JP5929157B2 - Centrifugal compressor - Google Patents

Description

  The present invention relates to a centrifugal compressor.

  2. Description of the Related Art Conventionally, there is a centrifugal compressor that compresses a fluid using centrifugal force generated by rotation of an impeller. This type of compressor is provided with a motor having a rotor attached to a rotating shaft to which an impeller is connected and a stator provided on the outer peripheral side of the rotor, and receives an axial load acting on the rotating shaft. For this purpose, there are some which are further provided with a thrust bearing. In recent years, it has been desired to rotate the rotor of the motor at high speed. For this reason, a magnetic bearing may be provided as a thrust bearing from the meaning of improving rotational accuracy and suppressing wear.

  Here, when a magnetic bearing is used as the thrust magnetic bearing, it is necessary to provide a planar member having a plane extending in the radial direction perpendicular to the axial direction as a member that receives the magnetic force of the thrust magnetic bearing. For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-263291), two compressors are arranged such that their planar portions face each other, and the planar portions receive the magnetic force of a thrust magnetic bearing. It is composed.

  In the technique disclosed in Patent Document 1, since the planar portions of the two impellers receive the magnetic force of the thrust magnetic bearing, there is no need to separately provide a planar member, which contributes to downsizing of the compressor. However, since the impeller disclosed in Patent Document 1 has a blade that protrudes in the axial direction from a plane portion that receives the magnetic force of the thrust magnetic bearing, only the one end surface in the axial direction receives the magnetic force of the thrust magnetic bearing. Cannot function as part. For this reason, in the technique disclosed in Patent Document 1, it is necessary to arrange the planar portions of a plurality of impellers so as to face each other, and application to a single-stage compression compressor having one impeller is difficult.

  Accordingly, an object of the present invention is to provide a centrifugal compressor that can be reduced in size with a simple structure.

A centrifugal compressor according to a first aspect of the present invention includes an impeller that sucks refrigerant by rotation, a rotating shaft that is connected to the impeller and rotates the impeller, and a thrust magnetic bearing that restrains the impeller in the axial direction of the rotating shaft. Prepare. The thrust magnetic bearing has electromagnets disposed on both sides in the axial direction of the impeller, and the impeller is a magnetic body having a disk shape, and receives the magnetic force of the thrust magnetic bearing on both sides in the axial direction. .

  In the present invention, the impeller functions as a planar member that receives the magnetic force of the thrust magnetic bearing. Thereby, since it is not necessary to provide a separate planar member, size reduction can be achieved. Even if the centrifugal compressor according to the present invention is a compressor having a single-stage compression structure, the magnetic force of the thrust magnetic bearing can be received by using the impeller as the planar member. As described above, the present invention can be downsized with a simple structure.

Moreover, in the present invention, the impeller receives the magnetic force generated by the electromagnet of the thrust magnetic bearing, so that the position of the impeller in the thrust direction (axial direction) can be maintained. In addition, this makes it possible to maintain the position in the thrust direction (axial direction) of the rotating shaft connected to the impeller.

の関係が成り立つ円盤形状を有する。 A centrifugal compressor according to a second aspect of the present invention is the centrifugal compressor according to the first aspect of the present invention, wherein the impeller protrudes in an axial direction from a ring-shaped hub and a suction side surface of the hub. A plurality of blades. The impeller has a height in the axial direction of the radially inner portion of the blade as H1, a height in the axial direction of the radially outer portion of the blade as H2, and a radius of the hub as D.

It has a disk shape that satisfies the following relationship.

  Miniaturization can be achieved by using an impeller that satisfies the above equation. Further, even if the centrifugal compressor according to the present invention is a compressor having a single-stage compression structure, by using the impeller that satisfies the above formula, the impeller is used as a planar member that receives the magnetic force of the thrust magnetic bearing. Can function.

The centrifugal compressor which concerns on the 3rd viewpoint of this invention is a centrifugal compressor which concerns on the 1st or 2nd viewpoint of this invention, Comprising: It is provided between the impeller and the electromagnet, The axial direction between an impeller and an electromagnet A gap sensor for detecting the gap.

