Variable stiffness spring and design method thereof

Abstract

The invention provides a variable stiffness spring and a design method thereof. The variable stiffness spring comprises an outer sleeve and an inner sleeve. The outer sleeve sleeves the outer side of the inner sleeve, the outer sleeve and the inner sleeve are in sliding connection, and a telescopic cavity is formed in the outer sleeve and the inner sleeve. And a wave spring is mounted in the telescopic cavity. The two ends of the wave spring abut against the outer sleeve and the inner sleeve respectively. The wave spring is spirally arranged along the axis of the outer sleeve. The wave spring is arranged in the telescopic cavity formed in the outer sleeve and the inner sleeve, the wave spring can be prevented from being interfered by dust, gravel and oil dirt, the service life of the wave spring is prolonged, the telescopic cavity limits the deformation direction of the wave spring, deflection or torque of the wave spring is avoided, it is ensured that the wave spring provides stable elastic force, and the stability of a system is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of springs, and in particular relates to a variable-rigidity spring and a design method thereof. Background Art

[0002] With the improvement of people's living standards and the enhancement of environmental awareness, my country has made significant progress in battery technology. Combined with a series of preferential policies, electric vehicles have occupied an increasingly higher market share, and the electric vehicle industry has developed rapidly. The battery pack is the core component of electric vehicles. In order to ensure that the vehicle has sufficient driving range, the battery pack is often designed to be relatively large. Traditional shock absorbers need to occupy a large space, which is not conducive to the vehicle space layout, and may even occupy the space inside the vehicle, affecting the vehicle's ride comfort. Wave springs are a special elastic element composed of multiple peaks and troughs. During the compression process, the peaks and troughs are close to each other. The required height of this spring in the axial direction is lower than that of the coil spring, and it can provide the required elastic force in a smaller space, but the stiffness of the traditional wave spring cannot be changed. In order to improve driving comfort, the vehicle shock absorber is usually designed to be softer in the initial stage and harder in the subsequent stage. Traditional wave springs cannot meet the above requirements.

[0003] Therefore, the above problems need to be solved urgently. Summary of the invention

[0004] Purpose of the invention: In order to overcome the above shortcomings, the present invention provides a variable stiffness spring and a design method thereof, which has a compact structure in the axial direction, can provide elastic force that meets the requirements in a smaller space, and can provide precise elastic force within a smaller deformation range, has sufficient bearing capacity under a larger load, is soft in the initial stage, and as the deformation increases, the bearing capacity increases, the buffering performance and impact resistance are enhanced, and has different stiffness characteristics at different deformation stages.

[0005] Technical solution: In order to achieve the above-mentioned purpose, the present invention provides a variable stiffness spring, including an outer sleeve and an inner sleeve. The outer sleeve is sleeved on the outside of the inner sleeve, and the outer sleeve and the inner sleeve are slidably connected, and a telescopic cavity is formed in the outer sleeve and the inner sleeve. A wave spring is installed in the telescopic cavity. The two ends of the wave spring are respectively abutted against the outer sleeve and the inner sleeve. The wave spring is spirally arranged along the axis of the outer sleeve. The present invention arranges the wave spring in the telescopic cavity formed in the outer sleeve and the inner sleeve, which can prevent the wave spring from being disturbed by dust, gravel and oil, and extend the service life of the wave spring. The telescopic cavity limits the deformation direction of the wave spring, avoids the wave spring from being deflected or torqued, ensures that the wave spring provides a stable elastic force, and improves the stability of the system.

[0006] Furthermore, in the above-mentioned variable stiffness spring, each coil of the wave spring is provided with a number of crests and troughs, and the crests and troughs of adjacent coils of the wave spring are arranged in a staggered manner. The staggered arrangement of the crests and troughs of the wave spring can evenly distribute the force on the entire wave spring, avoid stress concentration, improve the bearing capacity, reduce the possibility of cracks in the wave spring, and increase the service life of the wave spring. The staggered arrangement of the crests and troughs of adjacent coils helps to achieve a smoother elastic force deformation curve. The stiffness can be adjusted by changing the crest height, cross-sectional width and thickness of the wave spring. For example, by making one end of the wave spring thinner, the initial end of the wave spring is softer and absorbs small vibrations, which can improve the absorption and buffering capacity and achieve variable stiffness of the wave spring.

