Internal combustion engine comprising a device for scavenging a flow path, and method for operating such an internal combustion engine

Abstract

The invention relates to an internal combustion engine comprising: at least one combustion chamber; and at least one device, installed in the charge air path of the internal combustion engine, for compressing the engine charge air during engine operation of the internal combustion engine, characterised in that an engine controller is provided which is designed to actuate the device in such a way that, when the internal combustion engine is deactivated, it is possible to temporarily generate a scavenging air flow which extends along at least one flow path within the internal combustion engine and brings about scavenging of the flow path in order to eliminate contamination within the flow path.

Description

[0001] Internal combustion engine with a device for flushing a flow path and method for operating such an internal combustion engine

[0002] The invention relates to an internal combustion engine having at least one combustion chamber and at least one device installed in the charge air path of the internal combustion engine for compressing the engine charge air during engine operation of the internal combustion engine.

[0003] The use of gaseous fuels for long-distance trucks or mobile work machines is becoming increasingly important. Among gaseous fuels, hydrogen, for example, offers the option of a virtually climate-neutral "well-to-tank" supply. For vehicles and mobile work machines powered by hydrogen combustion engines, etc., even strict exhaust emission limits can be met with a very significant reduction in the exhaust gas aftertreatment system, which promises a significant partial compensation of the additional costs of such vehicles, mobile work machines, etc. powered by hydrogen combustion engines compared to those powered by diesel engines. Numerous modifications are already known with regard to hydrogen engines, which affect the fuel supply path (e.g., an adaptation of the fuel injectors) into the combustion chambers and those which have a direct influence on combustion (e.g.,an adjustment of the piston bowl).

[0004] The term hydrogen engines does not mean that the group of internal combustion engines under consideration is operated exclusively with pure hydrogen, but rather with a fuel that contains a certain proportion of molecular hydrogen.

[0005] Ammonia is another possible fuel with great future potential. It has long been produced on an industrial scale for other applications and a transition to renewable-based production is already technically feasible today. There is no doubt that the use of ammonia as a fuel has some disadvantages compared to hydrogen; for example, its toxic effects and its comparatively poor flammability. However, the major advantage of ammonia over hydrogen is its considerably higher volumetric energy density. Even below a temperature of -33°C, ammonia exists in liquid form. The volumetric energy density is 3.3 kWh / l, whereas the volumetric energy density of liquid hydrogen at -253°C is only 2.4 kWh / l and the volumetric energy density of pressurized hydrogen at 1000 bar is only 1.7 kWh / l.

[0006] After an internal combustion engine has been switched off, small amounts of unburned fuel and water vapor may remain in parts of the engine and within fuel lines, among other things.

[0007] • along a section of the air intake path, particularly in the case of a single or multi-point fuel supply,

[0008] • within a combustion chamber,

[0009] • along the exhaust gas path,

[0010] • along an optional exhaust gas recirculation path,

[0011] • along the blow-by path, and

[0012] • if present within a pre-chamber. Remaining unburned fuel quantities in the aforementioned areas can pose a safety risk after the internal combustion engine is shut down if the fuel used is or may be in gaseous form in one of the aforementioned areas after the engine is shut down and is a highly flammable fuel. This particularly applies to fuels with a comparatively high molecular hydrogen content.

[0013] The presence of hydrogen in fuels results in water vapor being present in the engine exhaust after it has been used in an internal combustion engine. This water vapor remains in the engine's cavities after the internal combustion engine is switched off, including in the engine periphery where the engine exhaust gases are permeated. The cooling that occurs after the engine is switched off causes condensation to form on the surfaces that were previously exposed to engine exhaust gases during engine operation. This can lead to icing after an internal combustion engine has been switched off and left idle for a certain period of time if the ambient temperature is low. Due to wetting with the condensed water or the resulting icing, the effectiveness of certain affected functional elements of an internal combustion engine can be limited or even fail completely.An example of this is a chemically active functional surface that is part of the exhaust aftertreatment system and is wetted with condensation or affected by icing. Condensation of water or widespread icing can cause an exhaust flow path, e.g., the section extending through a radiator, to freeze partially or completely.

[0014] The water vapor remaining in these areas after the engine is shut down can also cause progressive damage to the internal combustion engine, which only becomes apparent after a longer period of time through functional impairment. For example, the condensate can lead to corrosion on certain components of the internal combustion engine and / or certain peripheral components. Since the damage is particularly severe for an internal combustion engine powered by ammonia due to this causal relationship, the explanation will be based on the example of an internal combustion engine powered by ammonia-containing fuel.

[0015] As can be seen from the corresponding chemical reaction equation for the combustion of ammonia (4NH3 + 3O2 - 2N2 + 6H2O), a comparatively high amount of water vapor is released during combustion. Due to the comparatively poor flammability of ammonia, a comparatively high ammonia slip will occur when used in an internal combustion engine, despite counteracting design and operation of the internal combustion engine. This slip can only be removed at the correspondingly optimized stage in the exhaust aftertreatment system. The exhaust gas upstream of this stage contains a comparatively high amount of unburned ammonia. Furthermore, ammonia is highly soluble in water and is highly corrosive in the presence of water.This results in a particularly unfavorable chain of events when an ammonia-powered internal combustion engine is shut down, as the cooling of the surfaces previously exposed to exhaust gases during engine operation results in condensation with a relatively high amount of water. In particular, a comparatively high amount of ammonia-water mixture is present in the exhaust condensate, which, after the engine shutdown, flows along a blow-by path and within the exhaust tract upstream of the EGR stage designed to degrade the ammonia.

[0016] What type of decontamination, ie the

[0017] (i) the disposal of unburned or partially burned fuel or

[0018] (ii) Whether moisture removal is more important depends on the type of fuel used, the fuel quality, the engine oil quality, the ambient conditions of the internal combustion engine, and the wear status of the relevant engine components. For example, if we focus on the EGR path for an ammonia-fueled internal combustion engine, which operates fully satisfactorily due to its technically sound condition, and the presence of moderate ambient temperatures of, for example, 10°C, corrosion would pose the greatest risk of adverse impact.

[0019] The present invention aims to develop an internal combustion engine or an operating method for such an internal combustion engine that can eliminate, after an engine shutdown, a residual amount of unburned or partially burned fuel, combustion intermediates, and water vapor within the aforementioned ranges. The internal combustion engine or method according to the invention should be designed in such a way that the required modification / expansion is as minimal as possible compared to today's standard internal combustion engines. Ideally, equipping an internal combustion engine with the appropriate additional equipment should enable a further advantage for engine operation.

[0020] According to the invention, for an internal combustion engine having at least one combustion chamber and at least one device installed in the charge air path of the internal combustion engine for compressing the engine charge air during engine operation, it is proposed that said device also be used to purge at least one flow path of the internal combustion engine when the internal combustion engine is in the deactivated operating state. Thus, an engine control system of the internal combustion engine is configured to control the device such that a purge air flow is temporarily generated when the internal combustion engine is deactivated. The purge air flow generated by the device flows along at least one flow path functionally associated with the internal combustion engine and thereby purges it, whereby existing contamination within that flow path can be removed.

