High-speed motors usually refer to motor speeds exceeding 10000r/min. They have the following advantages: First, because of high rotational speed, so the motor power density is high, and the volume is far less than the power of ordinary motor, can effectively save materials. Second, it can be connected with the original motive, cancel the traditional deceleration mechanism, the transmission efficiency is high, the noise is small. Third, because of the small inertia of high speed motor, the dynamic response is fast.
Based on the above advantages, high-speed motor in the following areas have broad application prospects:
(1) High-speed motor in air-conditioning or refrigerator centrifugal compressors and other occasions to be applied, and with the development of science and technology, the special requirements more and more, its application will be more and more extensive.
(2) with the development of automobile industry HEV, the small size, light weight of high-speed generators will be fully valued, and in the hybrid electric vehicle, aviation, shipbuilding and other fields have a good application prospects.
(3) The High speed generator driven by gas turbine has the advantages of small volume, high maneuverability, can be used in standby power supply for some important facilities, as well as independent power supply or small power station, which can make up the shortage of centralized power supply, which has important practical value.
Because the centrifugal force on the rotor of the high speed motor is proportional to the square of the line speed, the high speed motor requires high mechanical strength, and because of the high speed motor frequency, the iron consumption is large, the magnetic density in the iron heart should be lowered in the design, and the core material with low loss is adopted.
Bearing research is also closely related to high-speed motor content, because ordinary bearings are difficult to withstand the high-speed system in the long run, the need to adopt new materials and structure of the bearings. At present, people are studying the types of pneumatic bearings and magnetic bearings.
High-speed motor can have a variety of structural forms, such as induction motor, permanent magnet motor and reluctance motor. The centrifugal force of the motor at high speed spins is very big, when the line speed reaches 200m/s above, the conventional laminated rotor is difficult to withstand the centrifugal force produced by the high-speed rotation, which requires special high-strength laminated or solid rotors.
1. The overview of High speed machining technology is increasingly being recognized as one of the most promising advanced manufacturing technologies in the 21st century, not only for greater productivity but also for high processing quality and lower production costs. In advanced industrial countries, this technology has been widely used in aviation, aerospace and tooling industries. In the past five years, China's technology has also made great strides. Is the precondition of realizing high speed cutting, the high speed of machine tool is the development trend of machine tool at present. Both the High speed machine tool and the virtual Axis machine tool are the major changes of the machine tool breakthrough. Whether it is a common CNC machine tool or a virtual Axis machine tool, the realization of high-speed key components is still the spindle unit. Spindle high Speed common DN value (DN value refers to the spindle bearing average diameter (mm) and spindle limit speed (min) of the product) to measure, high-speed spindle often refers to the DN value of 1.0x106 above the spindle. With the bearing technology, the rotational speed of the spindle has been improved. In the data display, in the 80 's, the DN value of the spindle bearing under the condition of Grease can only reach 0.5x106, but when the oil and gas conditioner is developed, the DN value is rapidly increased to 1.0x106, the DN value of the spindle bearing is increased to 2 after the angular contact ceramic ball bearing is adopted. By the 90 's, the new way of moistening-jet plus slide, so that the DN value of the spindle reached 3.0x106. For the rotational speed in the 10000r/min above the spindle unit, through the belt or coupling to drive is no longer appropriate, the more reasonable way is to use the internal motor Direct drive, the motor rotor will be installed directly on the spindle, the stator installed in the spindle sleeve, the form of the so-called electric spindle. The spindle has the advantages of compact structure, easy balance and high transmission rate, and is the ideal structure of high speed spindle. The performance of the electric spindle is influenced by many factors besides the bearing and its slip technology, including the control of the preload of the bearing, the heating and cooling of the inner motor, the dynamic balance of the spindle and the connection of the parts on the shaft. In addition, the spindle end design is also the high-speed electric spindle should not be ignored.
2. Selection of electric spindle bearing and its pretension technology used in high-speed spindle unit bearings are mainly angular contact ball bearings, magnetic bearings, water-based hydrodynamic bearings, air dynamic pressure bearings. Because of the high price, the control system is complicated and the heating problem is difficult to be solved, the maglev bearing cannot be popularized in the high-speed spindle unit. Hydrostatic bearing is one of the most popular research topics in China, it is the use of water with a larger heat capacity, the bearing temperature rise is smaller, part of the general dynamic and static pressure bearing heating serious problems, mainly used in low speed overload occasions. Air dynamic and static pressure bearings have low radial stiffness and impact, but high speed performance, generally used in ultra-high speed, light load, precision spindle. The DN value of angular contact ball bearing is in 2. The application of the High speed spindle unit below 0x106, whether it is speed limit, carrying capacity, rigidity, accuracy and so on all aspects can meet the requirements well and has been standardized, low price, the current 90% of the spindle components of this type of bearings. The type of bearings can also improve performance in the following ways.