EP1613856A1

EP1613856A1 - Fuel injector provided with a pressure transmitter controlled by a servo valve

Info

Publication number: EP1613856A1
Application number: EP04717030A
Authority: EP
Inventors: Matthias Eisenmenger; Hans-Christoph Magel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-04-02
Filing date: 2004-03-04
Publication date: 2006-01-11
Anticipated expiration: 2024-03-04
Also published as: JP2006522254A; WO2004088122A1; EP1613856B1; US20060243252A1; US7320310B2

Abstract

The invention relates to a fuel injector for injecting a fuel into the combustion chamber (23) of an internal combustion engine. The inventive injector (18) comprises a pressure transmitter (3) whose pressure relay piston (4) separates the working chamber (5) continuously receiving the fuel supplied by a pressure source (1,2) from a differential decompression pressure chamber (6). A pressure fluctuation is produced in said differential pressure chamber (6) by means of a servo valve (24) which closes or opens a hydraulic connection (21, 39, 42) between the differential pressure chamber (6) and a first return run (28) on a low-pressure side. The servo valve (24) comprises a piston (32) arranged between a control chamber (36) and first hydraulic chamber (38). A hydraulic surface (44) which continuously brings the piston (32) in the open position thereof when the pressure system is actuated, and a sealing surface (40) which closes or opens a return run (28) on a low pressure side are formed on said piston.

Description

Servo-controlled fuel injector with pressure intensifier

Technical field

Stroke-controlled injection systems with a high-pressure storage space (common rail) are used to introduce fuel into direct-injection internal combustion engines. The advantage of these injection systems is that the injection pressure can be adjusted to the load and speed in a wide range. A high injection pressure is required to reduce emissions and achieve high specific performance. The achievable pressure level of high-pressure fuel pumps is limited for reasons of strength, so that pressure boosters in the fuel injectors are used to further increase the pressure in fuel injection systems.

State of the art

DE 101 23 913 relates to a fuel injection device for internal combustion engines with a fuel injector that can be supplied by a high-pressure fuel source. A pressure-translating device having a movable pressure booster piston is connected between the fuel injector and the high-pressure fuel pressure source. The pressure booster piston separates a space that can be connected to the high-pressure fuel source from a high-pressure space that is connected to the fuel injector. The fuel pressure in the high-pressure chamber can be varied by filling a rear area of the pressure booster device with fuel or by emptying the rear area of fuel. The fuel injector has a movable closing piston for opening and closing injection openings. The closing piston protrudes into a closing pressure chamber, so that fuel pressure can be applied to the closing piston to achieve a force acting on the closing piston in the closing direction. The closing pressure chamber and the rear chamber are formed by a common closing pressure rear chamber, all partial areas of the closing pressure rear chamber being permanently connected to one another for the exchange of fuel. A pressure chamber is provided for supplying fuel to the injection openings and for applying a force acting in the opening direction to the closing piston. A high-pressure chamber is connected to the high-pressure fuel source in such a way that, apart from pressure fluctuations, at least the fuel pressure of the high-pressure fuel source can constantly be present in the high-pressure chamber, the pressure chamber and the high-pressure chamber being connected by a common spray room are formed. All parts of the injection chamber are permanently connected to each other for the exchange of fuel.

DE 102 294 15.1 relates to a device for damping the needle stroke on pressure-controlled fuel injectors. A device for injecting fuel into a combustion chamber of an internal combustion engine is disclosed which comprises a fuel injector which can be acted upon by fuel under high pressure via a high-pressure source. The fuel injector is actuated via a metering valve, an injection valve member being enclosed by a pressure chamber and the injection valve member being acted upon in the closing direction by a closing force. The injection valve member is assigned a damping element which can be moved independently of it and which delimits a damping space and has at least one overflow channel for connecting the damping space to a further hydraulic space. According to DE 102 294 15.1, the control of the fuel injector is carried out with a 3/2-way valve, whereby although an inexpensive and space-saving injector can be represented, this valve has to control a relatively large return flow rate of the pressure booster.

Instead of the embodiment of a 3/2 valve known from DE 102 294 15.1, it is also possible to use servo valves which are designed to be leak-free on the guide section when the servo valve is in the idle state, which has a favorable effect on the efficiency of a fuel injector. A disadvantage, however, is the fact that when the servo valve piston of the 3/2-way valve is open, no pressure surface pointing in its opening direction is subjected to system pressure. This makes the movement of the servo valve piston in its housing very sensitive to tolerances. Furthermore, a slow opening speed of the servo valve piston cannot be achieved, as a result of which the small quantity capability of a servo valve configured in this way is restricted. In the open state of the servo valve piston, an insufficient closing force is established on a second valve seat formed on this, which can lead to leaks and increased wear.

