DE102018200565A1 - Injector for metering gaseous fuel, Gaseinblassystem with such an injector and method for operating this injector - Google Patents

Abstract

Injector for metering gaseous fuel with an injector body (1), in which a piston-shaped nozzle needle (2) is longitudinally displaceable, with a sealing surface (4) with a nozzle seat (5) formed in the injector body (1) for opening and closing a flow cross-section (11) cooperates, can flow through the gaseous fuel to a Eindüsöffnung (8). A control chamber (10) is bounded by the sealing surface facing away from the end face (32) of the nozzle needle (2) and is filled with a liquid medium, wherein in the control chamber (10) an alternating fluid pressure is adjustable and by the pressure in the control chamber (10) has a closing force in the direction of the sealing seat (5) on the nozzle needle (2) is applied. In the injector body (1), a counterpressure space (12) is formed, which can be filled with the liquid medium and which acts on a mating surface (33) of the nozzle needle (2) so that a hydraulic, in the axial direction of the nozzle needle (2) acting force is exerted, which is opposite to the hydraulic force in the control chamber (10).

Description

The invention relates to an injector for metering of gaseous fuel, as used, for example, to introduce gaseous fuels directly into a combustion chamber of an internal combustion engine. Moreover, the invention relates to a gas injection system with such an injector and a method for operating such an injector.

State of the art

Injectors for introducing gaseous fuel directly into a combustion chamber of an internal combustion engine are known from the prior art, for example from the DE 10 2015 209 134 A1 , The injector has a nozzle needle which is arranged longitudinally movably in an injector body and which cooperates with a nozzle seat for opening and closing a flow cross-section. Downstream of the flow cross-section, a plurality of injection openings are formed in the injector body, through which the gaseous fuel passes, so that it is optimally distributed into the combustion chamber. The einzudüsende gas is under a relatively high pressure of 300 to 500 bar, which causes correspondingly high forces on the nozzle needle in particular in the longitudinal direction. To control the longitudinal movement of the nozzle needle, a servo-hydraulic principle is used. For this purpose, the nozzle needle with its end faces away from the injection openings delimits a control chamber which can be filled with a liquid medium, for example a liquid fuel, which is under a pressure which is similar to the pressure in the gas-filled areas of the injector. By a control valve, the pressure in the control chamber can be varied, so that thus the force acting in the closing direction hydraulic force can be changed to the nozzle needle. This gives a control possibility of the nozzle needle.

The gaseous fuel is provided via a compressor and a gas high pressure accumulator to which the injector is connected. The system is designed to provide the maximum gas pressure, eg 500 bar. Depending on the load point of the internal combustion engine, however, it may also be necessary to introduce a lower gas pressure into the combustion chamber, for example during idling or in a partial load range. For this purpose, in the systems known hitherto, the gas pressure must be lowered, which is most rapidly achieved by the fact that gas is returned from the high-pressure accumulator into the tank or is otherwise blown off. Since gas is well compressible, a relatively large amount of gas must be removed from the high-pressure accumulator, which is already held there compacted and then, when the full injection pressure is needed again with a lot of energy and compressed again the high-pressure accumulator must be supplied. This is energetically unfavorable and affects the efficiency of the internal combustion engine.

Advantages of the invention

In contrast, the injector for metering gaseous fuel according to the invention has the advantage that an internal combustion engine can be operated with high efficiency, it being possible for different gas pressures to be injected into the combustion chamber without the gas pressure of the supply system having to be lowered. For this purpose, the injector has an injector body, in which a piston-shaped nozzle needle is arranged longitudinally displaceable, which cooperates with a sealing surface with a nozzle seat formed in the injector body for opening and closing a flow cross-section through which gaseous fuel can flow to an injection opening. In the injector further a control chamber is formed, which is bounded by the sealing surface facing away from the end face of the nozzle needle and which can be filled with a liquid medium, wherein in the control chamber an alternating fluid pressure is adjustable, wherein the pressure in the control chamber a closing force in the direction of the sealing seat on the nozzle needle is exercised. In the injector, a counter-pressure space is formed, which is filled with the liquid medium and which acts on a counter surface of the nozzle needle so that thereby a hydraulic force acting in the axial direction of the nozzle needle force is applied, which is directed opposite to the hydraulic force in the control chamber.

