Magnetic grid sensor and detection equipment

Abstract

The utility model provides a magnetic grid sensor which comprises a magnetic grid and a magnetic head. The magnetic grid comprises a plurality of south-pole magnets and north-pole magnets, and the south-pole magnets and the north-pole magnets are alternately arranged; the magnetic head comprises at least one magnetic resistance unit, and the magnetic resistance of the magnetic resistance unit is of a Vortex structure. The magnetic grid sensor is not sensitive to external field interference and temperature change, the measurement precision and accuracy are improved, and therefore errors existing in the displacement measurement process are reduced.

Description

Technical Field

[0001] The present invention relates to the field of magnetic field sensing / measurement, and in particular to a magnetic grating sensor and detection equipment. Background Art

[0002] With the development of modern science and technology and the improvement of automation level, a large number of displacement sensors that can truly and reliably reflect the position information of the measured object are needed in the fields of aerospace, mechanical manufacturing, high-precision CNC machine tools, etc., and the displacement sensor system is required to have high resolution, small size, light weight, fast response speed, and be able to work stably under various ambient temperatures, etc., and higher and higher requirements are placed on the anti-interference ability of the sensor.

[0003] Among them, the magnetic grating sensor is the most commonly used and basic type of digital displacement sensor. Due to its high vibration and impact resistance, it is suitable for use in industrial environments such as water, oil, dust, and high temperature. It also has a simple structure, small size, and high precision, and is therefore widely used.

[0004] The magnetic grating sensor is a displacement sensor that measures displacement based on the magnetoresistance effect. It can measure displacement by using the magnetic interaction between the magnetic grating and the magnetic head. The existing magnetic grating sensor is used in conjunction with the sensor and the magnetic grating. During use, the sensor will not only sense the magnetic field signal of the magnetic grating, but may also sense signals from other interfering magnetic fields, thus affecting the final output accuracy. However, the interfering magnetic field is not only in the sensitive direction (magnetic grating direction). In most cases, there are also interfering components and interfering magnetic fields from all directions. In fact, the influence of interfering magnetic gratings is difficult to avoid. In addition to the environmental magnetic fields such as the geomagnetic field, these interferences also come from the assembly process of the sensor and the movement of the magnetic head relative to the magnetic grating. This part of the interference that affects the magnetic field is not only often ignored, but also the measurement influence it brings is difficult to eliminate.

[0005] During the displacement process, the magnetic grating sensor will not only sense the magnetic field of the object, but will also be disturbed by the noise magnetic field outside the object magnetic field (such as changes in the working environment temperature), which will cause corresponding errors in the displacement measurement results. Utility Model Content

[0006] The embodiment of the present application provides a magnetic grating sensor to solve the technical problem of errors in the process of measuring displacement in the prior art.

[0007] The present application provides a magnetic grating sensor, which includes a magnetic grating and a magnetic head; the magnetic grating includes a plurality of south pole magnets and north pole magnets, and the south pole magnets and the north pole magnets are placed alternately; the magnetic head includes at least one magnetoresistance unit, and the magnetoresistance of the magnetoresistance unit is the magnetoresistance of a free layer having a Vortex magnetic domain structure.

[0008] In the above scheme, the free layer of the magnetoresistor in the magnetoresistive unit adopts the Vortex magnetic domain structure. Since the Vortex magnetic domain structure has the characteristics of high thermal stability, topological protection and zero static magnetism, the magnetic grating sensor using the vortex structure magnetoresistor is not sensitive to temperature changes. In other words, in the process of measuring displacement by the relevant magnetic head, the measurement result is not easily affected by temperature, has high measurement precision and accuracy, and has a small error in the process of measuring displacement by the magnetic head.

[0009] As an optional manner, the magnetoresistance unit includes multiple magnetoresistances; the multiple magnetoresistances are connected in series, in parallel, or in series and parallel; the multiple magnetoresistances can be equivalent to at least two equivalent magnetoresistances with equal magnetic sensitivity coefficients, the same magnetic sensitivity directions, and connected in series or in parallel.

[0010] In the above scheme, since the magnetic sensitivity coefficients of the two equivalent magnetic resistors are equal in magnitude and in the same direction, the equivalent magnetic resistors can offset each other's response components of the interference field and enhance the effective signal in the measurement field in combination with the spatial position between the equivalent magnetic resistors, so that the magnetic grating sensor can have higher accuracy and stability.

[0011] As an optional manner, the magnetoresistance of the magnetoresistance unit at least includes: two magnetoresistances having the same pinning layer direction and being connected in series or in parallel.

[0012] As an optional manner, the magnetic head is further connected to a signal processing circuit, which is used to process the output signal of the magnetic resistance unit of the magnetic head to obtain the moving distance of the magnetic head relative to the magnetic grid.

