EP1381774A1

EP1381774A1 - Fuel injection device with two coaxial valve elements and fuel system for internal combustion engines, as well as internal combustion engine

Info

Publication number: EP1381774A1
Application number: EP02729851A
Authority: EP
Inventors: Detlev Potz; Gerhard Mack; Thomas Kuegler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-04-17
Filing date: 2002-04-04
Publication date: 2004-01-21
Anticipated expiration: 2022-04-04
Also published as: PL358121A1; JP4076142B2; JP2004518907A; DE50207439D1; EP1381774B1; DE10118699A1; BR0204830A; WO2002084110A1

Abstract

The invention relates to a fuel injection device (10) for internal combustion engines, comprising an elongated housing (12) with a closed injection end (28). A recess (34) extends within said housing (12) in the longitudinal direction thereof and can be linked with a fuel inlet (20). At least two axially spaced apart outlet openings (30, 32) are provided on the injection end (28). At least two coaxially and axially movable valve elements (40, 42) are disposed in the recess (34) and cooperate with valve seats in the area of the outlet openings (30, 32). In order to allow for a fuel injection device (10) that is as simple and small as possible in design, the valve elements (40, 42) comprise a driving connection (52, 72) which allows the one valve element (40; 42), when travelling a certain path (S1), to axially contact the other valve element (42; 40), thereby taking it along.

Description

FUEL INJECTION DEVICE WITH TWO COAXIAL VALVE ELEMENTS AND FUEL SYSTEM FOR INTERNAL COMBUSTION ENGINES AND COMBUSTION ENGINE

State of the art

The invention relates to a fuel injection device for internal combustion engines, with an elongated housing with an injection end, with a recess in the housing in its longitudinal direction, which can be connected to a fuel inlet, with at least two axially spaced outlet openings at the injection end, with at least two coaxial and axially movable valve elements, which are arranged at least in regions in the recess and cooperate with valve seats in the region of the outlet openings.

Such a fuel injection device is known from DE 40 23 223 AI. This shows a fuel injection nozzle, in the elongated housing of which two valve needles which are coaxial to one another are guided. At the injection end, the housing is closed and comprises two axially spaced rows of spray holes distributed over the circumference. There is a separating sleeve between the valve needles, and the valve needles can be operated independently of one another via separate fuel inlets. Such fuel -

Injectors are used for direct-injection internal combustion engines. The purpose of the two valve needles is to adapt the Injection characteristics to the operating load, which is important for the emission behavior of the internal combustion engine.

There is usually only little space available on the cylinder head of the internal combustion engine for installing the fuel injection device. It is therefore the object of the present invention to develop a fuel injection device of the type mentioned at the outset in such a way that it is as small as possible.

This object is achieved in a fuel injection device of the type mentioned at the outset in that the valve elements work together in such a way that the one valve element causes the other valve element to move during a movement along a specific path.

Advantages of the invention

In the fuel injection device according to the invention, the valve elements are no longer moved independently of one another. Instead, the movement of one valve element is coupled to a movement of the other valve element. This makes it possible to dispense with separate control of the two valve elements. In this way, the fuel injector can be made smaller.

Advantageous developments of the invention are specified in the subclaims.

In a first development it is stated that the axially spaced outlet openings are fluidly connected to one another when both valve elements are lifted off the associated valve seats. at In this development, there is therefore no separating element between the two valve elements, which further reduces the external dimensions of the fuel injection device according to the invention. In addition, fewer parts are present, in particular at the highly loaded injection end of the fuel injection device, which improves the reliability during operation of the fuel injection device according to the invention.

It is further proposed that the outer valve element open first and cause movement of the inner valve element when moving along a certain path. Alternatively, the inner valve element can also open first and cause the outer valve element to move in a certain way.

It is particularly preferred if a driver connection is provided in such a way that the one valve element axially comes into contact with the other valve element at least indirectly during a movement and thereby moves the same. This mechanical driver connection is simple and robust.

The driver connection ^" can be designed such that it comprises a shoulder on one valve element, which cooperates with a shoulder on the other valve element, the shoulder and the shoulder being axially spaced apart from one another in the closed state of the injection device. Such a driver connection is simple to produce The shoulder and heel can also be manufactured very precisely, so that the distance that the valve element that opens first has to travel until the second valve element also opens can be precisely determined fuel according to the invention Injection device is thus precisely predictable, which is useful for the consumption and emission-optimized operation of an internal combustion engine equipped with the fuel injection device according to the invention.

