Method for controlling a hybrid powertrain system and hybrid powertrain system

Abstract

Method for controlling a hybrid powertrain system (20) for a vehicle (100) comprising an internal combustion engine (40) and an electric machine (34, 36) mechanically coupled via a transmission (50) to generate mechanical power transferable to a powertrain and electrical energy, wherein the electrical energy is storable on an energy storage device (25), the method comprising: Determining an operator-selected mode and charging operation for the energy storage device (25); for the operator-selected mode and charging operation for the energy storage device (25): Determining a first speed / load range at which the internal combustion engine (40) is in an OFF state, wherein the first speed / load range is defined by the output torque and the vehicle speed, Determining a second speed / load range which has a speed preferred for the operation of the internal combustion engine (40), wherein the second speed / load range is defined by the output torque and the vehicle speed and wherein the preferred speed is essentially not perceptible in a passenger compartment of the vehicle (100); Determining an output torque requirement and a current vehicle speed; Operating the internal combustion engine (40) at the preferred engine speed, which is not perceptible in the passenger compartment, when the output torque requirement and the current vehicle speed are within the second operating range; and Controlling the electric machine (34, 36) and the internal combustion engine (40) to work together to generate the output torque in response to the output torque request when the output torque request is greater than a maximum output torque state associated with the vehicle speed of the second operating range.

Description

TECHNICAL AREA

[0001] This invention relates to powertrain systems that use multiple torque-generating devices and associated dynamic system controls. In particular, the invention relates to a method for controlling a hybrid powertrain system and to a hybrid powertrain system.

[0002] For example, DE 10 2016 209 851 A1 discloses a method for controlling a hybrid powertrain system in which the combustion engine and the electric machine are controlled in such a way that no audible engine noise occurs.

[0003] Regarding the further state of the art, reference should be made at this point to the publications DE 10 2010 039 653 A1, US 8 323 147 B2 and WO 02 / 042 110 A1, which also deal with the noise reduction of internal combustion engines. BACKGROUND

[0004] Hybrid powertrain systems generate drive torque from two or more energy sources, e.g., from hydrocarbon-based fuels through an internal combustion engine, and from electrical energy through one or more electric machines, with the drive torque being transmitted via a transmission train to an output element coupled to a powertrain.

[0005] Control systems for the operation of hybrid drive systems manage the torque output of the engine and electric machine(s) and employ torque transmission elements in the transmission to transfer torque in response to driver-directed output torque demands, taking into account fuel consumption, emissions, drivability, and other factors. A control system monitors various inputs from the vehicle and the operator and provides operational control of the hybrid powertrain, including controlling the transmission operating mode and gear shifting, controlling torque outputs from the engine and electric machine(s), and regulating the electrical power exchange between the electrical energy storage device and the electric machines to manage the transmission outputs, including torque and speed.

[0006] Hybrid powertrain systems can operate in an electric vehicle (EV) mode, where all drive torque is generated by the electric machine(s) with the internal combustion engine in an OFF state, and in electrically variable operating modes (EVT), where the internal combustion engine is in an ON state and can generate some or all of the drive torque or transfer it to an electric machine to generate electrical energy that can be transferred to the electric machine(s) to generate drive torque.

[0007] Operating a hybrid powertrain system in EV mode can increase customer satisfaction. However, operating in EV mode at or near the system's limits for such operation can decrease customer satisfaction related to engine startability and tip-in response. SUMMARY

[0008] A method for controlling a hybrid powertrain system for a vehicle is described and includes the features of claim 1. Furthermore, a hybrid powertrain system with the features of claim 9 is proposed. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The following describes one or more exemplary designs with reference to the attached drawings, in which: Fig. Figure 1 schematically represents a hybrid drive system comprising an internal combustion engine, transmission and electric combustion machines coupled to a drive train, according to the disclosure; Fig. Figure 2 schematically illustrates a signal flow diagram for a powertrain control routine for controlling an embodiment of the powertrain system, which refers to Fig. 1 described, including the advantageous operation of the internal combustion engine within a speed range that is not perceptible in the passenger compartment under conditions defined by the output torque requirement and the vehicle speed, according to the disclosure; Fig. Figure 3 illustrates a variety of operating ranges defined by a vehicle speed and a transmit output power associated with a first control strategy, including the operation of the powertrain system in the normal mode with charge depletion of the energy storage device according to the disclosure; Fig. Figure 4 graphically illustrates a variety of operating ranges defined by the vehicle speed and the transmission output power associated with the second control strategy, including the operation of the powertrain system in the engine normal operating mode, the energy storage device, in accordance with the disclosure; Fig. Figure 5 graphically illustrates a variety of operating ranges defined by vehicle speed and transmission output power associated with the second control strategy, including operation of the powertrain system in Sport mode with charge depletion of the energy storage device as disclosed; and Fig. Figure 6 graphically illustrates a variety of operating ranges defined by vehicle speed and transmission output power, which are associated with the fourth control strategy including the operation of the powertrain system mode, the energy storage device, in accordance with the disclosure. DETAILED DESCRIPTION

