| 摘要 |
PURPOSE:To prevent collision between an outer piston and an inner piston and attain better lubrication and cooling for various portions by providing a spool valve which can open or close every passage in response to a supplied oil pressure in a distribution hole formed in a compression ratio variable piston. CONSTITUTION:When a supplied oil pressure stays at a prescribed low pressure, a port 30 only is connected with a distribution hole 29 and pressure oil is supplied to an upper hydraulic chamber 22 and an outer piston 20 keeps the position of a high compression ratio. Since a lower hydraulic chamber 25 is in air tight condition at this time, its collision with the inner piston is prevented, even though the outer piston 20 moves itself in response to an inertia force. When a supplied oil pressure stays at a prescribed high pressure, a spool valve 52 is moved toward the left, ports 34, 33, 31 are opened, the pressure oil is supplied to the lower hydraulic chamber 25, and the outer piston keeps the position of a low compression ratio. At this time, the pressure oil in the distribution hole 29 flows into an annular recessed portion 51 located at the top of the inner piston 21 through the port 33, and flows out to the outside through the port 31. Therefore, the lubrication and cooling around the outer/piston is enhanced in a high load area with a big calorific value of an engine.
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