Presentation of the invention

In order to achieve a defined movement of a servo valve piston of a servo valve for actuating a fuel injector, a servo valve designed as a 3/2-way valve is proposed which has a hydraulically effective surface which can be acted upon in the opening direction and which is constantly subjected to system pressure. The system pressure corresponds to the pressure level prevailing in the high-pressure storage space. With this measure, the movement of the servo valve piston can easily be adjusted of the inlet or outlet throttle on the servo valve. A slow opening movement of the servo valve piston ensures that small pre-injection quantities can be displayed easily and that the pressure builds up without vibration. Because of the defined opening force, the servo valve proposed according to the invention becomes tolerance-insensitive to the effects of friction, so that tolerance variations due to production and the associated strong scattering of injection quantities can be avoided.

Furthermore, the servo valve proposed according to the invention and designed as a 3/2-way valve does not have any leakage flows occurring at a guide section in the idle state. This means a significant improvement in injector efficiency; Because of the small guide lengths that are possible on the servo valve piston, a small overall length of the servo valve can be made possible, which has a favorable effect on the overall height of a fuel injector with a pressure booster in an injector body, which comprehensively affects the servo valve, i.e. The space requirement of a fuel injector designed in this way is considerably reduced.

If a sealing seat formed on the servo valve piston of the servo valve is designed as a flat seat, the housing of the servo valve can advantageously be designed as a multi-part housing, with which an axial offset of components from one another can be compensated for. This possibility of compensating for manufacturing-related component tolerances and the good accessibility to the production of the sealing seat ensures simple and inexpensive manufacture of the servo valve proposed according to the invention.

drawing

The invention is described in more detail below with the aid of the drawing:

It shows:

Figure 1 shows a first variant of a 3/2-way valve

Servo valves with pilot valve pistons without leakage,

2 shows a further embodiment variant of a servo valve piston of a 3/2 servo valve with a first seat designed as a conical sealing seat and a further seat designed as a slide seal,

Figure 3 shows a variant, a 3/2-servo valve with a servo valve piston on which a control sleeve is received and Figure 4 shows a variant of a 3/2-way servo valve with an elongated servo valve piston.

- Design variants

FIG. 1 shows a first embodiment variant of a 3/2 servo valve proposed according to the invention for controlling a fuel injector containing a pressure intensifier.

A working space 5 of a pressure booster 3 is acted upon by fuel under high pressure via a pressure source 1 and a high-pressure feed line 2 connected to it. The working space 5 is permanently pressurized with the fuel of the drain source 1, which is under high pressure. The pressure booster 3 comprises a one-piece booster piston 4, which separates the working space 5 from a differential pressure space 6 (rear space). The booster piston 4 is acted upon by a return spring 8, which is supported on the one hand on a support disk 7 embedded in an injector body 19 and on the other hand on a stop disk attached to a pin of the booster piston 4. The pressure booster 3 also includes a compression chamber 9 which is connected via an overflow line 10 to a control chamber 12 for an injection valve member 14. Iα of the overflow line 10 from the differential pressure chamber 6 (rear chamber) to the control chamber 12 for the injection valve member 14, a first throttle point 11 is added.

In the control chamber 12 for the injection valve member 14, a spring element 13 is received, which acts on an end face of the needle-shaped injection valve member 14. The injection valve member 14 comprises a pressure stage which is enclosed by a pressure chamber 16. The pressure chamber 16 is acted upon by a fuel under pressure, via a pressure chamber inlet 17, which branches off from the compression chamber 9 of the pressure converter 3. A control line 21 runs from the differential pressure chamber 6 of the pressure intensifier 3 into the first housing part 26 of the servo valve housing 25. The end face of the intensifier piston 4 which acts on the compression chamber 9 of the pressure intensifier 3 is identified by reference numeral 20. On the basis of the pressure stage on the injection valve member 14, this performs an opening movement when pressure is applied to the pressure chamber 16, so that fuel flows from the pressure chamber 16 along an annular gap into injection openings 22 and enters a combustion chamber 23 of a self-igniting internal combustion engine. The control chamber 12 acting on the injection valve member 14 is in a hydraulic connection via a second throttle point 15 with the compression chamber 9 of the pressure converter 3.

A servo valve housing 25 is arranged above the injector body 19 of a fuel injector 18 and accommodates a servo valve 24. In the embodiment variant shown in FIG. 1, the servo valve housing 25 is constructed in two parts and comprises a first housing part 26 and a second housing part 27. The two-part design of the servo valve housing 25 according to the embodiment variant shown in FIG. 1 allows good accessibility for machining the sealing seat and one Slider edge, which results in a simple and inexpensive manufacturability of the servo valve 24.

