Bearing system, turbo compressor, refrigeration system, and method for detecting abnormality in bearing system

Abstract

In a first operation, a control unit (80) controls a support unit (11) such that a shaft (20) moves in the circumferential direction of a touchdown bearing (50) while being in contact with the inner circumferential surface of the touchdown bearing (50). In a second operation, the control unit (80) outputs first information indicating an abnormality when there is no line symmetry in a waveform indicating a change in a data value that changes in accordance with an amplitude change of a signal outputted from a displacement sensor (70) when the first operation is being performed.

Description

Bearing system, turbo compressor, refrigeration system, and method for detecting abnormalities in a bearing system

[0001] The present disclosure relates to a bearing system, a turbo compressor, a refrigeration system, and a method for detecting an abnormality in a bearing system.

[0002] Patent Document 1 discloses a bearing device equipped with a magnetic bearing and a touchdown bearing. The magnetic bearing supports a rotating shaft in a non-contact manner by magnetic force. The touchdown bearing is an auxiliary bearing that protects the magnetic bearing.

[0003] JP 2024-017670 A

[0004] In a bearing system such as that described in Patent Document 1, factors such as dimensional variations in the components and assembly errors can cause "abnormal contact," in which "at least one of the shaft and the elements rotating with the shaft" comes into contact with another part that is not the touchdown bearing before the shaft comes into contact with the touchdown bearing.

[0005] A first aspect of the present disclosure relates to a bearing system, the bearing system comprising: a shaft (20); a support part (11) that supports the shaft (20) in a non-contact manner by electromagnetic force; a touchdown bearing (50) that supports the shaft (20) by contacting the shaft (20) when the support part (11) does not support the shaft (20) in a non-contact manner; a displacement sensor (70) that is arranged around the shaft (20) and outputs a signal whose amplitude changes depending on the distance from the shaft (20); and a control part (80), wherein the control part (80) performs a first operation of controlling the support part (11) so that the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner surface of the touchdown bearing (50); and a second operation of outputting first information indicating an abnormality when a waveform indicating a change in data value that changes depending on a change in amplitude of the signal output from the displacement sensor (70) when the first operation is being performed does not have linear symmetry.

[0006] In the first aspect, if abnormal contact occurs in the bearing system (10), the shaft (20) cannot be moved in the circumferential direction of the touchdown bearing (50) while in contact with the inner peripheral surface of the touchdown bearing (50) during the period during which the first operation is being performed while the abnormal contact is occurring. When abnormal contact occurs in the bearing system (10), the symmetry between the increase and decrease in the distance between the shaft (20) and the displacement sensor (70) is disrupted. As a result, the waveform indicating the change in amplitude of the signal output from the displacement sensor (70) no longer has line symmetry. Therefore, by outputting the first information when the waveform indicating the change in data value corresponding to the change in amplitude of the signal output from the displacement sensor (70) during the first operation does not have line symmetry, it is possible to notify the user that an abnormality (specifically, abnormal contact) has occurred in the bearing system (10).

[0007] A second aspect of the present disclosure is a bearing system according to the first aspect, further comprising a first displacement sensor (70a) and a second displacement sensor (70b) that are arranged around the shaft (20) and each output a signal whose amplitude changes depending on the distance from the shaft (20), wherein the position of the second displacement sensor (70b) in the circumferential direction is different from the position of the first displacement sensor (70a) in the circumferential direction, the displacement sensor (70) is either the first displacement sensor (70a) or the second displacement sensor (70b), and the control unit (80) monitors, during the second operation, a first data value that changes depending on a change in amplitude of the signal output from the first displacement sensor (70a) when the first operation is being performed, and a second data value that changes depending on a change in amplitude of the signal output from the second displacement sensor (70b) when the first operation is being performed.

[0008] In the second aspect, by monitoring the first data value and the second data value, the first information can be output more accurately than when only one data value (a data value that changes in response to a change in the amplitude of the signal output from the displacement sensor (70)) is monitored, thereby enabling accurate notification of the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0009] A third aspect of the present disclosure is a bearing system in which, in the bearing system of the second aspect, the control unit (80) outputs the first information when, during the second operation, the waveform indicating the change in the first data value or the waveform indicating the change in the second data value does not have the linear symmetry.

[0010] In the third aspect, even if linear symmetry appears in the waveform indicating changes in the data values ​​corresponding to one of the first displacement sensor (70 a) and the second displacement sensor (70 b), the waveform indicating changes in the data values ​​corresponding to the other of the first displacement sensor (70 a) and the second displacement sensor (70 b) will not have linearity. Therefore, by monitoring the waveform indicating changes in the first data value and the waveform indicating changes in the second data value, it is possible to accurately notify the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0011] A fourth aspect of the present disclosure is a bearing system according to any one of the first to third aspects, further comprising a magnetic bearing (30) having a plurality of electromagnets (35) arranged around the shaft (20) and supporting the shaft (20) in a non-contact manner by a combined electromagnetic force of the plurality of electromagnets (35), and the support part (11) is the magnetic bearing (30).

[0012] A fifth aspect of the present disclosure is a bearing system according to any one of the first to third aspects, further comprising a bearingless motor (90) having a support winding (95) that generates an electromagnetic force for supporting the shaft (20) in a non-contact manner when current is applied, and a drive winding (96) that generates an electromagnetic force for driving the shaft (20) to rotate when current is applied, and the support part (11) is the bearingless motor (90).

[0013] A sixth aspect of the present disclosure is a turbocompressor including the bearing system according to any one of the first to fifth aspects.

[0014] A seventh aspect of the present disclosure is a refrigeration system including the turbo compressor of the sixth aspect.

[0015] An eighth aspect of the present disclosure relates to a method for detecting an abnormality in a bearing system including a shaft (20), a support part (11) that supports the shaft (20) in a non-contact manner by electromagnetic force, a touchdown bearing (50) that supports the shaft (20) by contacting the shaft (20) when the support part (11) does not support the shaft (20) in a non-contact manner, and a displacement sensor (70) that is arranged around the shaft (20) and outputs a signal whose amplitude changes depending on the distance from the shaft (20). This method for detecting an abnormality in a bearing system includes a first step of controlling the support part (11) so that the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner surface of the touchdown bearing (50), and a second step of outputting first information indicative of an abnormality when a waveform indicating a change in data value that changes depending on a change in amplitude of the signal output from the displacement sensor (70) when the first step is being performed does not have linear symmetry.

[0016] In the eighth aspect, when the waveform indicating the change in data value that changes in accordance with the change in amplitude of the signal output from the displacement sensor (70) when the first operation is being performed does not have linear symmetry, the first information can be output to notify that an abnormality (specifically, abnormal contact) has occurred in the bearing system (10).

[0017] A ninth aspect of the present disclosure is a bearing system abnormality detection method according to the eighth aspect, wherein the bearing system includes a first displacement sensor (70a) and a second displacement sensor (70b) arranged around the shaft (20), each outputting a signal whose amplitude changes depending on the distance from the shaft (20), the second displacement sensor (70b) being positioned in the circumferential direction different from the position of the first displacement sensor (70a), the displacement sensor (70) being the first displacement sensor (70a) or the second displacement sensor (70b), and in the second step, the first information is output when a waveform indicating a change in a first data value that changes depending on a change in amplitude of the signal output from the first displacement sensor (70a) while the first step is being performed or a waveform indicating a change in a second data value that changes depending on a change in amplitude of the signal output from the second displacement sensor (70b) while the first step is being performed does not have the linear symmetry.

[0018] In the ninth aspect, even if linear symmetry appears in the waveform indicating changes in the data values ​​corresponding to one of the first displacement sensor (70 a) and the second displacement sensor (70 b), the waveform indicating changes in the data values ​​corresponding to the other of the first displacement sensor (70 a) and the second displacement sensor (70 b) does not have linearity. Therefore, by monitoring the waveform indicating changes in the first data value and the waveform indicating changes in the second data value, it is possible to accurately notify the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0019] FIG. 1 is a longitudinal sectional view illustrating the configuration of a turbo compressor of an embodiment. FIG. 2 is a transverse sectional view illustrating the configuration of a radial magnetic bearing. FIG. 3 is a longitudinal sectional view illustrating the configuration of a thrust magnetic bearing. FIG. 4 is a transverse sectional view illustrating the configuration of a touchdown bearing. FIG. 5 is a longitudinal sectional view illustrating normal contact in a bearing system. FIG. 6 is a longitudinal sectional view illustrating abnormal contact in a bearing system. FIG. 7 is a schematic diagram illustrating the arrangement of a displacement sensor and the movement of a shaft due to a first operation during normal contact. FIG. 8 is a diagram illustrating the amplitude change of a signal from a radial displacement sensor and the trajectory of the shaft during normal contact. FIG. 9 is a schematic diagram illustrating the arrangement of a displacement sensor and the movement of a shaft due to a first operation during abnormal contact. FIG. 10 is a diagram illustrating the amplitude change of a signal from a radial displacement sensor and the trajectory of the shaft during abnormal contact. FIG. 11 is a transverse sectional view illustrating the configuration of a bearingless motor. FIG. 12 is a schematic diagram illustrating the configuration of a refrigeration system.

[0020] Hereinafter, embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and their description will not be repeated. Furthermore, the present disclosure is not limited to the embodiments shown below, and various modifications are possible within the scope of the technical concept of the present disclosure. Since each drawing is intended to conceptually explain the present disclosure, dimensions, ratios, or numbers may be exaggerated or simplified as necessary to facilitate understanding.

[0021] (Embodiment) Fig. 1 illustrates the configuration of a turbo compressor (1) according to an embodiment. The turbo compressor (1) draws in and compresses a fluid, and discharges the compressed fluid. In this example, the turbo compressor (1) includes a casing (2), an impeller (3), and a bearing system (10). The bearing system (10) includes a shaft (20), a first radial magnetic bearing (30a), a second radial magnetic bearing (30b), a first thrust magnetic bearing (40a), a second thrust magnetic bearing (40b), a first touchdown bearing (50a), a second touchdown bearing (50b), and a motor (60).

