JP2017044126A - Rotary machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary machine which effectively prevents the slipping-off of an impeller from a rotary shaft, by preventing the looseness of attachment of the impeller.SOLUTION: A cryogenic temperature rotary machine 10 transporting a main refrigerant Mf is equipped with an impeller 12 which transports the main refrigerant Mf by rotations; and a rotary shaft 13 which penetrates the impeller 12 and is equipped with a tip end portion 50 screwed with the impeller 12. A fastening rotating direction of the impeller screwed with the rotary shaft 13 is a reversed rotation direction Db opposite to a normal rotation direction Da transporting the main refrigerant Mf. A shaft tip end piece 60 regulating the rotations of the impeller 12 when the impeller 12 receives force in the normal rotation direction Da, is attached to the tip end portion 50.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a rotating machine that transfers a fluid, for example, a cryogenic fluid such as helium, by rotation of an impeller.

  Conventionally, for example, helium has been used to cool a superconducting magnet at a cryogenic temperature, and a cryogenic temperature of 4K or less has been achieved by reducing liquid helium to a cryogenic pressure with a cryogenic exhaust compressor. . Patent Document 1 discloses a cryogenic exhaust compressor, and a technique for transferring a cryogenic fluid using this type of low-temperature rotating machine is known. In this low-temperature rotating machine, an impeller is attached to the tip of the rotating shaft. There are various ways of attaching the impeller to the rotating shaft. For example, there is an embodiment in which the impeller is screwed and fixed to a screw portion provided at the tip of the rotating shaft. When the impeller is screwed and fixed to the tip of the rotating shaft, the fastening rotation direction by the screwing of the impeller is opposite to the normal rotation direction for transferring the fluid, and the impeller is prevented from being tightened during the fluid transfer. .

JP 2000-35191 A

  However, when the impeller stops, a force acts in the forward rotation direction due to the inertial force, which may cause the impeller to loosen.

  An object of the present invention is to provide a rotating machine that prevents the impeller from loosening and effectively prevents the impeller from falling off the rotating shaft.

  One aspect of the present invention is a rotating machine that transfers fluid, and includes an impeller that transfers fluid by rotation, and a rotary shaft that penetrates the impeller and includes a tip portion that is screwed to the impeller. The fastening rotation direction of the impeller screwed to the rotation shaft is the reverse direction opposite to the forward rotation direction in which the fluid is transferred, and the impeller receives a force in the forward rotation direction when the impeller receives a force in the forward rotation direction. A drop-off prevention unit that restricts rotation is attached.

  In this rotating machine, the rotating shaft rotating in the forward direction decelerates or stops, and as a result, even if a force in the forward direction, for example, an inertial force, acts on the impeller, Since the rotation is restricted, the impeller can be prevented from loosening, and the impeller can be effectively prevented from falling off the rotating shaft. In addition, when the impeller receives a force in the forward rotation direction, it means when a force for rotating the impeller in the forward rotation direction acts on the rotation shaft.

  In some embodiments, the tip end portion is provided with a screw hole and an inlay hole along the axial direction in order from the back side, and the drop-off prevention portion includes a screw shaft portion that is screwed into the screw hole, and an impeller. A head portion that contacts and locks the screw shaft portion and the head portion, and an interference fitting portion that is press-fitted into the slot, and a fastening rotation direction by screwing of the screw shaft portion is It can be set as the aspect which is the normal rotation direction of an impeller. When the impeller stops, a force in the forward direction such as an inertial force applied to the impeller acts in a direction in which the screw shaft portion of the drop-off preventing portion is tightened, and the impeller is prevented from loosening. On the other hand, during forward rotation of the impeller, the interference fitting portion acts to prevent the drop prevention portion from being loosened. As a result, it is possible to effectively prevent the impeller from falling off the rotating shaft.

  In the above aspect, the drop-off prevention portion has a smaller thermal expansion coefficient than the tip portion of the rotating shaft, and the tip portion is pressure-bonded to the screw shaft portion and the interference fitting portion as the fluid becomes lower in temperature. Can do. For example, when a fluid such as cryogenic helium is transferred, the drop-off prevention unit can more effectively prevent the impeller from dropping off in this aspect.

