EP1709319B1 - Fuel injector with direct needle control - Google Patents

Description

Technical area

To fuel the combustion chambers of internal combustion engines with fuel fuel injectors are used. In particular, in self-igniting internal combustion engines, the injection pressure is provided via a high-pressure accumulator. Due to the large amount of fuel in the high-pressure accumulator compared to the injection quantity, pressure fluctuations during the injection process are avoided. The operation of the fuel injectors is carried out hydraulically with the fuel provided via the high-pressure accumulator.

State of the art

Fuel injectors, as used in the prior art for high-pressure storage systems, z. B. from Mollenhauer, Manual Diesel Engines, Second Edition, Springer-Verlag, Berlin, 2002 known. In fuel injectors for high-pressure storage systems, both the opening and the closing operation is hydraulically controlled. For this purpose, a control chamber in which fuel is under injection pressure, closed by a control valve. The fuel pressure acts on the rear side of a control piston, which acts into the control chamber, and on a pressure shoulder on an injection valve closing the injection openings. In this case, the hydraulic force on the back of the control piston of the hydraulic force acting on the pressure shoulder, opposite. Due to the larger area on the control piston, the nozzle remains closed. As soon as the control valve opens the control chamber, the pressure in the control chamber is reduced and the hydraulic force on the pressure shoulder is greater than the pressure force acting on the back of the control piston. This causes the injection valve member to open.

In the case of the fuel injectors known from the prior art, the fuel supply of both the control chamber and a pressure chamber, from which the fuel passes via injection openings into the combustion chamber, takes place via supply lines in the injector housing. In addition, known from the prior art fuel injectors with injection valve member, control piston and control valve have a complex structure.

Out WO 03/081020 A1 For example, a fuel injector is known in which a pressure booster connected to a piezo actuator acts on an injection valve member via a booster chamber. The booster chamber is delimited by a pot-shaped sleeve, the fuel passing via the sleeve via a bypass to a pressure chamber located upstream of the injection openings. In the cup-shaped sleeve of the pressure booster and the injection valve member is received in guides, so that the booster chamber is hydraulically sealed by the guides.

Further fuel injectors go out of the documents DE 19642441 A1 and EP 03 900 32 A1 out. In these fuel injectors, the pressure booster and the injection valve member are each guided in fixed housing parts, wherein the booster chamber is bounded by the axially adjacent guides.

Presentation of the invention

The fuel injector designed according to the invention provides a fuel injector for high-pressure storage systems with a compact construction. For this purpose, an actuator of the fuel injector acts directly on a pressure booster designed as a booster piston. The actuator is z. As a piezoelectric actuator, an electromagnet or a hydraulic / mechanical actuator. To control the fuel injector, the actuator acts directly on an upper end face of the booster piston. A lower end face of the pressure booster forms one side of a booster chamber, and an end face of a stepped injection valve member bounds the booster chamber on the opposite side. A shoulder is formed in the interpreter room, so that the interpreter room tapers from a large to a smaller diameter. The larger diameter of the booster chamber faces the pressure translator of the same diameter, while the region of the small diameter booster chamber faces the injection valve member.

The injection valve member is stepped in a translator area, a guide area and an original area. To open injection openings, the injection valve member moves in the direction of the pressure booster. In this case, the end face of the compiler area of the injection valve member moves into the interrupter space.

The compiler area of the injection valve member is surrounded by a spring space in which a spring element is accommodated. The spring element is preferably designed as a spiral spring. On one side, the spring element is supported on a ring, which rests on an extension formed between the compiler area and the guide area of the injection valve member. On the other hand, the spring element is supported against an end face of a ring surrounding the compiler portion of the injection valve member sleeve. On the opposite side of the face, the sleeve is provided with a biting edge. By means of the force exerted by the field element spring force the sleeve is pressed with the biting edge against the injector and thus limits the side of the translator space and seals it off.

