The present application claims priority under 35 U.S.C. § 119 to Japanese patent Application No. 2017-115808 filed on Jun. 13, 2017 the entire contents of which is incorporated herein by reference.
The present invention relates to an image forming device and particularly relates to a technology in which a sheet ejected from a sheet ejection roller after fixing is prevented from being wrinkled.
An electrophotographic image forming device such as a copy machine or a printer is provided with a fixing device that thermally fixes a toner image transferred on a sheet, and a sheet subjected to thermal fixing is ejected to a sheet ejection tray via a sheet ejection roller or fed to post processing device in a subsequent stage.
Meanwhile, it is found that in a case of feeding a sheet to a post processing device, the sheet is wrinkled depending on a size of a fed sheet when a passageway of the post processing device is curved.
A reason for this phenomenon is studied by the inventor of the present application, and it is found that a folded wrinkle is caused because: when an end region in a width direction orthogonal to a conveyance direction of the sheet (hereinafter simply referred to as “width direction”) passes through a nip between sheet ejection rollers in a curled state, a portion of the sheet located on a more inner side than the nip is deflected, and the sheet enters the curved portion of the passageway of the post processing device without correcting the deflected portion.
An object of the present invention is to provide an image forming device in which deflection in a sheet width direction is suppressed at the time of passing through a sheet ejection roller, and even in a case where there is a curved portion in a passageway of a post processing device or the like in a subsequent stage, a sheet is prevented from being wrinkled.
To achieve the abovementioned object, according to an aspect of the present invention, there is provided an image forming device, reflecting one aspect of the present invention, having a guide member that guides a sheet having passed through a fixing device to a pair of sheet ejection rollers, wherein the pair of sheet ejection rollers has a plurality of pairs of sub-rollers installed at a rotary shaft at predetermined intervals, and a nip is formed by a pair of sub-rollers facing each other, the plurality of pairs of sub-rollers includes a specific pair of sub-rollers that nips an end region in a width direction orthogonal to a sheet conveyance direction when a sheet of a prescribed size passes, and the guide member includes a pressing member that presses a curl in a direction to correct the curl, the curl being caused at an end region in the width direction of the sheet on a more upstream side in the sheet conveyance direction than a position where a leading end of the sheet enters a nip between the specific pair of sub-rollers.
The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention:
Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.
In the following, an image forming device according to an embodiment of the present invention will be described by exemplifying an image forming system in which the image forming device and a post processing device are combined.
(1) External Appearance of Image Forming System
The MFP 100 also has functions as a scanner, a color copy machine, and a color laser printer.
As illustrated in
This MFP 100 is a so-called in-body sheet ejection type. In other words, a sheet ejection tray 132 is detachably installed in a gap SP between the scanner 120 and the printer 130, and stores a sheet ejected from a sheet ejection port 131 located in a deep side of the gap SP.
A known electrophotographic printer is adopted as the printer 130. In other words, a peripheral surface of a photoreceptor drum is charged so as to have uniform potential, and then an electrostatic latent image is formed by performing exposure and scanning by an exposure device. In the structure, the electrostatic latent image is developed with a toner so as to form a toner image, and the toner image is transferred to a sheet fed from the sheet feeding cassette 133, then the toner image is thermally fixed by passing the sheet through a fixing device, and the sheet is ejected through a pair of sheet ejection rollers.
The relay unit 140 has a plurality of pairs of conveyance rollers arranged inside thereof, and plays a role to receive a sheet from the sheet ejection port 131 of the MFP 100 and convey the sheet to the post processing device 150.
The post processing device 150 performs, in accordance with a command from the MFP 100, post processing for a bundle of sheets received from the sheet ejection port 131 through the relay unit 140. This post processing includes, for example, processing to align a bundle of sheets, processing to staple the bundle with staples, and the like.
The post processing device 150 has two sheet ejection trays 151 and 152. In the upper sheet ejection tray 151, a sheet is stacked in a state fed from the sheet ejection port 131. In the lower sheet ejection tray 152, the bundle of sheets is stacked in a state aligned or stapled with staples.
When the post processing device 150 is coupled to the MFP 100, the sheet ejection tray 132 of the MFP 100 is removed, the post processing device 150 is moved in a direction indicated by an arrow, the relay unit 140 is inserted into the gap SP, and the sheet ejection port 131 of the MFP 100 and a sheet entrance port of the relay unit 140 are set so as to face each other. Additionally, a control unit inside the MFP 100 and a control unit inside the post processing device 150 are connected so as to be able to communicate via a connector and a cable not illustrated.
(2) Structure of Sheet Ejection Unit of MFP 100
A broken line in
The fixing device 10 includes a heat roller 11 and a pressure roller 12, and a sheet transferred from a lower side and having no toner image fixed passes through a nip between the heat roller 11 and the pressure roller 12, thereby thermally fixing a toner image onto the sheet. The toner image is formed on the sheet on the heat roller 11 side.
The sheet fixed with the toner image is further conveyed to a downstream side via a pair of post-fixing conveyance rollers 21, 22, guided by guide members 28, 29, 23, 24, 25, and then advances to a pair of sheet ejection rollers 26, 27 while the sheet is largely curved leftward at a portion D.
Note that the guide member 23 also functions as a switching claw that switches a conveyance path of a sheet in order to guide the sheet toward an upper reversing path at the time of executing double-sided printing, but a description thereof will be omitted here.
