EP1593838B1 - Control method for influencing the opening velocity of a control valve of a fuel injector - Google Patents

Description

To supply combustion chambers of self-igniting internal combustion engines with fuel, both pressure-controlled and stroke-controlled injection systems can be used. As fuel injection systems come next pump-nozzle units, pump-line-nozzle units and accumulator injection systems (common rail) are used. Storage injection systems advantageously make it possible to adapt the injection pressure to the load and speed of the internal combustion engine. In order to achieve high specific performance and to reduce the emissions of the internal combustion engine, a high injection pressure is generally required.

State of the art

One out WO 02/092997 A1 known fuel injection device is used on an internal combustion engine. 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. The out WO 02/092997 A1 known fuel injector has a pressure booster with a movable pressure booster piston, which separates a connectable to the high pressure source space from a high-pressure chamber connected to the fuel injector. The high-pressure fuel chamber can be varied by filling a back space (differential pressure chamber) of the pressure booster with fuel or by emptying this pressure chamber of fuel. For this purpose, a control valve is used with a movable valve member. The valve member is actuated by a piezoactuator, which acts by means of a transmission piston on the valve member. Between the piezoelectric actuator and transmission piston, a hydraulic coupler space is arranged.

The fuel injector comprises a movable closing piston for opening or closing the injection openings facing the combustion chamber. The closing piston protrudes into a closing pressure chamber, so that it can be acted upon by fuel pressure. This achieves a force acting on the closing piston in the closing direction. The closing pressure room and another room are formed by a common working space, wherein all portions of the working space are permanently interconnected to exchange fuel.

With the out WO 02/092997 A1 known solution is achieved by controlling the pressure booster on the back space (differential pressure chamber) by means of the control valve that the drive losses in the high-pressure fuel system compared to a control via a temporarily connected to the high-pressure fuel source working space can be kept small. Furthermore, the high-pressure chamber is only relieved to the pressure level of the high-pressure accumulator chamber (common rail) and not up to its level of leakage pressure. On the one hand this improves the hydraulic efficiency, on the other hand, a faster pressure reduction can take place up to system pressure level (pressure level in the high-pressure reservoir), so that the time intervals between the injection phases can be considerably shortened.

With the out WO 02/092997 A1 known solution is also provided that the piezoelectric actuator is electrically controlled so that the valve member passes quickly from the rest position to the end position, with slow valve actuation, the voltage applied to the piezoelectric actuator voltage is slowly increased, so that the valve member at low speed off the rest position reaches the end position.

Out US Pat. No. 6,286,483 B1 a fuel injector with a pressure booster or a pressure booster, with a control valve and with a delay element for the control valve is known. The delay element has a damping piston and is arranged between the control valve and the pressure booster. The control valve and the delay element are arranged separately from each other and connected by means of a hydraulic connection. By means of the delay element, the opening speed of the control valve is varied, wherein the control valve both the pressure booster and a control chamber of a nozzle needle is driven so that so that a delay between pre-injection and main injection can be generated.

DE 102 29 418 A1 refers to a fuel injector for injecting fuel into 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 booster comprises a working space and a control space, which are separated from each other by an axially movable piston. A pressure change in the control chamber of the pressure booster results in a pressure change in a compression space, which acts on a fuel inlet via a nozzle chamber. The nozzle chamber surrounds an injection valve member, which may be formed, for example, as a nozzle needle. A nozzle spring chamber which acts on the injection valve member can be filled from the compression space of the pressure booster via a line containing an inlet throttle point. On the outlet side, the nozzle spring chamber is connected to a space of the pressure booster via a line which contains an outlet throttle point.

DE 102 29 415 A1 refers to a device for Nadelhubdämpfung pressure-controlled fuel injectors. The device for injecting fuel comprises a fuel injector, which can be acted upon by a high-pressure source with high-pressure fuel and actuated via a metering valve. The injection valve is associated with one of these independently movable damping element which limits a damping chamber. The damping element has at least one overflow channel for connecting the damping chamber with a further hydraulic space.

Finally, out of the German patent application DE 103 34 771 A1 a pressure compensated switching valve for a fuel injector with pressure booster known. According to this solution, the fuel injector comprises a pressure booster, which is supplied by a pressure source with high-pressure fuel. A working space of the pressure booster is separated from a differential pressure chamber of the pressure booster via a booster piston.

The pressure relief and the pressurization of the differential pressure chamber (back space) of the pressure booster via a switching valve. This switching valve is connected to the differential pressure chamber (back space) of the pressure booster via a control line. A pressure chamber on an injection valve is connected via a pressure space supply line to a compression space of the pressure intensifier. The switching valve is designed as a direct switching 3/2-way valve, whose valve needle pressure is balanced and has both a sealing seat and a slide seal.

