EP1961949A2 - Injector with additional servo-valve - Google Patents

Abstract

The injector has a high pressure connector (2,3) and an actuator control valve with a control fluid-discharge path (18) from a control chamber (20). The control chamber is actively connected with a servo valve (31), by which a fuel discharge path (26) is released or blocked from another control chamber (28), which is supplied with fuel from second high pressure connection. The latter control chamber is actively connected with a needle (7).

Description

State of the art

The invention relates to an injector for injecting fuel into a combustion chamber of an internal combustion engine, in particular a common rail injector according to the preamble of claim 1.

One from the DE 102 07 227 A1 known common rail injector comprises a controlled by an electromagnetic actuator control valve for blocking and opening a fuel drain path from a control chamber which is supplied via an inlet throttle with fuel from a high-pressure fuel storage. By means of the control valve, the fuel pressure can be influenced within the control chamber. By varying the fuel pressure within the control chamber, a valve element (nozzle needle) is moved axially between an open position and a closed position, wherein the nozzle needle releases the fuel flow into the combustion chamber of an internal combustion engine in its open position.

From the DE 197 44 723 A1 a similar injector principle is known in which the control valve is supplied via a separate inlet channel within the injector with fuel under high pressure.

A disadvantage of the known injectors, in which the electromagnetically operated control valve with a non-pressure balanced Ball seat is provided is that the maximum by means of the control valve switchable control pressure (with reasonable space and recoverable power requirements) is limited.

Therefore, for example, in the EP 1 612 403 A1 described injectors with a so-called. Pressure-balanced control valve with a valve sleeve developed. A disadvantage of such injectors, however, is that with pressure-balanced control valves, a permanent leakage from the high-pressure region occurs in the low-pressure region of the injector due to the design. The permanent leakage reduces the overall efficiency of the injection system.

Disclosure of the invention Technical task

The invention has for its object to provide an injector, by means of which injection pressures beyond 2000 bar, preferably injection pressures of 3000 bar or above, can be realized.

Technical solution

This object is achieved with the features of claim 1. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two of the features specified in the description, the claims and / or the figures also fall within the scope of the invention.

The invention is based on the idea of providing a servo valve in addition to the control valve, which is preferably operated by means of an electromagnetic actuator, wherein the pressure within a control chamber assigned to the servo valve can be varied by means of the actuator-operated control valve, whereby the servo valve can in turn be switched. The servo valve itself in turn controls the pressure in a second control chamber associated with the actual injection valve, such that a one-piece or multi-part nozzle needle is adjustable between a closed position and an open position releasing the fuel flow through a nozzle hole arrangement into a combustion chamber of an internal combustion engine. It is essential to the invention that the first control chamber of the control valve, in particular via an inlet throttle, is supplied with control fluid flowing from a first high-pressure port of the injector, while an additional second high-pressure port is provided for supplying the second control chamber of the servo valve. The fuel flowing in through the second high-pressure connection is fed, in particular via an inlet throttle, to the second control chamber of the servo valve. The injector is preferably also supplied with the fuel volume to be injected through the nozzle hole arrangement via the second high-pressure connection.

Theoretically, it is conceivable to form the actuator of the injector according to the invention as a piezoelectric actuator. It is advantageous, however, if the actuator is designed as an electromagnetic actuator due to its greater travel. The control valve is preferably designed as a 2/2-way valve, in particular with a ball / conical seat, by means of which the control fluid pressure level at the servo valve (in the first control chamber) is controlled. Since the servo valve is designed with an individually adapted excess force via the pressure difference between the two control chambers, the injection valve can be acted on with the pressure level optimal for injection into the combustion chamber.

