JP2005331576A - Electrophotographic system fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic system fixing device with which a low friction sheet member can be supported in a suitable state even when receiving slide friction resistance applied by a fixing belt sliding over the low friction sheet member in the course of a fixing process, and to provide an image forming apparatus. <P>SOLUTION: A pressure pad 56 disposed inside the fixing belt 54 presses a heat roll 52 via the fixing belt 54, thereby forming a nip section where recording paper 24 is nipped. Locking pieces 64 in the form of small projections are formed in a plurality of parts of the main body 63 of the pad member, which are located in a straight line. Locking holes are made through the low friction sheet member 66 and away from a fixed distance from one edge of the sheet member 66. The locking pieces 64 are inserted and locked into the corresponding locking holes of the low friction sheet member 66, and the other edge of the low friction sheet member 66 is disposed opposite the pressure pad 56 and the fixing belt 54. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device used in a copying machine or a printer configured as an electrophotographic system, and an electrophotographic image forming apparatus using the fixing device.

  In general, in an image forming apparatus such as a copying machine or a printer using an electrophotographic system, for example, a photoconductor formed in a drum shape is uniformly charged, and the photoconductor is exposed with light controlled based on image information. Thus, an electrostatic latent image is formed on the photoreceptor. The electrostatic latent image is converted into a visible image (toner image) with toner, and the toner image is further transferred onto a recording sheet and fixed by a fixing device to form an image.

  An electrophotographic image forming apparatus includes a color image forming apparatus that forms a full-color image. This color image forming apparatus is roughly classified into a type using an intermediate transfer member and a type not using an intermediate transfer member. The image forming apparatus using the intermediate transfer member temporarily transfers the toner image formed on the photosensitive member to the intermediate transfer member once, so that the primary transfer can be performed regardless of the material of the recording medium. This is advantageous for improving image quality.

  In addition, color image forming apparatuses using an intermediate transfer member include a so-called “4-cycle method” and a so-called “tandem method”. This four-cycle color image forming apparatus performs primary transfer in a state where toner images of respective colors such as yellow, magenta, cyan, and black, which are sequentially formed on a single photosensitive member, are superimposed on an intermediate transfer member. After that, the toner images of yellow, magenta, cyan, black, etc. transferred in multiple onto the intermediate transfer member are secondarily transferred onto a recording medium by a secondary transfer roll, thereby forming a color image.

  On the other hand, a “tandem type” color image forming apparatus uses toner images of different colors, such as yellow, magenta, cyan, and black, formed on a plurality of (for example, four) photosensitive members, as intermediate transfer members. After primary transfer in a state of being overlaid on each other, toner images of yellow, magenta, cyan, black, etc. transferred in multiple onto the intermediate transfer member are secondarily transferred onto a recording medium by a secondary transfer roll. Thus, a color image is formed.

  The fixing device used in the various types of image forming apparatuses as described above, for example, allows a recording paper carrying an unfixed toner image to pass between a fixing roll and a pressure roll, and for the unfixed toner image. Then, the toner image is fixed on the recording paper by heating and pressing.

  In such a fixing device for an electrophotographic system, the fixing speed can be increased, image quality can be improved by preventing the occurrence of fixing unevenness and paper wrinkles, the fixing device can be downsized, and the fixing device at room temperature can be fixed. It is desired to shorten the warm-up time until the state is brought up.

  In order to meet this demand, a so-called free belt nip fuser (Free Belt Nip Fuser) has been put into practical use. This free belt nip fuser has a fixing surface in which the belt nip width is expanded and the exit side of the sheet is locally elastically deformed with respect to a fixing belt slidably disposed on the surface of a fixed pressure pad. The heat roll is configured to be press-contacted so as to be formed.

  The free belt nip fuser configured in this manner is used when a sheet on which a toner image has been transferred is nipped between a rotationally driven heat roll and a fixing belt, and is moved along with the fixing belt while passing through the fixing surface. The toner image is fixed to the toner by heat and pressure bonding, and the sheet is peeled off from the fixing belt and carried out.

  This free belt nip fuser can widen the belt nip width, speed up the fixing process, reduce the size of the fixing device, and reduce the amount of heat taken from the heat roll to the fixing belt and pressure pad side. The amount of temperature drop at the nip portion can be reduced, the efficiency of using heat for melting the toner can be increased, and the toner fixability can be improved and the warm-up time can be shortened.

  Also, in such a free belt nip fuser, a sliding friction is reduced by providing a low friction layer with a small friction coefficient and wear resistance between the surface of the fixed pressure pad and the inner peripheral surface of the fixing belt. Has been proposed (see, for example, Patent Document 1).

