Efficient variable pitch stator with passive control

A three element fluid torque converter, being disposed between an engine and a transmission, comprising:

• a bladed impeller, being rotatively fixed to the engine;
• a bladed turbine, being rotatively fixed to a transmission input element;
• and
• a stator, being rotatively fixed to a stationary shaft when subjected to torque in a first direction, rotating freely about the stationary shaft when subjected to torque in a second direction, being disposed in a flow path from the turbine to the impeller, the stator comprising:
• a stator core, having a concave spherical core surface, the core surface having a center disposed on a torque converter axis;
• a stator shell, having a convex spherical shell surface, radially disposed within the core surface, the shell surface having a center common with the core surface center;
• a plurality of stator blades, being distributed around the torque converter axis between the core surface and the shell surface, the blades typically having a concave spherical edge surface proximate to and complementary to the shell surface, the blades having a convex spherical edge surface proximate to and complementary to the core surface, the blades having an axis of rotation passing through the center of the stator shell and core, the blades being rotatable between an open position and a closed position, the blades in the closed position blocking approximately 75% to 90% of an annular area between the shell and the core, the blades having a closed position inlet angle between the torque converter axis and a line from the center of rotation of the blade to a tip of the blade, the closed position inlet angle being between 30 degrees and 70 degrees, the closed position inlet angle for a particular stator varying inversely with the number of stator blades, the closed position inlet angle selected being sufficiently large to diminish a flow of fluid from the turbine to the impeller, thereby reducing torque converter torque transmitting capacity in the closed position by approximately 50% over the torque transmitting capacity of the torque converter with the blades in the open position, consequently producing low creep torque, while producing appreciably less driveline noise and vibration than a stator with rotatable vanes blocking near 100% of the annular area between the shell and the core in the closed position;
• and
• means for rotating the stator blades between the open position and the closed position, biasing the blades toward the closed position, with fluid exiting the turbine overcoming the bias, thereby rotating the blades to the open position.