FLOW PATH STRUCTURE AND DEVICE TO INCREASE THE DEGREE OF FREEDOM FOR TUNING THE DAMPING FORCE OF SEMI ACTIVE DAMPER FOR AUTOMOBILE

The present invention relates to a flow path structure and a device to increase the tuning degree of freedom in damping force of a semi-active damper for a vehicle. A flow path structure which can generally be applied to the existing piston-cylinder type fluid damper is formed, and a device to tune damping force is added. According to a relative motion between a piston rod and a damper cylinder, a piston descends during a compression stroke but ascends during a tension stroke, and in this instance, the flow path structure is changed in accordance to the structure of the damper; and in accordance to the inflow and outflow characteristics of a damping fluid flowing in the flow path, compression damping force and tension damping force are generated. The present invention proposes a method and an apparatus to separately control compression damping force and tension damping force by forming a new side flow path structure added to the flow path structure of the existing damper and mounting a flow path opening and closing means or a check valve. Therefore, the present invention solves several problems that the compression damping force and the tension damping force cannot separately be controlled because the existing semi-active damper having a damping force variable valve cannot change the ratio of tension damping force to compression damping force and that the semi-active damper cannot satisfy changes in driving situations or a driver′s taste due to the unnecessary restriction in the tuning degree of freedom, and reduces the costs to solve such problems and maximizes its effect because there is no need to add expensive damping force variable valve to solve such problems.