Abstract: A water pump with a pump body, a chamber defined inside the pump body, and a rotor rotatable inside the chamber around a rotation axis with a plurality of vanes movable along respective radial directions. A tilting stator is arranged inside the chamber in an eccentric position with respect to the rotor. The tilting stator is pivoted at a rotation pin. A ring is interposed between the tilting stator and the rotor and is in contact with a radially inner surface of the tilting stator and with radially outer ends of the vanes. Adjusting members for adjusting the pump displacement are active on the tilting stator to move the tilting stator with respect to the rotor and place the tilting stator in at least one predetermined operating position defined between a maximum eccentricity position and a minimum eccentricity position.

Abstract: A water pump with a stator, a chamber defined inside the stator, a ring arranged inside said chamber having a radially outer surface in contact with a radially inner surface of the stator, and a rotor arranged inside the ring and rotatable around a rotation axis. The rotor has a plurality of vanes movable along respective radial directions and having respective radially outer ends in contact with a radially inner surface of the ring. The ring is made of a material having a friction coefficient lower than friction coefficient of metal materials.