Drive system, turbo-compressor, refrigeration device

Abstract

The rotation angle detector (60) outputs a first signal (S1) that is a signal whose amplitude varies with a change in the rotation angle of the shaft (20), possibly superimposed with a specific frequency component. The signal processing section (80) performs reduction processing for reducing the specific frequency component contained in the first signal (S1) on the basis of the first signal (S1), thereby generating a second signal (S2). The control section (90) detects the rotation angle of the shaft (20) on the basis of the second signal (S2). The frequency of the specific frequency component is lower than the frequency of a first frequency component (C1) that is an alternating-current frequency component of a non-direct-current component, is a frequency component contained in the first signal (S1), and is a frequency component corresponding to a change in the rotation angle of the shaft (20).

Description

Technical Field

[0001] This disclosure relates to a drive system, a turbo compressor, and a refrigeration device. Background Technology

[0002] Patent Document 1 discloses a rotation detection device including a rotation detector, a shaft runout detector, and a signal processing unit. The rotation detector detects the rotation of a rotating body in a non-contact manner. The shaft runout detector detects the shaft runout of the rotating body in a non-contact manner. The signal processing unit processes the rotation detection signal from the rotation detector and the shaft runout detection signal from the shaft runout detector, removing the shaft runout component from the signal components of the rotation detection signal.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Publication No. 2001-201362 Summary of the Invention

[0006] -The technical problem the invention aims to solve-

[0007] In the device described in Patent Document 1, two sensors (a rotation detector and a shaft runout detector) are required to detect changes in the rotation angle of the rotating body. Therefore, it is difficult to reduce the number of sensors used to detect changes in the rotation angle of the rotating body.

[0008] - Technical solutions for solving technical problems -

[0009] The first aspect of this disclosure relates to a drive system including a shaft 20, a support 11, a drive unit 12, a single rotation angle detector 60, a signal processing unit 80, and a control unit 90. The support 11 supports the shaft 20 non-contactly using electromagnetic force. The drive unit 12 drives the shaft 20 to rotate using electromagnetic force. The rotation angle detector 60 outputs a first signal S1, the amplitude of which varies with the rotation angle of the shaft 20. A specific frequency component may be superimposed on the first signal S1. The signal processing unit 80, based on the first signal output from the rotation angle detector 60... Signal S1 is used to reduce the specific frequency component contained in the first signal S1, thereby generating a second signal S2. The control unit 90 controls the support unit 11 and the drive unit 12. The control unit 90 detects the rotation angle of the shaft 20 based on the second signal S2 generated by the signal processing unit 80. The frequency of the specific frequency component that is reduced in the reduction process is lower than the frequency of the first frequency component C1. The first frequency component C1 is an AC frequency component that is not a DC component. It is the frequency component contained in the first signal S1 and is the frequency component that corresponds to the change in the rotation angle of the shaft 20.

[0010] In the first aspect, only a single rotation angle detector 60 is needed to detect changes in the rotation angle of the shaft 20, thus reducing the number of sensors required to detect changes in the rotation angle of the shaft 20.

[0011] The second aspect of this disclosure is based on the drive system of the first aspect, wherein the shaft 20 has a measured part 25, and the rotation angle detector 60 is a gap sensor that outputs a signal whose amplitude varies with the distance between the rotation angle detector 60 and the measured part 25, the measured part 25 being configured such that the distance between the measured part 25 and the rotation angle detector 60 varies with the rotation angle of the shaft 20, and the first frequency component C1 is a frequency corresponding to the rotation frequency of the shaft 20 driven by the drive unit 12 and the shape of the measured part 25.

[0012] In the second aspect, when the rotation angle of shaft 20 changes, the distance between the measured part 25 of shaft 20 and the rotation angle detector 60 changes, resulting in a change in the first signal S1 output from the rotation angle detector 60. Thus, the first signal S1 output from the rotation angle detector 60 can be made into a "signal whose amplitude changes with the rotation angle of shaft 20".

[0013] The third aspect of this disclosure is based on the drive system of the first or second aspect, wherein the specific frequency component reduced in the reduction process includes the frequency component with the largest amplitude among the frequency components with a frequency lower than the frequency of the first frequency component C1.

[0014] In the third aspect, during the reduction process, it is possible to reduce the frequency component with the largest amplitude among the frequency components that are lower than the frequency of the first frequency component C1, which may be superimposed on the first signal S1. As a result, the second signal S2 can be generated with high precision in a manner in which the amplitude changes with the rotation angle of the shaft 20, and thus the rotation angle of the shaft 20 based on the second signal S2 can be accurately detected.

[0015] The fourth aspect of this disclosure is based on the drive system of the first or second aspect, wherein the specific frequency component reduced in the reduction process includes the shaft runout component CX with the largest amplitude among a plurality of shaft runout components CX corresponding to the runout of the shaft 20, which is supported in a non-contact manner, from a reference position.

[0016] In the fourth aspect, during the reduction process, the "axis runout component CX with the largest amplitude" among the multiple axis runout components CX that may be superimposed on the first signal S1 can be reduced. As a result, the second signal S2 can be generated with high precision in a manner in which the amplitude changes with the rotation angle of the axis 20, and thus the rotation angle of the axis 20 based on the second signal S2 can be accurately detected.

[0017] The fifth aspect of this disclosure is based on the driving system of any one of the first to fourth aspects, wherein the reduction processing is a process for reducing the frequency component in a specific frequency band contained in the first signal S1, the specific frequency band being a frequency band containing the frequency of the specific frequency component, and being a frequency band lower than the frequency of the first frequency component C1.

[0018] In the fifth aspect, frequency components with frequencies higher than the first frequency component C1 (frequency components that may be used to detect changes in the rotation angle of the shaft 20) can be prevented from being reduced during the reduction process. As a result, the second signal S2 can be generated with high precision in a manner in which the amplitude changes with the rotation angle of the shaft 20, thus enabling accurate detection of the rotation angle of the shaft 20 based on the second signal S2.

[0019] The sixth aspect of this disclosure is based on a drive system of any one of the first to fifth aspects, wherein the signal processing unit 80 has a first processing unit 81 and a second processing unit 82, the first processing unit 81 generating a threshold Th1 corresponding to the specific frequency component based on the first signal S1, and the second processing unit 82 generating a second signal S2 by comparing the amplitude of the first signal S1 with the threshold Th1 generated by the first processing unit 81.

[0020] In the sixth aspect, by comparing the amplitude of the first signal S1 with a threshold Th1 corresponding to a specific frequency component, the "signal with the specific frequency component reduced" obtained by the comparison can be used as the second signal S2.

[0021] The seventh aspect of this disclosure is based on the driving system of the sixth aspect, wherein the first processing unit 81 generates the threshold Th1 by extracting frequency components within a specific frequency band contained in the first signal S1, wherein the specific frequency band is a frequency band containing the frequency of the specific frequency component and is a frequency band lower than the frequency of the first frequency component C1.

[0022] In the seventh aspect, by extracting a frequency component within a specific frequency band from the first signal S1, the extracted frequency component can be used as a "threshold Th1 corresponding to the specific frequency component".

[0023] The eighth aspect of this disclosure is based on the drive system of the sixth aspect, wherein the first processing unit 81 selectively performs a first extraction process and a second extraction process. In the first extraction process, the threshold Th1 is generated by extracting a frequency component within a specific frequency band contained in the first signal S1. In the second extraction process, the threshold Th1 is generated by extracting a DC component from the first signal S1. The specific frequency band is a frequency band containing the frequency of the specific frequency component, and is a frequency band lower than the frequency of the first frequency component C1.

[0024] In the eighth aspect, the threshold Th1 can be appropriately switched according to the operating status of the drive system 10.

[0025] The ninth aspect of this disclosure is based on the drive system of the sixth aspect, wherein the first processing unit 81 generates the threshold Th1 by repeatedly performing a process of setting the value derived from the amplitude of the first signal S1 within a predetermined period as the threshold Th1.

[0026] In the ninth aspect, by repeatedly performing the process of "setting a value derived from the amplitude of the first signal S1 within a specified period as a threshold Th1", the threshold Th1 can be made to change accordingly with a specific frequency component. Thus, a threshold Th1 corresponding to a specific frequency component can be generated.

[0027] The tenth aspect of this disclosure is based on a drive system of any one of the first to fifth aspects, wherein the signal processing unit 80 has a first processing unit 81 and a second processing unit 82, the first processing unit 81 reducing the specific frequency component contained in the first signal S1, and the second processing unit 82 generating the second signal S2 by comparing the signal obtained by the first processing unit 81 with a threshold Th1.

[0028] In the tenth aspect, by comparing the amplitude of the first signal S1, whose specific frequency component has been reduced, with a threshold Th1, the "signal whose specific frequency component has been reduced" obtained by the comparison can be used as the second signal S2.

[0029] The eleventh aspect of this disclosure is based on a drive system of any one of the first to tenth aspects, the drive system comprising a bearingless motor 30 having a support winding 35 and a drive winding 36, the support winding 35 being a winding that generates an electromagnetic force for supporting the shaft 20 in a non-contact manner by being energized, and functions as a support portion 11, the drive winding 36 being a winding that generates an electromagnetic force for driving the shaft 20 to rotate by being energized, and functions as a drive portion 12.

[0030] The twelfth aspect of this disclosure relates to a turbo compressor comprising a drive system according to any one of the first to eleventh aspects.

[0031] The thirteenth aspect of this disclosure relates to a refrigeration apparatus, which includes the turbine compressor of the twelfth aspect. Attached Figure Description

[0032] Figure 1 This is a simplified diagram illustrating the structure of a refrigeration device according to an embodiment.

[0033] Figure 2 This is a cross-sectional view illustrating the structure of a turbo compressor according to an embodiment.

[0034] Figure 3 This is a cross-sectional view illustrating the structure of the first shaft portion, which is the part being measured.

[0035] Figure 4 This is a cross-sectional view illustrating the structure of the second shaft portion, which is the part being measured.

[0036] Figure 5 This is a cross-sectional view illustrating the structure of a bearingless electric motor.

[0037] Figure 6 This is a cross-sectional view illustrating the structure of a radial magnetic bearing.

[0038] Figure 7 This is a waveform diagram illustrating the variation of the first signal caused by shaft runout.

[0039] Figure 8 This is a graph illustrating the axis runout components.

[0040] Figure 9 This is a diagram illustrating the relationship between the shaft runout component and the first frequency component, as well as the shaft runout frequency band.

