Two-cycle utility internal combustion engine

In a two-cycle internal combustion engine, the method of introducing fuel into a cylinder of the engine, which comprises:

• providing an accumulator-type fuel injector in said two-cycle engine arranged for direct in-cylinder injection, said injector having a needle normally spring-biased downwardly to a closed position, an accumulator cavity located so as to provide an upward opening force on said needle when pressurized, and a control cavity above said needle located so as to provide a downward closing force on said needle when pressurized;
• substantially simultaneously pressurizing said accumulator and control cavities with fuel through respective accumulator and control cavity feed conduits to about the same pressure level above that which would be sufficient for the upward force of accumulator pressure on said needle to overcome said spring biasing but for the downward force of control cavity pressure on said needle;
• at least partially depressurizing said accumulator cavity feed conduit for a substantial portion of the combustion cycle while preventing unrestricted return fuel flow through said accumulator cavity feed conduit from said accumulator cavity;
• and
• venting fuel pressure from said control cavity via operation of a two-way solenoid-actuated vent valve in communication with said control cavity so that said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder;
• wherein
• said pressurizing and depressurizing steps comprise mechanically reciprocating a high pressure fuel pump plunger in a first direction to produce said pressurizing and in a second direction to produce said depressurizing.

In a two-cycle internal combustion engine, the method of introducing fuel into a cylinder of the engine, which comprises:

• providing an accumulator-type fuel injector in said two-cycle engine arranged for direct in-cylinder injection, said injector having a needle normally spring-biased downwardly to a closed position, an accumulator cavity located so as to provide an upward opening force on said needle when pressurized, and a control cavity above said needle located so as to provide a downward closing force on said needle when pressurized;
• substantially simultaneously pressurizing said accumulator and control cavities with fuel through respective accumulator and control cavity feed conduits to about the same pressure level above that which would be sufficient for the upward force of accumulator pressure on said needle to overcome said spring biasing but for the downward force of control cavity pressure on said needle;
• at least partially depressurizing said accumulator cavity feed conduit for a substantial portion of the combustion cycle while preventing unrestricted return fuel flow through said accumulator cavity feed conduit from said accumulator cavity;
• and
• venting fuel pressure from said control cavity via operation of a two-way solenoid-actuated vent valve in communication with said control cavity so that said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder;
• wherein
• said pressurizing and depressurizing steps are performed by a reciprocating plunger high pressure pump, wherein the pump pressure output produced by the motion of said plunger rises from a predetermined low pressure to a predetermined peak pressure and then falls back to said predetermined low pressure, wherein said step of preventing unrestricted return fuel flow comprises providing a flow-restriction device in said accumulator cavity feed conduit to limit fuel backflow toward said pump so as to maintain accumulator pressure substantially higher than control cavity pressure prior to injection, injection being initiated by venting of said control cavity by backflow of fuel from said control cavity toward the pump as pressure thus falls back from said peak pressure toward said low pressure.

A two-cycle internal combustion engine, which comprises:

• an accumulator-type fuel injector mounted in the two-cycle engine and arranged for direct in-cylinder injection, said injector having a needle normally spring-biased downwardly to a closed position, an accumulator cavity located so as to provide an upward opening force on said needle when pressurized, and a control cavity above said needle located so as to provide a downward closing force on said needle when pressurized;
• a source of fuel;
• a high pressure fuel pump having an input operatively connected to said fuel source and having an output in fluid communication with said accumulator and control cavities through respective accumulator and control cavity feed conduits so as to substantially simultaneously and periodically provide pressurized fuel at about the same pressure level to said accumulator and control cavities and to periodically at least partially depressurize at least a portion of said accumulator cavity feed conduit for a substantial portion of the combustion cycle, said pressure level being sufficient for the upward force of accumulator pressure on said needle to overcome said spring-biasing but for the downward force of control cavity pressure on said needle, said accumulator cavity. feed conduit having a device located therein to prevent unrestricted return fuel flow therethrough when said accumulator cavity feed conduit is depressurized;
• and
• a two-way solenoid-actuated vent valve, in fluid communication with said control cavity, for periodically venting fuel pressure from said control cavity, whereby upon such venting said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder.

