Method for determining fuel leakage in a combustion chamber of an internal combustion engine

Abstract

A method for operating an internal combustion engine having one or more combustion chambers, an injection system, in particular a direct injection system, an ignition system and a starting system is proposed, which method comprises a transition of the internal combustion engine from a standstill state to a rotating state, the transition of the internal combustion engine from the standstill state to the rotating state comprising a rotationally driving by means of the starting system and an activation of an injection of fuel by means of the injection system, wherein the ignition system is activated before the injection is activated, such that, if combustible leakage fuel is present in the combustion chamber, it is combusted by means of an ignition spark provided by means of the ignition system, the internal combustion engine being provided to carry out a detection and evaluation of a measured value, which is influenced by a mechanical work produced by a combustion of a fuel-air mixture containing the leakage fuel present in the combustion chamber, in a time period in which the ignition system has been activated and the injection has not yet been activated. An internal combustion engine, which can be operated using the method, and a computing unit and a computer program for carrying out the method are also proposed.

Description

Technical Field

[0001] The present invention relates to a method for determining fuel leakage in the combustion chamber of an internal combustion engine, an internal combustion engine that can be operated using the method, and a computing unit and computer program for performing the method. Background Technology

[0002] As is well known, internal combustion engines with gasoline direct injection use high-pressure injection valves or high-pressure injectors (hereinafter referred to as "injectors") to introduce the fuel required for combustion into the combustion chamber. Injectors are typically mounted in the cylinder head. When the injector is activated, fuel is injected directly into the combustion chamber through the nozzle. Typical injection pressures for gasoline direct injection are as high as 500 bar.

[0003] Internal combustion engines use different methods to form the fuel mixture. Besides direct gasoline injection, where fuel is injected directly into the combustion chamber at high pressure, port injection is also widely used. In this method, fuel is injected at a lower pressure into the intake manifold before the intake valves and only enters the combustion chamber when fresh air is drawn in.

[0004] Even with port injection, injector valve leakage can occur after the engine is shut down. Unburned fuel then accumulates in the intake manifold. Upon the next engine start, this accumulated fuel is drawn into the cylinders, leading to increased hydrocarbon emissions, especially during cold starts when the catalytic converter has not yet reached sufficient efficiency.

[0005] When the injector is closed (i.e., not activated), the fuel is sealed relative to the combustion chamber through a suitable sealing surface. However, due to manufacturing tolerances, some leakage is usually unavoidable when the injector is closed. This leakage is referred to below as "injector leakage." In principle, this applies to both liquid fuels (such as gasoline) and gaseous fuels such as compressed natural gas (CNG), liquefied natural gas (LNG), biogas, and hydrogen. Injection is understood as the introduction of liquid or gaseous fuel.

[0006] Injector leakage is typically so small that it does not negatively impact combustion during engine operation. This is because the time between combustion cycles is very short. However, during longer shutdown periods (i.e., the period when the injector is not activated but fuel acts on it under pressure), a considerable amount of fuel can accumulate due to injector leakage. This fuel buildup in the combustion chamber is largely expelled unburned during subsequent start-up due to gas exchange. Because of the lack of sufficient temperature during cold starts, no conversion occurs in the catalytic converter, resulting in some unburned fuel being released into the environment, leading to deteriorated exhaust performance.

[0007] Besides fuel ingress due to injector leaks, ignitable fuel mixtures at startup can also be present in the combustion chamber due to leaks in the fuel tank ventilation system or crankcase ventilation system. Injector leaks typically occur cylinder-by-cylinder. Other leaks are distributed across all cylinders according to their point of introduction.

[0008] To date, due to insufficient indicators, it is not possible to reliably detect relatively small specified injector leaks. Traditional methods can only theoretically diagnose leaks when the leak is large, typically several times the specified leak value. Summary of the Invention

[0009] According to the present invention, a method for determining fuel leakage in the combustion chamber of an internal combustion engine, an internal combustion engine operable using the method, and a computing unit and computer program for performing the method are provided, having the features of the independent claim. Advantageous designs are the subject matter of the dependent claims and the following description.

