Internal combustion engine with burner integrated into an exhaust system

Abstract

internal combustion engine • an internal combustion engine (1) forming at least one combustion chamber, • an exhaust gas stream (3) for discharging exhaust gas originating from the at least one combustion chamber, wherein a burner (4) is integrated into the exhaust gas stream (3), and • a fuel supply system with a tank (5), a high-pressure pump (8) and at least one fuel injector (2) assigned to the combustion chamber, wherein the tank (5) is connected to a suction side of the high-pressure pump (8) in a fuel-carrying manner and a pressure side of the high-pressure pump (8) is connected to the at least one fuel injector (2) in a fuel-carrying manner, characterized in that the pressure side of the high-pressure pump (8) is also connected to the burner (4) in a fuel-carrying manner.

Description

[0001] The invention relates to an internal combustion engine with a burner integrated into an exhaust system of the internal combustion engine. The invention further relates to a method for operating such an internal combustion engine.

[0002] The emission limits applicable to internal combustion engines are becoming increasingly stricter. This applies particularly to internal combustion engines designed to power motor vehicles. In order to comply with these emission limits, the exhaust aftertreatment devices integrated into the exhaust systems of these internal combustion engines must be capable of converting emissions as quickly as possible after a cold start. This requires that the exhaust aftertreatment devices reach their light-off temperatures (also known as "light-off temperatures") as quickly as possible after a cold start of the internal combustion engine, at which point sufficient effectiveness for exhaust aftertreatment can be assumed.

[0003] It is known to temporarily and specifically heat exhaust aftertreatment devices. This can be achieved both through engine-related measures aimed at causing an internal combustion engine to emit exhaust gas at a relatively high exhaust temperature, as well as through active heating measures, for example, using electric heaters or burners. Such a burner can, in particular, use the same fuel as the one intended for operating the internal combustion engine. The fuel is typically supplied to the burner at a relatively low pressure of well below 10 bar.

[0004] EP 2 863 026 A1, DE 10 2019 008 956 A1 and DE 10 2020 213 702 A1 each disclose a burner for actively heating an exhaust gas aftertreatment device of an internal combustion engine.

[0005] At relatively low fuel temperatures due to correspondingly low ambient temperatures, operation, and especially ignition, of the burner can be problematic. This is especially true when using diesel fuel as the fuel for the burner.

[0006] The invention is based on the object of improving the operation and in particular the ignition of a burner which is integrated into an exhaust system of an internal combustion engine, in particular at cold temperatures of the fuel used for its operation.

[0007] This problem is solved by the subject matter of the patent claims.

[0008] An internal combustion engine according to the invention comprises an internal combustion engine which forms at least one combustion chamber and an exhaust system for discharging exhaust gas originating from the at least one combustion chamber. The exhaust gas is discharged at least partially into the environment by means of the exhaust system. A burner is integrated into the exhaust system. A “burner” according to the invention is a device which burns fuel supplied separately (i.e. not via the exhaust gas) with oxygen which is also supplied separately, in particular as a component of air, and in this way generates a hot gas which can be used for direct heating, in particular as part of an admixture with the exhaust gas. The burner can in particular be assigned to at least one exhaust gas aftertreatment device, so that its operation is intended to heat the exhaust gas aftertreatment device in a targeted manner and as needed.Such heating can be provided, in particular, after a cold start of the internal combustion engine, when the exhaust gas aftertreatment device has a temperature that is significantly below its light-off temperature, at which sufficient effectiveness of the exhaust gas aftertreatment device can be assumed. However, such heating can also be provided to achieve a temporarily particularly high temperature of the exhaust gas aftertreatment device for the purpose of regeneration.

[0009] An internal combustion engine according to the invention further comprises a fuel supply system with a tank, a high-pressure pump that can preferably be driven directly by the internal combustion engine, and at least one fuel injector that is assigned to the combustion chamber, wherein the tank is connected to a suction side of the high-pressure pump in a fuel-conducting manner, and a pressure side of the high-pressure pump is connected to the at least one fuel injector in a fuel-conducting manner. A “high-pressure pump” is understood to mean a pump that can generate a fuel pressure of at least 100 bar, preferably of at least 1000 bar, or that generates this pressure at least temporarily during operation. A “fuel-conducting” connection is understood to mean a connection between two components that is designed to at least temporarily conduct fuel from the first-mentioned component to the second-mentioned component.Preferably, the connection can be arranged such that it can carry fuel exclusively from the first-mentioned component to the second-mentioned component (and not in the opposite direction).

