GB2503725A

GB2503725A - Hybrid powertrain control to split power between a combustion engine and motor generator based on the temperature upstream of an SCR

Info

Publication number: GB2503725A
Application number: GB1212021.8A
Authority: GB
Inventors: Gianmarco Brunetti
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-07-05
Filing date: 2012-07-05
Publication date: 2014-01-08
Also published as: GB201212021D0

Abstract

A method of operating a hybrid powertrain comprising a motor-generator electric unit (500, fig 1) and an internal combustion engine 110 equipped with an SCR device 287 in an exhaust line 275. The method comprising the steps of: determining an overall power to be delivered by the hybrid powertrain (105, fig 1), monitoring a parameter TSCRinj indicative of a temperature in the exhaust line 275 upstream of the SCR device 287, and splitting the overall power Ptot into a first contributing value Pice of power to be delivered by the internal combustion engine 110 and a second contributing value Pmgu of power to be delivered by the motor-generator electric unit (500, fig 1), wherein the splitting of the overall power comprises the step of increasing the first contributing power value Pice, if the monitored temperature parameter TSCRinj is lower than a predefined threshold.

Description

METHOD OF OPERATING A HYBRID POWERTRAIN

TECHNICAL FIELD

The present disclosure relates to a method of operating a hybrid powertrain of a motor vehicle.

BACKGROUND

It is known that any motor vehicle is equipped with a powertrain, namely with a group of components and/or devices that are provided for generating mechanical power and for delivering it to the final drive of the motor vehicle, such as for example the drive wheels of a car.

In particular, hybrid powertrains are known that comprise an internal combustion engine (ICE), such as for example a compression-ignition engine (Diesel engine) or a spark-ignition engine (gasoline or gas engine), and a motor-generator electric unit (MGU). The MGU can operate as an electric motor for assisting or replacing the ICE in propelling the motor vehicle, and can also operate as an electric generator, especially when the motor vehicle is braking, for charging an electrical energy storage device (such as a battery) connected thereto.

Besides, the battery is provided for powering the MGU when it operates as electric motor, so that the only source of energy necessary for operating the hybrid powertrain is the ICE fuel.

The hybrid powertrain is controlled by an electronic càntrol unit (ECU) according to a Hybrid Operating Strategy (HOS). During the traction of the motor vehicle, the 1105 provides for determining an overall value of mechanical power to be delivered to the final drive of the motor vehicle, for splitting this overall value in a first contributing value of mechanical power to be requested to the ICE and a second contributing value of mechanical power to be requested to the MGU, and then for operating the ICE and the MGU to deliver to the final drive of the motor vehicle the respective contributing value of mechanical power.

In greater details, the splitting of the overall power value is conventionally optimized by determining, among the infinite couples of contributing power values respectively from the ICE and from the MGU whose addition is equal to the overall power value, the couple of values that minimize a predetermined polynomial function, usually referred as target function, which quantifies an overall power that is lost due to the operation of the hybrid powertrain, namely a quantity of power that has been supplied to the hybrid powertrain through the ICE fuel, but that has not been delivered to the final drive of the motor vehicle, for example because it has been dissipated due to specific aspect of the hybrid power-train operation.

As a consequence of the F-lOS strategy, the contributing power value of the ICE is always positive, whereas the contributing power value of the MGU may be either positive or negative. If the contributing power value of the MGU is positive, the MGU is operated as an electric motor that actually supplies mechanical power to the final drive. If the contributing power value of the MGLS is negative, the MGU is operated as an electric generator that actually absorbs mechanical power from the final drive.

Turning now to the internal combustion engine, it generally comprises an engine block defining a plurality of cylinders, each of which accommodates a reciprocating piston coupled to rotate a crankshaft. A fuel and air mixture is disposed in each of the combustion chambers and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the pistons. The air is distributed to the engine cylinders through an intake manifold, and the exhaust gasses are conveyed from the engine cylinders to an exhaust manifold.

Internal combustion engines, in particular Diesel engines, are generally equipped with exhaust gas after-treatment systems in order to reduce pollution due to engine emissions.

Such after-treatment systems may comprise a plurality of aftertreatment devices located in the exhaust line, for degrading andfor removing pollutants from the exhaust gas before discharging it into the environment.

