Magnetic units, compressors, and refrigeration systems

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] This disclosure relates to magnetic units, compressors, and refrigeration systems. [Background technology]

[0002] Patent Document 1 describes a calibration method for a gap sensor provided in a magnetic bearing. The gap sensor detects the gap between a rotating body and a reference object that serves as a position reference in position control of a rotating body. The method described in Patent Document 1 includes a construction step in which three or more constraint conditions are set, which are conditions for relating the gap and the output signal of the gap sensor, and a conversion formula is constructed to convert 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 [Overview of the project] [Problems that the invention aims to solve]

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

[0005] The purpose of this disclosure is to provide a magnetic unit, a compressor, and a refrigeration device that can acquire information showing the relationship between the distance detected by the distance detection unit and the current flowing through the magnetically levitated part of a rotating body during magnetic levitation. [Means for solving the problem]

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

[0007] In the first embodiment described above, when the rotating body is magnetically levitated, information can be obtained showing the relationship between the distance detected by the distance detection unit and the current flowing through the magnetically levitated part.

[0008] A second aspect is that, in the first aspect, 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 the first position and the constant current is the first current; in the second maintenance control, the constant position is the second position and the constant current is the second current; and in the third maintenance control, the constant position is the third position and the constant current is the third current.

[0009] In the second embodiment described above, during magnetic levitation, the relationship between the distance detected by the distance detection unit (30) and the current flowing through the magnetically levitating part can be obtained for each of the first to third maintenance controls.

[0010] In the third embodiment, the first current, the second current, and the third current are different from each other, as in the second embodiment.

[0011] In the third embodiment, the first to third maintenance controls can be performed by varying the currents between them.

[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 embodiment, first to third maintenance control can be performed by keeping the positions the same for all of them while varying the currents they receive.

[0014] In the fifth embodiment, the first position, the second position, and the third position are different from each other, as in the second embodiment.

[0015] In the fifth embodiment, the first to third maintenance controls can be performed by making certain positions different from each other.

[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 embodiment, the first to third maintenance controls can be performed by setting different currents for the first and second maintenance controls, and setting different positions for the first and third maintenance controls.

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

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

[0020] The eighth aspect is the second aspect, in which 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 embodiment, the first to third maintenance controls can be performed such that the third current is either the largest or the smallest.

[0022] The ninth aspect is the second aspect, in which 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 distance detected by the distance detection unit (30) at the first position is defined as the first detection distance, the distance detected by the distance detection unit (30) at the second position is defined as the second detection distance, and the distance detected by the distance detection unit (30) at the third position is defined as the third detection distance, wherein the third detection distance is greater than each of the first detection distance and the second detection distance, or less than each of the first detection distance and the second detection distance.

[0023] In the ninth embodiment, the first to third maintenance controls can be performed such that the third detection distance is maximized or minimized.

[0024] The tenth embodiment is an embodiment of any one of the second to ninth embodiments in which 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 embodiment, the control parameter (W1) can be updated based on the first and second maintenance controls, and the third maintenance control can be performed based on the updated control parameter (W2).

[0026] The eleventh embodiment is one embodiment of the first to tenth embodiments in which any two of the plurality of maintenance controls differ by a first predetermined value or more in the certain position, or by a second predetermined value or more in the certain current.

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

[0028] The twelfth embodiment is, in any one embodiment of the first to eleventh embodiments, 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, wherein the constant position is the position of the rotating body in the first or second direction, and the constant current includes the current supplied to the first actuator (51) and the second actuator (52).

[0029] In the twelfth embodiment, a magnetic levitation section can be placed between the first actuator and the second actuator to perform maintenance control.

[0030] The thirteenth embodiment is one of the first to twelfth embodiments, wherein the controller (40) controls the current flowing to the magnetic levitation part based on the constant position and constant current in each of the multiple maintenance controls after performing the multiple maintenance controls.

[0031] In the 13th embodiment, the control parameter (W1) can be updated based on a plurality of maintenance controls, and the current flowing through the magnetically levitating part can be controlled based on the updated control parameter (W2).

[0032] In the 14th embodiment, in any one embodiment of the first to 13th embodiments, the controller (40) outputs equilibrium information indicating the equilibrium 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 in the central position based on a plurality of the equilibrium pieces of information.

[0033] In the 14th embodiment, the distance between the magnetically levitating portion and the rotating body located at the central position can be output with high accuracy.

[0034] The 15th embodiment is one of the first to 14th embodiments, wherein the magnetic levitation portion has a plurality of electromagnets arranged around the rotating body and generating an electromagnetic force by energizing 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 15th embodiment, a rotating body can be supported non-contactually by the electromagnetic force generated by each of the multiple electromagnets.

[0036] A compressor according to the 16th embodiment comprises a magnetic unit according to any one of the first to 15 embodiments, a rotating body, and a compression mechanism connected to the rotating body.