[0010] According to the invention, the pressure side of the high-pressure pump is also connected to the burner in a fuel-carrying manner. The burner can therefore be operated using fuel that is pumped at a correspondingly high pressure by the high-pressure pump. A relatively high fuel pressure can lead to good atomization of the fuel even at a relatively low fuel temperature and thus to advantageous mixture formation between the fuel and oxygen, which can also be supplied to the burner, in particular as a component of air. In addition, the increase in fuel pressure by means of the high-pressure pump and / or throttling of this pressure increase (to a still relatively high fuel pressure) can lead to heating of the fuel, which can also have a beneficial effect on mixture formation.

[0011] A method according to the invention for operating such an internal combustion engine therefore provides that fuel is supplied to the burner for its operation at least temporarily via the connection to the pressure side of the high-pressure pump. In this case, it can be provided that fuel is always supplied to the burner for its operation via the connection to the pressure side of the high-pressure pump. However, this can be energetically disadvantageous if a correspondingly high pressure of the fuel supplied to the burner is not necessary for its safe operation and in particular for safe commissioning. Accordingly, it can preferably be provided that fuel is only supplied to the burner for its operation via the connection to the pressure side of the high-pressure pump when a temperature of the fuel is lower than a defined limit value or corresponds to this limit value. This limit value can be, for example, 10°C, 0°C, or -10°C.

[0012] The information stating that a connection is provided between two components or sides of components is to be understood as meaning that corresponding connecting lines are provided which are integrated into the fuel supply system in such a way that the fuel pressures at their ends are those assigned to the components or sides of these components.

[0013] Preferably, it can be provided that a preferably adjustable and, in particular, controllable pressure control valve is integrated into the connection from the pressure side of the high-pressure pump to the burner, and in particular into the preferably provided fuel distributor, thereby making it possible to supply fuel to the burner at a pressure that is lower than the pressure initially generated by the high-pressure pump. In particular, this makes it possible to supply fuel to the fuel injector(s) at a different, in particular higher, pressure than the burner.

[0014] According to a preferred embodiment of an internal combustion engine according to the invention, it can be provided that the suction side of the high-pressure pump is also or additionally connected to the burner in a fuel-carrying manner, wherein a valve device is provided which alternatively only releases the connection from the suction side or from the pressure side of the high-pressure pump. This makes it possible to supply fuel to the burner in an energetically advantageous manner from the suction side of the high-pressure pump, for example when the temperature of the fuel is sufficiently high to ensure reliable operation of the burner even with the pressure of the fuel present on the suction side of the high-pressure pump. Accordingly, a method according to the invention can provide that fuel is supplied to the burner for its operation via the connection from the suction side of the high-pressure pump when the temperature of the fuel is greater than the defined limit value.

[0015] Preferably, the valve device can comprise at least one passive valve that switches automatically based on a pressure difference, thereby allowing a structurally simple design. This can require that the connection from the pressure side of the high-pressure pump to the tank can be interrupted by means of a valve, or the pressure therein can be throttled below the pressure in the connection from the pressure side. For this purpose, the pressure control valve integrated into the connection from the pressure side of the high-pressure pump to the tank can preferably be designed accordingly.

[0016] Preferably, the valve device can comprise a pressure change valve having a valve body that, in a first valve body position, interrupts the connection from the suction side and releases the connection from the pressure side, and in a second valve body position, releases the connection from the suction side and interrupts the connection from the pressure side. Alternatively, a check valve can be integrated into each of the connection from the suction side and the connection from the pressure side, with these check valves each interrupting the associated connection in the event of excess pressure on the burner side.

[0017] Connecting the suction side of the high-pressure pump to the burner can be particularly useful if, as is preferably provided, a low-pressure pump (preferably driven by an electric motor) is integrated into the connection between the tank and the suction side of the high-pressure pump, which low-pressure pump can then generate a sufficiently high pressure for safe operation of the burner, for example between 4 bar and 10 bar. Accordingly, it can also preferably be provided that a branch of the connection from the suction side of the high-pressure pump to the burner branches off from the connection from the tank to the high-pressure pump downstream of the low-pressure pump. According to the invention, a “low-pressure pump” is understood to mean a pump that can generate a fuel pressure of at most 100 bar, preferably of at most 10 bar, or generates this at least temporarily during operation.A further advantage that can result from such an integration of a low-pressure pump into the connection of the tank with the suction side of the high-pressure pump is to ensure a reliable supply of fuel to the high-pressure pump.

