CN204575225U - A kind of piezomagnetic strain gauge - Google Patents

Abstract

The utility model provides a piezomagnetic stress sensor. The sensor includes a supporting shell, a stress receiving body connected to the outside of the supporting shell, and a first magnet located inside the supporting shell; the first magnet is a magnetostrictive material; both ends of the first magnet are fixed to the inner wall of the supporting shell Connection; in the working state, external stress acts on the stress-receiving body, and the deformation of the supporting shell causes the deformation of the first magnet, so that the magnetic properties of the first magnet change, and its impedance changes accordingly. The sensor has simple structure, high sensitivity, and low cost, and can be used for high-stress monitoring such as expressway weight toll systems and industrial automatic weighing systems, and can also be used for micro-stress and strain monitoring.

Description

A piezomagnetic stress sensor

technical field

The utility model relates to the field of stress detection, in particular to a piezomagnetic stress sensor.

Background technique

The stress sensor is one of the commonly used sensors in the industry. It is widely used in the field of industrial automatic control, involving water conservancy and hydropower, railway transportation, intelligent buildings, production automation, aerospace, military, machine tools and many other industries.

With the development of flexible electronics and wearable devices, stress sensors have attracted more and more attention. Traditional stress sensors are mainly mechanical structural devices, which use the elastic deformation of elastic elements or the pressure difference of the liquid column to feedback the applied pressure. The disadvantages are large size, heavy volume, and inability to provide power output, which is not conducive to system integration.

With the development of science and technology, new materials and new physical effects are continuously applied to stress sensors, which has made great progress in stress sensors. Divided according to the working principle, the stress sensor can be divided into piezoresistive, capacitive, piezoelectric, optical fiber and piezomagnetic.

The piezoresistive stress sensor works on the principle that the resistance of metal or semiconductor changes with the change of external pressure. The piezoresistive stress sensors currently used are mainly silicon-based pressure sensors, which have the advantages of high measurement accuracy, good repeatability, good stability, wide test pressure range, strong output signal, small size, and easy integration. However, the operating temperature of silicon-based pressure sensors is generally lower than 125°C, and cannot be used at high temperatures, and the lower limit of the measured pressure is generally 1000 Pa, which cannot measure ultra-micro pressure. The capacitive stress sensor works on the principle that the capacitance changes with the pressure. It has the advantages of simple structure, high measurement accuracy, good stability, low power consumption, good linearity, small size and easy integration. However, capacitive strain sensors are susceptible to parasitic capacitance in the connecting wires and therefore place high demands on the measurement circuit. The piezoelectric strain sensor is a pressure sensor made according to the piezoelectric effect, which has the advantages of high measurement accuracy, wide test pressure range, wide temperature range, small size, and easy integration. However, the piezoelectric stress sensor is very sensitive to the measured temperature, and usually needs to be calibrated with an internal temperature measurement system or a constant temperature system; in addition, the piezoelectric stress sensor is mainly used for the measurement of acceleration and angular velocity, and is generally not used for static pressure measurement . The optical fiber strain sensor works on the principle that when the external stress changes, the light intensity, phase or polarization properties of the light propagating in the optical fiber change with the change of the external stress, but the sensor requires complex optical path processing equipment and is expensive .

The main material in piezomagnetic stress sensor is magnetostrictive material. Magnetostrictive materials have a magnetostrictive effect, that is, under the action of an external magnetic field, the shape of the magnetostrictive material changes; on the other hand, when the magnetostrictive material deforms, its magnetism changes, that is, the inverse magnetostrictive effect. The piezomagnetic stress sensor works by utilizing the inverse magnetostrictive effect. When the magnetostrictive material deforms under stress, its magnetism changes, resulting in a change in the impedance of the magnetostrictive material or the impedance of the components located in its magnetic field.

The piezomagnetic stress sensor has the advantages of high sensitivity, good linearity, good temperature stability, high output power and long service life, so it has been paid more and more attention by people. At present, piezomagnetic stress sensors with simple structure, high sensitivity and stable performance are the research hotspots of scientific and technological workers and have good application prospects.

Utility model content

The technical purpose of the utility model is to provide a piezomagnetic stress sensor with simple structure, high sensitivity and stable performance.

In order to achieve the above technical purpose, the technical solution adopted by the utility model is: a piezomagnetic stress sensor, including a supporting shell, a stress receiving body connected to the outside of the supporting shell, and a first magnet;

The first magnet is a magnetostrictive material, that is, has magnetostriction;

In the supporting shell, the part connected with the stress receiving body is a pressure receiving part, and the pressure receiving body is located on the outer wall of the pressure receiving part;

Both ends of the first magnet are fixedly connected to the inner wall of the pressure-bearing part, or both ends of the magnet are fixedly connected to the inner wall of the pressure-bearing part through a connecting body;

In the working state, the external stress acts on the stress-receiving body, and the pressure-bearing part is deformed by the compressive stress, and the deformation of the pressure-bearing part weakens around the position connected with the stress-receiving body; the pressure-bearing part The deformation causes the first magnet to deform, and the deformation of the first magnet causes the magnetic change of the first magnet, and the impedance of the first magnet changes accordingly, and the impedance is output by the conductor connected to the two ends of the first magnet.

