Screw compressor

Abstract

The housing of the screw compressor of the present application has a discharge-side inner wall surface opposite to the discharge-side end surfaces of the male rotor and the female rotor. The discharge-side inner wall surface of the housing has a shielding region that shields at least a portion of the locus of an axial communication path that is a gap sandwiched by the trailing faces of the male rotor and the female rotor that periodically appears at the discharge-side end surfaces in accordance with changes in meshing produced by rotation of the male rotor and the female rotor. A groove group composed of a plurality of grooves having a long side direction is provided in the shielding region of the housing. The plurality of grooves are arranged in the circumferential direction of at least one of the male rotor and the female rotor so as to be arranged in a manner in which edges extending in the long side direction are adjacent to each other. The plurality of grooves are configured so as to be inclined in the long side direction from the inner peripheral side to the outer peripheral side of one of the rotors in the same direction as the rotational direction of the one rotor with respect to the radial direction of the one rotor.

Description

Technical Field

[0001] The present invention relates to screw compressors, and more specifically, to screw compressors in which liquid is supplied from outside the compressor to the working chamber. Background Technology

[0002] One representative cause of performance degradation in screw compressors is internal leakage of compressed gas. Internal leakage refers to the backflow of compressed gas from a high-pressure space where pressure increases as compression progresses to a relatively low-pressure space before compression began or before compression started. In this internal leakage, energy is required for the compressed gas to return to its low-pressure state, resulting in energy loss.

[0003] As an example of a means to suppress internal leakage of compressed gas, the technology described in Patent Document 1 is known. In the oil-cooled screw compressor disclosed in Patent Document 1, a plurality of labyrinth grooves are provided on the discharge side end wall of the rotor chamber between the rotor shafts of a pair of screw rotors, with the direction between the rotor shafts as the length direction.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2006-226160 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the technology described in Patent Document 1, a portion of the gap (hereinafter sometimes referred to as the discharge side end face gap) formed between the discharge side end face of the screw rotor and the discharge side end wall of the rotor chamber, specifically the compression space located during the highest pressure discharge stroke and the compression space with the lowest pressure adjacent to this high-pressure compression space, is sealed. However, in addition to the aforementioned portion of the discharge side end face gap, multiple internal gaps exist that become pathways for internal leakage of compressed gas. In the technology described in Patent Document 1, the suppression of internal leakage of compressed gas through internal gaps other than the aforementioned portion of the discharge side end face gap is not considered, leaving room for improvement in reducing internal leakage.

[0009] As an example of internal clearance, there is a clearance known as the axial connection path. The axial connection path is a clearance that appears periodically on the discharge-side end face due to the meshing changes caused by the rotation of the male and female rotors. It is a crescent-shaped opening formed by the rear inlet faces of the two rotors clamping each other and opening only axially. The axial connection path connects the working chamber (the relatively low-pressure space of the intake stroke) to the discharge flow path (the relatively high-pressure space), thus becoming a major cause of compressed gas backflow. Regarding internal leakage paths via the axial connection path, even among multiple internal leakage paths existing on the discharge-side end face, the pressure difference between the high-pressure space at the leakage source and the low-pressure space at the leakage location is particularly large, thus tending to increase the leakage amount. Internal leakage via the axial connection path is a common problem in both liquid-free screw compressors driven without supplying liquid to the working chamber and liquid-supply screw compressors that supply liquids such as oil to the working chamber, as described in Patent Document 1.

[0010] The present invention was proposed to solve the above-mentioned problems, and one of its objectives is to provide a screw compressor capable of reducing internal leakage of compressed gas via the axial communication path.

[0011] Technical solutions for solving the problem

[0012] This application includes several means for solving the above-mentioned problems. One example is a screw compressor comprising: a male rotor having a first discharge side end face on one axial side; a female rotor having a second discharge side end face on one axial side; and a housing having a receiving chamber for housing the male rotor and the female rotor in a manner capable of rotating in an engaged state. The housing has a discharge side inner wall surface opposite to the first discharge side end face of the male rotor and the second discharge side end face of the female rotor. The discharge side inner wall surface of the housing has a shielding region that shields at least a portion of the trajectory of an axial communication path, the axial communication path being generated according to the rotation of the male rotor and the female rotor. The gaps that periodically appear on the first discharge side end face and the second discharge side end face due to changes in the meshing state are sandwiched between the rear inlet faces of the male rotor and the female rotor. A groove group consisting of multiple grooves having a long side direction is provided in the shielded area of ​​the housing. The multiple grooves of the groove group are arranged in the circumferential direction of at least one of the male rotor and the female rotor. The multiple grooves of the groove group are arranged so that their sides extending in the long side direction are adjacent to each other. The multiple grooves of the groove group are respectively configured such that the long side direction from the inner circumference side to the outer circumference side of the rotor is inclined in the same direction as the rotation direction of the rotor relative to the radial direction of the rotor.

[0013] Invention Effects

[0014] According to one embodiment of the invention, liquid in multiple grooves disposed on the inner wall of the discharge side of the housing flows along its long side due to shear force and is subsequently blocked, thereby increasing the pressure. This allows a high-pressure liquid film to form near the axial communication path in the gap between the discharge side end faces. This reduces internal leakage of compressed gas via the axial communication path.

[0015] Other issues, structures, and effects not described above will be clarified through the following description of the implementation methods. Attached Figure Description

[0016] Figure 1 This is a longitudinal cross-sectional view of a screw compressor according to the first embodiment of the present invention and a system diagram showing the external path for supplying oil to the screw compressor.

[0017] Figure 2 From Figure 1 The diagram shown is a cross-sectional view of the screw compressor according to the first embodiment of the present invention, viewed from direction II-II.

[0018] Figure 3 It is Figure 2 The enlarged portion of the diagram shown by reference numeral L1 is a diagram illustrating the axial connection path.

[0019] Figure 4 From Figure 1 The diagram shown is a cross-sectional view of the screw compressor according to the first embodiment of the present invention, viewed from direction IV-IV.

[0020] Figure 5 This is a diagram showing the groove structure of the housing in the screw compressor according to the first embodiment of the present invention. Figure 4 The figure shown by reference numeral L2 is an enlarged portion of the figure.

[0021] Figure 6 It means from Figure 5 The diagram shown is a cross-sectional view of the groove structure of the housing in the screw compressor of the first embodiment of the present invention, viewed from direction VI-VI.

[0022] Figure 7 This is a diagram illustrating the function of the groove structure of the housing in the screw compressor according to the first embodiment of the present invention.

[0023] Figure 8 From and Figure 4 A cross-sectional view of a screw compressor of a modified example of the first embodiment of the present invention is viewed with the same arrow direction.

[0024] Figure 9 This is a diagram showing the groove structure of the housing in a screw compressor according to a modified example of the first embodiment of the present invention. Figure 8 The figure shown by reference numeral L3 is an enlarged portion of the figure.

[0025] Figure 10 This is a diagram illustrating the function of the groove structure of the housing in a modified example of the screw compressor according to the first embodiment of the present invention.

[0026] Figure 11 From and Figure 2 A cross-sectional view of the screw compressor of the second embodiment of the present invention is viewed with the same arrow direction.

[0027] Figure 12 This diagram illustrates the slot structure of the screw rotor in the screw compressor according to the second embodiment of the present invention. Figure 11 The enlarged portion of the figure shown by reference numeral L4 in the attached diagram.

[0028] Figure 13 From Figure 12 The diagram shown is a cross-sectional view of the slot structure of the screw rotor in the screw compressor of the second embodiment of the present invention, viewed from XIII-XIII direction.

[0029] Figure 14 This is a diagram illustrating the function of the slot structure of the screw rotor in the screw compressor according to the second embodiment of the present invention.

[0030] Figure 15 From and Figure 2 A cross-sectional view of a screw compressor of a modified example of the second embodiment of the present invention is viewed with the same arrow direction.

[0031] Figure 16 This is a diagram showing the slot structure of the screw rotor in a screw compressor according to a modified example of the second embodiment of the present invention. Figure 15 The enlarged portion of the figure shown by reference numeral L5 in the attached diagram.

[0032] Figure 17 This is a diagram illustrating the function of the slot structure of the screw rotor in a modified example of the screw compressor according to the second embodiment of the present invention.

[0033] Figure 18A This is a diagram illustrating a first example of a deformation of the groove structure of the housing in a screw compressor according to the first embodiment and its variations of the present invention.

[0034] Figure 18B This is a second example of a deformation of the groove structure of the housing in a screw compressor according to the first embodiment and its variations of the present invention.

[0035] Figure 18C This is a third example of a deformation of the groove structure of the housing in a screw compressor according to the first embodiment and its variations of the present invention.

[0036] Figure 19AThis is a diagram illustrating a first example of a modification of the slot structure of the screw rotor in a screw compressor according to the second embodiment and its modifications of the present invention.

[0037] Figure 19B This is a second example of a variation of the slot structure of the screw rotor in a screw compressor according to the second embodiment and its variations of the present invention.

[0038] Figure 19C This is a third example of a variation of the slot structure of the screw rotor in a screw compressor according to the second embodiment and its variations of the present invention.

[0039] Figure 19D This is a fourth example of a variation of the slot structure of the screw rotor in a screw compressor according to the second embodiment and its variations of the present invention.

[0040] Figure 19E This is a fifth example of a variation of the slot structure of the screw rotor in a screw compressor according to the second embodiment and its variations of the present invention.

[0041] Figure 19F This is a sixth example of a variation of the slot structure of the screw rotor in a screw compressor according to the second embodiment and its variations of the present invention. Detailed Implementation

[0042] Hereinafter, embodiments of the screw compressor of the present invention will be described by way of example using the accompanying drawings. This embodiment is an example of the application of the present invention to an oil-supply screw compressor for compressed air.

[0043] [First Implementation]

[0044] use Figure 1 and 2 The basic structure of the screw compressor of the first embodiment will be described. Figure 1 This is a longitudinal cross-sectional view of a screw compressor according to the first embodiment of the present invention and a system diagram showing the external path for supplying oil to the screw compressor. Figure 2 It means from Figure 1 The cross-sectional view of the screw compressor according to the first embodiment of the present invention is shown in the direction of arrow II-II. Figure 1 In the image, the left side represents the axial suction side of the screw compressor, and the right side represents the axial discharge side. Figure 2 In the diagram, the thick arrow indicates the direction of rotation of the screw rotor, and the double-dotted line represents the discharge port of the housing, projected onto the discharge side end face of both the male and female rotors. Additionally, Figure 2 The outer peripheral surface of the shell is omitted.

[0045] exist Figure 1In the oil-supply screw compressor 1 (hereinafter referred to as screw compressor), oil (liquid) is supplied from the outside to the inside of the compressor. Therefore, an external oil supply system 100 for supplying oil is connected to the screw compressor 1. The external oil supply system 100 consists, for example, of devices such as an oil separator 101, an oil cooler 102, and an oil filter 103, and pipelines 104 connecting them.

