JP6641843B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device that thermally fixes a developer image transferred to a sheet.

  2. Description of the Related Art Conventionally, as a fixing device for thermally fixing a developer image transferred to a sheet such as paper, there is known a fixing device including an endless belt and a guide member having a guide surface for guiding an inner peripheral surface at an end portion of the endless belt. Have been. Patent Literature 1 discloses a fixed guide as a guide member and a movable guide that is movable with respect to the fixed guide in the sheet conveying direction and is urged by an elastic body against the inner peripheral surface of the endless belt. Is disclosed. According to such a fixing device, since a pressing force can be applied to the end of the endless belt from the inside, it is possible to suppress the occurrence of the deviation and deflection of the endless belt.

JP 2005-10201 A

  By the way, in the conventional technology, a gap that becomes wider or narrower with the movement of the movable guide is formed between the fixed guide and the movable guide, so that the inner peripheral surface of the rotating endless belt contacts the edge of the gap. Could be. If the inner peripheral surface of the endless belt contacts the edge of the gap, the rotation of the endless belt may become unstable, or the inner peripheral surface of the endless belt may be damaged, and the durability of the endless belt may be reduced. is there.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a fixing device that can improve the rotation stability of an endless belt and the durability of the endless belt.

In order to achieve the above object, a fixing device of the present invention includes an endless belt, a first guide member, a second guide member, a support member, and a biasing member.
The endless belt rotates in a predetermined rotation direction.
The first guide member includes a base that guides the inner peripheral surface of the endless belt, a guide surface that extends from the base to the downstream side in the rotation direction of the endless belt, and guides the inner peripheral surface of the endless belt in a predetermined guide direction. And an extending part having the same.
The second guide member receives the inner peripheral surface of the endless belt separated from the extending portion and guides the inner peripheral surface.
The support member is configured such that, with respect to one of the first guide member and the second guide member, a first position where the first surface, which is the surface on which the extending portion of the base is disposed, is closer to the second guide member; The first surface is movably supported between a first position and a second position farther from the second guide member.
The urging member urges one of the first guide member and the second guide member toward the second position.
Then, the first surface forms a gap between the second guide member and the second guide member that expands when one of the first guide member and the second guide member moves toward the second position.
The extension extends to the downstream side in the guide direction over the gap.
The boundary or gap between the second guide member and the opposite surface, which is the surface opposite to the guide surface of the extension, is open on the downstream side in the guide direction.

  According to such a configuration, the extension extends to the downstream side in the guide direction beyond the gap, and the boundary between the opposite surface of the extension and the second guide member or the downstream in the guide direction of the gap is open. Therefore, the gap formed between the first surface of the first guide member and the second guide member can be covered by the extension having the guide surface. Thereby, contact between the inner peripheral surface of the rotating endless belt and the edge of the gap can be suppressed, so that the rotation stability of the endless belt and the durability of the endless belt can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the stability of rotation of an endless belt and the durability of an endless belt can be improved.

FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus including a fixing device according to an embodiment. FIG. 3 is a cross-sectional view of the fixing device. It is a perspective view of a belt unit. It is a perspective view showing a cover member, a movable guide member, and a coil spring. It is an expanded sectional view of a belt unit. It is sectional drawing of a belt unit, The figure (a) which shows the state when a movable guide member is in a 1st position, and the figure (b) which shows the state when it is in a 2nd position. It is a figure which shows the structure of the extension part which concerns on a 1st modification, The figure (a) which shows the state when a movable guide member is in a 1st position, and the figure (b) which shows the state when it is in a 2nd position. ). It is the perspective view (a) of the edge part of the belt unit which concerns on a 2nd modification, and sectional drawing (b) of a belt unit.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the schematic configuration of the image forming apparatus including the fixing device according to the embodiment will be briefly described, and then, the detailed configuration of the fixing device will be described.

  In the following description, directions are described based on a user who uses the image forming apparatus. That is, the right side in FIG. 1 is “front”, the left side is “rear”, the near side is “left”, and the far side is “right”. The up-down direction in FIG. 1 is referred to as “up-down”.

  As shown in FIG. 1, a laser printer 1 as an image forming apparatus includes a paper supply unit 3 that supplies a sheet S, an exposure device 4, and a process cartridge that transfers a toner image onto the sheet S in a main body housing 2. 5 and a fixing device 100 for thermally fixing the toner image transferred to the sheet S.

  The paper feed unit 3 is provided at a lower portion in the main body housing 2, and mainly includes a paper feed tray 31, a paper pressing plate 32, and a paper feed mechanism 33. The sheet S stored in the sheet feed tray 31 is moved upward by the sheet pressing plate 32, and is supplied by the sheet feed mechanism 33 between the photosensitive drum 61 of the process cartridge 5 and the transfer roller 63.

