JP2013195736A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of deformation such as buckling of an endless belt in a fixing device of an image forming apparatus.SOLUTION: There is provided a fixing device which comprises: a roll 104 in contact with a first surface of a recording medium P; and a belt assembly 110 in contact with a second surface of the recording medium. The belt assembly comprises: an endless belt 111; long supports 117 and 118 in an axial direction supporting a structure of the belt assembly in the inside of the endless belt; nip forming members 114 and 116 which are attached to the supports and pressure fixed to the endless belt to the roll to form a nip; and a belt regulating member 120 having a wide curved surface guide part 120a in an axial direction surface-contacting with the inner peripheral surface when the endless belt is deformed inward on the upstream side from the nip forming members toward the rotation direction of the endless belt, and the belt regulating member provides a fixing device 29 which is disposed so that the fixing device is separated at a predetermined space from the inner peripheral surface of the endless belt and the first end part in the rotation direction is close to the nip forming members.

Description

  The present invention relates to a fixing device used in an electrophotographic image forming apparatus.

  In an electrophotographic image forming apparatus that forms an image on a recording medium using powdered toner, a toner image is formed by transferring the toner to a latent image due to a difference in electrostatic potential formed on an image carrier. After the toner image is electrostatically transferred directly onto the recording medium, or after the primary transfer to the intermediate transfer member and the secondary transfer onto the recording medium, the recording medium is sandwiched using a fixing device, and the toner image is formed. A method of fixing on a recording medium by heating and pressing is known.

  There are various types of apparatuses for fixing a toner image on a recording medium. For example, the side for heating the fixing surface on which the toner image is provided on the recording medium and the side for supporting and pressing the back side of , One having both a heating side and a pressure side as a roll, a heating side as a roll and a pressure side as a belt, a heating side as a belt and a pressure side as a roll, and a heating side A belt using both sides on the side to be pressurized is known. In any of these, the fixing surface of the recording medium is heated with a heating roll or belt, and both contact portions are pressed with an opposing pressure belt or roll, whereby a molten unfixed toner image is recorded on the recording medium. And fixing to the recording medium.

  In such a fixing device, each component member needs to ensure sufficient rigidity against the pressing force generated between each roll and the belt. For example, it is preferable to use a high-rigidity structure with a certain thickness for the heating roll. However, when a large-diameter roll is required to ensure high rigidity, the heat capacity increases, and after the start-up of the apparatus, When returning from the standby state, it takes time to heat the surface, and a long warm-up time is required.

  In particular, in color fixing, the toner is heated and melted sufficiently, and the surface of the toner is finished with a high gloss so as to develop a color. It must be secured and sufficient heat applied. However, such a large-diameter roll requires a thick roll base material to ensure rigidity, and the heat capacity of the entire roll including the thick rubber layer is large, causing a problem in shortening the warm-up time. Accordingly, the present applicant proposed a form in which an endless belt is applied to the roll, and the belt is pressed and fixed to the recording medium by a nip forming member to secure a contact area between the toner and the roll. The heat capacity was reduced by adopting a small-diameter roll composed of a rubber layer. As a result, the warm-up time has been significantly shortened, energy consumption has been reduced, and miniaturization has been achieved.

  By the way, as the pressure belt, for example, a belt having a base layer of a heat-resistant resin such as a thin polyimide having a thickness of 80 to 85 μm is used. When such a thin belt is used, the thin belt may be deformed such as buckling inwardly on the upstream side or downstream side of the pressure-fixing portion. For example, an irregular event occurs when a part of the recording medium is folded and reaches the pressure fixing unit, or when multiple recording media are conveyed to the pressure fixing unit with multiple recording media overlapped In this case, the belt may be pushed inward and deformed on the upstream side of the pressure fixing unit. If a part of the belt that has been deformed enters the pressure-fixing part, there is a risk that wrinkles or creases will occur on the belt and streaks will appear in the image after fixing.

  In such a fixing device using a thin belt, an invention for preventing the deformation of the belt on the upstream side and the downstream side of the pressure fixing unit is disclosed in Patent Document 1, as shown in FIG. Specifically, Patent Document 1 discloses a fixing device provided with a cylindrical fixing belt. In the fixing device 929, the fixing nip N is used to prevent the fixing belt from being deformed inward in the radial direction. Are provided with deformation preventing ribs 910 and 920 on the respective inlet side and outlet side of the fixing belt 911 with a clearance from the inner peripheral surface of the fixing belt 911 so that the fixing belt 911 is radially inward. A means for preventing the fixing belt 911 from further deforming inward in the radial direction by the inner peripheral surface of the fixing belt 911 coming into contact with the deformation preventing ribs 910 and 920 when being pushed and deformed is disclosed. doing.

