Integrated Optimum Design of a Torsion Spring-Compensated Automotive Engine Hood Linkage Mechanism

A torsion spring-assisted automotive hood linkage with joint friction is statically balanced for its entire range of motion. The four-bar linkage dimensions are to be synthesized. Coulomb friction at the joints can assist in the balancing. The magnitude of friction at the joints are unknown, and so are the torsion spring characteristics. All the aforementioned unknowns are determined in an integrated procedure such that the linkage dimensions, joint friction as well as the torsion spring are all designed optimally together in one go. The objective is to require the lowest force to close and to open the engine hood, with the entire design procedure to be performed in just one-step. Only three specifications are known: The mass characteristics (weight and center of gravity location) of the hood, the two acceptable regions of the hinge locations either on the engine hood or on the car body, as well as, the closed and opened positions of the engine hood. Thirty different design configurations (scenarios) are investigated and the results are discussed. The optimal results for a torsion spring-assisted hood linkage when compared to a similar tension spring-assisted linkage, show much better load compensation characteristics: The magnitudes and fluctuations of the external lifting force are smaller. Moreover, problem specification for a torsion spring system is also simpler.