The movement of the nozzle needle is done by the interplay of hydraulic forces on the one hand in the control room and on the other hand in the counter-pressure space. If there is a relatively high pressure of the liquid medium, the opening forces on the nozzle needle are correspondingly high since, after a pressure reduction in the control chamber, a high hydraulic pressure in the counterpressure space acts on the nozzle needle. Thus, the nozzle needle can be moved quickly, in particular, it can be quickly move out of the seat throttle range, ie the area in which a throttle point is formed by a very small gap between the nozzle seat and the sealing surface of the nozzle needle. Thus, a large amount of gas can be introduced faster with the full gas pressure in the combustion chamber.

If the pressure of the liquid medium, with which the control chamber and the counterpressure space is flooded, is lowered, on the other hand, a correspondingly lower hydraulic opening force acts on the nozzle needle in the counterpressure space. If the pressure in the control chamber is lowered, these lower forces cause a comparatively slow movement the nozzle needle in the opening direction. This makes it possible to keep the nozzle needle relatively long in the seat throttle area, ie that the opening movement of the nozzle needle is stopped in time and thus passes through a partial stroke, so that a throttle point is formed between the sealing surface and the nozzle seat. At this throttle point so that a part of the gas pressure is reduced, so that at the injection openings a lower gas pressure is applied than is available in the injector. The injection of the gaseous fuel is carried out with a lower gas pressure, without a pressure reduction in the gas supply system is necessary and thus does not unnecessarily gaseous fuel must be expanded or blown off.

In a first advantageous embodiment, the nozzle needle has an enlarged diameter portion, on which the end face is formed and which limits the counter-pressure chamber with an opposite end surface of the opposite surface. As a result, hydraulic opposing forces can be generated on the nozzle needle, which act in the longitudinal direction of the nozzle needle in a structurally simple manner. In this case, the counter-pressure space is advantageously formed as an annular space surrounding the nozzle needle, which can also be implemented in a simple manner by a corresponding design of the injector body.

In a further advantageous embodiment, the control chamber can be filled with the liquid medium via an inlet throttle formed in the injector body. Thus, for example, via a controlled sequence of the pressure in the control room can be adjusted and thus the corresponding hydraulic closing force on the nozzle needle.

In a further advantageous embodiment, the nozzle needle is designed as a hollow needle having a longitudinal bore with a longitudinally displaceably arranged therein inner needle, which cooperates with an opening formed in the nozzle needle inner nozzle seat for releasing or closing an injection port. The additional nozzle needle also allows liquid fuel to be introduced into the combustion chamber at the same time or with a time offset to the gaseous fuel, advantageously forming a pressure space between the nozzle needle and the wall of the longitudinal bore which can be filled with the liquid medium, so that the liquid medium is ejected with the injection opening open by this. In this case, the liquid medium is advantageously a liquid fuel, which has two functions in the injector. On the one hand, it serves as fuel, which can be injected via the injector into the combustion chamber, and on the other hand as a hydraulic working medium for controlling the nozzle needle and the inner needle.

In a further advantageous embodiment, the counterpressure space is hydraulically connected to the pressure chamber. As a result, the counterpressure space can be filled in a simple manner, as well as the pressure chamber, which is formed between the inner needle and the longitudinal bore, so that the injector can be structurally easily implemented.

In a gas injection system according to the invention with an injector according to the invention, a high-pressure accumulator is provided, in which the liquid medium is kept, with which both the control chamber and the counter-pressure space is connected. Thus, the same high pressure source for the liquid medium can be used both for the injection and for the control of the nozzle needle or the inner needle. A pressure drop of the high-pressure reservoir for the liquid medium is relatively easy to do, since liquids are only slightly compressible, i. it only needs a small amount to be reduced in order to lower the pressure significantly. The energy losses due to such a pressure control are therefore low.

list of figures

• 1 ein erstes Ausführungsbeispiel des erfindungsgemäßen Injektors zusammen mit den schematisch dargestellten Systemkomponenten für das flüssige und das gasförmige Medium bzw. den gasförmigen Kraftstoff und
• 2 ein zweites Ausführungsbeispiel ebenfalls mit schematischer Darstellung der Systemkomponenten.