[0021] The contamination to be flushed out includes, for example, completely unburned fuel and / or a combustion intermediate of a fuel, particularly in the case of carbon-based fuels, and / or moisture, particularly from condensed water, and / or engine oil or components of engine oil or coked engine oil. The core idea of ​​the invention is to fully or largely use components for the flushing procedure that are required anyway for regular engine operation or can at least be used effectively during regular engine operation.It is therefore also conceivable that additional components are installed and integrated into the internal combustion engine, which is primarily motivated by their use during the flushing procedure, whereby these components can then also be used during regular engine operation and, in particular, can be operated temporarily as required, resulting in additional added value for regular engine operation. Consequently, no or only a minor physical modification of the internal combustion engine is necessary; ideally, it is sufficient to have a dedicated software extension within the existing engine control system to carry out the flushing process. But even if the executability of the procedure according to the invention requires additional or modified physical components, these are also used or integrated according to the invention during regular operation of the internal combustion engine.These can be used selectively, achieving added value, within the regular operation of the internal combustion engine. It is essential that the purging device can be used independently of the engine operation of the internal combustion engine, and thus a purge air flow can be generated via this device even when the internal combustion engine is switched off.

[0022] Particularly preferably, the internal combustion engine is operated with ammonia NH3 as fuel, or the fuel used contains NH3 (ammonia) with a weight fraction of at least 10%, preferably at least 30%, and particularly preferably at least 50%. Alternatively, the internal combustion engine can be operated with a gaseous fuel, preferably with a fuel that has a molecular hydrogen content of at least 10%, preferably at least 30%, and particularly preferably at least 50%. As already described in the introduction, contamination, in particular when using the aforementioned fuel types, poses an increased risk in terms of safety and component durability, which makes a corresponding purging process according to the invention urgently necessary and is very advantageously available and implementable according to the present invention.

[0023] Since the purging process is to be carried out with the internal combustion engine deactivated, a conventional exhaust gas turbocharger, whose turbine is driven by a partial exhaust gas flow, cannot be used. According to an advantageous embodiment of the invention, it is therefore proposed that at least one compressor be used within the device to generate the purge air flow, which compressor can also be operated with the internal combustion engine deactivated. Therefore, the selection falls in particular on an electrically or hydraulically driven compressor or on a compressor that can be driven correspondingly by the usual operation of a compressor in a different operating mode, wherein this compressor is integrated into the charge air path of the internal combustion engine.This at least one compressor can be used during regular engine operation, at least temporarily, for charge air compression during the working operation of the internal combustion engine, either as the sole compressor for charge air compression or in combination with an additional means for charge air compression, in particular with an exhaust gas turbocharger. In particular, the preferably electrically or hydraulically driven compressor is used during engine operation when a load-related increase in the speed-torque requirement can be more effectively met by means of additional charge air compression.

[0024] Particularly preferably, an electrified exhaust gas turbocharger is used as the compressor within the device. This is a structural unit in which an electric drive with a particularly narrow design is used, wherein the rotor of the electric motor is firmly connected to the shaft of the compressor impeller. In particular, a high-speed electric motor is used whose diameter is particularly small in relation to its power. Obviously, this high-speed electric motor is installed on the compressor side. With a uniform load on the internal combustion engine, this high-speed electric motor can operate in generator mode, and the electrical power generated can be used to charge the on-board network battery and / or to directly cover the current electrical power demand.Such an electrified turbocharger can, with regard to its operating time during the working operation of the internal combustion engine, largely obtain its entire energy requirement, which is necessary for a momentarily sufficiently high charge air compression, from the exhaust gas energy. During those operating phases of the internal combustion engine in which the momentary limitation of the charge air quantity would be a significant limiting factor for insufficient dynamic capability of the internal combustion engine if the exhaust gas energy were used alone, the charge air quantity can be increased using that high-speed electric machine, thereby achieving a better approximation of the dynamics required by the internal combustion engine up to the point of its complete fulfillment.According to the invention, when the internal combustion engine is deactivated and a corresponding need exists at the same time, the high-speed electric machine is used to generate an air flow by supplying electrical energy, whereby operation for scavenging the internal combustion engine is possible.

[0025] According to an advantageous embodiment of the invention, the device is suitable for generating a purge air flow performing the purge function along a flow path that extends over a partial section of the regular air supply path of the internal combustion engine, ideally over the entire regular air supply path of the internal combustion engine.

[0026] According to a further advantageous embodiment of the invention, the device is suitable for generating a purge air flow performing the purge function along a flow path that extends over a partial section of the regular exhaust gas path of the internal combustion engine, ideally over the entire regular exhaust gas path.

[0027] According to a further advantageous embodiment of the invention, the device is suitable for generating a purge air flow that performs the purge function along a flow path that extends at least over a portion of the return path of an exhaust gas recirculation system. The generated purge air flow preferably runs through the return path in a flow direction that is opposite to the flow direction of a recirculated exhaust gas portion that exists during engine operation.

[0028] If the internal combustion engine is equipped with an EGR system, a throttle valve installed in the air path is preferably used to direct the purge air flow through the exhaust gas recirculation path during the respective purge operation, in order to avoid the need for additional corresponding switching devices (assuming one is present). The engine control unit is configured to ensure, through appropriately coordinated control of the throttle valve, the EGR valve, and the respective compressor, that a dimensioned partial air flow is directed into the exhaust gas recirculation path to effect purge of the EGR path. Ideally, the throttle valve located within the air path is completely or almost completely closed during purge of the exhaust gas recirculation path.

[0029] According to a further advantageous embodiment of the invention, the device is suitable for generating a purge air flow performing the purge function along a flow path that extends through at least one of the combustion chambers along the air intake and outlet ducts of the internal combustion engine. Ideally, such a purge air flow can be generated that extends through each of the combustion chambers along the respective functionally associated air intake and outlet ducts. As a rule, the valve trains of an internal combustion engine are actuated mechanically by the camshaft rotation and the resulting engagement of the cam contour, whereby, in interaction with the valve spring, the valve tappets move in the axial direction without there being any further possibility of influencing the currently existing opening widths of a gas exchange valve.In an appropriately designed internal combustion engine, the supply of the combustion chambers with the scavenging air flow that performs the scavenging function and the exhaust takes place in the same way as when the engine is running; obviously with the difference that there is no fuel supply and the device for generating the scavenging air flow is permanently active and preferably at a high level of utilization. In order for this scavenging process to take place, the crankshaft drive of the internal combustion engine must obviously rotate, which is preferably done via the electric motor responsible for so-called ramp-up of the internal combustion engine in order to exceed the engine starting speed, i.e. the so-called engine starter. In this case, the valves are only open in some of the combustion chambers at the same time. Preferably, scavenging of a single combustion chamber or of different combustion chambers takes place here.a group of combustion chambers at different phases / time corridors.

[0030] As an alternative to mechanical actuation of the valve trains, the internal combustion engine could also be equipped with directly and individually selectively controllable intake and / or exhaust valves. This would allow individual valves to be opened or closed in a targeted manner by the engine control unit to scavenge the respective combustion chambers. Such a design also permits simultaneous scavenging of several combustion chambers. Furthermore, such equipment makes it possible to keep the intake and exhaust valves of a combustion chamber permanently open at the same time, which in turn allows direct flow through the combustion chambers. Preferably, the crankshaft drive for the combustion chamber currently scheduled for scavenging is aligned in such a way that the corresponding cylinder has assumed the position of its bottom dead center. This means that not just part of the combustion chamber is subjected to scavenging, but the entire combustion chamber.

[0031] According to a further advantageous embodiment of the invention, the device is suitable for generating an air flow performing the scavenging function along a flow path that extends through the entire or a partial section of a blow-by main line of the internal combustion engine, wherein the partial section is preferably at least one partial section of the blow-by path that runs through the entire interior of the engine block and / or one or more devices for separating aerosols from the blow-by gas. In order to introduce the scavenging air flow generated by the compressor into the blow-by path, the device can have at least one suitable switching element downstream of the compressor. Depending on its switching state, the outlet of the compressor can be connected optionally to the blow-by path or the combustion chambers of the internal combustion engine. It is preferred if the switching element is in its neutral position, ieWhen not activated, a connection between the compressor and the combustion chambers is ensured, ensuring normal operation of the internal combustion engine in the event of a malfunction. The switching element is preferably implemented as two throttle valves. The respective valve position determines the volume of air flow entering the blow-by path or the combustion chambers.

