弹性密封振动减摩特性及其在气缸中的应用研究

发布时间：2018-05-04 19:07

本文选题：气缸摩擦力 + 振动减摩　；参考：《哈尔滨工业大学》2017年博士论文

【摘要】：气压传动具有清洁度高、维护简单、成本较低、便于集中供气和中远距离输送等特点,因此被广泛应用于食品、药品加工、半导体与微电子制造业,以及医疗辅助器械等领域。活塞式气缸中的弹性橡胶圈在提供气缸腔体间密封或与外界的密封的同时引入了不可避免的摩擦力,它是影响气缸定位精度和传递稳定性的最重要因素之一。振动减摩,即作用于摩擦副表面的高频振动可以减小摩擦力的现象,引起了很多相关领域学者的重视。因此,将高频振动作用于气缸摩擦副成为了一种全新的改善气缸摩擦力特性的方法。本文首先分析了一般摩擦副的摩擦力模型,并对气缸摩擦力模型进行了比较与分析,然后对几种不同方向振动对弹性密封摩擦副之间摩擦力减小的特性进行研究。得到通过振动方式减小气缸摩擦力的理论与实验基础。当振动方向与摩擦副所在平面平行时,高频振动的引入时刻在改变摩擦力的方向,因而通过计算可以得到摩擦力的平均值有明显的减小。分别基于库伦摩擦力模型及达尔摩擦力模型研究了振速-滑动速度比对振动摩擦系数的影响,探索更适用于描述气缸在振动条件下的摩擦力规律的物理模型。当振动方向垂直于摩擦副所在平面时,摩擦力是通过减小实际接触面积而降低的。通过理论分析得到,振幅这一参数对减摩幅度起到非常重要的作用,即振幅越大,摩擦力越小。通过对激振区域为减摩效果产生影响的理论计算得知,优化被激振体的位置从而使得摩擦副间的平均振幅得到提高将有助于减摩效果的提升。这也对后续减摩气缸的研制提供了理论依据。通过研究平面接触的橡胶与铝合金材料之间的振动减摩效果初步证实了将振动应用于气缸减摩的可行性。然后经过等效后的密封圈与缸筒摩擦副之间的摩擦力特性进一步论证了橡胶圈与缸筒材料间的接触形式的振动减摩适用性。在一个更加贴近于气缸真实工作条件的摩擦力环境下,高频振动有效提高了整合了压电叠堆的气缸结构的摩擦特性。通过实验研究了与振动密切相关的一些主要参数对减摩的影响,以指导后续利用振动方式减小气缸摩擦力的研究。上述主要参数包括振动下的法向压力、振幅、振-滑速度比、激振区域等。验证了无论有、无振动,库伦定律均适用于气缸摩擦副,同时,随着振幅的增大,摩擦副间的静摩擦力随之减小,其数值最大可以减小为初始摩擦力的22.6%。在有润滑剂存在时,振动减摩效应依然存在,其减摩比例在50%左右。在对振速-滑动速度比对振动摩擦系数的影响的实验中发现,通过基于达尔摩擦力模型计算出的结果是更适用于描述振动条件下的摩擦力变化规律的。它考虑了摩擦副材料的剪切刚度及其在微观条件下的滑前位移,因此更适用于描述气缸中的摩擦力在振动下的变化。在对橡胶材料与金属平板之间摩擦力的研究中发现,当摩擦副处于振动平板的平均振幅最大的位置上可以实现最佳的减摩效果,这为后续对减摩气缸结构的合理研制提供了依据。基于对本研究中振动条件下气缸摩擦力及其影响因素的分析,提出了一种基于压电叠堆的逆压电效应、可实现弯曲振动与纵向振动两种模态的减摩气缸。搭建了能够完成对气缸样机进行静、动摩擦力测试的摩擦力测试系统。通过分别测试两种模态下气缸的摩擦力变化情况来检验气缸在两种振动模态下的摩擦力特性。弯曲、纵向振动模态下气缸的静摩擦力可以分别降低为原摩擦力的33%和52.6%左右。通过对气缸在两种模态下的动摩擦力研究,并进一步比较两种条件下的减摩效果可以看出,具有振幅放大作用的弯振模态具有更好的减摩效果,在谐振频率下其减摩比可以达到50%。当工况条件下提高气缸的工作压力时,减摩效果被削弱。在对振速与滑动速度的比对振动摩擦系数的影响的研究中发现,工作于纵向振动模态的减摩气缸出现减摩效果的条件是振速与滑动速度之比要大于1,即当振幅与频率一定时,滑动速度要低于某个临界值。为了使减摩气缸的体积更小、结构更加简单、集成化程度更高,从而在一些特定应用场合中有更大的应用潜力,提出了一种可实现气缸活塞杆密封处径向振动模态的减摩气缸。利用直线电机辅助驱动的的摩擦力实验台完成对气缸样机的静、动摩擦力测试。通过实验测试的手段分析与验证振动气缸的减摩原理,在谐振频率为144 k Hz左右的径向振动模态下,气缸的静摩擦力可以降低为原摩擦力的53.3%左右。在工况条件下提高气缸的工作压力时,减摩效果被削弱,这也为该领域研究中气体压力对减摩气缸的影响提供参考。在对低速动摩擦力的研究中发现,增大气缸摩擦副处的振幅将使得其位移及动摩擦力曲线更加光滑,从而使粘-滑现象消失,运动变得更加平稳。这也进一步表明了摩擦副间处于振动状态有利于提高气缸低速运动时速度与力的稳定性。这为后续开展通过振动方式来减小气缸摩擦力,提高气缸低速运动稳定性与定位精度的应用研究提供基础。
[Abstract]:Pneumatic transmission has the characteristics of high cleanliness, simple maintenance, low cost, easy to centralized gas supply and medium distance transportation, so it is widely used in the fields of food, drug processing, semiconductor and microelectronic manufacturing, and medical auxiliary instruments. The elastic rubber ring in piston cylinder is used to provide the seal of cylinder cavity or the density of the outside. The inevitable friction force is introduced at the same time. It is one of the most important factors that affect the positioning accuracy and transmission stability of the cylinder. Vibration reduction, that is, the high-frequency vibration of the surface of the friction pair can reduce the friction force, which has aroused the attention of many scholars in the related fields. Therefore, the high frequency vibration is applied to the cylinder friction pair. In order to improve the friction force characteristics of cylinder, this paper first analyzes the friction force model of the general friction pair, compares and analyzes the friction force model of the cylinder, and then studies the characteristics of the friction force decreasing between the different directions of vibration on the friction pairs of the elastic seal. When the vibration direction is parallel to the plane of the friction pair, the introduction time of the high frequency vibration is changed in the direction of the friction force, so the average value of the friction force can be obviously reduced by calculation. Based on the friction force model in Kulun and the Dahl friction force model, the velocity slip velocity ratio is studied respectively. The effect of the vibration friction coefficient is explored more suitable for describing the physical model of the friction law of the cylinder under the vibration condition. When the direction of the vibration is perpendicular to the plane of the friction pair, the friction force is reduced by reducing the actual contact area. The greater the amplitude, the smaller the friction force. Through the theoretical calculation of the effect of the excitation region on the effect of friction reduction, it is found that the optimization of the position of the excited vibrator and the increase of the average amplitude of the friction pair will help to improve the friction reduction effect. This also provides a theoretical basis for the development of the subsequent friction reducing cylinder. The vibration reduction effect between the contact rubber and the aluminum alloy material preliminarily confirms the feasibility of applying the vibration to the friction reduction of the cylinder. Then the applicability of the friction between the rubber ring and the cylinder cylinder material is further demonstrated by the frictional force characteristic between the equivalent seal ring and the cylinder cylinder friction pair. The applicability of the vibration reduction in the contact form between the rubber