Acoustic sensor and acoustic monitoring system

Abstract

The utility model provides an acoustic sensor and an acoustic monitoring system, and belongs to the technical field of acoustic monitoring devices. The acoustic sensor comprises a hollow cylindrical shell which is provided with a signal detection end and a signal output end; the back gasket is arranged in the shell, the side wall of the back gasket is in contact fit with the inner wall of the shell, and the end part, close to the signal detection end, of the back gasket is provided with a mounting space; the piezoelectric wafer and the mass block are arranged in the installation space, the mass block is located on the piezoelectric wafer, and the negative electrode of the piezoelectric wafer is connected with the inner wall of the shell; the diaphragm is arranged at the signal detection end of the shell and is not in contact with the piezoelectric wafer; the wiring terminal is fixed at the signal output end of the shell; the wiring terminal is connected with the positive electrode of the piezoelectric wafer through a wire penetrating through the backing pad and used for outwards conveying electric charges generated by vibration of the piezoelectric wafer. The utility model has the advantages of simple structure, low cost, convenience in use, wide response frequency range and high sensitivity.

Description

Technical Field

[0001] This utility model relates to the field of acoustic monitoring device technology, specifically to an acoustic sensor and an acoustic monitoring system. Background Technology

[0002] During operation, process equipment can suffer damage due to factors such as loads, resulting in defects that, under certain conditions, release energy and generate elastic stress waves, i.e., acoustic emission waves. Currently, acoustic emission is widely used in monitoring structural component damage. The characteristics of acoustic emission signals from active defects are: transient, dynamic, and weak sound. The signals can only be detected momentarily, lack repeatability, have low intensity, and are easily affected by environmental noise, placing higher demands on the sensors used to acquire these signals.

[0003] Existing narrowband sensors do not fully cover or are below or above specific frequency ranges, resulting in inaccurate signal acquisition. Broadband sensors, on the other hand, are expensive and have lower sensitivity to signals in specific frequency bands, and cannot accurately and comprehensively reflect the process of material damage and change in equipment. Utility Model Content

[0004] The purpose of this utility model embodiment is to provide an acoustic sensor and an acoustic monitoring system. This acoustic sensor is used to solve the problems of existing narrowband sensors not fully covering or being below or above a specific frequency range, resulting in inaccurate signal acquisition, while broadband sensors are expensive and have low sensitivity to signals in specific frequency bands, and cannot accurately and comprehensively reflect the damage and change process of equipment materials.

[0005] To achieve the above objectives, this utility model provides an acoustic sensor, which includes:

[0006] The internally hollow cylindrical shell has a signal output terminal and a signal detection terminal at its upper and lower ends, respectively.

[0007] The backing pad is installed inside the housing by contacting and fitting with the inner wall of the housing through the side wall, and the lower end of the backing pad is provided with an installation space;

[0008] A piezoelectric wafer and a mass block are disposed in the installation space, with the mass block located on top of the piezoelectric wafer, and the negative electrode of the piezoelectric wafer is connected to the inner wall of the housing;

[0009] A diaphragm is disposed at the signal detection end of the housing and does not contact the piezoelectric crystal.

[0010] A terminal block is fixed to the signal output end of the housing; the terminal block is connected to the positive electrode of the piezoelectric crystal through a wire passing through the backing pad, and is used to transport the charge generated by the vibration of the piezoelectric crystal outward.

[0011] Optionally, the installation space includes: a first installation space and a second installation space, wherein a first step is formed between the first installation space and the second installation space;

[0012] The piezoelectric wafer is disposed in the first mounting space, and the mass block is disposed in the second mounting space, with the mass block in contact with the step surface of the first step portion.

[0013] Optionally, the piezoelectric wafer is a multilayer lead zirconate titanate piezoelectric film.

[0014] Optionally, the response frequency of the acoustic sensor is 20-400 kHz.

[0015] Optionally, the signal detection end of the housing is provided with a second step, and the diaphragm is fixed on the second step.

[0016] Optionally, the signal output terminal of the housing is provided with a third step, and the wiring terminal is fixed on the third step.

[0017] Optionally, the outer surface of the housing is provided with a connecting piece, and the connecting piece has a mounting hole.

[0018] Optionally, the outer surface between the signal detection end of the housing and the connecting piece is provided with external threads.

[0019] Optionally, the housing is made of metal; the backing pad is made of damping material.

[0020] On the other hand, this utility model provides an acoustic monitoring system, including at least one of the above-mentioned acoustic sensors, which are fixed on the device to be monitored.

