Internal combustion engine adapted to operate selectively with injection of gasoline or LPG

Claim 1

Internal combustion engine, provided with a gasoline feed system, including many gasoline injection devices which are respectively associated with the cylinders of the engine, and an LPG feed system, including many LPG injection devices respectively associated with the cylinders of the engine, said engine being adapted to operate selectively with gasoline or LPG injection, characterized by the combination of the following features: the engine includes, for each cylinder, an adaptor member provided both with a seat for a gasoline injector, and with a seat for an LPG injector, said adaptor member having an inner cavity communicated to said seats and opening into an outlet hole, said outlet hole being formed through a portion of said adaptor member which is to be fitted within a seat of the engine originally provided for receiving the gasoline injection device, said engine further comprising a distributing conduit or rail for feeding LPG to all the LPG injection devices, the LPG feed system comprises: the plurality of said LPG injectors respectively associated with the various cylinders of the engine, said distributing conduit or rail for feeding LPG to the injectors, separate from the gasoline feed rail, an LPG reservoir, means for feeding LPG from the reservoir to the feed rail while keeping the LPG in a liquid state, said means including a pump which takes LPG from the reservoir and feeds it to the rail, a re-flow conduit for returning the quantity of LPG fed in excess to the injectors into the reservoir, a pressure adjuster, interposed in the reflow conduit for throttling this conduit so that said pump provides an increase from the pressure of LPG within the reservoir up to the pressure at which LPG is fed to the injectors, means associated with said pressure adjuster, able to detect the pressure of LPG within the reservoir, which is a function of the temperature, and to vary as a consequence the degree of throttling of the adjuster so as to keep said pressure increase at a substantially constant level, sensor means of the LPG feed pressure to the injectors, and electronic control means which receives output signals from said sensor means of the injector feed pressure and controls as a consequence the time during which the injectors remain open.