In the drawing, two embodiments of the injector according to the invention with the essential system components are shown. Show it

• 1 a first embodiment of the injector according to the invention together with the system components shown schematically for the liquid and the gaseous medium or the gaseous fuel and
• 2 a second embodiment also with a schematic representation of the system components.

Description of the embodiments

In 1 a first embodiment of the injector according to the invention is shown schematically in longitudinal section, wherein the add-on components are shown only schematically. The injector has an injector body 1 on, in which a nozzle needle 2 is arranged longitudinally displaceable, wherein the nozzle needle 2 a longitudinal axis 9 has and is substantially piston-shaped. The nozzle needle 2 has at its end facing the combustion chamber a conical sealing surface 4 on, with the nozzle needle 2 with a likewise conical nozzle seat 5 cooperates to open and close a flow cross-section, the between the sealing surface 4 and the nozzle seat 5 can be controlled. Here is the nozzle needle 2 from a gas room 3 surrounded by one in the injector body 1 extending feed bore 6 can be filled with gaseous fuel. The nozzle seat 5 downstream is in the nozzle needle 2 an annular groove 7 formed, in which the gaseous fuel from the gas space 3 when it flows in between the sealing surface 4 and the nozzle seat 5 flowing. In the nozzle body 1 are moreover several injection openings 8th formed with the ring groove 7 are connected, so that the gaseous fuel from the annular groove 7 through the injection opening 8th can be exterminated. The ring groove 7 ensures that the gaseous fuel evenly on the injection ports 8th is distributed.

With her face 32 that the sealing surface 4 turned away, limits the nozzle needle 2 a control room 10 that inside the nozzle body 1 is formed and radially outward from the nozzle body 1 and at the upper side in the drawing by a throttle plate 13 is limited. The control room 10 is via an inlet throttle 14 filled with a liquid medium under a working pressure. About a drain throttle 15 can the liquid medium from the control room 10 be discharged, leaving an alternating hydraulic pressure in the control room 10 is adjustable. The nozzle needle 2 indicates at its the sealing surface 4 opposite end of a diameter-expanded section 102 on, on which the end face 32 is trained. Through the extended section 102 is at the front 32 opposite side of the extended section 102 an annular disc-shaped counter surface 33 educated. With this counter surface 33 limits the diameter-expanded section 102 a back pressure chamber 12 , which is designed as an annulus and the nozzle needle 2 surrounds. Via an inlet bore 28 can the counterpressure space 12 also be filled with the liquid medium, so that by the pressure in the back pressure chamber 12 a hydraulic force on the nozzle needle 2 is exercised, that of the hydraulic power of the control room 10 on the nozzle needle 2 directed against.

To supply the injector with the liquid medium is a liquid tank 23 available. The liquid medium is transferred via a liquid line 26 a pump 24 fed, which compresses the liquid medium and it via a second liquid line 26 ' in a high-pressure accumulator 25 initiates where the compressed liquid medium is kept. From the high-pressure accumulator 25 leads a pressure line 27 starting in a first pressure line 27 ' and a second pressure line 27 " branches, wherein the first pressure line 27 ' into the inlet bore 28 flows and thus the supply of the counter-pressure space 12 serves while the second pressure line 27 " into the inlet throttle 14 flows and thus the control room 10 filled with the liquid medium. The outlet throttle 15 is via a control valve 29 with a return line 30 connectable, the back to the liquid tank 23 leads. The control valve 29 is designed as an example, electromagnetically actuated 2/2-way valve, so that the connection of the control chamber 10 over the outlet throttle 15 with the tank 23 can be opened or closed electrically controlled.

The supply of the injector with the gaseous medium comprises a gas tank 17 from which via a first gas line 19 a gaseous fuel a compressor 18 is fed, which compresses the gaseous fuel to the required working pressure and a second gas line 19 ' a gas pressure accumulator 20 feeds, where the compressed gaseous medium or the gaseous fuel is kept. The gas pressure accumulator 20 is via a gas high pressure line 21 with the feed hole 6 connected so that thereby the gas space 3 is filled with the compressed gaseous fuel.

