This patent application is based on and claims priority pursuant to 35 U.S.C. § 119 to Japanese Patent Applications No. 2017-115020, filed on Jun. 12, 2017 in the Japanese Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
The present disclosure relates to a fixing device and an image forming apparatus using the fixing device.
Recently, in order to reduce energy consumption and shorten wait time, that is, warming-up time, many new fixing devices used in image forming apparatuses such as printers, copiers, and fax machines have a so-called on-demand type structure that directly heats a small heat-capacity endless film-like belt.
Such new fixing devices using a quick-start-up (QSU) method include a rotatable endless free belt, a heater that is disposed inside a loop formed by the free belt and which directly heats the free belt, an elastic roller that contacts an outer surface of the free belt, and a pad that is disposed inside the loop formed by the free belt and extends in a longitudinal direction of the elastic roller. The pad, which is also called a nip formation pad and which elastically deforms the elastic roller, serves to broaden a contact region between a sheet of recording media and the free belt, that is, a nip width, if the belt is a relatively narrow one.
The free belt and the pad situated inside the loop formed by the free belt are set at a predetermined position with respect to the elastic roller, which is fixed on a shaft driven to rotate, to press the elastic roller and form a fixing nip while printing and, after printing, to move to a release position separate from the belt, in which the free belt does not press the elastic roller to avoid compression set of the elastic roller.
It is to be noted here that, conventionally, the heater and the pad are fixed together on a holder that is supported by a side plate and from which the free belt is suspended because the heater needs to be disposed at a predetermined constant clearance with respect to the free belt and the pad when the free belt and the pad press against the elastic roller and form the fixing nip.
This specification describes an improved fixing device and an image forming apparatus using the fixing device.
In one illustrative embodiment, the fixing device includes an endless belt, a pressure rotator that contacts an outer surface of the endless belt, a nip formation pad enclosed in a loop formed by the endless belt to form a fixing nip between the endless belt and the pressure rotator, a heater enclosed in the loop formed by the endless belt to heat the endless belt, a stay to support the nip formation pad, a contact-separation mechanism that presses the nip formation pad against the pressure rotator in a releasable manner, a holder disposed on the outer side in a width direction of the belt and movable between a nip formation position and a release position to limit movement of the endless belt in the width direction and support the stay, and an adjustment mechanism. The holder is provided with a slot to support the heater relatively movable with respect to the holder. The adjustment mechanism makes a distance between the heater and the nip formation pad when the holder is at the nip formation position larger than a distance between the heater and the nip formation pad when the holder is at the release position.
The aforementioned and other aspects, features, and advantages of the present disclosure would be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
The accompanying drawings are intended to depict embodiments of the present disclosure 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.
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.
Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable.
Referring now to the drawings, embodiments of the present disclosure are described below. In the drawings illustrating the following embodiments, the same reference codes are allocated to elements (members or components) having the same function or shape and redundant descriptions thereof are omitted below.
A description is provided of embodiments of the present disclosure below. As illustrated in
A detailed description is now given of a construction of the elastic roller 6. The elastic roller 6, having a diameter in a range of, for example, from 20 mm to 40 mm, is constructed of a hollow cored bar and an elastic layer coating the cored bar. The elastic layer is made of solid rubber such as silicone rubber or fluoro-rubber. A heater source such as a halogen heater may be inside the elastic roller 6. When the heat source is not inside the elastic roller 6, sponge rubber such as foamed silicone rubber with excellent thermal insulation may be used as the elastic layer. A thin release layer made of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), or the like may be disposed on a surface of the elastic layer to facilitate separation of a sheet from the elastic roller 6. An end of the elastic roller 6 mounts a driving gear as well known, and the elastic roller 6 is driven and rotated clockwise, that is in an arrow direction in
A detailed description is now given of a construction of the fixing belt 1. The fixing belt 1 is a thin endless belt like a film, made to have a diameter, for example, from 15 mm to 120 mm (about 30 mm in the present embodiment), and driven and rotated counterclockwise, that is, an arrow direction in
The base layer of the fixing belt 1 has a thickness of, e.g., about 30 μm to about 100 μm, and is made of a metal material, such as nickel or stainless steel, or a resin material such as polyimide. The elastic layer of the fixing belt 1 has a thickness of, e.g., about 100 μm to about 300 μm, and is made of a rubber material such as silicon rubber, silicon rubber foam, or fluoro rubber. The elastic layer absorbs slight surface asperities of the fixing belt 1 at the fixing nip, facilitating even heat conduction from the fixing belt 1 to a toner image on the sheet and thereby suppressing formation of an orange peel image on the sheet. The release layer of the fixing belt 1 may be made of PFA, PTFE, polyimide (PI), polyamide imide (PAI), polyether imide (PEI), polyether sulfide (PES), polyether ether ketone (PEEK), or the like.