The fuel used for the operation of the internal combustion engine flows from a high-pressure accumulator into an annular space surrounding the actuator. About absorbed in the injector bypasses the fuel flows from the annulus in the spring chamber. About guide leakage between the compiler area of the injection valve member and the sleeve fuel enters the interrupter space. The guide region of the injection valve member is provided with at least one bevel, so that the fuel between the Bevel and the needle guide flows in a surrounding the nozzle needle portion of the injection valve member annular pressure chamber. The formation of a bevel in the guide region of the injection valve member, along which the fuel can flow, ensures that system pressure prevails in the pressure chamber. The system pressure is preferably in the range of 150 to 2000 bar. Furthermore, can be dispensed with by the bevel on a supply line from the spring chamber in the pressure chamber. This simplifies the manufacturing process of the fuel injector.

When using a piezoelectric actuator for controlling the fuel injector, the piezoelectric actuator is energized to close the injection openings. When energized, the piezocrystals in the piezo actuator expand and the piezo actuator lengthens. The elongation of the piezoelectric actuator causes a force on the upper end face of the pressure booster. As a result, the pressure booster moves in the direction of the injection openings, thus reducing the size of the booster chamber arranged on the underside of the pressure booster. Due to the decrease in volume of the interpreter room, the pressure in the interpreter room increases. As a result, a larger hydraulic force acts on the end face of the translator part of the injection valve member. Due to the hydraulic force acting on the end face of the translator part of the injection valve member and acting on the extension between the compiler area and the guide portion of the injection valve member spring force, the injection valve member is placed on a combustion chamber facing the sealing edge of the pressure chamber. As a result, the at least one injection opening is closed in the combustion chamber.

If the energization of the piezo actuator is canceled, the piezo crystals contract and the piezo actuator contracts. Due to the force acting on the lower end face of the pressure booster compressive force of the pressure booster is moved in the direction of the piezoelectric actuator. This increases the volume of the booster chamber, whereby at the same time decreases the hydraulic force on the end face of the booster section of the injection valve member. In the spring space surrounding the compiler area of the injection valve member and in the pressure space surrounding the nozzle needle area of the injection valve member, system pressure still prevails due to the hydraulic connection to the high-pressure accumulator. In this way acts on the extension between the compiler area and the guide area and on a trained above the sealing edge pressure stage in the nozzle needle portion of the injection valve member, as well as the transition from the guide portion in the nozzle needle portion of the injection valve member, a hydraulic force, the hydrau-lic force on the face of the compiler area the injection valve member is directed opposite. Once the sum of the hydraulic forces on the extension between the translator area and guide area, the transition from the guide area to the nozzle needle area and the pressure level in the nozzle needle area of the injection valve member is greater than the hydraulic force on the end face of the compiler area of the injection valve member and the spring force acting by the spring element, the injection valve member moves from the sealing edge and thus releases the at least one injection port.

To close the Einspitzöffnungen the piezoelectric actuator is energized, causing the piezoelectric crystals expand and the piezoelectric actuator lengthened. The piezoelectric actuator acts on the upper end face of the pressure booster, whereby it moves in the direction of the injection openings. As a result, the volume of the interpreter room is reduced, and at the same time, the pressure in the interpreter room increases. As a result, the force acting on the end face of the compiler portion of the injection valve member hydraulic force increases. As soon as the force acting on the end face of the translator section of the Einseititzventilgliedes hydraulic force and the spring force of the spring element are greater than acting on the extension between the translator area and guide area, the transition from the guide area to the nozzle needle area and the pressure level at the nozzle needle portion of the injection valve member hydraulic force, the injection valve member on placed the sealing edge and so closed the at least one injection port.

drawing

In the following the invention will be described in more detail with reference to a drawing

The single FIGURE shows a fuel injector designed according to the invention.

variants

In FIG. 1 an inventively designed fuel injector is shown.

The injection valve member 3 is preferably divided into a translator area 4, a guide area 5 and a nozzle needle area 6. The diameter d _{2 of} the translator area 4 of the injection valve member 3 is greater than the one diameter d ₃ of the guide portion 5 of the injection valve member 3. Further, the diameter d ₁ of the nozzle needle portion 6 is preferably smaller than the diameter d ₃ of the guide portion 5 of the injection valve member. 3

The control of the fuel injector 1 is preferably carried out by means of a piezoelectric actuator 7. In addition to the piezoelectric actuator 7, however, the control can also be effected by an electromagnet or a hydraulic / mechanical actuator.

