JP2010204587A - Fixing device, image forming apparatus and endless belt for fixing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device or the like which prevent leak of lubricant supplied to the inner peripheral surface of an endless belt. <P>SOLUTION: The fixing device is provided with: a fixing belt (endless belt) 62 having a rough surface part 621 formed at the center part in the axial direction of the inner peripheral surface, and smooth parts 622 formed on both ends in the axial direction of the inner peripheral surface, respectively; a rotating body which forms a pressurization part to which paper is supplied between the rotating body and the fixing belt 62, rotated and driven; a lubricant supply member which supplies the lubricant to the rough surface part 621 of the fixing belt 62 while contacting the inner peripheral surface of the fixing belt 62; and a lubricant wiping member which wipes off the lubricant from the smooth parts 622 of the fixing belt 62 while contacting the inner peripheral surface of the fixing belt 62. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device, an image forming apparatus, and an endless belt for fixing.

In an image forming apparatus such as a copying machine using an electrophotographic system, a heat fixing method is widely adopted. As a fixing device used in this heat fixing method, a belt nip method has been developed in which an endless belt is pressed against a fixing roll to form a nip portion that sandwiches paper (see Patent Document 1). In the belt nip method, the endless belt is pressed against the fixing roll by a pressure applying member (pressure pad). In this case, sliding friction is generated between the pressure applying member and the endless belt. Therefore, the lubricant is applied to the inner peripheral surface of the endless belt.
For example, Patent Document 2 includes a fixing roll, an endless belt having irregularities formed on the inner peripheral surface, and a pressure pad, and improves the holding ability of the lubricant on the inner peripheral surface of the endless belt. A fixing device for forming a high-quality image is described.
In addition, means for wiping off the lubricant leaking from the inner peripheral surface of the endless belt has been reported. For example, Patent Document 3 includes a fixing roll, an endless belt having an inner peripheral surface coated with a lubricant, and a pressure pad. The lubricant wiping member causes leakage of lubricant from the inner peripheral surface of the endless belt. A fixing device that suppresses this is described.

Japanese Patent No. 3298354 JP 2005-173441 A JP-A-2005-300983

  An object of the present invention is to prevent leakage of a lubricant supplied to the inner peripheral surface of an endless belt.

The invention according to claim 1 includes an endless belt having a rough surface portion formed at an axially central portion of an inner peripheral surface and smooth portions respectively formed at both axial end portions of the inner peripheral surface, and the endless belt A rotating body that forms a pressing portion to which paper is supplied between the belt and rotates, and a lubricant supply member that supplies the lubricant to the rough surface portion of the endless belt while being in contact with the inner peripheral surface of the endless belt And a lubricant wiping member for wiping off the lubricant from the smooth portion of the endless belt while being in contact with the inner peripheral surface of the endless belt.
The invention according to claim 2 is characterized in that the smooth portion of the endless belt is provided on the outer side in the axial direction of the endless belt with respect to the maximum sheet passing width of the paper supplied to the pressing portion with the rotating body. The fixing device according to Item 1.
The invention according to claim 3 is characterized in that the smooth portion of the endless belt is provided on the outer side in the axial direction of the endless belt from the maximum pressure portion in the pressing portion with the rotating body. The fixing device described.
The invention according to claim 4 is characterized in that the lubricant wiping member has an inner circumference of the endless belt such that a contact pressure at the smooth portion of the endless belt is higher than a contact pressure at the rough surface portion of the endless belt. The fixing device according to claim 1, wherein the fixing device is in contact with a surface.

  The invention according to claim 5 is a toner image forming portion that forms a toner image, a transfer portion that transfers a toner image formed by the toner image forming portion onto a recording material, and a toner image that is transferred to the recording material. A fixing portion for fixing the recording material on the recording material, the fixing portion having a cylindrical shape, provided with a rough surface portion at an axially central portion of the inner peripheral surface, and at both axial end portions of the inner peripheral surface. Each of the fixing belt provided with a smooth portion, a pressure roll that forms a pressing portion to which a recording material is supplied between the fixing belt and rotationally driven, and a lubricant while being in contact with the inner peripheral surface of the fixing belt An image forming apparatus comprising: a lubricant supply member to be supplied; and a lubricant wiping member for wiping the lubricant from a portion corresponding to the smooth portion of the fixing belt.

