Screw compressor and its assembly method

Abstract

To provide a screw compressor that can improve the assemblability of a pair of screw rotors having a rotor structure in which a lead angle changes, and a method for assembling the same.SOLUTION: A screw compressor 1 comprises male and female rotors 2, 3 that are accommodated in a casing 4 so as to be in mesh with each other and rotatable about parallel rotation axes A1, A2. The male and female rotors 2, 3 each include a rotor teeth portion 21, 31 having spiral teeth 21a, 31a, a suction-side shaft portion 22, 32, and a discharge-side shaft portion 23, 33. The rotor teeth portions 21, 31 of the male and female rotors 2, 3 are each configured such that a lead angle changes. Each of the male and female rotors 2, 3 has, on either one of the suction-side shaft portion 22, 32 and the discharge-side shaft portion 23, 33, an engaging portion 25, 35 that engages with a positioning jig 100 used during assembly in order to restrict the distance between the rotation axes A1, A2 of the male and female rotors 2, 3.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a screw compressor having a pair of screw rotors and an assembling method thereof.

Background Art

[0002] Screw compressors are widely used as air compressors and refrigeration and air-conditioning compressors. In recent years, energy conservation has been strongly demanded, and high energy efficiency and a large air volume (high performance) have become increasingly important.

[0003] Some screw compressors are of a twin rotor type having a pair of male and female screw rotors that rotate while meshing with each other. The twin rotor type screw compressor sucks and compresses gas by the volume of a plurality of working chambers formed by the tooth grooves of both screw rotors and the inner wall surface of the casing surrounding them increasing and decreasing as both screw rotors rotate.

[0004] As one method for improving the efficiency of a twin rotor type screw compressor, there is one in which the lead angle or lead of the screw rotor is made relatively larger than that of a conventional screw rotor. The lead angle is the angle formed by a plane perpendicular to the axis of the screw rotor and the helical winding of the screw rotor. The lead is the distance traveled in the axial direction when the helical winding of the screw rotor makes one revolution. In a twin rotor type screw compressor, when the lead angle (lead) is relatively large, the range of the rotation angle corresponding to the compression stroke from the start of compression to discharge becomes small. Therefore, the time from the start to the completion of compression is shortened, so that internal leakage, which is a factor causing efficiency reduction, can be reduced. On the other hand, when the lead angle (lead) is relatively small, the number of simultaneously formed working chambers (compression chambers) increases, so that the exciting force, which is a factor causing vibration and noise, can be reduced.

[0005] In fluid machinery, some designs employ a rotor structure that changes the lead angle (lead) in the axial direction, i.e., a rotor structure with a changing pitch, in order to combine the advantages of both relatively large and relatively small lead angles. For example, Patent Document 1 discloses a dry screw pump equipped with a pair of rotor assemblies configured to switch between a large lead section, a medium lead section, and a small lead section from the suction end to the discharge end. Patent Document 2 discloses a screw compressor equipped with a pair of screw rotors (male screw rotor and female screw rotor) whose pitch changes axially from the suction end face to the discharge end face. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-183572 [Patent Document 2] Japanese Patent Publication No. 2021-60003 [Overview of the project] [Problems that the invention aims to solve]

[0007] In a twin-rotor screw compressor, if a rotor structure with a constant lead angle regardless of axial position (equal-pitch rotor structure) is employed, the compressor is generally assembled in the following procedure: First, one screw rotor is housed in the bore of the casing. Next, while rotating the screw rotor housed in the casing, the other screw rotor is fitted into the axial end of the other screw rotor, thereby housing the other screw rotor in the bore of the casing.

[0008] However, when a rotor structure with a changing lead angle (a rotor structure with a changing pitch) is employed, the assembly procedure for a constant-pitch rotor structure, which involves "rotating one screw rotor housed in the casing while engaging one axial end of the other screw rotor, thereby housing the other screw rotor in the casing's bore," is geometrically invalid. Therefore, a different assembly procedure is required for a rotor structure with a changing pitch. Specifically, the assembly is performed using the following procedure: First, the pair of screw rotors are pre-engaged. Next, while maintaining the engagement state of both screw rotors, both screw rotors are simultaneously housed in the casing's bore.

[0009] In the case of a dry screw pump equipped with a pair of screw rotors having rectangular tooth grooves in longitudinal cross-section, even if the rotor structure has a variable lead, the pair of screw rotors mesh with each other in a parallel state without their two central axes tilting, so the meshing of the two screw rotors is uniquely determined. Therefore, it is easy to house both screw rotors in the casing at the same time.

[0010] In contrast, in the case of a screw compressor described in Patent Document 2, where a pair of screw rotors have a pitch-changing rotor structure and a curved tooth groove in their longitudinal cross-section, the two screw rotors may mesh with their rotation axes not parallel but tilted. Therefore, unless the distance between the two rotation axes is constrained, the meshing cannot be uniquely determined. For this reason, it is difficult to house both screw rotors simultaneously within the casing bore. For this reason, there is a demand to improve the ease of assembly of a screw compressor equipped with a pair of screw rotors having a pitch-changing rotor structure and a curved tooth groove in their longitudinal cross-section.

[0011] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a screw compressor and a method for assembling the same that can improve the ease of assembling a pair of screw rotors having a rotor structure in which the lead angle changes. [Means for solving the problem]

[0012] The present invention includes multiple means for solving the above problems, but to give one example, it comprises a pair of screw rotors that mesh and rotate with each other, and a casing that houses the pair of screw rotors in a state in which their rotation axes are parallel to each other, each of the pair of screw rotors includes a rotor tooth portion having helical teeth, and a first shaft portion and a second shaft portion provided on one and the other axial side of the rotor tooth portion, respectively, the rotor tooth portion is configured such that the lead angle, which is the angle between a plane perpendicular to the rotation axis and the tooth tip line of the teeth, changes in at least a portion of the total length of the rotor tooth portion in the axial direction, and each of the pair of screw rotors has an engaging portion on either the first shaft portion or the second shaft portion that engages with a positioning jig used during assembly to restrain the distance between the rotation axes of the pair of screw rotors. The engaging portion is a keyway provided on the cylindrical surface of either the first shaft portion or the second shaft portion. . [Effects of the Invention]

[0013] According to the present invention, when assembling a screw compressor, a positioning jig is engaged with an engaging portion provided on each of the pair of screw rotors to restrain the distance between the rotation axes of the pair of screw rotors. This allows the pair of screw rotors, which are meshed with each other and have parallel rotation axes, to be simultaneously inserted into the casing, thus facilitating the assembly of the pair of screw rotors. In other words, the ease of assembly of a pair of screw rotors having a rotor structure in which the lead angle changes can be improved. Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0014] [Figure 1] This is a cross-sectional view showing a screw compressor according to the first embodiment of the present invention. [Figure 2]It is a cross-sectional view of the screw compressor according to the first embodiment shown in FIG. 1 as viewed from the arrow II-II direction. [Figure 3] It is an explanatory diagram showing the relationship between the lead angle and the lead in the screw rotor. [Figure 4] It is a cross-sectional view showing the normal meshing state of a pair of screw rotors in the screw compressor according to the first embodiment. [Figure 5] It is a cross-sectional view showing the abnormal meshing state of a pair of screw rotors in the screw compressor according to the first embodiment. [Figure 6] It is a perspective view showing a jig used for assembling a pair of screw rotors in the screw compressor according to the first embodiment and the structure of the pair of screw rotors corresponding to the jig. [Figure 7] It is a cross-sectional view of the male rotor of the screw compressor according to the first embodiment shown in FIG. 6 as viewed from the arrow VII-VII direction. [Figure 8] It is a perspective view showing an assembling method using a jig for a pair of screw rotors in the screw compressor according to the first embodiment. [Figure 9] It is a perspective view showing a jig used for assembling a pair of screw rotors in the screw compressor according to the second embodiment of the present invention and the structure of the pair of screw rotors corresponding to the jig. [Figure 10] It is an external view showing the structure of one screw rotor (male rotor) according to the second embodiment shown in FIG. 9. [Figure 11] It is a cross-sectional view of the male rotor according to the second embodiment shown in FIG. 10 as viewed from the arrow XI-XI direction. [Figure 12] It is an external view showing the structure of the other screw rotor (female rotor) according to the second embodiment shown in FIG. 9. [Figure 13] It is a perspective view showing an assembling method using a jig for a pair of screw rotors in the screw compressor according to the second embodiment. [Figure 14]Front view showing a jig used for assembling a pair of screw rotors in a screw compressor according to a modification of the second embodiment, and a cross-sectional view showing the structure of a pair of screw rotors (discharge-side shaft portion) corresponding to the jig. [Figure 15] Perspective view showing a jig used for assembling a pair of screw rotors in a screw compressor according to a third embodiment of the present invention, and the structure of a pair of screw rotors corresponding to the jig. [Figure 16] Perspective view showing a jig used for assembling a pair of screw rotors in a screw compressor according to a fourth embodiment of the present invention, and the structure of a pair of screw rotors corresponding to the jig. [Figure 17] Front view showing a jig used for assembling a pair of screw rotors in a screw compressor according to a modification of the fourth embodiment, and a cross-sectional view showing the structure of a pair of screw rotors (discharge-side shaft portion) corresponding to the jig. [Figure 18] Perspective view showing a jig used for assembling a pair of screw rotors in a screw compressor according to a fifth embodiment of the present invention, and the structure of a pair of screw rotors corresponding to the jig. [Figure 19] Perspective view showing a jig used for assembling a pair of screw rotors in a screw compressor according to a modification of the fifth embodiment, and the structure of a pair of screw rotors corresponding to the jig. [Embodiments for Carrying Out the Invention]

[0015] Hereinafter, embodiments of a screw compressor according to the present invention will be exemplified and described with reference to the drawings. [First Embodiment] The configuration of the screw compressor according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view showing the screw compressor according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the screw compressor according to the first embodiment shown in FIG. 1 as viewed from the arrow II-II. In FIGS. 1 and 2, the left side is the suction side in the axial direction of the screw compressor, and the right side is the discharge side in the axial direction.

[0016] In Figures 1 and 2, the screw compressor 1 comprises a male rotor 2 and a female rotor 3, which are a pair of screw rotors that mesh and rotate with each other, and a casing 4 that rotatably houses the male rotor 2 and the female rotor 3 in a meshed state. The male rotor 2 and the female rotor 3 are arranged so that their respective rotation axes A1 and A2 are parallel. The male rotor 2 is rotatably supported on one side and the other side in its axial direction (left-right direction in Figures 1 and 2) by an intake bearing 6 and discharge bearings 7 and 8, respectively. The female rotor 3 is rotatably supported on one side and the other side in its axial direction by an intake bearing 10 and discharge bearings 11 and 12, respectively.

[0017] The male rotor 2 is composed of a rotor tooth portion 21 having spirally twisted male teeth 21a (lobes), and a suction-side shaft portion 22 and a discharge-side shaft portion 23 provided at both axial ends of the rotor tooth portion 21. The rotor tooth portion 21 has a suction-side end face 21b and a discharge-side end face 21c at one axial end (left end in Figures 1 and 2) and the other end (right end in Figures 1 and 2), respectively, which are perpendicular to the axial direction (rotation axis A1). In the rotor tooth portion 21, the male teeth 21a extend from the suction-side end face 21b to the discharge-side end face 21c, and tooth grooves are formed between the male teeth 21a. The suction-side shaft portion 22 extends to the outside of the casing 4, for example, and is connected to a rotation drive source (not shown). The rotor tooth portion 21 of the male rotor 2 has a rotor structure in which the degree of twisting of the male teeth 21a changes in the axial direction. Details regarding the degree of twisting of the male teeth 21a of the male rotor 2 will be described later.