A two-cycle internal combustion engine, which comprises:

• an accumulator-type fuel injector mounted in the two-cycle engine and arranged for direct in-cylinder injection, said injector having a needle normally spring-biased downwardly to a closed position, an accumulator cavity located so as to provide an upward opening force on said needle when pressurized, and a control cavity above said needle located so as to provide a downward closing force on said needle when pressurized;
• a source of fuel;
• a high pressure fuel pump having an input operatively connected to said fuel source and having an output in fluid communication with said accumulator and control cavities through respective accumulator and control cavity feed conduits so as to substantially simultaneously and periodically provide pressurized fuel at about the same pressure level to said accumulator and control cavities and to periodically at least partially depressurize at least a portion of said accumulator cavity feed conduit for a substantial portion of the combustion cycle, said pressure level being sufficient for the upward force of accumulator pressure on said needle to overcome said spring-biasing but for the downward force of control cavity pressure on said needle, said accumulator cavity feed conduit having a device located therein to prevent unrestricted return fuel flow therethrough when said accumulator feed conduit is depressurized,
• wherein said pump comprises a reciprocating plunger high pressure pump, wherein the pump pressure output produced by the motion of said plunger rises from a predetermined low pressure to a predetermined peak pressure and then falls back to said predetermined low pressure, injection being initiated by venting of said control cavity by venting of fuel from said control cavity toward the pump as pressure thus falls back from said peak pressure toward said low pressure, whereby upon such venting said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder.

A method of introducing fuel into a cylinder of a two-cycle engine, which comprises:

• (A) providing
• (1) a high pressure fuel pump plunger, and
• (2) an accumulator-type fuel injector in said two-cycle engine arranged for direct in-cylinder injection, said injector having
• (a) a needle normally spring-biased downwardly to a closed position,
• (b) an accumulator cavity (i) located so as to provide an upward opening force on said needle when pressurized and (ii) communicating with said pump via an accumulator cavity feed conduit in which is disposed a check valve permitting fuel flow into said accumulator cavity from said pump but preventing reverse flow therethrough, and
• (c) a control cavity (i) located above said needle so as to provide a downward closing force on said needle when pressurized, and (ii) communicating with said pump via a control cavity feed conduit in which is disposed a flow-restricting orifice;
• (B) reciprocating the pump plunger, thereby cyclically varying the pump output pressure from a predetermined low pressure to a peak pressure, thereby periodically (1) substantially simultaneously pressurizing said accumulator and control cavities to about the same pressure level above that which would be sufficient for the upward force of accumulator pressure on said needle to overcome said spring biasing but for the downward force of control cavity pressure on said needle, and then (2) partially depressurizing said accumulator cavity feed conduit while maintaining said peak pressure in said accumulator due to operation of said check valve;
• and
• (C) venting fuel pressure from said control cavity via operation of a two-way solenoid-actuated vent valve so that said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder, wherein, due to the presence of said flow-restricting orifice, fuel inflow through said control cavity feed conduit does not interfere with solenoid vent valve venting of said control cavity.

A method of introducing fuel into a cylinder of a two-cycle engine, which comprises:

• (A) providing
• (1) a high pressure fuel pump plunger, and
• (2) an accumulator-type fuel injector in said two-cycle engine arranged for direct in-cylinder injection, said injector having
• (a) a needle normally spring-biased downwardly to a closed position,
• (b) an accumulator cavity (i) located so as to provide an upward opening force on said needle when pressurized and (ii) communicating with said pump via an accumulator cavity feed conduit, and
• (c) a control cavity located above said needle so as to provide a downward closing force on said needle when pressurized;
• (B) reciprocating the pump plunger, thereby cyclically varying the pump output pressure from a predetermined low pressure to a peak pressure, thereby periodically (1) substantially simultaneously pressurizing said accumulator and control cavities to about the same pressure level above that which would be sufficient for the upward force of accumulator pressure on said needle to overcome said spring biasing but for the downward force of control cavity pressure on said needle, and then (2) partially depressurizing said accumulator cavity feed conduit;
• (C) pressure relieving said pump pressure output at a maximum pressure slightly below said peak pressure so as to assure a uniform pressurization of said accumulator cavity and said control cavity despite manufacturing tolerances, wherein said pressure relieving of said pump pressure output is accomplished by a pressure relief valve comprising a spring biased closure device and by varying the spring biasing force on said closure device so as to vary pump output maximum pressure;
• and
• (D) venting fuel pressure from said control cavity via operation of a two-way solenoid-actuated vent valve so that said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder.

