Patent Application
20170305405
This disclosure relates to hybrid powertrain systems, and transmission gear selection related thereto.
Hybrid powertrain systems may employ internal combustion engines and transmissions that are arranged in a parallel configuration with a torque machine to generate traction power for vehicle propulsion. Selection of a preferred gear range for operating the transmission may be affected by power output from the torque machine.
A hybrid powertrain system is described, and includes an internal combustion engine and a transmission arranged in a parallel configuration with a non-combustion torque machine to transfer traction power to a driveline of a vehicle. A method of controlling the hybrid powertrain system includes monitoring vehicle speed and an accelerator pedal position and determining a traction power command based thereon. A motor power that is input to the driveline from the torque machine is determined, and an adjusted engine power command is determined based upon the traction power command and the motor power from the torque machine is determined. An adjusted accelerator pedal position is determined based upon the adjusted engine power command and the vehicle speed, and a preferred transmission state is determined based upon the adjusted accelerator pedal position and the vehicle speed. The transmission is controlled to the preferred transmission state.
The above features and advantages, and other features and advantages, of the present teachings are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings, as defined in the appended claims, when taken in connection with the accompanying drawings.
One or more embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:
Referring now to the drawings, wherein the showings are for the purpose of illustrating certain exemplary embodiments only and not for the purpose of limiting the same,
The embodiment of the powertrain system 20 shown with reference to
The internal combustion engine 40 and the second torque machine 34 couple to the gear train 50 and are controllable to generate traction power that may be described in terms of an output torque and a rotational speed. The traction power is transferred to the driveline 60 to propel the vehicle 100. Other embodiments of a powertrain system that include an internal combustion engine arranged in parallel with at least one torque machine to generate traction power may be employed within the scope of this disclosure. By way of definition, ‘output torque’ refers to both positive (tractive) torque and negative (braking) torque, both which can be generated by the powertrain system 20 and transferred to the output member 62. The vehicle 100 may include, by way of non-limiting examples, a passenger vehicle, a light-duty or heavy-duty truck, a utility vehicle, an agricultural vehicle, an industrial/warehouse vehicle, or a recreational off-road vehicle.
The powertrain system 20 includes the internal combustion engine 40, the first torque machine 36 and the second torque machine 34 generate output torque that is transferred via the driveline 60 to the first drive wheels 66 and to the second drive wheels 68 to generate propulsion torque. The crankshaft 44 of the internal combustion engine 40 couples via a torque converter 46 to the transmission 48, and its output member 49 rotatably couples to a gear of the gear train 50. The gear train 50 may be any suitable geared mechanism.
The engine 40 is preferably a multi-cylinder internal combustion engine that converts fuel to mechanical torque through a thermodynamic combustion process. The engine 40 is equipped with a plurality of actuators and sensing devices for monitoring operation and delivering fuel to form in-cylinder combustion charges that generate an expansion force that is transferred via pistons and connecting rods to the crankshaft 44 to produce torque. Operation of the engine 40 is controlled by an engine controller (ECM) 45.
The transmission 48 may be any suitable transmission device for transferring torque between a torque-generating device, e.g., engine 40, and the output member 49. The transmission 48 may be commanded to one of a plurality of gear ranges, including, e.g., Park, Reverse, Neutral and Drive. In one embodiment, the transmission 40 is a multi-step gear transmission that includes a plurality of meshable gears and selectively activatable clutches that are configured to transfer torque generated by the internal combustion engine 40 to the output member 49 in one of a plurality of fixed gear ratios. The fixed gear ratios may be automatically selectable or operator-selected. Alternatively, the transmission 48 may be a continuously-variable transmission (CVT) that employs a variator that is controllable to a speed ratio of output speed to input speed, wherein the speed ratio that is infinitely variable over a predetermined range of operation. CVTs are known and not described in further detail herein. The transmission 48 may include a mechanically-driven hydraulic pump, a hydraulic circuit, a clutch assembly, and other torque transfer elements including, by way of non-limiting examples, planetary gear sets, clutches, brakes, and the like. A transmission controller (TCM) 57 monitors rotational speeds of various rotating members and controls operation of various controllable components, including the clutches of the transmission 48 and a torque converter clutch of the torque converter 46. The TCM 57 includes executable code to control the transmission 48 to a preferred state in response to operating conditions. The preferred state may be a selected transmission gear and associated gear ratio when the transmission 48 is a step-gear transmission. The preferred state may be a selected transmission speed ratio when the transmission 48 is a CVT.
