Seal Structure for Fuel Cell and Method for Producing Same

Abstract

A seal structure for impregnating the circumferential edge of a GDL constituting an MEA with a rubber composing a seal lip line in which lowering in power generation capacity is suppressed by controlling the width of a rubber impregnation region for the circumferential edge of the GDL appropriately, thereby preventing the MEA reaction region from becoming narrow. In order to achieve the purpose, an MEA ( 2 ) arranged between a pair of separators ( 5 ), a rubber sheet ( 6 ) arranged on its planar extension on the outer circumferential side of the MEA ( 2 ), and a gasket-like lip line ( 7 ) formed on the opposite sides of the rubber sheet ( 6 ) integrally therewith to be close contact with the separators ( 5 ) are provided. At the circumferential edge of the MEA ( 2 ), a rubber impregnated portion ( 8 ) for integrating the rubber sheet ( 6 ) with the MEA ( 2 ) when the GDL ( 4 ) constituting the MEA ( 2 ) is impregnated with a part of the rubber composing the rubber sheet ( 6 ) is provided. On the immediately inner circumferential side of the rubber impregnated portion ( 8 ) in the plane of the MEA ( 2 ), a GDL constricted portion ( 9 ) for regulating the rubber impregnated portion is provided.

1 . A seal structure for the fuel cell comprising;
 a membrane-electrode assembly (MEA) provided between a pair of separators;
 a rubber sheet provided on a plane extending from the MEA and at the outer peripheral side of the MEA; 
 lip lines which have gasket configuration, are integrally formed on the respective surfaces of the rubber sheet and are closely contacted with the separators; 
 rubber impregnated portions which are provided at the periphery of said MEA to integrate said rubber sheet and said MEA by a part of rubber constituting said rubber sheet being impregnated into gas diffusion layers (GDLs) constituting said MEA; and 
 GDL narrowed portions provided immediately inner peripheral side of said rubber impregnated portions in a plane with the MEA to define a rubber impregnated area of said rubber. 
   
   
   
       2 . A The seal structure as claimed in  claim 1 , wherein distance restricting portions are formed integrally with the rubber sheet at both or at least one of inner peripheral side and outer peripheral side of the lip lines to define distance (c) between the separators by said portion being held by a pair of the separators when assembling a stack. 
   
   
       3 . The method for producing the seal structure as claimed in  claim 1 , comprising steps of:
 preparing a mold comprising split molds which have step-like pressing portions facing to each other in order to form the GDL narrowed portions by compressing of parts of the GDLs to reduce thickness of the parts at a time of mold clamping;   inserting the MEA, with which the rubber sheet is to be molded, into the mold; and carrying out injection molding to form the rubber sheet under a condition of the parts of the GDLs being compressed to reduce the thickness by the pressing portions formed in the mold.   
   
   
       4 . The method for producing the seal structure as claimed in  claim 3 , wherein the GDLs are compressed by the pressing portions at a compressibility ratio of 30-50%, while being compressed by portions other than the pressing portions of the mold at a compressibility ratio of 0-20%.