GB2498534A - Operation of hybrid vehicle with NOx trap regeneration - Google Patents

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 a lean NOx trap (281 see fig 2), wherein the operating method comprises the steps of: monitoring a value (EL see fig 5) of a parameter indicative of an engine load, and generating a request (R1 see fig 5) for operating the motor-generator electric unit 500 as electric generator, if a DeSOx regeneration phase of the lean NOx trap (281) is enabled and the monitored value (EL) of the engine load parameter is below a first predetermined thresh­old. The invention allows for efficient regeneration when driving conditions, excluding generator operation, would not demand a sufficiently high engine load.

Description

METHOD FOR OPERATING A HYBRID POWERTRAIN

TECHNICAL FIELD

The present invention relates to a method for operating a hybrid powertrain, in particular 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 designed for generating mechanical power and for delivering it to the final drive of the motor vehicle, such as for instance to the drive wheels of a car.

An 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 eiectric motor for assisting or replacing the ICE in propelling the final drive of the motor vehicle, or can operate as electric generator, especially when the motor vehicle is braking, for charging an electrical energy storage device (battery) connected thereto. The battery is used 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 electmnic control unit (ECU) according to a Hy- brid Optimization Strategy (HOS). In particular, the HOS uses a plurality of engine oper-ating parameters for setting a first torque value to be provided by the ICE and a second torque value to be provided by the MGU, and then for operating the ICE and the MGU accordingly. While the first torque value is always positive, the second torque value may be either positive or negative. If the second torque value is positive, the MGU is operated as electric motor. If the second torque value is negative, the MGU is operated as electric generator.

The exhaust gas produced by the fuel combustion within the ICE is discharged into the environment through an exhaust system, which conventionally comprises an exhaust manifold in communication with the engine cylinders, an exhaust pipe coming off the ex-haust manifold, and one or more aftertreatment devices located in the exhaust pipe for trapping and/ar changing the composition of the pollutant contained in the exhaust gas.

Among these aftertreatment devices, the ICE (especially if it is a Diesel engine) may comprise a Lean NO Trap (LNT).

The LNT isa catalytic device containing catalysts, such as Rhodium, Platinum and Lead, as well as adsorbents, such as barium based elements, which provide active sites suit-able for binding the nitrogen oxides contained in the exhaust gas. Due to the sulphur contained in the fuel and in the engine lubricating oil, the exhaust gas produced by the ICE generally contains also sulphur oxides (SO), which can be responsible for a pro- gressive poisoning of the LNT. For this reason, whenever the quantity of sulphur accu- 1 0 mulated in the LNT exceeds a predetermined critical threshold value thereof, the ECU enables a desuiphurization process, also referred as De8O regeneration phase, which reduces the accumulated SO, and restore the original efficiency of the LNT.

The reduction of the SO< generally requires an high temperature and a rich atmosphere.

However, the reduced amount of oxygen associated with the rich atmosphere promotes the production of sulphur Hydroxide (H,S). Therefore, the DeSO regeneration phase is conventionally obtained by increasing the temperature of the LNT, typically up to 600- 650°C, while operating the internal combustion engine to perform an alternation of rich and lean combustion modes, according to a so called wobbling strategy.

A rich combustion mode occurs when the fuel and air mixture ignited in the engine cylin-ders has an air to fuel ratio lower than the stoichiornetric value (lambda c 1). During a DeSO regeneration phase, the rich combustion modes are conventionally attained by injecting additional quantities of fuel inside the engine cylinders, by means of one or more after-injections. The after-injections are small fuel quantities that are injected in an engine cylinder, once the respective piston has passed the Top Dead Center (TDC) posi- tion. The after-injected fuel burns inside the engine cylinder, thereby increasing the tem-perature of the exhaust gas that flows through the LNT creating also the rich atmosphere that is required for the reduction of the SQ.

