DE102011006920A1 - Method for controlling regeneration of diesel particulate filter in exhaust gas passage of diesel engine of vehicle, involves carrying out regeneration process in extended regeneration phase without utilizing post-injections - Google Patents

Abstract

The method involves initiating and controlling combustion of particles in a particulate filter (42) during a regeneration process by intervention with an air flow rate and additional fuel injections. The regeneration process is divided into an existing regeneration phase and an extended regeneration phase for rapid oxidation of soot particles in the particulate filter. The regeneration process is carried out in the extended regeneration phase without utilizing post-injections that are applied in the existing regeneration phase. An independent claim is also included for a device for controlling regeneration of a particulate filter in an exhaust gas passage of a combustion engine.

Description

State of the art

The invention relates to a method for controlling the regeneration of a particulate filter in the exhaust passage of an internal combustion engine having in its air supply duct a throttle and exhaust gas recirculation with an exhaust gas recirculation valve between the air supply channel and the exhaust passage, wherein the combustion of particles in the particulate filter during a regeneration process by interfering with the air flow and additional fuel injections are initiated and controlled.

The invention further relates to a corresponding device for carrying out the method according to the invention.

Frequently, internal combustion engines, in particular diesel internal combustion engines are equipped with exhaust aftertreatment systems, which may in particular comprise a diesel particulate filter (DPF). This particulate filter settles during operation with soot and must therefore be regenerated at certain intervals.

• – Abschätzen der Rußbeladung, welche im Partikelfilter gespeichert ist,
• – Steuerung/Kontrolle der aktiven Regeneration und
• – Koordination der Regeneration innerhalb der verschiedenen Betriebsphasen der Brennkraftmaschine.

This requires control equipment that implements management for DPF regeneration. The functionality can be divided into three basic function blocks:

• Estimating the soot load stored in the particulate filter,
• - Control / control of active regeneration and
• - Coordination of regeneration within the various operating phases of the internal combustion engine.

The purpose of the last function block is to start the regeneration as fast as possible when a certain soot load value is reached or exceeded. However, this must be done under favorable operating conditions of the internal combustion engine. The function block control / control of the active regeneration includes all control measures on the internal combustion engine, which allows oxidation of the soot particles stored in the DPF. This process is performed periodically to free the particulate filter from soot.

In the EP 1 364 110 B1 For example, a method and an apparatus for controlling an internal combustion engine is described, which includes a arranged in an exhaust aftertreatment particulate filter in which a regeneration process for reducing the loading of the particulate filter is provided, wherein a characteristic (the filter temperature TF) in dependence on at least one operating characteristic ( Speed N, injected fuel quantity QK, intake air quantity ML and / or oxygen concentration O2) of the internal combustion engine and at least one operating parameter (combustion rate AV, intake air volume ML, exhaust gas temperature TA and / or charge state DP) of the particulate filter is determined, which is a future intensity of a reaction in the Particle filter characterizes. It is provided that when a threshold value is exceeded by the parameter TF at least one measure is taken, which reduces the oxygen concentration in the exhaust gas of the internal combustion engine, with the aim that the characteristic TF does not reach the threshold.

The maximum soot loading of the particulate filter depends critically on the substrate material of the filter, such as the porosity, the cell density, and the geometry of the channels, and in particular on the melting temperature and on the thermal capacity.

The heat release during regeneration is proportional to the soot load in the particulate filter and is critically responsible for the maximum temperature in the particulate filter.

Conventional regeneration strategies are based on special injection profiles and air flow rates, so that an increased temperature in the exhaust passage of the internal combustion engine is achieved and the oxidation of the soot can take place. For this purpose, a variety of measures are taken because the necessary high exhaust gas temperatures of 600 ° C to 650 ° C in the normal operation of a diesel engine are only achieved near full load. In particular, in the case of low engine loads and speeds in addition to air system intervention (throttle) injection-side measures required to o. G. Adjust temperature range. These include measures such as a retardation of the main injection quantity (MI), the discontinuation of a post-injection burning in the engine (Pol2) and the discontinuation of a post-injection (Pol1) burning at the Diesel Oxidation Catalyst (DOC). In this case, a certain residual oxygen content in the exhaust gas must be guaranteed in order to allow this oxidation.

