CN111562733A - Belt conveying device, fixing device, and image forming apparatus - Google Patents
Belt conveying device, fixing device, and image forming apparatus Download PDFInfo
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- CN111562733A CN111562733A CN201910841777.3A CN201910841777A CN111562733A CN 111562733 A CN111562733 A CN 111562733A CN 201910841777 A CN201910841777 A CN 201910841777A CN 111562733 A CN111562733 A CN 111562733A
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Images
Classifications
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/20—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat
- G03G15/2003—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat
- G03G15/2014—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using contact heat
- G03G15/2017—Structural details of the fixing unit in general, e.g. cooling means, heat shielding means
- G03G15/2032—Retractable heating or pressure unit
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/20—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat
- G03G15/2003—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat
- G03G15/2014—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using contact heat
- G03G15/2017—Structural details of the fixing unit in general, e.g. cooling means, heat shielding means
Abstract
The invention provides a belt conveying device, a fixing device and an image forming apparatus. The belt conveying device is provided with: an endless belt that rotates; a nip forming unit that forms a nip by contacting the tape; and a holding unit having an inner peripheral surface contact portion that contacts an inner peripheral surface of the belt, an end surface contact portion that contacts an end surface of the belt in a longitudinal direction at least on an entrance side and an exit side of the nip portion, and an end surface non-contact portion that does not contact the end surface of the belt in the longitudinal direction, the holding unit holding an end portion of the belt in the longitudinal direction, a curvature radius of a portion of the belt that contacts the end surface contact portion on the entrance side of the nip portion being smaller than a curvature radius of a portion of the belt that contacts the end surface contact portion on the exit side of the nip portion.
Description
Technical Field
The present disclosure relates to a belt conveying device, a fixing device, and an image forming apparatus.
Background
Conventionally, as a fixing device, there is a fixing device using an endless belt as at least one of a pressurizing unit and a heating unit. Unlike a hot roller or a pressure roller, an endless belt is allowed to move in the longitudinal direction, and there is a technical problem that it is difficult to control the operation of the belt in the longitudinal direction. As a technique relating to a fixing device using such a belt, a technique disclosed in japanese patent No. 5959848 has been proposed.
The japanese patent No. 5959848 is configured such that, when the sheet is viewed from the longitudinal direction of the sheet, the curvature radius of a 1 st region, which is a region near the entrance of the nip portion of the sheet, and the curvature radius of a 2 nd region, which is a region near the exit of the nip portion of the sheet, are both smaller than the curvature radius of a 3 rd region, which is a region farthest from the nip portion of the sheet in the rotational direction of the sheet, the region of the facing surface of the sheet facing the 3 rd region is farther from the end surface of the sheet than the region of the facing surface of the sheet facing the 1 st region and the region of the facing surface of the sheet facing the 2 nd region in the longitudinal direction of the sheet, and the curvature radius of the 1 st region of the sheet is equal to the curvature radius of the 2 nd region of the sheet.
The purpose of the present disclosure is to suppress deformation of the end portion of the belt in the longitudinal direction, as compared with the case where the radius of curvature of the belt is equal at the end face contact portions on the inlet side and the outlet side of the nip portion.
Disclosure of Invention
According to the 1 st aspect of the present disclosure, there is provided a belt conveying device including: an endless belt that rotates; a nip forming unit that forms a nip by contacting the belt; and a holding unit having an inner peripheral surface contact portion that contacts an inner peripheral surface of the belt, an end surface contact portion that contacts an end surface of the belt in a longitudinal direction at least on an entrance side and an exit side of the nip portion, and an end surface non-contact portion that does not contact the end surface of the belt in the longitudinal direction, and holding an end portion of the belt in the longitudinal direction, a radius of curvature of a portion where the belt contacts the end surface contact portion on the entrance side of the nip portion being smaller than a radius of curvature of a portion where the belt contacts the end surface contact portion on the exit side of the nip portion.
According to the 2 nd aspect of the present disclosure, the degree of curvature or the degree of curvature of the area of the inner peripheral surface contact portion of the holding unit corresponding to the end surface contact portion on the inlet side of the nip portion is larger than the degree of curvature or the degree of curvature of the area corresponding to the end surface contact portion on the outlet side of the nip portion.
According to claim 3 of the present disclosure, the end surface non-contact portion of the holding unit is longer than the end surface contact portion in a rotation direction of the belt.
According to the 4 th aspect of the present disclosure, the holding unit has a 3 rd end face contact portion that contacts an end face of the belt in the longitudinal direction on the opposite side of the nip portion.
According to the 5 th aspect of the present disclosure, the radius of curvature of the belt increases in the order of the inlet side of the nip portion, the outlet side of the nip portion, and the opposite side of the nip portion.
According to the 6 th aspect of the present disclosure, the holding unit may be inclined with respect to the longitudinal direction of the belt centering on a fulcrum provided on an end surface of the holding unit on the outer side in the longitudinal direction of the belt.
According to the 7 th aspect of the present disclosure, the holding unit is set such that, of the inlet side of the nip portion and the outlet side of the nip portion, a distance from the fulcrum to the end face contact portion is shorter on a side where a contact area of the end portion of the belt in the longitudinal direction with the end face contact portion is larger than on a side where a contact area of the end portion of the belt in the longitudinal direction with the end face contact portion is smaller.
According to the 8 th aspect of the present disclosure, the holding unit is set such that the distance from the fulcrum to the end face contact portion is from short to long in order of a contact area in which the end portion of the belt in the longitudinal direction is in contact with the end face contact portion being from large to small.
According to a 9 th aspect of the present disclosure, there is provided a fixing device including the belt conveying device according to any one of the 1 st to 8 th aspects, the fixing device fixing an image on a recording medium using the belt.
According to a 10 th aspect of the present disclosure, there is provided an image forming apparatus including: an image forming unit that forms an unfixed toner image on a recording medium; and a fixing unit that fixes an unfixed toner image formed on the recording medium, the image forming apparatus using the fixing device as the fixing unit.
(Effect)
According to the above-described aspect 1, deformation of the end portion of the belt in the longitudinal direction can be suppressed, as compared with the case where the radius of curvature of the belt is equal at the end face contact portions on the inlet side and the outlet side of the nip portion.
According to the above-described means 2, the curvature radius of the belt can be set to a desired magnitude relationship by changing the degree of bending or the degree of bending of the regions of the inner peripheral surface contact portion of the holding unit corresponding to the end surface contact portions on the inlet side and the outlet side of the nip portion.
According to the above-described aspect 3, as compared with the case where the end surface non-contact portion of the holding means is shorter than the end surface contact portion in the rotation direction of the belt, contact with a portion weak against buckling of the belt can be reliably suppressed.
According to the above-described aspect 4, the belt can be brought into contact with the holding unit at positions other than the inlet side and the outlet side of the nip portion, as compared with the case where the holding unit does not have the 3 rd end face contact portion that comes into contact with the end face of the belt in the longitudinal direction on the opposite side of the nip portion.
According to the above-described aspect 5, compared to a case where the radius of curvature of the belt is not set from small to large in the order of the entrance side of the nip portion, the exit side of the nip portion, and the opposite side of the nip portion, deformation of the end portion of the belt in the longitudinal direction can be reliably suppressed.
According to the above-described aspect 6, compared to the case where the inclination of the holding means is restricted with respect to the longitudinal direction of the belt, when the end portion of the belt in the longitudinal direction abuts against the holding means, the deformation of the end portion of the belt in the longitudinal direction can be suppressed by inclining the holding means with respect to the longitudinal direction of the belt.
According to the above 7 th aspect, the end portions of the belt in the longitudinal direction can be brought into contact with the respective end face contact portions on the inlet side and the outlet side of the nip portion of the holding unit substantially uniformly.
According to the 8 th aspect, the end portions of the belt in the longitudinal direction can be brought into contact with the respective end face contact portions on the inlet side and the outlet side of the nip portion of the holding unit and on the opposite side of the nip portion substantially uniformly.
According to the 9 th aspect, the deformation of the end portion of the belt in the longitudinal direction can be suppressed.
According to the above-described aspect 10, deformation of the end portion of the belt in the longitudinal direction can be suppressed, and the fixing device can have a longer life.
Drawings
Fig. 1 is a schematic configuration diagram showing an image forming apparatus to which a fixing apparatus according to embodiment 1 is applied.
Fig. 2 is a configuration diagram showing a fixing apparatus to which the belt conveying apparatus of embodiment 1 is applied.
Fig. 3 is a sectional configuration diagram showing a fixing device of embodiment 1.
Fig. 4 is a sectional configuration diagram showing a fixing device of embodiment 1.
Fig. 5 is a perspective view showing the pressing belt.
Fig. 6 is a perspective view showing the pressing member and the support member.
Fig. 7 is a perspective view showing the 1 st and 2 nd sheet metal members.
Fig. 8 is a structural view showing a guide member.
Fig. 9 is a structural view showing a guide member.
Fig. 10 is a side view showing the arm member.
Fig. 11 is a cross-sectional configuration view showing a nip-released state of the fixing apparatus.
Fig. 12 is a schematic view showing buckling generated at the pressing belt.
Fig. 13 is an explanatory diagram showing a compression load acting on the pressing belt.
Fig. 14 is a sectional view showing the pressing belt.
Fig. 15 is a schematic diagram showing a main part of the fixing device of embodiment 1.
Fig. 16 is a schematic view showing a contact state of the pressing belt with the guide member.
Fig. 17 is a configuration diagram showing a main part of a fixing device according to embodiment 2.
Fig. 18 is a configuration diagram showing a main part of a fixing device according to embodiment 3.
Fig. 19 is a schematic sectional view showing a fixing device according to embodiment 4.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[ embodiment 1]
Fig. 1 and 2 are diagrams illustrating an image forming apparatus including a fixing device to which the belt conveying device of embodiment 1 is applied. Fig. 1 shows an outline of the entire image forming apparatus, and fig. 2 shows an enlarged view of a fixing device of the image forming apparatus. In the figure, an arrow X shows a width direction in a horizontal direction, Y shows a height direction in a vertical direction, and Z shows a depth direction in the horizontal direction.