  In some embodiments, the tip portion includes a tip surface exposed from the impeller and a male screw portion protruding from the tip surface, and the drop-off prevention portion is a plurality of nuts that are screwed onto and overlap the male screw portion. The fastening rotation direction by the combination can be an aspect in which the impeller is forwardly rotated. When the impeller stops or the like, a forward force such as an inertial force applied to the impeller acts in a direction in which the nut of the drop-off preventing portion is tightened, and the impeller is prevented from loosening. On the other hand, by using a plurality of nuts, it functions as a so-called double nut, and during the forward rotation of the impeller, loosening of the drop-off prevention portion is prevented, and as a result, the impeller can be effectively prevented from falling off the rotating shaft.

  Further, in the above aspect, the plurality of nuts have a smaller coefficient of thermal expansion than the distal end portion of the rotating shaft, and the plurality of nuts are pressure-bonded to the male screw portion and the distal end surface as the fluid becomes lower in temperature. Can do. For example, when transferring a fluid such as cryogenic helium, in this aspect, the plurality of nuts that are the drop-off prevention unit can more effectively prevent the impeller from dropping off.

  In one embodiment of the present invention, a rotating shaft including an impeller including a screw hole and a tip portion provided with a male screw that is screwed into the screw hole and further provided with a fastening portion different from the male screw. And a drop-off prevention portion fastened to the fastening portion, and the fastening rotation direction of the screw hole and the male screw is opposite to the fastening rotation direction of the drop-off prevention portion and the fastening portion.

  In this rotating machine, if a force acts in the direction in which the impeller loosens, that is, the direction opposite to the fastening rotation direction of the screw hole and the male screw, a force acts in the fastening rotation direction on the drop-off prevention portion. Can be prevented, and the impeller can be effectively prevented from falling off the rotating shaft.

  In some embodiments, the fastening portion is a second screw hole provided in the tip portion, and the drop-off prevention portion is a shaft tip piece including a screw shaft portion that is screwed into the second screw hole. be able to. When a force acts in the direction in which the impeller is loosened, the screw shaft portion of the shaft tip piece is fastened to the second screw hole. As a result, it is possible to effectively prevent the impeller from falling off the rotating shaft.

  In some embodiments, the fastening portion may be a second male screw protruding from the tip portion, and the drop-off preventing portion may be a nut that is screwed with the second male screw. When a force acts in the direction in which the impeller is loosened, the nut is fastened to the second male screw. As a result, it is possible to effectively prevent the impeller from falling off the rotating shaft.

  According to some aspects of the present invention, it is possible to effectively prevent the impeller from falling off the rotating shaft.

It is a schematic explanatory drawing which shows the whole cooling system. It is a side view which shows the cryogenic rotary machine which concerns on 1st Embodiment partially fractured | ruptured. It is sectional drawing which expands and shows the front-end | tip part of the rotating shaft, impeller, and axial tip piece which concern on this embodiment. It is sectional drawing which decomposes | disassembles and shows the front-end | tip part of the rotating shaft which concerns on this embodiment, an impeller, and a shaft tip piece. It is a schematic side view which shows typically the drop-off prevention part which concerns on 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

  First, the cooling system 1 provided with the cryogenic rotating machine 10 will be described with reference to FIG. The cooling system 1 is a system for cooling the superconducting magnet 2 with a circulating fluid. In this cooling system 1, helium is used as the circulating fluid, but depending on the object to be cooled, a fluid such as nitrogen, hydrogen, neon, or the like may be used. In the present embodiment, the cryogenic rotating machine 10 will be described as an example of a rotating machine.

  The cooling system 1 includes a circulation line 3 through which helium (hereinafter referred to as “main refrigerant”) Mf circulates, a cryogenic rotating machine 10 such as a circulator pump that pumps the main refrigerant Mf passing through the circulation line 3, and a circulation line 3. The cooling device 4 that cools the main refrigerant Mf that passes through to about 4K (very low temperature), the first heat exchanger 5 that connects the superconducting magnet 2 and the circulation line 3 so that heat exchange is possible, and the superconductivity of the circulation line 3 The second heat exchanger 6 is disposed downstream of the magnet 2 and connects the cooling device 4 and the circulation line 3 so that heat exchange is possible.

