JP2004102180A - Image forming apparatus equipped with toner image spot preventing function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a spot-free toner image even on a sheet with large heat capacity like thick paper and OHT. <P>SOLUTION: A printer 51 is equipped with a fixing roller couple 145 which heat and carry a sheet to fix an unfixed toner image transferred to a sheet and a fixing and carrying roller couple 243 which clamp and carry the sheet where the toner image is fixed by the fixing roller couple, and the length L1 of a continuous fixing and paper discharging opposite roller 242 of the fixing and carrying roller couple 243 is made longer than the maximum width W of a toner image formation surface. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus for forming a toner image on a sheet, and more particularly, to an image forming apparatus provided with a roller having a length longer than the width of a toner image so as to prevent toner image unevenness (unevenness) on the sheet.
[0002]
[Prior art]
Image forming apparatuses that form a toner image on a transfer material, which is a sheet, include a copying machine, a printer, a facsimile, and a multifunction peripheral thereof. Further, the image forming apparatuses include monochrome and color copying machines, printers, and the like. The sheet is configured to transfer the toner image. Examples of the sheet include plain paper, a thin resin sheet which is a substitute for plain paper, OHT, thin paper, cardboard, postcard, and letter. The sheet is also called a transfer material.
[0003]
2. Description of the Related Art In image forming apparatuses, there are many face-down discharges (hereinafter, referred to as “FD discharges”) for discharging a transfer material with a toner image forming surface facing down. In some cases, the apparatus also has a function of performing face-up discharge (hereinafter, referred to as “FU discharge”) in which the toner image is formed with the toner image forming surface facing upward.
[0004]
FIG. 11 is a cross-sectional view of a four-color color printer, which is an example of a conventional image forming apparatus, which is cut along a conveying direction of a material to be transferred.
[0005]
The printer 50 includes a paper feeder 130, a paper transport unit 170, an intermediate transfer belt unit 120, an optical unit 100, photosensitive drums 101Y, 101M, 101C, 101Bk, a fixing unit 140, a paper discharge transport unit 150, and the like.
[0006]
The transfer target material P is sent to the paper transport unit 170 via the feed roller 131, the retard roller 132, and the transport roller pair 133. The toner image is formed by irradiating the surface of a photosensitive drum of each color provided in an image forming station having a developer (toner) of each color in the order of yellow, magenta, cyan, and black with laser scanner devices 100Y, 100M, 100C corresponding to the respective colors. It is formed on the surface of the photosensitive drum by exposing and developing with a laser beam emitted from 100Bk. The laser scanner devices 100Y, 100M, 100C, and 100Bk form the optical unit 100.
[0007]
The photosensitive drums 101 </ b> Y, 101 </ b> M, 101 </ b> C, and 101 </ b> Bk on which the toner images have been formed perform primary transfer onto the intermediate transfer belt 121 rotated clockwise by the drive roller 122. Then, secondary transfer of the toner image is performed by the secondary transfer roller 135 to the transfer target material P transported by the paper transport unit 170. The transfer material P to which the toner image has been transferred passes through the fixing unit 140 as it is, and the toner image is fixed. The transfer target material P is sent out of the fixing unit 140 by the fixing discharge roller 141.
[0008]
When the transfer target material P is discharged in FU, the discharge port switching flapper 30 is switched upward in FIG. 11, and the transfer target material P is guided to the lower surface side of the discharge port switching flapper 30, and the FU discharge is performed. The FU is discharged to the FU discharge tray 13 by the rollers 11.
[0009]
When the transfer target material P is discharged by FD, the discharge port switching flapper 30 is switched downward in FIG. 11, and the transfer target material P is guided to the upper surface side of the discharge port switching flapper 30, and is discharged and conveyed. It is sent to the unit 150. The transfer material P is conveyed to the upper part of the printer 50 by the lower discharge conveyance roller 151 and the upper discharge conveyance roller 153, and is discharged to the FD discharge tray 23 above the printer 50 by the FD discharge roller 21. It is loaded.
[0010]
Since the transfer material P is discharged after passing through the fixing unit 140, when the FU discharge is performed, the nip portion between the fixing discharge roller 141 and the fixing discharge opposing roller 142, the FU discharge roller 11 and the FU discharge It must pass through the nip of the opposing roller 12. In the case of FD discharge, the nip portion between the fixing discharge roller 141 and the fixing discharge opposing roller 142, the nip portion between the discharge discharge lower roller 152 and the discharge discharge lower roller 151, and the discharge discharge upper opposing roller 154. The paper must pass through the nip portion of the upper discharge conveyance roller 153 and the nip portion of the FD discharge roller 21 and the FD discharge opposing roller 22.