  In the present invention, it is possible to easily manage the gap between the impeller and the electromagnet.

The centrifugal compressor according to the first and second aspects of the present invention can adopt a single-stage compression structure by using an impeller as a planar member. Further, it is possible to reduce the size with a simple structure. Further, the position of the impeller and the rotation shaft in the axial direction can be maintained.

In the centrifugal compressor according to the third aspect of the present invention, the gap between the impeller and the electromagnet can be easily managed.

The schematic block diagram of the air conditioning apparatus as an example of the freezing apparatus by which the centrifugal compressor based on this invention was employ | adopted. The schematic sectional drawing of a centrifugal compressor. The figure which looked at the impeller from the axial direction front side. Sectional drawing at the time of cut | disconnecting an impeller to an axial direction through a rotation center. The control block diagram of a centrifugal compressor.

  Hereinafter, an embodiment of an air conditioner 1 as an example of a refrigeration apparatus in which a centrifugal compressor 2 according to the present invention is employed will be described based on the drawings.

(1) Configuration of Air Conditioner 1 FIG. 1 is a schematic configuration diagram of an air conditioner 1 as an example of a refrigeration apparatus in which a centrifugal compressor 2 according to the present invention is employed.

  The air conditioner 1 is a refrigeration apparatus that performs air conditioning of a target space by a vapor compression refrigeration cycle. The air conditioner 1 can perform a cooling operation, and mainly includes a centrifugal compressor 2, a heat source side heat exchanger 3, a first expansion mechanism 4, and a use side heat exchanger 5. In the present embodiment, a carbon dioxide refrigerant that operates in a supercritical region is used as the refrigerant.

(1-1) Centrifugal compressor 2
The centrifugal compressor 2 is a single-stage compressor in which a single compression unit is incorporated. The centrifugal compressor 2 sucks the low-pressure refrigerant flowing through the suction pipe 6 through the suction port 21, compresses the refrigerant sucked through the suction port 21 into a high-pressure refrigerant, and then passes through the discharge port 22. And discharged to the discharge pipe 7. The suction pipe 6 is a refrigerant pipe that guides the refrigerant from the use side heat exchanger 5 to the suction side (suction port 21) of the centrifugal compressor 2, and the discharge pipe 7 is a discharge port from the centrifugal compressor 2. This is a refrigerant pipe that guides the refrigerant discharged through 22 to the inlet of the heat source side heat exchanger 3. The configuration of the centrifugal compressor 2 will be described in detail later.

(1-2) Heat source side heat exchanger 3
The heat source side heat exchanger 3 functions as a refrigerant radiator that radiates heat of the refrigerant discharged from the centrifugal compressor 2 by exchanging heat with water or air as a cooling source. One end of the heat source side heat exchanger 3 is connected to the discharge port 22 of the centrifugal compressor 2 via the discharge pipe 7, and the other end is connected to the first expansion mechanism 4. .

(1-3) First expansion mechanism 4
The first expansion mechanism 4 is a mechanism that depressurizes the refrigerant radiated by the heat source side heat exchanger 3, and an electric expansion valve is used. The first expansion mechanism 4 is configured such that one end is connected to the heat source side heat exchanger 3 and the other end is connected to the use side heat exchanger 5.

(1-4) Use side heat exchanger 5
The use side heat exchanger 5 functions as a refrigerant heater that heats the refrigerant decompressed by the first expansion mechanism 4 by exchanging heat with water or air as a heating source. The use side heat exchanger 5 is configured such that one end is connected to the first expansion mechanism 4 and the other end is connected to the suction port 21 of the centrifugal compressor 2 via the suction pipe 6.

  The centrifugal compressor 2, the heat source side heat exchanger 3, the first expansion mechanism 4, and the use side heat exchanger 5 described above are sequentially connected by the refrigerant pipe including the suction pipe 6 and the discharge pipe 7. Thus, the main path 11 through which the refrigerant circulates is configured.