[0007] Furthermore, in the above-mentioned variable stiffness spring, the cross section of the wave spring is inclined. When an external force acts on the wave spring, the inclined cross section can decompose the force into forces in multiple directions, transmit part of the force in the inclined direction, reduce stress concentration, improve the bearing capacity of the wave spring, and increase the effective deformation space of the wave spring. In the normal use process, the elastic force is mainly provided by the peaks and troughs of the wave spring that abut each other. At this time, it has a larger effective elastic deformation range and can still maintain good elasticity under a larger deformation amount. When the wave spring is under a large load or impacted, as the wave spring is compressed and deformed, the cross section of the wave spring begins to deform in the horizontal direction, and the bearing capacity and impact resistance of the wave spring are increased, so that when there is a small impact, the wave spring provides less resistance, ensuring the flexibility of the vehicle. When encountering a larger impact force, the wave spring resistance increases, providing strong support and buffering, and avoiding the vehicle from vibrating at a distance due to excessive impact force. In addition, the inclined design of the wave spring cross section can enhance the wave spring's anti-torque ability, improve the vehicle's anti-roll ability, and improve the vehicle's handling.

[0008] Furthermore, in the above-mentioned variable stiffness spring, a spring is provided outside the inner sleeve. The two ends of the spring abut against the outer sleeve and the inner sleeve respectively, and the spring keeps the outer sleeve and the inner sleeve at a distance. The spring connects the outer sleeve and the inner sleeve. When the outer sleeve and the inner sleeve move relative to each other, the spring is compressed or stretched, providing a guide for the movement of the outer sleeve and the inner sleeve, and connecting the outer sleeve and the inner sleeve, applying a preload force to the wave spring to ensure structural stability.

[0009] Furthermore, in the above-mentioned variable stiffness spring, a first annular groove is provided at the bottom of the outer sleeve, a second annular groove is provided at the bottom of the inner sleeve, and both ends of the wave spring are respectively arranged in the first annular groove and the second annular groove. Placing both ends of the wave spring in the annular groove ensures accurate positioning of the wave spring, avoids displacement, and improves stability and reliability.

[0010] Furthermore, in the variable stiffness spring, elastic rings are respectively provided at the bottom of the first annular groove and the second annular groove, and the two ends of the wave spring are respectively in contact with the elastic rings. The elastic rings are provided at both ends of the wave spring to isolate the wave spring from the outer sleeve and the inner sleeve, thereby reducing the impact force on the wave spring, improving the buffering and shock absorbing performance, reducing the wear of the wave spring, and extending the service life. The elastic rings can absorb small vibrations and improve the shock absorbing performance.

[0011] Furthermore, in the above-mentioned variable stiffness spring, an elastic ring is connected to the inner side wall of the second annular groove, and a gap is left between the elastic ring and the wave spring. The elastic ring can reduce the friction between the wave spring and the second annular groove, reduce noise, and at the same time, when the elastic ring is squeezed and deformed, the diameter of the elastic ring gradually increases. When the diameter of the wave spring increases to fill the gap between the elastic ring and the wave spring, the wave spring and the elastic ring abut and rub, so that the elastic ring participates in the buffering process, so that the impact force is transmitted to the elastic ring, and the elastic ring and the wave spring jointly bear the impact and vibration, forming a multi-level buffer, and improving the adaptability of the spring. At the same time, the elastic ring is restricted by the second annular groove and cannot deform outward, which limits the deformation of the wave spring to a certain extent, prevents the wave spring from exceeding its elastic limit to produce irreversible deformation or damage, prevents the spring from failing, and extends the service life of the spring.

[0012] Furthermore, in the above-mentioned variable stiffness spring, the first annular groove includes a first outer wall, the second annular groove includes a second outer wall, a convex key is provided on the inner side of the first outer wall, and the convex key is arranged axially along the outer sleeve. A keyway is provided on the second outer wall, and the keyway and the convex key are arranged accordingly, the convex key is inserted into the keyway, and the convex key slides along the keyway. The convex key and the keyway are arranged to improve the connection stability between the outer sleeve and the inner sleeve.

[0013] The design method of the variable stiffness spring comprises the following steps: S1: Determine the usage scenario, perform preliminary optimization based on load, deformation characteristics, space, and life requirements, and obtain a preliminary optimal solution for the wave spring.

