JP2017203873A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the ends of a belt from being damaged in a belt system fixing device including a protection member (driven ring).SOLUTION: There is provided a fixing device comprising: an endless belt; a nip forming member that is disposed inside the belt; a rotatable pressure member that is in a relative pressure state with the nip forming member with the belt therebetween to form a fixing nip part; a belt holding member that rotatably holds the belt at the ends of the belt; and a protection member that is arranged between the belt holding member and the ends of the belt and rotated through contact with the ends of the belt for protecting the ends of the belt, the fixing device conveying a recording material carrying an unfixed image to the fixing nip part to fix the unfixed image to the recording material, wherein in a state where the protection member is rotated following the rotation of the belt, the protection member is in contact with the belt on an inclined surface where the ends of the belt are inclined toward the inner periphery.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a fixing device that fixes an image on a recording material, and an image forming apparatus equipped with the fixing device.

  In an electrophotographic image forming apparatus such as a printer, a copier, a facsimile, or a multifunction machine having at least two functions thereof, a toner image transferred on a recording material (also referred to as paper, transfer paper, or recording paper) is fixed. A belt-type fixing device is used as the fixing device. The “recording material” is a concept including thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet and the like in addition to plain paper.

  As a belt type fixing device, it supports an endless belt that can be rotated with a heat source, a roller that presses and rotates from the outside, and a belt that is fixedly arranged on the inner peripheral side of the belt and that is pressed against the roller. And a pressing member (nip forming member) for forming a fixing nip portion between the belt and the roller. By passing the recording material through the fixing nip portion, the unfixed toner image on the recording material is heated and A configuration for fixing by applying pressure is known. And from the viewpoint of recent energy savings, in particular, in order to shorten the waiting time from the power-on of the image forming apparatus to the image forming executable state (quick start property) or to reduce the power consumption during standby (power saving), In fixing devices, there is a great demand for low heat capacity, high thermal conductivity, and miniaturization, and endless belts are also thinned, and belts having a small heat capacity, which are also called “films”, have come to be used.

  In a fixing device using such a thin endless belt, generally, a regulating member is provided for regulating the movement of the endless belt in the axial direction. For example, in the fixing device described in Patent Document 1, as shown in FIG. 11, both ends of the endless belt 100 are rotatably held and fixed to restrict the endless belt 100 from moving in the axial direction. A flange 600 is provided. Further, in this fixing device, a driven ring 700 (protective member) that protects the end of the endless belt 100 is provided between the fixed flange 600 and the end of the endless belt 100. When the endless belt 100 receives an axial force and moves toward one side, the end of the endless belt 100 abuts against the driven ring 700, so that the driven ring 700 rotates together with the endless belt 100. This prevents the end of the endless belt 100 from rubbing against the fixed flange 600.

  Further, in the fixing nip portion, the endless belt is pushed toward the inner diameter of the belt by a roller pressed from the outside, and if the pushing amount is large, the endless belt 100 is moved from the inner peripheral edge of the driven ring 700 in the fixing device shown in FIG. Will also go inside. Therefore, when the endless belt 100 is deviated, as shown in FIG. 12, the end of the endless belt 100 is located at the position where the endless belt 100 enters inside the inner peripheral surface of the driven ring 700. It will slidably contact the edge E of the inner peripheral surface. As a result, in addition to the indentation deformation at the fixing nip portion of the endless belt, there is a problem that this sliding contact further applies a load and the belt end portion is more easily damaged. In particular, in the case of a thin film, the possibility of such breakage increases. Therefore, in patent document 2, the proposal which provides an inclined surface in the edge part of the inner peripheral circle of the driven ring which is a protection member is made.

  However, in any case, the driven ring, which is a protective member, receives the belt shifting force on a plane perpendicular to the shifting direction (rotating shaft direction) of the endless belt. At this time, a compressive force is generated at the end of the endless belt. When this shifting force is increased, the end face of the endless belt is buckled and deformed in an easily deformable outer circumferential direction (trumpet shape). When the endless belt end is deformed in the outer circumferential direction, a tensile force is generated at the belt end. If the offset force is further increased, the belt end portion is eventually torn and damaged.

  Therefore, in view of such circumstances, an object of the present invention is to make it difficult for the belt end portion to be damaged in a belt-type fixing device including a protective member (driven ring).

  In order to solve the above problems, in the present invention, an endless belt, a nip forming member disposed inside the belt, and a fixing state in which the belt is pressed relative to the nip forming member across the belt. A rotatable pressure member that forms a nip portion; a belt holding member that rotatably holds the belt at an end portion of the belt; and the belt holding member and an end portion of the belt disposed between the belt holding member and the belt end portion. A protection member for protecting the belt end portion that is rotated by contact with the end portion of the belt, and transports a recording material carrying an unfixed image to the fixing nip portion to fix the unfixed image on the recording material. In the fixing device, in a state in which the protection member rotates with the belt, the protection member contacts the belt with an inclined surface in which a belt end portion is inclined toward the inner peripheral side.

