Micro Brushless Motors Featuring Ceramic Air Bearing Design

BENSENVILLE, ILLINOIS: SANYO DC Micro Motor Division has developed a micro motor featuring a ceramic air bearing design. The new SANYO PM Series brushless motor is ideal for applications requiring high speed and quiet operation at high temperatures. The ceramic air bearing design, using air as a "lubricant", solves the problems encountered with typical motors lubricated with oil, which tends to break down over the life of the motor or at high temperature operation. The new series is available in a 20 mm size with a 14 mm size to come. The first application for the new design was a rear projection television color wheel because it must run at high speeds and high temperatures but be very quiet. Also being targeted are medical applications requiring high reliability and for which an out-gassing oil bearing might cause an unacceptable level of contamination. Micro motors designed with ceramic air bearings in a new concept. The sleeve and shaft of the ceramic air bearings contain a 3- to 5-micron gap between them. At the top of the shaft, magnets repel each other, and once the motor starts spinning, static air pressure is created in the gap. This allows the motor to operate without contact between the sleeve and the shaft. Available in a 20 mm size, the sensorless motor is extremely reliable, as the motor will operate as long as the bearing is in good condition. "It would last as long as it would take the air to wear out the ceramic," explains Shane Snipe, manager and mechanical engineer for Sanyo's DC Micro Motor division. Ceramic is very hard and the frictional wear of air is minimal, so the motor could last indefinitely at constant operation. In addition, the motor has been tested at over one million starts and stops. Standard operating voltage is 12 VDC. Load current is approximately 70mA. Typical speed is 10,000 rpm. Operating temperature range is 0¡ãC ~ +90¡ãC. Storage temperature range is -20¡ãC ~ +90¡ãC. The motor measures only 20 mm diameter in the sleeve, with an 8.4 mm high, 25 mm diameter rotor and a total height of only 25 mm.