Vehicular suspension system utilizing variable damping force shock absorber

A vehicular suspension system comprising:

• a variable damping force shock absorber disposed between a vehicle body and at least one of a plurality of road wheels and including a variable semi-active hydraulic damper which is operable between a plurality of different damping characteristics;
• a sensor for detecting an absolute vertical velocity of a sprung mass of the vehicle to generate an absolute vertical velocity indicative signal;
• and
• a control unit responsive to said vertical velocity, for generating a control signal based on said vertical velocity to adjust the damping characteristic of said damper;
• wherein said control unit includes a dead-band controlling means for adjusting the damping characteristic to a minimum damping characteristic only when the control signal value is maintained within a controlled dead-band threshold value;
• wherein said dead-band controlling-means initially sets the dead-band threshold value by multiplying a ratio of a damping force generated at a minimum damping characteristic to a damping force generated at a maximum damping characteristic at a predetermined piston speed of said damper with an initially-set maximum characteristic threshold above which the damping characteristic of said damper is adjusted to said maximum damping characteristic;
• wherein said dead-band controlling means renews said initially-set maximum damping characteristic threshold with a current value of said control signal and varies said initially set dead-band threshold value in proportion to changes in said renewed maximum damping characteristic threshold, until the control signal value reaches a peak value, at which peak value a rate of change in said detected vertical velocity is equal to zero, from the time when the control signal value exceeds the initially-set maximum damping characteristic threshold;
• and
• wherein said ratio of the damping force generated at the minimum damping characteristic to the damping force generated at the maximum damping characteristic is varied depending on a vehicle speed.

A vehicular suspension system comprising:

• a variable damping force shock absorber disposed between a vehicle body and one of its road wheels and including a variable semi-active hydraulic damper which is operable between a plurality of different damping characteristics;
• a sensor for detecting an absolute vertical velocity of a sprung mass of the vehicle to generate an absolute vertical velocity indicative signal;
• and
• a control unit responsive to said vertical velocity, for generating a control signal based on said vertical velocity to adjust the damping characteristic of said damper;
• wherein said control unit includes a dead-band controlling means for adjusting the damping characteristic to a minimum damping characteristic only when the control signal value is maintained within a controlled dead-band threshold value,
• wherein said dead-band controlling-means initially sets the dead-band threshold value by multiplying a ratio of a damping force generated at a minimum damping characteristic to a damping force generated at a maximum damping characteristic at a predetermined piston speed of said damper with an initially-set maximum characteristic threshold above which the damping characteristic of said damper is adjusted to said maximum damping characteristic;
• wherein said dead-band controlling means renews said initially-set maximum damping characteristic threshold with a current value of said control signal and varies said initially set dead-band threshold value in proportion to changes in said renewed maximum damping characteristic threshold, until the control signal value reaches a peak value, at which peak value a rate of change in said detected vertical velocity is equal to zero, from the time when the control signal value exceeds the initially-set maximum damping characteristic threshold;
• and
• wherein an initial threshold value of the dead band of said vertical velocity for the extension phase of said shock absorber and an initial threshold value of the dead band of said vertical velocity for the compression phase of said shock absorber are set independently to different values.

A vehicular suspension system comprising:

• a variable damping force shock absorber disposed between a vehicle body and either one of road wheels and including a variable semi-active hydraulic damper which is operable between a plurality of different damping characteristics;
• a sensor for detecting an absolute vertical velocity of a sprung mass of the vehicle to generate an absolute vertical velocity indicative signal;
• and
• a control unit responsive to said vertical velocity, for generating a control signal based on said vertical velocity to adjust the damping characteristic of said damper;
• wherein said control unit includes a dead-band controlling means for adjusting the damping characteristic to a minimum damping characteristic only when the control signal value is maintained within a controlled dead-band threshold value;
• wherein said dead-band controlling-means initially sets the dead-band threshold value by multiplying a ratio of a damping force generated at a minimum damping characteristic to a damping force generated at a maximum damping characteristic at a predetermined piston speed of said damper with an initially-set maximum characteristic threshold above which the damping characteristic of said damper is adjusted to said maximum damping characteristic;
• wherein said dead-band controlling means renews said initially-set maximum damping characteristic threshold with a current value of said control signal and varies said initially set dead-band threshold value in proportion to changes in said renewed maximum damping characteristic threshold, until the control signal value reaches a peak value, at which peak value a rate of change in said detected vertical velocity is equal to zero, from the time when the control signal value exceeds the initially-set maximum damping characteristic threshold;
• and
• wherein said damper is operable between an extension-phase hard region in which the damping characteristic for the extension phase is variably adjusted and the damping characteristic for the compression phase is stationarily maintained at the lowest damping characteristic, a compression-phase hard region in which the damping characteristic for the compression-phase is variably adjusted and the damping characteristic for the extension phase is stationarily maintained at the lowest damping characteristic, and a soft region in which the damping characteristics for the extension phase and the compression phase are both maintained at the lowest damping characteristics, and said control unit adjusts the damping characteristic of said damper into said extension phase hard region when the direction of said vertical velocity is an upward direction and the control signal value exceeds an upper threshold value of the dead band, and into said compression-phase hard region when the direction of said vertical velocity is a downward direction and the control signal value exceeds a lower threshold value of the dead band, and into said soft region when said vertical velocity is within said dead band.