Research On Geometric Theory And Performance Of Novel Three-Claw Rotors For Claw Vacuum Pumps

Claw vacuum pumps are rotary positive displacement machines with built-in compression.The claw rotor is the core component of the claw vacuum pump and determines its working performance.The problems of the existing line-arc type three-claw rotors are complex curves,strict constraint conditions and inflexible geometric parameters.In order to solve the above problems,the conjugate eaquations of eccentric involute and sinusoidal curve were derived based on the meshing theory.Then an eccentirc involute type three-claw rotor and a sinusoidal curve tye three-claw rotor were proposed,and the profile equations of these two rotors were derived.According to the conditions that adjacent curves must satisfy smooth connection,the maximum addendum arc of line-arc type,eccentric involute type and sinusoidal type three-claw rotors were analyzed,and the internal leakages of the vacuum pumps with these three rotors were compared.In addition,the undercutting distinguishing formula of the envelope of the sinusoidal curve was obtained,and effects of the geometric parameters on the sinusoidal type rotor were analyzed.The design method of the novel discharge port was proposed,and the theoretical working process of three-claw vacuum pumps was investigated.The study results indicate that the proposed three-claw rotor with sinusoidal curve has advantages of simple profile,good sealing properity,large area efficiency and big internal volume ratio.The novel discharge port allows gases to be exhausted quickly,and avoids the recompression of the gas in the carry-over.The area efficiency and interal volume ratio increase with the augment of ratio of arc radius ? and addendum arc angle ?.Furthermore gas compression is achieved by leakages through clearances during the isometric transport process,and the biggest leakge is located at the gap between two intermeshing rotors.Stresses and deformations of rotors are mainly affected by the temperature loads.The contents of this paper are of great significance to optimize the three-claw rotors and reveal the characteristic of the flow field for three-claw vacuum pumps.