[0022] Hereinafter, the first radial magnetic bearing (30a) and the second radial magnetic bearing (30b) will be collectively referred to as "radial magnetic bearing (30)", the first thrust magnetic bearing (40a) and the second thrust magnetic bearing (40b) will be collectively referred to as "thrust magnetic bearing (40)", and the first touchdown bearing (50a) and the second touchdown bearing (50b) will be collectively referred to as "touchdown bearing (50)".

[0023] In the following description, the direction of the axis of a member will be referred to as the "axial direction" of that member. A direction perpendicular to the axis of a member will be referred to as the "radial direction" of that member. A direction around the axis of a member will be referred to as the "circumferential direction" of that member. For example, the axial direction of the shaft (20) is the direction of the rotation axis of the shaft (20). The radial direction of the shaft (20) is the direction perpendicular to the rotation axis of the shaft (20). The circumferential direction of the shaft (20) is the direction around the rotation axis of the shaft (20). In the following description, for convenience of explanation, the terms "front," "rear," "left," "right," "upper," and "lower" are used with reference to the direction when the installed turbo compressor (1) is viewed from the front side (the impeller (3) side).

[0024] [Casing] The casing (2) is formed in a cylindrical shape with both ends closed. The space inside the casing (2) is divided into two spaces by a wall portion (2a), one space forming an impeller chamber (S1) and the other space forming a motor chamber (S2). The impeller (3) is accommodated in the impeller chamber (S1). The motor chamber (S2) accommodates a radial magnetic bearing (30), a thrust magnetic bearing (40), a touchdown bearing (50), and a motor (60), which are fixed to the inner circumferential wall of the motor chamber (S2). In this example, the casing (2) is arranged so that the axis of the casing (2) (cylinder axis) is horizontal.

[0025] [Shaft] The shaft (20) is housed in the casing (2). The shaft (20) extends from the impeller chamber (S1) through the wall portion (2a) to the motor chamber (S2). The impeller (3) is fixed to one end of the shaft (20). For example, the shaft (20) is made of a magnetic material such as iron.

[0026] In this example, the shaft (20) has a recess (21). The recess (21) is provided near the other end of the shaft (20). The recess (21) is formed over the entire circumference of the shaft (20). In this example, a first touchdown bearing (50a), a first thrust magnetic bearing (40a), a first radial magnetic bearing (30a), a motor (60), a second radial magnetic bearing (30b), a second thrust magnetic bearing (40b), and a second touchdown bearing (50b) are arranged in this order from one end of the shaft (20) to the other end.

[0027] [Impeller] The impeller (3) has a plurality of blades and is formed so as to have a substantially conical outer shape. The impeller (3) is housed in an impeller chamber (S1) while being fixed to one end of the shaft (20). An intake pipe (P1) and a discharge pipe (P2) are connected to the impeller chamber (S1). The intake pipe (P1) is provided for guiding fluid from the outside to the impeller chamber (S1). The discharge pipe (P2) is provided for guiding the high-pressure fluid compressed in the impeller chamber (S1) to the outside. In this example, the impeller (3) and the impeller chamber (S1) form a compression mechanism.

[0028] [Radial Magnetic Bearing] The first radial magnetic bearing (30a) and the second radial magnetic bearing (30b) have the same configuration. The radial magnetic bearing (30) controls the radial position of the shaft (20) in a non-contact manner by using electromagnetic force.

[0029] As shown in Figures 1 and 2, in this example, the radial magnetic bearing (30) has a stator (31) and a rotor (32). The stator (31) is formed in a cylindrical shape and is fixed to the inner circumferential wall of the casing (2). The rotor (32) is formed in a cylindrical shape and is fixed to the shaft (20). The rotor (32) is arranged inside the stator (31) so as to face the stator (31) with a predetermined gap therebetween in the radial direction of the shaft (20).

[0030] As shown in FIG. 2 , the stator (31) includes a stator core (310) and a plurality of coils (315). The stator core (310) is made of a magnetic material and is formed into a cylindrical shape. The stator core (310) includes a cylindrical back yoke (311) and a plurality of teeth (312) provided on the inner circumferential surface of the back yoke (311). The plurality of coils (315) are wound around the plurality of teeth (312). The coils (315) are wound around the teeth (312) to form a radial electromagnet (35).

[0031] In this example, the radial magnetic bearing (30) includes a first radial electromagnet (35a), a second radial electromagnet (35b), a third radial electromagnet (35c), and a fourth radial electromagnet (35d). The first radial electromagnet (35a) and the second radial electromagnet (35b) face each other across the shaft (20). The third radial electromagnet (35c) and the fourth radial electromagnet (35d) face each other across the shaft (20). The opposing direction of the third radial electromagnet (35c) and the fourth radial electromagnet (35d) is perpendicular to the opposing direction of the first radial electromagnet (35a) and the second radial electromagnet (35b).

[0032] By energizing the coils (315) of the first radial electromagnet (35a), the second radial electromagnet (35b), the third radial electromagnet (35c), and the fourth radial electromagnet (35d), an electromagnetic force is generated to support the shaft (20) in a non-contact manner in the radial direction of the radial magnetic bearing (30). Then, by controlling the current flowing through the coils (315) of the first radial electromagnet (35a) and the second radial electromagnet (35b), the position of the shaft (20) in the opposing direction of the first radial electromagnet (35a) and the second radial electromagnet (35b) is controlled. Furthermore, by controlling the current flowing through the coils (315) of the third radial electromagnet (35c) and the fourth radial electromagnet (35d), the position of the shaft (20) in the opposing direction of the third radial electromagnet (35c) and the fourth radial electromagnet (35d) is controlled.

[0033] In this example, the first radial electromagnet (35a) and the second radial electromagnet (35b) face each other in the vertical direction, and the third radial electromagnet (35c) and the fourth radial electromagnet (35d) face each other in the horizontal direction.

[0034] The radial magnetic bearing (30) has a plurality of radial electromagnets (35) arranged around the shaft (20), and supports the shaft (20) in a non-contact manner by the electromagnetic forces of the plurality of radial electromagnets (35). The radial magnetic bearing (30) functions as a support part (11) that supports the shaft (20) in a non-contact manner by the electromagnetic forces. The radial magnetic bearing (30) is an example of the support part (11).

[0035] [Thrust Magnetic Bearing] The first thrust magnetic bearing (40a) and the second thrust magnetic bearing (40b) have the same configuration. The thrust magnetic bearing (40) controls the axial position of the shaft (20) in a non-contact manner by using electromagnetic force.

[0036] As shown in Figures 1 and 3, in this example, the thrust magnetic bearing (40) has a stator (41) and a rotor (42). The stator (41) is formed in an annular shape and is fixed to the inner circumferential wall of the casing (2). The rotor (42) is formed in an annular shape and is fixed to the shaft (20). The rotor (42) is disposed so as to face the stator (41) with a predetermined gap therebetween in the axial direction of the shaft (20).

[0037] As shown in Fig. 3, the stator (41) includes a stator core (411) formed in an annular shape and a coil (415) wound in an annular shape. An annular groove (412) is formed in the stator core (411), and the coil (415) is accommodated in the groove (412) of the stator core (411). The annularly wound coil (415) is accommodated in the annular groove (412), thereby forming a thrust electromagnet (45).

[0038] By energizing the coil (415) of the thrust electromagnet (45) of the thrust magnetic bearing (40), an electromagnetic force is generated to support the shaft (20) in a non-contact manner in the axial direction of the thrust magnetic bearing (40). Then, by controlling the current flowing through the coil (415) of the thrust electromagnet (45) of the thrust magnetic bearing (40), the position of the shaft (20) in the axial direction of the thrust magnetic bearing (40) is controlled.

[0039] [Touchdown Bearing] The first touchdown bearing (50a) and the second touchdown bearing (50b) have the same configuration. The touchdown bearing (50) comes into contact with the shaft (20) to support the shaft (20) when the support portion (11) does not support the shaft (20) in a contactless manner.

[0040] 1 and 4, the touchdown bearing (50) is formed in an annular shape. The shaft (20) is inserted through the touchdown bearing (50).

[0041] <First Touchdown Bearing> The first touchdown bearing (50a) is disposed between one end of the shaft (20) (the end to which the impeller (3) is fixed) and the first radial magnetic bearing (30a), and is provided on the wall portion (2a) of the casing (2). In this example, the first touchdown bearing (50a) constitutes a radial touchdown bearing.

[0042] Specifically, the first touchdown bearing (50a) supports the shaft (20) by having the inner peripheral surface of the first touchdown bearing (50a) come into contact with the shaft (20) moving in the radial direction of the first touchdown bearing (50a). Furthermore, contact between the shaft (20) and the inner peripheral surface of the first touchdown bearing (50a) can avoid "contact between the stator (61) and rotor (62) of the motor (60)" and "contact between the stator (31) and rotor (32) of the radial magnetic bearing (30)" which will be described later.

[0043] <Second Touchdown Bearing> The second touchdown bearing (50b) is arranged to face the recessed portion (21) of the shaft (20). Specifically, the inner peripheral surface of the second touchdown bearing (50b) faces the bottom surface of the recessed portion (21) of the shaft (20), and both axial end surfaces of the second touchdown bearing (50b) face both side surfaces of the recessed portion (21) of the shaft (20). In this example, the second touchdown bearing (50b) constitutes a radial thrust touchdown bearing.

