JP2013207864A - Compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compressor which efficiently cools a motor while maintaining high efficiency.SOLUTION: A compressor 1 includes a hollow cylindrical shaped cooling bush (a ring member) 9 which is made of a material having heat conductivity larger than those of a main shaft 4 and a motor casing 8 and arranged between the motor casing 8 and a stator 5. In the cooling bush 9, a spiral shaped groove is provided on an outer peripheral surface from one end side of axial end parts to the other end side of them. The cooling bush 9 is hermetically joined to the motor casing 8 side so that the outer peripheral surface closely contacts with an inner peripheral surface of the motor casing 8 and has an inner cooling passage (a first cooling fluid passage) 18 formed by the groove and the inner peripheral surface.

Description

  The present invention relates to a compressor, and more particularly to a cooling structure for a high-speed motor of a turbo compressor.

  Power devices such as superconducting power cables, superconducting transformers, and superconducting motors use high temperature superconductors that operate at liquid nitrogen temperature levels. For cooling the high-temperature superconductor, a Brayton cycle refrigerator using helium gas or neon gas as a circulating gas (also referred to as refrigerant gas) is used.

  As a compressor of this Brayton cycle refrigerator, a turbo compressor in which a high-speed motor is integrated with a main shaft of the compressor is used. Similarly, a turbo expander in which a high-speed motor is integrated with a main shaft of a turbine is used for a turbine of a Brayton cycle refrigerator.

  By the way, the circulating gas (refrigerant gas) of the Brayton cycle refrigerator is sealed in the refrigerator at a pressure considerably higher than the atmospheric pressure of 0.5 MPa to 3 MPa in consideration of downsizing and high efficiency of the refrigerator. ing. In the Brayton cycle refrigerator for cooling the high-temperature superconducting power equipment, the minimum temperature of the circulating gas is lower than the liquid nitrogen temperature of −196 ° C. (77 K), for example, −213 ° C. (60 K). For this reason, magnetic bearings and gas bearings that can rotate at high speed without contact are often used as bearings for turbo compressors and turbo expanders.

  In general, when a motor that drives a turbo compressor or turbo expander is rotated at high speed, heat generation due to copper loss or iron loss of the motor, heat generation due to fluid friction in the gap between the stator and rotor, and gas bearings or magnetic bearings Heat is generated due to fluid friction in the bearing clearance. In addition, when a magnetic bearing is used, since current flows through the electromagnet coil, heat is generated due to copper loss, iron loss, and the like as in the motor. And as the number of rotations of the motor increases, heat generation due to fluid friction loss increases rapidly.

  Here, the fluid friction loss is proportional to the density of the fluid. Therefore, if the pressure of the circulating gas increases, the density increases and the fluid friction loss increases. In particular, when neon gas is used as the circulating gas, the density of the neon gas is higher than that of helium and is sealed at a higher pressure. .

  As a cooling method for suppressing the temperature rise due to heat generated by such a high-speed motor, air or liquid is used from the outer periphery of the casing housing the motor, and the stator is fixed to the motor casing and the motor spindle. In general, a method for cooling the rotor is known (see, for example, Patent Documents 1 and 2). As another cooling method, there is known a method in which a coolant passage is formed inside a casing for housing a motor to cool the main shaft, stator and rotor of the motor more efficiently (for example, Patent Document 3). See).

  Incidentally, as disclosed in Patent Documents 1 and 2, in the method of cooling the main shaft, stator and rotor of the motor from the outer peripheral portion of the casing housing the motor by heat conduction of the casing, the motor is efficiently cooled. For this, it is important that the casing material that houses the motor has a high thermal conductivity.

  For example, when comparing the thermal conductivity of austenitic stainless steel, which is resistant to corrosion, and aluminum alloy or copper alloy, the thermal conductivity λ of austenitic stainless steel is 16 (W / m / K). The thermal conductivity λ of copper alloy is approximately 120 (W / m / K). Thus, since the thermal conductivity of aluminum alloy and copper alloy is 7 to 8 times larger than that of austenitic stainless steel, the temperature of the motor can be increased by using aluminum alloy or copper alloy as the casing material for housing the motor. The rise can be kept low.

Moreover, as a method of fixing the motor stator to the motor casing, a shrink fitting method is generally adopted. However, when an aluminum alloy is used as the material of the motor casing, the motor stator made of an iron-based material and aluminum The coefficient of thermal expansion differs between the motor casing made of an alloy. That is, the thermal expansion coefficient of an aluminum alloy (β = 23 × 10 ⁻⁶ / ° C.) and the thermal expansion coefficient of a copper alloy (β = 11 × 13 ⁻⁶ / ° C.) (β = 20 × 10 ⁻⁶ / ° C) is larger, so that a gap is generated between the motor stator and the motor casing due to the temperature rise of the motor, which acts as a contact thermal resistance to cool the motor efficiently. There was a problem that could not.

