Magnetic unit, compressor, and refrigeration device

Abstract

To make it possible to obtain information indicating a relation between a distance detected by a distance detection unit and a current flowing through a magnetic levitation unit when a rotating body is magnetically levitated.SOLUTION: A magnetic unit includes: a magnetic levitation part that generates an electro-magnetic force by electric conduction to support a rotating body in a non-contact manner; a distance detection part (30) that detects a distance between the rotating body and the magnetic levitation part; and a controller (40) that controls a position of the rotating body during magnetic levitation and a current flowing through the magnetic levitation part on the basis of the distance detected by the distance detection part (30). The controller (40) performs multiple maintenance controls to maintain the current flowing through the magnetic levitation part at a constant current while maintaining the position of the rotating body at a constance position, and when any two of the multiple maintenance controls are compared, the constant positions are different from each other or the constant currents are different from each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a magnetic unit, a compressor, and a refrigeration device. [Background technology]

[0002] Patent Document 1 describes a method for calibrating a gap sensor provided in a magnetic bearing. The gap sensor detects the gap between a rotor and a reference object that serves as a position reference for position control of the rotor. The method described in Patent Document 1 includes a construction step of setting three or more constraint conditions that are conditions for relating the gap to the output signal of the gap sensor, and constructing a conversion equation that converts the output signal of the gap sensor into a gap using the constraint conditions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 064469 Summary of the Invention [Problem to be solved by the invention]

[0004] If there is variation in the product dimensions of a magnetic bearing relative to the design dimensions, it is expected that when the rotating body is magnetically levitated, this variation will significantly change the relationship between the gap between the rotating body and the current flowing in the electromagnet (magnetic levitation part) of the magnetic bearing.

[0005] An object of the present disclosure is to provide a magnetic unit, a compressor, and a refrigeration device that can obtain information indicating the relationship between the distance detected by a distance detection unit and the current flowing through the magnetic levitation unit when a rotating body is magnetically levitated. [Means for solving the problem]

[0006] The magnetic unit of the first aspect comprises a magnetic levitation part that generates an electromagnetic force when current is passed through it to support a rotating body in a non-contact manner, a distance detection part (30) that detects the distance between the rotating body and the magnetic levitation part, and a controller (40) that controls the position of the rotating body during magnetic levitation and the current flowing through the magnetic levitation part based on the distance detected by the distance detection part (30), and the controller (40) performs multiple maintenance controls to maintain the position of the rotating body at a constant position while maintaining the current flowing through the magnetic levitation part at a constant current, and when any two of the multiple maintenance controls are compared, the constant positions are different from each other or the constant currents are different from each other.

[0007] In the first aspect, when the rotating body is magnetically levitated, information indicating the relationship between the distance detected by the distance detection unit and the current flowing through the magnetic levitation unit can be obtained.

[0008] A second aspect is the first aspect, wherein the plurality of maintenance controls include a first maintenance control, a second maintenance control, and a third maintenance control, and in the first maintenance control, the constant position is a first position and the constant current is a first current, in the second maintenance control, the constant position is a second position and the constant current is a second current, and in the third maintenance control, the constant position is a third position and the constant current is a third current.

[0009] In the second aspect, during magnetic levitation, the relationship between the distance detected by the distance detector (30) and the current flowing through the magnetic levitation part can be obtained for each of the first to third maintenance controls.

[0010] A third aspect is the second aspect, wherein the first current, the second current, and the third current are different from each other.

[0011] In the third aspect, the first to third maintenance controls can be performed by making the constant currents different from one another.

[0012] A fourth aspect is the third aspect, wherein the first position, the second position, and the third position are the same as each other.

[0013] In the fourth aspect, the first to third maintenance controls can be performed by making the constant currents different from one another while keeping the constant positions the same.

[0014] A fifth aspect is the second aspect, wherein the first position, the second position, and the third position are different from each other.

[0015] In the fifth aspect, the first maintenance control to the third maintenance control can be performed by making the fixed position different from one another.

[0016] A sixth aspect is the second aspect, wherein the first current and the second current are different from each other, and the first position and the third position are different from each other.

[0017] In the sixth aspect, the first maintenance control to the third maintenance control can be performed by making the constant currents for the first maintenance control and the second maintenance control different from each other, and making the constant positions for the first maintenance control and the third maintenance control different from each other.

[0018] A seventh aspect is the second aspect, wherein the first current, the second current, and the third current are different from one another, and the first position, the second position, and the third position are different from one another.

[0019] In the seventh aspect, the first to third maintenance controls can be performed by varying the constant currents and further varying the constant positions.

[0020] The eighth aspect is the second aspect, wherein the first maintenance control, the second maintenance control, and the third maintenance control are performed in the order of the first maintenance control, the second maintenance control, and the third maintenance control, and the third current is greater than each of the first current and the second current, or less than each of the first current and the second current.

[0021] In the eighth aspect, the first maintenance control to the third maintenance control can be performed so that the third current becomes the largest or smallest.

[0022] A ninth aspect is the second aspect, wherein the first maintenance control, the second maintenance control, and the third maintenance control are performed in the order of the first maintenance control, the second maintenance control, and the third maintenance control, and when the distance detected by the distance detection unit (30) at the first position is defined as a first detection distance, the distance detected by the distance detection unit (30) at the second position is defined as a second detection distance, and the distance detected by the distance detection unit (30) at the third position is defined as a third detection distance, the third detection distance is greater than each of the first detection distance and the second detection distance, or is smaller than each of the first detection distance and the second detection distance.

[0023] In the ninth aspect, the first maintenance control to the third maintenance control can be performed so that the third detection distance becomes the largest or smallest.

[0024] A tenth aspect is any one of the second to ninth aspects, wherein the first maintenance control, the second maintenance control, and the third maintenance control are performed in the order of the first maintenance control, the second maintenance control, and the third maintenance control, and the controller (40) performs the third maintenance control based on the first current, the second current, the first position, and the second position.

[0025] In the tenth aspect, the control parameter (W1) is updated based on the first maintenance control and the second maintenance control, and the third maintenance control can be performed based on the updated control parameter (W2).

[0026] An eleventh aspect is any one of the first to tenth aspects, wherein any two of the plurality of maintenance controls differ in the constant position by more than a first predetermined value, or in the constant current by more than a second predetermined value.

[0027] In the eleventh aspect, a plurality of maintenance controls can be performed such that the constant positions differ by a first predetermined value or more, or the constant currents differ from each other by a second predetermined value or more.

[0028] A twelfth aspect is any one of the first to eleventh aspects, wherein the magnetic levitation part includes a first actuator (51) that generates a magnetic attraction force on the rotating body in a first direction, and a second actuator (52) that generates a magnetic attraction force on the rotating body in a second direction opposite to the first direction, the constant position is the position of the rotating body in the first direction or the second direction, and the constant current includes a current flowing through the first actuator (51) and the second actuator (52).

[0029] In a twelfth aspect, a magnetic levitation unit can be disposed between the first actuator and the second actuator to perform maintenance control.

[0030] A thirteenth aspect is any one of the first to twelfth aspects, wherein the controller (40) controls the current flowing through the magnetic levitation part based on the constant position and the constant current in each of the plurality of maintenance controls after performing the plurality of maintenance controls.

[0031] In the thirteenth aspect, the control parameter (W1) can be updated based on a plurality of maintenance controls, and the current flowing through the magnetic levitation portion can be controlled based on the updated control parameter (W2).

[0032] A fourteenth aspect is any one of the first to thirteenth aspects, wherein the controller (40) outputs balance information indicating the balance of forces of the rotating body based on the corresponding constant position and the constant current for each maintenance control, and outputs information indicating the distance between the rotating body and the magnetic levitation part when the rotating body is located at a central position based on a plurality of pieces of balance information.

[0033] In the fourteenth aspect, the distance between the magnetic levitation part and the rotor located at the central position can be output with high precision.

[0034] A fifteenth aspect is any one of the first to fourteenth aspects, wherein the magnetic levitation part has a plurality of electromagnets arranged around the rotating body and which generate electromagnetic force when energized to support the rotating body in a non-contact manner, and the controller (40) controls the current flowing through each of the plurality of electromagnets.

[0035] In the fifteenth aspect, the rotating body can be supported in a non-contact manner by the electromagnetic force generated by each of the plurality of electromagnets.

[0036] A compressor according to a sixteenth aspect includes the magnetic unit according to any one of the first to fifteenth aspects, the rotating body, and a compression mechanism connected to the rotating body.

