A fuse for accelerating the speed of current over-flow melting

Abstract

The application discloses a fuse for accelerating the speed of overcurrent melting at medium multiple, and relates to the technical field of fuses. The fuse for accelerating the speed of overcurrent melting at medium multiple is characterized in that: it comprises a first terminal, a second terminal, and a first current-carrying device and a second current-carrying device connected in parallel between the first terminal and the second terminal; the first current-carrying device comprises at least one first fuse body connecting the first terminal and the second terminal; the second current-carrying device comprises at least one medium-multiple fast-melting branch circuit connecting the first terminal and the second terminal; the medium-multiple fast-melting branch circuit comprises a second fuse body and a disconnecting device connected in series, and the disconnecting device is disconnected before the first fuse body and the second fuse body when overcurrent at medium multiple occurs. The fuse of the application combines the first current-carrying breaking device and the second current-carrying breaking device, thereby ensuring the maximum breaking capacity of the fuse, realizing fast melting when overcurrent at medium multiple occurs, and preventing the damage of the rear-end facilities caused by continuous overcurrent.

Description

Technical Field

[0001] This invention relates to the field of fuses, and more particularly to a fuse that accelerates the melting speed of medium-rate overcurrent circuits. Background Technology

[0002] Currently, the lithium battery industry primarily uses a combination of relays and fuses for protection. In the event of a high-current short circuit, the fuse provides overcurrent protection. Non-current anomalies are mainly detected by the battery management system, which then triggers a relay to disconnect the abnormal circuit. However, existing lithium battery systems require consideration of the temperature rise during high-current charging and discharging, as well as the pulse current issue during high-capacity output when selecting fuses. Consequently, fuse specifications are generally chosen to be too large, for example, selecting a short-circuit protection current greater than 3kA. In the event of a current less than 5 times the rated current, the fuse may not trip in time, leading to damage to the downstream circuit board or the lithium battery.

[0003] The frequent occurrence of premature blowout due to abnormal overcurrent in existing fuses is mainly due to the selection of a fuse that is too small. However, when a fuse is selected that is too large, it cannot provide timely protection under medium-rate overcurrent conditions. Summary of the Invention

[0004] In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a fuse that accelerates the melting speed of medium-rate overcurrent, so that the fuse can melt in time to provide circuit breaking protection under medium-rate overcurrent conditions.

[0005] To achieve the above objectives, the present invention provides a fuse for accelerating the melting speed of medium-rate overcurrent, comprising a first terminal, a second terminal, and a first current-carrying device and a second current-carrying device connected in parallel between the first terminal and the second terminal;

[0006] The first current-carrying device includes at least one first melt connecting the first terminal and the second terminal;

[0007] The second current-carrying device includes at least one medium-rate fast-melting branch connecting the first terminal and the second terminal;

[0008] The medium-rate fast-melting branch includes a second melt and a disconnecting device connected in series. The disconnecting device disconnects before the first melt and the second melt during medium-rate overcurrent.

[0009] Furthermore, the first melt and the second melt are fused wires or fused sheets with narrow diameters.

[0010] Furthermore, the first melt and the second melt are one of copper, silver, aluminum, or copper-based alloys, silver-based alloys, aluminum-based alloys, or copper-silver composite materials.

[0011] Furthermore, the first melt is one of copper, silver, aluminum, or copper-based alloys, silver-based alloys, aluminum-based alloys, or copper-silver composite materials; the second melt is nickel.

[0012] Furthermore, the disconnecting device comprises a low-melting-point metal.

[0013] Furthermore, the disconnecting device also includes a fluxing agent coated on the surface of a low-melting-point metal.

[0014] Furthermore, the disconnection device also includes a heating device, which is activated during the medium-rate overcurrent to actively heat the low-melting-point metal to accelerate the melting of the low-melting-point metal.

[0015] Furthermore, the melting point range of the low-melting-point metal is 70℃~450℃.

