Patent ID: 8511261
Filing Date: 2013-08-20
Classification: F01M,F01P,F02F

Abstract:
1. A piston cooling device, comprising: a piston for an internal combustion engine in which a cooling passage is provided, the cooling passage having a circumferential passage extending in a circumferential direction, and an inlet passage and an outlet passage communicating with the circumferential passage respectively, wherein the circumferential passage comprises introduction passages communicated with the inlet passage at most upstream portions; and main passages communicated with the introduction passages at most upstream portions, and the introduction passages are diffuser passages which extend upward and bend in circumferential directions so as to be communicated with the main passages, and cross-sectional areas thereof continuously increase toward the downstream; and an oil jet which injects an oil from an injection port placed below the inlet passage opening downward when the piston reciprocates in an up-and-down direction, the oil injected from the injection port flows into the inlet passage and flows out of the outlet passage through the circumferential passage, wherein the oil jet injects the oil at every stroke of the piston and an injection speed of the oil at the injection port is equal to or less than a maximum speed of the piston when the internal combustion engine is operated at a maximum output operation such that a gas-liquid two-phase plug flow composed of a gas and the oil is formed in the cooling passage at least when the internal combustion engine is operated at the maximum output, and wherein an increasing rate R which is defined by the following equation is equal to or greater than 0.06 and is equal to or less than 0.8, where S (m) is a distance from the most upstream portions on a passage center line of the introduction passages, and A (m