[0018] An embodiment of an internal combustion engine according to the invention with a connection from the intake side of the high-pressure pump to the burner and with a low-pressure pump can further enable the burner to be supplied with fuel even when the high-pressure pump is not operating. This can be particularly the case when the high-pressure pump is driven by the internal combustion engine and the internal combustion engine is not running. This makes it possible to operate the burner even before commissioning, and in particular before a cold start of the internal combustion engine.

[0019] According to the invention, it can be provided to switch from supplying the burner with fuel via the connection to the suction side of the high-pressure pump to supplying it via the connection to the pressure side of the high-pressure pump, provided that it is recognized that sufficiently safe operation cannot be guaranteed with the fuel supplied via the connection to the suction side. For example, it can be recognized that a higher fuel pressure is required for reliable mixture formation.

[0020] Preferably, it can be provided that the internal combustion engine has a plurality of combustion chambers, each of which is assigned a fuel injector. Furthermore, it can then also preferably be provided that a (same) fuel distributor is integrated into the connections of the fuel injectors and the burner to the pressure side of the high-pressure pump. Such a fuel distributor, known as a "common rail", serves to distribute the fuel coming from the high-pressure pump, in particular to the fuel injectors, and in the process also to form a reservoir for the high-pressure fuel, so that the fuel injectors can be supplied with fuel within limits independently of the current delivery of fuel by the high-pressure pump and can therefore in particular also be supplied with a relatively constant pressure.The fuel distributor, which an internal combustion engine with several combustion chambers can in principle have, can therefore be used advantageously to also supply the burner with fuel.

[0021] According to a preferred embodiment of an internal combustion engine according to the invention, the burner can be connected to the tank and / or to the intake side of the high-pressure pump via a preferably adjustable and, in particular, controllable pressure relief valve. This can support the most precise setting of a defined fuel pressure in the burner. Furthermore, it can be made possible to pump fuel that was delivered by the high-pressure pump and that exceeds the current burner requirement in a circuit, thereby accelerating the heating of the total available fuel.This can not only have a beneficial effect on the operation of the burner and the combustion engine due to favorable mixture formation, but also prevent the fuel filter, which is preferably integrated into the connection between the tank and the intake side of the high-pressure pump, from becoming clogged. When the burner is connected to the intake side of the high-pressure pump, it can therefore be provided that the preferably provided fuel filter is arranged between an opening of this connection and the high-pressure pump, so that fuel returned via this connection is guided through the fuel filter.

[0022] The pressure relief valve can preferably be designed in such a way that it allows a relatively small leakage flow of the fuel to pass through even in a closed state, which in particular makes it possible to remove gas bubbles contained in the fuel from the burner.

[0023] Connecting the burner to the tank can enable a relatively simple design of the pressure relief valve because the tank, as is preferably provided, can be designed without pressure, so that essentially the ambient pressure prevails therein or at least no defined pressure difference to the ambient pressure is established. Setting a defined fuel pressure at the burner by means of the pressure relief valve can therefore be achieved depending on the essentially constant tank pressure, which enables a correspondingly simple design of the pressure relief valve.

[0024] Connecting the burner to the intake side of the high-pressure pump, on the other hand, can offer the advantage that the relatively warm fuel, which can be returned via this connection, is fed directly to the high-pressure pump or a fuel filter upstream of it, either bypassing the tank, thereby enabling effective use of the fuel's thermal energy. Since the pressure at the connection between the tank and the intake side of the high-pressure pump can be significantly higher than the tank pressure, a pressure relief valve integrated into this connection may require a more complex design because it must be able to compensate for possible fluctuations in this pressure in order to set a defined fuel pressure at the burner.

[0025] Preferably, an actively controllable switching valve can be integrated into the connection between the burner and the tank, by means of which the connection can be enabled or interrupted. Such a switching valve can be particularly advantageous if both a connection between the burner and the tank and a connection between the burner and the suction side of the high-pressure pump are provided, in order to be able to specifically utilize the connection between the burner and the suction side of the high-pressure pump.

