US 7,320,579 B2
Roots type fluid machine
Takayuki Hirano, Kariya (Japan); Kazuho Yamada, Kariya (Japan); and Toshiro Fujii, Kariya (Japan)
Assigned to Kabushiki Kaisha Toyota Jidoshokki, (Japan)
Filed on Dec. 08, 2006, as Appl. No. 11/608,615.
Claims priority of application No. 2005-355957 (JP), filed on Dec. 09, 2005.
Prior Publication US 2007/0148030 A1, Jun. 28, 2007
Int. Cl. F01C 21/10 (2006.01); F03C 2/00 (2006.01); F04C 2/00 (2006.01)
U.S. Cl. 418—150  [418/206.1; 418/206.5] 10 Claims
OG exemplary drawing
 
1. A roots type fluid machine comprising:
a housing;
a pair of parallel rotary shafts rotatably supported by the housing;
a two-lobe rotor disposed on each rotary shaft in a rotor chamber of the housing so that the rotors engage with each other, each of the rotors comprising:
two lobe portions each having a profile of convex arc with a radius R; and
two well portions each having a profile of concave arc which is an envelope of the convex arc of the lobe portion,
wherein the rotor has a configuration defined by a curve which includes the convex arc, the concave arc and further an involute curve with a base radius r between the convex and concave arcs,
wherein the base radius r is set in a range L/(2√{square root over ( )}2)<r<0.3(√{square root over ( )}2)L where distance between axes of the rotary shafts is L, and the radius R is set in a range {(√{square root over ( )}2)/16}πL<R<{(27−5√{square root over ( )}2)/56}L.