小球式旋转直驱压力伺服阀卡滞机理研究

针对小球式旋转直驱压力伺服阀（BRDDPSV）静态测试卡滞问题，建立阀芯运动全局函数，包括基于缝隙流理论建立倾斜阀芯径向力模型，基于Coulomb摩擦理论建立阀肩触壁静摩擦-滑动摩擦模型. 理论解析曲线合理复现了静态测试卡滞问题：偏心驱动下阀芯逆时针旋转倾斜，右侧阀肩触壁，初始静摩擦导致阀芯卡滞，逐渐提升的电流水平克服摩擦形成阀芯运动超调. 为了保证电流指令与控制压力的近似比例特性，阀芯回拉复位，形成重复的正向驱动阀芯卡滞. 基于阀肩不触壁原则，获得阀芯是否卡滞阈值条件. 研究结果表明：增大阀芯与阀套初始半径间隙或减小小球偏离阀芯轴线的初始偏心量，均可以提高阀芯不卡滞的输出压力阈值；对于21 MPa系统压力及0~8 MPa输出压力的实际需求，在不改变其他参数的情况下，将初始半径间隙和初始偏心距分别调整为5.1 μm和0.2 mm，可以在维持原有性能的基础上获得阀芯运动全局不卡滞的最优解.

Spool stuck mechanism of ball-type rotary direct drive pressure servo valve

Aiming at the sticking problem of ball-type rotary direct drive pressure servo valve (BRDDPSV), the global motion function of the spool was established, including the radial force model of inclined spool based on gap flow theory and the static-sliding friction between the spool shoulder and sleeve wall based on Coulomb friction theory. Sticking problem was reasonably reappeared by theoretical analysis curve: spool rotates and tilts counterclockwise by eccentric force, then the right shoulder of spool contact sleeve wall, initial static friction leads to spool sticking, gradually rising current overcomes friction to form spool movement overshoot. The valve core is pulled back to form a repetitive positive drive spool block in order to ensure the approximate proportion of current command and control pressure. The threshold condition of the sticking problem was obtained based on the principle of non-contact between spool shoulder and sleeve wall. Results show that increasing the initial radius gap between spool and bush or decreasing the initial eccentricity of ball from spool axis can increase the output pressure threshold of non-stuck. For the actual demand of 21 MPa system pressure and 0-8 MPa output pressure, the initial radius clearance and the initial eccentricity were adjusted to 5.1 μm and 0.2 mm respectively. The optimal solution of global non-sticking can be obtained by maintaining the original performance.