GB2493740A - A method of operating a hybrid power train using a polynomial equation - Google Patents

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 after treatment device, e.g. a catalytic converter 281, 282. The operating method comprises determining an overall value (Prot) of power to be delivered by the hybrid powertrain and using this overall value (Prot) and a predetermined polynomial function to determine a contributing values of power (Pice, Pmgu) to be requested for the engine 110 and for the motor-generator electric unit (500). The engine 110 and motor (500) are operated to deliver these values of power (Pice, Pmgu) and the predetermined polynomial equation comprises a term whose value is zero, if no regeneration phase of the catalytic converter 281, 282 is active, and it depends on a value (PSG) of a thermal power lost by the internal combustion engine 110 to heat the catalytic converter 281, 282, if a regeneration phase of the catalytic converter 281, 282 is active.

Description

METH) FOR OPEPWG A HYBRID PCgEPTBAnT TEcRCL FI&D The present invention relates to a method for operating a hybrid pa-wertrain of a motor vehicle.

It is known that any motor vehicle is eqiñpped 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.

A hybrid powertrain particularly comprises an internal coithustiori en-gine (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 elec-tric 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 breaking, for charging an electrical energy storage device (battery) connected thereto. The battery is then pro-vided for powering the 1GU, when it operates as electric motor, so that the only source of energy necessary for operating the hybrid po-wertrain is the ICE fuel.

The ICE and the MOO are controlled by an electronic control unit (ECU) according to a Hybrid Operating Strategy (HOS). During the pro-pulsion of the motor vehicle, the HOS 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 MOO, and then for operating the ICE and the MOO to deliver to the final drive of the motor vehicle the respective contributing value of mechanical power.

The splitting of the power overall value is optimized by determining, among the infinite couples of first and second contributing values whose addition is equal to the overall value, the couple that minim- ize the result of a predetermined polynomial function, usually re-ferred as target function, whose variables include an unknown value of the ICE power contribution and an unknown value of the MOO power contribution.

The target function comprises several terms, each of whidi depends on a power loss that is correlated to a specific aspect of the operation of the hybrid powertrain. The power loss is intended as a quantity of power that has been supplied to the hybrid powertrain by the ICE fuel, but that cannot be delivered to the final drive of the motor vehicle, for example because it has been dissipated or howsoever used in that specific aspect of the hybrid powertrain operation.

More particularly, a conventional target function generally comprises a first term, whose value depends on a power quantity lost by the ICE (due to its thermo-mechanical efficiency and to the friction loss in the kinematical chain connecting the ICE to the final drive of the motor vehicle), a second term, whose value depends on a power quanti-ty that is lost by the ICE due a possible slowing down of the ICE warm-up phase caused by the operation of the MGU and vice versa, a third term, whose value depends on a power quantity that is lost by the MGU (due to its electromechanical efficiency and the friction loss in the kinematical chain connecting the I'4GTJ to the final drive of the motor vehicle) and by the electrical battery connected thereto (due to it chemical efficiency), and finally a fourth term, whose value depends on a fictitious loss of power quantity that accounts for the state of charge of the electric battery.

However, this conventional I-lOS has the drawback of disregarding the fact that scmetimes the ICE is used also to perform a regeneration phase of an aftertreatment device, such as a particulate filter and/or a NO, trap. In fact, it is known that the exhaust gas produced by the fuel combustion within the cylinders of an internal combustion engine is discharged into the environment trough an exhaust system, which generally comprises an exhaust manifold in cccumunication with the engine cylinders, an exhaust pipe coming off the exhaust mani-fold, and one or more aftertreatment devices located in the exhaust pipe for trapping and/or changing the composition of the pollutant contained in the exhaust gas. Among these aftertreatment devices, an internal combustion engine (in particular a Diesel engine) may com- prise a Diesel Particulate Filter (DEF) for trapping and thus remov-ing diesel particulate matter (soot) from the exhaust gas, and a Lean NO,< Trap (I2T) for trapping nitrogen oxides (NOX) and sulphur oxides (SOy) Each of the DPF and the LNT is periodically subjected to a regenera-tion phase, in order to remove the accumulated soot from the DPF and the nitrogen oxides and the sulphur oxides from the LNT. The DPF re-generation phase is generally performed more frequently than the LNT regeneration phase, but the LNT regeneration phase is always per-formed during a DPF regeneration phase, as they basically require the same thermal conditions.

