Vehicle suspension system

In a vehicle suspension system having a suspension unit comprised of a shock absorber equipped with a damping-capacity switching mechanism and an air-spring chamber equipped with a spring-constant switching mechanism:

• car-height sensor means for detecting at least one of the compressed and stretched conditions of a suspension unit and producing a corresponding output signal;
• control means for feeding a control signal to said damping-capacity switching mechanism and spring-constant switching mechanism in order to change the damping capacity of the shock absorber and the spring constant of the air-spring chamber in accordance with the output signal produced from said car-height sensor means, said control means being operative to supply said control signal for increasing both the damping capacity of the shock absorber and the spring constant of the air-spring chamber to said damping-capacity switching mechanism and said spring-constant switching mechanism when the car height detected by said car-height sensor means differs from a standard car-height by such a value as to exceed a preset value;
• said shock absorber comprising a cylinder supporting an axle, a piston slidably fitted in said cylinder to divide the space therein into two chambers and being equipped with an orifice passage interconnecting said two chambers, a piston rod connected to said piston and extending upward with its top end supported by a vehicle body;
• said damping-capacity switching mechanism of the shock absorber comprising a control valve for changing the effective area of said orifice passage of the pistion, and a first actuator for driving said control valve;
• said air-spring chamber comprising a main air-spring chamber disposed coaxially with the piston rod and the cylinder in such a manner as to surround said piston rod and cylinder for supporting the vehicle weight, and an auxiliary air-spring chamber disposed above said main air-spring chamber coaxially with the piston rod in such a manner as to surround said piston rod;
• said spring-constant switching mechanism of the air-spring chamber comprising a control rod extending in the interior of said piston rod in the longitudinal direction of the piston rod and being movably mounted so as to vary its position with respect to the piston rod, and a second actuator for changing the position of said control rod;
• a wall portion of said piston rod surrounding said control rod having openings communicating with said main air-spring chamber and said auxiliary air-spring chamber respectively;
• and said control rod having an air passage intercommunicating said main air-spring chamber with said auxiliary air-spring chamber through said openings on the wall portion of the piston rod so that the connection and disconnection between said main and auxiliary air-spring chambers are selectively executed by moving said control rod relative to said piston rod.