The invention according to claim 6 has a cylindrical shape, and has a rough surface portion formed at an axially central portion of the inner peripheral surface, and smooth portions respectively formed at both axial end portions of the inner peripheral surface. In addition, the fixing endless belt is driven and rotated while being in contact with a rotating body that is driven to rotate.
In the invention according to claim 7, the rough surface portion of the inner peripheral surface has an uneven shape capable of holding the lubricant supplied to the rough surface portion, and the smooth portion can wipe the lubricant. The endless belt for fixing according to claim 6, which has a smooth surface.
The invention according to claim 8 is characterized in that the rough surface portion of the inner peripheral surface has a surface roughness Ra of 0.3 to 2 μm, and the smooth portion has a surface roughness Ra of 0.1 μm or less. An endless belt for fixing according to claim 6 or 7.

  According to the first aspect of the present invention, the lubricant supplied to the inner peripheral surface of the endless belt is prevented from leaking as compared with the case where this configuration is not provided.

  According to the invention which concerns on Claim 2, compared with the case where it does not have this structure, the leakage of the lubricant from the both ends of the endless belt is further prevented.

  According to the invention which concerns on Claim 3, compared with the case where it does not have this structure, the lubricant supplied to the inner peripheral surface of an endless belt is wiped off more efficiently.

  According to the invention which concerns on Claim 4, compared with the case where it does not have this structure, a lubricant can be wiped off more reliably from the inner peripheral surface of an endless belt.

  According to the fifth aspect of the present invention, a high-quality image can be formed over a long period of time by suppressing the occurrence of paper wrinkles and image misalignment as compared with the case without this configuration.

  According to the sixth aspect of the present invention, when used as a fixing belt, the lubricant supplied to the inner peripheral surface of the endless belt is prevented from leaking as compared with the endless belt not having this configuration.

  According to the invention which concerns on Claim 7, compared with the case where it does not have this structure, the retention property of the lubricant in the inner peripheral surface and the removability of the lubricant can be compatible.

  According to the invention which concerns on Claim 8, compared with the case where it does not have this structure, the retention property of the lubricant and the removability of the lubricant on the inner peripheral surface can be achieved more reliably.

1 is a schematic configuration diagram of an image forming apparatus to which the exemplary embodiment is applied. It is a diagram illustrating an example of a fixing device to which the exemplary embodiment is applied. FIG. 3 is a diagram illustrating a structure of an inner peripheral surface of a fixing belt. FIG. 6 is a diagram illustrating the position of a smooth portion on the inner peripheral surface of the fixing belt.

  Embodiments of the present invention will be described below. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. Also, the drawings used are used to describe the present embodiment and do not represent the actual size.

(Image forming device)
FIG. 1 is a schematic configuration diagram of an image forming apparatus to which the exemplary embodiment is applied. Here, an intermediate transfer type image forming apparatus generally called a tandem type will be described as an example. An image forming apparatus 100 illustrated in FIG. 1 includes a plurality of image forming units 1Y, 1M, 1C, and 1K that form toner images of respective color components by an electrophotographic method as an image forming unit. Next, as a transfer unit, a primary transfer unit 10 that sequentially transfers (primary transfer) each color component toner image formed by each of the image forming units 1Y, 1M, 1C, and 1K to an intermediate transfer belt (image holding member) 15; A secondary transfer unit 20 that collectively transfers (secondary transfer) the superimposed toner image transferred onto the transfer belt 15 onto a sheet of recording material. Further, the image forming apparatus includes a fixing device 60 that fixes the second-transferred image on a sheet as a fixing unit. Moreover, it has the control part 40 which controls operation | movement of each apparatus (each part).

  As shown in FIG. 1, each of the image forming units 1Y, 1M, 1C, and 1K includes a photosensitive drum 11 that rotates in the direction of arrow A, a charger 12 that charges the photosensitive drum 11, and a photosensitive drum 11. It has a laser exposure device 13 for writing an electrostatic latent image, and a developing device 14 that accommodates each color component toner and visualizes the electrostatic latent image on the photosensitive drum 11 with the toner. Further, a primary transfer roll 16 that transfers each color component toner image formed on the photosensitive drum 11 to the intermediate transfer belt 15 in the primary transfer unit 10, a drum cleaner 17 that removes residual toner on the photosensitive drum 11, and Have These image forming units 1Y, 1M, 1C, and 1K are arranged substantially linearly in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side of the intermediate transfer belt 15. ing.

