Displacement sensor, rotating shaft displacement detection method, compressor and air conditioner

Abstract

The invention provides a displacement sensor, a rotating shaft displacement detection method, a compressor and an air conditioner. The displacement sensor comprises a sensor stator (1), a plurality of pole probes (2) are arranged on the sensor stator (1) at intervals in the circumferential direction, each pole probe (2) comprises an inner side probe (21) located on the radial inner side of the sensor stator (1), and a stator groove (11) is formed between every two adjacent pole probes (2); and the stator coils (3) are wound in the stator slots (11) in a back-wound structure, two groups of stator coils (3) are arranged in each stator slot (11), the winding directions of the two groups of stator coils (3) in the same stator slot (11) on the sensor stator (1) are opposite, and the directions of magnetic linkages are opposite. According to the displacement sensor provided by the invention, the problems that the coil slot fullness rate of the displacement sensor is low, and the detection of smaller shaft diameter and higher pole number is difficult to realize can be solved.

Description

Technical Field

[0001] This invention relates to the field of shaft displacement detection technology, and more specifically, to a displacement sensor, a shaft displacement detection method, a compressor, and an air conditioner. Background Technology

[0002] Magnetic levitation bearings suspend the shaft in mid-air using electromagnetic force during operation, preventing mechanical contact between the shaft and the stator. Compared to mechanical bearings, they offer advantages such as no mechanical wear, no lubrication required, long service life, high speed, and high reliability. Therefore, they are widely used in high-speed rotating industrial manufacturing fields such as flywheel energy storage, molecular pumps, compressors, and aerospace. To ensure continuous and stable rotation of the shaft, displacement sensors are needed to monitor its axis trajectory. Currently, the non-contact displacement sensors widely used in magnetic levitation bearing systems mainly include eddy current displacement sensors and inductive displacement sensors. Eddy current displacement sensors require high-frequency AC signals above 400kHz, have weak electromagnetic interference resistance, and are highly susceptible to temperature fluctuations, resulting in lower detection accuracy.

[0003] Inductive displacement sensors detect changes in shaft displacement by altering the inductance of the probe coil due to changes in the magnetic field area corresponding to the coil probe and the rotating shaft. The sensitivity and accuracy of inductive displacement sensors depend on the detection surface area of ​​the sensor probe and the gap between the probe and the rotating shaft. However, existing inductive displacement sensors all employ an internally wound stator structure. This traditional stator structure, limited by spatial constraints and coil slot fill factor, struggles to achieve smaller shaft diameters and higher pole counts. Summary of the Invention

[0004] The main objective of this invention is to provide a displacement sensor, a shaft displacement detection method, a compressor, and an air conditioner that can solve the problem of low coil fill factor in displacement sensors, making it difficult to achieve detection of smaller shaft diameters and higher pole numbers.

[0005] To achieve the above objectives, according to one aspect of the present invention, a displacement sensor is provided, comprising:

[0006] The sensor stator has multiple pole probes spaced circumferentially on it. The pole probes include an inner probe located on the radial inner side of the sensor stator, and a stator slot is formed between adjacent pole probes.

[0007] The stator coils are wound in a back-wound structure in the stator slots. Each stator slot has two sets of stator coils. The two sets of stator coils in the same stator slot are wound in opposite directions on the sensor stator, and the magnetic flux directions are opposite.

[0008] Furthermore, the pole probe adopts an all-N magnetic pole arrangement.

[0009] Furthermore, the pole probe also includes an outer probe located radially outside the sensor stator, which forms a circumferential limit on the stator coil radially outside.

[0010] Furthermore, the number of pole probes is N groups, and each group of pole probes includes two pole probes distributed at both ends of the sensor stator radially, where N≥4.

[0011] Furthermore, each stator coil and the adjacent pole probe form an independent detection circuit.

[0012] Furthermore, the stator coil is wound using a self-inductive winding method.

[0013] Furthermore, the displacement sensor uses polar coordinates to output the angle θ and eccentricity ρ of the rotor eccentricity state.

