Magnetic unit, compressor, and refrigeration device

Abstract

This magnetic unit comprises: a distance detection unit (30) that detects the distance between a rotating body and a magnetic levitation unit that generates electromagnetic force by energization and supports the rotating body in a non-contact manner; and a controller (40) that controls the position of the rotating body during magnetic levitation and the current flowing through the magnetic levitation unit on the basis of the distance detected by the distance detection unit (30). The controller (40) performs a plurality of maintenance controls for maintaining the current flowing in the magnetic levitation unit at a constant current while maintaining the position of the rotating body at a constant position. Comparing any two of the plurality of maintenance controls, the constant positions are different from each other, or the constant currents are different from each other.

Description

Magnetic unit, compressor and refrigeration device

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

[0002] Patent Document 1 describes a method for calibrating a gap sensor provided in a magnetic bearing. The gap sensor detects a 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.

[0003] International Publication No. 2019 / 064469

[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.

[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), wherein the controller (40) performs a plurality of maintenance controls that maintain the current flowing through the magnetic levitation part at a constant current while maintaining the position of the rotating body at a constant position, and when any two of the plurality of 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 one another.

[0011] In the third aspect, the first to third maintenance controls can be performed by varying the constant currents.

[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 one another.

[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 also varying the constant positions.

[0020] An 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 a ninth aspect of 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 a first predetermined value or more, or differ in the constant current by a second predetermined value or more.

[0027] In an 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 unit includes a first actuator (51) that generates a magnetic attractive force on the rotating body in a first direction, and a second actuator (52) that generates a magnetic attractive 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 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 supporting the rotating body in a non-contact manner by generating electromagnetic force when current is passed through them, 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 apparatus according to a seventeenth aspect includes the compressor according to the sixteenth aspect.

[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.

[0039] FIG. 1 shows an example of the configuration of a compressor according to an embodiment, and is a cross-sectional view of the compressor when the compressor is cut along the axial direction of the rotating shaft of the compressor. FIG. 2 shows an example of the configuration of a radial magnetic bearing, and is a cross-sectional view of the radial magnetic bearing when the radial magnetic bearing is cut along the radial direction of the rotating shaft of the compressor. FIG. 3 shows an example of the configuration of a radial magnetic bearing, and is a cross-sectional view of the radial magnetic bearing when the radial magnetic bearing is cut along the axial direction of the rotating shaft of the compressor. FIG. 4 is a plan view of a thrust magnetic bearing as seen from the axial direction of the rotating shaft of the compressor. FIG. 5 shows an example of the configuration of a thrust magnetic bearing, and is a cross-sectional view of the thrust magnetic bearing when the thrust magnetic bearing is cut along the axial direction of the rotating shaft of the compressor. FIG. 6 is a block diagram showing an example of the configuration of a controller. FIG. 7 is a block diagram showing an example of the configuration of a controller in which control parameters have been updated. FIG. 8 is a flow chart showing procedures for multiple maintenance controls. FIG. 9 is a diagram showing a first example of maintenance control. FIG. 10 is a diagram showing a second example of maintenance control. FIG. 11 is a diagram showing a third example of maintenance control. FIG. 12(a) is a diagram showing a fourth example of maintenance control. 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. Fig. 13 is a diagram showing a fifth example of maintenance control. Fig. 14 is a diagram showing a sixth example of maintenance control. Fig. 15 is a flow chart showing an example of the operation of the controller. Figs. 16(a) and 16(b) are diagrams showing modified examples of magnetic bearings.

[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. 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] [Rotating Shaft] The rotating shaft (5) has a supported portion containing a magnetic material and a detected portion that serves 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 the compression mechanism (3) and the electric motor (4) that serves as the 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 conical, and is fixed to one end of the rotating shaft (5).

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

[0046] [Touchdown Bearings] 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)). The magnetic bearing (20) 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 in between, and are configured to support the supported portion of the rotor in a non-contact manner by a resultant 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 facing the first electromagnet (51) and the supported portion of the rotor. The electromagnetic force (F2) is generated in the direction facing the second electromagnet (52) and 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, the 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). Note that, hereinafter, 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 Figures 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, 45° intervals) along the inner peripheral surface of the back yoke (62). Each tooth protrudes radially inward from the inner peripheral surface of the back yoke (62), and each inner peripheral surface (protruding end surface) faces 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. In this example, eight electromagnet sections (first to eighth electromagnet sections (71 to 78)) are thereby formed. 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 portions (71, 72) are connected in series to form the first electromagnet (51). The coils (65) of the third and fourth electromagnet portions (73, 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 portions (71, 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 portions (73, 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, thereby controlling 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 portions (75, 76) are connected in series to form the third electromagnet (53). The coils (65) of the seventh and eighth electromagnet portions (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 portions (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 portions (77, 78)). Then, 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] 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 end to which the impeller (3 a) is fixed) includes a disk portion (5 a) that protrudes radially outward and is formed in a disk shape, and this disk portion (5 a) 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 (5 a)) between them, 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. Furthermore, 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), respectively. Thus, in this example, two electromagnets (a first electromagnet (51) and a second electromagnet (52)) are configured. 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 Figure 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 (5a)) 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. 5.

