Heating device, fixing device, and image forming apparatus

A heating device includes a rotator that rotates and a heater that heats the rotator. A rotator holder holds each lateral end of the rotator in a longitudinal direction of the rotator. The rotator holder is adhered with one of silicone oil and silicone grease, that contains siloxanes that are not smaller than a dodecamer and not greater than a heptadecamer and have a concentration not greater than 1,250 ppm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application Nos. 2022-076067, filed on May 2, 2022, and 2022-185661, filed on Nov. 21, 2022, in the Japan Patent Office, the entire disclosure of each of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

Embodiments of this disclosure relate to a heating device, a fixing device, and an image forming apparatus.

Related Art

Related-art image forming apparatuses, such as copiers, facsimile machines, printers, and multifunction peripherals (MFP) 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.

Such image forming apparatuses are installed with a heating device. As one example, the heating device is a fixing device that heats a recording medium such as a sheet to fix an unfixed image on the recording medium.

SUMMARY

This specification describes below an improved heating device. In one embodiment, the heating device includes a rotator that rotates and a heater that heats the rotator. A rotator holder holds each lateral end of the rotator in a longitudinal direction of the rotator. The rotator holder is adhered with one of silicone oil and silicone grease, that contains siloxanes that are not smaller than a dodecamer and not greater than a heptadecamer and have a concentration not greater than 1,250 ppm.

This specification further describes an improved fixing device. In one embodiment, the fixing device includes an endless belt that rotates and an opposed rotator disposed opposite an outer circumferential face of the endless belt. A heater heats the endless belt. A belt holder holds each lateral end of the endless belt in a longitudinal direction of the endless belt. The belt holder is adhered with one of silicone oil and silicone grease, that contains siloxanes that are not smaller than a dodecamer and not greater than a heptadecamer and have a concentration not greater than 1,250 ppm.

This specification further describes an improved image forming apparatus. In one embodiment, the image forming apparatus includes an image forming device that forms an image and a heating device that heats the image on a recording medium. The heating device includes a rotator that rotates and a heater that heats the rotator. A rotator holder holds each lateral end of the rotator in a longitudinal direction of the rotator. The rotator holder is adhered with one of silicone oil and silicone grease, that contains siloxanes that are not smaller than a dodecamer and not greater than a heptadecamer and have a concentration not greater than 1,250 ppm.

DETAILED DESCRIPTION

Referring to the attached drawings, the following describes embodiments of the present disclosure. In the drawings for explaining the embodiments of the present disclosure, identical reference numerals are assigned to elements such as members and parts that have an identical function or an identical shape as long as differentiation is possible and a description of the elements is omitted once the description is provided.

FIG.1is a schematic cross-sectional view of an image forming apparatus100according to an embodiment of the present disclosure. The image forming apparatus100is a printer. Alternatively, the image forming apparatus100may be a copier, a facsimile machine, a printing machine, a multifunction peripheral (MFP) having at least two of printing, copying, facsimile, scanning, and plotter functions, or the like. Image formation described below denotes forming an image having meaning such as characters and figures and an image not having meaning such as patterns.

Referring toFIG.1, a description is provided of an overall construction and operation of the image forming apparatus100according to an embodiment of the present disclosure.

As illustrated inFIG.1, the image forming apparatus100according to the embodiment includes an image forming portion200, a fixing portion300, a recording medium supply portion400, and a recording medium ejecting portion500. The image forming portion200forms a toner image on a sheet P serving as a recording medium. The fixing portion300fixes the toner image on the sheet P. The recording medium supply portion400supplies the sheet P to the image forming portion200. The recording medium ejecting portion500ejects the sheet P onto an outside of the image forming apparatus100.

The image forming portion200includes four process units1Y,1M,1C, and1Bk, an exposure device6, and a transfer device8. The process units1Y,1M,1C, and1Bk serve as image forming units or image forming devices, respectively. The exposure device6forms an electrostatic latent image on a photoconductor2of each of the process units1Y,1M,1C, and1Bk. The transfer device8transfers the toner image onto the sheet P.

The process units1Y,1M,1C, and1Bk basically have similar constructions, respectively. However, the process units1Y,1M,1C, and1Bk contain toners, serving as developers, in different colors, that is, yellow, magenta, cyan, and black, respectively, which correspond to color separation components for a color image. For example, each of the process units1Y,1M,1C, and1Bk includes the photoconductor2, a charger3, a developing device4, and a cleaner5. The photoconductor2serves as an image bearer that bears an image (e.g., an electrostatic latent image and a toner image) on a surface of the photoconductor2. The charger3charges the surface of the photoconductor2. The developing device4supplies the toner as the developer to the surface of the photoconductor2to form a toner image. The cleaner5cleans the surface of the photoconductor2.

The transfer device8includes an intermediate transfer belt11, primary transfer rollers12, and a secondary transfer roller13. The intermediate transfer belt11is an endless belt that is stretched taut across a plurality of support rollers. The four primary transfer rollers12are disposed within a loop formed by the intermediate transfer belt11. The primary transfer rollers12are pressed against the photoconductors2, respectively, via the intermediate transfer belt11, thus forming primary transfer nips between the intermediate transfer belt11and the photoconductors2. The secondary transfer roller13contacts an outer circumferential surface of the intermediate transfer belt11to form a secondary transfer nip therebetween.

The fixing portion300includes a fixing device20serving as a heating device that heats the sheet P transferred with the toner image. The fixing device20includes a fixing belt21and a pressure roller22. The fixing belt21heats the toner image on the sheet P. The pressure roller22contacts the fixing belt21to form a nip (e.g., a fixing nip) therebetween.

The recording medium supply portion400includes a sheet tray14(e.g., a paper tray) and a feed roller15. The sheet tray14loads a plurality of sheets P serving as recording media. The feed roller15picks up and feeds a sheet P from the sheet tray14. According to the embodiments below, a sheet (e.g., a sheet P) is used as a recording medium. However, the recording medium is not limited to paper as the sheet. In addition to paper as the sheet, the recording media include an overhead projector (OHP) transparency, cloth, a metal sheet, plastic film, and a prepreg sheet pre-impregnated with resin in carbon fibers. In addition to plain paper, the sheets include thick paper, a postcard, an envelope, thin paper, coated paper, art paper, and tracing paper.

The recording medium ejecting portion500includes an output roller pair17and an output tray18. The output roller pair17ejects the sheet P onto the outside of the image forming apparatus100. The output tray18is placed with the sheet P ejected by the output roller pair17. The image forming apparatus100further includes a timing roller pair16.

Referring toFIG.1, a description is provided of printing processes performed by the image forming apparatus100according to the embodiment.

When the image forming apparatus100receives an instruction to start printing, a driver starts driving and rotating the photoconductor2of each of the process units1Y,1M,1C, and1Bk clockwise inFIG.1and the intermediate transfer belt11of the transfer device8counterclockwise inFIG.1. The feed roller15starts rotation, feeding a sheet P from the sheet tray14. As the sheet P fed by the feed roller15comes into contact with the timing roller pair16, the timing roller pair16temporarily halts the sheet P. Thus, the timing roller pair16temporarily interrupts conveyance of the sheet P until the toner image, that is to be transferred onto the sheet P, is formed on the intermediate transfer belt11.

The charger3of each of the process units1Y,1M,1C, and1Bk charges the surface of the photoconductor2evenly at a high electric potential. The exposure device6exposes the charged surfaces of the photoconductors2, respectively, according to image data (e.g., print data) sent from a terminal. Alternatively, if the image forming apparatus100is a copier, the exposure device6exposes the charged surfaces of the photoconductors2, respectively, according to image data created by a scanner that reads an image on an original. Accordingly, the electric potential of an exposed portion on the surface of each of the photoconductors2decreases, forming an electrostatic latent image on the surface of each of the photoconductors2. The developing device4of each of the process units1Y,1M,1C, and1Bk supplies toner to the electrostatic latent image formed on the photoconductor2, forming a toner image thereon. When the toner images formed on the photoconductors2reach the primary transfer nips defined by the primary transfer rollers12in accordance with rotation of the photoconductors2, respectively, the primary transfer rollers12transfer the toner images formed on the photoconductors2onto the intermediate transfer belt11driven and rotated counterclockwise inFIG.1successively such that the toner images are superimposed on the intermediate transfer belt11. Thus, the superimposed toner images form a full color toner image on the intermediate transfer belt11. Alternatively, one of the four process units1Y,1M,1C, and1Bk may be used to form a monochrome toner image or two or three of the four process units1Y,1M,1C, and1Bk may be used to form a bicolor toner image or a tricolor toner image. After the toner image formed on the photoconductor2is transferred onto the intermediate transfer belt11, the cleaner5removes residual toner and the like remaining on the photoconductor2therefrom.

The full color toner image formed on the intermediate transfer belt11is conveyed to the secondary transfer nip defined by the secondary transfer roller13in accordance with rotation of the intermediate transfer belt11and is transferred onto the sheet P conveyed by the timing roller pair16. Thereafter, the sheet P transferred with the full color toner image is conveyed to the fixing device20where the fixing belt21and the pressure roller22fix the full color toner image on the sheet P under heat and pressure. The sheet P is conveyed to the recording medium ejecting portion500where the output roller pair17ejects the sheet P onto the output tray18. Thus, a series of printing processes is finished.

Referring toFIGS.2and3, a description is provided of a basic construction of the fixing device20according to an embodiment of the present disclosure.

FIG.2is a cross-sectional view of the fixing device20according to the embodiment, taken on a center M depicted inFIG.3of the fixing belt21in a longitudinal direction thereof. The longitudinal direction of the fixing belt21denotes a longitudinal direction X illustrated inFIG.3and is parallel to an axial direction of the pressure roller22or a width direction of the sheet P passing through a fixing nip N formed between the fixing belt21and the pressure roller22. The width direction of the sheet P is perpendicular to a sheet conveyance direction DP in which the sheet P is conveyed. A longitudinal direction described below is also defined as described above.

As illustrated inFIGS.2and3, in addition to the fixing belt21and the pressure roller22, the fixing device20according to the embodiment includes heaters23, a nip formation pad24, a stay25, a reflector26depicted inFIG.2, belt holders27depicted inFIG.3, and a temperature sensor28depicted inFIG.2.

The fixing belt21serves as a rotator (e.g., a first rotator or a fixing rotator) or an endless belt that contacts an unfixed toner image bearing side of a sheet P, which bears an unfixed toner image, and fixes the unfixed toner image (e.g., unfixed toner) on the sheet P. The fixing belt21rotates in a rotation direction D21.