  In the air conditioning apparatus 1 according to the present embodiment, a low-pressure refrigerant is allowed to flow in the motor casing 32 (described later) in order to cool the motor 25 (described later). Therefore, the air conditioning apparatus 1 in the present embodiment further includes the first bypass pipe 17 and the return pipe 18.

(1-5) First bypass piping 17
The first bypass pipe 17 is a refrigerant pipe that constitutes the first bypass path 12 that guides the refrigerant radiated by the heat source side heat exchanger 3 to an inlet 35 (described later) of the motor casing 32, and one end of the first bypass pipe 17 is a heat source. The side heat exchanger 3 is connected to the outlet, and the other end is connected to the inlet 35 of the motor casing 32. The first bypass pipe 17 is provided with a second expansion mechanism 12a as a pressure reducing mechanism. The second expansion mechanism 12a is an electric expansion valve capable of adjusting the opening degree. By the second expansion mechanism 12a, the high-pressure refrigerant after being radiated by the heat source side heat exchanger 3 is decompressed to a low pressure in the refrigeration cycle.

(1-6) Return pipe 18
The return pipe 18 is a refrigerant pipe for constituting the return path 13 that guides the low-pressure refrigerant flowing in the motor casing 32 to the use-side heat exchanger 5, and one end thereof is connected to a discharge port 36 (described later) of the motor casing 32. The other end is connected to the inlet of the use side heat exchanger 5.

  As described above, in the air conditioning apparatus 1 of the present embodiment, the refrigerant path 10 through which the refrigerant flows is formed by the main path 11, the first bypass path 12, and the return path 13.

(2) Detailed Configuration of Centrifugal Compressor 2 FIG. 2 is a schematic sectional view of the centrifugal compressor 2. In the following, the center axis of the rotating shaft 26 is OO, and the center of rotation of the rotating shaft 26 is O. The direction extending along the central axis OO is the axial direction or the front-rear direction (note that the suction side of the centrifugal compressor 2 is the front), the direction orthogonal to the axial direction is the radial direction, and the axial direction The surrounding direction is the circumferential direction.

  The centrifugal compressor 2 is a so-called oilless compressor that does not require lubricating oil. As shown in FIG. 2, the centrifugal compressor 2 mainly includes a compressor casing 23, a compression unit 24, a motor 25, a rotary shaft 26, a radial magnetic bearing 27, a plurality of inlet guide vanes 30, and a thrust. And a magnetic bearing 28. In the centrifugal compressor 2, a compression unit 24, a motor 25, a rotating shaft 26, a radial magnetic bearing 27, a thrust magnetic bearing 28, and a plurality of inlet guide vanes 30 are accommodated in a hermetic compressor casing 23. It is configured as follows.

(2-1) Compressor casing 23
The compressor casing 23 is a substantially cylindrical hermetic container extending in the axial direction, and includes a compressor casing 31 and a motor casing 32.

(2-1-1) Compression section casing 31
The compression section casing 31 constitutes an axial front side portion (suction side portion) of the compressor casing 23, and the inner surface of the compression section casing 31 is positioned on the suction side of the compression section 24 and the compression space S1 that houses the compression section 24. A suction space S3 through which the suction refrigerant flows from 21 toward the compression section 24 and a magnetic bearing arrangement space S4 are formed. The magnetic bearing space S4 is located on the rear side of the impeller 41 in the axial direction.

  The compressor casing 31 is mainly formed with a suction port 21 for sucking a refrigerant and a discharge port 22 for discharging the refrigerant. The suction port 21 opens toward one axial end (front end) of the compressor casing 23 and is connected to the suction pipe 6. The discharge port 22 opens toward the radially outer end of the compressor casing 23 and is connected to the discharge pipe 7.

