Eddy current position sensor and electric motor

Abstract

The utility model provides a kind of eddy current position sensor and motor, eddy current position sensor includes stator and target wheel, stator includes stator circuit board, and be located on the excitation coil and inductive coil of stator circuit board, target wheel includes with the coaxial setting ring of excitation coil and inductive coil, and n blade parts of equidistance being located in the circumferential outer edge of ring, n is the pole pair number of eddy current position sensor, the angle corresponding to inner circle arc line of blade part is a, the angle corresponding to outer circle arc line is b, the angle of pole distance included angle of target wheel is c, target wheel is set to satisfy: b / c<0.7, a>b. The utility model improves the structure of target wheel, so that the inner circle pole arc ratio of target wheel is greater than outer circle pole arc ratio, improves inductive voltage amplitude, and then improves the precision of 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 low accuracy 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 target wheel. The stator includes a stator circuit board, and an excitation coil and an induction coil disposed on the stator circuit board. The target wheel includes a ring portion coaxially disposed with the excitation coil and the induction coil, and n blade 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. The angle corresponding to the inner arc of the blade portion is a, the angle corresponding to the outer arc is b, and the angle of the pole pitch of the target wheel is c. The target wheel is configured to satisfy: b / c < 0.7, a > b.

[0008] In one or more embodiments of this utility model, the target wheel is set to satisfy: a / c=0.85~0.9, b / c=0.55~0.65.

[0009] In one or more embodiments of this utility model, the target wheel is set to satisfy: a / c=0.9, b / c=0.6.

[0010] In one or more embodiments of this utility model, the outer arc radius of the blade portion is greater than the outer ring radius of the excitation coil.

[0011] In one or more embodiments of this utility model, the difference between the outer arc radius of the blade portion and the outer ring radius of the excitation coil is between 1 mm and 2 mm.

[0012] In one or more embodiments of this utility model, the inner arc radius of the blade portion is smaller than the inner circle radius of the induction coil.

[0013] In one or more embodiments of this utility model, the difference between the inner arc radius of the blade portion and the inner circle radius of the induction coil is between 1 mm and 2 mm.

[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, a control circuit is electrically connected to an 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] On the other hand, a specific embodiment of the present invention provides a motor that includes the aforementioned eddy current position sensor.

[0017] Compared with the prior art, this utility model improves the structure of the target wheel, making the inner circle polar arc ratio of the target wheel greater than the outer circle polar arc ratio, thereby increasing the amplitude of the induced voltage and thus 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 target wheel of the eddy current position sensor in one embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the polar arc ratio of the target wheel of the eddy current position sensor in one embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the target wheel in the prior art;

[0023] Figure 5 This is a cloud map showing the distribution of induced voltage amplitude under different inner and outer arc ratios.

[0024] Explanation of main reference numerals: 1. Stator, 11. Excitation coil, 12. Induction coil, 13. Control circuit, 2. Target wheel, 21. Ring section, 22. Blade section. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] 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.

[0028] Figure 5The induced voltage contour plots for different inner and outer ring arc ratios show that these ratios significantly affect the induced voltage amplitude. The inner ring arc ratio is the ratio of the angle corresponding to the inner arc of the target wheel's blade section to the angle between the target wheel's pole pitch. The outer ring arc ratio is the ratio of the angle corresponding to the outer arc of the target wheel's blade section to the angle between the target wheel's pole pitch. The pole pitch angle is the angle between the central axes of two adjacent blade sections on the target wheel.

[0029] Figure 4 The traditional target wheel structure features blades that are roughly fan-shaped. The angles corresponding to the inner and outer arcs of the blades are both 'd', and the pole pitch angle is 'e'. Therefore, the inner pole pitch ratio (approximately d / e) of the traditional target wheel is roughly equal to the outer pole pitch ratio (approximately d / e). Consequently, when using a traditional target wheel design, the amplitude of the induced voltage from the eddy current position sensor is approximately distributed within... Figure 5 On line 1#, when the inner and outer arc ratio is approximately 0.68, the induced voltage amplitude reaches its maximum, and the root mean square value of the induced voltage amplitude is approximately 493mV.

[0030] from Figure 5 It can also be seen that when the outer ring polarity ratio is less than 0.7, increasing the inner ring polarity ratio to make it greater than the outer ring polarity ratio can increase the amplitude of the induced voltage.

[0031] Therefore, based on the above patterns, and referring to... Figures 1 to 3 As shown, one embodiment of this application provides an eddy current position sensor. The eddy current position sensor makes a differentiated design for the inner and outer rim arc ratio of the target wheel, thereby increasing the amplitude of the induced voltage of the eddy current position sensor and improving the detection accuracy.

[0032] Specifically, the eddy current position sensor includes a stator 1 and a target wheel 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 11 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 coils 12 have 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 high-frequency alternating signals to the excitation coil 11 and convert the AC signals generated by the induction coil 12 into differential signals or digital signals.

