Injector for directly injecting a gas into the combustion chamber of a reciprocating internal combustion engine and method for operating a reciprocating internal combustion engine

Abstract

An injector (2), a reciprocating internal combustion engine and a method for operating a reciprocating internal combustion engine are proposed. The injector (2) is hydraulically actuated. The injector (2) is supplied with fuel gas and pressurized hydraulic fluid via a horizontal bore (1.5) in the cylinder head (1), which opens into a receiving shaft (1.4) for the injector (2).

Description

[0001] The invention relates to an injector for injecting fuel gas into a combustion chamber of a reciprocating piston internal combustion engine.

[0002] The invention is applicable to all reciprocating internal combustion engines (hereinafter referred to as "reciprocating engine" for linguistic simplicity) that are operated with a gaseous fuel (fuel gas). The application is primarily aimed at the use of hydrogen gas (H2). However, other gaseous fuels can also be used according to this invention, e.g., methane (CH4), ammonia, or gas mixtures. State of the art

[0003] Fuel gas injection systems for reciprocating piston internal combustion engines are state-of-the-art. Such systems can be divided into three groups.

[0004] In the systems of the first group, a fuel gas mass flow is metered into the total air mass flow upstream of the turbocharger at a single point, i.e., centrally. This type of metering is also referred to as central mixture formation. In the simplest case, the metering occurs continuously via a Venturi mixer.

[0005] In the second group of systems, fuel gas is introduced into at least one intake port of each engine cylinder unit. Preferably, the fuel gas is introduced intermittently through a so-called PFI injector (port fuel injection).

[0006] In the third group of systems, fuel gas is injected directly into the engine's combustion chambers. In this case, the fuel gas injection must be intermittent, using a so-called DI injector (direct injection).

[0007] Intermittently operating injectors are state-of-the-art. Intermittently operating injectors typically feature a movable valve element, which is preferably pressed against a stationary seat by a closing spring. If the injector is to open an inlet cross-section, an opening force must be applied against this spring force.

[0008] In most injectors, this opening force is applied by an electromagnet. This type of injector actuation is referred to as electromagnetic direct actuation. It enables short opening and closing times as well as high precision, i.e., minimal lift profile deviations. The short opening and closing times result in correspondingly high average lift speeds and, consequently, high seat impact speeds. However, using comparatively complex electronic controls, the touchdown speed can be actively reduced. This strategy is referred to as a soft landing strategy.

[0009] For large-displacement engine cylinders, a correspondingly large inlet cross-sectional area must be provided to ensure sufficient fuel gas can be metered in within the available time. The closing force exerted by the closing spring correlates with the inlet cross-sectional area and, in turn, determines the opening force required. Electromagnetic direct actuation can only be implemented economically up to a certain cylinder displacement.

[0010] Very large opening forces can be generated with pilot-operated injection systems. The opening force is applied by a pneumatic or hydraulic actuator. This type of injector actuation is referred to as indirect actuation. The injector according to the invention is indirectly actuated.

[0011] From DE 10 2020 127 020 B3 of the applicant, a pneumatically actuated injector is known in which the pressurized fuel gas is used as the working fluid to open the injector.

[0012] During each injection event into the combustion chamber, a certain mass of fuel gas must be discharged without pressure. This fuel gas mass is referred to below as the actuating fuel gas mass. To be used in the combustion process, this fuel gas mass is fed into the engine's air intake system.

[0013] In the H2 engine, the indicated specific piston work (w i ) by the fuel gas mass introduced per working cycle (m B ). The ratio of specific work at maximum load (full load operation) and minimum load (idle operation) is typically 20:1. Assuming a constant indicated efficiency (n i) the fuel mass added must be varied in the same ratio.

[0014] If the injector is operated supercritically at constant pressure, the introduced fuel gas mass (m B ) is proportional to the time cross-section (A). The time cross-section must then also exhibit the specified spread of 20:1 (equivalent to a range of 5% to 100%). "Supercritical operation" is characterized by the pressure in the gas connection being at least a factor of two higher than the pressure in the combustion chamber.

[0015] The tests have shown that such a high spread of the time cross-section is fundamentally feasible, considering the time available at a speed of 2000 rpm. However, this is only possible with the realized prototype if the injector is operated ballistically at low time cross-sections. During ballistic operation, the time cross-sections fluctuate unacceptably.

[0016] The invention is based on the object of providing an injector for the direct injection of gaseous fuels that exhibits improved operating behavior, can be easily integrated into internal combustion engines originally operated with liquid fuel (retrofit), and is easily adaptable to various internal combustion engines. Furthermore, only a low pressure, for example, of 20 bar, should be sufficient to inject a gaseous fuel. The injector should exhibit low wear and its service life should be as long as that of the internal combustion engine in which it is used.

[0017] The injector should be widely scalable in terms of throughput while maintaining virtually unchanged opening and closing behavior. Steady-state throughput requirements of greater than 100 kg / h should be achievable.

[0018] The injector should be able to be integrated into selected existing cylinder heads with minor rework of the cylinder head.

[0019] This object is achieved according to the invention by an injector for a fuel gas, comprising a valve and a hydraulically actuated actuator, wherein the injector comprises a nozzle and a one-part or multi-part housing and is characterized in that a first sealing element is provided in the region of the valve and a second sealing element is provided in the region of the actuator, that at least one inlet bore is formed in the housing between the first sealing element and the second sealing element, that a lance is sealingly connected to the housing and that the lance is hydraulically connected to the actuator.

[0020] This design makes it possible to feed the fuel gas into the injector via at least one inlet bore. The inlet bore opens into a second gas guide channel formed between the intake shaft in the cylinder head of the internal combustion engine and the injector housing, allowing the gas to be easily directed into the injector valve.

[0021] This results in a very compact design that is particularly suitable for retrofitting diesel engines that will be powered by gas in the future.

[0022] The range of injection times achievable with this injector is sufficient to control an internal combustion engine in the entire range between idle and full load and thus to realize the desired torque requirements.

[0023] In a further advantageous embodiment of the invention, the injector has a plunger and a closing spring, wherein a sealing surface is formed at a first end of the plunger and the actuator comprises a piston which is arranged at an end of the plunger opposite the sealing surface, wherein the piston is guided in the injector housing in a sealing and axially displaceable manner, wherein a spring force exerted by the closing spring on the plunger seeks to move the plunger in the direction of a seat plate and wherein the piston delimits a pressure chamber.

