Variable reluctance proximity sensor with high reliability

Abstract

The invention discloses a variable reluctance type proximity sensor with high reliability. The variable reluctance type proximity sensor comprises a target; the induction unit comprises a shell and an induction assembly, the induction assembly comprises a magnetic core, an excitation coil and a printed board, the excitation coil is wound on the framework through an enameled wire and arranged on the magnetic core, the excitation coil and the magnetic core are integrally inserted into the bushing ring, and the excitation coil is led out of the shell after being connected with the printed board. The whole induction assembly is encapsulated in the shell through sealant. The excitation coil generates an alternating magnetic field under the action of an excitation signal, and when the target is close to the induction surface of the induction unit, the magnetic resistance in the magnetic field is changed, so that the self inductance of the excitation coil is changed; the excitation coil is connected with the detection circuit, and inductance value changes of the excitation coil are obtained through the detection circuit and converted into electric signals capable of representing the approaching state of the target to be output. An integrated packaging structure is adopted, components and passive sensing assemblies are not arranged inside, good reliability is achieved, approaching / departing position detection can be achieved by installing the target on a detected object, and the target can be suitable for various complex and long-distance position detection.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a highly reliable variable magnetoresistive proximity sensor. Background Technology

[0002] In fields such as aviation, aerospace, and shipbuilding, there is a significant demand for displacement detection. Existing displacement sensors are generally divided into contact and non-contact types. Contact displacement sensors work by having a contact element directly contact the object being measured. Displacement information is obtained by measuring the relative displacement between the contact element and the object. Commonly used contact displacement sensors include potentiometer-type, differential transformer-type, and Hall effect sensors. These contact displacement sensors require the sensor itself to be connected to the object being measured. They offer high measurement accuracy, but their use is limited for mechanisms with large-scale movement or angular actions, such as hatches, landing gear retraction / extension, and turning angle limits. These applications do not require precise displacement measurement; the primary concern is whether the object has reached a designated position. Therefore, non-contact proximity sensors are typically used in these applications.

[0003] When used in fields such as aviation, aerospace, and shipbuilding to monitor the approach / remote state of objects, there are high requirements for the operating temperature, corrosion resistance, and reliability of sensors. For example, the reliability of the connection between the coil and the electrical interface is crucial. Conventional methods cannot meet the requirements of drastic temperature changes and vibration environments, and solder joints are prone to falling off, making it difficult to guarantee the reliability of the sensor. Summary of the Invention

[0004] The purpose of this invention is to provide a highly reliable variable magnetoresistive proximity sensor to solve the problem of low reliability of existing non-contact proximity sensors in extreme application scenarios.

[0005] This invention is achieved through the following technical solution: Highly reliable variable magnetoresistive proximity sensors include: Target; The sensing unit includes a housing and a sensing component. The sensing component includes a magnetic core, an excitation coil, and a printed circuit board. The excitation coil is made of enameled wire wound on a frame and set on the magnetic core. The excitation coil and the magnetic core are inserted into the bushing. The excitation coil is connected to the printed circuit board and led out to the outside of the housing. The sensing component is encapsulated in the housing with sealant. The excitation coil generates an alternating magnetic field under the action of the excitation signal. When the target approaches the sensing surface of the sensing unit, the magnetic reluctance in the magnetic field changes, causing the inductance of the excitation coil to change. The excitation coil is connected to the detection circuit, which obtains the change in inductance of the excitation coil and converts it into an electrical signal output that can characterize the approach state of the target.

[0006] In some embodiments of the present invention, the magnetic core is made of 1J79 soft magnetic alloy, the target is made of stainless steel, and the housing is made of stainless steel and demagnetized.

[0007] In some embodiments of the present invention, the excitation signal is an AC signal with a frequency of 1000Hz and a current of 20mA.

[0008] In some embodiments of the present invention, a compensation coil is formed by reverse winding on the skeleton and connected in series with the excitation coil. The excitation coil and the compensation coil are respectively connected to a lock-in amplifier circuit to determine the approach or distance of the target based on the phase and amplitude.

[0009] In some embodiments of the present invention, the magnetic core includes a main magnetic core and a compensation magnetic core. The main magnetic core is made of 1J79 soft magnetic alloy, and the compensation magnetic core is made of nanocrystalline Finemet. The compensation magnetic core and the main magnetic core are glued together to form a series connection. The length ratio of the main magnetic core to the compensation magnetic core is 4-5:1.

[0010] In some embodiments of the present invention, a sealing alloy is formed on the bottom of the housing by laser cladding to form a weld seal at the bottom of the housing.

[0011] In some embodiments of the present invention, a shielding layer is provided on the inner wall of the housing, the shielding layer including a magnetic shielding layer and an electrical shielding layer.

[0012] In some embodiments of the present invention, the magnetic shielding layer is a resin composite material coating with iron powder incorporated, the electrical shielding layer is a Ni-C conductive plastic, the magnetic shielding layer is disposed on the inner wall of the housing, the electrical shielding layer is disposed on the magnetic shielding layer, and the shielding layer is grounded at a single point with the housing.