The duration of the regeneration depends on the soot oxidation rate and the amount of soot in the particulate filter. The main influencing factors for the oxidation rate are the oxygen content and the temperature of the filter substrate.

The driving conditions thereby decisively influence the ability of the internal combustion engine to increase the exhaust gas temperature for a complete regeneration. Especially in urban driving with low loads and frequent overrun it is difficult to get the required high temperature range for optimal regeneration. The result is an extension of the regeneration phase compared to regeneration phases, which are carried out under favorable driving conditions. Such favorable driving conditions are, for example, speedy highway rides.

As a significant side effect is the o. G. Regeneration strategies for the particulate filter observed a lubricating oil dilution or mixture with fuel due to the injection profile and the post-injection quantity. This leads to a negative impact of fuel on the cylinder wall. In the case of a high degree of oil dilution / mixture can be damaged as a result, the mechanics of the internal combustion engine, which field losses have already shown.

• – Einspritzprofil (Zeitpunkt und Einspritzmenge)
• – Ruß-Emissionsrate, welche die DPF-Beladungsrate und die Regenerationshäufigkeit begrenzt sowie
• – Regenerationsdauer, welche den Treibstoffeintrag im Öl bei jeder Regeneration bestimmt.

The main influencing variables for the oil dilution / mixture were identified:

• - injection profile (time and injection quantity)
• Soot emission rate, which limits DPF loading rate and regeneration frequency, and
• - Regeneration time, which determines the fuel input in the oil during each regeneration.

Another requirement is the requirement that the DPF regeneration for the driver without noticeable loss of performance and without additional noise.

It is therefore an object of the invention to provide a method with which a particle filter can be regenerated and the oil dilution / mixture and the fuel consumption can be reduced.

It is a further object of the invention to provide a device suitable for carrying out the method.

Disclosure of the invention

The object of the method is solved by the features of claims 1 to 7.

The method according to the invention provides that the regeneration process is divided into a conventional regeneration phase and an extended regeneration phase for rapid oxidation of soot particles in the particulate filter, wherein post-injections, as used in the conventional regeneration phase, are dispensed with within the extended regeneration phase , The conventional regeneration phase, which is typically used for 1 to 3 minutes, initially ensures heating of the exhaust gas purification system including the particulate filter (DPF). With the extended regeneration phase, the temperature is additionally increased to accelerate soot burn-up. As a result, the duration of the entire regeneration phase can be significantly reduced. Since the usual post-injection is dispensed with in this second phase, the oil dilution or oil mixing can be reduced, characterized in that the conventional regeneration phase lasts only 1-3 minutes, instead of the usual 10-15 min.

The extended regeneration phase, after reaching the starting temperature for the oxidation of the soot particles, as provided by a preferred method variant, by reducing a Zuluftstrom in the supply air channel by at least partially closing the throttle and / or by increasing the proportion of recirculated exhaust gas due to at least partial opening of the exhaust gas recirculation valve be initiated in conjunction with a deactivation of the post-injections. With these measures, the gas flow in the exhaust passage upstream of the particulate filter can be reduced and the O ₂ concentration can be increased. This assists in temperature increase within the particulate filter since the cooling effect of the gas flow is reduced during the exothermic oxidation reaction and the O ₂ concentration increases the rate of the reaction.

The extended regeneration phase, d. H. the beginning of the oxidation of the soot particles, is advantageously initiated upon reaching a temperature of 580 ° C to 610 ° C. Fast soot oxidation is enabled when the heat release due to soot combustion increases the temperature in the DPF until soot oxidation is complete and thus the temperature is reduced again. This self-regulating "chain reaction" therefore leads to short-term high peak temperatures in the particulate filter, which is determined by the soot concentration, the oxygen concentration and the temperature level in the particulate filter.

With regard to limiting the maximum permissible temperature or the maximum permissible temperature gradient for the substrate material and / or the substrate coating of the particulate filter, it is provided in a preferred variant of the method that the regeneration process is initiated at a lower predicted soot loading of the particulate filter.

