Title of Invention

A ROTOR OF A TURBO COMPRESSOR

Abstract

The invention provides a rotor 17 of a turbo compressor having an impeller 21 and a rotary shaft 12 that supports the impeller 21. The rotor includes a fastening mechanism 70 having a mechanical joint 71 formed at an end face of each of the impeller 21 and the rotary shaft 12, a tension bolt 74 inserted through a through-hole formed in the center of rotation of the impeller 21, a fastening nut 80 screwed to a first male thread 77 formed at one end of the tension bolt 74, a housing hole 78 formed at an end face of the rotary shaft 12 to house a portion of an elongated portion 75 of the tension bolt 74, and a female thread 78 formed at a bottom face of the housing hole 78 and screwed to a second male thread 76 formed at the other end of the tension bolt 74. According to the invention, the amount of elongation of the tension bolt is increased, so that the efficiency of coupling work can be improved, and stabilization can be achieved.

Full Text

1A BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a tension bolt for a compressor. Priority is claimed on Japanese Patent Application No. 2006-318822, filed November 27, 2006, the content of which is incorporated herein by reference. Description of the Related Art As industrial turbo compressors, a turbo compressor that compresses air, etc. at a plurality of stages is known. In this turbo compressor, a rotary shaft to which an impeller is connected is rotated via a gear train by a driving motor. There is a rotor in which an impeller is connected only to one end of a rotary shaft, a rotor in which impellers are respectively connected to both ends of a rotary shaft, or a rotor in which a plurality of such rotary shafts are provided. In any of them, a curvic coupling is used for a coupling joint between the rotary shaft and the impeller, and a tension bolt is used for a fastening mechanism of the joint. The curvic coupling that couples the rotary shaft and the impeller is made to generate a high pressing force by the axial force of the tension bolt, thereby preventing the occurrence of looseness by an acute temperature change or a vibration (refer to JP-A-4-321724 (FIG. 1)). When the curvic coupling between the rotary shaft and the impeller is fastened using the tension bolt, a fastening nut is screwed when the tension bolt is pulled to a predetermined range of the amount of elongation. The amount of elongation of the tension bolt is measured by a dial gauge. By controlling the amount of elongation of the tension bolt, the axial force (tensile force during fastening) of the tension bolt is 2 controlled indirectly. Although it is desirable that the axial force by the tension bolt be larger, an upper limit by the elastic limit of a material for the bolt exists. Further, a lower limit of the axial force that is determined from the viewpoint of prevention of looseness of the tension bolt, etc. also exists. For this reason, the tensile force of the tension bolt needs to be controlled between the lower limit and the upper limit. However, since the amount of elongation of the tension bolt is extremely small, operation will be repeated many times in order to obtain the amount of elongation targeted. As a result, there is a problem in that the operating efficiency may be lowered. SUMMARY OF THE INVENTION The invention has been made in view of the above situations, and it is therefore an object of the invention to provide a rotor of a turbo compressor capable of increasing the amount of elongation of a tension bolt for fastening an impeller and a rotary shaft of the turbo compressor, thereby improving the efficiency of coupling operation, and achieving stabilization. The following means have been adopted in the rotor of a turbo compressor according to the invention in order to solve the above problems. A first invention provides a rotor of a turbo compressor having an impeller and a rotary shaft that supports the impeller. The rotor includes a fastening mechanism having a mechanical joint formed at an end face of each of the impeller and the rotary shaft, a tension bolt inserted through a throueh-hole formed in the center of rotation of the impeller, a fastening nut screwed to a first male thread formed at one end of the tension bolt, a housing hole formed at an end face of the rotary shaft to house a portion of an elongated portion of the tension bolt, and a female thread formed at a bottom face of the housing hole and screwed to a second male thread formed at the other end of the tension bolt. Preferably, the depth of the housing hole is