An incremental range wide temperature range LVDT sensor and coil winding method

Abstract

The present invention relates to the technical field of linear sensors, specifically to an incremental range wide temperature range LVDT sensor and a coil winding method. It can adapt to wide temperature changes and strong magnetic field environments, and has a compact structure. The present invention includes a fixed frame and a movable frame; a movable frame end convex ring, a movable frame middle convex ring and a connecting rod are provided on the movable frame, and a primary coil is wound on the movable frame rod body, and the primary coil includes: a primary coil cylindrical section, and a primary coil left index section and a primary coil right index section distributed at both ends, and the connecting rod is used to connect the object to be measured. The present invention breaks the technical tradition of relying on magnetic material cores in this field, and innovatively proposes a LVDT displacement sensor solution of "non-magnetic material core" and "variable diameter coil". Environmental adaptability and measurement accuracy are higher; for the same size, the measurement area of ​​the present invention is larger; for the same measurement area, the size of the present invention is smaller.

Description

Technical Field

[0001] The invention relates to the technical field of linear sensors, and in particular to an improvement on a linear variable differential transformer sensor and a coil winding method thereof. Background Art

[0002] The linear variable differential transformer displacement sensor (LVDT) is a linear displacement sensor that can convert displacement signals into electrical signals. The three-stage LVDT sensor structure of the existing technical solution is as follows: Fig.11 , mainly composed of primary coil β, secondary coil 1 α1 and secondary coil 2 α2, skeleton and soft magnetic material core γ. The winding shape of primary coil β, secondary coil 1 α1 and secondary coil 2 α2 is generally cylindrical. The primary coil β is arranged in the middle of the skeleton, and the secondary coil 1 α1 and secondary coil 2 α2 are arranged on both sides of the primary coil β respectively. The soft magnetic material core γ is set at the center of the sensor axis and can move axially. The equivalent circuit schematic diagram of the existing technical solution is as follows Fig.12 , when a sinusoidal voltage (U1) of a constant frequency is applied to the primary coil β, a magnetic field is generated near the primary coil β. According to Faraday's law of electromagnetic induction, the secondary coil α1 and the secondary coil α2 will also induce induced voltages (e21 and e22). At this time, when the iron core γ moves axially in the coil, the mutual inductance (M1, M2) of the secondary coil α1 and the secondary coil α2 to the primary coil β will change, resulting in changes in the induced voltage (e21 and e22) of the secondary coil α1 and the secondary coil α2. Different positions of the iron core result in different mutual inductances, different induced voltages, and different differential voltages (U0) output by the two secondary coils, thereby realizing the transformation of the iron core displacement to the voltage.

[0003] The three-stage LVDT sensor of the prior art has magnetic leakage at the outer ends of the two secondary coils, such as Fig.13 The prior art LVDT displacement and secondary coil mutual inductance curve and Fig.14 The displacement and differential voltage curve. Since the three-stage LVDT sensor structure of the prior art is highly symmetrical on the left and right, Fig.13 The technical description is based on the unidirectional displacement of the sensor and the change of the mutual inductance of the secondary coil. Fig.13 The horizontal axis is the displacement of the soft magnetic material core γ (median). The vertical axis H represents the inductance value. Fig.13 The curve with several points in the middle) is the mutual inductance of the secondary coil α1 to the primary coil, and the M2 curve ( Fig.13 The curve with several points in it) is the mutual inductance of the secondary coil α2 to the primary coil, and the M1-M2 curve (i.e. Fig.13The curve with several ▲ points in the middle is the difference between the M1 curve and the M2 curve. This difference has a certain relationship with the final output voltage U. Fig.13 It can be clearly seen that with the increase of the γ displacement of the soft magnetic material core, the inductance difference changes nonlinearly.

[0004] Fig.14 The horizontal axis represents the displacement generated by the soft magnetic material core γ, and the vertical axis is the difference in voltage generated by the two secondary coils, that is, Fig.12 The U0 value in the figure, where x is located on the positive and negative semi-axes, respectively representing the direction in which the core γ moves from the middle position, and the positive and negative values ​​of the ordinate voltage also only represent the direction. It represents the ideal maximum range of the displacement sensor in the negative direction. The ideal maximum range of the displacement sensor in the positive direction is the position of L3. Fig.14 Curve A in the figure is the actual curve of displacement and differential voltage in the prior art, and curve B is the ideal fitting curve.

[0005] Combination Fig.11 , 12 It can be seen that the outer ends of the two secondary coils α1 and α2 have a reduction in the mutual inductance (M1, M2) of the primary coil β, resulting in insufficient induced voltage (U0) of the secondary coil. Fig.14 The opening shape at the tail end of the A and B curves, as the displacement increases, at L1, L2, and L3, which are equally spaced at the two outer ends, voltage drops ΔU1, ΔU2, and ΔU3 appear relative to the ideal curve, causing the measurement stroke of this section to become a nonlinear region, that is, the core displacement and the secondary coil induced voltage do not change according to the set fixed ratio, resulting in a waste of the effective measurement range. If you want to achieve a larger measurement range, the sensor must be lengthened, which wastes materials and increases the volume. However, in some application scenarios with strict volume restrictions, due to the limited installation space of the sensor, there is a dilemma of "to expand the range, the overall size of the device must be increased; to consider the compact structure, it is difficult to achieve accurate measurement."