In particular, these thermal conditions include the fact that the DPF and the LNT must be heated up and maintained at temperature values that promote the burning of the accumulated soot and the reduction of the accumulated NO and SO, respectively. A conventional strategy for increasing the OPE and the LNT temperature provides for operating the internal contustion engine according to a dedicated fuel injection pattern, which comprises after-injections and post-injections of fuel. The after-injections are small fuel quantities that are in-jected in an engine cylinder once the respective piston has passed the Top Dead Center (Tm) position. These after-injected fuel quanti-ties burn inside the engine cylinder without generating torque to the crankshaft, but increasing the temperature of the exhaust gases that will flow through the OFF and the LNT. The post-injections are small fuel quantities that are injected into an engine cylinder when the respective exhaust valves are already open, so that they exit unburnt from the engine cylinder without generating torque to the crankshaft.

These post-injected fuel quantities burn in the exhaust system fur-ther increasing the temperature of the DPE' and the LNT.

The quantity of fuel supplied by means of the above mentioned after-injections and post-injections generally depends on the mechanical power that, during the regeneration phase, is requested to be deli-vered by the ICE (engine load). In fact, the greater is the requested power the greater is the quantity of fuel that is injected in the en- gine cylinders to generate that power and the greater is the tempera-ture of the exhaust gases, so that a smaller amount of after-injected and post-injected fuel is generally needed to effectively perform the regeneration phase, as well as a smaller regeneration time to com-plete the DPF and LNT cleaning up.

In view of the above, it is an object of the present invention to provide an improved hybrid powertrain strategy which is able, during a DPF and/or LNT regeneration phase, to increase the power contribu-tion of the ICE and ccrrespondently to reduce the power contribution of the MGU, in order to reduce the quantities of after and post in-jected fuel to be supplied, the duration of the regeneration phase and therefore the overall fuel consumption in this phase. Pnother ob- ject is to reach this goal with a simple, rational and rather inex-pensive solution.

DISCLOSURE

These and/or other objects are attained by the characteristics of the embodiments of the invention as reported in independent claims. The dependent claims recite preferred and/or especially advantageous fea-tures of the embodiments of the invention.

In particu]ar, an embodiment of the invention provides a method for operating a hybrid powertrain comprising a motor-generator electric unit and an internal combustion engine equipped with at least an af- tertreatment device, such as a DPF and/or a LNT, wherein the operat-ing method comprises the steps of: -determining an overall value of power to be delivered by the hy-brid powertrain, using this overall value and a predetermined polynomial function having as variables an unkr-iowri value of power to be delivered by the internal combustion engine and an unimown value of power to be delivered by the motor-generator electric unit, to determine a contributing value of power to be requested to the internal com-bustion engine and a contributing value of power to be requested to the motor-generator electric unit, and -operating the internal combustion engine and the motor-generator electric unit to deliver the respective contributing value of power, and wherein the predetermined polynomial equation comprises a term whose value is zero, if no regeneration phase of the aftertreatment device is active, and it depends on a value of a thermal power lost by the internal combustion engine to heat the aftertreatment device, if a regeneration phase of the aftertreatment device is active.

Thanks to this term of the target function, while determining the ICE power contribution and the MGU power contribution, the hybrid operat-ing strategy takes effectively into account the thermal power lost by the internal combustion engine to heat the aftertreatrnent device dur-ing a regeneration phase thereof, thereby leading to an increase of the ICE power contribution which is advantageously able to reduce the fuel consumption as mentioned above. In particular, it is possible to increase the ICE power contribution to the point that the related [EU power contribution becomes negative, with the consequence that the MGU operates as an electric generator for recharging the battery. In this way, the heat generated by the ICE during the regeneration phase of the aftertreatrnent device may be advantageously used not only to perform the regeneration phase itself but also to generate electrical power.

According to an aspect of the invention, the value of the thermal power lost by the internal coirbustion engine to heat the aftertreat-ment device is determined with the steps of: -determining a value of a fuel quantity to be supplied to the in-ternal combustion engine by means of after-injections during the regeneration phase, -determining a value of a fuel quantity to be supplied to the in-ternal combustion engine by means of post-injections during the regeneration phase, -calculating the thermal power value as a function of these deter-mined values of the fuel quantity and a heating value of the fuel, for example the low heating value (LI-TV).

