Frame structure for buggy, method of manufacturing frame structure, and jig for use in manufacturing frame structure

摘要

A pair of front and rear arm brackets for supporting swing arms extends between and is integrally joined to a pair of laterally spaced lower frames, and a steering bracket for supporting a steering shaft is disposed between the front and rear arm brackets and between the lower frames, and is integrally joined to the front and rear arm brackets and the lower frames. The front and rear arm brackets and the steering bracket are assembled and welded together into a lower component before being joined to the lower frames. The lower component is positioned on a positioning table, and then positioned with respect to the lower frames by a setting jig for high positional accuracy. The setting jig has lateral cylinder units for laterally gripping the arm brackets and front and rear cylinder units having positioning pins for being inserted into attachment holes defined in the arm brackets to position the arm brackets. The setting jig also has a vertical cylinder unit having a piston rod which can be inserted into a holder hole defined in the steering bracket. The piston rod has projecting plungers which engage and press the lower component against the lower frames when the piston rod is retracted. With the lower component thus pressed against the lower frames, contacting portions thereof are welded to each other for keeping the attachment holes and the holder holes at a desired level of positional accuracy.