Research on Stick & Sprag-Slip Phenomenon of Door Waist Belts

The squeak noise generated during the moving of the door glass has a influence on the performance of vehicles felt by the consumer. In order to improve the noise, it is necessary to understand the principle of a friction vibration. In this paper, it is confirmed that the principle on the waist belt is most closely related to stick-slip and sprag-slip among various vibration characteristics. Stick-slip is expressed by energy accumulation and divergence due to difference in static and dynamic friction coefficient. Sprag-slip define instability of geometric structure due to angle of lips on the belt. In this paper, the physical model and the energy equation are established for the above two phenomena. Stick-slip can be solved by decreasing the difference of the static and dynamic friction coefficient. Sprag-slip is caused by the ratio of compressive and shear stiffness of the lips. The belt uses flocking to ensure durability, not coating. Therefore five factors that can be considered in the production of flocking are selected such as thickness. This study introduces an approach to improve the noise using DFSS. To predict the sprag-slip, the lips was modeled by a spring-damper system, and the stiffness value could be derived by applying shear deformation after compression load. The shapes of the lips were designed with 18 cases and the guide for the optimum was provided. It is found that positional deviation occurs due to the equilibrium of forces rather than merely by the tolerance when the glass of the vehicles can be moved from 0 to 2.6 mm. The optimization was confirmed that no squeak noise occurred even under the condition of 3 mm.