[0044] Specifically, the second touchdown bearing (50b) supports the shaft (20) by bringing the inner peripheral surface of the second touchdown bearing (50b) into contact with the bottom surface of the recess (21) of the shaft (20) that moves in the radial direction of the second touchdown bearing (50b). Furthermore, contact between the bottom surface of the recess (21) of the shaft (20) and the inner peripheral surface of the second touchdown bearing (50b) can avoid "contact between the stator (61) and rotor (62) of the motor (60)" and "contact between the stator (31) and rotor (32) of the radial magnetic bearing (30)," which will be described later.

[0045] The second touchdown bearing (50b) supports the shaft (20) by contacting an axial end face of the second touchdown bearing (50b) with a side surface of the recess (21) of the shaft (20) that moves in the axial direction of the second touchdown bearing (50b). Furthermore, contact between the side surface of the recess (21) of the shaft (20) and the second touchdown bearing (50b) can be avoided between the stator (41) and the rotor (42) of the thrust magnetic bearing (40).

[0046] [Motor] The motor (60) drives the shaft (20) to rotate. In this example, the motor (60) has a stator (61) and a rotor (62). The stator (61) is cylindrical and fixed in the casing (2). The rotor (62) is fixed to the shaft (20) so as to be coaxial with the shaft (20). The rotor (62) is arranged in the stator (61) so that the outer peripheral surface of the rotor (62) faces the inner peripheral surface of the stator (61) with a predetermined gap therebetween.

[0047] Various sensors for detecting various physical quantities are provided in the turbo compressor (1) and the bearing system (10). Various pieces of information obtained by these sensors are transmitted to a control unit (80) described below.

[0048] As shown in Figure 1, the bearing system (10) is provided with a plurality of radial displacement sensors (70) and a thrust displacement sensor (75). The plurality of radial displacement sensors (70) are arranged around the shaft (20). Each of the plurality of radial displacement sensors (70) outputs a signal corresponding to the radial position of the shaft (20). The thrust displacement sensor (75) outputs a signal corresponding to the axial position of the shaft (20). The radial displacement sensors (70) and the thrust displacement sensor (75) will be described in detail later.

[0049] Although not shown, the bearing system (10) is also provided with a current sensor that detects the current flowing through the coil (315) of the stator (31) of the radial magnetic bearing (30), a current sensor that detects the current flowing through the coil (415) of the stator (41) of the thrust magnetic bearing (40), a current sensor that detects the current flowing through the coil of the stator (61) of the motor (60), a rotation angle sensor that detects the rotation angle of the shaft (20), a rotation speed sensor that detects the rotation speed of the shaft (20), and the like.

[0050] The various sensors described above may be sensors provided to directly detect the physical quantities described above, or may be sensors provided to indirectly detect or estimate the physical quantities described above.

[0051] [Storage Unit] The bearing system (10) also includes a storage unit (85). The storage unit (85) stores various types of information and data. For example, the storage unit (85) stores information and data (e.g., set values ​​such as thresholds) used for controlling the bearing system (10) and the turbo compressor (1), information and data (e.g., measurement values) obtained by various sensors provided in the bearing system (10) and the turbo compressor (1), and the like.

[0052] [Control Unit] The bearing system (10) also includes a control unit (80). The control unit (80) is connected to various sensors provided in the bearing system (10) and the turbo compressor (1) via signal lines, and receives signals output from the various sensors. The control unit (80) is also connected to the components of the bearing system (10) and the turbo compressor (1) via signal lines, and controls these components.

[0053] The control unit (80) performs various processes. Specifically, the control unit (80) acquires information and data from each part of the bearing system (10) and the turbo compressor (1), and performs various processes based on the information and data. The processes performed by the control unit (80) will be described in detail later.

[0054] For example, the control unit (80) is configured by a computer (microcomputer) including a processor, a memory, an input / output interface, etc. The memory is electrically connected to the processor and stores programs and data for operating the processor. The processor executes the programs to realize various functions of the control unit (80).

[0055] The control unit (80) also includes components for control (such as electric circuits and electronic circuits), such as a power supply unit that supplies power (current or voltage) in response to commands from the processor.

[0056] [Reference Position of Shaft] Next, the reference position of the shaft (20) supported in a non-contact manner will be described. At the start-up and during operation of the turbo compressor (1), the control unit (80) controls the support part (11) so that the position of the shaft (20) is at a predetermined reference position.

[0057] In this example, the reference position is the position of the shaft (20) when the rotation axis of the shaft (20) coincides with a predetermined "reference axis" and the axial position of the shaft (20) is the predetermined "reference axial position." For example, the reference axis is set to the axis of the stator (31) of the motor (60). The reference axial position is set to the axial position of the shaft (20) when the "distance between the stator (41) and the rotor (42) of the first thrust magnetic bearing (40a)" and the "distance between the stator (41) and the rotor (42) of the second thrust magnetic bearing (40b)" are equal to each other.

[0058] [Ideal Settings for Each Part of the Bearing System] Next, a description will be given of ideal settings for each part of the bearing system 10. The ideal settings (dimension settings, etc.) for each part of the bearing system 10 are as follows:

[0059] The radial magnetic bearing (30) is arranged so that its axis coincides with a reference axis (for example, the axis of the stator (61) of the motor (60)). The touchdown bearing (50) is arranged so that its axis coincides with the reference axis. The inner diameter of the touchdown bearing (50) is smaller than the inner diameter of the stator (31) of the radial magnetic bearing (30) (the diameter of the imaginary cylindrical surface that contacts the tips of the teeth (312)). The distance (radial distance) between various sensors such as the radial displacement sensor (70) and the reference axis is longer than the inner diameter of the touchdown bearing (50).

[0060] When the position of the shaft (20) is the reference position, the gap between the first touchdown bearing (50a) and the shaft (20) is narrower than both the "gap between the stator (31) and rotor (32) of the radial magnetic bearing (30)" and the "gap between the stator (61) and rotor (62) of the motor (60)."

[0061] When the position of the shaft (20) is the reference position, the gap between the second touchdown bearing (50b) and the bottom surface of the recess (21) of the shaft (20) is narrower than both the "gap between the stator (31) and rotor (32) of the radial magnetic bearing (30)" and the "gap between the stator (61) and rotor (62) of the motor (60)."

[0062] Furthermore, when the position of the shaft (20) is at the reference position, the gap between the second touchdown bearing (50b) and one side surface of the recessed portion (21) of the shaft (20) is narrower than the gap between the stator (41) and the rotor (42) of the first thrust magnetic bearing (40a). The gap between the second touchdown bearing (50b) and the other side surface of the recessed portion (21) of the shaft (20) is narrower than the gap between the stator (41) and the rotor (42) of the second thrust magnetic bearing (40b).

[0063] [Normal Contact and Abnormal Contact] Next, "normal contact" and "abnormal contact" in the bearing system (10) will be described. Hereinafter, the assembly of the "shaft (20)" and "elements that rotate together with the shaft (20)" will be referred to as a "rotating body." Examples of elements that rotate together with the shaft (20) include the impeller (3), the rotor (32) of the radial magnetic bearing (30), the rotor (42) of the thrust magnetic bearing (40), and the rotor (62) of the motor (60).

[0064] <Normal Contact> Normal contact refers to normal contact in which the touchdown bearing (50) comes into contact with the shaft (20) before the rotating body comes into contact with other parts other than the touchdown bearing (50), thereby preventing contact between the rotating body and the other parts.

[0065] Examples of components other than the touchdown bearing (50) include the casing (2), the stator (31) of the radial magnetic bearing (30), the stator (41) of the thrust magnetic bearing (40), the stator (61) of the motor (60), the radial displacement sensor (70), and the thrust displacement sensor (75).

[0066] As shown in Figure 5, when the settings of each part of the bearing system (10) are the above-mentioned "ideal settings," normal contact occurs in the bearing system (10). This makes it possible to avoid unintended contact in the bearing system (10). Unintended contact in the bearing system (10) refers to unintended contact between a rotating body and a part other than the touchdown bearing (50).

[0067] Examples of unintended contact in the bearing system (10) include contact between the stator (61) and rotor (62) of the motor (60), contact between the stator (31) and rotor (32) of the radial magnetic bearing (30), contact between the impeller (3) and the casing (2), and contact between the shaft (20) and the radial displacement sensor (70).

[0068] <Abnormal Contact> Abnormal contact refers to abnormal contact in which at least a part of the rotating body (at least one of the shaft (20) and the element rotating together with the shaft (20)) comes into contact with another part other than the touchdown bearing (50) before the shaft (20) comes into contact with the touchdown bearing (50). Factors that cause such abnormal contact include dimensional variations of the components and assembly errors.

[0069] For example, as shown in Fig. 6, if the axis of the second radial magnetic bearing (30b) is set below the reference axis, the axis of the second radial magnetic bearing (30b) will not coincide with the axis of the touchdown bearing (50). As a result, when the shaft (20) moves upward, abnormal contact will occur between the stator (31) of the second radial magnetic bearing (30b) and the rotor (32).

[0070] [Displacement Sensor] Next, the radial displacement sensor (70) will be described. The radial displacement sensor (70) is an example of a displacement sensor that outputs a signal whose amplitude changes depending on the distance from the shaft (20).

[0071] In this example, the radial displacement sensor (70) is a gap sensor that outputs a signal according to the distance between the gap sensor and the object to be measured. The longer the distance between the gap sensor and the object to be measured, the higher the level (amplitude value) of the signal output from the gap sensor.

[0072] In this example, four radial displacement sensors (70) are provided for one radial magnetic bearing (30). Specifically, as shown in Fig. 7, a first radial displacement sensor (71), a second radial displacement sensor (72), a third radial displacement sensor (73), and a fourth radial displacement sensor (74) are provided so as to surround the periphery of the shaft (20). These radial displacement sensors (70) are arranged so as to face the reference axis (R).

[0073] The first radial displacement sensor (71), the second radial displacement sensor (72), the third radial displacement sensor (73), and the fourth radial displacement sensor (74) correspond to the first radial electromagnet (35a), the second radial electromagnet (35b), the third radial electromagnet (35c), and the fourth radial electromagnet (35d) of the radial magnetic bearing (30), respectively.