specified according to the amount of elongation of the tension bolt. Preferably, the depth of the housing hole is 10% or more of the length of the elongated portion. Preferably, the rotor of a turbo compressor further includes a washer that is fitted on one end of the tension bolt and is provided between the impeller and the fastening nut. Here, a combined length of the depth of the housing hole and the thickness of the washer may be 10% or more of the length of the elongated portion. A second invention provides a rotor of a turbo compressor having an impeller and a rotary shaft that supports the impeller. The rotor includes a fastening mechanism having a mechanical joint formed at an end face of each of the impeller and the rotary shaft, a tension bolt inserted through a through-hole formed in the center of rotation of the impeller, a fastening nut screwed to a first male thread formed at one end of the tension bolt, n female i'hrend formed at an end face of the rotarv shaft and screwed to a second male thread formed at the other end of the tension bolt, and a protruding portion formed so as to protrude from a rear central portion of the impeller to house a portion of an elongated portion of the tension bolt. Preferably, the protruding amount of the protruding portion is specified according to the amount of elongation of the tension bolt. Preferably, the protruding amount of a protruding portion is 10% or more of the length of the elongated portion. Preferably, the rotor of a turbo compressor further includes a washer that is fitted on one end of the tension bolt and is provided between the impeller and the fastening nut. 4 Here, a combined length of the protruding amount and the thickness of the washer may be 10% or more of the length of the elongated portion. According to the invention, the following effects can be obtained. In the rotor of the turbo compressor according to the invention, in the fastening mechanism that fastens the impeller to one end of the rotary shaft, the total length of the tension bolt can be increased. Thus, the control width of the amount of elongation of the tension bolt during assembling (upper limit of the amount of elongation - lower limit of the amount of elongation) can be increased, and adjustment work can be facilitated. Accordingly, the workability and working efficiency of assembling can be improved. Further, a portion of the tension bolt is housed in the housing hole formed at the end face of the rotary shaft or in the protruding portion formed at the rear central portion of the impeller. Thus, even if the length of the tension bolt becomes long, the total length of a unit in which the impeller is fastened to the rotary shaft can be made unchanged. Accordingly, stable operation can be achieved without lowering the critical velocity of the rotary shaft. Further, the shape change of other members is also unnecessary and consequently a cost rise can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view showing a schematic configuration of a turbo compressor 1 according to embodiments of the invention; FIG. 2 is a sectional view showing principal parts of the turbo compressor 1 including rotors 17 and 18 according to the embodiments of the invention; FIG. 3 is an exploded sectional view showing a fastening mechanism 70 according to a first embodiment of the invention; FIG. 4 A is a sectional view of the fastening mechanism 70 according to the first 5 embodiment of the invention, and FIG. 4B is a conventional example of a fastening mechanism; FIG. 5 is a sectional view showing a modified example of the fastening mechanism 70 according to the first embodiment; and FIG. 6A is a sectional view of a fastening mechanism 90 according to a second embodiment of the invention, and FIG. 6B is an exploded perspective view of the fastening mechanism. DETAILED DESCRIPTION OF THE INVENTION Hereinafter, embodiments of rotors of a turbo compressor according to the invention will be described with reference to the accompanying drawings. FIG. 1 is a top view showing a schematic configuration of a turbo compressor 1 according to the present embodiment. FIG. 2 is a sectional view showing principal parts of the turbo compressor 1 including rotors 17 and 18 according to the embodiment of the invention; The turbo compressor 1 includes a driving motor 2, a gear unit 10 that is connected to an output shaft 3 of the driving motor 2. a first stage compressor 6 that has a first impeller 21 that is rotated at an increased speed by the gear unit 10, a second stage compressor 7 that has a second impeller 22 that is rotated at an increased speed by the gear unit 10, a third stage compressor 8 that has a third impeller 23 that is rotated at an increased speed by the gear unit 10, a fourth stage compressor 9 that has a fourth impeller 24 that is rotated at an increased speed by the gear unit 10, and the like. Further, the turbo compressor 1 includes a gas flow passage for leading the gas A, such as oxygen, which has been sucked from the outside, in order of the second stage compressor 7, the third stage compressor 8, and the fourth stage compressor 9 from the first stage compressor 6, to discharge it to the outside. 