PatentDe  


Dokumentenidentifikation EP1055814 29.06.2006
EP-Veröffentlichungsnummer 0001055814
Titel Kraftstoffeinspritzsystem für einen Diesel Motor
Anmelder Mack Trucks, Inc., Allentown, Pa., US
Erfinder Suder, Timothy Andrew, Greencastle, PA 17225, US
Vertreter derzeit kein Vertreter bestellt
DE-Aktenzeichen 60028125
Vertragsstaaten AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LI, LU, MC, NL, PT, SE
Sprache des Dokument EN
EP-Anmeldetag 08.03.2000
EP-Aktenzeichen 001049501
EP-Offenlegungsdatum 29.11.2000
EP date of grant 24.05.2006
Veröffentlichungstag im Patentblatt 29.06.2006
IPC-Hauptklasse F02M 45/08(2006.01)A, F, I, 20051017, B, H, EP
IPC-Nebenklasse F02M 45/06(2006.01)A, L, I, 20051017, B, H, EP   

Beschreibung[en]
BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to a diesel engine fuel injector system, and more particularly to an electronically controlled spill port for a fuel injector.

2. Description of the Background Art

Fuel injectors are devices used to meter out precise volumes of fuel into a cylinder of an engine. They are commonly used for purposes of precise fuel control, increased fuel economy, and emissions reduction. By accurately controlling the rate and volume of injected fuel and the time in the engine cycle when the fuel is injected, a fuel injector can be used to achieve the above goals.

The onset, rate, and duration of fuel injected into a diesel engine has been proven to affect BsNOx and BsPt emissions levels, as well as affecting BsFC. BsNOx is a measure of Brake specific Nitrogen Oxide emissions, such as NO and NO2 pollutants. BsPt is a measure of Brake specific lead (Pt) emissions, another pollutant generated by an engine. BsFC is the Brake specific Fuel Consumption, which is a measure of fuel rate in pounds per hour divide by power output (lb/hp-hr).

A high cam velocity and high hydraulic flow nozzle (short injection durations) can provide minimum fuel consumption. However, with this aggressive injection system, injection timing cannot be retarded enough to meet U.S. 1998 BsNOx standards without misfire and a rapid increase in BsPt emissions levels. The reason for this is the high fuel injection rate associated with a high velocity cam and high hydraulic flow nozzle, as shown in the chart of Fig. 1A. It has been well documented that the fuel injection rate significantly impacts BsNOx emissions levels, especially the injection rate during the first 5-10 engine degrees of injection. As the injection rate increases, the BsNOx emissions levels also increase.

The effort to reduce emissions through more precise control of fuel injection has led to several related art approaches. One simple method uses a slower velocity cam and a lower hydraulic flow nozzle, as shown in the chart of Fig. 1B. This allows low BsNOx and BsPt emissions levels without retarding injection timing so much as to cause misfire. This system will, however, increase injection duration and will therefore impact highway fuel consumption.

Another more complicated method for allowing lower BsNOx emissions levels to be obtained with any injection system is to inject a small quantity of "pilot" fuel before the main injection (i.e., pilot injection). Pilot injection is depicted in the chart of Fig. 1C. This small pilot quantity of fuel does not reduce the rate of injection but will allow more retarded main injection timings without misfire, thus allowing lower BsNOx emission levels without a rapid increase in BsPt emissions levels. However, as main injection timing is retarded to control BsNOx, the BsPt solids emissions levels will gradually increase due to a later occurring end of injection. It is therefore possible that a system optimized for minimum fuel consumption (very high rate of injection) would require such retarded timings to meet U.S. 1998 BsNOx emissions standards that the BsPt emissions levels may exceed the 1998 targets, even if pilot injection is utilized. At any rate, very retarded injection timings can cause several other problems such as poor fuel consumption, high heat rejection, excessive turbo wheel speed and the requirement of a large timing range designed into the cam profile.