For example, the fixing belt21is an endless belt that includes a base layer serving as an inner circumferential surface layer, an elastic layer disposed on the base layer, and a release layer disposed on the elastic layer and serving as an outer circumferential surface layer. The base layer has a layer thickness in a range of from 30 μm to 50 μm and is made of a metal material such as nickel and stainless steel or a resin material such as polyimide. The elastic layer has a layer thickness in a range of from 100 μm to 300 μm and is made of a rubber material such as silicone rubber, silicone rubber foam, and fluororubber. Since the fixing belt21incorporates the elastic layer, the elastic layer prevents slight surface asperities from being produced on a surface of the fixing belt21at the fixing nip N. Accordingly, heat is quickly conducted from the fixing belt21to the toner image on the sheet P evenly. The release layer has a layer thickness in a range of from 10 μm to 50 μm. The release layer is made of perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE), polyimide, polyether imide, polyether sulfone (PES), or the like. As the fixing belt21incorporates the release layer, the release layer facilitates separation and peeling of toner of the toner image formed on the sheet P from the fixing belt21. In order to decrease the size and the thermal capacity of the fixing belt21, the fixing belt21preferably has a total thickness not greater than 1 mm and a diameter not greater than 30 mm.

The pressure roller22serves as a rotator (e.g., a second rotator or an opposed rotator) that is disposed opposite an outer circumferential face21aof the fixing belt21. The pressure roller22rotates in a rotation direction D22.

For example, the pressure roller22includes a core metal that is solid and made of iron, an elastic layer that is disposed on an outer circumferential face of the core metal, and a release layer that is disposed on an outer circumferential face of the elastic layer. Alternatively, the core metal may be hollow. The elastic layer is made of silicone rubber, silicone rubber foam, fluororubber, or the like. The release layer is made of fluororesin such as PFA and PTFE.

Each of the heaters23serves as a heat source that heats the fixing belt21. According to the embodiment, a halogen heater is used as each of the heaters23. Alternatively, instead of the halogen heater, each of the heaters23may be other heater employing a radiant heating system, such as a carbon heater and a ceramic heater, or a heat source employing an electromagnetic induction heating system. According to the embodiment, the two heaters23are disposed within a loop formed by the fixing belt21. Alternatively, the fixing device20may incorporate a single heater23or three or more heaters23.

The nip formation pad24is disposed within the loop formed by the fixing belt21. The nip formation pad24is disposed opposite the pressure roller22via the fixing belt21, forming the fixing nip N between the fixing belt21and the pressure roller22. The nip formation pad24includes a base pad29and a slide sheet30.

The base pad29extends continuously in the longitudinal direction X of the fixing belt21and is secured to the stay25. The base pad29receives pressure from the pressure roller22, defining a shape of the fixing nip N. The base pad29is preferably made of a heat-resistant material that has a heat-resistant temperature of 200 degrees Celsius or higher. For example, the base pad29is made of general heat-resistant resin such as polyether sulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyether nitrile (PEN), polyamide imide (PAI), and polyether ether ketone (PEEK). As the base pad29is made of the heat-resistant material described above, the base pad29is immune from thermal deformation in a fixing temperature range, stabilizing the shape of the fixing nip N. As illustrated inFIG.2, the fixing nip N is recessed or curved. Alternatively, the fixing nip N may be planar or may have other shapes.

The slide sheet30is interposed between the base pad29and an inner circumferential face21bof the fixing belt21and is made of a low friction material. Since the slide sheet30is interposed between the base pad29and the fixing belt21, the slide sheet30decreases sliding friction with which the fixing belt21slides over the base pad29via the slide sheet30. If the base pad29is made of the low friction material, the nip formation pad24may not incorporate the slide sheet30.

The stay25serves as a support that contacts a stay opposed face of the nip formation pad24, that is opposite to a pressure roller opposed face of the nip formation pad24, that is disposed opposite the pressure roller22, thus supporting the nip formation pad24. As the stay25supports the nip formation pad24, the stay25suppresses a bend of the nip formation pad24by pressure from the pressure roller22. For example, the stay25suppresses a bend of the nip formation pad24throughout an entire span of the nip formation pad24in the longitudinal direction X of the fixing belt21. Thus, the stay25causes the nip formation pad24to form the fixing nip N that has an even length in the sheet conveyance direction DP throughout an entire span of the fixing belt21in the longitudinal direction X thereof. The stay25is preferably made of a ferrous metal material such as stainless used steel (SUS) and steel electrolytic cold commercial (SECC) to achieve rigidity.

The reflector26reflects radiant heat (e.g., infrared light) radiated from the heaters23. The reflector26reflects radiant heat emitted by the heaters23toward the fixing belt21, facilitating heating of the fixing belt21. The reflector26is interposed between the stay25and the heaters23, thus also suppressing conduction of heat to the stay25. Accordingly, the reflector26suppresses conduction of heat to an element that does not directly contribute to fixing of the toner image on the sheet P, saving energy. The reflector26is made of a metal material such as aluminum and stainless steel. For example, if the reflector26is constructed of a base layer made of aluminum and coated with silver having an enhanced reflectance by vapor deposition, the reflector26improves efficiency in heating the fixing belt21further.

The belt holders27serve as a pair of rotator holders that rotatably holds or supports the fixing belt21. As illustrated inFIG.3, the belt holders27are inserted into an interior within the loop formed by the fixing belt21at both lateral ends of the fixing belt21in the longitudinal direction X thereof, respectively. The belt holders27contact the inner circumferential face21bof the fixing belt21, rotatably holding or supporting the fixing belt21. In the present disclosure, both lateral ends and a lateral end of the fixing belt21in the longitudinal direction X thereof are not limited to both outermost lateral edges and an outermost lateral edge of the fixing belt21in the longitudinal direction X thereof, respectively. In addition to both outermost lateral edges and the outermost lateral edge of the fixing belt21in the longitudinal direction X thereof, both lateral ends and the lateral end of the fixing belt21in the longitudinal direction X thereof also denote an arbitrary position within a span having a length from a lateral edge to a divided position on the fixing belt21in the longitudinal direction X thereof when the fixing belt21is divided into three equal parts in the longitudinal direction X thereof. Accordingly, the belt holder27holds or supports a region (e.g., the lateral end of the fixing belt21) encompassing the outermost lateral edge of the fixing belt21in the longitudinal direction X thereof. Additionally, the belt holder27may hold or support a region (e.g., the lateral end of the fixing belt21) not encompassing the lateral edge of the fixing belt21in the longitudinal direction X thereof.

For example, the belt holder27includes an insertion portion27a, a restricting portion27b, and a secured portion27c. The insertion portion27ais C-shaped in cross section and is inserted into the interior within the loop formed by the fixing belt21at the lateral end of the fixing belt21in the longitudinal direction X thereof. The restricting portion27bhas an outer diameter that is greater than an outer diameter of the insertion portion27a. The secured portion27cis secured to a side plate of the fixing device20described below. The restricting portion27bhas an outer diameter that is greater than at least an outer diameter of the fixing belt21. If the fixing belt21is skewed or moved in the longitudinal direction X thereof, the restricting portion27brestricts skew or motion of the fixing belt21. As the insertion portion27ais inserted into the interior within the loop formed by the fixing belt21at the lateral end of the fixing belt21in the longitudinal direction X thereof, the insertion portion27acontacts the inner circumferential face21bof the fixing belt21, thus rotatably holding or supporting the fixing belt21.

The belt holder27is made of a resin material called super engineering plastic such as polyphenylene sulfide, polyether ether ketone, polyarylate, liquid crystal polymer, polyimide, polybenzimidazole, and polybutylene naphthalate. In view of machining and heat resistance, liquid crystal polymer is preferable. If the belt holder27is made of the super engineering plastic mixed with glass fiber, the belt holder27is preferably immune from deformation caused by temperature change.

The temperature sensor28serves as a temperature detector that detects a temperature of the fixing belt21. According to the embodiment, the temperature sensor28is anon-contact type temperature sensor that does not contact the outer circumferential face21aof the fixing belt21. In this case, the temperature sensor28detects an ambient temperature at a position in proximity to the outer circumferential face21aof the fixing belt21as a surface temperature of the fixing belt21. Alternatively, instead of the non-contact type temperature sensor, the temperature sensor28may be a contact type temperature sensor that contacts the fixing belt21and detects the surface temperature of the fixing belt21. For example, general temperature sensors such as a thermopile, a thermostat, a thermistor, and a normally closed (NC) sensor are used as the temperature sensor28.

A description is provided of operation of the fixing device20according to the embodiment.

As a driver disposed inside an apparatus body of the image forming apparatus100drives and rotates the pressure roller22in the rotation direction D22depicted inFIG.2, the pressure roller22drives and rotates the fixing belt21in the rotation direction D21. As the heaters23generate heat, the heaters23heat the fixing belt21. For example, a controller controls a heat generation amount of the heaters23based on a temperature of the fixing belt21, that is detected by the temperature sensor28, thus retaining a predetermined fixing temperature of the fixing belt21at which the fixing belt21fixes the toner image on the sheet P. In a state in which the fixing belt21has the predetermined fixing temperature, as a sheet P bearing an unfixed toner image is conveyed through the fixing nip N formed between the fixing belt21and the pressure roller22, the fixing belt21and the pressure roller22fix the unfixed toner image on the sheet P under heat and pressure.

A description is provided of a construction of a first comparative fixing device.

The first comparative fixing device includes a rotator such as a belt and a slide aid such as a nip formation pad and a belt holder. The rotator slides over the slide aid relatively. See Japanese Unexamined Patent Application Publication No. 2013-164453, for example. In order to decrease sliding friction between the slide aid and the rotator, the first comparative fixing device generally uses a substance having lubricity such as oil and grease (hereinafter referred to as a lubricant). The substance having lubricity denotes a substance that is interposed between parts and decreases frictional resistance between the parts.

Environmental awareness increases in overseas countries, especially in Europe. Image forming apparatuses using electrophotography, such as copiers, multifunction peripherals, and printers, are also applied with various accreditation criteria for volatile organic compounds (VOC), ozone, dust, and fine particles, that generate during image formation. For example, a research institute of the German government authorizes an ecolabel called the Blue Angel mark. Usage of the ecolabel is permitted to products and services that are accredited.

Sales is not prohibited for products that are not accredited with the Blue Angel mark. However, the products that are not accredited with the Blue Angel mark are often regarded as being not environmentally friendly, especially in government offices. Hence, whether or not the products are accredited with the Blue Angel mark may affect sales of the products substantially.