(2-1-2) Motor casing 32
The motor casing 32 constitutes an axial rear side portion of the compressor casing 23 and is a substantially cylindrical container extending in the axial direction. The motor casing 32 has a substantially cylindrical tubular portion 32a having both ends opened in the axial direction, and a tubular shape. It has closure parts 32b and 32c which close the opening of part 32a from the axial direction both sides. The motor casing 32 forms a motor housing space S2 for housing the motor 25 therein.

  The motor casing 32 is mainly formed with an introduction port 35 and a discharge port 36. The introduction port 35 is an opening for introducing the low-pressure liquid refrigerant after being decompressed by the second expansion mechanism 12a in the first bypass pipe 17 into the motor casing 32 (that is, the motor housing space S2). 1 Bypass piping 17 is connected. The discharge port 36 is an opening for discharging the refrigerant that has flowed in the motor casing 32 (motor housing space S2) to the outside of the motor housing space S2 (return pipe 18), and is connected to the return pipe 18. .

  The axial rear end surface of the compression portion casing 31 and the axial front end surface of the motor casing 32 (the axial front end surface of the closing portion 32b) function as a partition portion that partitions the compression space S1 and the motor housing space S2. ing.

(2-2) Compression unit 24
The compression unit 24 is a part that compresses the suction refrigerant flowing into the suction space S3 through the suction port 21, and is disposed in the compression space S1. The compression unit 24 mainly includes an impeller 41 that is connected to an axial one end portion (specifically, a front end portion) of the rotary shaft 26 and is rotatable. The impeller 41 is a magnetic body. Here, in the present embodiment, an impeller arrangement space S1a in which the impeller 41 is arranged, a diffuser space S1b located on the radially outer side of the impeller arrangement space S1a, and a scroll space S1c located on the radially outer side of the diffuser space S1b Are collectively referred to as a compression space S1. Here, the diffuser space S1b is a space for converting the kinetic energy of the refrigerant whose flow rate has been increased by the rotation of the impeller 41 into pressure energy to obtain a high-pressure refrigerant. The scroll space S1c is a space for decelerating and rectifying the flow velocity.

  In the centrifugal compressor 2, the impeller 41 of the compression unit 24 is rotated by the rotation of the rotating shaft 26. Then, the rotating shaft 26 rotates the impeller 41 of the compressing unit 24 to suck in the refrigerant from the front side in the axial direction and cause the sucked refrigerant to flow out to the outside in the radial direction by applying a centrifugal force while compressing. ing. The detailed configuration of the impeller 41 will be described later.

(2-3) Motor 25
The motor 25 is disposed on the axially rear side of the compression unit 24 and mainly includes a rotor 52 and a stator 53 that faces the rotor 52. The motor 25 (the rotor 52 and the stator 53) is accommodated in the motor casing 32 (that is, the motor accommodating space S2) together with the radial magnetic bearing 27.

  In the present embodiment, as described above, the low-pressure liquid refrigerant that flows through the first bypass pipe 17 and is decompressed by the second expansion mechanism 12a enters the inlet 35 in the motor casing 32 (motor housing space S2). Is supplied through. The liquid refrigerant flows into the rotary shaft 26. The refrigerant flowing in the rotating shaft 26 is heated by the heat from the motor 25 and evaporates, so that when it goes out of the motor casing 32 from the motor casing 32 through the discharge port 36, it becomes a gas refrigerant. .

(2-3-1) Rotor 52
The rotor 52 is attached to the rotary shaft 26 by being fitted into the rotary shaft 26 to which the impeller 41 of the compression unit 24 is coupled. When the rotor 52 rotates, the rotating shaft 26 rotates, and when the rotating shaft 26 rotates, the impeller 41 of the compression unit 24 connected to the rotating shaft 26 is driven (rotated). Thereby, the impeller 41 of the compression part 24 compresses a refrigerant | coolant.

  The rotor 52 mainly has a rotor core 52a and a plurality of magnets (not shown). The rotor core 52a is a substantially cylindrical member in which a rotation shaft is fitted into a central hole, and is formed by stacking electromagnetic steel plates in the axial direction. The plurality of magnets are made of rare earth magnets, for example, and are fitted into the rotor core 52a with a predetermined interval in the circumferential direction.