A disadvantage of the above-outlined embodiments according to the prior art with only one valve, is the lack of flexibility of the injection pressure curve (rateshaping) of such fuel injectors, compared to fuel injectors having two independent actuators.

Presentation of the invention

With the fuel injector according to the invention it is achieved that for controlling the fuel injector, a direct 3/2-way valve can be used as a control valve, whose opening movement is slowed down via the damping unit.

By varying the activation current levels of a solenoid valve, the opening speeds can be influenced. Be the control edges of the 3/2 way valve designed accordingly, it can be achieved with different opening speeds of the control valve, a shaping of the injection pressure, ie that pressure which prevails at the combustion chamber end of the Einspritzvenilgliedes.

Furthermore, since only one control valve is used for the fuel injector, the manufacturing expense for the production and assembly of the operated according to the invention proposed driving method fuel injector does not increase. Likewise, the effort with regard to a modification of the control unit used in an internal combustion engine remains low since only one final stage is required per fuel injector used on the internal combustion engine.

drawing

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

Figur 1

das hydraulische Schaltschema eines Kraftstoffinjektors, der mit dem erfindungsgemäß vorgeschlagenen hydraulischen Dämpfer betreibbar ist,

Figur 2

dass an einem Magnetventil einstellbare Stromniveau zur Erzielung unterschiedlicher Öffnungsgeschwindigkeiten,

Figur 3

den Hubverlauf eines Ventilgliedes eines Steuerventils,

Figur 4

das sich am brennraumseitigen Ende einstellenden Druckniveau eines Einspritzventilgliedes,

Figur 5

den Hubverlauf des Einspritzventilgliedes des Kraftstoffinjektors gemäß Figur 1.

It shows:

FIG. 1

the hydraulic circuit diagram of a fuel injector, which is operable with the hydraulic damper proposed according to the invention,

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 representation according to FIG. 1 is a fuel injector removable, which can be actuated via the proposed driving method of a control valve actuating this.

The representation according to FIG. 1 is a pressure accumulator 1 (common rail) refer, which is connected via a high pressure line 2 to a fuel injector 3. The fuel injector 3 comprises an injector housing 4 preferably designed in several parts to facilitate assembly, in which a pressure booster 5 is accommodated. The pressure booster 5 comprises a working chamber 8, which is permanently connected to the pressure accumulator 1, a compression chamber 12 and a differential pressure chamber 9 (rear chamber), via which the pressure booster is activated or deactivated.

In the pressure booster 5 is a first piston part 6, which is acted upon by a return spring 7, which resets the first piston part 6 of the booster 5 in its rest position. The return spring 7 is supported on a received in the working space 8 of the booster 5 annular stop 10. The pressure booster 5 further comprises a second piston part 13, whose end face 14 pressurizes the compression space 12. From the differential pressure chamber 9 (back space) of the pressure booster 5, an overflow line 15, in which a first throttle point 16 is formed, extends. 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 body 21 is formed. The damping piston 19 is acted upon by a spring 22 which is supported on a wall of the pressure chamber 17 and on an annular stop of the damping piston 19. The damping piston 19 has a in the in FIG. 1 illustrated embodiment, a rounded end face, which acts on an upper end face of a one-piece injection valve member 18 here.

The injection valve member 18 is provided in the region of a nozzle chamber 24 with a pressure stage 25. The nozzle chamber 24 is connected via a nozzle chamber inlet 23 with the compression chamber 12 of the booster 5. According to the pressure transmission ratio of the booster 5, which depends on its interpretation, compressed fuel flows in the compression chamber 12 upon actuation of the booster by pressure relief of the differential pressure chamber 9 via the nozzle chamber inlet 23 into the nozzle chamber 24 and from there, along the Einspritzvenilgliedes, 18 injection ports 26 the the combustion chamber end of the fuel injector 3 to.

The differential pressure chamber 9 (back space) of the pressure booster 5 is connected via the control line 11 with a first hydraulic chamber 28 of a control valve 27 in connection. The control valve 27 is preferably designed as a directly controlled 3/2 way valve. The control valve 27 comprises, in addition to the first hydraulic chamber 28, a second hydraulic chamber 29, which is attributable to the low-pressure region. The control valve 27 further includes a valve member 30. In the 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 is formed on a housing part of the multi-part housing of the control valve 27. From the second hydraulic chamber 29 of the control valve 27 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 separated from the first hydraulic chamber 28. The valve member 30 of the control valve 27 comprises a piston extension 35, which in the FIG. 1 shown closed position of the flat seat 33 is located in the second hydraulic chamber 29 of the control valve 27.

At the vertically movable valve member 30 of the control valve 27, there is an annular magnet armature plate 37, which faces a current-supply solenoid 38. 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 solenoid 38 of the control valve 27, the flat seat 33 is closed to the second low-pressure side hydraulic chamber 29.

