Wireless passive pressure sensor for detecting bolt pretightening force

Abstract

The invention belongs to the technical field of pressure sensors, and particularly relates to a wireless passive pressure sensor for detecting bolt pretightening force, which comprises a pressure-sensitive capacitor and an outer ring encapsulation ring, the voltage-sensitive capacitor comprises an inner ring basin cavity, and an upper insulation pad, an upper polar plate, an elastic cushion layer, a lower polar plate and a lower insulation pad which are sequentially arranged in the inner ring basin cavity from top to bottom, the bottom of the inner ring pelvic cavity, the upper insulating pad, the upper polar plate, the elastic cushion layer, the lower polar plate and the lower insulating pad are provided with concentric holes to form a central through hole of the voltage-sensitive capacitor; the outer ring potting ring wraps the outer ring of the inner ring basin cavity, and a circuit and an antenna are arranged in the outer ring potting ring; the circuit is a frequency conversion circuit which is connected with the upper polar plate and the lower polar plate; and the circuit is also connected with the antenna. The sensor realizes wireless passive real-time monitoring, is convenient to install, does not need direct current power supply, does not have a signal processing unit inside, only transmits frequency signals, and is high in response speed.

Description

Technical Field

[0001] The invention relates to the technical field of pressure sensors, in particular to a wireless passive pressure sensor for detecting bolt preload, and belongs to the technical field of intelligent automation. Technical Background

[0002] Bolt connections play an indispensable role in ensuring the integrity, reliability and safety of equipment structures, and are widely used in aerospace, rail transit, petrochemical, new energy and other fields. In actual working processes, when the connection parts are subjected to long-term stress, vibration, impact and other environments, the decrease in bolt preload will cause the bolt connection to loosen, resulting in a decrease in connection strength, and may even cause structural failure or equipment failure. Therefore, real-time monitoring of bolt preload is crucial to ensure the safe operation and working stability of industrial equipment.

[0003] In a long-term, unmaintained environment, wired active sensors used to measure bolt preload have problems such as the need for external power supply, high cost, and complex maintenance, while passive wireless sensors used to measure bolt preload do not have such problems. Currently, the only bolt preload measurement sensor that can achieve passive wireless and does not damage the bolt structure is the ultrasonic measurement sensor. Ultrasonic preload measurement sensors are easily affected by the propagation medium, ambient temperature, and bolt surface material, and are expensive and cannot be used on a large scale. Summary of the invention

[0004] Aiming at the problem that bolt preload monitoring in the prior art requires external functions, and ultrasonic measurement sensors are costly and easily affected by environmental factors, the present invention provides a gasket-type passive wireless pressure sensor with high load-bearing capacity.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A wireless passive pressure sensor for detecting bolt preload, comprising a piezoceramic capacitor and an outer ring potting ring;

[0007] The varistor capacitor has a central through hole, and the varistor capacitor includes an inner ring basin, and an upper insulating pad, an upper electrode plate, an elastic pad layer, a lower electrode plate and a lower insulating pad located in the inner ring basin;

[0008] The upper insulating pad, the upper electrode plate, the elastic pad, the lower electrode plate and the lower insulating pad are arranged in sequence from top to bottom;

[0009] The bottom of the inner ring basin cavity and the upper insulating pad, the upper electrode plate, the elastic pad layer, the lower electrode plate, and the lower insulating pad have concentric holes, forming a central through hole of the varistor capacitor;

[0010] The outer ring potting ring is wrapped around the outer ring of the inner ring pelvic cavity, and a circuit and an antenna are arranged inside the outer ring potting ring;

[0011] The circuit is a frequency conversion circuit, and the frequency conversion circuit is connected to the upper plate and the lower plate;

[0012] The circuit is also connected to the antenna.