  According to the present invention, in the state where the protective member (driven ring) is rotated around the fixing belt, the protective member abuts the belt on the inclined surface such that the belt end portion is inclined toward the inner peripheral side. It is possible to avoid the belt end surface from being torn and broken as in the case of buckling deformation in the narrowing direction and buckling deformation in the direction of opening to the outer peripheral side, and the belt end portion is hardly damaged.

1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic view of a fixing device according to an embodiment of the present invention. FIG. 3 is a configuration diagram illustrating a configuration around an end portion of a fixing belt according to a first configuration example from a side surface. FIG. 3 is a configuration diagram illustrating a configuration around an end portion of a fixing belt according to a first configuration example from an upper surface. FIG. 6 is an explanatory diagram illustrating a contact area in a configuration around an end portion of a fixing belt. FIG. 5 is a conceptual diagram illustrating buckling deformation around an end portion of a fixing belt according to a first configuration example. FIG. 6 is a configuration diagram illustrating a configuration around an end portion of a fixing belt according to a second configuration example from an upper surface. FIG. 9 is a conceptual diagram illustrating buckling deformation around an end portion of a fixing belt according to a second configuration example. FIG. 10 is a configuration diagram illustrating a configuration around an end portion of a fixing belt according to a third configuration example from an upper surface. FIG. 10 is a conceptual diagram illustrating buckling deformation around an end portion of a fixing belt according to a third configuration example. FIG. 9 is a perspective view illustrating a configuration of a belt holding member and a driven ring provided on an end portion side of an endless belt in a conventional fixing device. FIG. 6 is a view showing a state in which an end of an endless belt is in contact with an inner edge of a driven ring in a conventional fixing device.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus according to an embodiment of the present invention. Incidentally, the mechanism of the entire image forming apparatus is basically the same as the conventional one, and those skilled in the art can immediately understand the basic configuration and operation. In each drawing, members having the same function or shape and components thereof are denoted by the same reference numerals as much as possible to simplify the description.

  The image forming apparatus 1 is a color printer, and a paper feed tray 10 that stores paper P as a recording material, a paper feed roller 11 that carries the paper P out of the paper feed tray 10, and the like are provided at the lower part of the apparatus main body. The image forming unit is arranged in the center of the apparatus main body above the paper tray 10. A paper discharge tray 14 is formed on the upper surface of the apparatus for stocking paper discharged outside the apparatus. In addition to the paper feed tray 10, a manual paper feed mechanism may be provided.

  An endless loop-shaped intermediate transfer belt 30 is disposed in the image forming unit, and yellow (Y), magenta (M), and cyan (C) are sequentially arranged from the upstream side along the lower traveling side of the intermediate transfer belt 30. Four image forming units 4Y, 4M, 4C, and 4K each having drum-shaped photoconductors 5Y, 5M, 5C, and 5K for black (K) are arranged side by side. The construction of each image forming unit is the same except that the developer of each color of yellow, magenta, cyan, and black corresponding to the color separation component of the color image is accommodated. In the following, alphabets (Y, A description will be given omitting M, C, and K). As is well known, a charging device 6, a developing device 7, a cleaning device 8 and the like are provided around the photoreceptor 5 of each image forming unit. Laser light from the optical system unit 9 is applied to the photosensitive member 5 from between the charging device 6 and the developing device 7. The optical system unit 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of the photoreceptor 5 with laser light based on image data. The primary transfer roller 31 is disposed on the inner side of the lower running side of the intermediate transfer belt 30 so as to contact the respective photoconductors 5 so as to contact the intermediate transfer belt 30.

  The transfer device 3 having the intermediate transfer belt 30 further includes four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, a secondary transfer backup roller 32, and a cleaning backup roller 33. And a tension roller 34 and a belt cleaning device 35. The intermediate transfer belt 30 is wound and stretched by a secondary transfer roller 36, a secondary transfer backup roller 32, and a cleaning backup roller 33. When the secondary transfer backup roller 32 is driven to rotate, a direction indicated by an arrow in the figure. It is designed to run around (rotate). The intermediate transfer belt 30 is held in contact with the four color image forming units (photosensitive members) in the case of color printing, and only in the black image forming unit (photosensitive members) in the case of monochrome printing. It is comprised so that the state which contacts may be hold | maintained.

  Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 between each photoconductor 5 to form a primary transfer nip. Each primary transfer roller 31 is applied with a predetermined DC voltage (DC) and / or AC voltage (AC). The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Like the primary transfer roller 31, the secondary transfer roller 36 also has a predetermined direct current. A voltage (DC) and / or an alternating voltage (AC) is applied.

  The belt cleaning device 35 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 30 and is connected to a waste toner container through a waste toner transfer hose as is well known.