[0006] In addition, the existing technical solution uses a high magnetic permeability soft magnetic core γ to affect the mutual inductance (M1, M2) of the secondary coil to the primary coil. The magnetic permeability (μ) is a property of the material, but the magnetic permeability of the soft magnetic material itself has nonlinear characteristics. Fig.15 It is a curve of the magnetic permeability (μ) of a high magnetic permeability material under temperature (T) changes. Fig.15 The horizontal axis T represents the ambient temperature, and the vertical axis is the magnetic permeability μ. The curve in the figure is the temperature-magnetic permeability change curve of the high magnetic permeability material. Fig.15It can be seen that when the external temperature (T) changes, the magnetic permeability of the high permeability soft magnetic core will change under the influence of temperature. In some cases, when the temperature (T) increases, the magnetic permeability (μ) will decrease. Therefore, in general, only a relatively linear section can be taken as its temperature applicable range. When the temperature exceeds the applicable range, the cliff-like drop in magnetic permeability cannot meet the needs of precise work, and may even fail.

[0007] like Fig.16 The BH curve and permeability change of a high magnetic permeability material. Fig.16 The horizontal axis H is the magnetic field intensity, and the vertical axis B is the magnetic induction intensity. The curve C in the figure is the BH curve, and its slope is the magnetic permeability (μ). Fig.16 It can be seen from the figure that the BH curve of soft magnetic material has two inflection points a and b (H1, B1). The inflection point a is the inflection point formed from the origin O to a lower magnetic field strength, which is nonlinear; the magnetic permeability (μ) between the inflection points ab increases linearly; but after the inflection point b, the magnetic permeability (μ) no longer increases linearly, which reflects that the differential displacement sensor will cause the magnetic failure of the high magnetic permeability soft magnetic core when the external magnetic field interference is large, affecting the measurement accuracy.

[0008] To sum up, it is explained that temperature and external magnetic field strength will affect the high magnetic permeability soft magnetic core, causing the magnetic material performance of the soft magnetic core to weaken, which in turn leads to a decrease in the accuracy of the displacement sensor. Therefore, the high magnetic permeability core is not perfect in high temperature and strong magnetic field environments.

[0009] In view of the above-mentioned prior art, finding an LVDT design solution that can not only maintain high precision and a large linear measurement range under the interference of temperature changes and drastic magnetic field changes, but also ensure miniaturization has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0010] In response to the above technical problems, the present invention provides an incremental range wide temperature range LVDT sensor and a coil winding method that can adapt to wide temperature changes and strong magnetic field environments, has a more compact structure, a larger effective measurement range at the same axial length, and higher measurement accuracy.

[0011] An incremental range wide temperature range LVDT sensor of the present invention comprises a fixed frame 1, wherein the fixed frame 1 is provided with a middle hole, and is characterized in that it also comprises a moving frame 2 which is provided in the middle hole and is coaxial with the fixed frame 1;

[0012] The two ends of the fixed frame 1 are respectively provided with a certain frame end convex ring 12, and the middle part of the fixed frame 1 is provided with a certain frame middle convex ring 11; a secondary coil 1 31 is wound between the fixed frame middle convex ring 11 and the fixed frame end convex ring 12 at one end, and a secondary coil 2 32 is wound between the fixed frame middle convex ring 11 and the fixed frame end convex ring 12 at the other end, and the secondary coil 1 31 and the secondary coil 2 32 are symmetrically arranged on the fixed frame middle convex ring 11, and the two are differentially connected in anti-phase; the secondary coil 1 31 and the secondary coil 2 32 respectively include: a secondary coil cylindrical segment IV close to the fixed frame middle convex ring 11, and a secondary coil index segment V close to the fixed frame end convex ring 12;

[0013] The moving frame 2 is in the shape of a solid rod as a whole, and is provided with a moving frame end convex ring 21, a moving frame middle convex ring 22 and a connecting rod 23. A primary coil 4 is wound around the moving frame rod of the moving frame end convex ring 21 and the moving frame middle convex ring 22. The primary coil 4 includes: a primary coil cylindrical section II, and a primary coil left index section I and a primary coil right index section III distributed at both ends. The connecting rod 23 is used to connect the object to be measured;

[0014] A lead hole 221 is provided on the middle convex ring 22 of the dynamic frame.

[0015] Furthermore, the voltages of the secondary coil 1 31 and the secondary coil 2 32 are connected in anti-phase to form the anti-phase differential connection.

[0016] Furthermore, the secondary coil cylindrical segment IV and the secondary coil index segment V are an integral coil, and starting from the intersection of the secondary coil cylindrical segment IV and the secondary coil index segment V, the number of winding turns of the secondary coil index segment V increases regularly, so that the secondary coil index segment V is horn-shaped as a whole.

[0017] Furthermore, the primary coil left index segment I, the primary coil cylindrical segment II and the primary coil right index segment III are an integral coil, and starting from the intersection of the primary coil cylindrical segment II with the primary coil left index segment I and the primary coil right index segment III, the number of winding turns of the primary coil left index segment I and the primary coil right index segment III increases regularly, so that the primary coil left index segment I and the primary coil right index segment III respectively form a trumpet shape with the outer diameter gradually expanding towards both ends.