[0010] The following text refers to the drawings, the illustrations of which serve only to demonstrate certain exemplary embodiments, whereby Fig. Figure 1 is a schematic diagram of a vehicle 100, which includes a drive system 20 coupled to a final drive 60 and is controlled by a control system 10. The same reference numerals refer to the same elements throughout the description. The drive system 20 includes several torque-generating devices, including an internal combustion engine (motor) 40 and a first and second torque machine (electric machines) 34 and 36, respectively, which rotate to couple a transmission 50. An output element 62 couples between the transmission 50 and a drive system 60. Therefore, the internal combustion engine and the transmission 40, as well as the first and second electric machines 34 and 36, are engaged with the transmission 50 and can be controlled to generate an output torque, which is transmitted to the drive shaft 60 as the drive torque for the vehicle 100.

[0011] Other embodiments of a multimodal powertrain system, comprising an internal combustion engine and an electric machine arranged to generate drive torque and also to generate electrical energy, may instead be employed within the scope of this disclosure. For the purpose of definition, “output torque” refers to a positive (tracting) torque and a negative (braking) torque generated by the powertrain system 20 that can be transmitted to the output component 62. The powertrain system 20 is “hybrid” in that it uses two or more energy sources for vehicle propulsion.Some examples of suitable vehicles with some form of hybrid powertrain system include, but are not limited to, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric range extender electric vehicles (EREVs), dual-mode hybrids, power steering hybrids, series hybrids, parallel hybrids, series / parallel hybrids, power-split hybrids, belt-driven alternator-starter hybrids, hydraulic hybrids, pneumatic hybrids, etc. These vehicles may be passenger cars, crossover vehicles, SUVs, recreational vehicles, trucks, buses, commercial vehicles, etc. Although the following description is provided in the context of an exemplary plug-in hybrid electric vehicle (PHEV) with a range-extending series hybrid configuration, it should be understood that the present procedure can be used with any hybrid vehicle and is not limited to any particular type.

[0012] An embodiment of the motor and transmission 40 and the first and second electric motors 34, 36, which are coupled to the transmission train 50 and generate an output torque that is transmitted to the drive train 60 to generate a drive torque, is now described. A crankshaft 44 of the internal combustion engine 40 is connected to an input component 41, which is connected to a rotor of the first electric motor 34 via a third coupling 55. An output component of the rotor of the first electric motor 34 is connected via a second coupling 53 to a ring gear 56 of the gear train 50. The second electric motor 36 is rotatably connected to a sun gear 52 of the gear train 50. A planetary gear carrier 54 of the gear train 50 is connected to the drive system 60 via an output component 62. The ring gear 56 can be coupled to a body mass via a first coupling / brake 51.In one embodiment, the gear drive 50 is a simple planetary gear set comprising a sun gear 52, a planet gear and carrier 54, and a ring gear 56. A transmission control unit 57 monitors the rotational speeds of various rotating components and controls the activation of the first, second, and third clutches 51, 53, and 55.

[0013] The engine 40 is preferably a multi-cylinder internal combustion engine that converts fuel into mechanical torque via a thermodynamic combustion process. The engine 40 is equipped with several actuators and sensor devices for operational monitoring and for fuel supply to form cylinder-internal combustion charges to generate an expanding force, which is transmitted via pistons and connecting rods to the crankshaft 44 to generate torque. The operation of the engine 40 is controlled by an engine control module (ECM) 45. In one embodiment, the engine 40 may include an electromagnetically actuated low-voltage electric starter 42 for starting the engine in response to a starting event initiated with a key. The engine 40 is designed to perform engine start and stop operations, including automatic start and stop routines during vehicle operation.The engine 40 can be configured to execute auto-start and auto-stop control programs, fuel cut-off control programs, and cylinder deactivation control programs during the operation of the powertrain system 20. The engine 40 is considered off when it is not rotating. The engine 40 is on when it is rotating, including one or more FCO states in which it rotates without a fuel supply. The transmission can be any suitable device and is a multi-stage transmission configured to transmit engine speed and torque at one of several fixed gear ratios in response to operator input in one embodiment.