[0021] This technical solution achieves the detection of acoustic emission signals by setting mutually matched backing pads, piezoelectric crystals, and mass blocks inside the housing. It has the advantages of simple structure, low cost, low noise, easy use, wide response frequency range, and high sensitivity.

[0022] Other features and advantages of this utility model embodiment will be described in detail in the following detailed description section. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0024] Figure 1 This is a schematic diagram of the structure of the acoustic sensor provided by this utility model;

[0025] Figure 2 This is a cross-sectional schematic diagram of the acoustic sensor provided by this utility model;

[0026] Figure 3 This is a cross-sectional schematic diagram of the shell and backing pad provided by this utility model.

[0027] Explanation of reference numerals in the attached figures

[0028] 1-Housing; 2-Backing pad; 3-Piezoelectric crystal;

[0029] 4-Mass block; 5-Diaphragm; 6-Terminal;

[0030] 7-Wire; 8-Connecting piece; 11-Second step;

[0031] 12 - Third step; 13 - External thread; 21 - Installation space;

[0032] 81 - Mounting hole; 101 - Signal detection terminal; 102 - Signal output terminal;

[0033] 211 - First installation space; 212 - Second installation space; 213 - First step. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0035] In this embodiment of the utility model, unless otherwise stated, directional terms such as "up," "down," "left," and "right" generally refer to the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the utility model product is usually placed when in use.

[0036] The terms “first,” “second,” “third,” etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0037] The terms "parallel" and "perpendicular" do not mean that the components must be absolutely parallel or perpendicular, but rather that they can be slightly tilted. For example, "parallel" simply means that its direction is more parallel than "perpendicular," not that the structure must be completely parallel, but that it can be slightly tilted.

[0038] The terms "horizontal," "vertical," and "sag" do not imply that a component must be absolutely horizontal, vertical, or sagging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," not that the structure must be completely horizontal, but can be slightly tilted.

[0039] Furthermore, terms like "roughly" and "basically" are used to indicate that the content does not require absolute precision, but rather allows for a certain degree of deviation. For example, "roughly equal" does not simply mean absolute equality; in actual production and operation, achieving absolute "equality" is difficult, and a certain degree of deviation is generally present. Therefore, besides absolute equality, "roughly equal to" also includes the aforementioned situation where a certain degree of deviation exists. Using this as an example, in other cases, unless otherwise specified, terms like "roughly" and "basically" have similar meanings.

[0040] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0041] Figure 1 This is a schematic diagram of the structure of the acoustic sensor provided by this utility model; Figure 2 This is a cross-sectional schematic diagram of the acoustic sensor provided by this utility model; Figure 3 This is a cross-sectional schematic diagram of the shell and backing pad provided by this utility model.

[0042] Example 1

[0043] In this embodiment, as Figure 1-3 As shown, this embodiment provides an acoustic sensor, which includes:

[0044] The shell 1 is hollow inside, and the upper and lower ends of the shell 1 are the signal output terminal 102 and the signal detection terminal 101, respectively.

[0045] The backing pad 2 is disposed inside the housing 1 through contact and cooperation with the inner wall of the housing 1 via its side wall. The end of the backing pad 2 near the signal detection end 101 is provided with an installation space 21.

[0046] A piezoelectric wafer 3 and a mass block 4 are disposed in the installation space 21, with the mass block 4 located on top of the piezoelectric wafer 3, and the negative electrode of the piezoelectric wafer 3 is connected to the housing 1;

[0047] The diaphragm 5 is disposed at the signal detection end 101 of the housing 1 and does not contact the piezoelectric crystal 3;

[0048] Terminal 6 is fixed to the signal output terminal 102 of the housing 1; terminal 6 is connected to the positive electrode of the piezoelectric crystal 3 through a wire 7 passing through the backing pad 2, and is used to transmit the charge generated by the vibration of the piezoelectric crystal 3 to the outside.

[0049] In this embodiment, the housing 1 can be configured as a cylindrical structure; the backing pad 2 is connected and fixed to the housing 1 by adhesive.

[0050] The piezoelectric crystal 3 achieves signal conversion through the piezoelectric effect. The mechanism is as follows: piezoelectric crystals have low symmetry. When deformed under external force, the relative displacement of positive and negative ions in the unit cell causes the centers of positive and negative charges to no longer coincide, leading to macroscopic polarization of the crystal. The surface charge density of the crystal is equal to the projection of the polarization intensity onto the surface normal. Therefore, when a piezoelectric material deforms under pressure, opposite charges appear on its two ends. When receiving an acoustic emission signal, the crystal vibrates, generating opposite charges. When the piezoelectric material is polarized in an electric field, the displacement of the charge centers causes material deformation. In addition to self-supporting capabilities, it also possesses self-diagnostic, self-adaptive, and self-repairing functions.

