WO2007009641A1

WO2007009641A1 - Fuel injector

Info

Publication number: WO2007009641A1
Application number: PCT/EP2006/006796
Authority: WO
Inventors: Slocinski Holmer
Original assignee: L'orange Gmbh
Priority date: 2005-07-15
Filing date: 2006-07-12
Publication date: 2007-01-25
Also published as: JP4869342B2; JP2009501289A; DE502006003778D1; EP1907686B1; DE102005033123B3; ATE431901T1; EP1907686A1; KR101001002B1; KR20080028377A

Abstract

The invention relates to a fuel injector which is used to inject fuel, which is maintained in a fuel accumulator (1) at high pressure, into a combustion chamber in an internal combustion engine, under at least two different high injection pressures. Said fuel injector comprises an injector housing (11), a nozzle needle (6) which is arranged in a longitudinally displaceable manner in the housing (11), an injection nozzle (7) which can be opened, optionally, by the nozzle needle (6), through which the fuel can be injected into the combustion chamber of the internal combustion engine, a control chamber (12) which co-operates with the nozzle needle (6) in order to open the injection nozzle (7) and which is pressurised by fuel and a pressure converter (19) which is used to supply fuel which is to be injected at high pressure. The pressure converter (19) is controlled by means of a 3/2-control valve, by pressure of the fuel in the control chamber (12).

Description

fuel injector

The invention relates to a fuel injector for injecting in a fuel storage under high pressure held fuel into the combustion chamber of an internal combustion engine according to the preamble of claim 1.

For injecting fuel, which is kept in a fuel storage under high pressure, in the combustion chamber of an internal combustion engine (common rail injection system) pressure-translated fuel injectors are known with which the fuel for, for example, a pre- and / or post-injection with a first , Lower pressure and for, for example, main injection with a second, higher pressure in the combustion chamber of the internal combustion engine can be injected.

From DE 199 39 423 A1, a pressure-intensified fuel injector is known, which contains a hydraulic pressure booster piston, which communicates with the injection nozzle communicating delivery volume with a first, smaller cross section and an optionally acted upon by the fuel pressure working volume with a second, larger cross section having. The working volume is by an electrically controlled 3/2 -way valve either to trigger the power stroke with the fuel pressure of the stored in the fuel tank under high pressure fuel or Return of the pressure booster piston to its original position for pressure relief with a leakage line connectable. The electrically actuated control valve means additional effort and requires its own electrical control.

Another pressure-translated fuel injector is known from DE 100 60 089 A1. Here, the control of a pressure booster piston, which is constructed similar to the previously described known pressure-translated Kraftstoffinj ector, by depressurizing a differential space, which corresponds to the difference of the cross sections of working volume and flow, via an electrically controlled 2/2-way valve.

From DE 102 29 413 Al a pressure-intensified fuel injector is known to be known, in which for the control of the differential space of the pressure booster piston with low pressure or the fuel pressure can be applied. The control piston coupled to the nozzle needle has a dual function. Depending on the position of the control piston, which forms a slide valve, a line leading to the differential space is connected to low pressure or the low pressure connection is blocked. In the blocking position, the differential space is acted upon by another, throttled line connection to the fuel pressure.

The object of the invention is to provide an improved fuel injector of the presumed kind. In particular, a pressurized Kraftstoffinj is to be created ector, which is controlled with little effort and ensures reliable operation. The object is achieved by a fuel injector with the features of claim 1.

Advantageous developments and embodiments of the fuel injector according to the invention are specified in the subclaims.

The invention provides a fuel injector for injecting fuel stored in a fuel reservoir under high pressure into the combustion chamber of an internal combustion engine under at least two different injection pressures, comprising an injector housing, a longitudinally displaceably arranged nozzle needle in the housing and an injector nozzle to be selectively opened by the nozzle needle , by which the fuel is injectable into the combustion chamber of the internal combustion engine, a cooperating with the nozzle needle, acted upon by the fuel pressure control chamber which is depressurable in the sense of opening the injector by means of a first control valve and a pressure booster for conveying fuel to be injected under elevated pressure, said the pressure booster is controllable by a second control valve which is hydraulically connected to the control chamber for actuation by the pressure of the fuel in the control chamber. According to the invention, the second control valve (8) is designed as a 3/2-way valve which has a valve body (8a) acted upon by a fuel pressure prevailing in the control chamber (12) on a control piston surface (8b).

The fuel injector according to the invention is advantageously suitable for injecting fuel, in particular also of heavy oil into the combustion chamber of an internal combustion engine with different pressure levels, in particular for a pre- and / or post-injection of fuel with the pressure in the fuel reservoir (common rail) below high pressure held fuel, as well as for a main injection with a maximum pressure caused by the pressure booster.

