Patent Application
20230103454
This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2021-164881, filed on Oct. 6, 2021, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
Embodiments of this disclosure relate to a transfer device and an image forming apparatus.
A quadruple-tandem-type color image forming apparatus is known in which four photoconductor drums as image bearers corresponding to four colors of cyan (C), magenta (M), yellow (Y), and black (K) are arranged side by side such that outer circumferential surfaces of the photoconductor drums are positioned on the same plane.
In this image forming apparatus, for example, toner images of respective colors formed on the outer circumferential surfaces of respective photoconductor drums by developing units are superimposed and transferred onto an intermediate transfer belt as an image bearer by primary transferors disposed corresponding to the respective photoconductor drums.
In the above-described image forming apparatus, the surface speed (moving speed) of the intermediate transfer belt and the surface speed (moving speed) of the recording medium are preferably matched when the toner image on the intermediate transfer belt is secondarily transferred to the recording medium by secondary transferor.
In an embodiment of the present disclosure, there is provided a transfer device that includes a transfer roller and a transfer counter roller. The transfer roller has an elastic layer on an outer surface of the transfer roller, contacts with and separates from an image bearer including a belt-shaped elastic body to bear a toner image, and nips a recording medium between the image bearer and the transfer roller. The transfer counter roller has an elastic layer on an outer surface of the transfer counter roller, is disposed facing the transfer roller via the image bearer, and nips the image bearer with the transfer roller. The transfer counter roller or the transfer roller is configured to be applied with a bias to transfer the toner image on the image bearer onto the recording medium. Each of the elastic layer of the transfer roller and the elastic layer of the transfer counter roller has an Asker C hardness of 75 or less. A difference in thickness between the elastic layer of the transfer roller and the elastic layer of the transfer counter roller is ±3% or less.
In another embodiment of the present disclosure, there is provided an image forming apparatus that includes the transfer device and the image bearer.
A more complete appreciation of the disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:
The accompanying drawings are intended to depict embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.
Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
An image forming unit 1 includes a photoconductor 2 that functions as an image bearer and further includes, for example, a photoconductor cleaning blade 6, a charging device 3, an exposure device 4, and a developing device 5 around the photoconductor 2. During full-color image formation, the printer 30 forms visible images on the respective photoconductors 2 in the order of the image forming unit 1Y for yellow, the image forming unit 1M for magenta, the image forming unit 1C for cyan, and the image forming unit 1K for black. The visible images of the four colors formed on the respective photoconductors 2 are superimposed and transferred onto the intermediate transfer belt 7 to form a full-color toner image on the intermediate transfer belt 7.
The intermediate transfer belt 7 made of an elastic body is stretched over a plurality of rollers such as a drive roller 8, a tension roller 9, and a secondary transfer counter roller 16. An intermediate transfer drive motor 17 drives the drive roller 8 to rotate. Thus, the intermediate transfer belt 7 is driven to travel in a clockwise direction in
Each primary transfer roller 10 is disposed at a contact portion between each photoconductor 2 and the intermediate transfer belt 7. A predetermined transfer bias is applied to each primary transfer roller 10. Among the primary transfer rollers 10, each of the primary transfer rollers 10Y, 10M, and 10C for color is supported by a corresponding primary-transfer-contact-and-separation mechanism and is contacted with and separated from the intermediate transfer belt 7 by an operation of the primary-transfer-contact-and-separation mechanism. The primary transfer roller 10K for black constantly contacts the intermediate transfer belt 7. With this configuration, in a monochrome mode in which image formation is performed using only the black toner, the image formation is performed by contacting only the primary transfer roller 10K with the intermediate transfer belt 7 and separating the other primary transfer rollers 10Y, 10M, and 10C from the intermediate transfer belt 7. In a full-color mode, the image formation is performed by contacting all the primary transfer rollers 10 with the intermediate transfer belt 7.
