This patent application is based on and claims priority pursuant to 35 U.S.C. §119 to Japanese Patent Application No. 2015-054962, filed on Mar. 18, 2015, in the Japanese Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
Technical Field
Exemplary aspects of the present disclosure relate to a fixing device and an image forming apparatus, and more particularly, to a fixing device for fixing a toner image on a recording medium and an image forming apparatus incorporating the fixing device.
Description of the Background
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having two or more of copying, printing, scanning, facsimile, plotter, and other functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of a photoconductor; an optical writer emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device supplies toner to the electrostatic latent image formed on the photoconductor to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the photoconductor onto a recording medium or is indirectly transferred from the photoconductor onto a recording medium via an intermediate transfer belt; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium, thus forming the image on the recording medium.
Such fixing device may include a fixing rotator, such as a fixing roller, a fixing belt, and a fixing film, heated by a heater and a pressure rotator, such as a pressure roller and a pressure belt, pressed against the fixing rotator to form a fixing nip therebetween through which a recording medium bearing a toner image is conveyed. As the recording medium bearing the toner image is conveyed through the fixing nip, the fixing rotator and the pressure rotator apply heat and pressure to the recording medium, melting and fixing the toner image on the recording medium.
This specification describes below an improved fixing device. In one exemplary embodiment, the fixing device includes an endless belt rotatable in a predetermined direction of rotation and a nip formation pad disposed opposite an inner circumferential surface of the endless belt. A pressure rotator presses against the nip formation pad via the endless belt to form a fixing nip between the endless belt and the pressure rotator, through which a recording medium bearing a toner image is conveyed. A slide sheet is sandwiched between the nip formation pad and the endless belt and is a twill fabric containing a lubricant. The slide sheet includes a first sheet contacting the nip formation pad and including a first gutter defined by a first twill line in a first direction angled relative to the direction of rotation of the endless belt and a second sheet layered on the first sheet and contacting the endless belt. The second sheet includes a second gutter defined by a second twill line in a second direction angled relative to the direction of rotation of the endless belt.
This specification further describes an improved image forming apparatus. In one exemplary embodiment, the image forming apparatus includes an image bearer to bear a toner image and a fixing device disposed downstream from the image bearer in a recording medium conveyance direction to fix the toner image on a recording medium. The fixing device includes an endless belt rotatable in a predetermined direction of rotation and a nip formation pad disposed opposite an inner circumferential surface of the endless belt. A pressure rotator presses against the nip formation pad via the endless belt to form a fixing nip between the endless belt and the pressure rotator, through which the recording medium bearing the toner image is conveyed. A slide sheet is sandwiched between the nip formation pad and the endless belt and is a twill fabric containing a lubricant. The slide sheet includes a first sheet contacting the nip formation pad and including a first gutter defined by a first twill line in a first direction angled relative to the direction of rotation of the endless belt and a second sheet layered on the first sheet and contacting the endless belt. The second sheet includes a second gutter defined by a second twill line in a second direction angled relative to the direction of rotation of the endless belt.
A more complete appreciation of the disclosure and the many attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In describing exemplary 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 operate in a similar manner and achieve a similar result.
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, in particular to
It is to be noted that, in the drawings for explaining exemplary embodiments of this disclosure, identical reference numerals are assigned, as long as discrimination is possible, to components such as members and component parts having an identical function or shape, thus omitting description thereof once it is provided.
Referring to
The image forming apparatus 1 is a color printer employing a tandem system in which a plurality of image forming devices for forming toner images in a plurality of colors, respectively, is aligned in a rotation direction of a transfer belt. Alternatively, the image forming apparatus 1 may employ other systems and may be a copier, a facsimile machine, a printer, a multifunction peripheral or a multifunction printer (MFP) having at least one of copying, printing, scanning, facsimile, and plotter functions, or the like.
The image forming apparatus 1 forms yellow, cyan, magenta, and black toner images in separation colors, respectively. Hence, the image forming apparatus 1 employs a tandem structure in which four photoconductive drums 20Y, 20C, 20M, and 20K serving as image bearers that bear yellow, cyan, magenta, and black toner images in separation colors, respectively, are aligned.
Visible images, that is, the yellow, cyan, magenta, and black toner images formed on the photoconductive drums 20Y, 20C, 20M, and 20K, respectively, are primarily transferred successively onto an endless transfer belt 11 serving as an intermediate transferor disposed opposite the photoconductive drums 20Y, 20C, 20M, and 20K as the transfer belt 11 rotates in a rotation direction A1 such that the yellow, cyan, magenta, and black toner images are superimposed on a same position on the transfer belt 11 in a primary transfer process. Thereafter, the yellow, cyan, magenta, and black toner images superimposed on the transfer belt 11 are secondarily transferred onto a sheet S serving as a recording medium collectively in a secondary transfer process. Thus, a color toner image is formed on the sheet S.
