DE10333210A1 - Hybrid vehicle and method for operating a hybrid vehicle - Google Patents

Abstract

The invention relates to a hybrid vehicle with an internal combustion engine (20) and an electric motor (10), each of which can output a torque, in particular in order to drive at least one vehicle wheel. DOLLAR A The internal combustion engine (20) is associated with an exhaust system (50) with a catalyst system (60, 70) whose conversion activity is dependent on predetermined activity parameters. DOLLAR A According to the invention, the value of the conversion activity is determined in a predetermined time interval T_Kat. To achieve a predetermined conversion threshold of the conversion activity of the catalyst system (60, 70), if the value of the conversion activity is below said threshold value, the torque output of the electric motor (10) is preferably increased as needed and the torque output of the internal combustion engine (20) is reduced. For this purpose, a device (90a) for controlling the torque output of the internal combustion engine (20) and the electric motor (10) is provided. DOLLAR A The invention further comprises a method for operating a hybrid vehicle.

Description

The The invention relates to a hybrid vehicle and a method of operation a hybrid vehicle according to the preambles the independent one Claims.

vehicles with parallel hybrid drives have one Internal combustion engine and at least one electric motor, the same over or another drive train of the internal combustion engine, at least a vehicle wheel drives. As far as the electric motor as a generator can be operated is in almost every point of the vehicle operating map thereby a motor support or regenerative additional load by the electric motor and a certain Decoupling from internal combustion engine operation possible.

This is accompanied by a change in the exhaust gas quality, in particular with regard to the exhaust gas mass flow, the exhaust gas temperature and the pollutant composition. Such a change in the exhaust gas quality has an effect on the function and efficiency of a catalytic converter connected downstream of the engine. From the EP 1 182 074 A2 It is known to increase the load of the internal combustion engine at a catalyst temperature below a characteristic light-off temperature (light-off temperature) by regenerative operation of the electric motor and thus to achieve an increased exhaust gas temperature and a faster popping of the catalyst system after a cold start. It is also proposed to bring about a discharge of the internal combustion engine when the engine warm or warm catalytic converter system by motor operation of the electric motor.

These Operation is very one-sided designed to shorten the light-off phase, because not considered is that with the load of the internal combustion engine also the raw emissions, especially the raw emissions of hydrocarbons, clearly increase. The reduction of pollutant emissions, in particular of hydrocarbons, by shortening the light-often phase of the Catalyst system can therefore overcompensated by an increase in raw emissions and under circumstances increased overall Total emissions downstream of the catalyst system (tail pipe emissions) to lead.

From the DE 100 41 535 A1 Furthermore, a hybrid vehicle is known in which, when the catalyst is not activated, a generator generates electrical energy and thus increases the load of the internal combustion engine. Thus, the temperature of the engine, the temperature of the exhaust gas discharged from the internal combustion engine or the temperature of the cooling water of the internal combustion engine for accelerated activation of the catalyst is increased.

task The present invention is to provide a hybrid vehicle and a method of operating a hybrid vehicle, in which by an optimized torque output of the internal combustion engine and the electric motor has a conversion activity of the internal combustion engine associated Catalyst system to achieve a predetermined conversion threshold can be influenced.

These The object is achieved by the independent claims solved.

at the hybrid vehicle according to the invention is a device according to the invention for controlling the torque output of the internal combustion engine and the Electric motor provided by means of the value of the conversion activity of the catalyst system determined and depending from this value for a predetermined time interval T_Kat the torque output of the electric motor elevated and the torque output of the internal combustion engine compared to a Operation of the hybrid vehicle without providing a torque is reduced by the electric motor. Preferably, this control is done depending on demand with regard to a torque specification.

By the reduction of the torque output of the internal combustion engine can for the given time interval a raw emission, in particular of hydrocarbons, be diminished while at the same time the conversion activity of the catalyst system favorable to Achievement of the predetermined conversion threshold influenced becomes. The inventive method allows an optimized use of the torque output of internal combustion engine and electric motor with regard to the achievement of a given Konversionsschwellwertes.

