Hybrid powertrain system

A powertrain system is described, and includes an internal combustion engine including a crankshaft and an electric machine including a rotatable shaft, wherein the rotatable shaft is coupled to a motor pulley. A torque converter includes an impeller and a pump, wherein the pump is coupled to an outer sheave. An off-axis mechanical drive system includes the outer sheave of the torque converter rotatably coupled to the motor pulley of the electric machine. The electric machine is coupled to the pump of the torque converter via the off-axis mechanical drive system, and the crankshaft is coupled to the pump of the torque converter via a clutch.

BACKGROUND

Known hybrid powertrain systems include internal combustion engines and electric motor/generators that are coupled to transmissions to transfer torque to a driveline for tractive effort. Known electric motor/generators are supplied electric power from energy storage systems. Powertrain systems may operate in various modes to generate and transfer propulsion power to vehicle wheels.

SUMMARY

A powertrain system is described, and includes an internal combustion engine including a crankshaft and an electric machine including a rotatable shaft, wherein the rotatable shaft is coupled to a motor pulley. A torque converter includes an impeller and a pump, wherein the pump is coupled to an outer sheave. An off-axis mechanical drive system includes the outer sheave of the torque converter rotatably coupled to the motor pulley of the electric machine. The electric machine is coupled to the pump of the torque converter via the off-axis mechanical drive system, and the crankshaft is coupled to the pump of the torque converter via a clutch.

An aspect of the disclosure includes the clutch being a selectable one-way clutch.

Another aspect of the disclosure includes a starter rotatably coupled to the crankshaft.

Another aspect of the disclosure includes the electric machine being electrically connected to an inverter that is electrically connected to an electric power source, wherein the electric power source is configured to operate at a voltage level that is less than 60 V DC.

Another aspect of the disclosure includes the outer sheave of the torque converter being rotatably coupled to the motor pulley of the electric machine via a continuous belt.

Another aspect of the disclosure includes the outer sheave of the torque converter being rotatably coupled to the motor pulley of the electric machine via a chain.

Another aspect of the disclosure includes the outer sheave of the torque converter being rotatably coupled to the motor pulley of the electric machine via meshed gears.

Another aspect of the disclosure includes a transmission including an input member and an output member, and a driveline, wherein the input member of the transmission is coupled to the impeller of the torque converter and the output member of the transmission is coupled to the driveline.

Another aspect of the disclosure includes a controller operatively connected to the powertrain system, wherein the controller includes an instruction set that is executable to autostop the internal combustion engine and control operation of the powertrain system in an electric-only drive mode to transfer propulsion power to the driveline.

Another aspect of the disclosure includes a controller operatively connected to the powertrain system, wherein the controller includes an instruction set that is executable to control operation of the powertrain system in an engine/electric-assist drive mode to transfer propulsion power to the driveline.

Another aspect of the disclosure includes a controller operatively connected to the powertrain system, wherein the controller includes an instruction set that is executable to control operation of the powertrain system in a regenerative mode to transfer propulsion power to the driveline.

Another aspect of the disclosure includes a controller operatively connected to the powertrain system, wherein the controller includes an instruction set that is executable to control operation of the powertrain system in an engine-only drive mode to transfer propulsion power to the driveline.

Another aspect of the disclosure includes the internal combustion engine, transmission and driveline being disposed in a front-wheel drive configuration of a vehicle.

Another aspect of the disclosure includes the internal combustion engine, transmission and driveline being disposed in a rear-wheel drive configuration of a vehicle.

DETAILED DESCRIPTION

The components of the disclosed embodiments, as described and illustrated herein, may be arranged and designed in a variety of different configurations. Thus, the following detailed description is not intended to limit the scope of the disclosure, as claimed, but is merely representative of possible embodiments thereof. In addition, while numerous specific details are set forth in the following description in order to provide a thorough understanding of the embodiments disclosed herein, some embodiments can be practiced without some of these details. Moreover, for the purpose of clarity, certain technical material that is known in the related art has not been described in detail in order to avoid unnecessarily obscuring the disclosure.