To display injection processes at different pressure levels, the valve body of the control valve is expediently acted upon with a delay in time with the fuel pressure prevailing in the control chamber. In particular, a pre-injection and post-injection and the beginning of the main injection at a lower pressure level than the main injection is possible, since the pressure ratio responds with a time delay.

According to a particularly advantageous embodiment of the invention, it is provided that the pressure booster comprises a pressure booster piston having at its front a communicating with the injection nozzle, a first, smaller cross-section having promotional volume and on its back a second, larger cross-section having working volume , wherein the working volume via the second control valve in the sense of conveying fuel through the pressure booster piston under increased pressure optionally acted upon with the fuel pressure.

According to another advantageous embodiment of the invention, it is provided that the pressure booster includes a pressure booster piston having at its front a communicating with the injection nozzle, a first, smaller cross-section having promotional volume and on its back a second, larger cross-section having working volume in which a differential volume, which has a third cross section and which corresponds to a difference between the cross sections of the working volume and delivery volume and which is still present on the front side of the pressure booster piston, is conveyed via the second control valve in the sense of Conveying fuel through the pressure booster piston under elevated pressure is optionally pressure relieved.

Expediently, the control valve (8) connects a line leading from the control valve (18) to the pressure booster piston (9) either with a leakage line (3) or with a fuel line (15) in communication with the fuel reservoir (1).

It is preferably provided, in particular, that the control piston surface is coupled via a line connection to the control chamber, which contains a throttle which determines the temporal response of the second control valve.

According to an advantageous embodiment of the invention, it is provided that the throttle is connected in parallel in the flow direction from the control chamber to the control piston surface of the second control valve non-return valve.

According to an advantageous embodiment of the invention, it is provided that temporal response of the second control valve is dimensioned such that at a short pressure relief of the control chamber for a pre-injection and / or post-injection of fuel with non-elevated pressure release of the injector without effective control of the pressure booster and at a longer pressure relief of the control chamber for a main injection of fuel with increased pressure, a release of the nozzle needle with effective control of the pressure booster takes place.

In the following an embodiment of the invention Kraftstoffinj ector is explained with reference to the drawing. Show it :

Figure 1 is a schematic representation of a pressure translated Kraftstoffinj injector according to an embodiment of the invention;

Figures 2a) to d) respective hydraulic plans of the pressure-translated fuel injector according to the embodiment of the invention, which show four different states in the operation of the same; and

Figure 3a) to f) timing diagrams of the courses of different pressures, piston movement and injection rate in the pressure-translated Kraftstoffinj ector according to the described embodiment.

FIG. 1 shows a fuel injector which is provided for injecting fuel stored in a fuel reservoir 1 (common rail) under high pressure. The fuel injector comprises an injector housing 11, which is shown only partially, in which a nozzle needle 6 is arranged so as to be displaceable in the longitudinal direction and selectively releases an injection nozzle 7 provided at its front end for injecting the fuel. At the back of the nozzle needle 6, which is biased by a spring 13 in the closing direction, a control chamber 12 is provided, which is acted upon by an inlet throttle 4 of the fuel stored in the fuel tank 1 under high pressure fuel and a first control valve 2 is optionally pressure relieved. The held in the fuel tank 1 under high pressure fuel is a tip of the nozzle needle 6 annularly surrounding the nozzle front chamber 14 via a fuel passage 15. Weiterbar contains the fuel injector a Drucküberset ^¬ zer 19, which comprises a pressure transmission piston 9, a first, smaller cross section exhibiting Air flow 16 is provided and on its rear side a second, larger cross section exhibiting the working volume 17 at the front thereof. The delivery volume 16 of the pressure booster piston 9 is also connected in the course of the fuel passage 15 to the nozzle front chamber 14, wherein upstream of the delivery volume 16 in the fuel passage 15 is a check valve 10 which prevents a return flow of fuel from the delivery volume 16 to the upstream. A further provided second control valve 8 is provided in the form of a 3/2 -way valve, which connects the provided at the rear of the pressure booster piston 9 working volume 17 optionally with the fuel passage 15 or depressurized via a leakage line 3.

The second control valve 8 includes a valve body 8a, on which a control piston surface 8b is provided, which is acted upon via a control line 12a of the pressure prevailing in the control chamber 12 fuel pressure. By acting on the control piston surface 8b fuel pressure of the control chamber 12, the valve body 8a of the second control valve 8 is forced to a first, closed position in which an influx of the high-pressure fuel from the fuel passage 15 to-working volume 17 of the pressure booster piston 9 locked and on the other hand, the connection of the working volume 17 is released to the leakage line 3.