[0018] The female rotor 3 is composed of a rotor tooth portion 31 having spirally twisted female teeth 31a (lobes), and a suction-side shaft portion 32 and a discharge-side shaft portion 33 provided at both axial ends of the rotor tooth portion 31. The rotor tooth portion 31 has a suction-side end face 31b and a discharge-side end face 31c at one axial end (left end in Figure 2) and the other end (right end in Figure 2), respectively, which are perpendicular to the axial direction (rotation axis A2). In the rotor tooth portion 31, the female teeth 31a extend from the suction-side end face 31b to the discharge-side end face 31c, and tooth grooves are formed between the female teeth 31a. The rotor tooth portion 31 of the female rotor 3 is arranged so that the axial positions of the suction-side end face 31b and the discharge-side end face 31c coincide with the axial positions of the suction-side end face 21b and the discharge-side end face 21c of the rotor tooth portion 21 of the male rotor 2. The rotor teeth 31 of the female rotor 3, which mesh with the rotor teeth 21 of the male rotor 2, also have a rotor structure in which the degree of twisting of the female teeth 31a changes in the axial direction. Details of the degree of twisting of the female teeth 31a of the female rotor 3 will be described later.

[0019] The casing 4 comprises a main casing 41 and a discharge-side casing 42 attached to the discharge side (right side in Figures 1 and 2) of the main casing 41. Inside the casing 4, a housing chamber 45 is formed to house the rotor teeth 21 of the male rotor 2 and the rotor teeth 31 of the female rotor 3 in a meshed state. The housing chamber 45 is formed by closing the opening on one axial side (right side in Figures 1 and 2) of a bore formed in the main casing 41 such that two cylindrical spaces partially overlap, with the discharge-side casing 42. The inner wall surface forming the containment chamber 45 is composed of a substantially cylindrical first inner circumferential surface 46 that covers the radially outer side of the rotor teeth 21 of the male rotor 2, a substantially cylindrical second inner circumferential surface 47 that covers the radially outer side of the rotor teeth 31 of the female rotor 3, a suction-side inner wall surface 48 on one axial side (left side in Figures 1 and 2) facing the suction-side end faces 21b, 31b of the rotor teeth 21, 31 of both the male and female rotors 2 and 3, and a discharge-side inner wall surface 49 on the other axial side (right side in Figures 1 and 2) facing the discharge-side end faces 21c, 31c of the rotor teeth 21, 31 of both the male and female rotors 2 and 3. Multiple working chambers C1, C2, C3, and C4 are formed by the rotor teeth 21, 31 of the male and female rotors 2, 3 and the inner wall surfaces of the casing 4 surrounding them (first inner circumferential surface 46, second inner circumferential surface 47, suction side inner wall surface 48, discharge side inner wall surface 49).

[0020] The main casing 41 has an intake-side bearing 6 on the male rotor 2 side and an intake-side bearing 10 on the female rotor 3 side at its intake end. The discharge-side casing 42 has discharge-side bearings 7 and 8 on the male rotor 2 side and discharge-side bearings 11 and 12 on the female rotor 3 side. The discharge-side casing 42 is fitted with a discharge-side cover 43 that covers the discharge-side bearings 7 and 8 and the discharge-side bearings 11 and 12.

[0021] As shown in Figure 1, the casing 4 is provided with a suction channel 51 for drawing gas into the working chamber C. The suction channel 51 connects the outside of the casing 4 to the containment chamber 45 (working chamber). The casing 4 is also provided with a discharge channel 52 for discharging compressed gas from the working chamber to the outside of the casing 4. The discharge channel 52 connects the containment chamber 45 (working chamber) to the outside of the casing 4. The discharge channel 52 has a discharge port 52a formed on the discharge-side inner wall surface 49 of the casing 4.

[0022] In the screw compressor 1 configured in this way, when the male rotor 2 shown in Figure 2 is driven by a drive source (not shown), the female rotor 3, which is meshed with the male rotor 2, also rotates. As a result, the volume of the working chamber increases with the rotation of both the male and female rotors 2 and 3, drawing in gas from the outside through the suction passage 51 shown in Figure 1. The volume of the working chamber then compresses the gas as it is sequentially reduced as shown in C1, C2, C3, and C4 in Figure 2. The screw compressor 1 compresses the gas drawn in through the suction passage 51 to a predetermined pressure and finally discharges it to the outside through the discharge passage 52 shown in Figure 1.

[0023] Next, the rotor structure (degree of tooth twist) of the pair of screw rotors in the screw compressor according to the first embodiment will be explained using Figures 2 and 3. Figure 3 is an explanatory diagram showing the relationship between the lead angle and the lead in the screw rotor. Here, only the degree of twist of the female teeth of the female rotor will be explained in detail, and the explanation of the degree of twist of the male teeth of the male rotor will be simplified. Since both the male and female rotors rotate while meshed, the degree of twist of the male teeth of the male rotor 2 will be the same as the degree of twist of the female teeth of the female rotor.

[0024] In the following explanation, the tooth tips, which are the set of tooth tip points of the rotor teeth 31 of the female rotor 3 shown in Figure 2, will be referred to as the helix line. Furthermore, in the helix line of the female rotor 3, the side closer to the discharge end face 31c will be referred to as the leading side, and the side closer to the suction end face 31b will be referred to as the trailing side.

[0025] The female rotor 3 is configured such that the lead angle of the rotor teeth 31 gradually increases from the suction-side end face 31b to the discharge-side end face 31c. The lead angle of the female rotor 3 (rotor teeth 31) represents the inclination of the helix line at each tooth tip point of the female rotor 3, and is the angle made between the helix line and a plane that passes through a point (tooth tip point) on the helix line of the rotor teeth 31 and is perpendicular to the axial direction (rotation axis A2) of the rotor teeth 31. That is, as shown in Figure 2, it is the angle between the inclination line Lh of the helix line of the female rotor 3 (tangent to the helix line at each tooth tip point) and a reference line Ld parallel to the suction-side end face 31b of the female rotor 3. Figure 2 shows the lead angles at the tooth tip point and the leading tooth tip point of the suction-side end face 31b of the female rotor 3, which are located on a certain baseline Lb parallel to the rotation axis A2 of the female rotor 3. The inclination of the helix line Lh relative to each reference line Ld at each tooth tip point (i.e., the lead angle) increases as it approaches the discharge end face 31c (φ1 < φ2 < φ3). In other words, the female rotor 3 is configured such that the lead angle gradually increases along the entire length of the rotor teeth 31 from the suction end face 31b to the discharge end face 31c.

[0026] In this explanation, the length advanced in the axial direction when the helix wire of the female rotor 3 is assumed to have rotated once is defined as the lead. The relationship between the lead angle and the lead is shown in Figure 3. As is clear from the relationship shown in Figure 3, it can be said that the female rotor 3 is configured such that the lead increases from the suction side to the discharge side in the axial direction. Furthermore, the female rotor 3 is configured such that the lead gradually changes along the entire length of the rotor teeth 31 from the suction side end face 31b to the discharge side end face 31c.

[0027] In a female rotor 3 having a rotor structure in which the lead angle (lead) increases from the suction side to the discharge side in the axial direction, the twist of the female teeth 31a is reduced as it moves from the suction side to the discharge side. In this case, under the condition that the tooth profile of the female rotor 3 in a cross section perpendicular to the axial direction (rotation axis A2) is substantially the same at any position in the axial direction, the tooth tip thickness t1 of the female rotor 3 in a cross section perpendicular to the extension direction of the helix wire becomes relatively thicker from the suction side to the discharge side in accordance with the size of the lead angle (lead). Also, the length of the seal wire Sf extending along the helix wire of the female rotor 3 is shorter than in the case of a female rotor with equal lead angles (equal lead) at the same rotational position.

[0028] An increase in the tooth tip thickness t1 means that the width (distance) of the boundary between adjacent working chambers in the female rotor 3 increases. In other words, the width of the gap (referred to as the outer diameter gap) formed between the second inner circumferential surface 47 of the casing 4 (the inner wall surface of the housing chamber 45) and the tooth tip of the female rotor 3 increases, meaning that the length of the leakage flow path between adjacent working chambers increases. As a result, the flow resistance of compressed gas passing through the outer diameter gap between adjacent working chambers increases, and leakage of compressed gas through the outer diameter gap can be suppressed.

[0029] Furthermore, a shorter length of the sealing wire Sf at the tooth tip of the female rotor 3 means a shorter overall length of the outer diameter gap, which is the region where compressed gas leaks out. This makes it possible to suppress the leakage of compressed gas through the outer diameter gap between adjacent working chambers.

[0030] Similar to the female rotor 3, the male rotor 2 that meshes with the female rotor 3 is configured such that the lead angle increases from the suction side to the discharge side in the axial direction, and the lead angle gradually changes along the entire length of the rotor teeth 21 from the suction side end face 21b to the discharge side end face 21c. In other words, the male rotor 2 is also configured such that the lead increases from the suction side to the discharge side in the axial direction, and the lead gradually changes along the entire length of the rotor teeth 21 from the suction side end face 21b to the discharge side end face 21c. This means that in the male rotor 2 as well, the twist of the male teeth 21a is reduced as it moves from the suction side to the discharge side. In this case, the length of the seal wire Sm extending along the helix of the male rotor 2 is shorter than that of a male rotor with equal lead angles (equal lead) at the same rotational position.

[0031] Thus, in the screw compressor 1 of this embodiment, the tooth tip thickness t1 of the female rotor 3 is thicker than in the case of a female rotor with equal leads, and the lengths of the seal lines Sm and Sf at the tooth tips of the male rotor 2 and female rotor 3 are shorter than in the case of a male rotor and female rotor with equal leads. These two structural differences make it possible to suppress the leakage of compressed gas through the outer diameter gap between adjacent working chambers.

[0032] Next, the assembly method of the screw compressor according to the first embodiment will be described with reference to Figures 2, 4, and 5. Figure 4 is a cross-sectional view showing the normal meshing state of a pair of screw rotors in the screw compressor according to the first embodiment. Figure 5 is a cross-sectional view showing the abnormal meshing state of a pair of screw rotors in the screw compressor according to the first embodiment.

[0033] The screw compressor 1 according to the first embodiment, as shown in Figure 2, is equipped with male and female rotors 2 and 3, each having a rotor structure (unequal lead rotor structure) in which the lead angle gradually changes from the suction side (left side in Figure 2) to the discharge side (right side in Figure 2) in the axial direction. In this case, the assembly procedure for a screw compressor equipped with a pair of screw rotors having a constant lead angle (equal lead rotor structure) cannot be adopted. Therefore, in the case of an unequal lead rotor structure, a different procedure from the assembly method in the case of an equal lead rotor structure must be used.