[0024] This combination of valve and actuator is very compact and provides a design that is easy to manufacture and can be manufactured with the highest precision, best surface quality and cost-effectively.

[0025] By changing the oil pressure acting on the piston, the injector can be opened or closed as desired. If the force acting on the piston resulting from the oil pressure (the pressure of the control fluid) is less than the force exerted on the piston by the closing spring, the piston moves into its closed position until the piston plunger rests on a seat plate of the injector. The connection between at least one inlet bore and the nozzle is then interrupted, and the injector is closed.

[0026] However, as soon as the hydraulic force exerted by the pressure chamber on the piston exceeds the force exerted by the closing spring, the piston, and with it the sealing surface, lifts off the seat plate, creating a connection between at least one inlet bore and the injector nozzle. In other words: the injector is open.

[0027] In an advantageous development of the invention, a leakage discharge bore and at least one relief bore are formed in the piston. These bores allow both hydraulic fluid leaks from the fluid chamber and gas leaks from the valve to be discharged into the environment via the at least one relief bore and the leakage discharge bore.

[0028] In an advantageous embodiment, the closing spring is accommodated in a spring chamber and the leakage discharge bore opens into the spring chamber.

[0029] The principle according to the invention can be implemented with injector valves that open outwards or inwards.

[0030] The object underlying the invention is also achieved by a reciprocating piston internal combustion engine, comprising at least one cylinder and at least one cylinder head, wherein each cylinder head comprises at least one inlet channel, a receiving shaft for an injector as well as a fuel gas connection and a horizontal bore, wherein the horizontal bore opens into the receiving shaft, wherein the fuel gas connection opens into the horizontal bore and wherein the lance is arranged in the horizontal bore, and wherein an injector according to one of the preceding claims is arranged in the receiving shaft.

[0031] This design makes it possible to supply the fuel gas to the injector through the horizontal bore and at the same time to supply the injector's actuator with hydraulic fluid, which is supplied in the lance.

[0032] This allows for a very simple conversion (retrofit) of previously diesel-powered reciprocating piston internal combustion engines to fuel gas operation. Furthermore, this type of fuel gas and hydraulic fluid supply is very compact.

[0033] The lance and the horizontal bore on the one hand, as well as the receiving shaft and the injector on the other, are shaped and dimensioned such that a first gas guide channel is formed between the lance and the horizontal bore, into which the fuel gas connection opens. Furthermore, an annular gap-shaped second gas guide channel is formed between the injector and the receiving shaft, and the horizontal bore or the first gas guide channel and the inlet bore of the injector open into the second gas guide channel.

[0034] This allows the injector or its valve to be supplied with pressurized fuel gas via the horizontal bore and the second gas guide channel. As soon as the injector valve opens, the fuel gas flows from the second gas guide channel via the inlet bores and through the valve and nozzles into the combustion chamber.

[0035] In a further advantageous embodiment of the invention, the lance of each injector is hydraulically connected to a hydraulic control system, and the hydraulic control system is designed to control the pressure in the lance of each injector. As already explained, this opens or closes the injector, thus allowing the injection of fuel gas into the combustion chamber to be controlled within wide limits.

[0036] The control unit of the hydraulic control system is designed and configured to carry out a method according to one of the method claims 14ff.

[0037] The method according to the invention is based on an injector according to the invention and a hydraulic control system according to the invention. It comprises the steps of determining the duration and position of the injection process as a function of the torque requirement and / or the speed of the reciprocating internal combustion engine, and controlling the injector(s) so that they are opened according to the previously determined duration and position of the injection process. This allows the desired amount of fuel gas to be injected into the combustion chamber, depending on the current operating point of the internal combustion engine, thus enabling efficient operation of the internal combustion engine with low pollutant emissions.

[0038] In a further advantageous embodiment of the method, at the beginning of an injection process, the pressure in the lance is increased to such an extent that the injector valve opens. Similarly, at the end of the injection process, the pressure in the lance is reduced to such an extent that the injector valve closes.

[0039] Further advantages and advantageous embodiments of the invention can be found in the following drawings and their description. drawing

[0040] They show: Fig. 1 shows a perspective view of a single cylinder head (ZK) of a reciprocating piston internal combustion engine. Fig. 2 shows a top view of the single cylinder head from Fig. 1. It shows the position of the cutting planes. Fig. 3 shows a sectional view of the single cylinder head from Fig. 1 along the AA axis. The injector and the lance are not shown in section. Fig. 4 shows the sectional view from Fig. 3, where the injector and the lance are shown in section. Fig. 5 shows a sectional view of the single cylinder head from Fig. 1 along the axis BB. Fig. 6 shows a sectional view of the single cylinder head from Fig. 1 along the CC axis. Fig. 7 shows a sectional view of the injector, which is used in the single cylinder head of Fig. 1 is installed. The sectional view runs along the AA axis. Fig. 8 shows a first detailed view of Fig. 7. Fig. 9 shows a second detailed view from Fig. 7. Fig. 10 shows a hydraulic circuit diagram of the direct injection system. Fig. 11 shows a first functional diagram of a hydraulically operated injector Fig. 12 shows a second functional diagram of a hydraulically operated injector Fig. 13 shows a perspective view of a hydraulic control system Fig. 14 shows a sectional view of the valve block from Fig. 13 Description of the embodiments

[0041] The injector according to the invention is hydraulically actuated. The figures show both the injector and its integration into an internal combustion engine. The same reference symbols are used for the same assemblies and components in all figures. For reasons of clarity, not all reference symbols are shown in all figures.

[0042] Fig. 10 shows the two subsystems of the direct injection system according to the invention comprising a hydraulically operated injector 201 for each engine cylinder and an associated hydraulic control system 202.

[0043] The injector 201 comprises a control fluid connection 201.1, a fuel gas connection 201.2, a leakage connection 201.3, and a controllable fuel gas outlet 201.4. The fuel gas enters the combustion chamber of the reciprocating internal combustion engine through the fuel gas outlet 201.4. The controllable fuel gas outlet 201.4 is implemented in an injector 201.

[0044] The hydraulic control system 202 provides the hydraulic fluid required to control the injector. Such hydraulic control systems 202 are known to those skilled in the art.

