GB2498593A

GB2498593A - Hybrid powertrain response to EGR cooler clogging

Info

Publication number: GB2498593A
Application number: GB1201212.6A
Authority: GB
Inventors: Gianmarco Brunetti
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-01-23
Filing date: 2012-01-23
Publication date: 2013-07-24
Also published as: GB201201212D0

Abstract

An embodiment of the invention provides a method for operating a hybrid powertrain 100 comprising a motor-generator electric unit 500 and an internal combustion engine 110 equipped with an EGR cooler (310 see fig 2), wherein the operating method comprises the steps of determining an overall power value to be delivered by the hybrid power-train 100, splitting the overall power value into a first contributing power value to be delivered by the internal combustion engine 110 and a second contributing power value to be delivered by the motor-generator electric unit 500; monitoring an index indicative of a clogging level of the EGR cooler (310); and increasing the first contributing power value, if the monitored EGR cooler clogging level index fulfils a predetermined condition. The invention integrates EGR cooler protection strategy with hybrid control to enable reduced NOx emissions even during urban driving.

Description

METHOD FOR OPERATING A HYBRID POWERTRAIN

TECHNICAL FIELD

The present invention relates to a method for 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 ofa car.

A hybrid powertrain particularly comprises 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 op- erate as an electric motor for assisting or replacing the ICE in propelling the motor vehi-cle, and can also operate as an electric generator, especially when the motor vehicle is braking, for charging an electrical energy storage device (battery) connected thereto. Be-sides, 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 control system according to a dedi-cated hybrid control strategy. During the traction of the motor vehicle, the hybrid control strategy provides for determining an overall value of mechanical power to be delivered to the wheels 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 me-chanical power to be requested to the MGU, and then for operating the ICE and the MGU to deliver to the wheels of the motor vehicle the respective contributing value of mechanical power.

In greater details, the splitting of the above mentioned overall power value is convention-ally optimized by determining, among the infinite couples of first and second contributing power values whose addition is equal to the overall power value, the couple that mini-mize the 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 exam- pie because it has been dissipated due to specific aspect of the hybrid powertrain opera-tion.

As a consequence of this optimization, the first contributing power value is always posi-tive, whereas the second contributing power value may be &ther positive or' negative. ii the second contributing power value is positive, the MGU is operated as an electric mo-tor that actually supplies mechanical power to the final drive. If the second contributing power value is negative, the MGU is operated as an electric generator that actually ab-sorbs 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 cou-pled 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.

In order to reduce the amount of nitrogen oxides (NOr) produced during the fuel combus-tion, the internal combustion engine may be equipped with an exhaust gas recirculation (EGR) provided for routing back and mixing an appropriate amount of exhaust gas with the induction air. Conventional EGR systems essentially comprise an EGR conduit that fluidly connects the exhaust manifold with the intake manifold and an EGR valve for regulating the flow rate of exhaust gas through the EGR conduit. In order to improve the NO reduction effect, the EGR systems may further comprise an EGR cooler, which is located in the EGR conduit to cool down the exhaust gases before they are mixed with the induction air.

A side effect of these EGR systems is that the wet soot and the Hydrocarbon (HC) con-tained in the exhaust gases may stick to the internal walls of the EGR cooler, thereby progressively clogging the latter and thus reducing the efficiency of the entire EGR sys-tern. This event, usually referred as EGR cooler fouling, happens when the EGR cooler operates under certain critical conditions. These critical conditions are generally met when the ICE produces high quantities of soot, high quantities of HC, exhaust gases having low temperatures and/or when the temperature of the coolant in the EGR cooler is low. By contrast, there are other EGR cooler operating conditions, under which the ex- haust gases flowing through the EGR cooler 310 are able to clean the latter from the ac- cumulated soot and HC. These cleaning condition are generally met when the ICE pro-duces exhaust gases having high temperatures and/or when the temperature of the coolant in the EGR cooler is high.

For these reasons, many engine control units (ECU) implements an EGR cooler protec-tion strategy, which provides for diagnosing whether the EGR cooler is operating under a critical condition or under a cleaning condition. This diagnosis is generally performed on the bess of a p!ura!ity of angina operating pararrieters, such as for exampie engine speed and engine load, and sometimes also on the basis of the EGR coolant tempera- ture. lithe EGR cooler is diagnosed to operate under a critical condition, the ECU incre-ments the value of an index representative of the clogging level of the EGR cooler itself.

lithe EGR is diagnosed to operate under a cleaning condition, the ECU decrements the value of the clogging level index. The EGR may also be diagnosed to operate neither under a critical condition nor under a cleaning condition. In this case, the ECU does not modify the value of the clogging level index. As a mailer of fact, the clogging level index is a counter that account for the clogging level of the EGR cooler. When the clogging level index exceeds a calibrated threshold value thereof, the ECU closes the EGR valve so that the exhaust gases bypass the EGR system. Afterwards, the EGR valve is opened only when a cleaning operating condition for the EGR cooler is diagnosed.

