EP1636480A1

EP1636480A1 - Injector for internal combustion engines

Info

Publication number: EP1636480A1
Application number: EP04729037A
Authority: EP
Inventors: Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-06-10
Filing date: 2004-04-23
Publication date: 2006-03-22
Also published as: KR20060021352A; JP2006510851A; DE10326045A1; WO2004111429A1; US20060289681A1

Abstract

The invention relates to an injector (1) for an internal combustion engine, comprising a nozzle body (2) having at least one injection hole (5) that can be controlled with a first injector needle (8) and at least a second injection hole (6) that can be controlled with a second injector needle (15). A simplified construction of said injector (1) can be realized by coupling a first drive piston (18) to the first injector needle (8), wherein said drive piston has a first transmission surface (20) that is hydraulically coupled to a control surface (40) of a control piston (38) by means of a first pressure transmission path (44). A second drive piston (28) is coupled to the second injector needle (15) and has a second transmission surface (30) that can be hydraulically coupled to a control surface (43) of the control piston (38) by means of a second activatable and deactivatable hydraulic pressure transmission path (47). Activation and deactivation of the second pressure transmission path (47) is controlled depending on the control piston stroke.

Description

Injection nozzle for internal combustion engines

State of the art

The present invention relates to an injection nozzle for internal combustion engines with the features of the preamble of claim 1.

Such an injection nozzle is known for example from DE 100 58 153 Al and has a nozzle body on which at least one first spray hole and at least one second spray hole are formed. A first nozzle needle designed as a hollow needle is guided in a first needle guide of the nozzle body, with which the injection of fuel through the at least one first spray hole can be controlled. A second nozzle needle is arranged coaxially in the first nozzle needle, with which the injection of fuel through the at least one second spray hole can be controlled. In the known injection nozzle, the second nozzle needle is drive-connected to a drive piston which, in a control chamber, has a control surface which is effective when pressure is applied in the closing direction. The second nozzle needle has a pressure stage, ie a cross-sectional area of a second valve seat formed between the second nozzle needle and the nozzle body is smaller than a cross-sectional area of one formed in the first nozzle needle for guiding the second nozzle needle. When the first nozzle needle is open, the pressure stage of the second nozzle needle is pressurized, the pressure stage of the second nozzle needle acting in the opening direction. If the second nozzle needle is also to be opened with the first nozzle needle, the pressure in the control chamber can be reduced so that the opening force at the pressure stage of the second nozzle needle predominates. The effort required to actuate the second nozzle needle is relatively large.

Advantages of the invention

The injection nozzle according to the invention with the features of the independent claim has the advantage over the fact that only a single actuator or actuator is required to control both nozzle needles. This results in a considerably simplified structure for the injection nozzle, so that it can be manufactured more cost-effectively.

The invention is based on the general idea of controlling the pressures applied to the drive pistons of the two nozzle needles with only a single control piston, a hydraulic pressure transmission path being provided between the control piston and the respective drive piston serving to actuate the associated nozzle needle. While the first hydraulic pressure transmission path formed between the control piston and the first drive piston provided for actuating the first nozzle needle is permanently active, the invention proposes to make the second hydraulic pressure transmission path designed between the control piston and the second drive piston provided for actuation of the second nozzle needle controllable that the second pressure transmission path between an activated and is switchable in a deactivated state. The switchover between the activated state and the deactivated state is controlled as a function of the control piston stroke. This means that an opening stroke of the control piston always causes an opening stroke of the first nozzle needle and, after the stroke-controlled switching between deactivated state and activated state, additionally causes an opening stroke of the second nozzle needle.

Both nozzle needles can thus be controlled directly with only a single control piston, that is to say with a single actuator, which simplifies the construction of the injection nozzle according to the invention. Furthermore, the injection behavior or the injection characteristic of the injection nozzle can be improved, in particular extremely short injection times can be achieved.

According to a particularly advantageous development, the second hydraulic pressure transmission path can switch between its activated and its deactivated state during a predetermined control piston stroke, this control piston stroke then being selected such that when the control piston moves in an opening stroke until the predetermined control piston stroke is reached, the first nozzle needle performs an opening stroke, while the second nozzle needle remains in its closed position, and that the opening nozzle movement also carries out an opening stroke when the opening of the control piston moves beyond the predetermined control piston stroke. Via the predefined control piston stroke, a stroke range is thus defined for the control piston, in which the control piston actuates only the first nozzle needle. Only when the opening stroke goes beyond the predetermined control piston stroke does the control piston also actuate the second nozzle needle. This makes it particularly easy to make one Perform fuel injection either only through the at least one first spray hole or both through the at least one first spray hole and through the at least one second spray hole. The time between the opening of the first nozzle needle and the opening of the second nozzle needle is virtually free to choose.

According to particularly advantageous embodiments, a second control chamber, which is used to actuate the second drive piston, can be connectable via a controllable hydraulic connection to a supply line which supplies fuel under high pressure to the spray holes. This hydraulic connection is controlled as a function of the control piston position for opening and locking, the second hydraulic pressure transmission path being deactivated when the hydraulic connection is open and activated when the hydraulic connection is blocked. In this embodiment, the incompressibility of the hydraulic medium used, ie the fuel, is used to activate or deactivate the second pressure transmission path. As long as the hydraulic connection is open, the second control chamber communicates with the feed line, with the result that the second pressure transmission path to the feed line is open. Hydraulic medium displaced within the second pressure transmission path, which is conveyed into the second control chamber or displaced or sucked out of the second control chamber, can then be picked up directly by the feed line or replaced via the feed line. The pressure in the second control room remains virtually constant and corresponds to the pressure prevailing in the supply line.

However, as soon as the hydraulic connection is blocked, the second pressure transmission path is quasi hermetically sealed, at least for dynamic processes, with the result that Hydraulic medium, which is conveyed into the second control chamber or is sucked in or displaced from the second control chamber, generates a corresponding pressure increase or pressure drop in the second control chamber.

In an expedient development, a section of the hydraulic connection can be formed in the control piston. This design results in a direct relationship between the control piston stroke and shift actuation of the second pressure transmission path.