[0032] As an alternative to the latter switching element, the air path section through which the air branching or redirection from the air path provided for engine operation takes place when required can also have a closure flap installed, allowing the air path to be completely interrupted. If this closure flap and the previously mentioned throttle valve are present within the regular air path, the switching element can be omitted because this functionality can be achieved through appropriately coordinated use of the closure and throttle valves. It is sensible to integrate the closure and throttle valves into the overall system in terms of their functionality and controllability in such a way that the scavenging air flow introduced into the blow-by path can be fed either to the air intake tract or the exhaust tract of the internal combustion engine.

[0033] It is preferred if the device has a further switching element along the blow-by path, which in turn is preferably present downstream of a functional unit arranged along the blow-by path with respect to the flow direction, which serves to condition the exhaust gas to be recirculated, such as an EGR cooler or a separation device for aerosols or an oxidation catalyst, etc. Downstream, this further switching element has a first connection, i.e. a first outlet, from which a fluid connection to the regular air supply path of the internal combustion engine is present, wherein this opening with respect to the air path is preferably downstream of the first compressor stage with respect to the flow direction of the charge air.A fluid connection to the exhaust tract exists from a second outlet of the further switching element, with the inlet preferably being downstream of the last turbine in relation to the flow direction of the exhaust gas and at the same time preferably upstream of any devices used for chemical exhaust gas aftertreatment. The further switching element is sensibly integrated into the overall system in terms of its functionality and controllability in such a way that the purge air flow introduced into the blow-by path can be fed optionally to the air intake tract or the exhaust tract of the internal combustion engine. The further switching element can preferably also be implemented by two throttle valves, one of which controls the volume of the purge air flow into the air intake tract and the second throttle valve controls the volume of the purge air flow into the exhaust tract.

[0034] Alternatively and equally preferably, the said further switching element can be omitted at the branching of the blow-by path, wherein instead a closure flap is used along each of the two continuations, which is integrated into the overall system in terms of its functionality and controllability in such a way that the purge air flow introduced into the blow-by path can be fed selectively to the air intake tract or the exhaust tract of the internal combustion engine, in the same location as the previously described embodiment in which the switching element is used instead of two closure flaps.

[0035] The engine control unit is logically configured to introduce the contaminated purge air flow into the exhaust path at the beginning of the purge process. Towards the end of the purge process, when less contamination is suspected in the purge air flow or, in the case of appropriate instrumentation, a decrease is detected by sensors, the engine control unit can activate the relevant additional switching element to introduce the purge air flow into the charge air path. It is also conceivable for the additional switching element to split the purge air flow exiting the blow-by path to supply a first partial purge air flow to the exhaust path and a second partial purge air flow to the charge air path.According to a further modification, a throttle element can be provided downstream of the switching element in at least one of the paths to the exhaust tract or intake tract, the throttle effect of which can be controlled by means of a corresponding actuation, which is preferably initiated via the engine control unit, whereby the size ratio between those partial flows can be adjusted during the purging process.

[0036] According to an advantageous embodiment, it can be provided that the engine control is configured, by means of corresponding actuations within the device, whereby a sequential flushing of the plurality of flow paths can be implemented in an advantageously selected sequence. It is conceivable that after the internal combustion engine has been switched off, the engine control carries out the flushing of the aforementioned flow paths as part of a follow-up sequence by controlling the aforementioned actuators according to a fixedly defined sequence, wherein the possibility exists that within a sequence, i.e. before each of the different flow paths has been flushed once by the relevant air flow, the repeated flushing of a specific flow path is already carried out. It is equally conceivable that the sequence is selected randomly or prioritized depending on the expected degree of contamination.

[0037] Furthermore, it is conceivable that the respective time periods within which a specific scavenging process takes place are set to a specific time grid, whereby the respective time periods are preferably set individually for the different flow paths. Furthermore, it is conceivable that a time period for the individual scavenging of a flow path is also measured according to demand, in which at least one available measured variable is used to determine the scavenging requirement. This is preferably done via a so-called digital twin. The input variables here are measured values ​​that are already available for operating the internal combustion engine and / or that can be determined from already available measured variables. Examples of corresponding operating variables can be in particular: the engine speed, the instantaneous fuel consumption, for example.based on the setpoint of the fuel injection, the engine oil temperature, the engine coolant temperature, the EGR rate, the exhaust gas temperature, the pressure difference along a flow path section, etc. Clearly, for the implementation of a particularly advantageous embodiment of the invention, it may be expedient to use additional sensors, such as a humidity sensor or a hydrogen sensor, to detect particularly important or particularly meaningful operating variables.

[0038] Furthermore, it is conceivable that the component that generates the purge air flow is operated at different levels of utilization, depending on the flow path currently in the purge process and / or depending on certain measured variables, as described in the previous section.

[0039] Furthermore, it is conceivable that the sequence in which the different flow paths are flushed one after the other is determined depending on certain measured variables, as described in the previous section in the context of the needs-based determination of the time periods for the individual flushing processes.

[0040] It is also conceivable for multiple flow paths to be purged synchronously by splitting the purge air flow. In particular, the device can be suitable for effecting a corresponding splitting of the purge air flow performing the purge function, whereby a first partial flow extends along the blow-by path and a second partial flow extends via the air distributor and downstream of it via the exhaust path. The ratio of the partial flows can be adjusted by the engine control system, preferably by appropriately controlling a throttle valve.

[0041] According to a preferred embodiment, the engine control unit can be configured to execute the purge air flow by means of the device in response to an engine shutdown, in particular an ignition key shutdown, as an engine run-on function. If the internal combustion engine is equipped with a start-stop function, the run-on sequence or a purge of at least part of the flow paths could also be triggered by an engine shutdown executed by the start-stop function.

[0042] In this regard, it is conceivable that the sequence in which the different flow paths are flushed one after the other is subject to a predetermined sequence, but is not purely statically predetermined, but occurs individually. Accordingly, there could be a first sequence that is always applied when an engine shutdown triggered by the start-stop function has occurred, while a different sequence is followed when the engine deactivation has occurred based on a shutdown triggered by the ignition key.

[0043] The invention further relates to a vehicle or a work machine, in particular a mobile work machine, with an internal combustion engine according to the invention. The vehicle and the work machine are therefore characterized by the same advantages and properties as the internal combustion engine according to the invention.

[0044] The invention further relates to a method for operating an internal combustion engine having at least one combustion chamber and at least one device installed in the charge air path of the internal combustion engine for compressing the engine charge air during engine operation of the internal combustion engine. According to the invention, the device generates a temporary purge air flow when the internal combustion engine is deactivated, which extends along at least one flow path within the internal combustion engine and purges that flow path to remove any contamination within the flow path. Further aspects of the method emerge from the above description of the internal combustion engine, so that reference is made to the above at this point to avoid repetition.Further advantages and embodiments of the invention will be explained in more detail below with reference to an exemplary embodiment illustrated in the figures. They show:

[0045] Figure 1: a block diagram of a preferred embodiment of the internal combustion engine according to the invention,

[0046] Figure 2: the block diagram according to Figure 1 during the purging of the EGR path,

[0047] Figure 3: the block diagram according to Figure 1 during the purging of the regular fuel-exhaust path,

[0048] Figure 4: the block diagram according to Figure 1 during the purging of a blow-by path,

[0049] Figure 5: a modified embodiment of the internal combustion engine according to the invention during the purging of the blow-by path, and

[0050] Figure 6: a further modified embodiment of the internal combustion engine according to the invention during the purging of the blow-by path.

