EP1682769B1 - Fuel injector with a multipart, directly controlled injection valve element - Google Patents

Abstract

A fuel injector for a common rail injection system for injecting fuel into a combustion chamber of an internal combustion engine includes an injector body and a nozzle body with an injection valve member embodied in multiple parts received in the nozzle body. A hydraulic booster assembly connected downstream of a piezoelectric actuator. Control chambers are associated with the multi-part injection valve member for actuating it. The hydraulic booster assembly actuated by the piezoelectric actuator has booster chambers, which are each directly connected hydraulically with control chambers that actuate the needle parts of the injection valve member.

Description

Technical area

On self-igniting Verbrennungsltraftmaschinen storage injection systems are used for fuel injection, which allow a speed and load-independent adjustment of the injection pressure. In the storage injection systems (Conunon-Rail) are pressure generation and injection and locally decoupled. The injection pressure is generated by a separate high-pressure pump. This does not have to be driven synchronously with the injections. The pressure can be adjusted independently of the engine speed and the injection quantity. In place of druckgesteuelier injectors occur in this fuel injection system electrically actuated injectors, with their Ansteuerzeitpunkt and Ansteuerdauer the start of injection and the injection quantities are determined in the combustion chambers of the internal combustion engine. In common-rail injection systems, there is a high degree of freedom with regard to the design and formation of multiple or split injection processes.

State of the art

Out DE-190 55 271 A1 is a pressure / stroke controlled injector with hydraulic translator known. In an injector 2/2-way control valves are included, the vertical movement is mechanically coupled via a bridge to each other. The 2/2-way control valves are arranged on the inlet side and on the outlet side and upstream of a hydraulic booster. The hydraulic booster pressurizes a pressure chamber surrounding a nozzle needle with high pressure fuel. The two 2/2-way control valves are housed opposite to each other in the injector of the fuel injector.

A disadvantage of the DE 190 55 271 A1 known solution is the large number of items that are required to implement a pressure / stroke controlled Injektoransteuerung according to this solution.

Out DE 199 46 838 C1 a valve for controlling fluids is known. The valve comprises a valve member axially displaceable in a bore of a valve body. This has a valve closing member forming the valve head, which cooperates with a provided on the valve body seat for opening and closing the valve. Furthermore, a piezoelectric unit for actuating the valve member and a tolerance compensation element to compensate for elongation tolerances of the piezoelectric unit and / or other valve components is provided. With regard to its direction of action, the piezoelectric unit is arranged essentially at right angles to the axial movement direction of the valve member and can be acted upon by an electric current such that the piezoelectric unit exerts a tilting movement on an actuator serving as a lever arm, which is operatively connected to the valve member.

Presentation of the invention

The proposed solution according to the invention is characterized in that different injection cross-sections in the combustion chamber of a self-igniting internal combustion engine can be released with a multi-part, needle-shaped injection valve member, wherein the multi-part injection valve member is in particular controlled directly. For direct control of the multi-part, needle-shaped injection valve member, a hydraulic transmission arrangement is provided between a piezoelectric actuator and the multi-part, needle-shaped injection valve member, which has two booster chambers. Each of the two translator chambers acts on a control chamber for controlling an inner needle part and for driving an outer needle part of the multi-part, needle-shaped injection valve member.

The inner and the outer needle part of the multipart injection valve member have pressure stages which allow for pressurization of a nozzle chamber in the nozzle body and pressure relief of the control chambers a time-delayed opening of the needle parts of the multi-part injection valve member. As a result, during a first phase of the injection of fuel into the combustion chamber of a self-igniting internal combustion engine via a first Einspritzöffnungsquerschnitt and later in the injection at later time opening the inner needle part of the multi-part injection valve member, the release of a further opening cross-section, so that towards the end of the injection process more fuel enters the combustion chamber, as at the beginning of the injection process. Accordingly, in the partial load operation of the internal combustion engine only one injection cross-section is released while at full load of the internal combustion engine both needle parts of the multi-part design Injection valve member are open, so that the maximum injection quantity can be injected into the combustion chamber of the internal combustion engine.

By designing pressure stages formed on the outer needle part of the multi-part injection valve member, the hydraulic forces acting on the outer needle part can be adjusted such that the smallest quantity capability of the fuel injector is ensured even at very low pressures. Due to the formation of two pressure stages on the outer needle part of the multi-part injection valve member this opens very early, whereas the inner needle part of the multi-part injection valve member opens later, since the pressure formed at this stage is designed to be very small. Due to this design of the two pressure levels on the outer needle part and the pressure level on the inner needle part can be achieved that the two needle parts of the multi-part, needle-shaped injection valve member can be switched to different pressure levels.

drawing

With reference to the drawing, the invention will be explained in more detail below.

