Abstract: A torsion beam type suspension device is provided in which a trailing arm part and a torsion beam part are formed as a unit by press-forming a tailored blank material in which end parts of plate materials having different thicknesses are butt-welded via a weld part. A weld part of the tailored blank material comprises a U-shaped cross section in which front and rear side wall portions are connected via a bottom wall portion, and a pair of cutouts are formed at the edge of each of the side wall portions at positions sandwiching the weld part, and therefore, when the torsion beam part is twistedly deformed, shifting the concentration of stress from the weld part to the cutout enables peeling apart of the weld end part to be prevented and the durability of the torsion beam type suspension device to be enhanced.

Abstract: A torsion beam type suspension device is provided in which a trailing arm part and a torsion beam part are formed as a unit by press-forming a tailored blank material in which end parts of plate materials having different thicknesses are butt-welded via a weld part. A weld part of the tailored blank material comprises a U-shaped cross section in which front and rear side wall portions are connected via a bottom wall portion, and a pair of cutouts are formed at the edge of each of the side wall portions at positions sandwiching the weld part, and therefore, when the torsion beam part is twistedly deformed, shifting the concentration of stress from the weld part to the cutout enables peeling apart of the weld end part to be prevented and the durability of the torsion beam type suspension device to be enhanced.

Abstract: In an arrangement for retaining an outer collar (13) of a compliance bush assembly, an internal bore of a corresponding retaining collar (9) which may be welded to a front end of a trailing arm (2, 3) is provided with an increased diameter portion (20) defining an annular step (21) adjacent to a leading axial end thereof at the time of the press fitting process. When the outer collar is press fitted into the internal bore of the retaining collar, the part of the outer collar facing the increased diameter portion is allowed to bulge out as a result of creep deformation. Thus, even when the outer collar undergoes a creep deformation, and this causes the pressure acting between the outer collar and retaining collar to diminish, the part of the outer collar facing the increased diameter section that has bulged out prevents the outer collar from shifting or dislodging from the retaining collar.