EP1763628B1 - Injector - Google Patents

Abstract

The invention relates to an injection nozzle for an internal combustion engine having a nozzle needle or needle unit for controlling an injection of fuel through at least one injection orifice and an actuator for driving a coupling piston. The nozzle needle or needle unit has a control surface that at least partially delimits a control chamber which communicates with a coupling chamber that is at least partially delimited by the coupling piston. The control surface is situated at the end of the nozzle needle or nozzle unit oriented away from the at least one injection orifice and the actuator drives the coupling piston to open the nozzle needle in such a way that a volume of the coupling chamber increases.

Description

State of the art

The invention relates to an injection nozzle for an internal combustion engine, in particular in a motor vehicle, having the features of the preamble of claim 1.

Out US 4,022,166 For example, such an injection nozzle is known, which has a nozzle needle for controlling an injection of fuel through at least one injection hole. The injection nozzle comprises a piezoelectric actuator for driving a coupling piston, which dips into a coupling space or at least partially delimits this with an end face. The nozzle needle has a control surface, which faces away from the injection hole is arranged on the nozzle needle. The coupling piston is driven by the actuator such that a pulling movement of the coupling piston increases the volume of the coupling space.

Another injector with an actuator for driving a coupling piston and a nozzle needle for injecting fuel is out EP 1174 615 A2 known. Here, the coupling piston is designed in the form of a sleeve which limits the coupling space substantially. The actuator drives the coupling piston in such a way that here also a pulling movement of the coupling piston causes an enlargement of the volume of the coupling space.

From the US 6,520,423 B1 a further injection nozzle is known and has a nozzle needle for controlling an injection of fuel through at least one injection hole. Furthermore, the injection nozzle comprises a piezoelectric actuator for driving a coupling piston, which dips into a coupling space or at least partially limited. The nozzle needle or a needle assembly comprising the nozzle needle has a control surface which at least partially delimits a control chamber and that with the coupling space communicated. In the known injection nozzle, the control surface facing the at least one spray hole is arranged on the nozzle needle or on the needle assembly. To open the nozzle needle of the actuator drives the coupling piston in the known injection nozzle so that it dips deeper into the coupling space and thereby reduces the volume of the coupling space. By reducing the coupling space volume, the pressure in it increases, which leads to a corresponding increase in pressure in the control room communicating therewith. Accordingly, the control surface is subjected to the increased pressure in the control chamber, whereby a force directed away from the at least one injection hole is introduced into the nozzle needle or into the needle assembly. As a result, the opening forces acting on the nozzle needle or on the needle assembly predominate, so that the nozzle needle lifts from its seat and allows fuel injection through the at least one injection hole.

In the known injection nozzle, the control of the nozzle needle is therefore carried out with the help of an overpressure, which can be well above the usual prevailing in the coupling space and the control chamber pressure. Conventionally, when the nozzle needle is closed, a comparatively high injection pressure prevails both in the coupling space and in the control chamber, so that relatively tight manufacturing tolerances must be maintained in order to avoid undesirably high leakages. However, tight manufacturing tolerances are associated with comparatively high production costs. Furthermore, in the known injection nozzle, the control surface is formed on a control piston which drives the nozzle needle or forms part of the needle assembly. Depending on the pressurization of the control chamber or the control surface more or less pronounced lateral forces can attack the control piston, which can be transmitted due to the coupling with the nozzle needle on this. This can lead to increased friction of the nozzle needle in its needle guide, which can affect the proper operation of the nozzle needle.

Advantages of the invention

The injection nozzle according to the invention with the features of claim 1 has the advantage that the nozzle needle can be controlled directly with a negative pressure, whereby it is in principle possible to specify the production tolerances less closely. An enlarged leadership game however, reduces the manufacturing costs. Furthermore, in the case of the injection nozzle according to the invention, the pressurization or pressure reduction of the control surface can readily be designed such that no transverse forces are introduced into the nozzle needle or into the needle assembly, which improves the functionality of the injection nozzle.