  In order to solve this problem, a method of eliminating contact thermal resistance with the motor casing by casting the motor stator with an aluminum alloy has been proposed (see, for example, Patent Document 4).

  By the way, in the turbo compressor, an impeller as a rotating body and a shroud ring having a fixed wall facing the front surface of the impeller are housed in a casing of the compressor body. The compressor body casing is fixed to the motor casing, and the shroud ring is fixed to the compressor body casing. On the other hand, the impeller is attached to the spindle end of the motor. A gap (generally about 0.3 to 0.6 mm) called a shroud clearance is provided between the impeller blade passage and the shroud ring fixed wall.

  However, in order to efficiently cool the motor, if a motor casing made of aluminum alloy or copper alloy with high thermal conductivity is used, due to the difference in thermal expansion coefficient from the main spindle of the motor made of magnetic iron-based material The axial extension amounts of the motor casing and the main shaft are different. As a result, the above-described shroud clearance is increased, and there has been a problem that the efficiency of the impeller (that is, the efficiency of the compressor) is greatly reduced.

  Therefore, when the cooling passage of the coolant is formed on the outer periphery of the motor casing and the motor stator is cooled by heat conduction in the radial direction of the casing, aluminum alloy or copper alloy having high thermal conductivity is used as the casing material. It can be a small rotating machine with a very short spindle length, a rotating machine where the impeller efficiency is not so high, or the working fluid is liquid and the working fluid is supplied to the inside of the motor to generate heat and fluid from the motor. There is a problem that the heat generation due to friction loss is limited to that which can be removed.

JP 2000-097186 A JP 2002-168184 A JP 2004-343857 A JP 07-163107 A

  This invention is made | formed in view of the said situation, Comprising: It aims at providing the compressor which can cool a motor efficiently, maintaining high efficiency.

  According to a first aspect of the present invention, there is provided a main shaft provided with a rotor at a central portion, a stator facing the rotor, a bearing that rotatably holds the main shaft, the main shaft, the stator, and the bearing. A high-speed motor having at least a motor casing that holds the stator, an impeller provided on at least one end of the main shaft, a shroud ring having a fixing wall facing the front surface of the impeller, and the impeller And a compressor body having at least a compressor body casing that houses the shroud ring and holds the shroud ring, and the motor casing and the compressor body casing are coupled to each other. The thermal conductivity between the motor casing and the stator is larger than that of the main shaft and the motor casing. A hollow cylindrical ring member made of a material is provided, and the ring member is provided with a spiral groove portion from one end side to the other end side of the axial end portion on the outer peripheral surface, and the outer peripheral surface and the inner periphery of the motor casing It is a compressor characterized by having a first cooling fluid flow path which is airtightly joined to the motor casing side so as to be in close contact with the surface, and which is constituted by the groove and the inner peripheral surface.

  According to the compressor according to claim 1, the structure includes a hollow cylindrical ring member (cooling bush) having a first cooling fluid passage formed airtight on the outer peripheral surface between the motor casing and the stator. It has become. Thus, since the ring member having the cooling flow path is provided inside the motor casing so as to be in contact with the stator, the stator can be cooled from the inside of the motor casing. Moreover, since the material of the ring member is a material having a higher thermal conductivity than that of the main shaft and the motor casing, the cooling ability of the cooling bush can be increased and heat can be effectively removed from the stator.

  In addition, since the ring member is made of a material having a higher thermal conductivity than that of the main shaft and the motor casing and takes charge of the cooling function, a material having a low coefficient of thermal expansion can be selected for the main shaft and the motor casing. Thereby, since the difference in the axial extension amount between the main shaft and the motor casing can be suppressed, the efficiency of the compressor can be maintained without reducing the efficiency of the impeller.

  According to a second aspect of the present invention, the motor casing is provided on the outer peripheral surface from the one end side of the axial end portion to the other end side of the spiral second cooling fluid channel, the outer peripheral surface of the motor casing, The first cooling fluid channel and the second cooling fluid channel are communicated with each other through the through hole, and the first cooling fluid channel and the second cooling fluid channel communicate with each other. This is a compressor.

  According to the compressor which concerns on Claim 2, it has the structure by which a 2nd cooling fluid flow path is provided in the outer peripheral surface of a motor casing. Thereby, heat generating parts other than rotors, such as a bearing part accommodated in the motor casing, can be cooled.

