Solenoid coil, method for manufacturing the same, and magnetic measuring device including the solenoid coil

Abstract

The present invention relates to a solenoid coil, a method for manufacturing the solenoid coil, and a magnetic measurement device including the solenoid coil. According to one embodiment, a solenoid coil may include a plurality of coil turns, and the plurality of coil turns are uniformly wound in the axial direction of the solenoid coil. In the direction from the center of the axis of the solenoid coil toward both ends, the diameter of the solenoid coil gradually decreases. Preferably, in a cross section passing through the axis of the solenoid coil, the solenoid coil has a parabolic shape that is symmetrical about the axis of the solenoid coil. The solenoid coil is capable of providing a uniform magnetic field in its internal space, thereby meeting the needs of various magnetic measurement applications.

Description

Technical Field

[0001] The present invention generally relates to the technical field of magnetic field measurement, and more particularly, to a solenoid coil capable of generating a uniform magnetic field, a manufacturing method thereof, and a magnetic measurement device comprising the solenoid coil. Background Art

[0002] Magnetic measurement equipment such as magnetometers and nuclear magnetic resonance gyroscopes usually include a device for generating a uniform magnetic field, for example, for offsetting the ambient magnetic field, or for balancing and thereby determining the magnetic field to be measured. Common devices for generating a uniform magnetic field include solenoid coils and Helmholtz coils. The Helmholtz coil includes two coaxial circular coils with a radius of R, and the axial distance h between the two coils is set to be equal to the radius R, thereby generating a magnetic field with a minimized degree of unevenness at the axial center position of the two coils, that is, the second-order inverse of the axial magnetic field is zero. However, the Helmholtz coil requires a skeleton to relatively fix the two coils to a predetermined position, so the manufacturing process is complicated and it is difficult to miniaturize. In addition, the current required for the Helmholtz coil to generate a predetermined magnetic field is larger than that of the solenoid coil, and the energy efficiency is not high. Therefore, for some magnetic measurement applications with a small volume and a large range, the Helmholtz coil is not the best choice.

[0003] The solenoid coil is easy to wind, no skeleton is needed, and smaller coils can be easily wound, so it can be widely used in magnetic measurement equipment of various specifications. Theoretically, when the solenoid coil is infinitely long, the magnetic field generated inside the solenoid coil is uniform. However, when the solenoid coil has a finite length L, such as Figure 1 As shown, the magnetic lines of force 11 diverge at both ends of the solenoid 10, causing the internal magnetic field to become non-uniform. Therefore, how to improve the uniformity of the magnetic field inside the solenoid coil has been a topic of research.

[0004] Invention patent application 201811304808.3 entitled “A solenoid with unequal spacing” discloses a solenoid coil, which compensates for the magnetic field strength at both ends of the coil and improves the uniformity of the magnetic field by gradually increasing the spacing between adjacent coils from both ends of the coil toward the center. Invention patent application 201910465922.2 entitled “A device for measuring the measurement range and gradient tolerance index of a magnetometer” discloses another solenoid coil, which compensates for the magnetic field strength at both ends of the solenoid and improves the uniformity of the magnetic field by additionally winding a plurality of compensation coils around the periphery of the coil at both ends of the solenoid coil. However, these methods all require precise control of the coil winding process to wind the coil turns at predetermined positions, which makes the construction difficult, and process deviations during winding may cause the uniformity of the magnetic field actually generated to fail to meet the design requirements. Summary of the invention

[0005] One aspect of the present invention is to provide a solenoid coil, which may include a plurality of coil turns, the plurality of coil turns are uniformly wound in the axial direction of the solenoid coil, and the diameter of the solenoid coil gradually decreases in the direction from the center of the axis of the solenoid coil toward both ends.

[0006] In a cross section passing through an axis of the solenoid coil, the solenoid coil may have a parabolic shape that is symmetrical about the axis of the solenoid coil.

[0007] The parabolic shape can satisfy the formula Wherein L is the length of the solenoid coil, γ is the ratio between the length L of the solenoid coil and the maximum diameter D at the center position, x is the distance from the center of the axis in the axial direction of the solenoid coil, and a is the quadratic term coefficient.

[0008] The value range of the quadratic term coefficient a can be Preferably, the value of the quadratic term coefficient a is approximately

[0009] The solenoid coil may further include a skeleton, the skeleton may have a hollow structure, and the plurality of coil turns may be uniformly wound on the skeleton. In a cross section passing through an axis of the solenoid coil, the skeleton may have the parabolic shape.

[0010] One aspect of the present invention is to provide a method for manufacturing a solenoid coil, comprising: manufacturing a skeleton, wherein the skeleton has a circular shape in a cross section perpendicular to the axis of the skeleton, and the diameter of the skeleton gradually decreases in a direction from the center of the axis of the skeleton toward both ends; and winding a plurality of coil turns on the skeleton, wherein the plurality of coil turns are evenly wound in a direction along the axis of the skeleton.

