Method for heating a catalytic converter

Abstract

The invention relates to a method for heating a catalytic converter (48) arranged in an exhaust device (44) of an externally ignited internal combustion engine (10). Here, a control device (68) issues corresponding adjustment parameters to an electrically driven additional compressor (20) and injection valves (52, 54). By opening the injection valves (52, 54), the air compressed by the additional compressor (20) can be fed into the exhaust device (44) downstream of the exhaust valve of the internal combustion engine (10). Signals from oxygen sensors (64, 66) are provided to a regulator (72) of the control device (68), and the oxygen content in the exhaust gas applied to the catalytic converter (48) is measured by means of the oxygen sensors. The method comprises the following steps: a) switching on the additional compressor (20); b) at least partially opening the injection valves (52, 54); c) setting an air-fuel ratio λ < 1 for combustion in the combustion chamber (12) of the internal combustion engine (10); d) measuring an actual value of the oxygen content in the exhaust gas; e) comparing the actual value with a target value of the oxygen content, wherein the target value corresponds to the oxygen content set when the air-fuel ratio for combustion in the combustion chamber (12) of the internal combustion engine (10) is approximately λ = 1 in the region of the catalytic converter (48). When the actual value reaches one of the two end values of the numerical range in which the target value lies, the adjustment parameter output by the regulator (72) based on the difference between the actual value and the target value remains constant. The end values deviate from the target value by approximately 3%.

Description

Field of the Invention

[0001] The present invention relates to a method for heating a catalytic converter in an exhaust device of an externally ignited / spark-ignited (fremdgezündeten) internal combustion engine while reducing raw emissions. Background Art

[0002] DE 44 16 870 C2 describes a method for supplying fuel and combustion air to an internal combustion engine, wherein, in addition to the combustion air, compressed air is supplied to the internal combustion engine as additional combustion air. A catalytic converter is provided in the exhaust gas line of the internal combustion engine, and its function is adjusted according to the respective state of the fuel-air mixture of the internal combustion engine. In this case, the adjustment of the catalytic converter is interrupted by an electronic control means only when the supply of additional combustion air is switched on.

[0003] It is considered disadvantageous here that the catalytic converter, which then operates in an unadjusted manner, can no longer fully perform its function of converting harmful substances contained in the exhaust gas. Summary of the Invention

[0004] Therefore, the object of the present invention is to provide a method for heating a catalytic converter, by means of which improved conversion of harmful substances can be achieved.

[0005] This object is achieved by a method having the features of the present invention. Advantageous designs with suitable inventive improvements are described in the respective embodiments and the following description.

[0006] In the method according to the present invention for heating a catalytic converter in an exhaust device of an externally ignited internal combustion engine, a control device outputs corresponding adjustment parameters / control variables to an electrically driven additional compressor and at least one injection valve. In this case, the air compressed by the additional compressor can be fed into the exhaust device downstream of the exhaust valve of the internal combustion engine by at least partially opening the at least one injection valve. The exhaust valve belongs to a corresponding combustion chamber of the internal combustion engine. The signal of at least one oxygen sensor is supplied to the regulator / controller of the control device. By means of the at least one oxygen sensor, the oxygen content in the exhaust gas fed to the catalytic converter is measured.

[0007] The method comprises the following steps:

[0008] a) Switch on the additional compressor;

[0009] b) At least partially open the at least one injection valve;

[0010] c) Set the combustion air-fuel ratio λ < 1 in the combustion chamber of the internal combustion engine;

[0011] d) Measuring an actual value of the oxygen content in the exhaust gas by means of the at least one oxygen sensor;

[0012] e) Comparing the actual value with a target value of the oxygen content, wherein the target value corresponds to the following oxygen content in the exhaust gas, which will be set when the air-fuel ratio for combustion in the combustion chamber of the internal combustion engine is approximately λ = 1 in the region of the catalytic converter, and wherein when the actual value reaches one of the two limit values / end values of the numerical range in which the target value lies, the adjustment parameter output by the adjuster based on the difference between the actual value and the target value is kept constant / held steady, where the two end values defining the numerical range deviate from the target value by approximately 3%.

[0013] Since in step e) the adjustment parameter output by the adjuster is only kept constant when the actual value reaches one of the two end values, it can be ensured that the adjustment parameter is only approximately frozen when the actual value is relatively close to the target value. In this way, undesired fluctuations of the adjuster can be suppressed as much as possible and the target value can be reliably reached. In particular, one of the two end values is approximately 3% higher than the target value, and the other of the two end values is approximately 3% lower than the target value.

[0014] It is also conceivable that the target value of the oxygen content in the exhaust gas is fixed to a value for which there is an exhaust gas λ value of approximately 1.05 for the exhaust gas. Due to the deviation of approximately + / - 3% of the oxygen content in the exhaust gas from the predetermined target value as specified by the present invention, the exhaust gas λ value thus remains greater than 1, whereby advantageously a relatively small amount of the harmful substances discharged can be emitted into the ambient air. When the target value is fixed to 1.05, the exhaust gas λ value also remains less than 1.1, so that advantageously the catalytic converter is not cooled by the secondary air.

[0015] An improved conversion of harmful substances can be obtained by means of this method. That is, in particular, the raw emissions of an internal combustion engine, preferably a motor vehicle internal combustion engine, can be minimized especially after a cold start of the internal combustion engine.

[0016] In addition, the catalytic converter heating duration can be significantly shortened, so that the catalytic converter very rapidly reaches its starting temperature or light-off temperature. Therefore, the conversion of the harmful emissions of the internal combustion engine can be ensured early by means of the catalytic converter. For this purpose, the blowing-in of compressed air or secondary air realized by means of an electrically driven additional compressor is a very efficient means.