[0011]
[Problems to be solved by the invention]
2. Description of the Related Art In recent years, an image forming apparatus has been improved in media flexibility so that printing can be performed on a transfer material of any material, and a toner image has been printed on a transfer material at a high speed. Also, when a user uses a transfer material having a large heat capacity, such as cardboard or OHT, the transfer material is often discharged while retaining the heat heated by the fixing device. In such a case, the transfer material is discharged from the image forming apparatus without the toner image being completely dried. For this reason, like the transfer material P shown in FIG. 12, when the sheet is conveyed in the direction of arrow a by, for example, the lower discharge roller 152 of the conveyance roller pair, the lower conveyance roller of the discharge conveyance is applied to the toner image Pa. A portion Pb touches 152 and a portion that does not touch occur, and the heat of the touched portion rapidly decreases to dry the toner image, or the toner image is slightly disturbed, so that a spot-like pattern appears on the toner image Pa. It is in.
[0012]
For example, FIG. 12 shows a sheet discharge conveyance unit 150. When the transfer material P is conveyed in the direction of the arrow a, the portion of the transfer material P that touches the lower roller 152 is discharged, and the portion that does not touch the lower roller 152 is discharged. It is transported while it is still warm and is cooled down. At that time, a spot-like pattern rarely appears.
[0013]
As a configuration to cope with such a problem, a configuration in which the transfer target material can be immediately discharged from the fixing unit can be discharged only to the FU discharge port, and a contact pressure of a driven roller of a transport roller pair is reduced. There is a configuration. However, with such a configuration, there is a possibility that another problem that a user's needs such as high-speed printing and high image quality and media flexibility cannot be met.
[0014]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which forms a toner image without unevenness even on a sheet having a large heat capacity such as cardboard or OHT.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to the present invention includes a fixing roller pair configured to heat and convey an unfixed toner image transferred to a sheet to the sheet by heating and conveying the sheet, and the fixing roller pair. And a conveying roller pair for nipping and conveying the sheet on which the toner image is fixed, wherein the length of a roller in contact with the toner image forming surface of the sheet is set to the length of the toner image forming surface. It is longer than the maximum width.
[0016]
In the image forming apparatus of the present invention, the length of the roller of the transport roller pair is equal to or greater than the width of the toner image forming surface.
[0017]
In the image forming apparatus of the present invention, at least the rollers of the pair of transport rollers that come into contact with the toner image forming surface have the same outer diameter.
[0018]
In the image forming apparatus of the present invention, the roller that comes into contact with the toner image forming surface of the pair of transport rollers is formed in an arc shape such that the diameter decreases from an intermediate portion to an end in the longitudinal direction. The rollers are formed to have the same outer diameter with a continuous outer shape.
[0019]
In the image forming apparatus of the present invention, a roller that contacts the toner image forming surface of the pair of transport rollers is a driven roller that rotates following the rotation of the other roller.
[0020]
In the image forming apparatus according to the present invention, a release layer is provided on at least a surface of the roller contacting the toner image forming surface, the surface of the roller contacting the toner image forming surface.
[0021]
In the image forming apparatus according to the present invention, at least a surface of the roller that contacts the toner image forming surface and a surface of the roller that contacts the sheet is made of resin.
[0022]
In the image forming apparatus of the present invention, the surface of the roller contacting the toner image forming surface, which is in contact with the sheet on the back side of the toner image forming surface, is made of rubber.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
A four-color printer, which is an example of an image forming apparatus according to an embodiment of the present invention, will be described.
[0024]
The image forming apparatus is configured to form a toner image on a transfer material as a sheet. The image forming apparatus includes a copying machine, a printer, a facsimile, and a multifunction peripheral thereof. Further, the image forming apparatuses include monochrome and color copying machines, printers, and the like. Therefore, the present invention can be applied not only to a printer but also to a copying machine, a facsimile, and the like, but not to a printer.
[0025]
Further, the sheet is configured to transfer the toner image. Examples of the sheet include plain paper, a thin resin sheet which is a substitute for plain paper, OHT, thin paper, cardboard, postcard, and letter. The sheet is also called a transfer material.
[0026]
FIG. 1 is a cross-sectional view of a four-color printer, which is an example of an image forming apparatus according to an embodiment of the present invention, in which the four-color printer is cut along a conveying direction of a transfer material.