[0011] In a cross section passing through the axis, an outer surface of the skeleton may have a parabolic shape that is symmetrical about the axis.

[0012] The parabolic shape can satisfy the formula Wherein L is the length of the skeleton, γ is the ratio between the length L of the skeleton and the maximum diameter D at the center position, x is the distance from the center of the axis in the axial direction of the skeleton, and a is the quadratic coefficient.

[0013] The value range of the quadratic term coefficient a can be Preferably, the value of the quadratic term coefficient a is approximately

[0014] The method may further include removing the bobbin after winding the plurality of coil turns.

[0015] One aspect of the present invention is to provide a magnetic measuring device, which comprises any one of the solenoid coils described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A prior art solenoid coil is shown.

[0017] Figure 2 A solenoid coil according to an exemplary embodiment of the present invention is shown.

[0018] Figure 3 Graph showing the range of values ​​of the coefficient of the quadratic term of the parabolic shape of the solenoid coil.

[0019] Figure 4 A solenoid coil according to another exemplary embodiment of the present invention is shown.

[0020] Figure 5 is a flow chart illustrating a method of manufacturing a solenoid coil according to an exemplary embodiment of the present invention.

[0021] Figure 6 The figure shows the comparison of magnetic field uniformity in the inner space of the solenoid coil according to the embodiment of the present invention and the solenoid coil in the prior art. DETAILED DESCRIPTION

[0022] Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

[0023] Figure 2 1 shows a solenoid coil 100 according to an exemplary embodiment of the present invention, which includes a plurality of coil turns 110. Figure 2 As shown, the diameter of the solenoid coil 100 gradually decreases in a direction from the center point O of the axis X of the solenoid coil 100 toward both ends.

[0024] Figure 2 1 shows a cross-sectional view of the solenoid coil 100 in the XY plane, wherein the X-axis is the central axis of the solenoid coil 100 and the Y-axis is a vertical axis passing through the solenoid center point O on the X-axis. In the X-axis direction, the plurality of coil turns 110 may be wound uniformly. Figure 2 A densely wound layer of coil turns 110 is shown, but a plurality of coil turns 110 may be wound evenly spaced apart, or multiple layers of coil turns 110 may be wound. Figure 2It is easy to see in the cross-sectional view that the diameter of the solenoid coil 100 gradually decreases from the center point O toward both ends. Although not shown, in a cross section perpendicular to the X-axis, the solenoid coil 100 may have a circular shape. The solenoid coil 100 may have a length L, corresponding to a value on the X-axis from -L / 2 to +L / 2. The solenoid coil 100 has a maximum diameter D at the center point O, from which the aspect ratio γ=L / D of the solenoid coil 100 can be determined. When the diameter of the solenoid coil 100 decreases toward both ends, the unevenness caused by the divergence of the magnetic lines of force at both ends can be compensated, thereby significantly improving the uniformity of the magnetic field within the solenoid coil 100.

[0025] Preferably, in a cross section passing through the X-axis (ie, the XY plane), Figure 2 As shown, the solenoid coil 100 may have a parabolic shape that is symmetrical about the X-axis. Figure 2 In order to clearly show the parabolic shape, dotted lines corresponding to the shape of the coil turn 110 are shown on the upper and lower sides of the coil turn 110, which are only used to show the parabolic shape of the coil turn 110, rather than a specific structure included in the solenoid coil 100. Figure 2 In the XY plane coordinate system shown, the parabolic shape of the solenoid coil 100 can be expressed by the following formula (1):

[0026]

[0027] Wherein, L is the length of the solenoid coil 100, γ is the ratio between the length L of the solenoid coil and the maximum diameter D at the center position O, x is the distance from the center position O in the X-axis direction of the solenoid coil 100, a is the quadratic term coefficient, and Y is the position of the coil turn 110 on the Y-axis, that is, |Y| is the radius of the coil turn 110 at the x position.

[0028] For some magnetic measurement applications, the solenoid coil length L and the maximum diameter D may be predetermined. At this time, by optimizing the value of the quadratic term coefficient a, the shape of the solenoid coil 100 can be adjusted to improve the magnetic field uniformity in the interior space of the solenoid coil 100 . Figure 3 The optimal range of the quadratic term coefficient a is shown. Figure 3 As shown, the value range of the quadratic term coefficient a can be expressed by the following formula (2):

[0029]

[0030] Preferably, the value of the quadratic term coefficient a can be approximately

[0031] Figure 4 A solenoid coil 200 according to another exemplary embodiment of the present invention is shown. Figure 2 Similar to the solenoid coil 100 shown, the solenoid coil 200 may also include a plurality of coil turns 110, and the diameter of the solenoid coil 200 gradually decreases from the center point O of the axis X of the solenoid coil 200 toward both ends. The solenoid coil 200 may also have other features of the solenoid coil 100.

