阅读说明：本技术 一种微小型超高温压电振动加速度传感器及其装配方法 (Microminiature ultra-high temperature piezoelectric vibration acceleration sensor and assembly method thereof ) 是由 于法鹏 刘学良 房浩然 杨勇 马庆宇 赵显� 于 2020-06-16 设计创作，主要内容包括：本发明涉及一种微小型超高温压电振动加速度传感器及其装配方法,属于电子材料与器件领域,包括安装底座、装配基面、压电模块和外壳；压电模块包括多片压电晶片和两个质量块,压片晶片为剪切式RECOB晶片,RECOB晶片的化学式为RECa<Sub>4</Sub>O(BO<Sub>3</Sub>)<Sub>3</Sub>(RE为Y和稀土元素)；外壳为一端开口的矩形壳体,与安装底座固定连接形成传感器的密封内腔；安装底座上还设置有通孔,通孔内安装有用于信号传输的双屏蔽高温铠装电缆。本发明体积较小,结构简单稳定,低介电损耗、热释电小、温度漂移小于5％,且该传感器耐温高达1000℃,并可在高达1000℃的极端环境下长时间服役。(The invention relates to a microminiature ultra-high temperature piezoelectric vibration acceleration sensor and an assembly method thereof, belonging to the field of electronic materials and devices, and comprising an installation base, an assembly base surface, a piezoelectric module and a shell; the piezoelectric module comprises a plurality of piezoelectric wafers and two mass blocks, wherein the pressing wafer is a shear type RECOB wafer, and the chemical formula of the RECOB wafer is RECa 4 O(BO 3 ) 3 (RE is Y and a rare earth element); the shell is a rectangular shell with an opening at one end and is fixedly connected with the mounting base to form a sealed inner cavity of the sensor; the installation base is further provided with a through hole, and a double-shielding high-temperature armored cable for signal transmission is installed in the through hole. The invention has the advantages of small volume, simple and stable structure, low dielectric loss, small pyroelectric, less than 5% of temperature drift, temperature resistance of the sensor up to 1000 ℃, and long-time service under the extreme environment of up to 1000 ℃.)

1. A microminiature ultra-high temperature piezoelectric vibration acceleration sensor is characterized by comprising an installation base, an assembly base surface, a piezoelectric module and a shell;

the assembling base surface is a rectangular plane and is integrated with the mounting base into a whole, the mounting base is provided with a mounting hole, and the assembling base surface is provided with a central hole for mounting the piezoelectric module;

the piezoelectric module comprises a plurality of piezoelectric wafers and two mass blocks, the piezoelectric modules are symmetrically arranged on an assembly base plane, the piezoelectric wafers are shear type RECOB wafers, and the chemical formula of the RECOB wafers is RECa₄O(BO₃)₃；

The shell is a rectangular shell with an opening at one end and is fixedly connected with the mounting base to form a sealed inner cavity of the sensor, and the piezoelectric module is positioned in the sealed inner cavity;

the mounting base is further provided with a through hole, a double-shielding high-temperature armored cable for signal transmission is mounted in the through hole, and one end of the double-shielding high-temperature armored cable is fixedly connected with one mass block.

2. The micro ultra-high temperature piezoelectric vibration acceleration sensor according to claim 1, wherein the piezoelectric module further comprises a bolt and a nut that are engaged with each other, the bolt is inserted into the central hole, the mass block comprises a mass block a and a mass block B, the mass block a, a ceramic tube and the mass block B are sequentially sleeved on the bolt, the mass block a and the mass block B are welded on the bolt, the ceramic tube and the bolt are engaged with each other by screw threads, a plurality of piezoelectric wafers are sleeved on the ceramic tube, the nut is pressed against the mass block B and fixed on the bolt to provide pre-tightening force for the piezoelectric module, wherein the plurality of piezoelectric wafers are symmetrically distributed on both sides of an assembly base plane, and the mass block a and the mass block B are also;

preferably, the mounting base is provided with a mounting surface at the joint with the housing, the open end of the housing is fixedly connected with the mounting surface, and after mounting, the surface of the housing is flush with the surface of the mounting base.

3. The micro ultra-high temperature piezoelectric vibration acceleration sensor according to claim 2, wherein the number of the piezoelectric wafers is 2 or 6, that is, 1 or 3 piezoelectric wafers are distributed on both sides of the substrate surface.

4. The microminiature ultra high temperature piezoelectric vibration acceleration sensor of claim 1, wherein the direction of the mounting hole is parallel or perpendicular to the assembly base plane for monitoring the vertical and horizontal vibration signals of the vibration, respectively.

5. The microminiature ultra high temperature piezoelectric vibration acceleration sensor according to claim 1, wherein the piezoelectric wafers are square pieces with holes opened in the middle, and two adjacent piezoelectric wafers are connected in parallel with each other with the negative electrode facing each other and the positive electrode facing each other;

preferably, the piezoelectric wafer has a work roughness of 0.1 μm and a parallelism of 0.02 mm.