(2-3-2) Stator 53
The stator 53 is disposed on the outer peripheral side of the rotor 52, and is fixed to the inner peripheral surface of the cylindrical portion 32a of the compressor casing 23 (motor casing 32) by shrink fitting. The stator 53 mainly has a stator core 53a and windings (not shown) attached to the stator core 53a. The stator 53 is configured such that a rotating magnetic field is generated by energizing each winding. The stator 53 is configured such that an air gap t as a gap is formed between the inner peripheral surface of the stator 53 and the rotor 52 (the outer peripheral surface of the rotor 52).

(2-4) Radial magnetic bearing 27
The radial magnetic bearing 27 is a bearing that, together with the thrust magnetic bearing 28, rotatably supports the rotary shaft 26 without contact. The radial magnetic bearing 27 supports a load in the radial direction (radial direction) of the rotating shaft 26. In this embodiment, the radial magnetic bearing 27 is arrange | positioned 1 each on the axial direction both sides of the motor 25 so that the motor 25 may be pinched | interposed from both sides in an axial direction. That is, in this embodiment, there are two radial magnetic bearings 27.

  Specifically, the radial magnetic bearing 27 mainly has a plurality of (in this embodiment, four poles) electromagnets 61 including coils (not shown). The plurality of electromagnets 61 are arranged at predetermined intervals in the circumferential direction on the radially outer side of the rotating shaft 26. That is, the four-pole electromagnet 61 is arranged so that two poles face each other with the rotation shaft 26 in the radial direction. The radial magnetic bearing 27 generates a magnetic field between the plurality of electromagnets 61 and the rotating shaft 26 when a current flows through the coil, and the rotating shaft 26 is magnetically levitated by a magnetic force (magnetic attractive force) generated in the radial direction. By doing so, the rotating shaft 26 is supported in a non-contact manner. That is, the radial magnetic bearing 27 holds the radial position of the rotary shaft 26 by the radial magnetic force generated by the electromagnet 61, that is, constrains the rotary shaft 26 in the radial direction. Thus, since the radial magnetic bearing 27 supports the rotating shaft 26 in a non-contact manner, friction between the rotating shaft and the bearing and wear due to friction can be suppressed.

  In the present embodiment, the radial gap dimension of the radial gap between the rotary shaft 26 and the radial magnetic bearing 27 is detected between the rotary shaft 26 and the radial magnetic bearing 27 (a plurality of electromagnets 61). A radial gap sensor 93 (see FIG. 5) is provided, and the radial gap sensor 93 detects the radial position of the rotary shaft 26. The amount of current flowing through the coil of the radial magnetic bearing 27 and, consequently, the magnetic force is controlled by the radial gap size detected by the radial gap sensor 93, and the radial direction of the rotary shaft 26 is controlled. The position has been determined. The amount of current that flows through the coil of the radial magnetic bearing 27 is controlled by the control unit 9 described later.

(2-5) Entrance guide vane 30
The plurality of inlet guide vanes 30 are arranged in the suction space S3 (that is, the suction side of the compression unit 24) in order to adjust the flow rate and flow direction of the suction refrigerant sucked by the rotation of the impeller 41 of the compression unit 24. It is a rotatable blade member. The plurality of inlet guide vanes 30 are arranged side by side in the circumferential direction, and are driven by a driving device 30a (see FIG. 5, for example, a motor). Note that the drive shaft of the drive device 30a is disposed so as to extend in the radial direction, and the inlet guide vane 30 rotates around an axis extending in the radial direction. And the inclination with respect to the radial direction horizontal surface spread in the radial direction of the inlet guide vane 30 is changed by this rotation. As a result, the flow rate and flow direction of the intake refrigerant described above are adjusted.