Each of the photoconductive drums 20Y, 20C, 20M, and 20K is surrounded by image forming components that form the yellow, cyan, magenta, and black toner images on the photoconductive drums 20Y, 20C, 20M, and 20K as the photoconductive drums 20Y, 20C, 20M, and 20K rotate clockwise in
Taking the photoconductive drum 20K that forms the black toner image, the following describes an image forming operation to form the black toner image. The photoconductive drum 20K is surrounded by a charger 30K, a developing device 40K, a primary transfer roller 12K, and a cleaner 50K in this order in the rotation direction D20 of the photoconductive drum 20K. Similarly, the photoconductive drums 20Y, 20C, and 20M are surrounded by chargers 30Y, 30C, and 30M, developing devices 40Y, 40C, and 40M, primary transfer rollers 12Y, 12C, and 12M, and cleaners 50Y, 50C, and 50M in this order in the rotation direction D20 of the photoconductive drums 20Y, 20C, and 20M, respectively. After the charger 30K charges the photoconductive drum 20K, an optical writing device 8 writes an electrostatic latent image on the photoconductive drum 20K.
As the transfer belt 11 rotates in the rotation direction A1, the yellow, cyan, magenta, and black toner images formed on the photoconductive drums 20Y, 20C, 20M, and 20K, respectively, are primarily transferred successively onto the transfer belt 11, thus being superimposed on the same position on the transfer belt 11. In the primary transfer process, the primary transfer rollers 12Y, 12C, 12M, and 12K disposed opposite the photoconductive drums 20Y, 20C, 20M, and 20K via the transfer belt 11, respectively, apply a primary transfer bias to the photoconductive drums 20Y, 20C, 20M, and 20K successively from the upstream photoconductive drum 20Y to the downstream photoconductive drum 20K in the rotation direction A1 of the transfer belt 11.
The photoconductive drums 20Y, 20C, 20M, and 20K are aligned in this order in the rotation direction A1 of the transfer belt 11. The photoconductive drums 20Y, 20C, 20M, and 20K are located in four image forming stations that form the yellow, cyan, magenta, and black toner images, respectively.
The image forming apparatus 1 includes the four image forming stations that form the yellow, cyan, magenta, and black toner images, respectively, a transfer belt unit 15, a secondary transfer roller 5, a transfer belt cleaner 13, and the optical writing device 8. The transfer belt unit 15 is situated above and disposed opposite the photoconductive drums 20Y, 20C, 20M, and 20K. The transfer belt unit 15 incorporates the transfer belt 11 and the primary transfer rollers 12Y, 12C, 12M, and 12K. The secondary transfer roller 5 serves as a secondary transferor disposed opposite the transfer belt 11 and driven and rotated in accordance with rotation of the transfer belt 11. The transfer belt cleaner 13 is disposed opposite the transfer belt 11 to clean the transfer belt 11. The optical writing device 8 is situated below and disposed opposite the four image forming stations.
The optical writing device 8 includes a semiconductor laser serving as a light source, a coupling lens, an fθ lens, a troidal lens, a deflection mirror, and a rotatable polygon mirror serving as a deflector. The optical writing device 8 emits light beams Lb corresponding to the yellow, cyan, magenta, and black toner images to be formed on the photoconductive drums 20Y, 20C, 20M, and 20K thereon, forming electrostatic latent images on the photoconductive drums 20Y, 20C, 20M, and 20K, respectively.
The image forming apparatus 1 further includes a sheet feeder 61 and a registration roller pair 4 (e.g., a timing roller pair). The sheet feeder 61 incorporates a paper tray that loads a plurality of sheets S to be conveyed to a secondary transfer nip formed between the transfer belt 11 and the secondary transfer roller 5. The registration roller pair 4 conveys a sheet S conveyed from the sheet feeder 61 to the secondary transfer nip formed between the transfer belt 11 and the secondary transfer roller 5 at a predetermined time when the yellow, cyan, magenta, and black toner images superimposed on the transfer belt 11 reach the secondary transfer nip. The image forming apparatus 1 further includes a sensor that detects a leading edge of the sheet S as the sheet S reaches the registration roller pair 4.