[0037] The refrigeration system of the 17th embodiment includes the compressor described in the 16th embodiment. [Effects of the Invention]

[0038] During magnetic levitation of a rotating body, information can be obtained showing the relationship between the distance detected by the distance detection unit and the current flowing through the magnetically levitating part. [Brief explanation of the drawing]

[0039] [Figure 1] Figure 1 shows an example of the configuration of a compressor according to an embodiment, and is a cross-sectional view of the compressor when it is cut along the axial direction of the compressor's rotating shaft. [Figure 2] Figure 2 shows an example of a radial magnetic bearing configuration, and is a cross-sectional view of the radial magnetic bearing when it is cut along the radial direction of the rotating shaft of the compressor. [Figure 3] Figure 3 shows an example of a radial magnetic bearing configuration, and is a cross-sectional view of the radial magnetic bearing when it is cut along the axial direction of the compressor's rotating shaft. [Figure 4]Figure 4 is a plan view of the thrust magnetic bearing as seen from the axial direction of the compressor's rotating shaft. [Figure 5] Figure 5 shows an example of a thrust magnetic bearing configuration, and is a cross-sectional view of the thrust magnetic bearing when it is cut along the axial direction of the compressor's rotating shaft. [Figure 6] Figure 6 is a block diagram showing an example of the controller configuration. [Figure 7] Figure 7 is a block diagram showing an example of a controller configuration with updated control parameters. [Figure 8] Figure 8 is a flowchart illustrating multiple maintenance and control procedures. [Figure 9] Figure 9 shows a first example of maintenance control. [Figure 10] Figure 10 shows a second example of maintenance control. [Figure 11] Figure 11 shows a third example of maintenance control. [Figure 12] Figure 12(a) shows a fourth example of maintenance control. Figure 12(b) shows the relationship between position command value and time when maintenance control is performed while expanding the levitation conditions from the initial conditions. [Figure 13] Figure 13 shows the fifth example of maintenance control. [Figure 14] Figure 14 shows the sixth example of maintenance control. [Figure 15] Figure 15 is a flowchart showing an example of the controller's operation. [Figure 16] Figures 16(a) and 16(b) show modified examples of magnetic bearings. [Modes for carrying out the invention]

[0040] The embodiments will be described in detail below with reference to the drawings. Note that the same or corresponding parts in the drawings are denoted by the same reference numerals, and their descriptions will not be repeated.

[0041] (Compressor) Figure 1 shows an example configuration of a compressor (1) according to an embodiment. The compressor (1) is installed in a refrigeration system. The refrigeration system includes a refrigerant circuit into which refrigerant is filled, and the refrigerant circuit performs a refrigeration cycle by circulating the refrigerant. 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 that serves as a reference for distance detection. The detected portion of the rotating shaft (5) is the part of the rotating shaft (5) that the distance detection unit (30), described later, uses as a reference when detecting the distance to 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 by energizing to support the supported portion of the rotating shaft (5) without contact. The rotating shaft (5) is connected to a drive source and transmits the power of the drive source by rotating due to 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, and transmits the power of the electric motor (4) to the compression mechanism (3) by rotating due to the power of the electric motor (4). As a result, the compression mechanism (3) compresses 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 positioned so that the cylindrical axis is horizontal. The space inside the casing (2) is divided by a wall (2a), with the space to the right of the wall (2a) forming the compression mechanism chamber (S1) which houses the compression mechanism (3), and the space to the left of the wall (2a) forming the motor chamber (S2) which houses the motor (4). A rotating shaft (5) extending axially inside the casing (2) connects the compression mechanism (3) and the motor (4). The axial direction is parallel to the axis of the rotating shaft (5) and parallel to the direction in which the cylindrical axis extends.

[0044] [Compression mechanism] The compression mechanism (3) is configured to compress a fluid. In this example, the compression mechanism (3) consists of an impeller (3a). The impeller (3a) is formed by multiple blades to have an outer shape that is approximately trapezoidal-conical and is fixed to one end of the rotating shaft (5).

[0045] [Electric motor] The electric motor (4) is configured to rotationally drive the 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 also formed in a cylindrical shape and is rotatably inserted into the inner circumference of the stator (4a). An axial hole is formed in the center of the rotor (4b), and the rotating shaft (5) is inserted through and fixed into this axial 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 floating).

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

[0048] <Magnetic bearings> The magnetic bearing (20) is arranged around the supported portion of the rotating body (in this example, the supported portion of the rotating shaft (5)) and has a plurality of electromagnets that generate an electromagnetic force (magnetic attractive force) when energized to support the supported portion of the rotating body in a non-contact manner. The plurality of electromagnets have pairs of electromagnets (for example, first and second electromagnets (51, 52)) that face each other with the supported portion of the rotating body in between, and are configured to support the supported portion of the rotating body in a non-contact manner by the combined electromagnetic force (F) of the electromagnetic forces (F1, F2) generated by each of the electromagnet pairs. The electromagnetic force (F1) is generated in the direction opposite to the first electromagnet (51) and the supported portion of the rotating body. The electromagnetic force (F2) is generated in the direction opposite to the second electromagnet (52) and the supported portion of the rotating body. In this embodiment, the first and second electromagnets (51, 52) are arranged to face each other in a first opposing direction (Z1) with the supported portion of the rotating body in between. Therefore, the electromagnetic forces (F1, F2) are generated in opposite directions to each other in the first opposing direction (Z1) of the first and second electromagnets (51, 52). In the magnetic bearing (20), the combined electromagnetic force (F) of the electromagnet pair can be controlled by controlling the current pair flowing through the electromagnet pair (for example, the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52), respectively), thereby controlling the position of the rotating body in the opposing 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 the "first radial magnetic bearing (21)" and the other as the "second radial magnetic bearing (21)".

[0050] Radial magnetic bearings As shown in Figures 2 and 3, the radial magnetic bearing (21) has 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 the combined electromagnetic force (F) of the first and second electromagnets (51, 52) supports the supported portion of the rotating shaft (5) without contact. The third and fourth electromagnets (53, 54) face each other across the supported portion (shaft portion) of the rotating shaft (5), and the combined electromagnetic force (F) of the third and fourth electromagnets (53, 54) supports the supported portion of the rotating shaft (5) without contact. 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 from the axial direction. The first opposing direction (Z1) and the second opposing direction (Z2) are directions perpendicular to the axial direction of the rotation axis (5), i.e., the radial direction of the rotation axis (5). The first electromagnet (51) is an example of the first actuator. The second electromagnet (52) is an example of the second actuator. One side of the first opposing direction (Z1) is an example of the first direction. The other side of the first opposing direction (Z1) is an example of the second direction.