[0026] The combustion engine of an internal combustion engine according to the invention can, in particular, be a (self-igniting and quality-controlled) diesel engine, because relatively low temperatures, especially with diesel fuel, can have a negative impact on its properties, particularly with regard to its flowability. However, it is also possible for the combustion engine to be a (spark-ignition and quantity-controlled) gasoline engine or a functional combination of a diesel and gasoline engine, e.g., a combustion engine with homogeneous compression ignition. The combustion engine can, in particular, be operated with liquid fuel (i.e., diesel or gasoline).

[0027] The invention also relates to a motor vehicle, in particular a land vehicle, particularly preferably a wheel-based and non-rail-bound motor vehicle (preferably a car or a truck), with an internal combustion engine according to the invention. The internal combustion engine of the internal combustion engine can be provided, in particular, for the (direct or indirect) provision of the traction drive power for the motor vehicle.

[0028] The invention is explained in more detail below with reference to exemplary embodiments shown in the drawings. The drawings show, in simplified form: Fig. 1: an internal combustion engine according to the invention according to a first embodiment; Fig. 2: an internal combustion engine according to the invention according to a second embodiment; Fig. 3: an internal combustion engine according to the invention according to a third embodiment; and Fig. 4: an alternative integration of a burner into a fuel supply system of an internal combustion engine according to the Fig. 1 to 3.

[0029] The Fig. The internal combustion engine shown in Figure 1 comprises a merely schematically illustrated combustion engine 1, which forms, for example, four combustion chambers (not shown), each of which is assigned a fuel injector 2 of a fuel supply system of the internal combustion engine. The fuel injectors 2 are integrated into the internal combustion engine 1 in such a way that they can be used to introduce fuel directly into the combustion chambers.

[0030] The internal combustion engine further comprises an exhaust system 3, also shown only schematically, for discharging exhaust gas originating from the combustion chambers. A burner 4 is integrated into this exhaust system 3. This burner 4 is designed to generate hot gas as needed, which is used to heat one or more exhaust aftertreatment devices (not shown), which are also integrated into the exhaust system 3.

[0031] The fuel supply system of the internal combustion engine comprises, in addition to the fuel injectors 2, a tank 5 for holding fuel, which is primarily intended for operating the internal combustion engine 1. Arranged within the tank 5 is an electric motor-driven low-pressure pump 6, which can be controlled by a control device 7 of the internal combustion engine. The low-pressure pump 6 is connected via fuel lines to a suction side of a high-pressure pump 8, with a fuel-carrying connection, wherein a fuel filter 9 and, between the fuel filter 9 and the high-pressure pump 8, a first sensor device 10 for locally measuring the pressure and temperature of the fuel are integrated into this connection. The high-pressure pump 8 is driven by the internal combustion engine 1 through a mechanical coupling to an output shaft (not shown) of the internal combustion engine 1.The high-pressure pump 8 is preferably designed to be controllable with regard to the delivery rate, ie its delivery capacity can also be influenced independently of the drive speed at which it is driven.

[0032] The pressure side of the high-pressure pump 8 is connected to a fuel distributor 11 for the purpose of conveying fuel, with separate connections leading from this fuel distributor 11 to all of the fuel injectors 2 and to the burner 4, so that the pressure side of the high-pressure pump 8 is connected to the fuel injectors 2 and the burner 4 via the fuel distributor 11. A pressure control valve 12 is also integrated into the connection between the pressure side of the high-pressure pump 8 and the burner 4. This pressure control valve 12 makes it possible to reduce the very high fuel pressure that can be provided by the high-pressure pump 8 and which, for example, can be between 180 bar and 2500 bar depending on the operating state of the internal combustion engine 1, to a level that is sufficient for the safe operation of the burner 4.

[0033] The fuel supply system further comprises a fuel-carrying connection between the suction side of the high-pressure pump 8 and the burner 4, wherein a valve device 13 is provided which alternatively only opens the connection from the suction side or from the pressure side of the high-pressure pump 8. This valve device 13 comprises a pressure change valve having a valve body which, depending on the valve body position, interrupts the connection from the suction side or from the pressure side and opens the other connection. Alternatively (not shown), a check valve can also be integrated into each of the two connections, wherein these check valves each close when there is excess pressure on the burner 4 side.

