Patent Application
20160297633
The present invention relates to a sheet feeding device and an image forming apparatus, and particularly to a device that feeds a sheet using an electrostatic adsorbing force.
An image forming apparatus such as a copying machine or a printer in the related art is provided with a sheet feeding device which feeds a sheet such as plain paper, coated paper, or OHP paper. In general, the image forming apparatus conveys the sheet fed by the sheet feeding device to the image forming section to form an image on the sheet. As such a sheet feeding device, there are a friction feeding method in which the uppermost sheet is separately fed out of a cassette loaded with a sheet bundle using a friction force of a feeding roller, and an air feeding method which adsorbs and conveys the sheet using the air.
By the way, in recent years, noise damping is required in the sheet feeding device, and it is important that the operation sound is suppressed as low as possible. However, in the sheet feeding device using the friction force by the feeding roller, there occurs screechy noises between the sheet and the roller or between the sheets. Further, in the air feeding method, the apparatus is increased in size so that the operation sound is also increased.
As a feeding method receiving the attention in recent years, there is an electrostatic adsorption method in which the sheet is adsorbed using static electricity and conveyed. Further, according to the electrostatic adsorption method, the sheet can be fed without using the friction force, so that it is advantageous for the sound damping. As a sheet feeding device of such an electrostatic adsorption method, the sheet is adsorbed to an adsorption member having an electrostatic adsorption function, and then the adsorption member horizontally moves to convey the sheet (see Patent Literature 1).
Herein, in a case where an adsorption member adsorbing the sheet is configured to be horizontally moved likely to the sheet feeding device disclosed in a conventional electrostatic adsorption method, there is a need to widen a surface contact area between the adsorption member and an uppermost sheet in order to securely separate the sheet. However, in order to widen the surface contact area, the length of the adsorption member is necessarily increased. Further, when the length of the adsorption member is increased, the apparatus is increased in size.
The invention has been made in view of the circumstances, and an object thereof is to provide a sheet feeding device and an image forming apparatus which can separate and feed the sheet with safety without causing the length of the adsorption member to be increased.
The invention provides a sheet feeding device which includes a loading portion configured to be loaded with a sheet, a rotation member configured to be disposed on an upper side of the loading portion, and an adsorption member configured to have ends and to be provided such that a part of the adsorption member is fixed to the rotation member and the sheet loaded on the loading portion is electrically adsorbed. The adsorption member includes an adsorption portion which comes into contact with the sheet loaded on the loading portion, and a support portion which is provided at a position near the rotation member from the adsorption portion and has a rigidity lower than that of the adsorption portion with respect to a force applied from a sheet feeding direction.
According to the invention, a flexible adsorption member is configured such that a rigidity of a fixed portion of the adsorption member is lower than that of an adsorption portion of the adsorption member where a sheet is adsorbed, so that the sheet can be separated and fed with safety without causing the length of the adsorption member to be increased.
Hereinafter, embodiments of the invention will be described in detail using the drawings.
The image forming section 100B includes process cartridges 7 (7Y, 7M, 7C, and 7K) which form toner images of four colors (yellow, magenta, cyan, and black). Further, the process cartridges 7 include photosensitive drums 1 (1Y, 1M, 1C, and 1K) which serve as image bearing members rotatably driven by a driving unit (a driving source; not illustrated) in a direction of arrow A (a counterclockwise direction), and is mounted to be detachably attachable to the printer body 100A.
In addition, the image forming section 100B includes a scanner unit 3 which is disposed on the upper side of the process cartridges 7 in a vertical direction, irradiates the photosensitive drums 1 with laser beams based on image information, and forms electrostatic latent images on the photosensitive drums 1. Further, the process cartridges 7 includes, besides the photosensitive drums 1, developing units 4 (4Y, 4M, 4C, and 4K) which attach toner to the electrostatic latent images to visualize the latent images, and charging rollers 2 (2Y, 2M, 2C, and 2K) which evenly charge the surfaces of the photosensitive drums.