  The intermediate transfer belt 15 is circulated and driven in the direction of arrow B shown in FIG. As various rolls, a drive roll 31 that drives the intermediate transfer belt 15, a support roll 32 that supports the intermediate transfer belt 15, a tension roll 33 that applies a constant tension to the intermediate transfer belt 15 to prevent meandering, and a secondary transfer. A backup roll 25 provided in the section 20 and a cleaning backup roll 34 provided in a cleaning section for scraping the residual toner on the intermediate transfer belt 15 are provided.

  The primary transfer unit 10 includes a primary transfer roll 16 that faces the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. The secondary transfer unit 20 is disposed on the back side of the intermediate transfer belt 15 as a secondary transfer roll (transfer member) 22 disposed on the toner image holding surface side of the intermediate transfer belt 15 and a counter electrode of the secondary transfer roll 22. And a power supply roll 26 that applies a secondary transfer bias to the backup roll 25.

  An intermediate transfer belt cleaner 35 for removing residual toner and paper dust on the intermediate transfer belt 15 is provided on the downstream side of the secondary transfer unit 20. A reference sensor (home position sensor) 42 that generates a reference signal for taking an image forming timing in each of the image forming units 1Y, 1M, 1C, and 1K is disposed upstream of the yellow image forming unit 1Y. Further, an image density sensor 43 for adjusting image quality is disposed on the downstream side of the black image forming unit 1K.

  The paper transport system includes a paper storage unit 50, a pickup roll 51 that takes out and transports the paper (P) in the paper storage unit 50, a transport roll 52 that transports the paper, and the paper to the secondary transfer unit 20. A conveyance chute 53 to be fed, a conveyance belt 55 that conveys the sheet secondarily transferred by the secondary transfer roll 22 to the fixing device 60, and a fixing inlet guide 56 that guides the sheet to the fixing device 60.

Next, a basic image forming process of the image forming apparatus 100 will be described.
In the image forming apparatus 100 as shown in FIG. 1, after image processing is performed on image data output from an image reading apparatus (IIT) (not shown) or the like, the image data is converted into four of Y, M, C, and K. The color is converted into color material gradation data and output to the laser exposure unit 13. For example, each of the photosensitive drums that rotates the exposure beam Bm emitted from the semiconductor laser in the direction of arrow A of the image forming units 1Y, 1M, 1C, and 1K according to the input color material gradation data. 11 is irradiated. After the surface of each photoconductive drum 11 is charged by the charger 12, the surface is scanned and exposed by the laser exposure device 13 to form an electrostatic latent image. The formed electrostatic latent image is developed as a toner image of each color of Y, M, C, and K by each of the image forming units 1Y, 1M, 1C, and 1K.

Next, the toner image formed on the photosensitive drum 11 is sequentially superimposed on the surface of the intermediate transfer belt 15 in the primary transfer unit 10 to perform primary transfer. The intermediate transfer belt 15 moves in the arrow B direction and conveys the toner image to the secondary transfer unit 20. The paper transport system supplies paper from the paper storage unit 50 in synchronization with the timing of transporting the toner image to the secondary transfer unit 20.
In the secondary transfer unit 20, the unfixed toner image held on the intermediate transfer belt 15 is electrostatically transferred onto a sheet sandwiched between the intermediate transfer belt 15 and the secondary transfer roll 22. Thereafter, the sheet on which the toner image has been electrostatically transferred is conveyed to the fixing device 60 by the conveying belt 55, and the fixing device 60 processes the unfixed toner image on the sheet with heat and pressure and fixes it on the sheet. The sheet on which the fixed image has been formed is conveyed to a paper discharge placement unit provided in the discharge unit of the image forming apparatus 100.

(Fixing device 60)
Next, the fixing device will be described with reference to FIGS. FIG. 2 is a diagram illustrating an example of a fixing device to which the exemplary embodiment is applied. As shown in FIG. 2, the fixing device 60 includes a fixing roll 61 as an example of a rotating body that is rotationally driven in a rotational direction C, a fixing belt 62 as an example of an endless belt for fixing that is driven to rotate in a rotational direction C ′, and fixing. A pressure pad portion 64 (here, constituted by an elastic pressure pad 64a and a high-rigidity pad 64b) as a pressure member pressed from the fixing roll 61 via the belt 62, and a sheet-like sliding member 68 are used. The part is composed.
Further, a peeling member 70 is installed on the downstream side of the pressing portion N as an auxiliary means for peeling. The peeling member 70 includes a peeling baffle 71 that is disposed in a direction facing the rotation direction C of the fixing roll 61 (counter direction) in a state of being close to the fixing roll 61, and a holder 72 that holds the peeling baffle 71. ing.

