US 5,685,273 A · Method and apparatus for controlling fuel injection in an internal combustion engine

Abstract

Fuel delivery to an engine from a cyclically pressurizable, electronically controlled accumulator-type fuel injector is controlled by "wasting" at least a portion of the pressurization stroke of the engine's high pressure pump so that a designated portion of the pressurization stroke of the pump does not result in accumulator cavity pressurization. Metering is effected simply by extending the period that the system's existing solenoid vent valve is open into a portion of the succeeding pressurization stroke of the pump so that a portion of the pumped fuel flows directly to vent. Additional electrical load on the engine can be minimized by using a latching type solenoid valve as the vent valve. The metering scheme 1) is more precise than metering schemes heretofore available for injectors of the disclosed type, 2) does not adversely effect injection timing or other injection parameters, 3) and requires no additional hardware.

A method comprising

(A) providing a two-cycle engine comprising a cylinder and an accumulator-type fuel injector arranged to inject fuel directly into said cylinder, said fuel injector having a needle normally spring-biased downwardly to a closed position, an accumulator cavity located so as to impose an upward opening force on said needle when pressurized, and a control cavity located so as to impose a downward closing force on said needle when pressurized;
(B) substantially simultaneously pressurizing said accumulator and control cavities with fuel through respective accumulator cavity 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, said pressurizing step comprising mechanically reciprocating a high pressure fuel pump plunger in a first direction;
(C) at least partially depressurizing said accumulator cavity feed conduit while preventing unrestricted return fuel flow through said accumulator cavity feed conduit from said accumulator cavity, said depressurizing step comprising mechanically reciprocating said high pressure fuel pump plunger in a second direction;
(D) opening a two-way solenoid-actuated solenoid vent valve located in fluid communication with said control cavity, thereby venting fuel pressure from said control cavity so that said upward force of accumulator pressure on said needle overcomes all 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, then lowering said needle to a closed position to terminate fuel injection when downward forces imposed on said needle overcome said upward force of accumulator pressure imposed on said needle;
(E) maintaining said solenoid vent valve in its open position;
(F) while said solenoid vent valve is in its open position, mechanically reciprocating said high pressure fuel pump plunger in said first direction to force fuel through said vent passage without pressurizing said accumulator cavity or said control cavity;
(G) closing said solenoid vent valve to prevent further fluid flow through said vent passage;
then
(H) continuing to mechanically reciprocate said high pressure pump plunger in said first direction, thereby substantially simultaneously pressurizing said accumulator and control cavities with fuel through said accumulator and control cavity feed conduits to a peak pressure level below a peak pressure level obtained during the step (B);
then
(I) mechanically reciprocating said high pressure fuel pump plunger in said second direction to at least partially depressurize said accumulator cavity feed conduit while preventing unrestricted return fuel flow through said accumulator cavity feed conduit from said accumulator cavity;
and
(J) opening said solenoid vent valve, thereby venting fuel pressure from said control cavity so that said upward force of accumulator pressure on said needle overcomes all downward forces on said needle and raises said needle to said open position for injection of fuel from said accumulator injector directly into the cylinder, wherein a total quantity of fuel injected during the step (J) is smaller than a total quantity of fuel injected during the step (D).

10 more elements

Method and apparatus for controlling fuel injection in an internal combustion engine

Life of this patent

Method and apparatus for controlling fuel injection in an internal combustion engine

Life of this patent

Abstract

Claims19