[0016] Furthermore, the disconnecting device also includes a mechanical breaking device, which is located near the low-melting-point metal. The mechanical breaking device is activated during medium-rate overcurrent to actively cut off the low-melting-point metal.

[0017] Furthermore, the mechanical breaking device is an elastic breaking mechanism, the movable end of which contacts the low melting point metal and is in an energy storage state, used to cut off the low melting point metal in an overflow softened state.

[0018] Furthermore, the mechanical cutting device is a pyrotechnic explosion cutting mechanism. The cutter of the pyrotechnic explosion cutting mechanism is located on the side of the low melting point metal. The pyrotechnic explosion cutting mechanism is activated during medium-rate overcurrent to actively cut off the low melting point metal.

[0019] Furthermore, the disconnecting device includes a conductor and a mechanical breaking device; the conductor and the second melt are connected in series and are provided with structural weakening points for mechanical breaking.

[0020] Furthermore, the mechanical cutting device is a pyrotechnic explosion cutting mechanism. The cutter of the pyrotechnic explosion cutting mechanism contacts the conductor. The control circuit of the pyrotechnic explosion cutting mechanism is activated when there is an overcurrent at a medium rate, thereby actively cutting off the conductor.

[0021] Furthermore, the current carrying ratio of the first melt of the first current-carrying device and the medium-rate fast melting branch of the second current-carrying device ranges from 5:1 to 1:5.

[0022] Furthermore, the fuse also includes a first housing, a first end cap, a second end cap, a first solder pad, and a second solder pad;

[0023] The second current-carrying device and the first current-carrying device are installed inside the first housing;

[0024] The two ends of the second current-carrying device and the first current-carrying device are respectively soldered to the first pad and the second pad;

[0025] The first end cap and the second end cap are the lead electrodes of the fuse. The first end cap and the second end cap are fixed at both ends of the first housing and are electrically connected to the first solder pad and the second solder pad, respectively.

[0026] Furthermore, the first housing is provided with a T-shaped cavity, and the disconnecting device extends to the protruding part in the middle of the T-shaped cavity.

[0027] This invention achieves the following technical effects:

[0028] The fuse of the present invention adopts a combination of a first current-carrying breaking device and a second current-carrying breaking device to ensure that the maximum breaking capacity of the fuse is consistent with the breaking capacity of the structure when there is no breaking device in the second current-carrying device; a fuse with a larger nominal current can be selected to handle the large temporary large current when the whole machine is working, while achieving rapid melting during medium-rate overcurrent, preventing continuous overcurrent from causing damage to downstream facilities.

[0029] The voltage across the disconnecting device in the second current-carrying device at the moment of disconnection is only the impedance voltage drop of the first current-carrying device, and basically no arc is generated. Therefore, there is no need or difficulty in arc extinguishing when designing the structure. Only the withstand voltage needs to be met, and the disconnecting device can be designed to be minimized. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the fuse of the present invention;

[0031] Figure 2 This is a circuit diagram of the first embodiment of the present invention;

[0032] Figure 3 This is a product structure diagram of the first embodiment of the present invention;

[0033] Figure 4 This is a cross-sectional view of the product structure according to the first embodiment of the present invention;

[0034] Figure 5 yes Figure 4 A magnified view of a portion of the image;

[0035] Figure 6 This is the current-time fusing curve of the first embodiment of the present invention;

[0036] Figure 7 This is a circuit diagram of the second embodiment of the present invention;

[0037] Figure 8 This is a product structure diagram of the second embodiment of the present invention;

[0038] Figure 9 This is the current-time fusing curve of the second embodiment of the present invention;

[0039] Figure 10 This is a circuit diagram of the third embodiment of the present invention;

[0040] Figure 11 This is a product structure diagram of the third embodiment of the present invention;

[0041] Figure 12 This is a cross-sectional view of the product structure according to the third embodiment of the present invention;

[0042] Figure 13 This is a schematic diagram of the structure of the present invention, which uses an elastic breaking mechanism for mechanical breaking;

[0043] Figure 14 This is a schematic diagram of the structure of the present invention, which uses a pyrotechnic explosion cutting mechanism for mechanical separation.