[0018] Furthermore, the outer diameter of the middle convex ring 11 of the fixed frame is smaller than the outer diameters of the end convex rings 12 of the fixed frame at both ends.

[0019] Furthermore, the fixed frame 1 is made of a non-metallic material with a certain strength, and the movable frame 2 is made of a non-magnetic metal material.

[0020] The present invention provides a coil winding method for an incremental range wide temperature range LVDT sensor, comprising the following steps:

[0021] 1) Pre-processing of components,

[0022] Processing a fixed frame 1 and a movable frame 2, wherein the fixed frame 1 has two winding parts, left and right, and the movable frame 2 has one winding part;

[0023] 2) Primary coil winding,

[0024] The metal wire is wound evenly and smoothly on the winding part of the dynamic frame 2 until the number of turns of the primary coil cylindrical section II is reached, and then the primary coil left index section I and the primary coil right index section III are wound;

[0025] 3) Secondary coil winding,

[0026] On the winding part of the fixed frame 1, the metal wire is wound evenly and smoothly until the number of turns of the secondary coil cylindrical section IV is reached, and then the secondary coil index section V is wound.

[0027] Furthermore, the specific method of winding the primary coil is: winding a wire from left to right, the wire having an inlet wire end 411 and an outlet wire end 421, the length of the inlet wire end 411 meets the length of the left index segment I of the winding primary coil;

[0028] Then, the left root of the winding part of the dynamic frame 2 is set as the columnar segment winding starting point 41 and wound evenly until the number of turns of the primary coil columnar segment II is reached, and the columnar segment winding end point 42 is set at the top root of the right columnar segment of the winding part;

[0029] Next, the incoming wire head 411 is used to wind the left index segment I of the primary coil, and the rear end wire of the cylindrical segment winding end 42 continues to wind the right index segment III of the primary coil on the right side;

[0030] The incoming wire end 411 and the outgoing wire end 421 are led out from the lead-in hole 221 , respectively.

[0031] Furthermore, the diameter reduction measures of the primary coil left index section I, the primary coil right index section III and the secondary coil index section V are as follows:

[0032] The length of each winding part is a, and the axial length of each index segment is x. , the starting outer diameter of each index segment , ending outer diameter ,

[0033] The outer diameter of the variable diameter coil in each index segment as x changes is: , ,

[0034] ,

[0035] Wherein k is the adjustment coefficient, 0<k<1, b is the growth coefficient of the outer diameter of the exponential segment coil, c is the diameter of the cylindrical segment, and e is a natural constant.

[0036] The present invention breaks the technical tradition of relying on magnetic material cores in this field, and innovatively proposes a LVDT displacement sensor solution of "non-magnetic material core" and "variable diameter coil".

[0037] First, an electromagnetic dynamic skeleton (core) is used to replace the traditional magnetic material iron core in the existing technology, so that the sensor can adapt to the changing environment of wide temperature range and high-intensity magnetic field.

[0038] Secondly, the primary coil and secondary coil wound on the moving frame and the fixed frame have adopted "diameter changing" measures, which has changed the technical status quo of the "straight cylinder" shape of conventional coils in the prior art. When applied to the actual device of the present invention, not only is the magnetic field uniformity better, but the magnetic field at the end of the coil is also significantly increased; the nonlinear area is effectively converted into an effective range for utilization, thereby achieving the "incremental range" goal.

[0039] Finally, the present invention solves the problems of unstable output performance and poor reliability of sensors in high temperature and strong magnetic field environments in the prior art, as well as reduced sensor accuracy caused by weakening of the magnetic field at the end of the sensor in the prior art. Compared with the prior art, the incremental range wide temperature range LVDT sensor of the present invention has enhanced anti-interference ability, higher environmental adaptability and measurement accuracy; with the same size, the present invention has a larger measurement area; with the same measurement area, the present invention has a smaller size. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 It is a structural schematic diagram of the present invention,

[0042] Figure 2 is a schematic diagram of the structure of the dynamic skeleton in the present invention,

[0043] Figure 3 It is a schematic diagram of the structure of the fixed skeleton in the present invention,

[0044] Figure 4 is a segmented cross-sectional view of the primary coil in the present invention,

[0045] Figure 5 is a segmented cross-sectional view of the secondary coil 2 in the present invention,

[0046] Figure 6 This is a comparison diagram of the axial distribution of the magnetic field in the prior art and the present invention.

[0047] Figure 7 It is a curve diagram of the relationship between the actual differential voltage and displacement of the prior art and the present invention.

[0048] Figure 8 is a schematic diagram of a coil winding method of the present invention,

[0049] Fig. 9 The schematic diagram of the coil winding of the present invention is shown in FIG. Figure 1 ,

[0050] Fig.10 The schematic diagram of the coil winding of the present invention is shown in FIG. Figure 2 ,

[0051] Fig.11 The schematic diagram of the structure of the three-section LVDT sensor provided by the prior art is as follows:

[0052] Fig.12 The circuit equivalent schematic diagram of the three-section LVDT sensor provided by the prior art is as follows:

[0053] Fig.13 The displacement curve of the core of the three-section LVDT and the mutual inductance of the secondary coil 1 and the secondary coil 2 in the prior art is shown in FIG.

