Development of a High-speed Spindle System with a Preload Adjusting Mechanism

滚珠轴承通常用于预加载的主轴系统。这是影响机床在切割过程中静态和动态行为的一个重要因素。然而，在高速运行时，过大的预紧力会导致轴承温度突然升高和轴承卡住。因此，轴承上的预紧力应根据加工条件进行调整。在本研究中，通过安装压电式和液压执行器的预紧力调整机构，开发了一种新的主轴系统。将压电喷嘴应用于油气混合装置，研制了一种新型的油气润滑系统。通过脉冲力响应试验和切削试验对所研制的主轴系统进行了性能评价。通过试验获得的结果总结如下。(1)采用压电式油气混合装置代替传统的混合装置，提高了润滑质量。(2)通过低水平调节预紧力，有效地抑制了高速运行时轴承的温升，并抑制了轴承卡住的发生。(3)通过在较高水平调整预紧力，改善了主轴系统的静、动态性能。(4)通过增加预紧力，有效地抑制了颤振的发生。(5)用压电式执行器代替液压执行器，获得了更高的静、动态刚度，所研制的新型主轴系统不仅适用于重型切割作业，也适用于高速切割作业。

Ball bearings are usually used for spindle systems under preloading. This is an important factor affecting static and dynamic behaviors of machine tools during cutting operations. However, an excessive preload causes a sudden rise of bearing temperature and bearing seizure at high-speed operations. Therefore, the preload on bearings should be adjusted according to the cutting conditions.In this research, a new spindle system was developed by installing a preload adjusting mechanism using piezo-electric and hydraulic actuators. A new type of oil-air lubrication system was also developed by applying piezoelectric nozzles to the oil-air mixing equipment. The performance of the developed spindle system was evaluated through the impulse-force response test and cutting test. The results obtained through the tests are summarized below. (1) The quality of lubrication was improved by using the piezoelectric oil-air mixing equipment instead of the conventional type. (2) The temperature rise of bearings during high speed operations is effectively suppressed by adjusting a preload at low level, and the occurrence of bearing seizure is also suppressed. (3) The static and the dynamic behaviors of the spindle system are improved by adjusting a preload at high level. (4) By increasing a preload, the occurrence of chatter vibration is effectively suppressed. (5) Higher static and dynamic stiffness are obtained by using the piezo-electric actuators instead of the hydraulic actuators.The developed new spindle system can be applied not only heavy duty cutting operations but also high-speed cutting operations.