Particularly favorable operating phases for such a regeneration arise when the regeneration of the particulate filter is initiated during an inner-city driving operation, in which the engine load and the rotational speed are rather low. In this phase of operation, the amount of fuel injected in relation to the amount of available air is small, so that the gas flow can be drastically reduced and still enough residual oxygen is available for soot burning. In a conventional regeneration of the particulate filter, in contrast to the above-mentioned process variant, this operating phase is the most critical, since the soot loading is highest due to a high smoke level and also quite long Regenrationsphasen result, resulting in high fuel inputs into the engine oil. An urban driving operation is therefore the most critical case in a conventional regeneration. For the proposed regeneration method, however, precisely this operating phase offers a great potential for improvement.

During periods of high engine load and high speed operation, typically during off-highway driving (eg fast highway driving), the extended regeneration phase, as described above, can not be applied because the fuel injection amount is quite high and with a significant reduction in gas flow enough residual oxygen is available for soot burn-up and not enough torque can be provided. Therefore, it is provided that after initiation of regeneration when switching from inner-city driving into an extra-urban driving operation, the extended regeneration phase, if already activated, is aborted and replaced by the conventional regeneration phase, which is carried out until at least partially successful soot reduction becomes.

Due to the high engine load, after initiating the regeneration of the particulate filter during a non-urban driving operation, only a conventional regeneration phase can be carried out, the extended regeneration phase being started when the regeneration is still in progress, provided the predicted soot load still has a high value.

A preferred application of the method, as described above, provides a control of the regeneration of particulate filters in the exhaust aftertreatment system of a designed as a diesel engine internal combustion engine, as a filter material for these diesel particulate filter cheaper, but less temperature-stable filter materials can be used. An example of this are basic bodies made of cordierite, which can be protected by the process.

The object concerning the device is achieved in that the burnup of particles in the particle filter during a regeneration process by means of a control unit by intervention in the air flow and additional fuel injections can be introduced and controlled, wherein the control unit means for performing the method according to the invention with its process variants, as before have been described.

It can be provided in a preferred embodiment that the functionality of the method with its variants is implemented by software as an add-on to a conventional regeneration strategy within the control unit. The application effort is therefore low and can be easily retrofitted by a software update. The control unit can be an integral part of a higher-level engine control (for example, within the engine control unit ECU).

The invention will be explained in more detail below with reference to an embodiment shown in FIGS. Show it:

1 in a schematic representation of the technical environment in which the method according to the invention can be used,

2 a temperature profile diagram for a conventional regeneration of a particulate filter,

3 a temperature profile diagram for a regeneration of the particulate filter according to the inventive method,

4 an injection history diagram for different phases of regeneration,

5 a temperature profile diagram as a function of a loading state of the particulate filter,

6 a schematic representation of various load profiles of the internal combustion engine and

7 a schematic representation of the temporal soot burnup.

1 shows a schematic representation of the technical environment in which the invention can be used. Shown is an internal combustion engine 10 in the form of a diesel engine with a fuel metering system 11 , an air supply duct 20 in which a supply air flow 21 is guided, and an exhaust duct 30 in which an exhaust gas mass flow 46 the internal combustion engine 10 is guided. Along the air supply channel 20 are in the flow direction of the supply air 21 a Zuluftmesseinrichtung 27 For example, in the form of a hot film measuring system (HFM), a compression stage 23 a turbocharger 22 and a throttle 24 arranged. An exhaust gas recirculation 25 connects via an exhaust gas recirculation valve 26 (EGR) and a radiator 28 the Air supply duct 20 with the exhaust duct 30 , In the flow direction of the exhaust gas mass flow 46 are in the example shown after the internal combustion engine 10 an exhaust gas turbine 31 of the turbocharger 22 as well as components of an exhaust aftertreatment system 40 a lambda probe 43 , an oxidation catalyst 41 in the form of a Diesel Oxidation Catalyst (DOC), a temperature probe 44 and another separate temperature probe (not shown here), as well as a particle filter 42 in the form of a diesel particulate filter (DPF) and a silencer 45 shown. Basically, other sensor arrangements for the determination of the oxygen content and the temperature in the exhaust passage 30 in front of the particle filter 42 possible. In addition, in the exhaust duct 30 between the internal combustion engine 10 and the exhaust gas turbine 31 in the region of the exhaust manifold of the individual cylinders of the internal combustion engine 10 as further components of the exhaust aftertreatment system 40 so-called pre-turbo catalysts or PTC's (Pre Turbo Catalyst) may be arranged.

