Uniaxial eccentric screw pump

An uniaxial eccentric screw pump including:

• a male thread-like rotor directly coupled to a driving shaft;
• a stator rotatably supported via a sliding bearing, the sliding bearing formed of at least one of a self-lubricating bearing or a submerged bearing and the stator having a female thread-like inner surface and an axis of rotation eccentrically disposed with respect to an axis of rotation of the rotor, wherein a fluid is pumped from an intake side to a discharge side while the rotor is rotating and eccentrically moving with respect to a shaft center of the stator, the pump comprising:
• a first annular small-diameter portion axially extending toward the discharge side from an end of the discharge side of the stator;
• a first seal member in sliding contact with a circumferential surface of the first annular small-diameter portion to hermetically seal an end of the sliding bearing and the stator at the discharge side;
• a second annular small-diameter portion axially extending toward the intake side from an end of the intake side of the stator;
• and
• a second seal member in sliding contact with a circumferential surface of the second annular small-diameter portion to hermetically seal an end of a sliding portion and the stator at the intake side,
• wherein an external diameter of the first annular small-diameter portion is smaller than an external diameter of the sliding portion at the intake side of the stator, and an area of the first annular small-diameter portion and an opening of the first annular small-diameter portion, when viewed in an axial direction, is larger than an area of an opening of the discharge side of the stator when viewed in the axial direction.