6 This gas flow passage is provided with a first intercooler 41 that cools the gas A compressed by the first stage compressor 6, a second intercooler 42 that cools the gas A compressed by the second stage compressor 7, and a third intercooler 45 that cools the gas A compressed by the third stage compressor 8. Further, the turbo compressor 1 also includes an oil storage chamber (not shown) that stores oil R for lubricating the gear unit 10. The driving motor 2 is attached to a gear case 5 that houses the gear unit 10 via a flange. The output shaft 3 of the driving motor 2 is connected to a first rotary shaft 11 of the gear unit 10 via a joint. As shown in FIG. 2, the first rotary shaft 11 is rotatably supported by the gear case 5. The output shaft 3 of the driving motor 2 is connected to one end of the first rotary shaft 11 through a bearing, and a first gear 14 having a large diameter is attached to the other end of the first rotary shaft 11. The first gear 14 meshes with a second gear 15 having a small diameter provided in a second rotary shaft 12 and a third gear 16 having a small diameter provided in a third rotary shaft 13. This "ear unit 10 accelerates the rotation of the output shaft 3 of the driving motor 2, and transmits the rotation to the second rotary shaft 12 and the third rotary shaft 13. The second rotary shaft 12 is rotatably supported by the gear case 5 in a position parallel to the first rotary shaft 11. Also, the first impeller 21 and the second impeller 22 are respectively provided at both ends of the second rotary shaft 12. The second rotary shaft 12 is supported so as to extend towards both sides of the gear unit 10. The first impeller 21 is arranged at the end of the second rotary shaft on the side opposite the driving motor, and the second impeller 22 is arranged at the end of the second rotary shaft on the side of the driving motor. 7 The third rotary shaft 13 is rotatably supported by the gear case 5 in a position parallel to the first rotary shaft 11 and opposite to the second rotary shaft 12 with respect to the first rotary shaft 11. Also, the third impeller 23 and the fourth impeller 24 are respectively provided at both ends of the third rotary shaft 13. The third rotary shaft 13 is supported so as to extend towards both sides of the gear unit 10. The third impeller 23 is arranged at the end of the third rotary shaft on the side opposite the driving motor, and the fourth impeller 24 is arranged at the end of the third rotary shaft on the side of the driving motor. Here, the second rotary shaft 12, the first impeller 21, and the second impeller 22 are called a first rotor 17, and the third rotary shaft 13, the third impeller 23, and the fourth impeller 24 are called a second rotor 18. The first impeller 21 is housed in a cylindrical recessed portion 25 formed in a side portion of the gear case 5. The second impeller 22 is housed in a cylindrical recessed portion 26 formed in a side portion on the side opposite to the first impeller 21 across the gear case 5. Similarly, the third impeller 23 is housed in a recessed portion 27, and the fourth impeller 24 is housed in a recessed portion 28. A vortex chamber, a suction passage, and a diffuser are formed in these recessed portions 25 to 28. In addition, the gear case 5 can be split vertically in a horizontal section, and the first to third rotary shafts 11 to 13, and the first and third gears 14 to 16 can be detached by removing an upper lid of the gear case 5. FIG, 3 is an exploded sectional view showing a fastening mechanism 70 according to a first embodiment. A fastening mechanism 70 fastens the second rotary shaft 12 and the first impeller 21 or second impeller 22 in the first rotor 17. Further, the fastening 8 mechanism fastens the third rotary shaft 13 and the third impeller 23, or fourth impeller 24 in the second rotor 18. Hereinafter, the fastening mechanism 70 that fastens the second rotary shaft 12 and the first impeller 21 will now be described. The fastening mechanism 