A preferred embodiment of a fuel injection device according to the invention consists in that the driver connection comprises at least one ball trapped in one valve element, which cooperates with a shoulder on the other valve element, the shoulder and the ball being axially spaced apart from one another in the closed state of the injection device , Such a fuel injection device is particularly low in friction and wear.

Further, it is possible that on ^'the remote from the injection end of the end of a valve element, a pressure chamber is present, on the one hand connected via a flow throttle to a low pressure area and on the other hand is connected via a transverse flow duct to the fuel inlet, the connection between the pressure chamber and the fuel inlet is interrupted by the other valve element when it has moved a certain distance. In this case, no mechanical means are required to cause the other valve element to move. This fuel injection device thus works without wear and therefore has a particularly long service life.

It is particularly preferred if there is at least one opening in the other valve element, which in the closed state of the injection device covers access to the flow channel from the fuel inlet by a distance.

In a particularly preferred development of According to the fuel injection device according to the invention, a switchable stroke limitation is provided, by means of which the stroke of the valve element which opens first can be limited such that the driver connection between the two valve elements does not yet engage. This development makes it possible to operate the fuel injection device either with only one valve element in the open state or with both valve elements in the open state. For example, in a simple manner. it is possible to double or halve the fuel delivered by the fuel injection device.

It is particularly preferred that the stroke limitation operates hydraulically. In this case, electrical components in the area of the fuel injection device can be dispensed with. This increases the operational safety of the fuel injection device.

Furthermore, the first opening valve can be connected to a first pressure surface, which delimits a control chamber, and the control chamber can be fluidically closable. If the control chamber is closed fluidically, due to its low compressibility, the fluid volume enclosed in the control chamber acts like a mechanical stop against which the first pressure surface rests. In this way, the stroke of the valve element opening first is limited.

The first opening valve element can be connected to a second pressure surface, which causes an opening movement of the valve element when pressure is applied, the first pressure surface being larger than the second pressure surface. This makes it possible to keep the pressure in the control room as low as possible.

According to the invention it is also proposed that in the wall there is an outlet opening in the control chamber and that a control element is connected to the valve element which opens first, which is spaced apart from the outlet opening when the fuel injector is closed and which seals the outlet opening in the course of a movement of the valve element. Through this development, the fluidic encapsulation of the control chamber is produced in a particularly simple manner according to a specific path covered by the valve element that opens first.

The fluidic closure of the control chamber can be released in a simple manner in that the fuel injection device has a switchable valve via which the control chamber can be connected to an outlet. Such a removal of the fluidic closure of the control chamber removes the stroke limitation, so that the valve element that opens first can cover the full opening distance and can take the second valve element with it.

In order to be able to dispense with electrical components in the area of the fuel injection device, it is particularly advantageous if the valve can be switched hydraulically.

To limit the opening movement of the valve elements, a mechanical stop can be provided, which limits the path during an opening movement of at least one of the valve elements. Such a mechanical stop is easy and inexpensive to produce and provides fUn ^¬ defined and constant aperture ratios.

In a particularly preferred development of the fuel injection device according to the invention, the valve element which opens later is connected to a third pressure surface which, when pressurized, does so Valve element presses on the valve seat. This ensures that when the valve element that opens first lifts off the valve seat and, for example, the stroke limitation is switched on, the other valve element continues to be pressed onto the valve seat.

The invention further relates to a fuel system for an internal combustion engine with a fuel tank, with at least one fuel pump which delivers from the fuel tank, with at least one fuel manifold, and with at least one fuel injector which is connected to the fuel manifold and injects the fuel directly into a combustion chamber, the fuel injection device having an elongated housing with a closed injection end, a recess running in the longitudinal direction of the housing and being connectable to a fuel inlet, at least two axially spaced outlet openings at the injection end , and at least two coaxial and axially movable valve elements, which are arranged at least in regions in the recess and cooperate with valve seats in the region of the outlet openings.

In order to be able to build such a fuel system as small as possible overall, it is proposed that the fuel injection device be designed in the above manner.

The invention also relates to an internal combustion engine, in particular for a motor vehicle, with a

Fuel system which is a combustion chamber of the

Internal combustion engine supplied with fuel. For a soclhe

Internal combustion engine, it is advantageous if that

Fuel system is designed in the above manner. drawing

Several exemplary embodiments of the

Invention with reference to the accompanying drawing in

Explained in detail. The drawing shows:

Fig. 1: a longitudinal section through a first

Embodiment of a fuel injection device;

2: a detailed view of a region of the fuel injection device of FIG. 1,

3: a detailed representation of a further area of the fuel injection device of FIG. 1,

4 shows a longitudinal section through a second exemplary embodiment of a fuel injection device;

Fig. 5: a detailed view of a first area of the

4; and

FIG. 6: a detailed view of a second region of the fuel injection device from FIG. 4.