However, in such a free belt nip fuser, the fixing belt and the low friction layer formed in the form of a sheet are disposed between the pressure pad and the heat roll with a relatively strong pressure, and the low friction layer When the inner peripheral surface of the fixing belt is slid on the surface, a relatively large sliding resistance acts on the low friction layer. Moreover, a lubricant for reducing the frictional resistance with the inner peripheral surface of the fixing belt adheres to the low friction layer formed in the sheet shape. For this reason, in the free belt nip fuser, it is difficult to keep the low friction layer formed in a sheet shape in a position covering the surface corresponding to the nip portion of the pressure pad against a relatively large sliding resistance. There's a problem.
Japanese Patent Application Laid-Open No. 11-133776

  In view of the above problems, the present invention holds the low friction sheet member in a state of covering the surface corresponding to the nip portion of the pressure member, and the fixing belt and the low friction sheet member are relatively disposed between the pressure member and the roll. An electronic device that can support the low friction sheet member in an appropriate state even if it is subjected to frictional resistance when the fixing belt slides on the low friction sheet member by rotating the roll while being held with a strong force. It is an object of the present invention to newly provide a fixing device and an image forming apparatus for a photographic system.

  The fixing device for an electrophotographic system according to claim 1 is a fixing device for fixing a toner image carried on a recording medium, the surface of which is elastically deformed, a rotating member that is rotationally driven, and a rotating device A nip portion is formed between the fixing belt formed in the shape of an endless belt that is in contact with the member and the rotating member that is inside the fixing belt and presses the rotating member via the fixing belt. A pressing member, a locking piece projecting in a protruding shape at each of a plurality of positions along the longitudinal direction of the pressing member, and a plurality of locking pieces respectively drilled on the pressing member side And a low-friction sheet member that is inserted into the engagement hole and is engaged, and is disposed so as to face the pressure member and the fixing belt.

  According to a second aspect of the present invention, in the fixing device for an electrophotographic system according to the first aspect, the engaging hole is a through hole surrounded by a smooth curve.

  According to a third aspect of the present invention, in the fixing device for an electrophotographic system according to the first aspect, the low friction sheet member is formed of a porous fluororesin fabric.

  An image forming apparatus according to a fourth aspect includes the fixing device according to any one of the first to third aspects.

  With the configuration as described above, when the fixing process is executed by the fixing device, the fixing belt and the low friction sheet member are pressed with a relatively strong force between the pressure member and the rotating member. Thus, an operation in which the inner peripheral surface of the fixing belt slides on the surface of the low friction sheet member is performed, and a relatively large sliding resistance acts on the low friction sheet member. At this time, the large sliding resistance acting on the low friction sheet member is supported by the locking pieces respectively engaged with the respective engagement holes. That is, a large sliding resistance load is applied to each engagement hole. This large sliding resistance load is supported by the entire portion of the low friction sheet member on the side where the engagement holes are formed, so that the load can be supported without causing damage to the low friction sheet member. Further, when the engagement hole formed in the low-friction sheet member is a through hole surrounded by a smooth curve, stress can be concentrated around the engagement hole 68 to prevent the breakage from starting. Therefore, the load bearing performance can be improved.

  According to the fixing device and the image forming apparatus for the electrophotographic system of the present invention, the roll is rotationally driven in a state where the fixing belt and the low friction sheet member are sandwiched between the pressure member and the roll with a relatively strong force. When the fixing process is performed, even if the low friction sheet member receives the friction resistance when the fixing belt slides on the low friction sheet member, the low friction sheet member corresponds to the nip portion of the pressure member. There is an effect that the surface can be kept covered and the fixing process can be stably performed over a long period of time.

  Embodiments relating to a fixing device and an image forming apparatus for an electrophotographic system according to the present invention will be described with reference to FIGS.

  A four-cycle full-color printer as an image forming apparatus provided with a fixing device for an electrophotographic system according to the present embodiment is shown in a diagram inside the full-color printer main body 10 as shown in the schematic cross-sectional configuration diagram of FIG. A photosensitive drum 12 serving as an image carrier is rotatably arranged at an upper right part slightly toward the center. The photosensitive drum 12 is composed of, for example, a conductive cylinder having a diameter of about 47 mm and having a surface coated with a photosensitive layer made of OPC or the like, and is about 150 mm / second along the direction of arrow A by a driving means (not shown). Driven at a process speed of sec.

  The surface of the photosensitive drum 12 is charged to a predetermined potential by rolling contact with a charging roll 14 as a charging unit. After that, image exposure with a laser beam (LB) is performed by a ROS 16 (Raster Output Scanner) as exposure means arranged at a position directly below the photosensitive drum 12, and an electrostatic latent image corresponding to the image information is generated. It is formed.

  The electrostatic latent image formed on the surface of the photoconductive drum 12 passes through the developing devices 15Y, 15M, 15C, and 15K for each color of yellow (Y), magenta (M), cyan (C), and black (K). The toner is developed by a rotary developing device 15 arranged along the direction, and becomes a toner image of a predetermined color. At this time, on the surface of the photosensitive drum 12, the charging, exposure, and development processes are repeated a predetermined number of times according to the color of the image to be formed.

  The rotary developing device 15 is rotationally driven at a predetermined timing, and the developing devices 15Y, 15M, 15C, and 15K corresponding to the color to be developed move to a developing position facing the photosensitive drum 12. For example, in the case of forming a full-color image, the charging, exposure, and development processes on the surface of the photosensitive drum 12 are yellow (Y), magenta (M), cyan (C), and black (K). Repeated four times for each color. A toner image corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K) is sequentially formed on the surface of the photosensitive drum 12.

