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EP-4194955-B1 - NIP FORMING DEVICE AND IMAGE FORMING APPARATUS

EP4194955B1EP 4194955 B1EP4194955 B1EP 4194955B1EP-4194955-B1

Inventors

  • Furuichi, Yuusuke
  • SHIMADA, HIROYUKI
  • SOMEYA, YUKIMICHI

Dates

Publication Date
20260513
Application Date
20221117

Claims (15)

  1. A nip forming device (9) comprising: an endless belt (20) that is flexible, the endless belt (20) configured to rotate; a nip former (22) disposed opposite an inner circumferential face (20a) of the endless belt (20); a pressure rotator (21) configured to press against the nip former (22) via the endless belt (20) to form a nip (N) between the endless belt (20) and the pressure rotator (21), the nip (N) through which a conveyed object (P) is conveyed; and a separator (310) disposed downstream from the nip (N) in a conveyance direction of the conveyed object (P), the separator (310) configured to separate the conveyed object (P) from the endless belt (20), the separator (310) including: a non-contact portion (311) separated from the endless belt (20); and contact portions (313) configured to contact the endless belt (20), the contact portions (313) configured to retain a gap (G2) having a predetermined size between the non-contact portion (311) and the endless belt (20), wherein the nip forming device further includes: a flange (400) to support both lateral sides of the endless belt in an axial direction of the endless belt, characterized in that a slack rate, Sr, which is defined as [Sa/Di]x100, is in a range of 0.1% to 10%, wherein Sa represents a difference in height coordinate of a top of the endless belt (20) before and after the top of the endless belt (20) is pressed against the flange (400), and Di represents a diameter of the endless belt (20).
  2. The nip forming device (9) according to claim 1, further comprising a guide (400) configured to guide each lateral end of the endless belt (20) in a longitudinal direction of the endless belt (20).
  3. The nip forming device (9) according to claim 1 or 2, wherein the separator (310) is configured to move toward the endless belt (20) in an approach direction and separate from the endless belt (20) in a separation direction.
  4. The nip forming device (9) according to claim 3, further comprising a motion restrictor (301) including: a first restricting portion (321a) configured to restrict motion of the separator (310) in the approach direction; and a second restricting portion (321b) configured to restrict motion of the separator (310) in the separation direction.
  5. The nip forming device (9) according to claim 4, wherein the second restricting portion (321b) is configured to restrict motion of the separator (310) in the separation direction at a position where the separator (310) does not come into contact with the pressure rotator (21).
  6. The nip forming device (9) according to any one of claims 3 to 5, further comprising a biasing member (330) configured to bias the separator (310) in the approach direction.
  7. The nip forming device (9) according to claim 6, wherein the nip former (22) is configured to move with respect to the pressure rotator (21) between a pressurization position where the pressure rotator (21) presses against the nip former (22) via the endless belt (20) at the nip (N) and a separation position where the pressure rotator (21) releases pressure applied at the nip (N), and wherein the nip former (22) is configured to move to the separation position in a state in which the first restricting portion (321a) restricts motion of the separator (310).
  8. The nip forming device (9) according to claim 6 or 7, wherein the separator (310) includes a separation plate (310) configured to move.
  9. The nip forming device (9) according to claim 8, further comprising a side plate (320) configured to support the separation plate (310).
  10. The nip forming device (9) according to claim 9, wherein the motion restrictor (301) is interposed between the separation plate (310) and the side plate (320).
  11. The nip forming device (9) according to claim 10, wherein the side plate (320) has a motion restricting hole (321) defined by the first restricting portion (321a) and the second restricting portion (321b) disposed opposite the first restricting portion (321a), and wherein the motion restrictor (301) further includes a motion restricted tab (312) mounted on a lateral end of the separation plate (310) in a longitudinal direction of the separation plate (310), the motion restricted tab (312) inserted into the motion restricting hole (321).
  12. The nip forming device (9) according to claim 10 or 11, further comprising a support shaft (322) projecting from the side plate (320), wherein the separation plate (310) is configured to pivot about the support shaft (322).
  13. The nip forming device (9) according to any one of claims 1 to 12, wherein the contact portions (313) are disposed outboard from a conveyance span in a longitudinal direction of the endless belt (20), the conveyance span where the conveyed object (P) is conveyed over the endless belt (20).
  14. The nip forming device (9) according to any one of claims 1 to 13, wherein the nip former (22) includes: a center heater (35B) disposed opposite a center span of the endless belt (20) in a longitudinal direction of the endless belt (20), the center heater (35B) configured to heat the center span of the endless belt (20); and a plurality of lateral end heaters (35A, 35C) disposed opposite both lateral end spans of the endless belt (20) in the longitudinal direction of the endless belt (20), respectively, the plurality of lateral end heaters (35A, 35C) configured to heat the lateral end spans of the endless belt, (20) respectively.
  15. An image forming apparatus (100) comprising the nip forming device (9) according to any one of claims 1 to 14.

