Parametric Study of a Typical Rocker Switch

Rocker switches are common electro-mechanical components used to close or open electrical connections. Solteam Electronics Corporatoin, a famous electronics manufacturer in Taiwan, sought cooperation with mechanical engineering students at National Taiwan University in order to get more insights of the design parameters of a typical rocker switch MR22 (see Fig. 1). This project mainly focused on two subjects, the first was the effects of geometric parameters on mechanical performance indices like maximum force required and stroke length, the second one was the validation of a simplified mathematical model predicting electrical contact resistance and the equilibrium temperature.

Fig. 1 Partially sectioned model of rocker switch MR22

A virtual model of  rocker switch MR22 was first built (see Mov. 1) to verify the applicability of ADAMS simulation. Using experiment setup shown in Fig. 2, where a linear linear actuation platform was used to trigger the snap-through behavior and monitored by CCD camera, the simulation results coincided well kinematically with the test data (Fig. 3).

Mov. 1 Simulation of the actuation process of rocker switch MR22 using ADAMS

Fig. 2 Experiment CCD camera image and ADAMS simulation clips

Fig. 3 Comparison of test data and simulation results with respect to displacement v.s. time

The next step was to construct a simplified model, with essential features built only and geometric parameters being design variables (see Fig. 4). Through parametric study function of ADAMS, it was possible to determine the sensitivity of design parameters with respect to attentive mechanical performance indices like maximum torquue/force required, stroke length, maximum contact bounce, and final contact force. With the aid of this parametric model, engineers can obtain acceptable specification quickly by simply tuning several design variables.

Fig. 4 Parametric model of rocker switch MR22 (DV stands for Design Variables)

Knowing the mechanical performance indices, the next step was to take a further look on electrical and thermal properties. To gain more insights on contact resistance, an empirical formula with 94% accuracy was aproposed based on theory of contact resistance developed by R. Holm. Then A multi-physical model was built in ABAQUS environment (see Mov. 2), and then verified by experiments using IR and thermal couples (see Fig. 5).

Mov. 2 Electro-thermal simulation of rocker switch MR22 using ABAQUS
(color legend bar indicates magnitude of temperature increase)

Fig. 5 IR image and temperature history of rocker switch MR22