Preferably, the piezomagnetic stress sensor further includes a second magnet, which is located inside the support housing and provides a bias magnetic field for the first magnet. When the first magnet is deformed, the distance between it and the second magnet is The change causes the bias magnetic field received by the first magnet to change, which causes a change in the magnetic properties of the first magnet, which is equivalent to amplifying the magnetic change amount of the first magnet, which is beneficial to improving the sensing sensitivity.

Preferably, the connecting bodies are two fixed blocks connected to the inner wall of the supporting end. One end of the first magnet is fixedly connected to one of the fixed blocks by a fastener, and the other end of the first magnet is fixedly connected to the other fixed block by a fastener. Alternatively, each fixing block is provided with an insertion hole, one end of the first magnet is inserted into the insertion hole of one of the fixing blocks, and the other end of the first magnet is inserted into the insertion hole of the other fixing block. Or, the two ways are combined, that is, each fixed block is provided with a jack, one end of the first magnet is inserted into the jack of one of the fixed blocks, and the other end of the first magnet is inserted into the jack of the other fixed block, and at the same time Fasteners are used to secure the end of the first magnet in each fixed block.

The fastener includes a conductive screw or a non-conductive screw. When a conductive screw is selected, a wire can be drawn from the screw for outputting an impedance value.

In order to further improve the sensitivity of the piezomagnetic stress sensor, a coil can also be arranged on the periphery of the first magnet, that is, the first magnet passes through the inside of the coil; when the magnetic properties of the first magnet change, the coil The impedance changes accordingly, and the impedance value of the coil is output from both ends of the coil. In this case, preferably, the number of the coils is greater than or equal to two, there is a space between adjacent coils, and the coils are connected in series, so as to further increase the change amount of the coil impedance, thereby improving the sensitivity. More preferably, the piezomagnetic stress sensor also includes at least one force conductor, one end of the force conductor is fixedly connected to the inner wall of the support end, and the other end is fixedly connected to the position between the two ends of the first magnet, for connecting the pressure-bearing part The compressive stress is directly transmitted between the two ends of the first magnet, thereby increasing the amount of deformation at the position between the two ends of the first magnet, thereby increasing the overall deformation of the first magnet, which is beneficial to improving the sensing sensitivity.

Preferably, the coil is located on a bracket to facilitate adjustment of the position of the coil. The support structure is not limited, and may be a fixed frame and/or a fixed rod fixed inside the supporting shell.

The first magnet is a magnetostrictive material system, including magnetostrictive metal, magnetostrictive alloy, amorphous magnetostrictive material and the like. Preferably, iron-based and cobalt-based amorphous magnetostrictive materials are selected, including FeSiB, FeCuNbSiB, FeNiSiB, FeCoSiB, GdFeCo, CoSiB and the like.

The supporting shell can be made of stainless steel, Al, Cu, plastic or the like. In order to prevent the external magnetic field from generating the magnetic field inside the supporting shell, preferably, the supporting shell material is made of soft magnetic material, or a layer of soft magnetic material is arranged around the supporting shell to magnetically shield the external magnetic field.

The impedance output end (including the conductor end connected to the two ends of the first magnet, and/or the two ends of the coil) is connected to the impedance analyzer; or, the impedance output end and the resistor form a Wheatstone bridge structure, and The impedance output terminal is a bridge arm of the Wheatstone bridge, and the output of the Wheatstone bridge is connected with a voltmeter or an ammeter or an impedance analyzer.

In summary, the utility model provides a piezomagnetic stress sensor, through the design of the structure, the external stress acts on the stress receiving body to generate compressive stress, and the stress receiving body transmits the compressive stress to the bearing of the supporting shell. The pressure part, the pressure part is deformed, the deformation is strong in the center and gradually weakens around the distribution, thus causing the deformation of the first magnet connected to the pressure part, so that the magnetism of the first magnet with magnetostrictive properties occurs Changes, its impedance changes accordingly, and the impedance of the coils arranged around it also changes accordingly. The stress detection can be realized by detecting the impedance change value of the first magnet or the impedance conversion value of the coil.

The sensor has the advantages of simple structure, high sensitivity, easy installation, easy maintenance, low cost, and wireless detection compatibility. Tank scales, storage scales, and hopper scales in the detection system; high-stress monitoring systems such as vehicle-mounted item weighing, can also be used for micro-stress monitoring, such as micron-level displacement measurement, micro-stress and strain measurement, and other fields.