  The fixing roll 61 is configured by laminating a heat-resistant elastic body layer 612 and a release layer 613 around a metal core (cylindrical cored bar) 611. In the present embodiment, the outer diameter and the wall thickness of the core 611 are normally 20 mm to 40 mm. The wall thickness is about 1 mm to 3 mm for aluminum, and about 0.4 mm to 1.5 mm for SUS or iron. Examples of the material of the heat-resistant elastic layer 612 include silicone rubber and fluororubber having a hardness of about 15 to 45 ° (JIS-A). In this embodiment mode, the release layer 613 includes a fluororesin. Examples of the fluororesin include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and the like. Further, those composite materials, or those in which fillers such as carbon, alumina, and barium sulfate are blended can be used. The thickness of the release layer 613 is preferably 5 μm to 50 μm, more preferably 10 μm to 40 μm.

  Inside the fixing roll 61, a halogen heater 66 is disposed as a heat source. On the other hand, a temperature sensor 69 is disposed in contact with the surface of the fixing roll 61. The control unit 40 (see FIG. 1) of the image forming apparatus 100 (see FIG. 1) controls the lighting of the halogen heater 66 based on the temperature measurement value by the temperature sensor 69, and the surface temperature of the fixing roll 61 is set to the set temperature (see FIG. 1). For example, it is adjusted to maintain 170 ° C.).

The fixing belt 62 is rotatably supported by a pressure pad portion 64 and a belt travel guide 63 disposed inside, and an edge guide disposed at both ends, although not shown. The belt running guide 63 is formed of a low friction material, and the sliding resistance with the inner peripheral surface of the fixing belt 62 is reduced. Further, the belt running guide 63 is made of a low heat conductive material and suppresses heat conduction from the fixing belt 62.
The fixing belt 62 forms a pressing portion (N) to which the paper (P) is supplied with the fixing roll 61, and is disposed in pressure contact with the fixing roll 61 at the pressing portion (N). . The structure of the fixing belt 62 will be described later.

The pressure pad portion 64 is disposed inside the fixing belt 62, is pressed against the fixing roll 61 via the fixing belt 62, and forms a pressing portion (N) with the fixing roll 61. The pressure pad portion 64 is supported by the holder 65, and an elastic pressure pad 64a (for pre-nip) is disposed on the inlet side of the pressing portion (N) to ensure a wide pressing portion (N). Further, a high-rigidity pad 64b (for the peeling nip) is disposed on the exit side of the pressing portion (N), and the fixing roll 61 is distorted.
Examples of the material of the elastic pressure pad 64a include elastic bodies such as silicone rubber and fluorine rubber, and leaf springs. Further, it has a concave shape so as to follow the outer peripheral surface of the fixing roll 61.
Examples of the material of the high-rigidity pad 64b include heat-resistant resins such as polyphenylene sulfide (PPS), polyimide, polyester, and polyamide, materials that are reinforced by adding glass fibers to these resins, and metals such as iron, aluminum, and SUS. It is done.

A sliding member 68 is provided on the surface of the elastic pressure pad 64a and the high-rigidity pad 64b in contact with the fixing belt 62 to reduce the sliding resistance between the inner peripheral surface of the fixing belt 62 and the pressure pad portion 64. Examples of the material of the sliding member 68 include a sintered molded PTFE resin sheet, a glass fiber sheet impregnated with a fluororesin, and a laminated sheet in which a fluororesin film sheet is heat-fused and sandwiched with glass fibers.
Note that the nip pressure between the pressure pad portion 64 and the fixing roll 61 is loaded by a member such as a spring (not shown), and the load is an apparatus corresponding to A4 size (corresponding to A4SEF sheet passing width) and is 100 N. It is about 350N and A3 size compatible (A4LEF paper passing width), and is about 150N to 450N.