At the end face, which is opposite to the second hydraulic chamber 29 of the valve member 30, there is a hydraulic damper 40. The hydraulic damper 40 is traversed by a through hole 41 and biased by a spring element 42. The spring element 42 is located within a damper chamber 43. Controlled fuel volume is discharged therefrom via the third throttle point 44 into the low-pressure region of the fuel injection system. The hydraulic damper 40 and the valve member 30 lie along a contact surface 45 in FIG. 1 illustrated switching state of the control valve 27 to each other, however, represent two separate components.

In the deactivated state of rest of the booster 5, the control valve 27 is closed due to the action of the closing spring 39. Thus, the first control edge 31 is closed below the flat seat 33 on the valve member 30. 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. Above the closed flat seat 33, the control line 11 is separated from the first return 34 and the second return 36 in the low-pressure region of the fuel injection system.

To control the pressure booster 5, the differential pressure chamber 9 (back space) is pressure relieved. For this purpose, the control valve 27 is activated, ie opened. There is an energization of the solenoid 38, so that the magnet armature 37 against the action of Closing spring 39 is tightened, whereby the flat seat 33 is opened at the first control edge 31 of the control valve 27. Via the control line 11, fuel flowing from the differential pressure chamber 9 (backspace) flows into the first hydraulic chamber 28 and via the opened first control edge 31, the first return 34 and the second return 36 on the low-pressure side of the fuel injection system. 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 region. By now in the compression chamber 12 retracting second piston part 13 of the pressure booster, there rises the pressure corresponding to the transmission ratio of the booster 5 and flows through the nozzle chamber inlet 23, the nozzle chamber 24 to. The injection valve member 18 opens and releases the injection openings 26 at the combustion-chamber-side end of the fuel injector 3 at the pressure stages 25 formed in the region of the nozzle chamber 24 on the one-piece injection valve member FIG. 1 not shown combustion chamber of 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 at the end of the flow of the solenoid 38 of the control valve 27 by the action of the closing spring 39 back into its closed position. In the closed position, the first control edge 31 is closed below the flat seat 33. As a result, 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 booster 5, so that it goes back to its rest position. 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. Due to the building up in the differential pressure chamber 9 (back space) of the booster 5 system pressure, i. the pressure level, which prevails in the pressure accumulator 1 (common rail), the pressure booster 5 is deactivated. The second piston part 13 moves out of the compression chamber 12 and due to the decreasing pressure in the nozzle chamber 24, the injection valve member 18 is again placed in its closing the injection openings 26 position.

Above the movable in the vertical direction when energizing the solenoid 38 valve member 30 is the hydraulic damper 40. By this is a slow, approximately linear opening movement of the in the illustration FIG. 1 one-piece injection valve member 18 achieved. When opening the valve member 30, ie when energizing the solenoid 38, the hydraulic damper 40 performs the displaced amount via the third throttle body 44 in a FIG. 1 not shown low pressure range of the fuel injection system from. Due to the hydraulic damper 40, the opening movement of the valve member 30, when energized, the solenoid 38 is slowed down.

The closing movement of the valve member 30 of the control valve 27, however, is not affected by the hydraulic damper 40. This is achieved by 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 quick closing movement of the valve member 30 can be achieved during which the hydraulic damper 40 a contact surface 45 separates from the valve member 30. As a result, the valve member 30 can move unhindered into its closed position, 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 can be reset to its starting position very quickly. This is at high speeds of self-igniting internal combustion engine, in terms of closely spaced injection events of great importance.

The opening speed of the valve member 30 of the control valve, can be adjusted by the dimensioning of the third throttle body 44 which is associated with the damper chamber 43. The opening speed of the valve member 30, which adjusts itself continues to be dependent on the magnetic force which is achieved in the energization of the solenoid 38 of the control valve 27. The magnetic force of the magnetic coil 38 of the control valve 27 can be adjusted via the Bestromungsniveau.

At a lower energization level of the solenoid 38, a slower opening of the control valve 27, i. a slower opening of the valve member 30. Thus, a delayed, gradually successful pressure build-up at the beginning of an injection phase can be achieved, which sets a substantially ramp-shaped course of the injection rate.

If, however, the magnetic coil 38 of the control valve 27 is energized with a second higher activation current, a rapid opening of the control valve 27 takes place. This makes it possible to achieve a faster pressure build-up at the beginning of a respective injection, which results in an injection rate that is too rectangular.

FIG. 2 are different Bestromungsmöglichkeiten the control valve to operate the fuel injector.

According to FIG. 2 the current flow curve 50 of the magnetic coil 38 is plotted over time [t]. At a triggering time 53, the energization of the magnetic coil 38, either with the first Ansteuerstromniveau 51 or the second - dashed lines - Ansteuerstromniveau 52 take place.

FIG. 3 are the corresponding to the Bestromungsniveau resulting Hubverläufe the control valve removed.

