During the intake phase of an overhead valve (OHV) internal combustion engine, rotational energy from the camshaft is transferred through a series of internal valve train components to admit the air-fuel mixture. Arrange the following mechanical events in the correct chronological order from initial camshaft lobe contact to the opening of the intake port.
- 1The camshaft lobe rotates past its base circle, forcing the valve lifter (tappet) upward.
- 2The upward motion of the lifter pushes the pushrod up through the engine block toward the cylinder head.
- 3The pushrod forces the outer end of the rocker arm upward, causing the rocker arm to pivot on its fulcrum.
- 4The valve-side tip of the rocker arm presses down on the valve stem, overcoming valve spring tension.
- 5The intake valve head lifts off the valve seat, allowing the incoming charge to flow into the cylinder.
Answer
The correct sequence begins with the camshaft lobe lifting the valve lifter, followed by the lifter driving the pushrod upward, the pushrod pivoting the rocker arm on its fulcrum, the rocker arm depressing the valve stem against spring tension, and finally the valve head separating from the valve seat to unseal the intake port.
In an overhead valve (OHV) engine, the camshaft resides inside the cylinder block. As the camshaft lobe rotates, it lifts the valve lifter (tappet). The lifter pushes the pushrod upward into the cylinder head. The top of the pushrod presses against the outer arm of the rocker arm, causing it to pivot on its shaft or fulcrum. The downward-moving inner tip of the rocker arm pushes against the valve stem tip, compressing the valve spring and moving the valve head off its seat to open the port.
Step-by-Step Solution
Key Concept
Mechanical force transfer sequence in an OHV valve train
Estimated Time:1m 15s