Small engine fuel injection system

For a two-stroke spark ignited internal combustion engine having a cylinder, a piston received for reciprocation in the cylinder, a crankshaft driven to rotate by the piston, a crankcase communicating with the piston and in which the crankshaft is received, a primary air intake port communicating with the crankcase, a transfer passage communicating with the crankcase and having a transfer port communicating with the cylinder, an exhaust port communicating with the cylinder, and an intake port communicating directly with the cylinder, a fuel injection system comprising:

• a tuned tube having a pair of ends, the tuned tube adjacent one end communicating with the cylinder intake port of the engine, and adjacent the other end communicating with the crankcase of the engine,
• a body,
• a primary air intake passage in the body having an inlet communicating with the atmosphere and an outlet constructed and arranged to communicate with the engine crankcase air intake port,
• a separate fuel injector passage in the body and having an inlet communicating with the atmosphere and an outlet constructed and arranged to communicate with the tuned tube adjacent its one end and upstream of the engine cylinder intake port,
• a fuel pump carried by the body and actuated by pressure variations produced by the operating engine to supply fuel to a fuel metering assembly,
• a fuel metering assembly having a fuel metering chamber receiving fuel from the fuel pump and in operation maintaining fuel in the metering chamber at a substantially constant pressure,
• a fuel circuit supplying fuel from the metering chamber to the fuel injector passage in operation to form a rich fuel and air mixture to be delivered to the turned tube and injected directly into the engine cylinder through the intake port,
• a first throttle valve in the primary air intake passage movable between substantially closed and wide open throttle positions to control in operation the flow of air through the primary air intake passage,
• a second throttle valve in the fuel injector passage and movable between substantially closed and wide open throttle positions to control the flow of air through the fuel injector passage, and
• an actuator connected with the first and second throttle valves to move them between their substantially closed and wide open throttle positions in operation to provide proportional air flow through the primary air intake and fuel injector passages so that under engine idle and wide open throttle operating conditions at least most of the total engine fuel requirement is supplied by a rich fuel and air mixture formed in the fuel injector passage and delivered by the tuned tube directly through the intake port to the engine cylinder and most of the engine air intake requirement is supplied through the primary air intake passage.

A two-stroke spark ignited internal combustion engine comprising a cylinder, a piston received for reciprocation in the cylinder, a crankshaft driven to rotate by the piston, a crankcase communicating with the piston and in which the crankshaft is received, a primary air intake port communicating with the crankcase, a transfer passage communicating with the crankcase and having a transfer port communicating with the cylinder, an exhaust port communicating with the cylinder, and an intake port communicating directly with the cylinder, and a fuel injection system comprising:

• a tuned tube having a pair of ends, the tuned tube adjacent one end communicating with the cylinder intake port of the engine, and adjacent the other end communicating with the crankcase of the engine,
• a body,
• a primary air intake passage in the body having an inlet communicating with the atmosphere and an outlet communicating with an engine crankcase intake port,
• a separate fuel injector passage in the body and having an inlet communicating with the atmosphere and an outlet communicating with the tuned tube adjacent its one end and upstream of the engine cylinder intake port,
• a fuel pump carried by the body and actuated by pressure variations produced by the operating engine to supply fuel to a fuel metering assembly,
• a fuel metering assembly having a fuel metering chamber receiving fuel from the fuel pump and in operation maintaining fuel in the metering chamber at a substantially constant pressure,
• a fuel circuit supplying fuel from the metering chamber to the fuel injector passage in operation to form a rich fuel and air mixture to be injected by the tuned tube directly into the engine cylinder through the intake port,
• a first throttle valve in the primary air intake passage movable between substantially closed and wide open throttle positions to control in operation the flow of air through the primary air intake passage,
• a second throttle valve in the fuel injector passage and movable between substantially closed and wide open throttle positions to control the flow of air through the fuel injector passage, and
• an actuator connected with the first and second throttle valves to move them between their substantially closed and wide open throttle positions in operation to provide proportional air flow through the primary air intake and fuel injector passages so that under engine idle and wide open throttle operating conditions at least most of the total engine fuel requirement is supplied by a rich fuel and air mixture formed in the fuel injector passage and delivered by the tuned tube directly through the intake port to the engine cylinder and most of the engine air intake requirement is supplied through the primary air intake passage.

A charge-forming device for an internal combustion engine having an injector apparatus supplying at least a portion of the fuel requirements of the engine, said charge-forming device comprising:

• a body,
• a primary air intake passage in the body having an inlet communicating with the atmosphere and an outlet constructed and arranged to communicate with an engine crankcase intake port,
• a fuel injector passage in the body having an inlet communicating with the atmosphere and an outlet constructed and arranged to communicate with an engine cylinder intake port,
• a fuel metering assembly having a fuel metering chamber receiving fuel from a fuel source and in operation maintaining fuel in the metering chamber at a substantially constant pressure,
• a fuel circuit supplying fuel from the metering chamber to the fuel injector passage in operation to form a rich fuel and air mixture to be delivered to the engine,
• a first throttle valve in the primary air intake passage movable between substantially closed and wide open throttle positions to control in operation the flow of air through the primary air intake passage,
• a second throttle valve in the fuel injector passage and movable between substantially closed and wide open throttle positions to control the flow of air through the fuel injector passage, and
• an actuator connected with the first and second throttle valves to move them between their substantially closed and wide open throttle positions in operation to provide proportional air flow through the primary air intake and fuel injector passages so that under engine idle and wide open throttle operating conditions at least most of the total engine fuel requirement is supplied by a rich fuel and air mixture formed in the fuel injector passage and delivered directly through the intake port to the engine cylinder and most of the engine air intake requirement is supplied through the primary air intake passage.