In another embodiment, the controllable hydraulic connection can be formed internally in the second pressure transmission path, with a first transmission space, in which a first transmission surface of the first drive piston is arranged, to a second transmission space, in which a second transmission surface of the second drive piston is arranged, via the hydraulic connection is connectable. The hydraulic connection is again controlled as a function of the control piston position for opening and blocking, the second pressure transmission path being activated in contrast to the embodiment mentioned above when the hydraulic connection is open and deactivated when the hydraulic connection is blocked. In this embodiment, the construction of the hydraulic route guidance within the injection nozzle is simplified, since the second pressure transmission route can coincide with the first pressure transmission route up to the controllable hydraulic connection.

A further development is expedient here, in which a section of the hydraulic connection is formed in the first drive piston. Accordingly, the hydraulic connection is then only controlled indirectly as a function of the control piston stroke and instead directly as a function of the Opening strokes of the first nozzle needle, which is connected to the first drive piston. This is of particular advantage since the second nozzle needle can be actuated to open exactly when the first nozzle needle has performed a predetermined preliminary stroke when opening.

Further important features and advantages of the injection nozzle according to the invention result from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

drawings

Embodiments of the injection nozzle according to the invention are shown in the drawings and are explained in more detail below, the same reference numerals referring to the same or similar or functionally identical components. Each shows schematically:

Fig. 1 to 4 each a greatly simplified principle- longitudinal section through an injection nozzle according to the invention, in different embodiments.

Description of the embodiments

1, an injection nozzle 1 according to the invention has a nozzle body 2 that is only partially shown. The injection nozzle 1 is used to supply fuel to a cylinder of an internal combustion engine, in particular in a motor vehicle. In the assembled state, a nozzle tip 3 projects into a combustion chamber 4 or into a premixing chamber 4 of the respective cylinder, in such a way that at least one first spray hole 5 and at least one second spray hole 6 when the injection nozzle 1 is actuated accordingly, fuel can be injected into the combustion chamber / premixing chamber 4. It is clear that the injection nozzle 1 can have a plurality of first spray holes 5 and / or a plurality of second spray holes 6, which are then expediently each arranged in a ring, distributed in the circumferential direction along the nozzle tip 3.

The nozzle body 2 contains a first needle guide 7 in which a first nozzle needle 8 is mounted so as to be stroke-adjustable. The first nozzle needle 8 is used to control the at least one first spray hole 5. For this purpose, a first sealing seat 10 is formed between a first needle tip 9 of the first nozzle needle 8 facing the spray holes 5, 6 and the nozzle tip 3, which is used to supply the at least one fuel with fuel first spray hole 5 is arranged upstream of the at least one first spray hole 5.

The fuel supply to the spray holes 5, 6 takes place via a supply line 11 which is formed in the nozzle body 2, is supplied with fuel at high pressure on the inlet side and opens into a nozzle chamber 12 on the outlet side. An annular space 13, which is formed radially between the first nozzle needle 8 and the nozzle body 2, leads from the nozzle space 12 to the spray holes 5, 6. In order to supply the supply line 11 with fuel under high pressure, the supply line 11 can be connected to a high-pressure manifold, not shown here, which is connected to a high-pressure pump is fed and to which the supply lines 11 of several injection nozzles 1 are connected (“common rail principle”). It is also possible to connect the supply line 11 directly to a corresponding high-pressure pump. The first nozzle needle 8 is designed as a hollow needle and contains a second needle guide 14, in which a second nozzle needle 15 is mounted in a stroke-adjustable manner coaxial with the first nozzle needle 8. The second nozzle needle 15 is used to control the at least one second spray hole 6. For this purpose, a second sealing seat 17 is formed between a second needle tip 16 facing the spray holes 5, 6 and the nozzle tip 3, which is downstream of the at least one first spray hole 5 and upstream of the at least one second spray hole 6 is arranged. The sealing seats 10, 17 each extend in the circumferential direction in an annular and linear manner.

When the first nozzle needle 8 is closed, both the at least one first spray hole 5 and the at least one second spray hole 6 are separated from the fuel supply. When the first nozzle needle 8 is open and the second nozzle needle 15 is closed, the at least one first spray hole 5 communicates with the fuel supply, while the at least one second spray hole 6 is shut off from the fuel supply. When both nozzle needles 8, 15 are open, all spray holes 5, 6 communicate with the fuel supply.

For driving the first nozzle needle 8, a first drive piston 18 is provided, which is mounted in a stroke-adjustable manner in the nozzle body 2 and is drive-coupled to the first nozzle needle 8. In the embodiment shown here, the first drive piston 18 is supported on the first nozzle needle 8 via a disk 19. Since, during operation of the injection nozzle 1, forces permanently act on the first drive piston 18 and on the first nozzle needle 8, which press the first drive piston 18 against the first nozzle needle 8, it is not absolutely necessary that the first nozzle needle 8 be fixed to the first drive piston 18 connected is. The individual components (first nozzle needle 8, disk 19, first drive piston 18) can therefore in particular lie loosely on one another. The components 8, 19, 18 mentioned form a functional unit which is completely adjustable in terms of stroke. An embodiment is also possible in which the first drive piston 18 is fixedly connected to the first nozzle needle 8, in particular the first drive piston 18 and the first nozzle needle 8 can also be formed in one piece.

The first drive piston 18 has a first translator surface 20, which is arranged in a first translator chamber 21 and can be pressurized there. The first translator surface 20 faces the spray holes 5, 6 and is thus effective when pressure is applied in the opening direction of the first nozzle needle 8. The first drive piston 18 also has a first compensator surface 22, which is arranged in a first compensator chamber 23 and can be pressurized there. The first compensator surface 22 is arranged opposite to the first translator surface 20 and thus facing away from the spray holes 5, 6, so that the first compensator surface 22 is effective when pressure is applied in the closing direction of the first nozzle needle 8. Furthermore, a first spring 24 is provided, which prestresses the first nozzle needle 8 in the closing direction. For this purpose, the first spring 24 is supported here at one end on the nozzle body 2 and at the other end via the disk 19 on the first nozzle needle 8. The first nozzle needle 8 is additionally equipped with a first pressure stage 25, which faces the spray holes 5, 6 and thus acts when the first nozzle needle 8 is pressurized in the opening direction. The first pressure stage 25 results from the difference between the cross-sectional area of the first needle guide 7 and the cross-sectional area of the first Sealing seat 10. The first pressure stage 25 is arranged here partly in the nozzle chamber 12 and partly in the annular chamber 13.