  A bottle container 2 is provided in the upper part of the apparatus main body, and four toner bottles 2Y, 2M, 2C, and 2K containing replenishing toner are detachably attached to the bottle container 2. As is well known, a replenishment path is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7, and each development from each toner bottle 2Y, 2M, 2C, 2K is performed via this replenishment path. The toner is supplied to the device 7.

  In the apparatus main body, a conveyance path R is provided for discharging the paper P from the paper feed tray 10 through the secondary transfer nip and out of the apparatus. In the transport path R, a pair of registration rollers 12 serving as transport means for transporting the paper P to the secondary transfer nip is disposed upstream of the secondary transfer roller 36 in the paper transport direction. Further, a fixing device 20 for fixing the unfixed image transferred to the paper P is disposed downstream of the secondary transfer roller 36 in the paper transport direction. Further, a pair of paper discharge rollers 13 is provided downstream of the fixing device 20 in the paper conveyance direction of the conveyance path R, and the paper P discharged outside the apparatus by the paper discharge rollers 13 is stocked on the paper discharge tray 14. Is done.

  Next, the basic operation when forming a full-color image for printing will be described. In this example, on the basis of image data input from the outside, the optical system unit 9 rotates and drives the charging device 6 with a predetermined polarity corresponding to each color separated into yellow, magenta, cyan and black color information. Each of the uniformly charged photoreceptors 5 is exposed to form a latent image, which is visualized by each developing device 7, and sequentially transferred to each intermediate transfer belt 30 that runs around each toner image in each primary transfer nip. By transferring, a color toner image is sent to the secondary transfer nip. The toner on each photoconductor 5 that has not been completely transferred to the intermediate transfer belt 30 is removed by the cleaning device 8.

  On the other hand, the paper P is sent out from the paper feed tray 10 to the transport path R by the paper feed roller 11 and is once abutted against the registration roller 12 to be timed, and the color toner image is transferred at the secondary transfer nip. The At this time, residual toner on the intermediate transfer belt 30 that has not been completely transferred onto the paper P is removed by the belt cleaning device 35. The sheet P on which the color toner image has been transferred is conveyed to the fixing device 20 where the toner image is fixed. Then, the paper P is discharged out of the apparatus by the paper discharge roller 13 and stocked on the paper discharge tray 14.

  Next, the basic configuration of the fixing device 20 will be described with reference to FIG. The fixing device 20 includes a thin, flexible, rotatable endless fixing belt 21, a pressure roller 22 as a pressure member facing the fixing belt 21 and in contact with the belt from the outside, and a fixing belt 21. A halogen heater 23 which is disposed in the inner peripheral area of the belt and heats the belt, and a nip forming member 24 which is in contact with the fixing belt 21 from the inside and forms a fixing nip portion N in a pressing state relative to the pressure roller 22. As a main part thereof. Further, the stay 25 that supports the nip forming member 24, the reflection member 26 that reflects the light emitted from the halogen heater 23 to the inner peripheral surface of the fixing belt 21, the temperature sensor 27 that detects the temperature of the fixing belt 21, and the fixing A separation member 28 for separating the paper from the belt 21 is also provided. Further, as is well known, shielding members for shielding heat from the halogen heater 23 are disposed between the fixing belt 21 and the halogen heater 23 at both axial ends of the fixing belt 21.

  The fixing belt 21 is a mode in which the fixing belt 21 is held by members fixed at both ends in the width direction. The fixing belt 21 includes a base material layer formed of a metal material such as nickel or SUS or a resin material such as polyimide (PI), and a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (hereinafter referred to as PFA). And a release layer formed of a fluororesin such as polytetrafluoroethylene (hereinafter referred to as PTFE). An elastic layer formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber may be interposed between the base material layer and the release layer. Further, an inner surface layer of fluororesin such as PTFE may be provided on the innermost peripheral side of the fixing belt 21.

  The pressure roller 22 includes a cored bar 22a, an elastic layer 22b made of foamable silicone rubber, silicone rubber, fluororubber, etc. provided on the surface of the cored bar 22a, and PFA and PTFE provided on the surface of the elastic layer 22. It is comprised by the mold release layer 22c which consists of etc., and it drives by the drive source provided in the apparatus main body. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 at the fixing nip portion N, and the fixing belt 21 is driven to rotate. Further, the pressure roller 22 is pushed toward the belt side by an elastic means, as is well known, and is pressed against the nip forming member 24 via the belt, and the elastic layer 22b is crushed and deformed, so that a predetermined amount is obtained. The nip width is secured. The pressure roller 22 is a solid roller in this example, but may be a hollow roller. In that case, a heat source may be provided inside the pressure roller 22, but in the case where there is no heat source, sponge rubber is used for the elastic layer to enhance the heat insulation property, so that the heat of the fixing belt 21 can be made difficult to be taken away. .