To open the injector (lifting the one-piece or multi-part nozzle needle from its needle seat), the control valve is first opened by means of, in particular electromagnetic actuator, whereby control fluid from the first control chamber can flow through a fuel drain path in a low pressure region of the injector. The inlet to the first control chamber and the outflow of control fluid through the fuel drain path out of the first control chamber are matched to one another such that when the control valve is open, a net outflow from the first control chamber results. As a result, the pressure in the first control chamber, whereby the operatively connected to the first control valve servo valve opens, in particular by a servo piston lifts from its sealing seat and thus releases the fuel flow from the actual injection valve (nozzle needle) associated second control chamber, wherein the inlet for and the outflow of fuel from the second control chamber are matched to one another such that when the servo valve is open, a net outflow of fuel from the second control chamber results. Upon reaching a sufficiently large pressure drop, the nozzle needle lifts from its needle seat and gives the nozzle hole arrangement for under high pressure, in particular about 3000 bar, stagnant fuel, which preferably flows through the second high pressure port, released into the combustion chamber of an internal combustion engine.

To close the injection valve, the control valve of the actuator is closed, whereby the pressure in the first control chamber increases, which causes the servo valve closes and thereby the pressure in the second control chamber increases. This in turn causes the nozzle needle to be moved axially into its needle seat.

According to a preferred embodiment, the pressure level of the control fluid flowing in from the first high-pressure port is lower than the pressure level of the fuel flowing in from the second high-pressure port, which is supplied via the nozzle hole arrangement to the combustion chamber of an internal combustion engine. As a result, the actuator only controls the comparatively low pressure level of the control fluid, while the servo valve controls the fuel which is under (maximum) high pressure (injection pressure) and which is to be injected. This makes it possible, in particular, electromagnetic actuators whose travel is advantageously greater than that of piezoelectric actuators, use at injection pressures beyond the 2000 bar limit. To realize different pressure levels, two separate high-pressure accumulators for the control fluid and the fuel to be injected can be provided, for example, which are supplied with control fluid or fuel with differently sized high-pressure pumps. For certain operating states of internal combustion engines, it may be advantageous if the pressure level of the first high-pressure port and the pressure level of the second high-pressure port are approximately equal.

In a further development of the invention is advantageously provided that the actuator control valve, in particular designed as a 2/2-way valve solenoid control valve, preferably with a ball / cone valve seat or a flat / flat valve seat is formed. These valves have the advantage over pressure-balanced valves that (almost) no leakage occurs in the closed position. However, it is also conceivable to form the control valve as a pressure balanced valve. The servo valve is preferably a servo piston valve with a ball / cone valve seat or a flat / flat valve seat.

In an embodiment of the invention is advantageously provided that each of the two control chambers are associated with an inlet throttle and an outlet throttle, wherein the respective cooperating throttles are dimensioned such that when the control valve is open or when the servo valve open a net outflow from the respective control chamber results.

For the design of the return situation of the control amounts from the two control chambers, there are two different alternatives. According to a first alternative, the injector is provided with two separate return ports for the different control amounts. Likewise, according to a second alternative, it is conceivable, in particular when the control fluid is fuel, to supply both control quantities to a common return connection. The separate return ports may be configured to operate at a different pressure level.

In particular, for the realization of a common return port, it is advantageous if the fuel drainage path From the second control chamber first opens into an intermediate chamber and fuel flows from there via at least one throttle to the low pressure region of the injector. In the same low-pressure region, the control fluid drain path also advantageously opens out of the first control chamber, so that only a single return connection has to be provided.

In order to avoid a double (axially spaced) guide a servo piston of the servo valve, it is advantageous to form the servo valve as a so-called. Flip-flop valve, wherein the particular spherical valve element between two, in particular opposite sealing seats is adjustable. In the first sealing seat, the valve element obstructs the fuel drain path from the first control chamber into the intermediate chamber (valve chamber), while the valve element in the second sealing seat blocks a, in particular throttle-free, connecting channel in the direction of the low-pressure region of the injector, so that fuel is only via a throttle channel can flow out of the intermediate chamber in the direction of the low pressure region.

It is conceivable that the control fluid, which is connected to the actuator-operated control valve, for example, water, oil or air.

However, an embodiment is advantageous in which the control fluid is also fuel, in particular at a low pressure level than the fuel flowing in via the second high-pressure port. This embodiment allows the provision of only a single return port.