[0013] The present invention is a wireless passive pressure sensor for detecting bolt preload, which uses a high-voltage-resistant sensitive capacitor as a key component for bolt pressure detection, and performs automatic wireless detection through a circuit and antenna arranged inside the outer ring potting ring. When the pressure-sensitive capacitor is subjected to pressure, the capacitance value between the upper and lower plates will change. At this time, the electromagnetic wave emitted by the signal transmitter acts on the sensor antenna to generate a resonant current, which serves as a wireless energy supply to drive the circuit. The circuit detects the capacitance of the pressure-sensitive capacitor and generates electromagnetic waves of the corresponding frequency, which are transmitted back to the receiver through the antenna to achieve wireless passive real-time monitoring. The sensor of the present invention does not require DC power supply, has a natural frequency conversion characteristic, is easy to achieve high-sensitivity long-distance transmission, and does not have an internal signal processing unit, only transmits frequency signals, and has a fast response speed.

[0014] Moreover, the wireless passive pressure sensor of the present invention utilizes the inner ring pelvic cavity to protect the upper insulating pad, upper electrode plate, elastic cushion layer, lower electrode plate, and lower insulating pad of the piezoceramic capacitor, and realizes the limiting effect, thereby increasing the compressive strength of the pressure sensor. In this way, the circuit, antenna, and the stress-bearing part of the piezoceramic capacitor in the inner pelvic cavity are separated, thereby improving the stability and accuracy of signal transmission. In particular, the sensor integrates the capacitor, circuit, and antenna into one, which is convenient for installation.

[0015] Furthermore, a notch is provided on the side of the inner ring basin, the upper electrode plate is connected to the upper electrode, and the lower electrode plate is connected to the lower electrode; the upper electrode and the lower electrode are led out through the notch and connected to the circuit.

[0016] Preferably, the width of the notch is greater than the width of the upper electrode and the lower electrode extending from the notch, so as to prevent the inner ring cavity from being connected to the upper and lower electrode plates, thereby causing structural failure.

[0017] Preferably, the width L0 of the notch, the width L1 of the portion of the upper electrode extending from the notch, and the width L2 of the portion of the lower electrode extending from the notch, L0 / L1≥1.1, and L0 / L2≥1.1.

[0018] Furthermore, the upper insulating pad, the elastic pad layer, and the outer wall of the lower insulating pad are arranged closely against the inner wall of the pelvic cavity.

[0019] Furthermore, a gap is set between the upper pole plate, the lower pole plate and the inner wall of the pelvic cavity.

[0020] Furthermore, the upper insulating pad, the upper electrode plate, the elastic cushion layer, the lower electrode plate and the lower insulating pad are bonded and arranged in sequence.

[0021] Furthermore, the upper insulating pad is annular, and the outer diameter of the upper insulating pad is equal to the inner diameter of the inner ring pelvic cavity. Preferably, the upper insulating pad is annular and made of rubber material.

[0022] Since the lower surface of the upper insulating pad is bonded to the upper surface of the upper electrode plate, it is ensured that the upper electrode plate and the bolt will not be in contact and conduct, and the upper insulating pad will not be laterally offset when it is under pressure.

[0023] Further, the upper electrode plate is annular, and the outer diameter of the upper electrode plate is smaller than the inner diameter of the inner ring basin. Preferably, the upper electrode plate is made of annular carbon steel material.

[0024] The upper plate is connected to the upper electrode. Since the upper plate is bonded to the upper insulating pad and the surface of the elastic pad, it is ensured that the upper plate will not be laterally deflected when under pressure, and will not directly contact the inner ring pelvic cavity to form an electrical path. It is ensured that the upper plate will not be conductive with the inner ring pelvic cavity.

[0025] Furthermore, the elastic cushion layer is annular, and the outer diameter of the elastic cushion layer is equal to the inner diameter of the inner ring pelvic cavity. Preferably, the elastic cushion layer is annular rubber material.

[0026] The elastic cushion layer is bonded to the contact surfaces of the upper electrode plate and the lower electrode plate respectively, so as to ensure that no lateral displacement occurs when the upper and lower electrode plates are subjected to pressure.

[0027] Further, the lower electrode plate is annular, and the outer diameter of the lower electrode plate is smaller than the inner diameter of the inner ring basin. Preferably, the lower electrode plate is made of annular carbon steel material.

