EP1125054B1 - Fuel injection method and device - Google Patents

Abstract

A fuel injection is effected by means of a high-pressure pump (2) and a pressure reservoir chamber (6) for generating and storing a first system pressure. This system pressure is not used for injection; instead, by means of the pressure booster unit (9), a higher injection pressure is generated during the injection, and this injection pressure can be reduced to shape the course of injection. By means of this invention, an improved capability of metering the fuel injection and an improved execution of fast switching times are achieved.

Description

State of the art

The invention relates to a method and a device for carrying out a Fuel injection,

For a better understanding of the description and the claims, some terms are explained below: The fuel injection according to the invention can be performed both stroke-controlled and pressure-controlled. In the context of the invention is meant a hubaesteuerte Kraftstoffeinsoritzung that the opening and closing of the injection port by means of a displaceable valve member due to the hydraulic interaction of the fuel pressures in a nozzle chamber and in a control chamber. A pressure reduction within the control chamber causes a stroke of the valve member. Alternatively, the deflection of the valve member by an actuator (actuator, actuator) take place. In a pressure-controlled Kraftstoffeinsoritzung according to the invention, the valve member is moved against the pressure prevailing in the nozzle chamber of an injector fuel pressure against the action of a closing force (spring), so that the injection port for injection of fuel from the nozzle chamber is released into the cylinder. The pressure with which fuel exits the nozzle chamber into a cylinder of an internal combustion engine is referred to as injection pressure , while a system pressure is understood to mean the pressure below which fuel is available or stored in the fuel injector. Fuel metering means to provide a defined amount of fuel for injection. Leakage is understood to mean an amount of fuel that arises during operation of the fuel injection device (eg a pilot leakage ), is not used for injection and is conveyed back to the fuel tank. The pressure level of this leakage may have a steady state pressure, with the fuel subsequently being expanded to the pressure level of the fuel tank.

A stroke-controlled injection is for example by DE 196 19 523 A1 known. The achievable injection pressure is here through the pressure storage space (rail) and the high pressure pump limited to about 1600 to 1800 bar.

To increase the injection pressure, a pressure booster unit is possible, as they For example, from US 5,143,291 or US 5,522,545 is known. The disadvantage of this pressure-translated systems lies in a lack of flexibility of injection and a poor quantity tolerance in the metering of small amounts of fuel.

In a fuel injection device described in JP 08277762 A are for Increasing the flexibility of the injection and the metering accuracy of the pilot injection two pressure accumulator spaces provided with different pressures. These two Pressure accumulator rooms require a high manufacturing cost and high Production costs, wherein the maximum injection pressure continues through the fuel pump and the accumulator space is limited.

From the document US 5,423,484 is a system with a Fuel injection with a high pressure pump and a pressure storage room to Generation and storage of a first system pressure with a Pressure booster unit, by means of which during the injection a higher Injection pressure is generated, known. The shaping of the injection pressure is carried out by Absteuerung via a pressure relief valve or a bypass piston.

Advantages of the invention

For better dosing of the injection and implementation of fast switching times According to the invention, a method according to claim 1 and a device according to Proposed claim 8. Inventive developments are in the Claims 2 to 7 contain. The pre and post injection with one opposite the main injection lower injection pressure can be carried out reproducibly. It is a high injection pressure at a low pressure in the central pressure storage space realizable. The high pressure generation of the fuel takes place directly in the area of the injection (Metering) instead, so that the efficiency as a result of a smaller High-pressure volume increased. The use of engine oil to control the Pressure booster unit of one embodiment ensures increased safety the implementation of the procedure. The injection pressure can be at another Embodiment hydraulically generated during the mechanical means of a High pressure pump generated portion stored in the accumulator room and not to Injection is used. It comes due to the low pressure to a reduced Load the high-pressure pump, because this only for filling the accumulator space not but is used for injection itself.

drawing

Fig. 1

eine erste hubgesteuerte Kraftstoffeinspritzeinrichtung;

Fig. 2

eine zweite hubgesteuerte Kraftstoffeinspritzeinrichtung;

Fig. 3

eine dritte hubgesteuerte Kraftstoffeinspritzeinrichtung mit Verwendung eines separaten Druckfluids;

Fig. 4

eine vierte hubgesteuerte Kraftstoffeinspritzeinrichtung mit Verwendung einer Druckbegrenzung in der Druckübersetzungseinheit;

Fig. 5

eine erste druckgesteuerte Kraftstoffeinspritzeinrichtung;

Fig. 6

eine zweite druckgesteuerte Kraftstoffeinspritzeinrichtung;

Fig. 7

eine dritte druckgesteuerte Kraftstoffeinspritzeinrichtung mit Verwendung eines separaten Druckfluids;

Fig. 8

eine vierte druckgesteuerte Kraftstoffeinspritzeinrichtung mit Verwendung einer Druckbegrenzung in der Druckübersetzungseinheit.