Of particular advantage is an embodiment in which the amount of fuel flowing out of the second control chamber is not vented (at least not directly) into the low-pressure region of the injector, but is merely expanded to the closest pressure level of the fuel from the first high-pressure port. This arrangement avoids permanent leakage of the servo piston from the injector-pressurized portion of the injector to the reduced-pressure region. Furthermore, in such an embodiment, the efficiency of the injector with respect to the compression and control effort improves. Furthermore, the temperature level in the return is reduced. By increasing the efficiency of the entire injection system can be realized with a smaller volume.

In a further development of the invention is advantageously provided that flows from the fuel flow path of the second control chamber control amount (fuel) flows into an injector, which is coupled to a valve element (servo piston) of the servo valve, that the pressure level in this with fuel the first high-pressure port supplied injector, in particular by a rapid opening movement of the valve element, below the pressure level of the fuel in the first high-pressure port decreases, whereby the pressure level of the first high-pressure port at least in certain operating conditions can be equal to the pressure level of the second high pressure port and yet a drain of fuel through the Fuel drain path of the second control chamber with open servo valve is feasible. The injector area into which the fuel drain path opens out of the second control chamber, thus has a temporarily below the pressure level of the second high-pressure port pressure level.

Brief description of the drawings

Fig. 1:

in einer schematischen Darstellung den allgemeinen Aufbau eines Injektors mit einem Steuerventil und einem zusätzlichen Servoventil,

Fig. 2:

eine schematische Teilansicht eines alternativen Injektors, bei dem ein Ventilelement des Servoventils als Ventilkugel ausgebildet ist,

Fig. 3:

eine schematische Teilansicht eines alternativen Injektors, bei dem ein Kraftstoff-Ablaufweg aus einer zweiten Steuerkammer zunächst in eine Zwischenkammer und von dort aus über eine Drossel in einen Niederdruckbereich des Injektors strömt,

Fig. 4:

eine schematische Teilansicht eines Injektors, bei dem das Servoventil als Flip-Flop-Ventil ausgebildet ist,

Fig. 5:

eine detailgetreue Darstellung eines Injektors mit zwei Hochdruckanschlüssen;

Fig. 5a:

eine Detailvergrößerung aus Fig. 5;

Fig. 5b:

eine weitere Detailvergrößerung aus Fig. 5;

Fig. 6:

eine schematische Darstellung eines Injektors, bei dem der Kraftstoff-Ablaufweg aus der zweiten Steuerkammer in ein mit Kraftstoff aus dem ersten Hochdruckanschluss versorgten Injektorbereich mündet,

Fig. 7:

eine schematische Teildarstellung eines Injektors, bei dem der Injektorbereich, in den der Kraftstoff-Ablaufkanal mündet, über eine Drossel mit Kraftstoff aus dem ersten Hochdruckanschluss versorgt wird,

Fig. 8:

eine schematische Teildarstellung eines Injektors, bei dem eine Drossel, die den Injektorbereich in den der Kraftstoff-Ablaufweg aus der zweiten Steuerkammer mündet, in ein Ventilelement des Servoventils integriert ist,

Fig. 9:

eine schematische Teildarstellung eines Injektors, bei dem der Injektorbereich, in den der Kraftstoff-Ablaufweg aus der zweiten Steuerkammer mündet, über eine in dem Ventilelement des Servoventils vorgesehene Drossel mit der ersten Steuerkammer verbunden ist, die über diese Drossel mit Kraftstoff aus dem ersten Hochdruckanschluss versorgt wird und

Fig. 10:

eine schematische Darstellung eines Injektors, bei dem der Kraftstoff-Ablaufweg aus der zweiten Steuerkammer in eine Zwischenkammer mündet und der Kraftstoff von dort aus über zwei separate Drosseln der ersten Steuerkammer zugeführt wird.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings; these show in:

Fig. 1:

2 shows a schematic representation of the general structure of an injector with a control valve and an additional servo valve,

Fig. 2:

a schematic partial view of an alternative injector, in which a valve element of the servo valve is designed as a valve ball,

