Variable axial force energy absorption box

Abstract

This invention discloses a variable axial force energy-absorbing box, comprising a front connecting plate, a shell, and a rear connecting plate. The front connecting plate is installed at the front end of the shell, and the rear connecting plate is installed at the rear end. The shell contains a variable force structure sealed at both ends, filled with magnetorheological fluid. The outer wall of the variable force structure and the inner wall of the shell form a cavity. The side wall of the variable force structure has a pressure-deformable and conductive pressure-relieving structure. The rear connecting plate has a magnetic field coil and several connecting holes, through which the cavity communicates with the outside. This invention offers multi-level adjustable energy absorption, efficient control logic, good collapsible deformation coordination, uniform structural stress distribution, excellent overall reliability and sealing, optimized magnetorheological fluid flow path, high damping adjustment linearity, compact structure, high feasibility for processing, assembly, and mass production, wide application range, and outstanding safety protection.

Description

Technical Field

[0001] This invention relates to a variable axial force energy-absorbing box. Background Technology

[0002] In vehicle collisions, energy-absorbing boxes, as core buffer components at the front or rear of the vehicle, directly affect the efficiency of collision energy absorption and the integrity of the occupant survival space. Traditional energy-absorbing boxes mostly adopt thin-walled metal structures, achieving fixed-mode energy absorption through preset crumple paths. However, they cannot adjust the energy absorption effect according to dynamic conditions such as collision speed and obstacle type, making it difficult to achieve optimal protective performance in different collision scenarios.

[0003] To address the challenge of adjustable energy absorption performance, intelligent energy absorption devices utilizing magnetorheological fluids have emerged in existing technologies. As a smart material, magnetorheological fluids exhibit millisecond-level reversible changes in viscosity and shear strength under the influence of an external magnetic field. By adjusting the magnetic field strength, precise control of flow damping can be achieved, thereby altering the reaction force output characteristics of the energy absorption device. For example, patent number 2016109727222 also utilizes magnetorheological fluids, applying an internal magnetic field to alter the flow damping of the fluid, thus changing the force on the piston to achieve different energy absorption effects. However, currently available piston devices using magnetorheological fluids have a maximum piston speed of 1 mm / ms. Excessively high piston speeds lead to a sharp increase in viscous damping force, reducing controllability. Therefore, the speed of mass-produced magnetorheological fluid piston devices typically does not exceed 1 mm / ms. Achieving performance at high speeds greater than 1 mm / ms is difficult. The crushing force of an automotive energy-absorbing box is approximately 150 kN, with a length of about 200 mm. The actual crushing displacement is about 150 mm, and the length after crushing deformation is about 50 mm. Currently, the mainstream design for the crushing time of automotive energy-absorbing boxes is 25 ms to 30 ms, taking the larger value of 30 ms. Assuming the speed of the current magnetorheological fluid piston device is 1 mm / ms, the displacement within 30 ms is 30 mm, which is much smaller than the crushing displacement of traditional energy-absorbing boxes. Assuming the displacement of the magnetorheological fluid piston is 150 mm within 30 ms, the piston speed would be 5 mm / ms, which is difficult to achieve with current materials and designs, especially since the piston also integrates permanent magnets and electromagnets. Currently, the mainstream energy-absorbing boxes in automobiles absorb 15,000 joules of energy. With a piston displacement of 30 mm, the average force applied to the piston is 500 kN, which is much greater than the yield force of the longitudinal beam of about 230 kN. If the accessories connected to the piston are to withstand a force of 500 kN, the requirements for materials and design are extremely high, making it virtually impossible to achieve.

[0004] In conclusion, while the principle of using a magnetorheological fluid piston device to alter the energy absorption effect is plausible, its practical implementation is extremely difficult. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a variable axial force energy absorption box.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A variable axial force energy-absorbing box includes a front connecting plate, a shell, and a rear connecting plate. The front connecting plate is installed at the front end of the shell, and the rear connecting plate is installed at the rear end. The shell contains a variable force structure sealed at both ends, filled with magnetorheological fluid. The outer wall of the variable force structure and the inner wall of the shell form a cavity. The side wall of the variable force structure has a pressure-deformable and conductive pressure-relieving structure. The rear connecting plate has a magnetic field coil and several connecting holes. The cavity communicates with the outside through these holes. The magnetic field coil can generate magnetic fields of different intensities by passing different currents, thereby regulating the flow damping of the magnetorheological fluid and achieving adjustable control of the axial energy absorption effect of the energy-absorbing box.