  The exposure device 4 is disposed at an upper part in the main body housing 2 and includes a laser light emitting unit (not shown), a polygon mirror, a lens, a reflector, and the like, which are omitted from reference numerals. The exposure device 4 exposes the surface of the photoconductor drum 61 by performing high-speed scanning on the surface of the photoconductor drum 61 with a laser beam (see a chain line) based on image data emitted from the laser light emitting unit.

  The process cartridge 5 is disposed below the exposure device 4, and is configured to be detachably attached to the main housing 2 from an opening formed when the front cover 21 provided on the main housing 2 is opened. I have. The process cartridge 5 includes a drum unit 6 and a developing unit 7.

  The drum unit 6 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 7 is configured to be detachably attached to the drum unit 6, and includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and a container 74 that stores toner. Mainly prepared.

  In the process cartridge 5, after the surface of the photosensitive drum 61 is uniformly charged by the charger 62, the surface is exposed by the high-speed scanning of the laser beam from the exposure device 4, so that the image data is formed on the photosensitive drum 61. , An electrostatic latent image is formed. Further, the toner in the storage section 74 is supplied to the developing roller 71 via the supply roller 72, and enters between the developing roller 71 and the layer thickness regulating blade 73 to form a thin layer having a constant thickness on the developing roller 71. It is carried.

  The toner carried on the developing roller 71 is supplied from the developing roller 71 to an electrostatic latent image formed on the photosensitive drum 61. Thereby, the electrostatic latent image is visualized, and a toner image is formed on the photosensitive drum 61. Thereafter, the sheet S is conveyed between the photosensitive drum 61 and the transfer roller 63, so that the toner image on the photosensitive drum 61 is transferred onto the sheet S.

  The fixing device 100 is disposed behind the process cartridge 5 and mainly includes a belt unit 110 and a pressure roller 120 as shown in FIG. The belt unit 110 mainly includes an endless belt 111, a halogen lamp 112, a nip member 113, a reflection member 114, and a stay 115.

  The endless belt 111 is a tubular belt having heat resistance and flexibility, and is formed of, for example, stainless steel. The endless belt 111 has a predetermined rotation direction, specifically, in the present embodiment, the inner peripheral surfaces of both end portions in the longitudinal direction are guided by a cover member 200 and a movable guide member 300 described later. It rotates clockwise in FIG.

  The halogen lamp 112 is a heater that heats the toner transferred to the sheet S by heating the nip member 113 and the endless belt 111 by generating heat when energized, and is disposed inside the endless belt 111.

  The nip member 113 is a plate-shaped member that receives radiant heat from the halogen lamp 112, and is arranged inside the endless belt 111 so as to contact the inner peripheral surface of the endless belt 111. The nip member 113 is formed of, for example, an aluminum plate or the like having a high thermal conductivity in order to transmit radiant heat received from the halogen lamp 112 to the toner on the paper S via the endless belt 111.

  The reflecting member 114 is a member that reflects radiant heat from the halogen lamp 112 toward the nip member 113, and is arranged inside the endless belt 111 so as to surround the halogen lamp 112. The reflection member 114 is formed by, for example, bending an aluminum plate or the like having a large reflectance in infrared and far infrared rays into a substantially U-shape in cross section.

  The stay 115 is a member that secures the rigidity of the nip member 113 to which a load is applied from the pressure roller 120 by supporting the nip member 113 via the reflection member 114, and is arranged so as to cover the reflection member 114. The stay 115 is formed by bending a relatively large rigidity, for example, a steel plate or the like.

  The pressure roller 120 is a roller that conveys the sheet S to and from the nip member 113 via the endless belt 111, and is disposed below the nip member 113 so as to sandwich the endless belt 111 between the pressure roller 120 and the nip member 113. I have. The pressure roller 120 is rotated counterclockwise in FIG. 2 while the endless belt 111 is driven to rotate by the driving force transmitted from a motor (not shown) provided in the main body housing 2. Accordingly, the fixing device 100 conveys the sheet S between the belt unit 110 and the pressure roller 120 in a predetermined conveyance direction, specifically, in the present embodiment, from front to back.

  In the fixing device 100, the sheet S to which the toner image is transferred is conveyed between the belt unit 110 and the pressure roller 120, so that the toner image is thermally fixed to the sheet S. The paper S on which the toner image has been thermally fixed is discharged onto a paper discharge tray 22 by conveyance rollers 23 and 24 as shown in FIG.