[0059] <Distance Detection Unit> The distance detection unit (30) detects the distance between the distance detection unit (30) and a detected portion 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 (e.g., a set of first and second electromagnets (51, 52)) facing each other across a supported portion of the rotating body (in this example, the supported portion of the rotating shaft (5)), and detects the distance between the distance detection unit (30) and the detected portion 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 detection unit> 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 pair 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 pair 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 pair 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 pair of third and fourth electromagnets (53, 54) of the second radial magnetic bearing (21). In the radial distance detection section (31), the distance between the radial distance detection section (31) and a supported portion of the rotating body located between the pair of electromagnets is detected, so that the supported portion of the rotating body and the detected portion 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 rotating shaft (5)) in the first opposing direction (Z1). In the present 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 the present 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 central 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 where tolerances are assumed to be zero, or in products where manufacturing errors are so small that they can 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 electromagnet gaps of one side and the electromagnet gap of the other side will be equal. Also, at this time, the electromagnet gaps of one side and the electromagnet gap of the other side 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 portion to be detected of the rotor (a portion to be detected of the rotor 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 the portion to be detected of the rotor 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 addition, 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 Detection Unit> 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 addition, in terms of design, when the detectable 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 detectable 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 detectable part of the rotating body (disk part (5a)).

[0064] <Controller> The controller (40) controls one or more magnetic bearings (20) so that a supported portion of the rotating body (in this example, the supported portion of the rotating shaft (5)) is supported in a contactless manner. 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 portion of the rotating body follows the position command value (x*). The levitation control is to control the current flowing through the electromagnets (magnetic levitation portion) of the magnetic bearings (20) so that the position (x) of the supported portion 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]

[0066]

[0067] In addition, "i １ " corresponds to the first current (i1) flowing through the first electromagnet (51). ２ " 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 detection target of the rotating body (in this example, the detection target 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] Also, "g ０" corresponds to the distance (hereinafter referred to as the reference distance (g0)) between the detection part of the rotating body and the first and second electromagnets (51, 52) when the detection part 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 part 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] <Configuration of Controller> 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 Unit>> 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-described formulas 1 and 2 are satisfied.

[0071] <<Second Radial Control Unit>> The second radial control unit (41) calculates the position (x) of the detected part of the rotating body in the second opposing direction (Z2) based on the detection value of the second radial distance detection unit (31), and performs levitation control for the third and fourth electromagnets (53, 54) of the first radial magnetic bearing (21) based on the position (x) of the detected part of the rotating body in the second opposing direction (Z2). Specifically, the second radial control section (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 Unit>> 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-described formulas 1 and 2 are satisfied.

[0073] <<Fourth Radial Control Unit>> The fourth radial control unit (41) calculates the position (x) of the detection target 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 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 Unit>> 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-described formulas 1 and 2 are satisfied.

[0075] <Details of Controller> Next, the controller (40) will be described in detail with reference to Fig. 6. The controller (40) controls the position of the detection target 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 (in this example, four radial control units (41) and one thrust control unit (42)) corresponding to the respective electromagnet pairs (in this example, five electromagnet pairs) 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 the position (x) of the detection target of the rotor calculated based on the 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 are satisfied. 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 Unit>> 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 detected 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 detected 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 Unit>> The current calculation unit (84) calculates 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 (i) calculated 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 (i) and a predetermined reference distance (g). Specifically, the current calculation unit (84) calculates the first current command value (i1*) and the second current command value (i2*) by substituting these parameter values ​​(i, i, x, g, a) into the calculation formula shown in FIG. 6 .

