CAR SEAT LUMBAR SUPPORT UNIT WITH SIMPLIFIED STRUCTURE AND IMPROVED RESPONSIVENESS

A car seat lumbar support unit performs an elevating operation of an upper bracket relative to a lower bracket which determines a degree of curvature of a seat back by using a first motor, a first transfer screw, and a first nut member (first elevating unit) that are easily designed and manufactured, and performs an elevating operation of the lower bracket and the upper bracket which determines a curved position of the seat back by using a second motor, a second transfer screw, and a second nut member (second elevating unit), wherein a rotary cylinder is organically coupled so that the first elevating unit and the second elevating unit are independently operable without being restricted by each other.