EP1078160B1 - Fuel injection system - Google Patents

Description

State of the art

The invention relates to a fuel injection device according to the preamble of claim 1

For a better understanding of the description and the claims, some terms are explained below: The fuel injection device according to the invention may be formed both stroke-controlled and pressure-controlled. In the context of the invention, a stroke-controlled fuel injection device is understood to mean that the opening and closing of the injection opening takes place by means of a displaceable valve member due to the hydraulic interaction of the fuel pressures in a nozzle space and in a control space. 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 fuel injection device according to the invention, the pressure prevailing in the nozzle chamber of an injector fuel pressure, the valve member against the action of a closing force (spring) is moved, so that the injection port for injection of the 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 OE 196 19 523 A1 known. The achievable injection pressure is here by the Pressure accumulator (rail) and the high pressure pump to about 1600 to 1800 bar limited.

To increase the injection pressure, a pressure booster unit is possible, as is known for example from US 5,143,291 or US 5,522,545. The disadvantage of these pressure-translated systems is 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 to increase the flexibility of the injection and the metering accuracy of Pre-injection two pressure accumulation chambers with different pressures intended. These two pressure storage rooms require a high Production costs and high production costs, with the maximum Injection pressure continues through the fuel pump and the accumulator chamber is limited.

According to the teaching of US 5,803,028 a consuming ausgestaltetes valve for Filling a pressure chamber of the pressure booster unit to be actuated. A constant filling of the pressure chamber with standing under rail pressure Fuel is not provided.

A pressure booster unit arranged in the injector is known from EP 0 691 471 A1 known. A bypass line for a pressure injection and a Pressure chamber of the pressure booster unit are in series, so that the bypass line is only continuous, as long as a sliding piston of the Pressure booster unit is not moved and completely retracted.

Advantages of the invention

To increase the flexibility and the maximum injection pressure is a Fuel injection device according to claim 1 proposed. Each injector one Common Rail Systems is assigned a hydraulic pressure booster unit, the both increasing the maximum injection pressure to high pressures, e.g. greater 1800 bar, as well as the provision of a second injection pressure allows. The bypass line leads to the supply line at the end of the pressure chamber of the pressure booster unit Nozzle space or in the supply line from the pressure booster unit to the nozzle chamber. A Injection of lower pressure fuel can be independent of the position of the Pressure medium of the pressure booster unit done. By the pressure booster unit are the accumulator chamber and the injector with a lower stand pressure (rail pressure) acted upon and thus have a longer life. Likewise, the High pressure pump less stressed. There is the possibility of a dosable Pre-injection with low tolerances due to low (untranslated) injection pressure. By switching between the injection pressures can be a flexible Post-injection or multiple post-injections at high or low Realize injection pressure.

drawing

Fign. 1 und 2 Fign. 5 und 6

hubgesteuerte Kraftstoffeinspritzeinrichtungen;

Fign. 3 und 4 Fig. 7

druckgesteuerte Kraftstoffeinspritzeinrichtungen;

Fig. 8 und 9

Beispiele möglicher schematischer Kraftstoffeinspritzdruckverläufe.

Seven examples of a fuel injection device, of which the according to the figures 5 and 6 according to the invention, are shown in the schematic drawing and are explained in the following description. Show it:

FIGS. 1 and 2 Figs. 5 and 6

stroke controlled fuel injectors;

FIGS. 3 and 4 Fig. 7

pressure controlled fuel injectors;

8 and 9

Examples of possible schematic fuel injection pressure curves.