[0034] A second sensor device 14 for locally determining the pressure and temperature of the fuel is integrated into each of the connections from the suction side and the pressure side of the high-pressure pump 8 to the burner 4, specifically into an integral section thereof. This second sensor device 14 can preferably be positioned as close as possible to the burner 4 in its fuel supply or, more preferably, integrated into it.

[0035] The fuel supply system further comprises a fuel-carrying connection from the burner 4 to the tank 5, specifically to a first return line 15, which leads from the high-pressure pump 8 to the tank 5. A pressure relief valve 16 is integrated into this connection between the burner 4 and the tank 5. This pressure relief valve can preferably be designed to be electronically controllable.

[0036] A portion of the fuel delivered from the low-pressure pump 6 to the high-pressure pump 8 can be returned to the tank 5 via the first return line 15, provided that the low-pressure pump 6 delivers a larger quantity of fuel compared to the high-pressure pump 8.

[0037] A second return line 17, into which a pressure-maintaining valve 18 can be integrated, leads from the fuel injectors 2 to the tank 5, with the first return line 15 and the second return line 17 being integrally formed in sections. Excess fuel that was not introduced into the combustion chambers by the fuel injectors 2 can be returned to the tank 5 via the second return line 17.

[0038] For use of the burner 4 during operation of the internal combustion engine, fuel is supplied to it. This occurs either via the connection between the suction side or the pressure side of the high-pressure pump 8 and the burner 4. Supplying the burner 4 with fuel via the connection from the suction side of the high-pressure pump 8 is only provided if the fuel has a temperature greater than a defined limit value, which may be, for example, 10°C. The temperature can be measured, for example, using the second sensor device 14. The relatively low pressure of, for example, approximately 5 bar, with which the fuel is fed to the burner 4 via this connection and which is provided by the low-pressure pump 6, is then sufficient to ensure safe operation of the burner 4.If, however, the fuel temperature corresponds to or is lower than the limit value, fuel is supplied to the burner 4 via the connection from the pressure side of the high-pressure pump 8. As a result, the fuel has a significantly higher pressure, for example, between 20 bar and 100 bar, which ensures sufficiently good mixture formation in the burner 4 despite the relatively cold fuel. Furthermore, the significant increase in fuel pressure by means of the high-pressure pump 8 and, in particular, the partial relief of this pressure by means of the pressure control valve 12 leads to a significant heating of the fuel, which also has a beneficial effect on the mixture formation and thus the operation of the burner 4.

[0039] The connection of the burner 4 to the tank 5 and the pressure relief valve 16 integrated into this connection, in conjunction with the pressure control valve 12, enable sufficiently precise regulation of a specified fuel pressure in the area of ​​the burner 4. Since the tank 5 is designed to be pressureless, the pressure relief valve 16 can be designed with a relatively simple construction, since the essentially constant tank pressure acts as the counterpressure applied to the pressure relief valve 16 in addition to the fuel pressure to be regulated in the area of ​​the burner 4. The pressure relief valve 16 can therefore be designed as a simple check valve, optionally with a defined leakage.

[0040] Furthermore, via the connection of the burner 4 to the tank 5, fuel at a relatively high temperature can be returned to the tank 5, thereby increasing the temperature of the fuel in the tank 5 as a whole and thus also the temperature of the fuel pumped by the low-pressure pump 6 and flowing through the fuel filter 9. This can, in particular, counteract so-called gelling of the fuel filter 9. This refers to the clogging of the fuel filter 9 due to flocculation of the fuel at relatively cold temperatures, which occurs particularly with diesel fuels.These flocculants dissolve again at a sufficiently high fuel temperature, so that it is necessary to reach this sufficiently high fuel temperature at least in the area of ​​the fuel filter 9 before it becomes too largely clogged by flocculants and would thereby restrict or prevent operation of the internal combustion engine.

[0041] For a targeted return of fuel via the connection of the burner 4 to the tank 5, the high-pressure pump 8 can be operated with a higher delivery rate than is required for the operation of the internal combustion engine 1 and the burner 4. This can always be provided when fuel is supplied to the burner 4 via the connection from the pressure side of the high-pressure pump 8. However, it may also be sufficient to operate the high-pressure pump 8 with a higher delivery rate for a targeted return of fuel if the temperature of the fuel is below a second limit value that is lower than the limit value above which a supply of fuel to the burner 4 from the pressure side of the high-pressure pump 8 is provided.

