Catalytic heater for exhaust gas plant, exhaust gas plant and method for operating same

Abstract

The invention relates to a catalytic heater for an exhaust gas system of an internal combustion engine. The device comprises at least one electrically actuatable heating element (14), a hydrocarbon output assembly (20) for outputting liquid hydrocarbons (K) to the at least one electrically actuatable heating element (14), and an oxidation catalyst assembly (26) for oxidizing hydrocarbons (K) heated on the at least one electrically actuatable heating element (14).

Description

Field of the Invention

[0001] The present invention relates to a catalytic heater for an exhaust gas device of an internal combustion engine, for example in a vehicle, an exhaust gas device equipped with such a catalytic heater, and a method for operating such an exhaust gas device. Background Art

[0002] In order to reduce the duration during which the content of pollutants in the exhaust gas of an internal combustion engine cannot be substantially reduced due to too low a temperature of an exhaust gas treatment component, such as a catalytic converter, provided in an exhaust gas device when the internal combustion engine in a vehicle starts to operate, it is known to use an electric heater which generates heat when a voltage is applied and transfers this heat to the exhaust gas discharged from the internal combustion engine. The exhaust gas further heated in this way causes faster heating of the exhaust gas treatment component located downstream of such a heater and thus shortens the duration until efficient exhaust gas treatment starts after the internal combustion engine starts to operate. Summary of the Invention

[0003] It is an object of the present invention to provide a heater for an exhaust gas device of an internal combustion engine, an exhaust gas device equipped with such a heater, and a method for operating such an exhaust gas device, by means of which efficient heating of the components of the exhaust gas device can be achieved with a reduced energy input.

[0004] According to a first aspect of the present invention, this object is achieved by a catalytic heater for an exhaust gas device of an internal combustion engine, which comprises:

[0005] at least one electrically excitable heating element,

[0006] a hydrocarbon output assembly for outputting a liquid hydrocarbon onto the at least one electrically excitable heating element,

[0007] an oxidation catalytic converter assembly for oxidizing the hydrocarbon heated on the at least one electrically excitable heating element.

[0008] With the catalytic heater constructed according to the present invention, most of the heat to be transferred to the exhaust gas flowing in the exhaust gas device or the components of the exhaust gas device can be generated not by the electrical excitation of the at least one heating element, but by catalytic oxidation and the energy released thereby. This leads on the one hand to a reduction in the load on the vehicle's on-board voltage system and on the other hand to a significantly faster and stronger heating of system areas, such as catalytic converters, which are to be thermally regulated for the operation of the internal combustion engine or the exhaust gas device.

[0009] In order to provide a large surface area for the catalytic oxidation of hydrocarbons to be carried out in a catalytic heater, the oxidation catalyst assembly may include an oxidation catalyst block arranged on the outlet side of the at least one electrically excitable heating element for receiving and oxidizing the hydrocarbons evaporated on the at least one electrically excitable heating element.

[0010] In order to make efficient and full use of the heat released at the at least one electrically excitable heating element, it is proposed that the oxidation catalyst assembly includes an oxidation catalyst material coating on the at least one electrically excitable heating element. Thus, the oxidation catalyst material coating can very quickly reach the operating temperature required for carrying out the catalytic oxidation of hydrocarbons even at relatively low ambient temperatures through direct physical contact and the resulting heat conduction.

[0011] According to another aspect of the present invention, this object is achieved by an exhaust gas device for an internal combustion engine, which exhaust gas device includes at least one exhaust gas treatment assembly and a catalytic heater having the construction according to the present invention upstream of the at least one exhaust gas treatment assembly with respect to the exhaust gas flow direction.

[0012] The at least one exhaust gas treatment assembly may include a first exhaust gas treatment assembly having an oxidation catalyst and / or a particulate filter. Depending on the type of internal combustion engine used in combination with the exhaust gas device, i.e., a diesel engine or an Otto engine, and thus the type of hydrocarbons used in the catalytic heater, the oxidation catalyst may be configured either as a diesel oxidation catalyst or as a three-way catalyst.

[0013] For even more efficient exhaust gas purification, especially in the design of the internal combustion engine as a diesel engine, the at least one exhaust gas treatment assembly may include a second exhaust gas treatment assembly having an SCR catalyst.

[0014] Here, the first exhaust gas treatment assembly may be arranged upstream of the second exhaust gas treatment assembly with respect to the exhaust gas flow direction.

[0015] The catalytic heater may be arranged, for example, downstream of an exhaust gas turbocharger in the exhaust gas flow direction. If the catalytic heater is arranged downstream of a third exhaust gas treatment assembly in the exhaust gas flow direction and, for example, the third exhaust gas treatment assembly includes an SCR catalyst, an enhanced reduction in the nitrogen oxide fraction in the exhaust gas discharged from the internal combustion engine can be achieved.

