DE102017211676A1 - Method for optimizing an exhaust aftertreatment system for a hybrid vehicle - Google Patents

Abstract

A method is provided for optimizing an exhaust aftertreatment system for a hybrid vehicle, wherein the exhaust aftertreatment system comprises at least one particulate filter, upon detection that regeneration of the particulate filter is necessary or will be soon, the state of charge of the energy storage is detected, and if the state of charge of the energy storage for the duration of an at least partial regeneration of the particulate filter in purely electric driving sufficient to fulfill the driving desire and maintaining the torque of the engine in overrun, at least the particulate filter is heated in a first step, and in a second step, the regeneration is performed.

Description

The invention relates to a method for optimizing an exhaust aftertreatment system for a hybrid vehicle.

In many vehicles, currently mainly diesel powered vehicles, particulate filters are incorporated to reduce emissions. These particulate filters must always be regenerated, i. the particulate matter collected in the particulate filter must be removed from the filter because the exhaust back pressure increases when the particulate filter is laden with soot and thus more emissions are emitted.

From a certain level of loading, the filter must therefore be regenerated, which is often referred to as freewheeling. For this purpose, the filter must be as hot as possible and oxygen must be supplied, so as to cause a reaction in which the particles are burned under very hot temperatures. The oxygen present in the ambient air usually suffices for this purpose. This means that before the regeneration first a heating phase of the exhaust system must be done. Thereafter, oxygen, which is needed for the implementation of the soot, sucked by the piston engine from the ambient air or fed separately via a secondary air pump. To heat the exhaust line engages the engine management z. B. by means of multiple injection, Zündwinkelspätziehung and / or Auslassspreizung.

To pump the oxygen or ambient air needed to burn it into the exhaust line without a secondary air pump, the particulate filter relies on random coasting initiated by the driver, in which the injection is shut off and fresh air is pumped through the piston engine. These phases can not be planned and, because of the high oxygen storage capacity of the catalyst, are often too short to ensure effective reaction in the particle filter.

Particle filters will soon become mandatory for hybrid vehicles as well. Hybrid vehicles, e.g. Plug-in hybrids will then be equipped with a particulate filter and a traction e-machine that is strong enough to at least partially drive the driver. The hybrid vehicle will then, like the previously known vehicles, the degree of loading of the particulate filter and the need for a discharge, i. Regeneration, recognize.

From the DE 10 2008 035 451 A1 For example, a method of optimizing a hybrid operation of a hybrid vehicle is known in which a power output of an electric motor is controlled such that a power output of an internal combustion engine is controlled to an optimal load point for an operating state of the internal combustion engine, wherein a total output of the Hybrid vehicle, which is composed of the power of the electric motor and the power of the engine, remains constant or continues to meet the specification of the driver.

All previously known strategies for the regeneration of particulate filters have advantages, but are still in need of improvement. Therefore, it is an object of this invention to provide a method that provides optimization of the exhaust aftertreatment system in hybrid vehicles. This object is achieved by the features of the independent claims. Advantageous embodiments are the subject of the dependent claims.

A method is proposed for optimizing an exhaust gas aftertreatment system for a hybrid vehicle, wherein the exhaust aftertreatment system has at least one particle filter, upon detection that regeneration of the particulate filter is necessary or will be soon, the state of charge of the energy storage is detected, and if the state of charge of the energy storage for the duration of an at least partial regeneration of the particulate filter in purely electric driving sufficient to fulfill the driving desire and maintaining the torque of the engine in overrun, at least the particulate filter is heated in a first step, and in a second step, the regeneration is performed.

Thus, if it is detected that the state of charge of the energy storage is sufficient so that the internal combustion engine can operate in overrun operation in purely electric driving, ie acts as a primary air pump, and the driver's request can be met, no intervention in the energy operating strategy must take place. Rather, the heating phase can be started immediately, so that it is then possible to proceed to the step in which the regeneration is started.

