WO2007147667A1

WO2007147667A1 - Fuel injection device for an internal combustion engine

Info

Publication number: WO2007147667A1
Application number: PCT/EP2007/054146
Authority: WO
Inventors: Hans-Christoph Magel
Original assignee: Robert Bosch Gmbh
Priority date: 2006-06-23
Filing date: 2007-04-27
Publication date: 2007-12-27
Also published as: DE102006028918A1; EP2035685A1

Abstract

Disclosed is a fuel injection device (10) for an internal combustion engine, comprising at least one injection valve element (24) which delimits a hydraulic control chamber (38) and can open or block fuel discharge ducts (30). Additionally, a control valve (64) is provided for influencing the pressure in the hydraulic control chamber (38). According to the invention, a control valve element (66) of the control valve (64) is at least essentially pressure-compensated.

Description

description

title

Fuel injection device for an internal combustion engine

State of the art

The invention relates to a fuel injection device for an internal combustion engine according to the preamble of claim 1.

For introducing fuel into the combustion chambers of direct-injection diesel engines

Internal combustion engines are increasingly used stroke-controlled common rail systems. Their advantage lies in the fact that the injection pressure can be adapted to load and speed. In such controlled systems fuel injectors are used, which include an injection valve element which is hydraulically controlled by the pressure in a hydraulic control chamber. Via the injection valve element, fuel outlet channels can be connected to or disconnected from a high-pressure connection. To control the pressure in the hydraulic control chamber, an electromagnetic control valve is used, which has a ball as a control valve element. When the control valve is open, the hydraulic control chamber connected to the high-pressure port via an inlet throttle is connected to a low-pressure port, whereby the pressure in the hydraulic control chamber drops.

Disclosure of the invention

Technical task

The present invention has the object to provide a fuel injection device of the type mentioned, with the very short multiple injections are possible. At the same time, the fuel injection device should be inexpensive and compact.

Technical solution

This object is achieved by a fuel injection device having the features of claim 1. Advantageous developments of the invention are specified in subclaims. In addition, find essential features of the invention in the following description and the drawings. In this case, the features may also be essential for the invention in completely different combinations without explicit reference being made thereto.

Advantageous effects

The use of a separate valve piece facilitates in manufacture the introduction of the control chamber and / or the control valve chamber and the corresponding guides for the

Control valve member. As a result, the production costs are reduced. Since the injection valve element is received in a generally associated with the high-pressure port receiving space, a pressure stage on the injection valve element is not required, as was previously provided for generating a hydraulic force acting in the opening direction. By being able to dispense with such a pressure level, an otherwise existing leakage line can be omitted, which dissipates the inevitably occurring at such a pressure level leakage fluid. Thus, the structure of the fuel injection device is again significantly simplified.

A particularly advantageous embodiment of the fuel injection device according to the invention is characterized in that the valve member in the region of the guide of the control valve element radially outside at least partially, for example, in an extension-like portion, is surrounded by an annular space which is constantly connected to the high pressure port. As a result, widening of the guidance of the control valve element is counteracted by the high pressure transferred from the high pressure, whereby a very small leakage through this guide can be realized. Especially when the leadership of the control valve element and the hydraulic control chamber and the control valve chamber and / or other high-pressure channels and spaces are arranged in this area surrounded by high pressure, the load is reduced to the valve piece, which allows a compact design and its Improved sealing function.

In addition to the guidance of the control valve element, the valve piece can also take over the guidance of an end region of the injection valve element. Since the valve piece is a separate part, and the guide for the injection valve element can be introduced with high precision and cost.

To reduce the assembly costs, it is advantageous if the valve piece is in one piece. However, the manufacturing is simplified if the valve piece is multi-piece with a first part valve piece and a second part valve piece, as this accessibility to the control valve chamber and the hydraulic control chamber and the control valve seat is improved. For sealing the one part of the valve piece with respect to the other part valve piece, an additional seal or a sealing edge may be provided. Also, the two part valve pieces can be centered to each other by means of a centering device or by means of a centering.

