Magnetic bearing device and compressor

Abstract

To provide a magnetic bearing device which can suppress a windage loss.SOLUTION: A magnetic bearing device includes a magnetic bearing unit having a gas passage. The gas passage is in communication with a return space for turning a flow direction of cooling gas to a flow direction along an axial direction of a rotation shaft.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a magnetic bearing device and a compressor. [Background technology]

[0002] A known cooling system is a turbo chiller that includes a compressor that compresses a refrigerant. The compressor includes an impeller that rotates at high speed and a magnetic bearing device that rotates the impeller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-071533 [Patent Document 2] Japanese Patent Application Publication No. 8-061366 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-283813 [Patent Document 4] Japanese Patent Application Publication No. 2018-028296 [Patent Document 5] Japanese Patent Application Laid-Open No. 2015-183650 Summary of the Invention [Problem to be solved by the invention]

[0004] The compressor is configured to compress a refrigerant having a density higher than that of air by rotating an impeller at high speed. When the rotating parts of the magnetic bearing device (including the rotating shaft and motor) rotate at high speed together with the impeller, windage loss occurs inside the magnetic bearing device.

[0005] Such windage loss has various adverse effects on the performance of the magnetic bearing device. For example, as windage loss increases, the energy loss of the magnetic bearing device increases, resulting in increased power consumption of the magnetic bearing device.

[0006] The amount of heat generated by the motor of a magnetic bearing device depends on the magnitude of windage loss. Therefore, as windage loss increases, the amount of heat generated by the motor increases, which can result in demagnetization of the motor rotor. Furthermore, the components of the magnetic bearing device (e.g., electromagnets, sensors, molding resin, etc.) can become too hot beyond their heat-resistant temperature, and in the worst case scenario, the components of the magnetic bearing device can fail.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a magnetic bearing device and a compressor that can suppress windage loss. [Means for solving the problem]

[0008] In one aspect, there is provided a magnetic bearing device comprising: a motor including a rotating shaft, a rotor fixed to the rotating shaft, and a stator disposed radially outward of the rotor; a casing accommodating the rotating shaft and the motor; a magnetic bearing unit having a gas inlet port for introducing a cooling gas into an internal space of the casing, a gas outlet port for discharging the cooling gas introduced into the internal space of the casing, and a gas flow path for allowing the cooling gas introduced from the gas inlet port to flow into the internal space of the casing. The gas flow path communicates with a turning space for redirecting the flow direction of the cooling gas to a flow direction along the axial direction of the rotating shaft.

[0009] In one aspect, the gas flow path has a radial flow path extending in a radial direction of the rotating shaft and communicating with the gas introduction port, and an axial flow path connected to the radial flow path and extending in the axial direction, and the axial flow path opens at the turning space. In one aspect, the magnetic bearing unit has a plurality of gas flow passages, including the gas flow passage, arranged along the circumferential direction of the rotating shaft. In one aspect, the magnetic bearing device includes an axial disk fixed to the rotating shaft, and the gas exhaust port is arranged radially outward of the axial disk and connected to the bottom of the casing.

[0010] In one aspect, when the magnetic bearing unit is defined as a first magnetic bearing unit, the gas flow path is defined as a first gas flow path, and the gas inlet port is defined as a first gas inlet port, the magnetic bearing device includes a second magnetic bearing unit arranged on the opposite side of the motor from the first magnetic bearing unit, and a second gas inlet port communicating with a second gas flow path formed in the second magnetic bearing unit. In one embodiment, the magnetic bearing device includes an axial disk fixed to the rotating shaft, the axial disk having a first surface that comes into contact with the cooling gas flowing through the first gas flow path, and a second surface that is positioned opposite the first surface and comes into contact with the cooling gas flowing through the second gas flow path, and each of the first surface and the second surface has a plurality of delivery grooves that deliver the cooling gas radially outward from the axial disk. In one embodiment, each of the plurality of delivery grooves extends radially from an inner peripheral edge of the axial disk toward an outer peripheral edge of the axial disk in a direction opposite to a rotation direction of the axial disk.

[0011] In one aspect, each of the plurality of delivery grooves has a sloped bottom that traps the cooling gas. In one embodiment, the magnetic bearing device includes an axial disk fixed to the rotating shaft, the axial disk having a first surface that comes into contact with the cooling gas flowing through the gas flow path and a second surface located downstream of the first surface in the flow direction of the cooling gas, the first surface having a plurality of delivery grooves that deliver the cooling gas radially outward of the axial disk, and the second surface having a plurality of delivery grooves that deliver the cooling gas radially inward of the axial disk. In one aspect, each of the plurality of feed grooves extends radially from the inner peripheral edge of the axial disk toward the outer peripheral edge of the axial disk along the direction opposite to the rotation direction of the axial disk, and each of the plurality of feed grooves extends radially from the inner peripheral edge of the axial disk toward the outer peripheral edge of the axial disk along the rotation direction of the axial disk.

[0012] In one aspect, each of the plurality of outlet grooves and each of the plurality of inlet grooves has a sloped bottom that traps the cooling gas. In one embodiment, the gas inlet port is disposed on one end side of the casing, and the gas outlet port is disposed on the other end side opposite to the one end.

