CN101430369B - Self-generating broadband laminated magneto-inducible piezoelectric effect AC magnetic field sensor and manufacturing method - Google Patents

Abstract

A power generation type AC magnetic field sensor based on magneto piezoelectric effect is a laminated structure consisting of magnetostrictive rod, a piezoelectric material, the magnetostrictive rod and a permanent magnetic material; the upper surface and the lower surface of the piezoelectric material are provided with silver membrane electrode respectively, and the magnetostrictive rods is equipped with a signal output lead. The sensor can detect the alternating current without power supply, so the sensor is an energy-saving device with zero power consumption. The sensor has the advantages of small volume and low weight, can detect the AC magnetic field bandwidth ranging from 500Hz to 70kHz, and keeps a good linear relation between the output voltage and the magnetic field amplitude. The sensor adopts a thin rod structure, thus greatly reducing the volume of the sensor, enhancing the sensitivity and the bandwidth of the sensor. A bias magnetic field provided for the thin rod is greatly reduced for using small size of the magnetostrictive material, and can be integrated with a sensitive body. The sensor can be applicable to passive detection of the alternating magnetic fields.

Description

Self-generating broadband laminated magneto-inducible piezoelectric effect AC magnetic field sensor and manufacturing method

technical field

The invention relates to a novel AC magnetic field sensor, in particular to a power generation type broadband laminated magneto-induced piezoelectric effect AC magnetic field sensor.

Background technique

With the development of information technology, the requirements for sensors are getting higher and higher. In the fields of automotive electronics, aerospace, transportation, automatic control, robotics and other fields, new, miniature, passive, high-sensitivity, linear, broadband, fast response , small mass, and low-cost sensors demand more and more intense.

In fields such as electromagnetic compatibility, power engineering, and electrical engineering, it is necessary to monitor physical quantities related to magnetic signals, such as space stray alternating magnetic fields, magnetic fields generated by motors, and magnetic fields generated by currents. The sensors currently on the market for dynamic magnetic field measurement mainly include: Hall effect sensors, anisotropic magnetoresistance (AMR) sensors, giant magnetoresistance (GMR) effect sensors, giant magnetoresistance (GMI) effect sensors, these sensors The alternating magnetic field can be measured, but these sensors need power supply to work, the temperature stability of the Hall sensor is poor, and the sensitivity of the Hall sensor and the AMR sensor is small. The sensors that do not need power supply and can measure magnetism mainly include electromagnetic coils based on Faraday’s electromagnetic induction principle, but the output signal of this coil changes with the frequency of the measured signal, and the output signal is very weak at small sizes and low frequencies.

The sensor produced by the present invention can work without power supply, and has the characteristics of high sensitivity, linearity, broadband, fast response and small quality, and can be widely used in transportation, mechanical processing industry, aerospace, earth environment, electric power engineering , automatic control and other industries, has broad application prospects.

Literature search found that the research paper on the concept of piezomagnetic effect of such laminated composite materials was published in Applied Physics letters in 2002, Vol. Terfenol-D/polyvinylidenedifluoridecomposites". Afterwards, Dong Shuxiang et al. in Virginia, USA published in AppliedPhysics letters, Vol.83, p4812-4814 in the United States in 2003 about the structural devices of sheet magnetostrictive materials/piezoelectric materials/sheet magnetostrictive materials. The research paper on magnetoelectric effect, the bias magnetic field in its experiment is produced by large-scale electromagnet, their research focuses on carrying out experiment discussion to this effect and the theory of this effect is carried out comparatively in-depth research, does not constitute the present invention's proposed sensor. Wen Yumei from Chongqing University in China has studied the electromagnetic transducers with Terfenol-D and PZT ultrasonic horn structures in the Journal of Sensing Technology (Journal of Sensing Technology, Vol.20, No.8, 2007, P1742-1746), they have also conducted research on "The longitudinal vibration magnetoelectric response of GMM/elastic plate/PZT layered composite structure" (Acta Physica Acta, Vol.57, No.7, 2008, P4545-4551), but they The proposed device structure is quite different from the proposed sensor structure of the present invention.

