EP1952011A1

EP1952011A1 - Fuel injection apparatus for an internal combustion engine having direct fuel injection

Info

Publication number: EP1952011A1
Application number: EP06807052A
Authority: EP
Inventors: Andreas Rettich; Thomas Pauer; Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2005-11-15
Filing date: 2006-10-06
Publication date: 2008-08-06
Anticipated expiration: 2026-10-06
Also published as: WO2007057252A1; EP1952011B1; DE102006012078A1

Abstract

A fuel injection apparatus (10) comprises a housing (12), in which a valve element (18) is arranged. Said valve element (18) has a hydraulic pressure face (20, 22) which acts in the opening direction and delimits a high-pressure space (28) which is connected to a high-pressure connection (54). Furthermore, there is a hydraulic control face (46) on the valve element (18), which hydraulic control face (46) acts in the closing direction and delimits a control space (48), in which a variable control pressure prevails during operation. It is proposed that the valve element (18) interacts in a throttling manner with a housing region (26) in an open position or an open position region in such a way that a pressure which is lower than the pressure in the high-pressure space (28) prevails at least on one part of the pressure face (20, 22).

Description

06.03.2006 kna / jmr-neg

Robert Bosch GmbH, 70442 Stuttgart

Fuel injection device for an internal combustion engine with fuel direct injection

State of the art

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

DE 100 24 702 Al and DE 100 24 703 Al each show a fuel injection device with which the

Fuel can be injected directly into its associated combustion chamber of an internal combustion engine. For this purpose, a valve element is arranged in a housing, which in the region of a fuel outlet opening has a pressure surface acting overall in the opening direction of the valve element. At the opposite end of the valve element acting in the closing direction control surface is present, which limits a control chamber.

When the fuel injection device is closed, a high fuel pressure is present at a region of the pressure surface acting in the opening direction and at the control surface acting in the closing direction, as is provided, for example, by a fuel rail. The force excess acting in the closing direction is achieved by the pressure surface acting in the opening direction at least when the valve element is closed is smaller than the control surface acting in the closing direction.

To open the valve element, the pressure applied to the control surface is lowered until the hydraulic force resultant in the opening direction on the pressure surface exceeds the forces acting in the closing direction. As a result, opening of the valve element is effected.

In both known fuel injectors

the valve element "floats" in high fuel pressure. In the case of the valve element shown in DE 199 24 703 A1, moreover, the pressure surface acting in the opening direction and the control surface acting in the closing direction, on a plane orthogonal to the longitudinal axis of the valve element, are of equal size. In order nevertheless to be able to ensure a safe closing of the valve element, measures are proposed with which the pressure in the control chamber can be raised again very quickly after lowering.

Object of the present invention is to develop a fuel injection device of the type mentioned so that it closes very quickly.

This object is achieved by a fuel injection device having the features of claim 1. Furthermore, the object is achieved by a method having the features of the independent method claim. Advantageous developments are specified in dependent claims.

Advantages of the invention

According to the invention, the closing of the valve element is assisted by the fact that when the valve element is open is lowered at the acting in opening direction pressure surface (or at least at a part thereof) applied pressure. This is possible, for example, by a corresponding throttling between the valve element and a housing-side valve seat area and / or by an additional valve slide section.

By means of a corresponding shaping on the one hand of the housing-side valve seat portion and on the other hand, a corresponding sealing region on the valve element, the

Throttling can be adjusted so that at least slightly open valve element, the force acting in the opening direction is smaller than when the valve element is closed. As a result, the closing process is supported and accelerated. The valve element is "sucked" to close the quasi to the valve seat.

The invention makes it possible in a special way to design the pressure surface acting in the opening direction and the control surface acting in the closing direction, each projecting onto a plane perpendicular to the direction of movement of the valve element, at least approximately the same size. This allows a low-cost production of the valve element.

It is also proposed, in all lying between the control chamber and pressure chamber spaces surrounding the valve element, during operation at least temporarily and at least approximately prevails at the high pressure connection prevailing high fuel pressure. This can be realized, for example, in that the recess in which the valve element is accommodated in its entirety is connected to the high-pressure connection. A low pressure area is therefore no longer available ("pressure balanced" valve). Thus, no leakage between the high and such Low pressure area occur, so that the corresponding seal and a leaking line required for this purpose can be omitted.

This allows a simpler structure of the fuel injection device with fewer parts, which on the one hand facilitates the assembly and on the other hand allows a smaller design. In addition, the inventive fuel injection device operates with a high efficiency, since the existing in earlier devices leakage between the valve element and the housing is no longer available. A return line can be designed smaller in the sequence.