For closing at least one injection opening 8, the piezoelectric actuator 7 is energized. By energizing the piezocrystals expand and the piezoelectric actuator 7 lengthens. The piezoelectric actuator 7 acts directly on a piezoelectric actuator 7 facing upper end face 9 of the pressure booster 2. As a result, designed as a piston pressure booster 2 is moved in the direction of at least one injection port 8. With a lower end face 10 of the pressure booster 2 limits a booster chamber 11. By the movement of the pressure booster 2 in the direction of the at least one injection port 8, the volume of the booster chamber 11 is reduced. As a result, the pressure in the booster chamber 11 increases. At the lower end face 10 of the booster chamber 11 opposite side of the booster chamber 11 is bounded by an end face 12 of the booster section 4 of the injection valve member 3. By acting on the end face 12 of the translator portion 4 of the injection valve member 3 hydraulic force the injection valve member 3 is placed on a above the at least one injection port 8 arranged sealing edge 13. As a result, the at least one of the injection opening 8 is closed.

A spring force, which is generated by a spring element 15 received in a spring chamber 14, supports the hydraulic force acting on the end face 12 of the booster region 4 of the injection valve member 3 when the injection valve member 3 is closed. The spring element 15 used is preferably a helical spring. The spring element 15 rests with one side preferably on a ring 16, which in turn rests on a step 18 formed by an extension 17 between the compiler area 4 and the guide area 5. On the other side, the spring element 15 is preferably supported against an end face 20 of the sleeve 19.

At the end face 20 opposite side of the sleeve 19, a biting edge 21 is formed. Due to the force exerted by the spring element 15 on the end face 20 of the sleeve 19 spring force the biting edge 21 of the sleeve 19 is pressed against a shoulder 22 in the injector 23. This results in a liquid-tight and thus pressure-tight connection between the shoulder 22 of the injector housing 23 and the sleeve 19. The inside 24 of the sleeve 19 serves as a guide for the translator section 4 of the injection valve member 3 and at the same time as a lateral boundary and seal of the translator chamber eleventh

For fuel supply, the fuel injector 1 is connected via a feed line 25 to a high pressure accumulator 26. In the high-pressure accumulator 26, the fuel passes from a fuel reservoir 27 via a high pressure pump 28. By the high pressure pump 28, the system pressure of 150 to 2000 bar is provided. From the high-pressure accumulator 26, the fuel flows via the feed line 25 into an annular space 29 surrounding the piezoelectric actuator 7. The fuel flows via at least one of the annular space 29 Bypass 30 in the spring chamber 14. In order to ensure an undisturbed fuel flow, an annular gap 32 is formed between the outer side 31 of the sleeve 19 and the wall of the injector 23. From the spring chamber 14, the fuel passes along a bevel 33 in the guide region 5 of the objection valve member 3 in a pressure chamber 34 surrounding the nozzle needle portion 6 of the injection valve member 3. By the at least one bevel 33 in the guide portion 5 of the injection valve member 3 is a bypass between the guide portion 5 of the injection valve member 3 and a needle guide 35 formed in the nozzle part 36 of the injector 23. By connecting the pressure chamber 34 with the spring chamber 14 along the polished section 33, the connection of the spring chamber 14 with the annular space 29 via the at least one bypass 30 and the connection of the annular space 29 with the high-pressure accumulator 26 via the supply line 25 prevail both in the annular space 29 as also in the spring chamber 14 and in the pressure chamber 34 system pressure, which is preferably in the range of 150 to 2000 bar.

During the operation of the Kraffstoffinjektors the pressure in the booster chamber 11 changes. When the piezoelectric actuator 7 is energized, the pressure in the booster chamber 11 is preferably higher than the system pressure. When not energized piezoelectric actuator 7, the pressure is preferably lower than the system pressure. Therefore, a pressure-tight connection between the sleeve 19 and the shoulder 22 of the injector is required.