A supply line 29 branches off into the valve housing 25 from the high-pressure supply line 2, via which the working space 5 of the pressure intensifier 3 is pressurized with fuel under high pressure. The supply line 29 opens into a first hydraulic space 38 of the first housing part 26 of the servo valve housing 25. The first hydraulic space 38 encloses a servo valve piston 32, which comprises a through channel 33. A third throttle point 34 is formed in the through channel 33 of the servo valve piston 32. Fuel flows from the first hydraulic chamber 38 into a control chamber 36 of the servo valve 24 via the passage channel 33. The pressure in the control chamber 36 is relieved when a switching valve 30 is actuated, when it is opened, the control volume from the control chamber 36 is via an outlet throttle point 37 (fourth throttle point) containing return is connected to a further low-pressure side return 31 and fuel can be derived therein. The control chamber 36 of the servo valve 24 is delimited by an end face 35 on the upper side of the servo valve piston 32. At the head of the servo valve piston 32, this lies opposite an annular surface which is effective in the opening direction of the servo valve piston 32 and which is acted upon by the pressure prevailing in the first hydraulic chamber 38. A first sealing seat 40 in a second hydraulic chamber 39 and a control edge 41 are also formed on the servo valve piston 32. Via the first sealing seat 40, the connection to an outlet control chamber 42, from which a low-pressure-side return 28 branches off, is released or closed. By means of the control edge 41, which in the embodiment variant of the servo valve 24 shown in FIG. 1 is designed as a slide sealing edge 43, the first hydraulic chamber 38, which is under system pressure, is sealed against the second hydraulic chamber 39 when the servo valve piston 32 moves in the vertical direction. The two returns 28, 31 on the low-pressure side are combined to form one return, which opens into a fuel tank. To support the movement of the servo valve piston 32 in the first housing part 26, although not shown in FIG. 1, spring forces can be applied to the servo valve piston 32 via springs. The first embodiment variant of the servo valve 24 shown in FIG. 1 allows the servo valve 24 to have an extremely compact construction. In the illustration according to FIG. 1, the first sealing seat 40 of the servo valve 24 is designed as a flat seat, but could also be a conical seat (see illustration according to FIG. 2) ) Ball seat or also be designed as a slide edge. The design of the first sealing seat 40 as a flat seat advantageously allows a multi-part valve body 25 to be used. By means of the first sealing seat 40, which is designed as a flat seat, it is possible to compensate for axial misalignments which may occur during production. Furthermore, the closing force applied in the control chamber 36 of the servo valve 24 on the flat seat of the first sealing seat 40 results in a very high surface pressure and thus a good seal. The first sealing seat 40 can either be designed as a sealing edge or as a sealing surface. The sealing force can be adjusted via the drain surface in relation to the sequence control room 42. As a result, when using a sealing surface, an optimal design of the surface pressure is possible, whereby on the one hand sufficient sealing as well as less wear can be achieved.

FIG. 2 shows a further embodiment variant of the servo valve proposed according to the invention, the first sealing seat of which is designed as a conical sealing seat.

The illustration according to FIG. 2 also shows a fuel injector 18 which contains a drain converter 3. The working space 5 of the pressure converter 3 is supplied with fuel under high pressure via a pressure source 1 (Cornmon Rail) via high pressure line 2. In contrast to the design of the pressure booster 3 according to the embodiment variant according to FIG. 1, the booster piston 4 of the pressure booster 3 is of multi-part design as shown in FIG. In the injector body 19 of the fuel injector 18, a support disk 7 is embedded, which represents an upper stop surface for the upper part of the multi-part booster piston 4. The lower part of the booster piston 4 is acted upon by a return spring 8 which is supported on the housing side; the compression space 9 of the pressure booster 3 is limited by the end face 20 of the lower part of the booster piston 4. An overflow line 10 containing the first throttle point 11 branches off from the differential pressure space 6 (rear space) of the drain converter 3. The overflow line 10 connects the differential pressure chamber 6 (rear chamber) of the pressure intensifier 3 to the control chamber 12 for controlling the lifting movement of the needle-shaped injection valve element 14. The pressure chamber inlet 17 runs from the compression chamber 9 of the pressure intensifier 3 and opens into the pressure chamber 16 surrounding the injector element 14. The injection valve member 14 comprises a drain stage, which has a hydraulically effective surface. This is where the Pressure chamber 16 pending fuel pressure and opens the injection valve member 14, so that fuel is injected via opening of the injection valve member 14 injection openings 22, which open into the combustion chamber 23 of the self-igniting internal combustion engine.

In contrast to the embodiment variant shown in FIG. 1, a damping piston 51 is accommodated in the control chamber 12 for the injection valve member 14. The damping piston 51 is traversed by a vertically extending channel 53. The channel 53 is hydraulically connected to the control chamber 12 via a fifth throttle point 52 in the conversion of the damping piston 51. An annular surface 55 formed on the damping piston 51 is acted upon by a spring element 54 which is supported on the housing side. A filling line 56, which contains a refilling valve 50, which can be designed as a non-return valve, runs from the control chamber 12 for the injection valve member 14 to the compression chamber 9 of the pressure booster 3. Via the filling line 56 containing the refilling valve 50, the compression chamber 9 of the Discharge intensifier 3 refilled with fuel.

