Roots pump containing rotors that capture and discharge a foreign substance

A roots pump comprising:

• a housing;
• a rotor chamber that is defined in the housing and includes a suction hole from which fluid is drawn and a discharge hole from which the fluid is discharged;
• a pair of rotary shafts rotatably supported in the housing;
• and
• a pair of rotors, the pair of rotors that is attached to the pair of the rotary shafts, respectively, and rotates in the rotor chamber,
• the rotor chamber including a rotor chamber peripheral surface that is formed of a pair of arc surfaces connecting the suction hole and the discharge hole in a radial direction of each of the rotors and that faces a pair of distal end portions of each of the rotors with a predetermined radial clearance comprising a first radial clearance and a second radial clearance,
• in response to rotation of the pair of rotors, in the rotor chamber, fluid drawn from the suction hole being guided to the pair of the arc surfaces of the rotor chamber peripheral surface and being discharged from the discharge hole, wherein
• each of the pair of the distal end portions of each of the rotors includes:
• a pair of rotor peripheral surfaces that faces the rotor chamber peripheral surface with the first radial clearance, the pair of the rotor peripheral surfaces facing the rotor chamber peripheral surface having a pair of predetermined widths in a rotational direction of each of the rotors;
• and
• a distal end peripheral surface that is formed between the pair of the rotor peripheral surfaces in the rotational direction, faces the rotor chamber peripheral surface with the second radial clearance greater than the first radial clearance, and captures a foreign substance in the rotor chamber at a time of rotation of the pair of the rotors, and
• a width of the rotor chamber peripheral surface facing the distal end peripheral surface in the rotational direction is greater than a sum of the pair of the predetermined widths of the rotor chamber peripheral surface facing the pair of the rotor peripheral surfaces.