[0037] A refrigeration device according to a seventeenth aspect includes the compressor according to the sixteenth aspect. [Effects of the Invention]

[0038] When the rotating body is magnetically levitated, information indicating the relationship between the distance detected by the distance detection unit and the current flowing through the magnetic levitation unit can be obtained. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 shows an example of the configuration of a compressor according to an embodiment, and is a cross-sectional view of the compressor taken along the axial direction of a rotary shaft of the compressor. [Figure 2] FIG. 2 shows an example of the configuration of a radial magnetic bearing, and is a cross-sectional view of the radial magnetic bearing taken along the radial direction of the rotating shaft of the compressor. [Figure 3] FIG. 3 shows an example of the configuration of a radial magnetic bearing, and is a cross-sectional view of the radial magnetic bearing taken along the axial direction of the rotating shaft of the compressor. [Figure 4]FIG. 4 is a plan view of the thrust magnetic bearing as seen from the axial direction of the rotating shaft of the compressor. [Figure 5] FIG. 5 shows an example of the configuration of a thrust magnetic bearing, and is a cross-sectional view of the thrust magnetic bearing taken along the axial direction of the rotating shaft of the compressor. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of the controller. [Figure 7] FIG. 7 is a block diagram showing an example of the configuration of a controller in which control parameters are updated. [Figure 8] FIG. 8 is a flow diagram showing a plurality of maintenance control procedures. [Figure 9] FIG. 9 is a diagram illustrating a first example of maintenance control. [Figure 10] FIG. 10 is a diagram showing a second example of maintenance control. [Figure 11] FIG. 11 is a diagram illustrating a third example of maintenance control. [Figure 12] Fig. 12(a) is a diagram showing a fourth example of maintenance control, and Fig. 12(b) is a diagram showing the relationship between the position command value and time when maintenance control is performed while expanding the levitation conditions from the initial conditions. [Figure 13] FIG. 13 is a diagram illustrating a fifth example of maintenance control. [Figure 14] FIG. 14 is a diagram illustrating a sixth example of maintenance control. [Figure 15] FIG. 15 is a flow diagram showing an example of the operation of the controller. [Figure 16] 16(a) and 16(b) are diagrams showing modified examples of the magnetic bearing. DETAILED DESCRIPTION OF THE INVENTION

[0040] Hereinafter, embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0041] (Compressor) FIG. 1 shows an example of the configuration of a compressor (1) according to an embodiment. The compressor (1) is provided in a refrigeration device. The refrigeration device includes a refrigerant circuit filled with a refrigerant, and the refrigerant circulates through the refrigerant circuit to perform a refrigeration cycle. The refrigerant compressed by the compressor (1) flows through the refrigerant circuit. The compressor (1) includes a casing (2), a compression mechanism (3), an electric motor (4), a rotating shaft (5), a radial touchdown bearing (6), a thrust touchdown bearing (7), and a magnetic unit (10).

[0042] [Rotation axis] The rotating shaft (5) has a supported portion containing a magnetic material and a detected portion serving as a reference for distance detection. The detected portion of the rotating shaft (5) is a portion of the rotating shaft (5) that serves as a reference when a distance detection unit (30), described later, detects the distance from the distance detection unit (30). The supported portion of the rotating shaft (5) is supported by an electromagnet of a magnetic bearing (20), described later. The electromagnet of the magnetic bearing (20) generates an electromagnetic force when energized, thereby supporting the supported portion of the rotating shaft (5) in a non-contact manner. The rotating shaft (5) is connected to a drive source and rotates using the power of the drive source to transmit the power of the drive source. In this embodiment, the rotating shaft (5) is connected to a compression mechanism (3) and an electric motor (4), which is a drive source. The rotating shaft (5) rotates using the power of the electric motor (4) to transmit the power of the electric motor (4) to the compression mechanism (3). This causes the compression mechanism (3) to compress the fluid. The rotating shaft (5) is an example of a rotating body.

[0043] [Casing] The casing (2) is formed in a cylindrical shape with both ends closed and is disposed so that the cylindrical axis is horizontal. The space inside the casing (2) is partitioned by a wall (2a), with the space to the right of the wall (2a) forming a compression mechanism chamber (S1) that houses the compression mechanism (3), and the space to the left of the wall (2a) forming an electric motor chamber (S2) that houses the electric motor (4). A rotating shaft (5) extending axially inside the casing (2) connects the compression mechanism (3) and the electric motor (4). The axial direction is parallel to the axis of the rotating shaft (5) and parallel to the extension direction of the cylindrical axis.

[0044] [Compression mechanism] The compression mechanism (3) is configured to compress a fluid. In this example, the compression mechanism (3) is configured by an impeller (3a). The impeller (3a) is formed with a plurality of blades so that its outer shape is substantially trapezoidal cone-shaped, and is fixed to one end of the rotary shaft (5).

[0045] [Electric motor] The electric motor (4) is configured to rotate a rotary shaft (5). In this example, the electric motor (4) has a stator (4a) and a rotor (4b). The stator (4a) is cylindrical and fixed inside the casing (2). The rotor (4b) is cylindrical and rotatably inserted around the inner periphery of the stator (4a). A shaft hole is formed in the center of the rotor (4b), and the rotary shaft (5) is inserted and fixed in the shaft hole.

[0046] [Touchdown bearing] The radial touchdown bearing (6) and the thrust touchdown bearing (7) are configured to support the supported portion of the rotating shaft (5) when the magnetic unit (10) is not energized (i.e., when the rotating shaft (5) is not levitated).

[0047] [Magnetic unit] The magnetic unit (10) includes one or more (three in this example) magnetic bearings (20), one or more (five in this example) distance detection units (30), and a controller (40).

[0048] <Magnetic bearing> The magnetic bearing (20) is arranged around the supported portion of the rotor (in this example, the supported portion of the rotating shaft (5)) and has a plurality of electromagnets that, when energized, generate electromagnetic forces (magnetic attractive forces) to support the supported portion of the rotor in a non-contact manner. The plurality of electromagnets include pairs of electromagnets (e.g., first and second electromagnets (51, 52)) facing each other with the supported portion of the rotor between them, and are configured to support the supported portion of the rotor in a non-contact manner by a composite electromagnetic force (F) of electromagnetic forces (F1, F2) generated by each of the pair of electromagnets. The electromagnetic force (F1) is generated in the direction in which the first electromagnet (51) faces the supported portion of the rotor. The electromagnetic force (F2) is generated in the direction in which the second electromagnet (52) faces the supported portion of the rotor. In this embodiment, the first and second electromagnets (51, 52) are arranged to face each other in the first facing direction (Z1) with the supported portion of the rotor sandwiched therebetween, and therefore, electromagnetic forces (F1, F2) are generated in opposite directions to each other in the first facing direction (Z1) of the first and second electromagnets (51, 52). In the magnetic bearing (20), by controlling a pair of currents flowing through the electromagnet pair (for example, first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52), respectively), it is possible to control the resultant electromagnetic force (F) of the electromagnet pair and thereby control the position of the rotor in the facing direction of the electromagnet pair.

[0049] In this example, two radial magnetic bearings 21 and one thrust magnetic bearing 22 constitute three magnetic bearings 20. In the following, one of the two radial magnetic bearings 21 will be referred to as a "first radial magnetic bearing 21," and the other will be referred to as a "second radial magnetic bearing 21."

[0050] Radial magnetic bearing As shown in FIGS. 2 and 3, the radial magnetic bearing (21) includes first to fourth electromagnets (51 to 54) and constitutes a heteropolar radial magnetic bearing. The first and second electromagnets (51, 52) face each other across the supported portion of the rotating shaft (5) and support the supported portion of the rotating shaft (5) in a non-contact manner by a composite electromagnetic force (F) of the first and second electromagnets (51, 52). The third and fourth electromagnets (53, 54) face each other across the supported portion (shaft portion) of the rotating shaft (5) and support the supported portion of the rotating shaft (5) in a non-contact manner by a composite electromagnetic force (F) of the third and fourth electromagnets (53, 54). The second opposing direction (Z2) of the third and fourth electromagnets (53, 54) is perpendicular to the first opposing direction (Z1) of the first and second electromagnets (51, 52) when viewed in the axial direction. The first opposing direction (Z1) and the second opposing direction (Z2) are directions perpendicular to the axial direction of the rotating shaft (5), i.e., radial directions of the rotating shaft (5). The first electromagnet (51) is an example of a first actuator. The second electromagnet (52) is an example of a second actuator. One side of the first opposing direction (Z1) is an example of a first direction. The other side of the first opposing direction (Z1) is an example of a second direction.