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

[0052] The eight coils (65) are each wound around the eight teeth (63) of the magnetic bearing core (61). This results in eight electromagnet sections (the 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 a clockwise direction in Figure 2.

[0053] The first and second electromagnet sections (71, 72) are configured as the first electromagnet (51) by connecting their respective coils (65) in series. The third and fourth electromagnet sections (73, 74) are configured as the second electromagnet (52) by connecting their respective coils (65) in series. 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, 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, 74)). Furthermore, by controlling the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52), the combined 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 rotation axis (5) in the first opposing direction (Z1).

[0054] The fifth and sixth electromagnet sections (75, 76) are configured as a third electromagnet (53) by connecting their respective coils (65) in series. The seventh and eighth electromagnet sections (77, 78) are configured as a fourth electromagnet (54) by connecting their respective coils (65) in series. 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)). Furthermore, by controlling the third and fourth currents (i3, i4) flowing through the third and fourth electromagnets (53, 54), the combined electromagnetic force (F) of the third and fourth electromagnets (53, 54) can be controlled to control the position of the supported portion (shaft portion) of the rotation axis (5) in the second opposing direction (Z2).

[0055] Furthermore, 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 the direction that pulls the supported part (shaft) 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 magnetic flux is generated in the direction of the arrow shown in Figure 2.

[0056] Thrust magnetic bearing As shown in Figures 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 (3a) is fixed) includes a disc portion (5a) that protrudes radially outward and is formed in the shape of a disc, and this disc portion (5a) constitutes the supported portion of the thrust magnetic bearing (22). The first and second electromagnets (51, 52) face each other with the supported portion (disc portion (5a)) of the rotating shaft (5) in between, and the combined electromagnetic force (F) of the first and second electromagnets (51, 52) supports the supported portion of the rotating shaft (5) without contact.

[0057] Specifically, in this example, the thrust magnetic bearing (22) comprises 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 at a predetermined distance apart on both axial sides of the supported portion (disk portion (5a)) of the rotating shaft (5). Furthermore, a circumferential groove is formed around the axis of the rotating shaft (5) on the opposing surfaces of the two magnetic bearing cores (61) facing each other. The two coils (65) are each housed in the circumferential grooves of the two magnetic bearing cores (61). 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). Furthermore, by controlling the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52), the combined 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 rotation axis (5) in the third opposing direction (Z3) (i.e., the axial direction, or 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 the direction that pulls the supported part (disk part (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 magnetic flux is generated in the direction of the arrow shown in Figure 5.

[0059] <Distance detection unit> The distance detection unit (30) detects the distance between the distance detection unit (30) and the detected part of the rotating body. The distance detection unit (30) is, for example, a position sensor or a distance sensor. As shown in Figure 1, the distance detection unit (30) corresponds to a pair of electromagnets (for example, a set of first and second electromagnets (51, 52)) that face each other across the supported part of the rotating body (in this example, the supported part of the rotation axis (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 electromagnet pair. 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 comprised of a radial distance detection unit corresponding to the first and second electromagnets (51, 52) of the first radial magnetic bearing (21) (hereinafter referred to as the "first radial distance detection unit (31)"), a radial distance detection unit corresponding to the third and fourth electromagnets (53, 54) of the first radial magnetic bearing (21) (hereinafter referred to as the "second radial distance detection unit (31)"), a radial distance detection unit corresponding to the first and second electromagnets (51, 52) of the second radial magnetic bearing (21) (hereinafter referred to as the "third radial distance detection unit (31)"), and a radial distance detection unit corresponding to the third and fourth electromagnets (53, 54) of the second radial magnetic bearing (21) (hereinafter referred to as the "fourth radial distance detection unit (31)"). 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 electromagnet pair 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 the detected part of the rotating body (the detected part of the rotating shaft (5)) in the first opposing direction (Z1). In this embodiment, the first radial distance detection unit (31) is positioned 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 the detected part of the rotating body in the first opposing direction (Z1). In this embodiment, the third radial distance detection unit (31) is positioned near the second electromagnet (52) of the second radial magnetic bearing (21). In the design, when the detected part of the rotating body is located in the center position, the distance between the first electromagnet (51) and the detected part of the rotating body is the same distance (g0) as the distance between the second electromagnet (52) and the detected part of the rotating body. The central position of the detected part of the rotating body indicates that the detected part of the rotating body is located at the center of the touchdown bearings (6,7). Regarding the central position, in the radial direction (radial direction of the rotation axis (5)), it indicates the position where the gap between the inner ring of the radial touchdown bearing (6) and the outer circumference of the detected part of the rotating body that opposes it is constant around the entire circumference. In the thrust direction (axial direction of the rotation axis (5)), it indicates the position where the gap between the detected part of the rotating body and the thrust touchdown bearing (7) located on the impeller (3a) side is equal to the gap between the detected part of the rotating body and the thrust touchdown bearing (7) located on the opposite side from the impeller (3a) side. The central position is predetermined. When the detected part of the rotating body is located at the central position, the electromagnet gap of one electromagnet pair (the distance between one electromagnet and the detected part of the rotating body) and the electromagnet gap of the other electromagnet pair (the distance between the other electromagnet and the detected part of the rotating body) are not necessarily equal. In drawings where tolerances are assumed to be zero, or in products where manufacturing errors are negligibly small, the centers of the touchdown bearings (6,7) and the centers of the opposing electromagnets coincide. In this 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 electromagnets become equal. Furthermore, at this time, the distance (g0) between the gaps of the two electromagnets is the same.