[0013] In one aspect, there is provided a compressor including the magnetic bearing device described above and an impeller configured to be rotatable by the magnetic bearing device.

[0014] In one embodiment, the cooling gas is a refrigerant gas that is introduced into the compressor and circulates through a refrigerator. [Effects of the Invention]

[0015] The magnetic bearing unit has a gas flow path that communicates with the turning space, so that the cooling gas changes direction in the turning space and flows smoothly along the axial direction of the rotating shaft, reducing the temperature of the rotating components and suppressing windage loss around the rotating shaft. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of a refrigerator. [Figure 2] FIG. 1 illustrates an embodiment of a compressor. [Figure 3] 1 is a diagram illustrating an embodiment of a magnetic bearing device. [Figure 4] FIG. 2 is a diagram showing a magnetic bearing unit. [Figure 5] FIG. 10 is a view of a plurality of gas flow paths as viewed from the turning space side along the axial direction. [Figure 6] FIG. 1 is a diagram showing an axial disk fixed to a rotating shaft. [Figure 7] FIG. 7(a) is a diagram showing the first surface of the axial disc, and FIG. 7(b) is a diagram showing the delivery grooves formed on the first surface of the axial disc. [Figure 8] FIG. 8(a) is a diagram showing the second surface of the axial disc, and FIG. 8(b) is a diagram showing the delivery grooves formed on the second surface of the axial disc. [Figure 9] FIG. 10 is a diagram showing another embodiment of the magnetic bearing device. [Figure 10] FIG. 10(a) is a diagram showing the first surface of the axial disc, and FIG. 10(b) is a diagram showing the delivery grooves formed on the first surface of the axial disc. [Figure 11] FIG. 11(a) is a diagram showing the second surface of the axial disc, and FIG. 11(b) is a diagram showing the feed grooves formed on the second surface of the axial disc. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings described below, identical or corresponding components are designated by the same reference numerals, and duplicated descriptions will be omitted. In the multiple embodiments described below, the configuration of an embodiment that is not particularly described is the same as that of other embodiments, and therefore duplicated descriptions will be omitted.

[0018] Fig. 1 is a schematic diagram showing one embodiment of a refrigerator. In the embodiment shown in Fig. 1, the refrigerator CH is a small turbo refrigerator that can be placed in the installation space of, for example, semiconductor manufacturing equipment. The refrigerator CH includes a compressor CP that compresses a refrigerant gas, a condenser 1 that condenses the refrigerant gas compressed by the compressor CP, a pressure reduction mechanism 5 that reduces the pressure of the refrigerant liquid condensed by the condenser 1, and an evaporator 10 that evaporates the refrigerant liquid reduced in pressure by the pressure reduction mechanism 5.

[0019] The refrigerator CH includes a refrigerant gas introduction line 22 connected to the compressor CP and the condenser 1, and a heat transfer tube 11 connected to the condenser 1. The condenser 1 is configured to condense high-temperature, high-pressure refrigerant gas introduced from the compressor CP through the refrigerant gas introduction line 22.

[0020] The heat transfer tubes 11 are configured to cool the refrigerant gas introduced into the condenser 1 by cooling water flowing inside the heat transfer tubes 11. The condenser 1 is cooled by the heat transfer tubes 11 and stores the liquefied refrigerant gas (i.e., refrigerant liquid).

[0021] The refrigerator CH includes a refrigerant liquid transfer line 24 connected to the condenser 1 and the evaporator 10. A pressure reducing mechanism 5 is attached to the refrigerant liquid transfer line 24. The pressure reducing mechanism 5 includes, for example, an expansion valve. Most of the refrigerant liquid in the condenser 1 is transferred to the evaporator 10 through the refrigerant liquid transfer line 24. The refrigerant liquid passing through the refrigerant liquid transfer line 24 is sent to the evaporator 10 in a state where it has been reduced in pressure by the pressure reducing mechanism 5.

[0022] The refrigerator CH is equipped with a refrigerant liquid supply line 14 connected to the condenser 1 and the compressor CP (more specifically, to the magnetic bearing device MB described later). A portion of the refrigerant liquid in the condenser 1 is supplied to the magnetic bearing device MB through the refrigerant liquid supply line 14.

[0023] The refrigerator CH includes heat transfer tubes 12 connected to an evaporator 10. The refrigerant liquid sent to the evaporator 10 through the refrigerant liquid transfer line 24 absorbs heat (latent heat of evaporation) from the cooling water flowing inside the heat transfer tubes 12 and evaporates.

[0024] The refrigerator CH includes an evaporator 10 and a refrigerant gas introduction line 20 connected to the compressor CP. The refrigerant liquid (i.e., refrigerant gas) evaporated in the evaporator 10 is introduced into the compressor CP through the refrigerant gas introduction line 20. The refrigerant gas introduced into the compressor CP is introduced again into the condenser 1 through the refrigerant gas introduction line 22.

[0025] In this way, the refrigerator CH is a cooling system that cools the space to be cooled (for example, the installation space of a semiconductor manufacturing device) by circulating a refrigerant between the condenser 1 and the evaporator 10 and the compressor CP to form a refrigerant cycle.