The first torque machine 36 may be any suitable non-combustion torque machine, and is a high-voltage multi-phase electric motor/generator in one embodiment, and as shown. The first torque machine 36 includes the rotor and a stator, and electrically connects to a high-voltage DC power source (battery) 25 via a first inverter circuit 35 and a high-voltage DC bus 29. Other torque machines may include, by way of non-limiting examples, a pneumatically-powered torque machine or a hydraulically-powered torque machine. Pneumatically-powered torque machines and hydraulically-powered torque machines are known to those skilled in the art, and not described in detail herein. The first torque machine 36 is configured to convert stored electric energy to mechanical power and convert mechanical power to electric energy that may be stored in the battery 25. The battery 25 may be any high-voltage DC power source, e.g., a multi-cell lithium ion device, an ultracapacitor, or another suitable device without limitation. In one embodiment, the battery 25 may electrically connect via an on-vehicle battery charger 24 to a remote, off-vehicle electric power source for charging while the vehicle 100 is stationary. The battery 25 electrically connects to the first inverter module 35 via the high-voltage DC bus 29.
The first inverter module 35 is configured with suitable control circuits including power transistors, e.g., IGBTs for transforming high-voltage DC electric power to high-voltage AC electric power and transforming high-voltage AC electric power to high-voltage DC electric power. The first inverter module 35 is controlled to transfer high-voltage DC electric power to the first torque machine 36 in response to control signals originating in the control system 10. The first inverter module 35 preferably employs pulsewidth-modulating (PWM) control to convert stored DC electric power originating in the high-voltage battery 25 to AC electric power to drive the first torque machine 36 to generate torque. Similarly, the first inverter module 35 converts mechanical power transferred to the first torque machine 36 to DC electric power to generate electric energy that is storable in the battery 25, including as part of a regenerative power control strategy. The first inverter module 35 is configured to receive motor control commands and control inverter states to provide the motor drive and regenerative braking functionality.
The second torque machine 34 and second inverter module 33 may be analogous devices to the first torque machine 36 and the first inverter module 35, respectively, although they may be suitably sized at different torque and power ratings.
In one embodiment, a DC/DC electric power converter 23 electrically connects to a low-voltage bus 28 and a low-voltage battery 27, and electrically connects to the high-voltage DC bus 29. Such electric power connections are known and not described in detail. The low-voltage battery 27 electrically connects to an auxiliary power system 26 to provide low-voltage electric power to low-voltage systems on the vehicle, including, e.g., electric windows, HVAC fans, seats, and the low-voltage solenoid-actuated electrical starter.
The driveline 60 may include a differential gear device 65 that mechanically couples to an axle, transaxle or half-shaft 64 that mechanically couples to the first wheels 66 that interact with a road surface in one embodiment. The driveline 60 transfers propulsion torque between the gear train 50 and the first drive wheels 66 to the road surface.
An operator interface 14 of the vehicle 100 includes a controller that signally connects to a plurality of human/machine interface devices through which the vehicle operator commands operation of the vehicle 100. The human/machine interface devices include, e.g., an accelerator pedal 15, a brake pedal 16, and a transmission range selector 17. Other human/machine interface devices preferably include an ignition switch to enable an operator to crank and start the engine 40, a steering wheel, and a headlamp switch. The accelerator pedal 15 provides signal input indicating an accelerator pedal position (PPS) and the brake pedal 16 provides signal input indicating a brake pedal position (BPS). The transmission range selector 17 provides signal input indicating direction of operator-intended motion of the vehicle (PRNDL) including a discrete number of operator-selectable positions indicating the preferred rotational direction of the output member 62 in either a forward direction, a reverse direction, or neutral. An output speed sensor 61 is employed to monitor rotational speed of the output member 62, and may be any suitable device, e.g., a Hall effect sensor. Signal output from the output speed sensor 61 may be employed to determine a rotational speed of the drive wheel 66, and thus determine a vehicle speed based thereon.
The control system 10 includes controller 12 that signally connects to the operator interface 14. The controller 12 is depicted as a single device for ease of illustration, but may be composed from a plurality of discrete devices that are co-located with the individual elements of the powertrain system 20 to effect operational control of the individual elements of the powertrain system 20 in response to operator commands and powertrain demands. The controller 12 may also include a control device that provides hierarchical control of other control devices. The controller 12 communicatively connects to each of the high-voltage battery 25, the first inverter module 35, the ECM 45 and the TCM 57, either directly or via a communications bus 18 to monitor and control operation thereof.
The controller 12 commands operation of the powertrain system 20, including selecting and commanding operation in one of a plurality of operating modes to generate and transfer torque between the torque generative devices, e.g., the engine 40, the first torque machine 36, the second torque machine 34 when employed, and the first and second drive wheels 66, 68, in response to traction power commands, engine power commands and motor power commands.