In the area of the disc 19, a leakage space 26 is formed in the nozzle body 2, which is connected via a leakage channel 27 to a relatively unpressurized reservoir, e.g. Fuel tank, communicates. The first spring 24 is also accommodated in this leakage space 26.

To drive the second nozzle needle 15, a second drive piston 28 is provided, which is suitably drive-coupled to the second nozzle needle 15. Analogous to the coupling between the first drive piston 18 and the first nozzle needle 8, the second drive piston 28 can also rest loosely on the second nozzle needle 15 at a dividing line 29. A fixed connection between the second drive piston 28 and the second nozzle needle 15 is also possible. In any case, the second drive piston 28 and the second nozzle needle 15 also form a functional unit which is adjustable as a whole. The second drive piston 28 has a second translator surface 30, which is arranged in a second translator chamber 31 and can be pressurized there. The second translator surface 30 faces away from the spray holes 5, 6 and is therefore effective when pressure is applied in the closing direction of the second nozzle needle 15. In the area of the second translator space 31, a second spring 32 is provided, which prestresses the second nozzle needle 15 in the closing direction. For this purpose, the second spring 32 is supported at one end on the nozzle body 2 and at the other end via the second drive piston 28, on the second translating surface 30, on the second nozzle needle 15.

The second nozzle needle 15 is equipped with a second pressure stage 33, which is determined by the difference between the Cross-sectional area of the second needle guide 14 and the cross-sectional area of the second sealing seat 17 is formed. When pressure is applied, the second pressure stage 33 acts in the opening direction of the second nozzle needle 15. When the first nozzle needle 8 is closed, the second pressure stage 33 is inactive, so that the full closing forces of the second spring 32 and the second transmission surface 30 act. When the first nozzle needle 8 is open, a pressure is present at the second pressure stage 33, which acts in the opening direction of the second nozzle needle 15 and reduces the opening forces required to open the second nozzle needle 15.

The first translator room 21 communicates with a first control room 35 via a first control channel 34. In a corresponding manner, the second translator room 31 also communicates with a second control room 37 via a second control channel 36.

The injection nozzle 1 also contains a control piston 38 which is mounted in a stroke-adjustable manner in the nozzle body 2. The control piston 38 is drive-connected to an actuator or actuator, not shown in FIG. 1, e.g. via a drive rod 39. The control piston 38 has a first control surface 40 which is formed at a first end 41 of the control piston 38, is arranged in the first control chamber 35 and can be pressurized there. At a second end 42 opposite the first end 41, the control piston 38 has a second control surface 43 which is arranged in the second control chamber 37 and can be pressurized there.

A first hydraulic pressure transmission path 44 is thus formed between the control piston 38 and the first drive piston 18, via which the first booster surface 20 with the first control surface 40 is hydraulic is coupled. The first control chamber 35 communicates via a feed line 45 with the feed line 11, a feed valve 46 being arranged in the feed line 45, which is designed here as a non-return check valve and is permeable to the first control chamber 35 and is designed to block the feed line 11. In this way, at least approximately the same pressure as in the supply line 11 prevails in the first control chamber 35 and thus in the first booster chamber 21.

In a corresponding manner, a second hydraulic pressure transmission path 47 is formed between the control piston 38 and the second drive piston 28, via which the second control surface 43 is hydraulically coupled to the second booster surface 30. The second control chamber 37 can be connected to the feed line 11 via a hydraulic connection 48, so that the communicating state in the second control room 37 and thus also in the second booster chamber 31 is the same pressure as in the feed line 11. The hydraulic connection 48 is designed to be controllable in such a way that it can be opened and locked. This is achieved in that the hydraulic connection 48 is laid in the nozzle body 2 such that the control piston 38 operates in the manner of a slide and, depending on its stroke position, blocks or releases the hydraulic connection 48.

In the present case, a section 49 of the hydraulic connection 48 is formed within the control piston 38. This section 49 communicates on the one hand with the second control chamber 37 and on the other hand with an annular space 50 of the hydraulic connection 48, which communicates with the supply line 11 via a channel 51 of the hydraulic connection 48. In the starting position shown here, there is an overlap between the annular space 50 facing end of section 49 and the annular space 50, so that the hydraulic connection 48 is opened.

In the event of a stroke adjustment of the control piston 38 in an opening direction 52 indicated by an arrow, the connection between the section 49 and the annular space 50 is cut off after a predetermined stroke distance "53, ie the hydraulic connection 48 is then blocked and there is no longer a communicating connection between the feed line 11 and the second control room 37.

The compensator chamber 23 communicates with the supply line 11 via a compensator channel 54.

The injection nozzle 1 according to the embodiment according to FIG. 1 functions as follows:

In the starting position shown in Fig. 1, both nozzle needles 8, 15 are closed. The pressure of the supply line 11 prevails in the compensator chamber 23 and in the nozzle chamber 12. Likewise, the pressure of the supply line 11 prevails in the first control chamber 35 and thus in the first booster chamber 21. Since the hydraulic connection 48 is open in this starting position, the second control chamber 37 also prevails in the second booster chamber 31 the same pressure as in the supply line 11. The balance of forces on the unit consisting of the first nozzle needle 8 and the first drive piston 18 leads to a resultant force acting in the closing direction. Likewise, the balance of forces on the unit consisting of the second nozzle needle 15 and the second drive piston 28 also leads to a force acting in the closing direction.

If fuel is to be injected into the combustion chamber or premixing chamber 4 through the at least one first spray hole 5, the control piston 38 is moved in the opening direction 52. Here, the control piston 38 penetrates into the first control chamber 35 with its first control surface 40. The associated increase in pressure is transmitted via the first hydraulic pressure transmission path 44 directly into the first translator space 21 and thus to the first translator surface 20. As a result, the balance of forces on the first drive piston 18 is changed in such a way that the first nozzle needle 8 has an opening force. Accordingly, the first nozzle needle 8 lifts off from the first sealing seat 10. When the first nozzle needle 8 is open, the at least one first spray hole 5 is connected to the nozzle chamber 12 and can accordingly inject fuel into the combustion chamber or premix chamber 4.

