Fuel injection system for internal combustion engines with needle stroke damping

A fuel injection system for internal combustion engines with a fuel injector that can be supplied from a high-pressure fuel source has an injection valve, with injection nozzles pointing toward the combustion chamber, and coaxial inner and outer nozzle needles assigned to the injection nozzles are triggerable as a function of pressure to open and close various injection cross sections at the injection nozzles. Each of the nozzle needless is assigned a respective damping piston, and the damping pistons are movable relative to one another and act on a damping chamber which can be made to communicate with a low-pressure return system via an outlet throttle. In addition to the damping chamber, a closing chamber is provided, to which an end face of the outer nozzle needle is exposed in the closing direction. The closing chamber can be made to communicate with the low-pressure return system as well, via a closing chamber throttle; the outlet throttle has a greater throttling action than the closing chamber throttle, so that the pressure in the closing chamber drops first, and only after a delay does the pressure in the damping chamber drop as well.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an improved fuel injection system for internal combustion engines.

2. Description of the Prior Art

A fuel injector with two rows of injection nozzles in the form of holes, to each of which an inner nozzle needle and coaxial to it an outer nozzle needle are assigned, is known for instance from German Patent Disclosure DE 102 05 970 A1. Such injection nozzles, which when triggered as a function of pressure open various injection cross sections, are also known as Vario nozzles. The outer and inner nozzle needles are each assigned a respective control piston, and each of these pistons acts on a fuel-filled hydraulic chamber, so that the hydraulic chambers act as actively connected control chambers. The two control chambers communicate hydraulically with one another via a connecting conduit. The control chamber of the outer nozzle needle can be made to communicate with a low-pressure return system via an outlet throttle. The connecting conduit is dimensioned such that upon opening of the outlet throttle, first the pressure in the control chamber of the outer nozzle needle drops, and only after a delay does the pressure in the control chamber of the inner nozzle needle drop.

To increase the injection pressure, which is above the pressure level of the pressure reservoir (common rail), German Patent Disclosure DE 103 29 417 A1 discloses a fuel injection system with a pressure booster device, in which to improve the injection characteristic in addition and to increase the efficiency, a Vario nozzle is likewise employed. The Vario nozzle has two coaxially disposed nozzle needles. The opening pressure of the inner nozzle needle is set either to a constant level with spring support, or to a defined ratio between the rail pressure and the opening pressure with the aid of an additional assisting pressure. As a result, it is possible to adapt the hydraulic flow through the fuel injector to the load point of the engine. The inner nozzle needle is set such that it opens only at relatively high pressures, for instance of greater than 1500 bar, in order to achieve good emissions values in the partial load state of the engine. The setting of the constant opening pressure for the inner nozzle needle is very vulnerable to tolerances, since an abrupt change in the injection quantity occurs upon the opening of the inner nozzle needle. To this extent, variations from one manufactured item to another make themselves especially unpleasantly felt. In the other variant of attaining the opening pressure of the inner nozzle needle via the constant ratio between the assisting pressure and the nozzle pressure also opens the inner nozzle needle even at partial load of the engine.

To prevent the effects of variations in the triggering duration of the control valve on the injection quantity in fuel injection systems with a pressure booster, it has already been proposed in German Patent Disclosure DE 102 29 415.1 that the opening speed of a single nozzle needle be damped, without impairing fast closure of the nozzle needle. A damping piston that defines a damping chamber and that communicates with the closing chamber of the nozzle needle via an overflow conduit is located, axially guided, in the closing chamber of the nozzle needle.

OBJECT AND SUMMARY OF THE INVENTION

The fuel injection system of the invention has the advantage that the opening speed of the inner nozzle needle and thus the injection rate can be adapted. The inner nozzle needle of the Vario nozzle can be switched actively or passively, so that the nozzle opening pressure of the inner nozzle needle can be set in such a way that it does not open until there is a demand for it in the full-load range. As a result, improved capability at extremely small quantities and a shallow injection quantity performance graph for fuel injectors with a Vario nozzle can be attained, so that further improvement in terms of emissions and noise is attained. To this extent, with the goal of reducing noise without using preinjection, an adapted injection rate course is possible over wide load ranges, even at extremely high-pressure injection systems with pressures over 2000 bar.