[0014] According to another aspect of the present invention, a compressor is provided, including a housing and the aforementioned displacement sensor, the displacement sensor being mounted on the housing.

[0015] According to another aspect of the present invention, an air conditioner is provided, comprising the displacement sensor described above or the compressor described above.

[0016] According to another aspect of the present invention, a method for detecting shaft displacement using the above-described displacement sensor is provided, comprising:

[0017] The polar coordinate expression for obtaining the center position O of the rotation axis in the X direction is:

[0018] ;

[0019] Real-time detection of the shaft's displacement in the X direction;

[0020] When the position point detected by the first polar probe (2) in the X direction becomes point M', and the position point detected by the second polar probe (2) becomes point N', the polar coordinates of these two points are expressed as M'(ρ m ',θ),N'(ρ n ',180°+θ),

[0021] The polar coordinate expression of the center point O' in the X direction after obtaining the shaft displacement is:

[0022] ;

[0023] Calculate the displacement of the rotating shaft.

[0024] The displacement sensor, employing the technical solution of this invention, comprises a sensor stator and stator coils wound in a back-wound structure. This solves the problem of decreased detection accuracy in existing inductive displacement sensors for small-diameter rotor displacement detection due to X and Y direction coupling effects. By adopting a back-wound structure, each stator slot contains two sets of coils with opposite winding directions. This design reduces mutual interference and improves signal linearity and resolution. When the rotor shifts, the change in the air gap between the back-wound coils and the rotor causes a change in the coil inductance, which in turn affects the coil impedance. The sensor can accurately detect rotor position changes based on impedance changes. Due to the back-wound layout of the coils within the stator slots, the number of coil turns can be significantly increased, thereby improving the slot fill factor and enabling the detection of more poles with a smaller shaft diameter, thus increasing the sensor's sensitivity and accuracy. Attached Figure Description

[0025] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 A three-dimensional structural schematic diagram of a displacement sensor according to an embodiment of the present invention is shown;

[0027] Figure 2 A schematic diagram of the magnetic pole arrangement and magnetic flux direction of a displacement sensor according to an embodiment of the present invention is shown.

[0028] Figure 3 A schematic diagram of the working state of a displacement sensor according to an embodiment of the present invention when the shaft is offset in the X direction is shown.

[0029] The above figures include the following reference numerals:

[0030] 1. Sensor stator; 11. Stator slot; 2. Pole probe; 21. Inner probe; 22. Outer probe; 3. Stator coil; 4. Shaft. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] See also Figures 1 to 3As shown, according to an embodiment of the present invention, the displacement sensor includes: a sensor stator 1, on which a plurality of pole probes 2 are arranged circumferentially, each pole probe 2 including an inner probe 21 located radially inside the sensor stator 1, and a stator slot 11 is formed between adjacent pole probes 2; and a stator coil 3, which is wound in the stator slot 11 in a back-wound structure, with two sets of stator coils 3 arranged in each stator slot 11, the two sets of stator coils 3 located in the same stator slot 11 having opposite winding directions on the sensor stator 1 and opposite magnetic flux directions.

[0033] The displacement sensor using the technical solution of this embodiment includes a sensor stator and stator coils wound in a back-wound structure. This solves the problem of decreased detection accuracy caused by X and Y direction coupling effects in existing inductive displacement sensors when detecting displacement of small-diameter rotors. By adopting a back-wound structure, each stator slot contains two sets of coils with opposite winding directions. This design reduces mutual interference and improves signal linearity and resolution. When the rotor is displaced, the change in the air gap between the back-wound coils and the rotor causes a change in the coil inductance, which in turn affects the coil impedance. The sensor can accurately detect the rotor position change based on the impedance change. Due to the back-wound layout of the coils in the stator slots, the number of turns of the coils can be significantly increased, thereby improving the slot fill factor and enabling the detection of more poles with a smaller shaft diameter, thus increasing the sensitivity and accuracy of the sensor.