By doing a seal between the in

Opening direction acting pressure surface and acting in the closing direction control surface is no longer required in the previous sense, the valve element can be arranged in total in a connected to the high pressure port high-pressure chamber. In order to still be able to achieve a pressure reduction in the control room, then simply a sealing sleeve can be provided. This can be radially free, that is without guidance, so that manufacturing tolerances can be easily compensated. The control of the control chamber can then be done by an existing example in the sleeve control channel.

In order to be able to inject even minute amounts in the range of 1 mm ³ with the fuel injection device according to the invention, a "compression" of the valve element is set by a corresponding length or material selection of the valve element. All of the foregoing measures allow operation of the fuel injector even at very high pressures of up to 1800 bar. It is also advantageous if the valve element is multi-part and at least two parts of the valve element are coupled together via a hydraulic coupler. As a result, the freedom in the design of the fuel injection device is significantly increased. The manufacture of the device is simplified.

In a further development, it is proposed that the two parts of the valve element in the hydraulic coupler, when the valve element rests against the valve seat, are spaced from each other. As a result, a direct mechanical coupling of the two parts and thus a possible bouncing is prevented.

In this case, the hydraulic coupler may comprise an intermediate disc which geometrically separates a first coupling space from a second coupling space. This simplifies the production.

It is possible that the hydraulic coupler comprises a connecting channel which hydraulically interconnects the two coupling spaces. This allows the optimization of the coupler, for example by designing the connection channel as a flow restrictor.

At least one of the parts of the valve element can be designed as an elastic pressure rod such that an opening movement of the control chamber limiting part of the valve element is delayed in time with the

Valve seat transmits cooperating part of the valve element. In this way, despite the use of a cheap solenoid valve to control the pressure in the control room and very short opening times and thus the Ability to inject even very small quantities can be realized.

drawing

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

FIG. 1 shows a partial section through a region of a first embodiment of a fuel injection device;

FIG. 2 shows a diagram in which a profile of a force acting in the opening direction is plotted over the stroke of a valve element of the fuel injection device of FIG. 1;

FIG. 3 shows a partial section through a region of a second embodiment of a fuel injection device; and

Figure 4 is a view similar to Figure 1 of a third embodiment of a fuel injection device.

Description of the exemplary embodiments

In FIG. 1, a fuel injection device bears overall the reference numeral 10. It comprises a housing 12, which in turn comprises a nozzle body 12a, a Injector body 12b, and a nozzle lock nut 12c includes. In the housing 12, a stepped recess 14 is present in its longitudinal direction, from whose lower end in FIG. 1 fuel outlet channels 16 emerge, which pass through the wall of the nozzle body 12a.

In the recess 14, a needle-like valve element 18 is arranged. This has an overall substantially constant diameter D. At its lower end in FIG. 1, the valve member 18 has a conical tip formed by a first conical annular surface 20 and a second conical end surface 22. The annular surface 20 and the end surface 22 have a different conicity, so that a sealing edge 24 is formed between them. This is at a closed valve member 18 at an opposite also conical valve seat surface 26 in the lower end portion of the recess 14 in Figure 1 in the nozzle body 12a. In this way, the valve element 18 can separate the fuel discharge passages 16 from an annular high-pressure space 28 present upstream of the sealing edge 24 between the valve element 18 and the housing 12.

The upper pressure chamber 28 extends over the entire length of the recess 14 or of the valve element 18. The latter is guided in the housing 12 above all via a guide section 30 which has only a small axial length and which has a complementary guide section 32 at the upper end of FIG Nozzle body 12a cooperates. The high pressure chamber 28 is through the two

However, guide sections 30 and 32 are not interrupted: in the region of the guide section 30, the valve element 18 has four flattened portions 34 distributed over its circumference, through which the corresponding guide sections 30 and 32 pass Stromungskanale be formed, which are also part of the high-pressure chamber 28. The flats 34 are dimensioned such that a throttling of the flow, which flows through the flow channels formed, is substantially zero.

The recess 14 is closed in Figure 1 at the top by a Ventilstuck 36. This projects with a Hulsenabschnitt 38 a piece far into the recess 14, so that in the Hulsenabschnitt 38 one of the

Fuel outlet ducts 60 opposite end portion 40 of the valve member 18 axially displaceable, but is received largely fluid-tight. The valve stub 36 is fastened in a manner not shown in more detail on the injector body 12 b. Between the Hulsenabschnitt 38 and a slightly spaced from this annular collar 42 on the valve member 18, a spring 44 is clamped, by which the valve element 18 is applied very easily in the closing direction.