The embodiment of the invention has the consequence that the coupling piston is driven by the actuator to the at least one injection hole, which allows a particularly compact design for the injection nozzle.

Advantageously, an embodiment in which the coupling piston is mounted in a cylinder space adjustable in stroke, which is formed in an insert part, which is arranged axially between the actuator or the needle assembly. Such an insert part can be manufactured particularly easily with sufficient accuracy, which reduces the manufacturing costs for the injection nozzle. In a further development, a Rückstellfe can be arranged in the cylinder chamber, which at one end on the coupling piston and the other at a bottom of the cylinder chamber supported. With the help of such a return spring can be biased to close the nozzle needle of the coupling piston with a defined restoring force in its initial position, which simultaneously leads to a defined pressure increase in the coupling space and thus in the control room. As a result, the forces acting in the closing direction on the nozzle needle can be increased. The proposed return spring thus supports the closing movement of the nozzle needle.

Further important features and advantages of the injection nozzle according to the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

drawings

Fig. 1

einen vereinfachten Längsschnitt durch eine Einspritzdüse nach der Erfindung,

Fig. 2

eine vergrößerte Detailansicht eines in Fig. 1 mit II gekennzeichneten Längsabschnitts der Einspritzdüse.

An embodiment of the injection nozzle according to the invention is shown in the drawings and will be explained in more detail below, wherein like reference numerals refer to the same or similar or functionally identical components. Show, in each case schematically,

Fig. 1

a simplified longitudinal section through an injection nozzle according to the invention,

Fig. 2

an enlarged detail view of an in Fig. 1 marked with II longitudinal section of the injector.

Description of the exemplary embodiment

Corresponding Fig. 1 An injector 1 according to the invention comprises a nozzle body 2 in which an actuator 3 and a nozzle needle 4 are arranged. The actuator 3 is preferably designed as a piezoelectric actuator 3, that is to say a piezo actuator 3 which increases its axial length when current is applied and if the actuator fails Electricity supply reduced again. The nozzle needle 4 is used to control an injection of fuel through at least one injection hole 5, which is housed in a nozzle tip 6. Usually, the injection nozzle 1 includes a plurality of injection holes 5, which may be arranged quasi star-shaped with respect to a longitudinal central axis 7 of the nozzle needle 4 and the injection nozzle 1. The nozzle needle 4 cooperates with a needle seat 8. In the closed state of the nozzle needle 4, this sits in its needle seat 8 and separates the at least one injection hole 5 of a unspecified here Fuel supply from, in which the fuel to be injected is provided under a relatively high injection pressure. In the open state, the nozzle needle 4 is lifted from the needle seat 8, whereby the at least one injection hole 5 is connected to the fuel supply. As a result, there is an injection of fuel into an injection chamber 9, which may be a combustion chamber or a mixture formation space.

The injection nozzle 1 is used for injecting fuel into the combustion chamber of a cylinder of a Brennkmfanaschme, which may be arranged in particular in a vehicle. In this case, each cylinder of the internal combustion engine is assigned a separate injection nozzle 1. In the so-called "common rail system", a common fuel supply is provided for several, in particular for all, injection nozzles 1 of the internal combustion machine, which provides the fuel to be injected at the relatively high level of the injection pressure.

The nozzle needle 4 forms here a part of a needle assembly 10, which in addition to the nozzle needle 4 here also exemplarily a coupling rod 11 and a control piston 12 may have. The individual components of the needle assembly 10 form a common hubverstellbare unit which is suitable at least for the transmission of compressive forces. It is in principle possible that two adjacent components of the needle assembly 10 only lie loosely against each other. It is also possible that two adjacent components of the needle assembly 10 are firmly connected to each other, for. B. by a weld or solder joint. It is also possible that at least two components of the needle assembly 10 are made in one piece from one piece.

The actuator 3 drives a piston rod 14 via a joint-like coupling point 13 and via this a coupling piston 15.

