Method for manufacturing screw rotor, screw rotor and screw compressor

Abstract

Each spiral groove (40) of the screw rotor (30) is divided into a first portion (41) including an end portion on the first end (31) side of the workpiece (35) and a second portion (42) including an end portion on the second end (32) side of the workpiece (35). The first end (31) of the workpiece (35) is mounted on a holding portion (61) of a machine tool (60), and the first portion (41) of each spiral groove (40) is finished by cutting. Thereafter, the workpiece (35) is first removed from the holding portion (61), and the second end (32) of the workpiece (35) is then mounted on the holding portion (61). In this state, the second portion (42) of each spiral groove (40) is finished by cutting.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a screw rotor, a screw rotor, and a screw compressor. Background Art

[0002] Patent Document 1 describes the technical content of manufacturing a screw rotor for a screw compressor using a five-axis multi-process automatic tool-changing CNC machine tool. The five-axis multi-process automatic tool-changing CNC machine tool performs cutting processing on a workpiece while moving a cutting tool such as an end mill mounted on a rotating spindle and a workpiece mounted on a holding portion.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 4229213 Summary of the invention

[0006] -Technical problem to be solved by the invention-

[0007] The spiral groove formed on the screw rotor is a groove with a shape in which the depth gradually decreases from the axial center of the screw rotor toward both ends. Therefore, when one end of the workpiece is fixed to the holding portion, when the portion of the spiral groove close to the other end of the workpiece is processed, the angle between the rotation center axis of the cutting tool and the center axis of the workpiece becomes smaller, and the holding portion holding the workpiece is closer to the rotation main axis holding the cutting tool.

[0008] On the other hand, the five-axis multi-process automatic tool change CNC machine tool needs to avoid interference between the rotating spindle holding the cutting tool and the holding part holding the workpiece. Therefore, in the past, in order to process the screw rotor, even when processing the part of the spiral groove close to the other end of the workpiece, it is necessary to use a special five-axis multi-process automatic tool change CNC machine tool with a structure that does not contact the rotating spindle.

[0009] The purpose of the present disclosure is to process a screw rotor using a machine tool of common structure.

[0010] -Technical solutions to solve technical problems-

[0011] A first aspect of the present disclosure is a method for manufacturing a screw rotor 30, which is used in a screw compressor by forming a plurality of spiral grooves 40 on a cylindrical workpiece 35. In the method for manufacturing the screw rotor 30, the plurality of spiral grooves 40 are divided into a first portion 41 and a second portion 42, the first portion 41 including an end portion on the first end 31 side of the workpiece 35, and the second portion 42 including an end portion on the second end 32 side of the workpiece 35. In the method for manufacturing the screw rotor 30, a first mounting step 84, a first finishing step 92, a disassembly step 94, a second mounting step 95, and a second finishing step 98 are performed. In the first installation process 84, the first end 31 of the workpiece 35 is installed on the holding part 61 of the machine tool 60; after the first installation process 84 is completed, the first finishing process 92 uses cutting to finish the first part 41 of each of the multiple spiral grooves 40; after the first finishing process 92 is completed, the disassembly process 94 removes the workpiece 35 from the holding part 61; in the second installation process 95, the second end 32 of the workpiece 35 removed from the holding part 61 in the disassembly process 94 is installed on the holding part 61; after the second installation process 95 is completed, the second finishing process 98 uses cutting to finish the second part 42 of each of the multiple spiral grooves 40.

[0012] In the first aspect, the second finishing process 98 is performed after the first finishing process 92. In the first finishing process 92, the first portion 41 of the spiral groove 40 is cut by the workpiece 35 whose first end 31 is mounted on the holding portion 61 of the machine tool 60. Therefore, in the first finishing process 92, the holding portion 61 holding the workpiece 35 is held in a state separated from the structure of the machine tool 60 other than the holding portion 61. In addition, in the second finishing process 98, the second portion 42 of the spiral groove 40 is cut by the workpiece 35 whose second end 32 is mounted on the holding portion 61 of the machine tool 60. Therefore, in the second finishing process 98, the holding portion 61 holding the workpiece 35 is held in a state separated from the structure of the machine tool 60 other than the holding portion 61.

[0013] Therefore, according to the first aspect, even when the screw rotor (30) is machined using a machine tool (60) of a conventional structure, the entire spiral groove (40) of the screw rotor (30) can be machined while the holding portion (61) holding the workpiece (35) is held in a state separated from the structure of the machine tool (60) other than the holding portion (61).

[0014] According to a second aspect of the present disclosure, in addition to the first aspect, in the method for manufacturing the screw rotor (30), one of the plurality of spiral grooves (40) is used as the specific spiral groove (40a). In the method for manufacturing the screw rotor (30), a first measuring step (93), a second measuring step (96), and a correction step (97) are performed. The first measuring process 93 measures the position of the first part 41 of the specific spiral groove 40a in the direction of the central axis 33 of the workpiece 35 after the first finishing process 92 is completed and before the disassembly process 94 is started; the second measuring process 96 measures the position of the first part 41 of the specific spiral groove 40a in the direction of the central axis 33 of the workpiece 35 after the second installation process 95 is completed and before the second finishing process 98 is started; in the correction process 97, the displacement angle is calculated based on the position of the first part 41 measured in the first measuring process 93 and the position of the first part 41 measured in the second measuring process 96, and the processing origin of the first finishing process 92 is corrected by the calculated displacement angle, wherein the displacement angle is an angle around the central axis 33 of the workpiece 35, indicating the change in the circumferential position of the workpiece 35 at the end of the second installation process 95 relative to the circumferential position of the workpiece 35 at the end of the first finishing process 92; in the second finishing process 98, cutting is performed according to the processing origin corrected in the correction process 97.

