DE102018009400A1 - Internal combustion engine for a motor vehicle with a burner arranged in an exhaust tract, and method for operating such an internal combustion engine - Google Patents

Abstract

The invention relates to an internal combustion engine (10) for a motor vehicle, with an exhaust tract (16) through which exhaust gas from the internal combustion engine (10) can flow, and with a burner (56) arranged in the exhaust tract (16) and having a combustion chamber (64), in which a fuel is to be burned by means of the burner (56) in order to heat the exhaust gas to form an open flame, the exhaust gas tract (16) being an exhaust gas pipe (66) through which the exhaust gas can flow, in which the exhaust gas pipe (66) flowing through the exhaust gas pipe Exhaust gas through which the combustion chamber (64) is arranged, and has a flap (53), by means of which, depending on a load and a speed of the internal combustion engine (10), a first quantity flowing through the exhaust pipe (66) and a second quantity bypassing the combustion chamber (64) The amount of exhaust gas can be adjusted.

Description

The invention relates to an internal combustion engine for a motor vehicle, in particular for a motor vehicle, according to the preamble of claim 1. In addition, the invention relates to a method for operating such an internal combustion engine.

Such an internal combustion engine for a motor vehicle, in particular for a motor vehicle, is already the example DE 10 2012 024 260 A1 as known. The internal combustion engine has an exhaust tract through which exhaust gas from the internal combustion engine can flow and a burner arranged in the exhaust tract and comprising a combustion chamber. In the combustion chamber, a fuel is burned by the burner to heat the exhaust gas to form an open flame.

Furthermore, the DE 10 2008 032 601 A1 a method for setting a state of an exhaust gas flow of an internal combustion engine of a motor vehicle, with an exhaust gas system connected downstream of the internal combustion engine and through which the exhaust gas flow flows, and with a burner assigned to the exhaust gas flow. In addition, the DE 35 32 778 A1 a device for regenerating soot filters as known.

The object of the present invention is to further develop an internal combustion engine and a method of the type mentioned in the introduction such that the internal combustion engine can be operated with particularly low fuel consumption and emissions.

This object is achieved by an internal combustion engine with the features of claim 1 and by a method with the features of claim 5. Advantageous refinements with expedient developments of the invention are specified in the remaining claims.

In order to further develop an internal combustion engine of the type specified in the preamble of patent claim 1 in such a way that the internal combustion engine can be operated with particularly low fuel consumption and emissions, the exhaust gas tract has an exhaust pipe through which the exhaust gas can flow and in which the combustion chamber is arranged . As a result, the exhaust gas flowing through the exhaust pipe can flow through the combustion chamber. In addition, the exhaust tract has a flap, by means of which, depending on a load and depending on a speed of the internal combustion engine, a first quantity of the exhaust gas flowing through the exhaust pipe and a second quantity of the exhaust gas bypassing the combustion chamber or the exhaust pipe and thus the combustion chamber can be set. The feature that the second quantity bypasses the combustion chamber or the burner as a whole means that the second quantity of the exhaust gas does not flow through the combustion chamber.

The burner is an additional burner, by means of which high temperatures of the exhaust gas can advantageously be achieved, for example during a cold start. In the context of the invention, the fuel for operating the burner can be designed in particular as the fuel with which the internal combustion engine is also operated. As a result, an exhaust gas aftertreatment device arranged in the exhaust tract and, for example, downstream of the burner can be heated or kept warm. In other words, by heating the exhaust gas by means of the burner, a sufficiently high temperature of the exhaust gas aftertreatment device can be ensured, so that, for example, an oxidation catalyst and / or an SCR catalyst and / or a particle filter of the exhaust gas aftertreatment device can advantageously be heated or kept warm by heating the exhaust gas. As a result, the emission of nitrogen oxide emissions (NO _x emissions) can be greatly reduced, in particular when the internal combustion engine is cold started.

As part of a method for operating the internal combustion engine, it is provided that the burner, which acts as an additional burner, is ignited only in a low-load range and with a cold exhaust gas aftertreatment device, that is to say to activate it. The low-load range is characterized in that the effective mean pressure of the internal combustion engine is less than or equal to approximately 4 bar. The exhaust gas aftertreatment device is cold when the exhaust gas aftertreatment device or the exhaust gas upstream of the burner has a temperature which is lower than a light-off temperature, also referred to as the light-off temperature, of the oxidation catalyst, which is designed, for example, as a diesel oxidation catalyst. In one embodiment of this method for operating the internal combustion engine, it is provided to adjust the flap, which is also referred to as the exhaust flap, in such a way that the exhaust gas is passed essentially completely through to the burner and through the combustion chamber.

In particular, when the internal combustion engine has a high speed, the flap is set such that the exhaust gas at least partially the burner and thus the combustion chamber deals. In this regard, it was found that the exhaust gas has such a high flow velocity in the exhaust tract at high engine speeds that the flame cannot stabilize, particularly due to the high flow velocity and especially when the exhaust gas aftertreatment device is cold. Because at least part of the exhaust gas now bypasses the combustion chamber, a stable flame can form, as a result of which the exhaust gas can be heated effectively and efficiently.

In an advantageous embodiment of the invention, the internal combustion engine has a metering device by means of which the, in particular unburned, fuel can be injected into the exhaust pipe or into the exhaust gas flowing through the exhaust pipe. The injection of the fuel into the exhaust gas is also referred to as the addition of secondary fuel and takes place, for example, as a function of an amount of residual oxygen contained in the exhaust gas, the amount being calculated, for example, using air and injection models and with at least one lambda probe arranged in the exhaust tract or using NO _x - Sensors, which can also measure a lambda value of the exhaust gas, are detected.

In an advantageous embodiment of the internal combustion engine according to the invention, the fuel for operating the burner in the exhaust tract is designed as a fuel for operating the internal combustion engine, which fuel can be injected into the internal combustion engine by means of at least one post-injection. With this embodiment of the invention, a metering device for fuel in the exhaust tract specially provided for the addition of the fuel can advantageously be saved. A metering device for the continuous addition of small amounts of fuel is technically demanding. In this embodiment of the invention, the already existing fuel metering system of the internal combustion engine can be used particularly advantageously. It is also conceivable that the fuel that is injected into the internal combustion engine for the operation of the burner in the exhaust tract is injected into the internal combustion engine in several post-injections.

