| 摘要 |
PURPOSE:To realize such a valve characteristic that accords with engine running conditions, by raising each lift of both suction and exhaust valves, improving exhaust capacity ever so better, while adjusting valve timing so as to keep off any interference between a piston head part and the valve. CONSTITUTION:In an on-off mechanism for a suction valve or an exhaust valve, there are provided with a device adjusting a lift value of the valve and another device adjusting on-off timing of the valve. When an engine is driven at high speed and high load to valve characteristics A and B in the exhaust valve and the suction valve being set up so as to accord with low engine speed, the lift value of the suction valve or the exhaust valve is made to be larger and a valve opening period is made to be longer whereby suction capacity or exhaust capacity is improved. In order to keep off any interference between a piston head part and the valve due to an increase in the lift value, timing of the suction valve or the exhaust valve is adjusted, making it to be just like a valve characteristic B', and a clearance l between the piston head part and the valve is secured. With this constitution, suction-exhaust capacity is improved and a dead space in a combustion chamber is reduced. |