[0014] S2: Based on the preliminary optimal solution of the wave spring, Hooke's law is used to calculate the preload according to the working environment and load characteristics.

[0015] S3: The preload force is obtained by calculation, and the wire diameter and pitch of the spring are estimated in combination with the length and inner diameter of the spring.

[0016] S4: Preliminary optimal solution of the wave spring is used to establish a three-dimensional model of the wave spring.

[0017] S5: Input the three-dimensional model of the wave spring into a simulation environment and perform finite element analysis. Fix one end of the wave spring and compress the other end of the wave spring to output displacement values, stress values ​​and reaction force values.

[0018] S6: Determine the stress level based on the obtained displacement values, stress values, and reaction force values, optimize the model, and repeat S5 until the model stress level meets the design requirements.

[0019] S7: Make wave spring samples, conduct experiments on a test platform that simulates the actual working environment, and optimize according to the experimental data.

[0020] It can be seen from the above technical scheme that the present invention has the following beneficial effects: the variable stiffness spring and its design method of the present invention set the wave spring in the telescopic cavity formed in the outer sleeve and the inner sleeve, which can prevent the wave spring from being disturbed by dust, gravel and oil, and extend the service life of the wave spring. The telescopic cavity limits the deformation direction of the wave spring, avoids the deflection or torque of the wave spring, ensures that the wave spring provides a stable elastic force, and improves the stability of the system. The staggered arrangement of the wave crests and troughs of adjacent circles helps to achieve a smoother elastic force deformation curve. Stiffness adjustment is achieved by changing the wave crest height, cross-sectional width and thickness of the wave spring. The inclined setting of the cross section of the wave spring can decompose the force into forces in multiple directions, transmit part of the force in the inclined direction, reduce stress concentration, improve the bearing capacity of the wave spring, and increase the effective deformation space of the wave spring. An elastic ring is arranged. When the wave spring is subjected to force, its diameter increases to fill the gap between the elastic ring and the wave spring. The wave spring and the elastic ring abut against each other and rub against each other, so that the elastic ring participates in the buffering process and transmits the impact force to the elastic ring. The elastic ring and the wave spring jointly bear the impact and vibration to form a multi-stage buffer, thereby improving the adaptability of the spring. The elastic ring can prevent the wave spring from exceeding its elastic limit to produce irreversible deformation or damage, thereby preventing the spring from failing and extending the service life of the spring. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a front view of the variable stiffness spring of the present invention; Figure 2 for Figure 1 Exploded diagram of Figure 3 for Figure 1 A cross-sectional view of Figure 4 is a cross-sectional view of the wave spring.

[0022] In the figure: 1, outer sleeve, 11, first annular groove, 111, first outer wall, 112, convex key, 2, inner sleeve, 21, second annular groove, 211, second outer wall, 3, wave spring, 31, spring, 4, elastic ring, 5, elastic ring. DETAILED DESCRIPTION

[0023] Example 1 like Figure 1-2A variable stiffness spring shown includes an outer sleeve 1 and an inner sleeve 2. The outer sleeve 1 is sleeved on the outer side of the inner sleeve 2, and the outer sleeve 1 and the inner sleeve 2 are slidably connected, and a telescopic cavity is formed in the outer sleeve 1 and the inner sleeve 2. A wave spring 3 is installed in the telescopic cavity. The two ends of the wave spring 3 are respectively abutted against the outer sleeve 1 and the inner sleeve 2. The wave spring 3 is spirally arranged along the axis of the outer sleeve 1. Each circle of the wave spring 3 is provided with a plurality of crests and troughs, and the crests and troughs of adjacent circles of the wave spring 3 are staggered. A spring 31 is provided on the outer side of the inner sleeve 2. The two ends of the spring 31 are respectively abutted against the outer sleeve 1 and the inner sleeve 2, and the spring 31 keeps the outer sleeve 1 and the inner sleeve 2 at a distance. The spring 31 connects the outer sleeve 1 and the inner sleeve 2. When the outer sleeve 1 and the inner sleeve 2 move relative to each other, the spring 31 is compressed or stretched, providing a guide for the movement of the outer sleeve 1 and the inner sleeve 2, and connecting the outer sleeve 1 and the inner sleeve 2, and applying a preload force to the wave spring 3.

