System and method for controlling damping force characteristic of shock absorber applicable to automotive suspension

A method for controlling a damping force of a vehicular damper, said damper having damping force adjusting means for adjusting a damping force characteristic of the damper at a plurality of stages in response to a control signal, comprising the steps of:

• a) deriving a vertical velocity of a vehicle body of the vehicle on the basis of an output signal of a vertical acceleration sensor and outputting a first signal indicative thereof;
• b) detecting a relative velocity between the sprung mass and the unsprung mass of the vehicle and outputting a second signal indicative thereof;
• c) providing a predetermined dead zone for the relative velocity between the sprung mass and the unsprung mass, determining a stroke direction of the damper on the basis of the relative velocity, shifting the predetermined dead zone by a predetermined quantity toward a direction opposite to the determined stroke direction;
• and
• d) determining whether a direction of the vertical velocity of the vehicular body coincides with a direction of the relative velocity, outputting the control signal to control a damping force of the damper toward a high damping force side when the direction of the vertical velocity of the vehicle body coincides with the direction of the relative velocity and when determining that the relative velocity exceeds the predetermined dead zone, and outputting the control signal to control the damping force of the damper toward a lower damping force side when determining that the direction of the vertical velocity of the vehicular body does not coincide with the direction of the relative velocity.

A damping force controlling system for a vehicular suspension damper, comprising:

• a) a damping force adjusting means for adjustably controlling a damping force of the damper at any one of a plurality of stages in response to a control signal;
• b) a vertical acceleration sensor for detecting a vertical acceleration of a vehicle body and outputting a first signal indicative thereof;
• c) first velocity detecting means for detecting a vertical velocity of the vehicle body on the basis of the first signal derived from the vertical acceleration sensor and outputting a second signal indicative thereof;
• d) second velocity detecting means for detecting a relative velocity between a sprung mass of the vehicle body and an unsprung mass of the vehicle and outputting a third signal indicative thereof;
• e) control means for providing the control signal to said damping force adjusting means so that the damping force is increased within a direction of the vertical velocity indicated by the second signal and a direction of the relative velocity indicated by the third signal coincide and simultaneously when a magnitude of the third signal exceeds a first limit of a predetermined dead zone, said predetermined dead zone is shifted by a predetermined quantity in a stroke direction which is opposite to the stroke direction in which said damping force change is being carried out in response to the third signal, and for providing the control signal to said damping force adjusting means so that the damping force is reduced when the direction indicated by the second signal and the direction indicated by the third signal are non-coincident, and simultaneously when the magnitude of the third signal exceeds a second limit of the predetermined dead zone, said predetermined dead zone is shifted by the predetermined quantity in a stroke direction which is opposite to the stroke direction in which the damping force change is being carried out in response to the third signal.

A damping force controlling system for a vehicular suspension damper, comprising:

• a) damping force adjusting means, responsive to a control signal, for adjustably controlling a damping force of the damper;
• b) a vertical acceleration sensor for detecting a vertical acceleration of a vehicle body and outputting a first signal indicative thereof;
• c) first velocity determining means for determining a vertical velocity of the vehicle body using said first signal and outputting a second signal indicative of the vertical velocity;
• d) relative velocity determining means for determining a relative velocity between a sprung mass of the vehicle body and an unsprung mass of the vehicle and outputting a third signal indicative thereof;
• and
• e) control means for:
• comparing the relative velocity indicated by said third signal with a predetermined dead zone and shifting said predetermined dead zone by a predetermined amount in a stroke direction which is opposite to the stroke direction indicated by said third signal when the magnitude of the third signal exceeds a limit of said predetermined dead zone for producing said control signal;
• providing the control signal to said damping force adjusting means so that the damping force is increased when a direction of the vertical velocity indicated by said second signal is the same as a direction of the relative velocity indicated by said third signal, and
• providing the control signal to said damping force adjusting means so that the damping force is reduced when the direction of the vertical velocity indicated by said second signal is different from the direction of the relative velocity indicated by said third signal.