WO2009132878A1

WO2009132878A1 - Fuel injection system having an unrestricted fuel supply to the injectors

Info

Publication number: WO2009132878A1
Application number: PCT/EP2009/052542
Authority: WO
Inventors: Andreas Kellner; Matthias Burger; Martin Katz; Hans-Christoph Magel
Original assignee: Robert Bosch Gmbh
Priority date: 2008-04-28
Filing date: 2009-03-04
Publication date: 2009-11-05
Also published as: DE102008001423A1; EP2271836A1; EP2271836B1

Abstract

The invention relates to a fuel injection system (41) having at least one injector (1), wherein a storage space (6) is disposed in an injector body (2) in which a nozzle needle (12) is positioned. A fuel supply (8) feeds the highly pressurized fuel to an inlet space (29) via an inlet channel (7). In order to simplify a tuning of the fuel injection system (41), the inlet channel (7) communicates with a high-pressure source (9) in an unrestricted manner. The tuning of the injector with the fuel injection system is carried out via the closing throttle (32).

Description

FUEL INJECTION SYSTEM WITH UNFORESEEN FUEL ACCUMULATION TO INJECTORS

Technical area

The present invention relates to a fuel injection system of an internal combustion engine, in particular in a motor vehicle, having the features of the preamble of the claim

1.

From DE 10 2007 011 685 09.03.2007 an injector is known, which has an at least one injection hole injector body which contains a communicating with the at least one injection hole storage space for fuel. in the

Storage space is arranged a nozzle needle having at one end a needle tip for controlling a fuel injection through the at least one injection hole and the other end has a control piston. With the aid of a control device, the pressure in a control chamber can be controlled, which is axially limited by the control piston and radially by a arranged in the injector bearing sleeve, in which the control piston is axially displaced stroke. In the injector body an annular inlet space is arranged, which is bounded radially outside of the injector body and radially inward of the bearing sleeve, wherein an injector extending in the inlet passage is provided, which opens one end in the inlet space and the other end to the fuel at a high pressure providing fuel supply can be connected , At least one

Inlet throttle connects the inlet chamber throttled with the control room. In the known injector, the inlet space to the storage space is open or the supply space is in the storage space. As a result, inlet chamber and storage space are connected to each other unthrottled. The provision of such storage space within the injector body results in a reduction of pressure waves between the injector and the fuel supply to which the injector is connected. By reducing the interaction between the fuel supply and the injector, the injection processes can be realized more precisely. Especially with multiple injections, the spread of

Effectively dampen pressure waves to supply fuel.

In order to be able to tune such an injector within the fuel injection system, it is necessary in conventional fuel injection systems, to throttle the inlet channel or the connection between the injector and the fuel supply, which takes place by means of a so-called Raildrossel. However, the tuning of such a Raildrossel is only comparatively coarse possible, which affects the precision of injection operations in terms of injection quantity and injection time. The term "rail throttle" is derived from the term "common rail system", which is present when several such injectors are connected to the same fuel supply, whose "rail" by a common

High-pressure fuel line is formed, which serves as a high pressure source.

Advantages of the invention

The fuel injection system according to the invention with the features of claim 1 has the opposite advantage that the inlet channel is unthrottled connected to the high pressure fuel supply source. As a result, interactions that arise through a rail throttle can be avoided. Due to the construction according to the invention can thus be dispensed with the rail throttle. For this purpose, according to the inlet channel in

Installation condition of the injector unthrottled with the fuel supply or with its high-pressure source or high-pressure line or accumulator connected. The term "unthrottled" describes the circumstance that the inlet channel is connected to the fuel supply without a specific throttle point, so that the high pressure is applied to the inlet channel even during dynamic processes ,

Particularly advantageous is an embodiment in which the inlet channel throttled communicates with the storage space. This is achieved by at least one closing throttle, via which the inlet channel is connected to the storage space. By using at least one such closing throttle, pressure oscillations or pressure waves are transmitted only attenuated from the storage space into the inlet channel, whereby adverse interactions between the respective injector and the fuel supply can be reduced in addition to the damping effect of the large storage space. On the other hand can be dispensed with by the use of at least one such closing throttle without significant disadvantage to a rail throttle. The vote of the respective injector on the fuel injection system can then take place via the at least one closing throttle. As a result, the vote is greatly simplified. As a result, the injector according to the invention allows the implementation of

Injection processes with increased precision in terms of injection quantity and injection times.