70 includes a curvic coupling 71 (curvic: registered trademark) that fastens the second rotary shaft 12 and the first impeller 21 so that their axes may coincide with each other, a tension bolt 74 that pinches and supports the second rotary shaft 12 and the first impeller 21 under predetermined pressure, a fastening nut 80, and the like. The curvic coupling 71 consists of a curvic toothed portion 72 formed in the shape of a face gear at an end face 12a of the second rotary shaft 12, and a curvic toothed portion 73 formed in the shape of a face gear at a rear central end face 21a of the first impeller 21. By making the curvic toothed portion 72 and the curvic toothed portion 73 face each other and mesh with each other, the axis of rotation of the second rotary shaft 12 and the axis of rotation of the first impeller 21 coincide with each other. As shown in FIG. 3, the tension bolt 74 is obtained by forming male threads 76 and 77 at both ends of a high-strength steel rod, and adds a tensile force during attachment to press (pinch) a member arranged between the male threads 76 and 77 by a reaction force (axial force) to the tensile force. The tension bolt 74 consists of the male threads 76 and 77 formed at both ends, and an elongated portion 75 between the male threads76 and 77. The size of the male thread 76 or 77 is, for example, about Ml 2 to M22, and although the length of the elongated portion 75 is specified according to the length of the first impeller 21, it is, for example, about 150 mm. A housing hole 78 in which the male thread 76 and a portion of the elongated 9 portion 75 of the tension bolt 74 are housed is formed at the end face 12a of the second rotary shaft 12. Furthermore, a female thread 79 that is screwed to the male thread 76 is formed at a bottom face 78a of the housing hole 78. Accordingly, when the male thread 76 of the tension bolt 74 is inserted into the housing hole 78 formed at the end face 12a of the second rotary shaft 12 and further, the male thread 76 is screwed to the female thread 79, the tension bolt 74 is erected perpendicularly to the end face 12a of the second rotary shaft 12. In addition, the total depth of the housing hole 78 and female thread 79 is greater than the length of the male thread 76 of the tension bolt 74. Accordingly, when the male thread 76 of the tension bolt 74 is screwed to the female thread 79, a portion of the elongated portion 75 of the tension bolt 74 in the vicinity of the male thread 76 will be inevitably housed in the housing hole 78. Meanwhile, a through-hole 21c for allowing the tension bolt 74 to be inserted therethrough is formed in the center of rotation (axis) of the first impeller 21. The length of the first impeller 21 (distance from the rear central end face 21a to a front central end face 21b) is made slightly greater than the length of the elongated portion 75 protruding from the end face 12a of the second rotary shaft 12. Accordingly, when the tension bolt 74 that is erected perpendicularly to the end face 12a of the second rotary shaft 12 is inserted through the through-hole 21c of the first impeller 21, the male thread 77 of the tension bolt 74 protrudes from the front central end face 21b of the first impeller 21. Then the first impeller 21 is fastened to the end face 12a of the second rotary shaft 12 by screwing the fastening nut 80 to the male thread 77. Next, the assembling sequence of the fastening mechanism 70 will now be described. 10 As described above, the tension bolt 74 is inserted into the housing hole 78 formed at the end face 12a of the second rotary shaft 12, and further the male thread 76 of the tension bolt 74 is screwed to the female thread 79 formed at the bottom face of the housing hole 78. Next, the tension bolt 74 erected from the end face 12a of the second rotary shaft 12 is inserted into the first impeller 21, thereby making the curvic toothed portion 72 formed at the end face 12a of the second rotary shaft 12 and the curvic toothed portion 73 formed at the rear central end face 21a of the first impeller 21 mesh with each other. Then, the fastening nut 80 is screwed to the male thread 77 of the tension bolt 74 protruding from the front central end face 21b of the first impeller 21, thereby performing temporary stopping. Next, when the fastening nut 80 is fastened and is fixed, a hydraulic tension device (not shown) is connected to the male thread 77 of the tension bolt 74, thereby giving a desired tensile force to the tension bolt 74. Then, the fastening nut 80 is finally fastened to the tension bolt 74 with the tensile force