Cranktrain phase adjuster for variable compression ratio

A method of adjusting a phase between an input gear and an output gear, the method comprising:

• providing:
• an input gear connected to an input shaft via an interface assembly configured to provide axial movement between the input gear and the input shaft, and rotational locking between the input gear and the input shaft;
• a piston plate connected to the input shaft, the piston plate defining at least one inner spiral bidirectional raceway;
• a seal plate arranged adjacent to the piston plate;
• an output gear configured to be driven by the input shaft, the output gear at least partially defining at least one outer spiral bidirectional raceway;
• and
• at least one first rolling element arranged between the at least one inner bidirectional raceway and the at least one outer spiral bidirectional raceway;
• and
• supplying oil to either a first chamber or a second chamber defined on opposite sides of the seal plate such that the seal plate axially displaces the piston plate to adjust the phase between the input gear and the output gear.