An engine having improved volumetric efficiency may include a cylinder, an intake valve, a piston, an exhaust valve and a crankshaft. The cylinder may include a cylinder bore. The intake valve may be configured to introduce a fuel and an air into the cylinder bore. The piston may be slidably arranged in the cylinder bore. The piston may be configured to convert an explosive power of an exhaust gas, which may be generated by combusting the fuel, into a linear driving force. The exhaust valve may be configured to exhaust the exhaust gas from the cylinder bore. The crankshaft may be connected with the piston to convert the linear driving force into a rotary driving force. The intake valve and the exhaust valve may be simultaneously opened within a rotation angle of about 3° to about 12° of the crankshaft.
1. An engine comprising:
a cylinder having a cylinder bore;
an intake valve configured to introduce an air and a fuel into the cylinder bore;
a piston slidably arranged in the cylinder bore to convert an explosive force, which is generated by combusting the fuel, into a linear driving force;
an exhaust valve configured to exhaust an exhaust gas from the cylinder bore; and
a crankshaft connected with the piston to convert the linear driving force into a rotational driving force,
wherein the intake valve and the exhaust valve are simultaneously opened within a rotation angle of 3° to 12° of the crankshaft, the intake valve is opened within the rotation angle of 1° to 2° of the crankshaft before a top dead point of the piston, and the exhaust valve is closed within the rotation angle of 2° to 10° of the crankshaft after a top dead point of the piston.
2. The engine of claim 1 , wherein the intake valve and the exhaust valve are simultaneously opened within the rotation angle of 3° to 6° of the crankshaft.
3. The engine of claim 1 , wherein a section after a top dead point of the piston in a total section in which the intake valve and the exhaust valve are simultaneously opened is wider than a section before the top dead point of the piston in the total section in which the intake valve and the exhaust valve are simultaneously opened.
4. The engine of claim 1 , further comprising a camshaft connected with the crankshaft to operate the intake valve and the exhaust valve.
5. The engine of claim 4 , wherein the intake valve and the exhaust valve are simultaneously opened within a rotation angle of 1.5° to 3° of the camshaft.
6. The engine of claim 5 , further comprising:
an intake cam combined with the camshaft to open and close the intake valve; and
an exhaust cam combined with the camshaft to open and close the exhaust valve,
wherein a phase difference between a nose of the intake cam in the intake valve and a nose of the exhaust cam in the exhaust valve is 107.75° to 112.25°.
7. The engine of claim 6 , wherein a closing angle of the intake cam is 65° to 69°, and an opening angle of the exhaust cam is 73° to 77°.
8. The engine of claim 1 , wherein the engine comprises a compressed natural gas (CNG) engine.
9. The engine of claim 8 , further comprising a fuel supply system configured to supply CNG to the cylinder.
10. An engine comprising:
a cylinder having a cylinder bore;
an intake valve configured to introduce an air and a fuel into the cylinder bore;
an exhaust valve configured to exhaust an exhaust gas from the cylinder bore;
a camshaft configured to operate the intake valve and the exhaust valve;
an intake cam combined with the camshaft to open and close the intake valve; and
an exhaust cam combined with the camshaft to open and close the exhaust valve,
wherein a phase difference between a nose of the intake cam and a nose of the exhaust cam is 107.75° to 112.25°.
11. The engine of claim 10 , wherein the intake valve and the exhaust valve are simultaneously opened within the rotation angle of 1.5° to 3° of the camshaft.
12. The engine of claim 10 , wherein a closing angle of the intake cam is narrower than an opening angle of the exhaust cam.
13. The engine of claim 12 , wherein the closing angle of the intake cam is 65° to 69°, and the opening angle of the exhaust cam is 73° to 77°.