Method and apparatus for controlling vehicle suspension such that suspension characteristics are changed at a point in time when a vehicle wheel reaches a road surface irregularity detected in front of the vehicle

A vehicular suspension control apparatus for controlling a suspension having at least one of spring rigidity and damper rigidity characteristics, which is provided between at least one wheel and a body of a vehicle, comprising:

• suspension characteristic changing means for changing at least one of said spring rigidity and damper rigidity characteristics of said suspension;
• a forward road surface sensor means attached to said vehicle body for detecting an irregularity of a road surface located in front of said vehicle body at a predetermined distance from said sensor when said vehicle body is at a predetermined height and a predetermined inclination, said predetermined height and said predetermined inclination jointly referred to as a predetermined attitude;
• a vehicle speed sensor for detecting a vehicle speed;
• control means, responsive to said vehicle speed sensor, for calculating a point in time when said wheel reaches the irregularity of the road surface, in accordance with said vehicle speed detected by said vehicle speed sensor, when the irregularity of the road sensor is detected by said forward road surface sensor, and delivering a command signal, for lowering at least one of said spring rigidity and said damper rigidity characteristics of said suspension, to said suspension characteristic changing means not later than said calculated point in time;
• and
• vehicle body attitude sensing means for detecting a vehicle height and an inclination of said vehicle body;
• wherein said control means corrects said predetermined distance in accordance with a variation of said detected vehicle height and said detected vehicle body inclination from said predetermined attitude, and calculates said point in time in accordance with said corrected predetermined distance and said vehicle speed detected by said vehicle speed sensor;
• wherein said vehicle includes front and rear wheels;
• wherein said vehicle body attitude sensing means includes vehicle height sensing means for detecting vehicle heights at least at the respective locations of said front and rear wheels;
• and
• wherein said control means executes said correction of said predetermined distance when any of said vehicle heights detected by said vehicle height sensing means deviates from a range defined by predetermined upper and lower limit values.

A method of controlling a vehicular suspension having spring rigidity and damper rigidity characteristics, which is provided between at least one wheel and a body of vehicle, and which extensibly and retractably supports said vehicle body on said wheel, the method comprising the steps of:

• (a) detecting an irregularity of a road surface located in front of said vehicle body using a forward road surface sensor;
• (b) detecting a vehicle speed;
• (c) calculating a point in time when said wheel reaches the irregularity of the road surface in accordance with said detected vehicle speed when the irregularity of the road surface is detected;
• (d) detecting a vehicle height and an inclination of said vehicle body;
• (e) correcting said point in time in accordance with said detected vehicle height and inclination of said vehicle body, and said detected vehicle speed;
• (f) delivering a command signal, for lowering at least one of said spring rigidity and said damper rigidity characteristics of said suspension, to a suspension characteristic changing means not later than said calculated point in time;
• (g) changing at least one of said spring rigidity and damper rigidity characteristics of said suspension using said suspension characteristics changing means based on said command signal.