[0013] As an optional method, the distance between the two equivalent magnetic resistances of the magnetic resistance unit along the reference direction is d, and the d is set to be proportional to the magnetic grid distance L according to the interference harmonics to be eliminated; the reference direction is the arrangement direction of the NS poles in the magnetic grid, and the magnetic grid distance L is the distance between the adjacent N poles and S poles of the magnetic grid in the reference direction. In the above scheme, the appropriate distance setting can eliminate specific harmonics in the resistance change of the magnetic resistance unit, thereby reducing the error in the process of measuring displacement.

[0014] As an optional method, the distance d is: n is an integer greater than 1.

[0015] As an optional manner, the circuit formed by the magnetoresistance unit of the magnetic grid sensor includes a first half-bridge, the first half-bridge includes two magnetoresistance units, and the output signal of the first half-bridge is drawn out from between the two magnetoresistance units; the distance between the two magnetoresistance units of the two bridge arms of the same half-bridge along the arrangement direction of the NS poles of the magnetic grid is L, L is the magnetic grid pitch, that is, the distance between adjacent N poles and S poles of the magnetic grid in a reference direction, and the reference direction is the arrangement direction of the NS poles in the magnetic grid.

[0016] As an optional manner, the magnetic grid sensor includes at least one Wheatstone full bridge, and the Wheatstone full bridge includes two of the first half bridges; the distance between the magnetic resistance units of the upper bridge arms of the two half bridges, or the distance between the magnetic resistance units of the lower bridge arms along the arrangement direction of the magnetic grid NS is

[0017] An embodiment of the present application further provides a detection device, which includes the magnetic grating sensor in any of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A structural block diagram of a magnetic grating sensor provided by the present application in one embodiment;

[0019] Figure 2 for Figure 1 A schematic diagram of the positions of the magnetic grid and the magnetic head in the embodiment shown;

[0020] Figure 3 is a schematic diagram of two equivalent magnetoresistance units connected in series in some embodiments;

[0021] Figure 4 A schematic diagram of two equivalent magnetic resistances of a magnetic resistance unit in parallel in some other embodiments;

[0022] FIG5( a ) is a measured curve of the sensitivity of the magnetic grating sensor to external magnetic interference in the X direction provided by an embodiment of the present application;

[0023] FIG5( b ) is a measured curve of the sensitivity of the magnetic grating sensor to external magnetic interference in the Y direction provided in an embodiment of the present application;

[0024] Illustration: 100 - magnetic grid sensor; 110 - magnetic grid; 120 - magnetic head; 130 - signal processing circuit; 140 - magnetic resistance. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only some embodiments of the utility model, not all embodiments. Generally, the components of the embodiments of the utility model described and shown in the drawings here can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the utility model provided in the accompanying drawings is not intended to limit the scope of the utility model claimed for protection, but merely represents selected embodiments of the utility model. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0027] In the description of this embodiment, it should be noted that, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" 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 directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.

[0028] In one embodiment, the magnetic grating sensor provided by the present application is as follows: Figure 1 shown. Figure 1 This is a structural block diagram of a magnetic grating sensor provided in an embodiment of the present application. The magnetic grating sensor 100 may include a magnetic grating 110 , a magnetic head 120 and a signal processing circuit 130 .

[0029] Specifically, the magnetic grid 110 may include a plurality of south pole magnets and north pole magnets, and the south pole magnets and the north pole magnets are placed alternately to generate magnetic signals as a reference scale for measuring displacement. As an embodiment, the magnetic grid 110 is made by coating a uniform magnetic film on a grid base made of a non-magnetic material, and recording a magnetic signal of a certain wavelength (small magnetic poles arranged at equal distances). For example, a steel material with a layer of anti-magnetic material coated on the surface is used as the scale base, and the anti-magnetic material can be 0.15-0.20mm thick copper, and then a layer of magnetic film with a thickness of 0.10-0.20mm is uniformly coated on the surface of the scale base, and a Ni-Co-P alloy is commonly used, and then a magnetic signal of a certain wavelength (small magnetic poles arranged at equal distances) is recorded.

[0030] Figure 2 for Figure 1 Schematic diagram of the location of the magnetic grid and magnetic head. Figure 2As can be seen from the figure, the magnetic head 120 is located on one side of the magnetic grid 110. The magnetic head 120 includes at least one magnetic resistance unit composed of a plurality of magnetic resistors 140. The plurality of magnetic resistors 140 are connected in series, in parallel, or in series and in parallel. In this way, when the magnetic head 120 and the magnetic grid 110 move relative to each other, the magnetic head 120 will output an electrical signal corresponding to the magnetic signal on the magnetic grid 110. The free layer of the magnetic resistor 140 has a Vortex magnetic domain structure. When the magnetic head 120 and the magnetic grid 110 move relative to each other, the magnetic head 120 will output an electrical signal corresponding to the magnetic signal on the magnetic grid 110.

