Screw Compressor

Abstract

To provide a screw compressor capable of reducing acceleration loss caused by deceleration of a working fluid in a suction flow channel.SOLUTION: A suction flow channel 60 of a screw compressor has: a male-side flow channel 72 axially opened to a working chamber of a suction stroke on a male rotor 2 side and extending from a start end 75 on one side of a virtual plane Pv to a first terminal end 76 on the other side; and a female-side flow channel 73 axially opened to a working chamber of a suction stroke on a female rotor 3 side and extending from the start end 75 to a second terminal end 77 on the other side of the virtual plane Pv. A flow channel wall of the male-side flow channel 72 includes a male-side first flow channel wall 81 facing a rotor tooth portion 21 side, and a flow channel wall of the female-side flow channel 73 includes a female-side first flow channel wall 91 facing a rotor tooth portion 31 side. The male-side first flow channel wall 81 or the female-side first flow channel wall 91 approaches the rotor tooth portion 21 or the rotor tooth portion 31 from a start end side toward the first terminal end side or the second terminal end side at least in a partial section from the start end 75 to the first terminal end 76 or the second terminal end 77.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a screw compressor, and more particularly to a screw compressor having a suction passage that opens into a working chamber during the suction stroke. [Background technology]

[0002] A screw compressor includes a pair of male and female screw rotors that rotate while meshing with each other, and a casing that houses both screw rotors. In this compressor, multiple working chambers are formed by the tooth grooves of both screw rotors and the inner wall surface of the casing that surrounds them. The casing is provided with an inlet passage that guides gas (working fluid) from the outside to the working chambers and a discharge passage that guides compressed gas from the working chambers to the outside. The working chambers move axially as the both screw rotors rotate, increasing their volume to draw in gas through the inlet passage, then decreasing their volume to compress the gas, and finally discharging the compressed gas through the discharge passage. In this way, the working chambers sequentially repeat an inlet stroke in which gas is drawn in through the inlet passage, a compression stroke in which the gas is compressed, and a discharge stroke in which the compressed gas is discharged through the discharge passage.

[0003] The suction flow passage of a screw compressor includes a male rotor suction flow passage and a female rotor suction flow passage that are connected to the working chamber in the suction stroke in the rotor axial direction and are located downstream of an imaginary plane passing through the central axes of both the male and female rotors (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-28474 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a liquid-feed screw compressor, if one tries to make it smaller in size to reduce costs, it is unavoidable to increase the speed of the screw rotor.Since a non-feed screw compressor cannot expect the sealing effect of a liquid feed that is provided by a liquid-feed type, the screw rotor is often operated at a high speed to reduce leakage loss in the working chamber.

[0006] When the screw rotor is operated at high speed, the working fluid flowing from the suction passage into the working chamber is accelerated to match the high speed of rotation. If the working fluid flowing through the suction passage slows down, the velocity of the working fluid flowing from the suction passage into the working chamber decreases accordingly, and the amount of acceleration of the working fluid increases. This means that the driving power of the screw compressor increases. Therefore, the increase in the acceleration amount of the working fluid due to the deceleration of the working fluid flowing through the suction passage results in energy loss (hereinafter sometimes referred to as acceleration loss), which reduces the efficiency of the screw compressor.

[0007] In the screw compressor described in Patent Document 1, working fluid flows from the branching sides of the male rotor-side suction passage and the female rotor-side suction passage, which are connected to the working chamber in the rotor axial direction, toward the downstream side of an imaginary plane during the suction stroke (see the white arrows in Figure 4 of Patent Document 1). At this time, as the working fluid flows from the branching sides of the male rotor-side suction passage and the female rotor-side suction passage toward the downstream side along the rotor circumferential direction, it is gradually sucked into the working chamber through the axial opening. Therefore, the flow rate of the working fluid gradually decreases from the branching sides of the male rotor-side suction passage and the female rotor-side suction passage toward the downstream end by the amount of working fluid sucked into the working chamber.

[0008] In the screw compressor described in Patent Document 1, the cross-sectional areas of the male rotor suction passage and the female rotor suction passage are considered to be substantially constant from the branching side to the downstream end. In the male rotor suction passage and the female rotor suction passage with such a structure, when the flow rate of the working fluid gradually decreases toward the downstream side, the flow velocity of the working fluid correspondingly decreases toward the downstream side. Therefore, as described above, acceleration loss occurs due to the deceleration of the working fluid flowing through the male rotor suction passage and the female rotor suction passage, and the efficiency of the screw compressor deteriorates.

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a screw compressor that can reduce acceleration loss caused by deceleration of the working fluid flowing through the suction passage. [Means for solving the problem]

[0010] The present application includes a plurality of means for solving the above-mentioned problems, and one example thereof is a rotor having a male rotor with a first rotor tooth portion and rotatable around a first axis, a female rotor having a second rotor tooth portion and rotatable around a second axis, and a casing having an accommodation chamber for accommodating the first rotor tooth portion and the second rotor tooth portion in a state of meshing with each other, and forming a plurality of working chambers together with the first rotor tooth portion and the second rotor tooth portion, wherein the casing is externally accessible. Made by The suction passage has a suction passage for introducing a working fluid into the working chamber, memorandum a male side flow path that opens in the axial direction of the male rotor to the male rotor side working chamber of the moving chamber, and that extends from a first start end, which is located on one side of an imaginary plane passing through the first axis and the second axis and is the inflow side of the working fluid, to a first end end, which is located on the other side of the imaginary plane; memoranduma female side flow passage that opens in the axial direction of the female rotor to the female rotor side working chamber of the working chamber and extends from a second start end located on the one side of the imaginary plane and being an inflow side of the working fluid to a second end end located on the other side of the imaginary plane, a flow passage wall that forms the male side flow passage includes a male side first flow passage wall that faces the suction side end face of the first rotor tooth portion and extends from the first start end to the first end, and a flow passage wall that forms the female side flow passage includes a female side first flow passage wall that faces the suction side end face of the second rotor tooth portion and extends from the second start end to the second end, The wall , the first start Edge From the first end Edge The first starting point in at least a part of the range Side or from the first end On the side As we head towards 、 the first rotor tooth Gradually approaching The female-side first flow path wall has a first inclined surface and a first flat surface equidistant from the first rotor tooth portion, and the first flat surface extends closer to the first end end side than the first inclined surface, or the female-side first flow path wall has a second inclined surface that gradually approaches the first rotor tooth portion from the second start end side toward the second end end side in at least a portion of the range from the second start end to the second end end, and a second flat surface equidistant from the second rotor tooth portion, and the second flat surface extends closer to the second end end side than the second inclined surface. It is characterized by: [Effects of the Invention]