A method of introducing fuel into a cylinder of a two-cycle engine, which comprises:

• (A) providing
• (1) a high pressure fuel pump plunger, and
• (2) an accumulator-type fuel injector in said two-cycle engine arranged for direct in-cylinder injection, said injector having
• (a) a needle normally spring-biased downwardly to a closed position,
• (b) an accumulator cavity (i) located so as to provide an upward opening force on said needle when pressurized and (ii) communicating with said pump via an accumulator cavity feed conduit, and
• (c) a control cavity located above said needle so as to provide a downward closing force on said needle when pressurized;
• (B) reciprocating the pump plunger, thereby cyclically varying the pump output pressure from a predetermined low pressure to a peak pressure, thereby periodically (1) substantially simultaneously pressurizing said accumulator and control cavities to about the same pressure level above that which would be sufficient for the upward force of accumulator pressure on said needle to overcome said spring biasing but for the downward force of control cavity pressure on said needle, and then (2) partially depressurizing said accumulator cavity feed conduit;
• (C) boosting the pump fuel inlet pressure via operation of a transfer pump located in a pump fuel inlet conduit;
• (D) varying the fuel pressure output of said transfer pump so as to vary the high pressure pump output pressure;
• and
• (E) venting fuel pressure from said control cavity via operation of a two-way solenoid-actuated vent valve so that said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder.

A two-cycle internal combustion engine which comprises:

• (A) an accumulator-type fuel injector mounted in said two-cycle engine and arranged for direct in-cylinder injection, said injector having
• (1) a needle normally spring-biased downwardly to a closed position,
• (2) an accumulator cavity (a) located so as to provide an upward opening force on said needle when pressurized and (b) receiving pressurized fuel via an accumulator cavity feed conduit,
• (3) a check valve disposed in said accumulator cavity feed conduit and permitting fuel flow into said accumulator cavity from said pump but preventing reverse flow therethrough,
• (3) a control cavity (a) located above said needle so as to provide a downward closing force on said needle when pressurized, and (b) receiving pressurized fuel via a control cavity feed conduit, and
• (4) a flow-restricting orifice provided in said control cavity feed conduit;
• (B) a source of fuel;
• (C) a high pressure fuel pump having an input operatively connected to said fuel source and having an output in fluid communication with said accumulator and control cavities through the accumulator and control cavity feed conduits so as to substantially simultaneously and periodically provide pressurized fuel at about the same pressure level to said accumulator and control cavities and to periodically at least partially depressurize at least a portion of said accumulator feed conduit for a substantial portion of the combustion cycle, said pressure level being sufficient for the upward force of accumulator pressure on said needle to overcome said spring-biasing but for the downward force of control cavity pressure on said needle;
• and
• (D) a two-way solenoid-actuated vent valve, in fluid communication with said control cavity, for periodically venting fuel pressure from said control cavity, whereby upon such venting said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder, and whereby, due to the presence of said flow-restricting orifice, fuel inflow through said control cavity feed conduit does not interfere with solenoid vent valve venting of said control cavity.

A two-cycle internal combustion engine which comprises:

• (A) an accumulator-type fuel injector mounted in said two-cycle engine and arranged for direct in-cylinder injection, said injector having
• (1) a needle normally spring-biased downwardly to a closed position,
• (2) an accumulator cavity (a) located so as to provide an upward opening force on said needle when pressurized and (b) receiving pressurized fuel via an accumulator cavity feed conduit, and
• (3) a control cavity (a) located above said needle so as to provide a downward closing force on said needle when pressurized, and (b) receiving pressurized fuel via a control cavity feed conduit;
• (B) a source of fuel;
• (C) a reciprocating plunger type high pressure fuel pump having an input operatively connected to said fuel source and having an output in fluid communication with said accumulator and control cavities through the accumulator and control cavity feed conduits so as to substantially simultaneously and periodically provide pressurized fuel at about the same pressure level to said accumulator and control cavities and to periodically at least partially depressurize at least a portion of said accumulator cavity feed conduit for a substantial portion of the combustion cycle, said pressure level being sufficient for the upward force of accumulator pressure on said needle to overcome said spring-biasing but for the downward force of control cavity pressure on said needle;
• (D) a cam lobe, mounted directly on the engine crankshaft, which reciprocates the plunger of said pump so that the pump pressure output produced by said plunger rises from a predetermined low pressure to a predetermined peak pressure;
• (E) a pressure relief valve comprising a spring-biased closure device in fluid communication with said pump output and set to pressure-relieve said pump output at a maximum pressure slightly below said peak pressure so as to assure a uniform pressurization of said accumulator cavity and said control cavity despite manufacturing tolerances;
• (F) means for varying the spring biasing force on said closure device so as to vary said pump output maximum pressure;
• and
• (G) a two-way solenoid-actuated vent valve, in fluid communication with said control cavity, for periodically venting fuel pressure from said control cavity, whereby upon such venting said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder.