In a particularly advantageous embodiment, the following features can be implemented cumulatively - as far as appropriate - and alternatively. The injector has a fuel port communicating with the storage space, to which a fuel supply providing the fuel under a high pressure can be connected. In the injector body, an annular inlet space is provided, which is bounded radially on the outside of the injector body and radially inward of the bearing sleeve. The aforementioned fuel connection opens in the inlet space. For this purpose, it can have a feed channel extending in the injector body. The injector has at least one inlet throttle, which throttles the inlet chamber with the control chamber. Finally, the injector has at least one closing throttle, which connects the inlet space with the storage space. As a result, the inlet space communicates more or less throttled with the storage space. By using at least one such closing throttle pressure oscillations or pressure waves are only attenuated from the storage space in the

Transfer inlet space, whereby adverse interactions between the respective injector and the fuel supply can be reduced in addition to the damping effect of the large storage space. To be able to tune such an injector within the fuel injection system, it may be necessary to throttle the inlet channel or the connection between the injector and the fuel supply, usually with a so-called Raildrossel. However, the tuning of such a Raildrossel is only comparatively coarse possible, which affects the precision of injection operations in terms of injection quantity and injection time. The term "Raildrossel" derives from the term "common rail system", which is present when several such injectors are connected to the same fuel supply, whose - A -

By using at least one such closing throttle, it is now possible to dispense with such a rail throttle The tuning of the respective injector to the fuel injection system can then take place via the at least one closing throttle. As a result, the injector according to the invention makes it possible to carry out injection processes with increased precision with regard to injection quantity and injection times.

Appropriately, the throttle effect of the closing throttle in comparison to the throttling effect of the inlet throttle is very small, so that only a slightly throttled connection between

Zulaufraum and storage space results. This makes it possible in particular to realize short closing times or high closing speeds for the nozzle needle.

According to another advantageous embodiment, the inlet space can be separated from the storage space by means of at least one sealing element. The at least one

Closing throttle surrounds the at least one sealing element. The use of such a sealing element allows a comparatively simple structure for the injector to realize therein the separate from the storage space Zulaufraum.

Further important features and advantages of the injector according to the invention will become apparent from the subclaims, from the drawing and from the associated description of the figures with reference to the drawing.

drawing

Embodiments of the fuel injection system according to the invention are shown in the drawing and are explained in more detail below.

The only Fig. 1 shows a greatly simplified principle longitudinal section through a

Injector of a fuel injection system.

Description of the embodiments According to FIG. 1, an injector 1 comprises an injector body 2, which may be assembled, for example, from a plurality of separate sections 3a, 3b, 3c and 3d. The injector body 2 has at least one injection hole 4, through which an injection of fuel into an injection space 5 can be carried out. If several spray holes 4 are provided, their arrangement is advantageously star-shaped with respect to a

Longitudinal center axis of the injector 1. The injector body 2 contains a storage space 6, which communicates with the at least one injection hole 4. Furthermore, the injector body 2 has an inlet channel 7 which extends in the injector body 2 and to which a fuel supply 8 is connected in the installed state shown. The fuel supply 8 is in the operation of the injector 1 under a high pressure fuel

Available with the aid of the injector 1 in the spray chamber 5 can be injected. For this purpose, the fuel supply 8 has a high-pressure line 9, which also serves as a high-pressure source or as an accumulator. The high-pressure line 9 is connected on the output side via a supply line 10 to the inlet channel 7 of the respective injector 1. In a so-called common rail system, a plurality of injectors 1 are separate

Supply lines 10 connected to a common high-pressure line 9. The high pressure line 9 is connected on the input side via a supply line 11 to a high pressure fuel pump, not shown here. The fuel supply 8 as well as the respective injector 1 forms part of a fuel injection system 41 of an internal combustion engine, which is otherwise not shown, in particular in a

Motor vehicle may be arranged.

