Patent Grant
8843043
The present application is based on and claims priority to Japanese Patent Application No. 2010-041952, filed on Feb. 26, 2010, in the Japan Patent Office, which is hereby incorporated herein by reference in its entirety.
1. Field of the Invention
Exemplary aspects of the present invention 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 including the fixing device.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of an image carrier; an optical writer emits a light beam onto the charged surface of the image carrier to form an electrostatic latent image on the image carrier according to the image data; a development device supplies toner to the electrostatic latent image formed on the image carrier to make the electrostatic latent image visible as a toner image; the toner image is directly transferred from the image carrier onto a recording medium or is indirectly transferred from the image carrier onto a recording medium via an intermediate transfer member; a cleaner then cleans the surface of the image carrier after the toner image is transferred from the image carrier onto the recording medium; 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.
The fixing device used in such image forming apparatuses may include a fixing belt to apply heat to the recording medium bearing the toner image.
In order to provide a shortened warm-up time and reduced power consumption compared to the fixing device 50R1 using the fixing belt 25, the fixing device may instead employ a fixing film formed into a loop and having a smaller heat capacity than the fixing belt 25.
With the fixing film 14 having a smaller heat capacity than the fixing belt 25, the fixing device 50R2 can be heated to a predetermined fixing temperature by turning on the ceramic heater 13 immediately before an image forming operation is started. Thus, the fixing device 50R2 is warmed up quickly while at the same time reducing power consumption.
However, the fixing device 50R2 using the fixing film 14 has a drawback in that the fixing film 14 may wear due to friction generated between the stationary ceramic heater 13 and the rotating fixing film 14 that slides over the ceramic heater 13. Accordingly, the worn fixing film 14 with a roughened inner circumferential surface may increase friction between the fixing film 14 and the ceramic heater 13, resulting in unstable rotation of the fixing film 14 and increased driving torque of the fixing device 50R2. The fixing device 50R2 also has a drawback in that the fixing film 14 is heated by the ceramic heater 13 only at the fixing nip, and therefore the fixing film 14 is coolest when entering the fixing nip. Accordingly, when the fixing film 14 is rotated at a high speed, the fixing film 14 may not have been heated to a desired fixing temperature by the time the fixing film 14 enters the fixing nip and contacts the recording medium there.
To address these problems, the fixing device may instead employ a combination of a looped fixing belt and a cylindrical metal heat conductor instead of the fixing film 14 and the ceramic heater 13. For example, the metal heat conductor fixedly mounted inside the looped fixing belt receives heat from a heater provided inside the cylindrical metal heat conductor, and then transmits the heat to the fixing belt. A pressing roller presses the fixing belt against the metal heat conductor to form a fixing nip between the pressing roller and the fixing belt through which the recording medium bearing the toner image passes. With this configuration, the entire fixing belt is heated by the metal heat conductor, which faces substantially the entire portion of the fixing belt as the rotating fixing belt slides over the metal heat conductor. Further, the inner diameter of the fixing belt is set greater than the outer diameter of the metal heat conductor to reduce friction between the metal heat conductor and the fixing belt.
However, the fixing belt and the metal heat conductor have a drawback in that the fixing belt may slacken at a position downstream from the fixing nip in the direction of rotation of the fixing belt. Specifically, the rotating pressing roller pulls the upstream portion of the fixing belt provided upstream from the fixing nip in the direction of rotation of the fixing belt to the fixing nip in such a manner that the upstream portion of the fixing belt is stretched over the metal heat conductor. By contrast, the rotating pressing roller does not stretch the downstream portion of the fixing belt provided downstream from the fixing nip in the direction of rotation of the fixing belt, slackening the downstream portion of the fixing belt. Accordingly, the slackened fixing belt heated by the metal heat conductor contacts the recording medium bearing the fixed toner image at the position downstream from the fixing nip in the direction of rotation of the fixing belt for a longer time, and therefore heats the recording medium excessively, causing hot offset of the toner image fixed on the recording medium. Moreover, the slackened fixing belt disturbs separation of the recording medium discharged from the fixing nip from the fixing belt, causing jamming of the recording medium.
