초록 ▼

A novel injection-pump plunger used in a unit injector for an EMD-type diesel engine has its upper (cut-off) control edge shaped to retard start of injection at full power from what it is with standard plungers, and to provide in a straight-line manner a relatively small increase in retardation from

A novel injection-pump plunger used in a unit injector for an EMD-type diesel engine has its upper (cut-off) control edge shaped to retard start of injection at full power from what it is with standard plungers, and to provide in a straight-line manner a relatively small increase in retardation from full load to idle. In a preferred form, the plunger has one or more steps in its upper (cut-off) control edge, the step or steps being formed between adjacent segments of the edge that are associated with different load points. A method of improving emissions/fuel-economy of EMD diesel engines comprises using prototype injection-pump plungers shaped within certain parameters, assessing their performance, selecting new patterns of timing based on the assessment, making new prototype plungers and assessing them, and repeating the steps of selecting, making and assessing if and as required until an assessment indicates compliance with applicable performance standards.

대표청구항 ▼

1. A plunger to be used in the plunger-and-bushing assembly of an EMD type injector for an EMD type diesel engine, said plunger having a port-closing edge associated with the fill port of the bushing and a spill edge associated with the spill port of the bushing, said fill and spill ports being sepa

1. A plunger to be used in the plunger-and-bushing assembly of an EMD type injector for an EMD type diesel engine, said plunger having a port-closing edge associated with the fill port of the bushing and a spill edge associated with the spill port of the bushing, said fill and spill ports being separate from each other, said port-closing edge comprising a series of adjacent edge segments each of 0 degrees helix angle, each edge segment in said series being joined to each neighboring segment at a common boundary region between said each edge segment and each of the one or two edge segments that neighbor it, each of said edge segments in said series being associated with its own one of a corresponding series of rotative positions of said plunger so as to be rotatively centered on said fill port and to angularly extend a distance to each side of the fill port at said associated rotative position, each rotative position in said series of rotative positions corresponding to one of a series of load settings progressing from full load position to lowest position, each of said edge segments being located at an associated timing distance along the length of the plunger to thereby establish for that segment an associated timing of fill-port closing relative to crank degrees of an associated engine piston, the members of one or more adjacent pairs of said edge segments having different associated timing distances, such members forming a step and being joined by a step riser at their common boundary region, the height of said riser being equal to the difference between their respective associated timing distances. 2. A plunger to be used in the plunger-and-bushing assembly of an EMD type injector for an EMD type diesel engine, said plunger having a port-closing edge associated with the fill port of the bushing and a spill edge associated with the spill port of the bushing, said port-closing edge comprising a series of adjacent edge segments each of 0 degrees helix angle, each edge segment in said series being joined to each neighboring segment at a common boundary region between said each edge segment and each of the one or two edge segments that neighbor it, each of said edge segments in said series being associated with its own one of a corresponding series of rotative positions of said plunger so as to be rotatively centered on said fill port and to angularly extend a distance to each side of the fill port at said associated rotative position, each rotative position in said series of rotative positions corresponding to one of a series of load settings progressing from full load position to lowest position, each of said edge segments being located at an associated timing distance along the length of the plunger to thereby establish for that segment an associated timing of fill-port closing relative to crank degrees of an associated engine piston, the members of one or more adjacent pairs of said edge segments having different associated timing distances, such members forming a step and being joined by a step riser at their common boundary region, the height of said riser being equal to the difference between their respective associated timing distances, the number of steps formed in said part-closing edge being between one and a second number that is two less than the number of load settings. 3. A plunger to be used in the plunger-and-bushing assembly of an EMD type injector for an EMD type diesel engine, said plunger having a port-closing edge associated with the fill port of the bushing and a spill edge associated with the spill port of the bushing, said port-closing edge comprising a series of adjacent edge segments each of 0 degrees helix angle, each edge segment in said series being joined to each neighboring segment at a common boundary region between said each edge segment and each of the one or two edge segments that neighbor it, each of said edge segments in said series being associated with its own one of a corresponding seri es of rotative positions of said plunger so as to be rotatively centered on said fill port and to angularly extend a distance to each side of the fill port at said associated rotative position, each rotative position in said series of rotative positions corresponding to one of a series of load settings progressing from full load position to lowest position, each of said edge segments being located at an associated timing distance along the length of the plunger to thereby establish for that segment an associated timing of fill-port closing relative to crank degrees of an associated engine piston, the members of one or more adjacent pairs of said edge segments having different associated timing distances, such members forming a step and being joined by a step riser at their common boundary region, the height of said riser being equal to the difference between their respective associated timing distances, the timing distance of the edge segment associated with the highest load setting corresponding to about a 3 to 5 degree retardation from the timing of the helix edge associated with the highest load setting in a standard plunger for said EMD type injector. 