Corresponding Fig. 2 the coupling piston 15 limits a coupling space 16 at least partially. This coupling space 16 communicates via a connection path 17 with a control chamber 18. This control chamber 18 is at least partially delimited by the control piston 12 or by a control surface 19. The control surface 19 is formed here on the control piston 12. It is also possible to arrange the control surface 19 directly on the nozzle needle 4 or on another component of the needle assembly 10.

According to the invention, the control surface 19 is arranged on the nozzle needle 4 or on the needle dressing 10 such that it faces away from the at least one injection hole 5. This means that a pressure prevailing in the control chamber 18 pressure acts on the control surface 19 so that it can initiate a force acting in the closing direction of the nozzle needle 4 force in the nozzle needle 4 and in the needle assembly 10. Furthermore, in the present invention, the arrangement of the coupling piston 15 relative to the coupling space 16 is selected such that the actuator 3, when actuated to open the nozzle needle 4, drives the coupling piston 15 such that a volume of the coupling space 16 increases.

In the embodiment shown here, the coupling piston 15 at least partially limits the coupling space 16 at a side 20 facing the at least one spray hole 5. As a result, the coupling piston 15 has a coupling surface 21 facing away from the at least one spray hole 5, which is arranged in the coupling space 16 or partially delimits it. In order to increase the volume of the coupling space 16, the actuator 3 thus drives the coupling piston 15 in the direction of the at least one injection hole 5.

In the preferred embodiment shown here, the coupling piston 15 is mounted in a cylinder space 22 adjustable in stroke. In this cylinder chamber 22, a return spring 23 is arranged, which is also referred to below as the coupling piston return spring 23. The coupling piston return spring 23 is supported in the axial direction at one end on the coupling piston 15 and at the other end on a base 24 of the cylinder chamber 22. The cylinder chamber 22 is also connected in a manner not shown here to a leakage system, so that a stroke adjustment of the coupling piston 15, the volume in the cylinder chamber 22 can change without causing a significant pressure change in the cylinder chamber 22.

The cylinder chamber 22 is formed in an insert part 25 designed as a separate component, which is arranged axially between the actuator 3 and the nozzle needle 4 or needle assembly 10. In this case, the insert 25 is supported in the embodiment shown here in the axial direction at one end to a part of the nozzle body 2 and the other end z. B. from a sealing plate 26 from. In the embodiment shown here, the insert part 25 has on an end facing the actuator 3 an axially projecting, radially outwardly arranged annular collar 27 which is axially supported on the sealing plate 26, thereby axially between the sealing plate 26 and the insert part 25 of Coupling space 16 is formed. Furthermore, in the embodiment shown here, the connection path 17 is integrated into the insert part 25. By way of example, the connection path 17 can be formed from two holes 28 and 29 communicating with one another, of which one 28 is connected to the coupling space 16 and the other 29 to the control space 18.

In the embodiment shown here, the piston rod 14 penetrates the sealing plate 26 centrally and is supported axially on the coupling piston 15. Again, it is in principle possible that piston rod 14 and coupling piston 15 only lie loosely against each other. Likewise, coupling piston 15 and piston rod 14 can be firmly connected to each other or made in one piece from one piece. The piston rod 14 projects into the coupling space 16, d. H. the piston rod 14 passes through the coupling space 16 in the axial direction to the coupling piston 15. In this case, the piston rod 14 has at least within the coupling space 16 an outer cross section 30 which is smaller than an outer cross section 31 of the coupling piston 15. In this way, the coupling surface 21 is realized or In this way, the dependence of the coupling space volume on the stroke position of the coupling piston 15 and the piston rod 14 is realized. In the present case, the piston rod 14 and / or the coupling piston 15 is / are cylindrical, in particular circular-cylindrical.

Corresponding Fig. 1 can be arranged between the sealing plate 26 and a support plate 32 axially supported on the actuator 3, a further return spring 33, which is also referred to below as the actuator return spring 33. The actuator return spring 33 is supported in the axial direction on the one hand on the support plate 32 and on the other hand on the sealing plate 26 and is thus supported on the insert member 25 on the nozzle body 2. The actuator 3 is connected centrally via the coupling point 13 through the support plate 32 to the piston rod 14.

