| 摘要 |
PROBLEM TO BE SOLVED: To prevent enlargement of a crankcase in a four-cycle engine in which the workload of the engine is increased by setting the exhaust volume larger than the suction volume so as to improve thermal efficiency and to decrease the pumping loss in the intake stroke. SOLUTION: A planetary gear 43 coaxial with a crankpin 38 is fixed to a hollow eccentric axis 40 which is enabled to rotate around the axial line circumference coaxial with a crank pin 38 and interposed between the large end part 39a of a connecting rod 39 and the crank pin 38. A san gear 44 having a half of the outer diameter of the planetary gear 43 and engaging to the planetary gear 43 is arranged on the same axis as the crank shaft 11. The position of a piston 15 at the bottom dead center of the expansion stroke is set closer to the side of the crank shaft 11 than the position of the piston 15 at the bottom dead center of the suction stroke.
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