To provide an air spring which sufficiently swells the central portion of a diaphragm and stabilizes its performance at a low cost.
Ring shape fittings 3, 4 are attached to a forming drum having a ball shape portion to spherically swell. Inside surface unvulcanized rubber 9a is wound on the ball shape portion of the forming drum. A reinforcing cord 10 is spread on the ring shape fitting 3, 4 at a specified tilting angle (β) along the outside surface of the inside surface unvulcanized rubber 9a. A reinforcing cord layer 8 is formed by repeatedly spreading the reinforcing cord 10 so as to be arranged circumferentially while tilting the reinforcing cord 10 with respect to the central axis of the ring shape fitting 3, 4. A cylindrical unvulcanized rubber membrane 9 is composed by winding outside surface unvulcanized rubber 9b outside the reinforcing cord layer 8. The unvulcanized rubber membrane 9 is vulcanized and formed while lengthening/shortening an axial length (B) and enlarging the outside diameter (d) at the central portion by changing the tilting angle and the pitch of the reinforcing cord 10.
UETSUBO KAZUHARU
OSHIKATA MITSUO
Shuzo Hinode
Seiji Goto
Junko Ohara