The image forming apparatus 1 further includes a fixing device 100, an output roller pair 7, an output tray 17, and toner bottles 9Y, 9C, 9M, and 9K. The fixing device 100 employing a quick start-up (QSU) system that fixes the color toner image formed by the yellow, cyan, magenta, and black toner images secondarily transferred from the transfer belt 11 onto the sheet S thereon. The output roller pair 7 ejects the sheet S bearing the fixed color toner image onto an outside of the image forming apparatus 1, that is, the output tray 17. The output tray 17 is disposed atop the image forming apparatus 1 and stacks the sheet S ejected by the output roller pair 7. The toner bottles 9Y, 9C, 9M, and 9K are situated below the output tray 17 and replenished with fresh yellow, cyan, magenta, and black toners, respectively.
The fixing device 100 includes a pressure roller 102 serving as a pressure rotator or a pressure member and a fixing belt 104, that is, a flexible endless belt serving as a fixing rotator or a fixing member. As the sheet S bearing the unfixed color toner image is conveyed through a fixing nip formed between the fixing belt 104 and the pressure roller 102, the fixing belt 104 and the pressure roller 102 fix the color toner image on the sheet S under heat and pressure. A detailed description of a construction of the fixing device 100 is deferred.
The transfer belt unit 15 includes a driving roller 72 and a driven roller 73 over which the transfer belt 11 is looped, in addition to the transfer belt 11 and the primary transfer rollers 12Y, 12C, 12M, and 12K.
Since the driven roller 73 also serves as a tension applicator that applies tension to the transfer belt 11, a biasing member (e.g., a spring) biases the driven roller 73 against the transfer belt 11. The transfer belt unit 15 incorporating the transfer belt 11 and the primary transfer rollers 12Y, 12C, 12M, and 12K, the secondary transfer roller 5, and the transfer belt cleaner 13 constitute a transfer device 71.
The sheet feeder 61 is situated in a lower portion of the image forming apparatus 1. The sheet feeder 61 includes a feed roller 3 that contacts an upper side of an uppermost sheet S of the plurality of sheets S loaded on the paper tray of the sheet feeder 61. As the feed roller 3 is driven and rotated counterclockwise in
The transfer belt cleaner 13 of the transfer device 71 includes a cleaning brush and a cleaning blade being disposed opposite and contacting the transfer belt 11. The cleaning brush and the cleaning blade scrape a foreign substance such as residual toner particles off the transfer belt 11, removing the foreign substance from the transfer belt 11 and thereby cleaning the transfer belt 11.
The transfer belt cleaner 13 further includes a waste toner conveyer that conveys the residual toner particles removed from the transfer belt 11.
Referring to
As illustrated in
The pressure roller 102 is pressed against the nip formation pad 150 via the fixing belt 104 to form a fixing nip 122 between the fixing belt 104 and the pressure roller 102. As the pressure roller 102 rotates in a rotation direction R1, the fixing belt 104 rotates in a rotation direction R2 in accordance with rotation of the pressure roller 102. The inner circumferential surface of the fixing belt 104 slides over the nip formation pad 150 via the slide sheet 153 coating a surface of the nip formation pad 150. As a sheet S bearing a toner image T conveyed in a sheet conveyance direction DS to the fixing device 100 passes through the fixing nip 122, the fixing belt 104 and the pressure roller 102 fix the toner image T on the sheet S under heat and pressure. Thereafter, the sheet S bearing the fixed toner image T is ejected from the fixing device 100.
As illustrated in
A detailed description is now given of a construction of the fixing belt 104.
The fixing belt 104 is an endless belt or film made of metal such as nickel and SUS stainless steel or resin such as polyimide. The fixing belt 104 is constructed of a base layer and a release layer. The release layer constituting an outer surface layer is made of fluoro resin such as tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA) and polytetrafluoroethylene (PTFE) to facilitate separation of toner of the toner image T on the sheet S from the fixing belt 104. An elastic layer, made of silicone rubber or the like, may be sandwiched between the base layer and the release layer.
If the fixing belt 104 does not incorporate the elastic layer, the fixing belt 104 has a decreased thermal capacity that improves fixing property of being heated quickly to a desired fixing temperature at which the toner image T is fixed on the sheet S. However, as the pressure roller 102 and the fixing belt 104 sandwich and press the toner image T on the sheet S passing through the fixing nip 122, slight surface asperities of the fixing belt 104 may be transferred onto the toner image T on the sheet S, resulting in variation in gloss of the solid toner image T that may appear as an orange peel image on the sheet S. To address this circumstance, the elastic layer made of silicone rubber has a thickness not smaller than 100 micrometers. As the elastic layer deforms, the elastic layer absorbs slight surface asperities of the fixing belt 104, preventing formation of the faulty orange peel image. Instead of metal and polyimide, the base layer of the fixing belt 104 may be made of heat resistant resin such as fluoro resin, polyamide, polyamide imide, polyether ether ketone (PEEK), polyether sulfone (PES), and polyphenylene sulfide (PPS).
