Sma door unlock device in response to battery pack over temperature

Abstract

The utility model relates to a kind of SMA vehicle door unlocking device in response to battery pack overtemperature, it is related to vehicle safety technical field.The device includes a shell made of heat-conducting material and with battery pack thermal connection, and temperature sensing shape memory wire is arranged in its inside.Metal wire one end is fixed to shell, the other end is as free telescopic end and is connected to vehicle door unlocking puller.When battery pack overheating, heat conduction makes the temperature in shell reach the phase transition trigger temperature of metal wire, metal wire will occur shrinkage deformation, directly mechanically pull unlocking puller, to drive door lock mechanism to realize vehicle door unlocking.The utility model uses pure mechanical structure, does not need power, in the emergency situation that battery thermal runaway leads to whole vehicle power failure, for passenger provides a reliable, automatic safety escape passage.

Description

Technical Field

[0001] This utility model relates to the field of new energy vehicle safety technology, specifically to an SMA door unlocking device that responds to battery pack overheating. Background Technology

[0002] In recent years, with the popularization of new energy vehicles for home use, the safety performance of these vehicles in the event of an accident or malfunction has received increasing attention. Pure electric and hybrid vehicles are generally equipped with low-voltage power supplies for communication and control, which are prone to short circuits and other malfunctions that can cause fires or even explosions after an accident, resulting in extremely short escape time for occupants. At the same time, new energy vehicles often use electronically controlled door systems; when the vehicle loses power or the circuit fails, the doors often cannot be opened electrically. If occupants are incapacitated, this will greatly hinder external rescue efforts and exacerbate personal safety risks. The "Safety Technical Requirements for Automobile Door Handles" clearly requires that electric door handles be equipped with independent mechanical unlocking devices to ensure reliable door opening in emergencies.

[0003] In existing technologies, there are various solutions aimed at solving the emergency door unlocking problem. For example, some solutions trigger door unlocking based on airbag ignition signals, collision sensor signals, or complex multi-sensor information fusion algorithms. However, these solutions still rely on the vehicle's electronic control unit (ECU) and circuit system for logical judgment and signal transmission, posing a risk of malfunction if the circuit system fails before the triggering condition. Other solutions use independent temperature-sensitive memory metal elements on the door, but their installation location is far from the battery pack, a major source of heat risk, resulting in a long heat transfer path and significant response delay, which is detrimental to rapid escape in time-sensitive emergencies.

[0004] Therefore, there is an urgent need in the field for an automatic mechanical door unlocking solution that can fundamentally avoid dependence on the vehicle's main circuitry and can quickly respond to battery pack thermal risks. Utility Model Content

[0005] In response to the problems and shortcomings of existing technologies, this utility model provides an SMA door unlocking device that responds to battery pack overheating. It aims to drive the door lock mechanism to achieve purely mechanical unlocking by directly responding to the heat source of the battery pack through a temperature-sensitive shape memory metal wire. This allows for the rapid creation of escape conditions for occupants before the environment in the passenger compartment deteriorates, and significantly improves the efficiency of external rescue.

[0006] The technical solution of this utility model is as follows: A SMA (Surface Mounted Car Door) unlocking device responsive to battery pack overheating is characterized by comprising a housing made of thermally conductive material, configured to connect to the vehicle battery pack and conduct heat from the battery pack to the housing. Within the housing is at least one temperature-sensitive shape memory metal wire, one end of which is fixedly connected to the housing, and the other end is a freely retractable end connected to the vehicle's door unlocking pull. When the ambient temperature of the housing reaches the phase transition trigger temperature of the temperature-sensitive shape memory metal wire, the wire contracts, thereby actuating the door unlocking pull and mechanically unlocking the door. This provides a reliable and safe unlocking mechanism in case of battery pack overheating.

[0007] Unless otherwise specified, the term "connection" in this patent should be broadly interpreted to include direct or indirect connections. For example, the connection between the aforementioned free telescopic end and the vehicle door unlocking pull can be a direct connection or a connection through a transmission mechanism.

[0008] Furthermore, the housing can be attached to the top or side of the battery pack to accommodate different installation space and heat conduction path requirements. The housing includes a body and a top cover. The body has mounting holes for connecting to the battery pack, and the top cover has connection holes for connecting to the top cover, facilitating assembly and ensuring structural stability.