[0013] Compared with the prior art, the present invention has the following advantages and beneficial effects: The sensor of this invention adopts an integrated package structure for its sensing unit, with no internal components or passive sensing components, which has good reliability. By installing the target on the object to be detected, it can realize the position detection of approach / distance, and can be applied to various complex and long-distance position detection. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram illustrating the working principle of the variable magnetoresistive proximity sensor in an embodiment of the present invention.

[0016] Figure 2 This is a schematic diagram of the variable magnetoresistive proximity sensor structure in an embodiment of the present invention.

[0017] Figure 3 This is a structural diagram of the variable magnetoresistive proximity sensor in an embodiment of the present invention.

[0018] in: 10. Target; 20. Induction component; 21. Housing; 22. Excitation coil; 23. Magnetic core; 24. Connector. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, specific embodiments of this application will be described in further detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely for explaining this application and not for limiting it. It should also be noted that, for ease of description, only the parts relevant to this application are shown in the drawings, not all of them. Before discussing exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe operations (or steps) as sequential processes, many of these operations can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but may also have additional steps not included in the drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0020] Reference Figure 1 and Figure 2 In some embodiments of the present invention, a highly reliable variable magnetoresistive proximity sensor includes: Target 10; The sensing unit includes a housing 21 and a sensing component 20. The sensing component 20 includes a magnetic core 23, an excitation coil 22 and a printed circuit board. The excitation coil is wound on a frame with enameled wire and set on the magnetic core. The excitation coil and the magnetic core are inserted into the bushing. After the excitation coil is connected to the printed circuit board, it is led out to the outside of the housing. The sensing component is encapsulated in the housing with sealant. The excitation coil generates an alternating magnetic field under the action of the excitation signal. When the target approaches the sensing surface of the sensing unit, the magnetic reluctance in the magnetic field changes, causing the inductance of the excitation coil to change. The excitation coil is connected to the detection circuit, which obtains the change in inductance of the excitation coil and converts it into an electrical signal output that can characterize the target's approach state.

[0021] The proximity sensor uses variable magnetoresistive technology to detect metallic targets, specifically soft magnetic metal targets. Its detection principle is as follows: Figure 1 and 2 As shown.

[0022] As the target moves toward the proximity sensor, the change in air gap thickness causes a change in the magnetic reluctance of the proximity sensor's coil circuit. The coil's inductance value... L It can be calculated using the following formula: ...(1) in, W The number of coil turns. RM The total magnetic reluctance of the magnetic circuit. The length of the magnetic flux passing through the magnetic core. μ 1 represents the permeability of the magnetic core. S 1 represents the core area. The length of the magnetic flux passing through the target. μ 2 represents the magnetic permeability of the target. S 2 represents the target area. S 0 represents the cross-sectional area of ​​the air gap. μ 0 represents the air gap permeability.

[0023] Due to air gap magnetic resistance Much greater than the magnetic reluctance of the core and target Since the magnetic reluctance of the magnetic core and the target can be ignored, equation (1) can be expressed as: ...(2) Therefore, variable magnetoresistive proximity sensors L Value and total magnetic reluctance of the magnetic circuit RM and δ , S 0 and μ The parameters are independent of the magnetic reluctance and inductance. Based on the changes in these parameters, it is possible to achieve qualitative and quantitative detection of the approach / remote state of the object being detected.

[0024] like Figure 1 As shown, when a target object with a metal target approaches the proximity sensor, it causes a change in the magnetoresistance inside the sensor, which in turn causes a step change in the inductance. The back-end acquisition unit calculates the inductance and outputs a switching signal indicating approach or departure.

[0025] The target is made of 15-5PH stainless steel, with a diameter of 16mm and a thickness of 2.5mm.

[0026] The proximity sensor housing is made of 316L stainless steel and undergoes further demagnetization treatment through heat treatment.

[0027] The proximity sensor's socket uses a D3899 series sealed socket, which is laser-welded to the housing to form an integral structure, and is connected to connector 24 via a nut, as shown below. Figure 3 As shown.

[0028] The excitation coil uses polyimide enameled wire with a diameter of Ф0.08mm, which is wound around a bobbin with a diameter of Ф6mm.

[0029] The magnetic core uses 1J79 soft magnetic alloy, which has high permeability and low coercivity under low magnetic field, and good time and temperature stability.

[0030] The excitation signal uses an AC signal with a frequency of 1000Hz and an amplitude of 20mA; it can achieve an inductance L>27.31mH when the target is close and an inductance L<26.45mH when the target is far away.

[0031] In some embodiments, a compensation coil is formed by reverse winding on the skeleton and connected in series with the excitation coil. The excitation coil and the compensation coil are respectively connected to a lock-in amplifier circuit to determine the target's approach or distance state based on the phase and amplitude.