Fig. 9

eine fünfte druckgesteuerte Kraftstoffeinspritzeinrichtung mit einer Vario-Einspritzdüse

Eight embodiments of the fuel injection device according to the invention are shown in the schematic drawing and are explained in the following description. Show it:

Fig. 1

a first stroke-controlled fuel injection device;

Fig. 2

a second stroke-controlled fuel injection device;

Fig. 3

a third stroke-controlled fuel injector using a separate pressurized fluid;

Fig. 4

a fourth stroke-controlled fuel injection device using a pressure limitation in the pressure booster unit;

Fig. 5

a first pressure-controlled fuel injection device;

Fig. 6

a second pressure controlled fuel injector;

Fig. 7

a third pressure controlled fuel injector using a separate pressurized fluid;

Fig. 8

a fourth pressure-controlled fuel injection device with use of a pressure limiting in the pressure booster unit.

Fig. 9

a fifth pressure controlled fuel injector with a Vario injector

Description of the embodiments

In the illustrated in Fig. 1 the first embodiment of a fuel injection device 1 promotes a volume-controlled fuel pump 2 fuel 3 from a reservoir 4 via a feed line 5 in a central pressure storage chamber 6 (common rail). Starting from the accumulator chamber 6, a plurality of pressure lines 7 corresponding to the number of individual cylinders lead to the individual injectors 8. Within each of the injectors 8 protruding into the combustion chamber of the internal combustion engine to be supplied (injection device), only one of the injectors 8 is shown in FIG - Is a pressure booster unit 9 is arranged. The pressure line 11 can be connected either by means of a valve unit 10 for pressure transmission control (3/2-way valve) to the pressure line 7 or connected to a leakage line 12. In the accumulator chamber 6, a system pressure of about 200 bar to 1000 bar can be stored, which is further amplified by means of the pressure booster unit 9.

The pressure means 17 can with the help of the valve unit 10 and the pressure line 7 at one end be pressurized. A differential space 17 'is by means of the leakage line 15th depressurized, so that the pressure medium 17 to reduce the volume of a Pressure chamber 13 can be moved. The pressure medium 17 is in Compression direction moves, so that in the pressure chamber 13 compressed fuel (first Injection pressure) a control chamber 19 and a nozzle chamber 20 can be supplied. One Check valve 14 prevents the return of compressed fuel in the Pressure storage chamber 6. By means of a suitable area ratio in a primary chamber 13 'and the pressure chamber 13 can be generated in this way a second higher pressure become. If the primary chamber 13 'by means of the valve unit 10 to the leakage line 12th connected, the provision of the pressure medium 17 and the refilling of the Pressure chamber 13. Due to the pressure conditions in the pressure chamber 13 and the Primary chamber 13 'opens the check valve 14, so that the pressure chamber 13 under Rail pressure (pressure of the accumulator chamber 6) is and the pressure means 17 hydraulically one or more springs can be arranged in the spaces 13, 13 'and 17'.

By throttling within one of the valves 10 or 29 may be during the injection variable injection pressure and thus a shaping of the injection curve by a Cross-sectional control can be achieved, the pressure in the control chamber 19 at a Control of the cross section of the valve 29 is affected, and thus throttling the Injection pressure at the valve sealing surface 22 via the valve member 21 is achieved. to Realization of a continuous cross-section control are piezo actuators as well also fast magnetic actuators conceivable. By execution of multi-stage valves can take place a continuous shaping of the injection pressure several different Injection pressure levels during injection through various throttle positions be generated.

In a communicating with the pressure chamber 13 in communication pressure line 18 builds up Pressure, which is also present in the control chamber 19 and the nozzle chamber 20. The injection takes place via a fuel metering with the help of a in a guide bore axially slidable piston-shaped valve member 21 with a conical valve sealing surface 22 at its one end, with which it has a valve seat on the injector housing Injector unit 8 interacts. At the valve seat surface of the injector are Injection openings provided. Within the nozzle space 20 is one in the opening direction of the valve member 21 facing pressure surface exposed to the pressure prevailing there, the is supplied via the pressure line 18 to the nozzle chamber 20. Coaxial with a valve spring 23 further engages the valve member 21 to a pressure piece 24 which, with its valve sealing surface 22 facing away from end 25 the control chamber 19 limited. The control room 19 has from Fuel pressure port forth an inlet with a first throttle 26 and a drain to a pressure relief line 27 with a second throttle 28 passing through a 2/2-way valve 29 is controlled.