[0017] Since the air-fuel ratio λ for combustion is set to be < 1 in step c), the exhaust gas formed during rich combustion contains a large amount of hydrocarbons (HC) and carbon monoxide (CO). This is particularly applicable when setting the air-fuel ratio for rich combustion in the combustion chamber of an internal combustion engine in step c) within the range from approximately λ = 0.7 to λ = 0.9. The HC emissions and CO emissions of the internal combustion engine are exothermically oxidized by oxygen, which is introduced into the exhaust gas conveyed to the catalytic converter together with the compressed air or secondary air. The compressed air is sent into the exhaust gas due to the additional compressor driven electrically, and at least one injection valve is at least partially opened simultaneously, and thus it can also be referred to as a compressor air injection valve.

[0018] The exothermic oxidation of hydrocarbons (HC emissions) and carbon monoxide (CO emissions) is used to increase the temperature of the exhaust gas conveyed to the catalytic converter. That is, the harmful substances in the form of hydrocarbons and carbon monoxide contained in the raw emissions of the internal combustion engine react with oxygen, and the catalytic converter is heated or warmed up very quickly through this exothermic reaction.

[0019] Furthermore, it is advantageous to set the air ratio for rich combustion λ < 1 (especially λ = 0.7 - 0.9) in the combustion chamber of the internal combustion engine, because in this way very little nitrogen oxide emissions are maintained in the combustion chamber. Therefore, due to the exothermic secondary combustion of HC emissions and CO emissions, on the one hand, the at least one catalytic converter is heated very rapidly. At the same time, the raw emissions discharged into the surrounding environment of a motor vehicle equipped with an internal combustion engine through the exhaust system are significantly reduced.

[0020] The exothermic reaction occurring upstream of the catalytic converter results in a reduction in the harmful substances contained in the raw emissions of the internal combustion engine, and in addition, the catalytic converter is heated particularly rapidly, especially after a cold start of the internal combustion engine. Thus, the internal combustion engine can operate at its ideal efficiency earlier, and the harmful substances are converted correspondingly earlier in the heated catalytic converter.

[0021] Therefore, during the actual operation of the internal combustion engine or internal combustion motor, the emissions can be regulated as well and durably as when the air-fuel ratio for combustion λ = 1. In this way, particularly significant emission conversion is obtained.

[0022] This also applies to the case where heating and / or regeneration of a particulate filter, especially a gasoline particulate filter, installed in the exhaust system also occur, and it still applies even when the internal combustion engine operates at a rich air-fuel ratio for combustion, i.e., an air-fuel ratio for combustion λ < 1, for high power output of the internal combustion engine.

[0023] Furthermore, when the internal combustion engine already inherently has an additional compressor that is electrically driven or can be electrically driven, the additional structural expenditure is particularly low. Because in this case, at least one pipeline is only routed from the additional compressor to the inlet location where the air compressed by the additional compressor is fed into the exhaust of the internal combustion engine. In addition, an injection valve should also be installed on such a pipeline. It can also be implemented with a very simple structure and low expenditure.

[0024] By adjusting the additional compressor or the injection valve with a regulator, the optimal oxygen content of the exhaust gas fed to the catalytic converter can be set for the conversion of HC emissions and CO emissions. The exhaust gas lambda can be adjusted accordingly at different operating points of the driving cycle.

[0025] Preferably, the higher-level operating strategy implemented in the control device takes into account the engine operating point, i.e., the operating point of the internal combustion engine, and / or environmental data. In this case, in particular, the route planning data of the navigation system of the motor vehicle with the internal combustion engine can be considered, but vehicle-to-vehicle information can also be considered.

[0026] In particular, based on such parameters, the adjustment strategy for the optimal exhaust gas lambda can be adjusted in a coordinated combination with the enrichment of the mixture of combustion air and fuel supplied to the combustion chamber of the internal combustion engine. Ignition angle adjustment can also be completed, i.e., the ignition timing of the spark plug assigned to each combustion chamber can be shifted to a later time.

[0027] The air compressed by the additional compressor can in particular be fed into the exhaust manifold of the exhaust device. In this case, it is advantageous that the inlet location for adding compressed air or secondary air is arranged as close as possible to the respective exhaust valve of the internal combustion engine combustion chamber.

[0028] As a secondary air pump, an electrically driven additional compressor is used in this case, and it can in particular be connected to the 48-volt on-vehicle power supply of the internal combustion engine. Advantageously, the additional compressor installed on the internal combustion engine is designed to increase the performance or power output and / or torque output of the internal combustion engine as needed, by feeding additional compressed air into the combustion chamber of the internal combustion engine with the help of the electrically driven additional compressor.

[0029] The electrically driven additional compressor is preferably provided as a supplement to the compressor of the exhaust gas turbocharger, and its turbine impeller is subjected to the exhaust gas flowing through the exhaust device during the operation of the internal combustion engine.

[0030] This method is advantageous compared to catalytic converter heating technical means - which may in principle also be in the form of technical means inside the engine - such as ignition angle retard and increasing the idling speed of the internal combustion engine. It is also possible to avoid the expenditure involved in installing a separate secondary air pump on the cylinder head of the internal combustion engine. Because when secondary air is fed into the exhaust with such a separate secondary air pump on the cylinder head, structural space and pipelines must be provided in particular for the separate air pump.

[0031] Such an intervention may particularly disadvantageously affect the cooling power of the internal combustion engine cooling system, especially when the cooling jacket of the internal combustion engine is intervened. This may in turn lead to the inability to provide the desired power of the internal combustion engine because sufficient cooling of the internal combustion engine cannot be ensured.

[0032] In addition, such a structural intervention must be individually checked and adjusted for each type of internal combustion engine. Therefore, it is necessary to protect the durability of the cylinder head during both the continuous operation of the internal combustion engine and the bench test. The aforementioned disadvantages can be advantageously avoided in the method having steps a) to e).

[0033] In particular, steps a), b), c) and d) of the method can be completed simultaneously or in an order different from the order that can be assumed by alphabetical order.

[0034] It is preferably provided that the speed / rotation speed of the additional compressor is pre-adjusted / pilot-controlled (Vorsteuerung), and the opening size of the injection valve is adjusted so as to set a predetermined target value of the exhaust gas oxygen content.

[0035] Alternatively or additionally, it is provided that the opening size of the at least one injection valve is pre-adjusted, and the rotation speed of the additional compressor is adjusted so as to set a predetermined target value of the exhaust gas oxygen content.