Further, the belt running guide 63 rubs against the inner peripheral surface of the fixing belt 62. Examples of the material of the belt traveling guide 63 include heat resistant resins such as PFA and PPS.
A lubricant supply member 67 is disposed in the holder 65 along the longitudinal direction of the fixing device 60. The lubricant supply member 67 is disposed so as to be in contact with the inner peripheral surface of the fixing belt 62 and supplies an appropriate amount of lubricant such as amino-modified silicone oil. Thereby, the lubricant is supplied to the sliding portion between the fixing belt 62 and the sliding member 68, and the sliding resistance between the fixing belt 62 and the pressure pad portion 64 via the sliding member 68 is further reduced.

  A lubricant wiping member 675 for wiping off the lubricant supplied to the inner peripheral surface of the fixing belt 62 is disposed inside the fixing belt 62. The lubricant wiping member 675 is arranged so as to eat back on the inner peripheral surface of the fixing belt 62. The lubricant wiping member 675 is made of a heat-resistant fiber felt, non-implanted cloth, heat-resistant sponge, or the like. The arrangement of the lubricant wiping member 675 will be described later.

(Fixing belt 62)
Next, the fixing belt 62 will be described.
In this embodiment, an example of the pressure-side fixing belt 62 pressed against the fixing roll 61 is shown, but the present invention is not necessarily limited thereto. For example, an endless belt is pressed by a pressure applying member from the inside to form a nip portion with an opposing rotating body, and lubricates between the endless belt and the pressure applying member (or a low friction member provided thereon). If the agent is supplied, a belt on the fixing side may be used, and the present invention is also applicable to a fixing device using belts on both the fixing side and the pressure side.

The fixing belt 62 to which this embodiment is applied includes a base layer (not shown) formed in a cylindrical shape and a release layer (not shown) coated on the surface or both surfaces of the base layer on the fixing roll 61 side. Z)). In the present embodiment, the diameter of the fixing belt 62 is 30 mm. In the present embodiment, the length of the fixing belt 62 in the axial direction is usually 24 cm to 37 cm.
The base layer is formed of a heat resistant resin such as polyimide and a thin metal such as SUS. In the case of a heat resistant resin, the thickness of the base layer is 30 μm to 200 μm. Moreover, in the case of a metal, it is 10 micrometers-100 micrometers. The release layer is formed of a fluororesin, a composite material of fluororesin, or a composition in which a filler is blended with fluororesin. The thickness of the release layer is 5 μm to 100 μm. An elastic layer may be provided between the release layer and the base layer.

FIG. 3 is a view for explaining the structure of the inner peripheral surface of the fixing belt 62.
As shown in FIG. 3A, the inner peripheral surface of the fixing belt 62 includes a rough surface portion 621 formed in the center portion of the cylindrical axial direction (arrow D direction) and both end portions in the axial direction of the inner peripheral surface. And a smooth portion 622 formed respectively. The arrow C ′ is the moving direction (rotating direction) of the fixing belt 62.
In the present embodiment, the rough surface portion 621 on the inner peripheral surface has a fine uneven shape. When the surface roughness Ra (arithmetic mean roughness, JIS 94) of the rough surface portion 621 is measured in the axial direction (direction of arrow D) of the fixing belt 62, Ra = 0.3 μm to 2.0 μm, preferably Ra = 0.4 μm to 1.2 μm.

FIG. 3B is a diagram illustrating an example of the rough surface portion 621. As shown in FIG. 3B, a plurality of convex portions and grooves are formed on the rough surface portion 621 so as to go around the inner peripheral surface along the moving direction C ′ of the fixing belt 62 (moving). Directional groove type).
FIG.3 (c) is sectional drawing of the axial direction XX 'in FIG.3 (b). As shown in FIG. 3C, the rough surface portion 621 is formed with convex portions and grooves alternately and continuously.

  As described above, the rough surface portion 621 may have irregular irregularities formed on the inner peripheral surface in addition to the moving direction groove type in which convex portions and grooves are continuously formed. For example, an uneven shape (groove sandblast type) in which grooves are formed on the inner peripheral surface along the moving direction of the fixing belt 62 and further subjected to sandblasting on the entire surface (groove sandblasting type); compared to the entire inner peripheral surface of the fixing belt 62 An uneven shape (small sandblast type) subjected to a fine sandblast treatment; an uneven shape (large sandblast type) subjected to a relatively rough sandblast treatment on the entire inner peripheral surface of the fixing belt 62.