[0011] According to the present invention, the first male flow path wall or first female flow path wall in the male flow path or female flow path that opens in the rotor axial direction to the working chamber during the suction stroke approaches the first rotor tooth portion or second rotor tooth portion as it moves toward the first end end or second end end, so the flow path cross-sectional area of ​​the male flow path or female flow path decreases toward the first end end or second end end. This suppresses deceleration of the working fluid flowing through the male flow path or female flow path, thereby reducing acceleration loss caused by deceleration of the working fluid flowing through the suction flow path. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a vertical cross-sectional view showing a screw compressor according to a first embodiment of the present invention. [Figure 2] 2 is a longitudinal sectional view of the screw compressor according to the first embodiment shown in FIG. 1, taken along the line II-II. [Figure 3] FIG. 3 is a cross-sectional view of the screw compressor according to the first embodiment shown in FIG. 2, taken along the line III-III. [Figure 4] 4 is a view of the screw compressor according to the first embodiment as seen from the arrows IV-IV in FIG. 2. FIG. [Figure 5] 5 is an explanatory view showing an example of the shape of a first flow path wall (the shape of a recess forming the suction flow path) in the suction flow path of the screw compressor according to the first embodiment shown in FIG. 4. FIG. [Figure 6] 5 is an explanatory view showing another example of the shape of the first flow path wall (the shape of the recess forming the suction flow path) in the suction flow path of the screw compressor according to the first embodiment. FIG. [Figure 7] FIG. 2 is a longitudinal sectional view showing a screw compressor as a comparative example to the first embodiment of the present invention. [Figure 8] FIG. 8 is a vertical cross-sectional view of the screw compressor of the comparative example shown in FIG. 7, taken along arrows VIII-VIII. [Figure 9] FIG. 9 is a view of the screw compressor of the comparative example shown in FIG. 7 as viewed from the arrows IX-IX. [Figure 10] 10 is an explanatory view showing the shape of a first flow path wall (the shape of a recess forming the suction flow path) in the suction flow path of the screw compressor of the comparative example shown in FIG. 9. FIG. [Figure 11] FIG. 4 is a vertical cross-sectional view showing a screw compressor according to a second embodiment of the present invention. [Figure 12] FIG. 12 is a cross-sectional view of the screw compressor according to the second embodiment shown in FIG. 11, taken along the line XII-XII. [Figure 13] 13 is a view of the screw compressor according to the second embodiment shown in FIG. 11, as viewed from the arrows XIII-XIII. [Figure 14] 3 is a cross-sectional view of a screw compressor according to a third embodiment of the present invention, taken along the same arrow as that shown in FIG. 2 along the line III-III. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a screw compressor according to the present invention will be described with reference to the drawings.

[0014] [First embodiment] A schematic configuration of a screw compressor according to a first embodiment will be described with reference to Figs. 1 to 3. Fig. 1 is a longitudinal sectional view showing the screw compressor according to the first embodiment of the present invention. Fig. 2 is a longitudinal sectional view of the screw compressor according to the first embodiment shown in Fig. 1, taken along arrows II-II. Fig. 3 is a transverse sectional view of the screw compressor according to the first embodiment shown in Fig. 2, taken along arrows III-III.

[0015] 1 and 2, the screw compressor 1 includes a male rotor 2 and a female rotor 3 as a pair of screw rotors that rotate in mesh with each other, and a casing 4 that houses both the male and female rotors 2, 3. The male rotor 2 is supported by a suction side bearing 6 and a discharge side bearing 7 so as to be rotatable about an axis Lm. The female rotor 3 is supported by a suction side bearing 8 and a discharge side bearing 9 so as to be rotatable about an axis Lf that is parallel to the axis Lm of the male rotor 2.

[0016] The male rotor 2 is composed of a rotor tooth portion 21 having a plurality of spiral male teeth, and a suction-side shaft portion 22 and a discharge-side shaft portion 23 provided on both axial end portions of the rotor tooth portion 21. The rotor tooth portion 21 has a suction-side end face 21a and a discharge-side end face 21b at one axial end (left end in Figures 1 and 2) and the other axial end (right end in Figures 1 and 2), respectively, which are perpendicular to the axial direction (axis Lm). In the rotor tooth portion 21, tooth grooves are formed between the plurality of male teeth. The suction-side shaft portion 22 is configured to penetrate, for example, the casing 4, and is connected to a rotational drive source (not shown). The rotational drive source may be, for example, an electric motor.

[0017] The female rotor 3 is composed of a rotor tooth portion 31 having a plurality of spiral female teeth, and a suction-side shaft portion 32 and a discharge-side shaft portion 33 provided on both axial end portions of the rotor tooth portion 31. The rotor tooth portion 31 has a suction-side end face 31a and a discharge-side end face 31b at one axial end (left end in FIG. 2) and the other axial end (right end in FIG. 2), respectively, which are perpendicular to the axial direction (axis Lf). In the rotor tooth portion 31, tooth spaces are formed between the plurality of female teeth.

[0018] The casing 4 has a cylindrical main casing 41 with a bottom that is open on one axial side (the left side in Figures 1 and 2) that is the suction side, and a suction-side casing 42 that is a separate member from the main casing 41 and is attached to the main casing 41 so as to close the opening of the main casing 41. The casing 4 has a bore 45 that serves as an accommodation chamber that accommodates the rotor teeth 21 of the male rotor 2 and the rotor teeth 31 of the female rotor 3 in a mutually meshed state. As shown in Figure 3, the bore 45 is formed in the main casing 41 so that the cylindrical hole that accommodates the rotor teeth 21 of the male rotor 2 and the cylindrical hole that accommodates the rotor teeth 31 of the female rotor 3 partially overlap. As shown in Figures 1 to 3, the wall surfaces that form the storage chamber of the casing 4 are composed of a male-side inner wall surface 45a that covers the radial outside of the rotor tooth portion 21 of the male rotor 2, a female-side inner wall surface 45b that covers the radial outside of the rotor tooth portion 31 of the female rotor 3, a suction-side inner wall surface 45c (a part of the end surface 42a (see Figure 4 described later) of the suction-side casing 42 on the main casing 41 side) on one axial side (left side in Figures 1 and 2) that faces the suction-side end faces 21a, 31a of the rotor tooth portions 21, 31 of both the male and female rotors 2, 3, and a discharge-side inner wall surface 45d on the other axial side (right side in Figures 1 and 2) that faces the discharge-side end faces 21b, 31b of the rotor tooth portions 21, 31 of both the male and female rotors 2, 3. Multiple working chambers C are formed by the tooth grooves of the rotor tooth portions 21, 31 of the male rotor 2 and female rotor 3 housed in the housing chamber (bore 45) and the inner wall surfaces of the casing 4 surrounding them (male side inner wall surface 45a, female side inner wall surface 45b, suction side inner wall surface 45c, discharge side inner wall surface 45d).

[0019] 1 and 2, a discharge side bearing 7 for the male rotor 2 and a discharge side bearing 9 for the female rotor 3 are disposed in the main casing 41, and a discharge side cover 43 is attached to cover the discharge side bearing 7 and the discharge side bearing 9. A suction side bearing 6 for the male rotor 2 and a suction side bearing 8 for the female rotor 3 are disposed in the suction side casing 42.

[0020] As shown in Fig. 1, the casing 4 is provided with a discharge flow path 50 that guides compressed gas from the working chamber C to the outside of the casing 4. The discharge flow path 50 connects the working chamber C in the discharge stroke with the outside of the casing 4, and has a discharge port 51 that forms an opening on the outer wall side of the casing 4, and a discharge port 52 that forms an opening on the bore 45 side. The discharge port 52 is provided on the other axial side of the bore 45 (right side in Fig. 1) and on one side of an imaginary plane Pv that passes through the axes Lm, Lf of both the male rotor 2 and the female rotor 3 (lower side in Fig. 1).