ring and the cylinder material is further demonstrated. High frequency vibration effectively improves the friction characteristics of the cylinder structure integrating the piezoelectric stack under the friction environment of the cylinder's actual working conditions. The effect of some main parameters closely related to the vibration on the friction reduction is investigated by experiments to guide the subsequent use of vibration mode to reduce the friction force of the cylinder. The dynamic pressure, amplitude, the ratio of vibration and sliding velocity, the excitation region, etc., verify that no matter, no vibration, the Kulun law is applicable to the cylinder friction pair. At the same time, as the amplitude increases, the static friction between the friction pairs decreases, and the maximum value can be reduced to the initial friction force of 22.6%. in the presence of lubricants, vibration reduction effect. It still exists, the friction reduction ratio is about 50%. In the experiment on the effect of the velocity to sliding velocity ratio on the vibration friction coefficient, it is found that the results calculated by the Dahl friction force model are more suitable for describing the law of the friction force change under the vibration condition. It takes into account the shear stiffness of the friction material and its micro conditions. The sliding front displacement is more suitable for describing the change of the friction force in the cylinder. In the study of the friction between the rubber material and the metal plate, it is found that the best friction reduction effect can be achieved when the friction pair is at the maximum average amplitude of the vibrating plate, which is the reasonable development of the subsequent anti friction cylinder structure. Based on the analysis of the friction force of cylinder and its influencing factors under the vibration condition in this study, a kind of anti piezoelectric effect based on piezoelectric stack is proposed, which can realize two modes of friction reducing cylinder with bending vibration and longitudinal vibration. A friction force testing system can be built to test the static and dynamic friction force of the cylinder prototype. The friction force characteristics under the two modes of cylinder are tested by testing the friction force changes of the cylinder in two modes. The static friction force of the cylinder can be reduced to 33% and 52.6% of the original friction force respectively under the bending and longitudinal vibration modes. The dynamic friction force of the cylinder in two modes is studied and compared further. The anti friction effect of the two conditions can be seen that the bending vibration mode with amplitude amplification has better friction reduction effect. Under the resonant frequency, the antifriction effect can be reduced when the working pressure of the cylinder is raised under the working condition of 50%.. The study on the effect of the ratio of vibration friction coefficient to the vibration velocity and the sliding velocity has been studied. It is found that the friction reducing effect of the friction reducing cylinder working in the longitudinal vibration mode is more than 1, that is, the sliding velocity is lower than a certain critical value when the amplitude and the frequency are fixed. In order to make the cylinder smaller, the structure is simpler and the integration degree is higher, and in some specific applications. With greater application potential, a friction reducing cylinder which can realize the radial vibration mode of cylinder piston rod seal is put forward. The static and dynamic friction force test of the cylinder prototype is completed by the friction force test bench driven by the linear motor. The friction reducing principle of the cylinder is analyzed and verified by the means of experimental test. The resonant frequency is at the resonant frequency. Under the radial vibration mode of 144 K Hz, the static friction force of the cylinder can be reduced to about 53.3% of the original friction force. When the working pressure of the cylinder is raised under working conditions, the friction reduction effect is weakened. This also provides a reference for the effect of gas pressure on the friction reducing cylinder in this field. The amplitude of the cylinder friction supplement will make the displacement and the dynamic friction curve more smooth, so that the stick slip phenomenon is disappearing and the motion becomes more stable. This further indicates that the vibration state between the friction pairs is helpful to improve the stability of the velocity and force when the cylinder is moving at low speed. This will reduce the cylinder by the vibration mode. Friction provides the basis for improving the stability and positioning accuracy of cylinders at low speed.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TH138.51

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