[0044] Figure 15 It is the current-time fusing curve of a fuse that uses a pyrotechnic explosion cutting mechanism.

[0045] Wherein: 1-shell; 2-nickel strip; 3-low melting point metal; 4-pad; 5-end cap; 6-silver strip; 7-quartz sand; 8-heating element; 9-T-cavity; 10-elastic breaking mechanism; 11-pyrotechnic explosion cutting mechanism; 30-temperature fuse; 32-upper cover; 33-lower cover; 34-fluxing agent; 80-heating device; 82-temperature fuse; 83-upper cover; 84-support; 85-lower cover; 100-first current-carrying device; 101-first melt; 200-second current-carrying device; 201-second melt; 202-breaking device; 2021-low melting point metal; 2022-elastic breaking mechanism; 2023-conductor; 2024-pyrotechnic explosion cutting mechanism. Detailed Implementation

[0046] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, primarily used to illustrate the embodiments and to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0047] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0048] like Figure 1As shown, the present invention provides a fuse for accelerating the melting speed of medium-rate overcurrent, including a first terminal P1, a second terminal P2, and a first current-carrying device 100 and a second current-carrying device 200 connected in parallel between the first terminal P1 and the second terminal P2; the first current-carrying device 100 includes at least one first fusible element 101 connecting the first terminal and the second terminal; the second current-carrying device 200 includes at least one medium-rate fast-melting branch connecting the first terminal P1 and the second terminal P2; the medium-rate fast-melting branch includes a second fusible element 201 and a disconnecting device 202 connected in series, wherein the disconnecting device 202 disconnects before the first fusible element 101 and the second fusible element 201 during medium-rate overcurrent.

[0049] In the specific implementation process, different disconnection devices 202 can be set to achieve rapid melting of the fuse when the current is medium.

[0050] Example 1

[0051] like Figures 2 to 6 As shown, the present invention provides a fuse that accelerates the melting speed of medium-rate overcurrent. In this embodiment, the first melt 101 of the first current-carrying disconnecting device 100 is mainly made of copper, silver, aluminum or copper-based alloys, silver-based alloys, aluminum-based alloys or copper-silver composite materials, etc. The disconnecting device 202 of the second current-carrying disconnecting device 200 is a low-melting-point metal, and the second melt 201 can be made of copper, silver, aluminum or copper-based alloys, silver-based alloys, aluminum-based alloys or copper-silver composite materials, etc. More preferably, the second melt 201 is made of high resistance temperature coefficient materials such as nickel strip connected in series.

[0052] exist Figure 2 In the circuit, ATCO1 and ATCO2 are low-melting-point metals, the second melt 201 is a nickel strip, and ATCO1 and melt 201, as well as ATCO2 and melt 201, form two branches of the second current-carrying disconnect device; the two first melts 101 form two branches of the first current-carrying disconnect device. P1 and P2 are the leads of the fuse.

[0053] Silver / copper / silver-copper composite materials, used as the fusible element in conventional fuses, have high melting points (copper 1083℃, silver 960℃) and high electrical conductivity. Compared to other low-melting-point fusible elements of the same size, the fusible element has a higher rated current, lower resistance, and lower power consumption, easily meeting the requirements for high breaking current capacity. By designing parallel structures with different numbers of fusible elements according to current-carrying requirements, the first current-carrying breaking device is formed.

