| 摘要 |
PROBLEM TO BE SOLVED: To reduce a secondary oscillation ingredient caused by a lower link 6 in a double-linked piston crank mechanism. SOLUTION: This mechanism is provided with an upper link 3 connected to a piston 1, a lower link 6 connected to the upper link 3 and a crank pin 5 of a crankshaft 4, and a control link 9 for controlling the flexibility of the lower link 6 by connecting it to an eccentric cam 10A. The top dead center position of the piston 1 and then a compression ratio vary by the turning position of a control shaft 10. The center of gravity W of the lower link 6 is set in such a manner that the distance rc from it to the center of the crank pin 5 is shorter than those r1 and r2 to the first and second link pins 7 and 8, and preferably coincides with the center of the crank pin 5. The more the center of gravity W approximates the center of the crank pin, the higher order oscillation ingredients as well as the secondary one are reduced.
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