At higher loads of in particular more than 4 bar effective mean pressure and especially when the temperature of the exhaust gas or the exhaust gas aftertreatment device is higher than the light-off temperature of the oxidation catalytic converter, in one embodiment of the method for operating the internal combustion engine the fuel on the burner and also referred to as secondary fuel is used injected into the combustion chamber, and the flap is set such that essentially all of the exhaust gas flows through the combustion chamber and is thus directed past a nozzle of the burner. Here, the burner or the metering device functions as a metering device in order to inject unburned fuel and thus unburned hydrocarbons into the exhaust gas. Ignition of the fuel caused by the burner is preferably not carried out, the injected fuel being oxidized on and thereby burned by the sufficiently warm oxidation catalyst. This embodiment of the method for operating the internal combustion engine also causes a temperature increase in the exhaust gas, as a result of which the oxidation catalytic converter and / or other elements of the exhaust gas aftertreatment device downstream of the oxidation catalytic converter, such as the SCR catalytic converter, can advantageously be heated. The process, also referred to as the “catalytic burner”, can be used throughout the operating range to increase the temperature significantly. The temperature rise depends on the residual oxygen in the exhaust gas. This can advantageously be changed by air management, in particular by means of a wastegate position in the case of a wastegate or bypass turbine, or by adjusting a turbine geometry in the case of a variable turbine (VTG).

In the internal combustion engine according to the invention, a particularly advantageous temperature management, also referred to as thermal management, can be represented, by means of which advantageous temperatures, in particular in the exhaust tract, can be achieved in different operating areas. The burner functions in particular as a part-load burner system, which is preferably activated only in a part-load range or only when the effective mean pressure of the internal combustion engine is less than or equal to approximately 4 bar.

The burner system can represent a measure outside the engine in order to heat the exhaust gas outside the combustion chambers of the internal combustion engine. The burner system is preferably provided for the lower speed / load range. In particular for inner-city applications and / or vehicles with low loads, journeys with a high idle rate, as well as on disadvantageous routes with a high percentage of overrun. The thermal management preferably also includes a motor or internal engine thermal management, within the scope of which, for example, advantageously high temperatures of the exhaust gas can be achieved by internal engine measures. In-engine thermal management is intended in particular for the upper speed / load range of the internal combustion engine. For example, in the simplest case, only the engine idling and thrust range is through the Burner supports. For example, the complete fuel or its energy content is used as energy in the exhaust gas in order to heat the exhaust gas. This makes it possible to achieve an advantageous availability of the SCR catalytic converter, which can therefore always be active, and the internal combustion engine, which is also referred to as an internal combustion engine or motor and which is designed, for example, as a diesel engine, can always be operated in a consumption-optimized manner without thermal management.

The burner system manages, for example, with simple secondary air compressors or can completely dispense with secondary air, for example by using oxygen contained in the exhaust gas to burn the fuel. Alternatively or additionally, the oxidation catalytic converter can be used for an exothermic temperature increase in that unburned fuel, which was previously injected into the exhaust gas by means of the metering device or by means of the burner, is oxidized exothermically on the oxidation catalytic converter and thus burned.

In a further embodiment of the invention, it is provided that the aforementioned particle filter and / or the aforementioned oxidation catalyst and / or the aforementioned SCR catalyst are arranged in the exhaust tract downstream of the burner. If the internal combustion engine is designed, for example, as a diesel engine, the particle filter is preferably designed as a diesel particle filter (DPF). Furthermore, for example, the oxidation catalytic converter is then designed as a diesel oxidation catalytic converter (DOC).

A further embodiment is characterized in that the burner is designed to heat the exhaust gas when the effective mean pressure of the internal combustion engine is less than or equal to approximately 4 bar and the exhaust gas upstream of the burner or the exhaust gas aftertreatment device has a temperature which is lower than that Starting temperature of the oxidation catalyst is.

The invention also includes a method for operating an internal combustion engine according to the invention. The invention is based in particular on the following findings: Sufficiently high exhaust gas temperatures are advantageous for efficient exhaust gas purification. Especially in superstoichiometric applications, such as in diesel engines, the exhaust gas temperature drops due to the lean operation in the lower partial load, which can lead to a strong interaction between the engine and exhaust gas aftertreatment or exhaust gas aftertreatment device. Modern diesel engines have at least one or more exhaust gas turbochargers or combined supercharging systems and an intercooler. Depending on the application, the turbine is designed as a fixed geometry turbine, as a wastegate or bypass turbine or as a variable turbine. Many modern engines have a cooled, regulated exhaust gas recirculation system to reduce raw nitrogen oxide emissions.

A modern exhaust gas aftertreatment includes an oxidation catalyst designed, for example, as a diesel oxidation catalyst, a particle filter designed, for example, as a diesel particle filter, and an SCR catalyst (SCR - Selective Catalytic Reduction - selective catalytic reduction). Furthermore, a so-called barrier catalytic converter, which is also referred to as an ammonia slip catalyst (ASC), can be provided. In order to denit the exhaust gas or at least partially remove any nitrogen oxides contained in the exhaust gas, a reducing agent, in particular a liquid reducing agent, which is in the form of an aqueous urea solution, is metered into a mixing section, for example, which is arranged upstream of the SCR catalytic converter.