A further refinement of the precise control of fuel injection is the use of a spill valve. A spill valve allows the spilling of fuel from the injector during the injection cycle. Spill valves are used because fuel injectors are mechanical devices, driven off of a camshaft. A cylinder within the injector is driven by the cam, and provides a fuel volume and pressure as dictated by the timing and aggressiveness of the cam. The operation of the injector cylinder is mechanically fixed by the cam, and cannot be varied during operation of the engine. In order to more precisely control the fuel injection, such as by electronic means, a spill valve is used to discard some of the pressurized fuel. The spill valve can be opened at any time in the injection cycle (i.e., when the injector cylinder is pressurizing the fuel) to spill excess or unneeded fuel.

One approach is to have a spill valve designed into the plunger/barrel assembly of an injector. This approach is currently utilized by Navistar with the HEUI (PRIME) system and is illustrated in FIGs. 2A and 2B. The spill valve is fixed in location and spills a portion of the high pressure fuel during the initial part of an injection stroke, as can be seen in Fig. 2A. However, the HEUI (PRIME) system is a fixed spill valve which cannot vary the injection opening timing and flow rate in order to minimize emissions levels for a full range of engine loads.

Another approach in the related art is given in Cananagh, U.S. Patent No. 5,333,588. Cananagh discloses a fuel injector having an electromagnetically controlled spill valve, and may include two such spill valves. Cananagh proposes two spill ports in order to cope with large displacements of fuel per injector plunger stroke. The purpose of dual spill valves in Cananagh is to increase the flow area through which fuel can escape from the injector pumping chamber. In addition, Cananagh discloses a non-synchronized opening of the spill valves where one valve can be energized slightly before the other to provide variation of the initial rate of delivery of fuel. This is apparently done to forestall a premature high fuel pressure at the inlet of the injection nozzle. If the fuel pressure exceeds a nozzle opening pressure, the injector nozzle may open prematurely. Apparently the goal of Cananagh in early closing of one spill valve is to delay the opening of the injector nozzle by forestalling a high fuel pressure.

EP 0 283 155 to Cavanagh describes a fuel pumping apparatus for supplying fuel to an internal combustion engine that includes a pumping plunger mounted in a bore and movable inwardly by an engine driven cam to displace fuel through an outlet to an injection nozzle. The quantity of fuel supplied to the nozzle is controlled by a spill valve. The apparatus also includes a restricted flow path through which fuel can flow to reduce the initial rate of fuel delivery through the nozzle, the flow path including a valve formed by the plunger and the bore so that fuel can flow through the flow path only during the initial inward movement of the plunger.

What is needed therefore is a spill valve system wherein more than one fuel injection rate can be obtained in order to rate shape the fuel injection profile.

The later published document WO 00/53 920 shows a fuel injector system with a control valve assembly of the spool type having an intermediate stable position between a closed and an open one.

SUMMARY OF THE INVENTION

A diesel engine fuel injection system is provided according to a first aspect of the invention. The diesel engine fuel injection system comprises a fuel injector for injecting fuel into a corresponding engine cylinder, each fuel injector having a pump chamber, a fuel injecting plunger for reciprocating within the pump chamber, a supply line connected to the pump chamber for receiving fuel, and a discharge nozzle connected to the pump chamber and to the corresponding cylinder for injecting fuel into the corresponding cylinder, a cam shaft having a respective cam operably connected to the plunger of the corresponding fuel injector so that rotation of the cam causes reciprocation of the plunger and movement of fuel from the supply line through the chamber to the corresponding cylinder, and a spill valve positioned between the chamber and the nozzle for controlling a rate of fuel injection to the corresponding cylinder, the spill valve having a first position providing a maximum fuel injection rate, a second position providing a substantially zero fuel injection rate, and at least one intermediate position providing an intermediate fuel injection rate between the maximum fuel injection rate and the zero fuel injection rate.

A method for rate shaping a fuel injecction profile in a diesel engine is provided according to a second aspect of the invention. The method comprises the steps of pressurizing fuel fed to a fuel injector nozzle, partially opening a spill valve communicating with the fuel injector nozzle, so that the fuel injector injects fuel into a corresponding engine cylinder at a first fuel injection rate for a predetermined first period of time during an engine fuel injection cycle, and fully opening the spill valve so that the fuel injector injects fuel into the corresponding engine cylinder at a second fuel injection rate for a remainder of the engine fuel injection cycle, wherein the first injection rate and the second injection rate shape a fuel flow rate of injected fuel.