A lean combustion mode occurs when the fuel and air mixture ignited in the engine cylin-ders has an air to fuel ratio greater than the stoichiometric value (lambda > 1). During a DeSO regeneration phase, the lean combustion modes are conventionafly attained by injecting additional quantities of fuel inside the engine cylinders, by means of one or more post injections. 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 unburned from the engine cylinder without consuming oxygen. In this way, the atmos- phere inside the LNT is enriched with oxygen that promotes the production of SO2 in- stead of M2S. Besides, the post-injected fuel bums inside the LNT itself, keeping its tem-perature at high level and burning off the accumulated Hydrocarbon (NC).

Due to combustion and temperature limitations correlated especially with the rich com-bustion modes, the DeSO regeneration phase of the LNT may be effectively performed only if the values of the engine load and of the engine speed fulfil certain criteria. In par- ticular, it is necessary that the engine load value is comprised in a specific range of al-lowable values, which generally depend on the engine speed value. If the engine load value is below or above that specific range, the DeSO regeneration phase cannot be ef-fectively performed. This limitation is particularly critical because reduces the possibility to perform an efficient DeSO regeneration phase when the driving conditions imply too low values of the engine load, such as for example during urban driving conditions.

To overcome this drawback it is known to force the engine load value to increase, for ex-ample by voluntarily activating other power consuming devices associated to the internal combustion engine or to the motor vehicle, even if the function performed by these de-vices is not actually requested, thus leading to a waste of power that increases the fuel consumption.

An object of an embodiment of the present invention is therefore to improve the power management of a hybrid powertrain during a DeSO regeneration phase of the LNT, in order to globally reduce the fuel consumption and achieve all the benefits related thereto, such as for example in terms of reduction of polluting emissions.

Another object is that of attaining the above mentioned goal 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 the 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 (MGU) and an internal combustion engine equipped with a Lean NO Trap (LNT), wherein the operating method comprises the steps of: -monitoring a value of a parameter indicative of an engine toad, and -generating a request for operating the MGU as electric generator, if a DeSO regenera-tion phase of the LNT is enabled and the monitored value of the engine load parameter is below a first predetermined threshold thereof.

Thanks to this solution, when the DeSO regeneration phase is enabled, it is advanta- geously possible to operate the MGU as electric generator, in order to increase the en-gine load and therefore to achieve at least two benefits. A first benefit is that the DeSO regeneration phase may be completed even under driving conditions that usually imply too low engine loads, such as for example urban driving conditions. A second benefit is that the additional fuel that is injected in the ICE to increase the engine load is not wasted, but it is efficiently used to recharge the battery of the MGU, thereby accumulat-ing electrical power that may be advantageously used later on during the operation of the hybrid powertrain.

According to an aspect of the invention, the operating method may comprise the addi-tional step of actually operating the MGU as electric generator, if the request thereof is generated, independently from other condition or criterion. In other words, if that request is generated, the MGU is substantially forced to operate as electric generator.

An alternative aspect of the invention provides for applying the request for operating the MGU as electric generator to an optimization strategy that comprises the steps of: -using this request to determine a value of torque to be provided by the MGU, and -actually operating the MGU as electric generator, if the determined torque value is negative.

This aspect of the invention has the advantage of coordinating the present strategy with other criteria conventionally used for deciding whether it is advisable to operate the MGU as electric generator or not. As a consequence, if the whole of the criteria returns that the dptimal decision is not to operate the MGU as electric generator, the activation of this operating mode may be prevented even if the request thereof has been actually gener-ated.

In any case, once the MGU is operated as electric generator, an aspect of the invention provide for controlling the MGU such as to raise and then to keep the monitored value of the engine load parameter above the first threshold value.

This aspect of the invention has the advantage of allowing the DeSO regeneration phase to be effectively completed.

According to another aspect of the invention, the method may comprise the additional steps of: -monitoring a value of an engine speed parameter, and -adjusting the first threshold value of the engine load parameter on the basis of the monitored value of the engine speed parameter.