[0034] The screw compressor 1 is assembled, for example, by the following procedure. First, the suction bearing 6 for the male rotor 2 and the suction bearing 10 for the female rotor 3 are placed in the main casing 41 shown in Figure 2. Next, the male rotor 2 and the female rotor 3 are meshed together before being inserted into the casing 4. Then, while maintaining the meshed state of the male and female rotors 2 and 3, both the male and female rotors 2 and 3 are simultaneously inserted into the housing chamber 45 of the casing 4 (the bore of the main casing 41), and the suction shaft portions 22 and 32 of the male and female rotors 2 and 3 are simultaneously attached to the suction bearings 6 and 10 placed in the main casing 41.

[0035] In assembling the screw compressor 1 according to this embodiment, as shown in Figure 4, it is necessary to mesh the male and female rotors 2 and 3 so that the positions of the suction end face 21b and discharge end face 21c of the male rotor 2 coincide with the positions of the suction end face 31b and discharge end face 31c of the female rotor 3, while the rotation axis A1 of the male rotor 2 and the rotation axis A2 of the female rotor 3 are parallel without tilting. However, as shown in Figure 5, it is possible that the male and female rotors 2 and 3 mesh with their rotation axes A1 and A2 tilted rather than parallel. If the male and female rotors 2 and 3 are in the abnormal meshing state shown in Figure 5, rather than the normal meshing state shown in Figure 4, it is difficult to insert both the male and female rotors 2 and 3 into the housing chamber 45 (bore) of the casing 4 and attach them to the casing simultaneously.

[0036] In the screw compressor 1 according to this embodiment, the meshing of the male and female rotors 2 and 3 cannot be uniquely determined unless the distance between the rotation axes A1 and A2 of the male and female rotors 2 and 3 is constrained. Therefore, the assembly method of the screw compressor 1 according to this embodiment aims to easily achieve the normal meshing state of the male and female rotors 2 and 3 shown in Figure 4 by using a positioning jig 100 (see Figures 6 and 8 described later).

[0037] Next, the assembly method of the screw compressor according to the first embodiment will be described with reference to Figures 6 to 8, along with the structure of the jig used for assembly and the structure of the pair of screw rotors corresponding to the jig. Figure 6 is a perspective view showing the jig used for assembling the pair of screw rotors in the screw compressor according to the first embodiment and the structure of the pair of screw rotors corresponding to the jig. Figure 7 is a cross-sectional view of the male rotor of the screw compressor according to the first embodiment shown in Figure 6, viewed from the direction of arrow VII-VII. Figure 8 is a perspective view showing the assembly method of the pair of screw rotors in the screw compressor according to the first embodiment using the jig.

[0038] As shown in Figures 6 and 7, the discharge-side shaft portion 23 of the male rotor 2 and the discharge-side shaft portion 33 of the female rotor 3 are provided with a first engaging portion 25 and a second engaging portion 35 that engage with the positioning jig 100. The first engaging portion 25 of the male rotor 2 is a flattened portion created by cutting a portion of the cylindrical surface of the discharge-side shaft portion 23 into a flat shape. The second engaging portion 35 of the female rotor 3 is also a flattened portion created by cutting a portion of the cylindrical surface of the discharge-side shaft portion 33 into a flat shape, similar to the first engaging portion 25 of the male rotor 2.

[0039] As shown in Figure 6, the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3 are configured such that their axial positions from the discharge-side end face 21c of the male rotor 2 and the discharge-side end face 31c of the female rotor 3 are approximately the same. Furthermore, the flat surface of the first engaging portion 25 of the male rotor 2 and the flat surface of the second engaging portion 35 of the female rotor 3 are configured such that their axial width W (see Figure 1) (extending direction of the rotation axes A1 and A2) is approximately constant and equal to each other. Moreover, the flat surface of the first engaging portion 25 of the male rotor 2 and the flat surface of the second engaging portion 35 of the female rotor 3 are formed to be parallel and facing each other when the normally meshing male rotor 2 and female rotor 3 are at predetermined rotation positions (first rotation position and second rotation position). For example, as shown in Figure 7, the first engaging portion 25 of the male rotor 2 is provided at a position corresponding to the angular position of a certain tooth tip 21t on the discharge-side end face 21c of the male rotor 2. On the other hand, as shown in Figure 6, the second engaging portion 35 of the female rotor 3 is provided at a position corresponding to the angular position of the tooth root on the discharge-side end face 31c of the female rotor 3 that engages with a certain tooth tip on the discharge-side end face 21c of the male rotor 2. That is, when the male rotor 2 and the female rotor 3 are engaged with each other, they have rotational positions such that the flat surface of the first engaging portion 25 and the flat surface of the second engaging portion 35 are parallel to and facing each other.

[0040] The positioning jig 100 shown in Figures 6 and 8 has the function of restricting the distance between the rotation axes A1 and A2 of the male and female rotors 2 and 3, aligning the positions of the suction-side end face 21b and discharge-side end face 21c of the male rotor 2 with the positions of the suction-side end face 31b and discharge-side end face 31c of the female rotor 3, and restricting the rotation of the male and female rotors 2 and 3. The positioning jig 100 is, for example, a plate-shaped member with a constant thickness extending in one direction, and has a first notch 102 provided at one end in the extending direction and a second notch 103 provided at the other end in the extending direction. The positioning jig 100 is configured such that the first notch 102 engages with the first engaging portion 25 (flat surface) of the male rotor 2, and the second notch 103 engages with the second engaging portion 35 (flat surface) of the female rotor 3. The main body 101 located between the first notch 102 and the second notch 103 is the part that constrains the distance between the rotation axes A1 and A2 of the male and female rotors 2 and 3.

[0041] In the assembly method of the screw compressor according to this embodiment, as shown in Figure 6, firstly, the male rotor 2 is positioned at a predetermined first rotational position and the female rotor 3 at a predetermined second rotational position by positioning the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3 to be substantially opposite each other. Secondly, the male rotor 2 and the female rotor 3 are meshed together at these rotational positions. Thirdly, with the male rotor 2 and the female rotor 3 meshed together, the main body 101 of the positioning jig 100 is inserted between the discharge-side shaft portion 23 of the male rotor 2 and the discharge-side shaft portion 33 of the female rotor 3, and the first notch 102 and the second notch 103 of the positioning jig 100 are engaged with the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3. That is, as shown in Figure 8, both end faces of the main body 101 of the positioning jig 100 are engaged by sandwiching them between the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3. The main body 101 of the positioning jig 100, which is sandwiched between the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3, restricts the distance between the rotation axis A1 of the male rotor 2 and the rotation axis A2 of the female rotor 3, and restricts the rotation of both the male and female rotors 2 and 3. This aligns the axial positions of the suction-side end face 21b and discharge-side end face 21c of the male rotor 2 and the suction-side end face 31b and discharge-side end face 31c of the female rotor 3. This engagement of the male and female rotors 2 and 3 with the positioning jig 100 maintains a normal meshing state of the male and female rotors 2 and 3, where both rotation axes A1 and A2 are parallel.

[0042] Next, with the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3 engaged with the first notch 102 and the second notch 103 of the positioning jig 100, both the male and female rotors 2 and 3 are simultaneously inserted into the housing chamber 45 (bore) of the main casing 41 and attached to the main casing 41 via the suction-side bearings 6 and 10. After that, the positioning jig 100 is removed from the male rotor 2 and female rotor 3, and the discharge-side casing 42 is attached to the main casing 41. In this way, by engaging the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3 with the positioning jig 100, both the male and female rotors 2 and 3 can be easily inserted simultaneously into the housing chamber 45 (bore) of the casing 4.

[0043] As described above, the screw compressor 1 according to the first embodiment comprises a male rotor 2 and a female rotor 3 (a pair of screw rotors) that mesh and rotate with each other, and a casing 4 that houses the male rotor 2 and the female rotor 3 (a pair of screw rotors) with their respective rotation axes A1 and A2 parallel. Each of the male rotor 2 and the female rotor 3 (a pair of screw rotors) includes rotor tooth portions 21 and 31 having helical teeth 21a and 31a, and suction-side shaft portions 22 and 32 and discharge-side shaft portions 23 and 33 (first shaft portion and second shaft portion) provided on one and the other axial side of the rotor tooth portions 21 and 31, respectively. The rotor tooth portions 21 and 31 are configured such that the lead angle φ, which is the angle between a plane perpendicular to the rotation axes A1 and A2 and the tooth tip lines of the teeth 21a and 31a, changes in at least a portion of the total axial length of the rotor tooth portions 21 and 31. Each of the male rotor 2 and female rotor 3 (a pair of screw rotors) has engaging portions 25 and 35 on either the suction-side shaft portions 22 and 32 or the discharge-side shaft portions 23 and 33 (first shaft portion and second shaft portion) that engage with a positioning jig 100 used during assembly to constrain the distance between the rotation axes A1 and A2.

[0044] With this configuration, when assembling the screw compressor 1, the positioning jig 100 is engaged with the engaging parts 25 and 35 provided on the male rotor 2 and female rotor 3 (each of the pair of screw rotors), thereby constraining the distance between the rotation axes A1 and A2 of the male rotor 2 and female rotor 3 (the pair of screw rotors). This allows the male rotor 2 and female rotor 3 (the pair of screw rotors) to be simultaneously inserted into the casing 4 while meshing with each other and with both rotation axes A1 and A2 parallel, thus facilitating the assembly of the male rotor 2 and female rotor 3 (the pair of screw rotors). In other words, the ease of assembly of the male rotor 2 and female rotor 3 (the pair of screw rotors) having a rotor structure in which the lead angle changes can be improved.

[0045] Furthermore, in this embodiment, the engaging portions 25 and 35 of the male rotor 2 and female rotor 3 (each screw rotor) are flattened by cutting a portion of the cylindrical surface of either the suction-side shaft portion 22 and 32 or the discharge-side shaft portion 23 and 33 (first shaft portion and second shaft portion) into a planar shape.

[0046] With this configuration, the structure of the engaging portions 25 and 35 of the male and female rotors 2 and 3 is simple, making it easy to process the engaging portions 25 and 35.

[0047] Furthermore, in this embodiment, the male rotor 2 and the female rotor 3 (a pair of screw rotors) are configured such that the axial widths of the flat surfaces that serve as the engaging portions 25 and 35 are equal to each other.

[0048] This configuration makes it possible to construct the positioning jig 100, which engages with the engagement portions 25 and 35 of the male rotor 2 and female rotor 3 (a pair of screw rotors), as a plate-shaped member, thereby simplifying the structure of the positioning jig 100.

[0049] Furthermore, in this embodiment, the male rotor 2 and the female rotor 3 (a pair of screw rotors) have rotational positions such that the flat surfaces of the engaging portions 25 and 35 are parallel to each other when they are meshed together.

[0050] With this configuration, the male rotor 2 and the female rotor 3 can be easily brought into a normal meshing state by engaging them at a rotational position where the flat surfaces 25 of the male rotor 2 and the flat surfaces 25 of the female rotor 3 are parallel to each other.

[0051] Furthermore, in this embodiment, the male rotor 2 and the female rotor 3 (a pair of screw rotors) are in a state where they are meshed with each other, and their flat surfaces, which serve as the engaging portions 25 and 35, are positioned opposite each other during rotation.

[0052] With this configuration, the male rotor 2 and the female rotor 3 can be easily brought into a normal meshing state by engaging them at a rotational position where the flat edges 25 of the male rotor 2 and the flat edges 25 of the female rotor 3 face each other.