3:

1 is a schematic partial view of an alternative injector, in which a fuel discharge path from a second control chamber initially flows into an intermediate chamber and from there via a throttle into a low-pressure region of the injector,

4:

1 is a schematic partial view of an injector in which the servo valve is designed as a flip-flop valve,

Fig. 5:

a detailed representation of an injector with two high-pressure connections;

Fig. 5a:

an enlarged detail Fig. 5 ;

Fig. 5b:

another detail enlargement Fig. 5 ;

Fig. 6:

a schematic representation of an injector, in which the fuel drain path from the second control chamber opens into an area supplied with fuel from the first high pressure port injector,

Fig. 7:

a schematic partial view of an injector, wherein the injector, in which opens the fuel flow passage, is supplied via a throttle with fuel from the first high-pressure port,

Fig. 8:

1 is a schematic partial representation of an injector in which a throttle, which opens the injector region into which the fuel drain path from the second control chamber opens, is integrated into a valve element of the servo valve,

Fig. 9:

a schematic partial view of an injector, wherein the injector, in which the fuel drain path from the second control chamber opens, is connected via a provided in the valve element of the servo valve throttle with the first control chamber, which supplies via this throttle with fuel from the first high-pressure port will and

Fig. 10:

a schematic representation of an injector, wherein the fuel drain path from the second control chamber opens into an intermediate chamber and the fuel is supplied from there via two separate throttles of the first control chamber.

Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

Based on Fig. 1 the principle of operation of an injector 1 designed as a common-rail injector is explained below. All embodiments have in common that the injector 1 is supplied via a first high-pressure port 2 and a second high-pressure port 3. About the first high pressure port 2 flows as a control fluid serving to fuel, while on the second high-pressure port 3, inter alia, the fuel volume flows, which is injected into the combustion chamber, not shown, of an internal combustion engine. Furthermore, all embodiments have in common that the injector 1 is provided with a single return port 4, via the fuel to a fuel reservoir and from there, for example via two different sized high-pressure pumps, not shown, two different high-pressure fuel storage 5, 6 is supplied. In particular, in the event that fuel is not supplied as the control fluid via the first high-pressure port 2, the injector 1 can also be provided with two separate return ports 4.

Within the injector 1, a one-piece nozzle needle 7 is received, which in the area of a needle tip 8 is provided with a closing surface 9 is, with which it can be brought into tight contact with a needle seat 10.

When the nozzle needle 7 abuts the needle seat 10, i.e., is in a closed position, the fuel outlet from a nozzle hole assembly 11 is blocked. If, on the other hand, it is lifted by the needle seat 10, fuel flowing in from the second high-pressure port 3 can flow from an annular space 12 past the needle tip 8 to the nozzle hole arrangement 11 and from there be sprayed into a combustion space substantially under high pressure (rail pressure).

The nozzle needle 7 is biased by a closing spring 13, which is arranged in a pressure chamber 14 of the injector 1 and at one end on a component 15 and the other end on a peripheral collar 16 of the nozzle needle 7, biased toward its closed position.

The injector 1 is equipped with a designed as a 2/2-way solenoid valve 17 actuator control valve 17. By means of the actuator control valve 17 is a Steuerfluid- (fuel) drain path 18 from a disposed within an injector body 19 first control chamber 20 in a low pressure region 21 of the injector 1 can be unlocked and blocked. In this case, the control fluid drainage path 18 is provided with a first outlet throttle 22. Via a first inlet throttle, the first control chamber 20 is supplied via the first high-pressure port 2 with under high pressure (p1) standing fuel (control fluid). The first outlet throttle 22 and the first inlet throttle 23 are matched to one another such that when the actuator control valve 17 is open, a net outflow from the control chamber 20 into the low-pressure region 21 of the injector 1 and from there into the return port 4 results.

