This invention relates in general to vehicular seats which helps the driver and/or passenger feel more comfort and less fatigue. In particular, this invention relates to automotive seats with a mobile seat back which is adjustable to the contours of the driver's body, and which thereby reduces fatigue of the driver and results in a more comfortable ride.
In general, automotive seats have been designed in such ways that minimize the fatigue of the driver during driving, i.e., the seat backs have been designed with optimum stress-strain relationship. It has been reported that positioning a vehicle seat back in the position shown in FIG. 4 such that the maximum stress range (the stress of 60 g/cm.sup.2 range in the Figure) is located at the second and third lumbar vertebra gives a driver minimum fatigue and maximum comfort during driving. However, such seat back designs fit the body contour of an average driver, and depending upon body contours of individual drivers and the reclining angle of the particular seat, deviation from the optimum stress distribution takes place, thus increasing fatigue and discomfort of the driver. In addition, even if the driver sits in the optimum seating configuration, sitting in the same position for prolonged time causes constant stress on the same parts of the body, which often leads to fatigue and discomfort of the driver.