[0027]
The printer 51 includes a paper feeder 130, a paper transport unit 170, an intermediate transfer belt unit 120, an optical unit 100, photosensitive drums 101Y, 101M, 101C, 101Bk, a fixing unit 240, a paper discharge transport unit 250, and the like.
[0028]
The transfer target material P is sent to the paper transport unit 170 via the feed roller 131, the retard roller 132, and the transport roller pair 133. The toner image is formed by irradiating the surface of a photosensitive drum of each color provided in an image forming station having a developer (toner) of each color in the order of yellow, magenta, cyan, and black with laser scanner devices 100Y, 100M, 100C corresponding to the respective colors. It is formed on the surface of the photosensitive drum by exposing and developing with a laser beam emitted from 100Bk. The laser scanner devices 100Y, 100M, 100C, and 100Bk form the optical unit 100.
[0029]
The photosensitive drums 101 </ b> Y, 101 </ b> M, 101 </ b> C, and 101 </ b> Bk on which the toner images have been formed perform primary transfer onto the intermediate transfer belt 121 rotated clockwise by the drive roller 122. Then, secondary transfer of the toner image is performed by the secondary transfer roller 135 to the transfer target material P transported by the paper transport unit 170. The transfer material P to which the toner image has been transferred passes through the fixing unit 240 as it is, and the toner image is fixed. The transfer target material P is sent out of the fixing unit 240 by the fixing discharge roller 241.
[0030]
When performing face-up discharge (hereinafter referred to as “FU discharge”) for discharging the transfer material P to the FU discharge tray 13 with the toner image facing upward, the discharge port switching flapper 30 is switched upward in FIG. The transfer material P is discharged to the FU paper discharge tray 13 by the FU paper discharge roller 211 through the lower surface side of the paper discharge port switching flapper 30.
[0031]
When performing face-down discharge (hereinafter, referred to as “FD discharge”) for discharging the transfer material P to the FD discharge tray 23 with the toner image facing down, the discharge port switching flapper 30 switches downward in FIG. The transfer target material P passes through the upper surface of the paper discharge port switching flapper 30 and is sent to the paper discharge transport unit 250. The transfer material P is conveyed to the upper portion of the printer 51 by the lower discharge conveyance roller 251 and the upper discharge conveyance roller 253, and is discharged to the FD discharge tray 23 above the printer 51 by the FD discharge roller 221. It is loaded.
[0032]
(Explanation of roller relation of the first embodiment)
FIG. 2 shows the fixing unit 240. FIG. 2A shows a fixing discharge roller 241 that forms a pair of conveyance rollers, for example, a pair of fixing conveyance rollers 243, and a continuous fixing discharge roller 242 that faces the fixing discharge roller 241.
[0033]
The transfer target material P passes through the nip between the fixing roller 143 and the pressure roller 144 of the fixing roller pair 145, and is conveyed from right to left in the drawing in the direction of arrow a. The transfer target material P is further conveyed while being sandwiched between the fixing discharge roller 241 and the fixing discharge continuous counter roller 242. At this time, as shown in FIG. 2B, the fixed discharge continuous opposing roller 242 has a length L1 in a direction perpendicular to the transport direction indicated by the arrow a, which is equal to or larger than the maximum print width W, and whose outer diameter is It has a continuous shape. That is, the length L1 of the roller portion 242a of the fixing / discharge continuous facing roller 242 is set to be equal to or longer than the maximum printing width W of the maximum toner image Pc.
[0034]
In the printer 51 of the present embodiment, since the fixing and discharging continuous facing roller 242 has such a shape, the fixing and discharging continuous facing roller 242 comes into uniform contact with the entire surface of the toner image, causing unevenness and disturbance in the toner image. The transfer target material P can be transported from the fixing unit 240 without causing the transfer.
[0035]
A case in which the transfer material P is FU-discharged to the FU discharge tray 13 will be described. The transfer material P discharged from the fixing unit 240 is guided to the lower surface side 30a of the discharge port switching flapper 30 whose upstream end is rotated upward in FIG. The sheet is sent to the FU sheet discharge roller 211 and discharged to the FU sheet discharge tray 13.
[0036]
FIG. 3 shows the FU discharge unit 260. FIG. 3A shows a FU discharge roller 211 and a FU discharge continuous opposing roller 212 which constitute a pair of conveyance rollers, for example, a FU discharge conveyance roller pair 213.
