Lumbar support device

Abstract

A lumbar support device for a vehicle seat is comprised a seat back frame comprising the side frames and an upper frame connecting an upper portion of each side frame, a spring member, and a support body supporting a part of the spring member so as to be movable in front and back directions relative to the seat back by a drive device. The lumbar support device also includes a retracting restriction mechanism disposed between the support body and the drive device or between the support body and the spring member to prevent the spring member from moving backward relative to the seat back when a load applied to the spring member is equal to or more than a predetermined value.

What is claimed is:  
     
         1 . A lumbar support device for a vehicle seat comprising; 
 a seat back frame comprising a pair of side frames located right and left sides of a seat back and extending in a vertical direction relative to the seat back and an upper frame connecting an upper portion of each side frame;    a spring member provided in an inner space of the seat back frame;    a support body supporting a part of the spring member so as to be movable in front and back directions relative to the seat back by a drive device; and    a retracting restriction mechanism disposed between the support body and the drive device or between the support body and the spring member to prevent the spring member from moving backward of the seat back when a load applied to the spring member is equal to or more than a predetermined value.    
     
     
         2 . A lumbar support device as recited in  claim 1 , wherein the retracting restriction mechanism includes a leaf spring which is fixed to the support body, a support plate which is connected to the support body through the leaf spring and which moves the spring member and a stopper which is disposed between the leaf spring and the support plate and which is able to contact with the leaf spring and the support plate when the load applied to the spring member is equal to or more than the predetermined value.  
     
     
         3 . A lumber support device as recited in  claim 2 , wherein the support plate includes a projection which is projected toward the support body and which is contacted with the support body when the load applied to the spring member is equal to or more than the predetermined value.  
     
     
         4 . A lumbar support device as recited in  claim 1 , wherein the retracting restriction mechanism includes an arm which is fixed to the support body, a support spring which is disposed between the support body and the drive device so as to urge the support body in the front direction of the seat back relative to the drive device and a stopper which is disposed between the arm and the drive device and which is able to contact with the arm and the drive device when the load applied to the spring member is equal to or more than the predetermined value.