[0014] The first and second electric machines 34, 36 are preferably high-voltage multiphase electric motors / generators electrically connected via a first and a second inverter circuit 33 and 35, respectively, to a high-voltage energy storage device (battery) 25. The terms "energy storage device" and "battery" are used interchangeably throughout this description. The first and second electric motors 34, 36 are configured to convert the stored electrical energy into mechanical energy and the mechanical energy into electrical energy, which can be stored in the battery 25. The battery 25 can be a high-voltage energy storage device, i.e., a multi-cell lithium-ion device, an ultracapacitor, or any other suitable device.In one embodiment, the battery 25 can be connected to a remote, external electrical power source via a built-in battery charger 24 to charge the vehicle 100 while stationary. The battery 25 is electrically connected to the first inverter module 33 via the high-voltage direct current line 29 to transmit high-voltage direct current energy to the first electric motor 34 in response to signals from the control system 10. Likewise, the battery 25 is electrically connected to the second inverter module 35 via the high-voltage direct current line 29 to transmit high-voltage direct current energy to the second electric motor 36 in response to signals from the control system 10.

[0015] Each of the first and second electric motors 34, 36 comprises a rotor and a stator and is electrically connected to the high-voltage battery 25 via the corresponding first and second inverter circuits 33, 35 and the high-voltage DC line 29. The first and second inverter modules 33, 35 are both configured with suitable control circuits comprising power transistors, i.e., IGBTs, for converting high-voltage DC energy to high-voltage AC energy and vice versa. Each of the first and second inverter modules 33, 35 preferably uses pulse-width modulation (PWM) control to convert stored DC energy from the high-voltage battery 25 into AC energy to drive the first and second electric motors 34, 36, respectively, to generate torque.Similarly, the first and second inverter modules 33, 35 convert mechanical energy transferred to the respective first and second electric motors 34, 36 into direct current energy to generate electrical energy that can be stored in the battery 25, including as part of a regenerative energy control strategy. The first and second inverter modules 33, 35 are both configured to receive motor control commands and control the inverter states to provide motor drive and regenerative vehicle braking functionality. In one embodiment, an electrical DC / DC energy converter 23 is electrically connected to a low-voltage line 28, a low-voltage battery 27, and the high-voltage DC line 29. Such electrical connections are known and are not described in detail here.The low-voltage battery 27 provides an electrical connection to an additional network system 26 to supply low-voltage electrical current to the vehicle's low-voltage systems, which include, for example, electric windows, HVAC fans, seats and the electromagnetically operated low-voltage electrical switch 42.

[0016] The drive system 60 can include a differential gear drive device 65, which is mechanically connected to an axle, a trans-axle, or a half-axle 64, which in one embodiment is mechanically connected to a wheel 66. The drive system 60 transmits drive torque between the wheel drive 50 and a road surface.

[0017] A driver interface 14 of the vehicle 100 includes a controller that is connected via signaling to a variety of human-machine interface devices through which the driver controls the operation of the vehicle 100. The human-machine interface devices include, for example, an accelerator pedal 15, a brake pedal 16, and a transmission mode selector (PRNDL) 17. Other human-machine interface devices preferably include an ignition switch to allow an operator to start and operate the engine 40, a steering wheel, and a headlight switch. The accelerator pedal 15 provides a signal input indicating an accelerator pedal position, and the brake pedal 16 provides a signal input indicating a brake pedal position.The transmission range selection device 17 provides a signal input that specifies a direction of vehicle movement intended by the operator, including a discrete number of operator-selectable positions that indicate a preferred direction of rotation of the output component 62 in either a forward or reverse direction. As shown, the transmission range selection device 17 can also select a preferred powertrain operating mode, such as a normal mode, a sport mode, a hill mode, or another suitable powertrain operating mode. The powertrain operating modes are used to provide operator preferences for the vehicle control 12, such preferences including one of several preferred transmission shift patterns and one of several preferred battery state of charge (SOC) levels.One of the many preferred transmission shift patterns can be selected based on preferred shift patterns associated with speed and load, such as an aggressive shift pattern or one that maximizes fuel economy. One of a variety of preferred battery state of charge (SOC) levels can be selected depending on the expected operation of the vehicle, such as climbing a grade or discharging, to achieve a minimum SOC in anticipation of reaching a target point.