For the injection of fuel into a combustion chamber 37 of the internal combustion engine, the current supply required for closing the piezoelectric actuator 7 is terminated. As a result, the piezocrystals in the piezoactuator 7 contract and the piezoactuator 7 contracts. Due to the force acting on the lower end face 10 of the pressure booster 2 hydraulic force of the pressure booster 2 is moved in the direction of the piezoelectric actuator 7. As a result, the volume of the booster chamber 11 increases, which leads to a decrease in the pressure in the booster chamber 11, compared with the pressure prevailing in the spring chamber 14 system pressure. As a result, the hydraulic force acting on the end face 12 of the translator area 4 of the injection valve member 3 decreases. At the same time acts on a at the extension 17 between the compiler area 4 and the guide portion 5 of the injection valve member 3 formed first pressure stage 38, formed on a formed between the guide portion 5 and the nozzle needle portion 6 second pressure stage 39 and on the needle tip of the injection valve member 3 directly formed above the sealing edge 13 third pressure stage 40 a constant hydraulic force, which is directed against the hydraulic force on the end face 12 of the compiler area 4 of the injection valve member 3 opposite. The hydraulic force on the first pressure stage 38, the second pressure stage 39 and the third pressure stage 40 is constant, because the spring chamber 14 and the pressure chamber 34 constantly with system pressure are charged. As soon as acting on the end face 12 of the compiler area 4 of the injection valve member 3 hydraulic force and the spring force of the spring element 15 are smaller than the force acting on the first pressure stage 38, the second pressure stage 39 and the third pressure stage 40 hydraulic force, the injection valve member 3 lifts from the sealing edge 13 and releases the at least one injection opening 8.

A safe operating behavior of the fuel injector 1 is achieved in that the diameter d _{4 of} the pressure booster 2 is greater than the diameter d _{2 of} the translator section 4 of the injection valve member 3. The diameter of the booster chamber 11 corresponds in the region of the pressure booster 2 the diameter d _{4 of} the pressure booster second and in the area of the booster region 4 of the injection valve member 3 to the diameter d ₂ of the booster region 4. the transition from the diameter of the pressure booster 2 to the diameter of the booster section 4 of the injection valve member 3 is effected by means of paragraph 22nd

For closing the at least one injection opening 8, the piezoelectric actuator 7 is energized again. As a result, the piezo crystals expand in the piezoelectric actuator 7 and the piezoelectric actuator 7 lengthens. As a result, the pressure booster 2 moves in the direction of the at least one injection opening 8. In this case, the lower end face 10 of the pressure booster 2 moves into the booster chamber 11 and thus reduces its volume. As a result, the pressure in the booster chamber 11 increases and thus the force acting on the end face 12 of the booster section 4 of the injection valve member 3 hydraulic force. As soon as the hydraulic force acting on the end face 12 of the compiler area 4 of the injection valve member 3 and the spring force of the spring element 15 is greater than the constant hydraulic forces acting on the first pressure stage 38, the second pressure stage 39 and the third pressure stage 40 on the injection valve member 3, the nozzle needle 3 is placed on the sealing edge 13 and thus closes the at least one injection opening eighth

Characterized in that the diameter d _{3 of} the guide portion 5 of the injection valve member 3 is smaller than the diameter d _{2 of} the compiler region 4 of the injection valve member 3 and further the diameter d ₂ of the compiler portion 4 of the injection valve member 3 is smaller than the diameter d _{4 of} the pressure booster 2, is improves the opening behavior of the fuel injector 1 at low system pressures; by increasing the speed at which the injection valve member 3 opens at low system pressures and thus releasing the at least one injection opening 8 more quickly.

In order to mount the fuel injector 1 and to be able to produce the at least one bypass 30, the injector housing 23 is constructed in several parts. Thus, the piezoelectric actuator 7 is surrounded by an upper housing part 42, the pressure booster 2 is of a middle Housing part 43 surrounded, on which also the shoulder 22 is formed. The sleeve 19 surrounding the annular gap 32 and the spring chamber 14 are formed by a lower housing part 44. To the lower housing part 44, the nozzle part 36 connects, in which the needle guide 35, the pressure chamber 34 and the at least one injection port 8 are added. The connection points of the housing parts 42, 43, 44, 36 are characterized by division joints 41. The connection of the housing parts 42, 43, 44, 36 is preferably carried out positively, for. B. by welding.