[0034] Specifically, in this embodiment, the displacement sensor features a back-wound structure. Two sets of stator coils 3, each located in a stator slot 11, are wound in opposite directions with opposite magnetic flux linkages. This design overcomes the limitations of traditional internally wound coil designs. In conventional coil winding, the coil typically enters from one side of the stator slot, passes through the bottom of the slot, and exits from the other side. This winding method severely restricts the space occupied by the coil and the wiring path, resulting in limitations on the number of coil turns and slot fill factor. The back-wound structure allows the coil to be wound from outside the slot, with one end entering from one side of the slot and the other end from the other, forming a closed coil. This allows the coil to fill the slot more tightly and efficiently, significantly increasing the number of coil turns.

[0035] Slot fill factor refers to the proportion of the coil filling the stator slots. Back-wound structures, due to optimized coil winding paths, can more effectively utilize stator slot space, avoiding the problem of excessive space occupation by the coil in traditional winding methods. In back-wound designs, stator slots can be designed more compactly, and coils can be arranged more densely, thus significantly improving the slot fill factor, typically reaching over 75%, while the slot fill factor of traditional in-wound designs is mostly between 50% and 60%.

[0036] The high slot fill factor of the back-wound structure allows for a more compact stator design, enabling the detection of smaller shaft diameters. In space-constrained applications, such as precision instruments, small motors, or magnetic bearing systems, small shaft diameter sensor design is crucial. The back-wound design, through its efficient coil filling method, makes it possible to achieve a higher pole count within a smaller space. A sensor with more poles provides finer positional information, improving detection accuracy.

[0037] The back-wound design allows for more stator coils 3 to be placed on each pole probe 2. These coils can operate independently to detect magnetic field changes at different locations. On the sensor stator 1, multiple pole probes 2 are spaced circumferentially, forming stator slots 11 between adjacent probes. The stator coils 3 are wound in a back-wound structure using these slots, enabling the detection of magnetic fields with a higher pole number. Each additional pole provides more precise angle and position information, which is particularly important for the detection of small-diameter rotors.

[0038] The back-wound design, by placing two sets of coils in each stator slot with opposite directions, optimizes the magnetic field distribution and improves its linearity and uniformity. This optimization reduces the impact of magnetic field nonlinearity on detection accuracy and enhances the sensor's sensitivity to displacement changes.

[0039] In back-wound designs, the distribution and winding method of the coils significantly reduce interference and coupling effects between adjacent coils. In multi-pole sensors, this ensures that each coil independently and accurately detects the magnetic field changes at its corresponding position, avoiding mutual interference between signals and improving the sensor's detection accuracy and reliability.

[0040] In one embodiment, the pole probe 2 adopts an all-N magnetic pole arrangement.

[0041] In this embodiment, the magnetic levitation bearing displacement sensor adopts a full N-back-wound stator structure. The inner and outer rings of the sensor stator 1 are arranged with 2N (N≥4) pole probes. The stator coil 3 is wound and fixed to the stator slot to overcome the limitations of traditional slot fill factor, achieving detection with a smaller shaft diameter and more poles. The use of back-wound windings (such as reverse nesting or back-wiring) significantly improves the slot fill factor (reaching over 75%, compared to only 50-60% in traditional designs), enabling the stator to achieve more poles with a smaller shaft diameter (e.g., a 30% reduction in shaft diameter). More poles directly improve the polar coordinate detection resolution: at the same rotation angle, an increased number of poles means a longer signal period. For example, with 24 poles, the angular resolution can reach 15° (compared to only 30° with 12 poles in traditional designs). Combined with the optimized magnetic field linearity of the back-wound design, the angular resolution is improved to within 0.5°, and the eccentricity detection accuracy is improved by more than 2 times.

[0042] In this embodiment, the all-N magnetic pole arrangement of the pole probe 2 means that all pole probes use the N pole as their magnetic polarity when arranged, without using the S pole. However, this design is not simply eliminating the S pole, but rather simulating the effect of the traditional alternating N and S pole arrangement by adopting specific strategies in the coil winding and circuit design of each pole probe, thereby still achieving accurate displacement detection.