Next, a detailed configuration of the fixing device 100 will be described.
As shown in FIGS. 2 and 3, the belt unit 110 of the fixing device 100 includes, in addition to the endless belt 111 described above, a cover member 200 as an example of a second guide member and a support member, and a first member. A movable guide member 300 as an example of a guide member, a coil spring 400 as an example of an urging member, and a regulating member 500 are provided. The cover member 200, the movable guide member 300, and the regulating member 500 are formed of, for example, resin.

  The cover member 200 is a member that covers the stay 115 on the side opposite to the halogen lamp 112 with the stay 115 interposed therebetween, and is formed to extend in the longitudinal direction of the endless belt 111, specifically, in the left-right direction in this embodiment. Have been. The cover member 200 mainly has an upper side wall 201, a front side wall 202 extending downward from a front end of the upper side wall 201, and a rear side wall 203 extending downward from a rear end of the upper side wall 201.

  As shown in FIG. 4, the cover member 200 includes a first fixed guide portion 210, a second fixed guide portion 220, a second engagement portion 230, a second spring engagement portion 240, and a regulating portion 250. Is provided.

  As shown in FIG. 3, the first fixed guide portions 210 are formed one by one at both ends in the longitudinal direction of the endless belt 111. As shown in FIG. 2, each of the first fixed guide portions 210 extends from the front end of the upper side wall 201 to the front side wall 202, and stays 115 disposed inside the cover member 200 from the upper side wall 201 and the front side wall 202. It is provided so as to protrude in a direction away from the like.

  The outer peripheral surface of the first fixed guide portion 210, which is a surface facing the inner peripheral surface of the endless belt 111, has a substantially arc-shaped curved surface in cross section. The outer peripheral surface of the first fixed guide portion 210 has a first fixed guide surface 211 as an example of a second guide surface that contacts the inner peripheral surface of the endless belt 111 and guides the inner peripheral surface of the endless belt 111. I have.

  The first fixed guide surface 211 receives the inner peripheral surface of the endless belt 111 separated from an extension 320 described later of the movable guide member 300 with the rotation of the endless belt 111, and guides the inner peripheral surface. The endless belt 111 is guided toward a nip between the nip member 113 and the pressure roller 120.

  The first fixed guide portion 210 has a second surface 212 as a rear surface extending downward from the upstream end of the outer peripheral surface in the rotation direction of the endless belt 111.

  The second fixed guide portion 220 is provided so as to protrude rearward from the lower end of the rear wall 203 in a range extending in the longitudinal direction of the endless belt 111.

  The outer peripheral surface of the second fixed guide portion 220 facing the inner peripheral surface of the endless belt 111 has a substantially arc-shaped curved surface in cross section. The outer peripheral surface of the second fixed guide portion 220 has a second fixed guide surface 221 that contacts the inner peripheral surface of the endless belt 111 and guides the inner peripheral surface of the endless belt 111.

  The second fixed guide surface 221 receives the inner peripheral surface of the endless belt 111 coming out of the nip between the nip member 113 and the pressure roller 120 as the endless belt 111 rotates, and guides the inner peripheral surface. Thus, the endless belt 111 is guided toward a movable guide surface 301 of the movable guide member 300 described later.

  As shown in FIG. 4, the second engaging portions 230 are provided to extend rearward from both left and right ends of the second surface 212 of the first fixed guide portion 210. Specifically, the second engagement portion 230 is provided with a pair of side walls 231 provided so as to be substantially perpendicular to the longitudinal direction of the endless belt 111, and from the upper end of each side wall 231 to the other side wall 231. And a pair of upper wall portions 232 that extend.

  The second spring engagement part 240 is provided near the center of the second surface 212 of the first fixed guide part 210. Specifically, the second spring engaging portion 240 has a concave portion 241 that is concave with respect to the second surface 212 and a substantially cylindrical convex portion 242 that projects rearward from the bottom of the concave portion 241. It is configured. The coil spring 400 is arranged in a state where its end enters the concave portion 241 of the second spring engaging portion 240 and is engaged with the convex portion 242.

  Returning to FIG. 2, the restricting portion 250 is formed to extend from the rear end of the upper surface of the second fixed guide portion 220 to the downstream side (upper side) in the rotation direction of the endless belt 111. When the movable guide member 300 is at a second position described later (see FIG. 6B), the movable guide member 300 comes into contact with the regulating portion 250. Thus, the position of the movable guide member 300 can be regulated, and the movable guide member 300 can be prevented from falling off the cover member 200.

  The movable guide member 300 is a member that guides the inner peripheral surface of the endless belt 111 together with the first fixed guide portion 210 and the second fixed guide portion 220 of the cover member 200. The first fixed guide portion 210 is located between the downstream end of the first fixed guide portion 210 and the downstream end of the first fixed guide portion 210.

