Internal combustion engine for gaseous fuel and method for operating an internal combustion engine

Abstract

[Solution] The present invention relates to an internal combustion engine (10; 10a; 10b; 10c) for gaseous fuel, comprising: at least one combustion chamber (26) for burning gaseous fuel; a gas tank (12) in which the gaseous fuel is kept under operating pressure and can be supplied in the direction of at least one combustion chamber (26) via a supply line (14); an exhaust system (42) including an exhaust line (44) and an exhaust catalyst (46), wherein the exhaust line (44) is connected to at least one combustion chamber (26); and an intake path (34) including an intake manifold (32) that can supply fresh air to at least one combustion chamber (26).

Description

Technical Field

[0001] The present invention relates to an internal combustion engine for gaseous fuels, which is characterized by a particularly advantageous release of combustible gases still present in the internal combustion engine into the atmosphere in connection with the shutdown of the internal combustion engine. Furthermore, the present invention relates to a method for operating such an internal combustion engine.

Background Art

[0002] Internal combustion engines that burn gaseous fuels, particularly hydrogen, are known from the prior art. Applicant's Patent Document 1 shows an internal combustion engine in which gaseous fuel is stored in a high-pressure tank and is formed as described in the preamble of claim 1. Hydrogen under high pressure is fed from the high-pressure tank to the internal combustion engine via a supply line, burned in the combustion chamber of the internal combustion engine, and mechanical energy is obtained from the combustion energy. The exhaust gas is led to the outside through an exhaust catalyst in the exhaust system, where in particular nitrogen oxides, but also unburned hydrogen, are decomposed. In that case, hydrogen can be introduced directly into each combustion chamber of the internal combustion engine (so-called direct injection) and mixed with the fresh air fed into the combustion chamber. Instead of this, hydrogen can already be mixed with air in the feed line and then the hydrogen-air mixture can be introduced into the combustion chamber (intake manifold injection). In addition to the original cylinder, in the area of the internal combustion engine that also has an intake path and an exhaust system for feeding fresh air, there is typically still combustible gas present after the internal combustion engine has been switched off, and this combustible gas can only be retained in the area of the internal combustion engine at very high technical costs by means of corresponding sealing measures. To avoid this cost, it is also known from the prior art to introduce the gas present in the intake or supply path into the exhaust path by so-called "purging" during the shutdown phase of the internal combustion engine and to discharge it into the surrounding environment via the exhaust catalyst.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] An internal combustion engine for gaseous fuel having the features of claim 1 according to the present invention has the advantage that, even in unfavorable situations such as engine stalling during a purge process, the risk of undesirable leakage of gas or hydrogen into the environment from the injection system is avoided while the engine is stopped. This also avoids the need to restart the engine to perform the purge process, especially in such cases.

[0005] The present invention is based on the idea of ​​purging the intake system at least partially or completely using an additional airflow from the intake manifold of the intake path to the exhaust system while the engine is stopped. This additional airflow from the intake manifold to the engine's exhaust system can be generated, for example, by a secondary air pump or compressor. Thus, a system for discharging and releasing unburned gases is provided, independent of engine operation.

[0006] Therefore, with respect to the above description, the invention relates to an internal combustion engine for a gaseous fuel having the features of claim 1, wherein the intake path is coupled to a device for generating airflow from the intake path to the exhaust system, and further includes a control device designed to operate the device for generating airflow during the switch-off and / or stop phases of the internal combustion engine.

[0007] An advantageous development of the internal combustion engine for gaseous fuel according to the present invention is described in the dependent claims.

[0008] In a first structural embodiment of an internal combustion engine used for intake manifold injection, a device for generating airflow has an intake line that opens in a region of the intake manifold close to the combustion chamber. The region close to the combustion chamber means a region in the intake manifold where injectors for injecting fuel are located, or a region that opens in the intake manifold.

[0009] A preferred development of the last proposed design involves the provision of an additional or separate intake line opening in the intake manifold or air filter region far from the combustion chamber, and the presence of a switching device that allows control of the airflow from one of the two intake lines. Such a design of the internal combustion engine allows for the optimal extraction of air or combustible gas from different regions of the intake path.

[0010] In order to remove gas from the area of ​​the internal combustion engine that supplies combustible gas to the combustion chamber when the engine stops, another variant of the internal combustion engine has a supply line coupled to a rail, from which branch lines branch off to gas injectors for each combustion chamber, and the gas injectors are designed to inject gaseous fuel into the combustion chamber or into the intake manifold in an area close to the combustion chamber, and the rail is coupled to a drain valve controllable by a control device, which discharges the gaseous fuel from the rail at least indirectly into the exhaust system. Thus, in this case, the discharge of gaseous fuel from the rail in the event of engine stop occurs directly into the exhaust system (upstream of the catalyst), and the gaseous fuel is pushed or pushed into the catalyst via a device for generating airflow and from there discharged into the surrounding environment.