The closed particulate filter, for example, collects soot contained in the exhaust gas, which accumulates on the particulate filter. This increases the loading of the particle filter and thus the exhaust gas back pressure. Either it can be provided to passively oxidize the soot in the particle filter, also referred to simply as a filter, at about 300 to 450 degrees Celsius by nitrogen dioxide (NO ₂ ), which comes, for example, from the engine and from the oxidation catalytic converter, or the soot in the filter becomes active at about 600 degrees Celsius oxidized with oxygen. For this purpose, the oxidation catalyst, which is arranged upstream of the particle filter in particular, should be brought above its light-off temperature, which is approximately 220 to 300 degrees Celsius and is dependent on the noble metal and the aging of the oxidation catalyst. Thereafter, in particular additional fuel is introduced into the exhaust gas, the fuel being, for example, the aforementioned fuel. The unburned fuel that is introduced into the exhaust gas can, for example, burn or be burned on and by the oxidation catalyst, so that the oxidation catalyst is used as a catalytic burner. For example, a temperature of 550 to 600 degrees Celsius is set on the filter, which causes the soot to oxidize with oxygen. For the rest of the time, the aim is to have a sufficiently high SCR temperature for the catalytic reduction of nitrogen oxides. The minimum dosage release for the reducing agent is, for example, around 180 degrees Celsius. However, higher temperatures of around 200 to 240 degrees Celsius are advantageous for the high efficiency of the SCR.

In connection with a regeneration of the particle filter, various ways of thermal management have been established in recent years by reducing the combustion lambda by intervening in an air control or air control. Intake air throttling is a common and inexpensive method. Exhaust throttling can be done by a variable turbine or by an adjustable exhaust flap. However, combined systems are also in use. An innovation is a variable exhaust valve control or an exhaust gas recirculation valve offset in the manifold. There are numerous other concepts by means of which the combustion air ratio (λ or lambda) can be reduced. These can include variable valve trains such as early or late intake valve closing or early or late performance of the Miller process, internal exhaust gas recirculation, phase adjustment of the intake camshaft, opening the early exhaust valve, and combined applications with decompression braking systems. By reducing the boost pressure, the exhaust gas temperature can be increased significantly. A variable turbine geometry, a wastegate turbocharger or a strong Miller cycle with early or late intake valve has proven to be very fuel efficient.

In the lower load range at an effective mean pressure of 0 to 2 bar, for example, a significant increase in the exhaust gas temperature is only possible through additional gas exchange work and lowering the combustion air ratio, as is possible through throttle systems in fresh air or exhaust gas, but also through variable control times. This exhaust gas temperature increase is inefficient and usually not sufficient in the idling range. In critical applications or journeys with a long idle period, the SCR catalytic converter cools down excessively below its light-off temperature after a long period of time and / or particle filter regeneration that has already started must be interrupted, which significantly extends the regeneration period. In addition, applications that are critical for installation space usually do not have an exhaust gas aftertreatment close to the engine, but rather an on-board exhaust gas treatment, which additionally makes temperature losses more difficult to operate catalytic converters. In subsequent driving, the SCR catalytic converter must then be heated to or above its light-off temperature, which can result in increased nitrogen oxide emissions. A fuel-efficient temperature management usually comprises a combination of engine temperature management for the upper load range and one or the burner system described above for the lower load range.

The burner has, for example, a fuel supply line and an air supply line and an ignition source such as a spark plug. The initially cold exhaust gas is heated by the burner and thereby discharged with a temperature difference ΔT. The burner output depends on the fuel supply and the amount of air required. The fuel-air mixture is ignited at the ignition source, for example on a spark plug or on a glow plug. Different temperature sensors and sensors for lambda control are provided for regulation. In the burner, for example, the fuel and the air can in particular be mixed stoichiometrically by an injection nozzle. The resulting fuel-air mixture is ignited using the ignition source. The ignition source can be designed as a glow or plasma spark plug. Igniting the fuel-air mixture creates the open flame of the burner.

In the simplest case, only the area near the engine idling and the lower thrust area are supported by the burner, which is designed as a diesel burner, for example. This can solve the problem of external air consumption. The burner output is or is limited by the air made available. The air can be handled due to the restricted area of application. The external air can optionally be provided by a small secondary air blower or by a compressed air system on the vehicle side of the motor vehicle, which is designed, for example, as a commercial vehicle. To decouple the vehicle's compressed air network, the burner should have an additional compressed air tank. A simple, small secondary air blower can be used for the application area mentioned in the lower speed / load range due to the low back pressure influence, as is used, for example, in petrol engine areas. As a result, costly secondary air compressors can be avoided.

Here, the entire fuel or its entire energy content can be used to bring about a temperature increase in the exhaust gas. As a result, this thermal management process is highly efficient in the lower load range and is superior to many conventional motor processes, in particular for rapid heating of the exhaust gas aftertreatment device. In city cycles or in applications with a high idling ratio and in overrun phases, the exhaust gas aftertreatment device, which is also referred to as the exhaust gas aftertreatment system, in particular the SCR catalytic converter, can be heated up much more quickly via its own temperature or excessive cooling is prevented.

For example, with an arrangement of the burner close to the exhaust gas treatment, the light-off temperature of the oxidation catalytic converter can be reached very quickly. Additional metering of unburned hydrocarbons by means of the burner, late internal injection and / or secondary fuel injection (SKE) close to the engine can also result in a temperature increase with the residual oxygen in the exhaust gas via the oxidation catalytic converter. As a result, the thermal heating output can be increased significantly, which means that the burner output can be reduced or even deactivated. This can greatly reduce air consumption.

When the burner is arranged, for example, the oxidation catalytic converter and the particle filter are first heated, whereupon the SCR catalytic converter is heated. For example, sheets and catalytic converters arranged in the exhaust tract have an appreciable heat capacity, so that the temperature increase of the SCR catalytic converter is greatly delayed. A faster temperature increase can be achieved by placing the burner immediately after the particle filter and, for example, in front of a metering point at which the reducing agent can be introduced into the exhaust gas. Depending on the burning quality, an additional particle filter element is advantageous. Thus, for example, a filter element is provided in addition to the particle filter, which is arranged downstream of the burner and upstream of the particle filter. By means of the filter element, which is arranged, for example, at a certain distance directly after the combustion chamber, soot resulting from the combustion of the fuel can be collected in the filter. Due to the high burner temperature, soot burn-off of the soot in the filter element can be achieved at any time with a low oxygen content. The oxygen is represented either cyclically or by a slightly lean burner operation.