  The number of rotations of the photosensitive drum 12 when a toner image is formed in this manner varies depending on the size of the image. For example, in the case of an A4 size, the photosensitive drum 12 is used to form a single color image. Rotates 3 times. In other words, each time the photosensitive drum 12 rotates three times, toner images corresponding to yellow (Y), magenta (M), cyan (C), and black (K) colors are sequentially formed on the surface of the photosensitive drum 12. It is formed. The toner images sequentially formed on the photosensitive drum 12 are primarily transferred in a state of being superimposed on the intermediate transfer belt 18 when passing through the primary transfer position.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photosensitive drum 12 are belt-shaped image carriers on the outer periphery of the photosensitive drum 12. At the primary transfer position where the intermediate transfer belt 18 as an (intermediate transfer body) is wound, the primary transfer is performed by the primary transfer roll 20 while being superimposed on the intermediate transfer belt 18. The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred in multiple onto the intermediate transfer belt 18 are fed by the secondary transfer roll 22 at a predetermined timing. Secondary transfer is performed collectively on a recording sheet 24 as a recording medium.

  The secondary transfer roll 22 is rotationally driven via a gear from a driving source (not shown). The recording paper 24 is fed by a pickup roll 28 from a paper feeding unit 26 disposed at the lower part of the full-color printer main body 10 and is fed in a state where it is rolled one by one by a feed roll 30 and a retard roll 32. The toner image is transferred to the secondary transfer position of the intermediate transfer belt 18 in synchronization with the toner image transferred onto the intermediate transfer belt 18 by the registration roll 34. The secondary transfer roll 22 is configured to come in contact with and separate from the surface of the intermediate transfer belt 18 at a predetermined timing.

  The intermediate transfer belt 18 is stretched by a plurality of rolls, and is configured to rotate at a predetermined process speed (about 150 mm / sec) synchronized with the rotation of the photosensitive drum 12. That is, the intermediate transfer belt 18 intermediately transfers a wrap-in roll 36 that specifies the wrap position of the intermediate transfer belt 18 on the upstream side in the rotation direction of the photosensitive drum 12 and a toner image formed on the photosensitive drum 12. A primary transfer roll 20 that is transferred onto the belt 18, a wrapped roll 38 that specifies the wrap position of the intermediate transfer belt 18 on the downstream side of the wrap position, and a backup that contacts the secondary transfer roll 22 via the intermediate transfer belt 18. The roll 40, the first cleaning backup roll 44 facing the cleaning device 42 of the intermediate transfer belt 18, and the second cleaning backup roll 46 are stretched with a predetermined tension.

  Further, in the full-color printer main body 10, in order to improve the maintainability of the intermediate transfer belt 18 and the rotary developing device 15 that occupies a large space while achieving the downsizing of the apparatus, the intermediate transfer belt 18 is not photosensitive. The image forming unit 48 including the body drum 12, the charging roll 14, and the secondary transfer roll 22 is integrally configured. By opening the upper cover portion of the full-color printer main body 10, the entire image forming unit 48 is configured. The image forming unit 48 is detachable so that it can be taken out of the full-color printer main body 10.

  Further, the cleaning device 42 for the intermediate transfer belt 18 includes a scraper and a cleaning brush (not shown) that are mounted so as to be slidable from the separated position to the surface of the intermediate transfer belt 18 at a necessary timing. Prepare. Residual toner and paper dust removed by these scrapers and cleaning brushes are collected inside the cleaning device 42.

  In this full-color printer, the surface of the photosensitive drum 12 after the toner image transfer process is completed is disposed at a position obliquely below the photosensitive drum 12 every time the photosensitive drum 12 rotates once. Residual toner and the like are removed by a cleaning blade 35 so as to prepare for the next image forming process.

The recording paper 24 onto which the toner image has been transferred from the intermediate transfer belt 18 as described above is conveyed to the fixing device 50 and pressed under heat to fix the toner image on the recording paper 24.
(Fixing device)
As shown in FIGS. 1 to 4, the fixing device 50 is configured as a so-called free belt nip fuser (free belt nip fuser) system, and includes a heat roll 52 as a rotationally driven rotating member, and the heat roll A main part is configured by a pressure pad 56 which is a pressure member 52 which is pressed by a fixing belt 54.

  Although not shown, the heat roll 52 is configured by laminating a heat-resistant elastic body layer and a release layer around a metal core (cylindrical cored bar) formed in a cylindrical shape having a predetermined length. The core of the heat roll 52 is composed of a cylindrical body made of a metal having high thermal conductivity such as iron, aluminum, SUS, etc. (here, a thin high-tensile steel pipe is used). The outer shape and thickness of the core can be reduced in diameter and thickness because the pressing force of the pressure pad 56 in the fixing device 50 is small.

  Further, any material can be used for the heat-resistant elastic layer in the heat roll 52 as long as it is an elastic body having high heat resistance. In particular, it is preferable to use an elastic body such as rubber or elastomer having a rubber hardness of about 25 to 40 degrees (JIS? A). Specifically, silicone rubber, fluorine rubber, or the like can be used.

