Method for operating an internal combustion engine

Abstract

Method for operating an internal combustion engine with multiple cylinders, namely a method for determining the component-selective oil consumption of the individual components of the internal combustion engine, in particular individual cylinders and / or turbochargers, wherein each component of the internal combustion engine for which a component-selective oil consumption determination is to be carried out is assigned an individual exhaust gas sensor, wherein each exhaust gas sensor is exposed to a reference gas for a defined period of time during operation of the internal combustion engine and subsequently again to exhaust gas, wherein a component-specific sensor drift is determined for each exhaust gas sensor, and wherein the component or components exhibiting increased oil consumption relative to the other component or components are determined from the component-specific sensor drift of all exhaust gas sensors.

Description

[0001] The invention relates to a method for operating an internal combustion engine with several cylinders, namely a method for determining a cylinder-selective oil consumption of the cylinders of the internal combustion engine. Internal combustion engines, such as

[0002] Marine diesel engines must comply with increasingly stringent emission limits. In the context of meeting these limits, it is crucial to determine the oil consumption of individual engine components. This is because oil, whether burned or unburned, can enter the exhaust aftertreatment system, damaging components such as catalytic converters and thus impairing the effectiveness of the exhaust gas purification. Oil contains additives like phosphorus, zinc, and calcium, which can damage the catalytic converters. Therefore, determining the oil consumption of individual engine components allows for preventative measures, such as initiating appropriate maintenance, to counteract increased oil consumption and thus avoid damage to the exhaust aftertreatment system or the engine itself.

[0003] So far, practical experience has only shown that the total oil consumption of an internal combustion engine can be determined, for example, using level sensors in an engine oil tank. However, determining the total oil consumption in this way does not allow for attributing the oil consumption to individual components of the internal combustion engine, such as individual cylinders.

[0004] Methods are known from DE10 2005 056 152 A1, DE10 2006 058 880 A1 and DE10 2009 000 298 A1 which compensate for the drift of exhaust gas sensors during the operation of an internal combustion engine or which calibrate these sensors.

[0005] Based on this, the present invention aims to create a novel method for operating an internal combustion engine, with the help of which the cylinder-selective oil consumption of the cylinders of the internal combustion engine can be determined.

[0006] This problem is solved by a method for operating an internal combustion engine according to claim 1. According to the invention, each cylinder of the internal combustion engine, for which a cylinder-selective determination of oil consumption is to be carried out, is assigned an individual exhaust gas sensor, wherein each exhaust gas sensor is exposed to a reference gas for a defined period of time during operation of the internal combustion engine and subsequently again to exhaust gas, wherein a cylinder-specific sensor drift is determined for each exhaust gas sensor, and wherein the cylinder or cylinders that exhibit increased oil consumption relative to the other cylinder or cylinders are determined from the cylinder-specific sensor drift of all exhaust gas sensors.The invention proposes, for the first time, a method for operating a multi-cylinder internal combustion engine that allows for the simple and reliable determination of cylinder-selective oil consumption in each cylinder. If increased oil consumption is detected in at least one cylinder, maintenance or service work can be initiated on that cylinder to reduce oil consumption and prevent potential damage to the catalysts of the engine's exhaust aftertreatment system.

[0007] According to a first advantageous embodiment of the invention, in an internal combustion engine with overrun cut-off, i.e., in an internal combustion engine in which no fuel is burned in the cylinders during overrun operation, the exhaust gas sensors are supplied with the reference gas during an active overrun cut-off, wherein the charge air leaving the cylinders serves as the reference gas, the oxygen content of which corresponds to the oxygen content of the ambient air.

[0008] According to a second advantageous embodiment of the invention, in an internal combustion engine without overrun cut-off, the exhaust gas sensors are supplied with the reference gas in such a way that the exhaust gas sensors are shielded from the exhaust gas by supplying the measuring chambers in which the exhaust gas sensors are positioned with reference gas while displacing the exhaust gas from the measuring chambers.