[0037]
The discharge port switching flapper 30 rotates in the direction of arrow b. The transfer target material P is guided in the lower surface side 30a of the discharge port switching flapper 30 and is conveyed in the direction of arrow a. At this time, as shown in FIG. 3B, the FU discharge continuous opposing roller 212 facing the FU discharge roller 211 has a length L2 in a direction perpendicular to the transport direction indicated by an arrow a with a maximum print width W. This is the shape that has the above and the outer diameter is continuous. That is, the length L2 of the roller portion 212a of the FU continuous discharge roller 212 is set to be equal to or longer than the maximum printing width W of the maximum toner image Pc.
[0038]
In the printer 51 of the present embodiment, since the FU continuous discharge roller 212 has such a shape, the continuous FU continuous discharge roller 212 uniformly contacts the entire surface of the toner image, causing unevenness in the toner image. The transfer target material P can be discharged to the FU discharge tray 13 without causing any disturbance or disturbance.
[0039]
A case in which the transfer material P is FD-discharged to the FD discharge tray 23 will be described. The transfer material P discharged from the fixing unit 240 is guided to the upper surface side 30b (see FIG. 3A) of the discharge port switching flapper 30 in which the upstream end rotates downward in FIG. The sheet is conveyed to the sheet discharge conveying unit 250. Thereafter, the transfer material P is conveyed to the FD paper discharge roller 221 through the paper discharge conveyance unit 250, and is discharged by the FD paper discharge roller 221 to the FD paper discharge tray 23 with the toner image facing down.
[0040]
FIG. 4 shows the paper discharge transport unit 250. The paper discharge transport unit 250 transports the transfer material P in the direction of arrow c from below in FIG. 4, and the paper discharge transport lower roller 251 constituting a transport roller pair, for example, a discharge lower transport roller pair 255. The transfer material P is transferred to the printer 51 by the discharge / transport lower continuous facing roller 252 and the discharge / transport upper roller 253 and the discharge / transport upper continuous roller 254 that constitute a pair of transport rollers, for example, a discharge upper transport roller pair 256. It has a function of transporting it to the upper part of the device.
[0041]
The discharge-conveying lower continuous roller 252 and the discharge-conveying upper continuous opposing roller 254 that oppose the discharge-conveying lower roller 251 and the paper-discharging upper roller 253, respectively. As in the case of the opposing roller 242, the lengths L3 and L4 in the direction perpendicular to the transport direction indicated by the arrow c are equal to or larger than the maximum printing width W and have a continuous outer diameter. That is, the length L3 of the roller portion 252a of the continuous discharge roller 252 and the roller portion 254a of the continuous discharge roller 254 are longer than the maximum print width W of the maximum toner image Pc. It has been set to.
[0042]
In the printer 51 of the present embodiment, the discharge / transport lower continuous facing roller 252 and the discharge / transport upper continuous facing roller 254 have such a shape. The roller 254 uniformly contacts the entire surface of the toner image on the transfer material P, and conveys the transfer material P to the FD discharge roller 221 without causing unevenness or disturbance in the toner image. can do.
[0043]
FIG. 5 shows, for example, an FD paper discharge unit 270 that is a pair of transport rollers. FIG. 5A shows the FD discharge roller 221 and the FD discharge continuous opposing roller 222. The transfer material P transported to the FD paper discharge roller 221 by the paper discharge transport unit 250 is transported in the direction of arrow c by the FD paper discharge roller 221 and the FD paper discharge continuous opposing roller 222, and is transferred to the FD paper discharge tray 23. Is discharged. At this time, as shown in FIG. 5B, in the FD discharge continuous opposing roller 222, the length L5 in the direction perpendicular to the transport direction indicated by the arrow c is equal to or larger than the maximum print width W, and the outer diameter is It has a continuous shape. That is, the length L5 of the roller portion 222a of the FD continuous discharge roller 222 is set to be equal to or longer than the maximum print width W of the maximum toner image Pc.
[0044]
In the printer 51 of the present embodiment, since the FD discharge continuous opposing roller 222 has such a shape, the FD discharge continuous opposing roller 222 comes into uniform contact with the entire surface of the toner image, causing unevenness in the toner image. The transfer target material P can be discharged to the FD discharge tray 23 without causing any disturbance or disturbance.
[0045]
(Explanation of roller relation of the second embodiment)
FIG. 6 shows a continuous fixing unit 240A according to the second embodiment. The same parts as those of the fixing unit 240 of the first embodiment shown in FIG. 2 are denoted by the same reference numerals, and the description of those parts will be omitted. The continuous fixing unit 240A includes a fixing discharge continuous roller 241A and a fixing discharge continuous opposing roller 242 constituting a pair of conveying rollers 243A, for example.
