A novel experimental method for measuring oil film thickness in balanced vane pumps

Investigation of Oil Film Thickness (OFT) in balanced vane pumps is particularly relevant as they could experiment both loss of contact and elasto-hydrodynamic lubrication condition of the vane tip, detrimental to Noise-Vibration-Harshness behaviour and durability, respectively. Accordingly, this paper proposes an experimental method for measuring the OFT between the vane tip and stator by means of capacitive sensors. The transducer is housed in the cam ring of a prototypical pump for automatic transmissions and the OFT is acquired in different positions of the pump cycle at different operating conditions. The steps followed to modify the pump parts to house the sensor are reported. Moreover, the dedicated test bench and experimental procedure are described. An original post-processing procedure is proposed to obtain the OFT quantity. Finally, attention is devoted to the influence of the lubricant dielectric constant variation, due to the wear of components, showing its great influence on the results.