In this way, it is advantageously possible to take into account the impact of the engine speed on the minimum engine load level requested to effectively perform the DeSO re-generation phase, thereby increasing the DeSO regeneration efficiency.

Another aspect of the invention provides that the method comprises the additional steps of: S -generating a request for operating the MGU as electric motor, if a DeSO regeneration phase of the LNT is enabled and the monitored value of the engine load parameter is above a second predetermined threshold value thereof, wherein the second threshold value is greater than the first threshold value.

Thanks to this solution, during a DeSO, regeneration phase, it is advantageously possi- ble to operate the MGLJ as electric motor, in order to reduce the engine load and there-fore to achieve at least two benefits. A first benefit is that the DeSO regeneration phase may be completed under driving conditions that usually imply too high engine loads, such as for example during a strong acceleration. A second benefit is that the additional torque provided by the MGU operating as electric motor allows the parallel hybrid power-train to deliver the entire power requested by the driving conditions.

According to an aspect of the invention, the operating method may comprise the addi- tional step of actually operating the MGU as electric motor, if the request thereof is gen-erated, independently from any other condition or criterion. In other words, if that request is generated, the MGU is substantially forced to operate as electric motor.

An alternative aspect of the invention provides for applying the request for operating the MGU as electric motor to an optimization strategy that comprises the steps of: -using this request to determine a value of torque to be provided by the MGU, and -activating the MGU to operate as electric motor, if the determined torque value is posi-tive.

This aspect of the invention has the advantage of coordinating the present strategy with other criteria conventionally used for deciding whether it is advisable to operate the MGU as electric motor or not. As a consequence, if the whole of the criteria returns that the op-timal decision is not to operate the MGU as electric motor, the activation of this operating mode may be prevented even if a request thereof has been generated.

In any case, once the MGU is actually operated as electric motor, an aspect of the inven-tion provide for controlling the MGU such as to decrease and then to keep the monitored value of the engine load parameter below the second threshold value.

This aspect of the invention has the advantage of allowing the DeSO, regeneration phase to be effectively completed.

According to another aspect of the invention, the method may comprise the additional steps of:: -monitoring a value of an engine speed parameter, and -adjusting the second threshold value of the engine load parameter on the basis of the monitored value of the engine speed parameter.

In this way it is advantageously possible to take into account the impact of the engine speed on the maximum engine load level allowable to effectively perform the DeSO re-generation phase, thereby increasing the regeneration efficiency.

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 de-scribed above! and in the form of a computer program product comprising the computer program. 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 program to carry out all steps of the method.

Another embodiment of the present invention provides an apparatus for operating a by-brid powertrain comprising a MGU and an internal combustion engine equipped with a LNT, wherein the apparatus comprises; -means for monitoring a value of an engine load parameter, and -means for generating a request for operating the MGU as electric generator, ira DeSO regeneration phase of the LNT is enabled and the monitored value of the engine load pa-rameter is below a first predetermined threshold thereof This embodiment of the invention has the same advantage of the method disclosed above, particularly that of improving the management if the hybrid powertrain during a OeSO regeneration phase of the LNT.

Still another embodiment of the invention provides a hybrid powertrain comprising a MGU and an internal combustion engine equipped with a LNT, and an electronic control unit configured to: -monitor a value of an engine load parameter, and -generate a request for operating the MGU as electric generator, if a DeSO regenera-tion phase of the LNT is enabled and the monitored value of the engine load parameter is below a first predetermined threshold thereof.

Also this embodiment of the invention has the advantage of the method disclosed above, particularly that of improving the management if the hybrid powertrain during a DeSO regeneration phase of the LNT.

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 parallel hybrid powertrajn of a motor vehicle.

Figure 2 shows in greater details an internal combustion engine belonging to the parallel S 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 representing a DeSO, enabling strategy for the hybrid powertrain of figure 1.