One of these system is the 8CR (Selective Catalytic Reduction), namely a catalytic device in which the nitrogen oxides (NO) contained in the exhaust gas are reduced into diatomic nitrogen (N2) and water (F-120), with the aid of a gaseous reducing agent, typically ammonia (NH3) that can be obtained by urea (CH4N2O) thermo-hydrolysis and that is absorbed inside catalyst. Typically, urea is injected in the exhaust line and mixed with the exhaust gas upstream the SCR. Other fluids can be used in the SCR in lieu of urea and are generally referred to as Diesel Exhaust Fluids (DEF).

Hybrid powertrains, even though offer a lower Fuel Consumption (FC) than conventional powertrains, show higher Cold Start Penalties, due to a longer warm-up phase.

Cold Start Penalties influence Fuel Consumption performances.

Also, the engine warm-up phase results longer because of lower fuel consumption and lower heat released, due to the electric part of the hybrid powertrain.

One of the main issues of Diesel powertrains, due to stringent emission regulations, is aftertreatment warm-up.

In fact, systems such as 5CR require high temperatures of exhaust gases to properly operate.

The temperature upstream of the SCR catalyst can be raised, for example, by operating the internal combustion engine with after injections.

In particular, fuel after-injections are fuel injections in a cylinder of the engine that occur after the Top Dead Center (TDC) of the piston and that do not supply torque. Part of the fuel injected by means of aftar-injections burns in the exhaust line raising the temperature thereof.

Moreover1 urea injection into the 5CR is enabled only above a certain threshold of temperature (for example 180°C), in order to perform catalytic reduction.

On many driving conditions such temperature is not reached until a late time.

According to experimental results in fact, the urea injection is enabled by the ECU if a certain temperature at 5CR inlet is reached1 therefore not all potential benefit on NO reduction are achieved over lifecycle of the vehicle.

Therefore, low temperature in the exhaust line upstream of the SCR catalyst lead to a longer SCR warm-up and consequently to a lower NO conversion efficiency.

An object of an embodiment of the invention is to provide a method of operating of a hybrid powertrain of a motor vehicle that allows an earlier warm up of the SCR device

with respect to the prior art.

Another object of the invention is to provide a method of operating of a hybrid powertrain that allows substantial benefits in term of increasing NO conversion efficiency.

Another object is to overcome the above mentioned drawbacks of the prior art without using complex devices and by taking advantage from the computational capabilities of the Electronic Control Unit (ECU) of the vehicle.

Another object of the present disclosure is to meet these goals by means of a simple, rational and inexpensive solution.

These objects are achieved by a method, by an engine, by an apparatus, by an hybrid powertrain, by a computer program and a computer program product, and by an electromagnetic signal having the features recited in the independent claims.

The dependent claims delineate preferred and/or especially advantageous aspects.

SUMMARY

An embodiment of the disclosure provides for a method for operating a hybrid powertrain comprising a motor-generator electric unit and an internal combustion engine equipped with an SCR device in an exhaust line, wherein the operating method comprises the steps of: -determining an overall power to be delivered by the hybrid powertrain, -monitoring a parameter indicative of a temperature in the exhaust line upstream of the SCR device, and -splitting the overall power into a first contributing value of power to be delivered by the internal combustion engine and a second contributing value of power to be delivered by the motor-generator electric unit, -wherein the splitting of the overall power comprises the step of increasing the first contributing power value, if the monitored parameter is lower than a predefined threshold.

According to this embodiment of the invention, if the predetermined condition is fulfilled, part of the power to be requested to the motor-generator electric unit is shifted and added to the power to be requested to the internal combustion engine. In this way, the internal combustion engine may be forced to operate such as to create conditions that are advantageous with regard to the increase of temperature upstream of the SCR catalyst, for example by generating exhaust gases having higher temperature. At the same time, the extra power requested to the internal combustion engine may correspond to an electric generation of the motor-generator electric unit that leads to a positive energy balance.

Therefore this and other embodiments of the invention give the possibility of using the SCR device even at lower aftertreatment temperatures, typical of urban driving or of Full Hybrid vehicles, due to frequent ICE shut-off, achieving low NO emission at tailpipe, even during urban driving.