[0046] exist Figure 1 and Figure 2 In this screw compressor 1, a male rotor 2 (male-type screw rotor) and a female rotor 3 (female-type screw rotor) rotate in meshing motion, and a housing 4 houses the two rotors 2 and 3 in a manner that allows them to rotate in the meshing state. The male rotor 2 and the female rotor 3 are arranged parallel to each other on their central axes A1 and A2. The axial direction of the male rotor 2 ( Figure 1 The left and right sides of the rotor 3 are rotatably supported by the suction side bearing 6 and the discharge side bearings 7 and 8, respectively, and are connected to the motor 90, which serves as the rotation drive source. The axial sides of the female rotor 3 are rotatably supported by the suction side bearing and the discharge side bearing (neither shown).

[0047] The male rotor 2 consists of multiple (in) Figure 2 The rotor teeth 21, consisting of four externally twisted teeth (lobes) 21a, and the suction sides (in the axial direction) respectively provided at both ends of the rotor teeth 21. Figure 1 The shaft portion 22 (left side) and the discharge side (in) Figure 1 The shaft portion 23 (located on the right side) is formed. The rotor teeth 21 are located at one end in the axial direction (in... Figure 1 The middle is the left end) and the other end (in Figure 1 The middle (right end) has an intake side end face 21b and an exhaust side end face 21c. The intake side shaft portion 22 extends outward from the housing 4, for example, it is an integral structure with the shaft portion of the motor 90. An oil seal or mechanical seal or other shaft sealing component 9 is installed in the intake side shaft portion 22 at a position closer to the front end of the intake side bearing 6.

[0048] The female rotor 3 consists of multiple (in) Figure 2 The rotor teeth 31, consisting of six internal torsional teeth (lobe) 31a, and the axially arranged teeth 31 of the rotor teeth 31, are respectively provided in the rotor teeth 31. Figure 2 The rotor tooth 31 is composed of a suction-side shaft portion (not shown) and a discharge-side shaft portion 33 at both ends of the rotor (in the direction orthogonal to the paper plane). The rotor tooth portion 31 has a suction-side end face (not shown) and a discharge-side end face 31c at one end and the other end in the axial direction, respectively.

[0049] Housing 4 includes a main housing 41 and an axial discharge side mounted on the main housing 41 (in Figure 1 The discharge side housing 42 (right side in the middle).

[0050] A receiving chamber 45 is formed inside the housing 4 to house the rotor teeth 21 of the male rotor 2 and the rotor teeth 31 of the female rotor 3 in a meshing state. One side of the two partially overlapping cylindrical spaces formed in the main housing 41 is closed by the discharge-side housing 42. Figure 1 The opening (right side) forms a receiving chamber 45. The wall of the receiving chamber 45 is composed of a generally cylindrical inner circumferential surface 46 covering the radially outer side of the rotor teeth 21 of the male rotor 2, a generally cylindrical inner circumferential surface 47 covering the radially outer side of the rotor teeth 31 of the female rotor 3, an inner wall surface 48 opposite to the suction side end face 21b of the rotor teeth 21 and 31 of the two rotors 2 and 3, and an inner wall surface 49 opposite to the discharge side end faces 21c and 31c of the rotor teeth 21 and 31 of the two rotors 2 and 3. The rotor teeth 21 and 31 of the two rotors 2 and 3 are arranged with a gap of tens to hundreds of μm relative to the inner circumferential surface 46 and the inner circumferential surface 47 of the female rotor 4. Furthermore, the discharge-side end faces 21c and 31c of the male and female rotors 2 and 3 are separated from the discharge-side inner wall surface 49 of the housing 4 by a gap of tens to hundreds of μm (hereinafter referred to as the discharge-side end face gap G1). Multiple working chambers C with different pressures are formed by the rotor teeth 21 and 31 of the male and female rotors 2 and 3 and the inner wall surfaces (male-side inner circumferential surface 46, female-side inner circumferential surface 47, suction-side inner wall surface 48, and discharge-side inner wall surface 49) of the receiving chamber 45 surrounding it.

[0051] like Figure 1 As shown, suction-side bearings 6 for the male rotor 2 and female rotor 3 are arranged at the end of the main housing 41 on the motor 90 side, and a suction-side cover 43 is installed to cover the suction-side bearings 6. Discharge-side bearings 7 and 8 for the male rotor 2 and female rotor 3 are arranged on the discharge-side housing 42.

[0052] The housing 4 is provided with an intake passage 51 for drawing air into the working chamber C (receiving chamber 45). Furthermore, the housing 4 is provided with an exhaust passage 52 for discharging compressed air from the working chamber C to the outside. The exhaust passage 52 connects the receiving chamber 45 (working chamber C) to the outside of the housing 4 and is connected to an external oil supply system 100. The exhaust passage 52 has an outlet 52a formed on the inner wall surface 49 of the exhaust side of the housing 4. Figure 2 (The part in the middle is marked with double dots). In addition, the housing 4 is provided with an oil supply passage 53 for supplying oil from the external oil supply system 100 to the working chamber C (receiving chamber 45). The oil supply passage 53 is, for example, an opening in the receiving chamber 45 where the working chamber C becomes the area of ​​the compression stroke.

[0053] In the screw compressor 1 having the above structure Figure 1 The electric motor 90 shown drives the male rotor 2, thereby Figure 2The female rotor 3 shown is driven to rotate. As a result, the working chamber C moves axially along with the rotation of both male and female rotors 2 and 3. At this time, the working chamber C increases its volume by allowing air to pass through from the outside... Figure 1 The suction flow path 51 shown draws in air and compresses it to a specified pressure by reducing its volume. When the working chamber C is connected to the discharge port 52a, the compressed air in the working chamber C is discharged to the oil separator 101 of the external oil supply system 100 through the discharge flow path 52 via the discharge port 52a.

[0054] In the screw compressor 1, oil is supplied to the working chamber C, thus the discharged compressed air contains oil. The oil contained in this compressed air is separated by the oil separator 101. The compressed air, with the oil removed by the oil separator 101, is supplied to external equipment as needed.

[0055] On the other hand, the oil separated from the compressed air by the oil separator 101 is cooled by the oil cooler 102 of the external oil supply system 100 and then injected into the working chamber C via the oil supply line 53 of the screw compressor 1. The oil supply to the screw compressor 1 can be carried out without the use of a power source such as a pump, but by using the pressure of the compressed air flowing into the oil separator 101 as the driving source.

[0056] Next, use Figure 2 and Figure 3 The axial communication path, which is one of the internal clearances of the screw compressor, is explained. Figure 3 It is Figure 2 The enlarged portion of the diagram indicated by reference numeral L1 is a diagram illustrating the axial connectivity path. Figure 3 In the diagram, the thick arrow indicates the rotation direction of the male and female rotors, and the double-dotted line indicates the discharge port projected onto the discharge side end face of the male and female rotors.

[0057] In this instruction, such as Figure 3 As shown, with the tooth tip of the male rotor 2 as the boundary, the tooth surface on the rotation direction side is defined as the forward surface 21d of the male rotor 2, and the tooth surface on the opposite side of the rotation direction is defined as the backward surface 21e of the male rotor 2. Similarly, with the tooth root of the female rotor 3 as the boundary, the tooth surface on the rotation direction side is defined as the forward surface 31d of the female rotor 3, and the tooth surface on the opposite side of the rotation direction is defined as the backward surface 31e of the female rotor 3.

[0058] Figure 2 and Figure 3 The meshing state of the male and female rotors 2 and 3 at a certain rotation angle is shown. For example... Figure 3As shown, the male rotor 2 and the female rotor 3 theoretically have a meshing state at the discharge side end faces 21c and 31c at a total of three points of contact: a first contact point P1 where the rear inlet face 21e of the male rotor 2 contacts the rear inlet face 31e of the female rotor 3; a second contact point P2 where the portion of the rear inlet face 21e of the male rotor 2 near the tooth tip side contacts the portion of the rear inlet face 31e of the female rotor 3 near the tooth root side compared to the first contact point P1; and a third contact point P3 where the forward face 21d of the male rotor 2 contacts the forward face 31d of the female rotor 3.

[0059] The area enclosed by the first contact point P1, the second contact point P2, and the tooth profiles of the male and female rotors 2 and 3 is the internal clearance referred to as the axial communication path G2. The axial communication path G2 is sandwiched between the rear inlet surfaces 21e and 31e of the male and female rotors 2 and 3, and is a crescent-shaped opening on the discharge side end faces 21c and 31c that opens only axially. The axial communication path G2 appears periodically on the discharge side end faces 21c and 31c according to the meshing changes caused by the rotation of the male and female rotors 2 and 3.

[0060] Specifically, the axial connection path G2 is on the outer diameter line D1 of the male rotor 2. Figure 3 The dashed line in the middle) and the pitch circle D2 of the female rotor 3 ( Figure 3 The outlet 52a is located near the intersection of the dotted lines in the diagram. As the male and female rotors 2 and 3 rotate, the opening area (size) expands and extends towards the area between the central axes A1 and A2 of the male and female rotors 2 and 3. Figure 2 The rotor moves from the top (center) and eventually disengages at the three contact points, thus eliminating the axial connection path G2. The first contact point P1 is located inside the pitch circle D2 of the female rotor 3, and the second contact point P2 is located inside the outer diameter line D1 of the male rotor 2.

[0061] The center of the pitch circle D2 of the female rotor 3 is the same as the center axis A2 of the female rotor 3, and its diameter dpf is calculated by the following formula (1).

[0062] [Formula 1]

[0063]

[0064] Here, a, Zm, and Zf represent the distance between the central axis A1 of the male rotor 2 and the central axis A2 of the female rotor 3, the number of teeth of the male rotor 2, and the number of teeth of the female rotor 3, respectively.

[0065] The axial connection path G2 is connected to the working chamber C, which is a relatively low-pressure space for the suction stroke, while on the other hand, as... Figure 2 and Figure 3 As shown, the discharge flow path 52 (refer to) is located near the relatively high-pressure space. Figure 1The location of the discharge chamber Cd, which is connected to the discharge outlet 52a, is the main reason why compressed air flows backward from the discharge path 52, the discharge chamber Cd, to the intake chamber C.

[0066] Therefore, in order to suppress internal leakage of compressed air via the axial communication path G2, the discharge side inner wall surface 49 of the housing 4 has a shielding region 49a (described later) that shields at least a portion, preferably most of, the trajectory of the axial communication path G2. Figure 4 However, a portion of the compressed air in the discharge flow path 52 of the discharge stroke chamber Cd passes through the discharge side end face gap G1 between the discharge side end faces 21c and 31c of the male and female rotors 2 and 3 and the shielded area 49a of the discharge side inner wall surface 49 of the housing 4 (see reference). Figure 1 It reaches the axial connecting path G2 and flows back into the low-pressure space. This is one of the main reasons for the decline in the compressor's compression performance and energy-saving performance.