[0053] Furthermore, as described above, the assembly method for the screw compressor 1 according to the first embodiment is a screw compressor assembly method in which a pair of male rotors 2 and female rotors 3, each including rotor tooth portions 21, 31 having helical teeth 21a, 31a and suction-side shaft portions 22, 32 and discharge-side shaft portions 23, 33 (first shaft portion and second shaft portion) provided on one and the other axial side of the rotor tooth portions 21, 31 respectively, are meshed together and housed in a casing 4 so as to be rotatable around mutually parallel rotation axes A1, A2, and the lead angle, which is the angle φ between a plane perpendicular to the rotation axes A1, A2 and the tooth tip lines of the teeth 21a, 31a, is configured to change in at least a portion of the total axial length of the rotor tooth portions 21, 31, and the suction-side shaft portion 22 and discharge-side shaft portion 23 (first shaft portion and second shaft portion) The male rotor 2, having a first engaging portion 25 provided on either the suction-side shaft portion 32 or the discharge-side shaft portion 33 (first shaft portion or second shaft portion), and the female rotor 3, having a second engaging portion 35 provided on either the suction-side shaft portion 32 or the discharge-side shaft portion 33 (first shaft portion or second shaft portion), are engaged at a predetermined rotational position. A positioning jig 100 for constraining the distance between the rotational axes A1 and A2 of the male rotor 2 and the female rotor 3 is engaged with the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3. With the male rotor 2 and the female rotor 3 engaged and the positioning jig 100 engaged with the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3, the male rotor 2 and the female rotor 3 are simultaneously inserted into the casing 4 and attached to the casing 4, and the positioning jig 100 is removed from the male rotor 2 and the female rotor 3.

[0054] According to this method, when assembling the screw compressor 1, the positioning jig 100 is engaged with the engaging parts 25 and 35 provided on the male rotor 2 and female rotor 3 to restrain the distance between the rotation axes A1 and A2 of the male rotor 2 and female rotor 3. This allows the male rotor 2 and female rotor 3 to be simultaneously inserted into the casing 4 in a state where they are meshed together and their rotation axes A1 and A2 are parallel, thus facilitating the assembly of the male rotor 2 and female rotor 3. In other words, the ease of assembly of the male rotor 2 and female rotor 3, which have a rotor structure in which the lead angle changes, can be improved.

[0055] Furthermore, in the assembly method of the screw compressor according to this embodiment, the first engaging portion 25 of the male rotor 2 and the second engaging portion 35 of the female rotor 3 are flattened by cutting a part of the cylindrical surface of either the suction-side shaft portion 32 or the discharge-side shaft portion 33 (first shaft portion and second shaft portion) into a flat shape, and the positioning jig 100 is a plate-shaped member that engages with the flattened portions that make up the first engaging portion 25 and the second engaging portion 35.

[0056] According to this method, the first engaging portion 25 and the second engaging portion 35 of both the male and female rotors 2 and 3 are made of a simple flat surface structure, and the positioning jig 100 is made of a simple plate-shaped member, making it easy to process the first engaging portion 25 and the second engaging portion 35 and to manufacture the positioning jig 100.

[0057] [Second Embodiment] Next, a screw compressor and its assembly method according to the second embodiment will be illustrated with reference to Figures 9 to 13. Figure 9 is a perspective view showing a jig used for assembling a pair of screw rotors in a screw compressor according to the second embodiment of the present invention, and the structure of a pair of screw rotors corresponding to the jig. Figure 10 is an external view showing the structure of one screw rotor (male rotor) according to the second embodiment shown in Figure 9. Figure 11 is a cross-sectional view of the male rotor according to the second embodiment shown in Figure 10, viewed from the direction of arrow XI-XI. Figure 12 is an external view showing the structure of the other screw rotor (female rotor) according to the second embodiment shown in Figure 9. Figure 13 is a perspective view showing the assembly method of a pair of screw rotors using a jig in a screw compressor according to the second embodiment. Note that in Figures 9 to 13, parts with the same reference numerals as those in Figures 1 to 8 are similar parts, so a detailed explanation of them will be omitted.

[0058] The screw compressor and assembly method according to the second embodiment shown in Figure 9 differ from those of the first embodiment (see Figures 6 and 8) in that the structure of the positioning jig 100A is different, and the structure of the engaging parts 25A and 35A of the male and female rotors 2A and 3A that engage with the positioning jig 100A is different.

[0059] Specifically, as shown in Figures 10 and 11, the male rotor 2A according to this embodiment has two first engaging portions 251A and 252A on the discharge-side shaft portion 23A that engage with a positioning jig 100A (see Figures 9 and 13). Both first engaging portions 25A are beveled edges formed by cutting a portion of the cylindrical surface of the discharge-side shaft portion 23A into a planar shape. One first engaging portion 251A and the other first engaging portion 252A are formed in positions axially symmetric with respect to the rotation axis A1 of the male rotor 2A so that they are parallel to each other. For example, as shown in Figure 11, one first engaging portion 251A is provided at a position corresponding to the angular position of a certain tooth tip 21t on the discharge-side end face 21c of the male rotor 2. The other first engaging portion 252A is provided at a rotational angle of 180° relative to the first engaging portion 251A. Both first engaging portions 251A and 252A are configured such that their widths in the axial direction (the direction in which the rotation axis A1 extends) are approximately constant and equal to each other.

[0060] The female rotor 3A shown in Figures 9 and 12, like the male rotor 2A, has two second engaging portions 351A and 352A on the discharge-side shaft portion 33A that engage with the positioning jig 100A. Both second engaging portions 35A are beveled edges, where a portion of the cylindrical surface of the discharge-side shaft portion 33A is cut into a planar shape. One second engaging portion 351A and the other second engaging portion 352A are formed in positions axially symmetric with respect to the rotation axis A2 of the female rotor 3A so that they are parallel to each other. Both second engaging portions 351A and 352A are configured to have approximately constant and equal widths in the axial direction (the direction in which the rotation axis A2 extends).

[0061] As shown in Figure 9, both first engaging portions 25A of the male rotor 2A and both second engaging portions 35A of the female rotor 3A are configured such that their axial positions from the discharge-side end face 21c of the male rotor 2A and the discharge-side end face 31c of the female rotor 3A are approximately the same. Furthermore, the bevels of the first engaging portion 25A of the male rotor 2A and the bevels of the second engaging portion 35A of the female rotor 3A are configured such that their axial widths (the direction of extension of the rotation axes A1 and A2) are equal. The bevels of one of the first engaging portions 251A of the male rotor 2A and the bevels of one of the second engaging portions 351A of the female rotor 3A are formed to be parallel and facing each other when the normally meshing male rotor 2A and female rotor 3A are at predetermined rotation positions (first rotation position and second rotation position). In other words, when the male rotor 2A and the female rotor 3A are meshed together, they have rotational positions such that the flat surface of one first engaging portion 251A and the flat surface of the other second engaging portion 351A are parallel to and facing each other.

[0062] As shown in Figure 9, the positioning jig 100A is a plate-shaped member with a constant thickness and extending in one direction, and has a first engagement groove 102A provided at one end in the extending direction and a second engagement groove 103A provided at the other end in the extending direction. The first engagement groove 102A engages with the first engagement portions 251A and 252A on the discharge-side shaft portion 23A of the male rotor 2A and is formed in a rectangular shape. The second engagement groove 103A engages with the second engagement portions 351A and 352A on the discharge-side shaft portion 33A of the female rotor 3A and is formed in a rectangular shape. The main body portion 101A of the positioning jig 100A, located between the first engagement groove 102A and the second engagement groove 103A, is the portion that is inserted between the discharge-side shaft portions 23A and 33A of both the male and female rotors 2 and 3. The positioning jig 100A has a positioning function that prevents the distance between the rotation axes A1 and A2 of the male and female rotors 2A and 3A from becoming smaller or larger than a predetermined value, and also restricts the rotation of the male and female rotors 2A and 3A.

[0063] In the assembly method of the screw compressor according to this embodiment, as shown in Figure 9, first, one first engaging portion 251A of the male rotor 2A (opposite side of the other first engaging portion 252A) and one second engaging portion 351A of the female rotor 3A are positioned so that they are substantially opposite each other, thereby setting the male rotor 2A to a predetermined first rotation position and the female rotor 3A to a predetermined second rotation position. Second, the male rotor 2A and the female rotor 3A are engaged at these rotation positions. Third, with the male rotor 2A and the female rotor 3A engaged, the first engaging groove 102A of the positioning jig 100A is inserted into and engaged with the portions of both first engaging portions 251A and 252A on the discharge side shaft portion 23A of the male rotor 2A, and the second engaging groove 103A is inserted into and engaged with the portions of both second engaging portions 351A and 352A on the discharge side shaft portion 33A of the female rotor 3A. The engagement of the positioning jig 100A with the first engaging portions 251A and 252A of the male rotor 2A and the second engaging portions 351A and 352A of the female rotor 3A constrains the distance between the rotation axis A1 of the male rotor 2A and the rotation axis A2 of the female rotor 3A from two directions, restricts the rotation of both the male and female rotors 2A and 3A, and aligns the axial positions of the suction-side end face 21b and discharge-side end face 21c of the male rotor 2A and the suction-side end face 31b and discharge-side end face 31c of the female rotor 3A. This engagement of both the male and female rotors 2 and 3 with the positioning jig 100 maintains a normal meshing state of the male and female rotors 2A and 3A where both rotation axes A1 and A2 are parallel.

[0064] Next, with both first engaging portions 251A and 252A of the male rotor 2A and both second engaging portions 351A and 352A of the female rotor 3A engaged with the first engaging groove 102A and the second engaging groove 103A of the positioning jig 100A, both male and female rotors 2A and 3A are simultaneously inserted into the housing chamber 45 (bore) of the main casing 41 and attached to the main casing 41 via the suction side bearings 6 and 10. After that, the positioning jig 100A is removed from the male rotor 2A and female rotor 3A, and the discharge side casing 42 is attached to the main casing 41. In this way, by engaging both first engaging portions 251A and 252A of the male rotor 2A and both second engaging portions 351A and 352A of the female rotor 3A with the positioning jig 100A, both male and female rotors 2A and 3A can be easily inserted simultaneously into the housing chamber 45 (bore) of the casing 4.

[0065] According to the screw compressor and assembly method of the second embodiment described above, similar to the first embodiment, when assembling the screw compressor 1, the positioning jig 100A is engaged with the engaging portions 25A and 35A provided on the male rotor 2A and female rotor 3A to restrain the distance between the rotation axes A1 and A2 of the male rotor 2A and female rotor 3A. This allows the male rotor 2A and female rotor 3A, which are meshed with each other and have parallel rotation axes A1 and A2, to be simultaneously inserted into the casing 4, thus facilitating the assembly of the male rotor 2A and female rotor 3A. In other words, the ease of assembly of the male rotor 2A and female rotor 3A having a rotor structure in which the lead angle changes can be improved.

[0066] Furthermore, in the screw compressor according to this embodiment, the male rotor 2 and the female rotor 3 (each of the pair of screw rotors) have two flat surfaces that serve as engaging portions 25A and 35A. The two flat surfaces 251A and 252A on the male rotor 2 and the two flat surfaces 351A and 352A on the female rotor 3 are formed in positions axially symmetric with respect to the rotation axes A1 and A2.