This specification describes below an improved fixing device. In one exemplary embodiment of the present invention, the fixing device includes a flexible, endless belt-shaped fixing member, a substantially cylindrical metal heat conductor, a pressing member, and a separator. The flexible, endless belt-shaped fixing member rotates in a predetermined direction of rotation, and is formed into a loop. The substantially cylindrical metal heat conductor is provided inside the loop formed by the fixing member and faces an inner circumferential surface of the fixing member. The pressing member presses the fixing member against the metal heat conductor to form a nip between the fixing member and the pressing member through which a recording medium bearing a toner image passes. The separator, which presses the fixing member against the metal heat conductor, is provided downstream from the nip in the direction of rotation of the fixing member and contacts the recording medium discharged from the nip to separate the recording medium from the fixing member and guide the recording medium out of the fixing device.
This specification further describes an image forming apparatus. In one exemplary embodiment, the image forming apparatus includes the fixing device described above.
A more complete appreciation of the invention 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
As illustrated in
The image forming portion 110 forms a toner image on a recording medium by electrophotography and includes image forming devices 1a, 1b, 1c, and 1d, an intermediate transfer belt 7, first transfer rollers 8a, 8b, 8c, and 8d, support rollers 15a and 15b, a second transfer roller 18, and a belt cleaner 19.
The four image forming devices 1a, 1b, 1c, and 1d have an identical structure but use toners in colors different from each other, for example, black, magenta, cyan, and yellow toners to form black, magenta, cyan, and yellow toner images, respectively.
The image forming devices 1a, 1b, 1c, and 1d include photoconductors 2a, 2b, 2c, and 2d, chargers 3a, 3b, 3c, and 3d, development devices 4a, 4b, 4c, and 4d, and cleaners 5a, 5b, 5c, and 5d, respectively.
The photoconductors 2a, 2b, 2c, and 2d serving as electrostatic latent image carriers having a drum shape are surrounded by the chargers 3a, 3b, 3c, and 3d, the development devices 4a, 4b, 4c, and 4d, and the cleaners 5a, 5b, 5c, and 5d, respectively. The photoconductors 2a, 2b, 2c, and 2d rotate clockwise in
The exposure device 9 is disposed diagonally with respect to a horizontal plane below the four image forming devices 1a, 1b, 1c, and 1d in such a manner that the exposure device 9 is disposed parallel to the four image forming devices 1a, 1b, 1c, and 1d. The exposure device 9 includes optical units including a light source, a polygon mirror, fθ lenses, and reflection mirrors, and exposes the photoconductors 2a, 2b, 2c, and 2d charged by the chargers 3a, 3b, 3c, and 3d according to black, magenta, cyan, and yellow image data sent from a client computer, for example, to form electrostatic latent images corresponding to the black, magenta, cyan, and yellow image data on the photoconductors 2a, 2b, 2c, and 2d, respectively.
As the electrostatic latent images formed on the photoconductors 2a, 2b, 2c, and 2d pass through the development devices 4a, 4b, 4c, and 4d in accordance with rotation of the photoconductors 2a, 2b, 2c, and 2d, the development devices 4a, 4b, 4c, and 4d supply black, magenta, cyan, and yellow toners to the electrostatic latent images formed on the photoconductors 2a, 2b, 2c, and 2d to make the electrostatic latent images visible as black, magenta, cyan, and yellow toner images, respectively.
The toner bottles 20a, 20b, 20c, and 20d are provided in the upper portion of the image forming apparatus 100, and contain black, magenta, cyan, and yellow toners to be supplied to the development devices 4a, 4b, 4c, and 4d through conveyance paths, respectively.