[0011] In the first structural development of this modified form, the drain valve is intended to be directly connected to the exhaust system via a connecting line. This structural embodiment is particularly characterized by its ease of implementation or minimal effort.

[0012] In a solution involving more design effort, it is also conceivable that the drain valve is instead coupled to a collection container, which is designed to release the gaseous fuel within the collection container into the intake path via a connecting line using a discharge device controllable by a control device. This structural embodiment has the advantage that, when the engine is stopped, the gaseous fuel can be burned by first collecting it in the collection container and then releasing it into the intake path when the engine is restarted. This thus minimizes the consumption of gaseous fuel or its emission into the environment.

[0013] Furthermore, the present invention includes a method for operating an internal combustion engine designed according to the present invention as described herein, the method characterized in that a control device is activated by a control device for generating an airflow from the intake path to the exhaust system in order to release gaseous fuel from the intake path and exhaust system during engine stop and / or engine afterrun phase.

[0014] An advanced version of this general method involves activating a switching device to ensure that intake air is drawn from one of the two intake lines.

[0015] A preferred development of the method as described above is to additionally intend for the gaseous fuel to be led from the rail to the exhaust system via a drain valve. It is also advantageous that the gaseous fuel in the collection container is injected into the intake path when the engine is restarted.

[0016] Other advantages, features, and details of the present invention will become apparent from the following description of preferred embodiments of the present invention and from the drawings. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram of a first embodiment of an internal combustion engine according to the present invention. [Figure 2] This is a schematic diagram of an exemplary embodiment of a modified internal combustion engine. [Figure 3]This is a schematic diagram of an exemplary embodiment of a modified internal combustion engine. [Figure 4] This is a schematic diagram of an exemplary embodiment of a modified internal combustion engine. [Figure 5] This is a schematic diagram of the gas collection container used in Figure 4. [Modes for carrying out the invention]

[0018] In the diagram, elements that are the same or have the same function are given the same reference numeral.

[0019] The internal combustion engine 10 schematically shown in Figure 1 preferably uses hydrogen as a gaseous fuel or operating gas. In this case, the combustion engine or internal combustion engine 10 can be designed for both commercial and passenger vehicles. The present invention can also be used in stationary engines, "range extender" engines for hybrid vehicles, railway vehicle drive systems, marine engines, or block combined heat and power plants.

[0020] The internal combustion engine 10 includes a gas tank 12 in which a gaseous fuel is kept under operating pressure in a manner known to itself. The gas tank 12 is connected to a (gas) rail 16 via a supply line 14. A pressure sensor 17 is used to detect the gas pressure in the rail 16. A tank valve 18 and a pressure control valve 20, controllable by a control device 25, may be interposed in the connection line 14.

[0021] In the illustrated exemplary embodiment, the internal combustion engine 10 comprises an engine block having four combustion chambers 26 that burn gaseous fuel or gas, thereby generating mechanical energy in a manner known per se. In the case of so-called direct injection, for this purpose a supply line 28 extends from the rail 16 to each combustion chamber 26, and the supply line is connected to a gas injector 30. The gas injector 30 blows the gas directly into each combustion chamber 26. In the case of so-called intake manifold injection, supply lines 28a, each indicated by a dashed line and likewise connected to a gas injector 30a, extend from the rail 16, but the gas injector 30a blows the gas into the intake manifold 32 in a region close to the combustion chamber of the combustion chamber 26, i.e., outside each combustion chamber 26.

[0022] It is additionally noted for the sake of simplicity that in the illustration of FIG. 1 only one supply line 28, 28a and one gas injector 30, 30a are shown respectively. However, of course, one corresponding supply line 28, 28a and gas injector 30, 30a are provided for each combustion chamber 26.

[0023] The intake manifold 32 is a component of an intake passage 34 for supplying fresh air to the combustion chambers 26. The intake passage 34 comprises an air filter 36 through which ambient air is inhaled. Each branch pipe 38 branches from the intake manifold 32 to each combustion chamber 26, and in the case of intake manifold injection, the injector 30a blows the gas in a region close to the combustion chamber in the region of each branch pipe 38.

[0024] Furthermore, each combustion chamber 26 is connected to an exhaust line formed as an exhaust pipe 44 via an exhaust manifold 40 that is a component of the exhaust system 42. The exhaust pipe 44 opens into an (exhaust) catalyst 46. In the exhaust pipe 44, a gas sensor 48, and in the case of using hydrogen, a hydrogen sensor, are further arranged near the catalyst 46, and their signals are fed to the control device 25 as input quantities. Furthermore, the internal combustion engine 10 has a rotational speed sensor 50, and its signal is also fed to the control device 25 as an input quantity.

