| 摘要 |
PROBLEM TO BE SOLVED: To suppress the generation of noise caused by a collision of a worm gear and a worm wheel.SOLUTION: A variable compression ratio internal combustion engine which can change a mechanical compression ratio by the relative movement of a cylinder block to a crank case comprises: an operation shaft which is constituted so that a relative position between the cylinder block and the crank case is changed when the operation shaft rotates; a worm wheel connected to the operation shaft; a worm gear engaged with the worm wheel; and an actuator which is connected to the worm gear, and drives the operation shaft via the worm gear and the worm wheel. When the cylinder block is relatively moved to the crank case so as to lower the mechanical compression ratio, the actuator is driven so that a rotational speed of the actuator reaches a speed in a region other a setting prohibition region, and the setting prohibition region is set so as to be a relatively-high speed region as an engine rotation number becomes high.SELECTED DRAWING: Figure 6 |