In order to obtain accreditation of the Blue Angel mark, the products are requested to pass various examinations. Examinations for ultrafine particles are very difficult to pass. For example, a number of the ultrafine particles that have a size in a range of from 5.6 nm to 560 nm and generate from an image forming apparatus is measured with a particle measurement device, that is, a fast mobility particle sizer (FMPS), and is requested to be smaller than 3.5×1011pieces per 10 minutes. More strict criteria are expected in the future. The number of the ultrafine particles is not classified by a type and a status of a substance of an ultrafine particle. For example, the number of the ultrafine particles is not classified by whether the ultrafine particles are organic or inorganic and whether the ultrafine particles are solid or liquid (e.g., mist). The size and the number of the ultrafine particles are concerned.

The image forming apparatus includes various elements that generate the ultrafine particles. However, as the first comparative fixing device of the image forming apparatus starts, a generation amount of the ultrafine particles increases substantially. Hence, the first comparative fixing device is regarded as a main source of the ultrafine particles. As the lubricant described above is heated to a high temperature, the ultrafine particles are detected. Hence, the lubricant is one of sources of the ultrafine particles. As the lubricant is heated to the high temperature, a very small part of components of the lubricant is volatilized as hot gas. Thereafter, the gas is cooled and is subject to condensation into the ultrafine particles. Accordingly, the lubricant is requested not to be exposed in a hot environment so as to suppress generation of the ultrafine particles from the image forming apparatus.

A description is provided of a construction of a second comparative fixing device disclosed by Japanese Unexamined Patent Application Publication No. H8-262903.

The second comparative fixing device includes a heating-fixing roll, an endless belt, and a pressure pad. The heating-fixing roll (e.g., a pressure roller) is rotatable. The endless belt (e.g., a fixing belt) contacts the heating-fixing roll. The pressure pad (e.g., a nip formation pad) presses against the heating-fixing roll via the endless belt. The pressure pad is disposed within a loop formed by the endless belt such that the pressure pad does not rotate. The pressure pad presses the endless belt against the heating-fixing roll. Accordingly, a surface of the heating-fixing roll is deformed elastically, forming a belt nip between the endless belt and the heating-fixing roll. A recording sheet (e.g., a recording medium or a recording material that bears a toner image) is conveyed through the belt nip. The second comparative fixing device having the construction described above decreases heat loss at the belt nip. Additionally, the second comparative fixing device prevents a difference between a conveyance speed at which the recording sheet is conveyed and a rotation speed at which the heating-fixing roll rotates and prevents air or vapor within the belt nip from degrading a toner image formed on the recording sheet.

However, if a coefficient of friction between an inner circumferential face of the endless belt and the pressure pad (e.g., the nip formation pad) increases, a driving torque of the heating-fixing roll increases. Accordingly, stress applied on a gear bearing may increase, causing breakage of a gear and a core. If friction between the endless belt and the pressure pad becomes too great to ignore, compared to a driving force with which the heating-fixing roll drives and rotates the endless belt, slippage may generate between the heating-fixing roll and the endless belt, shifting an unfixed toner image on a recording sheet.

A description is provided of a construction of a third comparative fixing device disclosed by Japanese Unexamined Patent Application Publication No. H10-213984 that overcomes the disadvantages described above.

The third comparative fixing device includes a pressure pad (e.g., a pressing pad), an endless belt, and a heating-fixing roll. Modified silicone oil as a lubricant is interposed between the pressure pad and the endless belt. Accordingly, the third comparative fixing device attains stable motion (e.g., rotation) of the endless belt without degrading separation of a recording sheet from the heating-fixing roll.

The third comparative fixing device disclosed by Japanese Unexamined Patent Application Publication No. H10-213984 includes a low-friction sheet that covers a surface of the pressure pad so that the endless belt slides over the pressure pad via the low-friction sheet that has a decreased coefficient of friction. However, the third comparative fixing device does not consider surface wettability of the modified silicone oil that is applied on the low-friction sheet or the endless belt. Accordingly, the third comparative fixing device may not retain the modified silicone oil stably, rendering maintenance to be difficult.

A description is provided of a construction of a fourth comparative fixing device disclosed by Japanese Unexamined Patent Application Publication No. 2010-211220 that overcomes the disadvantages described above.

The fourth comparative fixing device includes a base, a non-porous sheet, a pressure pad, and an endless belt. The base is uneven. The non-porous sheet is mounted on the base and is made of heat-resistant resin contained in at least a slide face. The non-porous sheet serves as a sheet slide aid that is interposed between the pressure pad (e.g., a nip formation pad) and the endless belt (e.g., a tubular resin film).

A description is provided of a construction of a fifth comparative fixing device disclosed by Japanese Unexamined Patent Application Publication No. 2001-249558.

The fifth comparative fixing device includes a tubular film and a pressure pad (e.g., a nip formation pad) that has a slide contact face over which the tubular film slides. The slide contact face is applied with lipophilic fluororesin or applied with a lipophilic agent and fluororesin. Accordingly, the fifth comparative fixing device improves wettability with respect to a lubricant, suppressing drying up of oil. Accordingly, the fifth comparative fixing device attains stable sliding of the tubular film over the pressure pad, retaining improved quality of a toner image fixed on a sheet and an improved fixing property.

In a fixing device, for example, the first comparative fixing device, the second comparative fixing device, the third comparative fixing device, the fourth comparative fixing device, and the fifth comparative fixing device described above, a lubricant such as silicone oil is interposed between a slide contact face of a nip formation pad (e.g., a pressure pad) and an inner circumferential face of a fixing belt (e.g., an endless belt), improving efficiency in energy consumption and saving energy. Hence, the fixing device is installed in image forming apparatuses.

The image forming apparatus includes various elements that generate the ultrafine particles. As the fixing device of the image forming apparatus is driven, a generation amount of the ultrafine particles increases substantially. Hence, the fixing device is regarded as a main source of the ultrafine particles. When an image having a decreased image area is printed, a generation amount of the ultrafine particles decreases. Hence, toner is related to generation of the ultrafine particles.

The ultrafine particles described in the present disclosure also denote fine particles (FP) and ultrafine particles (UFP) measured under measurement conditions used to examine a relation illustrated inFIG.5as described below. Hence, the ultrafine particle denotes a particle having a particle diameter in a range of from 5.6 nm to 560 nm.

Components of an ultrafine particle are analyzed in detail. The proceedings 211-212 (2017) of the 34th Japan Association of Aerosol Science and Technology meeting report that the components of the ultrafine particle include cyclic siloxanes that are not smaller than a dodecamer (D12) and are not greater than a heptadecamer (D17) in addition to paraffin and higher alcohol contained in toner.

The cyclic siloxanes from the dodecamer to the heptadecamer are usually contained in silicone rubber or silicone oil, as impurities.

A description is provided of a construction of a sixth comparative fixing device disclosed by Japanese Patent No. 4985803.

The sixth comparative fixing device includes a roller made of silicone rubber that generates siloxanes as the ultrafine particles. However, a source that generates a substantial amount of the cyclic siloxanes from the dodecamer to the heptadecamer is not disclosed.

As the fixing belt is heated to a higher temperature, an amount of the ultrafine particles generated from the fixing device is subject to increase. To address increase in the amount of the ultrafine particles caused by temperature increase of the fixing belt, low melting toner is used. The low melting toner allows a preset low temperature of the fixing belt for fixing, thus suppressing generation of the ultrafine particles. Under a condition in which the fixing belt has the preset low temperature, as silicone oil interposed between the nip formation pad and the fixing belt, silicone oil that is not removed of low molecular siloxanes and is available at a low cost is employed.

However, as the fixing belt rotates at an increased speed to address a request for increasing a print speed, although a surface temperature of the fixing belt is unchanged, the ultrafine particles generate. As the fixing belt rotates at the increased speed, in order to retain a constant temperature of the fixing belt, a heater that heats the fixing belt conceivably increases output. For example, as the heater, that increases output, heats silicone oil applied on an inner circumferential face of the fixing belt directly, the silicone oil is subject to temperature increase. Accordingly, the silicone oil conceivably generates the ultrafine particles.

A description is provided of a construction of a seventh comparative fixing device disclosed by Japanese Patent No. 6213313.

The seventh comparative fixing device includes a fixing belt and a nip formation pad. In order to suppress generation of the ultrafine particles from the silicone oil applied on an inner circumferential face of the fixing belt, the silicone oil is interposed between an outer slide contact face of the nip formation pad and the inner circumferential face of the fixing belt (e.g., an endless belt), that contacts and slides over the outer slide contact face of the nip formation pad. The silicone oil contains siloxanes from an undecamer to a heptadecamer in an amount of 2,000 ppm or smaller.

For example, in the seventh comparative fixing device disclosed by Japanese Patent No. 6213313, the silicone oil interposed between the nip formation pad and the fixing belt conceivably generates the ultrafine particles. Therefore, in order to verify that most of the ultrafine particles generated from the fixing device generated from the silicone oil interposed between the fixing belt and the nip formation pad, the silicone oil containing a decreased amount of the siloxanes from the undecamer to the heptadecamer was applied between the fixing belt and the nip formation pad and a toner image was fixed on a sheet. However, generation of the ultrafine particles was not suppressed effectively.

A description is provided of a construction of an eighth comparative fixing device disclosed by Japanese Patent No. 5153251.

The eighth comparative fixing device includes a fixing belt and a nip formation pad. Silicone oil containing an extremely small amount of cyclic siloxanes from a trimer to an icosamer was applied between the fixing belt and the nip formation pad. Similarly, generation of the ultrafine particles was not suppressed effectively.

Verification was performed in detail to identify a source in the fixing device, that generated a substantial amount of the ultrafine particles. The substantial amount of the ultrafine particles generated at a position in proximity to a lateral end of the fixing belt in a longitudinal direction thereof. In an early stage of verification, silicone oil interposed between the fixing belt and the nip formation pad conceivably generated the ultrafine particles. During the verification to identify the source of the ultrafine particles, silicone oil interposed between an outer circumferential face of a belt holder and an inner circumferential face of the fixing belt was not considered. For example, an amount of the silicone oil adhered to the belt holder was overwhelmingly smaller than an amount of the silicone oil interposed between the fixing belt and the nip formation pad. Additionally, the belt holder was separated from a heater that heated the fixing belt. Hence, in the early stage of verification, the silicone oil applied on the belt holder barely concerned generation of the ultrafine particles conceivably.

However, when the silicone oil adhered to the belt holder was removed and a blank sheet bearing no toner was conveyed over the fixing belt, a generation amount of the ultrafine particles decreased substantially. Accordingly, the silicone oil interposed between the belt holder and the fixing belt was identified as a main source of the fixing device, that generated the ultrafine particles.

