GB2511062A

GB2511062A - Method of operating a hybrid powertrain

Info

Publication number: GB2511062A
Application number: GB1303065.5A
Authority: GB
Inventors: Gabriele Giraudo; Roberto Romanato
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2013-02-21
Filing date: 2013-02-21
Publication date: 2014-08-27
Also published as: GB201303065D0

Abstract

An embodiment of the invention provides a method of operating a hybrid powertrain (100 see fig 1) comprising a motor-generator electric unit (500 see fig 1) equipped with a battery (600 see fig 1). The powertrain (100) is configured to receive a torque request typically involving an accelerator pedal (446 see fig 2) wherein the operating method comprises the step of monitoring a parameter AccPed representative of the torque request, and the step of raising a minimum state of charge limit of the battery (600) to a predetermined value when the monitored parameter value is lower than a predetermined threshold. The invention is aimed at not unnecessarily depleting the battery in association with a period 735 of low demand driving, especially when the vehicle may subsequently be subjected to a more demanding situation such as sport driving with a high level of demand 750.

Description

METHOD OF OPERATING A HYBRID POWER TRAIN

TEaCCa FD The present disclosure relates to a method of operating a hybrid powertrain, in particular a hybrid powertrain installed on a motor vehicle.

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 13 drive of the motor vehicle itself, such as for instance to the drive wheels.

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 (MCD) . The MGU can operate as electric 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 powettrain is the ICE fuel.

The hybrid powertrain is controlled by an electronic control unit (ECU) according to a Hybrid Optimization Strategy (HOg). [n particular, the HOS uses a plurality of engine operating parameters for setting a first torque value to be provided by the ICE and a second torque value to be provided by the MCD, and then operates the ICE and the MCD 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 MCD is operated as electric motor. If the second torque value is negative, the MCD is operated as electric generator.

The internal combustion engine (ICE) basically comprises a cylinder block defining one or more cylinders, each of which accorrmodates a reciprocating piston coupled to rotate a crankshaft. The reciprocal movement of the pistons is due to the combustion of a fuel and air mixture, which is fed and ignited into the engine cylinders. The fuel is provided by fuel injectors which are individually located inside a respective engine cylinder, and which receive fuel at high pressure from a fuel rail that is in fluid communication with a high pressure fuel pump.

The fuel injectors are operated by the ECU, which is configured to acquire the first torque value determined by the HOS, and to determine a value of a fuel quantity that is requested to be injected in the engine cylinders, in order to generate that value of torque.

The requested fuel quantity value is then used by the ECU to determine a value of a time interval (energizing time) for which the fuel injectors should remain open in order to supply that value of fuel quantity, and to operate the fuel injectors according to this determined energizing time.

In particular, concerning hybrid powertrains two different performance targets that have opposite requirements in terms of battery State Of Charge (5cC) management have to be taken into account On one hand, fuel consumption and emissions optimization requires to avoid overloading the engine to recharge the battery, with the so-called opportunity charging procedure, during normal driving.

On the other hand, during full load maneuvers such as sport driving, electrical torque assist may be needed, namely the use of the MGU as an electric motor to assist the internal combustion engine providing a further contribution of positive torque.

To perfonn this electrical torque assist procedure, it is required to always recharge the battery in order to have some power and energy available during such procedure, in particular during sport driving.

In this respect, it is lo-iown to set a minimum State Of Charge (MIN SOC Limit) for the battery beyond which it is not recorrrrtended to go in order not to discharge too much the battery and eventually damage it.

A problem that may arise with this procedure is that, during highway driving, any slowing down may help in recharging the battery, while in urban driving the speed of the vehicle is generally always low and the battery is recharged very little or not at all, leaving its State Of Charge oscillating at values close to the MIN SOC Limit.

In these conditions, however, there might not be enough charge in the battery to perform an electrical torque assist procedure during sport driving.

In such situations, it may happen that, when the driver desires to perform sport driving, the vehicle responds with an acceleration that is lower than expected.

An object of an embodiment of the invention is to guarantee an electrical torque assist guaranteed during sport driving in repeatable mode, in order to keep driving experience constant and

predictable.

Another object of an embodiment of the invention is to achieve the above effect while, at the same time, guarantee normal fuel consumption and emissions during normal driving and no impact on homologat ion cycle.