[0041] Figure 10 This is a block diagram illustrating the structure of the signal processing unit.

[0042] Figure 11 It is an example of waveform diagrams of various signals processed in the signal processing unit.

[0043] Figure 12 This is a waveform diagram illustrating the changes in various signals during rotation angle detection and processing.

[0044] Figure 13 This is a block diagram illustrating the structure of the signal processing unit in Modified Example 1 of the embodiment.

[0045] Figure 14 This is a block diagram illustrating the structure of the signal processing unit in Modified Example 2 of the embodiment.

[0046] Figure 15 The example is in Figure 14 The waveform diagrams of the various signals processed in the signal processing unit are shown.

[0047] Figure 16 This is a block diagram illustrating the structure of the signal processing unit in Modified Example 3 of the embodiment.

[0048] Figure 17 The example is in Figure 16 The waveform diagrams of the various signals processed in the signal processing unit are shown.

[0049] Figure 18 This is a block diagram illustrating the structure of the signal processing unit in Modified Example 4 of the embodiment.

[0050] Figure 19 The example is in Figure 18 The waveform diagrams of the various signals processed in the signal processing unit are shown.

[0051] Figure 20 This is a block diagram illustrating the structure of the signal processing unit in Modified Example 5 of the embodiment.

[0052] Figure 21 The example is in Figure 20 The waveform diagrams of the various signals processed in the signal processing unit are shown.

[0053] Figure 22 This is a block diagram illustrating the structure of the signal processing unit in Modified Example 6 of the embodiment.

[0054] Figure 23 The example is in Figure 22 The waveform diagrams of the various signals processed in the signal processing unit are shown. Detailed Implementation

[0055] The embodiments will now be described in detail with reference to the accompanying drawings. It should be noted that identical or corresponding parts in the drawings are labeled with the same symbols and will not be described again.

[0056] (Refrigeration unit)

[0057] Figure 1 The structure of the refrigeration device RR according to the embodiment is illustrated. The refrigeration device RR has a refrigerant circuit RR1 filled with refrigerant. The refrigerant circuit RR1 has a turbo compressor 1, a heat exchanger RR5, a pressure reducing mechanism RR6, and an evaporator RR7. In this example, the pressure reducing mechanism RR6 is an expansion valve. The refrigerant circuit RR1 performs a vapor compression refrigeration cycle.

[0058] In the refrigeration cycle, the refrigerant injected from the turbo compressor 1 releases heat in the heat exchanger RR5. The refrigerant flowing out of the heat exchanger RR5 is depressurized in the pressure reducing mechanism RR6 and evaporates in the evaporator RR7. Then, the refrigerant flowing out of the evaporator RR7 is drawn back into the turbo compressor 1.

[0059] In this example, the refrigeration unit RR is an air conditioner. An air conditioner can be either a dedicated refrigeration unit or a dedicated heating unit. Additionally, an air conditioner can also be one that switches between cooling and heating modes. In this case, the air conditioner has a switching mechanism (e.g., a four-way reversing valve) to switch the refrigerant circulation direction. Alternatively, the refrigeration unit RR can also be a water heater, a cooling unit, or a cooling device that cools the air inside a storage facility. Cooling devices cool the air inside cold storage rooms, freezers, containers, etc.

[0060] (Turbo compressor)

[0061] Figure 2The structure of a turbo compressor 1 according to an embodiment is illustrated. The turbo compressor 1 draws in fluid and compresses the fluid, then ejects the compressed fluid. In this example, the turbo compressor 1 includes a housing 2, an impeller 3, and a drive system 10. The drive system 10 includes a shaft 20, a bearingless electric motor 30, a magnetic bearing 40, and a bottom-contact bearing 50.

[0062] In the following description, the direction of the axis of a component is denoted as its "axial direction". The direction orthogonal to the axis of a component is denoted as its "radial direction". The direction about the axis of a component is denoted as its "circumferential direction". For example, the axial direction of shaft 20 is the direction of its axis of rotation. The radial direction of shaft 20 is the direction orthogonal to its axis of rotation. The circumferential direction of shaft 20 is the direction about its axis of rotation.

[0063] 〔chassis〕

[0064] The housing 2 is formed as a cylinder closed at both ends. The space inside the housing 2 is divided into two spaces by the wall 2a: one space constitutes the impeller chamber S21, and the other space constitutes the motor chamber S22. The impeller 3 is housed in the impeller chamber S21. The bearingless motor 30, the magnetic bearing 40, and the bottom bearing 50 are housed in the motor chamber S22 and are fixed to the inner peripheral wall of the motor chamber S22. In this example, the housing 2 is arranged horizontally with the axis of the housing 2 (cylinder axis) as the horizontal direction.

[0065] 〔axis〕

[0066] The shaft 20 is housed within the casing 2. The shaft 20 extends from the impeller chamber S21 through the wall 2a and into the motor chamber S22. An 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.

[0067] In this example, the shaft 20 has a disc portion 21, a recess 22, and a measuring portion 25. The disc portion 21 is provided at one end of the shaft 20. The recess 22 is provided near the other end of the shaft 20. The recess 22 is formed over the entire circumference of the shaft 20. The measuring portion 25 is provided between one end of the shaft 20 and the recess 22.

[0068] The measured portion 25 is configured such that the distance between the measured portion 25 and the rotation angle sensor 60 (described later) changes with the rotation angle of the shaft 20. Furthermore, in this example, the measured portion 25 is configured such that the distance between the measured portion 25 and the rotation reference sensor 65 (described later) changes with the position of the rotation reference of the shaft 20. The measured portion 25 is formed in a shaft shape. A plurality of first step portions 201 and second step portions 202 are provided on the measured portion 25.

[0069] Multiple first step portions 201 are arranged at predetermined intervals in the circumferential direction of the shaft 20. The multiple first step portions 201 are provided for detecting changes in the rotation angle of the shaft 20.

[0070] like Figure 3 As shown, in this example, eight first step portions 201 are equally spaced along the circumference of the shaft 20. The first step portion 201 is a recess (groove). The shaft portion of the measured portion 25 of the shaft 20, where the first step portions 201 are provided (hereinafter referred to as "first shaft portion"), becomes the measurement object of the rotation angle sensor 60 described later.

[0071] The second step portion 202 is provided on the shaft portion adjacent to the first shaft portion (the shaft portion provided with multiple first step portions 201) in the axial direction of the shaft 20. The second step portion 202 is provided for detecting the rotation reference of the shaft 20.

[0072] like Figure 4 As shown, in this example, a second step portion 202 is provided. The second step portion 202 is a recess (groove). The shaft portion 25 of the shaft 20 with the second step portion 202 (hereinafter referred to as "second shaft portion") becomes the measurement object of the rotation reference sensor 65 described later.

[0073] 〔impeller〕

[0074] The impeller 3 has multiple blades and is generally conical in shape. The impeller 3 is housed in the impeller chamber S21, fixed to one end of the shaft 20. An intake pipe P1 and an outlet pipe P2 are connected to the impeller chamber S21. The intake pipe P1 is provided to guide fluid from the outside into the impeller chamber S21. The outlet pipe P2 is provided to guide the high-pressure fluid compressed within the impeller chamber S21 to the outside. In this example, the impeller 3 and the impeller chamber S21 constitute a compression mechanism.

[0075] [Bearingless electric motor]

[0076] The bearingless motor 30 has a rotor 31 and a stator 32, and uses electromagnetic force to support and drive the shaft 20 to rotate in a non-contact manner. The rotor 31 is fixed to the shaft 20, and the stator 32 is fixed to the inner peripheral wall of the housing 2. In this example, the bearingless motor 30 is arranged between one end of the shaft 20 (the end where the impeller 3 is fixed) and the measuring part 25.

[0077] Specifically, the bearingless motor 30 has a support winding 35 and a drive winding 36. The support winding 35 and the drive winding 36 are disposed on the stator 32.

[0078] The support winding 35 is a winding that generates electromagnetic force by being energized to support the shaft 20 in a non-contact manner. The support winding 35 functions as a support portion 11 that supports the shaft 20 in a non-contact manner using electromagnetic force. The support winding 35 is an example of the support portion 11.

[0079] The drive winding 36 is a winding that generates an electromagnetic force for rotating the drive shaft 20 by being energized. The drive winding 36 functions as a drive unit 12 that uses electromagnetic force to drive the shaft 20 to rotate. The drive winding 36 is an example of the drive unit 12.

[0080] like Figure 5 As shown, in this example, the bearingless motor 30 is composed of an alternating pole bearingless motor.

[0081] <Rotor>

[0082] The rotor 31 has a rotor core 310 and a plurality of permanent magnets 311. The rotor core 310 is made of magnetic material and is cylindrical. For example, the rotor core 310 is made of a laminated core, which is formed by stacking circular electromagnetic steel plates. A shaft hole for inserting the shaft 20 is provided in the center of the rotor core 310. The plurality of permanent magnets 311 are arranged at predetermined angular intervals in the circumferential direction of the rotor 31.

[0083] In this example, four permanent magnets 311 are provided on the rotor 31. The four permanent magnets 311 are arranged at 90° intervals in the circumferential direction of the rotor 31 and are embedded in the outer periphery (near the outer peripheral surface) of the rotor core 310. In addition, the four permanent magnets 311 are formed in an arc shape along the outer peripheral surface of the rotor core 310, and the outer peripheral surface side of the four permanent magnets 311 is the N pole.

[0084] With this structure, the portion of the outer periphery of the rotor core 310 located between the four permanent magnets 311 in the circumferential direction of the rotor 31 is approximately designated as the S pole. It should be noted that the outer periphery of the four permanent magnets 311 can also be configured as the S pole. In this case, the portion of the outer periphery of the rotor core 310 located between the four permanent magnets 311 in the circumferential direction of the rotor 31 is approximately designated as the N pole.

[0085] <stator>

[0086] The stator 32 and rotor 31 are positioned opposite each other with a predetermined air gap. The stator 32 has a stator core 320, a support winding 35, and a drive winding 36. The stator core 320 is made of a magnetic material. For example, the stator core 320 is made of a laminated core, which is formed by stacking annular electromagnetic steel plates. The stator core 320 has a cylindrical back yoke and a plurality of teeth (not shown) arranged on the inner circumferential surface of the back yoke.