[0046]
As shown in FIG. 6B, the fixing / discharge continuous roller 241A has a shape in which the length L6 in the direction perpendicular to the transport direction indicated by the arrow a is equal to or larger than the maximum print width W and the outer diameter is continuous. Has become. That is, the length L6 of the roller portion 241Aa of the fixing / discharge continuous roller 241A is set to be longer than the maximum printing width W of the maximum toner image Pc.
[0047]
In the printer of the present embodiment, the fixing / discharge continuous roller 241A is formed in such a shape so that the fixing / discharge continuous opposing roller 242 moves in the transport direction indicated by the arrow a on the toner image transferred to the transfer material P. Can be touched positively and evenly in the perpendicular direction. Thus, the transfer target material P can be discharged to the FU discharge tray 13 without causing unevenness or disorder in the toner image.
[0048]
FIG. 7 shows a continuous FU discharge unit 260A according to the second embodiment. FIG. 7A shows the FU discharge continuous roller 211A. The same parts as those of the FU discharge unit 260 of the first embodiment shown in FIG. 3 are denoted by the same reference numerals, and the description of those parts will be omitted. The continuous FU sheet discharging unit 260A includes a FU sheet discharging continuous roller 211A and a FU sheet discharging continuous opposing roller 212, for example, forming a FU discharging and conveying roller pair 213A as a conveying roller pair.
[0049]
As shown in FIG. 7B, the FU discharge continuous roller 211A has a shape in which the length L7 in the direction perpendicular to the transport direction indicated by the arrow a is equal to or larger than the maximum print width W and the outer diameter is continuous. Has become. That is, the length L7 of the roller portion 211Aa of the FU discharge continuous roller 211A is set to be equal to or longer than the maximum printing width W of the maximum toner image Pc.
[0050]
The printer according to the present embodiment has the FU paper discharge continuous roller 211A having such a shape, so that the FU paper discharge continuous opposing roller 212 applies the toner image transferred to the transfer material P in the transport direction indicated by the arrow a. Can be touched positively and uniformly in the right angle direction. As a result, the transfer target material P can be discharged from the FU discharge port 10 to the FU discharge tray 13 without causing unevenness or disorder in the toner image.
[0051]
FIG. 8 shows a continuous sheet discharging and conveying unit 250A according to the second embodiment. The same reference numerals are given to the same parts as those of the paper discharge transport unit 250 of the first embodiment shown in FIG. 4, and the description of those parts will be omitted.
[0052]
This paper discharge conveyance unit 250A also conveys the transfer material P in the direction of arrow c from the lower direction in FIG. 8, and forms a pair of conveyance rollers, for example, a discharge lower conveyance roller pair 255A. The transfer material P is formed by a roller 251A, a discharge-conveying lower continuous opposing roller 252, and a discharge roller continuous-conveying upper roller 253A and a discharge-conveying upper continuous opposing roller 254 which constitute a pair of conveying rollers, for example, a discharge upper conveying roller pair 256A. To the upper part of the printer 51.
[0053]
The discharge-conveying lower continuous roller 251A and the discharge-conveying upper continuous roller 253A have lengths L8 and L9 in the direction perpendicular to the conveying direction indicated by the arrow c, the maximum printing width W or more, and the outer diameter is continuous. Shape. That is, the length L8 of the roller portion 251Aa of the lower continuous discharge roller 251A and the length L9 of the roller portion 253Aa of the upper continuous discharge roller 253A are set to be equal to or longer than the maximum printing width W of the maximum toner image Pc. It has been set.
[0054]
In the printer according to the present embodiment, the discharge / transport lower continuous roller 251A and the discharge / transport upper continuous roller 253A have such a shape. 252 and the continuous discharge upper roller 254 can positively and uniformly touch each other in a direction perpendicular to the transport direction indicated by the arrow c. Thus, the transfer target material P can be transported from the continuous paper discharge transport unit 250A to the FD paper discharge roller 221 without causing unevenness or disturbance in the toner image.
[0055]
FIG. 9 shows, for example, a continuous FD sheet discharging unit 270A which is a pair of conveying rollers. FIG. 9A shows an FD discharge continuous roller 221A and an FD discharge continuous opposing roller 222. The same reference numerals are given to the same portions as those of the FD discharge unit 270 shown in FIG.
[0056]
The FD discharge continuous roller 221A has a shape in which the length L10 in the direction perpendicular to the transport direction indicated by the arrow c is equal to or larger than the maximum print width W and the outer diameter is continuous. That is, the length L10 of the roller portion 221Aa of the FD paper discharge continuous roller 221A is set to be longer than the maximum printing width W of the maximum toner image Pc.