The single FIGURE shows a section through the present invention proposed fuel injector with multi-part trained, needle-shaped injection valve member and a hydraulic transmission arrangement on the booster chambers control spaces which are respectively associated with the inner and the outer needle portion of the multipart injection valve, pressure relieving or druckbeaufschlagbar.

variant

The fuel injector 1 shown in the drawing comprises an injector body 2 and a nozzle body 3. The injector body 2 and the nozzle body 3 are in the assembled state at a butt joint 4 to each other. The fuel flows through a high-pressure accumulator injection system, not shown in the drawing (common rail), to the injector body 2 via a fuel inlet 5. In the upper region of the injector body 2, an actuator 6 is accommodated, to which a hydraulic transmission device 9 is assigned. From the fuel inlet 5, a high-pressure feed line 7 branches off in the injector body 2, via which the high-pressure fuel flowing to the injector body 2 flows into a nozzle chamber 8. The nozzle chamber 8 is located in the nozzle body 3 and encloses a multi-part injection valve member 21, which is movably received in the nozzle body 3 in the vertical direction.

The hydraulic transmission device 9 comprises a booster piston 10. The booster piston 10 has a first end face 11, which is opposite to the actuator 6. A second end face 12 of the booster piston 10 defines a first booster chamber 13 of the hydraulic transmission device 9. On the booster piston 10 is a booster piston extension 14, which is formed in a smaller diameter compared to the diameter of the booster piston 10. An end face 15 of the translator piston extension 14 projects into a second translator chamber 17. From the second booster chamber 17 from a channel 16 which opens into a first control chamber 19 extends. Parallel to the channel 16 extends an overflow 18, via which the first booster chamber 13 and a second control chamber 20 communicate with each other hydraulically.

The multi-part needle-shaped injection valve member 21 has an outer needle part 22 and an inner needle part 23 arranged movably in this needle part. The inner needle part 23 is acted upon by the first control chamber 19, which is in communication with the second booster chamber 17 of the hydraulic transmission arrangement, while the outer needle part 22 via the second control chamber 20 which communicates via the overflow 18 with the first booster chamber 13, is pressed. The outer needle part 22 has a second control chamber 20 limiting control-space-side end face 24 and a first pressure step 25 on the outside and a further, second pressure step 26, which is formed on the inside of the outer needle member 22. Between the outer needle part 22 and the inner needle part 23, a pressure chamber 29 is formed, which is bounded by an annular part 27 formed on the inner needle part 23. The application of the internal pressure chamber 29 via pressure chamber inlets 30, which pass through the wall of the outer needle member 22. Through the pressure chamber inlets 30 is an overflow of fuel which flows under high pressure into the nozzle chamber 8, guaranteed in the inner pressure chamber 29 between the outer needle member 22 and the inner needle member 23.

At the combustion chamber end of the outer needle part 22, a seat 31 is formed on the outer circumference, which has a first seat diameter 32. The seat edge formed in the first seat diameter 32 interacts with the wall of the nozzle body 3. On the inner needle part 23, which is guided in the outer needle part 22 of the multi-part injection valve member 21, a cooperating with the wall of the nozzle body second seat 33 is formed. The seat diameter of the seat 33 of the inner needle member 23 is formed in a second seat diameter 34 (d ₁ ) which is considerably smaller than the first seat diameter 32 of the outer needle member 22. In the illustrated in the drawing, the closed state of the multi-part injection valve member 21, first injection ports 35 are separated by the closed seat 31 of the outer needle member 22 of an annular gap 41, in which over the nozzle chamber 8 is under high pressure fuel. By means of the seat 33 of the inner needle part 23, which is also shown in its closed state in the drawing, second injection openings 36 are likewise closed against the fuel which is present in the annular gap 41 and is under high pressure. In the illustrated in the drawing closed state of the multi-part needle-shaped injection valve member 21, 23 forms a wedge-shaped annular space 42 between the seat 31 of the outer needle member 22 and the seat 33 of the inner needle member. The combustion chamber, in which fuel is injected either via the first injection openings 35 or via the opened first and second injection openings 35, 36 when the multi-part injection valve member 21 is open, is identified by reference number 43.

The outer needle part 22 of the multi-part, needle-shaped injection valve member 21 is received in a guide length 37 in the nozzle body 3, while the inner needle member 23 in a guide length 38 extending between the Druckraumzuläufen 30 of the outer needle member 23 and its seat 31 in this body 3 , is limited. Although not shown in detail in the drawing, the outer needle member 22 may be performed in the nozzle body 3 in a plurality of, for example, 120 ° offset from each other formed guide surfaces.