[0008] Preferably, the variable force structure includes a metal cavity and a sealing sleeve. The sealing sleeve is fitted and nested inside the metal cavity. The metal cavity is fixedly connected between the front connecting plate and the rear connecting plate of the energy-absorbing box. The cavity is located between the outer wall of the metal cavity and the inner wall of the energy-absorbing box. Both ends of the metal cavity and the sealing sleeve are sealed. The pressure-deformable and conductive pressure relief structure includes several pressure relief holes and several weakened areas. The pressure relief holes are opened on the metal cavity, and the weakened areas are opened on the side wall of the sealing sleeve. The weakened areas are the elastic weak points of the sealing sleeve, and their structural strength is lower than that of the rest of the sealing sleeve. The pressure relief holes and the weakened areas are aligned. The metal cavity, the sealing sleeve, and the energy-absorbing box can all deform under axial pressure. The weakened areas deform synchronously when the sealing sleeve is compressed to form a fluid channel. After the pressure is released, the weakened areas can elastically reset to maintain the airtightness of the sealing sleeve.

[0009] Preferably, the weakened area is a thinning structure of the sidewall of the sealing sleeve, wherein the wall thickness of the thinning structure is less than the wall thickness of the other sidewalls of the sealing sleeve.

[0010] Preferably, the weakened areas are distributed in an array along the axial and circumferential directions of the sealing sleeve.

[0011] Preferably, the pressure relief holes are arranged in an array along the axial and circumferential directions of the metal cavity.

[0012] Preferably, both the metal cavity and the sealing sleeve are cylindrical.

[0013] Preferably, the weakened area is circular.

[0014] Preferably, several connecting holes are evenly distributed along the circumference of the rear connecting plate of the energy-absorbing box.

[0015] Preferably, the sealing sleeve and the weakened area are made of polyurethane rubber, and the metal cavity is made of aluminum alloy.

[0016] Preferably, the magnetic field coil is coaxially arranged with the variable force structure, and the generated magnetic field covers the magnetorheological fluid region inside the metal cavity.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. The energy absorption effect of this invention is adjustable in multiple levels, and the control logic is highly efficient:

[0019] This invention achieves flexible adaptation of energy absorption effect through a dual control mechanism: on the one hand, the magnetic field coil can be supplied with current of different intensities to generate a gradient magnetic field and precisely cover the magnetorheological fluid inside the metal cavity, realizing millisecond-level reversible adjustment of the flow damping of the magnetorheological fluid, thereby dynamically changing the reaction force output of the energy absorption box; on the other hand, by adjusting the size of the metal cavity, the number and diameter of the pressure relief holes, and the structural parameters of the weakened area of ​​the sealing sleeve, the upper and lower limits of the energy absorption range can be preset. Within this range, the continuous adaptation of energy absorption can be achieved by fine-tuning the magnetic field, meeting the personalized energy absorption needs in different scenarios.

[0020] 2. Excellent collapsibility and deformation coordination, suitable for large displacement working scenarios:

[0021] The variable force structure adopts a nested design of "metal cavity + sealing sleeve". Both can deform synchronously under axial pressure, allowing the metal cavity to collapse along with the energy-absorbing box. This directly converts the collapse displacement of the energy-absorbing box into the extrusion force of the magnetorheological fluid, eliminating the need for an additional transmission structure. The close nesting relationship between the sealing sleeve and the metal cavity, combined with the alignment design of the pressure relief hole and the weakened area, ensures a stable discharge path of the magnetorheological fluid during collapse. Even under large displacement collapse conditions, it can maintain the synergy and reliability of the structural action, adapting to the actual working characteristics of automotive collisions.

[0022] 3. The structure exhibits uniform stress distribution, resulting in excellent overall reliability and sealing performance.

[0023] The metal cavity is made of aluminum alloy, combining structural strength and collapsibility. The sealing sleeve is made of polyurethane rubber, which has good elasticity and sealing performance. The combination of these materials allows the variable force structure to withstand axial pressure during collisions while also buffering impact forces through elastic deformation. The fixed connection design between the metal cavity and the front and rear connecting plates of the energy-absorbing box, combined with the sealing settings at both ends of the sealing sleeve, ensures the overall stability of the structure. The weakened area, as an elastically weak point, can be reset through its own elastic rebound after being subjected to pressure deformation, effectively maintaining the airtightness of the sealing sleeve and ensuring the stable storage of the magnetorheological fluid in non-working conditions.

