Patent ID: 7540562
Filing Date: 2009-06-02
Classification: B60N

Abstract:
1. A structure of a seat back of a vehicle seat in combination with a headrest, wherein said headrest has a stay portion and is displaceable between a home position where the headrest normally supports a head of a seat occupant on the vehicle seat and an upward displaced point to which the headrest is to be displaced upward from said home position, wherein a pressure receiving element is movably provided in the seat back, wherein a biasing means having a predetermined biasing force is provided, so that said headrest is normally biased by said biasing means to said home position, and wherein, in case of a rear-end collision, upon a load in excess of said predetermined biasing force being applied in a direction back from the seat back of said pressure receiving element under inertia of said seat occupant, the headrest is caused to displace from said home position to said upward displaced point, wherein said seat back has a seat back frame provided therein, said seat back frame comprising: an upper frame member defined upward from the seat back; and right-side and left-side lateral frame members extending downward from said upper frame member; wherein a pair of right-side and left-side rotating links, each having a first pivotal point, a second pivotal point, and a third pivotal point, are pivotally connected, at the respective first pivotal points thereof, with said right-side and left-side lateral frame members of said seat back frame, wherein a support shaft is rotatably connected between said second pivotal point of one of said pair of right-side and left-side rotating links and said second point another of said pair of right-side and left-side rotating links, such that rotation of said pair of right-side and left-side rotating links about the respective first pivotal points causes vertical displacement of said support shaft along an arcuate path relative to said first pivotal points, wherein a holder bracket of a cylindrical configuration is integrally provided to said support shaft; wherein a stay portion of said headrest is inserted and retained in said holder bracket; wherein a guide element is fixed on said upper frame member of said seat back frame, with such an arrangement that said holder bracket is slidingly movable and inclinable through said guide element, and that, when said pair of right-side and left-side rotating links are rotated due to said load in excess of said predetermined biasing force, said holder bracket is moved through said guide element in a direction upward of said seat back frame, so that said headrest is displaced to said upward displaced point, while being inclined relative to said guide element in a direction forward of said seat back frame; wherein a cross pressure-receiving element is provided for receiving a load to be applied from a dorsal part of said seat occupant; wherein a pair of right-side and left-side actuator link assemblies are provided, each being of such a type wherein the body thereof is stretchable and contractible, and having an upper end portion disposed at the upper region of the seat cushion frame; wherein said cross pressure-receiving element is operatively connected with said pair of right-side and left-side actuator link assemblies; wherein said upper end portion of each of said pair of right-side and left-side actuator link assemblies is pivotally connected with said third pivotal point associated with each of said pair of right-side and left-side rotating links at a point below said support shaft, with such an arrangement that, upon receiving said load applied from said dorsal part of said seat occupant, said cross pressure-receiving element is forcibly displaced in a direction backwardly of said seat back frame, which causes said pair of right-side and left-side actuator link assemblies to stretch to thereby cause said rotation of said pair of right-side and left-side rotating links to displace said headrest to said upward displaced point, and that, upon arrival of the headrest at the upwardly displaced point, said pair of right-side and left-side support link assembles are stretched to an extent of acting upon said pair of right-side and left-side rotating links so as to retain said headrest at said upward displaced point; and wherein said first and second pivotal points of each of said pair of right-side and left-side rotating links are arranged in such a manner that, when said headrest reaches said upward displaced point, said pair of right-side and left-side rotating links are rotated by an angle of rotation relative to the respective first pivotal points, with the second pivotal points being located at a predetermined position with respect to said angle of rotation, at which time, upon another load being applied in a direction backward from the seat back towards and exerted on said headrest, a corresponding force is transmitted to said second pivotal points respectively of said pair of right-side and left-side rotating links through said headrest, said stay portion, said holder bracket and said support shaft, thus generating a component force of said another load at said second pivotal points, and at the same time, said component force is applied in a direction to said first pivotal points respectively of said pair of right-side and left-side rotating links and blocked thereby, which attempts to retain said second pivotal points at said predetermined position, so that said headrest is retained at said upward displaced point against said predetermined biasing force of said biasing means.