This application claims priority from Japanese Patent Application No. 2016-070189 filed on Mar. 31, 2016, the content of which is incorporated herein by reference in its entirety.
Aspects disclosed herein relate to a fixing device.
Belt-fixing type fixing devices have been known as fixing devices that are included in, for example, printers or copying machines, and that fix a toner image onto a sheet by heating the sheet. Some fixing device includes a belt, a nip member, a sliding sheet, and a fastening member. The nip member is disposed inside a loop of the belt. The sliding sheet is sandwiched between the belt and the nip member. The fastening member is disposed opposite to the belt relative to the nip member. In such a fixing device, end portions of the sliding sheet in a circumferential direction of the belt are fastened to the fastening member by elastic force of plate springs.
The sliding sheet may be used for reducing sliding resistance occurring at a fixing nip area during rotation of the belt, and may have a contact surface that may contact an inner circumferential surface of the belt. Therefore, the sliding sheet may be configured such that a frictional force to be caused by sliding of the contact surface of the sliding sheet relative to the inner circumferential surface of the belt is smaller than a frictional force to be caused by sliding of the sliding sheet relative to a surface of the nip member. Nevertheless, the frictional force of the contact surface of the sliding sheet relative to the inner circumferential surface of the belt may increase due to long-term usage of the fixing device. The increase of the frictional force may further cause increase of a force pulling the sliding sheet along the circumferential direction of the belt. In the known fixing device, the sliding sheet may be fastened to the fastening member while the both end portions of the sliding sheet in the circumferential direction of the belt are pressed by the elastic force of the plate springs. Nevertheless, this configuration may let one of the end portions of the sliding sheet, more specifically, for example, the upstream end portion of the sliding sheet in a belt rotating direction, slip off from between the plate springs and the fastening member. In another case, the sliding sheet may have been stretched due to pulling of the sliding sheet in the belt rotating direction, and become larger than the original size. In a state where the sliding sheet has become larger, when the nip of the belt at the fixing nip area is released and the belt is nipped again at the fixing nip area, the sliding sheet may crease or wrinkle at its portion sandwiched between the nip member and the belt.
Accordingly, some embodiments of the disclosure provide for a technique for solving at least one of the above-described problems.
According to one aspect, there is provided a fixing device comprising: an endless belt; a roller being in contact with an outer surface of the endless belt; a nip plate disposed in the endless belt; a supporting member disposed in the endless belt and supporting the nip plate; a spring member disposed in the endless belt between the nip plate and the supporting member, the spring member urged in a first direction away from the nip plate toward the supporting member; and a sliding sheet having a first surface and a second surface opposite the first surface, the sliding sheet is nipped with the endless belt between the nip plate and the roller, the first surface is in contact with an inner surface of the endless belt and the second surface of the sliding sheet is in contact with the nip plate. The sliding sheet is fastened to a facing surface of the spring member that is facing toward the supporting member and away from the nip plate, and the second surface contacts the spring member.
According to another aspect, there is provided a fixing device comprising: an endless belt, a roller being in contact with an outer surface of the endless belt, a nip plate disposed in the endless belt, a supporting member supporting the nip plate, a plate portion located between the nip plate and the supporting member, a spring portion urging the plate portion in a first direction away from the nip plate toward the supporting member, and a sliding sheet being in contact with an inner surface of the endless belt and nipped with the endless belt between the nip plate and the roller, the sliding sheet being fastened to the plate portion.
The technique disclosed in the disclosure may be implemented by various manners, for example, may be implemented in fixing devices or image forming apparatuses including fixing devices.
Aspects of the disclosure are illustrated by way of example and not by limitation in the accompanying figures in which like reference characters indicate similar elements.
Hereinafter, a printer 10 according to an illustrative embodiment will be described.
As illustrated in
The sheet feeding unit 200 includes a tray 210 and a pickup roller 220. The tray 210 is configured to accommodate one or more sheets W therein. The pickup roller 220 picks up, one by one, the one or more sheets W accommodated in the tray 210 and to feed the picked sheet W toward the image forming unit 400.