  The halogen heaters 23 whose positions are fixed at both ends are configured so as to generate heat by being output-controlled by a power supply unit provided in the apparatus main body, and the output control is based on the surface temperature of the fixing belt 21 by the temperature sensor 27. This is performed based on the detection result. By such output control of the heater 23, the temperature of the fixing belt 21 can be set to a desired temperature (fixing temperature). As a heat source for heating the fixing belt 21, an IH, a resistance heating element, a carbon heater, or the like can be used in addition to the halogen heater.

  The nip forming member 24 is disposed longitudinally in the width direction of the fixing belt 21 or the axial direction of the pressure roller 22, and is fixedly supported by a stay 25. Thus, the nip forming member 24 is prevented from being bent by the pressure of the pressure roller 22, and a uniform nip width is obtained in the axial direction of the pressure roller 22. The stay 25 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the function of preventing the nip forming member 24 from bending. Furthermore, by forming the stay 25 so as to have a horizontally long cross section extending in the pressure direction of the pressure roller 22, it is possible to increase the section modulus and improve the mechanical strength of the stay 25. .

  The nip forming member 24 is composed of a heat resistant member having a heat resistant temperature of 200 ° C. or higher. Accordingly, it is possible to prevent the nip forming member 24 from being deformed by heat in the toner fixing temperature region, and to secure a stable state of the fixing nip portion N, thereby stabilizing the output image quality. For the nip forming member 24, polyether sulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyether nitrile (PEN), polyamide imide (PAI), polyether ether ketone (PEEK), etc. It is possible to use a typical heat resistant resin. In this example, TI-8000 manufactured by Toray Industries, Inc., which is an LCP, is used.

  The nip forming member 24 may have a low friction sheet on the surface thereof. When the fixing belt 21 rotates, the fixing belt 21 rubs against the low friction sheet, so that the driving torque generated in the fixing belt 21 is reduced and the load due to the frictional force on the fixing belt 21 is reduced. As a material of the low friction sheet, for example, Toyoflon (registered trademark) 401 manufactured by Toray Industries, Inc. is preferable.

  The reflection member 26 is disposed between the stay 25 and the halogen heater 23 and is fixed to the stay 25. By disposing the reflection member 26 in this way, the light emitted from the halogen heater 23 toward the stay 25 is reflected to the fixing belt 21, and the amount of light irradiated to the fixing belt 21 can be increased. 21 can be efficiently heated. Further, it is possible to suppress the radiant heat from the halogen heater 23 from being transmitted to the stay 25 and the like, and energy saving can be achieved. A shielding member provided between the fixing belt 21 and the halogen heater 23 at both ends in the axial direction of the fixing belt 21 also performs the same function.

  In addition, the fixing device 20 is devised in various ways in order to further improve energy saving and first print time. For example, in order to reduce the heat capacity of the fixing belt 21, the fixing belt 21 is made thinner and smaller in diameter. Specifically, the thicknesses of the base material layer, the elastic layer, and the release layer constituting the fixing belt 21 are set in a range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the total thickness is 1 mm or less. It is set to. Further, the diameter of the fixing belt 21 is set to 20 to 40 mm. In order to further reduce the heat capacity, the thickness of the entire fixing belt 21 is desirably 0.2 mm or less, and more desirably 0.16 mm or less. The diameter of the fixing belt 21 is desirably 30 mm or less.

  The diameter of the pressure roller 22 is set to 20 to 40 mm, and is configured to be approximately equal to the diameter of the fixing belt 21. However, the configuration is not limited to such a configuration. For example, the fixing belt 21 may be formed so that the diameter thereof is smaller than the diameter of the pressure roller 22. In that case, since the curvature of the fixing belt 21 at the fixing nip N is smaller than the curvature of the pressure roller 22, the paper P discharged from the fixing nip N is easily separated from the fixing belt 21.

  As described above, as a result of reducing the diameter of the fixing belt 21, the space inside the fixing belt 21 is reduced. However, the stay 25 is formed in a concave shape bent at both ends, and inside the portion formed in the concave shape. By accommodating the halogen heater 23, the stay 25 and the halogen heater 23 can be disposed even in a small space.

  Further, the nip forming member 24 is compactly formed in order to arrange the stay 25 as large as possible even in a small space. Specifically, the length of the nip forming member 24 in the paper transport direction is formed to be smaller than the length of the stay 25 in the paper transport direction. Further, in FIG. 2, the height of the nip forming member 24 at the upstream end 24a and the downstream end 24b in the sheet conveyance direction with respect to the fixing nip N or its virtual extension line E is h1 and h2, respectively. If the maximum height of the fixing nip portion N or its virtual extension line E in the portion of the nip forming member 24 other than the portion 24a and the downstream end portion 24b is h3, h1 ≦ h3 and h2 ≦ h3. Yes. With this configuration, the upstream end 24 a and the downstream end 24 b of the nip forming member 24 are interposed between the bent portions on the upstream and downstream sides of the stay 25 in the sheet conveying direction and the fixing belt 21. Therefore, each bent portion can be disposed close to the inner peripheral surface of the fixing belt 21. As a result, the stay 25 can be disposed as large as possible in a limited space in the fixing belt 21, and the strength of the stay 25 can be ensured. As a result, it is possible to prevent the nip forming member 24 from being bent by the pressure roller 22 and to improve the fixability.

