Power battery pack intelligent grading pressure relief valve and thermal runaway protection method

Abstract

This invention relates to the field of battery management technology and discloses an intelligent graded pressure relief valve for power battery packs and a method for preventing thermal runaway. The valve body has independent venting and pressure relief channels at its upper part. A venting diaphragm is installed at the outlet end of the venting channel. A backfire prevention component is installed at the outlet end of the pressure relief channel. A weakened diaphragm with an anti-arched grooved structure is installed at a preset position away from the outlet end of the pressure relief channel. The weakened diaphragm has a normal state and a flipped state under the influence of internal valve body pressure. In the middle of the valve body, an independent discharge channel for the fire extinguishing medium component extends into the venting channel. The discharge port of the independent discharge channel faces the bottom of the valve body and is aligned with the inside of the battery pack. A shear pin locking trigger mechanism is connected to the weakened diaphragm. The shear pin locking trigger mechanism is driven by the weakened diaphragm in the flipped state to trigger the fire extinguishing medium component to operate. This invention achieves intelligent and reliable battery protection from daily differential pressure and airflow balance to emergency pressure relief and active fire extinguishing.

Description

Technical Field

[0001] This invention relates to the field of battery management technology, specifically to an intelligent graded pressure relief valve for a power battery pack and a method for preventing thermal runaway. Background Technology

[0002] Lithium-ion batteries may experience thermal runaway under abnormal operating conditions such as overcharging, over-discharging, short circuits, and thermal abuse, generating large amounts of high-temperature flammable gases and electrolyte vapors, leading to a sharp increase in internal pressure of the battery pack. According to GB 38031-2020 / 2025, battery packs must have reliable pressure relief protection capabilities.

[0003] However, existing pressure relief devices have the following problems: Limited functionality: traditional explosion-proof valves can only relieve pressure and cannot extinguish fires or prevent backfire; gas ejection after thermal runaway may still cause external fires; delayed response: most existing pressure relief valves are single-stage, unable to distinguish between daily ventilation and emergency pressure relief; frequent daily gas production triggers pressure relief, affecting sealing; and untimely response in emergency situations; lack of linkage: pressure relief and fire extinguishing are independent, lacking a mechanical linkage triggering mechanism; the BMS may have failed in the event of thermal runaway, and electrically triggered fire extinguishing is unreliable; risk of accidental activation due to vibration: existing flat-plate rupture discs are prone to fatigue crack propagation under vehicle vibration (GB38031 requires 3-7g, 10-2000Hz), leading to accidental rupture of the diaphragm and accidental activation of the fire extinguishing device; according to industry data, the fatigue life of flat-plate rupture discs is only 10... 3 ~10 4 The number of cycles is far lower than the number of vibrations throughout the entire life cycle of a car; in addition, the latch-type trigger mechanism is also at risk of accidental disengagement due to fretting wear in a vibration environment. Summary of the Invention

[0004] The present invention aims to provide an intelligent graded pressure relief valve for power battery packs and a thermal runaway protection method. By optimizing the structure of the pressure relief valve, a multi-level linkage, purely mechanical thermal runaway defense system is constructed, realizing intelligent and safe battery protection from daily pressure difference airflow balance to emergency pressure relief and active fire extinguishing.

[0005] The basic solution provided by this invention is: an intelligent graded pressure relief valve for a power battery pack, comprising a hollow valve body; The upper part of the valve body has an independent venting channel and a pressure relief channel; the middle part of the valve body is equipped with a fire extinguishing medium component; the bottom of the valve body is equipped with a mounting flange for connecting to the inside of the battery pack. A breathable diaphragm is installed at the outlet end of the venting channel to allow gas to flow between the inside and outside of the valve body; A backfire prevention component is installed at the outlet end of the pressure relief channel to facilitate the flow of gas between the inside and outside of the valve body and to prevent backfire. A weakening diaphragm with an anti-arch grooved structure is installed at a preset position away from the outlet end of the pressure relief channel; the weakening diaphragm is affected by the internal pressure of the valve body and has a normal state and an overturned state, which are used to partially block and avoid the pressure relief channel respectively. The independent discharge channel of the extinguishing medium assembly extends into the venting channel; the discharge port of the independent discharge channel faces the bottom of the valve body; The weakened diaphragm is connected to a shear pin locking trigger mechanism that aligns with the fire extinguishing medium assembly; the shear pin locking trigger mechanism is driven by the switching and flipping state of the weakened diaphragm to trigger the action of the fire extinguishing medium assembly.

