EP1682769A1

EP1682769A1 - Fuel injector with a multipart, directly controlled injection valve element

Info

Publication number: EP1682769A1
Application number: EP04786717A
Authority: EP
Inventors: Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-10-18
Filing date: 2004-09-06
Publication date: 2006-07-26
Anticipated expiration: 2024-09-06
Also published as: DE502004004907D1; DE10348925A1; JP2007508487A; KR20060096049A; WO2005040595A1; JP4273153B2; US20070204837A1; ATE372457T1; EP1682769B1

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

Fuel injector with multi-part, directly controlled injection valve member

Technical field

Storage injection systems for fuel injection are used on self-igniting ner internal combustion engines, which allow the injection pressure to be set independently of the speed and load. In the memory injection systems (common rail), pressure generation and injection are locally decoupled from one another. 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 set independently of the engine speed and the injection quantity. In this fuel injection system, electrically actuated injectors take the place of pressure-controlled injection valves, the timing and duration of which determine the start of injection and the injection quantities into the combustion chambers of the internal combustion engine. Common rail injection systems offer a high degree of freedom with regard to the design and shaping of multiple or split injection processes.

State of the art

From DE-190 55 271 AI a pressure / stroke controlled injector with a hydraulic translator is known. 2/2-way control valves are accommodated in an injector housing, the vertical movement of which is mechanically coupled to one another via a bridge. The 2/2-way control valves are arranged on the inlet and outlet side and connected upstream of a hydraulic intensifier. The hydraulic translator acts on a pressure chamber surrounding a nozzle needle with fuel under high pressure. The two 2/2-way control valves are accommodated in the injector housing of the fuel injector opposite to each other.

A disadvantage of the solution known from DE 190 55 271 AI is the large number of individual parts which are required to implement a pressure / stroke-controlled injector control according to this solution. A valve for controlling liquids is known from DE 199 46 838 C1. The valve comprises a valve member which is axially displaceable in a bore of a valve body. This has a valve head forming the valve closing member, which cooperates with a seat provided on the valve body for opening and closing the valve. Furthermore, a piezoelectric unit for actuating the valve member and a tolerance compensation element for compensating elongation tolerances of the piezoelectric unit and / or other valve components are provided. With regard to its direction of action, the piezoelectric unit is arranged essentially at right angles to the axial direction of movement of the valve member and can be supplied with an electric current such that the piezoelectric unit exerts a tilting movement on an actuator serving as a lever arm and in operative connection with the valve member.

Presentation of the invention

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

The inner and the outer needle part of the multi-part injection valve member have pressure stages which, when a nozzle chamber in the nozzle body is pressurized and when the control chambers are relieved of pressure, enable the needle parts of the multi-part injection valve member to be opened at different times. As a result, a further opening cross section is released during a first phase of the injection of fuel into the combustion chamber of a self-igniting internal combustion engine via a first injection opening cross section and in the further course of the injection when the inner needle part of the multi-part injection valve member is opened later, so that towards the end of the injection process, more fuel gets into the combustion chamber than at the start of the injection process. Accordingly, only one injection cross section is released in the part-load operation of the internal combustion engine, while both needle parts of the multi-part design are released at full load of the internal combustion engine 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 set in such a way that the smallest quantity capability of the fuel injector is ensured even at the lowest pressures. Due to the formation of two pressure stages on the outer needle part of the multi-part injection valve member, the latter opens very early, whereas the inner needle part of the multi-part injection valve member opens later, since the pressure stage designed thereon is designed to be very small. Due to this design of the two pressure stages on the outer needle part and the pressure stage on the inner needle part, it 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

The invention is explained in more detail below with the aid of the drawing.

