公开(公告)号：EP0944292A2

公开(公告)日：1999-09-22

申请号：EP99105479.2

申请日：1999-03-17

申请人： PIONEER ELECTRONIC CORPORATION ,  TOHOKU PIONEER ELECTRONIC CORPORATION

发明人： Sato, Masatoshi c/oTOHOKU PIONEER ELECTRONIC CORP. ,  Mitobe, Kunio c/oTOHOKU PIONEER ELECTRONIC CORP.

IPC分类号： H04R7/00

CPC分类号： H04R7/10 ,  H04R31/003 ,  H04R2307/029

摘要： An inorganic or organic filler in an amount of 3 to 30 % by weight is added to a resin containing a foaming agent. The resulting resin mixture material is injection molded into a loudspeaker diaphragm (1) having a three-layer structure in which a foamed layer (3) is covered with unfoamed skin layers (2). For forming the three-layer structure, a resin mixture material of polypropylene containing a foaming agent is injected into a cavity of a mold (20). Immediately after the injection and the completion of forming the skin layers (2), the mold (20) is separated so that the material may start foaming at its inside to form the foamed layer (3). Since the surfaces of the resin mixture material are in contact with the inner surfaces of the mold in the injection, the surfaces of the resin mixture material have solidified before the foaming takes place, so as to form the unfoamed skin layers (2). By adjusting the filler to the appropriate content, the loudspeaker diaphragm (1) is improved in appearance quality while keeping the other physical properties with favourable characteristics.