[0009] To improve transmission reliability and protect internal components, the device is also equipped with a flexible sleeve, one end of which is connected to the outer shell and the other end to the door lock housing; the door unlocking pull is inserted inside the flexible sleeve and can move along it, thereby avoiding external interference and ensuring smooth operation.

[0010] In one embodiment, the free-extending end of the temperature-sensitive shape memory wire is connected to the door unlocking pull via a transmission mechanism. This transmission mechanism is designed to amplify the transmission stroke of the contraction action of the temperature-sensitive shape memory wire in at least one transmission link, thereby achieving sufficient unlocking displacement with a small amount of wire contraction.

[0011] Specifically, the transmission mechanism can be a lever transmission mechanism, including a lever and a pull rod; one end of the lever is connected to the free extension end of the shape memory metal wire, and the other end is connected to one end of the pull rod, and a certain point in the length direction of the lever is connected to the outer shell through a rotating shaft, so that the length of the input end of the lever is less than the length of the output end, thereby forming a stroke amplification effect; the other end of the pull rod is connected to the door unlocking pull to realize the transmission of force.

[0012] More preferably, the lever is designed as a "T" shaped lever, with its head connected to the output end of the lever and its tail connected to the door unlocking lever; the lever has two parts and is symmetrically arranged on both sides of the head of the lever, and the input end of each lever is connected to the free extension end of a temperature-sensitive shape memory metal wire. The two metal wires are symmetrically arranged relative to the lever, which can balance the force and improve the reliability of the action.

[0013] In terms of structural guidance, the head of the pull rod slides into the first guide groove inside the housing, and the tail of the pull rod is connected to the door unlocking pull via the first connector; the first connector also slides into the second guide groove inside the housing, thus ensuring the accuracy of the movement direction. The movement direction of the pull rod is parallel to the extension and retraction direction of the temperature-sensitive shape memory metal wire, and the extension directions of the first and second guide grooves are also parallel to the axis of the metal wire. This optimizes the spatial layout of the transmission mechanism and the temperature-sensitive shape memory metal wire, thereby making the housing as small as possible within a limited space to meet installation requirements.

[0014] In another embodiment, the free extension end of the temperature-sensitive shape memory metal wire is connected to the door unlocking pull piece through a transmission mechanism. This transmission mechanism can change the direction of the temperature-sensitive shape memory metal wire multiple times, thereby increasing the arrangement length of the metal wire in a unit space, accumulating the total length, increasing the total shrinkage at the phase change trigger temperature, and enhancing the effectiveness of the unlocking action.

[0015] For example, the transmission mechanism can adopt a pulley direct transmission mechanism, including two rows of reversing wheels arranged in parallel and staggered manner; after the temperature-sensitive shape memory metal wire passes around the two rows of reversing wheels in a zigzag pattern, its free extension and retraction end is connected to the door unlocking pull piece, which effectively utilizes space and accumulates contraction displacement through multiple reversals.

[0016] In this pulley direct drive structure, the free extension end of the temperature-sensitive shape memory metal wire is connected to the door unlocking pull piece through the second connector, and the second connector slides into the third guide groove inside the housing; at the same time, a pre-tensioning spring is connected between the side of the second connector near the door unlocking pull piece and the end of the third guide groove, which is used to maintain the normal tension of the metal wire and reset it after action.

[0017] In another embodiment, the temperature-sensitive shape memory wire is also electrically connected to a control circuit, which is configured to energize the wire upon receiving a trigger signal, thereby heating it to the phase change trigger temperature through electrothermal means. This allows the device to be unlocked by an electrical signal even when it is not overheated, enhancing the applicability and control flexibility of the device.

[0018] It should be noted that this utility model aims to provide a new triggering mechanism for known door unlocking pullers in the prior art. Therefore, the SMA door unlocking device of this utility model should be protected as an independent product. The door unlocking puller can be fully adapted to various vehicles and models, and its functions can still be realized based on the specific designs of different vehicles, models, and door handles and locks. These functions include, but are not limited to: Ⅰ. The door handle can be ejected directly or the door can be opened automatically through the triggering mechanism provided by the SMA door unlocking device of this utility model; II. The door lock is switched to a manually operable state by means of the triggering mechanism provided by the SMA door unlocking device of this utility model (allowing the door to be opened further by operating the door handle). III. The triggering mechanism provided by the SMA door unlocking device of this utility model, in conjunction with other unlocking mechanisms, can collaboratively implement the functions in point I or point II above.