Over the air supply channel 20 becomes the internal combustion engine 10 Fresh air supplied. The fresh air is thereby from the compression stage 23 of the turbocharger 22 , which via the exhaust gas turbine 31 from the exhaust gas mass flow 46 is driven, compressed. Through the throttle 24 the amount of air supplied can be adjusted. For pollutant reduction is the supply air 21 via the exhaust gas recirculation 25 in from the operating parameters of the internal combustion engine 10 dependent amounts of exhaust gas from the exhaust duct 30 admixed. The exhaust gas recirculation rate can with the help of the exhaust gas recirculation valve 26 be set. The cooler 28 it cools the from the exhaust duct 30 originating exhaust stream.

In the exhaust aftertreatment system 40 be from the internal combustion engine 10 emitted pollutants implemented or filtered out. Thus, in the oxidation catalyst 41 Hydrocarbons as well as carbon monoxide oxidizes while the particulate filter 42 Retains soot particles.

Not shown are for the operation of the internal combustion engine 10 and the exhaust aftertreatment system 40 necessary control and regulation units, if necessary further temperature sensors as well as units for loading diagnosis of the particle filter 42 ,

By the operation of the internal combustion engine 10 fills the particle filter 42 until reaching its storage capacity is signaled. Thereupon, a regeneration phase of the particulate filter 42 in which the in the particle filter 42 stored particles are burned in an exothermic reaction. To initiate this exothermic reaction are in front of the particulate filter 42 Exhaust gas temperatures of 600 ° C to 650 ° C necessary. Because these temperatures during normal operation of the internal combustion engine 10 only be reached near full load, a temperature increase by additional measures must be effected.

2 shows in a temperature course diagram 100 (Temperature 101 vs. Time 102 ) the course of a DPF temperature 103 and a temperature before DPF 104 during an initiated regeneration of the particulate filter 42 (DPF). Shown is the temperature profile for a conventional regeneration strategy. Starting from a normal operating phase 120 follows after activation of the regeneration a heating phase 121 , which is initiated by certain motor measures. After reaching a reference temperature (about 600 ° C) is for the subsequent conventional regeneration phase 122 , in which the soot burn-off, held this temperature, whereby periodically these measures are applied until a certain soot loading level for the particulate filter 42 fell below and the conventional regeneration phase 122 is completed. It follows again the normal operating phase 120 ,

3 shows how in 2 already shown, in another temperature profile diagram 100 the course of the DPF temperature 103 as well as the temperature before DPF 104 for a regeneration strategy according to the invention. Unlike the in 2 shown temperature profile is already after the heating phase 121 and a subsequent short conventional regeneration phase 122 (typically 1 to 3 minutes) after reaching the reference temperature 105 the temperature until reaching a maximum DPF temperature 106 increased again (extended regeneration phase 123 ), which depend on the substrate material used or the substrate coating of the particle filter used 42 is. Opposite the in 2 shown conventional regeneration results in the in 3 regeneration shown a much shorter duration.

In 4 are in an injection history diagram 110 schematically the injection quantity 111 depending on the time 112 represented for different phases of the regeneration cycle.

In particular, in the case of lower engine loads and speeds are in addition to air system interventions, for example via the throttle 24 , further measures in the field of fuel injection via the fuel metering system 11 common. These can be engine-internal measures such as a late shift of the main injection 114 (MI) or one in the internal combustion engine 10 Torque-neutral burning post-injection 115 (Pol2) or one via a fuel supply in the exhaust passage 30 before the oxidation catalyst 41 supplied and to the oxidation catalyst 41 burning post-injection 116 (Pol1), where the post-injection 116 (Pol1) usually via the fuel metering system 11 he follows. Furthermore, a change in the exhaust gas recirculation rate via the exhaust gas recirculation valve 26 possible.