  Patent Document 1 is an example in which a fixing belt 911 is provided on the side that heats the fixing surface of the recording medium P, and a heating roll 904 is provided on the side that pressurizes the back surface. A support 917 that supports the nip forming member 914 is disposed inside the cylindrical fixing belt 911. As shown in FIG. 7, on the upstream side and downstream side of the nip forming member 914 inside the fixing belt 911, a large number of deformation prevention ribs 910, 920 are provided along the longitudinal ends of the support 917 at predetermined intervals. It is arranged with a gap.

JP 2010-26256 A

  However, in the fixing device described in Patent Document 1, the inner peripheral portion of the fixing belt 911 is pressed against and fixed to the outer peripheral portions of the deformation preventing ribs 910 and 920, so that the rotation path of the fixing belt 911 is secured to some extent. It is possible. However, when a large force that causes buckling is applied to the fixing belt 911 for some reason, such as when the recording medium P is double-fed or pulled in the opposite direction, the outer periphery of the deformation preventing ribs 910 and 920 The fixing belt 911 cannot be prevented from being deformed by only the portion, and buckling occurs in the fixing belt 911 in the gap between the deformation preventing ribs 910 and 920. In particular, when the fixing belt 911 is further thinned, or when the width is increased as the paper size increases, the occurrence of buckling becomes significant. If the fixing belt 911 is sandwiched between the pressure-fixing portions while being deformed due to buckling, the fixing belt 911 will be wrinkled or creased.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device capable of suppressing deformation such as buckling of a belt even when a large force is applied to the belt. And

In order to achieve the above object, the present invention provides the following means.
(1) A fixing device for fixing a toner image to a recording medium by pressurizing and heating a recording medium carrying an unfixed toner image, the roll contacting the first surface of the recording medium, and the roll A belt assembly disposed oppositely in contact with the second surface of the recording medium, wherein the belt assembly includes an endless belt and an axially supporting structure of the belt assembly within the endless belt. A long support, a nip forming member attached to the support and press-fixing the endless belt to the roll to form a nip, and an endless belt upstream of the nip forming member in the rotational direction of the endless belt A belt regulating member having a curved guide portion that is wide in the axial direction and is in surface contact with the inner circumferential surface of the endless belt. Spaced with a predetermined gap with respect to, and to provide a fixing device which is characterized in that the first end of the rotating direction is arranged so as to be close to the nip forming member.

(2) The fixing device according to (1) is provided, wherein the belt regulating member is positioned so as to contact the periphery of the central portion of the inner peripheral surface of the endless belt.

(3) The fixing device according to (1) or (2), wherein the curved surface guide portion has a width that gradually increases toward the nip forming member.

(4) The curved surface guide portion has corner portions subjected to C chamfering or R chamfering processing at both ends in the axial direction of the curved surface, as described in any one of (1) to (3) above A fixing device is provided.

(5) The belt regulating member has a hook for slidingly engaging with the support body on the inside thereof, and the support body has an opening for inserting the hook. A fixing device according to any one of (4) to (4) is provided.

(6) Any one of the above (1) to (5), wherein the nip forming member is attached to the support so as to prevent an axial shift of the belt regulating member engaged with the support. A fixing device according to one aspect is provided.

(7) The fixing device according to any one of (1) to (6), wherein the support is a pair of support plates.

(8) The fixing device according to any one of (1) to (7), wherein the support is formed of a rolled steel plate or an aluminum plate.

  According to the present invention, it is possible to provide a fixing device capable of suppressing deformation such as buckling of a belt even when a large force is applied to the belt.

1 is a schematic diagram illustrating a configuration example of an electrophotographic image forming apparatus to which a fixing device according to the present invention is applied. FIG. 3 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention, in which a central portion thereof is cut along a plane parallel to a recording medium conveyance direction. FIG. 3 is an exploded perspective view showing a configuration of a belt assembly included in the fixing device of FIG. 2. FIG. 4 is a perspective view showing a state where members excluding an endless belt and a frictional force reducing sheet are assembled in the belt assembly of FIG. 3. 3 and 4 are perspective views showing a modification of the shape of the curved surface guide portion of the belt regulating member. FIG. 5 is a perspective view showing a state immediately before the belt regulating member is temporarily assembled on the support and the head block as the nip forming member is attached next in FIG. 4. FIG. 10 is a cross-sectional view illustrating an example of a central portion of a conventional fixing device.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram showing a configuration example of an electrophotographic image forming apparatus 10 to which a fixing device 29 according to the present invention is applied.