[0054] Fig.14 The following is a graph showing the actual situation of the prior art and the ideal situation of the three-section LVDT core displacement and the secondary coil differential voltage.

[0055] Fig.15 It is a curve diagram of the change of magnetic permeability of a high magnetic permeability material under temperature change in the prior art.

[0056] Fig.16 The figure is a BH curve diagram and a magnetic permeability variation curve diagram of a high magnetic permeability material in the prior art.

[0057] In the figure, 1 is a fixed frame, 11 is a middle convex ring of the fixed frame, and 12 is a convex ring at the end of the fixed frame;

[0058] 2 is a moving frame, 21 is a convex ring at the end of the moving frame, 22 is a convex ring in the middle of the moving frame, 221 is a lead hole, and 23 is a connecting rod;

[0059] 31 is a secondary coil 1, 32 is a secondary coil 2;

[0060] 4 is the primary coil, 41 is the starting point of the cylindrical winding, 411 is the incoming wire end, 42 is the end point of the cylindrical winding, and 421 is the outgoing wire end;

[0061] Ⅰ is the left index segment of the primary coil, Ⅱ is the cylindrical segment of the primary coil, Ⅲ is the right index segment of the primary coil, Ⅳ is the cylindrical segment of the secondary coil, and Ⅴ is the index segment of the secondary coil. DETAILED DESCRIPTION

[0062] The following is combined with Figure 1-10 The technical solution of the present invention is further explained through specific implementation methods;

[0063] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on this patent; in order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0064] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "inner", "outer", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0065] In the description of the present invention, unless otherwise clearly specified and limited, if the term "connection" or the like appears to indicate the connection relationship between components, the term should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two components or the interaction relationship between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0066] An incremental range wide temperature range LVDT sensor of the present invention, such as Figure 1-5 , including a fixed frame 1, the fixed frame 1 is provided with a central hole, and also includes a movable frame 2 movably arranged in the central hole and coaxial with the fixed frame 1;

[0067] A certain frame end convex ring 12 is respectively provided at both ends of the fixed frame 1, and a certain frame middle convex ring 11 is provided at the middle part of the fixed frame 1; a secondary coil 1 31 is wound between the fixed frame middle convex ring 11 and the fixed frame end convex ring 12 at one end, and a secondary coil 2 32 is wound between the fixed frame middle convex ring 11 and the fixed frame end convex ring 12 at the other end, and the secondary coil 1 31 and the secondary coil 2 32 are symmetrically arranged on the fixed frame middle convex ring 11, and the two are differentially connected in anti-phase; the secondary coil 1 31 and the secondary coil 2 32 respectively include: a secondary coil cylindrical section IV close to the fixed frame middle convex ring 11, and a secondary coil index section V close to the fixed frame end convex ring 12;

[0068] The dynamic frame 2 is in the shape of a solid rod as a whole, and is provided with a dynamic frame end convex ring 21, a dynamic frame middle convex ring 22 and a connecting rod 23 on the dynamic frame 2. A primary coil 4 is wound around the dynamic frame rod of the dynamic frame end convex ring 21 and the dynamic frame middle convex ring 22. The primary coil 4 includes: a primary coil cylindrical section II, and a primary coil left index section I and a primary coil right index section III distributed at both ends. The connecting rod 23 is used to connect the object to be measured;

[0069] A lead hole 221 is provided on the middle convex ring 22 of the moving frame.

[0070] Among them, the voltages of the secondary coil 1 31 and the secondary coil 2 32 are connected in anti-phase to form an anti-phase differential connection. The differential output is generated, so that the differential voltage and displacement are linearly related, which is convenient for the subsequent circuit to accurately convert; the second is zero drift compensation. If a coil of the secondary coil deviates due to aging caused by environmental changes, this connection can offset part of the deviation and maintain the stability of the sensor.

[0071] The secondary coil cylindrical segment IV and the secondary coil index segment V are an integral coil. Starting from the intersection of the secondary coil cylindrical segment IV and the secondary coil index segment V, the number of winding turns of the secondary coil index segment V increases regularly, so that the secondary coil index segment V is horn-shaped as a whole.

[0072] The left index segment I of the primary coil, the cylindrical segment II of the primary coil and the right index segment III of the primary coil are an integral coil. Starting from the intersection of the cylindrical segment II of the primary coil and the left index segment I of the primary coil and the right index segment III of the primary coil, the number of winding turns of the left index segment I of the primary coil and the right index segment III of the primary coil increases regularly, so that the left index segment I of the primary coil and the right index segment III of the primary coil respectively form a trumpet shape with the outer diameter gradually expanding towards both ends.

[0073] The outer diameter of the middle convex ring 11 of the fixed frame is smaller than the outer diameter of the end convex rings 12 of the fixed frame at both ends. The middle convex ring 11 of the fixed frame plays a role of position guidance during the coil winding process, wherein the height of the coil winding cannot exceed the height of the middle convex ring 11 of the fixed frame, to ensure the neatness and consistency of the winding. Since the secondary coil 1 31 and the secondary coil 2 32 wound by the fixed frame have variable diameters, that is, the outer end is trumpet-shaped, and the outer diameter of the outer end is larger than the diameter of the coil near the middle convex ring, this design is made to guide the radial position of the coil.

