WO2019138009A1 - Injector for metering gaseous fuel, gas injection system having such an injector, and method for operating said injector - Google Patents

Abstract

The invention relates to an injector for metering gaseous fuel, comprising an injector body (1), in which a piston-shaped nozzle needle (2) is arranged in a longitudinally movable manner, which interacts with a sealing surface (4) by means of a nozzle seat (5) formed in the injection body (1) for opening and closing a flow cross-section (11), through which the gaseous fuel can flow toward an injection opening (8). A control chamber (10) is delimited by the end face (32) of the nozzle needle (2) facing away from the sealing surface and can be filled with a liquid medium, wherein a variable liquid pressure can be set in the control chamber (10) and a closing force is exerted in the direction of the sealing seat (5) on the nozzle needle (2) by the pressure in the control chamber (10). A counterpart pressure chamber (12) is formed in the injection body (1), which can be filled with the liquid medium and which acts on a counterpart surface (33) of the nozzle needle (2) such that a hydraulic force, which is directed opposite the hydraulic force in the control chamber (10), is thus exerted in the axial direction of the nozzle needle (2).

Description

 description

title

 Injector for metering gaseous fuel, gas blowing system with such an injector and method of operating this injector

The invention relates to an injector for metering of gaseous fuel, as used, for example, to introduce gaseous fuels directly into egg nen combustion chamber of an internal combustion engine. Moreover, the invention relates to a Gaseinblassystem with such an injector and a procedural ren 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, example, from DE 10 2015 209 134 Al. The injector has a longitudinally movably arranged in an injector nozzle needle, which cooperates with a nozzle seat for opening and closing a flow cross-section. Downstream of the flow cross-section, several 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 injection ports facing away from the end face a control chamber which is 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 Injek sector , By a control valve, the pressure in the control room can vary, so that thus also acting in the closing direction hydraulic force on the Dü sennadel can be changed. This is a control possibility of Düsenna del given.

The gaseous fuel is made available via a compressor and a high-pressure gas storage, with 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 bring a lower gas pressure into the combustion chamber, for example when 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 very compressible, a relatively large amount of gas has to be removed from the high-pressure accumulator, which is already kept compacted there and then, when the full injection pressure is required again, must be re-compressed with a great deal of energy and fed to the high-pressure accumulator. This is unfavorable ener table and affects the efficiency of the internal combustion engine.

Advantages of the invention

The injector for metering of gaseous fuel according to the invention has the advantage that it is an internal combustion engine with high efficiency operable, with different gas pressures can be gedüst in the combustion chamber without the gas pressure of the supply system must be lowered from. For this purpose, the injector on an injector, in which a piston-shaped nozzle needle is arranged longitudinally displaceable, which cooperates with a sealing surface with a nozzle body formed in the injector to open and close a flow cross-section, can flow through the gaseous ger fuel an injection port. 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 the nozzle needle is exercised. In the injector a counter-pressure chamber is out forms, 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 hydrauli's forces on the one hand in the control room and on the other hand in the counter-pressure chamber. If there is a relatively high pressure of the liquid medium, the opening forces are correspondingly high on the nozzle needle, since after a pressure drop in the control chamber, a high hydraulic pressure in the back pressure chamber acts on the nozzle needle. This allows the nozzle needle to move quickly, in particular, it can be quickly move out of the seat throttle area, ie the Be rich, 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 counter-pressure space is flooded, however, lowered, so acts in the back pressure chamber, a correspondingly lower hydraulic opening force on the nozzle needle. If the pressure in the control chamber is lowered, these lower forces cause a comparatively slow movement of the nozzle needle in the opening direction. This makes it possible to keep the nozzle needle relatively long in the seat throttle area, i. that the opening movement of the nozzle needle is stopped in time and so egg nen partial stroke passes through, so that a throttle point is formed between the sealing surface and the nozzle seat. At this throttle point so that part of the gas pressure is reduced, so that at the injection openings a lower gas pressure is available than in the injector is available. The injection of the gaseous fuel takes place 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 relaxed or blown off.