[0051] In this example, the radial magnetic bearing 21 includes a magnetic bearing core 61 and eight coils 65. The magnetic bearing core 61 is formed, for example, by laminating a plurality of electromagnetic steel plates, and includes a back yoke 62 and eight teeth 63. The back yoke 62 is cylindrical. The eight teeth 63 are arranged circumferentially at predetermined intervals (in this example, at 45° intervals) along the inner peripheral surface of the back yoke 62, each protruding radially inward from the inner peripheral surface of the back yoke 62, with each inner peripheral surface (protruding end surface) facing the outer peripheral surface of the supported portion of the rotating shaft 5 at a predetermined distance.

[0052] The eight coils 65 are wound around the eight teeth 63 of the magnetic bearing core 61, respectively. This forms eight electromagnet sections (first to eighth electromagnet sections 71 to 78) in this example. Specifically, the first electromagnet section 71, the second electromagnet section 72, the seventh electromagnet section 77, the eighth electromagnet section 78, the third electromagnet section 73, the fourth electromagnet section 74, the fifth electromagnet section 75, and the sixth electromagnet section 76 are arranged in this order in the clockwise direction in FIG. 2.

[0053] The coils 65 of the first and second electromagnet sections 71 and 72 are connected in series to form the first electromagnet 51. The coils 65 of the third and fourth electromagnet sections 73 and 74 are connected in series to form the second electromagnet 52. A first current i1 is supplied to the coil of the first electromagnet 51 (i.e., the coils 65 of the first and second electromagnet sections 71 and 72), and a second current i2 is supplied to the coil of the second electromagnet 52 (i.e., the coils 65 of the third and fourth electromagnet sections 73 and 74). By controlling the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52), the resultant electromagnetic force (F) of the first and second electromagnets (51, 52) can be controlled to control the position of the supported portion (shaft portion) of the rotating shaft (5) in the first opposing direction (Z1).

[0054] The coils 65 of the fifth and sixth electromagnet sections 75, 76 are connected in series to form the third electromagnet 53. The coils 65 of the seventh and eighth electromagnet sections 77, 78 are connected in series to form the fourth electromagnet 54. A third current i3 is supplied to the coil of the third electromagnet 53 (i.e., the coils 65 of the fifth and sixth electromagnet sections 75, 76), and a fourth current i4 is supplied to the coil of the fourth electromagnet 54 (i.e., the coils 65 of the seventh and eighth electromagnet sections 77, 78). By controlling the third and fourth currents (i3, i4) flowing through the third and fourth electromagnets (53, 54), the resultant electromagnetic force (F) of the third and fourth electromagnets (53, 54) can be controlled, thereby controlling the position of the supported portion (shaft portion) of the rotating shaft (5) in the second opposing direction (Z2).

[0055] The winding direction of the coil (65) and the direction of the current flowing through the coil (65) are set so that an attractive force (i.e., an electromagnetic force acting in a direction that attracts the supported portion (shaft portion) of the rotating shaft (5)) is generated in each of the first to fourth electromagnets (51 to 54). Specifically, the winding direction of the coil (65) and the direction of the current flowing through the coil (65) are set so that a magnetic flux is generated in the direction of the arrow shown in FIG. 2.

[0056] <<Magnetic Thrust Bearing>> 4 and 5, the thrust magnetic bearing (22) has first and second electromagnets (51, 52). The other end of the rotating shaft (5) (the end opposite to the one end to which the impeller (3a) is fixed) includes a disk portion (5a) that protrudes radially outward and is formed in a disk shape, and this disk portion (5a) constitutes a supported portion of the thrust magnetic bearing (22). The first and second electromagnets (51, 52) face each other with the supported portion of the rotating shaft (5) (disk portion (5a)) in between, and support the supported portion of the rotating shaft (5) in a non-contact manner by a combined electromagnetic force (F) of the first and second electromagnets (51, 52).

[0057] Specifically, in this example, the thrust magnetic bearing (22) includes two magnetic bearing cores (61) and two coils (65). The two magnetic bearing cores (61) are each formed in an annular shape and are arranged on both axial sides of the supported portion (disk portion (5a)) of the rotating shaft (5) at a predetermined distance. A circumferential groove is formed around the entire circumference of the rotating shaft (5) on the opposing surfaces of the two magnetic bearing cores (61). The two coils (65) are accommodated in the circumferential grooves of the two magnetic bearing cores (61). This forms two electromagnets (a first electromagnet (51) and a second electromagnet (52)) in this example. A first current (i1) is supplied to the coil (65) of the first electromagnet (51), and a second current (i2) is supplied to the coil (65) of the second electromagnet (52). By controlling the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52), the resultant electromagnetic force (F) of the first and second electromagnets (51, 52) can be controlled, thereby controlling the position of the supported portion (disk portion (5a)) of the rotating shaft (5) in the third opposing direction (Z3) (i.e., the axial direction, the left-right direction in FIG. 5) of the first and second electromagnets (51, 52).

[0058] The winding direction of the coil 65 and the direction of the current flowing through the coil 65 are set so that an attractive force (i.e., an electromagnetic force acting in a direction that attracts the supported portion (disk portion 5 a) of the rotating shaft 5) is generated in each of the first and second electromagnets 51, 52. Specifically, the winding direction of the coil 65 and the direction of the current flowing through the coil 65 are set so that a magnetic flux is generated in the direction of the arrow shown in FIG.

[0059] <Distance detection unit> The distance detection unit (30) detects the distance between the distance detection unit (30) and a detected part of the rotating body. The distance detection unit (30) is, for example, a position sensor or a distance sensor. As shown in FIG. 1 , the distance detection unit (30) corresponds to a pair of electromagnets (for example, a set of first and second electromagnets (51, 52)) facing each other across a supported part of the rotating body (in this example, the supported part of the rotating shaft (5)), and detects the distance between the distance detection unit (30) and the detected part of the rotating body in the opposing direction of the pair of electromagnets. In this example, four radial distance detection units (31) and one thrust distance detection unit (32) constitute five distance detection units (30).

[0060] <Radial distance detector> The four radial distance detection units (31) are composed of a radial distance detection unit (hereinafter referred to as the "first radial distance detection unit (31)") corresponding to the set of first and second electromagnets (51, 52) of the first radial magnetic bearing (21), a radial distance detection unit (hereinafter referred to as the "second radial distance detection unit (31)") corresponding to the set of third and fourth electromagnets (53, 54) of the first radial magnetic bearing (21), a radial distance detection unit (hereinafter referred to as the "third radial distance detection unit (31)") corresponding to the set of first and second electromagnets (51, 52) of the second radial magnetic bearing (21), and a radial distance detection unit (hereinafter referred to as the "fourth radial distance detection unit (31)") corresponding to the set of third and fourth electromagnets (53, 54) of the second radial magnetic bearing (21). In the radial distance detection unit (31), the distance between the radial distance detection unit (31) and the supported part of the rotating body located between the pair of electromagnets is detected, so the supported part of the rotating body and the detected part are the same.

[0061] The first radial distance detection unit (31) detects the distance between the first radial distance detection unit (31) and a detection target portion of the rotor (a detection target portion of the rotor shaft (5)) in the first opposing direction (Z1). In this embodiment, the first radial distance detection unit (31) is disposed near the second electromagnet (52) of the first radial magnetic bearing (21). The third radial distance detection unit (31) detects the distance between the third radial distance detection unit (31) and a detection target portion of the rotor in the first opposing direction (Z1). In this embodiment, the third radial distance detection unit (31) is disposed near the second electromagnet (52) of the second radial magnetic bearing (21). In terms of design, when the detection target portion of the rotor is located at the center position, the distance between the first electromagnet (51) and the detection target portion of the rotor is the same distance (g0) as the distance between the second electromagnet (52) and the detection target portion of the rotor. The central position of the rotor's detectable portion indicates that the rotor's detectable portion is located at the center of the touchdown bearings (6, 7). Regarding the central position, in the radial direction (the radial direction of the rotor shaft (5)), the central position refers to the position where the gap between the inner ring of the radial touchdown bearing (6) and the outer periphery of the rotor's detectable portion is constant around the entire circumference. Regarding the thrust direction (the axial direction of the rotor shaft (5)), the central position refers to the position where the gap between the rotor's detectable portion and the thrust touchdown bearing (7) located on the impeller (3a) side is equal to the gap between the rotor's detectable portion and the thrust touchdown bearing (7) located on the opposite side of the impeller (3a). The central position is predetermined. When the rotor's detectable portion is located at the central position, the electromagnet gap of one of the pair of electromagnets (the distance between one electromagnet and the rotor's detectable portion) and the electromagnet gap of the other electromagnet (the distance between the other electromagnet and the rotor's detectable portion) are not necessarily equal. On drawings that assume zero tolerance, or in products where manufacturing errors are small enough to be ignored, the center of the touchdown bearings (6, 7) and the center of the opposing electromagnets will coincide, and in that case, when the detected part of the rotating body is located in the center position, the gap between one electromagnet and the gap between the other electromagnet will be equal. Also, at this time, the gap between one electromagnet and the gap between the other electromagnet will be the same distance (g0).

