is in a counter clockwise direction during the compression and early expansion strokes fig4 a and 4 b this force acting through the eccentric against the cylinder generates a hydraulic pressure in chamber 50 which causes the oil to flow from chamber 50 out past the open check valve 58 through a pair of connecting passages 72 74 to open check valve 56 and enter chamber 48 the plungers are now free to move relative to the cylinders in response to the torsional force acting on the eccentric the auxiliary torque now turns the eccentric 14 counter clockwise while the teeth of the plungers 40 42 perform a rocking motion about the center of the basic crank journal 12 when the auxiliary torque changes its direction to clockwise during the latter part of the expansion stroke the hydraulic pressure in the chamber 48 becomes high which closes the check valve 56 and the reverse flow of oil from chamber 48 to 50 is prevented accordingly the eccentric turns only counter clockwise reducing the crank radius and increasing the clearance volume as shown in fig7 a since the eccentric turns in the same direction as the control cam lobe 68 was turned the neutral relative position of the cam lobe and the eccentric is eventually restored.