A detailed description is now given of a configuration of the stay 120.
The stay 120 situated inside the loop formed by the fixing belt 104 serves as a support that supports the nip formation pad 150 to form the fixing nip 122. As the nip formation pad 150 receives pressure from the pressure roller 102, the stay 120 supports the nip formation pad 150 to prevent bending of the nip formation pad 150. Thus, the stay 120 allows the nip formation pad 150 to produce an even nip length in the sheet conveyance direction DS throughout the entire width of the fixing belt 104 in an axial direction thereof.
The stay 120 is mounted on and held by a pair of flanges at both lateral ends of the stay 120 in a longitudinal direction thereof parallel to the axial direction of the fixing belt 104, respectively, thus being positioned inside the fixing device 100. The reflector 118 interposed between the halogen heater pair 116 and the stay 120 reflects light radiated from the halogen heater pair 116 to the reflector 118 toward the fixing belt 104, preventing the stay 120 from being heated by the halogen heater pair 116 with radiation heat and the like and thereby reducing waste of energy. Alternatively, instead of the reflector 118, an opposed face of the stay 120 disposed opposite the halogen heater pair 116 may be treated with insulation or mirror finish to reflect light radiated from the halogen heater pair 116 to the stay 118 toward the fixing belt 104.
Instead of the halogen heater pair 116, an induction heater, a resistive heat generator, a carbon heater, or the like may be employed as a heater that heats the fixing belt 104. The fixing device 100 illustrated in
A detailed description is now given of a construction of the pressure roller 102.
The pressure roller 102 is constructed of a cored bar 102a, an elastic rubber layer 102b coating the cored bar 102a, and a surface release layer 102d coating the elastic rubber layer 102b and being made of PFA or PTFE to facilitate separation of the sheet S from the pressure roller 102. As a driving force generated by a driver (e.g., a motor) situated inside the image forming apparatus 1 depicted in
A spring or the like presses the pressure roller 102 against the nip formation pad 150 via the fixing belt 104. As the spring presses and deforms the elastic rubber layer 102b of the pressure roller 102, the pressure roller 102 produces the fixing nip 122 having a predetermined length in the sheet conveyance direction DS. The pressure roller 102 may be a hollow roller or a solid roller. If the pressure roller 102 is a hollow roller, a heater such as a halogen heater may be disposed inside the hollow roller.
The elastic rubber layer 102b may be made of solid rubber. Alternatively, if no heater is situated inside the pressure roller 102, the elastic rubber layer 102b may be made of sponge rubber. The sponge rubber is more preferable than the solid rubber because the sponge rubber has an increased insulation that draws less heat from the fixing belt 104.
As the pressure roller 102 rotates in the rotation direction R1, the fixing belt 104 rotates in the rotation direction R2 in accordance with rotation of the pressure roller 102 by friction therebetween. As illustrated in
A detailed description is now given of a configuration of the lubricant circulator 154.
The lubricant circulator 154 is disposed opposite the inner circumferential surface of the fixing belt 104 and disposed upstream from the fixing nip 122 in the sheet conveyance direction DS. The lubricant circulator 154 absorbs a lubricant from the fixing belt 104 and applies the lubricant to the fixing belt 104 again. The lubricant circulator 154 includes a heat resistant, oily sheet wound round in multiple layers and impregnated with a lubricant such as silicone oil.
The lubricant circulator 154 is made of fiber of fluoro resin such as PFA and PTFE like the slide sheet 153 described below or a non-woven fabric made of felt or the like. If the lubricant circulator 154 is made of a fiber sheet, the fiber sheet is wound round in multiple layers into a roll of fabric to increase the size or the volume of the lubricant circulator 154 according to the size of a space available inside the loop formed by the fixing belt 104 so as to enhance retention of the lubricant by the lubricant circulator 154. A biasing member (e.g., a flat spring) presses the lubricant circulator 154 against the fixing belt 104. Alternatively, resilience of fiber or felt of the lubricant circulator 154 may press the lubricant circulator 154 against the fixing belt 104.
A detailed description is now given of a configuration of the holder 151 of the nip formation pad 150.