[0010] The proposed method is used to determine fuel leakage in one or more combustion chambers of an internal combustion engine, the engine having said one or more combustion chambers, an injection system (particularly a direct injection system or a port injection system), an ignition system, and a starting system. The method includes switching the internal combustion engine from a stationary state to a rotating state, wherein switching the engine from a stationary state to a rotating state includes rotating the engine by means of the starting system and activating fuel injection by means of the injection system. The ignition system is activated before the injection is activated, such that if combustible leaked fuel is present in the combustion chamber, it is ignited by an ignition spark provided by the ignition system. During the period when the ignition system is activated but the injection is not, a measurement is detected and evaluated, the measurement being affected by the mechanical work produced by the combustion of a fuel-air mixture containing leaked fuel present in the combustion chamber. This fuel-air mixture may also consist substantially of leaked fuel in its fuel composition.

[0011] Leaked fuel includes, in particular, fuel present in the combustion chamber solely due to leakage, especially fuel that is not actively injected by means of injectors (direct injection and port injection). As mentioned at the beginning, leaked fuel may leak through injectors, but it may also enter the combustion chamber, for example, through the fuel tank ventilation system or crankcase ventilation system.

[0012] The core aspect of this invention is to activate the ignition in the internal combustion engine as early as possible, in any case earlier than conventional methods, so that the existing fuel-air mixture can be burned even before active injection. For this purpose, ignition is activated immediately after the engine position is detected. The ignition output then occurs, particularly in the top dead center region, thus initiating combustion at the correct timing. This combustion introduces a positive torque into the crank mechanism, on which mechanical work is generated in a standardized and reproducible manner, upon which this invention detects leaks. At top dead center, leaked fuel that may have previously been in liquid form may have largely evaporated due to the heat of compression, thus increasing its flammability even at low temperatures.

[0013] Through combustion, leaked fuel (e.g., hydrocarbons) is converted into carbon dioxide and water, and possibly carbon monoxide and nitrogen oxides, depending on the degree of combustion. For other fuels mentioned above, additional combustion products are produced, the composition and proportions of which vary depending on the degree of combustion. Combustion of leaked fuel during the time interval between ignition system activation and injection system activation generates mechanical work, which affects, for example, the engine speed, but also, for example, starter torque or starter current consumption, and can therefore be used to determine the amount of leaked fuel or, in general, its presence. Since the duration since the last start-up process or the last ignition activation time is generally known, as well as other characteristic parameters such as fuel pressure, the leakage per unit time can be determined. Depending on the engine shutdown position, this method can also prevent or at least reduce the emission of fuel (e.g., unburned hydrocarbons or hydrogen) from the combustion chamber.

[0014] Therefore, within the scope of this invention, the amount of fuel (e.g., hydrocarbons or hydrogen) accumulated during the shutdown phase due to injector leakage, as well as the amount of fuel (hydrocarbons) from other sources (crankcase ventilation, fuel tank ventilation, etc.), is burned as early as possible during subsequent startup, thus allowing the leakage amount to be determined. If the leakage amount cannot be quantitatively determined, at least the presence of leaked fuel sufficient to trigger combustion can be identified. Based on this, by introducing appropriate measures, the proportion of unburned fuel (hydrocarbons or hydrogen) during startup can be reduced. Consequently, the emission of harmful substances, i.e., fuel (e.g., hydrocarbons or hydrogen), is also kept as low as possible.

[0015] In the proposed method, the measured values ​​or corresponding curves of the mechanical work produced by the combustion of the fuel-air mixture in the combustion chamber are correlated with the engine location. This correlation allows identification of the combustion chamber where an increase in leaked fuel can be observed. This increased leak is particularly caused by a leaking high-pressure injector, as, as mentioned at the beginning, other leaks typically do not affect a single combustion chamber.

[0016] In the proposed method, as previously described, the ignition system is activated to provide an ignition spark when the piston allocated to the combustion chamber is at top dead center. This allows for standardized detection of the generated mechanical work. For this purpose, engine position detection can be performed in a manner known per se, particularly before activating the ignition system or providing the corresponding ignition spark. This can be used to identify leaking high-pressure injectors.

[0017] In the proposed method, as described above, for example, speed signals, starter torque and / or starter current consumption, and other parameters derived therefrom, can be used as measured values, which are affected by the mechanical work generated by the combustion of the fuel-air mixture in the combustion chamber. There is no need to use other sensor values ​​or complex measurements (evaluating multiple metrics) because the aforementioned signals or values ​​are typically already present in the internal combustion engine.

