Abstract: A housing body of an axle housing is produced by: bending widthwise opposite portions of a sheet material having a substantially developed shape of the axle housing, bending inwards edge portions adjacent to widthwise opposite sides of the sheet material, and forming two longitudinally opposite end portions of the sheet material into a tubular shape. Further, a generally rhombic opening is formed in a longitudinally middle portion of the sheet material. The axle housing is produced by mounting a generally rhombic cover plate onto the housing body so as to cover the opening.

Abstract: The invention provides a method of manufacturing an irregular section tubular body and axle beam. The axle beam has a tubular worked body that has sealed liquid therein and is press-formed by upper and lower press molds. One of the press molds has a convex mold portion to form a concave portion concaved in an axis perpendicular direction at an axial part of the axle beam. The press-forming of the tubular worked body is completed by a one stroke process using liquid pressure that increases as the internal volume of the worked body decreases due to formation of the concave portion. The concave portion extends substantially the length of the axle beam and has a substantially U-shaped or V-shaped cross-section forming a closed and sealed space.

Abstract: The present invention intends to provide a manufacturing method of an irregular-section tubular body in which a manufacturing process is simplified, and complexing and large-sizing of an equipment, and increase of an equipment cost are avoided.

Abstract: A suspension arm in which the accuracy of a bush supporting portion is improved. The suspension arm is formed by respectively welding both side portions of an upper plate member and both side portions of a lower plate member to each other, the upper plate member and the lower plate member each having a substantially U-shaped cross-sectional configuration. The bush supporting portion is formed in such a manner that an upper cylindrical portion and a lower cylindrical portion are respectively formed by burring at rear ends of the upper plate member and the lower plate member. Further, clearances are respectively formed between the side portions of the upper plate member and the upper cylindrical portion, and between the side portions of the lower plate member and the lower cylindrical portion.

Abstract: In a suspension arm formed by press working a plate-shaped member, in a case in which, while a vehicle is traveling, a load is inputted to the suspension arm in a direction intersecting a direction in which the suspension arm swings, at least a region at which a maximum stress is generated is a non-end portion of the plate-shaped member. Accordingly, high rigidity can be ensured without an increase in weight.