[0074] The first radial displacement sensor (71) and the second radial displacement sensor (72) face each other with the shaft (20) interposed therebetween. The third radial displacement sensor (73) and the fourth radial displacement sensor (74) face each other with the shaft (20) interposed therebetween. The opposing direction of the third radial displacement sensor (73) and the fourth radial displacement sensor (74) is perpendicular to the opposing direction of the first radial displacement sensor (71) and the second radial displacement sensor (72). In this example, the opposing direction of the first radial displacement sensor (71) and the second radial displacement sensor (72) is the up-down direction, and the opposing direction of the third radial displacement sensor (73) and the fourth radial displacement sensor (74) is the left-right direction.

[0075] The first radial displacement sensor (71) and the second radial displacement sensor (72) output signals corresponding to the position of the shaft (20) in the opposing direction of the first radial electromagnet (35a) and the second radial electromagnet (35b) of the radial magnetic bearing (30). The third radial displacement sensor (73) and the fourth radial displacement sensor (74) output signals corresponding to the position of the shaft (20) in the opposing direction of the third radial electromagnet (35c) and the fourth radial electromagnet (35d) of the radial magnetic bearing (30).

[0076] The configuration of the thrust displacement sensor (75) may be the same as the configuration of the radial displacement sensor (70). For example, the thrust displacement sensor (75) may be a gap sensor. In this example, the thrust displacement sensor (75) is disposed in the axial direction of the shaft (20) so as to face the rotor (42) of the second thrust magnetic bearing (40b) at a predetermined distance, and outputs a signal corresponding to the distance from the rotor (42) of the second thrust magnetic bearing (40b).

[0077] [Processing by Control Unit] Next, processing by the control unit (80) will be described. The control unit (80) performs various processes including levitation position control and inspection processing.

[0078] [Floating position control] Floating position control is a process for controlling the position of the shaft (20) supported by the support portion (11) in a non-contact manner. The control portion (80) performs the levitation position control when the shaft (20) is supported by the support portion (11) in a non-contact manner. In the levitation position control, the control portion (80) detects the position of the shaft (20) based on signals output from each of the multiple radial displacement sensors (70) and the multiple thrust displacement sensors (75), and controls the support portion (11) so that the position of the shaft (20) is at a predetermined reference position.

[0079] Specifically, the control unit (80) detects the radial position (position of the rotation axis) of the shaft (20) based on signals output from the plurality of radial displacement sensors (70) and controls the current flowing through the coil (315) of the stator (31) of the radial magnetic bearing (30) so that the radial position of the shaft (20) is at a predetermined reference radial position (position of the reference axis). The control unit (80) also detects the axial position of the shaft (20) based on signals output from the thrust displacement sensor (75) and controls the current flowing through the coil (415) of the stator (41) of the thrust magnetic bearing (40) so that the axial position of the shaft (20) is at a predetermined reference axial position.

[0080] By repeating the above process, the position of the shaft (20) is maintained at the reference position.

[0081] [Inspection Process] The inspection process is a process for inspecting whether or not there is abnormal contact. For example, the control unit (80) performs the inspection process upon receiving an inspection instruction for starting the inspection process. The inspection process may be performed before the turbo compressor (1) is shipped from the factory, or after the turbo compressor (1) is shipped from the factory. In the inspection process, the control unit (80) performs a first operation and a second operation.

[0082] The inspection process by the control unit (80) is an example of a method for detecting an abnormality in the bearing system (10). The first and second operations are an example of a first step and a second step in the method for detecting an abnormality in the bearing system (10).

[0083] In the first operation, the control unit (80) controls the support unit (11) so that the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50). In the second operation, the control unit (80) outputs first information indicating an abnormality when a change in amplitude of a signal output from at least one of the plurality of radial displacement sensors (70) while the first operation is being performed is not an amplitude change that occurs when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50).

[0084] In this example, the change in amplitude of the signal output from the radial displacement sensor (70) is a change in the amplitude of the signal relative to a change in the position of the shaft (20) in the circumferential direction of the touchdown bearing (50). Furthermore, in the second operation, the control unit (80) outputs the first information when a waveform indicating a change in amplitude of the signal output from at least one of the plurality of radial displacement sensors (70) during the first operation does not have line symmetry when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while in contact with the inner circumferential surface of the touchdown bearing (50).

[0085] In this example, the control unit (80) monitors, in the second operation, the signals output from each of two or more radial displacement sensors (70) among the plurality of radial displacement sensors (70). Specifically, in the second operation, the control unit (80) monitors the signals output from each of two or more radial displacement sensors (70) including two radial displacement sensors (70) (e.g., the first radial displacement sensor (71) and the third radial displacement sensor (73)) that do not face each other in the radial direction of the radial magnetic bearing (30).

[0086] [Details of First Operation] Next, the first operation will be described in detail with reference to Fig. 7. Note that, hereinafter, the direction of movement of the shaft (20) in the first operation is the "clockwise direction," and the angle in the clockwise direction from the "reference line extending vertically downward from the reference axis (R)" to the "line extending from the reference axis (R) to the position of the shaft (20) (specifically, the position of the axis (Q) of the shaft (20))" will be referred to as the "rotational position angle (θ)."

[0087] At the start of the first operation, both the support part (11) and the drive part (12) are in a stopped state, and therefore the shaft (20) is located at the lowest point on the inner circumferential surface of the touchdown bearing (50) due to gravity (the point where the shaft (20) intersects with a reference line extending vertically downward from the reference axis (R)). The control part (80) activates the support part (11) and controls the support part (11) so that the rotational position angle (θ) of the shaft (20) gradually increases. As a result, the position of the shaft (20) in the circumferential direction of the touchdown bearing (50) gradually moves clockwise.

[0088] The position (rotational position angle (θ)) of the shaft (20) correlates with the direction of the electromagnetic force acting on the shaft (20) (in this example, the resultant electromagnetic force of the multiple radial electromagnets (35) of the radial magnetic bearing (30)). Specifically, since the shaft (20) is pressed against the inner circumferential surface of the touchdown bearing (50) in the direction of the "direction of the resultant electromagnetic force acting on the shaft (20)," it can be estimated that the position of the shaft (20) is in the direction of the "direction of the resultant electromagnetic force acting on the shaft (20)" when viewed from the reference axis (R). Such estimation (derivation) of the position of the shaft (20) is performed by the control unit (80).

[0089] Furthermore, the direction of the resultant electromagnetic force acting on the shaft (20) correlates with the direction and magnitude of the current flowing through each of the plurality of radial electromagnets (35). Therefore, by controlling the direction and magnitude of the current flowing through each of the plurality of radial electromagnets (35), the position (rotational position angle (θ)) of the shaft (20) can be moved to a desired position. Such control is performed by the control unit (80).

[0090] In this manner, the first operation by the control section (80) is continuously performed, and the position of the shaft (20) in the circumferential direction of the touchdown bearing (50) continues to move in the clockwise direction.

[0091] [Relationship between Presence or Absence of Abnormal Contact and Change in Signal Amplitude] Next, the relationship between "presence or absence of abnormal contact" and "change in amplitude of the signal output from the radial displacement sensor (70)" will be described with reference to Figures 7 to 10. The examples in Figures 7 and 8 are examples in which no abnormal contact occurs but normal contact occurs, while the examples in Figures 9 and 10 are examples in which abnormal contact occurs.

[0092] In the following description, the position at which the distance to the shaft (20) is smallest when the rotational position angle (θ) of the shaft (20) is “0°” will be referred to as the “0° position.” The same applies to the terms “90° position,” “180° position,” and “270° position.” In this example, the first radial displacement sensor (71) is disposed at the “0° position,” the second radial displacement sensor (72) is disposed at the “180° position,” the third radial displacement sensor (73) is disposed at the “90° position,” and the fourth radial displacement sensor (74) is disposed at the “270° position.”

[0093] As shown in FIGS. 7 and 8 , when no abnormal contact occurs, in the first operation, the increase and decrease in the distance between the shaft (20) and the radial displacement sensor (70) are symmetrical, and as a result, the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) includes a waveform portion having a shape indicating “linear symmetry corresponding to the symmetric increase and decrease in the distance between the shaft (20) and the radial displacement sensor (70).”

[0094] For example, in the first operation, the distance between the shaft (20) and the first radial displacement sensor (71) gradually increases as the rotational position angle (θ) of the shaft (20) gradually increases from 0° to 180°, reaches a maximum value when the rotational position angle (θ) of the shaft (20) reaches 180°, and then gradually decreases as the rotational position angle (θ) of the shaft (20) gradually increases from 180° to 360°.

[0095] As a result, as shown in FIG. 8 , during the first operation, the amplitude of the signal output from the first radial displacement sensor (71) increases and decreases in the same manner as the symmetric increase and decrease in the distance between the shaft (20) and the first radial displacement sensor (71). The waveform of the signal amplitude during the period when the rotational position angle (θ) of the shaft (20) is between 180° and 360° is line-symmetric (line symmetric about the 180° line) with respect to the waveform of the signal amplitude during the period when the rotational position angle (θ) of the shaft (20) is between 0° and 180°. In other words, when no abnormal contact occurs, the waveform indicating the change in the amplitude of the signal output from the first radial displacement sensor (71) includes a waveform portion that can be expressed by an even function. The same can be said for the second radial displacement sensor (72), the third radial displacement sensor (73), and the fourth radial displacement sensor (74).