The intermediate transfer belt 7 serving as an intermediate transfer member having an endless belt shape is disposed opposite the photoconductors 2a, 2b, 2c, and 2d in such a manner that the photoconductors 2a, 2b, 2c, and 2d contact an outer circumferential surface of the intermediate transfer belt 7. The intermediate transfer belt 7 is looped over a plurality of support rollers, that is, the support rollers 15a and 15b. For example, the support roller 15a is connected to a driving motor serving as a driver. When the driving motor is driven, the driving motor drives and rotates the support roller 15a, so that the rotating support roller 15a rotates the intermediate transfer belt 7 counterclockwise in
The first transfer rollers 8a, 8b, 8c, and 8d face an inner circumferential surface of the intermediate transfer belt 7, and are disposed opposite the photoconductors 2a, 2b, 2c, and 2d via the intermediate transfer belt 7. A high-voltage power source applies a first transfer bias to the first transfer rollers 8a, 8b, 8c, and 8d to primarily transfer the black, magenta, cyan, and yellow toner images formed on the photoconductors 2a, 2b, 2c, and 2d onto the outer circumferential surface of the intermediate transfer belt 7 to form a color toner image on the intermediate transfer belt 7.
After the transfer of the black, magenta, cyan, and yellow toner images, the cleaners 5a, 5b, 5c, and 5d remove residual black, magenta, cyan, and yellow toners not transferred and therefore remaining on the photoconductors 2a, 2b, 2c, and 2d from the photoconductors 2a, 2b, 2c, and 2d, respectively. Thus, the photoconductors 2a, 2b, 2c, and 2d become ready for a next image forming operation.
The second transfer roller 18 serving as a second transfer member is provided downstream from the first transfer rollers 8a, 8b, 8c, and 8d in a rotation direction of the intermediate transfer belt 7. The second transfer roller 18 is disposed opposite the support roller 15b via the intermediate transfer belt 7 in such a manner that the second transfer roller 18 and the support roller 15b form a second transfer nip therebetween via the intermediate transfer belt 7 at which the color toner image formed on the intermediate transfer belt 7 is secondarily transferred onto a recording medium.
The paper tray 10 loads recording media to be conveyed to the second transfer nip by the feed roller 41 and the registration roller pair 42. The fixing device 50 is provided downstream from the second transfer roller 18 in a recording medium conveyance direction, and applies heat and pressure to the recording medium bearing the toner image which is sent from the second transfer nip to fix the toner image on the recording medium. The output roller pair 43 is provided downstream from the fixing device 50 in the recording medium conveyance direction, and discharges the recording medium bearing the fixed toner image which is sent from the fixing device 50 onto an output tray provided atop the image forming apparatus 100 to receive and stack the recording medium discharged by the output roller pair 43.
The following describes image forming processes performed by the image forming apparatus 100.
When the image forming apparatus 100 receives an image forming signal from an external device such as a client computer, a driver drives and rotates the photoconductors 2a, 2b, 2c, and 2d clockwise in
Thereafter, the chargers 3a, 3b, 3c, and 3d uniformly charge the surfaces of the photoconductors 2a, 2b, 2c, and 2d having the initialized potential to have a predetermined polarity. The exposure device 9 emits laser beams onto the charged surfaces of the photoconductors 2a, 2b, 2c, and 2d according to black, magenta, cyan, and yellow image data sent from the external device to form desired electrostatic latent images on the surfaces of the photoconductors 2a, 2b, 2c, and 2d. The black, magenta, cyan, and yellow image data are obtained by separating desired full-color image data into image data corresponding to black, magenta, cyan, and yellow colors. As the electrostatic latent images formed on the photoconductors 2a, 2b, 2c, and 2d pass through the development devices 4a, 4b, 4c, and 4d, the development devices 4a, 4b, 4c, and 4d supply developer, that is, black, magenta, cyan, and yellow toners, to the electrostatic latent images to make the electrostatic latent images visible as black, magenta, cyan, and yellow toner images, respectively.