  The image forming apparatus 10 takes out recording media P one by one from the paper storage unit 31 and the manual feed device 43 that store the recording media P for printing in a stacked state, and the paper storage unit 31 or the manual feed device 43. A paper feed unit 35 and transport roller pairs 49 a and 49 b that transport the recording medium P taken out by the paper feed unit 35 to the transfer unit 28 are provided. The image forming apparatus 10 forms an unfixed toner image based on the image data, transfers the toner image to the recording medium P, and the recording medium P carrying the unfixed toner image. And a fixing device 29 for fixing the toner image by applying pressure and heating. A one-dot chain line with an arrow in the figure indicates a conveyance path of the recording medium P.

  The image forming unit 13 is a part that forms and transfers a toner image using an electrophotographic system. The image forming unit 13 includes a photosensitive drum 19 that rotates in the direction of the arrow. Around the photosensitive drum 19, a charger 44 for charging the image holding surface of the photosensitive drum 19, and an electrostatic latent image having a potential difference by irradiating the charged surface of the photosensitive drum 19 with light based on image data. A developing device 46 that develops the electrostatic latent image on the photosensitive drum 19 with toner to generate a toner image, a transfer unit 28 that transfers the toner image to the recording medium P, A cleaner 47 for removing the toner remaining on the surface of the photosensitive drum 19 after the transfer is completed and cleaning it is disposed.

  The photosensitive drum 19 is formed by forming an image holding surface of a photoconductive layer (photosensitive layer) made of an organic photosensitive material on a cylindrical substrate. As the charger 44, for example, a contact charging type in which a predetermined charging voltage is applied to a charging roll that rotates in contact with the surface of the photosensitive drum 19 can be used. The exposure device 45 is a device composed of an LED (light emitting diode) recording head, a semiconductor laser scanning device, or the like. The exposure device 45 inputs image data after performing predetermined image processing on image data input from an image reading device or a communication device such as a computer that is connected to the image forming device 10 to perform electrostatic latent image processing. Form an image.

  The heating roll 104 of the fixing device 29 is heated by a heating source so that the surface temperature is maintained at a predetermined temperature, and rotates in the direction of the arrow shown in FIG. Transport while heating. The endless belt 111 of the fixing device 29 is an endless belt that is disposed to face the heating roll 104 and performs fixing by inserting the recording medium P between the heating roll 104 and the endless belt 111 according to the width of the recording medium P. It is formed in a cylindrical shape with a wide width. The guide plate 102 guides the recording medium P to be fixed to the inlet of the pressure fixing unit NP.

  An outline process of image formation using the image forming apparatus 10 will be described.

  First, the photosensitive drum 19 is rotated in the image forming unit 13. Then, the surface of the rotating photosensitive drum 19 is charged to a predetermined potential by the charger 44, and then the surface of the charged photosensitive drum 19 is irradiated with light based on image data from the exposure device 45, An electrostatic latent image having a predetermined latent image potential is formed.

  Subsequently, the electrostatic latent image is moved with the rotation of the photosensitive drum 19, and the toner supplied from the developing roll 46 a of the developing device 46 is electrostatically attached to the latent image portion. In this way, the development of the toner image on the photosensitive drum 19 is completed.

  The toner image on the photosensitive drum 19 is electrostatically transferred to the recording medium P conveyed at a predetermined timing by the conveyance roller pair 49a and 49b in the transfer unit 28. The surface of the photoconductive drum 19 after the transfer of the toner image is cleaned by a cleaner 47.

  The recording medium P on which the toner image is formed in the image forming unit 13 is conveyed to the fixing device 29. Then, while being guided by the guide plate 102, it is introduced into the pressure contact fixing part NP between the heating roll 104 and the endless belt 111.

  In the pressure contact fixing unit NP in the fixing device 29, the recording medium P is conveyed while being sandwiched between the heating roll 104 and the endless belt 111 and in pressure contact therewith. At this time, the unfixed toner image is fixed on the recording medium P by being pressurized and heated. The recording medium P after fixing is discharged from the fixing device 29 and then transported by a transport roll pair 49c or the like, and is sent to a discharge storage unit. As a result, an image composed of toner is formed on one side of the recording medium P.

