Differential geared architecture for gas turbine engine

Abstract

A gas turbine engine includes first and second shafts rotatable about a common axis. A first turbine section is supported on the first shaft. Second compressor and turbine sections are supported on the second shaft. The gas turbine engine includes a fan, a first compressor section, and a differential gear train that couples the fan and the first compressor section to the first shaft.

What is claimed is: 
     
         1 . A gas turbine engine comprising:
 first and second shafts rotatable about a common axis;   a first turbine section supported on the first shaft;   second compressor and turbine sections supported on the second shaft;   a fan;   a first compressor section; and   a differential gear train coupling the fan and the first compressor section to the first shaft.   
     
     
         2 . The gas turbine engine according to  claim 1 , wherein the differential gear train is an epicyclic gear train including a sun gear, planetary gears arranged about and intermeshing with the sun gear, and a ring gear circumscribing and intermeshing with the planetary gears. 
     
     
         3 . The gas turbine engine according to  claim 2 , wherein the planetary gears are supported by a carrier, the carrier rotationally fixed to the first shaft. 
     
     
         4 . The gas turbine engine according to  claim 3 , wherein the first compressor section is supported by a compressor rotor, and the fan is supported by a fan shaft, one of the sun gear and the ring gear connected to the fan shaft, and the other of the sun gear and the ring gear connected to the compressor rotor. 
     
     
         5 . The gas turbine engine according to  claim 4 , wherein the sun gear is connected to the compressor rotor, and the ring gear is connected to the fan shaft. 
     
     
         6 . The gas turbine engine according to  claim 4 , wherein the ring gear is connected to the compressor rotor, and the sun gear is connected to the fan shaft. 
     
     
         7 . The gas turbine engine according to  claim 3 , wherein a speed change device interconnects the first shaft and the differential gear train, the speed change device configured to provide a speed reduction from the first shaft to the differential gear train. 
     
     
         8 . The gas turbine engine according to  claim 7 , wherein the speed change device interconnects the first shaft and the carrier. 
     
     
         9 . The gas turbine engine according to  claim 3 , wherein a speed change device interconnects the differential gear train and the fan shaft, the speed change device configured to provide a speed reduction from the differential gear train to the fan shaft. 
     
     
         10 . The gas turbine engine according to  claim 9 , wherein the speed change device interconnects the sun gear and the fan shaft. 
     
     
         11 . The gas turbine engine according to  claim 1 , wherein an inducer is operatively coupled to the differential gear train. 
     
     
         12 . The gas turbine engine according to  claim 1 , wherein first and second shafts respectively provide low and high spools, and the first compressor and turbine sections are low pressure compressor and turbine sections, and the second compressor and turbine sections are high pressure compressor and turbine sections. 
     
     
         13 . The gas turbine engine according to  claim 12 , wherein the low pressure turbine section includes a number of stages in the range of three to six. 
     
     
         14 . The gas turbine engine according to  claim 2 , wherein the epicyclic gear train has a geometry ratio in the range of 1.5 to 3.0. 
     
     
         15 . A gas turbine engine comprising:
 first and second shafts rotatable about a common axis;   a first turbine section supported on the first shaft;   second compressor and turbine sections supported on the second shaft;   a fan;   a first compressor section;   a differential gear train coupling the fan and the first compressor section to the first shaft, the differential gear train is an epicyclic gear train including a sun gear, planetary gears arranged about and intermeshing with the sun gear, and a ring gear circumscribing and intermeshing with the planetary gears, the planetary gears are supported by a carrier, the carrier rotationally fixed to the first shaft; and   wherein the first and second shafts respectively provide low and high spools, and the first compressor and turbine sections are low pressure compressor and turbine sections, and the second compressor and turbine sections are high pressure compressor and turbine sections.   
     
     
         16 . The gas turbine engine according to  claim 15 , wherein the first compressor section is supported by a compressor rotor, and the fan is supported by a fan shaft, one of the sun gear and the ring gear connected to the fan shaft, and the other of the sun gear and the ring gear connected to the compressor rotor. 
     
     
         17 . The gas turbine engine according to  claim 16 , wherein the sun gear is connected to the compressor rotor, and the ring gear is connected to the fan shaft. 
     
     
         18 . The gas turbine engine according to  claim 16 , wherein the ring gear is connected to the compressor rotor, and the sun gear is connected to the fan shaft. 
     
     
         19 . The gas turbine engine according to  claim 15 , wherein the low pressure turbine section includes a number of stages in the range of three to six. 
     
     
         20 . The gas turbine engine according to  claim 15 , wherein the epicyclic gear train has a geometry ratio in the range of 1.5 to 3.0.