[0025] The intake path 34 is connected to the exhaust system 42 via a device 55 for generating airflow from the intake path 34. For this purpose, the device 55 includes, for example, a secondary air pump 56 and a secondary air valve 58, both of which are controllable by the control device 25. The secondary air pump 56 is connected to a first intake line 62 via a switching device in the form of a switching flap 60, which is controllable by the control device 25, and this first intake line draws air from the region of the air filter 36. Similarly, a second intake line 64, which opens in the region of the switching flap 60, is connected to each of the branch pipes 38 via a check valve 66 in the region where the gas injector 30a opens or injects.

[0026] Furthermore, the internal combustion engine 10 has intake valves and discharge valves, respectively, in the region of each combustion chamber 26 in a manner known to itself. The function of the internal combustion engine 10 for releasing (unburned) gases when the internal combustion engine 10 is stopped is described below.

[0027] In the first alternative configuration, when using a direct injection gas injector 30 and when the crankshaft position of the internal combustion engine 10 is known, the control device 25 recognizes the crankshaft position when the engine is stopped and, therefore, recognizes which cylinder or combustion chamber 26's discharge valve is open. In that case, the device 55 is activated so that excess gas is released from the combustion chamber 26 to the exhaust pipe 44 via these cylinders or combustion chambers 26 and discharged into the surrounding environment via the catalyst 46.

[0028] If the control device 25 does not detect the crankshaft position of the internal combustion engine 10, the deflection flap (Umlenkklappe) 60 is switched so that air is drawn in from the region of the second intake line 64. Excess gas is released through all gas injectors 30 by the opening or operation of the gas injectors 30 by the control device 25. From cylinders or combustion chambers 26 with open discharge valves, the gas flows directly to the exhaust pipe 44; from cylinders or combustion chambers 26 with open intake valves, the gas flows to the intake manifold 32; and in cylinders or combustion chambers 26 with closed intake and discharge valves, the gas is confined within the combustion chamber 26. By the operation of the device 55, both the gas from the intake manifold 32 and the gas from the exhaust pipe 44 are discharged into the surrounding environment through the exhaust path 42 and the catalyst 46. In this case, the control device 25 can control the flow rate by appropriately controlling the device 55, thereby enabling optimal purification or leaning of the gas.

[0029] When the internal combustion engine 10 uses intake manifold injection or gas injector 30a, the control device 25 adjusts the switching valve 60 so that air is drawn in from the region of the second intake line 64. Furthermore, in this case, the control device 25 can release excess gas through the gas injector 30a. The gas flows from the intake manifold 32 through the second intake line 64 to the exhaust pipe 44 and is expelled from the exhaust system 42 via the catalyst 46 by the device 55.

[0030] Figure 2 shows an internal combustion engine 10a designed as a direct injection internal combustion engine 10a using a gas injector 30. In this case, for simplicity, only a single combustion chamber 26 and a single gas injector 30 are shown in Figure 2. Furthermore, a secondary air pump 56 and a secondary air valve 58 or device 55 are shown in a simplified or schematic manner. Unlike internal combustion engine 10, internal combustion engine 10a additionally has a drain valve in the form of a purge valve 70 connected to a rail 16. The purge valve 70 is directly connected to the exhaust pipe 44 via a connection line 72. Internal combustion engine 10a has the advantage that gas can be directly introduced into the exhaust system 42 from the area of ​​the rail 16, passing alongside each combustion chamber 26. This gas is also discharged into the surrounding environment via a catalyst 46 by device 55.

[0031] The internal combustion engine 10b shown in Figure 3 differs from the internal combustion engine 10a only in that it is an intake manifold injection type and is designed with gas injectors 30a provided for each combustion chamber 26. However, in terms of function, there is no difference between the two internal combustion engines 10a and 10b.

[0032] Finally, Figures 4 and 5 show the internal combustion engine 10c, in which the purge valve 70 introduces gas into the collection container 74, with intake manifold injection corresponding to the internal combustion engine 10a as an example. The collection container 74 is also connected to the intake manifold 32 via the supply line 76. It should be noted that the internal combustion engine 10c can also be designed as a direct injection internal combustion engine 10c.

[0033] The area of ​​the collection container 74, shown in detail in Figure 5, has a check valve 78 on the side facing the rail 16. A control valve 80 is further provided in the supply line 76 to the intake manifold 32. The internal space of the collection container 74 is divided by a membrane 82. The membrane 82 seals a first sub-space 84 for containing gas from a second sub-space 86 where an inert gas, particularly nitrogen, is stored. The second sub-space 86 is divided into two sub-regions 90 and 92 by a partition wall 88, which are connected to each other by a pressure pump 94. The pressure in the second sub-region 92 is lower than that in the first sub-region 90.