The image forming unit 400 includes an exposure unit 500, a process unit 600, and a fixing device 700. The exposure unit 500 irradiates a surface of a photosensitive drum 610 of the process unit 600 with laser light L (e.g., a light beam).
The process unit 600 includes the photosensitive drum 610, a charger 620, a developing unit 630, and a transfer roller 640. The charger 620 charges the surface of the photosensitive drum 610 uniformly. Subsequent to charging of the surface of the photosensitive drum 610 by the charger 620, the exposure unit 500 irradiates the surface of the photosensitive drum 610 with laser light L to form an electrostatic latent image thereon. Then, the developing unit 630 supplies toner onto the surface of the photosensitive drum 610 to develop the electrostatic latent image, and thus, a toner image is formed thereon. The toner image is then transferred onto a sheet W by the transfer roller 640 while the sheet W passes between the photosensitive drum 610 and the transfer roller 640.
The fixing device 700 fixes the toner image transferred onto the sheet W thereon by applying heat to the sheet W that has passed the process unit 600. Thus, an image is formed on the sheet W. The discharge rollers 130 discharge the sheet W that has passed the fixing device 700, onto the discharge tray 120 via the discharge port 110. Hereinafter, a path through which a sheet W is conveyed from the sheet feeding unit 200 to the discharge rollers 130 is referred to as a conveyance path R, and a direction that a sheet W moves at the fixing device 700 along the conveyance path R is referred to as a sheet conveyance direction F. More specifically, for example, a direction extending from a position where a sheet W enters a nip portion P of the fixing device 700 toward a position where the sheet W exits from the nip portion P of the fixing device 700 is referred to as the sheet conveyance direction F. The sheet conveyance direction F extends along the X axis.
The rotary heating unit 710 may have a cylindrical shape and is long in the width direction Y orthogonal to the sheet conveyance direction F. The width direction Y extends along the Y axis. The rotary pressure-application member 720 may be a roller rotatable on an axis extending substantially parallel to the width direction Y. The rotary pressure-application member 720 is pressed toward the rotary heating unit 710 and thus the rotary heating unit 710 and the rotary pressure-application member 720 form the nip portion P therebetween. The rotary pressure-application member 720 is an example of a backup member. The rotary heating unit 710 and the rotary pressure-application member 720 are disposed one above the other in a direction extending parallel to the Z axis. Hereinafter, a direction from the rotary pressure-application member 720 toward the rotary heating unit 710 is referred to as the pressing direction N. More specifically, the pressing direction N may be orthogonal to both the sheet conveyance direction F and the width direction Y and may extend along the Z axis. A relatively upstream side in the pressing direction N may be referred to as “above” or “upward”, and a relatively downstream side in the pressing direction N may be referred to as “below” or “downward”.
The rotary heating unit 710 includes a fixing belt 711, a halogen heater 713, the nip member 714, a reflector 715, a stay 716, a heat insulator 717, the plate spring 800, the sliding sheet 900, and the retainers 850. Each of the stay 716 and the heat insulator 717 is an example of a supporting member.
The fixing belt 711 may be an annular belt having a width along the width direction Y. The fixing belt 711 is configured to rotate on an axis extending along the width direction Y. The fixing belt 711 may be made of metal, for example, stainless steel or nickel. The halogen heater 713 may have a rod-like shape that is long in the width direction Y. The halogen heater 713 is configured to generate heat by application of power from an alternating-current power supply (not illustrated). The halogen heater 713 is disposed inside a loop of the fixing belt 711 while being spaced apart from an inner circumferential surface of the fixing belt 711. The fixing belt 711 is an example of an endless belt. The halogen heater 713 is an example of a heater.
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The plate spring 800 has female portions 813 of press fasteners in the plate portion 810. More specifically, for example, each of the female portions is defined in a middle portion of the plate portion 810 in the sheet conveyance direction F and between corresponding pairs of through holes 811 in the width direction Y. The through holes 811 in each pair are opposite to each other in the sheet conveyance direction F. Each of the female portions 813 has a lower end portion that protrudes downward relative to a lower surface of the plate portion 810. The plate portion 810 has pairs of recesses 812 in its upper surface. A single pair of recesses 812 is positioned each upstream and downstream of each of the female portions 813 in the sheet conveyance direction F. The recesses 812 in each pair are positioned side by side in the width direction Y.