  An object generally used as the recording medium P of an object for forming an image is a sheet-like object such as a recording sheet, a cardboard, a transparent sheet, a plastic sheet such as an OHP sheet. In addition to these, a bag-like object represented by an envelope can also be used. These recording media P are stored in advance in the paper storage unit 31 or the manual feed device 43, taken out using the paper supply unit 35 during image formation, and driven in the transport path by driving the transport roll pairs 49a and 49b. Are conveyed to a transfer position of the image forming unit 13 at a predetermined timing.

  Next, the configuration of the fixing device 29 will be described with reference to FIGS. FIG. 2 is a cross-sectional view illustrating a state where the central portion of the fixing device 29 is cut along a plane parallel to the conveyance direction of the recording medium P. FIG. 3 is an exploded perspective view showing the configuration of the belt assembly 110 included in the fixing device 29. FIG. 4 is a perspective view showing the belt assembly 110 excluding the endless belt 111 and the frictional force decreasing sheet 115. FIG. 5 is a perspective view showing a modified example of the shape of the curved surface guide portion 220 a in the belt regulating member 220.

  The fixing device 29 includes a heating source 108 that heats the recording medium P, a heating roll 104 that conveys the recording medium P while applying pressure, and an endless belt that forms the press-contact fixing unit NP by disposing the heating medium 104 facing the heating roll 104. 111. The fixing device 29 includes a guide plate 102 that guides the recording medium P conveyed in the Fw direction shown in FIG.

  The heating roll 104 is formed by forming an elastic layer and a release layer on the surface of a metal cylindrical base material wider than the maximum width of the recording medium P to be fixed. Both ends of the heating roll 104 are rotatably supported by a heating support frame via bearings. The heating roll 104 rotates in the direction indicated by the arrow in FIG. 2 in response to the transmission of rotational power from the rotational drive unit via a gear attached to one end thereof.

  As the heating source 108, for example, a halogen lamp installed in the cylinder of the heating roll 104 can be used. Both ends of the heating source 108 are fixed to the casing of the fixing device 29. The surface temperature of the heating roll 104 is detected by a temperature detector (not shown), and the temperature control is performed by controlling the heating of the heating source 108 based on the detected information.

  The endless belt 111 is a cylindrical endless belt for fixing by inserting the recording medium P in a press-fixing unit NP formed between the endless belt 111 and the heating roll 104. The width of the endless belt 111 is approximately the same as the width of the heating roll 104. Both ends of the endless belt 111 are rotatably supported by belt holding members 112 and 113, respectively. The flanges formed on the belt holding members 112 and 113 regulate the movement of the endless belt 111 in the width direction (W direction shown in FIGS. 3 and 4). Further, the cylindrical sliding surfaces formed on the belt holding members 112 and 113 guide the endless belt 111 in a rotatable manner, and the endless belt 111 with respect to the XY directions shown in FIGS. 3 and 4. Positioning. The endless belt 111 rotates as the heating roll 104 rotates. The endless belt 111 is a thin endless belt having a thickness of about 0.08 mm, and can be formed by using a synthetic resin such as polyimide as a base material and forming a release layer made of a fluorine-based resin or the like on the surface thereof. .

  As shown in FIG. 2, a pad 114 that receives a pressing force by the heating roll 104 is disposed inside the endless belt 111 in the press-fixing unit NP. The pad 114 is configured using an elastic body such as a rubber material or a silicon material. The pad 114 is a member for ensuring a predetermined length of the path length on the entrance side of the press contact fixing part NP formed between the heating roll 104 and the endless belt 111. As a material of the pad 114, an elongated plate-like silicon rubber having a length substantially the same as the width of the endless belt 111 can be used. In the embodiment shown in FIG. 2 and FIG. 3, a pad 114 having a pressing surface facing upward and a bottom surface fixed to a thin plate-like substrate is used. As shown in FIG. 3, a frictional force reducing sheet 115 is disposed between the pad 114 and the endless belt 111 to reduce the frictional force between the endless belt 111 and the pad 114 that increases due to pressing. doing.

  The pad 114 is held so as to be surrounded by the one-time large head block 116. The pad 114 and the head block 116 together serve as a nip forming member. The pad 114 forms a nip on the inlet side of the pressure contact fixing portion NP with respect to the rotation direction of the belt assembly 110, and the rotation direction of the belt assembly 110. The rear end of the head block 116 located on the outlet side forms a nip on the outlet side of the pressure fixing part NP. The head block 116 can be made of a material such as synthetic resin or metal. The head block 116 that holds the pad 114 is supported by supports 117 and 118 from the back side.

  As shown in FIGS. 3 and 4, the belt holding members 112 and 113 support the endless belt 111 rotatably, and support a pair of supports 117 and 118 inside the endless belt 111.

