EP2049788A1

EP2049788A1 - Fuel injection device for an internal combustion engine

Info

Publication number: EP2049788A1
Application number: EP07788067A
Authority: EP
Inventors: Georg Bachmaier; Gerit Ebelsberger; Bernhard Gottlieb; Michael HÖGE; Andreas Kappel; Erhard Magori; Randolf Mock; Thomas Vontz
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2006-08-09
Filing date: 2007-07-31
Publication date: 2009-04-22
Also published as: WO2008017614A1

Abstract

The present invention relates to a fuel injection device for an internal combustion engine with an intake opening (1), an outlet opening (10), a housing (2) and a piston (4), wherein the piston (4), comprising a front end and a rear end, is moveable in a recess located in the housing (2) between a closed position and an injection position, wherein a channel (8) runs from the front end of the piston (4) to the read end of the piston (4), wherein behind the rear end of the piston (4) a rear chamber (7) is located, the channel (8) merging therein, wherein in front of the front end of the piston (4) a front chamber (9) is located, wherein a fuel space (17) is located laterally between the housing (2) and the front end of the piston (4), and wherein the piston (4) in the closed position touches a sealing seat (14, 15) and thus closes the exhaust opening (10). By the intake opening (1) merging in the fuel space (17) and the channel (8) merging in the front chamber (9) in order to provide a pressur equalization between the front chamber (9) and the rear chamber (7), a particularly precise and quick injection is possible.

Description

description

Fuel injection device for an internal combustion engine

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

Such a fuel injection device for an internal combustion engine, which is known from DE 102 46 974 and is used, for example, for a common-rail injection system, comprises an inlet opening, an outlet opening, a housing and a piston as a nozzle needle, wherein the piston, which has a front end and a rear end, in a recess formed in the housing, between one

Closed position and an injection position is displaceable, wherein a channel extending from the front end of the piston to the rear end of the piston, wherein behind the rear end of the piston, a rear chamber is formed, in which the channel opens, wherein front of the front end of the piston Chamber is formed, wherein laterally between the housing and the front end of the piston, a fuel space is formed, and wherein the front end of the piston rests in the closed position on a sealing seat and thus closes the outlet opening.

The fuel injection device known from DE 102 46 974 enables a high injection pressure of the fuel to be injected, but can not achieve extremely fast and precise multiple direct injection as desired for diesel engines in order to achieve better combustion and reduce pollutant emissions.

The present invention has for its object to provide a fuel injection device for an internal combustion engine, which allows a particularly precise and fast Einsprit ^¬ tion. The object underlying the invention is achieved by a fuel injection device for an internal combustion engine having the features of patent claim 1.

According to the invention opens the inlet opening in the fuel ^¬ space, and opens the channel in the front chamber, so that a pressure equalization between the front chamber and the rear chamber takes place.

Advantageously, only a ringer ge ^¬ force is required to move the piston and the opening and closing of the outlet opening can be effected only by the displacement of the piston. In addition, the injection device is not particularly complex and therefore inexpensive to manufacture.

In a preferred embodiment, the piston is rotationally symmetrical, and the channel extends along the axis of symmetry through the piston.

Advantageously, the channel thus does not obstruct the Vorse ^¬ hung of shut-off elements between the housing and the piston.

In a further development of the preferred embodiment extends around the piston a stop edge which abuts in the closed ^¬ position against the sealing seat and so the outlet opening closing off opposite the inlet opening, and extends around the piston a further stop edge, which in the Schließstel- lung against the sealing seat abuts and thus shuts off the outlet opening opposite the channel.

Advantageously, a large number of injection holes can be formed between the two stop edges, as a result of which only a small dead volume between the two stop edges is required and the injection volume can be easily controlled. In addition, the two stop edges make a stable, tight and permanent shut-off of the outlet port.

In a further preferred embodiment, the piston is configured such that in the closed position, fuel at the rear end exerts a force on the piston along the piston (4, 4a) that is substantially equal in magnitude to a force that is fuel in the piston front chamber along the piston exerts.

Advantageously, it is possible to move the isobar piston with little effort from the closed position to the injection position. "Essentially" in this case means that a difference in the forces at the front end and at the rear end is negligible, the injection position in this context being any position of the piston in which the outlet opening is not closed.