A further object of an embodiment of the invention is to guarantee battery safety in all operating conditions of the hybrid powertrain.

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

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

StM4RY An embodiment of the disclosure provides a method of operating a hybrid powertrain comprising a motor-generator electric unit equipped with a battery, the hybrid powertrain being configured to receive a torque request wherein the operating method comprises the steps of: -monitoring a parameter representative of a torque request for the hybrid powertrain; -raising a minimum State Of Charge limit of the battery to a predetermined value when the monitored parameter value is lower than a predetermined threshcld.

An advantage of this entodiment is that, by raising the minimum State Of Charge Unit of the battery during normal driving, it is possible to avoid to discharge too much the battery in this phase, for example during urban driving, and therefore it is possible to maintain sufficient charge in the battery to electrically assist the internal combustion engine when an higher value of torque is requested to the hybrid powertrain, for example during sport driving.

According to a further embodiment of the invention, the minimum State Of Charge limit of the battery is set at a lowest value thereof when the value of the monitored parameter is higher than the predetermined threshold.

An advantage of this embodiment is that, it allows the battery the possibility to discharge further to provide electrical energy during sport driving.

According to a further embodiment of the invention, the State Of Charge limit of the battery is raised to the predetennined value, if the value of the monitored position remains lower than the predetermined threshold for a predetermined interval of time.

An advantage of this embodiment is that it allows to create a certain amount of hysteresis for debouncing the torque request signal, for example an accelerator pedal position signal.

According to still another embodiment of the invention, when the monitored parameter value is higher than the predetermined threshold, the battery discharges and the motor-generator electric unit provides a positive torque to the hybrid powertrain.

Pa-i advantage of this embodiment is that it allows to provide an additional amount of torque to the powertrain during sport driving.

According to still another embodiment of the invention, the parameter representative of a torque request for the hybrid powertrain can be expressed by a position of an accelerator pedal, by a derivative thereof, by a torque request from a subsystem of the hybrid powertrain or by a derivative thereof or by a combination of the above.

The invention also provides an apparatus for operating a hybrid powertrain comprising a motor-generator electric unit equipped with a battery, the hybrid powertrain being configured to receive a torque request, wherein the apparatus comprises: -means for monitoring a parameter representative of a torque request for the hybrid powertrain; -means for raising a minimum State Of Charge limit of the battery to a predetermined value when the monitored parameter value is lower than a predetermined threshold.

This embodiment of the invention has basically the same advantages of the method disclosed above, in particular to allow electrically assist the internal combustion engine when an higher value of torque is requested to the hybrid powertrain, for example during sport driving.

According to an aspect of the invention, means are provided to set the minimum State Of Charge limit of the battery at a lowest value S thereof when the monitored parameter value is higher than the predetermined threshold.

An advantage of this aspect is that, it allows the battery the possibility to discharge further to provide electrical energy during sport driving.

According to a further aspect of the invention, means are provided to raise the State Of Charge limit of the battery to the predetermined value, if the value of the parameter remains lower than the predetermined threshold for a predetermined interval of time.

En this way it is allowed to create a certain amount of hysteresis for debouncing the torque request signal, for example an accelerator pedal position signal.

According to a further aspect of the invention, means are provided to check if the monitored parameter value is higher than the predetermined threshold, and in the affirmative, to discharge the battery and to allow the motor-generator electric unit to provide a positive torque to the hybrid powertrain.

In this way, an additional amount of torque to the powertrain during sport driving is provided.

According to a further aspect of the invention, the means for monitoring a parameter representative of a torque request for the hybrid powertrain are configured to read a position of an accelerator pedal, a derivative thereof, a torque request from a subsystem of the hybrid powertrain or a derivative thereof or a combination of the above.

The invention provides also an automotive system comprising a hybrid powertrain comprising a motor-generator electric unit equipped with a battery, the hybrid powertrain being configured to receive a torque request and being managed by an Electronic Control Unit, the Electronic Contro1 Unit being configured to: -monitor a parameter representative of a torque request for the hybrid powertrain; -raise a minimum State Of Charge limit of the battery to a predetermined value when the monitored parameter value is lower than a predetermined threshold.