A drawback of this EGR cooler protection strategy is that the above mentioned critical operating conditions usually occur during the urban driving cycles of the motor vehicle, so that the EGR cooler is often bypassed and the internal combustion engine of the hy-brid powertrain emits great quantities of NON.

In view of the above, it is an object of the present invention to better integrate the EGR cooler protection strategy with the hybrid powertrain operating strategy.

Another object is that of providing an improved hybrid powertrain operating strategy which is able to reduce the NO emissions even during the urban driving cycles of the motor vehicle.

Still another abject is to reach these goals with a simple, rational and rather inexpensive solution.

SUMMARY

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 features of the embodiments of the invention.

In particular, 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 an EGR cooler, wherein the operating method comprises the steps of: -determining an overall power value to be delivered by the hybrid powertrain, -splitting the overall power value into a first contributing power value to be requested to the internal combustion engine and a second contributing power value to be requested to the motor-generator electric unit, -monitoring an index indicative of a clogging level of the EGR cooler, and -increasing the first contributing power value1 if the monitored EGR cooler clogging level index fulfils a predeterrn ned condfticn.

As a matter of fact, if the predetermined condition is fulfilled, part of the power to be re- quested to the motor-generator electric unit is shifted and added to the power to be re-quested 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 fouling of the EGR cooler, for example exhaust gases having higher temperature.

At the same time, the extra power requested to the internal combustion engine may cor- respond to an electric generation of the motor-generator electric unit that leads to a posi-tive energy balance.

According to an aspect of the invention, the predetermined condition for increasing the first contributing power value is fulfilled if the monitored EGR cooling clogging level index is increasing.

II means that the first contributing power value is forcedly increased if the EGR cooler is operating under a critical condition, namely a condition in which the internal combustion is producing high quantities of soot and/or high quantities of HC and/or exhaust gases having low temperatures. In this case, the increase of the first contributing power value causes the internal combustion engine to move from this critical condition towards oper-ating conditions under which there is a higher exhaust gas temperature, and/or a lower soot production and/or a lower HC production, thereby preventing the EGR cooler foul-ing.

According to another aspect of the invention, the predetermined condition for increasing the first contributing power value is fulfilled if the monitored EGR cooling clogging level index has exceeded a threshold value thereof.

It means that the first contributing power value is forcedly increased if the EGR cooler clogging level has already reached a critical value, for example a value for which the EGR cooler protection strategy has already closed the EGR valve so that the exhaust gases bypass the EGR system. In this case, the increase of the first contributing power value causes the internal combustion engine to create the cleaning condition under which the EGR cooler may be cleaned up, thereby removing the soot and the IC that have been already accumulated therein.

Another aspect of the invention provides that 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 that the first contributing power value is 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 solu-tion for performing the power shifting betwcen the motor-generator electric unit and the internal combustion engine, namely for increasing the first contributing power value while correspondently decreasing the second contributing power value.

According to an aspect of the invention, the method may comprise the steps of: -determining a desired value of power to be delivered by the internal combustion engine, -calculating a value of an extra quantity of fuel to be injected in the internal combustion engine to increase the power to be delivered by the internal combustion engine itself up to the desired power value, and -calculating the value of the above named additional term as a function of the calculated value of the extra fuel quantity.

This solution has the advantage of improving the power shifting between the motor-generator electric unit and the internal combustion engine.

An aspect of the invention provides for the method to comprise the steps of: -determining an actual value of a plurality of engine operating parameters, and -determining the desired power value to be delivered by the internal combustion engine from an empirically determined calibration map, on the basis of the determined actual values of the engine operating parameters.

In this way, the operating method may perform the power shifting using different desired Qalues of the power to be delivered by the internal combustion engine for different values of the engine operating parameters, thereby further improving the efficiency of the power shifting between the motor-generator electric unit and the internal combustion engine.

According to an aspect of the invention, the above mentioned engine operating parame-ters include engine speed and engine load.

This solution is advantageous because the cited parameters greatly affect the fouling of the EGR cooler.

The methods 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 de-scribed above, and in the farm of a computer program product on which the computer program is stored. The method can be also embodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represent a computer pro-dram to carry out all steps of the method.