[0096] The above "even function" is f （Ｘ０＋Ｘ） = f （Ｘ０－Ｘ） In an XY plane with the X axis as the horizontal axis and the Y axis as the vertical axis, an even function is symmetrical about a line passing through "X0" (the line where X = X0). A waveform showing a change in the amplitude of the signal output from the radial displacement sensor (70) can be expressed as a function in the XY plane with the "rotational position angle (θ) of the shaft (20)" as the X axis (horizontal axis) and the "amplitude of the signal" as the Y axis (vertical axis). When the waveform includes a waveform portion that can be expressed as an even function, the function expressing the waveform has a predetermined rotational position angle (θ) that becomes "X0" in the even function (a numerical value that defines the axis of symmetry of the even function).

[0097] Furthermore, the above-described line symmetry is independent of installation errors and individual differences of the radial displacement sensor (70). In other words, even if an installation error or individual differences occur in the radial displacement sensor (70), as long as there is no abnormal contact in the bearing system (10), the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) will have the above-described line symmetry.

[0098] On the other hand, as shown in FIGS. 9 and 10 , when abnormal contact occurs and the symmetry between the increase and decrease in the distance between the shaft (20) and the radial displacement sensor (70) is disrupted, the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) no longer has the above-mentioned “linear symmetry.”

[0099] In the example of FIG. 9 , during the period in which the rotational position angle (θ) of the shaft (20) increases from 180° to 270°, abnormal contact occurs in which the shaft (20) comes into contact with an obstacle (55), which is a component other than the touchdown bearing (50). In this case, during the period in which the abnormal contact occurs, the shaft (20) cannot be moved in the circumferential direction of the touchdown bearing (50) while being in contact with the inner circumferential surface of the touchdown bearing (50). Therefore, during the period in which the abnormal contact occurs, the change in amplitude of the signal output from the radial displacement sensor (70) is different from the "change in amplitude when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while being in contact with the inner circumferential surface of the touchdown bearing (50)."

[0100] As a result, as shown in Fig. 10 , the change in amplitude of the signal output from the first radial displacement sensor (71) does not exhibit a normal change (waveform change indicated by the solid line in Fig. 10 ) that shows a gradual decrease during the period in which the rotational position angle (θ) of the shaft (20) increases from 180° to 270°, but exhibits a more abrupt and linear change (waveform change indicated by the dashed line in Fig. 10 ) than the normal change. As a result, the waveform indicating the change in amplitude of the signal output from the first radial displacement sensor (71) no longer has the above-mentioned "line symmetry." The same can be said for the second radial displacement sensor (72), the third radial displacement sensor (73), and the fourth radial displacement sensor (74) as for the first radial displacement sensor (71).

[0101] [Details of Second Operation] Next, the second operation will be described in detail with reference to Fig. 8 and Fig. 10. In parallel with the first operation, the control unit (80) monitors the change in amplitude of the signal output from at least one of the plurality of radial displacement sensors (70). In this example, four signals output from four radial displacement sensors (70) are monitored.

[0102] Then, in the second operation, the control unit (80) determines, for each of the radial displacement sensors (70) (four radial displacement sensors (70) in this example) being monitored among the plurality of radial displacement sensors (70), whether or not the change in amplitude of the signal output from that radial displacement sensor (70) is “an amplitude change when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50) (hereinafter referred to as “normal change”).”

[0103] In this example, the control unit (80) determines whether or not the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) has "line symmetry when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while in contact with the inner peripheral surface of the touchdown bearing (50)." If the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) has the above-mentioned "line symmetry," the change in amplitude of the signal is a "normal change," and if not, the change in amplitude of the signal is not a "normal change."

[0104] For example, the control unit (80) detects an inflection point in the waveform indicating the amplitude change of the signal output from the radial displacement sensor (70) and derives the similarity between the "amplitude change of the signal when tracing back from the point of the inflection point during a predetermined period immediately before the inflection point" and the "amplitude change of the signal when tracing back from the inflection point during a predetermined period immediately after the inflection point." If the similarity exceeds a predetermined threshold, the control unit (80) determines that the amplitude change of the signal output from the radial displacement sensor (70) has the above-mentioned "line symmetry." If not, the control unit (80) determines that the amplitude change of the signal output from the radial displacement sensor (70) does not have the above-mentioned "line symmetry." Note that the similarity can be derived using a well-known similarity calculation technique.

[0105] When the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) has “line symmetry” (when the change in amplitude of the signal is “normal change”), the control unit (80) does not output first information indicating an abnormality, and continues to monitor the signal output from the radial displacement sensor (70). On the other hand, when the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) does not have “line symmetry” (when the change in amplitude of the signal is not “normal change”), the control unit (80) outputs first information indicating an abnormality.

[0106] The control unit (80) may output the first information by outputting an image or sound indicating the first information. Alternatively, the control unit (80) may output the first information by outputting light or sound corresponding to the first information. For example, the control unit (80) may output the first information by controlling a notification unit (not shown) that notifies various types of information. Examples of the notification unit include a display that displays an image indicating information to be notified, a speaker that outputs sound indicating information to be notified, a lamp that outputs notification light corresponding to the information to be notified, and a buzzer that outputs notification sound corresponding to the information to be notified.

[0107] The control unit (80) may be configured to output second information indicating normality when the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) has “line symmetry” (when the change in amplitude of the signal is “normal”). The output of the second information may be the same as the output of the first information.

[0108] Effect of the embodiment As described above, in the bearing system (10) of the embodiment, the control unit (80) performs a first operation of controlling the support unit (11) so that the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50), and a second operation of outputting first information indicating an abnormality when a change in amplitude of a signal output from at least one of the plurality of displacement sensors (70) while the first operation is being performed is not the same as the change in amplitude when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50).

[0109] In the above configuration, if abnormal contact occurs in the bearing system (10), the shaft (20) cannot be moved in the circumferential direction of the touchdown bearing (50) while in contact with the inner circumferential surface of the touchdown bearing (50) during the period in which the first operation is performed while the abnormal contact occurs. Therefore, during the period in which the abnormal contact occurs, the amplitude change of the signal output from the radial displacement sensor (70) is different from the "amplitude change when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while in contact with the inner circumferential surface of the touchdown bearing (50)." Therefore, by outputting the first information when the amplitude change of the signal output from the radial displacement sensor (70) is not the above-mentioned amplitude change, it is possible to notify the user that an abnormality (specifically, abnormal contact) has occurred in the bearing system (10).

[0110] In addition, in the bearing system (10) of the embodiment, the change in amplitude of the signal output from the radial displacement sensor (70) is the change in amplitude of the signal relative to the change in position of the shaft (20) in the circumferential direction of the touchdown bearing (50).

[0111] In the above configuration, by monitoring the change in amplitude of the signal (signal output from the radial displacement sensor (70)) corresponding to the "change in position of the shaft (20) in the circumferential direction of the touchdown bearing (50)," it is possible to appropriately output the first information even when the moving speed of the shaft (20) is not constant (when the change in signal amplitude over time is not constant). This makes it possible to appropriately notify the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0112] In addition, in the bearing system (10) of the embodiment, the control unit (80) outputs first information in the second operation when a waveform indicating the change in amplitude of the signal output from at least one of the multiple radial displacement sensors (70) when the first operation is being performed does not have linear symmetry when the shaft (20) moves circumferentially around the touchdown bearing (50) while in contact with the inner surface of the touchdown bearing (50).

[0113] In the above configuration, when no abnormal contact occurs in the bearing system (10), the increase and decrease in the distance between the shaft (20) and the radial displacement sensor (70) are symmetrical in the first operation. As a result, the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) includes a waveform portion having a shape that indicates "line symmetry corresponding to the symmetric increase and decrease in the distance between the shaft (20) and the radial displacement sensor (70)." On the other hand, when abnormal contact occurs in the bearing system (10), the symmetry between the increase and decrease in the distance between the shaft (20) and the radial displacement sensor (70) is disrupted. As a result, the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) no longer has the above-mentioned line symmetry. When this occurs, the first information is output. This makes it possible to notify the user that an abnormality (specifically, abnormal contact) has occurred in the bearing system (10).

[0114] The above-described line symmetry is independent of installation errors and individual differences of the radial displacement sensor (70). Therefore, the first information can be output with high accuracy without being affected by installation errors or individual differences of the radial displacement sensor (70). This allows for accurate notification of an abnormality occurring in the bearing system (10).

[0115] In the bearing system (10) of the embodiment, in the second operation, the control unit (80) monitors the signals output from each of two or more radial displacement sensors (70) out of the plurality of radial displacement sensors (70).

[0116] In the above configuration, by monitoring the signals output from each of the two or more radial displacement sensors (70), the first information can be output more accurately than when monitoring the signal output from only one radial displacement sensor (70), thereby enabling accurate notification of the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0117] Specifically, in the second operation, the control unit (80) monitors the signal output from each of two or more radial displacement sensors (70), including two radial displacement sensors (70) that do not face each other in the radial direction of the radial magnetic bearing (30). Note that, when abnormal contact occurs in the bearing system (10), linear symmetry may appear in the waveform indicating the change in amplitude of the signal output from the radial displacement sensor (70) that is arranged at a position facing the obstacle (55) in the radial direction of the radial magnetic bearing (30).

[0118] In the above configuration, when abnormal contact occurs in the bearing system (10), even if line symmetry appears in the waveform indicating the change in amplitude of the signal output from one of the two or more radial displacement sensors (70), the waveforms indicating the change in amplitude of the signal output from the other radial displacement sensors (70) will no longer have linearity. Therefore, by monitoring the signals output from each of the two or more radial displacement sensors (70), including two radial displacement sensors (70) that do not face each other in the radial direction of the radial magnetic bearing (30), it is possible to accurately notify the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0119] In the bearing system (10) of this embodiment, the control unit (80) may directly monitor the signal output from the displacement sensor (70), or may indirectly monitor the signal output from the displacement sensor (70) by monitoring a data value that changes in response to a change in the amplitude of the signal output from the displacement sensor (70). In this example, the displacement sensor (70) is a radial displacement sensor (70).