[0074] The fixed frame 1 is made of a non-metallic material with a certain strength, and PPS is preferred in this embodiment. The dynamic frame 2 is made of a non-magnetic metal material, and austenitic stainless steel is preferred in this embodiment. Since one of the innovative achievements of the present invention is: a magnetic core without permanent magnetic material, it can adapt to the application environment of a wide temperature range and a strong magnetic field. Under this technical measure, it can be ensured that the technical measure of the present invention does not have a magnetic core. PPS engineering plastic is used, and the outer frame diameter is relatively large. The strength of the engineering plastic is sufficient to ensure that the winding is uniform and flat and withstand the tension of the winding. The plastic not only ensures that it is non-magnetic, but also has a light overall weight. The diameter of the dynamic frame is very small. It not only needs to be wound, but also needs to move with the object to be measured. It is very easy to deform. The deformation of the fixed frame causes the device to be poorly centered, and it is easy to produce radial errors, resulting in a decrease in the accuracy of the sensor. Therefore, non-magnetic material and stainless steel with sufficient strength are selected. If the strength is sufficient, it can also be other alloy materials that do not contain magnetic conductive materials, such as ceramics.

[0075] The "wide temperature range" that the present invention can adapt to is further described as follows:

[0076] The prior art generally adopts a moving iron core design, which will cause magnetic saturation and permeability changes under temperature changes (especially in a high temperature environment of 80~150℃), resulting in nonlinear changes in the sensor output signal, thereby limiting its applicable temperature range. The applicable temperature range of the prior art is generally -20℃~80℃; the present invention adopts a moving coil design, which eliminates this factor. The structural design of the coil can better adapt to temperature changes, the electrical characteristics of the coil are relatively stable in extreme environments, the temperature drift is small, and the applicable temperature range is greatly increased to -40℃~150℃.

[0077] The purpose of using the combined variable diameter coil in the present invention is to improve the magnetic field so that the magnetic field distribution of the displacement sensor is more consistent with the sensor output characteristics. Fig.13 , 14According to the description, it can be determined that: with the increase of the γ displacement of the soft magnetic material core, the inductance difference changes nonlinearly. In this embodiment, the outer ends of the two secondary coils (secondary coil 1 31, secondary coil 2 32) will still reduce the mutual inductance (M1, M2) of the primary coil 4, resulting in insufficient induced voltage (U0) of the secondary coil, which in turn causes the measurement stroke to become a nonlinear region, resulting in a waste of effective measurement range. The technical measure of "combined variable diameter coil" innovatively proposed by the present invention uses coils with exponential outer diameter changes at the outer ends of the primary and secondary coils to compensate for the magnetic field, achieve an ideal fitting voltage at the ends, and achieve the purpose of nonlinear compensation.

[0078] like Figure 6 We compared the axial magnetic field distribution of the full-diameter cylindrical coil and the variable-diameter combination coil under the same conditions. The vertical axis in the figure is the magnetic field intensity, and the horizontal axis is the distance; the E curve represents the axial distribution of the variable-diameter combination coil, and the F curve represents the axial distribution of the full-diameter cylindrical coil.

[0079] The uniform range of the magnetic field generally refers to the area where the magnetic field strength remains constant. In the axial center area of ​​the cylindrical coil of equal diameter, it is generally believed that the magnetic field is relatively uniform and remains constant. The uniform range is defined as the area that does not exceed ±1% of the magnetic field strength at the center of the coil. Assuming that the lengths of the variable diameter combination coil and the cylindrical coil of equal diameter are both a, it is found that the magnetic field of the cylindrical coil of equal diameter (i.e. Figure 6 The uniform interval of the F curve is about half the length of the coil, that is, 0.5a, while the magnetic field of the variable diameter combined coil (that is Figure 6 The uniform interval length of the E curve in the middle reaches 0.85a. It proves that under the same coil length and the same current excitation, the variable diameter combination coil can produce a wider uniform magnetic field interval, making the sensor magnetic flux change in the coil consistent and improving the stability of the output induced electromotive force. At the same time, the sensor works in a more linear area, reducing the reduction of the induced electromotive force caused by the nonlinear attenuation of the magnetic field. Figure 6 It can be seen that the magnetic field of the full-diameter cylindrical coil at the end of the coil is approximately half of the center of the coil axis. This is the reason why the output voltage of the LVDT displacement sensor of the prior art solution drops when it moves to the end. The variable diameter combination coil in the example of this application not only has better magnetic field uniformity, but also has a significant increase in the magnetic field at the end of the coil. This shows that the variable diameter combination coil can change the magnetic field variation in space, and the magnetic field uniformity range is longer. The magnetic field distribution characteristics of the coil winding method of the present invention are more in line with the output characteristics of the displacement sensor.