  Any resin may be used for the release layer in the heat roll 52 as long as it is a heat-resistant resin. For example, a silicone resin, a fluorine resin, or the like can be used. From the viewpoint of wear resistance, a fluororesin is suitable. As the fluororesin, PFA, PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene hexafluoropropylene copolymer), or the like can be used. The thickness of the release layer is preferably 10 to 50 μm, more preferably 10 to 30 μm. If the thickness of the release layer is less than 10 μm, the recording paper 24 tends to be wrinkled based on the distortion of the heat roll 52, while if it exceeds 30 μm, the release layer becomes hard and the image has defects such as uneven gloss. This is because the possibility of occurrence increases and both are not preferable.

  Inside the heat roll 52, a halogen lamp is disposed as a heat source. A temperature sensor is brought into contact with the surface of the heat roll 52, and the control unit of the image forming apparatus controls lighting of the halogen lamp based on a temperature measurement value by the temperature sensor. Adjust to maintain a set temperature (eg, 170 ° C.).

  A fixing belt (formed in an endless belt shape) 54 that rotates in synchronization with the heat roll 52 while being in pressure contact is formed in an endless track shape (cylindrical shape of a predetermined length).

  The fixing belt 54 is configured as an endless belt (endless belt), and includes a base layer and a release layer coated on the surface or both surfaces of the base layer on the heat roll 52 side. The base layer is formed of a polymer such as polyimide, polyamide, or polyimideamide, or a metal such as SUS, nickel, or copper, and has a thickness of 30 to 200 μm, preferably 50 to 125 μm, and more preferably about 75 to 100 μm. The release layer coated on the surface of the base layer is formed of a fluororesin such as PFA, PTFE, or FEP, and has a thickness of about 5 to 100 μm, preferably about 10 to 30 μm.

  Further, the inner peripheral surface of the fixing belt 54 has a surface roughness Ra (arithmetic average roughness) set to 0.4 μm or less in order to reduce the rubbing resistance with the pressure pad 56. Further, the outer peripheral surface of the fixing belt 54 is set to have a surface roughness Ra of 1.2 to 2.0 μm so that the driving force from the heat roll 52 is easily received.

  The fixing belt 54 (formed in an endless belt shape) configured in this manner is supported by a pressure pad 56 slidably contacting the inner peripheral surface thereof and a slidably slidably contacting both inner peripheral surface portions thereof. It is supported by each edge guide 58 to be received so as to be freely rotatable (circular movement is possible). The fixing belt 54 is attached so that the nip portion corresponding to the pressure pad 56 is brought into rolling contact with the heat roll 52 with a predetermined pressure.

  The pressure pad 56 is inside the fixing belt 54, presses the heat roll 52 with a predetermined pressure distribution via the fixing belt 54, and forms a nip portion with the heat roll 52. Here, the nip portion is a region where the fixing belt 54 and the heat roll 52 are in rolling contact with each other while being elastically deformed, and has a predetermined length in the rotation direction of the fixing belt 54 and the heat roll 52 (the conveyance direction of the recording paper 24). A region having a rectangular shape in the plan view extending in the longitudinal direction of the fixing belt 54 and the heat roll 52.

  The pressure pad 56 includes a soft pad member 60 serving as a pressure member and a hard pad member 62 also serving as a pressure member. The soft pad member 60 is disposed on the entrance side of the nip portion in the conveyance direction, secures a wide nip portion with respect to the conveyance direction of the recording paper 24 as a recording medium, and is heated so that the recording paper 24 reaches a predetermined temperature. However, it is configured so that the required pressure can be applied. For example, the soft pad member 60 can be made of an elastic material such as silicone rubber or fluorine rubber, or a leaf spring.

  In this full-color printer, as shown in FIG. 3, the soft pad member 60 is configured by adhering an auxiliary member 60B formed of a metal long plate material to the bottom surface of an elastic material 60A formed in a prismatic shape. The upper surface of the elastic material 60 </ b> A is formed in a concave shape that substantially follows the outer peripheral surface of the heat roll 52.

  The hard pad member 62 of the pressure pad 56 is disposed on the exit side in the conveyance direction of the nip portion, and is strongly pressed against the heat roll 52 to elastically deform the heat-resistant elastic body layer and the release layer provided around the core. The recording paper 24 is peeled off from the surface of the heat roll 52.

  The hard pad member 62 can be formed using, for example, a heat-resistant resin such as PPS (polyphenylene sulfide), polyimide, polyester, or polyamide, or a metal such as iron, aluminum, or SUS. The shape of the hard pad member 62 is formed in a convex curved surface shape (so-called saddle shape) in which the outer surface shape at the nip portion has a constant radius of curvature.

  As shown in FIG. 3, the hard pad member 62 integrally forms an installation portion 62A of the soft pad member 60 adjacent to the upstream side in the transport direction along the longitudinal direction. That is, the hard pad member 62 is formed in a part of the rectangular elongated pad member main body 63, and the installation portion 62A of the rectangular groove-shaped soft pad member 60 is formed in a position adjacent to the hard pad member 62.

  Then, the soft pad member 60 is fitted into the installation portion 62A so as to be integrally assembled with the installation portion 62A as the bottom side. Thereby, the soft pad member 60 and the hard pad member 62 constitute one pressure pad 56 adjacent to each other in the longitudinal direction.