6. The microminiature ultra high temperature piezoelectric vibration acceleration sensor according to claim 5, wherein when the number of the piezoelectric wafers is 6, two paths of electrode pieces are respectively provided between the piezoelectric wafers located on both sides of the assembly base surface, each path of electrode piece including electrode rings on both sides and a connecting wire for connecting the electrode rings on both sides;

the piezoelectric wafers on both sides of the assembly base surface are: the electrode rings of one path of electrode plate are inserted between the cathodes of the piezoelectric wafers, and the electrode rings of the other path of electrode plate are inserted between the anodes of the piezoelectric wafers.

7. The microminiature ultra high temperature piezoelectric vibration acceleration sensor according to claim 6, wherein, for the piezoelectric wafer on the side of the assembly base plane, one path of electrode sheet is set between the two piezoelectric wafers closest to the mass block A and sleeved in the ceramic tube, and the tail end is set between the assembly base plane and the piezoelectric wafer closest thereto and sleeved in the ceramic tube, and the other path of electrode sheet is set between the mass block A and the piezoelectric wafer closest thereto and sleeved in the ceramic tube, and the tail end is set between the two piezoelectric wafers closest to the assembly base plane and sleeved in the ceramic tube;

for the piezoelectric wafers on the other side of the assembly base plane, the starting position of one path of electrode slice is arranged between the two piezoelectric wafers closest to the mass block B and sleeved in the ceramic tube, the tail end of the electrode slice is arranged between the assembly base plane and the piezoelectric wafer close to the assembly base plane and sleeved in the ceramic tube, the starting position of the other path of electrode slice is arranged between the mass block B and the piezoelectric wafer close to the mass block B and sleeved in the ceramic tube, and the tail end of the electrode slice is arranged between the two piezoelectric wafers closest to the assembly base plane and sleeved in the;

preferably, the inner diameter and the outer side length of the electrode plate are kept to be the same as the size of the piezoelectric wafer, and when the thickness of the piezoelectric wafer is 0.7mm, the length of the connecting wire is 3mm, and the width of the connecting wire is 2 mm;

the electrode plate is made of a platinum metal sheet or a platinum-plated nickel metal sheet.

8. The microminiature ultra-high temperature piezoelectric vibration acceleration sensor according to claim 1, wherein the mass block A and the mass block B are made of metal tungsten, and a platinum film with a thickness of 200-300nm is plated on the surface of the metal tungsten;

the screw thread fit is formed between the nut and the bolt, and between the ceramic tube and the bolt, and high-temperature insulating glue is filled between gaps;

preferably, the length of the ceramic tube is smaller than the sum of the thicknesses of the piezoelectric wafers and the mounting base surface, the ceramic tube is located in the center of the bolt, the ceramic tube is not in contact with the mass block A and the mass block B, and after the piezoelectric wafers and the mass block are symmetrically assembled, the pre-tightening torque of the nut is 0.3-0.4 N.m;

preferably, a counter bore is formed in the contact surface of the mass block B and the nut, after assembly, the nut is located in the counter bore, the counter bore is also formed in the mass block A, during assembly, a bolt head of the bolt sinks into the counter bore, the nut/the bolt head sinks into the counter bore to be tightly combined, and after a proper pre-tightening torque is applied, the bolt is welded with the nut, the bolt is welded with the mass block A, and the bolt is welded with the mass block B;

preferably, the ceramic tube is made of alumina ceramic with the purity of 99% or more, the nut and the bolt are made of Inconel601 alloy, and the mounting base, the assembly base surface and the shell are made of Inconel601 alloy.

9. The microminiature ultra-high temperature piezoelectric vibration acceleration sensor according to claim 1, wherein the double-shielded high temperature armored cable comprises a wire, a first insulating layer, a first shielding layer, a second insulating layer and a second shielding layer in sequence from inside to outside, the wire is made of 0.3mm nickel wire, the first insulating layer and the second insulating layer are filled high purity magnesium oxide, the first shielding layer is made of 316 stainless steel alloy pipe, and the second shielding layer is made of Inconel601 alloy pipe, namely, an armored sheath of the cable.

10. An assembling method of the microminiature ultra-high temperature piezoelectric vibration acceleration sensor as claimed in claim 1, characterized by comprising the steps of:

(1) firstly, respectively plating a 200-nm platinum film on the upper and lower surfaces of a piezoelectric wafer, a mass block A and a mass block B, sleeving the mass block A on a bolt close to the head end of the bolt, welding and fixing the mass block A, pouring diluted high-temperature insulating glue into a ceramic tube with internal threads, screwing the ceramic tube into the central part of the bolt in a rotating manner, keeping the ceramic tube and the mass block from being contacted, and putting the fixed bolt and the ceramic tube into a drying box at the temperature of 150-180 ℃ for 12-18 hours to finish the curing of the high-temperature insulating glue;