By way of example, the thermal power value may be simply calculated by multiplying the heating value of the fuel by the determined values of the fuel quantity to be supplied by means of the after-injections and by means of the post-injections.

This aspect of the invention has the advantage of providing a relia-ble determination of the thermal power lost during the regeneration phase of the aftertreatment device, since the after-injections and the post-injections are used only to this task and they do not gener-ate torque at the crankshaft.

According to an aspect of the invention, the fuel quantity value to be supplied by means of the after-injections and the fuel quantity value to be supplied by means of the post-injections are determined on the basis of the unknown value of power to be delivered by the in-ternal combustion engine.

In this way, the value of the target function term here concerned is advantageously correlated to the unknown ICE power value, thereby further optimizing the determination of the ICE power contribution and the NIGU power contribution.

According to another aspect of the invention, the fuel quantity value to be supplied by means of the after-injections and the fuel quantity value to be supplied by means of the post-injections may be deter-mined through an empirically calibrated map that correlates these fuel quantity values to at least the unknown value of the power to be delivered by the internal combustion engine.

As a matter of fact, this empirically calibrated map may be the same

B

map that is used by the ECU to operate the ICE during the regenera- tion phase of the aftertreatment device. As a consequence, this as-pect of the invention has the advantage of allowing the HOS to be carried out in a very simple way and with a minimum of computational effort.

The method according to the invention 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 a computer program product comprising the computer program. The method can be also erthodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represent a computer program to carry out all steps of the method.

Another errbodiment of the present invention provides an apparatus for operating a hybrid powertrain comprising a motor-generator electric unit and an internal corrtustion engine equipped with at least an af-tertreatment device, wherein the apparatus comprises: -means for determining an overall value of mechanical power to be delivered by the hybrid powertrain, -means for using the overall value of mechanical power and a pre-determined polynomial equation having as variables an unknown value of power to be delivered by the internal combustion engine and an unknown value of power to be delivered by the motor-generator electric unit, to calculate a contributing value of power to be requested to the internal combustion engine and a contributing value of power to be requested to the motor-generator electric unit, and -means for operating the internal cortustion engine and the motor-generator electric unit to deliver the respective contributing value of power, and wherein the predetermined polynomial equation comprises a term whose value is zero, if no regeneration phase of the aftertreatment device is active, and it depends on a value of a thermal power lost by the internal combustion engine to heat the aftertreatment device, if a regeneration phase of the aftertreatment device is active.

This embodiment of the invention has the same advantage of the method disclosed above, particularly that of allowing the hybrid operating strategy to increase the ICE power contribution and correspondently to decrease the MGU power contribution during a regeneration phase of the aftertreatment device.

Still another embodiment of the invention provides a hybrid power- train comprising an motor-generator electric unit, an internal corn- bustion engine equipped with an aftertreatment device, and an elec-tronic control unit (ECU) configured to: -determine an overall value of power to be delivered by the hybrid p owe rt ra in -use this overall value and a predetermined polynomial function having as variables an unknown value of power to be delivered by the internal combustion engine and an unknown value of power to be delivered by the motor-generator electric unit, to determine a contributing value of power to be requested to the internal com-bustion engine and a contributing value of power to be requested to the motor-generator electric unit, and -operate the internal coirbustion engine and the motor-generator electric unit to deliver the respective contributing value of power, wherein the predetermined polynomial equation comprises a term whose value is zero, if no regeneration phase of the aftertreatnient device is active, and it depends on a value of a thermal power lost by the internal combustion engine to heat the aftertreatrnent device, if a regeneration phase of the aftertreatment device is active.

Also this entodflnent of the invention has the advantage of the method disclosed above, particularly that of allowing the hybrid operating strategy to increase the ICE power contribution and correspondently to decrease the MGU power contribution during a regeneration phase of the aftertreatment device.

HRIEF DESCRIPTfl OF THE DRPCNGS The present invention will now be described, by way of example, with reference to the accompanying drawings.

Figure 1 schematically represents a hybrid powertrain of a motor ve-hicle.

Figure 2 is a flowchart of a method for operating the hybrid power-train of figure 1.