[0033] The target wheel 2 is made of a conductive material, such as stainless steel, aluminum alloy, or copper. The target wheel 2 and stator 1 are spaced apart along the thickness direction of the stator circuit board. The target wheel 21 includes a ring portion 21 and n blade portions 22. The ring portion 21 is coaxially arranged with the excitation coil 11 and the induction coil 12. The n blade portions 22 are equally spaced on the circumferential outer edge of the ring portion 21, where n is the number of pole pairs of the eddy current position sensor. The angle corresponding to the inner arc of the blade portion 22 is 'a', and the angle corresponding to the outer arc of the blade portion 22 is 'b'. The target wheel 21 is configured to satisfy the following conditions: the outer arc ratio (approximately equal to b / c) is less than 0.7, and the inner arc ratio (approximately equal to a / c) is greater than the outer arc ratio (approximately equal to b / c), i.e., b / c < 0.7 and a / c > b / c. Simplifying the above inequality, we obtain: b / c < 0.7 and a > b.

[0034] According to the above structural design of the target wheel 2, without significantly increasing the size of the eddy current position sensor, the frequency of the AC signal flowing into the excitation coil 11, the intensity of the excitation current, and the number of turns of the excitation coil 11, the amplitude of the induced voltage of the eddy current position sensor can be significantly improved, and the signal-to-noise ratio and sensor accuracy are also improved accordingly. The target wheel 2 has a greater adaptability to the axial tolerance and axial air gap of the rotating shaft, and can significantly improve the anti-interference capability of the eddy current position sensor.

[0035] Reference Figure 5 As shown in the figure, it can be clearly seen that the high induced voltage amplitude area is basically concentrated in... Figure 5 The upper left corner of the image is essentially concentrated in the region of "inner ring arc ratio a / c = 0.85~0.9, outer ring arc ratio b / c = 0.55~0.65". Therefore, in order to further improve the induced voltage amplitude of the eddy current position sensor, in one embodiment, the target wheel 2 is set to satisfy the inner ring arc ratio a / c = 0.85~0.9 and the outer ring arc ratio b / c = 0.55~0.65. When the inner ring arc ratio and the outer ring arc ratio are within the above-mentioned value range, the root mean square value of the induced voltage amplitude is basically above 505mV, and the induced voltage amplitude can be significantly improved.

[0036] Reference Figure 5 As shown, line 2# represents the optimal solution for the outer ring arc ratio when the inner ring arc ratio takes a fixed value within the range of 0.5 to 0.9. For example, when the inner ring arc ratio a / c = 0.9, the optimal solution for the outer ring arc ratio b / c is 0.6. At this time, the induced voltage amplitude reaches its maximum value when the inner ring arc ratio a / c = 0.9, and the induced voltage amplitude is also exactly [value missing]. Figure 5 The maximum value of the induced voltage amplitude.

[0037] In one embodiment, in order to increase the radial width of the blade portion 22, the outer arc radius R1 of the blade portion 22 is increased and the inner arc radius R2 of the blade portion 22 is decreased, so that the outer arc radius of the blade portion 22 is greater than the outer ring radius r1 of the excitation coil 11 and the inner arc radius R2 of the blade portion 22 is less than the inner ring radius r2 of the induction coil 12.

[0038] Furthermore, in order to limit the radial width of the blade portion 22 within a reasonable range, the difference between the outer arc radius R1 of the blade portion 22 and the outer ring radius r1 of the excitation coil 11 can be approximately controlled between 1mm and 2mm, and the specific difference can be set to 1mm, 1.25mm, 1.5mm, or 2mm. Similarly, the difference between the inner arc radius R2 of the blade portion 22 and the inner ring radius r2 of the induction coil 12 can be approximately controlled between 1mm and 2mm, and the specific difference can be set to 1mm, 1.25mm, 1.5mm, or 2mm.

[0039] In one embodiment, the target wheel 2 does not need to be mounted on the circuit board, but is instead mounted on the motor output shaft via a ring 21, or on a rotating shaft connected to the motor output shaft via a ring 21, thereby rotating synchronously with the motor output shaft.

[0040] On the other hand, one embodiment of this application provides a motor that includes the eddy current position sensor described in the above embodiment.

[0041] 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.

[0042] 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 target wheel (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 target wheel (2) includes a ring (21) coaxially disposed with the excitation coil (11) and the induction coil (12) and n blades (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. The angle corresponding to the inner arc of the blade (22) is a, the angle corresponding to the outer arc is b, and the angle of the pole pitch of the target wheel (2) is c. The target wheel (2) is set to satisfy: b / c < 0.7, a > b.

2. The eddy current position sensor according to claim 1, characterized in that, The target wheel (2) is set to satisfy: a / c=0.85~0.9, b / c=0.55~0.

65.

3. The eddy current position sensor according to claim 2, characterized in that, The target wheel (2) is set to satisfy: a / c=0.9, b / c=0.

6.

4. The eddy current position sensor according to claim 1, characterized in that, The outer radius of the blade section (22) is greater than the outer radius of the excitation coil (11).

5. The eddy current position sensor according to claim 4, characterized in that, The difference between the outer arc radius of the blade section (22) and the outer ring radius of the excitation coil (11) is between 1 mm and 2 mm.

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

7. The eddy current position sensor according to claim 6, characterized in that, The difference between the inner radius of the blade portion (22) and the inner radius of the induction coil (12) is between 1 mm and 2 mm.

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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