[0019] The beneficial effects of this utility model are: By directly connecting the device to the battery pack, a critical heat source, and utilizing a highly thermally conductive casing, the device can detect overheating signals in the battery pack immediately, significantly shortening the heat conduction path and time. This allows the temperature-sensitive shape memory wire to trigger unlocking before flames and high-temperature smoke spread to the crew compartment, creating a crucial "golden window" for occupant escape and external rescue.

[0020] The entire unlocking process does not rely on the vehicle's electrical system or any control unit. Even in the worst-case scenario where the vehicle is completely powered off and the electronic control system fails, it can still work reliably based on physical principles (thermotropic phase change of SMA), exhibiting extremely high robustness and security.

[0021] As a passive safety mechanism, this device can automatically unlock without any operation from occupants or rescue personnel. This is especially significant for occupants who may be unconscious or disabled during an accident, ensuring the automatic opening of rescue routes.

[0022] With its optimized transmission mechanism and flexible sheath design, the device has a simple and compact overall structure, making it easy to install and adapt within the limited layout space of a vehicle. It can meet the diverse needs of different vehicle models for the travel and layout path of the door unlocking pull. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the working principle of this embodiment; Figure 2 This is a schematic diagram of the overall structure of an embodiment of the present utility model; Figure 3This is a schematic diagram of the transmission mechanism of one example in an embodiment of the present utility model; Figure 4 This is a schematic diagram of the transmission mechanism in another example of this utility model embodiment.

[0024] The components represented by the reference numerals in the diagram are: 1. Outer shell; 11. Mounting hole; 12. First guide groove; 13. Second guide groove; 14. Top cover connecting hole; 15. Third guide groove; 2. Temperature-sensitive shape memory metal wire; 3. Lever transmission mechanism; 31. Lever; 311. Rotating shaft; 32. Pull rod; 33. First connecting piece; 4. Pulley direct transmission mechanism; 41. Reversing wheel; 42. Second connecting piece; 43. Preload spring; 5. Door unlocking pull piece; 6. Flexible protective sleeve. Detailed Implementation

[0025] The technical means adopted to achieve the intended purpose of this utility model will be further described below with reference to the accompanying drawings of the embodiments of this utility model.

[0026] Example 1 This embodiment provides an SMA door unlocking device responsive to battery pack overheating. Its core lies in using a mechanical structure to respond to battery pack overheating and automatically actuate the door unlocking mechanism, enabling door unlocking in emergency situations. See also Figures 1-4 The device mainly includes a housing 1, a temperature-sensitive shape memory metal wire 2 (SMA wire), and a transmission mechanism.

[0027] The outer casing 1, serving as the load-bearing and heat-conducting foundation for the entire device, is typically made of high-temperature resistant metal materials such as aluminum alloy, copper, and stainless steel, which combine good thermal conductivity with structural strength to minimize heat transfer time. Simultaneously, casing 1 is used to house, package, and secure other internal sub-components and other external devices necessary for door unlocking, and provides guidance for moving and traction components. See also Figure 1 It is designed to connect to the vehicle battery pack, preferably fixed to the top of the vehicle battery pack and as close as possible to the bottom of the passenger compartment to sense changes in battery pack temperature via the shortest path. Referring to Figure 2, the housing 1 preferably adopts a split structure, including a main body and a top cover fixed via a connecting hole 14, facilitating the installation and maintenance of internal components. The bottom of the main body is provided with mounting holes 11 for reliably installing the device at a designated location on the battery pack using bolts or other fasteners, ensuring efficient heat transfer to the interior of the housing.