Figure 3 shows in more details an internal combustion engine belong-ing to the hybrid powertrain of figure 1.

Figure 4 is a section A-A of the internal combustion engine of figure 3.

DEThILED DESCRIPTIQ4 Some embodiments may include a motor vehicle' s mild hybrid powertrain 100, as shown in Figures 1, that comprises an internal combustion en-gine (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 comunication with a memory system 460.

As shown in figure 3 and 4, the ICE 110 has an engine block 120 de- fining at least one cylinder 125 having a piston 140 coupled to ro-tate 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 chaIn- ber 150 and ignited, resulting in hot expanding exhaust gasses caus-ing reciprocal movement of the piston 140. The fuel is provided by at least one fuel injector 160 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector from a fuel rail 170 in fluid corratunication with a high pressure fuel pump 180 that increases 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 from the port 210 and alternately allow exhaust gases to exit through at least one exhaust port 220. In some examples, a cam phaser 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 pipe 205 may provide air from the artient environment to the intake manifold 200. In other errbodflnents, a throttle body 330 may be provided to regulate the flow of air into the manifold 200. In still other enbodiments, 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 intake pipe 205 and manifold 200. An intercooler 260 disposed in the intake pipe 205 may reduce the temperature of the air. The turbine 250 ro-tates 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. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 ar-ranged 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. Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled be-tween the exhaust manifold 225 and the intake manifold 200. The EGg system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the LOB system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

The exhaust gases exit the turbine 250 and are directed into an ex-haust system 270. The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices. The after- treatment devices may be any device configured to change the composi-tion of the exhaust gases. Some examples of aftertreatment devices include, but are not limited to, catalytic converters (two and three way), oxidation catalysts (IC) 280, lean NQ traps (LNT) 281, hydro-carbon adsorbers, selective catalytic reduction (5CR) systems, and particulate filters (OFF) 282.

During the operation of the ICE 110, both the LNT 281 and the DFF 282 are periodically subjected to a regeneration phase. The OFF regenera-tion phase provides for burning off the soot accumulated in the OFF 282, whereas the LNT regeneration phase provides for removing the ni- trogen oxides and the sulphur oxides from the LNT 281. The OFF rege-neration phase is generally activated by the ECU 450 when an actual value of a quantity of soot accumulated in the DPF 282 exceeds a threshold value thereof. The soot threshold value may be empirically determined during a calibration activity and stored in the memory system 460. The actual value of accumulated soot quantity can be de-termined by the ECU 450 using a sensor or using an estimating method.

The LNT regeneration phase is generally activated by the ECU 450 when a OFF regeneration phase is currently active and an actual value of a quantity of NQ and SQ accumulated in the LNT 281 exceeds a threshold value thereof. Also in this case, the NO and SQ threshold value may be empirically determined during a calibration activity and stored in the memory system 460, whereas the actual value of accumulated NQ and SQ quantity may be determined by the ECU 450 using a sensor or using an estimating method. As a result of these control strategies, the DPF regeneration phase is generally performed more frequently than the LNT regeneration phase, but every LNT regeneration phase is al- ways performed during a DPF regeneration phase. This fact is advanta-geous because the activation of both the DPF regeneration phase and the LNT regeneration phase requires to increase the temperature of the aftertreatment system 270, so as to heat up and maintain the DPF 282 and/or the LNT 281 at temperature values that promote the burning of the accumulated soot and the reduction of the accumulated NQ and SC,< respectively.

In order to attain this temperature increase, the ECU 450 may operate the fuel injectors 160 so as to perform after-injections and post- injections of fuel into the cylinders 125 of the ICE 110. The after-injections are small fuel quantities that are injected in an engine cylinder once the respective piston has passed the Top Dead Center (Tm) position. These after-injected fuel quantities burn inside the engine cylinder 125 without generating torque at the crankshaft 145, but increasing the temperature of the exhaust gases that will flow through the DPF 282 and LNT 281. The post-injections are small fuel quantities that are injected into an engine cylinder 125 when the re- spective exhaust valves 215 are already opened, so that they exit un-burnt from the engine cylinder 125 without generating torque to the crankshaft 125. As a consequence, these post-injected fuel quantities burn inside the aftertreatment system 270 raising the temperature of the DPF 282 and LINT 281. The number of after-injections and post-injections to be performed during the regeneration phase, as well as the fuel quantity injected by each of the after-injections and post- injections, are determined by the ECU 450 using an empirically cali- brated map stored in the memory system 460, which correlates the val- ue of these quantities to the value of a plurality of engine operat-ing parameters, including the mechanical power that the ICE 110 is requested to deliver to the crankshaft 145 (engine load) -In general, this empirical map is calibrated such that the greater is the engine load the smaller is the quantity of after and post injected fuel re-quested to carry out the regeneration phase.