[0087] The support winding 35 is wound on the radially outer portion of the teeth of the stator core 320. In this example, the bearingless motor 30 is provided with three types of support windings 35. Specifically, in Figure 5 The support winding 35, surrounded by a thick solid line, constitutes the support winding of phase U. In Figure 5 The support winding 35, surrounded by a thick dashed line, constitutes the support winding for phase V. Figure 5 The support winding 35, surrounded by a thin solid line, constitutes the support winding of phase W.

[0088] The drive winding 36 is wound on the radially inner portion of the teeth of the stator core 320. In this example, the bearingless motor 30 is provided with three types of drive windings 36. Specifically, in Figure 5 The drive winding 36, surrounded by a thick solid line, constitutes the drive winding of the U-phase. Figure 5 The drive winding 36, surrounded by thick dashed lines, constitutes the V-phase drive winding. Figure 5 The drive winding 36, surrounded by a thin solid line, constitutes the drive winding of phase W.

[0089] [Magnetic bearing]

[0090] The magnetic bearing 40 has multiple electromagnets, and the magnetic bearing 40 supports the shaft 20 in a non-contact manner using the electromagnetic force of these multiple electromagnets. The magnetic bearing 40 uses electromagnetic force to control the position of the shaft 20. The magnetic bearing 40 functions as a support portion 11 that supports the shaft 20 in a non-contact manner using electromagnetic force. The magnetic bearing 40 is an example of the support portion 11. In this example, the magnetic bearing 40 includes a radial magnetic bearing 41 and a thrust magnetic bearing 42.

[0091] Radial magnetic bearings

[0092] The radial magnetic bearing 41 uses electromagnetic force to control the radial position of the shaft 20 in a non-contact manner. In this example, the radial magnetic bearing 41 is arranged between the bearingless motor 30 and the measured part 25 of the shaft 20.

[0093] like Figure 6 As shown, in this example, the radial magnetic bearing 41 has a first radial electromagnet 41a, a second radial electromagnet 41b, a third radial electromagnet 41c, and a fourth radial electromagnet 41d. The first radial electromagnet 41a and the second radial electromagnet 41b are opposite to each other across the shaft 20. The third radial electromagnet 41c and the fourth radial electromagnet 41d are opposite to each other across the shaft 20. The relative directions of the third radial electromagnet 41c and the fourth radial electromagnet 41d are orthogonal to the relative directions of the first radial electromagnet 41a and the second radial electromagnet 41b.

[0094] Specifically, the radial magnetic bearing 41 has an iron core 410 and a plurality of windings 415. The iron core 410 is made of magnetic material and is formed in a cylindrical shape. The iron core 410 has a cylindrical back yoke 411 and a plurality of teeth 412 provided on the inner circumferential surface of the back yoke 411. The plurality of windings 415 are wound on the plurality of teeth 412. By winding the windings 415 on the teeth 412, a radial electromagnet is thus constituted.

[0095] By energizing the windings 415 of the first radial electromagnet 41a to the fourth radial electromagnet 41d, an electromagnetic force is generated to support the shaft 20 in a non-contact manner in the radial direction of the radial magnetic bearing 41. Furthermore, by controlling the current flowing through the windings 415 of the first radial electromagnet 41a and the second radial electromagnet 41b, the position of the shaft 20 in the relative direction between the first radial electromagnet 41a and the second radial electromagnet 41b is controlled. Additionally, by controlling the current flowing through the windings 415 of the third radial electromagnet 41c and the fourth radial electromagnet 41d, the position of the shaft 20 in the relative direction between the third radial electromagnet 41c and the fourth radial electromagnet 41d is controlled.

[0096] In this example, the radial magnetic bearing 41 is arranged such that the axis of the radial magnetic bearing 41 coincides with the axis of the stator 32 of the bearingless motor 30.

[0097] Thrust magnetic bearing

[0098] The thrust magnetic bearing 42 uses electromagnetic force to control the axial position of the shaft 20 in a non-contact manner. For example... Figure 2 As shown, in this example, the thrust magnetic bearing 42 has a first thrust electromagnet 42a and a second thrust electromagnet 42b. The first thrust electromagnet 42a and the second thrust electromagnet 42b are opposite each other across the disk portion 21 of the shaft 20.

[0099] Specifically, the first thrust electromagnet 42a has a ring-shaped iron core and a ring-shaped winding. For example, a ring-shaped slot is formed on the iron core of the first thrust electromagnet 42a, and the coil of the first thrust electromagnet 42a is housed in the slot of the iron core. The structure of the second thrust electromagnet 42b is the same as that of the first thrust electromagnet 42a.

[0100] By energizing the windings of the first thrust electromagnet 42a and the second thrust electromagnet 42b, an electromagnetic force is generated to support the shaft 20 in the axial direction of the thrust magnetic bearing 42 in a non-contact manner. Furthermore, by controlling the current flowing through the windings of the first thrust electromagnet 42a and the second thrust electromagnet 42b, the position of the shaft 20 in the relative direction between the first thrust electromagnet 42a and the second thrust electromagnet 42b is controlled.

[0101] [Reference position of the shaft]

[0102] For example, during the operation of the turbo compressor 1, the control support 11 is used to position the shaft 20 at a predetermined reference position. In this example, the reference position is the position of the shaft 20 when its rotation axis coincides with a predetermined reference axis and its axial position becomes a predetermined reference axial position. The reference axis is the axis of the stator 32 of the bearingless motor 30. The reference axial position is the axial position of the shaft 20 when the disc portion 21 of the shaft 20 is located at the center position between the first thrust electromagnet 42a and the second thrust electromagnet 42b of the thrust magnetic bearing 42.

[0103] [Bottom-out bearing]

[0104] When the support portion 11 does not provide non-contact support for the shaft 20, the bottom bearing 50 contacts the shaft 20 and supports the shaft 20 in a manner that allows the shaft 20 to rotate. In this example, the bottom bearing 50 is provided with a radial bottom bearing 51 and a radial thrust bottom bearing 52.

[0105] Radial bottom contact bearing

[0106] The radial bottom bearing 51 is formed in an annular shape. The shaft 20 is inserted into the radial bottom bearing 51. In this example, the radial bottom bearing 51 is arranged between one end of the shaft 20 (the end where the impeller 3 is fixed) and the bearingless motor 30. Specifically, the radial bottom bearing 51 is arranged on the wall 2a of the housing 2.

[0107] The radial bottom bearing 51 is arranged such that its axis coincides with the reference axis (specifically, the axis of the stator 32 of the bearingless motor 30 and the axis of the radial magnetic bearing 41). The inner diameter of the radial bottom bearing 51 is smaller than the inner diameter of the radial magnetic bearing 41 (the diameter of the imaginary cylindrical surface that contacts the tip of the tooth 412).

[0108] With the position of shaft 20 as the reference position, the clearance between the radial thrust bottom bearing 52 and shaft 20 is narrower than the clearance between the radial magnetic bearing 41 and shaft 20 and the clearance between the rotor 31 and stator 32 of the bearingless motor 30.

[0109] In this example, the radial bottom bearing 51 supports the shaft 20 in a rotatable manner by contacting the inner circumferential surface of the radial bottom bearing 51 with the shaft 20, which moves radially along the radial bottom bearing 51. In addition, the contact between the shaft 20 and the inner circumferential surface of the radial bottom bearing 51 avoids the contact between the rotor 31 and the stator 32 of the bearingless motor 30 and the contact between the shaft 20 and the radial magnetic bearing 41.

[0110] Radial thrust bottom-contact bearing

[0111] The radial thrust bottom bearing 52 is formed in an annular shape. The shaft 20 is inserted into the radial thrust bottom bearing 52. In this example, the radial thrust bottom bearing 52 is arranged between the measured portion 25 of the shaft 20 and the thrust magnetic bearing 42. Specifically, the radial thrust bottom bearing 52 is arranged opposite to the recess 22 of the shaft 20.

[0112] The radial thrust bottom bearing 52 is arranged such that its axis coincides with the reference axis (specifically, the axis of the stator 32 of the bearingless motor 30 and the axis of the radial magnetic bearing 41).

[0113] In this example, the radial thrust bottom bearing 52 is opposite to the recess 22 of the shaft 20. Specifically, the inner circumferential surface of the radial thrust bottom bearing 52 is opposite to the bottom surface of the recess 22 of the shaft 20, and the two axial end faces of the radial thrust bottom bearing 52 are opposite to the two side faces of the recess 22 of the shaft 20.

[0114] With the position of shaft 20 as the reference position, the gap between the radial thrust bottom bearing 52 and the bottom surface of the recess 22 of shaft 20 is narrower than the gap between the radial magnetic bearing 41 and shaft 20 and the gap between the rotor 31 and stator 32 of the bearingless motor 30.

[0115] Furthermore, with the position of shaft 20 as the reference position, the clearance between the radial thrust bottom bearing 52 and one side of the recess 22 of shaft 20 is narrower than the clearance between the first thrust electromagnet 42a of thrust magnetic bearing 42 and the disk portion 21 of shaft 20. The clearance between the radial thrust bottom bearing 52 and the other side of the recess 22 of shaft 20 is narrower than the clearance between the second thrust electromagnet 42b of thrust magnetic bearing 42 and the disk portion 21 of shaft 20.

[0116] In this example, the radial thrust bearing 52 supports the shaft 20 in a rotatable manner by contacting the bottom surface of the recess 22 of the shaft 20, which moves radially along the radial thrust bearing 52, with its inner circumferential surface in contact. Furthermore, the contact between the bottom surface of the recess 22 of the shaft 20 and the inner circumferential surface of the radial thrust bearing 52 prevents contact between the rotor 31 and stator 32 of the bearingless motor 30, as well as contact between the shaft 20 and the radial magnetic bearing 41.

[0117] Furthermore, in this example, the radial thrust bottom bearing 52 supports the shaft 20 in a rotatable manner by contacting the axial end face of the radial thrust bottom bearing 52 with the side surface of the recess 22 of the shaft 20, which moves axially along the radial thrust bottom bearing 52. Additionally, the contact between the side surface of the recess 22 of the shaft 20 and the radial thrust bottom bearing 52 prevents the disc portion 21 of the shaft 20 from contacting the thrust magnetic bearing 42.

[0118] [Various sensors]

[0119] In addition, the drive system 10 includes various sensors such as a rotation angle sensor 60, a rotation reference sensor 65, a position sensor 70, and a current sensor (not shown). The rotation angle sensor 60 is an example of a rotation angle detector. The rotation reference sensor 65 is an example of a rotation reference detector.