  A characteristic configuration of the fixing device 20 having the above basic configuration will be described in detail below. In the following, only the configuration around the one end of the fixing belt 21 will be described, but the configuration around the opposite end is the same. Further, for convenience of explanation, illustration of parts unnecessary for explanation such as a halogen heater is omitted.

  3 and 4 show a first configuration example around the end of the fixing belt 21. FIG. FIG. 3 is a configuration diagram of the first configuration example viewed from the side, and FIG. 4 is a configuration diagram viewed from the top. FIG. 5 is a diagram illustrating a first configuration example around the belt end portion, and second and third configuration examples described later.

  As shown in FIGS. 3 and 4, a belt holding member 40 that rotatably holds the fixing belt 21 is provided at the end of the fixing belt 21 as a member that regulates the lateral / axial movement of the belt. It has been. The end of the stay 25 in the axial direction is positioned and fixed to the belt holding member 40. The belt holding member 40 includes an insertion portion 40a that is inserted on the inner peripheral side at the end portion of the fixing belt 21, and a restriction portion 40b that has an outer diameter larger than that of the insertion portion 40a. The restricting portion 40b is formed to be larger than the outer diameter of the fixing belt 21, and restricts movement of the fixing belt 21 when the fixing belt 21 is shifted in the width direction (axial direction). As shown in FIG. 3, the insertion portion 40 a is formed in a C-shape that opens near the fixing nip portion N (position where the nip forming member 24 is disposed) when viewed from the insertion direction.

  As shown in FIGS. 3 and 4, a slip ring 41 as a protective member for protecting the end portion of the fixing belt 21 is interposed between the end portion of the fixing belt 21 and the regulating portion 40 b of the belt holding member 40. doing. The slip ring 41 has flexibility, is formed in an annular shape with a thickness T (for example, 0.5 mm), and is rotated by the fixing belt 21. Although the annular surface of the slip ring 41 faces the end surface of the fixing belt 21, as can be seen from FIG. 3, the end surface of the fixing belt 21 deviates inward from the inner circumferential circle of the slip ring 41 in the vicinity of the fixing nip portion N. As a material for the slip ring 41, a so-called super engineering plastic excellent in heat resistance and slidability, for example, PEEK, PPS, PAI, or the like is preferably used.

  The slip ring 41 is attached to a groove portion 40c (groove portion outer diameter <insert portion outer diameter) formed between the insertion portion 40a and the restriction portion 40b of the belt holding member 40. At the time of mounting, the slip ring 41 is inserted from the insertion portion 40a side and mounted in the groove portion 40c. The inner diameter of the slip ring 41 is smaller than the outer diameter of the insertion portion 40a. However, since the insertion portion 40a has a C-shaped cross section and has an opening in the vicinity of the fixing nip portion N, the slip ring 41 is elastically deformed to some extent. Thus, the slip ring 41 can be mounted in the groove 40c.

  As shown in FIG. 4, the groove portion 40c includes a restriction portion side inclined surface 40e formed on the restriction portion 40b side, and an insertion portion side inclined surface 40f formed on the insertion portion 40a side and substantially parallel to the restriction portion side inclined surface 40e. The groove width of the groove portion 40 c is formed at a predetermined interval wider than the thickness T of the slip ring 41.

  The inclined surfaces 40e and 40f are in the direction in which the right side is upward in FIG. 4, in other words, starting from the portion farthest from the fixing nip N (left end in FIG. 4), the fixing belt 21 width direction / belt holding member 40 axis It is formed so as to be at a predetermined angle (for example, 1 °) in a direction away from the fixing belt 21 with respect to a surface orthogonal to the direction (see FIG. 5, the vicinity of the fixing nip is in front of the page). Is in a position.)

  In this way, the slip ring 41 is held in the groove portion 40c of the belt holding member 40 formed to be inclined with a backlash in the vertical direction of FIG. When the fixing belt 21 is shifted by receiving the force in the width direction / axial direction during the rotation of the fixing belt 21 (upward in FIG. 4), the end of the fixing belt 21 is connected to the slip ring 41 and FIG. Touch on the left side of the. The slip ring 41 that has come into contact with the end of the fixing belt 21 rotates with the fixing belt 21 and moves together with the fixing belt 21 in a direction approaching the regulating portion side inclined surface 40e (upward in FIG. 4). The moved slip ring 41 is sandwiched between the regulating portion side inclined surface 40e and the end portion of the fixing belt 21. The slip ring 41 that has been sandwiched in this manner is inclined so as to follow the inclined surfaces 40e and 40f, and is slipped along with the fixing belt 21 and slid against the regulating portion side inclined surface 40e. At this time, the slip ring 41 contacts the fixing belt 21 in the region S1 in FIG. That is, a part of the end cylinder of the fixing belt 21 contacts the slip ring 41.

