Target internal stress sensor structure based on PVDF riveting packaging
By using riveting and pre-tightening, the problem of dynamic characteristic damage to PVDF stress sensors during the packaging process was solved, achieving high natural frequency and stability, and improving the measurement accuracy and reliability of the sensor.
Patent Information
- Application Number
- CN202423116536.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-17
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2034-12-17
AI Technical Summary
Existing packaging methods for PVDF stress sensors are prone to damaging dynamic characteristics, and traditional adhesive and threaded connections affect sensor performance.
A riveting and encapsulation method is adopted, combined with the application of pre-tightening force. A circular groove is designed between the sensor housing and the PVDF sensitive element, and a rolling method is used to form a ring riveting to ensure the dynamic characteristics and stability of the sensor.
This improves the sensor's inherent frequency and structural stability, simplifies the manufacturing process, reduces manufacturing costs, and enhances the sensor's measurement accuracy and reliability.
Smart Images
Figure CN223500548U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of metrology and testing technology, specifically to a target internal stress sensor structure based on PVDF riveting encapsulation. Background Technology
[0002] Testing the dynamic changes in internal stress of concrete targets under implosion, penetration, or external explosive loads is crucial for assessing target vulnerability. Using an embedded PVDF stress sensor with good dynamic characteristics is a common method for testing the internal stress of concrete targets. PVDF films are relatively soft and easily damaged; therefore, in practical applications, they are usually encapsulated in a metal shell to form the PVDF stress sensor, ensuring its protection during target casting and testing. To ensure accurate stress measurement, the dynamic characteristics of the stress sensor must meet testing requirements while encapsulating the PVDF film. The dynamic characteristics of the sensor are affected by various factors, including sensor size and structure, sensor material, and the preload of the sensitive element. Traditionally, sensor encapsulation methods often use threads or adhesive to encapsulate the PVDF film within the metal shell. Adhesive bonding can affect the sensor's dynamic characteristics, while threaded encapsulation can affect its linearity. Utility Model Content
[0003] To address the shortcomings of existing technologies, this invention proposes a target internal stress sensor structure based on PVDF riveting encapsulation. Compared to traditional encapsulation methods such as adhesive bonding and threaded connections, this sensor relies on riveting to encapsulate the PVDF piezoelectric film to form a stress sensor, applying a certain preload force during encapsulation to ensure sufficient dynamic characteristics. This avoids the influence of traditional adhesive connections on the sensor's natural frequency, resulting in the advantage of a high natural frequency.
[0004] To achieve the above objectives, the technical solution adopted by this utility model is as follows:
[0005] A target internal stress sensor structure based on PVDF riveting encapsulation includes a sensor housing, a mass block, a PVDF sensitive element, a charge amplification circuit for the built-in sensor, and a cable lead-out wire. The sensor housing is designed with a circular groove for placing the PVDF sensitive element, the diameter of which is equal to the diameter of the PVDF sensitive element. The PVDF sensitive element is placed inside the groove, close to the bottom. A thin, rounded edge for riveting is provided at the upper end of the circular groove. A slot for placing the charge amplification circuit for the built-in sensor is provided next to the circular groove. The slot of the charge amplification circuit is connected to the groove for the PVDF sensitive element. The PVDF sensitive element is connected to the charge amplification circuit for the built-in sensor via a wire. The charge amplification circuit is also connected to the cable lead-out wire for signal output. The mass block is placed above the PVDF sensitive element, and the lower surface of the mass block is equal to the diameter of the PVDF film in the PVDF sensitive element, transmitting external forces to the PVDF sensitive element.
[0006] As a further improvement of this utility model, the PVDF sensing element is composed of a PVDF film, two metal electrode plates, and a polyimide film outside the electrode plates. The two metal electrode plates are located on both sides of the PVDF film to collect the charge signal generated by the PVDF film. The electrode plates are connected to the charge amplification circuit of the built-in sensor through wires to transmit the charge signal to the charge amplification circuit to realize signal amplification. There are two polyimide films outside the metal electrode plates to separate the metal electrode plates from the sensor housing, so that the metal electrode plates are insulated from the sensor housing.
[0007] As a further improvement of this utility model, the upper surface edge of the mass block is chamfered at 45°. After the mass block is placed on the PVDF sensitive element, a certain pressure is applied to the thin edge of the sensor housing by rolling, so that the thin edge deforms and fits into the chamfer on the upper surface of the mass block to form a ring riveting package.