  In addition, a low friction sheet member 66 that is a rubbing member is engaged with the upstream end portion of the recording sheet 24 in the conveyance direction on the bottom surface of the pad member main body 63 at a plurality of positions spaced apart from each other in the longitudinal direction. A small rectangular protruding piece-like locking piece 64 for wearing is protruded.

  As shown in FIGS. 2, 3 and 5, the low friction sheet member 66 is disposed so as to sufficiently cover the surface of the soft pad member 60 and the hard pad member 62 in the pressure pad 56 corresponding to the nip portion. To do. The low friction sheet member 66 reduces the frictional resistance (friction resistance) when the pressure pad 56 is in sliding contact with the inner peripheral surface of the fixing belt 54 through the low friction sheet member 66 in a state where a strong pressure is applied. For example, a sheet having a small friction coefficient and excellent wear resistance and heat resistance (for example, a sheet made of a porous fluororesin fabric) is formed into a rectangular shape as shown in FIG. .

  Further, minute unevenness is formed on the surface of the low friction sheet member 66 on the fixing belt 54 side so that the lubricant applied to the inner peripheral surface of the fixing belt 54 can enter the sliding portion with the fixing belt 54. ing. For example, the roughness of the unevenness is formed such that Ra (arithmetic average roughness) is 5 to 30 μm. This is not appropriate if the roughness of the unevenness is less than Ra = 5 μm, because it is difficult to allow sufficient lubricant to enter the sliding portion with the fixing belt 54, while if it is greater than Ra = 30 μm, the unevenness is not suitable. This is based on the fact that the mark is not preferable because it is noticeable as uneven gloss when OHP or coated paper is fixed. Furthermore, the low-friction sheet member 66 is configured so as not to infiltrate the lubricant (difficult to pass through) so that the lubricant does not penetrate and leak from the back surface. The low-friction sheet member 66 includes a porous resin fiber cloth made of fluororesin as a base layer and a PET resin sheet wrapped around the surface of the heat roll 52, a sintered PTFE resin sheet, Teflon (registered) A glass fiber sheet impregnated with (trademark) can be used.

  The low friction sheet member 66 is provided with a locking hole 68 at each position corresponding to each locking piece 64 near one end in the longitudinal direction. One end of the low friction sheet member 66 in the longitudinal direction is continuous in a straight line, and a part thereof is not provided with a notch or a recess. Further, when the low friction sheet member 66 is made of a woven fabric, the direction in which one thread (weft or warp) woven in the woven fabric is aligned with the longitudinal direction of the low friction sheet member 66. It is desirable to be able to receive a load in a direction perpendicular to the entire length of the yarn.

  The engagement hole 68 formed in the low friction sheet member 66 is formed in a through hole surrounded by a smooth curve that is a semicircular straight circle or an ellipse or a shape having no corners or notches at both ends, and stress concentration. To avoid breaking. Further, in this low friction sheet member 66, the distance from each engagement hole 68 to one end portion in the longitudinal direction of the low friction sheet member is increased by a required amount so that the low friction sheet member 66 is engaged with the engagement hole 68. The reinforcing structure is such that it does not break from the portion to one end in the longitudinal direction. The low friction sheet member 66 is provided with a reinforcing structure such as increasing the thickness or stacking two sheets in a portion from each engaging hole 68 portion to one end portion in the longitudinal direction of the low friction sheet member. It may be provided.

  The low friction sheet member 66 is mounted so that the corresponding locking piece 64 of the pad member main body 63 is inserted into each engaging hole 68 and wound from the soft pad member 60 to the hard pad member 62. The low friction sheet member 66 mounted on the pad member main body 63 in this way is provided with a locking hole 68 for the low friction sheet member 66 when the pad member main body 63 is mounted in the mounting portion 74 as will be described later. The portion near one end in the longitudinal direction is engaged with an engagement structure in which a required pressure is applied between the vertical wall of the escape groove 74A and the vertical wall of the pad member main body 63, and the low friction sheet member It may be configured so that the load is not concentrated only on the engaging holes 68 of 66.

  The pad member main body 63 in which the soft pad member 60 and the low friction sheet member 66 are assembled in this way is attached to the holder member 70.

  As shown in FIGS. 2 to 4, the holder member 70 is made of a metal such as aluminum, and is formed in a deformed cylindrical shape in which one corner of a substantially rectangular cross section is projected in a small arc shape.

  The holder member 70 is installed with a guide corner 72 protruding in the shape of a small arc facing the upstream side in the conveyance direction of the recording paper 24, and the outer peripheral surface of the guide corner 72 is the inner side of the fixing belt 54. It slides on the peripheral surface and guides its circular motion.

  In addition, the holder member 70 forms a mounting portion 74 such as a pad member main body 63 on a side surface portion adjacent to the guide corner portion 72. The mounting portion 74 is formed in a rectangular shallow groove shape, and a clearance groove 74 </ b> A for loosely inserting the locking piece 64 is formed so as to be adjacent along the guide corner portion 72.