[0006] This invention also provides an intelligent graded pressure relief valve for a power battery pack and a method for preventing thermal runaway, utilizing an intelligent graded pressure relief valve for a power battery pack; the method for preventing thermal runaway includes: Once the internal air pressure of the valve body meets the first threshold condition, the first level of protection is implemented, including the circulation of gas inside and outside the valve body through the breathable diaphragm. After the internal air pressure of the valve body meets the second threshold condition, the second level of protection is implemented, including the weakening diaphragm switching from the normal state to the flip state and rupturing to avoid the venting channel and form a large-diameter venting channel, and the flow of gas inside and outside the valve body and the blocking of backfire through the anti-backfire component. The fire suppression linkage executes the third level of protection, including the weakening diaphragm switching from the normal state to the flip state, driving the shear pin to lock the trigger mechanism to trigger the action of the fire extinguishing medium assembly, so that the fire extinguishing medium inside the fire extinguishing medium assembly is sprayed from the discharge port through the bottom of the valve body into the battery pack. When the weakened diaphragm is in its normal state, the interlock status feedback hard-wired circuit is active, and the battery management system determines that it is normal; when the weakened diaphragm switches from the normal state to the flip state, the interlock status feedback hard-wired circuit is disconnected, and the battery management system alarms.

[0007] The working principle and advantages of this invention are as follows: This invention re-optimizes the pressure relief valve structure, constructing a multi-stage, purely mechanical thermal runaway defense mode through parallel-designed independent venting and pressure relief channels. This achieves intelligent and reliable battery protection, from daily pressure differential airflow balance to emergency pressure relief and active fire suppression. The core advantages are: First, tiered response and complementary functions: The first-stage independent venting channel with a built-in venting membrane meets the pressure difference balance requirements caused by daily charging and discharging and environmental temperature changes, ensuring that the battery cell is always in a comfortable working air pressure environment; the second-stage pressure relief channel has a specially designed anti-arched grooved weakening membrane that instantly loses elastic stability and flips over when the pressure rises sharply, forming a large-diameter pressure relief channel to achieve ultra-large flow pressure relief and quickly reduce the pressure inside the pack; the third stage uses the flipping action of the anti-arched grooved weakening membrane to trigger the fire extinguishing device. The three-stage functions are interlocked and work together to cover the risks throughout the battery's entire life cycle.

[0008] Secondly, the anti-vibration accidental triggering design ensures that the shear pin of the shear pin locking trigger mechanism only responds to axial force, preventing accidental triggering due to vibration. Combined with the anti-resonance measures of the damping ring designed between the shear pin and the spring, it has an extremely high safety margin in complex vehicle vibration environments, completely avoiding the risk of malfunction caused by fatigue or resonance in traditional solutions.

[0009] Third, reliability is improved in multiple ways: 1) The inverted arched grooved design weakens the compressive stress on the diaphragm, resulting in a fatigue life far greater than that of a flat diaphragm; the grooved design achieves a tear-free design, and the flipping process does not generate metal shavings, thus avoiding secondary damage to internal components from the source, combining functional integration, reliability, and safety; 2) The pure mechanical linkage mechanism (diaphragm flipping, linkage drive, shear pin breakage, spring puncture) does not rely on any electrical or electronic signals. Even if the BMS completely fails in thermal runaway, the pressure relief valve can still reliably trigger the fire extinguishing action, and the flipping process is an instantaneous elastic instability, without the intermediate state of failure caused by gradual loosening and slow leakage; 3) The independent discharge channel introduces the extinguishing agent laterally into the battery pack, which does not interfere with the full-flow exhaust of the pressure relief channel, ensuring smooth pressure relief and using the exhaust airflow to block the flame back, achieving intrinsic safety; 4) While ensuring the IP67 sealing rating, the overall structure adopts a hard-wired interlocking power-off function. The hard-wired signal is still available after power failure, without relying on CAN bus communication. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of an intelligent graded pressure relief valve for a power battery pack provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the three-stage pressure relief pressure-response curve provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the anti-arch grooved weakening film provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the fire extinguishing linkage execution process provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the fire extinguishing linkage triggering timing provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the anti-backfire assembly provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the normal state of the state feedback loop provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the trigger state of the state feedback loop provided in an embodiment of the present invention; The markings in the accompanying drawings include: valve body 1, partition 11, venting channel 2, pressure relief channel 3, venting diaphragm 4, sealing ring 41, support frame 42, weakening diaphragm 5, weakening groove 51, convex surface 52, backfire prevention assembly 6, labyrinth baffle 61, metal fire arrestor mesh 62, shear pin locking trigger mechanism 7, linkage mechanism 71, puncture needle 72, shear pin 73, spring 74, extinguishing medium assembly 8, independent discharge channel 81, extinguishing medium storage chamber 82, atomizing nozzle 83, one-way valve 84, mounting flange 9, sealing gasket 91, status feedback assembly 10, battery management system 101, micro switch 102, conductive contact 103, battery pack cover 12. Detailed Implementation