  Moreover, it has the through-hole which penetrates the outer peripheral surface and inner peripheral surface of a motor casing, and becomes a structure by which a 1st and 2nd cooling fluid flow path is connected by this through-hole. Thereby, since the cooling fluid used for the first cooling fluid channel inside the motor casing can be used also for the second cooling fluid channel, the amount of cooling fluid used can be reduced, and the cooling structure Can be simplified.

  The invention according to claim 3 is the compressor according to claim 1 or 2, wherein the main shaft and the motor casing are made of the same material or a material having substantially the same thermal expansion coefficient. .

  According to the compressor of the third aspect, since the main shaft and the motor casing are made of the same material or a material having substantially the same thermal expansion coefficient, the difference in these dimensional fluctuations during the operation of the compressor is reduced. can do. Thereby, since the clearance (shroud clearance) between the front surface of the impeller fixed to the main shaft end and the fixed wall of the shroud ring fixed to the motor casing via the compressor body casing is also maintained, the compressor High efficiency can be maintained.

  According to a fourth aspect of the present invention, at least a part of the motor casing that is in contact with the ring member is made of a material having a higher thermal conductivity than a material that constitutes another region of the motor casing. It is a compressor as described in any one of Claims 1 thru | or 3 characterized by these.

  According to the compressor which concerns on Claim 4, it is comprised using the material with big heat conductivity in the one part area | region of a motor casing. Since the region made of a material having a high thermal conductivity is provided so as to partially contact the ring member (cooling bush), there is little dimensional variation in the axial direction of the motor casing during operation. In addition, a ring member that bears a cooling function is joined to the inner peripheral surface of the motor casing, and since the region in contact with the ring member is made of a material having a high thermal conductivity, it is effectively cooled by the ring member. (I.e., at least a part of the region in contact with the ring member is cooled by the ring member, so that the dimensional variation is small). Further, when the second cooling fluid channel exists outside the partial area, the cooling is performed from the outside. Therefore, a material having high thermal conductivity can be used for the partial region of the motor casing.

  According to the compressor of the present invention, the motor can be efficiently cooled while maintaining high efficiency.

It is sectional drawing of the compressor which is 1st Embodiment to which this invention is applied. It is sectional drawing of the high-speed motor part which comprises the compressor which is 1st Embodiment. It is a figure for demonstrating the motor casing of a high-speed motor, (a) is sectional drawing, (b) is an enlarged side view. It is a side view of the cooling bush used for the compressor which is a 1st embodiment. It is sectional drawing of the high-speed motor part which comprises the compressor which is 2nd Embodiment.

  Hereinafter, a compressor according to an embodiment to which the present invention is applied will be described in detail with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

<First Embodiment>
First, the structure of the compressor which is 1st Embodiment to which this invention is applied is demonstrated. As shown in FIG. 1, the compressor 1 of this embodiment includes a high-speed motor 2 and a compressor main body 3 (3 </ b> A, 3 </ b> B), and a compressor main body at both axial ends of the high-speed motor 2. 3A and 3B are combined to form a schematic structure.

  As shown in FIG. 1, the high-speed motor 2 includes a main shaft 4 provided with a rotor 4a at the center thereof, a stator 5 opposed to the rotor 4a, and a bearing 6 that rotatably holds the main shaft 4. 6a, 6b) and the bearing 7 (7a, 7b), the motor casing 8 that houses the main shaft 4, the stator 5, and the bearings 6, 7, and the cooling bush provided between the motor casing 8 and the stator 5. (Ring member) 9 and at least.

  As shown in FIG. 1, the main shaft 4 is rotatably supported in a motor casing 8 by bearings 6 (6a, 6b) and bearings 7 (7a, 7b). Further, the main shaft 4 has an axial length longer than the axial length of the motor casing 8, and one end 4 </ b> A and the other end 4 </ b> B of both ends protrude from both ends of the motor casing 8. Impellers 19A and 19B, which will be described later, are fixed to the both ends 4A and 4B, respectively. Thereby, the main shaft 4 has a function as a main shaft of the compressor main bodies 3A and 3B as well as a rotation main shaft of the high-speed motor 2.

  The main shaft 4 is made of a magnetic iron-based material. The material of the main shaft 4 is preferably substantially the same as the material of the motor casing 8 as will be described later.

  The rotor 4 a is fixed to the central portion of the main shaft 4. The stator 5 is provided so as to surround the outer periphery of the rotor 4a. A field coil is attached to the stator 5 so as to sandwich the axial direction, and the main shaft 4 is rotated by transmitting a magnetic field generated by the field coil to the main shaft 4.