[0009] With both advantageous further developments of the invention, the exhaust gas sensors of the cylinders of the internal combustion engine can be easily and reliably supplied with reference gas, both on an internal combustion engine with overrun cut-off and on an internal combustion engine without overrun cut-off, in order to determine the oil consumption-dependent sensor drift for each exhaust gas sensor and thus the relative, cylinder-selective oil consumption of the cylinders in relation to the other cylinders of the internal combustion engine.

[0010] Preferably, the cylinder-specific sensor drift of all exhaust gas sensors is determined by evaluating measurement signals from the exhaust gas sensors obtained during exposure to reference gas, in particular by comparing these signals with a reference value. The deviation of the measurement signals from the reference value corresponds to the sensor drift of the exhaust gas sensors, and those cylinders whose exhaust gas sensors exhibit a relatively large sensor drift compared to the exhaust gas sensors of other cylinders show increased oil consumption. This determination and evaluation is simple and reliable.

[0011] According to an advantageous embodiment of the invention, NOx sensors and / or lambda sensors are used as exhaust gas sensors. Exhaust gas sensors designed as NOx sensors and lambda sensors are sensitive to oil additives, so these sensors exhibit a readily detectable, oil consumption-dependent sensor drift.

[0012] According to a further advantageous embodiment of the invention, in an internal combustion engine with an exhaust gas charging device comprising at least one exhaust gas turbocharger and therefore at least one compressor and at least one turbine, the sensor drift of an exhaust gas sensor positioned downstream of the respective turbine is further determined in order to ascertain the oil consumption of the respective turbine. With this embodiment of the invention, oil consumption in the region of a turbine of a charging device can also be determined. This makes it possible, in addition to the cylinder-selective oil consumption of the cylinders of the internal combustion engine, to also determine turbine-selective oil consumption and then, if the turbine-selective oil consumption is too high, to trigger a maintenance measure at the respective turbine.

[0013] Preferred embodiments of the invention are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being limited thereto. This shows: Fig. Figure 1: A schematic representation of an internal combustion engine with several cylinders and without exhaust gas charging device to illustrate the method according to the invention; and Fig. 2 : a schematic representation of an internal combustion engine with several cylinders and with Fig. 2 exhaust gas charging device to illustrate the method according to the invention.

[0014] The invention presented here relates to a method for operating an internal combustion engine, such as a marine diesel engine, namely a method for determining a cylinder-selective or cylinder-individual oil consumption of the cylinders of the internal combustion engine.

[0015] Fig. Figure 1 shows a highly schematic representation of an internal combustion engine 10 with several cylinders 11, as shown in Figure 1. Fig. 1 Number of six cylinders 11 as well as those in Fig. The grouping of these cylinders 11 into two cylinder banks shown in Fig. 1 is of an exemplary nature.

[0016] Charge air can be supplied to the cylinders 11 of the internal combustion engine 10 via a charge air line 12. Additionally, fuel is introduced into the cylinders 11 via fuel injectors (not shown). During the combustion of the fuel, exhaust gas is produced in the cylinders 11 of the internal combustion engine 10, which is discharged from the internal combustion engine 10 via an exhaust line 13.

[0017] Accordingly, each of the cylinders 11 of the internal combustion engine 10 is assigned an individual exhaust gas sensor 14. In Fig. 1. Viewed in the direction of exhaust gas flow, the exhaust gas sensor 14 assigned to the respective cylinder 11 is located downstream of the respective cylinder 11 and upstream of a junction 16 of an exhaust gas outlet channel 15 of the respective cylinder 11 with the exhaust gas line 13.

[0018] In order to establish a cylinder-individual or cylinder-selective oil consumption determination on the cylinders 11 of the internal combustion engine 10, each exhaust gas sensor 14 is exposed to a reference gas instead of exhaust gas for a defined period of time during operation of the internal combustion engine and then again to exhaust gas.