[0080] <<Current Control Unit>> 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 the first current command value (i1*) calculated 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 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] <Procedure of Acquisition Process> In each of a plurality of maintenance controls, the controller (40) performs current control so as to satisfy a condition that the position (x) of the detectable 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 detectable part of the rotating body is kept constant and the current flowing through the electromagnet of the magnetic bearing (20) is kept constant during the maintenance control. In this way, 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 output processing. The output processing is processing for outputting (calculating) 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 central position, based on information acquired in the acquisition processing (information acquired by performing multiple maintenance controls). The information acquired in the acquisition processing 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, 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 for each maintenance control 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]

[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 (the 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 through 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 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 g: distance between the first electromagnet (51) and the detected part of the rotating body (the detected part of the rotating shaft (5)) Ｌ : distance between the second electromagnet (52) and the part of the rotating body to be detected g ｕ０ g: 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 Ｌ０ i: distance between the second electromagnet (52) and the detected part of the rotating body when the detected part of the rotating body is located at the central position ｕ :1st current i Ｌ :Second current i ｕ (x １ ): A constant first current i during the first maintenance control ｕ (x ２ ): constant first current i during the second maintenance control Ｌ (x １ ): A constant second current i during the first maintenance control Ｌ (x ２ ): constant second current k during the second maintenance control ｕ : Electromagnetic force coefficient k of the first electromagnet (51) Ｌ : electromagnetic force coefficient of the second electromagnet (52) w: component of gravity in the first opposing direction (Z1) x １ : Constant position x during the first maintenance control ２ : Fixed position during the second maintenance control

[0093] In the above formula 3, g ｕ０ and g Ｌ０ is an unknown value, but iｕ (x １ ), i Ｌ (x １ ), i ｕ (x ２ ), i Ｌ (x ２ ) x １ , x ２ and w are known values. ｕ (x １ ) is the detection value of the first current detector (87) that is maintained constant during the first maintenance control. Ｌ (x １ ) is the detection value of the second current detector (88) that is maintained constant during the first maintenance control. ｕ (x ２ ) is the detection value of the first current detector (87) that is maintained constant during the second maintenance control. Ｌ (x ２ ) is the detection value of the second current detector (88) that is maintained constant during the second maintenance control. １ is a value obtained by calibrating the detection value of the first radial distance detection unit (31) that is maintained constant during the first maintenance control, and is calculated based on the detection value of the first radial distance detection unit (31) that is maintained constant during the first maintenance control. ２ is a value obtained by calibrating the first radial distance detection unit (31) that is maintained constant during the second maintenance control, and is calculated based on the first radial distance detection unit (31) that is 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 ｕ０ and distance g Ｌ０ can be solved, and the distance g 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 Ｌ０In 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) updates the first distance (g U0 ) and the second distance (g L0 ) and output the first distance (g U0 ) and the second distance (g L0 In the updating 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 detection target part of the rotor, a bias current (ib), a reference distance (g0), and a first distance (g U0 ) and the second distance (g L0 ) and the second current command value (i2*). That is, for the arithmetic expression (W1) (see FIG. 6) for determining the first current command value (i1*) and the second current command value (i2*), the reference distance (g0) in the numerator is converted to the first 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 calculation formula (W2). The controller (40) then performs further maintenance control using the calculation formula (W2). At this time, the above output process can be repeated to update the calculation formula (W1), for example, while widening the levitation conditions related to the distance from the detection 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 calculation formula (W1) to be updated with high accuracy.

[0096] Improved Levitation Control The controller (40) controls the first distance (g U0 ) and the second distance (g L0 ) and output the first distance (g U0 ) and the second distance (g L0 ) to perform levitation control so that the detection part of the rotor is positioned at the center position. That is, the controller (40) may perform levitation control using 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 a 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) of arithmetic formula (W1) (see FIG. 6) is used, and 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, 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 detection unit (30). In the output process, the information indicating the certain position is obtained by using x １、 and x ２ is obtained, and for information indicating a constant current, i ｕ (x １ ), i Ｌ (x １ ), i ｕ (x ２ ), and i ｕ (x ２ ) is obtained.

[0097] <Effects> 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 rotor is magnetically levitated. Also, 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), taking into account variations in the product dimensions of the magnetic unit (10) relative to the design dimensions.

[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, it is possible to perform control processing 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 central 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 will deviate due to the influence of manufacturing variations, assembly variations, etc. However, in this embodiment, by performing the above output process, 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] Furthermore, 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 rotor. The electromagnet gap (the distance between the electromagnet and the detected part of the rotor) 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 a 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 maintaining 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) for the first radial magnetic bearing (21) and / or the second radial magnetic bearing (21). 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 maintaining 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) for the thrust magnetic bearing (22).