[0026] Fig. 2 is a diagram showing one embodiment of a compressor. Fig. 3 is a diagram showing one embodiment of a magnetic bearing device. As shown in Fig. 2, the compressor CP includes a magnetic bearing device MB and impellers 50A and 50B configured to be rotatable by the magnetic bearing device MB. The impellers 50A and 50B have the same structure and are disposed on both sides of the magnetic bearing device MB. Hereinafter, in this specification, the impellers 50A and 50B may be simply referred to as impeller 50 without distinction.

[0027] In this embodiment, the compressor CP has multiple impellers 50 arranged on both sides of the magnetic bearing device MB, but in one embodiment, the compressor CP may have multiple impellers 50 arranged on one side of the magnetic bearing device MB, or a single impeller 50.

[0028] The magnetic bearing device MB includes a rotating shaft 51 to which impellers 50A and 50B are fixed, a motor 52 that rotates the rotating shaft 51, and a casing 55 that houses the rotating shaft 51 and the motor 52. The motor 52 is disposed between the impellers 50A and 50B.

[0029] Impellers 50A and 50B are fixed to both ends of rotary shaft 51 and are covered with impeller covers 59A and 59B. Impeller covers 59A and 59B may be components of casing 55 or may be separate components.

[0030] The casing 55 includes a partition wall 56A that separates the impeller 50A from the motor 52, a partition wall 56B that separates the impeller 50B from the motor 52, and a motor frame 57 disposed between the partition walls 56A and 56B.

[0031] The motor 52 includes a rotor 53 fixed to a rotating shaft 51, and a stator 54 disposed radially outward of the rotor 53 and forming a gap between the rotor 53 and the stator 54. The stator 54 includes a stator core 54a surrounding the rotor 53 and a plurality of coils 54b wound around the stator core 54a. The rotor 53 rotates due to a rotating magnetic field formed between the rotor 53 and the stator 54. The rotating shaft 51 to which the rotor 53 is fixed rotates together with the rotor 53.

[0032] The magnetic bearing device MB includes magnetic bearing units 60A and 60B for rotatably supporting the rotating shaft 51. The magnetic bearing unit 60A is disposed adjacent to the partition wall 56A, and the magnetic bearing unit 60B is disposed adjacent to the partition wall 56B.

[0033] The motor frame 57 is disposed around the motor 52 and is sandwiched between the magnetic bearing units 60A and 60B. The magnetic bearing units 60A and 60B and the motor frame 57 are disposed concentrically with the rotating shaft 51.

[0034] The magnetic bearing units 60A and 60B have the same structure. Hereinafter, in this specification, the magnetic bearing units 60A and 60B may not be distinguished from each other and may simply be referred to as magnetic bearing unit 60. Similarly, the partition walls 56A and 56B may not be distinguished from each other and may simply be referred to as partition wall 56.

[0035] 3, magnetic bearing unit 60 includes a radial magnetic bearing 68 that surrounds rotating shaft 51, a bearing holder 61 that holds radial magnetic bearing 68, and a radial displacement sensor 70 that detects radial displacement of rotating shaft 51. The radial direction of rotating shaft 51 is perpendicular to the direction of axis AX of rotating shaft 51.

[0036] The bearing holder 61 is fixed to the casing 55 (more specifically, the partition wall 56 and the motor frame 57). Two radial magnetic bearings 68 arranged on either side of the motor 52 along the direction of the axis AX are configured to support the rotating shaft 51 in a non-contact manner. More specifically, a magnetic body 69 is attached to the outer circumferential surface of the rotating shaft 51 at a position radially inward of the radial magnetic bearings 68, and a radial gap is formed between the magnetic body 69 and the radial magnetic bearings 68. The radial gap is a gap located radially outward of the rotating shaft 51.

[0037] The radial magnetic bearing 68 rotatably supports the rotating shaft 51 without contact so as to maintain a radial gap. The radial displacement sensor 70 is fixed to the bearing holder 61 and faces the outer peripheral surface of the rotating shaft 51. The radial displacement sensor 70 is configured to detect the tilt (displacement) of the rotating shaft 51 in the radial direction.

[0038] The magnetic bearing device MB includes a touchdown bearing 66 arranged between the bearing holder 61 and the rotating shaft 51, and a bearing supporter 67 that supports the touchdown bearing 66. The touchdown bearing 66 is a contact-type bearing (for example, a ball bearing) that rotatably supports the rotating shaft 51. The bearing supporter 67 is attached to the bearing holder 61 and supports the touchdown bearing 66.

[0039] The magnetic bearing device MB is equipped with a gas inlet port 62 for introducing cooling gas into the internal space of the casing 55 (i.e., the space surrounded by the partitions 56A, 56B and the motor frame 57), and a gas outlet port 90 for discharging the cooling gas introduced into the internal space of the casing 55.

[0040] In this embodiment, the magnetic bearing device MB has two gas introduction ports 62, the number of which corresponds to the number of magnetic bearing units 60 (two). The refrigerant gas supply line 16 branches midway and is connected to the two gas introduction ports 62. Therefore, a portion of the refrigerant gas in the condenser 1 is supplied to the internal space of the casing 55 through the refrigerant gas supply line 16 and the gas introduction ports 62.