(2) installing a piezoelectric module:

a. when the number of the piezoelectric wafers is 2, during installation, 1 of the piezoelectric wafers is sleeved on a cured ceramic tube, then a bolt penetrates into a central hole of an assembly base surface, the other piezoelectric wafer and a mass block B are sleeved on the bolt on the other side of the assembly base surface, a nut is screwed on the bolt for pre-tightening, the pre-tightening torque is 0.3-0.4 N.m, then the bolt is welded with the nut and the mass block B, the positive electrode of the piezoelectric wafer is contacted with the assembly base surface during installation, the negative electrode of the piezoelectric wafer is contacted with the mass block A or the mass block B, and when the number of the piezoelectric wafers is 2, electrode plates are not required to be arranged;

b. when the number of the piezoelectric wafers is 6, firstly, 3 piezoelectric wafers are overlapped in parallel in a mode that the negative electrodes are opposite and the positive electrodes are opposite, electrode plates are added between the piezoelectric wafers, connecting wires of two paths of the electrode plates are respectively folded, electrodes of one path of the electrode plate are respectively inserted between the positive electrodes of the piezoelectric wafers, and the electrode plate is contacted with an assembly base plane and is insulated from the mass block A; the other electrode plate is inserted between the cathodes of the piezoelectric wafers, and the electrode plate is contacted with the mass block A and insulated from the assembly base plane to form a crystal group A;

the rest 3 pieces of piezoelectric wafers are also overlapped in parallel in a mode that the negative electrode is opposite and the positive electrode is opposite, electrode plates are added between the piezoelectric wafers, connecting wires of the two electrode plates are respectively folded, the electrodes of one electrode plate are respectively inserted between the positive electrodes of the piezoelectric wafers, and the electrode plates are contacted with the assembly base surface and insulated from the mass block B; the other electrode plate is inserted between the cathodes of the piezoelectric wafers, and the electrode plate is contacted with the mass block B and insulated from the assembly base plane to form a crystal group B;

during installation, after the electrode ring at one end is inserted into a corresponding position, the connecting wire is bent directly, and the electrode ring at the other end is inserted into the corresponding position, so that welding spots in the assembly process of the sensor are reduced;

sleeving the crystal group A on the cured ceramic tube, then penetrating a bolt into a central hole of an assembly base surface, sequentially sleeving the crystal group B and the mass block B on the other side of the assembly base surface, finally screwing a nut thread into the bolt for pre-tightening, and welding the bolt and the nut as well as the nut and the mass block B;

(3) preparing a double-shielding high-temperature armored cable:

straightening and fixing the 316 stainless steel alloy pipe, penetrating a 0.3mm nickel wire into the 316 stainless steel alloy pipe, straightening to enable the 0.3mm nickel wire to be located at the center of the 316 stainless steel alloy pipe, placing high-purity magnesium oxide powder in a gap between the 316 stainless steel alloy pipe and the nickel wire, compacting, and sealing openings at two ends by using high-temperature insulating glue to obtain a single-layer armored cable;

straightening and fixing the single-layer armored cable and the Inconel601 alloy pipe which are placed in the vacuum glove box by using a clamp, inserting the single-layer armored cable into the Inconel601 alloy pipe without contacting, placing high-purity magnesium oxide powder in a gap between the Inconel601 alloy pipe and the single-layer armored cable, compacting, and sealing two ends by using high-temperature insulating glue;

(4) the piezoelectric module, the outer shell and the double-shielding high-temperature armored cable are placed in an inert gas atmosphere box, the gas pressure in the atmosphere box is larger than one atmospheric pressure, the double-shielding high-temperature armored cable is inserted into a through hole of the mounting base, the double-shielding high-temperature armored cable and the mounting base are fixed through a clamp, a lead in the double-shielding high-temperature armored cable is used as a signal wire and inserted into a reserved deep hole of the mass block, the lead is fixed through spot welding, and the outer shell is connected onto the mounting base in a sleeved mode and fixedly connected with the mounting;

(5) welding the piezoelectric module, the shell and the double-shielding high-temperature armored cable together by a laser welding machine to enable the piezoelectric module, the shell and the double-shielding high-temperature armored cable to be in close contact without a gap, and obtaining a sensor;

(6) and (4) putting the welded sensor into a high-temperature box for annealing treatment, and eliminating stress residues among devices.

Technical Field

The invention relates to a microminiature ultra-high temperature piezoelectric vibration acceleration sensor and an assembly method thereof, which can be used for monitoring the health condition of key parts during mechanical operation in a high temperature environment, can be used in the industries of aerospace, intelligent ships, rail trains, automobile industry, nuclear power energy and the like, and belongs to the technical field of electronic materials and devices.

Background

In aerospace propulsion systems, High Temperature (HT) sensors are essential for intelligent propulsion system design and operation, and are also essential to improve system stability and safety. The engine's combustion components (including injectors and valves) continue to operate under repeated high temperature cycles, requiring pulse shapes that monitor ignition timing and high combustion efficiency. For reliable monitoring, the sensor needs to be as close to the high temperature source (e.g., engine) as possible. These applications typically require high temperature sensors to function properly at high temperatures greater than 800 ℃.