The use of a pressure-balanced control valve element allows significantly smaller forces to be applied, for example, by an electromagnetic actuator which is connected to the control valve element. The term "pressure-balanced" means in the present case that at least in the closed state of the control valve, preferably also in the open state, the control valve element no or at least no significant hydraulic forces act. The strokes of such a pressure-balanced control valve element to be executed for influencing the pressure in the hydraulic control chamber are also comparatively small. Since smaller forces are to be applied for the movement of the control valve element, the corresponding actuator can build smaller, whereby the total mass, which is to be moved, lower and the damping behavior is improved.

All this allows a faster movement of the control valve element, so shorter switching times, which allow short distances between individual injections. In addition, will the proposed design of a pressure-balanced control valve element allows a simple and cost-effective structural design, which can lead to a highly integrated and compact design. This also meets the latest requirements for a reduced overall height of the fuel injection devices for reasons of pedestrian protection in motor vehicles.

A simple and inexpensive to build realization of a pressure-balanced control valve element comprises a valve piston with an at least substantially radially outer sealing edge. It is particularly advantageous if a control valve seat is designed as a flat seat. This can also be made simple and inexpensive and tolerates certain misalignments of the control valve element. In principle, however, other embodiments of the control valve seat are conceivable, for example, a ball seat or a conical seat.

In a particularly advantageous embodiment of the inventive fuel injection device is at least one connection channel, for example, a return, the

Control valve arranged in the control valve element. This simplifies the structural design of the fuel injection device.

It is also proposed that the control valve comprises a control valve chamber which is connected via an outflow throttle to the hydraulic control chamber and via an inflow throttle at least indirectly with a high-pressure port, and which is connected to a low-pressure port when the control valve is open. Thus, a filling of the control valve chamber is also possible via the outflow throttle when closing the control valve, which increases the closing speed of the control valve element.

It is furthermore particularly advantageous if the injection valve element has at least one control-chamber-side and one valve-seat-side section which are coupled to one another such that a bending moment is not transferred from one section to the other section or at least only reduced. In this way, transverse forces on the guide and / or the valve seat of the injection valve element are reduced or completely prevented, whereby the service life is prolonged and the free movement of the injection valve element is improved. In addition, the required manufacturing accuracy can be reduced in this way, because tensions of the injection valve element due to manufacturing inaccuracies are reduced or avoided altogether.

A manufacturing technology particularly simple realization of such a bending moment decoupling consists in a material weakening, which has a cardanic character. Alternatively or additionally, the two sections may also be hydraulically coupled to one another.

The latter is particularly advantageous if the injection valve element and the control valve element are arranged coaxially. In this case, lateral forces and

Bending moments of the fuel injection device particularly effectively kept away.

Brief description of the drawings

Hereinafter, particularly preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. In the drawing show:

1 shows a partial section through a first embodiment of a fuel

Injector;

2 shows a partial section through a second embodiment of a fuel

Injector; and

3 shows a partial section through a third embodiment of a fuel injection device.

Embodiments of the invention

In FIG. 1, a fuel injection device bears the reference numeral 10 as a whole. It is used for injecting fuel directly into an associated but not shown fuel

Combustion chamber of an internal combustion engine. For this purpose, the fuel injection device 10 has a high pressure port 12 which is connected to a pressure accumulator 14 ("rail"), is stored in the fuel under high pressure. The fuel injection device 10 comprises a housing 16 having a main portion 18 and a nozzle body 20. The housing 16 is penetrated almost over its entire length by a recess 22, in which among other things an injection valve element 24, which due to its very elongated shape as well "Nozzle needle" is called, is included. At its lower end in FIG. 1, a sealing edge 26, which cooperates with a housing-side injection valve seat 28, is present on the injection valve element 24. Depending on the position of the injection valve element 24, fuel is discharged into the combustion chamber from the fuel injection device 10 via fuel outlet channels 30 or such discharge is prevented.

