EP1771651A1

EP1771651A1 - Fuel injector comprising a direct multi-stage injection valve member control system

Info

Publication number: EP1771651A1
Application number: EP05749972A
Authority: EP
Inventors: Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-07-21
Filing date: 2005-05-13
Publication date: 2007-04-11
Anticipated expiration: 2025-05-13
Also published as: DE502005008285D1; DE102004035280A1; ATE445096T1; JP2008506888A; EP1771651B1; WO2006008200A1; US20080093483A1

Abstract

A fuel injector having an injection valve member for injecting fuel into the combustion chamber of an autoignition internal combustion engine. The injection valve member is directly controllable by means of an actuator that directly actuates a pressure booster, which is able to influence the pressure in a control chamber that acts on the injection valve member. The pressure booster has a first booster piston and a second booster piston coupled to each other by means of a driver that is able to move between a first stop side and a second stop side inside a recess.

Description

Fuel injector with direct multi-stage injection valve member activation

Technical area

On modern, self-igniting Verbrennungskraflmaschinen come today in addition to pump-nozzle fuel injection systems and high-accumulation memory injection system (common raü) are used. In high-bay storage injection systems, the individual fuel injectors assigned to the cylinders of the internal combustion engine are supplied with fuel from a high-pressure accumulator (common rail). The fuel injectors can be operated either via solenoid valves or via piezo actuators. If the fuel injectors are actuated via piezoactuators, an injection valve member which can be actuated directly via the piezoactuator can be realized.

State of the art

From DE 697 20 145 C2 an injection valve member is known. The injection valve comprises a

> Valve needle, which is tensioned against a seat surface by a spring located inside a spring chamber. The spring is embedded between a spring abutment, which is in communication with the valve needle and a movable stop. There is a restricted flow path through which fuel can flow from the spring chamber at a limited rate or in a limited amount. The injector further includes a valve including a movable stop surface, which valve may be actuated during operation of the injector such that fuel may exit the spring chamber at a second, higher rate. The valve is formed by a seat surface which is formed around an opening communicating with the spring chamber, wherein the movable stop can come into abutment with the seat surface so that the fuel flow through the opening can be controlled. The movable stop can be designed to be movable under the action of the fuel pressure within a pump chamber.

In order to be able to open the injection valve member in the case of fuel injectors with direct controllability of the injection valve member via an actuator, the actuator must overcome a high opening force. The high required opening force to apply through the actuator is, finds its cause in that the nozzle needle-shaped injector member formed with system pressure (pressure level in the high-pressure reservoir common rail) acted upon, is pressed in sei¬ nen seat. The force required to open the injection valve member from its seat is on the order of several hundred N, for example about 400 N. In order to ensure sufficient fuel flow with the injection valve member fully open through the injection openings into the combustion chamber of a self-igniting internal combustion engine , It is also necessary that the injection valve member a maxi¬ male walk of several 100 microns, for example in the order of 200 microns and 300 microns, performs. Said variables, ie the force of several 100 N required for opening the injection valve member, and the maximum representable stroke of the injection valve member from its fully closed position to its fully open position, are essentially the determining parameters for the size of a fuel injector integrating piezoelectric actuator. Although the length-Z diameter ratio of the piezoactuator can be varied by integrating a hydraulic ratio, the size of the actuator, also referred to as the actuator volume, is essentially proportional to the opening force to be applied and the maximum stroke travel of the needle-shaped injection valve member to be represented.

In solutions known from the prior art, the high required ratio of 1: 3-4 disadvantageous, which is necessary to control the stroke of the injection valve member in the required limits, since due to the high transmission ratio, the size of a piezoelectric actuator increases significantly.

Presentation of the invention

According to the invention, it is proposed to provide a control possibility for an injection valve member by means of a multi-stage, for example a two-stage transmission, which avoids the disadvantages listed above. By means of the solution according to the invention, an injection rate shaping can be represented, which is characterized in the lower partial stroke range of the injection valve member by a 1: 1, 5 times translation and thus offers a precisely fast and, in particular, stable activation option. In the upper stroke region of the injection valve member, the transmission ratio is at a higher level, e.g. 1: 4-7.