Particularly preferred is an embodiment of the invention in which a determination of an exhaust emission takes place downstream of the catalyst system and the increase or decrease in the torque output of the internal combustion engine or the electric motor is such that a predetermined emission limit downstream of the catalyst system is exceeded. This aims at overcoming the one-sided interpretation of the operation of a hybrid vehicle as well as a shortening of a light-off phase and takes into account the ratio of raw emission and conversion activity in the limitation of actually in the environment given exhaust emissions.

Especially is appropriate an increase in the Catalyst temperature by a shift of the ignition angle to late. In a another preferred embodiment can an efficiency deterioration of the internal combustion engine, in particular due to a shift of the ignition angle to late, through Operation with a higher air filling respectively. This allows the exhaust gas mass flow simultaneously with a increase the catalyst temperature can be increased.

Around a noticeable relief of a typical internal combustion engine reach, it is preferred that the electric motor has a maximum Power of at least 2 KW, preferably 3.5, particularly preferred 5 KW, each per ton of vehicle empty weight provides, preferably in a speed range of 700-1,500, Optimal 1,000 / min to 1,500 / min.

Especially high exhaust gas cleaning performance can be achieved with a catalyst reach, which at least one close to the engine pre-catalyst and at least one main catalytic converter arranged downstream of the primary catalytic converter includes. In particular, according to the invention the conversion activity of the precatalyst increases rapidly and effectively.

Further embodiments and advantages of the invention are also independent of their summary in the claims the following description and the drawings. The Drawings show in

1 a hybrid drive with control system for a hybrid vehicle according to the invention

2 a time course of engine torque and speed for a cold start according to the prior art without electrical assistance

3 a time course of engine torque and vehicle speed for a cold start according to the prior art with additional electrical generator load

4 a time course of engine torque and driving speed according to the invention

5 a time course of the cumulative hydrocarbon emissions after a near-engine precatalyst at different cold start modes.

1 shows a schematic representation of a hybrid drive 1 for an otherwise not shown hybrid vehicle. An electric motor 10 and an internal combustion engine 20 are with a gearbox 30 coupled with at least one - in the 1 not shown - vehicle wheel is coupled. Preferred is an arrangement of the electric motor 10 between a crankshaft output of the internal combustion engine 20 and a transmission input. The electric motor 10 is electrically coupled to an electrical energy storage device, such as a rechargeable battery or the like. The internal combustion engine 20 is an exhaust system 50 with a close to the engine pre-catalyst 60 and a downstream main catalyst 70 assigned. An engine control unit 90 receives from control sensors 80 , For example, the accelerator pedal module or an antilock braking system, control signals and sensors 100 Values of operating parameters of the hybrid vehicle, in particular of the electric motor 10 , the internal combustion engine 20 , the exhaust system 50 as well as other vehicle components.

In a preferred embodiment of the invention, the internal combustion engine 20 a lean-running direct-injection gasoline engine. Particularly preferred is a stratified charge directly injecting gasoline engine, since it can be achieved in lower load speed ranges considerable savings in fuel consumption over a conventional gasoline engine. In particular, in these embodiments of the invention, it is expedient to form the catalyst system such that the precatalyst 60 a 3-way catalyst and the main catalyst 70 is a NOx storage catalyst. The precatalyst 60 is preferably used for the purification of a stoichiometric exhaust gas, for the conversion of hydrocarbons (HC) in lean exhaust gas and to improve the exhaust gas purification at a cold start. In particular, in order to enable rapid heating of the precatalyst, it is provided that the precatalyst 60 at a distance of less than 500 mm, optionally less than 400 mm, more preferably less than 300 mm average exhaust run length of the cylinder head flange in the exhaust system 50 is arranged. The NOx storage catalyst 70 is preferably designed for storing nitrogen oxides (NOx) with lean exhaust gas. Depending on the load of NOx and possibly even further boundary conditions, a regeneration of the NOx storage catalyst with a stoichiometric to rich exhaust gas is required.

The conversion activity of the catalyst system or its components precatalyst 60 and NOx storage catalyst 70 is dependent on activity parameters, in particular the catalyst temperature. The conversion rate only exceeds a minimum temperature, the so-called Light-off temperature, a limit of 50%. In general, the light-off temperature of a catalyst is different for different pollutant components such as HC or NOx.