Another embodiment of the present invention provides an apparatus for operating a hy-brid powertrain comprising a motor-generator electric unit and an internal combustion engine equipped with an EGR cooler, wherein the apparatus comprises: -means for determining an overall power value to be delivered by the hybrid powertrain, -means for sphtting the overall power value into a first contributing power value to be de-livered by the interna! combustion engine and a second contributing power value to be delivered by the motor-generator electric unit, -means for monitoring an index indicative of a clogging level of the EGR cooler, and -means for increasing the first contributing power value, if the monitored EGR cooler clogging level index fulfils a predetermined condition.

This embodiment of the invention has the same advantages of the method disclosed above, in particular that of making the hybrid powertrain operating strategy interact with the EGR cooler protection strategy and vice versa, According to an aspect of this embodiment, the predetermined condition for the above named means for increasing the first contributing power value to actually increase the first contributing power value is fulfilled if the monitored EGR cooling clogging level index is increasing.

This aspect has the advantage of operating of the internal combustion engine so as to move from a critical condition for the EGR cooler fouling towards a not critical condition.

According to another aspect of this embodiment invention, the predetermined condition for the above named means for increasing the first contributing power value to actually increase the first contributing power value is fulfilled if the monitored EGR cooling clog-ging level index has exceeded a threshold value thereof.

This aspect has the advantage of operating of the internal combustion engine so as to create a cleaning condition under which the EGR cooler may be cleaned up, thereby re-moving the soot and the I-IC that have been already accumulated therein.

Another aspect of the embodiment provides that the means for splitting the overall power value comprise means for minimizing a predetermined polynomial function representing an overall power loss of the hybrid powertrain, and that the means for increasing the first contributing power value comprises means for adding to the predetermined polynomial function an additional term whose value represents an additional power loss of the inter-nal combustion engine.

This aspect 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 first contributing power value while correspondently decreasing the second contributing power value.

According to an aspect of this embodiment, the apparatus may also comprise: -means for determining a desired value of power to be delivered by the internal combus-tion engine, -means for calculating a value of an extra quantity of fuel to be injected in the internal combustion engine to increase the power to be delivered by the internal combustion en-gino itself up to the desired power value, arid -means for calculating the value of the above named additional term as a function of the calculated value of the extra fuel quantity.

An aspect of the embodiment provides for the apparatus to additionally comprise: -means for determining an actual value of a plurality of engine operating parameters, and -means for determining the desired power value to be delivered by the internal combus- tion engine from an empirically determined calibration map, on the basis of the deter-mined actual values of the engine operating parameter& In this way, the apparatus may perform the power shifting using different desired values of the power to be delivered by the internal combustion engine for different values of the engine operating parameters, thereby further improving the efficiency of the power shift-ing between the motor-generator electric unit and the internal combustion engine.

According to an aspect of this embodiment, the above mentioned engine operating pa-rameters include engine speed and engine load.

This solution is advantageous because the cited parameters greatly affect the fouling of the EGR cooler Still another embodiment of the invention provides a hybrid powertrain comprising an motor-generator electric unit, an internal combustion engine equipped with an EGR cooler, and an electronic control unit configured to: -determine an overall power value to be delivered by the hybrid powertrain, -split the overall power value into a first contributing power value to be delivered by the internal combustion engine and a second contributing power value to be delivered by the motor-generator electric unit, -monitor an index indicative of a clogging level of the EGR cooler, and -increase the first contributing power value, if the monitored EGR cooler clogging level index fulfils a predetermined condition.

Also this embodiment of the invention has the same advantages of the method disclosed above, in particular that of making the hybrid powertrain operating strategy interact with the EGR cooler protection strategy and vice versa.

According to an aspect of this embodiment, the predetermined condition for the elec-tronic control unit to increase the first contributing power value is fulfilled if the monitored EGR cooling clogging level index is increasing.

This aspect has the advantage of operating of the internal combustion engine so as to move from a critical condition for [he EGR cooierfouiing towards a not critical condition.

According to another aspect of this embodiment invention, the predetermined condition for the electronic control unit to actually increase the first contributing power value is ful-filled if the monitored EGR cooling clogging level index has exceeded a threshold value thereof.

This aspect has the advantage of operating of the internal combustion engine so as to create a cleaning condition under which the EGR cooler may be cleaned up, thereby re-moving the soot and the HC that have been already accumulated therein.

Another aspect of the embodiment provides that the electronic control unit is configured to split the overall power value by minimizing a predetermined polynomial function repre-senting an overall power loss of the hybrid powertrain, and that the electronic control unit is configured to increase the first contributing power value by adding to the predeter-mined 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 solu-tion for perforrriing the power shifting between the motor-generator electric unit and the internal combustion engine, namely for increasing the first contributing power value while correspondently decreasing the second contributing power value.