  By forming a fine concavo-convex shape on the inner peripheral surface of the fixing belt 62, the ability of retaining the lubricant on the inner peripheral surface is improved. Thereby, the lubricant is stably maintained in the sliding portion between the fixing belt 62 and the sliding member 68. The sliding resistance between the fixing belt 62 and the pressure pad portion 64 is reduced. As a result, it is possible to stably convey the paper with the fixing roller 61 at a constant speed, and the occurrence of image misalignment and paper flaws on the paper can be suppressed.

  The effect of the fine unevenness formed on the inner peripheral surface of the fixing belt 62 is considered as follows. As described above, the lubricant supply member 67 is disposed so as to be in contact with the inner peripheral surface of the fixing belt 62, and constantly supplies the lubricant to the inner peripheral surface of the fixing belt 62. The lubricant applied over the entire inner peripheral surface from the lubricant supply member 67 is mainly held in the concave portion of the fine uneven shape formed on the inner peripheral surface. In the recesses, the lubricants are each held in a minute aggregate and stably held. Further, the lubricant is leveled by the contact between the lubricant supply member 67 and the fine concavo-convex convex portion on the inner peripheral surface, the lubricant is reliably supplied to the fine concave portion, and the excess lubricant is lubricated. It is collected by the agent supply member 67. Therefore, the amount of lubricant retained in the recess is controlled to be substantially constant, and the lubricant is uniformly retained over the entire inner peripheral surface of the fixing belt 62.

Next, the smoothing unit 622 will be described.
As shown in FIG. 3A, the fixing belt 62 to which the present exemplary embodiment is applied is provided with smoothing portions 622 at both end portions in the axial direction (direction of arrow D) of the inner peripheral surface. The smooth portion 622 is formed as a belt-like portion that goes around the inner peripheral surface with a certain width along the moving direction of the fixing belt 62 on the outer side of the rough surface portion 621. The width of the smooth portion 622 in the axial direction is not particularly limited, but is 15 mm in the present embodiment.
The smoothing unit 622 does not perform a process such as surface roughening on the inner peripheral surface of the fixing belt 62, and maintains the original state of the inner peripheral surface as it is (smooth type). In the present embodiment, the surface roughness Ra (arithmetic average roughness) of the smooth portion 622 is Ra = 0.2 μm or less in any direction, preferably 0.1 μm or less.

By the way, as described above, if fine irregularities are formed on the inner peripheral surface of the fixing belt 62, the lubricant retention capability is improved, but the lubricant that has passed through the lubricant wiping member 675 may leak. It turns out.
That is, as described in the present embodiment, the belt nip type fixing device presses the fixing belt 62 against the fixing roll 61 by the pressure pad portion 64, so that the sliding between the pressure pad portion 64 and the fixing belt 62 occurs. Dynamic friction occurs. Therefore, a lubricant is applied to the inner peripheral surface of the fixing belt 62 to improve the slipping property between the pressure pad portion 64 and the fixing belt 62.

  Here, in the case of a small apparatus, it is difficult to arrange a supply mechanism or a member that stably supplies a certain amount of lubricant. For this reason, conventionally, in order to supply the lubricant to the rubbing surface between the pressure applying member and the endless belt, the lubricant is supplied from the lubricant supplying member arranged on the upstream side of both sliding portions to the inner peripheral surface of the endless belt. Is applied, and the lubricant is conveyed to the sliding portion as the endless belt rotates. In this system, it is difficult to apply a certain amount of lubricant stably over a long period of time. Therefore, even if the required amount is given to the lubricant supply member in the initial stage, the lubricant escapes into the gap between the pressure applying member and the like over time, and the application amount to the endless belt decreases. Then, sliding friction between the pressure applying member and the endless belt increases, and smooth rotation of the endless belt corresponding to the rotation of the fixing roll becomes difficult. As a result, the smooth conveyance of the paper at the pressing unit is hindered, and image defects such as paper jam and image misalignment may occur.

  Further, when trying to prevent the lubricant from withstanding over a long period of use, if an excessive amount of lubricant is applied in the initial stage, excess lubricant will leak from both ends of the endless belt. When the leaked lubricant adheres to the opposite surface of the fixing roll, it becomes a stain on the paper. When the lubricant is silicone oil, the silicone rubber in the elastic layer of the fixing roll swells due to the leaked oil. For this reason, there are cases where problems such as peeling of the elastic layer of the fixing roll and paper wrinkles due to deformation of the shape of the fixing roll may occur. As described above, it is necessary to strictly control the amount of oil applied to the initial lubricant supply member, and as a result, it has been difficult to obtain long-term lubricant sliding stability.