[0021] The casing 4 is also provided with an intake passage 60 that introduces gas from the outside of the casing 4 to the working chamber C. The intake passage 60 connects the outside of the casing 4 with the working chamber C in the intake stroke, and has an intake port 61 that forms an opening on the outer wall side of the casing 4, and an intake port 62 that forms an opening on the bore 45 side. The intake port 61 is provided, for example, on one axial side (left side in FIG. 1) of the outer peripheral surface of the casing 4 and on the other side (upper side in FIG. 1) of the imaginary plane Pv. The intake port 62 is formed, for example, as an axial intake port that is open only in the axial direction to the working chamber C in the intake stroke. Details of the structure, such as the shape of the intake passage 60 of this embodiment, will be described later.

[0022] In the screw compressor 1 configured as described above, when the male rotor 2 shown in FIG. 2 is driven by a rotary drive source, the male rotor 2 rotates the female rotor 3, and working fluid is drawn into the screw compressor 1. The working fluid is drawn from the suction passage 60 shown in FIG. 1 through the suction port 62 into the working chamber C. As the male and female rotors 2 and 3 shown in FIG. 2 rotate, the working chamber C moves axially and its volume increases and decreases. Specifically, the volume of the working chamber C first gradually increases as the male and female rotors 2 and 3 rotate, drawing in the working fluid (suction stroke). After the suction stroke ends, the volume of the working chamber C gradually decreases as the male and female rotors 2 and 3 rotate, compressing the working fluid (compression stroke). As the male and female rotors 2 and 3 continue to rotate, the working chamber C communicates with the discharge port 52, and the compressed fluid in the working chamber is discharged to the outside of the casing 4 through the discharge passage 50. The volume of the working chamber C eventually becomes almost zero, and the working chamber C again enters the suction stroke of sucking in the working fluid. The screw compressor 1 continuously compresses the working fluid by repeating these strokes.

[0023] The screw compressor 1 of this embodiment is configured so that the male rotor 2 is driven by a rotary drive source to drive the female rotor 3. However, the screw compressor 1 can also be configured so that the male rotor 2 is driven by the female rotor 3 being driven by a rotary drive source, or so that both the male and female rotors 2, 3 are driven synchronously.

[0024] Furthermore, the screw compressor 1 of this embodiment is illustrated as a liquid-free compressor that does not have an injection port for injecting a liquid such as oil or water into the working chamber C. However, it may also be a liquid-feed screw compressor that injects a liquid into the working chamber C through an injection port. When the screw compressor 1 is a liquid-free type, the rotor teeth 21 of the male rotor 2 and the rotor teeth 31 of the female rotor 3 must be rotated in a non-contact state, and a rotational engagement means such as a timing gear for rotationally engaging the male rotor 2 and the female rotor 3 is provided, but this rotational engagement means is not shown in Figures 1 and 2. Furthermore, the oil supply system for the suction-side bearings 6, 8 and the discharge-side bearings 7, 9 and the shaft seal means for the shafts of both the male and female rotors 2, 3 are also not shown.

[0025] Next, the details of the structure of the suction passage of the screw compressor according to the first embodiment will be described with reference to Figs. 1 to 6. Fig. 4 is a view of the screw compressor according to the first embodiment as seen from the direction of arrows IV-IV in Fig. 2. Fig. 5 is an explanatory view showing an example of the shape of the first passage wall in the suction passage of the screw compressor according to the first embodiment shown in Fig. 4 (the shape of the recessed portion forming the suction passage). Fig. 6 is an explanatory view showing another example of the shape of the first passage wall in the suction passage of the screw compressor according to the first embodiment (the shape of the recessed portion forming the suction passage). In Figs. 3 and 4, the thick arrows indicate the rotation direction of the screw rotor.

[0026] As shown in FIGS. 1 to 4, the suction flow passage 60 of the casing 4 has an introduction flow passage 71 extending from the suction port 61, a male branch flow passage 72 branching from the introduction flow passage 71 and extending along the circumferential direction of the male rotor 2 at the suction-side end face 21a of the rotor tooth portion 21 of the male rotor 2, and a female branch flow passage 73 branching from the introduction flow passage 71 and extending along the circumferential direction of the female rotor 3 at the suction-side end face 31a of the rotor tooth portion 31 of the female rotor 3. As shown in FIG. 3, the male branch flow passage 72 and the female branch flow passage 73 open to (communicate with) the working chamber C during the suction stroke to form a suction space for drawing the working fluid into the working chamber C. The introduction flow passage 71 guides the working fluid to the male branch flow passage 72 and the female branch flow passage 73, which form the suction space, and is not open to the working chamber C. Inlet flow passage 71 is configured to connect to male branch flow passage 72 and female branch flow passage 73 at a position on the other side (upper side in FIGS. 1 and 3) of imaginary plane Pv in casing 4 (i.e., a position on the opposite side of discharge port 52 from imaginary plane Pv). Inlet flow passage 71 is formed, for example, to extend along the rotor axial direction at a position radially outward of bore 45 of casing 4.

[0027] The male branch flow passage 72 and the female branch flow passage 73 extend from the connection position with the introduction flow passage 71 (i.e., the inflow position of the working fluid) to the position of the closing portion 42b of the casing 4 formed in an area on one side (lower side in Figures 1 and 3) of the imaginary plane Pv. The closing portion 42b closes the axial openings of the tooth grooves on the suction side end faces 21a, 31a of the rotor tooth portions 21, 31 of the male and female rotors 2, 3 when the working chamber C reaches a predetermined volume due to the rotation of the male and female rotors 2, 3. In this embodiment, as shown in Figure 4, the regions of male branch channel 72 and female branch channel 73 that are connected to introduction channel 71 and branch off from each other are referred to as starting ends 75 of male branch channel 72 and female branch channel 73, the end of male branch channel 72 on the closed section 42b side is referred to as male ending end 76, and the end of female branch channel 73 on the closed section 42b side is referred to as female ending end 77. In other words, male branch channel 72 extends from starting end 75 to male ending end 76 in the circumferential direction of male rotor 2. Female branch channel 73 extends from starting end 75 to female ending end 77 in the circumferential direction of female rotor 3.

[0028] As shown in FIG. 3, the male branch flow passage 72 is configured to open in the axial direction to the working chamber C during the suction stroke. As shown in FIGS. 1, 3, and 4, the flow passage walls forming the male branch flow passage 72 include a first flow passage wall 81 facing the suction-side end face 21a of the rotor tooth portion 21 of the male rotor 2, a second flow passage wall 82 located radially outward of the male rotor 2, and a third flow passage wall 83 located radially inward of the male rotor 2 relative to the second flow passage wall 82. Similar to the male branch flow passage 72, the female branch flow passage 73 is configured to open in the axial direction to the working chamber C during the suction stroke. The flow passage walls forming the female branch flow passage 73 include a first flow passage wall 91 facing the suction-side end face 31a of the rotor tooth portion 31 of the female rotor 3, a second flow passage wall 92 located radially outward of the female rotor 3, and a third flow passage wall 93 located radially inward of the second flow passage wall 92. 4, male-side branch flow path 72 and female-side branch flow path 73 can be formed by providing a C-shaped recess in end surface 42a of suction-side casing 42. That is, first flow path walls 81, 91 form the bottom surface of the recess in suction-side casing 42 that is recessed in the axial direction, and second flow path walls 82, 92 and third flow path walls 83, 93 form the side walls of the recess that is recessed in the axial direction.