  The outer peripheral surface of the movable guide member 300 facing the inner peripheral surface of the endless belt 111 is a curved surface having a substantially arc shape in cross section. The outer peripheral surface of the movable guide member 300 has a movable guide surface 301 that contacts the inner peripheral surface of the endless belt 111 and guides the inner peripheral surface of the endless belt 111.

  The movable guide surface 301 receives the inner peripheral surface of the endless belt 111 that has been guided by the second fixed guide surface 221 with the rotation of the endless belt 111, and guides the inner peripheral surface to form the endless belt 111. It guides toward the first fixed guide surface 211.

  The movable guide member 300 has a base 310 and a substantially eaves-like extending part 320 extending from the base 310 to the downstream side in the rotation direction of the endless belt 111 in a side view. As shown in FIG. 4, the base 310 includes a first engagement portion 330 that engages with the second engagement portion 230 and a first spring engagement portion 340 with which the end of the coil spring 400 engages. Is formed.

  As shown in FIG. 5, the base 310 is a part configuring the main body of the movable guide member 300. The base 310 has a base-side guide surface 311 that constitutes a part of the movable guide surface 301 on the outer peripheral surface facing the inner peripheral surface of the endless belt 111.

  The base 310 has a surface facing the cover member 200, as viewed from the longitudinal direction of the endless belt 111, the second surface 212 of the first fixed guide 210, the upper surface of the upper side wall 201, the rear surface of the rear side wall 203, and the second surface 212. 2 is formed in a stepped shape along the upper surface of the fixed guide portion 220.

  Specifically, the surface of the base 310 facing the cover member 200 includes a first facing surface 312 as an example of a first surface, a second facing surface 313 extending rearward from a lower end of the first facing surface 312, and a second facing surface. A third facing surface 314 extending downward from the rear end of the facing surface 313; a fourth facing surface 315 extending rearward from the lower end of the third facing surface 314; and a fifth facing surface extending downward from the rear end of the fourth facing surface 315. It has a surface 316 and a sixth opposing surface 317 extending rearward from the lower end of the fifth opposing surface 316 and connecting to the lower end of the outer peripheral surface.

  The movable guide member 300 has a first facing surface 312 and a third facing surface 314 facing the second surface 212, a second facing surface 313 and a fourth facing surface 315 facing the upper surface of the upper side wall 201, and a fifth facing surface. The surface 316 faces the rear surface of the rear side wall 203, and the sixth facing surface 317 faces the upper surface of the second fixed guide 220. In the movable guide member 300, the fourth opposing surface 315 is supported by the upper side wall 201, and the sixth opposing surface 317 is supported by the second fixed guide portion 220.

  The first facing surface 312 is a front end surface on the side where the extension 320 of the base 310 is arranged, and directly faces the second surface 212 of the cover member 200. The first opposing surface 312 is provided so as to extend downward from a rear end of the later-described opposite surface 322 of the extending portion 320, thereby forming a corner A <b> 1 with the opposite surface 322. In the present embodiment, the first opposing surface 312 and the second surface 212 are formed as surfaces orthogonal to the sheet S transport direction (front-back direction).

  The extending portion 320 is provided so as to extend from the upper end of the downstream end of the base 310 in the rotation direction of the endless belt 111 to the downstream side (front side). When viewed from the longitudinal direction of the endless belt 111, the extension portion 320 has a thickness T1 in the up-down direction (direction perpendicular to the guide direction) smaller than the thickness T2 in the up-down direction of the base 310. More specifically, when viewed from the longitudinal direction of the endless belt 111, the extending portion 320 has a thickness T1 in the vertical direction smaller than the thickness T3 in the vertical direction of the downstream end of the base 310 in the rotation direction of the endless belt 111. ing.

  The extension 320 has an extension-side guide surface 321 as an example of a guide surface constituting a part of the movable guide surface 301 on an outer peripheral surface that is an upper surface thereof. The extension-side guide surface 321 is formed as a continuous surface smoothly connected to the base-side guide surface 311. The inner peripheral surface of the endless belt 111 is formed in a predetermined guide direction, in this embodiment, substantially in the front-rear direction, In general, we will guide you forward later.

  Further, the extending portion 320 is a downstream side in the rotation direction of the endless belt 111 that connects the opposite surface 322 which is a lower surface opposite to the extending portion side guide surface 321 to the extending portion guide surface 321 and the opposite surface 322. And a downstream end surface 323 as an example of the side end surface.

  The opposite surface 322 is a surface along the urging direction of the coil spring 400, specifically, in the present embodiment, in the transport direction of the sheet S. Further, in the present embodiment, the opposite surface 322 is formed as a surface parallel to the transport direction of the sheet S. Further, the downstream end surface 323 is formed in a curved shape having a substantially arc shape when viewed from the longitudinal direction of the endless belt 111.