According to an aspect of this embodiment, the electronic control unit is also configured to: -determine a desired value of power to be delivered by the internal combustion engine, -calculate a value of an extra quantity of fuel to be injected in the internal combustion engine to increase the power to be delivered by the internal combustion engine itself up to the desired power value, and -calculate the value of the above named additional term as a function of the calculated value of the extra fuel quantity.

An aspect of this embodiment provides for the electronic control unit to be configured to: -determine an actual value of a plurality of engine operating parameters, and -determine the desired power value to be delivered by the internal combustion engine

B

from an empirically determined calibration map, on the basis of the determined actual values of the engine operating parameters.

In this way, the electronic control unit may perform the power shifting using different de-sired values of the power to be delivered by the internal combustion engine for different values of the engine operating parameters, thereby further improving the efficiency of the powersh iffing between the motor-generator electric unit and the internal combustion en-gine.

According to an aspect of the embodiment, the above mentioned engine operating pa-rameters include engine speed and engine load.

BRIEF DESCRIPTION OF THE DRAWINGS

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 vehicle.

Figure 2 shows in more details an internal combustion engine belonging to the hybrid powertrain of figure 1.

Figure 3 is a section A-A of the internal combustion engine of figure 2.

Figure 4 is a flowchart of a method for operating the hybrid powertrain of figure 1.

Figure 5 is a flowchart of an EGR cooler protection strategy involved in the operating method of figure 4.

DETAILED DESCRIPTION

Some embodiments may include a motor vehicle's mild hybrid powertrain 100, 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 de-vice (battery) 600 electrically connected to the MGU 500, and an electronic control unit (ECU) 450 in communication with a memory system 460.

As shown in figure 2 and 3, the 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 con-nected with a final drive of the motor vehicle, for example to the 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, re-sulting in hot expanding exhaust gasses that cause 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 160 from a fuel rail 170 in fluid communication 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 150 from the port 210 and alternately allow exhaust gases to exit through at least one exhaust port 220. In some examples, a cam phaser 155 may selectively vary the timing between the cam-shaft 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 ambient environment to the intake mani-fold 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 tur-bocharger 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 rotates by receiving ex-haust 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 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 andlor include a waste gate.

In order to reduce the amount of nitrogen oxides (NO) produced during the fuel combus-tion, the ICE 110 may include an exhaust gas recirculation (EGR) system 300, which is provided for routing back and mixing an appropriate amount of exhaust gas with the in-duction air. The EGR system 300 may include an EGR conduit 305 coupled between the exhaust manifold 225 and the intake manifold 200, and an EGR cooler 310 located in the EGR conduit 305 to reduce the temperature of the exhaust gases in the EGR system 300, before they are mixed with the induction air in the intake manifold 200. In the EGR cooler 310 the exhaust gases are cooled down by a coolant that flows in a coolant circuit (not shown). The coolant circuit may be integrated with an engine coolant circuit provided for cooling down the components of the ICE 110, including the engine block 120 and the cylinder head 130. An EGR valve 320 is located in the EGR conduit 305 to regulate the flow of exhaust gases in the EGR system 300.

The exhaust gases exit the turbine 250 and are directed into an exhaust system 270.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment devices include, but are not limited to, catalytic converters (two and three way), oxidation cata-lysts (DOC) 280, lean NO traps (LNT) 281, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, and particulate filters (DPF) 282.

The MGU 500 is an electric machine, namely an electra-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 electric-ity that charges the battery 600 (i.e., to operate as clactric generator). n geater deiaHs, 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 com-prise 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 mo-tor, 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 asyn-chronous 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 100, so as to be able to de-liver 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 ex- ample, the MG(J shaft 505 is connected with the ICE crankshaft 145 through a transmis-sian 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.

Turning now to the ECU 450, this apparatus may include a digital central processing unit (CPU) in communication with the memory system 460 and an interface bus. The memory system 460 may include various storage types including optical storage, magnetic stor- age, solid state storage, and other non-volatile memory. The interface bus may be con-figured 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.