Figure 5 is a flowchart representing a DeSO managing strategy for the hybrid powertrain of figure 1.

DETAILED DESCRIPTION

Some embodiments may include a motor vehicle's parallel hybrid powertrain 100! as shown in figures 1, that basically comprises an internal combustion engine (ICE) 110, in this example a Diesel engine, a motor-generator electric unit (MGU) 500, an electric en- ergy storage device (battery) 600 electrically connected to the MGU 500, and an elec-tronic 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 to 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 causing reciprocal movement of the piston 140.

The fuel is provided by at least one fuel injector 160 and the air through at least one in-take port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail in fluid communication with a high pressure fuel pump 180 that increases the pres-sure of the fuel received from a fuel source iga. 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 3D 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 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 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 and/or include a waste gate.

Other embodiments may include an exhaust gas recirculatiori (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR sys-tem 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 aftertueatment devices. The aftertreatment devices may be any device configured to dhange 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 (LNJT) 281, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, and particulate filters (DPF) 282.

The LNT 281 is a catalytic device containing catalysts, such as Rhodium, Platinum and Lead, as well as adsorbents such as barium based elements, which provide active sites suitable for binding the nitrogen oxides (NOX) contained in the exhaust gas. Due to the sulphur contained in the diesel fuel and in the engine lubricating oil, the exhaust gas pro- duced by the ICE 110 generally contains also sulphur oxides (SOy), which can be re- sponsiblefora progressive poisoning of the LNT251. Forthis reason, the LNT281 is pe-riodically subjected to a desulphurization process, also referred as DeSO regeneration phase, which reduces the accumulated SO. and restore the original efficiency of the LNT 281.

A DeSO regeneration phase is conventionally obtained by increasing the temperature of the LNT 281, typically up to 600-650°C, while operating the ICE 110 to perform an alter-nation of rich and lean combustion modes, according to a so called wobbling strategy.

The rich combustion modes are conventionally attained by injecting additional quantities

S

of fuel inside the engine cylinders 120, by means of one or more after injections. The af-ter-injected fuel burns inside the engine cylinder 120, thereby increasing the temperature of the exhaust gas that flows through the LNT 281 and creating the rich atmosphere re- quired for reducing the accumulated SO,,. The Jean combustion modes are convention-ally attained by injecting additional quantities of fuel inside the engine cylinders, by means of one or more post-injections. The post-injected fuel exits unburned from the en-gine cylinders 120 without consuming oxygen, so that the atmosphere inside the LNT 281 is enriched with oxygen which promotes the production of SO2 instead of H2S. Be-sides1 the post-injected burns inside the LNT 281 itself, keeping its temperature at high level and buming off the accumulated Hydrocarbon (I-IC).

The MGU 500 is an electric machine, namely an electro-mechanical energy converter, which is able either to convert electricity supplied by the battery 600 into mechanical power (i.e., to operate as an electric motor) or to convert mechanical power into electric-ity that charges the battery 600 (i.e., to operate as electric generator). In greater details, the MGU 500 may comprise a rotor, which is arranged to rotate with respect to a stator, in order to generate or respectively receive the mechanical power. The rotor may 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 MGIJ 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, to which is mechanically connected also the ICE 110. In this way, operating as an electric motor1 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 break-ing, the MGU 500 can charge the battery 600. In the present example, the MGU shaft 505 is connected with the ICE crankshaft 145 through a transmission belt 510, similarly to a conventional alternator starter. In order to switch between the motor operating mode and the generator operating mode, the MGU 500 may be equipped with an appropriate internal control system.

The ICE 110 and the MGU 500 are controlled by the ECU 450 according to a Hybrid Op- timization Strategy (HOS). In particular, the HOS uses a plurality of engine operating pa-rameters for setting a first torque value to be delivered by the ICE 110 and a second torque value to be delivered by the MGU 500, and then for operating the ICE 110 and the MGU 500 accordingly. While the first torque value is always positive, the second torque value may be either positive or negative. If the second torque value is positive, the MGU 500 is operated as electric motor. If the second torque value is negative, the MGU 500 is operated as electric generator.