  An elastic sheet member 76 is disposed on the mounting plane of the mounting portion 74 (a plane excluding the clearance groove 74A on the bottom surface of the mounting portion 74). The elastic sheet member 76 is formed of an elastic material having heat resistance such as a heat resistant rubber material. The elastic sheet member 76 is an elastic material excellent in heat resistance that can withstand heat of about 100 ° C. without absorbing oil and expanding, and has a rubber hardness of about 30 degrees (JIS? A). A long plate shape (band shape) is formed by an elastic material.

  The elastic sheet member 76 has the same shape as the mounting plane of the mounting portion 74, has a constant thickness, and is disposed on the mounting plane of the mounting portion 74.

  Further, the elastic sheet member 76 may be disposed corresponding to a portion where the hard pad member 62 receives pressure locally. In this case, the elastic sheet member 76 is formed as a single member or a plurality of members having a shape corresponding to a portion where the hard pad member 62 receives pressure locally, and each member is a hard surface on the mounting plane of the mounting portion 74. The pad member 62 is disposed in a portion that receives pressure locally.

  Further, the elastic sheet member 76 may be disposed only on the bottom surface portion immediately below the hard pad member 62 on the mounting plane of the mounting portion 74. Alternatively, the elastic sheet member 76 may be disposed only on the bottom surface portion directly below the hard pad member 62 and the soft pad member 60 on the mounting plane of the mounting portion 74. The elastic sheet member 76 may be disposed over the entire surface of the attachment portion 74.

  As shown in FIGS. 2 to 4, the holder member 70 is provided with a lubricant application member 78 on the outer side surface 79 of the side facing the mounting portion 74 in the longitudinal direction. The lubricant application member 78 is formed of a belt-like heat-resistant felt, and is impregnated with about 3 g of a lubricant such as amino-modified silicone oil having a viscosity of 300 cs, for example. The lubricant application member 78 is disposed so as to be in sliding contact with the inner peripheral surface of the fixing belt 54, and always supplies an appropriate amount of lubricant to the inner peripheral surface of the fixing belt 54 by osmotic pressure from the heat-resistant felt. It is configured as follows. In addition, it is desirable that the lubricant application member 78 is such that only the edge portion of the heat resistant felt is brought into contact with the inner peripheral surface of the fixing belt 54 so that the lubricant is not excessively supplied from the heat resistant felt. Thereby, the lubricant is supplied to the sliding portion between the fixing belt 54 and the low friction sheet member 66, and the friction resistance between the fixing belt 54 and the pressure pad 56 via the low friction sheet member 66 is further reduced, A smooth operation of the fixing belt 54 is achieved.

  In this way, the fixing belt 54 that slides on the pressure pad 56 is supported by the respective edge guides 58 so that the inner peripheral surface portions at both ends can be freely rotated (rotated freely). The edge guide 58 is provided outside the belt traveling guide member 59 having a substantially C-shaped cross section. Further, the belt traveling guide member 59 is formed of a material having a low coefficient of static friction and a low thermal conductivity in order to reduce the frictional resistance as much as possible and to reduce heat loss. Further, the belt travel guide member 59 is formed with a flange portion 61 projecting outside the edge guide 58 so as to protrude larger than the inner diameter of the fixing belt 54.

  Each belt traveling guide member 59 is fastened to both ends of the holder member 70 by fitting the screw parts 67 into the screw holes 65 provided in the cylindrical holes of the holder member 70, respectively.

  Further, in the fixing device 50, the interval between the inner surfaces of the flange portions 61 of the belt traveling guide member 59 attached to both ends of the holder member 70 is set so as to substantially match the width of the fixing belt 54. The movement (belt walk) of the fixing belt 54 in the width direction is restricted.

  Next, a basic image forming process of a full color printer which is an image forming apparatus provided with a fixing device for an electrophotographic system according to the present embodiment will be described.

  In a full-color printer as shown in FIG. 1, image data output from an image reading device (IIT) not shown or a personal computer (PC) not shown is subjected to predetermined image processing by an image processing device (IPS) not shown. After that, the image forming operation is executed by the developing device 15 (15Y, 15M, 15C, 15K). In this image processing apparatus (IPS), the input reflectance data is subjected to various image editing operations such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, and moving editing. Predetermined image processing is performed. The image data that has been subjected to image processing is converted into color material gradation data of four colors Y, M, C, and K, and is output to the ROS 16 that is a laser exposure device.

  The ROS 16 irradiates the photosensitive drum 12 of the developing device 15 with, for example, a laser beam LB emitted from a semiconductor laser in accordance with the input color material gradation data. In the developing device 15, after the surface is charged by the charging roll 14, the surface is scanned and exposed by the ROS 16 to form an electrostatic latent image.

  The electrostatic latent image formed on the surface of the photoconductive drum 12 passes through the developing devices 15Y, 15M, 15C, and 15K for each color of yellow (Y), magenta (M), cyan (C), and black (K). The toner is developed by a rotary developing device 15 arranged along the direction, and toner images corresponding to yellow (Y), magenta (M), cyan (C), and black (K) are sequentially formed. The toner images sequentially formed on the photosensitive drum 12 in this manner are primarily transferred in a state of being superimposed on the intermediate transfer belt 18 when passing through the primary transfer position.