The servo valve 24 according to the embodiment variant shown in FIG. 2 is accommodated in the valve body 25. The servo valve 24 comprises the control chamber 36, which can be relieved of pressure via the switching valve 30 into the second return line 31 on the low-pressure side. An outlet throttle 37 (fourth throttle point) is accommodated between the control chamber 36 and the switching valve 30. Opposite the control chamber 36 in the valve body 25 of the servo valve 24 is the first hydraulic chamber 38, which is separated by the control edge 41 from the second, here conically configured second hydraulic chamber 39. The second hydraulic chamber 39 is connected to the differential pressure chamber 6 (rear chamber) of the pressure booster 3 via the control line 21. In the embodiment variant of the servo valve 24 according to FIG. 2, the control edge 41 is also designed as a slide sealing edge 43. In contrast to the embodiment variant of the servo valve 24 shown in FIG. 1, the first sealing seat 40 of the servo valve piston 32 is designed as a conical seat. When the first sealing seat 40 is closed, the sequence control chamber 42 formed below the servo valve piston 32 in the valve body 25 is sealed, so that the first return 28 on the low-pressure side is closed.

In a modification of the servo valve piston 32 as shown in FIG. 1, the control chamber 36 and the first hydraulic chamber 38 are pressurized in parallel via the supply line 29, which branches off from the working chamber 5 of the drain intensifier 3. The system line is therefore via the supply line 29 both in the first hydraulic space 38, which is acted upon by the second supply line section 58, and via a first supply line section 57, the third throttle point 34 containing, in the control chamber 36 of the servo valve 24. Based on the identity of the pressures in the first hydraulic chamber 38 and in the control chamber 36, a guide leakage along the head of the servo valve piston 32 is excluded. The servo valve piston 32 is guided in the valve body 25 in a high-pressure-tight manner. In the idle state, system pressure is present on both sides within the guide region of the head of the servo valve piston 32, ie in the control chamber 36 and in the first hydraulic chamber 38, so that no leakage current occurs on the low-pressure side. The entire area of the servo piston 32, that is to say the control chamber 36, the first hydraulic chamber 38 and the second hydraulic chamber 39 and the control edge 41, is free of guide leakage against the sequence control chamber 42 and thus against the first low-pressure side via the first sealing seat 40 formed in the second hydraulic chamber 39 Return 28 sealed.

The basic mode of operation of the fuel injector proposed according to the invention, which is controlled via the servo valve 24, is described with reference to the illustration in FIG. 1.

The working space 5 of the pressure booster 3 is constantly connected to the pressure source 1 and is constantly below the pressure level prevailing there. The compression chamber 9 of the pressure intensifier 3 is continuously connected to the pressure chamber 16, which surrounds the injection valve member 14, via the pressure chamber inlet 17. The pressure intensifier 3 also includes the differential pressure space 6 (rear space) which is used to control the pressure intensifier 3 either with a system pack, i.e. is applied to the pressure level prevailing in the drain source 1 or is separated from it in the low pressure-side return 28 is relieved of pressure. In the deactivated state, the differential pressure chamber 6 (rear chamber) of the pressure translator 3 is connected to the pressure accumulator 1 via the discharge line 21, the open control edge 41, the supply line 29, so that the pressures in the working chamber 5 and in the differential pressure chamber 6 (rear chamber) of the pressure translator correspond to each other and the booster piston 4 is balanced and no boost boost takes place.

To activate the pressure booster 3, the differential pressure chamber 6 (rear space) is relieved of pressure. In order to bring about this pressure relief, the switching valve 30 is activated, ie opened, and the control chamber 36 of the servo valve 24 is pressure-relieved into the low-pressure side return 31 via the outlet throttle point 37. Due to the falling pressure in the control chamber 36, the servo valve piston 32 moves upwards in the vertical direction, moved by the pressure force acting on the opening surface 44 in the first hydraulic chamber 38. As a result, the first sealing seat 40 is opened while the control edge 41 is closed, since the slide edge 43 covers the housing edge of the valve body 25 opposite this. The design of the throttle point 34 in the through channel 33 of the servo valve piston 32 and the outlet throttle 37 means that the movement supply speed of the servo valve piston 32 is freely adjustable during its opening movement. Due to the defined opening surface 44 on the underside of the head of the servo valve 24, a pressure force acting on the servo valve piston 32 in the opening direction is constantly present. This allows an exact movement of the servo valve piston 32 and thus a stable persistence of the same at the opening stop in the open state of the servo valve piston 32.