4. A plunger to be used in the plunger-and-bushing assembly of an EMD type injector for an EMD type diesel engine, said plunger having a port-closing edge associated with the fill port of the bushing and a spill edge associated with the spill port of the bushing, said port-closing edge comprising a series of adjacent edge segments each of 0 degrees helix angle, each edge segment in said series being joined to each neighboring segment at a common boundary region between said each edge segment and each of the one or two edge segments that neighbor it, each of said edge segments in said series being associated with its own one of a corresponding series of rotative positions of said plunger so as to be rotatively centered on said fill port and to angularly extend a distance to each side of the fill port at said associated rotative position, each rotative position in said series of rotative positions corresponding to one of a series of load settings progressing from full load position to lowest position, each of said edge segments being located at an associated timing distance along the length of the plunger to thereby establish for that segment an associated timing of fill-port closing relative to crank degrees of an associated engine piston, the members of one or more adjacent pairs of said edge segments having different associated timing distances, such members forming a step and being joined by a step riser at their common boundary region, the height of said riser being equal to the difference between their respective associated timing distances, the number of steps formed in said port-closing edge being between one and a second number that is two less than the number of load settings, the timing distance of the edge segment associated with the highest load setting corresponding to about a 3 to 5 degree retardation from the timing of the helix edge associated with the highest load setting in a standard plunger for said EMD type injector. 5. An EMD-type unit injector having a plunger-and-bushing assembly in which the plunger is a plunger as set forth in claim 1. 6. An EMD-type diesel engine having for each of its cylinders an injector as set forth in claim 5. 7. A method of improving overall emissions/fuel economy performance of an EMD turbocharged diesel engine of a given model and application, using as a reference a set of standard EMD unit injectors for that EMD model, said reference standard EMD injectors each having an associated reference standard plunger, comprising the steps of:providing a set of prototype replacement plungers each having a port-closing edge located and shaped such that there is provided at each load setting a given associated timing of fill-port closing corresponding to a given number of crank degrees of an associated engine piston, and such that the t iming of closing changes in the retarding direction from the full-load setting down to the idle setting by an amount less than the amount by which the timing of closing changes in the retarding direction in said reference standard plungers, and such that the timing of closing at full load setting is retarded from the timing of closing at full-load setting of said reference standard plungers by an amount determined by first determining the amount of retardation of a standard plunger's upper control edge at full load setting that optimizes emissions/fuel-economy of the plunger at the full-load setting, and then using the equivalent timing distance as the exact or approximate timing distance for the control edge 17 A at full-load port closing,assessing, at each load setting and over all load settings, the emissions/fuel economy performance associated with the most recently provided set of prototype replacement plungers when installed and operated in said reference standard injectors,selecting a new pattern of timings of closing associated with the various load settings, said new pattern being such that the timing of closing will reflect a change, in the retarding direction, in a non-straight-line manner from the full load setting down to the lowest setting, said new pattern being modified from the pattern of timings of closing associated with said most recently made set of prototype replacement plungers such that at each load setting the direction and amount of timing adjustment, if any, are indicated to contribute to improved rating of overall emissions/fuel-economy over all load settings, taking into account regulatory weightings associated with each load setting, said selecting step including compromising between tentatively indicated timings associated with a given pair of adjacent load-setting positions if the difference in such indicated timings is relatively small compared to a difference or differences in indicated timing between another pair or other pairs of adjacent load setting positions, such compromise consisting of selecting for both members of such given pair a timing between such tentatively indicated timings, thereby taking into account that avoidance of change of timing between adjacent load settings contributes positively to fuel economy,making a new set of prototype replacement plungers each of whose pattern of timings associated with all the various load settings conforms to the most recent said new selected pattern, and repeating said assessing step,and then repeating said steps of selecting, making and assessing if and as required until an assessment indicates compliance of the newest prototype plunger with applicable performance standards,and using replacement plungers having the form of the complying prototype in injectors for said engine of said given model and application. 8. A method as in claim 7, said first step of providing a set of prototype replacement plungers including providing such plungers such that the upper control edge of each plunger comprises a series of adjacent edge segments each of 0 degrees helix angle.