  By the way, when the slip ring 41 sandwiched between the regulating portion side inclined surface 40e and the end portion of the fixing belt 21 is tilted and rotated so as to follow the inclined surface 40e, as shown in FIG. Is buckled and deformed toward the inner peripheral side of the fixing belt 21 by the shifting force. In this configuration example, since the groove portion 40 c is provided on the inner peripheral side around the end portion of the fixing belt 21, buckling deformation of the fixing belt 21 is not hindered.

  As in the prior art, the belt's shifting force is received by a surface perpendicular to the belt's shifting direction, and the belt end surface buckles and deforms in the outer circumferential direction, that is, in a trumpet shape (the shifting force at this time is F1). Compared to the case where the belt end portion is torn and broken (the shift force at this time is assumed to be F2), if the buckling deformation is performed so as to be constricted toward the inner peripheral side, a compressive force is generated on the belt end surface, and the belt end portion is torn. There is no. For this reason, the belt is not damaged even in the state where the belt offset force of F2 is generated. Of course, if the shifting force becomes larger than F2, the belt end surface may be squeezed and damaged (F3 is the shifting force at this time). If buckling deformation occurs, it can be seen that the end of the belt is difficult to break.

  When the inclination angles of the inclined surfaces 40e and 40f are increased, the contact surface between the end portion of the fixing belt 21 and the slip ring 41 is decreased, and a reaction force of a shift force is generated in a local region at the end portion of the fixing belt 21, thereby reducing the contact surface. The belt end buckles with force. Therefore, the inclination angle θ of the inclined surfaces 40e and 40f is preferably 2 ° or less (0 ° <θ <2 °).

  Further, if the width of the groove 40c is small, that is, if the length in the axial direction in which the end of the fixing belt 21 buckles (vertical direction in FIGS. 4 and 6) is short, the value of the force for buckling deformation of the belt end surface is set. Can be large (becomes able to withstand buckling). Therefore, it is desirable that the width of the groove 40 c is slightly larger than the thickness of the slip ring 41. As a result, it is possible to cope with a larger shift force of the fixing belt.

  In this configuration example, the groove for attaching the slip ring 41 is inclined in the belt holding member 40, and the contact surface between the slip ring 41 and the belt end is slightly inclined, so that the surface of the belt end is on the inner peripheral side. It becomes easy to buckle and deform in the direction of squeezing, and as a result, it becomes possible to cope with a larger belt shifting force. Further, the sliding contact between the inner circumferential edge of the slip ring 41 and the belt end surface can be prevented.

Next, a configuration example capable of handling a high linear velocity will be described.
7 and 8 show a second configuration example around the end of the fixing belt 21. FIG. FIG. 7 is a configuration diagram of the second configuration example as viewed from above, and FIG. 8 is a conceptual diagram for explaining buckling deformation. The second configuration example is different from the first configuration example in that the shape of each surface of the restriction portion 40b and the insertion portion 40a of the belt holding member 40 that defines the groove portion in which the slip ring 41 is mounted is different. In the following description, description of parts common to the first configuration example will be omitted or simplified.

  As shown in FIG. 7, the groove 40c ′ is formed on the restricting portion 40b side, and is formed on the restricting portion side inclined surface 40g inclined toward the center side (of the belt holding member 40) and on the insertion portion 40a side (belt). It is demarcated by the insertion portion side vertical surface 40h orthogonal to the axial direction (of the holding member 40). The groove width is wider than the width T of the slip ring 41 as in the first configuration example.

  The restricting portion side inclined surface 40g is formed so as to have a predetermined angle (for example, 1 °) in the upward direction in FIG. 7 from the outer peripheral end of the restricting portion 40b toward the center side, and accordingly, in the insertion portion 40a of the restricting portion 40b. The opposing surface has a conical shape in which the center side of the restricting portion 40b is thin. The slip ring 41 is held in the groove portion 40c 'of the belt holding member defined and formed as described above with a backlash in the vertical direction of FIG. Since the belt holding member 40 like this shape has a mold configuration in which an undercut occurs, it is difficult to integrally mold the belt holding member 40, and therefore, the belt holding member 40 is a part in which two parts are combined.

