Split ring gear planetary cam phaser

Abstract

A cam phaser ( 10 ) for dynamically adjusting a rotational relationship of a camshaft ( 24 ) of an internal combustion engine with respect to an engine crank shaft can include a planetary gear system ( 12 ) having a split ring gear ( 18 ) including a drive-side ring gear ( 18 a ) to be driven by the engine crank shaft through an endless loop power transmission member and an output-side ring gear ( 18 b ) connectable for rotation with the camshaft ( 24 ). A sun gear ( 14 ) can be located concentric with the split ring gear ( 18 ), and a number of planetary gears ( 16 a, 16 b, 16 c ) can be in meshing engagement between the sun gear ( 14 ) and the split ring gear ( 18 ). The output-side ring gear ( 18 b ) can have a different number of teeth (greater or lesser) than compared with the drive-side ring gear ( 18 a ) by a value corresponding to a multiple of the number of planetary gears to provide tooth alignment at an engagement position of each of the planetary gears ( 16 a, 16 b, 16 c ).

What is claimed is: 
     
         1 . In a cam phaser ( 10 ) for dynamically adjusting a rotational relationship of a camshaft ( 24 ) of an internal combustion engine with respect to an engine crank shaft, the cam phaser ( 10 ) including a planetary gear system ( 12 ) having a drive-side ring gear ( 18   a ) driven by the engine crank shaft through an endless loop power transmission member, a number of planetary gears ( 16   a,    16   b,    16   c ), and a centrally located sun gear ( 14 ), the improvement comprising:
 an output-side ring gear ( 18   b ) concentric with the sun gear ( 14 ) and connected to the camshaft ( 24 ), the output-side ring gear ( 18   b ) having a different number of teeth compared with the drive-side ring gear ( 18   a ) by a value corresponding to a multiple of the number of planetary gears ( 16   a,    16   b,    16   c ) to provide tooth alignment at an engagement position of each of the planetary gears ( 16   a,    16   b,    16   c ).   
     
     
         2 . The improvement of  claim 1  further comprising:
 the drive-side ring gear ( 18   a ) piloted radially by the output-side ring gear ( 18   b ). 
 
     
     
         3 . The improvement of  claim 1  further comprising:
 an electric motor ( 26 ) connected to the sun gear ( 14 ) for driving the sun gear ( 14 ) in relation to the planetary gears ( 16   a,    16   b,    16   c ), wherein the electric motor ( 26 ) rotates at a speed equal to the drive-side ring gear ( 18   a ) to maintain a constant phase position, while variance of the electric motor speed from a value equal to the drive-side ring gear ( 18   a ) causes a cam phase change function to occur. 
 
     
     
         4 . The improvement of  claim 1 , wherein the drive-side ring gear ( 18   a ), the output-side ring gear ( 18   b ), the number of planetary gears ( 16   a,    16   b,    16   c ), and the sun gear ( 14 ) define an epicyclic gear drive connection having a high numerical gear ratio allowing accurate phasing angle adjustment with a relatively low driving torque requirement. 
     
     
         5 . The improvement of  claim 1  further comprising:
 first and second carrier plates ( 20   a,    20   b ) axially piloted by the drive-side ring gear ( 18   a ) and the output-side ring gear ( 18   b ) for securing the number of planetary gears ( 16   a,    16   b,    16   c ) in an axial direction. 
 
     
     
         6 . A cam phaser ( 10 ) for dynamically adjusting a rotational relationship of a camshaft ( 24 ) of an internal combustion engine with respect to an engine crank shaft, the cam phaser ( 10 ) comprising:
 a planetary gear system ( 12 ) having a split ring gear ( 18 ) including a drive-side ring gear ( 18   a ) to be driven by the engine crank shaft through an endless loop power transmission member and an output-side ring gear ( 18   b ) connectable for rotation with the camshaft ( 24 ), the planetary gear system ( 12 ) having a sun gear ( 14 ) located concentric with the split ring gear ( 18 ), and a number of planetary gears ( 16   a ,  16   b,    16   c ) in meshing engagement between the sun gear ( 14 ) and the split ring gear ( 18 ).   
     
     
         7 . The cam phaser ( 10 ) of  claim 6  further comprising:
 the output-side ring gear ( 18   b ) having a different number of teeth compared with the drive-side ring gear ( 18   a ) by a value corresponding to a multiple of the number of planetary gears ( 16   a,    16   b,    16   c ) to provide tooth alignment at an engagement position of each of the planetary gears ( 16   a,    16   b,    16   c ). 
 
     
     
         8 . The cam phaser ( 10 ) of  claim 6  further comprising:
 the drive-side ring gear ( 18   a ) piloted radially by the output-side ring gear ( 18   b ). 
 
     
     
         9 . The cam phaser ( 10 ) of  claim 6  further comprising:
 an electric motor ( 26 ) connected to the sun gear ( 14 ) for driving the sun gear ( 14 ) in relation to the planetary gears ( 16   a,    16   b,    16   c ), wherein the electric motor ( 26 ) rotates at a speed equal to the split ring gear ( 18 ) to maintain a constant electric motor speed from an equal value causes a cam phase change function to occur. 
 
     
     
         10 . The cam phaser ( 10 ) of  claim 6 , wherein the drive-side ring gear ( 18   a ), the output-side ring gear ( 18   b ), the number of planetary gears ( 16   a,    16   b,    16   c ), and the sun gear ( 14 ) define an epicyclic gear drive connection having a high numerical gear ratio allowing accurate phasing angle adjustment with a relatively low driving torque requirement. 
     
     
         11 . The cam phaser ( 10 ) of  claim 6  further comprising:
 first and second carrier plates ( 20   a,    20   b ) axially piloted by the drive-side ring gear ( 18   a ) and the output-side ring gear ( 18   b ) for securing the number of planetary gears ( 16   a,    16   b,    16   c ) in an axial direction. 
 
     
     
         12 . A method for assembling and dynamically adjusting a rotational relationship of a camshaft ( 24 ) of an internal combustion engine with respect to an engine crank shaft comprising:
 assembling a planetary gear system ( 12 ) having a split ring gear ( 18 ) including a drive-side ring gear ( 18   a ) to be driven by the engine crank shaft through a sprocket ( 22 ) engaging an endless loop power transmission member and an output-side ring gear ( 18   b ) connectable for rotation with the camshaft ( 24 );   locating a sun gear ( 14 ) of the planetary gear system ( 12 ) concentric with respect to the split ring gear ( 18 );   engaging a number of planetary gears ( 16   a,    16   b,    16   c ) in meshing engagement between the sun gear ( 14 ) and the split ring gear ( 18 ); and   providing the output-side ring gear ( 18   b ) with a different number of teeth compared with the drive-side ring gear ( 18   a ) by a value corresponding to a multiple of the number of planetary gears ( 16   a,    16   b,    16   c ) to provide tooth alignment at an engagement position of each of the planetary gears ( 16   a,    16   b,    16   c ).   
     
     
         13 . The method of  claim 12  further comprising:
 rotating the planetary gear system ( 12 ) assembly as a unit with the sprocket ( 22 ) to minimize frictional losses. 
 
     
     
         14 . The method of  claim 12  further comprising:
 driving an electric motor ( 26 ) connected to the sun gear ( 14 ) at the same speed as the split ring gear ( 18 ) to maintain a constant phase position. 
 
     
     
         15 . The method of  claim 12  further comprising:
 driving an electric motor ( 26 ) connected to the sun gear ( 14 ) at a speed not equal to the split ring gear ( 18 ) to adjust a phase position.