Vibration damping device for vehicle body

A vibration damping device for a vehicle body, the vibration damping device comprising:

• a first hydraulic damper including a first end portion attached to a first attachment position of a vehicle body;
• and
• a second hydraulic damper coupled to a second end portion of the first hydraulic damper via a linking member, a first end portion of the second hydraulic damper, which is opposite to a second end portion coupled to the linking member, attached to a second attachment position of the vehicle body;
• wherein
• each of the first hydraulic damper and the second hydraulic damper includes:
• a hydraulic cylinder including an oil chamber filled with oil;
• a piston movably fitted in the hydraulic cylinder and that partitions the oil chamber into a first oil chamber and a second oil chamber;
• a piston rod connected to the piston and projecting from one end portion of the hydraulic cylinder;
• a free piston movably fitted in the hydraulic cylinder and that partitions the hydraulic cylinder into a gas chamber filled with a high-pressure gas and the oil chamber to pressurize the oil in the oil chamber;
• a spring that cancels an axial-direction force acting on the piston rod due to a difference between pressure-receiving areas of two surfaces of the piston;
• a working oil passage that allows the first oil chamber and the second oil chamber to communicate with each other;
• and
• a throttle in the working oil passage;
• the first hydraulic damper, the second hydraulic damper, and the linking member are aligned in a longitudinal direction of the vibration damping device;
• one of the hydraulic cylinder and the piston rod of the first hydraulic damper is coupled to the linking member, and the other of the hydraulic cylinder and the piston rod of the first hydraulic damper is attached to the first attachment position;
• one of the hydraulic cylinder and the piston rod of the second hydraulic damper is coupled to the linking member, and the other of the hydraulic cylinder and the piston rod of the second hydraulic damper is attached to the second attachment position;
• the linking member includes a round metal rod having a thickness that is greater than a thickness of the piston rod of the first hydraulic damper and a thickness of the piston rod of the second hydraulic damper;
• the round metal rod includes two flat surfaces on opposite circumferential sides of the round metal rod;
• and
• a first lock nut fastens a connecting portion between the linking member and the one of the hydraulic cylinder and the piston rod of the first hydraulic damper, and a second lock nut fastens a connecting portion between the linking member and the one of the hydraulic cylinder and the piston rod of the second hydraulic damper.