[0024] like Figure 3 In the variable stiffness spring shown, the bottom of the outer sleeve 1 is provided with a first annular groove 11, the bottom of the inner sleeve 2 is provided with a second annular groove 21, and the two ends of the wave spring 3 are respectively provided in the first annular groove 11 and the second annular groove 21. The bottoms of the first annular groove 11 and the second annular groove 21 are respectively provided with elastic rings 4, and the two ends of the wave spring 3 are respectively abutted against the elastic rings 4. The elastic rings 4 are provided at both ends of the wave spring 3 to isolate the wave spring 3 from the outer sleeve 1 and the inner sleeve 2, reduce the impact force on the wave spring 3, and improve the buffering and shock absorption performance. The inner side wall of the second annular groove 21 is connected with an elastic ring 5, and a gap is left between the elastic ring 5 and the wave spring 3. The elastic ring 5 can reduce the friction between the wave spring 3 and the second annular groove 21 and reduce noise. At the same time, when the elastic ring 5 is squeezed and deformed, the diameter of the elastic ring 5 gradually increases. When the diameter of the wave spring 3 increases to fill the gap between the elastic ring 5 and the wave spring, the wave spring 3 and the elastic ring 5 abut and rub, so that the elastic ring 5 participates in the buffering process. The elastic ring 5 and the wave spring 3 jointly withstand impact and vibration to form a multi-stage buffer. At the same time, the elastic ring 5 is restricted by the second annular groove 21 and cannot deform outward, which limits the deformation of the wave spring 3 to a certain extent, prevents the wave spring from exceeding its elastic limit to produce irreversible deformation or damage, and prevents the spring from failing. The first annular groove 11 includes a first outer wall 111, and the second annular groove 21 includes a second outer wall 211. A convex key 112 is provided on the inner side of the first outer wall 111, and the convex key 112 is arranged axially along the outer sleeve 1. The second outer wall 211 is provided with a keyway, and the keyway and the convex key 112 are arranged accordingly. The convex key 112 is inserted into the keyway, and the convex key 112 slides along the keyway. The convex key 112 and the keyway are arranged to improve the connection stability between the outer sleeve 1 and the inner sleeve 2.

[0025] The design method of the variable stiffness spring comprises the following steps: S1: Determine the usage scenario, perform preliminary optimization based on load, deformation characteristics, space, and life requirements, and obtain a preliminary optimal solution for the wave spring 3.

[0026] S2: Based on the preliminary optimal solution of wave spring 3, Hooke's law is used to calculate the preload according to the working environment and load characteristics.

[0027] S3: The preload force is obtained by calculation, and the wire diameter and pitch of the spring 31 are estimated in combination with the length and inner diameter of the spring 31 .

[0028] S4: Preliminary optimization solution of the wave spring 3 is obtained, and a three-dimensional model of the wave spring 3 is established.

[0029] S5: Input the three-dimensional model of the wave spring 3 into the simulation environment and perform finite element analysis. Fix one end of the wave spring 3 and compress the other end of the wave spring 3 to output displacement values, stress values ​​and reaction force values.

[0030] S6: Determine the stress level based on the obtained displacement values, stress values, and reaction force values, optimize the model, and repeat S5 until the model stress level meets the design requirements.

[0031] S7: Make a wave spring 3 sample, conduct experiments on a test platform simulating the actual working environment, and optimize according to the experimental data.

[0032] Example 2 This embodiment is different from Embodiment 1 in that Figure 4 The variable stiffness spring shown has a wave spring 3 with an inclined cross section. When an external force acts on the wave spring 3, the inclined cross section can decompose the force into forces in multiple directions, and transmit part of the force in the inclined direction, thereby reducing stress concentration, improving the bearing capacity of the wave spring, and increasing the effective deformation space of the wave spring. In normal use, the elastic force is mainly provided by the peaks and troughs of the wave spring 3 that abut against each other. At this time, it has a larger effective elastic deformation range and can maintain good elasticity under a larger deformation amount. When the wave spring 3 is under a large load or impacted, as the wave spring 3 is compressed and deformed, the cross section of the wave spring 3 begins to deform in the horizontal direction, and the bearing capacity and impact resistance of the wave spring 3 are increased, so that when there is a small impact, the wave spring 3 provides less resistance, ensuring the driving flexibility of the vehicle. When encountering a larger impact force, the resistance of the wave spring increases, providing strong support and buffering.