In addition, the image forming section 100B includes an intermediate transfer belt unit 100C, a secondary transfer portion N2, and a fixing portion 10. The intermediate transfer belt unit 100C includes an endless intermediate transfer belt 5, and primary transfer rollers 8 (8Y, 8M, 8C, and 8K) which are disposed inside the intermediate transfer belt 5 to face the photosensitive drums 1. The intermediate transfer belt 5 rotates in a direction of arrow B while abutting on all the photosensitive drums 1 and suspending on a drive roller 16, a secondary transfer counter roller 17, and a driven roller 18.
Herein, the primary transfer rollers 8 presses the intermediate transfer belt 5 toward the photosensitive drum 1, forms a primary transfer portion N1 which abuts on the intermediate transfer belt 5 and the photosensitive drum 1, and applies a transfer bias to the intermediate transfer belt 5 by a bias applying unit (not illustrated). Then, a primary transfer bias is applied to the intermediate transfer belt 5 by the primary transfer rollers 8, and the respective color toner images on the photosensitive drums are sequentially transferred onto the intermediate transfer belt 5, thereby forming a full-color image on the intermediate transfer belt.
In addition, the secondary transfer roller 9 is disposed at a position facing the secondary transfer counter roller 17 on an outer peripheral surface of the intermediate transfer belt 5, and comes in press contact with the secondary transfer counter roller 17 through the intermediate transfer belt 5 to form the secondary transfer portion N2. Then, the toner images on the intermediate transfer belt 5 are transferred onto a sheet P (the secondary transfer) by applying a bias having an opposite-polarity with respect to a normal charge polarity of the toner from a secondary transfer bias power source (a high-voltage power source) serving as a secondary transfer bias applying unit (not illustrated) to the secondary transfer roller 9.
The sheet feeding device 200 includes a sheet feeding cassette 20 serving as a storing unit which is mounted to be detachably attachable to the printer body 100A, and an adsorbing and feeding section 12 which adsorbs a plurality of sheets P stored in the sheet feeding cassette 20 and feeds the sheets. Then, when the sheet P stored in the sheet feeding cassette 20 is fed, the sheet P is adsorbed by the adsorbing and feeding section 12 and fed out.
Next, an image forming operation of the full-color laser beam printer 100 having such a configuration will be described. When an image reading apparatus (not illustrated) connected to the printer body 100A, or an image signal from a host machine such as a personal computer is input to the scanner unit 3, the photosensitive drum is irradiated with the laser beam corresponding to the image signal from the scanner unit 3. At this time, the surfaces of the photosensitive drums 1 are evenly charged with a polarity and a voltage determined in advance by the charging rollers 2. The electrostatic latent images are formed on the surfaces by irradiating with the laser beams from the scanner unit 3. Thereafter, the electrostatic latent images are developed and visualized by the developing units 4.
For example, first, the photosensitive drum 1Y is irradiated with the laser beam by the image signal of a yellow component from the scanner unit 3, and a yellow electrostatic latent image is formed in the photosensitive drum. Then, the yellow electrostatic latent image is developed by the yellow toner from the developing unit 4Y, and visualizes the latent image into a yellow toner image. Thereafter, the toner image reaches the primary transfer portion N1 where the photosensitive drum 1Y and the intermediate transfer belt 5 abut on each other according to the rotation of the photosensitive drum 1Y. Then, the yellow toner image on the photosensitive drum is transferred onto the intermediate transfer belt in the primary transfer portion N1 by the primary transfer bias applied to the primary transfer roller 8Y.
Next, when a portion carrying with the yellow toner image of the intermediate transfer belt 5 moves, a magenta toner image formed on the photosensitive drum 1M is transferred from above the yellow toner image to the intermediate transfer belt 5 by the method similar to the above description until this stage. Similarly, a cyan toner image and a black toner image are transferred onto the yellow toner image and the magenta toner image in an overlapping manner in the respective primary transfer portions as the intermediate transfer belt 5 moves. Therefore, a full-color toner image is formed on the intermediate transfer belt.