[0041] In this embodiment, the cooling gas supplied to the internal space of the casing 55 corresponds to the refrigerant gas that forms the refrigerant cycle of the refrigerator CH. In one embodiment, the cooling gas may be a gas other than the refrigerant gas.

[0042] The refrigerator CH includes an evaporator 10 and a refrigerant gas discharge line 18 connected to a gas discharge port 90 (see FIG. 1). Therefore, the cooling gas (refrigerant gas in this embodiment) supplied to the internal space of the casing 55 is discharged to the evaporator 10 through the gas discharge port 90 and the refrigerant gas discharge line 18. Below, a configuration for supplying the cooling gas to the internal space of the casing 55 and discharging the cooling gas from the internal space of the casing 55 will be described.

[0043] 4 is a diagram showing a magnetic bearing unit 60. As shown in FIG. 4, the magnetic bearing unit 60 has an annular groove 65 that communicates with a gas inlet port 62, and a plurality of gas flow paths 64 that are connected to the annular groove 65.

[0044] The annular groove 65 is formed on the outer peripheral surface of the bearing holder 61. Therefore, when the magnetic bearing unit 60 is attached to the motor frame 57, the annular groove 65 forms an annular flow path disposed between the inner peripheral surface of the motor frame 57 and the outer peripheral surface of the bearing holder 61.

[0045] With this configuration, the cooling gas flowing into the annular groove 65 through the gas inlet port 62 flows annularly along the circumferential direction of the magnetic bearing unit 60 and flows into each of the plurality of gas flow paths 64 .

[0046] The plurality of gas flow paths 64 are formed in an outer portion of the bearing holder 61. Each of the plurality of gas flow paths 64 has a radial flow path 64a that extends in the radial direction of the rotating shaft 51 and communicates with the gas inlet port 62 via an annular groove 65, and an axial flow path 64b that is connected to the radial flow path 64a and extends in the direction of the axis AX.

[0047] The axial flow path 64b opens into a turn-back space SP surrounded by the magnetic bearing unit 60 and the partition wall 56. The turn-back space SP forms a part of the internal space of the casing 55.

[0048] 5 is a view of the multiple gas flow paths as viewed from the turning space side along the axial direction. As shown in Fig. 5, the multiple gas flow paths 64 are arranged at equal intervals along the circumferential direction of the rotating shaft 51. Therefore, the cooling gas supplied to the annular groove 65 is introduced uniformly into each gas flow path 64 and flows into the turning space SP through each gas flow path 64.

[0049] The opening of the axial flow path 64b faces the partition wall 56. Therefore, the cooling gas passing through the axial flow path 64b collides with the wall surface of the partition wall 56 and changes its direction by 360 degrees (see FIG. 4). The cooling gas that has changed direction in the turning space SP is introduced into the annular gap between the magnetic bearing unit 60 and the outer peripheral surface of the rotating shaft 51.

[0050] The turning space SP is a space for changing the flow direction of the cooling gas to a flow direction along the axis AX. The cooling gas that has changed direction in the turning space SP flows along the axis AX and comes into contact with the touchdown bearing 66. The cooling gas that comes into contact with the touchdown bearing 66 passes through a gap formed in the touchdown bearing 66 and comes into contact with the radial magnetic bearing 68.

[0051] The radial magnetic bearing 68 is a heat-generating body. In particular, the radial magnetic bearing 68 may become hot due to windage loss that occurs between the radial magnetic bearing 68 and the rotating shaft 51 (more specifically, the magnetic body 69). The cooling gas flowing along the direction of the axis AX comes into contact with the radial magnetic bearing 68 and cools the radial magnetic bearing 68 (and the magnetic body 69). Furthermore, the cooling gas flows smoothly along the direction of the axis AX so as to change the airflow that occurs between the radial magnetic bearing 68 and the rotating shaft 51 from turbulent flow to laminar flow. Therefore, the cooling gas can suppress windage loss while cooling the radial magnetic bearing 68.

[0052] The cooling gas passing through the gap between the radial magnetic bearing 68 and the rotating shaft 51 flows into the motor space MS in which the motor 52 is disposed (see FIGS. 3 and 4). The cooling gas that flows into the motor space MS flows smoothly along the axis AX while cooling the motor 52, which serves as a heat-generating body. The cooling gas cools the air around the motor 52 and the rotating shaft 51, thereby reducing windage loss.

[0053] The magnetic bearing device MB includes a cooling jacket 40 disposed on the inner peripheral surface of the motor frame 57. The cooling jacket 40 is connected to a refrigerant liquid supply line 14 (see FIG. 1). Therefore, a portion of the refrigerant liquid in the condenser 1 is supplied to the cooling jacket 40 through the refrigerant liquid supply line 14.

[0054] The cooling jacket 40 is disposed radially outside the stator 54 and is disposed around the entire periphery of the motor frame 57. Therefore, the refrigerant liquid flowing through the cooling jacket 40 can cool the motor 52 (particularly the stator 54).