The operation of the injector is as follows: Set gas below the full injection pressure, as in the gas pressure accumulator 20 is maintained, are injected into the combustion chamber, so a high pressure of the liquid medium is required, with both the control room 10 as well as the backpressure room 12 are filled when the control valve 29 closed is. If an injection happen, then the control valve 29 opened and the hydraulic pressure in the control room 10 decreases, because of the outlet throttle 15 more liquid medium from the control room 10 flows out than in the same period via the inlet throttle 14 continues to flow. Due to the still high hydraulic pressure in the back pressure chamber 12 will have a high hydraulic opening force on the nozzle needle 2 exercised, so that these quickly from the nozzle seat 5 moved away and the flow cross-section between the sealing surface 4 and the nozzle seat 5 aufsteuert. This gaseous fuel flows from the gas space 3 in the ring groove 7 and from there into the injection openings 8th , At the injection openings 8th is thus virtually unthrottled to the full pressure of the gaseous medium, as in the gas pressure accumulator 20 is made available. To stop the injection, the control valve 29 closed again, so that the high hydraulic pressure in the control room 10 builds up again and the nozzle needle 2 pushes back to its closed position.

If, on the other hand, it is not intended to inject with the full gas pressure, the pressure in the hydraulic system is lowered, ie in the high-pressure accumulator 25 now there is a lower hydraulic pressure. This can be done, for example, by throttling the pump 24 done or by Absteuerung a portion of the liquid medium, the compressed in the high-pressure accumulator 25 is applied. This reduces the hydraulic closing force caused by the pressure in the control room 10 on the nozzle needle 2 is exercised, but remains the nozzle needle 2 closed further, as well as the hydraulic back pressure in the back pressure chamber 12 decreases accordingly. Going to happen now the control valve 29 opened, so again decreases the hydraulic pressure in the control room 10 off, the hydraulic opening force in the back pressure chamber 12 but is now lower, so the nozzle needle 2 only comparatively slowly moved in the opening direction. The flow cross section remains correspondingly long between the sealing surface 4 and the nozzle seat 5 small and thus throttles the gas flow into the annular groove 7 and to the injection ports 8th flows. At the injection openings 8th is thus a lower gas pressure than in the gas pressure accumulator 20 and in the gas room 3 , So that the nozzle needle 2 does not pass through their full opening stroke, the control valve 29 be closed before the nozzle needle 2 moved out of the seat throttle area, ie from the stroke area in which between the sealing surface 4 and the nozzle seat 5 a throttle gap is formed. For this purpose, the control valve can be opened and closed several times during an injection, so that the injection via the injection openings 8th always happens with throttled flow cross section and thus with a lower effective gas pressure at the injection openings 8th ,

The injector according to the invention thus enables injection with different effective gas pressures. Each desired effective gas pressure is associated with a corresponding pressure of the liquid medium or a corresponding pressure range in order to achieve this desired gas pressure by the nozzle needle is only moved so far that the required throttling of the gaseous fuel takes place. This correlation can be determined by experiments or simulation and stored for controlling the injector, for example, in a corresponding control unit.

In 2 shows a second embodiment of the injector according to the invention, wherein the same components compared to 1 are provided with the same reference numerals. A further explanation of the same components is therefore omitted. This injector has over the embodiment of the 1 a modified nozzle needle on, at the nozzle needle 2 as a hollow needle with a longitudinal bore 35 is executed. In the longitudinal bore 35 is a piston-shaped inner needle 38 arranged longitudinally displaceable, wherein between the nozzle needle 38 and the wall of the longitudinal bore 35 a pressure room 36 is formed, which is filled with the liquid medium. This is in the nozzle needle 2 a connection hole 50 formed the the back pressure chamber 12 with the pressure room 36 combines. The nozzle needle 38 has at its combustion chamber end an inner sealing surface 41 on, with the inner needle 38 with an inner nozzle seat 40 cooperates to open and close a flow cross section through which the liquid fuel to several, in the nozzle needle 2 trained injection ports 42 can flow.