[0016] In order to compensate for the increased flow resistance inevitably introduced into the exhaust gas device by the catalytic heater when the catalytic heater is no longer required to operate when the exhaust gas device is sufficiently heated, it is proposed that a selectively cut-off bypass flow path is provided in parallel with the catalytic heater.

[0017] Depending on the type of vehicle into which the exhaust gas device is to be integrated,

[0018] The catalytic heater can be arranged in the exhaust gas device section, which is to be positioned to extend downward or / and laterally away from the internal combustion engine in the height direction.

[0019] Or

[0020] The catalytic heater can be arranged in the exhaust gas device section, which is to be positioned to extend under the floor of the vehicle or to be positioned in the lateral area of the vehicle.

[0021] According to another aspect of the present invention, the object stated at the beginning is achieved by a method for operating an exhaust gas device constructed according to the present invention, in which the at least one electrically excitable heating element of the catalytic heater is operated such that the liquid hydrocarbons reaching the surface of the at least one electrically excitable heating element are heated and oxidized on the oxidation catalyst assembly to generate heat.

[0022] In order to ensure that the hydrocarbons injected in the direction of the at least one electrically excitable heating element are substantially completely converted by catalytic oxidation and thus to avoid the emission of unoxidized hydrocarbons into the surrounding environment, it is proposed that when the oxidation catalyst assembly has a predetermined temperature, preferably a temperature that allows the catalytic oxidation of hydrocarbons on the oxidation catalyst assembly, after the start of the excitation of the at least one electrically excitable heating element, and / or when a predetermined duration has elapsed since the start of the excitation of the at least one electrically excitable heating element, the injection of hydrocarbons onto the at least one electrically excitable heating element is started.

[0023] When the excitation of the at least one electrically excitable heating element is started before the internal combustion engine starts running, the duration during which the exhaust gas discharged from the internal combustion engine cannot or cannot be efficiently treated in the exhaust gas device to reduce the harmful substance content can be further shortened, for example.

[0024] If, in the method according to the present invention, the injection of hydrocarbons onto the at least one electrically excitable heating element is started with the start of the operation of the internal combustion engine or after the start of the operation, it is ensured that the hydrocarbons evaporated on the at least one electrically excitable heating element are conveyed, for example, to a downstream oxidation catalyst block by the exhaust gas already flowing in the exhaust gas device.

[0025] In an alternative process variant, the injection of hydrocarbons onto the at least one electrically excitable heating element can already be started before the internal combustion engine starts running. If an oxidation catalyst material coating is provided at the at least one electrically excitable heating element and thus heat is already released directly at the so-coated heating element by the oxidation of the heated hydrocarbons, this process variant results in particularly rapid and efficient heating.

[0026] Here, for efficient heating, it can be provided that

[0027] a) Before the internal combustion engine starts running, hydrocarbons are injected in a predetermined amount and / or for a predetermined duration during a pre-injection process.

[0028] b) After the pre-injection process ends, the internal combustion engine is driven to rotate without ignition.

[0029] c) Before the internal combustion engine starts running, hydrocarbons are injected in a predetermined amount and / or for a predetermined duration during a final pre-injection process.

[0030] The rotation of the internal combustion engine during this period, that is, the movement of the crankshaft and its pistons without ignition occurring in the cylinders, causes air and thus oxygen to be delivered to the exhaust gas device in order to provide oxygen for hydrocarbon oxidation during subsequent additional pre-injection processes.

[0031] Before measure c) is carried out, measures a) and b) can be repeated at least once. Since the final pre-injection process is carried out using measure c), the internal combustion engine can be made to run after or during measure c).

[0032] If repeated pre-injection processes have already led to sufficient heating of the exhaust gas device, the injection of hydrocarbons can be ended with the conclusion of measure c). For example, at relatively low ambient temperatures and a correspondingly cold exhaust gas device, if the injection of hydrocarbons is restarted or continued after measure c) ends and the internal combustion engine starts running, it may be advantageous for the exhaust gas device to be heated sufficiently and quickly. This means that, for example, with the conclusion of measure c), the injection of hydrocarbons can be continued without interruption when the internal combustion engine is running at this time, or the injection of hydrocarbons can be interrupted briefly after measure c) ends, and when it is determined that different system areas of the exhaust gas device, for example, have not been sufficiently heated, the injection of hydrocarbons is restarted and heat is released through its catalytic oxidation.

