A high-precision magnetic resistance micro-displacement detection device based on a magnetic grid structure

Abstract

This invention belongs to the technical field of micro-displacement detection devices, specifically relating to a high-precision magnetoresistive micro-displacement detection device based on a magnetic grating structure. It includes a permanent magnet substrate, a first permanent magnet, a second permanent magnet, a magnetic grating layer structure, and a magnetoresistive layer. A square groove is provided at the center of the permanent magnet substrate, and the first and second permanent magnets are embedded within this groove. The magnetic grating layer structure is disposed on the first and second permanent magnets, and the magnetoresistive layer is disposed on the magnetic grating layer structure. This invention combines a magnetic grating structure with a tunnel magnetoresistive sensing element, rationally utilizing their respective advantages to achieve high-precision micro-displacement measurement while ensuring anti-interference capability. Furthermore, the magnetic grating of this invention is constructed by electrochemically depositing a layer of nickel on a silicon wafer, and then magnetizing the nickel layer with a pair of permanent magnets with opposite magnetic properties below the silicon wafer, thereby generating a high-rate-of-change magnetic field in the space above the magnetic grating surface.

Description

Technical Field

[0001] This invention belongs to the technical field of micro-displacement detection devices, specifically relating to a high-precision magnetoresistive micro-displacement detection device based on a magnetic grating structure. Background Technology

[0002] Micro-displacement sensing technology is a sensing technology with significant impact on modern scientific research and industrial production, and it is widely used in various important sectors of the national economy, such as high-precision CNC machine tools, aerospace, and petrochemicals. To meet the growing demands of various industries, especially modern industrial production, micro-displacement measurement is developing towards higher precision, digitalization, anti-interference capabilities, and intelligence.

[0003] The working principle of a micro-displacement sensor is to convert the displacement of an object into a measurable electrical signal, and then analyze the electrical signal to determine the change in minute displacement. In industrial applications, common displacement sensors include resistive, capacitive, inductive, ultrasonic, grating, and magnetostrictive types. Resistive sensors have good linearity, simple structure, and good stability, making them the mainstream method in production process monitoring and automation. However, resistive displacement sensors also have disadvantages such as easy wear, short lifespan, and relatively low measurement accuracy. Capacitive displacement sensors measure displacement by converting changes in displacement into changes in capacitance. Besides the frictionless characteristic common to non-contact sensors, they also possess advantages such as a high signal-to-noise ratio, high accuracy and stability, and strong resistance to electromagnetic interference. They are particularly suitable for measuring high-frequency vibrations and minute displacements, but their disadvantages are also obvious, such as susceptibility to parasitic capacitance and nonlinear output characteristics. Grating sensors are based on the interference and diffraction phenomena of light, offering very high resolution for micro-displacement measurements, reaching 0.1µm. The advantages of grating displacement sensors include high resolution, good heat resistance, strong anti-electromagnetic interference capability, and low power consumption. However, in harsh environments such as dust and smoke, the interference and diffraction effects of light are easily affected, and the complex optical path also results in poor overall integration, limiting its application. Summary of the Invention

[0004] To address the technical challenges of grating-type displacement sensors, where light interference and diffraction effects are easily affected by harsh environments such as dust and smoke, and where complex optical paths lead to poor overall integration, this invention provides a high-precision magnetoresistive micro-displacement detection device based on a magnetic grating structure. The magnetic grating structure generates a magnetic field with a high rate of change in the detection direction of the micro-displacement. When there is a change in external displacement, a relative displacement occurs between the magnetic grating and the tunnel magnetoresistive junction. This change in micro-displacement is then converted into a change in the spatial magnetic field, which in turn leads to a change in the tunnel magnetoresistive resistance. This device features a reasonable overall structural design, simple manufacturing process, high feasibility, and high integration.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A high-precision magnetoresistive micro-displacement detection device based on a magnetic grating structure includes a permanent magnet substrate, a first permanent magnet, a second permanent magnet, a magnetic grating layer structure, and a magnetoresistive layer. The permanent magnet substrate has a square groove at its center, and the first permanent magnet and the second permanent magnet are embedded in the square groove. The magnetic grating layer structure is disposed on the first permanent magnet and the second permanent magnet, and the magnetoresistive layer is disposed on the magnetic grating layer structure.

