EP1593838A1 - Control method for influencing the opening velocity of a control valve of a fuel injector - Google Patents

Abstract

A fuel injector (FI) (3) has a control valve (CV) (27) for activating/deactivating the FI's pressure intensifier (5). The CV is designed as a directly controlled magnetic valve with its magnetic coil (38) fed by two or more triggering current levels different from each other so as to vary the opening speed of the CV's valve element (30). An independent claim is also included for a fuel injection device for triggering a fuel injector.

Description

Technical area

For supplying combustion chambers of self-igniting internal combustion engines with fuel, Both pressure-controlled and stroke-controlled injection systems can be used become. As fuel injection systems come next pump-nozzle units, pump-line-nozzle units also storage injection systems (common rail) are used. accumulator injection allow in an advantageous manner, the injection pressure to load and Adjust the speed of the internal combustion engine. To achieve high specific Achievements and to reduce the emissions of the internal combustion engine is general a high injection pressure required.

State of the art

DE 101 23 910.6 relates to a fuel injection device. This is at a Internal combustion engine used. The combustion chambers of the internal combustion engine are supplied with fuel via fuel injectors. The fuel injectors are acted upon by a high pressure source, further comprising the fuel injection according to DE 101 23 910.6 known solution a pressure booster, a movable Pressure booster piston having a connectable to the high pressure source Separates space from a high-pressure space connected to the fuel injector. Of the High-pressure fuel chamber can be filled by filling a backspace (differential pressure chamber) the pressure booster with fuel or by emptying this pressure chamber of fuel vary.

The fuel injector includes a movable closing piston for opening or closing the injection ports facing the combustion chamber. The closing piston protrudes a closing pressure space, so that it can be acted upon by fuel pressure. Thereby a force acting on the closing piston in the closing direction is achieved. Of the Closing pressure room and another room are shared by a working room formed, with all parts of the working space permanently for the exchange of Fuel are interconnected.

With the solution known from DE 101 23 910.6 can by controlling the pressure booster be achieved via the rear space that the drive losses in the high-pressure fuel system in comparison to a control over a temporary with the high-pressure fuel source connected work space can be kept small. Furthermore, the High-pressure chamber only up to the pressure level of the high-pressure reservoir (common rail) relieved and not up to its leakage pressure level. This improves the one hand the hydraulic efficiency, on the other hand, a faster pressure reduction to system pressure level (Pressure level in the high-pressure reservoir), so that the between the Injection phases lying temporal distances can be significantly shortened.

DE 102 29 418 relates to a fuel injection device for injecting Fuel in the combustion chambers of an internal combustion engine. The fuel injector includes a high-pressure accumulator, a pressure booster and a metering valve. The pressure intensifier comprises a working space and a control room, which are separated from each other are separated by an axially movable piston. A pressure change in the control room the pressure booster results in a pressure change in a compression chamber, the acted on a fuel inlet a nozzle chamber. The nozzle space surrounds an injection valve member, which may be formed, for example, as a nozzle needle. A the injection valve member acting nozzle spring chamber is on the high pressure side via an inlet throttle point containing line from the compression chamber of the pressure booster from fillable. On the outlet side, the nozzle spring chamber is contained via an outlet throttle point Line connected to a room of the pressure booster.

DE 102 29 415 relates to a device for Nadelhubdämpfung on pressure-controlled Fuel injectors. The device for injecting fuel comprises a A fuel injector operating at high pressure fuel high pressure fuel can be acted upon and actuated via a metering valve. The injection valve is a is associated with these independently movable damping element, which is a Damping space limited. The damping element has at least one overflow channel for connecting the damping chamber with another hydraulic space.

Finally, from R. 306018 [official file number still to learn] one Switching valve with pressure compensation for a fuel injector with pressure booster known. According to this solution, the fuel injector comprises a pressure booster, which is provided by a Pressure source is supplied with high pressure fuel. A workroom of the pressure booster is from a differential pressure chamber of the pressure booster via a Amplifier piston separated. The pressure relief and the pressurization of the differential pressure chamber (Backspace) of the pressure booster via a switching valve. This Switching valve is connected to the differential pressure chamber (backspace) of the pressure booster via a Control line connected. A pressure chamber on an injection valve is via a pressure chamber supply line connected to a compression space of the pressure booster. The switching valve is designed as a direct switching 3/2-way valve whose valve needle pressure is balanced is and has both a sealing seat and a slide seal.