7: a partial longitudinal section through a region of a third exemplary embodiment of a fuel injection device;

8 shows a longitudinal section through a fourth exemplary embodiment of a fuel injection device;

9 shows a longitudinal section through a region of the fuel injection device from FIG. 3; 10 shows a longitudinal section through a fifth exemplary embodiment of a fuel injection device; and

11: a longitudinal section through an area of the

Fuel injector of FIG. 10.

Description of the embodiments

First, the embodiment of a fuel injector shown in Figs. 1-3 is explained. The fuel injection device bears the reference symbol 10 overall. It comprises a housing 12 with a base section 14 in FIG. 1, a central section 16 and a nozzle body 18. The fuel injection device 10 can be supplied with a fuel via an inlet 20. High pressure line (not shown) can be connected. An outlet 22 may be connected to a low pressure area of a fuel system. Between the nozzle body 18 and the base section 14, an intermediate disk 24 and a control disk 26 are also arranged in the axial direction. The fuel injection device is used to inject fuel (gasoline or diesel) into the combustion chamber of an internal combustion engine (not shown).

In its lower area in FIG. 1, the nozzle body 18 has an injection cap 28, which is provided with two rows of outlet openings 30 and 32 distributed axially apart from one another (cf. FIG. 3). Except for the outlet openings 30 and 32, the nozzle body 18 is therefore closed at its lower end. A recess 34 extending in its longitudinal direction is provided in the interior of the nozzle body 18. In its upper region, the recess 34 has a bulbous widening 36 which communicates with the inlet 20 via a flow channel 38 is connected (Fig. 2). Two coaxial valve elements 40 and 42 designed as valve needles are arranged in the recess 34. The outer valve element 42 is tubular, the inner valve element 40 has a full cross section. Both valve elements 40 and 42 have sealing edges 44 and 4β at their lower end, which cooperate with corresponding valve seats (without reference numerals) between the outlet openings 30 and 32 or above the upper outlet openings 32. An annular space 48 extends from the injection tip 28 to the bulbous extension 36 between the outer valve element 42 and the inner wall (without reference number) of the recess 34.

The outer diameter of the outer valve element 42 is larger in an upper region than in a lower region. In the transition between the two areas, approximately at the level of the extension 36, a pressure surface 50 is formed, the meaning of which will be discussed in detail below. Approximately at the level of the bulbous extension 36 of the recess 34, an oblique shoulder 52 is formed on the inner lateral surface (without reference number) of the outer valve element 42. The outer valve element 42 extends beyond the upper side of the nozzle body 18 into a central recess 54 in the intermediate disk 24. There the upper end of the outer valve element 42 bears against a control piston 56 which slidably guided in the recess 54 in the intermediate disk 24 is.

The top of the control piston 56 overall forms a first pressure surface 57. Its outer edge is raised in a ring. A control pin 58 is supported on the upper side of the control piston 56 and extends almost completely through a central recess 60 in the control disk 26. Again, the blunt tip of a conical is supported on the top of the control pin 58 Spring bolt 62 from. A compression spring 64 bears against its base and is received in a recess 66 in the base section 14 of the housing 12. At its end remote from the spring pin 62, the compression spring 64 is supported on a ring-shaped adjusting disk 68, which is arranged at the upper end of the recess 66 in the base section 14 of the housing 12 in FIG. 1. The recess 66 is connected to the outlet 22 via a flow channel 70.

The inner valve element 40 is guided in the outer valve element 42. In the area of the shoulder 52 of the inner lateral surface of the outer valve element 42 ', a shoulder 72 is present on the outer lateral surface of the inner valve element 40. If the sealing edges 44 and 46 of the two valve elements 40 and 42 bear against their valve seats in the area of the injection cap 28 (this state is shown in FIGS. 1-3), the shoulder 52 and the shoulder 72 are spaced apart by a distance S1 ( see Fig. 2).

