Patent ID: 7798296

Claim:
A damper device comprising: a casing comprising a cylindrical inner circumferential surface and an opening; a shaft body located in a cylindrical space of the casing and supported in a freely turnable manner; a cover adapted for sealing the casing; viscous fluid which is stored in a sealed space formed between the shaft body and the casing; and a metal washer disposed between the casing and the cover; wherein the metal washer is made of material different from the cover; wherein the cylindrical inner circumferential surface of the casing comprises: a first inner circumferential surface which forms the sealed space in which the viscous fluid is stored; a second inner circumferential surface which faces a large diameter part of the shaft body; and a third inner circumferential surface along which an insert part formed in the cover is inserted into the casing; wherein the casing further comprises: a first engagement part which (1) is formed on an axially facing surface of a step on the third inner circumferential surface of the casing, (2) engages with the cover, and (3) is used as an ultrasonically welded part with the cover; and a second engagement part which is formed on an axially facing surface of a step between the second inner circumferential surface and the third inner circumferential surface of the casing at a position, in an axial direction of the shaft body, so as to be further from the opening of the casing than the first engagement part, and which is used as a positioning part in the axial direction for the cover; wherein the shaft body further comprises: a large diameter part which is positioned, in the axial direction, so as to be further from the opening of the casing than the second engagement part of the casing; and an O-ring for sealing is disposed between the second inner circumferential surface of the casing and the large diameter part of the shaft body; and wherein the metal washer is disposed between the second engagement part of the casing and the cover, so that a position of the cover, in the axial direction, is determined by the second engagement part of the casing via the metal washer when the first engagement part is ultrasonically welded with the cover.