Due to the associated pressure drop in the first control chamber 20, a servo piston 24 of a servo valve 31 moves with its in the drawing plane upper end face 25, the first control chamber 20, from the illustrated closed position in the drawing plane upwards into an open position in which he a fuel drain path 26 with a second outlet throttle 27 from a second control chamber 28 releases. In this case, the second control chamber 28 is bounded radially outwardly by the component 15 and in the drawing plane below by an upper end face 29 of the nozzle needle 7. The second control chamber 28 is supplied via an inlet throttle 30 with under high pressure (p2), in particular injection pressure, stagnant fuel from the pressure chamber 14, which in turn is supplied directly with fuel via the second high-pressure port 3 from the second high-pressure fuel reservoir 6. The flow cross sections of the second outlet throttle 27 and the inlet throttle 30 are matched to one another such that when the servo valve 31 is open, ie when the servo piston 24 is moved upward in the drawing plane, a net outflow of fuel from the second control chamber 28 results, whereby the pressure within the second control chamber 28 drops and the nozzle needle 7 lifts off from its needle seat 10 and thus releases the flow of fuel from the nozzle hole assembly 11.

When the actuator control valve 17 is closed, the pressure in the first control chamber 20 increases due to the fuel flowing through the inlet throttle 23 (control fluid) again, whereby the force acting on the servo piston 24 Pressure force increases, which in turn the servo piston 24 is moved in the plane of the drawing down on its valve seat 32 and thereby blocks the fuel drain path 26 from the second control chamber 28. As a result, the pressure in the second control chamber 28 increases (by the fuel flowing in through the inlet throttle 30), whereby the nozzle needle 7 is moved in the drawing plane down into its needle seat 10, which in turn terminates the injection process.

At the in Fig. 1 illustrated embodiment, the pressure level p1 of the first high-pressure accumulator 2 is lower than the pressure level p2 of the second high-pressure accumulator 3. The pressure level p2 corresponds to the injection pressure level.

The valve seat 32 of the servo valve 31 is formed as a flat / flat seat. With the servo piston 24 raised, high-pressure fuel (p2) flows into a valve chamber 33 of the servo valve 31 and from there via a connecting line 24 within the injector body 19 to the low-pressure region 21 of the injector 1 and thence to the return port 4.

The design has the advantage that by means of the actuator control valve 17, the injection pressure level does not have to be switched, but that by means of the actuator control valve 17 preferably pressures of up to 2000 bar must be switched, whereas the actual injection pressure of the means of the actuator control valve 17th actuated servo valve 31 is switched.

In order to avoid repetition, the description of the further exemplary embodiments will be given below only to the differences from the embodiment according to Fig. 1 received.

In the embodiment according to Fig. 1 the servo piston 24 cooperates with a valve element designed as a valve ball 35, which can be brought into tight contact with a conical valve seat 36. In contrast to the injector 1 according to Fig. 1 in which the servo piston 24 interacts with a lower end face directly with a valve seat designed as a flat seat, the valve ball / conical seat (FIG. Fig. 2 ) Manufacturing tolerances can be compensated improved, whereby leaks are avoided. Otherwise, the embodiment corresponds to Fig. 2 the embodiment according to Fig. 1 ,

In contrast to the embodiments according to the Fig. 1 and Fig. 2 opens the fuel drain path 26 with second outlet throttle 27 in the embodiment according to Fig. 3 first in a valve seat 32 of the servo valve 31 containing intermediate chamber 37, from where the fuel via another throttle 38 whose flow cross-section is preferably greater than the flow area of the second outlet throttle 27 in the limited by a shoulder of the servo piston 24 valve chamber 33 and from there from via the, in particular throttle-free connection line 34 to the low pressure region of the injector 1. The first outlet throttle 26 of the embodiments according to the Fig. 1 and Fig. 2 was in the injector 1 according to Fig. 3 in other words, divided to the second outlet throttle 26 and the additional throttle 38. This is advantageous because the pressure and temperature load of the throttle 26 is reduced by those from the throttle 38. The servo piston 24 is on the one hand on the lateral surface of its large diameter portion 39 and in the region of its small diameter portion 40 out.