[0008] As a further improvement of this utility model, the target stress sensor structure based on PVDF film is potted with epoxy resin.
[0009] As a further improvement of this utility model, a metal cover plate is welded to the slot of the charge amplification circuit of the built-in sensor, and a circular hole is opened in the metal cover plate, through which the cable lead connected to the charge amplification circuit of the built-in sensor is led out.
[0010] The beneficial effects of this utility model are as follows:
[0011] Innovative Packaging Method: This application proposes a riveting-based packaging technology for packaging target internal stress sensors. This packaging method offers significant advantages over traditional adhesive bonding and threaded connections. Riveting packaging not only simplifies the manufacturing process but also improves the sensor's structural stability and dynamic response characteristics.
[0012] Preload application: Through the riveting process, this application can apply a certain preload to the PVDF piezoelectric film during encapsulation. This preload ensures the accuracy and stability of the sensor in dynamic stress measurement, avoiding the inherent frequency reduction problem that may be caused by traditional adhesive bonding.
[0013] High natural frequency: Due to the use of riveting encapsulation and pre-tightening force application technology, the stress sensor of this application has a higher natural frequency. This means that the sensor can respond more accurately to high-frequency stress changes and is suitable for a wider range of measurement scenarios.
[0014] Structural design optimization: The sensor housing design fully considers the placement of the sensitive element and signal transmission. The circular groove has the same diameter as the sensitive element, ensuring good contact and stress transmission. Simultaneously, the groove design allows for easy connection and sealing of the built-in sensor's charge amplification circuit, improving the overall performance and reliability of the sensor.
[0015] Improved manufacturing process: A rolling process was used during encapsulation to deform the thin, circular edge structure at the top of the sensor housing groove, allowing it to fit snugly against the chamfer of the mass block, achieving reliable riveting encapsulation. This manufacturing process is simple, efficient, easy to implement, and easy to control in terms of quality.
[0016] Improved sealing: The slots in the sensor housing are sealed with stainless steel plates and connected using laser welding. This sealing method ensures the sensor's internal circuitry is protected against moisture, dust, and corrosion, improving the sensor's lifespan and reliability.
[0017] In summary, this application provides a high-performance and highly reliable target internal stress sensor through innovative packaging methods, pre-tightening force application, high natural frequency, optimized structural design, improved manufacturing process, and enhanced sealing. These technological innovations not only improve the sensor's measurement accuracy and stability but also reduce manufacturing costs and complexity, bringing new technological breakthroughs and application prospects to the field of stress measurement. Attached Figure Description
[0018] Figure 1 Sensor assembly drawing;
[0019] Figure 2 Schematic diagram of sensor housing structure;
[0020] Component Name:
[0021] 1. Sensor housing; 2. Mass block; 3. PVDF sensing element; 4. Charge amplification circuit for built-in sensor; 5. Cable lead-out wire. Detailed Implementation
[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:
[0023] This utility model discloses a target internal stress sensor structure based on PVDF riveted encapsulation, and a PVDF stress sensor based on riveted encapsulation, such as... Figure 1 As shown, it comprises a sensor housing 1, a mass block 2, a PVDF sensing element 3, a charge amplification circuit 4 with an internal sensor, and cable leads 5. The structure of the sensor housing is as follows: Figure 2 As shown, the sensor housing serves to protect the PVDF sensitive element 3 and the built-in charge amplification circuit 4. The sensor housing 1 is designed with a circular groove for placing the PVDF sensitive element 3. The diameter of the circular groove is equal to the diameter of the PVDF sensitive element 3, allowing the PVDF sensitive element 3 to be placed close to the bottom of the groove. A thin, rounded edge is provided at the upper end of the groove for riveting. Next to the circular groove is a slot for placing the built-in charge amplification circuit of the sensor. The slot for placing the circuit is connected to the groove for placing the PVDF sensitive element, thus connecting the PVDF sensitive element 3 and the built-in charge amplification circuit 4.
[0024] The PVDF sensing element 3 consists of a PVDF film, two metal electrode plates, and a polyimide film surrounding the electrode plates. The two electrode plates are located on opposite sides of the PVDF film to collect the charge signal generated by the PVDF film. The electrode plates are connected to the charge amplification circuit built into the sensor via wires, transmitting the charge signal to the amplification circuit for signal amplification. Two polyimide films separate the electrode plates from the housing, providing insulation between them.
