This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-061179 filed Mar. 25, 2016.
The present invention relates to a transfer device and an image forming apparatus.
According to an aspect of the invention, a transfer device includes a transfer member to which a bias voltage is applied and that transfers a toner image, which is carried on an image carrier, onto a sheet while nipping the sheet between the transfer member and the image carrier when the sheet is transported to the transfer member; and a pressing member that includes a spring member and a first rubber damper, which are arranged in series with each other, and that presses the transfer member against the image carrier.
Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:
Hereinafter, exemplary embodiments of the present invention will be described.
The image forming apparatus 1 includes a photoconductor drum 10. The photoconductor drum 10 is rotatably supported by a drum support frame 10A and rotates in the direction of arrow A. A charger 11, an exposure unit 12, and a developing unit 13 are disposed around the photoconductor drum 10. A toner image is formed on the surface of the photoconductor drum 10 through charging, exposure, and development processes; and the toner image is temporarily carried on the photoconductor drum 10.
One of sheets P, which are stacked on a sheet tray (not shown), is transported in the direction of arrow X and passes through a transfer region T between the photoconductor drum 10 and the transfer device 20 (described below in detail). While the sheet P passes through the transfer region T, the toner image on the photoconductor drum 10 is transferred onto the sheet P. The sheet P, to which the toner image has been transferred, is further transported in the direction of arrow Y and fed into a fixing device 30. The fixing device 30 includes a heating roller 31, which rotates in the direction of arrow D, and a pressing roller 32, which rotates in the direction of arrow E. The heating roller 31 and the pressing roller 32 contact each other to form a fixing region S. The sheet P, which has been transported in the direction of arrow Y, enters the fixing region S. While the sheet P passes through the fixing region S, the sheet P is heated and pressed, and the toner image on the sheet P is fixed onto the sheet P.
After the toner image has been transferred in the transfer region T, residual toner remains on the photoconductor drum 10. A cleaner 14 removes the residual toner from the photoconductor drum 10.
The transfer device 20 includes a transfer roller 21; a press-contact roller 22; a peel-off roller 23; and a transfer belt 24, which is an endless belt looped over these rollers. The transfer roller 21, the press-contact roller 22, and the peel-off roller 23 are rotatably supported by a transfer-unit support frame 20A.
The transfer roller 21 is an elastic roller whose roller surface is elastically deformable. The transfer roller 21 rotates in the direction of arrow B and drives the transfer belt 24. The transfer belt 24 is driven by the transfer roller 21 and rotates in the direction of arrow C. The transfer roller 21 is located upstream of the rotation axis of the photoconductor drum 10 in the sheet transport direction and presses the transfer belt 24 against the photoconductor drum 10 from the inside of the transfer belt 24. The transfer roller 21 defines an upstream edge of the transfer region T, in which the photoconductor drum 10 and the transfer belt 24 are in contact to each other.
The press-contact roller 22 is located downstream of the rotation axis of the photoconductor drum 10 in the sheet transport direction and presses the transfer belt 24 upward toward the photoconductor drum 10 from the inside of the transfer belt 24. The press-contact roller 22 defines a downstream edge of the transfer region T.
The diameter of the peel-off roller 23 is smaller than that of the transfer roller 21. The peel-off roller 23 sharply changes the direction in which the transfer belt 24 moves, so that the leading end of the sheet P on the transfer belt 24 is peeled off the transfer belt 24. The sheet P, which has been peeled off the transfer belt 24, is guided by a guide member 41 and moves in the direction of arrow Y. Then, as described above, while the sheet P passes through the fixing region S of the fixing device 30, a toner image is fixed onto the sheet P. Thus, an image, which is a fixed toner image, is formed on the sheet P. The sheet P, on which the image has been formed, is output onto a sheet output tray (not shown).
The transfer device 20 further includes a cleaner 25. The cleaner 25 removes toner and other substances adhering to the transfer belt 24 from the transfer belt 24.
The transfer roller 21 is connected to a power supply (not shown) that applies a transfer voltage to the transfer roller 21. Due to the effect of the transfer bias, a toner image on the photoconductor drum 10 is transferred onto the sheet P while the sheet P passes through the transfer region T.
The transfer roller 21 includes a rotary shaft 211, which is rotatably supported by a shaft support frame 212. The shaft support frame 212 is supported by the transfer-unit support frame 20A (see
In the region shown in
The rubber damper 213 corresponds to an example of a first rubber damper in the present invention. The rubber damper 213 and the spring member 214 are disposed at each end of the transfer roller 21 in the axial direction. Therefore, the effect of the rubber damper 213 and the spring member 214 is exerted over the entire length of the transfer roller 21.
In
The spring constant of the spring member 214 and the hardness of the rubber damper 213 will be examined below.
In the image forming apparatus 1 according to the present exemplary embodiment, the sheet feed speed is in the range of 400 mm/sec to 600 mm/sec, and the maximum thickness of a usable sheet is 0.4 mm.