As can be seen from FIG. 2, the inner valve element 40 ends just above the shoulder 72. The upper end face of the inner valve element 40 is concave. A recess 74 formed in this way is connected via radially extending openings 76 and corresponding radially extending channels 78 in the wall of the outer valve element 42 to the bulbous extension 36 of the recess 34 and thereby via the flow channel 38 to the inlet 20. The recess 74 also forms a pressure surface, the meaning of which will be discussed further below. A connecting bolt 80 is supported on the annular edge of the recess 74 and, in the position of the valve elements 40 and 42 shown in FIGS. 1-3, is likewise supported on the control piston 56 with its upper end. The control pin 58, which is arranged between the control piston 56 and the spring pin 62, has a circular cross section in a section 82 arranged at the bottom in FIG. 1, whereas it has a bevel 86 in an upper section 84 in FIG. 1. The diameter of the section 82 corresponds approximately to the diameter of the recess 60 in the control disk 26. In the closed state shown in FIGS. 1-3, the fuel injector 10, in which the sealing edges 44 and 46 of the valve elements 40 and 42 bear against the respective valve seats in the injection cap 28, the top of the control piston 56 is spaced from the bottom of the control disk 26 by a distance S2 (FIG. 1).

The height of the circular section 82 of the control pin 58 is selected such that it protrudes a distance S3 beyond the upper edge of the control piston 56, but is still spaced from the lower edge of the control disk 26 by a distance S4. A control chamber 88 is formed between the top 57 of the control piston 56 and the bottom of the intermediate plate 24. A control bore 90 extends obliquely outward from the control chamber 88 to an inlet space 92 of a spring-loaded ball valve 94. A control piston 96 of the ball valve 94 is guided in an eccentric longitudinal bore 98 in the intermediate disk 24. The control piston 96 can be acted on via a low-pressure control pressure connection 100, as a result of which the inlet space 92 of the ball valve 94 is connected to a leak oil drain to 102.

The fuel injection device 10 is operated as follows:

If only a comparatively small amount of fuel is injected into the combustion chamber of an internal combustion engine by the fuel injection device 10 1-3, only the upper outlet openings 32 in FIGS. 1-3 are connected to the fuel inlet 20, whereas the lower outlet openings 30 remain separate from the fuel inlet 20. For this purpose, the ball valve 94 is left in its closed state in which there is no connection between the control chamber 88 and the leak oil drain 102.

For an injection by the fuel injection device 10, a pressure wave is generated in a manner not shown here, which reaches the annular space 48 via the fuel inlet 20 and the flow channel 38. The pressure wave leads on the pressure surface 50 on the outer circumferential surface of the outer valve element 42 to a force directed axially away from the injection valve 28, by means of which the outer valve element 42 via the control piston 56, the control pin 58 and the spring pin 62 against the spring force of the compression spring 64 is moved up. In this way, the sealing edge 46 of the outer valve element 42 lifts off from the corresponding valve seat in the area of the injection cap 28 of the nozzle body 18, which ultimately connects the upper outlet openings 32 to the fuel inlet 20 via the annular space 48.

The sealing edge 44 of the inner valve element 40 remains in contact with the corresponding valve seat in the region of the injection dome 28 of the nozzle body 18, so that the lower outlet openings 30 remain separated from the fuel inlet 20. This is ensured by the fact that the pressure wave propagates via the radial channels 78 in the outer valve element 42 and the radial openings 76 in the inner valve element 40 into the concave recess 74 in the upper end face of the inner valve element 40. Characterized in that the resultant of the concave recess 74 forming the pressure surface in the opposite direction to Resulting from the pressure surface 50, the inner valve element 40 is acted upon in the opposite direction to the outer valve element 42 and thus pressed with its sealing edge 44 against the corresponding seat in the nozzle body 18.

The opening movement of the outer valve element 42 also pushes the control piston 56 and with it the control pin 58 upwards. The fuel in the control chamber 88 can flow upwards through the gap formed between the bevel 86 and the recess 60 in the control disk 26 the recess 66 escapes and flows through the flow channel 70 to the outlet 22. In the course of the movement of the control pin 58, however, the lower circular section 82 of the control pin 58 penetrates into the recess 60 in the control disk 26. In this case, there is no longer a gap between the control pin 58 and the recess 60 in the control disk 26. The fuel present in the control chamber 88 can therefore no longer escape from the control chamber 88.

A counterpressure thus builds up in the control chamber 88, which acts on the pressure surface 57 of the control piston 56. Since this pressure surface 57 on the control piston 56 is considerably larger than the pressure surface 50 on the outer valve element 42, a counterforce builds up even at a relatively low pressure in the control chamber 88, as a result of which the movement of the outer valve element 42 is stopped. The fuel enclosed in the control chamber 88 thus limits the stroke of the outer valve element 42.

The distance S4 between the top of the circular section 82 of the control pin 58 and the bottom of the control disk 26 in the closed state of the fuel Injection device 10 is smaller than the distance S1 between shoulder 52 on outer valve element 42 and shoulder 72 on inner valve element 40. This ensures that the movement of outer valve element 42 is stopped before shoulder 72 of inner valve element 40 comes into contact with the shoulder 52 of the outer valve element 42.