[0028] In addition to installation via mounting holes 11 and fasteners as shown in the diagram, this unlocking device can also be flexibly installed on the top, side, or adjacent area of ​​the battery pack using any method such as snap-fit, riveting, welding, or bonding. Furthermore, without deviating from the basic purpose of heat transfer, the device can be in direct or indirect contact with the battery pack. For example, to facilitate installation and heat transfer, and to optimize the heat-receiving area, other auxiliary installation or heat transfer components can be added between the device housing 1 and the battery pack. Alternatively, to optimize thermal management efficiency, a high thermal conductivity interface material (such as thermal grease or a phase change thermal pad) can be added between the device housing 1 and the battery pack to ensure timely and reliable heat transfer.

[0029] A temperature-sensitive shape memory wire 2 is disposed within the internal cavity of the outer casing 1. It is typically made of an alloy material with a significant shape memory effect, such as nickel-titanium alloy, and is trained to be in the martensitic phase at room temperature, possessing a relatively long length. When the temperature rises to its austenitic phase transformation completion temperature, the material undergoes a phase transformation, restoring to the short shape remembered during training, resulting in significant shrinkage deformation. In this embodiment, the temperature-sensitive shape memory wire 2 is made of nickel-titanium alloy, with the phase transformation temperature selected in the range of, for example, 85–95°C. One end of the temperature-sensitive shape memory wire 2 is connected to the inner wall of the outer casing 1 via a fixed point, while the other end is a free-extending end connected to the vehicle door unlocking pull member 5. To reliably transmit motion to the door lock body and adapt to the relative movement and wiring environment between the vehicle floor and the door, the door unlocking pull member 5 is made of a high-strength, fatigue-resistant material, and a flexible sheath 6 is fitted over the outside of the door unlocking pull member 5. One end of the flexible sleeve 6 is fixedly connected to the outer shell 1, and the other end is fixedly connected to the door lock housing. The door unlocking pull member 5 passes through the interior of the flexible sleeve 6 and can slide freely along the axial direction within it. During operation, the flexible sleeve can maintain the distance between the device and the door lock, thereby adapting to the distance requirements between the door lock and the device for different vehicle models, and facilitating the adaptation to different pull rod arrangement requirements. At the same time, the flexible sleeve 6 serves to prevent dust, water, and interference, and also guide the wiring harness.

[0030] Furthermore, the free extension end of the aforementioned temperature-sensitive shape memory metal wire 2 is connected to the vehicle door unlocking pull piece 5 through a transmission mechanism, and the transmission mechanism is configured such that the transmission stroke of the contraction action of the temperature-sensitive shape memory metal wire 2 is amplified in at least one transmission link.

[0031] The transmission mechanism is a key component that connects the retraction action of the temperature-sensitive shape memory metal wire 2 with the movement of the door unlocking pull piece 5, and it is located inside the housing 1. Depending on different spatial layouts and stroke amplification requirements, the transmission mechanism can have different implementation methods.

[0032] See Figure 3In this embodiment, the transmission mechanism adopts a lever transmission mechanism 3. This mechanism includes a lever 31 and a pull rod 32. A point on the length of the lever 31 is rotatably connected to the inner wall of the outer casing 1 through a pivot 311, forming a fulcrum. One end (input end) of the lever 31 is connected to the free extension end of the temperature-sensitive shape memory metal wire 2, and the other end (output end) is connected to one end of the pull rod 32. In order to amplify the limited contraction displacement of the temperature-sensitive shape memory metal wire 2, the lever 31 is usually designed as an unequal-arm lever, that is, the arm length of the input end is smaller than the arm length of the output end. The pull rod 32 is preferably arranged parallel to the temperature-sensitive shape memory metal wire 2 to optimize the spatial layout. The pull rod 32 can be designed as a "T"-shaped rod, with the upper part of its head (crossbar part) connected to the output end of the lever 31. In order to enhance the stability and reliability of the action, two temperature-sensitive shape memory metal wires 2 and two levers 31 can be symmetrically arranged, respectively connected to the two sides of the head of the "T"-shaped pull rod 32, to jointly drive the pull rod 32 to move. The head of the pull rod 32 slides into the first guide groove 12 located on the inner wall of the housing 1, while the tail (vertical rod portion) is connected to the door unlocking pull piece 5 extending to the outside of the housing via the first connector 33. The first connector 33 also has a structure that slides into the second guide groove 13 on the inner wall of the housing 1. Specifically, the lower parts of the head and tail of the pull rod 32 slide into the first guide groove 12 and the second guide groove 13, respectively. Furthermore, the extending directions of the first guide groove 12 and the second guide groove 13 are parallel to the axis of the temperature-sensitive shape memory metal wire 2. The first guide groove 12 and the second guide groove 13 work together to ensure that the pull rod 32 and the first connector 33 can only move along a predetermined straight trajectory, preventing skew and jamming, and improving transmission accuracy and reliability.