In addition, the space on the turbine of the aircraft engine is limited, and the size of the mounting hole is also limited, so that a sensor which is small in size, simple and convenient to mount and capable of being stably in service at the high temperature of more than 800 ℃ is urgently needed to better monitor the loose part of the turbine engine. Currently, the 6243M series high-temperature piezoelectric vibration acceleration sensor developed by Endevco corporation in the united states internationally is the most advanced high-temperature vibration sensor at present, but the working temperature of the series of sensors is limited to 650 ℃. The working temperature of the device is not high enough and is limited by the performance of the core piezoelectric material on one hand, and on the other hand, the structure of the device is not reasonable, so that the anisotropic advantage of the piezoelectric crystal cannot be effectively exerted, and the anisotropic compensation of the piezoelectric crystal is utilized to enhance the piezoelectric response. Therefore, the current sensor is limited in a service high-temperature area, or the high-temperature working stability is poor.

Disclosure of Invention

Aiming at the defects and application requirements of the prior art, the invention provides a microminiature ultra-high temperature piezoelectric vibration acceleration sensor and an assembling method thereof, the device has the advantages of small volume, simple structure, low dielectric loss, small pyroelectric and less than 5% of temperature drift, and the sensor can resist the temperature of 1000 ℃ and can be in service for a long time in the extreme environment of 1000 ℃.

Interpretation of terms:

1. piezoelectric effect: when some dielectrics are deformed by an external force in a certain direction, polarization occurs in the dielectrics, and charges of opposite polarities appear on two opposite surfaces of the dielectrics. When the external force is removed, it can be restored to an uncharged state, and this phenomenon is called positive piezoelectric effect. Conversely, when an electric field is applied in the polarization direction of the dielectrics, these dielectrics also undergo deformation, and after the electric field is removed, the deformation of the dielectrics disappears, which is called the inverse piezoelectric effect.

2. Shear piezoelectric constant: crystal anisotropy, in this case d in the parameters of the piezoelectric matrix₁₅、d₁₆、d₂₄、d₂₆、d₃₄、d₃₅。

3. RECOB: has the chemical formula of RECa₄O(BO₃)₃The Chinese name is rare earth borate series crystal, RE is rare earth element, and comprises single rare earth type YCOB, GdCOB, and rare earth mixed type crystal such as YGdCOB and YNDCOB, belonging to monoclinic system m point group.

The invention adopts the following technical scheme:

a microminiature ultra-high temperature piezoelectric vibration acceleration sensor comprises an installation base, an assembly base plane, a piezoelectric module and a shell;

the assembling base surface is a rectangular plane and is integrated with the mounting base into a whole, the mounting base is provided with a mounting hole, and the assembling base surface is provided with a central hole for mounting the piezoelectric module;

the piezoelectric module comprises a plurality of piezoelectric wafers and two mass blocks, the piezoelectric modules are symmetrically arranged on the assembly base surface, and the piezoelectric wafers are shear type RECOB wafers and RECOB wafersThe chemical formula of the tablet is RECa₄O(BO₃)₃；

The piezoelectric sensor comprises a shell, a mounting base, a piezoelectric module and a piezoelectric module, wherein the shell is a rectangular shell with an opening at one end and is fixedly connected with the mounting base to form a sealed inner cavity of the sensor;

the mounting base is further provided with a through hole, a double-shielding high-temperature armored cable for signal transmission is mounted in the through hole, and one end of the double-shielding high-temperature armored cable is fixedly connected with one mass block.

The mounting hole of the sensor is relatively far away from the mounting part of the piezoelectric wafer, so that the influence of strain generated by mounting the sensor on the performance of the sensor can be reduced.

The thickness shear piezoelectric constant (including d) of the piezoelectric crystal can be utilized in the present invention₁₅、d₁₆、d₂₄、d₂₆，d₃₄、d₃₅) Stable sensing signal output is obtained.

Preferably, YGdCOB crystal d is used in the present invention₂₆For example, the cut pattern is (YXt/θ), (YXt/θ) indicates: x is the X axis of physics, Y is the Y axis of physics, t is the rotation along the thickness direction Y of the piezoelectric chip, and theta is the rotation along the thickness direction with a specific value of theta.

According to the preferred embodiment of the invention, the piezoelectric module further comprises a bolt and a nut which are matched with each other, the bolt is arranged in the central hole in a penetrating mode, the mass block comprises a mass block A and a mass block B, the mass block A, a ceramic tube and the mass block B are sequentially sleeved on the bolt, the mass block A and the mass block B are welded on the bolt, the ceramic tube is in threaded fit with the bolt, a plurality of piezoelectric wafers are sleeved on the ceramic tube, the nut tightly presses the mass block B and is fixed on the bolt to provide pre-tightening force for the piezoelectric module, the piezoelectric wafers are symmetrically distributed on two sides of the assembly base surface, and the mass block A and the mass.

YGdCOB crystals d preferred according to the present invention₂₆In mode, the cut is (YXt/-30 °),namely theta is taken at-30 degrees;

the advantage of the design here is that the effective piezoelectric constant of the (YXt/-30 °) cut YGdCOB wafer is-12 pC/N, the cut crystal has the maximum piezoelectric constant of the crystal, and the piezoelectric constant change rate is less than 5% in the range from room temperature to 1000 ℃, and no phase change occurs from room temperature to 1500 ℃. The thermal expansion coefficient is linear change, has extremely high resistivity and particularly excellent high-temperature piezoelectric performance and temperature stability, so that the piezoelectric vibration sensor can resist high temperature up to 1000 ℃.