In addition, the sheet P stored in the sheet feeding cassette 20 is fed out by the adsorbing and feeding section 12 in parallel to the toner image forming operation, and then conveyed to a registration roller 15. Next, the sheet P conveyed to the registration roller 15 is conveyed to the secondary transfer portion N2 by the registration roller 15 in synchronization with timing. Then, in the secondary transfer portion N2, the four-color toner image on the intermediate transfer belt 5 is secondarily transferred onto the conveyed sheet P by applying a positive bias to the secondary transfer roller 9. Further, after the toner image is secondarily transferred, the toner left on the intermediate transfer belt 5 is removed by a belt cleaner 11. Next, the sheet P on which the toner image is transferred is conveyed to the fixing portion 10 and heated and pressed therein, so that the full-color toner image is fixed as a permanent image, and then discharged to the outside of the printer body 100A.
Next, the sheet feeding device 200 according to this embodiment will be described using
In addition, a conveyance guide plate 40 is provided on a downstream side in a sheet feeding direction of an adsorbing and feeding section 12. Then, the center portion in a width direction perpendicular to the sheet feeding direction of the conveyance guide plate 40 is cut off, and a width L1 of the cut-off shape of the conveyance guide plate 40 is set to be larger than a width L2 of an adsorption member 29 (L1>L2). In this way, it is possible to prevent that the conveyance guide plate 40 hinders the rotation of the adsorption member 29 by setting the width L1 of the cut-off shape of the conveyance guide plate 40, when the adsorption member 29 is rotated together with a holding member 24 as described below.
The holding member 24 is disposed on the upper side at the downstream end in the sheet feeding direction of a sheet feeding cassette 20, and one end of the adsorption member 29 is fixed to the center portion in the width direction of the holding member 24. The holding member 24 is an axial member formed of a conductive material (for example, SUS303), and rotatably held by a bearing 32 provided in a printer body 100A. In addition, the holding member 24 is rotated by a driving force of a servo motor M transmitted through a drive transmission gear train G. Then, when the holding member 24 is rotated, the adsorption member 29 is also rotated integrally with the holding member 24.
A rotary encoder 31 having a function of detecting a home position of the holding member 24 is attached to one end of the holding member 24. Then, a rotation angle θ of the holding member 24 can be detected by counting the number of pulses output from an angle sensor 71 (described below) serving as a detection unit illustrated in
In addition, an insulating tape 25 is attached to one of the holding member 24 as illustrated in
One end of the adsorption member 29 in the sheet feeding direction is fixed to the holding member 24 as illustrated in
In addition, the first comb-tooth electrode (a first electrode) 30a as one of the two electrodes is wired to the power electrode 26, and the second comb-tooth electrode (a second electrode) 30b as the other electrode is wired to the holding member 24. Then, in this embodiment, a negative voltage of −1 kV is applied from the high-voltage power source (a first power source) 110 to the power electrode 26 through the first power brush 43a, and a positive voltage of 1 kV is applied from the high-voltage power source (a second power source) 120 to the holding member 24 through the second power brush 43b.
In this way, an electrostatic adsorbing force can be applied between the surface of the adsorption member 29 as a dielectric material and the sheet by applying a positive voltage V1 one of the first and the second comb-tooth electrodes 30a and 30b, and a negative voltage V2 to the other one. Then, the adsorption member 29 adsorbs the sheet and holds it up by the electrostatic adsorbing force as described below. Further, the magnitude of the applying voltage is not limited as long as it causes an adsorbing force having the magnitude necessary for adsorbing the sheet to the adsorption member 29 as described below.
Further, as illustrated in
By the way, as illustrated in
Herein, in this embodiment, the adsorption member 29 is formed to have a small rigidity in the second region 29b provided on a side near the holding member (one end in the sheet feeding direction) from the first region 29a compared to the rigidity in the first region 29a of the adsorption member 29. Then, the second region 29b is made to be easily bent compared to the first region 29a by setting the rigidity in the first region 29a and the second region 29b as described above.
Further, the rigidity of the adsorption member 29 can be evaluated by a fixed end beam on one side and a free end beam on the other end. For example, a maximum bending amount at the time when a load F is intensively applied on the free end of the beam even in a width, a thickness, and a Young's modulus is expressed by the following equation using a length l, a width b, a Young's modulus E, and a thickness h of the beam.
In the above equation, the width b, the thickness h, and the Young's modulus E of the beam are the parameter affecting on the rigidity of the beam. Therefore, when at least one of the width b, the thickness h, and the Young's modulus E is changed, the rigidity in the first region 29a of the adsorption member 29 can be made different from the rigidity in the second region 29b. Herein, in this embodiment, the flexibility of the second region 29b is realized by narrowing the width of the second region 29b compared to the width of the first region 29a.
