Nonlinear springs with applications to flow regulation valves and mechanisms

Abstract

This thesis focuses on the application of nonlinear springs for fluid flow control valves where geometric constraints, or fabrication technologies, limit the use of available solutions. Types of existing nonlinear springs are discussed and categorized as either, single element springs or springs relying on external elements to provide nonlinear characteristics. This work discusses the design principles of, both, hardening and softening nonlinear springs and the development of a nonlinear spring system using a contact surface to increase or decrease stiffness. This work has been motivated by the development of a new automotive positive crankcase ventilation (PCV) valve that meets the flow requirements of the current production valve, yet resist stiction commonly associated with the freezing of the valve's internal components. The valve regulates the PCV system, which ventilates corrosive gases from the crankcase. Using the nonlinear spring design principles developed here, a valve has been designed that is estimated to cost 90% less than the current production valve, addresses the issue of freezing, reduces oil consumption by 54%, is less prone to hysteresis and eliminates flutter instabilities that cause the valve to violate flow specification. This thesis concludes with a discussion of the potential for this type of nonlinear spring in medical devices, toys, microsystems, mechanical couplings and fixturing.