Preferably, the number of the piezoelectric wafers is 2 or 6, that is, 1 or 3 piezoelectric wafers are respectively distributed on two sides of the base surface.

According to different requirements on impedance and sensitivity at high temperature, the number of the piezoelectric wafers is 2 or 6, the thickness of each piezoelectric wafer is 2mm when 2 wafers are used, and the thickness of each piezoelectric wafer is 0.7mm when 6 wafers are used.

According to the invention, the direction of the mounting hole is parallel to or perpendicular to the assembly base surface, and the vertical vibration signal and the horizontal vibration signal are respectively used for monitoring vibration, namely when the direction of the mounting hole is parallel to the assembly base surface, the vertical vibration signal is monitored, and when the direction of the mounting hole is perpendicular to the assembly base surface, the horizontal vibration signal is monitored.

According to the invention, the piezoelectric wafers are square sheets with holes in the middle, and two adjacent piezoelectric wafers are connected in parallel in a mode that the negative electrode is opposite and the positive electrode is opposite, so that the sensitivity of the piezoelectric vibration sensor is improved;

the shear mode piezoelectric vibration sensor has higher thermal shock resistance compared with the compression mode, the piezoelectric wafer is selected to be the shear mode of RECOB series crystal, and the shear mode d of YGdCOB crystal is selected₂₆To verify the performance of the sensor of the invention at high temperatures. Cut to (YXt/-30 DEG) and shear piezoelectric constant d of the direction₂₆For the maximum piezoelectric constant of the crystal, the square sheet can ensure that the tangential force generated by the mass block to the piezoelectric wafer is consistent with the direction of the tangent type when the sensor works, and the sensitivity of the sensor is effectively improved.

Preferably, the working roughness of the piezoelectric wafer is 0.1 μm, the working roughness is obtained by ensuring that the piezoelectric wafer and the electrode plate do not move under the pushing of 50g of transverse force, wherein the pretightening torque among the piezoelectric wafer, the electrode plate and the mass block is 0.3-0.4 N.m;

the parallelism of the piezoelectric wafer is 0.02mm, which is the maximum allowable value of the error of the parallelism of the upper surface relative to the lower surface, and the higher the parallelism is, the higher the ultimate stress of the wafer is.

Preferably, when the number of the piezoelectric wafers is 6, two paths of electrode plates are respectively arranged between the piezoelectric wafers positioned on two sides of the assembly base plane, and each path of electrode plate comprises electrode rings on two sides and a connecting line for connecting the electrode rings on two sides;

the piezoelectric wafers on both sides of the assembly base surface are: the electrode rings of one path of electrode plate are inserted between the cathodes of the piezoelectric wafers, and the electrode rings of the other path of electrode plate are inserted between the anodes of the piezoelectric wafers.

According to the invention, preferably, for the piezoelectric wafers on one side of the assembly base plane, the starting position of one path of electrode slice is arranged between the two piezoelectric wafers closest to the mass block A and sleeved in the ceramic tube, the tail end of the electrode slice is arranged between the assembly base plane and the piezoelectric wafer close to the assembly base plane and sleeved in the ceramic tube, the starting position of the other path of electrode slice is arranged between the mass block A and the piezoelectric wafer close to the assembly base plane and sleeved in the ceramic tube, and the tail end of the electrode slice is arranged between the two piezoelectric wafers closest to the assembly base plane and sleeved in the;

for the piezoelectric wafers on the other side of the assembly base plane, the starting position of one path of electrode slice is arranged between the two piezoelectric wafers closest to the mass block B and sleeved in the ceramic tube, the tail end of the electrode slice is arranged between the assembly base plane and the piezoelectric wafers close to the assembly base plane and sleeved in the ceramic tube, the starting position of the other path of electrode slice is arranged between the mass block B and the piezoelectric wafers close to the mass block B and sleeved in the ceramic tube, and the tail end of the electrode slice is arranged between the two piezoelectric wafers closest to the assembly base plane and sleeved in the.

Preferably, the inner diameter and the outer side length of the electrode plates are kept to be the same as the size of the piezoelectric wafer (the inner diameter is slightly larger than the diameter of the ceramic tube), and the length of the connecting line between the electrode plates is preferably as follows according to the thickness of the piezoelectric wafer: when the thickness of each piezoelectric wafer is 0.7mm, the length of the connecting line of the electrode plate is preferably 3mm, and the width of the connecting line of the electrode plate is preferably 2 mm;

preferably, the electrode plate is made of a platinum metal sheet or a platinum-plated nickel metal sheet.

According to the invention, the mass block A and the mass block B are preferably made of metal tungsten, and a platinum film with the thickness of 200-300nm is electroplated on the surface of the metal tungsten;

the design has the advantages that the platinum film can protect the metal tungsten from oxidation and other reactions at high temperature, and the metal tungsten can ensure that the elastic modulus of the structural rigidity of the sensor is still in a linear range at high temperature; compared with other high-temperature materials, the mass block is higher in density, and the mass of the mass block can be effectively improved, so that the sensitivity and the stability of the sensor are improved; a layer of platinum vapor-deposited on the bottom surface can ensure excellent electric contact during signal transmission of the sensor.

