Analysis and Modeling of an Electronically Controlled Pneumatic Hydraulic Valve for an Automotive Engine

This paper addresses the design and detailed modeling of a novel electronically controlled, pneumatic/hydraulic valve actuator (EPVA) for both the engine intake and engine exhaust valves. The valve actuator's main function is to provide variable valve timing and variable lift in an automotive engine. The design of the combination of pneumatic and hydraulic mechanisms allows the system to operate under low pressure with an energy saving mode. A system dynamics analysis is provided and is followed by a mathematical model. This modeling approach uses the Newton's law, mass conservation and thermodynamic principles. The air compressibility and liquid compressibility in the hydraulic latch are modeled. The discontinuous nonlinearity of the compressible flow due to choking is carefully considered. Provision is made for the nonlinear motion of the mechanical components due to the physical constraints. Validation experiments were performed on a Ford 5.4 liter 4-valve V8 engine head with different air supply pressures and different solenoid pulse inputs. Results of the experiments were satisfactory and the simulation responses agreed with the experimental results.