A disadvantage of the above outlined embodiments according to the prior art with only a valve, is the lack of flexibility of the injection pressure curve (rate-shaping) Such fuel injectors, compared to fuel injectors, the two independent Have actuators.

Presentation of the invention

According to the present invention, in view of the above-outlined technical problem Control method proposed, which by different opening speeds the control valve is a shaping of the injection pressure curve of fuel injectors allowed. The opening speeds of the control valve are according to the invention proposed control method, by the activation current level of Solenoid valve influenced. This allows the injection rate, i. the over time in the Combustion chamber of the self-igniting internal combustion engine injected fuel quantity, targeted influence. This allows the adjustment of the injection rate over that of the internal combustion engine assigned control unit. The adjustment of the injection rate over the Internal combustion engine associated engine control unit, allowed in an advantageous manner the injection quantity to the respective operating conditions of the self-igniting internal combustion engine adapt.

Following the invention proposed driving method is achieved that the Control of the fuel injector used a direct 3/2-way valve as a control valve can be slowed down, the opening movement of a damping unit. Due to differently selected activation current levels of a solenoid valve, the Opening speeds are affected. Be the control edges of the 3/2 way valve designed accordingly, so can be with different opening speeds of the control valve, a shaping of the injection pressure, i. to reach that pressure which prevails at the combustion chamber end of the Einspritzvenilgliedes.

Further, since only one control valve for the fuel injector is used, increases the production engineering effort for the production and assembly of the invention proposed driving method operated fuel injector not. Also remains the cost of a modification of the in an internal combustion engine used control unit low, as per on the internal combustion engine used fuel injector only one amplifier is needed.

drawing

Reference to the drawings, the invention will be described below in more detail.

It shows:

FIG. 1

the hydraulic circuit diagram of a fuel injector, with the According to the invention proposed driving method is operable,

FIG. 2

that adjustable current level at a solenoid valve to achieve different opening speeds,

FIG. 3

the stroke course of a valve member of a control valve,

FIG. 4

the pressure level of an injection valve member which adjusts at the combustion chamber end,

FIG. 5

the stroke course of the injection valve member of the fuel injector according to FIG. 1

variants

The illustration according to Figure 1, a fuel injector can be removed, which over the invention proposed driving method of this actuating control valve is operable.

The illustration according to Figure 1 is a pressure accumulator 1 (common rail) refer to the is connected via a high-pressure line 2 with a fuel injector 3. The fuel injector 3 comprises a preferably multi-part designed to facilitate assembly Injector 4, in which a pressure booster 5 is received. The pressure amplifier 5 comprises a constantly connected to the pressure accumulator 1 working space 8, a compression chamber 12 and a differential pressure chamber 9 (backspace), about which the pressure intensifier is activated or deactivated.

In the pressure booster 5 is a first piston part 6, which via a return spring 7 is acted upon, which the first piston part 6 of the booster 5 in its rest position resets. The return spring 7 is supported on a in the working space 8 of the booster 5 recorded annular stop 10 from. The pressure booster 5 includes above In addition, a second piston part 13, the end face 14 of the compression space 12th pressurized. From the differential pressure chamber 9 (back space) of the pressure booster 5, extends overflow line 15, in which a first throttle point 16 is formed. The overflow line 15 opens into a pressure chamber 17th

In the pressure chamber 17, a damping piston 19 is received, which passes through a bore 20, in which a second throttle 21 is formed. The damping piston 19 is over a spring 22 acted on a wall of the pressure chamber 17 and an annular Stop the damping piston 19 is supported. The damping piston 19 has a in the embodiment shown in Figure 1 on a rounded end face, which on a upper end face of a one-piece injection valve member 18 acts here.

The injection valve member 18 is in the region of a nozzle chamber 24 with a pressure stage 25 Mistake. The nozzle chamber 24 is via a nozzle chamber inlet 23 with the compression space 12 of the booster 5 is connected. According to the pressure transmission ratio the pressure booster 5, which depends on its design, flows in the compression space 12 compressed fuel when pressure booster is activated of the differential pressure chamber 9 via the nozzle chamber inlet 23 into the nozzle chamber 24th one and from there, along the Einspritzvenilgliedes, 18 injection openings 26 the combustion chamber side End of the fuel injector 3 to.