Further activity parameters of the catalyst system are values of an exhaust gas mass flow, the raw emission of exhaust gas components as well as the loading with NOx and / or sulfur oxides (SOx). The values of these activity parameters are dependent on the operating parameters of the internal combustion engine, possibly using a model of the catalyst system with the aid of signals from the sensors 100 , determined and in the control units 90 evaluated.

The control unit 90 includes in a preferred embodiment, one or more microprocessors, data storage and interfaces, and means 90a by means of in dependence on the control signals of the sensors 80 the total torque is determined by the electric motor 10 and the internal combustion engine 20 delivered and at least partially the gearbox 30 is made available. The coupling between the electric motor 10 and the internal combustion engine 20 allows both negative and positive torque transmission between these two components.

The detailed in 1 not shown in detail sensors 100 include sensors for measuring or determining operating parameters, preferably the memory device 40 , the electric motor 10 , the internal combustion engine 20 and the exhaust system 50 , In particular, lambda probes in the exhaust system 50 upstream of the precatalyst 60 , downstream of the precatalyst 60 , upstream of the main catalyst 70 or downstream of the main catalyst 70 be arranged. Furthermore, NOx, SOx or hydrocarbon sensors can be arranged at different locations of the exhaust systems. To measure the temperature of the exhaust gas or of the catalyst system, temperature sensors may be provided at various installation locations.

The method according to the invention aims at the torque output of the internal combustion engine and the electric motor for achieving a predetermined conversion threshold and the conversion activity of the catalyst system 60 . 70 to optimize. Such optimization is preferably provided in a time interval Temp_K after a cold start of the vehicle, but can, if necessary, also in other operating phases of the internal combustion engine 20 respectively. After a cold start, the temperature of the catalyst system is initially below the light-off temperature. The conversion activity is in this case below a light-off value of 50% or 80% and therefore must be for environmentally sound operation of the internal combustion engine 20 increase.

The following are first based on the 2 and 3 already known from the prior art procedures at a cold start described.

In 2 the time profile of an engine torque M of a conventional internal combustion engine during a cold start process is shown. In particular, the moment M includes the moments required for engine start, friction, operation of ancillaries and propulsion. F denotes the driving speed as a function of time.

at The starting process shown starts after an idling phase from the Time T_A a startup process with an acceleration and a corresponding Increase of the moment M. The combustion engine is so relative to a short time after starting a maximum achievable torque reserve M_Max, which can be used for catalyst heating. After a Standstill phase, the vehicle speed at time T_S again Zero reduced. Accordingly, the engine load decreases.

At the in 2 shown cold start process, the temperature of the catalyst system is initially below the light-off temperature, so that considerable parts of the raw emission of the engine are released to the environment. Only with heating of the engine or the exhaust gas, it also comes to a heating of the catalyst system, unless a separate catalyst heating is provided.

In the 3 shown in detail, known from the prior art operation at cold start aims to make each of the currently available torque reserve for heating the catalyst system available. In 3 is for the same travel curve F as in 2 a cold start operation is shown with additional electrical generator load, it being assumed that the catalyst temperature is below a light-off temperature. In the time interval between times T_A and T_B, to achieve particularly short catalyst heating times, the usually filling of the still cold engine is increased to the limits of stable engine operation. The load torque of the internal combustion engine is thus guided up to the maximum achievable torque reserve. However, usually with the engine load of the internal combustion engine, the raw emissions, especially for hydrocarbons, increase significantly. Reduced emissions due to the shortening of the light-often phase can therefore be explained by an increase in raw emissions be compensated and lead to an overall increased tailpipe emission.

Will like in the EP 1 182 074 the firing angle retarded, so that the temperature of the exhaust gas can be increased. However, if a further load request, for example by a start-up, so the air charge of the engine is not withdrawn. Rather, the ignition angle is shifted so far in the direction of early, that the required load can be provided by the associated improvement in efficiency. This energy fraction is then not available for heating the catalyst system. Therefore, when the load of the internal combustion engine is further increased by regenerative operation of the electric motor, the power available for catalyst heating can be lowered.