  The bearing 6 (6a, 6b) and the bearing 7 (7a, 7b) are made of a magnetic iron-based material. The bearing 6 and the bearing 7 are not particularly limited as long as they can support the main shaft 4 at high speed. Examples of such a bearing include a fluid bearing and a magnetic bearing. In the present embodiment, the bearing 6 (6a, 6b) is a radial bearing, and receives a load in the radial direction of the main shaft 4. The main shaft 4 is provided with a thrust plate 4b for receiving an axial load, and the bearings 7 (7a, 7b) are thrust (axial) bearings.

  As shown in FIGS. 1, 2 and 3A, the motor casing 8 is a hollow cylindrical member having flange portions 8a and 8b at both ends. As shown in FIG. 1, the motor casing 8 houses the main shaft 4, the stator 5, and the bearings 6 and 7 in an internal space. The motor casing 8 holds the stator 5 on the inner side through the cooling bush 9.

  The motor casing 8 is made of iron-based stainless steel. The material of the motor casing 8 is preferably substantially the same as the material of the main shaft 4 as described above. Furthermore, it is more preferable that the main shaft 4 and the motor casing 8 are made of the same material.

  As shown in FIGS. 3 (a) and 3 (b), the outer surface of the motor casing 8 spirals from one end side (flange 8a side) to the other end side (flange 8b side) of the axial end. The groove portion 10 is provided. Further, as shown in FIG. 3A, a hollow cylindrical cap (cover) member 11 is provided on the outer peripheral surface of the motor casing 8 so as to cover an area where the spiral groove 10 is provided. ing. The outer peripheral surface of the motor casing 8 and the inner peripheral surface of the cap member 11 are in close contact with each other. As a result, an outer cooling channel (second cooling fluid channel) 12 composed of the spiral groove 10 and the inner peripheral surface of the cap member 11 is formed on the outer peripheral surface of the motor casing 8.

  Here, in this embodiment, as shown in FIG. 1, the spiral groove 10 is provided in a region facing the cooling bush 9 from the bearing 7, but the position and range are not particularly limited. . For example, it may be provided in a region facing the bearings 6a and 6b that generate heat during operation of the high-speed motor 2, or the entire surface from one end side (flange 8a side) to the other end side (flange 8b side) of the outer peripheral surface of the motor casing 8. You may provide so that it may continue. As described above, by providing the spiral groove 10 (that is, the outer cooling flow path 12), the heat generating portion housed inside the motor casing 8 can be effectively cooled.

  As shown in FIG. 3A, the motor casing 8 is provided with a pair of through holes 13 and 14 that penetrates the outer peripheral surface and the inner peripheral surface of the motor casing 8. A coolant supply port 15 is provided on the outer peripheral surface side of the through hole 13. Thereby, the coolant can be supplied from the outside to the inside of the motor casing 8.

  The outer peripheral surface side of the through hole 14 communicates with one end side of the spiral groove 10. Thereby, the coolant can be supplied from the inside of the motor casing 8 to the outer cooling flow path 12.

  The cap member 11 is provided with a through hole (not shown) that penetrates the outer peripheral surface and the inner peripheral surface of the cap member 11. A coolant discharge port 16 is provided on the outer peripheral surface side of the through hole (not shown). Further, the inner peripheral surface side of the through hole (not shown) is provided so as to face the other end side of the spiral groove 10. Thereby, the coolant can be discharged from the outer cooling flow path 12 to the outside of the cap member 11 (that is, outside of the motor casing 8).

  The cooling bush (ring member) 9 is a hollow cylindrical member made of a material (specifically, copper alloy or aluminum alloy) having a higher thermal conductivity than the main shaft 4 and the motor casing 8. The cooling bush 9 is provided between the motor casing 8 and the stator 5 as shown in FIG. Specifically, the cooling bush 9 is joined to the motor casing 8 side so that the outer peripheral surface of the cooling bush 9 and the inner peripheral surface of the motor casing 8 are in close contact.

  Here, as shown in FIG. 2, the cooling bush 9 and the motor casing 8 are joined by inserting the cooling bush 9 inside the motor casing 8, and the outer peripheral surfaces 9 a and 9 b of both ends of the cooling bush 9 and the motor casing 8. The inner peripheral surface is joined by vacuum brazing (also called vacuum brazing) or the like. Thereby, a sealing function can be provided in the circumferential direction whole region of both-ends outer peripheral surface 9a, 9b of the cooling bush 9. FIG.

  Further, the stator 5 is held inside the cooling bush 9 by contacting the inner peripheral surface of the cooling bush 9 with the outer peripheral surface of the stator 5. Specifically, the stator 5 is inserted or shrink-fitted inside the cooling bush 9.