The division of the transmission ratio for a lower partial stroke range of the injection valve member and for the upper partial displacement range of the injection valve member can advantageously be realized in that a multi-stage pressure converter within a fuel injector comprises two pistons guided one inside the other coupled to a driver. The driver engages in a recess of a One of the piston, which is so dimensioned that the driver only a äb a certain partial stroke an outer, slidably mounted on an inner booster piston Über¬ setting piston takes. The ratio in the lower Teilhubbereich is given by the diameter ratio di to d ₂ , ie the diameter ratio between the diameter of the head portion of the injection valve member and the diameter of an internally arranged anordinary booster piston, while the effective in the upper Teilhübbereich Ein¬ injection valve member gear ratio by the diameter ratio d _! to d ₃ , ie the diameter of the head portion of the injection valve member and the Außen¬ diameter of a second booster piston is given, which is coupled via the aforementioned driver with the first booster piston.

drawing

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

The single FIGURE shows a section through a fuel injector with a multi-stage controllable directly actuated nozzle needle-shaped injection valve member.

variants

The FIGURE shows a fuel injector 1 which comprises an injector body 2, a washer 3 and a nozzle body 4. The injector 2 and the nozzle body 4 are screwed together by means of a nozzle lock nut 5; Before screwing the injector body 2 and the nozzle body 4, the washer 3 is applied to the nozzle body 4, which has at least two flow channels 26 and 40, which will be described in more detail below.

In addition, the fuel injector 1 comprises a needle-shaped injection valve member 6 which can be configured in one or more parts and with which injection rates, not shown in the drawing, formed on the combustion chamber end of the fuel injector 1, can be closed or released.

The intermediate disk 3 between the injector body 2 and the nozzle body 4 comprises an upper end face 7 which assigns a lower end face of the injector body 2 and a lower end face 8 which assigns the upper end face of the nozzle body 4.

In addition, a cavity 9 is formed in the injector body 2 of the fuel injector 1, in which an actuator 39 is formed which, for example, can be formed as a piezoelectric crystal from a piezocrystal. Stack constructed piezoelectric actuator can be formed. A fuel inlet 10 opens into the cavity 9 from a high-pressure accumulator (common rail), not shown in the drawing, in which fuel stored at system pressure is stored. Via the fuel inlet 10, this fuel, which is under system pressure (rail pressure), enters the hollow space 9 and flows from it along a multi-stage pressure booster 12 received in the fuel injector 1 to the channel 40 of the intermediate disk and from there into the nozzle body 4 ,

In the cavity 9 of the fuel injector 1 of the multistage pressure intensifier 12 is arranged. The multistage pressure booster 12 comprises a first booster piston 13 and a second booster piston 14 surrounding the first booster piston 13 and guided thereon. The first booster piston 13, formed in diameter (k), comprises a groove 30 for a ring-shaped driver 20, which fits into a The recess 19 in the second booster piston 14 is bounded by a first stop side 21 and a second stop side 22.

The outer, second booster piston 14 has an end face 16 which is acted upon by a spring element 15 which can be embodied as a spiral spring, which is supported on a support disk 11 formed below the piezoactuator 39, which undergoes a vertical movement when the actuator 39 is energized. The support disk 11 is supported by a pipe spring 17, which is supported with its end opposite the support disk 11 on the upper plane surface 7 of the intermediate disk 3. By means of the tubular spring 17, the support disk 11 is set in its rest position when the energization of the piezocrystal stack of the actuator 39 is canceled. The tubular spring 17 between the support plate 11 and the upper end surface 7 of the washer 3 surrounds a stop sleeve 18. The stop sleeve 18 extends below a shoulder of the second booster piston 14 and surrounds a spring 28, a control chamber 25 defining a first control chamber sleeve 27 to the upper Plane 7 of the washer 3 of the fuel injector 1 hires. The spring 28 is permanently tensioned due to the pressure prevailing in the cavity 9 fuel pressure, so that it is ensured that the first control chamber sleeve 27 is always employed with its formed on the underside biting edge 29 against the upper end face 7 of the washer 3, so that the STEU ¬ Erraum 25 is sealed. From the control chamber 25, the fuel contained in this and corresponding to the retraction movement of the first booster piston 13 and the second booster piston 14 or both pistons in the control chamber 25 corresponding compressed over the channel 26 flows below the lower end surface 8 of the washer 3 hydraulic space, the one head 31 of the needle-shaped Injektventil¬ member 6 hydraulically acted upon. The control chamber 25 is acted on the one hand by the upper end face 7 of the intermediate disc 3 and on the other hand both from the end face 23 of the first booster piston 13 and from the end face 24 of the second booster piston 14.