In the embodiment according to Fig. 4 the servo valve 31 is designed as a so-called flip-flop valve. The servo piston 24 also acts in this embodiment, as in the embodiment according to Fig. 2 , with a designed as a valve ball valve element 35 together, which in turn can be brought into close contact with two opposite conical seats 36, 41. The valve element 35 is housed in the intermediate chamber 37. The valve element 35 is in close contact with the lower in the plane of the cone seat 36, the fuel drain path 26 is locked from the second control chamber 28 into the intermediate chamber 37. When the valve element 35 is in tight engagement with the upper piston seat 41 opposite the lower conical seat 36 when the servo piston 24 is raised, the connecting channel 42 (annular channel) formed radially between the small diameter section 40 of the servo piston 24 and the injector body 19 or a disk component is axially interposed the intermediate chamber 37 and the valve chamber 33 is blocked, so that the fuel flow from the second control chamber 28 via the fuel drain path 26 and the intermediate chamber 37 via the additional throttle 38 to the valve chamber 33 and from there via the connecting line 34 in the low pressure region and can flow out there to the return port 4. In the embodiment shown, designed as a flip-flop valve servo valve 31 is compared to the embodiment according to Fig. 3 advantageous that the servo piston 24 must be performed only in the region of its large diameter portion 39.

The in Fig. 5 In detail illustrated injector 1 (see also detail enlargements according to Fig. 5a and 5b ) has a nozzle body 43 and an injector body 44, wherein the nozzle body 43 is braced against the injector body 44 by means of a union nut 45, which is penetrated by the nozzle body 43 in the axial direction. The nozzle needle 7 is arranged in a nozzle chamber 46 within the nozzle body 43 and is spring-loaded by means of the closing spring 13 in the direction of the needle seat 10. The nozzle chamber 46 is supplied via the second high pressure port 3 with under high pressure (injection pressure) of about 3000 bar standing fuel. Via supply lines 47 in a plate component 48, the second control chamber 28 is supplied with fuel from the nozzle chamber 46. In the supply lines 47, the second inlet throttle 30 is integrated. It can be seen that the conical seat 36 of the valve ball formed as a valve member 35 of the servo valve 31 is received in the plate member 48. The servo piston 24 is received in a stepped bore in the injector body 44. Between the servo piston 24 and the injector body 44, an annular space 49 is formed, which serves as a low-pressure region 21 of the injector 1 and into which the integrated into the plate member 48 second outlet throttle 27 of the second control chamber 28 opens. The low pressure region 21 is connected to the return port 4.

The servo piston 24 is spring-loaded by means of a compression spring 50 which is supported on a retaining ring 51 held on the servo piston 24 and on a position-fixed component 52 in the direction of the conical seat 36. The servo piston 24 limited with its upper surface in the plane of the drawing 25, the first control chamber 20, the over the first inlet throttle 23 is supplied with fuel at high pressure (p1, p1 <p2) from an annular space 53. The annular space 53 is connected directly to the first high-pressure port 2 and is formed between the component 52 and the injector body 44. The first outlet throttle 22 opening out of the first control chamber 20 is opened or closed by the actuator control valve 17. Fuel flows with the actuator control valve 17 open in the armature chamber 58 via the first outlet throttle 22, which is connected to the return line 21 via a channel, not shown. As can be seen, has a cooperating with a valve ball 54 piston 55 of the actuator control valve 17 in its upper in the plane of the drawing an armature 56 which cooperates with electromagnets 57.

In the embodiment according to Fig. 6 the fuel drain path 26 opens with second outlet throttle 27 in the valve chamber 33 of the servo valve 31 in the plane below the large diameter portion 39 of the servo piston 24. This valve chamber 33 is connected via a transverse channel to an annular space 60, which directly with fuel from the second high pressure port 3 is supplied. So that when the servo piston 24 is lifted fuel can flow out of the second control chamber 28, the pressure level p1 of the fuel flowing in via the first high-pressure port 2 must be lower than the pressure level p2 of the fuel flowing in via the second high-pressure port 3. The latter arrives in the pressure chamber 14 and from there via the second inlet throttle 30 into the second control chamber 28 or, when the nozzle needle 7 is raised from the needle seat 10, via the nozzle hole arrangement 11 into a combustion chamber of an internal combustion engine.

