Patent ID: 11946382
Assignee: ROLLS-ROYCE PLC
Field: Engines, pumps, turbines (Mechanical engineering)
Classification: CPC F  Y | IPC F

Claim 8:
9. A gas turbine engine for an aircraft, comprising:
an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;
a fan located upstream of the engine core, the fan comprising a plurality of fan blades; and
a gearbox configured to receive an input from the core shaft and provide an output drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, the gearbox comprising:
a sun gear;
a plurality of planet gears surrounding and engaged with the sun gear; and
a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin,
wherein:
a ratio of a length, L, of the internal and external sliding surfaces to a diameter, D, of each journal bearing is greater than 0.5;
a pitch circle diameter of the ring gear is no greater than 1200 mm;
the ratio of a radius of one of the fan blades at a hub to the radius of the fan blade at a tip is in a range of from 0.25 to 0.4;
a diameter of each journal bearing divided by a pitch circle diameter of the respective planet gear is greater than 0.50; and
a value of: (the ratio of the length, L, of the internal and external sliding surfaces to the diameter, D, of each journal bearing)/(the diameter of each journal bearing divided by the pitch circle diameter of the respective planet gear) is less than 2.8.