In 4 is the time course of a moment M and a travel speed F at a cold start operation according to the invention shown. It is assumed that the catalyst system has a temperature below a light-off temperature and therefore its conversion activity is below a conversion threshold. After the start of the internal combustion engine, this initially emits an idling torque M_L, which is made available in particular for carrying out the engine start, overcoming friction, and supplying ancillary equipment. Preferably, M_L is chosen so that an acceptable value of raw emissions in the relevant point of the operating map is not exceeded.

At time T_A, a torque request is made to perform a startup operation. At the time T_B the starting process is completed and there is a constant travel at a constant speed until the time T_S. In the time interval T_A to T_B according to the invention is an electromotive assistance of the internal combustion engine 20 through the electric motor 10 intended. In the said time interval, therefore, only a part of the total required torque output for the starting operation of the internal combustion engine 20 provided while the remaining required amount of torque from the electric motor 10 is done. The only prerequisite is that by the electrical storage device 40 available electric power allows this. At time T_S, the travel curve F shows a reduction in the vehicle speed, which leads to a transition to an idling at a later time. At this time at the latest, the torque output of the internal combustion engine 20 returned to the value M_L.

According to the invention, such an optimization of the torque output of the electric motor 10 and the internal combustion engine 20 within a time interval T_Kat, which is necessary to bring the catalyst system into a state in which the conversion threshold has been reached or exceeded. Typically, this condition is characterized by a catalyst temperature above the hydrocarbon light-off temperature.

In a preferred embodiment of the invention, the torque output of the internal combustion engine 20 during the time interval T_Kat is limited to the value M_L, so that any additional torque request from the electric motor 10 is served. Preferably, it is further provided that within T_Kat a torque requirement of at least 60%, preferably at least 80%, ideally at least 90% of the electric motor 10 is served.

Within the time interval T_Kat, the combustion efficiency of the internal combustion engine is increased according to the invention to increase an exhaust gas temperature 20 purposefully deteriorated. Such deterioration in efficiency is used to increase the exhaust gas temperature. One possible method of degrading efficiency is to delay the firing angle. This results in a higher proportion of the fuel energy converted in the combustion chamber into the exhaust gas. Part of the efficiency reduction of the engine can be compensated for by a higher charge operation by operating the engine at an increased mass air flow. Thus, a higher exhaust gas mass flow is generated, which further accelerates the heating of the catalyst.

As is known per se, occur at a relocation of the ignition angle after late due to the increased Exhaust temperature lower hydrocarbon concentrations upstream of the catalyst system. The inventive method therefore has in addition a higher one Energy input into the exhaust system and the catalyst system accordingly the advantage of lower raw emissions.

By the higher one Energy input into the exhaust system will cause a faster through-heating at least allows a particular near-engine part of the catalyst system. Thus, the heating of the catalyst system can be reduced. Prefers is a reduction according to the invention of for the heating of the catalyst system produced additional chemical-thermal energy input into the exhaust system. Additionally or alternatively, the time interval T_Kat may be more than 10%, preferably 25 %, more preferably 40% compared to a conventional heating of the catalyst system can be reduced.

There In most countries of the world the cleaning effect of the exhaust system by legal regulations for Exhaust emission limits are given, is the inventive method as well as the hybrid vehicle according to the invention preferably designed so that the statutory Limit values are reached or fallen below. In the EU countries will from the New European Driving cycle (NEDC) given a speed profile, the one typical city and overland traffic should correspond. The mentioned The interpretation is therefore such that in the NEDC the emissions at electrical according to the invention support the level in a conventional operating mode of a same At least not exceed internal combustion engine or hybrid vehicle.

In 5 the time course of cumulative hydrocarbon emissions downstream of a precatalyst is shown schematically. In each case, a cold start procedure is shown with the same travel curve designated by F. The emission curve denoted by A denotes a conventional catalyst heating method as shown in FIG 2 was presented. Curve B denotes a catalyst heating method in which negative torque is applied in the cold start phase, while curve C denotes operation according to the method of the present invention. The arrow from the top of each of the curves A to C indicates the time at which an 80% HC conversion rate at the precatalyst is exceeded.

Like the illustration in 5 shows, the operation of the invention allows a lower cumulative hydrocarbon emission and earlier reaching an 80% hydrocarbon conversion rate at the primary catalyst.