[0031] Optionally, the multiple magnetoresistors 140 in the magnetoresistance unit may be equivalent to at least two equivalent magnetoresistors having equal magnetic sensitivity coefficients and the same magnetic sensitivity directions and being connected in series or in parallel.

[0032] Optionally, the pinning layers of the plurality of magnetoresistors 140 in the magnetoresistance unit are in the same direction.

[0033] The signal processing circuit 130 is connected to the magnetic head 120. When the magnetic head 120 and the magnetic grid 110 move relative to each other, the magnetic head 120 will output an electrical signal corresponding to the magnetic signal on the magnetic grid 110. After being processed and amplified by the signal processing circuit 130, the electrical signal will output an electrical signal corresponding to the displacement, thereby realizing the measurement of displacement.

[0034] It should be noted that the embodiment of the present application does not specifically limit the specific implementation of the above-mentioned signal processing circuit 130, and those skilled in the art can make appropriate adjustments based on the existing technology.

[0035] The magnetoresistor 140 adopts a Vortex structure, or the free layer in the magnetoresistor 140 adopts a Vortex magnetic domain structure, which can not only weaken the interfering magnetic field, but also make the magnetic grating sensor 100 insensitive to temperature changes due to the characteristics of the Vortex structure. That is, when the temperature changes greatly, its sensitivity changes very little. In other words, in the process of displacement measurement, the measurement result is not easily affected by temperature, thereby reducing the error in the process of displacement measurement.

[0036] Specifically, the Vortex structure is a special magnetic structure whose magnetization intensity is distributed in a vortex shape in space. First, the magnetization intensity of the Vortex structure is zero at the center and maximum at the edge. This distribution makes the magnetization intensity of the Vortex structure insensitive to external magnetic fields of smaller intensity. Secondly, the magnetization intensity distribution of the Vortex structure has good symmetry, which makes the interaction between multiple magnetic resistors 140 smaller and can reduce the mutual interference between the magnetic resistors 140. It also has good temperature characteristics, and temperature changes have little effect on the magnetic grating sensor 100.

[0037] As an optional implementation, each of the multiple magnetic resistors 140 in the above embodiment may adopt a tunnel magnetoresistance (TMR).

[0038] At this time, the magnetoresistance 140 may include a magnetic tunnel junction (MTJ). Among them, the MTJ is a special magnetic structure, and its structure is a sandwich structure of a ferromagnetic film layer + a non-magnetic insulating film layer (about 0.1nm) + a ferromagnetic film layer. This structure can show a tunnel magnetoresistance effect, that is, when the angles of the magnetization directions of the two ferromagnetic film layers are different, the MTJ will show different resistances.

[0039] MTJ includes a pinned layer and a free layer. Both the free layer and the pinned layer refer to the ferromagnetic material layer in the MTJ. Among them, the free layer is a layer of ferromagnetic material in the MTJ, and its magnetization direction can change under the action of an external magnetic field, thereby realizing the magnetoresistance effect of the MTJ. The pinned layer is another layer of ferromagnetic material in the MTJ, and its magnetization direction is fixed and will not change under the action of an external magnetic field.

[0040] Based on the above magnetic grid sensor 100 , when the magnetic head 120 moves relative to the magnetic grid, the periodically changing magnetic field will pass through the magnetic sensitive part of the sensor to generate a changing magnetic field signal, thereby measuring the position and movement of the magnetic grid sensor 100 .

[0041] Furthermore, the multiple magnetoresistors 140 of the same magnetoresistance unit can be equivalent to at least two equivalent magnetoresistances with the same magnetic sensitivity direction and equal magnetic sensitivity coefficient. The distance d between the two equivalent magnetoresistances of the magnetoresistance unit along the reference direction is set to be in proportion to the magnetic grid distance L according to the interference harmonics to be eliminated as needed. The reference direction is the arrangement direction of the NS poles in the magnetic grid 110. The magnetic grid distance L is the distance between the adjacent N poles and S poles of the magnetic grid in the reference direction. In the above scheme, the appropriate distance setting can eliminate specific harmonics in the resistance change of the magnetoresistance unit, thereby reducing the error in the process of measuring displacement.

[0042] Furthermore, the distance d in the above embodiment is: n is an integer greater than 1.

[0043] like Figure 3 As shown, the two equivalent magnetic resistors R1 and R2 in the magnetic resistor unit are connected in series. Figure 4As shown, in some other embodiments, the two equivalent magnetic resistors R1 and R2 in the magnetic resistor unit are connected in parallel. In the above scheme, the equivalent magnetic resistors R1 and R2 are connected in series or in parallel, combined with their respective distance settings in space, which can not only enhance the amplitude of the effective signal, but also weaken the interference of the external magnetic field (thereby reducing the error in the process of measuring displacement).