[0105] <Example of Acquisition Process> Variations of a constant position and a constant current will be described when a plurality of maintenance controls are performed for the first radial magnetic bearing (21) to maintain the position (x) of the detected part of the rotor (the detected part of the rotating shaft (5)) in the first opposing direction (Z1) at a constant position while maintaining the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) at constant currents. In this example, the plurality of maintenance controls 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 rotating body (the detection part of the rotating shaft (5)) is maintained at a constant first position (x １ ), 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 (x １ ), i Ｌ (x １ The current value is a general term for the first and second currents, and the first value (character string) in the current value field indicates the first current, and the second value in the current value field indicates the second current.

[0108] The controller (40) performs the first maintenance control to maintain the detection target portion of the rotating body at the first position (x １ ) and a first current value (i ｕ (x １ ), i Ｌ (x １ )) and get.

[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 target part of the rotor is maintained at a constant second position (x ２ ), 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 (x ２ ), i Ｌ (x ２ )) will be maintained.

[0110] The controller (40) performs the second maintenance control to maintain the detection target portion of the rotor at the second position (x ２ ) and a second current value (i ｕ (x ２ ), i Ｌ (x ２ )) and get.

[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 part of the rotor is maintained at a constant third position (x ３ ), 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 (x ３ ), i Ｌ (x ３ )) will be maintained.

[0112] The controller (40) performs the third maintenance control to maintain the detection target portion of the rotor at the third position (x ３ ) and a third current value (i ｕ (x ３ ), i Ｌ (x ３ )) and get.

[0113] <First Example of Maintenance Control> As shown in FIG. 9, in the first example, the first current value (i ｕ (x １ ), i Ｌ (x １ ) to third current value (i ｕ (x ３ ), i Ｌ (x ３ )) are different from each other, and the first position (x １ ) ~ 3rd position (x ３ ) are the same as each other.

[0114] <Second Example of Maintenance Control> As shown in FIG. 10, in the second example, the first maintenance control to the third maintenance control are performed by setting the first current value (i ｕ (x １ ), i Ｌ (x １ )) and the second current value (i ｕ (x ２ ), i Ｌ (x ２ )) are different from each other, and the first position (x １ ) and the third position (x ３ ) are different from each other.

[0115] In the second example, the first current value (i ｕ (x １ )) and the third current value (i ｕ (x ３ ), i Ｌ (x ３ In the second example, the second current value (i ｕ (x ２ ), i Ｌ (x ２ )) and the third current value (i ｕ (x ３ ), i Ｌ (x ３ In the second example, the first position (x １ ) and the second position (x ２ ) may be the same as or different from each other. ２ ) and the third position (x ３ ) 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 (x １ ), i Ｌ (x １ ) to third current value (i ｕ (x ３ ), i Ｌ (x ３ )) are different from each other, and the first position (x １ ) ~ 3rd position (x ３ ) are different from each other.

[0117] <Fourth Example of Maintenance Control> As shown in FIG. 12(a), in the fourth example, in the first maintenance control to the third maintenance control, ３ ) is the first position (x １ ) and the second position (x ２ ) is smaller than each of the third position (x ３ ) is the first position (x １ ) and the second position (x ２ In other words, the first position (x １) is defined as the first detected distance, and the distance detected by the first radial distance detection unit (31) at the second position (x ２ ) is defined as a second detection distance, and the distance detected by the first radial distance detection unit (31) at the third position (x ３ ) is defined as the third detection distance, 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.

[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 a 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] <Fifth Example of Maintenance Control> As shown in FIG. 13, in the fifth example, the third current value (i ｕ (x ３ ), i Ｌ (x ３ )) is the first current value (i ｕ (x １ ), i Ｌ (x １ )) and the second current value (i ｕ (x ２ ), i Ｌ (x ２ )) or the first current value (i ｕ (x １ ), i Ｌ (x １ )) and the second current value (i ｕ (x ２ ), i Ｌ (x ２ Specifically, the first current (i1) is smaller than the current (i ｕ(x ３ )) is the current (i ｕ (x １ )) and the current during the second maintenance control (i ｕ (x ２ )), and the second current (i2) is smaller than the current (i Ｌ (x ３ )) is the current (i Ｌ (x １ )) and the current during the second maintenance control (i Ｌ (x ２ )) is greater than each of

[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] <Sixth Example of Maintenance Control> As shown in FIG. 14, in the sixth example, the first current value (i ｕ (x １ ), i Ｌ (x １ ) to third current value (i ｕ (x ３ ), i Ｌ (x ３ )) are the same as each other, and the first position (x １ ) ~ 3rd position (x ３ ) 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 (x １ ), i Ｌ (x １ ) to third current value (i ｕ (x ３ ), i Ｌ (x ３)) are the same as each other, and the first position (x １ ) ~ 3rd position (x ３ ) are different from each other.