< overall Structure of image Forming apparatus >
The image forming apparatus 1 according to embodiment 1 is configured as a monochrome printer, for example. As shown in fig. 1, the image forming apparatus 1 includes: an image forming apparatus 10 as an example of an image forming unit that forms a toner image developed with toner constituting a developer; a paper feeding device 20 that receives and feeds a recording sheet 5 as an example of a recording medium to be fed to a transfer position of the image forming apparatus 10; a conveying device 30 that conveys the recording paper 5 fed from the paper feeding device 20 along a conveying path indicated by a one-dot chain line in the figure; and a fixing device 40 or the like to which the belt conveying device of embodiment 1 is applied, for fixing the toner image transferred from the image forming apparatus 10 on the recording paper 5.
The image forming apparatus 10 includes a photosensitive drum 11 that rotates as an example of an image holding unit. The following devices are mainly arranged around the photosensitive drum 11. The main devices include the following devices: a charging device 12 that charges a circumferential surface (image holding surface) of the photosensitive drum 11 on which an image can be formed at a desired potential; an exposure device 13 that irradiates the charged circumferential surface of the photosensitive drum 11 with light based on image information (signal) to form an electrostatic latent image having a potential difference; a developing device 14 for developing the electrostatic latent image with black toner as a developer to form a toner image; a transfer device 15 for transferring the toner image onto the recording paper 5; and a drum cleaning device 16 for removing and cleaning adhering substances such as toner remaining after transfer and adhering to the image holding surface of the photosensitive drum 11.
The photosensitive drum 11 is obtained by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the circumferential surface of a cylindrical or columnar base material subjected to grounding treatment. The photosensitive drum 11 is supported to rotate in the direction indicated by the arrow a by power transmission from a drive device not shown.
The charging device 12 is constituted by a contact type charging roller disposed in contact with the photosensitive drum 11. The charging device 12 is supplied with a charging voltage. As the charging voltage, in the case where the developing device 14 is a developing device that performs reversal development, a voltage or a current having the same polarity as the charging polarity of the toner supplied from the developing device 14 is supplied. As the charging device 12, a non-contact type charging device such as a scorotron (scorotron) disposed in a non-contact state on the surface of the photosensitive drum 11 may be used.
The exposure device 13 is constituted by an LED print head that forms an electrostatic latent image by irradiating the photosensitive drum 11 with Light corresponding to image information using an LED (Light Emitting Diode) that is a plurality of Light Emitting elements arranged in the axial direction of the photosensitive drum 11. The exposure device 13 is movable to an exposure position close to the photosensitive drum 11 and a retracted position away from the circumferential surface of the photosensitive drum 11 and indicated by a broken line in fig. 1. As the exposure device 13, the following devices may be used: and a device for scanning laser light formed based on image information in an oblique manner in the axial direction of the photosensitive drum 11. When a device that performs skew scanning with laser light is used as the exposure device 13, exposure can be performed from a position away from the circumferential surface of the photosensitive drum 11, and therefore, retraction is not necessary.
The developing device 14 is configured by disposing the following components inside a housing 140 in which an opening and a developer accommodating chamber are formed: a developing roller 141 as an example of a developer holding unit that holds a developer and conveys the developer to a developing area facing the photosensitive drum 11; two agitating and conveying members 142, 143 such as augers that convey the developer through the developing roller 141 while agitating the developer; and a layer thickness regulating member 144 that regulates the amount of developer (layer thickness) held by the developing roller 141. In the developing device 14, a developing bias is supplied from a power supply device, not shown, between the developing roller 141 and the photosensitive drum 11. The developing roller 141 and the stirring and conveying members 142 and 143 are rotated in a desired direction by power transmission from a driving device not shown. Further, as the developer, a two-component developer containing a non-magnetic toner and a magnetic carrier is used.
The transfer device 15 is a contact transfer device including a transfer roller that rotates while contacting the periphery of the photosensitive drum 11 with the recording paper 5 therebetween during image formation, and to which a transfer voltage is supplied. A dc voltage having a polarity opposite to the charging polarity of the toner is supplied as a transfer voltage from a power supply device not shown.
The drum cleaning device 16 is constituted by: a container-shaped body having a part opened; a cleaning plate configured to contact the circumferential surface of the primary-transferred photosensitive drum 11 at a required pressure to remove and clean deposits such as residual toner; and a conveying member such as an auger, which conveys the toner removed by the cleaning plate to a collecting container, not shown, for collecting and conveying the toner. As the cleaning plate, a plate-like member (e.g., a blade) made of a material such as rubber is used.
As shown in fig. 1, the fixing device 40 is configured by arranging the following components inside a device case 43 in which an inlet and an outlet for recording paper 5 are formed: a heating roller 41 as an example of a rotating body for heating (nip forming means) that rotates in the direction indicated by the arrow and is heated by a heating means so that the surface temperature is maintained at a predetermined temperature; and a pressing belt 42 as an example of a rotating member (endless belt) for pressing, which rotates while contacting with a predetermined pressure in a state substantially along the axial direction of the heating roller 41. In the fixing device 40, a contact portion where the heating roller 41 contacts the pressure belt 42 serves as a fixing nip portion N where a required fixing process (heating and pressure) is performed. The structure of the fixing device 40 will be described in detail later.
The paper feed device 20 is disposed at a position below the image forming apparatus 10 in the vertical direction Y. The sheet feeding device 20 is mainly constituted by: a single (or a plurality of) sheet storage 22 that stores recording sheets 5 of a desired size, kind, and the like in a state where the recording sheets 5 are placed on the placement plate 21; and a feeding device 23 that feeds the recording paper 5 from the paper storage 22 one sheet at a time. The paper feed device 20 can be attached to and detached from the apparatus main body 1a of the image forming apparatus 1 by gripping and pulling out the grip portion 24 provided in the paper storage body 22 with a hand.
Examples of the recording paper 5 include plain paper, thin paper such as tracing paper, and OHP sheets used in copying machines and printers of an electrophotographic system. In order to further improve the smoothness of the surface of the image after fixing, the surface of the recording paper 5 is preferably as smooth as possible, and for example, a so-called thick paper having a relatively large basis weight such as coated paper coated with a resin or the like on the surface of plain paper or art paper for printing may be used.
As shown in fig. 1, a paper feed conveyance path 32 is provided between the paper feed device 20 and the transfer device 15, the paper feed conveyance path 32 is configured by a plurality of (or a single) paper conveyance roller pairs 31a and 31b that convey the recording paper 5 fed from the paper feed device 20 to a transfer position, and a conveyance guide (not shown), and the paper feed conveyance path 32 is provided in a shape that is curved toward the inside (X direction) of the device body 1a in the middle toward the upper side along the vertical direction Y of the device body 1 a. The paper transport roller pair 31b arranged at a position immediately before the transfer position in the paper feed transport path 32 is configured as a roller (registration roller) that adjusts the transport timing of the recording paper 5, for example. Further, between the transfer device 15 and the fixing device 40, a paper conveying path 33 for conveying the post-transfer recording paper 5 conveyed from the transfer device 15 to the fixing device 40 is provided in the horizontal direction X.
Further, a discharge transport path 37 is provided obliquely above the fixing device 40, and the discharge transport path 37 transports the sheet to the sheet discharge portion 36 via one transport roller pair 34 of the two sets of transport roller pairs 34 and 35 that share one transport roller, and discharges the sheet. The sheet discharge unit 36 is provided in an inclined state on the upper end surface of the apparatus main body 1 a.
A discharge roller pair 37b is disposed at an outlet 37a of the discharge conveyance path 37, and the front and back surfaces of the recording paper 5 are reversed by the discharge roller pair 37 b. The rotation direction of the discharge roller pair 37b can be switched between the normal rotation direction and the reverse rotation direction.
Further, a switching gate, not shown, for switching the conveyance direction of the recording paper 5 is provided in front of the discharge roller pair 37 b. When forming images on both sides of the recording paper 5, the conveying direction of the recording paper 5 is switched from the discharge conveying path 37 to the double-side conveying path 38 by a switching gate, not shown. At this time, after the trailing end of the recording paper 5 conveyed in the discharge direction passes through a switching gate (not shown), the rotation direction of the discharge roller pair 37b is switched from the normal rotation direction (discharge direction) to the reverse rotation direction. When the transport path of the recording paper 5 transported in the reverse direction by the discharge roller pair 37b is switched to be below the vertical direction Y by a switching gate not shown, the recording paper 5 is transported along the back surface of the apparatus main body 1a of the image forming apparatus 1 to the double-side transport path 38 via the transport roller pair 35, and the double-side transport path 38 is formed by being bent in the horizontal direction X from the vertical direction Y. The duplex conveying path 38 includes paper conveying roller pairs 39a and 39b for conveying the recording paper 5 to the paper conveying roller pair 31b with the front and back surfaces thereof reversed, and a conveying guide not shown.
A toner cartridge 145, which is an example of a developer storage container, is disposed above the developing device 14, and the toner cartridge 145 stores a developer including at least a toner to be supplied to the developing device 14. A toner supply device, not shown, provided with a supply roller for supplying the toner stored in the toner cartridge 145 to the developing device 14 is provided below the toner cartridge 145.
In embodiment 1, the photosensitive drum 11, the charging device 12, the developing device 14, the drum cleaning device 16, and the toner cartridge 145 are integrally assembled to constitute a process cartridge 300. As shown in fig. 1, the process cartridge 300 is attachable to and detachable from the apparatus main body 1a of the image forming apparatus 1 in a state where the exposure device 13 is moved to the retracted position shown by the broken line. The toner cartridge 145, which is frequently attached and detached, is configured to be attachable and detachable to and from the apparatus main body 1a of the image forming apparatus 1 separately from the process cartridge 300.