At the top of the valve member 18 in Figure 1, a control surface 46 is present. It represents a part of a boundary of a control chamber 48 formed between the sleeve portion 38 and the valve element 18. Via an inlet throttle 50, the control chamber 48 is connected to the high pressure chamber 28, which in turn is connected via a channel 52 in Injektorkorper 12 b with a high pressure port 54. This in turn is connected during operation of the fuel injection device 10 with a fuel rail ("rail"), which is not shown in Figure 1. In such a fuel rail fuel can be stored under very high pressure. To the fuel rail, a plurality of fuel injectors may be connected. An outlet throttle 56 connects the control chamber 48 further with a switching valve 58. This connects the control chamber 48 in the open state with a low pressure port 60. For this purpose, the switching valve 58 has in the present

Exemplary embodiment via a valve ball 62, which in turn is acted upon by a valve pusher 64, which in turn is actuated either hydraulically or directly via a corresponding actuator 66.

The fuel injection device 10 shown in Figure 1 is operated as follows: In an initial state, the switching valve 58 is closed. The high fuel pressure applied at the high pressure port 54 (up to 1800 bar) prevails in the high pressure chamber 28 and is characterized by the

Inlet throttle 50 is also transmitted to the control chamber 48. The high pressure is also applied to the conical annular surface 20 at the lower end of the valve element 18 in FIG. However, the hydraulic conical annular surface 20 acting in the opening direction is smaller overall than the control surface 46 acting in the closing direction. For this reason, a force resultant in the closing direction acts altogether on the valve element 18, which ensures that the sealing edge 24 of the valve element 18 abuts against the opposite valve seat surface 26 is printed. Thus, the connection of the high-pressure chamber 28 is interrupted to the fuel outlet channels 16.

In order for fuel to be delivered from the fuel injector 10, the switching valve 58 is opened.

The control chamber 48 is now connected via the outlet throttle 56 to the low pressure port 60. Since the inlet throttle 50 throttles more strongly than the outlet throttle 56, the pressure in the control chamber 48 and consequently also the action acting on the control surface 46 and acting in the closing direction decreases Force. As soon as it falls below the hydraulic force acting on the conical annular surface 20 and acting in the opening direction (less the force of the spring 44), the valve element 18 with the sealing edge 24 lifts away from the valve seat surface 26. Fuel now flows from the high-pressure chamber 28 to the fuel outlet channels 16.

In addition, a hydraulic pressure also acts on the conical end face 22, which generates an additional force acting in the opening direction on this conical end face 22 (the course of the force in relation to the stroke will be discussed in more detail below in connection with FIG. 2). As a result, the opening of the valve element 18 is accelerated. The conical annular surface 20 and the conical end surface 22 thus form a total acting in the opening direction pressure surface whose hydraulically effective cross-sectional area equal to the hydraulically effective cross-sectional area of the control surface 46.

In order to stop the injection of fuel through the fuel injection device 10, the switching valve 58 is closed. The connection of the control chamber 48 to the low pressure port 60 is therefore interrupted. Fuel can now nachström by the inlet throttle 50 back into the control chamber 48, so that there is the am

High pressure port 54 and 28 prevailing pressure in the high pressure chamber adjusts. That the valve element 18 now executes a closing movement, although the hydraulic cross-sectional area acting in the closing direction of the control surface 46 and acting in the opening direction hydraulic

Cross-sectional area of the pressure surfaces 20 and 22 are equal, is connected with the following: In the region of the sealing edge 24, the flow between the two annular surfaces 20 and 22 on the one hand and the opposite valve seat surface 26 on the other hand throttled very easily. This is at least at a portion of the conical end surface 22 to a pressure which is smaller than the pressure in the high-pressure chamber 28. This also depends on the outflow of the fuel through the fuel outlet channel 16.

Despite a total in the high-pressure chamber 28 and in the control chamber 48 same pressure and despite acting in the same direction in the closing direction and opening direction hydraulically effective cross-sectional areas so the sum acting on the conical annular surface 20 and the conical end surface 22 in the opening direction force is smaller than that at the control surface 46 force acting in the closing direction. The total resultant force acting on the valve element 18 thus acts in the closing direction, which leads to a closing movement of the valve element 18.