In a first advantageous embodiment, the nozzle needle has an enlarged diameter portion, on which the end face is formed and limits the counter-pressure space with one of the end face opposite Ge genfläche. As a result, hydraulic opposing forces can be generated on the nozzle needle in a structurally simple manner, the sennadel act in the longitudinal direction of the Dü. In this case, the counter-pressure space is formed in an advantageous manner as a ring space surrounding the nozzle needle, which can also be implemented in a simple manner by a corresponding shape 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 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 formed as a hollow needle having a longitudinal bore with a longitudinally displaceably arranged inside needle, the menwirkt together with a formed in the nozzle needle held Ren nozzle seat for releasing or closing an injection port. The additional nozzle needle also allows liquid fuel simultane- ously or offset in time to bring the gaseous fuel in the combustion chamber einzu, wherein advantageously a pressure space is formed between the nozzle needle and the wall of the longitudinal bore, which is filled with the liquid medium, so that the liquid medium is ejected with the injection opening open by them. 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. Thereby, the back pressure chamber can be filled in simp cher manner and also the pressure chamber, which is formed between the inner needle and the longitudinal bore, so that the injector structurally simple can be 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 held before, with which both the control chamber and the counter-pressure chamber 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 reduction in pressure of the high-pressure accumulator for the liquid medium is relatively easy to do, since liquids are only slightly compressible, ie it must be controlled only a small amount in order to lower the pressure significantly. The energy losses due to such a pressure control are therefore low.

drawing

In the drawing, two embodiments of the invention Injek sector are shown with the essential system components. Show it

Figure 1 shows a first embodiment of the invention

 Injector together with the system components shown schematically for the liquid and the gaseous medium or the gaseous fuel and

Figure 2 shows a second embodiment also with schematic

 Representation of the system components.

Description of the embodiments

1 shows 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, in which a nozzle needle 2 is arranged to be longitudinally displaceable, wherein the nozzle needle 2 has a longitudinal axis 9 and is substantially piston-shaped. The nozzle needle 2 has at its end facing the combustion chamber a koni cal sealing surface 4, with which the nozzle needle 2 with a conical Nozzle seat 5 for opening and closing a flow cross-section together menwirkt that can be controlled between the sealing surface 4 and the nozzle seat 5. In this case, the nozzle needle 2 is surrounded by a gas space 3, which can be filled via a running in the injector body 1 supply bore 6 with gaseous fuel. Downstream of the nozzle seat 5, an annular groove 7 is formed in the nozzle needle 2, in which the gaseous fuel flows from the gas space 3, when it flows between the sealing surface 4 and the nozzle seat 5. In the nozzle body 1 more Eindüsöffnungen 8 are also formed, which are connected to the annular groove 7, so that the gaseous fuel from the annular groove 7 can be emptied through the injection opening 8. The annular groove 7 ensures that the gaseous fuel is evenly distributed to the injection openings 8.

With its end face 32 facing away from the sealing surface 4, the nozzle needle 2 limits a control chamber 10 which is formed within the nozzle body 1 and radially outwardly of the nozzle body 1 and on the upper side in the drawing by a throttle plate 13 is limited. The control chamber 10 can be filled via a throttle to 14 with a liquid medium under a working pressure. Via an outlet throttle 15, the liquid medium can be removed from the control chamber 10, so that an alternating hydraulic pressure in the control chamber 10 is adjustable. The nozzle needle 2 has at its end facing away from the sealing surface 4 an enlarged diameter portion 102, on which the end face 32 is formed. Through the widened portion 102, an annular disk-shaped mating surface 33 is formed on the side of the widened portion 102 opposite the end face 32. With this mating surface 33 be the expanded diameter portion 102 defines a back pressure chamber 12 which is formed as an annulus and the nozzle needle 2 surrounds. About a to-bore 28, the back pressure chamber 12 can also be filled with the liquid Medi, so that by the pressure in the back pressure chamber 12 a hyd raulische force is exerted on the nozzle needle 2, the hydraulic force of the control chamber 10 directed against the nozzle needle 2 is.