In fig. 1, reference numeral 200 denotes a control device that generally controls the operation of the image forming apparatus 1. The control device 200 includes a CPU (Central Processing Unit), a ROM (Read only Memory), a RAM (Random Access Memory), a bus connecting the CPU and the ROM, a communication interface, and the like, which are not shown.
< basic operation of image Forming apparatus >
The following describes a basic image forming operation of the image forming apparatus 1.
The image forming apparatus 1 is controlled by the control device 200, and when command information for requesting an image forming operation (printing) for a single color is received from an operation panel, a user interface, a printer driver, and the like, not shown, mounted on the apparatus main body 1a, the image forming apparatus 10, the paper feeding device 20, the conveying device 30, the fixing device 40, and the like are started.
As shown in fig. 1, in the image forming apparatus 10, first, the photosensitive drum 11 is rotated in a direction indicated by an arrow a, and the charging device 12 charges the surface of the photosensitive drum 11 with a desired polarity (negative polarity in embodiment 1) and potential. Next, the exposure device 13 irradiates the surface of the charged photosensitive drum 11 with light emitted based on information of an image input to the image forming apparatus 1, and forms an electrostatic latent image having a desired potential difference on the surface thereof.
Next, the developing device 14 supplies black toner charged to a desired polarity (negative polarity) from the developing roller 141 to the electrostatic latent image formed on the photosensitive drum 11, and develops the electrostatic latent image by electrostatic adhesion. By this development, the electrostatic latent image formed on the photosensitive drum 11 is visualized as a toner image developed with black toner. At a desired timing, toner is supplied from the toner cartridge 145 to the developing device 14 via a toner supply device, not shown.
Next, when the toner image formed on the photosensitive drum 11 is conveyed to the transfer position, the transfer device 15 transfers the toner image onto the recording paper 5.
In the image forming apparatus 10 after the transfer, the drum cleaning device 16 scrapes off the adhering matter to clean the surface of the photosensitive drum 11. This allows the imaging apparatus 10 to perform the next imaging operation.
The paper feed device 20 feeds a desired recording paper 5 to the paper feed conveyance path 32 in cooperation with the image forming action. In the paper feed conveyance path 32, a paper conveyance roller pair 31b as registration rollers feeds the recording paper 5 to a transfer position in accordance with transfer timing.
Subsequently, the recording paper 5 to which the toner image is transferred is conveyed to the fixing device 40 via the paper conveying path 33. In the fixing device 40, the transferred recording paper 5 is introduced into the fixing nip N between the rotating heating roller 41 and the pressure belt 42 and passes through the fixing nip N, thereby performing a necessary fixing process (heating and pressure), and an unfixed toner image is fixed on the recording paper 5. When the recording paper 5 after the fixing is completed is subjected to an image forming operation for forming an image only on one side thereof, the recording paper 5 is discharged by the discharge roller pair 37b along the discharge transport path 37 to the paper discharge portion 36 provided at the upper end portion of the apparatus main body 1 a.
When images are formed on both sides of the recording paper 5, the recording paper 5 on one side of which images have been formed is conveyed to the discharge roller pair 37b by a switching gate not shown, and the recording paper 5 is temporarily conveyed in the discharge direction by the discharge roller pair 37 b. Then, the discharge roller pair 37b reverses the rotation direction with the trailing end of the recording paper 5 being sandwiched, and after reversing the front and back sides of the recording paper 5, conveys the recording paper 5 again to the transfer device 15 via the duplex conveying path 38, and transfers the toner image to the back side of the recording paper 5. The recording paper 5 with the toner image transferred on the back surface thereof is conveyed to the fixing device 40 via the paper conveying path 33, subjected to fixing treatment (heating and pressing) by the fixing device 40, and discharged to the paper discharge portion 36 by the discharge roller pair 37 b.
By the above operation, the recording paper 5 on which the monochrome image is formed on one side or both sides is output.
< Structure of fixing device >
Fig. 2 is a cross-sectional configuration diagram showing a fixing device to which the belt conveying device of embodiment 1 is applied.
The fixing device 40 adopts a so-called free belt clamping method. As shown in fig. 2, the fixing device 40 includes a device case 43 formed in an elongated box shape having a substantially rectangular cross section. Inside the apparatus casing 43, a pressure belt 42 as an example of a rotating endless belt and a heating roller 41 as an example of nip forming means that forms the fixing nip N by contacting the pressure belt 42 are arranged in a pressure-contact state. An introduction port 431 is provided below the left side surface of the apparatus casing 43 to introduce the recording paper 5 to which the unfixed toner image T is transferred. A guide plate 432 that guides the recording paper 5 to the fixing nip N formed by the pressure belt 42 and the heating roller 41 is disposed inside the introduction port 431 in a state of being inclined obliquely upward. Further, a discharge port 433 is provided above the right side surface of the apparatus casing 43, and the discharge port 433 discharges the recording paper 5 subjected to the fixing process by the heating roller 41 and the pressing belt 42 to the outside. The discharge port 433 is provided with a pair of exit rollers 434 for discharging the recording paper 5 to the outside of the apparatus case 43 so as to be rotatable. The recording paper 5 is conveyed with reference to the center in the direction intersecting the conveying direction (so-called center positioning).
An actuator 436, which is an example of a detection unit that detects the passage of the recording paper 5, is provided in the conveyance path 435 formed between the fixing nip N and the exit roller pair 434 of the fixing device 40 so as to be rotatable about the upper end as a fulcrum. The passage of the recording paper 5 is detected by detecting the rotational operation of the actuator 436 with an optical sensor or the like, not shown.
As shown in fig. 2, the fixing device 40 generally includes: a heating roller 41; and a pressing unit 44, the heating unit 44 having a pressing belt 42, the pressing belt 42 being disposed to be capable of contact separation with respect to the heating roller 41.
As shown in fig. 3, the heating roller 41 has: a cylindrical mandrel 411 made of metal such as stainless steel, aluminum, or iron (thin-walled high-tensile steel pipe); an elastic body layer 412 made of an elastic body having heat resistance such as silicone rubber or fluororubber covering the outer periphery of the mandrel 411; and a release layer 413 made of Polytetrafluoroethylene (PTFE), Perfluoroalkoxyalkane (PFA), or the like, which is thinly coated on the surface of the elastomer layer 412. As an example of the heating means (heat source), two halogen lamps 414a and 414b having different outer diameters are disposed inside the heating roller 41.
As shown in fig. 4, both end portions of the heat roller 41 in the longitudinal direction (axial direction) are rotatably supported by a frame 438 of the device case 43 via a bearing member 439. The heating roller 41 is rotationally driven at a desired speed in the direction of arrow C (see fig. 3) by a driving gear G attached to one end portion in the axial direction by a driving device (not shown). The pressing belt 42 is pressed against the rotationally driven heating roller 41 and is driven to rotate.
As shown in fig. 2, the surface temperature of the heating roller 41 is detected by a temperature sensor 437. The heating roller 41 is heated by controlling energization of the halogen lamps 414a and 414b based on the detection result of the temperature sensor 437 by a temperature control circuit (not shown) so that the surface thereof has a desired fixing temperature (e.g., about 170 ℃).
On the other hand, as shown in fig. 3, the pressurizing unit 44 includes: a pressing belt 42; a pressing member 45, which is an example of a pressing portion, disposed inside the pressing belt 42, and configured to press the pressing belt 42 against the surface of the pressing roller 41; a support member 46, which is an example of a support unit, is also disposed inside the pressing belt 42, supports the pressing member 45, and supports the pressing belt 42 at a part of a circulating orbit of the pressing belt 42; the 1 st and 2 nd sheet metal members 47 and 48 as an example of the attachment means for attaching the support member 46; a pair of guide members 49, 50 as an example of holding means for rotatably holding both end portions of the pressing belt 42 in the longitudinal direction; a slide sheet 51, which is an example of a sheet, interposed between the pressing belt 42 and the pressing member 45 and the supporting member 46 to reduce sliding resistance; and a felt member 52, which is an example of a lubricant retaining means, disposed inside the pressure belt 42, and retaining the lubricant applied to the inner circumferential surface of the pressure belt 42.
As shown in fig. 5, the pressing belt 42 is made of a flexible material, and is configured as a thin-walled cylindrical annular belt in a free shape before assembly. The pressing belt 42 includes a base material layer, an elastic body layer covering the surface of the base material layer, and a release layer covering the surface of the elastic body layer. The pressure belt 42 may be composed of a base material layer and a release layer directly covering the surface of the base material layer. The base layer is made of heat-resistant synthetic resin such as polyimide, polyamide, or polyimide amide, or metal such as stainless steel, nickel, or copper. The elastomer layer is made of an elastomer having heat resistance, such as silicone rubber or fluororubber. The release layer is formed of Polytetrafluoroethylene (PTFE), Perfluoroalkoxyalkane (PFA), or the like. The thickness of the pressing belt 42 may be set to about 50 to 200 μm, for example.
As shown in fig. 3 and 6, the pressing member 45 includes: a pressing pad 451 that presses the pressing belt 42 toward the surface of the heating roller 41; and a fixing member 452 that fixes the pressure pad 451.
As shown in fig. 6, the pressure pad 451 is formed of a heat-resistant elastic body such as silicone rubber or fluororubber in an elongated rectangular parallelepiped shape having a rectangular cross section. The pressure pad 451 is fixed to a concave portion 452a formed on the surface of the fixing member 452 on the heating roller 41 side by means of adhesion or the like.
On the other hand, the fixing member 452 is made of a synthetic resin having heat resistance and rigidity such as polyphenylene sulfide (PPS), polyimide, polyester, or polyamide, or a metal such as iron, aluminum, or stainless steel, and has a higher rigidity than the pressure pad 451.
As shown in fig. 6, the fixing member 452 is formed such that the end surface on the side of the heating roller 41 is longer than the end surface on the side opposite to the heating roller 41, has a relatively small thickness, and has a substantially trapezoidal cross section. As described above, the concave portion 452a for accommodating the pressure pad 451 is provided over substantially the entire length on the surface of the fixing member 452 facing the heating roller 41. The fixing member 452 is attached to the support member 46 by applying an adhesive or fastening with a screw.