In order to suppress generation of the ultrafine particles effectively, the lubricant such as the silicone oil is not advantageously interposed between the belt holder and the fixing belt. However, in this case, the fixing belt may not slide over the belt holder smoothly. Additionally, the lateral end of the fixing belt in the longitudinal direction thereof may be damaged, resulting in a shortened product life of the fixing device. For example, if the belt holder is made of a material containing glass fiber, the glass fiber exposed from a surface of the belt holder may damage the inner circumferential face of the fixing belt. Hence, in order to suppress damage to the inner circumferential face of the fixing belt, the lubricant such as the silicone oil is preferably interposed between the outer circumferential face of the belt holder and the inner circumferential face of the fixing belt.

To address the circumstances described above, according to embodiments of the present disclosure, in which a lubricant is interposed between a rotator such as a fixing belt and a rotator holder that holds the rotator, generation of the ultrafine particles from the lubricant is suppressed.

A description is provided of a method for suppressing generation of the ultrafine particles according to the embodiments of the present disclosure.

As described above, in the fixing device20according to the embodiment illustrated inFIGS.1to3, as the fixing belt21rotates, the fixing belt21slides over the nip formation pad24disposed within the loop formed by the fixing belt21. The lubricant is applied between the fixing belt21and the nip formation pad24. The lubricant decreases sliding friction that generates between the fixing belt21and the nip formation pad24, retaining smooth rotation of the fixing belt21and suppressing abrasion of the fixing belt21. Silicone oil, silicone grease, fluorine grease, fluorine oil, or the like is generally used as the lubricant. The lubricant is impregnated into the slide sheet30depicted inFIG.2interposed between the base pad29of the nip formation pad24and the inner circumferential face21bof the fixing belt21. As the lubricant seeps out of the slide sheet30, the lubricant is interposed between the nip formation pad24and the fixing belt21.

The fixing device20according to the embodiment incorporates the pair of belt holders27that rotatably holds both lateral ends of the fixing belt21in the longitudinal direction X thereof, respectively. Hence, the lubricant is also interposed between each of the belt holders27and the fixing belt21so that the lubricant decreases sliding friction with which the fixing belt21slides over the belt holders27. For example, if the belt holder27is made of a material containing glass fiber, the glass fiber exposed from a surface of the belt holder27may damage the fixing belt21, hinder rotation of the fixing belt21, and degrade quality of a toner image formed on a sheet P. To address the circumstance, the lubricant such as the silicone oil, the silicone grease, the fluorine grease, and the fluorine oil is preferably interposed between an outer circumferential face of the belt holder27and the inner circumferential face21bof the fixing belt21.

As described above, the fixing device20includes slide aids such as the nip formation pad24and the belt holder27over which the fixing belt21, that rotates, slides relatively. In order to improve sliding of the fixing belt21, the silicone oil, the silicone grease, the fluorine grease, the fluorine oil, or the like is generally used as the lubricant. Among the above-described lubricants, the silicone oil and the silicone grease have reasonable heat resistance and are available at reduced costs compared to the fluorine oil and the fluorine grease, thus being preferably used as the lubricant.

Generally, a surface temperature of a contact portion of the fixing belt21, that contacts a sheet P, affects quality of a toner image on the sheet P substantially, thus being managed strictly. Hence, the fixing device20according to the embodiment also manages the surface temperature of the contact portion of the fixing belt21. When the fixing belt21fixes an unfixed toner image on a sheet P, as the sheet P contacts the fixing belt21, heat is conducted from the fixing belt21to the sheet P and is consumed. In order to compensate for the consumed heat, the heaters23supply heat to the fixing belt21. Conversely, heat is barely consumed in a non-contact portion of the fixing belt21, that does not contact the sheet P, while the sheet P is conveyed over the fixing belt21. Accordingly, when a plurality of sheets P is conveyed over the fixing belt21continuously, the non-contact portion of the fixing belt21stores heat and is subject to temperature increase.

As illustrated inFIG.4, a non-conveyance span V is outboard from a maximum sheet conveyance span W (e.g., a maximum recording medium conveyance span) in the longitudinal direction X of the fixing belt21. A sheet P having a maximum width is conveyed in the maximum sheet conveyance span W. The fixing belt21is subject to temperature increase in the non-conveyance span V. As the fixing belt21suffers from temperature increase, the belt holder27that holds the fixing belt21in the non-conveyance span V also suffers from temperature increase. Accordingly, the silicone oil or the silicone grease that adheres to the belt holder27also suffers from temperature increase. For example, as illustrated inFIG.4, the heater23includes a heat generation portion H that extends beyond the maximum sheet conveyance span W in the longitudinal direction X of the fixing belt21. Accordingly, the fixing belt21in the non-conveyance span V suffers from notable temperature increase. Consequently, as the belt holder27suffers from temperature increase, the silicone oil or the silicone grease also suffers from notable temperature increase.

As a result, the silicone oil or the silicone grease interposed between the belt holder27and the fixing belt21suffers from temperature increase. As the siloxanes that are not smaller than the dodecamer and not greater than the heptadecamer and are contained in the silicone oil or the silicone grease volatilize, the ultrafine particles may generate.

FIG.5is a graph illustrating a relation between a temperature of a hot plate and a concentration of fine particles or ultrafine particles (FP/UFP) in a measurement ambience. The temperature of the hot plate was measured when the hot plate heated general silicone oil used for the belt holder27. The concentration of the FP/UFP denotes a number of the FP/UFP per 1 cm3.

In a test for examining the relation illustrated inFIG.5, silicone oil in a sample container was heated in a 1-cubic meter chamber that conformed to Japanese Industrial Standards JIS A 1901 at a ventilation rate of 5 times. As illustrated inFIG.6, a sample container1000is an aluminum plate having a length of 50 mm, a width of 50 mm, and a height of 5 mm. The sample container1000includes a cavity1000ahaving a diameter of 22 mm and a depth of 2 mm. A sample was placed in the cavity1000a. The sample container1000placed with the sample was placed on a hot plate of a heating device (e.g., the clean hot plate MH-180CS and the controller MH-3CS manufactured by AS ONE Corporation). The hot plate heated the sample at a preset temperature of 250 degrees Celsius. While a temperature of the hot plate was monitored, a number concentration of the FP/UFP in the chamber was measured with a measurement device (e.g., the Fast Mobility Particle Sizer™ (FMPS) spectrometer Model 3091 manufactured by TSI Incorporated) with a use averaging interval of 30 seconds during export. An amount of the sample (e.g., an amount of silicone oil) was 36 μl.FIG.5illustrates the temperature of the hot plate on a horizontal axis. Temperature increase of the hot plate changes approximately in sync with temperature increase of the lubricant. Hence, the temperature of the hot plate is regarded as the temperature of the silicone oil.

As illustrated inFIG.5, the FP/UFP started generating approximately when the temperature of the silicone oil reached 200 degrees Celsius. Approximately when the temperature of the silicone oil exceeded 210 degrees Celsius, the number concentration of the FP/UFP increased sharply. At a temperature not lower than 210 degrees Celsius at which the number concentration of the FP/UFP increased sharply, the number concentration of the FP/UFP in the chamber was 4,000 pieces/cm3or more.

As described above, when the temperature of the silicone oil generally used reaches 200 degrees Celsius, the siloxanes that are not smaller than the dodecamer and not greater than the heptadecamer and are contained in the silicone oil volatilize, generating the FP/UFP. AlthoughFIG.5does not illustrate, like the silicone oil, when the temperature of the silicone grease reaches 200 degrees Celsius, the silicone grease also generates the FP/UFP.

Accordingly, in the fixing device20in which the temperature of the belt holder27reaches 200 degrees Celsius or higher while fixing (e.g., conveying a plurality of sheets P continuously), in order to suppress generation of the ultrafine particles, the concentration of the siloxanes is requested to decrease. The siloxanes are in a range of from the dodecamer to the heptadecamer (e.g., not smaller than the dodecamer and not greater than the heptadecamer). The siloxanes are contained in the silicone oil or the silicone grease adhered to the belt holder27and are a main source of the ultrafine particles. To address the circumstance, according to the embodiment, the concentration of the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil or the silicone grease adhered to the belt holder27is not smaller than 0 ppm and not greater than 1.250 ppm. Accordingly, the fixing device20in which the temperature of the belt holder27reaches 200 degrees Celsius or higher while fixing also suppresses generation of the ultrafine particles effectively. In order to suppress generation of the ultrafine particles further, the concentration of the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil or the silicone grease adhered to the belt holder27is preferably not greater than 500 mm.

A description is provided of one example of the silicone oil used in the fixing device according to the embodiment.

According to the embodiment, the silicone oil interposed between the belt holder27and the fixing belt21is made of organo polysiloxanes as one example. For example, an organo polysiloxane is a compound defined by a general composition formula (1) below or a compound produced by repetition of a diorgano siloxane unit having a main chain defined by RbSiO2/2. Rbis similar to Ra.
RaSiO(4-a)/2(1)

In the formula (1), Rarepresents a univalent hydrocarbon group that may have a substituent having a carbon number in a range of from 1 to 20. A value a represents an arbitrary number in a range of from 1 to 2.5. For example, the univalent hydrocarbon group that may have the substituent having the carbon number in a range of from 1 to 20, that is represented by Ra, includes an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group, a cycloalkyl group such as a cyclohexyl group and a cycloheptyl group, an alkenyl group such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, and a butenyl group, an aryl group such as a phenyl group and a tolyl group, and an aralkyl group such as a benzyl group and a phenylethyl group. Among those, the methyl group is preferable.

If the univalent hydrocarbon group has the substituent, the substituent of modified silicone oil includes a substance in which at least a part of hydrogen of an unsubstituted hydrocarbon group is substituted for an amino group, an epoxy group, a carboxyl group, a carbinol group, a methacrylic group, an acryl group, a mercapto group, a phenol group, a hydroxyl group, a polyether group, an alkoxy group, a halogen atom such as fluorine, chlorine, and bromine, or the like.

Among various silicone oil described above, dimethyl silicone oil, that suppresses generation of the ultrafine particles further, is preferably used. In order to suppress generation of the ultrafine particles, the fixing device20according to the embodiment employs the silicone oil in which, among molecules that construct an organo polysiloxane, the siloxanes from the dodecamer to the heptadecamer have a concentration that is not greater than 1,250 ppm, preferably not greater than 500 ppm.

For example, methods for achieving the concentration of the siloxanes from the dodecamer to the heptadecamer, that is not greater than 1,250 ppm, include heating under reduced pressure, refining by solvent extraction with alcohols such as methanol, ethanol, and butanol, and refining by a liquid chromatography using a mixed solvent of toluene and acetone as eluent.

The fixing device20according to the embodiment advantageously employs the silicone oil having a viscosity at the fixing temperature, that is not greater than 10,000 cSt (10,000 mm2/s), preferably 5,000 cSt (5,000 mm2/s).