[0120] It should be noted that the number of rotation angle sensors 60 disposed in the drive system 10 is one. The drive system 10 includes a single rotation angle sensor 60. Similarly, the number of rotation reference sensors 65 disposed in the drive system 10 is one. The drive system 10 includes a single rotation reference sensor 65.

[0121] [Rotation angle sensor]

[0122] The rotation angle sensor 60 is provided for detecting the rotation angle of the shaft 20. The rotation angle sensor 60 outputs a signal corresponding to the rotation angle of the measured part 25 of the shaft 20. The signal output from the rotation angle sensor 60 is a signal whose amplitude changes with the rotation angle of the shaft 20. Hereinafter, the signal output from the rotation angle sensor 60 will be referred to as "first signal S1".

[0123] In this example, the rotation angle sensor 60 is a gap sensor that outputs a signal corresponding to the distance between the rotation angle sensor 60 and the measured part 25. The longer the distance between the gap sensor and the measured part 25, the higher the level (amplitude value) of the signal output from the gap sensor. For example, this gap sensor is an eddy current type gap sensor.

[0124] Specifically, the rotation angle sensor 60 is arranged opposite to the first shaft portion (the shaft portion provided with the first step portion 201) of the measured portion 25 of the shaft 20, and outputs a signal corresponding to the distance between the rotation angle sensor 60 and the first shaft portion of the measured portion 25 of the shaft 20. For example... Figure 3 As shown, with the position of shaft 20 as the reference position, the distance D11 between the first step portion 201 on the first shaft portion and the rotation angle sensor 60 is longer than the distance D10 between the remaining portion of the first shaft portion excluding the first step portion 201 and the rotation angle sensor 60. Therefore, when the rotation angle sensor 60 is opposite to the first step portion 201, the level (amplitude value) of the signal output from the rotation angle sensor 60 becomes higher.

[0125] [Rotating reference sensor]

[0126] The rotation reference sensor 65 is provided for detecting the position of the rotation reference of the shaft 20. The rotation reference sensor 65 outputs a signal corresponding to the position of the rotation reference of the measured part 25 of the shaft 20. The signal output from the rotation reference sensor 65 is a signal whose amplitude changes with the position of the rotation reference of the shaft 20. Hereinafter, the signal output from the rotation reference sensor 65 will be referred to as "first rotation reference signal SS1".

[0127] In this example, the rotating reference sensor 65 is a gap sensor that outputs a signal corresponding to the distance between the rotating reference sensor 65 and the measured part 25. The longer the distance between the gap sensor and the measured part 25, which is the object of measurement, the higher the level (amplitude value) of the signal output from the gap sensor. For example, this gap sensor is an eddy current type gap sensor.

[0128] The rotation reference sensor 65 is arranged opposite to the second shaft portion (the shaft portion provided with the second step portion 202) of the measured portion 25 of the shaft 20, and outputs a signal corresponding to the distance between the rotation reference sensor 65 and the second shaft portion of the measured portion 25 of the shaft 20. For example... Figure 4 As shown, with the position of shaft 20 as the reference position, the distance D21 between the second step portion 202 on the second shaft and the rotation reference sensor 65 is longer than the distance D20 between the remaining portion of the second shaft (excluding the second step portion 202) and the rotation reference sensor 65. Therefore, when the rotation reference sensor 65 is opposite the second step portion 202, the level (amplitude value) of the signal output from the rotation reference sensor 65 becomes higher.

[0129] It should be noted that, in this example, the rotation angle sensor 60 and the rotation reference sensor 65 are arranged vertically below the shaft 20. Furthermore, the rotation angle sensor 60 and the rotation reference sensor 65 are arranged facing the reference axis.

[0130] [Position sensor]

[0131] Position sensor 70 outputs a signal corresponding to the position of shaft 20. In this example, position sensor 70 is a gap sensor that outputs a signal corresponding to the distance between position sensor 70 and shaft 20.

[0132] Specifically, in this example, a radial position sensor 71 and a thrust position sensor 72 are provided as position sensors 70. Both the radial position sensor 71 and the thrust position sensor 72 are gap sensors that output signals corresponding to their respective distances from the object being measured. The longer the distance between the gap sensor and the object being measured, the higher the level (amplitude value) of the signal output from the gap sensor.

[0133] The radial position sensor 71 outputs a signal corresponding to the radial position of the shaft 20. In this example, the radial position sensor 71 is arranged opposite to the shaft portion of the measured portion 25 of the shaft 20 where neither the first step portion 201 nor the second step portion 202 is provided (hereinafter referred to as the "cylindrical surface portion"), and outputs a signal corresponding to the distance between the radial position sensor 71 and the cylindrical surface portion of the measured portion 25 of the shaft 20.

[0134] It should be noted that two types of radial position sensors (a first radial position sensor 71 and a second radial position sensor 71) are provided as radial position sensors 71. The first radial position sensor 71 outputs a signal corresponding to the position of the shaft 20 in the relative direction between the first radial electromagnet 41a and the second radial electromagnet 41b of the radial magnetic bearing 41. The second radial position sensor 71 outputs a signal corresponding to the position of the shaft 20 in the relative direction between the third radial electromagnet 41c and the fourth radial electromagnet 41d of the radial magnetic bearing 41. In addition, the radial position sensors 71 are arranged toward the reference axis.

[0135] The thrust position sensor 72 outputs a signal corresponding to the axial position of the shaft 20. In this example, the thrust position sensor 72 is arranged opposite to the other end face of the shaft 20, and outputs a signal corresponding to the distance between the thrust position sensor 72 and the other end face of the shaft 20.

[0136] [Axis runout component]

[0137] In the first signal S1, which is the output of the rotation angle sensor 60, a shaft runout component CX may be superimposed. The shaft runout component CX is a frequency component corresponding to the runout of the shaft 20, which is supported in a non-contact manner, from a reference position. For example, when in the measurement direction of the rotation angle sensor 60 ( Figure 3 When the axis 20 moves in the left-right direction (as in the example), the amplitude of the first signal S1 will change with the movement of the axis 20. The axis runout component CX is an example of a specific frequency component.

[0138] like Figure 7 As shown, when the amplitude of the first signal S1 varies with the jump of the shaft 20, even assuming that the change in the rotation angle of the shaft 20 is detected by comparing the "amplitude of the first signal S1" with the "threshold Th as a fixed value", there will be cases where the amplitude of the first signal S1 does not exceed the threshold Th during periods when the amplitude of the first signal S1 should exceed the threshold Th. Therefore, it is difficult to detect the change in the rotation angle of the shaft 20 with high precision.

[0139] Such runout of shaft 20 is caused by disturbances such as surge generated in the refrigeration unit RR. In other words, the runout component CX includes a runout component Cs corresponding to disturbances such as surge. Hereinafter, the runout component Cs corresponding to surge will be simply referred to as "runout component Cs".

[0140] It should be noted that surge refers to the phenomenon of periodic fluctuations in the pressure and flow rate of the fluid in the entire flow path containing the turbo compressor 1 due to a sudden change in the load of the turbo compressor 1. For example, if the load of the turbo compressor 1 suddenly changes from a high load to a light load during operation, the flow rate of the fluid (specifically, the refrigerant) in the entire flow path containing the turbo compressor 1 (specifically, the refrigerant circuit RR1) becomes unstable. This causes resonance in the turbo compressor 1 and the pipes constituting the flow path, resulting in periodic fluctuations in the pressure and flow rate of the fluid in the entire flow path containing the turbo compressor 1. Surge may occur when the electric motor installed in the turbo compressor 1 rotates at a high speed (e.g., 100 Hz).

[0141] It should be noted that, in this example, the electric motor installed in the turbo compressor 1 is a bearingless electric motor 30. Hereinafter, the electric motor installed in the turbo compressor 1 will be referred to as "electric motor".

[0142] In the runout of shaft 20 from its reference position, there is also runout of shaft 20 generated at a period corresponding to the rotational frequency of the motor. For example, this runout of shaft 20 is generated at a frequency that is an integer multiple of the rotational frequency of the motor. In other words, the shaft runout component CX contains a shaft runout component Cr corresponding to the rotational frequency of the motor. Hereinafter, the shaft runout component Cr corresponding to the rotational frequency of the motor will be abbreviated as "shaft runout component Cr".

[0143] Next, refer to Figure 8 The shaft runout components Cs and Cr are explained. Figure 8 The diagram illustrates five axis runout components Cr (from the first axis runout component Cr to the fifth axis runout component Cr). The frequencies of the first to fifth axis runout components Cr gradually increase from the first to the fifth axis runout component Cr. The frequency of the k-th axis runout component Cr is k times the motor's rotational frequency fr (where k is an integer). For example, the frequency of the second axis runout component Cr is 2fr, which is twice the motor's rotational frequency fr.

[0144] like Figure 8 As shown, the amplitude of the shaft runout component Cs tends to be larger than that of the shaft runout component Cr. Figure 8In the example, the amplitude of the axis runout component Cs is larger than that of the first axis runout component Cr. The amplitudes of the first to fifth axis runout components Cr tend to gradually decrease from the first to the fifth axis runout component Cr. The axis runout component Cs is the axis runout component CX with the largest amplitude among the multiple axis runout components CX.

[0145] In addition, such as Figure 8 As shown, the frequency fs of the shaft runout component Cs tends to be lower than the frequency of the shaft runout component Cr. Figure 8 In the example, the frequency fs of the shaft runout component Cs is lower than the frequency fr of the first shaft runout component Cr. The shaft runout component Cs is the lowest frequency shaft runout component CX among multiple shaft runout components CX. For example, the frequency fs of the shaft runout component Cs is around a few Hz to tens of Hz. When the motor rotates at high speed (high-speed rotation that may produce surge), the frequency of the first shaft runout component Cr is above 100 Hz.

[0146] Next, refer to Figure 9 The relationship between the frequency fs of the shaft runout component Cs and the frequency f1 of the first frequency component C1 will be explained. The first frequency component C1 is the frequency component contained in the first signal S1, and it is the frequency component corresponding to the change in the rotation angle of the shaft 20. In this example, the frequency f1 of the first frequency component C1 is the frequency obtained by multiplying the "rotation frequency of the motor" by the "number of first step portions 201 provided on the measured portion 25 of the shaft 20".

[0147] The aforementioned "rotation frequency of the motor" corresponds to the "rotation frequency of the shaft 20 driven to rotate by the drive unit 12". The aforementioned "number of first step portions 201 provided on the measured portion 25 of the shaft 20" corresponds to the number of "shapes of the measured portion 25". The aforementioned "frequency f1 of the first frequency component C1" corresponds to both the "rotation frequency of the shaft 20 driven to rotate by the drive unit 12" and the "shape of the measured portion 25".