[0011] The following detailed explanation illustrates the specific implementation methods: The basic implementation examples are as follows: Figure 1 As shown: A smart graded pressure relief valve for a power battery pack, including a hollow valve body 1; The upper part of the valve body 1 has an independent venting channel 2 and a pressure relief channel 3; the middle part of the valve body 1 is equipped with a fire extinguishing medium assembly 8; the bottom of the valve body 1 is provided with a mounting flange 9 for connecting to the inside of the battery pack. A breathable diaphragm 4 is installed at the outlet end of the venting channel 2 for the circulation of gas inside and outside the valve body 1. The outlet end of the pressure relief channel 3 is equipped with a backfire prevention component 6, which is used for the flow of gas inside and outside the valve body 1 and to prevent backfire. A weakening diaphragm 5 with an anti-arch grooved structure is installed at a preset position away from the outlet end of the pressure relief channel 3; the weakening diaphragm 5 is affected by the internal pressure of the valve body 1 and has a normal state and a flipped state, which are used to partially block and avoid the pressure relief channel 3 respectively. The independent discharge channel 81 of the extinguishing medium assembly 8 extends into the venting channel 2; the discharge port of the independent discharge channel 81 faces the bottom of the valve body 1. The weakened diaphragm 5 is connected to a shear pin locking trigger mechanism 7 that aligns with the fire extinguishing medium assembly 8; the shear pin locking trigger mechanism 7 is driven by the switching flip state of the weakened diaphragm 5 to trigger the action of the fire extinguishing medium assembly 8.

[0012] like Figure 2 As shown, this embodiment also provides a thermal runaway protection method for a power battery pack intelligent graded pressure relief valve, utilizing a power battery pack intelligent graded pressure relief valve; the thermal runaway protection method includes: After the internal air pressure of valve body 1 meets the first threshold condition, the first level of protection is implemented, including the circulation of gas inside and outside valve body 1 through the breathable diaphragm 4. After the internal air pressure of valve body 1 meets the second threshold condition, the second level of protection is implemented, including the weakening diaphragm 5 switching from the normal state to the flip state and rupturing to avoid the venting channel and form a large-diameter venting channel, and the backfire prevention component 6 to allow the internal and external gas flow of valve body 1 and block backfire. The fire suppression linkage executes the third level of protection, including the weakening diaphragm 5 switching from the normal state to the flip state, driving the shear pin to lock the trigger mechanism 7 to trigger the action of the fire extinguishing medium assembly 8, so that the fire extinguishing medium inside the fire extinguishing medium assembly 8 is sprayed from the discharge port through the bottom of the valve body 1 into the battery pack.

[0013] Understandably, the process and the effect are the same, as detailed below.

[0014] Specifically: It should be noted that, in order to more clearly illustrate the structural position, the terms "up," "down," "left," and "right" are defined and explained, but no specific limitation is actually imposed; the connection and fixation between each component and the valve body 1 shall adopt a reasonable conventional fixing and connection method based on the valve body 1 as long as it can achieve the effect of this embodiment, and no specific limitation is imposed.

[0015] like Figure 1 As shown, a partition extends from the top of valve body 1 to a predetermined position in the middle to form two parallel sections, serving as a venting channel 2 and a pressure relief channel 3 respectively, forming a parallel independent dual-channel structure. The two channels are physically independent and do not interfere with each other. In this embodiment, venting channel 2 (left side): cross-sectional area approximately 225mm² (Ø17mm circle), height approximately 60mm, volume approximately 13.5cm². 3 Pressure relief channel 3 (right side): cross-sectional area approximately 260 mm² 2 (Rectangle 16×16mm), height approximately 60mm, volume approximately 15.6cm² 3 The volume ratio is approximately 1:1.15, with a basically equal volume design to ensure that the two channels do not interfere with each other when working independently. The fire extinguishing medium assembly 8 is installed at the end of the partition facing the bottom of the valve body 1 and is connected to the partition; the shear pin locking trigger mechanism 7 is located in the pressure relief channel 3 and is installed on the partition, located above the fire extinguishing medium assembly 8. In this embodiment, it is illustrated for a pure electric vehicle power battery pack with a capacity of 50-100kWh (the same below). The valve body 1 is made of 6061-T6 aluminum alloy, with an overall size of Ø80×85mm. The diameter of the valve body 1 is Ø80mm: due to the installation space limitation of the battery pack cover plate 12, it needs to be adapted to 4×M6 bolt holes. The height is 85mm: including a flange of 15mm, the main body of the valve body 1 of 55mm, and the top sealing structure of 15mm; the design basis is to meet the installation requirements of 50-100kWh pure electric vehicle battery packs, and the overall size is within the range of industry-standard pressure relief valve sizes (refer to existing pressure relief valves Ø70-90mm). The partition is partition 11, the ventilation channel 2 is the left partition, and the pressure relief channel 3 is the right partition.