According to an aspect of the invention, the Electronic Control Unit may be configured to set the minimum State Of Charge limit of the battery at a lowest value thereof when the monitored parameter value is higher than the predetermined threshold.

Pn advantage of this aspect is that, it allows the battery the possibility to discharge further to provide electrical energy during sport driving.

According to another aspect of the invention, the Electronic Control Unit may be configured to raise the State Of Charge limit of the battery to the predetermined value, if the value of the parameter remains lower than the predetermined threshold for a predetermined interval of time.

In this way it is allowed to create a certain amount of hysteresis for debouncing the torque request signal, for example an accelerator pedal position signal.

According to another aspect of the invention, the Electronic Control Unit may be configured to check if the monitored parameter value is higher than the predetermined threshold, and in the affirmative, to discharge the battery and to allow *the motor-generator electric unit to provide a positive torque to the hybrid powertrain.

According to another aspect of the invention, the Electronic Control Unit may be configured to read a position of an accelerator pedal, a derivative thereof, a torque request from a subsystem of the hybrid powertrain or a derivative thereof or a combination of the above and interpret any of the above signals as a parameter representative of a torque request for the hybrid powertrain.

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

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

A still further aspect of the disclosure provides an internal combustion engine specially arranged for carrying out the method claimed.

BRIEF DESCRIPTIaT OF THE DBAWflTGS The various embodiments will now be described, by way of example, with reference to the accompanying drawings, wherein like niunerals denote like elements, and in which: Figure 1 is a schematic view of a motor vehicle equipped with a parallel hybrid powertrain; Figure 2 is a schematic view of an internal combustion engine belonging to the parallel hybrid powertrain of figure 1; Figure 3 is a schematic representation according to the section A-A of the internal combustion engine of Figure 2.

Figure 4 is a graph that represents a State of Charge profile of the battery in a hybrid powertrain according to the prior art; Figure 5 is a flowchart of an embodiment of the invention; and Figure 6 is a graph that represents the State of Charge of the battery in a hybrid powertrain, according to an embodiment of the invention.

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

Some embodiments may include a motor vehicle 10, as shown in figure 1, which comprises a parallel hkrid powertrain 100. The parallel hybrid powertrain 100 may comprise an internal combustion engine (ICE) 110, in this example a Diesel engine, a motor-generator electric unit (MGU) 500, an electric energy storage device (battery) 600 electrically connected to the MGU 500, and an electronic control unit (ECU) 450 in corrrnunication with a memory system 460.

As shown in figure 2 and 3, the internal combustion engine (ICE) has an engine engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145, which may be connected to a final drive of the motor vehicle 10, for example to a couple, of drive wheels 11. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the piston 140. The fuel is provided by at least one fuel injector 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 in fluid corunication 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 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 manifold 200. Tn other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200. In still other embodiments, a forced air system such as a turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. Rotation of the compressor 240 increases the pressure and temperature of the air in the 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 exhaust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 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 recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 reynlates a 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 catalysts (DOC) 280, lean NO, traps (LNT) 281, hydrocarbon adsorbers, selective catalytic reduction (5CR) systems, and particulate filters (DPF) 282.

The MOO 500 is an electric machine, namely an electro-mechanical energy converter, which is able either to convert electricity supplied by the battery 600 into mechanical power (i.e. to operate as an electric motor) or to convert mechanical power into electricity that charges the battery 600 (i.e. to operate as electric generator).

In greater details, the MGU 500 may comprise a rotor, which is arranged to rotate with respect to a stator, in order to generate or respectively absorb the mechanical power. The rotor may comprise means to generate a magnetic field and the stator may comprise electric windings connected to the battery 600, or vice versa. When the MGt.J 500 operates as electric motor, the battery 600 supplies electric currents to 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 NGU 500 may be of any Iciown type, for example a permanent magnet machine, a brushed machine or an induction machine. The MGU 500 may also be either an asynchronous machine or a synchronous machine.

The rotor of the MGU 500 may comprise a coaxial shaft 505, which is mechanically connected with pther components of the hybrid powertrain 100, so as to be able to deliver or absorb mechanical power to and from the final drive of the motpr vehicle 10, in this example the drive wheels 11. In this way, operating as an electric motor, the MOO 500 can assist or replace the ICE 110 in propelling the motor vehicle 10, whereas operating as an electric generator, especially when the motor vehicle 10 is braking, the MOO 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, sflnilarly to a conventional alternator starter. In order to switch between the motor operating mode and the generator operating mode, the MOO 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 conmunication with the memory system 460 and an interface bus. The memory system 460 may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors and control devices. The CPU is configured to execute instructions stored as a program in the memory system 460, and send and receive signals to/from the interface bus.