If it is desired that the two rows of orifices 30 and 32 be used for fuel injection, the low pressure control pressure port 100 in the washer 24 is pressurized. As a result, the ball valve 94 is lifted from its seat via the control piston 96, so that there is a fluidic connection from the control chamber 88 via the control bore 90, the inlet space 92 and the eccentric longitudinal bore 98 to the leak oil drain 102.

If a pressure wave now enters the recess 34 in the nozzle body 18, the outer valve element 42 is moved against the force of the compression spring 64 as described above. In contrast to that described above, the control chamber 88 is not fluidly closed even when the circular lower section 82 of the control pin 58 dips into the recess 60 in the control disk 26. Instead, the fluid present in the control chamber 88 can flow out to the leakage oil drain 102 via the control bore 90 in the manner described above. The movement of the outer valve element only ends when the annular edge of the control piston 56 abuts the underside of the control disk 26. In this case, the control piston 56 and with it the outer valve element 42 have covered the path S2.

Since the path S2 is greater than the distance between the shoulder 52 and the shoulder 72 at rest (S1), the shoulder 52 comes in the course of the movement of the outer one Valve element 42 in contact with the shoulder 72, whereby the inner valve element 40 is dragged along by the outer valve element 42. The sealing edge 44 of the inner valve element 40 thus also lifts off the corresponding valve seat in the injection cap 28 of the nozzle body 18, as a result of which the lower outlet openings 30 are also connected to the fuel inlet 20. If the pressure in the annular space 48 drops again, the inner valve element 40 is pressed again via the connecting pin 80 and the outer valve element 42 by the compression spring 64 with its sealing edges 44 and 46 against the corresponding valve seats in the injection cap 28 in the nozzle body 18.

Reference will now be made to 10 the second embodiment, _one fuel -Einspritzvorrichtung, which is shown in Figs. 4 to 6. For the sake of simplicity, those elements and parts which have functions equivalent to the exemplary embodiment shown in FIGS. 1 to 3 have the same reference symbols. They are not explained in detail again.

The fundamental difference between the first and the second exemplary embodiment relates to the sequence of the movements of the valve elements. At the first

The exemplary embodiment first opens the outer valve element 42. Depending on the switching position of the ball valve 94, it drags the inner valve element 40 with it in the course of its opening movement. In the exemplary embodiment shown in FIGS. 4 to 6, on the other hand, the inner valve element 40 first opens and, depending on the switching position of the ball valve 94, entrains the outer valve element 42 in the course of its opening movement. In the second exemplary embodiment, an additional spring 104 is provided which, in its idle state, seals the outer valve element 42 with the sealing edge 46 against the corresponding valve seat in the injection cap 28 of the nozzle body 18 presses.

The outer valve element 42 is guided on the inner valve element 40, and the inner valve element 40 is in turn guided at least indirectly in the intermediate disk 24 with its end remote from the injection cap 28. In this way, it is possible to make the extension 36 of the recess 34 in the nozzle body 18 accessible from the outside, so that they e.g. drilled and can be manufactured very easily. The outer valve element 42 is also guided through a constriction of the recess 34 in the nozzle body 18.

The term “indirect” guidance of the inner valve element 40 in the intermediate disk 24 is to be understood to mean that a sleeve 108 is additionally fastened to the upper end of the inner valve element 40 (cf. in particular FIG. 5). The attachment can be done for example by pressing. On the one hand, such a sleeve 108 offers the advantage of a larger pressure stage. This is to be understood to mean that the closing and opening pressures are closer to one another, which leads to a faster closing of the inner valve element 40. On the other hand, such a sleeve 108 enables a special choice of material for guiding the unit formed from sleeve 108 and inner valve element 40 in the intermediate disk 24.

The annular space 48, with which the fuel can reach the outlet openings 30 and 32, is provided between the inner valve element 40 and the outer valve element 42 in the exemplary embodiment shown in FIGS. 4-6. Access to the annular space 48 from the recess 34 in the nozzle body 18 is through radial channels 78 in the outer valve element 42. 4 and 6 two possible configurations of the injection cap 28 are shown. On the left side of FIGS. 4 and 6, the opening angle of the injection cap 28 is 60 °, whereas on the right side of FIGS. 4 and 6 it is 90 °. A smaller opening angle has advantages with regard to the size of the injection cap 28, whereas a larger angle has advantages with regard to the tightness between the sealing edges and the corresponding valve seats. Furthermore, the injection angle has an influence on the combustion behavior of the injected fuel.