[0148] It should be noted that, in Figure 9 In the example, the lower limit of the variation range B1 of the frequency f1 of the first frequency component C1 is exemplified as "the frequency f1 of the first frequency component C1". In other words, frequency components with frequencies above the frequency f1 of the first frequency component C1 are frequency components corresponding to the change in the rotation angle of the shaft 20, and are frequency components that can be used to detect the change in the rotation angle of the shaft 20.

[0149] like Figure 9As shown, the frequency fs of the shaft runout component Cs is smaller than the frequency f1 of the first frequency component C1. For example, when the motor rotates at high speed (high-speed rotation that may cause surge), the motor's rotational frequency is "100Hz", and the number of first step portions 201 provided on the measured portion 25 of the shaft 20 is "30", then the frequency f1 of the first frequency component C1 is "3000Hz (=100Hz×30)". The frequency fs of the shaft runout component Cs is approximately a few Hz to tens of Hz.

[0150] It should be noted that the frequency of the shaft runout component Cs is primarily the frequency corresponding to the resonant frequency of the components constituting the flow path including the turbine compressor 1 (in this example, the turbine compressor 1 constituting the refrigerant circuit RR1, the heat exchanger RR5, the evaporator RR7, the pipes, etc.). This resonant frequency is determined by the construction, weight, density, volume, and size of the components constituting the flow path including the turbine compressor 1. It is assumed that if the refrigeration unit RR is miniaturized or made lighter, the resonant frequency tends to increase, but there is also a tendency for the motor's rotational frequency to increase to ensure power. Therefore, the relationship that "the frequency fs of the shaft runout component Cs is lower than the frequency f1 of the first frequency component C1" will be maintained.

[0151] [Signal Processing Department]

[0152] Additionally, the drive system 10 includes a signal processing unit 80. The signal processing unit 80 performs a reduction process on a first signal S1 output from the rotation angle sensor 60, thereby generating a second signal S2. The reduction process is used to reduce the shaft runout component CX contained in the first signal S1.

[0153] Specifically, the reduction processing is used to reduce the frequency components within the shaft runout frequency band BX contained in the first signal S1. For example... Figure 9 As shown, the shaft jitter band BX is a frequency band that includes the shaft jitter component CX, and is a frequency band lower than the frequency f1 of the first frequency component C1. The shaft jitter band BX is an example of a specific frequency band that includes a specific frequency component.

[0154] In this example, the axial runout component CX that is reduced in the reduction process of the signal processing unit 80 is the axial runout component Cs. The reduction process performed by the signal processing unit 80 is a process for reducing at least the axial runout component Cs among the multiple axial runout components CX that may be superimposed on the first signal S1. Figure 8 As shown, the axis runout component Cs is the axis runout component CX with the largest amplitude among multiple axis runout components CX. Additionally, as... Figure 9 As shown, the shaft runout band BX is the frequency band containing the frequency fs of the shaft runout component Cs. The upper limit of the shaft runout band BX is preferably at least five times the upper limit of the frequency fs of the shaft runout component Cs.

[0155] For example, when the motor rotates at high speed (high-speed rotation that may cause surge), the motor's rotational frequency is "100Hz", and the number of first step portions 201 provided on the measured portion 25 of the shaft 20 is "30", then the frequency f1 of the first frequency component C1 is "3000Hz (=100Hz×30)". Since the frequency fs of the shaft runout component Cs is around a few Hz to tens of Hz, the shaft runout frequency band BX is a frequency band "below 500Hz".

[0156] [Internal structure of the signal processing unit]

[0157] Next, refer to Figure 10 The structure of the signal processing unit 80 will be described below. The signal processing unit 80 includes a first processing unit 81 and a second processing unit 82.

[0158] The first processing unit 81 generates a threshold Th1 corresponding to the shaft runout component CX based on the first signal S1. In this example, the first processing unit 81 generates the threshold Th1 by extracting the frequency component within the shaft runout frequency band BX contained in the first signal S1.

[0159] Specifically, the first processing unit 81 is composed of a low-pass filter 810. The low-pass filter 810 allows frequency components within the shaft runout frequency band BX contained in the first signal S1 to pass through, while reducing frequency components in other frequency bands besides the shaft runout frequency band BX contained in the first signal S1. The first signal S1, having passed through the low-pass filter 810, is output as a threshold Th1 corresponding to the shaft runout component CX. Figure 11 As shown, the threshold Th1 varies with a frequency corresponding to the frequency of the axis runout component CX.

[0160] The second processing unit 82 generates a second signal S2 by comparing the amplitude of the first signal S1 with a threshold Th1 generated by the first processing unit 81. Specifically, the second processing unit 82 is composed of a comparator 820 that takes the first signal S1 and the threshold Th1 as inputs. The output signal of the comparator 820 is output as the second signal S2.

[0161] like Figure 11 As shown, comparator 820 compares the first signal S1 with a threshold Th1. When the amplitude of the first signal S1 exceeds the threshold Th1, comparator 820 changes the signal level of the second signal S2 from low to high; when the amplitude of the first signal S1 is lower than the threshold Th1, comparator 820 changes the signal level of the second signal S2 from high to low. This generates a second signal S2 with a reduced shaft runout component CX. In this example, the first signal S1 is an analog signal, and the second signal S2 is a pulse signal (rectangular wave signal).

[0162] [Control Department]

[0163] Additionally, the drive system 10 includes a control unit 90. The control unit 90 is connected to various sensors installed in the drive system 10 via signal lines, and receives signals output from these sensors. The control unit 90 is also connected to the components of the drive system 10 via signal lines, and controls these components. In this example, the control unit 90 is connected to the bearingless motor 30, the radial magnetic bearing 41, the thrust magnetic bearing 42, the rotation angle sensor 60, the rotation reference sensor 65, the radial position sensor 71, and the thrust position sensor 72 via signal lines.

[0164] In addition, the control unit 90 receives various instructions, such as a start-up instruction, to begin operation. Furthermore, the control unit 90 performs various processing based on these instructions and signals output from various sensors. In this example, the control unit 90 performs buoyancy position control, rotation drive control, and rotation angle detection processing.

[0165] For example, the control unit 90 includes a processor, a memory, a power supply, etc. The memory is electrically connected to the processor and stores programs for making the processor work, and the power supply provides power according to the instructions of the processor.

[0166] [Floating position control]

[0167] While the support 11 is providing non-contact support for the shaft 20, the control unit 90 performs float position control. In float position control, the control unit 90 detects the position of the shaft 20 based on the signal output from the position sensor 70, and controls the support 11 to make the position of the shaft 20 a predetermined reference position.

[0168] Specifically, the control unit 90 detects the radial position (position on the rotation axis) of the shaft 20 based on the signal output from the radial position sensor 71, and controls the current flowing through the support winding 35 of the bearingless motor 30 and the current flowing through the winding 415 of the radial magnetic bearing 41, so that the radial position of the shaft 20 becomes a predetermined reference radial position (position on the reference axis). Additionally, the control unit 90 detects the axial position of the shaft 20 based on the signal output from the thrust position sensor 72, and controls the current flowing through the winding of the thrust magnetic bearing 42, so that the axial position of the shaft 20 becomes a predetermined reference axial position.

[0169] Rotary drive control

[0170] When the shaft 20 is being supported non-contactly by the support part 11 and driven to rotate by the drive part 12, the control part 90 performs rotation drive control. In rotation drive control, the control part 90 controls the drive part 12 to maintain the rotation speed of the shaft 20 at the target rotation speed.

[0171] Specifically, the control unit 90 detects the rotational speed of the shaft 20 based on the outputs of various sensors installed in the drive system 10, and controls the current flowing through the drive winding 36 of the bearingless motor 30 so that the rotational speed of the shaft 20 becomes the target rotational speed.

[0172] [Rotation Angle Detection and Processing]

[0173] While the shaft 20 is being driven to rotate by the drive unit 12, the control unit 90 performs rotation angle detection processing. In this rotation angle detection processing, the control unit 90 detects the rotation angle of the shaft 20 based on a second signal S2 generated by the signal processing unit 80. In this example, during the rotation angle detection processing, the control unit 90 detects the rotation angle of the shaft 20 based on the second signal S2 generated by the signal processing unit 80 and a first rotation reference signal SS1 output from the rotation reference sensor 65.

[0174] For example, rotation angle detection processing is performed in parallel with buoyancy position control and rotation drive control. The rotation angle of shaft 20 detected in the rotation angle detection processing is used in buoyancy position control and rotation drive control. The control unit 90 performs buoyancy position control and rotation drive control based on the rotation angle of shaft 20 detected in the rotation angle detection processing.

[0175] Next, refer to Figure 12 This section provides a detailed explanation of the rotation angle detection process. Figure 12 In order to simplify the illustration, we take the case where the first signal S1 does not have the superimposed axis runout component CX and the threshold Th1 is constant as an example.

[0176] like Figure 12 As shown, the signal processing unit 80 compares the level (amplitude value) of the first signal S1 with a threshold Th1, and generates a second signal S2 based on the comparison result. When the level of the first signal S1 exceeds the threshold Th1, the signal processing unit 80 changes the level of the second signal S2 from low to high; when the level of the first signal S1 is lower than the threshold Th1, the signal processing unit 80 changes the level of the second signal S2 from high to low.

[0177] It should be noted that the threshold Th1 is preferably set to be lower than the level of the first signal S1 when the first step portion 201 on the first shaft portion of the measured portion 25 of the shaft 20 is opposite to the rotation angle sensor 60, and higher than the level of the first signal S1 when the remaining portion of the first shaft portion of the measured portion 25 of the shaft 20, excluding the first step portion 201, is opposite to the rotation angle sensor 60.

[0178] Furthermore, the control unit 90 compares the level (amplitude value) of the first rotation reference signal SS1 output from the rotation reference sensor 65 with a predetermined rotation reference threshold Th2, and generates a second rotation reference signal SS2 based on the comparison result. When the level of the first rotation reference signal SS1 exceeds the rotation reference threshold Th2, the control unit 90 changes the level of the second rotation reference signal SS2 from low to high; when the level of the first rotation reference signal SS1 is lower than the rotation reference threshold Th2, the control unit 90 changes the level of the second rotation reference signal SS2 from high to low. In this example, the first rotation reference signal SS1 is an analog signal, and the second rotation reference signal SS2 is a pulse signal (rectangular wave signal).