The folded-back portions 820 extend downwardly toward the nip member 714 from respective ends of the plate portion 810 in the sheet conveyance direction F. When viewed in the width direction Y, directions that the respective folded-back portions 820 extend are angled relative to the pressing direction N. More specifically, for example, an angle which each of the folded-back portions 820 forms with the plate portion 810 is acute. In other words, a distance between the folded-back portions 820 decreases toward their distal ends.
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The sliding sheet 900 has a plurality of, for example, three, through holes 910 penetrating in each of the longer-side end portions. The through holes 910 defined in each of the longer-side end portions are spaced apart from each other in the width direction Y. The through holes 910 are larger in size than the through holes 811 of the plate portion 810. Each of the through holes 910 is an example of a second through hole. The sliding sheet 900 further includes a plurality of, for example, two, first tabs 920 at one of the longer-side end portions. Each of the first tabs 920 protrudes relative to one of longer-side ends of the sliding sheet 900 in the sheet conveyance direction F. The first tabs 920 are spaced apart from each other in the width direction Y. Each of the first tabs 920 is positioned between corresponding adjacent two of the through holes 910 in the sheet conveyance direction F. Each of the first tabs 920 includes a male portion 930 of the press fasteners. The male portion 930 is configured to engage the female portion 813 of the press fasteners. The sliding sheet 900 further includes, a plurality of, for example, two, second tabs 940 at the other of the longer-side end portions. Each of the second tabs 940 protrudes relative to the other of the longer-side ends of the sliding sheet 900 in the sheet conveyance direction F. The second tabs 940 are spaced apart from each other in the width direction Y. Each of the second tabs 940 is positioned between corresponding adjacent two of the through holes 910 in the sheet conveyance direction F. Each of the second tabs 940 has a through hole 950 penetrating therethrough. The through hole 950 is an example of a third through hole.
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According to the illustrative embodiment, the sliding sheet 900 is fastened to the plate portion 810 of the plate spring 800, and the plate portion 810 is urged in the direction away from the nip member 714 by the projecting portions 822 of the folded-back portions 820. With this configuration, therefore, tension is applied to the sliding sheet 900 in the sheet conveyance direction F. In other words, the central portion of the sliding sheet 900 is always pulled by the longer-side end portions of the sliding sheet 900, more specifically, by the first and second tabs 920 and 940. Therefore, this configuration may reduce occurrence of creases or wrinkles in the central portion of the sliding sheet 900. In the illustrative embodiment, the plate spring 800 is positioned between the stay 716 and the nip member 714. Therefore, as compared with a case where the plate portion and the spring portion are disposed upstream or downstream of the nip member 714 in the sheet conveyance direction F, the outside diameter of the fixing belt 711 may be reduced and therefore the fixing device 700 may be reduced in size.
The through holes 811 of the plate portion 810 are engaged with the respective protrusions 714B of the nip member 714. This configuration may reduce a positional deviation between the plate spring 800 and the nip member 714. The sliding sheet 900 has the through holes 910 for engaging the respective protrusions 714B of the nip member 714. With this configuration, the through holes 910 of the sliding sheet 900 are engaged with the respective protrusions 714B, whereby the sliding sheet 900 may be further surely fastened to the plate portion 810 of the plate spring 800.
The plate spring 800 includes the plate portion 810 as the plate portion and the projecting portion 822 as the spring portion that are in one piece and inseparable from each other. Therefore, as compared with a case where the plate portion and the spring portion are separate members, this configuration may enable reduction of the parts count. When viewed in the width direction Y, the projecting portions 822 are angled relative to the pressing direction N and the projecting portions 822 urge the plate portion 810 in the direction away from the nip member 714 by their restoring force occurring due to elastic deformation of the projecting portions 822. As described above, the spring portion may be provided readily in the plate spring 800 by bending. In the illustrative embodiment, the plate spring 800 includes the folded-back portions 820 at the respective ends thereof in the sheet conveyance direction F. Therefore, as compared with a case where the plate spring 800 includes only one of the folded-back portions 820 at one of the ends thereof in the sheet conveyance direction F, this configuration may enable the plate portion 810 to move always in the pressing direction N.