The above and other objects, faatures and advantages of the present invention will be further understood from the following description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

  • FIGS. 1A-1D show charts illustrating fuel flow versus engine crank angle for different fuel injector systems;
  • FIGS. 2A-2B show a prior art fuel injector system and related fuel flow characteristics;
  • Figs. 3A and 3B show tables of emissions levels under different engine conditions, wherein B0I is beginning of injection, ICR is initial C-rate and NEP is nozzle end pressure, and wherein maximum NEP at rated speed is equal (1430 bar) for both tests; and
  • FIGS. 4A-4C are diagrams of a three-position spill valve of the present invention in three different positions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figs. 3A and 3B show data which compares the effect of initial cam velocity or injection rate on BsNOx and BsPt emissions levels, as well as the effect on BsFC. As can be seen from the data of Figs. 3A and 3B, if the initial cam velocity is reduced from 3.3 meters per second (m/s) to 1.55 m/s, BsNOx emissions levels are reduced at all speeds and loads, but BsPt emissions levels increase at 50% and 90% engine loads. The increase in BsPt emissions levels at 50% and 90% engine loads is primarily due to an increase in solids particulate emissions as a result of lower nozzle end pressure (NEP) at part loads associated with the lower initial cam velocity (ICR) at the same nozzle hydraulic flow. Although nozzle end pressure is lower at 10% engine loads with the 1.55 m/s initial cam velocity, the BsPt emissions levels do not increase. At 10% engine loads, the BsPt emissions levels are comprised mostly of volatile compounds, which are more dependent on injection timing than on nozzle end pressure.

Test 1B of Figs. 3A and 3B (initial cam velocity = 1.55 m/s) produced transient BsNOx emissions levels 16% lower than test 1C, even though injection timing was 8 degrees more advanced in test 1B than in test 1C. Also, test 1B produced lower NOx limited fuel consumption levels than in test 1C, possibly as a result of the more advanced end of the injection cycle in test 1B. The increased injection durations of test 1B did, however, increase cylinder pressure limited fuel consumption. The cylinder pressure limited fuel consumption levels were particularly poor in test 1B due to the rising rate cam profile. As injection timing was advanced towards peak cylinder pressure limits, initial cam velocity continued to reduce, therefore target peak cylinder pressure limits could not be obtained at all speeds.

By examining the data of Figs. 3A and 3B, several conclusions can be made regarding the effect an injection system can bring to emissions levels and fuel consumption. For minimum cylinder pressure limited fuel consumption, a high velocity cam and high hydraulic flow nozzle are required. For low BsNOx emissions levels a low rate of injection (first 5 to 10 crank degrees) is required so that injection timing can be advanced enough to prevent misfire. A low rate of injection also optimizes the BsNOx-fuel consumption tradeoff. The rate of injection at any time during the injection event is function of nozzle end pressure, cam velocity, and nozzle hydraulic flow. Although BsPt emissions levels at 10% engine loads are not greatly dependent on nozzle end pressure, for low BsPt emissions levels at increased engine loads (50-100%) a high average nozzle end pressure is required, thus reducing the solids particulate emissions fractions. Therefore, an optimal injection system would utilize a high hydraulic flow nozzle and a low velocity cam for the first 5-10 crank degrees of fuel injection to allow low BsNOx emissions. In the optimal injection system, the cam velocity would then quickly increase to obtain high average nozzle end pressure at 50-100% loads. However, at peak cylinder pressure limits, the cam must be at a high velocity for the entire injection duration, otherwise injection duration would be increased and fuel consumption would be degraded.

Referring now to FIGS. 4A-4C, there is shown a first embodiment of the fuel injection system 100 of the present invention. The fuel injection system 100 includes an injector 104 having a plunger 107 and a nozzle 110, a fuel return line 114, a fuel supply line 117, and a spill valve 118 having a spill valve plunger 121.

