文档介绍：Engine Construction
The automobile is designed to travel on roads. The typical automobile has just an internal combusti has machined surfaces to provide a precision fit to mate parts. Inline four- and six-cylinder engines have one cylinder head. V6 and V8 engines have two cylinder heads. The head is essentially a flat plate of metal bolted to the top of the cylinder block with a gasket in between.
Engine Construction
Camshaft
The key parts of any camshaft are the lobes. As the camshaft spins, the lobes open and close the intake and exhaust valves in time with the motion of the piston. It turns out that there is a direct relationship between the shape of the cam lobes and the way the engine performs in different speed ranges.
Engine Construction
Valves
Valves are usually made from a steel alloy. Exhaust valves must withstand extremely high temperatures up to 815 degrees Celsius without damaging the valve. The valve face must seat evenly against the valve seat in the cylinder head to prevent leaks from the cylinder during the compression and power strokes. Many valve faces and seats have an angle of 45 degrees.
Engine Construction
There are intake valves and exhaust valves. On the intake side, the intake valve opens which lets the fuel-air mixture into the combustion chamber. At some point, the intake valve closes, the air-fuel mixture is compressed and ignit