[0029] As shown in Fig. 3, the second flow path wall 82 of the male side branch flow path 72 is configured to be located radially outward of the male rotor 2 relative to the male side inner circumferential wall surface 45a of the bore 45. Like the second flow path wall 82 of the male side branch flow path 72, the second flow path wall 92 of the female side branch flow path 73 is also configured to be located radially outward of the female rotor 3 relative to the female side inner circumferential wall surface 45b of the bore 45. The third flow path wall 83 of the male side branch flow path 72 is configured to approximately match the tooth bottom diameter of the rotor tooth portion 21 of the male rotor 2. Like the third flow path wall 83 of the male side branch flow path 72, the third flow path wall 93 of the female side branch flow path 73 is also configured to approximately match the tooth bottom diameter of the rotor tooth portion 31 of the female rotor 3. The rotor radial distance between second flow path wall 82 and third flow path wall 83 in male side branch flow path 72, i.e., the flow path width of male side branch flow path 72, is configured to be approximately constant at least in the region on the other side of imaginary plane Pv (lower side in FIG. 4), as shown in Figure 4. Similarly, the rotor radial distance between second flow path wall 92 and third flow path wall 93 in female side branch flow path 73, i.e., the flow path width of female side branch flow path 73, is configured to be approximately constant at least in the region on the other side of imaginary plane Pv (lower side in FIG. 4).

[0030] The first flow path wall 81 of the male side branch flow path 72 is configured to gradually approach the rotor teeth 21 of the male rotor 2 from the starting end 75 toward the male end 76 in at least a portion of the range from the starting end 75 to the male end 76. Similarly, the first flow path wall 91 of the female side branch flow path 73 is configured to gradually approach the rotor teeth 31 of the female rotor 3 from the starting end 75 toward the female end 77 in at least a portion of the range from the starting end 75 to the female end 77.

[0031] Specifically, first flow path wall 81 of male side branch flow path 72 and first flow path wall 91 of female side branch flow path 73 have a shape as shown in Fig. 5. Fig. 5 shows male side branch flow path 72 and female side branch flow path 73 shown in Fig. 4 expanded along dashed dotted lines Dm and Df.

[0032] First flow path wall 81 of male side branch flow path 72 is configured as a flat surface equidistant from suction side end face 21a of rotor tooth portion 21 of male rotor 2 in a section from point 81a located near starting end 75 of male side branch flow path 72 to point 81b, and is configured as an inclined surface that gradually approaches suction side end face 21a of male rotor 2 from point 81b to point 81c located at male side end 76. That is, first flow path wall 81, with the inclined surface approaching suction side end face 21a of male rotor 2, extends from a position on the other side (upper side in FIG. 4) of imaginary plane Pv to male side end 76. In other words, the axial depth of the recessed bottom surface that forms male side branch flow path 72 in suction casing 42 is configured to be approximately constant in the section from point 81a to point 81b, and to gradually become shallower from point 81b to point 81c. The point 81b is, for example, located closer to the starting end 75 than the imaginary plane Pv, perpendicular to the imaginary plane Pv, and passing through the axis Lm of the male rotor 2.

[0033] Similarly, the first flow path wall 91 of the female-side branch flow path 73 is configured as a flat surface equidistant from the suction-side end face 31a of the rotor teeth 31 of the female rotor 3 in a section from point 91a located near the start end 75 of the female-side branch flow path 73 to a point 91b, and is configured as an inclined surface that gradually approaches the suction-side end face 31a of the female rotor 3 from point 91b toward point 91c located at the female-side end end 77. That is, the inclined surface of the first flow path wall 91 approaching the suction-side end face 31a of the female rotor 3 extends from a position on the other side (upper side in FIG. 4) of the imaginary plane Pv to the female-side end end 77. In other words, the axial depth of the recessed bottom surface that forms the female-side branch flow path 73 in the suction casing 42 is configured to be approximately constant in the section from point 91a to point 91b, and to gradually become shallower from point 91b to point 91c. The point 91b is, for example, located closer to the starting end 75 than the imaginary plane Pv, perpendicular to the imaginary plane Pv, and passing through the axis Lf of the female rotor 3.

[0034] It is also possible to configure first flow path wall 81 of male side branch flow path 72 and first flow path wall 91 of female side branch flow path 73 in a shape such as that shown in Fig. 6. Fig. 6 shows male side branch flow path 72 and female side branch flow path 73 shown in Fig. 4 expanded along dashed dotted lines Dm and Df.

[0035] In detail, first flow path wall 81 of male side branch flow path 72 is configured as a plane that is equidistant from suction side end face 21a of male rotor 2 in the section from point 81a to point 81b (similar to the case of Figure 5), is configured as an inclined surface that gradually approaches suction side end face 21a of male rotor 2 as it moves from point 81b to point 81d just before reaching male side end end 76, and is configured as a plane that is equidistant from suction side end face 21a of male rotor 2 in the section from point 81d to point 81c located at male side end end 76. That is, first flow path wall 81 is configured as a plane in a predetermined section up to male side end end 76. In other words, the bottom surface of the recess forming male side branch flow path 72 in suction casing 42 is configured so that the axial depth is approximately constant in the section from point 81a to point 81b, and gradually becomes shallower as it moves from point 81b to point 81d just before reaching male side end end 76, and is configured so that the depth is approximately constant in the section from point 81d to point 81c located at male side end end 76.

[0036] Similarly, the first flow path wall 91 of the female-side branch flow path 73 is configured as a plane that is equidistant from the suction-side end face 31a of the female rotor 3 in the section from point 91a to point 91b (as in Figure 5), is configured as an inclined surface that gradually approaches the suction-side end face 31a of the female rotor 3 as it moves from point 91b to point 91d just before the female-side end end 77, and is configured as a plane that is equidistant from the suction-side end face 31a of the female rotor 3 in the section from point 91d to point 91c located at the female-side end end 77. That is, the first flow path wall 91 is configured as a plane in a predetermined section up to the female-side end end 77. In other words, the bottom surface of the recess forming the female side branch flow path 73 in the suction casing 42 is configured so that the axial depth is approximately constant in the section from point 91a to point 91b, and gradually becomes shallower as it moves from point 91b to point 91d just before reaching the female side end end 77, and is configured so that the depth is approximately constant in the section from point 91d to point 91c located at the female side end end 77.

[0037] In the intake passage 60 of the screw compressor 1 configured as described above, the working fluid flowing in from the introduction passage 71 flows from the starting end 75 of the male branch passage 72 toward the male end 76, and is sucked into the working chamber C through the intake port 62 that opens in the axial direction, and also flows from the starting end 75 of the female branch passage 73 toward the female end 77, and is sucked into the working chamber C through the intake port 62 that opens in the axial direction.

[0038] Next, the operation and effects of the screw compressor according to the first embodiment will be described in comparison with a screw compressor of a comparative example. First, the structure of the suction passage of the screw compressor of the comparative example will be described with reference to Figs. 7 to 10. Fig. 7 is a longitudinal sectional view showing a screw compressor of a comparative example compared to the first embodiment of the present invention. Fig. 8 is a longitudinal sectional view of the screw compressor of the comparative example shown in Fig. 7, taken along arrows VIII-VIII. Fig. 9 is a view of the screw compressor of the comparative example shown in Fig. 7, taken along arrows IX-IX. Fig. 10 is an explanatory view showing the shape of the first passage wall in the suction passage of the screw compressor of the comparative example shown in Fig. 9 (the shape of the recess forming the suction passage). In Figs. 7 to 10, the same reference numerals as those in Figs. 1 to 6 indicate similar parts, and detailed description thereof will be omitted.

