New cycloid rotor profiles design under different rolling circle radii for Roots vacuum pumps

Abstract

This study presents two new cycloid rotor profiles for Roots vacuum pump formed by different rolling circle radii to improve the volume utilization rate and compression ratio. A new rotor profile composed of a pin-tooth arc and a cycloid is design and analyzed where its rolling circle radius is larger than 1/4 of the pitch radius. As the rolling circle radius increases, the volume utilization rate continues to increase and can be greater than 60%, which is an increase of 20% relative to the standard cycloid profile. In addition, another new rotor profile composed of a large arc and a cycloid is designed and analyzed where its rolling circle radius is smaller than 1/4 of the pitch radius. As the rolling circle radius decreases, the length of the minimum gap between rotor profile and chamber increases, which is beneficial for improving the compression ratio and reducing backflow.