[0067] In the case of an oil-supply screw compressor, it is expected that the oil supplied to the working chamber C will form an oil film on a portion of the discharge side end face gap G1, thereby reducing the internal leakage of compressed air through the discharge side end face gap G1. However, regarding internal leakage through the axial connection path G2, compared to other internal leakage cases, the pressure difference between the high-pressure space of the leakage source (working chamber Cd in the discharge stroke, discharge flow path 52) and the low-pressure space of the leakage location (destination) (working chamber C in the suction stroke) is large. Therefore, the oil film formed in the discharge side end face gap G1 near the axial connection path G2 is difficult to maintain, and there is a tendency for the internal leakage reduction effect based on the oil film to be relatively small.

[0068] Therefore, this embodiment is characterized by having a groove structure for pressurizing the oil film formed in the discharge side end face gap G1 near the axial communication path G2. By forming a high-pressure oil film in the discharge side end face gap G1, the oil film can be maintained even for internal leaks with large pressure differences between the leak source and the leak destination.

[0069] Next, use Figures 4-6 Details of the slot structure of the screw compressor in the first embodiment will be described. Figure 4 From Figure 1 The cross-sectional view of the screw compressor of the first embodiment of the present invention is shown in the direction of arrow IV-IV. Figure 5 This is a diagram showing the groove structure of the housing in the screw compressor according to the first embodiment of the present invention. Figure 4 The figure shown by reference numeral L2 is an enlarged portion of the figure. Figure 6 From Figure 5The cross-sectional view of the groove structure of the housing in the screw compressor of the first embodiment of the present invention, as shown by arrows VI-VI, is observed in the direction of the arrows VI-VI. Figure 4 and Figure 5 In the diagram, the double-dotted line represents the shape obtained by projecting the discharge-side end faces of the male and female rotors axially onto the discharge-side inner wall of the housing at a certain rotation angle (when forming an axially connected path), and the thick arrow indicates the rotation direction of the two rotors. Additionally, Figure 4 The outer peripheral surface of the shell is omitted.

[0070] like Figure 4 As shown, a discharge flow path 52 is formed on the inner wall surface 49 of the discharge side of the housing 4 (see reference). Figure 1 The outlet 52a is the inlet of the rotor. In order to reduce the internal leakage of compressed air via the axial communication path G2, the outlet 52a is formed, for example, in a manner that does not overlap with the area obtained by projecting the trajectory of the axial communication path G2 onto the inner wall surface 49 of the discharge side in the rotor axis.

[0071] In other words, the discharge-side inner wall surface 49 has a shielding region 49a for suppressing internal leakage via the axial communication path G2. The shielding region 49a shields at least a portion, preferably most, of the trajectory of the axial communication path G2, and is configured to overlap at least a portion, preferably most, of the area obtained by projecting this trajectory onto the discharge-side inner wall surface 49 in the rotor axial direction. As a specific example, the shielding region 49a is the area closer to the discharge outlet 52a than the area between the central axes A1 and A2 of the male and female rotors 2 and 3, within the portion obtained by projecting the area bounded by the outer diameter line D1 of the male rotor 2 and the pitch circle D2 of the female rotor 3 onto the discharge-side inner wall surface 49 in the rotor axial direction. The outer edge of the shielding region 49a forms part of the outline of the discharge outlet 52a, for example, in the shape of a tongue-like protrusion projecting towards the center of the discharge outlet 52a. By utilizing the shielding region 49a of the discharge-side inner wall surface 49, the direct communication area (relative area) between the axial communication path G2 and the discharge outlet 52a is minimized as much as possible.

[0072] like Figure 4 and Figure 5 As shown, a group of grooves consisting of multiple grooves 60 into which a portion of the oil (liquid) supplied to the working chamber C can flow is formed in the shielded area 49a of the inner wall surface 49 on the discharge side. The multiple grooves 60 are arranged, for example, along the outline of the pitch circle D2 side (male rotor 2 side) of the female rotor 3 in the shielded area 49a. That is, the multiple grooves 60 are arranged circumferentially relative to the central axis A2 of the female rotor 3. Each groove 60 is formed as an elongated groove in the length direction, and the multiple grooves 60 are arranged such that their sides extending in the length direction are adjacent to each other.

[0073] like Figure 5As shown, one end 61 of each groove 60 in its longitudinal direction is located closer to the outer periphery of the female rotor 3 than the other end 62, for example, extending in a straight line from the other end 62 to one end 61. The groove 60 is configured such that the longitudinal direction from the other end 62 to one end 61 (from the inner periphery to the outer periphery of the female rotor 3) is inclined at an angle θcf relative to the radial direction R2 of the female rotor 3 in the same direction as the rotation direction of the female rotor 3. The groove 60 is confined to a position closer to the pitch circle D2 of the female rotor 3 and does not reach the outline of the shielding area 49a (the opening edge of the outlet 52a).

[0074] like Figure 6 As shown, the groove 60 has a generally certain depth. The groove 60 is intended to be a type of hydrodynamic groove, as will be described in detail later. The depth of the groove 60 as a hydrodynamic groove is an appropriate value depending on the magnitude of the shear force acting on the oil flowing into it, as will be described later. For example, when the discharge side end face gap G1 is about tens to 200 μm, the preferred depth of the groove 60 is in the range of 1 μm to 1 mm. In addition, the end face and bottom of one side end 61 (outer peripheral end) of the groove 60 are connected at approximately right angles. However, from a processability point of view, the end face and bottom of one side end 61 of the groove 60 can be connected by an inclined surface or a curved surface.

[0075] Next, use Figure 6 and Figure 7 The function and effect of the slot structure of the housing in the screw compressor of the first embodiment will be explained. Figure 7 This is a diagram illustrating the function of the groove structure of the housing in the screw compressor according to the first embodiment of the present invention. Figure 6 This shows the female rotor in a position opposite to the shielded area of ​​the housing. Figure 6 In the diagram, the thick arrows indicate oil flow. Figure 7 In the diagram, the double-dotted line is a graphic obtained by projecting the shape of the discharge side end face of the male and female rotors onto the discharge side inner wall surface of the housing along the rotor axis.

[0076] In the screw compressor 1 of this embodiment, for the flow formed in Figure 6 and Figure 7 The oil in each groove 60 of the shielded area 49a of the inner wall surface 49 on the discharge side of the housing 4 shown is, for example Figure 7 As shown, due to the discharge side end face 31c of the rotating female rotor 3, the shearing force Sf acts in the tangential direction (orthogonal to the radial direction R2 of the female rotor 3) and in the same direction as the rotation direction of the female rotor 3. This shearing force Sf can be decomposed into a first component force Sf1, which is a component force orthogonal to the length direction of the groove 60, and a second component force Sf2, which is a component force in the length direction of the groove 60.

[0077] In this embodiment, each groove 60 extends at a radial angle R2 relative to the female rotor 3, with its other end 62 as a base point, in the same direction as the rotational direction of the female rotor 3. Therefore, the second component force Sf2 becomes a force directed towards the outer periphery of the female rotor 3 along the length direction of the groove 60. Consequently, the oil within each groove 60 flows towards the outer periphery of the female rotor 3 along the length direction of the groove 60 due to the second component force Sf2 of the shear force Sf. Figure 6 and Figure 7 As shown, the oil flowing in the groove 60 undergoes kinetic energy (dynamic pressure) conversion due to being blocked by one end 61, which is the end of the outer periphery of the female rotor 3 in the long side direction of the groove 60. The static pressure increases, and the oil eventually flows out to the discharge side end face gap G1 (female rotor 3 side) in the region of one end 61. As a result, the oil pressure at the discharge side end face gap G1 becomes relatively high near one end 61 of the groove 60.

[0078] In this embodiment, such as Figure 7 As shown, multiple grooves 60 are arranged so that their sides, extending in the long direction, are adjacent to each other. Therefore, pressurized oil flows from one end 61 (the end on the outer periphery of the female rotor) of each of the multiple grooves 60 to the discharge end face gap G1. The high-pressure oil flowing from the multiple end 61s are connected, thereby promoting the formation of a high-pressure oil film W along one end 61 of the multiple grooves 60 in the discharge end face gap G1. Furthermore, the closer the end 61 of the groove 60 is to the outer periphery of the female rotor 3, the greater the shear force acting due to the rotation of the female rotor 3, and the greater the suppression effect of internal leakage caused by the pressurization of the oil film W.

[0079] In this way, not only is the oil in the groove 60 used to seal the discharge side end face gap G1, but the oil flowing out of the groove 60 also forms a high-pressure oil film W near the contour of the male rotor 2 side (pitch circle D2 side) in the shielded area 49a of the housing 4, which is higher than the surrounding pressure. With the axial communication path G2 overlapping the shielded area 49a across the discharge side end face gap G1, this high-pressure oil film W can suppress the discharge flow path 52 ( Figure 1 Compressed air in the discharge chamber Cd (high-pressure space) leaks from the edge of the male rotor 2 on the shielded area 49a through the axial connection path G2 into the suction chamber (low-pressure space). This improves the compression performance and energy efficiency of the screw compressor 1.

[0080] The groove structure (multiple grooves 60) of this embodiment converts dynamic pressure into static pressure by blocking the oil flowing due to shear force Sf at one end 61, thereby forming a high-pressure oil film W. It can be considered a type of dynamic pressure groove. By setting the depth of each groove 60 to a suitable value (e.g., in the range of 1 μm to 1 mm) that maximizes the pressure of the oil film W according to the magnitude of the shear force Sf acting on the oil and the size of the gap G1 at the discharge side end face, internal leakage via the axial communication path G2 can be further suppressed.

[0081] In this embodiment, each groove 60 is disposed inside the pitch circle D2 of the female rotor 3 and is formed in a manner that does not communicate with the discharge port 52a. This prevents multiple grooves 60 from simultaneously communicating with the discharge working chamber Cd and the axial communication path G2, thus preventing them from becoming paths for internal leakage.

[0082] In this embodiment, a plurality of slots 60 are provided in the housing 4, which is part of a stationary body. Therefore, the plurality of slots 60 do not move with the screw rotor but are fixed in position relative to the trajectory of the outlet 52a of the housing 4 and the axial communication path G2. Thus, a stable suppression effect can be expected for internal leakage via the axial communication path G2.

[0083] [First variation of the first embodiment]

[0084] Next, use Figures 8-10 An example of a screw compressor of the first modification of the first embodiment will be described. Figure 8 From and Figure 4 A cross-sectional view of a screw compressor of a modified example of the first embodiment of the present invention is viewed with the same arrow direction. Figure 9 This is a diagram showing the groove structure of the housing in a screw compressor according to a modified example of the first embodiment of the present invention. Figure 8 The figure shown by reference numeral L3 is an enlarged portion of the figure. Figure 10 This diagram illustrates the function of the groove structure in the housing of a screw compressor according to a modified example of the first embodiment of the present invention. Figure 8 The outer peripheral surface of the shell is omitted. Additionally, in... Figures 8-10 In, with Figures 1 to 7 The same reference numerals in the accompanying drawings indicate the same parts, therefore detailed descriptions are omitted.

[0085] Figure 8 and Figure 9 The screw compressor 1A of the first variation of the first embodiment shown has a structure that is substantially the same as that of the first embodiment, but the arrangement and shape of the plurality of grooves 60A formed on the discharge side inner wall surface 49 of the housing 4A are different.