The inner needle part 23 of the multi-part, needle-shaped injection valve member 21 has a second diameter 39 (d ₂ ) in the region above the inner pressure chamber 29, which exceeds the second seat diameter 34 (d ₁ ), ie d ₂ > d ₁ .

Due to the diameter ratio of d ₁ : d ₂ with d ₁ <d ₂ opens the inner needle portion 23 of the multi-part, needle-shaped injection valve member 21 later than the outer needle portion 22. The generated by the diameter difference d ₂ - d ₁ pressure stage 28 on the inner needle portion 23rd , Lying on the combustion chamber side tip, has a compared to the pressure levels 25, 26 significantly lower hydraulically effective area.

The operation of the inventively proposed fuel injector 1 according to the drawing is as follows:

In the closed state of the multi-part injection valve member 21 shown in the drawing, the actuator 6 is energized and extended. Due to the energization of the actuator 6, which is preferably designed as a piezoelectric actuator, its piezocrystals length, which are arranged one above the other in the form of a stack and thus act on the booster piston 10. Its second end face 12 moves into the first booster room 13 a. By the second end face 12 of the booster piston 10 and the booster piston extension 14 is retracted into the second booster chamber 17 of the hydraulic booster assembly 9. The first booster chamber 13 and the second booster chamber 17 are filled via the guide leaks between the outer needle part 22 and the nozzle body 3, the guide leak between the inner needle part 23 and the injector body 2 and the guide leakage between the booster piston 10 and the fuel inlet 5.

Due to the pressurization of the first booster chamber 13 and the second booster chamber 17 and the inner needle part 23 acted upon first control chamber 19 and the outer needle member 22 acted upon second control chamber 20 are pressurized, so that the inner needle member 23 and the outer needle member 22 in their seats 31 or 33 closing positions are provided.

Since at the same time high-pressure fuel in the nozzle chamber 8 is present via the high pressure supply line 7, and thus in the connected thereto, the outer needle part 22 surrounding annular gap 41, the fuel passes only to the closed seat 31 of the outer needle member 22 and can not the combustion chamber 43 are injected.

If the energization of the actuator 6 is canceled, the elongation of the piezoelectric crystals goes back and the booster piston 10, including the translator piston extension 14, moves in the vertical direction upwards. The stroke of the booster piston 10 and the booster piston extension 14 is in the range between 40 and 160 .mu.m.

Accordingly, the first control chamber 19, which acts on the inner needle part 23 and the second control chamber 20, which acts on the control-chamber-side end face 24 of the outer needle member 22, pressure relieved. Due to the high fuel pressure, which rests in the nozzle chamber 8, the outer needle part 22 opens sooner, since at this an outer first pressure stage 25 and an inner second pressure stage 26 are formed above the inner pressure chamber 29. Accordingly, at the beginning of the cancellation of the energization of the actuator 6 moves the control room-side end face 24 of the outer needle part 22 in the second control chamber 20, whereby the seat 31 of the outer needle member 22 is opened. As a result, the annular space 42 comes into communication with the annular gap 41, in which high-pressure fuel is present. The high-pressure fuel can be injected into the combustion chamber 43 via the first injection openings 35 during a first phase of the injection process.

During the first phase of the injection process, however, the inner needle portion 23 of the multipart, needle-shaped injection valve member 21 remains in its closed position, d. H. the seat 33 of the inner needle part 23 remains closed. In the course of the injection process, the inner needle part 23 of the multi-part injection valve member 21 opens, since the pressure stage 28 formed thereon is very small.

In the further course of the injection process, high-pressure fuel flows into the inner pressure space 29 between the outer needle part 22 and the inner needle part 23 via the pressure chamber inlets 30. The fuel flowing into the interior pressure chamber 29 is in contact with the annular surface 27 of the inner needle part 23 and continues to act on it in the closing direction. During the vertical movement of the outer needle part 22, the annular gap 41 enters the annular space 42 in connection. As a result, an effective in the opening direction hydraulic force at the pressure stage 28 at the combustion chamber end of the inner needle member 23 is effective, which moves this in the opening direction. As a result, the second seat 33 of the inner needle part 23 is also opened and fuel flows via the now opened second seat 33 to the second injection openings 36. When the inner needle part 23 and the outer needle part 22 are open at the same time, fuel flows from the nozzle chamber 8 via the annular gap 41 via both injection openings 35, 36 into the combustion chamber 43. The diameter of the inner needle part 23, i. the first diameter 39 is in the range between 1.5 and 2.5 mm, while the diameter of the second control chamber 20 may be between 3.5 and 5.6 mm, depending on the design of the fuel injector.