[0179] It should be noted that the rotation reference threshold Th2 is preferably set to be lower than the level of the first rotation reference signal SS1 when the second step portion 202 on the second shaft portion of the measured portion 25 of the shaft 20 is opposite to the rotation reference sensor 65, and higher than the level of the first rotation reference signal SS1 when the remaining portion of the second shaft portion of the measured portion 25 of the shaft 20, excluding the second step portion 202, is opposite to the rotation reference sensor 65.

[0180] Furthermore, the control unit 90 detects the rotation angle of the shaft 20 based on the "change in the rotation angle of the shaft 20" shown by the second signal S2 and the "change in the position of the rotation reference of the shaft 20" shown by the second rotation reference signal SS2.

[0181] Specifically, when the level of the second rotation reference signal SS2 changes from low to high, the control unit 90 sets the rotation angle of the shaft 20 to "0°". Furthermore, whenever the level of the second signal S2 changes from low to high, the control unit 90 increases the rotation angle of the shaft 20 by a predetermined amount (45° in this example). In this way, the rotation angle of the shaft 20 is detected.

[0182] [Effects of the Implementation Method]

[0183] As described above, the drive system 10 of this embodiment includes a single rotation angle sensor 60, a signal processing unit 80, and a control unit 90. The rotation angle sensor 60 outputs a first signal S1, the amplitude of which varies with the rotation angle of the shaft 20. This first signal S1 may contain a shaft runout component CX (a specific frequency component). The shaft runout component CX is a frequency component corresponding to the runout of the shaft 20, which is supported in a non-contact manner, from a reference position. Based on the first signal S1 output from the rotation angle sensor 60, the signal processing unit 80 performs a reduction process to decrease the shaft runout component CX (the specific frequency component) included in the first signal S1, thereby generating a second signal S2. The control unit 90 controls the support unit 11 and the drive unit 12. Furthermore, the control unit 90 detects the rotation angle of the shaft 20 based on the second signal S2 generated by the signal processing unit 80. The frequency of the shaft runout component CX (specific frequency component) that is reduced in the reduction process is lower than the frequency of the first frequency component C1, which is the AC frequency component of the non-DC component, the frequency component contained in the first signal S1, and the frequency component corresponding to the change in the rotation angle of the shaft 20.

[0184] Based on the above structure, only a single rotation angle sensor 60 is needed to detect changes in the rotation angle of the shaft 20, thus reducing the number of sensors required to detect changes in the rotation angle of the shaft 20.

[0185] Furthermore, in the drive system 10 of the embodiment, a reduction process is performed based on the first signal S1 output from the rotation angle sensor 60, thereby generating a second signal S2 from the signal whose shaft runout component CX is reduced (a signal whose amplitude changes with the rotation angle of the shaft 20). Thus, the rotation angle of the shaft 20 can be accurately detected based on the second signal S2.

[0186] It should be noted that in the device of Patent Document 1, two sensors (rotation detector and shaft runout detector) are provided to detect changes in the rotation angle of the rotating body. Therefore, due to differences in installation tolerances between these sensors or differences in output characteristics caused by individual variations, it may be impossible to accurately remove the shaft runout component from the signal component of the rotation detection signal.

[0187] On the other hand, in the drive system 10 of the embodiment, only a single rotation angle sensor 60 is required to detect the change in the rotation angle of the shaft 20, thus avoiding the influences such as those in Patent Document 1 (the influence caused by differences in the installation tolerances between sensors or differences in output characteristics caused by individual differences).

[0188] Furthermore, in the drive system 10 of the embodiment, the shaft runout component CX (specific frequency component) reduced during the reduction process includes the shaft runout component CX with the largest amplitude among a plurality of shaft runout components CX corresponding to the runout of the shaft 20 supported in a non-contact manner from the reference position. It should be noted that "the shaft runout component CX with the largest amplitude among a plurality of shaft runout components CX" is an example of "the frequency component with the largest amplitude among frequency components with a frequency lower than the frequency of the first frequency component C1".

[0189] Based on the above structure, in the reduction process, the "axis runout component CX with the largest amplitude" among the multiple axis runout components CX that may be superimposed on the first signal S1 can be reduced. As a result, the second signal S2 can be generated with high precision in a manner in which the amplitude changes with the rotation angle of the axis 20, and thus the rotation angle of the axis 20 based on the second signal S2 can be accurately detected.

[0190] Furthermore, in the drive system 10 of the embodiment, the frequency of the shaft runout component CX (specific frequency component) that is reduced in the reduction process is lower than the frequency of the first frequency component C1, which is the frequency component contained in the first signal S1 and is the frequency component corresponding to the change in the rotation angle of the shaft 20.

[0191] According to the above structure, in the reduction process, it is possible to reduce the frequency of "axis runout components CX with frequencies lower than the frequency of the first frequency component C1" among the multiple axis runout components CX that may be superimposed on the first signal S1. Therefore, it is possible to avoid reducing frequency components with frequencies higher than the first frequency component C1 (frequency components that may be used to detect changes in the rotation angle of the axis 20) in the reduction process. As a result, the second signal S2 can be generated with high precision in a manner where the amplitude changes with the rotation angle of the axis 20, thus enabling accurate detection of the rotation angle of the axis 20 based on the second signal S2.

[0192] Furthermore, in the drive system 10 of the embodiment, the reduction processing is a process for reducing the frequency components within the shaft runout frequency band BX (specific frequency band) included in the first signal S1. The shaft runout frequency band BX (specific frequency band) is a frequency band that includes the frequency of the shaft runout component CX (specific frequency component), and is a frequency band with a frequency lower than that of the first frequency component C1.

[0193] According to the above structure, frequency components with frequencies higher than the first frequency component C1 (frequency components that may be used to detect changes in the rotation angle of the shaft 20) can be avoided from being reduced during the reduction process. As a result, the second signal S2 can be generated with high precision in a manner in which the amplitude changes with the rotation angle of the shaft 20, and thus the detection of the rotation angle of the shaft 20 based on the second signal S2 can be performed accurately.

[0194] Furthermore, in the drive system 10 of this embodiment, the shaft 20 has a measured portion 25. The rotation angle sensor 60 is a gap sensor that outputs a signal whose amplitude varies with the distance between the rotation angle sensor 60 and the measured portion 25. The measured portion 25 is configured such that the distance between the measured portion 25 and the rotation angle sensor 60 varies with the rotation angle of the shaft 20. The first frequency component C1 is a frequency corresponding to the rotation frequency of the shaft 20 driven by the drive unit 12 and the shape of the measured portion 25.

[0195] According to the above structure, when the rotation angle of shaft 20 changes, the distance between the measured part 25 of shaft 20 and the rotation angle detector 60 changes, and as a result, the first signal S1 output from the rotation angle detector 60 changes. Thus, the first signal S1 output from the rotation angle detector 60 can be made into a "signal whose amplitude changes with the rotation angle of shaft 20".

[0196] Furthermore, in the drive system 10 of the embodiment, the signal processing unit 80 has a first processing unit 81 and a second processing unit 82. The first processing unit 81 generates a threshold Th1 corresponding to the shaft runout component CX (a specific frequency component) based on the first signal S1. The second processing unit 82 generates a second signal S2 by comparing the amplitude of the first signal S1 with the threshold Th1 generated by the first processing unit 81.

[0197] According to the above structure, by comparing the amplitude of the first signal S1 with the threshold Th1 corresponding to the shaft runout component CX, the "signal in which the shaft runout component CX is reduced" obtained by the comparison can be used as the second signal S2.

[0198] In addition, in the drive system 10 of the embodiment, the first processing unit 81 generates a threshold Th1 by extracting the frequency components in the shaft runout frequency band BX (specific frequency band) contained in the first signal S1.

[0199] According to the above structure, by extracting the frequency component within the shaft runout frequency band BX from the first signal S1, the extracted frequency component can be used as "threshold Th1 corresponding to the shaft runout component CX".

[0200] (Modification 1 of the implementation method)

[0201] In the drive system 10 of the modified embodiment 1, the structure of the signal processing unit 80 is different from that of the drive system 10 of the embodiment, but the other structures are the same as those of the drive system 10 of the embodiment.

[0202] Figure 13The structure of the signal processing unit 80 in Modification 1 of the embodiment is illustrated. In Modification 1 of the embodiment, the first processing unit 81 selectively performs a first extraction process and a second extraction process. The first extraction process generates a threshold Th1 by extracting the frequency component within the shaft jump frequency band BX (specific frequency band) contained in the first signal S1. The second extraction process generates the threshold Th1 by extracting the DC component from the first signal S1.

[0203] like Figure 13 As shown, in a modified example 1 of the embodiment, the first processing unit 81 is composed of a first low-pass filter 811, a second low-pass filter 812, and a switch 813.

[0204] The first low-pass filter 811 allows the frequency components within the shaft runout frequency band BX contained in the first signal S1 to pass through, while reducing the frequency components of other frequency bands besides the shaft runout frequency band BX contained in the first signal S1. The first signal S1, which has passed through the first low-pass filter 811, i.e., the first low-pass signal SL1, changes frequency corresponding to the frequency of the shaft runout component CX. The processing performed by the first low-pass filter 811 corresponds to the first extraction processing.

[0205] The second low-pass filter 812 allows the DC component contained in the first signal S1 to pass through, reducing the remaining frequency components contained in the first signal S1. The first signal S1 that has passed through the second low-pass filter 812, i.e., the second low-pass signal SL2, is a constant or approximately constant value. The processing performed by the second low-pass filter 812 corresponds to the second extraction processing.

[0206] For example, the cutoff frequency of the second low-pass filter 812 is lower than the cutoff frequency of the first low-pass filter 811. The second low-pass filter 812 extracts the frequency components in the first signal S1 that are "with an upper limit frequency lower than the upper limit frequency of the shaft runout frequency band BX and contain a DC component".

[0207] Switch 813 selects either "the first low-pass signal SL1 output from the first low-pass filter 811" or "the second low-pass signal SL2 output from the second low-pass filter 812", and supplies the selected signal as the threshold Th1 to the second processing unit 82. The signal selection performed by switch 813 can also be controlled by control unit 90.