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

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 ei nem compressor 18 is supplied, which compresses the gaseous fuel to the not agile working pressure and a second gas line 19 'a gas pressure accumulator 20th feeds, where the compressed gaseous medium or the gaseous fuel is kept. The gas pressure accumulator 20 is connected via a high-pressure gas line 21 to the supply bore 6, so that thus the gas space 3 is filled with the compressed gaseous fuel.

The operation of the injector is as follows: If gas under the full Eindüs pressure, as it is held in the gas pressure accumulator 20, a gedüst in the combustion chamber, so a high pressure of the liquid medium is required, with both the control chamber 10 and the back pressure chamber 12 are filled when the control valve 29 is closed. If an injection to be done, the control valve 29 is opened and the hydraulic pressure in the control chamber 10 decreases, as over the outlet throttle 15 more liquid medium from the control chamber 10 flows as flows in the same period on the inlet throttle 14. As a result of the still high hydraulic pressure in the counterpressure space 12, a high hydraulic opening force is exerted on the nozzle needle 2, so that it quickly moves away from the nozzle seat 5 and opens the flow cross section between the sealing surface 4 and the nozzle seat 5. Gas-fuel flows from the gas space 3 into the annular groove 7 and from there into the inlet. Düsöffnungen 8. At the injection openings 8 is practically unthrottled to the full pressure of the gaseous medium, as it is made available in the gas pressure accumulator 20. To end the injection, the control valve 29 is closed again, so that the high hydraulic pressure builds up again in the control chamber 10 and pushes the nozzle needle 2 back into its closed position.

If, on the other hand, it is not desired to inject with the full gas pressure, the pressure in the hydraulic system is lowered, ie. in the high-pressure accumulator 25 is now at a lower hydraulic pressure. This can be done for example by throttling the pump 24 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, which is exerted by the pressure in the control chamber 10 on the nozzle needle 2, but the nozzle needle 2 remains closed, as well as the hydraulic back pressure in the back pressure chamber 12 decreases accordingly. Now, the control valve 29 is opened, then decreases in turn as the hydraulic pressure in the control chamber 10, the hydraulic opening force in the back pressure chamber 12 but is now lower, so that the nozzle needle 2 is moved only comparatively slowly in the opening direction. Correspondingly long, the flow cross-section between the sealing surface 4 and the nozzle seat 5 remains small and thus throttles the gas flow, the injection openings 8 in the annular groove 7 and the A flows. Thus, the nozzle needle 2 does not pass through its full opening stroke, the control valve 29 must be ge closed before the nozzle needle 2 moves out of the seat throttle range forth, ie the gas nozzle. from the stroke range in which a throttle gap is formed between the sealing surface 4 and the nozzle seat 5. For this purpose, the control valve can be repeatedly opened and closed during an injection, so that the injection via the injection openings 8 always cross-section with throttled flow occurs and thus with a lower effective gas pressure at the injection openings. 8

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

2 shows a second embodiment of the injector according to the invention is shown, wherein the same components with respect to the figure 1 are provided with the same reference numerals. A renewed explanation of the same compo nents is therefore omitted. This injector has over the Ausfüh tion of Figure 1 a modified nozzle needle, wherein the Düsenna del 2 is designed as a hollow needle with a longitudinal bore 35. In the Längsboh tion 35, a piston-shaped inner needle 38 is arranged longitudinally displaceable, wherein between the nozzle needle 38 and the wall of the longitudinal bore 35, a pressure chamber 36 is formed, which is filled with the liquid medium. For this purpose, a connecting bore 50 is formed in the nozzle needle 2, which connects the Ge gendruckraum 12 with the pressure chamber 36. The nozzle needle 38 has at its combustion chamber end, an inner sealing surface 41, with the inner needle 38 with an inner nozzle seat 40 for opening and closing a Strö tion cross-section cooperates, through which the liquid fuel to several ren, formed in the nozzle needle 2 injection openings 42nd can flow.