Contents of the invention

The purpose of the present invention is to make the above theoretical research results in the laboratory into a sensor that can be realized in practice, and provides a specific method for making a power-generating broadband laminated magneto-piezoelectric effect miniature magnetic field sensor, especially In the present invention, a thin rod with a giant magnetostriction coefficient is used instead of a thin plate. Another main special feature is that the present invention combines a small piece of permanent magnet with the above laminated structure to form a real sensor. And can maintain a wide frequency band range.

The principle of the present invention is that the giant magnetostrictive material has a large magnetostrictive coefficient under the action of the bias magnetic field, and the alternating magnetic field will cause the magnetostrictive material to expand and contract, and the stress generated by the expansion and contraction is transmitted to the piezoelectric material, and the piezoelectric material is compressed. An alternating electric field is formed in the electric material, and the electric field corresponds to a voltage signal, which gives a qualitative principle explanation of the sensor, and its quantitative explanation is more complicated. However, theoretical results show that the magnetoelectric effect is related to parameters such as the volume ratio of the giant magnetostrictive material to the stacked structure, the piezoelectric coefficient of the piezoelectric material, and the electromechanical coupling coefficient.

The present invention is achieved through the following technical solutions:

A self-generating broadband laminated magnetostrictive piezoelectric effect AC magnetic field sensor, which is a laminated structure of magnetostrictive rod/piezoelectric material/magnetostrictive rod/permanent magnetic material; the upper and lower surfaces of the piezoelectric material have silver film electrodes , signal output leads are arranged on the magnetostrictive rod.

The above-mentioned sensor, wherein the magnetostrictive rod has a rectangular cross-section and an aspect ratio ≥ 5.

The above-mentioned sensor, wherein the piezoelectric material has the same length and width as the magnetostrictive rod.

In the aforementioned sensor, the permanent magnet material is smaller in length or width, or both in length and width than the magnetostrictive rod, and the permanent magnet material is arranged asymmetrically with respect to the center of the magnetostrictive rod.

In the aforementioned sensor, the magnetostrictive rod is a Td-Dy-Fe (Terfenol-D) rod with magnetostrictive properties.

Above-mentioned said sensor, wherein piezoelectric material is PZT material, also can be PMN-PT material, or other piezoelectric material with high piezoelectric coefficient; length direction) polarization; the silver film electrodes on the upper and lower surfaces of the piezoelectric material are polarized along the thickness direction.

In the aforementioned sensor, the permanent magnet material is Nd-Fe-B permanent magnet, and the magnetization is along the thickness direction.

The use of thin rods with giant magnetostrictive coefficients can reduce the volume of the sensor on the one hand, and on the other hand, due to the use of thin rod structures, the demagnetization field is greatly reduced, so the giant magnetostrictive rods can be used in a small bias magnetic field Therefore, the bias magnetic field provided by a small magnet can be used to make the sensor work, and can maintain a large magnetic field sensitivity; the combination of permanent magnetic material and laminated structure can make the sensor sensitive The improvement is due to a difference in the bias magnetic field generated by a single magnet in the two rods, forming a structure similar to a cantilever beam, which increases the sensitivity of the output voltage.

The steps of concrete preparation method of the present invention are as follows:

(1) make two identical magnetostrictive rods;

(2) Make a piezoelectric material with the same length and width as the magnetostrictive rod, which is polarized along the thickness direction or can be polarized in the longitudinal direction, and silver-plated on the upper and lower surfaces of the piezoelectric material to form a silver film electrode, Polarized along the thickness direction;

(3) bonding the magnetostrictive thin rod and the piezoelectric material with silver conductive glue, and applying pressure at a certain temperature;

(4) Leading out signal output leads on the magnetostrictive material, including making electrical signal leads on the piezoelectric material plating conductive layer;

(5) Paste a permanent magnet on one side of the above magnetostrictive rod, and the magnetization is along the thickness direction.