The nozzle chamber 20 is placed over an annular gap between the valve member 21 and the Guide bore continues to the valve seat surface of the injector. About the pressure in the Control chamber 19, the pressure member 24 is pressurized in the closing direction.

Upon actuation (opening) of the 2/2-way valve 29, the pressure in the control chamber 19 be degraded, so that in the sequence in the opening direction on the valve member 21st acting pressure force in the nozzle chamber 20 acting in the closing direction on the valve member 20 Pressure force exceeds. The valve sealing surface 22 lifts off the valve seat surface and fuel is injected. In this case, the pressure relief process of the control chamber 19 and Thus, the stroke control of the valve member 21 via the dimensioning of the throttle 26 and affect the throttle 28.

The end of the injection is achieved by pressing (closing) the 2/2-way valve again 29 introduced, which decouples the control chamber 19 again from the pressure relief line 27, so that in the control chamber 19, a pressure builds up again, the pressure piece 24 in Can move closing direction.

The valve units are powered by electromagnets for opening or closing or Switching operated. The electromagnets are controlled by a control unit, the various operating parameters (engine speed, ....) of the supplied Monitor and process internal combustion engine.

Instead of the solenoid-controlled valve units, piezo-actuator elements (actuator, Actuator) are used, the necessary temperature compensation and possibly a have required force or displacement ratio.

Hereinafter, only differences in the description of the figures 2 to 8 Fuel injection device treated according to Figure 1. Identical components will not be closer explained.

From the figure 2 it can be seen that the pressure booster unit 9 is arranged in a modification of the fuel injection device 1 outside of the injector 8 and now in the region of the pressure storage chamber 6. The size of the injector 8 decreases. The valve 10 can be arranged on the pressure storage space and the pressure booster unit can be arranged on the injector.

In the case of the fuel injection device according to FIG. 3 , the pressure storage space 6 for controlling the pressure booster unit 9 is filled via the delivery line 45 and the pump 42 with engine oil or another suitable pressure fluid 43 from a reservoir 44. The low pressure side 16 of the pressure means 17 can either be pressurized via the pressure line 47 or connected to a leakage line 48. The switching is achieved by the 3/2-way valve 10.

The pressure chamber 13 is via the check valve 14 with fuel from another Reservoir filled or can with the help of a feed pump - as shown - with a low pre-feed pressure. The injection takes place as in FIG. 1 described.

As an alternative to throttling the fuel in the area of the fuel metering, the second system pressure can be generated using a pressure-limiting valve in the form of a check valve 50 in the area of the pressure booster unit ( FIG. 4 ). The check valve 50 opens at a pressure of about 300 bar. The pressure chamber 13 is filled with the aid of a fuel pump from a reservoir via the check valve 14 with fuel. Here, the pressure chamber 13 remains at a low stroke of the first returned and then moved in the direction of the bottom of the pressure chamber 13 pressure medium 17 connected to the check valve 50, so that the pressure in the pressure chamber 13 is limited to 300 bar to fuel this pressure the pressure chamber 20 and the control room 19 zuzuleiten. The check valve 14 prevents the return of compressed fuel in the direction of the fuel pump second

With a larger stroke of the pressure medium 17 as a result of the pressurization of the pressure medium 17 with a fluid from the accumulator chamber 6 is the access of the pressure chamber 13 to Leakage line 49 closed, so that a higher injection pressure is achieved. In the Main injection can thus perform a so-called "boot injection", as well as a Pre-injection at low pressure.

In a modification of the preceding embodiments, a pressure-controlled fuel injection device 51 is shown in FIG . Again, a high-pressure pump 52 delivers fuel 53 from a reservoir 54 via a feed line 55 into a pressure storage chamber 56 storing the fuel 53 at a pressure of 300 to 800 bar, which is connected to individual injectors 58 via individual pressure lines 57. Starting from the pressure storage chamber 56, the injection pressure of each injector 58 is generated by a pressure transmission unit 59 arranged within each injector 58. By means of a valve unit 60 (3/2-way valve), the injection pressure controlled realized. A valve member 61 may move away from the valve seat surface 63 of the injector housing against the closing force of a compression spring 62 when a nozzle space 64 is filled with pressurized fuel. In the de-energized state of the valve unit 60, the pressure booster unit 59 is connected to a leakage line 66. A pressure chamber 67 can be filled via a check valve 68.

By a continuous cross-sectional control of the valve 60 may (as in Fig. 1) a Injection molding can be realized. When using multi-stage valves can also by different throttle positions different injection pressure levels be achieved. As actuators here also piezo plate or magnetic actuators are conceivable.

In FIG. 6 , the pressure booster unit 59 and the valve unit 60 are located outside the injector 58 in the region of the pressure storage chamber 56 in the case of a pressure-controlled fuel injection device 51.

