A high-temperature, low-drift piezoelectric vibration accelerometer and its fabrication method

Abstract

This invention relates to a high-temperature, low-drift piezoelectric vibration accelerometer and its fabrication method, belonging to the field of sensor technology. It includes: a high-temperature alloy pressure-resistant housing; a gradient thermal insulation base disposed inside the high-temperature alloy pressure-resistant housing; a high-temperature piezoelectric sensitive unit disposed on the gradient thermal insulation base; a constant-elastic alloy pre-tightening structure for pre-tightening the high-temperature piezoelectric sensitive unit; a high-temperature insulation system; a high-temperature signal conditioning and temperature compensation module electrically connected to the high-temperature piezoelectric sensitive unit; and an all-metal hermetically sealed package for sealing the high-temperature alloy pressure-resistant housing. This high-temperature, low-drift piezoelectric vibration accelerometer and its fabrication method, by employing a high Curie temperature gallium lanthanum silicate LGS crystal, combined with a differential shear structure and all-inorganic packaging, overcomes the bottleneck of depolarization and sensitivity drift of traditional piezoelectric materials above 300℃, enabling continuous long-term operation at 480℃.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, specifically to a high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method. Background Technology

[0002] Piezoelectric accelerometers are widely used for vibration and condition monitoring in high-temperature environments such as aero-engines, gas turbines, metallurgical furnaces, oil wells, and nuclear power equipment. Most existing high-temperature piezoelectric sensors use PZT piezoelectric ceramics, with a Curie temperature of approximately 300–350°C. Above 250°C, problems such as depolarization, sensitivity drift, decreased insulation resistance, and increased charge leakage occur.

[0003] Some high-temperature sensors use crystal materials such as quartz, LGS (lanthanum gallium silicate), and lithium niobate, and their structures are mostly compression or shear-type, but they still have the following technical defects:

[0004] 1. Material bottleneck: Ordinary PZT piezoelectric ceramics cannot work stably for a long time at 480℃. At high temperatures, the piezoelectric coefficient d33 decreases significantly, the resistivity decreases, and the noise increases.

[0005] 2. Structural defects: Lack of thermal stress isolation and high-temperature pre-tightening design, the heat conduction of the shell directly leads to chip temperature drift or even breakage;

[0006] 3. Encapsulation failure: Organic adhesives, ordinary solder joints, and plastic seals are prone to carbonization, failure, and leakage at temperatures above 400℃;

[0007] 4. Circuit shortcomings: The lack of high-temperature resistant ASIC and temperature compensation circuitry means that signal amplification and temperature compensation cannot operate stably at high temperatures;

[0008] 5. Insufficient lifespan: Although existing products can withstand 500℃ for a short period of time, they cannot maintain consistency and reliability at 480℃ for a long period of time (≥1000 hours).

[0009] Therefore, developing a piezoelectric vibration acceleration sensor that can operate stably at 480℃ for a long time with low drift and high reliability has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method. It features long-term stable operation at 480℃, high-temperature low drift, high insulation resistance, constant force pre-tightening without loosening, all-metal hermetically sealed packaging, and built-in high-temperature compensation. It solves the problems of material depolarization at high temperatures, sensitivity drift caused by thermal stress, organic packaging failure, lack of high-temperature signal conditioning, and insufficient long-term reliability of existing sensors.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] A high-temperature, low-drift piezoelectric vibration acceleration sensor, comprising:

[0013] High-temperature alloy pressure-resistant housing;

[0014] A gradient thermal insulation base is disposed inside the high-temperature alloy pressure-resistant shell. The gradient thermal insulation base is a double-layer composite structure, comprising an outer layer of high-temperature alloy and an inner layer of aluminum nitride ceramic. A ring-shaped suspended stress isolation structure is formed between the gradient thermal insulation base and the high-temperature alloy pressure-resistant shell.

[0015] The high-temperature piezoelectric sensing unit is disposed on the gradient thermal insulation base. The high-temperature piezoelectric sensing unit adopts a gallium lanthanum silicate LGS crystal and is formed into a differential shear structure.

[0016] A constant elastic alloy pre-tightening structure for pre-tightening the high-temperature piezoelectric sensitive unit;

[0017] A high-temperature insulation system, comprising a mica insulation layer and a glass sintered insulation component;

[0018] A high-temperature signal conditioning and temperature compensation module electrically connected to the high-temperature piezoelectric sensing unit;

[0019] An all-metal hermetic encapsulation for sealing the high-temperature alloy pressure-resistant housing.