The MGU 500 is an electric machine, namely an electro-mechanical energy converter, which is able either to convert electricity sup-plied 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 genera-tor) . 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 elec-tric windings conj-iected to the battery 600, or vice versa. When the NGU 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 op- erates as electric generator, the rotation of the rotor causes a rel-ative 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 ei-ther 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 power-train 100, so as to be able to deliver or receive mechanical power to and form 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 ge-nerator, especially when the motor vehicle is breaking, 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 con-trol system.

Turning now to the ECU 450, this apparatus may include a digital cen-tral processing unit (CPU) in conununication with the memory system 460 and an interface bus. The memory system 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 memory system 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. -17

In order to carry out these methods, the ECU 450 is in corrmunication 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 sig- nals from various sensors configured to generate the siguals in pro-portion to various physical parameters associated with the ICE 110, the MGU 500 and the battery 600. The sensors include, but are not li- mited to, a mass airflow and temperature sensor 340, a manifold pres-sure and temperature sensor 350, a combustion pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pres- sure sensor 400, a camshaft position sensor 410, a crankshaft posi-tion 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 state of charge of the battery 600. Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to con-trol the operation of the ICE 110 and the F4GU 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 corrinunication between the ECU 450 and the vari-ous sensors and devices, but some are omitted for clarity.

According to the present embodiment, the ICE 110 and the MGU 500 are controlled by the ECU 450 according an Hybrid Operating Strategy (HOS). During the propulsion of the motor vehicle, the HOS provides for continuously repeating the routine which is shown in the f low-chart of figure 2, and which ccmprises the essential steps of: -determining (block 10) an overall value P of mechanical power to be delivered to the final drive of the motor vehicle by the hybrid powertrain as a whole, -splitting (block 20) this overall value P0 in a contributing value F of mechanical power to be requested to the ICE 110, and a contributing value P of mechanical power to be requested to the ?4GU 500, and then of -operating (block 30) the ICE 110 to deliver the contributing val- ue P of mechanical power, and the £IGU 500 to deliver contribut-ing value P of mechanical power.

In the present example, where the 1GU shaft 505 is mechanically con-nected with the final drive of the motor vehicle through the ICE crankshaft 145, the value P could alternatively indicate the overall mechanical power to be delivered to the ICE crankshaft 145 itself. In that case, also the contributing values Pj and P 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.

The splitting of the overall value P may be performed by the ECU 450 with the aid of a predetermined polynomial function, hereafter re-ferred as target function, that quantifies the overall power losses PL0 of the hybrid powertrain 100, on the basis of an unknown value x of mechanical power to be delivered by the ICE 110 and an unknown value y of mechanical power to be delivered by the MGU 500: FL,,,, = f(x, y) In other words, the unknown value x and y are variables of the target function f(x, y). The predetermined target function f(x, y) may be stored in the memory system 460 associated to the ECU 450.

More particularly, the HOS provides for the ECU 450 to determine, among the infinite couples of power values (x, y) which satisfy the equation: IoI =X+Y the specific couple of power values which also minimize the target function, namely which minimize the value PL of the overall power losses of the hybrid powertrain 100.

The power values of the so determined couple are then respectively assumed as ICE contributing value (P1) and as MGU contributing value (P)1 so that the contributing values P) satisfies both the following conditions: = + 1flg7i = mm f(x, y) Two alternative approaches are known and may be used by the ECU 450 to determine the couple of power values P) which minimize the target function f(x, y): a step-by-step approach or an integral ap-proach.

It should be understood that the contrThuting value P of the MW 500 may result either positive or negative. If the contributing value P is positive, it means that the MW 500 is requested to operate as an electric motor that delivers torque to the final drive of the motor vehicle. If the contributing value P is negative, it means that the MGU 500 is requested to operate as an electric generator that charges the battery 600.