The support member 46 is made of, for example, a heat-resistant synthetic resin that is integrally molded into a desired cross-sectional shape by injection molding or the like. Examples of the heat-resistant synthetic resin include Liquid Crystal Polymer (LCP), polyether ether ketone (PEEK), polyphenylene sulfide (PPS) Polyethersulfone (PES), polyamide imide (PAI), Polytetrafluoroethylene (PTFE), Polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), and a composite material thereof.
As shown in fig. 3 and 6, the support member 46 is configured as an elongated rigid body having a substantially H-shaped cross section. The support member 46 includes: a main body 461 formed in a flat plate shape having a desired thickness and width; 1 st and 2 nd supporting portions 462, 463 integrally provided to protrude from the main body 461 toward the upstream side and the downstream side of the fixing nip N, respectively, and supporting the pressure belt 42; and 3 rd and 4 th supporting portions 464, 465 integrally provided to protrude from the main body 461 toward opposite sides of the fixing nip N, respectively, and supporting the pressing belt 42.
The 1 st and 2 nd supporting portions 462, 463 are formed in a plate shape whose thickness is set to be gradually thinner as going from the main body 461 of the supporting member 46 toward the distal end side extending toward the upstream side and the downstream side of the fixing nip portion N. The 1 st supporting portion 462 supports the inner peripheral surface of the pressure belt 42 by a required distance from the pressure pad 451 toward the upstream side of the fixing nip N in the moving direction of the pressure belt 42, and changes the moving direction of the pressure belt 42 by substantially 90 degrees from the opposite side of the fixing nip N toward the fixing nip N. The outer surface 462a of the 1 st support part 462 is in contact with the inner peripheral surface of the pressure belt 42 to support the pressure belt 42, similarly to the guide parts 492 and 502 of the guide members 49 and 50 described later. The end 462b of the 1 st support part 462 is arranged to form the same surface as the guide parts 492 and 502 of the guide members 49 and 50 described later.
In embodiment 1, as shown in fig. 3, a contact roller 53 for bringing the pressing belt 42 into contact with the supporting member 46 is disposed at a position corresponding to the outer surface 462a of the 1 st supporting portion 462. The contact roller 53 is biased by a biasing member 531 such as a coil spring, and contacts the support member 46 via the pressing belt 42. In addition, the contact roller 53 may not be provided.
On the other hand, the 2 nd support portion 463 is spaced from the pressure pad 451 toward the downstream side of the fixing nip portion N in the moving direction of the pressure belt 42 by a predetermined distance to support the inner peripheral surface of the pressure belt 42, and changes the moving direction of the pressure belt 42 by substantially 90 degrees from the fixing nip portion N side toward the opposite side of the fixing nip portion N. The outer side surface 463a of the 2 nd support portion 463 is in contact with the inner peripheral surface of the pressure belt 42 to support the pressure belt 42, similarly to the guide portions 492 and 502 of the guide members 49 and 50 described later.
The 3 rd supporting portion 464 partially supports the inner circumferential surface of the pressure belt 42 in the middle of moving toward the opposite side of the fixing nip portion N through the 2 nd supporting portion 463. Like the guide portions 492 and 502 of the guide members 49 and 50 described later, the distal end surface 464a of the 3 rd supporting portion 464 partially contacts the inner circumferential surface of the pressure belt 42 that has passed through the 2 nd supporting portion 463 and moved toward the opposite side of the fixing nip portion N, and supports the pressure belt 42.
Further, the 4 th supporting part 465 partially supports the inner circumferential surface of the pressing pad 451 moving from the opposite side of the fixing nip part N toward the 1 st supporting part 462. The distal end surface 465a of the 4 th support part 465 locally contacts the inner peripheral surface of the pressure belt 42 moving from the opposite side of the fixing nip N toward the fixing nip N, and supports the pressure belt 42, similarly to the guide parts 492 and 502 of the guide members 49 and 50, which will be described later.
As shown in fig. 3 and 6, fixing recessed grooves 466, 467 are formed over the entire length of the surface of the main body 461 of the support member 46 on the side opposite to the fixing nip N, and the fixing recessed grooves 466, 467 are fixed in a state of being fitted to the distal ends of the 1 st and 2 nd sheet metal members 47, 48. The bottom portions of the fixing grooves 466, 467 are formed with convex portions 466a, 467a, and the convex portions 466a, 467a are formed to be slightly narrower than the width of the fixing grooves 466, 467. The convex portions 466a, 467a of the fixing grooves 466, 467 are used to reliably transmit the supporting force of the 1 st and 2 nd sheet metal members 47, 48 to the main body 461 of the supporting member 46. As shown in fig. 3, the position at which the 1 st and 2 nd sheet metal members 47 and 48 are fixed to the main body 461 of the supporting member 46 is set so as to be parallel to the direction in which a straight line L1 drawn from the middle of the 1 st and 2 nd sheet metal members 47 and 48 toward the heating roller 41 passes through the center O of the heating roller 41. Further, the pressing pad 451 is disposed such that a straight line L1 passing through the center O of the heating roller 41 passes through the center in the width direction of the pressing pad 451.
The 1 st and 2 nd sheet metal members 47 and 48 are formed by bending a sheet material made of metal such as stainless steel, aluminum, or iron. As shown in fig. 3 and 7, the 1 st and 2 nd sheet metal members 47, 48 are formed in an L-shaped cross section by: vertical plate portions 471, 481 arranged substantially perpendicular to the surface of the heating roller 41; and horizontal plate portions 472, 482 which cross base end portions of the vertical plate portions 471, 481 and are bent in opposite directions so as to be brought close to each other after bending. The vertical plate portions 471, 481 of the 1 st and 2 nd sheet metal members 47, 48 are arranged in parallel with each other. The length of the vertical plate portion 481 of the 2 nd sheet metal member 48 is set longer than the length of the vertical plate portion 471 of the 1 st sheet metal member 47.
As shown in fig. 7, the 1 st and 2 nd sheet metal members 47, 48 have, at both end portions in the longitudinal direction of the vertical plate portions 471, 481, protruding portions 473, 483, 474, 484 for positioning and fixing the guide members 49, 50.
As shown in fig. 3, the felt member 52 is provided on the outer surface of the horizontal plate portion 482 of the 2 nd sheet metal member 48 over the entire length thereof by means of bonding or the like. The felt member 52 is formed thick so as to be elastically deformed to support the pressing belt 42 when a tensile force is applied to the pressing belt 42. In fig. 3, for convenience, the felt member 52 is shown before being deformed.
The felt member 52 is impregnated with a lubricant in a predetermined amount, and the lubricant is supplied in a state where the inner circumferential surface of the pressing belt 42 is coated with the lubricant. As the lubricant, for example, aminosilicone oil having a viscosity of 100 to 350cs or the like can be used. The lubricant is applied and supplied to the inner circumferential surface of the pressing belt 42 by being impregnated into the felt member 52 in advance, but is not limited to this, and may be supplied in a state where the inner circumferential surface of the pressing belt 42 is already coated in an initial stage.
As shown in fig. 4, the guide members 49, 50 are disposed at both ends of the pressing belt 42 in the longitudinal direction. As shown in fig. 8 and 9, the guide members 49 and 50 are formed in a left-right symmetrical shape. The guide members 49, 50 have substantially flat plate-like side plate portions 491, 501, which are formed in substantially pentagonal side shapes along the circulating path of the pressing belt 42, and whose outer peripheral ends project outward in the direction intersecting the longitudinal direction of the pressing belt 42, compared to the circulating path of the pressing belt 42. Arc-shaped guide parts 492 and 502 along the outer peripheral shape of the heating roller 41 are provided on the side plate parts 491 and 501 of the guide members 49 and 50 closer to the heating roller 41.
Here, the direction intersecting the longitudinal direction of the pressing belt 42 means a direction intersecting the central axis of the cylindrical pressing belt 42 before assembly, that is, a direction along the radial direction of the pressing belt 42, assuming the central axis, as shown in fig. 5. In the deformed pressing belt 42 after assembly, if an axis extending in the longitudinal direction is assumed in the inside thereof, the direction intersecting the axis is also referred to.
In other words, the direction intersecting the longitudinal direction of the pressing belt 42 can be said to be a direction from the inner circumferential surface side toward the outer circumferential surface side in the thickness direction of the pressing belt 42.
As shown in fig. 8 and 9, through holes 493, 503, 494, 504 are opened in the side plate portions 491, 501 of the guide members 49, 50, and the projecting portions 473, 483, 474, 484 of the 1 st and 2 nd sheet metal members 47, 48 are fitted in the through holes 493, 503, 494, 504 in a penetrating state. The length and width of the through holes 493, 503, 494, 504 are set larger than those of the protrusions 473, 483, 474, 484 of the 1 st and 2 nd sheet metal members 47, 48. In other words, gaps are provided between the through holes 493, 503, 494, 504 of the side plate portions 491, 501 and the protrusions 473, 483, 474, 484 of the 1 st and 2 nd sheet metal members 47, 48. As a result, the side plate portions 491, 501 of the guide members 49, 50 are attached so as to be movable obliquely within the range of the gap with respect to the protruding portions 473, 483, 474, 484 of the 1 st and 2 nd sheet metal members 47, 48 fixed to the device case 43 side. As shown in fig. 4, a small gap g that allows the side plate portions 491, 501 of the guide members 49, 50 to tilt is provided between the side plate portions 491, 501 of the guide members 49, 50 and the arm members 71, 72 described below attached in a state where the 1 st and 2 nd sheet metal members 47, 48 are fixed.