[0067] With this configuration, by engaging the positioning jig 100A with the four engaging parts of the two flat surfaces 251A and 252A of the male rotor 2 and the two flat surfaces 351A and 352A of the female rotor 3, the constraint on the distance between the rotation axes A1 and A2 of both the male and female rotors 2 and 3, and the restriction on the rotation of both the male and female rotors 2 and 3 are strengthened compared to the first embodiment, making it easier to assemble both the male and female rotors 2 and 3 into the casing 4 than in the first embodiment.

[0068] Furthermore, in the screw compressor assembly method according to this embodiment, the positioning jig 100A has a first engagement groove 102A (first groove portion) that can be inserted into the portion of the male rotor 2A's suction-side shaft portion 22 or discharge-side shaft portion 23A (first shaft portion or second shaft portion) that includes the first engagement portion 25A and engages with the first engagement portion 25A, and a second engagement groove 103A (second groove portion) that can be inserted into the portion of the female rotor 3A's suction-side shaft portion 32 or discharge-side shaft portion 33A (first shaft portion or second shaft portion) that includes the second engagement portion 35A and engages with the second engagement portion 35A.

[0069] According to this method, by simply engaging the first engagement groove 102A (first groove portion) and the second engagement groove 103A (second groove portion) of the positioning jig 100A with the first engagement portion 25A of the male rotor 2A and the second engagement portion 35A of the female rotor 3A, respectively, the male rotor 2A and the female rotor 3A can be made to mesh with each other and their two rotation axes A1 and A2 can be made parallel, so that both the male and female rotors 2 and 3 can be easily assembled into the casing 4 at the same time.

[0070] [Modified version of the second embodiment] Next, a modified screw compressor according to the second embodiment and its assembly method will be illustrated with reference to Figure 14. Figure 14 is a front view showing a jig used for assembling a pair of screw rotors in a modified screw compressor according to the second embodiment, and a cross-sectional view showing the structure of a pair of screw rotors (discharge side shaft portion) corresponding to the jig. In Figure 14, parts with the same reference numerals as those in Figures 1 to 13 are similar parts, so a detailed explanation of them will be omitted.

[0071] The screw compressor and its assembly method according to a modified version of the second embodiment shown in Figure 14 differ from the second embodiment (see Figure 9) in that the structure of the positioning jig 100B is different, and the structure of the engaging parts 25B and 35B of the male and female rotors 2B and 3B that engage with the positioning jig 100B is different.

[0072] Specifically, the male rotor 2B according to this modified example has two first engaging portions 251B and 252B on the discharge-side shaft portion 23B that engage with the positioning jig 100B. Both first engaging portions 251B and 252B are beveled edges formed by cutting a portion of the cylindrical surface of the discharge-side shaft portion 23B into a planar shape. Both first engaging portions 251A and 252A are configured to have approximately constant and equal widths in the axial direction (the direction in which the rotation axis A1 extends). One first engaging portion 251B and the other first engaging portion 252B are not formed axially symmetric with respect to the rotation axis A1 of the male rotor 2B, but are formed at positions shifted by a predetermined rotation angle (for example, 90°).

[0073] The female rotor 3B, like the male rotor 2B, has two second engaging portions 351B and 352B on the discharge-side shaft portion 33B that engage with the positioning jig 100B. Both second engaging portions 351B and 352B are beveled edges formed by cutting a portion of the cylindrical surface of the discharge-side shaft portion 33B into a planar shape. Both second engaging portions 351B and 352B are configured to have approximately constant and equal widths in the axial direction (the direction in which the rotation axis A2 extends). One second engaging portion 351B and the other second engaging portion 352B are not axially symmetric with respect to the rotation axis A2 of the female rotor 3B, but are formed at positions shifted by a predetermined rotation angle (for example, 90°).

[0074] The first engaging portions 251B and 252B of the male rotor 2B and the second engaging portions 351B and 352B of the female rotor 3B are formed so that when the male rotor 2B and female rotor 3B, which are properly meshing, are at predetermined rotational positions (first rotational position and second rotational position), they are located on the same side (upper side in Figure 14). In other words, when the male rotor 2B and female rotor 3B are meshing with each other, they have rotational positions such that the flat surfaces of the first engaging portions 251B and 252B and the flat surfaces of the second engaging portions 351B and 352B are located on the same side (upper side in Figure 14).

[0075] The positioning jig 100B has a first engagement groove 102B provided at one end in the extending direction and a second engagement groove 103B provided at the other end in the extending direction. The first engagement groove 102B engages with the two first engagement portions 251B and 252B on the discharge-side shaft portion 23B of the male rotor 2B and is formed in a trapezoidal shape. The second engagement groove 103B engages with the two second engagement portions 351B and 352B on the discharge-side shaft portion 33B of the female rotor 3B and is formed in a trapezoidal shape. The positioning jig 100B has a positioning function that prevents the distance between the rotation axes A1 and A2 of the male and female rotors 2B and 3B from becoming smaller or larger than a predetermined value, and also restricts the rotation of the male and female rotors 2B and 3B.

[0076] The assembly method of the screw compressor according to this modified example is the same as in the second embodiment. With the male rotor 2B and the female rotor 3B meshed at a predetermined rotational position, the first engagement groove 102B of the positioning jig 100B is inserted into and engaged with the two first engagement parts 251B and 252B on the discharge side shaft portion 23B of the male rotor 2B, and the second engagement groove 103B is inserted into and fitted with the two second engagement parts 351B and 352B on the discharge side shaft portion 33B of the female rotor 3B. As a result, the distance between the rotation axis A1 of the male rotor 2B and the rotation axis A2 of the female rotor 3B is constrained from two directions, and the rotation of both the male and female rotors 2B and 3B is restricted. This engagement of both the male and female rotors 2B and 3B with the positioning jig 100B makes it possible to maintain a normal meshing state of the male and female rotors 2A and 3A where the two rotation axes A1 and A2 are parallel. Therefore, by engaging both first engaging portions 251B and 252B of the male rotor 2B and both second engaging portions 351B and 352B of the female rotor 3B with the positioning jig 100B, it becomes possible to easily insert both the male and female rotors 2B and 3B into the housing chamber 45 (bore) of the casing 4 at the same time.

[0077] According to the modified screw compressor and its assembly method described above, the ease of assembly of the male rotor 2A and female rotor 3A, which have a rotor structure with a variable lead angle, can be improved, similar to the case of the second embodiment.

[0078] [Third Embodiment] Next, a screw compressor and its assembly method according to the third embodiment will be illustrated with reference to Figure 15. Figure 15 is a perspective view showing a jig used for assembling a pair of screw rotors in a screw compressor according to the third embodiment of the present invention, and the structure of a pair of screw rotors corresponding to the jig. In Figure 15, parts with the same reference numerals as those shown in Figures 1 to 14 are similar parts, so a detailed explanation of them will be omitted.

[0079] The screw compressor and assembly method according to the third embodiment shown in Figure 15 differ from the second embodiment (see Figure 9) in that the structure of the positioning jig 100C is different, and the structure of the engaging portions 25C and 35C of the male and female rotors 2C and 3C that engage with the positioning jig 100C is different.

[0080] Specifically, the male rotor 2C according to this embodiment has two first engaging portions 25C on the discharge-side shaft portion 23C. Both first engaging portions 25C are flattened portions formed by cutting a portion of the cylindrical surface of the discharge-side shaft portion 23C into a planar shape, and are formed from the axial end of the discharge-side shaft portion 23C. Both first engaging portions 25C are formed in positions axially symmetric with respect to the rotation axis A1 of the male rotor 2C so as to be parallel to each other. The portions of both first engaging portions 25C on the discharge-side shaft portion 23C are the parts that are inserted into and engage with the first engaging hole portion 102C of the positioning jig 100C, which will be described later.

[0081] The female rotor 3C, like the male rotor 2C, has two second engagement portions 35C on the discharge-side shaft portion 33C. Both second engagement portions 35C are flattened portions formed by cutting a portion of the cylindrical surface of the discharge-side shaft portion 33C into a planar shape, and are formed from the axial end of the discharge-side shaft portion 33C. Both second engagement portions 35C are formed in positions axially symmetric with respect to the rotation axis A2 of the female rotor 3C so as to be parallel to each other. The portions of the discharge-side shaft portion 33C where both second engagement portions 35C are located are the parts that are inserted into and engage with the second engagement hole portion 103C of the positioning jig 100C, which will be described later.

[0082] One first engaging portion 25C of the male rotor 2C and one second engaging portion 35C of the female rotor 3C are formed to be parallel and opposite to each other when the male rotor 2C and female rotor 3C are in predetermined rotational positions (first rotational position and second rotational position) when they are properly meshed together. In other words, when the male rotor 2C and female rotor 3C are meshed together, they have rotational positions such that the flat surface of one first engaging portion 25C and the flat surface of one second engaging portion 35C are parallel and opposite to each other.

[0083] The positioning jig 100C is a plate-shaped member with a constant thickness and extending in one direction, and has a first engagement hole 102C provided on one side in the extending direction and a second engagement hole 103C provided on the other side in the extending direction. The first engagement hole 102C is inserted into and engages with the portions of both first engagement portions 25C on the discharge-side shaft portion 23C of the male rotor 2C, and the second engagement hole 103C is inserted into and engages with the portions of both second engagement portions 35C on the discharge-side shaft portion 33C of the female rotor 3C. The positioning jig 100C has a positioning function that prevents the distance between the rotation axes A1 and A2 of the male and female rotors 2C and 3C from becoming smaller or larger than a predetermined value, and also restricts the rotation of the male and female rotors 2C and 3C.

[0084] In the assembly method of the screw compressor according to this embodiment, first, the male rotor 2C is positioned at a predetermined first rotation position and the female rotor 3C at a predetermined second rotation position by positioning one first engagement portion 25C of the male rotor 2C and one second engagement portion 35C of the female rotor 3C so that they are substantially opposite each other. Second, the male rotor 2C and the female rotor 3C are engaged at these rotation positions. Third, with the male rotor 2C and the female rotor 3C engaged, the first engagement hole 102C of the positioning jig 100C is inserted into and engaged with the portions of both first engagement portions 25C on the discharge side shaft portion 23C of the male rotor 2C, and the second engagement hole 103C of the positioning jig 100C is inserted into and engaged with the portions of both second engagement portions 35C on the discharge side shaft portion 33C of the female rotor 3C. The engagement of the positioning jig 100C with the discharge-side shaft portion 23C of the male rotor 2C and the discharge-side shaft portion 33C of the female rotor 3C restricts the distance between the rotation axis A1 of the male rotor 2C and the rotation axis A2 of the female rotor 3C from two directions, and also restricts the rotation of both the male and female rotors 2C and 3C. This engagement of the male and female rotors 2C and 3C with the positioning jig 100C maintains a normal meshing state of the male and female rotors 2C and 3C, where both rotation axes A1 and A2 are parallel.

[0085] Next, with both first engaging portions 25C of the male rotor 2C and both second engaging portions 35C of the female rotor 3C engaged with the first engaging hole 102C and the second engaging hole 103C of the positioning jig 100C, both male and female rotors 2C and 3C are simultaneously inserted into the housing chamber 45 (bore) of the main casing 41 and attached to the main casing 41 via the suction side bearings 6 and 10. After that, the positioning jig 100C is removed from the male rotor 2C and female rotor 3C, and the discharge side casing 42 is attached to the main casing 41. In this way, by engaging both first engaging portions 25C of the male rotor 2C and both second engaging portions 35C of the female rotor 3A with the positioning jig 100C, both male and female rotors 2C and 3C can be easily inserted simultaneously into the housing chamber 45 (bore) of the casing 4.