Moreover, the contributing power value delivered by the combustion engine is forcediy increased if the temperature upstream of the SCR catalyst is lower than a predefined threshold. In this case, the increase of the first contributing power value causes the internal combustion engine to move from this critical condition towards operating conditions under which an higher exhaust gas temperature is created, thereby achieving a faster warm up of the 6CR catalyst.

According to another embodiment of the invention, the splitting of the overall power value comprises the step of minimizing a predetermined polynomial function representing an overall power loss of the hybrid powertrain, and wherein the first contributing power value is forcedly increased by adding to the predetermined polynomial function an additional term whose value represents an additional power loss of the internal combustion engine.

This aspect of the invention has the advantage of providing a simple and effective solution for performing the power shifting between the motor-generator electric unit and the internal combustion engine, namely for increasing the contributing power value of the engine while correspondently decreasing the contributing power value to be delivered by the motor-generator electric unit.

Another embodiment of the invention comprises a step of calculating a value of the additional term as a function of a no-torque producing extra quantity of fuel injectable into the internal combustion engine to increase the temperature of the exhaust gas in the exhaust line up to the predefined temperature threshold.

An advantage of this embodiment is that it allows to translate the aim of achieving an higher temperature in the exhaust line into an increased value of power to be delivered by the internal combustion engine and, at the same time, avoiding adoption of after-injections.

In another embodiment of the invention, when the predefined temperature threshold is reached, urea is injected into the exhaust line upstream of the SCR device.

An advantage of this embodiment is that it allows to increase NO conversion efficiency.

Another embodiment of the invention provides an apparatus for operating a hybrid powertrain comprising a motor-generator electric unit and an internal combustion engine equipped with an 6CR device in an exhaust line, wherein the apparatus comprises: -means for determining an overall power to be delivered by the hybrid powertrain, -means for monitoring a parameter indicative of a temperature in the exhaust line upstream of the 6CR device, and -means for splitting the overall power into a first contributing value of power to be delivered by the internal combustion engine and a second contributing value of power to be delivered by the motor-generator electric unit, -wherein the means for splitting of the overall power comprise means for increasing the first contributing power value, if the monitored parameter is lower than a predefined threshold.

Another embodiment of the invention provides a hybrid powertrain comprising a motor-generator electric unit and an internal combustion engine equipped with an SCR device in an exhaust line, wherein the hybrid powertrain is managed by an electronic control unit configured to: -determine an overall power to be delivered by the hybrid powertrain, -monitor a parameter indicative of a temperature in the exhaust line upstream of the SCR device, and -split the overall power into a first contributing value of power to be delivered by the internal combustion engine and a second contributing value of power to be delivered by the motor-generator electric unit, -wherein the splitting of the overall power comprise the step of increasing the first contributing power value, if the monitored parameter is ower than a predefined threshold.

These last two embodiments have substantially the same advantages of the various embodiments of the method of the invention.

The method according to one of its aspects can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the method described above, and in the form of computer program product comprising the computer program.

The computer program product can be embodied as a control apparatus for an internal combustion engine, comprising an Electronic Control Unit (ECU), a data carrier associated to the ECU, and the computer program stored in a data carrier, so that the control apparatus defines the embodiments described in the same way as the method. In this case, when the control apparatus executes the computer program all the steps of the method described above are carried out.

The method according to a further aspect can be also embodied as an electromagnetic signal,, said signal being modulated to carry a sequence of data bits which represents a computer program to carry out all steps of the method.

A still further aspect of the disclosure provides an hybrid powertrain specially arranged for carrying out the method claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, wherein like numerals denote like elements, and in which: Figure 1 schematically represents a hybrid powertrain of a motor vehicle; Figure 2 shows in more details an internal combustion engine (ICE) belonging to the hybrid powertrain of figure 1; Figure 3 is a section of the ICE of figure 2; Figure 4 represents schematically a portion of an aftertreatment system of the hybrid powertrain of figure 1; Figure 5 is a flowchart of an embodiment of method for operating the hybrid powertrain of figure 1; and Figure 6 is a flowchart of another embodiment of a method for operating the hybrid powertrain of figure 1.

DETAILED DESCRIPTION

Exemplary embodiments will now be described with reference to the enclosed drawings without intent to limit application and uses.