By means of the characteristics of the invention, according to which the outer nozzle needle is additionally exposed with a pressure face to a closing chamber, and the outlet throttle communicating with the damping chamber has a greater throttling action, pressure ratios in the damping chamber and in the closing chamber are attained that cause the pressure to drop in the closing chamber first and that allow the pressure in the damping chamber also to drop only after a delay. As a result, the outer nozzle needle opens first, and only after the action of the outer nozzle needle, via the outer damping piston on the associated damping chamber, does the inner nozzle needle lift away.

An effective pressure-dependent control of the opening of the outer and inner nozzle needles as a function of the pressures prevailing in the damping chamber and in the closing chamber is attained if the pressure face of the outer nozzle needle, acting in the closing direction, is embodied between the outer damping piston and the nozzle needle and points into a dividing line embodied between the damping piston and the outer nozzle needle. It is especially expedient if the damping chamber communicates with the closing chamber via a hydraulic connection, and the hydraulic connection is formed by a connecting conduit, embodied between an outer damping piston assigned to the outer nozzle needle and an inner damping piston assigned to the inner nozzle needle, and by a dividing line, embodied between the end faces on the side toward the nozzle needle of the outer damping piston and the end face toward the damping piston of the outer nozzle needle. As a result, fast closure of the inner nozzle needle is made possible, and the inner nozzle needle closes approximately simultaneously with the outer nozzle needle. To reinforce the closing action of the inner nozzle needle, it is expedient if this needle has an additional pressure face in the closing chamber that acts in the closing direction. By means of an additional rail-pressure-dependent relief of the inner damping piston via a separate, inner damping chamber, the closing forces of the inner nozzle needle are added together in such a way that opening takes place only above a settable rail pressure.

A further embodiment, which requires no rail pressure reinforcement, provides that a separate damping chamber for the inner nozzle needle is filled with the aid of a control line and a throttle. When an opening pressure of 1000 bar, for instance, is attained, a check valve opens, and the inner nozzle needle can open as a function of the pressure in the damping chamber. The throttle must be designed such that the relief of the inner damping chamber, during the injection at rail pressure of less than 1000 bar, does not lead to an unwanted opening of the inner nozzle needle. The inertia of the check valve is adapted to the injection duration so that the check valve, after the pressure drops below the nominal opening pressure, remains open long enough to activate the inner nozzle needle.

In a further embodiment, which also requires no rail pressure reinforcement, the damping chamber is controlled by means of a combination of two check valves. The first check valve here has a substantially higher opening pressure than the second check valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The fuel injection system shown inFIGS. 1 through 6includes a fuel injector1and a high-pressure reservoir2(common rail); the fuel injector1is supplied with fuel that is at high pressure via the common rail2. The fuel injector1includes a pressure booster5, a control valve8, and an injection valve6, by way of which injection valve, fuel is injected into a combustion chamber, not shown, of an internal combustion engine, on the end toward the combustion chamber. The control valve8, embodied for instance as a 3/2-way valve, is actuated by an electromagnet, in the exemplary embodiments described herein. However, it is also possible to actuate the control valve8by means of a piezoelectric actuator.

The injection valve6has a coaxial nozzle needle, with an outer nozzle needle11and an inner nozzle needle12. The nozzle needles11,12are guided, resting one inside the other, and are actuatable independently of one another. The injection valve6furthermore has two rows of injection nozzles; outer injection nozzles61are assigned to the outer nozzle needle11, and inner injection nozzles62are assigned to the inner nozzle needle12. The outer nozzle needle11has a pressure shoulder63, inside a nozzle chamber27. Toward the combustion chamber, the inner nozzle needle12is embodied with a pressure face64, which is located upstream of the inner injection nozzles62. Located on the side facing away from the combustion chamber is a closing chamber29, in which the outer nozzle needle11rests, with an end face37acting in the closing direction and located toward a damping piston. The coaxial nozzle needle is assigned a damping device40, which will be described in further detail in conjunction with the individual exemplary embodiments.