[0054] The second molten material in the second current-carrying interrupter is preferably a nickel strip. This utilizes the high temperature coefficient of resistance of nickel during overcurrent, combined with the low-temperature melting characteristics of low-melting-point metals, to form a fast-melting device for medium-rate overcurrent. This accelerates the response time during medium-rate overcurrent while ensuring melting requirements for both low and high rate overcurrents. The temperature coefficient of resistance of nickel is approximately 6900 ppm / ℃, while that of silver / copper is approximately 4000 ppm / ℃. During overcurrent, nickel heats up due to its own resistivity, increasing its temperature and consequently its resistance, with a greater change than that of silver / copper. Low-melting-point metals are metals and alloys with melting points between 70℃ and 450℃, typically composed of low-melting-point metallic elements such as Bi, Sn, Pb, and In. At low overcurrent rates, the temperature rise of the nickel strip is small, and the temperature increase is not significant, resulting in a melting time comparable to that of a conventional fuse. At medium overcurrent rates, the temperature rise of the nickel strip enters a transition zone, causing it to heat up rapidly. This heat is transferred to the low-melting-point metal, causing it to melt and the current to be applied at a multiple to the first current-carrying disconnector, which then melts quickly, achieving safe disconnection. At high overcurrent rates, the temperature rise response rate of the nickel strip is insufficient to affect the low-melting-point metal; the effect is primarily due to the low melting point and internal resistance of the metal. As the current increases, the low-melting-point metal heats up due to its internal resistance, and its low melting point allows for rapid disconnection, with a response time comparable to that of the first current-carrying disconnector. In this application, the preferred melting point range for the low-melting-point metal is 100℃ to 250℃.

[0055] By combining a high-resistance temperature coefficient material with a low-melting-point metal, the temperature rise of the high-resistance temperature coefficient material during medium-rate overcurrent is used as the molten heat of the low-melting-point metal, causing the medium-rate fast-melting branch to melt and break. This, in turn, interrupts the current carrying capacity and allows the current to be carried at a multiple rate, thus shortening the melting response time. During medium-rate overcurrent, an earlier response can be achieved, preventing damage to downstream facilities caused by continuous overcurrent.

[0056] In this embodiment, the first current-carrying interrupting device is provided with two sets of current-carrying interrupting branches. The silver strip 6 serves as the first melt of the first current-carrying interrupting device. Figure 2 The first melt 101 is connected between the two end caps 5. In specific applications, different numbers or cross-sectional areas of the first melt can be connected in parallel according to the current carrying requirements to serve as the first current-carrying disconnection device.

[0057] In this embodiment, the second current-carrying disconnecting device is provided with two sets of medium-rate fast-melting branches. The medium-rate fast-melting branches are connected in series with nickel strip 2 (corresponding to...). Figure 2 The second melt 201) and the low-melting-point metal 3 (corresponding to Figure 2 It consists of ATCO1 and ATCO2.

[0058] like Figure 3 , Figure 5As shown, the surface of the low-melting-point metal 3 is coated with a fusing agent 34, and is sealed together by the upper cover 32 and the lower cover 33 to form a thermal fuse 30.

[0059] In this embodiment, the two ends of the low-melting-point metal 3 are connected to two nickel strips 2, and the other ends of the two nickel strips 2 are connected to two pads 4. In specific applications, the low-melting-point metal 3 can also be formed by connecting it to a nickel strip 2.

[0060] In specific applications, nickel strips 2 and thermal fuses 30 of different quantities or cross-sectional areas can be set according to current carrying requirements, serving as a second current carrying interruption device.

[0061] The first and second current-carrying disconnectors are spot-welded onto pad 4 to form a parallel assembly, which is then installed into housing 1. Housing 1 is made of high-strength, pressure-resistant insulating materials such as ceramic. End caps 5 are provided at both ends of housing 1, and end caps 5 and pad 4 can be fixedly connected by screws, spot welding, or other methods to bring out the electrodes of the fuse.

[0062] To ensure the normal melting of the first and second current-carrying disconnecting devices and to prevent abnormal arcing, the periphery of the first and second melts is filled with quartz sand 7 inside the shell 1.