The needle-shaped injector member 6, which is arranged in the manner of a needle and is arranged below the intermediate disk 3, has a head 31 which is formed in a diameter di. Compared to this diameter di, the second booster piston 14 has an outer diameter d ₃ , which exceeds both the diameter 0 ^* _{2 of} the first booster piston 13 and the head diameter d _{x of} the needle-shaped injection valve member 6. The hydraulic space between the lower planar surface 8 of the intermediate disc 3 and the upper end face of the needle-shaped injection valve member 6 is delimited by a second control chamber sleeve 32. The second control chamber sleeve 32 in turn is acted upon by a spring 33, which is supported on a support ring 34 which can be shrunk onto the peripheral surface of a needle-shaped injection valve member 6, ie by means of a press fit with the lateral surface of the needle-shaped injection valve member 6 connected is. Below the support ring 34, two or more free surfaces 36 are arranged on the circumference of the nadei¬ shaped injection valve member 6, via which fuel as seen in the flow direction 38 flows to an annular gap 37. Below the annular gap 37 between the needle-shaped injection valve member 6 and the nozzle body 4 are not shown in the drawing EinspritzöfF- calculations at the combustion chamber end of the fuel injector. 1

Depending on the design of the needle-shaped injection valve member 6, the free surfaces 36 can each be 120 °, in the case of the formation of three flow relief surfaces 36 or at an angle of 90 °, in the case of the formation of four flow relief surfaces 36 on the needle-shaped injection valve member 6 be oriented to each other.

In the closed state of the injection valve member 6, the piezocrystal stack of the actuator 39 is energized and thus elongated in the vertical direction. Accordingly, the support plate 11 is deflected in the vertical direction downwards and acts on the tube spring 17, so that it is biased against the vertical stroke direction of the actuator 39. Due to the energization of the piezocrystal stack of the actuator 39, both the first booster piston 13 and the second booster piston 14 of the multistage pressure booster 12 are retracted into the control chamber 25. In this, therefore, there is an increased pressure which acts on the hydraulic space above the Kop¬ fes 31 of the needle-shaped injection valve member 6 via the channel 26 in the washer 3. If the energization of the actuator 39 is now withdrawn, the piezocrystal stack of the actuator 39 contracts and its elongation in the vertical direction decreases. Due to the pre-tensioned tubular spring 17, the support disk 11 moves in the vertical direction in accordance with the Reduction of the elongation of the piezocrystal stack of the actuator 39 upwards, so that the first booster piston 13 with its the control chamber 25 facing end face 23 exit from the control chamber 25, whereby there the pressure decreases. Due to the pressure drop in the control chamber 25 and its hydraulic connection to the hydraulic space above the head 31 of the needle-shaped injection valve member 6 and the needle-shaped injection valve member 6 moves up and the Einspritzöffhungen be freigege ben. Within the sketched Teilhubbereiches the multi-stage trained Druck¬ translator 12 operates with a transmission ratio of 1: 1-1.5. The transmission ratio within the sketched Teilhubbereiches is defined by the diameter di / d ₂ , wherein di di denotes the diameter of the head 31 of the needle-shaped injection valve member 6 and d ₂ denotes the outer diameter of the first booster piston 13 of the multi-stage pressure booster 12. On account of the transmission ratio of 1: 1-1.5, which is effective in this partial stroke range, rapid, precise and stable opening of the injection openings formed on the combustion chamber end of the fuel injector 1 can take place.