[0045] Further down (after the description of the Fig. 9) details of the hydraulic control system 202 are described in more detail.

[0046] Based on the Fig. 11 and Fig. 12 explains the differences between inward and outward opening injectors 201.

[0047] The Fig. 11 shows the functional diagram of an inwardly opening hydraulically actuated injector 201 according to the invention from Fig. 10. The movable sealing element opens inward in the direction of arrow 106. A closing spring 2.4 presses the movable sealing element of the injector 201 against the stationary sealing surface. If a sufficiently high fluid pressure p is applied at the control fluid connection 201.1 ctr When the valve is closed, the hydraulic force exerted by the hydraulic fluid on the sealing element overcomes the force of the closing spring, and the movable sealing element lifts off the stationary sealing surface, thus clearing the opening cross-section. As a result, gas is injected into the combustion chamber.

[0048] The Fig. Figure 12 shows the functional diagram of an outward-opening, hydraulically actuated injector according to the invention from Figure 1. The movable sealing element opens outward in the direction of arrow 106. A closing spring 2.4 pulls the movable sealing element against the fixed sealing surface. If a corresponding fluid pressure p is applied to the control fluid connection 201.1, the pressure drops to ctr When the pressure is applied, the force of the closing spring 2.4 is overcome, and the movable sealing element lifts off the stationary sealing surface, thus clearing the opening cross-section. As a result, gas is injected into the combustion chamber.

[0049] The direct injection system according to the invention can be implemented with both inward-opening and outward-opening injectors. The invention is described below using an inward-opening injector as an example.

[0050] In the Fig. 1 to 6 illustrate the integration of the injector 2 into a single cylinder head 1 of a reciprocating piston internal combustion engine, which was originally designed to operate with liquid diesel fuel. Fig. The solution shown in Figures 1 to 6 enables the conversion of a diesel engine to operate with a gaseous fuel (combustion gas), requiring only relatively few modifications to the cylinder head of the internal combustion engine. The application example of a gas injection injector described here is a very advantageous retrofit solution because only a few modifications or rework are required on the individual cylinder heads.

[0051] The injector 2 according to the invention is applied to a reciprocating internal combustion engine such that the fuel gas outlet of each injector opens into a combustion chamber of the reciprocating internal combustion engine. Structurally, the injector 2 can be applied in a cylinder crankcase, in a cylinder head, or in an intermediate plate between the cylinder crankcase and the cylinder head.

[0052] The modification of the single cylinder head 1 essentially consists of the installation of a receiving shaft 1.3 for a spark plug 7 (see Fig. 6).

[0053] Single-cylinder heads are the most common design for large diesel and gas engines with a certain single-cylinder displacement above. The injectors 2 according to the invention can also be implemented in multi-cylinder heads.

[0054] The application example described below is based on a frequently encountered design of a single cylinder head 1 of a diesel reciprocating piston internal combustion engine according to Fig. 1.

[0055] The cylinder head 1 has two intake ports 1.1, each with an intake valve 1.7, and two exhaust ports 1.2, each with an exhaust valve 1.8 (see e.g. Fig. 5). It also includes a hole 1.5 on (see Fig. 3 and Fig. 4). Hole 1.5 is also called the "horizontal hole" because it runs horizontally in the figures; it could also run differently.

[0056] The single cylinder head 1 has a receiving shaft 1.4 for an injector 2 (see e.g. Fig. 3). In an internal combustion engine originally designed for diesel operation, the diesel injector is located in the receiving shaft 1.4.

[0057] The receiving shaft 1.4 is designed as a stepped bore. A thread (no reference symbol) is provided at the bottom of the receiving shaft 1.4.

[0058] In the retrofit application example according to the invention described here, the injector 2 is designed such that it fits into the receiving shaft 1.4 originally intended for a diesel injector. The receiving shaft 1.4 can also be reworked, if necessary, to make room for the injector 2 and a second gas guide channel 101 (see Fig. 3) to create.

[0059] The injector 2 is pressed axially against the bottom of the receiving shaft 1.4 by means of a claw 3 (see Fig. 3) clamped.

[0060] A longitudinal axis 1.4.1 of the rotationally symmetrical receiving shaft 1.4 generally runs coaxially with the cylinder axis of the corresponding engine cylinder, meaning that the injector 2 is located centrally. This is a common injector arrangement in diesel engines with 4-valve technology.

[0061] Also common in larger diesel engines is a 1.5 horizontal bore for each cylinder. These lead into the 1.4 mounting holes of the 1.

[0062] In a diesel engine, the liquid fuel is fed to the injector through a lance, which is arranged concentrically to this horizontal bore 1.5. The resulting annular gap 100 serves to drain fuel leaks and the so-called diversion quantity.

[0063] The horizontal bore 1.5 is also used in the retrofit application example according to the invention described here to accommodate a lance 5. By means of this lance 5, control fluid (usually pressurized oil) is fed to the injector 2 (see Fig. 4 and Fig. 3). The fuel gas is directed to injector 2 through an annular gap 100 between lance 5 and horizontal bore 1.5. The annular gap is also referred to as the first gas guide channel 100.

[0064] The lance 5 is clamped axially against the individual cylinder head 1 by means of a union nut 6 and penetrates into a housing 2.1 of the injector 2. A sealing ring 5.3 is provided between the lance 5 and the housing 2.1, so that a gas-tight connection is created ( Fig. 7).

[0065] A connection point 1.6 in the diesel engine serves for the pressureless discharge of fuel leakage. In the gas engine according to the invention, the fuel gas is guided into the individual cylinder head 1 via this connection point 1.6. From there, the fuel gas flows via the first gas guide channel 100, which is designed as an annular gap, and from there into the second gas guide channel 101, which is also annular, between the injector housing 2.1 and the receiving shaft 1.4 in the cylinder head (see Fig. 4).

[0066] The second gas guide channel 101 is sealed from the space above the cylinder head with an O-ring 2.10 or another sealing element (see Fig. 4).

[0067] In the described embodiment, the lance 5 is designed in two parts (see Fig. 4), whereby the two individual parts 5.1 and 5.2 are joined together by a material bond, for example, by welding or soldering. An O-ring 5.4 or another suitable sealing element seals the first gas guide channel 100 from the environment.

[0068] An O-ring 5.3 seals the first gas guide channel 100 from the control fluid guide channel 102 (see Fig. 4 and Fig. 7).