[0015] In the second aspect, the first measuring step 93 is performed between the first finishing step 92 and the disassembly step 94, and the second measuring step 96 and the correction step 97 are performed in sequence between the second mounting step 95 and the second finishing step 98. In the correction step 97, the displacement angle of the workpiece 35 is calculated based on the position of the first portion 41 measured in the first measuring step 93 and the position of the first portion 41 measured in the second measuring step 96. In addition, in the correction step 97, the machining origin in the first finishing step 92 is corrected based on the calculated displacement angle. In the second finishing step 98, the cutting process of the second portion 42 of the spiral groove 40 is performed based on the machining origin corrected in the correction step 97. Therefore, the error in the relative position of the first portion 41 and the second portion 42 of the spiral groove 40 can be suppressed to a small value.

[0016] According to a third aspect of the present disclosure, based on the second aspect, in the correction step 97, the displacement angle of the screw rotor 30 is calculated using the correlation between the position of the spiral groove 40 in the direction of the central axis 33 of the screw rotor 30 and the rotation angle of the screw rotor 30 determined based on the design value of the screw rotor 30, the position of the first portion 41 measured in the first measuring step 93, and the position of the first portion 41 measured in the second measuring step 96.

[0017] In the correction step (97) of the third aspect, a correlation determined based on the design value of the screw rotor (30) is used to calculate the displacement angle. The correlation is a correlation between the position of the spiral groove (40) in the direction of the central axis (33) of the screw rotor (30) and the rotation angle of the screw rotor (30).

[0018] The fourth aspect of the present disclosure is based on any one of the first to third aspects above, and in each of the multiple spiral grooves 40, the length of the first part 41 in the extension direction of the spiral groove 40 is longer than the length of the second part 42 in the extension direction of the spiral groove 40.

[0019] In the fourth aspect, the boundary line 43 between the first portion 41 and the second portion 42 in each spiral groove 40 is formed at a position close to the second end 32 of the workpiece 35 with respect to the center of the central axis 33 of the workpiece 35 .

[0020] The fifth aspect of the present disclosure is based on the fourth aspect above. In each of the multiple spiral grooves 40, the first part 41 is a part including the ejection side end 44 of the spiral groove 40, and in each of the multiple spiral grooves 40, the second part 42 is a part including the suction side end 45 of the spiral groove 40.

[0021] In the fifth aspect, the boundary line 43 between the first portion 41 and the second portion 42 in each spiral groove 40 is formed at a position close to the suction side end 45 of the spiral groove 40 with respect to the center in the direction of the central axis 33 of the workpiece 35 .

[0022] A sixth aspect of the present disclosure is a screw rotor (30) manufactured by the manufacturing method of any one of the first to fifth aspects.

[0023] The screw rotor (30) of the sixth aspect is manufactured by the manufacturing method of any one of the first to fifth aspects.

[0024] A seventh aspect of the present disclosure is a screw compressor (10), comprising a screw rotor (30) and a gate rotor (51) according to the sixth aspect, wherein a plurality of flat plate-shaped gates (52) meshing with the spiral groove (40) of the screw rotor (30) are radially arranged on the gate rotor (51), and a linear portion (i.e., a sealing line (53)) sliding relative to the wall surface of the spiral groove (40) of the screw rotor (30) is formed in each of the plurality of gates (52), and a boundary line (43) between the first portion (41) and the second portion (42) of each of the plurality of spiral grooves (40) of the screw rotor (30) is in a shape intersecting with the sealing line (53) of the gate (52) passing through the boundary line (43) from the suction side end (45) of the spiral groove (40) toward the discharge side end (44).

[0025] In the seventh aspect, the screw rotor (30) and the gate rotor (51) of the sixth aspect are provided in the screw compressor (10). The shape of the boundary line (43) between the first portion (41) and the second portion (42) in each spiral groove (40) of the screw rotor (30) is a shape that intersects with the seal line (53) of the gate (52) passing through the boundary line (43) from the suction side end (45) toward the discharge side end (44) of the spiral groove (40). Therefore, the force acting on the gate (52) in the process of passing through the boundary line (43) between the first portion (41) and the second portion (42) can be suppressed to be small. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a simplified longitudinal cross-sectional view of a single screw compressor;

[0027] Figure 2 It is shown Figure 1 A transverse cross-sectional view of a single screw compressor at section II-II;

[0028] Figure 3 It is the front view of the screw rotor;

[0029] Figure 4 is a perspective view of a screw rotor and a gate rotor showing the arrangement of the screw rotor and the gate rotor in a single screw compressor;

[0030] Figure 5 yes Figure 4 An enlarged view of the main part of

[0031] Figure 6 is a front view of a screw rotor and a gate rotor showing the arrangement of the screw rotor and the gate rotor in a single screw compressor;

[0032] Figure 7 is a process diagram showing a method for manufacturing a screw rotor;

[0033] Figure 8 is an explanatory diagram showing the relative positions of a holding portion and a rotating spindle of a machine tool during the process of machining a screw rotor;

[0034] Fig. 9 is a front view of the screw rotor which has been mounted on the holding portion of the machine tool in the first mounting step;

[0035] Fig.10 It is shown Fig. 9 A cross-sectional view of the screw rotor at section X-X;

[0036] Fig.11 is a front view of the screw rotor that has been installed on the holding portion of the machine tool in the second installation step;

[0037] Fig.12 It is shown Fig.11 A cross-sectional view of the screw rotor at section XII-XII;

[0038] Fig.13 These are a front view and a cross-sectional view of the screw rotor to be measured in the second measurement step. DETAILED DESCRIPTION

[0039] Embodiments will be described. First, the structure of the single screw compressor (10) will be described, and then a method for manufacturing the screw rotor (30) will be described.

[0040] - Single screw compressor -

[0041] The single screw compressor 10 (hereinafter referred to as "screw compressor") of this embodiment is provided in the refrigerant circuit of the refrigeration device that performs a vapor compression refrigeration cycle. The screw compressor 10 sucks and compresses the refrigerant evaporated in the evaporator, and discharges the compressed refrigerant to the condenser. The screw compressor 10 also performs two-stage compression.

[0042] 〈Overall structure of screw compressor〉

[0043] like Figure 1 and Figure 2 As shown, the screw compressor 10 includes a screw rotor 30 and two gate rotor assemblies 50. The screw compressor 10 also includes a housing 11, a motor 17 and a drive shaft 18.