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 pressure and temperature sensor 350, a corn-bustion pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a camshaft position sensor 410, a crankshaft position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, a sensor 445 of a position of an accelerator pedal 446, and a measuring circuit 605 capa-ble 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 opera-tion of the ICE 110 and the MGU 500, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, the cam phaser 155, and the above mentioned internal control system of the MGU 500. Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for clarity.

As already mentioned, the exhaust gas produced by the ICE 110 contains sulphur oxides (SO) that are progressively accumulated inside the LNT 281, reducing its efficiency. In order to tackle this problem, during the normal operation of the ICE 110, the ECU 450 is configured to periodically enable a DeSO regeneration phase through the strategy that is represented in figure 4.

This DeSO, enabling strategy provides for monitoring a value SL of a sulphur level pa-rameter (block 700), which is indicative of a quantity of sulphur accumulated in the LNT 281. The monitored value SL may be measured or estimated through a conventional sul-phur loading model, which uses as inputs a plurality of engine operating parameters. The monitored value SL of the sulphur level parameter is compared (block 705) with a prede- termine threshold value SL_th thereof. The threshold value SL_th may be empirically de-termined during a calibration activity and stored in the memory system 460. As long as the monitored value SL is below the threshold value SL_th, the strategy simply provides for repeating the monitoring. When the the monitored value SL is below the threshold value SL_th, the control strategy provides for enabling a DeSO regeneration phase (block 710). Once the DeSO regeneration phase has been enabled, the ECU 450 is configured to perform the DeSO managing strategy represented in figure 5.

The DeSO managing strategy comprises the steps of monitoring a value EL of an en-gine load (block 715) and a value ES of the engine speed (block 720). The engine load is a parameter indicative of the torque requested to the ICE 110. The engine load value EL may be determined by the ECU 450 on the basis of many inputs, including the position of the accelerator pedal 446, which can be measured by the accelerator pedal position sensor 445. The engine speed is parameter indicative of the rotational speed of the crankshaft 145. The engine speed value ES may be measured by the ECU 450 through the crankshaft position sensor 420.

The monitored values EL and ES of the engine speed and of the engine load are applied to a DeSO manager (block 725). The DeSO manager uses the values EL and ES of the engine speed and of the engine load, as well as other inputs, for activating and control-ling the wobbling of rich and lean combustion modes during the DeSO regeneration phase. The strategy implemented in the DeSO, manager is perse conventional.

At the same time, the monitored value ES of the engine speed is used to determine (block 730) a first threshold value EL_thi and a second threshold value EL_th2 of the engine load. The second threshold value EL_th2 is greater than the first threshold value EL_thi. The first and second threshold values EL_thi and EL_th2 represents the oppo- sife ends of a range of allowable values of the engine load, within which the DeSO, re-generation phase can be effectively performed. The first and second threshold values EL_thi and EL_th2 may be determined by means of a map (not shown), which corre-lates each value ES of the engine speed to a corresponding couple of threshold values EL_thi and EL_th2 of the engine load. All the couple of threshold values EL_thl and ELh2 memorized in the map may be empirically calibrated during an experimental ac-tivity, and the resulting map may be stored in the memory system 460.

Afterwards, the DeSO managing strategy provides for comparing the monitored value EL of the engine load with the first threshold value EL_thi thereof (block 735).

If the monitored value EL is below the first threshold value El_thi, for example because the parallel hybrid powertrain 100 is operated under urban driving conditions, the DeSO managing strategy provides for generating (block 740) a request Ri for operating the MGU 500 as electric generator, in order to increase the engine load and charge the bat-tery 600.