(2-6) Thrust magnetic bearing 28
The thrust magnetic bearing 28 is disposed in the compressor casing 31 and mainly includes a plurality of electromagnets 71 including coils (not shown). The plurality of electromagnets 71 are arranged one by one on both sides in the axial direction of the impeller 41 so as to face each other in the axial direction with the impeller 41 interposed therebetween. In addition, the electromagnet 71 arrange | positioned at the axial direction one end side (front side) of the impeller 41 is arrange | positioned in suction | inhalation space S3. Moreover, the electromagnet 71 arrange | positioned at the axial direction other end side (rear side) of the impeller 41 is arrange | positioned in magnetic bearing arrangement space S4.

  The thrust magnetic bearing 28 generates a magnetic field between the plurality of electromagnets 71 and the impeller 41 which is a magnetic body when a current flows through the coil, and the impeller 41 connected (fixed) to the rotating shaft 26 is axially moved. Is magnetically levitated by the magnetic force (magnetic attraction force) generated in And thereby, the rotating shaft 26 is supported without contact. That is, the thrust magnetic bearing 28 holds the axial position of the rotating shaft 26 and the impeller 41 by the axial magnetic force generated by the electromagnet 71, that is, restrains the rotating shaft 26 and the impeller 41 in the axial direction. ing.

  Thus, since the thrust magnetic bearing 28 supports the rotating shaft 26 in a non-contact manner, friction between the rotating shaft and the bearing and wear due to friction can be suppressed.

  In the present embodiment, the axial gap dimension of the axial gap between the thrust magnetic bearing 28 (electromagnet 71) and the impeller 41 is detected between the thrust magnetic bearing 28 (electromagnet 71) and the impeller 41. An axial clearance sensor 94 (see FIG. 5) is provided, and the axial clearance sensor 94 detects the position of the impeller 41 and, in turn, the rotational shaft 26 in the axial direction. Then, the amount of current flowing through the coil of the thrust shaft air bearing 28 and, consequently, the magnetic force is controlled by the axial clearance size detected by the axial clearance sensor 94, and the impeller 41 and the rotating shaft 26 are controlled. The position in the axial direction is determined. Note that the amount of current flowing through the coil of the thrust magnetic bearing 28 is controlled by the control unit 9.

(3) Detailed Configuration of Impeller 41 FIG. 3 is a view of the impeller 41 as viewed from the front side in the axial direction. FIG. 4 is a cross-sectional view of the impeller 41 when cut through the rotation center O in the axial direction.

  The impeller 41 has a substantially disk shape and is connected (fixed) to the front end of the rotating shaft 26 in the axial direction by a bolt. The impeller 41 mainly includes a hub 42 and a plurality of blades 43 as shown in FIGS. 3 and 4. The impeller 41 is rotated about the rotation shaft 26 as a driving force of the motor 25 is transmitted from the rotation shaft 26 extending in the front-rear direction of the hub 42. Specifically, the impeller 41 rotates in the rotation direction indicated by the arrow in FIG. 3 when the motor 25 is driven.

(3-1) Hub 42
The hub 42 is a ring-shaped disk member in which a hole 42a for passing the rotation shaft 26 is formed at the center thereof. The hub 42 is pivotally supported on the rotary shaft 26 so as to rotate integrally with the rotary shaft 26. The hub 42 is arranged such that a hub front surface 44 and a hub rear surface 45 which are circular planes extending in the radial direction face the front-rear direction (axial direction), respectively.

(3-2) Feather 43
The plurality of blades 43 are arranged on the radially outer end portion of the hub front surface 44 of the hub 42 such that each of the blades 43 is arranged at substantially equal intervals in the circumferential direction. Each of the plurality of blades 43 is formed in substantially the same size. The blades 43 are formed so as to protrude substantially vertically from the front surface 44 of the hub, which is the surface on the suction side of the hub 42, to the front side in the axial direction.