[0042] Basically, the heat energy of the fuel is returned to the tank 5 according to the Fig. 1 is used relatively inefficiently because the returned fuel is mixed with the fuel in the tank 5 and thus has only a slight effect on increasing the temperature of the fuel delivered by the low-pressure pump 6. To avoid this disadvantage, according to the Fig. 2, it can be provided that the return connection from the burner 4 does not open into the tank 5 or into the first return line 15, but rather into the connection between the tank 5 and the high-pressure pump 8 and thus upstream of the fuel filter 9. As a result, the relatively high temperature of the returned fuel can lead to a significantly greater increase in the temperature of the fuel fed via the connection from the tank 5 to the high-pressure pump 8. A disadvantage of this embodiment of an internal combustion engine according to the invention, however, is that the backpressure for regulating the pressure of the fuel in the region of the burner 4 depends on the fuel pressure that prevails in the connection between the tank 5 and the high-pressure pump 8 and that is significantly influenced by the operation of the low-pressure pump 6, which can make a more complex design of the pressure relief valve 16 used expedient.Such a relatively complex pressure relief valve 16 can provide for the use of the ambient pressure as the reference pressure for control. Corresponding pressure relief valves, particularly in diaphragm valve designs, are generally known.

[0043] When designing an internal combustion engine according to the Fig. 2, which provides a connection leading from the burner 4 to the suction side of the high-pressure pump 8 for the return of fuel, could be a relatively simple design of the pressure relief valve 16, as in the internal combustion engine according to the Fig. 1 can be used advantageously, can lead to insufficient controllability. This can at least be the case if the burner 4 is operated with fuel that is supplied at a relatively low pressure via the connection from the suction side of the high-pressure pump 8 to the burner 4, because then essentially the same pressure would be present on both sides via the pressure relief valve 16. It can therefore be particularly advantageous to design the internal combustion engines according to the invention according to the Fig. 1 and Fig. 2 regarding the traceability of fuel, as is the case with the internal combustion engine according to Fig. 3. There, both a (first) connection of the burner 4 with the tank or with the first return line 15 and a (second) connection of the burner 4 with the suction side of the high-pressure pump 8 are provided. In the first connection, a first pressure relief valve 16a is integrated, which can be designed relatively simply, as is already the case for the internal combustion engine according to Fig. 1. In contrast, a second pressure relief valve 16b is incorporated in the second connection, which may have a more complex design, as is the case in connection with the internal combustion engine according to Fig. 2. It is also possible to functionally combine these two pressure relief valves 16a, 16b into a single pressure relief valve 16 by setting two pressure levels for this pressure relief valve 16 by means of a controllable pressurization.

[0044] The design of an internal combustion engine according to the Fig. 3 enables, when the burner 4 is operated with fuel that was supplied to it at a relatively low pressure via the connection from the suction side of the high-pressure pump 8, some of the fuel to be returned to the tank 5 via the first connection, whereas when the burner 4 is operated with fuel that was supplied to it at a relatively high pressure via the connection from the pressure side of the high-pressure pump 8, the fuel can advantageously be returned via the second connection into the inlet to the high-pressure pump 8 or into the connection between the tank 5 and the high-pressure pump 8. It can be advantageous if the pressure to be limited by the first pressure-limiting valve 16a is lower, for example by between 0.2 bar and 0.5 bar lower, than the pressure to be limited by the second pressure-limiting valve 16b.For a targeted selection of one of the alternatively used connections of the burner 4 to either the tank 5 or the inlet to the high-pressure pump 8, a switching valve 19 integrated into the first connection (upstream or downstream of the first pressure relief valve 16a) can preferably be provided, which - depending on the switching position - opens the first connection and thus allows fuel to be returned via the first connection or interrupts the first connection and thus allows fuel to be returned via the second connection. Furthermore, a throttle can be integrated into the first connection upstream of the first pressure relief valve 16a and the switching valve 19 to protect these components from excessive flow.

