Disclosed is a piston cooling device wherein the cooling efficiency of a piston is improved by oil injected from an oil jet and supplied to a cooling passage provided in the piston, and the amount of cooling oil is reduced when an internal combustion engin...

The engine has an extension placed on a lower piston (20) to carry an active piston (26). An oil pump (54) acquires cooling fluid e.g. oil, present in a base of a case (14) for distributing it to distributing ducts. A supplying unit (58) supplies the fluid...