A detailed description is now given of a construction of the heater 5. The heater 5 is situated inside the loop formed by the fixing belt 1 and extends in a width direction of the fixing belt 1. Radiant heat generated by electric power controlled and output from a power source in a printer body directly heats the inner surface of the fixing belt 1. A halogen heater, a carbon heater, or the like may be used as the heater 5.
A detailed description is now given of a configuration of the nip formation pad 3. The nip formation pad 3, which is also called a fixing pad, is situated inside the loop formed by the fixing belt 1 and extends in the width direction of the fixing belt 1. The nip formation pad 3 contacts and presses the elastic roller 6 via the fixing belt 1 to form the fixing nip N. The inner circumference surface of the fixing belt 1 contacts and slides on the nip formation pad 3. A sheet member may be sandwiched between the nip formation pad 3 and the fixing belt 1 to reduce friction between the nip formation pad 3 and the fixing belt 1. A thermal conduction aid made of metal with high thermal conduction may be attached on a surface of the nip formation pad 3 in the side of the fixing belt 1 to enhance heat transfer in the width direction of the fixing belt 1.
A stay 4 is disposed on the nip formation pad 3 on the side opposite to the fixing nip N to support the nip formation pad 3. The stay 4 prevents bending of the nip formation pad 3 by the elastic roller 6 to keep the nip width uniform in the longitudinal direction. The stay 4 includes three metal plates, that is, a first part 4a whose cross-section is like a crossbar (−), a second part 4b whose cross-section is like an oblique bar, and a third part 4c whose cross-section is L-shaped. The third part 4c has a face to support the nip formation pad 3. The holder 2 holds both ends of the three metal plates in the longitudinal direction. In order to increase the rigidity of the stay 4, it is preferable that the cross section of the stay 4 has a large size in a pressing direction that is a crosswise direction in
A thermal insulation treatment or a specular surface treatment on a surface of the stay 4 reduces unnecessary energy consumption that does not contribute to belt heating due to radiant heat from the heater 5. Instead of such thermal insulation treatment or specular surface treatment, a reflector may be disposed between the heater 5 and the stay 4.
As illustrated in
The belt holder 2a protrudes toward the end of the fixing belt 1 and forms a partial cylinder. As seen in
Additionally, the side plate 2b includes a first support portion 2d to support a longitudinal end of the stay 4 and a second support portion 2e to support the heater 5 movable.
The first support portion 2d has a cutout corresponding to the cross section of the stay 4, the longitudinal end of the stay 4 fits into the cutout, and the holder 2 supports the stay 4. A portion 2f of the first support portion 2d that is not the cutout in a fixing nip side abuts a longitudinal end of the third part 4c having the face to support the nip formation pad 3, prevents movement of the stay 4 in the longitudinal direction, and positions the stay 4 in the longitudinal direction.
The second support portion 2e is a slot shaped as a rectangle with rounded corners, elongated in a direction in which the holder 2 slides with respect to the side plate of the fixing device 10. The heater 5 is inserted into the second support portion 2e from the longitudinal direction and is supported. In the illustrated embodiment, the second support portion 2e is the slot shaped the rectangle with rounded corners, but the second support portion 2e may be a general rectangular shape, an elliptical shape, or a polygonal shape as long as the second support portion 2e limits movement of the heater in the sheet conveyance direction.
With reference to
As illustrate in
As long as the heater 5 gets the position not to contact the stay 4 and the fixing belt 1 when the holder 2 moves to the release position, the heater 5 may not necessarily be supported movable in the loop formed by the fixing belt 1 when the heater 5 moves in the second support portion 2e of the holder 2. Instead of the pressing member 7 that is the elastic narrow plate-shaped member or the elastic strip-like member, a stopper 8 may be used to fix and support the heater 5 at a predetermined position. That is, the heater may not move with respect to the elastic roller 6 if it is possible for the heater 5 to get a relative positional relation for the nip formation pad 3 and the stay 4 in the loop formed by the fixing belt 1 such that the heater keeps a gap greater than a necessary distance with respect to the fixing belt 1 and the nip formation pad 3 when the fixing belt 1 and the nip formation pad 3 press the elastic roller 6 and does not contact the stay 4 and the fixing belt 1 when the holder 2 is in the release position. As a result, the load between the sealing part of the heater 5 and the harness 5a is not caused by the movement of the heater 5. In this case, since the stopper 8 is not elastically deformed like the pressing member 7, the end portion of the second support portion 2e of the holder 2 in the opposite side of the fixing nip is extended longer from the fixing nip than the one in the embodiment of the pressing member 7.