The injector 1 has a nozzle needle 12, which is arranged for this purpose in the storage space 6 in a stroke-adjustable manner. In this case, the nozzle needle 12 is arranged in the storage chamber 6 so that it is enveloped by the storage space 6 substantially over its entire axial length and quasi floats in the fuel. The nozzle needle 12 has at a the at least one injection port 4 facing the end of a needle tip 13, by means of which a fuel injection through the at least one spray hole 4 is controllable. At its end remote from the at least one spray hole 4, the nozzle needle 12 has a control piston 14, which on a side facing away from the needle tip 13 a side

Control surface 15 has. As can be seen, this is a so-called "long needle", which can have, for example, a length of 100 mm or more, which is made of one piece or consists of a fixed combination of several needle parts which are suitably connected to one another Control surface 15 of the control piston 14 axially bounds a control chamber 16 which is bordered or bounded radially by a bearing sleeve 17 is. The control piston 14 is arranged in this bearing sleeve 17 axially guided hub adjustable.

In order to control the pressure in the control chamber 16, a control device 18 is provided. This control device 18 is in the region of the control piston 14 in

Injector body 2 is arranged. Without restricting the generality, the control device 18 here has an electromagnetically operating control valve 19. This has in a low-pressure chamber 20 on a valve member 21 which is actuated by means of an electromagnet 22 for carrying out a Öffhungshubs and which is driven by means of a return spring 23 in a closed position. The valve member 21 controls a throttled Verbindungsöffhung 24, which connects the control chamber 16 with the low-pressure chamber 20. In the example, the connection opening 24 is formed in a plate body 25 which separates a needle region of the injector body 2 containing the nozzle needle 12 from a control region containing the control device 18. The low-pressure space 20 communicates via a low-pressure connection 26 with a comparatively pressure-free return. The low-pressure chamber 20 is supplied via a leakage in the region of the plate body 25 between the needle region and the control region of the injector body 2. In this case, a tolerable leakage quantity passes into an annular space 27 which surrounds the control device 18 and which via at least one bore 28 with the low-pressure chamber 20 communicates.

The bearing sleeve 17 can be supported axially on the plate body 25 without being attached thereto. Likewise, the bearing sleeve 17 may be attached to the plate body 25. Also, the plate body 25 may be integrally formed with the bearing sleeve 17.

It is clear that for the control device 18 in principle also another construction can be realized, for example with a piezoelectric actuator.

In addition, an annular inlet chamber 29 is formed in the injector body 2. This is bounded radially on the outside by the injector body 2 and radially inward by the bearing body 17. In the axial direction of the feed chamber 29 is bounded on the one hand by the plate body 25 and on the other hand by an annular sealing element 30. In this inlet chamber 29, the inlet channel 7 opens. As a result, the inlet space 29 is coupled directly to the fuel supply 8 or to the high-pressure line 9. In particular, this coupling can be realized essentially unthrottled. In the consequence prevails in the Inlet chamber 29, even in highly dynamic processes substantially always the high pressure of the high pressure line 9. The injector 1 also has at least one inlet throttle 31. This creates a throttled connection between the inlet chamber 29 and the control chamber 16.

Furthermore, the injector 1 according to the invention has at least one closing throttle 32, which connects the inlet chamber 29 with the storage chamber 6. For this purpose, the closing throttle 32 bypasses the sealing element 30 in a suitable manner. In the example, the closing throttle 32 passes through the bearing sleeve 17, in particular in the radial direction. In this case, an annular space 33 is formed in the bearing sleeve 17 at a side applied by the control chamber 16 side of the control piston 14. This annular space 33 is realized, for example, by virtue of the fact that the control piston 14 has a larger diameter than the adjoining body of the nozzle needle 12. The annular space 33 is open to the storage space 6, so that ultimately the supply space 29 via the closing throttle 32 and via the annular space 33 is connected to the memory space 6.

