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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.

This paper is an insight to the challenges and technical solutions chosen for design implementation of the Gen_VII permanent magnet stepper motor. Its primary function is to be used as an Idle Air Control Valve [IACV] in a small gasoline engine with a Mechanical Throttle Body [MTB] and Electronic Fuel Injection [EFI]. Stepper motors can also be referred to as Digital Linear Actuator [DLA]. The Gen_VII DLA is a 2-phase, fixed frequency, bipolar permanent magnet style stepper motor. There is discrete mechanical rotation every time one phase polarity reversal occurs. The output shaft has a moveable insert that translates this angular rotation into discrete linear movement. The Gen_I DLA is an automotive grade stepper motor that was designed to operate as an IACV in an automotive under hood environment. It has been in production for over 20 years. It is a robust design but too large in both size and mass for use on smaller engines.