丝杠传动作为一种将旋转运动转化为直线运动的精密机械结构，广泛应用于机床、自动化设备等领域。在实际运行中，回差是其难以完全避免的特性，这种传动过程中的空程间隙，既与结构设计密切相关，也受制造精度、使用磨损等因素影响，成为衡量传动系统性能的重要指标。

　　As a precision mechanical structure that converts rotational motion into linear motion, screw drive is widely used in fields such as machine tools and automation equipment. In actual operation, backlash is a characteristic that is difficult to completely avoid. The clearance during this transmission process is closely related to structural design and is also affected by factors such as manufacturing accuracy and wear during use, making it an important indicator for measuring the performance of the transmission system.

　　回差的本质源于结构间隙与弹性形变。丝杠与螺母的啮合部位是回差产生的核心区域。为保证传动的灵活性，丝杠螺纹与螺母螺纹之间必须保留一定的配合间隙，避免因过盈配合导致卡滞。当传动方向突然改变时，这种间隙会使螺母在丝杠上产生短暂的空转，直到螺纹侧面重新接触并传递力，形成可感知的位移滞后。此外，丝杠、螺母及支撑部件在受力时会发生微量弹性形变，尤其是在负载变化的瞬间，形变的恢复过程也会加剧回差现象。例如，高精度进给系统中，即使配合间隙控制在微米级，快速换向时仍能通过位移传感器捕捉到零点几微米的空程误差。

　　The essence of hysteresis stems from structural gaps and elastic deformation. The meshing area between the screw and nut is the core area where backlash occurs. To ensure the flexibility of transmission, a certain clearance must be maintained between the screw thread and the nut thread to avoid jamming caused by interference fit. When the transmission direction suddenly changes, this gap will cause the nut to briefly idle on the screw until the thread side re contacts and transmits force, forming a perceptible displacement lag. In addition, the screw, nut, and supporting components will undergo slight elastic deformation when subjected to force, especially at the moment of load change, and the recovery process of deformation will also exacerbate the hysteresis phenomenon. For example, in high-precision feed systems, even if the clearance is controlled at the micrometer level, a zero point deviation of a few micrometers can still be captured by displacement sensors during rapid reversing.

　　制造精度与装配工艺直接影响回差大小。丝杠螺纹的螺距误差、牙型半角偏差，螺母内螺纹的加工精度，都会导致啮合间隙不均匀。若丝杠表面存在局部凸起或螺母螺纹有微小凹陷，在传动过程中会形成间歇性的间隙放大，使回差呈现波动状态。装配时，轴承的预紧力调整不当也会引入额外回差：预紧力不足会使支撑部位产生松动，预紧力过大则可能导致丝杠弯曲变形，间接改变螺纹啮合状态。对于滚珠丝杠这类高精度传动结构，钢球与滚道的配合精度尤为关键，钢球直径的一致性、滚道的曲率半径偏差，都会影响接触点的分布，进而改变回差的稳定程度。

　　The manufacturing accuracy and assembly process directly affect the magnitude of backlash. The pitch error and half angle deviation of the screw thread, as well as the machining accuracy of the nut internal thread, can all lead to uneven meshing clearance. If there are local protrusions on the surface of the screw or small indentations on the nut thread, intermittent gap amplification will occur during the transmission process, causing the backlash to fluctuate. During assembly, improper adjustment of the pre tightening force of the bearing can also introduce additional backlash: insufficient pre tightening force can cause looseness in the support part, while excessive pre tightening force may cause the screw to bend and deform, indirectly changing the thread engagement state. For high-precision transmission structures such as ball screws, the accuracy of the fit between the steel ball and the raceway is particularly critical. The consistency of the steel ball diameter and the deviation of the curvature radius of the raceway will affect the distribution of contact points, thereby changing the stability of backlash.

　　使用环境与磨损进程加剧回差演变。在长期运行中，丝杠与螺母的接触表面会因摩擦产生磨损，尤其是在高速、重载工况下，螺纹工作面的金属微粒脱落会逐渐扩大配合间隙。粉尘、冷却液等杂质侵入啮合区域，会加速磨损过程，使回差随使用时间呈现非线性增长。温度变化也是不可忽视的因素：环境温度剧烈波动时，丝杠与螺母的材料因热膨胀系数差异产生形变，可能导致原本调整好的配合间隙发生变化，在低温时出现间隙增大，高温时因膨胀而间隙减小甚出现卡阻，这种温度敏感性进一步增加了回差的复杂性。

　　The use environment and wear process exacerbate the evolution of hysteresis. In long-term operation, the contact surface between the screw and the nut will wear due to friction, especially under high-speed and heavy load conditions. The metal particles on the threaded working surface will gradually expand the fit clearance. Impurities such as dust and coolant entering the meshing area can accelerate the wear process, causing a non-linear increase in backlash over time. Temperature changes are also an undeniable factor: when the ambient temperature fluctuates dramatically, the materials of the screw and nut deform due to differences in thermal expansion coefficients, which may cause changes in the originally adjusted fit clearance. At low temperatures, the clearance increases, while at high temperatures, it decreases or even becomes stuck due to expansion. This temperature sensitivity further increases the complexity of backlash.

　　回差对传动性能的影响具有双面性。在精密定位场景中，回差会降低系统的控制精度，例如数控机床在进行轮廓加工时，换向瞬间的空程可能导致工件表面出现刀痕；而在某些允许一定滞后的传动系统中，适度的回差反而能减少因刚性碰撞产生的冲击噪声，延长部件使用寿命。为平衡精度与可靠性，通常通过预紧装置（如双螺母预紧、垫片预紧）补偿回差，或采用消隙结构设计（如渐开线花键消隙、弹性螺母消隙），将回差控制在应用场景允许的范围内。

　　The impact of backlash on transmission performance is double-sided. In precision positioning scenarios, backlash can reduce the control accuracy of the system. For example, during contour machining on a CNC machine tool, the momentary gap in direction may cause tool marks on the surface of the workpiece; In some transmission systems that allow for a certain lag, moderate backlash can actually reduce the impact noise caused by rigid collisions and extend the service life of components. To balance accuracy and reliability, it is common to compensate for backlash through pre tightening devices such as double nut pre tightening and gasket pre tightening, or to use clearance structure designs such as involute spline clearance and elastic nut clearance to control backlash within the allowable range of the application scenario.

　　丝杠传动的回差是多种因素共同作用的结果，既包含不可避免的结构间隙，也涉及制造、装配、使用等环节的累积误差。理解回差的产生机制与演变规律，并非为了完全它，而是根据实际应用需求将其控制在合理区间，这既是机械设计的智慧，也是保障传动系统稳定运行的关键。

　　The backlash of screw drive is the result of multiple factors working together, including inevitable structural clearances and cumulative errors in manufacturing, assembly, and use. Understanding the mechanism and evolution law of hysteresis is not to completely eliminate it, but to control it within a reasonable range according to practical application needs. This is not only the wisdom of mechanical design, but also the key to ensuring the efficient and stable operation of the transmission system.

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