[0086] Specifically, a group of grooves consisting of multiple grooves 60A is formed in the shielding area 49a of the inner wall surface 49 on the discharge side of the housing 4A. The multiple grooves 60A are arranged along the outline of the outer diameter line D1 side (female rotor 3 side) of the male rotor 2 in the shielding area 49a. That is, the multiple grooves 60A are arranged circumferentially relative to the central axis A1 of the male rotor 2. Each groove 60A is formed as an elongated groove with a long side direction, and the multiple grooves 60A are arranged such that their sides extending in the long side direction are adjacent to each other.

[0087] like Figure 9 As shown, one end 61 of each slot 60A is located closer to the outer periphery of the male rotor 2 than the other end 62, for example, formed linearly from the other end 62 to one end 61. The slot 60A is configured such that, relative to the radial direction R1 of the male rotor 2, its long side direction from the other end 62 to one end 61 (from the inner periphery to the outer periphery of the male rotor 2) is inclined at an angle θcm in the same direction as the rotation direction of the male rotor 2. The slot 60A is confined to a position closer to the outer diameter line D1 of the male rotor 2 and does not reach the outline of the shielding area 49a (the opening edge of the outlet 52a).

[0088] In this variation, the inflow is formed at Figure 8 The oil in each groove 60A of the shielded area 49a of the inner wall surface 49 on the discharge side of the housing 4A shown is dragged by the discharge side end face 21c of the rotating male rotor 2. Thus, as... Figure 10 As shown, the shear force Sf acts on the oil in each groove 60A in the tangential direction (orthogonal to the radial direction R1 of the male rotor 2) and in the same direction as the rotation direction. The shear force Sf acting on the oil in the groove 60A can be decomposed into a first component force Sf1, which is a component force orthogonal to the long side direction of the groove 60A, and a second component force Sf2, which is a component force in the long side direction of the groove 60A.

[0089] In this variation, such as Figure 9 As shown, each slot 60A extends in an inclined manner relative to the radial direction R1 of the male rotor 2, with the other end 62 as a base point, in the same direction as the rotation direction of the male rotor 2. Thus, as... Figure 10 As shown, the second component force Sf2 becomes a force directed towards the outer periphery of the male rotor 2 along the long side of the slot 60A. Therefore, the oil in each slot 60A flows towards the outer periphery of the male rotor 2 along the long side of the slot 60A due to the second component force Sf2. The oil flowing in the slot 60A undergoes kinetic energy (dynamic pressure) conversion by being blocked by one end 61, which is the end of the outer periphery of the male rotor 2 along the long side of the slot 60A, resulting in an increase in static pressure. Finally, it flows out into the discharge side end face gap G1 (male rotor 2 side) in the region of one end 61. Thus, the oil pressure in the discharge side end face gap G1 becomes highest near one end 61 of the slot 60A.

[0090] In this variation, such as Figure 9 As shown, multiple slots 60A are arranged such that their sides, extending in the long direction, are adjacent to each other. Thus, as... Figure 10 As shown, pressurized oil flows from one end 61 (the end on the outer periphery of the male rotor) of each groove 60A to the discharge end face gap G1. The high-pressure oil flowing from multiple ends 61 connects, thereby promoting the formation of a high-pressure oil film W along one end 61 of the multiple grooves 60A in the discharge end face gap G1. Furthermore, the closer the end 61 of the groove 60A is to the outer periphery of the male rotor 2, the greater the shear force Sf acting due to the rotation of the male rotor 2; therefore, the suppression effect of internal leakage caused by the pressurization of the oil film W is correspondingly increased.

[0091] In this way, not only is the oil in the groove 60A used to seal the discharge side end face gap G1, but the oil flowing out of the groove 60A also forms a high-pressure oil film W near the contour of the female rotor 3 side (outer diameter line D1 side) in the shielded area 49a of the housing 4A. With the axial communication path G2 overlapping the shielded area 49a across the discharge side end face gap G1, this high-pressure oil film W can prevent the discharge flow path 52 (see reference) from being blocked. Figure 1 Compressed air in the discharge chamber Cd (high-pressure space) leaks from the edge of the female rotor 3 on the shielded area 49a through the axial connection path G2 into the suction chamber (low-pressure space). This improves the compression performance and energy efficiency of the screw compressor 1A.

[0092] In this modified example, each groove 60A is disposed inside the outer diameter line D1 of the male rotor 2 and is configured not to communicate with the discharge port 52a. This prevents multiple grooves 60A from simultaneously communicating with the discharge chamber Cd and the axial communication path G2, thus preventing them from becoming pathways for internal leakage.

[0093] The first embodiment and its variations are summarized below. The screw compressor 1, 1A of the first embodiment or its variations includes: a male rotor 2 having a first discharge side end face 21c on one axial side; a female rotor 3 having a second discharge side end face 31c on one axial side; and a housing 4 having a housing chamber 45 for housing the male rotor 2 and the female rotor 3 in a manner capable of rotating in an engaged state. The housing 4 has a discharge side inner wall surface 49 opposite to the first discharge side end face 21c of the male rotor 2 and the second discharge side end face 31c of the female rotor 3. The discharge side inner wall surface 49 of the housing 4 has a shielding region 49a that shields at least a portion of the trajectory of the axial communication path G2, wherein the axial communication path G2 is a gap that periodically appears on the first discharge side end face 21c and the second discharge side end face 31c and is sandwiched between the rear infeed surfaces of the male rotor 2 and the female rotor 3 due to changes in engagement caused by the rotation of the male rotor 2 and the female rotor 3. Within the shielding area 49a of the housing 4, a groove group consisting of multiple grooves 60, 60A extending along their long sides is provided. The grooves 60, 60A of the groove group are arranged circumferentially on at least one of the male rotor 2 and female rotor 3, and are configured such that their sides extending along their long sides are adjacent to each other. The grooves 60, 60A are each configured such that, along their long side from the inner circumference to the outer circumference of one rotor (male rotor 2 or female rotor 3), they are inclined relative to the radial direction of one rotor (male rotor 2 or female rotor 3) in the same direction as the rotation direction of that rotor (male rotor 2 or female rotor 3).

[0094] According to this structure, the oil (liquid) in the multiple grooves 60, 60A provided on the discharge side inner wall surface 49 of the housing 4 flows in the long side direction due to shear force, and is subsequently blocked, resulting in a static pressure increase. Therefore, a high-pressure oil film W (liquid film) can be formed near the axial communication path G2 in the discharge side end face gap G1. This reduces the internal leakage of compressed gas via the axial communication path G2.

[0095] [Second Implementation]

[0096] Next, use Figures 11-13 The structure and construction of the screw compressor of the second embodiment will be illustrated by example. Figure 11 From and Figure 2 A cross-sectional view of the screw compressor of the second embodiment of the present invention is viewed with the same arrow direction. Figure 12 This diagram illustrates the slot structure of the screw rotor in the screw compressor according to the second embodiment of the present invention. Figure 11 The enlarged portion of the figure shown by reference numeral L4 in the attached diagram. Figure 13 From Figure 12 The XIII-XIII arrows show a cross-sectional view of the slot structure of the screw rotor in the screw compressor of the second embodiment of the present invention, viewed from the direction of the arrows. Figure 11 and Figure 12 In the diagram, the double-dotted line represents the shape obtained by projecting the outline of the discharge port on the inner wall of the discharge side of the casing onto the discharge side end faces of the male and female rotors, and the thick arrow indicates the rotation direction of the two rotors. Figure 11 The outer peripheral surface of the shell is omitted. Additionally, in... Figures 11-13 In, with Figures 1-10 The same reference numerals in the accompanying drawings indicate the same parts, therefore detailed descriptions are omitted.

[0097] Figure 11 The screw compressor 1B of the second embodiment shown differs from that of the first embodiment in that the groove structure for forming the high-pressure oil film W is not formed on the inner wall surface 49 of the discharge side of the housing 4B, but rather on the discharge side end face 31c of the female rotor 3B. That is, the groove structure as in the first embodiment is not formed on the inner wall surface 49 (not shown) of the discharge side of the housing 4B.

[0098] Specifically, such as Figure 11 and Figure 12 As shown, a group of grooves consisting of multiple grooves 70 is formed in the region on the tooth tip side of each internal tooth 31a of the discharge side end face 31c of the female rotor 3B. The multiple grooves 70 are arranged in the thickness direction of the tooth tip. That is, the multiple grooves 70 are arranged in the circumferential direction relative to the central axis A2 of the female rotor 3B. Each groove 70 is formed as an elongated groove with a long side direction, and the multiple grooves 70 are arranged such that their sides extending in the long side direction are adjacent to each other.

[0099] like Figure 12 As shown, one end 71 of each groove 70 in the long side direction is located closer to the outer periphery of the female rotor 3B than the other end 72, for example, formed linearly from the other end 72 (inner periphery end) to one end (outer periphery end) 71. The groove 70 is configured such that, relative to the radial direction R2 of the female rotor 3B, the long side direction from the other end 72 (inner periphery end) to one end (outer periphery end) 71 is inclined at an angle θrf in the direction opposite to the rotation direction of the female rotor 3B. The groove 70 is confined to a position closer to the pitch circle D2 of the female rotor 3B and does not reach the outline of the internal teeth 31a of the female rotor 3B.

[0100] When the distance from the central axis A1 of the male rotor 2 to the outer diameter line D1 of the male rotor 2 is a1, the distance from the central axis A2 of the female rotor 3B to the pitch circle D2 of the female rotor 3B is a2, and the distance between the central axis A1 of the male rotor 2 and the central axis A2 of the female rotor 3B is b, the slot 70 is arranged within the range of the distance from the pitch circle D2 of the female rotor 3B to the central axis A2 of the female rotor 3B up to (a1+a2-b).

[0101] like Figure 13 As shown, the groove 70 has a generally certain depth. The groove 70 is intended to be a type of dynamic pressure groove, as will be described in detail later. The depth of the groove 70 as a dynamic pressure groove is an appropriate value based on the magnitude of the shear force acting on the oil flowing into it and the centrifugal force described later. For example, when the discharge side end face gap G1 is about tens to 200 μm, the preferred depth of the groove 70 is in the range of 1 μm to 1 mm.

[0102] Next, use Figure 13 and Figure 14 The function and effect of the slot structure of the female rotor in the screw compressor of the second embodiment will be explained. Figure 14 This diagram illustrates the function of the slot structure of the screw rotor in the screw compressor according to the second embodiment of the present invention. Figure 13 In the diagram, the thick arrows indicate oil flow. Figure 14 In the diagram, the double-dotted line represents the shape obtained by projecting the outline of the discharge port on the inner wall of the discharge side of the housing onto the discharge side end faces of the male and female rotors.

