Emergency locking seat hinge device and vehicle seat using the same

An emergency locking seat hinge device, comprising:

• a seat bottom bracket adapted to be attached to a seat bottom and defining an annular recess therein;
• a seat back bracket adapted to be attached to a seat back and pivotally attached to said scat bottom bracket about an axial center of said annular recess;
• an inner cam member integrally attached to said seat back bracket and received in said annular recess so as to jointly define a plurality of chambers each having a relatively wide central part and end parts which get progressively narrower circumferentially away from said central part;
• a plurality of rolling members each received in a corresponding one of said chambers, each rolling member being dimensioned so as to be narrower than said central part but wider than said end parts;
• a disk member which is pivotally and coaxially supported by said seat back bracket and provided with a plurality of projections for engaging each of said rolling members;
• spring members provided between said disk member and said inner cam member for producing a circurmferential centering spring force therebetween which resiliently retains said rolling members in said wide central parts via said projections of said disk member;
• and
• an acceleration sensitive locking device which engages said disk member with respect to said seat bottom bracket upon detection of an acceleration or deceleration exceeding a prescribed level.