[0033] To ensure that the injected hydrocarbons can be substantially completely converted on the oxidation catalytic converter assembly to release heat, the hydrocarbon injection rate can be determined based on the temperature of the oxidation catalytic converter assembly and / or based on the volume flow rate of the exhaust gas in the exhaust gas device. The higher the temperature of the oxidation catalytic converter assembly, the more efficiently the oxidation catalytic converter assembly can convert hydrocarbons, so that as the temperature of the oxidation catalytic converter assembly increases, there is also the possibility that the amount of energy released per unit of time is increased by increasing the hydrocarbon injection rate. A higher exhaust gas volume flow rate means a higher flow velocity and correspondingly also means a shorter residence time or also means a lower probability that the evaporated hydrocarbons conveyed in the exhaust gas stream come into contact with the surface of the oxidation catalytic converter assembly and are oxidized there. Therefore, it is advantageous to reduce the amount of hydrocarbons injected per unit of time as the exhaust gas volume flow rate increases to avoid the discharge of unoxidized hydrocarbons. For example, such parameters as the temperature of the oxidation catalytic converter assembly, for example also the temperature in its different regions, and the exhaust gas volume flow rate in the characteristic curve family defining the hydrocarbon injection rate can be considered as input parameters.

[0034] In particular, it can be provided here that as the temperature of the oxidation catalytic converter assembly increases, the hydrocarbon injection rate increases, and / or as the exhaust gas volume flow rate increases, the hydrocarbon injection rate decreases. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be described in detail below with reference to the accompanying drawings. Shown are:

[0036] Figure 1 A longitudinal sectional view of a catalytic heater for an exhaust gas device of an internal combustion engine is shown;

[0037] Figure 2 A schematic diagram of an exhaust gas device for receiving exhaust gas discharged from an internal combustion engine is shown;

[0038] Figure 3 Another schematic diagram of the exhaust gas device is shown;

[0039] Figure 4 Another schematic diagram of the exhaust gas device is shown. DETAILED DESCRIPTION OF THE INVENTION

[0040] Figure 1 The catalytic heater generally labeled 10 in the exhaust gas device 12 for an internal combustion engine is shown in a schematic longitudinal section.

[0041] The catalytic heater 10 includes an electrically excitable heating element 14 as a main component, which can be connected to a voltage source, such as the on-vehicle voltage system of a vehicle, via connection contacts 16. The electrically excitable heating element 14 can be configured as a heating conductor made of strip-shaped flat material, configured as a sheathed heater or the like and can be arranged, for example, in a helical winding structure, a meandering winding structure or otherwise wound such that the exhaust gas A to flow onto the heating element in, for example, a tubular exhaust gas guiding component 18 circulates around the heating element 14 and can absorb heat here. The hydrocarbon output assembly 20, which is also commonly referred to as an injector, is positioned upstream of the heating element 14. The hydrocarbon output assembly releases a liquid hydrocarbon K, such as diesel or gasoline, for example in the form of a spray or in the form of droplets in the direction of the inflow side 22 of the electrically excitable heating element 14.

[0042] On the outflow side 23 of the heating element 14, the oxidation catalyst block 24 of the oxidation catalyst assembly, generally labeled 26, is carried in the exhaust gas guiding assembly 18, for example by a fiber mat 28 or the like. The oxidation catalyst block 24 is formed, for example, by a substrate through which the exhaust gas A can flow and which has an oxidation catalyst material on its surface. Depending on the type of internal combustion engine used in combination with the exhaust gas device 12, in the case of a diesel engine, the oxidation catalyst material can be a diesel oxidation catalyst material, or in the case of an Otto engine, it can be a three-way catalyst material.

[0043] The oxidation catalyst assembly 26 optionally includes an oxidation catalyst material coating 30 on the electrically excitable heating element 14. The oxidation catalyst material coating can cover the surface of the electrically excitable heating element either substantially completely or only partially, and depending on the type of internal combustion engine and thus depending on the type of hydrocarbon K used, also includes, for example, a diesel oxidation catalyst material or a three-way catalyst material.

[0044] The hydrocarbon output assembly 20 used in the catalytic heater 10 can, for example, include an injector that outputs the hydrocarbon K symmetrically, i.e., in the form of a uniform spray cone, or can include an injector that outputs the hydrocarbon K asymmetrically, i.e., enhanced towards one side. As an alternative to being positioned, as visible in Figure 1 and inclined relative to the exhaust gas flow direction in a substantially linearly extending exhaust gas guiding assembly 18, the hydrocarbon output assembly 20 can also be positioned in an arcuate region of the exhaust gas guiding assembly 18 that is positioned upstream of the heating element 14, such that the main output direction of the hydrocarbon output assembly 20 substantially corresponds to the flow direction of the exhaust gas A directly upstream of the heating element 14. Thus, a compact structural form of the catalytic heater 10 or of the exhaust gas device 12 constructed therefrom can be achieved.

[0045] Figure 2An exhaust gas device 12 used in combination with an internal combustion engine 32 is shown. An exhaust gas turbocharger 34 is provided in the exhaust gas device 12 upstream of the catalytic heater 10. A first exhaust gas treatment assembly 40 and a second exhaust gas treatment assembly 46 are provided downstream of the catalytic heater 10. The first exhaust gas treatment assembly includes, for example, a diesel oxidation catalyst 36 and a particulate filter 38, and the second exhaust gas treatment assembly includes, for example, an SCR catalyst 42 with an associated injector 44. This design of the two exhaust gas treatment assemblies 44, 46 is particularly provided in association with an internal combustion engine 32 configured as a diesel engine.