[0018] In the proposed method, no fuel is introduced into the combustion chamber before fuel injection is activated by manipulating the injector. Therefore, the combustion resulting from the pre-activation of the ignition system involves only the amount of fuel introduced via leakage during the static state.

[0019] In the proposed design, the internal combustion engine can be part of a hybrid vehicle, which also has an electric motor for driving the hybrid vehicle. The internal combustion engine transitions from a stationary state to a rotating state after the hybrid vehicle has entered pure electric operation. Significant leakage may also occur during the corresponding pure electric operation phase.

[0020] In the proposed method's design, the injector can have a nominal or measured leakage rate, allowing for the estimation of the amount of fuel introduced through leakage from the corresponding injector. The proposed method and its design can then be used to determine whether the nominal or measured leakage rate has been exceeded. This is particularly relevant for commonly specified leakage rates, and at least when the leakage is not merely very small. In response, certain measures may and must be taken, such as replacing or repairing the relevant injector.

[0021] The proposed internal combustion engine has one or more combustion chambers, a fuel injection system, an ignition system, and a starting system. The internal combustion engine is configured to transition from a stationary state to a rotating state, the transition including rotation via the starting system and activation of injection via the injection system. The internal combustion engine is configured to activate the ignition system before activating injection, such that if combustible leaked fuel is present in the combustion chamber, it is ignited by an ignition spark provided by the ignition system. Furthermore, the internal combustion engine is configured to detect and evaluate a measurement value affected by the mechanical work generated by the combustion of a fuel-air mixture containing leaked fuel present in the combustion chamber during the period between the activation of the ignition system and the pre-activation of injection.

[0022] This internal combustion engine is specifically configured to perform the methods described in the aforementioned different design schemes. The corresponding design schemes also benefit from the advantages described regarding the respective method variants, and therefore these advantages can be referenced.

[0023] The computing unit according to the invention, such as a control unit for a motor vehicle, is particularly configured, in terms of programming technology, to cause an internal combustion engine to perform all the method steps described in the foregoing design. The features and advantages of the computing unit can also be referred to the above description.

[0024] This also applies to the proposed computer program, which, when executed on the computing unit, causes the computing unit to induce the internal combustion engine to perform all the method steps described in the aforementioned design scheme.

[0025] It is advantageous to implement the method of the invention in the form of a computer program or computer program product having program code for performing all method steps, because this results in particularly low costs, especially when the control unit used for execution is also used for other tasks and thus already exists.

[0026] Finally, a machine-readable storage medium is provided on which the computer program described above is stored. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical, and electrical memories, as are known in the art. The program can also be downloaded via a computer network. Such downloading can be wired or wireless.

[0027] Other advantages and design solutions of the present invention will become apparent from the specification and drawings.

[0028] The present invention is illustrated schematically in the accompanying drawings based on embodiments, and is described below with reference to the accompanying drawings. Attached Figure Description

[0029] Figure 1 The internal combustion engine is shown in a partial view.

[0030] Figure 2 A partial view shows an internal combustion engine operated according to a design scheme not of this invention.

[0031] Figure 3 The diagram illustrates three states of an internal combustion engine controlled according to the proposed design.

[0032] Figure 4 illustrates various aspects of the approach based on the proposed design scheme in the form of a signal diagram.

[0033] Figure 5 The various aspects of the approach based on the proposed design scheme are illustrated in the form of signal diagrams.

[0034] Figure 6 The various aspects of the approach based on the proposed design scheme are illustrated in the form of signal diagrams. Detailed Implementation

[0035] The embodiments described below are provided only to help the reader understand the claimed and previously set features. They are merely representative examples and should not be considered exhaustive and / or limiting of the features of the invention. It should be understood that the advantages, implementations, functions, features, structures, and / or other aspects described above and below should not be considered as limitations on the equivalents of the claims, and other implementations and modifications may be used without departing from the scope of the claimed invention.

[0036] Different embodiments of the present invention may include, have, other suitable combinations of the elements, components, features, parts, steps, devices, etc., constitute or substantially constitute them, even if such combinations are not specifically described herein.