  As shown in FIG. 4, a spiral groove 17 is provided on the outer peripheral surface of the cooling bush 9 from one end side (end portion 9a side) to the other end side (end portion 9b side) of the axial end portion. Yes. Here, although the upper surface of the spiral groove portion 17 is open, the cooling bush 9 is inserted into the motor casing 8 as described above, and the outer peripheral surface of the cooling bush 9 and the inner peripheral surface of the motor casing 8 are Are joined to the motor casing 8 side so that the upper surface of the spiral groove portion 17 is closed by the inner peripheral surface of the motor casing 8. As a result, an inner cooling channel (first cooling fluid channel) 18 composed of the spiral groove portion 17 and the inner peripheral surface of the motor casing 8 is formed on the outer peripheral surface of the cooling bush.

  The inner cooling flow path 18 communicates with the through hole 13 on the other end side (end portion 9b side) and the through hole 14 on one end side (end portion 9a side). Thereby, the inner cooling flow path (first cooling fluid flow path) 18 and the outer cooling flow path (second cooling fluid flow path) 12 are communicated. Therefore, the coolant can be supplied to the inner cooling flow path 18 from the outside of the motor casing 8 through the supply port 15 and the through hole 13. Further, the coolant after flowing through the inner cooling flow path 18 can be supplied to the outer cooling flow path 12 formed on the outer peripheral surface of the motor casing 8 through the through hole 14. Further, the coolant after flowing through the outer cooling flow path 12 can be discharged from the coolant discharge port 16 to the outside of the motor casing 8 through a through hole (not shown) provided in the cap member 11. .

  The length of the cooling bush 9 in the axial direction is not particularly limited, but is preferably substantially the same as the length of the stator 5 from the viewpoint of cooling. Further, the range of the spiral groove portion 17 provided on the outer peripheral surface of the cooling bush 9 is not particularly limited.

  The coolant that can be applied in the present embodiment is not particularly limited as long as it can effectively cool the main shaft 4, the stator 5, and the bearings 6 and 7 housed in the motor casing 8. Specific examples of such a coolant include water, antifreeze such as ethylene glycol and propylene glycol, and oil. Furthermore, instead of the coolant, a gas such as nitrogen, helium, neon, or the like may be used as the cooling fluid.

  As shown in FIG. 1, the compressor body 3 (3 </ b> A, 3 </ b> B) includes an impeller 19 (19 </ b> A, 19 </ b> B) provided at one end 4 </ b> A (the other end 4 </ b> B) of the main shaft and a fixed wall facing the front surface 19 a of the impeller 19. The shroud ring 20 (20A, 20B) having 20a, and the compressor main body casing 21 (21A, 21B) that houses the impeller 19 and the shroud ring 20 and holds the shroud ring 20 are provided. . Circulating gas (refrigerant gas) such as helium or neon is sealed inside the compressor main bodies 3A and 3B. In addition, the code | symbol 22 (22A, 22B) is an exit side of the impeller 19 (19A, 19B).

  Here, the compressor main body casing 21 </ b> A is coupled by a bolt or the like at the flange portion 8 a of the motor casing 8. The shroud ring 20A is fixed to the compressor body casing 21A. Therefore, the shroud ring 20A is coupled to the motor casing 8 via the compressor body casing 21A.

  A gap called a shroud clearance is provided between the front surface 19a of the impeller 19A and the fixed wall 20a of the shroud ring 20A. Here, the impeller 19 </ b> A is fixed to the main shaft 4, and the shroud ring 20 </ b> A is indirectly fixed to the motor casing 8. For this reason, when the high-speed motor 2 is driven and the axial extension between the main shaft 4 and the motor casing 8 changes, the value of the shroud clearance also changes.

Next, the cooling operation when the compressor 1 of this embodiment, that is, the high-speed motor 2 is driven will be described.
As shown in FIG. 1, when the main shaft 4 of the high-speed motor 2 starts rotating, the impellers 19A and 19B fixed to the end portions 4A and 4B of the main shaft 4 in the compressor main bodies 3A and 3B rotate at high speed. The impellers 19A and 19B adiabatically compress the circulating gas such as helium and neon, so that the temperatures of the outlet sides 22A and 22B of the impellers 19A and 19B rise. Specifically, for example, when the circulating gas at 30 ° C. is compressed to a pressure ratio of about 1.4, the outlet temperature rises to near 90 ° C. At this time, since the main shaft 4 and the motor casing 8 that are relatively high in temperature are made of materials having substantially the same thermal expansion coefficient, the difference in the amount of elongation in the axial direction is suppressed. Therefore, there is little influence on the shroud clearance, and there is no possibility that the efficiency of the compressor 1 is lowered.