Alternatively, the rotator holder according to the embodiment (e.g., the belt holder27) may be applied with the silicone grease instead of the silicone oil. The silicone grease uses the silicone oil as base oil and is semi-solidified with a thickener such as metal soap and polyfluoroethylene.

The following describes the technology of the present disclosure in detail with embodiments of the present disclosure and comparative examples. However, the technology of the present disclosure is not limited to the embodiments described below.

A description is provided of an adjustment1of silicone oil.

A description is now given of silicone oil used in embodiments and comparative examples depicted in a table 1 below.

A silicone oil1depicted in the table 1 is dimethyl silicone oil that is commercially available and has a kinetic viscosity of 104 mm2/s at 25 degrees Celsius. Other silicone oils2,3, and4are obtained by vacuum drying of the silicone oil1at 195 degrees Celsius, 215 degrees Celsius, and 230 degrees Celsius. The silicone oils1to4contain cyclic siloxanes from the dodecamer to the heptadecamer that have concentrations that are different from each other as illustrated in the table 1 below. See the concentrations in parentheses beside the silicone oils1to4in the table 1. The concentrations of the cyclic siloxanes are measured by gas chromatography under measurement conditions below.

The embodiment 1 used the fixing device20having the construction depicted inFIGS.2and3. The fixing device20incorporated the belt holder27made of a material containing glass fiber, carbon black, and glass beads in liquid crystal polymer. The silicone oil1was impregnated into the slide sheet30. The silicone oil3was applied onto the outer circumferential face of the belt holder27. The fixing belt21rotated for one rotation. The silicone oil1was interposed between the inner circumferential face21bof the fixing belt21and a slide portion of the slide sheet30, which contacted the inner circumferential face21bof the fixing belt21and over which the fixing belt21slid. The silicone oil3was interposed between the inner circumferential face21bof the fixing belt21, that contacted the belt holder27, and the belt holder27. The fixing device20configured as described above was installed in an image forming apparatus that printed at a print speed of 50 pages per minute (ppm). The image forming apparatus performed continuous printing for 10 minutes at an accredited test site for the German ecolabel, the Blue Angel mark. As a result, according to the embodiment 1, as illustrated in the table 1, the ultrafine particles generated at a generation speed of 3.0×1011pieces per 10 minutes during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as an accreditation criterion of the Blue Angel mark. The belt holder27had a highest temperature of 203 degrees Celsius during continuous printing for 10 minutes. Further, the image forming apparatus performed printing in an indoor environment and formed images on 50,000 sheets in total. No failure appeared on the lateral end of the fixing belt21in the longitudinal direction X thereof.

A description is provided of an embodiment 2.

According to the embodiment 2, the silicone oil4was applied on the outer circumferential face of the belt holder27. Other conditions of the embodiment 2 were identical to the conditions of the embodiment 1 described above. Like the embodiment 1, the image forming apparatus formed images at the accredited test site and the generation speed of the ultrafine particles was measured. As a result, as illustrated in the table 1, according to the embodiment 2, the ultrafine particles generated at a generation speed of 2.4×1011pieces per 10 minutes during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. The belt holder27had the highest temperature of 203 degrees Celsius during continuous printing for 10 minutes. After the image forming apparatus formed images on 50,000 sheets, no failure appeared on the lateral end of the fixing belt21in the longitudinal direction X thereof.

A description is provided of an embodiment 3.

According to the embodiment 3, the silicone oil2was applied on the outer circumferential face of the belt holder27. Other conditions of the embodiment 3 were identical to the conditions of the embodiment 1 described above. Like the embodiment 1, the image forming apparatus formed images at the accredited test site and the generation speed of the ultrafine particles was measured. As a result, as illustrated in the table 1, according to the embodiment 3, the ultrafine particles generated at a generation speed of 3.5×1011pieces per 10 minutes during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. The belt holder27had the highest temperature of 203 degrees Celsius during continuous printing for 10 minutes. After the image forming apparatus formed images on 50.000 sheets, no failure appeared on the lateral end of the fixing belt21in the longitudinal direction X thereof.

A description is provided of a comparative example 1.

According to the comparative example 1, the silicone oil1was applied on the outer circumferential face of the belt holder27. Other conditions of the comparative example 1 were identical to the conditions of the embodiment 1 described above. Like the embodiment 1, the image forming apparatus formed images at the accredited test site and the generation speed of the ultrafine particles was measured. As a result, as illustrated in the table 1, according to the comparative example 1, the ultrafine particles generated at a generation speed of 5.9×1011pieces per 10 minutes during continuous printing for 10 minutes, that was greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. The belt holder27had the highest temperature of 203 degrees Celsius during continuous printing for 10 minutes. After the image forming apparatus formed images on 50,000 sheets, no failure appeared on the lateral end of the fixing belt21in the longitudinal direction X thereof.

A description is provided of a comparative example 2.

According to the comparative example 2, no silicone oil was applied on the outer circumferential face of the belt holder27. Other conditions of the comparative example 2 were identical to the conditions of the embodiment 1 described above. Like the embodiment 1, the image forming apparatus formed images at the accredited test site and the generation speed of the ultrafine particles was measured. As a result, as illustrated in the table 1, according to the comparative example 2, the ultrafine particles generated at a generation speed of 1.6×1011pieces per 10 minutes during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. The belt holder27had a highest temperature of 205 degrees Celsius during continuous printing for 10 minutes. After the image forming apparatus formed images on 50,000 sheets, a substantial number of scratches appeared on the lateral end of the fixing belt21in the longitudinal direction X thereof.

A description is provided of an adjustment2of silicone oil.

A description is now given of silicone oil used in embodiments and comparative examples depicted in a table 2 below.

The table 2 illustrates silicone oils5,6, and7obtained by mixing and agitating the silicone oil1in ethanol, thereafter leaving, separating the silicone oil1from ethanol to extract the silicone oil1, treating the extracted silicone oil1with vacuum drying at 180 degrees Celsius, 200 degrees Celsius, and 220 degrees Celsius. The table 2 illustrates a silicone oil8obtained by refining the silicone oil1by liquid chromatography (LC) under conditions below.

According to the embodiment 4, the silicone oil5was impregnated into the slide sheet30and was applied on the outer circumferential face of the belt holder27. Other conditions of the embodiment 4 were identical to the conditions of the embodiment 1 described above. The fixing device20according to the embodiment 4 was installed in an image forming apparatus that had a print speed of 60 pages per minute (ppm). The image forming apparatus performed continuous printing for 10 minutes at the accredited test site for the German ecolabel, the Blue Angel mark. As a result, according to the embodiment 4, as illustrated in the table 2, the ultrafine particles generated at a generation speed of 3.0×1011pieces per 10 minutes during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. The belt holder27had a highest temperature of 212 degrees Celsius during continuous printing for 10 minutes.

A description is provided of an embodiment 5.

According to the embodiment 5, the silicone oil6was applied on the outer circumferential face of the belt holder27. Other conditions of the embodiment 5 were identical to the conditions of the embodiment 4 described above. Like the embodiment 4, the image forming apparatus formed images at the accredited test site and the generation speed of the ultrafine particles was measured. As a result, as illustrated in the table 2, according to the embodiment 5, the ultrafine particles generated at a generation speed of 2.6×1011pieces per 10 minutes during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. The belt holder27had the highest temperature of 212 degrees Celsius during continuous printing for 10 minutes.

A description is provided of an embodiment 6.

According to the embodiment 6, the silicone oil7was applied on the outer circumferential face of the belt holder27. Other conditions of the embodiment 6 were identical to the conditions of the embodiment 4 described above. Like the embodiment 4, the image forming apparatus formed images at the accredited test site and the generation speed of the ultrafine particles was measured. As a result, as illustrated in the table 2, according to the embodiment 6, the ultrafine particles generated at a generation speed of 1.5×1011pieces per 10 minutes during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. The belt holder27had the highest temperature of 212 degrees Celsius during continuous printing for 10 minutes.

A description is provided of an embodiment 7.

According to the embodiment 7, the silicone oil8was applied on the outer circumferential face of the belt holder27. Other conditions of the embodiment 7 were identical to the conditions of the embodiment 4 described above. Like the embodiment 4, the image forming apparatus formed images at the accredited test site and the generation speed of the ultrafine particles was measured. As a result, as illustrated in the table 2, according to the embodiment 7, the ultrafine particles generated at a generation speed of 0.8×1011pieces per 10 minutes during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. The belt holder27had the highest temperature of 212 degrees Celsius during continuous printing for 10 minutes.

A description is provided of a comparative example 3.

According to the comparative example 3, the silicone oil8was impregnated into the slide sheet30. The silicone oil1was applied on the outer circumferential face of the belt holder27. Other conditions of the comparative example 3 were identical to the conditions of the embodiment 4 described above. Like the embodiment 4, the image forming apparatus formed images at the accredited test site and the generation speed of the ultrafine particles was measured. As a result, as illustrated in the table 2, according to the comparative example 3, the ultrafine particles generated at a generation speed of 6.6×1011pieces per 10 minutes during continuous printing for 10 minutes, that was greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. The belt holder27had the highest temperature of 212 degrees Celsius during continuous printing for 10 minutes.

As described above, according to results depicted in the tables 1 and 2, according to each of the embodiments 1 to 7 in which the concentration of the cyclic siloxanes from the dodecamer to the heptadecamer, that were contained in the silicone oil, was not greater than 1,250 ppm, the ultrafine particles generated at a generation speed during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. Conversely, according to each of the comparative examples 1 and 3 in which the concentration of the cyclic siloxanes from the dodecamer to the heptadecamer, that were contained in the silicone oil, was greater than 1,250 ppm, the ultrafine particles generated at a generation speed during continuous printing for 10 minutes, that was greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. Accordingly, the concentration of the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil adhered to the belt holder27is not greater than 1, 250 ppm, thus suppressing generation of the ultrafine particles during continuous printing for 10 minutes effectively. The concentration of the siloxanes from the dodecamer to the heptadecamer is preferably not greater than 500 ppm, suppressing generation of the ultrafine particles further. Since the siloxanes from the dodecamer to the heptadecamer generate the ultrafine particles, as an amount of the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil decreases, an amount of the ultrafine particles decreases. The amount of the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil decreases by a general refining method, even to 0 ppm. For example, with the liquid chromatography (LC) used to refine the silicone oil8, refining is repeated three times to obtain the concentration of 0 ppm of the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil. With the silicone oil containing the siloxanes from the dodecamer to the heptadecamer, that had the concentration of 0 ppm, instead of the silicone oil8according to the embodiment 7, the image forming apparatus formed images similarly. The ultrafine particles generated at a generation speed of 0.8×1011pieces per 10 minutes during continuous printing for 10 minutes, that was not greater than 3.5×1011pieces per 10 minutes as the accreditation criterion of the Blue Angel mark. Hence, according to the embodiments 1 to 7 of the present disclosure, the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil have a concentration not smaller than 0 ppm and not greater than 1,250 ppm.