In operation, fuel is fed to the fuel injector 104 by the fuel supply line 117. The plunger 107 pressurizes the fuel, and the spill valve 118 controls the spilling of fuel above the injector plunger 107. The spill valve 118 shown in FIGS. 4A-4C is a three-position type of valve. The three positions are when the spill valve plunger 121 is open (FIG. 4A), when the spill valve plunger 121 is partially closed (FIG. 4B), and when the spill valve plunger 121 is fully closed (FIG. 4C). When the spill valve 118 is completely open, fuel is spilled at a rapid rate, and no increase in the fuel pressure occurs. When the spill valve 118 is partially closed, the fuel above the plunger 107 is pressurized, but due to the slight spilling action the spilling effectively reduces the cam velocity. When the spill valve 118 is completely closed, the fuel is completely pressurized and the nozzle 110 opens.

This spilling action may be electronically controlled, and may occur, for example, during the first (and critical) five to ten crank degrees of fuel injection. This is especially important for urban operation. It should be appreciated, however, that the electronically controlled spilling action may be performed at any time, and it is not strictly confined to the first five to ten crank degrees of fuel injection.

As indicated by the data of Figs. 3A and 3B, this spilling action would improve low BsNOx emissions capability and improve the BsNOx-BsFC relationship. The spilling effect would not be utilized at peak cylinder pressure limits so that the full benefit of a high velocity cam may be realized.

The effective reduction in cam velocity would be dependent on the spill area offered by the configuration of the spill valve 118. The duration of the spilling action would be dependent on the reaction capability of the spill valve 118 (i.e., how quickly the valve may be opened or closed). In the preferred embodiment, the three position spill valve 118 must be capable of moving to the partially closed position and dwelling at this position for approximately one millisecond before completely closing.

Although the preferred embodiment above discloses the use of a solenoid-type valve, it is contemplated that a magnetic latching valve may optionally be used. In addition, although a three-position spill valve is disclosed in the preferred embodiment, alternatively a spill valve may be used having more than three positions in order to provide an even more finely controlled flow of fuel.

The overall effect of the above invention is the capability to control the onset, rate and volumetric flow of injected fuel (e.g., rate shaping of the injected fuel). The rate shaped fuel flow is shown in Fig. 1D, where for the crank angle of approximately five to ten degrees the fuel flow rate is at a low level, and after that the fuel flow rate is comparable to the high cam velocity, high hydraulic flow fuel flow rate of Fig. 1A. Other considerations are the ease of control by electronic means, such as an engine control processor, simplicity of the design, ease of retro-fitting, and reliability.