[0043] The specific implementation method of the pole probe 2 using an all-N magnetic pole arrangement is as follows:

[0044] Each stator slot 11 contains two sets of stator coils 3. One set of stator coils 3 is wound clockwise from the N pole to the S pole, and the other set of stator coils 3 is wound counterclockwise from the N pole to the S pole. The starting point of the stator coils 3 is the S pole, and the ending point of the pole probe is always the N pole. By changing the winding direction and the direction of the magnetic flux, an alternating N and S magnetic field distribution is actually formed in each probe, that is, there is a complete N and S magnetic circuit in each stator slot.

[0045] Stator coil 3 is connected in the circuit via a differential connection, meaning coils in the same direction (e.g., X-axis, Y-axis, etc.) are connected in series, while coils with opposite phases (i.e., clockwise and counterclockwise coils) are differentially connected. This differential connection eliminates interference from the background magnetic field, retaining only the signal changes caused by the shaft displacement, thereby improving detection accuracy and signal clarity.

[0046] When the shaft 4 is displaced, the relative distance between its magnetic field and the stator coil changes, causing the inductance of the stator coil 3 to also change. Since a closed loop (NS) is formed between the stator coil 3 and the pole probe 2, and the magnetic flux of this closed loop passes through the shaft 4 and interacts with the magnetic field of the shaft 4, the displacement of the shaft can be measured by detecting the change in the coil inductance.

[0047] The sensor uses a polar coordinate displacement detection method based on the output angle θ and eccentricity ρ. This method can more intuitively reflect the actual eccentricity of the shaft in the magnetic levitation bearing and can effectively reduce the interference caused by the coupling effect in the X and Y directions, thereby improving the detection accuracy.

[0048] Therefore, in this embodiment, the all-N magnetic pole arrangement of the pole probe 2 is achieved through the back-wound winding and differential connection of the double coils, as well as the magnetic field interaction between the rotating shaft magnetic field and the pole probe of the displacement sensor, to jointly realize high-precision detection of the rotating shaft displacement. At the same time, the structural optimization also enables the sensor to achieve detection with a smaller shaft diameter and more poles, thus enhancing the overall sensitivity and detection capability of the sensor.

[0049] In inductive sensors, the use of all-N pole probes makes the angle and eccentricity signals less susceptible to magnetic field nonlinearity and winding asymmetry, resulting in more accurate detection results.

[0050] In one embodiment, the pole probe 2 can also adopt an all-S magnetic pole arrangement to achieve a similar effect.

[0051] In one embodiment, the pole probe 2 further includes an outer probe 22 located radially outside the sensor stator 1, the outer probe 22 forming a circumferential limit on the stator coil 3 radially outside.

[0052] In this embodiment, the pole probe 2 also includes an outer probe 22 located radially outside the sensor stator 1. The outer probe 22 forms a circumferential limit on the stator coil 3 radially outside, effectively improving the stability of the sensor coil and preventing coil slippage or displacement under high-speed rotation and external vibration conditions, thus ensuring the continuous reliability and detection accuracy of the sensor. The setting of the outer probe 22 not only spatially limits the coil, but also enhances the magnetic coupling between the stator coil 3 and the rotating shaft 4 through its structural characteristics, further improving the sensor's sensitivity to changes in the radial displacement of the rotating shaft. In the back-wound magnetic levitation bearing displacement sensor, the outer probe 22 cooperates with the inner probe 21 to achieve all-round monitoring of the rotor position. Especially in application scenarios with small shaft diameter and high pole number, its structural compactness and improved detection capability are particularly prominent. Furthermore, by optimizing the design of the outer probe 22, the slot fill factor of the stator is further improved, enabling the sensor to achieve a higher pole number distribution with a smaller shaft diameter. This results in finer angular resolution and more accurate eccentricity detection, significantly enhancing the sensor's dynamic monitoring capability of the rotor eccentricity and effectively improving the working efficiency and stability of the entire magnetic levitation bearing system.

[0053] In one embodiment, the number of pole probes 2 is N groups, and each group of pole probes 2 includes two pole probes 2 distributed at both ends of the radial direction of the sensor stator 1, where N≥4.