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,FIG. 1schematically shows an embodiment of a hybrid powertrain system100including multiple torque-generating devices including an internal combustion engine (engine)10and at least one electrically-powered torque machine (electric machine)30. The engine10and electric machine30are mechanically coupled via a torque converter50and an off-axis mechanical drive system40to transfer propulsion power via a transmission60and a driveline90to vehicle wheels96. The concepts described herein may apply to any suitable powertrain configuration that includes the internal combustion engine10and the electric machine30coupled via the torque converter50and the off-axis mechanical drive system40. Like numerals refer to like elements throughout the description. Operation of the powertrain system100may be controlled by a controller15, which is shown as a unitary device for ease of illustration. The powertrain system100may be advantageously employed on a vehicle to provide propulsion power, and the vehicle 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 system100is configured so that the engine10and the electric machine30mechanically couple to the transmission60employing the torque converter50and the off-axis mechanical drive system40. This enables the powertrain system100to be configured in a front-wheel drive arrangement and operate in one of multiple selectable modes, including an engine-only drive mode, an electric-only drive mode, a regenerative braking mode, and an engine/electric-assist mode. Alternatively, the powertrain system100can be configured in a rear-wheel drive arrangement or an all-wheel drive arrangement and be operable in one of multiple selectable modes, including an engine-only drive mode, an electric-only drive mode, a regenerative braking mode, and an engine/electric-assist mode. The configuration of the powertrain system100enables engine stop/start operations during powertrain system operation. The powertrain system100described herein advantageously employs the torque converter50, which results in improved drivability during acceleration events, transmission shifting events and deceleration events. Furthermore, the off-axis mechanical drive system40is preferably configured to spin the electric machine30at the engine speed, thereby eliminating need for an alternator to effect charging of a low-voltage battery78. Furthermore, there is no need for an auxiliary electrically-powered hydraulic pump for the transmission60since the electric machine30is configured to and can be controlled to spin the torque converter50when the engine10is in an OFF state. Furthermore, an engine disconnect clutch24may be integrated into the housing of the torque converter50, thus facilitating regenerative braking mode and coasting operations, which facilitates operation in the electric-only drive mode, and enhancing off-throttle sailing.

The engine10is preferably configured as a multi-cylinder internal combustion engine that converts fuel to mechanical torque through a thermodynamic combustion process. The engine10is 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 onto pistons, with such force transferred to a crankshaft12to produce torque. The engine10includes a starter20that includes a starter switch and a starter gear22, wherein the starter gear22meshingly engages gear teeth that are disposed on an outer circumference of a flywheel14that is coupled to the crankshaft12. The starter20is preferably configured as a single-phase electric motor including an output shaft that couples to the starter gear22, wherein the single-phase electric motor is electrically connected to the low-voltage battery78via activation of the starter switch. In one embodiment, the starter gear22is permanently meshingly engaged with the flywheel14. The flywheel14also couples to an input member18that is coupled via an engine disconnect clutch24to a pump portion56of the torque converter50. In one embodiment, the engine disconnect clutch24is a selectable one-way clutch. The actuators of the engine10, including the starter switch are preferably controlled by an engine controller.

The engine10is preferably mechanized with suitable hardware and the engine controller preferably includes suitable control routines to execute autostart and autostop functions, fueled and fuel cutoff (FCO) functions, and all-cylinder and cylinder deactivation functions during ongoing operation of the powertrain100. The engine10is considered to be in an OFF state when it is not rotating. The engine10is considered to be in an ON state when it is rotating. The all-cylinder state includes engine operation wherein all of the engine cylinders are activated by being fueled and fired. The cylinder deactivation state includes engine operation wherein one or a plurality of the engine cylinders are deactivated by being unfueled and unfired, and preferably operating with engine exhaust valves in open states to minimize pumping losses, while the remaining cylinders are fueled and fired and thus producing torque. The ON state may include the FCO state in which the engine10is spinning and unfueled. The ON state may include the cylinder deactivation state. The ON state may include the FCO state in combination with the cylinder deactivation state. Engine mechanizations and control routines for executing autostart, autostop, FCO and cylinder deactivation control routines are known and not described herein. Engine operation may be described in context of engine states, including an engine operation state, an engine fueling state and an engine cylinder state. The engine operation states preferably include the ON and the OFF state. The engine fueling states include the fueled state and the FCO state. The engine cylinder states include the all-cylinder state and the cylinder deactivation state.