The measures mentioned influence not only the exhaust gas temperature but also the composition of the exhaust gas, in particular its oxygen content. Since the oxygen content has a significant effect on the burning rate of the particulate filter 42 stored particles during the regeneration process and thus has the time per unit of energy released, it is known, for example, via a regulation of the oxygen content of the exhaust gas via the measures mentioned the course of Partikelabbrandes and thus to control the temperature of the particulate filter.

4 shows the injections described above for the normal operating phase 120 , for the heating phase 121 as well as for the conventional re-regeneration phase 122 , wherein in the diagrams shown a pre-injection (PI) 113 can be provided.

5 shows, as already in 3 shown in a further temperature course diagram 100 the course of the DPF temperature 103 for the regeneration strategy according to the invention. Due to different soot loadings of the particulate filter 42 For example, due to the above-described kinetics of soot oxidation, the peak temperature achieved may be different. Shown are the temperature curves for a DPF temperature (low) 103.1 ie with comparatively low soot loading, for a DPF temperature (medium) 103.2 , ie with a comparatively medium soot load and for a DPF temperature (high) 103.3 ie with comparatively high soot loading. With a view to limiting the maximum permissible temperature (maximum DPF temperature 106 ) or the maximum allowable temperature gradient for the substrate material and / or the substrate coating of the particulate filter 42 can be provided that the extended regeneration phase 123 depending on a predicted soot loading of the particulate filter 42 is limited in duration.

6 shows different operating phases in a load-speed diagram 130 for the internal combustion engine 10 , wherein for the course of an inner-city driving 133 and an extra-urban driving operation 134 weight 131 depending on the speed 132 is shown.

7 shows in a soot burn-up history diagram 140 the soot mass 141 depending on the time 142 , Registered are different loading levels 143 ... 146 ,

The loading level 0 143 provides a nearly soot-free particulate filter 42 (low residual soot loading), as can be seen shortly after a successful regeneration cycle. The loading level 1 144 stands for a partially successful regeneration. The loading level 2 145 corresponds to a particulate filter almost fully loaded with soot 42 , The loading level 3 146 corresponds to the trigger level for the start of the regeneration and represents the highest soot loading level.

Especially during dynamic driving changes the internal combustion engine 10 between operating phases with low load 131 and low speed 132 (Comp. 6 , Zone II according to an inner-city driving operation 133 ) and operating phases with high load 131 and high speed 132 (Comp. 6 , Zone I according to an extra-urban driving operation 134 ). The method according to the invention controls the different regeneration phases corresponding to the transitions between the different operating phases. There are four cases:
Case 1: During an urban driving operation 133 ( 6 , Zone II) the regeneration is started (reaching the loading level 3 146 . 7 ), wherein the inner-city driving 133 maintained throughout the regeneration period. In this case, the complete regeneration with the extended regeneration phase 123 (rapid soot oxidation) until the loading level 0 ( 7 ) and the particle filter 42 is almost empty burned.
Case 2: During an inner-city driving operation 133 ( 6 , Zone II) the regeneration is started (reaching the loading level 3 146 . 7 ), in which case a change in the extra-urban driving 134 ( 6 , Change to zone I). In this case, there is still the extended regeneration phase 123 carried out as long as the internal combustion engine 10 still in the inner city driving 133 located. The extended regeneration phase 123 is immediately interrupted and the conventional regeneration phase 122 initiated until the loading level 1 144 ( 7 ) is reached. Here it may happen that when switching to the extra-urban driving 134 already the predicted soot load below the loading level 1 144 is what comes to a successful regeneration.
Case 3: During an extra-urban journey 134 ( 6 , Zone I), the regeneration is started (reaching the loading level 3 146 . 7 ), where the extra-urban driving 133 maintained throughout the regeneration period. In this case, the complete regeneration with the conventional regeneration phase 122 carried out until the loading level 0 ( 7 ) and the particle filter 42 is almost empty burned.
Case 4: During an extra-urban journey 134 ( 6 , Zone I) is the regeneration with the conventional regeneration phase 122 started (reaching the loading level 3 146 . 7 ), in which case a change in the inner-city driving 133 ( 6 , Change to zone II). In this case, still the conventional regeneration phase 122 carried out as long as the internal combustion engine 10 still in the extra-urban driving 134 located. The extended regeneration phase 123 is started immediately as soon as the inner-city driving operation 133 is reached. In the case that the change predicted soot loading below the loading level 2 145 ( 7 ), the regeneration is aborted.