[0044] like Figure 1 As shown, the shell 11 is formed into a cylindrical shape with both ends closed. The shell 11 is arranged in a state where its length direction is approximately horizontal. The shell 11 includes a cylindrical portion 16. The cylindrical portion 16 is a portion formed into a cylindrical shape. The cylindrical portion 16 is arranged near the center of the shell 11 in the length direction. The screw rotor 30 is accommodated in the cylindrical portion 16.

[0045] The housing 11 is provided with a suction port 12 and a discharge port 13. The suction port 12 is formed at one end of the housing 11 ( Figure 1The ejection port 13 is formed at the other end ( Figure 1 The upper part of the right end portion in the figure).

[0046] A low-pressure chamber 14 and a high-pressure chamber 15 are formed inside the housing 11. The low-pressure chamber 14 is formed at a position close to one end of the housing 11 with respect to the cylindrical portion 16, and communicates with the suction port 12. The high-pressure chamber 15 is formed at a position close to the other end of the housing 11 with respect to the cylindrical portion 16, and communicates with the discharge port 13.

[0047] The motor 17 is installed in the low pressure chamber 14. The drive shaft 18 connects the motor 17 and the screw rotor 30. The motor 17 drives the screw rotor 30 to rotate.

[0048] like Figure 2 As shown, each gate rotor assembly 50 includes a gate rotor 51 and a support member 54. The gate rotor assembly 50 is a flat plate-shaped member made of resin. The support member 54 is a metal member. The support member 54 is provided to contact the back surface of the gate rotor 51 and support the gate rotor 51.

[0049] exist Figure 2 In the embodiment, the front surface of the gate rotor (51) of the gate rotor assembly (50) disposed on the right side of the screw rotor (30) faces upward; Figure 2 In the diagram, the gate rotor (51) of the gate rotor assembly (50) disposed on the left side of the screw rotor (30) faces downward.

[0050] 〈Screw rotor〉

[0051] like Figure 3 As shown in FIG. 1 , the screw rotor 30 is a metal cylindrical component. Figure 3 The left end in is the first end 31, Figure 3 The right end in FIG. 1 is the second end 32 . In the cylindrical portion 16 of the casing 11 , the first end 31 of the screw rotor 30 is located on the high pressure chamber 15 side, and the second end 32 is located on the low pressure chamber 14 side.

[0052] A plurality of (six in this embodiment) spiral grooves 40 are formed in the screw rotor 30. Each spiral groove 40 is a groove extending in a spiral shape in the direction of the central axis 33 of the screw rotor 30. The six spiral grooves 40 are arranged at equal angular intervals in the circumferential direction of the screw rotor 30. Each spiral groove 40 opens only toward the outer peripheral surface of the screw rotor 30. Therefore, in the screw rotor 30 of this embodiment, each spiral groove 40 does not open at the end surface of the screw rotor 30.

[0053] Each spiral groove 40 of the screw rotor 30 has a first side wall surface 46, a second side wall surface 47, and a bottom wall surface 48. The first side wall surface 46 and the second side wall surface 47 face each other. The first side wall surface 46 is located on the first end 31 side of the screw rotor 30. The second side wall surface 47 is located on the second end 32 side of the screw rotor 30.

[0054] The end of each spiral groove 40 on the first end 31 side of the screw rotor 30 is the discharge side end 44, and the end on the second end 32 side of the screw rotor 30 is the suction side end 45. The depth of each spiral groove 40 gradually increases from the suction side end 45 and the discharge side end 44 toward the center of the central axis 33 of the screw rotor 30. In addition, the depth of each spiral groove 40 is zero at the suction side end 45 and the discharge side end 44.

[0055] Each spiral groove 40 is divided into a first portion 41 and a second portion 42. Figure 3 In the figure, a black dot is added to the second portion 42 of each spiral groove 40. The first portion 41 is a portion including the discharge side end 44. The second portion 42 is a portion including the suction side end 45. The length of the first portion 41 in the extension direction of the spiral groove 40 (the direction from the suction side end 45 toward the discharge side end 44) ​​is longer than the length of the second portion 42 in the extension direction of the spiral groove 40.

[0056] A boundary line 43 is formed on the wall surface of each spiral groove 40 as a boundary line between the first part 41 and the second part 42. The boundary line 43 is a tiny step (for example, about 10 μm to 30 μm) formed on the wall surface of the spiral groove 40. The step constituting the boundary line 43 is preferably as small as possible. However, since it is impossible to completely eliminate the error during processing, it is impossible to make the step zero.

[0057] The boundary line 43 formed on the wall surface of each spiral groove 40 is inclined at a slight angle (eg, about 1° to 3°) with respect to the intersection line between the wall surface of the spiral groove 40 and the sealing plane 55. The sealing plane 55 will be described later.

[0058] 〈Gate rotor〉

[0059] like Figure 4 As shown, a plurality of (eleven in this embodiment) gates (52) are radially provided on the gate rotor (51). Each gate (52) is a substantially rectangular flat plate. The gates (52) enter the spiral groove (40) of the screw rotor (30) and slide against the wall surface of the spiral groove (40) to form compression chambers (21, 22).

[0060] like Figure 6 As shown, a sealing line 53 is formed on the side surface of each gate 52. The sealing line 53 is a linear region extending from the base end toward the tip end of the gate 52. The sealing line 53 of the gate 52 entering the spiral groove 40 slides relative to the wall surface of the spiral groove 40.

[0061] In the gate rotor 51, the sealing lines 53 of all the gates 52 are located on one plane. The plane where all the sealing lines 53 of the gate rotor 51 are located is a sealing plane 55. The sealing plane 55 is a plane offset from the front surface of the gate rotor 51 by a predetermined distance S (for example, 1 mm to 2 mm).

