A high-sensitivity LVDT sensor

Abstract

The present invention discloses a high-sensitivity LVDT sensor, which relates to the technical field of LVDT sensor structural design. The sensor comprises: a housing assembly, a connecting rod, an iron core, a skeleton, a primary coil, a first secondary coil, and a second secondary coil. The skeleton is nested within the housing assembly, and the iron core is movably disposed within the skeleton along its length. One end of the connecting rod is connected to one end of the iron core, and the other end extends from the housing assembly. The primary coil, the first secondary coil, and the second secondary coil are wound around the skeleton. The iron core is provided with an inner hole extending through both ends. The solution provided by the present invention can improve the measurement sensitivity of the LVDT sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of LVDT sensor structure design, in particular to a high-sensitivity LVDT sensor. Background Art

[0002] LVDT, short for Linear Variable Differential Transformer, is a linear displacement sensor. Due to its nearly unlimited mechanical life, unlimited resolution, and high zero-position repeatability, LVDT sensors are often used to detect small displacements, such as servo valve spool displacement and shaft runout. Applications such as servo valves require not only an extremely small LVDT sensor for easy integration into the servo valve, but also high sensitivity and excellent temperature drift characteristics. While conventional LVDT sensors can achieve nearly unlimited resolution, they require either an increased excitation signal amplitude or a significant increase in the number of secondary winding turns to achieve a higher secondary-to-primary turns ratio. Increasing the excitation signal amplitude increases output power and reduces output stability, while increasing the number of winding turns increases the size, making it difficult to meet the demands of compact applications. Furthermore, simply increasing the number of windings also results in losses and deteriorates the sensor's temperature characteristics. Summary of the Invention

[0003] The purpose of the present invention is to provide a high-sensitivity LVDT sensor to solve the problems existing in the above-mentioned prior art and improve the measurement sensitivity.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a high-sensitivity LVDT sensor, comprising: a housing assembly, a connecting rod, an iron core, a skeleton, a primary coil, a first secondary coil and a second secondary coil; the skeleton is nested in the housing assembly, and the iron core is movably arranged in the skeleton along the length direction; one end of the connecting rod is connected to one end of the iron core, and the other end extends from the housing assembly; the primary coil, the first secondary coil and the second secondary coil are wound around the outside of the skeleton; and an inner hole is provided in the iron core that passes through both ends.

[0006] Preferably, the primary coil is wound on the frame; the first secondary coil and the second secondary coil are wound on the primary coil to form a two-section laminated LVDT.

[0007] Preferably, a groove penetrating the inner and outer surfaces of the iron core is provided on the wall surface of the iron core.

[0008] Preferably, the slot passes through both ends of the core in the length direction.

[0009] Preferably, the groove is provided with one.

[0010] Preferably, the groove extends along a straight line.

[0011] Preferably, the wire diameter of the primary coil is larger than the wire diameters of the first secondary coil and the second secondary coil.

[0012] Preferably, the primary coil, the first secondary coil and the second secondary coil are made of constantan enameled wire.

[0013] Preferably, the primary coil, the first secondary coil and the second secondary coil are made of manganese copper enameled wire.

[0014] Preferably, the primary coil, the first secondary coil and the second secondary coil are made of nickel-chromium alloy enameled wire.

[0015] Compared with the prior art, the present invention has achieved the following technical effects:

[0016] 1. The high-sensitivity LVDT sensor provided by the present invention adopts a hollow iron core. Simulation analysis shows that the sensitivity of the hollow iron core is improved compared with the solid iron core, while the nonlinearity can be kept almost unchanged; therefore, the solution provided by the present invention can improve the sensitivity of the LVDT sensor.

[0017] 2. The basic structure of the high-sensitivity LVDT sensor proposed in the present invention is basically the same as that of the conventional LVDT. The output sensitivity can be improved without additional components, and it is easy to improve and implement.

[0018] 3. In the high-sensitivity LVDT sensor proposed in the present invention, slotting the iron core can further improve the sensitivity.

[0019] 4. In the high-sensitivity LVDT sensor proposed in the present invention, the wire diameter of the primary coil is larger than that of the secondary coil, which can achieve both sensitivity improvement and volume reduction.

[0020] 5. In the high-sensitivity LVDT sensor proposed in the present invention, the coil is wound with low-temperature drift enameled wire, which makes the sensor have excellent temperature characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. 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 paying any creative work.