The primary thermal insulator 151a is made of resin, for example, and has a thermal conductivity smaller than that of the thermal equalizer 152. The primary thermal insulator 151a extends partially in the longitudinal direction of the holder 151. For example, the primary thermal insulator 151a is disposed at three spans, that is, a center span and both lateral end spans, in the longitudinal direction of the holder 151. The primary thermal insulator 151a is sandwiched between the thermal equalizer 152 and the secondary thermal absorber 151d and does not overlap the primary thermal absorber 151c in the longitudinal direction of the holder 151. A width of the center, primary thermal insulator 151a in the longitudinal direction of the holder 151 corresponds to a width of an A6 size sheet S. The primary thermal insulator 151a that partially spans in the longitudinal direction of the holder 151 at the three spans does not absorb heat from the fixing belt 104 excessively. Accordingly, the fixing belt 104 is immune from temperature decrease in a conveyance span of the fixing belt 104 where the sheet S is conveyed over the fixing belt 104. Consequently, the fixing device 100 incorporating the fixing belt 104 and the holder 151 shortens a warm-up time and decreases power consumption. The warm-up time defines a time taken to warm up the fixing device 100 from an ambient temperature to a predetermined temperature (e.g., a reload temperature) at which printing is available after the image forming apparatus 1 is powered on.
The secondary thermal insulator 151b is made of resin, for example, and has a thermal conductivity smaller than that of the thermal equalizer 152. The secondary thermal insulator 151b is sandwiched between the thermal equalizer 152 and the primary thermal absorber 151c. The secondary thermal insulator 151b reduces an amount of heat conducted from the thermal equalizer 152 to the secondary thermal absorber 151d through the primary thermal absorber 151c.
If the secondary thermal insulator 151b is thick excessively, the thick secondary thermal insulator 151b may prohibit heat stored in the fixing belt 104 from being conducted to the secondary thermal absorber 151d, rendering the fixing belt 104 to be susceptible to overheating or temperature increase of a non-conveyance span produced at both lateral ends of the fixing belt 104 in the axial direction thereof where the sheet S is not conveyed over the fixing belt 104. It is requested to determine the thickness and the width of the secondary thermal insulator 151b based on the degree of overheating or temperature increase of the non-conveyance span of the fixing belt 104. For example, the thickness of the secondary thermal insulator 151b is smaller than that of the primary thermal insulator 151a.
The secondary thermal absorber 151d is made of a material having a thermal conductivity greater than that of the primary thermal insulator 151a and the secondary thermal insulator 151b. The secondary thermal absorber 151d extends entirely in the longitudinal direction of the holder 51 that is parallel to the axial direction of the fixing belt 104. The secondary thermal absorber 151d contacts the primary thermal insulator 151a and the primary thermal absorber 151c.
The primary thermal absorber 151c is made of a material having a thermal conductivity greater than that of the primary thermal insulator 151a and the secondary thermal insulator 151b. The primary thermal absorber 151c extends partially in the longitudinal direction of the holder 51 that is parallel to the axial direction of the fixing belt 104. The primary thermal absorber 151c is sandwiched between the secondary thermal insulator 151b and the secondary thermal absorber 151d. The primary thermal absorber 151c is disposed outboard from a center span of the fixing belt 104 in the axial direction thereof and disposed opposite the non-conveyance span of the fixing belt 104 where the fixing belt 104 is susceptible to overheating or temperature increase.
The thermal equalizer 152 facilitates conduction of heat in a longitudinal direction thereof parallel to the axial direction of the fixing belt 104, equalizing an amount of heat stored in the fixing belt 104 and thereby suppressing overheating or temperature increase of the non-conveyance span of the fixing belt 104. Conversely, the primary thermal absorber 151c and the secondary thermal absorber 151d facilitate conduction of heat in a thickness direction DT of the holder 151 perpendicular to the longitudinal direction thereof and absorb heat from the thermal equalizer 152. That is, the primary thermal absorber 151c and the secondary thermal absorber 151d supplement shortage of thermal capacity of the thermal equalizer 152. For example, the secondary thermal absorber 151d has an increased thermal capacity or an increased surface area to increase heat dissipation.