[0123] <Example of Operation of Controller> An example of 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 maintenance control described above. However, this example differs from the example of acquisition processing ( Fig. 8 ) in that the first radial control section (41) does not perform the first to third maintenance controls consecutively. The following mainly describes the differences from the example of acquisition processing 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, balance information during the first maintenance control (e.g., equation 1 of the above-mentioned equation 3) and force balance information during the second maintenance control (e.g., equation 2 of the above-mentioned equation 3) are output based on information acquired during the first maintenance control and the second maintenance control (detection values ​​of the distance detection unit (30) and the current detector), and the distance (g U0 , g L0 ) is output.

[0126] In step S2b, the controller (40) performs an update process in this example, where the calculation formula (W1) (see FIG. 6) for determining the first current command value (i1*) and the second current command value (i2*) is updated to the calculation 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, when the arithmetic expression (W2) is used for the first position (x １) and a constant first current value (i ｕ (x １ ), i Ｌ (x １ )) and a constant second position (x ２ ) and a constant second current value (i ｕ (x ２ ), i Ｌ (x ２ )) and a constant first position (x １ ) and a constant first current value (i ｕ (x １ ), i Ｌ (x １ )) and a constant second position (x ２ ) and a constant second current value (i ｕ (x ２ ), i Ｌ (x ２ )) and the third maintenance control is performed based on the above.

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

[0129] The controller (40) includes a processor and can be configured using an arithmetic circuit such as a CPU and a memory. Note that the components of the controller (40) may be integrated into one arithmetic circuit or distributed across multiple arithmetic 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 plural 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 include 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)). Alternatively, as shown in Fig. 16(b), the radial magnetic bearing (21) may be configured to include 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 above-mentioned descriptions such as "first," "second," "third," etc. are used to distinguish the words to which these descriptions are attached, and do not limit the number or order of the words.

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

[0135] REFERENCE SIGNS LIST 1 compressor 2 casing 3 compression mechanism 3a impeller 4 motor 5 rotating shaft 10 magnetic unit 20 magnetic bearing 21 radial magnetic bearing 22 thrust magnetic bearing 30 distance detection section 31 radial distance detection section 32 thrust distance detection section 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 section 85 first current control section 86 second current control section 87 first current detector 88 second current detector i1 first current i2 second current

Claims

1. A magnetic unit comprising: a magnetic levitation section that generates electromagnetic force when current is passed through it to support a rotating body in a non-contact manner; a distance detection section (30) that detects the distance between the rotating body and the magnetic levitation section; and a controller (40) that controls the position of the rotating body during magnetic levitation and the current flowing through the magnetic levitation section based on the distance detected by the distance detection section (30), wherein the controller (40) performs a plurality of maintenance controls to maintain the current flowing through the magnetic levitation section at a constant current while maintaining the position of the rotating body at a constant position, and when any two of 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 magnetic unit of claim 1, wherein the plurality of maintenance controls include a first maintenance control, a second maintenance control, and a third maintenance control, wherein 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.

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 each other.

6. The magnetic unit according to claim 2, 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.

7. The magnetic unit according to claim 2, 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.

8. The magnetic unit according to claim 2, 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.

9. The magnetic unit according to claim 2, 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 wherein 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 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. A magnetic unit as described in any one of claims 2 to 9, 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.

11. A magnetic unit as described in any one of claims 1 to 10, wherein any two of the plurality of maintenance controls have their constant positions differing by more than a first predetermined value or their constant currents differing by more than a second predetermined value.

12. A magnetic unit as described in any one of claims 1 to 11, wherein the magnetic levitation portion includes a first actuator (51) that generates a magnetic attractive force on the rotating body in a first direction, and a second actuator (52) that generates a magnetic attractive 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).

13. A magnetic unit as described in any one of claims 1 to 12, 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. A magnetic unit as described in any one of claims 1 to 13, wherein the controller (40) outputs balance information indicating the balance of forces of the rotating body based on the corresponding constant position and 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 multiple pieces of balance information.

15. A magnetic unit as described in any one of claims 1 to 14, wherein the magnetic levitation portion has a plurality of electromagnets arranged around the rotating body, which generate electromagnetic force when current is passed through them 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.

16. A compressor comprising: a magnetic unit according to any one of claims 1 to 15; the rotating body; and a compression mechanism (3) connected to the rotating body.

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

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