[0022] Figure 1 A schematic structural diagram of a high-sensitivity LVDT sensor provided in an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the core structure;

[0024] Figure 3 This is a comparison chart of the gain effect after opening different numbers of slots on the iron core;

[0025] In the figure: 1-connecting rod; 2-first end cover; 3-magnetic conductive shell; 4-first secondary coil; 5-primary coil; 6-skeleton; 7-iron core; 8-second secondary coil; 9-second end cover; 10-slot. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The following combination Figures 1 to 3 , describing embodiments of the present invention.

[0029] The present invention provides a high-sensitivity LVDT sensor, hereinafter referred to as LVDT sensor, such as Figure 1 As shown, it includes: a shell assembly, a connecting rod 1, an iron core 7, a skeleton 6, a primary coil 5, a first secondary coil 4 and a second secondary coil 8; the skeleton 6 is nested in the shell assembly, and the iron core 7 is movably arranged in the skeleton 6 along the length direction; one end of the connecting rod 1 is connected to one end of the iron core 7, and the other end extends from the shell assembly; the primary coil 5, the first secondary coil 4 and the second secondary coil 8 are wound around the outside of the skeleton 6; an inner hole passing through both ends is provided in the iron core 7.

[0030] The hollow core 7 improves sensitivity because, according to the LVDT operating principle, the primary coil 5 requires a sinusoidal excitation signal with a continuously varying amplitude. This excitation signal, when passed into the solenoid formed by the primary coil 5, generates an alternating magnetic field. This alternating magnetic field induces eddy currents within the core 7, which, according to Lenz's law, resist changes in the magnetic field, thereby reducing sensitivity. Using a hollow core 7 significantly suppresses these eddy currents, especially when using high-frequency excitation signals.

[0031] From the perspective of overall structure and main components, the biggest difference between the embodiment of the present invention and the conventional LVDT is that the iron core 7 in the LVDT sensor provided by the present invention is a hollow structure, while the conventional LVDT uses a solid iron core. Simulation analysis shows that the sensitivity of the hollow iron core 7 is improved from the original 818mV / mm to 1124mV / mm compared to the solid iron core, while the nonlinearity can be kept almost unchanged.

[0032] In some embodiments, the primary coil 5 is wound on the frame 6 ; the first secondary coil 4 and the second secondary coil 8 are wound on the primary coil 5 to form a two-section laminated LVDT.

[0033] The two-section laminated structure adopted in this embodiment can significantly improve the compactness of the LVDT sensor.

[0034] In some embodiments, such as Figure 2 As shown, a slot 10 is provided on the wall of the core 7, which passes through the inner and outer surfaces of the core 7. Specifically, the slot 10 passes through both ends of the core 7 in the longitudinal direction; one slot 10 is provided; and the slot 10 extends along a straight line (i.e., the axial direction of the core 7).

[0035] This embodiment further improves the sensitivity of the LVDT sensor. This embodiment adopts a slotting method based on the hollow iron core 7, as shown in the attached figure. Figure 2 The structure of the slotted and hollow iron core 7 is shown in the figure. The slotting direction is axial so that the iron core 7 is completely divided in the circumferential direction. Figure 3 As shown in the figure, the influence of the number of slots in the core 7 on the sensitivity is shown. It can be seen that the sensitivity remains basically unchanged when single slot, double slot, and four slots are opened. From the perspective of processing convenience, a single slot on the side of the hollow core 7 can meet the demand. Slotting the core 7 can increase the LVDT output sensitivity from 1085mV / mm to 1180mV / mm, an increase of about 8.7%.

[0036] Increasing the coil turns ratio as a traditional method to increase sensitivity will cause the LVDT sensor to be too large. In the traditional method, the wire diameter of the LVDT primary coil and the secondary coil are the same. Due to the LVDT range limitation, the length of the primary coil cannot be further reduced. The primary coil must be tightly wound and wound in at least two layers to produce an approximately uniform magnetic field, resulting in the number of turns of the primary coil cannot be reduced indefinitely. At the same time, in order to increase the turns ratio and minimize the increase in coil volume, the conventional practice is to select a primary coil and secondary coil with a smaller wire diameter for winding, which will cause the number of turns of the primary coil to increase simultaneously, so that the increase in the turns ratio is reduced. To solve the above problem. In some embodiments, the wire diameter of the primary coil 5 is larger than the wire diameter of the first secondary coil 4 and the second secondary coil 8.

