Explain working of over head valve mechanism with neat sketch.

Explain working of over head valve mechanism with neat sketch.
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1 Answer

Answer :

Overhead valve mechanism: Figure shows the valve mechanism to operate the valve when it is in the cylinder head (in I and F head design). This type of mechanism requires two additional moving parts the push rod and rocker arm. As the cam rotates, it lifts the valve- tappet or the lifter which actuates the push rod. The push rod rotates the rocker arm about a shaft- the rocker –arm shaft, or a ball joint in some designs to cause one end to push down on the valve stem to open the valve, thus connecting the valve port with the combustion chamber.

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Overhead valve mechanism : Working: As the camshaft rotates, each off-center (eccentric) cam lobe pushes against a lifter or tappet. The upward motion of the lifter transfers through the push rod to the rocker arm. This upward motion changes to downward motion as the rocker arm pivots. The downward motion opens the valve. As the camshaft continues to rotate, the lobe passes by the lifter and allows the valve to close. A spring (attached to the valve) returns the valve to its seated position.

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