[0007] The magnetic grating layer structure includes a magnetic grating substrate, an N-pole magnetization region, an S-pole magnetization region, and a magnetic grating. The magnetic grating substrate is disposed on a first permanent magnet and a second permanent magnet. The magnetic grating substrate has an N-pole magnetization region and an S-pole magnetization region. The magnetic grating is disposed between the N-pole magnetization region and the S-pole magnetization region.

[0008] The magnetoresistive layer includes a magnetoresistive substrate, a magnetoresistive element, a magnetoresistive lead, and a test electrode Pad. The magnetoresistive substrate is disposed on a magnetic grating substrate, and the magnetoresistive element is disposed on the magnetoresistive substrate. The magnetoresistive element is electrically connected to the test electrode Pad through the magnetoresistive lead.

[0009] The first permanent magnet and the second permanent magnet have opposite magnetic directions. Both the first permanent magnet and the second permanent magnet are made of N52 neodymium iron boron permanent magnet material. The first permanent magnet and the second permanent magnet are symmetrically fixed on both sides of the square groove in the permanent magnet substrate by adhesive.

[0010] The depth of the square groove in the permanent magnet substrate is greater than the thickness of the first permanent magnet and the second permanent magnet.

[0011] The N-pole magnetization region, S-pole magnetization region, and magnetic grating are all obtained by depositing a 20µm thick nickel layer on a silicon wafer using an electrochemical process.

[0012] The magnetoresistive element is a Q8V20 tunnel magnetoresistive element, which consists of 13 pairs of tunnel magnetoresistive junctions. Each pair of tunnel magnetoresistive junctions consists of two tunnel magnetoresistive junctions with opposite polarities arranged in parallel.

[0013] The magnetoresistive substrate is bonded to the magnetoresistive element, and a layer of gold is grown on the magnetoresistive substrate by magnetron sputtering.

[0014] The test electrode Pad is electrically connected to the phase shift circuit, which is electrically connected to the subdivision circuit. The subdivision chip of the subdivision circuit is an iC-TW8 chip.

[0015] The permanent magnet substrate is made of silicon, ceramic or glass.

[0016] Compared with the prior art, the beneficial effects of this invention are:

[0017] This invention combines a magnetic grating structure with a tunnel magnetoresistive sensing element, rationally utilizing the advantages of each to achieve high-precision micro-displacement measurement while ensuring anti-interference capabilities. Furthermore, the magnetic grating of this invention is constructed by electrochemically depositing a layer of nickel on a silicon wafer, then magnetizing the nickel layer with a pair of permanent magnets with opposite magnetic properties beneath the silicon wafer, thereby generating a high-rate-of-change magnetic field in the space above the surface of the magnetic grating. This invention employs the highly sensitive tunnel magnetoresistive effect for detection; under weak magnetic field changes, the resistance of the tunnel magnetoresistive element undergoes a drastic change, thus enabling the detection of minute displacements. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0019] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the permanent magnet substrate of the present invention;

[0022] Figure 3 This is a schematic diagram of the magnetic grating layer structure of the present invention;

[0023] Figure 4 This is a schematic diagram of the magnetoresistive layer structure of the present invention;

[0024] Figure 5 This is a magnetic field distribution diagram along the sensitive axis of the magnetic grating surface in this invention;

[0025] Figure 6 This is a schematic diagram of the TMR bridge structure of the magnetoresistive element of the present invention;

[0026] Figure 7 This is a flowchart of the phase-shifting subdivision circuit of the present invention;

[0027] Figure 8This is a schematic diagram of the phase-shifting circuit of the present invention;

[0028] Figure 9 This is a schematic diagram of the subdivision circuit of the present invention.