[0033] Under normal vehicle conditions, the temperature-sensitive shape memory wire 2 is in the martensitic phase and has a relatively long length. The lever transmission mechanism 3 is in its initial position, and the door remains locked. When the vehicle battery pack overheats due to a malfunction or other reasons, heat is rapidly transferred to the interior through the highly thermally conductive outer shell 1. When the internal ambient temperature of the outer shell 1 reaches the phase transformation trigger temperature of the temperature-sensitive shape memory wire 2, the wire 2 undergoes an austenitic phase transformation, and its length shortens dramatically. This contraction action generates a clockwise driving torque (e.g., ...) on the input end of the lever 31. Figure 3 As shown in the diagram, a leftward driving force and displacement are generated at the output end of lever 31. This displacement is amplified (because the arm length at the input end is less than the arm length at the output end) and ultimately achieves linear traction of the door unlocking pull member 5 via pull rod 32. The door unlocking pull member 5 overcomes the holding force of the door lock mechanism and moves to the unlocked position, thereby achieving mechanical unlocking of the door and providing a passage for occupant escape or external rescue. The entire process is completely mechanically driven, independent of the vehicle's electrical circuitry, and is fast-responding, safe, and reliable.

[0034] Example 2 See Figure 4In this embodiment, the transmission mechanism adopts a pulley direct transmission mechanism 4, which mainly includes two rows of parallel and staggered reversing wheels 41. The temperature-sensitive shape memory metal wire 2 passes around these reversing wheels 41 in a zigzag path, forming a transmission path similar to a pulley block. This increases the arrangement length of the temperature-sensitive shape memory metal wire 2 in a unit space, accumulating the total length to increase its total contraction at the phase change trigger temperature, thus ensuring the effectiveness of the unlocking action. The fixed end of the temperature-sensitive shape memory metal wire 2 is connected to the outer casing 1 through a wire terminal, while its movable end is connected to the door unlocking pull member 5 through a second connector 42. The bottom of the second connector 42 slides in conjunction with a third guide groove 15 located inside the outer casing 1 to ensure its direction of movement. This transmission method cleverly controls the length of the temperature-sensitive shape memory metal wire 2 in a limited space through the two rows of parallel and staggered reversing wheels 41, accumulating its total contraction deformation length at the phase change trigger temperature, thereby flexibly adapting to the needs of the unlocking action and simultaneously optimizing the overall volume of the device assembly.

[0035] In this embodiment, preferably, the pulley direct drive mechanism 4 is composed of one or more pulleys, bearings, buckles, and other components. Furthermore, the arrangement of the reversing wheels 41 in this embodiment is a preferred implementation, but other arrangements can also be used, such as circular or other irregular shapes, as long as they can increase the length of the temperature-sensitive shape memory metal wire 2 within a unit space, allowing its contraction at the phase change trigger temperature to achieve the unlocking displacement. Alternatively, the reversing wheels 41 can be replaced with other components capable of supporting the temperature-sensitive shape memory metal wire 2 arranged around or along them, with the aim of ensuring that the temperature-sensitive shape memory metal wire 2 is laid along a predetermined trajectory to achieve the unlocking length.

[0036] To maintain tension in the drivetrain when not triggered and to ensure the door unlocking pull 5 is in the accurate initial position, a preload spring 43 is provided between the side of the second connector 42 near the door unlocking pull 5 and the end of the third guide groove 15. Preferably, two preload springs 43 are arranged side-by-side to provide preload force to the door unlocking pull 5, reducing wasted stroke during operation.