[0036] It is preferably provided that steps a) to e) of the method are carried out after a cold start of the internal combustion engine.

[0037] It is preferably provided that steps a) to e) of the method are carried out when the rotation speed of the internal combustion engine exceeds a threshold value of about 100 revolutions per minute.

[0038] It is preferably provided that the catalytic converter operates as a three-way catalytic converter.

[0039] It is preferably provided that a proportional-integral regulator is used as the regulator.

[0040] Finally, it is preferably provided that in addition to the air-fuel ratio λ<1 for combustion in the combustion chamber of the internal combustion engine set in step c), the ignition timing of the internal combustion engine spark plug corresponding to each combustion chamber is additionally shifted to a later time than during the normal operation of the internal combustion engine. Description of the Drawings

[0041] Other advantages, features and details of the present invention are obtained from the following description of the preferred embodiments and in conjunction with the figures. 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 drawings and / or shown individually in the figures can be used not only in the respective combinations indicated, but also in other combinations or individually, without departing from the scope of the present invention, wherein:

[0042] Figure 1Schematically shows an internal combustion engine of a motor vehicle, in which air compressed by means of an electrically driven additional compressor can be selectively fed into the air supply line of the internal combustion engine or into the exhaust manifold of the internal combustion engine;

[0043] Figure 2 Shows the functional structure for the intake of the compressor leading to the exhaust manifold and for the regulation of the rotational speed of the additional compressor;

[0044] Figure 3 Shows a regulator structure with two adjustment variants comprising the functional structure according to Figure 2 ;

[0045] Figure 4 Shows an adjustment implementation possibility, in which the regulator adjustment parameters are frozen or held constant. Detailed description

[0046] In the figures, identical or functionally identical components carry the same reference numerals.

[0047] Figure 1 Schematically shows an internal combustion engine 10 of a motor vehicle, which is designed as an externally ignited internal combustion engine 10. Correspondingly, each combustion chamber 12 of the internal combustion engine 10 (only a few of which are provided with reference numerals in Figure 1 for the sake of overview) is assigned a respective spark plug 14. Only some of the spark plugs 14 are provided with reference numerals in Figure 1 either.

[0048] Compressed air can be supplied to the combustion chambers 12 of the internal combustion engine 10 via an air supply line 16. To compress this supply air, an exhaust gas turbocharger 18 is provided on the one hand and an electrically driven additional compressor 20 is provided on the other hand. The compressor impeller 22 of the exhaust gas turbocharger 18 is arranged in a line branch 24 of the air supply line 16 for sucking in the air to be compressed. Downstream of the compressor impeller 22, another line branch or branch line 26 branches off from the line branch 24.

[0049] In the branch line 26, a compressor impeller 28 of the additional compressor 20 which can be driven by means of a (not shown) electric motor is provided. Downstream of the compressor impeller 28 of the additional compressor 20, the branch line 26 opens back into the line branch 24. Downstream of the point where the branch line 26 opens into the line branch 24, a throttle valve 36 is provided in the line branch 24. When the throttle valve 36 is opened at least partially, compressed air can flow through an intercooler 30, which is arranged in the line branch 24 of the air supply line 16.

[0050] A first compressor air line 32 and a second compressor air line 34 branch off from the branch line 26 downstream of the compressor wheel 28 of the auxiliary compressor 20. The air compressed by means of the electrically driven auxiliary compressor 20 is fed into the exhaust gas of the internal combustion engine 10 via the compressor air lines 32, 34 downstream of the exhaust valves (not shown) of the internal combustion engine 10 which are associated with the respective combustion chambers 12.

[0051] Here, air taken from the air supply line 16 upstream of the throttle valve 36 and compressed by means of the additional compressor 20 is fed into the exhaust manifold 38 of the internal combustion engine 10. In this case, as exemplarily shown above, the exhaust manifold 38 can include a first exhaust gas flow 40 and a second exhaust gas flow 42.

[0052] The first exhaust gas flow 40 discharges exhaust gas from the first group of combustion chambers 12, for example, the first three combustion chambers of the six combustion chambers 12 shown here by way of example. In contrast, exhaust gas from the second group of combustion chambers 12 of the internal combustion engine 10, i.e., the first three combustion chambers of the six combustion chambers 12 shown here by way of example, is discharged via the second exhaust gas flow 42. Figure 1 The exhaust gases from three other combustion chambers 12 of a total of six combustion chambers 12 of the internal combustion engine 10 shown in the example.

[0053] If exhaust system 44 of internal combustion engine 10 is designed as a single-flow system, ie has only one exhaust gas flow, only one of compressor air lines 32 , 34 shown here by way of example needs to be provided in order to introduce air compressed by means of auxiliary compressor 20 or secondary air into the exhaust gas flow.

[0054] In the variant of internal combustion engine 10 shown here, air compressed by means of additional compressor 20 is introduced into first exhaust gas flow 40 via first compressor air line 32. Compressed air or secondary air is introduced into second exhaust gas flow 42 via second compressor air line 34 in a similar manner.

[0055] The exhaust gas flowing through the exhaust gas streams 40, 42 is supplied in a manner known per se to a turbine wheel 46 of the exhaust gas turbocharger 18, which is arranged in an exhaust gas device 44. Downstream of the turbine wheel 46, a first catalytic converter 48 is arranged in the exhaust gas device 44, and downstream of the first catalytic converter 48, a second catalytic converter 50 is arranged.

[0056] Here, the first catalytic converter 48 can be designed as a three-way catalytic converter, and the second catalytic converter 50 can be designed as a nitrogen oxide storage catalytic converter or can include a nitrogen oxide storage catalytic converter, for example. However, the following description also applies to the exhaust system 44 in which only the exhaust gas system 44 is arranged. Figure 1 One of the two catalytic converters 48, 50 is shown by way of example.

