The paper presents two displacement controls for IC Engine lubricating vane pumps. The main feature is the variable setting of the absolute pressure limiter that can switch from a high to a low level when a minimum threshold value of engine speed or oil temperature is exceeded. This is obtained by venting the displacement actuator of the pump by means of a two positions electrovalve or a temperature sensitive valve. Aim is the reduction of the circuit pressure in the less critical engine operating conditions in order to decrease the absorbed torque. These controls are contrasted with a traditional fixed setting device in terms of overall energy absorbed by the pump in the NEDC cycle. Comparisons are performed with a lumped parameters simulation model able to replicate the operating conditions encountered by the pump during the driving cycle, in terms of oil temperature and circuit permeability. Outcomes from simulation have been validated by experimental tests on pumps prototypes. Tests have been performed on a rig where the load on the pump is generated by a proportional throttle valve controlled in a closed loop in order to reproduce, for each temperature and velocity condition, the resistance of the lubricating circuit. The study brings to evidence that with both systems a significant reduction of the absorbed energy can be achieved in the NEDC without detrimental effects on engine lubrication.

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