[0016] Ventilation Channel 2 (Level 1 Protection): like Figure 1 As shown, the breathable diaphragm 4 allows gas flow between the inside and outside of the valve body 1 after the internal air pressure meets the first threshold condition. Figure 1 The arrow above the dashed box in the ventilation channel 2 indicates the direction from the inside of valve body 1 to the outside of valve body 1. In this embodiment, an ePTFE breathable membrane 4 with a pore size of 1-3 μm and a thickness of 0.3 mm is used. Gas inside valve body 1 is slowly discharged into the atmosphere through the ePTFE micropores, with an effective breathable area of ​​5-10 cm². 2 The first threshold condition is that it can be breathable under a pressure difference of 0.5 to 5 kPa (e.g., Figure 2 As shown in Figure ①, the permeable PTFE membrane responds to daily environmental changes (altitude, temperature), essentially driven by pressure difference. When the pressure difference reaches 0.5–5 kPa, the permeable diaphragm 4 can continue to function, meeting the daily pressure difference balance requirements. The permeable diaphragm 4 is fixed to the top stepped surface of the valve body 1 by the sealing ring 41. The back of the permeable diaphragm 4 facing the bottom of the valve body 1 is supported and fixed by the support frame 42. The support frame 42 is installed between the inner wall of the valve body 1 and the partition 11, so that the permeable diaphragm 4 is stably installed in the air passage 2 of the valve body 1.

[0017] Pressure relief channel 3 (secondary protection): A weakening diaphragm 5 with an anti-arched grooved structure (i.e., anti-arched grooved weakening diaphragm 5) is used to replace the traditional flat-plate scoring diaphragm. For example... Figure 3 As shown, the pre-pressed arched weakening diaphragm 5 includes a concave surface and a convex surface 52. The concave surface is engraved with a weakening groove 51 of a preset shape. In the normal state, the convex surface 52 faces the bottom of the valve body 1 (i.e., the inner side of the battery pack (pressure side)) to subject the weakening diaphragm 5 to compressive stress under normal conditions. The preset shape of the concave weakening groove 51 (groove) includes any one or a combination of cross-shaped, annular, and spiral shapes, such as... Figure 3 (c) Schematic diagram of cross-shaped and annular grooves.

[0018] Installation of the anti-arch grooved weakening diaphragm 5: This diaphragm is installed using a combination of a central single-point connection and an outer circumferential fixing method. The outer circumference of the diaphragm is fixed to the inner wall of the valve body 1 via a sealing structure. Figure 1 Not shown, but actually present (the outer edge of the diaphragm is fixed and not suspended), providing complete circumferential constraint; the center vertex of the convex surface 52 is connected to the shear pin locking trigger mechanism 7, specifically the connecting rod mechanism 71 (e.g. Figure 1 As shown, the diaphragm consists of the apex of the central convex surface 52, the linkage mechanism 71, the shear pin 73, the puncture needle 72, and the spring 74, transmitting only axial force. The absence of support below the central convex surface 52 is a normal design feature, providing space for diaphragm instability and overturning. The diaphragm is fixed within the valve body 1 at a height that is also compatible with the operating height of the shear pin locking trigger mechanism 7 and the fire extinguishing medium assembly 8.

[0019] When in use, the weakening diaphragm 5 is affected by the internal pressure of the valve body 1 and has a normal state and a flipped state, which are used to partially block and avoid the pressure relief channel 3 respectively.

[0020] Figure 3 (a) Figure 4 (a) shows the normal state of the anti-arched grooved weakening diaphragm 5, which partially blocks the pressure relief channel 3. The compressive stress (e.g., ...) of the anti-arched grooved weakening diaphragm 5 under normal conditions is... Figure 3 (a) indicated by the upward arrow) rather than tensile stress, resulting in a vibration fatigue life of up to 10 years. 6 More than once (flat type only 10) 3 ~10 4 The working pressure ratio reaches 90% (compared to only 50% for flat plate type), fundamentally eliminating the risk of accidental vibration.

[0021] like Figure 3 (b) Figure 4 (b) shows the flipped state of the anti-arch grooved weakening diaphragm 5. The second threshold condition is when the internal pressure of the valve body 1 rises to 15-25 kPa (e.g., Figure 2 The pressure level indicated by the diaphragm instability and flipping in point ② is the sudden increase in internal pressure in response to thermal runaway. Essentially, it is driven by absolute pressure. When the absolute pressure inside the pack reaches 15-25 kPa, the diaphragm instability and flipping occurs. The arched, grooved weakened diaphragm 5 (i.e., the arched shell) undergoes elastic instability and flipping (changing from the normal state to the flipped state, response time < 1 ms; the convex surface 52 of the diaphragm (facing the battery pack) is compressed; when the pressure reaches 15-25 kPa, the diaphragm instantly flips from the convex surface 52 state to the concave surface state, flipping upwards axially (towards the outlet of the pressure relief channel 3, non-rotational flipping), while simultaneously tearing along the grooves). Figure 3 (b) Figure 4 As shown in (b) (the upward arrow indicates the pressure relief direction), the weakened diaphragm 5 tears along the groove to release pressure (i.e., after the weakened diaphragm 5 flips and breaks, it avoids the pressure relief channel, and the pressure relief channel 3 is no longer blocked by the weakened diaphragm 5, forming a large-diameter pressure relief channel for large-flow pressure relief). The flip displacement H is in the range of 5-15mm, providing a reliable triggering source for fire suppression linkage. After the anti-arched diaphragm flips and tears, no metal fragments fly, and it will not damage the internal components of the battery pack.

