Eddy current position sensor and motor

Abstract

This invention provides an eddy current position sensor and a motor. The eddy current position sensor includes a stator and a rotor. The stator includes a stator circuit board, and an excitation coil and an induction coil disposed on the stator circuit board. The rotor includes a ring portion coaxially arranged with the excitation coil and the induction coil, and n shielding portions equally spaced on the outer circumferential edge of the ring portion, where n is the number of pole pairs of the eddy current position sensor. An unshielded area is formed between two adjacent shielding portions. The radian corresponding to the shielding portion is α, and the radian corresponding to the unshielded area is β. The shielding portions and the unshielded area are configured to satisfy: α > β. This invention improves the rotor structure, increases the rotor's duty cycle, and enhances the amplitude and stability of the induced voltage signal, thereby improving the accuracy of the eddy current position sensor.

Description

Technical Field

[0001] This utility model belongs to the field of position sensor technology, specifically relating to an eddy current position sensor and a motor. Background Technology

[0002] Eddy current sensor technology is a non-contact detection technique that uses electromagnetic induction principles to transmit and receive induced AC signals using corresponding coils at the transmitting and receiving ends, thereby calculating the rotor position. The target wheel of the eddy current sensor is fixed on the motor shaft and rotates together with the motor rotor. By measuring the speed and phase angle of the motor rotor, the relative position of the motor rotor and stator can be calculated.

[0003] Currently, eddy current sensors are widely used in motor rotor position detection. The accuracy of an eddy current sensor depends on the air gap between the coil and the target wheel. If the air gap or axial runout increases, the distance between the induction coil and the target wheel increases, the eddy current effect weakens, resulting in a decrease in the output signal voltage amplitude and an increase in the signal-to-noise ratio, thus affecting the system linearity.

[0004] To improve the accuracy of eddy current sensors, the size of the induction coil is often designed to be very large. This makes it impossible to fit motors with large installation space requirements into the larger eddy current sensors. Furthermore, even if the size of the eddy current sensor remains unchanged, improving the signal-to-noise ratio of the induction coil output signal requires increasing the frequency of the AC signal flowing into the excitation coil, increasing the excitation current intensity, or increasing the number of turns in the excitation coil. This results in an increase in magnetic field strength and a corresponding increase in external electromagnetic interference.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of this utility model and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Utility Model Content

[0006] The purpose of this invention is to provide an eddy current position sensor that solves the problem of reduced accuracy caused by increased axial displacement in existing eddy current position sensors.

[0007] To achieve the above objectives, a specific embodiment of this utility model provides an eddy current position sensor, including a stator and a rotor. The stator includes a stator circuit board, and an excitation coil and an induction coil disposed on the stator circuit board. The rotor includes a ring portion coaxially disposed with the excitation coil and the induction coil, and n shielding portions equally spaced on the circumferential outer edge of the ring portion, where n is the number of pole pairs of the eddy current position sensor. An unshielded area is formed between two adjacent shielding portions. The radian corresponding to the shielding portion is α, and the radian corresponding to the unshielded area is β. The shielding portion and the unshielded area are configured to satisfy: α > β.

[0008] In one or more embodiments of this utility model, the shielding part and the unshielded area are set to satisfy: α / (α+β)=0.53~0.7.

[0009] In one or more embodiments of this utility model, the outer arc radius of the shielding part is greater than the outer ring radius of the excitation coil.

[0010] In one or more embodiments of this utility model, the difference between the outer arc radius of the shield and the outer ring radius of the excitation coil is between 0.25mm and 1.5mm.

[0011] In one or more embodiments of this utility model, the inner arc radius of the shielding part is smaller than the inner circle radius of the induction coil.

[0012] In one or more embodiments of this utility model, the difference between the inner arc radius of the shielding part and the inner circle radius of the induction coil is between 0.25mm and 1.5mm.

[0013] In one or more embodiments of this utility model, the ring portion of the rotor is used to be sleeved on the motor output shaft or on a rotating shaft connected to the motor output shaft.

[0014] In one or more embodiments of this utility model, the stator further includes a control circuit disposed on the stator circuit board. The control circuit is electrically connected to the excitation coil and is used to transmit high-frequency alternating signals to the excitation coil.

[0015] In one or more embodiments of this utility model, the control circuit is electrically connected to the induction coil, and the control circuit is used to convert the AC signal generated by the induction coil into a differential signal or a digital signal.

[0016] In another aspect, this utility model also provides a motor that includes the aforementioned eddy current position sensor.

[0017] Compared with the prior art, this utility model improves the rotor structure, increases the rotor duty cycle, and improves the amplitude and stability of the induced voltage signal, thereby improving the accuracy of the eddy current position sensor. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1This is a schematic diagram of the stator structure of an eddy current position sensor according to one embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the rotor structure of an eddy current position sensor in one embodiment of the present invention;

[0021] Figure 3 This is a region division diagram of the rotor of the eddy current position sensor in one embodiment of the present invention.