[0020] Furthermore, the material of the high-temperature alloy pressure-resistant shell is GH4169 high-temperature alloy, with a wall thickness of ≥3mm and a high-temperature anti-oxidation coating on the surface.

[0021] Furthermore, the lanthanum gallium silicate LGS crystal in the high-temperature piezoelectric sensing unit has a thickness of 0.3–1.0 mm and an area of ​​Φ6–Φ12 mm, and its electrode is a platinum high-temperature sintered electrode.

[0022] Furthermore, the constant elasticity alloy preload structure is a preload sleeve, a tapered preload ring, or a micro-threaded preload structure, and its material is 3J63 constant elasticity alloy.

[0023] Furthermore, the insulation resistance of the telescopic high-temperature insulation system at 480℃ is ≥10 Ω·cm. 8 Ω, whose electrode leads are made of platinum-iridium alloy wire and sealed by glass sintering.

[0024] Furthermore, the high-temperature signal conditioning and temperature compensation module operates at a temperature of -55℃ to +500℃, and includes a charge amplification unit, a low-pass filter unit, a temperature acquisition unit, and a sensitivity temperature compensation unit, outputting an IEPE signal.

[0025] Furthermore, the all-metal hermetic encapsulation includes laser-sealed welding of the high-temperature alloy pressure-resistant shell, glass sintering electrodes, and internal filling with high-purity argon protective gas, with a hermeticity ≤1×10⁻ 9 Pa·m³ / s.

[0026] Furthermore, in the gradient thermal insulation base, the inner aluminum nitride ceramic is a high thermal conductivity and high insulation material, used to block the thermal stress and heat conduction of the high-temperature alloy pressure-resistant shell.

[0027] This invention also provides a method for fabricating a high-temperature, low-drift piezoelectric vibration acceleration sensor, comprising the following steps:

[0028] S1. Prepare a high-temperature alloy pressure-resistant shell and perform surface anti-oxidation treatment;

[0029] S2. A gradient thermal insulation base is formed by combining the aluminum nitride ceramic layer and the high-temperature alloy layer, and then fixed inside the high-temperature alloy pressure-resistant shell.

[0030] S3. Platinum high-temperature sintered electrodes are used to polarize the gallium lanthanum silicate LGS crystal and assemble it into a differential shear-type high-temperature piezoelectric sensing unit.

[0031] S4. The high-temperature piezoelectric sensitive unit is pre-tightened onto the gradient heat insulation base by a constant elastic alloy pre-tightening structure;

[0032] S5. A mica insulating layer is set around the high-temperature piezoelectric sensitive unit, and platinum-iridium alloy leads are drawn out through glass sintering process.

[0033] S6. Electrically connect the high-temperature signal conditioning and temperature compensation module to the high-temperature piezoelectric sensitive unit;

[0034] S7. Laser sealing welding is performed on the high-temperature alloy pressure-resistant shell, and high-purity argon gas is filled in to form an all-metal hermetically sealed package.

[0035] Furthermore, the preload of the constant elastic alloy preload structure in step S4 is set to maintain a constant elastic deformation at 480°C to ensure that the high-temperature piezoelectric sensitive unit does not loosen at high temperatures.

[0036] Compared with the prior art, the present invention provides a high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method, which has the following beneficial effects:

[0037] 1. This high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method, by using a high Curie temperature (Tc≈1470℃) gallium lanthanum silicate LGS crystal, combined with a differential shear structure and all-inorganic packaging, breaks through the bottleneck of depolarization and sensitivity drift of traditional piezoelectric materials above 300℃, and can work continuously for a long time at 480℃.

[0038] 2. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method, through the triple design of gradient heat-insulating base, annular suspended stress isolation structure and high-temperature signal conditioning and temperature compensation module, effectively block the influence of heat conduction and thermal stress on the sensitive chip of high-temperature alloy pressure-resistant shell, so that the sensor has small sensitivity temperature drift and low zero drift in the range of 25℃~480℃, and the high-temperature measurement accuracy is significantly improved.

[0039] 3. This high-temperature, low-drift piezoelectric vibration accelerometer and its fabrication method utilize an all-inorganic high-temperature insulating system consisting of mica, aluminum nitride ceramics, and high-temperature glass, without any organic materials, and maintains a stability of ≥10 at 480℃. 8 The high insulation resistance of Ω significantly reduces leakage current and noise, improving signal output stability and signal-to-noise ratio.