[0051] The illustrations in Figures 1 to 6 always refer to a 4-cylinder in-line engine, which is depicted purely schematically and in a largely identical manner. Obviously, an internal combustion engine according to the invention can have a different basic design—for example, a V-engine—and any number of cylinders.

[0052] The embodiment of Figures 1 to 4 shows an internal combustion engine comprising an engine block 10 with combustion chambers 11. An air distributor 12 and an exhaust manifold 13, including the respective air and exhaust connections to the individual combustion chambers 11, are installed on the engine block. As is known to those skilled in the art, what is known as blow-by gas is produced within a combustion chamber during the compression process. This gas is a small proportion, on the order of 0.5% to 2% of the gas contained in the combustion chamber, and is pressed into the crankcase regardless of the presence of piston rings. Consequently, there are several blow-by gas inlet areas within the crankcase. The blow-by gas collected therein is returned to the air intake tract via a dedicated path, the so-called blow-by path, as indicated in Figure 1.Also present within the blow-by gas are aerosols originating from the combustion chamber, the majority of which is water vapor. Along the section of its flow path extending through the crankcase, oil droplets are entrained by the blow-by gas. To ensure that the oil initially present is separated as completely as possible from the blow-by gas, at least one suitable device is located along a blow-by path. Figures 1 to 6 each show a schematically illustrated aerosol separator 14. With respect to its installation location, an aerosol separator 14 installed within the engine block is located above the valve train. As can now be seen, the representation of the blow-by path in the figures is very simplified, but this fact is known to those skilled in the art, and furthermore, the detailed design of a blow-by path is not part of the invention that is the focus here.

[0053] A central component of the internal combustion engine according to the invention is a device which, when the internal combustion engine is switched off, can generate a sufficiently strong air flow to thereby free one or more flow paths of the internal combustion engine from contamination. Contamination can arise from the build-up of unburned fuel, intermediate combustion products of a fuel, moisture (i.e. condensed water), engine oil or components of engine oil, or coked engine oil. A corresponding purge air flow can be guided through a dedicated flow path by controlling one or more actuators, each of these selectable flow paths being a component of the internal combustion engine. According to the exemplary embodiment according to the invention, the device comprises such a compressor 20, which is decoupled from the operation of the internal combustion engine orwhich can be operated decoupled therefrom, so that the compressor 20 can also be used according to the invention when the internal combustion engine is switched off. In the embodiment shown here, the compressor 20 can be driven by an external drive 21, which is preferably an electric motor. An electrified turbocharger is particularly preferably used. This is a structural unit in which an electric motor, which preferably has a particularly narrow design, is used, the rotor of this electric motor being firmly connected to the shaft of the compressor impeller. A high-speed electric motor is used for this purpose, the diameter of which is particularly small in relation to its power. Obviously, this high-speed electric motor is mounted on the compressor side.If the internal combustion engine is used evenly, the high-speed electric motor can operate in generator mode and the electrical power generated can be used to charge the on-board battery and / or to directly cover the current electrical power demand.

[0054] Regardless of the embodiment of the unit containing the compressor 20, the use of which generates a purge air flow when the internal combustion engine is switched off, the compressor 20 can also be used for charge air compression during engine operation of the internal combustion engine. This means that the compressor 20 is designed and integrated into the air path of the internal combustion engine according to the invention in such a way that the compressor 20 can enable a rapid increase in the combustion air supply during useful operation of the internal combustion engine. As a result, the compressor 20 can enable a temporary increase in the dynamic capability of the internal combustion engine during engine operation.

[0055] Such use of the compressor 20 is always appropriate when a tendency or even complete alignment of the actually achievable increase in the output power of the internal combustion engine with the required increase is possible due to the active action of the compressor 20. Preferably, such an additional system containing the compressor 20 is used, which enables variable and thus demand-oriented use.

[0056] Why such an implementation is particularly advantageous will be demonstrated by two examples that explain this context:

[0057] In a fictitious case, the increase in charge air volume required to meet the power increase demanded by the internal combustion engine can be achieved even if the compressor 20 operates at a capacity level of, for example, only 25% of its capacity limit. In this case, full-load operation of the compressor 20 would clearly be energetically disadvantageous.

[0058] In another fictitious case, the increase in fuel supply required to meet the power increase requirement can only be achieved to a degree of, for example, 30%, whereas an increase in the charge air quantity using compressor 20 would be possible, which would enable a significantly higher degree of meeting the power increase requirement of the charge air demand. Within the fictitious time frame in which the technically feasible increase in the charge air quantity is not the limiting factor, it is clearly also sensible to use compressor 20 in a partial load operation adapted to the existing limitations of the increase capability with regard to the fuel supply.

[0059] The compressor 20 is preferably activated by the engine control immediately after the internal combustion engine is switched off or after the fuel supply fails.

[0060] As already explained above, purge air flows can be generated through different flow paths of the internal combustion engine by means of the compressor 20, with the respective flow path being selected by means of at least one actuator controlled by the engine control unit. The individual possible flow paths, which are preferably executed sequentially as part of a run-on sequence after the internal combustion engine is shut down, will be briefly discussed in more detail below. In each phase of the run-on sequence, at least one specific flow path is purged. The individual phases are discussed in more detail below using the illustrations in Figures 2 to 6.

[0061] Phase - Flushing of the exhaust gas recirculation (EGR) (Figure 2)

[0062] Investigations on such internal combustion engines equipped with exhaust gas recirculation have shown that a comparatively high amount of condensate can form along the EGR path 30, in particular within the EGR cooler 31, after an engine shutdown and the resulting subsequent cooling.Even if all surfaces along the EGR flow path 30 are made of a particularly resistant metal, there is a high risk of severe chemical contamination of the contaminated surfaces due to the very high surface temperatures during engine operation and the significant difference to the significantly lower temperatures that occur after a longer downtime, as well as the contamination by completely untreated exhaust gas, the adhesion of combustion residues and the direct adhesion of condensed water to the free surface of the EGR flow path 30, but also the moisture that has accumulated on the said combustion residues.A more severe chemical contamination occurs when unburned or partially burned fuel or other residues are present in the exhaust gas, which are highly soluble in water, and this aqueous solution is highly corrosive. An example of a highly damaging potential is contamination impregnated with a water-ammonia mixture. Furthermore, not only the metal walls of pipes and functional surfaces are contaminated with the aforementioned residues, but also the existing seals.

[0063] The invention can also be applied to an optionally available EGR system or the relevant flow path of an internal combustion engine, via which exhaust gas recirculation occurs in the event of the relevant requirement during regular engine operation. Preferably, when such a purging process is used, the EGR path 30 is flowed through in the opposite direction to that provided for exhaust gas recirculation during engine operation. In such an embodiment, it is necessary to use an EGR valve 32 that can be flowed through bidirectionally.

[0064] It is important that a sufficiently high purge air mass flow can be provided so that any surfaces that may be contaminated with exhaust gas during exhaust gas recirculation are exposed to air with a sufficiently high intensity to virtually completely eliminate any residual moisture—water vapor and, where applicable, water that has already condensed in a colder environment—and also to remove as much of the potential deposits on the surface areas of the EGR path 30 as previously mentioned. To achieve the desired purge conditions, the compressor 20 must deliver a sufficiently high air mass flow, and secondly, the air path downstream of a branching of the air path and the EGR path 30 must be completely interrupted, or at least the air resistance in the partial path to the air distributor 12 must be increased in order to be able to supply the EGR path 30 with a sufficiently strong air flow for purging.