  As shown in FIGS. 1 and 2, the circulation line 3 includes a pipe 3 a through which the main refrigerant Mf passes, and is arranged in the heat insulating container 8 in order to avoid the influence of outside air temperature (normal temperature). . The inside of the heat insulating container 8 is kept in vacuum in order to prevent the temperature of the main refrigerant Mf from rising due to convection. A main portion 11 of the cryogenic rotating machine 10 is installed on the ceiling portion 8 a of the heat insulating container 8. The main part 11 of the cryogenic rotating machine 10 includes an impeller 12 that transfers the main refrigerant Mf by rotation, and a drive motor 14 that rotates the impeller 12 via a rotating shaft 13. In the present embodiment, the drive motor 14 will be described as an example of a drive unit.

  The cryogenic rotating machine 10 includes a casing 15 that houses the main part 11. The casing 15 includes a normal temperature side casing portion 16 that accommodates the drive motor 14 and a low temperature side casing portion 17 that accommodates the impeller 12. The normal temperature side casing portion 16 is disposed outside the heat insulating container 8, and has a low temperature. The side casing portion 17 is mainly disposed inside (inside) the heat insulating container 8.

  The low temperature side casing portion 17 accommodates the impeller 12, an impeller chamber 18 connected to the pipe 3 a of the circulation line 3, and a thin cylindrical cylindrical portion 19 erected from the impeller chamber 18 along the rotation shaft 13. And a fixed flange portion 20 provided so as to protrude from the upper end side of the cylindrical portion 19. The low temperature side casing portion 17 is passed through a circular hole formed in the partition wall 81 of the heat insulating container 8, and the fixing flange portion 20 is fixed to the partition wall 81 by welding.

  The room temperature side casing portion 16 is erected so as to surround the rotary shaft 13, and has a cylindrical body portion 16a that houses the drive motor 14, a lid portion 16b that closes an upper opening of the body portion 16a, and a lower end of the body portion 16a. And a flange portion 16c provided on the surface. The flange portion 16c overlaps the upper surface of the fixed flange portion 20 of the low temperature side casing portion 17, and is bolted to the fixed flange portion 20 while ensuring a sealed state with a seal member interposed therebetween. The main part 11 can be pulled out from the low temperature side casing part 17 by loosening the bolt of the flange part 16 c and detaching the normal temperature side casing part 16 from the low temperature side casing part 17. Specifically, the impeller 12, a part of a heat insulating part 23 to be described later, and the intermediate heat transfer part 27 can be pulled out from the low temperature side casing part 17 together with the rotating shaft 13 supported by the room temperature side casing part 16. Furthermore, the main part 11 can be easily maintained by opening the cover part 16b of the room temperature side casing part 16.

  Inside the normal temperature side casing portion 16, radial bearing portions 21 are arranged at two places above and below so as to sandwich the drive motor 14. Further, between the drive motor 14 and the lower radial bearing portion 21, A thrust bearing portion 22 that supports the rotary shaft 13 while receiving a load in the direction of the rotary shaft 13 is disposed.

  A heat insulating material is accommodated inside the low temperature side casing portion 17 to form a heat insulating portion 23. The heat insulating portion 23 is formed with a circular through hole 23 a through which the rotary shaft 13 passes. As a result, the heat insulating portion 23 surrounds a part of the rotary shaft 13. In the present embodiment, the heat insulating portion 23 is formed by accommodating a heat insulating material inside the low temperature side casing portion 17. However, a vacuum heat insulating chamber is formed inside the low temperature side casing portion 17, and further inside the heat insulating chamber. It is also possible to arrange a convection prevention material to form a heat insulating part.

