Suspension cross member

1. A suspension cross member adapted to be attached to an underside of a vehicle body in such a manner as to extend in a transverse direction of a vehicle, comprising:

upper and lower member plates disconnected from each other in a vicinity of bifurcation proximal end portions at ends of the suspension cross member where the suspension cross member extends to be bifurcated into a forward portion located on a longitudinally forward side of the suspension cross member and a rearward portion located on a longitudinally rearward side of the suspension cross member to define openings and which are joined together along circumferential edges thereof to thereby have a closed cross section;

support points for forward arms of a pair of lower arms that support wheels, the support points disposed on the forward portions of the upper and lower member plates at external positions to the closed cross section, respectively;

support points for rearward arms of the pair of lower arms which are inserted through the openings, the support points disposed on the rear portions at internal positions of the closed cross section, respectively; and

bulkheads provided between the upper and the lower member plates transversely and inwardly of the support points for the rearward arms in such a manner that a circumferential edge of each of the bulkheads extends longitudinally to a rear of the vehicle from a disconnection initiating point located on a forward arm side of the opening along inner sides of the upper and the lower plate members and each of the bulkheads being welded to the upper and lower plate members.

2. The suspension cross member as set forth in claim 1 , wherein opening dimensions of the opening increase gradually in the vicinity of the disconnection initiating point.

3. The suspension cross member as set forth in claim 1 , wherein a circumferential flange is provided along the circumferential edge of a bulkhead in such a manner as to extend toward the opening over a predetermined range including a location corresponding to the disconnection initiating point, the circumferential flange so provided is joined to the upper member plate and the lower member plate.

4. The suspension cross member as set forth in claim 1 , wherein said each of the bulkheads is welded to the upper and the lower member plates at least in the vicinity of the disconnection initiating point.

5. The suspension cross member as set forth in claim 1 , wherein a rear end of a bulkhead is welded to an inner surface of a rear wall of the upper and lower member plates.

6. A suspension cross member adapted to be attached to an underside of a vehicle body in such a manner as to extend in a transverse direction of a vehicle, comprising:

upper and lower member plates disconnected from each other in a vicinity of bifurcation proximal end portions at ends of the suspension cross member where the suspension cross member extends to be bifurcated into a forward portion located on a longitudinally forward side of the suspension cross member and a rearward portion located on a longitudinally rearward side of the suspension cross member to define openings and which are joined together along circumferential edges thereof to thereby have a closed cross section;

support points for forward arms of a pair of lower arms that support wheels, the support points disposed on the forward portions of the upper and lower member plates at external positions to the closed cross section, respectively;

support points for rearward arms of the pair of lower arms which are inserted through the openings, the support points disposed on the rear portions at internal positions of the closed cross section, respectively;

bulkheads provided between the upper and the lower member plates transversely and inwardly of the support points for the rearward arms in such a manner that a circumferential edge of each of the bulkheads extends longitudinally to a rear of the vehicle from a disconnection initiating point located on a forward arm side of the opening along inner sides of the upper and the lower plate members so as to be welded to the upper and lower plate members; and

support members each of which is provided between the upper and the lower member plates in such a manner that the support member is joined at one end thereof to a bulkhead in the vicinity of the disconnection initiating point and extends longitudinally toward the front of the vehicle along the inner sides of the upper and the lower member plates so as to be joined to the upper and the lower member plates.

7. A suspension cross member adapted to be attached to an underside of a vehicle body in such a manner as to extend in a transverse direction of a vehicle, comprising:

upper and lower member plates which are disconnected from each other in the vicinity of bifurcation proximal end portions at ends of the suspension cross member where the suspension cross member extends to be bifurcated into a forward portion located on a longitudinally forward side of the suspension cross member and a rearward portion located on a longitudinally rearward side of the suspension cross member to define openings and which are joined together along circumferential edges thereof to thereby have a closed cross section;

support points for forward arms of a pair of lower arms that support wheels, the support points disposed on the forward portions of the upper and lower member plates at external positions to the closed cross section, respectively;

support points for rearward arms of the pair of lower arms which are inserted through the openings, the support points disposed on the rear portions at internal positions of the closed cross section, respectively; and

bulkheads provided between the upper and the lower member plates transversely and inwardly of the support points for the rearward arms in such a manner that a circumferential edge of each of the bulkheads extends longitudinally to a rear of the vehicle from a disconnection initiating point located on a forward arm side of the opening along inner sides of the upper and the lower plate members so as to be joined to the upper and lower plate members, each of the bulkheads being joined to the upper and the lower member plates at least in the vicinity of the disconnection initiating point; and

support members each of which is provided between the upper and the lower member plates in such a manner that the support member is joined at one end thereof to the bulkhead in the vicinity of the disconnection initiating point and extends longitudinally toward the front of the vehicle along the inner sides of the upper and the lower member plates so as to be joined to the upper and the lower member plates.