  When the fixing belt 21 is shifted by receiving the force in the width direction / axial direction during the rotation of the fixing belt 21 (upward in FIG. 7), the end of the fixing belt 21 contacts the slip ring 41. . The slip ring 41 that has come into contact with the end of the fixing belt 21 rotates with the fixing belt 21 and moves together with the fixing belt 21 in a direction approaching the regulating portion side inclined surface 40g (upward in FIG. 7). The moved slip ring 41 is sandwiched between the conical regulating portion side inclined surface 40 g and the end portion of the fixing belt 21. The slip ring 41 that has been sandwiched in this way is deformed into a truncated cone shape so as to follow the restricting portion side inclined surface 40g, and rotates along with the fixing belt 21 while slipping, and the restricting portion side inclined surface 40g. Rub with. At this time, the slip ring 41 contacts the fixing belt 21 in the region S2 in FIG. As can be seen from FIG. 5, since the contact surface between the end of the fixing belt 21 and the slip ring 41 can be made wider than in the first configuration example (S1), the fixing device has a high linear velocity with a large belt shifting force. It is possible to respond.

  By the way, when the slip ring 41 sandwiched between the conical regulation-side inclined surface 40g and the end of the fixing belt 21 is deformed and rotated to follow the regulation-side inclined surface 40g, as shown in FIG. In addition, the end portion of the fixing belt 21 is buckled and deformed toward the inner peripheral side of the fixing belt 21 by the shifting force. In this configuration example, since the groove portion 40 c ′ is provided on the inner peripheral side around the end portion of the fixing belt 21, buckling deformation of the fixing belt 21 is not hindered.

  When the inclination angle of the regulating portion-side inclined surface 40g is increased, the contact surface between the end portion of the fixing belt 21 and the slip ring 41 is decreased, and a reaction force of a shift force is generated in a local region at the end portion of the fixing belt 21 and is small. The belt end buckles with force. Therefore, it is preferable that the inclination angle θ of the restricting portion side inclined surface 40g is an angle of 2 ° or less (0 ° <θ <2 °).

  If the width of the groove 40c ′ is small, that is, if the length in the axial direction (vertical direction in FIGS. 7 and 8) at which the end of the fixing belt 21 buckles is short, the value of the force that buckles and deforms the belt end surface. Can be increased (becomes able to withstand buckling). Therefore, it is desirable that the width of the groove portion 40 c ′ is slightly larger than the thickness of the slip ring 41. As a result, it is possible to cope with a larger shift force of the fixing belt.

  In the second configuration example, the belt holding member 40 is provided with the conical surface-shaped restricting portion side inclined surface 40g, and the slip ring 41 is deformed so as to follow the restricting portion side inclined surface 40g. Is likely to buckle and deform in a direction constricting toward the inner peripheral side, and as a result, it is possible to cope with a larger belt shifting force. Further, the sliding contact between the inner circumferential edge of the slip ring 41 and the belt end surface can be prevented. Compared with the first configuration example, the contact range between the belt end surface and the slip ring 41 is widened, so that a higher linear velocity can be accommodated.

  9 and 10 show a third configuration example around the end portion of the fixing belt 21. FIG. FIG. 9 is a configuration diagram of the third configuration example as viewed from above, and FIG. 10 is a conceptual diagram for explaining buckling deformation. The third configuration example is different from the second configuration example in that the shape of the surface of the regulation portion 40b of the belt holding member 40 that defines the slip ring 41 and the groove portion in which the ring is mounted is different. In the following description, description of parts common to the first configuration example will be omitted or simplified.

  As shown in FIG. 9, the groove portion 40c ″ is formed on the restricting portion 40b side and formed on the restricting portion side vertical surface 40j orthogonal to the axial direction (of the belt holding member 40) and the insertion portion 40a side (belt holding member). 40) and an insertion-unit-side vertical surface 40k perpendicular to the axial direction 40. On the other hand, the slip ring 41 ′ is formed on the regulating portion 40b side and an annular vertical surface 41a perpendicular to the axial direction (of the ring). And an annular inclined surface 41b that is formed on the insertion portion 40a side and is inclined toward the center (of the ring). The maximum width of the slip ring 41, that is, the ring width at the outer peripheral edge is defined by the groove portion 40c ″. It is narrower than the width.

  The annular inclined surface 41b on the insertion portion side is formed so as to have a predetermined angle (for example, 1 °) in the upward direction in FIG. 9 from the outer peripheral end of the slip ring 41 ′ toward the center side. The inner peripheral edge is thinner than the outer peripheral edge. For example, the inner peripheral side has a thickness of 0.5 mm, and the outer peripheral side has a thickness that increases by an inclination. The slip ring 41 'formed in this way is held in the groove 40c "perpendicular to the axial direction of the belt holding member with backlash in the vertical direction of FIG.

  When the fixing belt 21 is shifted by receiving the force in the width direction / axial direction during the rotation of the fixing belt 21 (upward in FIG. 9), the end of the fixing belt 21 contacts the slip ring 41. . The slip ring 41 ′ that contacts the end of the fixing belt 21 rotates with the fixing belt 21, moves together with the fixing belt 21 in a direction approaching the restricting portion side vertical surface 40 j (upward in FIG. 9), and eventually the fixing belt 21. The slip ring 41 ′ that has moved together is sandwiched between the regulating portion side vertical surface 40 j and the end portion of the fixing belt 21, slips along with the fixing belt 21, and slides on the regulating portion side inclined surface 40 g. . At this time, the slip ring 41 'contacts the fixing belt 21 in the region S2 in FIG. As can be seen from FIG. 5, since the contact surface between the end of the fixing belt 21 and the slip ring 41 can be made wider than in the first configuration example (S1), the fixing device has a high linear velocity with a large belt shifting force. It is possible to respond.