[0054] In this embodiment, the sensor stator 1 adopts an all-N back-wound design, containing at least N sets of pole probes, each set consisting of two probes symmetrically distributed radially, where N≥4. This layout allows the displacement sensor to achieve a higher pole density within a limited space, breaking through the limitations of traditional stator structures in terms of slot fill factor, thereby allowing for the detection of rotors with smaller shaft diameters and enhancing the sensor's adaptability to small-diameter and high-precision applications. The all-N magnetic pole arrangement ensures that each set of probes forms an independent magnetic circuit closed loop, improving angle detection accuracy. At the same time, the back-wound winding design optimizes the magnetic field distribution, increases the number of coil turns, and significantly improves the stator's slot fill factor to over 75%, compared to the traditional 50% to 60%. This means that the stator can carry more coils in a smaller volume, thereby achieving more accurate capture and analysis of rotor radial displacement.

[0055] In other embodiments not shown in the figure, the number and distribution of the pole probes can be adjusted according to the needs of different application scenarios to adapt to a wider range of detection requirements. Whether increasing the number of poles to improve angular resolution or optimizing the probe layout to enhance the sensitivity of eccentricity detection, the all-N back-wound inductive displacement sensor of this embodiment provides a flexible solution, ensuring high-precision and high-stability displacement monitoring in various complex environments. By adjusting the number and configuration of the pole probes, the sensor can capture the dynamic changes of the rotor more accurately, providing strong support for the condition monitoring of high-speed rotating equipment.

[0056] In one embodiment, each of the stator coils 3 and the adjacent pole probe 2 form an independent detection circuit.

[0057] In this embodiment, each stator coil 3 and its adjacent pole probe 2 form an independent detection circuit, enabling the sensor to independently detect each magnetic pole, significantly improving angle detection accuracy. By tightly integrating the stator coil 3 and pole probe 2 to form an independent circuit, the sensor can accurately capture minute displacement changes in the shaft 4. Even when the shaft 4 deviates in the X direction, the changes in inductance signals at the detection position M' of the first set of probes 5 and the detection position N' of the second set of probes 6 can be clearly identified, thereby calculating the eccentricity of the shaft 4. This independent circuit setup, combined with the all-N back-wound structure and polar coordinate displacement detection method, not only optimizes the linearity of electromagnetic induction but also effectively reduces interference caused by X and Y direction coupling effects, ensuring high sensitivity and high accuracy of the sensor in small-diameter rotor detection. Furthermore, the independent detection circuit design simplifies the signal processing flow, making the sensor output angle θ and eccentricity ρ more intuitive, facilitating direct reflection of the rotor's actual operating state during rotation, thus providing a foundation for precise control of the magnetic levitation bearing system.

[0058] In one embodiment, the stator coil 3 is self-inductively wound.

[0059] In this embodiment, the all-N back-wound inductive displacement sensor adopts a unique back-wound design, breaking through the slot fill factor limitation of traditional stator structures and enabling the detection of more poles with a smaller shaft diameter, greatly improving the sensor's angle detection accuracy. The inner and outer rings of the sensor stator 1 are respectively equipped with 2N (N≥4) pole probes, which are evenly distributed along the circumference. Each probe consists of an individual self-inductive coil, forming an independent magnetic flux path. The magnetic flux linkage of the coils is uniformly directed from the N direction to the S direction, ensuring the independent detection capability of each magnetic pole. This design not only reduces the coupling effect in the X and Y directions but also enables the sensor to directly measure the rotor's eccentricity, i.e., the angle θ and the eccentricity ρ, providing more intuitive and accurate displacement data.

[0060] Specifically, when the shaft is at its center position, the first set of probes, points M and N, monitor the displacement of the shaft, expressed in polar coordinates as M(ρ, θ) and N(ρ, 180°+θ). As the shaft's displacement in the X-direction changes, the probe detection points M' and N' also change, and their polar coordinate expressions are updated accordingly to M'(ρ_m', θ) and N'(ρ_n', 180°+θ). By analyzing the impedance changes of these probe coils, the displacement change of the shaft in the X-direction can be determined.

