Design and Analysis of Eccentric Large Arc Rotor Profile of Roots Vacuum Pump

Roots pump rotor profile design is the important contents of Roots pump research.The profile of the eccentric large arc rotor is composed of the arc whose center is located on the negative semi-axis of abscissa in the pitch circle,the pin tooth arc and its conjugate curve.First,the design parameters and range of the eccentric large arc,and the pin tooth arc on the top of the rotor are determined,and the conjugate curve is obtained corresponding to the eccentric large arc from the meshing characteristics.Then,according to the conversion relationship between the theoretical profile and the actual profile of the rotor,the design method of the actual profile is analyzed.Finally,according to the pumping speed,rotors center distance and rotors gap of the Roots pump,the theoretical and actual profiles of the rotor are designed.The study found that the volume utilization rate of the eccentric large arc rotor profile is higher than that of the circular arc rotor profile when the pitch radius and tip circle radius are the same.