[0120] For example, the data value increases as the amplitude of the signal output from the displacement sensor (70) increases and decreases as the amplitude of the signal output from the displacement sensor (70) decreases. Alternatively, the data value decreases as the amplitude of the signal output from the displacement sensor (70) increases and increases as the amplitude of the signal output from the displacement sensor (70) decreases. Examples of the data value include a data value that directly indicates the amplitude of the signal output from the displacement sensor (70) and a data value that indirectly indicates the amplitude of the signal output from the displacement sensor (70). For example, the data value may be a data value that indicates the amplitude of a signal (the signal output from the displacement sensor (70)) that has been subjected to processing such as smoothing using a low-pass filter (not shown).

[0121] In addition, in the second operation of the bearing system (10) of the embodiment, the control unit (80) may output first information indicating an abnormality when a waveform indicating a change in data value that changes in response to a change in amplitude of the signal output from the displacement sensor (70) when the first operation is being performed does not have linear symmetry.

[0122] In the above configuration, when no abnormal contact occurs in the bearing system (10), in the first operation, the increase and decrease in the distance between the shaft (20) and the displacement sensor (70) are symmetrical, and as a result, the waveform indicating the change in data value that changes in response to the change in amplitude of the signal output from the displacement sensor (70) has linear symmetry.

[0123] On the other hand, if abnormal contact occurs in the bearing system (10), during the period in which the abnormal contact occurs within the period in which the first operation is performed, it becomes impossible to move the shaft (20) in the circumferential direction of the touchdown bearing (50) while keeping it in contact with the inner peripheral surface of the touchdown bearing (50). In this way, when abnormal contact occurs in the bearing system (10), the symmetry between the increase and decrease in the distance between the shaft (20) and the displacement sensor (70) is disrupted, and as a result, the waveform indicating the change in amplitude of the signal output from the displacement sensor (70) no longer has line symmetry.

[0124] Therefore, when the waveform indicating the change in data value that changes in response to the change in amplitude of the signal output from the displacement sensor (70) when the first operation is being performed does not have linear symmetry, the first information can be output to notify that an abnormality (specifically, abnormal contact) has occurred in the bearing system (10).

[0125] Furthermore, the bearing system (10) of the embodiment may include a first displacement sensor (70a) and a second displacement sensor (70b). The displacement sensor (70) may be the first displacement sensor (70a) or the second displacement sensor (70b).

[0126] The first displacement sensor (70a) and the second displacement sensor (70b) are arranged around the shaft (20), and each outputs a signal whose amplitude changes depending on the distance from the shaft (20). The circumferential position of the second displacement sensor (70b) is different from the circumferential position of the first displacement sensor (70a). The second displacement sensor (70b) does not face the first displacement sensor (70a) in the radial direction (e.g., the radial direction of the radial magnetic bearing (30)). In this example, the first displacement sensor (70a) is the first radial displacement sensor (71) or the second radial displacement sensor (72). The second displacement sensor (70b) is the third radial displacement sensor (73) or the fourth radial displacement sensor (74).

[0127] In the second operation of the bearing system (10) of the embodiment, the control unit (80) may monitor a first data value that changes in response to a change in amplitude of the signal output from the first displacement sensor (70a) when the first operation is being performed, and a second data value that changes in response to a change in amplitude of the signal output from the second displacement sensor (70b) when the first operation is being performed.

[0128] In the above configuration, by monitoring the first data value and the second data value, the first information can be output more accurately than when only one data value (a data value that changes in response to a change in the amplitude of the signal output from the displacement sensor (70)) is monitored, thereby enabling accurate notification of the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0129] In addition, in the second operation of the bearing system (10) of the embodiment, the control unit (80) may output the first information when the waveform indicating the change in the first data value or the waveform indicating the change in the second data value does not have linear symmetry.

[0130] In addition, when abnormal contact occurs in the bearing system (10), linear symmetry may appear in the waveform indicating the change in the data value (the data value that changes according to the change in amplitude of the signal output from the displacement sensor (70)) corresponding to the displacement sensor (70) arranged at a position facing the obstacle (55) in the radial direction (for example, the radial direction of the radial magnetic bearing (30)).

[0131] In the above configuration, even if linear symmetry appears in the waveform indicating changes in the data values ​​corresponding to one of the first displacement sensor (70 a) and the second displacement sensor (70 b), the waveform indicating changes in the data values ​​corresponding to the other of the first displacement sensor (70 a) and the second displacement sensor (70 b) will no longer have linearity. Therefore, by monitoring the waveform indicating changes in the first data value and the waveform indicating changes in the second data value, it is possible to accurately notify the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0132] (First Modification of the Embodiment) The bearing system (10) of the first modification of the embodiment differs from the bearing system (10) of the embodiment in the second operation by the control unit (80). The other configurations and processes of the bearing system (10) of the first modification of the embodiment are similar to those of the bearing system (10) of the embodiment.

[0133] In a first variation of the embodiment, the control unit (80) outputs first information in the second operation when the trajectory of the shaft (20) derived based on the change in amplitude of the signals output from each of two or more radial displacement sensors (70) among the plurality of radial displacement sensors (70) when the first operation is being performed is not the trajectory when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner surface of the touchdown bearing (50).

[0134] [Details of Second Operation] Next, the second operation of the first modification of the embodiment will be described in detail with reference to Fig. 8 and Fig. 10. In this example, at least one of the first radial displacement sensor (71) and the second radial displacement sensor (72) facing each other, and at least one of the third radial displacement sensor (73) and the fourth radial displacement sensor (74) facing each other in a direction perpendicular to the facing direction of the first radial displacement sensor (71) and the second radial displacement sensor (72) are monitored.

[0135] Hereinafter, the opposing direction between the first radial displacement sensor (71) and the second radial displacement sensor (72) will be referred to as the "X-axis direction," and the opposing direction between the third radial displacement sensor (73) and the fourth radial displacement sensor (74) will be referred to as the "Y-axis direction."

[0136] The control unit (80) detects a “change in the position of the shaft (20) in the X-axis direction” corresponding to a change in the rotational position angle (θ) of the shaft (20) based on a change in the amplitude of the signal output from the first radial displacement sensor (71) (or the second radial displacement sensor (72)). Similarly, the control unit (80) detects a “change in the position of the shaft (20) in the Y-axis direction” corresponding to a change in the rotational position angle (θ) of the shaft (20) based on a change in the amplitude of the signal output from the third radial displacement sensor (73) (or the fourth radial displacement sensor (74)).

[0137] Next, the control unit (80) derives the trajectory of the shaft (20) (specifically, the trajectory of the axis (Q) of the shaft (20)) in the XY plane (the plane defined by the X-axis direction and the Y-axis direction) based on the “change in the position of the shaft (20) in the X-axis direction” corresponding to the change in the rotational position angle (θ) of the shaft (20) and the “change in the position of the shaft (20) in the Y-axis direction” corresponding to the change in the rotational position angle (θ) of the shaft (20).

[0138] Next, the control unit (80) determines whether the derived "trajectory of the shaft (20)" is the "trajectory when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50) (hereinafter referred to as the "normal trajectory")." If the derived trajectory of the shaft (20) is the "normal trajectory," the amplitude change of the signal (signal output from the radial displacement sensor (70)) used to derive the trajectory of the shaft (20) is a "normal change," and if not, the amplitude change of the signal is not a "normal change."

[0139] For example, the normal trajectory is a circular shape (specifically, a perfect circle) that is the shape of the inner peripheral surface of the touchdown bearing (50). In this case, the control unit (80) derives the circularity of the derived trajectory of the shaft (20), and if the circularity exceeds a predetermined threshold value, determines that the derived trajectory of the shaft (20) is a “normal trajectory,” and if not, determines that the derived trajectory of the shaft (20) is not a “normal trajectory.”

[0140] If the derived trajectory of the shaft (20) is a “normal trajectory” (if the change in amplitude of the signal is a “normal change”), the control unit (80) does not output first information indicating an abnormality, and continues to monitor the signal output from the radial displacement sensor (70). On the other hand, if the derived trajectory of the shaft (20) is not a “normal trajectory” (if the change in amplitude of the signal is not a “normal change”), the control unit (80) outputs first information indicating an abnormality.

[0141] Effect of Modification 1 of Embodiment In the bearing system (10) of Modification 1 of the embodiment, if abnormal contact occurs in the bearing system (10), the shaft (20) cannot be moved in the circumferential direction of the touchdown bearing (50) while in contact with the inner circumferential surface of the touchdown bearing (50) during the period in which the abnormal contact occurs within the period in which the first operation is performed. Therefore, during the period in which abnormal contact occurs, the trajectory of the shaft (20) has a shape that is different from the shape of "the trajectory when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while in contact with the inner circumferential surface of the touchdown bearing (50)." Therefore, when the trajectory of the shaft (20) is not the above-described trajectory, it is possible to notify that an abnormality (specifically, abnormal contact) has occurred in the bearing system (10) by outputting the first information.

[0142] In addition, in the bearing system (10) of the first modified embodiment, the control unit (80) may derive the trajectory of the shaft (20) based on a waveform indicating a change in the first data value that changes in accordance with a change in the amplitude of the signal output from the first displacement sensor (70a) and a waveform indicating a change in the second data value that changes in accordance with a change in the amplitude of the signal output from the second displacement sensor (70b).

[0143] In the bearing system (10) of the first modified embodiment, the control unit (80) may output the first information in the second operation when the trajectory of the shaft (20) derived based on the first data value and the second data value during the first operation is not symmetric. For example, a symmetric trajectory has a perfect circular shape. The control unit (80) may derive the circularity of the trajectory of the shaft (20) and determine that the trajectory of the shaft (20) is symmetric when the derived circularity is equal to or less than a predetermined threshold.