  As shown in FIG. 4, the first engagement portion 330 is provided so as to extend forward from the third facing surface 314 of the base 310. Specifically, two first engaging portions 330 are provided at intervals in the longitudinal direction of the endless belt 111, and are formed as convex portions that can be engaged with the second engaging portions 230. When the first engagement portion 330 is engaged with the second engagement portion 230, the movement of the movable guide member 300 in the vertical and horizontal directions is restricted.

  The first spring engaging portion 340 is provided between the two first engaging portions 330 on the third facing surface 314. Specifically, the first spring engagement portion 340 is formed as a substantially columnar projection projecting forward from the third facing surface 314. The coil spring 400 is arranged such that its end is engaged with the first spring engaging portion 340 between the two first engaging portions 330.

  The movable guide member 300 is provided movably with respect to the cover member 200 in the sheet S transport direction. Describing in more detail, the cover member 200 moves the movable guide member 300 between the first position shown in FIG. 6A and the second position shown in FIG. The sheet S is movably supported in the transport direction. The first position is a position where the first facing surface 312 of the base 310 is close to the second surface 212 of the first fixed guide portion 210. In the present embodiment, specifically, the first facing surface 312 is in contact with the second surface 212. It is a position to do. The second position is a position where the first facing surface 312 is farther from the second surface 212 of the first fixed guide portion 210 than the first position. In the present embodiment, specifically, the base 310 is It is a position where it comes into contact with the regulating portion 250.

  As shown in FIG. 5, the coil spring 400 is a member that urges the movable guide member 300 rearward with respect to the cover member 200, that is, toward the second position. The coil spring 400 has one end engaged with the first spring engaging portion 340 and the other end engaged with the second spring engaging portion 240, and the base 310 of the movable guide member 300 and the One fixed guide portion 210 is disposed between the two.

  The first facing surface 312 of the base 310 forms a gap C1 with the second surface 212 of the cover member 200. The gap C1 decreases when the movable guide member 300 moves toward the first position (front), and increases when the movable guide member 300 moves toward the second position (rear). Further, the first opposing surface 312 contacts the second surface 212 of the cover member 200 when the movable guide member 300 is at the first position, in other words, when the movable guide member 300 is closest to the second surface 212 of the cover member 200. (See FIG. 6A).

  The extension 320 extends downstream in the guide direction, that is, toward the front, beyond the gap C1 formed between the first facing surface 312 of the base 310 and the second surface 212 of the cover member 200. More specifically, the extending portion 320 has a gap C1 when the movable guide member 300 is at the second position (see FIG. 6B), that is, the gap between the first facing surface 312 and the second surface 212 is the largest. It extends to the front side beyond the gap C1 at the time.

  The extension 320 is arranged such that the opposite surface 322 is in contact with the end of the outer peripheral surface of the cover member 200 on the upstream side in the guide direction. The movable guide member 300 has a position where the opposite surface 322 of the extending portion 320 contacts the outer peripheral surface of the cover member 200 due to vibration or the like caused by the rotation of the endless belt 111, and a position where the opposite surface 322 of the extending portion 320 May move between a position distant from the outer peripheral surface of the camera.

  A boundary B1 between the opposite surface 322 of the extending portion 320 and the outer peripheral surface of the cover member 200 (or a gap when the opposite surface 322 is separated from the outer peripheral surface of the cover member 200) is located on the downstream side in the guide direction. The end is opened toward the downstream side in the guide direction, that is, toward the front. In other words, when viewed from the downstream side (front side) in the guide direction, the extending portion 320 is arranged in a state where all of the downstream end surface 323 is exposed so as not to overlap the cover member 200. For this reason, all the downstream end surfaces 323 of the extending portion 320 directly face the inner peripheral surface of the endless belt 111.

  As shown in FIGS. 2 and 3, the regulating members 500 are plate-shaped members having a substantially U-shape in side view, and are provided one by one in a state of being engaged with both longitudinal ends of the cover member 200. . The regulating member 500 has a regulating surface 510 on the inner surface in the longitudinal direction of the endless belt 111.

  The regulating surface 510 contacts the end surface of the endless belt 111 when the rotating endless belt 111 approaches one side in the longitudinal direction, and regulates the position of the endless belt 111 in the longitudinal direction. Even when the endless belt 111 is shifted to one side in the longitudinal direction, a pressure contact force from the movable guide member 300 to the end thereof, that is, a force in a direction in which the diameter of the endless belt 111 is to be expanded is applied. By acting, it moves back to the other side. Thereby, occurrence of deviation of the endless belt 111 can be suppressed.

