3B1-4 POWER STEERING Suction and discharge of the hydraulic oil is done by a pressure plate and side plate attached to both ends of the cartridge. Suction openings and discharge openings are provided in two locations each in symmetrical positions with re- spect to the axis of rotation, and because the load on the bearings due to the discharge pressure is balanced, a tandem oil pump is also called a balanced hydraulic pump. Because it has a double pump effect per rotation, this pump provides large discharge flow in proportion to the space it occupies.
Also, some of the hydraulic oil that is discharged is led to the base of the vanes and ensures the quality of the seal between the vane tips and the cam, and even if the vanes and cam rings become a lit- tle worn, the seal is hardly affected at all (with respect to discharge, oil tightness).