[0062] The second radial distance detection unit (31) detects the distance between the second radial distance detection unit (31) and the detected part of the rotating body (the detected part of the rotating shaft (5)) in the second opposing direction (Z2). In this embodiment, the second radial distance detection unit (31) is located 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 detected part of the rotating body in the second opposing direction (Z2). In this embodiment, the fourth radial distance detection unit (31) is located near the fourth electromagnet (54) of the second radial magnetic bearing (21). In the design, when the detected part of the rotating body is located at the center 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 detected part of the rotating body (the detected part of the rotating shaft (5)) in the third opposing direction (Z3). The distance between the thrust distance detection unit (32) and the detected part of the rotating body in the third opposing direction (Z3) represents the distance between the thrust distance detection unit (32) and the detected part of the rotating body (the disc part (5a)). In this embodiment, the thrust distance detection unit (32) is positioned 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 detected part of the rotating body represents the distance between the second electromagnet (52) of the thrust magnetic bearing (22) and the detected part of the rotating body (the disc part (5a)). Furthermore, in the design, when the detected part of the rotating body (disk portion (5a)) is located at the center 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 portion (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 portion (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 without contact. More specifically, the controller (40) performs levitation control for each of the electromagnet pairs (in this example, five electromagnet pairs) of 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*). Levitation control is the control of the current flowing through the electromagnets (magnetic levitation parts) 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 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 in the electromagnet pair is designated as the "first electromagnet (51)" and the other 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, such that equation 1 in Equation 1 and equation 2 in Equation 2 below hold true.

[0065]

number

[0066]

number

[0067] Note that "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 the current component (hereinafter referred to as control current (id)) that changes according to the displacement of the detected part of the rotating body (in this example, the detected part of the rotation axis (5)) in the opposing directions of the first and second electromagnets (51, 52). b This corresponds to a current component (hereinafter referred to as bias current (ib)) that represents a predetermined current value.

[0068] Furthermore, "g0" corresponds to the distance between the detected part of the rotating body and the first and second electromagnets (51, 52) when the detected part of the rotating body is located at the central position between the first and second electromagnets (51, 52) (i.e., the reference position) in the design (hereinafter referred to as the reference distance (g0)). The reference distance (g0) is preset. "x" is the position (x) of the detected 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) with respect to the touchdown bearings (6, 7). For example, by moving the rotating body to its 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. When the controller (40) acquires a value detected by the distance detection unit (30) during levitation control, it calculates the position (x) by offsetting the acquired value detected by the distance detection unit (30) so that the midpoint of the detection range of the distance detection unit (30) becomes x=0 (center position). Alternatively, the sensitivity of the position (x) may be corrected based on the design dimension of the difference between the inner diameter of the touchdown bearing (6) and the outer diameter of the rotating body 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 units (41) and one thrust control unit (42). The four radial control units (41) consist of a radial control unit corresponding to the first and second electromagnets (51, 52) of the first radial magnetic bearing (21) (hereinafter referred to as the "first radial control unit (41)"), a radial control unit corresponding to the third and fourth electromagnets (53, 54) of the first radial magnetic bearing (21) (hereinafter referred to as the "second radial control unit (41)"), a radial control unit corresponding to the first and second electromagnets (51, 52) of the second radial magnetic bearing (21) (hereinafter referred to as the "third radial control unit (41)"), and a radial control unit corresponding to the third and fourth electromagnets (53, 54) of the second radial magnetic bearing (21) (hereinafter referred to as the "fourth radial control unit (41)").

[0070] 《First Radial Control Unit》 The first radial control unit (41) calculates the position (x) of the detected part of the rotating body in the first opposing direction (Z1) based on the value detected by 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 detected part 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 equations 1 and 2 above hold true.

[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 value detected by 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 detected part of the rotating body 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) so that two equations similar to those in equations 1 and 2 above (i.e., two equations obtained by substituting the first current (i1), second current (i2), first electromagnet (51), and second electromagnet (52) in equations 1 and 2 with the third current (i3), fourth current (i4), third electromagnet (53), and fourth electromagnet (54), respectively) are satisfied.

[0072] 《Third Radial Control Unit》 The third radial control unit (41) calculates the position (x) of the detected part of the rotating body in the first opposing direction (Z1) based on the value detected by 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 detected part 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 equations 1 and 2 above hold true.

[0073] 《Fourth Radial Control Unit》 The fourth 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 value detected by 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 detected part 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 those in equations 1 and 2 above hold true.

[0074] Thrust Control Unit The thrust control unit (42) calculates the position (x) of the detected part of the rotating body in the third opposing direction (Z3) based on the value detected by 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 detected part 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 equations 1 and 2 above are satisfied.

[0075] <Controller Details> Next, the controller (40) will be described in detail with reference to Figure 6. The controller (40) controls the position of the detected part of the rotating body during magnetic levitation and the current flowing through the electromagnets of the magnetic bearing (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 one or more pairs of electromagnets of the magnetic bearing (20) (in this example, five pairs of electromagnets), and the control units have the configuration shown in Figure 6. Here, the configuration of the radial control unit (41) will be used as an example for explanation.

[0076] In levitation control, the radial control unit (41) determines a control current (id) according to 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 value detected by the distance detection unit (30) and a predetermined position command value (x*), and uses the control current (id) to control the first and second currents (i1, i2) so that equations 1 and 2 above 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 the current flowing through the coil (65) of the 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 the 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. It is also preferable that the correction coefficient (a) is set to a value greater than 1. The correction coefficient (a) may be a fixed value.

[0078] Position deviation calculation unit and position control unit The position deviation calculation unit (82) determines 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 value detected by the distance detection unit (30) and the position command value (x*). Specifically, the position deviation calculation unit (82) determines 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) determines the control current (id) based on the position deviation value (e) obtained by the position deviation calculation unit (82). Specifically, the position control unit (83) determines the control current (id) such that the control current (id) increases as the position deviation value (e) increases.