  In addition, each of the plurality of blades 43 has a shape in which the radially inner portion is shorter than the radially outer portion, and is mainly formed on the radially outer side of the short surface 43a and the short surface 43a. A small curved surface that gently connects the long surface 43b longer than 43a, the rotation-direction downstream portion of the short surface 43a, and the rotation-direction downstream portion of the long surface 43b so as to protrude from the rotation direction upstream side to the rotation direction downstream side. 43c, and a large curved surface 43d that gently connects the upstream portion in the rotational direction of the short surface 43a and the upstream portion in the rotational direction of the long surface 43b so as to protrude from the upstream side in the rotational direction to the downstream side in the rotational direction. Yes. The short surfaces 43a and the long surfaces 43b of the plurality of blades 43 are formed so as to be radially arranged around the rotation center O. And the blade | wing 43 is arrange | positioned so that the small curved surface 43c and the large curved surface 43d may oppose at predetermined intervals.

In addition, the axial height of the radially inner portion (specifically, the short surface 43a) of the blade 43 is H1, and the axial height of the radially outer portion (specifically, the long surface 43b) of the blade 43 is set to H1. When the height is H2, the blades 43 are formed so that the following (Formula 1) is established.

  That is, the front surface 43e of the blade 43 is substantially parallel to the hub front surface 44 and the hub rear surface 45 of the hub 42, and the plurality of blades 43 are formed in a so-called substantially two-dimensional airfoil.

The impeller 41 as a whole has the following (Equation 2), where D is the radius of the hub 42 (the distance from the rotation center O to the radially outer end surface 42b of the hub 42).

  As described above, the impeller 41 has a disk shape that satisfies the above-described (Expression 1) and (Expression 2). Therefore, in this embodiment, not only the hub rear surface 45 where the blades 43 are not formed, but also one end surface in the axial direction of the blades 43 arranged on the hub front surface 44 (that is, the front surface 43e facing the suction side) is thrust magnetic. It can function as a plane that receives the magnetic force of the bearing 28.

(4) Configuration of Control Unit 9 FIG. 5 is a control block diagram of the centrifugal compressor 2.

  As described above, the air conditioner 1 is the air conditioner 1 such as the first expansion mechanism 4, the second expansion mechanism 12 a, the motor 25, the radial magnetic bearing 27, the thrust magnetic bearing 28, and the drive device 30 a of the inlet guide vane 30. It further has a control unit 9 for controlling the operation of each element constituting the. The control unit 9 includes a CPU, a RAM, a ROM, and the like, and is connected to the radial gap sensor 93, the axial gap sensor 94, the flow rate sensor 95 that detects the flow rate of the refrigerant flowing through the suction space S3, and the like. Yes. And the operation | movement of each above-mentioned element is controlled in response to the detection result from these sensors.

(5) Features (5-1)
In the present embodiment, the impeller 41 has a disk shape in which the above (Formula 1) and (Formula 2) are satisfied. The impeller 41 is a magnetic body.

  Thereby, the surfaces on both sides of the impeller 41 (specifically, the hub rear surface 45 and the front surface 43e of the blade 43) can function as planar members that receive the magnetic force of the thrust magnetic bearing 28. Therefore, it is not necessary to provide a separate planar member, so that reduction in size and weight can be achieved. Further, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2001-263291), it is not necessary to provide two or more impellers. That is, even in a compressor having a single-stage compression structure as described in the present embodiment, the impeller 41 can be employed as a planar member that receives the magnetic force of the thrust magnetic bearing 28. As described above, the centrifugal compressor 2 of the present embodiment can be downsized with a simple structure.

  Conventionally, the impeller is formed with a three-dimensional airfoil blade. However, in this embodiment, the impeller 41 has a blade 43 formed in a two-dimensional airfoil, so that processing is easier than in the past. It is easy and the tolerance for deformation due to centrifugal force or heat increases.

(5-2)
In the present embodiment, the thrust magnetic bearing 28 (a plurality of electromagnets 71) is arranged so as to sandwich the impeller 41 in the axial direction. That is, the thrust magnetic bearing 28 (electromagnet 71) also has a function as a casing of the impeller 41. In the present embodiment, the axial clearance between the thrust magnetic bearing 28 (electromagnet 71) and the impeller 41 is detected. Thereby, the space | gap management between the thrust magnetic bearing 28 (electromagnet 71) which has a function of a casing, and the impeller 41 can be performed easily. Thereby, the leak of a refrigerant | coolant can be suppressed and compressor efficiency can be improved.