In the direction of flow of the exhaust gas flowing through the exhaust tract, the SCR catalytic converter can be the first catalyst through which the exhaust gas can flow. Using an upstream burner, it can be brought up to its starting temperature in a few seconds. The nitrogen oxide emissions can thus be reduced or kept low after a few seconds after a cold start.

With copper catalysts, oil and fuel can lead to sulfur poisoning and a reduction in the conversion rate. A high temperature is required for desulfurization, also known as desulfation. With conventional exhaust systems, this is achieved by high-temperature regeneration of approx. 550 to 600 ° C. This can be problematic if the oxidation catalytic converter is arranged downstream of the SCR catalytic converter.

By using an upstream burner, a sufficiently high exhaust gas temperature can be shown in idle or in an area close to idling, for example, to be able to achieve adequate desulfurization.

The burner is arranged, for example, in an exhaust pipe between the turbocharger and the exhaust gas aftertreatment device. To reduce thermal losses, the burner should be close to the exhaust gas aftertreatment device. In optimized systems, the burner is integrated in the exhaust gas aftertreatment device. The burner is located directly in front of the SCR catalytic converter for maximum nitrogen oxide reduction, i.e. for the fastest possible heating.

The burner can include the combustion chamber, an injection valve, an injection nozzle and a mixing element and an ignition system. The ignition system includes, for example, the aforementioned ignition source. In particular, the ignition system can comprise a spark plug with a coil and / or a simple glow plug. For example, the injection nozzle is protected in a dead space in the exhaust gas duct. The nozzle holes are relatively large and are closed by an injection needle. Depending on the design and boundary conditions, the injection nozzle can be cooled with engine cooling water and / or urea or reducing agent. For example, in order to operate the burner without secondary air and to activate the burner, the exhaust flap is closed so that, for example, all of the exhaust gas flows through the combustion chamber and thus through the burner. The exhaust gas is enriched with unburned hydrocarbons (HC), mixed and then ignited at or by means of the ignition source. The flap can be operated digitally and thus in black and white, so that the flap can only be moved, in particular pivoted, between exactly one open position and exactly one closed position. A possible leakage of the flap is determined in such a way that the exhaust gas back pressure is acceptable and a minimal residual oxygen is present, the exhaust gas back pressure initially being advantageous for increasing the engine temperature.

As an alternative to a digital design of the flap, the flap can be designed as a freely controllable flap, as a result of which the flap can be moved, in particular pivoted, into a number of different positions. This allows the mass flow in the burner to be regulated. The mass flow in the burner can either by a lambda measurement or Control according to the burner or via a delta-p determination. In view of an existing nitrogen oxide sensor with a lambda signal, pilot control with lambda control can be implemented inexpensively. The flow rate in the burner can be regulated and the operating range of the burner can be expanded by the mass flow distribution.

The exhaust back pressure results from the leakage of the exhaust flap and the minimal cross section in the bypass burner. The size of the burner depends on the area of application in the maximum speed in the combustion chamber. The back pressure can also be reduced by leakage of the bypass valve. As a result, a certain residual oxygen is available to the exhaust gas aftertreatment. The burner has a very good cold start capability because hot exhaust gas of at least 80 to 200 degrees Celsius is passed through the burner, especially the combustion chamber.

The burner can be arranged close to the engine with an exhaust gas aftertreatment close to the engine. With a variable turbine geometry turbine and / or by means of the exhaust flap, the exhaust gas is conducted via a bypass line. This directs the exhaust gas into the burner. The unburned hydrocarbons are generated in the engine and / or by secondary fuel injection in the bypass line. The burner can either work with an ignition source or a highly coated oxidation catalytic converter is used which has a very low light-off temperature, which means that internal heating measures can always exotherm the oxidation catalytic converter.

As soon as, for example, the oxidation catalytic converter is above its light-off temperature, the ignition source of the burner is deactivated and, for example, the injection nozzle of the burner doses unburned hydrocarbons in the exhaust gas. The maximum amount of unburned hydrocarbons in turn depends on the residual oxygen content of the exhaust gas and on the heating power required. However, the oxidation catalytic converter does not always require lambda = 1 to 1.1 and allows a much wider operating range. Due to the thermal inertia of the oxidation catalytic converter, the entire internal combustion engine map can be used in dynamic operation. The heat output can be increased by increasing the air mass flow, for example by closing the variable turbine geometry, by reducing the exhaust gas recirculation or by increasing the engine speed via the gear selection on the transmission. This increases the heating power and also shortens the cold start time of the SCR catalytic converter. The burner only activates the oxidation catalytic converter. As soon as the oxidation catalytic converter loses its light-off temperature, the burner is reactivated. However, the main heating power is provided by the oxidation catalytic converter, the extinction of the oxidation catalytic converter (light-out) being controlled by exhaust gas from the internal combustion engine that is too cold.

However, the flow rate must not be too high, otherwise the flame will be blown out. The flow rate results for a defined combustion chamber with a diameter of, for example, 45 millimeters or with a flow cross-section of 1600 square millimeters and a series application. The mass flow can be reduced further via the exhaust gas recirculation or other variables influencing the mass flow, such as variable turbine geometry, wastegate and throttle valve. As a result, the operating range can take place towards higher speeds and loads.

The metering of the fuel into the exhaust gas is adapted, for example, to the oxygen content of the exhaust gas. On the one hand, the mixture should be ignitable (lambda = 1 to 1.1), which defines the upper combustion air ratio (lambda), and on the other hand, the lambda is limited to 1. The additional, possible heating output is not constant and depends on the residual oxygen. In dynamic operation, for example when starting up, the burner support is switched off and the exhaust flap is opened. Depending on the design and requirements, the internal combustion engine works against the closed exhaust flap. If the flap leakage is high enough, the burner can work in the rich range (lambda <1) or the ignition is switched off. The unburned hydrocarbons are then burned, for example, in the oxidation catalyst and by means of the oxidation catalyst. As soon as the oxidation catalytic converter has exceeded its light-off temperature, the further temperature increase can take place via the oxidation catalytic converter. The burner's injection nozzle then replaces, for example, the in-engine or near-engine metering of unburned hydrocarbons.

