| 摘要 |
An internal combustion engine has a crankcase, a cylinder bank extending from the crankcase and a crankshaft disposed in the crankcase. A cylinder in the cylinder bank is closed by a cylinder head which carries intake and exhaust valves for regulating the flow of gasses through the cylinder. An intake and an exhaust camshaft are rotationally disposed within the crankcase and are driven by the crankshaft. The intake camshaft has a cam lobe which operates the intake valve through a pushrod extending between the cam lobe and the valve and the exhaust camshaft has a cam lobe which operates the exhaust valve through a pushrod extending between the cam lobe and the valve. The use of separate intake and exhaust camshafts separates the intake valve actuation event from that of the exhaust valve and allows the application of camshaft phasing to vary the opening relationship, or timing of the intake and the exhaust valves. In addition, the use of two camshafts facilitates the use of multi-step cam lobe.
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