading edge of the uppermost sheet Sa from the attracting member 200.
For example, when there is no speed difference between the second nipping and conveying roller pair 201 and the first nipping and conveying roller pair 202, the sheet Sa is conveyed while the attracting member 200 is still in a sagging state as illustrated in
The conveying operation illustrated in
In this case, the attracting position (position of reference symbol C) formed in the attracting member 200 by the voltages applied from the positive voltage supply unit 265a and the negative voltage supply unit 265b surely includes a region between the second nipping and conveying roller pair 201 and the first nipping and conveying roller pair 202. With this, the elimination of the attracting force at the leading edge of the uppermost sheet Sa is prevented, to thereby prevent the peeling of the leading edge of the uppermost sheet Sa from the attracting member 200.
With this, the uppermost sheet Sa is conveyed while being attracted to the attracting member 200 and maintaining a state in which at least the leading edge portion is separated from the sheet Sb positioned thereunder. After that, when the leading edge of the uppermost sheet Sa arrives at the vicinity of the curved portion of the attracting member 200 formed by the second nipping and conveying inner roller 201a, the leading edge of the uppermost sheet Sa is peeled off from the attracting member 200.
This peel-off occurs because the bending reactive force of the sheet Sa becomes larger than the electrostatic attracting force generated in the attracting member 200. In other words, in this embodiment, the magnitude of the electrostatic attracting force generated in the attracting member 200 is set so as to attract the sheet with a force smaller than the bending reactive force of the sheet Sa. That is, with this conveying operation, the attracting member 200 moves to a position at which the uppermost sheet Sa is separated (separating position).
Note that, after the leading edge is peeled off from the attracting member 200 as described above, the uppermost sheet Sa is increasingly peeled off from the leading edge, but the trailing edge region of the sheet Sa is attracted by the attracting member 200. With this, the sheet Sa is continuously conveyed by the attracting member 200, and through the leading edge detection at the sheet leading edge detection sensor 51c, the sheet Sa is passed to the pull-out roller pair 71. In a part of the attracting member 200 from which the sheet Sa is peeled off, a residual charge region E is generated.
The residual charge region E reaches the neutralization roller pair 250 through continuous conveyance of the attracting member 200. Even under a state in which voltages for attracting the sheet Sa to the attracting member 200 are applied, at the position of the neutralization roller pair 250 arranged outside of the attracting position (position of reference symbol C), no electric field is generated to inhibit the neutralization. Therefore, even under a state in which the sheet S is fed, the neutralization of the residual charge region E on the surface of the attracting member 200 can be executed by the neutralization outer roller 250b.
In this case, when the sheet Sa is not detected within a predetermined time period by the sheet leading edge detection sensor 51c, the control unit 70 (
With the above-mentioned six steps, only the one uppermost sheet Sa among the plurality of sheets S stacked on the cassette 51a is fed. Then, the six steps are repeated to enable continuous feeding of the sheets S one by one.
In this case, the voltages are continuously applied to the first and second electrode elements 205 and 206, but the present invention is not limited to this state. In the initial operation, the voltage supply may be stopped, and the voltages may be applied after the attracting member 200 and the uppermost sheet Sa are brought into contact with each other. The operation steps are managed with the number of rotation steps of the driving units 203 and 204, but the present invention is not limited to this method. Such a method that the speeds of the nipping and conveying roller pairs 201 and 202 are controlled while detecting the shape of the attracting member 200 or the timing of attraction of the uppermost sheet Sa may be employed.
Further, in
In this case, the attracting position is set to have a length that substantially matches with the distance between the second nipping and conveying inner roller 201a and the first nipping and conveying inner roller 202a (D1 in
Further, the voltages are not supplied to the first and second electrode elements 205 and 206 located at the position of the neutralization roller pair 250, and hence the residual charges on the surface of the attracting member 200, which may decrease the sheet attracting force, can be reliably removed by the neutralization roller pair 250.
With the above-mentioned configuration, it is possible to provide the sheet feeding apparatus 51 and capable of reliably and smoothly executing the operation steps illustrated in
In the above-mentioned embodiment, even under a state in which the voltages for attracting the sheet S to the attracting member 200 are continuously applied, the residual charges on the attracting member 200 can be reliably removed, and hence the neutralization can be executed in parallel while feeding the sheet without reducing the throughput.