More specific operations are:

1. Cut and process the giant magnetostrictive cylindrical material to produce a Td-Dy-Fe (Terfenol-D) with a rectangular cross-section with a length of 10-15mm and a cross-section of 1×1mm ² with giant magnetostriction properties. Thin rods, the resulting material has a large aspect ratio and aspect ratio;

2. Make PZT or other piezoelectric materials with high piezoelectric coefficient. The piezoelectric material can be PZT material or PMN-PT material. The material can be polarized along the thickness direction or along the longitudinal direction (length direction) Polarization, which has the same length and width as the above-mentioned giant magnetostrictive material, the upper and lower surfaces of the piezoelectric material are plated with silver to form silver film electrodes, and the piezoelectric material is polarized by adding an electric field along the thickness direction;

3. Bond the giant magnetostrictive thin rod with the piezoelectric material with silver conductive glue, and apply pressure at a temperature of 80°C;

4. Lead out a signal output lead wire on the giant magnetostrictive material;

5. Paste a 5×1×0.5mm ³ Nd-Fe-B permanent magnet with a mass of about 0.15g on one side of the above giant magnetostrictive material, and the magnet is magnetized along the thickness direction;

6. Encapsulate the above laminated structure to make a practical sensor.

The present invention has the following advantages:

The present invention utilizes Terfenol-D thin rods rather than Terfenol-D flakes. Because the demagnetization factor of the thin rod is small and easy to magnetize, it is possible to use tiny magnets to form the entire sensor;

(1) The miniature permanent magnet of the present invention is integrated with the Terfenol-D rod/piezoelectric material/Terfenol-D rod, so that the magnetic field sensor becomes a whole;

(2) The present invention adopts Terfenol-D rod, makes sensor volume reduce greatly, but can keep high sensitivity;

(3) the sensor volume that the present invention makes is little, and its resonant frequency is high, makes it have high frequency bandwidth;

(4) The asymmetric structure design of the magnet of the present invention can obviously enhance the sensitivity of the sensor;

(5) The present invention can reduce the mass of the permanent magnet material and increase the resonant frequency due to the use of thin rods.

Description of drawings

Fig. 1 is a structural schematic diagram of an example of a generator-type broadband laminated magneto-piezoelectric effect AC magnetic field sensor. In the figure, 1 is the NdFeB permanent magnet material, 2 and 8 are electrical signal output lines, 3 is the upper layer Terfenol-D giant magnetostrictive material, 4 is the silver-plated layer on the upper surface of the piezoelectric PZT material, 5 is the PZT piezoelectric material, 6 7 is the lower layer of Terfenol-D giant magnetostrictive material.

Detailed ways

Make further description below in conjunction with accompanying drawing:

Example 1:

The sensor shown in Figure 1 was prepared as follows:

(1) Cut the large-sized Terfenol-D cylindrical rod to obtain Terfenol-D thin rod 3 and thin rod 7 with a length of 10 mm, a width of 1 mm, and a height of 1 mm. The opposite sides of the thin rod 3 and thin rod 7 are polished. ;

(2) Make the same width as the Terfenol-D thin rod 3 described in (1), and the PZT-5H material 5 with a thickness of 0.8mm, silver-plated layers 4 and 6 respectively on the upper and lower surfaces of the piezoelectric material 5, use CLD- 5 Bake the conductive adhesive at 80°C for 30 minutes and raise the temperature to 120°C for 3 hours, then cool to room temperature, paste PZT-5H material 5 between Terfenol-D materials 3 and 7 to form Terfenol-D/piezoelectric material/ Terfenol-D laminated structure, the PZT material is polarized with a strong electric field along the thickness direction, and the voltage signal is output through the signal output lines 2 and 8 on the thin rod of Terfenol-D;

(3) Be 1mm wide, be 0.5mm thick, be 5mm long, the NdFeB permanent magnet 1 that quality is 0.15g sticks on the Terfenol-D rod 3 with adhesive agent, this magnet is magnetized along the thickness direction, and its surface magnetic field is 320Oe;

Example 2:

Use an Agilent33220A signal generator to generate a sinusoidal signal, and provide an excitation current to the Helmertz circle, thereby generating a simulated measured alternating magnetic field near the center of the Helmertz axis. Put the sensor made in Example 1 into this magnetic field, then The sensor will output an output voltage signal or charge signal that is proportional to the input alternating magnetic field. For laterally polarized PZT materials, the piezoelectric voltage coefficient reaches 35mV/Oe;

In the frequency range of 0.5 ~ 70KHz, the sensor output voltage remains unchanged under a constant input magnetic field. When the frequency increases to 80KHz, it is the resonance frequency point. At this time, the output voltage has a peak value. At this time, the dV/dH is very high, and the magnetic sensitivity can reach 1.5V/Oe during resonance.