When the valve member 30 of the control valve 27 is driven at the first drive current level 51, i. if the magnetic coil 38 is energized with a lower current level, a slower opening of the valve member 30 of the control valve 27 results. In this case, a first ramp 63 with a lower gradient curve is established.

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

If the solenoid 38 with the in FIG. 2 energized and represents the in FIG. 3 shown first stroke profile 61, so there is a first pressure curve 71 at the injection valve member.

In FIG. 5 Hubverläufe the injection valve member are shown.

FIG. 5 shows the first Ansteuerstromniveau 51 of the solenoid 38 of the control valve 27 corresponding first stroke profile 81 of the integrally formed injection valve member 18th

FIG. 2 also shows the Bestromungsverlauf 50 of the solenoid 38 when a second Ansteuerstromniveau 52 - dashed line - is set.

In this case arises according to FIG. 3 a second stroke profile 62, which is characterized by a second ramp 64, which differs by a significantly higher slope compared to the first ramp 63 at the first drive current level 61 of the solenoid 38. Because of this arises according to FIG. 4 the second pressure curve 72 at the injection nozzle, resulting in an approximately rectangular injection rate.

FIG. 5 also shows the adjusting during the energization of the solenoid 38 with the second Ansteuerstromniveau 52 second stroke profile 82, which differs only slightly from the first stroke profile 81, apart from a stronger increase at the beginning.

In addition to the mutually differing Ansteuerstromniveaus 51 and 52, with which the solenoid 38 of the control valve 27 can be energized, the opening speed of the valve member 30 can be adjusted via the third throttle body 44. The deceleration of the opening speed is also achieved by the hydraulic damper 40 according to the invention, which is accommodated in the upper region of the control valve 27, but does not affect the closing of the injection valve member 18 due to the separation from the valve member 30.

The in the FIGS. 3 to 5 illustrated injection rate with respect to the present invention proposed driving method of a control valve 27 achievable injection rates, can also vary over the self-igniting internal combustion engine associated control unit and adjust within appropriate maps in each optimal manner 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 (9)

1. Fuel injector (3) for injecting fuel into combustion chambers of an internal combustion engine having a pressure booster (5), having a control valve (27) with a valve element (30) and having a hydraulic damper (40) which is assigned to the valve element (30), with the pressure booster (5) being connected to a pressure accumulator (1) for the supply with highly pressurized fuel, which pressure accumulator (1) is activated and deactivated by means of the control valve (27) which is of direct-switching design, with the opening speed of the valve element (30) of the control valve (27) being varied in order to form an injection pressure profile (7), and with the opening speed of the valve element (30) of the control valve (27) being slowed by the hydraulic damper (40) which is assigned to the valve element (30), and with the hydraulic damper (40) and the valve element (30) being two separate components, characterized in that the hydraulic damper (40) has a through bore (41) which opens out into a control space (43) which can be relieved of pressure via a throttle point (44), wherein during the opening of the valve element (30), a displaced quantity is discharged via the throttle point (44).
2. Fuel injector according to Claim 1, characterized in that, during the closing of the valve element (30) of the control valve (27), the hydraulic damper (40) and the valve element (30) are separable from one another along the contact face (45).
3. Fuel injector according to Claim 1, characterized in that, during the closing of the valve element (30) of the control valve (27), the damper space (43) can be filled via the through bore (41) formed in the hydraulic damper (40).
4. Fuel injector according to Claim 1, characterized in that the valve element (30) of the control valve (27) is acted on in the closing direction by means of a closing spring (39).
5. Fuel injector according to Claim 1, characterized in that the hydraulic damper (40) is loaded against the valve element (30) by means of a spring (42).
6. Fuel injector according to Claim 1, characterized in that a magnet armature plate (37) is formed on the valve element (30) of the control valve (27) below a magnet coil (38), and the valve element (30) contains a seat (33) which has a seat (33) for closing off a second hydraulic space (29).
7. Fuel injector according to Claim 6, characterized in that, at a first activation current level (51), the magnet coil (38) of the control valve (27) sets a slow opening of the valve element (30) and a delayed pressure build-up at the start of the fuel injection, and therefore a first ramp-shaped injection rate (63, 71).
8. Fuel injector according to Claim 6, characterized in that, when the magnet coil (38) is supplied with current with a second activation current level (52), a fast opening of the valve element (30) is set and a fast pressure build-up at the start of the injection and a rectangularly-running injection rate (64, 72) is set.
9. Fuel injector according to Claim 1, characterized in that the control of the pressure booster (5) and of the injection valve element (18) takes place by means of the control valve (27), with the pressure booster (5) being activated or deactivated by means of the release of pressure from or pressurization of its differential pressure space (9), and the working space (8) of the pressure booster (5) being permanently connected to the pressure accumulator (1).

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