The electric machine30is preferably a multi-phase electric motor/generator configured to convert stored electric energy to mechanical power and convert mechanical power to electric energy that may be stored in a DC power source (48V battery)70. The 48V battery70is preferably configured at a nominal 48 Vdc voltage level. The electric machine30preferably includes a rotor and a stator, and electrically connects via the inverter module36to the 48V battery70. The rotor couples to a rotatable member32that couples to a motor pulley34that is an element of the off-axis mechanical drive system40. Alternatively, another non-combustion torque machine, such as a pneumatically-powered device or a hydraulically-powered device may be employed in place of the electric machine30. By way of definition, a non-combustion torque machine is any device capable of generating torque by converting a potential energy source to kinetic energy without combustion of the potential energy. Non-limiting examples of the potential energy source may include electric energy, pneumatic energy and hydraulic energy. Pneumatically-powered devices and hydraulically-powered devices are known and not described in detail herein.

The torque converter50is a rotatable torque coupling device arranged between the input member18of the engine10and an input member51of the transmission60. The torque converter50preferably includes a pump56rotatably coupled to the crankshaft12, a stator57, an impeller58rotatably coupled to the input member51to the transmission60, and a controllable clutch59. The torque converter50operates to provide fluid torque coupling between the pump56and the impeller58when the clutch59is deactivated or released, and provides mechanical torque coupling between the pump56and the impeller58when the clutch59is activated. Other details related to design of torque converters and torque converter clutches is known and not described in detail herein. The pump56is coupled to an outer sheave52, which may be disposed on an outer circumference of the pump56. One exemplary embodiment of a portion of the powertrain system100, including the torque converter50and the outer sheave52, is shown with reference toFIG. 2. Alternatively, the outer sheave52may be arranged on a separate pulley that is fixedly attached to the pump56to rotate therewith, with an outer circumference that is substantially equal an outer circumference of the pump56and is co-axial therewith.

The off-axis mechanical drive system40preferably includes, in one embodiment, the outer sheave52coupled to the pump56of the torque converter50, the motor pulley34coupled to the rotor of the electric machine30, and a continuous belt42. The outer sheave52and the motor pulley34are rotatably coupled via the continuous belt42to transfer torque therebetween. The outer sheave52and the motor pulley34may be suitably configured with belt contact surfaces that are in the form of a single circumferential groove, multiple circumferential grooves, radial teeth, or another suitable arrangement, and the continuous belt42is configured in accordance with the belt contact surfaces of the outer sheave52and the motor pulley34. Preferably, the off-axis mechanical drive system40includes a belt tensioner to ensure that the continuous belt42makes contact with at least 180° of the belt contact surfaces of the outer sheave52and the motor pulley34. The continuous belt42may be fabricated from Kevlar cords in one embodiment. In one embodiment, the pulley ratio between the outer sheave52and the motor pulley34is 2.5:1. Alternatively, the outer sheave52and the motor pulley34are rotatably coupled via a continuous chain to transfer torque therebetween. Alternatively, the outer sheave52and the motor pulley34are rotatably coupled via meshed gears to transfer torque therebetween.

The transmission60may be arranged in a step-gear configuration in one embodiment, and may include one or more differential gear sets and activatable clutches configured to effect torque transfer in one of a plurality of fixed gear states over a range of speed ratios between the engine10, the input member51and the output member62. The transmission60may include a first rotational speed sensor in the form of a Hall-effect sensor or another suitable sensor that may be configured to monitor rotational speed of the input member51and/or a second rotational speed sensor that may be configured to monitor rotational speed of the output member62. The transmission60includes any suitable configuration, and may be an automatic transmission that automatically shifts between the fixed gear states to operate at a gear ratio that achieves a preferred match between an output torque request and an engine operating point. The transmission60automatically executes upshifts to shift to a gear state having a lower numerical multiplication ratio (gear ratio) at preset speed/load points and executes downshifts to shift to a gear state having a higher numerical multiplication ratio at preset speed/load points. The transmission60may be controlled using a controllable hydraulic circuit that communicates with a transmission controller, which may be integrated into or separate from the controller15. The transmission controller preferably controls the torque converter clutch59. The transmission60executes upshifts to shift to a fixed gear that has a lower numerical multiplication ratio (gear ratio) and executes downshifts to shift to a fixed gear that has a higher numerical multiplication ratio. A transmission upshift may require a reduction in engine speed so the engine speed matches transmission output speed multiplied by the gear ratio at a gear ratio associated with a target gear state. A transmission downshift may require an increase in engine speed so the engine speed matches transmission output speed multiplied by the gear ratio at a gear ratio associated with the target gear state. Designs of transmissions and transmission shifting are known and not described in detail herein. Transmission operation may be described in context of a control variable that may be communicated to the transmission60that is related to a selected fixed gear state.