[0063] Nickel has a temperature coefficient of resistance of approximately 6900 ppm / ℃, while silver / copper has a temperature coefficient of resistance of approximately 4000 ppm / ℃. Under overcurrent conditions, nickel heats up due to its own resistivity, and as its temperature rises, its resistance also increases, with a greater change than that of silver / copper. Low-melting-point metals are metals and their alloys with melting points of 70℃ to 450℃, typically composed of low-melting-point metallic elements such as Bi, Sn, Pb, and In.

[0064] The current-time fusing curve of this embodiment is as follows: Figure 6As shown, curve 1 is the melting curve of conventional silver strip as the melt. When the specification is large, it meets the overcurrent carrying requirements of low ratio. For medium ratio overcurrent, the pre-arc response time will be delayed as a whole, which will cause damage to the downstream facilities due to continuous overcurrent. Curve 2 is an example of the 400A current-time fusing curve in this embodiment. At low overcurrent rates (less than 1.2kA), the temperature rise is small, and the temperature rise of the nickel strip is not significant, so its fusing time is comparable to that of a conventional fuse. At medium overcurrent rates (between 1kA and 10kA), the temperature rise of the nickel strip enters the transition region, and the nickel strip heats up rapidly. The heat is transferred to the low-melting-point metal, which melts. The current is applied to the first current-carrying interrupting device at a multiple, and the first current-carrying interrupting device melts quickly, achieving safe disconnection. At high overcurrent rates (above 10kA), the temperature rise response rate of the nickel strip is not fast enough to act on the low-melting-point metal. It is more due to the low melting point characteristics and internal resistance of the low-melting-point metal. As the current rises, the low-melting-point metal heats up due to its internal resistance. Because of its low melting point, the low-melting-point metal can quickly cut off the current, and its response time is comparable to that of the first current-carrying interrupting device.

[0065] In summary, the fuse in this embodiment combines a first current-carrying breaking device and a second current-carrying breaking device, which has the following technical advantages:

[0066] 1. The terminal voltage of the disconnecting device in the second current-carrying device at the moment of disconnection is only the impedance voltage drop of the first current-carrying device, and basically no arc is generated. Therefore, there is no need or difficulty in arc extinguishing when designing the structure. Only the withstand voltage needs to be met. The disconnecting device can be designed to be minimized.

[0067] 2. Ensure that the maximum breaking capacity of the fuse is consistent with the breaking capacity of the structure when there is no disconnection device in the second current carrier.

[0068] 3. A fuse with a larger nominal current can be selected to handle the large temporary high current when the whole machine is working, while also achieving rapid melting during medium-rate overcurrent, preventing damage to downstream facilities caused by continuous overcurrent.

[0069] Example 2

[0070] like Figure 7 As shown, based on Embodiment 1, the fuse can also be equipped with a self-heating heater PTC, which, together with overcurrent and overvoltage detection signals, enables controlled operation. When the system detects an overcurrent signal, it triggers the heater circuit to open, and the heater PTC starts to work and generate heat, providing heat to ATCO1 and ATCO2. ATCO1 and ATCO2 melt due to heat, that is, the second current-carrying interrupter disconnects, and the current is applied to the first current-carrying interrupter 100 at a multiple, increasing the temperature rise of the first fuse 101 and quickly cutting off the circuit. At the same time, the heater PTC continues to work, and ATCO3 melts due to heat, cutting off the heater circuit and stopping operation.

[0071] Figure 8 A sum was given Figure 7 Corresponding product embodiment. Among them, the heater PTC corresponds to the heating element 8; the first melt 101 corresponds to the silver strip 6; ATCO1 and ATCO2 correspond to the low melting point metal 3; and ATCO3 corresponds to the thermal fuse 82.