[0057] Since the internal combustion engine 10 shown in the current example has a first compressor air line 32 and a second compressor air line 34, two injection valves 52, 54 can also be provided. In this case, the first compressor air line 32 can be shut off or at least partially opened by means of the first injection valve 52. In a similar manner, the second compressor air line 34 can be shut off or at least partially opened by means of the second injection valve 54. The injection valves 52, 54 can also be referred to as compressor air injection valves.

[0058] Attempts to use pipes with an inner diameter of 18 mm for the compressor air lines 32, 34 have proven successful. Such pipes can be installed or laid out particularly simply and at low cost, as Figure 1 schematically illustrated by way of example.

[0059] When only one compressor air line is provided for feeding compressed air or secondary air into the exhaust downstream of the exhaust valve of the internal combustion engine 10, only one of the two injection valves 52, 54 shown here by way of example needs to be provided.

[0060] In a manner known per se, during operation of the internal combustion engine 10, fuel stored in the fuel tank 58 is supplied to the combustion chambers 12 by means of the respective injectors 56. In the corresponding fuel line 60, a high-pressure pump 62 is provided here, by means of which the pressure of the fuel fed into one of the respective combustion chambers 12 by means of one of the respective injectors 56 is increased.

[0061] Other components of the internal combustion engine 10, such as the engine oil circulation, the fuel tank ventilation device, and the coolant circulation, although Figure 1 shown therein, do not need to be described in detail here in connection with the relevant details.

[0062] During operation of the internal combustion engine 10, especially after a cold start of the internal combustion engine 10, the air-fuel ratio λ for combustion in the respective combustion chambers 12 is less than 1 and is in the range of λ = 0.7 to 0.9. As a result, rich combustion occurs between the fuel and the oxygen contained in the air fed into the combustion chambers 12 through the air supply pipe 16, and a large amount of HC emissions and CO emissions occur in the exhaust gas flowing out of the combustion chambers 12.

[0063] In addition, after a cold start of the internal combustion engine 10, compressed air or compressed fresh air is taken out from the branch line 26 downstream of the electrically driven additional compressor 20 and thus upstream of the throttle valve 36 and fed into the exhaust manifold 38 through the compressor air lines 32, 34, that is, here it is fed into the first exhaust gas stream 40 and the second exhaust gas stream 42. The oxygen contained in the compressed secondary air is used for the exothermic oxidation of unburned hydrocarbons (HC) and carbon monoxide (CO).

[0064] Furthermore, the temperature in the exhaust manifold 38 can be increased by a retarded combustion center (Verbrennungsschwerpunkt). This measure causes, in particular, the first catalytic converter 48 to be heated very rapidly and the first catalytic converter 48 thus reaches its starting temperature very rapidly.

[0065] The amount of air or secondary air introduced into the exhaust gas conveyed to the first catalytic converter 48 is regulated by the opening size of at least one injection valve 52, 54, i.e., by the respective opening cross-section of the bypass valve and / or by the rotational speed of the electrically driven additional compressor 20.

[0066] The compressor air lines 32, 34 or the bypass line or branch preferably lead into the exhaust gas device 44 in such a way as to be as close as possible to the exhaust valves of the internal combustion engine 10. The secondary air injection thus takes place Figure 1 in the region of the exhaust manifold 38 or in the cylinder head region of the internal combustion engine 10 and thus as close as possible to the exhaust valves of the combustion chamber 12 of the internal combustion engine 10.

[0067] As the injection valves 52, 54, a lift valve with a position feedback function can be used, for example. Furthermore, during a cold start of the internal combustion engine 10, parameters can be varied within a test range in order to obtain a favorable activation energy for the exothermic reaction by the position of the combustion center of gravity, the exothermic reaction taking place in the exhaust manifold 38 or in the exhaust ducts of the internal combustion engine 10.

[0068] In order to determine the oxygen content of the exhaust gas conveyed to the catalytic converter 48, at least one oxygen sensor can be used, which, for example, has the form of a first lambda probe 64 arranged in the exhaust gas device 44 upstream of the catalytic converter 48. Here, the first lambda probe 64 is designed as a broadband lambda probe. Furthermore, according to Figure 1 , as another oxygen sensor, another lambda probe 66 is arranged in the exhaust gas device 44 at the height of the catalytic converter 48. It is also possible to determine the oxygen content in the exhaust gas flowing through the catalytic converter 48 with the aid of another or second lambda probe 66.

[0069] In particular, the oxygen content of the exhaust gas and the exhaust lambda can be determined with the aid of the first lambda probe 64 arranged upstream of the catalytic converter 48. In this case, the rotational speed of the electrically driven additional compressor 20 can be regulated or adjusted in such a way that a suitable exhaust lambda occurs during the secondary air intake and thus during the heating phase of the catalytic converter 48.

[0070] The oxygen content in the exhaust gas measured by means of at least one lambda sensor, here in the form of one of lambda probes 64 , 66 , is adjusted during the heating phase of the catalytic converter 48 selectively by presetting at least one injection valve 52 , 54 in combination with a speed adjustment of the electrically driven additional compressor 20 or by presetting the speed of the electrically driven additional compressor 20 in combination with an adjustment of the opening size of at least one injection valve 52 , 54 or of the compressor air injection valve.

[0071] In this context, a meaningful operating strategy and activation strategy is created overall with regard to the control functionality of the additionally introduced control variables for presetting and regulating in the form of the opening size of at least one injection valve 52 , 54 and the rotational speed of the electrically driven additional compressor 20 .

[0072] Advantageously, components can be used in this method which have been tested in series and have therefore proven their functional reliability. Furthermore, only a small number of additional components are required. This is advantageous with regard to the reduction in weight and costs as well as the installation space occupied. In the latter case, it is particularly advantageous to use an electrically driven additional compressor 20 as a secondary air pump, which is provided anyway for improving the driving dynamics of the internal combustion engine 10.

[0073] Hereby Figure 1 The functional expansion of the engine control, which is only shown by way of example, which is implemented by the control device 68 for implementing the method for heating at least one catalytic converter 48, 50, is advantageously largely decoupled in a modular manner, except for considerations regarding the filling model. Therefore, no extensive adaptation or intervention in the basic functional structure of the engine control is required.