The first tabs 920 of the one of the longer-side end portions of the sliding sheet 900 and the second tabs 940 of the other of the longer-side end portions of the sliding sheet 900 are both fastened to the plate portion 810 of the plate spring 800. That is, the upstream end portion and the downstream end portion of the sliding sheet 900 in the sheet conveyance direction F are both fastened to the plate portion 810 of the plate spring 900. Therefore, as compared with a case where only either one of the longer-side end portions of the sliding sheet 900 is fastened to the plate portion 810, this configuration may enable uniform application of tension to the sliding sheet 900. In the illustrative embodiment, the first tabs 920 and the second tabs 940 of the sliding sheet 900 are fastened to the plate portion 810 with overlapping each other. Therefore, as compared with a case where the first tabs 920 and the second tabs 940 of the sliding sheet 900 are fastened to the plate portion 810 at respective different positions without overlapping each other, this configuration may enable reduction of the parts count.
The plate portion 810 of the plate spring 800 is longer in length than the sliding sheet 900 in the width direction Y. As illustrated in
Using the retainers 850 may enable the firm fastening of the sliding sheet 900 to the plate portion 810. In the illustrative embodiment, the stay 716 and the heat insulator 717 are positioned between the halogen heater 713 and the plate spring 800. Therefore, this configuration may enable reduction of heat transfer from the halogen heater 713 to the plate spring 800, which may further reduce deterioration of the plate spring 800 and the sliding sheet 900 due to exposure to heat.
In the illustrative embodiment, the sliding sheet 900 is fastened to the plate spring 800 by engagement of the male portions 930 and the female portions 813 of the press fasteners. Therefore, this configuration might not necessarily require use of adhesive for fastening the sliding sheet 900 to the plate spring 800.
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When viewed in the width direction Y, the second portion 820X of the plate spring 800X is angled relative to the pressing direction N and is spaced apart from the upper surface of the nip member 714X. A downstream end portion of the sliding sheet 900X in the sheet conveyance direction F is positioned on an upper surface of the second portion 820X of the plate spring 800X and the plate-shaped retainer 850X are positioned on the downstream end portion of the sliding sheet 900X. In this state, a screw 930X is screwed in a nut 950X via a through hole of the sliding sheet 900X and a through hole of the second portion 820X of the plate spring 800X. The nut 950X is positioned on a lower surface side of the second portion 820X of the plate spring 800X. Thus, the downstream end portion of the sliding sheet 900X is fastened with being sandwiched between the second portion 820X of the plate spring 800X and the retainer 850X. In this state, the downstream end portion of the second portion 820X is elastically deformed downward and thus the sliding sheet 900 X is held under tension by restoring force of the second portion 820X of the plate spring 800X. More specifically, for example, the downstream portion of the sliding sheet 900 in the sheet conveyance direction F is applied with greater tension than tension applied to the upstream portion of the sliding sheet 900 in the sheet conveyance direction F. The second portion 820X is another example of the plate portion and another example of the spring portion.
The sliding sheet 900X is pulled along the sheet conveyance direction F in response to rotation of the fixing belt 713. In a case where the sliding sheet 900 becomes non-contractile, therefore, the sliding sheet 900 becomes loose and the loose portion may tend to gather at a location downstream of the nip member 714X in the sheet conveyance direction F. According to the illustrative embodiment, the upstream end portion of the sliding sheet 900X in the sheet conveyance direction F is fastened to the nip member 714X and the downstream end portion of the sliding sheet 900X in the sheet conveyance direction F is fastened to the second portion 820X of the plate spring 800X. Therefore, tension may be applied to the downstream end portion of the sliding sheet 900X rather than the upstream end portion thereof. Therefore, this configuration may reduce or restrict the sliding sheet 900 from becoming loose and the loose portion from gathering at its portion downstream of the nip member 714X in the sheet conveyance direction F.
