| 摘要 |
PURPOSE:To obtain the correct valve timing and valve lift by a method wherein a hydraulic actuator is extended even at the starting, in which the supply of hydraulic pressure to the actuator retards, by providing the actuator with a spring made of shape memory metal and a bias spring. CONSTITUTION:The valve timing and valve lift are controlled by changing the location of the fulcrum of a rocker arm 17 with the inclined movement of a lever 20 caused by the extension and contraction of a hydraulic actuator 25. A spring 51 made of shape memory metal acts in the direction to contract the hydraulic actuator 25, while a bias spring 55 acts in the direction to extend the actuator 25. During the period of time when temperature is low such as at the starting, the spring 51 is soft and the bias spring 55 is superior to the spring 51, resulting in extending the actuator 25 and introducing oil in a hydraulic pressure chamber 25. Under the warm-up state of an engine, the shape memory metal becomes superior to and nullifies the bias spring 55. Even when the hydraulic pressure is not enough high, the correct valve characteristics are obtained. |