It is also conceivable to represent the metering of unburned hydrocarbons into the exhaust gas in the engine or via a metering device close to the engine. In this case, the burner itself does not have an injection valve for introducing unburned hydrocarbons into the exhaust gas. In this case, the exhaust flap should close very tightly so that any slippage of unburned hydrocarbons is small or avoided. The residual oxygen after the burner can over the Amount of unburned hydrocarbons can be adjusted.

The burner is preferably arranged close to the engine with an exhaust gas aftertreatment device close to the engine. A bypass valve, also known as a wastegate, can close a corresponding turbine flood of the turbine of the exhaust gas turbocharger by opening. This directs the exhaust gas into the burner. The unburned hydrocarbons are generated within the engine. The burner can either work with an ignition source or a highly coated oxidation catalyst is used that has a very low light-off temperature.

The target temperature of the burner is calculated, for example, from catalyst temperature sensors and the available oxygen content of the exhaust gas. In the case of concepts without secondary air, the residual oxygen for the catalytic processes must be taken into account. The temperature support is requested with a motor control or motor control as required. The logic and control are implemented in the engine control unit.

As soon as, for example, the oxidation catalyst, which is designed in particular as a diesel oxidation catalyst, is above its light-off temperature, additional fuel, that is to say unburned hydrocarbons (HC), is also metered in. This allows the exhaust gas heat output to be maximized. The heat output is limited by the oxygen content of the exhaust gas. This can possibly be influenced by motor measures. This can involve closing the variable turbine geometry, reducing exhaust gas recirculation and / or increasing the engine speed via the gear selection on the transmission. This shortens the cold start time even more. The burner output can also be reduced, which reduces the temperature losses up to the oxidation catalytic converter and the air consumption. This reduces the burner output required, which reduces the problem of the supply of combustion air.

The temperature of the SCR catalytic converter is greatly damped and delayed by the thermal mass of the upstream oxidation catalytic converter and the upstream particle filter. A temperature control for regulating a temperature of the SCR catalytic converter requires early temperature support if a temperature gradient at the SCR catalytic converter is negative and an inlet temperature at the oxidation catalytic converter is less than a target temperature of the SCR catalytic converter. Using a SCR temperature model, a required target temperature for the burner can be calculated and activated. If the starting temperature of the oxidation catalytic converter is exceeded, the burner output can also be split, that is to say split, by, for example, oxidizing unburned hydrocarbons via the oxidation catalytic converter.

Furthermore, the burner can only be activated for the lower speed / load range. In contrast, in the higher speed / load range, purely motor measures with sufficient heat output are sufficient and more fuel efficient. Absolute thresholds vary depending on the engine, temperature losses, SCR efficiency and efficiency requirements. For example, the inlet temperature at the oxidation catalyst is below 200 degrees Celsius, and the temperature of the SCR catalyst is less than 220 degrees Celsius. Looking ahead, the temperature of the SCR catalytic converter will drop so that temperature support is provided here. Then, for example, the temperature of the SCR catalytic converter is sufficiently high and is, for example, more than 250 degrees Celsius. If, for example, the exhaust gas temperature drops below 210 degrees Celsius and the temperature gradient of the SCR catalytic converter is strongly negative, then temperature support for the SCR catalytic converter is advantageous and provided in this case. A sufficiently high temperature of the SCR catalytic converter can then be ensured. If, for example, the exhaust gas temperature falls at least partially below 210 degrees Celsius and the temperature gradient at the SCR catalytic converter is strongly negative, a temperature increase is requested. Switch-on and switch-off conditions for the burner are coupled, for example, to the temperature of the oxidation catalytic converter with a hysteresis. The control is ideally carried out by a condition room observer (model), with whom thermal management support can be requested and controlled by burners or motor measures. The combustion support is not only used for the fictitious regeneration of the particle filter, but also to heat the SCR catalytic converter or to keep it sufficiently warm.

In the event of active regeneration of the particle filter, the burner supports the heating of the oxidation catalyst with maximum heating output. The burner output is then reduced or the burner is switched off, and a desired regeneration temperature for regenerating the particle filter is generated exothermic in the oxidation catalyst by introducing unburned hydrocarbons. Unburnt hydrocarbons can be provided or generated in the exhaust gas either in the classic internal engine, with a metering device near the engine, or by means of the burner.

Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments and from the drawing. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the combination indicated in each case, but also in other combinations or on their own, without the scope of Leaving invention.

• 1 eine schematische Darstellung einer erfindungsgemäßen Verbrennungskraftmaschine für ein Kraftfahrzeug; und
• 2 ausschnittsweise eine schematische und geschnittene Seitenansicht eines Abgastrakts der Verbrennungskraftmaschine.

The drawing shows in:

• 1 a schematic representation of an internal combustion engine according to the invention for a motor vehicle; and
• 2nd excerpts a schematic and sectional side view of an exhaust tract of the internal combustion engine.

1 shows a schematic representation of an internal combustion engine 10th for a motor vehicle, in particular for a commercial vehicle. The internal combustion engine 10th is designed for example as a diesel engine. The internal combustion engine 10th has, for example, a motor housing designed as a cylinder housing, in particular as a cylinder crankcase 12 on what cylinder 14 the internal combustion engine 10th are formed. During fired operation of the internal combustion engine 10th run in the cylinders 14 Combustion processes in the course of which a respective fuel-air mixture is burned. This results in exhaust gas from the internal combustion engine 10th , wherein the exhaust gas has a temperature also referred to as the exhaust gas temperature. The exhaust gas temperature can be detected or determined, for example, by means of at least one sensor.

The internal combustion engine 10th has one of the exhaust gases from the cylinders 14 flow-through exhaust tract 16 in which an exhaust gas aftertreatment device 18th is arranged for aftertreatment of the exhaust gas. The exhaust gas aftertreatment device 18th is also referred to as an exhaust system or exhaust aftertreatment system and comprises several exhaust aftertreatment elements 20th , 22 , 24th and 26 . In particular, the exhaust gas aftertreatment device 18th a box 28 include, in which the exhaust aftertreatment elements 20th , 22 , 24th and 26 are arranged.