According to the present entodiment, the target function may be de-scribed by the following equation: PL,1,, =f(x,y)=F1 -i-F2 ÷F3 +F4 -f-F5 wherein F1,..., F5 arethe so called terms of the polynomial target func-tion.

The first term FL of the target function may be described by the fol-lowing equation: F1 = PL1 wherein k1 is a constant and PL1 is a value that quantifies the power lost by the ICE 110, as a difference between the energy of the un-burned fuel and the energy actually delivered by the ICE 110 to the final drive of the motor vehicle. The value PLj may be calculated ac-cording to the following equation: PL1 =H, .Q1, -x=fl-z).Q,,, H1 so that: F =k.fl =k1 *(H *Q CJ-k [(1 7)Qfi,d.H] wherein H1 is the value of the heat of combustion of the fuel, is the value of the mass flow of fuel injected into the ICE 110, x is the unknown value of mechanical power to be delivered by the ICE 110, and r is the value of an efficiency parameter that accounts for both the thermo-inechanical 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 F of the target function may be described by the fol-lowing equation: F2 = k2 wherein k2 is a constant and PL,j is a value that quantifies an addi-tional 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 PL,1 may be calculated according to the following equation:

I

P L - 1ice 7,1cc -I \ ice, iW,n,, ,ve,crild,j so that: ( F2 = k, PLrice = k2 ICeWUnfl rice k ce, nunu -"icr.CO I,! ) wherein Tjwa is a nominal value of the ICE temperature after the completion of the warm-up phase, Tj,d is a nominal value of the ICE temperature before the warm-up phase, T1 is an actual value of the ICE temperature, and P is batt is the power supplied by the battery 600. The nominal values and Tj,1d can be determined during an experimental activity and stored in the memory system 460 associated with the ECU 450; the actual value T1 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 and oil temperature sensors 380, and the exhaust temperature sensors 430; the value P 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 fol-lowing equation: F; = PL,g1, wherein k3 is a constant and RL is a value that quantifies the power lost by the MW 500, as a difference between the chemical energy of the battery 600 and the energy actually delivered by the ["130 500 to the final drive of the motor vehicle, thereby taking into account the chemical efficiency of the battery 600, the electromechanical effi-ciency of the MW 500 and the friction loss in the kinematical chain connecting the MGU 500 to the final drive of the motor vehicle. The value FL1 may be calculated according to the following equation: PL,j:g,, = chcmbcill -= -Y so that: F3 = k3 = k3 (;,eniha,g -y) = k3. (J -.v) wherein is a value of an electric power generated by the bat-tery 600, I is a value of an electric current absorbed by the MOO 500, V is a value of a tension measured at battery 600 poles at open circuit, and y is the unknown value of mechanical power to be deli- vered by the MGU 500. The values I and V can be determined by mea-suring MaT 500 current and battery 600 voltage characteristics.

The fourth term F4 of the target function may be described by the fol-lowing equation: F4 = PL.

wherein k is a constant and PL is a value that quantifies a ficti-tious increase/decrease of power loss, which is introduced if the current value of the state of charge (SOC) 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 memory system 460 as-sociated with the ECU 450. The value PL3 may be calculated according to the following equation: = (&a,i -,xh) so that: F4 = = -(ha,, -ñau,slufl)j wherein C1,3 is a value of a non-dimensional quantity caprised be-tween -1 and +1, which is used to target the battery 600 state of charge within the acceptable range, Pi is a value of actual power absorbed or released by the battery 600, is a fictitious val- ue of battery power used to target the ideal state of charge of bat- tery 600. The values C1,8, Pj can be determined by a proper ca-libration activity, whereas P can be determined from the current and voltage measurement on the MGU 500.

The fifth term F'5 takes generally into account whether a regeneration phase of the DEE' 282 and/or of the LNT 2B1 is currently active or not.

In particular, the value of the fifth term F'5 is set to zero, whenever the ECU 450 detects that no regeneration phase is active, and it is evaluated, whenever the ECU 450 detects that a regeneration phase is currently active.

