Cam phasing systems and methods

1. A cam phasing system configured to vary a rotational relationship between a camshaft and a crankshaft of an internal combustion engine, the cam phasing system comprising:

a sprocket hub configured to be coupled to the crankshaft;

a cradle rotor configured to be coupled to the camshaft, wherein the cradle rotor includes a helical slot; and

an input rod including a helical protrusion, wherein the helical protrusion is configured to interact with the helical slot to vary a rotational relationship between the camshaft and the crankshaft; and

a compliance mechanism coupled between the input rod and an actuator and including a spring arranged to apply and maintain a force on the input rod in response to an input force being applied to the compliance mechanism by the actuator, and

wherein the interaction between the helical protrusion and the helical slot is configured to frictionally lock the cradle rotor to the input rod during rotary torque events.

2. The cam phasing system of claim 1 , wherein the actuator is coupled to the input rod.

3. The cam phasing system of claim 1 , wherein the force maintained on the input rod by the compliance mechanism is configured to ensure that the cradle rotor reaches a predetermined rotational offset relative to the sprocket hub.

4. A cam phasing system configured to vary a rotational relationship between a camshaft and a crankshaft of an internal combustion engine, the cam phasing system comprising:

a sprocket hub configured to be coupled to the crankshaft;

a cradle rotor configured to be coupled to the camshaft, wherein the cradle rotor includes a helical recess; and

a helix rod including a spline having a helical portion configured to interact with the helical recess of the cradle rotor to vary a rotational relationship between the camshaft and the crankshaft; and

an actuator coupled to the helix rod through a compliance mechanism including a spring, wherein the spring of the compliance mechanism is configured to transfer an input force from the actuator to the helix rod to ensure that the cradle rotor reaches a predetermined rotational offset relative to the sprocket hub, and

wherein the interaction between the helical recess and the helical portion is configured to frictionally lock the cradle rotor to the helix rod during rotary torque events.

5. The cam phasing system of claim 4 , wherein the actuator is configured to apply an input force on the helix rod.

6. The cam phasing system of claim 4 , wherein the helical recess defines a helix angle that is greater than approximately 50 degrees.

7. The cam phasing system of claim 4 , wherein the helical recess defines a helix angle that is greater than approximately 60 degrees.

8. The cam phasing system of claim 4 , further comprising an end plate coupled to the sprocket hub.

9. The cam phasing system of claim 8 , wherein the end plate includes a central aperture having a protrusion configured to engage the helix rod and inhibit the helix rod from rotating relative to the end plate.

10. The cam phasing system of claim 4 , wherein the cradle rotor includes a plurality of additional helical recesses arranged circumferentially around an inner bore of the cradle rotor.

11. The cam phasing system of claim 10 , wherein the helical recess and the plurality of additional helical recesses each define a radial recess in the inner bore that defines a helical profile as the helical recess and the plurality of additional helical recesses extend axially along the inner bore.

12. The cam phasing system of claim 4 , wherein the helix rod includes a plurality of additional splines arranged circumferentially on the helix rod, each one of the plurality of additional splines including an individual helical portion and an axial portion.

13. The cam phasing system of claim 4 , wherein the cradle rotor is configured to be rotated relative to the sprocket hub in a rotational range between 0 degrees and 360 degrees.

14. The cam phasing system of claim 4 , wherein the cradle rotor is configured to be received within an inner bore of the sprocket hub.

15. The cam phasing system of claim 14 , wherein the cradle rotor is inhibited from displacing axially relative to the sprocket hub.