Screw Compressor

Abstract

A screw compressor is provided which can reduce the pressure loss in a suction flow passage. A casing 12 of the screw compressor includes a bore 21 that accommodates a lobed portion 13A of a male rotor 11A and a lobed portion 13B of a female rotor 11B therein such that working chambers are formed in lobe grooves of the lobed portions, a suction port 22 located on an outer side in a rotor radial direction, and a suction flow passage 23 that communicates in a rotor axial direction with working chambers that are in a suction stroke. The suction flow passage 23 includes a male rotor side suction flow passage 26A located on an male rotor 11A side and besides on a downstream side with respect to a virtual plane C, and a female rotor side suction flow passage 26B located on an female rotor 11B side and besides on the downstream side with respect to the virtual plane C. The male rotor side suction flow passage 26A is formed such that a flow passage wall 27A on the outer side in the rotor radial direction is located at a position that is the same as that of a wall of the bore 21 as viewed in the rotor axial direction at least within a range of one half of an axial pitch P1 of the lobed portion 13A of the male rotor 11A from a suction side end surface of the lobed portion 13A in the rotor axial direction.

1 . A screw compressor, comprising:
 a male rotor having a lobed portion;   a female rotor having a lobed portion that engages with the lobed portion of the male rotor; and   a casing that accommodates the male rotor and the female rotor,   the casing including a bore that accommodates the lobed portion of the male rotor and the lobed portion of the female rotor therein such that working chambers on a male rotor side and working chambers on a female rotor side are formed in lobe grooves of the lobed portions, a suction port located on an outer side in a rotor radial direction with respect to the lobed portion of the male rotor and the lobed portion of the female rotor, and a suction flow passage formed so as to connect the suction port to working chambers that are in a suction stroke and communicating in a rotor axial direction with the working chambers that are in the suction stroke,   the suction flow passage including a male rotor side suction flow passage located on the male rotor side and besides on a downstream side with respect to a virtual plane that passes a central axis of the male rotor and a central axis of the female rotor, and a female rotor side suction flow passage located on the female rotor side and besides on the downstream side with respect to the virtual plane, wherein   the male rotor side suction flow passage is formed such that a flow passage wall on the outer side in the rotor radial direction is located at a position same as that of a wall of the bore as viewed in the rotor axial direction at least within a range of one half of an axial pitch of the lobed portion of the male rotor from a suction side end surface of the lobed portion in the rotor axial direction.   
     
     
         2 . The screw compressor according to  claim 1 , wherein
 the male rotor side suction flow passage is formed such that an area of each flow passage cross section that is a rotor axial cross section taken along each radial direction of the male rotor is same as an area of a rotor radial cross section of each working chamber on the male rotor side at least within a range of a rotational pitch of the lobed portion of the male rotor from the virtual plane in a direction of rotation of the male rotor.   
     
     
         3 . The screw compressor according to  claim 1 , wherein
 the female rotor side suction flow passage is formed such that a flow passage wall on the outer side in the rotor radial direction is located at a position same as that of the wall of the bore as viewed in the rotor axial direction at least within a range of one half of an axial pitch of the lobed portion of the female rotor from a suction side end surface of the lobed portion in the rotor axial direction.   
     
     
         4 . The screw compressor according to  claim 3 , wherein
 the female rotor side suction flow passage is formed such that an area of each flow passage cross section that is a rotor axial cross section taken along each radial direction of the female rotor is equal to an area of a rotor radial cross section of each working chamber on the female rotor side at least within a range of a rotational pitch of the lobed portion of the female rotor from the virtual plane in a direction of rotation of the female rotor.   
     
     
         5 . A screw compressor comprising:
 a male rotor having a lobed portion;   a female rotor having a lobed portion that engages with the lobed portion of the male rotor; and   a casing that accommodates the male rotor and the female rotor,   the casing including a bore that accommodates the lobed portion of the male rotor and the lobed portion of the female rotor therein such that working chambers on a male rotor side and working chambers on a female rotor side are form in lobe grooves of the lobed portions, a suction port located on an outer side in a rotor radial direction with respect to the lobed portion of the male rotor and the lobed portion of the female rotor, and a suction flow passage formed so as to connect the suction port to working chambers that are in a suction stroke and communicating in a rotor axial direction with the working chambers that are in the suction stroke,   the suction flow passage including a male rotor side suction flow passage located on the male rotor side and besides on a downstream side with respect to a virtual plane that passes a central axis of the male rotor and a central axis of the female rotor, and a female rotor side suction flow passage located on the female rotor side and besides on the downstream side with respect to the virtual plane, wherein   the female rotor side suction flow passage is formed such that a flow passage wall on the outer side in the rotor radial direction is located at a position same as that of a wall of the bore as viewed in a rotor axial direction at least within a range of one half of an axial pitch of the lobed portion of the male rotor from a suction side end surface of the lobed portion in the rotor axial direction.   
     
     
         6 . The screw compressor according to  claim 5 , wherein
 the female rotor side suction flow passage is formed such that an area of each flow passage cross section that is a rotor axial cross section taken along each radial direction of the female rotor is same as an area of a rotor radial cross section of each working chamber on the female rotor side at least within a range of a rotational pitch of the lobed portion of the female rotor from the virtual plane in a direction of rotation of the female rotor.