[0103] In the screw compressor 1B of this embodiment, unlike the first embodiment and its modifications, two main forces act on the oil flowing into the grooves 70 formed on the discharge side end face 31c of the female rotor 3B. For example... Figure 14 As shown, the first force is the centrifugal force Cf generated by the oil in the tank 70 rotating together with the female rotor 3B. The centrifugal force Cf acts in a radial direction R2 orthogonal to the rotation direction of the female rotor 3B and outwards. The second force is the force generated by the oil in each tank 70 rotating together with the female rotor 3B, acting on the inner wall surface 49 of the discharge side of the housing 4B (refer to...). Figure 13 The shear force Sf generated by dragging. The shear force Sf acts in the tangential direction of the rotation direction of the female rotor 3B (orthogonal to the radial direction R2 of the female rotor 3B) and in the opposite direction of the rotation direction.

[0104] The centrifugal force Cf acting on the oil in the tank 70 can be decomposed into a first component Cf1, which is orthogonal to the long side of the tank 70, and a second component Cf2, which is also orthogonal to the long side of the tank 70. Similarly, the shear force Sf acting on the oil in the tank 70 can be decomposed into a first component Sf1, which is orthogonal to the long side of the tank 70, and a second component Sf2, which is also orthogonal to the long side of the tank 70.

[0105] In this embodiment, each groove 70 extends in the opposite direction of the rotational direction of the female rotor 3B, with its radial direction R2 relative to the female rotor 3B and its other end 72 as a base point. Therefore, the second components of the centrifugal force Cf and the shear force Sf, Cf2 and Sf2, become forces in the long side direction of the groove 70 toward the outer periphery of the female rotor 3B. Consequently, the oil in each groove 70 flows toward the outer periphery of the female rotor 3B along the long side direction of the groove 70 due to the second components of the centrifugal force Cf and the shear force Sf, Cf2 and Sf2. Figure 13 and Figure 14 As shown, the oil flowing in the tank 70 undergoes kinetic energy (dynamic pressure) conversion by being blocked by one end 71, which is the end of the outer periphery of the female rotor 3B in the long side direction of the tank 70. The static pressure increases, and finally, it flows out towards the discharge side end face gap G1 (the discharge side inner wall surface 49 side of the housing 4B) in the region of one end 71. As a result, the oil pressure at the discharge side end face gap G1 becomes the highest near one end 71 of the tank 70.

[0106] Furthermore, in this embodiment, such as Figure 14 As shown, multiple grooves 70 are arranged so that their sides, extending in the long direction, are adjacent to each other. Therefore, pressurized oil flows from one end 71 (the end on the outer periphery of the female rotor) of each of the multiple grooves 70 to the discharge side end face gap G1. The high-pressure oil flowing from the multiple end 71s is connected, thereby promoting the formation of a high-pressure oil film W along one end 71 of the multiple grooves 70 in the discharge side end face gap G1. Furthermore, the closer the end 71 of the groove 70 is to the outer periphery of the female rotor 3B, the greater the centrifugal force Cf and shear force Sf acting due to the rotation of the female rotor 3B. Therefore, the suppression effect of internal leakage caused by the pressurization of the oil film W is correspondingly increased.

[0107] In this embodiment, a plurality of slots 70 are arranged within a distance (a1+a2-b) from the pitch circle D2 of the female rotor 3B to the central axis A2 of the female rotor 3B. Therefore, at a certain rotational position of the female rotor 3B, one end 71 of the slot 70 can exist at a position between the working chamber of the discharge stroke and the axial communication path G2.

[0108] Therefore, not only is the oil in the groove 70 of the female rotor 3B used to seal the discharge side end face gap G1, but the oil flowing out of the groove 70 of the female rotor 3B also forms an oil film W with a higher pressure than the surrounding area. With the axial connecting path G2 overlapping the shielding area 49a across the discharge side end face gap G1, this high-pressure oil film W can suppress the discharge flow path 52 (see reference). Figure 1Compressed air in the discharge chamber Cd (high-pressure space) leaks from the tooth tip side of the female rotor 3B through the axial connection path G2 to the suction chamber (low-pressure space). This method improves the compression performance and energy efficiency of the screw compressor 1B.

[0109] In this way, multiple grooves 70 formed on the discharge side end face 31c of the female rotor 3B intercept the oil flowing due to shear force Sf and centrifugal force Cf at one end 71, thereby converting dynamic pressure into static pressure to form a high-pressure oil film W, which can also be described as a type of dynamic pressure groove. By setting the depth of each groove 70 to an appropriate value (e.g., 1 μm to 1 mm) that maximizes the pressure of the oil film W according to the magnitude of the shear force Sf and centrifugal force Cf acting on the oil and the size of the discharge side end face gap G1, internal leakage via the axial communication path G2 can be further suppressed.

[0110] Furthermore, in this embodiment, the slot 70 is configured to be located inside the pitch circle D2 of the female rotor 3B and does not reach the outline of the female rotor 3B. This prevents multiple slots 70 from simultaneously connecting to the discharge chamber Cd and the axial communication path G2, thus preventing them from becoming paths for internal leakage.

[0111] Furthermore, in this embodiment, a groove 70 can be provided on the discharge side end face 31c of the female rotor 3B formed by casting or other machining processes, thus making the manufacturing process of the compressor easier.

[0112] [Modifications of the Second Embodiment]

[0113] Next, use Figures 15-17 An example of a screw compressor according to a modified embodiment of the second embodiment will be described. Figure 15 From and Figure 2 A cross-sectional view of a screw compressor of a modified example of the second embodiment of the present invention is viewed with the same arrow direction. Figure 16 This is a diagram showing the slot structure of the screw rotor in a screw compressor according to a modified example of the second embodiment of the present invention. Figure 15 The enlarged portion of the figure shown by reference numeral L5 in the attached diagram. Figure 17 This diagram illustrates the function of the slot structure of the screw rotor in a modified example of the screw compressor according to the second embodiment of the present invention. Figure 15 and Figure 16 In the diagram, the double-dotted line represents the shape obtained by projecting the outline of the discharge port on the inner wall of the discharge side of the casing onto the discharge side end faces of the male and female rotors, and the thick arrow indicates the rotation direction of the two rotors. Figure 15 The outer peripheral surface of the shell is omitted. Additionally, in... Figures 15-17 In, with Figures 1 to 14The same reference numerals in the accompanying drawings indicate the same parts, therefore detailed descriptions are omitted.

[0114] Figure 15 and Figure 16 The screw compressor 1C of the modified example of the second embodiment shown differs from the second embodiment in that the groove structure for forming the high-pressure oil film W is provided on the discharge side end face 21c of the male rotor 2C, instead of the discharge side end face 31c of the female rotor 3.

[0115] Specifically, in the region on the tooth tip side of each external tooth 21a in the discharge side end face 21c of the male rotor 2C, a groove group consisting of multiple grooves 70C is formed. The multiple grooves 70C are arranged in the thickness direction of the external teeth 21a. That is, the multiple grooves 70C are arranged in the circumferential direction relative to the central axis A1 of the male rotor 2C. Each groove 70 is formed as an elongated strip groove with a long side direction, and the multiple grooves 70C are arranged such that their sides extending in the long side direction are adjacent to each other.

[0116] like Figure 16 As shown, one end 71 of each slot 70C in the long side direction is located closer to the outer periphery of the male rotor 2C than the other end 72. For example, it is formed linearly from the other end 72 (inner periphery end) to one end (outer periphery end) 71. The slot 70C is configured such that, relative to the radial direction R1 of the male rotor 2C, the long side direction from the other end 72 (inner periphery end) to one end (outer periphery end) 71 is inclined at an angle θrm in the direction opposite to the rotation direction of the male rotor 2C. The slot 70C is confined to a position that is closer to the inner side than the outer diameter line D1 of the male rotor 2C and does not reach the outline of the outer tooth 21a of the male rotor 2C.

[0117] Similar to the second embodiment, when the distance from the central axis A1 of the male rotor 2C to the outer diameter line D1 of the male rotor 2C is a1, the distance from the central axis A2 of the female rotor 3 to the pitch circle D2 of the female rotor 3 is a2, and the distance between the central axis A1 of the male rotor 2C and the central axis A2 of the female rotor 3 is b (refer to...) Figure 12 The slots 70C are positioned within a distance of (a1+a2-b) from the outer diameter line D1 of the male rotor 2C to the central axis A1 of the male rotor 2C. Thus, at a certain rotational position of the male rotor 2C, one end 71 of the plurality of slots 70C can be located between the working chamber Cd of the discharge stroke and the axial communication path G2.

[0118] In this modified example, similar to the second embodiment, both centrifugal force Cf and shear force Sf act on the oil flowing into the grooves 70C formed on the discharge side end face 21c of the male rotor 2C. For example... Figure 17As shown, the centrifugal force Cf acts in a radial direction R1 orthogonal to the rotation direction of the male rotor 2C and outwards. The shear force Sf acts in a tangential direction (orthogonal to the radial direction R1 of the male rotor 2C) and in the opposite direction of rotation of the male rotor 2C. The centrifugal force Cf acting on the oil in the tank 70C can be decomposed into a first component Cf1, which is orthogonal to the long side direction of the tank 70C, and a second component Cf2, which is also a component of the long side direction of the tank 70C. Similarly, the shear force Sf acting on the oil in the tank 70C can be decomposed into a first component Sf1, which is orthogonal to the long side direction of the tank 70C, and a second component Sf2, which is also a component of the long side direction of the tank 70C.

[0119] In this variation, such as Figure 16 As shown, each slot 70C extends in the opposite direction of the rotation direction of the male rotor 2C, with the other end 72 as the base point, relative to the radial direction R1 of the male rotor 2C. Thus, as... Figure 17 As shown, the second components of the centrifugal force Cf and the shear force Sf, Cf2 and Sf2, become forces on the outer periphery of the sun rotor 2C along the long side of the tank 70C. Therefore, the oil in each tank 70C flows towards the outer periphery of the sun rotor 2C along the long side of the tank 70C due to the second components of the centrifugal force Cf and the shear force Sf, Cf2 and Sf2. The oil flowing in the tank 70C undergoes kinetic energy (dynamic pressure) conversion by being blocked by one end 71, which is the end of the outer periphery of the sun rotor 2C along the long side of the tank 70C, resulting in an increase in static pressure. Finally, it flows out towards the discharge side end face gap G1 (the discharge side inner wall surface 49 side of the housing 4B) in the region of one end 71. Thus, the oil pressure at the discharge side end face gap G1 becomes the highest near one end 71 of the tank 70C.

[0120] In this variation, such as Figure 16 As shown, multiple grooves 70C are arranged so that their sides, extending in the long direction, are adjacent to each other. Therefore, pressurized oil flows from one side end 71 (the end on the outer periphery of the male rotor) of each of the multiple grooves 70C to the discharge side end face gap G1. The high-pressure oil flowing from the multiple side ends 71 ​​are connected, thereby promoting the formation of a high-pressure oil film W along one side end 71 of the multiple grooves 70C in the discharge side end face gap G1. In this way, the multiple grooves 70C, by blocking the oil flowing due to shear force Sf and centrifugal force Cf with one side end 71, convert dynamic pressure into static pressure, thereby forming a high-pressure oil film W, which can be considered a type of dynamic pressure groove. Furthermore, the closer the one side end 71 of the groove 70C is to the outer periphery of the male rotor 2C, the greater the centrifugal force Cf and shear force Sf acting due to the rotation of the male rotor 2C, and therefore the greater the suppression effect of internal leakage caused by the pressurization of the oil film W.