[0062] As described above, the boundary line 43 formed on the wall surface of each spiral groove 40 is inclined relative to the intersection line between the wall surface of the spiral groove 40 and the sealing plane 55. Figure 5 As shown, the seal line 53 of the gate 52 that moves relatively from the suction side end 45 toward the discharge side end 44 of the spiral groove 40 intersects the boundary line 43 at one point in the process in which the gate 52 crosses the boundary line 43 from the second portion 42 toward the first portion 41. In this way, in the screw rotor 30 of the present embodiment, the shape of the boundary line 43 formed on the wall surface of the spiral groove 40 is a shape that intersects with the seal line 53 of the gate 52 that passes through the boundary line 43 from the suction side end 45 toward the discharge side end 44 of the spiral groove 40.

[0063] 〈Compression chamber〉

[0064] like Figure 1 and Figure 2 As shown, in the screw compressor 10, the compression chambers 21 and 22 are formed by the screw rotor 30, the gate rotor 51, and the cylindrical portion 16 of the casing 11. The compression chambers 21 and 22 are closed spaces surrounded by the wall surface of the spiral groove 40 of the screw rotor 30, the front surface of the gate 52 of the gate rotor 51, and the inner circumferential surface of the cylindrical portion 16. In the screw compressor 10 of this embodiment, Figure 2 The compression chamber on the lower side of the screw rotor 30 is the first compression chamber 21. Figure 2 The compression chamber on the upper side of the screw rotor (30) is the second compression chamber (22).

[0065] 〈Operation of screw compressor〉

[0066] In the screw compressor 10, the screw rotor 30 is driven by the motor 17. When the screw rotor 30 rotates, the gate rotor 51 meshing with the screw rotor 30 rotates. When the gate rotor 51 rotates, the gate 52 of the gate rotor 51 enters the spiral groove 40 of the screw rotor 30 and moves relatively from the suction side end 45 toward the discharge side end 44 of the spiral groove 40 entered. As a result, the volume of the compression chambers 21 and 22 is gradually reduced, and the refrigerant in the compression chambers 21 and 22 is compressed.

[0067] The screw compressor 10 of this embodiment performs two-stage compression. Specifically, the refrigerant flowing into the low-pressure chamber 14 through the suction port 12 flows into the first compression chamber 21 and is compressed. The refrigerant compressed in the first compression chamber 21 is ejected from the first compression chamber 21 and flows into the second compression chamber 22 through the passage formed in the shell 11. The refrigerant that has flowed into the second compression chamber 22 is compressed and then ejected into the high-pressure chamber 15. The refrigerant that has flowed into the high-pressure chamber 15 is ejected to the outside of the screw compressor 10 through the ejection port 13.

[0068] - Method for manufacturing screw rotor -

[0069] A method for manufacturing a screw rotor according to the present embodiment will be described.

[0070] like Figure 7 As shown, in the manufacturing method of this embodiment, the front stage process 71 and the back stage process 72 are performed in sequence. In the back stage process 72, the first groove processing step 81 and the second groove processing step 91 are performed in sequence. In the first groove processing step 81, the first rough cutting step 82, the first disassembly step 83, the first installation step 84 and the second rough cutting step 85 are performed in sequence. In the second groove processing step 91, the first finishing process 92, the first measuring step 93, the second disassembly step 94, the second installation step 95, the second measuring step 96, the correction step 97 and the second finishing process 98 are performed in sequence.

[0071] 〈Pre-process〉

[0072] In the front-stage process 71, the outer peripheral surface and the end surface of the workpiece 35 as a casting are cut. The workpiece 35 is machined using a lathe in the front-stage process 71. The workpiece 35 is machined in the front-stage process 71 so that the outer diameter and the total length of the workpiece 35 reach the design values ​​of the screw rotor 30. In addition, in the front-stage process 71, a hole is formed in the workpiece 35 for fully inserting the drive shaft 18.

[0073] 〈Back-end process〉

[0074] In the subsequent process 72, a spiral groove 40 is formed on the workpiece 35 processed in the previous process 71. The processing of the workpiece 35 in the subsequent process 72 is performed using a five-axis multi-process automatic tool-changing CNC machine tool as the machine tool 60. In this subsequent process 72, the workpiece 35 mounted on the holding portion 61 of the machine tool 60 is processed using an end mill 63 mounted on the rotating spindle 62 of the machine tool 60.

[0075] In the first groove machining step 81, the spiral groove 40 is formed in the cylindrical workpiece 35. In the second groove machining step 91, the first side wall surface 46, the second side wall surface 47, and the bottom wall surface 48 of the spiral groove 40 are finished so that the shape of the spiral groove 40 becomes the design value of the screw rotor 30. In the second groove machining step 91, the side surface of the end mill 63 is used to cut the workpiece 35.

[0076] In the following description, the end of the workpiece 35 that will become the first end 31 of the screw rotor 30 as a finished product is referred to as the first end 31 of the workpiece 35. In addition, the end of the workpiece 35 that will become the second end 32 of the screw rotor 30 as a finished product is referred to as the second end 32 of the workpiece 35.

[0077] 〈First Rough Cutting Process〉

[0078] The first rough cutting step 82 is performed in a state where the second end 32 of the workpiece 35 is mounted on the holding portion 61 of the machine tool 60. In the first rough cutting step 82, a portion of each spiral groove 40 including the suction side end 45 is formed by cutting. It should be noted that the length of the portion of each spiral groove 40 formed in the first rough cutting step 82 (the length in the extension direction of the spiral groove 40) may be the same as or different from the second portion 42 of the spiral groove 40 of the finished product, i.e., the screw rotor 30.

[0079] 〈First disassembly process〉

[0080] In the first disassembling step 83 , after the first rough cutting step 82 is completed, the workpiece 35 is disassembled from the holding portion 61 of the machine tool 60 .

[0081] 〈First installation step〉

[0082] In the first mounting step 84, the workpiece 35 removed from the holder 61 of the machine tool 60 in the first removal step 83 is mounted again on the holder 61. In the first mounting step 84, the first end 31 of the workpiece 35 is mounted on the holder 61 of the machine tool 60.

