Multi-speed transmission with axis transfer

This application claims the benefit of U.S. Provisional Application Ser. No. 61/152,854, filed Feb. 16, 2009, which is hereby incorporated by reference in its entirety.

The disclosure relates to a multi-speed transmission with transfer of torque from components defining a first rotational axis to components defining a second rotational axis.

Electrically-variable transmissions typically have an input member, an output member, and two electric motor/generators connected to different members of planetary gear sets. Clutches allow one or more electrically-variable modes of operation, fixed speed ratio modes, and an electric-only (battery-powered) mode. Electrically-variable transmissions may improve vehicle fuel economy in a variety of ways, primarily by using one or both of the motor/generators for vehicle braking and using the regenerated energy to power the vehicle electrically, with the engine off. The engine may be turned off at idle, during periods of deceleration and braking, and during periods of low speed or light load operation to eliminate efficiency losses due to engine drag. Braking energy captured via regenerative braking (or electrical energy generated during periods when the engine is operating) is utilized during these engine-off periods. Transient demand for engine torque or power is supplemented by the motor/generators during operation in engine-on modes, allowing for a smaller engine without reducing vehicle performance. Additionally, the electrically-variable modes may allow the engine to be operated at or near the optimal efficiency point for a given power demand.

It is challenging to package the two motor/generators, planetary gear sets, and multiple torque-transmitting mechanisms necessary to achieve the desired modes of operation, while meeting other applicable dimensional limitations and achieving relatively simple assembly requirements. Furthermore, although electrically variable transmissions are being mass-produced today, they are installed in only a very small fraction of the total number of vehicles produced today, and so engineering and tooling costs are likely to be a relatively larger portion of the total production costs as compared with those costs for other types of transmissions.

Various embodiments of electrically-variable transmissions are provided that have a first and a second motor-generator, a first and a second planetary gear set, and two torque-transmitting mechanisms, including a rotating-type clutch and a stationary-type clutch. An input member is connected for common rotation with a ring gear of the first planetary gear set. Carriers of both of the planetary gear sets are connected for common rotation with one another, and with an output member. The first motor/generator is connected for common rotation with the sun gear of the first planetary gear set. The second motor/generator is connected for common rotation with the sun gear member of the second planetary gear set.

A drive transfer assembly is provided that includes a drive member connected to the output member for rotation therewith, a driven member, and a gearing arrangement having first, second, and third members. The first member of the gearing arrangement is connected for rotation with the driven member. The drive transfer assembly includes a differential having a carrier connected for rotation with the second member of the gearing arrangement and first and second side gears. The third gear member of the gearing arrangement is connected to a stationary member such as a grounding member. An endless torque-transfer device, such as a chain, operatively connects the drive member to the driven member. The driven member, the gearing arrangement and the differential establish a second axis of rotation. Accordingly, the drive transfer assembly transfers torque from components establishing the first axis of rotation to components establishing the second axis of rotation.

The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.

FIG. 1 is a schematic illustration of a first embodiment of a hybrid electric powertrain including a first embodiment of an electrically variable transmission with a first embodiment of an output transfer assembly;

FIG. 2 is a schematic illustration of a second embodiment of an output transfer assembly;

FIG. 3 is a schematic illustration of a third embodiment of an output transfer assembly;

FIG. 4 is a schematic illustration of a fourth embodiment of an output transfer assembly;

FIG. 5 is a schematic illustration of a fifth embodiment of an output transfer assembly;

FIG. 6 is a schematic illustration of a second embodiment of a hybrid electric powertrain including a second embodiment of an electrically variable transmission with the fifth embodiment of an output transfer assembly;

FIG. 7 is a schematic illustration of a third embodiment of a hybrid electric powertrain including the second embodiment of an electrically variable transmission with a sixth embodiment of an output transfer assembly;

FIGS. 8-12 are schematic illustrations of additional transmission embodiments.

Referring to the drawings wherein like reference numbers refer to like components, FIG. 1 shows a powertrain 10 for a vehicle 11 . The powertrain 10 includes an engine 12 drivingly connected with an electrically variable transmission 14 . An output member of the engine 12 is connected for driving an input member 16 of the transmission 14 . The input member 16 rotates about and establishes an axis of rotation 18 .

A first motor/generator 20 and a second motor/generator 22 are packaged within a transmission casing 24 and are operatively connected between the input member 16 and three alternative transmission output members 26 , 26 A, 26 B. The transmission casing 24 is shown only in part, and is generally annular, surrounding the entire transmission 14 , with end walls closing off the axial ends and having access openings for the input member 16 and the output member 26 , 26 A or 26 B to extend therethrough. As discussed below, alternate locations serving as alternate transmission output members 26 , 26 A, 26 B are also provided. All of the potential output members 26 , 26 A, 26 B are interconnected to rotate commonly (i.e., at the same speed). Any one, but only one, of the transmission output members 26 , 26 A and 26 B may be connected with a drive transfer assembly to a final drive. The selection of which output location will serve as the output member connected with the drive transfer assembly will depend on packaging requirements of the powertrain 10 within the vehicle. As discussed below, in FIG. 1 , output member 26 B is connected with a drive transfer assembly 27 . The various drive transfer assemblies shown and described herein are not necessarily to scale; however, positioning of the drive transfer assembly within the transmission ensures appropriate component clearances.