The spring member 214 used in this example has a spring constant of 7 N/mm. The spring constant 7 N/mm is smaller than the spring constant 8.7 N/mm, with which the spring member 214 satisfies the predetermined vibration damping performance as shown in
In the example described above, the spring member 214 having the spring constant 7 N/mm is used. Also when the spring member 214 having the spring constant of 8 N/mm is used, the spring member 214 alone does not satisfy the target vibration damping performance. However, by using the rubber damper 213 described above in addition to the spring member 214, the target vibration damping performance is satisfied while suppressing the negative effect of high contact pressure.
In the example described above, the rubber damper 213 is disposed adjacent to the transfer roller 21, and the spring member 214 is fixed to the transfer-unit support frame 20A. Conversely, the spring member 214 may be disposed adjacent to the transfer roller 21, and the rubber damper 213 may be fixed to the transfer-unit support frame 20A.
Description of the first exemplary embodiment of the present invention has been finished. Next, a second exemplary embodiment of the present invention will be described.
The developing device according to the second exemplary embodiment further includes a rubber damper 215, in addition to the rubber damper 213 and the spring member 214 in the first exemplary embodiment. The rubber damper 215 is disposed at such a position that the spring member 214 is located between the rubber damper 213 and the rubber damper 215. The rubber damper 215 corresponds to an example of a second rubber damper in the present invention.
The developing device according to the second exemplary embodiment further includes a cam member 216. The cam member 216 corresponds to an example of a pressing-force control member in the present invention. The cam member 216 presses a serial body including the rubber damper 213, the spring member 214, and the rubber damper 215 toward the photoconductor drum 10 with a variable pressing force.
A motor 217 rotates the cam member 216 around a rotary shaft 216a back and force in the directions of arrows u and v (see
Also in the second exemplary embodiment, as in the first exemplary embodiment described above, a serial body including the rubber damper 213, the spring member 214, and the rubber damper 215, and the cam member 216 are disposed at each end of the transfer roller 21 in the axial direction. Therefore, the effect of these members is exerted over the entire length of the transfer roller 21.
The cam member 216 is rotated by the motor 217, which receives instruction from the controller 29, as follows.
Before the sheet P reaches the transfer region T illustrated in
Here, it is assumed that the sheet P, on which an image is to be formed in this example, is a long sheet having such a length that the leading end of the sheet P enters the fixing region S while a part of the sheet P still remains in the transfer region T. In the image forming apparatus 1, the distance between the transfer region T and the fixing region S is about 230 mm. If the size of the sheet P is not larger than A4, the leading end of the sheet P enters the fixing region S after the trailing end of the sheet P has exited the transfer region. However, if an A3-sized sheet is transported in its longitudinal direction, the trailing end of the sheet still remains in the transfer region T when the leading end of the sheet enters the fixing region S. In this case, transfer of a toner image is still being performed at a timing at which the leading end of the sheet enters the fixing region S. Therefore, if an impact that occurs when the leading end of the sheet enters the fixing region S is transmitted and the transfer roller 21 vibrates, a decrease of image quality due to transfer failure may occur.
In the second exemplary embodiment, the rubber damper 215 is made of a material whose property is adjusted to be suitable for damping vibration due to an impact that occurs when the leading end of the sheet enters the fixing region S. Accordingly, the rubber damper 215 effectively damps vibration due to an impact that occurs when the leading end of the sheet enters the fixing region S. That is, with the second exemplary embodiment, the rubber damper 213 effectively damps the vibration due to an impact that occurs when the leading end of the sheet enters the transfer region T, and the rubber damper 215 effectively damps the vibration due to an impact that occurs when the leading end of the sheet enters the fixing region S, and therefore a decrease of image quality, which may be caused by each impact, is suppressed.
In the example described above, the transfer device 20 is a belt-transfer-type transfer device including the transfer belt 24. However, the present invention is also applicable to a contact-type transfer device that does not include a transfer belt and in which a transfer roller directly contacts the photoconductor drum 10.
In the exemplary embodiments described above, the photoconductor drum 10 is used as an example of an image carrier in the present invention. However, the present invention is also applicable to a case where an intermediate transfer member, to which a toner image is first-transferred from a photoconductor drum and from which the toner image is second-transferred onto a sheet, is used as an example of an image carrier in the present invention.
The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
Number | Date | Country | Kind |
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2016-061179 | Mar 2016 | JP | national |
Number | Name | Date | Kind |
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20070008395 | Masubuchi | Jan 2007 | A1 |
20100278567 | Nakagawa | Nov 2010 | A1 |
Number | Date | Country |
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2007-286382 | Nov 2007 | JP |
2007-316427 | Dec 2007 | JP |
Number | Date | Country | |
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20170277084 A1 | Sep 2017 | US |