[0055] 6 is a diagram showing an axial disk fixed to a rotating shaft. The magnetic bearing device MB includes an axial disk 80 fixed to the rotating shaft 51, axial bearings 82, 82 arranged on both sides of the axial disk 80, and a spacer 81 that fixes the relative positions of the axial bearings 82, 82.

[0056] The axial disk 80 is made of a magnetic material and has a circular flange shape. An axial gap is formed between the axial disk 80 and the axial bearings 82, 82 in the direction of the axis AX of the rotating shaft 51. The axial bearings 82, 82 rotatably support the rotating shaft 51 via the axial disk 80 without contacting the axial gap so as to maintain the axial gap.

[0057] Although not shown, the magnetic bearing unit 60B is equipped with an axial displacement sensor that detects displacement of the rotating shaft in the direction of the axis AX. The axial displacement sensor is fixed to the bearing holder 61 and is configured to detect deviation (displacement) of the rotating shaft 51 in the direction of the axis AX.

[0058] The spacer 81 is an annular member disposed between the axial bearings 82, 82, and is disposed concentrically with the rotary shaft 51. The spacer 81 is disposed radially outside the axial disc 80, and is fixed to the axial bearings 82, 82. The axial bearings 82, 82 are fixed to the motor frame 57.

[0059] The magnetic bearing device MB has an annular space (i.e., an axial bearing space) AS formed between the axial bearings 82, 82. The cooling gas that has flowed into the motor space MS cools the motor 52 in the motor space MS, and then flows into the axial bearing space AS.

[0060] Returning to Figure 3, the cooling gas introduced into the internal space of the casing 55 through the gas inlet port 62 connected to the magnetic bearing unit 60B flows into the folded space SP formed between the partition wall 56B and the magnetic bearing unit 60B through the annular groove 65 and multiple gas flow paths 64 of the magnetic bearing unit 60B.

[0061] The cooling gas then changes direction in the turning space SP, forming a flow that follows the direction of the axis AX of the rotating shaft 51. The cooling gas that has changed direction passes through a gap formed in the touchdown bearing 66, and then passes through a gap between the radial magnetic bearing 68 and the rotating shaft 51 (more specifically, the magnetic body 69).

[0062] The cooling gas flows smoothly along the direction of the axis AX so as to change the airflow generated between the radial magnetic bearing 68 and the rotating shaft 51 from a turbulent flow to a laminar flow. Therefore, the cooling gas can suppress windage loss while cooling the radial magnetic bearing 68.

[0063] The cooling gas that has passed through the gap between radial magnetic bearing 68 and rotating shaft 51 passes through the gap between rotating shaft 51 and axial bearing 82, and is introduced into axial bearing space AS. In this way, the cooling gas introduced from the magnetic bearing unit 60A side and the cooling gas introduced from the magnetic bearing unit 60B side flow into axial bearing space AS.

[0064] Hereinafter, the cooling gas flowing into the axial bearing space AS from the magnetic bearing unit 60A side may be referred to as the first cooling gas, and the cooling gas flowing into the axial bearing space AS from the magnetic bearing unit 60B side may be referred to as the second cooling gas.

[0065] Figure 7(a) is a diagram showing the first surface of the axial disc, Figure 7(b) is a diagram showing the delivery grooves formed on the first surface of the axial disc, Figure 8(a) is a diagram showing the second surface of the axial disc, and Figure 8(b) is a diagram showing the delivery grooves formed on the second surface of the axial disc.

[0066] When the axial disk 80 rotates together with the rotating shaft 51, the axial disk 80 is configured to send out the first cooling gas and the second cooling gas that have flowed into the axial bearing space AS toward the radial outside of the axial disk 80 (i.e., toward the inner surface of the motor frame 57).

[0067] The axial disk 80 has a first surface 80a1 that comes into contact with the first cooling gas and a second surface 80a2 that comes into contact with the second cooling gas. The first surface 80a1 and the second surface 80a2 are disposed on opposite sides of each other.

[0068] The first surface 80a1 and the second surface 80a2 each have a plurality of delivery grooves 80b1, 80b2 that deliver the first cooling gas and the second cooling gas, respectively, to the outside in the radial direction of the axial disk 80.

[0069] In this embodiment, the delivery grooves 80b1 and 80b2 have the same structure, and therefore, hereinafter in this specification, the delivery grooves 80b1 and 80b2 may be referred to as the delivery groove 80b without any distinction between them.

[0070] The plurality of delivery grooves 80b extend radially from an inner peripheral edge 83 of the axial disk 80 to an outer peripheral edge 84 of the axial disk 80 in the direction opposite to the rotation direction of the axial disk 80.

[0071] In this embodiment, the radially extending discharge grooves 80b have a linear shape, but in one embodiment, the radially extending discharge grooves 80b may have an arc shape (in other words, a spiral shape) as long as they can discharge the cooling gas radially outward from the axial disk 80.

[0072] The delivery groove 80b has a sloped bottom that traps the cooling gas. More specifically, the delivery groove 80b has a vertical surface 85 that extends perpendicular to the surfaces of the axial disk 80 (i.e., the first surface 80a1 and the second surface 80a2) and an inclined surface 86 that extends at an angle to the surfaces of the axial disk 80. The vertical surface 85 and the inclined surface 86 are connected to each other.

