On the Development of an SMA Based Rear Mirror Folding Actuator

Nowadays electric motors are used for various applications in the automotive industry which affects the automobiles’ mass significantly. Small and medium sized electromotors are mainly used for comfort applications like locking systems or mirror folding drives. On the other hand, electromotor drives use often a reduction of a high speed rotation to a slow and powerful movement by the usage of gears. Due to the multistage gear ratio principle, such drives emit a noise level up which can be an inferiority attribute of an automotive system. Nevertheless, comfort applications are mainly driven by electromotor actuators in automobiles. Figure 1 shows a cut through a schematic side mirror of a car with two major electromotor drives comparable to the state of the art. The motor for mirror folding consists mainly of the complex gear box which has to fulfill a mirror movement of more than 65° in less than 5 seconds. To move the mirror with the motor has to have enough mechanical power to overcome this force and to move the mirror with a torque of more than 5 Nm.