  The extension 320 of the movable guide member 300 is disposed at a position overlapping with the regulating surface 510 when viewed from the longitudinal direction of the endless belt 111. In other words, the extension 320 of the movable guide member 300 is disposed inside the contour of the regulating surface 510 when viewed from the longitudinal direction of the endless belt 111. In the present embodiment, when viewed from the longitudinal direction of the endless belt 111, the entire movable guide surface 301 and the entire first fixed guide surface 211 are respectively disposed inside the contour of the regulating surface 510.

  According to the present embodiment described above, as shown in FIG. 5, the extension 320 extends downstream in the guide direction beyond the gap C1, and the boundary between the opposite surface 322 and the outer peripheral surface of the cover member 200. Since the downstream side in the guide direction of B1 is open, the gap C1 formed between the first opposing surface 312 of the movable guide member 300 and the second surface 212 of the cover member 200 is removed from the extension side guide surface 321. It can be covered by the extension 320 having. As a result, the contact between the inner peripheral surface of the rotating endless belt 111 and the edge of the gap C1 can be suppressed, so that the rotation stability of the endless belt 111 and the durability of the endless belt 111 can be reduced as compared with the conventional configuration. Performance can be improved.

  Further, since the opposite surface 322 of the extending portion 320 comes into contact with the outer peripheral surface of the cover member 200, the extending portion 320 can be supported by the cover member 200. Thereby, the movement of the extending portion 320 in the front-rear direction is stabilized, so that the rotation stability of the endless belt 111 can be further improved.

  Further, in the present embodiment, in particular, since the thickness T1 of the extension 320 is smaller and thinner than the thickness T2 of the base 310, even if the extension 320 is thin, the extension 320 is supported by the cover member 200. In addition, the bending of the extension 320 can be suppressed, and as a result, the rotation stability of the endless belt 111 can be improved.

  In addition, since the first facing surface 312 of the base 310 can contact the second surface 212 of the cover member 200, when the first facing surface 312 of the base 310 contacts the second surface 212 of the cover member 200, the movable guide member 300 Can be suppressed from moving further. Thus, the movable guide member 300 is prevented from moving more than necessary with respect to the cover member 200, and thus the rotation stability of the endless belt 111 can be further improved.

  Further, when viewed from the longitudinal direction of the endless belt 111, the extension 320 is disposed at a position overlapping the regulation surface 510 of the regulation member 500, so that the first fixed guide portion 210 of the cover member 200, the movable guide member 300, In the vicinity of the connecting portion, the behavior of the endless belt 111 can be stabilized. Thereby, the rotation stability of the endless belt 111 can be further improved.

  Further, since the downstream end surface 323 of the extending portion 320 is formed in a curved shape, the rotation of the endless belt 111 becomes unstable due to the contact between the inner peripheral surface of the endless belt 111 and the downstream end surface 323, or the endless belt 111 The possibility that the inner peripheral surface of the device will be damaged can be reduced.

  In addition, since the opposite surface 322 of the extending portion 320 is a surface along the biasing direction of the coil spring 400, the movable guide member 300 moves to the first position and the second position with respect to the cover member 200 along the biasing direction of the coil spring 400. When moving between the positions, the interference between the opposite surface 322 and the cover member 200 can be suppressed. Thereby, the movable guide member 300 can be satisfactorily moved, so that the rotation stability of the endless belt 111 can be further improved.

  Further, since the second guide member and the support member are provided integrally as the cover member 200, the number of components of the fixing device 100 can be reduced. This makes it possible to simplify the assembly of the fixing device 100 and to reduce the cost.

  The embodiment has been described above, but the present invention is not limited to the embodiment. The specific configuration can be appropriately changed without departing from the spirit of the invention as described below.

  For example, as shown in FIG. 7A, the extending portion 320 is hatched when the first facing surface 312 of the movable guide member 300 is at the first position close to the first fixed guide portion 210. Further, it may be provided so as to cover a part of the first fixed guide surface 211 of the first fixed guide portion 210. As shown in FIG. 7B, the first fixed guide surface 211 is provided at least when the first facing surface 312 of the movable guide member 300 is at the second position away from the first fixed guide portion 210. A surface that contacts the inner peripheral surface of the endless belt 111 and guides the inner peripheral surface of the endless belt 111.

  In the above-described embodiment, the opposite surface 322 of the extending portion 320 is arranged so as to contact the first fixed guide portion 210 of the cover member 200 as the second guide member. However, the present invention is not limited to this. . For example, as shown in FIG. 7, the opposite surface 322 of the extending portion 320 may be arranged in a state where there is a gap between the extension 320 and the cover member 200 without contacting the cover member 200.