[0073] In this embodiment, the delivery groove 80b, which has a vertical surface 85 and an inclined surface 86, has a triangular shape. Therefore, when the axial disk 80 rotates together with the rotation shaft 51, the cooling gas moving in the rotation direction of the axial disk 80 flows along the inclined surface 86 to the bottom of the delivery groove 80b and collides with the vertical surface 85. In this state, the cooling gas is delivered radially outward from the axial disk 80.

[0074] In this way, the delivery grooves 80b are configured to deliver the cooling gas while capturing the cooling gas in the axial bearing space AS. In this embodiment, the axial disk 80 having the plurality of delivery grooves 80b can change the flow of the refrigerant gas from a turbulent flow to a laminar flow, thereby suppressing windage loss around the axial disk 80.

[0075] The gas discharge port 90 is disposed radially outside the axial disk 80 and is connected to the bottom of the motor frame 57 (see FIG. 3). Therefore, the cooling gas sent to the radially outside of the axial disk 80 is introduced into the evaporator 10 through the gas discharge port 90 and the refrigerant gas discharge line 18 (see FIG. 1).

[0076] Refrigerant gas, which is an example of a cooling gas, may undergo a phase transition from a gaseous state to a liquid state in the axial bearing space AS due to changes in its temperature and pressure. In this embodiment, the gas discharge port 90 is connected to the lowermost part of the motor frame 57. Therefore, even if the refrigerant gas liquefies, the liquefied refrigerant gas (i.e., refrigerant liquid) is discharged to the outside of the magnetic bearing device MB through the gas discharge port 90 due to the action of gravity.

[0077] In this embodiment, the magnetic bearing device MB includes magnetic bearing units 60A, 60B arranged on both sides of the motor 52, and gas introduction ports 62, 62 that communicate with gas flow paths 64 formed in the magnetic bearing units 60A, 60B. The gas introduction ports 62, 62 are arranged on both sides of the axial disk 80 in the direction of the axis AX.

[0078] The cooling gas introduced into the internal space of the casing 55 through the gas inlet ports 62, 62 flows from both sides of the axial disk 80 toward the axial disk 80 along the direction of the axis AX, cooling the radial magnetic bearings 68, 68 of the magnetic bearing units 60A, 60B while suppressing windage loss.

[0079] The cooling gas then flows into the axial bearing space AS while cooling the axial bearing 82. As the axial disk 80 rotates, the cooling gas is sent out in a laminar flow state to the radially outer side of the axial disk 80, and is discharged to the outside of the magnetic bearing device MB (i.e., the evaporator 10) through the gas discharge port 90.

[0080] In this way, the first cooling gas introduced into the internal space of the casing 55 through the gas inlet port 62 arranged on the magnetic bearing unit 60A side passes through the folded space SP, motor space MS, and axial bearing space AS on the magnetic bearing unit 60A side in that order, cooling the heat-generating components of the magnetic bearing device MB (e.g., radial magnetic bearing 68, motor 52, axial bearing 82, etc.) while suppressing windage loss occurring in the magnetic bearing device MB.

[0081] The second cooling gas introduced into the internal space of the casing 55 through the gas inlet port 62 arranged on the magnetic bearing unit 60B side passes through the folded space SP and the axial bearing space AS on the magnetic bearing unit 60B side in that order, cooling the heat-generating components of the magnetic bearing device MB (e.g., the radial magnetic bearing 68, the axial bearing 82, etc.) while suppressing windage loss occurring in the magnetic bearing device MB.

[0082] Fig. 9 is a diagram showing another embodiment of a magnetic bearing device. In the embodiment shown in Fig. 9, the magnetic bearing device MB has a single gas inlet port 62 that communicates with a gas flow path 64 of the magnetic bearing unit 60A (or magnetic bearing unit 60B). A magnetic bearing device MB having such a structure can be manufactured more cheaply than the magnetic bearing devices MB according to the embodiments described with reference to Figs. 1 to 8.

[0083] In this embodiment, the gas inlet port 62 is connected to the magnetic bearing unit 60A, but may also be connected to the magnetic bearing unit 60B. In this embodiment, the gas inlet port 62 is arranged on one end side of the casing 55, and the gas outlet port 90 is arranged on the other end side opposite to the one end of the casing 55.

[0084] In other words, the gas inlet port 62 communicates with the gas flow path 64 in one of the magnetic bearing units 60A, 60B, and the gas outlet port 90 communicates with the gas flow path 64 in the other of the magnetic bearing units 60A, 60B.

[0085] In this way, the gas inlet port 62 and the gas outlet port 90 are arranged diagonally across the motor 52. Therefore, the cooling gas introduced from the gas inlet port 62 flows throughout the entire internal space of the casing 55 and is discharged from the gas outlet port 90.