The structure of the stay 4 having the set of the first part like the cross bar and the second part like the oblique bar to support the nip formation pad 3 at the upstream point and the downstream point in the sheet conveyance direction generates a space that is not used in the opposite side of the fixing nip from the stay 4 because the heater 5 is set not to contact the stay 4 when the holder 2 is in the release position in the embodiment which fix the position of the heater 5 similar to the other embodiment. A variation of the holder 2 that effectively uses such space and a mechanism corresponding to the variation to support and move the heater is described below. This structure also reduces the risk of damage to the sealing part of the heater 5.
As illustrated in
The mechanism in the present variation to support and move the heater 5 is a regulator 9 that sets limits of positions of the heater 5 in a direction in which the fixing belt 1 and the nip formation pad 3 moves to press and release the elastic roller 6 in
With reference to
In a conventional configuration in which the nip formation pad and the heater are integrally moved, the movement of the heater applies a considerable load between the heater and the heater harness. Reducing the movement amount of the heater 5 accompanying the slide of the holder 2 in the present embodiment and variations reduces the load between the heater 5 and the heater harness 5a. In particular, when the moving direction of the heater is orthogonal to a direction in which the harness 5a is bent, the radius of curvature of the harness 5a is substantially constant regardless of the slide of the holder 2, and the fluctuation of the force applied to the heater can be reduced.
Experiments were conducted to verify an effect of the present disclosure. The fixing device according to the present embodiment and a comparative fixing device in which the nip formation pad and the heater are integrally moved were provided. In both the fixing devices, the moving amount of the nip formation pad was set to be 2 mm, the movement of the nip formation pad to press and release the elastic roller was repeated, and whether breakage of the heater sealing portion occurred was confirmed. As a result, in the comparative fixing device, the heater sealed portion was broken at 120 thousand times, whereas the heater sealed portion in the present embodiment did not break even at 240 thousand times.
With reference to
A bottle housing 101 in an upper portion of a main body of the printer 100 accommodates four toner bottles 102Y, 102C, 102M, and 102K containing fresh yellow, cyan, magenta, and black toners, respectively, and being detachably attached to the bottle housing 101 for replacement. Under the bottle housing, there is provided an intermediate transfer belt unit 85. The image forming devices 24Y, 24C, 24M, and 24K respectively corresponding to yellow, cyan, magenta, and black are arranged in parallel, facing the intermediate transfer belt 78 of the intermediate transfer belt unit 85. The image forming devices 24Y, 24C, 24M, and 24K include photoconductor drums 25Y, 25C, 25M, and 25K, respectively. Each of the photoconductor drums a bottle housing 101 is surrounded by a charger 75, a developing device 76, a cleaner 77, and the like. To illustrate them clearly, reference numerals are assigned only for the black image forming device 24K in
The image forming devices 24Y, 24C, 24M, and 24K form different single-color images on the respective photoconductor drums 25Y, 25C, 25M, and 25K through a sequence of image forming processes, a charging process, an exposure process, a developing process, and a cleaning process. A drive motor drives and rotates the photoconductor drums 25Y, 25C, 25M, and 25K clockwise in
The toner images formed on the surfaces of the photoconductor drums 25Y, 25C, 25M, and 25K through the developing process are transferred onto the intermediate transfer belt 78 of the intermediate transfer belt unit 85 while being superimposed one atop another to form a color toner image on the intermediate transfer belt 78. The intermediate transfer belt unit 85 includes the intermediate transfer belt 78, the four primary transfer bias rollers 79Y, 79C, 79M, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer belt cleaner 80.
The intermediate transfer belt 78 is stretched taut across and supported by the three rollers, that is, the secondary transfer backup roller 82, the cleaning backup roller 83, and the tension roller 84. One of the three rollers, that is, the secondary transfer backup roller 82, drives and rotates the intermediate transfer belt 78 in a rotation direction indicated by arrow R1 in
The sheet P is transported by a sheet feeder 32 provided in the lower portion of the main body of the printer 100 to the secondary transfer nip via a sheet feed roller 97, pairs of conveyance rollers, and a registration roller pair 98. Specifically, multiple sheets P are stacked in the sheet feeder 32. The sheet feed roller 97 rotates counterclockwise in
Subsequently, the sheet P bearing the full-color toner image is transported to a fixing device 10. In the fixing device 10, a fixing belt 1 and an elastic roller 6 apply heat and pressure to the sheet P to fix the full-color toner image on the sheet P. Thereafter, the sheet P bearing the fixed toner image is ejected by an output roller pair 99 onto an outside of the printer 100. The sheet P ejected by the output roller pair 99 onto the outside of the printer 100 is stacked on an output tray 100 as a print. Thus, a sequence of image forming processes performed in the image forming apparatus is completed.
Numerous additional modifications and variations are possible considering 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 |
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2017-115020 | Jun 2017 | JP | national |