  Further, in the above-described embodiment, when the first opposing surface 312 of the base 310 is in the first position, the first opposing surface 312 is arranged to be in contact with the first fixed guide portion 210 of the cover member 200 as the second guide member. It is not limited to this. For example, as shown in FIG. 7A, the first opposing surface 312 of the base 310 does not contact the cover member 200 even when in the first position, and has a gap between itself and the cover member 200. It may be arranged in a state.

  In the above-described embodiment, the movable guide member 300 as an example of the first guide member having the extension 320 is movably supported by the cover member 200 as an example of the second guide member. However, the present invention is not limited to this. For example, the second guide member may be movably supported with respect to the first guide member.

  Specifically, as shown in FIGS. 8A and 8B, the belt unit 110 includes a cover member 600 as another example of the first guide member having the extending portion 620, and a cover member 600 other than the second guide member. And a movable guide member 700 as a second guide member may be movable with respect to a cover member 600 as a first guide member.

Here, the embodiment shown in FIG. 8 will be described in detail. Note that the same components as those in the above embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
The cover member 600 has an extension 620 extending from the rear end of the upper surface of the second fixed guide 220 to the downstream side (upper side) in the rotation direction of the endless belt 111, and an extension other than the extension 620 of the cover member 600. And a base 610 as a part.

  The base 610 has a first fixed guide surface 211 and a second fixed guide surface 221 that guide the inner peripheral surface of the endless belt 111. In addition, the base 610 has a fixed-side facing surface 612 as a first surface on the upper surface of the second fixed guide 220, which is the surface on which the extension 620 is disposed.

  The extension portion 620 has a guide surface that guides the inner peripheral surface of the endless belt 111 in a predetermined guide direction, in this embodiment, substantially in the vertical direction, specifically, from bottom to top, on the outer peripheral surface that is the rear surface. As the extension-side guide surface 621. The extension 620 has an opposite surface 622 that is a front surface opposite to the extension-side guide surface 621.

  The outer peripheral surface of the movable guide member 700, which is a surface facing the inner peripheral surface of the endless belt 111, is a curved surface having a substantially arc shape in cross section. The outer peripheral surface of the movable guide member 700 receives the inner peripheral surface of the endless belt 111 distant from the extending portion 620, and guides the inner peripheral surface to guide the endless belt 111 toward the first fixed guide surface 211. It has a movable guide surface 701.

  The cover member 600 supports the movable guide member 700 so as to be movable in the vertical direction. More specifically, the movable guide member 700 is opposed to the cover member 600 at a first position where the fixed side facing surface 612 of the base 610 approaches the movable side facing surface 712 of the movable guide member 700, and at a fixed side facing the first position. The surface 612 is movably supported between a second position away from the movable facing surface 712. A coil spring 800 as an urging member that urges the movable guide member 700 toward the second position is disposed between the base 610 of the cover member 600 and the movable guide member 700.

  The fixed-side facing surface 612 forms a gap C2 with the movable-side facing surface 712 of the movable guide member 700. The gap C2 decreases when the movable guide member 700 moves toward the first position (downward), and expands when the movable guide member 700 moves toward the second position (upward).

  The extension 620 extends downstream in the guide direction, that is, upward, beyond the gap C2 (specifically, the gap C2 when the interval between the fixed-side facing surface 612 and the movable-side facing surface 712 is the largest). In the gap B2 between the opposite surface 622 of the extending portion 620 and the outer peripheral surface of the movable guide member 700, the downstream end in the guide direction is open in the guide downstream direction, that is, upward. .

  In the embodiment shown in FIG. 8 as well, the gap C2 can be covered with the extending portion 620, so that contact between the inner peripheral surface of the endless belt 111 and the edge of the gap C2 can be suppressed, and the endless belt 111 The rotation stability and the durability of the endless belt 111 can be improved.

  Further, in the embodiment, the second guide member and the support member are provided integrally as the cover member 200. However, the present invention is not limited to this. For example, the support member is independent as a separate component from the second guide member. May be provided. Further, in the embodiment shown in FIG. 8, the cover member 600 as the first guide member also functions as a support member that movably supports the movable guide member 700 as the second guide member. Although the support member and the support member are provided integrally, the invention is not limited to this. For example, the support member may be provided independently as a separate component from the first guide member.

  In the above-described embodiment, the cover member 200 (that is, a guide member that is not on the movable side) having the first fixed guide portion 210 for guiding the inner peripheral surface of the endless belt 111 and the longitudinal position of the endless belt 111 are regulated. Although the regulating member 500 having the regulating surface 510 is provided as a separate component, it is not limited to this. For example, the guide member and the regulating member that are not on the movable side may be provided integrally as one component.