In this embodiment, with the electrode configuration capable of feeding power to the attracting member 200 regardless of the shape of the sheet attracting surface and capable of partially generating the electrostatic attracting force, the feeding of the sheet and the neutralization can be executed in parallel. Further, sheet feeding with reduced noise is possible without reducing the throughput of printing. As described above, without control of switching between power feeding and neutralization, the attracting member 200 can constantly maintain the electrostatic attracting force at the attracting position corresponding to the sheet S, and the generation of the electrostatic attracting force and the neutralization are both enabled to enable sheet feeding without reducing the productivity.
Next, a second embodiment of the present invention is described with reference to
This embodiment differs from the first embodiment in that, in order to reliably bring the attracting member 200 and the power feeding brushes 260a and 260b into contact with each other, a plate member 252 is arranged instead of the load torque applying unit 251 (see
As illustrated in
The attracting member 200 in this embodiment is brought into pressure-contact with the plate member 252 through the spring performance of the brush portions 261a and 261b of the power feeding brushes 260a and 260b. The surface of the plate member 252 is subjected to low frictional processing, and the plate member 252 is configured so as not to be a large conveyance resistance when the attracting member 200 is conveyed by the second nipping and conveying roller pair 201 and the first nipping and conveying roller pair 202.
In this embodiment having the above-mentioned configuration, it is possible to reliably bring the power feeding brushes 260a and 260b into contact with the power feeding electrodes 205a and 206a of the first and second electrode elements 205 and 206 on the attracting member 200. As described above, with a simpler configuration, the attracting member 200 and the power feeding brushes 260a and 260b can be reliably brought into contact with each other, and the attraction of the sheet S to the attracting member 200 and the neutralization of the surface of the attracting member 200 can be executed in parallel.
Next, a third embodiment of the present invention is described with reference to
This embodiment differs from the first embodiment mainly in the configuration of the attracting member 200 and the configuration of the power feeding unit. That is, the attracting member 200 in this embodiment includes, as in
The power feeding electrodes 205a and 206a are each set to have such a length that the attracting force generation electrodes 205c and 206c moving from the attracting position (C of
The power feeding electrodes 205a and 206a corresponding to the respective power feeding sections B1 at both end portions in the width direction are respectively arranged in a collective manner in the vicinity of both the end portions of the attracting member 200 in the width direction. Further, the power feeding electrodes 205a and 206a are wired to be oblique to the width direction of the attracting member 200.
As described above, the power feeding electrodes 205a and 206a of this embodiment are configured to have also the role of the connecting lines 205b and 206b in the first embodiment and the second embodiment.
In this embodiment described above, in the first and second electrode elements 205 and 206, at least the power feeding electrodes 205a and 206a are exposed on the inner peripheral surface of the attracting member 200. Then, the power feeding rollers 202d and 202e serving as the power feeding units also serve as the first nipping and conveying inner roller (first rotary member) 202a, and are brought into contact with the power feeding electrodes 205a and 206a exposed on the inner peripheral surface to feed power. Note that, in this embodiment, the power feeding rollers 202d and 202e also serve as the first nipping and conveying inner roller 202a, but the present invention is not limited thereto, and the power feeding rollers 202d and 202e may be configured to also serve as the second nipping and conveying inner roller (second rotary member) 201a.
With such a configuration, in the power feeding sections B1, different voltages are respectively applied to the first and second electrode elements 205 and 206 from the power feeding rollers 202d and 202e arranged on the back surface. In the attraction section B3, the electrostatic force can be generated at a position shifted in the peripheral direction (arrow H direction in
As described also in the first embodiment, in this embodiment as well, the material and the thickness of the attracting member 200 are adjusted so that the attracting member 200 is shaped to sag downward when the attracting member 200 approaches the sheet S. Thus, the attracting member 200 has an appropriate elasticity. Further, the principle of generating the electrostatic attracting force for attracting the sheet S to the attracting member 200, and the conditions for removing the residual charges on the surface of the attracting member 200 are the same as those described in the first embodiment.
Next, with reference to
As illustrated in
The power feeding rollers 202d and 202e are arranged so as to be respectively brought into contact with at least the power feeding electrodes 205a and 206a of the first and second electrode elements 205 and 206 in the power feeding sections B1 illustrated in
In this case, in the first and second electrode elements 205 and 206, as illustrated in
In this embodiment described above, the attracting member 200 is nipped between the first nipping and conveying outer roller 202b and the first nipping and conveying inner roller 202a (power feeding rollers 202d and 202e). With this configuration, even without the load torque applying unit 251 or the like described in the first embodiment, the voltages from the positive voltage supply unit 265a and the negative voltage supply unit 265b can be reliably supplied to the first and second electrode elements 205 and 206.