added. Whether or not the tensile force is a desired value is indirectly determined by measuring the amount of elongation of the tension bolt 74 (elongated portion 75). The amount of elongation of the tension bolt 74 (elongated portion 75) is measured by a vernier caliper, a micrometer, or a dial gauge 85. In addition, the measurement resolution of the dial gauge 85 is 0.01 mm. That is, when the amount of elongation of the tension bolt 74 (elongated portion 75) falls within a predetermined range, the fastening nut 80 is screwed to the tension bolt 74. Then, the tensile processing by the hydraulic tension device is stopped, and the hydraulic tension device is removed from the tension bolt 74. 11 By passing through such an operation, the curvic coupling 71 (curvic toothed portions 72 and 73) is always pressed under a predetermined pressure by the axial force of the tension bolt 74. Accordingly, the axis of rotation of the second rotary shaft 12 and the axis of rotation of the first impeller 21 coincide with each other, and the second rotary shaft 12 and the first impeller 21 are always coupled together without loosening. FIG. 4A is a sectional view of the fastening mechanism 70 according to the first embodiment, and FIG. 4B is a conventional example of a fastening mechanism. In the fastening mechanism 70, the total length of the tension bolt 74 is longer than that of a conventional example. To be exact, the length L of the elongated portion 75 is longer than the length LI of the conventional example (the length of the male thread 76 or 77 is the same). For this reason, when the tension bolt 74 and the tension bolt of the conventional example are pulled with the same force by the hydraulic tension device, the amount of elongation of the tension bolt 74 becomes greater by such amount that the elongated portion 75 is longer. In addition, a portion of the male thread 76 or 77 of the tension bolt 74 is also elongated integrally with the elongated portion 75. That is, the portion of the male thread 76 or 77 that is screwed to neither the female thread 79 nor the fastening nut 80 is elongated. Accordingly, to be exact, a combined portion of the portion of the male thread 76 or 77 that is screwed to neither the female thread 79 nor the fastening nut 80 and the elongated portion 75 becomes a substantially elongated portion. Meanwhile, as for a tensile force to be piven to the tension bolt 74 bv the hydraulic tension device, its upper limit and lower limit are set. The upper limit of the tensile force is specified according to the yield force of the tension bolt 74. On the other hand, the lower limit of the tensile force is specified 12 according to a force that is required to prevent looseness of the tension bolt 74 of the male thread 76 and 77, or a force that presses the first impeller 21 against the second rotary shaft 12 by means of the tension bolt 74. Specifically, the tensile force to be given to the tension bolt 74 is set to 0.5 to 0.7 of the yield stress ay of the tension bolt 74 (upper limit: 0.7 ay and lower limit: 0.5 ay). If the strength section of the tension bolt 74 is 10.9 (JIS B 1051:2000) and the length L of the elongated portion 75 is 150 mm, the control value width of the amount of elongation (upper limit of the amount of elongation - lower limit of the amount of elongation) will be set to about 0.13 mm when a tensile force within the above-mentioned range is given to the tension bolt 74. Accordingly, it is possible to manage the amount of elongation of the tension bolt 74 (elongated portion 75) with high precision by using the dial gauge 85. As described above, the amount of elongation of the tension bolt 74 becomes greater than that of the tension bolt of the conventional example by such an amount that the elongated portion 75 is longer. For this reason, as for the tension bolt 74, the control value rnrmc of the amount of elongation of. the lension bolt 74 becomes greater than before. Accordingly, since the attention that is needed to control the amount of elongation during assembling of the tension bolt 74 is more reduced than before, the operability and operating efficiency of the assembling is improved. Here, the depth of the housing hole 78 in which a portion of the elongated portion 75 of the tension bolt 74 (the male thread 76 side) is housed is set to be 10% or more (for example, 15 mm or more) of the total length of the elongated portion 75 (for example, 150 mm). 