Effect of lumbar support on vibration transmission of a car seat with occupant exposed to fore-and-aft whole-body vibration

Modern car seats are often equipped with adjustable lumbar supports for reducing fatigue and improving ride comfort in different driving conditions. Studies on the effect of lumbar support on seat dynamic performance and ride comfort are not often seen. This experimental study was designed to investigate how lumbar support affects static and dynamic characteristics of the driver seat of a sport utility vehicle. The load-deflection curves of the backrest cushion of the car seat were measured in three extra lumbar support conditions (regarded as “No”, “Half” and “Full” lumbar supports). The acceleration transmissibilities to the backrest and to the seat pan in the fore-and-aft direction with different lumbar support conditions were measured with 8 male subjects exposed to random fore-and-aft vibration from 1 to 30 Hz with three magnitudes (0.25, 0.5, 1.0 ms-2 r.m.s), using a Multi-Axis Simulation Table. It was found that the lumbar area of the backrest became stiffer with increased extra lumbar support. The peak at the resonance of the acceleration transmissibility from the seat base to the backrest decreased, while that in the transmissibility from the seat base to the seat pan increased, when increasing the lumbar support. The softening effect was also apparent with increasing vibration magnitude. It is anticipated that changing the lumbar support will affect the static comfort of the seat and also the vibration transmission through the seat to occupant.