The intermediate transfer belt 7 rotates counterclockwise in
On the other hand, the feed roller 41 picks up and feeds an uppermost recording medium of recording media loaded on the paper tray 10 toward the registration roller pair 42. Specifically, the feed roller 41 separates the uppermost recording medium from other recording media loaded on the paper tray 10, and conveys the uppermost recording medium to a nip formed between two rollers of the registration roller pair 42 which stops rotating temporarily. For example, a leading edge of the uppermost recording medium contacts the nip formed between the two rollers of the registration roller pair 42 and the recording medium is formed into a loop for its registration.
Thereafter, the registration roller pair 42 resumes rotating, and sends the recording medium toward the second transfer nip formed between the second transfer roller 18 and the support roller 15b via the intermediate transfer belt 7 at a proper time at which the recording medium contacts the full-color toner image formed on the intermediate transfer belt 7.
According to this exemplary embodiment, the second transfer roller 18 is applied with a transfer bias having a polarity opposite a polarity of the full-color toner image formed on the intermediate transfer belt 7 to transfer the full-color toner image onto the recording medium. Thus, the recording medium carries the unfixed toner image, and is conveyed to the fixing device 50. After the transfer of the full-color toner image onto the recording medium, the belt cleaner 19 removes and collects residual toner not transferred and therefore remaining on the intermediate transfer belt 7 from the intermediate transfer belt 7.
As the recording medium bearing the unfixed toner image passes through the fixing device 50, the fixing device 50 applies heat and pressure to the recording medium to fix the toner image on the recording medium as the semi-permanently fixed full-color toner image.
Thereafter, the recording medium bearing the fixed toner image is conveyed to the output roller pair 43. The output roller pair 43 discharges the recording medium bearing the fixed toner image onto the output tray, thus completing a series of image forming processes.
Referring to
The fixing belt 31 is a flexible endless belt serving as a fixing member that applies heat to a recording medium. According to this exemplary embodiment, the fixing belt 31 serves as a fixing member. Alternatively, instead of the fixing belt 31, an endless film may be used as the fixing member. The metal heat conductor 34 has a pipe shape or a hollow cylindrical shape, and is provided inside the loop formed by the fixing belt 31 in such a manner that the metal heat conductor 34 faces an inner circumferential surface of the fixing belt 31. For example, the metal heat conductor 34 is fixedly mounted close to the inner circumferential surface of the fixing belt 31 in a state in which the metal heat conductor 34 is not rotatable. The heater 35 (e.g., a halogen heater) is provided inside the hollow cylinder of the metal heat conductor 34, and heats the metal heat conductor 34. The pressing roller 6, serving as a pressing member, is pressed against the nip formation member 32 via the fixing belt 31 to form a fixing nip N between the pressing roller 6 and the fixing belt 31. With this configuration, the fixing belt 31 is heated by heat transmitted from the metal heat conductor 34 heated by the heater 35, and slides over an outer circumferential surface of the metal heat conductor 34 fixedly mounted inside the loop formed by the fixing belt 31 in accordance with rotation of the pressing roller 6. In other words, the fixing belt 31 is rotated by the rotating pressing roller 6.
The nip formation member 32 (e.g., a pad) is provided inside the loop formed by the fixing belt 31 in such a manner that the nip formation member 32 is provided between the metal heat conductor 34 and the fixing belt 31, and is pressed against the pressing roller 6 via the fixing belt 31 to form the fixing nip N between the fixing belt 31 and the pressing roller 6. The nip formation member 32 is supported by the metal heat conductor 34 via the heat insulator 36 that insulates the nip formation member 32 from heat held by the metal heat conductor 34 to improve heating efficiency of the metal heat conductor 34 for heating the fixing belt 31.
The support member 33 is fixedly mounted inside the hollow cylinder of the metal heat conductor 34, and supports a concave portion of the metal heat conductor 34 which supports the nip formation member 32. A lubricant (e.g., silicon oil or fluorine grease) is applied between the metal heat conductor 34 and the fixing belt 31 to decrease friction generated between the fixing belt 31 and the metal heat conductor 34 as the rotating fixing belt 31 slides over the outer circumferential surface of the metal heat conductor 34 fixedly mounted inside the fixing belt 31.