[0051] The positive and negative electrodes used in the piezoelectric crystal 3 are typically silver electrodes, which are easy to solder. The negative electrode of the piezoelectric crystal 3 is connected to the inner wall of the housing 1. Specifically, this can be done by using conductive adhesive to connect the negative electrode of the piezoelectric crystal 3 to the inner wall of the housing 1, thereby fixing the piezoelectric crystal 3 to the housing 1. Alternatively, a through hole can be provided on the backing pad 2, through which the negative electrode of the piezoelectric crystal 3 is connected to the inner wall of the housing 1.

[0052] The mass and position of mass block 4 significantly affect the sensor's measurement range and sensitivity. Generally, the heavier the mass block 4, the larger the sensor's measurement range, but the lower the sensitivity; conversely, the lighter the mass block 4, the smaller the sensor's measurement range, but the higher the sensitivity. Furthermore, the position of mass block 4 is also crucial, as it determines the corresponding output voltage value. Ideally, mass block 4 should be positioned at the sensor's center of gravity to minimize mechanical noise and ensure the sensor's sensitivity and accuracy.

[0053] More specifically, a through hole is provided in the middle of the terminal 6, and the wire is located in the through hole. The wire can be sealed and fixed in the housing 1 with insulating glue. When the positive electrode of the piezoelectric crystal 3 is located in the middle, the wire passes through the middle of the backing pad 2 and the corresponding mass block 4, and connects to the positive electrode of the piezoelectric crystal 3.

[0054] Furthermore, the installation space 21 includes: a first installation space 211 and a second installation space 212, wherein a first step portion 213 is formed between the first installation space 211 and the second installation space 212;

[0055] The piezoelectric wafer 3 is disposed in the first mounting space 211, and the mass block 4 is disposed in the second mounting space 212. The mass block 4 is in contact with the step surface of the first step portion 213.

[0056] In this embodiment, in order to install and fix the piezoelectric chip 3 and the mass block 4, an installation space 21 is provided at the end of the backing pad 2 near the signal detection end 101, and includes a first installation space 211 and a second installation space 212 with different accommodating spaces. A first step portion 213 is formed between the first installation space 211 and the second installation space 212, and the mass block 4 is locked and fixed through the first step portion 213.

[0057] Furthermore, the piezoelectric wafer 3 is a multilayer lead zirconate titanate piezoelectric thin film.

[0058] In this embodiment, the piezoelectric crystal 3 made of lead zirconate titanate is fabricated using a series-parallel stacked structure to achieve a narrow bandwidth effect. The stacked structure is bonded with conductive adhesive, resulting in a wide bandwidth, good electroacoustic conversion efficiency, and easier matching with the excitation circuit.

[0059] Furthermore, the acoustic sensor has a response frequency of 20-400 kHz.

[0060] Furthermore, the signal detection end 101 of the housing 1 is provided with a second step portion 11, and the diaphragm 5 is fixed on the second step portion 11.

[0061] In this embodiment, to ensure the structural strength and secure installation of the diaphragm 5, a second step 11 is provided at the signal detection end 101 of the housing 1. The diaphragm 5 is fixed by interference fit between it and the inner wall of the housing 1, or by adhesive bonding. The housing 1 protects the piezoelectric crystal 3, ensuring its service life. The diaphragm 5 can be made of a thin iron sheet, and through holes can be provided on the diaphragm 5 to transmit acoustic emission signals.

[0062] Furthermore, the signal output terminal 102 of the housing 1 is provided with a third step portion 12, and the wiring terminal 6 is fixed on the third step portion 12.

[0063] In this embodiment, in order to install and fix the terminal block 6 and ensure structural strength, a third step portion 12 is provided at the signal output end 102 of the housing 1. The terminal block 6 is fixed by interference fit with the inner wall of the housing 1 or by adhesive bonding.

[0064] Furthermore, the housing 1 is made of metal; the backing pad 2 is made of damping material.

[0065] In this embodiment, the housing 1 is made of metal and serves as the transmission medium to ground the housing. The backing pad 2 is a damping material used for vibration and noise to ensure the accuracy of the acquired signal. Specifically, it can be made of rubber, plastic damping plates, or a combination of rubber and foam plastic.

[0066] Example 2

[0067] In this embodiment, as Figure 1 As shown, based on the structure of Embodiment 1, a connecting piece 8 is provided on the outer surface of the housing 1, and a mounting hole 81 is provided on the connecting piece 8.