[0080] The invention provides a coil winding method for an incremental range wide temperature range LVDT sensor, such as Figure 8-10 , including the following steps:

[0081] 1) Pre-processing of components,

[0082] Processing a fixed frame 1 and a movable frame 2, wherein the fixed frame 1 has two winding parts, left and right, and the movable frame 2 has one winding part;

[0083] 2) Primary coil winding,

[0084] The metal wire is wound evenly and smoothly on the winding part of the dynamic frame 2 until the number of turns of the primary coil cylindrical section II is reached, and then the primary coil left index section I and the primary coil right index section III are wound;

[0085] The specific method of winding the primary coil is: winding the wire from left to right, the wire having an inlet wire end 411 and an outlet wire end 421, and the length of the inlet wire end 411 meets the length of the left index segment I of the winding primary coil;

[0086] Then, the left root of the winding part of the dynamic frame 2 is set as the columnar segment winding starting point 41 and is wound evenly until the number of turns of the primary coil columnar segment II is reached, and the columnar segment winding end point 42 is set at the top root of the right columnar segment of the winding part;

[0087] Next, the incoming wire head 411 is used to wind the left index segment I of the primary coil, and the rear end wire of the cylindrical segment winding end 42 continues to wind the right index segment III of the primary coil on the right side;

[0088] An incoming wire terminal 411 and an outgoing wire terminal 421 are led out from the lead-in hole 221 .

[0089] 3) Secondary coil winding,

[0090] On the winding part of the fixed frame 1, the metal wire is wound evenly and smoothly until the number of turns of the secondary coil cylindrical section IV is reached, and then the secondary coil index section V is wound.

[0091] The following combination Figure 8 The wire group wound by the coil winding method of the present invention is further described in detail:

[0092] 1. Variable diameter: First, the variable diameter parameters should be determined. Suppose the length of the primary coil is The length of the variable diameter section of the variable diameter coil should be from the left and right ends Starting from the diameter change, then The inner diameter of the cylindrical section of the primary coil is the same as the outer diameter of the winding section, which is d. The outer diameter of the intersection of the variable diameter coil and the cylindrical section coil is recorded as the starting outer diameter (minimum outer diameter) of the variable diameter coil. , the rightmost outer diameter of the variable diameter coil is recorded as the final outer diameter (maximum outer diameter) of the variable diameter coil Let the distance between the intersection of the variable diameter coil and the cylindrical segment coil be x, and the outer diameter of the variable diameter coil that changes with x is , then we have , this formula is an exponential function. As x increases, the outer diameter of the variable coil It will increase nonlinearly, and the closer to the end of the variable diameter coil, the faster the outer diameter of the variable diameter coil increases, which is consistent with Fig.14 The law of nonlinear increase between the voltage △U and x of the ideal curve B voltage and the actual voltage difference in the prior art. Where k is the adjustment coefficient ( , , In the primary coil, the maximum outer diameter of the variable diameter coil should be constrained by the inner diameter of the fixed frame and be smaller than the inner diameter of the fixed frame; in the secondary coil, the maximum outer diameter of the variable diameter coil should be constrained by the maximum radial dimension of the installation and be smaller than the maximum radial dimension of the installation; when , After k is determined, b and c in the above formula can be obtained, where b is the growth coefficient of the outer diameter of the exponential segment coil, c is the diameter of the cylindrical segment, and e is a natural constant.

[0093] It should be noted that: displacement sensors with different measuring ranges should adjust the coefficient k value according to actual conditions, which can be achieved by those skilled in the art based on the aforementioned technical concept of the present invention and will not be elaborated here.

[0094] 2. Determine the number of winding layers of the variable diameter coil: Assume that the diameter of the winding enameled wire is d1, then the outer diameter of the variable diameter coil The corresponding number of layers should be , Maximum number of winding layers of variable diameter coil .

[0095] 3. Determine the number of turns of the variable diameter coil: Then the maximum number of turns of the variable diameter coil (bottom layer) is , the number of turns in each subsequent layer is reduced by n turns, so the number of winding coils in the second layer is , then the number of circles in the third layer is equal to , the number of circles in the fourth layer is , until the number of winding layers reaches the maximum number of winding layers The number of turns n reduced per layer is not specifically limited here, and should be determined according to the degree of change in the diameter of the variable diameter coil. Considering the specific application environment of the present invention, an odd number of layers is generally used in the cylindrical section, and an even number of layers is used in each layer of the exponential section, which is convenient for the round trip during winding.

[0096] In order to clearly illustrate the technical solution in this embodiment, a comparison table of the number of turns of a variable diameter coil and a cylindrical coil of equal diameter in the prior art is given below, as shown in Table 1:

[0097] Table 1

[0098] Location 1 2 3 4 5 N1 <![CDATA[Z N ]]> <![CDATA[Z N+1 ]]> <![CDATA[Z N+2 ]]> <![CDATA[Z N+3 ]]> <![CDATA[Z N+4 ]]> N2 <![CDATA[Z N ]]> <![CDATA[Z N ]]> <![CDATA[Z N ]]> <![CDATA[Z N ]]> <![CDATA[Z N ]]>

[0099] In the table, N1 is the number of coupled turns of the variable diameter coil at the axial equal distance compensation position, and N2 is the number of coupled turns of the cylindrical coil at the axial equal distance position. The positions in the table represent any value of equal distance, and in implementation, the value of equal distance can be used according to the specific requirements of the product. Example: The number of coupled turns of the variable diameter coil compensation position at position 1 is Z N , the number of coupling turns at the compensation position of the variable diameter coil at position 2 increases by 2 turns, which is Z N+1 ; The coupling turns at the 3-position variable diameter compensation position are increased by Z compared to the 1-position 2 Turn, Z N+2 , and so on, relative to the cylindrical coil axial equidistant constant number of turns Z N The extra coupling turns are the compensation turns for this area, and the compensation turns vary nonlinearly. Within the same distance, the larger the compensation turns, the larger the compensated differential voltage. In the specific implementation, the value of N is arbitrary.