[0024] 4. Optimized magnetorheological fluid flow path, resulting in high linearity of damping adjustment:

[0025] The weakened area on the side wall of the sealing sleeve is aligned with the pressure relief hole of the metal cavity, and both are arrayed along the axial and circumferential directions. This creates a uniform and stable flow channel for the magnetorheological fluid during extrusion, preventing localized flow congestion or sudden pressure changes. Simultaneously, the outer wall of the variable force structure and the inner wall of the energy-absorbing box form a cavity. Combined with the evenly distributed connecting holes on the rear connecting plate of the energy-absorbing box, this enables smooth diversion and discharge of the magnetorheological fluid, reducing nonlinear fluctuations in damping force with velocity and improving control precision and the smoothness of the energy absorption process.

[0026] 5. Compact structure, high feasibility for processing, assembly, and mass production:

[0027] The core components of this invention include only the front and rear connecting plates of the energy-absorbing box, the shell, the metal cavity, the sealing sleeve, and the magnetic field coil, etc., without complex integrated structures. The components have regular shapes (e.g., the metal cavity and the sealing sleeve are both cylindrical), and the processing technology is mature. The metal cavity (aluminum alloy) and the sealing sleeve (polyurethane rubber) are both commonly used materials on the market, so the procurement cost is controllable. They do not require complex tooling equipment for production, which facilitates large-scale mass production and industrial application.

[0028] 6. Wide range of scenarios adaptability, with potential for both passive protection and intelligent integration:

[0029] The energy absorption regulation characteristics of this invention can be directly matched to different collision speed conditions. By preset the current curve of the corresponding magnetic field, the energy absorption box can achieve the best energy absorption effect under different impact intensities. At the same time, its magnetic field strength is adjustable and can be seamlessly integrated with the vehicle intelligent driving system. According to the obstacle type and collision prediction information identified by the intelligent driving system, the magnetorheological fluid damping parameters are dynamically adjusted to achieve a protection upgrade from "passive energy absorption" to "active adaptation", expanding the intelligent application scenarios of the energy absorption device.

[0030] 7. Balance between structural strength and cushioning performance, providing outstanding protection and safety:

[0031] The collapsible properties of the metal cavity and the elastic buffering function of the sealing sleeve work together. During a collision, the metal cavity collapses synchronously with the energy-absorbing box, which not only disperses the axial impact force but also provides stable power for the extrusion of the magnetorheological fluid. The polyurethane rubber material of the sealing sleeve has both wear resistance and extrusion resistance, and can maintain structural integrity even under high pressure deformation. Combined with the precise conduction design of the weakened area, it ensures the discharge efficiency and buffering effect of the magnetorheological fluid, effectively absorbs collision energy, and reduces the impact on the vehicle body and occupants. Attached Figure Description

[0032] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0033] Figure 2 This is a schematic diagram of the front connecting plate of the energy-absorbing box;

[0034] Figure 3 This is a three-dimensional structural diagram of the connecting plate at the rear end of the energy-absorbing box;

[0035] Figure 4 This is a cross-sectional view of the present invention;

[0036] Figure 5 This is a schematic diagram of the sealing sleeve.

[0037] Figure 6 A schematic diagram of the internal structure of the metal cavity;

[0038] Figure 7 This is a schematic diagram of the structure in actual application of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings:

[0040] like Figures 1 to 6 As shown, a variable axial force energy-absorbing box includes a front connecting plate 601, a shell 602, and a rear connecting plate 604. The front connecting plate 601 is installed at the front end of the shell 602, and the rear connecting plate 604 is installed at the rear end. The shell 602 has a variable force structure sealed at both ends, filled with magnetorheological fluid. The outer wall of the variable force structure and the inner wall of the shell 602 form a cavity 1. The side wall of the variable force structure has a pressure-deformable and conductive pressure-relieving structure. The rear connecting plate 604 has a magnetic field coil 603 and several connecting holes 605. The cavity 1 communicates with the outside through the connecting holes 605. The magnetic field coil 603 can generate magnetic fields of different intensities by passing different currents, thereby regulating the flow damping of the magnetorheological fluid and achieving adjustable control of the axial energy absorption effect of the energy-absorbing box. Several connecting holes 605 are evenly distributed along the circumference of the rear connecting plate 604 of the energy-absorbing box. The magnetic field coil 603 is coaxially arranged with the force-changing structure, and the magnetic field generated covers the magnetorheological fluid region inside the metal cavity 701. The magnetorheological fluid is composed of silicone oil, carbonyl iron powder, additives, etc.

