Axial flow fluid compressor

Claim 1

An axial flow fluid compressor comprising: a casing; a cylinder mounted in the casing for defining a compressing space; a columnar rotary member arranged in the cylinder so as to extend in the axial direction of the cylinder and be eccentric to the cylinder, and rotatable relative to the cylinder while part of the rotary member is in contact with the inner peripheral surface of the cylinder along a line longitudinal to the axis of the cylinder, the rotary member having a pair of spiral grooves on the outer peripheral surface thereof so as to define the compressing space into two symmetrical compressing sub-spaces each having a suction-side end and a discharge-side end, the spiral grooves having pitches narrowing gradually from the suction-side end toward the discharge-side end along the axial direction of the rotary member; a pair of spiral blades each fitted in the corresponding spiral groove so as to be slidable in the radial direction of the rotary member, having an outer peripheral surface intimately in contact with the inner peripheral surface of the cylinder, and dividing the corresponding compressing sub-space into a plurality of working chambers having volumes gradually decreasing from the suction-side end to the discharge-side end in proportion to the spiral pitch of the blade; driving means for relatively rotating the cylinder and the rotary member to successively transport a fluid introduced from the suction-side end toward the discharge-side end of the respective compressing sections through the working chambers; a pair of bearing means for supporting respective ends of the columnar rotary member; and a pair of opening means, each having the same area, formed at the respective ends of the rotary member for applying the pressure of the fluid in the cylinder equally to the pair of bearing means facing the respective ends of the rotary member.