13 In other words, the length L of the elongated portion 75 of the tension bolt 74 (for example, 150 mm) is greater than the length LI of the elongated portion of the conventional tension bolt (for example, 135 mm) by 10% or more. The length of the portion of the elongated portions 75 of the tension bolt 74 that is housed in the housing hole 78 (for example, 15 mm) will have an amount of elongation of 0.01 mm or more when a tensile force is given by a hydraulic tension device during assembling. Since the amount of elongation of 0.01 mm or more is more than the measurement resolution of the dial gauge 85, it is possible to reliably measure even the amount of elongation by the dial gauge 85. As described above, according to the turbo compressor 1 of the present embodiment, in the fastening mechanism 70 in which the first impeller 21 and the second impeller 22 are fastened to both ends of the second rotary shaft 12 of the first rotor 17, the total length (especially the length L of the elongated portion 75) of the tension bolt 74 is greater than that of the conventional example. Thus, the control value width of the amount of elongation of the tension bolt 74 during assembling (upper limit of the amount of elongation - lower limit of the amount of elongation) can be made greater than before. Accordingly, since the attention that is needed to control the amount of elongation is more reduced than before, the operability and operating efficiency of the assembling is improved. Moreover, a portion of the tension bolt 74 is housed in the housing hole 78 formed at the end face 12a of the second rotary shaft 12. Thus, even if the total length of the tension bolt 74 is greater then before, the total lenth of a unit in which the first impeller 21 and the second impeller 22 are fastened to the second rotary shaft 12 can be made the same as that of the conventional case. Accordingly, stable operation can be achieved without lowering the critical 14 velocity of a rotary shaft. Further, there are advantages in that the shape change of other members is unnecessary and the cost hardly rises. FIG. 5 is a sectional view showing a modified example of the fastening mechanism 90 according to the first embodiment. The fastening nut 80 is screwed to the male thread 77 of the tension bolt 74 via a washer 81. This makes it possible to further increase the length L of the elongated portion 75 of the tension bolt 74. That is, the length L of the elongated portion 75 can be increased by the thickness of the washer 81. Accordingly, the operability and operating efficiency of assembling can be further improved. [Second Embodiment] FIG. 6A is a sectional view of a fastening mechanism 90 according to a second embodiment, and FIG. 6B is a conventional example of a fastening mechanism. The fastening mechanism 90 fastens both ends of the second rotary shaft 12 to the first impeller 21 and the second impeller 22, similarly to the fastening mechanism 70 according to the first embodiment. Hereinafter, only portions different from the fastening mechanism 70 according to the first embodiment will be described, the same reference numerals are given to the same portions, and the description thereof is omitted herein. The fastening mechanism 90 includes a curvic coupling 71 that fastens the second rotary shaft 12 and the first impeller 21 so that their axes may coincide with each other, a tension bolt 74 that pinches and supports the second rotary shaft 12 and the first impeller 21 under predetermined pressure, a fastening nut 80, and the like. The curvic coupling 71 consists of a curvic toothed portion 72 formed at an end face 12a of the second rotary shaft 12, and a curvic toothed portion 73 formed at an end 15 face 21 a of a protruding portion 2 If that protrudes from the center of a rear face of the first impeller 21. The tension bolt 74 consists of the male threads 76 and 77 formed at both ends, and an elongated portion 75 between the male threads 76 and 77. The size of the male thread 76 or 77 is, for example, about M12 to M22, and although the length of the elongated portion 75 is specified according to the length of the first impeller 21, it is, for example, about 150 mm. A female thread 79 that is screwed to the male thread 76 of the tension bolt 74 is formed at the end face 12a of the second rotary shaft 12. When the male thread 76 is screwed to the female thread 79, the tension bolt 74 is erected perpendicularly to the end face 12a of the second rotary shaft 12. Meanwhile, a through-hole 21c for allowing the tension bolt 74 to be inserted therethrough is formed in the center of rotation (axis) of the first impeller 21. The through-hole 21c is also formed in the protruding portion 21 f that protrudes from the center of the