[0039] The main difference between screw compressor 101 of the comparative example and screw compressor 1 of the present embodiment is that, of suction passages 160 formed in casing 104, male side branch passage 172 and female side branch passage 173 formed in suction side casing 142 have different shapes. Other than that, the configuration of screw compressor 101 of the comparative example is similar to the configuration of screw compressor 1 of the present embodiment.

[0040] 7 to 9, first flow path wall 181 of male side branch flow path 172 of the comparative example is configured to be maintained equidistant from suction side end face 21a of rotor tooth portion 21 of male rotor 2 from starting end 75 to male side end 76. Similarly, first flow path wall 191 of female side branch flow path 173 is configured to be maintained equidistant from suction side end face 31a of rotor tooth portion 31 of female rotor 3 from starting end 75 to female side end 77.

[0041] Specifically, first flow path wall 181 of male side branch flow path 172 and first flow path wall 191 of female side branch flow path 173 have the shape shown in Fig. 10. Fig. 10 is a development of male side branch flow path 172 and female side branch flow path 173 shown in Fig. 9 along dash-dotted lines Dm and Df. First flow path wall 181 of male side branch flow path 172 is configured as a flat surface equidistant from suction side end surface 21a of male rotor 2 in a section from point 81a located near starting end 75 of male side branch flow path 172 to point 81c located at male side end 76. In other words, the bottom surface of the recess forming male side branch flow path 172 in suction side casing 142 is configured so that the axial depth is approximately constant from point 81a to point 81c located at male side end 76. Similarly, first flow path wall 191 of female-side branch flow path 173 is configured as a plane that is equidistant from suction-side end face 31a of female rotor 3 in the section from point 91a located near starting end 75 of female-side branch flow path 173 to point 91c located at female-side end 77. In other words, the bottom surface of the recess that forms female-side branch flow path 173 in suction-side casing 142 is configured so that the axial depth is approximately constant in the section from point 91a to point 91c located at female-side end 77.

[0042] In screw compressor 101 of the comparative example, working fluid that flows in from introduction flow path 71 of suction flow path 160 shown in Fig. 7 flows from start end 75 to male end 76 of male branch flow path 172 shown in Fig. 9, while being gradually drawn into working chamber C through suction port 62 (see Fig. 8) that opens in the axial direction, and also flows from start end 75 to female end 77 of female branch flow path 173, while being gradually drawn into working chamber C through suction port 62 that opens in the axial direction. For this reason, the flow rate of the working fluid that is drawn into working chamber C gradually decreases from start end 75 to male end 76 of male branch flow path 172, and gradually decreases from start end 75 to female end 77 of female branch flow path 173.

[0043] In screw compressor 101 of the comparative example, first flow path wall 181 of male side branch flow path 172 is maintained at approximately the same distance from suction side end face 21a of male rotor 2, and first flow path wall 191 of female side branch flow path 173 is maintained at approximately the same distance from suction side end face 31a of female rotor 3. For this reason, the working fluid flowing through male side branch flow path 172 and female side branch flow path 173 decelerates as it moves from start end 75 toward female side end 77. For this reason, the amount by which the decelerated working fluid is accelerated by male rotor 2 rotating at high speed when it is sucked into working chamber C through suction port 62 increases by the amount of deceleration, resulting in acceleration loss and a deterioration in the efficiency of the screw compressor.

[0044] In contrast, in the screw compressor 1 according to the present embodiment, the first flow path wall 81 of the male branch flow path 72 is configured to gradually approach the rotor teeth 21 of the male rotor 2 from the starting end 75 toward the male end 76 in at least a portion of the range from the starting end 75 to the male end 76. Similarly, the first flow path wall 91 of the female branch flow path 73 is configured to gradually approach the rotor teeth 31 of the female rotor 3 from the starting end 75 toward the female end 77 in at least a portion of the range from the starting end 75 to the female end 77. As a result, there are sections in which the flow path cross-sectional areas of the male branch flow path 72 and the female branch flow path 73 decrease toward the male end end 76 and the female end end 77, and therefore, the deceleration of the working fluid flowing through the male branch flow path 72 and the female branch flow path 73 can be suppressed more than in the configuration of the screw compressor 101 of the comparative example. Therefore, the amount of acceleration when flowing from the male branch flow path 72 and the female branch flow path 73 into the working chamber C via the suction port 62 can be reduced, and the energy efficiency of the screw compressor 1 can be improved.

[0045] As described above, the screw compressor 1 according to this embodiment includes the male rotor 2 having the rotor tooth portions 21 (first rotor tooth portions) and rotatable about the axis Lm (first axis), the female rotor 3 having the rotor tooth portions 31 (second rotor tooth portions) and rotatable about the axis Lf (second axis), and the casing 4 having an accommodation chamber 45 that accommodates the rotor tooth portions 21 (first rotor tooth portions) and the rotor tooth portions 31 (second rotor tooth portions) in a mutually meshed state, and forming a plurality of working chambers C together with the rotor tooth portions 21 (first rotor tooth portions) and the rotor tooth portions 31 (second rotor tooth portions). The casing 4 has a suction flow path 60 that introduces a working fluid from the outside of the casing 4 to the working chambers C in the suction stroke. The suction flow path 60 opens in the axial direction of the male rotor 2 to the working chamber C on the male rotor 2 side of the working chambers C in the suction stroke, and has a male side branch flow path 72 (male side flow path) that extends from a first start end 75, which is located on one side of an imaginary plane Pv passing through the axis Lm (first axis) and the axis Lf (second axis), and is on the inflow side of the working fluid, to a male side end end 76 (first end end) that is located on the other side of the imaginary plane Pv, and a female side branch flow path 73 (female side flow path) that opens in the axial direction of the female rotor 3 to the working chamber C on the female rotor 3 side of the working chambers C in the suction stroke, and extends from a second start end 75, which is located on the one side of the imaginary plane Pv and is on the inflow side of the working fluid, to a female side end end 77 (second end end) that is located on the other side of the imaginary plane Pv. The flow path wall forming the male side branch flow path 72 (male side flow path) includes a first flow path wall 81 (male side first flow path wall) facing the suction side end face 21a of the rotor tooth portion 21 (first rotor tooth portion) and extending from a first starting end 75 to a male side ending end 76 (first ending end), and the flow path wall forming the female side branch flow path 73 (female side flow path) includes a first flow path wall 91 (female side first flow path wall) facing the suction side end face 31a of the rotor tooth portion 31 (second rotor tooth portion) and extending from a second starting end 75 to a female side ending end 77 (second ending end).The first flow path wall 81 (male side first flow path wall) or the first flow path wall 91 (female side first flow path wall) is configured to approach the first rotor tooth portion) or the rotor tooth portion 31 (second rotor tooth portion) as it moves from the first starting end 75 side or the second starting end 75 side toward the male side end end 76 (first end end) or the female side end end 77 (second end end) in at least a portion of the range from the first starting end 75 or the second starting end 75 side to the male side end end 76 (first end end) or the female side end end 77 (second end end).

