二维电液比例换向阀动态特性及稳定性分析

二维电液比例换向阀兼具直动式和导控式比例阀的功能:正常工作压力下,比例电磁铁输出的推力通过压扭联轴器使阀芯转动,阀敏感腔的压力差动变化,驱动阀芯轴向移动,与此同时阀芯反向转动,敏感腔的压力又逐渐恢复为原来的值,阀芯到达一个新的平衡位置,实现对阀芯位移的液压先导比例控制;当工作压力为零时,则由比例电磁铁直接驱动阀芯。在正常的工作过程中,压扭联轴器不仅可以实现直线-旋转运动转换,还可将比例电磁铁的驱动力放大,使其能有效、可靠地驱动阀芯转动,从而提高其比例控制性能和工作可靠性。通过2D阀的建模、动态仿真及稳定研究,弄清2D阀的关键结构和工作参数对动态特性的影响,并建立2D阀的稳定条件,为其结构设计和优化提供理论依据。对2D阀试验研究,测得直动与导控两种工作状态下主要性能曲线与指标,试验表明2D电液比例换向阀不仅可以实现直动和导控的功能,而且通过先导控制可以有效克服液动力和摩擦力的不利影响,同时也证明了2D阀具有较快的响应速度和很好的稳定性。

Two-dimensional Electro-hydraulic Proportional Directional Valve

The 2D electro-hydraulic proportional directional valve is composed of 2D directional valve(flow valve), compression-torsion coupling and proportional electromagnet. Under the normal working pressure, the magnetic force of the proportional solenoid rotates the spool through the compression-torsion coupling and induces the pressure of the sensitive chamber on the two sides to vary differentially. Consequently, the spool axially slides under the hydrostatic imbalanced force. As the spool moves forward, it rotates inversely and the pressure of the sensitive chamber recovers and returns to its previous value. In this process, the spool arrives at a new axial position and the proportional control to the valve openings is achieved. While the working pressure of the system is zero, the spool is proportionally driven by the magnetic force directly. Thus, the 2D electro-hydraulic proportional directional valve can function both as a pilot directional valve or direct actuated valve. The compression-torsion coupling is used to realize motion conversion and amplify the thrust force of proportional electromagnet, therefore the unfavorable influence of friction force between spool and valve sleeve on proportional characteristics can be effectively overcome. Simulation analysis clarifies the effects of the key structural geometric parameters on the characteristics of the 2D valve. Moreover, the criteria of the 2D valve is also established by the utilization of the linear theory. Experiments are also carried out by measuring the characteristic curves under direct and pilot operation states. By comparing the characteristics under these two operation state, it is concluded the 2D valve has a fairly fast responding speed and the good stability.