Description of the embodiments

In the example shown in Fig. 1 first embodiment of a stroke-controlled fuel injection device 1 is a volume-controlled fuel pump 2 fuel 3 from a storage tank 4 via a feed line 5 in a central pressure reservoir 6 (common rail), from which a plurality of the number of individual cylinders corresponding pressure lines 7 to the individual, in the combustion chamber of the engine to be supplied protruding injectors 8 (injector) dissipate. In Fig. 1, only one of the injectors 8 is located. With the aid of the fuel pump 2, a first system pressure is generated and stored in the pressure storage chamber 6. This first system pressure is used for pre-injection and, if necessary and post-injection (HC enrichment for exhaust aftertreatment or soot reduction) and for displaying a course of injection with plateau (boat injection). For injecting fuel with a second higher system pressure, each injector 8 is assigned a respective local pressure booster unit 9, which is located within an injector 8. The pressure booster unit 9 comprises a valve unit for pressure transmission control (3/2-way valve) 10, a check valve 11 and a pressure means 12 in the form of a displaceable piston member. The pressure medium 12 can be connected at one end to the pressure line 7 with the aid of the valve unit 10, so that the pressure medium 12 can be pressurized at one end. A differential space 12 'is depressurized by means of a leakage line 13, so that the pressure medium 12 can be moved to reduce the volume of a pressure chamber 14. The pressure means 12 is moved in the compression direction, so that the fuel located in the pressure chamber 14 compressed and a control chamber 15 and a nozzle chamber 16 is supplied. The check valve 11 prevents the return of compressed fuel into the accumulator 6. By means of a suitable area ratio in a primary chamber 14 'and the pressure chamber 14, a second higher pressure can be generated. If the primary chamber 14 'connected by means of the valve unit 10 to the leakage line 13, the return of the pressure medium 12 and the refilling of the pressure chamber 14 takes place. Due to the pressure conditions in the pressure chamber 14 and the primary chamber 14' opens the check valve 11, so that the Pressure chamber 14 is under rail pressure (pressure of the pressure accumulator chamber 6) and the pressure fluid 12 is hydraulically returned to its initial position. To improve the restoring behavior, one or more springs in the spaces 12, 14 and 14 'may be arranged. By means of the pressure intensification, a second system pressure can thus be generated.

The injection takes place via a fuel metering with the help of one in one Guide bore axially displaceable piston-shaped valve member 18 with a conical Valve sealing surface 19 at one end, with which it has a valve seat surface on Injector housing of the injector 8 cooperates. At the valve seat surface of the Injector housing injection openings are provided. Within the nozzle chamber 16 is an in the opening direction of the valve member 18 facing pressure surface which prevails there Exposed to pressure which is supplied via a pressure line 20 to the nozzle chamber 16. Coaxial to a valve spring 21 also engages the valve member 18 to a pressure piece 22 which with its end facing away from the valve sealing surface 19 end face 23 delimits the control chamber 15. Of the Control chamber 15 has an inlet from the fuel pressure connection with a first throttle 24th and a drain to a pressure relief line 25 with a second throttle 26, the is controlled by a 2/2-way valve 27.

The nozzle chamber 16 is placed over an annular gap between the valve member 18 and the Guide bore continues to the valve seat surface of the injector. About the pressure in the Control chamber 15, the pressure member 22 is pressurized in the closing direction.

Under the first or second system pressure standing fuel constantly fills the Nozzle chamber 16 and the control chamber 15. When operating (opening) of the 2/2-way valve 27th the pressure in the control chamber 15 can be reduced, so that in the sequence in Opening direction on the valve member 18 acting pressure force in the nozzle chamber 16 in Closing direction on the valve member 18 acting pressure force exceeds. The valve sealing surface 19 lifts off the valve seat surface and fuel is injected. This can be the Pressure relief process of the control chamber 15 and thus the stroke control of the valve member 18 on the dimensioning of the throttle 24 and the throttle 26 influence.

The end of the injection is achieved by pressing (closing) the 2/2-way valve again Introduced 27, which decouples the control chamber 15 again from the leakage line 13, so that in the control chamber 15, a pressure builds up again, the pressure piece 22 in the closing direction can move.

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.

The fuel injection device 1 has the between the pressure accumulator chamber 6 and the Nozzle space 16 arranged pressure booster unit 9, whose pressure chamber 14 via the pressure line 20 is connected to the nozzle chamber 16, Furthermore, the to the Pressure accumulator 6 connected bypass line 28 is provided. The bypass line 28 is connected directly to the pressure line 20. The bypass line 28 is for a Injection with rail pressure usable and is arranged parallel to the pressure chamber 14, so that the bypass line 28 regardless of the movement and position of the displaceable Pressure medium 12 of the pressure booster unit 9 is continuous. The flexibility of Injection is increased.

Hereinafter, only differences in the description of Figures 2 to 9 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. This can be anywhere between accumulator chamber 6 and injector 8. The size of the injector 8 decreases. In this case, an integration of the pressure booster unit 9 with associated valve arrangement and the pressure storage chamber 6 in one component is possible. The valve arrangement can also be arranged outside the pressure booster unit 9.

A fuel injector 50 of FIG. 3 has a pressure accumulator 51 for fuel at a first system pressure. A higher system pressure is made possible by a pressure booster unit 52, which can be switched on by means of a valve unit 59. The pressure-controlled fuel metering takes place via a valve unit 55, for example a 3/2-way valve. A valve member 56 can be moved against the force of a valve spring 57 when the pressure applied to pressure surfaces 58 pressure exceeds the spring force of the valve spring 57. The 3/2-way valves 55 and 59 are located within an injector 60.

