Damper

1. A damper comprising:

a damper body that includes a piston head and a cylinder into which the piston head is slidably fitted such that the piston head divides an inner space of the cylinder into a first fluid chamber and a second fluid chamber each having a fluid filled therein;

a piston rod one end of which is fixed to the piston head and which is disposed in at a side of the second fluid chamber such that the piston head has,

a first surface which is in contact with the fluid in the first fluid chamber, and

a second surface which is in contact with the fluid in the second fluid chamber and which has surface area different than that of the first surface;

a spring provided to the damper body so as to generate an oscillation input to the damper;

a communicating path via which the first fluid chamber is in a fluid communication with the second fluid chamber, the communication path being disposed outside the cylinder and allowing the fluid to flow through the communication path;

a fluid pump provided to the communicating path;

an electromagnetic motor operatively connected to the fluid pump so as to receive the oscillation input from the spring and so as to regenerate an energy from the oscillation input and apply the energy as damping force to the spring through the fluid pump; and

a polarized capacitor having a positive electrode side electrically connected to an electrode of the electromagnetic motor, at which output voltage from the electromagnetic motor is positive when the piston head moves toward a side of the first fluid chamber side and at which the output voltage from the electromagnetic motor is negative when the piston head moves toward a side of the second fluid chamber side.

2. The damper according to claim 1 ,

wherein the damper is configured to compose an LC resonant circuit by an inductance of the electromagnetic motor and a capacitance of the capacitor.

3. The damper according to claim 2 ,

wherein the damper has a sprung resonant frequency above the spring and an unsprung resonant frequency below the spring, and

wherein an electrical resonant frequency defined by the inductance of the electromagnetic motor and the capacitance of the capacitor is set to a value within ±20% of the unsprung resonant frequency so as to suppress both an oscillation component to the sprung resonant frequency and an oscillation component to the unsprung resonant frequency.

4. The damper according to claim 1 , further comprising an electrical load which is connected to the capacitor.