Some embodiments may include a motor vehicle's mild hybrid powertrain 105, as shown in Figures 1, that comprises an internal combustion engine (ICE) 110, in this example a diesel engine, a motor-generator electric unit (MGU) 500, an electric energy storage device (battery) 600 electrically connected to the MGU 500, and an electronic control unit (ECU) 450 in communication with a memory system (or data carrier) 460.

As shown in Figures 2 and 3, the internal combustion engine (ICE) 110 has an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145, which may be connected with a final drive of the motor vehicle, for example to drive wheels. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the piston 140. The fuel is provided by at least one fuel injector and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increase the pressure of the fuel received from a fuel source 190.

Each of the cylinders 125 has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow air into the combustion chamber 150 from the port 210 and alternately allow exhaust gases to exit through a port 220. In some examples, a cam phaser 155 may selectively vary the timing between the camshaft 135 and the crankshaft 145.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200. An air intake duct 205 may provide air from the ambient environment to the intake manifold 200. In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200. In still other embodiments, a forced air system such as a turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. Rotation of the compressor 240 increases the pressure and temperature of the air in the duct 205 and manifold 200. An intercooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. The exhaust gases exit the turbine 250 and are directed into an exhaust system 270. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of the exhaust gases through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust system 270 may include an exhaust line 275 having one or more exhaust aftertreatment devices 280. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment devices 280 include, but are not limited to, catalytic converters (two and three way), oxidation catalysts, lean NO traps, hydrocarbon adsorbers, selective catalytic reduction (5CR) systems, and particulate filters.

More specifically a Selective Catalytic Reduction device (SCR) 287 may be provided.

Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

The MGU 500 is an electric machine, namely an electro-mechanical energy converter, which is able either to convert electricity supplied by the battery 600 into mechanical power (i.e., to operate as an electric motor) or to convert mechanical power into electricity that charges the battery 600 (i.e., to operate as electric generator). In greater details, the MGU 500 may comprise a rotor, which is arranged to rotate with respect to a stator, in order to generate or respectively receive the mechanical power.

The rotor may comprise means to generate a magnetic field and the stator may comprise electric windings connected to the battery 600, or vice versa. When the MGU 500 operates as electric motor, the battery 600 supplies electric currents in the electric windings, which interact with the magnetic field to set the rotor in rotation. Conversely, when the MGU 500 operates as electric generator, the rotation of the rotor causes a relative movement of the electric wiring in the magnetic field, which generates electrical currents in the electric windings. The MGU 500 may be of any known type, for example a permanent magnet machine, a brushed machine or an induction machine. The MGU 500 may also be either an asynchronous machine or a synchronous machine.

The rotor of the MGU 500 may comprise a coaxial shaft 505, which is mechanically is connected with other components of the hybrid powertrain 105, so as to be able to deliver or receive mechanical power to and from the final drive of the motor vehicle. In this way, operating as an electric motor, the MGU 500 can assist or replace the ICE 110 in propelling the motor vehicle, whereas operating as an electric generator, especially when the motor vehicle is braking, the MGU 500 can charge the battery 600. In the present example, the MGU shaft 505 is connected with the ICE crankshaft 145 through a transmission belt 510, similarly to a conventional alternator starter. In order to switch between the motor operating mode and the generator operating mode, the MGU 500 may be equipped with an appropriate internal control system.

The hybrid powertrain 105 may further include an electronic control unit (ECU) 450, in communication with the data carrier 460 and an interface bus. The data carrier 460 may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors and control devices. The CPU is configured to execute instructions stored as a program in the data carrier 460, and send and receive signals to/from the interface bus. The program may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110 and the MGU 500.

In order to carry out these methods, the ECU 450 is in communication with one or more sensors and/or devices associated with the ICE 110, the MGU 500 and the battery 600. The ECU 450 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the ICE 110, the MGU 500 and the battery 600. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, a combustion pressure sensor 360, coolant temperature sensor 385, oil temperature sensor 385, a fuel rail pressure sensor 400, a camshaft position sensor 410, a crankshaft position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, a sensor 445 of a position of an accelerator pedal 446, and a measuring circuit 605 capable of sensing the slate of charge of the battery 600.

Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control the operation of the ICE 110 and the MGU 500, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, the cam phaser 155, and the above mentioned internal control system of the MGU 500. Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for clarity.