When the first nozzle needle 8 is open, the high pressure prevailing in the feed line 11 also builds up at the second pressure stage 33 of the second nozzle needle 50, as a result of which the balance of forces on the unit consisting of the second nozzle needle 15 and the second drive piston 28 changes. Nevertheless, the forces acting in the closing direction prevail and the second nozzle needle 15 remains closed.

As long as the opening stroke movement of the control piston 38 is smaller than the stroke distance 53, the hydraulic connection 48 remains open. As a result, there is no pressure drop in the second control chamber 37 during the stroke adjustment of the control piston 38, although the control piston 38 is moved with its second control surface 43 out of the second control chamber 37, so that the volume of the second control chamber 37 increases. Hydraulic medium, that is to say fuel, can flow into the second control chamber 37 via the open hydraulic connection 48, driven by the high pressure in the train guide line 11. The pressure in the second control room 37 and thus also in the second translator room 31 does not essentially change. However, the increase in volume in the second control chamber 37 caused by the stroke adjustment of the control piston 38 does not lead to a pressure drop in the second control chamber 37, since the missing volume can be replaced immediately by the open hydraulic connection 48. The second hydraulic pressure transmission path 47 can therefore not transmit any pressure change from the second control surface 43 to the second booster surface 30, so that the second hydraulic pressure transmission path 47 is inactive or deactivated when the hydraulic connection 48 is open.

If the fuel injection via the at least one first spray hole 5 is insufficient and, in addition, fuel injection is to be carried out through the at least one second spray hole 6, the control piston 38 is adjusted in the opening direction 52 beyond the stroke distance 53. As a result, the hydraulic connection 48 is initially blocked, so that the hydraulic volume enclosed in the second hydraulic pressure transmission path 47 is hermetically sealed. In this way, the second hydraulic pressure transmission path 47 is activated so that it can transmit pressure changes that take place on the second control surface to the second booster surface 30. This means that when the stroke of the control piston 38 goes beyond the stroke distance 53, the increase in volume brought about in the second control chamber 37 produces a pressure drop in the second control chamber 37. This pressure drop propagates directly into the second booster chamber 31 via the second hydraulic pressure transmission path 47, so that the reduced pressure is then also applied to the second booster surface 30. As a result, the balance of forces on the unit comprising the second drive piston 28 and the second nozzle needle 15 is changed again, in such a way that a resultant force that is effective in the opening direction now results. Accordingly, the second nozzle needle 15 lifts off from the second sealing seat 17.

Subsequently, also the at least one second injection opening 6 is connected to the nozzle chamber ^"12 and can inject fuel into the premixing combustion chamber or the fourth

To close the second nozzle needle 15, the control piston 38 can be adjusted back to the stroke 53, whereby the hydraulic connection 48 opens again and enables pressure equalization from the supply line 11 to the second control chamber 37 and thus also to the second booster chamber 31. As a result, the closing forces again prevail on the unit comprising the second drive piston 28 and the second nozzle needle, so that the second nozzle needle 15 closes.

If the first nozzle needle 8 is then also to be closed, the control piston 38 returns to its starting position, as a result of which the increase in volume in the first control chamber 35 triggers a pressure drop in the first control chamber 35 and in the first booster chamber 21. The associated change in the force balance acting on the first nozzle needle 8 leads to the closing of the first nozzle needle 8.

It is noteworthy with the injection nozzle 1 according to the invention that when the first nozzle needle 8 is open, the second nozzle needle 15 can be opened and closed independently of the first nozzle needle 8. This results in particularly large degrees of freedom for the actuation of the injection nozzle 1. Furthermore, it is important that only a single actuator or only a single control piston 38 is required to directly control the first nozzle needle 8 and the second nozzle needle 15 independently of one another. The effort required for this is comparatively low. In the injection nozzle 1 according to the invention, the first hydraulic pressure transmission path 44 is thus permanently active, while the second hydraulic pressure transmission path 47 can be activated and deactivated according to the invention. The activation and deactivation of the second hydraulic pressure transmission path 47 takes place as a function of the control piston stroke, so that a stroke-controlled changeover between the activated state and the deactivated state results for the second hydraulic pressure transmission path 47. It is expedient for the stroke distance 53 of the control piston 38, in which the switching between the activated and deactivated state of the second hydraulic pressure transmission path 47 takes place, to be set to a predetermined switching value. Accordingly, the predetermined stroke 53 is also referred to as switching value 53 in the following. The switching value 53 is expediently selected such that when the control piston 38 opens or moves before or at the latest when the switching value 53 is reached, the first nozzle needle 8 is opened sufficiently to allow proper fuel injection through the at least one first spray hole 5. Only when the control piston 38 is adjusted beyond the switching value 53 in the opening direction 52 does the second nozzle needle 15 also open in order to effect fuel injection through the at least one second spray hole 6.

FIG. 2 shows a second exemplary embodiment of the injection nozzle 1 according to the invention, reference being made to what has been said regarding FIG. 1 with regard to components and functions because of the correspondences with the first exemplary embodiment according to FIG. 1, and only the differences are explained below. According to FIG. 2, the control piston 38 can be biased against the opening direction 52 by means of a return spring 55. In the variant shown here, this return spring 55 is supported on one end on the nozzle body 2 and on the other end on an actuator piston 56 which is driven directly by an actuator 57, in particular a piezo actuator.

The second drive piston 28 here has a piston head 58 and a piston rod 59, which can be firmly connected to one another or manufactured in one piece; they can also lie loosely on top of one another and remain in contact with the stroke forces due to the applied pressure forces. The second drive piston 28 has a second compensator surface 60, which is arranged in a second compensator chamber 61 and can be pressurized. The second compensator chamber 61 communicates with the feed line 11 via the compensator channel 54. The second compensator surface 60 is opposite to the second translator surface 30 and thus arranged away from the spray holes 5, 6, so that the second compensator surface 60 is subjected to pressure in the closing direction of the second nozzle needle 15 acts. In contrast to the variant according to FIG. 1, in the embodiment according to FIG. 2 no first compensator surface 22 and no first compensator space 23 are provided.

