Hydraulic Proportional Valves
The proportional valve can increase or decrease its output in keeping with the demands of the output. The valves control force, pressure flow, actuator position, velocity or torque and can synchronize the plungers of several valves to produce simultaneous movements. Hydraulic proportional valves are made from a variety of materials including
brass, stainless steel and polypropylene. Important specifications to consider regarding proportional valves are the maximum and minimum pressures, the diameter of the valves and tubes, the fluid type and the temperature range. These valves are used to remotely control valves for the
directional control of fluids and are used frequently in vehicles to reduce the brake fluid pressure to the rear brakes. They are also widely found in applications in the aerospace, aircraft, automobile, defense, construction and manufacturing industries.
Hydraulic proportional valves convert electrical energy into mechanical energy. When the wire coil receives a current, the resulting magnetic field acts on the plunger and causes it to move up or down, therefore making the valve open and close. In operation, solenoid force is balanced by spring force to position the spool in proportion to the input signal. Positioning accuracy can be improved by removing the centering springs and adding a positioning sensor to the end of the spool. The sensor signal then cancels the signal when the spool reaches the specified position. Proportional valves are an inexpensive way to control the force or velocity of a fluid moving at a high flow rate. They are also used to position parts of equipment, such as the bucket on a backhoe because the rams use hydraulic fluid to operate. Increasingly, hydraulic proportional valves are replacing
solenoids because proportional valves allow mechanical parts to move with minimal friction without being sensitive to contamination and pressure drops, like solenoids are. They are more cost effective to manufacture because they can be mass produced with greater tolerance allowances and looser fits than other valves. With the
electronic controls and feedback, they are able to deliver high performance in many situations.