In the exemplary embodiment of a pressure-controlled fuel injection device 71 according to FIG. 7 , the pressure generation and amplification of the fuel 74 supplied from a reservoir are realized with engine oil as the pressure fluid 72. The pressure booster unit 73 acts as a coupling element between the fuel supply and the pressure fluid supply. A second system pressure is achieved by throttling within a valve cross-section of a valve unit 75 (see also the description of FIGS. 1 to 6).

FIG. 8 shows a pressure-controlled fuel injection device 81 with a use of a pressure limitation of the fuel compressed in the pressure chamber 82 (see also the analog stroke-controlled variant of FIG. 4). With a slight stroke of the pressure medium 83, the pressure in the pressure chamber 82 of the pressure booster 84 is limited to about 300 bar, because the pressure chamber 82 is connected via a check valve with a leakage line 87. Upon further movement of the pressure medium 83 in the direction of arrow 85, this pressure limiting path closes and the full injection pressure is generated.

This allows a low pressure pilot injection by a separate actuation a valve unit 86. In a main injection can also be a boot injection produce. The valve unit 86 can by magnetic actuators (in throttling in the range of Valve seat surface must be formed a path control of the solenoid valve) directly or hydraulically supported or controlled (control piston and control chamber). Also by the use of a piezo actuator, an injection course forming (Bootinjektion) are realized in the main injection. This also applies to all Embodiments of the invention.

Fig. 9 relates to a pressure-controlled fuel injector 91 with an injection nozzle modified from those shown so far. Again, via a fuel pump, fuel or alternatively engine oil is conveyed into a pressure storage space at a pressure of about 300 to about 800 bar. Starting from this pressure storage space, the injection pressure is generated locally for each cylinder via a pressure booster unit. With engine oil as fuel, the pressure booster unit also acts as a coupler. About a 3/2-way valve 92 with a cross-sectional control or a piezoelectric actuator, the injection pressure controlled realized. In the de-energized state, the low pressure side of the pressure booster unit is on leak oil and can be filled via a check valve 93. By means of a throttling in the valve seat of the valve 92, a second injection pressure can be formed. Instead of the blind hole or seat hole nozzles already shown in the preceding figures, a Vario or Vario register nozzle is used. The available opening cross-section of the nozzle holes is variable. The course of injection can be better adapted to the requirements of the engine. With a Vario register nozzle, several nozzle rows can be opened step by step. The control for the hydraulic stroke stop 94 of the nozzle can take place simultaneously both within the injector 95 and centrally for all injectors.

In addition to the embodiments shown, the use of a Alternative piston similar to a pump-nozzle unit (PDE) conceivable.

Claims (8)

1. Method for carrying out fuel injection by means of a high-pressure pump (2; 52) and a pressure reservoir area (6; 56) for production and storage of a first system pressure, in which this system pressure is not used for injection, but a higher injection pressure is produced by means of a pressure step-up unit (9; 59; 73; 84) during the injection process, characterized in that the injection pressure is reduced in order to shape the injection profile, and the shaping of the injection pressure being produced by means of a controllable valve cross section of a value unit (10; 60; 75; 86; 92) which controls the pressure step-up unit.
2. Method according to Claim 1, characterized in that the pressure step-up unit (9; 59; 73; 84) is arranged at any desired point between the pressure reservoir area (6; 56) and a nozzle area (20; 64) of an injector (8; 58).
3. Method according to Claim 2, characterized in that the pressure step-up unit (9; 59; 73; 84) is integrated in the injector (8; 58; 95).
4. Method according to Claim 2, characterized in that the pressure step-up unit (9; 59; 73; 84) is arranged on the pressure reservoir area (6; 56), or is integrated in the pressure reservoir area (6; 56).
5. Method according to one of the preceding claims, characterized in that a medium which is not the same as the fuel, preferably an engine oil, is used as the pressure fluid (43; 72) for operation of the pressure step-up unit (9; 73).
6. Method according to one of the preceding claims, characterized in that the fuel injection is carried out on a travel-controlled basis.
7. Method according to one of Claims 1 to 6, characterized in that the fuel injection is carried out on a pressure-controlled basis.
8. Apparatus for fuel injection, in order to carry out the method according to one of the preceding claims, having a high-pressure pump and a pressure reservoir area for production and storage of a first system pressure, having a pressure step-up unit (9; 59; 73; 84) by means of which a higher injection pressure can be produced during the injection process and the injection pressure can be reduced in order to form the injection profile, and having a valve unit (10; 60; 75; 86; 92) for controlling the pressure step-up unit, in which the injection pressure is shaped by means of a controllable valve cross section of a valve unit.

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