[0086] The cooling gas introduced into the gas flow path 64 of the magnetic bearing unit 60A through the gas inlet port 62 passes through the gas flow path 64 and flows into the turning space SP. The cooling gas then changes direction in the turning space SP, passes through the touchdown bearing 66 and the radial magnetic bearing 68 in that order, and flows into the motor space MS. The cooling gas that flows into the motor space MS cools the motor 52, and then flows into the axial bearing space AS.

[0087] Figure 10(a) shows the first surface of the axial disc, and Figure 10(b) shows the feed grooves formed on the first surface of the axial disc. Figure 11(a) shows the second surface of the axial disc, and Figure 11(b) shows the feed grooves formed on the second surface of the axial disc.

[0088] The first surface 80a1 of the axial disk 80 according to the embodiment shown in Figures 10(a) and 10(b) has the same structure as the first surface 80a1 of the axial disk 80 according to the embodiment shown in Figures 7(a) and 7(b) (and Figures 8(a) and 8(b)). Therefore, the first surface 80a1 according to the embodiment shown in Figures 10(a) and 10(b) has a plurality of delivery grooves 80b1 that deliver the cooling gas radially outward from the axial disk 80.

[0089] On the other hand, the second surface 80a2 of the axial disk 80 according to the embodiment shown in Figures 11(a) and 11(b) has a plurality of feed grooves 80b2 that feed the cooling gas delivered to the radially outer side of the axial disk 80 to the radially inner side of the axial disk 80.

[0090] The multiple feed grooves 80b2 extend radially from an inner peripheral edge 83 of the axial disk 80 toward an outer peripheral edge 84 of the axial disk 80 along the rotation direction of the axial disk 80. In one embodiment, the radially extending feed grooves 80b2 may have a linear shape or an arc shape (in other words, a spiral shape) as long as they can feed the cooling gas radially inward of the axial disk 80.

[0091] Each of the plurality of feed grooves 80b2 has a sloped bottom portion that traps the cooling gas. More specifically, the feed groove 80b2 has a vertical surface 85 that extends perpendicular to the second surface 80a2 of the axial disk 80 and an inclined surface 86 that extends at an angle relative to the second surface 80a2 of the axial disk 80.

[0092] With this configuration, the cooling gas moving in the rotation direction of the axial disk 80 collides with the vertical surface 85 and is sent radially inward of the axial disk 80 along the inclined surface 86 as the axial disk 80 rotates.

[0093] In this manner, the inlet groove 80b2 is configured to inject the cooling gas while capturing the cooling gas. In this embodiment, the axial disk 80 also changes the flow of the refrigerant gas from a turbulent flow to a laminar flow, thereby suppressing windage loss around the axial disk 80.

[0094] The cooling gas passing through the motor space MS and flowing into the axial bearing space AS comes into contact with the first surface 80a1 of the axial disk 80 and is sent to the radially outer side of the axial disk 80 by the delivery grooves 80b1 of the rotating axial disk 80. Thereafter, the cooling gas sent to the radially outer side of the axial disk 80 is sent to the radially inner side of the axial disk 80 by the delivery grooves 80b2 of the rotating axial disk 80.

[0095] The first surface 80a1 and the second surface 80a2 of the axial disk 80 are arranged in this order in the flow direction of the cooling gas. Therefore, the cooling gas comes into contact with the first surface 80a1 and the second surface 80a2 of the axial disk 80 in this order and flows out of the axial bearing space AS.

[0096] The cooling gas then flows along the direction of the axis AX, comes into contact with the radial magnetic bearing 68 and the touchdown bearing 66, and flows into the turning space SP. The cooling gas flowing into the turning space SP collides with the partition wall 56B and changes direction by 360 degrees.

[0097] The cooling gas whose direction has been changed flows into gas flow path 64 of magnetic bearing unit 60B, and then flows into the annular flow path formed by motor frame 57 and annular groove 65. Gas discharge port 90 arranged on the magnetic bearing unit 60B side is arranged at the bottom of motor frame 57 and communicates with annular groove 65. Therefore, the cooling gas flowing into annular groove 65 is discharged to evaporator 10 through gas discharge port 90 and refrigerant gas discharge line 18.

[0098] In the embodiment shown in Figure 9, the cooling gas introduced into the internal space of the casing 55 through the gas inlet port 62 located on the magnetic bearing unit 60A side passes through the folded space SP on the magnetic bearing unit 60A side, the motor space MS, the axial bearing space AS, and the folded space SP on the magnetic bearing unit 60B side in that order, thereby suppressing windage loss occurring in the magnetic bearing device MB.

[0099] In the above-described embodiment, the magnetic bearing unit 60 has a structure (i.e., the annular groove 65 and the gas flow path 64) for introducing cooling gas into the internal space of the casing 55 through the gas inlet port 62. In one embodiment, the magnetic bearing unit 60 may have only the gas flow path 64 as long as it is possible to introduce cooling gas into the internal space of the casing 55. In this case, the magnetic bearing unit 60 may have a single gas flow path 64.