[0040] 4. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method maintain a constant preload at 480℃ through a constant elastic alloy preload structure, thus avoiding chip loosening, sensitivity drop, and resonant frequency drift caused by thermal expansion differences.

[0041] 5. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its manufacturing method, through laser welding + glass sintering electrodes + inert gas protection, all-metal hermetically sealed packaging, has the advantages of anti-oxidation, leak-proof, and resistance to media corrosion, and can achieve long life and maintenance-free operation in extreme high-temperature environments.

[0042] 6. This high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method integrate a high-temperature resistant ASIC circuit to achieve charge amplification, filtering, temperature acquisition, and software temperature compensation, outputting a standard IEPE signal. It eliminates the need for an external high-temperature front end, simplifies the system structure, and improves overall stability.

[0043] 7. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its manufacturing method combine structural strength and electromagnetic shielding functions through an integrated high-temperature alloy shell. It has strong resistance to base strain, lateral interference, and impact vibration, and is suitable for extreme high-temperature and harsh working conditions such as aero-engines, gas turbines, metallurgy, nuclear power, and oil wells. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of a high-temperature, low-drift piezoelectric vibration acceleration sensor according to the present invention.

[0045] In the figure: 1. High-temperature alloy pressure-resistant shell; 2. Gradient thermal insulation base; 3. Annular suspended stress isolation structure; 4. High-temperature piezoelectric sensitive unit; 41. Lanthanum gallium silicate LGS crystal; 42. Platinum high-temperature sintered electrode; 5. Constant elastic alloy pre-tightening structure; 6. High-temperature insulation system; 7. High-temperature signal conditioning and temperature compensation module; 8. All-metal hermetic encapsulation. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1:

[0048] Please see Figure 1 This embodiment provides a high-temperature, low-drift piezoelectric vibration acceleration sensor, comprising the following components:

[0049] 1. High-temperature alloy pressure-resistant outer shell 1:

[0050] Made of GH4169 high-temperature alloy, it is machined into a cylindrical integrated structure with a wall thickness of 3mm and a high-temperature anti-oxidation coating on the surface. This high-temperature alloy pressure-resistant shell 1 serves as both a structural support and electromagnetic shielding function, and can resist oxidation and creep for a long time at 480℃.

[0051] 2. Gradient thermal insulation base 2:

[0052] The gradient thermal insulation base 2 has a double-layer composite structure: the outer layer is a high-temperature alloy, and the inner layer is aluminum nitride ceramic. An annular suspended stress isolation structure 3 is formed between the gradient thermal insulation base 2 and the high-temperature alloy pressure-resistant outer shell 1. There is no direct contact between the inner aluminum nitride ceramic layer and the high-temperature alloy pressure-resistant outer shell 1, forming thermal blocking and stress isolation. The aluminum nitride ceramic possesses both high thermal conductivity and high insulation properties, effectively reducing the impact of heat conduction on the high-temperature piezoelectric sensitive unit 4.

[0053] 3. High-temperature piezoelectric sensing unit 4:

[0054] The high-temperature piezoelectric sensing element 4 uses a lanthanum gallium silicate LGS crystal 41 with a thickness of 0.5 mm and an area of ​​Φ8 mm. The electrode uses a platinum high-temperature sintered electrode 42. The high-temperature piezoelectric sensing element 4 is formed into a differential shear structure, which has strong anti-lateral interference capability and high sensitivity stability.

[0055] 4. High-temperature pre-tightening structure 5:

[0056] The high-temperature pre-tightening structure 5 uses a pre-tightening sleeve made of 3J63 constant elastic alloy to pre-tighten and fix the high-temperature piezoelectric sensing unit 4 to the mass block through a micro-thread. This high-temperature pre-tightening structure 5 maintains a constant pre-tightening force within the range of 25℃ to 480℃, without creep or relaxation.

[0057] 5. High-temperature insulation system 6:

[0058] A mica insulation layer is placed between the high-temperature piezoelectric sensing unit 4 and the high-temperature alloy pressure-resistant outer shell 1. The electrode leads are made of platinum-iridium alloy wire and are sealed to the outer shell electrodes through a glass sintering process. The entire insulation system contains no organic materials and has an insulation resistance ≥10 Ω at 480℃. 8 Ω.