(3) Causes of Wrinkle in Relay Unit 140
In the related art, a folded wrinkle is frequently formed on a sheet at a curved portion C (
In other words, curls K in which both of end regions in the width direction orthogonal to a sheet conveyance direction X are warped upward is likely to be formed as illustrated in
As described in
Since the sheet is curled in the width direction as illustrated in
Then, as illustrated in a view from a downstream side in the sheet conveyance direction (ejection side) of
(4) Curl Pressing Member (Curl Correction Member)
Therefore, it can be said that a wrinkle formed on a sheet at the relay unit 140 is caused by a fact that an end region of a sheet having passed through the fixing device 10 is curled in a manner warped upward.
Therefore, the inventor of the present invention considers correcting such a curl in the sheet end region before the sheet contacts the pair of sheet ejection rollers 26, 27.
As illustrated in
As illustrated in
In
In the present embodiment, a lowermost portion of the guide plate 241 contacts this virtual line L, and does not project lower than the virtual line L. It can be considered that the guide plate is not needed to project lower than the virtual line L in order to press and correct a curl in an end region of a sheet, and furthermore, in a case where the guide plate 241 projects lower than the virtual line L and a thick sheet is conveyed, a streak caused by pressing action of the guide plate 241 may remain on a surface of the thick sheet because the thick sheet has strong tensility.
Of course, as far as the lowermost portion of the guide plate 241 projects lower than a guide surface of the upper guide member 24 in the related art even without necessarily reaching and contacting the virtual line L, a certain curl correction effect can be obtained.
The guide plates 241 thus formed act such that force F indicated by broken lines in
As a result, the deflection St (
Meanwhile, as illustrated in
Additionally, in a case where an axial length of the guide plate 241 is too long, excessive friction may be applied to a sheet and sheet jam may be caused. Therefore, a width of about 8 mm to 26 mm may be preferable.
The embodiment of the present invention has been described above, but needless to mention that the present invention is not limited to the above-described embodiment and the following modified examples are conceivable.
(1) In the above embodiment, the MFP 100 is provided with the curl correction guide plate projecting downward and positioned close to the axially inner side of the pair of sub-rollers of the guide member where an end region of a sheet having a prescribed size passes through. The prescribed size is preferably a size corresponding to a sheet size having a maximum width that can be used at least in the MFP 100. The reason is that the larger the sheet width is, the larger a warped amount at the sheet end is and the larger a deflection St is when the end is nipped, and there is high necessity to correct such a deflection in advance.
In this case, the guide plate 241 as the pressing member is provided close to the sheet passage center side of pairs of sub-rollers located on both of outermost sides (in the present embodiment, the pair of sub-rollers 261, 271 and a pair of sub-rollers located at positions symmetric to the pair of sub-rollers 261, 271 with respect to the sheet passage center).
Needless to mention, any size of a sheet on which a folded wrinkle is possibly caused may be handled by providing, as partly illustrated in
Meanwhile, in the present specification, the wording “a pair of sub-rollers nips an end region of sheet (nipping)” is intended to include not only a case where an edge (point A) in the width direction of the sheet is nipped by the nip between the pair of sub-rollers 261, 271 as illustrated in
(2) In the above-described embodiment, the plate-like guide plate 241 is provided for curl correction, but not limited thereto, a similar effect can be obtained in correcting a curl at an end region of a sheet also by providing, at axially close intervals, a plurality of ribs 2414 each having a lower end extending to a position almost same as a lower surface of each guide plate 241 as illustrated in
Additionally, as illustrated in
In short, as far as a member is provided on the upstream side of a pair of sub-rollers nipping an end region of a sheet plays a role as the pressing member by pressing and correcting a curl caused at the end region of the sheet, a shape of the member may be any shape.
(3) Meanwhile, in the above-described embodiment, the guide plate 241 is provided on the upper guide member 24 side because a sheet has a route to pass the fixing device 10 from the lower side to the upper side and then advance to the pair of sheet ejection rollers 26, 27 via the curved portion D. The reason is that the sheet end region tends to be warped to an outer side of the curved portion D. Therefore, in a case of a machine model having a conveyance path in which a sheet passes the fixing device 10 from an upper side to a lower side, and is curved, and then reaches a sheet ejection roller, the guide plates 241 are preferably provided at the lower guide member 25 located on the outer side in the curved direction of the conveyance path.
(4) In the above-described embodiment, the MFP is described as the image forming device, but the image forming device may be a facsimile machine or a machine exclusively used as a printer as far as the image forming device is an electrophotographic image forming device including a fixing device and a pair of sheet ejection rollers at a final stage regardless of monochrome or color.
Additionally, in a case where the image forming device is not an in-body paper ejection type image forming device, the relay unit 140 is not necessary, and even in a case where a sheet is directly ejected to the passageway of the post processing device 150, the effects of the present invention can be obtained when there is a curved portion in the passageway of the post processing device 150.
(5) The above-described embodiment and modified examples may be combined as much as possible.
The present invention is useful as a technology to suppress a wrinkle caused in a sheet in a case of further conveying, via a different conveyance path, a sheet having passed through the fixing device and ejected from a pair of sheet ejection rollers.
Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.
Number | Date | Country | Kind |
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2017-115808 | Jun 2017 | JP | national |