Variable compression ratio engine

摘要

In a variable compression ratio engine with a connecting mechanism including a first control shaft to control the compression ratio of a variable compression ratio, a second control shaft to be rotated/retained by an actuator, and a lever interconnecting the first control shaft and the second control shaft, a speed reduction ratio from the actuator to the first control shaft through the rotation power transmission path is set to be maximum at the maximum compression ratio, at a preset compression ratio (i.e. at any given compression ratio between the minimum compression ratio and the maximum compression ratio) the speed reduction ratio is set to be minimum, and the reduction ratio is set higher at the maximum compression ratio as compared to the intermediate compression ratio.

主权项

1. A variable compression ratio engine comprising:
a variable compression ratio mechanism that changes an engine compression ratio in accordance with a rotation position of a first control shaft; an actuator that selectively changes and holds the rotation position of the first control shaft; a connecting mechanism that couples the actuator and the first control shaft, the connecting mechanism including a second control shaft disposed generally parallel to the first control shaft and a lever connecting the first control shaft and the second control shaft, wherein one end of the lever is connected to a tip of a first arm portion extending radially outwardly of a center of the first control shaft while another end of the lever is connected to a tip of a second arm portion extending radially outwardly of the center of the second control shaft; the engine compression ratio is set to be higher as the first control shaft rotates in a direction of a predetermined high compression ratio; a speed reduction ratio from the actuator to the first control shaft through a rotation power transmission path is at a maximum when the engine compression ratio is at a minimum compression ratio; the speed reduction ratio is at a minimum at an intermediate compression ratio; the speed reduction ratio is set greater when the engine compression ratio is at the maximum than at the intermediate compression ratio; anda load acting on the lever upon torque being applied about the first control shaft is set to be a maximum at the maximum compression ratio and is at the minimum within a set range between the minimum compression ratio and the intermediate compression ratio, wherein, between the maximum compression ratio and the intermediate compression ratio, a projecting direction of the second arm portion is set in a direction in which a decrease amount of the speed reduction ratio with respect to a decrease of the engine compression ratio is greater.