[0062] The second radial distance detection unit (31) detects the distance between the second radial distance detection unit (31) and a detected portion of the rotating body (a detected portion of the rotating shaft (5)) in the second opposing direction (Z2). In the present embodiment, the second radial distance detection unit (31) is disposed near the fourth electromagnet (54) of the first radial magnetic bearing (21). The fourth radial distance detection unit (31) detects the distance between the fourth radial distance detection unit (31) and a detected portion of the rotating body in the second opposing direction (Z2). In the present embodiment, the fourth radial distance detection unit (31) is disposed near the fourth electromagnet (54) of the second radial magnetic bearing (21). In terms of design, when the detected part of the rotating body is located at the center position of the third and fourth electromagnets (53, 54) in the second opposing direction (Z2), the distance between the third electromagnet (53) and the detected part of the rotating body is the same distance (g0) as the distance between the fourth electromagnet (54) and the detected part of the rotating body.

[0063] <Thrust distance detector> The thrust distance detection unit (32) detects the distance between the thrust distance detection unit (32) and the detection target of the rotor (the detection target of the rotor shaft (5)) in the third opposing direction (Z3). The distance between the thrust distance detection unit (32) and the detection target of the rotor in the third opposing direction (Z3) indicates the distance between the thrust distance detection unit (32) and the detection target of the rotor (the disk portion (5a)). In this embodiment, the thrust distance detection unit (32) is disposed near the second electromagnet (52) of the thrust magnetic bearing (22). The distance between the second electromagnet (52) of the thrust magnetic bearing (22) and the detection target of the rotor indicates the distance between the second electromagnet (52) of the thrust magnetic bearing (22) and the detection target of the rotor (the disk portion (5a)). In terms of design, when the detected part of the rotating body (disk part (5a)) is located at the center position of the first and second electromagnets (51, 52) in the third opposing direction (Z3), the distance between the first electromagnet (51) and the detected part of the rotating body (disk part (5a)) of the rotating shaft (5) is the same distance (g0) as the distance between the second electromagnet (52) and the detected part of the rotating body (disk part (5a)).

[0064] Controller The controller (40) controls one or more magnetic bearings (20) so that the supported part of the rotating body (in this example, the supported part of the rotating shaft (5)) is supported in a non-contact manner. More specifically, the controller (40) performs levitation control for each of the electromagnet pairs (in this example, five electromagnet pairs) of the one or more magnetic bearings (20). By performing the levitation control described below, the position (x) of the supported part of the rotating body follows the position command value (x*). The levitation control is to control the current flowing through the electromagnets (magnetic levitation part) of the magnetic bearings (20) so that the position (x) of the supported part of the rotating body follows the position command value (x*). In this embodiment, in the levitation control, the controller (40) controls the current pair flowing through the electromagnet pair based on the distance detected by the distance detection unit (30) corresponding to the electromagnet pair. Specifically, if one electromagnet of the pair of electromagnets is designated as the "first electromagnet (51)" and the other electromagnet is designated as the "second electromagnet (52)," the controller (40) controls the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52), respectively, so that the following equation 1 in equation 1 and equation 2 in equation 2 hold true:

[0065]

number

[0066]

number

[0067] Here, "i1" corresponds to the first current (i1) flowing through the first electromagnet (51). "i2" corresponds to the second current (i2) flowing through the second electromagnet (52). d " corresponds to a current component (hereinafter referred to as control current (id)) that changes in response to the displacement of the detected part of the rotating body (in this example, the detected part of the rotating shaft (5)) in the opposing direction of the first and second electromagnets (51, 52). b " corresponds to a current component (hereinafter referred to as bias current (ib)) indicating a predetermined current value.

[0068] Furthermore, "g0" corresponds to the distance (hereinafter referred to as the reference distance (g0)) between the detection portion of the rotating body and the first and second electromagnets (51, 52) when the detection portion of the rotating body is located at the center position (i.e., the reference position) between the first and second electromagnets (51, 52) in design. The reference distance (g0) is set in advance. "x" is the position (x) of the detection portion of the rotating body in the first opposing direction (Z1). The position (x) is calculated by the controller (40) based on the detection value of the distance detection unit (30). The position (x) is a value obtained by calibrating the detection value of the distance detection unit (30) based on the touchdown bearings (6, 7). For example, by moving the rotating body to the maximum extent within the touchdown bearings (6, 7) and recording the detection range of the distance detection unit (30) at this time, data indicating the detection range of the distance detection unit (30) linked to the movable range of the rotating body can be obtained in advance. During levitation control, when the controller (40) acquires a detection value from the distance detection unit (30), the controller (40) calculates the position (x) by offset-correcting the detection value acquired from the distance detection unit (30) so that the median value of the detection range of the distance detection unit (30) becomes x = 0 (center position). The controller (40) may also perform sensitivity correction of the position (x) based on the design dimension of the difference between the inner diameter of the touchdown bearing (6) and the outer diameter of the rotor facing it, and the output width of the distance detection unit (30). "a" corresponds to a predetermined correction coefficient (a).

[0069] <Controller configuration> In this example, the controller (40) includes four radial control sections (41) and one thrust control section (42). The four radial control sections (41) are configured by a radial control section (hereinafter referred to as the “first radial control section (41)”) corresponding to the set of first and second electromagnets (51, 52) of the first radial magnetic bearing (21), a radial control section (hereinafter referred to as the “second radial control section (41)”) corresponding to the set of third and fourth electromagnets (53, 54) of the first radial magnetic bearing (21), a radial control section (hereinafter referred to as the “third radial control section (41)”) corresponding to the set of first and second electromagnets (51, 52) of the second radial magnetic bearing (21), and a radial control section (hereinafter referred to as the “fourth radial control section (41)”) corresponding to the set of third and fourth electromagnets (53, 54) of the second radial magnetic bearing (21).

[0070] <First radial control section> The first radial control unit (41) calculates the position (x) of the detection target portion of the rotating body in the first opposing direction (Z1) based on the detection value of the first radial distance detection unit (31), and performs levitation control on the first and second electromagnets (51, 52) of the first radial magnetic bearing (21) based on the position (x) of the detection target portion of the rotating body in the first opposing direction (Z1). Specifically, the first radial control unit (41) controls the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) of the first radial magnetic bearing (21), respectively, so that the above formulas 1 and 2 are satisfied.

[0071] Second radial control section The second radial control unit (41) calculates the position (x) of the detection target portion of the rotor in the second opposing direction (Z2) based on the detection value of the second radial distance detection unit (31), and performs levitation control on the third and fourth electromagnets (53, 54) of the first radial magnetic bearing (21) based on the position (x) of the detection target portion of the rotor in the second opposing direction (Z2). Specifically, the second radial control unit (41) controls the third and fourth currents (i3, i4) flowing through the third and fourth electromagnets (53, 54) of the first radial magnetic bearing (21), respectively, so that two equations similar to the above-mentioned equations 1 and 2 hold (i.e., two equations obtained by replacing the first current (i1), the second current (i2), the first electromagnet (51), and the second electromagnet (52) in equations 1 and 2 with the third current (i3), the fourth current (i4), the third electromagnet (53), and the fourth electromagnet (54), respectively).