In one embodiment, upon detection, the state of charge of the energy store for the duration of an at least partial regeneration of the particulate filter with purely electrical Ride to meet the driving desire and the preservation of the torque of the internal combustion engine in overrun is insufficient, in a first step, an intervention in the energy management strategy of the vehicle. Here, in the first step, the energy storage for the operation of the electric motor charged by an amount such that the state of charge of the energy storage for a period of at least partial regeneration of the particulate filter in purely electric driving to meet the driving desire and the preservation of the torque of the engine is sufficient in overrun , And at least the particulate filter is heated, wherein in the subsequent second step, the regeneration is performed.

Thus, if it is detected that the state of charge of the energy storage is not sufficient so that the internal combustion engine can operate in overrun operation in purely electrical driving, thus acting as a primary air pump, and the driver's request can be met, an intervention in the energy management strategy must be done so that a corresponding Charge state is reached. The heating phase can then also take place advantageously parallel to the charging.

By the proposed method both material can be saved as well as a faster and more efficient regeneration of the particulate filter. In addition, the filter can be regenerated even if the driver has a very unfavorable driving profile - d. H. no or hardly any decay phases. Thus, it can be prevented that in a driver with unfavorable driving profile a workshop visit is required to clean or replace the particulate filter. Furthermore, other measures to induce coasting phases are less active, eg. B. a general prevention of switching off the engine to standstill, so that the consumption advantage of the hybrid vehicle comes to fruition more often. This also increases customer satisfaction.

Furthermore, it is provided that in the first step, the charging of the energy storage by raising the load point of the internal combustion engine takes place up to the predetermined state of charge. By raising the load point of the internal combustion engine, charging of the energy store and faster heating of the exhaust gas line take place.

Furthermore, it is provided that in the first step, the load point of the internal combustion engine is raised until a predetermined particle filter temperature, which is required for a start of a partial or complete regeneration, takes place. Depending on whether a complete or partial regeneration is sought and how fast regeneration is to take place, the load point can be raised to a predetermined value which fulfills the conditions.

Furthermore, it is provided that the combustion engine switched off in the second step serves as a primary air pump for supplying ambient air for the at least partial regeneration of the particulate filter. Thus, no additional pump for supplying ambient air needed.

Furthermore, it is provided that the energy storage is charged to a state of charge, which allows a complete regeneration of the particulate filter within a burn-off process. Thus, in a single operation, a fast and efficient burnout of the particulate filter can take place.

Furthermore, it is provided that the energy store is charged up to an at least predetermined state of charge, which enables a regeneration of the particulate filter of at least a predetermined percentage within a burn-off process. For example, it may be predetermined that 30% or more regeneration should be possible within a burnout process. This can be prevented that a burn-out takes place in a state of charge, which hinders a fast and efficient burnout of the particulate filter.

Furthermore, a control device is provided, which is configured to receive data which enable determination of the load state of a particulate filter in a hybrid vehicle, to process this data and to output signals in the event that regeneration of the particulate filter present in the hybrid vehicle is necessary. by which a regeneration of the particulate filter according to the described method is performed.

Furthermore, an exhaust gas aftertreatment system of a hybrid vehicle is provided, comprising a particle filter, wherein the regeneration of the particle filter is regulated by means of a described control device.

Furthermore, a hybrid vehicle with a described exhaust aftertreatment system is provided.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawing, the inventive details shows, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

• 1 zeigt ein Ablaufdiagramm des Verfahrens gemäß einer Ausführung der vorliegenden Erfindung.
• 2 zeigt eine schematische Darstellung wichtiger Komponenten zur Durchführung des Verfahrens in einem Hybridfahrzeug gemäß einer Ausführung der vorliegenden Erfindung.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings.

• 1 FIG. 3 shows a flowchart of the method according to an embodiment of the present invention.
• 2 shows a schematic representation of important components for performing the method in a hybrid vehicle according to an embodiment of the present invention.

As in 1 schematically illustrated, the inventive method comprises two steps. In the first step S1 the preparation of the regeneration of the particulate filter takes place, which in the second step S2 finally done. Before the first step S1 carried out, a detection, eg by a control unit, must be made that the particle filter 11 needs to be regenerated or that this will be necessary soon. Also, a time interval may be specified in which a regeneration must take place.

