Development of a novel brush-less DC motor for fuel pumps without dynamic seal shafts for increased reliability

Inhalt:
Electrically powered miniature drives promote several future technologies, such as small autonomous aerial vehicles for e.g. package delivery. However, for motor and electronics manufactures new challenges arise, such as to accommodate (power) electronics, motor control and motor into evermore decreasing spaces or increased power density and resulting needs for improved thermal management solutions. Therefore, new concepts and designs for highly reliable, maintenance-free, efficient and lightweight electrical drives are necessary. In this work the development of a brush-less DC motor for fuel pumps without a dynamic seal shaft is presented. Thereby, the stator and rotor of the brush-less drive are totally immersed in the used fuel during operation. In order to shield the stator windings from the fuel a polymer encapsulation is applied, which offers best media resistance against numerous fuel types (kerosene, gasoline, etc.) whilst not interfering with the electromagnetic field generated by the stator. Furthermore, a traditional design with a cylindric gap tube is not necessary, which in turn reduces losses, weight and costs further. As both stator and rotor are immersed in fuel an improved thermal deflection of the dissipated heat is achieved; thus, allowing a more compact sizing with increased weight-performance ratio. Further benefits of this electrical drive design are that reliability concerns of drives using a dynamic seal shaft such as sealing degradation (physical or chemical), sealing embrittlement or seized parts are eliminated. In order to keep the entire product dimensions as small as possible, an integrated motor control is directly attached at the backside of the stator. Furthermore, offering the benefit that a sensor- or sensorless rotor position detection, which is directly implemented within the motor-control electronics, is enabled; again, increasing integration density and reducing product size. The entire brush-less motor employing an immersed and encapsulated stator was virtually developed and optimized. The entire motor combined with the control unit entails outer dimensions of Ø 20 mm and L 40 mm. At the rotor shaft a gear pump is placed; leading to a system dimension of Ø 21 mm and L 58 mm. Consequently, the proposed seal-free electrical miniature drive enables a highly efficient, lightweight and powerful fuel pumps, with drastically enhance lifetime.