[0069] Based on the Fig. 4 and Fig. 7 explains, among other things, the installation of the injector 2 in the receiving shaft 1.4. In the Fig. 7 is the injector 2 without cylinder head 1 and a little more detailed than in the Fig. 4 shown.

[0070] A sealing washer 2.7 (see Fig. 7 and Fig. 8) seals the second gas guide channel 101 from the combustion chamber (see Fig. 4).

[0071] Fig. 7 shows a section through the complete injector. Fig. Figure 8 shows enlarged details of the lower end of injector 2.

[0072] In this embodiment, the injector 2 has an inward-opening sealing element with a flat seat. This type of seal is also referred to as a flat seat seal. A plunger 2.2 acts as the sealing element.

[0073] Its flat sealing surface 2.2.7 (at the lower end in the Fig. 7 and Fig. 8) is formed by its lower end face. The plunger 2.2 has a cylindrical outer guide surface 2.2.3. The injector housing 2.1 has a corresponding cylindrical inner guide surface 2.1.2. The fit formed by these two guide surfaces has a small clearance, preferably on the order of 1 / 100 mm. This fit is referred to below as the sealing gap 105. The tight fit ensures, on the one hand, precise guidance of the plunger 2.2 and, on the other hand, minimizes the leakage of control fluid.

[0074] To further reduce the leakage quantity, one or more first piston rings 2.8 can be provided (see Fig. 7 and Fig. 8).

[0075] Above the guide surface 2.1.2, the interior of the injector 2 expands and forms a pressure chamber 103 with the plunger 2.2. The lance 5 opens into the pressure chamber 103.

[0076] The Fig. Figure 9 shows the upper section of the injector 2 in detail. A piston 2.2.10 is formed in the upper section of the plunger 2.2. When the control fluid in the pressure chamber 103 is pressurized, an upward opening force (in the figures) is generated. This opening force is opposed to the force of the closing spring 2.4. The closing spring 2.4 presses the plunger 2.2 with the sealing surface 2.2.7, which forms the seat plate 2.5 (see Fig. 8). In this state, injector 2, or the fuel gas outlet 201.4, is closed.

[0077] The diameter of the piston 2.2.10 is selected so that the hydraulic opening force of the control fluid in the pressure chamber 103 is greater than the force of the closing spring 2.4 when the control fluid is under pressure.

[0078] Then the piston 2.2.10 and with it the piston 2.2 move in the Fig. 7 upwards, and the sealing surface 2.2.7 of the piston 2.2 lifts off the sealing plate 2.5. The valve or injector 2 is opened, and fuel gas flows into the combustion chamber through the inlet bores 2.2.1, the seat plate opening 2.5.1, and the exhaust bores 2.6.4 of the nozzle 2.6.

[0079] This opening force is the product of the pressure difference between the pressure in pressure chamber 103 and the (ambient) pressure prevailing in spring chamber 104, and the effective area. This effective area is calculated as follows: A=π4⋅(D2−d2)

[0080] D is the diameter of the piston 2.2.10 and d is the diameter of the guide surface 2.2.3 or the sealing gap 105.

[0081] When the pressure in the pressure chamber 103 is increased by actuating the hydraulic control system 202 (see Fig. 10) is lowered to ambient pressure, then the closing spring 2.4 moves the piston 2.2.10 and with it the plunger 2.2 in the Fig. 7 downward until the sealing surface 2.2.7 of the piston 2.2 rests on the sealing plate 2.5. The valve or injector 2 is closed, and no more fuel gas flows into the combustion chamber. In this case, a portion of the hydraulic fluid in the pressure chamber 103 is pushed back into the lance 5 by the piston 2.2.10.

[0082] A piston seal 2.9 seals the pressure chamber 103 from the spring chamber 104 above the piston 2.2.10 of the piston 2.2. Standard hydraulic seal systems from various manufacturers can be used for this purpose, such as the Type OE piston seal kit from Parker Hannefin. In this piston seal kit, the seal ring is made of PTFE with a bronze content of 40%. A radially compressed O-ring is used as a clamping element.

[0083] To avoid a double fit, the fit between the piston 2.2.10 and the injector housing 2.1 is less tight than the fit that forms the sealing gap 105.

[0084] The pressure chamber 103 is accessible via a vent hole 2.1.3 (see Fig. 9) fluidically connected to the space above cylinder head 1 or the environment. A guideline for the diameter of this hole is 0.5 mm. This hole is installed at the highest possible point in the injector housing 2.1, as shown in Fig. 9. Gas bubbles in the control fluid system can escape through the vent hole 2.1.3, ensuring fast and precise raising and lowering of the piston 2.2. This leakage oil is returned to the oil circuit via the oil return line in the cylinder head.

[0085] If you now return to the Fig. 8, it becomes clear that the lower area of ​​the piston 2.2 is provided with two grooves, each of which accommodates a radially sealing piston sealing ring 2.8. These piston sealing rings 2.8 seal the second gas guide channel 101 from the leakage discharge bore 2.2.1 in the piston 2.2. It is designed as a blind hole and is fluidically connected to the space above the cylinder head 1. Alternatively, this sealing task can also be achieved with just one sealing ring. Standard pneumatic sealing ring systems can be used here, such as the piston sealing set type OA from the manufacturer Parker Hannefin. In this piston sealing set, the sealing ring is made of PTFE with a carbon content of 25%. A radially pressed O-ring is used as a clamping element. Above these two piston sealing rings 2.8, an annular groove 2.2.8 is provided on the outer surface of the piston (see Fig. 8). This annular groove 2.2.8 is fluidically connected to the leakage discharge bore 2.2.1 via relief bores 2.2.2, ie the pressure in the annular groove 2.2.8 is approximately the same as in the space above the cylinder head 1. Since ambient pressure prevails above the cylinder head 1, the pressure in the annular groove 2.2.8 is approximately the same.

[0086] The control fluid leakage flowing through the sealing gap 105 is discharged without pressure into the space above the cylinder head via the annular groove 2.2.8 and the relief bores 2.2.2. The fuel gas leakage flowing through the piston sealing rings 2.8 is also discharged without pressure into the space above the cylinder head via the annular groove 2.2.8 and the relief bores 2.2.2.