[0041] like Figure 1 , Figures 4 to 6As shown, the variable force structure includes a metal cavity 701 and a sealing sleeve 702. The sealing sleeve 702 is fitted and nested inside the metal cavity 701. The metal cavity 701 is fixedly connected between the front connecting plate 601 and the rear connecting plate 604 of the energy absorption box. The cavity 1 is located between the outer wall of the metal cavity 701 and the inner wall of the energy absorption box shell 602. Both ends of the metal cavity 701 and the sealing sleeve 702 are sealed. The pressure-deformable and conductive pressure relief structure includes several pressure relief holes 801 and several weakening areas 802. The pressure relief holes 801 are opened on the metal cavity 701, and the several weakening areas 802 are opened on the side wall of the sealing sleeve 702. The weakening area 802 is the elastic weak part of the sealing sleeve 702, and its structural strength is lower than that of the other areas of the sealing sleeve 702. The pressure relief holes 801 and the weakening areas 802 are aligned. This refers to the fact that each pressure relief hole 801 is aligned with a weakened area 802. The metal cavity 701, sealing sleeve 702, and energy-absorbing box housing 602 can all deform under axial pressure. The weakened area 802 deforms synchronously with the sealing sleeve 702 during compression deformation, forming a fluid channel. After the pressure is released, the weakened area 802 can elastically reset to maintain the airtightness of the sealing sleeve 702. The weakened area 802 is a thinned structure of the sidewall of the sealing sleeve 702, and the wall thickness of the thinned structure is less than the wall thickness of the other sidewalls of the sealing sleeve 702. The weakened areas 802 are arranged in an array along the axial and circumferential directions of the sealing sleeve 702. The pressure relief holes 801 are also arranged in an array along the axial and circumferential directions of the metal cavity 701. Both the metal cavity 701 and the sealing sleeve 702 are cylindrical. The weakened area 802 is circular.

[0042] The sealing sleeve 702 and the weakened area 802 are both made of polyurethane rubber, and the metal cavity 701 is made of aluminum alloy.

[0043] Polyurethane rubber possesses extremely high mechanical strength, abrasion resistance, and extrusion resistance. The weakened zone 802 provides strong resilience and sealing pressure even in a thin layer, making it suitable for dynamic high-pressure sealing.

[0044] like Figure 7As shown, 901 is the anti-collision beam, and 902 is the longitudinal beam. The energy-absorbing box shell 602 is installed between the anti-collision beam 901 and the longitudinal beam 902. In the initial state, the weakened area 802 of the sealing sleeve 702 remains elastically closed, ensuring that the magnetorheological fluid is sealed and stored inside the sealing sleeve 702. When a collision occurs, the energy-absorbing box shell 602 is crushed by axial force, and the metal cavity 701 is squeezed by the axial force of the front connecting plate 601 of the energy-absorbing box. The metal cavity 701 and the sealing sleeve 702 begin to deform axially simultaneously. The metal cavity undergoes collapse deformation, and the sealing sleeve undergoes elastic compression deformation. With the coordinated deformation of the two, the internal volume of the sealing sleeve 702 continues to decrease. The filled magnetorheological fluid is squeezed and generates high pressure. This pressure directly acts on the weakened area 802 (the elastically weak part) of the sealing sleeve 702, causing the weakened area 802 to undergo local deformation and form a fluid channel. High-pressure magnetorheological fluid is discharged into the annular cavity 1 through the fluid channel formed by the weakening zone 802 and the aligned pressure relief holes 801. Subsequently, the energy-absorbing box shell 602 collapses and deforms, then flows into the vehicle body longitudinal beam through the evenly distributed connecting holes 605 on the rear connecting plate 604, completing the diversion and discharge of the magnetorheological fluid. During this process, the flow damping of the magnetorheological fluid directly determines its discharge resistance, thus affecting the reaction force output and energy absorption efficiency of the energy-absorbing box. By passing currents of different intensities into the magnetic field coil 603, different magnetic fields are generated, and the magnetorheological fluid exhibits different flow damping properties under the action of the magnetic field. During the complete extrusion of the magnetorheological fluid, a larger flow damping results in a larger force on the magnetorheological fluid, and a smaller flow damping results in a smaller force. The length of the energy-absorbing box shell 602 is constant, meaning the deformation displacement is constant. According to W=F*s*cosθ, the larger F is, the larger W is, and the more energy the energy-absorbing box absorbs.