[0100] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0101] 1 Condenser 5 Pressure reduction mechanism 10 Evaporator 11 Heat transfer tube 12 Heat transfer tube 14 Refrigerant liquid supply line 18 Refrigerant gas discharge line 20 Refrigerant gas introduction line 22 Refrigerant gas introduction line 24 Refrigerant liquid transfer line 40 Cooling jacket 50A, 50B impeller 51 Rotation axis 52 Motor 53 Rotor 54 Stator 54a stator core 54b coil 55 Casing 56A,56B Bulkhead 57 Motor Frame 59A, 59B Impeller cover 60A, 60B Magnetic bearing unit 61 Bearing holder 62 Gas inlet port 64 Gas flow path 64a Radial flow passage 64b Axial flow path 65 Annular groove 66 Touchdown bearing 67 Bearing supporter 68 Radial Magnetic Bearing 69 Magnetic material 70 Radial Displacement Sensor 80 axial disc 80a1 1st page 80a2 2nd side 80b1 Delivery groove 80b2 Feeding groove (feeding groove) 81 Spacer 82 Axial bearing 83 Inner edge 84 Outer edge 85 Vertical plane 86 Slope 90 Gas exhaust port CH refrigerator CP Compressor MB magnetic bearing device AX axis SP Folded Space MS Motor Space AS axial bearing space

Claims

1. A magnetic bearing device, A rotation axis; a motor including a rotor fixed to the rotary shaft and a stator disposed radially outside the rotor; a casing that houses the rotating shaft and the motor; a gas inlet port for introducing a cooling gas into the internal space of the casing; a gas discharge port for discharging the cooling gas introduced into the internal space of the casing; a magnetic bearing unit having a gas flow path that allows the cooling gas introduced from the gas introduction port to flow into the internal space of the casing, The magnetic bearing device, wherein the gas flow path communicates with a turning space for turning the flow direction of the cooling gas to a flow direction along the axial direction of the rotating shaft.

2. The gas flow path is a radial flow passage extending in a radial direction of the rotary shaft and communicating with the gas introduction port; an axial flow path connected to the radial flow path and extending in the axial direction, 2. The magnetic bearing device according to claim 1, wherein the axial flow path opens at the turning space.

3. 2. The magnetic bearing device according to claim 1, wherein the magnetic bearing unit has a plurality of gas flow passages, including the gas flow passage, arranged in the circumferential direction of the rotating shaft.

4. the magnetic bearing device includes an axial disk fixed to the rotating shaft, 2. The magnetic bearing device according to claim 1, wherein the gas discharge port is disposed radially outward of the axial disk and connected to the bottom of the casing.

5. When the magnetic bearing unit is defined as a first magnetic bearing unit, the gas flow path is defined as a first gas flow path, and the gas introduction port is defined as a first gas introduction port, The magnetic bearing device is a second magnetic bearing unit disposed on the opposite side of the motor from the first magnetic bearing unit; 2. The magnetic bearing device according to claim 1, further comprising: a second gas inlet port communicating with a second gas flow path formed in said second magnetic bearing unit.

6. the magnetic bearing device includes an axial disk fixed to the rotating shaft, The axial disc is a first surface that comes into contact with the cooling gas flowing through the first gas flow path; a second surface that is disposed on the opposite side to the first surface and that comes into contact with the cooling gas flowing through the second gas flow path, 6. The magnetic bearing device according to claim 5, wherein each of the first surface and the second surface has a plurality of delivery grooves for delivering the cooling gas radially outward of the axial disk.

7. 7. The magnetic bearing device according to claim 6, wherein each of the plurality of delivery grooves extends radially from an inner peripheral edge of the axial disk toward an outer peripheral edge of the axial disk in a direction opposite to a rotation direction of the axial disk.

8. 8. The magnetic bearing device according to claim 7, wherein each of the plurality of delivery grooves has a sloped bottom portion that traps the cooling gas.

9. the magnetic bearing device includes an axial disk fixed to the rotating shaft, The axial disc is a first surface that comes into contact with the cooling gas flowing through the gas flow path; a second surface disposed downstream of the first surface in the flow direction of the cooling gas, the first surface has a plurality of delivery grooves that deliver the cooling gas to the outside in the radial direction of the axial disk; 2. The magnetic bearing device according to claim 1, wherein the second surface has a plurality of inlet grooves for injecting the cooling gas into the radially inner side of the axial disk.

10. each of the plurality of delivery grooves extends radially from an inner peripheral edge of the axial disk toward an outer peripheral edge of the axial disk in a direction opposite to a rotation direction of the axial disk; 10. The magnetic bearing device according to claim 9, wherein each of the plurality of feed grooves extends radially from an inner peripheral edge of the axial disk toward an outer peripheral edge of the axial disk along the rotation direction of the axial disk.

11. 11. The magnetic bearing device of claim 10, wherein each of the plurality of outlet grooves and each of the plurality of infeed grooves has a sloped bottom that traps the cooling gas.

12. the gas introduction port is disposed on one end side of the casing, 2. The magnetic bearing device according to claim 1, wherein the gas discharge port is disposed on the other end side opposite to the one end side.

13. A compressor, A magnetic bearing device according to any one of claims 1 to 12; an impeller configured to be rotatable by the magnetic bearing device.

14. The compressor according to claim 13, wherein the cooling gas is a refrigerant gas circulating in a refrigerator and introduced into the compressor.

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