EP1392965B1 - Pressure amplifier for a fuel injection device - Google Patents

Description

State of the art

The invention relates to a pressure amplifier of 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 nozzle needle 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 nozzle needle. Alternatively, the deflection of the nozzle needle by an actuator (actuator, actuator) take place. In a pressure-controlled fuel injection device according to the invention, the nozzle needle is moved by 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 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 guide triangle), 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.

In a fuel injection device according to the teaching of DE 199 39 428 A1 must the entire high-pressure chamber in the injector and in the pressure booster at the Resetting the piston of the booster to be relaxed so that it too high relaxation losses comes.

In a circuit according to the teaching of DE 199 10 970 A1, an additional occurs Control quantity during the control of the pressure booster. These Control amount flows from the high pressure line via a throttle and the Differential space of the pressure intensifier in the leakage. This throttle should be for Reduction of leakage losses are designed to be small. To facilitate, faster recovery of the piston of the booster, however, is a greater design desirable, so that the provision is not too strong Forces must be overcome. In the space of the injector can be means to overcome the forces counteracting the return in the case of small ones Do not realize chokes. The provision slows down and can possibly not be completed until the next injection.

Advantages of the invention

To minimize the above problems is a Fuel injection device according to claim 1 proposed. According to the invention further developments of the inventions are in the claims. 2 to 6 included. On the one hand reduces the force, which only one in the piston trained control channel to the provision of the piston are expended would. On the other hand, the throttle in the permanent control channel to Prevention of leakage losses with activated pressure booster small be interpreted. When resetting after a successful piston stroke is the necessary restoring force reduced by an additional control channel.

In one embodiment of the invention, the control channel is replaced by a Relative movement of two pistons released during reset. At the Compression stroke, the additional control channel is closed, so that the Leakage losses can be reduced.

In another embodiment, the restoring force is through the control channel after a large piston stroke (> h) has occurred through the released control channel facilitated.

To further optimize the recovery behavior can also several additional Control channels are used.

drawing

Fig. 1

einen ersten Druckverstärker einer Kraftstoffeinspritzeinrichtung;

Fig. 2

einen zweiten Druckverstärker einer Kraftstoffeinspritzeinrichtung;

Fig. 3

einen dritten Druckverstärker einer Kraftstoffeinspritzeinrichtung;

Fig. 4

einen vierten Druckverstärker einer Kraftstoffeinspritzeinrichtung;

Fig. 5

eine Kraftstoffeinspritzeinrichtung nach dem Stand der Technik.

Three embodiments of the invention are shown schematically in the drawing and will be explained with reference to FIGS. For a better understanding of the invention, a known fuel injector is attached in FIG. It shows:

Fig. 1

a first pressure booster of a fuel injector;

Fig. 2

a second pressure amplifier of a fuel injector;

Fig. 3

a third pressure amplifier of a fuel injection device;

Fig. 4

a fourth pressure amplifier of a fuel injector;

Fig. 5

a fuel injection device according to the prior art.

Description of the embodiments of the invention

From Fig. 1 it can be seen that the pressure booster 9a of a first embodiment in a further development of the prior art according to FIG. 5 has a first piston 30a and a second piston 31a (two-part piston formation). There is a continuous power transmission from the first piston 30a to the second piston 31a instead, when a piston surface 32 is pressurized in the connection of the pressure booster 9a (open valve 15). During the connection of the pressure booster 9a, a control amount of fuel flows via a first control passage 33 with a first throttle 34 and a differential space 10a in the leakage line 16. In the first piston 30a, an additional second control channel 35 is formed, which includes a second throttle 36 , When the pressure booster 9a (open valve 15) is switched on, the plate spring 37a is compressed by the force transmission from the first piston 30a to the second piston 31a and a gap 38a is closed between the pistons 30a and 31a, whereby the second control channel 35 is closed.

With the pressure booster 9a switched off (closed valve 15) and reduced Power transmission between the pistons 30a and 31a becomes the gap 38a released, so that also via the second control channel 35 fuel from the low pressure side pressure booster chamber 13a flow into the differential space 10a can. On the one hand, the force is reduced, which in only one piston 30a trained control channel for returning the piston 30 a and 31 a expended would have to be. On the other hand, the throttle 34 for reducing Leakage losses are designed with switched on pressure booster 9a small.

Fig. 2 relates to a similar to FIG. 1 arrangement. Identical or similar components are designated by the same or similar reference numerals (9a ≈ 9b, 10a ≈ 10b, 13a ≈ 13b, 30a ≈ 30b, 31a ≈ 31b, 37a ≈ 37b, 38a ≈ 38b). Differences in the arrangement come about through the plate spring 37b, the sealing gap 38b and the contact surfaces of the pistons 30b, 31b.