  The heat insulation part 23 is divided into upper and lower two stages, and an intermediate heat transfer part 27 maintained at a constant temperature of about −190 ° C. is disposed between the upper heat insulation part 24 and the lower heat insulation part 25. The intermediate heat transfer section 27 is also called a thermal anchor, has a thermal conductivity equal to or higher than that of the rotary shaft 13, and is formed of, for example, a copper plate. The intermediate heat transfer section 27 is provided to reduce the amount of intrusion heat transmitted from the high temperature side to the low temperature side via the rotary shaft 13, and is also effective in reducing the amount of intrusion heat slightly transmitted through the heat insulating section 23. is there. The lower heat insulating portion 25 is further divided into an inner portion 25a and an outer portion 25b, and only the inner portion 25a is pulled out together with the rotating shaft 13 and the intermediate heat transfer portion 27 during maintenance.

  The intermediate heat transfer portion 27 contacts an annular protrusion 30 provided on the inner surface side of the tubular portion 19. The annular protrusion 30 is maintained at a constant temperature by helium (hereinafter referred to as “sub-refrigerant”) Sf that circulates while being maintained at about −190 ° C. The intermediate heat transfer section 27 is maintained at a constant temperature of about −190 ° C. by exchanging heat with the annular protrusion 30 for the amount of heat transferred from the rotary shaft 13. In the present embodiment, an example in which helium is used as the auxiliary refrigerant Sf is illustrated, but nitrogen or the like may be used as necessary.

  The cryogenic rotating machine 10 includes a cooling line 31 for circulating the sub refrigerant Sf (see FIG. 1). The flow path 30a of the sub-refrigerant Sf formed in the annular projecting portion 30 has an inlet and an outlet in one pass, and is formed so as to make one round around the intermediate heat transfer portion 27. The cooling line 31 is a line for circulating the sub refrigerant Sf, and includes a pipe 31 a connected to each of the inlet and the outlet of the sub refrigerant Sf formed in the annular protrusion 30, a circulator pump (not shown), and the like. ing. The cooling line 31 is disposed so as to be able to exchange heat with the cooling device 110 via the third heat exchanger 7, and the sub-refrigerant Sf after heat exchange is maintained at about −190 ° C. to be a cylindrical portion. The sub refrigerant Sf supplied to the 19 annular protrusions 30 and discharged from the annular protrusion 30 reaches the third heat exchanger 7 and is cooled again.

[Mounting structure of rotating shaft and impeller]
Next, with reference to FIG. 3 and FIG. 4, the attachment structure of the rotating shaft 13 and the impeller 12 which concerns on 1st Embodiment is demonstrated. The impeller 12 includes a boss portion 41 fixed to the rotating shaft 13 and a blade portion 42 provided on the outer periphery of the boss portion 41. The boss portion 41 has a screw hole along the axis La of the rotating shaft 13. 41a and the spigot hole 41b are formed along with the vertical direction. On the other hand, the front end portion 50 of the rotating shaft 13 is provided with a male screw 51 that is screwed into the screw hole 41a of the boss portion 41 and a spigot portion 52 that is press-fitted into the spigot hole 41b. The fastening rotation direction of the impeller 12 screwed into the male screw 51 of the rotation shaft 13 is a reverse direction Db opposite to the normal rotation direction Da in which the main refrigerant Mf is transferred by rotation.

  The distal end portion 50 of the rotating shaft 13 passes through the boss portion 41 of the impeller 12, and the distal end surface 50 a is exposed from the boss portion 41. The tip portion 50 is provided with a screw hole 50b and an inlay hole 50c along the axis La direction in order from the back side, and the open end of the inlay hole 50c is formed on the tip surface 50a of the rotary shaft 13. Yes.

  A shaft tip piece 60 that prevents the impeller 12 from falling off is attached to the tip portion 50 of the rotating shaft 13. The shaft tip piece 60 includes a screw shaft portion 61 that is screwed into the screw hole 50b of the tip portion 50, and a head portion 62 that engages with the boss portion 41 of the impeller 12 to prevent the impeller 12 from falling off. The outer surface of the head 62 is processed into a curved convex shape so as to be smoothly continuous with the shape of the blade portion 42 of the impeller 12. The fastening rotation direction by screwing of the screw shaft portion 61 of the shaft tip piece 60 is the normal rotation direction Da of the impeller 12 that transfers the main refrigerant Mf by rotation.