[0072] <<Third radial control section>> The third radial control unit (41) calculates the position (x) of the detection target portion of the rotating body in the first opposing direction (Z1) based on the detection value of the third radial distance detection unit (31), and performs levitation control on the first and second electromagnets (51, 52) of the second radial magnetic bearing (21) based on the position (x) of the detection target portion of the rotating body in the first opposing direction (Z1). Specifically, similar to the first radial control unit (41), the third radial control unit (41) controls the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) of the second radial magnetic bearing (21), respectively, so that the above formulas 1 and 2 are satisfied.

[0073] <<Fourth radial control section>> The fourth radial control unit (41) calculates the position (x) of the detection target portion of the rotating body in the second opposing direction (Z2) based on the detection value of the fourth radial distance detection unit (31), and performs levitation control on the third and fourth electromagnets (53, 54) of the second radial magnetic bearing (21) based on the position (x) of the detection target portion of the rotating body in the second opposing direction (Z2). Specifically, similar to the second radial control unit (41), the fourth radial control unit (41) controls the third and fourth currents (i3, i4) flowing through the third and fourth electromagnets (53, 54) of the second radial magnetic bearing (21), respectively, so that two equations similar to the above-described equations 1 and 2 are satisfied.

[0074] Thrust control section The thrust control unit (42) calculates the position (x) of the detection target portion of the rotating body in the third opposing direction (Z3) based on the detection value of the thrust distance detection unit (32), and performs levitation control on the first and second electromagnets (51, 52) of the thrust magnetic bearing (22) based on the position (x) of the detection target portion of the rotating body in the third opposing direction (Z3). Specifically, the thrust control unit (42) controls the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) of the thrust magnetic bearing (22), respectively, so that the above formulas 1 and 2 are satisfied.

[0075] <Controller details> Next, the controller (40) will be described in detail with reference to Fig. 6. The controller (40) controls the position of the detection target part of the rotor during magnetic levitation and the current flowing through the electromagnets of the magnetic bearings (20) based on the distance detected by the distance detection unit (30). The controller (40) has one or more control units (four radial control units (41) and one thrust control unit (42) in this example) corresponding to each of the electromagnet pairs (five electromagnet pairs in this example) of one or more magnetic bearings (20), and the control units have the configuration shown in Fig. 6. Here, the configuration of the radial control unit (41) will be described as an example.

[0076] In the levitation control, the radial control unit (41) calculates a control current (id) according to a position deviation value (e) corresponding to a difference between a position (x) of the detection target of the rotor calculated based on a detection value of the distance detection unit (30) and a predetermined position command value (x*), and controls the first and second currents (i1, i2) using the control current (id) so that the above equations 1 and 2 hold. Specifically, the radial control unit (41) includes a correction coefficient setting unit (81), a position deviation calculation unit (82), a position control unit (83), a current calculation unit (84), a first current control unit (85), a second current control unit (86), and a current detector (current detection circuit). The current detector detects a current flowing through a coil (65) of an electromagnet of the magnetic bearing (20). The current detector includes a first current detector (87) that detects the current flowing through the coil (65) of the first electromagnet (51), and a second current detector (88) that detects the current flowing through the coil (65) of the second electromagnet (52).

[0077] <<Correction coefficient setting section>> The correction coefficient setting unit (81) sets a correction coefficient (a). The correction coefficient (a) is a variable value. For example, the correction coefficient setting unit (81) is configured to change the correction coefficient (a) in response to external control. The correction coefficient (a) is preferably set to a value greater than 1. The correction coefficient (a) may also be a fixed value.

[0078] <<Position deviation calculation unit and position control unit>> The position deviation calculation unit (82) calculates a position deviation value (e) corresponding to the difference between the position (x) of the detection target part of the rotating body calculated based on the detection value of the distance detection unit (30) and the position command value (x*). Specifically, the position deviation calculation unit (82) calculates the position deviation value (e) by subtracting the position (x) of the detection target part of the rotating body from the position command value (x*). The position control unit (83) calculates a control current (id) based on the position deviation value (e) calculated by the position deviation calculation unit (82). Specifically, the position control unit (83) determines the control current (id) so that the control current (id) increases as the position deviation value (e) increases.

[0079] Current calculation section The current calculation unit (84) determines a first current command value (i1*) and a second current command value (i2*) based on the correction coefficient (a) set by the correction coefficient setting unit (81), the control current (id) determined by the position control unit (83), the position (x) of the detection target portion of the rotating body calculated based on the detection value of the distance detection unit (30), a predetermined bias current (ib), and a predetermined reference distance (g0). Specifically, the current calculation unit (84) determines the first current command value (i1*) and the second current command value (i2*) by substituting these parameter values ​​(id, ib, x, g0, a) into the calculation formula shown in FIG.

[0080] Current control section The first current control unit (85) controls the first voltage (V1) applied to the coil (65) of the first electromagnet (51) so that the first current (i1) flowing through the coil (65) of the first electromagnet (51) becomes equal to the first current command value (i1*) determined by the current calculation unit (84). Specifically, the first current control unit (85) controls the first voltage (V1) so that the first current (i1) detected by the first current detector (87) becomes equal to the first current command value (i1*).

[0081] The second current control unit (86) controls the second voltage (V2) applied to the coil (65) of the second electromagnet (52) so that the second current (i2) flowing through the coil (65) of the second electromagnet (52) becomes equal to the second current command value (i2*) determined by the current calculation unit (84). Specifically, the second current control unit (86) controls the second voltage (V2) so that the second current (i2) detected by the second current detector (88) becomes equal to the second current command value (i2*).

[0082] Acquisition process The controller (40) performs an acquisition process. The acquisition process is a process for acquiring information indicating the relationship between the distance detected by the distance detection unit (30) and the current flowing through the electromagnet of the magnetic bearing (20). In the acquisition process, a plurality of levitation controls are performed to maintain the position (x) of the detected part of the rotating body (the detected part of the rotating shaft (5)) at a constant position while maintaining the current flowing through the electromagnet of the magnetic bearing (20) at a constant current. Hereinafter, the levitation control control that maintains the position (x) of the detected part of the rotating body at a constant position while maintaining the current flowing through the electromagnet of the magnetic bearing (20) at a constant current may be referred to as a maintenance control. For each maintenance control, a pair consisting of a constant position and a constant current is set, and the plurality of maintenance controls correspond to the plurality of pairs.

[0083] <Acquisition process procedure> The controller (40) performs current control in each of the plurality of maintenance controls so as to satisfy a condition that the position (x) of the detection part of the rotating body is kept constant, and acquires the detection value of the distance detection part (30) and the detection value of the current detector when the position (x) of the detection part of the rotating body is kept constant during the maintenance control and the current flowing through the electromagnet of the magnetic bearing (20) is kept constant. As a result, the controller (40) acquires information indicating the relationship between the distance detected by the distance detection part (30) and the current flowing through the electromagnet of the magnetic bearing (20) when the rotating body is magnetically levitated.

[0084] The controller 40 performs the plurality of maintenance controls such that when any two of the plurality of maintenance controls are compared, the fixed positions are different from each other or the fixed currents are different from each other. The difference in the fixed positions or the difference in the fixed currents indicates that, of the fixed positions and the fixed currents, the fixed currents are the same but the fixed positions are different from each other, the fixed positions are the same but the fixed currents are different from each other, or both the fixed positions and the fixed currents are different from each other. The difference in any two of the plurality of maintenance controls indicates all combinations when two maintenance controls are selected from the plurality of maintenance controls.

[0085] <Output processing> The controller (40) performs an output process. The output process is a process of outputting (calculating) the distance between the detection target portion of the rotating body and the magnetic bearing (20) when the detection target portion of the rotating body is located at the center position, based on the information acquired in the acquisition process (information acquired by performing multiple maintenance controls). The information acquired in the acquisition process is specifically the detection value of the distance detection unit (30) and the detection value of the current detector, which are acquired for each maintenance control.

[0086] In the output process, for each maintenance control, balance information (see Equation 3 below) indicating the balance of forces of the supported part of the rotating body (supported part of the rotating shaft (5)) is output based on the corresponding constant position and constant current. Then, based on multiple pieces of balance information, the distance between the detected part of the rotating body and the magnetic bearing (20) when the detected part of the rotating body is located at the central position is output (calculated). The constant position is a value calculated based on the detection value of the distance detection unit (30) that is maintained constant during maintenance control. Specifically, the constant position is a value obtained by calibrating (by the above-mentioned offset correction, the above-mentioned sensitivity correction, etc.) the detection value of the distance detection unit (30) that is maintained constant during maintenance control. The constant current is the detection value of the current detector that is maintained constant during maintenance control.