[0025] Mass block 2 is placed above the PVDF sensing element, with its lower surface having the same diameter as the PVDF film in the sensing element. Its upper surface has the same diameter as the recess in the housing, allowing external forces to be transmitted to the PVDF sensing element 3. A 45° chamfer is machined on the edge of the upper surface of mass block 2. After the mass block is placed on the PVDF sensing element, a rolling process is used to apply pressure to the thin edge of the sensor housing, deforming it to fit against the chamfer on the upper surface of mass block 2, forming a ring-riveted seal. Simultaneously, the deformed riveting ring applies a downward force to the mass block, creating a preload between mass block 2, the PVDF sensing element 3, and the housing 1, increasing the contact stiffness between the parts and thus improving the sensor's natural frequency.
[0026] The charge amplification circuit 4 of the built-in sensor is connected to the electrode plates on both sides of the PVDF film via wires, placed in a groove on the side of the housing, and encapsulated with epoxy resin to ensure the shock resistance of the charge amplification circuit of the built-in sensor. The lead wire 5 of the connecting cable of the charge amplification circuit of the built-in sensor is used for signal output.
[0027] After the circuit is potted, a metal cover is welded to the slot where the circuit is placed to further protect the circuit and ensure the airtightness of the sensor. A circular hole is made in the cover, through which the cable lead 5, which is connected to the charge amplification circuit 4 of the built-in sensor, is led out.
[0028] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any other way. Any modifications or equivalent changes made based on the technical essence of the present utility model shall still fall within the scope of protection claimed by the present utility model.
Claims
1. A target internal stress sensor structure based on PVDF riveting encapsulation, comprising a sensor housing (1), a mass block (2), a PVDF sensitive element (3), a charge amplification circuit (4) with an embedded sensor, and a cable lead-out wire (5), characterized in that, The sensor housing (1) is designed with a circular groove for placing the PVDF sensitive element (3). The diameter of the circular groove is equal to the diameter of the PVDF sensitive element (3). The PVDF sensitive element (3) is placed in the groove and close to the bottom of the circular groove. The upper end of the circular groove has a thin circular edge for riveting. Next to the circular groove is a slot for placing the charge amplification circuit of the built-in sensor. The slot of the charge amplification circuit (4) of the built-in sensor is connected to the groove for placing the PVDF sensitive element (3). The PVDF sensitive element (3) is connected to the charge amplification circuit (4) of the built-in sensor through a wire. The charge amplification circuit (4) of the built-in sensor is also connected to a cable lead (5) for signal output. The mass block (2) is placed above the PVDF sensitive element (3). The lower surface of the mass block (2) is equal to the diameter of the PVDF film in the PVDF sensitive element (3) and transmits the force from the outside to the PVDF sensitive element (3).
2. The target internal stress sensor structure based on PVDF riveting encapsulation according to claim 1, characterized in that: The PVDF sensing element (3) consists of a PVDF film, two metal electrode plates, and a polyimide film outside the electrode plates. The two metal electrode plates are located on both sides of the PVDF film to collect the charge signal generated by the PVDF film. The electrode plates are connected to the charge amplification circuit (4) of the built-in sensor through wires to transmit the charge signal to the charge amplification circuit and realize the signal amplification. There are two polyimide films outside the metal electrode plates to separate the metal electrode plates from the sensor housing (1) so that the metal electrode plates are insulated from the sensor housing (1).
3. The target internal stress sensor structure based on PVDF riveting encapsulation according to claim 1, characterized in that: The upper surface edge of the mass block (2) is chamfered at 45°. After the mass block (2) is placed on the PVDF sensitive element (3), pressure is applied to the thin edge of the sensor housing (1) by rolling process, so that the thin edge is deformed and fits into the chamfer on the upper surface of the mass block (2) to form a ring riveting package.
4. The target internal stress sensor structure based on PVDF riveting encapsulation according to claim 1, characterized in that: The target internal stress sensor structure based on PVDF riveting encapsulation is potted with epoxy resin.
5. The target internal stress sensor structure based on PVDF riveting encapsulation according to claim 4, characterized in that: A metal cover plate is welded to the slot of the charge amplification circuit (4) of the built-in sensor. A circular hole is opened in the metal cover plate, and the cable lead-out line (5) connected to the charge amplification circuit (4) of the built-in sensor is led out in the circular hole.