VALVE MECHANISMS

#AUTOMOBILE_ENGINEERING
VALVE MECHANISM
A valve mechanism is a control system which is used for filling the combustible charges i.e. air and fuel mixture in a petrol engine, and only air in a diesel engine.
These are two basic types of valve mechanisms generally used in vehicles.
1.Overhead valve mechanism
2.Overhead camshaft mechanism
ROCKER ARMS
The motion of the camshaft is converted into vertical motion by the cams, and is transferred to the valves through rocker arms.
INTAKE AND EXHAUST VALVES
1. POPPET VALVE
2. SODIUM FILLED VALVE
3. SLEEVE VALVE
4. ROTARY VALVE
POPPET VALVE
Head
The valve having hollow and concave head is known as trumpet valve and is generally used for inlet valve.
The convex head valve is known as mushroom valve and is used as exhaust valve.
FACE:
This is generally machined at an angle of either 30° or 45° to sit on the similarly inclined surface of the valve seat and makes a tight joint.
STEM:
It is a working of the valve and this portion of the valve moves up and down in valve guide.
TIP:
It is the flat end of the stem over which the rocker arm acts to open the valve.
SODIUM COOLED VALVES
Sodium is used for cooling inside the valves, which are made hollow. Such valves are known as sodium cooled valves.
VALVE SPRINGS
The material used in making valve springs is generally heat resistant spring steel, chrome vanadium steel or silicon chrome steel.