[0029] Wherein: 1 is the permanent magnet substrate, 2 is the first permanent magnet, 3 is the second permanent magnet, 4 is the magnetic grating substrate, 5 is the N-pole magnetization region, 6 is the S-pole magnetization region, 7 is the magnetic grating, 8 is the magnetoresistive substrate, 9 is the magnetoresistive element, 10 is the magnetoresistive lead, 11 is the test electrode Pad, 12 is the phase shifting circuit, and 13 is the subdivision circuit. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. These descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the claims of the present invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0032] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0034] In this embodiment, as Figure 1 As shown, it is composed of a permanent magnet substrate 1, a first permanent magnet 2, a second permanent magnet 3, a magnetic grating substrate 4, an N-pole magnetization region 5, an S-pole magnetization region 6, a magnetic grating 7, a magnetoresistive substrate 8, a magnetoresistive element 9, a magnetoresistive lead 10, and a test electrode Pad 11. Figure 2As shown, the permanent magnet substrate 1 is square in shape and can be made of materials such as silicon, ceramic, or glass. A square groove is located at the center of the substrate 1, in which a pair of permanent magnets 2 and 3 with opposite magnetic directions are embedded. The depth of the groove is slightly greater than the thickness of the permanent magnets 2 and 3. The permanent magnets 2 and 3 are NdFeB permanent magnets (model N52), and both are identical in size, being cuboids of 3mm × 2mm × 1mm, with their length and width exceeding their thickness. The permanent magnets 2 and 3 are symmetrically fixed to both sides of the groove in the substrate 1 using adhesive. Inside the permanent magnet 2, the magnetic field lines point from the S pole on the lower surface to the N pole on the upper surface; inside the permanent magnet 3, the magnetic field lines point from the N pole on the lower surface to the S pole on the upper surface. Through this magnetization method, the permanent magnets 2 and 3 provide a pair of magnetizing magnetic fields of the same size but opposite directions to the magnetic grid 7.

[0035] In this embodiment, as Figure 3 As shown, the magnetic grating layer structure can be divided into three parts: the support frame 4, the N-pole magnetization region 5, the S-pole magnetization region 6, and the magnetic grating 7. Among them, the N-pole magnetization region 5, the S-pole magnetization region 6, and the magnetic grating 7 are realized by depositing a 20µm thick nickel layer on the silicon wafer through an electrochemical process.

[0036] when Figure 3 When the N-pole magnetization region 5 shown is magnetized by the first permanent magnet 2 directly below it, the connected portion of the magnetic grid will also be magnetized to the same magnetic properties as the N-pole magnetization region. Similarly, when the S-pole magnetization region 6 is magnetized by the second permanent magnet 3 directly below it, the other connected portion of the magnetic grid will be magnetized to the same magnetic properties as the S-pole magnetization region. In this way, the entire magnetic grid will generate a magnetic field similar to that of the N-pole magnetization region. Figure 5 The magnetic field shown exhibits a high rate of change with alternating polarities.

[0037] In this embodiment, as Figure 4 As shown, the magnetoresistive layer can be divided into three parts: magnetoresistive element 9, magnetoresistive lead 10, and test electrode Pad 11. The magnetoresistive element 9 used in this invention is a tunnel magnetoresistive element of model Q8V20 provided by Multidimensional Technology Co., Ltd. This magnetoresistive element 9 consists of 13 pairs of tunnel magnetoresistive junctions, each pair consisting of two tunnel magnetoresistive junctions with opposite polarities arranged in parallel. To detect the resistance change of the magnetoresistive element, this invention uses a bonding method to bond the magnetoresistive element 9 to the magnetoresistive substrate 8. Simultaneously, a layer of gold is grown on the magnetoresistive substrate 8 by magnetron sputtering to fabricate the magnetoresistive lead 10 and the test Pad 11.

[0038] In this embodiment, when the magnetoresistive displacement sensor is working, depending on different actual situations, the first permanent magnet 2, the second permanent magnet 3, and the magnetic grating layer can be placed on a fixed frame, and the magnetoresistive element 9 can be mounted on a horizontally movable displacement stage; alternatively, the magnetoresistive element can be placed on a fixed frame, and the first permanent magnet 2, the second permanent magnet 3, and the magnetic grating layer can be mounted on a horizontally movable displacement stage. That is, the relative positions of the first permanent magnet 2, the second permanent magnet 3, and the magnetic grating 7 are fixed, while the relative position with the magnetoresistive element 9 changes in the horizontal direction. During operation, the magnetoresistive element 9 is placed 100µm directly above the magnetic grating 7. When the two undergo relative displacement in the horizontal direction, the phase-shifting subdivision circuit flow is as follows: Figure 7 As shown, the magnetoresistive element 9 will sense, as Figure 5 The magnetic field change shown is achieved through, as... Figure 6 The bridge circuit shown can output two sinusoidal signals with a 90-degree phase difference. The sinusoidal signals output by the bridge circuit are then connected to the circuit as follows: Figure 8 In the phase-shifting circuit 12 shown, the phase-shifting circuit 12 can perform real-time phase shifting on the periodic sinusoidal signal generated during the micro-displacement test, effectively suppressing the amplitude and phase errors that may be introduced during the test, ensuring the orthogonality of the two sine and cosine signals, and then inputting the two orthogonal signals into the circuit as shown in the figure. Figure 9 The subdivision circuit 13 shown uses a dedicated DSP interpolator iC-TW8 manufactured by IC-Haus. This subdivision chip can provide different subdivision ratios according to different subdivision requirements. Thanks to the two orthogonal sine and cosine signals provided by the phase-shifting circuit, the subdivision circuit 13 can achieve a high-quality subdivision of 10,000 times for the displacement signal. Based on the size parameters of the magnetic grating, the output signal period after the bridge circuit is hundreds of micrometers. After 10,000 subdivisions by the subdivision circuit, the sensor resolution can reach the tens of nanometer level.