[0079] Current Calculation Unit The current calculation unit (84) determines the first current command value (i1*) and the second current command value (i2*) based on the correction coefficient (a) set by the correction coefficient setting unit (81), the control current (id) obtained by the position control unit (83), the position (x) of the detected part 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 Figure 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*) 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 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 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 the second current command value (i2*).

[0082] <Retrieval process> The controller (40) performs an acquisition process. The acquisition process is for acquiring information showing 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, multiple 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 control among the levitation controls 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 the maintenance control. A set consisting of a constant position and a constant current is set for each maintenance control, and multiple maintenance controls correspond to multiple such sets.

[0083] <Procedure for data acquisition> The controller (40) performs current control in each of the multiple maintenance control operations so as to satisfy the condition that the position (x) of the detected part of the rotating body is at a constant position. During the maintenance control, the controller acquires the detected value of the distance detection unit (30) and the detected value of the current detector when the position (x) of the detected part of the rotating body is maintained at a constant position and the current flowing through the electromagnet of the magnetic bearing (20) is maintained at a constant current. As a result, the controller (40) acquires information showing the relationship between the distance detected by the distance detection unit (30) and the current flowing through the electromagnet of the magnetic bearing (20) when the rotating body is magnetically levitated.

[0084] When comparing any two maintenance controls from among multiple maintenance controls, the controller (40) performs multiple maintenance controls such that the fixed positions are different from each other, or the fixed currents are different from each other. The fact that the fixed positions are different from each other means that, among the fixed positions and fixed currents, the fixed currents are the same but the fixed positions are different, the fixed positions are the same but the fixed currents are different, or both the fixed positions and fixed currents are different from each other. The term "any two maintenance controls from among multiple maintenance controls" refers to all combinations when selecting two maintenance controls from the multiple maintenance controls.

[0085] <Output Processing> The controller (40) performs output processing. The output processing is a process that outputs (calculates) the distance between the detected part of the rotating body and the magnetic bearing (20) when the detected part of the rotating body is in the central position, based on the information acquired in the acquisition processing (information acquired by performing multiple maintenance controls). Specifically, the information acquired in the acquisition processing is the detected value of the distance detection unit (30) and the detected value of the current detector, acquired for each maintenance control.

[0086] In the output processing, for each maintenance control, equilibrium information (see Equation 3 below) indicating the balance of forces at the supported part of the rotating body (the supported part of the rotating shaft (5)) is output based on a corresponding fixed position and a fixed current. Then, based on the multiple equilibrium 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 at the central position is output (calculated). The fixed position is a value calculated based on the detection value of the distance detection unit (30) which is maintained at a constant level during maintenance control. Specifically, the fixed position is a value obtained by calibrating (offset correction, sensitivity correction, etc.) the detection value of the distance detection unit (30) which is maintained at a constant level during maintenance control. The fixed current is the detection value of the current detector which is maintained at a constant level during maintenance control.

[0087] The following equation 3 shows the force equilibrium equation, which is an example of the equilibrium information mentioned above.

[0088]

Number

[0089] The above number 3 shows the force balance equation in the first opposing direction (Z1) for each maintenance control when multiple maintenance controls are performed to maintain 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) of the first radial magnetic bearing (21) while maintaining the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) at constant currents.

[0090] In the above number 3, Equation 1 shows the force balance equation for the first maintenance control, and Equation 2 shows the force balance equation for the second maintenance control. In the above number 3, the description of the force balance equation for the maintenance control after the third time is omitted. Note that the maintenance control may be performed two or more times.

[0091] The definitions of the symbols in Equation 1 and Equation 2 of the above number 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 detected part of the rotating body g u0 : Distance between the first electromagnet (51) and the detected part of the rotating body when the detected part of the rotating body is at the central position g L0 : Distance between the second electromagnet (52) and the detected part of the rotating body when the detected part of the rotating body is at the central position i u : First current i L : Second current i u (x1): Constant first current for 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): Constant second 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: Constant position during the first maintenance control. x2: Constant position during the second maintenance control.

[0093] In the above number 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 detected value of the first current detector (87) which is maintained constant during the first maintenance control. L (x1) is the detected value of the second current detector (88) which is maintained constant during the first maintenance control. u (x2) is the detected value of the first current detector (87) which is maintained constant during the second maintenance control. L (x2) is the detected value of the second current detector (88) which is maintained constant during the second maintenance control. x1 is the calibrated value of the detected value of the first radial distance detection unit (31) which is maintained constant during the first maintenance control, and is calculated based on the detected value of the first radial distance detection unit (31) which is maintained constant during the first maintenance control. x2 is the calibrated value of the first radial distance detection unit (31) which is maintained constant during the second maintenance control, and is calculated based on the first radial distance detection unit (31) which is maintained constant during the second maintenance control.

[0094] Based on the equilibrium information (the force equilibrium equation shown in Equation 3 above), the controller (40) determines the distance g between the detected part of the rotating body and the magnetic bearing (20) when the detected part of the rotating body is in the central position. u0 and distance g L0 The controller (40) outputs the distance g from a system of equations of multiple equilibrium information (equilibrium equations), for example. u0 and distance g L0 You can also solve this problem, and use the 2D Newton method to find the distance g u0 and distance g L0 You can solve this equation, or if there are three or more equilibrium equations, you can use the least squares method to find the distance g u0 and distance g L0 You can solve this problem. Below, the distance g u0 The first distance (g U0 ) and distance g L0 The second distance (g L0 ) is sometimes written as such.