When a regeneration phase is active, the value of the fifth tent's F5 may be calculated by the ECU 450 according to the following equation: F5 =k *PSrgg wherein k5 is a constant and PS is a value that quantifies a thermal power lost by the ICE 110 for heating up the aftertreatment system 270 during the regeneration phase of the DPF 282 and/or of the uqt 281. The value PS may be calculated according to the following equa-tion: PS Peg = pox! + Q jvxl,qpcr). LHV so that: F5 = PSpeg = k5. l(Qjuti,paw Qiue;.aj,er). LHV] wherein Qthe1,,st is a value of a fuel quantity to be injected during the regeneration phase by means of the post-injections, Q,after is a value of a fuel quantity to be injected during the regeneration phase by means of the after-injections, and LHV is the low heating value of the fuel. The low heating value of the fluid is a constant that may be stored in the memory system 460. The values Qf',st and Qeuei,aeter de-pend on the unknown value x of the mechanical power to be delivered by the ICE 110. In particular, the values and Qthel,aaer may be determined by the ECU 450 using the unknown value x as input of the empirically calibrated map that is used by the ECU 450 itself to con- trol the fuel injector 160 during the regeneration phase, as ex-plained before.

From the above it follows that, thanks to the fifth term F5 of the target function, the HOS takes effectively into account the thermal power lost by the ICE 110 to heat the aftertreatment system 270 dur- ing a regeneration phase of the 0FF 282 and/or LNT 281. As a conse-quence, during such a regeneration phase, the HOS may advantageously increase the ICE contributing value F1 in order to reduce the quanti-ties of after and post injected fuel to be supplied, the duration of the regeneration phase and therefore the overall fuel consumption in this phase. Jn addition, the HOS may increase the ICE contributing value P1 to the point that the corresponding MGU contributing value P becomes negative, with the consequence that the MGU 500 operates as an electric generator for recharging the battery 600. In this way, the heat generated by the ICE 110 during the regeneration phase may be advantageously used not only to perform the regeneration phase It-self but also to generate electrical power.

The value of the constants ki, k2, k3, k4, k5 involved in the target function are empirically calibrated and *stored in the memory system 460 associated to the ECU 450.

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 exam- pies, and are not intended to limit the scope, applicability, or con- figuration in any way. Rather, the forgoing summary and detailed de-scription will provide those skilled in the art with a convenient road map for implementing at least one exemplary enbodiment, it being understood that various changes may be made in the function and ar-rangement of elements described in an exemplary errbodijnent without departing from the scope as set forth in the appended claims and in their legal equivalents. PEE4S block block

30 block hybrid powertrain internal combustion engine engine block cylinder 130 cylinder head camshaft piston crankshaft combustion charter 155 cam phaser fuel injector fuel rail fuel pump fuel source 200 intake manifold 205 air intake pipe 210 intake port 215 valves 220 exhaust port 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine 260 intercooler 270 exhaust system 275 exhaust pipe 280 WC 281 LNT 282 DPF 290 VOT actuator 300 exhaust gas recirculation system 310 EGR cooler 320 EGR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 in-cylinder pressure sensor 380 coolant and oil temperature and level sensors 400 fuel rail pressure sensor 410 camshaft pcsition sensor 420 crankshaft position sensor 430 exhaust pressure and temperature sensors 440 EGR temperature sensor 445 accelerator pedal position sensor 446 accelerator pedal 450 ECU 460 memory system 500 motor-generator electric unit 505 MGU shaft 510 transmission belt 600 battery 605 measuring circuit

Claims (1)