As illustrated in
In this case,
First, the length necessary for the attracting position (position of reference symbol C) in
In this manner, the voltages are not supplied to the first and second electrode elements 205 and 206 located at the position of the neutralization roller pair 250, and hence the residual charges on the surface of the attracting member 200, which may decrease the sheet attracting force, can be reliably removed by the neutralization roller pair 250. With the above-mentioned configuration, in a sequence similar to the operation steps illustrated in
As described above, even when the power feeding rollers 202d and 202e are used to configure simpler power feeding units, the generation of the electrostatic force for attracting the sheet S to the attracting member 200 and the neutralization of the surface of the attracting member 200 can be executed in parallel. With this, the sheet can be fed without reducing the throughput.
Subsequently, a fourth embodiment of the present invention is described. Note that, the same configurations as the third embodiment are denoted by the same reference symbols, and detailed description thereof is omitted herein. This embodiment differs from the third embodiment in the electrode shape of the attracting member 200.
With reference to
The length of each of the power feeding electrodes 205a and 206a is set as follows. That is, the power feeding electrodes 205a and 206a are each set to have such a length that the attracting force generation electrodes 205c and 206c moving from the attracting position (C of
Note that, in the third embodiment, the attracting force generation electrodes 205c and 206c in the attraction section B3 are all independent of each other. However, in this embodiment, under a state in which each four of the attracting force generation electrodes 205c are electrically conducted with each other and each four of the attracting force generation electrodes 206c are electrically conducted with each other, the four attracting force generation electrodes 205c are connected to one power feeding electrode 205a in the power feeding section B1 and the four attracting force generation electrodes 206c are connected to one power feeding electrode 206a in the power feeding section B1. That is, under a state in which each plurality of the attracting force generation electrodes 205c in this embodiment are electrically conducted with each other and each plurality of the attracting force generation electrodes 206c in this embodiment are electrically conducted with each other, the plurality of the attracting force generation electrodes 205c are connected to corresponding one of the power feeding electrodes 205a and the plurality of the attracting force generation electrodes 206c are connected to corresponding one of the power feeding electrodes 206a. Note that, this configuration can be similarly implemented in the above-mentioned first to third embodiments.
In the respective power feeding sections B1 of the first and second electrode elements 205 and 206, the power feeding electrodes 205a and 206a are respectively wired in a collective manner in the vicinity of both the end portions of the attracting member 200. Then, the power feeding electrodes 205a and 206a are wired to be oblique to the width direction of the attracting member 200. Further, the back surface of the attracting member 200 is covered with the back surface layer 200c, and only a part of the power feeding section B1 is exposed on the back surface.
In this embodiment described above, it is not necessary to wire the power feeding electrodes 205a and 206a in a collective manner at narrow intervals in the power feeding sections B1, and the wiring of the power feeding electrodes 205a and 206a is extremely facilitated. Even with this configuration, the electrostatic force can be generated at a position shifted in the peripheral direction (arrow H direction) of the attracting member 200 with respect to the power feeding position.
Also in this embodiment, similarly to the third embodiment, the power feeding electrodes 205a and 206a are configured to have also the role of the connecting lines 205b and 206b in the first and second embodiments.
Note that, in this embodiment, each four of the attracting force generation electrodes 205c are conducted to corresponding one of the power feeding electrodes 205a and each four of the attracting force generation electrodes 206c are conducted to corresponding one of the power feeding electrodes 206a, but the present invention is not limited thereto. That is, it is sufficient that at least two of the attracting force generation electrodes 205c be conducted to corresponding one of the power feeding electrodes 205a and at least two of the attracting force generation electrodes 206c be conducted to corresponding one of the power feeding electrodes 206a. In this case, effects similar to the above can be obtained.
Also in this embodiment, the principle of generating the electrostatic attracting force for attracting the sheet S to the attracting member 200, and the conditions for removing the residual charges on the surface of the attracting member 200 are the same as those described in the third embodiment. Further, the sheet separation feeding operation by the sheet feeding apparatus 51 and 52 can be executed in a sequence similar to that in the first embodiment.
As described above, even with the configuration of this embodiment in which the electrode configuration of the attracting member 200 is simpler, the generation of the electrostatic force for attracting the sheet S to the attracting member 200 and the neutralization of the surface of the attracting member 200 can be executed in parallel. With this, the sheet can be fed without reducing the throughput.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2014-169230, filed Aug. 22, 2014, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-169230 | Aug 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/004074 | 8/17/2015 | WO | 00 |