[0046] In the case where the oxidation catalyst block 24 of the catalytic heater 10 has a sufficiently large size, for example, the diesel oxidation catalyst 36 of the first exhaust gas treatment assembly 40 can be dispensed with. Additionally, if necessary, a third exhaust gas treatment assembly 48 can be provided upstream of the catalytic heater 10 or downstream of the exhaust gas turbocharger 34. The third exhaust gas treatment assembly can include, for example, a pre-SCR catalyst 50 with an associated injector 52.

[0047] Figure 2 It is further shown that, in association with the catalytic heater 10, a bypass flow path 54 can be advantageously provided in parallel with the catalytic heater. The bypass flow path can be selectively released for flow through or blocked to prevent flow through by a valve 56 assigned to the bypass flow path. In a state where the catalytic heater 10 does not need to operate, the bypass flow path 54 can be released for flow through, so that the increased flow resistance introduced by the catalytic heater 10 can be compensated. When the bypass flow path 54 is released for flow through, for example, most of the exhaust gas A discharged from the internal combustion engine 32 can flow through the bypass flow path.

[0048] During the heating operation of the catalytic heater 10, the bypass flow path 54 is blocked by the valve 56, so that all the exhaust gas flow is guided through the catalytic heater 10 and thus heat can be transferred from the catalytic heater 10 to the downstream system area. It can also be provided here that when the heating operation of the catalytic heater 10 starts almost simultaneously with the start of the operation of the internal combustion engine 32, the valve 56 is opened, so that most of the exhaust gas A discharged from the internal combustion engine 32 flows through the bypass flow path 54 during the heating stage of the heating element 14. Thereby, only a relatively small part of the heat generated by exciting the heating element 14 is removed by the exhaust gas A circulating through the heating element 14, which results in the heating element 14 heating up faster and thus also reaching the state where the hydrocarbon K evaporates on the surface of the heating element 14 faster.

[0049] Figure 3 and Figure 4Shows different arrangement options for the catalytic heater 10 in the exhaust gas device 12. The exhaust gas device 12 can in principle be constructed such that it has an exhaust gas device section 58, commonly referred to as the downpipe, adjacent to the internal combustion engine 32 or the exhaust gas turbocharger 34, which section guides the exhaust gas away from the internal combustion engine 32, for example, downward and / or laterally. For example, a section 60 of the exhaust gas device that extends under the vehicle floor can be connected to this downward and / or laterally guiding exhaust gas device section 58. This section 58 can also lead to an exhaust gas treatment assembly located, for example, in the lateral area of a truck.

[0050] In Figure 3 the design example shown, the catalytic heater 10 is located in the section 58 of the exhaust gas device 12 that extends downward and / or laterally with respect to the internal combustion engine 32. Thus, the structural space is utilized efficiently and fully. The catalytic heater 10 is therefore located very close to the internal combustion engine 32, such that the exhaust gas A flowing through the internal combustion engine and additionally heated in the manner and method described below can efficiently contribute to heating the exhaust gas treatment assembly located further downstream.

[0051] In an alternative design, for example, when no structural space is available, the catalytic heater 10 is not located in the downward or laterally guiding section 58 of the exhaust gas device 12, but in the section 60 of the exhaust gas device 12, which is located, for example, under the vehicle floor or in the lateral area of the vehicle.

[0052] It should be noted that each design variant of the exhaust gas device 12 shown in Figure 3 and Figure 4 can be combined with different additional system areas, namely different exhaust gas treatment assemblies 40, 46, 48 or / and bypass flow paths 54, which are also shown in more detail in Figure 2 .

[0053] The operation of the catalytic heater 10 in the exhaust gas device 12 will be explained below to accelerate the heating of subsequent system areas in the exhaust gas flow path, namely especially the exhaust gas treatment assemblies 40, 46.

[0054] During operation of the catalytic heater 10, the hydrocarbon K that reaches the heating element 14 in liquid form is heated and vaporized here by excitation of the heating element 14, i.e., by applying a voltage to the heating element and by the heat generated here at the heating element 14. At the same time, this heat is mainly transferred by thermal radiation to the upstream end region of the oxidation catalyst block 24 and heats this upstream end region even in the case where there may not yet be an exhaust gas flow. The temperature in the upstream end region of the oxidation catalyst block 24 can be detected by the temperature sensor 62 and used in the control unit that controls the catalytic heater 10 in order to control or operate the catalytic heater 10 and, if necessary, further system regions of the exhaust gas device 12 based on this temperature.