According to the present example, the ICE 110 and the MGU 500 are controlled by the ECU 450 according a Hybrid Operating Strategy (HOS). During the traction of the motor vehicle, the HOS provides for continuously repeating the routine which is shown in the left part of the flowchart of figureS, and which comprises the general steps of: -determining (block 700) an overall value P0 of mechanical power to be delivered to the final drive cf the motor vehicle by the hybrid powertrain 105 as a whole, -splitting (block 705) this overall value P0 into a first contributing value P of mechanical power to be requested to the ICE 110, and a second contributing value Pmgu of mechanical power to be requested to the MGU 500, and then of -operating (block 710) the ICE 110 to deliver the first contributing value P of mechanical power, and the MGU 500 to deliver the second contributing value Pmgu of mechanical power.

In the present example, where the MGU shaft 505 is mechanically connected with the final drive of the motor vehicle through the ICE crankshaft 145, the value P0 could alternatively indicate the overall mechanical power to be delivered to the ICE crankshaft itself In that case, also the contributing values P1 and Pmgu would be referred to the ICE crankshaft 145.

The overall value P0 may be determined by the ECU 450 on the basis of the position of the accelerator pedal 446, which can be measured by the accelerator pedal position sensor 445.

It should be observed that the first contributing value Fjce is always positive, as the ICE 110 can only generate mechanical power to be transferred to the crankshaft 145.

Conversely, the second contributing value Pmgu may be either positive or negative. If the second contributing value Pmgu is positive, the MGU 500 is operated as an electric motor that actually generates mechanical power to the crankshaft 145. If the second contributing value Pmgu is negative, the MGU 500 is operated as an electric generator that actually absorbs mechanical power from the crankshaft 145 to charge the battery 600.

As seen in Figure 4, the exhaust line 275 of the Internal Combustion engine 110 may be equipped with a SCR Selective Catalytic Reduction device (SCR) 287.

The SCR catalyst 287 can be fed with a Diesel Exhaust Fluid (DEF), for example urea, that is stored in a DEF tank 820, in order to reduce the nitrogen oxides (NO) contained in the, exhaust into diatonic nitrogen (N2) and water (H20). The DEF is provided to a IJEF injector 800 by means of a DEF pump 810 that receives the DEF from the DEE tank 820. The DEF injector 800 can be controlled by the ECU 450 of the hybrid powertrain 105. Moreover1 a temperature sensor 530 is provided upstream of the SOR catalyst 287 and is connected to the ECU 450 and may be used to measure a temperature value TSCRfl1 in the exhaust line 275.

Turning now to the Hybrid Operating Strategy (HOS), the splitting of the overall power value P0 into the first Pice and the second Pmgu contributing power values may be performed by the ECU 450 with the aid of a predetermined polynomial function, hereafter referred as target function, which may be stored in the data carrier 460 associated to the ECU 450.

The target function quantifies an overall power loss PL0 of the hybrid powertrain as a function of the unknown first P1 and second Pmgu contributing power values: FL,0, = f(J., , In other words, the first Pjce and the second mgu contributing power values are variables of the target function.

The HOS provides for the ECU 45Q to determine, among the infinite couples of contributing power values (Pice, Puigu) that satisfy the equation: + rngu the specific couple of contributing power values which also minimize the target function, namely which minimize the value PL01 of the overall power loss of the hybrid powertrain 105: = minf Two alternative approaches are known and may be used by the ECU 450 to determine the couple of contributing power values (Pjce, mgu) which minimize the target function f: a step-by-step approach or an integral approach.

According to the present example, the target function may be described by the following polynomial equation: FL,0, =f(Fice,Fmg3=Fi+F+fi+Fi+P's wherein F1, F2, F, F4 and F5 are the so called terms of the polynomial target function.

The first term F1 of the target function may be described by the following equation: 13 =k1 PLice wherein k1 is a constant and PL is a value that quantifies the power lost by the ICE 110, as a difference between the energy of the unburned fuel and the energy actually delivered by the ICE 110 to the final drive of the motor vehicle. The value PL may be calculated according to the following equation: PL =1-li Qf,,, =O-q)Q,,, H1 so that: = k1 PL = k1 (H, *Qfi,f -I)= k [(1-q)*Qfrd H1] wherein H is the value of the heat of combustion of the fuel, Qfue' is the value of the mass flow of fuel injected into the ICE 110, Pice is the unknown first contributing value of mechanical power to be delivered by the ICE 110, and q is the value of an efficiency parameter that accounts for both the thermo-mechanical efficiency of the ICE 110 and the friction loss in the kinematical chain connecting the ICE 110 to the final drive of the motor vehicle.