[0022] Explanation of main reference numerals: 1. Stator, 11. Excitation coil, 12. Induction coil, 13. Control circuit, 2. Rotor, 21. Ring section, 22. Shielded section, 23. Unshielded area. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0024] In the description of this utility model, it should be understood that the terms "top", "bottom", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0025] Furthermore, the terms "second" and "first" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined as "second" or "first" may explicitly or implicitly include one or more of the stated features. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0026] Reference Figures 1 to 3As shown, one embodiment of this application provides an eddy current position sensor, which includes a stator 1 and a rotor 2. The stator 1 includes a stator circuit board, an excitation coil 11, an induction coil 12, and a control circuit 13. The excitation coil 11, the induction coil 12, and the control circuit 13 are disposed on the stator circuit board. The excitation coil 11 and the induction coil 12 are coaxially arranged, and the excitation coil 11 surrounds the induction coil 12. The excitation coil and the induction coil 12 are arranged in a four-layer board structure of the stator circuit board. Specifically, one set of excitation coils and two sets of induction coils 12 can be provided, with the two sets of induction coils 12 distributed at a 90° electrical angle. The excitation coil has three layers, and the induction coil 12 has two or four layers, with the number of layers being even. The control circuit 13 is electrically connected to the excitation coil 11 and the induction coil 12. The control circuit 13 is used to transmit a high-frequency alternating signal to the excitation coil 11 and convert the AC signal generated by the induction coil 12 into a differential signal or a digital signal. The rotor 2 is made of a conductive material, such as stainless steel, aluminum alloy, or copper. The rotor 2 and stator 1 are spaced apart along the thickness direction of the stator circuit board. The rotor 2 includes a ring portion 21 and n shielding portions 22. The ring portion 21 is coaxially arranged with the excitation coil 11 and the induction coil 12. The n shielding portions 22 are equally spaced along the outer circumferential edge of the ring portion 21, where n is the number of pole pairs of the eddy current position sensor. An unshielded area 23 is formed between adjacent shielding portions 22, and a total of n unshielded areas 23 are formed. The cross-section of the shielding portions 22 and the unshielded areas 23 is approximately fan-shaped, and the centers of the shielding portions 22 and the unshielded areas 23 coincide with the center of the ring portion 21.

[0027] Those skilled in the art will understand that the duty cycle of the rotor can be defined as α / (α+β), where α+β=2π / n, α is the radian corresponding to the shielding part 22, and β is the radian corresponding to the unshielded area 23. The duty cycle of the existing rotor is approximately 0.5, and the radian of the shielding part 22 is approximately equal to the radian of the unshielded area 23.

[0028] Therefore, in order to improve the duty cycle, the shielding part 22 and the unshielded area 23 of the rotor 2 in this application are configured to satisfy α > β, so that the duty cycle is above 0.5, thereby improving the amplitude and stability of the induced voltage signal.

[0029] It should be noted that the arc α of the shielding part 22 represents the angle between the two radial sides of the shielding part 22 and the center of the ring part 21, and the arc β of the unshielded area 23 represents the angle between the two radial sides of the unshielded area 23 and the center of the ring part 21.

[0030] As an example, if the eddy current position sensor has 4 pole pairs, then the rotor 2 has 4 shielded sections 22 and 4 unshielded areas 23. The sum of the radians of the shielded sections 22 and the unshielded areas 23 is equal to 2π / 4, that is, α+β=π / 2 (α+β corresponds to an angle of 90°). α can be set to π / 3 (corresponding to an angle of 60°), and β can be set to π / 6 (corresponding to an angle of 30°). In this case, α / (α+β)≈0.67.

[0031] Furthermore, the shielding part 22 is a conductive area on the rotor 2. Generally, the larger the curvature of the shielding part 22, the wider the coverage area, and the greater the increase in the signal amplitude of the induced voltage. However, if the curvature of the shielding part 22 is too large, it can easily lead to an imbalance in the magnetic field distribution, causing high-frequency harmonics and affecting the signal decoding accuracy of the induced voltage.

[0032] For the reasons mentioned above, in order to ensure the balance between the various performance parameters of the eddy current position sensor, the duty cycle should be controlled within a reasonable range, that is, the value range of α / (α+β) should be controlled within a reasonable range, so as to avoid the excessive curvature of the shielding part 22 from reducing the overall performance of the eddy current position sensor.

[0033] To obtain a reasonable range of duty cycle, the amplitude of induced voltage under different duty cycle conditions was experimentally verified. The data in the table below are the experimental results.

[0034]

[0035] The experimental results in the table above show that the induced voltage amplitude is positively correlated with the duty cycle; the larger the duty cycle, the larger the induced voltage amplitude. When the duty cycle is 0.5~0.55 and 0.7~0.8, the rate of change in the increase of the induced voltage amplitude is relatively small, indicating that the duty cycle cannot significantly improve the induced voltage amplitude within these two ranges, and the influence of the duty cycle on the induced voltage amplitude is relatively weak. Furthermore, those skilled in the art will understand that, based on extensive experimental verification in the field, after the duty cycle reaches a certain level, further increasing the duty cycle will actually reduce the accuracy of the eddy current position sensor. Therefore, in practical applications, the lower limit of the duty cycle range should be controlled at 0.5~0.55, and the upper limit should be controlled at 0.7~0.8.