[0061] In one embodiment, the displacement sensor uses polar coordinates to output the angle θ and eccentricity ρ of the rotor eccentricity state.

[0062] In this embodiment, the magnetic levitation bearing displacement sensor adopts a fully N-back-wound stator structure, in which 2N (N≥4) pole probes are evenly distributed on both the inner and outer rings of the stator. The magnetic flux of each probe coil runs from the N-direction to the S-direction, forming a complete loop, and each magnetic pole can be detected individually. This design breaks through the limitation of traditional stator slot fill factor, enabling the sensor to adapt to the detection requirements of smaller shaft diameters and higher pole numbers, significantly enhancing the sensor's integration and detection capability. During detection, the sensor reflects the displacement of the rotating shaft through the change in magnetic flux between the probe coil and the rotating shaft.

[0063] The sensor incorporates a polar coordinate displacement detection method, converting the shaft displacement information into intuitive angle θ and eccentricity ρ, thus avoiding the impact of X and Y direction coupling errors on detection accuracy when detecting small-diameter rotors. The use of back-wound windings further increases the slot fill factor to over 75%, compared to the traditional 50%~60%, allowing the sensor to achieve higher pole density in a more compact space. This directly optimizes the electromagnetic basis of polar coordinate detection, improves polar coordinate detection resolution, and reduces the impact of coupling effects, thereby achieving more accurate angle detection (±0.1°) and eccentricity resolution (≤0.01mm). This effectively improves the sensor's detection accuracy and sensitivity, especially in the detection of small-diameter rotors, enhancing the overall stability and reliability of the system.

[0064] In other embodiments not shown in the figure, the number of pole probes and the winding method of the sensor can also be adjusted to adapt to different environments and detection requirements. For example, increasing the number of pole probes or optimizing the winding layout can further improve detection accuracy and response speed. Furthermore, the sensor's detection method is not limited to X-axis offset; offset detection in the Y, Y1, and X1 directions all follow the same principle. By outputting the eccentricity and angle, the eccentricity state of the rotor is intuitively reflected, significantly improving the sensor's detection efficiency and the intuitiveness of data analysis.

[0065] In one embodiment, the sensor employs a differential connection design, with probe coils in the same direction connected in series and coils in different directions connected differentially. This not only improves the signal-to-noise ratio but also enables the sensor to accurately capture minute displacement changes, maintaining high-precision detection even with small shaft diameters. Based on the polar coordinate detection method, the sensor can output the real-time angle and eccentricity of the rotating shaft, greatly facilitating the monitoring and diagnosis of rotating machinery conditions. For example, it enables early identification of motor shaft vibration and early warning of bearing wear trends, thus playing a crucial role in maintenance and fault prevention.

[0066] According to an embodiment of the present invention, the compressor includes a housing and the displacement sensor described above, the displacement sensor being mounted on the housing.

[0067] The sensor's stator is mainly mounted and fixed on the compressor housing. Radial positioning can be achieved through the outer probe, protecting the coil winding from frictional contact with the housing.

[0068] According to an embodiment of the present invention, the air conditioner includes the displacement sensor described above or the compressor described above.

[0069] According to an embodiment of the present invention, the method for detecting shaft displacement using the above-described displacement sensor includes:

[0070] The polar coordinate expression for obtaining the center position O of the 4X axis of rotation is:

[0071] ;

[0072] Real-time detection of the displacement of shaft 4 in the X direction;

[0073] When the position point detected by the first polar probe 2 in the X direction becomes point M', and the position point detected by the second polar probe 2 becomes point N', the polar coordinates of these two points are expressed as M'(ρ m ',θ),N'(ρ n ',180°+θ),

[0074] The polar coordinate expression of the center point O' in the X direction after obtaining the displacement of axis 4 is:

[0075] ;

[0076] Calculate the displacement of shaft 4.

