Explosion-proof flame-retardant piezoresistor

Abstract

The utility model discloses an explosion-proof flame-retardant piezoresistor which comprises a shell and a piezoresistor, the shell is filled with a flame-retardant epoxy resin and quartz sand mixture, and the piezoresistor is wrapped in the flame-retardant epoxy resin and quartz sand mixture; the piezoresistor comprises a body and two pins, one pin comprises a first extension section, a second extension section and a low-temperature alloy wire section connected between the first extension section and the second extension section, the low-temperature alloy wire section is close to the body, and a fluxing agent layer is coated outside the low-temperature alloy wire section. A piezoresistor is attached to a low-temperature alloy wire, and the surface of the low-temperature alloy wire is coated with a fluxing agent layer; and a mixture of flame-retardant epoxy resin and quartz sand is filled in the shell to wrap the piezoresistor body. And when the piezoresistor is overheated due to abnormity, the low-temperature alloy wire is quickly melted to completely break the pin, so that the circuit is permanently cut off, and the piezoresistor is prevented from firing and burning.

Description

Technical Field

[0001] This utility model relates to the field of varistor technology, and in particular to an explosion-proof and flame-retardant varistor. Background Technology

[0002] In current explosion-proof technology, common solutions include encapsulating the varistor in quartz sand and a plastic shell, or soldering low-temperature solder wire and a series thermal fuse to the leads before encapsulation. These methods aim to prevent the varistor from igniting under abnormal voltage through physical isolation and temperature-responsive elements. However, these solutions have significant shortcomings: the heat-absorbing properties of quartz sand make it difficult for the protective element to respond in a timely manner, and the lack of an effective circuit disconnection mechanism means that the varistor cannot be quickly isolated from the circuit when overheated, thus failing to effectively prevent ignition.

[0003] Given the limitations of existing technologies, there is an urgent need for a new explosion-proof solution that can rapidly disconnect the circuit when the varistor overheats abnormally, preventing it from igniting. This solution needs to overcome the slow response and insufficient protection issues of existing technologies, providing a more reliable and effective circuit protection mechanism to meet growing safety demands and reduce potential fire risks. Utility Model Content

[0004] In view of this, the present invention addresses the deficiencies of existing technologies, and its main objective is to provide an explosion-proof and flame-retardant varistor. This varistor is constructed by bonding a varistor to a low-temperature alloy wire, coating the surface of the low-temperature alloy wire with a flux layer, and encapsulating the varistor body within a housing filled with a mixture of flame-retardant epoxy resin and quartz sand. When the varistor overheats due to an abnormality, the low-temperature alloy wire rapidly melts, completely disconnecting the leads and permanently cutting off the circuit, thus preventing the varistor from catching fire.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An explosion-proof and flame-retardant varistor includes a housing and a varistor. The housing is filled with a mixture of flame-retardant epoxy resin and quartz sand, and the varistor is encased in the mixture of flame-retardant epoxy resin and quartz sand. The varistor includes a body and two leads, one of which includes a first extension, a second extension, and a low-temperature alloy wire segment connected between the first and second extensions. The low-temperature alloy wire segment is close to or attached to the surface of the body and is coated with a flux layer.

[0007] As a preferred embodiment, the material of the low-temperature alloy wire segment is low-temperature tin wire.

[0008] As a preferred embodiment, at least two-thirds of the length of the low-temperature alloy wire segment is located above the body and close to or in close contact with the upper surface of the body.

[0009] As a preferred embodiment, the flux layer has a cross-section that is narrower at the top and wider at the bottom, and includes a bottom portion close to the upper surface of the body, a top portion away from the upper surface of the body, and a side portion that extends in an arc shape from the top to both sides and connects downward to the two sides of the bottom.

[0010] As a preferred embodiment, the ratio of flame-retardant epoxy resin to quartz sand in the flame-retardant epoxy resin and quartz sand mixture is 100:10.

[0011] As a preferred embodiment: the front end of the second extension segment has a bend that extends its rear end downward below the upper surface of the body, and the bend is connected to the rear end of the low-temperature alloy wire segment near the edge of the body.