According to the comparative example 2 depicted in the table 1, the substantial number of scratches appeared on the lateral end of the fixing belt21in the longitudinal direction X thereof. In order to suppress generation of the scratches, the lubricant such as the silicone oil is to be interposed between the belt holder27and the fixing belt21. Conversely, according to the embodiments 1 to 7, since the silicone oil was interposed between the belt holder27and the fixing belt21, no failure appeared on the lateral end of the fixing belt21in the longitudinal direction X thereof. Hence, the embodiments 1 to 7 suppress damage to the lateral end of the fixing belt21in the longitudinal direction X thereof, extending a life of the fixing device20and suppressing generation of the ultrafine particles. As described above, according to the embodiments 1 to 7 of the present disclosure, even with the construction of the fixing device20in which the silicone oil is interposed between the belt holder27and the fixing belt21to suppress damage to the fixing belt21, the fixing device20suppresses generation of the ultrafine particles, attaining an extended life and a reduced generation amount of the ultrafine particles.

Generally, as productivity of image formation increases, for example, as a print speed increases, an amount of heat supplied from the heaters23to the fixing belt21increases. Hence, the belt holder27is also subject to temperature increase. For example, if an image forming apparatus performs image formation at a print speed of 50 ppm or higher at which images are formed on 50 or more sheets having an A4 size per minute, the belt holder27may likely have a temperature of 200 degrees Celsius or higher. Hence, in the image forming apparatus, the silicone oil or the silicone grease adhered to the belt holder27may have a temperature of 200 degrees Celsius or higher at which the ultrafine particles generate, thus generating a substantial amount of the ultrafine particles.

For example, temperature increase of the belt holder27, that generates the ultrafine particles, becomes more pronounced as the image forming apparatus increases a number of prints per unit time. Hence, the embodiments 1 to 7 of the present disclosure are more advantageous if the embodiments 1 to 7 are applied to the image forming apparatus that prints on an increased number of sheets.FIG.7illustrates a relation between a print speed and a generation speed (e.g., a number) of the FP/UFP generated. The number of the FP/UFP generated from the fixing device20during continuous printing for 10 minutes increases sharply approximately at a print speed exceeding 50 ppm. Hence, the embodiments 1 to 7 of the present disclosure are more advantageous if the embodiments 1 to 7 are applied to the fixing device20or the image forming apparatus100that prints at a print speed of 50 ppm or higher.

If a highest temperature of the belt holder27reaches a highest temperature range not lower than 200 degrees Celsius and not higher than 240 degrees Celsius during continuous printing for 10 minutes, the temperature of the silicone oil or the silicone grease may likely reach 200 degrees Celsius or higher at which the ultrafine particles generate. Hence, the embodiments 1 to 7 of the present disclosure are more advantageous if the embodiments 1 to 7 are applied to the fixing device20in which the belt holder27has the highest temperature range not lower than 200 degrees Celsius and not higher than 240 degrees Celsius during continuous printing for 10 minutes.

The temperature of the belt holder27reaches the highest temperature range not lower than 200 degrees Celsius and not higher than 240 degrees Celsius during continuous printing for 10 minutes, because the image forming apparatus100is frequently used for continuous printing within a few minutes in a general market and is barely used for continuous printing for five minutes or longer. To address the circumstance, according to the embodiments of the present disclosure, suppression of generation of the ultrafine particles at least during continuous printing for 10 minutes is satisfactory.

The highest temperature of a belt holder (e.g., the belt holder27) during continuous printing for 10 minutes denotes a maximum temperature of the belt holder27measured with processes described below. The processes for temperature measurement include placing an image forming apparatus (e.g., the image forming apparatus100) installed with a fixing device or a heating device (e.g., the fixing device20) in a test chamber at an ambient temperature of 23 degrees Celsius, turning on a power supply of the image forming apparatus to start the image forming apparatus, and sending a print instruction after a standby time for 60 minutes, for example, elapses. As print conditions, a mode in which a highest print speed is set as a default print speed is selected. Sheets having a paper weight of 70 g/m2and an A4 size or a letter size are used. Sheets for which conveyance in landscape orientation is available are conveyed in landscape orientation. Sheets for which conveyance in landscape orientation is not available are conveyed in portrait orientation. Conveyance in landscape orientation denotes that a sheet is conveyed in a state in which a long side of the sheet extends in an orthogonal direction perpendicular to a conveyance direction of the sheet. Conveyance in portrait orientation denotes that a sheet is conveyed in a state in which a short side of the sheet extends in the orthogonal direction perpendicular to the conveyance direction of the sheet. From a print start time when a first sheet is ejected from a sheet tray (e.g., the sheet tray14), a thermocouple measures a temperature of the belt holder for 10 minutes. However, if a continuous print time is restricted to 10 minutes or shorter in relation to a capacity of an output tray (e.g., the output tray18) and a capacity of the sheet tray, the temperature of the belt holder is measured within the continuous print time. In addition to the processes for temperature measurement described above, the temperature of the belt holder may be measured with a device and a condition that conform to criteria of the Blue Angel mark for the ultrafine particles.

The above describes the embodiments of the present disclosure. However, application of the technology of the present disclosure is not limited to the fixing device20having the construction depicted inFIGS.2to4. The technology of the present disclosure is also applied to fixing devices having other constructions. The following describes constructions of fixing devices applied with the technology of the present disclosure.

Referring toFIGS.8and9, a description is provided of a construction of a fixing device40according to an embodiment of the present disclosure.

The fixing device40includes a fixing belt41serving as a first rotator, a rotator, or an endless belt, a pressure roller42serving as a second rotator or an opposed rotator, a heater43serving as a heat source, a heater holder44serving as a heat source holder, a pressure stay45serving as a support, a thermistor48serving as a temperature detector, and flanges47serving as rotator holders depicted inFIG.9.

The fixing belt41and the pressure roller42depicted inFIG.8have functions and constructions that are basically equivalent to those of the fixing belt21and the pressure roller22depicted inFIG.2, respectively.

The heater43is a ceramic heater that includes a platy substrate and resistive heat generators mounted on the substrate. As power is supplied to the resistive heat generators, the heater43generates heat. The heater43contacts an inner circumferential face of the fixing belt41. As the heater43generates heat, the heater43heats the inner circumferential face of the fixing belt41. The heater43also serves as a nip formation pad that forms the fixing nip N at which the heater43and the pressure roller42sandwich the fixing belt41.

The heater holder44serves as the heat source holder that holds the heater43. The heater holder44is made of heat-resistant resin, for example. The heater holder44is semicircular in cross section along the inner circumferential face of the fixing belt41. The heater holder44restricts a rotation orbit of the fixing belt41.

The pressure stay45serves as a support that supports the heater holder44. As the pressure stay45supports the heater holder44, the pressure stay45prevents the heater holder44and the heater43from being bent by pressure from the pressure roller42. Accordingly, the fixing nip N, having an even length in the sheet conveyance direction DP throughout an entire span of the fixing belt41in a longitudinal direction thereof, is formed between the fixing belt41and the pressure roller42. The pressure stay45is preferably made of a metal material such as stainless used steel (SUS) to achieve rigidity.

The pressure stay45mounts the thermistor48serving as the temperature detector. The thermistor48is disposed opposite the inner circumferential face of the fixing belt41such that the thermistor48contacts or does not contact the inner circumferential face of the fixing belt41, thus detecting the temperature of the fixing belt41.

Like the belt holders27, the flanges47serve as a pair of holders, rotator holders, or belt holders that holds both lateral ends of the fixing belt41in the longitudinal direction thereof, respectively. Each of the flanges47includes a backup portion47aand a flange portion47b. The backup portion47aserves as an insertion portion that is inserted into a loop formed by the fixing belt41. The flange portion47bserves as a restrictor that restricts motion of the fixing belt41in the longitudinal direction thereof. As a biasing member such as a spring biases each of the flanges47against each lateral end of the fixing belt41in the longitudinal direction thereof, each of the flanges47is held within the loop formed by the fixing belt41in a state in which each of the flanges47is inserted into the loop formed by the fixing belt41.

With the above-described construction of the fixing device40also, as the heater43generates heat, the temperature of the flanges47increases. Accordingly, the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil or the silicone grease adhered to the flanges47may volatilize, generating the ultrafine particles. To address the circumstance, the fixing device40depicted inFIGS.8and9is also applied with the technology of the present disclosure, suppressing generation of the ultrafine particles.

A description is provided of a construction of a fixing device50according to an embodiment of the present disclosure.

As illustrated inFIGS.10and11, the fixing device50includes a heater53(e.g., a ceramic heater) like the fixing device40depicted inFIGS.8and9. For example, the fixing device50depicted inFIGS.10and11includes a fixing belt51serving as a first rotator, a rotator, or an endless belt, a pressure rotator52(e.g., a pressure roller) serving as a second rotator or an opposed rotator, the heater53serving as a heat source and a nip formation pad, a heater holder54serving as a heat source holder, a reinforcement55serving as a support, belt holders57serving as rotator holders depicted inFIG.11, thermosensitive elements58serving as temperature detectors depicted inFIG.11, and covers59depicted inFIG.11.

The fixing belt51, the pressure rotator52, the heater53, the heater holder54, the reinforcement55, and the belt holders57depicted inFIGS.10and11have functions and constructions that are basically equivalent to those of the fixing belt41, the pressure roller42, the heater43, the heater holder44, the pressure stay45, and the flanges47depicted inFIGS.8and9, respectively.

The thermosensitive elements58are mounted on an opposite face of the heater holder54, that is opposite to a heater holding face of the heater holder54, that holds the heater53. The thermosensitive elements58detect a temperature of the heater53through the heater holder54. A controller controls heat generation of the heater53based on the temperature of the heater53, that is detected by the thermosensitive elements58, thus retaining a predetermined fixing temperature of the fixing belt51.

Each of the covers59is a box made of heat-resistant resin. As the covers59are disposed opposite the heater holder54via the thermosensitive elements58within a loop formed by the fixing belt51, the covers59cover the thermosensitive elements58disposed opposite the covers59, respectively.

As described above, the fixing device50applied with the technology of the present disclosure includes the thermosensitive elements58that detect the temperature of the heater53and the covers59that cover the thermosensitive elements58.

A description is provided of a construction of a fixing device60according to an embodiment of the present disclosure.