When the servo valve piston 32 is in its open position, the differential pressure space 6 (rear space) of the pressure booster 3 is decoupled from the system pressure, i.e. of the pressure level prevailing in the pressure accumulator 1. When the control edge 41 is closed, a control quantity flows out of the differential pressure chamber 6 (rear chamber) via the control line 21 into the second hydraulic chamber 39, and via the opened first sealing seat 40 into the drain control chamber 42. From there, the one controlled from the differential pressure chamber 6 (rear chamber) flows Fuel quantity in the low-pressure side return 28.

On the basis of the entry movement of the end face 20 of the booster piston 4 into the compression chamber 9, there is an increase in pressure therein, so that fuel under increased pressure flows into the pressure chamber 16, which surrounds the injection valve member 14, via the pressure chamber inlet 17 in accordance with the transmission ratio of the pressure booster 3. Due to the pressure stage formed on the injection valve member 14 in the area of the pressure chamber 16, the latter opens against the action of the spring 13, so that the injection nozzles 22 at the end of the fuel injector 18 on the combustion chamber side are opened and fuel can be injected into the combustion chamber 23 of the internal combustion engine. When the injection valve member 14 is completely open, the second throttle point 15 between the control chamber 12 and the compression chamber 9 of the pressure booster 3 is closed, so that no leakage current occurs during the injection process.

To end the injection process, the switching valve 30 is actuated again, and this is moved into its closed position, so that in the control chamber 36 via the passage 33, the first hydraulic chamber 38 and the supply line 29 opening into it, the system pressure prevailing in the accumulator 1 is built up. Due to the pressure force building up in the control chamber 36, the servo valve piston 32 moves downward into its starting position, the first sealing seat 40 being closed to the return 28 on the low pressure side and the control edge 41 being opened. Since the end face 35, on which the pressure prevailing in the control chamber 36 acts, is dimensioned larger than the opening drain surface 44 in the first hydraulic chamber 38, a defined and rapid closing movement of the servo valve piston 32 into its closed position is achieved. To support the lifting movement of the servo valve piston 32, additional springs could also be arranged in the first housing part 26.

In the differential pressure chamber 6 (rear chamber) of the drain amplifier and in the control chamber 12, via which the injection valve member 14 is controlled, pressure is now built up to the pressure level prevailing in the pressure accumulator 1 via the supply line 29, which branches off from the high-pressure supply line 2 of the high-pressure accumulator 1, the open control edge 41, the second hydraulic chamber 39 and the control line 21, which opens into the differential pressure chamber 6 (rear chamber). From there, a drain build-up takes place via the overflow line 10, which contains the first throttle point 11, into the control chamber 12.

At the same time, when the pressure in the differential pressure chamber 6 (rear chamber) of the pressure intensifier builds up, the compression chamber 9 is refilled via the line branching from the control chamber 12 for actuating the injection valve member 14, in which the second throttle point 15 is formed.

The first sealing seat 40 can be designed both as a flat seat, which enables a high surface pressure, and as a conical seat (see comparisons according to FIG. 2) as a ball seat or as a slide edge. An axial offset that may occur due to production can be compensated for via the flat seat shown in FIG. 1 as the first sealing seat 40. A sufficient closing force is generated via the high pressure level present in the control chamber 36, so that a high surface pressure is created on the first sealing seat 40 in its closed position and a good sealing effect is thus ensured.

With the embodiment variant shown in FIG. 2 using a damping piston 51, which acts on the injection valve member 14, a reduction in the opening speed of the needle-shaped injection valve member 14 can be achieved. The damping behavior of the damping piston 51 can be adjusted by the dimensioning of this spring element 54 acting on it as well as by the dimensioning of the throttle element 52 formed in the wall of the damping piston 51. According to the embodiment variant shown in FIG. 2, the compression chamber 9 of the pressure intensifier 3 is not refilled via the second throttle point 15 as in the embodiment variant according to FIG. 1, but via a filling line 56 branching off from the control chamber 12 of the injection valve member 14, in which a check valve Refill valve 50 is added. The 3/2-servo valve 24 proposed according to the invention can be used to control all pressure intensifiers 3, which are actuated via a pressure change in their differential pressure chamber 6 (rear chamber).

FIG. 3 shows an embodiment variant of a 3/2 servo valve with a servo valve piston, on which a control sleeve is received.

The embodiment variant shown in FIG. 3 of a fuel injector 18 with pressure intensifier 3 is acted upon by a high pressure fuel 1 via the high pressure supply line 2 with fuel under high pressure. Via the high-pressure line 2, the working space 5 of the pressure booster 3 is filled with system pressure, in which a return spring 8 is accommodated, which is supported on the one hand on a support disk 7 and, on the other hand, prestresses the booster piston 4, which separates the working space 5 from the differential pressure space 6. The end face 20 of the booster piston 4 delimits the compression space 9, from which, when the pressure booster 3 is activated, the fuel space 16 is acted upon by the fuel chamber 16 via the pressure chamber inlet 17.