[0077] The working principle of the inductive displacement sensor is as follows: when the X-axis displacement of the rotating shaft 4 changes, the impedance of the stator coil 3 of the displacement sensor will change accordingly, thus obtaining the axial displacement of the rotating shaft 4 in the X-axis based on the impedance change of the stator coil 3. Furthermore, to solve the signal coupling problem that occurs when detecting the displacement of small-diameter rotors, a polar coordinate detection method is proposed. The eccentricity ρ and angle θ are themselves polar coordinate representations of the eccentricity vector, while the rectangular coordinates X / Y are Cartesian decompositions, inevitably resulting in coupling. Using the polar coordinate displacement detection method, the angle θ (rotor eccentricity direction) and the eccentricity ρ (displacement magnitude) can be directly output. Polar coordinates naturally decouple the components. For small shaft diameters, the X / Y displacements are strongly coupled due to geometric constraints (e.g., an eccentricity of 1µm simultaneously generates a 0.7µm component in both the X and Y axes).

[0078] Existing inductive displacement sensors (such as those based on linear windings or traditional slot fill factor designs) can typically only output rotation angle or displacement, while radial eccentricity (i.e. the offset of the rotor center relative to the stator center) needs to be calculated indirectly by additional sensors (such as eddy current sensors) or complex algorithms, resulting in system redundancy, increased cost and reduced accuracy.

[0079] The displacement sensor in this embodiment adopts a back-wound winding design, which can break through the slot fill factor limitation, making the stator magnetic field distribution more uniform and the pole density higher. For example, the pole number can be increased to 1.5 to 2 times that of the traditional design, which directly optimizes the electromagnetic basis of polar coordinate detection.

[0080] In the polar coordinate framework, angle (θ) represents the rotor's rotational position, and eccentricity (r) represents radial displacement (such as bearing eccentricity or shaft alignment displacement). This embodiment utilizes the symmetrical design of the back-wound winding to simultaneously decouple the amplitude and phase of the inductance signal into angle and eccentricity. Without additional signal processing, it directly outputs two independent parameters via differential operation, achieving an angle accuracy of ±0.1° and an eccentricity resolution of ≤0.01mm. This realizes "single sensor, dual-parameter output," and in rotating machinery condition monitoring (such as motor shaft vibration diagnosis and bearing wear early warning), eccentricity can directly reflect the health status of the shaft system.

[0081] When the rotating shaft 4 is in the center position, the probe detection points in the X direction are points M and N, and the polar coordinates of these two points are M(ρ, θ) and N(ρ, 180°+θ). At this time, the polar coordinate expression of the center position O of the rotating shaft in the X direction is:

[0082]

[0083] That is, the polar coordinates of point O at the center position along the X-axis are O (0, 0).

[0084] When the rotating shaft 4 shifts towards the first set of probes in the X direction, the detection position point of the first set of polar probes in the X direction becomes point M', and the detection position point of the second set of polar probes becomes point N'. The polar coordinates of these two points are then expressed as M'(ρm', θ) and N'(ρn', 180°+θ). Therefore, the polar coordinate expression for the corresponding center position O' of the rotating shaft in the X direction is:

[0085]

[0086] Then, the polar coordinates of point O' at the center position along the X-axis are O' ( , ).

[0087] The offset of shaft 4 can be accurately measured using the above method.

[0088] This formula applies to offsets in other directions.

[0089] When using the magnetic levitation bearing displacement sensor of this application for shaft displacement detection, multiple pole probes on the sensor stator are initially positioned in a preset location, ready to monitor the radial displacement change of the shaft. When the shaft shifts in the X direction due to changes in load or operating conditions, the coil impedance in the corresponding pole probe changes accordingly. This change is captured by the sensor and converted into an electrical signal. The signal processing circuit analyzes this signal to determine the shaft's displacement in the X direction. Unlike previous methods that output X and Y displacement information using a Cartesian coordinate system, the sensor of this application uses a polar coordinate displacement detection method, directly outputting the angle θ and eccentricity ρ of the shaft's eccentricity. By monitoring the shaft's movement from the center position O (O(0,0)) to the new offset position O′ in real time, the sensor can quickly and accurately identify the shaft's displacement change. During the detection process, when the shaft shifts towards the first set of probes in the X direction, the detection position of the first set of probes in the X direction changes from point M to point M′, and the detection position of the second set of probes changes from point N to point N′. At this time, the new position of the shaft is expressed as M′(ρ_m′,θ) and N′(ρ_n′,180°+θ), thereby calculating the eccentricity state of the shaft.