[0057]
In the printer of the present embodiment, since the FD discharge continuous roller 221A has such a shape, the FD discharge continuous opposing roller 222 applies the toner image transferred onto the transfer material P in the transport direction indicated by the arrow c. Positive and uniform touch in the perpendicular direction. As a result, the toner image can be discharged from the FD discharge port 20 to the FD discharge tray 23 without causing unevenness or disorder in the toner image.
[0058]
Further, in the printer of the present embodiment, the length L1 of the roller portion 242a of the continuous fixing / discharge continuous roller 242 and the length L6 of the roller portion 241Aa of the continuous fixing / discharge roller 241A in the continuous fixing unit 240A (see FIG. 6). In the continuous FU discharge unit 260A (see FIG. 7), the length L2 of the roller portion 212a of the FU continuous discharge roller 212, the length L7 of the roller portion 211Aa of the FU continuous discharge roller 211A, and the continuous discharge conveyance unit At 250A (see FIG. 8), the length L3 of the roller portion 252a of the continuous discharge lower continuous roller 252, the length L8 of the roller portion 251Aa of the lower continuous discharge roller 251A, and the upper continuous discharge roller 254 of the discharge conveyance. The length L4 of the roller portion 254a, the length L9 of the roller portion 253Aa of the continuous roller In the FD discharge unit 270A (see FIG. 9), the length L5 of the roller portion 222a of the FD continuous discharge roller 222 and the length L10 of the roller portion 221Aa of the FD continuous roller 221A are determined by the maximum toner image Pc. Because the length is set to be equal to or greater than the print width W, the unit pressure can be reduced without changing the total pressure, which is the contact pressure of the pair of transport rollers, and media that can handle large heat capacity sheets such as thick paper and OHT. Flexibility can be improved.
[0059]
Further, since the printer according to the present embodiment uses a continuous roller pair as the transport roller pair provided in the paper discharge transport path of the plurality of paper output ports 10, 20, the FU paper output port 10 and the FD paper output from the fixing unit. The transfer material without spots can be discharged from the paper port 20.
[0060]
Among the rollers described above, the fixed discharge continuous facing roller 242 that contacts the toner image Pc formed on the transfer material P, the FU continuous discharge facing roller 212, the discharge continuous lower facing roller 252, and the paper continuous upper continuous. The opposing roller 254 and the FD discharge continuous opposing roller 222 are driven rollers that rotate following the opposing roller.
[0061]
In addition, these driven rollers may be provided with a release layer that facilitates peeling from the toner image on the surface of the roller portions 242a, 212a, 252a, 254a, 222a that contacts the toner image. Further, these driven rollers may be made entirely of resin, or may be made of a resin layer on the surface that comes into contact with the toner image, in order to easily separate the driven roller from the toner image. As the resin, a resin containing a relatively large amount of fluorine or PFA (tetrafluorostyrene-perfluoroalkylvinyl copolymer) is used.
[0062]
The fixing paper discharge roller 241, the FU paper discharge roller 211, the paper discharge conveyance lower roller 251, the paper discharge conveyance upper roller 253, the FD paper discharge roller 221, the fixing paper discharge continuation roller 241A, and the FU paper continuation facing the driven roller. The roller 211A, the paper discharge transport lower continuous roller 251A, the paper discharge transport upper continuous roller 253A, and the FD paper discharge continuous roller 221A come into contact with the surface on the opposite side to the surface of the transfer material on which the toner image is formed. This is a driving roller for transporting the transfer material. These drive rollers may be made entirely of rubber, or may be made of a rubber layer on the surface in contact with the material to be transferred, so that the material to be recorded can be transported reliably.
[0063]
(Explanation of roller relation of the third embodiment)
As shown in FIG. 10A, the rollers described above are disposed at right angles to the sheet conveyance direction, and the length of the roller portion 300a of the roller 300 that comes into contact with the toner image forming surface is the maximum printing width. It has the same length and the same outer diameter. In addition, a force for pressing the roller 300 against the transfer material P is applied to the shaft portions 300b, 300b at both ends of the roller 300. For this reason, the roller 300 may bend into a shape such that the intermediate portion 300c rises from the transfer material P. The amount of bending increases as the maximum printing width W increases, and the amount of lifting of the intermediate portion 300c of the roller portion 300a increases. As a result, the roller 300 may not be able to press the recording material P with a uniform force over the entire width of the recording material P.