Optionally, the mesh-like lubrication sheet 37 may be provided between the nip formation member 32 and the fixing belt 31 to decrease friction generated between the nip formation member 32 and the fixing belt 31 at the fixing nip N.
The hollow pipe-shaped metal heat conductor 34 is manufactured by bending a thin sheet of metal (hereinafter “sheet metal”) such as aluminum, iron, or stainless steel into a generally cylindrical shape. For example, the metal heat conductor 34 has a thickness in a range of from about 0.1 mm to about 0.4 mm. The metal heat conductor 34 has substantially a circular shape in cross-section except for the concave portion of the metal heat conductor 34, which houses the nip formation member 32. However, the shape of the metal heat conductor 34 in cross-section is not limited thereto, and alternatively, the metal heat conductor 34 may have another shape in cross-section, such as an oval shape or a polygonal shape, provided that it retains the generally looped form of the fixing belt 31 while allowing the fixing belt 31 to rotate without significant friction.
The heater 35 provided inside the hollow, pipe-shaped or cylindrical metal heat conductor 34 heats the metal heat conductor 34. Heat diffused from the metal heat conductor 34 heated by the heater 35 is transmitted to the entire fixing belt 31 substantially uniformly so that a surface temperature of the fixing belt 31 is increased to a desired fixing temperature. A rate or power for turning on the heater 35 is controlled based on an output of a temperature sensor (e.g., the thermistor 38) to adjust or maintain the surface temperature of the fixing belt 31.
According to this exemplary embodiment, the heater 35 is a halogen heater provided inside the metal heat conductor 34. Alternatively, an induction heater, a resistance heat generator, or a carbon heater may be used as the heater 35. Further, when the support member 33 is configured to receive radiation heat generated by the heater 35, the support member 33 may include a heat insulation layer as a surface layer or may be mirror-finished to reflect radiation heat of the heater 35. Thus, the processing performed on the surface of the support member 33 prevents temperature increase of the support member 33 and reduces wasteful energy consumption.
The fixing belt 31 is a flexible endless belt having a thickness not greater than about 1 mm, and is constructed of a base layer and a release layer provided on the base layer. The base layer is made of a metal material such as nickel and SUS stainless steel or a resin material such as polyimide. The release layer is made of tetrafluoroethylene perfluoroalkylvinylether copolymer (PFA) and/or polytetrafluoroethylene (PTFE), and is coated on the base layer to provide a separation property for preventing a toner image on the recording medium from adhering to the fixing belt 31. Optionally, an elastic layer made of silicon rubber may be provided between the base layer and the release layer, but is not essential. The fixing belt 31 without the elastic layer has a smaller heat capacity that improves fixing property. However, when the fixing belt 31 and the pressing roller 6 apply pressure to a recording medium bearing an unfixed toner image to fix the toner image on the recording medium, slight surface asperities on an outer circumferential surface of the fixing belt 31 are transferred onto the toner image, roughening the solid toner image into an orange-peel image. To address this problem, the elastic layer made of silicon rubber and having a thickness not smaller than about 100 μm may be preferably provided so that the elastic layer is deformed to absorb slight surface asperities of the fixing belt 31 so as to suppress formation of the orange-peel image.
The pressing roller 6 is constructed of a hollow metal roller, a silicon rubber layer provided on the metal roller, and a release layer provided on the silicon rubber layer as a surface layer. The release layer is made of PFA or PTFE, and provides separation of the recording medium from the pressing roller 6. The pressing roller 6 receives a driving force transmitted from a driver (e.g., a motor) provided in the image forming apparatus 100 depicted in
Alternatively, the pressing roller 6 may be a solid roller. However, the hollow pressing roller 6 has a desired smaller heat capacity. Optionally, a heater (e.g., a halogen heater) may be provided inside the hollow pressing roller 6. The silicon rubber layer of the pressing roller 6 may be made of solid rubber. Alternatively, when no heater is provided inside the pressing roller 6, the pressing roller 6 may be made of sponge rubber that can improve heat insulation to suppress heat transmission from the fixing belt 31 to the pressing roller 6.