[0019] For each exhaust gas sensor, a cylinder-specific sensor drift is then determined, whereby this cylinder-specific sensor drift depends on the previous oil consumption of the respective cylinder 11 of the internal combustion engine 10, since during the combustion of engine oil in the cylinders 11 of the internal combustion engine 10, additives of the engine oil are deposited on the respective exhaust gas sensor 14 and can thus lead to its aging.

[0020] From the cylinder-specific sensor drift of all exhaust gas sensors 14, the cylinder 11(s) with increased oil consumption relative to each other cylinder 11 are identified. Maintenance or service work can then be initiated on such cylinders 11 with increased engine oil consumption.

[0021] Then, if the internal combustion engine 10 is an internal combustion engine 10 with overrun fuel cut-off, i.e., if no fuel is supplied to the cylinders 11 of the internal combustion engine 10 during overrun operation and consequently no fuel is burned in the cylinders 11 of the internal combustion engine 10 during overrun operation, exhaust gas sensors 14 are supplied with the reference gas during an active overrun fuel cut-off by using the charge air leaving the cylinders as the reference gas, the oxygen content of which then corresponds to the oxygen content of the ambient air as a result of combustion not taking place in the cylinders.

[0022] However, if the internal combustion engine 10 is an internal combustion engine without overrun fuel cut-off, the exhaust gas sensors 14 can be supplied with reference gas in such a way that they are shielded from the exhaust gas. This is achieved by supplying the measuring chambers in which the exhaust gas sensors 14 are positioned with reference gas, thereby displacing the exhaust gas from these chambers. In this context, a reference gas, e.g., ambient air, is used whose reference gas pressure in the respective measuring chamber is higher than the exhaust gas pressure in order to remove the exhaust gas from the measuring chambers. The measuring chambers are preferably supplied with reference gas continuously to prevent exhaust gas from entering the measuring chambers during the defined period in which the measured values ​​for determining the oil consumption-dependent sensor drift at the exhaust gas sensors 14 are determined.

[0023] Such a measuring chamber for an exhaust gas sensor 14 can be provided, for example, by surrounding the respective exhaust gas sensor 14 with a membrane and separating it from a flow channel of the respective exhaust gas outlet channel 15 via the membrane. In a first operating state, when no reference gas is present in the measuring chamber, exhaust gas can flow into the respective measuring chamber via such a membrane. Conversely, when the respective measuring chamber is supplied with reference gas, the exhaust gas can be removed from the measuring chamber via the membrane.

[0024] As explained above, each exhaust gas sensor 14 is exposed to a reference gas instead of exhaust gas for a defined period during operation of the internal combustion engine. Each exhaust gas sensor 14 provides a measured value or signal, and a cylinder-specific sensor drift is determined for each sensor 14 from the measurement signals obtained during this period of exposure to the reference gas. For this purpose, the measurement signal obtained during the exposure of each exhaust gas sensor 14 to the reference gas is compared with a reference value, and the deviation of the respective measurement signal from the reference value corresponds to the sensor drift of the respective exhaust gas sensor 14. Those cylinders whose exhaust gas sensors 14 exhibit a relatively large sensor drift compared to the exhaust gas sensors 14 of other cylinders 11 are characterized by increased oil consumption.A maintenance or service measure is then preferably initiated on these cylinders 11 of the internal combustion engine 10 in order to reduce the engine oil consumption of this cylinder 11 again.

[0025] NOx sensors and / or lambda sensors are used as exhaust gas sensors 14, since NOx and lambda sensors are sensitive to engine oil additives that accumulate on the exhaust gas sensor 14 of the respective cylinder 11 depending on the cylinder-specific engine oil consumption, and therefore exhibit a corresponding sensor drift. Resistive, capacitive, or current-based lambda sensors are particularly suitable.