[0065] The aforementioned significant increase in air resistance along the combustion chambers 11 or the complete interruption of such an air flow can be achieved, for example, by the presence of a throttle valve 15 located in the air path directly upstream of the air distributor 12 with respect to the flow direction, which can be throttled accordingly or, preferably, completely closed. In a correspondingly designed / equipped internal combustion engine, the individually actuated combustion chamber gas exchange valves can alternatively or additionally be closed, causing the respective air flow to flow through the EGR path 30, thereby performing the purge function.

[0066] During the previously described section of the run-on sequence, the EGR valve 32 and the EGR cooler 31 and the corresponding lines are decontaminated. Furthermore, line sections and components located downstream of the exhaust manifold 13 are also decontaminated. These include, for example, a turbine 41 of an optional exhaust gas turbocharger, the EGR system, corresponding pipe sections and seals, etc. Furthermore, decontamination can also be achieved along the air path. If the air path is constructed according to the exemplary embodiments shown in Figures 1 to 6, the described phase of the run-on sequence also cleans the compressor 42 associated with the exhaust gas turbocharger. The compressor 42 is driven by the turbine 41, which in turn draws its energy from the exhaust gas.At least one charge air cooler, which is not shown in the figures for the sake of simplicity, can also be purged during the respective process within the described sequence. In Figure 2, the flow path of the generated purge air flow is highlighted by a double line. A single connecting line represents those connections that do not carry air flow during the respective follow-up sequence phase. Such marking of the respective purge air flow flow path is also used in Figures 3-6.

[0067] Phase - Flushing of the air path, combustion chambers and exhaust gas path

[0068] In order for appropriate scavenging of all combustion chambers 11 and the corresponding combustion chamber gas exchange valves with the associated channels to take place within the said after-run sequence, it must be possible for all of these valves to be opened even when the internal combustion engine is switched off. This is naturally the case if the crankshaft drive can be towed when the internal combustion engine is switched off, i.e., the rotation of the crankshaft is possible when the internal combustion engine is switched off. In mobile work machines, there is generally no separating clutch via which the power connection between the internal combustion engine and the hydraulic pumps driven by it can be interrupted, which is why the components and parts involved in towing operation of the internal combustion engine (the starter battery, the electric starter motor, etc.)) must be designed for greater load capacity than is necessary for an internal combustion engine that can be decoupled from all powerful consumers during start-up. (Obviously, these hydraulic working pumps remain within their idle mode, but corresponding friction losses must still be overcome and a small amount of oil must be transferred for self-lubrication.)

[0069] To purge the air path, the combustion chambers 11, and the exhaust path, the EGR valve 32 is preferably completely closed. Mechanical power is supplied to the first compressor 20 via its external drive 21, causing intake air to flow through the air path, the individual combustion chamber units—i.e., the combustion chambers 11 and the associated intake and exhaust ducts—and the exhaust path. In the described flow path, water vapor, possibly unburned and partially burned fuel, and possibly also certain combustion residues are removed.

[0070] Reducing the consideration to the air distance (best seen in Figure 3)

[0071] In Figure 3, the flow path of the generated purge air flow is highlighted by the use of a double line. A single connecting line represents those connections which do not carry any air flow during the respective after-run sequence phase. The inventive operation of the first compressor 20 causes water vapor to be discharged along the entire air path, which in the exemplary embodiment has a second compressor 42 which is part of an exhaust gas turbocharger. In general, an air path includes at least one heat exchanger for cooling the charge air. In multi-stage charging, the use of several charge air coolers is not uncommon. For the sake of simplicity, those components are not shown in the respective figures. Even those parts of these aforementioned components through which the charge air flows orThe air streams that are flowed against the exhaust air are penetrated by the purge air flow used for purging or dehumidification during the corresponding phase of the after-run sequence. The same applies to other components and parts of an engine air path that are not present in the exemplary embodiment or that are not explicitly referenced. Reduction of the consideration to the combustion chambers 11 and the exhaust path (best seen in Figure 3).

[0072] By properly operating the combustion chamber gas exchange valves, compressed air is supplied sequentially to each of the combustion chambers 11 in portions by the first compressor 20 during a corresponding purging process. Following additional compression within the respective combustion chamber 11, this air enters the exhaust system after the exhaust valves open. This allows any residues of unburned or partially burned fuel, fuel gas, and / or moisture present in both the combustion chambers and the exhaust system to be purged.

[0073] The functional actuation of the combustion chamber gas exchange valves for this phase of the run-on sequence can be achieved by operating the crankshaft drive using an existing engine starter (i.e., the electric motor, which is normally powered by the on-board battery). By rotating the crankshaft drive at a defined speed, individual gas paths can be cyclically flushed with air, thereby achieving appropriate cleaning / purging of all these gas paths.

[0074] In an advantageous embodiment, the system design of the starter and its electrical supply can be configured such that the starter is actuated during the coasting sequence at a reduced input power, which is entirely sufficient for a defined adjustment of the crank mechanism, since a speed significantly lower than that required to achieve an engine start can be entirely sufficient. This allows energy consumption and, above all, wear on the affected components and units to be reduced.

[0075] Blow-by (general)

[0076] It is known that during operation of an internal combustion engine, a small proportion of the fluids located in the combustion chambers 11 does not enter the exhaust tract, but rather a small proportion brushes along the piston rings and reaches the interior of the crankcase. This applies to (clearly uncleaned) exhaust gas, which contains, among other things, water and small amounts of unburned and partially burned fuel, as well as small amounts of engine oil or components of engine oil and / or coked engine oil. Assuming intact oil separation between the oil separation rings attached to the pistons and their running surface, i.e. the cylinder bore or the cylinder liner, the vast majority of the engine oil ultimately located in the blow-by gas enters the blow-by gas as it flows through the crankcase due to oil droplets being entrained.Because blow-by gas contains a high proportion of air pollutants, it must not be released into the environment as such. Therefore, the blow-by gas is fed into the air intake tract of the internal combustion engine, with at least one and often two purification stages along the return path. Typically, the first stage, known as the oil separator, is formed by a passageway designed such that the oil droplets and any aerosols contained in the blow-by gas—such as water, unburned or partially burned fuel, and possibly other suspended particles—collect at the bottom of that passageway and from there ultimately reach the oil pan. Returning engine oil to the oil pan is clearly advantageous, as it is available for reuse during continued engine operation.Separating such gas bubbles and particles entrained in the engine oil is technically relatively simple due to their significantly different specific weights and comparatively good filterability. As long as the engine is running, separating water from the blow-by gas is relatively unimportant, since its flow into the intake tract of the internal combustion engine is not critical. Since the blow-by gas flow into the air passage of the internal combustion engine is orders of magnitude smaller than the fresh air flow, no application-relevant effect occurs even if an existing lack of air is the decisive factor for a momentary, unintended restriction of engine dynamics.

[0077] However, the retention of water or water vapor in the blow-by path after an engine shutdown is a disadvantage. Condensed water dripping into the engine oil pan should / must be avoided as much as possible, because oil dilution by water reduces the lubricity of the engine oil. Furthermore, moisture remaining in the blow-by path after an engine shutdown can lead to icing at low temperatures. If it occurs at certain components or transition points (e.g., the oil separator or the gas lines), this can lead to temporary restrictions in engine operation and even engine damage.

[0078] For the aforementioned reasons, removing moisture along the blow-by path is also important during engine shutdown, especially if the internal combustion engine in question is powered by a fuel with a high hydrogen content. From the above, it now goes without saying that the aforementioned after-run sequence should include purging the blow-by path, for which the first compressor 20 can also be used.