  Further, due to high-speed rotation of the main shaft 4, heat generation due to motor copper loss, iron loss, etc., heat generation due to fluid friction in the gap between the stator 5 and the rotor 4a, and heat generation due to fluid friction in the bearing clearances of the bearings 6 and 7 are achieved. Occurs. Thereby, the temperature of the stator 5, the rotor 4a, the bearings 6a and 6b, the bearings 7a and 7b, and the main shaft 4 itself increases.

  Therefore, in the compressor 1 of this embodiment, the coolant is supplied from the supply port 15 to the inner cooling flow path 18. As the coolant flows along the inner cooling flow path 18, the entire cooling bush 9 is cooled. The stator 5 can be directly cooled from the inside of the motor casing 8 by the cooling bush 9. In addition, since the cooling bush 9 is formed of a material having a large thermal expansion coefficient such as a copper alloy or an aluminum alloy, the stator 5 can be cooled more effectively.

  Next, the coolant after flowing through the inner cooling channel 18 is supplied from the through hole 14 to the outer cooling channel 12 formed on the outer peripheral surface of the motor casing 8. That is, the cooling liquid absorbs heat from the stator 5 in the process of flowing along the inner cooling flow path 18 and is discharged to the outside of the motor casing 8. When the coolant flows along the outer cooling flow path 12, the bearing 7 (7 a, 7 b) disposed inside the motor casing 8 can be cooled.

  Finally, the coolant after flowing through the outer cooling flow path 12 is discharged from the discharge port 16. That is, in the process of flowing along the outer cooling flow path 12 provided on the outer peripheral surface of the motor casing 8, the coolant absorbs heat from the bearing 7 housed inside the motor casing 8 and is then discharged outside the system. The

  As described above, according to the compressor 1 of the present embodiment, the hollow cylinder in which the inner cooling flow path (first cooling fluid flow path) 18 is provided on the outer side between the motor casing 8 and the stator 5. Therefore, the stator 5 can be directly cooled from the inside of the motor casing 8. Further, since the cooling bush 9 is made of a copper alloy or an aluminum alloy having a thermal conductivity higher than that of the main shaft 4 and the motor casing 8, heat can be effectively removed from the stator 5.

  Further, since the cooling bush 9 is made of a material having a higher thermal conductivity than the main shaft 4 and the motor casing 8 and is responsible for the cooling function, a material having a large thermal expansion coefficient is selected for the main shaft 4 and the motor casing 8. be able to. Thereby, since the difference in the amount of elongation in the axial direction between the main shaft 4 and the motor casing 8 can be suppressed, the efficiency of the compressor 1 can be maintained without reducing the efficiency of the impeller 19 (19A, 19B). Can do.

  Further, according to the compressor 1 of the present embodiment, the outer cooling flow path (second cooling fluid flow path) 12 is provided on the outer peripheral surface of the motor casing 8. Thereby, heat generating parts other than the rotor 5 such as the bearing 7 accommodated inside the motor casing 8 can be effectively cooled.

  In addition, a through hole 14 that penetrates the outer peripheral surface and the inner peripheral surface of the motor casing 8 is provided, and the inner and outer cooling passages 12 and 18 are communicated with each other through the through hole 14. Thereby, since the cooling liquid used for the inner side cooling flow path 18 can be used for the outer side cooling flow path 12, the usage-amount of a cooling liquid can be halved. Furthermore, since the number of coolant supply pipes can be halved, the cooling structure can be simplified.

  Furthermore, according to the compressor 1 of this embodiment, since the main shaft 4 and the motor casing 8 are made of the same material or a material having substantially the same thermal expansion coefficient, for example, stainless steel, the operation of the compressor 1 is performed. The difference in the amount of elongation in the axial direction can be reduced. Thereby, the front surface 19a of the impeller 19 (19A, 18B) fixed to the spindle end 4A, 4B and the shroud ring 20 (20A, 20B) fixed to the motor casing 8 via the compressor body casing 21 (21A, 21B). 20B), the amount of change in the gap (shroud clearance) between the fixed wall 20a and the fixed wall 20a can be suppressed, so that the compressor 1 can maintain high efficiency.

  By the way, according to the compressor cooling structure disclosed in Patent Document 3 described above, the motor stator can be efficiently cooled by forming a cooling liquid cooling passage on the inner peripheral surface of the motor casing. . In the cooling structure, a cooling method is described in which the coolant is sprayed directly from the coolant passage provided inside the motor casing to the end portion of the motor winding. However, these gases are enclosed in a turbo compressor or a turbo expander of a refrigerator that uses helium or neon as a circulating gas. For this reason, when the cooling liquid is sprayed on the stator or the like, the circulating gas inside the refrigerator is contaminated, and as a result, there is a problem that the cooling liquid is solidified in the low temperature portion of the refrigerator. In addition, rare and expensive circulating gases such as helium and neon leak to the coolant passage side, and there is a problem in that the circulating gas sealing pressure is lowered and the capacity of the refrigerator is lowered.