[0074] The control device 68 is designed to control and / or regulate at least one injection valve 52, 56 and to control and / or regulate the electrically driven additional compressor 20. Accordingly, the control device 68 can output respective control parameters 90, 106 to at least one injection valve 52, 54 and the additional compressor 20. This should be referred to Figure 2 To explain.

[0075] Figure 2 The functional blocks of a plurality of operating situations are shown, which can be realized during the heating of the catalytic converter 48 by means of the compressor air intake and the speed control of the electrically driven auxiliary compressor 20 which is then carried out.

[0076] exist Figure 2 In the operating strategy 70 represented by the first block, different regulator variants are proposed, which can be used depending on the application or the operating mode of the internal combustion engine 10 .

[0077] On the one hand, the compressor intake air can be adjusted by means of the regulator 72 of the control device 68 (see Figure 1)to adjust the opening sizes of at least one of the injection valves 52, 54, wherein the rotational speed of the electrically driven additional compressor 20 is pre-set.

[0078] In another regulator variant, the compressor intake, i.e. the opening sizes of at least one of the injection valves 52, 54, are pre-set and the rotational speed of the electrically driven additional compressor 20 is adjusted.

[0079] It can also be provided that not only the compressor intake and thus the opening sizes of the injection valves 52, 54 are adjusted, but also the rotational speed of the electrically driven additional compressor 20 is adjusted.

[0080] Such an additional function for heating the catalytic converter 48 can be enabled depending on relevant engine parameters. The corresponding parameters taken into account in the operating strategy 70 can include a requirement made by the control device 68, namely that the catalytic converter 48 should be heated.

[0081] Furthermore, an enabling time for setting a maximum duration can be applied in the operating strategy 70, during which the catalytic converter 48 should be heated. Furthermore, the operating strategy 70 can selectively include a temperature threshold of the exhaust device 44. This is particularly advantageous when a suitable temperature sensor 74 (see Figure 1 ) is available, by means of which the temperature of the exhaust gas flowing through the catalytic converter 48 can be measured. It is also conceivable to determine the temperature for determining the temperature threshold from a computational model. Additionally, a temperature can also be set as the stop criterion for heating the catalytic converter 48, or the duration or enabling time of heating the catalytic converter 48 can be determined based on the determined and / or measured temperature.

[0082] Furthermore, it can be provided within the scope of the operating strategy 70 that the rotational speed of the internal combustion engine 10 should be higher than a threshold of approximately 100 revolutions per minute, so that a usable function permission occurs only when the internal combustion engine 10 is started, rather than when the ignition of the motor vehicle having the internal combustion engine 10 is switched on.

[0083] In this case, a time period for resetting the regulator 72 can be utilized, so that the pre-set values for the rotational speed of the electrically driven additional compressor 20 and the compressor intake, i.e. the opening sizes of at least one of the injection valves 52, 54, take effect immediately, but the regulator 72 is started with a delay. Alternatively, the regulator can only be started when the wide-band lambda probe 64 is measurement-ready.

[0084] Other engine control parameters that can be adjusted within the operating strategy 70 can include the lambda target value during heating of the catalytic converter 48 and / or a basic pre-set factor for the air mass supplied to the internal combustion engine 10 via the air supply line 16.

[0085] In addition, it is possible to implement a respective enabled delay for the application software or the calculation model. For example, it can be stipulated to wait for the validity of the measured value or to grant the enabling only after a fault diagnosis. In this regard, it can be stipulated especially after the internal combustion engine 10 has been started, wherein, in particular, at least one fault diagnosis of the lambda probes 64, 66 can first be completed.

[0086] In Figure 2 a first arrow 76 indicates the pre-adjustment 78 of the at least one injection valve 52, 54 being enabled. Another arrow 80 indicates the regulator 72 being enabled. Correspondingly, after the regulator 72 has been enabled, an adjustment 82 of the at least one injection valve 52, 54 can be completed, that is, the opening size of the at least one injection valve 52, 54 is adjusted. In this case, a lambda adjustment of the opening size can be completed.

[0087] The regulator 72 can in particular be designed as a proportional-integral regulator 72 (PI regulator). In this case, it is preferably possible to adjust the proportional regulator magnification (Kp) and the integral regulator magnification (Ki) according to the control deviation.

[0088] According to Figure 2 , a pre-adjustment part of the compressor intake and a regulator part of the compressor intake can be provided to the node 84. An arrow 86 starting from the node 84 indicates the triggering of a fault diagnosis in the fault diagnosis block 88, in which the adjustment parameter limitation can be completed.

[0089] The result of the first branch of the functional structure as Figure 2 shown is output to the adjustment parameter 90 of the at least one injection valve 52, 54 (see Figure 1 ). That is, because the adjustment parameter 90 is output, the opening size of the respective injection valve 52, 54 is adjusted.

[0090] In Figure 2 the second branch of the functional structure shown, another arrow 92 indicates the enabling of the pre-adjustment 94, wherein, when designing the pre-adjustment 94, the rotational speed of the electrically driven additional compressor 20 is pre-adjusted. For the respective pre-adjustments 78, 94, static characteristic curves that can take into account the load and rotational speed of the internal combustion engine 10 can be used.

[0091] In a similar manner to that described for the at least one injection valve 52, 54, in Figure 2 the second branch, another arrow 96 indicates the enabling of the regulator 72 for adjusting 98 the rotational speed of the electrically driven additional compressor 20. In this case, a lambda adjustment can also be completed, where the regulator 72, which is preferably designed as a PI regulator, is used (see Figure 1 ). Here too, it is preferably possible to adjust the regulator magnification in the form of the proportional magnification (Kp) and the integral magnification (Ki) according to the control deviation.

[0092] The corresponding arrow leads from the block in Figure 2 representing the pre - adjustment 94 and adjustment 98 of the additional compressor 20 and leads to the node 100, just as in the first branch of the functional structure. Thus, the pre - adjustment part of the rotational speed of the additional compressor 20 or the regulator part of the rotational speed of the additional compressor 20 can be provided to the node 100.