The terms controller, control module, module, control, control unit, processor and similar terms refer to any one or various combinations of Application Specific Integrated Circuit(s) (ASIC), electronic circuit(s), central processing unit(s), e.g., microprocessor(s) and associated non-transitory memory component in the form of memory and storage devices (read only, programmable read only, random access, hard drive, etc.). The non-transitory memory component is capable of storing machine readable instructions in the form of one or more software or firmware programs or routines, combinational logic circuit(s), input/output circuit(s) and devices, signal conditioning and buffer circuitry and other components that can be accessed by one or more processors to provide a described functionality. Input/output circuit(s) and devices include analog/digital converters and related devices that monitor inputs from sensors, with such inputs monitored at a preset sampling frequency or in response to a triggering event. Software, firmware, programs, instructions, control routines, code, algorithms and similar terms mean any controller-executable instruction sets including calibrations and look-up tables. Each controller executes control routine(s) to provide desired functions, including monitoring inputs from sensing devices and other networked controllers and executing control and diagnostic instructions to control operation of actuators. Routines may be executed at regular intervals, for example each 100 microseconds during ongoing operation. Alternatively, routines may be executed in response to occurrence of a triggering event. Communication between controllers, and communication between controllers, actuators and/or sensors may be accomplished using a direct wired point-to-point link, a networked communication bus link, e.g., bus 18, a wireless link or any other suitable communication link. Communication includes exchanging data signals in any suitable form, including, for example, electrical signals via a conductive medium, electromagnetic signals via air, optical signals via optical waveguides, and the like. The data signals may include discrete, analog or digitized analog signals representing inputs from sensors, actuator commands, and communication between controllers. The term “signal” refers to any physically discernible indicator that conveys information, and may be any suitable waveform (e.g., electrical, optical, magnetic, mechanical or electromagnetic), such as DC, AC, sinusoidal-wave, triangular-wave, square-wave, vibration, and the like, that is capable of traveling through a medium. The term ‘model’ refers to a processor-based or processor-executable code and associated calibration that simulates a physical existence of a device or a physical process.
The motor power 106 may be associated with operating the first and/or second torque machine 36, 34 as a torque motor to provide positive motor power to the gear train 50, i.e., discharging, which increases the traction power from the powertrain system 100 in response to an acceleration command. The motor power 106 may be associated with operating the either the first and/or second torque machine 36, 34 as a generator to provide negative motor power, i.e., charging, to the gear train 50, wherein negative motor power is employed to generate electric power that may be stored on the battery 25. Negative motor power, i.e., charging may be commanded in response to a demand to increase a state of charge (SOC) of the battery 25, or in response to a deceleration command, such as either coasting or braking. As such, negative motor power may be associated with increased regenerative braking power and decreased traction power from the powertrain system 100. A traction power command 112 from the powertrain system 100 to the driveline 60 is determined based upon VSS 102 and the PPS 104, with power contributed from either or both the engine 40 and the first torque machine 36. When the SOC of the battery 25 is greater than an upper threshold SOC, the controller 12 may choose to employ the first torque machine 36 to contribute additional traction power to reduce the SOC. When the SOC of the battery 25 is less than a lower threshold SOC, the controller 12 may choose to employ the first torque machine 36 to generate additional electric energy to increase the SOC, regardless of the vehicle speed and the total traction power.
The VSS 102 and the PPS 104 are periodically provided to a pedal map 110 to determine the traction power command 112. The traction power command 112 may be employed to determine an initial engine power command, which is a magnitude of engine power that is required to operate the powertrain system 100 in response to the VSS 102 and the PPS 104 when all of the traction power is originating from the engine 40 and the motor power 106 that is input from the first torque machine 36 is zero. As appreciated by one skilled in the art, the engine power output values including the initial engine power command may instead be referred to as a torque command, a throttle command or another suitable related term.
Referring again to the control routine 101 described with reference to
The adjusted engine power command 116 and the VSS 102 are provided to an inverse pedal map 120 to determine an adjusted accelerator pedal position (PPS*) 122.
Referring again to the control routine 101 described with reference to
Referring again to the control routine 101 described with reference to
The concepts described herein facilitate optimization of selection of a gear state for a parallel hybrid powertrain architectures that employs the same shift schedule and pedal map as a non-hybrid powertrain architecture. This reduces development effort, and permits optimization of operation for fuel economy with minimal changes in control routine while maintaining drivability.
The flowchart and block diagrams in the flow diagrams illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It will also be noted that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, may be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. These computer program instructions may also be stored in a computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.
As used in this specification and claims, the terms “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation. Furthermore, in reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.
The detailed description and the drawings or figures are supportive and descriptive of the present teachings, but the scope of the present teachings is defined solely by the claims. While some of the best modes and other embodiments for carrying out the present teachings have been described in detail, various alternative designs and embodiments exist for practicing the present teachings defined in the appended claims.