[0095] <Update process> The controller (40) determines the first distance (g U0 ) and the second distance (g L0 When you output ), the first distance (g U0 ) and the second distance (g L0 The update process may be performed using ). In the update process, as shown in Figure 7, the current calculation unit (84) of the controller (40) uses a correction coefficient (a), a control current (id), the position of the detected part of the rotating body (x), a bias current (ib), a reference distance (g0), and a first distance (g U0 ) and the second distance (g L0 Based on this, the first current command value (i1*) and the second current command value (i2*) are determined. That is, in the calculation formula (W1) (see Figure 6) for determining the first current command value (i1*) and the second current command value (i2*), the reference distance (g0) in the numerator is set to the first distance (g U0 ) or second distance (g L0The calculation formula (W2) is updated to the modified formula (W2), and the first current command value (i1*) and the second current command value (i2*) are determined using the calculation formula (W2). Then, the controller (40) performs further maintenance control using the calculation formula (W2). At this time, for example, the above output processing can be repeated while expanding the levitation conditions related to the distance between the rotating body and the detected part and / or the first and second currents (i1, i2) from the initial conditions (see Figure 12(b)), thereby updating the calculation formula (W1). As a result, maintenance control can be performed under a wide range of levitation conditions, and the calculation formula (W1) can be updated with high accuracy.

[0096] <Improved Levitation Control> The controller (40) determines the first distance (g U0 ) and the second distance (g L0 When you output ), the first distance (g U0 ) and the second distance (g L0 The controller (40) may use the first distance (g) to perform levitation control so that the detected part of the rotating body is positioned in the center. U0 ) and the second distance (g L0 If the output is ), the above output and update processes may be omitted, and normal operation may be performed. Normal operation indicates that the magnetic unit (10) operates in such a way that the product equipped with the magnetic unit (10) functions, as if the refrigeration system were operating due to the refrigeration cycle. First distance (g U0 ) and the second distance (g L0 The levitation control performed so that the detected part of the rotating body is positioned in the center is sometimes referred to as improved levitation control. In improved levitation control, calculation formula (W2), which is an updated version of calculation formula (W1) (see Figure 6), is used, and the first current command value (i1*) and the second current command value (i2*) are determined using calculation formula (W2). According to this, the first distance (g) output based on the sensing results of the actual product is U0 ) and the second distance (g L0The first current command value (i1*) and the second current command value (i2*) are determined using ), thereby improving the accuracy of the first current command value (i1*) and the second current command value (i2*). As a result, the control stability of the levitation control can be improved. The sensing result indicates that, as described in the output processing above, information indicating a certain position and information indicating a certain current are obtained by sensing the magnetic unit (10) using the current detector and distance detection unit (30). In the output processing above, for the information indicating a certain position, x 1、 And x2 is obtained, and for information indicating a constant current, i u (x1), i L (x1), i u (x2), and i u (x2) is obtained.

[0097] <effect> By performing multiple maintenance controls, information can be obtained showing the relationship between the distance detected by the distance detection unit (30) and the current flowing through the magnetic levitation part (electromagnet) during magnetic levitation of the rotating body. Furthermore, considering the variation in product dimensions relative to the design dimensions of the magnetic unit (10), the relationship between the distance detected by the distance detection unit (30) and the current flowing through the magnetic levitation part (electromagnet) can be understood.

[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, for example, to improve the stability of the levitation control of the rotating body, to suppress errors included in the distance detected by the distance detection unit (30), and to detect abnormalities or malfunctions of the magnetic unit (10).

[0099] Furthermore, regarding the distance between the detected part of the rotating body and the magnetic bearing (20) when the detected part of the rotating body is in the central position, the reference distance (g0) is a design distance (design dimension) as described above, so when compared with the actual product, there is a possibility that the distance may deviate due to the effects of manufacturing variations and assembly variations. However, in this embodiment, by performing the output processing described above, information showing 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 obtained for each maintenance control, and the first distance (g) is determined based on the obtained information, i.e., the sensing results of the actual product. U0 ) and the second distance (g L0 The output will be the first distance (g) which will be a more accurate value when compared with the design reference distance (g0). U0 ) and the second distance (g L0 It can output (this).

[0100] Furthermore, in magnetic bearings, levitation control is often achieved 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 the relationship between the current i and the electromagnetic force f, f = k(i 2 / g 2 Because it acts as described above, a deviation of the true value of the electromagnet gap g from the design value will worsen the accuracy of the electromagnetic force output, which in turn will lead 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 This allows for accurate output of the true value and suppresses the discrepancy between the true value and the design value, thereby preventing a decrease in the stability of the levitation control.

[0101] Furthermore, because the electromagnet gap of magnetic bearings is designed to be smaller than that of other general machinery, the ratio of variation in product dimensions to the design value tends to be large. However, in this embodiment, the output processing described above allows the first distance (g U0 ) and the second distance (g L0 Because it outputs (), even if there is variation in the product dimensions relative to the design values, it is possible to suppress a decrease in the stability of levitation control.

[0102] Furthermore, since the electromagnet gap is located inside the product casing (inside the casing (2) of the compressor (1)), it is difficult to directly measure the electromagnet gap after the manufacturing of the magnetic unit (10). However, in this embodiment, by performing the acquisition process and output process described above, the first distance (g), which is the electromagnet gap, can be measured without accessing the inside of the casing. U0 ) and the second distance (g L0 This allows for the output of the electromagnet gap. As a result, the electromagnet gap can be easily output.

[0103] Furthermore, in this embodiment, by performing multiple maintenance controls, multiple equilibrium information is output as shown in Equation 3 above, and the electromagnet gap is output based on the multiple equilibrium information. Therefore, the electromagnet gap is output not only based on one position condition (constant position) and current condition (constant current), but also on multiple position conditions and current conditions. As a result, the electromagnet gap can be output with high accuracy.