In addition, the second translator surface 30 acts when pressure is applied in the opening direction of the second nozzle needle 15. The first translator surface 20 acts here when pressure is applied in the closing direction of the first nozzle needle 8. Furthermore, the second nozzle needle 15 manages here without an associated second spring 32. The first control chamber 35 communicates with the annular chamber 50 via a throttle path 62, so that the first control chamber 35 communicates in a throttled manner with the supply line 11. The throttle path 62 is formed radially between the control piston 38 and a control piston guide 63. The design or dimensioning of the throttle path 62 is such that, in the case of static states of the control piston 38 and / or in the event of slow actuating movements of the control piston 38, a pressure equalization is formed between the first control chamber 35 and the feed line 11, while in dynamic processes, in particular in the case of rapid adjustment strokes of the control piston 38, a pressure equalization between the first control chamber 35 and the feed line 11 cannot take place or cannot take place quickly enough.

The injection nozzle 1 according to the embodiment according to FIG. 2 functions as follows:

In the starting position shown in FIG. 2, the high pressure of the supply line 11 prevails in the first hydraulic pressure transmission path 44, which results in a balance of forces at the first nozzle needle 8, the resultant of which acts in the closing direction. The first pressure stage 25 counteracts the closing forces of the first spring 24 and the first translator surface 20. The first nozzle needle 8 is accordingly closed. Furthermore, the hydraulic connection 48 is open, so that the same pressure as in the supply line 11 also prevails in the second hydraulic pressure transmission path 47. The second hydraulic pressure transmission path 47 is thus deactivated. When the first nozzle needle 8 is closed, the second pressure stage 33 is relatively depressurized. Overall, this results in a balance of forces with a resulting force acting in the closing direction for the first nozzle needle 15, so that the second nozzle needle 15 is also closed. If a fuel injection is now to be carried out through the at least one first spray hole 5, the control piston 48 is actuated with the aid of the actuator 57 in such a way that it carries out a stroke movement in the opening direction 52 which is smaller than the stroke distance 53, which again has the switching value 53 forms. With an opening stroke adjustment of the control piston 38, the volume of the first control chamber 53 is increased. Since the adjustment movement of the control piston 38 takes place at a very high actuating speed, the throttle path 62 is quasi impermeable, so that the opening stroke adjustment of the control piston 38 is accompanied by a drop in pressure in the first control chamber 35. This pressure drop propagates through the first control channel 34 into the first translator space 21. As a result, the balance of forces at the first nozzle needle 8 is changed such that a force acting in the opening direction now results. Consequently, the first nozzle needle 8 lifts off from the first sealing seat 10 and the at least one first spray hole 5 communicates with the nozzle chamber 12. When the first nozzle needle 8 is open, the desired injection can take place via the at least one first spray hole 5. When the first nozzle needle 8 is opened, pressure is also applied to the second pressure stage 33, as a result of which the resulting closing force acting on the second nozzle needle 15 is reduced.

During the opening stroke adjustment of the control piston 38, the second control surface 43 plunges deeper into the second control chamber 37, as a result of which the volume in the second control chamber 37 is reduced. When the second hydraulic pressure transmission path 47 is deactivated, however, no pressure can build up in the second control chamber 37, since the displaced hydraulic fluid, that is to say fuel, via the open one Hydraulic connection 48 can escape into the feed line 11.

If a larger quantity of fuel is to be injected per unit of time, the injection can also be carried out through the at least one second spray hole 6. For this purpose, the actuator 57 actuates the control piston 48 to an opening stroke adjustment which goes beyond the switching value 53, as a result of which the hydraulic connection 48 is initially blocked when the switching value or the stroke distance 53 is exceeded. As a result, the second hydraulic pressure transmission path 47 is activated for stroke adjustments of the control piston 38 that go beyond the switching value 53. Accordingly, the reduction in volume of the second control chamber 37 causes an increase in pressure in the second control chamber 37, which propagates into the second booster chamber 31 via the second control channel 36.

Accordingly, the opening force introduced at the second translator surface 30 increases, as a result of which the balance of forces at the second nozzle needle 15 changes such that the opening forces now predominate and the second nozzle needle 15 lifts off the second sealing seat 17. Accordingly, the at least one second spray hole 6 is then connected to the nozzle chamber 12 and can inject fuel into the combustion chamber or premix chamber 4.

To close the second nozzle needle 15, the control piston 38 is adjusted back until the hydraulic connection 48 is opened and the second hydraulic pressure transmission path 47 is thus deactivated again and the pressure in the second booster chamber 31 drops again. The first nozzle needle 8 is closed in a corresponding manner by moving the control piston 48 back into its starting position. The associated reduction in volume in the first control chamber 35 produces an increase in pressure in the first control chamber 35, which is transferred to the first translator chamber 21 and generates a corresponding closing force there on the first translator surface 20.

FIG. 3 shows a third exemplary embodiment of the injection nozzle 1 according to the invention, reference being made to what has been said regarding FIGS. 1 and 2 because of the correspondence with the examples described above with regard to components and functions, and only the differences are explained below.

3, in the embodiment of the injection nozzle 1 shown here, the first drive piston 18 is drive-connected to the first nozzle needle 8 via a plurality of pins 64, the pins 64 being formed as separate components or in one piece on the first drive piston 18 and / or on the first nozzle needle 8 can.

The first translator surface 20 is arranged here in the first control room 35, so that a separate first translator room 21 can be omitted here. Because of this design, the first hydraulic pressure transmission path 44 is simplified since the surfaces connected to one another, namely the first translator surface 20 and the first control surface 40, are located in the same room, namely in the first control room 35.