FIG. 4 shows a fuel injector 61 similar to FIG. 3, whose fuel metering 62 (3/2-way valve) and pressure-increasing drive 63 (3/2-way valve) are disposed outside the injector 64. In the fuel injector 61, it is also possible to arrange both valves separately from each other.

A simplified and loss-optimized control of a pressure booster unit 70 results from FIG. 5 . In order to control the pressure booster unit 70, the pressure in the differential space 71 formed by a transition from a larger to a smaller piston cross section is used. For refilling and deactivating the pressure booster unit, this differential space is acted upon by a supply pressure (rail pressure). Then prevail at all pressure surfaces of a piston 72, the same pressure conditions (rail pressure). The piston 72 is pressure balanced. By an additional spring 73, the piston 72 is pressed into its initial position. In order to activate the pressure booster unit 70, this differential space 71 is depressurized and the pressure booster unit generates a pressure boost according to the area ratio. By this type of control can be achieved that for resetting the pressure booster unit 70 and for refilling a pressure chamber 74, a large primary chamber 70 'does not have to be depressurized. With a small hydraulic ratio, the relaxation losses can be greatly reduced.

To control the pressure booster unit 70 may instead of a complex 3/2-way valve a throttle 75 and a simple 2/2-way valve 76 may be used. The Throttle 75 connects the differential chamber 71 with under supply pressure standing Fuel from a pressure accumulator 77. The 2/2-way valve closes the Difference space 71 to a leakage line 78 at. The throttle 75 should be as small as possible be designed, but still so large that the piston 72 between the injection cycles returns to its original position. As a throttle can also be a pilot leak of the Piston 72 can be used. With closed 2/2-way valve 76 is no Leakage in the guides of the piston 72, since the differential space 71 is pressurized. The throttle can also be integrated in the piston.

If the 2/2-way valves 76 and 79 are closed, the injector is under pressure of the accumulator 77. The pressure booster unit is located in the Starting position. Now can be done by the valve 79 an injection with rail pressure. If an injection with higher pressure is desired, the 2/2-way valve 76 triggered (opened) and thus achieved a pressure boost.

To control the pressure in the differential space, a 3/2-way valve can also be used. Fig. 6 shows the control via a 3/2-way valve in a stroke-controlled injection system. Fig. 7 shows the control via a 3/2-way valve in a pressure-controlled injection system.

For the stroke-controlled systems results in an injection pressure curve according to FIG. 8, starting from the idle state (pressure booster unit deactivated and in the starting position). By connecting the valve unit 27 and deactivated switching valve 10 of the pressure booster unit, a pre-injection with low (rail) pressure is initiated via the bypass at the beginning of the injection cycle. By closing valve 27 (see Fig. 1), the pilot injection is terminated. By multiple wiring and multiple pilot injections are possible. For the main injection, the upstream of the pressure booster unit valve unit 10 can be energized, so that there is a corresponding ratio in the injector increased pressure in the nozzle chamber and control chamber. By opening the valve 27 now a main injection is initiated (dash-dotted line). The completion of the main injection is then again by closing the 2/2-way valve 27. If the pressure booster unit is activated simultaneously with the valve 27, so there is an injection starting at the rail pressure level with a ramp rising edge to the translated pressure (in the Figure 8 not shown). If the connection of the pressure booster unit is further delayed, it is first injected with rail pressure and by connecting the pressure booster unit results in a boot-shaped injection curve when activating the pressure booster unit. The length of the high-pressure part depends on the activation time of the pressure booster unit. The main injection is terminated by closing the valve 27. If the pressure booster unit is deactivated prior to closing the valve 27, the result is a ramp-down of the injection pressure up to the rail pressure level, as is known from pressure-controlled systems. In the case of post-injection, it is possible to choose between a high and a low injection pressure level. Thus, at a close distance after the main injection, a post-injection with high pressure for reducing soot or a remote post-injection at low injection pressure for exhaust aftertreatment can take place.