The nip member 714X further includes a plurality of protrusions 714B similar to the nip member 714. Therefore, the plate spring 800X is positioned in one of spaces, each of which is provided between the pairs of protrusions 714B in the width direction Y. That is, the plate spring 800X has a smaller dimension in the width direction Y than the distance (e.g., the space) between adjacent protrusions 714B in the width direction Y. In this case, it is preferable that a plurality of plate springs 800X are disposed in the width direction Y. More specifically, a single plate spring 800X may be disposed in each of the spaces provided between the pairs of protrusions 714B in the width direction Y.
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According to this alternative embodiment, the plate portion and the spring portion may be provided by an extremely simple process (e.g., folding a metal plate in half).
While the disclosure has been described in detail with reference to the specific embodiments thereof, these are merely examples, and various changes, arrangements and modifications may be applied therein without departing from the spirit and scope of the disclosure.
In other embodiments, for example, a plurality of plate springs may be provided. In this case, each of the plate springs may have a width substantially equal to or shorter than the width of the space between corresponding pairs of protrusions 714B of the nip member 714 in the width direction Y. The protrusions 714B in each pair are opposite to each other in the sheet conveyance direction F. Each of the plate springs may be disposed in a corresponding one of the spaces therebetween.
In other embodiments, for example, the sliding sheet 900 may be fastened to the plate spring 800 or the nip member 714 by swaging or using staples, as well as the press fasteners or screws. In another example, adhesive may be used for fastening the sliding sheet 900 to the plate spring 800 or the nip member 714.
In other embodiments, for example, the distance between the folded-back portions 820 of the plate spring 800 may increase toward the distal ends of the folded-back portions 820. In other embodiments, for example, the plate spring 800 may include either one of the folded-back portions 820 only. In other embodiments, for example, the folded-back portions 820 may extend downward toward the nip member 714 from respective ends of the plate portion 810 in the width direction Y.
In the illustrative embodiment, each of the through holes 811 is defined by an endless edge. Nevertheless, in other embodiments, for example, each through hole may be defined by an edge having ends that might not be joined if each of the through holes is capable of engaging a corresponding protrusion 714B of the nip member 714 against restring force of the plate spring 800.
In other embodiments, for example, each of the retainers 850 may include the male portion of the press fasteners. In this case, the male portion of each of the retainers 850 may be engaged with a corresponding one of the female portions 813 of the press fasteners of the plate spring 800 via a through hole (not illustrated) of the first tab 920 and the through hole 950 of the second tab 940. Through the engagement of the male portions and the respective female portions of the press fasteners, the longer-side end portions of the sliding sheet 900 may be fastened to the nip member 714. In other embodiments, for example, the plate spring 800 may have the male portions of the press fasteners and each of the first tabs 920 of the sliding sheet 900 or each of the retainers 850 may have the female portion of the press fasteners.
The printer 10 is an example of an image forming apparatus including the fixing device 700. In the illustrative embodiment, the printer 10 performs printing using toner of a single color (e.g., black). Nevertheless, the toner colors and the number of toner colors are not limited to the specific example. In other embodiments, for example, the image forming apparatus may include copying machines, facsimile machines, and multifunction devices as well as printers. The disclosure may be applied to those devices. The fixing device 700 may be included in any device as well as the image forming apparatus.
In the illustrative embodiment, the halogen heater 713 is taken as an example of the heater of the fixing device. Nevertheless, in other embodiments, for example, the heater may be an infrared heater or a carbon heater. The heater may be disposed outside the loop of the endless belt.
Number | Date | Country | Kind |
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2016-070189 | Mar 2016 | JP | national |
Number | Name | Date | Kind |
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20100202809 | Shinshi | Aug 2010 | A1 |
Number | Date | Country |
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2010-181821 | Aug 2010 | JP |
2013-214039 | Oct 2013 | JP |
2014-145858 | Aug 2014 | JP |
Number | Date | Country | |
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20170285539 A1 | Oct 2017 | US |