The single figure shows a section through the fuel injector proposed according to the invention with a multi-part, needle-shaped injection valve member and a hydraulic translation arrangement via the translation spaces of which control spaces are assigned to the inner or outer needle part of the multi-part injection valve, which can be depressurized or pressurized.

variant

The force of 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 rest in the assembled state. a butt joint 4 to each other. The fuel flows to the injector body 2 via a high-pressure storage space (common rail), not shown in the drawing, of a high-pressure accumulator injection system via a fuel inlet 5. In the upper area of the injector body 2, an actuator 6 is accommodated, to which a hydraulic transmission device 9 is assigned. A high-pressure feed line 7 branches off from the fuel feed 5 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 accommodated in the nozzle body 3 so as to be movable in the vertical direction.

The hydraulic booster device 9 comprises a booster piston 10. The booster piston 10 has a first end face 11, which lies opposite the actuator 6. A second end face 12 of the booster piston 10 delimits a first booster chamber 13 of the hydraulic booster device 9. A booster piston extension 14 is located on the booster piston 10, which extension is made smaller in comparison to the diameter of the booster piston 10. An end face 15 of the translator piston extension 14 projects into a second translator space 17. A channel 16 extends from the second translator room 17 and opens into a first control room 19. An overflow line 18 runs parallel to the channel 16, via which the first booster chamber 13 and a second control chamber 20 are hydraulically connected to one another.

The multi-part, needle-shaped injection valve member 21 has an outer needle part 22 and an inner needle part 23 movably arranged therein. The inner needle part 23 is acted upon by the first control chamber 19, which is connected to the second translator chamber 17 of the hydraulic transmission arrangement, while the outer needle part 22 via the second control chamber 20, which is connected to the first transmission chamber 13 via the overflow line 18, is operated. The outer needle part 22 has an end face 24 on the control chamber side delimiting the second control chamber 20, as well as a first pressure stage 25 on the outside and a further, second pressure stage 26, which is formed on the inside of the outer needle part 22. A pressure chamber 29 is formed between the outer needle part 22 and the inner needle part 23 and is delimited by an annular surface 27 formed on the inner needle part 23. The internal pressure chamber 29 is acted upon via pressure chamber inlets 30 which penetrate the wall of the outer needle part 22. Through the pressure chamber inlets 30, an overflow of fuel, which flows into the nozzle chamber 8 under high pressure, into the inner pressure chamber 29 between the outer needle part 22 and the inner needle part 23 is ensured.

At the combustion chamber end of the outer needle part 22, a seat 31 is formed on its 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 second seat 33, which also cooperates with the wall of the nozzle body, is formed. The seat diameter of the seat 33 of the inner needle part 23 is formed in a second seat diameter 34 (d) which is considerably smaller than the first seat diameter 32 of the outer needle part 22. In the closed state shown in the drawing of the multi-part injection valve member 21, first injection openings 35 are separated by the closed seat 31 of the outer needle part 22 from an annular gap 41, in which fuel under high pressure is present via the nozzle chamber 8. Due to 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 also closed against the fuel under high pressure which is present in the annular gap 41. In the closed state of the multi-part, needle-shaped injection valve member 21 shown in the drawing, a wedge-shaped annular space 42 is formed between the seat 31 of the outer needle part 22 and the seat 33 of the inner needle part 23. The combustion chamber, in which fuel is injected either through the first injection openings 35 or through the opened first and second injection openings 35, 36 when the multi-part injection valve member 21 is open, is identified by reference numeral 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 part 23 in a guide length 38, which extends between the pressure chamber inlets 30 of the outer needle part 23 and its seat 31 in this body 3 , is limited. Even if not shown in detail in the drawing, the outer needle part 22 in the nozzle body 3 can also be guided in a plurality of guide surfaces, for example offset by 120 °.

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

Due to the diameter ratio of d _\ : d ₂ with d _! <d ₂ , the inner needle part 23 of the multi-part, needle-shaped injection valve member 21 opens later than its outer needle part 22. The pressure stage 28 generated by the diameter difference d - d _t on the inner needle part 23, lying on its tip on the combustion chamber side, has one in comparison to that Pressure levels 25, 26 have a significantly lower hydraulically effective area.