In the leading of the control chamber 12 to the control piston surface 8b of the valve body 8a control line 12a, a throttle 5 is arranged, through which the temporal response of the second control valve 8 to pressure changes in the control chamber 12 in response to opening and closing of the first control valve 2 is determined. This throttle 5 is a check valve 5a connected in parallel, which is continuous in the direction of the control chamber 12 to the control piston surface 8b. The pressure booster 19 is thus controlled in response to the pressure prevailing in the control chamber 12 pressure by the second Steuerven ^¬ til 8.

With reference to the figures 2a) to d) now different phases during operation of the pressure-translated Kraftstoffinj invention are to be described.

FIG. 2a) shows the initial state in which the first control valve 12 is not actuated electromagnetically. The nozzle needle 6 keeps the injection nozzle 7 closed and the second control valve 8 is in the closed position shown in Figure 1, in which the working volume 17 of the pressure booster piston 9 is shut off from the voltage applied in the fuel passage 15 fuel pressure and instead connected to the leakage line 3 ,

In the state shown in FIG. 2b), the first control valve 2 is now actuated electromagnetically and causes a pressure drop in the control chamber 12 above the nozzle needle 6, which leads to the opening of the injection nozzle 7. The fuel present in the nozzle front chamber 14 at the tip of the nozzle needle 6 is injected into the combustion chamber of the internal combustion engine under the pressure supplied by the fuel reservoir 1. Due to the time delay caused by the throttle 5, the second control valve 8 is not yet actuated, that is, the pressure drop caused by the opening of the first control valve 2 in the control chamber 12 does not yet arrive at the control piston surface 8b of the valve body 8a of the second control valve 8 Effect. Upon termination of the control by the first control valve 2 before the pressure drop in the control raum 12 on the second control valve 8 is an injection only under the pressure of the fuel tank 1 without actuation of the pressure booster 19 instead. In this way, a pre-injection and / or post-injection with a first, lower pressure level can be realized.

However, when the first control valve 2 is energized for a longer period of time, the third operating state shown in Fig. 2c) becomes effective. Via the throttle 5, the pressure drop occurring in the control chamber 12 is now also effective on the control piston surface 8b of the valve body 8a of the second control valve 8, so that by an opening movement of the valve body 8a a connection from the fuel passage 15 to the working volume 17 at the back of the pressure booster piston. 9 takes place, which leads a movement of the pressure booster piston 9 in the sense of a promotion of fuel from the located at its front flow volume 16 to the nozzle front chamber 14 at the injection nozzle 7. As a result, the fuel pressure during the injection is increased accordingly, wherein a return flow of fuel from the delivery volume 16 to the fuel passage 15 is prevented by the check valve 10. During the movement of the pressure booster piston 9, in a differential volume 18, which corresponds to the difference between the cross sections of working volume 17 and delivery volume 16, fuel flows into the leakage line 3. 1

At the end of the injection process, cf. FIG. 2d), the first control valve 2 is closed by the end of the energization, whereby a re-increase of the pressure of the control chamber 12 is accompanied by subsequent flow of fuel from the fuel channel 15 via the inlet throttle 4. This increase in the fuel pressure in the control chamber 12 is planted via the throttle 5 located in the control line 12a after a short time Time to the control piston surface 8b on the valve body 8a of the second control valve 8 on, so that this closed and the working volume 17 of the pressure booster piston 9 is separated from the fuel passage 15. At the same time the second control valve 8 opens the flow of the working volume 17 to the leakage line 3, whereby the pressure booster piston 9 is returned to its initial position. The pressure drop occurring in the nozzle antechamber 14 causes a closing of the nozzle needle 6 and thus an end of the injection process.

Figures 3a) to f) show the time course of various pressures on Kraftstoffinj ector and piston movement and injection rate during the phases described with reference to Figures 2a) to d) during the injection process.

FIG. 3 a) shows the time-constant pressure in the fuel accumulator 1, that is to say the pressure of the common rail. FIG. 3b) shows the pressure in the control chamber 12 at the rear side of the nozzle needle 6.

FIG. 3c) shows the pressure on the control piston surface 8b of the valve body 8a of the second control valve 8.

FIG. 3d) shows the movement of the pressure booster piston 9.

FIG. 3 e) shows the pressure in the nozzle front chamber 14 in front of the injection nozzle 7.

Finally, FIG. 3f) shows the course of the injection rate of the fuel injected by the injection nozzle 7 into the combustion chamber of the internal combustion engine.