[0045] After the collision, the axial impact force disappears, and the weakened area 802 of the sealing sleeve 702 rebounds and resets due to the elastic properties of the polyurethane rubber, reclosing the fluid channel and restoring the magnetorheological fluid to its sealed storage state. If a magnetorheological fluid recovery and reflux system is subsequently added, the energy-absorbing box can be reused, further expanding its application value.

[0046] Magnetorheological fluids (MRFs) are fluids with good flow properties in the absence of a magnetic field. However, once a magnetic field is applied, their viscosity or shear strength undergoes a significant and reversible change within milliseconds, sometimes even instantly transforming them into a solid-like state. MRFs utilize mineral oil and silicone oil to provide basic flowability, with the addition of micron-sized (1-10 μm) soft magnetic particles (such as carbonyl iron powder), which form the main active component. Dispersants and anti-wear agents are also added to prevent particle sedimentation. The working principle of MRFs is that in the absence of a magnetic field, the particles are randomly distributed, allowing the fluid to flow freely. When a magnetic field is applied, the particles are magnetized and arrange themselves into chain-like or columnar structures along the magnetic field lines. These structures resist the shear motion of the fluid, macroscopically manifested as a dramatic increase in viscosity and the generation of yield stress, thus transmitting or resisting shear force. After the magnetic field disappears, the structure disintegrates, and the fluid returns to its fluid state.

[0047] This invention achieves a wide range of energy absorption effects through a dual approach of "pre-setting structural parameters + fine-tuning magnetic field":

[0048] First level of control (limit setting): By adjusting the material of the energy-absorbing box housing 602, the material (such as aluminum alloy) and size (diameter and length) of the metal cavity 701, and the size and number of pressure relief holes 801, the minimum and maximum limits of energy absorbed by the energy-absorbing box can be preset to ensure that the basic requirements of vehicle body load-bearing and collision protection are met.

[0049] The second level of regulation (range fine-tuning): Within the preset energy absorption limit range, by adjusting the input current intensity of the magnetic field coil 603, the flow damping of the magnetorheological fluid is changed, thereby continuously adjusting the discharge resistance of the magnetorheological fluid, so as to achieve precise adaptation of energy absorption within the limit range and meet the protection requirements of dynamic working conditions such as different collision speeds and obstacle types.

[0050] Taking a specific set of parameters as an example, the feasibility of the working principle of this invention is verified: Assume the metal cavity 701 has a diameter of 25mm (smaller than the energy-absorbing box size) and a length of 150mm, filled with an equivalent fluid (water). Within 30ms, an axial force of 150KN drives the energy-absorbing box to collapse by 150mm (co-deformation with the metal cavity), and the 150KN force acts entirely on the internal fluid. Fluid dynamics calculations show that the total area of ​​the required pressure relief hole 801 is only 3.14mm², while the lateral area of ​​the metal cavity 701 reaches 11781mm², providing ample space for arrangement on the sides. This ensures the reasonable layout of the pressure relief hole 801 and the smooth discharge of the magnetorheological fluid, verifying the engineering feasibility of the working principle of this invention.

[0051] In actual use, the vehicle travels normally at a certain speed. When an obstacle is detected ahead, it is judged whether there is a risk of collision. If there is a risk of collision, the corresponding current is provided to the magnetic field coil according to the speed, generating a corresponding magnetic field. The magnetic field changes the flow damping characteristics of the magnetorheological fluid, thereby changing the magnitude of the crushing force of the metal cavity. Since the metal cavity is inside the energy absorption box, it changes the magnitude of the crushing force of the energy absorption box, ultimately changing the energy absorption effect of the energy absorption box.

[0052] This invention utilizes an innovative pistonless "metal cavity + sealing sleeve" synergistic deformation structure, combined with magnetorheological fluid diversion and dual control logic, offering multiple advantages in adaptability, reliability, and practicality. It perfectly adapts to the large displacement and high-speed crumpling requirements of automotive collisions, ensuring smooth discharge of the magnetorheological fluid through ample space for pressure relief holes. Furthermore, the coaxial design of the magnetic field coil and the variable force structure, along with gradient magnetic field control, enables millisecond-level precise adjustment of flow damping. Combined with the dual logic of preset structural parameters and fine-tuning of the magnetic field, it meets the energy absorption adaptation requirements under different working conditions. Simultaneously, its compact structure, mature material selection, and low processing and assembly difficulty, along with reliable sealing and resetting capabilities and reusability, effectively improve the safety and engineering feasibility of automotive collision protection, and facilitate mass production.