[0079] Phase - Flushing and dehumidification of the blow-by path

[0080] Figures 4 - 6 show three different embodiments for flushing the blow-by path.

[0081] According to the exemplary embodiment shown in the figures, a switching element 50 is provided, which is integrated into the air path downstream of the compressor 20. The switching element 50 can be used to adjust whether ambient air, which is guided via the air filter 16 and the two compressor stages 20, 42 and accordingly conditioned, is either (i) supplied to the combustion chambers 11 or (ii) fed into the blow-by path via a specially provided inlet. The switching element 50 can be actuated, for example, electrically, by the engine control unit.

[0082] In terms of its implementation, a switching element 50, 50', 60, 60' can be embodied by two throttle valves that can be operated in a correspondingly coordinated manner. A coordination of two throttle valves operating in pairs that is advantageous or even necessary with regard to the respective functionality to be provided, as well as their respective preferred throttle valve position, which should be present in the event of a lack of control, can be identified by the actuators and the return spring indicated on the circuit symbols.

[0083] In the exemplary embodiment of Figures 1-4, the switching element 50 is held in a switching position without external control by the spring force, in which the ambient air, which has been treated by filtering, compression and cooling (not shown), reaches the combustion chambers 11 via the air distributor 12. In the relevant phase of the after-run sequence intended for cleaning the blow-by path, the restoring force applied by the spring is overcome by appropriate control of the switching element 50. The valve 50 is thereby transferred to the second switching position, in which the treated ambient air is not fed to the combustion chambers 11, but directly into the blow-by path, which clearly results in a purging of the functional section of the blow-by path, i.e. the aerosol separator 14.The term "functional section" refers to the section of the blow-by path in which the aerosols to be discharged via it are both introduced into the blow-by path and separated from it. Components used to purify the blow-by gas, particularly the separation of engine oil for its immediate reusability within the engine oil circuit, are familiar to those skilled in the art. Filters and vortex separators that utilize the coalescence principle are commonly used for this purpose, sometimes in combination.

[0084] The image element symbolizing the aerosol separator 14 shown in Figures 1 to 5 is reminiscent of a filter based on the coalescence principle, although no further filter stage is depicted. An appropriately selected oxidation catalyst 17 or another system selected for its appropriate function can optionally be present along the blow-by path. This measure is intended to break down unburned or partially burned fuel that enters the blow-by gas before it is fed into the air path. Obviously, the oxidation catalyst 17 or the other system in question is arranged downstream of those components whose function is to separate the solid and liquid aerosols from the blow-by path.It is particularly sensible or even necessary to equip an internal combustion engine with an oxidation catalyst 17 or a correspondingly functionally equivalent component for the operation of which a fuel is used which has a high proportion of molecular hydrogen or is generally particularly flammable or for which there is a particularly high toxic effect, in relation to the chemically unchanged fuel including its combustion intermediates.

[0085] The subsystem according to the invention, which enables purging of the blow-by path, has a further switching element 60, which can be used to recirculate the blow-by gas into the air path in the usual way during regular operation of the internal combustion engine, and to supply it to the exhaust tract during that subsection of the after-run sequence in which the purge flow used to clean the blow-by path can be supplied. The latter preferably takes place downstream of the last turbine 41 of the exhaust gas turbocharger with respect to the flow direction of the exhaust gas, and, if a fuel cell 18 is present in the exhaust path, upstream thereof, and in any case upstream of the EGR system. The EGR system is not directly related to the invention and is therefore not shown in any of the figures.

[0086] As can be seen, the overall system is designed with regard to the two switching elements 50, 60 with regard to their configuration and their installation in the overall system network such that, in the absence of control, the two switching elements 50, 60 assume a switching position which must be present during the working operation of the internal combustion engine (cf. Figures 1 - 3), whereas with regard to the exemplary embodiment, an active control of both switching elements 50, 60 is necessary so that the corresponding follow-up can take place (cf. Figure 4).

[0087] Figure 5 shows a slightly modified circuit diagram. The corresponding purging of the air path, the combustion chambers 11, the exhaust path, and the EGR path 30 takes place in the manner already explained. The only difference is the channel routing provided for purging the blow-by path, since the first switching element 50' used here differs from the design of the first switching element 50 in Figures 1 to 4, and the second switching element 60 has been completely omitted. The resulting different channel routing for purging the blow-by path is described in the following text.

[0088] In the first switching element 50' located downstream of the first compressor 20, the presence of the second switching position (shown here) during the after-run sequence for purging the blow-by path leads to a flow split if the flow resistances along those two partial paths are at least partially equalized. For this, the throttle valve 15 must be brought within a certain position range or degree of opening. During operation of the first compressor 20 and a corresponding balancing of the throttle valve position, a certain proportion of air leaves the system under consideration along the air-exhaust path, while a remaining proportion of air flows through the blow-by path and is then mixed with newly introduced air into the system under consideration. Thus, the air used to clean the blow-by path is diluted with fresh air upstream of the first compressor 20.Downstream of this, a portion of that air mixture ultimately leaves the internal combustion engine via the flow path that extends across the engine air path, the combustion chambers 11, and the exhaust gas path, whereby the quantity of aerosols previously removed in the blow-by path continually decreases until a correspondingly low degree of contamination is established in the affected flow section. A certain proportion of the aerosols immediately previously removed from the blow-by path are inevitably fed back into the blow-by path. However, aerosols are removed there within a freely selectable time corridor, and thus the quantity of aerosols within the blow-by path is continuously reduced until a quasi-stationary degree of purification is reached.

[0089] The embodiment shown in Figure 5 also enables purging of the blow-by path during engine operation, provided that the first compressor 20 is not yet sufficiently close to its power limit to be able to provide the air supply required for the current operation of the internal combustion engine. Except in the case of a corresponding fault, the accumulation of such quantities of unburned and partially burned fuel and moisture remaining in the crankcase is a slowly progressing process, whereby in an engine application, operating phases occur within certain time intervals during which a corresponding power reserve of the first compressor 20 is available, which is sufficient to carry out active crankcase ventilation under the influence of the first compressor.

[0090] Figure 6 shows a further modified circuit diagram. For a system constructed in this way, the air path, the combustion chambers 11, the exhaust gas path, and the EGR path 30 are purged in the manner already explained. There is a difference for purging the blow-by path, which will be explained in the following text. The switching element 60' used downstream of the aerosol separator stage 14 differs fundamentally from the switching element 60 used in Figures 1-4, which is explained in the following text explaining the functional relationship. In addition, within the path section provided for the blow-by gas, a further throttle valve 61 is integrated between the switching element 60' and the feed into the intake tract, and a throttle element 62 is included between the second switching element 60' and the inlet into the exhaust tract.If a corresponding control is not provided, the switching element 60' is in the switching position in which the blow-by gas is supplied to the intake tract for the working operation of the internal combustion engine due to the restoring force of the spring in question.

[0091] The follow-up sequence for flushing the blow-by path can be divided into three different operating states A, B, C.

[0092] At the beginning of the run-on sequence phase for cleaning the blow-by path using the active compressor 20, operating state A is assumed, in which the purge flow that has flowed through the section of the blow-by path located within the internal combustion engine is completely introduced into the exhaust tract. Due to the required actuation of the switching element 60', the blow-by path can be split due to its nature and the switching position shown downstream of the oxidation catalyst 17. Since the throttle valve 61 is completely closed during the run-on sequence within operating state A, the purge flow is completely introduced into the exhaust tract.