For the pressure-controlled systems results in an injection pressure curve according to FIG. 9, starting from the idle state (pressure booster unit deactivated and in the starting position). By connecting the valve unit 55 and deactivated switching valve of the pressure booster unit, a pre-injection is initiated with low rail pressure via the bypass at the beginning of the injection cycle. By multiple wiring and multiple pilot injections are possible. The pressure increase in the nozzle chamber results in a ramp-shaped injection pressure curve in all subregions of the injection. For the main injection, the valve unit 59 arranged upstream of the pressure booster unit can be energized simultaneously with the valve 55, so that a ramp-shaped course of the injection pressure results up to the translated maximum pressure (dot-dashed line). The termination of the main injection is then again by closing the valve 55. If the connection of the pressure booster unit is delayed, it is first injected with rail pressure and by connecting the pressure booster unit results in a boat-shaped injection course. The length of the high-pressure part depends on the activation time of the pressure booster unit. The main injection is stopped by closing the valve 55, whereby the injection pressure decays in turn ramped by relieving the nozzle chamber to the leakage pressure level and the injection is terminated. In the case of post-injection, it is possible to choose between a high and a low injection pressure level. Thus, at a close distance after the main injection, a post-injection with high pressure for reducing soot or a remote post-injection at low injection pressure for exhaust aftertreatment can take place.

In addition to the aforementioned boot injections for both systems, it is conceivable through a suitable shape of the valve member (nozzle needle) and the shape of the nozzle space a to realize so-called rate-shaping-nozzle. This makes it possible in the low pressure part of the Boot injection or in all injections to realize another print plateau. As well it is again conceivable in the high pressure part of the injection (during operation of the Pressure booster unit) through relief holes on the piston of Pressure Translation unit to realize a further shaping of the injection curve.

LIST OF REFERENCE NUMBERS

1

Fuel injection system

2

Fuel pump

3

fuel

4

Fuel tank

5

delivery line

6

Pressure reservoir

7

pressure line

8th

injector

9

Pressure booster unit

10

valve unit

11

check valve

12

lever

12 '

differential chamber

13

leakage line

14

pressure chamber

14 '

primary chamber

15

control room

16

nozzle chamber

18

valve member

19

Valve sealing surface

20

pressure line

21

valve spring

22

Pressure piece

23

front

24

throttle

25

Pressure relief line

26

throttle

27

2/2 way valve

28

Bypass line

50

Fuel injection system

51

Pressure reservoir

52

Pressure booster unit

53

check valve

54

Bypass line

55

3/2-way valve

56

valve member

57

valve spring

58

print area

59

valve unit

60

injector

61

Fuel injection system

62

Valve unit for metering fuel

63

Valve unit for pressure intensification control

64

injector

70

Pressure booster unit

70 '

primary chamber

71

differential chamber

72

piston

73

feather

74

pressure chamber

75

throttle

76

2/2 way valve

77

Pressure reservoir

78

leakage line

79

2/2 way valve

Claims (6)

1. Fuel injection device (1; 50; 61) having a pressure intensification unit (9; 52; 70) which is arranged between a pressure storage space (6; 51; 77) and a nozzle space (16) and has a displaceable pressure medium (12) for dividing the pressure intensification unit (9; 52; 70) at one end into a pressure chamber (14; 37; 74) and at the other end into a primary chamber (14') and a differential space (12'), the pressure chamber (14; 74) being connected to the nozzle space (16) via a pressure line (20), and having a bypass line (28; 54) which is connected to the pressure storage space (6; 51; 77) and directly to the pressure line (20), characterized in that the pressure chamber (14; 74), the primary chamber (14') for receiving fuel for pressurizing the pressure medium (12) in the direction of the pressure chamber (14; 74) and the nozzle space (16) are connected in a continuously permeable manner to the pressure storage space (6; 51; 77) via a pressure line (7, 8), and in that a valve for connecting the differential space (12'), which is provided for receiving fuel for the pressurization or pressure release of the pressure medium (12), to a leakage line or to the pressure storage space (6; 51; 77) is provided.
2. Fuel injection device according to Claim 1, characterized in that the bypass line (28; 54) contains a nonreturn valve (11; 53).
3. Fuel injection device according to Claim 1 or 2, characterized in that the pressure intensification unit (9) is arranged within the injector (8).
4. Fuel injection device according to Claim 1 or 2, characterized in that the pressure intensification unit (9) is arranged outside the injector (8).
5. Fuel injection device according to one of the preceding claims, characterized in that the fuel injection device (50; 61) comprises means for the pressure-controlled injection of fuel.
6. Fuel injection device according to one of Claims 1 to 4, characterized in that the fuel injection device (1) comprises means for the stroke-controlled injection of fuel.

Images