The driveline90may include a differential gear device92that mechanically couples to axle(s)94that mechanically couples to wheel(s)96in one embodiment. The driveline90transfers tractive power between an output member of the transmission60and a road surface via the wheel(s)96. The powertrain100is illustrative, and the concepts described herein apply to other powertrain systems that are similarly configured.

The inverter module36is configured with suitable control circuits including power transistors, e.g., integrated gate bipolar transistors (IGBTs) for transforming DC electric power to AC electric power and transforming AC electric power to DC electric power. The inverter module36preferably employs pulsewidth-modulating (PWM) control of the IGBTs to convert stored DC electric power originating in the 48V battery70to AC electric power to drive the electric machine30to generate torque. Similarly, the inverter module36converts mechanical power transferred to the electric machine30to DC electric power to generate electric energy that is storable in the 48V battery70, including as part of a regenerative braking control strategy. The inverter module36receives motor control commands from the controller15and controls inverter states to provide a desired motor drive operation or a regenerative braking operation. In one embodiment, an auxiliary DC/DC electric power converter76electrically connects to the bus and provides electric power to charge the low-voltage battery78via a low-voltage bus. Such electric power connections are known and not described in detail. The low-voltage battery78provides low-voltage electric power to low-voltage systems on the powertrain system100and the vehicle, including, e.g., the starter20, electric windows, HVAC fans, seats, and other devices. In one embodiment the low-voltage battery78is configured to operate at a nominal 12 Vdc voltage level.

The 48V battery70is preferably disposed to supply electric power at a nominal voltage level of 48 Vdc, and may be any DC power source, e.g., a multi-cell lithium ion device, an ultra-capacitor, or another suitable device without limitation. Monitored parameters related to the 48V battery70preferably include a state of charge (SOC), temperature, and others. In one embodiment, the 48V battery70may electrically connect via an on-vehicle battery charger to a remote, off-vehicle electric power source for charging while the vehicle is stationary.

The controller15may signally connect to an operator interface (not shown) and provides hierarchical control of a plurality of control devices to effect operational control of individual elements of the powertrain100, including, e.g., the inverter module36, the engine controller and the transmission controller. The controller15communicates with each of the inverter module36, the engine controller and the transmission controller, either directly or via a communications bus16to monitor operation and control operations thereof.

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 routines to control operation of actuators. Routines may be periodically executed at regular intervals, or 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 link, a networked communications bus link, a wireless link, a serial peripheral interface bus or any another suitable communications link. Communications 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. Data signals may include signals representing inputs from sensors, signals representing actuator commands, and communications signals between controllers.

Vehicle operation responsive to operator requests includes operating modes of acceleration, braking, steady-state running, coasting, and idling. The acceleration mode includes an operator request to increase vehicle speed. The braking mode includes an operator request to decrease vehicle speed. The steady-state running mode includes vehicle operation wherein the vehicle is presently moving at a rate of speed with no operator request for either braking or accelerating, with the vehicle speed determined based upon the present vehicle speed and vehicle momentum, vehicle wind resistance and rolling resistance, and driveline inertial drag. The coasting mode includes vehicle operation wherein vehicle speed is above a minimum threshold speed and the operator request to the accelerator pedal is at a point that is less than required to maintain the present vehicle speed. The idle mode includes vehicle operation wherein vehicle speed is at or near zero.

The powertrain system100is operative in one of a plurality of modes, which may be selected and implemented during ongoing powertrain operation to effect vehicle operations of acceleration, braking, steady-state running, coasting, and idling. The powertrain modes include the engine-only drive mode, an electric-only drive mode, a regenerative mode, and an engine/electric-assist drive mode, with accompanying engine autostart/autostop operations. In the engine-only drive mode, the engine10is controlled to generate propulsion power while the electric machine30freewheels. This mode may be commanded during vehicle acceleration or steady-state running. In the electric-only drive mode, the electric machine30is controlled as a motor to generate propulsion power, while the engine10in in the OFF state and disconnected by action of the engine disconnect clutch24. This mode may be commanded during idle, vehicle acceleration or steady-state running. In the regenerative mode, the electric machine30is controlled as a generator to react driveline torque and generate electric power, while the engine10either at idle or in in the OFF state and disconnected by action of the engine disconnect clutch24. This mode may be commanded during coasting and vehicle braking. In the engine/electric-assist drive mode, the engine10and the electric machine30are controlled to generate propulsion power. This mode may be commanded during vehicle acceleration or steady-state running.