If there is a further reduction in the energization of the actuator 39, its piezoelectric crystal stack continues to contract, ie its elongation in the vertical direction is further reduced. As a result, the first booster piston 13, with its end face 23 acting on the control chamber 25, also moves further and further out of the control chamber 25. If the upper side of the ring-shaped driver 20 strikes a first stop side 21 of the recess 19 in the second booster piston 14, the second booster piston 14, which is slidably received on the circumference of the first booster piston 13, is moved after overcoming the stroke designated by hi. taken up by the driver. As a result, the ring-shaped end face 24 of the second booster piston 14, which likewise acts on the control chamber 25, continues to move out of this. After overcoming the stroke hi, the multi-stage pressure converter now operates with a second transmission ratio of 1: 4 -7, which is defined by the diameter ratio of is defined. With di is - as already mentioned above - the head diameter of the head 31 of the needle-shaped injection valve member 6 denotes, while d ₃ denotes the outer diameter of ver¬ displaceably movable on the first booster piston second booster piston 14. As a result of the end surfaces 23 and 24 extending from the control chamber 25 from above, the pressure in the control chamber 25 decreases faster compared to the state in which only the end face 23 of the first booster piston 13 leaves the control chamber 25. Due to this, a complete opening of the needle-shaped injection valve member 6 can be achieved by a small actuator stroke by moving a larger hydraulic surface (23 +24), which is important in the full load range of the internal combustion engine. If, however, the crystal stack of the piezoelectric actuator 39 is energized again, then an elongation of this crystal stack corresponding to the energization level of the piezocrystal stack sets in, whereby the support disk 11 is compressed against the action of the tubular spring 17, which is supported on the upper planar surface 7 of the intermediate disk 3. The tube spring 17 surrounds the stop sleeve 18, which in turn engages with its upper edge a shoulder on the outer circumference of the second booster piston 14 and defines its basic position. If the support disk 11 travels downwards in a vertical direction due to the elongation of the piezocrystal stack of the actuator 39, the inner, first booster piston 13 is first moved with its end face 23 into the control chamber 25 and, as soon as the lower side of the driver 20 on the second stop side 22 of the recess 19 abuts - and the second booster piston 14 is moved to its normal position, which is defined by the stop sleeve 18, which is also supported on the upper end face 7 of the washer 3.

Via the inlet 10, fuel that is under system pressure (rail pressure) enters the cavity 9 in the injector body 2 and flows via the channel 40 provided in the washer 3 to the nozzle body 4. Due to the action of the biting edges 29 on the first control chamber sleeve 27 and the biting edge 35 of the second control chamber sleeve 32, the control volume received in the control chamber 25 and in the hydraulic space above the head 31 of the needle-shaped injection valve member 6 is from the injection valve member 6 separated flowing fuel.

The fuel flows into the nozzle body 4 via the channel 40 and enters into an annular gap 37 via the free surface 36 provided on the circumference of the needle-shaped injection valve member 6 which defines between the outer circumference of the needle-shaped injection valve member 6 and the inside of the nozzle body 4 is. The fuel volume flowing in the flow direction 38 flows to the injection openings formed at the combustion chamber end of the fuel injector 1 and, via this, when the injection valve member 6 is open or only partially opened, enters the combustion chamber of the self-igniting internal combustion engine.

The proposed solution according to the invention is characterized in particular by the fact that in the first Teilhubbereich the needle-shaped injection valve member 6 opening the needle-shaped injection valve member with a high rigidity, effected by the small ratio of 1: 1-1.5, realized between Aktorhub and injection valve member can be. As a result, the opening of the injection chamber arranged on the combustion chamber side in the first partial lift region of the injection valve member is controlled, ie, occurring due to the needle-shaped injection valve member 6 opening too fast Volume jumps with regard to the amount of fuel introduced into the combustion chamber are avoided, so that the production of soot in combustion recedes to a considerable extent. Due to the common after reaching the Teilhύbes hi Druckentlastungsbewe¬ tion of the two booster piston 13, 14 of the multi-stage pressure booster 12, a higher ratio between 1: 4-7 of the multilevel Druck¬ translator 12 then turns on when the partial stroke hi is overcome in Öfmungsrichtung , In this way, a further opening of the needle-shaped injection valve member 6 with a larger ratio can be effected by a small actuator stroke since the end faces 23 and 24 are moved together.

Due to the proposed solution according to the invention, in contrast to the solutions known from the prior art Aktorbauvolumen can be significantly reduced. By the two partial strokes of the needle-shaped Einspritzventilglie¬ 6 corresponding ratios of 1: 1-1.5 in the first Teilhubbereich and 1: 4-7 in the next Teilhubbereich can be a shaping of the injection curve in the combustion chamber of the self-igniting internal combustion realize, insbesonde ¬ re the requirement is taken into account that the nadeiförmig trained Einspritzven¬ tilglied 6 controlling actuator 39 space as possible to accommodate in the cavity 9 of the fuel injector 1 ¬.