In order to form the respective fuel-air mixture, a liquid fuel, for example, is placed in the respective cylinder 14 introduced, in particular directly injected. This is done, for example, by means of a respective cylinder 14 assigned injector. The fuel is preferably a liquid fuel. The fuel is preferably a diesel fuel. In addition, the respective cylinder 14 supplied with air that is an intake tract 30th the internal combustion engine 10th flows through. The internal combustion engine 10th is designed as a supercharged internal combustion engine and consequently has at least one exhaust gas turbocharger 32 on. The exhaust gas turbocharger 32 includes one in the intake tract 30th arranged compressor 34 and one in the exhaust tract 16 arranged turbine 36 . The turbine 36 can be driven by the exhaust gas, the compressor 34 from the turbine 36 is drivable. By driving the compressor 34 can the intake tract 30th air flowing through the compressor 34 be compressed. The air is heated by compressing the air. In order to nevertheless achieve high degrees of charging, is in the intake tract 30th downstream of the compressor 34 a charge air cooler 38 arranged. Using the charge air cooler 38 the compressed and thus warmed air is cooled.

Downstream of the charge air cooler 38 is in the intake tract 30th a throttle valve 40 arranged, by means of which, for example, a quantity of the cylinders 14 air to be supplied can be adjusted. Upstream of the compressor 34 shows the intake tract 30th air flowing through, for example, a first pressure p1 on, the air for example downstream of the charge air cooler 38 a print P2s having. The pressure p2s is also referred to as boost pressure, on which the air by means of the compressor 34 and thus by means of the exhaust gas turbocharger 32 can be brought. First three of the cylinders 14 are to a first flood of exhaust gases 42 of the exhaust tract 16 merged, and three second of the cylinders 14 are to a second flood of exhaust gases 44 of the exhaust tract 16 merged. In the flood 42 has the exhaust gas upstream of the turbine 36 a print p32 on, and in the exhaust gas flood 44 has the exhaust gas upstream of the turbine 36 a print p31 on.

The internal combustion engine according to the invention 10th can also replace the double-flow turbine 36 , especially double-flow asymmetrical turbine 36 out 1 have a differently designed turbine, and / or have a variable turbine geometry. The internal combustion engine according to the invention 10th can within the scope of the invention one of those in the 1 shown number of six cylinders 14 different number of cylinders 14 exhibit.

The turbine 36 is a bypass device also known as a wastegate 46 assigned which is a bypass line 48 having. The bypass line 48 is fluid at a first point and at a second point with the exhaust system 16 connected. The first place is upstream of the turbine 36 arranged, and the second location is downstream of the turbine 36 arranged. This allows at least part of the exhaust tract 16 flowing exhaust gas at the first point from the exhaust tract 16 branched off and into the bypass line 48 be initiated. That from the exhaust system 16 branched off and into the bypass line 48 Introduced exhaust gas flows through the bypass line 48 and bypasses the turbine 36 . So this becomes the bypass line 48 exhaust gas flowing through not used to the turbine 36 to drive. The bypass line 48 Exhaust gas flowing through flows back into the exhaust tract at the second point 16 a. The bypass facility 46 includes a valve also referred to as a wastegate valve 50 , by means of which a lot of the bypass line 48 flowing exhaust gas can be adjusted. Downstream of the turbine 36 , in particular downstream of the second point, is in the exhaust tract 16 one in 1 particularly schematically illustrated flap and also referred to as an exhaust flap 52 arranged.

Out 2nd can be seen that the flap 52 in an exhaust pipe 54 is arranged. Downstream of the turbine 36 the exhaust gas has a pressure p4 on. In the exhaust system 16 is also a burner 56 arranged, which looks particularly good 2nd is recognizable. The burner 56 is preferably downstream of the turbine 36 and upstream of the exhaust gas aftertreatment device 18th arranged. The exhaust aftertreatment element 20th is designed, for example, as an oxidation catalyst, in particular as a diesel oxidation catalyst. The exhaust aftertreatment element 22 is designed, for example, as a particle filter, in particular as a diesel particle filter, the exhaust gas aftertreatment element 22 can be designed as a coated diesel particle filter (CDPF). The exhaust aftertreatment element 24th is designed, for example, as an ammonia slip catalyst (ASC). The exhaust aftertreatment element 26 is designed, for example, as an SCR catalytic converter.

In the exhaust system 16 is also a dosing device 58 arranged, by means of which a preferably liquid reducing agent such as, for example, an aqueous urea solution can be introduced, in particular injected, into the exhaust gas for denitrification of the exhaust gas. The dosing device 58 is preferably arranged upstream of the SCR catalytic converter. The dosing device is present 58 downstream of the exhaust aftertreatment element 22 and upstream of the exhaust aftertreatment element 26 arranged. Near the dosing device 58 a temperature sensor is advantageously provided. The exhaust aftertreatment element 20th is downstream of the burner 56 and upstream of the exhaust aftertreatment element 22 arranged, the exhaust gas aftertreatment element 22 downstream of the exhaust aftertreatment element 20th and upstream of the exhaust aftertreatment element 26 is arranged. The exhaust aftertreatment element 24th is downstream of the exhaust aftertreatment element 26 arranged.

In the exhaust system 16 is also a first sensor 60 arranged, which is a nitrogen oxide sensor. By means of the nitrogen oxide sensor, for example, a nitrogen oxide value can be recorded which characterizes a quantity of nitrogen oxides contained in the exhaust gas. The sensor is present 60 downstream of the burner 56 and upstream of the exhaust aftertreatment element 20th arranged. The sensor is preferably 60 in the box 28 arranged. Furthermore, is in the exhaust tract 16 , especially in the box 28 , another sensor 62 arranged, which is designed for example as a further nitrogen oxide sensor. Also by means of the sensor 62 For example, a value can be recorded which characterizes an amount of nitrogen oxides contained in the exhaust gas. The sensor is present 62 downstream of the exhaust aftertreatment element 24th arranged. Adjacent to the sensors 60 and 62 a temperature sensor is advantageously provided in each case. Near the dosing device 58 a temperature sensor is also advantageously provided. With the nitrogen oxide sensors 60 and 62 In addition, the lambda in the exhaust gas can be determined, whereby the hydrocarbon oxidation in the catalytic converter can be checked and monitored from the temperature sensors and the lambda values set on the burner. The ignition source 74 can optionally be designed as a glow plug or as a spark plug. With a spark plug, the flame can be diagnosed and regulated via the ion current.