The embodiment variant of the fuel injector 18 shown in FIG. 3 includes the control chamber 12, which is delimited by a control chamber sleeve 62. The control chamber sleeve 62 is prestressed via the spring 13, the spring 13 being supported on a collar of the injection valve member 14. On the injection valve member 14, inlet surfaces 64 designed as polished sections are formed below the collar. Via these inlet surfaces 64, the fuel flows in from the pressure chamber to injection openings 22 which open into the combustion chamber 23 of the self-igniting internal combustion engine. The control chamber 12 of the fuel injector 18 is supplied with fuel on the one hand via a first throttle point 11 which branches off from the pressure chamber inlet 17; the pressure relief of the control chamber 12 takes place via the second throttle point 15 when a switching valve 60 is actuated. If the switching valve 60 is actuated, a discharge quantity is derived via the second throttle point 15 into an injector return 61.

The pressure intensifier 3 according to the embodiment variant shown in FIG. 3 is actuated via the servo valve 24. The servo valve 24 comprises the valve piston 32, which has a servo valve piston section 65. The servo valve piston 32, 65 is controlled via the pressurization or pressure relief of the control chamber 36. On the pressure side, the control chamber 36 of the servo valve 24 is acted upon by fuel under high pressure via the first supply line section 57, in which the throttle point 34 is accommodated. The control chamber 36 of the servo valve 24 is depressurized by actuating the switching valve 30. Control volume from the pressure-relieved control chamber 36 of the servo valve 24 via the outlet throttle 37 (4th throttle point) into the return 31 provided on the low-pressure side.

The servo valve 24 comprises a housing 25 which comprises a plurality of housing parts 26, 27.

The servo valve piston 32, 65 is enclosed by the first hydraulic space 38 and the second hydraulic space 39. The first hydraulic chamber 38 is supplied with fuel under high pressure via the supply line 29, which branches off from the high-pressure line 2. The control line 21 opens into the second hydraulic chamber 39, via which the differential pressure chamber 6 (rear chamber) of the drain converter 3 is relieved of pressure.

The servo valve piston 32 also comprises the hydraulic surface 44, on which a pressure force which moves the servo valve piston 32 in the open position acts when the control chamber 36 of the servo valve 24 is relieved of pressure. First recesses 63, which have slide sealing edges 43, are formed in the servo valve piston section 65. The slide sealing edges 43 of the first recesses 63 interact with a control edge 41 formed on the second housing part 27. On the servo valve piston section 65, a control sleeve 67 is received, which is biased by a control sleeve spring 68, which in turn is supported on the first housing part 26 of the servo valve housing 25. The control sleeve 67 has a sleeve recess 71. The first sealing seat 40 according to the embodiment variant shown in FIG. 3 is designed as a flat seat and seals the control chamber 42 (low-pressure chamber) against the return 28 on the low-pressure side. The functioning of the embodiment variant shown in FIG. 3 of the fuel injector 18 controlled by the servo valve 24 with pressure intensifier 3 is as follows:

In the initial state, there is system pressure in the control chamber 36 of the servo valve 24, which is present in the control chamber 36 via the third throttle point 34 when the switching valve 30 is closed. Due to the pressure force within the control chamber 36 of the servo valve piston, which acts on the end face 35 of the servo valve piston 32 and which is greater than the opening pressure force, which is applied to the servo valve piston 32 via the hydraulic surface 44 acting in the opening direction, the servo valve piston 32 is in its lower position hazards. In this position, the control edge 41 and the slide sealing edge 43 on the servo valve piston section 65 are open, whereas the slide seal 69 on the servo valve piston section 65 is closed. Furthermore, the first sealing seat 40 is located in its closed position against the control chamber 42 (low-pressure chamber). Since the second hydraulic chamber 39 is sealed off from the control chamber 42 (low-pressure chamber) by the first sealing seat 40, when the servo valve piston 32, 65 is closed, there is no leakage flow into the return 28 on the low-pressure side, which means lower requirements the guide leakage (guide length and play) of the control sleeve 67 received on the servo valve piston section 65 can be set.

The first sealing seat 40 can be designed in a variety of ways. In addition to the configuration of the first sealing seat 40 shown in FIG. 3 as a flat seat, it can also be designed as a conical seat or a ball seat in accordance with the embodiment variants shown in FIG. 2. The embodiment of the first sealing seat 40 shown in FIG. 3 as a flat seat in connection with a multi-part servo valve housing 25 is particularly advantageous. A multi-part valve body, such as housing parts 26, 27 and 66, makes it easy to manufacture the valve seat of the first sealing seat 40 , A possible misalignment of the valve bodies relative to one another is compensated for by the flat seat shown in FIG. The embodiment variant shown in FIG. 3 also has a large closing pressure force, exerted by the fuel present in the control chamber 36, on the first sealing seat 40, as a result of which a high surface pressure and thus an excellent sealing effect are established.