[0093] The arrow 102 starting from the node 100 leads to the fault diagnosis block 104, where the adjustment parameter limitation can be completed. The result of the second branch of the functional structure or functional strategy as Figure 2 shown is the adjustment parameter 106 that can be output by the control device 68 to the electric drive of the additional compressor 20 (see Figure 1 ). That is, because of the output of this adjustment parameter 106, the rotational speed of the electric drive of the additional compressor 20 is regulated.

[0094] Figure 2 Another arrow 107 in

[0095] shows the possible adjustment of parameters in the engine control implemented in the control device 68. The parameters can include, as explained, the λ target value during the heating of the catalytic converter 48 and the basic pre - adjustment factor of the air quantity supplied to the internal combustion engine 10 through the air supply duct 16.

[0096] Measures are taken here to reduce the fluctuations of the adjustment parameter λ. The measures include freezing or keeping the respective regulator adjustment parameters, here one of the adjustment parameters 90, 106, constant near the target value.

[0097] Thus, in particular, it can be stipulated that once the adjustment parameter 90 is near the target value, the opening size of at least one of the injection valves 52, 54, which is the adjustment parameter 90 output by the regulator 72 (see Figure 1 ), is kept constant. In this regulator variant, the rotational speed of the additional compressor 20 is pre - adjusted by means of the regulator 72. That is, the pre - adjustment 94 of the additional compressor 20 and the adjustment 82 of the opening size of at least one of the injection valves 52, 54 (see Figure 2 ) are continuously implemented until the actual value of the oxygen content in the exhaust gas delivered to the catalytic converter 48 approaches the target value 114 of the oxygen content (see Figure 4 ) to a sufficient extent due to the output of the adjustment parameter 90. The actual value of the oxygen content can be detected, for example, by means of the first λ - probe 64.

[0098] In an alternative regulator variant, once the adjustment parameter 106 is near the target value, the rotational speed of the additional compressor 20, which is the adjustment parameter 106 output by the regulator 72, is kept constant. In this alternative regulator variant, the opening sizes of at least one of the injection valves 52, 54 are pre-adjusted by means of the regulator 72. That is, the pre-adjustment 78 of the opening sizes of at least one of the injection valves 52, 54 and the adjustment 98 of the additional compressor 20 (see Figure 2 ) are continuously achieved until the actual value of the oxygen content of the exhaust gas applied to the catalytic converter 48 approaches the target value 114 of the oxygen content to a sufficient extent by outputting this adjustment parameter 106 (see Figure 4 ). Here, the actual value of the oxygen content can also be measured, for example, by means of the first lambda probe 64.

[0099] In other words, when the actual value is sufficiently close to the target value 114, the adjustment parameters 90, 106 output by the regulator 72 based on the difference between the actual value of the exhaust gas oxygen content and the target value 114 of the oxygen content can be kept constant, that is, the regulator 72 is approximately frozen.

[0100] The corresponding adjustment means can be used in different combinations according to a series of input parameters to ensure the effective heating of at least one of the catalytic converters 48, 50. For example, the operating point of the internal combustion engine 10 can be considered, such as the load and / or rotational speed and / or temperature and / or dynamics of the internal combustion engine 10, etc.

[0101] In addition, environmental information consisting of the route planning of the navigation system of the motor vehicle having the internal combustion engine 10 and / or vehicle-to-vehicle information can be considered.

[0102] In particular, it has been shown that when statically checking the internal combustion engine 10 on the test bench, the combined use of the pre-adjustment 78 of the opening sizes of at least one of the bypass valves or injection valves 52, 54 and the adjustment 98 of the rotational speed of the electrically driven additional compressor 20 is well-suited for achieving low emissions in the exhaust gas leaving the exhaust device 44 and entering the environment. However, in the dynamic operation of the internal combustion engine 10, a different variant may be particularly well-suited, so the corresponding variant can be stored in the operating strategy 70 (see Figure 2 ).

[0103] For example, it can be stipulated that the regulator variant in which the opening sizes of at least one of the injection valves 52, 54 remain constant after the initial adjustment 82 and the rotational speed of the additional compressor 20 is pre-adjusted is switched to the regulator variant in which the rotational speed of the additional compressor 20 remains constant after the initial adjustment 98 and the opening sizes of at least one of the injection valves 52, 54 are pre-adjusted. This switch can be made especially when a dynamic increase is recognized in relation to the load and / or rotational speed of the internal combustion engine 10. These two regulator variants can also be used in combination and can also be used as a multi-parameter adjustment system as needed.

[0104] InFigure 3 In this case, multiple arrows 108 represent input parameters supplied to the regulator 72. The input parameters may include operating point information such as the load and / or rotational speed and / or temperature of the internal combustion engine 10.

[0105] Furthermore, this or these input parameters may include the actual value of the oxygen content in the exhaust gas fed to the catalytic converter 48. Curves 110, 128, 134 indicating possible actual values of the oxygen content are shown in Figure 4 This. The actual value can be provided in particular by the first lambda probe 64 and / or the second lambda probe 66.

[0106] The input block containing the arrow 108 is separated from the calculation block 112 as shown in Figure 3 This, and the calculation block basically includes two branches of the functional structure including the respective fault diagnosis blocks 88, 104 as shown in Figure 2 This. As explained above, for example, when the actual value of the oxygen content approaches the target value 114 represented by the horizontal line in Figure 4 This, freezing of the adjustment parameter 90 may occur when adjusting the opening size of at least one injection valve 52, 54 of the adjustment 82 to achieve stable operation of the regulator 72.

[0107] In a similar manner, when the pre-adjustment 78 of at least one injection valve 52, 54 is enabled and the rotational speed of the electrically driven additional compressor 20 is first adjusted, i.e., the adjustment 98 takes effect (see Figure 2 ) This, freezing of the adjustment parameter 106 can be completed. Freezing or constant holding of the adjustment parameter 106 is also preferably carried out when the actual value of the oxygen content in the exhaust gas fed to the catalytic converter 48 approaches the target value 114 represented by the horizontal line in Figure 4 This.