To carry out the method according to the invention for optimizing an exhaust gas aftertreatment system for a hybrid vehicle 100 with particle filter 11 takes place upon detection, eg by a control unit 2 in that a regeneration of the particulate filter 11 is necessary or will soon be, an intervention in the energetic operating strategy of the vehicle, when it was detected that the state of charge SOC of the energy storage 321 is not sufficient to meet the driver's request and at the same time keep the combustion engine in overrun mode, so that it acts as a primary air pump. Therefore, in such a case, in a first step S1 the energy store 321 for operation of the electric motor 32 charged by a predetermined amount. This charging process takes place until the state of charge SOC of the energy store 321 has reached an amount for the duration of an at least partial regeneration of the particulate filter 11 in a purely electric drive, so switched off and coupled combustion engine 31 , is necessary. It should be noted that the amount of charge or to be reached state of charge SOC of the energy storage 321 is chosen such that it fulfills the driving desire 40 and the maintenance of the torque of the internal combustion engine 31 in overrun mode, ie in the switched off, but not decoupled mode, sufficient. The driving desire 40 can eg via the position of the accelerator pedal or via an adjustment of driver assistance systems eg from a control unit 2 be determined.

To charge the energy storage 321 an intervention in the energetic operating strategy of the vehicle takes place 100 eg by the control unit 2 , so that advantageously the load point of the internal combustion engine 31 is raised. This is additionally advantageous to heat the exhaust line, which in turn means that a faster regeneration is possible.

However, if it has been detected that the state of charge SOC of the energy storage 321 sufficient to satisfy the driver's request and at the same time to keep the combustion engine in overrun so that it acts as a primary air pump, then no intervention in the energetic operating strategy must be made, since the regeneration can be started immediately.

After charging or when it has been detected that regeneration can begin immediately, the internal combustion engine becomes 31 in a second step S2 brought into the state coupled fuel cut. The traction electric machine, so the electric motor 32 , fulfills the driving desire within its possibilities 40 and holds the torque required to turn the engine 31 necessary is. Thus, an efficient regeneration of the particulate filter 11 respectively.

The charging strategy or the specification of the state of charge SOC has as a goal that both conditions, ie meeting the driving desire 40 and holding the torque can be met. This is usually done by calculating or predicting a required state of charge SOC based on existing data such as traffic information, route, driver characteristics, etc. Should, however, an unforeseen driving desire 40 take place during the phase of regeneration, it can also be shortened or divided into several phases depending on the performance of the electrical system, ie electric motor and energy storage, which is dependent on the state of charge SOC or even an existing degradation.

For switching from normal driving to this state of preparation and execution of regeneration, entry conditions are, among others, a minimum state of charge of the high-voltage battery and a powerful electrical system, i. Electric motor and energy storage, in which no or little degradation is present, necessary. There are also several heating or regeneration cycles possible if the entry conditions are not met or, as mentioned above, an unforeseen driving request or other unforeseen event prevents the planned duration of regeneration.

Important for the charging phase in the first step S1 is the requirement that the exhaust line is hot enough to start a regeneration. In addition, given as a further condition that the driving desire 40 met and the required torque of the disconnected, but coupled internal combustion engine 31 is obtained. This means that the electrical system must have sufficient capacity to provide the driver's request, so that the electric motor 32 the basic friction of the coupled combustion engine 31 can overcome at fuel cut. The energy storage 321 itself must have a state of charge with which the intended duration of the Regeneration cycle can also be completely passed through.

At the second step S2 It should be noted that by switching off the internal combustion engine 31 this works as a primary air pump, ie that it pumps the oxygen required for regeneration or the ambient air into the exhaust system. Thus, no further pump, often referred to as a secondary air pump needed.

This effect is achieved by deliberately lowering the efficiency of the internal combustion engine 31 in towing mode, ie when the internal combustion engine is switched off but coupled 31 , reached. As a result, a faster regeneration of the particulate filter 11 , as well as an emission advantage through the rapid reusability of the particulate filter 11 reached.