  The supports 117 and 118 are members that support the pad 114 via the head block 116 inside the rotating endless belt 111. The pad 114 is a member that receives a pressing force (see FIG. 2) in the X direction generated between the heating roll 104 and the pad 114. The support members 117 and 118 that indirectly hold the pad 114 are made of a material that does not increase in deformation even when subjected to a pressing force in the X direction (see FIG. 2) generated between the support members 114 and 118, A shape is required.

  Furthermore, since the inside of the fixing device 29 is in a high temperature environment of about 80 to 250 ° C., it is preferable to use a steel plate or an aluminum plate as a material for the supports 117 and 118 so as to function in such a temperature environment. . From the viewpoint of manufacturing cost, it is preferable to use a rolled material (sheet metal) that does not require side processing. The thicknesses of the supports 117 and 118 are selected from the viewpoint of installation space, cost, and the like. For example, a material having a thickness of 1.0 to 2.0 mm can be used. In the case where a steel plate is used as the material of the supports 117 and 118, for example, a material subjected to surface treatment such as galvanization or nickel plating can be used.

  As described above, the supports 117 and 118 receive a pressing force with the heating roll 104 via the head block 116 that holds the pad 114. When a rolled material is used as the material for the supports 117 and 118, the cut end portions with high dimensional accuracy are fixed to the head block 116 by pressure contact. Accordingly, the head block 116 can be brought into close contact with almost no gap. On the other hand, since the attachment portions of the support members 117 and 118 to the belt holding members 112 and 113 are also formed at the same time by cutting, accumulation from the belt holding members 112 and 113 to the head block 116 is cumulative. Tolerance can be reduced. Therefore, the head block 116 can be supported with high accuracy.

  The shapes of the supports 117 and 118 are shapes in which both ends of the supports 117 and 118 are supported by the belt holding members 112 and 113 inside the small-diameter endless belt 111. Furthermore, it is necessary to counter the pressing force received from the heating roll 104 while both ends are supported. For these reasons, as shown in FIG. 2, it is preferable to use a sheet metal material having a rectangular cross section whose longitudinal direction is the X direction to which force is applied, as the cross section of the supports 117 and 118. Further, in order to stably support the head block 116 holding the pad 114, it is possible to support two portions of the head block 116 along the longitudinal direction using the end surfaces of the two support members 117 and 118. preferable.

  Of the two supports 117 and 118, one support 117 is formed by bending a portion between the belt holding members 112 and 113 at a right angle along the longitudinal direction so that the cross-sectional shape is an L shape. It is. By performing the bending process in this way, the rigidity against bending and twisting in the longitudinal direction can be improved, and the right side surface formed by the bending process is formed on the inner peripheral surface of the endless belt 111. A felt 119 for applying a lubricant can be applied. The felt 119 may be one impregnated with a lubricant such as a release agent oil.

  A belt regulating member 120 that regulates deformation of the endless belt 111 inward by being in surface contact with the inner peripheral surface of the center of the endless belt 111 at the center in the longitudinal direction of the supports 117 and 118. It is arranged. The belt regulating member 120 is disposed with a gap with respect to the inner peripheral surface of the endless belt 111. Therefore, in a normal use state, the belt regulating member 120 and the endless belt 111 are not in contact with each other.

  When the recording medium P is conveyed to the fixing device 29 in a state where a plurality of recording media P overlap (in the case of double feeding), or when the user pulls out the recording medium P from the fixing device 29 during an emergency stop operation, When an excessive force is applied to the endless belt 111 for some reason, a buckling force is applied to the thin endless belt 111 and wrinkles having a wave shape are generated. If the endless belt 111 is in a state where wrinkles are generated and enters the pressure-fixing portion NP, the wrinkles are pressed in a folded state, and the wrinkles are fixed. If there are wrinkles on the endless belt 111, a problem such as streaks in the image or characters shown on the recording medium P after fixing will occur.

  Therefore, when the endless belt 111 tries to deform inwardly in the cylindrical shape, the belt regulating member 120 in which the inner peripheral surface of the endless belt 111 and the curved surface guide portion 120a are in surface contact with each other is placed inside the endless belt 111. Arranged. By disposing the belt regulating member 120 inside the endless belt 111, deformation due to buckling of the endless belt 111 can be regulated. As described above, a configuration in which a deformation preventing rib that is in line contact with the inner surface of the endless belt 111 is conventionally known. However, as the endless belt 111 becomes wider or thinner, wrinkles generated between the deformation prevention ribs have become a problem. By arranging the belt regulating member 120 in which the curved surface guide portion 120a having a predetermined area is formed inside the endless belt 111, the occurrence of wrinkles of the endless belt 111 that has conventionally occurred between the deformation prevention ribs is suppressed. Thus, the endless belt 111 can be sent to the pressure-fixing unit NP without wrinkles.