[0108] Therefore, the pre-adjustment 78 of at least one injection valve 52, 54 for the compressor intake or the pre-adjustment 94 of the rotational speed of the electrically driven additional compressor 20 is carried out according to the operating state of the internal combustion engine 10. The pre-adjustment value can be stored as a fixed value depending on the specific application. Alternatively, the pre-adjustment value can be derived from a physics-based model method.

[0109] In addition to pre-adjusting the compressor intake air or adjusting the rotational speed of the electrically driven additional compressor 20, the adjustments 82, 98 of the adjusted combustion lambda value are meaningful for obtaining as rapid heating of the catalytic converter 48 as possible under favorable raw emissions.

[0110] As the operating principle of the regulator 72 for adjusting the compressor intake air, i.e., the opening size of at least one injection valve 52, 54 or the rotational speed of the electrically driven additional compressor 20, a proportional-integral regulator 72 (PI regulator) is preferably provided. In this case, the regulator magnification can preferably be adjusted respectively according to the control deviation, and this can be depending on the specific application or according to the operating strategy 70 (seeFigure 2 ) under the set conditions.

[0111] Furthermore, the respective adjustment parameters 90, 106 of the regulator 72 are frozen or held constant near the target value. The freezing or constant holding of the respective adjustment parameters 90, 106 can be required by the operating strategy 70.

[0112] Figure 4 Schematically shows how the freezing or constant holding of the adjustment parameters 90, 106 output by the regulator 72 can be achieved when the actual value is close to the target value 114.

[0113] In Figure 4 In the first section 116 of the shown curve graph, the curve 110 shows that fluctuations in the actual value of the oxygen content in the exhaust gas delivered to at least one catalytic converter 48, 50 may occur. The oxygen content can be detected by means of at least one oxygen sensor in the form of one of the lambda probes 64, 66.

[0114] Figure 4 Another curve 118 in shows the corresponding fluctuations in the adjustment parameter 90 output by the regulator 72 in the adjustment 82 of the opening sizes of the injection valves 52, 54 (see Figure 2 ), where the rotational speed of the additional compressor 20 is pre-set. In a similar manner, such fluctuations in the adjustment parameter 106 as indicated by the curve 118 may occur when the opening sizes of at least one of the injection valves 52, 54 are pre-set and the regulator 72 completes the adjustment 98 of the rotational speed of the additional compressor 20 (see Figure 2 ).

[0115] The changes in the respective adjustment parameters 90, 106 represented by the curve 118 can be caused in such a way that, due to the design of the air path for the compressor intake, i.e., due to the design of the compressor air lines 32, 34 (see Figure 1 ), a delay occurs between the output of the respective adjustment parameters 90, 106 and the resulting oxygen content that should occur in the exhaust gas. However, the oxygen content should originally be adjusted as accurately as possible by the amount of compressor air that should be provided by the additional compressor 20.

[0116] To cope with the fluctuations or variations in the adjustment parameters 90, 106, once the actual value enters the numerical range 120 in which the target value 114 is located (see Figure 4 ), the adjustment parameters 90, 106 output by the regulator 72 based on the deviation between the actual value and the target value 114 are held constant or frozen here.

[0117] As Figure 4 shown, the numerical range 120 is bounded by the upper endpoint value 122 and the lower endpoint value 124. The upper endpoint value 122 is in this case at Figure 4is represented by a horizontal dotted line in the middle, and the lower endpoint value 124 is also represented by a horizontal dotted line. Once the actual value reaches one of the two endpoint values 122 and 124, the adjustment parameters 90 and 106 output by the adjuster 72 are kept constant, so that no further adjustment 82 of the opening sizes of the injection valves 52 and 54 is performed (see Figure 2 ), or no further adjustment 98 of the rotational speed of the additional compressor 20 is performed (see Figure 2 ).

[0118] In Figure 4 in another section 126, it is represented by a curve 128 as follows. Here, the actual value of the oxygen content reaches the lower endpoint value 124. The actual value of the oxygen content in the exhaust gas delivered to the catalytic converter 48 is thus represented by the curve 128 in the section 126.

[0119] Another curve 130 in Figure 4 represents the time curves of the adjustment parameters 90 and 106 output by the adjuster 72 in the adjustment 82 or in the adjustment 98 (see Figure 2 ). That is, if the adjustment 82 takes effect first, the adjustment parameter 90 is kept constant as the lower endpoint value 124 is reached. And if the adjustment 98 takes effect first, the adjustment parameter 106 is kept constant as the lower endpoint value 124 is reached.

[0120] The output of the constant adjustment parameters 90 and 106 in Figure 4 is represented by the horizontal trend of the curve 130 in the section 126. The horizontal trend starts when the curve 128 intersects the line indicating the lower endpoint value 124.

[0121] In a similar manner, in Figure 4 in another section 132, a possible time curve of the actual value of the oxygen content is represented by another curve 134. The actual value of the oxygen content is detected in the exhaust gas device 44 by means of at least one lambda probe 64 and 66 during the opening size adjustment 82 or during the rotational speed adjustment 98 (see Figure 2 ).

[0122] However, in another section 132, the curve 134 reaches the upper endpoint value 122. When the actual value reaches the upper endpoint value 122, the adjustment parameters 90 and 106 output by the adjuster also remain constant. But when the adjustment 82 has taken effect first, the adjustment parameter 90 is thus also kept constant here, and when the adjustment 98 has taken effect first, the adjustment parameter 106 is kept constant (see Figure 2 ).

[0123] The constant holding of the adjustment parameters 90 and 106 output by the adjuster in Figure 4 is represented by another curve 136 in another section 132. Once the curve 134 intersects the one in Figure 4The line representing the upper endpoint value 122 intersects, and another curve 136 shown in the section 132 also shows a horizontal time curve.

[0124] In the case as shown in Figure 4 in the second section 126 and in the case as shown in Figure 4 in the third section 132, the curves 128, 134 indicating the actual values ultimately reach the target value 114.