  The shaft tip piece 60 includes an interference fit portion 63 provided between the screw shaft portion 61 and the head portion 62. The interference fitting portion 63 has a cylindrical shape whose diameter is slightly larger than the inner diameter of the spigot hole 50c of the tip portion 50, and is press-fitted into the spigot hole 50c of the tip portion 50. In the present embodiment, the shaft tip piece 60 is described as an example of a drop-off prevention unit.

  The shaft tip piece 60 is made of a material having a smaller coefficient of thermal expansion than the tip portion 50 of the rotating shaft 13. For example, the rotating shaft 13 is made of a stainless steel material or the like, and the shaft tip piece 60 is made of a titanium material or the like. It is formed. The main refrigerant Mf transferred by the impeller 12 is at a very low temperature. In other words, after the rotary shaft 13, the impeller 12, and the shaft tip piece 60 are attached at room temperature, when the main refrigerant Mf is actually transferred, due to the difference in thermal expansion coefficient between the rotary shaft 13 and the shaft tip piece 60, the tip The part 50 is crimped to the screw shaft part 61 and the interference fitting part 63.

  In the cryogenic rotary machine 10 described above, the fastening rotation direction of the impeller 12 screwed to the rotation shaft 13 is the reverse direction Db opposite to the normal rotation direction Da for transferring the main refrigerant Mf. When the main refrigerant Mf is transferred, the impeller 12 receives a force in the reverse direction Db by the transferred main refrigerant Mf while rotating in the normal rotation direction Da. As a result, the impeller 12 is fastened to the rotating shaft 13. Next, when the rotation of the rotating shaft 13 in the forward rotation direction Da is decelerated or stopped suddenly, a force in the forward rotation direction Da such as an inertial force acts on the impeller 12. The force in the forward rotation direction Da is a force for rotating the impeller 12 in the forward rotation direction Da relative to the rotation shaft 13. Here, rotating the impeller 12 in the forward rotation direction Da with respect to the rotating shaft 13 means that the impeller 12 is loosened with respect to the rotating shaft 13, but the shaft tip piece 60 is attached to the rotating shaft 13. Since the rotation of the impeller 12 is restricted by the shaft tip piece 60, the impeller 12 can be prevented from loosening, and the impeller 12 can be effectively prevented from falling off the rotating shaft 13.

  Specifically, the tip 50 of the rotating shaft 13 is provided with a screw hole 50b and an inlay hole 50c. The shaft tip piece 60 has a screw shaft 61 that is screwed into the screw hole 50b, and an inlay. An interference fitting portion 63 to be press-fitted into the hole 50c is provided. The fastening rotation direction by screwing of the screw shaft portion 61 is the forward rotation direction Da of the impeller 12. Here, when the rotating shaft 13 decelerates or stops suddenly, a force to rotate the rotating shaft 13 in the normal rotation direction Da acts on the impeller 12 and the shaft tip piece 60. The force in the forward rotation direction Da acts to loosen the impeller 12 while acting on the screw shaft portion 61 in a tightening direction. As a result, the shaft tip piece 60 suppresses the impeller 12 from falling off. become. During forward rotation of the impeller 12, the interference fitting portion 63 acts to prevent the shaft tip piece 60 from being loosened. As a result, it is possible to effectively prevent the impeller 12 from falling off the rotating shaft 13.

  Further, the impeller 12 that has received the force in the forward rotation direction Da comes into contact with the head 62 of the shaft tip piece 60 as a result, and the impeller 12 causes the shaft tip to pass through the head 62 due to friction acting at that time. This acts in the direction of tightening the screw shaft portion 61 of the piece 60. As a result, the rotation of the shaft tip piece 60 in the fastening rotation direction is promoted.