An intermediate transfer belt cleaner 31 that cleans an outer circumferential surface of the intermediate transfer belt 7 is disposed in the vicinity of the outer circumferential surface of the intermediate transfer belt 7. The intermediate transfer belt cleaner 31 includes, for example, the brush counter roller 14, a blade counter roller 32, a belt cleaning blade 11, a solid lubricant 12, and a brush roller 13. The intermediate transfer belt 7 is stretched over the blade counter roller 32. Thus, the blade counter roller 32 is driven to rotate with the traveling movement of the intermediate transfer belt 7. The belt cleaning blade 11 made of urethane rubber is contacted and pressed against the blade counter roller 32 via the intermediate transfer belt 7 and blocks and cleans foreign substance such as the toner adhering to the intermediate transfer belt 7. The brush roller 13 is disposed in contact with the brush counter roller 14 via the intermediate transfer belt 7. Thus, the solid lubricant 12 is contacted and pressed against the brush roller 13. With this configuration, an appropriate amount of lubricant scraped off from the solid lubricant 12 by a rotation of the brush roller 13 is uniformly applied to the outer circumferential surface of the intermediate transfer belt 7 to reduce adhesion of the foreign substance.
A secondary transfer unit 25 as a transfer device is disposed below the center of the intermediate transfer belt 7. The secondary transfer unit 25 includes a secondary transfer roller 15 and the secondary transfer counter roller 16. The secondary transfer roller 15 has an elastic layer 15a (see
A sheet storage (sheet tray) 18 that stores transfer sheets S is disposed in a lower portion of the apparatus body 26 located below the secondary transfer unit 25. Although only one sheet storage 18 is disposed in the present embodiment, two or more sheet storages may be disposed. A feed roller 19 that feeds the uppermost sheet of the transfer sheets S stored in the sheet storage 18 to a feed conveyance passage 20 is disposed above the sheet storage 18. The transfer sheet S fed to the feed conveyance passage 20 by the feed roller 19 is conveyed toward the secondary transfer portion N by a conveying roller pair 22 disposed in the feed conveyance passage 20. Thus, the transfer sheet S is temporarily stopped by a registration roller pair 21 disposed downstream from the conveying roller pair 22 in a sheet conveyance direction. The registration roller pair 21 feeds the temporarily stopped transfer sheet S toward the secondary transfer portion N when the toner image formed on the intermediate transfer belt 7 has reached the secondary transfer portion N. The transfer sheet S fed by the registration roller pair 21 is conveyed by a conveyor 33 toward a fixing device 23 disposed downstream from the secondary transfer unit 25 in the sheet conveyance direction after the toner image is transferred from the intermediate transfer belt 7 onto the transfer sheet S at the secondary transfer portion N. The transfer sheet S on which the toner image is fixed by heat and pressure in the fixing device 23 is conveyed further downstream from the fixing device 23 by a conveyor 34. Thus, the transfer sheets S is ejected and stacked on an output tray 24.
In the above-described printer 30, a moving speed of the toner image formed on the intermediate transfer belt 7 and a moving speed of the transfer sheet S are preferably matched when the secondary transfer in which the toner image formed on the intermediate transfer belt 7 is transferred to the transfer sheet S is performed. In other words, a moving speed of a surface of the intermediate transfer belt 7 and a moving speed of a surface of the transfer sheet S are preferably matched. When a speed difference occurs between above-described moving speeds, the image magnification error variation described in the section of “Background Art” occurs at the time of the secondary transfer. For example, when the moving speed of the surface of the transfer sheet S is faster than the moving speed of the surface the intermediate transfer belt 7, a movement amount of the transfer sheet S per unit time is longer than a movement amount of the intermediate transfer belt 7 per unit time. For this reason, a size of the image formed on the transfer sheet S is larger than a size of the ideal image on the data. Thus, the image magnification error variation occurs.