In the idle state of the servo valve 24, the differential pressure chamber (rear chamber) 6 of the pressure booster 3 is pressurized with system pressure via the first recesses 63 on the servo valve piston 65 and the first hydraulic chamber 38, and the drain booster 3 remains the control line due to the hydraulic connection between the second hydraulic chamber 39 21 connected to the differential pressure space. On the basis of the same pressure level in the differential pressure space 6 and the work space 5, the pressure converter 3 is deactivated. When the switching valve 30 is actuated, the pressure in the control chamber 36 of the servo valve 24 is relieved, whereby the servo valve piston 32, 65 opens. Due to the opening force acting on the hydraulic surface 44 via the first hydraulic space 38, the servo valve piston 32 is opened exactly. When opening, the first sealing seat 40 is opened first and the slide sealing edge 43 is brought into overlap with the control edge 41. The control sleeve 67 is now set by the hydraulic pressure force in the second hydraulic space 39 on the third housing part 66, whereby a high pressure-tight connection is achieved. Only then does the slide seal 69 open when the servo valve piston section 65 releases the sleeve recess ring 71. As a result, there is no short-circuit leakage current from the first hydraulic space 38 into the return. The differential pressure chamber 6 (rear chamber) of the pressure booster 3 is now connected to the low-pressure side return 28 via the second hydraulic chamber 39, the slide seal 69, the first sealing seat 40 and the control chamber 42 (low-pressure chamber) and the pressure intensifier 3 is thus activated. If, on the other hand, the switching valve 30 is closed again, the servo valve piston 32, 65 moves into its starting position by the hydraulic pressure force acting in the closing direction in the control chamber 36. The hydraulic closing force ensures a precisely defined closing movement over the entire area of the servo valve piston 32, 65. In addition, a spring force can be provided to support the closing movement. When the servo valve piston 32, 65 is closed, the slide seal 69 is first closed. As a result, the differential pressure chamber 6 (rear chamber) of the drain converter 3 is decoupled from the return 28 on the low-pressure side. Only after a further closing stroke and thus after a delay time t _1; the control edges 41, 43 are opened, so that the drain converter 3 is completely deactivated. The first sealing seat 40 is then closed.

Due to the delay time ti between the closing of the slide seal 69 and the opening of the control edges 41 or the slide sealing edge 43, after the main injection, a drain cushion remains on the injection valve member 14 for a short time, which can be used for post-injection under high pressure. According to this switching sequence, an overlap of the opening cross sections on the slide seal 69 and the control edges 41, 43 is avoided.

The illustration according to FIG. 4 shows an embodiment variant with a servo valve piston of a servo valve which is of elongated design. In contrast to the embodiment variant of a fuel injector 18 shown in FIG. 3 and described above, which is actuated via a servo valve 24, the servo valve piston 32 has an elongated servo valve piston section 65. According to this embodiment variant, second cutouts 70 are formed at the end of the servo valve piston section 65 facing the control chamber 42 (low pressure chamber). Two or more cutouts 70 can be formed on the circumference of the servo valve piston section 65. According to this embodiment variant, the slide seal 69 is integrated directly into the first housing part 26 of the servo valve housing 25. According to this embodiment variant, the control sleeve 67 shown on the servo valve piston section 65 in FIG. 3 can be omitted.

The mode of operation of the embodiment variant shown in FIG. 4 is identical to the method of operation of this embodiment variant of the fuel injector 18 shown in connection with FIG. 3.

According to the illustration according to FIG. 4, a flat seat is formed on the end face of the servo valve piston section 65 facing the control chamber 42 (low-pressure chamber). In addition to the embodiment variants shown in FIGS. 1-4 with a first sealing seat 40 in the servo valve housing 25, the servo valve 24 can also be designed as a pure slide-slide valve. Care must be taken to ensure that there is sufficient overlap length on the slide seal 69 in order to keep the leakage flow small when the fuel injector 18 is at rest. In addition to the function described above as a 3/2-way valve, the servo valve 24 can also be designed as a 4/2-way valve in which the function of the check valve can be integrated into the slide valve.