As illustrated inFIG.12, the fixing device60includes a heater63(e.g., a halogen heater) serving as a heat source, like the fixing device20depicted inFIGS.2and3. For example, the fixing device60depicted inFIGS.12and13includes a fixing belt61serving as a first rotator, a rotator, or an endless belt, a pressure roller62serving as a second rotator or an opposed rotator, the heater63serving as a heat source, a nip formation pad64, a support65, a reflection plate66serving as a reflector, holding frames67serving as rotator holders depicted inFIG.13, and rings68serving as slide aids depicted inFIG.13.

The fixing belt61, the pressure roller62, the heater63, the nip formation pad64, the support65, the reflection plate66, and the holding frames67depicted inFIGS.12and13have functions and constructions that are basically equivalent to those of the fixing belt21, the pressure roller22, the heater23, the nip formation pad24, the stay25, the reflector26, and the belt holders27depicted inFIGS.2and3, respectively. The nip formation pad64includes a base pad640and a slide sheet641. The base pad640is made of metal. The slide sheet641is interposed between the base pad640and an inner circumferential face of the fixing belt61and is made of fluororesin.

Each of the holding frames67includes a tube67aand a securing plate67b. The ring68is attached to an outer circumferential face of the tube67athat serves as an insertion portion of the holding frame67and is inserted into a loop formed by the fixing belt61. The ring68is interposed between a lateral edge of the fixing belt61in a longitudinal direction thereof and the securing plate67bserving as a restrictor of the holding frame67. As the fixing belt61rotates, the rings68rotate in accordance with rotation of the fixing belt61or the fixing belt61slides over the rings68having low friction, thus decreasing sliding friction that generates between the fixing belt61and the holding frames67.

As described above, the fixing device60applied with the technology of the present disclosure includes the rings68.

A description is provided of a construction of a fixing device70according to an embodiment of the present disclosure.

As illustrated inFIGS.14and15, the fixing device70includes a halogen heater73serving as a heater or a heat source, like the fixing device20depicted inFIGS.2and3. For example, the fixing device70depicted inFIGS.14and15includes a fixing belt71serving as a first rotator, a rotator, or an endless belt, a pressure roller72serving as a second rotator or an opposed rotator, the halogen heater73serving as the heater or the heat source, a nip formation pad74, a reflector76, belt supports77serving as rotator holders depicted inFIG.15, a temperature sensor78serving as a temperature detector, and guides79.

The fixing belt71, the pressure roller72, the halogen heater73, the nip formation pad74, the reflector76, the belt supports77, and the temperature sensor78depicted inFIGS.14and15have functions that are basically equivalent to those of the fixing belt21, the pressure roller22, the heater23, the nip formation pad24, the reflector26, the belt holders27, and the temperature sensor28depicted inFIGS.2and3, respectively.

The reflector76depicted inFIGS.14and15reflects radiant heat (e.g., infrared light) emitted from the halogen heater73toward the nip formation pad74mainly, not the fixing belt71. The reflector76is U-shaped in cross section to cover an outer circumferential face of the halogen heater73. The reflector76includes an inner face76athat is disposed opposite the halogen heater73and serves as a reflection face having an enhanced reflectance. Accordingly, as the halogen heater73emits radiant heat, the inner face76aof the reflector76reflects the radiant heat toward the nip formation pad74.

Thus, the nip formation pad74is heated by the radiant heat emitted by the halogen heater73toward the nip formation pad74and the radiant heat reflected by the reflector76toward the nip formation pad74. The nip formation pad74conducts heat to the fixing belt71at the fixing nip N. The nip formation pad74forms the fixing nip N. Additionally, the nip formation pad74serves as a thermal conductor that conducts heat to the fixing belt71at the fixing nip N. Hence, the nip formation pad74is made of a metal material having an enhanced thermal conductivity, such as copper and aluminum.

The reflector76also serves as a support (e.g., a stay) that supports the nip formation pad74. The reflector76supports the nip formation pad74throughout an entire span of the fixing belt71in a longitudinal direction thereof, suppressing a bend of the nip formation pad74. Accordingly, the fixing nip N, having an even length in the sheet conveyance direction DP throughout the entire span of the fixing belt71in the longitudinal direction thereof, is formed between the fixing belt71and the pressure roller72. In order to achieve a function of the reflector76as the support, the reflector76is preferably made of a metal material having an enhanced rigidity such as SUS and SECC.

The guides79are disposed within a loop formed by the fixing belt71. The guides79contact and guide an inner circumferential face of the fixing belt71that rotates. Each of the guides79includes a guide face79athat is curved along the inner circumferential face of the fixing belt71. As each of the guides79guides the fixing belt71along the guide face79a, the fixing belt71rotates smoothly without substantial deformation.

As described above, the fixing device70applied with the technology of the present disclosure includes the nip formation pad74, having an enhanced thermal conductivity, through which heat generated by the halogen heater73is conducted to the fixing belt71, thus heating the fixing belt71.

A description is provided of a construction of a fixing device80according to an embodiment of the present disclosure.

As illustrated inFIG.16, the fixing device80includes a heater83(e.g., a ceramic heater) serving as a heat source, like the fixing device40depicted inFIGS.8and9. For example, the fixing device80depicted inFIGS.16and17includes a fixing belt81serving as a first rotator, a rotator, or an endless belt, a pressure roller82serving as a second rotator or an opposed rotator, the heater83serving as the heat source, a holder84serving as a heat source holder, a stay85serving as a support, arcuate guides87serving as rotator holders depicted inFIG.17, a thermal diffuser88serving as a thermal conductor and a nip formation pad, and a thermal insulation plate89serving as a thermal insulator.

The fixing belt81, the pressure roller82, the heater83, the holder84, the stay85, and the arcuate guides87depicted inFIGS.16and17have functions that are basically equivalent to those of the fixing belt41, the pressure roller42, the heater43, the heater holder44, the pressure stay45, and the flanges47depicted inFIGS.8and9, respectively. The holder84holds the thermal diffuser88and the thermal insulation plate89layered on the thermal diffuser88, in addition to the heater83.

The thermal diffuser88is made of a metal material such as stainless steel, an alloy of aluminum, and iron. The thermal diffuser88contacts an inner circumferential face of the fixing belt81. The thermal diffuser88conducts heat generated by the heater83to the fixing belt81. Additionally, the thermal diffuser88is disposed opposite the pressure roller82via the fixing belt81, forming the fixing nip N between the fixing belt81and the pressure roller82. Thermal grease is applied between the heater83and the thermal diffuser88, improving efficiency in conduction of heat from the heater83to the thermal diffuser88. In order to suppress conduction of heat from the heater83to the holder84and the stay85, the thermal insulation plate89is mounted on an opposite face of the heater83, that is opposite to a thermal diffuser opposed face of the heater83, that is disposed opposite the thermal diffuser88.

As the fixing belt81rotates, the fixing belt81slides over the thermal diffuser88. Hence, the silicone oil or the silicone grease is applied between the fixing belt81and the thermal diffuser88, as the lubricant that facilitates sliding of the fixing belt81over the thermal diffuser88. The thermal diffuser88includes a slide face that contacts the fixing belt81. The slide face includes a surface layer treated with glass coating or hard chromium plating that has low friction and abrasion resistance.

With the above-described construction of the fixing device80also, as the heater83generates heat and the temperature of the arcuate guides87increases, the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil or the silicone grease adhered to the arcuate guides87may volatilize, generating the ultrafine particles. To address the circumstance, the fixing device80is applied with the technology of the present disclosure, suppressing generation of the ultrafine particles.

A description is provided of a construction of a fixing device90according to an embodiment of the present disclosure.

As illustrated inFIGS.18and19, the fixing device90includes a belt91(e.g., an endless belt) serving as a first rotator or a rotator, a heating roller96serving as a heating rotator, a heater93serving as a heat source, a pressure roller92serving as a second rotator or an opposed rotator, a nip formation pad94, a support95, a guide98, a lubricant applicator99serving as a lubricant supply, and bearings97serving as rotator holders depicted inFIG.19.

As illustrated inFIG.18, the belt91is looped over the heating roller96, the nip formation pad94, and the guide98. As a spring or the like biases the heating roller96in a separation direction in which the heating roller96separates from the nip formation pad94, the heating roller96applies predetermined tension to the belt91. In a state in which the belt91is applied with the predetermined tension, as a driver drives and rotates the pressure roller92, the pressure roller92drives and rotates the belt91.

The nip formation pad94includes a pressure pad940and a slide sheet941. The slide sheet941is interposed between the pressure pad940and an inner circumferential face of the belt91and has low friction. Since the support95supports the pressure pad940, the pressure pad940receives pressure from the pressure roller92, forming the fixing nip N between the belt91and the pressure roller92.

The heater93is a halogen heater or the like and is disposed inside the heating roller96. As the heater93generates heat, the heater93heats the heating roller96that conducts heat to the belt91.

The lubricant applicator99contacts the inner circumferential face of the belt91, supplying the lubricant that improves sliding of the belt91to the inner circumferential face of the belt91. As the belt91rotates, the lubricant supplied to the inner circumferential face of the belt91is interposed between the guide98and the belt91and between the nip formation pad94and the belt91, facilitating smooth rotation of the belt91.

The bearing97such as a sliding bearing and a ball bearing holds the heating roller96such that the heating roller96is rotatable. The bearing97serving as the rotator holder is attached to each lateral end of the heating roller96in an axial direction thereof, that is, a longitudinal direction thereof. The bearing97is applied with the lubricant such as the silicone oil and the silicone grease that decreases sliding friction or rotation torque when the heating roller96rotates.

As the heater93heats the heating roller96and heat is conducted from the heating roller96to the bearings97, the temperature of the silicone oil or the silicone grease adhered to the bearings97increases. Accordingly, the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil or the silicone grease may volatilize, generating the ultrafine particles. To address the circumstance, the fixing device90depicted inFIGS.18and19is also applied with the technology of the present disclosure, decreasing the number of the ultrafine particles that generate from the silicone oil or the silicone grease, like the embodiments described above.

The technology of the present disclosure is also applied to a fixing device110having a construction illustrated inFIGS.20and21.

The fixing device110depicted inFIGS.20and21includes a fixing belt111serving as a first rotator, a rotator, or an endless belt, a fixing roller116, a pressure roller112serving as a second rotator or an opposed rotator, a heater113serving as a heat source, a pressure pad114serving as a nip formation pad, a guide115, a support117, a temperature sensor118serving as a temperature detector, a thermal conductor119, and belt holders122serving as rotator holders depicted inFIG.21.