[0046] According to this configuration, first flow path wall 81 (male side first flow path wall) or first flow path wall 91 (female side first flow path wall) in male side branch flow path 72 (male side flow path) or female side branch flow path 73 (female side flow path) that opens in the rotor axial direction to working chamber C during the suction stroke is formed to approach rotor tooth portion 21 (first rotor tooth portion) and rotor tooth portion 31 (second rotor tooth portion) as it moves toward male side end end 76 (first end end) or female side end end 77 (second end end), so the flow path cross-sectional area of ​​male side branch flow path 72 (male side flow path) or female side branch flow path 73 (female side flow path) decreases toward male side end end 76 (first end end) or female side end end 77 (second end end). This suppresses deceleration of the working fluid flowing through male side branch flow path 72 (male side flow path) or female side branch flow path 73 (female side flow path), thereby reducing acceleration loss due to deceleration of the working fluid flowing through suction flow path 60.

[0047] In addition, in this embodiment, the first flow path wall 81 (male side first flow path wall) or the first flow path wall 91 (female side first flow path wall) has an inclined surface that gradually approaches the rotor tooth portion 21 (first rotor tooth portion) and the rotor tooth portion 31 (second rotor tooth portion) as it moves from the male side end end 76 (first end end) side or the female side end end 77 (second end end) side to the male side end end 76 (first end end) side or the female side end end 77 (second end end) side.

[0048] According to this configuration, first flow path wall 81 (male side first flow path wall) forming male side branch flow path 72 (male side flow path) or first flow path wall 91 (female side first flow path wall) forming female side branch flow path 73 (female side flow path) has an inclined surface, so that the flow path cross-sectional area can be reduced without disturbing the flow of working fluid in male side branch flow path 72 (male side flow path) or female side branch flow path 73 (female side flow path).

[0049] In addition, in this embodiment, the inclined surface of the first flow path wall 81 (male side first flow path wall) or the first flow path wall 91 (female side first flow path wall) extends from a position on one side of the imaginary plane Pv to the male side end end 76 (first end end) or the female side end end 77 (second end end).

[0050] According to this configuration, by reducing the flow path cross-sectional area of ​​male side branch flow path 72 (male side flow path) or female side branch flow path 73 (female side flow path) up to male side end end 76 (first end end) or female side end end 77 (second end end), the effect of suppressing deceleration of the working fluid flowing through male side branch flow path 72 (male side flow path) or female side branch flow path 73 (female side flow path) can be enhanced.

[0051] In addition, in this embodiment, the inclined surface of the first flow path wall 81 (male side first flow path wall) or the first flow path wall 91 (female side first flow path wall) extends from the position on one side of the imaginary plane Pv to a certain position 81d, 91d before reaching the male side end end 76 (first end end) or the female side end end 77 (second end end), and the section from the certain position 81d, 91d to the male side end end 76 (first end end) or the female side end end 77 (second end end) is configured as a plane that is equidistant from the rotor tooth portion 21 (first rotor tooth portion) and the rotor tooth portion 31 (second rotor tooth portion).

[0052] According to this configuration, the inclined surface of the first flow path wall 81 (male side first flow path wall) or the first flow path wall 91 (female side first flow path wall) is limited to just before the male side end end 76 (first end end) or the female side end end 77 (second end end), so that processing of the first flow path wall 81 (male side first flow path wall) or the first flow path wall 91 (female side first flow path wall) in the section leading to the male side end end 76 (first end end) or the female side end end 77 (second end end) is easier than in the case of an inclined surface.

[0053] In addition, in this embodiment, the male side branch flow path 72 (male side flow path) is configured so that the direction from the first starting end 75 to the male side ending end 76 (first ending end) coincides with the rotation direction of the male rotor 2, and the female side branch flow path 73 (female side flow path) is configured so that the direction from the second starting end 75 to the female side ending end 77 (second ending end) coincides with the rotation direction of the female rotor 3.

[0054] With this configuration, the direction of the working fluid flowing through the male side branch flow path 72 (male side flow path) and the female side branch flow path 73 (female side flow path) coincides with the rotation direction of the male rotor 2 and the female rotor 3, so that the pressure loss of the working fluid when it flows from the male side branch flow path 72 and the female side branch flow path 73 into the working chamber C can be reduced.

[0055] In addition, in this embodiment, the casing 4 has a main casing 41 (first casing) that can accommodate the rotor tooth portion 21 (first rotor tooth portion) and the rotor tooth portion 31 (second rotor tooth portion), and a suction side casing 42 (second casing) that is a separate member from the main casing 41 (first casing) and has a male side branch flow path 72 (male side flow path) and a female side branch flow path 73 (female side flow path) and is attached to the main casing 41 (first casing).

[0056] [Second embodiment] Next, a screw compressor according to a second embodiment of the present invention will be described with reference to Figures 11 to 13. Figure 11 is a longitudinal sectional view showing a screw compressor according to the second embodiment of the present invention. Figure 12 is a transverse sectional view of the screw compressor according to the second embodiment shown in Figure 11, as seen from the direction of arrows XII-XII. Figure 13 is a view of the screw compressor according to the second embodiment shown in Figure 11, as seen from the direction of arrows XIII-XIII. Figure 14 is a transverse sectional view of a screw compressor according to a third embodiment of the present invention, as seen from the direction of arrows III-III shown in Figure 2. In Figures 11 to 13, the same reference numerals as those in Figures 1 to 10 denote similar parts, and detailed description thereof will be omitted.

[0057] The screw compressor 1A according to the second embodiment differs from the screw compressor 1 according to the first embodiment mainly in that the shapes of the male branch flow passage 72A and the female branch flow passage 73A formed in the suction side casing 42A of the suction flow passage 60A formed in the casing 4A are different. The other configurations of the screw compressor 1A according to the present embodiment are the same as those of the screw compressor 1 according to the first embodiment.

[0058] Specifically, among the flow path walls forming the male side branch flow path 72A, the second flow path wall 82A located radially outward of the male rotor 2 is configured to partially coincide with the male side inner peripheral wall surface 45a, which is the wall surface of the accommodation chamber (bore) 45 of the casing 4A, when viewed from the axial direction of the male rotor 2, as shown in Figures 11 and 12. More specifically, the second flow path wall 82A is configured to coincide with the male side inner peripheral wall surface 45a of the accommodation chamber (bore) 45 in the range from the position of the imaginary plane Pv to the male side end end 76. The radial position of the male rotor 2 on the second flow path wall 82A is the smallest position within the range that does not block the axial opening of the accommodation chamber (bore) 45. The second flow path wall 82A of this embodiment is configured to be closer to the third flow path wall 83 than the second flow path wall 82 of the first embodiment. That is, the rotor radial distance between second flow path wall 82A and third flow path wall 83 in male side branch flow path 72A (flow path width of male side branch flow path 72A) is narrower than the flow path width of male side branch flow path 72 in the first embodiment, as shown in Figure 13. Therefore, the flow path cross-sectional area of ​​male side branch flow path 72A is smaller than the flow path cross-sectional area of ​​male side branch flow path 72 in the first embodiment. This makes it possible to further suppress the decrease in flow velocity of working fluid flowing through male side branch flow path 72A compared to the first embodiment, thereby further reducing acceleration loss.