1. <claim-text>1. A method for operating a hybrid powertrain (100) comprising a mo- tor-generator electric unit (500) and an internal combustion en-gine (110) equipped with an aftertreatment device (281, 282), wherein the operating method comprises the steps of: -determining an overall value (F) of power to be delivered by the hybrid powertrain (100), -using this overall value (P) and a predetermined polynomi- al function having as variables an unknown value (x) of pow-er to be delivered by the internal combustion engine (110) and an unknown value (y) of power to be delivered by the mo- tor-generator electric unit (500), to determine a contribut-ing value (P) of power to be requested to the internal combustion engine and a contributing value (P) of power to be requested to the motor-generator electric unit (500), and -operating the internal combustion engine (110) and the mo-tor-generator electric unit (500) to deliver the respective contributing value of power (Pj, P), and wherein the predetermined polynomial equation comprises a term whose value is zero, if no regeneration phase of the after-treatment device (281, 282) is active, and it depends on a value (PS) of a thermal power lost by the internal combustion engine (110) to heat the after-treatment device (281, 282), if a regene-ration phase of the aftertreatinent device (281, 282) is active.</claim-text> <claim-text>2. A method according to claim 1, wherein the thermal power value (PS1) is determined with the steps of: -determining a value (Qtuei,atter) of a fuel quantity to be sup- plied to the internal combustion engine by means of after-injections during the regeneration phase, -determining a value of a fuel quantity to be sup- plied to the internal combustion engine by means of post-injections during the regeneration phase, -calculating the thermal power value as a function of these determined values (Qeuei,aeter, Qni,st) of the fuel quantity and a heating value (LHT) of the fuel.</claim-text> <claim-text>3. A method according to claim 2, wherein the thermal power value (PS) is calculated by multiplying the heating value (LI-iT) of the fuel by the determined values (Q,after, Qi,t) of the fuel quantity supplied by means of the after-injections and by means of the post-injections.</claim-text> <claim-text>4. A method according to any claim from 2 to 3, wherein the fuel quantity value (Qthel,after) to be supplied by means of the after-injections and the fuel quantity value (Qrues,est) to be supplied by means of the post-injections are determined on the basis of the unknown value (x) of power to be delivered by the internal combustion engine (110).</claim-text> <claim-text>S. A method according to claim 4, wherein the fuel quantity value (Qfuea,after) to be supplied by means of the after-injections and the fuel quantity value (Qei,t) to be supplied by means of the post-injections are determined through an empirically calibrated map that correlates these fuel quantity values (Qftel,aftet, Qfuel,çost) to the unknown value (x) of power to be delivered by the internal combustion engine (110).</claim-text> <claim-text>6. A computer program comprising a computer code suitable for per-forming the method according to any of the preceding claims.</claim-text> <claim-text>7. A computer program product on which the computer program of claim 6 is stored.</claim-text> <claim-text>8. n electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 6.</claim-text> <claim-text>9. .11⁄2n apparatus for operating a hybrid powertrain (100) comprising a motor-generator electric unit (500) and an internal combustion engine (110) equipped with an aftertreatnent device (281, 282), wherein the apparatus comprises: -means (445, 450) for determining an overall value (Ptht) of mechanical power to be delivered by the hybrid powertrain (100) -means (450) for using the overall value (P0) of mechanical power and a predetermined polynomial equation having as va-riables an unknown value (x) of power to be delivered by the internal combustion engine (110) and an unknown value (y) of power to be delivered by the motor-generator electric unit (500), to calculate a contributing value (P) of power to be requested to the internal combustion engine (110) and a contributing value (P) of pcwer to be requested to the mo-tor-generator electric unit (500), and -means (450) for operating the internal combustion engine (110) and the motor-generator electric unit (500) to deliver the respective contributing value of power (Pj, P) and wherein the predetermined polynomial equation comprises a term whose value is zero, if no regeneration phase of the after-treatment device (281, 282) is active, and it depends cn a value (PS) of a thermal power lost by the internal combustion engine (110) to heat the aftertreatment device (281, 282), if a regene-ration phase of the aftertreatment device (281, 282) is active.</claim-text> <claim-text>10. A hybrid powertrain (100) compriSing an motor-generator electric unit (500), an internal combustion engine (110) equipped with an aftertreatrrient device (281, 282), and an electronic control unit (450) configured to: -determine an overall value (Ptht) of power to be delivered by the hybrid powertrain (100), -use this overall value (Pwt) and a predetermined polynomial function having as variables an unknown value (x) of power to be delivered by the internal combustion engine (110) and an unknown value (y) of power to be delivered by the motor-generator electric unit (500), to determine a contributing value (P1) of power to be requested to the internal combus-tion engine (110) and a contributing value (P) of power to be requested to the motor-generator electric unit (500), and -operate the internal combustion engine (110) and the motor- generator electric unit (500) to deliver the respective con-tributing value of power (P1, wherein the predetermined polynomial equation comprises a term whose value is zero, if no regeneration phase of the aftertreat-ment device (281, 282) is active, and it depends on a value (PS) of a thermal power lost by the internal combustion engine (110) to heat the aftertreatment device (281, 282), if a regene-ration phase of the aftertreatment device (281, 282) is active.</claim-text>