US 12,393,145 B2
Fixing device and image forming apparatus with nip portion that prevents belt cracking and oil leakage
Shuhei Yasuda, Ibaraki (JP); Akiyoshi Shinagawa, Saitama (JP); Suguru Takeuchi, Chiba (JP); Yasuharu Toratani, Chiba (JP); Ayano Saito, Chiba (JP); Kengo Koyama, Chiba (JP); and Shigeru Tanaka, Tokyo (JP)
Assigned to Canon Kabushiki Kaisha, Tokyo (JP)
Filed by CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed on Jan. 29, 2024, as Appl. No. 18/425,575.
Claims priority of application No. 2023-014988 (JP), filed on Feb. 3, 2023.
Prior Publication US 2024/0264557 A1, Aug. 8, 2024
Int. Cl. G03G 15/20 (2006.01)
CPC G03G 15/2053 (2013.01) [G03G 15/2025 (2013.01); G03G 15/2064 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A fixing device comprising:
an endless belt configured to heat a recording material and having an inner circumferential surface coated with oil;
a pressure roller contacting an outer circumferential surface of the endless belt to form a nip portion; and
a pad disposed on the inner circumferential surface of the endless belt and configured to form the nip portion together with the pressure roller via the endless belt,
wherein the pressure roller applies heat and pressure to the recording material carrying a toner image at the nip portion together with the endless belt to fix the toner image to the recording material,
wherein a length of the endless belt is larger than a length of the pad in a width direction of the endless belt, and the pad includes a first surface forming the nip portion, a second surface facing the first surface, and a third surface connecting the first surface and the second surface in the width direction and formed in a conveyance direction of the recording material,
wherein the width direction of the endless belt is orthogonal to the conveyance direction of the recording material,
wherein the third surface has a curved shape in a cross section orthogonal to the conveyance direction of the recording material, and
wherein the third surface satisfies the following formula:
Et/156≤R≤0.637 L, where L [mm] is a length of the third surface in contact with the endless belt, E [MPa] is a Young's modulus of the endless belt, t [mm] is a thickness of the endless belt, R [mm] is a radius of curvature of the curved shape, and 156 indicates 156 MPa.