[0028] The lower plate is connected to the lower electrode, and the lower plate is bonded to the lower insulating pad and the contact surface of the elastic pad layer respectively, so as to ensure that the lower plate will not be lateral deflected when under pressure, and ensure that the lower plate will not be connected to the inner ring pelvic cavity.

[0029] Furthermore, the lower insulating pad is annular, and the outer diameter of the lower insulating pad is equal to the inner diameter of the inner ring pelvic cavity. Preferably, the lower insulating pad is made of annular rubber material.

[0030] The lower insulating pad is bonded to the lower electrode plate and the bottom of the inner ring basin respectively, ensuring that the lower electrode plate and the inner ring basin will not contact and conduct, and that the lower insulating pad will not be laterally offset when under pressure.

[0031] Furthermore, the outer diameters of the upper pole plate and the lower pole plate are D1, the diameter of the inner ring pelvic cavity is D0, and D1<D0.

[0032] Preferably, the outer rings of the upper and lower pole plates are provided with insulating layers to prevent direct contact with the inner ring cavity and avoid short circuit.

[0033] Furthermore, the upper electrode is made of carbon steel and is connected to the frequency conversion circuit.

[0034] Furthermore, the lower electrode is made of carbon steel and is connected to the frequency conversion circuit.

[0035] Furthermore, the inner ring basin is made of carbon steel.

[0036] Furthermore, the cavity diameter of the inner ring cavity is D1, the diameter of the through hole in the center of the inner ring cavity is D2, and D2 is less than 1 / 2×D1.

[0037] The through hole formed in the inner ring basin cavity is a component of the central through hole used for bolts. The diameter D2 of the hole is smaller than the diameter D1 of the lower insulating pad and plays the role of supporting the internal components of the basin cavity.

[0038] Furthermore, the upper insulating pad, the upper electrode plate, the elastic cushion layer, the lower electrode plate and the lower insulating pad are integrally formed by molding. In this way, the varistor is an integral structure in the inner ring cavity, and no part thereof will be laterally offset when under pressure.

[0039] Furthermore, the stacked height of the upper insulating pad, the upper electrode plate, the elastic pad layer, the lower electrode plate and the lower insulating pad is less than the depth of the inner ring basin.

[0040] Furthermore, the diameters of the concentric holes of the inner ring basin bottom and the upper insulating pad, upper electrode plate, elastic cushion layer, lower electrode plate, and lower insulating pad differ by no more than ±10%. In this way, the sizes of the central through hole formed by the concentric holes of the inner ring basin bottom and the upper insulating pad, upper electrode plate, elastic cushion layer, lower electrode plate, and lower insulating pad are substantially the same, with good stability, greater pressure bearing capacity, and less likely to produce a bottleneck effect.

[0041] Preferably, the diameters of the concentric holes of the upper electrode plate and the lower electrode plate are larger than the concentric holes of the elastic cushion layer.

[0042] Furthermore, the frequency conversion circuit and the pressure-sensitive capacitor form a resonant circuit. When the capacitance changes, the resonant circuit will feedback a signal by changing the resonant frequency.

[0043] Furthermore, the frequency conversion circuit includes nonlinear elements, and the nonlinear electronic components convert the resonant signal into a frequency which is then transmitted by the micro-antenna.

[0044] Further, the outer ring potting ring is formed by potting the antenna and the circuit with a potting material. For example, the outer ring potting ring is formed by potting the circuit and the antenna with a potting glue.

[0045] Furthermore, the potting material is at least one of epoxy, polyurethane, and silicone rubber.

[0046] Preferably, the potting material is epoxy resin or silicone rubber.

[0047] Furthermore, the antenna is a high-gain transceiver integrated antenna, and the antenna is connected to a frequency conversion circuit.

[0048] Preferably, the antenna is a high-gain transceiver integrated miniature antenna

[0049] Preferably, the antenna is a miniature passive antenna.

[0050] After receiving the electromagnetic waves from the transmitting end, the miniature passive antenna can convert the electromagnetic waves into current to supply power to the frequency conversion circuit, drive the resonant circuit to work, and at the same time transmit the resonant signals of different frequencies generated by the resonant circuit in the form of electromagnetic waves.

