Damping force variable valve assembly

A damping force variable valve assembly, which is installed in a damping force variable shock absorber to adjust a damping force of the shock absorber, the damping force variable valve assembly comprising:

• a solenoid configured to generate a magnetic force when an electric current is applied thereto;
• a spool configured to be moved by the magnetic force of the solenoid;
• a spool guide configured to surround the spool so as to guide a movement of the spool;
• a valve body which is installed in the spool guide;
• a main valve which is installed to cover a main passage formed in the valve body and generate a damping force;
• a back pressure chamber which is formed to have a back pressure pressurizing the main valve from the back of the main valve;
• a chamber forming body which is installed outside the valve body to form the back pressure chamber;
• and
• an elastic opening/closing portion which is installed in the valve body to open and close a pressure adjustment passage communicating the inside of the back pressure chamber with the outside of the back pressure chamber,
• wherein as an inner passage within the damping force variable valve assembly is changed by interaction between the spool and the spool guide, the damping force of the shock absorber is variable between a hard mode in which the back pressure of the back pressure chamber is increased and a soft mode in which the back pressure of the back pressure chamber is decreased, and
• in a case where a flow velocity of a working fluid is low in the hard mode, the elastic opening/closing portion opens the pressure adjustment passage when an internal pressure of the back pressure chamber exceeds a preset pressure.