Together with 2nd is recognizable that the burner 56 a combustion chamber 64 in which a fuel by means of the burner for heating the exhaust gas to form an open flame 56 is to be burned.

The burner is now used to achieve particularly low-emission and low-fuel operation 56 in an exhaust pipe 66 arranged. The exhaust pipe 66 is at a first junction V1 and at a second junction V2 fluidly with the exhaust pipe 54 connected. The exhaust pipes 54 and 66 are each from at least part of the exhaust gas of the internal combustion engine 10th flowable. Here is the connection point V2 downstream of the junction V1 arranged, and relative to the exhaust pipes 54 and 66 movable, in particular about a pivot axis 68 pivotable, flap 52 (Exhaust flap) is in the exhaust pipe 54 downstream of the junction V1 and upstream of the connection point V2 arranged. The exhaust flap can be between two end positions E1 and E2 , but not via the respective end position E1 respectively E2 be moved out. In addition, for example, the exhaust flap in at least one or more, between the end positions E1 and E2 lying positions are moved, in particular pivoted. The end position E1 is a closed position, in which, for example, the exhaust pipe 54 is blocked by means of the exhaust flap, in particular except for leaks in the exhaust flap, in particular to a maximum. The end position E2 is an open position in which the exhaust flap is the exhaust pipe 54 releases maximum.

As in 2nd by an arrow 70 can be illustrated at the junction V1 at least part of the initially the exhaust pipe 54 flowing exhaust gas from the exhaust pipe 54 branched off and into the exhaust pipe 66 be initiated. The one at the junction V1 branched off and into the exhaust pipe 66 introduced part of the exhaust gas flows through the exhaust pipe 66 . The exhaust pipe 66 ends at the junction V2 into the exhaust pipe 54 so that the exhaust pipe 66 exhaust gas flowing through at the connection point V2 from the exhaust pipe 66 off and back into the exhaust pipe 54 can flow in.

The combustion chamber 64 is in the exhaust pipe 66 arranged so that the combustion chamber 64 from which the exhaust pipe 66 flowing exhaust gas is flowable.

By means of the exhaust flap, the exhaust flap can be moved, in particular pivoted, relative to the exhaust pipes 54 and 66 in particular depending on the load and the speed of the internal combustion engine 10th , one the exhaust pipe 66 as well as the combustion chamber 64 flowing through the first amount of exhaust gas. In addition, by moving, in particular pivoting, the exhaust flap, the exhaust flap can be used to move the exhaust pipe 54 and the combustion chamber 64 immediate second amount of exhaust gas can be set. That the combustion chamber 64 immediate exhaust gas passes through the exhaust flap and flows, for example, from the connection point V1 to the junction V2 without going through the exhaust pipe 66 and therefore without going through the combustion chamber 64 to pour.

At the in 2nd shown embodiment has the burner 56 or the internal combustion engine 10th a dosing device 72 on, by means of which, in particular unburned, fuel in the exhaust pipe 66 and thus into the exhaust pipe 66 flowing exhaust gas can be injected. This forms, for example, in the exhaust pipe 66 a fuel-air mixture, which by means of the metering device 72 into the exhaust pipe 66 injected fuel and air or oxygen includes that in the exhaust gas that the exhaust pipe 66 flows through, is included.

The burner 56 also includes an ignition source 74 , by means of which, for example, in the combustion chamber 64 at least one spark can be generated. The fuel-air mixture can be in the combustion chamber by means of the ignition spark 64 ignited and subsequently burned to form an open flame. This heats the exhaust gas.

As part of a method for operating the internal combustion engine 10th for example, at least three operating areas are provided. In a first of the operating ranges, the effective mean pressure of the internal combustion engine is, for example 10th less than about 4 bar, which corresponds to a quarter of full load, for example. Here is the internal combustion engine 10th for example, in their overrun operation or in their train operation in a low-load range. In addition, for example, the internal combustion engine 10th low speeds in the first operating range. In the first operating range, for example, by means of the metering device 72 unburned hydrocarbons and thus unburned fuel are introduced into the exhaust gas. The flap is in the first operating area 52 preferably in its end position E1 , causing the flap 52 is closed, and the fuel or the air-fuel mixture is by means of the ignition source 74 ignited. All of the exhaust gas flows through the combustion chamber 64 and is heated advantageously, effectively and efficiently.

In a second of the operating ranges, the effective mean pressure of the internal combustion engine is 10th for example, more than about 4 bar, and the internal combustion engine 10th may have high speeds. In the second operating area, the exhaust flap is, for example, in one between the end positions E1 and E2 lying intermediate position, so that a first part of the exhaust gas in and through the exhaust pipe 66 flows and a second part of the exhaust gas the exhaust pipe 66 and thus the combustion chamber 64 deals. This allows a flow rate of the combustion chamber 64 flowing exhaust gas can be kept low, which can be avoided that the flame is blown out. In other words, the flame can develop as a stable flame.

In the third operating range, the internal combustion engine 10th for example, a high load. The burner is not ignited in the third operating range. In other words, the fuel-air mixture, for example, is not by means of the ignition source 74 ignited. Since non-combusted hydrocarbons are still used with the metering device 72 are introduced into the exhaust gas an increase in the exhaust gas temperature through an exothermic oxidation of the unburned hydrocarbons to the oxidation catalyst.

At the internal combustion engine 10th and by means of the method, an advantageous temperature increase of the exhaust gas during a cold start and / or in low load ranges such as, for example, during a long downhill run can be realized.

