Tham khảo tài liệu 'advanced vehicle technology 2 episode 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fig. Tandem trailing arm rolling diaphragm air sprung suspension Fig. Tandem trailing arm bellows spring suspension with rubber anti-roll blocks central levelling valve at the front Fig. and a pair of levelling valves on each side of the first tandem axle. These levelling valves are bolted to the chassis but they are actuated by an arm and link rod attached to the axles. It is the levelling valves function to sense any change in the chassis to axle height and to increase or decrease the air pressure supply passing to the air springs thereby raising or reducing the chassis height respectively. The air pressure actually reaching the springs may vary from bar fully laden down to bar when the vehicle is empty. To improve the quality of ride extra volume tanks can be installed in conjunction with the air springs to increase the volume of air in the system. This minimizes changes in overall pressure and reduces the spring rate spring stiffness thus enabling the air springs to provide their optimum frequency of spring bounce. An additional feature at the front end of the suspension is an isolating valve which acts both as a junction to split the air delivery to the left and right hand air springs and to permit air to pass immediately to both air springs if there is a demand for more compressed air. This valve also slows down the transfer of air from the outer spring to the inner spring when the body rolls while the vehicle is cornering. Levelling valve Figs and a and b A pre-determined time delay before air is allowed to flow to or from the air spring is built into the valve unit. This ensures that the valves are not operated by axle bump or rebound movement as the vehicle rides over rough road surfaces or by increased loads caused by the roll of the body on prolonged bends or on highly cambered roads. The valve unit consists of two parts a hydraulic damper and the air control valve Fig. a and b . Both the damper .