[0072] In this embodiment, the heating device 80 consists of heating elements 8 connected in series and a thermal fuse 82, and is encapsulated together with a top cover 83, a bottom cover 85, a bracket 84, and two branches of low-melting-point metal 3. The thermal fuse 82 heats up and melts when continuously operating at a medium-rate current, thereby preventing the heating device 80 from continuing to operate after the fuse blows.

[0073] Specifically, the heating element 8 is placed between the two low-melting-point metals 3 of the second current-carrying disconnecting device and fixed by the bracket 84. At the same time, the low-melting-point metals 3 of the two branches are fixed to both sides of the heating element 8 by the upper cover 83, the lower cover 85 and the bracket 84, thereby ensuring that the heating element 8 uniformly heats the low-melting-point metals 3 of the two branches in a controlled manner, so that the low-melting-point metals 3 of the two branches melt and then the current is applied to the first current-carrying disconnecting device at a multiple, so that the first current-carrying disconnecting device melts quickly and the whole device achieves safe disconnection.

[0074] The current-time fusing curve of this embodiment is as follows: Figure 9 As shown, curve 1 is the fusing curve of conventional silver strip as the molten material; curve 2 is an example of the 400A current-time fusing curve of this embodiment. The first inflection point (the left inflection point) indicates that the heating device is started at a lower current, and the protection response time is shortened by the passive melting of the lower melting point metal. The second inflection point (the right inflection point) indicates that the protection response time is further shortened when the device is started at a higher current. The two inflection points of the dashed line indicate that the starting current of the breaking is different. The larger the starting current, the faster the breaking speed and the shorter the breaking time. At low overcurrent rates (less than 1.2kA), the temperature rise is small, and the temperature rise of the nickel strip is not significant, so its melting time is comparable to that of a conventional fuse. At medium overcurrent rates (between 1kA and 10kA), the low-melting-point metal is directly heated by the heater, and the current is applied to the first current-carrying disconnecting device at a multiple, causing the first current-carrying disconnecting device to melt quickly, thus achieving safe disconnection. At high overcurrent rates (above 10kA), the temperature rise response rate of the nickel strip and the heating of the heater are insufficient to act on the low-melting-point metal. The low-melting-point metal's low melting point and internal resistance play a larger role. As the current rises, the low-melting-point metal heats up due to its internal resistance. Because of its low melting point, the low-melting-point metal can quickly disconnect, and its response time is comparable to that of the first current-carrying disconnecting device.

[0075] In practical implementation, the distribution of the current-carrying capacity of each current-carrying breaking branch can be adjusted by changing the number of branches or the wire diameter of the fusible link. Preferably, the current-carrying ratio of the current-carrying breaking branch of the first current-carrying breaking device and the medium-rate fast-melting branch of the second current-carrying breaking device is generally set between 5:1 and 1:5. Preferred values ​​include 3:1, 2:1, 1:1, 1:2, and 1:3, etc.

[0076] Example 3

[0077] like Figures 10 to 12 As shown, the fuse housing 1 may be provided with a T-shaped cavity 9, thereby extending the thermal fuse 30 or low-melting-point metal 3 of the second current-carrying disconnecting device to the protrusion in the middle of the T-shaped cavity. In this structure, the thermal fuse 30 is kept at a certain distance from other molten materials, its melting is not affected or is less affected by the temperature rise of other molten materials, and sufficient structural space is provided to install a mechanical breaking device.

[0078] To achieve rapid disconnection of the second current-carrying disconnection device, a mechanical breaking device can be used for mechanical breaking.

[0079] Example 4

[0080] In this embodiment, the disconnecting device includes a low-melting-point metal 2021 and a spring-loaded breaking mechanism 2022, which serves as a mechanical breaking device, such as... Figure 13 As shown. In this embodiment, one end of the elastic breaking mechanism 2022 is fixed (e.g., fixed to the housing), and the other end abuts against the low-melting-point metal 2021, so that the entire elastic breaking mechanism is in an energy-storing state. When the low-melting-point metal softens due to heat and its structural strength decreases, its structural strength cannot withstand the elastic force applied by the elastic breaking mechanism. Therefore, the elastic breaking mechanism releases its stored energy and breaks the low-melting-point metal. After breaking, sufficient safety clearance and electrical insulation strength are formed at the break point.