[0055] The hydrocarbon K heated and vaporized at the heating element 14 is further conveyed in the direction towards the oxidation catalyst block 24 in the manner and method described in detail below and can be oxidized at its surface using the oxygen that is also present in the exhaust gas device 12. Heat is released in this catalytic oxidation reaction, and this heat contributes to further heating the oxidation catalyst block 26 and thus also to heating the exhaust gas A flowing through this oxidation catalyst block during operation of the internal combustion engine 32. The exhaust gas A conveys the heat received at the catalytic heater 10 in the downstream direction towards the subsequent exhaust gas treatment assemblies 40, 46 and transfers at least a part of the heat to these exhaust gas treatment assemblies. As a result, the exhaust gas treatment assemblies 40, 46 are heated more quickly, especially in the starting phase of the operating run of the internal combustion engine 32, so that the catalytic reactions to be carried out if necessary therein can start earlier and the duration during which the exhaust gas A is discharged essentially untreated is thus significantly shortened.

[0056] If an oxidation catalyst material coating 30 is additionally provided on the heating element 14, at least a part of the hydrocarbon K that reaches the heating element and is vaporized by the heating element can already be oxidized in a catalytic reaction on the heating element 14. Heat is also released here, which on the one hand contributes to heating the heating element 14 more quickly and more intensively and on the other hand also additionally contributes to heating the oxidation catalyst block 24 or the exhaust gas A flowing in the exhaust gas device 12 more quickly.

[0057] Since with this catalytic heater 10, the system regions of the exhaust gas or the more downstream exhaust gas device 12 are not heated only by the heat generated by the electrical excitation of the heating element 14, but rather the vast majority of the thermal energy released in the region of the catalytic heater 10 is provided by the catalytic oxidation reaction of the hydrocarbon K, it is possible to achieve a significantly stronger and faster heating of the different system regions of the exhaust gas device 12 with a significantly reduced use of electrical energy. This allows, for example, the heating element 14 to be operated at a lower operating voltage, such as the 24 V voltage provided in the vehicle electrical voltage network.

[0058] The following describes different operating modes of the exhaust gas device 12 or the catalytic heater 10, by means of which it is possible to ensure efficient heating of the system areas present in the exhaust gas device 12 for exhaust gas purification, in particular the exhaust gas treatment components 40, 46.

[0059] When the vehicle or the internal combustion engine 32 starts operating, the heating element 14 can also be excited, that is, a voltage is applied to the heating element in order to generate heat in the area of the heating element. Since exhaust gas A also starts to be output from the internal combustion engine 32 when the internal combustion engine 32 starts operating, a part of the heat generated in the heating element 14 is transferred by the exhaust gas flow in the direction downstream of the oxidation catalyst block 24. A part of the heat can also be directly transferred from the heating element 14 to the end area upstream of the oxidation catalyst block 24 by thermal radiation.

[0060] If it is recognized, for example, by means of the output signal of the temperature sensor 62 that the oxidation catalyst block 24 has a temperature sufficient to carry out the catalytic oxidation of the hydrocarbon K at least in its upstream end area, which temperature can be, for example, 250° or greater, then the injection of the liquid hydrocarbon K can be started in the direction of the heating element 14. The liquid hydrocarbon K evaporates on the surface of the heated heating element 14 and is conveyed by the exhaust gas flow in the direction of the oxidation catalyst block 24. Then, at the oxidation catalyst block 24, the oxidation of the hydrocarbon K takes place using the oxygen contained in the exhaust gas device 12 or conveyed in the exhaust gas A in this state. In this oxidation, heat is released, which heat not only heats the exhaust gas A that then continues to flow downstream in addition to the heat released by exciting the heating element 14, but also helps to more rapidly heat the oxidation catalyst block 24, especially also in the direction of its downstream area. This results in the entire oxidation catalyst block 24 relatively quickly reaching the temperature required for carrying out the catalytic oxidation of the hydrocarbon K after the start of the oxidation reaction at the oxidation catalyst block 24.

[0061] In order to be able to reach this temperature earlier or to contribute earlier to heating the exhaust gas A that heats the more downstream system areas of the exhaust gas device 12, the heating element 14 can also be excited, for example, 5 to 20 seconds before the internal combustion engine 32 starts operating. As a trigger for this, events in the vehicle can be used, which indicate that the internal combustion engine 32 will most probably be put into operation within a foreseeable time. For example, the unlocking of the vehicle door or the insertion of the ignition key into the ignition lock can be used as an event to trigger the excitation of the heating element 14.

[0062] For example, the injection of hydrocarbons can be used when the heating element has reached a sufficiently high temperature in the range of, for example, 200 to 400 °C, preferably at least 350 °C. This temperature can either be detected by a temperature sensor assigned to the heating element 14 or determined empirically and associated with the duration since the start of energizing the heating element 14, so that the injection of hydrocarbons can start after a predetermined duration since the start of energizing the heating element 14. If the energization of the heating element 14 has started before the start of operation of the internal combustion engine 32, then since there is no exhaust gas flow in this stage, it is possible to heat the heating element 14 more quickly to the desired temperature.