[0036] Within the range of 0.5 to 0.55, it can be seen that the induced voltage amplitude at a duty cycle of 0.53 is significantly improved compared to the induced voltage amplitude at a duty cycle of 0.52. Therefore, the lower limit of the duty cycle can be set to 0.53.

[0037] Within the range of 0.7 to 0.8, considering that a larger duty cycle would affect the signal decoding accuracy of the induced voltage and reduce the overall performance of the eddy current position sensor, the upper limit of the duty cycle should be the minimum value within this range. The upper limit of the duty cycle can be set to 0.7.

[0038] In summary, in practical applications, the duty cycle can be controlled within the range of 0.53 to 0.7, that is, the value of α / (α+β) should be controlled within the range of 0.53 to 0.7.

[0039] In addition to the rotor's duty cycle, the area of ​​the shielding part 22 can be increased so that it can cover a larger area, thereby increasing the amplitude of the induced voltage by utilizing the edge effect of the magnetic field.

[0040] For the shielding part 22, its area is related to its curvature and radial width. Increasing the duty cycle is equivalent to increasing the curvature of the shielding part 22. Therefore, the radial width of the shielding part 22 can also be increased to increase the amplitude of the induced voltage.

[0041] In one embodiment, reference is made to Figure 1 and Figure 3 As shown, in order to increase the radial width of the shielding part 22, the outer arc radius R1 of the shielding part 22 is increased and the inner arc radius R2 of the shielding part 22 is decreased, so that the outer arc radius R1 of the shielding part 22 is greater than the outer ring radius r1 of the excitation coil 11, and the inner arc radius R2 of the shielding part 22 is smaller than the inner ring radius r2 of the induction coil 12.

[0042] Furthermore, in order to limit the radial width of the shielding portion 22 within a reasonable range, the difference between the outer arc radius R1 of the shielding portion 22 and the outer ring radius r1 of the excitation coil 11 can be approximately controlled between 0.25mm and 1.5mm, with the specific difference set to 0.25mm, 0.5mm, 0.75mm, 1mm, 1.25mm, or 1.5mm. Similarly, the difference between the inner arc radius R2 of the shielding portion 22 and the inner ring radius r2 of the induction coil 12 can be approximately controlled between 0.25mm and 1.5mm, with the specific difference set to 0.25mm, 0.5mm, 0.75mm, 1mm, 1.25mm, or 1.5mm.

[0043] In one embodiment, the rotor 2 does not need to be mounted on the rotor 2 circuit board, but is instead mounted on the motor output shaft via the ring 21, or mounted on the rotating shaft connected to the motor output shaft via the ring 21, thereby rotating synchronously with the motor output shaft.

[0044] On the other hand, one embodiment of this application provides a motor that includes the eddy current position sensor described in the above embodiment.

[0045] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0046] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An eddy current position sensor, characterized in that, The device includes a stator (1) and a rotor (2). The stator (1) includes a stator circuit board and an excitation coil (11) and an induction coil (12) disposed on the stator circuit board. The rotor (2) includes a ring (21) coaxially disposed with the excitation coil (11) and the induction coil (12) and n shielding portions (22) equally spaced on the outer circumferential edge of the ring (21), where n is the number of pole pairs of the eddy current position sensor. An unshielded area (23) is formed between two adjacent shielding portions (22). The radian corresponding to the shielding portion (22) is α, and the radian corresponding to the unshielded area (23) is β. The shielding portion (22) and the unshielded area (23) are set to satisfy: α > β.

2. The eddy current position sensor according to claim 1, characterized in that, The shielding part (22) and the unshielded area (23) are set to satisfy: α / (α+β)=0.53~0.

7.

3. The eddy current position sensor according to claim 1, characterized in that, The outer arc radius of the shield (22) is greater than the outer ring radius of the excitation coil (11).

4. The eddy current position sensor according to claim 3, characterized in that, The difference between the outer arc radius of the shield (22) and the outer ring radius of the excitation coil (11) is between 0.25 mm and 1.5 mm.

5. The eddy current position sensor according to claim 1, characterized in that, The inner radius of the shield (22) is smaller than the inner radius of the induction coil (12).

6. The eddy current position sensor according to claim 5, characterized in that, The difference between the inner radius of the shield (22) and the inner radius of the induction coil (12) is between 0.25 mm and 1.5 mm.

7. The eddy current position sensor according to claim 1, characterized in that, The ring portion (21) of the rotor (2) is used to be sleeved on the motor output shaft or on a rotating shaft connected to the motor output shaft.

8. The eddy current position sensor according to claim 1, characterized in that, The stator (1) also includes a control circuit (13) disposed on the stator circuit board. The control circuit (13) is electrically connected to the excitation coil (11) and is used to transmit high-frequency alternating signals to the excitation coil (11).

9. The eddy current position sensor according to claim 8, characterized in that, The control circuit (13) is electrically connected to the induction coil (12), and the control circuit (13) is used to convert the AC signal generated by the induction coil (12) into a differential signal or a digital signal.

10. An electric motor, characterized in that, The motor includes an eddy current position sensor as described in any one of claims 1 to 9.

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