The differential pressure chamber 9 (back space) of the pressure booster 5 is above the control line 11 with a first hydraulic chamber 28 of a control valve 27 in conjunction. The Control valve 27 is preferably designed as a directly controlled 3/2 way valve. The Control valve 27 includes, in addition to the first hydraulic chamber 28, a second hydraulic Room 29, which is attributed to the low-pressure area. The control valve 27 comprises In addition, a valve member 30. In multi-part housing of the control valve 27 are a first control edge 31 in the region of a flat seat 33 and a second Control edge 32, which on a housing part of the multi-part housing of the control valve 27 is formed. From the second hydraulic chamber 29 of the control valve 27th branch both a first return 34, and a second return 36 in the low pressure region of the fuel injection system. The second hydraulic chamber 29 is in the Closed position of the valve member 30, due to the then closed flat seat 33 from first hydraulic space 28 separated. The valve member 30 of the control valve 27 comprises a piston extension 35, the closed position of the flat seat 33 shown in FIG is located in the second hydraulic chamber 29 of the control valve 27.

On the vertically movable valve member 30 of the control valve 27, is located a ring-shaped magnet armature plate 37, which is a power supply solenoid 38th opposite. The valve member 30 is acted upon in the closing direction by a closing spring 39, so that it is ensured that in the non-energized state of the magnetic coil 38 of the Control valve 27 of the flat seat 33 to the second low-pressure side hydraulic chamber 29th closed is.

At the end face opposite the second hydraulic chamber 29 of the valve member 30, is a hydraulic damper 40. The hydraulic damper 40 is of a through hole 41 passed through and biased by a spring element 42. The Spring element 42 is located within a damper chamber 43. Controlled fuel volume is from this via the third throttle point 44 in the low pressure region of the Fuel injection system dissipated. The hydraulic damper 40 and the valve member 30 lie along a contact surface 45 in the switching state of the control valve shown in Figure 1 27 to each other, however, represent two separate components.

In the deactivated state of rest of the booster 5, the control valve 27 is due to the Effect of the closing spring 39 is closed. Thus, the first control edge 31 is below the Flat seat 33 on the valve member 30 is closed. Thus, the control line 11 is closed, so that in the differential pressure chamber 9 (back space) of the pressure booster 5, the same pressure level as in the pressure accumulator 1 (common rail) connected working space 8 prevails. The pressure booster 5 is deactivated because pressure is balanced and there is no pressure boost instead of. About the closed flat seat 33, the control line 11 from the first Return 34 and from the second return 36 in the low pressure region of the fuel injection system separated.

To control the pressure booster 5, the differential pressure chamber 9 (back space) depressurized. For this, the control valve 27 is activated, i. open. There is a Energizing the solenoid 38, so that the armature 37 against the action of Closing spring 39 is tightened, whereby the flat seat 33 at the first control edge 31 of the Control valve 27 is opened. Via the control line 11 flows from the differential pressure chamber. 9 (Back space) flowing fuel into the first hydraulic chamber 28 and over the opened first control edge 31, the first return 34 and the second return 36th on the low pressure side of the fuel injection system too. This results in a decoupling of the differential pressure chamber 9 (back space) of the pressure booster 5 from the pressure accumulator. 1 (Common Rail) and its pressure relief in the returns 34, 36 in the low pressure range. By now in the compression chamber 12 retracting second piston part 13th of the pressure booster, there increases the pressure according to the transmission ratio the pressure booster 5 and flows through the nozzle chamber inlet 23, the nozzle chamber 24th to. At the in the region of the nozzle chamber 24 on integrally formed injection valve member trained pressure levels 25 encompassing hydraulic force, opens the injection valve member 18 and 16, the injection openings 26 at the combustion chamber end of the fuel injector 3 free, so that about this fuel, in a combustion chamber, not shown in Figure 1 an internal combustion engine can be injected.

To complete the injection, the control valve 27 is again deactivated, i. closed. The valve member 30 moves upon completion of the flow of the solenoid 38 of the control valve 27 by the action of the closing spring 39 back in its closed position. In the closed position, the first control edge 31 is closed below the flat seat 33. This is done via the pressure accumulator 1 (common rail) extending High pressure line 2, the first hydraulic chamber 28 and the control line 11, a pressure build-up in the differential pressure chamber 9 (back space) of the pressure booster 5, so that this again in his rest position drives. During the closing movement of the valve member 30 of the control valve 27, the second control edge 32 of the control valve 27 is opened. Because of himself in the differential pressure chamber 9 (back space) of the pressure booster 5 building system pressure, i.e. the pressure level, which prevails in the pressure accumulator 1 (common rail), is the Pressure booster 5 deactivated. The second piston part 13 moves out of the compression space 12 off and due to the decreasing pressure in the nozzle chamber 24, the injection valve member 18 again placed in its the injection openings 26 closing position.