[0063] If the heating element 14 has a coating 30 of oxidation catalyst material, then the energization of the heating element 14 can also start with the start of operation of the internal combustion engine 32 or a short time before it, and the injection of hydrocarbons K can start with the start of operation of the internal combustion engine 32. Since in this design where the heating element 14 has a coating 30 of oxidation catalyst material, a part of the hydrocarbons K that are heated and also evaporated on the heating element 14 are already oxidized on the coating 30 of oxidation catalyst material, the heating element 14 is heated faster and provides more heat, which is transferred to the oxidation catalyst block 24 by thermal radiation and convection. The exhaust gas A flowing in the exhaust gas device 12 since the start of operation of the internal combustion engine 32 can also absorb heat intensively in the region of the heating element 14 and can also transport this heat to further downstream system regions of the exhaust gas device 12.

[0064] The increase in heat generated in the region of the heating element 14, in addition to causing more intense evaporation of the liquid hydrocarbons K, also causes faster heating of all downstream system regions, so that the oxidation catalyst block 24 reaches its maximum capacity for catalytic oxidation of hydrocarbons K more quickly, and the system regions further downstream in the exhaust gas device 12 also reach their operating temperatures required to meet the corresponding exhaust gas purification functions more quickly.

[0065] In another alternative process variant, both the energization of the heating element 14 and the injection of hydrocarbons K can be carried out before the start of operation of the internal combustion engine 32. For example, first, when the internal combustion engine 32 is not yet running, the heating element 14 provided with a coating 30 of oxidation catalyst material can be energized until it reaches a rated temperature in the range of at least 300 °C, preferably at least 400 °C. This temperature can be detected sensorially or determined in combination with an empirically determinable duration, assuming that this temperature exists after a duration of, for example, 5 to 20 seconds depending on the construction form of the heating element 14. This duration can be relatively short because there is no exhaust gas flowing in the exhaust gas device 12 in this stage.

[0066] After reaching the desired temperature or after a preset duration, a predetermined amount of fuel can be injected onto the heating element 14 or the oxidation catalyst material coating 30. The liquid hydrocarbon K is heated, and if necessary evaporated, on the surface of the heating element 14 or on the oxidation catalyst material coating 30 and oxidized using the oxygen present in the surroundings of the heating element 14 in the exhaust gas device 12. In this oxidation, a relatively large amount of heat is released compared to the heat released by activating the heating element 14. This heat causes an enhanced heating of the heating element 14 itself and has also caused the upstream region of the oxidation catalyst material block 24 to be heated mainly by thermal radiation. The heating element 14 can reach a temperature of 600 °C to 800 °C in this stage.

[0067] Subsequently, the internal combustion engine 32 can be put into operation and the injection of the hydrocarbon K can be continued, so that on the one hand the heat is conveyed downstream from the region of the heating element 14, in particular also to the oxidation catalyst block 24, by the exhaust gas flow that is also put into use, and the hydrocarbon K evaporated by the exhaust gas A flowing in the exhaust gas device 12 is conveyed into the region of the oxidation catalyst block 24, where catalytic oxidation of the evaporable hydrocarbon K can then also take place first of all at least on its upstream and already heated region. With the start of operation of the internal combustion engine 12 and the use of the exhaust gas flow, the amount of the injected hydrocarbon K can also be increased, for example, because the complete conversion of the hydrocarbon K takes place not only on the oxidation catalyst material coating 30, but also or mainly on the surface of the oxidation catalyst block 24. The oxidation of the hydrocarbon K that then begins on the oxidation catalyst block 24 causes the oxidation catalyst block 24 to be heated relatively quickly even in its downstream end region, so that the duration until the maximum oxidation capacity of the oxidation catalyst block 24 is reached can be further shortened by the injection of the hydrocarbon K that has already started before the start of operation of the internal combustion engine 32.

[0068] It is also possible to use the injection of the liquid hydrocarbon K even before the start of operation of the internal combustion engine 12 in order to raise the temperature in the region of the heating element 14 and in the upstream region of the oxidation catalyst block 24 to the desired temperature more quickly within one or more pre-injections.

[0069] Here, first, after the excitation of the heating element 14 and heating of the heating element to a temperature of at least 300 °C, preferably at least 400 °C, hydrocarbons K are injected in the pre-injection process in the direction of the heated heating element 14 or the correspondingly heated oxidation catalyst material coating 30. When the hydrocarbons K hit the surface of the heating element 14 or the oxidation catalyst material coating 30, they are heated, evaporated if necessary, and oxidized in a catalytic reaction using the oxygen present in this region of the exhaust gas device 12. The heat generated hereby contributes to heating the heating element 14 or the upstream region of the oxidation catalyst block 24 more strongly and more quickly. After the end of this pre-injection process and the substantially complete catalytic oxidation of the injected hydrocarbons K, the internal combustion engine 32 is driven to rotate by a starter, a starter / generator, etc., without ignition taking place in its cylinders during this time. Through the pistons that move when the crankshaft of the internal combustion engine 12 rotates, air and thus oxygen are ejected from the cylinders of the internal combustion engine 32 in the direction of the upstream region of the exhaust gas device 12, i.e., into the region in which the catalytic heater 10 is also located. Thus, it is ensured that sufficient oxygen is provided again for a further pre-injection process in order to be able to completely oxidize the hydrocarbons K injected within the scope of this further pre-injection process.