[0090] The entire detection process fully utilizes the characteristics of the all-N back-wound stator structure. Each magnetic pole forms an independent detection circuit, improving the sensor's angle detection accuracy. Simultaneously, the back-wound coil layout significantly increases the slot fill factor, enabling the sensor to operate with smaller shaft diameters and higher pole numbers, enhancing detection sensitivity and accuracy. This detection method simplifies the signal processing flow, directly reflecting the rotor's eccentricity, and is particularly suitable for high-precision displacement detection of small-diameter rotors, effectively improving system stability and reliability. During shaft displacement detection, the sensor's outer probe radially limits the coil windings, preventing stator coil slippage during high-speed rotation, further ensuring the accuracy of the detection results. By employing the displacement sensor of this embodiment, high-speed rotating equipment such as compressors and air conditioners can monitor the radial displacement of the shaft in real time, adjust the control system promptly, maintain stable equipment operation, and reduce maintenance costs and failure rates.

[0091] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0092] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in sequences other than those illustrated or described herein.

[0093] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A displacement sensor, characterized in that, include: A sensor stator (1) is provided with a plurality of pole probes (2) spaced apart along the circumference of the sensor stator (1). Each pole probe (2) includes an inner probe (21) located on the radial inner side of the sensor stator (1). A stator slot (11) is formed between adjacent pole probes (2). The stator coil (3) is wound in the stator slot (11) in a back-wound structure. Two sets of the stator coil (3) are provided in each stator slot (11). The two sets of the stator coil (3) located in the same stator slot (11) have opposite winding directions on the sensor stator (1) and opposite magnetic flux directions.

2. The displacement sensor according to claim 1, characterized in that, The pole probe (2) adopts an all-N magnetic pole arrangement.

3. The displacement sensor according to claim 1, characterized in that, The pole probe (2) also includes an outer probe (22) located radially outside the sensor stator (1), the outer probe (22) forming a circumferential limit on the stator coil (3) radially outside.

4. The displacement sensor according to claim 1, characterized in that, The number of the pole probes (2) is N groups, and each group of pole probes (2) includes two pole probes (2) distributed at both ends of the radial direction of the sensor stator (1), where N≥4.

5. The displacement sensor according to claim 1, characterized in that, Each of the stator coils (3) and the adjacent pole probes (2) form an independent detection circuit.

6. The displacement sensor according to claim 1, characterized in that, The stator coil (3) is self-inductively wound.

7. The displacement sensor according to claim 1, characterized in that, The displacement sensor uses polar coordinates to express the rotor eccentricity state, and outputs the angle θ and eccentricity ρ.

8. A compressor, characterized in that, It includes a housing and a displacement sensor according to any one of claims 1 to 7, wherein the displacement sensor is mounted on the housing.

9. An air conditioner, characterized in that, It includes the displacement sensor according to any one of claims 1 to 7 or the compressor according to claim 8.

10. A method for detecting shaft displacement using a displacement sensor according to any one of claims 1 to 7, characterized in that, include: The polar coordinate expression for obtaining the center position O of the rotation axis in the X direction is: ； Real-time detection of the displacement of the rotating shaft (4) in the X direction; When the position point detected by the first polar probe (2) in the X direction becomes point M', and the position point detected by the second polar probe (2) becomes point N', the polar coordinates of these two points are expressed as M'(ρ m ',θ),N'(ρ n ',180°+θ), The polar coordinate expression of the center point O' in the X direction after obtaining the displacement of the rotating shaft (4) is: ； Calculate the displacement of the rotating shaft (4).

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