  By the way, the annular inclined surface 41b of the slip ring 41 'sandwiched between the restricting portion side vertical surface 40j and the end portion of the fixing belt 21 is a conical surface whose inner peripheral side is inclined at a predetermined angle in the upward direction in FIG. The end portion of the fixing belt 21 is buckled and deformed toward the inner peripheral side of the fixing belt 21 by the shifting force. In the present configuration example, since the groove portion 40c ″ is provided on the inner peripheral side around the end portion of the fixing belt 21, the buckling deformation of the fixing belt 21 is not hindered.

  When the inclination angle of the annular inclined surface 41b is increased, the contact surface between the end portion of the fixing belt 21 and the slip ring 41 'is decreased, and a reaction force of a shift force is generated in a local region at the end portion of the fixing belt 21 to reduce a small force. The belt end will buckle. Therefore, the inclination angle θ ′ of the annular inclined surface 41b is preferably set to an angle of 2 ° or less (0 ° <θ ′ <2 °).

  If the width of the groove 40c ″ is small, that is, if the length in the axial direction (vertical direction in FIGS. 9 and 10) at which the end of the fixing belt 21 buckles is short, the value of the force that buckles and deforms the belt end surface. Therefore, it is desirable to make the width of the groove 40c ″ slightly larger than the maximum thickness of the slip ring 41 ′. As a result, it is possible to cope with a larger shift force of the fixing belt.

  In the third configuration example, the slip ring 41 ′ is provided with a conical annular inclined surface 41b, and the contact surface between the slip ring 41 ′ and the belt end is slightly inclined, so that the surface of the belt end is on the inner peripheral side. It becomes easy to buckle and deform in the direction of squeezing, and as a result, it becomes possible to cope with a larger belt shifting force. Further, the sliding contact between the inner circumferential edge of the slip ring 41 and the belt end surface can be prevented. Compared with the first configuration example, the contact range between the belt end surface and the slip ring 41 ′ is widened, so that a higher linear velocity can be accommodated.

  The present invention has been described based on the embodiments. The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the present invention. In the above-described embodiment, one slip ring is used. However, the present invention is not limited to this aspect. For example, in the case of the first and second configuration examples, a plurality of slip rings may be used in an overlapping manner. As a result, the fixing belt and the slip ring are more easily rotated, and the belt end portion can be easily protected even in a high linear velocity fixing device. Further, for example, the inclined surface can be provided on both the belt holding member and the slip ring. When the fixing belt is thick, the angle of the inclined surface can be set to 2 ° or more.

DESCRIPTION OF SYMBOLS 20 Fixing device 21 Fixing belt 22 Pressure roller 23 Halogen heater 24 Nip forming member 25 Stay 40 Belt holding member 40a Insertion part 40b Restriction part 40c, 40c ', 40c "Groove part 41, 41' Slip ring (protection member)
N Fixing nip P Paper

JP 2009-288284 A Japanese Patent No. 5737629

Claims (7)

An endless belt, a nip forming member disposed inside the belt, and a rotatable pressure member that forms a fixing nip portion in a pressing state relative to the nip forming member across the belt A belt holding member that rotatably holds the belt at the end of the belt, and is arranged between the belt holding member and the end of the belt and is rotated by contact with the end of the belt, A fixing device that protects the belt end portion and transports a recording material carrying an unfixed image to the fixing nip portion to fix the unfixed image on the recording material.
The fixing device according to claim 1, wherein the protection member is in contact with the belt with an inclined surface in which a belt end portion is inclined toward an inner peripheral side in a state where the protection member is rotated around the belt.   The surface of the belt holding member in contact with the protective member is inclined so that the side closer to the fixing nip portion is farther from the end of the belt than the side farther from the side. Fixing device.   The fixing device according to claim 1, wherein a surface of the belt holding member that contacts the protection member is inclined so as to be away from an end portion of the belt toward a center side.   The surface of the belt holding member in contact with the protective member has an inclination angle θ of 0 ° <θ <2 ° with a surface perpendicular to the axial direction of the belt. Or the fixing device according to 3;   The fixing device according to claim 1, wherein a surface of the protection member that contacts the end surface of the belt is inclined so as to be away from the end portion of the belt toward a center side.   The surface of the protective member that contacts the end surface of the belt has an inclination angle θ ′ of 0 ° <θ ′ <2 ° between the surface orthogonal to the axial direction of the belt. Item 6. The fixing device according to Item 5.   An image forming apparatus comprising the fixing device according to claim 1.

Images