[0051] Furthermore, the varistor capacitor is a high withstand voltage sensitive capacitor.

[0052] Preferably, the high withstand voltage sensitive capacitor is a high withstand voltage sensitive capacitor.

[0053] Furthermore, the concentric holes of the bottom of the inner ring basin and the upper insulating pad, the upper pole plate, the elastic pad, the lower pole plate, and the lower insulating pad are concentric circular holes.

[0054] The present invention also provides a method for using the wireless passive pressure sensor, which determines the basic frequency signal of the sensor by calibration to accurately analyze and judge the change of the bolt preload force. The LC resonant frequency is calibrated with a standard pressure sensor to determine the frequency of the sensor.

[0055] A calibration method for the wireless passive pressure sensor comprises the following steps:

[0056] S1. Insert the wireless passive pressure sensor and the standard pressure sensor into the bolt as bolt washers;

[0057] S2, tighten the bolts;

[0058] S3, turning on the signal transmitter to transmit electromagnetic waves to the wireless passive pressure sensor;

[0059] S4. Turn on the receiver to receive the electromagnetic waves of the corresponding frequency emitted by the wireless passive pressure sensor, and combine it with the standard pressure sensor data to measure the bolt preload force.

[0060] The LC resonant frequency of the wireless passive pressure sensor of the present invention is calibrated using a standard pressure sensor. When the sensor is subjected to different pressures, the sensitive capacitor will produce different capacitance values, and the circuit will produce electromagnetic waves with different resonant frequencies. The change and magnitude of the pressure are detected by observing the change in frequency. The sensor calibration is completed in advance to determine the specific data of the wireless passive sensor. When the detection is performed, according to the characteristic that the capacitance value between the upper and lower plates of the high-voltage sensitive capacitor will change when it is subjected to pressure, the electromagnetic wave emitted by the signal transmitter will generate a resonant current when it acts on the sensor, drive the circuit to work, generate electromagnetic waves of corresponding frequencies, and transmit the electromagnetic waves at this time to the receiver through the antenna, realizing wireless passive real-time monitoring.

[0061] Compared with the prior art, the wireless passive pressure sensor of the present invention has the following advantages:

[0062] 1. The preferred solution of the wireless passive pressure sensor of the present invention can be prepared by integrally molding a piezoceramic capacitor, and the product batches have good stability, high compressive strength, and are convenient for industrial production.

[0063] 2. The sensitive capacitor of the present invention uses an inner ring basin to separate the circuit from the antenna and the stress-bearing part of the sensor. During the compression process, the antenna and the circuit will not be displaced, providing a stable working environment for the circuit and the antenna, and improving the stability and accuracy of signal transmission. In addition, the preferred solution can bond the upper insulating pad, the upper electrode, the elastic cushion layer, the lower electrode, and the lower insulating pad into an integrated structure. During the compression process, the upper electrode and the lower electrode will not be offset, and the performance is stable and reliable.

[0064] 3. The sensor of the present invention is a wireless passive sensor, does not require DC power supply, has a natural frequency conversion characteristic, is easy to achieve high-sensitivity long-distance transmission, and has no signal processing unit inside, only transmits frequency signals, and has a fast response speed.

[0065] 4. The sensor of the present invention has a high degree of integration, integrating the signal antenna, circuit, and varistor into one, which is convenient for installation and does not require special settings. It is arranged according to conventional bolts and gaskets, and is stimulated by external electromagnetic waves of a specific frequency to feedback a signal of a certain frequency. The installation and detection process is very simple and does not increase the difficulty of installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic diagram of the external structure of the present invention.

[0067] Figure 2 It is an internal structure diagram (cross-sectional view) of the present invention.

[0068] Figure 3 It is a schematic diagram of the external structure of the high withstand voltage sensitive capacitor of the present invention.

[0069] Figure 4 It is a schematic diagram of the external structure of the outer ring potting ring of the present invention.