[0026] As previously explained, the exhaust gas sensors 14 of cylinders 11 are exposed to the reference gas only for a defined period of time in order to determine the measured values ​​for the cylinder-specific sensor drift of all exhaust gas sensors 14, after which the exhaust gas sensors 14 are again exposed to exhaust gas. The exhaust gas sensors 14 are then available again for regular measurement operation to analyze the exhaust gas.

[0027] To shorten the time required to displace the reference gas from the measuring chamber of the respective exhaust gas sensor 14 and to refill the measuring chamber of the respective exhaust gas sensor 14 with exhaust gas as quickly as possible, it can be provided that exhaust gas is drawn into the measuring chamber of the respective exhaust gas sensor 14. This can be achieved, for example, by coupling the measuring chamber of the respective exhaust gas sensor 14 with a fresh air intake side of the internal combustion engine, for example, downstream of an air filter and upstream of a compressor 17 (see) of an exhaust gas turbocharger 18, if present, in the direction of fresh air flow. In such a compressor 17 (see Fig. 2) In an exhaust gas turbocharger 18, intake charge air is compressed before it is supplied to the cylinders 11 of the internal combustion engine 10 via the charge air line 12, whereby the energy required for the compression of the charge air in the compressor 17 is obtained by expanding exhaust gas, which is discharged from the cylinders 11 of the internal combustion engine via the exhaust line 13, in a turbine 19 of the exhaust gas turbocharger 18.

[0028] Due to a negative pressure that can develop downstream of an air filter during operation, exhaust gas can be drawn into the measuring chamber of the respective exhaust gas sensor 14 and subsequently into the fresh air intake. To prevent corrosion of the engine due to sulfur compounds in the exhaust gas, a sulfur trap can be integrated into the aforementioned flow connection between the respective measuring chamber of the respective exhaust gas sensor 14 and the fresh air intake side of the internal combustion engine 10.

[0029] In the case of the internal combustion engine Fig. 2. It is also possible to use a pressure difference between a pressure upstream of the turbine 19 and a pressure downstream of the turbine 19 of the exhaust gas turbocharger 18 for the rapid filling of the respective measuring chamber of the exhaust gas sensor 14 (Fig. 2). The exhaust gas sensor 14 can then be arranged in a measuring chamber that is coupled on one side to the pressure upstream of the turbine 13 and on the other side to the pressure downstream of the turbine 13. Exhaust gas is then forced into the respective measuring chamber due to this pressure ratio.

[0030] In the variant of Fig.In Figure 2, in which the internal combustion engine 10 includes an exhaust gas turbocharger 18, a further exhaust gas sensor 20 is assigned to the turbine (Fig. 2 19), specifically downstream of the turbine 19. The exhaust gas sensor 20 can, in accordance with the exhaust gas sensors 14 of the cylinders 11, be supplied with reference gas instead of exhaust gas for a defined period of time in order to determine an oil consumption-dependent sensor drift of the exhaust gas sensor 20 from the measurement signal obtained during this exposure to reference gas, and to infer the oil consumption of the turbine 19 of the exhaust gas turbocharger 18 based on this sensor drift. The evaluation of the measurement signal of the exhaust gas sensor 20 is carried out in an analogous manner to the evaluation of the measurement signals of the exhaust gas sensors 14.

[0031] The present invention thus makes it possible to determine an individual or selective oil consumption for each cylinder 11 of an internal combustion engine 10 and, optionally, additionally for each turbine 19 of each exhaust gas turbocharger 18 of the internal combustion engine 10. For this purpose, the respective exhaust gas sensors 14, 10 are exposed to a reference gas, for example, fresh air, instead of exhaust gas for a defined period of time. The measurement signals obtained during the exposure of the exhaust gas sensors 14, 20 to the reference gas are evaluated in order to determine an individual sensor drift for each exhaust gas sensor 14, 20.

[0032] This individual sensor drift depends on the previous oil consumption of the respective cylinder 11 or turbine 19, since, depending on the engine oil consumption, engine oil additives are deposited on the respective exhaust gas sensor 14 or 20, which are responsible for the sensor drift.