[0087] The outer surface of the plunger 2.2 is advantageously and optionally slightly offset radially inward below the annular groove 2.2.8. This radially offset area 2.2.9 has a greater clearance relative to the guide surface 2.1.2 in the injector housing 2.1 than the sealing gap 105; preferably, the clearance is approximately 6 / 100 mm.

[0088] Fig. Figure 8 further shows an advantageous embodiment of the seat geometry in detail. The punch 2.2 has an outer recess 2.2.5 at its lower end, which in the simplest case is designed as a chamfer. Furthermore, the punch 2.2 has an inner recess 2.2.6 attached to the front side, which in the illustrated embodiment is designed as a circular recess. This leaves a flat, circular sealing surface 2.2.7 at the "lower" end of the punch 2.2, which is delimited by two concentric circles.

[0089] The diameter of the inner relief 2.2.6 is advantageously slightly larger than the diameter of the round seat plate opening 2.5.1. It is preferably 0.2 mm larger. The outer relief allows the size of the sealing surface 2.2.7 and thus also the surface pressure of the sealing surface 2.2.7 to be precisely adjusted.

[0090] The size of the sealing surface 2.2.7 required to ensure the required service life can be determined experimentally. As a first guideline, a size of 14 mm is used. 2 specified.

[0091] The seat plate 2.5, with its seat plate opening 2.5.1, has two plane-parallel end faces, which are preferably produced on both sides by surface lapping. The seat plate 2.5 is preferably made of a ceramic material, preferably ZrO2. A guideline for its thickness is 4 mm.

[0092] The dimensioning of the seat plate opening 2.5.1 is carried out as described in DE 10 2020 127 020 B3. As a guideline for the required cross-sectional area [mm 2 ] relative to the volume [dm 3 ] of the individual cylinder, which is supplied with fuel gas by injector 2, a guideline value of approx. 4.3 mm 2 / dm 3 This value applies to the following boundary conditions: Speed ​​n = 2200 min -1 , indicated specific piston work w i = 1.6 kJ / dm 3 , indicated efficiency 35%, Injection crank angle interval 90° (corresponding to a quarter engine revolution) Injection pressure 20 bar.

[0093] The stroke of the piston 2.2 is preferably selected such that the resulting cylindrical inflow area is larger than the cross-sectional area of ​​the seat plate opening 2.5.1. This condition is met if the stroke height of the piston 2.2 is greater than a quarter of the diameter of the seat plate opening.

[0094] The stroke h of the punch 2.2 is adjusted via the distance between a stop surface 2.2.4 on the punch 2.2 and a stop surface 2.3.1 on the spring holder 2.3 (see Fig. 9).

[0095] The closing spring 2.4 imparts a closing force to the piston 2.2. It must be dimensioned such that the piston 2.2 is pressed against the seat plate 2.5 with sufficient residual force, even at the highest possible pressure in the combustion chamber.

[0096] The spring holder 2.3, which receives and supports the closing spring 2.4, is located on an upper end face of the injector housing 2.1 (see Fig. 4 and Fig. 7).

[0097] The seat plate 2.5 rests against a lower end face of the injector housing 2.1. When installed, the spring retainer 2.3, the injector housing 2.1, the seat plate 2.5, and the sealing disc 2.7 are axially clamped against one another by the claw 3, and the sealing disc 2.7 is pressed against the contact surface 1.4.2. It is also conceivable to connect the spring retainer 2.3 and the housing 2.1 either detachably (screwed) or permanently.

[0098] The nozzle 2.6 has an external thread 2.6.2; it is screwed into the cylinder head 1 until a collar contact surface 2.6.3 rests on the contact surface 1.4.2 (see Fig. 3) of the cylinder head 1. To apply a tightening or loosening torque, the nozzle 2.6 has a driver 2.6.1, which is preferably designed as a hexagon socket.

[0099] Preferably, the sealing disc 2.7 has a slightly greater thickness than a collar 2.6.5 of the nozzle 2.6. This ensures that the second gas guide channel 101 is sealed from the combustion chamber.

[0100] The nozzle 2.6 has several exhaust openings 2.6.4. The number, positioning, and orientation of these openings can be adjusted and optimized for the mixture formation process. The exhaust openings 2.6.4 are manufactured by drilling, milling, or EDM.

[0101] The sum of the cross-sections of all blow-out openings 2.6.4 is preferably slightly larger than the cross-section of the seat plate opening 2.5.1.

[0102] It is also possible to manufacture the nozzle using 3D metal printing. This makes it possible to design the exhaust openings (2.6.4) not as cylindrical, but as curved tubes, for example, to impart a swirling motion to the fuel gas. The cross-section can also be shaped like an ellipse, for example. Such measures can further improve mixture formation.

[0103] The ultimately optimal design of the exhaust openings 2.6.4 must be determined by 3D flow simulations and confirmed during engine operation.

[0104] The nozzles 2.6 according to the invention can be replaced without disassembling the individual cylinder heads 1, which is a great advantage, especially during the development phase. Furthermore, an injector 2 can be optimally adapted to a specific engine via the nozzle configuration.

[0105] The injector housing 2.1 is partially exposed to hydrogen gas and should therefore be made of a material that is not prone to hydrogen embrittlement. Alternatively, a material susceptible to embrittlement can be used if it is coated with a suitable barrier layer. Water condensate is expected to form in the lower area, so appropriate corrosion resistance must also be ensured there.

[0106] The piston 2.2 is pressurized with hydrogen gas in the area below the annular groove 2.2.8 and in the leakage vent hole 2.2.1. Contact with water occurs only on the outer surface below the annular groove. Therefore, the same requirements apply to the piston 2.2 with regard to the choice of material and coating as for the injector housing 2.1.

[0107] Furthermore, care must be taken to prevent the guide surfaces 2.1.2 and 2.2.3 from welding together, which is also known as "galling." Appropriate material pairings or coatings must be selected in this case.

[0108] The sealing surface 2.2.7 of the punch 2.2 is subjected to shock loads and should have corresponding wear resistance.

[0109] In an advantageous embodiment of the injector, the plunger 2.2 and the injector housing 2.1 are made of stainless steel. A suitable material, for example, is stainless steel with the material identification number 1.4404, which is designated 316L according to the US AISI standard.

[0110] To prevent seizure, the punch is provided with a so-called diamond-like carbon (DLC) coating at least on the guide surface 2.2.3.

