Patent ID: 8668436

Claim:
A turbomolecular pump comprising: a plurality of stages that are arranged alternately with rotors having a plurality of blades radially extending from a rotating body and stators having a plurality of blades radially extending toward the rotating shaft of said rotating body, wherein the blades provided on at least either of said rotor or said stator are formed as twisted blades having a blade angle of said blades set by an equation in which the radius from said rotational shaft is a variable; and the equation of said blade angle comprises a first equation which provides the optimum angle of each blade located outside of a predetermined radius and a second equation which provides the blade angle that suppresses reverse flow of gas molecules inside the predetermined radius wherein the blade angle α in said first equation decreases monotonically toward the outer side to satisfy the condition, αout≦α≦αb, and the blade angle α in said second equation decreases monotonically or is constant toward the inner side to satisfy the condition, αb≧α≧αin, where αb is the blade angle at said predetermined radius, αin is the blade angle at the innermost periphery of said blade and αout is the blade angle at the outermost periphery of said blade.