  On the other hand, according to the compressor 1 of the present embodiment, the cooling bush 9 is inserted inside the motor casing 8, and both the outer peripheral surfaces 9 a and 9 b of the cooling bush 9 and the inside of the motor casing 8 facing this are arranged. The peripheral surface is joined by vacuum brazing or the like to provide a sealing function. Thereby, it is possible to prevent a rare and expensive circulating gas such as helium or neon from leaking to the coolant side (that is, inside the inner cooling flow path 18). Therefore, it is possible to prevent a reduction in the capacity of the refrigerator without reducing the sealed pressure of the circulating gas.

  Further, according to the compressor 1 of the present embodiment, both the inner and outer cooling flow paths 12 and 18 of the coolant are provided at the boundary where the inner member and the outer member are in close contact with each other. Openings above the spiral grooves 10 and 17 provided on the outer peripheral surface of the member are closed by the inner peripheral surface of the outer member. Here, since the spiral groove portions 10 and 17 are formed on the outer peripheral surface of the member, the processing is easy as compared with the case where the spiral groove portions 10 and 17 are formed on the inner peripheral surface of the member.

<Second Embodiment>
Next, a second embodiment to which the present invention is applied will be described. In the present embodiment, the configuration of the motor casing is different from that of the motor casing 8 of the first embodiment, and the other configurations are the same as those of the first embodiment, and thus the description thereof is omitted.

  As shown in FIG. 5, the motor casing 28 of the present embodiment includes casing members 28A and 28B provided at both ends in the axial direction, and a casing member provided between the casing members 28A and 28B in the center in the axial direction. 28C.

  The casing members 28A and 28B provided at both ends in the axial direction are preferably made of a material having a low thermal conductivity and the same material as the main shaft or a material having substantially the same thermal expansion coefficient, for example, stainless steel. Casing members 28A and 28B located at both ends of motor casing 28 in the axial direction are close to impellers 19A and 19B of motor casing 28, and become high temperature by driving a high-speed motor. Here, if the casing members 28A and 28B are made of a material having a high thermal conductivity, for example, a copper alloy or an aluminum alloy, the temperature rise of the main shaft 4 and the bearings 6a, 6b, 7a, 7b inside the motor casing 28 due to the heat conduction. It is because it will promote.

  On the other hand, the casing member 28C provided at the center in the axial direction is preferably made of a material having high thermal conductivity, for example, copper alloy or aluminum alloy. An outer cooling channel 12 is provided outside the casing member 28C, and has a structure in contact with the coolant. Here, the casing member 28C is effectively cooled by the flow of the coolant by making the casing member a material having a high thermal conductivity. Thereby, while being provided in the position which opposes the outer side cooling flow path 12 on both sides of the casing member 28C, it becomes possible to cool effectively the bearings 7a and 7b which are contacting in the inner peripheral surface of this casing member 28C. Become.

  The stainless steel casing members 28A and 28B and the copper alloy casing member 28C are joined by diffusion welding, explosive pressure welding, or the like. Here, reference numerals 23a and 23b shown in FIG. 5 indicate the joining surfaces of different metals.

  By the way, as mentioned above, the motor casing 8 used in the first embodiment is a single member made of stainless steel. On the other hand, the motor casing 28 of this embodiment has a configuration in which a casing member 28C made of a copper alloy having a high thermal conductivity is arranged in the central portion of the casing, and the motor casing 28 as a whole extends in the axial direction. There is a concern that the amount differs from the amount of elongation of the main shaft 4.

  However, the casing member 28C has a structure in which the inner peripheral surface is in contact with the inner cooling flow path 18 (and the outer peripheral surface of the cooling bush 9) and the outer peripheral surface is in contact with the outer cooling flow path 12. Here, the casing member 28C is made of a material having a high thermal conductivity, and is effectively cooled by the inner and outer cooling channels 12 and 18 filled with the coolant. Therefore, even if the casing member 28C is made of a copper alloy, it remains at substantially room temperature, and the axial extension due to thermal expansion during steady operation is slight. In other words, the casing portion made of copper alloy is a portion that is cooled and hardly rises in temperature, and does not cause a dimensional change due to thermal expansion.

  On the other hand, it is the stator 5, the bearings 6, 7 and the main shaft 4 that rise in temperature due to heat generation during steady operation and reach a high temperature, and extends in the axial direction due to thermal expansion. Further, the thermal expansion coefficients of the stainless steel casing members 28A and 28B joined to both ends of the casing member 28C are substantially equal to those of the stator 5, the bearings 6 and 7 and the main shaft 4 made of a magnetic iron-based material. .

