Small engine fuel injection system
AssigneeWalbro Japan, Inc.
InventorTakashi Abei
Life of this patent
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Abstract
A fuel injection system injects a rich mixture of fuel-and-air directly into a cylinder of a two cycle engine through an intake port for combustion. A charge forming device of the fuel injection system carries a primary air intake passage which flows air into the crankcase of the engine, and a rich fuel-and-air mixing passage which flows the majority of fuel into the cylinder, preferably via a tuned injector tube. To control air flow through the air intake passage and simultaneously control fuel flow into the fuel-and-air mixing passage, a rotary throttle valve rotateably and axially moveably traverses both passages. A mixture of fuel and oil is drawn into the air intake passage via a fuel bleed passage only during wide open throttle conditions for lubrication of moving parts and bearings contained within the crankcase.
Claims12
A 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 engine intake port communicating directly with the cylinder, the fuel injection system comprising:
- a body;
- a primary air intake passage in the body and having an inlet port communicating with atmosphere and an outlet port constructed and arranged to communicate with the primary air intake port of the engine;
- a separate fuel-and-air mixing passage in the body and having an inlet communicating with the atmosphere and an outlet constructed and arranged to communicate with the engine intake port;
- a rotary throttle valve having a valve chamber, a cylindrical rotary member, and a needle, the valve chamber carried by the body and communicating transversely through the air intake passage, the rotary member disposed rotatably and vertically movably within the valve chamber, the rotary member having a throttle bore communicating laterally through the member, the throttle bore being aligned to the air intake passage when the rotary throttle valve is rotated to a wide open throttle position and partially mis-aligned to the air intake passage when the rotary throttle valve is rotated to an idle position, wherein the needle projects concentrically from the rotary member;
- a fuel metering assembly carried by the body and having a fuel metering chamber at a substantially constant pressure;
- a fuel feed tube defining a fuel feed passage communicating between the metering chamber and the fuel-and-air mixing passage for supplying a majority of fuel flow of a rich fuel-and-air mixture to the cylinder through the engine intake port;
- and
- a fuel nozzle carried by the fuel feed tube and communicating with the fuel-and-air mixing passage, the needle of the rotary throttle valve extending axially into the fuel feed passage, wherein the needle is constructed and arranged to move axially into and out of the nozzle in response to rotation of the throttle valve to vary the degree of opening of the nozzle and thus fuel flow entering the fuel-and-air mixing passage from the metering chamber.
A 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, and an exhaust port communicating with the cylinder, the fuel injection system comprising:
- a tuned injector tube extending between an engine intake port communicating directly with the cylinder and a crankcase port communicating with the crankcase;
- a connecting tube communicating with the tuned injector tube near the engine intake port;
- and
- a charge forming device having:
- a body,
- a primary air intake passage in the body and having an inlet communicating with atmosphere and an outlet constructed and arranged to communicate with the primary air intake port of the engine,
- a separate fuel-and-air mixing passage in the upper body and having an inlet communicating with the atmosphere and an outlet constructed and arranged to communicate with the connecting tube,
- a rotary throttle valve having a valve chamber, a cylindrical rotary member, and a needle, the valve chamber carried by the body and communicating transversely through the air intake passage, the rotary member disposed rotatably and vertically movably within the valve chamber, the rotary member having a throttle bore communicating laterally through the member, the throttle bore being aligned to the air intake passage when the rotary throttle valve is rotated to a wide open throttle position and partially mis-aligned to the air intake passage when the rotary throttle valve is rotated to an idle position, wherein the needle projects concentrically from the rotary member,
- a fuel metering assembly carried by the body and having a fuel metering chamber at a substantially constant pressure,
- a fuel feed tube defining a fuel feed passage communicating between the metering chamber and the fuel-and-air mixing passage for supplying a majority of fuel flow of a rich fuel-and-air mixture to the cylinder through the engine intake port;
- and
- a fuel nozzle carried by the fuel feed tube and communicating with the fuel-and-air mixing passage, the needle of the rotary throttle valve extending axially into the fuel feed passage, wherein the needle is constructed and arranged to move axially into and out of the nozzle to vary the degree of opening of the nozzle and thus fuel flow entering the fuel-and-air mixing passage from the metering chamber.
Dependencies are inferred from the claim text.