[0087] The following equation 3 shows a force balance equation, which is an example of the balance information.

[0088]

number

[0089] The above equation 3 shows the force balance equation in the first opposing direction (Z1) for each maintenance control performed on the first radial magnetic bearing (21) while maintaining the position (x) of the supported part of the rotating body (supported part of the rotating shaft (5)) in the first opposing direction (Z1) at a constant position, and maintaining the first and second currents (i1, i2) flowing in the first and second electromagnets (51, 52) at constant currents.

[0090] In the above formula 3, formula 1 represents the force balance equation for the first maintenance control, and formula 2 represents the force balance equation for the second maintenance control. In the above formula 3, the force balance equation for the third and subsequent maintenance controls is omitted. Note that the maintenance control may be performed two or more times.

[0091] The definitions of the symbols in the formulas 1 and 2 of the above-mentioned formula 3 are as follows:

[0092] f u : Electromagnetic force (F1) of the first electromagnet (51) f L : Electromagnetic force (F2) of the second electromagnet (52) g u : Distance between the first electromagnet (51) and the detected part of the rotating body (the detected part of the rotating shaft (5)) g L : Distance between the second electromagnet (52) and the part of the rotating body to be detected g u0 : The distance between the first electromagnet (51) and the part to be detected of the rotating body when the part to be detected of the rotating body is located at the center position g L0 The distance between the second electromagnet (52) and the part to be detected of the rotating body when the part to be detected of the rotating body is located at the center position i u :1st current i L :Second current i u (x1): Constant first current during the first maintenance control i u (x2): Constant first current during the second maintenance control i L (x1): Constant second current during the first maintenance control i L (x2): Second constant current during the second maintenance control k u : Electromagnetic force coefficient of the first electromagnet (51) k L : Electromagnetic force coefficient of the second electromagnet (52) w: Component of gravity in the first opposing direction (Z1) x1: Fixed position during the first maintenance control x2: Fixed position during the second maintenance control

[0093] In the above formula 3, g u0 and g L0 is an unknown value, but i u (x1), i L (x1), i u (x2), i L (x2) x1, x2 and w are known values. u (x1) is the detection value of the first current detector (87) that is maintained constant during the first maintenance control. L (x1) is the detection value of the second current detector (88) that is maintained constant during the first maintenance control. u (x2) is the detection value of the first current detector (87) that is maintained constant during the second maintenance control. L (x2) is the detection value of the second current detector 88 maintained constant during the second maintenance control. x1 is a value obtained by calibrating the detection value of the first radial distance detector 31 maintained constant during the first maintenance control, and is calculated based on the detection value of the first radial distance detector 31 maintained constant during the first maintenance control. x2 is a value obtained by calibrating the first radial distance detector 31 maintained constant during the second maintenance control, and is calculated based on the first radial distance detector 31 maintained constant during the second maintenance control.

[0094] The controller (40) calculates the distance g between the detection part of the rotating body and the magnetic bearing (20) when the detection part of the rotating body is located at the central position based on the balance information (the force balance equation shown in the above equation 3). u0 and distance g L0 The controller (40) outputs, for example, the distance g from a simultaneous equation of multiple balance information (balance equations). u0 and distance g L0 can be solved, and the distance g can be calculated using the two-dimensional Newton method. u0 and distance g L0 Alternatively, if there are three or more pieces of balance information (three equations), the distance g can be calculated using the least squares method. u0 and distance g L0 In the following, we will consider the distance g u0 the first distance (g U0 ) and the distance g L0 the second distance (g L0 ) is sometimes written as

[0095] <Update process> The controller (40) determines the first distance (g U0 ) and the second distance (g L0 ) is output, the first distance (g U0 ) and the second distance (g L0 ) may be used for the update process. In the update process, as shown in FIG. 7, the current calculation unit (84) of the controller (40) calculates a correction coefficient (a), a control current (id), a position (x) of the detected part of the rotating body, a bias current (ib), a reference distance (g0), and a first distance (g U0 ) and the second distance (g L0 ), the first current command value (i1*) and the second current command value (i2*) are calculated. That is, for the calculation formula (W1) (see FIG. 6) for calculating the first current command value (i1*) and the second current command value (i2*), the reference distance (g0) in the numerator is calculated by multiplying the reference distance (g U0 ) or the second distance (g L0), and calculates the first current command value (i1*) and the second current command value (i2*) using the equation (W2). The controller (40) then performs further maintenance control using the equation (W2). At this time, the controller (40) can repeatedly perform the output process described above to update the equation (W1), for example, while widening the levitation conditions related to the distance from the detection target portion of the rotating body and / or the first and second currents (i1, i2) from the initial conditions (see FIG. 12(b)). This allows maintenance control to be performed under a wide range of levitation conditions, thereby enabling the equation (W1) to be updated with high accuracy.

[0096] Improved levitation control The controller (40) determines the first distance (g U0 ) and the second distance (g L0 ) is output, the first distance (g U0 ) and the second distance (g L0 ) may be used to perform levitation control so that the detection part of the rotating body is positioned at the center position. That is, the controller (40) may use the first distance (g U0 ) and the second distance (g L0 ), normal operation may be performed without repeating the above-described output process and update process. Normal operation indicates that the magnetic unit (10) operates so that the product equipped with the magnetic unit (10) can function as if a refrigeration device were operating by performing a refrigeration cycle. U0 ) and the second distance (g L0 ) so that the detected part of the rotating body is positioned at the center position is sometimes referred to as improved levitation control. In improved levitation control, an updated arithmetic formula (W2) is used, which is an updated version of arithmetic formula (W1) (see Figure 6). The first current command value (i1*) and the second current command value (i2*) are calculated using arithmetic formula (W2). According to this, the first distance (g U0 ) and the second distance (g L0) to determine the first current command value (i1*) and the second current command value (i2*), the accuracy of the first current command value (i1*) and the second current command value (i2*) is improved. As a result, the control stability of the levitation control can be improved. As described in the output process above, the sensing result indicates that information indicating a certain position and information indicating a certain current are obtained by performing sensing on the magnetic unit (10) using the current detector and the distance detector (30). In the output process above, the information indicating the certain position is obtained by using x 1、 and x2 are obtained, and information indicating a constant current is u (x1), i L (x1), i u (x2), and i u (x2) is obtained.

[0097] <effect> By performing multiple maintenance controls, it is possible to obtain information indicating the relationship between the distance detected by the distance detection unit (30) and the current flowing through the magnetic levitation unit (electromagnet) when the rotating body is magnetically levitated. Also, taking into account the variation in the product dimensions of the magnetic unit (10) relative to the design dimensions, it is possible to understand the relationship between the distance detected by the distance detection unit (30) and the current flowing through the magnetic levitation unit (electromagnet).

[0098] Furthermore, based on the relationship between the distance detected by the distance detection unit (30) and the current flowing through the magnetic levitation unit, control processing can be performed, such as improving the stability of the levitation control of the rotating body, suppressing errors contained in the distance detected by the distance detection unit (30), and detecting abnormalities or failures in the magnetic unit (10).

[0099] Furthermore, with regard to the distance between the detection part of the rotating body and the magnetic bearing (20) when the detection part of the rotating body is located at the center position, the reference distance (g0) is a design distance (design dimension) as described above, and therefore, when compared with an actual product, there is a possibility that the distance may deviate due to the influence of manufacturing variations, assembly variations, etc. However, in this embodiment, by performing the above output processing, information indicating the relationship between the distance detected by the distance detection unit (30) and the current flowing through the electromagnet of the magnetic bearing (20) is acquired for each maintenance control, and the first distance (g U0 ) and the second distance (g L0 ) is output, so the first distance (g U0 ) and the second distance (g L0 ) can be output.

[0100] In addition, in many cases, magnetic bearings achieve levitation control by directly controlling the current i to adjust the electromagnetic force f that supports the detected part of the rotating body. The electromagnet gap (the distance between the electromagnet and the detected part of the rotating body) g is given by f = k(i 2 / g 2 ), deviation of the true value of the electromagnet gap g from the design value results in a deterioration in the accuracy of the electromagnetic force output, which in turn leads to a decrease in the stability of the levitation control. However, in this embodiment, the first distance (g U0 ) and the second distance (g L0 ) can be output with high accuracy, and the deviation between the true value and the design value can be reduced, so that the stability of the levitation control can be prevented from decreasing.