When current flows through the piezoelectric actuator 6, which is arranged in the fuel inlet 5 from the high-pressure accumulator not shown in the drawing, its piezocrystal stack expands, so that the booster piston 10 together with the translating piston extension 14 executes a closing movement acting in the direction of the combustion chamber 43. As a result, the fuel volumes contained in the first booster chamber 13 and in the second booster chamber 17 are compressed and the control chambers 19 and 20 are pressurized via the channel 16 and the overflow line 18, respectively. Since the control spaces 19 and 20 delimiting, hydraulically effective surfaces, ie the upper end face of the inner needle member 23 and Control chamber-side end face 24 of the outer needle member 22 hydraulically effective surfaces of the compression stages 25, 26 of the outer needle member 22 and the effective in the opening direction hydraulic surface π (d ₂ ² - d ₁ ² ) / 4 of the pressure stage 28 at the combustion chamber end of the inner needle member 23 exceed Both needle parts 22, 23 of the multi-part injection valve member 21 are again placed in their closed position.

LIST OF REFERENCE NUMBERS

1

fuel injector

2

injector

3

nozzle body

4

butt joint

5

Fuel supply

6

piezo actuator

7

High pressure supply line

8th

nozzle chamber

9

hydraulic translator assembly

10

Booster piston

11

first end face

12

second end face

13

first translator room

14

Intensifier piston extension

15

End of the translator piston extension

16

channel

17

second translator room

18

overflow

19

first control room

20

second control room

21

multi-part injection valve member

22

outer needle part

23

inner needle part

24

control room-side end face of 22

25

first pressure level of 22

26

second pressure level of 22

27

Ring surface inner needle part 23

28

Pressure stage inner needle part 23

29

inside pressure room

30

Pressure chamber inlet

31

Seat outer needle part

32

first seat diameter

33

Seat inner needle part

34

second seat diameter

35

first injection openings

36

second injection openings

37

Guide length outer needle part 22

38

Guide length inner needle part 23

39

first diameter inner needle part 23

41

annular gap

42

annulus

43

combustion chamber

Claims (10)

1. Fuel injector (1) for a common rail injection system for injecting fuel into a combustion chamber (43) of an internal combustion engine, having an injector body (2) and a nozzle body (3), in which an injection valve member (21) of multiple-part configuration is accommodated, and having a piezoelectric actuator (6), behind which a hydraulic transmitter arrangement (9) is connected, the injection valve member (21) of multiple-part configuration being assigned control spaces (19, 20) for its actuation, characterized in that the hydraulic transmitter arrangement (9) which is actuated by the piezoelectric actuator (6) has transmitter spaces (13, 17) which are connected hydraulically in each case directly to the control spaces (19, 20) which actuate needle parts (22, 23) of the injection valve member (21).
2. Fuel injector according to Claim 1, characterized in that the first transmitter space (13) is connected via a channel (16) to the second control space (20) for the outer needle part (22) and the second transmitter space (17) is connected to the first control space (19) for the inner needle part (23).
3. Fuel injector according to Claim 1, characterized in that a pressure space (29) which can be filled by a nozzle space (8) which surrounds the injection valve member (21) of multiple-part configuration is formed between the needle parts (22, 23) which are guided into one another of the injection valve member of multiple-part configuration.
4. Fuel injector according to Claim 1, characterized in that a first and a second compression stage (25, 26) which act in the opening direction are formed on the outer needle part (22) of the injection valve member (21) of multiple-part configuration.
5. Fuel injector according to Claims 3 and 4, characterized in that the second compression stage (26) is formed in the pressure space (29).
6. Fuel injector according to Claim 1, characterized in that a compression stage (28) is formed on the inner needle part (23) at the combustion-chamber-side end, the hydraulic surface area of which compression stage (28) which acts in the opening direction of the inner needle part (23) is smaller than the hydraulically active surfaces areas of the first and second compression stages (25, 26) of the outer needle part (23).
7. Fuel injector according to Claim 1, characterized in that those surface areas of the compression stages (25, 26) of the outer needle part (22) which act hydraulically in the opening direction exceed the hydraulically acting surface area (28) n (d₂ ² - d₁ ²) /4 at the combustion-chamber-side end of the inner needle part (23).
8. Fuel injector according to Claim 1, characterized in that a first seat (31) is formed on the outer needle part (22) and a second seat (33) is formed on the inner needle part (23), which seats (31, 33) interact with a wall of the nozzle body (3).
9. Fuel injector according to Claim 1, characterized in that the piezoelectric actuator (6) is integrated into the fuel feed line (5).
10. Fuel injector according to Claim 1, characterized in that first injection openings (35) which can be opened or closed on the nozzle body (3) by the first seat (31) in the direction of the combustion chamber (43) and second injection openings (36) which can be opened or closed by the second seat (33) are formed.

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