Above the movable in vertical direction when energizing the solenoid 38 valve member 30 is the hydraulic damper 40. This is a slow, approximately linear opening movement of the one-piece representation in FIG trained injection valve member 18 reached. When opening the valve member 30, i. at Energizing the solenoid 38, the hydraulic damper 40 performs the displaced amount via the third throttle point 44 in a not shown in Figure 1 low pressure range of the fuel injection system. Due to the hydraulic damper 40 is the Opening movement of the valve member 30, slowed down when energizing the solenoid 38.

The closing movement of the valve member 30 of the control valve 27, however, is controlled by the hydraulic damper 40 is not affected. This is achieved by the fact that Closing the valve member 30, i. the cancellation of the energization of the solenoid 38 due to the action of the closing spring 39, a rapid closing movement of the valve member 30, during which the hydraulic damper 40 a contact surface 45th separates from the valve member 30. This allows the valve member 30 unhindered in its closed position method, wherein a rapid filling of the damper chamber 43 via the through hole 41 of the hydraulic damper 40 takes place. This means that the hydraulic Damper 40 is very quickly reset to its original position. This is at high Speeds of self-igniting internal combustion engine, in terms of close to each other following injections of high importance.

The opening speed of the valve member 30 of the control valve, via the dimensioning the third throttle body 44, which is assigned to the damper chamber 43, set become. The opening speed of the valve member 30, which adjusts itself Furthermore, dependent on the magnetic force, which in the energization of the solenoid 38 of the Control valve 27 is reached. The magnetic force of the solenoid 38 of the control valve 27th can be adjusted by its current level.

At a lower current level of the solenoid 38 results in a slower Opening the control valve 27, i. a slower opening of the valve member 30. This can be a delayed, gradually occurring pressure build-up at the beginning of an injection phase reach, resulting in a substantially ramp-shaped course of the injection rate established.

If, however, the solenoid 38 of the control valve 27 with a second higher activation current energized, there is a quick opening of the control valve 27. This can be Achieve a faster pressure build-up at the beginning of each injection, resulting in a resulting in rectangular injection rate.

Figure 2 are different Bestromungsmöglichkeiten of the control valve for actuating the Remove fuel injector.

According to Figure 2, the Bestromungsverlauf 50 of the magnetic coil 38 over the time [t] is plotted. At a drive time 53, the energization of the solenoid 38, either with the first Ansteuerstromniveau 51 or the second - dashed lines - Ansteuerstromniveau 52 done.

FIG. 3 shows the stroke characteristics of the flow rate corresponding to the power level Removable control valve.

If the valve member 30 of the control valve 27 is driven with the first drive current level 51, i.e. If the magnetic coil 38 is energized with a lower current level results a slower opening of the valve member 30 of the control valve 27. It turns a first ramp 63 with a lower pitch gradient.

FIG. 4 shows adjusting pressure profiles at the injection valve member.

If the magnetic coil 38 with the first Ansteuerstromniveau 51 shown in Figure 2 energized and adjusts the first stroke profile 61 shown in Figure 3, it follows on Injection valve member, a first pressure curve 71st

In Figure 5 Hubverläufe the injection valve member are shown.

FIG. 5 shows the first drive current level 51 of the magnet coil 38 of the control valve 27 corresponding first stroke profile 81 of the integrally formed injection valve member 18th

FIG. 2 also shows the current flow path 50 of the magnet coil 38 when a second drive current level 52 - dashed line - is set.

In this case, according to FIG. 3, a second stroke profile 62 arises, which is interrupted by a second stroke profile 62 Ramp 64 is characterized by a significantly higher slope compared to the first ramp 63 at the first driving current level 61 of the magnetic coil 38 is different. Because of this, according to FIG. 4, the second pressure curve 72 is established at the injection nozzle which results in an approximately rectangular injection rate.

FIG. 5 also shows that when the magnet coil 38 is energized with the second drive current level 52 adjusting second stroke 82, which is only slightly from the first Stroke course 81, apart from a stronger rise at the beginning, differs.

In addition to the differing Ansteuerstromniveaus 51 and 52, with the solenoid 38 of the control valve 27 can be energized, the opening speed of the valve member 30 are also set via the third throttle point 44. The Slowing the opening speed is also due to the hydraulic damper 40 reaches, which is housed in the upper region of the control valve 27, the closing of the However, injector member 18 is not affected due to the separation from the valve member 30.