FIG. 7 shows a modification of the exemplary embodiment shown in FIGS. 4-6. In the embodiment shown in FIG. 7, the sleeve 108 is dispensed with. Instead, the inner valve element 40 is guided directly in the intermediate disk 24. This is easier to make.

8 and 9, a fourth embodiment of a fuel injection pre-seal 10 is shown. In these two figures, too, those elements and parts which have functions equivalent to parts and elements of FIGS. 1-7 have the same reference numerals. They are not explained in detail again.

In the illustrated in FIGS. 8 and 9

Embodiment opens the outside. Valve element 42 in front of the inner valve element 40. The pressure surfaces on the outer valve element 42, which are to cause an axial opening movement of the outer valve element 42 when a pressure wave is introduced via the inlet 20 and the flow channel 38, are present at two locations on the outer valve element 42:

On the one hand, the outer surface of the outer carries Valve element 42 has a constriction 110 in the region of the confluence of the flow channel 38. The diameter of the outer valve element 42 above this constriction 110 is larger than the diameter below the constriction 110. This already leads to the occurrence of a pressure wave in the pressure space 36 formed by the constriction 110 a resultant force that moves the outer valve member 42 upward.

In addition, an annular space 48 is present between the area of the outer valve element 42 below the constriction 110 and the recess 34 in the nozzle body 18, through which the pressure wave extends up to a conical taper 112 on the injection tip 28. Propagates tip of the outer valve member 42 (Fig. 9). The area of the conical taper 112 up to the sealing edge 46 acts as a pressure surface, on which a resultant force occurs during a pressure wave, by means of which the outer valve element 42 with the sealing edge 46 lifts off the corresponding valve seat. Because the pressure chamber 36 is created entirely by the constriction 106 in the outer valve element, the production of the recess 34 in the nozzle body 18 is considerably simplified and the production costs of the fuel injection device 10 are thereby reduced.

A further difference from the exemplary embodiments of a fuel injection device illustrated in FIGS. 1-7 is that the inner valve element 40 is received in a blind hole 114 in the outer valve element 42. The blind hole 114 extends coaxially to the longitudinal axis of the outer valve element 42 and is introduced into the outer valve element 42 from the end facing the injection cap 28. The inner valve element 40 also has a constriction 72 in its upper region. In the wall of the blind hole 114 in the outer valve element 42 there are several radial openings 116 distributed over the circumference which, when the fuel injection device 10 is closed, lie approximately at the same height as the constriction 72 in the inner valve element 40. In each of the openings 116, a ball 118 is received, the diameter of which is greater than the wall thickness of the outer valve element 42 in the region of the blind hole 114. The openings 116 and the balls 52 are dimensioned and positioned such that when the fuel injection device 10 is closed the balls 52 are at a distance S1 from the upper flank of the constriction 72 in the inner valve element 40 in FIGS. 8 and 9. The balls 5 _. 2, the openings 116 and the constriction 72 together form a driver connection, by means of which the inner valve element 40 is dragged when the outer valve element 42 is moved by a distance which is greater than S1.

If the ball valve 94 is switched in such a way that the outer valve element 42 can only move by a distance which is smaller than S1, then it is ensured in the following manner that the inner valve element 40 remains with its sealing edge 44 on the corresponding valve seat:

The injection pressure is transmitted via the annular space 48 to radial openings 118 in the peripheral wall of the outer valve element 42 delimiting the blind hole 114. A pressure chamber 120 is fluidly connected to the annular chamber 48 via the openings 118. The pressure chamber 120 is formed between the end face 74 remote from the injection tip 28 and the base of the blind hole 114. A spring 104 is tensioned between the end face 74 of the inner valve element 40 and the base of the blind hole 114.

The pressure chamber 120 and this in turn pressurizes the pressure surface 74 with the injection pressure, whereby the inner valve element 40 is pressed with its sealing edge 44 against the corresponding valve seat in the injection cap 28. In addition, the spring 104 provides a basic force that presses the inner valve element 40 with its sealing edge 44 against the corresponding seat in the injection cap 28 even in the unpressurized state.

The advantage of the embodiment shown in FIGS. 8 and 9 is its simpler and therefore less expensive production and the implementation of a particularly low-friction driver connection with the balls 52 _.

A fifth embodiment of a fuel injection device 10 is shown in FIGS. 10 and 11. It also applies here that parts and elements which have functions equivalent to parts and elements of the preceding figures have the same reference numerals. They are also not explained in detail again.

The essential difference between the exemplary embodiment of a fuel injection device 10 shown in FIGS. 10 and 11 compared to the previously described exemplary embodiments relates to the design of the driver connection. Instead of a mechanical driver connection, a hydraulic driver connection is provided here.