[0093] In the subsequent operating state B, the throttle valve 61 is opened by such a step width that a division of the purge flow takes place downstream of the switching element 60' and, as a result, a first partial flow thereof is fed to the air path and a second partial flow is fed to the exhaust tract.

[0094] In a particularly advantageous embodiment, the throttle valve 61 is not immediately positioned in its end position during the transition from the first to the second phase, but rather the transition in question takes place gradually or continuously. Accordingly, initially preferably all or at least a large part of the purge flow is fed to the exhaust tract. After some time, the proportion of the purge flow fed to the air path increases and, accordingly, the proportion of the purge flow fed to the exhaust tract decreases. At the end of the phase for cleaning the blow-by path, operating state C is assumed, in which the purge air flow flowing through the blow-by path is preferably fed completely to the intake tract of the internal combustion engine.

[0095] For a more detailed explanation of operating mode B:

[0096] When the first compressor 20 is operated with appropriate balancing of the throttling by means of the throttle valve 61, a first partial flow enters the exhaust tract, while a second partial flow is fed to the intake tract and then mixed with air newly introduced into the system in question. Preferably, this throttle valve 61 is located within the flow path between the last-mentioned switching element 60' and the blow-by gas feed into the intake tract. Accompanying this, and with reference to the switching position of the respective switching element 60' shown in Figure 6, the two channels located therein and participating in the currently existing flow paths are designed such that the flow resistance between the inlet and the outlet that is fluidically connected to the intake tract has a higher value than the remaining one.

[0097] At the beginning of the purging process occurring in operating state B, the partial flow that directly enters the exhaust tract is significantly larger than the partial flow that directly enters the intake tract. Accordingly, by far the largest proportion of the gas inflow used for purging is fed directly into the exhaust tract from the section of the blow-by path that is comparatively heavily contaminated with aerosols. After some time, a continuous or abruptly decreasing throttling in the connecting line to the intake tract occurs via the throttle valve 61. As a result, the proportion of the gas inflow used for purging that is fed directly into the exhaust tract becomes increasingly smaller. Accordingly, the purifying effect of the gas inflow used for this purpose is increasingly focused on the remaining part of the blow-by path.This type of operation offers the advantage that a comparatively high discharge of aerosols located along the aerosol separator 14 or the separators is fed as directly as possible to the exhaust tract and only a small proportion of it is introduced into the air path.

[0098] In order to remove the latter entry as completely as possible, it is recommended to repeat the previously described phase for flushing the air path, the combustion chambers and the exhaust path.

[0099] Further modifications of the embodiments are described below.

[0100] Electrified exhaust gas turbocharger

[0101] In the embodiments of Figures 1 to 6, the overall system always comprises an exhaust gas turbocharger with the turbine 41 and the compressor 42 driven by the turbine, as well as the additional compressor 20, which can be driven by the external drive 21. Instead of the combination of exhaust gas turbocharger 41, 42 and compressor 20, only an electrified exhaust gas turbocharger could be used. If the compression power required for the desired charge air compression cannot be extracted from the exhaust gas due to a currently insufficient amount of exhaust energy available, the charge air compression can be assisted by an electric motor integrated into the exhaust gas turbocharger.In the case of sufficient exhaust gas energy availability, the electrified exhaust gas turbocharger can fully perform the desired charge air compression without the active participation of the said electric motor, thus eliminating the respective conversions between electrical and mechanical energy and the associated power losses.

[0102] Fuel cell in the exhaust path

[0103] Upstream of the EGR system (not specifically identified), a fuel cell 18 or another corresponding component can be installed such that the exhaust gas flows through it. Such a component continues the combustion of completely unburned or partially burned fuel quantities that may still be contained in the untreated exhaust gas. In addition or alternatively, and for the same purpose, a fuel cell 17 or another corresponding component can be installed along the blow-by gas path, preferably downstream of the last oil separation stage with respect to the main exhaust gas flow direction, through which the blow-by gas flows. (In the event that there is a possibility of a branching along the blow-by gas path due to the presence of the switching element 60, 60' (cf.Figure 6), the latter fuel cell 17 or the correspondingly other functionally suitable component is installed upstream of that branch in a preferred system embodiment. Instead of or in addition to the latter fuel cell 17, an oxidation catalyst can be used at the relevant position. If a suitable component is present and, moreover, if it is installed correctly, this ensures that, after completion of the run-on program according to the invention, no easily flammable fuel quantities remain in the internal combustion engine. The air path can have a heating device with which preheating of the charge air is possible if necessary. Heating devices are already known with the objective of increasing the cold-start capability of the internal combustion engine.Heating devices motivated in this way for preheating the charge air are positioned in such a way as to achieve the introduction of thermal power in relation to the length of the charge air path close to the combustion chambers 11. If the preheating of the charge air is motivated by the desire to remove moisture from components and parts belonging to the air path, because the internal combustion engine in question is likely to be switched off relatively frequently after a short operating phase before the corresponding components have reached a certain operating temperature, a heating device 15 for preheating the charge air close to the air inlet into the engine air path may be useful as an alternative or in addition to the aforementioned arrangement, preferably upstream of an air filter 16. Advantageous embodiment for flushing the combustion chambers.

[0104] The valve train can be designed such that all gas exchange valves (intake and exhaust valves) can be opened and remain open regardless of the camshaft's rotational angle position. In such a case, during the follow-up sequence, within those time corridors in which the combustion chambers 11 with their associated gas exchange valves are purged, the camshaft's respective cam contour for engine operation is omitted. Instead, within the respective time corridors, the valve tappets are actuated in such a way that the corresponding gas exchange valves are permanently open. To achieve this, the internal combustion engine can be equipped with a different type of valve train, namely one that no longer even requires a camshaft, but in which the opening and closing of the valves is instead achieved via an electrically controllable and hydraulic actuation.Ultimately, to put it simply, such a fundamental change to the valve train would allow for completely flexible valve timing. More precisely, the instantaneous opening width of each individual gas exchange valve or pair of gas exchange valves could be implemented depending on the engine operating state (e.g., the speed-torque operating point).

[0105] Replacing the mechanical system, in which the valve train is controlled by a camshaft, with a corresponding electrohydraulic system is state of the art and is primarily motivated, initially and presumably in the future, by the fact that this enables completely free adjustment of the lift and control times of the gas exchange valves. However, the additional application capability described here for a particularly advantageous embodiment of the invention offers additional added value for the combustion chamber scavenging process.

[0106] Optional sensors within the flow paths to be flushed

[0107] Within at least one of the flow paths that can be purged in the manner according to the invention, there is at least one sensor for detecting moisture and / or other contamination. The sensor output signal(s) are fed to the engine control unit, which can then evaluate and determine whether purging of a specific gas path should occur. The operator can be informed of such a situation so that, at an appropriate opportunity, they can shut down the internal combustion engine in order to initiate the specific purge in question, the complete sequence of different purges, or selectively some of the possible purges. If the internal combustion engine is equipped with an engine start-stop system, these standstill phases of the internal combustion engine can be used to complete the corresponding purges.