In order to solve such a problem, a technique including a lubricant wiping member for wiping off a lubricant leaking from the inner peripheral surface of an endless belt has been proposed. However, if the inner peripheral surface of the endless belt is a rough surface, the long-term sliding stability is improved, but the lubricant retained on the rough surface slips through the lubricant wiping member. Therefore, it has been difficult to prevent lubricant leakage from the end of the endless belt for a long time.
The present inventor has solved the above technical problem by forming smooth portions 622 at both ends of the inner peripheral surface of the fixing belt 62.

FIG. 4 is a diagram illustrating the position of the smooth portion 622 on the inner peripheral surface of the fixing belt 62. As shown in FIG. 4A, on the inner peripheral surface of the fixing belt 62, the smooth portions 622 are formed at both ends on the outer side of the rough surface portion 621 formed at the center portion. Here, W is the maximum sheet passing width of the sheet. Lubricant wiping members 675 are arranged so as to come into contact with the smooth portions 622 formed at both ends.
That is, according to the results of examination by the inventors, it has been found that the sliding resistance of the fixing belt 62 increases in a region where the nip pressure increases (maximum sheet passing width W), and both ends of the fixing belt 62 are low. . Accordingly, a rough surface portion 621 is provided in a region where the nip pressure on the inner peripheral surface of the fixing belt 62 is high (maximum sheet passing width W), and smooth portions are provided at both ends that are outside the fixing belt 62 in the axial direction from the maximum sheet passing width W. 622 was provided.

  Here, as shown in FIG. 4A, the lubricant wiping member 675 may be disposed so as to contact only the portion corresponding to the smooth portion 622 on the inner peripheral surface of the fixing belt 62, and the fixing. You may arrange | position so that the whole axial direction of the internal peripheral surface of the belt 62 may be contacted. In that case, the thickness and hardness of the lubricant wiping member 675 may be adjusted so that the contact pressure to the portion corresponding to the smooth portion 622 on the inner peripheral surface of the fixing belt 62 may be increased.

As described above, when the smooth portions 622 are provided at both ends of the inner peripheral surface of the fixing belt 62, lubrication that contacts the smooth portion 622 while ensuring slidability in the rough surface portion 621 provided at the center portion of the fixing belt 62. The agent wiping member 675 prevents the lubricant from slipping through.
The result of the paper passing test by the fixing device 60 equipped with the fixing belt 62 is as follows. In other words, even after 200,000 sheets were passed by A4LEF, paper flaws, image misalignment, motor load abnormality, and the like did not occur on the inner peripheral surface of the fixing belt 62 due to an increase in sliding resistance. Further, no lubricant leaked from both ends of the fixing belt 62.

When a fixing device 60 equipped with an endless belt having a rough surface formed on the entire inner peripheral surface is used in a similar sheet passing test, 8000 sheets of A4 LEF passing through the endless belt end due to oil leakage from the endless belt. An oil stain occurred. Thereafter, peeling and deformation due to oil swelling occurred at the end of the heat-resistant elastic body layer 612 of the fixing roll 61.
Further, when the fixing device 60 equipped with an endless belt having a smooth surface with a surface roughness Ra of 0.1 μm or less on the entire inner peripheral surface is used, the sliding resistance of the inner surface of the endless belt increases with 4000 sheets of A4LEF paper. , Paper jam or image misalignment occurred.
As described above, by using the fixing belt 62 to which the present exemplary embodiment is applied, it is possible to prevent the lubricant supplied to the inner peripheral surface of the fixing belt 62 from leaking and to increase the long-term sliding resistance. It can be seen that the effect of suppressing the occurrence of paper jam and image misalignment can be obtained.

Further, FIG. 4B is a diagram illustrating the nip pressure distribution Pw of the fixing device 60 and the position of the smoothing unit 622. In the graph of FIG. 4B, the horizontal axis indicates the axial position M of the fixing belt 62. The vertical axis indicates the nip pressure P. Pw represents the nip pressure distribution when no paper is passed.
As shown in FIG. 4B, on the inner peripheral surface of the fixing belt 62, the smoothing unit 622 has an axis of the fixing belt 62 from the maximum nip pressure portion of the nip pressure distribution Pw (non-sheet passing) of the fixing device 60. It is formed in a part corresponding to the outside in the direction.