[0059] Similarly, among the flow path walls forming the female-side branch flow path 73A, the second flow path wall 92A located radially outward of the female rotor 3 is configured to partially coincide with the female-side inner circumferential wall surface 45b, which is the wall surface of the accommodation chamber (bore) 45 of the casing 4A, when viewed in the axial direction of the female rotor 3, as shown in Figures 11 and 12. Specifically, the second flow path wall 92A is configured to coincide with the female-side inner circumferential wall surface 45b of the accommodation chamber (bore) 45 in the range from the position of the imaginary plane Pv to the female-side end end 77. In other words, the rotor radial distance between the second flow path wall 92A and the third flow path wall 93 in the female-side branch flow path 73A (flow path width of the female-side branch flow path 73A) is narrower than the flow path width of the female-side branch flow path 73 of the first embodiment, as shown in Figure 13. Therefore, the flow path cross-sectional area of ​​the female-side branch flow path 73A is smaller than the flow path cross-sectional area of ​​the female-side branch flow path 73 of the first embodiment. This makes it possible to further suppress a decrease in the flow velocity of the working fluid flowing through the female branch flow path 73A compared to the first embodiment, thereby making it possible to further reduce acceleration loss.

[0060] According to the second embodiment described above, as in the first embodiment, first flow path wall 81 (male side first flow path wall) or first flow path wall 91 (female side first flow path wall) in male side branch flow path 72A (male side flow path) or female side branch flow path 73A (female side flow path) that opens in the rotor axial direction to working chamber C during the suction stroke is formed so as to approach rotor tooth portion 21 (first rotor tooth portion) and rotor tooth portion 31 (second rotor tooth portion) as it moves toward male side end end 76 (first end end) or female side end end 77 (second end end), so that the flow path cross-sectional area of ​​male side branch flow path 72A (male side flow path) or female side branch flow path 73A (female side flow path) decreases as it moves toward male side end end 76 (first end end) or female side end end 77 (second end end). This suppresses the deceleration of the working fluid flowing through the male side branch flow path 72A (male side flow path) or the female side branch flow path 73A (female side flow path), thereby reducing acceleration loss caused by the deceleration of the working fluid flowing through the suction flow path 60A.

[0061] In addition, in this embodiment, the radially outer second flow path wall 82A of the male rotor 2 which forms the male side branch flow path 72A (male side flow path) or the radially outer second flow path wall 92A of the female rotor 3 which forms the female side branch flow path 73A (female side flow path) is configured to at least partially coincide with the male side inner wall surface 45a or the female side inner wall surface 45b which is the wall surface of the accommodating chamber (bore) 45 when viewed from the axial direction of the male rotor 2 or the axial direction of the female rotor 3.

[0062] With this configuration, the flow component of the working fluid heading from male side branch flow channel 72A (male side flow channel) toward working chamber C is less likely to have a rotor radial component, so pressure loss can be reduced.

[0063] In addition, in this embodiment, the second flow path wall 82A of the male side branch flow path 72A (male side flow path) or the second flow path wall 92A of the female side branch flow path 73A (female side flow path) is configured to coincide with the male side inner wall surface 45a or the female side inner wall surface 45b, which is the wall surface of the accommodating chamber (bore) 45, in the range from the position of the imaginary plane Pv to the male side end end 76 (first end end) side or the female side end end 77 (second end end), when viewed from the axial direction of the male rotor 2 or the female rotor 3.

[0064] According to this configuration, the flow path cross-sectional area of ​​the male side branch flow path 72A (male side flow path) or the female side branch flow path 73A (female side flow path) is smaller than in the configuration of the first embodiment, so the amount of acceleration by the male rotor 2 or female rotor 3 rotating at high speed when sucked from the male side branch flow path 72A (male side flow path) or the female side branch flow path 73A (female side flow path) into the working chamber C can be further reduced, and deterioration in the efficiency of the screw compressor due to acceleration loss can be suppressed.

[0065] [Third embodiment] Next, a screw compressor according to a third embodiment of the present invention will be described with reference to Fig. 14. Fig. 14 is a cross-sectional view of the screw compressor according to the third embodiment of the present invention, as seen from the same direction as the arrow III-III shown in Fig. 2. In Fig. 14, the same reference numerals as those shown in Figs. 1 to 13 denote similar parts, and detailed description thereof will be omitted.

[0066] The screw compressor 1B according to the second embodiment differs from the screw compressor 1 according to the first embodiment mainly in that, of the suction passage 60B formed in the casing 4B, the shapes of the male branch passage 72B and the female branch passage 73B formed in the suction-side casing 42B are different. Other configurations of the screw compressor 1B according to the present embodiment are similar to those of the screw compressor 1 according to the first embodiment.

[0067] Specifically, of the flow path walls that form the male side branch flow path 72B, second flow path wall 82B located radially outward of male rotor 2 is configured to partially coincide with male side inner circumferential wall surface 45a, which is the wall surface of housing chamber (bore) 45 of casing 4B, when viewed in the axial direction of male rotor 2, as shown in Fig. 14. In more detail, second flow path wall 82B is configured to gradually approach male side inner circumferential wall surface 45a of housing chamber (bore) 45 from the radial outside of male rotor 2 as it moves from the position of imaginary plane Pv toward male side end end 76, before finally coinciding with it. In this embodiment, second flow path wall 82B is configured to approach third flow path wall 83 toward male side end end 76. In other words, as shown in Figure 14, the rotor radial distance between the second flow path wall 82B and the third flow path wall 83 in the male side branch flow path 72B (flow path width of male side branch flow path 72B) narrows toward the male side end end 76, so the flow path cross-sectional area of ​​the male side branch flow path 72B becomes smaller toward the male side end end 76.

[0068] Similarly, among the flow path walls that form the female-side branch flow path 73B, the second flow path wall 92B located radially outward of the female rotor 3 is configured to partially substantially coincide with the female-side inner circumferential wall surface 45b, which is the wall surface of the accommodation chamber (bore) 45 of the casing 4B, when viewed from the axial direction of the female rotor 3. In detail, the second flow path wall 92B is configured to gradually approach the female-side inner circumferential wall surface 45b of the accommodation chamber (bore) 45 from the radial outside of the female rotor 3 as it moves from the position of the imaginary plane Pv toward the female-side end end 77, and then to coincide with it. The second flow path wall 92B in this embodiment is configured to approach the third flow path wall 93 toward the female-side end end 77. In other words, as shown in Figure 14, the rotor radial distance between the second flow path wall 92B and the third flow path wall 93 in the female side branch flow path 73B (flow path width of the female side branch flow path 73B) narrows toward the female side end end 77, so the flow path cross-sectional area of ​​the female side branch flow path 73B becomes smaller toward the female side end end 77.

[0069] The structure of male side branch flow path 72B and female side branch flow path 73B of this embodiment is suitable in cases where, due to the miniaturization of the screw compressor, it is difficult to lengthen the section over which second flow path wall 82B and second flow path wall 92B are aligned with male side inner circumferential wall surface 45a and female side inner circumferential wall surface 45b, which are the wall surfaces of accommodating chamber (bore) 45 of casing 4B.

[0070] According to the third embodiment described above, as in the first embodiment, first flow path wall 81 (male side first flow path wall) or first flow path wall 91 (female side first flow path wall) in male side branch flow path 72B (male side flow path) or female side branch flow path 73B (female side flow path) that opens in the rotor axial direction to working chamber C during the suction stroke is formed so as to approach rotor tooth portion 21 (first rotor tooth portion) and rotor tooth portion 31 (second rotor tooth portion) as it moves toward male side end end 76 (first end end) or female side end end 77 (second end end), so that the flow path cross-sectional area of ​​male side branch flow path 72B (male side flow path) or female side branch flow path 73B (female side flow path) decreases toward male side end end 76 (first end end) or female side end end 77 (second end end). This suppresses the deceleration of the working fluid flowing through the male side branch flow path 72B (male side flow path) or the female side branch flow path 73B (female side flow path), thereby reducing acceleration loss caused by the deceleration of the working fluid flowing through the suction flow path 60B.