[0083] 〈Second Rough Cutting Process〉

[0084] In the second rough cutting step 85, the workpiece 35 mounted on the holding portion 61 of the machine tool 60 is processed to form the remaining portion of the spiral groove 40. In the second rough cutting step 85, the remaining portion of each spiral groove 40 that was not formed in the first rough cutting step 82 is formed. At the end of the second rough cutting step 85, the workpiece 35 is in a state where all the spiral grooves 40 are formed integrally.

[0085] 〈First finishing process〉

[0086] like Figure 8 As shown, in the first finishing process 92, the workpiece 35 whose first end 31 is mounted on the holding portion 61 of the machine tool 60 is subjected to cutting processing for making the shape of the first portion 41 of each spiral groove 40 the shape determined when the screw rotor 30 is designed. In the first finishing process 92, rough machining, intermediate finishing, and finishing are sequentially performed.

[0087] In the first finishing process 92 , the machine tool 60 performs cutting processing on the workpiece 35 while changing the relative positions of the workpiece 35 mounted on the holding portion 61 and the end mill 63 mounted on the rotating spindle 62 .

[0088] like Figure 8 As shown by the solid line, when processing the portion of the spiral groove 40 close to the first end 31 of the workpiece 35 mounted on the holding portion 61, the holding portion 61 of the machine tool 60 is far away from the rotating spindle 62. Figure 8 As shown by the two-dot chain line, as the portion cut by the end mill 63 approaches the second end 32 of the workpiece 35 , the interval between the holding portion 61 of the machine tool 60 and the rotating spindle 62 gradually narrows.

[0089] Therefore, in the first finishing process 92, the first portion 41, which is a part of the first end 31 side of the workpiece 35 in each spiral groove 40, is cut to perform a wall surface cutting of the first portion 41. As a result, the machine tool 60 can perform the processing of the workpiece 35 in the first finishing process 92 without interference between the holding portion 61 and the rotating spindle 62.

[0090] Fig.10 The cross section of the workpiece 35 at the end of the first finishing step 92 is shown. The cross section of the workpiece 35 is a cross section on a plane offset by a distance S from the center axis 33 of the workpiece 35. The distance S represents the offset amount of the seal plane 55 from the front surface of the gate rotor 51.

[0091] In the first finishing process 92, Fig.10 The workpiece 35 is cut with the point O of the Z axis as the origin of the Z axis. The origin O of the Z axis is located on the central axis 33 of the workpiece 35 mounted on the holding portion 61 of the machine tool 60. In addition, the origin O of the Z axis is at a distance L from the end surface of the holding portion 61. 1D Point. Distance L 1D It is determined by the design value of the screw rotor 30.

[0092] Will be located at Fig.10 The spiral groove 40 in the middle of the upper side is set as a specific spiral groove 40a. Fig.10The Z-axis coordinate of the midpoint of the width direction of the specific spiral groove 40a in the cross section shown is set to zero, and the wall surfaces 46, 47, and 48 of the first portion 41 of each spiral groove 40 are machined. It should be noted that the Z-axis is a coordinate axis that coincides with the central axis 33 of the workpiece 35 mounted on the holding portion 61 of the machine tool 60.

[0093] 〈First measurement process〉

[0094] In the first measurement step 93, the position of the first portion 41 of the specific spiral groove 40a in the direction of the center axis 33 (Z-axis direction) of the workpiece 35 is measured with the workpiece 35 in a state where the first end 31 is mounted on the holding portion 61 of the machine tool 60 after the machining in the first finishing step 92 is completed. Fig. 9 and Fig.10 The first measurement step 93 will be described. Fig.10 yes Fig. 9 A cross section of a workpiece 35 is shown.

[0095] In the first measuring step 93, the total length L of the workpiece 35 is measured. M It should be noted that the total length L of the workpiece 35 is M The measurement can also be performed during the period from the end of the previous step 71 to the start of the first measurement step 93.

[0096] Furthermore, in the first measuring step 93, as an index for determining the position of the first portion 41 of the specific spiral groove 40a, the measured Fig.10 The Z-axis coordinate of the wall surface of the first portion 41 of the specific spiral groove 40a in the cross section shown. Fig.10 The measured value of the Z-axis coordinate of the first side wall surface 46 of the specific spiral groove 40a shown is set to "-W D1M ", and the measured value of the Z-axis coordinate of the second side wall surface 47 of the specific spiral groove 40a shown in the figure is set as "W S1M If the machining error is zero, then W S1M =W D1M However, in reality, it is impossible for the machining error to be zero, so W S1M ≠W D1M .

[0097] Will Fig.10 The Z-axis coordinate of the center of the width direction of the specific spiral groove 40a in the cross section is set to the coordinate value C 1M . Coordinate value C 1M W S1M -W D1M ) / 2(C 1M =(W S1M -W D1M ) / 2). If the machining error is zero, the coordinate value C1M However, in reality, it is impossible for the machining error to be zero, so the coordinate value C 1M ≠0(zero).

[0098] 〈Second disassembly process〉

[0099] In the second disassembly step 94 , after the first measurement step 93 is completed, the workpiece 35 is disassembled from the holding portion 61 of the machine tool 60 .

[0100] 〈Second installation process〉

[0101] In the second mounting step 95, the workpiece 35 removed from the holding portion 61 of the machine tool 60 in the second disassembly step 94 is mounted again on the holding portion 61. Fig.11 As shown, in the second mounting step 95 , the second end 32 of the workpiece 35 is mounted on the holding portion 61 of the machine tool 60 .

[0102] 〈Second measurement process〉

[0103] In the second measuring step 96, the position of the first portion 41 of the specific spiral groove 40a in the direction of the center axis 33 (Z-axis direction) of the workpiece 35 is measured with the second end 32 mounted on the holding portion 61 of the machine tool 60 in the second mounting step 95. Fig.11 and Fig.12 The second measurement step 96 will be described. Fig.12 yes Fig.11 A cross section of a workpiece 35 is shown.