The program may errbody the methods disclosed in the present description, allowing the CPU to carry cut the steps of such methods and control the ICE 110 and the MGU 500.

In order to perform these tasks, the ECU 450 is in connunication 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 M 500 and the battery 600. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, a combustion pressure sensor 360, an engine coolant temperature sensors 380, an engine lubricant (oil) temperature sensor 335, an engine metal temperature sensor 390 (namely a sensor of the temperature of a metallic block of the ICE 110, such as for example the engine block 120), 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, a first measuring circuit 605 capable of sensing the state of charge of the battery 600, and a second measuring circuit 610 capable of providing an instant-by-instant measure of the torque that the MGU 500 is actually delivering or absorbing to/from the crankshaft 145. By way of example, the second measuring circuit 610 may be configured to sense a nurrber of electrical parameters of the electrical currents circulating in the electrical wirings of the MGU 500, and to use these electrical parameters to generate an output signal indicative of the torque delivered or absorbed by the MGU 500, which can be acquired and processed by the ECU 450.

Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control the operation of the ICE and the MW 500, including, but not limited to, the fuel injectors 160, the throttle body 330, the ECR 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.

Turning now to Figure 4 a battery State of Charge curve C in a hybrid powertrain according to the prior art is represented.

In this case a minimum and a maximum State of Charge of the battery 600 are predetermined.

In particular, the minimum State of Charge MinSOC is predefined as a minimum State Of Charge threshold that allows to always have a residual minimum charge of the battery 600 to avoid damaging its components.

The battery 600 may be maintained in a State Of Charge not significantly lower than the minimum State of Charge 1inSOCIA,,it, for example, by measuring the State Of Charge of the battery by means of a State of Charge sensor connected to ECU 450 and by operating the MGU as an electric generator to recharge the battery 600 when the State of Charge is lower than said minimum State of Charge MinSOC±.

Figure 4 shows a curve A representing a series of actions on the accelerator pedal 446. For simplicity, two states of the accelerator pedal 446 are represented, namely a state in which the accelerator pedal 446 is not depressed and a state in which the accelerator pedal 446 is fully depressed (Acc 100%), whereby it is intended that the accelerator pedal 446 may also assume intermediate positions.

The accelerator pedal position AccPed may be measured by the accelerator pedal position sensor 445 and compared to a predetermined accelerator position threshold AccFedm.

The predetermined accelerator position threshold AccPedm may be expressed as a percentage of depression of the accelerator pedal, in such a way that when the accelerator pedal is partially or fully depressed, the value of AccPed may be higher than the threshold AccPed and when the accelerator pedal is not depressed at all or only moderately depressed, the value of AccPed may be lower than the threshold AccPed.

Tn Figure 4 also the level of the minimum State Of Charge of the battery 600 is represented (curve D).

Following curve C it can been seen that the State Of Charge (SOC) of the battery 600 is influenced by the position of the accelerator pedal 446, namely if the accelerator pedal 446 is not depressed, the motor-generator unit (MGU) 500 may operate as electric generator and recharge the battery 600, while if the accelerator pedal 446 is fully depressed the [IOU 500 may operate as electric motor to provide additional torque to the vehicle but, in order to do so, the battery 600 must provide energy and therefore loses charge.

En Figure 4 this process continues until the state of charge oscillates around the minimum State of Charge (Mm SOC Limit), as seen in area 690.

This situation of the prior art may refer to the case in which the driver has performed urban driving for a certain amount of time and therefore the battery has not had good opportunities to recharge with the kinetic energy, or to other driving situations.

In this case, therefore if the battery State of Charge value is in area 690, there is no possibility for the battery to provide enough energy to the electric motor to perform a torque assist during a sport driving maneuver.

Pn entodiment of the invention will be now disclosed with reference to the flowchart of Figure 5.

