Inlet valve, internal combustion engine and transportation apparatus including the same

An engine unit comprising:

• an inlet valve provided in an inlet port in communication with a combustion chamber;
• a cylinder head provided with the inlet port;
• a cylinder block coupled with a bottom of the cylinder head;
• and
• a piston arranged in the cylinder block so as to be reciprocable therein, and defining the combustion chamber, which is in communication with the inlet port, together with the cylinder head and the cylinder block;
• wherein
• the inlet valve includes a valve head and a valve stem including a first end coupled with a tip of the valve head and a second end extending upward;
• and
• the valve head includes a valve surface within a circumferential edge portion of the valve head, and a single annular circumferential edge groove disposed in the circumferential edge portion and radially inside the valve surface.

A transportation apparatus comprising an engine unit that includes:

• an inlet valve provided in an inlet port in communication with a combustion chamber;
• a cylinder head provided with the inlet port;
• a cylinder block coupled with a bottom of the cylinder head;
• and
• a piston arranged in the cylinder block so as to be reciprocable therein, and defining the combustion chamber, which is in communication with the inlet port, together with the cylinder head and the cylinder block;
• wherein
• the inlet valve includes a valve head and a valve stem including a first end coupled with a tip of the valve head and a second end extending upward;
• and
• the valve head includes a valve surface within a circumferential edge portion of the valve head, and a single annular circumferential edge groove disposed in the circumferential edge portion and radially inside the valve surface.