[0081] Example 5

[0082] In this embodiment, the disconnecting device includes a conductor 2023 and a pyrotechnic explosion cutting mechanism 2024, which serves as a mechanical breaking device, such as... Figure 14As shown. Fireworks explosion cutting-off mechanisms are commonly used in circuit breakers. The main circuit electrode of the circuit breaker has structural weakening points such as narrow apertures. Upon receiving a command, the fireworks explosion cutting-off mechanism actuates and breaks these structural weakening points. The fireworks explosion cutting-off mechanism includes components such as a piston and an ignition device. When the fireworks explosion cutting-off mechanism actuates upon receiving a command, the piston, propelled by the explosion gas flow, acts on the narrow aperture to break the main circuit electrode, ensuring sufficient safety clearance and electrical insulation strength at the break point. Because the fireworks explosion cutting-off mechanism 2024 has a large impact force and strong breaking capacity, the conductor 2023 can be made of copper or aluminum strips with narrow apertures (which do not melt during medium-rate overcurrent), or it can be made of low-melting-point metals (which can melt during medium-rate overcurrent). Similarly, low-melting-point metals are also structural weakening points in the circuit. When the structural strength of the low-melting-point metal decreases, it can break when the fireworks explosion cutting-off mechanism 2024 actuates, ensuring sufficient safety clearance and electrical insulation strength at the break point. The current-time melting curve of this embodiment is shown below. Figure 15 As shown, curve 1 is the fusing curve of conventional silver strip as the melt, and curve 2 is an example of the current-time fusing curve using a pyrotechnic explosion cutting mechanism. The first inflection point (the left inflection point) indicates that the pyrotechnic explosion cutting mechanism is started at a lower current, and the protection response time is shortened due to the passive melting of the lower melting point metal. The second inflection point (the right inflection point) indicates that the protection response time is further shortened when started at a higher current. Compared with the technical solution using a heating device in Example 2, the technical solution using a pyrotechnic explosion cutting mechanism has a faster fusing speed and a shorter protection response time. The two inflection points of the dashed line indicate that the starting current of the break is different. The larger the starting current, the faster the response break speed and the shorter the response break time.

[0083] In summary, the fuse in the above embodiments also has the following technical advantages:

[0084] 1. When the disconnecting device in the second current-carrying device is equipped with a fireworks explosion cut-off mechanism or a heating device, the function of rated overcurrent protection can be realized.

[0085] 2. When the disconnecting device in the second current-carrying device is equipped with a pyrotechnic explosion cut-off mechanism or a heating device, if the detection circuit malfunctions or the ignition voltage input line or heating current input line is accidentally disconnected, the fuse still has the basic functions of a fuse, such as overload protection disconnection and maximum capacity safe disconnection of short-circuit current.

[0086] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A fuse that accelerates the melting speed of medium-rate overcurrent circuits, characterized in that: It includes a first terminal, a second terminal, and a first current-carrying device and a second current-carrying device connected in parallel between the first terminal and the second terminal; The first current-carrying device includes at least one first melt connecting the first terminal and the second terminal; The second current-carrying device includes at least one medium-rate fast-melting branch connecting the first terminal and the second terminal; The medium-rate fast-melting branch includes a second melt and a disconnection device connected in series, wherein the second melt is made of a material with a high temperature coefficient of resistance. During the medium-rate overcurrent, the second melt generates heat due to the overcurrent, and the heat is transferred to the disconnecting device, accelerating the melting of the disconnecting device. The melting of the disconnecting device occurs before the melting of the first melt and the second melt.

