Valve with wilder opening and pressure regulator equipped with such a valve

Valve comprising:

• a valve body comprising:
• an internal chamber having a longitudinal axis comprising an upstream compartment and a downstream compartment, said upstream compartment being of cylindrical cross section and of diameter Dam and said downstream compartment being of cylindrical cross section and of diameter Dav, with Dam<Dav,
• at least one fluid inlet orifice formed in the wall of said valve body and opening into the upstream compartment of the internal chamber, and at least one fluid outlet orifice;
• and
• a piston body movable in translation along the longitudinal axis inside at least one part of said internal chamber and located between said fluid inlet orifice and said fluid outlet orifice,
• said piston body having a front face located on a same side as the fluid inlet orifice, a rear face located on a same side as the fluid outlet orifice, and a lateral wall located between said front face and said rear face,
• said lateral wall of the piston body having at least a first portion of cylindrical cross section and of first diameter D1 and at least a second portion of cylindrical cross section and of second diameter D2, with D1<D2, D2<Dav, and D2<Dam,
• a wall of said valve body has an internal face forming an end wall of the upstream compartment, the front face of the piston body normally bearing against said internal face.