[0108] To reduce the number of corresponding sensors, they are preferably installed only at critical positions along the gas paths where there is a correspondingly low correlation between the respective contamination levels. The principle of the so-called digital twin can be used to determine when a specific purge process or the entire sequence should be triggered, or to set the relevant bit so that such a process is triggered at the next available opportunity. List of reference symbols:

[0109] Engine block 10

[0110] Combustion chamber 11

[0111] Air distributor 12

[0112] Exhaust manifold 13

[0113] Aerosol separator 14

[0114] Throttle valve 15

[0115] Air filter 16

[0116] Component, e.g. designed as a fuel cell or oxidation catalyst 17

[0117] Fuel cell 18

[0118] Device for preheating the charge air 19

[0119] Compressor 20

[0120] External drive 21

[0121] AGR Path 30

[0122] EGR cooler 31

[0123] EGR valve 32

[0124] Turbine 41

[0125] Compressor 42 first switching element 50 first switching element 50' second switching element 60 second switching element 60' further throttle valve 61

[0126] Throttle element 62

Claims

Claims 1. Internal combustion engine with at least one combustion chamber (11) and at least one device installed in the charge air path of the internal combustion engine for compressing the engine charge air during engine operation of the internal combustion engine, characterized in that an engine control is provided which is configured to control the device in such a way that, when the internal combustion engine is deactivated, a purge air flow can be temporarily generated which extends along at least one flow path existing within the internal combustion engine and causes the flow path to be purged in order to remove contamination within the flow path.

2. Internal combustion engine according to claim 1, characterized in that the device comprises at least one electrically or hydraulically driven compressor (20), in particular an electrified exhaust gas turbocharger, for generating the purge air flow, wherein the at least one compressor (20) is used in regular engine operation at least temporarily for charge air compression during the working operation of the internal combustion engine, in particular when a load-related increase in the speed / torque requirement cannot be met without additional charge air compression, as determined primarily thereby.

3. Internal combustion engine according to claim 1 or 2, characterized in that the device is suitable for generating a purge air flow performing the purge function along a flow path which extends over a partial section of the regular air supply path of the internal combustion engine, ideally over the entire regular air supply path of the internal combustion engine.

4. Internal combustion engine according to one of the preceding claims, characterized in that the device is suitable for generating a purge air flow performing the purge function along a flow path which extends over a partial section of the regular exhaust gas path of the internal combustion engine, ideally over the entire regular exhaust gas path.

5. Internal combustion engine according to one of the preceding claims, characterized in that the device is suitable for generating a purge air flow performing the purge function along a flow path which extends at least over a partial section of the recirculation path (30) of an exhaust gas recirculation.

6. Internal combustion engine according to claim 5, characterized in that the device is further suitable for generating the purge air flow through the recirculation path (30) with a flow direction which is opposite to the flow direction of a recirculated exhaust gas portion during engine operation.

7. Internal combustion engine according to claim 5 or 6, characterized in that the engine control is configured to increase an air resistance in the charge air path for purging the return path (30), preferably by partially or completely closing a throttle valve (15).

8. Internal combustion engine according to one of the preceding claims, characterized in that the device is suitable for generating a purge air flow performing the purge function along a flow path which extends through at least one of the combustion chambers (11) along the air inlet and air outlet ducts of the internal combustion engine.

9. Internal combustion engine according to claim 8, characterized in that a scavenging air flow can be generated by the device, which extends through each of the combustion chambers along the air inlet and air outlet channels, in particular by the air flow performing the scavenging function flowing through different combustion chambers (11) at different phases / time corridors.

10. Internal combustion engine according to claim 9, characterized in that the engine control is configured to activate an actuation of the crank mechanism during the scavenging of the combustion chambers (11), in order to thereby effect an indirect and temporary opening of the valves of the individual combustion chambers (11) for the respective scavenging, ideally by controlling an engine starter, and / or to directly control a suitable actuation of the inlet and / or outlet valves of the individual combustion chambers. 11 . Internal combustion engine according to one of the preceding claims 9 or 10, characterized in that the device is suitable for generating a purge air flow in order to precisely one To flush the combustion chamber (11) along the air inlet and air outlet channels or a predetermined group of combustion chambers (11) by the generated flushing air flow and / or to flush all combustion chambers (11) simultaneously by the air flow performing the flushing function.

12. Internal combustion engine according to one of the preceding claims, characterized in that the device is suitable for generating an air flow performing the scavenging function along a flow path which extends through the entirety or a partial section of a blow-by main line of the internal combustion engine, wherein the partial section is preferably at least one such partial section of the blow-by path which runs through the interior of the engine block and / or one or more devices for separating aerosols from the blow-by gas.

13. Internal combustion engine according to claim 12, characterized in that the device has at least one switching element (50, 50') downstream of the compressor (20) in order to guide a generated purge air flow of the compressor (20) selectively through the combustion chambers (11) or the blow-by path.

14. Internal combustion engine according to one of the preceding claims, characterized in that the device has a further switching element (60, 60') along the blow-by path in order to supply the purge air flow guided through the blow-by path selectively to the air intake tract and / or the exhaust tract of the internal combustion engine, wherein the ratio between a partial flow of the purge air flow guided to the intake tract and a partial flow of the purge air flow guided to the exhaust tract is preferably adjustable by an integrated throttle element (61) in one of the paths.

15. Internal combustion engine according to claim 14, characterized in that the device is suitable for effecting a corresponding splitting of the air flow performing the scavenging function, whereby a first partial flow thereof extends along the blow-by path and a second partial flow extends via the air distributor (12) and downstream thereof via the exhaust gas path.

16. Internal combustion engine according to one of the preceding claims, characterized in that the engine control is configured to purge a selection of several flow paths sequentially one after the other in the form of a sequence by controlling the device and, if appropriate, with a repetition of a purging process for at least one specific flow path within the single run-through of the complete sequence, and / or the device is suitable for purging several flow paths in parallel by splitting the purge air flow.

17. Internal combustion engine according to claim 16, characterized in that the engine control is further configured to select the sequence for the sequential purging of the included flow paths as a function of an event that leads to the deactivation of the internal combustion engine and / or as a function of any measured variables and / or operating variables.

18. Internal combustion engine according to one of the preceding claims, characterized in that the engine control is configured such that the respective time periods within which a particular scavenging process takes place for at least one flow path are set to a specific time grid, wherein the respective time periods are preferably set individually for the different flow paths.

19. Internal combustion engine according to claim 18, characterized in that the engine control is further configured to determine at least one period of time as needed using at least one relevant measured variable, ideally on the basis of the measured value of at least one humidity and / or hydrogen sensor installed directly or indirectly in the respective flow path, and / or using one or more operating variables, such as the engine speed, the instantaneous fuel consumption, the engine oil temperature, the engine coolant temperature, the EGR rate, the exhaust gas temperature, the pressure difference along a flow path section.

20. Internal combustion engine according to one of the preceding claims, characterized in that the engine control is configured to adjust the utilization of the device, in particular of the compressor of the device, depending on the flow path to be purged.

21. Internal combustion engine according to one of the preceding claims, characterized in that the engine control is configured to execute the purge air flow by means of the device in response to an engine shutdown, in particular an ignition key shutdown, as an engine run-on function and / or in the event of a temporary engine shutdown triggered by a possible start-stop function.

22. Internal combustion engine according to one of the preceding claims, characterized in that the internal combustion engine is operable or is operated with ammonia or with a fuel which contains ammonia and whose weight proportion is at least 10%, preferably at least 30% and particularly preferably at least 50%.

23. Internal combustion engine according to one of the preceding claims, characterized in that the internal combustion engine is operable or is operated with a gaseous fuel which comprises at least a weight fraction of 10% of molecular hydrogen, preferably at least 30% and particularly preferably at least 50% of molecular hydrogen.

24. Motor vehicle, in particular a mobile work machine, with an internal combustion engine according to one of the preceding claims.

25. Method for operating an internal combustion engine with at least one combustion chamber (11) and at least one device installed in the charge air path of the internal combustion engine for compressing the engine charge air during engine operation of the internal combustion engine, characterized in that the device, when the internal combustion engine is deactivated, a temporary purge air flow is generated which extends along at least one flow path existing within the internal combustion engine and causes the flow path to be purged to remove contamination within the flow path.

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