[0111] Alternatively, the stamp 2.2 can also be coated with so-called chemical nickel. To prevent the coating from chipping off in the area of ​​the sealing surface 2.2.7, this area is covered with a protective cap, for example, during the coating process.

[0112] In the illustrated injector design, the individual parts are first assembled in the cylinder head. The assembly sequence is as follows: Screw in the nozzle 2.6. Place the sealing washer 2.7. Place the seat plate 2.5. Insert the injector housing 2.1 with the pre-mounted plunger 2.2. Align the injector housing 2.1 so that the lance 5 can be mounted. Insert the lance 5 and secure it with the union nut 6. Place the firing spring 2.4. Place the spring retainer 2.3. Place the clamp 3 and screw it down with screw 4.

[0113] Alternatively, the spring retainer 2.3 could be screwed onto the injector housing 2.1. This would preload the closing spring 2.4.

[0114] In a further variant, the seat plate 2.5 can be securely joined to the injector housing 2.1. Preferably, the seat plate 2.5 is pressed into a corresponding recess on the injector housing 2.1.

[0115] In another variant, the nozzle 2.6 could also be joined to the injector housing 2.1, e.g., by screwing it to the injector housing 2.1. Then the seat plate 2.5 is held over the nozzle 2.6 and no longer needs to be pressed.

[0116] In the lower part of the Fig. Figure 10 shows a hydraulic circuit diagram of the hydraulic control system 202. It comprises a tank 202.1. Different pressure fluids can be used as the control fluid. Preferably, the lubricating oil already present in the internal combustion engine is used as the control fluid. Preferably, the lubricating oil is taken directly from the engine's oil pan. In this case, the Fig. The tank 202.1 shown in Figure 10 forms the engine's oil pan. A hydraulic pump 202.2 draws control fluid from the tank 202.1 via the control fluid intake line 202.8 and delivers it to the control fluid pressure line 202.7. Alternatively, this pump can also draw lubricating oil downstream of the engine's lubricating oil pump. This has the advantage that a certain pre-pressure is already present at the hydraulic pump 202.1. The hydraulic pump preferably operates according to the displacement principle. Suitable pump types include internal gear pumps, external gear pumps, trochoid pumps, all variants of piston pumps, and diaphragm pumps. Hydraulic pumps are standard components in oil hydraulics. They are offered with different delivery capacities and discharge pressures.

[0117] A pressure relief valve 202.3 is connected to the control fluid pressure line 202.7, ensuring a constant pressure level in the control fluid pressure line 202.7. Pressure relief valves are standard components in oil hydraulics and are therefore very familiar to the relevant specialist.

[0118] Furthermore, a hydraulic pressure accumulator 202.4 is connected to the control fluid pressure line 202.7. This reduces pressure pulsations in the control fluid pressure line resulting from intermittent control fluid withdrawals. Hydraulic pressure accumulators are standard components in oil hydraulics. Examples of suitable accumulators include bladder accumulators and piston accumulators.

[0119] One or more 3 / 2-way valves 202.5 are connected to the control fluid pressure line 202.7. Preferably, a separate 3 / 2-way valve is installed for each injector installed on the engine. The working ports 202.5.3 of the 3 / 2-way valves are each fluidically connected to the control fluid port 201.1 of the respective injector 2 via a separate control fluid working line 202.10.

[0120] The 3 / 2-way valves are preferably moved by a spring 202.5.4 into the switching position, in which the pump connection 202.5.1 is closed and the working connection 202.5.3 is fluidly connected to the tank connection 202.5.2. The tank connections 202.5.2 open into a common control fluid return line 202.9.

[0121] Preferably, the 3 / 2-way valves are actuated by an electromagnetic actuator 202.5.5. The electromagnetic actuator is controlled intermittently via an electronic control unit 202.6. In this way, the opening and closing of each injector 2, and thus the start and end of the injection process, can be controlled.

[0122] The functions of the electronic control unit 202.6 can also be implemented in an engine control unit.

[0123] As an alternative to the electromagnetic actuation of the 3 / 2-way valves, the actuation can also be purely mechanical, e.g. via a camshaft rotating at half engine speed.

[0124] Then the start and end of the blowing process cannot be freely controlled.

[0125] The injection system primarily serves to intermittently inject fuel gas into the combustion chambers. Alternatively, it can also be used to intermittently or continuously inject fuel gas into the intake ports or other areas of the intake tract.

[0126] It is also possible to provide two injectors 2 for each cylinder. The first injector 2 injects the fuel gas directly into the combustion chamber. A second injector 2 injects the fuel gas into the intake port 1.1. Whether the fuel gas is injected into the combustion chamber or into the intake port 1.1 depends on the operating point of the reciprocating internal combustion engine.

[0127] Another possible application of the injector according to the invention is the injection of fuel gas into the exhaust tract or the exhaust port 1.2 upstream of the turbine of an exhaust gas turbocharger. The injected fuel gas can be ignited by the hot exhaust gas or by an ignition source installed at the injection point. In this way, the enthalpy flow to the turbine is increased to actively accelerate the turbocharger's rotor assembly, e.g., during a load step. This can significantly improve the transient behavior of an engine. At the same time, a high air-to-combustion ratio can be maintained, which, among other things, has a positive effect on exhaust emissions.

[0128] Intermittent injections can be triggered one or more times per engine cycle. With direct injection, typically only one injection is triggered per cycle. Preferably, injection begins only after the air intake valve is closed to prevent backfiring.

[0129] If there is no tendency for backfiring at an engine operating point and the air displacement effect is not disruptive, injection can also be started during the intake phase. This is the case at partial load. This increases the time for mixture homogenization.

[0130] Fig. Figure 13 shows an advantageous embodiment of a hydraulic control system of the gas injection system described in this invention. The hydraulic control system is designed as an example for use in an 8-cylinder engine with a V configuration. It is placed between the two cylinder banks in the inner V. The hydraulic pump 10.2 is driven by a gear from the engine's timing drive. The hydraulic pump is designed so that it can be installed as a replacement for a high-pressure diesel injection pump. An external gear pump is used as the pump type here.

[0131] The 3 / 2-way valves, the pressure relief valve 10.9 and the hydraulic pressure accumulator 10.3 are integrated in the valve block 10.1 or attached to it.