Further, the area of the first region 29a for adsorbing the sheet is determined according to an adsorption performance. For example, in the adsorption member 29 having an adsorption performance of 0.00095 N/mm2, in a case where 0.22 N is necessary for peeling off a sheet, a required area becomes 232 mm2, so that the shape of the first region 29a is set to have an area equal to or more than the required area.
Herein, the ease bending is advantageous for the adsorption member 29 to enable the sheet surface to be adsorbed upward when the sheet is separated. However, when the bending amount in section BC is large, a deformation may be generated with time, and flatness of the sheet may be not secured at the time of adsorption. Therefore, an adsorption member which is easily bent in section AB as depicted with the plotted line d and hardly bent in section BC is ideal rather than an adsorption member bending in section BC as depicted by the plotted line Ref of
Since the width of the second region 29b is made narrow compared to that of the first region 29a as described above, the adsorption member 29 depicted with the plotted line a of
For this reason, in this embodiment, the shape of the adsorption member 29 is made as illustrated in
Further, the shape of the adsorption member 29 may have the shape illustrated in (a) to (d) of
In this way, in a case where the first region and the second region are formed to have the same thickness, the first region corns to have a small volume compared to that of the second region by forming at least one of the round holes 55, the slits 56, the notches 57, and the tapper shape 58 in the second region. Herein, when the thickness is set to be equal, the volume is proportionate to the width of the adsorption member 29. Therefore, when the volume of the second region is set to be small, the width of the cross section of the second region can be made small. In other words, in this embodiment, reducing the volume of the second region means that the width of the second region becomes narrow.
Herein, the section formed with the holes in the second region of the adsorption member having the shape illustrated in (a) of
Next, a sheet separating and feeding operation of a sheet feeding device 200 according to this embodiment will be described using
Next, when a feeding job of the sheet P starts, the CPU 70 dives the servo motor M to make the holding member 24 start to rotate from the initial state to the sheet feeding direction indicated with arrow R (S101). Further, at this time, there is no voltage application to the electrodes 30a and 30b as illustrated in
Thereafter, the adsorption member 29 is deformed along the uppermost sheet P1 as illustrated in (c) of
As illustrated in (d) of
Then, when a voltage is applied to the electrodes 30a and 30b, a potential pattern in a stripe shape is alternately formed in the surface of the adsorption member 29 by the electrodes 30a and 30b and causes an electric field to generate the adsorbing force, so that the uppermost sheet P1 is adsorbed to the first region 29a of the adsorption member 29. Herein, since the electric field is generated only in the vicinity of the surface of the adsorption member 29, the adsorbing force by the electric field works only on the uppermost sheet P1. Therefore, only the uppermost sheet P1 among the loaded sheets P is adsorbed to the adsorption member 29.
Further, (a) of
Therefore, a radius r2 of curvature at the boundary between the first region 29a and the second region 29b becomes smaller than the radius of curvature of the second region 29b, so that the flatness of the first region 29a is secured and an adsorbing area with respect to the uppermost sheet P1 can be safely secured. On the contrary, in the case of the adsorption member 53 having an even rigidity in the related art, a radius r1 of curvature at the boundary of the contact surface of the uppermost sheet P1 is large as illustrated in (b) of
In this state, when the holding member 24 is rotated, the adsorption member 29 is pulled up by the holding member 24. Then, as illustrated in (e) of
Then, the uppermost sheet P1 is conveyed toward a registration roller 15 by the conveyance guide 40a, and then engaged into the registration roller 15. Further, in this embodiment, when the uppermost sheet P1 is engaged into the registration roller 15, the rotation angle θ of the holding member 24 becomes θ2. Then, when it is determined that the rotation angle θ of the holding member 24 becomes θ2 (Y in S107), the CPU 70 stops the voltage application to the electrodes 30a and 30b in the first region as illustrated in
In this way, the adsorption of the uppermost sheet P1 by the adsorption member 29 is released by stopping the voltage application to the electrode 30. Thereafter, as illustrated in (g) of
As described above, in this embodiment, the first region 29a can be hardly bent by making the width of the second region 29b narrower than that of the first region 29a of the adsorption member 29 (in other words, by making the volume of the second region 29b smaller than that of the first region 29a). Therefore, the flatness of the first region 29a at the time when the sheet is adsorbed can be secured, and the adsorption area required for the adsorption can be safely secured. As a result, the sheet can be separately fed with safety without causing the length of the adsorption member 29 to be increased.