In a development of the further preferred embodiment, the piston is formed so that in the closed position ^¬ fuel in the fuel space exerts substantially no force on the front end.

Advantageously, then pressure differences affect Zvi ^¬ rule the fuel in the rear chamber and the fuel in the area at the front end, in which the inlet port opens, not isobaric equilibrium of forces.

In a further development, a sleeve between the rear end of the piston and the housing is provided.

Advantageously, the sleeve makes it possible to form the piston in such a way that, in the closed position, fuel in a region at the front end, in which the inlet opening opens, exerts substantially no force on the front end. In a further development, the piston is designed such that in the closed position, fuel at the rear end exerts a force on the piston along the piston which is substantially equal in magnitude to a force that is fuel in a region at the front end. in which the channel opens, along which piston exerts.

Advantageously, in the closed position, an equilibrium of forces can then also be set if the fuel in the rear chamber has a different pressure than the fuel in an area at the front end in which the inlet opening opens.

In yet another preferred embodiment, the piston is formed so that in the injection position, a force exerted by fuel at the rear end of the piston along the piston, in absolute value, the fuel is a Kraftdiffe ^¬ rence smaller than a force of the front end on the piston along the piston exerts.

Advantageously, an area on the front side of the piston between the two stop edges, which covers the outlet opening, can thus be created.

In a development of the further preferred embodiment, a spring is provided which exerts a force on the rear end along the piston in the injection position, which is the same magnitude as the force difference.

Advantageously, can thus also in the injection Stel ^¬ development an equilibrium of forces acting on the piston forces produced. Brief description of the drawings

In the following the invention will be described in more detail with reference to the drawing ^¬ voltages.

Show it:

FIG. 1 is a cross section of a fuel injection device;

FIG. FIG. 2 shows a cross section of a further fuel injection device; FIG.

FIG. 3 is a detailed view of the front end of the fuel injector of FIG. 1; and

FIG. 4 is a detailed view of the front end of the fuel injector of FIG. Second

Embodiments of the invention

FIG. 1 shows a cross section through a force injection device for an internal combustion engine. At least one outlet opening ^¬ A 1 in the housing 2 is connected to a collecting line (common rail, not shown), in which

Fuel under high pressure (about 2000 bar) is located, and opens, at least in the closed position in a recess in the interior of the housing 2 at the height of a groove 3, the ring ^¬ runs around a cylindrical piston 4, the recess in the recess is recorded and represents a nozzle needle. ^{Lich ¬} Lich between the housing 2 and the front end of the piston 4, a fuel space 17 is formed, while the piston 4 is guided tightly between the groove 3 and the rear chamber. The piston 4 is connected at its rear end with a drive rod 5, which runs through a cylindrical Antriebsstan ^¬ genführung 6 and is preferably formed integrally with the piston 4. The drive rod 5 and thus the piston 4 are reciprocated along the recess between a closed position and an injection position by a piezoelectric actuator (not shown) disposed behind the drive rod guide 6 integral with the housing 2. The drive rod 5 is actuated by a Ak ^¬ tor, such as a servo valve or a piezoelekt ^¬ step actuator. At the rear end of the piston 4 a rear chamber 7 is provided which can be constricted in the injection Stel ^¬ lung to a narrow slot and egg NEN channel 8, which is arranged along the axis of symmetry S of the piston 4, with a front chamber 9 connected to the front end of the piston 4. In the front chamber 9, which may also be narrowed in the closed position to a narrow slot, open several outlet openings 10. From the outside of the housing 2 run a plurality of leakage holes 11 to the recess in the housing 2 in height of the piston 4 and the drive rod guide 6. From the front chamber 9 can leak some leakage on the tight leadership of the piston 4 in the housing 2.

FIG. 3 shows a detailed view of the front end of the fuel injection device of FIG. 1. In the area in front of the annular groove 3, a fuel space 17 is formed as a gap between the piston 4 and the housing 2, so that fuel in the injection position can flow along the gap from the inlet port 1 to the outlet ports 10. However, the fuel injection device is located in FIG. 3 in the closed position.