LIST OF REFERENCE NUMBERS

1

fuel injector

2

Pressure intensifier

3

Injection valve member

4

Translation area

5

guide region

6

needle area

7

piezo actuator

8th

Injection ports

9

upper face

10

lower end face

11

Booster chamber

12

Face of the translator section 4

13

sealing edge

14

spring chamber

15

spring element

16

ring

17

extension

18

stages

19

shell

20

End face of the sleeve 19

21

biting edge

22

paragraph

23

injector

24

Inside the sleeve 19th

25

supply

26

High-pressure accumulator

27

Fuel tank

28

high pressure pump

29

annulus

30

bypass

31

Outer wall of the sleeve 19

32

annular gap

33

bevel

34

pressure chamber

35

needle guide

36

nozzle part

37

combustion chamber

38

first pressure level

39

second pressure level

40

third pressure level

41

dividing

42

Upper housing part

43

middle housing part

44

lower housing part

d ₁

Diameter of the needle area 6

d ₂

Diameter of translator area 4

d ₃

Diameter of the guide area 5

d ₄

Diameter of the pressure booster 2

Claims (10)

1. Fuel injector for internal combustion engines having a high-pressure store (26), having an injection valve member (3) which is divided in a stepped fashion into a booster region (4), a guide region (5) and a needle region (6), with it being possible for the booster region (4) to be moved with an end surface (12) into a booster chamber (11) in order to open at least one injection opening (8), and with the booster chamber (11) being delimited, on the side opposite the end surface (12) of the booster region (4) of the injection valve member (3), by a lower end surface (10) of a pressure booster (2), with the pressure booster (2) being actuated directly by an actuator (7), with a spring element (15) being held around the booster region (4) of the injection valve member (3), which spring element (15) is supported at one side on a ring (16) arranged at the transition from the booster region (4) to a guide region (5) of the injection valve member (3) and at the other side against a sleeve (19) which surrounds the booster region (4) of the injection valve member (3), with the fuel passing from the high-pressure store (26) via at least one bypass (30) into a spring chamber (14) which surrounds the booster region (4) of the injection valve member (3), and with an annular gap (32) being formed between the outer wall (31) of the sleeve (19) and the injector housing (23), via which annular gap (32) the at least one bypass (30) is connected to the spring chamber (14), characterized in that the sleeve (19) is provided, on the side facing away from the spring element (15), with a biting edge (21) which is pressed against the injector housing (23) and thereby laterally delimits the booster chamber (11).
2. Fuel injector according to Claim 1, characterized in that the fuel furthermore passes from the spring chamber (14), and from there via at least one ground portion (33) in the guide region (5) of the injection valve member (3), into a pressure chamber (34) which surrounds the needle region (6).
3. Fuel injector according to Claim 1, characterized in that the spring element (15) is a spiral spring.
4. Fuel injector according to Claim 1, characterized in that the actuator is a piezoelectric actuator (7).
5. Fuel injector according to Claim 1, characterized in that a widened portion (17) is formed at the transition from the booster region (4) to the guide region (5) of the injection valve member (3).
6. Fuel injector according to Claim 5, characterized in that that side of the widened portion (17) which points towards the combustion chamber is a first pressure stage (38).
7. Fuel injector according to Claim 1, characterized in that the transition from the guide region (5) to the needle region (6) of the injection valve member (3) acts as a second pressure stage (39).
8. Fuel injector according to Claim 1, characterized in that a third pressure stage (40) is formed in the needle region (6) of the injection valve member (3).
9. Fuel injector according to Claim 1 and 5, characterized in that the ring (16) rests on a step (18), which points towards the booster region (4) of the injection valve member (3), of the widened portion (17).
10. Fuel injector according to one of Claims 1 to 9, characterized in that the injector housing (23) comprises an upper housing part (42), a central housing part (43), a lower housing part (44) and a nozzle part (36).

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