[0086] According to the screw compressor and assembly method of the third embodiment described above, similar to the second embodiment, when assembling the screw compressor 1, the positioning jig 100C is engaged with the engaging portions 25C and 35C provided on the male rotor 2C and female rotor 3C to restrain the distance between the rotation axes A1 and A2 of the male rotor 2C and female rotor 3C. This allows the male rotor 2C and female rotor 3C, which are meshed with each other and have parallel rotation axes A1 and A2, to be simultaneously inserted into the casing 4, thus facilitating the assembly of the male rotor 2C and female rotor 3C. In other words, the ease of assembly of the male rotor 2C and female rotor 3C, which have a rotor structure in which the lead angle changes, can be improved.

[0087] Furthermore, in the screw compressor assembly method according to this embodiment, the positioning jig 100C has a first engagement hole 102C (first hole) that can be inserted into the portion of the male rotor 2C's suction-side shaft portion 22 or discharge-side shaft portion 23C (first shaft portion or second shaft portion) that includes the first engagement portion 25C and engages with the first engagement portion 25C, and a second engagement hole 103C (second hole) that can be inserted into the portion of the female rotor 3C's suction-side shaft portion 32 or discharge-side shaft portion 33C (first shaft portion or second shaft portion) that includes the second engagement portion 35C and engages with the second engagement portion 35C.

[0088] According to this method, by simply engaging the first engagement hole 102C (first hole) and the second engagement hole 103C (second hole) of the positioning jig 100C with the first engagement portion 25C of the male rotor 2C and the second engagement portion 35C of the female rotor 3C, respectively, the male rotor 2C and the female rotor 3C can be meshed with each other and their rotation axes A1 and A2 can be made parallel, so that both the male and female rotors 2C and 3C can be easily assembled into the casing 4 at the same time.

[0089] [Fourth Embodiment] Next, a screw compressor and its assembly method according to the fourth embodiment will be illustrated with reference to Figure 16. Figure 16 is a perspective view showing a jig used for assembling a pair of screw rotors in a screw compressor according to the fourth embodiment of the present invention, and the structure of a pair of screw rotors corresponding to the jig. In Figure 16, parts with the same reference numerals as those shown in Figures 1 to 15 are similar parts, so a detailed explanation of them will be omitted.

[0090] The screw compressor and its assembly method according to the fourth embodiment shown in Figure 16 differ from the third embodiment (see Figure 15) in that the structure of the positioning jig 100D is different, and the structure of the engaging parts 25D and 35D of the male and female rotors 2D and 3D that engage with the positioning jig 100D is different.

[0091] Specifically, the positioning jig 100D according to this embodiment comprises a positioning member 101D, which is a plate-shaped member of constant thickness extending in one direction, and a key 107, which is a mounting device for attaching the positioning member 101D to the discharge-side shaft portion 23D of the male rotor 2D and the discharge-side shaft portion 33D of the female rotor 3D. The positioning member 101D has a first engagement hole portion 102D that fits into the discharge-side shaft portion 23D of the male rotor 2D, and a second engagement hole portion 103D that fits into the discharge-side shaft portion 33D of the female rotor 3D. The first engagement hole portion 102D and the second engagement hole portion 103D have groove portions 105 that engage with the key 107 at a predetermined position on the periphery (for example, on one side in a direction perpendicular to the extending direction of the positioning member 101D). The first engagement hole portion 102D is engaged with the first engagement portion 25D of the male rotor 2D via the key 107 engaged with the groove portion 105. The second engagement hole 103D engages with the second engagement portion 35D of the female rotor 3D via a key 107 engaged with the groove 105. The positioning jig 100D, including the positioning member 101D and the key 107, has a positioning function that prevents the distance between the rotation axes A1 and A2 of the male and female rotors 2D and 3D from becoming smaller or larger than a predetermined value, and also restricts the rotation of the male and female rotors 2D and 3D.

[0092] The male rotor 2D has one first engagement portion 25C on the discharge-side shaft portion 23C, which serves as a keyway for engaging with the key 107. The first engagement portion 25D, which serves as a keyway, extends axially on the cylindrical surface of the discharge-side shaft portion 23D. The female rotor 3D has one second engagement portion 35D on the discharge-side shaft portion 33D, which serves as a keyway for engaging with the key 107. The second engagement portion 35D, which serves as a keyway, extends axially on the cylindrical surface of the discharge-side shaft portion 33D.

[0093] The first engaging portion 25D (keyway) of the male rotor 2D and the second engaging portion 35D (keyway) of the female rotor 3D are formed so that when the male rotor 2C and female rotor 3C, which mesh properly, are at predetermined rotational positions (first rotational position and second rotational position), they face the same direction (upward in Figure 16). In other words, when the male rotor 2D and female rotor 3D are meshed with each other, they have rotational positions such that the keyway of the first engaging portion 25D and the keyway of the second engaging portion 35D face the same direction (upward in Figure 16).

[0094] In the assembly method of the screw compressor according to this embodiment, first, the male rotor 2D is positioned at a predetermined first rotational position and the female rotor 3D at a predetermined second rotational position by aligning the first engaging portion 25D (keyway) of the male rotor 2D and the second engaging portion 35C (keyway) of the female rotor 3D in the same direction. Second, the male rotor 2D and the female rotor 3D are engaged at these rotational positions. Thirdly, with the male rotor 2D and the female rotor 3D engaged, the first engagement hole 102D of the positioning member 101D is fitted onto the discharge-side shaft portion 23D of the male rotor 2C, and the key 107 is engaged with the groove 105 of the first engagement hole 102D and the first engagement portion 25D (keyway) of the male rotor 2D. At the same time, the second engagement hole 103D of the positioning member 101D is fitted onto the discharge-side shaft portion 33D of the female rotor 3D, and the key 107 is engaged with the groove 105 of the second engagement hole 103D and the second engagement portion 35D (keyway) of the female rotor 3D. The engagement of the positioning jig 100D with the discharge-side shaft portion 23D of the male rotor 2D and the discharge-side shaft portion 33D of the female rotor 3D constrains the distance between the rotation axis A1 of the male rotor 2D and the rotation axis A2 of the female rotor 3D, and restricts the rotation of both the male and female rotors 2D and 3D. This engagement of the male and female rotors 2D and 3D with the positioning jig 100D maintains a normal meshing state of the male and female rotors 2D and 3D, where both rotation axes A1 and A2 are parallel.

[0095] Next, with the first engagement hole 102D and the second engagement hole 103D of the positioning jig 100D engaged with the discharge-side shaft portion 23D of the male rotor 2D and the discharge-side shaft portion 33D of the female rotor 3D via the key 107, both the male and female rotors 2D and 3D are simultaneously inserted into the housing chamber 45 (bore) of the main casing 41 and attached to the main casing 41. After that, the positioning jig 100D is removed from the male rotor 2D and the female rotor 3D, and the discharge-side casing 42 is attached to the main casing 41. In this way, by engaging the positioning member 101D with the first engagement portion 25D of the male rotor 2D and the second engagement portion 35D of the female rotor 3D via the key 107, both the male and female rotors 2D and 3D can be easily inserted simultaneously into the housing chamber 45 (bore) of the casing 4.

[0096] According to the screw compressor and assembly method of the fourth embodiment described above, similar to the third embodiment, when assembling the screw compressor 1, the positioning jig 100D is engaged with the engaging portions 25D and 35D provided on the male rotor 2D and female rotor 3D to restrain the distance between the rotation axes A1 and A2 of the male rotor 2D and female rotor 3D. This allows the male rotor 2D and female rotor 3D, which are meshed with each other and have parallel rotation axes A1 and A2, to be simultaneously inserted into the casing 4, thus facilitating the assembly of the male rotor 2D and female rotor 3D. In other words, the ease of assembly of the male rotor 2D and female rotor 3D having a rotor structure in which the lead angle changes can be improved.

[0097] Furthermore, in the screw compressor according to this embodiment, the engaging portions 25D and 35D of the male rotor 2D and the female rotor 3D are keyways provided on the cylindrical surface of either the suction-side shaft portion 22 or the discharge-side shaft portion 23D (first shaft portion or second shaft portion).

[0098] With this configuration, the positioning member 101D of the positioning jig 100D can be engaged with the engaging portions 25D and 35D of the male rotor 2D and female rotor 3D via the key 107, so that the rotation of both the male and female rotors 2D and 3D can be easily restricted by the positioning jig 100D.

[0099] Furthermore, in the screw compressor assembly method according to this embodiment, the first engaging portion 25D of the male rotor 2D and the second engaging portion 35D of the female rotor 3D are keyways provided on the cylindrical surface of either the suction-side shaft portion 22, 32 or the discharge-side shaft portion 23D, 33D (first shaft portion or second shaft portion), and the positioning jig 100D is a plate-shaped member having a first engaging hole portion 102D (first hole portion) that can be inserted into the portion of the male rotor 2D's suction-side shaft portion 22 or discharge-side shaft portion 23D (first shaft portion or second shaft portion) that includes the first engaging portion 25D, and a second engaging hole portion 103D (second hole portion) that can be inserted into the portion of the female rotor 3D's suction-side shaft portion 32 or discharge-side shaft portion 33D (first shaft portion or second shaft portion) that includes the second engaging portion 35D.

[0100] According to this method, by simply inserting the first engagement hole 102D (first hole) and the second engagement hole 103D (second hole) of the positioning jig 100D into the suction-side shaft portions 22, 32 or discharge-side shaft portions 23D, 33D (first shaft portion or second shaft portion) of the male rotor 2D and female rotor 3D, respectively, the male rotor 2D and female rotor 3D can be made to mesh with each other and their rotational axes A1 and A2 can be made parallel, so that both the male and female rotors 2D and 3D can be easily assembled into the casing 4 at the same time.

[0101] Furthermore, in the assembly method of the screw compressor according to this embodiment, the positioning member 101D, which is a plate-shaped member, has a first engagement hole 102D (first hole) that engages with the first engagement portion 25D of the male rotor 2D via a key 107, and a second engagement hole 103D (second hole) that engages with the second engagement portion 35D of the female rotor 3D via a key 107.

[0102] According to this method, the rotation of both the male and female rotors 2D and 3D can be easily restricted simply by engaging the first engagement hole 102D (first hole) and the second engagement hole 103D (second hole) of the positioning jig 100D with the first engagement portion 25D of the male rotor 2D and the second engagement portion 35D of the female rotor 3D via the key 107, making it possible to easily assemble both the male and female rotors 2D and 3D into the casing 4 at the same time.

[0103] [Modified version of the fourth embodiment] Next, a modified screw compressor according to the fourth embodiment will be illustrated and described using Figure 17. Figure 17 is a front view showing a jig used for assembling a pair of screw rotors in a modified screw compressor according to the fourth embodiment, and a cross-sectional view showing the structure of a pair of screw rotors (discharge side shaft portion) corresponding to the jig. In Figure 17, parts with the same reference numerals as those shown in Figures 1 to 16 are similar parts, so a detailed explanation of them will be omitted.