As can be seen, causes a brief activation of the first control valve 2 at the beginning of the injection process only one short lowering of the pressure in the control chamber 12, see Figure 3b), associated with a short pilot injection of fuel into the combustion chamber of the internal combustion engine, see Figure 3f).

In a subsequent longer activation of the first control valve 2, the pressure in the control chamber 12 decreases for a long time, see Figure 3b), this pressure drop via the throttle 5 transmits to the second control valve 8, see Figure 3c), whereby a movement see the pressure translation piston 9, see Figure 3d), in the sense of a promotion of fuel under elevated pressure, see Figure 3e) is effected. This results in the main injection shown in Figure 3f) with increased injection rate.

After elimination of the first control valve 2, the nozzle needle 6 return to its closed state and the pressure booster piston 9 to its original position.

In a still following further brief energization of the first control valve 2, a post-injection is effected at low pressure, similar to the pre-injection described above.

Notwithstanding the exemplary time profiles described with reference to FIG. 3, the injection process can of course also be controlled in a different manner. LIST OF REFERENCE NUMBERS

Fuel reservoir First control valve (common rail) Leakage line Inlet restrictor Throttle a Check valve Nozzle needle Injector second control valve a Valve body b Spool area Pressure transfer piston 0 Check valve 1 Injector housing 2 Control chamber 2a Control line 3 Spring 4 Nozzle vestibule 5 Fuel channel 6 Delivery volume 7 Working volume 8 Differential volume 9 Compressor

Claims

claims

Kraftstoffinj injector for injecting in a fuel storage (1) held high pressure fuel into the combustion chamber of an internal combustion engine under at least two different injection pressures, comprising an injector (11), a longitudinally displaceable in the housing (11) arranged nozzle needle (6) and a from the nozzle needle (6) selectively openable injection nozzle (7) through which the fuel is injected into the combustion chamber of the internal combustion engine, a cooperating with the nozzle needle (6), acted upon by the fuel pressure control chamber (12) in the sense of opening the injector (7) by means of a first control valve (2) is pressure-relieved, and containing a pressure booster (19) for conveying fuel to be injected under elevated pressure, wherein the pressure booster (19) by a second control valve (8) is controllable, the actuation by the Pressure of the fuel in the control chamber (12) hydraulically with the Steuerr aum (12) is coupled, characterized in that the second control valve (8) is designed as a 3/2 way valve having a on a control piston surface (8b) of the prevailing in the control chamber (12) fuel pressure valve body (8a).

2. fuel injector according to claim 1, characterized in that the valve body (8 a) delayed in time with the in the control chamber (12) prevailing KraftStoffdruck can be acted upon.

3. fuel injector according to claim 1 or 2, characterized in that the pressure booster (19) includes a pressure booster piston (9) having at its front a with the injection nozzle (7) in connection, a first, smaller cross-section having promotional volume (16 ) and on its rear side a working volume (17) having a second, larger cross-section, wherein the working volume (17) can be acted upon by the fuel pressure via the second control valve (8) in the sense of conveying fuel through the pressure transmission piston (9) under elevated pressure is.

4. fuel injector according to claim 1 or 2, characterized in that the pressure booster (19) includes a pressure booster piston (9) having at its front a with the injection nozzle (7) in connection, a first, smaller cross-section having promotional volume (16 ) and at its rear side a working volume (17) having a second, larger cross-section, wherein a differential volume (18), which has a third cross-section and which remains at the front side of the pressure-transmitting piston (9), corresponds to a difference of the cross-sections of working volume (17). and delivery volume (16), via the second control valve (8) in Sense of conveying of fuel through the pressure booster piston (9) under pressure is relieved of pressure.

5. fuel injector according to one of claims 1 to 4, characterized in that the control valve (8) from the control valve (18) to the pressure booster piston (9) leading line either with a leakage line (3) or one with the fuel storage (1) in Connecting fuel line (15) connects.

6. fuel injector according to one of claims 1 to 5, characterized in that the control piston surface (8 b) via a line connection to the control chamber (12) is coupled, which contains a temporal response of the second control valve (8) defining the throttle (5) ,

7. Fuel injector according to claim 6, characterized in that the throttle (5) in the flow direction from the control chamber (12) to the control piston surface (8b) of the second control valve (8) continuous check valve (5a) is connected in parallel.

8. Fuel injector according to claim 6 or 7, characterized in that temporal response of the second control valve (8) is dimensioned such that at a short pressure relief of the control chamber (12) for a pre- and / or post-injection of fuel at a non-elevated pressure Release of the injection nozzle (7) without effective control of the pressure booster (19) and at a longer pressure relief of the control chamber (12) for a main injection of fuel with increased pressure release of the nozzle needle (7) with effective control of the pressure booster (19).