Said annular space 33 is limited in the axial direction on the one hand by the control piston 14 and on the other hand open. In the radial direction, the annular space 33 is bounded on the outside by the bearing sleeve 17 and inside by the nozzle needle 12.

To bias the nozzle needle 12 in its closing direction, a closing compression spring 34 is provided. This is in the example on the one hand in an axial end face of the bearing sleeve 17 and on the other hand axially supported on a collar 35, wherein the collar 35 is formed or fixed to the nozzle needle 12.

Furthermore, the injector 1 has a centering sleeve 36. This is mounted axially adjustable on the needle tip 13. In this case, the centering sleeve 36 is supported axially on the one hand on the injector body 2 and on the other hand via an opening pressure spring 37 on the nozzle needle 12, for which purpose it has a further collar 38. The needle tip 13 is arranged axially displaced in the centering sleeve 36. The centering sleeve 36 realizes a centering of the needle tip 13 relative to a needle seat 39 which is formed in the injector body 2. When the nozzle needle 12 is seated with its needle tip 13 in the needle seat 39, the at least one injection hole 4 is decoupled from the storage space 6. As soon as the needle tip 13 lifts off from the needle seat 39, there is a communicating connection between the storage space 6 and the at least one spray hole 4, so that fuel from the Storage space 6 can be injected through the at least one injection hole 4 in the injection chamber 5. For an undisturbed communicating connection between the storage space 6 and the at least one spray hole 4 with the nozzle needle 12 open, the centering sleeve 36 may have at least one transverse bore 40.

By at least one closing throttle 32, the throttle effect is considerably smaller than the throttling effect of the inlet throttle 31, on the one hand ensures that pressure waves that arise when opening and closing the nozzle needle 12 in the storage space 6, only steamed or throttled get to the inlet chamber 29 and Accordingly, only steamed to reach the fuel supply 8. As a result, the already provided by the relatively large volume memory space 6 damping effect is additionally strengthened. Furthermore, it is basically possible to supply the high-pressure fuel to the inlet throttle 31 virtually unthrottled. In particular, can be dispensed with a so-called Raildrossel. The fine-tuning of the respective injector 1 with the fuel injection system can over the at least one

Closing throttle 32 can be realized. This fine-tuning can be performed more accurately than is possible in conjunction with a rail throttle. Overall, injection processes, in particular with multiple injections, can be realized with increased precision with regard to injection duration and injection quantity.

The injector 1 works as follows:

In the initial state shown, there is no fuel injection. The nozzle needle 12 is seated in the needle seat 39. In the inlet chamber 29 there is the high fuel pressure, which also prevails in the annular space 33, in the storage space 6 and in the control chamber 16. In the low pressure room

20, the pressure of the return line 26 prevails. For this purpose, the solenoid 22 is deactivated, so that the return spring 23, the valve member 21 biases for closing the Verbindungsöffhung 24.

To carry out an injection of fuel, the control device 18 is driven accordingly. As a result, the solenoid 22 attracts the valve member 21 against the biasing force of the return spring 23, whereby the connection opening 24 is opened. As a result, the pressure in the control chamber 16 drops. Consequently, the hydraulic forces acting in the closing direction on the nozzle needle 12, via the control surface 15, also decrease. Once in the direction of opening at the Nozzle needle 12 predominate effective hydraulic forces, lifts them with their needle tip 13 from the needle seat 39 from. Subsequently, fuel can enter under high pressure from the storage space 6 through the injection holes 4 in the injection chamber 5. To end the injection process, the control device 18 is actuated to close the control valve 19. For this purpose, the energization of the electromagnet 22 is stopped. As a result, the return spring 23 can drive the valve member 21 to close the communication hole 24. About the inlet throttle 31 can in the control chamber 16 again build the high pressure and retract the control piston 14 and thus the nozzle needle 12 with its needle tip 13 in the needle seat 39 via the control surface 15. This closing movement is supported by the closing compression spring 34.

