Ford Motor Company Limited

Daniel M McCoy

Gary J Gloceri

Douglas C Campbell

Joseph M Raad

Jerome Charles Ivan

Thomas G Reichenbach

Lenard J Duchnowski

In vehicles having drive wheel selections, accessed for example through a transfer case, drive wheel settings are used to determine a desired vehicle ride height at which the vehicle is maintained by a vehicle suspension control system. Preferably, both vehicle speed and transfer case setting are combined to determine the desired vehicle ride height. With two wheel drive selected, the desired vehicle ride height is set to a low ride height which provides the most aerodynamic airflow for the vehicle. However, if four wheel drive is selected, the speed is checked to determine the desired vehicle ride height. If four wheel drive (automatic four wheel drive) is selected, low ride height is still selected for speeds in excess of a first defined speed. For speeds at or below the first defined speed, a high ride height approximately 1 inch above the low ride height is set for the desired ride height. If four wheel drive low is selected, typically in contemplation of off-road operation, a higher still ride height or off-road ride height approximately 1 inch above high ride height is set for the desired ride height.

Ride height setting based on transfer case setting

Vehicle speed is measured and used to calculate lateral acceleration of the vehicle and speed dependent thresholds to which the lateral acceleration of the vehicle is compared to determine when to change a controllable suspension system of the vehicle to improve operation of the suspension system. The controllable suspension system includes air springs and variable damping shock absorbers switchable between soft and firm damping rates. At speeds above a given speed, lateral accelerations exceeding first speed dependent thresholds will result in switching the shock absorbers to firm and/or closing gate valves which intercouple the left and right air springs to decrease vehicle roll. For slower speeds less than the given speed, the suspension system control is desensitized such that lateral accelerations of the same given magnitudes, for example due to entering a parking space or other low speed maneuver, do not alter the suspension. Switch back of shock absorbers from firm to soft and opening of the gate valves can be based on expiration of an elapsed time period or detection of the lateral acceleration of the vehicle falling below second speed determined thresholds.

Speed dependent suspension control

One or more vehicle suspension signals, preferably already generated within a controllable suspension system, is utilized to perform switches of the damping state of variable damping shock absorbers in the suspension system while the velocity of the shock absorbers is close to zero velocity. In particular, signals generated by height sensors within a controllable suspension system are utilized as vehicle suspension signals which are filtered to generate signals to enable switching of the shock absorbers while the shock absorbers are close to zero velocity. In addition, performance of the suspension system is improved by utilizing the vehicle suspension signals as one criterion to determine when switching from soft damping to firm damping or from firm damping to soft damping is desirable. Switch enable signals are determined from vehicle suspension signals by filtering at a resonant body frequency and comparison to an appropriate threshold. Soft-to-firm/firm-to-soft switch request signals are determined from vehicle suspension signals by filtering at a resonant wheel frequency and comparison to appropriate thresholds. Preferably, firm-to-soft switches are made after expiration of predefined time periods.

Damping factor switching in vehicle shock absorbers

Load leveling height control is provided for a vehicle by replacing a conventional scheduled vehicle height with a load leveling height which is sensed upon detection of the opening of at least one compartment of the vehicle. Load leveling height control raises and lowers the vehicle to maintain the load leveling height. While either a passenger compartment or a cargo compartment can be monitored, preferably both are monitored to protect the vehicle from potential damage both below and above the vehicle due to changes in vehicle height as a vehicle is loaded and/or unloaded. Any currently active leveling activity is aborted such that a load leveling height or open compartment height can be read and maintained as long as a compartment remains open or until vehicle speed reaches a predefined speed, for example 16 kilometers per hour (10 miles per hour), at which time the conventional scheduled vehicle height is once again utilized.

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Shelby Township, MI, United States of America

Daniel M McCoy