  Then, the yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred in multiple onto the intermediate transfer belt 18 are recorded on a recording sheet as a recording medium by the secondary transfer roll 22. Secondary transfer is performed on 24 at once.

  The recording paper 24 onto which the toner image has been transferred from the intermediate transfer belt 18 in this way is carried into the fixing device 50.

  In the fixing device 50, the heat roll 52 is rotated in the direction of arrow B by a drive motor (not shown), and the fixing belt 54 is also driven to rotate by this rotation, and the recording paper 24 on which the toner image is electrostatically transferred is transferred to the heat roll 52. And the pressure pad 56 are carried into a nip portion. When the recording paper 24 passes through the nip portion, the toner image on the recording paper 24 is fixed by the pressure acting on the nip portion and the heat supplied from the heat roll 52.

  In this fixing device 50, the nip portion can be broadly configured by the concave soft pad member 60 that substantially follows the outer peripheral surface of the heat roll 52, so that stable fixing performance can be ensured. In addition to this, in the fixing device 50, the hard pad member 62 protruded so as to bite into the outer peripheral surface of the heat roll 52 causes distortion of the surface layer of the heat roll 52 in the exit region (peeling nip portion) of the nip portion. Therefore, when the recording paper 24 after the fixing process passes through the peeling nip portion, the recording paper 24 passes through the locally formed distortion, and reliably peels off without being wound around the heat roll 52. Is done. That is, it is possible to locally increase the distortion of the heat roll 52 by the hard pad member 62 and obtain high peeling performance with a small distortion amount. Therefore, even when a thin heat-resistant resin is used as the release layer of the heat roll 52, the occurrence of paper wrinkles on the recording paper 24 can be suppressed. Further, peeling between the heat-resistant elastic body layer and the release layer hardly occurs, and the reliability of the component performance over a long period can be improved together with the maintenance of the peeling performance.

  Furthermore, since the distortion amount of the heat roll 52 can be formed small, the heat roll 52 can thin its heat-resistant elastic layer. Therefore, since the heat capacity of the heat roll 52 can be reduced, the warm-up time can be shortened and the power consumption can be reduced. In addition, since the heat-resistant elastic layer having a low thermal conductivity can be thinned, the thermal resistance between the inner surface and the outer surface of the heat roll 52 is reduced and the thermal response can be improved. Also suitable for.

  In the fixing device 50 according to the present embodiment, the pad member main body 63 is attached to the attachment portion 74 of the holder member 70 via the elastic sheet member 76. Therefore, in the fixing device 50, when a strong load is locally applied to the hard pad member 62, the hard pad member 62 in the pad member main body 63 is locally elastically deformed at a portion where the strong load is applied. (The elastic sheet member 76 is deformed so as to be locally bent so as to be crushed) and dispersed so that the load is not concentrated.

  That is, when the fixing device 50 fixes a locally thick recording medium (for example, an envelope), the locally thick part of the recording medium is located between the heat roll 52 and the hard pad member 62. When passing through the nip portion of the position, a large load is applied to a place where a locally thick portion of the recording medium is placed on the hard pad member 62. Then, the hard pad member 62 is elastically deformed so as to be locally bent so as to be recessed away from the heat roll 52 while elastically deforming the elastic sheet member 76 at a portion where a large load is applied, and escapes. For this reason, the hard pad member 62 is subjected to an average load over the entire length of the portion to which the load in the longitudinal direction is applied, and the distribution of the load in the longitudinal direction on the hard pad member 62 is allowed. Within the range, appropriate fixing processing (for example, fixing processing without wrinkles on the recording paper 24 or wrinkles due to plastic deformation on the surface of the heat roll 52) can be performed. In the fixing device 50, when the elastic sheet member 76 is not pulled between the mounting portion 74 of the holder member 70 and the hard pad member 62, there is no room for the hard pad member 62 to be elastically deformed. A local load is applied to the side 52, and the recording paper 24 is likely to wrinkle, or the surface of the heat roll 52 is likely to wrinkle due to plastic deformation.

  In the fixing device 50, as described above, the recording paper 24 on which the toner image has been electrostatically transferred passes through the nip portion, whereby the toner image is fixed on the recording paper 24. The conveying force at the time of passing is received from the heat roll 52 on the driving side. That is, the recording paper 24 is conveyed by receiving a frictional force from the heat roll 52 as the heat roll 52 rotates. Therefore, when the recording paper 24 passes through the nip portion, the recording paper 24 receives a transport force from the heat roll 52 and also receives a force in the direction opposite to the transport direction (reverse transport force) from the fixing belt 54 side. It becomes.

  By the way, the fixing belt 54 is pressed by the hard pad member 62 at the nip portion, and therefore receives a force in the direction opposite to the rotation direction from the pressure pad 56 as a rubbing resistance. Therefore, as described above, the low friction sheet member 66 is interposed between the fixing belt 54 and the hard pad member 62, and a lubricant is applied to the inner peripheral surface of the fixing belt 54 from the lubricant application member 78. The friction resistance between the fixing belt 54 and the hard pad member 62 is configured to be reduced as much as possible.