2. The fuse for accelerating the melting speed of medium-rate overcurrent as described in claim 1, characterized in that: The first melt and the second melt are fused wires or fused sheets with narrow diameters.

3. The fuse for accelerating the fusing speed of medium-rate overcurrent as described in claim 2, characterized in that: The first melt is one of copper, silver, aluminum, or copper-based alloy, silver-based alloy, aluminum-based alloy, or copper-silver composite material; the second melt is nickel.

4. The fuse for accelerating the fusing speed of medium-rate overcurrent as described in claim 1, characterized in that: The disconnecting device comprises a low-melting-point metal.

5. The fuse for accelerating the melting speed of medium-rate overcurrent as described in claim 4, characterized in that: The disconnecting device also includes a fluxing agent coated on the surface of a low-melting-point metal.

6. The fuse for accelerating the melting speed of medium-rate overcurrent as described in claim 4, characterized in that: The disconnection device also includes a heating device, which is activated during the medium-rate overcurrent to actively heat the low-melting-point metal to accelerate the melting of the low-melting-point metal.

7. The fuse for accelerating the melting speed of medium-rate overcurrent as described in claim 4, characterized in that: The melting point range of the low-melting-point metal is 70℃~450℃.

8. The fuse for accelerating the melting speed of medium-rate overcurrent as described in claim 4, characterized in that: The disconnecting device also includes a mechanical breaking device, which is located near the low-melting-point metal. The mechanical breaking device is activated during medium-rate overcurrent to actively cut off the low-melting-point metal.

9. The fuse for accelerating the fusing speed of medium-rate overcurrent as described in claim 8, characterized in that: The mechanical breaking device is an elastic breaking mechanism. The movable end of the elastic breaking mechanism contacts the low melting point metal and is in an energy storage state, used to cut the low melting point metal in an overflow softened state.

10. The fuse for accelerating the fusing speed of medium-rate overcurrent as described in claim 8, characterized in that: The mechanical cutting device is a pyrotechnic explosion cutting mechanism. The cutter of the pyrotechnic explosion cutting mechanism is located on the side of the low melting point metal. The pyrotechnic explosion cutting mechanism is activated when the current is at a medium rate, thereby actively cutting off the low melting point metal.

11. The fuse for accelerating the melting speed of medium-rate overcurrent as described in claim 1, characterized in that: The disconnecting device includes a conductor and a mechanical breaking device; the conductor and the second melt are connected in series and are provided with structural weakening points for mechanical breaking.

12. The fuse for accelerating the fusing speed of medium-rate overcurrent as described in claim 11, characterized in that: The mechanical cutting device is a pyrotechnic explosion cutting mechanism. The cutter of the pyrotechnic explosion cutting mechanism comes into contact with the conductor. The control circuit of the pyrotechnic explosion cutting mechanism is activated when there is an overcurrent at a medium rate, thereby actively cutting off the conductor.

13. The fuse for accelerating the melting speed of medium-rate overcurrent as described in claim 1, characterized in that: The current carrying ratio of the first melt of the first current-carrying device and the medium-rate fast melting branch of the second current-carrying device is in the range of 5:1 to 1:

5.

14. The fuse for accelerating the melting speed of medium-rate overcurrent as described in claim 1, characterized in that: The fuse also includes a first housing, a first end cap, a second end cap, a first solder pad, and a second solder pad; The second current-carrying device and the first current-carrying device are installed inside the first housing; The two ends of the second current-carrying device and the first current-carrying device are respectively soldered to the first pad and the second pad; The first end cap and the second end cap are the lead electrodes of the fuse. The first end cap and the second end cap are fixed at both ends of the first housing and are electrically connected to the first solder pad and the second solder pad, respectively.

15. The fuse for accelerating the melting speed of medium-rate overcurrent as described in claim 14, characterized in that: The first housing is provided with a T-shaped cavity, and the disconnecting device extends to the protruding part in the middle of the T-shaped cavity.

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