[0037] The explanations regarding apparatus, devices, arrangements, systems, etc., according to embodiments of the present invention can also be applied to methods, processes, modes, etc., according to embodiments of the present invention, and vice versa. Components, method steps, etc., that are identical, functionally identical, correspond to each other, have the same structure, or are similarly constructed, may be represented by the same reference numerals.

[0038] The conjunction "and / or" if it precedes the last element in an enumeration should be understood to mean that all terms in the enumeration can be combined with each other in any way. In other words, "A, B and / or C" means "A and / or B and / or C" or "at least one of the elements A, B, and C in any combination".

[0039] As previously stated, a core aspect of this invention is to activate the ignition of the gasoline engine as early as possible, thereby enabling combustion of the fuel-air mixture present in the combustion chamber even without active injection. Ignition of the gasoline engine can be activated immediately upon detection of the engine position. The engine position can be determined based on inertial coasting recognition still derived from previous driving cycles, or detected using crankshaft and / or camshaft sensors when the crankshaft begins to rotate. Depending on the configuration, position determination occurs no later than 180° kW (crankshaft angle) or 360° kW. By knowing the engine position, the ignition coil can then be positioned correctly so that the ignition spark ignites at the spark plug at the desired time point (top dead center). Thus, even without active injection, it is possible to ignite any fuel-air mixture that may be present (from leaks).

[0040] Through combustion, fuel (hydrocarbons) is converted into carbon dioxide and water, and possibly carbon monoxide and nitrogen oxides, depending on the degree of combustion. Hydrocarbons may remain. For fuels with different chemical compositions, such as carbon-free fuels like hydrogen, exhaust gases will contain unburned hydrogen, water and water vapor, nitrogen oxides, and carbon dioxide, carbon monoxide, and particulate matter due to partially burned lubricants. Depending on the engine's off position, this can avoid or at least reduce the emission of unburned fuel (hydrocarbons, hydrogen).

[0041] Figure 1 A partial view shows an internal combustion engine 100, more precisely a cylinder 10 with a piston 11 and a combustion chamber 12, as well as an injector 13, a spark plug 14, an intake valve 15, an exhaust valve 16, an intake manifold 17, and an exhaust manifold 18. An exemplary direct injection system 20, an ignition system 30, and a starting system 40 are shown in a very simplified manner, wherein the injector 13 is part of the direct injection system 20, and the spark plug 14 is part of the ignition system. The internal combustion engine 100 can, in particular, be part of a hybrid vehicle, such that the starting system 40 can also include an electric motor for electrically driving the hybrid vehicle. A control unit 50, schematically shown, is used to control the internal combustion engine 100.

[0042] The internal combustion engine 100 shown herein with a direct injection system 20 is one embodiment of the internal combustion engine 100, in which the problems described at the beginning may exist, and the solutions described herein are intended to improve these problems. As mentioned, the problem may also exist in an internal combustion engine 100 with an intake port injection system. Therefore, the solutions proposed herein are also solutions for internal combustion engines 100 of this alternative embodiment.

[0043] Figure 1The diagram shows the state of the internal combustion engine 100 after a prolonged period of inactivity. Therefore, as indicated by the dots, fuel leaks from the injector 13 and accumulates in the combustion chamber over a period of time. This is due to the fuel pressure acting on the injector 13. The amount of fuel entering the combustion chamber 12 depends on the degree of seal, the elapsed time, and the fuel pressure at the injector 13.

[0044] Figure 2 Basically, it shows the relationship with Figure 1 The same components. For clarity, these components will not be explained again, and reference will be made to the [reference needed]. Figure 1 The explanation.

[0045] Figure 2 The diagram illustrates that, according to conventional methods, the internal combustion engine 100 is driven to rotate in the presence of fuel in the combustion chamber 12 until a specific speed is reached and other criteria (such as rail pressure or intake manifold vacuum) are met, without activating the injection and injectors. As indicated by arrow 11a, the piston 11 moves upward and expels the fuel from the combustion chamber 12, causing the fuel to flow out through the exhaust valve 18 into the exhaust pipe 18, as indicated by arrow 18a.