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 prcssure and temperature seisor 350, a com-bustion pressure sensor 360, coolant temperature sensor 385, oil temperature sensor 385, a fuel rail pressure 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 cir-cuit 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 control the operation of the ICE 110 and the MGU 500, including, but not limited to, the fuel in-jectors 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 accord-ing a hybrid control strategy. During the traction of the motor vehicle, the hybrid control strategy provides for continuously repeating the routine which is shown in the flowchart of figure 4, and which comprises the general steps of: -determining (block 700) an overall value P0 of mechanical power to be delivered to the final drive of the motor vehicle by the hybrid powertrain 100 as a whole, -splitting (block 705) this overall value P0 into a first contributing value Pice of mechani- cal power to be requested to the ICE 110, and a second contributing value P of me-chanical power to be requested to the MGU 500, and then of -operating (block 710) the ICE 110 to deliver the first contributing value Pi of mechani-calpower, and the MGU 500 to deliver the second contributing value P9 of mechanical power.

In the present example, where the MGU shaft 505 is mechanically connected with the fi- nal drive of the motor vehicle through the ICE crankshaft 145, the value PtOL could alter-natively indicate the overall mechanical power to be delivered to the ICE crankshaft 145 itself. In that case, also the contributing values P 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 P is always positive, as the ICE can only generate mechanical power to be transferred to the crankshaft 145. Con- versely, the second contributing value Pmgu may be either positive or negative. If the sec-and contributing value P, is positive, the MGU 500 is operated as an electric motor that actua!y generates mecharcaI power to the crankshaft 145. if the second contributing value P9 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.

During the operation of the ICE 110, it may happen that the wet soot and the hydrocar-bon (HC) contained in the exhaust gases stick to the internal walls of the EGR cooler 310, thereby progressively clogging the EGR cooler 310 itself and thus reducing the effi-ciency of the whole EGR system 300. As explained in the preamble, this event, usually referred as EGR cooler fouling, happens when the EGR cooler 310 operates under cer- tain critical conditions. These critical conditions are generally met when the ICE 110 pro-duces high quantities of soot, and/or high quantities of HC, and or exhaust gases having low temperatures and/or when the temperature of the coolant in the EGR cooler is low.

By contrast, there are other EGR cooler operating conditions, under which the exhaust gases flowing through the EGR cooler 310 are able to clean the later from the accumu- lated soot and NC, These cleaning condition are generally met when the ICE 110 pro-duces exhaust gases having high temperatures and/or when the coolant temperature is high. Moreover, there are normal EGR cooler operating conditions (i.e. neither critical nor cleaning), under which the exhaust gases flowing through the EGR cooler 310 has sub-stantially no effect on the fouling of the EGR cooler 310.

For these reasons, the ECU 450 implements an EGR cooler protection strategy, which uses an index indicative of the clogging level of the EGR cooler 310 related to the fouling of the EGR cooler 310. More particularly, the clogging level index is a counter, whose value is initially set to zero and then progressively updated by the ECU 450 with a cycli-cal routine which is schematically illustrated in the flowchart of figure 5.

This routine firstly provides for diagnosing whether the EGR cooler 310 is currently oper-ating under a critical condition, under a cleaning condition, or under a normal condition (block 800). This diagnosis may be performed by the ECU 450 on the basis of a value of the engine load, for example the contributing power value Pice currently requested to the ICE, and a current value of the engine speed. The engine speed value may be measured by the ECU 450 through the crankshaft position sensor 420. By way of example, the en- gina load value and the engine speed value may be applied to a map, that correspon-dently returns whether the ICE 110 is currently operating under a critical condition or a cleaning condition. This map may be empirically calibrated during an experimental activ-ity and then stored in the memory system 460. In other embodiments, the map may use as input also a value of the coolant temperature, which can be measured by the ECU 450 through the coolant temperature sensor 380, If the diagnosis returns that the EGR cooler 310 is operating under a critical condition, then the current va!ue (fl) i tho dogging ICV& ndex is calculated as the addition of an old value l(fl1) thereof determined during the last preceding cycle and a predetermined quantity x (block 805). If conversely the diagnosis returns that the EGR cooler is operat-ing under a cleaning condition, then the current value 1(n) of the clogging level index is calculated as the difference between the old value l(fl.1) and a predetermined quantity y (block 810). If the diagnosis returns that the EGR cooler 310 is operating under a normal condition, then the current value 1(n) of the clogging level index is maintained equal to the old value 1(n-1)-The current value 1(n) of the clogging level index is then compared with a threshold value th thereof, which represents a condition for which the EGR cooler 310 is considered completely clogged (block 815). The threshold value lth may be empirically determined with an experimental activity and then stored in the memory system 460.

As long as the current value (n) of the clogging level index is below the threshold value l, the cyclical routine is simply repeated. If the current value 1(n) of the clogging level in-dex exceeds the threshold value the ECU 450 closes the EGR valve 320 completely1 such that the exhaust gases bypass the EGR system 300 thereby protecting the EGR cooler 310.