[0059] 6. High-temperature signal conditioning and temperature compensation module 7:

[0060] The high-temperature signal conditioning and temperature compensation module 7 uses a high-temperature resistant ASIC with an operating temperature range of -55℃ to +500℃. It integrates charge amplification, low-pass filtering, temperature acquisition, and sensitivity compensation functions. The high-temperature signal conditioning and temperature compensation module 7 is electrically connected to the high-temperature piezoelectric sensing unit 4, outputs an IEPE standard signal, and is supplied with a voltage of 18 to 28V.

[0061] 7. All-metal hermetic encapsulation 8:

[0062] After the high-temperature alloy pressure-resistant outer shell 1 is assembled, it undergoes full-circumference welding using laser sealing welding technology. The internal cavity is then evacuated and filled with high-purity argon gas. The electrode leads are sealed with sintered glass, achieving an overall airtightness of ≤1×10⁻⁻. 9 Pa·m³ / s.

[0063] Example 2:

[0064] This embodiment modifies the high-temperature pre-tightening structure 5 based on Embodiment 1. A conical pre-tightening ring replaces the pre-tightening sleeve, and constant force pre-tightening of the high-temperature piezoelectric sensing unit 4 is achieved through axial compression. This structure is more suitable for miniaturized sensor designs with limited space. It also uses 3J63 constant elasticity alloy material to ensure constant pre-tightening force at high temperatures.

[0065] Example 3:

[0066] This embodiment expands upon Embodiment 1 by extending the output format of the high-temperature signal conditioning and temperature compensation module 7. In addition to the IEPE output, a digital interface unit is added to the module, supporting RS485 or CAN bus output, making it suitable for distributed monitoring systems. The module still uses a high-temperature resistant ASIC, and the overall packaging remains unchanged, ensuring long-term stable operation at 480℃.

[0067] Example 4:

[0068] This embodiment also provides a method for preparing the above-mentioned sensor, including the following steps:

[0069] S1. Process GH4169 high-temperature alloy pressure-resistant shell 1, wall thickness 3mm, surface sprayed with high-temperature anti-oxidation coating.

[0070] S2. The aluminum nitride ceramic layer and the high-temperature alloy layer are combined to form a gradient heat insulation base 2, which is then fixed inside the high-temperature alloy pressure-resistant shell 1 by a ring-shaped suspension method.

[0071] S3. Platinum electrodes are sintered on the lanthanum gallium silicate LGS crystal 41 and assembled into a differential shear-type high-temperature piezoelectric sensing unit 4.

[0072] S4. A 3J63 constant elastic alloy pre-tightening structure 5 is adopted, and the high-temperature piezoelectric sensitive unit 4 is pre-tightened to the base through a micro-thread method. The pre-tightening force is set to maintain a constant elastic deformation at 480℃.

[0073] S5. A mica insulating layer is set around the high-temperature piezoelectric sensitive unit 4, and a platinum-iridium alloy lead wire is drawn out using a glass sintering process.

[0074] S6. Connect the high-temperature signal conditioning and temperature compensation module 7 to the high-temperature piezoelectric sensitive unit 4 and perform functional testing.

[0075] S7. Laser sealing welding is performed on the high-temperature alloy pressure-resistant shell 1. After the inside is evacuated, high-purity argon gas is filled in to complete the all-metal hermetic encapsulation 8.

[0076] Through the above structural design and fabrication method, the sensor of this embodiment can operate stably for a long time at 480℃, with a sensitivity temperature drift of less than ±5% and an insulation resistance ≥10. 8 Ω, with airtightness meeting the requirements for long-term use at high temperatures, is suitable for vibration monitoring in extreme high-temperature environments such as aero engines, gas turbines, metallurgy, and nuclear power.

[0077] The installation, connection, or setting methods disclosed in this embodiment are all common mechanical connection methods. Any method that can achieve its beneficial effect can be implemented. In addition, the electrical components in this embodiment are all electrically connected to the main controller and the power supply. The main controller can be a conventional known device such as a computer that plays a control role. Those skilled in the art can control the electrical components through simple programming. Moreover, the existing disclosed power connection technology is also common knowledge in the field. Therefore, the control method and circuit connection will not be explained in detail in this embodiment.