The thermal equalizer 152 is disposed opposite the fixing belt 104 via the slide sheet 153. The thermal equalizer 152 includes an upstream arm 152b and a downstream arm 152c (e.g., bent portions) disposed at an upstream end and a downstream end of the thermal equalizer 152 in the sheet conveyance direction DS, respectively. The holder 151 and the upstream arm 152b and the downstream arm 152c of the thermal equalizer 152 sandwich the slide sheet 153 at an upstream portion and a downstream portion of the slide sheet 153 in a slide direction identical to the sheet conveyance direction DS in which the fixing belt 104 slides over the slide sheet 153, thus securing the slide sheet 153 to the nip formation pad 150 precisely. Accordingly, the fixing belt 104 is immune from temperature decrease in the conveyance span of the fixing belt 104 where the sheet S is conveyed over the fixing belt 104. Consequently, the fixing device 100 shortens the warm-up time and decreases power consumption.
The location of the primary thermal absorber 151c is not limited to the positions of the primary thermal absorber 151c illustrated in
The upstream arm 152b and the downstream arm 152c of the thermal equalizer 152 facilitate installation of the primary thermal insulator 151a, the secondary thermal insulator 151b, the primary thermal absorber 151c, and the secondary thermal absorber 151d on the thermal equalizer 152. The thermal equalizer 152 accommodates the primary thermal insulator 151a, the secondary thermal insulator 151b, the primary thermal absorber 151c, and the secondary thermal absorber 151d precisely. Alternatively, a projection may project from an inner face, that is, an upper face in
A description is provided of a construction of a comparative fixing device incorporating a fixing belt.
The comparative fixing device is requested to facilitate smooth rotation of the fixing belt so as to prevent a sheet conveyed through a fixing nip formed between the fixing belt and a pressure roller from being jammed between the fixing belt and the pressure roller. To address this request, the comparative fixing device includes a slide sheet containing a lubricant that is sandwiched between the fixing belt and a nip formation pad.
The slide sheet is a fabric made of a heat resistant, twisted fiber that generates a decreased friction and facilitates separation of the fixing belt from the slide sheet. For example, the fiber is made of PFA, PTFE, or the like. The slide sheet includes a pressed face that receives pressure from the pressure roller and a non-pressed face that does not receive pressure from the pressure roller. The pressed face has a diagonal twill line directed opposite a diagonal twill line of the non-pressed face to prevent the lubricant from leaking from one end of the slide sheet in an axial direction of the fixing belt through a gutter created on the slide sheet along the twill line.
However, the slide sheet in which the diagonal twill line on the pressed face is directed opposite the diagonal twill line on the non-pressed face abutting the pressed face is manufactured at increased costs. Additionally, since the diagonal twill line is open at both lateral ends of the pressed face and the non-pressed face, even if the diagonal twill line on the pressed face is directed opposite the diagonal twill line on the non-pressed face, the lubricant may leak from both lateral ends of the pressed face and the non-pressed face slightly. Alternatively, the lubricant may have an increased viscosity to prevent leakage from the slide sheet. However, the lubricant may increase a torque that rotates the fixing belt at a slide portion of the fixing belt that slides over the slide sheet, increasing a load imposed to the comparative fixing device.
Alternatively, the slide sheet may be a fabric produced by a plain weave. A direction of a texture of the slide sheet is identical to a rotation direction of the fixing belt. Since a gutter created by the texture of the slide sheet is parallel to the rotation direction of the fixing belt, the lubricant does not leak from both lateral ends of the slide sheet. However, the plain weave is disadvantageous in fiber strength and basis weight compared to a twill weave, degrading strength and durability against abrasion of the slide sheet.
A detailed description is now given of a configuration of the slide sheet 153.
As illustrated in
In a twill weave, each weft yarn floats across warp yarns in a progression of interlacing to the right or left, forming a distinct diagonal line defined by a gutter (e.g., a recess) and a ridge (e.g., a projection) on a surface of a fabric macroscopically. Accordingly, if the slide sheet 153 is constructed of a single sheet, the diagonal gutters on the surface of the fabric direct the lubricant rightward or leftward unevenly. Consequently, the lubricant may leak from a right end or a left end of the slide sheet 153.
To address this circumstance, the slide sheet 153 according to this exemplary embodiment has the double-layer structure in which the diagonal line on the first sheet 153a crosses the diagonal line on the second sheet 153b.