In the fixing device 50 having the above-described structure, the fixing belt 31 rotates and slides over the outer circumferential surface of the metal heat conductor 34 in accordance with rotation of the pressing roller 6. The fixing belt 31 is guided by the metal heat conductor 34 at a position other than the fixing nip N in such a manner that the fixing belt 31 is isolated from the metal heat conductor 34 with a predetermined distance G therebetween. Accordingly, heat is diffused from the metal heat conductor 34 heated by the heater 35 toward the fixing belt 31 to uniformly heat the entire fixing belt 31 isolated from the metal heat conductor 34 by the predetermined distance G. Consequently, the entire fixing belt 31 is heated quickly, stabilizing operation of the fixing device 50.
While the pressing roller 6 rotates in the rotation direction R2, the pressing roller 6 presses the fixing belt 31 against the metal heat conductor 34 via the nip formation member 32 at the fixing nip N. However, in order to cause the fixing belt 31 to slide over the outer circumferential surface of the metal heat conductor 34 smoothly, an inner diameter of the loop formed by the fixing belt 31 needs to be greater than an outer diameter of the metal heat conductor 34. In other words, clearance is required between the inner circumferential surface of the fixing belt 31 and the outer circumferential surface of the metal heat conductor 34 in a diametrical direction of the fixing belt 31.
When the downstream portion of the fixing belt 31 goes slack, the recording medium bearing the fixed toner image, which is discharged from the fixing nip N, is conveyed along the slackened fixing belt 31 in a state in which the recording medium contacts the slackened fixing belt 31. Accordingly, the recording medium bearing the fixed toner image receives an excessive amount of heat from the heated fixing belt 31, generating hot offset of the toner image. Moreover, when the fixing belt 31 goes slack, the recording medium bearing the fixed toner image does not separate from the fixing belt 31 easily. For example, the fixing belt 31 cannot separate the recording medium from the fixing belt 31 by its curvature. Accordingly, the recording medium gets wound around the fixing belt 31 and is jammed.
To address these problems, the fixing device 50 according to this exemplary embodiment includes a separator 80 as illustrated in
The separator 80 is provided at a position downstream from the fixing nip N in the rotation direction R1 of the fixing belt 31 depicted in
The separator 80 is made of sheet metal, in such a manner that a leading edge of the sheet metal that faces the fixing nip N has a thickness in a range of from about 0.1 mm to about 0.3 mm. The separator 80 contacts the recording medium to separate the recording medium discharged from the fixing nip N from the fixing belt 31 and guide the recording medium to the conveyance path that leads to the output roller pair 43 so as to facilitate conveyance of the recording medium. The pressing portions 81 are provided at lateral ends of the separator 80 in a longitudinal direction of the separator 80 parallel to an axial direction of the fixing belt 31, respectively.
According to this exemplary embodiment, the separator 80 is made of sheet metal. Alternatively, the separator 80 may be manufactured by molding a resin material. However, when the resin material is used, the resin material is curled during a molding process and is deformed during a heating process, decreasing dimensional accuracy. Moreover, the leading edge of the separator 80 facing the fixing nip N is not thinned easily with the resin material. Therefore, sheet metal is preferably used. For example, when the sheet metal is processed into the separator 80, the leading edge of the separator 80 can be made thinner. Accordingly, the separator 80 having the thinner leading edge provides improved separation of the recording medium from the fixing belt 31, and is disposed closer to the downstream portion of the fixing belt 31 provided downstream from the fixing nip N in the rotation direction R1 of the fixing belt 31.