[0208] For example, the signal selection performed by switch 813 is based on the operating conditions of the drive system 10, such as the rotational speed of the motor (in this example, the bearingless motor 30) installed in the turbo compressor 1. Specifically, when the motor installed in the turbo compressor 1 is rotating at a high speed (e.g., a rotational frequency higher than 100Hz that may cause surge), switch 813 selects a first low-pass signal SL1 as the threshold Th1; when the motor installed in the turbo compressor 1 is rotating at a low speed (e.g., a rotational frequency lower than 100Hz that will not cause surge), switch 813 selects a second low-pass signal SL2 as the threshold Th1.

[0209] As described above, in the drive system 10 of the modified embodiment 1, the threshold Th1 can be appropriately switched according to the operating conditions of the drive system 10 (e.g., the rotational speed of the electric motor installed in the turbo compressor 1).

[0210] (Modification 2 of the implementation method)

[0211] In the drive system 10 of the modified embodiment 2, the structure of the signal processing unit 80 is different from that of the drive system 10 of the embodiment, but the other structures are the same as those of the drive system 10 of the embodiment.

[0212] Figure 14 The structure of the signal processing unit 80 in Modification 2 of the embodiment is illustrated. In Modification 2 of the embodiment, the first processing unit 81 generates the threshold Th1 by repeatedly performing a process of setting a value derived from the amplitude of the first signal S1 within a predetermined period (specifically, the average value of the amplitude of the first signal S1 within the predetermined period) as the threshold Th1.

[0213] like Figure 14 As shown, in variation 2 of the embodiment, the first processing unit 81 is composed of an extraction circuit 830. The extraction circuit 830 extracts the average value of the first signal S1 in the immediately preceding second period T2 every first period T1, and supplies the extracted average value as a threshold Th1 to the second processing unit 82.

[0214] like Figure 15 As shown, the extraction circuit 830 in the kth first period T1 (k) The first period T1 is exported internally. (k) The kth second period T2 immediately preceding (k) The average value of the first signal S1 within the range is used as the derived average value as the k-th threshold Th1. (k) Supply to the second processing unit 82. The k-th threshold Th1 (k) During the k-th first period T1 (k)The k+1th first period T1 immediately following (k+1) The threshold Th1 is used internally. By repeatedly performing this process every first period T1, the threshold Th1 changes at a frequency corresponding to the frequency of the axis jitter component CX (a specific frequency component).

[0215] For example, the duration of the first period T1 is set to the duration corresponding to 1 / 4 of the cycle of the first signal S1, and the duration of the second period T2 is set to the duration corresponding to 1 cycle of the first signal S1.

[0216] As described above, in the drive system 10 of the modified embodiment 2, by repeatedly performing the "process of setting the value derived from the amplitude of the first signal S1 within a predetermined period as the threshold Th1", the threshold Th1 can be changed accordingly with the shaft runout component CX. Thus, a threshold Th1 corresponding to the shaft runout component CX can be generated.

[0217] (Modification 3 of the implementation method)

[0218] In the drive system 10 of the modified embodiment 3, the structure of the signal processing unit 80 is different from that of the drive system 10 of the embodiment, but the other structures are the same as those of the drive system 10 of the embodiment.

[0219] Figure 16 The structure of the signal processing unit 80 in Modification 3 of the embodiment is illustrated. In Modification 3 of the embodiment, the first processing unit 81 generates the threshold Th1 by repeatedly performing a process of setting a value derived from the amplitude of the first signal S1 within a predetermined period (specifically, the maximum value of the amplitude of the first signal S1 within the predetermined period) as the threshold Th1.

[0220] like Figure 16 As shown, in variation 3 of the embodiment, the first processing unit 81 is composed of a peak holding circuit 840 and a subtraction circuit 841.

[0221] like Figure 17As shown, the peak holding circuit 840 detects and holds the maximum value of the amplitude of the first signal S1 arriving at predetermined intervals, i.e., the "peak value," and outputs a peak signal SP representing the held peak value. The level (amplitude value) of the peak signal SP corresponds to the peak value. The subtraction circuit 841 reduces the level of the peak signal SP output from the peak holding circuit 840 by a predetermined amount. For example, the predetermined amount is set to half the difference between the maximum and minimum values ​​of the amplitude of the first signal S1 without superimposed shaft runout component CX (specific frequency component). The output signal of the subtraction circuit 841 is supplied to the second processing unit 82 as a threshold Th1. By repeatedly performing this processing at predetermined intervals, the threshold Th1 changes at a frequency corresponding to the frequency of the shaft runout component CX (specific frequency component).

[0222] As described above, in the drive system 10 of the modified embodiment 3, similarly to the drive system 10 of the modified embodiment 2, by repeatedly performing the "process of setting the value derived from the amplitude of the first signal S1 within a predetermined period as the threshold Th1", the threshold Th1 can be changed accordingly with the shaft runout component CX. Thus, a threshold Th1 corresponding to the shaft runout component CX can be generated.

[0223] (Modification 4 of the implementation method)

[0224] In the drive system 10 of the modified embodiment 4, the structure of the signal processing unit 80 is different from that of the drive system 10 of the embodiment, but the other structures are the same as those of the drive system 10 of the embodiment.

[0225] Figure 18 The structure of the signal processing unit 80 in Modification 4 of the embodiment is illustrated. In Modification 4 of the embodiment, the first processing unit 81 generates the threshold Th1 by repeatedly performing a process of setting a value derived from the amplitude of the first signal S1 within a predetermined period (specifically, the minimum value of the amplitude of the first signal S1 within the predetermined period) as the threshold Th1.

[0226] like Figure 18 As shown, in variation 4 of the embodiment, the first processing unit 81 is composed of a base value holding circuit 850 and an addition circuit 851.

[0227] like Figure 19As shown, the minimum amplitude of the first signal S1 arriving at predetermined intervals, i.e., the "minimum value," is detected and held, and outputs a minimum value signal SB representing the held minimum value. The level (amplitude value) of the minimum value signal SB corresponds to the minimum value. The adder circuit 851 increases the level of the minimum value signal SB output from the minimum value holding circuit 850 by a predetermined amount. For example, the predetermined amount is set to half the difference between the maximum and minimum amplitudes of the first signal S1 without the superimposed shaft runout component CX (a specific frequency component). The output signal of the adder circuit 851 is supplied to the second processing unit 82 as a threshold Th1. By repeatedly performing this processing at predetermined intervals, the threshold Th1 changes at a frequency corresponding to the frequency of the shaft runout component CX (a specific frequency component).

[0228] As described above, in the drive system 10 of Embodiment Modification 4, similarly to the drive system 10 of Embodiment Modification 2, by repeatedly performing the "process of setting the value derived from the amplitude of the first signal S1 within a predetermined period as the threshold Th1", the threshold Th1 can be changed accordingly with the shaft runout component CX. Thus, a threshold Th1 corresponding to the shaft runout component CX can be generated.

[0229] (Modification 5 of the implementation method)

[0230] In the drive system 10 of the modified embodiment 5, the structure of the signal processing unit 80 is different from that of the drive system 10 of the embodiment, but the other structures are the same as those of the drive system 10 of the embodiment.

[0231] Figure 20 The structure of the signal processing unit 80 in the modified embodiment 5 is illustrated. In the modified embodiment 5, the first processing unit 81 generates the threshold Th1 by repeatedly performing a process of setting a value derived from the amplitude of the first signal S1 within a predetermined period (specifically, the maximum and minimum values ​​of the amplitude of the first signal S1 within the predetermined period) as the threshold Th1.

[0232] like Figure 20 As shown, in variation 5 of the embodiment, the first processing unit 81 is composed of a peak holding circuit 840, a bottom holding circuit 850, and an averaging circuit 860.

[0233] like Figure 21 As shown, the averaging circuit 860 derives the average value of the peak signal SP output from the peak holding circuit 840 and the average value of the bottom signal SB output from the bottom holding circuit 850, and supplies this derived average value as a threshold Th1 to the second processing unit 82. By repeatedly performing this process at predetermined intervals, the threshold Th1 changes at a frequency corresponding to the frequency of the shaft runout component CX (a specific frequency component).

[0234] As described above, in the drive system 10 of Embodiment Modification 5, similarly to the drive system 10 of Embodiment Modification 2, by repeatedly performing the "process of setting the value derived from the amplitude of the first signal S1 within a predetermined period as the threshold Th1", the threshold Th1 can be changed accordingly with the shaft runout component CX. Thus, a threshold Th1 corresponding to the shaft runout component CX can be generated.

[0235] (Modification 6 of the implementation method)

[0236] In the drive system 10 of the modified embodiment 6, the structure of the signal processing unit 80 is different from that of the drive system 10 of the embodiment, but the other structures are the same as those of the drive system 10 of the embodiment.

[0237] Figure 22 The structure of the signal processing unit 80 in Modification 6 of the embodiment is illustrated. In Modification 6 of the embodiment, the first processing unit 81 reduces the axial runout component CX (specific frequency component) included in the first signal S1. The second processing unit 82 generates the second signal S2 by comparing the signal obtained by the first processing unit 81 with a threshold Th1.

[0238] like Figure 22 As shown, in Variation 6 of the embodiment, the first processing unit 81 is configured with a high-pass filter 870. The second processing unit 82 is configured with a comparator 820. The high-pass filter 870 reduces the frequency components within the shaft jitter frequency band BX (a specific frequency band) included in the first signal S1, allowing frequency components of other frequency bands besides the shaft jitter frequency band BX included in the first signal S1 to pass through. The first signal S1 that has passed through the high-pass filter 870, i.e., the high-pass signal SH, is supplied to the second processing unit 82.

[0239] Furthermore, in variation 6 of the embodiment, the second processing unit 82 is composed of a comparator 820 that receives a high-pass signal SH and a threshold Th1 as inputs. The output signal of the comparator 820 is output as a second signal S2. The threshold Th1 is a constant value (fixed value).

[0240] like Figure 23 As shown, comparator 820 compares the high-pass signal SH with a threshold Th1. When the amplitude of the high-pass signal SH exceeds the threshold Th1, comparator 820 changes the signal level of the second signal S2 from low to high; when the amplitude of the high-pass signal SH is lower than the threshold Th1, comparator 820 changes the signal level of the second signal S2 from high to low. This generates a second signal S2 with a reduced shaft runout component CX (a specific frequency component). In this example, the high-pass signal SH is an analog signal, and the second signal S2 is a pulse signal (rectangular wave signal).

[0241] As described above, in the drive system 10 of the modified embodiment 6, by comparing the amplitude of the first signal S1 in which the shaft runout component CX is reduced with the threshold Th1, the "signal in which the shaft runout component CX is reduced" obtained by the comparison can be used as the second signal S2.

