Automatic level control system for automotive vehicle with fail-safe system therefor

A height control system for an automotive vehicle comprising:

• a suspension strut disposed between a vehicle body and a vehicular wheel axle;
• a first pneumatic chamber associated with said suspension strut and adapted to adjust the vertical separation between said vehicle body and said wheel axle by controlling a pressure therein so as to hold vehicle height at a given height;
• a second pneumatic chamber connected to said first pneumatic chamber through a communication passage;
• a pneumatic pressure supply circuit connected to said first pneumatic chamber for introducing and exhausting the pneumatic pressure into and from said first pneumatic chamber for adjusting the pneumatic pressure within the latter;
• a pressure control valve means disposed within said pneumatic pressure supply circuit, for controlling introduction and exhausting of the pneumatic pressure in said first pneumatic chamber;
• a damper control valve means disposed within said communication passage for establishing and blocking communication between said first and second pneumatic chambers for adjusting the effective volume of the first pneumatic chamber;
• a vehicle height sensor for monitoring vehicle height and producing a vehicle height indicative signal;
• a detector responsive to said vehicle height indicative signal for detecting when the vehicle height lies outside of a predetermined height range;
• and
• a controller responsive to said detector detecting said vehicle height outside of said predetermined height range for operating said pressure control valve means so as to adjust vehicle height to within said predetermined height range, said controller also operating said damper control valve means so as to hold said damper control valve means open during vehicle height adjustment.

In a height control system for an automotive vehicle comprising:

• a suspension strut disposed between a vehicle body and a vehicular wheel axle;
• a first pneumatic chamber associated with said suspension strut and adapted to adjust the vertical separation between said vehicle body and said wheel axle by controlling a pressure therein so as to hold vehicle height at a given height;
• a second pneumatic chamber connected to said first pneumatic chamber through a communication passage;
• a pneumatic pressure supply circuit connected to said first pneumatic chamber for introducing and exhausting the pneumatic pressure into and from said first pneumatic chamber for adjusting the pneumatic pressure within the latter;
• a pressure control valve means disposed within said pneumatic pressure supply circuit, for controlling introduction and exhausting of the pneumatic pressure in said first pneumatic chamber;
• a damper control valve means disposed within said communication passage for establishing and blocking communication between said first and second pneumatic chambers for adjusting the effective volume of the first pneumatic chamber;
• a vehicle height sensor for monitoring vehicle height and producing a vehicle height indicative signal;
• a detector responsive to said vehicle height indicative signal for detecting when the vehicle height lies outside of a predetermined height range, and a controller for controlling operation of said pressure control valve means and said damper control valve means,
• a process for performing vehicle height control comprising the steps of:
• monitoring varition of said vehicle height indicative signal value and detecting when vehicle height lies outside of a predetermined range;
• opening said damper control valve in response to a vehicle height indicative signal value indicative of a vehicle height outside of said predetermined range;
• measuring elapsed time starting from detection of said vehicle height indicative signal value indicative of vehicle height outside of said predetermined range and continuing for as long as the vehicle height remains outside of said predetermined range;
• when said elapsed time exceeds a predetermined period, operating said pressure control valve so as to adjust pnuematic pressure in said first pneumatic chamber in order to return the vehicle height within said predetermined range;
• and
• holding said damper control valve open during said pressure control valve operation step.