Around the front end of the tapered piston 4 extends an annular groove 13, so that two stop edges 14 and 15 are formed. The front stop edge 14 abuts di ^¬ rectly before the exhaust ports 10 which are annularly arranged along the inner wall, so that fuel, which is located in the rear chamber 7 or the front chamber 9, not escape from the housing 2 from the exhaust ports 10 can. The rear stop edge 15 abuts directly behind the outlet openings 10 against the housing 2, so that fuel can not flow from the at least one inlet opening 1 to the outlet openings 10. Instead of the stop edges 14 and 15 and annular projections may be provided which extend below or above the outlet openings 10 along the inner wall of the recess (or to the piston 4) and in the closed position against the piston 4. The front and rear stop edge 14, 15 form sealing edges which close the outlet openings 10 in the closed position and separate the fuel space 20 from the front chamber 9.

In the closed position, fuel at the rear end of the piston exerts a force F _h of the piston, the product ei ^¬ ner rear effective cross-sectional area A _h (cross-section of the piston π-R ² minus the cross-sectional area of the on ^¬ rod π-r _s ² and the pressure p in the rear chamber

(F _h = A _h -p = π- (R ² -r _s ² ) -p) where r _{s is} the radius of the drive rod 5 and R is the radius of the piston 2.

This force counteracts in the closed position a force F _v at the front end of the piston 2, which is the sum of the force, the product of an effective cross-sectional area A _v = π-r ^{2 of} the front chamber and the pressure p in the front

Chamber is where r _{v is} the distance of the front abutment edge 14 from the axis of symmetry S of the piston, and the pressure p in the front chamber 9 is the same as in the rear chamber 7, and the force is the effect of an effective ^¬ the cross-sectional area A _κ = π- (R ² -r ² ) of the fuel space 17 and the pressure p in the fuel space is F _v = (A _v + A _κ ) -p = π- (R ² -r ² + r ² ) -p, where r _{h is} the distance of the rear abutment edge 15 from the axis of symmetry S of the piston, where it is ^¬ assumed that the pressure in the rear chamber 7 corresponds to the pressure that has fuel in the manifold.

The variables R, r _s , r _v , r _h are chosen so that in the closed ^¬ position, the force on the front end of the piston is equal to the force acting on the rear end of the piston (F _h = F _v ), ie A _h = A _v + A _k . This results in an isobaric design of the piston of the fuel injection device in the closed position, for which a minimum force is sufficient to move the piston from the closed position and to maintain it in the closed position.

As soon as the piston 4 is pushed back and the abutment edges 14, 15 move away from the housing 2, so that the piston 4 is moved out of the closed position, the force exerted by the fuel on the piston 4 changes. If a possible pressure change due to the outflow of the fuel is negligible, the sole cause of this is the pressure exerted on the additional surface between the front stop edge 14 and the rear stop edge 15. This force can be compensated in the injection Stel ^¬ lung by a spring 12 (FIG. 1), which is designed so that it only in the injection position exerts a force.

FIG. Fig. 2 shows another fuel injection device. The same elements are denoted by the same reference numerals followed by a lower case letter "a." The other fuel injection device differs from the fuel injection device of Fig. 1 by a sleeve 16a surrounding the rear end of the piston 4a The sleeve 16a may be fixedly connected to the housing 4a.The fuel injector also has no spring 12. By suitable design of the piston 2a and sleeve 16a, fuel in the fuel chamber 17a is prevented from applying force to the forward end The piston is further configured such that fuel at the rear end exerts on the piston 2a a force equal in magnitude to a force which exerts fuels in the front chamber 9a on the piston 2a. FIG. 4 shows a detailed view of the front end of the fuel injection device of FIG. 2. The distance r _{h of} the sleeve 16a and thus also the edge of the annular groove 3a, which bears against the sleeve 16a, from the axis of symmetry S of the piston 4a corresponds to the distance r _{h of} the rear stop ^¬ edge 15a of the axis of symmetry S of the piston 4a, so that fuel exerts in the fuel space 17a, no force on the front ^¬ broader end of the piston 2a because the opposite ge ^¬ oriented effective cross-sectional areas, to which the fuel in the fuel space exerts 17a pressure are equal (ie it applies to the effective cross-sectional area of the fuel space A _κ = 0). The variables R, r _s , r _h , r _v are ^chosen such that the rear effective cross-sectional area A _{h is} as large as the effective cross-sectional area A _{k of} the front chamber. The rear effective cross-sectional area A _h is in the present case because of the sleeve 16 a given by A _h = π - ((Rr _h ) ² -r _s ² ).