[0012] As a preferred embodiment: the flux layer extends from both ends toward the rear end of the first extension section and the front end of the second extension section to form a tapered portion, and the tapered portion completely covers the connection position between the low-temperature alloy wire and the first and second extension sections.

[0013] As a preferred embodiment: the end of the housing extending toward the pin forms a quadrilateral perimeter, with a notch provided on each perimeter.

[0014] As a preferred embodiment: the flame-retardant epoxy resin and quartz sand mixture forms a recessed step on the end face of the housing, and the pins of the varistor extend from the recessed step.

[0015] As a preferred embodiment, the main body is located at the rear and lower part of the housing.

[0016] This invention has significant advantages and beneficial effects compared to existing technologies. Specifically, as described above, by combining a varistor with a low-temperature alloy wire, the varistor and the low-temperature alloy wire are fitted together, and a flux layer is coated on the surface of the low-temperature alloy wire. A mixture of flame-retardant epoxy resin and quartz sand is filled inside the housing to encapsulate the varistor body. When the varistor overheats due to abnormal operation, the low-temperature alloy wire rapidly responds and melts at its rated melting temperature. Under surface tension and the action of the flux, the low-temperature alloy wire quickly melts and forms a spherical shape attached to the ends of the first and second extension sections, completely disconnecting the pin. This permanently cuts off the circuit, preventing the varistor from catching fire. The mixture of flame-retardant epoxy resin and quartz sand further enhances the flame-retardant properties of the product, ensuring the safety and integrity of the circuit under extreme conditions. This design provides a fast and reliable circuit protection solution suitable for electronic devices requiring high safety standards.

[0017] To more clearly illustrate the structural features and effects of this utility model, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description

[0018] Figure 1 This is a three-dimensional schematic diagram of the varistor of this utility model;

[0019] Figure 2 This is a longitudinal sectional view of the varistor of this utility model;

[0020] Figure 3 This is a schematic diagram of the varistor of this utility model from another longitudinal sectional view.

[0021] Figure 4 This is a three-dimensional schematic diagram of the varistor of this utility model separated from the housing;

[0022] Figure 5 This is a cross-sectional schematic diagram of the varistor of this utility model;

[0023] Figure 6 This is a top view schematic diagram of the varistor of this utility model;

[0024] Figure 7 This is an exploded three-dimensional schematic diagram of the varistor of this utility model.

[0025] Explanation of reference numerals in the attached diagram:

[0026] 10. Housing; 11. Edge; 12. Notch; 13. Recessed step; 20. Varistor; 21. Lead; 211. Low-temperature alloy wire segment; 212. Flux layer; 2121. Bottom; 2122. Side; 2123. Top; 2124. Tapered section; 213. Bending section; 214. First extension section; 215. Second extension section; 22. Body; 30. Flame-retardant epoxy resin and quartz sand mixture. Detailed Implementation

[0027] This utility model is as follows Figures 1 to 7 As shown, an explosion-proof and flame-retardant varistor includes a housing 10 and a varistor 20, wherein:

[0028] The housing 10 is filled with a mixture of flame-retardant epoxy resin and quartz sand 30 (filler), and the varistor 20 is encapsulated in the mixture of flame-retardant epoxy resin and quartz sand 30; in this embodiment, the ratio of flame-retardant epoxy resin to quartz sand in the mixture of flame-retardant epoxy resin and quartz sand 30 is 100:10.

[0029] The varistor 20 includes a body 22 and two leads 21. One lead 21 includes a first extension 214, a second extension 215, and a low-temperature alloy wire segment 211 connected between the first extension 214 and the second extension 215. The rear end of the first extension 214 does not extend beyond the edge of the body 22. The low-temperature alloy wire segment 211 is close to the body 22 and is coated with a flux layer 212. The flux layer 212 has a cross-section that is narrower at the top and wider at the bottom. It includes a bottom 2121 close to the upper surface of the body 22, a top 2123 away from the upper surface of the body 22, and side portions 2122 extending arcuately from the top 2123 to both sides and connecting downward to both sides of the bottom 2121. The bottom 2121 is close to or in close contact with the upper surface of the body 22. The large contact area allows the heat generated by the body 22 to be quickly transferred to the flux layer 212, and then conducted to the low-temperature alloy wire segment 211.