The geometry of the conical annular surface 20 and the conical end surface 22, in particular the Konizitat these two surfaces 20 and 22, relative to the valve seat surface 26 is selected so that over a stroke H a course of force acting in the opening direction force F is achieved, as shown in FIG 2 is shown. It can be seen from this that the force acting in the opening direction has a value F ₀ at the stroke H = O (ie when the valve element 18 is in contact with the valve seat surface 26 with the sealing edge 24). When the valve element 18 is slightly open, ie approximately at a stroke Hi, the force Fi acting in the opening direction is smaller than the force F ₀ acting in the opening direction due to throttling effects. Only at a further increased stroke H acts in the opening direction, a force F ₂ , which is significantly greater than the force F ₀ . This means, conversely, during the closing process just described that the valve element 18 is almost "sucked" towards the end of the closing process and closes accordingly fast. A force progression, as shown in FIG. 2, can additionally or intensively also be brought about by the formation of a valve slide section (not shown in FIG. 1), which cooperates with a corresponding housing-side section.

It is understood that must be lowered so far for a safe opening of the pressure in the control chamber 48 such that the force acting on the control surface 46 in the closing direction of the force of the spring 44 is smaller than the force F zuzuglich. ₁

It can be seen from FIG. 1 that the valve element 18 is overall one-piece. By an appropriate choice of material and geometry is between the sealing edge 24 on the one hand and the control chamber 48 a certain

Federelastizitat set that causes a certain compression with closed valve element 18, which can be used to inject even the smallest fuel quantities in the range of 1 mm ³ targeted and precise.

An alternative embodiment of a fuel injection device is shown in FIG. Here and below, such elements and areas, which have already been explained in connection with Figure 1, carry the same reference numerals. They are not explained again in detail. In the fuel injection device 10 shown in FIG. 3, the sleeve section 38 is designed as a separate part from the valve piece 36. It is pushed onto the end region 40 of the valve element 18 and is acted upon by the spring 44 against the valve stump 36. In the radial direction of the sleeve portion 38 is not held. The guide of the valve element 18 thus takes place exclusively by the guide portion 30 on the valve element 18 and the guide portion 32 on

Nozzle body 12a. As a result, a smooth movement of the valve element 18 is ensured despite certain manufacturing tolerances. The sealing of the control chamber 48 is thereby improved.

It is understood that by the term of the hydraulically effective cross-sectional area on the one hand the pressure surface 20, 22 and on the other hand the control surface 46 the area of the conical annular surface 20, the conical end surface 22, and the control surface 46 is meant, which is perpendicular to the direction of movement of the valve element 18 lying level is projected. Since the diameter of the valve element 18 is constant (value D), these hydraulically effective cross-sectional areas are identical.

A further modified third embodiment is shown in FIG 4. In this, the valve element 18 is divided into two, with a nozzle needle 68 and a control piston 70. The control piston 34 is comparatively long and dimensioned so that, as will be explained in more detail below, a significant elasticity has. Nozzle needle 68 and control piston 70 are coupled to each other via a hydraulic coupler 72 comprising two hydraulic coupling chambers 74a and 74b. The two coupling spaces 74a and 74b are through a housing side

Intermediate disc 76 geometrically separated from each other, but via a connecting channel 78 hydraulically connected to each other. The upper coupling space 74a is bounded radially by a sleeve 80a, the lower of a sleeve 80b. The sleeves are each pressed against the intermediate disc 76 in a spring 81a and 81b, which is supported on the housing side (spring 81a) or on the nozzle needle 68 (spring 81b). The control piston 70 defines with an end face 82 axially the upper coupling space 74a, the nozzle needle with an end face 84 the lower coupling space 74b.

If the pressure in the control chamber 60 is lowered by triggering the actuator 66 (in this case a magnetic actuator), the control piston 70 in FIG. 4 moves upwards. As a result, the pressure in the upper coupling chamber 74a decreases, which transfers via the connecting channel 78 into the lower coupling space 74b and also leads there to a pressure reduction. As a result, the nozzle needle 68 is quasi wound up.

It can be seen from FIG. 4 that the control piston 70 and the nozzle needle 68 "float" in the high pressure of the high pressure spaces 28a and 28b lying above and below the intermediate disk 76. For this purpose, corresponding passages (without reference numerals) are present in the intermediate disk 76. As a result, the sealing problem is reduced.

Due to the elasticity and length L especially of the

Control piston 34, it is possible that with the fuel injection device 18 also very small amounts of fuel can be injected. This is due to the fact that the control piston initially, when the nozzle needle 68 rests against the housing-side valve seat, is elastically compressed by the high pressure in the control chamber 48. At a pressure reduction in the control chamber 48, the control piston 70 must first be lengthen to bring about the above-mentioned pressure reduction in the coupling chambers 74a and 74b. In the embodiment of Figure 4 can by an appropriate selection of the ratios of the diameter Dl of the end face 84 of the nozzle needle 68 to the diameter D2 of the end face 82 of the control piston 70 (translation) and the diameter D2 to the diameter D3 of the control surface 46 (pressure stage) the Kraftverhaltnisse easy way and yet be set precisely.