A two-cycle internal combustion engine which comprises:

• (A) an accumulator-type fuel injector mounted in said two-cycle engine and arranged for direct in-cylinder injection, said injector having
• (1) a needle normally spring-biased downwardly to a closed position,
• (2) an accumulator cavity (a) located so as to provide an upward opening force on said needle when pressurized and (b) receiving pressurized fuel via an accumulator cavity feed conduit, and
• (3) a control cavity (a) located above said needle so as to provide a downward closing force on said needle when pressurized, and (b) receiving pressurized fuel via a control cavity feed conduit;
• (B) a source of fuel;
• (C) a reciprocating plunger type high pressure fuel pump having an input operatively connected to said fuel source and having an output in fluid communication with said accumulator and control cavities through the accumulator and control cavity feed conduits so as to substantially simultaneously and periodically provide pressurized fuel at about the same pressure level to said accumulator and control cavities and to periodically at least partially depressurize at least a portion of said accumulator cavity feed conduit for a substantial portion of the combustion cycle, said pressure level being sufficient for the upward force of accumulator pressure on said needle to overcome said spring-biasing but for the downward force of control cavity pressure on said needle;
• (D) a cam lobe, mounted directly on the engine crankshaft, which reciprocates the plunger of said pump so that the pump pressure output produced by said plunger rises from a predetermined low pressure to a predetermined peak pressure;
• (E) a fuel transfer pump means, operatively associated with said high pressure pump input, for boosting the pressure of fuel supplied to said pump input, said pump transfer means having a variable pressure output so as to vary the high pressure pump output pressure;
• and
• (F) a two-way solenoid-actuated vent valve, in fluid communication with said control cavity, for periodically venting fuel pressure from said control cavity, whereby upon such venting said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder.

A method of introducing fuel into a cylinder of a two-cycle engine, which comprises:

• (A) providing an accumulator-type fuel injector in said two-cycle engine arranged for direct in-cylinder injection, said injector having a needle normally spring-biased downwardly to a closed position, an accumulator cavity located so as to provide an upward opening force on said needle when pressurized, and a control cavity above said needle located so as to provide a downward closing force on said needle when said control cavity is pressurized;
• (B) translating a plunger of a pump in a first direction to substantially simultaneously pressurize said accumulator and control cavities with fuel through respective accumulator and control cavity feed conduits to about the same pressure level above that which would be sufficient for the upward force of accumulator pressure on said needle to overcome said spring biasing but for the downward force of control cavity pressure on said needle;
• (C) reversing the direction of pump plunger movement to at least partially depressurize said accumulator cavity feed conduit for a substantial portion of the combustion cycle while preventing unrestricted return fuel flow through said accumulator cavity feed conduit from said accumulator cavity, wherein the motion of said plunger, when plotted against time, generally follows a sine curve having a period equal to a sine curve followed by the engine piston;
• and
• (D) venting fuel pressure from said control cavity via operation of a two-way solenoid-actuated vent valve in communication with said control cavity so that said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder, wherein both the timing and quantity of fuel injection are dependent upon the timing of solenoid valve opening relative to pump plunger position.