[0018] The control system 10 includes a controller 12, which is connected to the operator interface 14 via signal technology. The controller 12 preferably includes several discrete devices which, together with the individual elements of the drivetrain system 20, are arranged to effect operational control of the individual elements of the drivetrain system 20 in response to operator and drivetrain commands. The controller 12 may also include a control device that provides hierarchical control of other control devices. The controller 12 is communicatively connected to the high-voltage battery 25, the first and second inverter modules 33, 35, the motor control 45, and the transmission control 57, either directly or via a communication line 18, in order to monitor and control their operation.

[0019] The controller 12 controls the operation of the powertrain system 20, including selecting and controlling operation in one of several operating modes for generating torque and transmitting it between the torque-generating devices, e.g., between the motor 40 and the first and second electric motors 34, 36 and the drive system 60. The operating modes preferably include one or more electric vehicle (EV) modes, in which the motor 40 is switched off and the first and / or second electric motor 34, 36 generates drive torque. The operating modes preferably also include an electrically variable mode in which the motor 40 and one or both of the first and / or second electric motors 34, 36 generate drive torque.The operating modes preferably also include an electric vehicle range extension mode in which the motor 40 is switched on and generates electrical energy through the first electric motor 34, and the second electric motor 36 generates drive torque. The electric vehicle range extension mode, the electric vehicle mode, and the electrically variable mode each have an associated battery charging mode, which can be either a charge maintenance mode or a charge discharge mode. The charge discharge mode can involve operating the motor 40 in the OFF state, and the charge maintenance mode can involve operating the motor 40 in the ON state. The charge maintenance mode initiates powertrain operation in which the state of charge of the battery 25 is preferably maintained at a predetermined level, with the possibility of short-term deviations resulting from vehicle operation.The charge discharge mode initiates a powertrain operation in which the state of charge of battery 25 is preferably discharged at a predetermined rate, with the possibility of short-term deviations resulting from vehicle operation.

[0020] The terms controller, control module, module, controller, control unit, processor, and similar terms refer to one or more combinations of application-specific integrated circuits (ASICs), electronic circuits, central processing units (CPUs), e.g., microprocessors, and associated non-volatile memory components in the form of memory and storage devices (read memory, programmable read memory, direct access memory, hard disk, etc.). The non-volatile memory component is capable of storing machine-readable instructions in the form of one or more software or firmware programs or routines, combinational logic circuits, input / output circuits and devices, signal conditioning and buffer circuits, and other components that can be accessed by one or more processors to provide a described functionality.Input and output devices and circuits include analog-to-digital converter-related devices that monitor sensor inputs at a predetermined polling frequency or in response to a trigger event. Software, firmware, programs, instructions, control routines, code, algorithms, and similar terms refer to any set of instructions executable by a controller, such as calibrations and lookup tables. Each controller executes a control program (or programs) for the desired functions, including monitoring inputs from sensor devices and other networked controllers, and executing control and diagnostic programs to manage actuator operation. Programs may be executed at regular intervals, for example, every 100 milliseconds, 3.125 ms, 6.25 ms, 12.5 ms, 25 ms, and 100 ms during continuous engine and vehicle operation. Alternatively, routines may be executed in response to a trigger event.

[0021] The powertrain system 20 includes a communication scheme that incorporates the communication line 18 to facilitate communication in the form of sensor signals and actuator command signals between the control system 10, the vehicle 100, and the powertrain system 20. The communication scheme uses one or more communication systems and devices, including, for example, the communication bus 18, a direct connection, a LAN bus, a Serial Peripheral Interface bus, and wireless communication, to transmit information. Communication between controllers and between controllers, actuators, and / or sensors can be accomplished via direct wiring, a networked communication bus connection, a wireless connection, or any other suitable communication link. Communication content includes the exchange of data signals in any suitable manner, including, for example,Electrical signals are transmitted via a conductive medium, electromagnetic signals via air, optical signals via fiber optics, and the like. Data signals can include, among other things, signals representing sensor inputs, signals representing actuator commands, and communication signals between controllers. As used here, the term "dynamic" describes steps or processes that are executed in real time and are characterized by monitoring or otherwise determining parameter states and regularly or periodically updating parameter states during the execution of a routine or between iterations of the routine.

[0022] Methods and systems in the form of control routines and associated calibrations can be used to provide improved powertrain system responsiveness to operator commands, such as accelerator pedal peak events. Such responsiveness can provide enhanced operator perception associated with powertrain operation in EV mode, including operation in any of a variety of operator-selectable modes. This involves a control routine that can manipulate motor speed and torque at various vehicle speeds and axle torque commands, based on different operator-selectable modes, in such a way that the operator is less likely to perceive motor operation.The control routine controls the motor to act differently based on the state of charge, the selectable operating mode, the vehicle speed and the axle torque commands, while generating an output torque that responds to the output torque request.

