Abstract: A silicone oil (18) is filled inside a housing (12) of rotation damper (10), and a rotor brake plate (24) provided to be connected to a lower end portion of a rotating shaft (22) of a rotor (20) is rotatably housed inside the housing (12). Also, an O-ring (30) is disposed between the housing (12) and the rotating shaft (22) to prevent the silicone oil (18) from leaking outside of the housing (12). The O-ring (30) is formed by a silicone rubber having a hardness of 25 degrees or above and 45 degrees or less according to the Durometer Hardness Testing (type A) of JIS K 6253.

Abstract: A rotary damper (D) is constituted by: housings (11, 51); a silicon oil (21) being housed inside the housings (11, 51); a rotor (31) wherein a resistive portion (36) moving through the silicon oil 21 inside the housings (11, 51) is provided in an axial portion (32) which is housed inside the housings (11, 51) and projects from the housings (11, 51); and an O-ring (61) preventing the silicon oil (21) from leaking between the axial portion (32) and the housing (51), and multiple arc-like through-bores (37) are provided in the resistive portion (36) on a concentric circle, and depressed grooves (38) communicating with the arc-like through-bores (37) are provided. Accordingly, during the assembly, the air being mixed into the housing is not allowed to be excessively compressed, so that even if the rotor rotates bi-directionally, the noise being caused by the air being mixed into the housing can be prevented.

Abstract: A rotary damper is provided so that air incorporated into a housing during assembly is, not excessively compressed, whereby a generation of a peculiar sound due to the air incorporated into the housing can be prevented even though the rotor rotates in both directions, and so that the air is stopped and captured in a fixed place whereby influence on the generated torque can be reduced, and irregularity of the torque can be reduced progressively. A rotary damper includes a housing (11, 51), silicon oil housed inside the housing (11, 51), a rotor 31 housed inside the housing (11, 51), and having a shaft member (32) projecting from the housing (11, 51) and having a resistance member (36) moving through the silicon oil (21) inside the housing (11, 51), and an O-ring (61) for preventing leakage of the silicon oil (21) from between the shaft member (32) and the housing (51). A circumferential groove (54) is provided on an inner face of the housing (51) facing the resistance member (36).

Abstract: A rotary damper (D) is constituted by: housings (11, 51); a silicon oil (21) being housed inside the housings (11, 51); a rotor (31) wherein a resistive portion (36) moving through the silicon oil 21 inside the housings (11, 51) is provided in an axial portion (32) which is housed inside the housings (11, 51) and projects from the housings (11, 51); and an O-ring (61) preventing the silicon oil (21) from leaking between the axial portion (32) and the housing (51), and multiple arc-like through-bores (37) are provided in the resistive portion (36) on a concentric circle, and depressed grooves (38) communicating with the arc-like through-bores (37) are provided. Accordingly, during the assembly, the air being mixed into the housing is not allowed to be excessively compressed, so that even if the rotor rotates bi-directionally, the noise being caused by the air being mixed into the housing can be prevented.