[0132] The valve block 10.1 is connected to the Fig. 13, not shown. The control fluid return line 10.6 is designed as a tubular construction and directs excess delivered or diverted control fluid back into the gear case of the cylinder crankcase (not shown) without pressure.

[0133] Control fluid flows to hydraulic pump 10.2 via control fluid intake line 10.4. A connector 10.4.1 is screwed into a connection point in the cylinder crankcase (not shown) pressurized with oil. Control fluid flows from hydraulic pump 10.2 to valve block 10.1 via control fluid pressure line 10.5. The control fluid working lines 10.7 connect the working ports 10.1.1.2 of valve block 10.1 to lance 5 of the respective injector 2. Preferably, all control fluid working lines 10.7 are approximately the same length.

[0134] Fig. 14 shows an advantageous embodiment of the valve block 10.1 from Fig. 13. In this example, the valve block housing 10.1.1 is designed as a milled part, preferably made of aluminum. The 3 / 2-way valves are designed as sliding seat valves, consisting of a valve cylinder 10.1.2, a valve piston 10.1.3, and a valve spring 10.1.5.

[0135] The clearance between the valve cylinder and the valve piston is on the order of 1 / 100 of a mm. The valve piston 10.1.3 is preferably made of aluminum and is provided with a wear protection coating. This can be a hard anodizing treatment, also known as hard anodizing or hard coating.

[0136] The stroke of the valve piston 10.1.3 is adjusted via the stop piece 10.1.4. This should preferably be in the order of 2 mm. The valve is actuated by electromagnetic actuators 10.8. These have tappets 10.8.1, which, when electrically energized, exert an actuating force on the valve piston 10.1.3 and move it into the Fig. 14 shown switching position.

[0137] If the current supply is interrupted, the valve spring 10.1.5 pushes the valve body 10.1.3 back to its original position.

[0138] The valve block housing 10.1.1 has a central pressure oil gallery 10.1.2, through which control fluid flows to all valve cylinders 10.1.2. The control fluid working lines 10.7 are connected to the working ports 10.1.1.2. In the switching position shown, the working ports 10.1.1.2 are fluidly connected to the pressure oil gallery 10.1.2. The control fluid pressure is thus applied to the pressure chamber 103 of the respective injector 2 to open it and release fuel gas.

[0139] In the non-energized initial position of the valve, the respective working port 10.1.1.2 is fluidly connected to the space above the valve block housing 10.1.1. The control fluid flowing back from injector 2 thus enters the space above the valve block housing. It can flow back pressureless via the control fluid return line 10.6 into the cylinder crankcase (not shown).

[0140] The base plate 10.1.6 is screwed to the lower flange surface of the valve block housing 10.1.1. It features leakage channels 10.1.6.1, which are fluidically connected to the control fluid return line 10.6. The upper section of the valve block 10.1 is closed by a cover (not shown).

[0141] The delivery volume of the hydraulic pump 10.2 is dimensioned such that there is always an excess supply of control fluid under all conditions.

[0142] In this case, the hydraulic pump 10.2 is driven by the crankshaft, with the gear ratio between the hydraulic pump and the crankshaft being 1:1. This means they have the same rotational speed; that is, the pump chamber volume is pumped once for each revolution of the crankshaft.

[0143] In a four-stroke reciprocating piston engine with eight cylinders, four fuel gas injections occur within one crankshaft revolution. This means that the control fluid volume taken from the injectors is four times the displacement volume of an injector 2. The displacement volume is the product of the effective area and the stroke of the piston 2.2.

[0144] If multiple injections are to be possible, the required flow volume increases accordingly. Furthermore, leakage and the hydraulic efficiency of the pump must be taken into account during the design.

[0145] With a fixed thermal state of the combustion gas upstream of the injectors and when a supercritical pressure ratio is present, the injected combustion gas quantity is proportional to the injector's opening time cross-section. This opening time cross-section corresponds to the integral of the opening cross-sectional area over time. To adjust the engine load, the combustion gas mass injected per working cycle and per cylinder must be precisely and reproducibly adjustable within a range of 5 to 100% of the maximum quantity. This corresponds to a quantity spread of 1:20. Such a large spread will be difficult to achieve across the opening time cross-section. Therefore, the combustion gas connection pressure should preferably be variably adjusted using a pressure reducer, preferably electronically controlled. At least two pressure stages should be provided. In the lower load range, a low combustion gas pressure of, for example,10 bar is selected, and a pressure of 20 bar is set in the upper load range. Ideally, the fuel gas pressure can also be continuously regulated. List of reference symbols 1 single cylinder head 1.1 Inlet channel 1.2 Exhaust channel 1.3 Spark plug receptacle 1.4 Injector mounting slot 1.4.1 Injector mounting shaft, axle 1.4.2 Single cylinder head, injector mounting shaft, contact surface 1.5 Horizontal drilling 1.6 Fuel gas connection 1.7 intake valve 1.8 exhaust valve 2 injectors 2.1 Injector housing 2.1.1 Inlet bore 2.1.2 Guide surface 2.1.3 Vent hole 2.2 Stamp 2.2.1 Longitudinal drilling 2.2.2 Relief borehole 2.2.3 Guide surface 2.2.4 Stop surface 2.2.5 External release 2.2.6 Internal exemption 2.2.7 Sealing surface 2.2.8 Ring groove 2.2.9 Radially offset area 2.2.10 Piston 2.3 Spring mount 2.3.1 Stop surface 2.3.2 Ventilation opening 2.4 Closing spring 2.5 Seat plate 2.5.1 Seat plate opening 2.5.2 upper front surface 2.5.3 lower front surface 2.6 Nozzle 2.6.1 Driving surface 2.6.2 External thread 2.6.3 Collar contact surface 2.6.4 Blow-out hole 2.6.5 Bund 2.7 Sealing disc 2.8 First piston seal 2.9 Second piston seal 2.10 O-ring 3 claws 4 screw 5 Lance 5.1 Pipe part 5.2 Cone part 5.3 first O-ring 5.4 second O-ring 6 union nut 7 Spark plug 10 Hydraulic control system 10.1 Valve block 10.1.1 Valve block housing 10.1.1.1 Pressure oil gallery 10.1.1.2 Working connection 10.1.2 Valve cylinder 10.1.3 Valve piston 10.1.4 Stop piece 10.1.5 Valve spring 10.1.6 Base plate 10.1.6.1 Leakage channel 10.2 Hydraulic pump 10.2.1 Gear 10.3 hydraulic pressure accumulator 10.4 Control fluid intake line 10.4.1 Connector 10.5 Control fluid pressure line 10.6 Control fluid return line 10.7 Control fluid working line 10.8 electromagnetic actuator 10.8.1 Tappet 10.9 Pressure relief valve 10.10 Holder 100 First gas duct 101 Second gas duct 102 Control fluid guide channel 103 Printing room 104 spring chamber 105 Sealing gap 106 Arrow opening direction 200 direct injection system 201 Injector 201.1 Control fluid connection 201.2 Fuel gas connection 201.3 Leakage connection 201.4 Fuel gas leak 202 Hydraulic control system 202.1 Tank 202.2 Hydraulic pump 202.3 Pressure relief valve 202.4 hydraulic pressure accumulator 202.5 3 / 2-way valve 202.5.1 3 / 2-way valve, pump connection 202.5.2 3 / 2-way valve, tank connection 202.5.3 3 / 2-way valve, working connection 202.5.4 3 / 2-way valve, spring 202.5.5 3 / 2-way valve, electromagnetic actuator 202.6 Electronic control unit 202.7 Control fluid pressure line 202.8 Control fluid intake line 202.9 Control fluid return line 202.10 Control fluid working line QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] DE 10 2020 127 020 B3 [0011, 0092]