[0037] Under normal vehicle conditions, the temperature-sensitive shape memory metal wire 2 is in the martensitic phase and has a relatively long length. The door unlocking pull 5 is in its initial position under the action of the pre-tension spring, and the door remains locked. When the vehicle battery pack overheats due to malfunction or other reasons, the heat is rapidly transferred to the interior through the highly thermally conductive outer shell 1. When the internal ambient temperature of the outer shell 1 reaches the phase transformation trigger temperature of the temperature-sensitive shape memory metal wire 2, the wire undergoes an austenitic phase transformation, and its length shortens drastically. Because the temperature-sensitive shape memory metal wire 2 is wound in multiple zigzag patterns along multiple guide wheels, its length within the limited space of the outer shell 1 reaches a length sufficient for the total contraction during shortening to pull the door lock mechanism to unlock, and is ultimately unlocked by the door unlocking pull 5.

[0038] As can be seen, the above embodiments of this utility model, by directly arranging the SMA door unlocking device, which responds to battery pack overheating, in the critical hot area of ​​the battery pack, especially at the top, and in conjunction with a high thermal conductivity shell, can quickly detect battery overheating, significantly shortening the heat conduction path and time. The temperature-sensitive shape memory metal wire 2 can therefore trigger unlocking before flames and high-temperature smoke spread to the passenger compartment, providing a crucial "golden window" for occupant escape and external rescue. Furthermore, the unlocking process responding to battery temperature does not rely on the vehicle's electrical system or control unit. Even in extreme situations such as vehicle power failure or electronic control malfunction, it can still operate reliably based on the SMA thermo-phase change principle, exhibiting extremely high robustness and safety.

[0039] Example 3 This embodiment, based on Embodiment 1 or Embodiment 2, further enhances the applicability of the device by selecting the following two parallel heating paths: ① directly transferring heat to the temperature-sensitive shape memory metal wire 2 through the environment and the outer casing; ② controlling the circuit to energize the temperature-sensitive shape memory metal wire 2 to achieve an electrothermal effect. In this embodiment, the temperature-sensitive shape memory metal wire 2 is connected to a control circuit that can receive trigger signals from vehicle collision sensors, smoke detectors, or other safety systems. Upon receiving a signal, the control circuit energizes the temperature-sensitive shape memory metal wire 2, utilizing its own resistance to generate Joule heating, rapidly raising its temperature to the phase change trigger temperature, thereby achieving active unlocking in the electrical trigger mode as a supplement to the thermal trigger mode. This further achieves the beneficial effect of using the same trigger mechanism for different accident types.

[0040] It should be noted that the embodiments of this utility model are intended to provide a new triggering mechanism for the door unlocking pull member 5. The door unlocking pull member 5 can be designed to be compatible with various vehicles and models. Its length, spatial routing, and layout can be customized according to the door lock and battery pack positions and installation space of different models. The specific force range required for the temperature-sensitive shape memory metal wire 2 in the above embodiments (for example, the unlocking pull force required for a certain model is not less than 250N) can also be easily designed or tested and adjusted as needed. This is all within the basic capabilities of those skilled in the art. Moreover, based on the working principle described in the embodiments of this utility model, this utility model has wide applicability to various vehicles in the prior art. It can be directly coupled to rigid and / or flexible unlocking components such as door unlocking pull rods and pull cables of various vehicles (including traditional hybrid vehicles and electric vehicles) to drive the door to unlock. The door lock structure and working principle involved are all well-known technologies in the field. For specific details, please refer to existing technologies such as CN101963020A, CN206600085U, CN107448073B, and CN120625990A for door lock devices or unlocking mechanisms. Those skilled in the art, after understanding the principle of this utility model, can directly combine the technical solution of this utility model with the aforementioned existing technologies and other similar existing technologies that are easily accessible to those skilled in the art, or replace or modify them using well-known technical means. Therefore, the SMA door unlocking device of this utility model should be protected as an independent product.

Claims

1. A SMA door unlocking device responsive to battery pack overheating, characterized in that, include: The housing (1), made of a thermally conductive material, is configured to be connected to the vehicle battery pack and the heat of the battery pack can be conducted to the housing (1); At least one temperature-sensitive shape memory metal wire (2) is disposed inside the housing (1), one end of which is fixedly connected to the housing (1), and the other end is a free telescopic end, which is connected to the vehicle door unlocking pull piece (5); When the ambient temperature of the outer shell (1) reaches the phase change trigger temperature of the temperature-sensitive shape memory metal wire (2), the temperature-sensitive shape memory metal wire (2) contracts and drives the door unlocking pull (5) to move, thereby realizing the mechanical unlocking of the door.