[0032] The solenoid coil 200 may further include a skeleton 120, which may have a hollow structure. The skeleton 120 may be used to support the coil turns 110 during the manufacture and use of the solenoid coil, improve the yield rate of the solenoid coil, and increase the strength of the solenoid coil. The plurality of coil turns 110 may be evenly wound on the skeleton 120, and optionally, the skeleton 120 may be wound on an axis passing through the solenoid coil 200 (e.g., Figure 4 In a cross section (eg, an XY plane) of the coil 120 , the skeleton 120 may have a parabolic shape that is symmetrical about the X-axis and has the same shape as the solenoid coil 200 .

[0033] The structure of the skeleton 120 is not limited to a hollow structure. For example, when the skeleton 120 can be removed from the finished product of the solenoid coil, the skeleton 120 can also have a non-hollow structure, such as a structure containing a filler or a solid structure. The method of removing the skeleton will be discussed later.

[0034] Figure 5 FIG. 3 shows a flow chart of a method 300 for manufacturing a solenoid coil according to an exemplary embodiment of the present invention. Figure 5 As shown, the method 300 for manufacturing a solenoid coil includes a step S310 of preparing a skeleton and a step S320 of winding a coil on the skeleton. The skeleton manufactured in step S310 may be Figure 4 The skeleton 120 shown is parallel to the axis of the skeleton 120 (eg, Figure 4 In a cross section perpendicular to the X-axis shown in FIG. 1 , the skeleton 120 may have a circular shape. Also, in a cross section perpendicular to the X-axis shown in FIG. 1 , the skeleton 120 may have a circular shape. Figure 4 The diameter of the skeleton 120 gradually decreases in the direction from the origin (O) toward the two ends.

[0035] The skeleton 120 can be made of polytetrafluoroethylene, polyvinylidene fluoride or polyimide, or can be made of ceramic material or non-magnetic metal material. In the case of using plastic materials such as polytetrafluoroethylene, polyvinylidene fluoride or polyimide, it can be formed by general thermoplastic processing methods, such as extrusion, injection molding, molding, etc. In the case of using ceramic materials, it can be formed by methods such as extrusion molding, dry pressing molding, hot die casting, injection molding, film rolling molding, isostatic pressing, hot pressing molding and tape casting. In the case of using non-magnetic metal materials such as aluminum materials, it can be formed by methods such as extrusion. Alternatively, the skeleton 120 can be formed by 3D printing.

[0036] In step S320, a plurality of coil turns 110 may be wound on the frame 120, along the axis of the frame 120 (eg Figure 4 In the direction of the X-axis (shown), the plurality of coil turns 110 may be wound uniformly.

[0037] The solenoid coil 100 and / or the solenoid coil 200 may be wound with a conductive wire or a thin film cable, and a wire groove may be provided on the frame 120 to facilitate winding.

[0038] Optionally, refer to Figure 4 In a cross section (XY plane) passing through the X-axis of the solenoid coil 200 , the outer surface of the skeleton 120 may have a parabolic shape that is the same shape as the solenoid coil 200 and is symmetrical about the X-axis.

[0039] exist Figure 4 In the XY plane coordinate system shown, the parabolic shape of the skeleton 120 can be expressed by the following formula (3):

[0040]

[0041] Wherein, L is the length of the skeleton 120, γ is the ratio between the length L of the skeleton 120 and the maximum diameter D at the center position O, x is the distance from the center position O in the X-axis direction of the skeleton 120, a is the quadratic coefficient, and Y is the position of the skeleton 120 on the Y-axis, that is, |Y| is the radius of the skeleton 120 at the x position.

[0042] For some magnetic measurement applications, the skeleton length L and the maximum diameter D may be predetermined. In this case, by optimizing the value of the quadratic term coefficient a, the shape of the skeleton 120 can be adjusted, thereby improving the uniformity of the magnetic field in the internal space of the skeleton 120. The value range of the quadratic term coefficient a can be expressed by the following formula (4):

[0043]

[0044] Preferably, the value of the quadratic term coefficient a can be approximately

[0045] like Figure 5 As shown, the method 300 for manufacturing a solenoid coil may further include a step S330 of removing the skeleton 120 after winding a plurality of coil turns 110. The method for removing the skeleton 120 may be a crushing method, for example, crushing the skeleton 120 of a ceramic material by an impact force. Alternatively, the method for removing the skeleton 120 may be a dissolving method, for example, dissolving the skeleton 120 of a material such as polyvinylidene fluoride by a solvent such as NN dimethylacetamide or the like. Those skilled in the art may recognize that the method for removing the skeleton 120 is not limited thereto, and any method that can remove the skeleton 120 without damaging the solenoid coil may be adopted. By removing the skeleton, the energy loss of the solenoid coil may be reduced, and the weight may be reduced, making the solenoid coil easier to install.