Between the recess 22 and the injection valve element 24, except for the upper end of the injection valve element 24 in FIG. 1, an annular high-pressure space 32 is formed, which is constantly in communication with the high-pressure connection 12. The injection valve element 24 thus "floats" during operation of the fuel injection device 10 in the high pressure chamber 32 in the high pressure fuel. The upper end of the injection valve element 24 in FIG. 1 is fluid-tight, but in sliding fit, guided in a valve piece 34, which closes off the high-pressure chamber 32 at the top. The upper end face of the injection valve element 24 in FIG. 1 forms a hydraulic control surface 36 which, together with a recess (without reference numeral) in the valve piece 34, delimits a hydraulic control chamber 38. Between the valve member 34 and a circumferential collar (without reference numeral) on the injection valve element 24, a valve spring 40 is clamped, which urges the injection valve element 24 in the closing direction against the injection valve seat 28.

In the area of the valve spring 40, two lateral incisions 42a and 42b are present in the injection valve element 24 at a first axial position, between which only a comparatively thin material web 44 has remained. Axially spaced therefrom, there are two further lateral cuts in the injection valve element 24, which are arranged rotated by 90 ° relative to the lateral cuts 42a and 42b, so that only the lateral cut 46a and the corresponding material web 48 are visible in FIG. The lateral incisions 42a and 42b and 46a (and the invisible lateral incision 46b) form a material weakening 50 in this respect, which has a cardanic character, by a bending moment of the located above the material weakening 50 portion of the Injection valve element 24 is transferred to the located below this material weakening 50 section only reduced. A similar material weakening 52 is also located on the injection valve element 24 approximately at the level of the transition between the main portion 18 and the nozzle body 20 of the housing 16.

In the embodiment of a fuel injection device 10 shown in Figure 1, the injection valve element 24 is formed in two parts with a control chamber side portion 54 and a valve seat side portion 56. The two sections 54 and 56 are coupled by a hydraulic Kopp ler 58 with each other, but could also be mechanically coupled be. In one embodiment, not shown, the injection valve element 24 is integrally formed, so that can be dispensed with a hydraulic coupler. The valve seat side portion 56 of the injection valve member 24 is guided in the nozzle body 20, wherein the continuity of the high-pressure chamber 32 is ensured to the fuel discharge channels 30 by flats 60 on the valve seat side portion 56. The valve seat-side section 56 moreover has a conical hydraulic pressure surface 62 acting in the opening direction of the injection valve element 24.

The pressure in the hydraulic control chamber 38 is influenced by the position of an electromagnetic control valve 64. The latter has a control valve element designed as a valve piston 66, which is guided in the valve piece 34. At its upper end in FIG. 1, an armature 68 is attached to the control valve element 66, wherein in an exemplary embodiment, not shown, the control valve and the armature can also be made in one piece. The armature 68 cooperates with an electromagnetic coil 70. The control valve element 66 is acted upon by a valve spring 72 in its closed position. In this, it lies with its in Figure 1 lower end with a circumferential and substantially radially outer sealing edge 74 on a formed in the valve member 34 as a flat seat control valve seat 76.

The control valve seat 76 is arranged in a control valve chamber 78, which communicates via an inflow throttle 80 with the high-pressure chamber 32. Also the hydraulic

Control chamber 38 is connected via such a flow restrictor 82 with the high-pressure chamber 32 in constant communication. Radially outside of the control valve seat 76 opens into the control valve chamber 78, a connection (without reference numeral) from the hydraulic control chamber 38 ago, in a Outflow throttle 84 is arranged. The control valve element 66 is penetrated in its longitudinal direction by a connection channel 86 which opens on the upper side of the control valve element 66 into an armature space 88, which in turn is connected to a low-pressure connection 90.

