Numerical and experimental analysis of variable displacement vane pumps

Variable displacement vane pumps represent one of the most innovative type of pump for automotive engines. The vane pump with a sliding ring, is a mechanism that makes it possible to change the capacity of the pump as a function of the engine speed, allowing to optimize of the oil flow, according to the engine demand, with considerable power saving. The main components of a variable displacement vane pumps are: vanes, rotor, inner rings and a sliding ring. During operation, the vanes are in contact with the inner surface of the outer (sliding) ring due to the effect of centrifugal loads; in addition high slip velocities occur in the contact area; as a consequence, a critical aspect of this kind of pumps is represented by the wear which takes place on the contact surfaces. Another potential mechanism of damaging process is attributed to vanes sticking in rotor cavities, causing a sudden increase in contact loads. This paper illustrates a summary of a research activity, which was carried out with the aim of analyzing the operating conditions of vanes pumps. The study was conducted with reference to pumps with vanes number ranging from 5 to 9, in order to evidence the influence of some design parameters on results. The numerical analysis were carried out by using multi-body models, that were developed with MSC.Adams® code. In these analyses any effect of the viscous oil inside the pump was neglected, focusing the attention on mechanisms geometry; moreover, the hypothesis of plane analysis was assumed. Some experimental tests were also carried out with a prototype, which was tested up to very hard conditions in order to highlight wear and damage mechanisms