[0023] Fig. Figure 2 schematically shows a signal flow diagram for a powertrain control routine 200 for controlling a powertrain system comprising an internal combustion engine and an electric machine mechanically coupled via a transmission linkage. The powertrain control routine 200 advantageously operates the internal combustion engine at a preferred speed within a speed range that is imperceptible to the driver in the passenger compartment under conditions defined by the output torque requirement and the vehicle speed. The powertrain system operates to generate an output torque that can be transferred to a drivetrain and either generates or consumes electrical energy, which can be stored on an energy storage device. A non-restrictive embodiment includes the vehicle 100 and the powertrain system 20, which, with reference to Fig. 1 are described.

[0024] The powertrain control routine 200 involves determining an operator-selected operating mode 204 and determining charging information related to the energy storage device, which can be used when selecting a preferred charging operating mode 202. The charging information includes factors such as state of charge (SOC), battery temperature, and other related factors. The operator-selected mode can be one of a normal mode, sport mode, mountain mode, etc., and displays user-selectable preferences for shipment displacement, battery charging, and other elements. The preferred charging mode can be one of a charge maintenance mode or a charge depletion mode. The charge depletion mode and charge maintenance mode refer to control routines for managing the state of charge (SOC) of the energy storage device.In charge depletion mode, the powertrain control system manages powertrain operation such that the state of charge (SOC) of the energy storage device reaches a minimum state during a vehicle start-up or acceleration cycle, and it manages the torque from the internal combustion engine and the torque of the electric machine(s) based thereon. In charge maintenance mode, the powertrain control system manages powertrain operation such that the SOC of the energy storage device at the end of a vehicle journey is at or near the same level as it was at the beginning of the journey, and it manages the torque from the internal combustion engine and the torque of the electric machine(s) based thereon. The operator-selected mode 204 and the preferred charging mode 202 are compiled 206.

[0025] If a first operator-selectable mode, e.g., normal mode, is selected 208 and the preferred charging mode is charge degradation mode, a first control strategy 300 is selected to determine a first preferred engine speed 301 while the operation of the powertrain system is controlled depending on an output torque requirement 201 and an output speed 203. The output torque requirement 201 and the output speed 203 can be easily translated to the output power and vehicle speed based on factors that are easily determined. The first control strategy 300 is selected with reference to Fig. 3 described.

[0026] When the first operator-selectable mode is chosen, e.g., normal mode 208, and the preferred charging mode is charge maintenance mode, a second control strategy 400 is selected to determine a second preferred motor speed 401 while the operation of the powertrain system is controlled depending on an output torque request 201 and an output speed 203. The second control strategy 400 is selected with reference to Fig. 4 described.

[0027] If a second operator-selectable mode is chosen, e.g., Sport mode 210, and the preferred charging mode is charge depletion mode, a third control strategy 500 is selected to determine a third preferred engine speed 501 while the operation of the powertrain system is controlled depending on an output torque request 201 and an output speed 203. The third control strategy 500 is selected with reference to Fig. 5 described.

[0028] When the second operator-selectable mode is chosen, e.g., Sport mode 210, and the preferred charging mode is charge maintenance mode, a fourth control strategy 600 is selected to determine a fourth preferred engine speed 601 while the operation of the powertrain system is controlled depending on an output torque request 201 and an output speed 203. The fourth control strategy 600 is selected with reference to Fig. 6 described.

[0029] With reference to Fig. Figure 3 graphically represents a variety of speed / load operating ranges assigned to the first control strategy 300, and these are assigned to the normal mode for powertrain operation with energy storage device charge depletion. The numerical values ​​are non-restrictive and for illustrative purposes only. Speed ​​302 is shown on the horizontal axis in the form of vehicle speed (mph), and load 304 is shown on the vertical axis in the form of transmission output power (kW). The orders of magnitude for speed 302 and load 304 are only for illustrative purposes of a non-restrictive embodiment. Line 303 shows a maximum charge power, which corresponds to a maximum negative value for load 304. Line 305 shows a speed / load limit, indicating a transition between the motor ON and OFF states.Line 325 illustrates a second speed / load limit line.

[0030] A first speed / load range 310 is defined by lines 303 and 305 and indicates speed / load operating points where the internal combustion engine is in an OFF state and all drive torque is supplied by the electric machine(s).