When the transfer sheet S passes through a nip portion between the secondary transfer roller 36 and the secondary transfer counter roller 37 formed at the secondary transfer portion N1, the image magnification error variation occurs if the nip portion is formed in a curved surface as illustrated in
However, as illustrated in
As described above, according to the secondary transfer unit 25 of the present embodiment, the difference between the thickness B1 of the elastic layer 15a of the secondary transfer roller 15 and the thickness B of the elastic layer 16a of the secondary transfer counter roller 16 is set to ±3% or less so that the amount of deformation of the elastic layer 15a and the amount of deformation of the elastic layer 16a are substantially equal to each other at the time of pressure contact. Thus, the nip portions of the secondary transfer roller 15 and the secondary transfer counter roller 16 at the secondary transfer portion N can be flattened. As a result, the length A of the upper surface and the length A1 of the lower surface of the transfer sheet S at the time of secondary transfer can be equal to each other. Thus, a transfer device and an image forming apparatus can be provided that can reduce the occurrence of image magnification error variation without generating a waste sheet. The preferable range of the difference between the thickness B1 of the elastic layer 15a and the thickness B of the elastic layer 16a depends on the difference in hardness between the elastic layer 15a and the elastic layer 16a. For example, when the elastic layers 15a and 16a have the same hardness, the smaller the difference between the thicknesses B1 and B, the more preferable.
The inventors of the present disclosure have made a difference in hardness between the elastic layers 15a and 16a and have confirmed to what extent the difference in hardness affects the image magnification error variation. In the confirmation test, the elastic layers 15a and 16a having a hardness difference from each other were used, the difference between the thicknesses B1 and B was set to ±3% or less, image formation was performed. Thus, the image lengths of output materials on which the images were formed were measured, and the differences from the ideal image lengths on the data were obtained. The inventors of the present disclosure determined whether the image magnification error variation was reduced. As a result of the determination, reducing the occurrence of the image magnification error variation was confirmed when the difference in hardness between the elastic layers 15a and 16a is an Asker C hardness of 15 or less. However, when the difference in hardness between the elastic layers 15a and 16a exceeds an Asker C hardness of 15, the image magnification error variation rarely occurs. As a result, setting the difference in hardness between the elastic layers 15a and 16a to be an Asker C hardness of 15 or less can further reduce the occurrence of image magnification error variation.
As a result of the determination, the inventors of the present disclosure have confirmed that the surface of the intermediate transfer belt 7 made of an elastic body is easily crushed and the followability of the intermediate transfer belt 7 with respect to the surface of the transfer sheet S is improved when the hardness of the elastic layer 15a is higher than the hardness of the elastic layer 16a. As a result, transferability in a case of using uneven paper or rough paper which has been used more frequently in recent years can be enhanced. The inventors of the present disclosure performed image formation by changing the hardness of the intermediate transfer belt 7 and confirmed the influence of the hardness of the intermediate transfer belt 7 on the image formation. In the confirmation test, the inventors used belts having different hardnesses as the intermediate transfer belt 7. The hardness of each of the elastic layers 15a and 16a was set to an Asker C hardness of 75 or less, the difference between the thicknesses B1 and B was set to ±3% or less, and image formation was performed. Thus, the inventors checked the output materials on which images were formed. As a result of the confirmation, the inventors found that setting the hardness of the intermediate transfer belt 7 to a micro rubber hardness of 70 or less improved the followability of the intermediate transfer belt 7 with respect to the unevenness of the surface of the transfer sheet S. Thus, the inventors confirmed that the transferability in the case of using an uneven paper sheet or a rough paper sheet is further improved.
In the present embodiment, an example in which the printer 30 is described as an image forming apparatus, but the image forming apparatus is not limited thereto. The present disclosure is applicable to a copier, a facsimile machine, a multifunction peripheral (MFP), and color image forming apparatuses. In the present embodiment, the transfer sheet S is mentioned as an example of the recording medium on which an image is formed. However, the recording medium is not limited to a recording paper sheet but also includes thick paper, a postcard, an envelope, plain paper, thin paper, coated paper, art paper, tracing paper, an overhead projector transparency (OHP sheet or OHP film), a resin film, and any other sheet-shaped material on which an image can be formed.
Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the above teachings, the present disclosure may be practiced otherwise than as specifically described herein. With some embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the present disclosure and appended claims, and all such modifications are intended to be included within the scope of the present disclosure and appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-164881 | Oct 2021 | JP | national |