[0104] First, in the second measurement step 96, the origin O of the Z axis is determined for the workpiece 35 in a state where the second end 32 is mounted on the holding portion 61 of the machine tool 60. Specifically, the distance from the end surface of the holding portion 61 is (L M -L 1D ) is used as the origin O of the Z axis after the second mounting process 95 is completed. As described above, L M is the measured value of the total length of workpiece 35, L 1D This is a distance determined based on the design value of the screw rotor (30).

[0105] In the second measuring step 96, as an index for determining the position of the first portion 41 of the specific spiral groove 40a, the measured Fig.12 The Z-axis coordinate of the wall surface of the first portion 41 of the specific spiral groove 40a in the cross section shown. Fig.12 The measured value of the Z-axis coordinate of the first side wall surface 46 of the specific spiral groove 40a shown is set as “W D2M ", and the measured value of the Z-axis coordinate of the second side wall surface 47 of the specific spiral groove 40a shown in the figure is set to "-WS2M ”.

[0106] 〈Correction process〉

[0107] In the correction step 97 , a process is performed to calculate the displacement angle θ of the workpiece 35 and to correct the machining origin in the first finishing step 92 based on the calculated displacement angle θ.

[0108] The displacement angle θ is an angle around the central axis 33 of the workpiece 35. The displacement angle θ represents the amount of change in the circumferential position of the workpiece 35 at the end of the second mounting process 95 relative to the circumferential position of the workpiece 35 at the end of the first finishing process 92.

[0109] In the correction step 97, the displacement angle θ is calculated using the correlation between the position of the spiral groove 40 in the direction of the central axis 33 of the screw rotor 30 and the rotation angle of the screw rotor 30, which is determined based on the design value of the screw rotor 30, the position of the first portion 41 measured in the first measuring step 93, and the position of the first portion 41 measured in the second measuring step 96.

[0110] Reference Fig.13 The process of calculating the displacement angle θ of the workpiece 35 will be described.

[0111] Fig.13 (a) shows the workpiece 35 at the end of the second mounting step 95 assuming that the displacement angle θ is 0°. In this case, Fig.12 The absolute value W of the Z-axis coordinate of the first side wall surface 46 of the spiral groove 40 in the cross section is D2M The absolute value W of the Z-axis coordinate of the first side wall surface 46 measured in the first measuring step 93 D1M Consistent (W D2M =W D1M ). In addition, in this case, Fig.12 The absolute value W of the Z-axis coordinate of the second side wall surface 47 of the spiral groove 40 in the cross section is S2M The absolute value W of the Z-axis coordinate of the second side wall surface 47 measured in the first measuring step 93 S1M Consistent (W S2M =W S1M ).

[0112] However, in reality, it is impossible for the positions of the workpiece 35 immediately before the second disassembly step 94 and the workpiece 35 immediately after the second assembly step 95 to be completely identical in the circumferential direction of the workpiece 35. Fig.13 As shown in (b), W D2M ≠W D1M , W S2M ≠WS1M .

[0113] Will Fig.12 The Z-axis coordinate of the center of the width direction of the specific spiral groove 40a in the cross section shown is set to the coordinate value C 2M . Coordinate value C 2M W D2M -W S2M ) / 2(C 2M =(W D2M -W S2M ) / 2). Then, when the workpiece 35 in the second mounting step 95 is not displaced in the circumferential direction (refer to Fig.13 (a)) When the workpiece 35 is displaced in the circumferential direction in the second mounting step 95 (refer to Fig.13 (b)) When making a comparison, Fig.12 The displacement E of the specific spiral groove 40a in the cross section shown in the figure in the direction of the central axis 33 of the workpiece 35 is (C 2M -C 1M )(E=C 2M -C 1M ).

[0114] The spiral groove 40 of the screw rotor 30 is a groove extending in a spiral shape from the first end 31 side toward the second end 32 side of the screw rotor 30. When the screw rotor 30 is designed, the inclination angle of the spiral groove 40 with respect to the direction of the central axis 33 of the screw rotor 30 is determined. Therefore, there is a correlation between the position of the cross section of the spiral groove 40 in the direction of the central axis 33 of the screw rotor 30 and the rotation angle of the screw rotor 30, which is determined according to the design value of the screw rotor 30. Therefore, the displacement angle θ of the workpiece is calculated using this correlation and the displacement amount E of the specific spiral groove 40a in the direction of the central axis 33 of the workpiece 35.

[0115] In the correction step 97, the machining origin in the first finishing step 92 is corrected based on the calculated displacement angle θ of the workpiece 35. Fig.13 In the example shown, the machining origin in the first finishing step 92 is corrected to a machining origin based on the premise that the workpiece 35 is rotated by the displacement angle θ in the counterclockwise direction in the figure.

[0116] 〈Second finishing process〉

[0117] In the second finishing process 98, the workpiece 35 whose second end 32 is mounted on the holding portion 61 of the machine tool 60 is subjected to cutting so that the shape of the second portion 42 of each spiral groove 40 becomes the shape determined when the screw rotor 30 is designed. In the second finishing process 98, rough machining, intermediate finishing, and finishing are sequentially performed. The cutting in the second finishing process 98 is performed based on the machining origin corrected in the correction process 97.

[0118] Here, even when the correction step 97 is performed, it is impossible to completely eliminate the positional error between the first portion 41 and the second portion 42 of each spiral groove 40. Therefore, in the workpiece 35 (in other words, the finished screw rotor 30) that has been subjected to the second finishing step 98, a minute step is formed on the wall surface 46, 47, 48 of each spiral groove 40 as the boundary line 43 between the first portion 41 and the second portion 42.

[0119] - Features of the embodiment (1) -

[0120] In the method for manufacturing the screw rotor ( 30 ) of the present embodiment, the second finishing step ( 98 ) is performed after the first finishing step ( 92 ).

[0121] In the first finishing process 92, the first portion 41 of the spiral groove 40 is cut with the workpiece 35 whose first end 31 is mounted on the holding portion 61 of the machine tool 60. Therefore, in the first finishing process 92, the holding portion 61 holding the workpiece 35 is held in a state separated from the structure of the machine tool 60 other than the holding portion 61 (specifically, the rotating spindle 62 to which the cutting tool is mounted).

