Reconfigurable powersplit powertrain for an electric vehicle

A powertrain includes a gearset including a sun gear, a carrier, a ring gear connected to a countershaft, pinions supported on the carrier and meshing with the sun gear and ring gear; a second gearset connectable to an engine, for overdriving a generator; a clutch for releasably connecting the engine and carrier; a second clutch for releasably connecting the sun gear and the generator; and a motor connected to a countershaft. Operation of the powertrain can be readily switched between powersplit mode and series mode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a powersplit powertrain for an electric vehicle.

2. Description of the Prior Art

The powertrain of a hybrid electric vehicle (HEV) includes an engine, electric motor/generator and traction battery, wherein the engine and motor can drive the wheels individually, the engine can charge the traction battery through the electric machine operating as a generator, and vehicle kinetic energy can be recovered and regenerated using the wheel brakes to drive the generator and recharge the battery.

In the powertrain for a plug-in hybrid (PHEV), the traction battery is significantly increased in capacity so that electrical energy from the electric grid can be used to drive the vehicle. As a result, a much greater use of electric drive is expected. The direct connection of the generator to the wheel speed causes the generator shaft to rotate as the vehicle moves when the engine is off. This causes several issues including (i) as the vehicle increases in speed, the generator speed gets excessively high causing a durability concern for the bearing, planetary gearset and generator; (ii) lowering of available torque needed to start the engine; (iii) since the generator is not being used, it generates an unnecessary spin loss; and (iv) in reverse gear with the engine running, the motor must react, thereby reducing the torque provided to the wheels.

SUMMARY OF THE INVENTION

A powertrain includes a gearset including a sun gear, a carrier, a ring gear connected to a countershaft, pinions supported on the carrier and meshing with the sun gear and ring gear; a second gearset connectable to an engine, for overdriving a generator; a clutch for releasably connecting the engine and carrier; a second clutch for releasably connecting the sun gear and the generator; and a motor connected to a countershaft.

The powertrain is reconfigurable in that operation of the powertrain can be readily switched from powershift mode to series mode and from series mode to powershift mode.

In a charge sustaining mode, the engine runs in either a series mode or a powersplit mode.

The powertrain provides full torque to the wheels from the traction motor, a benefit over a single mode powersplit powertrain.

The powertrain provides the high fuel economy and driveability of a powersplit powertrain with improved towing and vehicle launch capability.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first toFIG. 1, a powertrain10includes a power source such as an internal combustion engine12, such as a diesel engine or gasoline engine; a first planetary gearset14; an electric motor16; layshaft gearing18; a differential mechanism20; an electric generator22; a countershaft24, which is driveably connected to differential mechanism20, output pinion40and motor16; and a second planetary gearset26. Each electric machine16,22is a motor-generator, although conventionally electric machine16is referred to as a motor or traction motor, and electric machine22is referred to as a generator.

The sun gear27of the planetary gearset14is connected by clutch28to the generator22. The carrier32of the planetary gearset14is connected by clutch30to the engine12through a torsion damper34and shaft36. The ring gear39of gearset14is driveably connected to countershaft24by engaged output pinion40and gear42, which form a layshaft gear pair40-42. Planet pinions43, supported on carrier32, are in continual meshing engagement with ring gear39and sun gear27.

The rotor44of motor16is connected to countershaft24through the gear pair46-48.

Motor16is electrically connected to a traction battery50through an inverter52and a high voltage DC/DC converter54. Similarly, generator22is electrically connected to battery50through an inverter56and converter54.

Countershaft24is connected through a pinion60and ring gear62of the differential mechanism20, which transmits power to the vehicle wheels64,66, through halfshafts or axle shafts68,70.

An oil pump72is driveably connected to shaft36and the engine output by a pinion74and gear76.

The sun gear80of planetary gearset26is connected by clutch82to the generator22. The carrier86of the planetary gearset26is connected by clutch84to the engine12through a torsion damper34and shaft36. The ring gear88of gearset26is fixed against rotation due to its connection to case90. Planet pinions92, supported on carrier86, are in continual meshing engagement with ring gear88and sun gear80.

Powertrain10operates in powersplit mode when clutches28,30are engaged and clutches82,84are disengaged. Engine12is connected through clutch30to carrier32, and the rotor of generator22is connected through clutch28to sun gear27. In powersplit operation power produced by engine12and, if the battery50is supplying electric energy to generator, power produced by generator22is transmitted through gearset14and gear pair40-42to countershaft24, and power produced by motor16is transmitted by gear pair46-48to countershaft24. Final drive gear pair60-62transmits the power from engine12, motor16and generator22to differential mechanism20, which transmits power differentially to the vehicle wheels64,66, through shafts68,70. In powersplit operation with generator22operating as an electric generator, engine12supplies power to generator22, thereby allowing the battery50to be recharged.