The inner needle 38 has on its side facing away from the inner sealing surface 41 an end face 44, with which the inner needle 38 defines an inner control chamber 43 which is filled with the liquid medium from the high-pressure accumulator 25 via egg ne inlet throttle 45. Via an outlet throttle 46, the inner STEU erraum 43 with the return line 30 is connected, said connection via a second control valve 48 leads, which in turn is designed as a 2/2-way valve and, for example, an electromagnetically operated valve. In the same way as the control chamber 10 so can the hydraulic pressure in the inner control chamber 43 by opening and closing the second control valve 48 SET len and thus control the longitudinal movement of the inner needle 38. Also in this embodiment, the opening speed of Düsenna del 2 can be adjusted via the counterplay between the pressure in the control room 10 and in the back pressure chamber 12 and thus a corresponding seat throttling between the sealing surface 4 and the nozzle seat 5, which thus reduces the pressure of the gaseous fuel at the injection openings 8.

Claims

claims 1. injector for metering of gaseous fuel with an injector body (1) in which a piston-shaped nozzle needle (2) is longitudinally displaceable angeord net with a sealing surface (4) with a in the injector body (1) ausgebil Deten nozzle seat (5) for opening and closing a flow cross section (11) through which gaseous fuel of an injection opening (8) can flow to ^¬ , and with a control chamber (10) which is bounded by the dichtflächenab- facing end face (32) of the nozzle needle (2) and the with egg nem liquid medium can be filled, wherein in the control chamber (10) a change in the liquid pressure is adjustable and by the pressure in the control chamber (10) a closing force in the direction of the sealing seat (5) is practiced on the nozzle needle (2),  characterized,  in that the injector body (1) has a counterpressure space (12) which can be filled with the liquid medium and which acts on a mating surface (33) of the nozzle needle (2) in such a way that a hydraulic, in the axial direction of the nozzle needle (2) acting force is exerted, which is the hydraulic power rule in the control chamber (10) directed opposite. 2. An injector according to claim 1, characterized in that the nozzle needle (2) has a diameter-enlarged portion (102) on which the end face (32) is formed and the counter-pressure space (12) with one of the end face (32) opposite Countered surface (33). 3. An injector according to claim 2, characterized in that the counter-pressure chamber (12) is designed as an annular space surrounding the nozzle needle (2). 4. An injector according to claim 1, characterized in that the control chamber via a in the injector body (1) formed inlet throttle (14) is filled with the liquid medium FLÜS. 5. An injector according to 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. 6. An injector according to claim 5, characterized in that between the in needle needle (38) and the wall of the longitudinal bore (35), a pressure chamber (36) is formed, which is filled with the liquid medium, so that the liq sige medium when opened Injection opening (42) is ejected through this. 7. An injector according to claim 6, characterized in that the counter-pressure chamber (12) to the pressure chamber (36) is hydraulically connected. 8. Injector according to one of claims 1 to 7, characterized in that the liquid medium is a liquid fuel. 9. gas injection system with an injector according to one of claims 1 to 8, 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 space (12) are connected. 10. A method for operating an injector according to one of claims 1 to 8, characterized by the following method steps:  - Set the desired injection pressure of the gaseous fuel. Determine what is required to achieve this injection pressure  Pressure of the liquid medium, which is supplied to the injector.  - Supplying the liquid medium to the injector, so that in all filled with the liquid medium spaces of the injector, this pressure is a. - 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 gaseous fuel to achieve the gewünsch th Eindüsdrucks. 11. The 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 inlet nozzle pressure.