床垫用垂向变刚度空气弹簧静力学特性及其计算模型

Static characteristics and calculation model of air spring with vertical variable stiffness for mattress

床垫的支撑特性对于用户的卧姿脊柱形态以及“人-床垫”界面缓压效果有重要影响,可变刚度床垫理论上能够为用户提供个性化、可调节的支撑。然而,目前市场上现有床垫配置固定刚度弹簧层,并不能满足个性化及睡眠过程卧姿变换的支撑需求;此外,一些床垫使用可调刚度的气包作为铺垫层,但是现有研究结果表明,床垫铺垫层并不能改变床垫芯层硬度以及卧姿脊柱形态。为了研究床垫可变刚度的弹簧层,本研究设计并制作了一种基于热塑性聚氨酯涂层织物复合材料的垂向变刚度空气弹簧,通过准静态单轴压缩实验研究了其力学性能以及刚度与初始容积、初始内部压强以及材质密度的关系,最终通过多项式拟合建立了空气弹簧的力学计算模型。结果表明:随着空气弹簧压缩量增加,刚度与内部气压均非线性增加;空气弹簧刚度与初始容积之间存在非线性负相关关系,与初始内部压强及材质密度之间存在正相关关系。该空气弹簧及其工程控制计算模型使可变刚度床垫设计成为了可能,并提供了变刚度弹簧的基础理论依据。

Stiffness property of mattress significantly affects the spinal alignment and the pressure relief of human-mattress interface.Therefore,the variable stiffness mattress can theoretically provide personalized and adjustable support for users.However,the existing mattresses in the market are commonly equipped with a fixed stiffness spring layer,which cannot meet the needs of personalized support and the change of sleeping posture.In addition,some mattresses use air bags with adjustable stiffness as bedding layer,but existing studies have shown that bedding layer of the mattress mainly affects the pressure distribution at the mattress interface,which has little relation with the shape of the spine.Changing bedding layer hardness can only change the surface layer hardness of mattress and cannot change the core layer hardness of mattress.Therefore,to overcome the existing mattress stiffness problems,it is desired to develop mattresses with adjustable stiffness of core layer.In order to study the variable stiffness spring layer of mattress,a kind of air spring with vertical variable stiffness was designed and manufactured with thermoplastic polyurethane coating fabric composite materials.Through quasi-static uniaxial compression experiments,the mechanical properties and the relationship between the stiffness and the initial volume,initial internal pressure and material density were studied.Finally,the mechanical calculation model of air spring was established by polynomial fitting.The results showed that the stiffness and internal pressure increased non-linearly with the increase of air spring compression.There was a nonlinear negative correlation between the stiffness of the air spring and the initial volume,and a positive correlation between the initial internal pressure and material density.It was concluded that the air spring and its engineering control calculation model made the design of variable stiffness mattress possible,which can provide the basic theory basis of variable stiffness spring.As the basis of the study on the softness adjustable mattress,this study proves that the air spring can adjust the softness and hardness of mattress.On this basis,the influence of the air spring assembly on the mechanical properties and support characteristics of the mattress will be further studied.