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

[0105] <Example of acquisition process> This section describes variations in the fixed position and fixed current when performing multiple maintenance controls for the first radial magnetic bearing (21), which 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 fixed position while maintaining the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) at a fixed current. In this example, the multiple maintenance controls performed are the first maintenance control, the second maintenance control, and the third maintenance control.

[0106] The procedure for performing the first to third maintenance controls will be explained below.

[0107] As shown in Figure 8, in step S1, the controller (40) performs first maintenance control. In first maintenance control, the position (x) of the detected part of the rotating body (the detected part of the rotating shaft (5)) is maintained at a constant first position (x1), while the first and second currents (i1, i2) flowing through the first and second electromagnets (51, 52) are kept at a constant first current value (i u (x1), i L (x1)) is maintained. The current value is a general term for the first and second currents; the first value (string) listed among the current values ​​indicates the first current, and the second value indicates the second current.

[0108] The controller (40) performs first maintenance control, and the detected value of the first radial distance detection unit (31) when the detected part of the rotating body is in the first position (x1) and the detected value of the first and second current detectors (87, 88) are used to determine the first current value (i u (x1), i L (x1)) is obtained.

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

[0110] The controller (40) performs second maintenance control, and the detected value of the first radial distance detection unit (31) when the detected part of the rotating body is in the second position (x2) and the second current value (i) which is the detected value of the first and second current detectors (87, 88) u (x2), i L (x2)) is obtained.

[0111] In step S3, after performing the second maintenance control, the controller (40) performs the third maintenance control. In the third maintenance control, while the position (x) of the detected portion of the rotating body is maintained at a constant third position (x3), 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] By performing the third maintenance control, the controller (40) obtains the detection value of the first radial distance detector (31) when the detected portion of the rotating body is located at the third position (x3), and the third current value (i u (x3), i L (x3)), which are the detection values of the first and second current detectors (87, 88).

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

[0114] <Second Example of Maintenance Control> As shown in FIG. 10, in the second example, in the first to third maintenance controls, the first current values (i u (x1), i L [[ID=3,6]](x1)) and the second current values (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 values (i u (x3), i L (x3)) may be the same as or different from each other. In the second example, the second current values (i u (x2), i L (x2)) and the third current values (iu (x3), i L (x3)) may be the same as or different from each other. 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 Figure 11, in the third example, in the first maintenance control to the third maintenance control, the first current value (i u (x1), i L (x1)) ~ 3rd current value (i u (x3), i L (x3)) are all different, and the first position (x1) to the third position (x3) are all different.

[0117] <Fourth example of maintenance control> As shown in Figure 12(a), in the fourth example, during the first to third maintenance controls, the third position (x3) becomes smaller than both the first position (x1) and the second position (x2). Alternatively, 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 either greater than both the first and second detection distances, or smaller than both the first and second detection distances.

[0118] When performing multiple maintenance controls, the configuration shown in the fourth example can be used to repeatedly perform the output processing described above while expanding the levitation conditions related to the position (position command width) of the detected part of the rotating body from the initial conditions, as shown in Figure 12(b), thereby updating the calculation formula (W1) (see Figure 7) each time a maintenance control is performed. Furthermore, as shown in Figure 12(b), in each of the multiple maintenance controls, if the state in which the position of the detected part of the rotating body and the detected value of the current detector are both approximately constant values ​​continues for a predetermined confirmation waiting time (ts), a constant current and a constant position may be determined. The predetermined confirmation waiting time (ts) is, for example, 5 seconds.

[0119] <Fifth example of maintenance control> As shown in Figure 13, in the fifth example, in the first maintenance control to the third maintenance control, 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)) is greater than each of the first current values ​​(i u (x1), i L (x1)) and the second current value (i u (x2), i L It becomes smaller than each of (x2). Specifically, for the first current (i1), the current during the third maintenance control (i u (x3)) is the current (i) during the first maintenance control. u (x1)) and the current (i) during the second maintenance control. u (x2)) becomes smaller than each of the second current (i2) and the current during the third maintenance control (i L (x3)) is the current (i) during the first maintenance control. L (x1)) and the current (i) during the second maintenance control. L Each of (x2) will be greater than the others.

[0120] When performing multiple maintenance controls, the configuration shown in the fifth example can be used to repeatedly perform the above output processing while expanding the levitation conditions for the first and second currents (i1, i2) from the initial conditions each time maintenance control is performed, thereby updating the calculation formula (W1) (see Figure 7) (see Figure 12(b)).

[0121] <Example 6 of Maintenance Control> As shown in Figure 14, in the sixth example, in the first maintenance control to the third maintenance control, the first current value (i u (x1), i L (x1)) ~ 3rd current value (i u (x3), i L (x3)) are the same for all of them, and the first position (x1) to the third position (x3) are different for all of them.

[0122] The configuration shown in Example 6 can be realized, for example, by adopting a configuration in which the load other than the electromagnetic force acting on the supported part of the rotating body (load) is variable. Normally, the load is gravity and is constant, but in Example 6, the load is made variable. Then, by changing the load for each maintenance control, the first current value (i u (x1), i L (x1)) ~ 3rd current value (i u (x3), i L Keep (x3) the same for all of them, while making the first position (x1) to the third position (x3) different for all of them.

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

[0124] As shown in Figure 15, in step S1, the controller (40) performs first maintenance control. In step S2, after performing first maintenance control, the controller (40) performs second maintenance control. After the controller (40) performs second maintenance control, the process moves to step S2a.