The second term F2 of the target function may be described by the following equation: = k2 /L, wherein k2 is a constant and PLTj is a value that quantifies an additional amount of power that is lost by the ICE 110 due a possible slowing down of the ICE warm-up phase caused by the operation of the MGU 500 and vice versa. The value PLT,ice may be calculated according to the following equation: FL. . =1 cwarn; Ce.9 I -ban ce warn; ,cec,,1,I so that: y (cewar,,, ice 2"2 Tice"2 -T bait k ice,warn, ice cold) wherein Tice,warm is a nominal value of the ICE temperature after the completion of the warm-up phase, 1i,Id is a nominal value of the ICE temperature before the warm-up phase, Tjce is an actual value of the ICE temperature, and Pbat is Pban is the power supplied by the battery 600. The nominal values lice warm and TjId can be empirically determined during an experimental activity and stored in the data carrier 460 associated with the ECU 450; the actual value Tice can be measured with the aid of one or more of the temperature sensor of the ICE, including, but not limited to, the manifold temperature sensor 350, the coolant temperature sensor 380, the oil temperature sensor 385 and the exhaust temperature sensors 430; the value Pbaft can be determined from the voltage and current absorption of the MGU 500.

The third term F3 of the target function may be described by the following equation: F3 = k3 PLmgu wherein k3 is a constant and PLmgu is a value that quantifies the power lost by the MGU 500, as a difference between the chemical energy of the battery 600 and the energy actually delivered by the MGU 500 tothe final drive of the motor vehicle, thereby taking into account the chemical efficiency of the battery 600, the electromechanical efficiency of the MGU 500 and the friction loss in the kinematical chain connecting the MGU 500 to the final drive of the motor vehicle.

The value PLmgu may be calculated according to the following equation: PLrnga = boo - = A V0 -Pmgp so that: F3 = Ic3 *PL11, =k3 (1'che,nbot, -P,)= Ic3 *(A*V0 -P,0) wherein Pehembatt is a value of an electric power generated by the battery 600, A is a value of an electric current absorbed by the MGU 500, V0 is a value of a tension measured at battery 600 poles at open circuit, and Pmgu is the unknown value of the second contributing value of mechanical power to be delivered/absorbed by the MGU 500. The values A and V0 can be determined by measuring MGU 500 current and battery 600 voltage characteristics.

The fourth term F4 of the target function may be described by the following equation: P =/c4 *PLcoc wherein k4 is a constant and PL50 is a value that quantifies a fictitious increase/decrease of power loss, which is introduced if the current value of the state of charge (5CC) of the battery 600 exits from a predetermined range of allowable values thereof. The current soc value can be determined through the measuring circuit 605. The range of allowable values may be stored in the data carrier 460 associated with the ECU 450. The value PL50 may be calculated according to the following equation: = --a1/,shEfl) so that: F4 = . = . [c, -(Pha,, -haa shift wherein C10 is a value of a non-dimensional quantity comprised between -1 and +1, which is used to target the battery 600 state of charge within the acceptable range, Pbau is a value of actual power absorbed or released by the battery 600, Pbaftshift is a fictitious value of battery power used to target the ideal state of charge of battery 600. The values CIsoc, Pa11 shift can be determined by a proper calibration activity, whereas Pba can be determined from the current and voltage measurement on the MGU 500.

According to an embodiment of the invention, the fifth term F5 is generally used to take into account the extra fuelling needed to rise engine load achieving the temperature required to perform a fast warm up the SCR catalyst.

The temperature upstream of the 5CR catalyst 287 can be raised, for example, by operating the internal combustion engine 110 with after injections.

