Camshaft-in-camshaft apparatus of variable valve duration system

Abstract

A camshaft-in-camshaft apparatus may include a hollow outer shaft having at least one slot formed along a length direction of the hollow outer shaft, an inner shaft rotatably inserted inside the outer shaft and having at least one pin hole formed on the inner shaft, a position of each of the at least one pin hole corresponding to that of each of the at least one slot, one or more first cam lobes fixedly mounted on an exterior circumference of the outer shaft, one or more second cam lobes fixedly mounted on the inner shaft to be rotatable on the corresponding slot of the outer shaft, a cam phaser changing a phase angle between the outer shaft and the inner shaft by rotating any one of the outer shaft and the inner shaft, and at least one torsional spring mounted between any one of the one or more first cam lobes and any one of the one or more second cam lobes.

What is claimed is: 
     
         1 . A camshaft-in-camshaft apparatus comprising:
 a hollow outer shaft having at least one slot formed along a length direction thereof;   an inner shaft rotatably inserted inside the outer shaft and having at least one pin hole formed thereon, a position of each of the at least one pin hole corresponding to that of each of the at least one slot;   one or more first cam lobes fixedly mounted on an exterior circumference of the outer shaft;   one or more second cam lobes fixedly mounted on the inner shaft to be rotatable on the corresponding slot of the outer shaft;   a cam phaser changing a phase angle between the outer shaft and the inner shaft by rotating any one of the outer shaft and the inner shaft; and   at least one torsional spring mounted between any one of the one or more first cam lobes and any one of the one or more second cam lobes.   
     
     
         2 . The camshaft-in-camshaft apparatus of  claim 1 ,
 wherein a first cam hole is formed at any one of the one or more first cam lobes and a second cam hole is formed at any one of the one or more second cam lobes, and   wherein both ends of one or each of the at least one torsional spring engage respectively with the first cam hole and the second cam hole.   
     
     
         3 . A camshaft-in-camshaft apparatus comprising:
 a hollow outer shaft having at least one slot formed along a length direction thereof;   an inner shaft rotatably inserted inside the outer shaft and having at least one pin hole formed thereon, a position of each of the at least one pin hole corresponding to that of each of the at least one slot;   one or more first cam lobes fixedly mounted on an exterior circumference of the outer shaft;   one or more second cam lobes fixedly mounted on the inner shaft to be rotatable on the corresponding slot of the outer shaft; and   a cam phaser changing a phase angle between the outer shaft and the inner shaft by rotating any one of the outer shaft and the inner shaft,   wherein the cam phaser includes a stator connected to one of the outer shaft and the inner shaft and a rotor connected to the other of the outer shaft and the inner shaft, and a torsional spring is mounted between the stator and the rotor.   
     
     
         4 . The camshaft-in-camshaft apparatus of  claim 3 ,
 wherein a first fixing part is formed or mounted on the stator and a second fixing part is formed or mounted on the rotor, and   wherein both ends of the torsional spring are fixed to or engaged respectively with the first fixing part and the second fixing part.   
     
     
         5 . The camshaft-in-camshaft apparatus of  claim 4 ,
 wherein the first fixing part is a clamp screwed to the stator and the second fixing part is a fixing groove formed in the rotor.