From the common rail2, represented schematically, fuel passes via a combined check valve/throttle valve13and a rail pressure line14into a pressure chamber15of the pressure booster5. Besides the pressure chamber15already mentioned, the pressure booster5includes a differential pressure chamber16and a high-pressure chamber25. Inside the pressure booster5, an axially displaceable stepped piston9is received, which includes a first partial piston18that is embodied with a larger-diameter, enabling guidance, in comparison to a second partial piston19. The stepped piston9may be made of two separate components or be manufactured as a single component. The stepped piston9furthermore has a piston rod17, protruding into the pressure chamber15, with a spring holder20for a restoring spring21, which rests, in the opposite direction from the spring holder20, against a disk22. The second partial piston19, with its end face, defines the high-pressure chamber25, to which a high-pressure line26is connected that subjects the nozzle chamber27of the injection valve6to fuel that is at very high pressure.

From the differential pressure chamber16of the pressure booster5, a first line23and a second line24branch off; the first line23leads to a connection of the control valve8, and the second line24leads, via a closing chamber throttle31, into the closing chamber29of the injection valve6. The closing chamber29is moreover connected to the high-pressure line26via a check valve32.

The second connection of the control valve8communicates with the pressure chamber15of the pressure booster5, via a control line33. The third connection of the control valve8is connected to a return line34, which leads into a low-pressure return system35.

In the exemplary embodiment shown inFIGS. 1 and 2, the damping device40has a first, outer damping piston41, which is guided in a bore42adjoining the closing chamber29, and a second, inner damping piston43, which in the form of a piston rod is passed through the first damping piston41. The outer damping piston41is prestressed by means of a compression spring44in the closing chamber29and inside the closing chamber29, it has an end face47, on the side toward the nozzle needle, that rests on the end face37, on the side toward the damping piston, of the outer nozzle needle11. Between the end face47on the side toward the nozzle needle and the end face37on the side toward the damping piston, a dividing line45is embodied. The outer damping piston41furthermore has an annular end face51. The inner damping piston43has a circular end face52and is operatively connected to the inner nozzle needle12; the inner damping piston43can be produced either in one piece or in two pieces with the inner nozzle needle12. The annular end face51of the outer damping piston41and the circular end face52of the inner damping piston43each point into a damping chamber50. Between the inner damping piston43and the inner cylindrical wall of the outer damping piston41, a flow conduit46in the form of an annular gap is embodied, which leads from the damping chamber50to the dividing line45. The damping chamber50is connected to the second line24via a line53with an outlet throttle54.

For reinforcing the inner nozzle needle12, a further pressure face36is embodied on the inner damping piston43and acts for instance in the closing direction inside the flow conduit46. Thus the opening of the inner nozzle needle12is dependent both on the pressure in the closing chamber29and on the pressure inside the common damping chamber50.

In a basic state, in which the nozzles61,62of the outer and inner nozzle needles11,12are closed, all the pressure chambers in the pressure booster5are subjected to rail or system pressure. The stepped piston9is in pressure equilibrium. In this state, the pressure booster5is deactivated; the stepped piston9has been restored to its outset position via the restoring spring21, in the process the pressure chamber15has been filled via the check valve13. In the basic state, rail pressure also prevails in the closing chamber29and in the damping chamber50. Because of the ratios of the areas of the end faces51,52and the pressure faces63,64, a hydraulic closing force acts on the inner and outer nozzle needles11,12. The compression spring44acting on the outer damping piston41and thus on the outer nozzle needle11moreover reinforces the closing process. As a consequence, the rail pressure can prevail constantly in the nozzle chamber27without the outer nozzle needle11coming open.