LIST OF REFERENCE NUMBERS

pressure source

High pressure supply line

Drackübersetzer

Booster piston

working space

Differential pressure space (rear space)

support disc

Return spring

compression chamber

overflow

1st choke point

Control room for injection valve member

feather

Injection valve member

2nd throttling point

Drackraum

Drackraumzulauf

fuel injector

injector

Front surface of the intensifier piston 4

diversion line

Injection port

combustion chamber

servo valve

Servo valve housing

1. Housing part

2. Housing part return on the low-pressure side

Supply line servo valve

Switching valve for further return on the low-pressure side

Servo valve piston

Through channel

3rd throttling point

Control surface of the servo valve piston

Control room servo valve

Discharge throttle (4th throttle point) 1. hydraulic room

2. hydraulic room first sealing seat

control edge

Control room (low pressure room)

Slide sealing edge

Opening area

Wiederbefüllventil

damping piston

5th throttling point

channel

spring element

ring surface

BefülUeitung

1. Supply line section

2. Supply line section

Injektorschaltventil

injector return

Control chamber sleeve

1. Cutouts

Inlet surfaces (bevel)

Sei-voventilkolbenabschnitt

3. Housing part

control sleeve

Control sleeve spring

slide seal

2. Cutouts

Steuerhülsenausparang

Claims

claims

1. Fuel injector for injecting fuel into a combustion chamber (23) of an internal combustion engine with a pressure booster (3), the booster piston (4) of which, via a pressure source (1, 2), permanently exposed to fuel in a working space (5) that can be relieved of pressure by a pressure differential pressure chamber (5) 6), whereby a change in pressure in the differential pressure chamber (6) takes place by actuating a servo valve (24) which releases or closes a hydraulic connection (21, 39, 42) of the differential pressure chamber (6) to a return (28) on the low-pressure side , characterized in that the servo valve (24) is located between a control room

(36) and a first hydraulic chamber (38) guided servo valve piston (32, 65), on which an effective hydraulic surface (44) constantly acted upon in the opening direction of the servo valve piston (32) by a system pressure, and a servo valve (24) against a first sealing seat (40) which seals a return on the low-pressure side (28) is formed.

2. Fuel injector according to spoke 1, characterized in that the control chamber (36) and the first hydraulic chamber (38) via a one from the pressure accumulator (1) outgoing supply line (29) are acted upon with system pressure.

3. Fuel injector according to spoke 2, characterized in that the control chamber (36) of the servo valve (24) via a through the servo valve piston (32) extending passage (33) from the first hydraulic chamber (38), in which the supply line (29) flows, is loaded with system dirt.

4. Fuel injector according to claim 3, characterized in that the through channel (33) of the servo valve piston (32) contains an integrated throttle point (34).

5. Fuel injector according to spoke 2, characterized in that the control chamber (36) via a second supply line section (58) branching off from the supply line (29) and the first hydraulic chamber (38) via a supply line section branching off from the supply line (29) ) are loaded with system rack in parallel.

6. Fuel injector according to spoke 5, characterized in that the first supply line section (57) contains a first throttle point (34).

7. Fuel injector according to spoke 1, characterized in that the servo valve piston (32) releases or closes the low-pressure side return (28). ßenden first sealing seat (40) and a control edge (41) separating the first hydraulic chamber (38) from a second hydraulic chamber (39).

Fuel injector according spoke 7, characterized in that the first sealing seat

(40) is designed as a flat seat or as a conical seat and closes a discharge control chamber (42) arranged on the low-pressure side.

Fuel injector according spoke 7, characterized in that the control edge

(41) is designed as a slide sealing edge (43).

10. Fuel injector according to spoke 1, characterized in that the differential pressure chamber (6), which can be relieved of pressure via the servo valve (24) in the low-pressure-side return line (28), is hydraulically coupled to a control chamber (12) for an injection valve member (14) receiving a damping piston (51) The damping piston (51) comprises a throttle point (52) that defines the opening speed of the injection valve member (14), and the control chamber (12) for actuating the injection valve member (14) via a filling line (56) either with the control chamber (12 ) or one of the hydraulic rooms (5, 6, 9) of the drain converter (3) is connected.

11. Fuel injector according to claim 1, characterized in that the actuation of the servo valve (24) via a control chamber (36) with a return (31) connecting switching valve (30).

12. Fuel injector according spoke 1, characterized in that the servo valve piston (32) comprises a reduced-diameter servo piston section (65) on which a prestressed control sleeve (67) is received.

13. Fuel injector according to claim 1, characterized in that the control sleeve (67) with the servo valve piston portion (65) forms a slide control edge (69).

14. Fuel injector according to spoke 13, characterized in that the slide control edge (69) controls the connection to the low-pressure side return (28).

15. Fuel injector according to spoke 12, characterized in that the servo valve piston portion (65) of the servo valve piston (32) has first recesses (63) which comprise a slide sealing edge (43) which cooperate with a control edge (41) formed on the servo valve housing side. -ΔλJ-

16. Fuel injector according to claim 12, characterized in that the control sleeve (67) is acted upon by a spring element (68) which is supported on a housing part (26) of the servo valve housing (25).

17. The fuel injector according to spoke 12, characterized in that the servo valve piston section (65) of the servo valve piston (32) forms first recessing rods (63) between the first hydraulic chamber (38) and the second hydraulic chamber (39) and a slide seal (69) Ausausangen (70) includes.