[0104] The screw compressor and its assembly method according to the modified fourth embodiment shown in Figure 17 differ from the fourth embodiment (see Figure 16) in that the configuration and structure of the positioning jig 100E are different, and the positions of the engaging portions 25E and 35E of the male and female rotors 2E and 3E are different.

[0105] Specifically, the positioning jig 100E comprises only a positioning member 101E as a plate-shaped member with a constant thickness and extending in one direction, and does not include a key as a mounting device. The positioning member 101E has a first engagement hole 102E that fits into the discharge-side shaft portion 23E of the male rotor 2E, and a second engagement hole 103E that fits into the discharge-side shaft portion 33E of the female rotor 3E. The first engagement hole 102E and the second engagement hole 103E have projections 105E at predetermined positions on their periphery (for example, positions facing each other) that engage with the first engagement portion 25E of the male rotor 2E and the second engagement portion 35E of the female rotor 3E. The projection 105E of the first engagement hole 102E engages with the first engagement portion 25D of the male rotor 2D, and the projection 105E of the second engagement hole 103E engages with the second engagement portion 35E of the female rotor 3E. The positioning jig 100D has a positioning function that prevents the distance between the rotation axes A1 and A2 of the male and female rotors 2D and 3D from becoming smaller or larger than a predetermined value, and also restricts the rotation of the male and female rotors 2D and 3D.

[0106] The keyway, which serves as the first engaging portion 25E of the male rotor 2E, and the keyway, which serves as the second engaging portion 35E of the female rotor 3E, are formed to face each other when the male rotor 2E and female rotor 3E, which are properly meshed, are at predetermined rotational positions (first rotational position and second rotational position). That is, when the male rotor 2E and female rotor 3E are meshed together, they have rotational positions such that the keyway, which serves as the first engaging portion 25E, and the keyway, which serves as the second engaging portion 35E, face each other. The other structures of the first engaging portion 25E (keyway) of the male rotor 2E and the second engaging portion 35E (keyway) of the female rotor 3E are the same as in the fourth embodiment.

[0107] In the assembly method of the screw compressor according to this modified example, the male rotor 2E is positioned at a predetermined first rotational position and the female rotor 3E at a predetermined second rotational position by aligning the first engaging portion 25E (keyway) of the male rotor 2E and the second engaging portion 35E (keyway) of the female rotor 3E with each other. Secondly, the male rotor 2E and the female rotor 3E are engaged at these rotational positions. Thirdly, with the male rotor 2E and the female rotor 3E engaged, the projection 105E of the first engagement hole 102E of the positioning jig 100E is engaged with the first engagement portion 25E (keyway) of the male rotor 2E, and the discharge-side shaft portion 23E of the male rotor 2E is fitted into the first engagement hole 102E. At the same time, the projection 105E of the second engagement hole 103E of the positioning jig 100E is engaged with the second engagement portion 35E (keyway) of the female rotor 3E, and the discharge-side shaft portion 33E of the female rotor 3E is fitted into the second engagement hole 103E. The engagement of the positioning jig 100E with the discharge-side shaft portion 23E of the male rotor 2E and the discharge-side shaft portion 33E of the female rotor 3E restricts the distance between the rotation axis A1 of the male rotor 2E and the rotation axis A2 of the female rotor 3E, and restricts the rotation of both the male and female rotors 2E and 3E. The engagement of the male and female rotors 2E and 3E with the positioning jig 100E allows for the maintenance of a normal meshing state between the male and female rotors 2E and 3E, where their rotational axes A1 and A2 are parallel.

[0108] According to the modified screw compressor and its assembly method described above, the ease of assembly of the male rotor 2D and female rotor 3D having a rotor structure with a variable lead angle can be improved, similar to the case of the fourth embodiment.

[0109] Furthermore, in the screw compressor according to this modified example, the male rotor 2E and female rotor 3E (a pair of screw rotors) have rotational positions such that, when they are meshed together, the keyway of the first engaging portion 25E and the keyway of the second engaging portion 35E face each other.

[0110] With this configuration, the male rotor 2E and the female rotor 3E can be easily brought into a normal meshing state by engaging them at a rotational position where the keyway 25E of the male rotor 2E and the keyway 35E of the female rotor 3E face each other.

[0111] Furthermore, in the assembly method of the screw compressor according to this modified example, the plate-shaped member as the positioning member 101E has a projection 105E (first projection) on the periphery of the first engagement hole 102E (first hole) that protrudes inward from the first engagement hole 102E (first hole), and a projection 105E (second projection) that protrudes inward from the second engagement hole 103E (second hole). The plate-shaped member as the positioning member 101E has the first projection 105E of the first engagement hole 102E (first hole) engaged with the first engagement portion 25E of the male rotor 2E, and the projection 105E (second projection) of the second engagement hole 103E (second hole) engaged with the second engagement portion 35E of the female rotor 3E.

[0112] According to this method, a key is not required when engaging the positioning member 101E with the first engaging portion 25E of the male rotor 2E and the second engaging portion 35E of the female rotor 3E, thus reducing the effort required to attach the positioning member 101E to the first engaging portion 25E of the male rotor 2E and the second engaging portion 35E of the female rotor 3E.

[0113] [Fifth Embodiment] Next, a screw compressor and its assembly method according to the fifth embodiment will be illustrated with reference to Figure 18. Figure 18 is a perspective view showing a jig used for assembling a pair of screw rotors in a screw compressor according to the fifth embodiment of the present invention, and the structure of a pair of screw rotors corresponding to the jig. In Figure 18, parts with the same reference numerals as those shown in Figures 1 to 17 are similar parts, so a detailed explanation of them will be omitted.

[0114] The screw compressor and its assembly method according to the fifth embodiment shown in Figure 18 differ from the first embodiment (see Figure 6) in that the configuration of the positioning jig 100F is different. Specifically, the positioning jig 100F consists of a first gear 111 attached to the discharge-side shaft portion 23 of the male rotor 2, a second gear 112 attached to the discharge-side shaft portion 33 of the female rotor 3 and meshing with the first gear 111, and a set screw 117 as a mounting device for fixing the first gear 111 and the second gear 112 to the discharge-side shaft portion 23 of the male rotor 2 and the discharge-side shaft portion 33 of the female rotor 3, respectively. The first gear 111 and the second gear 112 have screw holes 115 into which the set screw 117 is screwed. The screw holes 115 are configured to extend radially in the first gear 111 and the second gear 112. The positioning jig 100F has the function of aligning the positions of the suction end face 21b and discharge end face 21c of the male rotor 2 with the positions of the suction end face 31b and discharge end face 31c of the female rotor 3 by meshing the first gear 111 and the second gear 112 with the rotation axes A1 and A2 of the male and female rotors 2 and 3.

[0115] The discharge-side shaft portion 23 of the male rotor 2 and the discharge-side shaft portion 33 of the female rotor 3 are provided with a first engaging portion 25, which is a bevel formed by cutting a portion of the cylindrical surface of the discharge-side shaft portion 23 into a flat shape, and a second engaging portion 35, which is a bevel formed by cutting a portion of the cylindrical surface of the discharge-side shaft portion 33 into a flat shape, similar to the first embodiment (see Figure 6). The first engaging portion 25 and the second engaging portion 35 are the parts to which the set screw 117 of the positioning jig 100F is pressed and engaged.

[0116] In the assembly method of the screw compressor according to this embodiment, the first gear 111 is fitted onto the discharge-side shaft portion 23 of the male rotor 2 and fixed by pressing the set screw 117 against the first engagement portion 25 of the male rotor 2 to engage it. Similarly, the second gear 112 is fitted onto the discharge-side shaft portion 33 of the female rotor 3 and fixed by pressing the set screw 117 against the second engagement portion 35 of the female rotor 3 to engage it. The male rotor 2 and the female rotor 3 are positioned so that the set screw 117 of the first gear 111 attached to the male rotor 2 and the set screw 117 of the second gear 112 attached to the female rotor 3 are almost opposite each other, and the first gear 111 and the second gear 112 are meshed together, and the male rotor 2 and the female rotor 3 are meshed together. The meshing of the first gear 111 and the second gear 112 of the positioning jig 100F constrains the distance between the rotation axis A1 of the male rotor 2 and the rotation axis A2 of the female rotor 3, thereby aligning the axial positions of the suction-side end face 21b and discharge-side end face 21c of the male rotor 2 and the suction-side end face 31b and discharge-side end face 31c of the female rotor 3. This maintains a normal meshing state of the male and female rotors 2 and 3, where both rotation axes A1 and A2 are parallel.

[0117] Next, with the first gear 111 and the second gear 112 of the positioning jig 100F meshed together, both the male and female rotors 2 and 3 are simultaneously inserted into the housing chamber 45 (bore) of the main casing 41 and attached to the main casing 41. After that, the first gear 111 and the second gear 112 of the positioning jig 100F are removed from the male rotor 2 and female rotor 3, and the discharge-side casing 42 is attached to the main casing 41. In this way, by engaging the set screw 117 with the first engaging portion 25 of the male rotor 2 to mesh the first gear 111 fixed to the discharge-side shaft portion 23, and by engaging the set screw 117 with the second engaging portion 35 of the female rotor 3 to mesh the second gear 112 fixed to the discharge-side shaft portion 33, both the male and female rotors 2 and 3 can be easily inserted simultaneously into the housing chamber 45 (bore) of the casing 4.

[0118] According to the screw compressor and assembly method of the fifth embodiment described above, when assembling the screw compressor 1, the set screws 117 are engaged with the engaging portions 25 and 35 provided on the male rotor 2 and female rotor 3, and the first gear 111 and second gear 112 of the positioning jig 100F are attached to the male rotor 2 and female rotor 3 and meshed, thereby making it possible to restrain the distance between the rotation axes A1 and A2 of the male rotor 2 and female rotor 3. Due to the meshing of the first gear 111 and the second gear 112, the male rotor 2 and female rotor 3, which are meshed with each other and have parallel rotation axes A1 and A2, can be simultaneously inserted into the casing 4, making the assembly of the male rotor 2 and female rotor 3 easier. In other words, the ease of assembly of the male rotor 2D and female rotor 3, which have a rotor structure in which the lead angle changes, can be improved.

[0119] Furthermore, in the screw compressor assembly method according to this embodiment, the positioning jig 100F includes a first gear 111 attached to the suction-side shaft portion 22 or discharge-side shaft portion 23 (first shaft portion or second shaft portion) of the male rotor 2 having a first engagement portion 25, and a second gear 112 attached to the suction-side shaft portion 32 or discharge-side shaft portion 33 (first shaft portion or second shaft portion) of the female rotor 3 having a second engagement portion 35, and meshing with the first gear 111. The first gear 111 is fixed to the male rotor 2 by engaging a set screw 117, which serves as a first mounting device, with the first engagement portion 25 of the male rotor 2, and the second gear 112 is fixed to the female rotor 3 by engaging a set screw 117, which serves as a second mounting device, with the second engagement portion 35 of the female rotor 3. By meshing the first gear 111 and the second gear 112, the male rotor 2 and the female rotor 3 are meshed at a predetermined rotational position.

[0120] According to this method, by meshing the first gear 111 fixed to the male rotor 2 with the second gear 112 fixed to the female rotor 3, the distance between the rotation axis A1 of the male rotor 2 and the rotation axis A2 of the female rotor 3 can be easily constrained, making it possible to easily insert both the male and female rotors 2 and 3 into the casing 4 simultaneously.