  Therefore, the shroud clearance (see FIG. 1) between the front surface 19a of the impeller 19 attached to the tip end of the main shaft 4 and the fixed wall 20a decreases. As the shroud clearance decreases, the impeller efficiency improves. Therefore, by assembling in advance in consideration of the decrease, it is possible to suppress the temperature rise of the stator 5 and the bearings 6 and 7 with high performance. Possible compressors can be provided.

  The axial range of the copper alloy casing member 28C is not particularly limited. The casing member 28C made of a material having a high thermal conductivity and the cooling ring 9 inserted inside the casing member 28C only need to face each other in at least a part of the region (they should be in contact).

  As described above, also in this embodiment, the same effect as that of the first embodiment can be obtained. In addition, according to the present embodiment, the casing member 28 </ b> C made of a material having a high thermal conductivity is used for a part of the motor casing 28. Since the casing member 28C is used so as to partially contact the cooling bush 9, there is little dimensional variation in the axial direction of the entire motor casing 28 during operation.

  In addition, a cooling bush 9 that bears a cooling function is joined to the inner peripheral surface of the motor casing 28, and the casing member 28C in contact with the cooling bush 9 is made of a material having a high thermal conductivity, so that it is effectively cooled. In other words, the casing member 28 </ b> C that contacts at least a part of the cooling bush 9 is cooled by the cooling bush 9, so that the dimensional variation is small.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the first and second embodiments described above, as shown in FIG. 1, the compressor bodies 3 </ b> A and 3 </ b> A are attached to both ends of the high-speed motor 2 in which the impellers 19 </ b> A and 19 </ b> B are respectively fixed to both ends 4 </ b> A and 4 </ b> B of the main shaft 4. Although the structure provided with 3B was demonstrated, the structure provided with only one compressor main body 3 with which the impeller 19 was fixed to either one end of the main shaft 4 may be sufficient. Moreover, it is good also as an expander instead of a compressor.

DESCRIPTION OF SYMBOLS 1 ... Compressor 2 ... High-speed motor 3, 3A, 3B ... Compressor main body 4 ... Main shaft 4a ... Rotor 5 ... Stator 6, 6a, 6b, 7, 7a, 7b ... Bearing 8, 28 ... Motor casing 9 ... Cooling bush (ring member)
10, 17 ... spiral groove 11 ... cap member 12 ... outer cooling channel (second cooling fluid channel)
13, 14 ... Through hole 15 ... Supply port 16 ... Discharge port 18 ... Inner cooling channel (first cooling fluid channel)
19, 19A, 19B ... impeller 19a ... front surface 20, 20A, 20B ... shroud ring 20a ... fixed wall 21, 21A, 21B ... compressor body casing 22, 22A, 22B ... Impeller outlet side 23a, 23b ... Joint surfaces 28A, 28B, 28C of different metals

Claims (4)

A main shaft provided with a rotor in the center, a stator facing the rotor, a bearing for rotatably holding the main shaft, the main shaft, the stator and the bearing are housed, and the stator is A high-speed motor having at least a motor casing to be held; an impeller provided at at least one end of the main shaft; a shroud ring having a fixed wall facing the front surface of the impeller; and the impeller and the shroud ring are housed. A compressor body having at least a compressor body casing for holding the shroud ring, the compressor having the motor casing and the compressor body casing coupled to each other,
Between the motor casing and the stator, provided with a hollow cylindrical ring member made of a material having a larger thermal conductivity than the main shaft and the motor casing,
The ring member is provided with a spiral groove on the outer peripheral surface from one end side to the other end side of the axial end portion, and the outer peripheral surface and the inner peripheral surface of the motor casing are in close contact with each other on the motor casing side. A compressor characterized in that it has a first cooling fluid flow path which is airtightly joined and is constituted by the groove and the inner peripheral surface. The motor casing has a spiral second cooling fluid flow path provided on the outer peripheral surface from one end side to the other end side of the axial end portion;
A through hole penetrating the outer peripheral surface and the inner peripheral surface of the motor casing,
The compressor according to claim 1, wherein the first cooling fluid channel and the second cooling fluid channel are communicated with each other through the through hole.   The compressor according to claim 1 or 2, wherein the main shaft and the motor casing are made of the same material or a material having substantially the same thermal expansion coefficient.   2. The motor casing according to claim 1, wherein at least a part of the region in contact with the ring member is made of a material having a higher thermal conductivity than a material constituting another region of the motor casing. 4. The compressor according to any one of 3.

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