rear face of the first impeller 21. That is, a portion of the elongated portion 75 of the tension bolt 74 is housed in the protruding portion 21 f. The length of the first impeller 21 (distance from the rear central end face 21a to a front central end face 21b) is made slightly greater than the length of the elongated portion 75 protruding from the end face 12a of the second rotary shaft 12. Accordingly, when the tension bolt 74 that is erected perpendicularly to the end face 12a of the second rotary shaft 12 is inserted through the through-hole 21c of the first impeller 21, the male thread 77 of the tension bolt 74 protrudes from the front central end face 21b of the first impeller 21. Then, the first impeller 21 is fastened to the end face 12a of the second rotary shaft 12 by fitting the washer 81 onto the male thread 77, and further screwing the 16 fastening nut 80 thereto. In addition, the washer 81 may not be provided. Also, the length of the protruding portion 21 f that protrudes from the center of the rear face of the first impeller 21 is set to be 10% or more (for example, 15 mm or more) of the total length (for example, 150 mm) of the elongated portion 75 of the tension bolt 74. By such a configuration, the fastening mechanism 90 can obtain the same effects as the fastening mechanism 70 according to the first embodiment. That is, since the total length of the tension bolt 74 (especially the length L of the elongated portion 75) is greater than that of the conventional example, the control value width of the amount of elongation of the tension bolt 74 during assembling (upper limit of the amount of elongation - lower limit of the amount of elongation) can be made greater than before. Accordingly, since the attention that is needed to control the amount of elongation is more reduced than before, the operability and operating efficiency of the assembling is improved. Further, a portion of the tension bolt 74 is housed in the protruding portion 21f protruding from the center of the rear face of the first impeller 21, and the length of the second rotary shaft 12 becomes short by that much. Thus, even if the total length of the tension bolt 74 is greater than before, the total length of a unit in which the first impeller 21 and the second impeller 22 are fastened to the second rotary shaft 12 can be made the same as that of the conventional case. Accordingly, there are advantages in that the shane chanee of other members is unnecessary and the cost hardlv rises- Here, the operation sequence or various shapes or combinations of respective constructional members shown in the above-described embodiments are merely examples, and various changes may be made on the basis of process conditions, design 17 requirements, or the like without departing from the spirit or scope of the invention. Although the above-described embodiment has been described for the case where the turbo compressor 1 is of a so-called uniaxial two-stage type, the invention is not limited thereto. For example, the turbo compressor may be a so-called biaxial two-stage type, biaxial three-stage type, a biaxial four-stage type, etc. Further, the invention can also be applied to a uniaxial one-stage type. Even if the turbo compressor is of any one of these types, the fastening mechanisms 70 and 90 can be used as means that fasten a rotary shaft and an impeller of a rotor. The number of washers 81 and fastening nuts 80 to the male thread 77 of the tension bolt 74 can be changed according to design conditions. For example, two fastening nuts 80 may be attached for prevention of looseness. Although the dial gauge 85 has been described as a measuring device that measures the amount of elongation of the tension bolt 74, the invention is not limited thereto. The measuring device may be a micrometer and a vernier caliper. Further, a non-contact measuring device, such as a laser length-measuring device, may be used. Further, although the case where a hydraulic tension device is used has been described as the method of applying a tensile force to the tension bolt 74, the invention is not limited thereto. A case where the fastening nut 80 is fastened by a wrench and the amount of elongation of the tension bolt 74 is measured may be adopted. Although the case where the curvic coupling 71 is used has been described as a mechanical joint provided between the second rotary shaft 12, and the first impeller 21 or second impeller 22, a Hirth coupling, etc. can be used. Although the preferable embodiments of the invention have been described hitherto, the invention is not limited to these embodiments. Additions, omissions, 18 substitutions, and other alternations of components can be made without departing from the spirit of the invention. The invention is not limited by the above description and is limited by only the scope of the appended claims. 