[0101] Furthermore, since the electromagnetic gap of the magnetic bearing is designed to be smaller than that of other general machines, the ratio of the variation in the dimensions of the product to the design value tends to be large. However, in this embodiment, the first distance (g U0 ) and the second distance (g L0 ), it is possible to prevent a decrease in the stability of levitation control even if there is variation in the dimensions of the product relative to the design value.

[0102] Furthermore, since the electromagnetic gap is located inside the casing of the product (inside the casing (2) of the compressor (1)), it is difficult to directly measure the electromagnetic gap after manufacturing the magnetic unit (10). However, in this embodiment, by performing the above-described acquisition process and the above-described output process, it is possible to measure the first distance (g U0 ) and the second distance (g L0 ) can be output. As a result, the electromagnet gap can be easily output.

[0103] Furthermore, in this embodiment, by performing multiple maintenance controls, multiple pieces of balance information are output as shown in the above equation 3, and the electromagnetic gap is output based on the multiple pieces of balance information, so the electromagnetic gap is output based on multiple position conditions and current conditions, rather than just one position condition (constant position) and current condition (constant current).As a result, the electromagnetic gap can be output with high accuracy.

[0104] The acquisition process, the output process, the update process, and / or the improved levitation control may also be performed on a magnetic bearing other than the first radial magnetic bearing 21. Specifically, the acquisition process, the output process, the update process, and / or the improved levitation control may be performed on the second radial magnetic bearing 21 by performing a plurality of maintenance controls to maintain the first and second currents (i1, i2) flowing through the first and second electromagnets 51, 52 at constant currents while maintaining the position (x) of the detected part of the rotating body (the detected part of the rotating shaft 5) in the first opposing direction (Z1) at a constant position. The acquisition process, the output process, the update process, and / or the improved levitation control may be performed by performing a plurality of maintenance controls for the first radial magnetic bearing (21) and / or the second radial magnetic bearing (21) to maintain the third and fourth currents (i3, i4) flowing through the third and fourth electromagnets (53, 54) at constant currents while maintaining the position (x) of the detection portion of the rotor at a constant position in the second opposing direction (Z2).The acquisition process, the output process, the update process, and / or the improved levitation control may be performed by performing a plurality of maintenance controls for the thrust magnetic bearing (22) to maintain the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) at constant currents while maintaining the position (x) of the detection portion of the rotor at a constant position in the third opposing direction (Z3).

[0105] <Example of acquisition process> The following describes variations of a constant position and a constant current when performing multiple maintenance controls for the first radial magnetic bearing (21) to maintain the position (x) of the detected part of the rotating body (the detected part of the rotating shaft (5)) in the first opposing direction (Z1) at a constant position and to maintain the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) at constant currents. In this example, the multiple maintenance controls performed are a first maintenance control, a second maintenance control, and a third maintenance control.

[0106] The procedures for carrying out the first maintenance control to the third maintenance control will be described.

[0107] As shown in FIG. 8, in step S1, the controller (40) performs first maintenance control. In the first maintenance control, the position (x) of the detection part of the rotor (the detection part of the rotation shaft (5)) is maintained at a constant first position (x1), and the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) are maintained at a constant first current value (i u (x1), i L The current value is a general term for the first and second currents, and the first value (character string) in the current value indicates the first current, and the second value indicates the second current.

[0108] The controller (40) performs the first maintenance control to obtain a first current value (i u (x1), i L (x1)) and

[0109] In step S2, the controller (40) performs the first maintenance control and then the second maintenance control. In the second maintenance control, the position (x) of the detection part of the rotor is maintained at a constant second position (x2), and the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) are maintained at a constant second current value (i u (x2), i L (x2)).

[0110] The controller (40) performs the second maintenance control to obtain a second current value (i u (x2), i L (x2)) and

[0111] In step S3, the controller (40) performs the second maintenance control and then the third maintenance control. In the third maintenance control, the position (x) of the detection target of the rotor is maintained at a constant third position (x3), and the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) are maintained at a constant third current value (i u (x3), i L (x3)).

[0112] The controller (40) performs the third maintenance control to obtain a third current value (i u (x3), i L (x3)) and

[0113] <First example of maintenance control> As shown in FIG. 9, in the first example, the first current value (i u (x1), i L (x1)) to the third current value (i u (x3), i L (x3)) are different from each other, and the first position (x1) to the third position (x3) are the same from each other.

[0114] <Second example of maintenance control> As shown in FIG. 10, in the second example, the first current value (i u (x1), i L (x1)) and the second current value (i u (x2), i L (x2)) are different from each other, and the first position (x1) and the third position (x3) are different from each other.

[0115] In the second example, the first current value (i u (x1)) and the third current value (i u (x3), i L (x3)) may be the same as or different from each other. u (x2), i L (x2)) and the third current value (iu (x3), i L In the second example, the first position (x1) and the second position (x2) may be the same as or different from each other. In the second example, the second position (x2) and the third position (x3) may be the same as or different from each other.

[0116] <Third example of maintenance control> As shown in FIG. 11, in the third example, the first current value (i u (x1), i L (x1)) to the third current value (i u (x3), i L (x3)) are different from each other, and the first position (x1) to the third position (x3) are different from each other.

[0117] <Fourth example of maintenance control> 12(a), in the fourth example, in the first maintenance control to the third maintenance control, the third position (x3) is smaller than both the first position (x1) and the second position (x2). Note that the third position (x3) may be larger than both the first position (x1) and the second position (x2). In other words, when the distance detected by the first radial distance detection unit (31) at the first position (x1) is defined as the first detection distance, the distance detected by the first radial distance detection unit (31) at the second position (x2) is defined as the second detection distance, and the distance detected by the first radial distance detection unit (31) at the third position (x3) is defined as the third detection distance, the third detection distance is larger than both the first detection distance and the second detection distance, or is smaller than both the first detection distance and the second detection distance.

[0118] By using the configuration shown in the fourth example when performing multiple maintenance controls, as shown in FIG. 12(b), the levitation conditions for the position of the detected part of the rotor (position command width) are expanded from the initial conditions each time maintenance control is performed, and the above output process is repeated to update the calculation formula (W1) (see FIG. 7). Note that, as shown in FIG. 12(b), a configuration may be adopted in which a constant current and a constant position are confirmed when the state in which the position of the detected part of the rotor and the detection value of the current detector each remain approximately constant continues for a predetermined confirmation wait time (ts) in each of the multiple maintenance controls. The predetermined confirmation wait time (ts) is, for example, 5 seconds.

[0119] <5th example of maintenance control> As shown in FIG. 13, in the fifth example, the third current value (i u (x3), i L (x3)) is the first current value (i u (x1), i L (x1)) and the second current value (i u (x2), i L (x2)) or the first current value (i u (x1), i L (x1)) and the second current value (i u (x2), i L Specifically, the first current (i1) is smaller than the current (i u (x3)) is the current during the first maintenance control (i u (x1)) and the current during the second maintenance control (i u (x2)), and the second current (i2) is smaller than the current (i L (x3)) is the current during the first maintenance control (i L (x1)) and the current during the second maintenance control (i L (x2)).

[0120] By using the configuration shown in the fifth example when performing multiple maintenance controls, the levitation conditions for the first and second currents (i1, i2) are expanded from the initial conditions each time maintenance control is performed, and the above output process is repeated, thereby updating the calculation formula (W1) (see Figure 7) (see Figure 12(b)).

[0121] <Example 6 of Maintenance Control> As shown in FIG. 14, in the sixth example, the first current value (i u (x1), i L (x1)) to the third current value (i u (x3), i L (x3)) are the same, and the first position (x1) to the third position (x3) are different from each other.

[0122] The configuration shown in the sixth example can be realized by, for example, employing a configuration in which a load (applied load) other than the electromagnetic force acting on the supported portion of the rotating body is variable. Normally, the applied load is gravity and is constant, but in the sixth example, the applied load is variable. Then, by changing the applied load for each maintenance control, the first current value (i u (x1), i L (x1)) to the third current value (i u (x3), i L The first position (x1) to the third position (x3) are made different from one another while the first position (x1) to the third position (x3) are made the same.

[0123] <Example of controller operation> An example of the operation of the controller (40) will be described with reference to FIG. 15. In this example, the controller (40) performs, for example, any one of the first to sixth examples of the maintenance control. However, in this example, the first radial control unit (41) does not perform the first to third maintenance controls consecutively, which is different from the example of the acquisition process (FIG. 8). The following mainly describes the differences from the example of the acquisition process shown in FIG. 8.