For example, a first inclination angle θa is defined by the diagonal wale of the first sheet 153a, that is, the first twill line La, relative to a direction perpendicular to the rotation direction R2 of the fixing belt 104. A second inclination angle θb is defined by the diagonal wale of the second sheet 153b, that is, the second twill line Lb, relative to the direction perpendicular to the rotation direction R2 of the fixing belt 104. Each of the first inclination angle θa and the second inclination angle θb is 45 degrees. Alternatively, each of the first inclination angle θa and the second inclination angle θb is not limited to 45 degrees and varies depending on a pattern of the twill weave. The diagonal, first twill line La on the first sheet 153a crossing the diagonal, second twill line Lb on the second sheet 153b offsets or reduces motion of the lubricant directed rightward or leftward, that is, to one lateral end or another lateral end of the slide sheet 153 in the axial direction of the fixing belt 104. Motion of the lubricant along the first twill line La of the first sheet 153a and the second twill line Lb of the second sheet 153b is entirely or partially converted into motion of the lubricant along the rotation direction R2 of the fixing belt 104 that crosses the first twill line La of the first sheet 153a and the second twill line Lb of the second sheet 153b.
The first direction D153a and the second direction D153b illustrating a direction of the first twill line La and a direction of the second twill line Lb, respectively, in
Accordingly, the lubricant does not flow unevenly rightward or leftward and therefore does not leak from the right end or the left end of the slide sheet 153, that is, one lateral end or another lateral end of the slide sheet 153 in the axial direction of the fixing belt 104. For example, the lubricant infiltrates the entire second sheet 153b of the slide sheet 153 evenly by capillarity and is retained by the second sheet 153b, improving retention of the lubricant by the slide sheet 153. Consequently, the fixing device 100 and the image forming apparatus 1 incorporating the fixing device 100 facilitate sliding of the fixing belt 104 over the slide sheet 153 for an extended period of time, improving the life of the fixing belt 104.
In order to allow the force exerted in the first direction D153a that moves the lubricant leftward in
If the slide sheet 153 is constructed of a single sheet, the whole slide sheet 153 is replaced with new one when the slide sheet 153 suffers from abrasion. However, with the slide sheet 153 constructed of the first sheet 153a and the second sheet 153b layered on the first sheet 153a, the second sheet 153b that suffers from abrasion is replaced with new one. Accordingly, a combination of a material of the first sheet 153a and a material of the second sheet 153b is adjusted to reduce replacement costs of the slide sheet 153.
For example, although the first sheet 153a placed under the second sheet 153b contacts the nip formation pad 150, the first sheet 153a does not contact the fixing belt 104. Hence, the first sheet 153a is requested to achieve resistance against heat and oil mainly. Conversely, since the fixing belt 104 slides over the second sheet 153b, the second sheet 153b is requested to achieve a decreased friction in addition to resistance against heat and oil mainly.
Accordingly, in view of manufacturing costs, the second sheet 153b over which the fixing belt 104 slides is a heat resistant, woven fabric made of fluoro resin, such as aramid fiber, PPS fiber, and nylon fiber, to achieve resistance against heat and oil and the decreased friction.
Conversely, the first sheet 153a not contacting the fixing belt 104 directly is a woven fabric made of non-fluoro resin fiber of aramid, PPS, or nylon. Generally, those materials are available at reduced costs compared to fluoro resin. Thus, the slide sheet 153 is produced with the woven fabric made of those fibers at reduced manufacturing costs.
A description is provided of a construction of a slide sheet 153S constructed of a single folded sheet.
As described above, the slide sheet 153 depicted in
The folded portion 153c of the slide sheet 153S is selectively placed at three positions (1), (2), and (3) described below to attain different advantages. At each of the positions (1), (2), and (3), the folded portion 153c adjoins a downstream side 153bD depicted in
A detailed description is now given of placement of the folded portion 153c at the position (1).
As illustrated in a solid line in
A detailed description is now given of a configuration of the grip portion 102c of the pressure roller 102.
The grip portion 102c is disposed on each lateral end span of the pressure roller 102 in an axial direction thereof, that is, a non-conveyance span of the pressure roller 102 where the sheet S is not conveyed over the pressure roller 102. The grip portion 102c has an increased friction coefficient to drive and rotate the fixing belt 104 supplementarily. For example, the grip portion 102c is made of heat resistant foam such as silicone rubber foam and fluoro rubber foam. The grip portion 102c having the increased friction coefficient, as the grip portion 102c is pressed against the fixing belt 104, grips the fixing belt 104 sufficiently, driving and rotating the fixing belt 104 stably in accordance with rotation of the pressure roller 102.
The grip portion 102c has a decreased epaxial hardness compared to the release layer 102d depicted in
As described above, the thickness of the folded portion 153c is greater than the thickness of other portions of the slide sheet 153S. Accordingly, the folded portion 153c may receive a local stress from the pressure roller 102. Similarly, the fixing belt 104 may receive a local stress from the pressure roller 102 and therefore may move unstably in the axial direction of the fixing belt 104.