[0070] Markings in the figure: 1-inner ring pelvic cavity, 2-outer ring potting ring, 3-upper insulating pad, 4-upper electrode, 5-elastic cushion, 6-lower electrode, 7-lower insulating pad, 8-circuit, 9-antenna, 10-notch, 11-upper electrode, 12-lower electrode, 13-central through hole, 14-inner ring pelvic cavity opening, 15-inner ring pelvic cavity bottom, 16-pelvic cavity inner wall, 17-potting material. DETAILED DESCRIPTION

[0071] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0072] Example 1

[0073] like Figure 1 to Figure 2 As shown, a wireless passive pressure sensor for detecting bolt preload includes a varistor and an outer ring potting ring 2. The varistor has a central through hole 13, and the varistor includes an inner ring basin 1 made of carbon steel, and an upper insulating pad 3, an upper electrode plate 4, an elastic pad 5, a lower electrode plate 6 and a lower insulating pad 7 arranged in sequence from top to bottom in the inner ring basin 1. The bottom 15 of the inner ring basin and the upper insulating pad 3, the upper electrode plate 4, the elastic pad 5, the lower electrode plate 6 and the lower insulating pad 7 have concentric holes, which constitute the central through hole 13 of the varistor. And the diameters of the concentric holes of the upper electrode plate 4 and the lower electrode plate 6 are larger than the concentric holes of the elastic pad 5.

[0074] The outer ring potting ring 2 is wrapped around the outer ring of the inner ring basin 1, and a circuit 8 and an antenna 9 are connected to each other inside the outer ring potting ring 2. The circuit 8 is a frequency conversion circuit, and the frequency conversion circuit is connected to the upper plate 4 and the lower plate 6. The frequency conversion circuit forms a resonant circuit with the pressure-sensitive capacitor. When the capacitance changes, the resonant circuit will feedback the signal by changing the resonant frequency. The frequency conversion circuit contains nonlinear elements, and the nonlinear electronic components convert the resonant signal into frequency and transmit it through the micro antenna 9.

[0075] The outer ring potting ring 2 is formed by potting the antenna 9 and the circuit 8 with epoxy resin material. A high-gain transceiver integrated miniature passive antenna is selected as the antenna 9, and the antenna 9 is pre-connected with the frequency conversion circuit 8; the frequency conversion circuit 8 and the upper plate 4 and the lower plate 6 are connected through the upper electrode 11 and the lower electrode 12; then, the epoxy resin material is potted and wrapped around the outer ring of the inner ring basin 1 to form an outer ring potting ring 2 for protection. After receiving the electromagnetic wave from the transmitting end, the miniature passive antenna 9 can convert the electromagnetic wave into current to supply power to the frequency conversion circuit, drive the resonant circuit to work, and at the same time transmit the resonant signals of different frequencies generated by the resonant circuit in the form of electromagnetic waves.

[0076] Further, if Figure 1 As shown, a notch 10 is provided on the side of the inner ring basin 1, the upper electrode plate 4 is connected to the upper electrode 11, and the lower electrode plate 6 is connected to the lower electrode 12; the upper electrode 11 and the lower electrode 12 are led out through the notch 10 and connected to the circuit 8. The width of the notch 10 is L0, the width of the part of the upper electrode 11 led out from the notch 10 is L1, and the width of the part of the lower electrode 12 led out from the notch 10 is L2, L0 / L1≥1.1, L0 / L2≥1.1. Prevent the inner ring basin 1 from being connected to the upper and lower electrodes 12, resulting in structural failure.

[0077] like Figure 2 As shown, the upper insulating pad 3, the upper electrode plate 4, the elastic pad 5, the lower electrode plate 6 and the lower insulating pad 7 are bonded in sequence. Specifically, the upper insulating pad 3, the elastic pad 5 and the lower insulating pad 7 are annular structures of rubber materials, and the outer diameters of the upper insulating pad 3, the elastic pad 5 and the lower insulating pad 7 are equal to the inner diameter of the inner ring basin 1. The upper electrode plate 4 and the lower electrode plate 6 are annular carbon steel materials, and the outer diameters of the upper electrode plate 4 and the lower electrode plate 6 are smaller than the inner diameter of the inner ring basin 1. The upper insulating pad 3, the upper electrode plate 4, the elastic pad 5, the lower electrode plate 6 and the lower insulating pad 7 are bonded into an integrated structure to ensure that the upper electrode plate 4 and the lower electrode plate 6 will not be laterally offset when under pressure. Ensure that the upper electrode plate 4 and the lower electrode plate 6 will not be conductive with the inner ring basin 1.