[0031] A second speed / load range 320 is defined by lines 305 and 325 and indicates speed / load operating points where the internal combustion engine is in the ON state, its operation being restricted in a manner that renders it essentially imperceptible to the passenger compartment and the driver. The limits associated with the second speed / load range 320 can be empirically determined for a vehicle and powertrain system configuration. This may involve taking acoustic measurements at one or more locations within a vehicle interior under frictionless road conditions at various road load states over a range of speed and load conditions for the engine and electric machine.The operation of the internal combustion engine can be perceived as essentially imperceptible in the passenger compartment and by the driver if the sound energy in decibels generated by the operation of the internal combustion engine is lower than the sound energy generated by the operation of the vehicle on a level road surface in conjunction with the operation of the internal combustion engine under known speed and load conditions. The sound energy of interest is preferably at a low frequency, e.g., between 50 Hz and 250 Hz.

[0032] The second speed / load range 320 can be subdivided into several subranges, including, for example, subranges 322, 324, and 326. The first subrange 322 comprises the section of the second range 320 where the load is negative, i.e., when the vehicle is coasting or braking. The internal combustion engine is in the ON state, preferably in a fuel cut-off state, and is rotating at a predetermined speed, e.g., 1200 rpm. The second subrange 324 comprises the section of the second range 320 where the load is low, and most or all of the drive torque is generated by the electric machine(s). The internal combustion engine is in the ON state and operates at low speed and low torque. The third subrange 326 comprises the section of the second range 320 where the load is moderate, and the electric machine(s) is...The electric machines operate at or near their maximum torque output, generating additional drive torque from the internal combustion engine.

[0033] The third area, 330, encompasses the speed / load operating points at which the motor's operation may be perceptible in the passenger compartment and to the driver. Such operation involves running the electric motor(s) at or near their maximum torque output, thereby generating additional drive torque from the internal combustion engine.

[0034] With reference to Fig. Figure 4 graphically represents a variety of speed / load operating ranges associated with the second control strategy 400 and is assigned to the normal mode for powertrain operation and the charge maintenance mode of the energy storage system. The numerical values ​​are non-limiting and serve for illustrative purposes. The speed 402 is shown on the horizontal axis in the form of vehicle speed (mph), and the load 404 is shown on the vertical axis in the form of transmission output power (kW). The values ​​for speed 402 and load 404 are only intended to illustrate a non-limiting embodiment. Line 403 indicates a maximum charging power, which is associated with a maximum negative value for load 404. Line 405 illustrates a speed / load limit indicating a transition between the motor ON and OFF states. Line 425 shows a second speed / load limit line.

[0035] A first speed / load range 410 is defined by lines 403 and 405 and indicates speed / load operating points where the internal combustion engine is in an OFF state and all drive torque is supplied by the electric machine(s).

[0036] A second speed / load range 420 is bounded by lines 405 and 425 and indicates speed / load operating points where the internal combustion engine is in the ON state, its operation restricted in a manner that renders its operation imperceptible to the driver in the passenger compartment. The limits associated with the second speed / load range 420 can be empirically determined for a vehicle and powertrain system configuration as described herein. The second speed / load range 420 can be subdivided into several sub-ranges, including, for example, sub-ranges 422 and 426. The first sub-range 422 comprises the portion of the second range 420 where the load is negative, i.e., where the vehicle is coasting or braking. The internal combustion engine is in the ON state, preferably in a fuel cut-off state, and is rotating at a predetermined speed, for example, 1200 rpm.The second sub-area 426 comprises the section of the second area 420 where the load is low or moderate, and most or all of the drive torque is generated by the electric machine(s). The internal combustion engine is in the ON state and operates at low speed and low torque, and the electric machine(s) operate at or near their maximum torque output, generating additional drive torque from the internal combustion engine.

[0037] The third area, 430, encompasses the speed / load operating points at which the motor operation may be perceptible in the passenger compartment and to the driver. Such operation involves running the electric motor(s) at or near their maximum torque output, thereby generating additional drive torque from the internal combustion engine.

[0038] With reference to Fig. Figure 5 graphically represents a variety of speed / load operating ranges associated with the third control strategy 500 and the sport mode for powertrain operation with energy storage device charge depletion. The numerical values ​​are non-limiting and serve for illustration purposes. Speed ​​502 is shown on the horizontal axis in the form of vehicle speed (mph), and load 504 is shown on the vertical axis in the form of transmission output power (kW). The values ​​for speed 502 and load 504 are merely for illustrating a non-limiting embodiment. Line 503 indicates a maximum charging power, which is associated with a maximum negative value for load 504. Line 505 illustrates a speed / load limit indicating a transition between the engine ON and OFF states. Line 525 shows a second speed / load limit line.