Since the invention facilitates the achievement of a light-off value of the catalyst system or at least one of its components, the noble metal content of the catalysts used in such a hybrid vehicle can be reduced. This applies in particular to vehicles with directly injecting and / or stratified charge Otto engine. In the prior art, direct injection and / or stratified charge Otto engines, such as in the NEDC with thermally-undamaged catalyst systems, which at a temporal Schichtbetriebsanteil of at least 250 seconds, a hydrocarbon emission of 0.07 g / km and a NOx emission of> 0 , 05 g / km, catalysts with a noble metal content of <110 g / km / ft ³ (3.95 g / dm ³ ) or even <130 g / ft ³ (4.76 g / dm ³ ) are used. In this case, the catalyst system consists of a pre-catalyst close to the engine and at least one downstream NOx storage catalytic converter with a stored sulfur mass of> 0.2 grams / liter of catalyst volume.

According to the invention, the noble metal content of at least one or the precatalysts is lowered to less than 100 g / ft ³ (3.59 g / dm ³ ), in particular to ≥ 80 g / ft ³ (2.87 g / dm ³ ). Preference is given to lowering to less than 60 g / ft ³ (2.16 g / dm ³ ). This makes it possible that even after aging of the at least one pre-catalyst with lowered precious metal content for four hours at 1,100 degrees Celsius in an atmosphere of 2% O2 and 10% H2O and a NOx storage catalyst with lowered precious metal content for four hours at 850 degrees Celsius in a Atmosphere of 2% O2 and 10% H2O in otherwise the same vehicle by using the method according to the invention in NEDC a hydrocarbon emission of not more than 0.1 g / km and a NOx emission of 0.08 g / km is achieved.

The electric motor 20 has a maximum power of at least 2 KW, preferably 3.5 KW, more preferably 5 KW per ton of vehicle empty weight. Preferred is a speed range of 700-1,500, ideally 1,000 1 / min to 1,500 1 / min.

1

hybrid drive with control system

10

electric motor

20

internal combustion engine

30

transmission

40

battery

50

exhaust system

60

precatalyzer

70

main catalyst

80

sensors

90

Engine control unit

90a

Facility for controlling the torque output

100

sensors

Claims (21)