[0037] In the embodiment of the present invention, the primary coil 5 and the secondary coil are wound with wires of different diameters, so that the wire diameter of the primary coil 5 is larger than the wire diameter of the secondary coil.

[0038] In some examples, compared with conventional LVDT sensors, this example does not change the wire diameter of the secondary coil, but increases the wire diameter of the primary coil 5. This can significantly reduce the number of primary coil turns without changing the original LVDT sensor skeleton structure and the number of secondary coil turns, thereby effectively improving the secondary coil and primary coil turns ratio; in other examples, the primary coil wire diameter can be kept unchanged, and the secondary coil can be wound with a smaller wire diameter for the same length or number of layers, which can simultaneously achieve the purpose of increasing the coil turns ratio and reducing the volume.

[0039] Conventional LVDT coils are mostly wound with copper enameled wire. Copper has a lower resistivity, which can significantly reduce primary coil losses and improve the sensor's temperature characteristics. By studying the temperature characteristics of this material, this paper proposes using low-temperature drift wire, such as constantan, for winding the coils. According to the temperature drift data for constantan enameled wire published in GB / T6145-2010, the average resistance temperature coefficient is 40*10 -6 / ℃, compared with the average resistance temperature coefficient of pure copper is 43*10 -4 / °C, the average resistance temperature coefficient of constantan enameled wire is only 1% of that of pure copper, which can significantly improve the output temperature characteristics of the sensor. Similarly, coils can be wound using materials with good temperature drift parameters such as manganese copper enameled wire and nickel-chromium alloy enameled wire, which can also significantly improve the temperature characteristics of the sensor.

[0040] Therefore, in the embodiment of the present invention, the primary coil 5 , the first secondary coil 4 and the second secondary coil 8 are made of constantan enameled wire, manganese copper enameled wire or nickel-chromium alloy enameled wire.

[0041] In the high-sensitivity LVDT sensor proposed in the embodiment of the present invention, the coil is wound with low-temperature drifted enameled wire, so that the sensor has excellent temperature characteristics.

[0042] In some embodiments, the end of the connecting rod 1 is inserted into the inner hole of the iron core 7 from one end of the inner hole and fixed therein.

[0043] The connection method of this embodiment can effectively improve the coaxiality of the connecting rod 1 and the iron core 7.

[0044] In some embodiments, such as Figure 1 As shown, the housing assembly includes a first end cover 2 , a magnetic conductive housing 3 and a second end cover 9 .

[0045] Note: The present invention does not limit the size of the inner hole of the iron core 7. The degree of sensitivity improvement varies depending on the size of the inner hole. The optimal inner hole size is related to the primary coil excitation frequency of the LVDT sensor and its actual structural parameters, and requires accurate calculation through detailed simulation analysis.

[0046] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A high-sensitivity LVDT sensor, characterized in that: include: A shell assembly, a connecting rod, an iron core, a skeleton, a primary coil, a first secondary coil and a second secondary coil; the skeleton is nested in the shell assembly, and the iron core is movably arranged in the skeleton along the length direction; one end of the connecting rod is connected to one end of the iron core, and the other end extends from the shell assembly; the primary coil, the first secondary coil and the second secondary coil are wound around the outside of the skeleton; an inner hole passing through both ends is provided in the iron core; the primary coil is wound around the skeleton; the first secondary coil and the second secondary coil are wound around the primary coil to form a two-section laminated LVDT; a groove passing through the inner and outer surfaces of the iron core is provided on the wall of the iron core; the groove passes through both ends of the iron core in the length direction.

2. The high-sensitivity LVDT sensor according to claim 1, characterized in that: The groove is provided with one.

3. The high-sensitivity LVDT sensor according to claim 2, characterized in that: The groove extends along a straight line.

4. The high-sensitivity LVDT sensor according to claim 1, characterized in that: The wire diameter of the primary coil is larger than that of the first secondary coil and the second secondary coil.

5. The high-sensitivity LVDT sensor according to claim 1, characterized in that: The primary coil, the first secondary coil and the second secondary coil are made of constantan enameled wire.

6. The high-sensitivity LVDT sensor according to claim 1, characterized in that: The primary coil, the first secondary coil and the second secondary coil are made of manganese-copper enameled wire or nickel-chromium alloy enameled wire.

7. The high-sensitivity LVDT sensor according to claim 1, characterized in that: The end portion of the connecting rod is inserted into the inner hole of the iron core from one end of the inner hole and fixed therein.

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