The generation of the request Ri may actually force the MGU 500 to operate as electric generator, disregarding any other criterion implemented in the HOS. In this case, the re-quest Ri may be embodied as a command signal that directly causes the MGU 500 to operate as electric generator.

However, the DeSO managing strategy of the present example provides for applying the request Ri to a HOS 800, which is configured to use the request Ri, as well as other conventional inputs, for determining a target value T_ICE of the torque to be provided by the ICE 110 and a target value T_MGU of torque to be provided by the MGU 500. As a consequence of this solution, the MGU 500 is actually operated as electric generator, only if the target value T_MGU determined by the HOS 800 is negative.

As a matter of fact, this solution implies that the request Ri becomes one of the many inputs considered by the HOS 800 to optimize the operation of the parallel hybrid power-train 100 and that it is not a sufficient condition to operate the MGU as electric generator.

Nonetheless, the request Ri should have at least the effect of prompting the HOS 800 to operate the MGU 500 as electric generator, for example acting in such a way to reduce the target value T_MGU with respect of that that would be determined by a conventional HOS in the same conditions. In this context, the request Ri may be embodied as any in-put or action that affects the behaviour of the HOS 800.

If conversely the monitored value EL of the engine load is above the first threshold value El_thi, then the DeSO managing strategy provides for comparing the monitored value EL with the second threshold value EL_th2 of the engine load (block 745).

If the monitored value EL is above the second threshold value EI_th2, for example be-cause the parallel hybrid powertrain 100 is requested to per-form a strong acceleration of the motor vehicle, the DeSO managing strategy provides for generating (block 750) a request R2 for operating the MGU 500 as electric motor, in order to consequently reduce the engine load while guaranteeing that the parallel hybrid powertrain 100 supplies the overall torque requested by the driving conditions.

The generation of the request R2 may actually force the MGU 500 to operate as electric motor, disregarding any other criterion implemented in the HOS. In this case, the request R2 may be embodied as a command signal that directly causes the MGU 500 to operate as electric motor.

However1 the DeSO managing strategy of the present example provides for applying the request R2 to the HOS 800, which is configured to use the request R2, as well as other conventional inputs, for determining a target value T_ICE of the torque requested to the ICE 110 and a target value T_MGU of torque requested to the MGU 500, which will be used to actually operate the ICE 110 and the EGU 500. As a consequence of this solu-tion, the MGU 500 is actually operated as electric motor, only if the target value T_MGU determined by the HOS 800 is positive.

As a matter of fact, this solution implies that the request R2 becomes one of the many inputs considered by the HOS 800 to optimize the operation of the parallel hybrid power-train 100, and that it is not a sufficient condition to operate the MGU as electric motor.

Nonetheless, the request R2 should have at least the effect of prompting the HOS 800 to operate the MGU 500 as electric motor, for example acting in such a way to enhance the target value T_MGU with respect of that that would be determined by a conventional HOS in the same conditions. In this context, the request R2 may be embodied as any in-put or action that affects the behaviour of the HOS 800.

The DeSO managing strategy described above is then repeated until the DeSO regen-eration phase is completed, and the efficiency of the LNT 281 restored.

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 scope1 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 cylinder 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 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 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 block 720 block 725 block 730 block 735 block 740 block 745 block 750 block 800 Hybrid Optimization Strategy (HOS) SL sulphur level parameter value SL_th sulphur level parameter threshold value EL engine load value EL_thi engine load first threshold value EI_th2 engine load second threshold value ES engine speed value Ri request R2 request T_ICE ICE torque target value T_MGLJ MGU torque target value

Claims (1)