[0078] In a preferred implementation of this embodiment, an insulating layer is also provided on the outer ring of the upper electrode plate 4 and the lower electrode plate 6 to prevent direct contact with the inner ring basin cavity 1 and avoid short circuit.

[0079] Example 2

[0080] like Figures 1 to 4 As shown, a wireless passive pressure sensor for detecting bolt preload includes a high-voltage-resistant sensitive capacitor and an outer ring potting ring 2. The high-voltage-resistant sensitive capacitor includes an inner ring basin 1, an upper insulating pad 3, an upper electrode 4, an elastic pad 5, a lower electrode 6, and a lower insulating pad 7. The upper insulating pad 3, the upper electrode 4, the elastic pad 5, the lower electrode 6, and the lower insulating pad 7 are arranged in the inner ring basin 1 to form the core part of the varistor capacitor, and the varistor capacitor has a through hole, and the bottom of the inner ring basin is also a through hole. These through holes are arranged in concentric circles to form a central through hole 13. The outer ring potting ring 2 is composed of a circuit 8, an antenna 9, and a potting material 17.

[0081] Among them, Figure 2 As shown, the inner ring cavity 1 is provided with an upper insulating pad 3, an upper electrode plate 4, an elastic cushion layer 5, a lower electrode plate 6, and a lower insulating pad 7 in sequence. Figure 1As shown, the upper electrode plate 4 and the lower electrode plate 6 are connected to the upper electrode 11 and the lower electrode 12 respectively. There is a notch 10 on the side of the inner ring basin 1 for leading out the upper electrode 11 and the lower electrode 12. The width of the notch 10 is greater than the width of the upper electrode 11 and the lower electrode 12 to prevent the inner ring basin 1 from being connected to the upper electrode 11 and the lower electrode 12. Figure 2 As shown, a through hole is opened at the bottom of the pelvic cavity, and the diameter of the through hole is larger than the inner diameter of the upper electrode plate 4 and the lower electrode plate 6, and smaller than the inner diameter of the inner ring pelvic cavity opening 14, which plays the role of supporting the internal components of the pelvic cavity; the height of the pelvic cavity inner wall 16 is greater than the sum of the thicknesses of the upper insulating pad 3, the upper electrode plate 4, the elastic pad 5, the lower electrode plate 6, and the lower insulating pad 7, so as to prevent the internal components from being lateral offset when under pressure.

[0082] The inner ring pelvic cavity 1, the upper electrode plate 4, the lower electrode plate 6, the upper electrode 11, and the lower electrode 12 are all made of carbon steel. The outer walls of the upper insulating pad 3, the elastic pad layer 5, and the lower insulating pad 7 are arranged close to the pelvic cavity inner wall 16, and a gap is set between the upper electrode plate 4, the lower electrode plate 6, and the pelvic cavity inner wall 16. The upper insulating pad 3 is an annular rubber material, and the outer diameter is equal to the diameter of the pelvic cavity inner wall 16. The lower surface of the upper insulating pad 3 is bonded to the upper surface of the upper electrode plate 4 to ensure that the upper electrode plate 4 and the bolts will not contact and conduct, and the upper insulating pad 3 will not produce lateral displacement when under pressure. The elastic pad layer 5 is an annular rubber material, and the outer diameter is equal to the diameter of the pelvic cavity inner wall 16. The elastic pad layer 5 is bonded to the surface of the upper electrode plate 4 and the lower electrode plate 6 to ensure that the upper electrode plate 4 will not produce lateral displacement when under pressure. The lower insulating pad 7 is made of annular rubber material, and its outer diameter is equal to the diameter of the inner wall 16 of the pelvic cavity. The lower insulating pad 7 is bonded to the lower electrode plate 6 and the bottom of the pelvic cavity to ensure that the lower electrode plate 6 and the bottom of the pelvic cavity will not contact and conduct, and the lower insulating pad 7 will not produce lateral displacement when under pressure.