[0064]
However, the strength of the roller 300 is set so that the roller 300 does not bend as much as the toner image is spotted. This is the roller 301 shown in FIG. The roller 301 is a roller that comes into contact with the toner image forming surface, and is formed such that the diameter increases as the roller portion 301a approaches the intermediate portion 301c. That is, the roller portion 301a is formed in an arc shape and formed symmetrically with respect to the middle portion 301c. For this reason, even if a force that presses the roller 301 against the recording material P is applied to the shaft portions 301 b and 301 b of the roller 301 and the roller 301 bends, the deformation due to the bending causes the intermediate portion 301 c to be recorded by the arcuate portion. The material P does not float up.
[0065]
The roller facing the roller 301 has a shape with a continuous outer shape. Although the arc in FIG. 10B is exaggerated for easy understanding of the description, it is actually substantially a straight line.
[0066]
Therefore, when the rollers shown in FIGS. 1 to 9 are formed into the shapes shown in FIG. 10B, the rollers can be more reliably and uniformly contacted with the recording material P, and the toner image has unevenness. Nothing happens.
[0067]
【The invention's effect】
In the image forming apparatus of the present invention, the length of the roller in contact with the toner image forming surface of the sheet is set to be equal to or longer than the maximum width of the toner image forming surface of the pair of conveying rollers. And a high quality image can be formed on the sheet without causing unevenness or disturbance in the toner image.
[0068]
In the image forming apparatus of the present invention, since the lengths of both rollers of the pair of conveying rollers are set to be equal to or longer than the width of the toner image forming surface, the total pressure which is the contact pressure of the pair of conveying rollers is not changed. The unit pressure can be reduced, and the media flexibility that can be applied to a sheet having a large heat capacity such as cardboard or OHT can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a four-color printer, which is an example of an image forming apparatus according to an embodiment of the present invention, in which a four-color printer is cut along a conveying direction of a material to be transferred.
FIG. 2 is a schematic diagram of a fixing unit in the printer of FIG.
FIG. 3A is a schematic perspective view of a fixing unit.
FIG. 3B is a schematic plan view of the fixing unit.
FIG. 3 is a schematic diagram of an FU paper discharge unit in the printer of FIG. 1;
FIG. 2A is a schematic perspective view of an FU sheet discharging unit.
FIG. 3B is a schematic plan view of the FU sheet discharging unit.
FIG. 4 is a schematic perspective view of a paper discharge transport unit in the printer of FIG. 1;
FIG. 5 is a schematic diagram of an FD paper discharge unit in the printer of FIG. 1;
FIG. 3A is a schematic perspective view of an FD sheet discharging unit.
FIG. 3B is a schematic bottom view of the FD sheet discharging unit.
FIG. 6 is a schematic view of a continuous fixing unit according to a second embodiment.
FIG. 3A is a schematic perspective view of a continuous fixing unit.
FIG. 3B is a schematic bottom view of the continuous fixing unit.
FIG. 7 is a schematic view of a continuous FU sheet discharging unit according to a second embodiment.
FIG. 3A is a schematic perspective view of a continuous FU sheet discharging unit.
FIG. 3B is a schematic bottom view of the continuous FU sheet discharging unit.
FIG. 8 is a schematic perspective view of a continuous sheet discharging and conveying unit according to a second embodiment.
FIG. 9 is a schematic view of a continuous FD discharge unit according to a second embodiment.
FIG. 3A is a schematic perspective view of a continuous FD sheet discharging unit.
FIG. 3B is a schematic plan view of the continuous FD sheet discharging unit.
FIG. 10 is a diagram of another embodiment of the roller.
(A) is a diagram showing the shape of the roller used in FIGS. 1 to 9.
FIG. 10B is a diagram of a roller according to another embodiment having a different shape from the roller used in FIGS. 1 to 9.
FIG. 11 is a cross-sectional view of a four-color color printer, which is an example of a conventional image forming apparatus, which is cut along a conveying direction of a transfer material.
FIG. 12 is a diagram illustrating a state in which a toner image formed by the color printer in FIG.
