| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To suppress consumption of energy required for driving a hydraulic actuator 31 for variable control of a compression ratio. <P>SOLUTION: In the variable compression-ratio mechanism, a compression ratio is determined by the position of an eccentric cam part 19 of a control shaft 18, which is driven by the hydraulic actuator 31 in the rotation direction. The hydraulic actuator 31 comprises a double action piston-cylinder mechanism, and is driven by switching between introduction and discharge of a hydraulic fluid into/out of oil chambers 55 and 56 by a direction selector valve 59. In this case, a hydraulic pressure upstream of the valve 59 is detected by a pressure sensor 67 and controlled by a variable relief valve 66 so as to make it an objective hydraulic pressure. An oil pump 60 is driven mechanically by a crank pulley 63. The energy consumption can be decreased by lowering the hydraulic pressure in an extent necessary for retention of a rotation position of the control shaft 18 and responsiveness. <P>COPYRIGHT: (C)2004,JPO</p> |