[0022] The backfire prevention component 6 is used for gas flow between the inside and outside of the valve body 1 and to prevent external flames from propagating back into the battery pack through the inside of the valve body 1. The backfire prevention component 6 includes a labyrinth-type baffle 61 and a metal flame arrestor mesh 62. In this embodiment, as... Figure 6As shown, the labyrinth baffle is fixed to the top of valve body 1 by clips. Each baffle is staggered to form an S-shaped airflow channel. The contraction ratio of each baffle is greater than a preset ratio, ensuring that the airflow area is not less than a preset ratio of the original cross-section. The flame arrestor is fixed above the labyrinth outlet by a pressure ring, covering the entire outlet cross-section of the pressure relief channel 3. During operation, the released gas enters the labyrinth baffle inlet from the pressure relief channel 3. Figure 6 (As indicated by the arrow pointing to the left at the top); the gas flows in an S-shaped transverse back-and-forth motion between multiple staggered baffles ( Figure 6 (as shown by the horizontal arrow in the middle), plus a certain channel contraction ratio ( Figure 6 (As shown in the channel 61), the gas is forced to repeatedly change direction, and the heat is fully dissipated on the baffle wall; the gas then passes through the metal flame arrestor mesh 62, where the flame is extinguished by the metal mesh; the cooled gas is discharged horizontally from the flame arrestor mesh. Figure 6 (As indicated by the bottom arrow) to the upper cavity of valve body 1; after the gas gathers in the upper cavity of valve body 1, it is discharged upwards to the atmosphere from the top opening of valve body 1. That is, inside valve body 1 ( Figure 6 The discharge is horizontal, and the valve body 1 outlet ( Figure 1 The upward arrow indicates upward discharge into the atmosphere; both represent different stages of the same exhaust process.

[0023] In this embodiment, the anti-arch grooved weakening diaphragm 5 is made of 301 stainless steel, with a diameter of Ø30mm, an arch height h in the range of 3-5mm, and a thickness of 0.2mm; the concave surface of the weakening diaphragm 5 is engraved with 4 radial (cross-shaped) and 1 annular combination of weakening grooves 51, as shown... Figure 3 (c) shows that the depth of the weakening groove 51 (groove) is approximately 70% of the wall thickness, with a residual wall thickness of approximately 0.06 mm. Under normal conditions, the convex surface 52 of the weakening diaphragm 5 faces the inside of the battery pack and is subjected to compressive stress. When the internal pressure rises to 18 kPa, the arch shell becomes unstable and flips over, tearing along the groove. The flip displacement H is approximately 10 mm, forming a large-diameter venting channel. The vented gas passes through the backfire prevention component 6 (using a 3-stage labyrinth baffle 61 with a shrinkage ratio ≥60% and a 100-mesh metal flame arrestor mesh 62 with an effective area ≥420 mm²). 2 After meeting the flow rate requirement of 500-2000 L / min, it is discharged into the atmosphere, while simultaneously blocking the flame backflow.

[0024] Firefighting linkage (Level 3 protection), such as Figure 2 ③ Linked release of extinguishing agent: Install a shear pin locking trigger mechanism 7 to replace the traditional latch-type trigger. For example... Figure 1 As shown, the shear pin locking trigger mechanism 7 includes a puncture needle 72, a shear pin 73, a spring 74, and a linkage mechanism 71; the spring 74 is fixed at a preset position inside the valve body 1 (in this embodiment, it is fixed on the partition plate 11); one end of the linkage mechanism 71 is connected to the weakening diaphragm 5 (specifically, connected to the center of the convex surface, such as...). Figure 1As shown), the other end is connected to the shear pin 73; one end of the puncture needle 72 is connected to the spring 74, and the other end is connected to the shear pin 73; a rubber damping ring is provided between the puncture needle 72 and the spring 74.

[0025] In practical use, such as Figure 4 As shown in (a), when the weakened diaphragm 5 is in its normal state, the puncture needle 72 is fixed in the position to be triggered, aligned with the extinguishing medium assembly 8, under the combined action of the spring 74 and the shear pin 73, which are in a compressed and energy-storing state. Figure 4 As shown in (b), when the weakened diaphragm 5 becomes unstable and flips over, the drive linkage mechanism 71 pulls the shear pin 73, causing the shear pin 73 to break under axial shear force. Simultaneously, the spring 74 is released, driving the puncture needle 72 to pierce the sealing membrane at the top of the extinguishing medium storage chamber 82. The entire linkage logic timing is shown in the diagram below. Figure 5 As shown, during the process, the shear pin 73 only responds to the axial tensile force, and the vibration direction is perpendicular to the shear plane, so there will be no accidental shearing. The shear pin locking trigger mechanism 7 adopts a purely mechanical linkage (diaphragm flipping, linkage driving, shear pin 73 breaking, spring 74 releasing energy, puncture), which does not rely on electricity. Even if the BMS fails during thermal runaway, it can still reliably trigger the mechanism. The anti-arching type instability and overturning is an instantaneous elastic instability, without a gradual process, and there is no intermediate state of slow leakage after vibration.