As shown in fig. 4, arm members 71 and 72 attached in a state where the guide members 49 and 50 are fixed are disposed on the outer sides of the guide members 49 and 50 in the longitudinal direction of the pressing belt 42, respectively. As shown in fig. 10, the arm members 71 and 72 are made of a metal plate material having a substantially L-shaped side surface. The arm members 71, 72 have through holes 715, 725, 716, 726 opened therein, and the projecting portions 473, 483, 474, 484 of the 1 st and 2 nd sheet metal members 47, 48 are attached to the arm members 71, 72 in a state of being inserted into the through holes 715, 725, 716, 726. Further, no gap is provided between the projection 473, 483, 474, 484 of the 1 st and 2 nd sheet metal members 47, 48 and the through hole 715, 725, 716, 726 of the arm member 71, 72, and the 1 st and 2 nd sheet metal members 47, 48 are fixed to the arm members 71, 72.
As shown in fig. 3, the arm members 71 and 72 are attached to a frame 438 (see fig. 4) of the fixing device 40 in such a manner as to be rotatable about fulcrums 712 and 722 provided at base end portions 711 and 721 thereof. Coil springs 73, 74 as an example of biasing means are connected to the end portions 713, 723 of the arm members 71, 72, and the coil springs 73, 74 bias the pressing means 44 in a direction in which the pressing means 44 is pressed against the heating roller 41. One ends of the coil springs 73, 74 are engaged with engagement holes 714, 724 provided in the end portions 713, 723 of the arm members 71, 72. The other ends of the coil springs 73 and 74 are fixed to a frame 438 of the fixing device 40. Further, the eccentric cams 75, 76, which are an example of advancing and retreating means for moving the distal end portions 713, 723 of the arm members 71, 72 in the directions of contacting with the heating roller 41 and separating from the heating roller 41, are brought into contact with the distal end portions 713, 723. The eccentric cams 75 and 76 are rotationally driven by a drive motor, not shown.
The pressing unit 44 is configured to be movable to a fixing position (fig. 3) where the pressing unit 44 is pressed against the surface of the heating roller 41 by the biasing force of the coil springs 73 and 74 and to a retracted position (fig. 11) by rotational driving of the eccentric cams 75 and 76; in the retracted position, the pressing unit 44 is separated from the surface of the heating roller 41 against the urging force of the coil springs 73 and 74.
As shown in fig. 11, the pressing belt 42 is not applied with tension at the retreat position. In the retracted position, the pressure belt 42 is not tensioned and can be freely deformed even if it is separated from the surface of the heating roller 41 or brought into contact with the surface of the heating roller 41, and a recording sheet (not shown) having a conveyance failure (jam) in the fixing nip portion N can be easily removed.
In contrast, as shown in fig. 3, the pressure belt 42 is moved to the fixing position and is applied with tension by being pressed against the surface of the heat roller 41 with a desired fixing pressure. The tension is applied to the pressure belt 42 at the fixing position because the length of the circulating path of the pressure belt 42 at the fixing position is set to be longer than the circumferential length of the pressure belt 42 in a free state.
The slider 51 is formed of an elongated flat rectangular plate. As the slide sheet 51, for example, a slide sheet having a structure comprising a base layer made of a fluororesin such as Polytetrafluoroethylene (PTFE) and a woven fabric or knitted fabric laminated on both surfaces of the front and back surfaces of the base layer, the woven fabric or knitted fabric being made of glass fibers, polyamide fibers or the like, can be used. The slide sheet 51 may be formed of only a single layer of woven fabric or knitted fabric made of glass fibers, polyamide fibers, or the like. The thickness of the slider 51 may be set to about 100 to 200 μm.
A plurality of oblong locking holes, not shown, are opened in the longitudinal direction at the upper end of the slider 51 in the rotation direction of the pressure belt 42. As shown in fig. 3, the slide piece 51 is assembled by locking a plurality of locking holes, not shown, with the locking convex portions 511 provided on the back surface of the 1 st supporting portion 462 of the supporting member 46. The slide 51 is disposed so that the upstream side of the slide 51 in the rotation direction of the pressure belt 42 reaches the fixing nip N via the end 462b of the 1 st supporting part 462 of the supporting member 46 while being along the outer surface 462a of the 1 st supporting part 462 of the supporting member 46. The slide sheet 51 is disposed so that an end of the slide sheet 51 on the downstream side in the rotation direction of the pressure belt 42 extends by a predetermined length along the outer side surface 463a of the 2 nd support portion 463 of the support member 46 after passing through the fixing nip portion N.
Further, due to various factors such as the pressure distribution in the axial direction of the heating roller 41, the arrangement (arrangement) of the heating roller 41 and the pressing belt 42, and the variation (tolerance) in the outer diameters, thicknesses, and the like of the heating roller 41 and the pressing belt 42, as shown in fig. 4, the pressing belt 42 of the fixing device 40 configured as described above may be moved toward the end in the longitudinal direction, so-called a movement phenomenon. The movement phenomenon generated in the pressing belt 42 fluctuates due to the influence of disturbances such as skew of the recording paper 5.
If the pressure belt 42 moves, as shown in fig. 12, the end of the pressure belt 42 collides with one of the side plate portions 491, 501 of the guide members 49, 50, or the end of the pressure belt 42 is deformed such as buckled B or bent inward, and in an extreme case, the bent end of the pressure belt 42 may be broken, and the fixing device 40 may not be used.
Therefore, the present inventors have conducted various material mechanics studies in order to suppress deformation such as buckling of the end portion of the pressing belt 42 in the longitudinal direction. As a result, it was found that, when physical quantities such as the thickness and the young's modulus of the pressure belt 42 are uniformed, the ease of buckling of the pressure belt 42 depends on the profile (curved shape) of the pressure belt 42 in the circumferential direction.
As shown in fig. 12, consider buckling B occurring at the end of the pressing belt 42 when the end of the pressing belt 42 in the longitudinal direction collides with any one of the guides 49, 50. As shown in fig. 13, buckling occurring in a substantially cylindrical long column such as the pressing belt 42 can be understood as deformation occurring in the long column (cylindrical body) when a load F is applied to the long column from both ends in the longitudinal direction. It is known that buckling of a long column follows the governing equation shown in equation 1 below. The governing equation is a relational expression established with respect to the bending buckling stress of the long column subjected to the compressive load.
[ equation 1]
By solving the dominant equation, it is known that buckling occurs when a certain load (buckling load) is applied to the long column. The buckling load PcrThe calculation is performed by the euler equation shown in equation 2 below.
[ equation 2]
Here, C is a terminal condition coefficient depending on the fixed state of both ends of the long column, E is young's modulus, I is a sectional moment of inertia, and L is a length of the column.
When the length L of the pressing belt 42 is constant, the buckling load P in which buckling occurs at the end portion of the pressing belt 42 in the longitudinal direction is known from equation 2crIs proportional to the bending stiffness (EI) which is the product of the young's modulus E and the moment of area inertia I of the pressing belt 42.
Therefore, the bending load P increases as the bending rigidity (EI) of the pressing belt 42 increasescrThe higher the value of (A), the more difficult the buckling is generated. When the Young's modulus E is set to a certain value, the bending rigidity (EI) of the pressing belt 42 is determined by the second moment of area I.
Now, as shown in fig. 14 (b), when the cross-sectional shape of the pressing belt 42 is assumed to be a thin-walled cylinder (t < D) having a thickness t and an outer diameter D, I ═ pi tD is passed3The section moment of inertia I of the thin-walled cylinder is provided by/8.
In embodiment 1, as shown in fig. 3, the cross-sectional shapes of both end portions of the pressing belt 42 in the longitudinal direction are defined by the guide members 49 and 50.
As shown in fig. 14 (a), the pressure belt 42 actually used has a thin-walled cylinder shape, but has a profile cross-sectional shape different from a thin-walled cylinder in that the radius of curvature differs depending on the position in the circumferential direction. Fig. 14 (a) shows the shape of the end surface of the pressure belt 42 in the longitudinal direction supported by the guide members 49, 50 at the time of fixing.
Next, when the shape of the end portion of the pressing belt 42 in the longitudinal direction is defined by the guide members 49 and 50, it is preferable to examine how the radius of curvature is set in accordance with the position in the circumferential direction of the pressing belt 42, that is, in the pressing belt 42 having a special-shaped cross-sectional shape in which the radius of curvature differs depending on the position in the circumferential direction, how the local moment of inertia I varies depending on the magnitude of the radius of curvature of the curved portion.
In the semicircular region of the pressing belt 42 having a radius of curvature R shown in fig. 15 (a) and the circular arc region of R (2R) having the same area as the semicircular region and having a radius of curvature 2 times that of the pressing belt 42 shown in fig. 15 (b), the moment of inertia I of the cross section is taken into considerationx. Let t be the thickness of the pressing belt 42.
In general, as shown in fig. 15 (c), the second moment of area I of a member having a specific cross-sectional shape is given by equation 3 shown belowx。
[ equation 3]
Ix＝∫y2dA
The second moment of inertia I of the cross section of the semicircular region and the circular arc region having the same area and different radii of curvature is obtained from equation 3xHowever, for easy determination, x-y coordinates with the centroid of the semicircular region and the arc region as the origin are considered as shown in fig. 15 (d). Accordingly, the white portions as the common portions have the same shape on the x-y coordinates, and therefore the sectional moments of inertia I have the same value. In addition, it can be determined that the value of the y coordinate of the semicircular region is larger than the value of the y coordinate of the circular arc region with respect to the second moment of area I of the remaining portion to which the oblique lines in the opposite directions are applied.
Therefore, when the second moment of area I of the semicircular region having the same cross-sectional area and the radius of curvature r and the second moment of area I of the circular arc region having the radius of curvature 2 times are obtained from equation 3, the value of the semicircular region having the larger y coordinate and the smaller radius of curvature is larger than the value of the circular arc region in the portion to which the oblique lines in the opposite directions are applied as the remaining portion.
The semicircular region having a smaller radius of curvature has a larger second moment of area I than the radius of curvatureThe large arc-shaped region has a large cross-sectional moment of inertia I, which means that the buckling load P is givencrEquation 2, the buckling load P of the semicircular region with a small radius of curvature can be determinedcrLarge, it is difficult to generate buckling.