[0068] Acoustic sensors with this structure are suitable for monitoring devices with through holes, such as those with through-holes. During installation, the signal detection end 101 is inserted into the through-hole, and the connecting piece 8 is fixed to the device under monitoring using screws passing through the mounting hole 81, thus securing the acoustic sensor. The connecting piece 8 can be replaced with a flange. To reduce vibration, a rubber damping ring is fitted onto the housing 1. After the acoustic sensor is fixed, the rubber ring absorbs vibration, ensuring more accurate data acquisition.

[0069] Example 3

[0070] In this embodiment, as Figure 1 As shown, based on the structure of Embodiment 2, an external thread 13 is provided on the outer surface between the signal detection end 101 of the housing 1 and the connecting piece 8.

[0071] Acoustic sensors with this structure are suitable for monitoring devices with through holes, where internal threads are provided. During installation, the signal detection end 101 is inserted into the through hole, and a threaded connection is achieved between the external thread 13 on the outer surface of the housing and the internal thread of the through hole. Furthermore, the depth of the signal detection end 101 can be controlled by rotating the acoustic sensor to ensure more accurate data acquisition.

[0072] Example 4

[0073] This utility model embodiment also provides an acoustic monitoring system, including at least one of the above-described acoustic sensors, which are fixed on the device to be monitored.

[0074] The equipment to be monitored can be static or dynamic equipment such as petrochemical equipment. Acoustic sensors are installed on the equipment to collect acoustic emission signals. Combined with post-filtering of the instrument, the interference signal shielding effect is enhanced, enabling more accurate characterization, assessment, and early warning of damage status of the equipment. The number of acoustic sensors required is determined by the structure of the equipment in actual use.

[0075] The optional embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present utility model, various simple modifications can be made to the technical solutions of the present utility model, and these simple modifications all fall within the protection scope of the present utility model.

[0076] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this embodiment.

[0077] Furthermore, various different implementation methods of this utility model can be arbitrarily combined, as long as they do not violate the spirit of this utility model, they should also be regarded as the content disclosed by this utility model.

Claims

1. An acoustic sensor, characterized by The acoustic sensor comprises: an internally hollow cylindrical shell (1), the upper and lower ends of the shell (1) being a signal output end (102) and a signal detection end (101) respectively; a backing pad (2) arranged in the shell (1) through contact and cooperation with the inner wall of the shell (1), the lower end of the backing pad (2) being provided with a mounting space (21); a piezoelectric wafer (3) and a mass block (4) arranged in the mounting space (21), the mass block (4) being located above the piezoelectric wafer (3), the negative electrode of the piezoelectric wafer (3) being connected with the inner wall of the shell (1); a diaphragm (5) arranged at the signal detection end (101) of the shell (1) and not in contact with the piezoelectric wafer (3); a wiring terminal (6) fixed at the signal output end (102) of the shell (1), the wiring terminal (6) being connected with the positive electrode of the piezoelectric wafer (3) through a lead wire (7) penetrating through the backing pad (2) and used for conveying the electric charge generated by the vibration of the piezoelectric wafer (3) outward.

2. The acoustic sensor of claim 1, wherein, The mounting space (21) comprises: a first mounting space (211) and a second mounting space (212), a first step portion (213) being formed between the first mounting space (211) and the second mounting space (212); the piezoelectric wafer (3) is arranged in the first mounting space (211), and the mass block (4) is arranged in the second mounting space (212), the mass block (4) being in contact with the step surface of the first step portion (213).

3. The acoustic sensor of claim 1, wherein, The piezoelectric wafer (3) is a multi-layer lead zirconate titanate piezoelectric film.

4. The acoustic sensor of claim 1, wherein, The response frequency of the acoustic sensor is 20-400kHZ.

5. The acoustic sensor of claim 1, wherein, The signal detection end (101) of the shell (1) is provided with a second step portion (11), and the diaphragm (5) is fixed on the second step portion (11).

6. The acoustic sensor of claim 1, wherein, The signal output end (102) of the shell (1) is provided with a third step portion (12), and the wiring terminal (6) is fixed on the third step portion (12).

7. The acoustic sensor of claim 1, wherein, The outer surface of the shell (1) is provided with a connecting sheet (8), and a mounting hole (81) is formed in the connecting sheet (8).

8. The acoustic sensor of claim 7, wherein, An external thread (13) is arranged on the outer surface between the signal detection end (101) of the shell (1) and the connecting sheet (8).

9. The acoustic sensor of claim 1, wherein, The shell (1) is made of metal material, and the backing pad (2) is made of damping material.

10. An acoustic monitoring system, characterized in that The acoustic sensor comprises at least one acoustic sensor according to any one of claims 1-9, and the acoustic sensor is fixed on a device to be monitored.

Images