The fuel injection device shown in FIGS. 10 and 11 is again designed in such a way that the outer valve element 42 opens first. As in the last-described exemplary embodiment, the end of the outer end facing the injection tip 28 Valve element 42 is introduced into a bore 114 which is coaxial with the longitudinal axis of the outer valve element 42. However, this is not designed as a blind hole, but is connected via a throttle channel 122 with a relatively small cross section to an outflow space 124, which in turn extends to the upper end of the outer valve element 42 in FIGS. 10 and 11. There are radial openings 126, via which the outflow chamber 124 is connected to the leak oil drain 102.

The inner valve element 40 also differs from that of the last described embodiment:

An annular groove 128 is introduced into the outer lateral surface of the inner valve element 40 approximately at the level of its half longitudinal extent. At the level of the annular groove 128, the inner valve element 40 is penetrated by a transverse bore 130. In turn, a longitudinal bore 132 extends from the pressure surface 74 of the inner valve element 40 to the transverse bore 130. Radial bores 134 are made in the wall of the recess 114 in the outer valve element 42 and are distributed over the circumference. When the fuel injection device 10 is closed, the radial bores 134 lie approximately at the level of the annular groove 128 with a distance S1 between axially opposite edges of the bores 134 and the annular groove 128.

The fuel injection device 10 shown in FIGS. 10 and 11 operates as follows:

If only the outer valve element 42 with its sealing edge 46 is to lift off the corresponding valve seat in the injection cap 28, the ball valve 94 is accordingly held in the closed state. The hydraulic stop formed in this way is designed such that the outer valve element 42 can only move by a distance, which is smaller than Sl. In this case, the pressure wave continues through the annular space 48, the radial bores 134, the annular groove 128, the transverse bore 130 and the longitudinal bore 132 into the pressure space 120. Due to the small flow cross section of the throttle channel 122, the pressure in the pressure chamber 120 is largely maintained and presses the inner valve element 40 with its sealing edge 44 against the corresponding valve seat in the injection cap 28 of the nozzle body 18 via the pressure surface 74.

However, if the ball valve 94 is actuated in such a way that the outer valve element 42 can move by a distance which is greater than S1, then in the course of this movement of the outer valve element 42 the radial bores 134 move out of the area of the annular groove 128. The fluid connection between the pressure space 120 and the annular space 48 is thus interrupted. This means that the pressure in the pressure chamber 120 drops suddenly, since the fluid can flow out via the throttle channel 122 to the leakage oil outlet 102, but no new fluid flows in via the longitudinal bore 132. Since the sealing edge 46 of the outer valve element 42 has already been lifted from the corresponding seat in the injection tip 28, the pressure wave can act on the conical taper 136 located upstream of the sealing edge 44, as seen in the direction of flow. As a result, an axial force acts on the inner valve element 40, by means of which the inner valve element 40 lifts against the force acting by the spring 104 with the sealing edge 44 from the corresponding valve seat in the injection cap 28.

The advantage of the fuel injection device 10 shown in FIGS. 10 and 11 is that no mechanical parts are required for the driver connection between the inner valve element 40 and the outer valve element 42. Thus, no wear can occur at this point, which increases the operational safety of this Fuel injector 10 improved. The transverse bore 130 is arranged approximately half the length of the inner valve element 40. This ensures that the pressure wave arrives at the conical taper 112 of the outer valve element 42 and in the pressure chamber 120 at approximately the same time, so that on the one hand the opening force acting on the outer valve element 42 and on the other hand the closing force acting on the inner valve element 40 occur simultaneously.

At this point it should be pointed out that the terms “above” and “below” only refer to the representations in the figures. The real installation positions can differ from this.

Claims

Expectations

1. Fuel injection device (10) for internal combustion engines, with an elongated housing (12) with a closed injection end (28), with a recess (34) running in the longitudinal direction in the housing (12), which has a fuel inlet ( 20) can be connected, with at least two axially spaced outlet openings (30, 32) at the injection end

(28), with at least two coaxial and axially movable valve elements (40, 42), which are arranged at least in regions in the recess (34) and cooperate with valve seats in the region of the outlet openings (30, 32), characterized in that the valve elements ( 40, 42) work together in such a way that one Vencil element (40; 42) causes the other valve element (42; 40) to move when moving along a certain path (S1).

2. Fuel injection device (10) according to claim 1, characterized in that the axially spaced outlet openings (30, 32) when both valve elements (40, 42) are lifted from the associated valve seats are fluidly connected to each other.