[0034] Because the pressure in rail 16 is relatively high, gas can flow from rail 16 through check valve 78 into collection container 74 until pressure equilibrium is achieved. To actively supply gas to collection container 74, pressure pump 90 can supply inert (compensatory) gas from the second partial space 86 from the second partial region 92 to the first partial region 90. When the engine is restarted, the gas is released from collection container 74 and then through control valve 80 into intake manifold 32.

[0035] The internal combustion engines 10, 10a-10c described can be modified or altered in various ways without departing from the concept of the present invention. In particular, the device 55 can be operated even during the switch-off phase, that is, at the start of engine stop for the internal combustion engines 10, 10a-10c. [Explanation of Symbols]

[0036] 10, 10a, 10b, 10c Internal combustion engine 12 gas tanks 14 Supply lines 16 rails 17 Pressure Sensor 18 Tank valve 20 Pressure control valve 25 Control device 26 Combustion chamber 28, 28a supply line 30, 30a gas injector 32 Intake Manifold 34 Intake path 36 Air filter 38 Branch pipes 40 Exhaust Manifold 42 Exhaust System 44 Exhaust pipe, exhaust line 46 Catalyst 48 Gas Sensor 50 Rotation speed sensor 55. Apparatus for generating airflow 56 Secondary air pump 58 Secondary air valve 60. Switching flap, switching device 62 Intake line 64 Intake line 66 Check valve 70 Purge valve, drain valve 72 connection lines 74 Collection container 76 feeding lines 78 Check valve 80 Control Valve 82 membrane 84 The first subspace 86 Second subspace 90 subregion 92 Partial area 94 Pressure pump

Claims

1. An internal combustion engine for gaseous fuel (10; 10a; 10b; 10c) comprising: at least one combustion chamber (26) for burning gaseous fuel; a gas tank (12) in which the gaseous fuel is kept under operating pressure and can be supplied in the direction of the at least one combustion chamber (26) via a supply line (14); an exhaust system (42) including an exhaust line (44) and an exhaust catalyst (46), wherein the exhaust line (44) is connected to the at least one combustion chamber (26); and an intake path (34) including an intake manifold (32) that can supply fresh air to the at least one combustion chamber (26), An internal combustion engine characterized in that the intake path (34) is coupled to a device (55) for generating an airflow from the intake path (34) to the exhaust system (42), and a control device (25) designed to operate the device for generating the airflow during the switch-off phase and / or stop phase of the internal combustion engine (10; 10a; 10b; 10c).

2. The internal combustion engine according to claim 1, characterized in that the device (55) for generating the airflow has an intake line (64) that opens in a region close to the combustion chamber of the intake manifold (32).

3. The internal combustion engine according to claim 2, characterized in that there is another intake line (62) that opens in a region of the intake manifold (32) far from the combustion chamber or in the air filter (36), and there is a switching device (60) that enables control of the airflow from one of the two intake lines (62, 64).

4. An internal combustion engine according to any one of claims 1 to 3, characterized in that the supply line (14) is connected to a rail (16), and from the rail, a supply line (28; 28a) having a gas injector (30; 30a) branches off for each combustion chamber (26), and the gas injectors are designed to inject the gaseous fuel into the combustion chamber (26) or into the intake manifold (32) in a region close to the combustion chamber, and the rail (16) is connected to a drain valve (70) controllable by the control device (25), and the drain valve discharges the gaseous fuel from the rail (16) at least indirectly to the exhaust system (42).

5. The internal combustion engine according to claim 4, characterized in that the drain valve (70) is connected to the exhaust system (42) via a connecting line (72).

6. The internal combustion engine according to claim 4, characterized in that the drain valve (70) is connected to a collection container (74), and the collection container is designed to release gaseous fuel in the collection container (74) to the intake path (34) via a supply line (76) when the engine is started.

7. A method for operating an internal combustion engine (10; 10a; 10b; 10c) designed according to any one of claims 1 to 6, characterized in that the control device (25) operates the device (55) for generating an airflow from the intake passage (34) to the exhaust system (42) in order to release the gaseous fuel from the intake passage (34) and the exhaust system (42) during engine stop and / or afterrun phase.

8. The method according to claim 7, characterized in that by operating the switching device (60), intake air is drawn in from one of the two intake lines (62, 64).

9. The method according to claim 7 or 8, further characterized in that gaseous fuel is introduced from the rail (16) to the exhaust system (42) via the drain valve (70).

10. The method according to any one of claims 7 to 9, characterized in that when the engine is restarted, the gaseous fuel in the collection container (74) is injected into the intake passage (34).

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