Unlike the general spindle components, one of the most prominent problems of the electric spindle is the heat generation of the built-in high-speed motor. Because the motor is installed in the center of the two support bearings of the main shaft, the heating of the electric motor directly affects the working accuracy of the main shaft bearing, that is, affects the working accuracy of the main shaft. One of the solutions is to add a spiral cooling aluminum cooling jacket 3 outside the motor stator (see Figure 1(a)). When the machine tool works, the cooling oil-water constantly flows in the spiral groove, so that the heat generated by the motor is taken away in time. The flow of cooling oil-water can be determined based on the heat generated by the motor. Figure 2 shows the oil-water heat exchange system of the GD-2 electric spindle developed by Guangdong University of Technology.
(a) The motor is placed between the front and rear of the spindle and the two bearings; (b) The motor is placed behind the rear bearing. Fig. 1 Built-in motorized spindle structure
Figure 2 GD-2 electric spindle oil-water heat exchange system
At the same time, the problem of heating of the spindle bearings must also be solved. Due to the high rotational speed of the motor spindle, the dynamic and thermal characteristics of the spindle bearings are very strict. In addition to individual ultra-high-speed electric spindle using magnetic bearings or hydrostatic bearings, the current majority of high-speed motor spindles at home and abroad are using angular contact Si3N4 ceramic ball bearings, in order to reduce the temperature rise of the spindle bearings, GD-2 spindle bearings used The oil-air lubrication system is shown in Figure 3. It uses distribution valves to supply oil-air mixtures regularly and quantitatively to different parts of the required lubrication, in accordance with their actual needs, so as to ensure that the different parts of the bearing are neither lack of lubrication nor greater due to excessive lubrication. The temperature rise can minimize oil mist pollution.
Fig. 3 GD-2 electric spindle bearing oil-air lubrication system