This invention relates generally to an electronic fuel regulation system, and more particular, to an electronic fuel regulation system for small internal combustion engines, which in the preferred embodiment are hand-held garden implements utilizing a conventional two-cycle engine design. The invention may also be used in other small internal combustion engines and in other applications, such as in a four stroke engine and/or non-hand-held applications. While the invention is described in detail with respect to those applications, those skilled in the art will recognize the wider applicability of the inventive aspects described herein.
Small gasoline engines presently have wide application, being ubiquitous in the marketplace for a variety of applications, including, for example, hedge trimmers, blowers and lawn edgers. The standard fuel delivery system for such engines currently is a somewhat simplified carburetor based system. However, such carburetor based systems are relatively fuel inefficient, resulting in undesirable levels of emissions caused by engine operations that generate excessive hydrocarbons and evaporative emissions. Additionally, carburetor based systems usually require high maintenance and are difficult to adjust for maximum efficiency. Carburetor based systems also can be hard to start in certain conditions and are difficult to operate in normal use. The starting problem is particularly evident with small two cycle engines employed with edgers and blowers, for example, whose overall designs, normally of a rope pull nature, make starting the engines difficult, even when the fuel systems are fully functional.
To rectify some of the problems associated with carburetor based fuel delivery systems, a number of attempts have been made to design fuel management systems for the engines. These attempts usually have involved fuel injector based systems. Often, the fuel injection systems are simply scaled down versions of conventional automobile fuel injection technology. In addition, the application of the technology to relatively low cost hand-held implements has heretofore been hindered by the excessive costs associated with the fuel systems. To control the fuel delivery and fuel mixture in previously known fuel injector based systems, various timing and sensing components are required. This complexity has resulted in substantial cost, and merely adopting or scaling prior art solutions to the problem has not resulted in commercially viable systems for smaller applications. Certain prior art designs are directed at lowering costs. In particular, it is noted that U.S. Pat. No. 6,343,596 (“the '596 patent” hereinafter), assigned to the assignee of the present invention, has achieved success in that regard. The '596 patent is incorporated herein by reference. As indicated, the '596 patent works well for its intended purpose, but is not adaptable to low cost, small gasoline engines to which the present disclosure applies. While the '596 patent includes a microprocessor, a thermocouple, exhaust gas temperature sensor, and a fuel regulating valve installed in a low-pressure fuel delivery system between the fuel tank and the carburetor, the application of that technology to smaller engines is cost prohibitive in the form described in the '596 patent. In order to overcome the cost problems to which the present disclosure is directed, a number of innovative designs were employed, as more fully described in the following specification and accompanying drawings. The designs include a low cost injector, which is shrunk in size to facilitate use in its intended application and a simplified method of adjusting the injector for mass projection. The carburetor of the prior art convention systems is replaced by a throttle body in which we have mounted an electronic control unit (ECU) which receives input from a throttle position sensor. The throttle body also has provisions for an intake air temperature sensor passage, a pump, a fuel pressure regulator, a diagnostic port and the injector described above. The fuel pressure regulator is adapted to provide a constant fuel pressure and allow for easy prime of the system at all times, with excess fuel being pushed or returned to the fuel tank through the throttle body.
In order to ignite the fuel provided by the operation of the fuel regulation system, an ignition module is provided in which a power generation and spark control advanced circuitry is integrated on the ignition module board. As indicated, the electronic control unit is positioned on the throttle body, and variable spark advance is controlled through the electronic control unit. The ignition module includes the capability of providing additional DC power for battery charging, if desired. Finally, an adaptive algorithm based on speed of the engine, prime start and what is referred to hereinafter as smart choke positioning utilizes the electronic control unit to provide operational commands to this system.