1. Field of the Invention
The present invention relates generally to an image forming device having a fuser module and particularly to a fuser module that reduces force variability and positional variability within the fuser module.
2. Description of the Related Art
In an electro photographic image forming device such as a laser printer, an image forming unit transfers a toner image to a media sheet. After the toner image is transferred to the media sheet, the media sheet moves to a fuser module that applies heat and pressure on the media sheet in order to fuse the toner image to the media sheet.
The fuser module generally includes a backup roll, a fuser belt, and at least one heater. The backup roll and the fuser belt form a nip that is heated by the heater. When the media sheet enters the nip, it is gripped between the roller and the belt and is driven along the media path as the back-up roll and the fuser belt rotate, thereby fusing the toner image to the media sheet by the application of heat and pressure and eventually directing the media sheet out of the imaging apparatus. Typically, an entry guide is disposed upstream from the nip to guide the media sheet towards the nip.
An example of a conventional fuser module 10 is illustrated in
The position of the nip 18 often varies (shown by the arrow) due to several factors, such as wearing of the backup roll 14, thermal expansion of the backup roll 14, and variation in the media sheet thickness. However, a fuser module with the above geometry is unable to adjust itself in response to the above variations, thereby resulting in print defects.
For example, when the nip location varies (as shown by the arrow) due to the above reasons, the end cap 20 slides within the slot 22, thereby compressing or decompressing the spring 24 to accommodate for the nip location variation. Due to the compression and decompression of the spring 24, a large frictional force is developed between the end cap 20 and the side frame 12 of the image forming device around the slot 22. Also, the frictional force that is generated around the slot 22 directly affects the pressure that is maintained at the nip 18 in part due to a 1:1 aspect ratio (ratio of width to height) of the end cap 20. In other words, a considerable amount of the generated frictional force is deducted from the pressure that is maintained at the nip 18 and leads to application of decreased pressure on the media sheet passing through the nip 18. This relatively large force variation at the nip 18 causes inadequate fusing of the toner image to the media sheet resulting in compromised print quality.
Further, the stationary entry guide 26 that is fixed to the side frame 12 is independent of the movement of the nip 18, as well as the end cap 20. Also, a tip 28 of the entry guide 26 is placed at a certain distance from the nip 18. Thus, as the nip location varies due to the above reasons, the stationary entry guide 26 fails to adjust itself accordingly and the gap between the tip 28 of the entry guide 26 and the nip 18 increases, resulting in decreased media control. Consequently, this results in positional variation in the fuser module.
The introduction of the above-mentioned positional and force variability in the fuser module causes print defects, paper jams, belt skew, treeing, and smudging of the image on a media sheet passing through the nip. Thus, there is a need for a fuser module that addresses at least some of the above problems.
Disclosed herein is a fuser module for fixing a toner image to a media sheet in an image forming device including a backup roll, a fuser belt extending between two ends and engaging with the backup roll to form a nip, a movable entry guide disposed in a spaced relationship with the nip, and at least one pivot able end cap enclosing at least a portion of one end of the fuser belt and attached to the movable entry guide, the at least one pivot able end cap capable of maintaining the movable entry guide in the spaced relationship with the nip.
In some embodiments, the fuser belt rotates about a fuser axis, the fuser axis being disposed at a first distance from a pivot center of the at least one pivot able end cap.
In another embodiment, the wheel to axle ratio of the at least one pivot able end cap is about 18:1.
In yet another aspect of the invention, disclosed is an image forming device including an image transfer station adapted to transfer a toner image to a media sheet, and a fuser module located downstream the image forming unit and configured to fuse the toner image to the media sheet, the fuser module including, a backup roll, a fuser belt extending between two ends and engaging with the backup roll to form a nip, the fuser belt rotating about a fuser axis, a movable entry guide disposed in a spaced relationship with the nip, and at least one pivot able end cap enclosing at least a portion of one end of the fuser belt and attached to the movable entry guide, the at least one pivot able end cap pivoting about a pivot center that is disposed at a first distance from the fuser axis, the at least one pivot able end cap capable of maintaining the movable entry guide in the spaced relationship with the nip.
In yet another aspect of the invention, disclosed herein is a fuser module for fixing a toner image to a media sheet in an image forming device including a backup roll, a fuser belt extending between two ends and engaging with the backup roll to form a nip, the fuser belt rotating about a fuser axis, at least one pivot able end cap enclosing at least a portion of one end of the fuser belt and pivoting about a pivot center defined by a shaft having a radius, the pivot center being disposed at a first distance from the fuser axis and at a second distance from the nip, a wheel to axle ratio of the at least one pivot able end cap defined by ratio between the second distance and the radius of the shaft being about 18:1, and a movable entry guide disposed in a spaced relationship with the nip and attached to the at least one pivot able end cap, the at least one pivot able end cap capable of maintaining the movable entry guide in the spaced relationship with the nip.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Reference will now be made in detail to the exemplary embodiment(s) of the invention as illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.
The end cap 454 is mounted in a slot 480 on one of the side frames 210 of the image forming device 200 and slides within the slot 480 while pivoting about its pivot center 456 when the nip 434 moves (shown by arrow a-b). As already discussed above, the nip 434 moves due to various factors like wearing of the backup roll 430, thermal expansion of the backup roll 430, and variation in the media sheet thickness, leading to positional variation of the nip 434. Thus, when the diameter of the backup roll 430 decreases due to wearing, the nip 434 moves forward, toward direction ‘a’, leading to pivoting of the end cap 454 in an counterclockwise direction, and when the diameter of the backup roll 430 increases due to thermal expansion, the nip 434 moves backward, towards direction ‘b’, leading to pivoting of the end cap 454 in a clockwise direction.
The entry guide 460 is mounted on the end cap 454 such that when the end cap 454 pivots about its pivot center 456, the entry guide 460 moves along with the end cap 454. One end 464 of the entry guide 460 that lies closer to the nip 434 is placed at a certain gap from the nip 434, thereby having a spaced relation with the nip 434. The other end 466 of the entry guide 460 that lies away from the nip 434 is attached to the side frame 210 of the image forming device. When the end cap 454 pivots due to movement of the nip location 434, the entry guide 460 that is attached to the end cap 454 also rotates accordingly, thereby keeping the gap between the one end 464 of the entry guide 460 and the nip 434 constant. Therefore, the present geometry of the fuser module, and more particularly, the geometry of the end cap addresses the problem of positional variation within the fuser module effectively.
The present invention also replaces the sliding end cap having a 1:1 aspect ratio, as seen in the prior art end cap geometry (illustrated in
It should be noted that the pressure maintained at the nip 434 and the spaced relation of the one end 464 of the entry guide 460 relative to the nip 434 varies between different media sheets, different fuser modules, and different image forming devices. However, the fuser module according to the present invention ensures the consistency of the above two factors between various kinds of media sheets, fuser modules, and image forming devices, owing to the criticality of the above factors in a fuser module of an image forming device.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the adapted claims and their equivalents.
Number | Name | Date | Kind |
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20060147231 | Aruga et al. | Jul 2006 | A1 |
Number | Date | Country |
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2003295642 | Oct 2003 | JP |
2006003695 | Jan 2006 | JP |
Entry |
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Kobayashi et al. (JP 2003-295642 A) JPO Machine Translation. |
Number | Date | Country | |
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20110158691 A1 | Jun 2011 | US |