The burner 56 is preferably arranged just before the SCR catalytic converter. It is also conceivable that the burner 56 is arranged just before the oxidation catalyst.

The internal combustion engine 10th also has an exhaust gas recirculation device 76 on. This allows at least part of the exhaust gas flood 44 exhaust gas flowing through the return line 78 out of the flood 44 branched off and to the intake tract 30th be returned. In this way, exhaust gas recirculation can be implemented.

The exhaust gas recirculation device 76 includes an exhaust gas recirculation cooler 80 which is in the return line 78 is arranged. Using the exhaust gas recirculation cooler 80 can be returned and in the intake tract 30th exhaust gas to be introduced are cooled. The exhaust gas recirculation device also includes 76 an exhaust gas recirculation valve 82 , by means of which a lot of the recycled and in the intake tract 30th exhaust gas to be introduced can be adjusted.

By means of the intake air throttle valve 40 , the exhaust gas recirculation valve 82 and the wastegate 50 the oxygen content in the exhaust gas and the mass flow can be regulated. In addition, with a variable flap 52 the burner mass flow can be set. This allows the flow rate in the combustion chamber 64 reduced and the operating range of the burner can be expanded.

In a further embodiment, not shown in the figures, the burner can 56 downstream of the oxidation catalyst or downstream of the exhaust gas aftertreatment element 20th and upstream of the SCR catalytic converter or upstream of the exhaust gas aftertreatment element 26 be arranged. Then, for example, the metering device 58 downstream of the burner 56 arranged. If the burner 56 downstream of the particle filter 22 is provided in the exhaust tract is downstream of the burner 56 or advantageously to provide a particle filter disc at the burner outlet, since otherwise very small particles get into the environment.

Alternatively or additionally, it is conceivable that upstream of the exhaust gas aftertreatment element 20th or upstream of the oxidation catalyst and preferably downstream of the burner 56 a further exhaust gas aftertreatment element, not shown in the figures, is arranged, which comprises, for example, an SCR catalytic converter and / or an ammonia slip catalytic converter (ASC). A further metering device is then provided, for example, by means of which a reducing agent for denitrifying the exhaust gas can be introduced, in particular injected, into the exhaust gas. The further metering device is then, for example, upstream of the further exhaust gas aftertreatment element, in particular upstream of the burner 56 , and downstream of the turbine 36 arranged. The further exhaust gas aftertreatment element is preferably in the box 28 and upstream of the exhaust gas aftertreatment element 20th arranged.

It is also conceivable that the metering device 72 not applicable. Then, for example, unburned hydrocarbons, which are by means of the ignition source 74 can be ignited and thereby burned, introduced into the exhaust gas in that the unburned hydrocarbons directly in at least one cylinder 14 be injected and from the cylinder 14 in the exhaust system 16 and further into the combustion chamber 64 reach.

It has also proven to be particularly advantageous if, for example, in the exhaust pipe 66 downstream of the combustion chamber 64 and thus upstream of the exhaust gas aftertreatment device 18th a filter designed as a particle filter, in particular as a diesel particle filter, is arranged, by means of which, for example, soot caused by the combustion of the fuel in the combustion chamber 64 can arise, can be filtered at least partially from the exhaust gas.

Reference symbol list

10th

Internal combustion engine

12

Engine housing

14

cylinder

16

Exhaust system

18th

Exhaust aftertreatment device

20th

Exhaust aftertreatment element

22

Exhaust aftertreatment element

24th

Exhaust aftertreatment element

26

Exhaust aftertreatment element

28

box

3rd

Intake tract

32

Exhaust gas turbocharger

34

compressor

36

turbine

38

Intercooler

40

throttle

42

Exhaust gas flood

44

Exhaust gas flood

46

Bypass facility

48

Bypass line

50

Valve

52

flap

54

Exhaust pipe

56

burner

58

Dosing device

60

sensor

62

sensor

64

Combustion chamber

66

Exhaust pipe

68

Swivel axis

70

arrow

72

Dosing device

74

Ignition source

76

Exhaust gas recirculation device

78

Return line

80

Exhaust gas recirculation cooler

82

Exhaust gas recirculation valve

E1

End position

E2

End position

p1

print

p2s

print

p32

print

p31

print

p4

print

V1

Liaison

V2

Liaison

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102012024260 A1 [0002]
• DE 102008032601 A1 [0003]
• DE 3532778 A1 [0003]

Claims (6)

Internal combustion engine (10) for a motor vehicle, with an exhaust tract (16) through which exhaust gas from the internal combustion engine (10) can flow, and with a burner (56) arranged in the exhaust tract (16), which has a combustion chamber (64) in which for heating of the exhaust gas, with the formation of an open flame, a fuel is to be burned by means of the burner (56), characterized in that the exhaust gas tract (16) has an exhaust pipe (66) through which the exhaust gas can flow, in which the exhaust gas flowing through the exhaust pipe (66) flowable combustion chamber (64) is arranged, and has a flap (53), by means of which, depending on a load and a speed of the internal combustion engine (10), a first quantity flowing through the exhaust pipe (66) and a second quantity bypassing the combustion chamber (64) of the exhaust gas are adjustable. Internal combustion engine (10) after Claim 1 , characterized by a metering device (72) by means of which the fuel can be injected into the exhaust gas flowing through the exhaust pipe (66). Internal combustion engine (10) after Claim 1 , characterized by the fuel being designed as a fuel for the operation of the internal combustion engine (10) which can be injected into the internal combustion engine (10) by means of at least one post-injection. Internal combustion engine (10) according to one of the preceding claims, characterized in that in the exhaust tract downstream of the burner (56) a particle filter (22) and / or an oxidation catalyst (20) and / or an SCR catalyst (26) is arranged. Internal combustion engine (10) after Claim 4 , characterized in that the burner (56) is designed to heat the exhaust gas when an effective mean pressure of the internal combustion engine (10) is less than or equal to approximately 4 bar and / or the exhaust gas upstream of the burner (56) has a temperature , which is lower than a light-off temperature of the oxidation catalyst (20). Method for operating an internal combustion engine (10) according to one of the preceding claims.

Images