In particular, fuel after-injections are fuel injections in a cylinder of the engine that occur after the Top Dead Center (TDC) of the piston. Pad of the fuel injected by means of after-injections burns in the exhaust line 275 raising the temperature thereof More specifically, the value of the fifth term F5 of the target function f may be expressed by the following equation: F; = flag5 tk5.

wherein PLSCR is a value that accounts for an extra fuel quantity to be injected in the ICE 110, in order to operate a so called "power shifting"1 namely to forcedly increase the first contributing power value P0 and correspondently decrease the second contributing power value PmQu, k5 is a constant weight factor of the power losses related to SCR warm up and flag5 is a variable that may be set equal to zero or to one depending on a temperature value TscRfl1 upstream the SCR catalyst 287.

The value of PbSCR may be calculated according to the following expression: PLSCR -H, . wherein H is the lower heating value of the fuel! Qafier,rexhdes is the value of the Fuel S Consumption due to the after-injections injected into the ICE 110 in order to warm-up the exhaust line if the strategy according to the various embodiments of the invention described is not adopted.

The tower heating value H of the fuel and the value q of the efficiency parameter may be empirically or theoretically determined and then stored in the data carrier 460.

The value Qocr,mxhdc of the Fuel Consumption due to the after-injections may be determined through a map, which correlates the values of the fuel injected to corresponding values of power P to be generated by the ICE 110. This map may be an empirically determined calibration map that is stored in the data carrier 460. In this way, the ECU 450 may determine the value r,Th,d1 of the Fuel Consumption by applying to this additional map the power value Rice.

The target value i'1 may be determined by the ECU 450 through a map, which correlates target Fuel Consumption values If Texhdes to corresponding values of a plurality of engine operating parameter& In other words, the ECU 450 may be configured to determine an actual value of these engine operating parameters, and then to determine a target value from the above mentioned map, on the basis the determined actual values of the engine operating parameters.

In this way, the ECU 450 may perform the "load shifting" using different target values Qafi.miM for different values of the engine operating parameters. These engine operating parameters may include the engine speed and the engine load. The value of the engine speed may be measured by the ECU 450 through the crankshaft position sensor 420. The value of the engine load corresponds to the torque requested by the driver by pressure of the gas pedal to the powertrain 105. The map may be an empirically determined calibration map, namely a* map that is determined during an experimental activity and then stored in the memory system 460. In other embodiments, the map may useas input also a value of the engine coolant temperature, which can be measured by the ECU 450 through the coolant temperature sensor 380.

Thanks to the expression of the fifth term F5 above explained, while minimizing the target function, the Hybrid Optimization Strategy (HOS) automatically tends to minimize also the extra fuelvalue PLSCR.

As shown in figure 5, the value of the parameter flag5 is determined on the basis of the monitored parameter indicative of the temperature TscRinj in the exhaust line 276 upstream of the SCR catalyst 287, which may be measured by temperature sensor 530.

More particularly, the temperature parameter TscRjnj is applied to a conditional block 715, which is configured to check whether the temperature parameter TscRiflj fulfils a predetermined condition or nor.

The predetermined condition may be fulfilled if the monitored parameter is lower than a predefined temperature threshold Tth. An exemplary value for the temperature threshold may be 180 °C.

If this predetermined condition is not fulfilled, then the parameter f/ag5 is set to zero (block 720), so that the fifth term F5 of the target function is disregarded and has no effect on the determination of the first rice and second Pflgu contributing power values.

If conversely the predetermined condition is fulfilled, then the parameter flag5 is set to one (block 725), so that the fifth term F5 of the target function is actually taken into account, thereby causing the above mentioned "load shifting".

Figure 6 is a flowchart of another embodiment of a method for operating the hybrid powertrain 105.

The method starts by measuring the value TSCRInj of the temperature in the exhaust line upstream of the SCR device 287, using temperature sensor 530 (block 900).

This temperature value TSCRIr,j is compared with a threshold temperature value Tm thereof (block 910).

If the measured temperature value T501 is higher than the threshold temperature value Tth, then the ECU 450 activates the DEF pump 810 in order to inject urea into the exhaust gas portion upstream of the SCR catalyst 287 (block 960).

If the measured temperature value TSCRIflJ is lower than the threshold temperature value Tth. then the parameter flag5 is set equal to one (block 920).

This has the effect to rise the losses calculated by the target function f described by the polynomial equation: -FL,0, 1 + P2 +P +F ÷F since the fifth tent F5 is now different from zero (block 930).

