PM流量控制器参数对液体静压导轨性能影响的研究

Research on the Influence of PM Controller Parameters on the Performance of Hydrostatic Slide for NC Machine Tool

在介绍PM流量控制器基本结构、工作原理以及流量压力特性基础上,推导出基于PM控制器的矩形对置油垫的承载能力、油膜刚度及动态传递函数的表达式。以某机床静压导轨的一对对置油垫为例,重点分析研究PM控制器的三个性能参数比流量cr、初始流量q0和泵压ps之间的相互关系及对油膜承载能力、静刚度及动态特性的影响。研究表明,给定初始流量q0和泵压ps,静刚度随cr增大而逐渐增加,在cr=6.2时静刚度有峰值,这对静压导轨的正常工作不利。比流量cr的合理取值范围为1.2～5.2,此时对置油垫静刚度随着q0的增大和pp减小而增大。基于油膜厚度传递函数表达式,研究敏感油路体积Vo=500 cm3时,在阶跃载荷作用下,不同的比流量cr、初始流量q0以及泵压ps对油膜在时域及频域内动态特性的影响。研究表明:在时域内,cr、q0、pp主要影响着油膜厚度的超调量,随着cr、q0增大以及泵压pp减小,其超调量明显增加。为提高油膜承载的稳定性,减小过渡过程的超调量,可减小cr、q0,增大泵压pp;在频域内,幅频特性曲线峰值处的频率为油液振动的固有频率。随着cr、q0的增加和pp减小,幅值越大,对应的固有频率也有所增大,失稳区频率范围变宽。当作用频率很高时,参数cr、q0、ps对幅值影响很小。研究工作对基于PM流量控制器的液体静压导轨的设计具有参考价值。

Based on the introduction of the structure,the operating principle and the pressure-flow characteristics of the PM flow controller,the bearing capacity,the oil-film stiffness and the dynamic transfer function of the rectangular contra-positive oil pocket with PM flow controller are derived.Taking a pair of contra-positive oil pockets of a machine tool for an example,the mutual relationship among the flow ratio cr,the initial flow q0,the pump pressure ps,and the influence of three parameters on the bearing capacity,the static stiffness and the dynamic characteristics are analyzed.The research indicates that,if the initial flow q0 and the pump pressure ps are determined,the static stiffness gets larger gradually with the increase of cr.There is a peak value of the static stiffness when cr= 6.2,and it is detrimental to the normal operation of the hydrostatic slide.The reasonable value scope of cr is 1.2～5.2.Meanwhile,the larger the q0,the smaller the pp,and the larger the static stiffness of the oil pocket.Based on the transfer function expression of the oil film thickness,when the volume of the sensitive oil circuit Vo=500 cm3,the influence of the different flow ratio cr,the initial flow q0,the pump pressure ps on oil film dynamic characteristics in time and frequency domain under the step load is considered.The research has shown that in time domain cr,q0 and pp affect the overshoot of the oil film thickness.The overshoot increases obviously with the increase of cr,q0 and the decrease of pp.To improve the bearing stability of the oil film and decrease the overshoot during the transient process,it is best to decrease cr,q0 and increase pp.In frequency domain,the peak frequency of the amplitude-frequency characteristic curve is the nature frequency of the oil vibration.With the increase of cr,q0 and the decrease of pp,the amplitude and the nature frequency get larger,and the frequency scope of the instability zone becomes wider.When the frequency is very high,the influence of cr,q0 and pp on the amplitude is small.The research on the design of the hydrostatic slide based on the PM flow controller has certain reference value.