Presented by,Sachin Goel

Sudhanshu Nahata

Electro-Pneumatic ValvesOn-Off type

Simple on-off functionsServo Valves

high linear control accuracy in pneumatic actuators

Costly, complex and bulky

ObjectiveTo develop electro-pneumatic valve with

following characteristics:High linear control accuracy in pneumatic

actuatorsLow-CostSimpleCompact

Working PrincipleWorking principle is the “Fast

Switching” using ‘pulse-width modulation(PWM)’ technique

Fast Switching is also achieved by designing the valve in efficient way which is to be explained

Design of Valve

Why Fast Switching?As the valve begins to open, the flow force

helps the magnetic force to keep the valve open.

The travel distance of the disc is kept as small as possible in order to benefit from high magnetic attraction force.

Application

Electro-pneumatic position control system with four prototype valves.

WorkingWhen valves 1 and 3 are open, the cylinder

extendsWhen valves 2 and 4 are open, the cylinder

retracts When all valves are closed, the cylinder restsThe electromagnet can be actuated using pulse

width modulation (PWM) technique with control implemented via analog circuits, digital logic circuits or a microprocessor-based system

The dimensions of the valve were chosen in order to supply the required amount of air

Switching CharacteristicsOptimum working gap: 0.6 mm of total gap,

0.14 mm of holding gap and 0.46 mm of travel distance

An applied current of 6 A or higher provides a sufficient magnetic force to overcome the spring force at the beginning of switching of the valve

At the end of switching, about 1.75 A of applied current is just enough to hold the disc against to the spring force with 0.14 mm of holding gap

Current reduced to holding level after the end of switching This improves the switching time of the valve closing

Time DelayTime delay (opening) is governed by (Td):

Spring force, magnetic force and pressure forceFrom experiments:

-Total time – 4.65 ms-Delay time – 3.2 ms, Travel time – 1.45ms

Time delay (closing) is governed by : Force balance btw spring force, fluid force and the magnetic holding force

From experiments:- Total time – 3.05 ms-Delay time – 1.6 ms

Thank You…