Afterwards, the EGR valve 320 is kept completely closed until the ECU 450 diagnoses that a cleaning operating condition for the EGR cooler 310 has been met. When it hap-pens, the ECU 450 immediately opens the EGR valve 320 and the current value 1(r) of the clogging level index is progressively decremented according to the routine explained above.

Turning now to the hybrid control strategy, the splitting of the overall power value P0 into the first Pice and the second Puigu contributing power values may be performed according to an hybrid optimization strategy (HOS) using a predetermined polynomial function, hereafter referred as target function, which may be stored in the memory system 460 as-sociated to the ECU 450.

The target function quantifies an overall power loss PL0 of the hybrid powertrain 100 as a function of the unknown first Pjce and second Pmgu contributing power values: PLr1,r =f(PjcPmgu) In other words, the first P1 and the second Pmgu contributing power values are variables of the target function.

The I-lOS provides for the ECU 450 to determine, among the infinite couples of contribut-ing power values (P1, Pmgu) that satisfy the equation: got = ,cc + the specific couple of contributing power values which also minimize the target function, namely which minimize the value PL of the overall power loss of the hybrid powertrain 100: f(1ce.'mgu) = mm f Two alternative approaches are known and may be used by the ECU 450 to determine the couple of contributing power values (Pe, Pnigu) 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: PL, ,P,,,,,,)= F +F2 +F +F +P wherein F1, F2, F3, 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: = . FL, wherein k1 is a constant and PLce 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 de- livered by the ICE 110 to the final drive of the motor vehicle. The value PL1 may be cal-culated according to the following equation: =H, .Q _p =(111)Qi,ei [1, so that: = k *PLk = k -(H, Q1i,ei icc) = Ic1 *[(1-q)-Qr,, -II,] wherein H, is the lower heating value of the fuel, Qruei 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 ac-counts 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: F2 = PLTI.C, wherein k2 is a constant and PLt, 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 PLTJCe may be calcu-lated according to the following equation: = [ cc',wurnj -T, ]2.

Tk worm -"ice cold so that: 1 1icc,watin 1Ice 2 -2 lice "2 I T T I halt 1⁄4 ica,wan:i -ice cold) wherein Tjcewm is a nominal value of the ICE temperature after the completion of the warm-up phase, Ticecold is a nominal value of the ICE temperature before the warm-up phase, is an actual value of the ICE temperature, and Pbaft is P is the power sup- plied by the battery 600. The nominal values Iiwarm and TI,coId can be empirically de- termined during an experimental activity and stored in the memory system 460 associ-ated with the ECU 450; the actual value can be measured with the aid of one or more of the temperature sensor of the ICE, including, but not limited to, the manifold tempera-ture 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=kaPLmgzi 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 ac-tually delivered by the MGU 500 to the 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 fol-lowing equation: = -Pg,4 = A -V. -TJrgu so that: = 1c3 *PLmgu =k, X1chem,ba,, P,,,gj)= Ic3 (A.V, -P) wherein Pohen,,ban is a value of an electdc power generated by the battery 600, A is a value of an electric current absorbed by the MGU 500, V is a value of a tension meas-ured 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: F4 = Ic4.

wherein k4 is a constant and PL is a value that quantifies a fictitious 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 associated with the ECU 450. The value PL0 may be calculated according to the following equation: PL = -aIt,sh,fl) so that: F4 = . PL = . -(Pb,, - ii wherein CI,s 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, Pba is a value of actual power absorbed or released by the battery 600, Ptausnjn is a fictitious value of battery power used to target the ideal state of charge of battery 600. The values Ci,soç, PbashIn can be determined by a proper calibration activity, whereas Pbaft can be de-termined from the current and voltage measurement on the MGU 500.

The fifth term F5 is generally used to take into account the fouling condition of the EGR cooler 310.

In particular, the value of the fifth term F5 may be expressed by the following equation: F = Ic5.

wherein k5 is a constant and PLegr is a value that accounts for an extra fuel to be injected in the ICE 110, in order to operate a so called "power shifting", namely to forcedly in-crease the first contributing power value Pice and correspondently decrease the second contributing power value Pmgu.

The value FLegr may be calculated according to the following expression: PLcgr Q.e,icc H, -q wherein H1 is the lower heating value of the fuel, Rice is the unknown first contributing value of power to be requested to the ICE 110, is the value of the Brake Specific Fuel Consumption (BSFC) of the ICE 110 when it generates the first contributing power value P1cc, Pegr is a target value of power that the ICE 110 is desired to generate, is the value of the Brake Specific Fuel Consumption (BSFC)of the ICE 110 when itgen- erates the target power value Pgç, and q is the value of an efficiency parameter that ac-counts for both the thermo-mechariical 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.