LIST OF REFERENCE NUMBERS

1 fuel injector

2 injector bodies

3 washer

4 nozzle body

5 nozzle retaining nut

6 injection valve member

7 upper plane

8 lower plane

9 cavity

10 fuel intake (from common rail)

11 support disk

12 multi-stage intensifier

13 first booster piston

14 second booster piston

15 Spring element for first booster piston

16 end face of the second booster piston 14th

17 Bourdon tube

18 stop sleeve

19 recess

20 driver h _x forward lift driver 20

21 first stop side recess 19

22 second stop side recess 19

23 end face of the first booster piston 13

24 front side second Überseizerkolben 14th

25 control room

26 channel

27 first control chamber sleeve

28 spring

29 biting edge v. 27

(I ₁ head diameter injection valve member 6 d ₂ diameter of the first booster piston 13 d ₃ diameter of the second booster piston 14

30 Aufhahmemit for drivers 20

31 head injection valve member 6

32 second control chamber sleeve feather

support ring

Biting edge v. 32

Open spaces (120 °, 90 °)

annular gap

Flow direction fuel

actuator

Claims

claims

1. Fuel injector with an injection valve member (6) for injecting fuel into the combustion chamber of a self-igniting internal combustion engine, wherein the Ein¬ injection valve member (6) via an actuator (39) can be controlled, which directly actuates a pressure booster (12), with which the pressure in a the injection valve member (6) beauf- striking control chamber (25) can be influenced, characterized in that the

Pressure intensifier (12) has a first and a second booster piston (13,14) auf¬ has, via a within a recess (19) between a first Anschlag¬ page (21) and a second stop side (22) movable cam (20) coupled are.

2. KraflstofEnjektor according to claim 1, characterized in that the second Über¬ setting piston (14) of the multi-stage pressure booster (12) slidably on the first, in¬ nenliegenden booster piston (13) is mounted.

3. Fuel injector according to claim 1, characterized in that a zerkolben the Überset¬ (13, 14) associated transmission element (11) by a in the Injektor¬ body (2) supporting tubular spring element (17) is acted upon

4. Fuel injector according to claim 1, characterized in that within a first Teilhubbereiches the needle-shaped injection valve member (6), which corresponds to a pre-stroke hi, upon withdrawal of the energization of the actuator (39) of the first booster piston (13) from the control chamber (25) extending.

5. Fuel injector according to claim 1, characterized in that after exceeding the one Vorhub hi corresponding first Teilhubbereiches the needle-shaped aus¬ formed injection valve member (6) of the driver (20) the second booster piston (14) from the control chamber (25) together with the first booster piston (13) moves.

6. Fuel injector according to claim 1, characterized in that the Vorhüb hi the distance of a plan side of the driver (20) from a first stop side (21) of a

Recess (19) on the second booster piston (14) corresponds.

7. Fuel injector according to claim 1, characterized in that either via the end face (23) of the first booster piston (13) or via the end faces (23, 24) the control chamber (25) which can be acted upon by the first booster piston (13) and the second booster piston (14) is hydraulically connected via a hydraulic channel (26) to a hydraulic space above a head region (31) of the needle-shaped injection valve member (6).

8. fuel injector according to claim 7, characterized in that both the Steuer¬ space (25) and the hydraulic space above the needle-shaped Ein¬ injection valve member (6) via spring-loaded control chamber sleeves (27, 32) are limited.

9. fuel injector according to claim 8, characterized in that the first Steuer¬ space sleeve (27) on a biting edge (29) on an upper plane surface (7) of a Zwischen¬ disc (3) of the fuel injector (1).

10. Fuel injector according to claim 8, characterized in that the second control space sleeve (32) with its biting edge (35) on the lower end face (8) of a Zwischen¬ disc (3) of the fuel injector (1).

11. Fuel injector according to claim 1, characterized in that the first control erraumhülse (27) to the upper end face (7) of the intermediate disc (3) adjusting spring

(28) on an annular shoulder of the first booster piston (13) slidably mounted second booster piston (14) rests.

12. Fuel injector according to claim 1, characterized in that an end face (16) of the second booster piston (14) of the multi-stage pressure booster (12) via a

Spring element (15) is acted upon, which in turn is supported on the transmission element (11) below the piezoelectric actuator (39).