[0144] (Second Modification of the Embodiment) A bearing system (10) according to a second modification of the embodiment includes a bearingless motor (90) shown in Fig. 11. The bearingless motor (90) may be provided in place of the radial magnetic bearing (30) and the motor (60), or may be provided together with the radial magnetic bearing (30) and the motor (60).

[0145] 11 , the bearingless motor (90) has a rotor (91) and a stator (92), and supports the shaft (20) in a non-contact manner by electromagnetic force and drives the shaft (20) to rotate. The rotor (91) is fixed to the shaft (20), and the stator (92) is fixed to the inner circumferential wall of the casing (2).

[0146] The bearingless motor (90) has a support winding (95) and a drive winding (96). The support winding (95) and the drive winding (96) are provided on the stator (92).

[0147] The support winding (95) is a winding that generates an electromagnetic force for supporting the shaft (20) in a non-contact manner when energized. The support winding (95) functions as a support portion (11) that supports the shaft (20) in a non-contact manner by the electromagnetic force. The support winding (95) is an example of the support portion (11).

[0148] The drive winding (96) is a winding that generates an electromagnetic force for rotationally driving the shaft (20) when energized. The drive winding (96) functions as a drive unit (12) that rotationally drives the shaft (20) by the electromagnetic force. The drive winding (96) is an example of the drive unit (12).

[0149] As described above, the bearingless motor (90) is an example of the support unit (11) and an example of the drive unit (12). In this example, the bearingless motor (90) is a consequent-pole type bearingless motor. The rotor (91) and the stator (92) have the following configurations.

[0150] <Rotor> The rotor (91) has a rotor core (910) and a plurality of permanent magnets (911). The rotor core (910) is made of a magnetic material and is formed in a cylindrical shape. For example, the rotor core (910) is made of a laminated core in which disc-shaped electromagnetic steel plates are stacked. A shaft hole for inserting the shaft (20) is provided in the center of the rotor core (910). The plurality of permanent magnets (911) are arranged at a predetermined angular pitch in the circumferential direction of the rotor (91).

[0151] In this example, the rotor (91) is provided with four permanent magnets (911). The four permanent magnets (911) are embedded in the outer periphery (near the outer periphery) of the rotor core (910) and arranged at an angular pitch of 90° in the circumferential direction of the rotor (91). The four permanent magnets (911) are formed in an arc shape along the outer periphery of the rotor core (910), with the outer periphery side serving as the north pole.

[0152] With this configuration, the portions of the outer periphery of the rotor core (910) that are located between the four permanent magnets (911) in the circumferential direction of the rotor (91) become pseudo south poles. Note that the outer periphery of the four permanent magnets (911) may also become south poles. In this case, the portions of the outer periphery of the rotor core (910) that are located between the four permanent magnets (911) in the circumferential direction of the rotor (91) become pseudo north poles.

[0153] <Stator> The stator (92) faces the rotor (91) across a predetermined air gap. The stator (92) has a stator core (920), a support winding (95), and a drive winding (96). The stator core (920) is made of a magnetic material. For example, the stator core (920) is made of a laminated core in which annular electromagnetic steel sheets are stacked. The stator core (920) has a cylindrical back yoke and a plurality of teeth (not shown) provided on the inner circumferential surface of the back yoke.

[0154] The support windings (95) are wound around the radially outer portions of the teeth of the stator core (920). In this example, three types of support windings (95) are provided in the bearingless motor (90). Specifically, the support windings (95) surrounded by a thick solid line in FIG. 11 constitute U-phase support windings. The support windings (95) surrounded by a thick dashed line in FIG. 11 constitute V-phase support windings. The support windings (95) surrounded by a thin solid line in FIG. 11 constitute W-phase support windings.

[0155] The drive windings (96) are wound around the radially inner portions of the teeth of the stator core (920). In this example, three types of drive windings (96) are provided in the bearingless motor (90). Specifically, the drive windings (96) surrounded by a thick solid line in FIG. 11 constitute U-phase drive windings. The drive windings (96) surrounded by a thick dashed line in FIG. 11 constitute V-phase drive windings. The drive windings (96) surrounded by a thin solid line in FIG. 11 constitute W-phase drive windings.

[0156] (Refrigeration System) FIG. 12 illustrates the configuration of a refrigeration system (RR). The refrigeration system (RR) has a refrigerant circuit (RR1) filled with a refrigerant. The refrigerant circuit (RR1) has a turbo compressor (1), a radiator (RR5), a pressure reduction mechanism (RR6), and an evaporator (RR7). In this example, the pressure reduction mechanism (RR6) is an expansion valve. The refrigerant circuit (RR1) performs a vapor compression refrigeration cycle.

[0157] In the refrigeration cycle, the refrigerant discharged from the turbo compressor (1) dissipates heat in the radiator (RR5). The refrigerant flowing out of the radiator (RR5) is decompressed in the pressure reducing mechanism (RR6) and evaporated in the evaporator (RR7). The refrigerant flowing out of the evaporator (RR7) is then drawn into the turbo compressor (1).

[0158] In this example, the refrigeration system (RR) is an air conditioner. The air conditioner may be a dedicated cooling unit or a dedicated heating unit. The air conditioner may also be an air conditioner that switches between cooling and heating. In this case, the air conditioner has a switching mechanism (e.g., a four-way switching valve) that switches the refrigerant circulation direction. The refrigeration system (RR) may also be a water heater, a chiller unit, a cooling device that cools the air inside a storage unit, etc. The cooling device cools the air inside a refrigerator, freezer, container, etc.

[0159] (Other Embodiments) In the above description, the following configurations or processes may be used.

[0160] The radial displacement sensor (70) is not limited to an eddy current gap sensor. For example, the gap sensor may be an ultrasonic gap sensor, an optical gap sensor, or another type of gap sensor. The radial displacement sensor (70) may also be a sensor capable of measuring distance without contact, such as a laser displacement meter.

[0161] In the second operation, the control unit (80) may be configured to monitor the signal output from only one radial displacement sensor (70).

[0162] The "normal change," which is the change in amplitude of the signal when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50), may be set to a normal amplitude change measured in advance (for example, an amplitude change measured when no abnormal contact occurs). In this case, the control unit (80) may derive a similarity between the "change in amplitude of the signal output from the radial displacement sensor (70)" and a predetermined "normal change," and may determine that the change in amplitude of the signal output from the radial displacement sensor (70) is a "normal change" if the similarity exceeds a predetermined threshold value, or may determine that the change in amplitude of the signal output from the radial displacement sensor (70) is not a "normal change" if the similarity does not exceed a predetermined threshold value.

[0163] The opposing direction between the first radial electromagnet (35a) and the second radial electromagnet (35b) is not limited to the up-down direction, and the opposing direction between the third radial electromagnet (35c) and the fourth radial electromagnet (35d) is not limited to the left-right direction. The same applies to the "opposing direction between the first radial displacement sensor (71) and the second radial displacement sensor (72)" and the "opposing direction between the third radial displacement sensor (73) and the fourth radial displacement sensor (74)."

[0164] For example, the opposing direction of the first radial electromagnet (35a) and the second radial electromagnet (35b) may be "a direction from the lower left to the upper right (a direction tilted 45° clockwise with respect to the up-down direction in Figure 2)", and the opposing direction of the third radial electromagnet (35c) and the fourth radial electromagnet (35d) may be "a direction from the lower left to the upper right (a direction tilted 45° counterclockwise with respect to the up-down direction in Figure 2)".

[0165] The number of radial displacement sensors (70) is not limited to four. The number of radial displacement sensors (70) may be less than four or more than four. The same applies to the other components.

[0166] The inspection process may be performed after the installation of the turbo compressor (1). By performing the inspection process after the installation of the turbo compressor (1), it is possible to detect abnormal contact caused by abnormal factors after shipment from the factory. Examples of abnormal factors after shipment from the factory include vibrations applied to the turbo compressor (1) during transportation from the factory to the installation site, distortion due to piping connections made during installation of the turbo compressor (1), and the slope of the installation site of the turbo compressor (1).

[0167] The movement of the shaft (20) in the first operation (movement in the circumferential direction of the touchdown bearing (50)) may be one or more rotations or less than one rotation. For example, the control unit (80) may control the support unit (11) so that, in the first operation, the shaft (20) moves a predetermined amount (a movement amount less than one rotation) in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50). In this case, the control unit (80) may be configured to perform the second operation each time the first operation is performed, while repeating the first operation so that the shaft (20) rotates once in the circumferential direction of the touchdown bearing (50). Alternatively, the control unit (80) may be configured to perform the second operation by switching the signal (or data value) of the displacement sensor (70) to be monitored each time the first operation is performed, while repeating the first operation so that the shaft (20) rotates once in the circumferential direction of the touchdown bearing (50).

[0168] The control unit (80) may be configured with a single processor and memory, or may be configured with multiple processors and memories. The multiple processors and memories may be provided together in a single device (housing), or may be provided in different devices (housings). For example, the processor that performs the second operation may be the same as the processor that performs the first operation, or may be a processor different from the processor that performs the first operation. Furthermore, the memory unit (85) may be configured with a single storage device, or may be configured with multiple storage devices.

[0169] Although the embodiments and modifications have been described, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. Furthermore, elements of the above-described embodiments, modifications, and other embodiments may be combined or substituted as appropriate.

[0170] (Additional Note) The present disclosure may be implemented as follows.

[0171] A first aspect relates to a bearing system, the bearing system comprising: a shaft (20); a support section (11) that supports the shaft (20) in a non-contact manner by electromagnetic force; a touchdown bearing (50) that supports the shaft (20) by contacting the shaft (20) when the support section (11) does not support the shaft (20) in a non-contact manner; a plurality of displacement sensors (70) that are arranged around the shaft (20), each outputting a signal whose amplitude changes depending on the distance from the shaft (20); and a control section (80), The control unit (80) performs a first operation of controlling the support unit (11) so that the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while in contact with the inner surface of the touchdown bearing (50), and a second operation of outputting first information indicating an abnormality when a change in amplitude of a signal output from at least one of the plurality of displacement sensors (70) while the first operation is being performed is not the same as the change in amplitude when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while in contact with the inner surface of the touchdown bearing (50).