[0046] In the case of step S330 of removing the skeleton 120, the skeleton 120 may not be limited to a hollow structure, but may be, for example, a structure containing a filler or an integral solid structure, thereby increasing the choice of skeletons during the solenoid coil manufacturing process.

[0047] According to an embodiment of the present invention, a magnetic measurement device (not shown) may be provided, comprising the solenoid coil described in the above embodiment. The magnetic measurement device may be, for example, a magnetometer, a nuclear magnetic resonance gyroscope, and the like.

[0048] Figure 6 The figure shows the comparison of magnetic field uniformity in the inner space of the solenoid coil according to the embodiment of the present invention and the solenoid coil in the prior art.

[0049] exist Figure 6 In the figure, the dotted line and the solid line respectively show the magnetic field strength of the solenoid coil of the prior art and the technical solution of the embodiment of the present invention at different distances from the center 0.0, the distance unit is meter (m), and the magnetic field strength is Oersted (Oe). Figure 6As shown, the magnetic field intensity in the internal space of the solenoid coil of the prior art shown by the dotted line decreases sharply as the distance from the center 0.0 increases, and the half-tube length uniformity ranges from 0 to -0.6%. The magnetic field intensity at the half position on one side of the center (i.e., at the positions of -L / 4 and L / 4 when the tube length is L) decreases by 0.6% compared with the magnetic field intensity at the center. The magnetic field intensity in the internal space of the solenoid coil of the preferred technical solution of the embodiment of the present invention shown by the solid line (for example, the quadratic term coefficient a adopts a preferred value) remains constant as a whole as the distance from the center 0.0 increases, and the half-tube length uniformity ranges from 0 to -0.08%. The magnetic field intensity at the half position on one side of the center (i.e., at the positions of -L / 4 and L / 4 when the tube length is L) decreases by 0.08% compared with the magnetic field intensity at the center.

[0050] Compared with the solenoid coil in the prior art, the solenoid coil in the embodiment of the present invention has a significant improvement in magnetic field uniformity and can provide a uniform magnetic field in its internal space, thereby meeting the needs of various magnetic measurement applications.

[0051] Although the embodiments of the present invention have been shown and described, the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the scope of protection of the present invention. For those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A solenoid coil, comprising a frame and a plurality of coil turns, wherein: The plurality of coil turns are uniformly wound on the frame in the axial direction of the solenoid coil; The diameter of the solenoid coil gradually decreases in the direction from the center of the axis of the solenoid coil toward both ends. wherein, in a cross section passing through the axis of the solenoid coil, the solenoid coil has a parabolic shape that is symmetrical about the axis of the solenoid coil, and The parabola shape satisfies the following formula: Wherein, L is the length of the solenoid coil, γ is the ratio between the length L of the solenoid coil and the maximum diameter D at the center position, x is the distance from the center of the axis in the axial direction of the solenoid coil, a is the quadratic term coefficient, |Y| is the radius of the coil turn, and the value range of the quadratic term coefficient a is: The skeleton has a hollow structure, and in a cross section passing through the axis of the solenoid coil, the skeleton has the parabolic shape.

2. The solenoid coil of claim 1, wherein: The value of the quadratic term coefficient a is 3. A method of manufacturing a solenoid coil, comprising: manufacturing a skeleton having a circular shape in a cross section perpendicular to the axis of the skeleton, the diameter of the skeleton gradually decreasing in a direction from the center of the axis of the skeleton toward both ends; and A plurality of coil turns are wound on the frame, and the plurality of coil turns are wound evenly in a direction along an axis of the frame. Wherein, in a cross section passing through the axis, the outer surface of the skeleton has a parabolic shape symmetrical about the axis, and the parabolic shape satisfies the following formula: Wherein, L is the length of the skeleton, γ is the ratio between the length L of the skeleton and the maximum diameter D at the center position, x is the distance from the center of the axis in the axial direction of the skeleton, a is the quadratic coefficient, |Y| is the radius of the skeleton in the cross section perpendicular to the axial direction of the skeleton, and the value range of the quadratic coefficient a is 4. The method of claim 3, wherein: The value of the quadratic term coefficient a is 5. The method of claim 3, further comprising removing the bobbin after winding the plurality of coil turns.

6. A magnetic measuring device comprising the solenoid coil according to claim 1 or 2.

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