[0121] [Modified version of the fifth embodiment] Next, a modified screw compressor according to the fifth embodiment and its assembly method will be illustrated with reference to Figure 19. Figure 19 is a perspective view showing a jig used for assembling a pair of screw rotors in a modified screw compressor according to the fifth embodiment, and the structure of a pair of screw rotors corresponding to the jig. In Figure 19, parts with the same reference numerals as those in Figures 1 to 18 are similar parts, so a detailed explanation of them will be omitted.

[0122] The modified version of the fifth embodiment shown in Figure 19 differs from the fifth embodiment in that the mounting device for attaching the first gear 111G and the second gear 112G of the positioning jig 100G to the discharge-side shaft portion 23G of the male rotor 2G and the discharge-side shaft portion 33G of the female rotor 3G is a key 117G, and the first engaging portion 25G of the male rotor 2G and the second engaging portion 35G of the female rotor 3G are keyways corresponding to the key 117G of the positioning jig 100G. The first gear 111G and the second gear 112G of the positioning jig 100G have grooves 115G that engage with the key 107. The first engaging portion 25G of the male rotor 2G and the second engaging portion 35G of the female rotor 3G are keyways that engage with the key 117G of the positioning jig 100G. The first engagement portion 25G (keyway) of the male rotor 2G and the second engagement portion 35G (keyway) of the female rotor 3G are formed so that when the male rotor 2G and female rotor 3G, which are properly meshing, are at predetermined rotational positions (first rotational position and second rotational position), they face the same direction (upward in Figure 19). In other words, when the male rotor 2G and female rotor 3G are meshing with each other, they have rotational positions such that the keyway of the first engagement portion 25G and the keyway of the second engagement portion 35G face the same direction (upward in Figure 19).

[0123] In the assembly method of the screw compressor according to this modified example, the first gear 111G is fitted onto the discharge-side shaft portion 23G of the male rotor 2G and fixed by engaging the key 117G with the first engagement portion 25G (keyway) of the male rotor 2G. Similarly, the second gear 112G is fitted onto the discharge-side shaft portion 33G of the female rotor 3G and fixed by engaging the key 117G with the second engagement portion 35G (keyway) of the female rotor 3G. The male rotor 2G and the female rotor 3G are positioned so that the key 117G for fixing the first gear 111G to the male rotor 2G and the key 117G for fixing the second gear 112G to the female rotor 3G face in the same direction, and the first gear 111G and the second gear 112G of the positioning jig 100G are meshed together. The meshing of the first gear 111G and the second gear 112G constrains the distance between the rotation axis A1 of the male rotor 2G and the rotation axis A2 of the female rotor 3G, thereby aligning the axial positions of the suction end face 21b and discharge end face 21c of the male rotor 2G and the suction end face 31b and discharge end face 31c of the female rotor 3G. This maintains a normal meshing state of the male and female rotors 2G and 3G, where both rotation axes A1 and A2 are parallel. In this way, by engaging the key 117G with the first engaging portion 25G (keyway) of the male rotor 2G, the first gear 111G fixed to the discharge-side shaft portion 23G is engaged with the key 117G with the second engaging portion 35G (keyway) of the female rotor 3G, and by engaging the key 117G with the second gear 112G fixed to the discharge-side shaft portion 33G, both the male and female rotors 2G and 3G can be easily inserted simultaneously into the housing chamber 45 (bore) of the casing 4.

[0124] According to the modified screw compressor and its assembly method described above, the ease of assembly of the male rotor 2G and female rotor 3G, which have a rotor structure with a variable lead angle, can be improved, similar to the case of the fifth embodiment.

[0125] [Other embodiments] It should be noted that the present invention is not limited to the embodiments described above, and includes various modifications. The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described. That is, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0126] For example, in the embodiment described above, an example was shown in which the male rotor 2 is driven by a rotational drive source. However, a configuration in which the female rotor 3 is driven by a rotational drive source is also possible. Furthermore, a configuration in which both the male and female rotors 2 and 3 are driven synchronously is also possible.

[0127] Furthermore, in the embodiments described above, an example was shown in which the lead angle (lead) of both the male and female rotors gradually changes along the entire length from the suction-side end faces 21b, 31b to the discharge-side end faces 21c, 31c of the rotor teeth 21, 31. However, it is also possible to configure both the male and female rotors so that the lead angle (lead) changes only in a portion of the entire length of the rotor teeth 21, 31.

[0128] Furthermore, in the above-described embodiment, an example was shown in which both male and female rotors are configured such that the lead angle (lead) of the rotor teeth 21 and 31 increases from the suction side to the discharge side. However, it is also possible to configure both male and female rotors so that the lead angle (lead) of the rotor teeth 21 and 31 decreases from the suction side to the discharge side.

[0129] Furthermore, in the first embodiment, an example was shown in which the formation position of the engaging portion 25 of the male rotor 2 was set based on the tooth tip 21t of the discharge end face 21c. However, the formation position of the engaging portion 25 of the male rotor 2 can also be set based on a different position on the discharge end face 21c. Similarly, the formation position of the engaging portion 35 of the female rotor 3 can also be set based on a specific position on the discharge end face 31c. In this case, the formation position of the engaging portion 25 of the male rotor 2 is set based on the position of the engaging portion 35 of the female rotor 3. [Explanation of Symbols]

[0130] 1...Screw compressor, 2, 2A, 2B, 2C, 2D, 2E, 2G...Male rotor (screw rotor), 3, 3A, 3B, 3C, 3D, 3E, 3G...Female rotor (screw rotor), 4...Casing, 21...Rotor teeth, 21a...Male teeth, 22...Suction side shaft, 23, 23A, 23B, 23C, 23D, 23E, 23G...Discharge side shaft, 25, 25A, 25B, 25C, 25D, 25E, 25G...First engagement part, 251A, 251B, 252A, 252B...First engagement part, 31...Rotor teeth, 31a...Female teeth, 32...Suction side shaft, 33, 33A, 33B, 33C, 33D, 33E, 33G... Discharge side shaft section, 35, 35A, 35B, 35C, 35D, 35E, 35G... Second engaging section, 351A, 351B, 352A, 352B... Second engaging section, 100, 100A, 100B, 100C, 100D, 100E, 100F, 100G... Positioning jig, 102A, 102B... First engaging groove, 102C, 102D, 102E... First engaging hole section, 103A, 103B... Second engaging groove, 103C, 103D, 103E... Second engaging hole section, 105E... Projection, 107... Key, 111, 111G... First gear, 112, 112G... Second gear, 117... Set screw (mounting fixture), 117G... Key (mounting fixture), A1... Rotation axis, A2... Rotation axis

Claims

1. A pair of screw rotors that mesh with each other and rotate, The casing comprises the pair of screw rotors, with their rotational axes parallel to each other. Each of the pair of screw rotors is A rotor tooth section having spiral teeth, The rotor teeth include a first shaft portion and a second shaft portion, respectively, provided on one and the other axial side of the rotor teeth. The rotor teeth are configured such that the lead angle, which is the angle between a plane perpendicular to the axis of rotation and the tip line of the tooth, changes in at least a portion of the total length of the rotor teeth in the axial direction. Each of the pair of screw rotors has an engaging portion on either the first shaft portion or the second shaft portion that engages with a positioning jig used during assembly to constrain the distance between the rotation axes of the pair of screw rotors, The engagement portion is a keyway provided on the cylindrical surface of either the first shaft portion or the second shaft portion. A screw compressor characterized by the following features.

2. A screw compressor according to claim 1, When the pair of screw rotors are meshed together, they have rotational positions such that their keyways face each other. A screw compressor characterized by the following features.

3. A method for assembling a screw compressor, wherein a pair of male and female rotors, each including a rotor tooth portion having helical teeth and a first shaft portion and a second shaft portion provided on one and the other axial side of the rotor tooth portion, are housed in a casing so as to be rotatable around mutually parallel axes of rotation, and the rotor tooth portion is configured such that the lead angle, which is the angle between a plane perpendicular to the axis of rotation and the tip line of the teeth, changes in at least a portion of the total length of the rotor tooth portion in the axial direction, The male rotor having a first engaging portion provided on either the first shaft portion or the second shaft portion and the female rotor having a second engaging portion provided on either the first shaft portion or the second shaft portion are engaged at a predetermined rotational position. A positioning jig for constraining the distance between the rotational axes of the male rotor and the female rotor is engaged with the first engaging portion of the male rotor and the second engaging portion of the female rotor. With the male rotor and the female rotor engaged and the positioning jig engaged with the first engaging portion of the male rotor and the second engaging portion of the female rotor, the male rotor and the female rotor are simultaneously inserted into the casing and attached to the casing. Remove the positioning jig from the male rotor and the female rotor. A method for assembling a screw compressor, characterized by the following features.

4. A method for assembling a screw compressor according to claim 3, The first engaging portion of the male rotor and the second engaging portion of the female rotor are flattened by cutting a part of the cylindrical surface of either the first shaft portion or the second shaft portion into a planar shape. The positioning jig is a plate-shaped member that engages with the planar cutting. A method for assembling a screw compressor, characterized by the following features.

5. A method for assembling a screw compressor according to claim 4, The positioning jig is A first groove or first hole that is insertable into the portion of the first shaft portion or the second shaft portion of the male rotor that includes the first engaging portion and engages with the first engaging portion, The female rotor has a second groove or second hole that is insertable into the portion of the first shaft portion or the second shaft portion including the second engaging portion and engages with the second engaging portion. A method for assembling a screw compressor, characterized by the following features.

6. A method for assembling a screw compressor according to claim 3, The first engaging portion of the male rotor and the second engaging portion of the female rotor are keyways provided on the cylindrical surface of either the first shaft portion or the second shaft portion. The positioning jig is a plate-shaped member having a first hole that can be inserted into the portion of the male rotor including the first engaging portion on the first shaft portion or the second shaft portion, and a second hole that can be inserted into the portion of the female rotor including the second engaging portion on the first shaft portion or the second shaft portion. A method for assembling a screw compressor, characterized by the following features.

7. A method for assembling a screw compressor according to claim 6, The plate-shaped member is such that the first hole is engaged with the first engagement portion of the male rotor via a key, and the second hole is engaged with the second engagement portion of the female rotor via a key. A method for assembling a screw compressor, characterized by the following features.

8. A method for assembling a screw compressor according to claim 6, The plate-like member has a first projection on the periphery of the first hole that protrudes inward from the first hole, and a second projection on the periphery of the second hole that protrudes inward from the second hole. The plate-shaped member is configured such that the first projection of the first hole engages with the first engagement portion of the male rotor, and the second projection of the second hole engages with the second engagement portion of the female rotor. A method for assembling a screw compressor, characterized by the following features.

9. A method for assembling a screw compressor according to claim 3, The positioning jig comprises a first gear attached to the first or second shaft portion having the first engagement portion of the male rotor, and a second gear attached to the first or second shaft portion having the second engagement portion of the female rotor, which meshes with the first gear. The first gear is fixed to the male rotor by engaging the first mounting fixture with the first engaging portion of the male rotor. The second gear is fixed to the male rotor by engaging the second mounting fixture with the second engaging portion of the female rotor. By meshing the first gear and the second gear, the male rotor and the female rotor are meshed at the predetermined rotational position. A method for assembling a screw compressor, characterized by the following features.

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