High-sensitivity LVDT sensor

Abstract

The invention, which relates to the technical field of LVDT sensor structure design, discloses 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 framework is nested in the shell assembly, and the iron core is movably arranged in the framework in the length direction; one end of the connecting rod is connected to one end of the iron core, and the other end of the connecting rod extends out of the shell assembly; the primary coil, the first secondary coil and the second secondary coil are wound outside the framework; an inner hole penetrating through the two ends is formed in the iron core. According to the scheme provided by the invention, the measurement sensitivity of the LVDT sensor can be improved.

Description

Technical Field

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

[0002] LVDT is the abbreviation of Linear Variable Differential Transformer, which belongs to linear displacement sensor. LVDT sensor has the characteristics of nearly infinite mechanical life, infinite resolution and high zero position repeatability. It is often used in servo valve spool displacement and shaft diameter runout and other small displacement detection occasions. Applications such as servo valves not only require LVDT sensors to have a very small volume for easy integration into servo valves, but also require them to have high sensitivity and excellent temperature drift characteristics. Although conventional LVDT sensors can achieve nearly infinite resolution, they need to increase the amplitude of the excitation signal or increase the number of secondary winding turns to obtain a higher secondary to primary coil turns ratio. Increasing the amplitude of the excitation signal will increase the output power and make its output stability worse. Increasing the number of winding turns will increase the volume and make it difficult to meet the needs of compact applications. At the same time, blindly increasing the number of coils will also cause losses and deteriorate the temperature characteristics of the sensor. 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 component, 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 component, 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 component; the primary coil, the first secondary coil and the second secondary coil are wound outside the skeleton; and an inner hole penetrating through both ends is arranged in the iron core.

[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 through the inner and outer surfaces of the core is provided on the wall surface of the core.

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

[0009] Preferably, the groove has 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, and 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 consistent with that of the conventional LVDT, and the output sensitivity can be improved without the need for additional components, and it is easy to improve and implement.

[0018] 3. In the high-sensitivity LVDT sensor proposed by 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 the wire diameter of the secondary coil, which can take into account 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 drifting enameled wire, so that the sensor has 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 drawings required for use in the embodiments 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 paying creative work.

[0022] Figure 1 A schematic diagram of the structure 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 be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work 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] Combine the following Figures 1 to 3 , describing an embodiment 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 penetrating both ends is arranged in the iron core 7.

[0030] The principle that the hollow iron core 7 can improve the sensitivity is that according to the working principle of LVDT, the primary coil 5 needs to input a sinusoidal excitation signal with a constantly changing amplitude. After the excitation signal is passed into the solenoid formed by the primary coil 5, an alternating magnetic field will be generated. The iron core 7 inside the coil will generate induced eddy current under the action of the alternating magnetic field. According to Lenz's law, the eddy current hinders the change of the magnetic field, thereby reducing its sensitivity. The use of a hollow iron core 7 can suppress the eddy current of the iron core to a great extent, especially when a high-frequency excitation signal is applied.

[0031] From the perspective of the 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 adopts a solid iron core. Simulation analysis shows that after applying the hollow iron core 7, the sensitivity is increased from the original 818mV / mm to 1124mV / mm compared with the solid iron core, and 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 stacked 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 penetrating the inner and outer surfaces of the core 7 is provided on the wall surface of the core 7. Specifically, the slot 10 penetrates both ends of the core 7 in the length direction; the slot 10 is provided with one; 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 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 FIG. 1 , the influence of the number of slots in the core 7 on the sensitivity can be seen. 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. The slots in the core 7 can increase the LVDT output sensitivity from 1085mV / mm to 1180mV / mm, with 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 limitation of the LVDT range, the length of the primary coil cannot be further reduced. The primary coil must be tightly wound and at least two layers are wound 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 the coil volume, the conventional practice is to select a primary coil and a secondary coil with a smaller wire diameter for winding, which will cause the number of turns of the primary coil to increase synchronously, 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 wire diameter of the primary coil 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 wires. Copper has a lower resistivity and can significantly reduce the loss of the primary coil 5 and improve the temperature characteristics of the sensor. The present invention proposes to use constantan and other low-temperature drift wires to wind the coils by studying the temperature characteristics principle. According to the standard constantan enameled wire temperature drift data published in GB / T6145-2010, its average resistance temperature coefficient is 40*10 -6 / ℃, compared with the average resistance temperature coefficient of pure copper is 43*10 -4 / ℃, the average resistance temperature coefficient of constantan enameled wire is only 1% of pure copper, which can significantly improve the output temperature characteristics of the sensor. Similarly, coils can be wound with materials such as manganese copper enameled wire and nickel-chromium alloy enameled wire with good temperature drift parameters, 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 provided in the embodiment of the present invention, the coil is wound with low-temperature drifting 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 needs to be accurately calculated 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 used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood 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 penetrating both ends is arranged in the iron core.

2. The high-sensitivity LVDT sensor according to claim 1, characterized in that: 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.

3. The high-sensitivity LVDT sensor according to claim 1, characterized in that: A groove penetrating the inner and outer surfaces of the iron core is provided on the wall surface of the iron core.

4. The high-sensitivity LVDT sensor according to claim 3, characterized in that: The slot passes through both ends of the core in the length direction.

5. The high-sensitivity LVDT sensor according to claim 4, characterized in that: The groove is provided with one.

6. The high-sensitivity LVDT sensor according to claim 5, characterized in that: The groove extends along a straight line.

7. The high-sensitivity LVDT sensor according to claim 2, characterized in that: The wire diameter of the primary coil is larger than the wire diameters of the first secondary coil and the second secondary coil.

8. 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.

9. 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.

10. The high-sensitivity LVDT sensor according to claim 1, characterized in that: The end 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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