A fuel injection device according to FIG. 3 comprises a pressure booster or pressure intensifier 51 with a first piston 52 and a second piston 53. The first piston 51 has a first control channel 55 and a second Control channel 54 with a throttle. The two pistons 52 and 53 are such movably arranged relative to each other, that in the provision of a gap occurs, an additional connection between niederduckseitigem Booster chamber 56 and differential space 57 releases through the channel 54. The Relative movement of the pistons 52 and 53 is by a stop (Connecting means 58) and a spring 59 limited. During the delivery stroke the pistons 52 and 53 abut each other as shown in Fig. 3 and thus close the additional control channel 54. The opening and the Closing of the gap are by the piston stroke of the pistons 52 and 53 - in similar to that shown in Fig. 1 and described - controlled.

In Fig. 4 is a pressure amplifier 61 of an embodiment in development of a prior art shown in FIG. 5. In this embodiment are a first control channel 62 with a first throttle 63 and a second control channel 64 with a second throttle 65 in a piston 66 of the pressure intensifier 61st educated. The first control channel 62 connects the low-pressure side control chamber 67 permanently with a differential space 68. The second control channel 64 provides a piston stroke-dependent connection between the rooms 67 and 68 ago. After one Piston stroke h, the connection is released. On provision after a successful large piston stroke (> h) is the restoring force through the control channels 62 and 64th facilitated. At a small piston stroke (<h), the control channel 64 is sufficient, so that Leakage losses can be kept within limits.

Description of the Related Art

In the stroke-controlled fuel injection device 1 shown in FIG. 5 promotes a volume-controlled fuel pump 2 fuel 3 from a Storage tank 4 via a feed line 5 in a central pressure storage chamber. 6 (Common rail), of which several, corresponding to the number of individual cylinders Pressure lines 7 to the individual, in the combustion chamber to be supplied Remove internal combustion engine protruding injectors 8 (injector). In the FIG. 3 shows only one of the injectors 8. With the help of Fuel pump 2, a first system pressure is generated and in the pressure storage space 6 stored. This first system pressure is used for pre-injection and when needed and Post-injection (HC enrichment for exhaust aftertreatment or soot reduction) and to represent a course of injection with plateau (boat injection) used. To inject fuel with a second higher system pressure is everyone Injector 8 each associated with a local pressure booster 9, which is within a Injector 8 is located.

During operation of the pressure booster 9, the pressure in through a transition of a larger formed to a smaller piston cross section differential space 10 used. For refilling and deactivation of the booster 9 is the differential space 10 with a supply pressure (rail pressure) acted upon. Then prevail at all pressure surfaces of a piston 11, the same pressure conditions (Rail pressure). The piston 11 is pressure balanced. By an additional spring the piston 11 is pressed into its initial position. To activate the Pressure booster 9, the differential space 10 is depressurized and the Pressure booster generates a pressure boost according to the area ratio. Through this type of control can be achieved that to return the Pressure booster 9 and for refilling a high-pressure side Booster chamber 12 a low-pressure side pressure booster chamber 13 not relieves pressure. At a small hydraulic ratio can so that the relaxation losses are greatly reduced.

For controlling the pressure booster 9, a throttle 14 and a 2/2-way valve 15 used. The throttle 14 connects the differential space 10 with below Supply pressure of stationary fuel from an accumulator 6. The 2/2-way valve 15 connects the differential space 10 to a leakage line 16 at. are the 2/2-way valves 15 and 17 closed, the injector 8 is below the Pressure of the pressure storage chamber 6. The pressure booster 9 is located in the Starting position. Now can through the valve 17 an injection with rail pressure to be controlled. If an injection with higher pressure is desired, then the 2/2-way valve 15 is activated (opened) and thus a pressure boost reached. The piston 11 can be moved in the compression direction, so that the Compressed in the pressure booster chamber 12 located fuel and a control room 18 and a nozzle chamber 19 is supplied. A check valve 20 prevents the return flow of compressed fuel into the pressure storage space 6.

The injection takes place via a fuel metering with the help of one in one Guide bore axially displaceable nozzle needle 21 with a conical Valve sealing surface at one end, with which it has a valve seat on Injector housing of the injector 8 cooperates. At the valve seat surface of the Injector housing injection openings are provided. Inside the nozzle chamber 19 is a in the opening direction of the nozzle needle 21 facing pressure surface there subjected to prevailing pressure, via a pressure line 22 to the nozzle chamber 19th is supplied. Coaxial with a valve spring also engages the nozzle needle 21 Pressure piece 23 on, with its side facing away from the valve sealing face 24th limited the control room 18. The control chamber 18 has the fuel pressure connection fro an inlet with a first throttle 25 and a drain to a Pressure relief line 26 with a second throttle 27, through the 2/2-way valve 17 is controlled.

The nozzle chamber 19 is placed over an annular gap between the nozzle needle 21st and the guide bore continues to the valve seat surface of the injector housing. about the pressure in the control chamber 18, the pressure member 22 in the closing direction pressurized.