[0039] A first speed / load range 510 is defined by lines 503 and 505 and indicates speed / load operating points where the internal combustion engine is in the OFF state and all drive torque is supplied by the electric machine(s).

[0040] A second speed / load range 520 is bounded by lines 505 and 525 and indicates speed / load operating points where the internal combustion engine is in the ON state, its operation restricted in such a way as to render its operation imperceptible to the driver in the passenger compartment. The boundaries associated with the second speed / load range 520 can be empirically determined for a vehicle and powertrain system configuration as described herein. This may involve taking acoustic measurements at one or more locations within a vehicle interior under frictionless road conditions and under various road load conditions. The second speed / load range 520 can be subdivided into several subranges, including, for example, subranges 522, 524, and 526. The first subrange 522 contains the portion of the second range 520 where the load is negative, i.e.,in which the vehicle coasts or brakes. The internal combustion engine is in the ON state, preferably in a fuel cut-off state, and is rotating at a predetermined speed, e.g., 1200 rpm. The second sub-section 524 comprises the portion of the second section 520 where the load is low, and most or all of the drive torque is generated by the electric machine(s). The internal combustion engine is in the ON state and operates at low speed and low torque. The third sub-section 526 comprises the portion of the second section 520 where the load is moderate, and the electric machine(s) operates at or near their maximum torque output, generating additional drive torque from the internal combustion engine.

[0041] The third area, 530, encompasses the speed / load operating points at which the motor operation may be perceptible in the passenger compartment and to the driver. Such operation involves running the electric motor(s) at or near their maximum torque output, thereby generating additional drive torque from the internal combustion engine.

[0042] With reference to Fig. Figure 6 graphically represents a variety of speed / load operating ranges associated with the fourth control strategy 600 and is linked to the sport mode for powertrain operation with the charge maintenance mode of the energy storage device. The numerical values ​​are non-limiting and serve for illustration purposes. Speed ​​602 is shown on the horizontal axis in the form of vehicle speed (mph), and load 604 is shown on the vertical axis in the form of transmission output power (kW). The values ​​for speed 602 and load 604 are only intended to illustrate a non-limiting embodiment. Line 603 indicates a maximum charging power, which is associated with a maximum negative value for load 604. Line 605 illustrates a speed / load limit indicating a transition between the engine ON and OFF states. Line 625 shows a second speed / load limit line.

[0043] A first speed / load range 610 is defined by lines 603 and 605 and indicates speed / load operating points where the internal combustion engine is in an OFF state and all drive torque is supplied by the electric machine(s).

[0044] A second speed / load range 620 is bounded by lines 605 and 625 and indicates speed / load operating points where the internal combustion engine is in the ON state, its operation restricted in such a way as to render its operation imperceptible to the driver in the passenger compartment. The limits associated with the second speed / load range 620 can be empirically determined for a vehicle and powertrain system configuration as described herein. This may involve taking acoustic measurements at one or more locations within a vehicle interior under frictionless road conditions and under various road load conditions. The second speed / load range 620 can be subdivided into several subranges, including, for example, subranges 622 and 626. The first subrange 622 comprises the portion of the second range 620 where the load is negative, i.e.,in which the vehicle coasts or brakes. The internal combustion engine is in the ON state, preferably in a fuel cut-off state, and is rotating at a predetermined speed, e.g., 1200 rpm. The second sub-section 626 comprises the portion of the second section 620 where the load is low or moderate, and most or all of the drive torque is generated by the electric machine(s). The internal combustion engine is in the ON state and operates at low speed and low torque, and the electric machine(s) operates at or near their maximum torque output, generating additional drive torque from the internal combustion engine.

[0045] The third area, 630, encompasses the speed / load operating points at which the motor operation may be perceptible in the passenger compartment and to the driver. Such operation involves running the electric motor(s) at or near their maximum torque output, thereby generating additional drive torque from the internal combustion engine.

[0046] With reference to Fig.2, one of the first, second, third, and fourth preferred motor speeds 301, 401, 501, and 601 is selected 220 and used to determine a final transmission state 222 and a final selected motor speed 224, which are used to control the operation of the powertrain system in response to operator commands. As such, the powertrain control routine 200 controls the electric machine(s) to produce an output torque in response to the output torque request when the output torque request and the vehicle speed are within the first respective operating range 310, 410, 510, 610.