[0033] The sensor drift of all exhaust gas sensors 14, 20 is compared to identify the cylinder 11 of the internal combustion engine 10 and the turbine 19 of the internal combustion engine 10 that exhibits increased engine oil consumption. Maintenance or service is then initiated on this component of the internal combustion engine to reduce its oil consumption.

[0034] The invention ensures that the oil consumption of the internal combustion engine components is kept to a minimum, thus preventing engine oil that has been burned or partially burned in the cylinders 11 or engine oil that has been consumed in the turbine 19 from entering the area of ​​a catalyst of an exhaust aftertreatment system and damaging the respective catalyst.

[0035] The entire process can be carried out fully automatically via a motor control unit, in which the results can be stored and from which the results can be read out when routine maintenance work is carried out. Reference symbol list 10 Internal combustion engine 11 cylinders 12 Charge air pipe 13 Exhaust pipe 14 Exhaust gas sensor 15 Exhaust outlet channel 16 Meeting Point 17 compressors 18 exhaust gas turbochargers 19 Turbine 20 Exhaust gas sensor

Claims

[1] Method for operating an internal combustion engine with several cylinders, namely a method for determining the component-selective oil consumption of the individual components of the internal combustion engine, in particular individual cylinders and / or turbochargers, wherein each component of the internal combustion engine for which a component-selective oil consumption determination is to be carried out is assigned an individual exhaust gas sensor, wherein each exhaust gas sensor is exposed to a reference gas for a defined period of time during operation of the internal combustion engine and subsequently to exhaust gas again, wherein a component-specific sensor drift is determined for each exhaust gas sensor, and wherein the component or components that exhibit increased oil consumption relative to the other component or components are determined from the component-specific sensor drift of all exhaust gas sensors. [2] Method according to claim 1, characterized by , that in an internal combustion engine with overrun cut-off, i.e. in an internal combustion engine in which no fuel is burned in the cylinders during overrun operation, the exhaust gas sensors are supplied with the reference gas during an active overrun cut-off, whereby the charge air leaving the cylinders serves as the reference gas, the oxygen content of which corresponds to the oxygen content of the ambient air. [3] Method according to claim 1, characterized by , that in an internal combustion engine without overrun cut-off, the exhaust gas sensors are supplied with the reference gas in such a way that the exhaust gas sensors are shielded from the exhaust gas by supplying the measuring chambers in which the exhaust gas sensors are positioned with reference gas while displacing the exhaust gas from the measuring chambers. [4] Method according to claim 3, characterized bythat the measuring chambers are preferably periodically supplied with a reference gas whose reference gas pressure is higher than an exhaust gas pressure. [5] Method according to any one of claims 1 to 4, characterized by , that the component-specific sensor drift of all exhaust gas sensors is determined in such a way that measurement signals of the exhaust gas sensors obtained during the exposure of the exhaust gas sensors to reference gas are evaluated. [6] Method according to claim 5, characterized by , that the assembly-specific sensor drift of all exhaust gas sensors is determined in such a way that measurement signals of the exhaust gas sensors obtained during the exposure of the exhaust gas sensors to reference gas are compared with a reference value, whereby the deviation of the measurement signals from the reference value corresponds to the sensor drift of the respective exhaust gas sensor. [7] Method according to claim 6, characterized bythat those assemblies whose exhaust gas sensors exhibit a relatively large sensor drift compared to the exhaust gas sensors of other assemblies show increased oil consumption. [8] Method according to any one of claims 1 to 7, characterized by , that NOx sensors and / or lambda sensors are used as exhaust gas sensors. [9] Method according to any one of claims 1 to 8, characterized by , that in an internal combustion engine with an exhaust gas charging device comprising at least one compressor and at least one turbine, a sensor drift of an exhaust gas sensor positioned downstream of the respective turbine is further determined and, if necessary, compared with the drift of at least one sensor arranged upstream of the exhaust gas turbine in order to determine an oil consumption of the respective turbine.

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