And the nuts and the bolts and the ceramic tubes and the bolts are in threaded fit, and high-temperature insulating glue (double-bond chemical DB5012) is filled between gaps.

Preferably, the length of the ceramic tube is slightly smaller than the sum of the thicknesses of the piezoelectric wafers and the mounting base surface, the ceramic tube is located in the center of the bolt, the ceramic tube is not in contact with the mass block A and the mass block B, and after the piezoelectric wafers and the mass block are symmetrically assembled, the pre-tightening torque of the nut is 0.3-0.4 N.m;

after the nut with the pre-tightening effect fixes the mass block A/mass block B and the piezoelectric wafer under the pre-tightening torque of 0.3-0.4 N.m, the nut, the bolt and the mass block A/B are welded together, so that the bolt looseness of the sensor under the high-temperature and strong vibration effects is prevented, the ceramic tube with the insulating effect is fixed, the sensor is prevented from generating transverse signal interference in the vibration process, and the use reliability and precision of a sensing device are effectively improved.

Preferably, a counter bore is formed in the contact surface of the mass block B and the nut, after assembly, the nut is located in the counter bore, the counter bore is also formed in the mass block A, during assembly, a bolt head of the bolt sinks into the counter bore, the nut/bolt head sinks into the counter bore to be tightly combined, and after a proper pre-tightening torque is applied, the bolt is welded with the nut, the bolt is welded with the mass block A, and the bolt is welded with the mass block B.

According to the invention, the ceramic tube is preferably made of alumina ceramic with the purity of more than or equal to 99%, and the nut and the bolt are made of Inconel601 alloy;

the mounting base, the assembly base surface and the shell are all made of Inconel601 alloy, and the mounting base and the assembly base surface are an integral piece.

According to the invention, the double-shielded high-temperature armored cable comprises a conducting wire, a first insulating layer, a first shielding layer, a second insulating layer and a second shielding layer in sequence from inside to outside, wherein the conducting wire adopts a 0.3mm nickel wire, the first insulating layer and the second insulating layer are filled with high-purity magnesium oxide (99%), the first shielding layer adopts a 316 stainless steel alloy pipe, and the second shielding layer adopts an Inconel601 alloy pipe, namely an armored outer skin of the cable.

The double-shielding high-temperature armored cable provided by the invention has two metal shielding layers, high-purity magnesium oxide is used as an insulating protection material, a 316 stainless steel alloy pipe is arranged outside a first insulating layer, the ductility of the cable is good, the first shielding layer is protected, an Inconel601 alloy pipe is arranged outside a second insulating layer, and the alloy has excellent performances of corrosion resistance, oxidation resistance and the like at high temperature (below 1300 ℃), so that the cable can protect a high-temperature cable and the second shielding layer.

The lead in the double-shielding high-temperature armored cable is used as a signal wire and inserted into a reserved deep hole of the mass block and is welded and fixed, the other end of the double-shielding high-temperature armored cable is welded with a normal-temperature connector (M5, M6) to facilitate connection with a charge amplifier, a second shielding layer (namely, an armored sheath) is welded with the sensor mounting base, the shell is welded with the mounting base, a gas-tight sealing space is formed inside the sensor, inert gas is filled in the space, and the service life of the sensor at high temperature is prolonged; the wires of the double-shielding high-temperature armored cable, which are positioned in the sensor and welded on the mass block, are used as signal output wires of the sensor, and are in a fixed state after being assembled, so that the generated perturbation in the signal transmission process is reduced.

The diameter of the deep hole is preferably 0.5mm, the depth is 5mm, the deep hole can be arranged on the mass block A or the mass block B, and the mass block with the deep hole is required to be close to the welding through hole of the mounting base when being mounted.

The assembly method of the microminiature ultrahigh temperature piezoelectric vibration acceleration sensor comprises the following steps:

(1) firstly, respectively plating a 200-nm platinum film on the upper and lower surfaces of a piezoelectric wafer, a mass block A and a mass block B, sleeving the mass block A on a bolt close to the head end of the bolt, welding and fixing the mass block A, pouring diluted high-temperature insulating glue into a ceramic tube with internal threads, screwing the ceramic tube into the central part of the bolt in a rotating manner, keeping the ceramic tube and the mass block from being contacted, and putting the fixed bolt and the ceramic tube into a drying box at the temperature of 150-180 ℃ for 12-18 hours to finish the curing of the high-temperature insulating glue;

the diluted high-temperature insulating glue is preferably used after being diluted by 1.5-2 g of the high-temperature insulating glue and 1mL of diluent;