[0242] (Other implementation methods)

[0243] The above description uses the case where the drive system 10 includes a bearingless motor 30 and magnetic bearings 40 (specifically, radial magnetic bearings 41 and thrust magnetic bearings 42) as an example, but it is not limited to this.

[0244] For example, the drive system 10 may also include another bearingless motor 30 in place of the radial magnetic bearing 41. The support winding 35 of the bearingless motor 30 functions as a support portion 11. The drive winding 36 of the bearingless motor 30 functions as a drive portion 12.

[0245] Alternatively, the drive system 10 may include another radial magnetic bearing 41 and an electric motor that drives the rotation of shaft 20 only, instead of the bearingless motor 30. The radial magnetic bearing 41 functions as a support 11. The electric motor functions as a drive 12.

[0246] Furthermore, the above explanation uses the case where the first step portion 201 is concave as an example, but it is not limited to this. For example, the first step portion 201 can also be convex. The same applies to the second step portion 202.

[0247] Furthermore, while the above description uses an eddy current type gap sensor as an example, it is not limited to this. For example, the gap sensor can also be an ultrasonic type, an optical type, or other types of gap sensors. Additionally, if the measured part 25 of the shaft 20 includes a magnetic material, the rotation angle sensor 60 can also be a Hall sensor, an MR sensor, or other magnetic sensor.

[0248] Furthermore, the description of the embodiments uses the example of a "first shaft portion having multiple first step portions 201" and a "second shaft portion having second step portions 202" being adjacent in the axial direction of the shaft 20, but it is not limited to this. For example, the second shaft portion may also be arranged at a position away from the first shaft portion.

[0249] Furthermore, as described above, the thrust magnetic bearing 42 can also be divided into a front thrust magnetic bearing and a rear thrust magnetic bearing. In this case, the front thrust magnetic bearing is arranged on the impeller side (front side) in the axial direction of the shaft 20, and the rear thrust magnetic bearing is arranged on the side opposite to the impeller side in the axial direction of the shaft 20 (rear side).

[0250] Additionally, in the above description, if the method is sensorless (the method of detecting the position of the shaft 20 without using the position sensor 70), the position sensor 70 can also be omitted.

[0251] Furthermore, the above description illustrates an example where the impeller 3 is positioned at the front end of the shaft 20 along the axial direction, and the radial bottom bearing 51, the bearingless motor 30, the radial magnetic bearing 41, the radial thrust bottom bearing 52, and the thrust magnetic bearing 42 are arranged sequentially from the impeller 3 towards the rear end along the axial direction. However, this is not the only possible arrangement. For example, the thrust magnetic bearing 42 can also be positioned on the impeller side (front side) along the axial direction. The other components are similarly arranged arbitrarily.

[0252] Furthermore, in the above description, the impeller 3 is not limited to one; there can be two or more. Additionally, the installation position of the impeller 3 is not limited to the front end of the shaft 20; it can also be the rear end of the shaft 20, or a position other than the end of the shaft 20. For example, two impellers 3 can be continuously installed at the front end of the shaft 20, or one impeller 3 can be installed at the front end and one at the rear end of the shaft 20.

[0253] Alternatively, as described above, two or more bearingless motors 30 can be provided for shaft 20. Furthermore, the low-pass filter and high-pass filter can also be band-pass filters or notch filters.

[0254] Furthermore, while the above explanation cited the case where the specific frequency component is the shaft runout component CX as an example, it is not limited to this. Other examples of specific frequency components include: frequency components corresponding to noise generated in the output of the rotation angle sensor 60 due to changes in the external magnetic or electric field of the rotation angle sensor 60 (e.g., a gap sensor); and frequency components corresponding to noise generated in the output of the rotation angle sensor 60 due to noise (e.g., common-mode noise) generated by the inverter (not shown) of the drive support 11 or drive unit 12. It should be noted that the aforementioned inverter is, for example, included in the power supply unit that constitutes part of the control unit 90.

[0255] Furthermore, as described above, the signal processing unit 80 may also be constructed using dedicated circuitry. Alternatively, the signal processing unit 80 may also be constructed, similarly to the control unit 90, using a processor and a memory electrically connected to the processor and storing programs for operating the processor. For example, the signal processing unit 80 may also be included within the control unit 90. In other words, the signal processing unit 80 may also be implemented as part of the functionality of the control unit 90.

[0256] The embodiments and variations have been described above. However, it should be understood that various changes can be made to the methods and specific circumstances without departing from the spirit and scope of the claims. Furthermore, the elements involved in the above embodiments, variations, and other embodiments can be appropriately combined or substituted.

[0257] -Industry Applicability-

[0258] In summary, this disclosure is useful as a drive system, a turbo compressor, and a refrigeration device.

[0259] - Symbol Explanation -

[0260] 1. Turbine compressor

[0261] 2. Housing

[0262] 3 Impeller

[0263] 10 Drive System

[0264] 11 Support section

[0265] 12 Drive Unit

[0266] 20-axis

[0267] 25. Measured part

[0268] 201 First Step Section

[0269] 202 Second Step Section

[0270] 30 Bearingless Electric Motor

[0271] 31 Rotor

[0272] 32 stator

[0273] 35 Support winding

[0274] 36 drive windings

[0275] 40 magnetic bearings

[0276] 41 Radial magnetic bearing

[0277] 42 Thrust magnetic bearing

[0278] 50 bottom-contact bearing

[0279] 60 Rotation Angle Sensor (Rotation Angle Detector)

[0280] 65 Rotating reference sensor

[0281] 70 Position Sensor

[0282] 71 Radial Position Sensor

[0283] 72 Thrust Position Sensor

[0284] 80 Signal Processing Department

[0285] 81 First Processing Department

[0286] 82 Second Processing Department

[0287] 90 Control Department

Claims

1. A drive system, characterized in that: The drive system includes a shaft (20), a support (11), a drive unit (12), a single rotation angle detector (60), a signal processing unit (80), and a control unit (90). The support (11) supports the shaft (20) in a non-contact manner using electromagnetic force. The drive unit (12) uses electromagnetic force to drive the shaft (20) to rotate. The rotation angle detector (60) outputs a first signal S1, which is a signal whose amplitude changes with the rotation angle of the shaft (20). When a specific frequency component is superimposed on the first signal S1, the signal processing unit (80) performs a reduction process on the first signal S1 output from the rotation angle detector (60) to reduce the specific frequency component contained in the first signal S1, thereby generating a second signal S2. The control unit (90) controls the support unit (11) and the drive unit (12). The control unit (90) detects the rotation angle of the shaft (20) based on the second signal S2 generated by the signal processing unit (80). The frequency of the specific frequency component that is reduced in the reduction process is lower than the frequency of the first frequency component C1, which is the AC frequency component of the non-DC component, the frequency component contained in the first signal S1, and the frequency component corresponding to the change in the rotation angle of the shaft (20).

2. The drive system according to claim 1, characterized in that: The shaft (20) has a measuring part (25). The rotation angle detector (60) is a gap sensor that outputs a signal whose amplitude varies with the distance between the rotation angle detector (60) and the measured part (25). The measured part (25) is configured such that the distance between the measured part (25) and the rotation angle detector (60) changes with the rotation angle of the axis (20). The first frequency component C1 is a frequency corresponding to the rotation frequency of the shaft (20) driven by the drive unit (12) and the number of first step portions (201) provided on the measured portion (25) of the shaft (20).

3. The drive system according to claim 1, characterized in that: The specific frequency component that is reduced in the reduction process includes the frequency component with the largest amplitude among the frequency components that are lower than the frequency of the first frequency component C1.

4. The drive system according to claim 1, characterized in that: The specific frequency component that is reduced in the reduction process includes the shaft runout component CX with the largest amplitude among a plurality of shaft runout components CX corresponding to the runout of the shaft (20) which is supported in a non-contact manner from the reference position.

5. The drive system according to claim 1, characterized in that: The reduction process is used to reduce the frequency components within a specific frequency band contained in the first signal S1. The specific frequency band is a frequency band that includes the frequency of the specific frequency component, and is a frequency band with a frequency lower than that of the first frequency component C1.

6. The drive system according to claim 1, characterized in that: The signal processing unit (80) has a first processing unit (81) and a second processing unit (82). The first processing unit (81) generates a threshold Th1 corresponding to the specific frequency component based on the first signal S1. The second processing unit (82) generates the second signal S2 by comparing the amplitude of the first signal S1 with the threshold Th1 generated by the first processing unit (81).

7. The drive system according to claim 6, characterized in that: The first processing unit (81) generates the threshold Th1 by extracting frequency components within a specific frequency band contained in the first signal S1. The specific frequency band is a frequency band that includes the frequency of the specific frequency component, and is a frequency band with a frequency lower than that of the first frequency component C1.

8. The drive system according to claim 6, characterized in that: The first processing unit (81) selectively performs a first extraction process and a second extraction process. In the first extraction process, the threshold Th1 is generated by extracting frequency components within a specific frequency band contained in the first signal S1. In the second extraction process, the threshold Th1 is generated by extracting the DC component from the first signal S1. The specific frequency band is a frequency band that includes the frequency of the specific frequency component, and is a frequency band with a frequency lower than that of the first frequency component C1.

9. The drive system according to claim 6, characterized in that: The first processing unit (81) generates the threshold Th1 by repeatedly performing a process that sets the value derived from the amplitude of the first signal S1 within a specified period as the threshold Th1.

10. The drive system according to claim 1, characterized in that: The signal processing unit (80) has a first processing unit (81) and a second processing unit (82). The first processing unit (81) reduces the specific frequency component contained in the first signal S1. The second processing unit (82) generates the second signal S2 by comparing the signal obtained by the first processing unit (81) with the threshold Th1.

11. The drive system according to claim 1, characterized in that: The drive system includes a bearingless motor (30) having a support winding (35) and a drive winding (36). The support winding (35) is a winding that generates an electromagnetic force by being energized to support the shaft (20) in a non-contact manner, and functions as the support part (11). The drive winding (36) is a winding that generates an electromagnetic force to drive the shaft (20) to rotate by being energized, and functions as the drive unit (12).

12. A turbo-compressor characterized by: The turbo compressor includes the drive system described in any one of claims 1 to 11.

13. A refrigeration device, characterized in that: The refrigeration device includes the turbo compressor as described in claim 12.

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