In the embodiment shown here, as in the variant according to FIG. 2, the first control chamber 35 is communicatively connected to the feed line 11 via a throttle path 65. The throttle path 65 runs radially between here the first drive piston 18 and a piston guide 66 formed on the nozzle body 2. The throttle path 65 is thus connected to the annular space 50 of the hydraulic connection 48. It is also possible to form the throttle path 65 radially between the control piston 38 and the first drive piston 18.

Alternatively, the pressure feed into the first control chamber 35 can, for. B. analogous to the embodiment of FIG. 1 by means of a feed line 45 with feed valve 46, which connects the first control chamber 35 to the feed line 11.

Another special feature of this embodiment is seen in the fact that the control piston guide 63 is formed here in the first drive piston 18, which is formed for this purpose by a high cylinder. The control piston 38 is thus arranged coaxially in the first drive piston 18 and is mounted thereon in an adjustable manner.

In the embodiment shown here, the second hydraulic pressure transmission path 47 comprises a coupling piston 67, which is likewise mounted in a stroke-adjustable manner in the first drive piston 18. The coupling piston 67 has, at a first end 68 distant from the spray holes 5, 6, a first coupling surface 69 which is arranged in the second control chamber 37 and can be pressurized there. The first coupling surface 69 lies opposite the second control surface 63. On a second end 70 of the coupling piston 67, which is opposite the first end 68, a second coupling surface 71 is formed, which is opposite the first coupling surface 69 and is arranged in the second booster chamber 31. The coupling piston 67 is designed as a hollow cylinder that is open on one side and is pushed onto the end of the second drive piston 28 that is remote from the spray holes 5, 6. In other words, the second drive piston 28 is mounted with its piston head 58 in a stroke-adjustable manner in the coupling piston 67. Accordingly, the second compensator chamber 61 is formed in the coupling piston 67, the second spring 32 also being supported in the second compensator chamber 61 on the coupling piston 67. A first section 72 of the compensator channel 54 is formed in the coupling piston 67 for connecting the second compensator chamber 61 to the feed line 11. A second section 73 of the compensator channel 54 is formed in the first drive piston 18. Finally, a third section 74 of the compensator channel 54 is formed in the nozzle body 2. The dimensioning and arrangement of the compensator channel sections 72, 73, 74 takes place in such a way that a communicating connection between the compensator chamber 61 and the feed line 11 is ensured for all relative positions between the nozzle body 2, the first drive piston 18 and the coupling piston 67 that occur during the correct operation of the injection nozzle 1. For this purpose, additional annular spaces 75 and 76 may be provided, one annular space 75 being formed in the area of the first compensator channel section 72 in the first drive piston 18, while the other annular space 76 is being formed in the area of the second compensator channel section 73 in the nozzle body 2.

The injection nozzle 1 according to the embodiment according to FIG. 3 functions as follows:

In the starting position shown in Fig. 3, the two nozzle needles 8, 15 are closed. The high pressure of the supply line 11 prevails in the first control chamber 35. The hydraulic connection 48 is open, so that also in the second Control room 37 of the high pressure of the feed line 11 prevails. The high pressure of the feed line 11 also prevails in the second compensator chamber 61. The pressure in the second booster chamber 31 expediently also has the same pressure as in the feed line 11. This can be achieved, for example, by a further throttle path 77, which is radial between the piston head 58 of the second drive piston 28 and the Coupling piston 67 is formed and connects the second compensator chamber 61 to the second translator chamber 31.

To open the first nozzle needle 8, the control piston 38 is adjusted in the opening direction 52. This results in a pressure drop in the first control chamber 35, which is also effective directly on the first translator surface 20. As a result, the balance of forces on the first nozzle needle 8 changes in such a way that a resulting force acting in the opening direction acts on it. As a result, the first nozzle needle 8 lifts off the first sealing seat 10.

If only the first nozzle needle 8 is to be opened, the stroke adjustment movement of the control piston 38 is less than the predetermined stroke distance 53 or less than the predetermined switching value 53, so that the hydraulic connection 48 remains open when the control piston 38 is adjusted. When the hydraulic connection 48 is open, the second hydraulic pressure transmission path 47 is deactivated. Accordingly, the volume of the second control chamber 37 can decrease without there being an increase in pressure in the second control chamber 37. The volume which is displaced by the retraction of the control piston 38 into the second control chamber 37 can escape into the supply line 11 via the open hydraulic connection 48. If the second nozzle needle 15 is now also to be opened, the control piston 38 is adjusted beyond the switching value 53 in the opening direction 52. When the stroke distance 53 is exceeded, the hydraulic connection 48 is blocked, so that the second hydraulic pressure transmission path 47 is hermetically sealed, at least with regard to dynamic processes. The second hydraulic pressure transmission path 47 is thereby activated. A stroke adjustment movement of the control piston 38 that goes beyond the switching value 53 then leads to a pressure increase in the second control chamber 37, which acts on the first coupling surface 69. The consequence of this is that the coupling piston 67 is also adjusted in the opening direction 52 of the control piston 38. This opening stroke of the coupling piston 67 generates a pressure increase in the second booster chamber 31, by means of which the second drive piston 28 is driven in the opening direction of the second nozzle needle 15. Accordingly, the balance of forces of the second nozzle needle 15 changes such that the opening forces predominate and the second nozzle needle lifts off the second sealing seat 17.

The second nozzle needle 15 and the first nozzle needle 8 are closed in a corresponding manner when the control piston 38 is retracted.

FIG. 4 shows a fourth exemplary embodiment of the injection nozzle 1 according to the invention, reference being made to what has been said regarding FIGS. 1 to 3 because of the correspondences with the exemplary embodiments described above with regard to components and functions, and only the differences are explained below.

In the variant according to FIG. 1, only a single control chamber 78 is provided, in which a control surface 79 of the in the control piston 38 immersing the control chamber 78 and can be pressurized. The control chamber 78 communicates with the first booster chamber 21 via a control channel 80. The first hydraulic pressure transmission path 44 thus leads from the control surface 79 to the first booster surface 20.

In contrast, the second hydraulic pressure transmission path 47 leads from the control surface 79 to the second booster surface 30. This means that the first hydraulic pressure transmission path 44 and the second hydraulic pressure transmission line 47 run together from the control chamber 78 to the first booster chamber 21, or forms the first hydraulic one Pressure transmission path 44 a first section of the second hydraulic pressure transmission path 47.