Therefore, the present inventors have focused on the contour (curved shape) of the pressing belt 42 in the circumferential direction based on such a study, and have adopted the following configuration: the curvature radius of the portions of the pressure belt 42 that are in contact with the inlet- side guide members 49, 50 of the fixing nip portion N, where buckling load is likely to act on the pressure belt, is set to be smaller than the portions of the pressure belt that are in contact with the outlet- side guide members 49, 50.
Here, the reason why the bending load is more likely to act on the entrance side of the pressure belt 42 to the fixing nip N than on the exit side of the fixing nip N is that although the pressure belt 42 is driven by the rotation of the heating roller 41, the pressure belt 42 is easily conveyed in a state of being pressed against the guide members 49 and 50 by causing the driving force to act on the pressure belt 42 by the pressing force against the heating roller 41 on the entrance side of the fixing nip N. On the other hand, the pressing belt 42 is difficult to press against the guide members 49 and 50 because the pressing force against the heating roller 41 is free on the exit side of the fixing nip N.
Further, as shown in fig. 8 and 9, the guide members 49 and 50 include guide portions 495 and 505 as an example of inner peripheral surface contact portions, and the guide portions 495 and 505 contact the inner peripheral surface of the end portion of the pressure belt 42 in the longitudinal direction. The side plate portions 491, 501 of the guide members 49, 50 are configured to have end surface contact portions that contact the end surfaces of the pressure belt 42 in the longitudinal direction at least on the inlet side and the outlet side of the fixing nip portion N, and end surface non-contact portions that do not contact the end surfaces of the pressure belt 42 in the longitudinal direction. The guide portions 495 and 505 of the guide members 49 and 50 are set so that the degree of bending or bending of the end surface contact portion is smaller on the inlet side than on the outlet side of the fixing nip portion N.
In other words, the pressing belt 42 is provided with the guide portions 495 and 505 along the circumferential direction of the pressing belt 42 in a region where the radius of curvature is relatively small and a region where the bending moment I and the bending rigidity (EI) are large, and the pressing belt 42 is configured to be in contact with the side plate portions 491 and 501 of the guide members 49 and 50 in a region where the radius of curvature is relatively small and the moment I and the bending rigidity (EI) are small, and the pressing belt 42 is configured not to be in contact with the side plate portions 491 and 501 of the guide members 49 and 50 in a region where the radius of curvature is relatively large and the moment I and the bending rigidity (EI) are small.
That is, as shown in fig. 8 and 9, the side plate portions 491, 501 of the guide members 49, 50 are integrally provided with guide portions 495, 505 (an example of an inner peripheral surface contact portion) on the inner side surface of the surface located on the inner side in the longitudinal direction of the pressure belt 42, the guide portions 495, 505 are shaped along the circulating orbit of the pressure belt 42, and the guide portions 495, 505 protrude in a short cylindrical shape toward the inner side in the longitudinal direction of the pressure belt 42 and contact the inner peripheral surface of the pressure belt 42. The guide portions 495 and 505 are formed in a cylindrical shape having a desired thickness and a special cross section, and are provided so as to be present over the entire circumference in the rotation direction (circumferential direction) of the pressing belt 42.
As shown in fig. 8 and 9, the guide members 495 and 505 of the guide members 49 and 50 include: 1 st bent portions 495a, 505a located on the inlet side of the fixing nip N corresponding to the circulating path of the pressure belt 42 and bent from the opposite side of the fixing nip N toward the fixing nip N at a 1 st bent angle α 1; 2 nd bent portions 495b, 505b located on an outlet side of the fixing nip portion N and bent from the fixing nip portion N toward an opposite side of the fixing nip portion N at a 2 nd bent angle α 2; 3 rd and 4 th bent portions 495c, 495d, 505c, 505d which are located on opposite sides of the fixing nip portion N and are bent in two stages from a direction away from the fixing nip portion N toward the fixing nip portion N via a short flat portion to form 3 rd and 4 th bent angles α 3; a 5 th bent portion 495e, 505e which is located between the 2 nd bent portion 495b, 505b and the 3 rd bent portion 495c, 505 c; and 6 th bent portions 495f, 505f which are located intermediate the 4 th bent portions 495d, 505d and the 1 st bent portions 495a, 505 a. The corners of the 1 st to 6 th bent portions 495a to 495f and 505a to 505f are chamfered and have a minute rounded shape.
The inner peripheral surface contact portion of the guide member is set so that the degree of bending of a region corresponding to the end surface contact portion on the inlet side of the fixing nip portion is greater than the degree of bending of a region corresponding to the end surface contact portion on the outlet side of the fixing nip portion. Here, the flexing means "bending. "the degree of bending" means the degree of bending, and is specifically defined by the angle α of the bent portion.
As described above, both end portions of the pressing belt 42 in the longitudinal direction move along the guide portions 495, 505 of the guide members 49, 50. At this time, since the pressure belt 42 has flexibility, when passing through the 1 st to 6 th bent portions 495a to 495f and 505a to 505f of the guide portions 495 and 505, it is bent into a circular arc shape having a radius of curvature corresponding to the bend angles α 1 to α 6 of the 1 st to 6 th bent portions 495a to 495f and 505a to 505 f.
As shown in fig. 16, when the pressure belt 42 passes through the 1 st to 6 th bent portions 495a to 495f, 505a to 505f of the guide portions 495 and 505 of the guide members 49 and 50, the curved shape of the pressure belt 42 can be approximated to an arc shape. The curved shape of the pressing belt 42 corresponds to the 1 st to 6 th curved portions 495a to 495f, 505a to 505f of the guide portions 495 and 505, and can be expressed by a radius of curvature r1，r2，r3，r4，r5Is circular arc shape. Since the 3 rd and 4 th bent portions 495c, 495d, 505c, and 505d are disposed adjacent to each other, the pressing belt 42 is bent to have the same radius of curvature r in correspondence with both the 3 rd and 4 th bent portions 495c, 495d, 505c, and 505d3The shape of (2). In fig. 16, the slide piece 51 is omitted for convenience.
The curved shape of the pressing belt 42 is set to follow the curvature radius r of the 1 st bent portions 495a, 505a1Radius of curvature r of minimum and 2 nd bent portions 495b and 505b2Next to the small, 3 rd and 4 th bends 495c, 495d, 505c, 505d, 6 th and 5 th bends 495e, 495f, 505e, 505f, the order of the radii of curvature (r)3<r5<r4) And increases in turn.
As shown in fig. 8 and 9, the guides 495 and 505 include: 1 st straight portions 496a and 506a located on the downstream side of the 1 st bent portions 495a and 505a in the moving direction of the pressure belt 42; 2 nd straight portions 496b and 506b located on the upstream side of the 2 nd bent portions 495b and 505b in the moving direction of the pressure belt 42; 3 rd straight portions 496c and 506c located between the 2 nd bent portions 495b and 505b and the 5 th bent portions 495e and 505 e; 4 th straight portions 496d and 506d located between the 5 th bent portions 495e and 505e and the 3 rd bent portions 495c and 505 c; 5 th straight portions 496e and 506e that are short and located between the 3 rd bent portions 495c and 505c and the 4 th bent portions 495d and 505 d; 6 th straight portions 496f and 506f located between the 4 th bent portions 495d and 505d and the 6 th bent portions 495f and 505 f; and 7 th straight portions 496g and 506g located between the 6 th bent portions 495f and 505f and the 1 st bent portions 495a and 505 a.
The 1 st linear portions 496a and 506a and the 2 nd linear portions 496b and 506b are provided so as to be continuous with the guide portions 496h and 506h provided in the arc-shaped guide portions 492 and 502 of the side plate portions 491 and 501.
As shown in fig. 8 and 9, the side plate portions 491, 501 of the guide members 49, 50 are provided with 3 end surface contact portions, and the 3 end surface contact portions are constituted by: 1 st end surface contact portions 491a, 501a whose end surfaces in the longitudinal direction of the pressure belt 42 are in contact with 1 st bent portions 495a, 505a on the inlet side of the fixing nip N; a 2 nd end surface contact portion 491b, 501b whose end surface in the longitudinal direction of the pressure belt 42 contacts the 2 nd bending portion 495b, 505b on the exit side of the fixing nip portion; and 3 rd end surface contact portions 491c, 501c whose end surfaces in the longitudinal direction of the pressure belt 42 are in contact with both the 3 rd and 4 th bent portions 495c, 505c, 495d, 505d on the opposite side of the fixing nip portion N.
The 1 st end surface contact portions 491a, 501a are formed into a substantially fan shape having a central angle β 1 formed by straight lines extending in a direction intersecting the 1 st straight line portions 496a, 506a and the 7 th straight line portions 496g, 506 g. Similarly, the 2 nd end surface contact portions 491b, 501b are formed into a substantially fan shape having a central angle formed by straight lines extending in a direction intersecting the 2 nd straight line portions 496b, 506b and the 3 rd straight line portions 496c, 506c at an angle β 2. The 3 rd end surface contact portions 491c, 501c are formed in a substantially fan shape having a central angle formed by straight lines extending in a direction intersecting the 4 th straight line portions 496d, 506d and the 6 th straight line portions 496f, 506f, which forms an angle β 3.
The center angles β 1 to β 3 of the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c are set so as to satisfy the following relationships: that is, the angle (β 1< β 3< β 2) at which the 1 st end surface contact portions 491a, 501a are smallest, the 3 rd end surface contact portions 491c, 501c are second smallest, and the 2 nd end surface contact portions 491b, 501b are largest.
When the pressing belt 42 moves, the end surface of the pressing belt 42 in the longitudinal direction contacts only the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c of the side plate portions 491, 501 provided in the guide members 49, 50, and does not contact the side plate portions 491, 501 other than the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501 c.