[0030] Furthermore, the flux layer 212 extends from both ends toward the rear end of the first extension segment 214 and the front end of the second extension segment 215 to form tapered portions 2124, which completely cover the connection points between the cryogenic alloy wire and the first extension segment 214 and the second extension segment 215. When the varistor 20 experiences overcurrent or overvoltage and malfunctions, it will rapidly heat up, and the flux layer 212 will transfer the temperature to the cryogenic alloy wire segment 211. When the rated operating temperature of the cryogenic alloy wire is reached, the cryogenic alloy wire melts and, under the action of surface tension and flux, rapidly melts to form spherical shapes attached to the ends of the first extension segment 214 and the second extension segment 215. The tapered portions 2124 can reduce the resistance to the formation of spherical bodies at both ends when the cryogenic alloy wire melts, thus completely disconnecting the first extension segment 214 and the second extension segment 215, thereby permanently cutting off the circuit and preventing the varistor 20 from catching fire. The second extension segment 215 has a bend 213 at its front end that extends its rear end downward below the upper surface of the body 22. The bend 213 is connected to the rear end of the low-temperature alloy wire segment 211 near the edge of the body 22.

[0031] The low-temperature alloy wire segment 211 is made of low-temperature tin wire; at least two-thirds of the length of the low-temperature alloy wire segment 211 is located above the body 22 and close to or in close contact with the upper surface of the body 22. The low-temperature tin wire is on the surface of the varistor 20 body 22, making it easier to sense the heat generated by the varistor 22, and the low-temperature tin wire melts faster, greatly reducing the risk of fire in the varistor 20. A flux layer 212 is coated on the low-temperature tin wire. After the tin wire melts, the flux layer 212 not only melts the low-temperature tin wire into a spherical shape and adheres it to both ends, but also helps with circuit isolation, providing electrical isolation and avoiding the risk of secondary connections.

[0032] The end of the housing 10 extending towards the pin 21 forms a quadrilateral perimeter 11, with a notch 12 on each side of the perimeter 11. The flame-retardant epoxy resin and quartz sand mixture 30 forms a recessed step 13 on the end face of the housing 10, and the pin 21 of the varistor 20 extends from the recessed step 13. The notch 12 and the recessed step 13 are mainly for cooperation with other components to improve the installation stability of the varistor 20. The body 22 of the varistor 20 is located at the rear and lower position inside the housing 10. This design can reduce the direct impact of heat on surrounding circuits or other components, reducing the risk of heat accumulation and fire spread. This layout helps to confine heat and possible flames within the housing 10 when the varistor 20 overheats, reducing the impact on external circuits.

[0033] Quartz sand, as a hard material, when mixed with epoxy resin, not only improves the mechanical strength of the overall structure and protects the varistor 20 from physical damage, but also, due to its good thermal conductivity, helps the heat generated by the varistor 20 to be quickly dispersed, reducing the risk of local overheating.

[0034] By encapsulating the varistor 20 within a sealed housing 10 using potting technology, isolating it from other circuits, it is possible to prevent the varistor 20 from emitting smoke, catching fire, or exploding in the event of failure, thus avoiding the spread of smoke and flames from the varistor 20. This isolation technology is a simple and effective method, especially when other backup protections fail, providing an additional safety guarantee and effectively reducing the fire risk caused by a short-circuit failure of the varistor 20, thereby improving the overall safety of the circuit.

[0035] Explosion-proof test conditions: Install the varistor 20 on the test equipment, apply an AC voltage of 220V, then increase it at a rate of 100V / min to the required maximum permissible AC voltage and hold it for 2 minutes, and then increase it at a rate of 20V / min until there is no current in the circuit.

[0036] Experimental results showed that the varistor 20 did not explode, and no open flame was observed. After the test, the low-temperature alloy wire broke, but the varistor showed no breakdown, effectively preventing the risk of fire.

[0037] Thermal stability test conditions: The test specimen is connected to a mains power supply with a sufficiently high voltage to allow current to flow through the SPD. For this test, the current is adjusted to a constant value, with an error of ±10%. For the first test specimen, the test starts at 2mA true RMS value, or at Uc if the leakage current of the specimen at Uc exceeds 2mA true RMS value. Then, the test current is increased in increments of 2mA or 5% of the previously adjusted test current (whichever is greater). For the other two test specimens, the starting point should be changed from 2mA to the current value of the first 5 steps before the tripping current of the first test specimen. Each step is maintained until thermal equilibrium is reached (i.e., temperature change is less than 2K within 10 minutes). Continuously monitor the surface temperature of the hottest spot of the SPD (only for accessible SPDs) and the current flowing through the SPD.

