| 摘要 |
PURPOSE:To discharge oil quickly at time of stoppage of an internal combustion engine, and prevent the deterioration from occurring, by installing a relief valve, discharging the oil in an oil chamber, in the inner piston inserted into a piston body, and opening this relief valve according to the supplied hydraulic pressure. CONSTITUTION:When am internal combustion engine is stopped, a main oil pump 11 is stopped as well. And, when the engine temperature detected by a sensor 27 is lower than the specified value, an auxiliary oil pump 12 is also stopped by a control circuit 26. And, pressure to be led into a pressure receiving chamber via a pilot through hole 40 of the inner piston 2 fitted, free of slide molten, in the inner part of a piston body 1, is lowered to some extent, whereby a relief valve 33 is put back and plural relief through holes are interconnected with each other. With this constitution, oil in the first oil chamber 5 formed in space between the piston body 1 and the inner piston 2 is promptly discharged to an oil pan 20 through a relief passage 32, thus such a possibility that oil is left behind in the first oil chamber 5 and heated is prevented from occurring.
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