Thanks to this expression of the fifth ten-n F5, while minimizing the target function, the Hybrid Optimization Strategy (HOS) automatically tends to minimize also the extra fuel value PLegr, thereby causing the first contributing power value Pice to be equal (or almost equal) to the target value Peg,. In other words, the target power value Pegr represents the value of mechanical power that the ICE 110 is forced to generate due to the activation of the "power shifting".

The target power value P, may be determined by the ECU 450 through a map, which correlates target power values to corresponding values of a plurality of engine operating parameters. In other words, the ECU 450 may be configured to determine an actual value of these engine operating parameters, and then to determine target power value Pegr 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 "power shifting" using different target values Pegr 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 may be the power value P10 requested to the ICE 110 before the activation of the "power shifting'. The map may be an empiri- cally determined calibration map namely a map that is determined during an experimen-tal activity and then stored in the memory system 460. In other embodiments, the map may use as input also a value of the engine coolant temperature, which can be meas-ured by the ECU 450 through the coolant temperature sensor 380.

The lower heating value H1 of the fuel and the value q of the efficiency parameter may be empirically or theoretically determined and then stored in the memory system 460.

The values and of the Brake Specific Fuel Consumption may be deter- mined through an additional map, which correlates the values of the BSFC to corre-sponding values of power to be generated by the ICE 110. Also this additional map may be an empirically determined calibration map that is stored in the memory system 460. ri this way, the ECU 450 may determine the values and i"r of the BSFC by applying to this additional map the power values P1 and Peg1 respectively.

As shown in figure 4, the value of the constant k5 is determined on the basis of the moni- tored index indicative of the clogging level of the EGR cooler 310, which is evaluated ac-cording to the EGR cooler protection strategy described before. More particularly, the clogging level index is applied to a conditional block 715, which is configured to check whether the clogging level index fulfils a predetermined condition or nor.

If this predetermined condition is not fulfilled, then the constant K5 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 P0 and second P,,,9 contributing power values.

If conversely the predetermined condition is fulfilled, then the constant K5 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 "power shifting.

Ingreater details, the predetermined condition implemented in the conditional block 715 may be fulfilled if the clogging level index is increasing, namely If the current value Ifl) thereof is greater than the old value l(fl.1) that has been determined by the EGR cooler protection strategy during the last preceding cycle: 1(a) > (n-I) When this condition is fulfilled, namely if the clogging level index is currently increasing, it means that the ICE 110 is operating such as to create a critical for the fouling of the EGR cooler. As a consequence, the "power shifting" caused by the fifth term F5 of the target function in this case, may have the effect of moving the internal combustion engine from this critical condition towards an operating conditions which is safer for the EGR cooler, for example towards an operating condition under which there is a higher exhaust gas terhperature, and/or a lower soot production, andior a lower HC production. As a matter of fact, the "power shifting" activated according to this specific condition has basically the effect of preventing the EGR cooler fouling.

Other embodiments may provide that the predetermined condition implemented in the conditional block 715 is fulfilled if the clogging level index has exceeded the threshold value 1th thereof, namely if the current value 1(n) of the clogging level index exceeds the threshold value lIh: in) > th When this condition is fulfilled, namely if the clogging level index has exceeded the threshold value l, it means that the EGR cooler 310 is completely clogged and that the EGR cociGr protectbn strategy has closed the EGR valve 320 completely. As a conse-quence, the "power shifting" caused by the fifth term F5 of the target function in this case, may have the effect of moving the internal combustion engine 110 towards operating conditions under which the EGR cooler 310 may be cleaned up, for example an operat-ing condition under which there is a higher exhaust gas temperature, and/or a lower soot production, and/or a lower HG production. As matter of fact, the power shifting' activated according to this latter condition has basically the effect of allowing a more frequent and effective regeneration of the EGR cooler.

Still other embodiments may provide that the predetermined condition implemented in the conditional block 715 is fulfilled either if the clogging level index is increasing, or if the clogging level index has exceeded the threshold value ltb.

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 forgoing 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 in their legal equivalents.