[0044] 5 , FIG5( a ) is a measured curve of the sensitivity of the magnetic grating sensor provided in the embodiment of the present application to external magnetic interference in the X direction, and FIG5( b ) is a measured curve of the sensitivity of the magnetic grating sensor provided in the embodiment of the present application to external magnetic interference in the Y direction. In FIG5 , an external field is applied in any direction horizontally or vertically to the sensitive direction. Within a certain range of external field interference, the magnetic grating sensor 100 is not sensitive to external magnetic interference.

[0045] In addition, by changing the working environment temperature of the magnetic grating sensor 100 in the embodiment of the present application, the sensitivity change results are shown in the following table:

[0046]

[0047] It can be seen that applying different ambient temperatures has little effect on the sensitivity of the magnetic grating sensor 100 in the embodiment of the present application.

[0048] Furthermore, the circuit formed by the magnetoresistive unit of the magnetic head 120 also includes a first half bridge, the first half bridge includes two magnetoresistive units, and the output signal of the first half bridge is drawn from between the two magnetoresistive units. The distance between the two magnetoresistive units of the two bridge arms of the same half bridge along the arrangement direction of the NS poles of the magnetic grid is the magnetic grid distance L. The magnetic grid distance L is the distance between the adjacent N poles and S poles of the magnetic grid 110 in the reference direction, and the reference direction is the arrangement direction of the NS poles in the magnetic grid 110.

[0049] Furthermore, the magnetic grating sensor 100 includes at least one Wheatstone full bridge, and the Wheatstone full bridge includes two of the first half bridges; the distance between the magnetic resistance units of the upper bridge arms of the two half bridges, or the distance between the magnetic resistance units of the lower bridge arms along the arrangement direction of the magnetic grating NS is

[0050] The present application also provides a detection device, which includes the magnetic grating sensor in any of the above embodiments, such as an inclinometer based on a magnetic grating sensor in the field of building safety monitoring, an oil-water interface detector based on a magnetic grating sensor in the petroleum industry, etc.

[0051] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnetic grating sensor, characterized in that: The magnetic grating sensor includes a magnetic grating and a magnetic head; the magnetic grating includes a plurality of south pole magnets and north pole magnets, and the south pole magnets and the north pole magnets are placed alternately; the magnetic head includes at least one magnetoresistance unit, and the magnetoresistance of the magnetoresistance unit is the magnetoresistance of the free layer having a Vortex magnetic domain structure.

2. The magnetic grating sensor according to claim 1, characterized in that: The magnetoresistance unit includes a plurality of magnetoresistances; the plurality of magnetoresistances are connected in series, in parallel, or in series and in parallel; the plurality of magnetoresistances can be equivalent to at least two equivalent magnetoresistances having equal magnetic sensitivity coefficients, the same magnetic sensitivity directions, and being connected in series or in parallel.

3. The magnetic grating sensor according to claim 1, characterized in that: The magnetoresistance of the magnetoresistance unit at least includes: two magnetoresistances with the same pinning layer direction and connected in series or in parallel.

4. The magnetic grating sensor according to claim 1, characterized in that: The magnetic head is also connected to a signal processing circuit.

5. The magnetic grating sensor according to claim 2, characterized in that: The distance between at least two equivalent magnetic resistances of the magnetic resistance unit along the reference direction is d, and the d is set to be in corresponding proportion to the magnetic grid distance L according to the interfering harmonics to be eliminated; the reference direction is the arrangement direction of the NS poles in the magnetic grid, and the magnetic grid distance L is the distance between adjacent N poles and S poles of the magnetic grid in the reference direction.

6. The magnetic grating sensor according to claim 5, characterized in that: The distance d is: n is an integer greater than 1.

7. The magnetic grating sensor according to any one of claims 1 to 6, characterized in that: The circuit formed by the magnetoresistive unit of the magnetic grid sensor includes a first half bridge, the first half bridge includes two magnetoresistive units, and the output signal of the first half bridge is drawn from between the two magnetoresistive units; the distance between the two magnetoresistive units of the two bridge arms of the same half bridge along the arrangement direction of the NS poles of the magnetic grid is L, L is the magnetic grid distance, that is, the distance between adjacent N poles and S poles of the magnetic grid in the reference direction, and the reference direction is the arrangement direction of the NS poles in the magnetic grid.

8. The magnetic grating sensor according to claim 7, characterized in that: The magnetic grating sensor comprises at least one Wheatstone full bridge, and the Wheatstone full bridge comprises two of the first half bridges; the distance between the magnetic resistance units of the upper bridge arms of the two half bridges, or between the magnetic resistance units of the lower bridge arms along the arrangement direction of the magnetic grating NS is 9. A detection device, characterized in that: The invention comprises the magnetic grating sensor according to any one of claims 1 to 8.

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