抄録
In a variable displacement vane pump, the vane jumping phenomenon-vanes detaching from the cam ring-causes the pressure fluctuations and decreases the volumetric efficiency.
This paper describes the reason why the marked detachment of vanes takes place in the process of compression from the suction port to the delivery port. We have measured the movements of the vane by an eddy current displacement sensor which was mounted in the rotor. Setting the eccentricities of the cam ring to the rotor, we could show the motion locus of the vane tip, and also obtain the angular position of the detachment and re attachment of the jumping vane. It was found that the maximum distance between the jumping vane and the cam ring reaches to about 0.8mm.
By examining the pressure of the pumping chamber, it is clear that the vane jumping is caused by excess pre-compression at the dead-volume zone, not by the surge pressure due to back-flows from the delivery side. Furthermore, in order to compare with the experimental results, the pressure of the pumping chamber and the motion of the vane tip have been simulated by applying an equation of continuity to the pumping chamber and an equation of motion to its forward vane respectively. Consequently, the calculation results approximately agree with the experimental values regarding the positional deviation of the eccentricities.