The mode of operation of the fuel injector 1 proposed according to the invention as shown in 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 piezo actuator, its piezo crystals, which are arranged one above the other in the form of a stack, lengthen and consequently act on the booster piston 10. Its second end face 12 moves into the first booster chamber 13. Through the second end face 12 of the booster piston 10, the booster piston extension 14 has also moved into the second booster chamber 17 of the hydraulic booster arrangement 9. The first translator space 13 and the second translator space 17 are filled via the guide leakage between the outer needle part 22 and the nozzle body 3, the guide leakage between the inner needle part 23 and the injector body 2 and the guide leakage between the translator piston 10 and the fuel feed 5.

Due to the pressurization of the first translator chamber 13 and the second translator chamber 17, the first control chamber 19 acting on the inner needle part 23 and the second control chamber 20 acting on the outer needle part 22 are also pressurized, so that the inner needle part 23 and the outer needle part 22 are in their the seats 31 and 33 are closed positions.

Since simultaneously high-pressure fuel is present in the nozzle chamber 8 via the high-pressure supply line 7, and thus also in the annular gap 41 connected to it and surrounding the outer needle part 22, the fuel only reaches the closed seat 31 of the outer needle part 22 and cannot enter the combustion chamber 43 are injected.

If the current supply to the actuator 6 is released, the lengthening of the piezo crystals decreases and the booster piston 10 together with the booster piston extension 14 moves upwards in the vertical direction. The stroke of the booster piston 10 or the booster piston extension 14 is in the range between 40 and 160 μm.

Accordingly, the first control chamber 19, which acts on the inner needle part 23 and the second control chamber 20, which acts on the end face 24 of the outer needle part 22 on the control chamber side, is relieved of pressure. Due to the high fuel pressure which is present in the nozzle chamber 8, the outer needle part 22 opens earlier, since 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 de-energization of the actuator 6, the end face 24 of the outer na delteiles 22 in the second control chamber 20, whereby the seat 31 of the outer needle part 22 is opened. As a result, the annular space 42 comes into connection with the annular gap 41, in which fuel under high pressure is present. The fuel under high pressure 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 part 23 of the multi-part, needle-shaped injection valve member 21 remains in its closed position, ie. H. the seat 33 of the inner needle part 23 remains closed. In the further course of the injection process, the inner needle part 23 of the multi-part injection valve member 21 opens, since the drainage step 28 formed thereon is made very small.

In the further course of the injection process, fuel under high pressure flows through the pressure chamber inlets 30 into the internal pressure chamber 29 between the outer needle part 22 and the inner needle part 23. The fuel flowing into the internal 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 ascending movement of the outer needle part 22, the annular gap 41 comes into contact with the annular space 42. As a result, a hydraulic force acting in the opening direction becomes effective at the pressure stage 28 at the end of the inner needle part 23 on the combustion chamber side, which moves the latter in the opening direction. As a result, the second seat 33 of the inner needle part 23 is also opened and fuel flows through the now open second seat 33 to the second injection openings 36. When the inner needle part 23 and outer needle part 22 are open at the same time, fuel flows from the nozzle space 8 through the annular gap 41 into the combustion space 43 via both injection openings 35, 36. The diameter of the inner needle part 23, i.e. the first diameter 39 is in the range between 1.5 and 2.5 mm, while the diameter of the second control chamber 20 can be between 3.5 and 5.6 mm, depending on the design of the fuel injector.