FIG. 3schematically illustrates an isometric view of portion of an embodiment the off-axis mechanical drive system340that is coupled to an electrically-powered torque machine (electric machine)330via a torque converter350that is coupled to an output member of an internal combustion engine (not shown) that is part of an embodiment of a hybrid powertrain system300that includes multiple torque-generating devices. The hybrid powertrain system300further includes a transmission and a driveline (not shown) to transfer propulsion power to vehicle wheels (not shown) in response to operator inputs. The concepts described herein may apply to any suitable front-wheel drive, rear-wheel drive or all-wheel drive powertrain configuration, with operation controlled by a controller. In this embodiment, the off-axis mechanical drive system340is preferably configured as a belt drive, including an outer sheave352that is annular to and coupled to a pump356of the torque converter350. Other elements of the off-axis mechanical drive system340include a motor pulley332that is coupled to a rotor of the electric machine330, a continuous belt342, and a belt tensioner334. The belt tensioner334is disposed to urge the continuous belt342to ensure that the continuous belt342makes contact with at least 180° of the belt contact surfaces of the outer sheave352and the motor pulley332, thus minimizing or totally eliminating belt slippage. In one embodiment, and as shown the belt tensioner334is a two-sided belt tensioner. Alternatively, the belt tensioner may be configured as a single-sided device. The outer sheave352and the motor pulley332are rotatably coupled via the continuous belt342to transfer torque therebetween. The outer sheave352and the motor pulley334may be suitably configured with belt contact surfaces, and are arranged to have multiple circumferential grooves in their respective annular surfaces. Some of the circumferential grooves in the annular surface of the outer sheave352are indicated by numeral353. The continuous belt342is preferably configured in accordance with the circumferential grooves in the annular surface of the outer sheave352and the motor pulley334, and thus has a plurality of internal-facing circumferential grooves. The continuous belt342may be fabricated from Kevlar cords in one embodiment. In one embodiment, the pulley ratio between the outer sheave352and the motor pulley334is 2.5:1.

FIG. 4schematically illustrates an isometric view of portion of another embodiment the off-axis mechanical drive system440that is coupled to an electrically-powered torque machine (electric machine)430via a torque converter450that is coupled to an output member of an internal combustion engine (not shown) that is part of an embodiment of a hybrid powertrain system400that includes multiple torque-generating devices. The hybrid powertrain system400further includes a transmission and a driveline (not shown) to transfer propulsion power to vehicle wheels (not shown) in response to operator inputs. The concepts described herein may apply to any suitable front-wheel drive, rear-wheel drive or all-wheel drive powertrain configuration, with operation controlled by a controller. In this embodiment, the off-axis mechanical drive system440is preferably configured as a belt drive, including an outer sheave452that is annular to and coupled to a pump456of the torque converter450. Other elements of the off-axis mechanical drive system440include a motor pulley432that is coupled to a rotor of the electric machine430and a continuous belt442. There is no belt tensioner in this embodiment. The outer sheave452and the motor pulley432are rotatably coupled via the continuous belt442to transfer torque therebetween. The outer sheave452and the motor pulley434may be suitably configured with belt contact surfaces, and are arranged to have multiple radial teeth in their respective annular surfaces. Some of the radial teeth in the annular surface of the outer sheave452are indicated by numeral453. The continuous belt442is preferably configured in accordance with the circumferential grooves in the annular surface of the outer sheave452and the motor pulley434, and thus has a plurality of internal-facing radial teeth. The continuous belt442may be fabricated from Kevlar cords in one embodiment. In one embodiment, the pulley ratio between the outer sheave452and the motor pulley434is 2.5:1. In this embodiment, the belt tension is achieved by tensioner devices (not shown) that are adjusted during assembly or belt installation.