Apparatus and method for controlling damping force exhibited in vehicular damping force variable shock absorber

A control apparatus for an automotive vehicle, comprising:

• a) determining means for determining a behavior of a vehicle body and outputting a signal related to a sprung mass vertical velocity with respect to the vehicle body;
• b) controlling means, responsive to the signal derived from said determining means, for calculating a damping force according to a magnitude and direction of the output signal from said determining means and for outputting a control signal corresponding to the calculated damping force;
• c) actuating means, responsive to said control signal output from said controlling means, for actuating a valve body associated with said actuating means to rotate from a position through an angle to a target position determined according to a magnitude and direction of the control signal output from said controlling means;
• d) damping means, interposed between a sprung mass member of the vehicle and an unsprung mass member of the vehicle and having the valve body, a piston assembly, and upper and lower working fluid chambers defined by said piston assembly, for providing a target damping force at least either of extension or compression phase determined according to the rotated target position of said valve body and whether said target damping force is exhibited at either of the extension phase or compression phase being dependent upon a vertical movement of the piston assembly with respect to the vehicle body;
• e) dead zone setting means for setting positive and negative dead zone threshold values defining a dead zone in which said controlling means does not output said control signal to said actuating means according to the magnitude and direction of the output signal of said determining means so that said valve body is not rotated from said position and each of the damping forces at both extension and compression phases emanated from said damping means gives a minimum damping force;
• f) positive and negative sprung mass vertical velocity upper and lower limit threshold value setting means for setting positive and negative sprung mass vertical velocity upper and lower limit threshold values, whose absolute values are larger than those of said positive and negative dead zone threshold values, said controlling means outputting the control signal to said actuating means so that said valve body is rotated to a maximum target position so as to provide a maximum damping force at either of said extension or compression phase depending on at least a direction of the output signal from said determining means when said output signal of said determining means becomes equal to or exceeded said either of positive or negative sprung mass vertical velocity upper or lower limit threshold value:
• and
• g) dead zone threshold value changing means for reducing an absolute value of at least either of said positive or negative dead zone threshold value by a predetermined value when said output signal of said determining means becomes equal to or exceeded either of said positive or negative sprung mass vertical velocity upper or lower limit threshold value.