In this case, a splitting occurs between the values of the first Pice and the second contributing power that has the consequence that engine load results higher (block 940), while the motor-generator electric unit (MGU) may operate as an electric generator.

The higher load of the engine is useful to raise the temperature of exhaust gas (block 950).

This cycle may be repeated until the measured temperature value TscRiflj is higher than the threshold temperature value Tlh, and therefore the ECU 450 may activate the DEE pump 810 in order to inject urea into the exhaust gas portion upstream of the SCR catalyst 287 (block 960).

With this embodiment therefore the temperature in the exhaust line 275 upstream of the SCR device 287 is raised quickly and the SCR device can be operated sooner.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCE NUMBERS

powertrain internal combustion engine (ICE) engine block 125 cylinder cylinder head camshaft piston crankshaft 150 combustion chamber cam phaser fuel injector fuel rail fuel pump 190 fuel source intake manifold 205 air intake duct 210 intake air part 215 valves of the cylinder 220 exhaust gas port 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine 260 intercooler 270 exhaust system 275 exhaust line 280 exhaust aftertreatment device 287 SCR device 290 VGT actuator 300 EGR system.

310 EGRcooler 320 EGR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 combustion pressure sensor 380 coolant and oil temperature and level sensors 400 fuel rail pressure sensor 410 cam position sensor 420 crank position sensor 430 exhaust pressure and temperature sensor 445 accelerator pedal position sensor 446 accelerator pedal 450 electronic control unit (ECU) 460 data carrier 500 motor-generator electric unit 505 MGU shaft 510 transmission belt 600 battery 605 measuring circuit 700 block 705 block 710 block 715 block 720 block 725 block 800 DEE injector, 810 DEF pump 820 DEE tank 900 block 910 block 920 block 930 block 940 block 950 block 960 block

Claims

CLAIMS1. A method of operating a hybrid powertrain (105) comprising a motor-generator electric unit (500) and an internal combustion engine (110) equipped with an SCR device (287) in an exhaust line (275), wherein the operating method comprises the steps of: -determining an overall power (P0t) to be delivered by the hybrid powertrain (105), -monitoring a parameter (TSCRflJ) indicative of a temperature in the exhaust line (275) upstream of the SCR device (287), and -splitting the overall power (P0) into a first contributing value (P) of power to be delivered by the internal combustion engine (110) and a second contributing value (Pmgu) of power to be delivered by the motor-generator electric unit (500), -wherein the splitting of the overall power (P1) comprises the step of increasing the first contributing power value (P1), if the monitored parameter (TscRIflj) is lower than a predefined threshold (Ith).
2. A method according to any of the preceding claims, wherein the splitting of the overall power (F101) comprises the step of minimizing a predetermined polynomial function representing an overall power loss of the hybrid powertrain (105), and wherein the first contributing power value (Pice) is increased by adding to the predetermined polynomial function an additional term (PLSCR) whose value represents an additional power loss of the internal combustion engine (110)
3. A method according to claim 2, comprising a step of calculating a value of the additional term (PLSCR) as a function of a no-torque producing extra quantity of fuel injectable into the internal combustion engine (110) to increase the temperature of the exhaust gas in the exhaust line (275) up to the predefined temperature threshold (Tth).
4. A method according to claim 3, wherein the value of the extra quantity of fuel may be determined by means of a map which correlates values of the extra quantity of values to corresponding values of a plurality of engine operating parameters.
5. A method according to claim 3, wherein when the predefined temperature threshold (Tb) is reached, a Diesel Exhaust Fluid (DEF) is injected into the exhaust line (275) upstream of the SCR device (287).
6. A hybrid powertrain (105) comprising a motor-generator electric unit (500) and an internal combustion engine (110) equipped with an SCR device (287) in an exhaust line (275), the hybrid powertrain (105) being managed by an Electronic Control Unit (ECU) configured for carrying out the method according to any of the preceding claims.
7. A computer program comprising a computer-code suitable for performing the method according to any of the claims 1-5.
8. Computer program product on which the computer program according to claim 7 is stored.
9. Control apparatus for an internal combustion engine, comprising an Electronic Control Unit, a data carrier associated to the Electronic Control Unit and a computer program according to claim 7 stored in the data carrier.
10. An electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 7.