Description of drawings

Fig. 1 is a structural schematic diagram of a piezomagnetic stress sensor in Embodiment 1 of the present utility model;

Fig. 2 is a structural schematic diagram of a piezomagnetic stress sensor in Embodiment 2 of the present utility model;

Fig. 3 is a structural schematic diagram of a piezomagnetic stress sensor in Embodiment 3 of the present invention.

Detailed ways

The utility model is described in further detail below in conjunction with the accompanying drawings.

Reference numerals in Fig. 1 and Fig. 2 are: housing 1, base 2, perforation 3, stress bearing body 4, column 5, fixing rod 6, second magnet 7, fixing column 8, fixing frame 9, first magnet 10. Screw 11, coil barrel 12, enameled wire 13, fixing jack 14, force conductor 15.

Example 1:

In this embodiment, the structure of the piezomagnetic stress sensor is shown in Figure 1, including a supporting shell, a stress receiving body 4 connected to the outside of the supporting shell, and a first magnet 10 and a second magnet located inside the supporting shell. 7.

The supporting shell is composed of a base 2 and a shell 1 .

The stress bearing body 4 is connected to the top position of the supporting shell, which is the pressure bearing part of the supporting shell, the stress bearing body 4 is located on the outer wall surface of the pressure bearing part, and the inner wall surface of the pressure bearing part is fixedly connected with two fixing frames 9.

Each fixing bracket 9 is provided with a fixing socket 14 . One end of the first magnet 10 is inserted into the insertion hole of one of the fixing blocks, and the other end of the first magnet is inserted into the insertion hole of the other fixing block. At the same time, screw 11 is used to contact and fix the end of the first magnet in each fixed block.

The second magnet 7 is located on the upright 5 , and the upright 5 is fixed on the base 2 and fixed on the side wall of the housing 1 through the fixing rod 6 .

The first magnet 10 is made of FeCoSiB material, which is a strip with a width of 0.5 mm and a thickness of 30 microns.

The housing 1 is made of stainless steel, and its periphery is plated with soft magnetic permalloy.

The side wall of the housing 1 is provided with a perforation 3 . The screw 11 is a conductive screw, and the lead wire of the conductive screw passes through the through hole 3 and is connected with the impedance analyzer.

In the working state, external stress acts on the stress-receiving body 4, and the top of the casing is deformed by compressive stress, and the deformation of the top of the casing weakens around the position where the top of the casing is connected to the stress-receiving body as the center. Deformation of the top of the housing causes deformation of the first magnet 10 . The deformation of the first magnet 10 causes a magnetic change of the first magnet 10 . Simultaneously, because the second magnet 7 provides the bias magnetic field for the first magnet 10, when the first magnet 10 deforms, its distance from the second magnet 7 changes, which makes the bias magnetic field suffered by the first magnet 10 change, This will cause a magnetic change of the first magnet 10 , which is equivalent to amplifying the magnetic change amount of the first magnet 10 . In this embodiment, the screw is a conductive screw, and the lead wire of the conductive screw passes through the through hole 3 and is connected to an impedance analyzer, and the applied stress can be detected by measuring the change of the impedance of the first magnet 10 .

In this embodiment, the first magnet 10 is made of FeCoSiB material, and the change of its magnetic permeability reaches 10 ⁵ under the action of unit strain, so it can detect the micro strain of 10 ⁻⁶ level.

Example 2:

In this embodiment, the structure of the piezomagnetic stress sensor is shown in Figure 2, which is basically the same as that of the piezomagnetic stress sensor in Embodiment 1, except that the first magnet 10 is provided with coils on the periphery, that is, A magnet 10 passes inside the coil. The coil is composed of a coil barrel 12 and an enameled wire 13 wound outside the coil barrel 12. Both ends of the enameled wire 13 pass through the perforation 3 and are connected to an impedance analyzer. The second magnet 7 is located directly below the coil. The coil is mounted on the second magnet 7 via a fixing post 8 .

In the working state, external stress acts on the stress-receiving body 4, and the top of the casing is deformed by compressive stress, and the deformation of the top of the casing weakens around the position where the top of the casing is connected to the stress-receiving body as the center. Deformation of the top of the housing causes deformation of the first magnet 10 . The deformation of the first magnet 10 causes a magnetic change of the first magnet 10 . Simultaneously, because the second magnet 7 provides the bias magnetic field for the first magnet 10, when the first magnet 10 deforms, its distance from the second magnet 7 changes, which makes the bias magnetic field suffered by the first magnet 10 change, This will cause a magnetic change of the first magnet 10 , which is equivalent to amplifying the magnetic change amount of the first magnet 10 . When the magnetism of the first magnet 10 changes, the impedance of the first magnet 10 changes thereupon, and the impedance of the first magnet 10 is output by the lead connected with the screw 11; meanwhile, the coil impedance changes accordingly, and the impedance value of the coil Output from both ends of the coil.