[0083] The outer ring potting ring 2 surrounds the outside of the inner ring basin 1, and the outer ring potting ring 2 is equipped with a circuit 8 and an antenna 9. The circuit 8 is a frequency conversion circuit, which is connected to the upper electrode 11 and the lower electrode 12. The antenna 9 is a high-gain transceiver integrated micro antenna, which is connected to the frequency conversion circuit. After the upper electrode 11, the lower electrode 12, the circuit 8, and the antenna 9 are connected, the outer ring potting ring 2 is formed by potting the outer part of the inner ring basin 1 with a silicone rubber potting material to prevent the circuit 8 and the antenna 9 from being affected by the external environment when they are working.

[0084] When the high withstand voltage sensitive capacitor, the capacitance value between the upper plate 4 and the lower plate 6 will change. At this time, when the electromagnetic wave emitted by the signal transmitter acts on the antenna 9, a resonant current will be generated, the driving circuit will work, and the LC resonant circuit formed by the circuit 8 and the high withstand voltage sensitive capacitor will generate electromagnetic waves of corresponding frequencies and transmit the electromagnetic wave signal at this time to the receiver through the antenna 9, realizing wireless passive real-time monitoring.

[0085] Disassemble the high-voltage sensitive capacitor and the outer ring potting ring, respectively. Figure 3 and Figure 4 As shown, Figure 3 This is a top view of the internal high-voltage sensitive capacitor. Figure 3 The protruding parts of the circular ring are the upper and lower electrodes. Figure 4 This is a separate schematic diagram of the outer ring potting ring. The internal high-voltage sensitive capacitor bears the pressure of the bolt structure and is used for detection. The outer ring potting ring of the outer ring is wrapped around the outer ring of the high-voltage sensitive capacitor, and the pressure sensor detection and feedback are performed through the circuit and antenna potted inside it.

[0086] In addition, the annular structures described in this embodiment are all concentric circles.

[0087] It is worth noting that when the sensor of the present invention is subjected to different pressures, the sensitive capacitor will produce different capacitance values, and react with the circuit to produce electromagnetic waves with different resonant frequencies, and the change and magnitude of the pressure can be detected by observing the change in frequency. Therefore, when performing detection, according to the characteristic that when the high-voltage sensitive capacitor is subjected to pressure, the capacitance value between the upper and lower plates will change, and when the electromagnetic wave emitted by the signal transmitter acts on the sensor, a resonant current will be generated, the driving circuit will work, and electromagnetic waves of corresponding frequencies will be generated, and the electromagnetic waves at this time will be transmitted to the receiver through the antenna, thereby realizing wireless passive real-time monitoring. Compared with the ultrasonic sensor in the prior art, the sensor of this embodiment makes full use of the pelvic limiter, which not only increases the compressive strength of the pressure sensor, but also uses the inner ring pelvic cavity to separate the circuit from the antenna and the force-bearing part of the sensor. During the compression process, the antenna and the circuit will not be displaced, thereby improving the stability and accuracy of signal transmission.

[0088] In addition, the above sensor needs to be calibrated with a standard pressure sensor to calibrate the LC resonant frequency. After the calibration is completed, the method of use of the present invention is as follows:

[0089] S1. Insert the wireless passive pressure sensor as a bolt gasket into the bolt;

[0090] S2, tighten the bolts;

[0091] S3, turning on the signal transmitter to transmit electromagnetic waves to the wireless passive pressure sensor;

[0092] S4. Turn on the receiver to receive the electromagnetic waves of corresponding frequency emitted by the wireless passive pressure sensor, and the bolt preload force can be measured.

[0093] In summary, the wireless passive pressure sensor for detecting bolt preload proposed by the present invention integrates the signal antenna, circuit, and capacitor into a small and highly integrated pressure sensor, which is easy to install. The sensor is made into a wireless passive sensor through the LC resonance principle. The sensor does not require DC power supply, has a natural frequency conversion characteristic, is easy to achieve high-sensitivity long-distance transmission, and does not have an internal signal processing unit, only transmits frequency signals, and has a fast response speed.

