Patent ID: 8646789

Claim:
A torsion beam type suspension device comprising left and right trailing arm parts ( 15 ) that extend in a fore-and-aft direction of a vehicle body, have front ends thereof vertically swingably pivoted on the vehicle body, and axially and rotatably support a wheel (W) at a rear end thereof, and a torsion beam part ( 14 ) that extends in a lateral direction of the vehicle body and has opposite ends thereof connected to the left and right trailing arm parts ( 15 ), the trailing arm parts ( 15 ) and the torsion beam part ( 14 ) being formed as a unit by press-forming a tailored blank material ( 13 ) in which end parts of plate materials having different thicknesses are butt-welded via a weld part ( 17 ), characterized in that the torsion beam part ( 14 ) comprises a U-shaped cross section in which front and rear side wall portions ( 32 , 33 ) are connected via a bottom wall portion ( 31 ), the device comprises an upper member ( 16 ) that forms the trailing arm part ( 15 ) and the torsion beam part ( 14 ) and a lower member ( 18 ) that is welded to the upper member ( 16 ) to form a closed cross section straddling the weld part ( 17 ), and the lower member comprises a first extending portion ( 18 b ) that extends into an interior of the torsion beam part ( 14 ) and is welded to inner faces of the front and rear side wall portions ( 32 , 33 ), and the first extending portion ( 18 b ) is inclined upward so as to be closer to the bottom wall portion ( 31 ) toward the vehicle body center line.