Analysis of Pressure Signals Inside the Chambers of a Lubricating Vane Pump: a Lump-Parameter Model of the Transducers Dynamic Response

Variable-displacement lubricating pumps are an attractive solution to avoid waste of power and, consequently, to reduce fuel consumption and emissions in ICE. This kind of pumps require appropriate control strategies. In this prospective, modelling and experimental analysis are mandatory steps for a deep understanding of pump operation and for effectively implementing pump control. The paper illustrates a zero-dimensional model of a 7-vane pump. Simulation results were compared with the experimental data of dynamic piezo-resistive pressure transducers fitted into the casing of a pump prototype, which was operated under steady-state conditions at different rotational speeds and eccentricity values. Owing to the reduced dimensions of the investigated pump a connecting tubing installation was performed to connect the transducers used for measurements of static and dynamic pressure signals to the pressure source in the pump chambers. The effects of the tube length and diameter on a pulse train pressure signal in the hydraulic system have been analysed theoretically. Also the effect of the air dissolved in the hydraulic fluid was investigated. Theoretical equations to predict the natural frequency and the damping coefficient of the system are obtained so that the proper length and diameter of tubing can be selected for minimum distortion of the step input signal. Agreement between theoretical predictions and experimental measurements was found to be reasonably good. The investigation shows that the transducer dynamics deteriorate as the diameter or length of the connections increase and as the dissolved air quantity increases.