Description

BACKGROUND Technical Field Embodiments of this disclosure relate to a nip forming device and an image forming apparatus, and more specifically, to a nip forming device including a separator for separating a conveyed object having passed through a nip from an endless belt and an image forming apparatus incorporating the nip forming device. Related Art Related-art image forming apparatuses, such as copiers, facsimile machines, printers, and multifunction peripherals (MFP) having two or more of copying, printing, scanning, facsimile, plotter, and other functions, typically form an image on a recording medium according to image data. Such image forming apparatuses include a fixing device that fixes an image on a recording medium such as a sheet. The fixing device employs a belt fixing method using an endless belt as disclosed by Japanese Unexamined Patent Application Publication No. 2015-011167. The fixing device disclosed by Japanese Unexamined Patent Application Publication No. 2015-011167 includes a fixing belt as the endless belt and a sheet separation plate disposed in proximity to the fixing belt. The sheet separation plate separates a sheet from the fixing belt. If a gap between the fixing belt and the sheet separation plate is excessively small, the sheet separation plate comes into contact with the fixing belt easily, damaging the fixing belt and resulting in formation of a faulty image. If the gap between the fixing belt and the sheet separation plate is excessively great, the sheet passes through the gap easily and is wound around the fixing belt, causing the sheet to be jammed. Hence, the sheet separation plate is requested to be closer to the fixing belt without contacting the fixing belt. The fixing device includes a sheet separation plate mover that adjusts and optimizes the gap. However, the sheet separation plate mover includes a driver that drives the sheet separation plate and a plurality of sensors, causing the construction of the fixing device to be complex and increasing costs. To address the circumstances described above, the fixing device is requested to optimize the gap between the fixing belt and the sheet separation plate with a simple construction so as to improve separation of a conveyed object (e.g., a sheet) from the fixing belt. JP 2015 200702 A discloses a fixing device comprising a fixing member heated by a heat source, a pressure member pressed against the fixing member to form a fixing nip with the fixing member, and a separation mechanism for separating the sheet passing through the fixing nip from the surface of the fixing member, wherein the separation mechanism has a leading edge opposite to a sheet passing area of the sheet in the fixing member. JP 2010 204543 A discloses an image heating apparatus disposed so as to be opposed to a rotating body, a pressure rotating body that presses against the rotating body to form a heating nip of a recording material, and close to the surface of the rotating body and a separating member for separating the recording material from the rotating body using the tip. US 2014/029989 A1 discloses a fixing device including a supporting mechanism and contact members, the supporting mechanism pivotably supporting a separating member. US 2014/301751 A1 discloses a fusing device including a first roller, a second roller forming a fusing nip part together with the first roller, an adjustment mechanism changing posture of the first roller between first and second postures, a separation member, a turning mechanism, an abutting member, and an isolation mechanism. US 2021/003946 A1 discloses an attachment attached to a holding shaft and including a first hollow axial portion including a first slit that receives the holding shaft.EP 2 778 796 A2 discloses a fixing device including an endless, rotary fixing member; a heat source to heat the fixing member; an opposed member disposed opposite the fixing member and to form a fixing nip with the fixing member; and a biasing member disposed opposite the opposed member, to press the fixing member from a back side of the fixing member against the opposed member at the fixing nip. US 2009/110452 A1 discloses a fixing device including a fixing member configured to heat and melt a toner image to fix it onto a recording medium. US 2015/030358 A1 discloses a fixing device including a fixing member, a pressing member and a separating member. SUMMARY It is a general object of the present disclosure to provide an improved and useful nip forming device as defined in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein: FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present disclosure;FIG. 2 is a schemat