  In particular, in a state where the shaft tip piece 60 is attached to the tip of the rotating shaft 13, it is possible to provide a mode in which a gap is provided between the head 62 of the shaft tip piece 60 and the boss portion 41 of the impeller 12. . This gap works more effectively when the shaft tip piece 60 exhibits the function of preventing the impeller 12 from falling off. Specifically, when the impeller 12 rotates in the forward rotation direction Da and loosens and moves in the direction of dropping from the rotating shaft 13, this gap disappears, and the boss portion 41 comes into contact with the head 62. Here, when the boss 41 of the impeller 12 contacts the head 62 with rotation, the rotational force of the impeller 12 in the forward rotation direction Da is more strongly transmitted to the head 62. As a result, rotation of the shaft tip piece 60 in the fastening rotation direction (forward rotation direction Da) is promoted, and the function of preventing the impeller 12 from falling off by the shaft tip piece 60 works more effectively.

  Furthermore, since the shaft tip piece 60 has a smaller coefficient of thermal expansion than the tip portion 50 of the rotating shaft 13, the tip portion 50 has a screw shaft portion 61 and a lower temperature as the main refrigerant (fluid) Mf to be transferred becomes lower in temperature. It becomes the aspect crimped | bonded to the interference fitting part 63, and the shaft tip piece 60 can prevent the impeller 12 from dropping off more effectively.

  The cryogenic rotating machine 10 according to the present embodiment includes an impeller 12 including a screw hole 41a and a rotating shaft 13 provided with a male screw 51 that is screwed into the screw hole 41a. A screw hole (second screw hole) 50b, which is a fastening portion different from the male screw 51, is provided at the distal end portion 50 of the rotary shaft 13, and the screw hole 50b includes a shaft that is an example of a drop-off preventing portion. The screw shaft portion 61 of the tip piece 60 is screwed and fastened. Furthermore, the fastening rotation direction of the screw hole 41a and the male screw 51 is opposite to the fastening rotation direction of the shaft tip piece 60 and the screw hole 50b.

  In the cryogenic rotating machine 10 according to the present embodiment, even if a force is applied in the direction in which the impeller 12 is loosened, that is, in the direction opposite to the fastening rotation direction of the screw hole 41a and the male screw 51, the force in the opposite direction is It acts in the direction in which the tip piece 60 is fastened. As a result, the shaft tip piece 60 prevents the impeller 12 from loosening and prevents the impeller 12 from falling off the rotating shaft 13. In particular, since the shaft tip piece 60 is used as a drop-off preventing portion and the screw shaft portion 61 of the shaft tip piece 60 is screwed into the screw hole 50b, when a force acts in the direction in which the impeller 12 is loosened, the screw shaft of the shaft tip piece 60 is The portion 61 is fastened to the screw hole 50b, and the impeller 12 can be effectively prevented from falling off the rotating shaft 13.

  Note that the fastening rotation direction of the screw hole 41 a and the male screw 51 in this embodiment, that is, the fastening rotation direction of the screw hole 41 a with respect to the male screw 51 is the reverse direction Db of the impeller 12. The fastening rotation direction between the shaft tip piece 60 and the screw hole 50b, that is, the fastening rotation direction of the shaft tip piece 60 (screw shaft portion 61) with respect to the screw hole 50b is the forward rotation direction Da of the impeller 12. However, from the viewpoint of preventing the impeller 12 from falling off the rotating shaft 13, it is sufficient that the fastening rotation direction of the screw hole 41a and the male screw 51 and the fastening rotation direction of the shaft tip piece 60 and the screw hole 50b are reversed. Therefore, the relationship between each fastening rotation direction and the forward rotation direction Da and the reverse direction Db of the impeller 12 may be reversed.

  Next, with reference to FIG. 5, the attachment structure of the rotating shaft 13 and the impeller 12 which concerns on 2nd Embodiment is demonstrated. Note that, in the mounting structure according to the second embodiment, members that are substantially the same as or similar to the mounting structure according to the first embodiment, or similar structures, are denoted by the same reference numerals and detailed description thereof is omitted. .

  The distal end portion 50 of the rotating shaft 13 is provided with a male screw 51 that is screwed into the screw hole 41a of the boss portion 41, and a spigot portion 52 that is press-fitted into the spigot hole 41b. The fastening rotation direction of the impeller 12 screwed into the male screw 51 of the rotation shaft 13 is a reverse direction Db opposite to the normal rotation direction Da in which the main refrigerant Mf is transferred by rotation.