[0046] like Figure 2 As shown, the discharge of unburned fuel may lead to the aforementioned negative effects, especially because, as previously mentioned, the catalytic converter may not have reached its operating temperature, thus unburned fuel (such as hydrocarbons or hydrogen) is released into the environment.

[0047] The measures proposed here overcome these problems, such as Figure 3 Three partial views, A through C, are shown. Downward piston movement is indicated by arrow 11b, and upward piston movement by arrow 11a. In Figure 3 In partial views A through C, the results are again essentially shown respectively. Figure 1 and Figure 2 The same components are omitted from the re-illumination of the direct injection system 20, ignition system 30, starting system 40, and control unit 50 due to a lack of direct relevance. For clarity, the components shown again will not be explained further. Figure 3 Refer to again Figure 1 The explanation.

[0048] Depending on the stationary position of the internal combustion engine 100, when the internal combustion engine 100 is switched from a stationary state to a rotating state, some cylinders 10 may initially draw in more fresh air, such as... Figure 3 As shown in view A. If the rotational motion of the internal combustion engine 100 begins with the compression stroke of the cylinder 10, the leaking fuel is compressed directly along with the air that has previously coasted in the internal combustion engine 100. This is as follows: Figure 3As shown in view B. At or slightly after top dead center, the compressed fuel-air mixture is ignited and combusted, as... Figure 3 View C is shown, where the area shaded by short horizontal lines represents the combustion zone. As a result, the piston moves downwards and, through... Figure 3 In partial view C, connecting rod P transmits force to crankshaft K. Therefore, the work generated by burning leaking fuel affects torque or rotational speed. Figure 2 Compared to the steps not shown in this invention, according to the proposed design, the emitted fuel is not unburned fuel, but combustion gases, which, depending on the fuel, ideally contain only carbon dioxide and water, or in the case of hydrogen, only water or water vapor.

[0049] exist Figure 4A The text shows the involvement of... Figure 2 The diagram shows the traditional method. Figure 4B The diagrams illustrate the proposed design scheme. Figure 4A and Figure 4B In the chart, the signal or measurement value is shown relative to time (in seconds) on the horizontal axis.

[0050] Figure 4A and Figure 4B The above charts respectively involve engine speed curves, where, according to Figure 4A The crankshaft rotation begins at 30.6 seconds, meaning the internal combustion engine 100 is driven to rotate from that point onwards. According to... Figure 4A In the non-inventive method, the direct injection system 20 and the ignition system 30 are not activated until approximately 31.05 seconds later, as shown in the middle and lower diagrams, where the corresponding control signals are shown respectively.

[0051] according to Figure 4B The crankshaft begins rotating approximately 43.4 seconds prior. Around this time, from about 43.4 seconds, the ignition system 30 is activated, as shown in the diagram below. Subsequently, from about 43.9 seconds, the direct injection system 20 is activated, as shown in the middle diagram.

[0052] The proposed method and its design can, in principle, be applied to any (Otto four-stroke) internal combustion engine. In engines with gasoline or hydrogen injection, this can reduce the negative emissions caused by high-pressure injection valve leakage. Early ignition activation can be achieved within the engine control unit (via software). This implementation requires no additional components (sensors or actuators). Therefore, this invention can be used in current and future projects or engine control.

[0053] exist Figure 5In the upper chart, the curves of engine speed R and starter torque M are plotted on the vertical axis relative to time (in seconds) on the horizontal axis. In the lower chart, the position signal curves of a typical engine position sensor are plotted on the vertical axis relative to the same time axis. The start of engine rotation, such as activation of the starting system 40, is denoted by S, and the start of activation of the ignition system 30 is denoted by Z. It can be seen that at approximately 52.5 seconds, the starter torque M drops sharply, indicating a considerable amount of leaked fuel, thus creating a combustible fuel-air mixture in the combustion chamber 12.

[0054] Figure 5 The curves shown are based on a method where, once the engine location is detected, ignition is activated, causing the combustible fuel-air mixture containing leaked fuel to ignite and burn. The resulting mechanical work or corresponding torque leads to an increase in the speed gradient, such as... Figure 5 This is also evident in the above, and it leads to a reduction in starter torque, as discussed.

