HARDNESS ADJUSTMENT UNIT, SEAT, AND SEAT ADJUSTMENT SYSTEM

A hardness adjustment unit includes an elastic frame, a barrier, and a field generator. An enclosed space is provided inside the elastic frame and filled with a fluid filling. The barrier is arranged in the enclosed space and divides the enclosed space into an upper space and a lower space. The upper space communicates with the lower space. The field generator is arranged outside the elastic frame and used to apply a field to the fluid filling to adjust a viscosity of the fluid filling, thereby adjusting a flow damping of the fluid filling in the upper space and the lower space to control a deformation of the elastic frame.