In the present exemplary embodiment, the second hydraulic pressure transmission path 47 contains a hydraulic connection 81, via which the first translation space 21 can communicate with the second translation space 31. This hydraulic connection 81 is controllable, ie it can be opened and locked. When the hydraulic connection 81 is open, the two translation spaces 21, 31 communicate with one another, but not when the hydraulic connection 81 is blocked. When the hydraulic connection 81 is blocked, the second hydraulic pressure transmission path 47 is interrupted, so that there is then no pressure transmission from the control surface 79 to the second booster surface 30. This means that the second hydraulic pressure transmission path 47 is deactivated when the hydraulic connection 81 is blocked. In contrast, pressures can be transmitted from the control surface 79 to the second booster surface 30 when the hydraulic connection 81 is open, in other words, at opened hydraulic connection 81, the second hydraulic pressure transmission path 47 is activated.

The hydraulic connection 81 consists of at least a first connection channel 82 and at least a second connection channel 83. The first connection channel 82 is formed in the first drive piston 18 and opens into the first booster chamber 21. The second connection channel 83 is formed in the nozzle body 2 and opens into the second booster chamber 31. The ends of the connecting channels 82, 83 which are distant from the respective translator space 21 and 31, respectively, are arranged relative to one another such that they are spaced apart from one another in the stroke direction in the starting position shown here, in which both nozzle needles 8, 15 are closed are. This distance corresponds to a stroke distance 84 of the first nozzle needle 8 or a switching value 84. In the starting position, the hydraulic connection 81 is thus blocked, ie. H. the second hydraulic pressure transmission path 47 is deactivated. Only when the first drive piston 18 or the associated first nozzle needle 8 performs an opening stroke by the stroke 84 or the switching value 84, do the two mutually facing ends of the connecting channels 82, 83 overlap, as a result of which the hydraulic connection 81 opens and thus the second hydraulic pressure transmission path 47 is activated.

In contrast to the exemplary embodiments shown above, in the injection nozzle 1 shown here, a compensator chamber 23 or 61 is provided for both the first drive piston 18 and for the second drive piston 28. The two compensator spaces 23, 61 communicate with one another via transverse bores 85 and via the compensator channel 54 with the feed line 11. The injection nozzle 1 according to the embodiment according to FIG. 4 functions as follows:

In the initial state shown in FIG. 4, both nozzle needles 8, 15 are closed. The high pressure of the supply line 11 prevails in the single control chamber 78. Accordingly, this high pressure also prevails in the first booster chamber 21. Via a throttle path 86, which is formed, for example, radially between the piston head 58 of the second drive piston 28 and an associated piston guide 87 of the nozzle body 2, and which throttled second compensator chamber 81 with the second translator chamber 31, a pressure equalization between the second compensator chamber 61 and the second translator chamber 31 is achieved at least in static or quasi-static conditions. Accordingly, in the initial state, the high pressure of the feed line 11 also prevails in the second booster chamber 31.

If fuel injection is now to be carried out through the at least one first spray hole 5, the control piston 38 is actuated in the opening direction 52. The control piston 38 then dips into the control chamber 78 and thereby reduces the volume of the control chamber 78. Accordingly, there is an increase in pressure on the control surface 79, which extends via the first hydraulic pressure transmission path 44 into the first booster chamber 21 and the first booster surface 20 propagates. Since the hydraulic connection 81 is blocked in the initial state and the second hydraulic pressure transmission path 47 is thus deactivated, the increased pressure cannot propagate from the control surface 79 into the second booster space 31 to the second booster surface 30. Due to the pressure increase in the first booster chamber 21, the balance of forces of the first nozzle needle 8 is changed in such a way that a resulting force that is effective in the opening direction arises. Consequently, the first nozzle needle 8 lifts off from the first sealing seat 10. When the second hydraulic pressure transmission path 47 is deactivated, the pressure in the second booster chamber 31 remains constant, so that the second nozzle needle 15 does not lift even if its second pressure stage 33 is pressurized when the first nozzle needle 8 is open. The second nozzle needle 15 therefore remains closed. The opening stroke adjustment of the control piston 38 is dimensioned such that the opening stroke of the first drive piston 18 remains smaller than the predetermined stroke distance 84.

If an additional fuel injection is also to be carried out through the at least one second spray hole 6, the control piston 38 is actuated in such a way that it dips deeper into the control chamber 78 in the opening direction 52. As a result, the opening stroke of the first nozzle needle 8 and thus of the first drive piston 18 increases. As soon as the opening movement of the first drive piston 18 reaches or exceeds the switching value 84, the mutually facing ends of the connecting channels 82, 83 overlap, so that the hydraulic connection 81 is opened, whereby the second hydraulic pressure transmission path 47 is activated. Accordingly, the pressure prevailing on the control surface 79 can now be transmitted to the second booster surface via the second hydraulic pressure transmission path 47

30 are transferred, so that in the second translator room

31 forms an increase in pressure. As a result, the balance of forces of the second nozzle needle 15 is changed in such a way that a resulting force that is effective in the opening direction now results. Accordingly, the second nozzle needle 15 then lifts off the second sealing seat 17. The second nozzle needle 15 and the first nozzle needle 8 are closed in a correspondingly reversed manner when the control piston 38 is reset.

An essential difference between the embodiment shown in FIG. 4 and the variants shown in FIGS. 1 to 3 is seen in the fact that, in the fourth embodiment, the first drive piston 18 operates as a control slide, so that the switching between the activated state and the deactivated state of the second hydraulic pressure transmission path 47 is controlled directly as a function of the stroke position of the first nozzle needle 8. In this way, a predetermined advance stroke can be set particularly precisely for the first nozzle needle 8, up to which the first nozzle needle 8 is to lift off the first sealing seat 10 before the second nozzle needle 15 is to open. However, since the stroke movement of the first nozzle needle 8 correlates with the stroke movement of the control piston 38, this also results in (indirect) control of the second hydraulic pressure transmission path 47 as a function of a predetermined control piston stroke.

