高温环境对射流管伺服阀偶件配合及特性的影响

针对射流管伺服阀高温试验中出现的不规则、不可重复的特性,提出将阀体、阀套、阀芯均简化为规则金属体,根据带残余应力的规则金属体在变温度场内的尺寸变化规律,分析了温升对偶件配合的影响及其与伺服阀故障之间的映射关系。结果表明：高温环境下,铝阀体与钢阀套的径向间隙变大,且阀套在轴向获得一定的自由移动空间,破坏了压装其上的接收器与射流喷嘴的空间位置关系,导致伺服阀性能不规则且不可重复;同种钢质但配合表面发生磨削烧伤的阀芯与阀套之间的径向间隙会减小,易出现卡滞,导致伺服阀流量波动或跳跃。提出了改进措施：将接收器尾部增设定位销,使阀体与阀套连为一体;增设锁紧螺钉防止在长期温度交替时接收器由于阀体的膨胀收缩而"拔出";锁紧环内侧加装蝶形簧片,其预压缩变形量大于阀体与阀套伸长量之差时,可消除阀套的轴向自由活动;磨削过程中,适当加大冷却液的流速可加快散热,并对阀芯、阀套的配合表面进行硬度筛查。高温试验结果与理论分析相一致。

Influence of High Temperature on Couples Matching and Characteristics of Jet Pipe Electrohydraulic Servovalve

In view of anomalous and non reproducible test results of jet pipe servovalves under high temperature, it is proposed that the valve body, sleeve and spool can be simplified into regular metal frames, based on the deformation rule of regular metal frame with residual stress under variable temperature field, change of couples' fitting state and its mapping relationship with servovalve failures are analyzed. It shows that in high temperature environment, radial clearance between aluminum valve body and steel sleeve enlarges, and the sleeve obtains some axis space moving randomly, which destroys the fitting relationship between the jet-pipe nozzle and the receiver held in the sleeve, leading to anomalous and non reproducible test results; radial clearance between steel spool and sleeve with grinding burn on the mating surface reduces, which is likely to block and result in flow fluctuation or jump of the valve. Improvements include changing the tail of the receiver into a dowel, which connects the valve body and sleeve as a whole; adding lock bolts to prevent "pull out" of the receiver by expansion and contraction of the valve body under long term temperature alternation; adding butterfly spring inner beside the lock ring, ensures its pre-compression is greater than the elongation difference between the aluminum valve body and the steel sleeve, and eradicates the sleeve's axis free space; increasing the flow rate of coolant to enhance heat dissipation in grinding, and add a hardness screening process for the mating surface of spool and sleeve. Elevated temperature experimental results are in good agreement with the theoretical analysis.