  In the above-described embodiment, the coil spring 400 is exemplified as the urging member. However, the present invention is not limited to this, and the urging member may be a torsion spring, a leaf spring, or the like. Further, the biasing member may be provided integrally as a part of the first guide member or the second guide member.

  In the above-described embodiment, the laser printer 1 that forms a monochrome image on the sheet S is exemplified as an image forming apparatus including the fixing device of the present invention. However, the present invention is not limited thereto. A possible printer may be used. Further, the image forming apparatus is not limited to a printer, and may be, for example, a copying machine or a multifunction peripheral including a document reading device such as a flatbed scanner.

Reference Signs List 100 fixing device 111 endless belt 200 cover member 210 first fixed guide portion 211 first fixed guide surface 300 movable guide member 310 base 312 first opposing surface 320 extension 321 extension portion guide surface 322 opposite surface 323 downstream end surface 400 coil spring 500 Control member 510 Control surface A1 Corner B1 Boundary C1 Gap T1 Thickness

Claims (10)

An endless belt that rotates in a predetermined rotation direction,
An extension having a base that guides the inner peripheral surface of the endless belt, and a guide surface that extends from the base to the downstream side in the rotation direction of the endless belt and guides the inner peripheral surface of the endless belt in a predetermined guide direction. And a first guide member having:
A second guide member that receives the inner peripheral surface of the endless belt away from the extending portion and guides the inner peripheral surface;
Against the first guide member to the second guide member between a first position closer to the first surface and the second guide member and the distal portion of the base is a surface of the deployed side, the first position A support member that supports the first surface so as to be movable between a second position separated from the second guide member and
An urging member for urging the first guide member toward the second position,
The first surface forms a gap between the second guide member and the first guide member , the gap expanding when the first guide member moves toward the second position.
The extending portion extends downstream in the guide direction beyond the gap including a time when a distance between the first surface and the second guide member is maximum, and extends inside the endless belt of the second guide member. A fixing device, which covers a part of an outer peripheral surface along an inner peripheral surface of the endless belt facing the peripheral surface . 2. The fixing device according to claim 1, wherein an opposite surface of the extending portion opposite to the guide surface of the extending portion contacts the second guide member. 3.   The fixing device according to claim 2, wherein the extension has a thickness in a direction orthogonal to the guide direction, as viewed from a longitudinal direction of the endless belt, smaller than the base. The first surface forms a corner between the extension surface and an opposite surface that is an opposite surface to the guide surface ,
4. The fixing device according to claim 1 , wherein the first surface is capable of contacting the second guide member. 5. A regulating member having a regulating surface that contacts an end surface of the endless belt and regulates a position in a longitudinal direction of the endless belt,
5. The fixing device according to claim 1, wherein the extension portion is disposed at a position overlapping the regulation surface when viewed from the longitudinal direction. 6.   The end face on the downstream side in the rotation direction of the extending portion is formed in a curved shape when viewed from the longitudinal direction of the endless belt, according to any one of claims 1 to 5, characterized in that: Fixing device. The said extension part, The opposite surface which is the surface opposite to the said guide surface of the said extension part is a surface along the urging | biasing direction of the said urging | biasing member, The Claims 1-6 characterized by the above-mentioned. The fixing device according to claim 1. The fixing device according to claim 1, wherein the support member is provided on the second guide member . The second guide member has a second guide surface that guides an inner peripheral surface of the endless belt,
The extended portion, the first guide member fixing device according to any one of claims 1 to 8, characterized in that covers a portion of the second guide surface when in the first position . An endless belt that rotates in a predetermined rotation direction,
An extension having a base that guides the inner peripheral surface of the endless belt, and a guide surface that extends from the base to the downstream side in the rotation direction of the endless belt and guides the inner peripheral surface of the endless belt in a predetermined guide direction. And a first guide member having:
A second guide member that receives the inner peripheral surface of the endless belt away from the extending portion and guides the inner peripheral surface;
Against the second guide member to the first guide member, a first position closer to the first surface and the second guide member and the distal portion of the base is a surface of the deployed side, the first position A support member that supports the first surface so as to be movable between a second position separated from the second guide member and
An urging member for urging the second guide member toward the second position,
The first surface forms a gap between the second guide member and the second guide member, the gap expanding when the second guide member moves toward the second position;
The extending portion extends downstream in the guide direction beyond the gap including a time when the distance between the first surface and the second guide member is maximum, and extends inside the endless belt of the second guide member. A fixing device, which covers a part of an outer peripheral surface along an inner peripheral surface of the endless belt facing the peripheral surface .

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