[0125] Possibly, the fluctuation effect shown in the first section 116 can be improved or avoided by accurately considering the compressor air volume in the engine control filling model. However, especially in the dynamic operation of the internal combustion engine 10, the freezing or constant holding of the adjustment parameters 90, 106 output by the regulator 72 is helpful. Therefore, once the actual value reaches one of the two endpoint values 122, 124 between which the target value 114 lies, the constant holding of the adjustment parameters 90, 106 is preferably completed.

[0126] The two endpoint values 122, 124 defining the numerical range 120 can, for example, deviate from the target value 114 by approximately 3%. In this way, it can be ensured that the adjustment parameters 90, 106 are only frozen or constantly held when the actual value is correspondingly close enough to the target value 114.

[0127] List of reference numerals

[0128] 10 Internal combustion engine

[0129] 12 Combustion chamber

[0130] 14 Spark plug

[0131] 16 Air supply pipe

[0132] 18 Exhaust gas turbocharger

[0133] 20 Additional compressor

[0134] 22 Compressor impeller

[0135] 24 Pipeline branch

[0136] 26 Branch pipeline

[0137] 28 Compressor impeller

[0138] 30 Charge air cooler

[0139] 32 Compressor air pipeline

[0140] 34 Compressor air pipeline

[0141] 36 Throttle valve

[0142] 38 Exhaust manifold

[0143] 40 Exhaust flow

[0144] 42 Exhaust flow

[0145] 44 Exhaust equipment

[0146] 46 Turbine impeller

[0147] 48 Catalytic converter

[0148] 50 Catalytic converter

[0149] 52 Injection valve

[0150] 54 Injection valve

[0151] 56 Injector

[0152] 58 Fuel tank

[0153] 60 Fuel line

[0154] 62 High-pressure pump

[0155] 64 λ probe

[0156] 66 λ probe

[0157] 68 Control device

[0158] 70 Operating strategy

[0159] 72 Regulator

[0160] 74 Temperature sensor

[0161] 76 Arrow

[0162] 78 Presetting

[0163] 80 Arrow

[0164] 82 Adjustment

[0165] 84 Node

[0166] 86 Arrow

[0167] 88 Fault diagnosis block

[0168] 90 Regulation parameter

[0169] 92 Arrow

[0170] 94 Presetting

[0171] 96 Arrow

[0172] 98 Adjustment

[0173] 100 nodes

[0174] 102 arrow

[0175] 104 fault diagnosis block

[0176] 106 adjustment parameter

[0177] 107 arrow

[0178] 108 arrow

[0179] 110 curve

[0180] 112 calculation block

[0181] 114 target value

[0182] 116 section

[0183] 118 curve

[0184] 120 numerical range

[0185] 122 endpoint value

[0186] 124 endpoint value

[0187] 126 section

[0188] 128 curve

[0189] 130 curve

[0190] 132 section

[0191] 134 curve

[0192] 136 curve

Claims

1. A method for heating a catalytic converter (48) disposed in an exhaust device (44) of an externally ignited internal combustion engine (10), characterized in that, a control device (68) outputs corresponding adjustment parameters to an electrically driven additional compressor (20) and at least one injection valve (52, 54), wherein by at least partially opening the at least one injection valve (52, 54), air compressed by the additional compressor (20) can be fed into the exhaust device (44) downstream of the exhaust valve of the internal combustion engine (10), the exhaust valve being assigned to a corresponding combustion chamber (12) of the internal combustion engine (10), wherein a signal from at least one oxygen sensor (64, 66) is provided to an adjuster (72) of the control device (68), and the oxygen content in the exhaust gas fed to the catalytic converter (48) is measured by means of the oxygen sensor, and wherein the method comprises the following steps: a) Switch on the additional compressor (20); b) At least partially open the at least one injection valve (52, 54); c) Set the air-fuel ratio λ < 1 for combustion in the combustion chamber (12) of the internal combustion engine (10); d) Measure the actual value of the oxygen content in the exhaust gas by means of the at least one oxygen sensor (64, 66); e) Compare the actual value with a target value (114) of the oxygen content, wherein the target value corresponds to the oxygen content in the exhaust gas that will be set in the region of the catalytic converter (48) when the air-fuel ratio for combustion in the combustion chamber (12) of the internal combustion engine (10) is approximately λ = 1, and wherein when the actual value reaches one of the two end values (122, 124) of a numerical range (120) in which the target value (114) lies, the adjustment parameters (90, 106) output by the adjuster (72) based on the difference between the actual value and the target value (114) are kept constant, wherein the two end values (122, 124) defining the numerical range (120) differ from the target value (114) by approximately 3%.

2. The method according to claim 1, characterized in that, Pre-adjust the rotational speed of the additional compressor (20) and adjust the opening size of the at least one injection valve (52, 54) in such a way that, i.e., a predetermined target value of the oxygen content in the exhaust gas is set.

3. The method according to claim 1, wherein the pre- Adjust the opening size of the at least one injection valve (52, 54) and adjust the rotational speed of the additional compressor (20) in such a way that, i.e., a predetermined target value of the oxygen content in the exhaust gas is set.

4. The method according to any one of claims 1 to 3, characterized in that Steps a) to e) of the method are carried out after a cold start of the internal combustion engine (10).

5. The method according to any one of claims 1 to 3, characterized in that, When the rotational speed of the internal combustion engine (10) exceeds a threshold value of approximately 100 revolutions per minute, steps a) to e) of the method are carried out.

6. The method according to any one of claims 1 to 3, characterized in that, The catalytic converter (48) operates as a three-way catalytic converter.

7. The method according to any one of claims 1 to 3, characterized in that, A proportional-integral controller is used as the adjuster (72).

8. The method according to any one of claims 1 to 3, characterized in that, in In step c), in addition to setting the air-fuel ratio λ < 1 for combustion in the combustion chamber (12) of the internal combustion engine (10), the ignition timing of the spark plug (14) assigned to the corresponding combustion chamber (12) of the internal combustion engine (10) is shifted to a later time than during normal operation of the internal combustion engine (10).

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