Developing countries, facing greater challenges related to air pollution, are enacting more stringent emission rules for small engines. Idle Air Control Valve [IACV] along with Electronic Fuel Injection [EFI] is widely used for emission control in the large engine automotive market. This combination is also considered as one of the best solutions to aid in reducing the tailpipe emissions from small engines. One regulatory board for small engine use in USA is the California Air Resource Board [CARB]. CARB has a separate small engine emission category for nonautomotive Small Off-Road Engine [SORE] consisting of off-road spark-ignition engines below 25 horsepower, including all small off-road engines such as lawn mowers, weed trimmers, garden and other maintenance utility equipment [1]. SORE emission regulations for the handheld equipment were initially implemented in 1995 with most recently Tier II reductions of exhaust emissions in 2010.
The Gen_VII IACV was designed for use on smaller engines, such as in motorcycle applications (refer to Figure 1). The IACV is a stepper motor having a permanent magnet rotor integrated with a threaded drive mechanism that transforms rotary motion to linear motion. This actuator is a digitally controlled bi-polar, 2-phase, linear stepper motor designed to operate as an IACV. It's recommended to be electrically controlled using a full step bipolar L/R drive circuit operating from 7.5 to 14_Vdc. The IACV is required to work in extreme engine environments and has critical operational requirements. This paper presents some challenges and technical solutions in the design and implementation of this Gen_VII IACV.
The development of the smaller Gen_VII stepper motor was a continuation of collaborative efforts from Continental location in Asia, Europe, and North America.