  Even if the curved surface guide portion 120a is disposed only in the center portion in the longitudinal direction of the endless belt 111, generation of wrinkles can be effectively suppressed. By using the configuration in which the curved surface guide portion 120a is disposed only in the center portion in the longitudinal direction of the endless belt 111, the length of the belt regulating member 120 can be shortened. When the length of the belt regulating member 120 is short, the warp generated in the belt regulating member 120 can be reduced. In addition, the belt regulating member 120 can be easily manufactured, the surface accuracy of the curved surface guide portion 120a can be improved, and the belt regulating member 120 can be manufactured at low cost. In particular, when the belt regulating member 120 is manufactured by injection molding of resin, it is preferable to configure the belt regulating member 120 so that the width of the belt regulating member 120 does not become long.

  The curved surface guide part 120a is preferably arranged adjacent to the pressure fixing part NP. Further, the curved guide 120a is disposed in the vicinity of the upstream side of the pressure-fixing unit NP (in the vicinity of the upstream side of the pad 114 with respect to the rotation direction of the endless belt 111 and on the supply side of the recording medium P). It is possible to suppress wrinkles from occurring when a plurality of sheets are conveyed to the fixing device 29 in a state where a plurality of sheets are stacked. A function for automatically releasing the pressing force between the heating roll 104 and the endless belt 111 in the fixing device 29 when the image forming apparatus 10 is performing an emergency stop operation due to clogging of the recording medium P or the like is installed. There is something that is. When the image forming apparatus 10 is equipped with this function, there is no factor that applies a reverse force (force in the Rw direction shown in FIG. 2) to the endless belt 111. In this case, the occurrence of wrinkles in the endless belt 111 can be prevented only by arranging the curved surface guide portion 120a in the vicinity of the upstream side of the pressure-fixing portion NP.

  In general, in the image forming apparatus 10, when the user pulls out the recording medium P from the fixing device 29 after performing an emergency stop operation during normal printing and during the fixing process of the recording medium P, the recording medium P is illustrated. In principle, it is moved in the Fw direction shown in FIG. However, after performing the emergency stop operation, the user may pull out the recording medium P in the reverse direction (Rw direction).

  As described above, when there is a possibility that a force is applied in the direction in which the endless belt 111 is rotated in the reverse direction, the curved surface guide portion 120a is located near the downstream side of the pressure-fixing portion NP (near the downstream side of the pad 114, On the discharge side.) By disposing the curved surface guide portion 120a also in the vicinity of the downstream side of the pressure-fixing portion NP, even when the recording medium P is pulled in the reverse direction (Rw direction shown in FIG. 2), the wrinkle generated in the endless belt 111 Can be suppressed.

  Next, the end shape of the curved surface guide portion in the belt regulating member will be described. The curved surface guide portion 220a of the belt regulating member 220 may be configured with the same width as shown in FIGS. 3 and 4, and the width Ew increases as it approaches the pad 114 as in the modification shown in FIG. You may form in a shape (front view trapezoid shape).

  When the ridge line of the curved surface guide portion in the belt regulating member coincides with the rotation direction of the endless belt 111, the predetermined position on the inner surface of the endless belt 111 repeats contact with the ridge line of the curved surface guide portion. Then, depending on the material of the endless belt 111 and the like, there is a possibility that a scratch along the rotation direction may enter the inner surface. Therefore, in the modification shown in FIG. 5, the ridgeline of the curved surface guide portion 220a is suppressed while suppressing the generation of wrinkles in the endless belt 111 by making the width Ew of the curved surface guide portion 220a increase as it approaches the pad 114. Prevents repeated contact with a predetermined position on the inner surface of the endless belt 111. And the malfunction that the inner surface of the endless belt 111 is damaged can be suppressed. Note that the circumferential height Ey (see FIG. 5) of the curved guide portion 220a is preferably set to be equal to or less than the radius of the endless belt 111.

  For the same reason, it is preferable to shape the ridge lines 120b and 220b of the curved surface guide portions 120a and 220a into an R chamfered shape or a C chamfered shape. Moreover, it is preferable to use the material corresponding to the use in a high temperature environment as the material of the belt regulating members 120 and 220. When using resin as the material of the belt regulating members 120 and 220, it is preferable to use a material having heat resistance such as PET (polyethylene terephthalate).