[0045] An energetically advantageous use of the connection between the suction side of the high-pressure pump 8 and the burner 4 is, as described, possible if the temperature of the fuel is sufficiently high to ensure reliable operation of the burner 4 even with the relatively low pressure that the fuel then has. In principle, this connection between the suction side of the high-pressure pump 8 and the burner 4 can be dispensed with and the burner 4 can always be supplied with fuel from the pressure side of the high-pressure pump 8. The connection between the suction side of the high-pressure pump 8 and the burner 4 can therefore be dispensed with in all embodiments of internal combustion engines according to the invention according to the Fig. 1 to 3 can be omitted.

[0046] The Fig. The embodiments shown in Figures 1 to 3 provide for a direct connection of both the fuel supply connections and the fuel return connection(s) to the burner 4, which also enables flushing of the burner 4 itself with the aim of removing gas bubbles via the returned fuel. Alternatively, it may also be provided to integrate the burner 4 into all of these connections via a single branch line, as shown in the Fig. 4. This can simplify the structural design of the burner 4 and in particular of a fuel injector thereof, because it only needs to have a single fuel connection. List of reference symbols 1 combustion engine 2 fuel injector 3 Exhaust system 4 burners 5 tanks 6 Low pressure pump 7 Control device 8 High pressure pump 9 Fuel filter 10 first sensor device 11 Fuel rail 12 Pressure control valve 13 Valve device 14 second sensor device 15 first return line 16 Pressure relief valve 16a first pressure relief valve 16b second pressure relief valve 17 second return line 18 Pressure holding valve 19 Switching valve QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2 863 026 A1

[0004] DE 10 2019 008 956 A1

[0004] DE 10 2020 213 702 A1

[0004]

Claims

[1] Internal combustion engine with • an internal combustion engine (1) which forms at least one combustion chamber, • an exhaust line (3) for discharging exhaust gas originating from the at least one combustion chamber, wherein a burner (4) is integrated into the exhaust line (3), and • a fuel supply system with a tank (5), a high-pressure pump (8) and at least one fuel injector (2) which is assigned to the combustion chamber, wherein the tank (5) is connected in a fuel-carrying manner to a suction side of the high-pressure pump (8) and a pressure side of the high-pressure pump (8) is connected in a fuel-carrying manner to the at least one fuel injector (2), characterized by that the pressure side of the high-pressure pump (8) is also connected to the burner (4) in a fuel-carrying manner. [2] Internal combustion engine according to claim 1, characterized bythat the internal combustion engine (1) has a plurality of combustion chambers, each of which is assigned a fuel injector (2), wherein a fuel distributor (11) is integrated into the connections of the pressure side of the high-pressure pump (8) to the fuel injectors (2) and to the burner (4). [3] Internal combustion engine according to claim 1 or 2, characterized by that in addition the suction side of the high-pressure pump (8) is connected to the burner (4) in a fuel-carrying manner, wherein a valve device (13) is provided which alternatively only releases the connection from the suction side or from the pressure side of the high-pressure pump (8). [4] Internal combustion engine according to one of the preceding claims, characterized by that a low-pressure pump (6) is integrated into the connection between the tank (5) and the suction side of the high-pressure pump (8). [5] Internal combustion engine according to one of the preceding claims, characterized bythat a pressure control valve (12) is integrated into the connection between the pressure side of the high-pressure pump (8) and the burner (4). [6] Internal combustion engine according to one of the preceding claims, characterized by that the burner (4) is connected to the tank (5) via a pressure relief valve (16) and / or to the suction side of the high-pressure pump (8) via a pressure relief valve (16) in a fuel-carrying manner. [7] Internal combustion engine according to claim 6, characterized by that an actively controllable switching valve (19) is additionally integrated into the connection between the burner (4) and the tank (5). [8] Method for operating an internal combustion engine according to one of the preceding claims, characterized by that fuel is supplied to the burner (4) for its operation via the connection from the pressure side of the high-pressure pump (8). [9] Method according to claim 8, characterized bythat fuel is supplied to the burner (4) for its operation via the connection from the pressure side of the high-pressure pump (8) only when a temperature of the fuel is lower than a defined limit value or corresponds to this limit value. [10] A method according to claim 9 for operating an internal combustion engine according to claim 3 or any of the claims dependent on claim 3, characterized by that fuel is supplied to the burner (4) for its operation via the connection to the suction side of the high-pressure pump (8) when the temperature of the fuel is greater than the defined limit value.

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