From the pressurized fuel from the first high pressure port 2 annulus 60 of the fuel passes through the first inlet throttle 23 in the first control chamber 20 and from there with the actuator control valve 17 open in the low pressure region 21 of the injector 1 and from there into the return port . In Fig. 6 It can be seen that the servo piston 24 of the servo valve 31 is spring-loaded by means of the compression spring 50 in the direction of its valve seat 32. This compression spring 50 is for clarity in the Fig. 1 to Fig. 4 Not shown.

The following embodiments according to the FIGS. 7 to 10 have in common that the voltage applied to the first high pressure port fuel pressure and the voltage applied to the second high pressure port 3 fuel pressure p2, at least for some operating conditions or even permanently can be the same. This is achieved in that the fuel flowing out of the second control chamber 28 from the second fuel drain path 26 with outflow throttle 27 flows into an injector region which is supplied with fuel flowing from the first high-pressure port 2, but the pressure in this injector region temporarily ceases an opening movement of the servo piston 24 drops below the pressure level p1 of the fuel flowing in through the first high-pressure port 2, whereby fuel can only flow out of the fuel drain path 26 in the first place.

In the embodiment according to Fig. 7 The fuel drain path 26 opens into the valve chamber 33 below the large diameter portion 29 of the servo piston 24. This valve chamber 33 is connected via a throttle 61 to the first high-pressure port 2. The throttle 61 is located in a channel 62, which connects the valve chamber 33 with the first control chamber 20 and is fed into the fuel from the first high pressure port 2. When the actuator control valve 17 is opened, the pressure in the first control chamber 20 decreases, and the control piston 24 performs a rapid lifting movement. As a result, the volume of the valve chamber 33 is suddenly reduced, whereby the pressure in the valve chamber 33 falls below the pressure p1 in the first high-pressure fuel accumulator 5. As a result, at high pressure (p2, eg p2 = p1), stationary fuel can flow out of the second control chamber 28 via the fuel drain path 26 into the valve chamber 33. The throttle 61 ensures that fuel from the first high pressure port 2 can flow into the valve chamber 33 only slowly. If the actuator control valve 17 is closed, the compression spring 50 ensures that the servo piston 24 is adjusted again to its valve seat 32.

Fig. 8 shows an alternative embodiment in which the fuel drain path 26 with outlet throttle 27 also opens into the valve chamber 33 of the servo valve 31. The valve chamber 33 is hydraulically connected via the throttle 61, which is introduced into the large diameter portion 39 of the servo piston 24, to the first control chamber 20, which is supplied with fuel from the first high-pressure port 2 directly via the first inlet throttle 23. The throttle 61 ensures again that at a rapid opening movement of the servo piston 24 fuel flows slowly from the first high pressure port 2 and in this case from the first control chamber 20 into the valve chamber 33, whereby the pressure within the valve chamber 33 at least during the opening movement of the servo piston 24 below the pressure level p1 of the first High-pressure port 2 of incoming fuel drops, whereby fuel can escape via the fuel drain path 26 from the second control chamber 28.

The embodiment according to Fig. 9 essentially corresponds to the embodiment according to Fig. 8 with the only difference that the first inlet throttle 23 is incorporated to supply the first control chamber 20 in the large diameter portion 39 of the servo piston 24 and that the valve chamber 33 is supplied directly via the throttle 61 with high-pressure fuel from the first high-pressure port 2, so the first control chamber 20 is filled indirectly via the valve space 33. In this embodiment, the pressure in the valve chamber 33, so the injector, in which the fuel drain path 26 opens from the second control chamber 28 drops below the pressure p1 in the first high-pressure fuel storage, so that fuel with open servo valve 31 from the second control chamber 28 in the Valve chamber 33 and from there via the first inlet throttle 23 and the control fluid drain path 18 in the low pressure region 21 of the injector 1 and from there to the return port 4 can flow.

