An electronically controlled fluid suspension system for adjusting a vehicle's attitude rapidly controls the vehicle height: by providing and blocking the fluid communication between fluid springs and reserve tanks; and by shifting the damping force of shock absorbers to a higher degree in response to the change of the vehicle height. As a result, it can avoid the late control of the vehicle height and prevent the vibration of the vehicle body due to the vehicle height's adjustment, thereby enhancing riding comfort.
A suspension control system employs an acceleration sensor for monitoring an inertial force affecting for vehicular attitude. A control system coacting therewith includes a mechanism for lowering the level of an output signal of the acceleration sensor to eliminate therefrom any error corresponding a resonance frequency of the acceleration sensor for obtaining higher accuracy inertially indicative data.
An apparatus for controlling a damping force of a shock absorber provided between a wheel of a vehicle and a body thereof includes a road surface condition detecting unit for detecting a roughness of a road surface on which the vehicle is traveling, and a damping force characteristic alteration unit for altering the setting of the damping force of the shock absorber on the basis of the roughness of the road surface detected by the road surface condition detecting unit. The apparatus also includes a damping force detecting unit, for detecting a magnitude of the damping force of the shock absorber, and an alteration speed control unit for controlling, on the basis of the magnitude of the damping force detected by the damping force detecting unit, an alteration speed at which the setting of the damping force is altered so that the alteration speed decreases as the magnitude of the damping force increases.
An active suspension system is provided with a fail detector for detecting failure of control system which includes sensors, control unit, control valves and so forth. Fail-safe operation is taken place by closing a fluid circuit across a working chamber in a suspension system disposed between a vehicular body and a road wheel and a pressure control valve for adjusting the fluid pressure in the working chamber, and by adjusting the fluid pressure in the closed circuit substantially at a predetermined neutral pressure. The system further includes a vehicular driving condition monitor for monitoring vehicular driving condition. When faulty condition of the control system is cured or terminated, active suspension control is resumed at a timing when the vehicular driving condition monitor detects a predetermined vehicular driving condition stable enough for permitting resumption of active suspension control.
The invention relates to a closed level control system for a vehicle. The closed level control system includes a pump which transfers a pressurized medium between a pressurized medium supply vessel (4) and pressurized medium chambers (2a to 2d). The input (8) of the pump (6) is connected to the supply vessel (4) and the output (10) of the pump (6) is connected to the pressurized medium chambers (2a to 2d) when the pressurized medium is to be pumped from the supply vessel (4) into the pressurized medium chambers (2a to 2d). If, in contrast, pressurized air is to be pumped from a pressurized medium chamber (2a to 2d) into the supply vessel (4), then the input (8) of the pump (6) is connected to the pressurized medium chamber and the output (10) of the pump (6) is connected to the supply vessel (4). The above-mentioned connections preferably take place via controllable directional valves (14, 18). The level control system makes it possible that the pump (6) has to always run only in one direction.
An active suspension system is provided which includes hydraulic cylinders for suppressing rolling motion of a vehicle body. The system is responsive to lateral acceleration acting on the vehicle body to provide a control signal for supplying hydraulic pressure to the cylinders for anti-rolling control. The control signal includes first and second pressure control signals. The first pressure control signal commands supply of hydraulic pressure for providing an anti-rolling moment, while the second pressure control signal commands supply of hydraulic pressure for supporting a portion of the static load of the vehicle body to maintain the vehicle body at a target height level. The system is further responsive to increase in lateral acceleration to modify the second pressure control signal to reduce the hydraulic pressure for supporting the portion of static load, thereby compensating for forces acting to raise the vehicle body caused by the anti-rolling control for establishing a constant vehicular height level irrespective of variation in the lateral acceleration acting on the vehicle body.