To bring about opening of the outer nozzle needle11, the pressure in the nozzle chamber27must increase above the rail pressure; this is attained by switching on the pressure booster5. As shown inFIGS. 1 through 7, this is initiated by a pressure relief of the differential pressure chamber16of the pressure booster5, by putting the control valve8into the switching position shown by means of activating the electromagnet. As a result, the differential pressure chamber16is disconnected from the rail pressure or from the system pressure supply and is made to communicate with the return line34and thus with the low-pressure return system35. The pressure in the differential pressure chamber16drops, and as a result the pressure booster5is activated, and in the process the stepped piston9, with the partial piston19, compresses the fuel located in the high-pressure chamber25. The compressed fuel is carried into the nozzle chamber27via the high-pressure line26. Simultaneously, the closing chamber29is relieved via the closing chamber throttle31, so that by the action of the high pressure on the pressure shoulder63, the outer nozzle needle11is lifted and as a result the injection begins via the outer injection nozzles61. By means of the resultant upward motion of the outer nozzle needle11, a volume in the damping chamber50is compressed by the end face51of the first damping piston41, and the compressed fuel can flow out of the damping chamber50via the outlet throttle54into the relieved line24. The outlet throttle54has a greater throttling action than the closing chamber throttle31, so that the damping action of the outer damping piston41in the damping chamber50can come about. By suitable dimensioning of the outlet throttle54, the opening speed of the outer nozzle needle11and thus the injection rate can be adapted. After the outer nozzle needle11has lifted and the outer injection nozzles61have been uncovered, the pressure in the nozzle chamber27also acts on the pressure face64of the inner nozzle needle12. Because of the pressure acting on the end face52in the damping chamber50and the pressure acting on the pressure face64of the nozzle needle12, a resultant closing force becomes operative that opens the inner nozzle needle12. The instant of opening of the inner nozzle needle12can be varied by way adapting the area of the end face52via the diameter of the inner damping piston43and the flow through the outlet throttle54. The end face52of the inner damping piston43is expediently dimensioned such that the inner nozzle needle12opens when the maximum stroke of the outer nozzle needle11is attained. By means of this adaptation, the inner nozzle needle12opens passively over a wide rail pressure range, including partial load, by reaching the stroke stop of the outer nozzle needle11.

The closing process of the Vario nozzle is initiated by a further switching of the control valve8thereby subjecting the control line33to pressure; as a result, via the lines23,24, the differential pressure chamber16and the closing chamber29are again subjected to the rail pressure or system pressure. The closure of the outer injection nozzles61is effected by filling of the closing chamber29and by means of the pressure applied there, which acts via the dividing line45upon the end face37, toward the damping piston and acting in the closing direction, of the outer nozzle needle11, as well as with reinforcement from the compression spring44acting on the outer damping piston41. Because the throttling action of the outlet throttle54is greater than the throttling action of the closing chamber throttle31, a pressure difference occurs between the closing chamber29and the damping chamber50. Because of the pressure difference, a force first acts via the dividing line45upon the end face37, toward the damping piston and acting in the closing direction, of the outer nozzle needle11. Simultaneously, by the uncovering of the dividing line45, fuel is introduced substantially unthrottled into the damping chamber50by way of the hydraulic connection of the dividing line45and the flow conduit46, so that given the pressures on the end face52and the pressure face64, a resultant closing force also acts on the inner nozzle needle12, and this force moves this needle downward to close the inner injection nozzles62. As a result, a fast closure of the inner nozzle needle12that ensues simultaneously with the closure of the outer nozzle needle11, is attained.

The sequence of the motions of the nozzle needles11and12and of the pressure at the pressure faces of the nozzle needles11,12and in the damping chamber50, as well as the resultant closing force for the inner nozzle needle12, will be explained below in terms of the force and pressure courses shown inFIG. 7; the nozzle pressure at the pressure faces of the nozzle needles11,12are designated by P1, the damper pressure in the damping chamber50by P2, and the closing force on the inner nozzle needle12, resulting from the pressure forces acting on the pressure face64and the end face52of the inner nozzle needle12, by Fs. Initially, the nozzle pressure P1and the damper pressure P2have the value of the rail pressure PR, for instance 1350 bar. The closing force Fs, as the resultant force between the pressure forces at the pressure face64and at the end face52, is positive until this point. The time t1represents the switching time of the control valve8at which the control valve8initiates a pressure relief of the differential pressure chamber16of the pressure booster5by means of the switching position shown inFIG. 1. With somewhat of a delay, because of the motion of the step piston9, a compression of the fuel in the high-pressure chamber25begins, so that the nozzle pressure P1rises, and as a result the outer nozzle needle11lifts, and injection occurs via the outer injection nozzles61. Simultaneously, the outer damping piston41is moved in the direction of the damping chamber50, which initially causes a slight pressure increase in the damper pressure P2, until a time t2. The slight drop in the closing force Fson the inner nozzle needle12is due to the fact that, because of the opening of the outer nozzle needle11and the pressure increase in the damping chamber50, initially only a slight displacement of forces ensues at the inner nozzle needle12. At time t2, the outer nozzle needle11and thus the outer damping piston41are at the upper end stop, and the pressure P2in the damping chamber50drops sharply thereafter. Simultaneously, the closing force Fsacting on the inner nozzle needle12abruptly drops to below zero; that is, the force acting on the pressure face64exceeds the force acting on the end face52. The result is opening of the inner nozzle needle12, shortly after t2. The time t3is the second switching time of the control valve8, which concludes the relief of the line23via the return line24, so that the buildup of a pressure-balanced system now begins. At time t3, rail or system pressure is again built up in the closing chamber29via the closing chamber throttle31and also in the damping chamber50via the outlet throttle54, the dividing line45, and the flow conduit46. Simultaneously, the stepped piston9is put in its outset position by the restoring spring21. The pressure P2in the damping chamber50thus rises again, and simultaneously the force component on the end face52increases and the closing force Fsalso rises, so that at the zero crossover, a positive closing force Fsagain acts on the inner nozzle needle12, and the inner injection nozzles62are closed at time t4. Because of the reinforcement of the compression spring44, at the same instant, the outer nozzle needle11has closed the outer injection nozzles61. Simultaneously, the course of the nozzle pressure P1has reached the rail pressure PRof 1350 bar again, at time t4. The swing downward in the nozzle pressure P1is tripped by the brief decompression of the pressure chamber25by the restoring motion of the stepped piston9. Shortly after that, at time t5, the steady state is attained; the system is in pressure equilibrium, and the injection nozzles61,62are closed. A new opening event of the injection nozzles61,62ensues with the next triggering of the control valve8.