The aim is a loading level 1 or 2 during normal driving 144 . 145 , This can be a good compromise between performance and fuel economy.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• EP 1364110 B1 [0006]

Claims (10)

Method for controlling the regeneration of a particulate filter ( 42 ) in the exhaust duct ( 30 ) an internal combustion engine ( 10 ) in their air supply duct ( 20 ) a throttle valve ( 24 ) and an exhaust gas recirculation ( 25 ) with an exhaust gas recirculation valve ( 26 ) between the air supply duct ( 20 ) and the exhaust channel ( 30 ), wherein the combustion of particles in the particle filter ( 42 ) is initiated and controlled during a regeneration process by intervention in the air flow rate and additional fuel injections, characterized in that the regeneration process into a conventional regeneration phase ( 122 ) and in an extended regeneration phase ( 123 ) for the rapid oxidation of soot particles in the particle filter ( 42 ), whereby within the extended regeneration phase ( 123 ) on post injections ( 115 . 116 ), as in the conventional regeneration phase ( 122 ), is waived. Method according to claim 1, characterized in that the extended regeneration phase ( 123 ) by reducing a supply air flow ( 21 ) in the supply air duct ( 20 ) by at least partially closing the throttle valve ( 24 ) and / or by increasing the proportion of recirculated exhaust gas due to an at least partial opening of the exhaust gas recirculation valve ( 26 ) in connection with a deactivation of the post-injections ( 115 . 116 ) is initiated. Method according to claim 1 or 2, characterized in that the extended regeneration phase ( 123 ) is initiated when reaching a temperature of 580 ° C to 610 ° C. Method according to one of claims 1 to 3, characterized in that the entire regeneration process ( 123 ) at a lower predicted carbon black loading of the particulate filter ( 42 ) is started. Method according to one of claims 1 to 4, characterized in that the regeneration of the particulate filter ( 42 ) during an inner-city driving operation ( 133 ) is initiated. A method according to claim 5, characterized in that after initiation of the regeneration when changing from inner-city driving ( 133 ) in a non-urban driving operation ( 134 ) the extended regeneration phase ( 123 ), if this is already activated, stopped and through the conventional regeneration phase ( 122 ), this being done until an at least partially successful soot reduction is achieved. Method according to one of claims 1 to 4, characterized in that after initiation of the regeneration of the particulate filter ( 42 ) during a non-urban driving operation ( 134 ) only a conventional regeneration phase ( 122 ), whereby when changing into the inner-city driving ( 122 ) during the ongoing regeneration the extended regeneration phase ( 123 ) is started if the predicted soot load still has a high value. Application of the method according to one of the preceding claims for controlling the regeneration of particulate filters ( 42 ) in the exhaust aftertreatment system ( 40 ) of a trained as a diesel engine internal combustion engine ( 10 ) with a base body with comparatively low temperature stability. Device for controlling the regeneration of a particulate filter ( 42 ) in the exhaust system of an internal combustion engine ( 10 ) in their air supply duct ( 20 ) a throttle valve ( 24 ) and an exhaust gas recirculation ( 25 ) with an exhaust gas recirculation valve ( 26 ) between the air supply duct ( 20 ) and the exhaust channel ( 30 ), wherein the combustion of particles in the particle filter ( 42 ) during a regeneration process by means of a control unit by intervention in the air flow rate and additional fuel injections can be introduced and controlled, characterized in that the control unit comprises means for carrying out the method according to claims 1 to 7. Apparatus according to claim 9, characterized in that the functionality of the method according to one of claims 1 to 7 is implemented by software as an add-on to a conventional regeneration strategy within the control unit.

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