[0026] The extinguishing medium assembly 8 is installed at the confluence of the venting channel 2 and the pressure relief channel 3. In this embodiment, the extinguishing medium assembly 8 is installed at the end of the partition facing the bottom of the valve body 1 and is connected to the partition. In this embodiment, the extinguishing medium assembly 8 includes a built-in extinguishing medium storage chamber 82, which communicates with the independent discharge channel 81; a sealing membrane is provided on the top of the extinguishing medium storage chamber 82 corresponding to the shear pin locking trigger mechanism 7; the independent discharge channel 81 is provided with an atomizing nozzle 83 near the discharge port and a one-way valve 84 at a preset position away from the discharge port. In practical use, the extinguishing medium storage chamber 82 is filled with extinguishing medium, driven by a certain low-pressure nitrogen (N2). After being atomized by the atomizing nozzle 83, it is sprayed into the battery pack from the nozzle outlet through the independent discharge channel 81 and the bottom of the valve body 1. The driving pressures of 0.5MPa (low-pressure nitrogen drive, suitable for 50-100kWh pure electric vehicles) and 1.2MPa (high-pressure nitrogen drive, suitable for high-energy-density battery packs or scenarios requiring stronger extinguishing capabilities) are much greater than the internal pressure (0-0.02MPa, a difference of 20-60 times), and there is no pressure cancellation. The independent discharge channel 81 extends to the venting channel 2 rather than the pressure relief channel 3, avoiding the conflict between the extinguishing agent discharge and the large-flow exhaust of the pressure relief channel 3, ensuring that the pressure relief channel 3 is completely unobstructed and that the large-flow exhaust is smooth. A one-way valve 84 is provided at the end of the independent discharge channel 81 near the medium discharge port to prevent gas backflow from the battery pack.

[0027] In this embodiment, when the weakening diaphragm 5 flips, the center displacement pulls the Ø0.8mm brass shear pin 73 via the linkage mechanism 71. The shear pin 73 breaks under axial shear force, releasing the pre-tensioned spring 74 (spring 74 force 15~25N), driving the puncture needle 72 downward to pierce the sealing membrane at the top of the storage cavity. 50mL of perfluorohexanone in the storage cavity is driven by 0.5MPa low-pressure N2, atomized by the atomizing nozzle 83 (8×Ø0.8mm nozzles, 60° diffusion angle), and sprayed downward into the battery pack through an independent discharge pipeline (located on the side of the venting channel 2). The one-way valve 84 prevents gas backflow into the battery pack. An O-ring rubber damping ring is provided between the puncture needle 72 and the spring 74 to prevent the spring 74 from resonating and amplifying under vibration. At the same time, the natural frequency of the weakening diaphragm 5 is designed to be >2000Hz, which is higher than the upper limit of the vibration test frequency in GB38031.

[0028] The valve body 1 is equipped with a status feedback component 10, such as... Figure 7 and Figure 8 As shown, the state feedback component 10 is an interlocked state feedback hard-wired loop, which connects the weakening diaphragm 5 and the external battery management system 101 of the valve body 1, and is used to trigger the response of the battery management system 101 through the state switching of the weakening diaphragm 5.

[0029] In this embodiment, HVIL interlock status feedback is adopted, similar to the hard-wired loop design of high-voltage interlock (HVIL): Loop connection mode (normal state): BMS 12V output → conductive contact 103 (normally closed) → micro switch 102 (normally closed) → shear pin 73 (not broken, conductive) → return to BMS, forming a complete hard-wired loop. The BMS detects the loop continuity and determines that it is normal. Loop connection mode (trigger state): shear pin 73 breaks → loop is broken → BMS detects the open circuit → alarm is triggered. Independent of CAN bus: hard-wired signal, still usable after power failure (short-term detection is maintained by capacitor energy storage).

[0030] Specifically, a micro switch 102 is used to connect to the shear pin 73, and the micro switch 102 is connected to the battery management system 101 through conductive contacts 103. For example... Figure 7 As shown, under normal conditions, the shear pin 73 is not broken, the conductive contact 103 is closed, the interlocking state feedback hard-wired circuit is conducting, and the battery management system 101 determines that it is normal; Figure 8 As shown, when the weakening diaphragm 5 switches from the normal state to the flip state, the shear pin 73 breaks, the conductive contact 103 disconnects, the interlock state feedback hard wire circuit is disconnected, and the battery management system 101 alarms.

[0031] In this embodiment, during installation, as follows: Figure 1As shown, the mounting flange 9 is connected to the battery pack cover plate 12, and a sealing gasket 91 is provided between the mounting flange 9 and the battery pack cover plate 12 to ensure the sealing of the contact position between the valve body 1 and the battery box, meeting the IP67 protection requirements, and is fixed by 4 M6 bolts.

