| 摘要 |
PURPOSE: To keep lubricant oil pressure approximately constant in an arrangement in which an exterior piston part is engaged with an interior piston part vertically movably by forming a control oil groove communicating with a main oil bore of a piston in a part around a large-end bearing of a connecting rod. CONSTITUTION: A piston 1 comprises an interior piston part 3 connected to a small-end ring 7 of a connecting rod 6 by a piston pin 5, and an exterior piston part 2 retained vertically movably on the part 3. An upper control chamber 10 is formed between the two piston parts 2, 3. The chamber 10 communicates with a lower control chamber 11 via a parallel circuit of a throttle 13 and a check valve 14 and a connecting bore 12. To increase compression height, pressured oil is fed to the upper control chamber 10 via a check valve 17. In this case, bearing rings 25, 26 forming a control oil groove 24 in a part of an inner surface of the connecting rod 6 are engaged with an large-end bearing 8 supported by a crank pin 9. The pressured oil from a main oil bore 28 runs through the control oil groove 24 and a vertical bore 23. |