[0125] In step S2a, the controller (40) performs output processing. In the output processing of this example, based on the information acquired in the first and second maintenance controls (the detected value of the distance detection unit (30) and the detected value of the current detector), the controller outputs equilibrium information during the first maintenance control (for example, Equation 1 of Equation 3 above) and force equilibrium information during the second maintenance control (for example, Equation 2 of Equation 3 above). Based on these two equilibrium information values, the controller outputs the distance (g) between the detected part of the rotating body and the magnetic bearing (20) when the detected part of the rotating body is in the central position. U0 , g L0 Outputs ).

[0126] In step S2b, the controller (40) performs an update process. In this example, the calculation formula (W1) (see Figure 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 Figure 7.

[0127] In step S3, the controller (40) performs third-stage maintenance control. In this example, the controller (40) performs third-stage maintenance control using the calculation formula (W2). That is, the calculation formula (W2) is a constant first position (x1) and a constant first current value (i) of the first-stage maintenance control. u (x1), i L (x1)) and a constant second position (x2) and a constant second current value (i u (x2), i L (x2)) is created 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 The third maintenance control is performed based on (x2).

[0128] (Other embodiments) Any two of the multiple maintenance controls may differ by a certain position by a first predetermined value or by a certain current by a second predetermined value or by a certain value. This allows multiple maintenance controls to be performed such that the certain positions differ by a first predetermined value or by a certain current differs from each other by a second predetermined value or by a certain value.

[0129] The controller (40) includes a processor and can be configured using arithmetic circuits such as a CPU and memory. The components of the controller (40) may be provided together in a single arithmetic circuit or distributed across multiple arithmetic circuits.

[0130] Furthermore, although the example given was that the radial magnetic bearing (21) constitutes a heteropolar radial magnetic bearing, the radial magnetic bearing (21) may also constitute a homopolar radial magnetic bearing.

[0131] Furthermore, the number of electromagnets in the magnetic bearing (20) can be any number, and is not limited to the number shown in the embodiment. For example, as shown in Figure 16(a), the radial magnetic bearing (21) may be configured to have first electromagnets (51) to sixth electromagnets (56) so that first electromagnetic forces (f1) to sixth electromagnetic forces (f6) act on the supported part of the rotating body (the supported part of the rotating shaft (5)). Alternatively, as shown in Figure 16(b), the radial magnetic bearing (21) may be configured to have first electromagnets (51) to third electromagnets (53) so that first electromagnetic forces (f1) to third electromagnetic forces (f3) act on the supported part of the rotating body (the supported part of the rotating shaft (5)).

[0132] While embodiments and modifications have been described above, it will be understood that a variety of changes 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 they do not impair the functions covered by this disclosure.

[0133] The designations "1st," "2nd," "3rd," etc., mentioned above are used to distinguish between the terms to which these designations are attached, and do not limit the number or order of those terms. [Industrial applicability]

[0134] As described above, this disclosure is useful for magnetic units, compressors, and refrigeration systems. [Explanation of Symbols]

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

Claims

1. A magnetic levitation unit that generates electromagnetic force by applying an electric current to support a rotating body without contact, A distance detection unit (30) for detecting the distance between the rotating body and the other, A controller (40) 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 unit (30). Equipped with, The controller (40) is Multiple maintenance controls are performed to maintain the position of the rotating body at a constant position while maintaining the current flowing through the magnetically levitating part at a constant current. When comparing any two of the aforementioned multiple maintenance controls, if the fixed positions are different from each other, or if the fixed currents are different from each other, The controller (40) outputs equilibrium 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 in the central position based on a plurality of equilibrium pieces of information. In each of the aforementioned plurality of equilibrium information, the distance between the rotating body and the magnetic levitation part when the rotating body is at the central position is an unknown value, and the electromagnetic force included in the force is expressed using the unknown value. The controller (40) is a magnetic unit that outputs a solution for the unknown value based on the plurality of equilibrium information.

2. The aforementioned 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 the first position, and the constant current is the first current. In the second maintenance control, the constant position is the second position, and the constant current is the second current. The magnetic unit according to claim 1, wherein in the third maintenance control, the constant position is the third position and the constant current is the 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 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 each other. The magnetic unit according to claim 2, wherein the first position, the second position, and the third position are different from each other.

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. At the first position, the distance detected by the distance detection unit (30) is defined as the first detected distance. At the second position, the distance detected by the distance detection unit (30) is defined as the second detected distance. When the distance detected by the distance detection unit (30) at the third position is defined as the third detected distance, The magnetic unit according to claim 2, wherein the third detection distance is greater than each of the first detection distance and the second detection distance, or less than each of 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. The magnetic unit according to any one of claims 2 to 9, 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. The magnetic unit according to any one of claims 1 to 9, wherein any two of the plurality of maintenance controls differ by a first predetermined value or more in the certain position, or differ by a second predetermined value or more in the certain current.

12. The aforementioned magnetic levitation portion is A first actuator (51) generates a magnetic attractive force in a first direction relative to the rotating body, A second actuator (52) generates a magnetic attractive force on the rotating body in a second direction opposite to the first direction, and Includes, The aforementioned certain position is the 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 supplied to the first actuator (51) and the second actuator (52).

13. The magnetic unit according to any one of claims 1 to 9, wherein the controller (40) controls the current flowing to the magnetic levitation part based on the fixed position and the fixed current in each of the plurality of maintenance controls after performing the plurality of maintenance controls.

14. The magnetic levitation portion has a plurality of electromagnets arranged around the rotating body that generate electromagnetic force by energizing 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.

15. A magnetic unit according to any one of claims 1 to 9, The rotating body and, A compression mechanism (3) connected to the rotating body, A compressor equipped with the following features.

16. A refrigeration apparatus comprising the compressor described in claim 15.

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