The fuel injector 10 operates as follows:

At rest, the control valve member 66 is pressed by the valve spring 72 with the sealing edge 74 against the control valve seat 76. Thus, the hydraulic control chamber 38 is separated from the low pressure port 90. Due to the connection via the inflow throttle 82 to the high-pressure chamber 32, the high pressure of the high-pressure chamber 32 prevails in it. Through the corresponding force acting in the closing direction on the hydraulic control surface 36 and the force of the valve spring 40, the sum of the pressure at the pressure surface 62 in When the opening direction is exceeded, the injection valve element 24 with the sealing edge 26 is pressed against the injection valve seat 28. The fuel outlet channels 30 are therefore separated from the high pressure chamber 32, it can escape fuel.

For an injection, the coil 70 is energized, so that the control valve member 66 lifts with its sealing edge 74 from the control valve seat 76. Now fuel can flow from the hydraulic control chamber 38 via the outflow throttle 84, the control valve chamber 78 and the connecting channel 86 to the low pressure port 90. The pressure in the high-pressure chamber 32 drops, and when the forces acting in the closing direction are below the force acting in the opening direction on the pressure surface 62, the sealing edge 26 of the injection valve element 24 lifts off from the injection valve seat 28. Now fuel can be discharged from the high-pressure chamber 32 via the fuel outlet channels 30 into the combustion chamber.

To end the injection, the energization of the coil 70 is terminated, whereby the control valve member 66 is pressed by the valve spring 72 with the sealing edge 74 against the control valve seat 76 again. The connection of the control valve chamber 78 with the low pressure port 90 is thus interrupted. The pressure in the control valve chamber 78 increases via the inflow throttle 80, and as a result and also because of the inflow throttle 82, the pressure in the hydraulic control chamber 38. As soon as the forces acting in the closing direction exceed the force acting in the opening direction, the injection valve element 24 closes. It can be seen from FIG. 1 that the valve piece 34 is surrounded by the annular high-pressure chamber 32, in particular in the region of the control chamber 38, the control valve chamber 78 and the guide of the control valve element 66 and the injection valve element 24. A widening of the guides of the injection valve element 24 and the control valve element 66 in the valve piece 34 by the high pressure is therefore reduced, and thus the leakage is reduced in this area. In general, the strength load of the valve piece 34 is reduced by this configuration. It can also be seen that virtually no hydraulic forces acting in its opening or closing direction act on the control valve element 66 in the closed state. So this is "pressure balanced". For a simple, inexpensive and compact design of the control valve 64 and thus also the fuel injection device 10 is possible.

The arrangement of the connection channel 86 in the control valve element 66 also prevents or at least reduces the influence of the movement of the armature 68 by the flow of the fuel from the control valve chamber 78 to the low-pressure connection 90. The control valve 66 and the armature 68 can be dimensioned very small, whereby small moving masses are achieved. This allows the realization of fast valve switching times and reduces bouncing when hitting the control valve element 66 on the control valve seat 76. It can also be seen from Figure 1 that a leakage line due to the arrangement of the injection valve element 24 as in the high-pressure chamber "floating" valve element is not required. The size of the high pressure chamber 32 also causes it to have an accumulator function.

A further embodiment is shown in FIG. 2. Here, as below, such elements and regions which have equivalent functions to previously described elements and regions bear the same reference numerals and are not explained again in detail.

The fuel injection device 10 of Figure 2 differs from that shown in Figure 1, especially in its lower portion: This corresponds to the currently known from the market fuel injectors 10, in which the injection valve element 24 is not in the high pressure "floats ". Instead, there is a low pressure in an annular space 92 present above the nozzle body 20. Also a hydraulic coupler is not available. From the high-pressure chamber 32, which is present in the fuel injection device 10 shown in Figure 2 only in the region of the pressure surface 62 and is connected via a channel 93 to the high pressure port 12, the low pressure chamber 92 passing leakage fluid (the flats 60 are in this area at the injection valve element 24 not present) is discharged from a leakage line 94.