Powertrain10operates in series mode when clutches28,30are disengaged and clutches82,84engaged. Engine12is connected through clutch84to carrier86of gearset26, sun gear80is overdriven relative to the speed of engine12, and clutch82connects overdriven sun gear80to the rotor of generator22. In series operation power produced by engine12drives generator26at a relatively high speed, thereby recharging battery50, and power produced by motor16is transmitted by gear pair46-48to countershaft24. Final drive gear pair60-62transmits the power produced by motor16to differential mechanism20.

InFIG. 3, clutch84is deleted, thereby directly, continually connecting carrier86of gearset26to engine12through shaft36and torsion damper34. The powertrain94ofFIG. 3operates in powersplit mode when clutches28,30are engaged and clutch82is disengaged. Engine12is connected through clutch30to carrier32, and the rotor of generator22is connected through clutch28to sun gear27. In powersplit operation, power produced by engine12and generator26is transmitted through gearset14and gear pair40-42to countershaft24, and power produced by motor16is transmitted by gear pair46-48to countershaft24. Final drive gear pair60-62transmits the power from engine12, motor16and generator22to differential mechanism20. In powersplit operation with generator22operating as an electric generator, engine12supplies power to generator22, thereby allowing the battery50to be recharged.

The powertrain94ofFIG. 3operates in series mode when clutches28,30are disengaged and clutch82is engaged. Engine12is connected directly to carrier86of gearset26, sun gear80and the rotor of generator are overdriven relative to the speed of engine12, and clutch82connects overdriven sun gear80to the rotor of generator22. In series operation, power produced by engine12drives generator22at a relatively high speed, thereby recharging battery50, and power produced by motor16is transmitted by gear pair46-48to countershaft24. Final drive gear pair60-62transmits the power produced by motor16to differential mechanism20.

InFIG. 5, clutch84is present, but clutch82is deleted, thereby directly, continually connecting sun gear80of gearset26to the rotor of generator22. The powertrain96ofFIG. 5operates in powersplit mode when clutches28,30are engaged and clutch84is disengaged. Engine12is connected through clutch30to carrier32, and the rotor of generator22is connected through clutch28to sun gear27. In powersplit operation, power produced by engine12and generator26is transmitted through gearset14and gear pair40-42to countershaft24, and power produced by motor16is transmitted by gear pair46-48to countershaft24. Final drive gear pair60-62transmits the power from engine12, motor16and generator22to differential mechanism20. In powersplit operation with generator22operating as an electric generator, engine12supplies power to generator22, thereby allowing the battery50to be recharged.

The powertrain96ofFIG. 5operates in series mode when clutches28,30are disengaged and clutch84is engaged. Engine12is connected through clutch84to carrier86of gearset26, sun gear80is overdriven relative to the speed of engine12and connected directly to the rotor of generator22. In series operation, power produced by engine12drives generator26at a relatively high speed, thereby recharging battery50, and power produced by motor16is transmitted by gear pair46-48to countershaft24. Final drive gear pair60-62transmits the power produced by motor16to differential mechanism20.

Powertrain98ofFIG. 7includes a shaft102, connected to the rotor of generator22; a pinion100, gear104meshing with pinion102; a second countershaft106secure to gear104and to a pinion108; a gear110, meshing with pinion108; a clutch112for opening and closing a drive connection between shaft36and gear110; a clutch114for opening and closing a drive connection between shaft36and carrier32of gearset14; a clutch116for opening and closing a drive connection between sun gear27and shaft102; and a clutch118for opening and closing a drive connection between shaft102and pinion100.

Powertrain98operates in powersplit mode when clutches114,116are engaged and clutches112,118are disengaged. Engine12is connected through clutch112to carrier32, and the rotor of generator22is connected through clutch116to sun gear27. In powersplit operation, power produced by engine12and, if the battery50is supplying electric energy to generator, power produced by generator22is transmitted through gearset14and gear pair40-42to countershaft24, and power produced by motor16is transmitted by gear pair46-48to countershaft24. Final drive gear pair60-62transmits the power from engine12, motor16and generator22to differential mechanism20, which transmits power differentially to the vehicle wheels64,66, through shafts68,70. In powersplit operation with generator22operating as an electric generator, engine12supplies power to generator22, thereby allowing the battery50to be recharged.

Powertrain10operates in series mode when clutches112,118are engaged and clutches114,116are disengaged. Engine12is connected through clutch112, gear110, pinion108, countershaft106, gear104, pinion100and shaft102to the rotor of generator22, which is overdriven relative to the speed of engine12. In series operation, power produced by engine12drives generator22at a relatively high speed, thereby recharging battery50, and power produced by motor16is transmitted by gear pair46-48to countershaft24. Final drive gear pair60-62transmits the power produced by motor16to differential mechanism20.