  The distal end portion 50 of the rotating shaft 13 passes through the boss portion 41 of the impeller 12, and the distal end surface 50 a is exposed from the boss portion 41. Further, the distal end portion 50 is provided with a male threaded portion 53 protruding from the distal end surface 50a along the axis La direction. The male screw portion 53 protrudes from the boss portion 41 of the impeller 12 and is screwed into the male screw portion 53 so that two (plural) nuts 72 overlap. Further, the male screw portion 53 protrudes from the nut 72, and a cap portion 73 is fixed so as to be screwed into the protrusion. The fastening rotation direction by screwing of the nut 72 is the forward rotation direction Da of the impeller 12 that transfers the main refrigerant Mf by rotation. In the present embodiment, the two nuts 72 are described as an example of the drop-off prevention unit.

  The nut 72 screwed into the male screw portion 53 is made of a material having a smaller coefficient of thermal expansion than the tip portion 50 of the rotating shaft 13. For example, the rotating shaft 13 is made of a stainless steel material or the like, and the nut 72 is made of titanium. Depending on the system material etc. The main refrigerant Mf transferred by the impeller 12 is at a very low temperature. That is, after the rotary shaft 13, the impeller 12, and the nut 72 are attached at normal temperature, when the main refrigerant Mf is actually transferred, the tip 50 is a nut due to the difference in thermal expansion coefficient between the rotary shaft 13 and the nut 72. Crimp to 72. Specifically, when the tip portion 50 is contracted more than the nut 72, the force with which the thread of the tip portion 50 engages with the thread groove of the nut 72 is increased, and the tip surface 50 a is crimped to the nut 72. To do.

  In the cryogenic rotating machine 10 according to the second embodiment, the fastening rotation direction of the impeller 12 screwed to the rotation shaft 13 is the reverse direction Db opposite to the normal rotation direction Da for transferring the main refrigerant Mf. Therefore, the impeller 12 is fastened to the rotating shaft 13 when the main refrigerant Mf is transferred. Next, even if the rotation of the impeller 12 stops and, for example, the impeller 12 receives a force in the forward rotation direction Da due to an inertial force, the rotation of the impeller 12 is restricted by the two nuts 72. Can be prevented, and the impeller 12 can be effectively prevented from falling off the rotating shaft 13.

  Specifically, when the impeller 12 stops, the inertial force acts in the direction in which the nut 72 is tightened, and the impeller 12 is prevented from loosening. On the other hand, by using a plurality of nuts 72, it functions as a so-called double nut, and during the forward rotation of the impeller 12, the drop-off preventing portion is prevented from loosening, and as a result, the impeller 12 is effectively removed from the rotating shaft 13. Can be prevented.

  Furthermore, since the nut 72 has a larger coefficient of thermal expansion than the tip portion 50 of the rotating shaft 13, the tip portion 50 is pressed against the nut 72 as the main refrigerant (fluid) Mf to be transferred becomes lower in temperature. The nut 72 can prevent the impeller 12 from dropping off more effectively.

  The cryogenic rotating machine 10 according to the present embodiment includes an impeller 12 including a screw hole 41a and a rotating shaft 13 provided with a male screw 51 that is screwed into the screw hole 41a. The distal end portion 50 of the rotating shaft 13 is provided with a male screw portion (second male screw) 53 that is a fastening portion different from the male screw 51, and the male screw portion 53 has a nut 72 that is an example of a drop-off preventing portion. Are screwed together. Further, the fastening rotation direction between the screw hole 41 a and the male screw 51 is opposite to the fastening rotation direction between the nut 72 and the male screw portion 53.

  In the cryogenic rotating machine 10 according to the present embodiment, even if a force is applied in the direction in which the impeller 12 is loosened, that is, in the direction opposite to the fastening rotation direction of the screw hole 41a and the male screw 51, the force in the opposite direction is Acts in the direction to fasten 72. As a result, the nut 72 prevents the impeller 12 from loosening and prevents the impeller 12 from falling off the rotating shaft 13. In particular, the nut 72 is used as the drop-off preventing portion, and the nut 72 is screwed into the male screw portion 53. Therefore, when a force acts in the direction in which the impeller 12 is loosened, the nut 72 is tightened to the male screw portion 53 and the impeller from the rotating shaft 13 12 can be effectively prevented from falling off.