[0053] It should be noted that the above examples are merely one specific embodiment of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. In short, all variations that can be directly derived or conceived by those skilled in the art from the content disclosed in this invention should be considered within the scope of protection of this invention.

Claims

1. A variable axial force energy absorption box, comprising an energy absorption box front end connecting plate (601), an energy absorption box shell (602), an energy absorption box rear end connecting plate (604), the energy absorption box front end connecting plate (601) is installed at the front end of the energy absorption box shell (602), the energy absorption box rear end connecting plate (604) is installed at the rear end of the energy absorption box shell (602), characterized in that, The energy-absorbing box housing (602) has a variable force structure sealed at both ends inside. The variable force structure is filled with magnetorheological fluid. The outer wall of the variable force structure and the inner wall of the energy-absorbing box housing (602) enclose a cavity (1). The side wall of the variable force structure has a pressure relief structure that can be deformed and conduct under pressure. The rear connecting plate (604) of the energy-absorbing box has a magnetic field coil (603) and several connecting holes (605). The cavity (1) is connected to the outside through the connecting holes (605). The magnetic field coil (603) can generate magnetic fields of different intensities by passing in different currents, so as to regulate the flow damping of the magnetorheological fluid and realize the adjustable control of the axial energy absorption effect of the energy-absorbing box.

2. The variable axial force energy-absorbing box according to claim 1, characterized in that, The variable force structure includes a metal cavity (701) and a sealing sleeve (702). The sealing sleeve (702) is fitted and nested inside the metal cavity (701). The metal cavity (701) is fixedly connected between the front connecting plate (601) and the rear connecting plate (604) of the energy absorption box. The cavity (1) is located between the outer wall of the metal cavity (701) and the inner wall of the energy absorption box shell (602). Both ends of the metal cavity (701) and the sealing sleeve (702) are sealed. The pressure relief structure that can be deformed and conducts under pressure includes several pressure relief holes (801) and several weakening zones (802). The several pressure relief holes (801) are opened in... On the metal cavity (701), several weakened areas (802) are formed on the side wall of the sealing sleeve (702). The weakened area (802) is the elastic weak part of the sealing sleeve (702), and its structural strength is lower than that of the other areas of the sealing sleeve (702). The pressure relief hole (801) is aligned with the weakened area (802). The metal cavity (701), the sealing sleeve (702), and the energy absorption box shell (602) can all deform under axial pressure. The weakened area (802) deforms synchronously when the sealing sleeve (702) is compressed to form a fluid channel. After the pressure is released, the weakened area (802) can elastically reset to maintain the airtightness of the sealing sleeve (702).

3. The variable axial force energy-absorbing box according to claim 2, characterized in that, The weakened area (802) is a thinning structure of the side wall of the sealing sleeve (702), and the wall thickness of the thinning structure is less than the wall thickness of the other side walls of the sealing sleeve (702).

4. The variable axial force energy-absorbing box according to claim 2, characterized in that, The weakened areas (802) are arrayed along the axial and circumferential directions of the sealing sleeve (702).

5. The variable axial force energy-absorbing box according to claim 2, characterized in that, The pressure relief holes (801) are arranged in an array along the axial and circumferential directions of the metal cavity (701).

6. The variable axial force energy-absorbing box according to claim 2, characterized in that, Both the metal cavity (701) and the sealing sleeve (702) are cylindrical.

7. The variable axial force energy-absorbing box according to claim 2, characterized in that, The weakened region (802) is circular.

8. The variable axial force energy-absorbing box according to claim 2, characterized in that, The plurality of connecting holes (605) are evenly distributed along the circumference of the rear connecting plate (604) of the energy-absorbing box.

9. The variable axial force energy-absorbing box according to claim 2, characterized in that, The sealing sleeve (702) and the weakening area (802) are both made of polyurethane rubber, and the metal cavity (701) is made of aluminum alloy.

10. A variable axial force energy-absorbing box according to claim 2, characterized in that, The magnetic field coil (603) is coaxially arranged with the variable force structure, and the magnetic field generated covers the magnetorheological fluid region inside the metal cavity (701).

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