Anspruch[de]
Kraftstoffeinspritzsystem (100) für einen Dieselmotor, umfassend: eine Kraftstoffeinspritzvorrichtung (104) zum Einspritzen von Kraftstoff in einen entsprechenden Motorenzylinder, wobei die benannte Kraftstoffeinspritzvorrichtung (104) eine Pumpenkammer, einen Kraftstoffeinspritz-Kolben (107) zur Hin- und Herbewegung in der Pumpenkammer, eine mit der Pumpenkammer verbundene Zuleitung (117) zur Kraftstoffaufnahme und eine mit der Pumpenkammer und mit dem entsprechenden Zylinder verbundene Austrittsdüse (110) zum Einspritzen von Kraftstoff in den entsprechenden Zylinder; eine Kurbelwelle mit einem Nocken, funktionell so mit dem Kolben (107) der Kraftstoffeinspritzvorrichtung (104) verbunden, dass die Drehung des Nockens eine Hin- und Herbewegung des Kolbens (107) sowie eine Bewegung von Kraftstoff von der Zuleitung (117) durch die benannte Kammer zu dem entsprechenden Zylinder bewirkt; ein Überströmventil (118), das in einer Kraftstoffrückleitung (114) angeordnet ist, die mit der benannten Kammer und der benannten Düse (110) in Verbindung steht, um die Geschwindigkeit der Kraftstoffeinspritzung in den entsprechenden Zylinder zu steuern, wobei das Überströmventil (118) einen Überströmventilkolben (121) besitzt; dadurch gekennzeichnet, dass der Überströmventilkolben (121) eine geschlossene Position, die eine maximale Kraftstoffeinspritzgeschwindigkeit liefert, eine offene Position, die eine im Wesentlichen Null betragende Kraftstoffeinspritzgeschwindigkeit liefert, und zumindest eine Zwischenposition, bei der der Überströmventilkolben (121) verweilt und die eine Kraftstoffeinspritzgeschwindigkeit liefert, die zwischen der maximalen Kraftstoffeinspritzgeschwindigkeit und der Null betragenden Kraftstoffeinspritzgeschwindigkeit liegt. Einspritzsystem nach Anspruch 1, dadurch gekennzeichnet, dass die benannte dazwischenliegende Kraftstoffeinspritzgeschwindigkeit für eine anfängliche Kraftstoffeinspritzphase verwendet wird und die benannte maximale Kraftstoffeinspritzgeschwindigkeit für eine Kraftstoffeinspritz-Hauptphase verwendet wird. Einspritzsystem nach Anspruch 1, dadurch gekennzeichnet, dass eine Betätigung des Überströmventil (118) elektronisch gesteuert wird und zu einer beliebigen Zeit während eines Arbeitszyklus erfolgen kann. Einspritzsystem nach Anspruch 1, dadurch gekennzeichnet, dass das Überströmventil (118) durch eine Magnetspule betätigt wird. Einspritzsystem nach Anspruch 1, dadurch gekennzeichnet, dass das Überströmventil (118) ein magnetisch verriegelndes Überströmventil (118) ist. Einspritzsystem nach Anspruch 1, dadurch gekennzeichnet, dass das Überströmventil (118) in der Lage ist, bei der benannten Zwischenposition für etwa eine Millisekunde zu verweilen. Einspritzsystem nach Anspruch 1, dadurch gekennzeichnet, dass das Überströmventil (118) in der Lage ist, die zumindest eine Zwischenposition während der ersten fünf Kurbelwellengrade der Kraftstoffeinspritzung zu erreichen. Verfahren zur Gestaltung eines Geschwindigkeitsprofils der Kraftstoffeinspritzung in einem Dieselmotor, die Schritte umfassend: einer Kraftstoffeinspritzvorrichtung (104) zugeführten Kraftstoff unter Druck zu setzen; einen Überströmventilkolben (121) in einem Überströmventil (118) in einer Kraftstoffrückleitung (114), die mit der Kraftstoffeinspritzvorrichtung (104) in Verbindung steht, zu einer ersten Position zu bewegen; Kraftstoff mit der benannten Kraftstoffeinspritzvorrichtung (104) während einer vorbestimmten ersten Zeitperiode während eines Kraftstoffeinspritzzyklus des Motors mit einer ersten Kraftstoffeinspritzgeschwindigkeit in einen Zylinder des Motors einzuspritzen; und den Überströmventilkolben (121) zum vollen Verschluss des Überströmventils (118) zu bewegen, so dass die Kraftstoffeinspritzvorrichtung (104) Kraftstoff während eines verbleibenden Teils des Kraftstoffeinspritzzyklus des Motors mit einer zweiten Kraftstoffeinspritzgeschwindigkeit in den entsprechenden Zylinder einspritzt; dadurch gekennzeichnet, dass die erste Position eine teilweise geöffnete Position ist;

der Überströmventilkolben (121) in der teilweise geöffneten Position verweilt; und