The side plate portions 491, 501 of the guide members 49, 50 include: 1 st end surface non-contact portions 497a, 507a that do not contact the end surfaces of the pressing belt 42 in the longitudinal direction between the 2 nd end surface contact portions 491b, 501b and the 3 rd end surface contact portions 491c, 501 c; and 2 nd end surface non-contact portions 497b, 507b that do not contact the end surfaces of the pressing belt 42 in the longitudinal direction between the 3 rd end surface contact portions 491c, 501c and the 1 st end surface contact portions 491a, 501 a.
As shown in fig. 8 and 9, the 1 st end surface non-contact portions 497a and 507a and the 2 nd end surface non-contact portions 497b and 507b are disposed at positions outside the end surface contact portions 491a, 501a to 491c, and 501c in the longitudinal direction of the pressing belt 42. Inclined portions 497a ', 507 a', 497b ', and 507 b' are formed between the 1 st end surface non-contact portions 497a and 507a and the 2 nd end surface non-contact portions 497b and 507b and the end surface contact portions 491a, 501a to 491c, and 501c, and are inclined outward in the longitudinal direction of the pressing belt 42 from the end surface contact portions 491a, 501a to 491c, and 501 c. Further, the 1 st end surface non-contact portions 497a, 507a and the 2 nd end surface non-contact portions 497b, 507b are set longer in length in the rotation direction of the pressing belt 42 than the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501 c.
In addition, end surface non-contact regions 497c, 507c, 497d, and 507d that do not contact the end surface of the pressure belt 42 in the longitudinal direction are set in regions of the side plate portions 491, 501 of the guide members 49, 50 that correspond to the fixing nip portion N in a broad sense, that is, on the downstream side of the 1 st bent portions 495a, 505a in the moving direction of the pressure belt 42 and on the upstream side of the 2 nd bent portions 495b, 505b in the moving direction of the pressure belt 42. The end surface non-contact regions 497c, 507c, 497d, and 507d are provided in a state of being inclined toward the outside in the longitudinal direction of the pressing belt 42, similarly to the 1 st end surface non-contact portions 497a and 507a and the 2 nd end surface non-contact portions 497b and 507 b.
The end surfaces of the pressing belt 42 in the longitudinal direction contact the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c of the side plate portions 491, 501 of the guide members 49, 50, and the pressing belt 42 receives a reaction force from the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c of the side plate portions 491, 501 of the guide members 49, 50. At this time, there is a fear that: when there is a large difference in the reaction force applied to the end surface of the pressing belt 42 in the longitudinal direction from the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c of the side plate portions 491, 501, the end surface of the pressing belt 42 does not contact the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c of the side plate portions 491, 501 uniformly, but contacts a part of the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c with a large force.
Therefore, in embodiment 1, the distances L1 to L3 from the tilt fulcrums 498 and 508 provided on the outer side surfaces of the side plate portions 491 and 501 of the guide members 49 and 50 to the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, and 501c (the arm lengths) are set to be short to long in order of increasing the contact area with the end surfaces of the pressure belt 42 in the longitudinal direction from 1 st to 3 rd end surface contact portions 491a, 501a to 491c, and 501 c.
That is, the 2 nd end surface contact portions 491b, 501b having the largest contact area with the end surfaces of the pressing belt 42 in the longitudinal direction among the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c are set so that the distance (arm length) L2 from the tilt fulcrums 498, 508 to the 2 nd end surface contact portions 491b, 501b becomes the shortest, the second largest 3 rd end surface contact portions 491c, 501c, which have contact areas with the end surfaces of the pressing belt 42 in the longitudinal direction, are set so that the distance (arm length) L3 from the tilt fulcrums 498, 508 to the 3 rd end surface contact portions 491c, 501c is the second longest, the 1 st end surface contact portions 491a, 501a having the smallest contact area with the end surfaces of the pressure belt 42 in the longitudinal direction are set so that the distance L1 (arm length) from the tilt fulcrums 498, 508 to the 1 st end surface contact portions 491a, 501a is long (L2< L3< L1).
Further, since the thickness t of the pressing belt 42 is constant, the contact area where the pressing belt 42 contacts the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, and 501c is determined by the length of the pressing belt 42 wound around the 1 st, 2 nd, 3 rd, and 4 th bending portions. That is, the lengths of the pressing belt 42 wound around the 1 st, 2 nd, 3 rd and 4 th bends are set so that the 2 nd end surface contact portions 491b, 501b are the longest, the 3 rd end surface contact portions 491c, 501c are the second longest, and the 1 st end surface contact portions 491a, 501a are the shortest.
As shown in fig. 8 and 9, the tilt fulcrums 498 and 508 provided on the outer side surfaces of the side plate portions 491 and 501 of the guide members 49 and 50 are formed in a protruding hemispherical shape, and come into contact with the inner side surfaces of the arm members 71 and 72 disposed on the outer sides of the guide members 49 and 50 in the longitudinal direction of the pressure belt 42 to allow the guide members 49 and 50 to tilt (tilt).
< operation of fixing device >
In the fixing device 40 of this embodiment, deformation of the end portion of the pressure belt 42 in the longitudinal direction is suppressed as compared with the case where the radius of curvature of the pressure belt 42 is equal at the end face contact portions on the inlet side and the outlet side of the fixing nip N.
When receiving the instruction information of the request for the monochrome image forming operation (printing), the fixing device 40 rotates the eccentric cams 75 and 76 by the unillustrated drive motor as shown in fig. 11, rotates the arm members 71 and 72 to which the pressing unit 44 is attached counterclockwise by the biasing force of the coil springs 73 and 74, and presses the pressing belt 42 of the pressing unit 44 against the heating roller 41 at the fixing nip N as shown in fig. 3.
Meanwhile, as shown in fig. 4, in the fixing device 40, the heating roller 41 is rotationally driven via a drive gear G fitted to one end portion thereof in the axial direction. Further, the heating roller 41 starts to be heated by energizing the halogen lamps 414a, 414 b.
As shown in fig. 3, the fixing device 40 is driven to rotate by a frictional force acting between the pressure belt 42 pressed against the heating roller 41 and the heating roller 41 at the fixing nip portion N in accordance with the rotation of the heating roller 41.
In this case, if there are various factors such as the pressure distribution in the axial direction of the heating roller 41, the arrangement (arrangement) of the heating roller 41 and the pressing belt 42, and the variation (tolerance) in the outer diameters, thicknesses, and the like of the heating roller 41 and the pressing belt 42, as shown in fig. 4, a so-called moving phenomenon may occur in which the pressing belt 42 moves toward the end portion in the longitudinal direction.
In the fixing device 40 according to embodiment 1, as shown in fig. 8 and 9, the 1 st end surface contact portions 491a, 501a are provided at positions corresponding to the inlet sides of the fixing nip portions N in the guide portions 495, 505 of the guide members 49, 50, and the 2 nd end surface contact portions 491b, 501b are provided at positions corresponding to the outlet sides of the fixing nip portions N, and the radius of curvature r of the portion where the pressure belt 42 contacts the 1 st end surface contact portions 491a, 501a1The radius of curvature r is set to be larger than that of a portion in contact with the 2 nd end surface contact portions 491b, 501b on the exit side2Is small.
As a result, the radius of curvature r of the pressing belt 42 is set to be smaller than that of the belt1The smaller cross-sectional moment of inertia I and bending stiffness (EI) of the 1 st end surface contact 491a, 501a is larger than the radius of curvature r2The relatively large 2 nd end surface contact portions 491B, 501B are large, and hence the buckling load P against the buckling B generated at the end portions of the pressing belt 42 in the longitudinal direction is largecrAnd is increased.
In the pressure belt 42, due to the rotation upon receiving the driving force from the heating roller 41, the contact force at the time of contact with the side plate portions 491, 501 of the guide members 49, 50 tends to be higher in the region corresponding to the 1 st end surface contact portions 491a, 501a on the inlet side of the fixing nip portion N than in the 2 nd end surface contact portions 491b, 501b on the outlet side of the fixing nip portion N, and buckling is more likely to occur than on the outlet side of the fixing nip portion N.
In embodiment 1, as described above, in the pressing belt 42, the buckling load P corresponding to the buckling B of the 1 st end surface contact portions 491a, 501a is larger than the 2 nd end surface contact portions 491B, 501BcrTherefore, the buckling B is less likely to occur, and the deformation such as buckling B can be suppressed from occurring at the end portion of the pressing belt 42 in the longitudinal direction.
In embodiment 1, the end portions of the pressing belt 42 in the longitudinal direction are in contact with the side plate portions 491, 501 of the guide members 49, 50 only at the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c, and the other end portions of the pressing belt 42 in the longitudinal direction are not in contact with the 1 st and 2 nd end surface non-contact portions 497a, 507a, 497b, 507b of the side plate portions 491, 501 of the guide members 49, 50.
Therefore, in embodiment 1, the pressing belt 42 has a relatively large radius of curvature r, a small moment of area inertia I and bending rigidity (EI), and a buckling load PcrSince the relatively small 1 st and 2 nd end surface non-contact portions 497a, 507a, 497b, and 507b do not contact the side plate portions 491 and 501 of the guide members 49 and 50, buckling may not occur.
In embodiment 1, the distances L1 to L3 from the tilt fulcrums 498 and 508 are set to be short in the 1 st to 3 rd end surface contact portions 491a, 501a to 491c and 501c depending on the contact areas where the ends of the pressing belt 42 in the longitudinal direction contact the side plate portions 491 and 501 of the guide members 49 and 50, and therefore, when the ends of the pressing belt 42 in the longitudinal direction contact the side plate portions 491 and 501 of the guide members 49 and 50, the moments acting on the side plate portions 491 and 501 of the guide members 49 and 50 approach each other.
Thus, even when the pressing belt 42 moves and the end portions of the pressing belt 42 in the longitudinal direction contact the side plate portions 491, 501 of the guide members 49, 50, the moments acting on the 1 st to 3 rd end surface contact portions 491a, 501a to 491c, 501c are close to each other, and it is suppressed that a large moment acts on a part of the end surface contact portions 491a, 501a to 491c, 501c and extremely inclines on the side plate portions 491, 501 of the guide members 49, 50.