The embodiment according to Fig. 10 is characterized in that the fuel drain path 26 from the second control chamber 28 opens into the intermediate chamber 37 and from there via the additional throttle 38 in the actual valve chamber 33 below the large diameter portion 39 of the servo piston 24 of the servo valve 31. This valve space 33rd is hydraulically connected to the first control chamber 20 via the integrated in the large diameter portion 39 throttle 21, which via the first directly connected to the first high pressure port 2 first Supply throttle 23 is supplied with fuel under high pressure (p1). With a fast opening movement of the servo piston 24 with the actuator control valve 17 open, the pressure within both the intermediate chamber 37 and within the valve chamber 33 drops below the pressure p1 at the first high pressure port 2. The throttle 61 prevents too rapid a pressure increase in the valve chamber 33 and the additional Throttle 38 additionally reduces the rate of pressure rise in the intermediate chamber 37, allowing fuel to flow out of the second control chamber 28 via the fuel drain path.

Claims (11)

Injector for injecting fuel into a combustion chamber of an internal combustion engine, in particular a common-rail injector, with a first high-pressure port (2) and with an actuator control valve (17) with a control fluid drainage path (18) from a first control chamber (20) , which is supplied with control fluid from the first high-pressure port (2), is releasable or lockable, and with a nozzle needle (7), between an opening the fuel flow in the combustion chamber of an internal combustion engine opening position and a closed position in which the nozzle needle (2) is applied to a needle seat (10), is adjustable,
characterized,
in that the first control chamber (20) is operatively connected to a servo valve (31) by means of which a fuel discharge path (26) can be released or blocked from a second control chamber (28) which is supplied with fuel from a second high-pressure port (3) and in that the second control chamber (28) is operatively connected to the nozzle needle (7) such that the nozzle needle lifts from its needle seat (10) with the fuel drain path (26) released from the servo valve (31). Injector according to claim 1, characterized in that the pressure level (p1) of the control fluid flowing from the first high pressure port (2) is equal to or lower than the pressure level (p2) of the fuel flowing in from the second high pressure port (3). Injector according to one of claims 1 or 2, characterized in that the actuator control valve (17) is a magnetic control valve designed in particular as a 2/2-way valve. Injector according to one of the preceding claims, characterized in that a first outlet throttle (22) is provided in the control fluid drainage path (18), and in that the first control chamber (20) is supplied with control fluid via a first inlet throttle (23) Fuel drain path (26) is provided a second outlet throttle (27), and that the second control chamber (28) via a second inlet throttle (30) is supplied with fuel. Injector according to one of the preceding claims, characterized in that a common return port (4) is provided for the control fluid flowing out of the control fluid drainage path (18) and the fuel flowing out of the fuel drainage path (26). Injector according to one of the preceding claims, characterized in that the fuel discharge channel (26) opens into an intermediate chamber (37) which is connected via a throttle to a low-pressure region (21) of the injector (1). Injector according to claim 6, characterized in that the servo valve (31) as a flip-flop valve with a, in particular spherical valve element (35) is formed, which in a first sealing position the fuel drain path (26) in the intermediate chamber (37) blocks and in a second sealing position the fuel drainage path (26) releases and simultaneously blocks a throttle-free connection channel (42) to a low-pressure region (21) of the injector (1). Injector according to one of the preceding claims, characterized in that the control fluid is water, oil or air. Injector according to one of claims 1 to 7, characterized in that the control fluid is fuel. Injector according to claim 9, characterized in that the fuel discharge path (26) of the second control chamber (28) opens into an injector area which is acted upon by fuel flowing out of the first high-pressure port (2). Injector according to Claim 10, characterized in that the injector area is supplied with fuel from the first high-pressure port (2) via a throttle (61) and that the fuel pressure in the injector area during an adjusting movement, preferably during an opening movement, of a servo piston (24) of the Servo valve (31) below the pressure level (p1) of the fuel in the first high-pressure port (2) decreases.

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