To address this circumstance, the folded portion 153c is disposed opposite the grip portion 201c of the pressure roller 102. The grip portion 102c has the decreased epaxial hardness compared to other portions of the pressure roller 102 and exerts decreased pressure to the sheet S conveyed through the fixing nip 122. To address this circumstance, the folded portion 153c is disposed opposite the grip portion 102c, reducing the local stress exerted from the pressure roller 102 to the folded portion 153c and the fixing belt 104, preventing damage to the folded portion 153c, achieving the extended life of the slide sheet 153S, and stabilizing motion of the fixing belt 104.
A detailed description is now given of placement of the folded portion 153c at the position (2).
As illustrated in a dashed line in
As described above, the thickness of the folded portion 153c is greater than the thickness of other portions of the slide sheet 153S. If the folded portion 153c is disposed opposite the fixing belt 104, the thick folded portion 153c lifts the fixing belt 104, degrading stable motion of the fixing belt 104 throughout the entire axial span of the fixing belt 104. To address this circumstance, the folded portion 153c is disposed outboard from the nip formation pad 150 in the longitudinal direction thereof and disposed opposite the fixing belt 104 at an outboard span that is outboard from the pressure roller 102 in the axial direction thereof. Accordingly, the pressure roller 102 does not press the fixing belt 104 against the folded portion 153c directly, preventing the fixing belt 104 from being exerted with the local stress. In other words, the folded portion 153c is disposed opposite a non-pressurization span in the axial direction of the fixing belt 104 where the folded portion 153c does not receive pressure from the pressure roller 102.
A detailed description is now given of placement of the folded portion 153c at the position (3).
As illustrated in a long dashed double-short dashed line in
As described above, since the thickness of the folded portion 153c is greater than the thickness of other portions of the slide sheet 153S, the folded portion 153c changes motion of the fixing belt 104, degrading stable motion of the fixing belt 104 throughout the entire axial span of the fixing belt 104. To address this circumstance, the folded portion 153c is disposed outboard from the fixing belt 104 in the axial direction thereof. In other words, the folded portion 153c is disposed opposite the non-pressurization span in the axial direction of the fixing belt 104 where the folded portion 153c does not receive pressure from the pressure roller 102. Accordingly, the above-described disadvantageous circumstance is overcome.
The folded portion 153c may mount a lubricant absorber 155 made of heat resistant felt or the like as illustrated in
The construction and the configuration of the fixing device 100 are not limited to those of the exemplary embodiments described above. The present disclosure is not limited to the details of the exemplary embodiments described above and various modifications and improvements are possible.
A description is provided of advantages of the fixing device 100.
As illustrated in
As illustrated in
Accordingly, flow of the lubricant in the first direction D153a through the first gutter Ga on the first sheet offsets flow of the lubricant in the second direction D153b through the second gutter Gb on the second sheet, preventing the lubricant from moving unevenly rightward or leftward, that is, to one lateral end or another lateral end of the slide sheet in an axial direction of the endless belt, and therefore preventing the lubricant from leaking from one lateral end or another lateral end of the slide sheet in the axial direction of the endless belt. Consequently, the endless belt slides over the slide sheet smoothly, preventing the torque of a driver (e.g., the pressure roller 102) that drives and rotates the endless belt from increasing and thereby achieving the extended life of the fixing device 100.
For example, the first sheet and the second sheet of the slide sheet prevent the lubricant from leaking from both lateral ends of the slide sheet in the axial direction of the endless belt precisely at reduced costs, preventing the lubricant from staining the peripherals of the fixing device 100 due to leakage of the lubricant and preventing increase in the torque of the pressure rotator. Further, the first sheet and the second sheet achieve a sufficient strength and a sufficient durability against abrasion, extending the life of the slide sheet.
According to the exemplary embodiments described above, the fixing belt 104 serves as an endless belt. Alternatively, a fixing film, a fixing sleeve, or the like may be used as an endless belt. Further, the pressure roller 102 serves as a pressure rotator. Alternatively, a pressure belt or the like may be used as a pressure rotator.
The present disclosure has been described above with reference to specific exemplary embodiments. Note that the present disclosure is not limited to the details of the embodiments described above, but various modifications and enhancements are possible without departing from the spirit and scope of the disclosure. It is therefore to be understood that the present disclosure may be practiced otherwise than as specifically described herein. For example, elements and/or features of different illustrative exemplary embodiments may be combined with each other and/or substituted for each other within the scope of the present disclosure.
Number | Date | Country | Kind |
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2015-054962 | Mar 2015 | JP | national |
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20160274515 A1 | Sep 2016 | US |