In addition, in this embodiment, since the portion Z of the sheet on the downstream side in the sheet feeding direction is not adsorbed (in other words, when the sheet is adsorbed, the leading end of the sheet is not attached to the adsorption member 29), the sheet can be separated from the adsorption member 29 without a neutralization mechanism. Therefore, it is possible to reliably guide the leading end of the sheet without causing the sheet to be folded.
The description hitherto has been made about an example in which the width (volume) of the second region is made to be narrower (smaller) than the width (volume) of the first region in order to make the first region of the adsorption member hardly bent, but the invention is not limited thereto. For example, the first region of the adsorption member can be made to be hardly bent by changing the thickness or the Young's modulus of the first region and the second region of the adsorption member.
Next, the description will be made about a second embodiment according to the invention in which the first region of the adsorption member is made to be hardly bent by changing the thicknesses of the first region and the second region of the adsorption member.
Further, in
In consideration of the above description, in this embodiment, the shape of the adsorption member 51 is formed as a shape as illustrated in (a) and (b) of
In addition, the adsorption member 51 illustrated in (b) of
As described above, in this embodiment, since the thickness of the second region 51b is made to be thinner than that of the first region 51a of the adsorption member 51, the rigidity of the second region 51b can be lowered compared to that of the first region 51a, and the first region 51a can be made hardly bent. Therefore, the flatness of the first region 51a at the time when the sheet is adsorbed can be secured, and the adsorption area required for the adsorption can be safely secured. As a result, the sheet can be separately fed with safety without causing the length of the adsorption member 51 to be increased.
Further, in this embodiment, the thickness is changed by stacking the same two sheets on the front and rear surfaces of the flexible resin sheet, but the thickness of the sheet may be increased by coating the sheet. In addition, the material of the adsorption member 51 is not limited, and the second region may be suitably manufactured using the flexible resin sheet. In this case, the adsorption member 51 can be formed in a simply process. Further, in the adsorption member according to the first embodiment described above, the thickness of the first region 51a may be made to be thicker than that of the second region 51b similarly to this embodiment. In other words, this embodiment may be implemented by being combined with the first embodiment.
Next, the description will be made about a third embodiment of the invention in which the first region of the adsorption member is made to be hardly bent by changing the Young's moduli of the first region and the second region of the adsorption member.
In
Further, in
In consideration of the above description, in this embodiment, the adsorption member 52 is made by selecting materials such that the material of the first region 52a has a Young's modulus El which is larger than a Young's modulus E2 of the material of the second region. Then, the adsorption member 52 is formed by thermally fusing the selected materials having different Young's modulus.
As described above, in this embodiment, the rigidity of the second region 52b can be lowered than that of the first region 52a by making the Young's modulus of the second region 52b lower than that of the first region 52a of the adsorption member 52, and the first region 52a can be hardly bent. Therefore, the flatness of the first region 52a at the time when the sheet is adsorbed can be secured, and the adsorption area required for the adsorption can be safely secured. As a result, the sheet can be separately fed with safety without causing the length of the adsorption member 52 to be increased.
Further, in this embodiment, the material of the adsorption member 52 is not limited, and the adsorption member may be manufactured by suitably combining the flexible resin sheets used in the respective portions to make the Young's modulus of the second region 52b lowered compared to that of the first region 52a. Then, the respective regions can be given with different functions through the selection of the materials by forming the first region and the second region with the different materials.
In addition, in the adsorption member according to the first and the second embodiments described above, the Young's moduli of the first regions 29a and 51a may be made to be lower than those of the second regions 29b and 51b similarly to this embodiment. In other words, this embodiment may be implemented by being combined with the first and the second embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-083582 | Apr 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/057765 | 3/20/2014 | WO | 00 |