1. <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 a Lean NO Trap (281), wherein the operating method comprises the steps of: -monitoring a value (EL) of a parameter indicative of an engine load, and -generating a first request (Ri) for operating the motor-generator electric unit (500) as electric generator, if a DeSO regeneration phase of the Lean NO Trap (281) is enabled and the monitored value (EL) of the first parameter is below a first predetermined thresh-old value (EL_thi).</claim-text> <claim-text>2. A method according to claim 1, comprising the additional step of operating the mo- tor-generator electric unit (500) as an electric generator if the first request (Ri) is gener-ated.</claim-text> <claim-text>3. A method according to claim 1, wherein the request (Ri) is applied as an input to an optimization strategy (800) that comprises the steps of: -using the first request (RI) to determine a value (T_MGU) of torque to be provided by the motor-generator electric unit (500), and -operating the motor-generator electric unit (500) as electric generator, if the determined torque value (T_MGU) is negative.</claim-text> <claim-text>4. A method according to claim 2 or 3, wherein the motor-generator electric unit (500) is controlled by first raising and then keeping the monitored value (EL) above the first threshold value (EL_thi).</claim-text> <claim-text>5. A method according to any of the preceding claims, comprising the additional steps of: -monitoring a value (ES) of an engine speed parameter, and -adjusting the first threshold value (EL_thi) on the basis of the monitored value (ES) of the engine speed parameter.</claim-text> <claim-text>6. A method according to any of the preceding claims, comprising the additional steps of: -generating a second request (R2) for operating the motor-generator electric unit (500) as an electric motor if a DeSO regeneration phase of the Lean NO Trap (281) is en- abled and the monitored value (EL) of the engine load parameter is above a second pre-determined threshold value (EL_th2) wherein the second threshold value (EL_th2) is greater than the first threshold value (EL_thi).</claim-text> <claim-text>7. A method according to claim 6, comprising the additional step of operating the mo- tor-generator electric unit (500) as an electric motor if the second request (R2) is gener-ated.</claim-text> <claim-text>8. A method according to claim 1, wherein the second request (R2) is applied as an input to an optimization strategy that comprises the steps of: -using the second request to determine a value (T_MGU) of torque to be provided by the motor-generator electric unit (500), and -operating the motor-generator electric unit (500) as an electric motor if the determined torque value (T_MGU) is positive.</claim-text> <claim-text>9. A method according to claim 7 or 8, wherein the motor-generator electric unit (500) is operated as an electric motor and is controlled by first decreasing and then keeping the monitored value (EL) of the engine load parameter below the second threshold value (EL_th2).</claim-text> <claim-text>10. A method according to any claim from 6 to 9, comprising the additional steps of: -monitoring the value (ES) of the engine speed parameter, and -adjusting the second threshold value (EL_th2) on the basis of the monitored value (ES).</claim-text> <claim-text>11. A computer program comprising a computer code suitable for performing the method according to any of the preceding claims.</claim-text> <claim-text>12. A computer program product on which the computer program of claim 11 is stored.</claim-text> <claim-text>13. An electromagnetic signal modulated as a carrier for a sequence of data bits repre-senting the computer program according to claim 11.</claim-text> <claim-text>14. An apparatus for operating a hybrid powertrain (100) comprising a motor-generator electric unit (500) and an internal combustion engine (110) equipped with a Lean NO Trap (281), wherein the apparatus comprises: -means for monitoring a value (EL) of an engine load parameter, and -means for generating a request (Ri) for operating the motor-generator electric unit (500) as an electric generator first if a DeSO regeneration phase of the Lean NO Trap (281) is enabled and the monitored value (EL) of the engine load parameter is below a first predetermined threshold (EL_thi).</claim-text> <claim-text>15. A hybrid powertrain (100) comprising a motor-generator electric unit (500) and an internal combustion engine (110) equipped with a Lean NO Trap (281), and an elec-tronic control unit (450) configured to: -monitor a value (EL) of an engine load parameter, and -generate a first request (Ri) for operating the motor-generator electric unit (500) as electric generator if a DeSO regeneration phase of the Lean NO Trap (281) is enabled and the monitored value (EL) of the engine load parameter is below a first predetermined threshold (EL_thi) value.</claim-text>