2. The SMA door unlocking device in response to battery pack overheating according to claim 1, characterized in that, The outer casing (1) is attached to the top or side of the battery pack.

3. The SMA door unlocking device in response to battery pack overheating according to claim 1, characterized in that, The housing (1) includes a body and a top cover. The body is provided with a mounting hole (11) for connecting to a battery pack and a top cover connection hole (14) for connecting to the top cover.

4. The SMA door unlocking device in response to battery pack overheating according to claim 1, characterized in that, It also includes a flexible sheath (6), one end of which is connected to the outer shell (1) and the other end is connected to the door lock housing. The door unlocking puller (5) passes through the interior of the flexible sheath (6) and can move along it.

5. The SMA door unlocking device in response to battery pack overheating according to any one of claims 1-4, characterized in that, The free telescopic end is connected to the vehicle door unlocking pull piece (5) through a transmission mechanism. The transmission mechanism is configured such that the transmission stroke of the contraction action of the temperature-sensitive shape memory metal wire (2) is amplified in at least one transmission link.

6. The SMA door unlocking device in response to battery pack overheating according to claim 5, characterized in that, The transmission mechanism is a lever transmission mechanism (3), including a lever (31) and a pull rod (32). One end of the lever (31) is connected to the free extension end of the temperature-sensitive shape memory metal wire (2), and the other end is connected to one end of the pull rod (32). A point in the length direction of the lever (31) is connected to the outer shell (1) through a pivot (311), so that the length of the input end of the lever (31) is less than the length of the output end. The other end of the pull rod (32) is connected to the door unlocking pull piece (5) of the vehicle.

7. The SMA door unlocking device in response to battery pack overheating according to claim 6, characterized in that, The pull rod (32) is a "T" shaped rod, with its head connected to the output end of the lever (31) and its tail connected to the door unlocking pull piece (5). The lever (31) has two parts, which are symmetrically arranged on both sides of the head of the pull rod (32). The input end of each lever (31) is connected to the free extension end of a temperature-sensitive shape memory metal wire (2). The two temperature-sensitive shape memory metal wires (2) are symmetrically arranged relative to the pull rod (32).

8. The SMA door unlocking device in response to battery pack overheating according to claim 7, characterized in that, The head of the pull rod (32) is slidably engaged with the first guide groove (12) provided in the housing (1), and the tail of the pull rod (32) is connected to the door unlocking pull member (5) through the first connector (33); the first connector (33) is slidably engaged with the second guide groove (13) provided in the housing (1).

9. The SMA door unlocking device in response to battery pack overheating according to any one of claims 1-4, characterized in that, The free telescopic end is connected to the vehicle door unlocking pull piece (5) through a transmission mechanism. The transmission mechanism is configured to change the direction of the temperature-sensitive shape memory metal wire (2) multiple times, increase the arrangement length of the temperature-sensitive shape memory metal wire (2) in a unit space, accumulate the total length, and increase the total shrinkage at the phase change trigger temperature.

10. The SMA door unlocking device in response to battery pack overheating according to claim 9, characterized in that, The transmission mechanism is a pulley direct transmission mechanism (4), which includes two rows of parallel and staggered reversing wheels (41). The temperature-sensitive shape memory metal wire (2) passes around the two rows of reversing wheels (41) in a zigzag pattern, and its free extension end is connected to the door unlocking pull piece (5).

11. The SMA door unlocking device in response to battery pack overheating according to claim 10, characterized in that, The free extension end of the temperature-sensitive shape memory metal wire (2) is connected to the door unlocking pull member (5) through the second connector (42). The second connector (42) is slidably engaged with the third guide groove (15) provided in the housing (1). A pre-tensioning spring (43) is connected between the side of the second connector (42) near the door unlocking pull member (5) and the end of the third guide groove (15).

12. The SMA door unlocking device in response to battery pack overheating according to any one of claims 1-4, characterized in that, The temperature-sensitive shape memory metal wire (2) is also electrically connected to a control circuit, which is configured to energize the temperature-sensitive shape memory metal wire (2) after receiving a trigger signal, so as to heat it to the phase change trigger temperature by electrothermal means.

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