When the piezo actuator 6 is energized, which is arranged in the fuel inlet 5 of the high-pressure accumulator (not shown in the drawing), the stack of piezo crystals expands, so that the booster piston 10 together with the booster 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 converter chamber 13 and in the second converter chamber 17 are compressed and the control chambers 19 and 20 are pressurized via the channel 16 and the overflow line 18. Since the hydraulically effective surfaces delimiting the control spaces 19 and 20, ie the upper end face of the inner needle part 23 and Front surface 24 of the outer needle part 22 on the control chamber side hydraulically effective areas of the drainage stages 25, 26 of the outer needle part 22 and the hydraulic surface area π (d ² - di ² ) / 4 of the pressure stage 28 on the combustion chamber end of the inner needle part 23, both of which will be effective Needle parts 22, 23 of the multi-part injection valve member 21 are returned to their closed position.

LIST OF REFERENCE NUMBERS

Fuel injector 34 second seat diameter injector body 35 first injection orifices nozzle body 36 second injection orifices butt joint 37 guide length outer needle part 22 fuel inlet 38 guide length inner needle part 23 piezo actuator 39 first diameter inner needle part 23 high pressure feed line nozzle space 41 annular gap hydraulic translator arrangement 42 annular space translator piston 43 combustion chamber first end face second face face second translation space Translator piston extension channel second translator chamber overflow line first control chamber second control chamber multi-part injection valve member outer needle part inner needle part control chamber end face of 22 first pressure stage of 22 second pressure stage of 22 annular surface inner needle part 23 pressure stage inner needle part 23 inner pressure chamber pressure chamber inlet seat outer needle part first seat diameter seat inner needle part

Claims

claims

1. Fuel injector (1) for a storage injection system for injecting fuel into a combustion chamber (43) of a crimping engine, with an injector body (2) and a nozzle body (3), in which a multi-part injection valve member (21) is received and with a piezo actuator (6), which is followed by a hydraulic translator arrangement (9), wherein the multi-part injection valve member (21) is assigned control rooms (19, 20) for its actuation, characterized in that the hydraulic translator arrangement actuated by the piezo actuator (6) (9) Translator rooms (13, 17) which are each hydraulically connected directly to the needle parts (22, 23) of the injection valve member (21) actuating control rooms (19, 20).

2. Fuel injector according to claim 1, characterized in that the first translation space (13) via a channel (16) with the second control space (20) for the outer needle part (22) and the second translation space (17) with the first control space (19) for the inner needle part (23) are connected.

3. Fuel injector according to spoke 1, characterized in that a pressure chamber (29) is formed between the needle parts (22, 23) of the multi-part injection valve member, which can be filled by a nozzle chamber (8) surrounding the multi-part injection valve member (21) ,

4. Fuel injector according spoke 1, characterized in that a first and a second pressure stage (25, 26) acting in the opening direction are formed on the outer needle part (22) of the multi-part injection valve member (21).

5. Fuel injector according to claims 3 and 4, characterized in that the second pressure stage (26) is formed in the pressure chamber (29).

Fuel injector according to claim 1, characterized in that a pressure stage (28) is formed on the inner needle part (23) at the end of the combustion chamber, the hydraulic surface of which is smaller in the opening direction of the inner needle part (23) is the hydraulically effective surfaces of the first and second pressure stage (25, 26) of the outer needle part (23).

7. Fuel injector according to claim 1, characterized in that the hydraulically effective surfaces of the pressure stages (25, 26) of the outer needle part (22) in the opening direction have the hydraulically active surface (28) π (d ₂ ² - di ² ) / 4 climb over at the brake chamber end of the inner needle part (23).

8. Fuel injector according to spoke 1, characterized in that on the outer needle part (22) a first seat (31) and on the inner needle part (23) a second seat (33) are formed, which with a wall of the nozzle body (3) interact.

9. Fuel injector according to spoke 1, characterized in that the piezo actuator (6) is integrated in the fuel inlet (5).

10. Fuel injector according to spoke 1, characterized in that in the direction of the combustion chamber (43) on the nozzle body (3) through the first seat (31) releasable or closable first injection openings (35) and through the second seat (33) releasable or closable second Injection openings (36) are formed.