Lumbar support device

Abstract

An object of the present invention is to provide a lumbar support device in which a driving unit is not to be large. The lumbar support device includes: a seat back frame ( 7 ) that has horizontal portions ( 7 j, 7 k ) extending in a horizontal direction and is provided on the seat back for supporting a back of a seated person; a curved plate ( 23 ) that has hinge portions ( 23 b ) provided at one end portion so as to be rotatably engaged with the horizontal portions ( 7 j, 7 k ); and a driving mechanism ( 9 ) which is provided on the seat back frame ( 7 ) and is connected to the other end portion of the curved plate ( 23 ) and which makes the other end portion approach and separate from the one end portion to change the degree of curvature of the curved plate ( 23 ).

1 . A lumbar support device comprising:
 a seat back frame, which has a horizontal portion extending in a horizontal direction and is provided on a seat back for supporting a back of a seated person;   a curved plate, which is provided with a hinge portion to be rotatably engaged with the horizontal portion at one end portion; and   a driving mechanism, which is provided on the seat back frame and is connected to the other end portion of the curved plate and which makes the other end portion approach and separate from the one end portion to change the degree of curvature of the curved plate.   
     
     
         2 . The lumbar support device according to  claim 1 ,
 wherein the hinge portions is formed integrally with the curved plate, and   wherein the hinge portions is a groove into which the horizontal portions of the seat back frame is inserted from an opening.   
     
     
         3 . The lumbar support device according to  claim 2 , further comprising:
 a retaining portion, which has elasticity and face the opening of the grooves with spaces interposed therebetween and which are elastically deformed to allow the horizontal portions of the seat back frame to be inserted into the grooves, and which prohibit the horizontal portions of the seat back frame from leaving from the grooves in a normal state.   
     
     
         4 . The lumbar support device according to  claim 1 ,
 wherein the connection of the driving mechanism with the other end portion of the curved plate is a hinge connection.   
     
     
         5 . The lumbar support device according to  claim 1 ,
 wherein the driving mechanism has a threaded rod and a nut member,   wherein one of the threaded rod and the nut member is attached to the seat back frame,   wherein the other of the threaded rod and the nut member is attached to the curved plate,   wherein a rod extending in a direction intersecting with the threaded rod is provided, on the member attached to the curved plate, and   wherein the curved plate has a hole into which the rod is loosely fit.