Claims

[1] Injector for a fuel gas comprising a valve and a hydraulically operated actuator, wherein the injector (2) comprises a nozzle (2.6) and a one-part or multi-part housing (2.1), characterized by , that a first sealing element (2.7) is provided in the region of the valve and a second sealing element (2.10) is provided in the region of the actuator, that at least one inlet bore (2.1.1) is formed in the housing (2.1) between the first sealing element (2.7) and the second sealing element (2.10), that a lance (5) is sealingly connected to the housing (2.1), and that the lance (5) is hydraulically connected to the actuator (). [2] Injector according to claim 1, characterized bythat it comprises a plunger (2.2) and a closing spring (2.4), that a sealing surface (2.2.7) is formed at a first end of the plunger (2.2), and that the actuator comprises a piston (2.2.10) which is arranged at an end of the plunger (2.2) opposite the sealing surface (2.2.7), that the piston (2.2.10) is guided in the injector housing (2.1) in a sealing and axially displaceable manner, that a spring force exerted by the closing spring (2.4) on the plunger (2.2) seeks to move the plunger (2.2) in the direction of a seat plate (2.5), and that the piston (2.2.10) delimits a pressure chamber (103). [3] Injector according to claim 2, characterized by that the pressure chamber (103) is hydraulically connected to the lance (5), and that a hydraulic force exerted by the hydraulic fluid in the pressure chamber (103) on the piston (2.2.2) is directed opposite to the spring force exerted by the closing spring (2.4) on the plunger (2.2). [4] Injector according to one of claims 2 or 3, characterized by that the sealing surface (2.2.7) interacts with the seat plate (2.5) in such a way that when the valve is closed, a connection between the at least one inlet bore (2.1.1) and the nozzle (2.6) is interrupted, and that when the valve is open, fuel gas flows through the at least one inlet bore (2.1.1) and the nozzle (2.6). [5] Injector according to one of the preceding claims, characterized by that a leakage discharge bore (2.2.1) and at least one relief bore (2.2.2) are formed in the piston (2.2), and that both leakages of hydraulic fluid from the pressure chamber (103) and gas leakages from the valve can be discharged via the at least one relief bore (2.2.2) and the leakage discharge bore (2.2.1). [6] Injector according to one of the preceding claims, characterized bythat the closing spring (2.4) is accommodated in a spring chamber (2.3) and that the leakage discharge bore (2.2.1) opens into the spring chamber (2.3). [7] Injector according to one of the preceding claims, characterized by that the valve opens outwards or inwards. [8] Injector according to one of the preceding claims, characterized by that the housing (2.1) has a rotationally symmetrical outer contour at least in the region of the second sealing element (2.10). [9] Reciprocating piston internal combustion engine comprising at least one cylinder and at least one cylinder head (1), wherein each cylinder head (1) comprises at least one inlet channel (1.1), a receiving shaft (1.4) for an injector (2), as well as a fuel gas connection (1.6) and a horizontal bore (1.5), wherein the horizontal bore (1.5) opens into the receiving shaft (1.4), wherein the fuel gas connection (1.6) opens into the horizontal bore (1.5) and wherein the lance (5) is arranged in the horizontal bore (1.5), and wherein an injector (2) according to one of the preceding claims is present in the receiving shaft (1.4). [10] Reciprocating piston internal combustion engine according to claim 9, characterized by that a first gas guide channel (100) is formed between the lance (5) and the horizontal bore (1.5), and that the fuel gas connection (1.6) opens into the first gas guide channel (100). [11] Reciprocating piston internal combustion engine according to claim 9 or 10, characterized bythat an annular second gas guide channel (101) is formed between the injector (2) and the receiving shaft (1.4), and that the horizontal bore (1.5) or the first gas guide channel (100) opens into the second gas guide channel (101) and the inlet bore (2.1.1) opens into the second gas guide channel (101). [12] Reciprocating piston internal combustion engine according to one of claims 8 to 11, characterized by that the lance (5) of each injector (2) is hydraulically connected to a hydraulic control system (202), and that the hydraulic control system (202) controls the pressure (pctr) in the lance (5) of each injector (2). [13] Reciprocating piston internal combustion engine according to claim 12, characterized by that the hydraulic control system (202) comprises a control unit (202.6) for controlling the at least one injector (2), and that the control unit (202.6) is designed and configured to carry out a method according to one of the method claims. [14] A method for operating a reciprocating internal combustion engine according to any one of claims 7 to 12, comprising the steps: - Determination of the duration and position of the injection process depending on the torque requirement [Nm] and / or the speed [rpm] of the reciprocating internal combustion engine, - Controlling the injector(s) (2) so that they are opened according to the previously determined duration and position of the injection process. [15] Method according to claim 14, characterized by that at the beginning of an injection process the pressure (p CTR ) in the lance (5) is increased to such an extent that the valve of the injector (2) opens. [16] Method according to claim 14, characterized by that at the end of an injection process the pressure (p CTR ) in the lance (5) is lowered so far that the valve of the injector (2) closes.

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