[0039] The above description only illustrates the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. A high-precision magneto-resistive micro-displacement detection device based on a magnetic grid structure, characterized in that: The application relates to a magnetic sensor, which comprises a permanent magnet substrate (1), a first permanent magnet (2), a second permanent magnet (3), a magnetic grid layer structure and a magnetic resistance layer, wherein a square recess is arranged at the center of the permanent magnet substrate (1), the first permanent magnet (2) and the second permanent magnet (3) are inlaid in the square recess of the permanent magnet substrate (1), the magnetic grid layer structure is arranged on the first permanent magnet (2) and the second permanent magnet (3), and the magnetic resistance layer is arranged on the magnetic grid layer structure; the magnetic grid layer structure comprises a magnetic grid base (4), an N-pole magnetization area (5), an S-pole magnetization area (6) and a magnetic grid (7), the magnetic grid base (4) is arranged on the first permanent magnet (2) and the second permanent magnet (3), the N-pole magnetization area (5) and the S-pole magnetization area (6) are arranged on the magnetic grid base (4), and the magnetic grid (7) is arranged between the N-pole magnetization area (5) and the S-pole magnetization area (6); the magnetic resistance layer comprises a magnetic resistance base (8), a magnetic resistance element (9), a magnetic resistance lead (10) and a test electrode Pad (11), the magnetic resistance base (8) is arranged on the magnetic grid base (4), the magnetic resistance element (9) is arranged on the magnetic resistance base (8), and the magnetic resistance element (9) is electrically connected with the test electrode Pad (11) through the magnetic resistance lead (10).

2. The high-precision magnetoresistive micro-displacement detection device based on magnetic grid structure according to claim 1, characterized in that: The magnetic directions of the first permanent magnet (2) and the second permanent magnet (3) are opposite, the first permanent magnet (2) and the second permanent magnet (3) are both made of neodymium-iron-boron permanent magnet material with the model number N52, and the first permanent magnet (2) and the second permanent magnet (3) are symmetrically fixed in two sides of the square recess of the permanent magnet substrate (1) through the adhesive mode.

3. The high-precision magnetoresistive micro-displacement detection device based on magnetic grid structure according to claim 1, characterized in that: The depth of the square recess of the permanent magnet substrate (1) is greater than the thickness of the first permanent magnet (2) and the second permanent magnet (3).

4. The high-precision magnetoresistive micro-displacement detection device based on magnetic grid structure according to claim 1, characterized in that: The N-pole magnetization area (5), the S-pole magnetization area (6) and the magnetic grid (7) are all obtained by depositing a 20um-thick nickel layer on a silicon wafer through an electrochemical process.

5. The high-precision magnetoresistive micro-displacement detection device based on magnetic grid structure according to claim 1, characterized in that: The magnetic resistance element (9) is a tunneling magnetoresistance element with the model number Q8V20, and the magnetic resistance element (9) is composed of 13 pairs of tunneling magnetoresistance junctions, each pair of tunneling magnetoresistance junctions is composed of two tunneling magnetoresistance junctions with opposite polarities.

6. The high-precision magnetoresistive micro-displacement detection device based on magnetic grid structure according to claim 1, characterized in that: The magnetic resistance base (8) is bonded with the magnetic resistance element (9), and a layer of gold is grown on the magnetic resistance base (8) through magnetron sputtering.

7. The high-precision magnetoresistive micro-displacement detection device based on magnetic grid structure according to claim 1, characterized in that: The test electrode Pad (11) is electrically connected with a phase-shifting circuit (12), the phase-shifting circuit (12) is electrically connected with a subdivision circuit (13), and the subdivision chip of the subdivision circuit (13) is an iC-TW8 chip.

8. The high-precision magnetoresistive micro-displacement detection device based on magnetic grid structure according to claim 1, characterized in that: The material of the permanent magnet substrate (1) is silicon, ceramic or glass.

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