[0032] This embodiment provides a thermal runaway protection method for a power battery pack intelligent graded pressure relief valve, utilizing the aforementioned intelligent graded pressure relief valve for a power battery pack; the thermal runaway protection method includes: The internal air pressure of valve body 1 meets the first threshold condition (e.g.) Figure 2 After passing through the dotted line shown in ①, the first level of protection is implemented, including the circulation of gas inside and outside the valve body 1 through the breathable diaphragm 4; during the first level of protection and before the second level of protection is implemented, the weakened diaphragm 5 is in a normal state to partially block the discharge channel, and the shear pin locks the trigger mechanism 7 in a ready-to-be-triggered state. The internal air pressure of valve body 1 meets the second threshold condition (e.g.) Figure 2 After passing through the dotted line in ②, the second level of protection is implemented, including the weakening diaphragm 5 switching from the normal state to the flip state and breaking to avoid the venting channel and form a large-diameter venting channel, and the backfire prevention component 6 to allow the gas to flow inside and outside the valve body 1 and block backfire; during the second level of protection, the first level of protection continues to be implemented (i.e., the venting diaphragm 4 continuously allows the gas to flow inside and outside the valve body 1). Firefighting coordination implements Level 3 protection (such as...) Figure 2 As shown in ③, the weakening diaphragm 5 switches from the normal state to the flip state, driving the shear pin locking trigger mechanism 7 to trigger the action of the extinguishing medium assembly 8, so that the extinguishing medium inside the extinguishing medium assembly 8 is sprayed from the discharge port through the bottom of the valve body 1 into the battery pack; during the third-level protection process, the first-level protection continues to be performed and the backfire prevention assembly 6 is used to allow the gas flow inside and outside the valve body 1 and block backfire. When the weakened diaphragm 5 is in normal state, the interlock status feedback hard-wire circuit is connected, and the battery management system 101 determines that it is normal; when the weakened diaphragm 5 switches from normal state to flip state, the interlock status feedback hard-wire circuit is disconnected, and the battery management system 101 alarms.

[0033] It is understandable that the pressure relief valve described above can perform the above method, with the same process and effect, so it will not be described again here.

[0034] This embodiment provides an intelligent graded pressure relief valve and thermal runaway protection method for a power battery pack. By optimizing the structure of the pressure relief valve, a multi-level linkage, purely mechanical thermal runaway defense system is constructed, realizing intelligent and safe battery protection from daily pressure difference airflow balance to emergency pressure relief and active fire extinguishing.

[0035] Example 2 Unlike Embodiment 1, this embodiment is applicable to high-energy-density battery packs or scenarios requiring stronger fire extinguishing capabilities, and provides a high-pressure storage type intelligent graded pressure relief valve.

[0036] The valve body 1 is made of 316L stainless steel, offering enhanced corrosion resistance. The weakening diaphragm 5 is made of TA2 titanium alloy, with a diameter of Ø35mm, a thickness of 0.25mm, an arch height of 4-6mm, and six spiral weakening grooves 51 engraved on its concave surface (groove depth approximately 80% of the wall thickness), and a burst pressure of 20kPa. The extinguishing medium is 30mL aerosol, stored under 1.2MPa high pressure. The atomizing nozzle 83 has 12×Ø0.6mm nozzle holes and a 90° diffusion angle. The backfire prevention assembly 6 is a 4-level labyrinth with two layers of 150-mesh metal fire-resistant mesh 62, and the labyrinth channel cross-sectional area is ≥50%. The shear pin 73 is made of Ø1.0mm stainless steel, suitable for higher spring force 74.

[0037] Example 3 Unlike Embodiments 1 and 2, this embodiment provides an active control type intelligent graded pressure relief valve. A method for thermal runaway protection of an intelligent graded pressure relief valve for a power battery pack includes: A pressure sensor (range 0-100kPa) and a temperature sensor (range 0-200℃) are installed inside the valve body 1. The data is transmitted to the battery management system 101 via a CAN bus. The collected pressure and temperature data are used to trigger the fire suppression linkage in advance according to a preset strategy. When the sensor detects that the internal pressure is close to the rupture threshold (e.g., >12kPa) or the temperature rises abnormally (e.g., >80℃), the BMS can actively control the solenoid valve group to trigger the fire suppression linkage in advance, realizing dual protection of passive triggering and active prevention. The specific strategy can be reasonably set according to the actual battery conditions.