[0124] As shown in Fig. 15, in step S1, the controller (40) performs first maintenance control. In step S2, the controller (40) performs the first maintenance control and then performs second maintenance control. After the controller (40) performs the second maintenance control, the process proceeds to step S2a.

[0125] In step S2a, the controller (40) performs output processing. In the output processing of this example, based on information acquired in the first maintenance control and the second maintenance control (the detection value of the distance detection unit (30) and the detection value of the current detector), balance information during the first maintenance control (for example, equation 1 of the above equation 3) and force balance information during the second maintenance control (for example, equation 2 of the above equation 3) are output, and based on these two pieces of balance information, the distance (g U0 , g L0 ) is output.

[0126] In step S2b, the controller (40) performs an update process. In the update process of this example, the arithmetic formula (W1) (see FIG. 6) for determining the first current command value (i1*) and the second current command value (i2*) is updated to the arithmetic formula (W2) shown in FIG.

[0127] In step S3, the controller (40) performs the third maintenance control. In this example, the controller (40) performs the third maintenance control using the arithmetic expression (W2). That is, the arithmetic expression (W2) is used to calculate the third maintenance control using the constant first position (x1) and the constant first current value (i u (x1), i L (x1)), and a constant second position (x2) and a constant second current value (i u (x2), i L (x2)) is generated based on a constant first position (x1) and a constant first current value (i u (x1), i L (x1)), a constant second position (x2), and a constant second current value (i u (x2), i L (x2)), the third maintenance control is performed.

[0128] (Other embodiments) Any two of the plurality of maintenance controls may have a difference in constant position by a first predetermined value or more, or a difference in constant current by a second predetermined value or more, thereby allowing a plurality of maintenance controls to be performed such that the difference in constant position by a first predetermined value or more, or the difference in constant current by a second predetermined value or more, is mutually different.

[0129] The controller 40 includes a processor and can be configured using a calculation circuit such as a CPU and a memory. The components of the controller 40 may be integrated into one calculation circuit or distributed across multiple calculation circuits.

[0130] Furthermore, although the radial magnetic bearing (21) is a heteropolar type radial magnetic bearing, the radial magnetic bearing (21) may be a homopolar type radial magnetic bearing.

[0131] The number of electromagnets in the magnetic bearing 20 may be more than one and is not limited to the number shown in the embodiment. For example, as shown in Fig. 16(a), the radial magnetic bearing 21 may be configured to have a first electromagnet 51 to a sixth electromagnet 56, so that a first electromagnetic force f1 to a sixth electromagnetic force f6 act on the supported portion of the rotating body (the supported portion of the rotating shaft 5). As shown in Fig. 16(b), the radial magnetic bearing 21 may be configured to have a first electromagnet 51 to a third electromagnet 53, so that a first electromagnetic force f1 to a third electromagnetic force f3 act on the supported portion of the rotating body (the supported portion of the rotating shaft 5).

[0132] Although the embodiments and modifications have been described above, it will be understood that various modifications in form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments, examples, modifications, and other embodiments may be combined or substituted as appropriate as long as the functionality of the subject matter of the present disclosure is not impaired.

[0133] The terms "first," "second," "third," etc. mentioned above are used to distinguish the terms to which these terms are attached, and do not limit the number or order of the terms. [Industrial Applicability]

[0134] INDUSTRIAL APPLICABILITY As described above, the present disclosure is useful for magnetic units, compressors, and refrigeration devices. [Explanation of symbols]

[0135] 1 Compressor 2 Casing 3. Compression mechanism 3a impeller 4 Electric motor 5 Rotation Axis 10 Magnetic Unit 20 Magnetic bearings 21 Radial magnetic bearing 22 Thrust magnetic bearing 30 Distance detection unit 31 Radial distance detector 32 Thrust distance detector 40 Controller 41 Radial control section 42 Thrust control section 51 First electromagnet 52 Second electromagnet 81 Correction coefficient setting section 82 Position deviation calculation section 83 Position control section 84 Current calculation unit 85 First current control section 86 Second current control section 87 First current detector 88 Second current detector i1 1st current i2 2nd current

Claims

1. a magnetic levitation unit that generates electromagnetic force when current is passed through it to support the rotating body in a non-contact manner; a distance detection unit (30) for detecting the distance to the rotating body; a controller (40) for controlling the position of the rotor during magnetic levitation and the current flowing through the magnetic levitation portion based on the distance detected by the distance detection portion (30); Equipped with The controller (40) performing a plurality of maintenance controls to maintain the current flowing through the magnetic levitation unit at a constant current while maintaining the position of the rotor at a constant position; A magnetic unit, wherein when any two maintenance controls among the plurality of maintenance controls are compared, the constant positions are different from each other or the constant currents are different from each other.

2. the plurality of maintenance controls include a first maintenance control, a second maintenance control, and a third maintenance control; In the first maintenance control, the constant position is a first position and the constant current is a first current; In the second maintenance control, the constant position is a second position and the constant current is a second current; The magnetic unit according to claim 1 , wherein in the third maintenance control, the constant position is a third position and the constant current is a third current.

3. The magnetic unit according to claim 2 , wherein the first current, the second current, and the third current are different from each other.

4. The magnetic unit according to claim 3 , wherein the first position, the second position, and the third position are the same as each other.

5. The magnetic unit according to claim 2 , wherein the first position, the second position, and the third position are different from one another.

6. the first current and the second current are different from each other, The magnetic unit according to claim 2 , wherein the first position and the third position are different from each other.

7. the first current, the second current, and the third current are different from one another; The magnetic unit according to claim 2 , wherein the first position, the second position, and the third position are different from one another.

8. the first maintenance control, the second maintenance control, and the third maintenance control are performed in the order of the first maintenance control, the second maintenance control, and the third maintenance control; The magnetic unit according to claim 2 , wherein the third current is greater than each of the first current and the second current, or less than each of the first current and the second current.

9. the first maintenance control, the second maintenance control, and the third maintenance control are performed in the order of the first maintenance control, the second maintenance control, and the third maintenance control; The distance detected by the distance detection unit (30) at the first position is defined as a first detection distance, the distance detected by the distance detection unit (30) at the second position is defined as a second detection distance; When the distance detected by the distance detection unit (30) at the third position is defined as a third detection distance, The magnetic unit according to claim 2 , wherein the third detection distance is greater than both the first detection distance and the second detection distance, or is smaller than both the first detection distance and the second detection distance.

10. the first maintenance control, the second maintenance control, and the third maintenance control are performed in the order of the first maintenance control, the second maintenance control, and the third maintenance control; 10. The magnetic unit according to claim 2, wherein the controller (40) performs the third maintenance control based on the first current, the second current, the first position, and the second position.

11. 10. The magnetic unit according to claim 1, wherein any two of the plurality of maintenance controls have the constant position different by a first predetermined value or more, or the constant current different by a second predetermined value or more.

12. The magnetic levitation unit includes: a first actuator (51) that generates a magnetic attraction force in a first direction on the rotor; a second actuator (52) that generates a magnetic attraction force on the rotor in a second direction opposite to the first direction; Including, the fixed position is a position of the rotating body in the first direction or the second direction, The magnetic unit according to any one of claims 1 to 9, wherein the constant current includes a current flowing through the first actuator (51) and the second actuator (52).

13. 10. The magnetic unit according to claim 1, wherein the controller (40) controls the current flowing through the magnetic levitation portion based on the constant position and the constant current in each of the plurality of maintenance controls after performing the plurality of maintenance controls.

14. 10. The magnetic unit according to claim 1, wherein the controller (40) outputs balance information indicating the balance of forces of the rotating body based on the corresponding constant position and the constant current for each maintenance control, and outputs information indicating the distance between the rotating body and the magnetic levitation part when the rotating body is located at a central position based on a plurality of the balance information.

15. the magnetic levitation unit has a plurality of electromagnets that are arranged around the rotating body and generate electromagnetic forces when energized to support the rotating body in a non-contact manner; The magnetic unit according to any one of claims 1 to 9, wherein the controller (40) controls the current flowing through each of the plurality of electromagnets.

16. A magnetic unit according to any one of claims 1 to 9; The rotating body; a compression mechanism (3) connected to the rotor; A compressor comprising:

17. A refrigeration system comprising the compressor according to claim 16.

Images