REFERENCES

hybrid powertrain internal combustion engine 120 engine block cy!ir.der cylinder head camshaft piston 145 crankshaft combustion chamber cam phaser fuel injector fuel rail 180 fuel pump fuel source 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 DOC 281 LNT 282 DPF 290 VGT actuator 300 exhaust gas recirculation system 305 EGR conduit 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 temperature sensor 385 cii temperature sensor 400 fuel rail pressure sensor 410 camshaft position 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 700 block 705 block 710 block 715 conditional block 720 block 725 block 800 block 805 block 806 block 810 block 815 block 820 block Pt overall power value Pice first contributing power value P9 second contributing power value 1(o) clogging level index current value l(n1) clogging level index old value x quantity y quantity 91 clogging level index threshold value S Peg, target power value I' fl5 LAIIlLdIIt

Claims

<claim-text>CLAIMS1. A method for operating a hybrid powertrain (100) comprising a motor-generator electric unit (500) and an internal combustion engine (110) equipped with an EGR cooler (310), wherein the operating method comprises the steps of: -determining an overall power value (P) to be delivered by the hybrid powertrain (100), -sp!itting the overall power valut (rth) nto a first contributing power value (Pice) to be de-livered by the internal combustion engine (110) and a second contributing power value (Pmgu) to be delivered by the motor-generator electric unit (500), -monitoring an index (1(n)) indicative of a clogging level of the EGR cooler (510), and -increasing the first contributing power value (Pee), if the monitored EGR cooler clogging level index (1(n)) fulfils a predetermined condition.</claim-text> <claim-text>2. A method according to claim 1, wherein the predetermined condition is fulfilled if the monitored EGR cooling clogging level index (1(n)) is increasing.</claim-text> <claim-text>3. A method according to any of the preceding claims, wherein the predetermined condition is fulfilled if the monitored EGR cooling clogging level index (1(n)) has exceeded a threshold value (Ith) thereof.</claim-text> <claim-text>4. A method according to any of the preceding claims, wherein the splitting of the overall power value (Pbf) comprises the step of minimizing a predetermined polynomial function representing an overall power loss of the hybrid powertrain (100), and wherein the first contributing power value (P1) is increased by adding to the predetermined poly-nomial function an additional term whose value represents an additional power loss of the internal combustion engine (110).</claim-text> <claim-text>5. A method according to claim 4, comprising the steps of: -determining a desired value (Pegr) of power to be delivered by the internal combustion engine (110), -calculating a value of an extra quantity of fuel to be injected in the internal combustion engine (110) to increase the power to be delivered by the internal combustion engine (110) itself up to the desired power value (Pr), -calculating the value of the additional term as a function of the calculated value of the extra fuel quantity.</claim-text> <claim-text>6. A method according to claim 5, comprising the steps of: -determining an actual value of a plurality of engine operating parameters, and -determining the desired power value (Pegr) to be delivered by the internal combustion engine (110) from an empirically determined calibration map, on the basis of the deter-mined actual values of the engine operating parameters.</claim-text> <claim-text>7. A method according to claim 6, wherein the engine operating parameters include engine speed and engine load.</claim-text> <claim-text>8. A computer program comprising a computer code suitable for performing the method according to any of the preceding claims.</claim-text> <claim-text>9. A computer program product on which the computer program of claim 8 is stored.</claim-text> <claim-text>10. An electromagnetic signal modulated as a carrier for a sequence of data bits repre-seiitir)g the coFriputer prograrri according to ciaim 8.</claim-text> <claim-text>11. An apparatus for operating a hybrid powertrain (100) comprising a motor-generator electric unit (500) and an internal combustion engine (110) equipped with an EGR cooler (310), wherein the apparatus comprises: -means for determining an overall power value (P) to be delivered by the hybrid power-train (100), -means for splitting the overall power value (P) into a first contributing power value (Pice) to be delivered by the internal combustion engine and a second contributing power value (Pmgu) to be delivered by the motor-generator electric unit (500), -means for monitoring an index (1(n)) indicative of a clogging level of the EGR cooler (510), and -means for increasing the first contributing power value (Pice), if the monitored EGR cooler clogging level index (1(n)) fulfils a predetermined condition.</claim-text> <claim-text>12. A hybrid powertrain (100) comprising an motor-generator electric unit (500), an in-ternal combustion engine (110) equipped with an EGR cooler (310), and an electronic control unit (450) configured to: -determine an overall power value (Pt0) to be delivered by the hybrid powertrain (100), -split the overall power value (P01) into a first contributing power value (P9) to be deliv-ered by the internal combustion engine and a second contributing power value (Fmgu) to be delivered by the motor-generator electric unit (500), -monitor an index (1(n)) indicative of a clogging level of the EGR cooler (510), and -increase the first contributing power value (P), if the monitored EGR cooler clogging level index (1(n)) fulfils a predetermined condition.</claim-text>