Corresponding Fig. 2 the control chamber 18 is formed axially between the insert part 25 and the control piston 12, wherein it is also enclosed here radially by a sleeve 34. In this sleeve 34, the control piston 12 is mounted adjustable in stroke. Out Fig. 2 In this case, it becomes clear that the laying of the connection path 17 within the insert part 25 can advantageously be specifically realized in such a way that the connection path 17 opens here centrally via the bore 29 into the control space 18. In this way, a particularly uniform pressure build-up or pressure reduction in the control chamber 18 can be achieved in order to avoid lateral forces on the control piston 12 and thus on the needle assembly 10. Coming back to Fig. 1 a further return spring 35 may be provided, which is also referred to below as the needle return spring 35. The needle return spring 35 is supported in the axial direction at one end to the sleeve 34 and the other end to a support ring 36, which in turn is supported on the needle assembly 10 or forms part of the needle assembly 10.

The injection nozzle 1 according to the invention operates as follows:

In an initial state, the nozzle needle 4 is closed, d. H. the nozzle needle 4 is seated in the needle seat 8 and thus blocks the connection of the fuel supply to the at least one spray hole 5. In this initial state, the same pressure prevails in the control chamber 18 and in the coupling chamber 16, in particular the crankshaft high pressure. This high fuel pressure can be adjusted, for example, by a targeted and / or unavoidable leakage of the coupling space 16 and / or the control chamber 18 and / or the connection path 17 with respect to the fuel supply. The effective in the control chamber 18 pressure generated at the control surface 19 oriented in the closing direction of the nozzle needle 4 force. Furthermore, the needle return spring 35 also introduces a closing force into the needle assembly 10. Overall, the needle dressing 10 outweigh the forces acting in the closing direction forces.

The actuator return spring 33 has biased the actuator 3 in its shortened starting position. The coupling piston return spring 23 keeps the coupling piston 15 biased against the force acting in the coupling space 16 force.

In order to initiate an injection process through the at least one spray hole 5, the actuator 3 is actuated or activated, whereby this increases its length and thereby drives the coupling piston 15 axially via the piston rod 14 in the direction of the at least one injection hole 5. As a result, the coupling surface 21 of the coupling piston 15 exposed to the coupling space 16 is adjusted relative to the coupling space 16 such that the volume of the coupling space 16 increases. With the enlargement of the coupling space volume, a pressure drop in the coupling space 16 is accompanied, which propagates via the connection path 17 into the control space 18. Due to the reduced pressure in the control chamber 18, the forces acting on the control surface 19 in the closing direction are reduced, so that now the forces acting in the opening direction predominate on the needle dressing 10. Consequently, the nozzle needle 4 lifts from its needle seat 8, which is the connects at least one injection hole 5 with the fuel supply and allows the injection process.

To terminate the injection process, the actuator 3 is deactivated, whereby its length is reduced. The tensioned by the opening process return springs 23, 33 and 35 can now unfold their restoring force with deactivated actuator 3 and drive back in the sequence the actuator and the coupling piston 15 and the nozzle needle 4 in the starting position. Important for the closing operation of the nozzle needle 4 is that the coupling piston 15 driven by the coupling piston return spring 23, the volume of the coupling chamber 16 again reduced, which is accompanied by a corresponding increase in pressure in the coupling chamber 16 and thus in the control chamber 18. The increased pressure in the control chamber 18 increases to a corresponding extent initiated via the control surface 19 in the needle assembly 10 closing forces. As soon as the nozzle needle 4 retracts into it needle seat 8, the connection of the at least one injection hole 5 is interrupted with the fuel supply and the injection process is completed.

The injection nozzle 1 according to the invention is thus controlled directly via the pressure or negative pressure at the control surface 19, which is variable by means of the actuator 3. It is noteworthy here that the hydraulically operating components of the injection nozzle 1 are maximally exposed to the injection pressure, since the pressure in the control chamber 18 is lowered to actuate the nozzle needle 4. As a result, the hydraulic components manufacturing technology can be manufactured with less effort. In particular, a lesser clearance and larger tolerances can be allowed, which has an advantageous effect on the manufacturing costs. Furthermore, there is no direct coupling between the nozzle needle 4 and the needle assembly 10 on the one hand and the coupling piston 15 on the other hand, which reduces adverse interactions between said components or eliminated.