Claims

claims

A fuel injector (10) for an internal combustion engine with direct fuel injection, comprising a housing (12), with a valve element (18) arranged in the housing (12) and having an in

Opening direction acting hydraulic pressure surface (20, 22) defining a high-pressure chamber (28) which is connected to a high-pressure port (54), and with a closing direction acting in the hydraulic control surface (46) which limits a control chamber (48) in the In operation, a variable control pressure prevails, characterized in that the valve element (18) in an open position (Hi) or an open position range with a Gehausebereich (26) throttling cooperates in such a way that at least on a part of the pressure surface (20, 22) a Pressure is applied, which is smaller than the pressure in the high-pressure chamber (28).

2. Fuel injection device (10) according to claim 1, characterized in that the valve element (18) is received in total in a high-pressure chamber (28).

3. Fuel injection device (10) according to any one of claims 1 or 2, characterized in that when the valve element (18), the hydraulically active pressure surface (20, 22) and the hydraulically effective Control surface (46), each projected onto a plane perpendicular to the direction of movement of the valve element (18) are at least approximately the same size.

4. Fuel injection device (10) according to one of the preceding claims, characterized in that in between control chamber (48) and high-pressure chamber (28) lying spaces (28) surrounding the valve element (18), at least temporarily and at least in operation about the high pressure connection (54) prevailing high fuel pressure prevails.

5. Fuel injection device (10) according to one of the preceding claims, characterized in that the valve element (18) has a valve spool portion which at least temporarily, in particular during closing, with a Gehauseseitigen area (12) throttling cooperates such that at least on a part of the pressure surface (20, 22) acting pressure below the pressure in the high-pressure chamber (28) decreases.

6. Fuel injection device (10) according to any one of the preceding claims, characterized in that with slightly open valve element (18) acting in the opening direction force (Fi) is smaller than the force acting in the opening direction of force (F ₀ ) with the valve element (18 ).

7. Fuel injection device (10) according to one of the preceding claims, characterized in that the

Control chamber (48) from the high-pressure chamber (28) by a Hulsenabschnitt (38) is fluidically separated, which is not guided radially from the housing (12).

8. Fuel injection device (10) according to one of the preceding claims, characterized in that the

Valve element (18) has a Fuhrungsabschnitt (30), at which it is guided in the housing (12) fluidly permeable (32).

9. Fuel injection device (10) according to any one of the preceding claims, characterized in that the length and / or the material of the valve element (18) are selected so / is that a certain spring elasticity between the control surface (46) and the one Fuel outlet channel (16) facing end portion of the valve element (18) which allows injection of very small amounts in the range of lmm ³ .

10. Fuel injection device (10) according to any one of the preceding claims, characterized in that the valve element (18) is in several parts (68, 70) and at least two parts (68, 70) of the valve element (18) via a hydraulic coupler (72 ) are coupled together.

11. Fuel injection device (10) according to claim 10, characterized in that the two parts (68, 70) of the valve element (18) in the hydraulic coupler (72) when the valve element (18) against the valve seat (26), spaced apart from each other.

12. Fuel injection device (10) according to claim 11, characterized in that the hydraulic coupler (72) comprises an intermediate disc (76) which geometrically separates a first coupling space (74a) from a second coupling space (74b).

13. Fuel injection device (10) according to claim 12, characterized in that the hydraulic coupler (72) comprises a two coupling spaces (74a, 74b) hydraulically interconnecting connecting channel (78).

14. Fuel injection device (10) according to one of the preceding claims, characterized in that at least one of the parts (70) of the valve element (18) is formed as an elastic pressure rod such that an opening movement of the control chamber (48) delimiting part (70) of the valve element (18) delayed in time with the valve seat (26) cooperating part (68) of the valve element (18) transmits.

15. A method for operating a fuel injection device (10) for an internal combustion engine with direct fuel injection, in which at an acting in opening direction hydraulic pressure surface (20, 22) of a valve element (18) an opening pressure and at a closing in the direction of hydraulic control surface ( 46), a control pressure is applied, characterized in that during or after the opening and / or closing of the valve element (18) the pressure applied to at least one region of the pressure surface (20, 22) opening pressure is lowered.