Gas turbine engine gear train

Abstract

An epicyclic gear train includes a carrier that supports star gears that mesh with a sun gear. A ring gear surrounds and meshes with the star gears. The star gears are supported on respective journal bearings. Each of the journal bearings includes a peripheral journal surface and each of the star gears includes a radially inner journal surface that is in contact with the peripheral journal surface of the respective journal bearing. The epicyclic gear train has a gear reduction ratio of greater than or equal to about 2.3

1 . A gear apparatus, comprising:
 an epicyclic gear train including a carrier supporting star gears that mesh with a sun gear, and a ring gear surrounding and meshing with the star gears, the star gears being supported on respective journal bearings, each of the journal bearings including a peripheral journal surface and each of the star gears including a radially inner journal surface in contact with the peripheral journal surface of the respective journal bearing, wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to about 2.3.   
     
     
         2 . The gear apparatus as recited in  claim 1 , wherein the radially inner journal surface of each of the star gears is in contact with the peripheral journal surface of the respective journal bearing along an axial length with respect to a rotational axis of the respective star gear. 
     
     
         3 . The gear apparatus as recited in  claim 1 , wherein the radially inner journal surface of each of the star gears is in contact with the peripheral journal surface of the respective journal bearing along a substantially full axial length of the respective star gear with respect to a rotational axis of the respective star gear. 
     
     
         4 . The gear apparatus as recited in  claim 1 , wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to 2.3. 
     
     
         5 . The gear apparatus as recited in  claim 1 , wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to about 2.5. 
     
     
         6 . The gear apparatus as recited in  claim 1 , wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to 2.5. 
     
     
         7 . A turbine engine comprising:
 a turbine shaft;   a fan; and   an epicyclic gear train coupled between the turbine shaft and the fan, the epicyclic gear train including a carrier supporting star gears that mesh with a sun gear, and a ring gear surrounding and meshing with the star gears, each of the star gears being supported on a respective journal bearing, each journal bearing including a peripheral journal surface and each of the star gears including a radially inner journal surface in contact with the peripheral journal surface of the respective journal bearing, wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to about 2.3.   
     
     
         8 . The turbine engine as recited in  claim 7 , wherein the radially inner journal surface of each of the star gears is in contact with the peripheral journal surface of the respective journal bearing along an axial length with respect to a rotational axis of the respective star gear. 
     
     
         9 . The turbine engine as recited in  claim 7 , wherein the radially inner journal surface of each of the star gears is in contact with the peripheral journal surface of the respective journal bearing along a substantially full axial length of the respective star gear with respect to a rotational axis of the respective star gear. 
     
     
         10 . The turbine engine as recited in  claim 7 , wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to 2.3. 
     
     
         11 . The turbine engine as recited in  claim 7 , wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to about 2.5. 
     
     
         12 . The turbine engine as recited in  claim 7 , wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to 2.5. 
     
     
         13 . The turbine engine as recited in  claim 7 , wherein the fan defines a bypass ratio of greater than about ten (10) with regard to a bypass airflow and a core airflow. 
     
     
         14 . The turbine engine as recited in  claim 7 , wherein the fan defines a bypass ratio of greater than about 10.5:1 with regard to a bypass airflow and a core airflow. 
     
     
         15 . The turbine engine as recited in  claim 7 , wherein the fan defines a bypass ratio of greater than ten (10) with regard to a bypass airflow and a core airflow. 
     
     
         16 . The turbine engine as recited in  claim 7 , wherein the fan defines a pressure ratio that is less than about 1.45. 
     
     
         17 . The turbine engine as recited in  claim 7 , wherein the fan defines a pressure ratio that is that is less than 1.45.