[0121] In this way, not only is the oil in the slot 70C of the male rotor 2C used to seal the discharge side end face gap G1, but the oil flowing out of the slot 70C of the male rotor 2C also forms an oil film W with a higher pressure than the surrounding area. With the axial connecting path G2 overlapping the shielding area 49a across the discharge side end face gap G1, this high-pressure oil film W can suppress the discharge flow path 52 (see reference). Figure 1 Compressed air in the discharge chamber Cd (high-pressure space) leaks from the edge of the female rotor 3 on the shielded area 49a through the axial connection path G2 into the suction chamber (low-pressure space). This method improves the compression performance and energy efficiency of the screw compressor 1C.

[0122] Furthermore, in this modified example, the groove 70C is positioned inside the outer diameter line D1 of the male rotor 2C, and is arranged in a manner that does not reach the tooth profile of the male rotor 2C. This prevents the groove 70C from simultaneously connecting with both the discharge chamber Cd and the axial communication path G2, thus preventing it from becoming a pathway for internal leakage.

[0123] In this modified example, multiple grooves 70C can be provided on the discharge side end face 21c of the male rotor 2C formed by casting or other machining processes, thus making the machining process in the compressor manufacturing process easier.

[0124] The second embodiment and its variations are summarized below. The screw compressors 1B and 1C of the second embodiment or its variations include: male rotors 2 and 2C, each having a first discharge side end face 21c on one axial side and rotatable about a first central axis A1; female rotors 3 and 3B, each having a second discharge side end face 31c on one axial side and rotatable about a second central axis A2; and a housing 4B having a housing chamber 45 for housing the male rotors 2 and 2C and the female rotors 3 and 3B in a rotatable manner in an engaged state. A groove group consisting of a plurality of grooves 70 and 70C having a long side direction is provided on the discharge side end face 21c and 31c of at least one of the male rotors 2C and 3B. The plurality of grooves 70 and 70C of the groove group are arranged circumferentially on one rotor (male rotor 2C or female rotor 3B) such that their sides extending in the long side direction are adjacent to each other.

[0125] According to this structure, oil (liquid) in multiple grooves 70, 70C located on the discharge side end faces 21c, 31c of a rotor (male rotor 2C or female rotor 3B) flows along its long side due to centrifugal force and shear force, and is subsequently blocked, causing a pressure increase. Therefore, a high-pressure oil film W (liquid film) can be formed near the axial connection path G2 at the discharge side end face gap G1. Consequently, internal leakage of compressed gas via the axial connection path G2 can be reduced.

[0126] [Modifications of the groove structure in the first embodiment and its variations]

[0127] Next, use Figures 18A to 18C Examples of deformations of the groove structure of the housing in the screw compressor of the first embodiment and its modifications will be described. Figure 18A , Figure 18B , Figure 18C These are figures showing the first, second, and third examples of variations of the groove structure of the housing in the screw compressor according to the first embodiment and its modifications. Figures 18A to 18C In the middle, the upper direction is the radial outer side (outer circumference) of the object screw rotor (male or female rotor), and the left direction is the rotational direction of the object screw rotor.

[0128] The groove structure (groove group) formed on the discharge side inner wall surface 49 of the housing 4, 4A in the screw compressors 1, 1A of the first embodiment and its modifications can be modified in various ways besides the aforementioned plurality of grooves 60, 60A. In principle, this groove structure (groove group) can be any structure in which the oil in the groove flows due to the shear force accompanying the rotation of the target screw rotor and is blocked at any position in the groove. That is, this groove structure (groove group) can function as a dynamic pressure groove.

[0129] like Figure 18A As shown, in the first example of the variation of the groove structure (groove group), each groove 60B is formed by combining a groove main body 64 with a long side direction that is formed in a straight line and an additional groove 65 connected to the groove main body 64 but with a different shape from the groove main body 64. The groove main body 64, like the grooves 60 and 60A in the first embodiment and its variations, is configured such that, relative to the radial direction of the target screw rotor (male rotor 2 or female rotor 3), its long side direction is inclined in the same direction as the rotation direction of the screw rotor, with the other end 62 of the groove 60B as the reference point. Therefore, similar to the cases of the grooves 60 and 60A in the first embodiment and its variations, the second component Sf2 of the shear force Sf acts on the oil inside the groove main body 64 along the long side direction of the groove main body 64 towards the outer periphery of the groove main body 64. The additional groove 65 is, for example, a short strip-shaped groove connected to the end of the outer periphery of the groove main body 64 and with an inclination angle larger than that of the groove main body 64. The auxiliary groove 65 can be selected in terms of shape and position to promote the formation of oil film W, pressure rise, and oil flow into groove 60B.

[0130] Therefore, in the first modified example, as in the first embodiment and its modifications, the oil in the multiple grooves 60B flows towards the additional groove portion 65, which is the outer peripheral end of the groove 60B, due to shear force Sf. It is blocked in the additional groove portion 65, causing the static pressure to rise. Finally, the pressurized oil flows out from the outer peripheral ends (additional groove portions 65) of the multiple grooves 60B to the discharge side end face gap G1 (screw rotor side) and connects with it, thereby forming a high-pressure oil film W along the additional groove portions 65 of the multiple grooves 60B in the discharge side end face gap G1.

[0131] exist Figure 18B In the second example of the variation of the groove structure (groove group) shown, each groove 60C is curved and not straight. The curved shape of the groove 60C is configured such that the tangent at each point relative to the radial direction of the target screw rotor (male rotor 2 or female rotor 3) is inclined in the same direction as the rotation direction of the target screw rotor. As a result, similar to the cases of grooves 60 and 60A in the first embodiment and its variations, the second component of the shear force Sf, Sf2, acts on the oil inside the groove 60C towards the outer periphery of the groove 60C.

[0132] Therefore, in the modified second example, similar to the first embodiment and its modifications, the oil in the multiple grooves 60C flows towards one side end (outer peripheral end) 61 of the groove 60C due to the second component Sf2 of the shear force Sf. At this end 61, the flow is blocked, causing a rise in static pressure. The pressurized oil eventually flows out from one side end 61 of the multiple grooves 60C and connects with the discharge side end face gap G1 (screw rotor side), thereby forming a high-pressure oil film W along one side end 61 of the multiple grooves 60C in the discharge side end face gap G1.

[0133] exist Figure 18C In the third example of the variation of the slot structure (slot group) shown, each slot 60D is formed in a V-shape, and multiple slots 60D are arranged in a herringbone pattern around the target screw rotor (male rotor 2 or female rotor 3). Each slot 60D is formed such that the V-shape opens in the opposite direction to the rotation direction of the target screw rotor.

[0134] That is, the slot 60D is composed of a first slot 67 on one side of the V-shape and a second slot 68 on the other side of the V-shape, located radially outward of the target screw rotor compared to the first slot 67. The first slot 67 is configured to be inclined in the same direction as the rotation direction of the screw rotor relative to the radial direction of the target screw rotor, while the second slot 68 is configured to be inclined in the opposite direction to the rotation direction of the screw rotor relative to the radial direction of the target screw rotor. Furthermore, each slot 60D is configured such that the connecting portion 69 (the corner of the V-shape) between the first slot 67 and the second slot 68 is located at a certain rotational position of the target screw rotor between the axial communication path G2 and the working chamber Cd of the discharge stroke.

[0135] Similar to the cases of grooves 60 and 60A in the first embodiment and its variations, the second component of the shear force Sf, Sf2, acts on the oil inside the first groove 67 towards the outer periphery. On the other hand, unlike the cases of grooves 60 and 60A in the first embodiment and its variations, the second component of the shear force Sf, Sf2, acts on the oil inside the second groove 68 towards the inner periphery.

[0136] Therefore, in the modified third example, in the multiple grooves 60D, the oil in the first groove 67 flows towards the connection 69 (the corner of the V-shaped groove 60D) between the first groove 67 and the second groove 68 due to the second component of the shear force Sf2, and the oil in the second groove 68 flows towards the connection 69 due to the second component of the shear force Sf2. Thus, the oil flowing from the first groove 67 and the oil flowing from the second groove 68 merge and block each other, resulting in a dynamic pressure conversion and a static pressure increase. The pressurized oil eventually flows out from the connection 69 (the corner of the V-shaped groove 60D) of the multiple grooves 60D and connects with the discharge side end face gap G1 (screw rotor side), thereby forming a high-pressure oil film W along the connection 69 (corner) of the multiple grooves 60D in the discharge side end face gap G1.

[0137] In the first to third examples of the deformation of the groove structure (groove group) of the housing, the oil in the multiple grooves 60B, 60C, and 60D flows due to the shear force Sf accompanying the rotation of the screw rotor. It is then blocked, resulting in increased pressure, and then flows out to the discharge side end face gap G1. Therefore, similar to the groove structure of the first embodiment and its variations, a high-pressure oil film W can be formed between the axial communication path G2 and the working chamber Cd (high-pressure space) of the discharge stroke, suppressing internal leakage via the axial communication path G2.

[0138] Furthermore, the screw compressor of the third modified example is characterized in that: the multiple slots 60D of the slot group are formed in a V shape and arranged in a herringbone shape around a rotor (male rotor 2 or female rotor 3), and the multiple slots 60D of the slot group are configured to open in the opposite direction of the rotation direction of a rotor (male rotor 2 or female rotor 3) in a V shape.

[0139] [Modifications of the groove structure in the second embodiment and its variations]

[0140] Next, use Figures 19A to 19F Examples of modifications to the slot structure (slot group) of the screw rotor in the screw compressor of the second embodiment and its modifications are described. Figure 19A , Figure 19B , Figure 19C , Figure 19D , Figure 19E , Figure 19FThe figures are respectively examples 1, 2, 3, 4, 5, and 6, illustrating modifications of the slot structure of the screw rotor in a screw compressor according to the second embodiment and its modifications of the present invention. Figures 19A to 19F In the middle, the upper direction is the radial outer side (outer circumference) of the object screw rotor (male or female rotor), and the left direction is the rotation direction of the object screw rotor.

[0141] The groove structure (groove group) of the discharge side end faces 21c and 31c of the screw rotors (male rotor 2C or female rotor 3B) in the screw compressors 1B and 1C of the second embodiment and its modifications can be modified in various ways besides the grooves 70 and 70C described above. In principle, this groove structure (groove group) can be any structure in which the oil in the groove flows due to at least one of the centrifugal force or shear force accompanying the rotation of the target screw rotor, and is blocked at any position in the groove. That is, this groove structure (groove group) can function as a dynamic pressure groove.