[0071] Furthermore, in this embodiment, when viewed from the axial direction of the male rotor 2 or the female rotor 3, the second flow path wall 82B of the male side branch flow path 72B (male side flow path) or the second flow path wall 92B of the female side branch flow path 73B (female side flow path) is configured to gradually approach the male side inner circumferential wall surface 45a or the female side inner circumferential wall surface 45b, which is the wall surface of the accommodating chamber (bore) 45, from the radial outside of the male rotor 2 or the female rotor 3 as it moves from the position of the imaginary plane Pv toward the male side end end 76 (first end end) or the female side end end 77 (second end end), before finally coinciding with them.

[0072] According to this configuration, the flow path cross-sectional area of ​​male side branch flow path 72B (male side flow path) or female side branch flow path 73B (female side flow path) gradually becomes smaller toward male side end end 76 (first end end) or female side end end 77 (second end end), thereby further suppressing the deceleration of the working fluid flowing through male side branch flow path 72B (male side flow path) or female side branch flow path 73B (female side flow path).

[0073] [Other embodiments] The present invention is not limited to the above-described embodiments, but includes various modifications. The above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. For example, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0074] For example, in the above-described embodiment, the suction port 62 of the suction passage 60 is configured to open only in the rotor axial direction relative to the working chamber C during the suction stroke. However, it is also possible to configure the suction port to also open in the rotor radial direction relative to the working chamber C during the suction stroke. However, in this configuration, the working fluid that has flowed into the working chamber leaks through the suction port that opens in the rotor radial direction due to centrifugal action. Therefore, a configuration in which the suction port 62 is open only in the rotor axial direction is more suitable for suppressing deceleration of the working fluid. [Explanation of symbols]

[0075] REFERENCE SIGNS LIST 1, 1A, 1B...Screw compressor, 2...Male rotor, 3...Female rotor, 4, 4A, 4B...Casing, 21...Rotor teeth portion (first rotor teeth portion), 31...Rotor teeth portion (second rotor teeth portion), 41...Main casing (first casing), 42, 42A, 42B...Suction side casing (second casing), 45...Bore (accommodating chamber), 45a...Male side inner circumferential wall surface (wall surface of accommodating chamber), 45b...Female side inner circumferential wall surface (wall surface of accommodating chamber), 60, 60A, 60B...Suction flow passage, 72, 72A, 72B...Male side branch flow passage (male side flow passage), 73, 73A, 73B...Female side branch flow passage (female side flow passage), 75...Start end (first start end, second start end), 76...Male side end end (first end end), 77...Female side end end (second end end), 81...First flow path wall (male side first flow path wall), 82, 82A, 82B...Second flow path wall, 81d...Certain point (certain position), 91...First flow path wall (female side first flow path wall), 91d...Certain point (certain position), 92, 92A, 92B...Second flow path wall, C...Working chamber, Lm...Axis (first axis), Lf...Axis (second axis), Pt...Imaginary plane

Claims

1. a male rotor having first rotor teeth and rotatable about a first axis; a female rotor having second rotor teeth and rotatable about a second axis; a casing having an accommodation chamber that accommodates the first rotor tooth portion and the second rotor tooth portion in a state where the first rotor tooth portion and the second rotor tooth portion are meshed with each other, and that forms a plurality of working chambers together with the first rotor tooth portion and the second rotor tooth portion; the casing has a suction passage that introduces working fluid from the outside of the casing to the working chamber, The suction flow path is a male side flow path that opens in the axial direction of the male rotor to one of the working chambers on the male rotor side, and that extends from a first start end, which is located on one side of an imaginary plane passing through the first axis and the second axis and is the inflow side of the working fluid, to a first end end, which is located on the other side of the imaginary plane; a female-side flow path that opens in the axial direction of the female rotor to one of the working chambers on the female rotor side, and that extends from a second start end that is located on the one side of the imaginary plane and is an inflow side of the working fluid to a second end end that is located on the other side of the imaginary plane, a flow path wall forming the male side flow path includes a male side first flow path wall facing a suction side end face of the first rotor tooth portion and extending from the first start end to the first end, a flow path wall forming the female side flow path includes a female side first flow path wall facing a suction side end face of the second rotor tooth portion and extending from the second start end to the second end end, the male side first flow path wall has a first inclined surface that gradually approaches the first rotor tooth portion from the first start end side toward the first end end side in at least a portion of the range from the first start end side to the first end end side, and a first flat surface that is equidistant from the first rotor tooth portion, and the first flat surface extends closer to the first end end side than the first inclined surface; or The female-side first flow path wall has a second inclined surface that gradually approaches the first rotor tooth portion from the second start end side toward the second end end side in at least a portion of the range from the second start end side to the second end end side, and a second flat surface that is equidistant from the second rotor tooth portion, and the second flat surface extends toward the second end end side beyond the second inclined surface. A screw compressor characterized by:

2. 2. The screw compressor according to claim 1, a second flow passage wall on the radially outer side of the male rotor, which forms the male side flow passage, is configured to at least partially coincide with a wall surface of the housing chamber when viewed from the axial direction of the male rotor, or A second flow path wall on the radially outer side of the female rotor, which forms the female side flow path, is configured to at least partially coincide with a wall surface of the accommodation chamber when viewed in the axial direction of the female rotor. A screw compressor characterized by:

3. 3. The screw compressor according to claim 2, the second flow path wall of the male side flow path is configured to gradually approach the wall surface of the accommodation chamber from the radially outer side of the male rotor and then coincide with it as it moves from the position of the imaginary plane toward the first end end when viewed in the axial direction of the male rotor, or The second flow path wall of the female side flow path is configured so that, as viewed in the axial direction of the female rotor, from the position of the imaginary plane toward the second end end, it gradually approaches the wall surface of the accommodation chamber from the radially outer side of the female rotor and then coincides with it. A screw compressor characterized by:

4. 3. The screw compressor according to claim 2, the second flow path wall of the male side flow path is configured to coincide with the wall surface of the accommodation chamber in a range from the position of the imaginary plane to the first end end when viewed in the axial direction of the male rotor, or The second flow path wall of the female side flow path is configured to coincide with the wall surface of the accommodation chamber in a range from the position of the imaginary plane to the second end end when viewed in the axial direction of the female rotor. A screw compressor characterized by:

5. 2. The screw compressor according to claim 1, the male side flow path is configured such that the direction from the first start end to the first end is aligned with the rotation direction of the male rotor, The female-side flow passage is configured such that the direction from the second start end to the second end end coincides with the rotation direction of the female rotor. A screw compressor characterized by:

6. 2. The screw compressor according to claim 1, The casing comprises: a first casing capable of accommodating the first rotor teeth portion and the second rotor teeth portion; a second casing that is a separate member from the first casing and that has the male side flow path and the female side flow path and is attached to the first casing; A screw compressor characterized by:

7. 2. The screw compressor according to claim 1, The suction passage is configured to open to the working chamber only in the axial direction of the male rotor and the female rotor. A screw compressor characterized by:

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