[0100] In the embodiment of the present application, considering the wide temperature range of the product and the interference of the external electromagnetic environment, the stability and reliability of the LVDT displacement sensor under these factors must be considered. In order to reduce the decrease in output accuracy and linearity of the LVDT displacement sensor caused by external factors, the high permeability magnetic core is removed in the embodiment of the present application. The following is the specific analysis process:

[0101] For the displacement sensor of the prior art, according to Faraday's law, when the high magnetic permeability iron core moves, it cuts the magnetic flux lines to generate an induced electromotive force. Then for the differential voltage U0 of the two secondary coils, let the magnetic flux inside the iron core be , for a secondary coil with N turns, we have

[0102] (1)

[0103] Also because (2)

[0104] have (3)

[0105] Where: t is time, N is the number of turns of the coupled secondary coil, B is the magnetic induction intensity, S is the cross-sectional area through which the core passes, μ is the magnetic permeability of the core, e 11 is the induced voltage generated by the secondary coil 31, e 12 is the induced voltage generated by the secondary coil 2 32, and H is the magnetic field strength.

[0106] From equations (1), (2), and (3), we can see that the differential voltage output by the displacement sensor is related to the magnetic permeability of the core. However, for a high magnetic permeability core, Fig.15, the magnetic permeability μ is not linear under the influence of temperature, and sometimes it drops sharply. Therefore, if the LVDT displacement sensor exceeds the high magnetic permeability core temperature range, the magnetic material performance of the sensor will be weakened, which will lead to a decrease in sensor output accuracy, poor linearity, and reduced sensitivity. Fig.16 The C curve in the figure represents the BH curve of the magnetic material. When the magnetic induction intensity reaches a certain level and exceeds the saturation magnetic flux density a (H1, B1), once the magnetic core reaches saturation, the induced electromotive force no longer increases with the increase of current. Therefore, considering comprehensively, under wide temperature range and high magnetic field working conditions, high magnetic permeability materials will affect the measurement accuracy of the displacement sensor. Therefore, it is decided to remove the use of high magnetic permeability iron core.

[0107] The combined variable diameter coil solution and coil winding method adopted by the present invention increase the measuring range of the sensor and improve the sensitivity while keeping the volume of the sensor unchanged. Figure 7 , Figure 7 The horizontal axis is the displacement of the moving coil (i.e. the moving frame 2 around which the primary coil 4 is wound), and the vertical axis U is the difference in voltage generated by the two secondary coils, that is, Fig.12 U0 in Figure 7 The curve A in the figure represents the technical effect produced by the present embodiment, that is, the relationship curve between the displacement of the moving coil and the output voltage, and the curve B is the relationship curve between the displacement of the iron core and the output voltage of the prior art.

[0108] from Figure 7 It can be clearly seen that compared with Fig.14 The ideal fitting curve B in the embodiment is that the relationship curve between the displacement of the moving coil and the output voltage is not only improved in linearity by the diameter change measure, but also has a fundamental change in slope (in this case, the curve A has completely deviated from the curve B). The change in slope means that the sensitivity of the sensor obtained in this embodiment is greatly increased compared with the sensor in the prior art, so that the sensor obtained by the present invention can adapt to more precise use requirements.

[0109] from Figure 7 It can also be seen that the left end of curve B is a linear segment, and the right end has obvious nonlinear factors. Taking the linear segment as the boundary, it can be estimated that the range of the prior art is 4L (L is the proportional factor). After adopting the solution in the example of this application, the effective range of the sensor is 5L, and the linearity of the sensor reaches 0.2%, which fully meets the requirements of large range, high precision and miniaturization.

[0110] It should be noted that the above specific implementations are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art should understand that various modifications, equivalent substitutions, changes, etc. can be made to the present invention based on the technical content disclosed in this application document. However, as long as these changes do not deviate from the spirit of the present invention, they should be within the scope of protection of the present invention. In addition, some terms used in the specification and claims of this application are not restrictive, but are only for the convenience of description.