die benannte erste Einspritzgeschwindigkeit und die benannte zweite Einspritzgeschwindigkeit eine Kraftstoffgeschwindigkeit des eingespritzten Kraftstoffs gestalten.
Das Geschwindigkeitsgestaltungsverfahren des Anspruchs 8, dadurch gekennzeichnet, dass die benannte erste Kraftstoffeinspritzgeschwindigkeit eine dazwischenliegende Kraftstoffeinspritzgeschwindigkeit ist und dass die benannte zweite Kraftstoffeinspritzgeschwindigkeit eine maximale Kraftstoffeinspritzgeschwindigkeit ist. Das Geschwindigkeitsgestaltungsverfahren des Anspruchs 8, dadurch gekennzeichnet, dass das Verfahren die Verwendung einer Pumpe höherer Geschwindigkeit für die Steuerung des Kraftstoffdrucks und eines Ventils für starken hydraulischen Durchfluss ermöglicht. Das Geschwindigkeitsgestaltungsverfahren des Anspruchs 8, dadurch gekennzeichnet, dass die benannte erste Kraftstoffeinspritzgeschwindigkeit während der ersten fünf Kurbelwellengrade der Kraftstoffeinspritzung vorliegt. Das Geschwindigkeitsgestaltungsverfahren des Anspruchs 8, dadurch gekennzeichnet, dass die benannte erste Kraftstoffeinspritzgeschwindigkeit nicht beim Zylinderspitzendruck verwendet wird.
Anspruch[en]
A diesel engine fuel injection system (100), comprising: a fuel injector (104) for injecting fuel into a corresponding engine cylinder, said fuel injector (104) having a pump chamber, a fuel injecting plunger (107) for reciprocating within said pump chamber, a supply line (117) connected to said pump chamber for receiving fuel, and a discharge nozzle (110) connected to said pump chamber and to said corresponding cylinder for injecting fuel into said corresponding cylinder; a cam shaft having a respective cam operably connected to said plunger (107) of said fuel injection (104) so that rotation of said cam causes reciprocation of said plunger (107) and movement of fuel from said supply line (117) through said chamber to said corresponding cylinder; a spill valve (118) positioned in a fuel return line (114) communicating with said chamber and said nozzle (110) for controlling a rate of fuel injection to said corresponding cylinder, said spill valve (118) having a spill valve plunger (121); characterized in that said spill valve plunger (121) has a closed position providing a maximum fuel injection rate, an open position providing a substantially zero fuel injection rate, and at least one intermediate position at which said spill valve plunger (121) dwells and which provides an intermediate fuel injection rate between said maximum fuel injection rate and said zero fuel injection rate. The injection system of claim 1, wherein said intermediate fuel injection rate is used for an initial fuel injection phase and said maximum fuel injection rate is used for a main fuel injection phase. The injection system of claim 1, wherein a spill valve (118) actuation is controlled electronically, and can occur at any time in an engine cycle. The injection system of claim 1, wherein said spill valve (118) is actuated by a solenoid. The infection system of claim 1, wherein said spill valve (118) is a magnetic-latching spill valve (118). The injection system of claim 1, wherein said spill valve (118) is capable of dwelling at said intermediate position for about one millisecond. The injection system of claim 1, wherein said spill valve (118) is capable of attaining said at least one intermediate position during a first five crank degrees of fuel injection. A method for shaping a fuel injection rate profile in a diesel engine, comprising the steps of: pressurizing fuel fed to a fuel injector (104); moving a spill valve plunger (121) in a spill valve (118) in a fuel return line (114) communicating with said fuel injector (104) to a first position; injecting fuel with said fuel injector (104) into an engine cylinder at a first fuel injection rate for a predetermined first period of time during an engine fuel injection cycle; and moving said spill valve plunger (121) to fully close said spill valve (118) so that said fuel injector (104) injects fuel into said corresponding engine cylinder at a second fuel injection rate for a remainder of said engine fuel injection cycle; characterized in that said first position is a partially opened position;