[0055] Figure 6 Again, the curves of speed and starter torque are shown relative to time (in seconds) on the horizontal axis, where the speed curve without fuel leakage is represented by R1, and the speed curve with fuel leakage is represented by R2. The starter torque curve without fuel leakage is represented by M1, and the starter torque curve with fuel leakage is represented by M2. From... Figure 6 As can be seen, the speed curve R2 increases due to the combustion of leaked fuel. Because of the combustion and positive engine torque, the starter torque M2 required to accelerate the engine during startup is significantly lower than the curve M1 without leaked fuel. The speed curve R1 remains constant in this region.

Claims

1. A method for determining fuel leakage in one or more combustion chambers (12) of an internal combustion engine (100), the internal combustion engine having said one or more combustion chambers (12), an injection system, an ignition system (30), and a starting system (40), the method comprising: The internal combustion engine (100) is switched from a stationary state to a rotating state, wherein switching the internal combustion engine (100) from a stationary state to a rotating state includes rotating it by means of the starting system (40) and activating fuel injection by means of the injection system, and The ignition system (30) is activated before the injection is activated, such that if there is combustible leaked fuel in the combustion chamber (12), the leaked fuel is burned by means of an ignition spark provided by the ignition system (30), and During the period when the ignition system (30) is activated but the injection is not activated, measurements are detected and evaluated, the measurements being affected by the mechanical work generated by the combustion of the fuel-air mixture containing the leaked fuel in the combustion chamber (12).

2. The method according to claim 1, wherein, The leaked fuel includes fuel present in the combustion chamber due to leakage, which enters the combustion chamber (12) via injector leakage, fuel tank ventilation system and / or crankcase ventilation system.

3. The method according to claim 1 or 2, wherein, The measured value or the corresponding measurement curve is correlated with the engine position, and the measured value is affected by the mechanical work generated by the combustion of the fuel-air mixture present in the combustion chamber.

4. The method according to any one of the preceding claims, wherein, The ignition system is activated to provide the ignition spark when the piston (11) assigned to the combustion chamber is at top dead center.

5. The method according to any one of the preceding claims, wherein, The engine speed signal and / or starter torque and / or starter current consumption of the internal combustion engine are used as the measured values, which are affected by the mechanical work generated by the combustion of the fuel-air mixture present in the combustion chamber.

6. The method according to any one of the preceding claims, wherein, The internal combustion engine is part of a hybrid vehicle, which also has an electric motor for driving the hybrid vehicle, wherein the internal combustion engine is switched from a stationary state to a rotating state after the hybrid vehicle is in pure electric operation.

7. The method according to any one of the preceding claims, wherein, Before the injection is activated, fuel is not introduced into the combustion chamber (12) by individually manipulating the injectors (13) of the injection system.

8. The method according to claim 7, wherein, The injector (13) has a nominal or measured leakage rate.

9. The method according to any one of the preceding claims, wherein, The fuel is injected by activating an injection system configured as a direct injection system or an intake manifold injection system.

10. An internal combustion engine (100) having multiple combustion chambers (12), an injection system, an ignition system (30), and a starting system (40), wherein, The internal combustion engine (100) is configured to transition from a stationary state to a rotating state, wherein the transition from a stationary state to a rotating state includes rotating by means of the starting system (40) and activating fuel injection by means of the injection system, wherein the internal combustion engine (100) is configured to activate the ignition system (30) before activating the injection, such that if there is combustible leaked fuel in the combustion chamber (12), the leaked fuel is combusted by means of an ignition spark provided by the ignition system (30), and wherein the internal combustion engine (100) is configured to detect and evaluate a measurement value during the time period when the ignition system (30) is activated but the injection is not activated, the measurement value being affected by the mechanical work generated by the combustion of the fuel-air mixture containing the leaked fuel present in the combustion chamber (12).

11. An internal combustion engine (100) configured to perform the method according to any one of claims 1 to 9.

12. A computing unit configured to cause the internal combustion engine (100) according to claim 10 or 11 to perform all the method steps of the method according to any one of claims 1 to 9.

13. A computer program product, when executed on a computing unit according to claim 12, causes the computing unit to cause the internal combustion engine (100) to perform all the method steps of the method according to any one of claims 1 to 9.

14. A machine-readable storage medium having stored thereon a computer program product according to claim 13.

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