LIST OF REFERENCE NUMBERS

1

injection

2

nozzle body

3

actuator

4

nozzle needle

5

spiracle

6

nozzle tip

7

Nozzle longitudinal central axis

8th

needle seat

9

Injection room

10

needle unit

11

coupling rod

12

spool

13

coupling point

14

piston rod

15

coupling piston

16

coupling space

17

connection path

18

control room

19

control surface

20

Page of 16

21

coupling surface

22

cylinder space

23

Return spring

24

Reason of 22

25

insert

26

sealing plate

27

gorget

28

drilling

29

drilling

30

External cross section of 16

31

External cross section of 15

32

support plate

33

Return spring

34

shell

35

Return spring

36

support ring

Claims (8)

1. Injection nozzle for an internal combustion engine, in particular in a motor vehicle,

   - having a nozzle needle (4) for controlling an injection of fuel through at least one spray hole (5),

   - having an actuator (3) for driving a coupling piston (15),

   - with the nozzle needle (4) or a needle assembly (10) which comprises the nozzle needle (4) having a control surface (19) which at least partially delimits a control chamber (18),

   - with the control chamber (18) communicating with a coupling chamber (16),

   - with the coupling piston (15) at least partially delimiting the coupling chamber (16),

   - with the control surface (19) being arranged on the nozzle needle (4) or on the needle assembly (10) so as to face away from the at least one spray hole (5),

   - with the actuator (3) driving the coupling piston (15) to open the nozzle needle (4) in such a way that a volume of the coupling chamber (16) is increased,

   characterized
   in that the coupling piston (15) has a coupling surface (21) which faces away from the at least one spray hole (5) and which at least partially delimits the coupling chamber (16), and in that, to increase the volume of the coupling chamber (16), the actuator (3) drives the coupling piston (15) in the direction of the at least one spray hole (5).
2. Injection nozzle according to Claim 1,
   characterized

   - in that the coupling piston (15) is mounted with stroke adjustability in a cylinder chamber (22),

   - in that the cylinder chamber (22) is formed in an insert part (25) which is arranged axially between the actuator (3) and the nozzle needle (4) or the needle assembly (10).
3. Injection nozzle according to Claim 2,
   characterized
   in that a restoring spring (23) is arranged in the cylinder chamber (22), which restoring spring (23) is supported at one end on the coupling piston (15) and at the other end on a base (24) of the cylinder chamber (22).
4. Injection nozzle according to Claim 2 or 3,
   characterized
   in that a connecting path (17), which connects the control chamber (18) to the coupling chamber (16) in communicating fashion, is formed in the insert part (25).
5. Injection nozzle according to one of Claims 1 to 4,
   characterized
   in that the actuator (3) drives the coupling piston (15) via a piston rod (14) which extends through the coupling chamber (16) as far as the coupling piston (15) and whose outer cross section (30) which is exposed to the coupling chamber (16) is smaller than that outer cross section (31) of the coupling piston (15) which is exposed to the coupling chamber (16).
6. Injection nozzle according to Claims 2 and 5,
   characterized
   in that the coupling chamber (16) is formed axially between the insert part (25) and a sealing plate (26) through which the piston rod (14) extends centrally.
7. Injection nozzle according to Claim 6,
   characterized

   - in that the sealing plate (26) is supported axially on the insert part (25) and/or

   - in that a further restoring spring (33) is supported on the sealing plate (26), which further restoring spring (33) is also supported directly or indirectly on the actuator (3).
8. Injection nozzle according to one of Claims 1 to 7,
   characterized
   in that a connecting path (17) which connects the control chamber (18) to the coupling chamber (16) in communicating fashion is connected axially and centrally to the control chamber (18).

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