3. Fuel injection device (10) according to one of claims 1 or 2, characterized in that the outer valve element (42) opens first and causes movement of the inner valve element (40) when moving after a certain path (Sl).

4. Fuel injection device (10) according to one of claims 1 or 2, characterized in that the inner valve element (40) opens first and causes movement of the outer valve element (42) when moving after a certain path (Sl).

5. Fuel injection device (10) according to one of the preceding claims, characterized in that a driver connection (52, 72) is provided such that the one valve element (40; 42) during a movement on the other valve element (42; 40 ) axially comes into contact at least indirectly and thereby moves it.

6. The fuel injection device (10) according to claim 5, characterized in that the driver connection comprises a shoulder on the one valve element, which cooperates with a shoulder (72) on the other valve element (40), the injection device (10 ) the shoulder (72) and the shoulder (52) are axially spaced apart (S1).

7. Fuel injection device (10) according to one of claims 5 or 6, characterized in that the driver connection comprises at least one ball (52) trapped in one valve element (42), which has a shoulder (72) on the other valve element ( 40) cooperates, the shoulder (72) and the ball (52) being axially spaced apart from one another in the closed state of the injection device (10).

8. Fuel injection device (10) according to one of claims 1 to 4, characterized in that at the end of the injection end (28) remote from the one valve element (40) there is a pressure chamber (120), on the one hand via a flow restrictor (122) connected to a low pressure area (102) and on the other hand via a transverse flow channel (130) can be connected to the fuel inlet (20), the connection between the pressure chamber (120) and the fuel inlet (20) being interrupted by the other valve element (42) when it has moved a certain distance (S1) ,

9. The fuel injector (10) according to claim 8, characterized in that in the other valve element there is at least one opening (134) which, in the closed state of the injector (10), provides access to the flow channel (130) from the fuel inlet covers a distance (Sl).

10. Fuel injection device (10) according to one of the preceding claims, characterized in that a switchable (94) stroke limitation is provided, by means of which the stroke of the valve element (40; 42) which opens first can be limited such that the driver connection (52 , 72) does not yet engage between the two valve elements (40; 42).

11. Fuel injection device (10) according to claim 10, characterized in that the stroke limitation works hydraulically.

12. The fuel injection device (10) according to claim 11, characterized in that the first opening valve element (40; 42) is connected to a first pressure surface (57) which delimits a control chamber (88), and in that the control chamber (88) is fluidically closable.

13. Fuel injection device (10) according to claim 12, characterized in that the first opening valve element (40; 42) is connected to a second pressure surface (50), which causes an opening movement of the valve element (40; 42) when pressure is applied, in which the first printing area is larger than the second printing area.

14. Fuel injection device (10) according to claim 12 or 13, characterized in that in the wall of the control chamber (88) there is an outlet opening (60) and that a control element (82) with the first opening λ / valve element (40; 42) is connected, which in the closed state of the fuel injection device (10) is spaced (54) from the drain opening (60) and in

Course of a movement of the valve element (40; 42) sealingly covers the drain opening (60).

15. Fuel injection device (10) according to one of claims 12 to 14, characterized in that it has a switchable valve (94), via which the control chamber (88) can be connected to an outlet (102).

16. Fuel injection device (10) according to claim 15, characterized in that the valve (94) is hydraulic

(100) is switchable.

17. Fuel injection device (10) according to one of the preceding claims, characterized in that it has a mechanical stop which limits the path (S2) during an opening movement of at least one of the valve elements (40; 42).

18. Fuel injection device (10) according to one of the preceding claims, characterized in that the valve element (42; 40) which opens later is connected to a third pressure surface (74) which, when pressurized, applies the valve element (42; 40) to the Valve seat presses.

19. Fuel system for an internal combustion engine with one Fuel tank, with at least one fuel pump that delivers from the fuel tank, with at least one fuel manifold, and with at least one fuel injection device (10), which is connected to the fuel manifold and injects the fuel directly into a combustion chamber, the Fuel injection device (10) an elongated housing (12) with a closed injection end (28), a recess (34) running in the longitudinal direction in the housing (12), which can be connected to a fuel inlet (20), at least two axially spaced outlet openings (30, 32) at the injection end (28), and at least two coaxial and axially movable valve elements (40, 42) which are arranged at least in regions in the recess (34) and with valve seats in the region of the outlet openings (30, 32) work together, characterized in that the fuel injection device (10) after one of claims 1 to 18 is formed.

20. Internal combustion engine, in particular for a motor vehicle, with a fuel system which supplies a combustion chamber of the internal combustion engine with fuel, characterized in that the fuel system is designed according to claim 19.