said spill valve plunger (121) dwells in said partially opened position; and

said first injection rate and said second injection rate shape a fuel flow rate of injected fuel.
The rate shaping method of claim 8, wherein said first fuel injection rate is an intermediate fuel injection rate and said second fuel injection rate is a maximum fuel injection rate. The rate shaping method of claim 8, wherein said method allows the use of a higher velocity pump driving a fuel pressure and a high hydraulic flow nozzle (110). The rate shaping method of claim 8, wherein said first fuel injection rate occurs during a first rive crank degrees of fuel injection. The rate shaping method of claim 8, wherein said first fuel injection rate is not used at peak cylinder pressure.
Anspruch[fr]
Un système d'injection de carburant (100) pour moteur diesel comprenant : un injecteur de carburant (104) pour injecter du carburant dans un cylindre de moteur correspondant, ledit injecteur de carburant (104) ayant une chambre de pompage, un plongeur d'injection de carburant (107), pour effectuer un mouvement en va et vient à l'intérieur de ladite chambre de pompage, une tuyauterie d'alimentation (117), reliée à ladite chambre de pompage pour recevoir du carburant, et une buse de décharge (110), reliée à ladite chambre de pompage et audit cylindre correspondant pour injecter du carburant dans ledit cylindre correspondant ; un arbre à came ayant une came respective, reliée fonctionnellement audit plongeur (107) dudit injecteur de carburant (104), de manière qu'une rotation de ladite came provoque un mouvement en va et vient dudit plongeur (107) et un déplacement de carburant de ladite tuyauterie d'alimentation (117) vers ledit cylindre correspondant, par l'intermédiaire de ladite chambre ; une soupape de décharge (118), positionnée dans une tuyauterie de retour de carburant (114), communiquant avec ladite chambre et ladite buse (110) pour commander un débit d'injection de carburant injecté audit cylindre correspondant, ladite soupape de décharge (118) ayant un plongeur de soupape de décharge (121) ; caractérisé en ce que ledit plongeur de soupape de décharge (121) présente une position fermée, fournissant un débit d'injection de carburant maximal, une position ouverte, fournissant un débit d'injection de carburant sensiblement de valeur zéro, et au moins une position intermédiaire, à laquelle ledit plongeur de soupape de décharge (121) réside et qui fournit un débit d'injection de carburant intermédiaire entre ledit débit d'injection de carburant maximal et ledit débit d'injection de carburant de valeur zéro. Le système d'injection selon la revendication 1, dans lequel ledit débit d'injection de carburant intermédiaire est utilisé pour une phase d'injection initiale de carburant et ledit débit d'injection maximal de carburant est utilisé pour une phase d'injection principale de carburant. Le système d'injection selon la revendication 1, dans lequel l'actionnement d'une soupape de décharge (118) est commandé électroniquement et peut se produire à tout moment dans un cycle du moteur. Le système d'injection selon la revendication 1, dans lequel ladite soupape de décharge (118) est actionnée par un solénoïde. Le système d'injection selon la revendication 1, dans lequel ladite soupape de décharge (118) est une soupape de décharge (118) à verrouillage magnétique. Le système d'injection selon la revendication 1, dans lequel ladite soupape de décharge (118) est capable de séjourner à ladite position intermédiaire, pendant une durée d'environ une milliseconde. Le système d'injection selon la revendication 1, dans lequel ladite soupape de décharge (118) est capable d'atteindre ladite au moins une position intermédiaire durant les cinq premiers degrés de vilebrequin de l'injection de carburant. Un procédé de modulation d'un profil de débit d'injection de carburant dans un moteur diesel, comprenant les étapes consistant à : pressuriser du carburant fourni à un injecteur de carburant (104) ; déplacer un plongeur de soupape de décharge (121) dans une soupape de décharge (118), dans une tuyauterie de retour de carburant (114) mise en communication avec ledit injecteur de carburant (104) à une première position ; injecter du carburant avec ledit injecteur de carburant (104) dans un cylindre de moteur, à un premier débit d'injection de carburant, pour une première période de temps prédéterminée durant un cycle d'injection de carburant de moteur; et déplacer ledit plongeur de soupape de décharge (121) pour complètement fermer ladite soupape de décharge (118), de manière que ledit injecteur de carburant (104) injecte du carburant dans ledit cylindre de moteur correspondant, à un deuxième débit d'injection de carburant, pour le reste dudit cycle d'injection de carburant du moteur; caractérisé en ce que ladite première position est une position partiellement ouverte ;

ledit plongeur de soupape de décharge (121) séjourne à ladite position partiellement ouverte ; et

ledit premier débit d'injection et ledit deuxième débit d'injection produisent une certaine forme du débit d'écoulement en carburant injecté.
Le procédé de modulation de débit selon la revendication 1, dans lequel ledit premier débit d'injection de carburant est un débit d'injection de carburant intermédiaire et ledit deuxième débit d'injection de carburant est un débit d'injection de carburant maximal. Le procédé de modulation de débit selon la revendication 8, dans lequel ledit procédé permet l'utilisation d'une pompe à plus haute vitesse, en fournissant une pression de carburant et une buse d'écoulement hydraulique (110) à caractéristique élevée. Le procédé de modulation de débit selon la revendication 8, dans lequel ledit premier débit d'injection de carburant se produit durant les cinq premiers degrés de vilebrequin de l'injection de carburant. Le procédé de modulation de débit selon la revendication 8, dans lequel ledit premier débit d'injection de carburant n'est pas utilisé à la pression de crête du cylindre.






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