Suspension device

1. A suspension apparatus for a vehicle, comprising:

a shock absorber which includes a motor having a stator coupled with one of sprung and unsprung members of the vehicle and a rotor rotatable in relation to the stator, wherein, due to an inductive electromotive force generated when the rotor is rotated as a result of approaching and separating motions between the sprung and unsprung members, an induction current flows through the motor, whereby a damping force is generated;

an electric circuit which establishes electrical connection between a first electricity supply terminal of the motor and a second electricity supply terminal of the motor; and

an electrical characteristic adjustment part which adjusts an electrical characteristic of the electric circuit so as to reduce an inertia corresponding current which is a current flowing through the motor and which represents an inertial force of a rotation body which includes at least the rotor and which rotates as a result of the approaching and separating motions between the sprung and unsprung members, wherein

the electrical characteristic adjustment part comprises:

an inverting amplification circuit which includes an operational amplifier, an input resistor, and a feedback resistor, the operation amplifier having an inverting input terminal connected to the first electricity supply terminal of the motor, a non-inverting input terminal connected to the second electricity supply terminal of the motor, and an output terminal; and

an inertia compensation capacitor connected to the output terminal, and wherein

the input resistor is connected to the inverting input terminal, and

the feedback resistor is provided between the output terminal and the inverting input terminal.

2. A suspension apparatus according to claim 1 , wherein

the inverting amplification circuit has an amplification factor of 1; and

the inertia compensation capacitor has a capacitance corresponding to the inertia of the rotation body.

3. A suspension apparatus for a vehicle, comprising:

a shock absorber which includes a motor having a stator coupled with one of sprung and unsprung members of the vehicle and a rotor rotatable in relation to the stator, wherein, due to an inductive electromotive force generated when the rotor is rotated as a result of approaching and separating motions between the sprung and unsprung members, an induction current flows through the motor, whereby a damping force is generated;

an electric circuit which establishes electrical connection between a first electricity supply terminal of the motor and a second electricity supply terminal of the motor; and

an electrical characteristic adjustment part which adjusts an electrical characteristic of the electric circuit so as to reduce an inertia corresponding current which is a current flowing through the motor and which represents an inertial force of a rotation body which includes at least the rotor and which rotates as a result of the approaching and separating motions between the sprung and unsprung members, wherein

the electrical characteristic adjustment part adjusts the electrical characteristic of the electric circuit such that an anti-resonance frequency of a parallel resonant circuit formed by the electric circuit and an inertia corresponding capacitor which is imaginarily connected in parallel to the electric circuit and which has a capacitance corresponding to the inertial force of the rotation body coincides with a predetermined frequency equal to or close to an unsprung resonance frequency.

4. A suspension apparatus according to claim 3 , wherein

an external resistor whose resistance is variable is connected to the electric circuit; and

the electrical characteristic adjustment part comprises:

a target damping force computation section which computes a target damping force which is a target value of the damping force generated by the shock absorber;

a required resistance computation section which computes, on the basis of the target damping force, a required resistance which is an external resistance required by the electric circuit so as to cause the shock absorber to generate the target damping force; and

a resistance correction section which corrects the resistance of the external resistor such that the resistance of the external resistor represents a combined impedance of the required resistance and a required impedance which is determined in advance as an external inductance required by the electric circuit so as to render the anti-resonance frequency coincident with the predetermined frequency equal to or close to the unsprung resonance frequency.

5. A suspension apparatus according to claim 1 , wherein

the electric circuit includes a first connection path (H 1 ) electrically connected to the first electricity supply terminal of the motor and a second connection path (H 2 ) electrically connected to the second electricity supply terminal of the motor,

the inverting input terminal connects to the first connection path (HI) via the input resister, and

the non-inverting input terminal connects to the second connection path (H 2 ).

6. A suspension apparatus according to claim 5 , wherein

the inverting input terminal connects to the first connection path (H 1 ) through a connection path (L 1 ),

the non-inverting input terminal connects to the second connection path (H 2 ) through a connection path (L 2 ), and

the input resister is provided on the connection path (L 1 ).

7. A suspension apparatus according to claim 6 , wherein

the inertia compensation capacitor connects to a connection path (L 3 ), and

a potential of the connection path (L 2 ) is the same as a potential of the connection path (L 3 ).