The frequency of the alternating signal is between 0 and 500 Hz. When the input amplitude is constant, the output increases as the frequency increases.

The sensor can not only detect the alternating magnetic field, but also detect other physical quantities related to the alternating magnetic field, and can also be designed to detect other physical quantities.

Claims (9)

1. a self-generation wide-band laminated magnetic induced piezoelectric effect AC magnetic field sensor is characterized in that, is the stepped construction of magnetostrictive rod/piezoelectric/magnetostrictive rod/permanent magnetic material; The upper and lower surface of said piezoelectric has silver-colored membrane electrode, and magnetostrictive rod is provided with the signal output lead; Wherein magnetostrictive rod is the square-section, length breadth ratio 〉=5; The magnetization of permanent magnetic material is along thickness direction.

2. according to the said sensor of claim 1, it is characterized in that wherein piezoelectric has length identical with magnetostrictive rod and width.

3. according to the said sensor of claim 1, it is characterized in that wherein the length of permanent magnetic material is less than magnetostrictive rod, permanent magnetic material is asymmetric setting with respect to the center of magnetostrictive rod.

4. according to the said sensor of claim 1, it is characterized in that wherein magnetostrictive rod is the Td-Dy-Fe rod with Magnetostrictive Properties.

5. according to the said sensor of claim 1, it is characterized in that piezoelectric wherein is the PZT material, also can be the PMN-PT material, or other has the piezoelectric of high piezoelectric modulus; Piezoelectric can also can longitudinally polarize along the thickness direction polarization; The upper and lower surface of piezoelectric has silver-colored membrane electrode.

6. according to the said sensor of claim 1, it is characterized in that permanent magnetic material wherein is a Nd-Fe-B permanent magnetism.

7. a method of making the described self-generation wide-band laminated magnetic induced piezoelectric effect AC magnetic field sensor of claim 1 is characterized in that, may further comprise the steps:

(1) make two identical magnetostrictive rods, magnetostrictive rod is the square-section, length breadth ratio 〉=5;

(2) make the piezoelectric that has same length and width with magnetostrictive rod, but this piezoelectric is silver-plated in the upper and lower surface of piezoelectric along thickness direction polarization or length direction polarization, forms silver-colored membrane electrode;

(3) with silver conductive adhesive that the thin rod of magnetostriction is bonding with piezoelectric, the processing of exerting pressure at a certain temperature;

(4) on magnetostriction materials, draw the signal output lead;

(5) paste a permanent magnetism on the one side of above magnetostrictive rod, magnetization is along thickness direction.

8. method for making according to claim 7, it is characterized in that permanent magnetism is asymmetric about piezoelectric and every layer of center line, i.e. piezoelectric both sides giant magnetostriction material, one side outside magnetostriction materials directly adds permanent magnetic material, and permanent magnetism is not the center that is placed in magnetostriction materials.

9. method for making according to claim 7 is characterized in that, concrete operations are:

(1) making length is 10～15mm, and the cross section is 1 * 1mm ²The Td-Dy-Fe with giant magnetostrictive driver characteristic carefully the rod;

(2) produce by PZT or other and have the piezoelectric of high piezoelectric modulus, the thin rod of Td-Dy-Fe has same length and width in piezoelectric and the step (1), and the upper and lower surface of piezoelectric is silver-plated, forms silver-colored membrane electrode, polarizes along thickness direction;

(3) with silver conductive adhesive that the thin rod of giant magnetostrictive driver is bonding with piezoelectric, the processing of under 80 ℃ of temperature, exerting pressure;

(4) on giant magnetostriction material, respectively draw a signal output lead;

(5) above Terfenol-D/ piezoelectric/Terfenol-D stacking material one side paste one 5 * 1 * 0.5mm ³, the Nd-Fe-B permanent magnetism of the about 0.15g of weight, this magnet magnetizes along thickness direction.