[0142] like Figure 19A As shown, in the first example of the deformation of the groove structure (groove group), each groove 70D is curved rather than straight. The curved shape of the groove 70D is configured such that the tangent at each point relative to the radial direction of the target screw rotor (male rotor 2C or female rotor 3B) is inclined in the opposite direction to the rotation direction of the screw rotor. As a result, similar to the cases of grooves 70 and 70C in the second embodiment and its variations, the second components of the centrifugal force Cf and the shear force Sf, Cf2 and Sf2, act on the oil inside the groove 70D towards the outer periphery of the groove 70D.

[0143] Therefore, in the first modified example, similar to the second embodiment and its modifications, the oil in the multiple grooves 70D flows towards one side end (outer peripheral end) 71 of the groove 70D due to the second components Cf2 and Sf2 of the centrifugal force Cf and the shear force Sf. At this end 71, the flow is blocked, causing a rise in static pressure. The pressurized oil eventually flows out from one side end 71 of the multiple grooves 70D and connects to the discharge side end face gap G1 (the discharge side inner wall surface 49 side of the housing 4B), thereby forming a high-pressure oil film W along one side end 71 of the multiple grooves 70D.

[0144] exist Figure 19B In the second example of the deformation of the groove structure (groove group) shown, each groove 70E is configured to extend in a straight line along the radial direction of the target screw rotor (male rotor 2C or female rotor 3B) in the long side direction. Therefore, the centrifugal force Cf of the oil acting within the groove 70E is only a component in the long side direction of the groove 70E. On the other hand, the shear force Sf of the oil acting within the groove 70E has a zero component in the long side direction of the groove 70E, and is only a component in the direction orthogonal to the long side direction.

[0145] Therefore, in the second modified example, the oil in the multiple grooves 70E flows towards one end (outer peripheral end) 71 of the groove 70E due to centrifugal force Cf, where it is blocked and the static pressure rises. The pressurized oil eventually flows out from one end 71 of the multiple grooves 70E to the discharge side end face gap G1 (the discharge side inner wall surface 49 side of the housing 4B) and connects, thereby forming a high-pressure oil film W along one end 71 of the multiple grooves 70E.

[0146] exist Figure 19C In the third example of the variation of the groove structure (groove group) shown, each groove 70F is formed by combining a groove main body 74 with a long side direction that is formed in a straight line and an additional groove 75 connected to the groove main body 74 but with a different shape from the groove main body 74. Similar to the groove 70E in the second variation, the groove main body 74 is configured to extend in a straight line along the radial direction of the target screw rotor (male rotor 2C or female rotor 3B) in the long side direction. Thus, similar to the case of the groove 70E in the second variation, the centrifugal force Cf acts on the oil inside the groove main body 74 towards the outer periphery of the groove main body 74. The additional groove 75 is, for example, a short strip-shaped groove connected to the outer periphery end of the groove main body 74. The shape and position of the additional groove 75 can be selected to promote the formation of oil film W, pressure rise, and oil inflow into the groove 70F.

[0147] Therefore, in the third modified example, similar to the second modified example, the oil in the main body 74 of the groove flows towards the auxiliary groove 75, which is the outer peripheral end of the groove 70F, due to centrifugal force Cf. The oil is blocked in the auxiliary groove 75, resulting in a rise in static pressure. The pressurized oil eventually flows out from the outer peripheral end (auxiliary groove 75) of the multiple grooves 70F and connects to the discharge side end face gap G1 (the discharge side inner wall surface 49 side of the housing 4B), thereby forming a high-pressure oil film W along the auxiliary groove 75 of the multiple grooves 70F.

[0148] Figure 19D The fourth variation of the groove structure shown is roughly the same as the third variation, but the orientation of the long side of the groove body 74G is different. Specifically, the groove body 74G is constructed such that it is inclined in the opposite direction of the rotation of the screw rotor (male rotor 2C or female rotor 3B) with the other end (inner circumferential end) 72 of the groove body 74G as a base point. Therefore, unlike the groove body 74 in the third variation, the second components of the centrifugal force Cf and the shear force Sf, Cf2 and Sf2, act on the oil inside the groove body 74G towards the outer circumference of the groove body 74G. The additional groove 75 is the same as in the third variation.

[0149] Therefore, in the fourth modified example of the multiple grooves 70G, the oil in the main groove portion 74G flows towards the additional groove portion 75, which is the outer peripheral end of the groove 70G, due to centrifugal force Cf and shear force Sf. It is blocked in the additional groove portion 75, resulting in a rise in static pressure. The pressurized oil eventually forms a high-pressure oil film W along the additional groove portion 75 of the multiple grooves 70G.

[0150] exist Figure 19E In the fifth example of the variation of the slot structure shown, each slot 70H is formed in a V-shape, and multiple slots 70H are arranged in a herringbone shape around the target screw rotor (male rotor 2C or female rotor 3B). Each slot 70H is formed such that the V-shape opens in the same direction relative to the rotation direction of the target screw rotor.

[0151] That is, the groove 70H is composed of a first groove portion 77 on one side of the V-shape and a second groove portion 78 on the other side of the V-shape, which is located radially outward of the target screw rotor compared to the first groove portion 77. The first groove portion 77 is configured to be inclined in the opposite direction to the rotation direction of the screw rotor relative to the radial direction of the target screw rotor, while the second groove portion 78 is configured to be inclined in the same direction as the rotation direction of the screw rotor relative to the radial direction of the target screw rotor. Furthermore, each groove 70H is configured such that the connecting portion 79 (the corner of the V-shape) between the first groove portion 77 and the second groove portion 78 is located between the axial communication path G2 and the working chamber Cd of the discharge stroke at a certain rotational position of the target screw rotor.

[0152] Similar to the cases of grooves 70 and 70C in the second embodiment and its variations, the second components of centrifugal force Cf and shear force Sf, Cf2 and Sf2, act on the oil inside the first groove 77 towards the outer periphery. Furthermore, unlike the cases of grooves 70 and 70C in the second embodiment and its variations, for the oil inside the second groove 78, the second component of shear force Sf, Sf2, acts towards the inner periphery of the second groove 78, while the second component of centrifugal force Cf, Cf2, acts towards the outer periphery of the second groove 78. Therefore, regarding the second groove 78 of 70H, the radial tilt angle of the second groove 78 relative to the screw rotor is set such that the second component of shear force Sf, Sf2, is greater than the second component of centrifugal force Cf, Cf2.

[0153] Therefore, in the fifth modified example, in the multiple grooves 70H, the oil in the first groove 77 flows towards the connection 79 (the corner of the V-shaped groove 70H) between the first groove 77 and the second groove 78 due to centrifugal force Cf and shear force Sf, and the oil in the second groove 78 flows towards the connection 79 due to shear force Sf. Thus, the oil flowing from the first groove 77 and the oil flowing from the second groove 78 obstruct each other, causing a rise in static pressure. The pressurized oil eventually forms a high-pressure oil film W along the connection 79 (corner) of the multiple grooves 70H.

[0154] In the first to fifth examples of the deformation of the slot structure (slot group) of the screw rotor, the oil in the multiple slots 70D, 70E, 70F, 70G, and 70H flows due to at least one of the centrifugal force Cf and shear force Sf accompanying the rotation of the screw rotor, and is subsequently blocked, thereby flowing out to the discharge side end face gap G1 after pressurization. Therefore, similar to the slot structure of the second embodiment and its variations, a high-pressure oil film W can be formed between the axial communication path G2 and the working chamber Cd (high-pressure space) of the discharge stroke, which can suppress internal leakage through the axial communication path G2.

[0155] Furthermore, the screw compressor of the fifth modified example is characterized in that: the multiple slots 70H of the slot group are formed in a V shape and arranged in a herringbone shape around a rotor (male rotor 2 or female rotor 3), and the multiple slots 70H of the slot group are configured to open in the same direction relative to the rotation direction of a rotor (male rotor 2 or female rotor 3) in a V shape.

[0156] In addition, Figure 19F In the sixth example of the groove structure variation shown, the depth of each groove 70J is not a fixed value, but varies radially along the target screw rotor (male rotor 2C or female rotor 3B). Specifically, the groove 70J is formed such that its depth gradually decreases from the other end 72 in the long side direction to one end 71 (from the inner circumference to the outer circumference of the target screw rotor). That is, the volume of the groove 70J gradually decreases from the other end 72 to one end 71. Therefore, the volume (mass) of the oil on the other end 72 side of the groove 70J is larger than the volume (mass) of the oil on the one end 71 side. Therefore, the centrifugal force acting on the oil on the other end 72 side of the groove 70J is greater than the centrifugal force acting on the oil on the one end 71 side by an amount corresponding to the greater mass. Consequently, the oil blocked by one end 71 in the groove 70J easily flows out to the discharge side end face gap G1 (the discharge side inner wall surface 49 side of the housing 4B).

[0157] [Other Implementation Methods]

[0158] Furthermore, while the above embodiments were described using screw compressors 1, 1A, 1B, and 1C for compressed air as examples, the present invention can be applied to screw compressors that compress various gases such as ammonia and CO2 refrigerant. Additionally, while oil-supply screw compressors 1, 1A, 1B, and 1C were described as examples, the present invention can also be applied to screw compressors that supply liquids other than oil. From the viewpoints of sealing performance and ease of liquid film formation, oil is preferred, but various liquids with properties sufficient to form a liquid film, such as water, can be used instead.

[0159] Furthermore, the slot structure in each embodiment can also be applied to screw compressors without a liquid supply, where no liquid such as oil is supplied to the working chamber. In the case of a screw compressor without a liquid supply, compressed air is present in the slots on the discharge side end face of the rotor or the discharge side inner wall of the housing, without oil.

[0160] As an example of use Figure 6 , Figure 7 The following explanation is provided. When oil is replaced with air, the air present in the groove 60 rubs against the discharge side end face 31c of the opposing female rotor 3 at a relative velocity, thus exerting a shear force Sf. The air in the groove 60 is subjected to force due to the shear force Sf and the reaction force of the groove 60 wall, flowing towards the outer periphery of the female rotor 3 along the long side of the groove 60. It is blocked at one end 61 of the groove 60, resulting in flow into the discharge side end face gap G1. Therefore, in the discharge side end face gap G1, a region W with a relatively higher air pressure than the surrounding air is generated near one end 61 of the groove 60.

[0161] The internal leakage of air through the end face gap increases with the greater the pressure difference between the high-pressure working chamber on the upstream side and the end face gap on the downstream side. When the groove 60 as described above is provided, the pressure near one end 61 of the groove 60 increases at the discharge side end face gap G1. Therefore, the pressure difference between the working chamber Cd during the discharge stroke and the discharge side end face gap G1 is reduced compared to when the groove 60 is not present. Thus, by providing the groove 60, internal air leakage can be suppressed.