In contrast to this, the second hydraulic pressure transmission path 47 in the other illustrated embodiments is controlled directly as a function of the predetermined control piston stroke, since there the control piston 38 works as a slide which opens or blocks the hydraulic connection 48. Since the opening movement of the control piston 38 correlates with the opening movement of the first nozzle needle 8, a desired advance stroke for the first nozzle needle 8 can also be implemented more or less precisely by a corresponding selection of the switching value 53. All embodiments have in common that only a single control piston 38 and, accordingly, only a single actuator is required in order to actuate both nozzle needles 8, 15 separately or in succession to open them. This results in a particularly simple and therefore inexpensive construction for the injection nozzle 1.

Although four different embodiments are described in detail here by way of example, it is clear that the invention is not limited to this and that, in particular, individual features of different embodiments can be combined with one another and / or exchanged for one another.

Claims

Expectations

1. Injection nozzle for an internal combustion engine, in particular in a motor vehicle, with a nozzle body (2) which has at least one first spray hole (5) and at least one second spray hole (6), with one in a first needle guide (7) of the nozzle body (2 ) guided, designed as a hollow needle, the first nozzle needle (8) with which the injection of fuel through the at least one first spray hole (5) can be controlled, and with a coaxial to the first nozzle needle (8) arranged second nozzle needle (15), with which the Injection of fuel through the at least one second spray hole (6) can be controlled, characterized in that a control piston (38) is provided which is drive-coupled to an actuator (57), that a first drive piston (18) is provided which is connected to the is connected to the first nozzle needle (8) and has a first translator surface (20) which extends over a first hydraulic pressure transmission path (44) is hydraulically coupled to a control surface (40; 79) of the control piston (38) such that a second drive piston (28) is provided which is drive-coupled to the second nozzle needle (15) and has a second transmission surface (30) which An activatable and deactivatable second hydraulic pressure transmission path (47) can be hydraulically coupled to a control surface (43; 79) of the control piston (38) such that the activation and deactivation of the second hydraulic pressure transmission path (47) is controlled as a function of the control piston stroke.

2. Injection nozzle according to claim 1, characterized in that a control piston stroke, in which the second hydraulic pressure transmission path (47) switches between its activated and deactivated state, is predetermined in such a way that the opening of the control piston (38) up to reaching this predetermined control piston stroke the first nozzle needle (8) performs an opening stroke while the second nozzle needle (15) remains in its closed position, and that when the opening movement of the control piston (38) exceeds this predetermined control piston stroke, the second nozzle needle (15) also performs an opening stroke.

3. Injection nozzle according to claim 1 or 2, characterized in that the control piston (38) at a first end (41) in a first control chamber (35) has a first control surface (40) and at a second end opposite the first end (41) ( 42) in a second Control room (37) has a second control surface (43) that the first control surface (40) is coupled to the first booster surface (20) with the first hydraulic pressure transmission path (20), that the second control surface (47) is connected to the second hydraulic pressure transmission path (47) 42) can be coupled to the second translator surface (30).

4. Injection nozzle according to claim 3, characterized in that the second control chamber (37) via a controllable hydraulic connection (48) can be connected to a feed line (11) which supplies the spray holes (5, 6) under high pressure fuel that the hydraulic connection ( 48) that the second hydraulic pressure transmission path is controlled as a function of the control piston stroke position for opening and locking

(47) deactivated when the hydraulic connection (48) is open and when the hydraulic connection is blocked

(48) is activated.

5. Injection nozzle according to claim 3 or 4, characterized in that the first translating surface (20) is arranged in a first translating space (21) which communicates via a first control channel (34) with the first control space (35) that the second translating surface (30 ) is arranged in a second translator room (31) which communicates with the second control room (37) via a second control channel (36).

6. Injection nozzle according to claim 3 or 4, characterized in that the first translator surface (20) is arranged in the first control room (35).

7. Injection nozzle according to one of claims 3, 4 or 6, d a d u r c h g e k e n n z e i c h n e t that the second hydraulic pressure transmission path (47) contains a coupling piston (67) having a first at a first end (68) in the second control chamber (37)

Coupling surface (69) and at a second end (70) opposite the first end (68) in one

Translator room (31) has a second coupling surface (71) that the second translator surface (30) in the

Translator room (31) is arranged -

8. Injection nozzle according to claim 7, d a d u r c h g e k e n n z e i c h n e t that the coupling piston (67) coaxially in the first

Drive piston (18) is mounted so as to be stroke-adjustable and / or that the coupling piston (67) is coaxial on the second

Drive piston (28) is mounted adjustable in stroke.

9. Injection nozzle at least according to claim 4, so that a section (49) of the hydraulic connection (48) is formed in the control piston (38).

10. Injection nozzle according to claim 1 or 2, characterized in that the control piston (38) in a control chamber (78) has a control surface (79), that the control surface (79) is coupled to the first transmission surface (20) with the first hydraulic pressure transmission path (44), that the control surface (79) can be coupled to the second transmission surface (30) with the second hydraulic pressure transmission path (47).

11. Injection nozzle according to claim 10, d a d u r c h g e k e n n z e i c h n e t that the second hydraulic pressure transmission path

(47) has a controllable hydraulic connection (81), via which a first translator space (21), in which the first translator surface (20) is arranged, to a second translator space (31), in which the second

Translator surface (30) is arranged, it can be connected that the hydraulic connection (81) depending on the

Spool position for opening and locking is controlled by the second hydraulic pressure transmission path

(47) activated when the hydraulic connection (81) is open and deactivated when the hydraulic connection (81) is blocked.

12. Injection nozzle according to claim 11, so that a section (82) of the hydraulic connection (81) is formed in the first drive piston (18).

13. Injection nozzle according to one of claims 3 to 12, characterized in that the second drive piston (28) has a compensator surface (60) opposite the second booster surface (30), which in a compensator chamber (61) is arranged, which communicates with the feed line (11).

14. Injection nozzle according to one of claims 3 to 13, characterized in that the first drive piston (18) has a compensator surface (22) opposite the first booster surface (20), which is arranged in a compensator chamber (23) which is connected to the supply line (11 ) communicates.