High-speed motors usually refer to motors with speeds in excess of 10,000 r / min. They have the following advantages: First, because the high speed, so the motor power density is high, and the volume is much smaller than the power of ordinary motor, can effectively save the material. Second, can be connected with the original motive, cancel the traditional slowdown mechanism, transmission efficiency, low noise. Third, due to high-speed motor inertia is small, so the dynamic corresponding fast. High-speed motors are becoming hotspots in the field of motors.
1. Overview High-speed machining technology is gaining more and more attention, not only to achieve greater productivity, but also to obtain high processing quality, and can reduce production costs, which is considered the most promising in the 21st century Advanced manufacturing technology. In advanced industrial countries, this technology has been widely used in aviation, aerospace and mold industry. In the past five years, China's technology has also made considerable progress. Is to achieve high-speed cutting of the prerequisite, the high speed of the machine is the current development trend of machine tools. High-speed machine tools and virtual axis machine tools are a major breakthrough in machine tools. Whether it is ordinary CNC machine tools or virtual axis machine tools, to achieve high-speed key components are still spindle unit. Spindle speed is often used dn value (dn value refers to the average diameter of the spindle bearing (mm) and the spindle speed limit (r / min) to measure the high-speed spindle often refers to the dn value of 1.0 × 106 or more spindle. With the bearing technology, the spindle speed increases year by year. In the data show that in the 1980s, the spindle bearing in the fat conditions under the dn value can only reach 0.5 × 106, but when the oil and gas device developed, dn value quickly increased to 1.0 × 106, the use of angular contact ceramic ball bearings , The spindle bearing dn value is further increased to 2.0 × 106. To the 90's, using the new Run-way - jet smoothing, so that the spindle dn value of 3.0 × 106. For a spindle unit with a speed of 10,000r / min or more, it is no longer appropriate to drive it through a belt or coupling. The more reasonable way is to use the built-in motor to drive directly. The rotor of the motor is mounted directly on the spindle. The stator is mounted on the spindle Tube, made of the so-called spindle form. The spindle has a compact structure, easy to balance, the higher the advantages of transmission, high-speed spindle is the ideal structure. The performance of the spindle in addition to the impact of bearing and its sliding technology, but also by the impact of many factors, including bearing preload control, built-in motor heating and cooling, spindle dynamic balance, shaft parts Wait. In addition, the design of the spindle shaft is also a high-speed spindle can not be ignored.
2. Spindle bearing selection and preloading technology used in high-speed spindle unit bearings are mainly angular contact ball bearings, magnetic bearings, water-based hydrostatic bearings, air and hydrostatic bearings. Magnetic suspension bearings due to expensive, complex control system, heat problems difficult to solve, and thus can not be extended in high-speed spindle unit applications. Water-based hydrostatic bearing is one of the most popular research topics in China. It is a feature that the water has a large heat capacity and a small bearing temperature rise. Some of the problems of the common dynamic and static pressure bearing are serious. Low speed heavy load occasions. Air static and dynamic bearings with low radial stiffness and impact, but high-speed performance is good, generally used in ultra-high speed, light load, precision spindle. Angular contact ball bearing dn value of 2.0 × 106 in the application of high-speed spindle unit, whether it is speed limit, load capacity, stiffness, accuracy and other aspects are well to meet the requirements and has been standardized, low prices, the current 90% The spindle assembly uses this type of bearing. This type of bearing can also be improved by the following methods.