[0122] Furthermore, in the second finishing process 98, the second portion 42 of the spiral groove 40 is cut with respect to the workpiece 35 whose second end 32 is mounted on the holding portion 61 of the machine tool 60. Therefore, in the second finishing process 98, the holding portion 61 holding the workpiece 35 is held in a state separated from the structure of the machine tool 60 other than the holding portion 61.

[0123] Therefore, according to the manufacturing method of this embodiment, even when the screw rotor (30) is machined using a machine tool (60) of a conventional structure, the entire spiral groove (40) of the screw rotor (30) can be machined while the holding portion (61) holding the workpiece (35) is held in a state separated from the structure of the machine tool (60) other than the holding portion (61).

[0124] - Features of the embodiment (2) -

[0125] In the method for manufacturing the screw rotor 30 of the present embodiment, the first measuring step 93 is performed between the first finishing step 92 and the second disassembly step 94 , and the second measuring step 96 and the correction step 97 are sequentially performed between the second mounting step 95 and the second finishing step 98 .

[0126] In the correction process 97, the displacement angle of the workpiece 35 is calculated based on the position of the first portion 41 measured in the first measurement process 93 and the position of the first portion 41 measured in the second measurement process 96. In the correction process 97, the machining origin in the first finishing process 92 is also corrected based on the calculated displacement angle. In the second finishing process 98, the second portion 42 of the spiral groove 40 is cut based on the machining origin corrected in the correction process 97. Therefore, the error in the relative position of the first portion 41 and the second portion 42 of the spiral groove 40 can be suppressed to a small value. As a result, the step constituting the boundary line 43 between the first portion 41 and the second portion 42 in each spiral groove 40 can be suppressed to a small value.

[0127] - Features of the embodiment (3) -

[0128] The spiral groove 40 of the screw rotor 30 is a groove extending in a spiral shape from the first end 31 side toward the second end 32 side of the screw rotor 30. When the screw rotor 30 is designed, the inclination angle of the spiral groove 40 with respect to the direction of the central axis 33 of the screw rotor 30 is determined. Therefore, there is a correlation between the position of the cross section of the spiral groove 40 in the direction of the central axis 33 of the screw rotor 30 and the rotation angle of the screw rotor 30, which is determined according to the design value of the screw rotor 30. This correlation is a correlation unique to the screw rotor 30 in which the spiral groove 40 is formed.

[0129] In the method for manufacturing the screw rotor (30) of the present embodiment, the displacement angle θ of the workpiece (35) at the end of the second mounting step (95) is calculated using a correlation determined based on the design value of the screw rotor (30). Therefore, the displacement angle θ can be calculated with high accuracy, and the error in the relative position of the first portion (41) and the second portion (42) of the spiral groove (40) can be suppressed to be small.

[0130] - Features of the embodiment (4) -

[0131] In each spiral groove 40 of the screw rotor 30 manufactured by the manufacturing method of the present embodiment, the boundary line 43 between the first portion 41 and the second portion 42 is formed at a position relatively close to the suction side end 45 of the spiral groove 40. Specifically, in each spiral groove 40 of the screw rotor 30 of the present embodiment, the boundary line 43 between the first portion 41 and the second portion 42 is formed at a position close to the suction side end 45 with respect to the center of the extension direction of the spiral groove 40.

[0132] The boundary line 43 between the first portion 41 and the second portion 42 is a small step. Therefore, when the gate 52 of the gate rotor 51 passes the boundary line 43 while sliding relative to the wall surfaces 46, 47, 48 of the spiral groove 40, the sealing between the wall surfaces 46, 47, 48 of the spiral groove 40 and the gate 52 may become insufficient.

[0133] On the other hand, the period when the gate 52 is located relatively close to the suction side end 45 of the spiral groove 40 is the initial stage of the compression stroke in the compression chambers 21 and 22. In the initial stage of the compression stroke, the pressure of the refrigerant in the compression chambers 21 and 22 has not increased much relative to the pressure of the refrigerant sucked into the compression chambers 21 and 22. Therefore, even if the sealing between the wall surfaces 46, 47, 48 of the spiral groove 40 and the gate 52 is insufficient at the initial stage of the compression stroke, the amount of refrigerant leaking from the compression chambers 21 and 22 is very small.

[0134] Therefore, in the manufacturing method of this embodiment, even when the first part 41 and the second part 42 of the spiral groove 40 of the screw rotor 30 are processed separately, the amount of refrigerant leaking from the compression chambers 21 and 22 of the screw compressor 10 can be suppressed to a small amount, and the efficiency of the screw compressor 10 can be maintained at a high level.

[0135] - Features of the embodiment (5) -

[0136] In the screw rotor 30 manufactured by the manufacturing method of the present embodiment, the boundary line 43 formed on the wall surface of each spiral groove 40 is inclined relative to the intersection line between the wall surface 46, 47, 48 of the spiral groove 40 and the sealing plane 55. Therefore, the sealing line 53 of the gate 52 that moves relatively from the suction side end 45 toward the discharge side end 44 of the spiral groove 40 intersects the boundary line 43 at one point in the process of the gate 52 crossing the boundary line 43 from the second portion 42 to the first portion 41 (see Figure 5 ).

[0137] In each spiral groove 40 of the screw rotor 30 of the present embodiment, the boundary line 43 between the first portion 41 and the second portion 42 is a tiny step. Therefore, if the boundary line 43 is formed on the "intersection line between the wall surfaces 46, 47, 48 of the spiral groove 40 and the sealing plane 55", when the gate 52 moving inside the spiral groove 40 crosses the boundary line 43 from the second portion 42 to the first portion 41, the sealing line 53 of the gate 52 will pass through the boundary line 43 as a step as a whole at the same time. When the sealing line 53 passes through the boundary line 43 as a whole at the same time, an impact force may act on the sealing line 53 of the gate 52, and the gate 52 may be damaged.