[0078] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0079] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-temperature, low-drift piezoelectric vibration acceleration sensor, characterized in that, include: High-temperature alloy pressure-resistant shell (1); The gradient heat insulation base (2) is disposed inside the high temperature alloy pressure-resistant shell (1). The gradient heat insulation base (2) is a double-layer composite structure. The gradient heat insulation base (2) includes an outer high temperature alloy and an inner aluminum nitride ceramic. An annular suspended stress isolation structure (3) is formed between the gradient heat insulation base (2) and the high temperature alloy pressure-resistant shell (1). The high-temperature piezoelectric sensing unit (4) is disposed on the gradient heat insulation base (2). The high-temperature piezoelectric sensing unit (4) adopts a gallium lanthanum silicate LGS crystal (41) and is formed into a differential shear structure. A constant elastic alloy pre-tightening structure (5) for pre-tightening the high-temperature piezoelectric sensitive unit (4); A high-temperature insulation system (6) comprising a mica insulation layer and a glass sintered insulation component; High-temperature signal conditioning and temperature compensation module (7) is electrically connected to the high-temperature piezoelectric sensitive unit (4); An all-metal hermetic encapsulation (8) for sealing the high-temperature alloy pressure-resistant housing (1).

2. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method according to claim 1, characterized in that, The high-temperature alloy pressure-resistant shell (1) is made of GH4169 high-temperature alloy with a wall thickness of ≥3mm and a high-temperature anti-oxidation coating on its surface.

3. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method according to claim 1, characterized in that, The thickness of the gallium lanthanum silicate LGS crystal (41) in the high-temperature piezoelectric sensitive unit (4) is 0.3 to 1.0 mm, and the area is Φ6 to Φ12 mm. Its electrode is a platinum high-temperature sintered electrode (42).

4. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method according to claim 1, characterized in that, The constant elastic alloy pre-tightening structure (5) is a pre-tightening sleeve, a tapered pre-tightening ring, or a micro-threaded pre-tightening structure, and its material is 3J63 constant elastic alloy.

5. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method according to claim 1, characterized in that, The insulation resistance of the high-temperature expansion insulation system (6) at 480℃ is ≥10 Ω·cm. 8 Ω, whose electrode leads are made of platinum-iridium alloy wire and sealed by glass sintering.

6. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method according to claim 1, characterized in that, The high-temperature signal conditioning and temperature compensation module operates at a temperature of -55℃ to +500℃ and includes a charge amplification unit, a low-pass filter unit, a temperature acquisition unit, and a sensitivity temperature compensation unit. Its output is an IEPE signal.

7. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method according to claim 1, characterized in that, The all-metal hermetic encapsulation (8) includes laser-sealed welding of the high-temperature alloy pressure-resistant shell (1), glass sintering electrodes, and internal high-purity argon protective gas, with a hermeticity ≤1×10⁻. 9 Pa·m³ / s.

8. The high-temperature, low-drift piezoelectric vibration acceleration sensor and its fabrication method according to claim 1, characterized in that, In the gradient thermal insulation base (2), the inner aluminum nitride ceramic is a high thermal conductivity and high insulation material, which is used to block the thermal stress and heat conduction of the high temperature alloy pressure shell (1).

9. A method for fabricating a high-temperature, low-drift piezoelectric vibration accelerometer, used to fabricate the high-temperature, low-drift piezoelectric vibration accelerometer as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Prepare a high-temperature alloy pressure-resistant shell (1) and perform surface anti-oxidation treatment; S2. The aluminum nitride ceramic layer and the high-temperature alloy layer are combined to form a gradient heat insulation base (2), and it is fixed inside the high-temperature alloy pressure-resistant shell (1); S3. The gallium lanthanum silicate LGS crystal (41) is polarized using a platinum high-temperature sintered electrode (42) and assembled into a differential shear type high-temperature piezoelectric sensing unit (4). S4. The high-temperature piezoelectric sensitive unit (4) is pre-tightened onto the gradient heat insulation base (2) by means of the constant elastic alloy pre-tightening structure (5); S5. A mica insulating layer is set around the high-temperature piezoelectric sensitive unit (4), and a platinum-iridium alloy lead wire is drawn out through the glass sintering process. S6. Connect the high temperature signal conditioning and temperature compensation module (7) to the high temperature piezoelectric sensing unit (4); S7. Laser sealing welding is performed on the high-temperature alloy pressure-resistant shell (1), and high-purity argon gas is filled in to form an all-metal hermetically sealed package (8).

10. The method for fabricating a high-temperature, low-drift piezoelectric vibration acceleration sensor according to claim 9, characterized in that, The pre-tightening force of the constant elastic alloy pre-tightening structure (5) in step S4 is set to maintain a constant elastic deformation at 480°C to ensure that the high-temperature piezoelectric sensitive unit (4) does not loosen at high temperature.

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