19 WE CLAIM: 1. A rotor of a turbo compressor having an impeller and a rotary shaft that supports the impeller, comprising a fastening mechanism including: a mechanical joint formed at an end face of each of the impeller and the rotary shaft; a tension bolt inserted through a through-hole formed in the center of rotation of the impeller; a fastening nut screwed to a first male thread formed at one end of the tension bolt; a housing hole formed at an end face of the rotary shaft to house a portion of an elongated portion of the tension bolt; and a female thread formed at a bottom face of the housing hole and screwed to a second male thread formed at the other end of the tension bolt. 2. The rotor of a turbo compressor according to Claim 1, wherein the depth of the housing hole is specified according to the amount of elongation of the tension bolt. 3. The rotor of a turbo compressor according to Claim 2, wherein the depth of the housing hole is 10% or more of the length of the elongated portion. 4. The rotor of a turbo compressor according to Claim 2, further comprising a washer that is fitted on one end of the tension bolt and is provided between the impeller and the 20 fastening nut. wherein a combined length of the depth of the housing hole and the thickness of the washer is 10% or more of the length of the elongated portion. 5. A rotor of a turbo compressor having an impeller and a rotary shaft that supports the impeller, comprising a fastening mechanism including: a mechanical joint formed at an end face of each of the impeller and the rotary shaft; a tension bolt inserted through a through-hole formed in the center of rotation of the impeller; a fastening nut screwed to a first male thread formed at one end of the tension bolt; a female thread formed at an end face of the rotary shaft and screwed to a second male thread formed at the other end of the tension bolt; and a protruding portion formed so as to protrude from a rear central portion of the impeller to house a portion of an elongated portion of the tension bolt. 6. The rotor of a turbo compressor according to Claim 5, wherein the protruding amount of the protruding portion is specified according to the amount of elongation of the tension bolt. 7. The rotor of a turbo compressor according to Claim 6, wherein the protruding amount of the protruding portion is 10% or more of the length of the elongated portion. 21 8. The rotor of a turbo compressor according to Claim 6, further comprising a washer that is fitted on one end of the tension bolt and is provided between the impeller and the fastening nut, wherein a combined length of the protruding amount and the thickness of the 5 washer is 10% or more of the length of the elongated portion. Dated this 21st day of November, 2007. The invention provides a rotor 17 of a turbo compressor having an impeller 21 and a rotary shaft 12 that supports the impeller 21. The rotor includes a fastening mechanism 70 having a mechanical joint 71 formed at an end face of each of the impeller 21 and the rotary shaft 12, a tension bolt 74 inserted through a through-hole formed in the center of rotation of the impeller 21, a fastening nut 80 screwed to a first male thread 77 formed at one end of the tension bolt 74, a housing hole 78 formed at an end face of the rotary shaft 12 to house a portion of an elongated portion 75 of the tension bolt 74, and a female thread 78 formed at a bottom face of the housing hole 78 and screwed to a second male thread 76 formed at the other end of the tension bolt 74. According to the invention, the amount of elongation of the tension bolt is increased, so that the efficiency of coupling work can be improved, and stabilization can be achieved.

Documents:

01581-kol-2007-abstract.pdf

01581-kol-2007-claims.pdf

01581-kol-2007-correspondence others.pdf

01581-kol-2007-description complete.pdf

01581-kol-2007-drawings.pdf

01581-kol-2007-form 1.pdf

01581-kol-2007-form 2.pdf

01581-kol-2007-form 3.pdf

01581-kol-2007-form 5.pdf

01581-kol-2007-priority document.pdf

1581-KOL-2007-(02-05-2012)-EXAMINATION REPORT REPLY RECIEVED.PDF

1581-KOL-2007-ASSIGNMENT.pdf

1581-KOL-2007-CORRESPONDENCE OTHERS 1.1.pdf

1581-KOL-2007-CORRESPONDENCE-1.2.pdf

1581-KOL-2007-ENGLISH TRANSLATION.pdf

1581-KOL-2007-FORM 3-1.1.pdf

1581-KOL-2007-GPA.pdf

abstract-01581-kol-2007.jpg