液压缸的无冲击缓冲技术研究及新型缓冲结构的CAD

发布时间：2018-09-17 13:46

【摘要】：液压缸是液压传动与控制系统中常用的执行部件。液压缸拖动部件运动至行程终端时,往往会发生剧烈的机械碰撞。这种机械冲击的产生,不仅会影响液压缸的工作性能,而且会损坏液压系统的其它元件,具有很大的危害性。因此液压缸的缓冲研究就显的尤为重要了。本文对现有固定节流口、圆柱形环隙节流、沟槽节流、圆锥形环隙节流、抛物线环隙节流五种常用的液压缸内置式缓冲装置进行了分析,对缓冲过程建立了数学模型并借助MATLAB进行了计算仿真,探讨了各缓冲装置的缓冲特性。分析表明缓冲性能各不相同,各缓冲装置缓冲过程压力峰值较大,虽然都保证了速度无突变,即无硬冲击存在,但固定节流口、沟槽节流以及抛物线环隙节流缓冲装置在缓冲起点或终点加速度变化太大,即存在软冲击。可见,五种常用缓冲装置都无法达到最佳缓冲特性。液压缸内置式缓冲装置一般保证了无硬冲击,但如果存在软冲击,依然会对液压缸造成危害。因此,最佳的液压缸缓冲装置应该结构简单容易实现,并且其理想的缓冲特性应该是在保证缓冲压力较小的情况下,避免硬冲击,减少或消除软冲击。本文以砌块成型机的推板油缸工况需求为例,依据理想缓冲特性求得的理论节流面积曲线设计了一种液压缸缓冲装置。该缓冲装置由沿轴向不等距不等数量的圆形小孔组成,结构紧凑,加工制造容易。以液压缸末端小孔相应位置的实际节流面积与理论节流面积的差值作为约束条件,对小孔数量和小孔位置进行了合理设计,使其实际节流面积与理论节流面积更为接近,性能更加趋近理想缓冲特性。同时对新结构建立了数学模型,对其性能进行仿真,验证其除具备无硬冲击和较低的软冲击的缓冲性能外,还具有良好的软启动特性。液压缸的缓冲性能除与缓冲结构有关外,还与负载有关,要达到无冲击或小冲击缓冲,就需要根据具体的工况设计液压缸的缓冲结构。新型缓冲结构可以实现无冲击缓冲过程,但设计计算过程繁杂,因此本文运用MATLAB和VB软件编程开发出了新型液压缸内置式缓冲装置的设计软件,用户只需在界面内输入不同的工况参数后,就可以得到新型液压缸内置式缓冲装置缓冲过程的速度与行程关系、加速度与行程关系以及理论节流面积变化曲线,同时获得最佳缓冲特性下的小孔数量和分布位置。从而在短时间内完成新型液压缸内置式缓冲装置设计,最后在实例的验证下证明了软件的实用价值。
[Abstract]:Hydraulic cylinder is commonly used in hydraulic transmission and control system. When the hydraulic cylinder drives the parts to the stroke terminal, violent mechanical collisions often occur. This kind of mechanical impact will not only affect the working performance of the hydraulic cylinder, but also damage other components of the hydraulic system. Therefore, the study of hydraulic cylinder buffer is particularly important. In this paper, five kinds of commonly used hydraulic cylinder internal buffer devices, such as fixed throttle, cylindrical annular throttle, groove throttle, conical annular throttle and parabolic annular throttle, are analyzed. The mathematical model of buffering process is established and simulated by MATLAB, and the buffering characteristics of each buffer device are discussed. The analysis shows that the buffering performance is different, and the peak pressure of each buffer device during the buffer process is large. Although all of them ensure that there is no sudden change in the speed, that is, there is no hard impact, the fixed throttle outlet is fixed. If the acceleration of groove throttling and parabolic ring gap throttling is too large at the buffer starting point or end point, there will be soft impact. Thus, five kinds of commonly used buffering devices can not achieve the optimal buffering characteristics. Generally speaking, there is no hard impact, but if there is soft impact, it will still cause harm to the hydraulic cylinder. Therefore, the optimal hydraulic cylinder buffer device should be simple and easy to realize, and its ideal buffer characteristic should be to avoid hard impact and reduce or eliminate soft impact under the condition of low buffer pressure. In this paper, a kind of hydraulic cylinder buffer device is designed according to the theoretical throttling area curve obtained from the ideal buffering characteristic, taking the working condition requirement of the push plate oil cylinder of the block forming machine as an example. The snubber consists of a number of circular holes, which are not equal in number along the axial direction, and are compact in structure and easy to process and manufacture. Taking the difference between the actual throttle area and the theoretical throttle area at the end of the hydraulic cylinder as the constraint condition, the number of orifice and the position of the orifice are reasonably designed, so that the actual throttling area is closer to the theoretical throttle area. The performance is closer to the ideal buffering characteristic. At the same time, the mathematical model of the new structure is established, and its performance is simulated. It is verified that the new structure not only has the buffering performance of no hard impact and low soft impact, but also has good soft start characteristics. The buffering performance of hydraulic cylinder is not only related to the buffer structure but also to the load. In order to achieve non-impact or small impact buffering, it is necessary to design the buffer structure of hydraulic cylinder according to the specific working conditions. The new buffer structure can realize the shock free buffer process, but the design and calculation process is complicated. Therefore, the design software of the new type hydraulic cylinder inner buffer device is developed by using MATLAB and VB software. After the user input different operating parameters in the interface, the speed and stroke relation, acceleration and stroke relation and theoretical throttling area change curve of the new type of hydraulic cylinder internal buffer device can be obtained, and the relationship between the speed and the stroke, the acceleration and the stroke, and the theoretical throttling area change curve can be obtained. At the same time, the number and distribution of holes under the optimum buffer characteristics are obtained. Thus, the design of the new type hydraulic cylinder inner buffer device is completed in a short time. Finally, the practical value of the software is proved under the verification of an example.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH137.51

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