(5-3)
Conventionally, a planar member that receives the magnetic force of a thrust magnetic bearing is fixed to the rotating shaft 26 by shrink fitting or the like. On the other hand, in the present embodiment, the impeller 41 is fixed to the rotating shaft 26 by a bolt. Therefore, in this embodiment, the attachment / detachment efficiency of the impeller 41 is improved. Therefore, in this embodiment, the accessibility to other parts (for example, the touchdown bearing provided for emergency) other than the impeller 41 is improved.

(6) Modifications The embodiment of the present invention has been described above with reference to the drawings. However, the specific configuration is not limited to the above-described embodiment, and can be changed without departing from the gist of the invention. .

(6-1) Modification A
In the above embodiment, the centrifugal compressor 2 has been described as a single-stage compressor in which a single compression unit is incorporated, but the present invention is not limited to this. For example, a centrifugal compressor having a single-shaft two-stage compression structure having two compression units may be used, or a multistage centrifugal compressor may be used rather than a two-stage compression type such as a three-stage compression type. Furthermore, a parallel multistage compression centrifugal compressor configured by connecting two or more multistage compression compressors in parallel may be used.

(6-2) Modification B
In the above embodiment, the air conditioner 1 capable of performing the cooling operation has been described as an example of the refrigeration apparatus. However, the present invention is not limited to this, and the present invention is an air conditioner capable of switching between cooling and heating. You may apply to an apparatus and may apply to a heat pump type hot-water supply apparatus.

(6-3) Modification C
In the above embodiment, the thrust magnetic bearing 28 has a plurality of electromagnets 71, and the plurality of electromagnets 71 have one pole on both sides in the axial direction of the impeller 41 so as to face each other in the axial direction with the impeller 41 interposed therebetween. However, the present invention is not limited to this, and the electromagnet 71 may be disposed on at least one of both sides of the impeller 41 in the axial direction.

  For example, the thrust magnetic bearing 28 has one electromagnet 71 and may be disposed only on one end side in the axial direction of the impeller 41. Conventionally, only one end face in the axial direction can function as a plane portion that receives the magnetic force of the thrust magnetic bearing. However, in the present invention, since the impeller 41 has a disk shape, the impeller 41 has both sides in the axial direction. In either case, the thrust magnetic bearing 28 can be disposed.

  The present invention can be applied to various centrifugal compressors equipped with thrust magnetic bearings.

2 Centrifugal compressor 26 Rotating shaft 28 Thrust magnetic bearing 41 Impeller 42 Hub 43 Blade 44 Hub front surface (hub suction side surface)
71 Electromagnet 94 Axial gap sensor (gap sensor)

JP 2001-263291 A

Claims (3)

An impeller (41) for sucking refrigerant by rotation;
A rotating shaft (26) connected to the impeller and rotating the impeller;
A thrust magnetic bearing (28) for restraining the impeller in the axial direction of the rotary shaft;
With
The thrust magnetic bearing has electromagnets (71) arranged on both sides in the axial direction of the impeller,
The impeller is a magnetic body having a disk shape, and receives the magnetic force of the thrust magnetic bearing on both sides in the axial direction .
Centrifugal compressor (2). The impeller is
A hub (42) having an annular shape, and a plurality of blades (43) protruding in the axial direction from the suction side surface (44) of the hub,
When the axial height of the radially inner portion of the blade is H1, the axial height of the radially outer portion of the blade is H2, and the radius of the hub is D,

It has a disk shape where the relationship of
The centrifugal compressor according to claim 1. A gap sensor (94) that is provided between the impeller and the electromagnet and detects an axial gap between the impeller and the electromagnet;
The centrifugal compressor according to claim 1 or 2 .

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