  Therefore, in the normal state, the rubbing resistance received by the fixing belt 54 from the hard pad member 62 is extremely small and can be smoothly rotated, so that the fixing belt 54 can rotate at the same speed as the recording paper 24. It is. In this case, the reverse conveying force received by the recording paper 24 is a frictional resistance from the hard pad member 62 via the fixing belt 54, and is at a level that can be ignored. Therefore, the recording paper 24 is stably conveyed at the same speed as the heat roll 52.

  Here, the lubricant applying member 78 is disposed so as to be in contact with the inner peripheral surface of the fixing belt 54, and constantly supplies a lubricant such as amino-modified silicone oil to the inner peripheral surface of the fixing belt 54. The lubricant is not limited to this, and a commonly used lubricating oil or the like having a required viscosity (for example, a viscosity of 100 cs to a viscosity of 350 cs) can be used as appropriate.

  On the other hand, when the fixing belt 54 circulates and returns to the arrangement position of the lubricant application member 78, it also has a function of collecting the lubricant applied to the inner peripheral surface of the fixing belt 54. In this way, the lubricant application member 78 always applies a certain amount of lubricant to the lubricant application member 78 by simultaneously collecting and supplying the lubricant to the inner peripheral surface of the fixing belt 54. The amount of lubricant retained is also kept constant.

  The fixing belt 54 to which the lubricant is applied by the lubricant applying member 78 is rotated and conveyed to the nip portion. Under the pressing force between the hard pad member 62 and the fixing belt 54 in the nip portion. However, since minute irregularities are formed on the surface of the low friction sheet member 66 on the fixing belt 54 side, most of the lubricant applied to the fixing belt 54 enters the recesses of the low friction sheet member 66. The low friction sheet member 66 and the fixing belt 54 are supplied to the sliding portion. In this way, the circulating use of the lubricant applied to the inner peripheral surface of the fixing belt 54 can be maintained, and the fixing belt 54 can be smoothly rotated over a long period of time. As a result, it is possible to suppress the occurrence of paper wrinkles and paper jams over a long period until the life of the fixing device 50 is reached.

  As described above, the recording paper 24 on which the toner image is fixed by the fixing device 50 and the image formation is completed is unloaded from the fixing device 50 and provided on the full color printer main body 10 as shown in FIG. It is discharged onto the discharge tray 80 and collected.

  The low-friction sheet member according to the present invention is not only used in the fixing device shown in FIGS. 1 to 5 described above, but also, although not shown, a fixing belt to which a heat source is pressed is used as a heating means. The present invention can also be used in a fixing device used in an electrophotographic image forming apparatus configured using a pressure roll as a means.

  In this case, for example, the fixing belt is disposed on the toner image carrying surface side of the recording paper, and a ceramic heater which is a pressure member having a heat generation source is disposed inside the fixing belt, and the ceramic heater is disposed at the nip portion. The fixing device is configured to supply heat. The ceramic heater is disposed over the entire width of the fixing region and forms a nip portion.

  Further, a low friction sheet member is disposed between the inner peripheral surface of the fixing belt and the ceramic heater in order to reduce the frictional resistance. This low friction sheet member is mounted by engaging a locking hole on a locking piece projecting on the ceramic heater side (for example, the holder or the ceramic heater itself) in the same manner as shown in FIGS. To do.

  Of course, the low-friction sheet member according to the present invention can be used in fixing devices having various configurations. Furthermore, it goes without saying that the present invention can have other various configurations without departing from the gist of the present invention.

1 is a schematic longitudinal sectional view of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a partial cross-sectional perspective view showing a main part of a fixing device used in the image forming apparatus according to the embodiment of the present invention. 1 is an exploded perspective view of a fixing device used in an image forming apparatus according to an embodiment of the present invention. 1 is an exploded perspective view of a main part of a fixing device used in an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a plan view showing a low friction sheet member of a fixing device used in the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Full-color printer main body 50 Fixing device 52 Heat roll 54 Fixing belt 56 Pressure pad 60 Soft pad member 62 Hard pad member 63 Pad member main body 64 Locking piece 66 Low friction sheet member 70 Holder member 74 Attachment part

Claims (4)

A fixing device for fixing a toner image carried on a recording medium,
A rotating member that is elastically deformed and rotationally driven;
A fixing belt formed in an endless belt shape that comes into contact with the rotating member;
A pressure member that is inside the fixing belt and forms a nip portion with the rotating member by pressing the rotating member through the fixing belt;
On the pressure member side, a locking piece projecting in a protruding shape at a plurality of positions on a straight line along the longitudinal direction of the pressure member,
A low-friction sheet member that is inserted and engaged with each engagement hole in which the plurality of locking pieces are respectively drilled, and is disposed so as to face between the pressure member and the fixing belt;
A fixing device for an electrophotographic system, comprising:   The fixing device for an electrophotographic system according to claim 1, wherein the engagement hole is a through hole surrounded by a smooth curve.   2. The fixing device for an electrophotographic system according to claim 1, wherein the low friction sheet member is made of a porous fluororesin fabric.   An image forming apparatus comprising the fixing device according to claim 1.

Images