[ embodiment 2]
Fig. 17 is a diagram illustrating a fixing device of embodiment 2. In the fixing device according to embodiment 2, the region that is provided in the guide portion of the guide member and bends the pressure belt is not a bent portion but a bent portion having a bent shape. Further, the degree of curvature of a region of the inner peripheral surface contact portion of the guide member corresponding to the inlet-side end surface contact portion of the fixing nip portion is set to be greater than the degree of curvature of a region corresponding to the outlet-side end surface contact portion of the fixing nip portion.
Here, the curved means "curved to be formed in an arcuate shape. Becomes an arch shape. ". The degree of curvature means the degree of curvature, and is specifically defined by the radius of curvature of the curved portion.
That is, in embodiment 2, as shown in fig. 17, the 1 st to 5 th curved portions 499a, 509a to 499e, and 509e that are curved in accordance with the curved shape of the pressure belt 42 are provided at the guide portions 495 and 505 of the guide members 49 and 50. Further, the 1 st to 5 th bent portions 499a, 509a to 499e, 509e are different from the bent portions, and one 3 rd bent portion 499c, 509c is provided corresponding to the 3 rd and 4 th bent portions. The 1 st to 5 th curved portions 499a, 509a to 499e, 509e are set so as to follow the radius of curvature r of the 1 st curved portions 495a, 505a1Radius of curvature r of minimum, 2 nd bend 495b, 505b2The order of the second small, 3 rd curved parts 499c, 509c, 4 th and 5 th curved parts 499d, 509d, 499e, 509e, the radius of curvature (r)3<r5<r4) And is increased.
In this way, even when the 1 st to 5 th curved portions 499a, 509a to 499e, 509e are provided in the guide portions 495 and 505 of the guide members 49 and 50, the pressure belt 42 can be guided by curving the pressure belt 42 to have a desired radius of curvature, as in embodiment 1.
Other structures and functions are the same as those of the above-described embodiment, and therefore, the description thereof is omitted.
[ embodiment 3]
Fig. 18 is a diagram showing a fixing device of embodiment 3. In the fixing device according to embodiment 3, the guide portions 495 and 505 of the guide members 49 and 50 are not provided with the 1 st to 7 th linear portions, and at least some of the 1 st to 7 th linear portions are not provided but omitted.
That is, in embodiment 3, as shown in fig. 18, the linear portions 496d and 506d, part of the linear portions 496f and 506f, and part of the linear portions 496g and 506g are not provided.
As described above, in embodiment 3, although the straight portions 496d and 506d, part of the straight portions 496f and 506f, and part of the straight portions 496g and 506g of the 1 st to 7 th straight portions are omitted, the straight portions 496d and 506d, part of the straight portions 496f and 506f, and part of the straight portions 496g and 506g correspond to the end surface non-contact portions of the guide members 49 and 50, and do not hinder the guide of the pressure belt 42.
In embodiment 3, the sliding resistance with the pressing belt 42 can be reduced by omitting the straight portions 496d, 506d and parts of the straight portions 496f, 506f, and parts of the straight portions 496g, 506g among the 1 st to 7 th straight portions.
Other structures and functions are the same as those of the above-described embodiment, and therefore, the description thereof is omitted.
[ embodiment 4]
Fig. 19 is a diagram showing an image forming apparatus to which the fixing device of embodiment 4 is applied. In embodiments 1 to 3, the case where the heating roller 41 is used as the fixing unit and the pressure belt 42 is used as the endless belt has been described, but in embodiment 4, the pressure roller is used as the fixing unit and the heating belt is used as the endless belt.
That is, as shown in fig. 19, the fixing device 40 according to embodiment 4 includes a heating belt 81 and a pressure roller 82 as an example of an endless belt. A pressure pad 85 is provided inside the heating belt 81, and the pressure pad 85 presses the heating belt 81 against the pressure roller 82 to form the fixing nip portion N. Further, a heating resistor 86 is provided on the pressure pad 85. Further, with respect to the heating belt 81, both end portions of the heating belt 81 in the longitudinal direction are guided by guide members 83, 84 as guide means.
A portion 85a of the pressure pad 85 on the upstream side of the fixing nip N in the rotation direction of the heating belt 81 is formed in the same shape as the tip 462b of the 1 st supporting portion 462 of embodiment 1.
The upstream and downstream sides of the fixing nip N of the guide members 83, 84 are formed in the same shape as the guide portions 495, 505 of the guide members 49, 50 of embodiment 1.
Other structures and functions are the same as those of the above-described embodiment, and therefore, the description thereof is omitted.
In the above-described embodiment, the case where the belt conveying device is applied to the fixing device has been described, but the belt conveying device is not limited to this, and it is needless to say that the belt conveying device may be applied to a curvature correction device that corrects deformation such as curvature of the recording medium. In the case where the belt conveying device is applied to a curve correcting device, for example, an endless belt may be used as the curve correcting belt, and a curve correcting roller that is in contact with the curve correcting belt may be used as the nip portion forming unit.
In the above-described embodiment, the case where the image forming apparatus of a single color is applied as the image forming apparatus is described, but it is needless to say that a full-color image forming apparatus having the image forming apparatuses 10(Y, M, C, K) of yellow (Y), magenta (M), cyan (C), and black (K) may be applied.
Claims (10)
1. A belt conveying device is provided with:
an endless belt that rotates;
a nip forming unit that forms a nip by contacting the belt; and
a holding unit having an inner peripheral surface contact portion that contacts an inner peripheral surface of the belt, an end surface contact portion that contacts an end surface of the belt in a longitudinal direction at least on an inlet side and an outlet side of the nip portion, and an end surface non-contact portion that does not contact the end surface of the belt in the longitudinal direction, and holding an end portion of the belt in the longitudinal direction,
the belt has a smaller radius of curvature at a portion in contact with the end surface contact portion on the inlet side of the nip portion than at a portion in contact with the end surface contact portion on the outlet side of the nip portion.
2. The belt conveying apparatus according to claim 1,
the degree of curvature or degree of bending of a region of the inner peripheral surface contact portion of the holding unit corresponding to the end surface contact portion on the inlet side of the nip portion is greater than the degree of curvature or degree of bending of a region of the inner peripheral surface contact portion corresponding to the end surface contact portion on the outlet side of the nip portion.
3. The belt conveying apparatus according to claim 2,
the end surface non-contact portion of the holding unit is longer than the end surface contact portion in a rotation direction of the belt.
4. The belt conveying apparatus according to claim 1,
the holding unit has a 3 rd end face contact portion that contacts an end face of the belt in the longitudinal direction on the opposite side of the nip portion.
5. The belt conveying apparatus according to claim 4,
the curvature radius of the belt increases in the order of the inlet side of the nip portion, the outlet side of the nip portion, and the opposite side of the nip portion.
6. The belt conveying apparatus according to any one of claims 1 to 5,
the holding means may be inclined with respect to the longitudinal direction of the belt about a fulcrum provided on an outer end surface of the holding means in the longitudinal direction of the belt.
7. The belt conveying apparatus according to claim 6,
the holding unit is set such that, of an inlet side of the nip portion and an outlet side of the nip portion, a distance from the fulcrum to the end surface contact portion is shorter on a side where a contact area of the end portion of the belt in the longitudinal direction with the end surface contact portion is larger than on a side where a contact area of the end portion of the belt in the longitudinal direction with the end surface contact portion is smaller.
8. The belt conveying apparatus according to claim 7,
the holding means is set such that the distance from the fulcrum to the end surface contact portion is from short to long in order of the contact area of the end portion of the belt in the longitudinal direction in contact with the end surface contact portion being from large to small.
9. A fixing device, wherein,
the fixing device is provided with the belt conveying device according to any one of claims 1 to 8,
the fixing device fixes an image on a recording medium using the belt.
10. An image forming apparatus includes:
an image forming unit that forms an unfixed toner image on a recording medium; and
a fixing unit that fixes an unfixed toner image formed on the recording medium,
the image forming apparatus uses the fixing device according to claim 9 as the fixing unit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2019-024351 | 2019-02-14 | ||
| JP2019024351A JP7255223B2 (en) | 2019-02-14 | 2019-02-14 | Belt conveying device, fixing device and image forming device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN111562733A true CN111562733A (en) | 2020-08-21 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910841777.3A Pending CN111562733A (en) | 2019-02-14 | 2019-09-06 | Belt conveying device, fixing device, and image forming apparatus |
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| Country | Link |
|---|---|
| JP (1) | JP7255223B2 (en) |
| CN (1) | CN111562733A (en) |
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| JP2017015934A (en) | 2015-07-01 | 2017-01-19 | 富士ゼロックス株式会社 | Fixation device and image formation apparatus |
| JP2017151318A (en) | 2016-02-25 | 2017-08-31 | 富士ゼロックス株式会社 | Fixation device and image forming apparatus |
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| JP2013130792A (en) * | 2011-12-22 | 2013-07-04 | Canon Inc | Image heating device |
| JP2013195736A (en) * | 2012-03-21 | 2013-09-30 | Fuji Xerox Co Ltd | Fixing device |
| CN104238323A (en) * | 2013-06-20 | 2014-12-24 | 京瓷办公信息系统株式会社 | fixing device and image forming apparatus |
| CN104516253A (en) * | 2013-09-30 | 2015-04-15 | 兄弟工业株式会社 | Image forming apparatus and fixing device |
| JP2016166918A (en) * | 2015-03-09 | 2016-09-15 | 富士ゼロックス株式会社 | Fixation device and image formation apparatus |
| JP2017107164A (en) * | 2015-11-27 | 2017-06-15 | 富士ゼロックス株式会社 | Fixing device and image forming apparatus |
| JP2017223746A (en) * | 2016-06-13 | 2017-12-21 | 株式会社リコー | Fixing device and image forming apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| JP7255223B2 (en) | 2023-04-11 |
| JP2020134578A (en) | 2020-08-31 |
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