  Next, how the belt regulating member 120 is attached will be described with reference to FIGS. 2, 3, and 6. FIG. 6 is a perspective view showing a state in which the belt regulating members 120 are temporarily assembled on the supports 117 and 118.

  First, the structure of each part used when the belt regulating member 120 is assembled to the supports 117 and 118 will be described with reference to FIG. As shown in FIG. 3, a pair of sliding assembly hooks 120e and 120f each having an L-shape are protruded on the back surface of the belt regulating member 120 (the back surface side with respect to the curved surface guide portion 120a). It is formed in the state. On the other hand, a pair of sliding assembly openings 117e and 118f for inserting and engaging the sliding assembly hooks 120e and 120f is provided in the supports 117 and 118 to which the belt regulating member 120 is attached. is there.

  Further, on the back surface of the belt regulating member 120 (the back surface side with respect to the curved surface guide portion 120a), the fixing projection 116c protruding from the back surface of the head block 116 after the belt regulating member 120 is temporarily assembled to the supports 117 and 118. The recessed part 120c for fixation for inserting is formed. By inserting the fixing protrusion 116c into the fixing recess 120c, the movement of the belt regulating member 120 in the width direction (W direction) can be restricted. As a result, the belt regulating member 120 can be positioned and fixed with respect to the supports 117 and 118.

  When the belt regulating member 120 is temporarily assembled to the support body 117, the pair of sliding assembly hooks 120 e formed on the back surface of the belt regulating member 120 is connected to the sliding assembly opening 117 e of the support body 117. After insertion, the belt regulating member 120 is slid in the + W direction. Then, the sliding assembly hook 120e engages with the support 117, and the belt regulating member 120 is temporarily assembled with the support 117.

  When the belt regulating member 120 is temporarily assembled to the support body 118, the pair of sliding assembly hooks 120 f formed on the back surface of the belt regulating member 120 are connected to the sliding assembly opening 118 f of the support body 118. After insertion, the belt regulating member 120 is slid in the + W direction. Then, the sliding assembly hook 120 f is engaged with the support 118, and the belt regulating member 120 is temporarily assembled with the support 118. When the belt regulating members 120 are temporarily assembled on the supports 117 and 118, the state shown in FIG. 6 is obtained. In this state, the belt regulating member 120 is in a state where movement is restricted in the X, Y, and + W directions, but is still slidable only in the -W direction.

  Next, the head block 116 is moved in the X direction and temporarily assembled to the supports 117 and 118. At this time, the fixing protrusion 116c protruding from the back surface of the head block 116 is inserted into the fixing recess 120c of the belt regulating member 120 (see FIG. 2). When the fixing protrusion 116c is inserted into the fixing recess 120c, the movement of the belt regulating member 120 in the −W direction is restricted. Then, the belt regulating member 120 is fixed to the supports 117 and 118. With this configuration, the belt regulating member 120 can be assembled to the supports 117 and 118 without using any special assembly tool (screw, rivet, etc.) or tool. By using this configuration, assembling work can be facilitated and an increase in cost can be suppressed.

  On the belt regulating member 120, a sliding assembly hook 120e to be engaged with the support body 117 and a sliding assembly hook 120f to be engaged with the support body 118 are arranged at different positions and at different pitches. It is. By configuring in this way, it is possible to prevent an error in the mounting direction of the belt regulating member 120. Further, the assembling work can be facilitated and the increase in the cost of the fixing device 29 can be suppressed. In addition, both the sliding assembly hook 120e to be engaged with the support member 117 and the sliding assembly hook 120f to be engaged with the support member 118 are separately formed at different positions on the belt regulating member 120. It is. With this configuration, one type of belt regulating member 120 can be disposed on both the upstream side and the downstream side of the pad 114.

  Further, the sliding assembly hook 120e and the sliding assembly hook 120f formed on the belt regulating member 120 are assembled by sliding in the width direction (W direction shown in FIG. 6) of the endless belt 111. Thus, the positioning accuracy of the belt regulating member 120 in the X direction (see FIG. 2) can be maintained with high accuracy. Thereby, the positioning accuracy of the curved surface guide part 120a in the vicinity of the pad 114 can be improved, and the generation of wrinkles in the endless belt 111 can be suppressed.

As described above, according to the present embodiment, when a belt is used on either the pressure side or the heating side, deformation such as buckling of the belt is suppressed even when a large force is applied to the belt. Can do.
Further, since the curved surface guide portion of the belt regulating member is in surface contact with the inner peripheral surface of the endless belt, there may be a case where a plurality of narrow belt regulating members are provided depending on the material or thickness of the endless belt. Deformation between the belt regulating members can be prevented.