[Explanation of symbols]
P Transfer material (sheet)
Pa toner image
Pc maximum toner image
W Maximum print width (Maximum width of toner image forming surface)
L1 Length of Roller Portion 242a of Continuous Roller 242
Length of Roller Part 212a of L2 FU Discharge Continuous Opposing Roller 212
L3 Length of Roller Portion 252a of Continuously Opposed Roller 252 under Discharge Conveyance
L4 Length of Roller Portion 254a of Continuous Opposite Roller 254 on Discharge Conveyance
L5 Length of Roller Portion 222a of FD Discharge Continuous Opposing Roller 222
L6 Length of Roller Portion 241Aa of Continuous Roller 241A
L7 Length of Roller Portion 211Aa of FU Discharge Continuous Roller 211A
L8 Length of Roller Portion 251Aa of Continuous Roller Lower Roller 251A
L9 Length of Roller Part 253Aa of Continuous Roller 253A on Discharge and Conveyance
L10 Length of Roller Portion 221Aa of FD Discharge Continuous Roller 221A
51 Printer (image forming apparatus)
101Y, 101M, 101C, 101Bk Photosensitive drum
130 paper feeder
143 fixing roller
144 pressure roller
145 fixing roller pair
211 FU discharge roller
211A FU discharge continuous roller
211Aa roller part
212 FU discharge continuous opposing roller (roller that contacts the toner image forming surface)
212a Roller part
213 FU discharge transport roller pair (transport roller pair)
213A FU discharge transport roller pair (transport roller pair)
221 FD discharge roller
221A FD discharge continuous roller
221Aa Roller part
222 FD discharge continuous opposing roller (roller that contacts the toner image forming surface)
222a Roller part
240 fixing unit
240A continuous fixing unit
241 fusing discharge roller
241A Continuous fuser discharge roller
241Aa roller part
242: Continuous roller for fixing and discharging paper (roller that contacts the toner image forming surface)
242a Roller part
243 Fixing conveyance roller pair (conveyance roller pair)
243A Fixing conveyance roller pair (conveyance roller pair)
250 paper discharge transport unit
250A continuous paper discharge transport unit
251 Lower roller for paper ejection
251A Continuous Roller Under Discharge Delivery
251Aa Roller part
252 Continuous discharge roller under discharge / conveyance (roller that contacts the toner image forming surface)
252a Roller part
253 Upper roller for paper discharge
253A Continuous Roller on Discharge and Conveyance
253Aa roller part
254 continuous discharge roller on discharge and transport (roller in contact with toner image forming surface)
254a Roller part
255 Discharge Roller Pair (Transport Roller Pair)
255A Lower transport roller pair (Transport roller pair)
256 discharge upper transport roller pair (transport roller pair)
256A discharge upper transport roller pair (transport roller pair)
260 FU discharge unit
260A continuous FU discharge unit
270 FD paper discharge unit (transport roller pair)
270A Continuous FD paper discharge unit (transport roller pair)
300 rollers (rollers that contact the toner image forming surface)
300a Roller part
300b Shaft
300c middle part
301 roller (roller that contacts the toner image forming surface)
301a Roller part
301b Shaft
301c middle part

Claims (8)

An unfixed toner image transferred to the sheet, a fixing roller pair that heats and conveys the sheet to fix the sheet,
A conveying roller pair for nipping and conveying the sheet on which the toner image is fixed by the fixing roller pair,
An image having a toner image spot prevention function, wherein a length of a roller of the pair of conveying rollers that contacts a toner image forming surface of the sheet is set to be equal to or longer than a maximum width of the toner image forming surface. Forming equipment. 2. The image forming apparatus according to claim 1, wherein the length of the rollers of the pair of conveying rollers is equal to or greater than the width of the toner image forming surface. 3. 3. The toner image unevenness preventing function according to claim 1, wherein at least a roller of the pair of transport rollers that comes into contact with the toner image forming surface is formed to have a continuous outer shape and the same diameter. Image forming device. A roller that contacts the toner image forming surface of the transport roller pair is formed in an arc shape so that a diameter decreases from an intermediate portion in the longitudinal direction to an end portion, and the other roller has the same outer shape that is continuous. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed to have a diameter. 5. The toner according to claim 1, wherein a roller that contacts the toner image forming surface of the pair of transport rollers is a driven roller that rotates following the rotation of the other roller. 6. An image forming apparatus having an image spot prevention function. 6. A roller according to claim 1, further comprising a release layer on at least a surface of the roller that contacts the toner image forming surface, the surface contacting the toner image forming surface. An image forming apparatus provided with the toner image unevenness preventing function according to the above item. 6. The roller according to claim 1, wherein at least a surface of the roller that contacts the toner image forming surface that contacts the sheet is made of resin. 7. An image forming apparatus provided with the toner image spot prevention function described above. 6. The roller according to claim 1, wherein a surface of the roller that contacts the toner image forming surface and a surface of the roller that contacts the sheet on the back side of the toner image forming surface is made of rubber. An image forming apparatus comprising the toner image spotting prevention function according to any one of the preceding claims.

Images