In this embodiment of the method, the ECU 450 monitors the position AccPed of the accelerator pedal 446. The position of the accelerator pedal 446 may be measured, for example, by accelerator position sensor 445 connected to the ECU 450 (block 700).

A check is made between the monitored position Accped of the accelerator pedal 446 and the predetermined threshold AccPed thereof (block 710) If the monitored position AccPed of the accelerator pedal 446 is lower than the predetermined threshold AccPed, the minimum limit of the State Of Charge of the battery 600 is raised to a predetermined higher level thereof Raised Mm SOC (block 720) On the contrary, if the monitored position AccPed is higher than the predetermined threshold AccFed, the minimum State Of Charge limit of the battery 600 is set at a lowest value thereof Lowest Mm SOCu (block 730) This procedure is the repeated during the driving of the vehicle and, in particular, the State Of Charge limit of the battery 600 is raised to the predetermined value Raised Mm SOC1, if the position AccPed of the accelerator pedal 446 remains lower than the predetermined threshold AccPed for a predetermined interval of time THt.

Waiting for the predetermined interval of time THt allows to debounce the accelerator pedal signal in order to change the minimum State Of Charge of the battery 600.

Figure 6 is a graph that represents the State of Charge of the battery 600 in a hybrid powertrain 100, according to an enbodixnent of the invention.

Also in this case, two states of the accelerator pedal 446 are represented, namely a state in which the accelerator pedal 446 is not depressed and a state in which the accelerator pedal 446 is fully depressed (Acc 100%), whereby it is intended that the accelerator pedal 446 may also assume intermediate positions (curve A).

In Figure 6 also the level of the predetermined threshold AccPed is represented (curve B) In order to perform a comparison with the prior art situation of Figure 4, the profile of the accelerator pedal 446 positions is the same (curve A).

In this case however, the minimum State of Charge limit MinS± is adjusted according to the procedure described with reference to Figure 6.

In particular, the minimum State of Charge Unit MinSOCLiIIit is raised to a predetermined value Raised MinSOC (curve D'), when the monitored position (AccPed) is lower than a predetermined threshold AccPed.

On the contrary, the minimum State Of Charge limit MinSOC of the battery 00 is set at a lowest value thereof Lowest MinSOC when the monitored position AccPed is higher than the predetermined threshold AccPed.

This has the effect that the State Of Charge (SOC) of the battery 600 follows a different curve C' in which, for example, when the accelerator pedal 446 is not depressed (phases 735), there is an opportunity charging of the battery 600 (areas 740) in order to reach an higher State Of Charge to enable a subsequent full load maneuver, when the accelerator pedal 446 is fully depressed (phases 750), such as in sport driving.

In this second case the battery 600 will be discharged providing the electric motor with enough energy to perform an additional torque output that may be felt by the driver in response to the depressing of the accelerator pedal beyond the accelerator pedal threshold AccFed.

This process can be repeated during the driving of the vehicle 10 providing therefore a sport driving performance of the hybrid powertrain 100 when needed.

The fact that the battery minimum SOC limit is set at the lowest possible level Lowest MinSOC guarantees, at the same time, battery safety and electrical torque assist.

For the sake of simplicity the various entodiments of the invention have been presented with reference to the fact that the parameter representative of a torque request for the hybrid powertrain 110 can be expressed by the position of an accelerator pedal 446, however, a torque request for the hybrid powertrain may be also expressed in a different way, for example by the derivative of the position of the aOcelerator pedal or by a torque request from a subsystem of the hybrid powertrain such as Cruise Control device.

The parameter representative of the torque request may also be expressed in terms of its derivative or by a contination of the above mentioned parameters.

In general, therefore any of the above parameters AccPed representative of a torque request for the hybrid powertrain 110 is monitored by the ECU 450 and the minimum State Of Charge limit NinSOC of the battery 600 is raised to a predetermined value Raised MinSOC, when the monitored parameter value AccPed is lower than the predetermined threshold AccPed.

Also, the minimum State Of Charge limit MinSOCu,ut of the battery 600 is set at a lowest value thereof Lowest MinS0Cw.s when the monitored parameter value AccPed is higher than the predetermined threshold AccPed.