[0047] Furthermore, the powertrain control routine controls the electric machine(s) to generate an output torque and controls the operation of the internal combustion engine at the final selected engine speed 224 within the operating range, which is not perceptible in the passenger compartment or to the driver, when the output torque requirement and the vehicle speed are within the second respective operating range 320, 420, 520, 620.

[0048] Furthermore, the powertrain control routine controls the electric machine(s) and the internal combustion engine to work together to generate the output torque at the final selected engine speed 224 in response to the output torque request, if the output torque request is greater than the maximum output torque state associated with the vehicle speed of the second respective operating range 320, 420, 520, 620.

[0049] As such, the motor speed and torque can be manipulated at different vehicle speeds and axle torque commands based on various operator-selectable operating modes, making it unlikely that the operator will perceive the operation of the internal combustion engine, thus creating an overall electric impression of vehicle operation. The motor behaves differently based on the state of charge, the selected operating mode, the vehicle speed, and the axle torque command.

Claims

[1] Method for controlling a hybrid powertrain system (20) for a vehicle (100) comprising an internal combustion engine (40) and an electric machine (34, 36) mechanically coupled via a transmission (50) to generate mechanical power transferable to a powertrain and electrical energy, wherein the electrical energy is storable on an energy storage device (25), the method comprising: Determining an operator-selected mode and charging operation for the energy storage device (25); for the operator-selected mode and charging operation for the energy storage device (25): Determining a first speed / load range at which the internal combustion engine (40) is in an OFF state, wherein the first speed / load range is defined by the output torque and the vehicle speed, Determining a second speed / load range which has a speed preferred for the operation of the internal combustion engine (40), wherein the second speed / load range is defined by the output torque and the vehicle speed and wherein the preferred speed is essentially not perceptible in a passenger compartment of the vehicle (100); Determining an output torque requirement and a current vehicle speed; Operating the internal combustion engine (40) at the preferred engine speed, which is not perceptible in the passenger compartment, when the output torque requirement and the current vehicle speed are within the second operating range; and Controlling the electric machine (34, 36) and the internal combustion engine (40) to work together to generate the output torque in response to the output torque request when the output torque request is greater than a maximum output torque state associated with the vehicle speed of the second operating range. [2] Method according to claim 1, further comprising controlling the electric machine (34, 36) to generate an output torque depending on the output torque requirement, while the internal combustion engine (40) is operated at the preferred engine speed, which is not perceptible in the passenger compartment when the output torque requirement and the vehicle speed are within the second operating range. [3] Method according to claim 1, further comprising controlling the electric machine (34, 36) to generate an output torque in response to the output torque request when the output torque request and the vehicle speed are within the first operating range. [4] Method according to claim 1, wherein the charging mode comprises a charge maintenance mode. [5] Method according to claim 1, wherein the charging mode comprises a charge depletion mode. [6] Method according to claim 1, wherein the mode selected by the operator comprises a normal mode which refers to a circuit diagram of the transmission. [7] Method according to claim 1, wherein the mode selected by the operator comprises a sport mode which relates to a circuit diagram of the transmission. [8] Method according to claim 1, wherein the preferred engine speed, which is essentially not perceptible in a passenger compartment of the vehicle (100), comprises an engine speed wherein a sound power generated by the operation of the internal combustion engine (40) is less than a sound energy generated by the operation of the vehicle (100) on a level road surface in conjunction with the operation of the internal combustion engine. [9] Hybrid powertrain system (20) for a vehicle (100), comprising: an internal combustion engine (40) and an electric machine (34, 36) mechanically coupled via a gear train (50) to generate mechanical power transferable to a drive train and electrical energy, wherein the electrical energy can be stored on an energy storage device (25); and a control unit (10) which includes a set of instructions that can be executed to do the following: Determining an operator-selected mode and charging operation for the energy storage device (25); for the operator-selected mode and charging operation for the energy storage device (25): Determining a first speed / load range at which the internal combustion engine (40) is in an OFF state, wherein the first speed / load range is defined by the output torque and the vehicle speed, Determining a second speed / load range which has a speed preferred for the operation of the internal combustion engine (40), wherein the second speed / load range is defined by the output torque and the vehicle speed and wherein the preferred speed is essentially imperceptible in a passenger compartment of the vehicle (100); Determining an output torque requirement and a current vehicle speed; Operating the internal combustion engine (40) at the preferred engine speed, which is not perceptible in the passenger compartment, when the output torque requirement and the current vehicle speed are within the second operating range; and Controlling the electric machine (34, 36) and the internal combustion engine (40) to work together to generate the output torque in response to the output torque request when the output torque request is greater than a maximum output torque state associated with the vehicle speed of the second operating range.

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