[0033] At the same time, the stiffness can be adjusted by changing the wave peak height, cross-sectional width and thickness of the wave spring 3. For example, one end of the wave spring can be made thinner to make the initial end of the wave spring softer and absorb small vibrations, thereby improving the absorption and buffering capabilities and achieving variable stiffness of the wave spring.

[0034] The above embodiments are exemplary, and their purpose is to illustrate the technical concept and features of the present invention so that people familiar with this field can understand the content of the present invention and implement it accordingly, and they cannot limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A variable stiffness spring, characterized in that: The invention comprises an outer sleeve (1) and an inner sleeve (2); the outer sleeve (1) is sleeved on the outer side of the inner sleeve (2); the outer sleeve (1) and the inner sleeve (2) are slidably connected; a telescopic cavity is formed in the outer sleeve (1) and the inner sleeve (2); a wave spring (3) is installed in the telescopic cavity; two ends of the wave spring (3) are respectively abutted against the outer sleeve (1) and the inner sleeve (2); the wave spring (3) is spirally arranged along the axis of the outer sleeve (1).

2. The variable stiffness spring according to claim 1, characterized in that: Each circle of the wave spring (3) is provided with a plurality of wave crests and wave troughs, and the wave crests and wave troughs of adjacent circles of the wave spring (3) are arranged alternately.

3. The variable stiffness spring according to claim 1, characterized in that: The cross section of the wave spring (3) is arranged obliquely.

4. The variable stiffness spring according to claim 1, characterized in that: A spring (31) is provided on the outside of the inner sleeve (2); two ends of the spring (31) are respectively in contact with the outer sleeve (1) and the inner sleeve (2), and the spring (31) maintains a distance between the outer sleeve (1) and the inner sleeve (2).

5. The variable stiffness spring according to claim 1, characterized in that: The outer sleeve (1) has a first annular groove (11) at its bottom, the inner sleeve (2) has a second annular groove (21) at its bottom, and two ends of the wave spring (3) are respectively disposed in the first annular groove (11) and the second annular groove (21).

6. The variable stiffness spring according to claim 5, characterized in that: Elastic rings (4) are respectively provided at the bottom of the first annular groove (11) and the second annular groove (21), and both ends of the wave spring (3) are respectively in contact with the elastic rings (4).

7. The variable stiffness spring according to claim 5, characterized in that: An elastic ring (5) is connected to the inner wall of the second annular groove (21), and a gap is left between the elastic ring (5) and the wave spring (3).

8. The variable stiffness spring according to claim 5, characterized in that: The first annular groove (11) comprises a first outer wall (111), and the second annular groove (21) comprises a second outer wall (211). A convex key (112) is provided on the inner side of the first outer wall (111), and the convex key (112) is arranged axially along the outer sleeve (1). The second outer wall (211) is provided with a keyway, and the keyway and the convex key (112) are arranged correspondingly. The convex key (112) is inserted into the keyway, and the convex key (112) slides along the keyway.

9. The design method of a variable stiffness spring according to any one of claims 1 to 8, characterized in that: The steps include: S1: Determine the usage scenario, perform preliminary optimization based on load, deformation characteristics, space, and life requirements, and obtain a preliminary optimal solution for the wave spring (3); S2: Based on the obtained preliminary optimal solution of wave spring (3), the preload force is calculated using Hooke's law according to the working environment and load characteristics; S3: estimating the wire diameter and pitch value of the spring (31) based on the preload force obtained by calculation and in combination with the length and inner diameter of the spring (31); S4: Preliminary optimal solution of the wave spring (3) is used to establish a three-dimensional model of the wave spring (3); S5: inputting the three-dimensional model of the wave spring (3) into a simulation environment to perform finite element analysis; fixing one end of the wave spring (3), compressing the other end of the wave spring (3), and outputting displacement values, stress values, and reaction force values; S6: Determine the stress level according to the obtained displacement value, stress value and reaction force value, optimize the model, and repeat S5 until the stress level of the model meets the design requirements; S7: Making a sample of the wave spring (3), conducting experiments on a test platform simulating an actual working environment, and optimizing the sample based on the experimental data.

Images