[0070] Depending on the length of the duration available for performing such a pre-injection process, the process of alternately injecting hydrocarbons K and rotating the internal combustion engine 32 can be repeated several times.

[0071] Then, after performing the last pre-injection process and the injection of the hydrocarbons K is completed, the internal combustion engine 32 can be started. Alternatively, the internal combustion engine 32 can also already be started during the execution of the last pre-injection process. With the end of the last pre-injection process, the injection of the hydrocarbons K can be set when the downstream system region of the exhaust gas device 12 has been sufficiently heated. However, since usually the entire exhaust gas device 12 cannot be sufficiently heated by the pre-injection, it may be necessary to inject the hydrocarbons K after performing the last pre-injection process or, if necessary, directly continue the pre-injection process and convey the heat released on the oxidation catalyst block 24 or also on the oxidation catalyst material coating 30 during the catalytic oxidation with the exhaust gas A to the system region to be heat-regulated in a more downstream region of the exhaust gas device 12.

[0072] The degree of rotation of the crankshaft of the internal combustion engine 32 to be performed within the scope of this pre-injection depends first of all on how many cylinders it has or how large the volume of the cylinders is. The degree of rotation should be coordinated with the amount of hydrocarbons K to be injected within the scope of the respective pre-injection process, so as to ensure that sufficient oxygen is available in the exhaust gas device 12 and especially in the surroundings of the heating element 14 for the complete oxidation of the hydrocarbons K injected during the pre-injection process.

[0073] To initiate such a pre-injection, an event indicating the start of operation of the internal combustion engine 32 can be used. For example, a signal indicating the opening of a vehicle door can be accessed. Alternatively or additionally, it is also possible that the vehicle user presets the time point of the planned start of operation of the vehicle, similar to what is implemented in connection with the auxiliary heater, so that, for example, also depending on the ambient temperature and thus on the temperature of the different system areas of the exhaust gas device 12 to be heated, the pre-injection can be started for a sufficient duration before the planned use of the vehicle begins. It is thus ensured that, with the start of operation of the internal combustion engine 32, the oxidation catalyst block 24 has been sufficiently heated so that efficient catalytic oxidation can be achieved and thus also efficient heat release can be achieved when hydrocarbon injection then starts or continues with the start of operation of the internal combustion engine 32.

[0074] The amount of hydrocarbons injected during or after excitation of the heating element 14 can be set according to different parameters. Parameters that are important for the catalytic conversion of hydrocarbon K are, for example, the temperature of the oxidation catalyst block 24 and the exhaust gas volume flow rate, i.e., the amount of hydrocarbon K with the guided exhaust gas A that flows through and evaporates from the oxidation catalyst block 24 per unit of time. The higher the temperature of the oxidation catalyst block 24, especially also in its downstream end region, the more efficiently the oxidation catalyst block oxidizes the hydrocarbon K reaching its surface. This means that as the temperature of the oxidation catalyst block 24 increases, the hydrocarbon injection rate can be increased, for example, up to the maximum value of the hydrocarbon injection rate. A larger exhaust gas volume flow rate (i.e., a larger amount of exhaust gas flowing through the oxidation catalyst block 24 per unit of time) results in a correspondingly shorter residence time of the hydrocarbon K conveyed in the exhaust gas A in the oxidation catalyst block 24. To avoid discharging unoxidized hydrocarbon K, it can be stipulated that as the exhaust gas volume flow rate increases, the hydrocarbon injection rate is reduced, for example, to a minimum value.

[0075] Taking into account such influencing variables, such as the temperature of the oxidation catalyst block 24 and the exhaust gas volume flow rate, but also, for example, the exhaust gas temperature, the nominal temperature that the exhaust gas should have after flowing through the oxidation catalyst block 24, the electrical heating power of the heating element 14, a family of characteristic curves can be defined that preset the hydrocarbon injection rate according to such input variables in such a way that, on the one hand, the maximum amount of heat can be released and, on the other hand, the discharge of unoxidized hydrocarbon K can be avoided.

Claims

1. A catalytic heater for an exhaust gas device of an internal combustion engine, the catalytic heater comprising: at least one electrically activatable heating element (14), a hydrocarbon output assembly (20) for outputting liquid hydrocarbons (K) to the at least one electrically activatable heating element (14), An oxidation catalytic converter component (26) for oxidizing hydrocarbons (K) heated by the at least one electrically activatable heating element (14).

2. The catalytic heater according to claim 1, It is characterized in that The oxidation catalytic converter assembly (26) comprises an oxidation catalytic converter block (24) arranged on the outflow side (23) of the at least one electrically activatable heating element (14) for receiving and oxidizing hydrocarbons (K) evaporated at the at least one electrically activatable heating element (14).