  Note that the fastening rotation direction of the screw hole 41 a and the male screw 51 in this embodiment, that is, the fastening rotation direction of the screw hole 41 a with respect to the male screw 51 is the reverse direction Db of the impeller 12. The fastening rotation direction of the nut 72 and the male screw portion 53, that is, the fastening rotation direction of the nut 72 with respect to the male screw portion 53 is the forward rotation direction Da of the impeller 12. However, from the viewpoint of preventing the impeller 12 from falling off the rotating shaft 13, the fastening rotation direction of the screw hole 41 a and the male screw 51 and the fastening rotation direction of the nut 72 and the male screw portion 53 may be reversed. The relationship between each fastening rotation direction and the forward rotation direction Da and reverse direction Db of the impeller 12 may be reversed.

  As mentioned above, although embodiment was described, this invention is not limited only to the above embodiment. For example, in the above-described embodiment, the mode of transferring the cryogenic fluid has been described. However, the present invention is not limited thereto, and may be a rotating machine that transfers a room temperature fluid or the like.

  The present invention can be widely applied to a rotating machine for transferring a fluid, and may be not only a fluid transferring means such as a circulator pump but also a compressor, a turbine, an inducer, and the like.

3 Circulation line 3a Piping 10 Cryogenic rotating machine (Rotating machine)
12 Impeller 13 Rotating shaft 50 Tip portion 50b Screw hole 50c Inlay hole 53 Male thread portion 60 Shaft tip piece (drop-off prevention portion)
61 Screw shaft part 63 Close fitting part 72 Nut (drop-off prevention part)
Da Forward direction Db Reverse direction

Claims (8)

A rotating machine for transferring fluid,
An impeller for transferring the fluid by rotation;
A rotary shaft that penetrates the impeller and has a tip portion screwed into the impeller, and
The fastening rotation direction of the impeller screwed to the rotation shaft is the reverse direction opposite to the normal rotation direction for transferring the fluid,
A rotary machine in which a drop-off preventing portion that restricts rotation of the impeller when the impeller receives a force in the forward rotation direction is attached to the tip portion. The tip portion is provided with a screw hole and an inlay hole along the axial direction in order from the back side,
The drop-off prevention portion is provided between a screw shaft portion that is screwed into the screw hole, a head portion that contacts and locks the impeller, and the screw shaft portion and the head portion. An interference fit portion to be press-fitted,
The rotating machine according to claim 1, wherein a fastening rotation direction by screwing of the screw shaft portion is a forward rotation direction of the impeller.   The said drop-off prevention part has a smaller coefficient of thermal expansion than the tip part of the rotating shaft, and the tip part is pressed against the screw shaft part and the interference fitting part as the fluid becomes colder. The rotating machine described. The tip portion includes a tip surface exposed from the impeller, and a male screw portion protruding from the tip surface,
The drop-off prevention part is a plurality of nuts that are screwed and overlapped with the male screw part,
The rotating machine according to claim 1, wherein a fastening rotation direction by screwing of the nut is a normal rotation direction of the impeller.   5. The plurality of nuts have a smaller coefficient of thermal expansion than the tip portion of the rotating shaft, and the plurality of nuts are pressure-bonded to the male screw portion and the tip surface as the fluid becomes colder. The rotating machine described. An impeller including a screw hole;
A rotating shaft including a male screw that is screwed into the screw hole, and a tip that is further provided with a fastening portion different from the male screw,
A drop-off prevention portion fastened to the fastening portion,
A rotating machine in which the fastening rotation direction of the screw hole and the male screw is opposite to the fastening rotation direction of the drop-off prevention portion and the fastening portion. The fastening portion is a second screw hole provided in the tip portion,
The drop-off prevention portion is a shaft tip piece including a screw shaft portion that is screwed into the second screw hole.
The rotating machine according to claim 6. The fastening portion is a second male screw protruding from the tip;
The drop-off prevention part is a nut screwed with the second male screw.
The rotating machine according to claim 6.

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