Claims

1. An incremental range wide temperature range LVDT sensor, comprising a fixed frame (1), wherein the fixed frame (1) is provided with a central hole, characterized in that: It also includes a movable frame (2) disposed in the middle hole and coaxial with the fixed frame (1); The two ends of the fixed frame (1) are respectively provided with a certain frame end convex ring (12), and the middle part of the fixed frame (1) is provided with a certain frame middle convex ring (11); a secondary coil 1 (31) is wound between the fixed frame middle convex ring (11) and the fixed frame end convex ring (12) at one end, and a secondary coil 2 (32) is wound between the fixed frame middle convex ring (11) and the fixed frame end convex ring (12) at the other end; the secondary coil 1 (31) and the secondary coil 2 (32) are symmetrically arranged on the fixed frame middle convex ring (11), and the two are differentially connected in anti-phase; the secondary coil 1 (31) and the secondary coil 2 (32) respectively include: a secondary coil cylindrical section (IV) close to the fixed frame middle convex ring (11), and a secondary coil index section (V) close to the fixed frame end convex ring (12); The moving frame (2) is in the shape of a solid rod as a whole. A moving frame end convex ring (21), a moving frame middle convex ring (22) and a connecting rod (23) are provided on the moving frame (2). A primary coil (4) is wound around the moving frame rod of the moving frame end convex ring (21) and the moving frame middle convex ring (22). The primary coil (4) comprises: a primary coil cylindrical section (II), and a primary coil left index section (I) and a primary coil right index section (III) distributed at both ends. The connecting rod (23) is used to connect to the object to be measured. A wire lead hole (221) is provided on the middle convex ring (22) of the moving frame; The voltages of the secondary coil 1 (31) and the secondary coil 2 (32) are connected in anti-phase to form the anti-phase differential connection; Generate differential output so that the differential voltage and displacement are linearly related, which is convenient for the subsequent circuit to accurately convert; and zero drift compensation. If one coil of the secondary coil deviates due to aging caused by environmental changes, the deviation can be offset to maintain the stability of the sensor.

2. The incremental range wide temperature range LVDT sensor according to claim 1, characterized in that: The secondary coil cylindrical section (IV) and the secondary coil index section (V) are an integral coil. Starting from the intersection of the secondary coil cylindrical section (IV) and the secondary coil index section (V), the number of winding turns of the secondary coil index section (V) increases regularly, so that the secondary coil index section (V) is horn-shaped as a whole.

3. The incremental range wide temperature range LVDT sensor according to claim 1, characterized in that: The primary coil left index section (I), the primary coil cylindrical section (II) and the primary coil right index section (III) are an integral coil. Starting from the intersection of the primary coil cylindrical section (II) with the primary coil left index section (I) and the primary coil right index section (III), the number of winding turns of the primary coil left index section (I) and the primary coil right index section (III) increases regularly, so that the primary coil left index section (I) and the primary coil right index section (III) respectively form a trumpet shape with an outer diameter gradually expanding toward both ends.

4. The incremental range wide temperature range LVDT sensor according to claim 1, characterized in that: The outer diameter of the middle convex ring (11) of the fixed frame is smaller than the outer diameters of the end convex rings (12) of the fixed frame at both ends.

5. The incremental range wide temperature range LVDT sensor according to claim 1, characterized in that: The fixed frame (1) is made of a non-metallic material with a certain strength, and the movable frame (2) is made of a non-magnetic metal material.

6. A coil winding method for an incremental range wide temperature range LVDT sensor as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: 1) Pre-processing of components, Processing a fixed frame (1) and a movable frame (2), wherein the fixed frame (1) has two winding parts, left and right, and the movable frame (2) has one winding part; 2) Primary coil winding, The metal wire is evenly and smoothly wound on the winding part of the dynamic frame (2) until the number of turns of the primary coil cylindrical section (II) is reached, and then the primary coil left index section (I) and the primary coil right index section (III) are wound; 3) Secondary coil winding, On the winding part of the fixed frame (1), the metal wire is evenly and evenly wound until the number of turns of the secondary coil cylindrical section (IV) is reached, and then the secondary coil index section (V) is wound.

7. The coil winding method of the incremental range wide temperature range LVDT sensor according to claim 6, characterized in that: The specific method for winding the primary coil is: winding a wire from left to right, the wire having an inlet wire end (411) and an outlet wire end (421), the length of the inlet wire end (411) meeting the length of the left index segment (I) of the primary coil; Then, the left root of the winding part of the dynamic frame (2) is set as the columnar segment winding starting point (41) and the winding is evenly wound until the number of turns of the primary coil columnar segment (II) is reached, and the columnar segment winding end point (42) is set at the top root of the right columnar segment of the winding part; Next, the incoming wire head (411) is used to wind the left index section (I) of the primary coil, and the rear end wire of the cylindrical section winding end point (42) is used to continue winding the right index section (III) of the primary coil on the right side; The incoming wire end (411) and the outgoing wire end (421) are respectively led out from the wire lead hole (221).

8. The coil winding method of the incremental range wide temperature range LVDT sensor according to claim 6, characterized in that: The diameter reduction measures of the primary coil left index section (I), the primary coil right index section (III) and the secondary coil index section (V) are as follows: The length of each winding section is a, and the axial length of each index segment is x, 0≤x≤a / 5, and the starting outer diameter of each index segment is Dmin, and the ending outer diameter is Dmax. The outer diameter of the variable diameter coil in each index segment changes with x is Dx, Dmin≤Dx≤Dmax, Dx=be kx +c, Wherein k is the adjustment coefficient, 0<k<1, b is the growth coefficient of the outer diameter of the exponential segment coil, c is the diameter of the cylindrical segment, and e is a natural constant.

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