Epicyclic 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. Each of the star gears is supported on a respective journal bearing. Each journal bearing includes an internal central cavity and at least one passage that extends radially from the internal cavity to a 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, each of the star gears being supported on a respective journal bearing, each journal bearing including an internal central cavity and at least one passage extending radially from the internal cavity to a 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 at least one passage includes a first passage and a second passage axially spaced from the first passage. 
     
     
         3 . The gear apparatus as recited in  claim 2 , wherein the internal cavity extends between axial ends, and the first passage and the second passage are non-uniformly spaced with regard to the axial ends. 
     
     
         4 . The gear apparatus as recited in  claim 1 , wherein the internal central cavity is axially blind. 
     
     
         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 2.3. 
     
     
         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 about 2.5. 
     
     
         7 . 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. 
     
     
         8 . 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 an internal central cavity and at least one passage extending radially from the internal cavity to a peripheral journal surface of the respective journal bearing, wherein the epicyclic gear train defines a gear reduction ratio of greater than or equal to about 2.3.   
     
     
         9 . The turbine engine as recited in  claim 8 , wherein the at least one passage includes a first passage and a second passage axially spaced from the first passage. 
     
     
         10 . The turbine engine as recited in  claim 9 , wherein the internal cavity extends between axial ends, and the first passage and the second passage are non-uniformly spaced with regard to the axial ends. 
     
     
         11 . The turbine engine as recited in  claim 8 , wherein the internal central cavity is axially blind. 
     
     
         12 . The turbine engine as recited in  claim 8 , wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to 2.3. 
     
     
         13 . The turbine engine as recited in  claim 8 , wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to about 2.5. 
     
     
         14 . The turbine engine as recited in  claim 8 , wherein the epicyclic gear train has a gear reduction ratio of greater than or equal to 2.5. 
     
     
         15 . The turbine engine as recited in  claim 8 , wherein the fan defines a bypass ratio of greater than about ten (10) with regard to a bypass airflow and a core airflow. 
     
     
         16 . The turbine engine as recited in  claim 8 , wherein the fan defines a bypass ratio of greater than about 10.5:1 with regard to a bypass airflow and a core airflow. 
     
     
         17 . The turbine engine as recited in  claim 8 , wherein the fan defines a bypass ratio of greater than ten (10) with regard to a bypass airflow and a core airflow. 
     
     
         18 . The turbine engine as recited in  claim 8 , wherein the fan has a pressure ratio that is less than about 1.45. 
     
     
         19 . The turbine engine as recited in  claim 8 , wherein the fan has a pressure ratio that is that is less than 1.45.