The injection form shown in Figures 3 to 5 with respect to the invention proposed driving method of a control valve 27 achievable injection rates, let about the self-igniting internal combustion engine respectively assigned Control unit also vary and within corresponding maps in each case optimal Adapt the way to the requirements of the internal combustion engine.

LIST OF REFERENCE NUMBERS

1

Accumulator (common rail)

2

High-pressure line

3

fuel injector

4

injector

5

booster

6

First piston part

7

Return spring

8th

working space

9

Differential pressure chamber

10

attack

11

control line

12

compression chamber

13

second piston part

14

face

15

overflow

16

first throttle point

17

pressure chamber

18

Injection valve member

19

damping piston

20

drilling

21

second throttle point

22

feather

23

Nozzle chamber inlet

24

nozzle chamber

25

pressure stage

26

Injection ports

27

Control valve (3/2)

28

first hydraulic room

29

second hydraulic chamber (low pressure)

30

valve member

31

first control edge

32

second control edge

33

flat seat

34

first return (ND)

35

Piston extension

36

second return (ND)

37

armature

38

solenoid

39

closing spring

40

hydraulic damper

41

Through Hole

42

feather

43

damper space

44

third throttle point

45

Support surface (separation point)

50

Current flow magnetic coil

51

first drive current level

52

second drive current level

53

control time

60

Hub control valve

61

first stroke course

62

second stroke course

63

first ramp

64

second ramp

70

Nozzle pressure curve

71

first pressure gradient

72

second pressure curve

80

Stroke course injection valve member

81

first stroke course

82

second stroke course

Claims (13)

Method for controlling a fuel injector (3) for injecting fuel into combustion chambers of an internal combustion engine, wherein the fuel injector (3) has a pressure booster (5) which is connected to a pressure accumulator (1) (common rail) for supplying fuel under high pressure is connected, which via a control valve (27) is activated or deactivated, which is executed directly switching, characterized in that the opening speed of a valve member (30) of the control valve (27) for forming an injection pressure curve (7) is varied. A method according to claim 1, characterized in that the opening speed of the valve member (30) by at least two mutually different Ansteuerstromniveaus (51, 52) of the magnetic coil (38) is varied. A method according to claim 1, characterized in that the opening speed of the valve member (30) of the control valve (27) by a valve member (30) associated with hydraulic damper action is slowed down. A method according to claim 3, characterized in that during the opening of the valve member (30) a displaced amount via a third throttle point (44) is discharged. A method according to claim 1, characterized in that when closing the valve member (30) of the control valve (27), the hydraulic damper (40) and the valve member (30) along a contact surface (45) from each other. A method according to claim 5, characterized in that when closing the valve member (30) of the control valve (27) a damper chamber (43) via a in the hydraulic damper (40) formed through bore (41) is filled. A method according to claim 2, characterized in that at a first Ansteuerstromniveau (51) of the solenoid (38) of the control valve (27) a slow opening of the valve member (30) and a delayed pressure build-up at the beginning of the fuel injection, and thus a first ramped injection rate (63, 71). A method according to claim 2, characterized in that upon energization of the solenoid coil (38) with a second Ansteuerstromniveau (52) adjusts a rapid opening of the valve member (30) and a rapid pressure build-up at the beginning of the injection and a rectangular injection rate (64, 72 ). A method according to claim 1, characterized in that the control of the pressure booster (5) and the injection valve member (18) by the control valve (27), wherein the pressure booster (5) by the pressure relief or pressurization of its differential pressure chamber (9) is activated or deactivated and the working space (8) of the pressure intensifier (5) is permanently connected to the pressure accumulator (1). Fuel injection device for controlling a fuel injector (3) according to one or more of the claims 1 to 7, characterized in that the control valve (27) has a hydraulic damper (40) associated with the injection valve member (30), the through-bore (41) of which passes over one Throttle (44) dischargeable control chamber (43) opens. Fuel injection device according to claim 10, characterized in that the valve member (30) of the control valve (27) via a closing spring (39) is acted upon in the closing direction. Fuel injection device according to claim 10, characterized in that the hydraulic damper (40) via a spring (42) to the valve member (30) is employed. Fuel injection device according to claim 10, characterized in that on the valve member (30) of the control valve (27) below the magnetic coil (38) has a magnet armature plate (37) is formed and the valve member (30) has a seat (33) for closing a second hydraulic chamber ( 29) having seat (33).

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