3. The catalytic heater according to claim 1 or 2, It is characterized in that The oxidation catalytic converter component (26) comprises a coating (30) of oxidation catalytic converter material of the at least one electrically activatable heating element (14).

4. An exhaust gas device for an internal combustion engine, comprising at least one exhaust gas treatment component (40, 46) and a catalytic heater (10) according to any one of claims 1 to 3 located upstream of the at least one exhaust gas treatment component (40, 46) with respect to the exhaust gas flow direction.

5. The exhaust gas device according to claim 4, It is characterized in that The at least one exhaust gas treatment component (40, 46) comprises a first exhaust gas treatment component (40) having an oxidation catalytic converter (36) and / or a particle filter (38).

6. The exhaust gas device according to claim 4 or 5, It is characterized in that The at least one exhaust gas treatment component (40, 46) includes a second exhaust gas treatment component (46) having an SCR catalyst (42).

7. The exhaust gas device according to claim 5 and claim 6, It is characterized in that The first exhaust gas treatment component (40) is arranged upstream relative to the second exhaust gas treatment component (46) in the exhaust gas flow direction.

8. The exhaust gas system according to any one of claims 4 to 7, It is characterized in that The catalytic heater (10) is arranged downstream of the exhaust gas turbocharger (34) and / or the third exhaust gas treatment component (48) in the exhaust gas flow direction.

9. The exhaust gas device according to claim 8, It is characterized in that The third exhaust treatment component (48) includes an SCR catalyst (50).

10. The exhaust gas system according to any one of claims 4 to 9, It is characterized in that A selectively cutoff bypass flow path (54) is provided in parallel with the catalytic heater (10).

11. The exhaust gas system according to any one of claims 4 to 10, It is characterized in that The catalytic heater (10) is arranged in an exhaust system section (58) to be positioned so as to extend downwardly and / or laterally away from the internal combustion engine (32) in a height direction. or The catalytic heater (10) is arranged in an exhaust system section (60) to be positioned so as to extend under the floor of the vehicle or to be positioned in a lateral region of the vehicle.

12. A method for operating an exhaust gas system according to any one of claims 4 to 11, in which method the at least one electrically energizable heating element (14) of the catalytic heater (10) is operated in such a way that liquid hydrocarbons (K) reaching the surface of the at least one electrically energizable heating element (14) are heated and oxidized on the oxidation catalyst component (26) to generate heat.

13. The method according to claim 12, It is characterized in that When, after the start of activation of the at least one electrically activatable heating element (14), the oxidation catalytic converter component (26) has a predetermined temperature, preferably a temperature that allows catalytic oxidation of hydrocarbons (K) on the oxidation catalytic converter component (26), and / or when a predetermined time period has elapsed since the start of activation of the at least one electrically activatable heating element (14), the injection of hydrocarbons (K) onto the at least one electrically activatable heating element (14) is started.

14. The method according to claim 12 or 13, It is characterized in that Before the internal combustion engine (32) starts operating, the at least one electrically activatable heating element (14) is activated.

15. The method according to claim 14, It is characterized in that Simultaneously with or after the start of operation of the internal combustion engine (32), the injection of hydrocarbons (K) onto the at least one electrically activatable heating element (14) is started.

16. The method according to claim 14 in combination with claim 3, It is characterized in that Before the internal combustion engine (32) starts operating, an injection of hydrocarbons (K) is started onto the at least one electrically activatable heating element (14).

17. The method according to claim 16, Features: a) injecting hydrocarbons (K) in a predetermined amount and / or for a predetermined duration in a pre-injection process before the internal combustion engine (32) starts operating, b) after the pilot injection process has ended, driving the internal combustion engine (32) to rotate without ignition, c) injecting hydrocarbons (K) in a predetermined amount and / or for a predetermined duration in a last pilot injection process before the internal combustion engine (32) starts operating.

18. The method according to claim 17, It is characterized in that Before carrying out measure c), measures a) and b) are repeated at least once, and / or the internal combustion engine (32) is put into operation after or during carrying out measure c).

19. The method according to claim 18, Features: With the completion of measure c), the injection of hydrocarbons (K) is terminated. or After completion of measure c) and after the internal combustion engine (32) has started operating, the injection of hydrocarbons (K) is resumed or continued.

20. The method according to any one of claims 12 to 19, It is characterized in that After the internal combustion engine (32) has started operating, the hydrocarbon injection rate is determined as a function of the temperature of the oxidation catalytic converter component (26) and / or as a function of the exhaust gas volume flow in the exhaust system (12).

21. The method according to claim 20, It is characterized in that The hydrocarbon injection rate is increased as the temperature of the oxidation catalyst component (26) increases and / or the hydrocarbon injection rate is decreased as the exhaust gas volume flow increases.

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