Basically, to carry out the process several components in the hybrid vehicle 100 necessary, as shown schematically in 2 shown. The hybrid vehicle 100 should have a drive range 3 that is an internal combustion engine 31 and an electric motor 32 has. Further, an exhaust aftertreatment system 1 present, which has a particle filter 11 having. The particulate filter is preferably an Otto particle filter, but may also be another particulate filter if the hybrid vehicle uses a different fuel in which a particulate filter is necessary, for example diesel. Other components may be present but are not required to carry out the process and are therefore not mentioned.

Furthermore, the hybrid vehicle 100 at least one control device 2 which can receive, process and forward data. The control unit 2 serves, based on the detection, that a regeneration of the particulate filter 11 is necessary or will soon be necessary, at least the energy management and the engine management of the hybrid vehicle 100 to influence, so that the inventive method can be performed. The detection that the particle filter 11 may need to be regenerated, by control unit 2 are either detected based on measurement data from existing sensors, or there are, for example, tables laid down, which prescribe a regeneration at predetermined times. That is, the controller 2 is not limited to receive and forward data only, but it can also perform their own processing, based on the result of a regeneration can be triggered. Furthermore, the controller receives 2 Information about the driving desire 40 , eg by detecting an accelerator pedal position or a request that takes place via a driver assistance system.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102008035451 A1 [0006]

Claims (10)

A method of optimizing an exhaust aftertreatment system (1) for a hybrid vehicle (100), wherein the exhaust aftertreatment system (1) comprises at least one particulate filter (11), upon detection that regeneration of the particulate filter (11) is necessary or soon to occur, the state of charge of the energy store (321) is detected, and if the state of charge of the energy store (321) for the duration of an at least partial regeneration of the particulate filter (11) during purely electric driving to fulfill the driving desire (40) and the maintenance of the torque of the internal combustion engine (31) sufficient in overrun operation, in a first step (S1) at least the particulate filter (11) is heated, and in a subsequent second step (S2), the regeneration is performed. Method according to Claim 1 , wherein upon detection that the state of charge of the energy store (321) for the duration of an at least partial regeneration of the particulate filter (11) in purely electric driving to meet the driving desire (40) and the maintenance of the torque of the internal combustion engine (31) in overrun is insufficient , in the first step (S1) an intervention in the energetic operating strategy of the vehicle (100) takes place, so that in the first step (S1) the energy store for operating the electric motor (32) is charged by an amount such that the state of charge of the Energy storage (321) for the duration of at least partial regeneration of the particulate filter (11) in purely electric driving to meet the driving desire (40) and the maintenance of the torque of the internal combustion engine (31) sufficient in overrun, and at least the particulate filter (11) is heated , wherein in the subsequent second step (S2), the regeneration is performed. Method according to Claim 2 , wherein in the first step (S1), the charging of the energy store (321) by raising the load point of the internal combustion engine (31) up to the predetermined state of charge. Method according to Claim 2 or 3 wherein in the first step (S1), the load point of the internal combustion engine (31) is raised until a predetermined particulate filter temperature, which is required for a start of a partial or complete regeneration, takes place. Method according to one of the preceding claims, wherein the shutdown in the second step (S2) internal combustion engine (31) serves as a primary air pump for supplying ambient air for at least partial regeneration of the particulate filter (11). Method according to one of Claims 2 to 5 wherein the energy store (321) is charged to a state of charge that allows complete regeneration of the particulate filter (11) within a burnout process. Method according to one of Claims 2 to 5 wherein the energy store (321) is charged to at least a predetermined state of charge, which allows regeneration of the particulate filter (11) from a predetermined percentage within a burnout process. Control unit (2), which is set up to receive data enabling a determination of the loading state of a particulate filter (11) in a hybrid vehicle (100), to process this data and in the event that a regeneration of the vehicle in the hybrid vehicle (100 ) existing particulate filter (11) is required to - output signals by which a regeneration of the particulate filter (11) according to the method of one of Claims 1 to 7 is carried out. Exhaust after-treatment system (1) of a hybrid vehicle (100), comprising a particle filter (11), wherein the regeneration of the particulate filter (11) by means of a control device (2) according to Claim 8 is regulated. Hybrid vehicle (100) with an exhaust aftertreatment system (1) according to Claim 9 ,

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