FIG. 2shows a refined embodiment of the exemplary embodiment ofFIG. 1; in addition to the outlet throttle54, a filling line55leads into the damping chamber50, and a check valve56is disposed between them, which counteracts an evacuation of the damping chamber50into the line24. As a result, in the switching position for closure of the nozzle needles11,12, an additional path to the outlet throttle54for filling the damping chamber50is created. In this embodiment, the additional filling of the damping chamber50via the dividing line45and the flow conduit46described in conjunction withFIG. 1can be omitted. However, it is equally conceivable to provide both filling paths.

In the second exemplary embodiment shown inFIG. 3, each damping piston41,43is assigned a separate damping chamber. The outer damping piston41points into a first damping chamber71. The inner damping piston43is formed by a control piston70, which is guided in a cylindrical chamber72, and the cylindrical chamber72has a second damping chamber73located above the control piston70and a control chamber74located below the control piston70. The second damping chamber73is connected with a line75and the line24to the differential pressure chamber16of the pressure booster5. The control chamber74communicates with the pressure chamber15of the pressure booster5via a further line76and is subjected to rail pressure. The control piston70has an end face77pointing into the second damping chamber73. The control piston70has an annular face78pointing into the control chamber74. Because of the control chamber subjected to rail pressure, the control piston70is additionally relieved as a function of rail pressure. By means of a restoring spring79, lifting of the control piston70from the damping piston43is prevented. Simultaneously, the restoring spring79offers better adaptability of the opening mechanism.

This exemplary embodiment requires the additional pressure face36, acting in the closing direction on the inner nozzle needle12, and this pressure face is embodied as a pressure step on the inner damping piston43. The closing force for the inner nozzle needle12thus results from an AND function of the force ratios at the control piston70and at the pressure step36. Thus the opening of the inner nozzle needle is dependent on both the rail pressure and the pressure ratios in the damping chamber71. Hence the opening of the inner nozzle needle12follows only above a rail pressure that can be set by way of the force ratios at the control piston70. For opening the coaxial nozzle needle, first the control valve8is put in the switching position shown, so that the differential pressure chamber16, closing chamber29, first damping chamber71and second damping chamber73are pressure-relieved. Because of the pressure relief of the differential pressure chamber16, compression the pressure chamber25occurs, as described for the exemplary embodiments inFIG. 1, so that a pressure increase is passed on via the high-pressure line26to the pressure shoulder63of the outer nozzle needle11. The outer nozzle needle11lifts from the outer injection nozzles61and moves the outer damping piston41into the position shown. As a result of the compression of the fuel in the first damping chamber71, damping of the outer nozzle needle11is effected by means of the damping piston41. Simultaneously, via the flow conduit46, the compressed fuel acts on the pressure step36of the inner nozzle needle12, causing this needle to remain in its closing position during the opening of the outer nozzle needle11. An opening of the inner nozzle needle12ensues, when the closing force acting in the closing direction on the nozzle needle12is less than the opening force acting on the pressure face64. The closing force is composed of the force acting on the pressure step36because of the pressure in the first damping chamber71and the force on the control piston70that results from the ratio of the areas of the end face77and the annular face78. Since the force at the pressure step36in the first damping chamber71is negligibly slight, the force for opening the inner nozzle needle12is dependent substantially on the force resulting on the control piston70, which can be defined on the basis of the rail pressure in the control chamber74.