[0032] A layer of reverse-connected compensation coil is wound on the skeleton. The number of turns of the compensation coil is 1 / 2 to 2 / 3 of the number of turns of the excitation coil. The outputs of the two coils are respectively sent to the lock-in amplifier. Δθ = ∠V1 – ∠V2 , ΔA = |V1| – |V2|; Where ∠V1 is the phase angle of the excitation coil voltage, ∠V2 is the phase angle of the compensation coil voltage, |V1| is the amplitude of voltage V1, |V2| is the amplitude of voltage V2, Δθ is the phase difference between the output voltages of the two coils, and ΔA is the amplitude difference between the output voltages of the two coils. When Δθ and ΔA both exceed the threshold, the target is determined to have entered the detection zone. This can effectively improve the target calibration distance to meet the needs of large gap detection in aircraft cabin doors.

[0033] The temperature coefficient μ of the 1J79 soft magnetic alloy can cause inductance drift within a certain temperature range, leading to false triggering. In some embodiments, the magnetic core is configured as a two-segment composite structure; Specifically, the magnetic core includes a main magnetic core and a compensation magnetic core. The main magnetic core is made of 1J79 soft magnetic alloy, and the compensation magnetic core is made of nanocrystalline Finemet. The compensation magnetic core and the main magnetic core are glued together to form a series connection. The length ratio of the main magnetic core to the compensation magnetic core is 4-5:1.

[0034] In some embodiments, a sealing alloy is formed on the bottom of the housing by laser cladding to create a weld cap. The sealing alloy can be FeNiCo, and the sensing component is made of vacuum-encapsulated silicone rubber, which is then laser-clad to form the weld cap. This creates a good seal within the housing and enables the sensor to withstand vibration and thermal shock, thus well meeting the requirements for aerospace-grade reliability.

[0035] In some embodiments, a shielding layer is provided on the inner wall of the housing. The shielding layer includes a magnetic shielding layer and an electrical shielding layer to improve the electromagnetic shielding performance of the sensor. The magnetic shielding layer is a resin composite material coating with iron powder to absorb low-frequency magnetic interference of 1-30MHz; the electrical shielding layer is made of Ni-C conductive plastic to form good electrical shielding; the magnetic shielding layer is disposed on the inner wall of the housing, and the electrical shielding layer is disposed on the magnetic shielding layer. The shielding layer is grounded at a single point with the housing to prevent eddy current loops and suppress sensitivity drift caused by eddy currents in the housing.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A variable reluctance proximity sensor with high reliability, characterized by, The utility model relates to a target proximity detection device, comprising: a target; an induction unit, the induction unit comprising a shell and an induction assembly, the induction assembly comprising a magnetic core, an excitation coil and a printed board, the excitation coil being wound on a framework with enameled wire and arranged on the magnetic core, the excitation coil and the magnetic core being integrally inserted into a gasket ring, the excitation coil being connected to the printed board and led out of the shell, the induction assembly being entirely sealed in the shell with sealing glue; the excitation coil generates an alternating magnetic field under the action of an excitation signal, when the target approaches the induction surface of the induction unit, the magnetic resistance in the magnetic field changes, causing the inductance of the excitation coil to change; the excitation coil is connected to a detection circuit, the inductance change of the excitation coil is obtained through the detection circuit and converted into an electrical signal output representing the proximity state of the target.

2. The variable-reluctance proximity sensor with high reliability according to claim 1, characterized by, The magnetic core is made of 1J79 soft magnetic alloy, the target is made of stainless steel, and the shell is made of stainless steel and subjected to demagnetization treatment.

3. The variable-reluctance proximity sensor with high reliability according to claim 1, characterized by, The excitation signal is an alternating signal with a frequency of 1000 Hz and a current of 20 mA.

4. The variable-reluctance proximity sensor with high reliability according to claim 1, characterized by, The framework is reversely wound to form a compensation coil in series with the excitation coil, the excitation coil and the compensation coil are respectively connected to a lock-in amplifier circuit, and the approaching and moving away states of the target are determined according to the phase and amplitude.

5. The variable-reluctance proximity sensor with high reliability according to claim 1, characterized by, The magnetic core comprises a main magnetic core and a compensation magnetic core, the main magnetic core is made of 1J79 soft magnetic alloy, the compensation magnetic core is made of nanocrystalline Finemet, the compensation magnetic core is glued to the main magnetic core to form a series connection, and the length ratio of the main magnetic core to the compensation magnetic core is 4-5:

1.

6. The variable-reluctance proximity sensor with high reliability according to claim 1, characterized by, An encapsulation alloy is formed on the bottom of the shell by laser cladding, and a welded cover is formed on the bottom of the shell.

7. The variable-reluctance proximity sensor with high reliability according to claim 1, characterized by, A shielding layer is arranged on the inner wall of the shell, the shielding layer comprising a magnetic shielding layer and an electric shielding layer.

8. The variable-reluctance proximity sensor with high reliability according to claim 7, characterized by, The magnetic shielding layer is made of a resin composite material coating doped with iron powder, the electric shielding layer is made of Ni-C conductive plastic, the magnetic shielding layer is arranged on the inner wall of the shell, the electric shielding layer is arranged on the magnetic shielding layer, and the shielding layer is single-point grounded to the shell.

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