A method for operating a hybrid vehicle with - an internal combustion engine and at least one electric motor, each for outputting a torque, in particular for driving at least one vehicle wheel, - wherein the internal combustion engine, an exhaust system is associated with a catalyst system for at least one exhaust gas component whose conversion activity of predetermined activity parameters is dependent, characterized in that to achieve a predetermined conversion threshold of the conversion activity for at least one exhaust gas component in a predetermined time interval T_Kat the value of the conversion activity determined and if this value is below said threshold value is, the torque output of the electric motor, preferably on demand, increased and the torque output of the internal combustion engine compared to an operation of the hybrid vehicle without providing a torque is reduced by the electric motor. Method according to claim 1, characterized in that that a determination of exhaust emission downstream of the catalyst system done and the increase or reduction of the torque output of the internal combustion engine or the electric motor is such that a predetermined emission limit Below the catalyst system is below. Method according to claim 1 or 2, characterized that the activity parameters at least one catalyst temperature or an exhaust gas mass flow include. Method according to at least one of the preceding Claims, characterized in that T_Kat is followed by a cold start. Method according to at least one of the preceding Claims, characterized in that within T_Kat a torque request at least 60%, preferably at least 80%, more preferably at least. 90%, is operated by the electric motor. Method according to at least one of the preceding Claims, characterized in that within T_Kat the combustion efficiency of the internal combustion engine to increase a Exhaust gas temperature and an exhaust gas mass flow deliberately deteriorated becomes. Method according to at least one of the preceding Claims, characterized in that to increase the catalyst temperature a displacement of the ignition angle after late he follows. Method according to claim 6 or 7, characterized that for at least partial compensation of a deterioration in efficiency of the internal combustion engine, in particular due to a relocation of the firing angle after late, the internal combustion engine is operated with a higher air charge. Method according to at least one of the preceding Claims, characterized in that a catalyst heating with a across from an operation without providing a torque by the electric motor reduced by at least 10%, 25% or preferably 40% chemical-thermal energy input is provided in the exhaust system. Method according to at least one of the preceding Claims, characterized in that a catalyst heating with a by at least 10%, 25% or 40% compared to a non-provisioned operation a torque through the electric motor time-reduced value is provided. Method according to at least one of the preceding Claims, characterized in that the electric motor has a maximum power of at least 2 KW, preferably 3.5 KW, more preferably 5 KW, each provides per ton of vehicle empty weight, preferably in a speed range of 700-1.55, ideal 1,000 rpm to 1,500 rpm. Method according to at least one of the preceding Claims, characterized in that the electric motor is between a crankshaft output of the internal combustion engine and a transmission input is arranged. Method according to at least one of the preceding Claims, characterized in that the catalyst system at least one close to the engine pre-catalyst and at least one downstream of the primary catalyst arranged main catalyst comprises. Method according to claim 13, characterized in that that the close-coupled precatalyst at a distance of less than 500 mm optionally less than 400 mm, more preferably, less as 300 mm medium exhaust run length is arranged from the cylinder head flange. Method according to at least one of the preceding Claims, characterized in that the conversion threshold value is a light-off value for at least one of the exhaust gas components hydrocarbon, carbon monoxide or Nitrogen oxide of the pilot and main catalyst is. Method according to at least one of the preceding Claims, characterized in that the internal combustion engine preferably lean executable directly injecting gasoline engine is. Method according to at least one of the preceding claims, characterized in that the internal combustion engine, preferably a mauflauffähiger directly Injecting stratified charge Otto engine is. A method according to claim 17, characterized in that the internal combustion engine in the New European driving cycle with thermally undamaged catalyst system, which at least one close to the engine pre-catalyst and at least one downstream NOx storage catalyst wherein at least one of the catalysts has a noble metal content of> 110 g / ft ³ and in a temporal Schichtbetriebsanteil of at least 250 sec. achieves a hydrocarbon emission of <0.07 g / km and a nitrogen oxide emission of <0.05 g / km without providing torque by the electric motor and is preferable when providing a torque by the electric motor and a noble metal content of the precatalyst of <100 g / ft ³ , <80 g / ft ³ , more preferably <60 g / ft ³ , achieved in the New European Driving Cycle a hydrocarbon emission of less than 0.1 g / km and a nitrogen oxide emission of less than 0.08 g / km. A method according to claim 18, characterized in that the precatalyst with lowered noble metal content of a furnace aging for 4 hours at 1100 ° C an atmosphere of 2% O ₂ and 10% H ₂ O and the NOx storage catalyst with lowered precious metal content for 4 hours at 850 ° C in an atmosphere of 2% O ₂ and 10% H ₂ O was subjected. Hybrid vehicle with - an internal combustion engine and at least one electric motor, each of which can deliver a torque, in particular, to drive at least one vehicle wheel, - being the internal combustion engine an exhaust system is associated with a catalyst system whose conversion activity of predetermined activity parameters dependent is characterized in that a means for controlling the torque output of the engine and the electric motor is provided, by means of which to achieve a predetermined conversion threshold the conversion activity of the catalyst system for at least one exhaust gas component in a predetermined time interval T_Kat determines the value of the conversion activity and if so Value is below the said threshold, the torque output of the Electric motor, preferably on demand, increases and the torque output the internal combustion engine an operation of the hybrid vehicle without providing a torque through the electric motor is reduced. Hybridfahrzug according to claim 20, characterized in that the internal combustion engine in the New European driving cycle with thermally undamaged catalyst system which has at least one near the engine pre-catalyst and at least one downstream NOx storage catalyst, wherein at least one of the catalysts have a noble metal content of> 110 g / ft ³ and in a time shift portion of at least 250 sec. achieved a hydrocarbon emission of <0.07 g / km and a nitrogen oxide emission of <0.05 g / km without providing torque by the electric motor and providing a torque by the electric motor and a noble metal content of the precatalyst of <100 g / ft ³ , preferably, <80 g / ft ³ , more preferably <60 g / ft ³ in the New European Driving Cycle achieves a hydrocarbon emission of less than 0.1 g / km and a nitrogen oxide emission of less than 0.08 g / km.