[0172] In the first aspect, if abnormal contact occurs in the bearing system (10), during the period in which the first operation is performed during which abnormal contact occurs, the shaft (20) cannot be moved in the circumferential direction of the touchdown bearing (50) while in contact with the inner circumferential surface of the touchdown bearing (50). Therefore, during the period in which abnormal contact occurs, the amplitude change of the signal output from the displacement sensor (70) is different from the "amplitude change when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while in contact with the inner circumferential surface of the touchdown bearing (50)." Therefore, by outputting the first information when the amplitude change of the signal output from the displacement sensor (70) is not the above-mentioned amplitude change, it is possible to notify the user that an abnormality (specifically, abnormal contact) has occurred in the bearing system (10).

[0173] A second aspect is a bearing system according to the first aspect, wherein the change in amplitude of the signal is a change in amplitude of the signal relative to a change in position of the shaft (20) in the circumferential direction of the touchdown bearing (50).

[0174] In the second aspect, by monitoring the change in amplitude of the signal (signal output from the displacement sensor (70)) corresponding to the "change in position of the shaft (20) in the circumferential direction of the touchdown bearing (50)," it is possible to appropriately output the first information even when the moving speed of the shaft (20) is not constant (when the change in the amplitude of the signal over time is not constant). This makes it possible to appropriately notify the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0175] A third aspect is a bearing system in which, in the bearing system of the second aspect, the control unit (80) outputs the first information when, during the second operation, a waveform indicating a change in amplitude of a signal output from at least one of the plurality of displacement sensors (70) when the first operation is being performed does not have linear symmetry when the shaft (20) moves circumferentially around the touchdown bearing (50) while in contact with the inner surface of the touchdown bearing (50).

[0176] In the third aspect, when no abnormal contact occurs in the bearing system (10), in the first operation, the increase and decrease in the distance between the shaft (20) and the displacement sensor (70) become symmetrical, and as a result, the waveform indicating the change in amplitude of the signal output from the displacement sensor (70) includes a waveform portion having a shape that indicates "linear symmetry corresponding to the symmetric increase and decrease in the distance between the shaft (20) and the displacement sensor (70)." On the other hand, when abnormal contact occurs in the bearing system (10), the symmetry between the increase and decrease in the distance between the shaft (20) and the displacement sensor (70) is disrupted, and as a result, the waveform indicating the change in amplitude of the signal output from the displacement sensor (70) no longer has the linear symmetry, and the first information is output. This makes it possible to notify that an abnormality (specifically, abnormal contact) has occurred in the bearing system (10).

[0177] A fourth aspect is the bearing system of the third aspect, wherein the control unit (80) monitors signals output from each of two or more displacement sensors (70) among the plurality of displacement sensors (70) during the second operation.

[0178] In the fourth aspect, by monitoring the signals output from each of the two or more displacement sensors (70), the first information can be output with higher accuracy than when monitoring the signal output from only one displacement sensor (70), thereby enabling accurate notification of the occurrence of an abnormality (specifically, abnormal contact) in the bearing system (10).

[0179] A fifth aspect is a bearing system in which, in the bearing system of the second aspect, the control unit (80) outputs the first information when, in the second operation, the trajectory of the shaft (20) derived based on the amplitude change of the signal output from each of two or more displacement sensors (70) of the plurality of displacement sensors (70) when the first operation is being performed is not the trajectory when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while in contact with the inner surface of the touchdown bearing (50).

[0180] In the fifth aspect, if abnormal contact occurs in the bearing system (10), the shaft (20) cannot be moved in the circumferential direction of the touchdown bearing (50) while in contact with the inner circumferential surface of the touchdown bearing (50) during the period in which the first operation is performed and in which the abnormal contact occurs. Therefore, during the period in which the abnormal contact occurs, the trajectory of the shaft (20) has a shape different from the shape of "the trajectory when the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while in contact with the inner circumferential surface of the touchdown bearing (50)." Therefore, when the trajectory of the shaft (20) is not the above-described trajectory, the first information is output, thereby making it possible to notify that an abnormality (specifically, abnormal contact) has occurred in the bearing system (10).

[0181] A sixth aspect is a bearing system according to any one of the first to fifth aspects, further comprising a magnetic bearing (30) having a plurality of electromagnets (35) arranged around the shaft (20) and supporting the shaft (20) in a non-contact manner by a combined electromagnetic force of the plurality of electromagnets (35), and the support part (11) is the magnetic bearing (30).

[0182] A seventh aspect is a bearing system according to any one of the first to fifth aspects, further comprising a bearingless motor (90) having a support winding (95) that generates an electromagnetic force for supporting the shaft (20) in a non-contact manner when current is applied, and a drive winding (96) that generates an electromagnetic force for driving the shaft (20) to rotate when current is applied, and the support part (11) is the bearingless motor (90).

[0183] An eighth aspect is a turbocompressor including the bearing system according to any one of the first to seventh aspects.

[0184] A ninth aspect is a refrigeration system including the turbo compressor of the eighth aspect.

[0185] INDUSTRIAL APPLICABILITY As described above, the present disclosure is useful as a bearing system, a turbo compressor, a refrigeration system, and a method for detecting an abnormality in a bearing system.

[0186] REFERENCE SIGNS LIST 1 turbo compressor 10 bearing system 11 support section 12 drive section 20 shaft 30 radial magnetic bearing (magnetic bearing) 35 electromagnet 40 thrust magnetic bearing 50 touchdown bearing 60 motor 70 radial displacement sensor (displacement sensor) 75 thrust displacement sensor 80 control section 85 storage section 90 bearingless motor 95 support winding 96 drive winding

Claims

1. A bearing system comprising: a shaft (20); a support part (11) that supports the shaft (20) in a non-contact manner by electromagnetic force; a touchdown bearing (50) that supports the shaft (20) by contacting the shaft (20) when the support part (11) does not support the shaft (20) in a non-contact manner; a displacement sensor (70) that is arranged around the shaft (20) and outputs a signal whose amplitude changes depending on the distance from the shaft (20); and a control part (80), wherein the control part (80) performs a first operation of controlling the support part (11) so that the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50); and a second operation of outputting first information indicating an abnormality when a waveform indicating a change in data value that changes depending on a change in amplitude of a signal output from the displacement sensor (70) while the first operation is being performed does not have line symmetry.

2. A bearing system according to claim 1, comprising a first displacement sensor (70a) and a second displacement sensor (70b) arranged around the shaft (20), each outputting a signal whose amplitude changes in accordance with the distance from the shaft (20), wherein the position of the second displacement sensor (70b) in the circumferential direction is different from the position of the first displacement sensor (70a) in the circumferential direction, wherein the displacement sensor (70) is either the first displacement sensor (70a) or the second displacement sensor (70b), and wherein the control unit (80) monitors, during the second operation, a first data value that changes in accordance with changes in the amplitude of the signal output from the first displacement sensor (70a) when the first operation is being performed, and a second data value that changes in accordance with changes in the amplitude of the signal output from the second displacement sensor (70b) when the first operation is being performed.

3. A bearing system according to claim 2, wherein the control unit (80) outputs the first information when, in the second operation, the waveform indicating the change in the first data value or the waveform indicating the change in the second data value does not have the line symmetry.

4. A bearing system according to any one of claims 1 to 3, comprising a magnetic bearing (30) having a plurality of electromagnets (35) arranged around the shaft (20), which supports the shaft (20) in a non-contact manner by the combined electromagnetic force of the plurality of electromagnets (35), and wherein the support part (11) is the magnetic bearing (30).

5. A bearing system according to any one of claims 1 to 3, comprising a bearingless motor (90) having a support winding (95) that generates an electromagnetic force for supporting the shaft (20) in a non-contact manner when energized, and a drive winding (96) that generates an electromagnetic force for driving the shaft (20) to rotate when energized, and the support part (11) is the bearingless motor (90).

6. A turbocompressor comprising the bearing system of any one of claims 1 to 5.

7. A refrigeration system comprising the turbocompressor of claim 6.

8. A method for detecting an abnormality in a bearing system comprising: a shaft (20); a support part (11) that supports the shaft (20) in a non-contact manner by electromagnetic force; a touchdown bearing (50) that supports the shaft (20) by contacting the shaft (20) when the support part (11) does not support the shaft (20) in a non-contact manner; and a displacement sensor (70) that is arranged around the shaft (20) and outputs a signal whose amplitude changes depending on the distance from the shaft (20), the method comprising: a first step of controlling the support part (11) so that the shaft (20) moves in the circumferential direction of the touchdown bearing (50) while contacting the inner peripheral surface of the touchdown bearing (50); and a second step of outputting first information indicating an abnormality when a waveform indicating a change in data value that changes depending on a change in amplitude of the signal output from the displacement sensor (70) while the first step is being performed does not have line symmetry.

9. A method for detecting an abnormality in a bearing system according to claim 8, wherein the bearing system comprises a first displacement sensor (70a) and a second displacement sensor (70b) arranged around the shaft (20), each outputting a signal whose amplitude changes in accordance with the distance from the shaft (20), the position of the second displacement sensor (70b) in the circumferential direction being different from the position of the first displacement sensor (70a) in the circumferential direction, the displacement sensor (70) being either the first displacement sensor (70a) or the second displacement sensor (70b), and in the second step, the first information is output if a waveform indicating a change in a first data value that changes in accordance with a change in amplitude of the signal output from the first displacement sensor (70a) while the first step is being performed or a waveform indicating a change in a second data value that changes in accordance with a change in amplitude of the signal output from the second displacement sensor (70b) while the first step is being performed does not have the line symmetry.

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