By forming the smooth portion 622 at a portion corresponding to the axially outer side of the fixing belt 62 from the maximum nip pressure portion, the lubricant from the end portion of the fixing belt 62 is prevented while preventing deterioration of the inner surface sliding property of the fixing belt 62. Can prevent leakage. In this case, the lubricant wiping member 675 may be disposed so as to contact only the portion corresponding to the smooth portion 622 of the inner peripheral surface of the fixing belt 62, or the entire axial direction of the inner peripheral surface of the fixing belt 62. You may arrange | position so that it may contact.
The results of the paper passing test using the fixing device 60 equipped with the fixing belt 62 having such a structure are as follows. That is, even after 200,000 sheets were passed by A4LEF, no paper sheet or image misalignment due to an increase in sliding resistance on the inner surface of the fixing belt 62, motor load abnormality, or the like did not occur. Further, no lubricant leaked from the end of the fixing belt 62.

1Y, 1M, 1C, 1K ... image forming unit, 11 ... photosensitive drum, 12 ... charger, 13 ... laser exposure device, 14 ... developer, 15 ... intermediate transfer belt, 16 ... primary transfer roll, 17 ... drum cleaner , 20 ... secondary transfer section, 22 ... secondary transfer roll, 31 ... drive roll, 40 ... control section, 50 ... sheet storage section, 60 ... fixing device, 61 ... fixing roll (rotary member), 62 ... fixing belt ( Endless belt), 64 ... pressure pad portion, 67 ... lubricant supply member, 621 ... rough surface portion, 622 ... smooth portion, 675 ... lubricant wiping member

Claims (8)

An endless belt having a rough surface portion formed at an axially central portion of an inner peripheral surface and smooth portions respectively formed at both axial end portions of the inner peripheral surface;
A rotating body that forms a pressing portion to which paper is supplied between the endless belt and rotationally drives the rotating body;
A lubricant supply member for supplying a lubricant to the rough surface portion of the endless belt while being in contact with the inner peripheral surface of the endless belt;
A lubricant wiping member for wiping off the lubricant from the smooth portion of the endless belt while contacting the inner peripheral surface of the endless belt;
A fixing device comprising:   The fixing device according to claim 1, wherein the smooth portion of the endless belt is provided on the outer side in the axial direction of the endless belt with respect to the maximum sheet passing width of the paper supplied to the pressing portion with the rotating body.   The fixing device according to claim 1, wherein the smooth portion of the endless belt is provided on the outer side in the axial direction of the endless belt than a maximum pressure portion in the pressing portion with the rotating body.   The lubricant wiping member contacts an inner peripheral surface of the endless belt so that a contact pressure at the smooth portion of the endless belt is higher than a contact pressure at the rough surface portion of the endless belt. The fixing device according to any one of claims 1 to 3. A toner image forming unit for forming a toner image;
A transfer unit that transfers the toner image formed by the toner image forming unit onto a recording material;
A fixing unit for fixing the toner image transferred to the recording material on the recording material,
The fixing unit is
A fixing belt having a cylindrical shape, provided with a rough surface portion at an axially central portion of the inner peripheral surface, and provided with smooth portions at both axial end portions of the inner peripheral surface;
A pressure roll that forms a pressing portion to which a recording material is supplied between the fixing belt and rotationally drives;
A lubricant supply member for supplying a lubricant while being in contact with the inner peripheral surface of the fixing belt;
A lubricant wiping member for wiping off the lubricant from the portion corresponding to the smooth portion of the fixing belt;
An image forming apparatus comprising: A rough surface portion having a cylindrical shape and formed in the axially central portion of the inner peripheral surface;
Smooth portions respectively formed at both axial ends of the inner peripheral surface,
An endless belt for fixing, wherein the belt is driven to rotate while being in contact with a rotating body to be rotated.   The rough surface portion of the inner peripheral surface has an uneven shape capable of holding the lubricant supplied to the rough surface portion, and the smooth portion has a smooth surface capable of wiping off the lubricant. The fixing endless belt according to claim 6.   The rough surface portion of the inner peripheral surface has a surface roughness Ra of 0.3 to 2 μm, and the smooth portion has a surface roughness Ra of 0.1 μm or less. The endless belt for fixing described.

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