[0038] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics of the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A smart graded pressure relief valve for a power battery pack, characterized in that, Including a hollow valve body; The upper part of the valve body has an independent venting channel and a pressure relief channel; the middle part of the valve body is equipped with a fire extinguishing medium component; the bottom of the valve body is equipped with a mounting flange for connecting to the inside of the battery pack. A breathable diaphragm is installed at the outlet end of the venting channel to allow gas to flow between the inside and outside of the valve body; A backfire prevention component is installed at the outlet end of the pressure relief channel to facilitate the flow of gas between the inside and outside of the valve body and to prevent backfire. A weakening diaphragm with an anti-arch grooved structure is installed at a preset position away from the outlet end of the pressure relief channel; the weakening diaphragm is affected by the internal pressure of the valve body and has a normal state and an overturned state, which are used to partially block and avoid the pressure relief channel respectively. The independent discharge channel of the extinguishing medium assembly extends into the venting channel; the discharge port of the independent discharge channel faces the bottom of the valve body; The weakened diaphragm is connected to a shear pin locking trigger mechanism that aligns with the fire extinguishing medium assembly; The shear pin locking trigger mechanism is driven by the weakened diaphragm switching flip state to trigger the action of the fire extinguishing medium assembly.

2. The intelligent graded pressure relief valve for a power battery pack according to claim 1, characterized in that, A partition extends from the top of the valve body to a preset position in the middle to form two parallel zones, which serve as a ventilation channel and a pressure relief channel, respectively. The fire extinguishing medium assembly is installed at the end of the partition facing the bottom of the valve body and is connected to the partition. The shear pin locking trigger mechanism is located in the pressure relief channel and is installed on the partition, above the fire extinguishing medium assembly.

3. The intelligent graded pressure relief valve for a power battery pack according to claim 1, characterized in that, The breathable diaphragm is fixed to the top stepped surface of the valve body by a sealing ring, and the back of the breathable diaphragm facing the bottom of the valve body is supported and fixed by a support frame.

4. The intelligent graded pressure relief valve for a power battery pack according to claim 1, characterized in that, The weakening diaphragm with an anti-arch grooved structure includes a convex surface and a concave surface; the concave surface is engraved with a weakening groove of a preset shape, and the convex surface faces the bottom of the valve body in the normal state so that the weakening diaphragm is subjected to compressive stress in the normal state; the outer circumference of the weakening diaphragm is installed on the inner wall of the valve body, and the center apex of the convex surface is connected to a shear pin to lock the trigger mechanism.

5. The intelligent graded pressure relief valve for a power battery pack according to claim 4, characterized in that, The preset shapes include any one or a combination of cross, ring, and spiral.

6. The intelligent graded pressure relief valve for a power battery pack according to claim 1, characterized in that, The shear pin locking trigger mechanism includes a puncture needle, a shear pin, a spring, and a linkage mechanism. The spring is fixed at a preset position inside the valve body. One end of the linkage mechanism is connected to the weakened diaphragm, and the other end is connected to the shear pin. One end of the puncture needle is connected to the spring, and the other end is connected to the shear pin. A rubber damping ring is provided between the puncture needle and the spring. When the weakened diaphragm is in its normal state, the puncture needle is fixed at the trigger position aligned with the extinguishing medium assembly under the combined action of the spring and the shear pin, which are in a compressed and energy-storing state.

7. The intelligent graded pressure relief valve for a power battery pack according to claim 1, characterized in that, The extinguishing medium assembly includes an extinguishing medium storage chamber connected to an independent discharge channel; the independent discharge channel is equipped with an atomizing nozzle near the discharge port and a one-way valve at a preset position away from the discharge port.

8. The intelligent graded pressure relief valve for a power battery pack according to claim 1, characterized in that, The valve body is equipped with an interlocking state feedback hard-wired loop, which connects the weakened diaphragm and the external battery management system, and is used to trigger the battery management system response through the state switching of the weakened diaphragm.

9. A method for thermal runaway protection of a smart graded pressure relief valve for a power battery pack, characterized in that, The method for thermal runaway protection utilizes an intelligent graded pressure relief valve for a power battery pack as described in any one of claims 1-8, comprising: Once the internal air pressure of the valve body meets the first threshold condition, the first level of protection is implemented, including the circulation of gas inside and outside the valve body through the breathable diaphragm. After the internal air pressure of the valve body meets the second threshold condition, the second level of protection is implemented, including the weakening diaphragm switching from the normal state to the flip state and rupturing to avoid the venting channel and form a large-diameter venting channel, and the flow of gas inside and outside the valve body and the blocking of backfire through the anti-backfire component. The fire suppression linkage executes the third level of protection, including the weakening diaphragm switching from the normal state to the flip state, driving the shear pin to lock the trigger mechanism to trigger the action of the fire extinguishing medium assembly, so that the fire extinguishing medium inside the fire extinguishing medium assembly is sprayed from the discharge port through the bottom of the valve body into the battery pack. When the weakened diaphragm is in its normal state, the interlock status feedback hard-wired circuit is active, and the battery management system determines that it is normal; when the weakened diaphragm switches from the normal state to the flip state, the interlock status feedback hard-wired circuit is disconnected, and the battery management system alarms.

10. A method for thermal runaway protection of a power battery pack intelligent graded pressure relief valve according to claim 9, characterized in that, Also includes: Pressure and temperature sensors are installed in the valve body, and the data is transmitted to the battery management system via CAN bus. The collected pressure and temperature data are used to trigger the fire suppression linkage in advance according to the preset strategy.

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