In addition, by providing a wide belt regulating member so as to contact the periphery of the central portion of the inner peripheral surface of the endless belt, it is possible to efficiently prevent the endless belt from being deformed according to the material and thickness of the endless belt. it can.
In addition, since the ridge line of the curved guide portion does not continue to contact the same portion of the inner peripheral surface of the endless belt, the inner surface of the endless belt can be hardly damaged.

Moreover, since the ridgeline of the curved surface guide portion does not have an acute corner, the inner peripheral surface of the endless belt can be hardly damaged.
Further, by inserting and engaging the sliding assembly hook provided on the inner side of the belt regulating member through the sliding assembly opening of the support body, while maintaining the assembly accuracy of the belt regulating member, Assembly work can be facilitated. In addition, it is possible to prevent an error in the assembly direction of the belt regulating member.

In addition, since the nip forming member is attached to the support so as to prevent the belt restricting member engaged with the support from being displaced in the axial direction, the belt restricting member is fixed to the support by the nip forming member. Axial movement can be restricted.
In addition, by using the support as a pair of support plates, the entire belt assembly can be reduced in weight and size.
Moreover, since the support was comprised with the rolled steel plate or the aluminum plate, the support which can be used under high temperature can be provided at low cost. Moreover, it becomes possible to shape | mold a support body only by a cutting process. As a result, the fixing device can be provided at low cost while maintaining high accuracy.

  As described above, as an embodiment of the present invention, an example in which a roll is used on the heating side and an endless belt is used on the pressing side has been described in detail. However, the gist of the present invention is not limited thereto, for example, on the heating side. The present invention can also be applied to a form in which a roll is used on the belt pressing side.

  The present invention can be applied to an electrophotographic image forming apparatus such as a printer and a copying machine.

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 13 ... Image forming part 19 ... Photosensitive drum 28 ... Transfer part 29 ... Fixing device 31 ... Paper storage part 35 ... Paper feed part 43 ... Manual feed device 44 ... Charger 45 ... Exposure apparatus 46 ... Developer 46a ... developing roll 47 ... cleaner 49a, 49b, 49c ... conveying roll pair 102 ... guide plate 104 ... heating roll 108 ... heating source 111 ... endless belt 110 ... belt assembly 112, 113 ... belt holding member 114 ... pad 115 ... friction force Reduction sheet 116 ... head block 116c ... fixing projection 117, 118 ... support 117e, 118f ... sliding assembly opening 119 ... felt 120, 220 ... belt regulating member 120a, 220a ... curved surface guide 120c ... fixing recess 120e , 120f ... sliding assembly hook NP ... pressure contact fixing part P ... Media

Claims (8)

A fixing device for fixing the toner image to the recording medium by heating and pressing a recording medium carrying an unfixed toner image,
A roll in contact with the first surface of the recording medium;
A belt assembly that is disposed so as to be in contact with the roll and is in contact with a second surface of the recording medium,
The belt assembly comprises:
An endless belt,
An axially long support for supporting the structure of the belt assembly within the endless belt;
A nip forming member attached to the support and forming a nip by pressing and fixing the endless belt to the roll;
A curved guide portion that is wide in the axial direction and is in contact with the inner peripheral surface of the endless belt when the endless belt is deformed inwardly on the upstream side of the nip forming member with respect to the rotational direction of the endless belt. A belt regulating member having
The belt restricting member is spaced apart from the inner peripheral surface of the endless belt with a predetermined gap, and the first end in the rotational direction is disposed close to the nip forming member. A fixing device characterized by the above.   The fixing device according to claim 1, wherein the belt regulating member is positioned so as to contact a periphery of a central portion of an inner peripheral surface of the endless belt.   The fixing device according to claim 1, wherein the curved surface guide portion has a width that gradually increases toward the nip forming member.   4. The fixing device according to claim 1, wherein the curved surface guide portion has corner portions subjected to C chamfering or R chamfering processing at both ends in the axial direction of the curved surface. 5.   The belt regulating member has a hook for slidingly engaging with the support on the inner side thereof, and the support has an opening for inserting the hook. 5. The fixing device according to any one of items 4 to 4.   The said nip forming member is attached to the said support body so that the shift | offset | difference of the axial direction of the said belt control member engaged with the said support body may be prevented. The fixing device according to 1.   The fixing device according to claim 1, wherein the support is a pair of support plates.   The fixing device according to claim 1, wherein the support is formed of a rolled steel plate or an aluminum plate.

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