In the image forming apparatus 100 depicted in
However, when the pressing portions 81 of the separator 80 press only lateral ends of the fixing belt 31 in the axial direction of the fixing belt 31 against the metal heat conductor 34 as illustrated in
Generally, the fixing devices including the fixing belt or the fixing film and the metal heat conductor provided inside the fixing belt or the fixing film, like the fixing device 50 according to this exemplary embodiment, are designed to use components having a smaller heat capacity to shorten a warm-up time of the fixing devices. Accordingly, the metal heat conductor 34 has a relatively smaller thickness in a range of from about 0.1 mm to about 0.4 mm, and therefore has a smaller strength. Consequently, when the biasing member applies a bias to the separator 80 to cause the separator 80 to press the fixing belt 31 against the metal heat conductor 34, the metal heat conductor 34 may be deformed over time.
To address this problem, the fixing device 50 may include the reinforcement member 60, which reinforces the metal heat conductor 34, provided at each lateral end of the metal heat conductor 34 in the longitudinal direction thereof. The reinforcement member 60 is provided inside the hollow cylinder of the metal heat conductor 34 in a circumferential region in which the pressing portion 81 of the separator 80 presses the fixing belt 31 against the metal heat conductor 34. Specifically, an outer circumferential surface of the reinforcement member 60 faces or contacts interior walls of the metal heat conductor 34 corresponding to a hatched circumferential region of the fixing belt 31 in
In the fixing device 50 depicted in
Referring to
The flange 61 is attached to the reinforcement member 60 and serves as an attachment member that attaches the reinforcement member 60 to a housing wall of the fixing device 50 or the image forming apparatus 100 depicted in
Referring to
The separator also presses the fixing member against the metal heat conductor (e.g., the metal heat conductor 34) at a position near the exit of the fixing nip. Accordingly, the fixing member rotates in a state in which the fixing member contacts the metal heat conductor at least before the fixing member passes the separator, reducing slack of the fixing member which may cause the fixing member to contact the recording medium at the position downstream from the fixing nip in the rotation direction R1 of the fixing member.
Further, the separator presses the fixing member against the metal heat conductor at each of the lateral ends of the fixing member in the axial direction of the fixing member, that is, the non-conveyance regions on the fixing member through which the recording medium does not pass. Accordingly, even if the separator contacting the fixing member scratches or damages the fixing member, the recording medium passes through the center portion of the fixing member in the axial direction of the fixing member, that is, the conveyance region on the fixing member, and therefore does not contact the damaged lateral ends of the fixing member in the axial direction of the fixing member. As a result, a toner image fixed on the recording medium is not damaged by the fixing member.
Moreover, the reinforcement members (e.g., the reinforcement members 60) are provided inside and/or outside the metal heat conductor on the interior walls and/or the exterior walls of the metal heat conductor, respectively, in each circumferential region in which the separator presses the fixing member against the metal heat conductor. Accordingly, the metal heat conductor reinforced by the reinforcement members is not deformed by pressure applied by the separator to the metal heat conductor.
Further, the attachment members (e.g., the flanges 61) can be added to the reinforcement members so that the metal heat conductor is fixed to the housing walls of the fixing device via the reinforcement members and the attachment members mounted on the reinforcement members, respectively. Thus, the fixing device is manufactured at reduced costs with fewer parts.
In the fixing device 50 according to the above-described exemplary embodiments, the pressing roller 6 is used as a pressing member. Alternatively, a pressing belt, a pressing pad, a pressing plate, or the like may be used as a pressing member to provide effects equivalent to the effects provided by the pressing roller 6. Further, the fixing belt 31 is used as a fixing member. Alternatively, an endless fixing sleeve, an endless fixing film, or the like may be used as a fixing member.
The present invention has been described above with reference to specific exemplary embodiments. Note that the present invention 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 invention. It is therefore to be understood that the present invention 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 invention.
| Number | Date | Country | Kind |
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| Number | Date | Country | |
|---|---|---|---|
| 20110211876 A1 | Sep 2011 | US |
