Piston cooling nozzle

A nozzle for cooling a piston of an internal combustion engine, including a nozzle body with a penetrating part shaped to engage in a bore of the engine and to receive a cooling fluid arriving via said bore, including an internal valve for modulating the flow of fluid as a function of its pressure, and including an outlet structure with a radial fluid passage in the nozzle body and an outlet tube, adapted to transmit cooling fluid leaving the internal valve and to direct it in the form of a jet at least against the back of the piston to be cooled, the internal valve including a piston, having a downstream section with a cylindrical lateral guide surface sliding longitudinally in a guide bore in the nozzle body, having a head oriented in the upstream direction defined with respect to the direction of flow of the cooling fluid to bear selectively against an annular seat in the nozzle body and through which the cooling fluid flows, and the internal valve including a compression coil spring, engaged axially between a downstream bearing surface in the nozzle body and a downstream surface of the piston to urge the piston in the upstream direction against the annular seat, wherein the guide bore in which the piston slides is essentially inside an upstream section of the nozzle body, on the upstream side of the radial fluid passage, and fluid passages convey the fluid axially from the downstream side of the annular seat to the radial fluid passage as soon as the piston moves off the annular seat, so that, when the internal valve is open, the piston is substantially on the upstream side of the radial fluid passage.