(2) installing a piezoelectric module:

a. when the number of the piezoelectric wafers is 2, during installation, 1 of the piezoelectric wafers is sleeved on a cured ceramic tube, then a bolt penetrates into a central hole of an assembly base surface, the other piezoelectric wafer and a mass block B are sleeved on the bolt on the other side of the assembly base surface, a nut is screwed on the bolt for pre-tightening, the pre-tightening torque is 0.3-0.4 N.m, then the bolt is welded with the nut and the mass block B, the positive electrode of the piezoelectric wafer is contacted with the assembly base surface during installation, the negative electrode of the piezoelectric wafer is contacted with the mass block A or the mass block B, and when the number of the piezoelectric wafers is 2, electrode plates do not need to be arranged;

b. when the number of the piezoelectric wafers is 6, firstly, 3 piezoelectric wafers are overlapped in parallel in a mode that the negative electrodes are opposite and the positive electrodes are opposite, electrode plates are added between the piezoelectric wafers, connecting wires of two paths of the electrode plates are respectively folded, electrodes of one path of the electrode plate are respectively inserted between the positive electrodes of the piezoelectric wafers, and the electrode plate is contacted with an assembly base plane and is insulated from the mass block A; the other electrode plate is inserted between the cathodes of the piezoelectric wafers, and the electrode plate is contacted with the mass block A and insulated from the assembly base plane to form a crystal group A;

the rest 3 pieces of piezoelectric wafers are also overlapped in parallel in a mode that the negative electrode is opposite and the positive electrode is opposite, electrode plates are added between the piezoelectric wafers, connecting wires of the two electrode plates are respectively folded, the electrodes of one electrode plate are respectively inserted between the positive electrodes of the piezoelectric wafers, and the electrode plates are contacted with the assembly base surface and insulated from the mass block B; the other electrode plate is inserted between the cathodes of the piezoelectric wafers, and the electrode plate is contacted with the mass block B and insulated from the assembly base plane to form a crystal group B;

during installation, after the electrode ring at one end is inserted into the corresponding position, the connecting wire can be bent directly, and the electrode ring at the other end is inserted into the corresponding position, so that welding spots in the assembly process of the sensor are reduced effectively;

sleeving the crystal group A on the cured ceramic tube, then penetrating a bolt into a central hole of an assembly base surface, sequentially sleeving the crystal group B and the mass block B on the other side of the assembly base surface, finally screwing a nut thread into the bolt for pre-tightening, and welding the bolt and the nut as well as the nut and the mass block B;

(3) preparing a double-shielding high-temperature armored cable:

straightening and fixing a 316 stainless steel alloy pipe, penetrating a 0.3mm nickel wire into the 316 stainless steel alloy pipe, straightening, determining that the 0.3mm nickel wire is positioned in the center of the 316 stainless steel alloy pipe by utilizing laser, placing high-purity magnesium oxide powder in a gap between the 316 stainless steel alloy pipe and the nickel wire by utilizing an injector, compacting, and sealing openings at two ends by utilizing high-temperature insulating glue to obtain a single-layer armored cable;

the single-layer armored cable and the Inconel601 alloy tube which are placed in the vacuum glove box are straightened and fixed by a clamp, the single-layer armored cable is inserted into the Inconel601 alloy tube and does not contact with the Inconel601 alloy tube, high-purity magnesium oxide powder is placed in a gap between the Inconel601 alloy tube and the single-layer armored cable by an injector and is compacted, and the two ends of the cable are sealed by high-temperature insulating glue;

(4) the method comprises the following steps of putting a piezoelectric module, a shell and a double-shielding high-temperature armored cable into an inert gas atmosphere box, wherein the gas pressure in the atmosphere box is slightly larger than one atmospheric pressure, inserting the double-shielding high-temperature armored cable into a through hole of an installation base, fixing the double-shielding high-temperature armored cable and the installation base by using a clamp, inserting a lead in the double-shielding high-temperature armored cable into a reserved deep hole of a mass block as a signal wire, fixing the lead by spot welding, and inserting a shell sleeve into the installation base for fixed connection;

(5) welding the piezoelectric module, the shell and the double-shielding high-temperature armored cable together by a laser welding machine to enable the piezoelectric module, the shell and the double-shielding high-temperature armored cable to be in close contact without a gap, and obtaining a sensor;

(6) and (4) putting the welded sensor into a high-temperature box for annealing treatment, and eliminating stress residues among devices.

Preferably, the annealing temperature is 550-650 ℃.

The invention relates to a micro high-temperature vibration acceleration sensor, which is characterized in that when the micro high-temperature vibration acceleration sensor works, a screw is utilized to fix the sensor on the surface of an engine to be detected through a mounting hole to enable the sensor to be tightly combined with the surface of the detected engine, vibration is generated when the engine works, periodic force generated by the vibration is transmitted to the sensor through a mechanical surface to cause a mass block in the sensor to generate inertia force, so that a piezoelectric wafer is forced to generate surface shear, charges with opposite signs and equal values are generated on the upper surface and the lower surface of the wafer, the charges are transmitted to a connector through a signal wire, the connector is transmitted to a charge amplifier through a high-temperature hard cable to convert charge signals into voltage signals, and the voltage signals are transmitted to a data acquisition card and a computer or an oscilloscope to perform.

The invention can manufacture the high-temperature vibration sensor with the performances of high temperature resistance, radiation resistance, high stability, wide frequency response, low temperature drift and the like, provides excellent front-section signal acquisition for health early warning systems in the fields of aerospace engines, nuclear energy and the like, and is convenient to produce and install, simple in process and convenient for large-scale production.

In the present invention, the details are not described in detail, and the present invention can be carried out by using the prior art.