As illustrated inFIG.20, the fixing belt111is looped over the fixing roller116, the pressure pad114, the guide115, and the thermal conductor119. As the pressure roller112drives and rotates the fixing belt111, the fixing belt111rotates the fixing roller116.

The heater113is a laminated heater or a platy heater such as a ceramic heater and is attached to the thermal conductor119. The thermal conductor119is interposed between the heater113and the fixing belt111and conducts heat generated by the heater113to the fixing belt111. The fixing device110further includes a spring120that is anchored to the support117. The spring120biases the thermal conductor119against an inner circumferential face of the fixing belt111so that the thermal conductor119contacts the inner circumferential face of the fixing belt111.

The fixing device110further includes another spring121that is anchored to the support117. The spring121biases the pressure pad114against the inner circumferential face of the fixing belt111so that the pressure pad114contacts the inner circumferential face of the fixing belt111. Thus, the spring121presses the pressure pad114against the pressure roller112via the fixing belt111, forming the fixing nip N between the fixing belt111and the pressure roller112.

The guide115is attached to and supported by the support117. The temperature sensor118is attached to the guide115and detects the temperature of the fixing belt111.

In the fixing device110depicted inFIGS.20and21also, the belt holders122hold both lateral ends of the fixing belt111in a longitudinal direction thereof, respectively. Hence, as the heater113heats the fixing belt111, the temperature of the silicone oil or the silicone grease adhered to the belt holders122increases. Accordingly, the siloxanes that are from the dodecamer to the heptadecamer and are contained in the silicone oil or the silicone grease may volatilize, generating the ultrafine particles. To address the circumstance, the fixing device110is also applied with the technology of the present disclosure, suppressing generation of the ultrafine particles effectively, like the embodiments described above.

Application of the technology of the present disclosure is not limited to a fixing device (e.g., the fixing devices20,40,50,60,70,80,90, and110) installed in an image forming apparatus (e.g., the image forming apparatus100) that forms an image by electrophotography. For example, the technology of the present disclosure is also applied to a heating device other than the fixing device, that is installed in an image forming apparatus employing an inkjet method. The heating device includes a dryer that dries liquid such as ink applied on a sheet.

FIG.22illustrates an inkjet image forming apparatus2000according to an embodiment of the present disclosure, that incorporates a dryer206.

As illustrated inFIG.22, the inkjet image forming apparatus2000includes a scanner202, an image forming device203, a sheet supply204, the dryer206, and a sheet output device207. A sheet aligner3000(e.g., a finisher) is disposed beside the inkjet image forming apparatus2000.

When the inkjet image forming apparatus2000receives an instruction to start printing, the sheet supply204supplies a sheet (e.g., paper) serving as a recording medium. When the sheet is conveyed to the image forming device203, a liquid discharge head214of the image forming device203discharges ink onto the sheet according to image data created by the scanner202that reads an image on an original or image data (e.g., print data) sent from a terminal, thus forming an image on the sheet.

The sheet bearing the image is selectively guided to a conveyance path222provided with the dryer206or a conveyance path223not provided with the dryer206. If the sheet is guided to the dryer206, the dryer206facilitates drying of ink on the sheet. The sheet is guided to the sheet output device207or the sheet aligner3000. Conversely, if the sheet is guided to the conveyance path223not provided with the dryer206, the sheet is guided to the sheet output device207or the sheet aligner3000without being dried by the dryer206. If the sheet is guided to the sheet aligner3000, the sheet aligner3000aligns the sheet and places the sheet on a tray.

As illustrated inFIG.23, the dryer206serving as a heating device includes a heating belt291serving as a first rotator, a rotator, or an endless belt, a heating roller292serving as a second rotator or an opposed rotator, a first heater293serving as a heater or a heat source that heats the heating belt291, a second heater294serving as a heat source that heats the heating roller292, a nip formation pad295, a stay296serving as a support, a reflector297, and a pair of belt holders298serving as rotator holders that rotatably hold the heating belt291.

The nip formation pad295presses against an outer circumferential face of the heating roller292via the heating belt291, forming the fixing nip N between the heating belt291and the heating roller292. As illustrated inFIG.23, as a sheet250bearing an image, that is, ink I, is conveyed through the fixing nip N of the dryer206, the heating belt291that rotates in a rotation direction D291and the heating roller292that rotates in a rotation direction D292heat the sheet250while conveying the sheet250. Thus, the dryer206facilitates drying of the ink I on the sheet250.

In the dryer206depicted inFIG.23, the pair of belt holders298disposed opposite both lateral ends of the heating belt291in a longitudinal direction thereof, respectively, rotatably holds the heating belt291. Hence, as the first heater293heats the heating belt291and the temperature of the belt holders298increases, the silicone oil or the silicone grease adhered to the belt holders298may generate the ultrafine particles. To address the circumstance, the dryer206is also applied with the technology of the present disclosure, suppressing generation of the ultrafine particles effectively.

The technology of the present disclosure is also applied to an image forming apparatus4000including a laminator401illustrated inFIG.24.

As illustrated inFIG.24, the image forming apparatus4000includes, in addition to the laminator401, an image forming device402including a plurality of image forming units411C,411M,411Y, and411Bk, an exposure device412, and a transfer device413, a fixing device403, and a sheet feeder404serving as a recording medium supply.

The laminator401serves as a heating device that heats and presses a sheet P inserted into and sandwiched between two sheets, thus bonding the sheets by thermocompression. For example, the laminator401includes a sheet supply420, a sheet peeler430, and thermal pressure rollers440. The sheet supply420supplies sheets450. The sheet peeler430peels the sheets450supplied from the sheet supply420into two sheets450. Each of the thermal pressure rollers440serves as a rotator that conveys the sheet P and the sheets450while heating and pressing the sheet P and the sheets450in a state in which the sheet P is inserted into a gap between the two peeled sheets450. The laminator401further includes a heat source such as a heater that heats the thermal pressure roller440. The laminator401further includes a pair of bearings serving as a pair of rotator holders that rotatably holds both lateral ends of the thermal pressure roller440in a longitudinal direction thereof, respectively.

In the image forming apparatus4000depicted inFIG.24, as the sheet feeder404supplies a sheet P serving as a recording medium to the image forming device402, the image forming device402forms an image and transfers the image onto the sheet P supplied from the sheet feeder404. The sheet P transferred with the image is conveyed to the fixing device403that fixes the image on the sheet P. Image forming operation and transfer operation of the image forming device402(e.g., operation of the image forming units411C,411M,411Y, and411Bk, the exposure device412, and the transfer device413) and fixing operation of the fixing device403are basically equivalent to those according to the embodiments described above. Therefore, a description of the image forming operation, the transfer operation, and the fixing operation is omitted.

The sheet P bearing the fixed image is conveyed to the laminator401and is inserted into the gap between the two sheets450that are peeled. The thermal pressure rollers440heat and press the sheets450and the sheet P sandwiched between the two sheets450, thus bonding the sheets450and the sheet P by thermocompression. The sheet P bonded with the sheets450is ejected to an outside of the image forming apparatus4000.

As the heat source such as the heater heats the thermal pressure roller440, the temperature of bearings that support the thermal pressure roller440increases. Accordingly, the silicone oil or the silicone grease adhered to the bearings may generate the ultrafine particles. To address the circumstance, the laminator401incorporating the thermal pressure rollers440is also applied with the technology of the present disclosure, suppressing generation of the ultrafine particles effectively.

The technology of the present disclosure encompasses at least a heating device, a fixing device, and an image forming apparatus that have configurations below.

A description is provided of a first configuration of the heating device (e.g., the fixing devices20,40,50,60,70,80,90,110, and403, the dryer206, and the laminator401).

The heating device includes a rotator (e.g., the fixing belts21,41,51,61,71,81, and111, the belt91, the heating belt291, and the thermal pressure roller440), a heater (e.g., the heaters23,43,53,63,83,93, and113, the halogen heater73, and the first heater293), and a rotator holder (e.g., the belt holders27,57,122, and298, the flange47, the holding frame67, the belt support77, the arcuate guide87, and the bearing97).

The rotator is rotatably held by the rotator holder. The heater heats the rotator. The rotator holder holds each lateral end of the rotator in a longitudinal direction thereof. The rotator holder is adhered with silicone oil or silicone grease. The silicone oil or the silicone grease contains siloxanes that are not smaller than a dodecamer and not greater than a heptadecamer and have a concentration not greater than 1,250 ppm.

A description is provided of a second configuration of the heating device.

With the first configuration of the heating device, the rotator holder contains glass fiber.

A description is provided of a third configuration of the heating device.

With the first configuration or the second configuration of the heating device, the rotator holder has a maximum temperature that is not lower than 200 degrees Celsius and is not higher than 240 degrees Celsius when the rotator conveys recording media continuously for 10 minutes (e.g., during continuous printing for 10 minutes).

A description is provided of a fourth configuration of the heating device.

With any one of the first configuration to the third configuration of the heating device, the silicone oil or the silicone grease contains the siloxanes that are not smaller than the dodecamer and not greater than the heptadecamer and have a concentration not greater than 500 ppm.

A description is provided of a fifth configuration of a fixing device (e.g., the fixing devices20,40,50,60,70,80,90,110, and403).

With any one of the first configuration to the fourth configuration of the heating device, the fixing device heats a recording medium bearing an unfixed image, thus fixing the unfixed image on the recording medium.

A description is provided of a sixth configuration of the fixing device.

With the fifth configuration of the fixing device, the fixing device includes an endless belt (e.g., the fixing belts21,41,51,61,71,81, and111, the belt91, and the heating belt291), an opposed rotator (e.g., the pressure rollers22,42,62,72,82,92, and112, the pressure rotator52, the heating roller292, and the thermal pressure roller440), and a nip formation pad (e.g., the nip formation pads24,64,74,94, and295, the heaters43and53, the thermal diffuser88, and the pressure pad114).

The endless belt serves as a rotator. The opposed rotator is disposed opposite an outer circumferential face of the endless belt. The nip formation pad is disposed opposite the opposed rotator via the endless belt to form a nip (e.g., the fixing nip N) between the endless belt and the opposed rotator.

A description is provided of a seventh configuration of an image forming apparatus (e.g., the image forming apparatuses100and4000and the inkjet image forming apparatus2000).

The image forming apparatus includes the heating device having any one of the first configuration to the fourth configuration or the fixing device having the fifth configuration or the sixth configuration.

Accordingly, the heating device, the fixing device, and the image forming apparatus suppress generation of ultrafine particles.

According to the embodiments described above, the fixing belt21serves as a rotator. Alternatively, a fixing film, a fixing sleeve, or the like may be used as a rotator. Further, the pressure roller22serves as an opposed rotator. Alternatively, a pressure belt or the like may be used as an opposed rotator.