Turbojet engine with offset fans with a differential system
A propulsion unit of an aircraft including a turbine ( 15 ), at least one fan ( 10 ) with an axis offset relative to the axis of the turbine and a power transmission mechanism between the turbine and the fan. The power transmission mechanism includes a speed reducing gear ( 20 ) with an input and a movement output, the input being in the extension of the axis ( 16 ) of the turbine and the output connected to the fan.
1. A propulsion unit of an aircraft comprising a turbine secured to a turbine shaft, at least two fans with offset axes relative to the axis of the turbine and a power transmission mechanism between the turbine and the fans, wherein the power transmission mechanism comprises a differential system comprising a casing, an axial input shaft connected to the turbine shaft, a planet carrier driven by the input shaft, planet gears mounted on the planet carrier, at least one idler gear supported by the casing and radial shafts each perpendicular to the axial input shaft, the radial shafts each driving one of said fans and being secured to idler gears, the planet carrier and the input shaft being coaxial, the planet carrier forming a hub on which the rotation axes of the planet gears are radially arranged.
2. The propulsion unit according to claim 1 , wherein the radial shafts are arranged on either side of the axis of the input shaft.
3. The propulsion unit according to claim 1 , wherein it comprises two mobile wheels rotatable around the input shaft, each wheel having a first toothed annular gear and a second toothed annular gear, each first annular gear of the mobile wheels meshing with the planet gears being arranged opposite therefrom, and each second annular gear meshing separately with one of said idler gears.
4. The propulsion unit according to claim 3 , wherein the shafts of the idler gears are placed in different planes perpendicular to the input shaft.
5. The propulsion unit according to claim 1 , wherein the shafts of the idler gears are in a same plane perpendicular to the input shaft, the radii of the two second annular gears of the rotating mobile wheels being different.
6. The propulsion unit according to claim 1 , wherein the axes of the radial shafts are parallel.
7. The propulsion unit according to claim 1 , wherein the axes of the radial shafts are transverse.
8. The propulsion unit according to claim 2 , wherein the rotating mobile wheels each have an axial journal mounted in the casing via a bearing.
9. The propulsion unit according to claim 8 , wherein the hub is supported by one of said journals via a bearing.
10. The propulsion unit according to claim 1 , wherein the different system is arranged between the shaft of the turbine and the radial shafts each driving one of said fans.
11. The propulsion unit according to claim 10 , the turbine of which is driven by a gas generator.
12. The propulsion unit according to claim 11 , wherein the gas generator is a gas turbine engine with an exhaust case comprising two concentric shrouds, one inner and the other outer, defining the engine gas tunnel downstream from the turbine, the differential system being housed inside the inner shroud.
13. The propulsion unit according to claim 12 , wherein the radial shafts traverse the shrouds of the exhaust case.