The invention has the beneficial effects that:

1) aiming at the requirement that the sensor is stably in service at high temperature (more than 800 ℃), the shear mode RECOB wafer which is stable in electrical performance and high in sensitivity at high temperature is used as a piezoelectric sensitive element, so that the high-temperature piezoelectric acceleration sensor can be in service for a long time in an environment at 1000 ℃;

2) according to the size requirement of the high-temperature sensor of the aircraft turbine engine, the assembled sensor is of a cuboid structure (without a double-shielding high-temperature armored cable), and the volume of the assembled sensor can be 14 × 14, 14 × 25mm³(as shown in fig. 1, the length of the two sides of the left and right surfaces of the sensor is 14mm, the side lengths are equal and are all represented by L1, and the length of the side edge of the sensor is 25mm, L2), so that the space of the engine can be greatly saved;

the mounting through hole is positioned on the mounting base, and the mounting hole of the sensor is relatively far away from the mounting part of the piezoelectric wafer, so that the influence of strain generated by mounting the sensor on the performance of the sensor is reduced; the direction of the mounting hole can be parallel to the assembly base surface or perpendicular to the assembly base surface, and the two modes can be used for respectively monitoring vertical and horizontal vibration signals of the aeroengine vibration;

3) the invention adopts the mode of parallel combination of sensitive elements, saves the internal space of the sensor and effectively improves the sensitivity of the sensor.

4) The Inconel601 alloy is adopted by the shell, the armored sheath and the mounting base of the double-shielding high-temperature armored cable, has excellent corrosion resistance at high temperature, can ensure the anti-interference capability of the sensor in the signal transmission process at high temperature, and greatly prolongs the service life of the sensor;

5) the mass block A/B of the invention adopts metal tungsten, and the alloy can ensure that the elastic modulus of the structural rigidity of the sensor is still in a linear range at high temperature; compared with other high-temperature materials, the mass block has higher density, and can effectively improve the weight of the mass block, thereby improving the sensitivity of the sensor; a layer of platinum vapor-deposited on the surface can ensure excellent electric contact during signal transmission of the sensor.

6) Aiming at the sealing performance and stability of the sensing device, the invention designs and selects the 99% alumina ceramic tube with high temperature resistance and stable property, the bolt and the ceramic tube are solidified by matching with high-temperature insulating glue, and the bolt, the nut and the mass block are fixed by proper pre-tightening torque, so that the performance of the sensor reaches the best.

7) The invention designs a double-shielding high-temperature armored cable, wherein a nickel wire in the double-shielding high-temperature armored cable is welded on a mass block A or a mass block B, and an armored outer skin of the double-shielding high-temperature armored cable is welded with a sensor mounting base together, so that a closed space for shielding electromagnetic interference is formed inside the sensor, the stability of the sensor is improved, and the service life of the sensor is prolonged.

Drawings

FIG. 1 is a schematic view of the overall structure of a microminiature ultra-high temperature piezoelectric vibration acceleration sensor of the present invention;

FIG. 2 is a schematic three-dimensional structure of an embodiment of the present invention;

FIG. 3 is a schematic view of an assembly structure according to an embodiment of the present invention;

FIG. 4(a) is a first schematic view of a mounting base structure according to an embodiment of the present invention;

FIG. 4(b) is a second schematic structural diagram of a mounting base according to an embodiment of the present invention;

FIG. 5 is a schematic view of a nut according to an embodiment of the present invention;

FIG. 6 is a schematic view of a bolt structure according to an embodiment of the present invention;

FIG. 7 is a schematic view of the assembly of a ceramic tube and a bolt according to an embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a housing according to an embodiment of the present invention;

FIG. 9 is a schematic structural diagram of a mass A according to an embodiment of the present invention;

FIG. 10 is a schematic structural diagram of a piezoelectric wafer according to an embodiment of the invention;

fig. 11 is a schematic structural view of an electrode line according to an embodiment of the present invention;

fig. 12 is a schematic structural view of a double-shielded high-temperature armored cable according to an embodiment of the present invention;

FIG. 13 is a graph illustrating the thermal drift rate of a sensor according to an embodiment of the present invention at high temperature;

FIG. 14 is a schematic diagram of a sensor according to an embodiment of the present invention operating at 1000 ℃;

FIG. 15 is a schematic diagram of a cut-out of a piezoelectric crystal used in accordance with one embodiment of the present invention;

the structure comprises 1-a nut, 2-a piezoelectric wafer, 3-an electrode plate, 4-a mass block A, 5-a bolt, 6-a through hole, 7-a mounting hole, 8-a shell, 9-a mounting base, 10-a double-shielded high-temperature armored cable, 11-an assembly base surface, 12-a ceramic tube, 13-a deep hole, 14-a wire, 15-an electrode ring, 16-a central hole, 17-a mounting surface, 18-a mass block B, 19-a connecting wire, 20-a first insulating layer, 21-a first shielding layer, 22-a second insulating layer and 23-a second shielding layer.

The specific implementation mode is as follows:

in order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific examples, but not limited thereto, and the present invention is not described in detail and is in accordance with the conventional techniques in the art.