[0038] Experimental conclusion: The cryogenic alloy wire was successfully broken during the experiment, and the experiment was successful.

[0039] The above tests verify that the explosion-proof varistor 20 has multiple protection functions.

[0040] 1. Aging failure disconnection: It can effectively protect against leakage current when the varistor 20 deteriorates (verified by thermal stability test).

[0041] 2. Abnormal overvoltage disconnection: In the explosion-proof test, the low-temperature alloy wire can effectively sense the temperature and disconnect within the effective time.

[0042] The key design feature of this invention lies in combining a varistor with a cryogenic alloy wire, placing the varistor and the wire in close contact, and coating the surface of the cryogenic alloy wire with a flux layer. The varistor body is then encapsulated within a housing filled with a mixture of flame-retardant epoxy resin and quartz sand. When the varistor overheats due to an abnormality, the cryogenic alloy wire rapidly reaches its rated melting temperature and melts. Under surface tension and the action of the flux, the cryogenic alloy wire quickly melts, forming a spherical shape that adheres to the ends of the first and second extension sections, completely disconnecting the pin. This permanently cuts off the circuit, preventing the varistor from catching fire. The mixture of flame-retardant epoxy resin and quartz sand further enhances the product's flame-retardant properties, ensuring the safety and integrity of the circuit under extreme conditions. This design provides a fast and reliable circuit protection solution suitable for electronic devices requiring high safety standards.

[0043] The above description is merely a preferred embodiment of the present utility model and does not constitute any limitation on the technical scope of the present utility model. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present utility model shall still fall within the scope of the technical solution of the present utility model.

Claims

1. An explosion-proof and flame-retardant varistor, characterized in that: The device includes a housing and a varistor. The housing is filled with a mixture of flame-retardant epoxy resin and quartz sand, and the varistor is encased in the mixture of flame-retardant epoxy resin and quartz sand. The varistor includes a body and two leads, one of which includes a first extension, a second extension, and a low-temperature alloy wire segment connected between the first and second extensions. The low-temperature alloy wire segment is close to or attached to the surface of the body and is coated with a flux layer.

2. The explosion-proof and flame-retardant varistor according to claim 1, characterized in that: The material of the low-temperature alloy wire segment is low-temperature tin wire.

3. The explosion-proof and flame-retardant varistor according to claim 1, characterized in that: At least two-thirds of the length of the cryogenic alloy wire segment is located above the body and close to or in close contact with the upper surface of the body.

4. The explosion-proof and flame-retardant varistor according to claim 1, characterized in that: The flux layer has a cross-section that is narrower at the top and wider at the bottom. It includes a bottom portion close to the upper surface of the body, a top portion away from the upper surface of the body, and a side portion that extends in an arc shape from the top to both sides and connects downward to the two sides of the bottom.

5. The explosion-proof and flame-retardant varistor according to claim 1, characterized in that: The second extension has a bend at its front end that extends its rear end downward below the upper surface of the body, and the bend is connected to the rear end of the low-temperature alloy wire segment near the edge of the body.

6. The explosion-proof and flame-retardant varistor according to claim 1, characterized in that: The flux layer extends from both ends toward the rear end of the first extension section and the front end of the second extension section to form a tapered portion, and the tapered portion completely covers the connection position between the low-temperature alloy wire and the first and second extension sections.

7. The explosion-proof and flame-retardant varistor according to claim 1, characterized in that: The end of the housing extending toward the pin forms a quadrilateral perimeter, with a notch provided on each perimeter.

8. The explosion-proof and flame-retardant varistor according to claim 1, characterized in that: The flame-retardant epoxy resin and quartz sand mixture forms a recessed step on the end face of the housing, and the pins of the varistor extend from the recessed step.

9. The explosion-proof and flame-retardant varistor according to claim 1, characterized in that: The main body is located at the rear and lower part of the shell.

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