预紧 预警是为了消除滚珠丝杠副之轴向间隙和提高刚度,最终是为了达到定位精长驱的需要。预紧的方法有多种,最普遍和最常用的是双螺母结构,见下图: 在两个螺母之间配有垫片来达到预紧,还有一种预紧是在单螺和丝杠之间通过控制中径,并调节增大钢直径,从而实现预紧目的,(见下图)常用于承载不大,预紧载荷小的场合。  当最大轴向工作载荷Fmax能确定时: Fao= Fmax/3 当最大轴向工作载荷Fmax不能确定时: Fao=ξCa Fao -- 预警载荷(KN) Fmax -- 最大载荷(KN) ξ -- 预警系数(见下表) Ca -- 额定动载荷(N) | 载荷类型 | 轻微载荷 | 轻载荷 | 中载荷 | 重载荷 | | ξ | 0.02 | 0.05 | 0.07 | 0.1 | | 预紧螺母 | 单螺母 | 双螺母 | 双螺母 | 双螺母 | 有预加载荷滚珠丝杠副(无任何外加载荷下,两端无防尘圈)的空载理论动态预警紧转矩 Tpo=Kp×Fao×Pho/(2π×103) Tpo--理论动态预紧转矩(Nm) Kp--预紧螺母内的摩擦系数(0.1~0.3) Pho--导程(m.m) Fao--预警载荷(N) | 动态预警转矩极限偏差 △Tpp(表) | 理论动态预紧转矩Tpo | 精度等级 | | 1 | 2 | 3 | 4 | 5 | 7 | 10 | | 大于 | 至 | Lu/d0≤40 △Tpp (Tpp 的百分数) | | 0.2 | 0.4 | ±35% | ±37% | ±40% | ±45% | ±50% | - | - | | 0.4 | 0.6 | ±25% | ±32% | ±40% | ±37% | ±40% | - | - | | 0.6 | 1.0 | ±25% | ±27% | ±30% | ±32% | ±35% | ±40% | - | | 1.0 | 2.5 | ±20% | ±22% | ±25% | ±27% | ±30% | ±35% | - | | 2.5 | 6.3 | ±15% | ±17% | ±20% | ±22% | ±25% | ±30% | - | | 6.3 | 1.0 | - | - | ±15% | ±17% | ±20% | ±30% | - | | | 40<Lu/d0≤60 △Tpp (Tpp 的百分数) | | 0.2 | 0.4 | ±40% | ±47% | ±50% | ±55% | ±60% | - | - | | 0.4 | 0.6 | ±35% | ±36% | ±40% | ±42% | ±45% | - | - | | 0.6 | 1.0 | ±30% | ±32% | ±35% | ±37% | ±40% | ±45% | - | | 1.0 | 2.5 | ±25% | ±27% | ±30% | ±32% | ±35% | ±40% | - | | 2.5 | 6.3 | ±20% | ±22% | ±25% | ±27% | ±30% | ±35% | - | | 6.3 | 10.0 | - | - | ±20% | ±22% | ±25% | ±35% | - |
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