Claims

1. A wireless passive pressure sensor for detecting bolt preload, comprising a piezoceramic capacitor and an outer ring potting ring (2); The varistor capacitor has a central through hole (13), and comprises an inner ring basin (1), and an upper insulating pad (3), an upper electrode plate (4), an elastic pad layer (5), a lower electrode plate (6) and a lower insulating pad (7) located in the inner ring basin (1); The upper insulating pad (3), the upper electrode plate (4), the elastic pad layer (5), the lower electrode plate (6) and the lower insulating pad (7) are arranged in sequence from top to bottom; The bottom (15) of the inner ring basin cavity and the upper insulating pad (3), the upper electrode plate (4), the elastic cushion layer (5), the lower electrode plate (6), and the lower insulating pad (7) have concentric holes, forming a central through hole (13) of the varistor capacitor; The outer ring potting ring (2) is wrapped around the outer ring of the inner ring pelvic cavity (1), and a circuit (8) and an antenna (9) are arranged inside the outer ring potting ring (2); The circuit (8) is a frequency conversion circuit (8), and the frequency conversion circuit (8) is connected to the upper electrode plate (4) and the lower electrode plate (6); The circuit (8) is also connected to the antenna (9).

2. According to claim 1, a wireless passive pressure sensor for detecting bolt preload is characterized in that: A notch (10) is provided on the side of the inner ring basin (1); the upper electrode plate (4) is connected to the upper electrode (11), and the lower electrode plate (6) is connected to the lower electrode (12); the upper electrode (11) and the lower electrode (12) are led out through the notch (10) and connected to the circuit (8).

3. According to claim 1, a wireless passive pressure sensor for detecting bolt preload is characterized in that: The width of the notch (10) is greater than the width of the portion of the upper electrode (11) and the lower electrode (12) extending from the notch (10).

4. According to claim 1, a wireless passive pressure sensor for detecting bolt preload is characterized in that: The upper insulating pad (3), the upper electrode plate (4), the elastic pad layer (5), the lower electrode plate (6) and the lower insulating pad (7) are bonded and arranged in sequence.

5. According to claim 1, a wireless passive pressure sensor for detecting bolt preload is characterized in that: The upper insulating pad (3) is annular, and the outer diameter of the upper insulating pad (3) is equal to the inner diameter of the inner ring pelvic cavity (1); The elastic cushion layer (5) is annular, and the outer diameter of the elastic cushion layer (5) is equal to the inner diameter of the inner ring pelvic cavity (1); The lower insulating pad (7) is annular, and the outer diameter of the lower insulating pad (7) is equal to the inner diameter of the inner ring pelvic cavity (1).

6. A wireless passive pressure sensor for detecting bolt preload according to claim 1, characterized in that: The upper pole plate (4) is annular, and the outer diameter of the upper pole plate (4) is smaller than the inner diameter of the inner ring pelvic cavity (1); The lower pole plate (6) is annular, and the outer diameter of the lower pole plate (6) is smaller than the inner diameter of the inner ring pelvic cavity (1).

7. A wireless passive pressure sensor for detecting bolt preload according to claim 1, characterized in that: An insulating layer is provided on the outer rings of the upper electrode plate (4) and the lower electrode plate (6).

8. The wireless passive pressure sensor for detecting bolt preload according to claim 1, characterized in that: The upper insulating pad (3), the upper electrode plate (4), the elastic cushion layer (5), the lower electrode plate (6), and the lower insulating pad (7) are integrally formed by molding.

9. A wireless passive pressure sensor for detecting bolt preload according to claim 1, characterized in that: The diameters of the concentric holes of the inner ring basin bottom (15) and the upper insulating pad (3), the upper electrode plate (4), the elastic pad layer (5), the lower electrode plate (6), and the lower insulating pad (7) differ by no more than ±10%.

10. The wireless passive pressure sensor for detecting bolt preload according to claim 1, characterized in that: The outer ring potting ring (2) is formed by potting the antenna (9) and the circuit (8) with a potting material (17).

Images