Yet another embodiment is shown in FIG. This corresponds in the lower part to that of FIG. 1. However, the valve piece 34 is differently configured, which unlike in FIGS. 1 and 2 is not formed in one piece but in two pieces with a first part valve piece 96 and a second part valve piece 98. The first TeilVentilstück 96 is acted upon by the valve spring 90 against the second TeilVentilstück 98. The control valve seat 76 is formed on the outside of the first TeilVentilstücks 96, which serves to guide the injection valve member 24 and for receiving the hydraulic control chamber 38 and has no direct connection to the low pressure port 90. In contrast, the control valve chamber 78 is present in the second part valve piece 98. By such a two-part embodiment of the

Valve piece 34, its manufacture can be simplified. For sealing, a sealing edge (not shown) and / or additionally an outer seal 100 may be provided between the two partial valve pieces 96 and 98. The two partial valve pieces 96 and 98 can also be centered relative to one another via centering means, so that the control valve element 66 and the injection valve element 24 are arranged coaxially as exactly as possible.

Claims

claims

1. Fuel injection device (10) for an internal combustion engine, with at least one injection valve element (24) which on the one hand limits a hydraulic control chamber (38) and on the other hand release or block fuel outlet channels (30), and with a control valve (64) for influencing the pressure in the hydraulic control chamber (38), characterized in that it comprises a valve piece (34) in which a control valve element (66) is guided and which closes a receiving space (32) for the injection valve element (24), the receiving space (34) 32) is constantly connected to a high pressure port (12).

2. Fuel injection device (10) according to claim 1, characterized in that the valve piece (34) in the region of the guide of the control valve element (66) radially outside at least partially surrounded by an annular space (32) which is constantly connected to the high pressure port (12 ) connected is.

3. Fuel injection device (10) according to any one of claims 1 or 2, characterized in that in the valve piece (34) in that region which is surrounded by the high-pressure connection connected to the annular space (32), the hydraulic control chamber (38) and / or a control valve chamber (78) and / or other high-pressure channels (80, 82, 84) and spaces are / is arranged.

4. Fuel injection device according to one of the preceding claims, characterized in that an end region of the injection valve element (24) in the valve piece (34) is guided.

5. Fuel injection device (10) according to one of the preceding claims, characterized in that the valve piece (34) is in one piece.

6. Fuel injection device (10) according to any one of the preceding claims, characterized in that the valve piece (34) at least a first part valve piece (96) for guiding of the injection valve element (24) and a second part valve piece (98) for guiding the control valve element (66), wherein a control valve seat (76) on the outside of the first part valve piece (96) is formed.

7. Fuel injection device according to one of the preceding claims, characterized in that a control valve element (66) of the control valve (64) at least in

Is essentially pressure balanced.

8. Fuel injection device (10) according to one of the preceding claims, characterized in that the control valve element comprises a valve piston (66) with an at least substantially radially outer sealing edge (74).

9. Fuel injection device (10) according to any one of the preceding claims, characterized in that a control valve seat is formed as a flat seat (76).

10. Fuel injection device (10) according to any one of the preceding claims, characterized in that at least one connection channel (86) of the control valve (64) in the control valve element (66) is arranged.

11. Fuel injection device (10) according to any one of the preceding claims, characterized in that the control valve (64) comprises a control valve chamber (78) which via an outflow throttle (84) with the hydraulic control chamber (38) and via an inflow throttle (80 ) is at least indirectly connected to a high pressure port (12), and which is connected to a low pressure port (90) when the control valve (64) is open.

12. Fuel injection device (10) according to any one of the preceding claims, characterized in that the injection valve element (24) has at least one control-chamber-side portion (54) and a valve seat side portion (56) which are coupled together such that a bending moment of a Section on the other section is not transferred or at least reduced only.

13. Fuel injection device (10) according to claim 12, characterized in that the two sections are coupled to each other via a gimbal having material weakening (50, 52) and / or a hydraulic Kopp ler (58), which or which does not transmit a bending moment from one section (54) to the other section (56), or at least only reduces it.

14. Fuel injection device (10) according to any one of the preceding claims, characterized in that injection valve element (24) and control valve element (66) are arranged coaxially.