Patent ID: 8240679

Claim:
A suspension system for a vehicle, comprising: (a) a suspension spring disposed between sprung and unsprung portions of the vehicle; (b) a hydraulic damper disposed in parallel with said suspension spring, and configured to generate a damping force against displacement of the sprung and unsprung portions relative to each other such that an amount of the damping force is changeable by a damping force changer that is included in said damper; (c) a displacement force generator disposed in parallel with said suspension spring, and configured to generate, based on a motor force generated by an electromagnetic motor that is included in said displacement force generator, a displacement force causing the sprung and unsprung portions to be displaced toward or away from each other; and (d) a controller including a damping-force controlling portion configured to control said damping force changer, so as to control the damping force that is to be generated by said damper, and a displacement-force controlling portion configured to control actuation of said electromagnetic motor, so as to control the displacement force that is to be generated by said displacement force generator, wherein said displacement-force controlling portion is configured to execute a sprung-portion vibration damping control for controlling the displacement force that is to be generated by said displacement force generator, such that the generated displacement force acts as a damping force against sprung-portion vibration which occurs in the sprung portion, and wherein said damping-force controlling portion is configured, upon execution of the sprung-portion vibration damping control by said displacement-force controlling portion, to execute a damping force reducing control for reducing the damping force that is to be generated by said damper, depending on unsprung-portion resonance frequency vibration which occurs in the vehicle and which has a resonance frequency of the unsprung portion, such that the damping force generated by said damper is made smaller in a low intensity situation in which an intensity of the unsprung-portion resonance frequency vibration is not higher than a threshold intensity value, than in a high intensity situation in which the intensity is higher than the threshold intensity value.