Fuel system for a multi-fuel internal combustion engine

What is this patent about?

’034 is related to the field of multi-fuel internal combustion engines, specifically those used in portable electric generators. These systems are designed to run on different fuel types, such as gasoline and liquefied petroleum gas (LPG), to provide flexibility during fuel shortages or for long-term storage. A significant challenge in these engines is the transition between fuels while the engine is running, as residual fuel in the carburetor can lead to an overly rich mixture, causing the engine to stumble or stall during the changeover.

The underlying idea behind ’034 is the use of an electro-mechanical valve system that acts directly on the internal fuel passages of the carburetor to enable seamless, on-the-fly fuel switching. By placing a solenoid downstream of the carburetor float bowl, the system can instantly stop the flow of liquid fuel even if the bowl is full. This prevents the engine from simultaneously consuming two different fuels, solving the problem of fuel overlap that typically occurs when switching from gasoline to a gaseous alternative.

The claims of ’034 focus on a multi-fuel engine architecture that utilizes a liquid cutoff solenoid integrated with the carburetor and a gaseous cutoff valve, both managed by a selector switch. The independent claims highlight the specific placement of the liquid solenoid to block the fuel path downstream of the float bowl and the inclusion of a multi-stage pressure regulation system. This regulation system is often mounted off-board to reduce the generator's footprint while ensuring the gaseous fuel reaches the engine at a stable, usable pressure.

In practice, the invention works by using an electrical switch to coordinate the state of multiple solenoids. When a user toggles the switch from gasoline to LPG, the carburetor cutoff solenoid immediately blocks the main fuel circuit, while the gaseous solenoid opens to admit fuel into the intake. To ensure a smooth transition without power loss, the system can be configured with electronic delay circuits that provide a precisely timed overlap, ensuring the engine never starves for fuel during the mechanical transition of the valves.

This approach differs from prior solutions that relied on manual fuel shut-off valves or simple line-inlet solenoids, which could not account for the gasoline already sitting in the carburetor. By utilizing a jet block for multi-gas configurations and a solenoid that targets the main fuel circuit, the invention allows for tri-fuel operation—such as gasoline, LPG, and natural gas—with minimal interruption. This level of control ensures that the air-fuel ratio remains stable, preventing the rough running or hard starting typically associated with bi-fuel generator systems.