[0138] In contrast, in the screw rotor 30 of the present embodiment, the boundary line 43 between the first portion 41 and the second portion 42 in the spiral groove 40 and the sealing line 53 of the gate 52 passing through the boundary line 43 from the suction side end 45 to the discharge side end 44 of the spiral groove 40 intersect at one point. Therefore, in the process where the gate 52 passes through the boundary line 43 between the first portion 41 and the second portion 42, the force acting on the gate 52 can be suppressed to be small, and the possibility of the gate 52 being damaged can be reduced, thereby maintaining the reliability of the screw compressor 10 at a high level.

[0139] - Modifications of the Implementation Methods -

[0140] The manufacturing method of this embodiment can also manufacture a screw rotor having a shape in which the suction-side end of the spiral groove opens at the first end of the screw rotor.

[0141] Furthermore, the screw rotor manufactured by the manufacturing method of the present embodiment may be provided in a screw compressor that performs single-stage compression.

[0142] The above describes the implementation and variants, but it should be understood that various changes can be made to their forms and specific circumstances without departing from the subject matter and scope of the claims. In addition, the elements involved in the above implementation, variants, and other implementations can also be appropriately combined or replaced. In addition, the words "first", "second", "third"... in the specification and claims are only used to distinguish sentences containing the above words, and are not intended to limit the number or order of the sentences. .

[0143] - Industrial Applicability -

[0144] As described above, the present disclosure is useful for a method for manufacturing a screw rotor, a screw rotor, and a screw compressor.

[0145] - Explanation of symbols -

[0146] 10 screw compressor

[0147] 30 screw rotor

[0148] 31 First End

[0149] 32 Second End

[0150] 33Center Axis

[0151] 35 Workpieces

[0152] 40 spiral grooves

[0153] 40a specific spiral groove

[0154] 41 Part 1

[0155] 42 Part 2

[0156] 43 Border Line

[0157] 44 ejection side end

[0158] 45 Suction side

[0159] 51 gate rotor

[0160] 52 gates

[0161] 53 Sealing line

[0162] 60 Machine Tools

[0163] 61 Holding unit

[0164] 84First installation process

[0165] 92First finishing process

[0166] 93First measurement process

[0167] 94 Disassembly process

[0168] 95 Second installation process

[0169] 96 Second measurement process

[0170] 97 Correction Process

[0171] 98 Second finishing process

Claims

1. A method for manufacturing a screw rotor (30), wherein the screw rotor (30) is manufactured by forming a plurality of spiral grooves (40) on a cylindrical workpiece (35), wherein the screw rotor (30) is used in a screw compressor, wherein: In the manufacturing method of the screw rotor (30), the plurality of spiral grooves (40) are respectively divided into a first portion (41) and a second portion (42), wherein the first portion (41) includes an end portion on the first end (31) side of the workpiece (35), and the second portion (42) includes an end portion on the second end (32) side of the workpiece (35). In the method for manufacturing the screw rotor (30), a first mounting step (84), a first finishing step (92), a disassembly step (94), a second mounting step (95), and a second finishing step (98) are performed. In the first mounting step (84), the first end (31) of the workpiece (35) is mounted on a holding portion (61) of a machine tool (60). The first finishing step (92) is to finish the first portion (41) of each of the plurality of spiral grooves (40) by cutting after the first mounting step (84) is completed. The disassembly step (94) is to disassemble the workpiece (35) from the holding portion (61) after the first finishing step (92) is completed. In the second mounting step (95), the second end (32) of the workpiece (35) removed from the holding portion (61) in the removal step (94) is mounted on the holding portion (61). The second finishing step (98) is to finish the second portion (42) of each of the plurality of spiral grooves (40) by cutting after the second mounting step (95) is completed.

2. The method for manufacturing a screw rotor (30) according to claim 1, characterized in that: In the method for manufacturing the screw rotor (30), one of the plurality of spiral grooves (40) is used as a specific spiral groove (40a), In the method for manufacturing the screw rotor (30), a first measuring step (93), a second measuring step (96), and a correction step (97) are performed. The first measuring step (93) measures the position of the first portion (41) of the specific spiral groove (40a) in the direction of the central axis (33) of the workpiece (35) after the first finishing step (92) is completed and before the disassembly step (94) begins, The second measuring step (96) measures the position of the first portion (41) of the specific spiral groove (40a) in the direction of the central axis (33) of the workpiece (35) after the second mounting step (95) is completed and before the second finishing step (98) begins, In the correction process (97), a displacement angle is calculated based on the position of the first part (41) measured in the first measuring process (93) and the position of the first part (41) measured in the second measuring process (96), and the processing origin of the first finishing process (92) is corrected using the calculated displacement angle, wherein the displacement angle is an angle around the central axis (33) of the workpiece (35), and represents the amount of change in the circumferential position of the workpiece (35) at the end of the second installation process (95) relative to the circumferential position of the workpiece (35) at the end of the first finishing process (92), In the second finishing step (98), cutting is performed based on the machining origin corrected in the correction step (97).

3. The method for manufacturing a screw rotor (30) according to claim 2, characterized in that: In the correction step (97), the displacement angle is calculated using the correlation between the position of the spiral groove (40) in the direction of the central axis (33) of the screw rotor (30) determined based on the design value of the screw rotor (30) and the rotation angle of the screw rotor (30), the position of the first portion (41) measured in the first measuring step (93), and the position of the first portion (41) measured in the second measuring step (96).

4. The method for manufacturing a screw rotor (30) according to any one of claims 1 to 3, characterized in that: In each of the plurality of spiral grooves (40), the length of the first portion (41) in the extension direction of the spiral groove (40) is longer than the length of the second portion (42) in the extension direction of the spiral groove (40).

5. The method for manufacturing a screw rotor (30) according to claim 4, characterized in that: In each of the plurality of spiral grooves (40), the first portion (41) is a portion including an ejection side end (44) of the spiral groove (40). In each of the plurality of spiral grooves (40), the second portion (42) is a portion including a suction side end (45) of the spiral groove (40).

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