| 摘要 |
<p>An internal combustion engine is described having a crankshaft, a camshaft (16) driven by the crankshaft through a drive wheel (10) at half the crankshaft speed and at least one cam on the camshaft (16) for actuating a spring biased poppet valve of the engine. To achieve variable event timing, a lost motion coupling (10, 20, 14) is arranged between the drive wheel (10) and the camshaft (16). During the opening of the valve the camshaft (16) rotates at substantially the same speed as the drive wheel (10) but during the closing of a valve, the camshaft (16) is accelerated by the valve spring to lead the drive wheel and thereby reduce the duration of the valve event. It is alternatively possible to collapse the opening phase of the valve event rather than the closing phase by reversing the operation of the coupling.</p> |