The inner needle 38 indicates at its inner sealing surface 41 opposite side an end face 44 on, with the inner needle 38 an inner control room 43 limited, with the liquid medium from the high-pressure accumulator 25 via an inlet throttle 45 is fillable. About a drain throttle 46 is the inner control room 43 with the return line 30 connectable, this connection via a second control valve 48 leads, which in turn is designed as a 2/2-way valve and, for example, is an electromagnetically operated valve. In the same way as the control room 10 so can the hydraulic pressure in the inner control room 43 by opening and closing the second control valve 48 adjust and thus the longitudinal movement of the inner needle 38 control. Also in this embodiment can be about the backlash between the pressure in the control room 10 and in the backpressure room 12 the opening speed of the nozzle needle 2 be adjusted and thus a corresponding seat throttling between the sealing surface 4 and the nozzle seat 5 , what with it the pressure of the gaseous fuel at the injection openings 8th decreases.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102015209134 A1 [0002]

Claims (11)

Injector for metering gaseous fuel with an injector body (1), in which a piston-shaped nozzle needle (2) is longitudinally displaceable, with a sealing surface (4) with a nozzle seat (5) formed in the injector body (1) for opening and closing a flow cross-section (11), through which gaseous fuel can flow to an injection opening (8), and with a control chamber (10), which is delimited by the sealing surface facing away from the end face (32) of the nozzle needle (2) and which can be filled with a liquid medium, wherein Control chamber (10) an alternating fluid pressure is adjustable and by the pressure in the control chamber (10) a closing force in the direction of the sealing seat (5) on the nozzle needle (2) is exercised, characterized in that in the injector body (1) has a counter-pressure chamber (12) is formed, which is filled with the liquid medium and which acts on a counter surface (33) of the nozzle needle (2) so that thereby hy draulic, in the axial direction of the nozzle needle (2) acting force is exerted, which is opposite to the hydraulic force in the control chamber (10). Injector after Claim 1 , characterized in that the nozzle needle (2) has a diameter-enlarged portion (102) on which the end face (32) is formed and which limits the counter-pressure chamber (12) with one of the end face (32) opposite counter surface (33). Injector after Claim 2 , characterized in that the counter-pressure chamber (12) is designed as an annular space which surrounds the nozzle needle (2). Injector after Claim 1 , characterized in that the control chamber via a in the injector body (1) formed inlet throttle (14) can be filled with the liquid medium. Injector after Claim 1 , characterized in that the nozzle needle (2) is designed as a hollow needle having a longitudinal bore (35) with a longitudinally displaceably arranged therein inner needle (38) formed with a in the nozzle needle (2) inner nozzle seat (40) for releasing or Closing at least one injection port (42) cooperates. Injector after Claim 5 , characterized in that between the inner needle (38) and the wall of the longitudinal bore (35), a pressure chamber (36) is formed which can be filled with the liquid medium, so that the liquid medium is ejected with the injection opening (42) open , Injector after Claim 6 , characterized in that the counter-pressure chamber (12) with the pressure chamber (36) is hydraulically connected. Injector after one of Claims 1 to 7 , characterized in that the liquid medium is a liquid fuel. Gas injection system with an injector according to one of Claims 1 to 8th , characterized in that a high-pressure accumulator (25) for the liquid medium is present, with which both the control chamber (10) and the counter-pressure chamber (12) are connected. Method for operating an injector according to one of Claims 1 to 8th characterized by the following method steps: - setting the desired injection pressure of the gaseous fuel. Determining the pressure of the liquid medium required to achieve this injection pressure, which pressure is supplied to the injector. - Supplying the liquid medium to the injector, so that sets in all filled with the liquid medium spaces of the injector, this pressure. - Injecting the gaseous medium with the injector by moving the nozzle needle, wherein the nozzle needle is moved only to the extent that it throttles the flow of the gaseous fuel to achieve the desired injection pressure. Method according to Claim 10 , characterized in that the pressure of the liquid medium at a desired high injection pressure is higher than the pressure of the liquid medium at a desired lower injection pressure.

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