LIST OF REFERENCE NUMBERS

1 inlet opening

Ia inlet opening

2 piston housing

2a piston housing

3 groove

3a groove

4 pistons

4a piston

5 drive rod

5a drive rod

6 drive rod guide

6a drive rod guide

7 rear chamber

7a rear chamber

8 channel

8a channel

9 front chamber

9a front chamber

10 outlet opening

10a outlet opening

11 leakage hole

IIa leakage hole

12 spring

13 groove

13a groove

14 front stop edge

14a front stop edge

15 rear stop edge

15a rear stop edge

16a sleeve

17 fuel space

17a fuel space S axis of symmetry of the piston

R Radius of the piston r _v Distance of the front stop edge r _h Distance of the rear stop edge

Claims

claims

1. Fuel injection device for a Brennkraftma ^¬ machine having an inlet opening (1 Ia), an outlet opening (10, 10a), a housing (2, 2a) and a Col ^¬ ben (4, 4a), said piston (4 , 4a) having a front end and a rear end in a Ausneh ^¬ mung that, Zvi ^¬ rule a closed position and an injection position in the housing (2, 2a) is designed to be displaceable, wherein a channel (8, 8a ) extends from the front end of the piston (4, 4a) to the rear end of the piston (4), wherein behind the rear end of the Kol ^¬ bens (4) a rear chamber (7, 7a) is formed, in which the channel (8 , 8a) opens, wherein before the front end of the piston (4, 4a) (a front chamber 9, 9a) is formed, laterally between the Gehäu ^¬ se (2, 2a) and the front end of the piston (4 , 4a) a fuel space (17, 17a) is formed, and wherein the front end of the piston (4, 4a) abuts in the closed position on a sealing seat and so the outlet ^¬ opening (10, 10a) closes, characterized in that the inlet opening (1, Ia) in the fuel space (17, 17a), and in that the channel (8, 8a) in the (before ^¬ whose chamber 9 , 9a), so that a pressure equalization between the front chamber (9, 9a) and the rear chamber (7, 7a) takes place.

2. Fuel injection according to one of the preceding claims, characterized in that the piston (4, 4a) is rotationally symmetrical, and the channel (8, 8a) along the axis of symmetry (S) through the piston (4, 4a).

3. Fuel injection device according to claim 2, characterized in that around the piston (4, 4a) to a ^¬ striking edge (15, 15a) extends which abuts in the closed position ^¬ against the sealing seat and so the outlet Opening (10, 10a) shuts off towards the inlet opening (1, Ia), and that to the piston (4, 4a) has a further stop edge (14, 14a) extends which abuts in the closed ^¬ position against the sealing seat and so the outlet - Opening (10, 10a) opposite the channel (8, 8a) shuts off.

4. Fuel injection device according to one of the preceding claims, characterized in that the Kol ^¬ ben (4, 4a) is formed so that in the closed position a force, the fuel at the rear En ^¬ de on the piston (4, 4a ) along the piston (4, 4a) is substantially equal in magnitude to a force exerting fuel at the front end on the piston (4, 4a) along the piston (4, 4a).

5. Fuel injection device according to claim 4, characterized in that the piston (4) is formed so that in the closed position fuel in the fuel chamber (17, 17 a) exerts substantially no force on the front end.

6. Fuel injection device according to claim 5, characterized in that a sleeve (16 a) between the rear ^¬ direct end of the piston (4, 4 a) and the housing (2, 2 a) is provided.

7. Fuel injection device according to claim 5 or claim 6, characterized in that the piston (4, 4a) is formed so that in the closed position fuel at the rear end of the piston (4, 4a) along the piston (4, 4a) a force substantially equal in magnitude to a force exerted by fuel in the front chamber (9, 9a) along the piston (4, 4a).

8. Fuel injection device according to one of the preceding claims, characterized in that the KoI- ben (4, 4a) is formed so that in the injection ^¬ position, a force that exerts fuel at the rear end of the piston (4, 4a) along the piston (4, 4a), the amount by a force difference smaller as a force that exerts fuel at the front end on the piston (4, 4a) along the piston (4, 4a).

9. Fuel injection device according to claim 8, characterized in that a spring (12) is provided, which exerts a force on the rear end along the piston (4, 4a) in the injection position, which is equal in magnitude to the force difference.