Screw Fluid Machine

A screw fluid machine, comprising:

• a male rotor including twisted male teeth and rotating about a first rotation center;
• a female rotor including twisted female teeth and rotating about a second rotation center parallel to said first rotation center;
• and
• a casing including an accommodating chamber that rotatably accommodates said male rotor and said female rotor in a meshed state,
• wherein said male rotor and said female rotor are rotated to convey a fluid between a suction port and a discharge port in a state where pressure of the fluid is changed,
• when viewed in an axial direction of a rotation axis, said male rotor is formed such that cross-sectional shapes orthogonal to the rotation axis are sequentially formed in sections having a second cross-sectional shape, a transition shape that changes continuously, and a first cross-sectional shape from a suction-side end face toward a discharge-side end face,
• a cross-sectional tooth profile in the section having said first cross-sectional shape has a cross-sectional shape coinciding with or located outside a pitch point-centered circle at a tooth tip and on an advancing surface side of said tooth tip,
• a cross-sectional tooth profile in the section having the second cross-sectional shape has a cross-sectional shape located inside said pitch point-centered circle at said tooth tip and on the advancing surface side of said tooth tip, and
• in the section having the transition shape, a cross-sectional tooth profile of said male rotor has a shape that changes continuously from the second cross-sectional shape to said first cross-sectional shape.

A screw fluid machine, comprising:

• a male rotor including twisted male teeth and rotating about a first rotation center;
• a female rotor including twisted female teeth and rotating about a second rotation center parallel to said first rotation center;
• and
• a casing including an accommodating chamber that rotatably accommodates said male rotor and said female rotor in a meshed state,
• wherein said male rotor and said female rotor are rotated to convey a fluid between a suction port and a discharge port in a state where pressure of the fluid is changed,
• said male rotor is configured such that cross-sectional shapes orthogonal to a rotation axis are sequentially formed in sections having a first cross-sectional shape, a second transition shape that changes continuously, a second cross-sectional shape, a first transition shape that changes continuously, and said first cross-sectional shape from a suction-side end face toward a discharge-side end face of the rotation axis,
• a cross-sectional tooth profile in the section having said first cross-sectional shape has a cross-sectional shape coinciding with or located outside a pitch point-centered circle at a tooth tip and on an advancing surface side of said tooth tip,
• a cross-sectional tooth profile in the section having the second cross-sectional shape has a cross-sectional shape located inside said pitch point-centered circle at said tooth tip and on the advancing surface side of said tooth tip,
• in the section having the second transition shape, a cross-sectional tooth profile changes continuously from the first cross-sectional shape to the second cross-sectional shape, and
• in the section having the first transition shape, a cross-sectional tooth profile changes continuously from the second cross-sectional shape to the first cross-sectional shape.