The resulting during opening and closing of the injector 1 and the nozzle needle 12 pressure waves in the storage chamber 6 are attenuated on the one hand by the relatively large volume of the storage space 6 to a considerable extent. On the other hand, the closing throttle 32 causes a damped coupling between the storage space 6 and the inlet chamber 29, whereby a further damping effect can be realized.

The throttling action of the closing throttle 32 is comparatively small, as a result of which sufficient fuel can always flow in to realize the desired injection process. On the other hand, this can be fast closing operations with high

Realize needle speeds.

Claims

28.04.08ROBERT BOSCH GMBH, 70442 Stuttgart claims

A fuel injection system for an internal combustion engine, especially in a motor vehicle, comprising a fuel supply (8) comprising a high pressure source (9) providing fuel under high pressure and to which a plurality of injectors (1) are connected,

wherein the respective injector (1) is equipped with an injector body (2) having at least one injection hole (4), which contains a storage space (6) for fuel which communicates with the at least one injection hole (4),

wherein the respective injector (1) is equipped with a jet needle (12) arranged in a stroke-adjustable manner in the storage space (6), which has a needle tip (13) for controlling a fuel injection through the at least one spray hole (4),

- wherein the respective injector (1) is equipped with a control device (18) for controlling the nozzle needle (12),

- Wherein the respective injector (1) is equipped with an inlet channel (7) which is connected to the high pressure source (9), characterized in that the inlet channel (7) unthrottled with the high pressure source (5) is connected.

2. Fuel injection system according to claim 1, characterized in that the storage space (6) via at least one closing throttle (32) with the inlet channel (7) is connected.

3. Fuel injection system according to claim 1 or 2, characterized in that the nozzle needle (12) has the needle tip (13) at one end and a control piston (14) at the other end.

4. Fuel injection system according to claim 3, characterized in that the control device (18) for controlling the nozzle needle (12) has a pressure in one

Control chamber (16) controls, the axially from the control piston (14) and radially in the injector body (2) arranged bearing sleeve (17) is limited, in which the control piston (14) axially guided stroke is adjustable.

5. Fuel injection system according to claim 4, characterized in that in the injector body (2) an annular inlet space (29) is arranged, which is bounded radially on the outside of the injector body (2) and radially inwardly of the bearing sleeve (17).

6. Fuel injection system according to claim 5, characterized in that the inlet channel (7) in the injector body (2) and / or in the inlet space (29) opens.

7. Fuel injection system according to claim 5 or 6, characterized in that at least one inlet throttle (31) is provided, which throttles the inlet chamber (29) connects to the control chamber (16),

8. Fuel injection system at least according to claim 5, characterized in that the at least one closing throttle (32) connects the inlet space (29) with the storage space (6).

9. Fuel injection system at least according to claim 7, characterized in that the throttling action of the at least one closing throttle (32) is smaller than the throttling effect of the at least one inlet throttle (31).

10. Fuel injection system at least according to claim 5, characterized in that the inlet space (29) with at least one sealing element (30) from the storage space (6) is separated, wherein the at least one sealing element (30) in particular radially between the bearing sleeve (17) and the Injector body (2) can be arranged and the supply chamber (29) can limit axially.

11. Fuel injection system according to one of claims 1 to 10, characterized

- That the at least one closing throttle (32) passes through the bearing sleeve (17), and / or

- That the at least one closing throttle (32) connects the inlet space (29) with a storage space (6) open annular space (33) formed in the bearing sleeve (17) on a side facing away from the control chamber (16) side of the control piston (14) , and or

- That the control device (18) in the region of the control piston (14) in the injector body (2) is arranged, and / or

- That a centering sleeve (36) is provided, in which the needle tip (13) is arranged axially displaced and which centered the needle tip (13) relative to a in the injector body (2) needle seat (39).