Example 3:

In this embodiment, the structure of the piezomagnetic stress sensor is shown in Figure 3. This structure is basically the same as that of the piezomagnetic stress sensor in Embodiment 2, except that the periphery of the first magnet 10 in this structure is provided with two The coils, that is, the first magnet 10 pass through the two coils, and there is a space between the two coils, and the two coils are connected in series. Secondly, the piezomagnetic stress sensor also includes a force conductor 15, one end of the force conductor 15 is fixedly connected to the top inner wall of the casing, and the other end is fixedly connected to the position between the two ends of the first magnet 10, which is used to connect the casing The compressive stress on the top of the body is directly transmitted between the two ends of the first magnet 10 to increase the deformation at the position between the two ends of the first magnet, thereby improving the overall deformation of the first magnet and improving the sensing sensitivity. In addition, the second magnet 7 is located directly below the middle position of the two coils, the second magnet 7 is located on the upright 5 , and the upright 5 is fixed on the base 2 . Each coil is mounted on the base 2 through a fixing post 8 , and the fixing post 8 is fixed on the side wall of the housing 1 through a fixing rod 6 .

The embodiments described above have described the technical solutions and beneficial effects of the utility model in detail. It should be understood that the above descriptions are only specific embodiments of the utility model, and are not intended to limit the utility model. Any modifications and improvements made within the scope of the principle should be included in the scope of protection of the present utility model.

Claims (9)

1. A piezomagnetic stress sensor, characterized in that it includes a support housing, a stress receiving body connected to the outside of the support housing, and a magnetostrictive first magnet positioned inside the support housing; In the supporting shell, the part connected with the stress receiving body is a pressure receiving part, and the pressure receiving body is located on the outer wall of the pressure receiving part; Both ends of the first magnet are fixedly connected to the inner wall of the pressure-bearing part, or both ends of the first magnet are fixedly connected to the inner wall of the pressure-bearing part through a connecting body; In the working state, the external stress acts on the stress-receiving body, and the pressure-bearing part is deformed by the compressive stress, and the deformation of the pressure-bearing part weakens around the position connected with the stress-receiving body; the pressure-bearing part The deformation causes the first magnet to deform, and the deformation of the first magnet causes the magnetic change of the first magnet, and the impedance of the first magnet changes accordingly, and the impedance is output by the conductor connected to the two ends of the first magnet. 2. The piezomagnetic stress sensor according to claim 1, further comprising a second magnet for providing a bias magnetic field to the first magnet. 3. The piezomagnetic stress sensor according to claim 1, characterized in that: the connecting body is two fixed blocks connected to the inner wall of the pressure-bearing part; One end of the first magnet is fixedly connected to one of the fixed blocks by a fastener, and the other end of the first magnet is fixedly connected to the other fixed block by a fastener; Or, each fixed block is provided with a socket, one end of the first magnet is inserted into the socket of one of the fixed blocks, and the other end of the first magnet is inserted into the socket of the other fixed block; Or, each fixed block is provided with a socket, one end of the first magnet is inserted into the socket of one of the fixed blocks, the other end of the first magnet is inserted into the socket of the other fixed block, and a fastener is used to fix each fixed block at the same time. core end in the block. 4. The piezomagnetic stress sensor according to any one of claims 1 to 3, further comprising at least one coil, the first magnet passing through each coil; A magnetic change of the first magnet causes a change in coil impedance, which is output from both ends of the coil. 5. The piezomagnetic stress sensor according to claim 4, characterized in that: the number of said coils is greater than or equal to two, there is a gap between adjacent coils, and the coils are connected in series. 6. The piezomagnetic stress sensor according to claim 4, characterized in that: it also includes at least one force conductor, one end of the force conductor is fixedly connected to the inner wall of the pressure-bearing part, and the other end is fixedly connected to the two ends of the first magnet. position between the ends. 7. The piezomagnetic stress sensor according to claim 6, characterized in that: the coil is located on the bracket. 8. The piezomagnetic stress sensor according to any one of claims 1 to 3, wherein said piezomagnetic stress sensor is characterized in that: said conductor is connected to an impedance analyzer; or, said The conductor and the resistor form a Wheatstone bridge structure, and the conductor is a bridge arm of the Wheatstone bridge, and the output of the Wheatstone bridge is connected to a voltmeter, an ammeter or an impedance analyzer. 9. The piezomagnetic stress sensor as claimed in claim 4, characterized in that: the two ends of the coil are connected to the impedance analyzer; or, the two ends of the coil and the resistor form a Wheatstone bridge structure, and The conductor is one arm of a Wheatstone bridge, and the output of the Wheatstone bridge is connected to a voltmeter, ammeter, or impedance analyzer.