Under the first or second system pressure standing fuel constantly fills the Nozzle chamber 19 and the control chamber 18. Upon actuation (opening) of the 2/2-way valve 17, the pressure in the control chamber 18 can be reduced, so that in the Follow the pressure force acting on the nozzle needle 21 in the opening direction Nozzle chamber 19 acting in the closing direction on the nozzle needle 21 compressive force exceeds. The valve sealing surface lifts off the valve seat surface and fuel is injected. In this case, the pressure relief process of the control room can be 19 and thus the stroke control of the valve member 17 via the dimensioning of Throttle 25 and the throttle 27 influence.

The end of the injection is achieved by pressing (closing) the 2/2-way valve again 17 introduced, the control chamber 18 again from the leakage line 26 decouples, so that in the control chamber 18 again builds up a pressure that the Pressure piece 23 can move in the closing direction.

Furthermore, the connected to the accumulator chamber 6 bypass line 28th intended. The bypass line 28 is connected directly to the pressure line 22. The bypass line 28 is usable for injection with rail pressure and is arranged parallel to the pressure booster chamber 12, so that the bypass line 28th regardless of the movement and position of the piston 11 is continuous.

LIST OF REFERENCE NUMBERS

1

Fuel injection system

2

Fuel pump

3

fuel

4

Fuel tank

5

pressure line

6

Pressure reservoir

7

supply

8th

injector

9

booster

9a

booster

9b

booster

10

differential chamber

10a

differential chamber

10b

differential chamber

11

piston

12

Pressure booster chamber

13

Pressure booster chamber

13a

Pressure booster chamber

13b

Pressure booster chamber

14

throttle

15

2/2 way valve

16

leakage line

17

2/2 way valve

18

control room

19

nozzle chamber

20

check valve

21

nozzle needle

22

pressure line

23

Pressure piece

24

face

25

throttle

26

leakage line

27

throttle

30a

first piston

30b

first piston

31

a second piston

31b

second piston

32

face

33

control channel

34

throttle

35

control channel

36

throttle

37a

Belleville spring

37b

Belleville spring

38a

seal gap

38b

seal gap

51

booster

52

piston

53

piston

54

control channel

55

control channel

56

Low-pressure side booster chamber

57

differential chamber

58

attack

59

feather

61

booster

62

control channel

63

throttle

64

control channel

65

throttle

66

piston

67

Low-pressure side booster chamber

68

differential chamber

Claims (6)

1. Pressure intensifier (9; 9a; 9b; 51; 61) of a fuel injection device (1), with a displaceable piston unit (11; 30a, 30b; 31a, 31b; 52, 53; 66) which at one end can be acted upon with pressure via a low-pressure-side pressure intensifier space (13, 13a; 13b; 56; 67) and at the other end has a high-pressure-side pressure intensifier space (12) for fuel compression, the piston unit (11; 30a, 30b; 31a, 31b; 52, 53; 66) having a second piston cross section reduced with respect to the first piston cross section provided for pressure action, for forming a difference space (10; 10a; 10b; 57; 68) connectable to a leakage line (16) via an activatable valve (15), at least one control duct (33, 35; 54, 55; 62, 64) connecting the low-pressure-side pressure intensifier space (13, 13a; 13b; 56; 67) to the difference space (10; 10a; 10b; 57; 68), and the low-pressure-side pressure intensifier space (13, 13a; 13b; 56; 67), the high-pressure-side pressure intensifier space and the difference space (10; 10a; 10b; 57; 68) being filled, when the valve (15) is closed, with fuel which is under system pressure, characterized in that an orifice of the control duct (33, 35; 54, 55; 62, 64) is closed or opened as a function of the movement of at least parts of the piston unit (30a, 31a; 30b, 31b; 52, 53; 66).
2. Pressure intensifier according to Claim 1, characterized in that the at least one control duct (33, 35; 54, 55; 62, 64) is integrated into the piston unit (30a, 30b; 31a, 31b; 52, 53; 66).
3. Pressure intensifier according to one of the preceding claims, characterized in that the at least one control duct (33, 35; 54, 55; 62, 64) contains a throttle (34, 36; 63, 65).
4. Pressure intensifier according to one of the preceding claims, characterized in that the piston unit is formed from at least 2 parts and the connection means (37a; 37b; 59) are formed in such a way that the pistons (30a, 31a; 30b, 31b; 52, 53) execute a movement in relation to one another between the conveying stroke of the pressure intensifier (9a; 9b; 51) and the return movement of the pressure intensifier (9a; 9b; 51), and the at least one control duct (35; 54) is opened or closed as a result of this relative movement.
5. Pressure intensifier according to Claim 4, characterized in that the orifice of the at least one control duct (35; 55) is arranged in a gap (38a; 38b) between a first piston (30a; 30b; 52) and a second piston (31a; 31b; 53) and is controlled via a spring (37a; 37b) in such a way that, with the pressure intensifier (9a; 9b; 51) cut in, the orifice is closed and, with the pressure intensifier (9a; 9b; 51) cut out, the orifice is opened as a result of the movement of the pistons (30a, 31a; 30b, 31b; 52, 53) in relation to one another.
6. Pressure intensifier according to one of Claims 1 to 3, characterized in that the orifice is opened in the case of a conveying stroke > h executed by a preferably one-part piston unit (66).

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