[0162] Furthermore, the present invention is not limited to the embodiments described above, and includes various modifications. The above embodiments are detailed descriptions provided to illustrate the present invention in an easily understandable manner, and do not necessarily include all the structures described. That is, a part of the structure of one embodiment can be replaced with the structure of another embodiment, and it is also possible to add the structure of another embodiment to the structure of one embodiment. In addition, for a part of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0163] For example, the structure of the first embodiment can be combined with the structures of other modifications. That is, the groove group (groove structure) provided in the shielding area 49a of the discharge side inner wall surface 49 of the housing has a first groove group (groove structure of the first embodiment) composed of a plurality of grooves 60 arranged circumferentially on the male rotor 2, and a second groove group (groove structure of a modification of the first embodiment) composed of a plurality of grooves 60A arranged circumferentially on the female rotor 3. By arranging the plurality of grooves 60 and 60A of the first groove group and the second groove group respectively in a non-interfering manner, the effects of both the first embodiment and its modifications can be obtained.

[0164] Furthermore, the structure of the first embodiment can be combined with the structure of the modified example of the second embodiment. That is, in addition to the first groove group (groove structure of the first embodiment) consisting of a plurality of grooves 60 provided in the shielding area 49a of the discharge side inner wall surface 49 of the housing, a third groove group (groove structure of the modified example of the second embodiment) consisting of a plurality of grooves 70C can be provided on the discharge side end face 21c of the male rotor 2C. By arranging the grooves 60 and 70C of the first groove group and the third groove group respectively in a non-interfering manner, the effects of both the modified examples of the first embodiment and the second embodiment can be obtained.

[0165] Furthermore, the structure of the modified example of the first embodiment can be combined with the structure of the second embodiment. That is, in addition to the second groove group (groove structure of the modified example of the first embodiment) consisting of a plurality of grooves 60A provided in the shielding area 49a of the discharge side inner wall surface 49 of the housing, a fourth groove group (groove structure of the second embodiment) consisting of a plurality of grooves 70 can be provided on the discharge side end face 31c of the female rotor 3B. By arranging the grooves 60A and 70 of the second groove group and the fourth groove group respectively in a non-interfering manner, the effects of both the modified example of the first embodiment and the second embodiment can be obtained.

[0166] Furthermore, the structure of the second embodiment and the structure of its variant can be combined. That is, the slot group (slot structure) provided on the discharge side end face of the screw rotor has a third slot group (slot structure of the variant of the second embodiment) composed of a plurality of slots 70C provided on the discharge side end face 21c of the male rotor 2C, and a fourth slot group (slot structure of the second embodiment) composed of a plurality of slots 70 provided on the discharge side end face 21c of the female rotor 3B. By arranging the plurality of slots 70 and 70C of the third slot group and the fourth slot group respectively in a non-interfering manner, the effects of both the second embodiment and its variant can be obtained.

[0167] Furthermore, in the above embodiments, as a processing method for the grooved housing or male / female rotor, processing methods such as forming and cutting can be used. However, the grooved housing or rotor, or both, can also be manufactured using a 3D forming equipment. The data used in the 3D forming equipment is generated by processing 3D data generated by CAD, CG software, or a 3D scanner into NC data using CAM (Computer-Aided Manufacturing). This data is then input into the 3D forming equipment using any method to create the model. Alternatively, NC data can be directly generated from 3D data using CAD / CAM software.

[0168] Explanation of reference numerals in the attached figures

[0169] 1, 1A, 1B, 1C... Screw compressor; 2, 2C... Male rotor; 3, 3B... Female rotor; 4, 4A, 4B... Housing; 21c... Discharge side end face (first discharge side end face); 21e... Rear inlet face; 31c... Discharge side end face (second discharge side end face); 31e... Rear inlet face; 45... Receiving chamber; 49... Discharge side inner wall surface; 49a... Shielding area; 60, 60A, 60B, 60 C, 60D... slot, 64... main body of slot, 65... additional slot, 70, 70C, 70D, 70E, 70F, 70G, 70H, 70J... slot, 74, 74G... main body of slot, 75... additional slot, G2... axial connection path, D1... outer diameter line of male rotor, D2... pitch circle of female rotor, A1... central axis (first central axis), A2... central axis (second central axis).

Claims

1. A screw compressor, characterized in that Comprising: a male rotor having a first discharge-side end surface on one axial side; a female rotor having a second discharge-side end surface on one axial side; and a housing having a housing chamber in which the male rotor and the female rotor are housed so as to be rotatable in a meshed state, the housing having a discharge-side inner wall surface opposite the first discharge-side end surface of the male rotor and the second discharge-side end surface of the female rotor, the discharge-side inner wall surface of the housing having a shield region that shields at least a portion of a locus of an axial communication path that is a gap sandwiched by trailing faces of the male rotor and the female rotor that periodically appears at the first discharge-side end surface and the second discharge-side end surface in accordance with a change in the meshed state due to rotation of the male rotor and the female rotor, a groove group composed of a plurality of grooves having a long direction being provided in the shield region of the housing, the plurality of grooves of the groove group being arranged in a circumferential direction of at least one of the male rotor and the female rotor, the plurality of grooves of the groove group being arranged with edges extending in the long direction adjacent to each other, the plurality of grooves of the groove group each being inclined in a direction identical to a rotation direction of the one rotor with respect to a radial direction of the one rotor from an inner circumferential side to an outer circumferential side of the one rotor.

2. The screw compressor according to claim 1, wherein: the groove group includes: a first groove group composed of a plurality of grooves arranged in a circumferential direction of the male rotor; and a second groove group composed of a plurality of grooves arranged in a circumferential direction of the female rotor.

3. The screw compressor according to claim 1, wherein: in a case where the one rotor is the female rotor, a third groove group composed of a plurality of grooves having a long direction is provided at the first discharge-side end surface of the male rotor, the plurality of grooves of the third groove group are arranged in a circumferential direction of the male rotor, the plurality of grooves of the third groove group are arranged with edges extending in the long direction adjacent to each other.

4. The screw compressor according to claim 1, wherein: in a case where the one rotor is the male rotor, a fourth groove group composed of a plurality of grooves having a long direction is provided at the second discharge-side end surface of the female rotor, the plurality of grooves of the fourth groove group are arranged in a circumferential direction of the female rotor, the plurality of grooves of the fourth groove group are arranged with edges extending in the long direction adjacent to each other.

5. The screw compressor according to claim 1, wherein: the plurality of grooves of the groove group are each composed of at least a groove main body portion having a long direction and an additional groove portion connected to the groove main body portion and different in shape from the groove main body portion, the groove main body portion is inclined in a direction identical to a rotation direction of the one rotor with respect to a radial direction of the one rotor from an inner circumferential side to an outer circumferential side of the one rotor.

6. The screw compressor according to claim 1, wherein: the plurality of grooves of the groove group are each curved.

7. The screw compressor according to claim 1, wherein: ​ The plurality of grooves of the groove group each have a depth in a range of 1 μm or more and 1 mm or less.

8. Screw compressor, characterized in that Comprise: a male rotor having a first discharge-side end face on one axial side and being rotatable around a first central axis; a female rotor having a second discharge-side end face on one axial side and being rotatable around a second central axis; and a housing having a housing chamber in which the male rotor and the female rotor are housed so as to be rotatable in a meshed state, a groove group composed of a plurality of grooves having a long-side direction is provided on the discharge-side end face of at least one of the male rotor and the female rotor, the plurality of grooves of the groove group are arranged on the one rotor in a circumferential direction of the one rotor, the plurality of grooves of the groove group are arranged so that edges extending in the long-side direction are adjacent to each other, the plurality of grooves of the groove group are each composed of at least a groove main body portion having a long-side direction and an additional groove portion connected to the groove main body portion and different in shape from the groove main body portion.

9. The screw compressor according to claim 8, wherein: the groove main body portion is composed so as to extend in the long-side direction in a radial direction of the one rotor, or so as to extend in the long-side direction from an inner peripheral side to an outer peripheral side of the one rotor so as to be inclined with respect to the radial direction of the one rotor in a direction opposite to a rotation direction of the one rotor.

10. The screw compressor according to claim 8, wherein: when a distance from the first central axis of the male rotor to an outer diameter line of the male rotor is a 1, a distance from the second central axis of the female rotor to a pitch circle of the female rotor is a 2, and a distance between the first central axis and the second central axis is b, in a case where the one rotor is the female rotor, the plurality of grooves of the groove group are arranged in a range of a distance of (a 1 + a 2 - b) from the pitch circle of the female rotor toward the second central axis, in a case where the one rotor is the male rotor, the plurality of grooves of the groove group are arranged in a range of a distance of (a 1 + a 2 - b) from the outer diameter line of the male rotor toward the first central axis.

11. The screw compressor according to claim 8, wherein: the groove group includes: a third groove group composed of a plurality of grooves provided on the first discharge-side end face of the male rotor; and a fourth groove group composed of a plurality of grooves provided on the second discharge-side end face of the female rotor.

12. The screw compressor according to claim 8, wherein: the plurality of grooves of the groove group each have a depth in a range of 1 μm or more and 1 mm or less. Comprise:

13. Screw compressor, characterized in that a male rotor having a first discharge-side end face on one axial side and being rotatable around a first central axis; a female rotor having a second discharge-side end face on one axial side and being rotatable around a second central axis; and a housing having a housing chamber in which the male rotor and the female rotor are housed so as to be rotatable in a meshed state, a groove group composed of a plurality of grooves having a long-side direction is provided on the discharge-side end face of at least one of the male rotor and the female rotor, the plurality of grooves of the groove group are arranged on the one rotor in a circumferential direction of the one rotor, ​ ​ The plurality of grooves of the groove group are configured adjacent to each other with edges extending in the one of the longitudinal directions, The plurality of grooves of the groove group are respectively configured so that their depths gradually become shallower as they go from the inner peripheral side to the outer peripheral side of the one of the rotors in the one of the longitudinal directions, and so that the end surface of the outer peripheral side of the one of the rotors in the one of the longitudinal directions can block the flow of fluid.

14. The screw compressor according to claim 13, wherein: The plurality of grooves of the groove group are respectively configured so that the longitudinal direction thereof is inclined in the opposite direction to the direction of rotation of the one of the rotors with respect to the radial direction of the one of the rotors as they go from the inner peripheral side to the outer peripheral side of the one of the rotors.

15. The screw compressor according to claim 13, wherein: The plurality of grooves of the groove group are respectively configured so that the longitudinal direction thereof extends in the radial direction of the one of the rotors.

16. The screw compressor according to claim 13, wherein: when a distance from the first central axis of the male rotor to the outer diameter line of the male rotor is al, a distance from the second central axis of the female rotor to the pitch circle of the female rotor is a2, and a distance between the first central axis and the second central axis is b, when the one of the rotors is the female rotor, the plurality of grooves of the groove group are disposed in a range of a distance of (al + a2 - b) from the pitch circle of the female rotor toward the second central axis, when the one of the rotors is the male rotor, the plurality of grooves of the groove group are disposed in a range of a distance of (al + a2 - b) from the outer diameter line of the male rotor toward the first central axis.

17. The screw compressor according to claim 13, wherein: The groove group includes: a third groove group composed of a plurality of grooves provided at the first discharge side end surface of the male rotor; and a fourth groove group composed of a plurality of grooves provided at the second discharge side end surface of the female rotor.

18. The screw compressor according to claim 13, wherein: The plurality of grooves of the groove group are respectively curved.

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