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

RflENE flNBS motor vehicle 11 drive wheels hybrid powertrain internal combustion engine engine block cylinder 130 cylinder head camshaft piston crankshaft combustion chamber 155 cain phaser fuel injector fuel rail fuel pump fuel source 200 intake manifold 205 air intake pipe 210 intake port 215 valves 220 exhaust port 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine - 260 intercooler 270 exhaust system 275 exhaust pipe 280 cc: 281 LNT 282 0FF 290 VGT actuator 300 exhaust gas recirculation system 310 EGR cooler 320 ECR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 in-cylinder pressure sensor 380 engine coolant temperature sensor 385 engine lubricant temperature sensor 390 engine metal 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 MCU shaft 510 transmission belt 600 battery 605 measuring circuit 610 measuring circuit 690 area 700 block 710 block 720 block 730 block 735 phase 740 area 750 phase aar

Claims

1. A method of operating a hybrid powertrain (100) comprising a motor-generator electric unit (500) equipped with a battery (600), the hybrid powertrain (110) being configured to receive a tcrque request wherein the operating method comprises the steps of: -monitoring a parameter (AccPed) representative of a torque request for the hybrid powertrain (110); -raising a minimum State Of Charge limit (MinSOC±tt) of the battery (600) to a predetermined value (Raised_inSinr±t) when the monitored parameter value (AccFed) is lower than a predetermined threshold (AccPedm).

2. A method according to claim 1, wherein the minimum State Of Charge limit (MinSOCuat) of the battery (600) is set at a lowest value thereof (Lowest MinSOCIAflItt) when the monitored parameter value (AccFed) is higher than the predetermined threshold (AccFedmi.

3. A method according to claim 1, wherein the State Of Charge limit (MinscCust) of the battery (600) is raised to the predetermined value (Raised_MinSOCtuat) if the value of the parameter (AccPed) remains lower than the predetermined threshold (AccPedmx) for a predetermined interval of time

4. A method according to claim 1, wherein when the monitored parameter value (AccEed) is higher than the predetermined threshold (AccFed), the battery (600) discharges and the motor-generator electric unit (500) provides a positive torque to the hybrid powertrain (100).

5. A method according to any of the preceding claims, wherein the parameter (AccFed) representative of a torque request for the hybrid powertrain (110) can be expressed by a position of an accelerator pedal (446), by a derivative thereof, by a torque request from a subsystem of the hybrid powertrain or by a derivative thereof or by a contination of the above.

6. Pn apparatus for operating a hybrid powertrain (100) comprising a motor-generator electric unit (500) equipped with a battery (600), the hybrid powertrain (110) being configured to receive a torque request, the apparatus comprising: - -means for monitoring a parameter (AccPed) representative of a torque request for the hybrid powertrain (110); -means for raising a minimum State Of Charge limit (MinSOCt) of the battery (600) to a predetermined value (Raised NinSOCun,it) when the monitored parameter value (Acc2ed) is lower than a predetermined threshold (AccFedmr).

7. An apparatus according to claim 6, wherein the means for monitoring the position of the accelerator pedal (446) comprise an accelerator pedal sensor (445) connected to an Electronic Control Unit (450) of the hybrid powertrain (100)

8. An automotive system comprising a hybrid powertrain (100) comprising a motor-generator electric unit (500) equipped with a battery (600), the hybrid powertrain (110) being configured to receive a torque request and being managed by an Electronic Control Unit (450), the Electronic Control Unit (450) being configured to: -monitor a parameter (AccPed) representative of a torque request for the hybrid powertrain (110); -raise a minimum State Of Charge limit (MinSiaxo±t) of the battery (600) to a predetermined value (Raised_MinSOCur:) when the monitored parameter value (AccPed) is lower than a predetenrd.ned threshold (AccPedrnr).

9. A hybrid powertrain (100), comprising a motor-generator electric unit (500) equipped with a battery (600), the hybrid powertrain (110) being configured to receive a torque request and being controlled by an Electronic Control Unit (450) configured for carrying out the method according to any of the claims 1-5.

10. A computer program comprising a computer-code suitable for performing the method according to any of the claims 1-5.U. computer program product on which the computer program according to claim 10 is stored.12. Control apparatus for a hybrid powertrain (100), comprising an Electronic Control Unit (450), a data carrier (460) associated to the Electronic Control Unit (450) and a computer program according to claim 10 stored in the data carrier (460).13. Pn electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 10.