For closing the coaxial nozzle needle, the control valve8is put into the second switching position, so that the control chamber29, the first damping chamber71, and the second damping chamber73are again subjected to rail pressure; because of the different throttling actions of the closing chamber throttle31and the outlet throttle54, the closing chamber29is filled faster. The fuel reaching the closing chamber29, however, also flows into the first damping chamber71via the dividing line45and the flow conduit46, so that a corresponding pressure acts on the end face51of the outer damping piston41and on the pressure step36of the inner damping piston43. Simultaneously, via the connecting line75and the further line76, a state of pressure equilibrium is established in the second damping chamber73and in the control chamber74. The resultant closing force for the inner nozzle needle12is attained via the additional pressure face36, and the restoring spring79reinforces the closing action of the inner nozzle needle12. The restoring spring79, in a two-part version of the control piston70and the inner damping piston43, also serves to avoid the creation of any gap between them or any separation of the components.

In the exemplary embodiment ofFIG. 4, once again a first damping chamber81and a second damping chamber82are provided; the second damping chamber82acts only on the inner nozzle needle12. The second damping chamber82is placed via a line83, to which a check valve84oriented counter to the inflow to the damping chamber82is inserted, and via the line24, in communication with the differential pressure chamber16of the pressure booster5. A further throttle85is connected parallel to the check valve84, and by way of it, filling of the second damping chamber82is effected. In this exemplary embodiment, with a separate second damping chamber82for the inner nozzle needle12, no rail pressure support is therefore necessary. The opening pressure for the inner nozzle needle12is set via the check valve84, so that when an opening rail pressure of 1000 bar, for instance, is reached, the check valve84opens, and the inner nozzle needle12opens as a function of the pressure in the first damping chamber81. The throttle85here must be designed such that the relief of the second damping chamber82during the injection at rail pressure of less than 1000 bar does not lead to an unwanted opening of the inner needle. The inertia of the check valve84is adapted to the injection duration of the injection valve6, so that after the pressure drops below the nominal opening pressure, the check valve84will remain open for long enough to activate the inner nozzle needle12.

In the exemplary embodiment ofFIG. 5, the second damping chamber82likewise requires no rail pressure reinforcement. Here, the second damping chamber82communicates with the line24via a further check valve86, instead of the throttle85inFIG. 4; the further check valve86acts in the opposite direction of the check valve84. The check valve84here again has an opening pressure of approximately 1000 bar, while the further check valve86has an opening pressure of only about 100 bar, for instance. As a result, the second damping chamber82is not relieved until at a rail pressure of greater than 1000 bar, yet it refills again from about 100 bar and up, via the further check valve86. In this exemplary embodiment as well, the inertia of the check valves84,86must be suitably adapted; the further check valve86should have as fast a switching behavior as possible, and the check valve84should have a more sluggish switching behavior.

FIG. 6shows an exemplary embodiment in which the second damping chamber82communicates with the differential pressure chamber16of the pressure booster5via the check valve84, as in the exemplary embodiments ofFIGS. 4 and 5. Here, an additional communication of the second damping chamber82exists, via a line87leading into the pressure chamber15of the pressure booster5, and a further throttle88is integrated with the line87. Thus the second damping chamber82is coupled to rail pressure via the throttle88. In this exemplary embodiment, an additional control quantity is necessary for the duration of the injection via the inner injection nozzles62.

In all the exemplary embodiments, the nozzles61,62and the damping chambers50,71,73,81,82are acted upon by pressure. To avoid leakage via the guidance between the inner nozzle needle12and the outer nozzle needle11, provisions known per se should be made, such as a double nozzle needle seat at the outer nozzle needle11, or else an additional means of leakage diversion should be provided between the nozzle needles11,12.

It is furthermore conceivable for the damping device40described in conjunction withFIGS. 1 through 7for the coaxial nozzle needle also to be employed without a pressure booster5. Then the line26leading into the high-pressure chamber25should be connected to rail pressure.