A method of introducing fuel into a cylinder of a two-cycle engine, which comprises:

• (A) providing an accumulator-type fuel injector in said two-cycle engine arranged for direct in-cylinder injection, said injector having a needle normally spring-biased downwardly to a closed position, an accumulator cavity located so as to provide an upward opening force on said needle when pressurized, and a control cavity above said needle located so as to provide a downward closing force on said needle when said control cavity is pressurized;
• (B) translating a plunger of a pump in a first direction to substantially simultaneously pressurize said accumulator and control cavities with fuel through respective accumulator and control cavity feed conduits to about the same pressure level above that which would be sufficient for the upward force of accumulator pressure on said needle to overcome said spring biasing but for the downward force of control cavity pressure on said needle;
• (C) reversing the direction of pump plunger movement to at least partially depressurize said accumulator cavity feed conduit for a substantial portion of the combustion cycle while (1) preventing unrestricted return fuel flow through said accumulator cavity feed conduit from said accumulator cavity (2) permitting return fuel flow through said control cavity feed conduit from said control cavity;
• and
• (D) venting fuel pressure from said control cavity so that said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder, wherein both the timing and quantity of fuel injection are dependent upon the timing of solenoid vent valve opening relative to pump plunger position, said venting step being performed via at least one of (1) operation of a two-way solenoid-actuated vent valve in communication with said control cavity, and (2) pump plunger reversal.

A two-cycle internal combustion engine, which comprises:

• (A) an accumulator-type fuel injector mounted in the two-cycle engine and arranged for direct in-cylinder injection, said injector having a needle normally spring-biased downwardly to a closed position, an accumulator control cavity located so as to provide an upward opening force on said needle when pressurized, and a control cavity above said needle located so as to provide a downward closing force on said needle when pressurized;
• (B) a source of fuel;
• (C) a high pressure fuel pump having an input operatively connected to said fuel source and having an output in fluid communication with said accumulator and control cavities through respective accumulator and control cavity feed conduits so as to substantially simultaneously and periodically provide pressurized fuel at about the same pressure level to said accumulator and control cavities and to periodically at least partially depressurize at least a portion of said accumulator cavity feed conduit for a substantial portion of the combustion cycle, said pressure level being sufficient for the upward force of accumulator pressure on said needle to overcome said spring-biasing but for the downward force of control cavity pressure on said needle, said accumulator cavity feed conduit having a flow restriction device located therein to prevent unrestricted return fuel flow therethrough from said accumulator cavity when said accumulator cavity feed conduit is depressurized;
• (D) a two-way solenoid-actuated vent valve, in fluid communication with said control cavity, for periodically venting fuel pressure from said control cavity, whereby upon such venting said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder, wherein said pump comprises a mechanically actuated reciprocating plunger pump driven by an eccentric circular cam which is mounted directly on the engine crankshaft and which provides a motion to said plunger which, when plotted against time, generally follows a sine curve having a period equal to a sine curve followed by the engine piston;
• and
• (E) means for controlling energization of said solenoid vent valve such that the quantity of fuel injected and the timing of fuel injection are dependent upon the timing of solenoid vent valve opening relative to pump plunger position.

A method comprising

• (A) providing a single cylinder two-cycle engine;
• (B) supplying pressurized fuel to a fuel injector having an injection nozzle communicating with said cylinder;
• (C) electronically controlling said fuel injector to periodically inject fuel into said cylinder;
• and
• (D) selectively varying the power output of said engine by causing noninjection of fuel from said injector during a designated number of crankshaft cycles, wherein the number of crankshaft cycles skipped between each injection event decreases with an increase in the desired power output from said engine;
• wherein
• said fuel injector includes an accumulator-type fuel injector in the head of said engine arranged for direct in-cylinder injection, said injector having a needle normally spring-biased downwardly to a closed position, an accumulator cavity located so as to provide upward opening force on said needle when pressurized, and a control cavity above said needle located so as to provide downward closing force on said needle when pressurized;
• wherein
• said injecting step includes
• substantially simultaneously pressurizing said accumulator and control cavities with fuel through respective accumulator and control cavity feed conduits to about the same pressure level above that which would be sufficient for the upward force of accumulator pressure on said needle to overcome said spring biasing but for the downward force of control cavity pressure on said needle, and then
• venting fuel pressure from said control cavity via operation of a two-way solenoid-actuated vent valve in communication with said control cavity so that said upward force of accumulator pressure on said needle overcomes said downward forces on said needle and raises said needle to an open position for injection of fuel from said accumulator injector directly into the cylinder;
• and wherein
• said step of causing noninjection comprises electronically controlling said solenoid vent valve.