The first motor/generator 20 includes an annular stator 30 A grounded to the transmission casing 24 , an annular rotor 32 A supported on and for rotation with a rotatable rotor hub 34 A and concentric about the first axis of rotation 18 . A battery 36 , power inverter 38 and electronic controller 43 are operatively connected with the stator 30 A via transfer conductor 41 A to control the functioning of the motor/generator 20 as a motor, in which stored electrical power is provided by the battery 36 to the stator 30 A, and a generator, in which torque of the rotating rotor 32 A is converted to electrical power stored in the battery 36 . The ability to control a motor/generator to function as a motor or as a generator is well known.

Similarly, the second motor/generator 22 includes an annular stator 30 B grounded to the transmission casing 24 , an annular rotor 32 B supported on a rotatable rotor hub 34 B and concentric about the axis of rotation 18 . The battery 36 , power inverter 38 and electronic controller 43 are operatively connected with the stator 30 B via transfer conductor 41 B to control the functioning of the motor/generator 22 as a motor and a generator.

The transmission 14 further includes first and second planetary gear sets 40 , 50 . Planetary gear set 40 has a first member that is a sun gear 42 , a second member that is a carrier 44 that rotatably supports a plurality of pinion gears 46 meshing with the sun gear 42 , and a third member that is a ring gear 48 meshing with the pinion gears 46 . Rotor hub 34 A is connected for common rotation with the sun gear 42 . Alternative output member 26 is connected to carrier 44 for rotation therewith.

Planetary gear set 50 has a first member which is a sun gear 52 , a second member that is a carrier 54 that rotatably supports a plurality of pinion gears 56 meshing with the sun gear 52 , and a third member that is a ring gear 58 meshing with the pinion gears 56 . Alternate output member 26 A is connected with the carrier 54 for rotation therewith. Rotor hub 34 B is connected for rotation with the sun gear 52 .

The transmission 14 includes two torque-transmitting mechanisms. A stationary-type clutch C 1 , also referred to as a brake, is selectively engagable to ground the ring gear 58 to the transmission casing 24 . Rotating-type clutch C 2 is selectively engagable to connect the sun gear 42 for common rotation with ring gear 58 . Those skilled in the art will recognize that only a portion of the transmission 14 above the input member 16 is shown schematically; and portions of the planetary gear sets 40 , 50 , clutches C 1 , C 2 and other components generally symmetrical about the input member 16 are not shown.

Annular sleeve shaft 60 forming output member 26 B concentric with the input member 16 , and hub members 66 and 68 connect the carriers 44 , 54 for common rotation with the shaft 60 , and with all of the alternate output members 26 , 26 A, 26 B. Hub member 70 extends from input member 16 to connect the ring gear 48 for common rotation therewith.

Transmission 14 is configured so that planetary gear set 40 is positioned axially between a radially-extending end wall (not shown) of the casing 24 and the motor/generator 20 . The end wall is to the left of the planetary gear set 40 as the transmission 14 is illustrated in FIG. 1 . Planetary gear set 50 is positioned axially between the motor/generators 20 , 22 . Clutch C 1 is positioned radially outward and aligned with the ring gear 58 of planetary gear set 50 . Clutch C 2 is positioned axially between motor/generator 20 and planetary gear set 50 and is aligned with ring gear 58 .

A first forward mode of operation is established by engaging clutch C 1 and releasing clutch C 2 . This mode of operation is an input-split operating mode, with planetary gear set 40 operating in a differential mode and planetary gear set 50 operating in a torque multiplication mode, engine 12 providing torque and motor/generator 20 motoring in a forward direction. A reverse electrically variable operating mode is established with the same clutch engagement, but with the motor/generator 20 motoring in a reverse direction.

A second forward mode of operation is established by engaging clutch C 2 and disengaging clutch C 1 . The shift between modes occurs when the speed of rotor 32 A is zero, and the speed of ring gear 58 is also zero (due to engagement of clutch C 1 ), so that the shift can occur without torque disturbance. A fixed forward speed ratio is established by engaging both C 1 and C 2 .

The drive transfer assembly 27 is shown driven by the output member 26 B to transfer torque from the transmission 14 to vehicle wheels. Specifically, a drive member 72 in the form of a sprocket is mounted to the output member 26 B for rotation therewith. An endless chain 74 connects the drive member 72 with a driven member 76 , also in the form of a sprocket, to transfer drive torque from the drive member 72 to the driven member 76 . The driven member 76 is operatively connected with a gearing arrangement 78 , a differential 80 and, ultimately to wheel axles 81 A, 81 B to deliver torque to vehicle wheels.

The gearing arrangement 78 is a planetary gear set with a sun gear 82 connected for rotation with driven member 76 , a ring gear 84 grounded to the transmission housing 24 , and a carrier 86 that rotatably supports pinion gears 87 that mesh with both the sun gear 82 and the ring gear 84 .

The differential 80 includes a carrier 88 that rotatably supports pinion gears 90 rotating on a pinion shaft 92 . The pinion gears 90 mesh with side gears 94 A and 94 B. Side gear 94 A is connected for common rotation with wheel axle 81 A, and side gear 94 B is connected for common rotation with wheel axle 81 B. The driven gear 76 , gearing arrangement 78 , side gears 94 A, 94 B and wheel axles 81 A, 81 B rotate about and establish a second axis of rotation 96 . Thus, the transmission 14 is configured to transfer torque from a first axis 18 , partially defined by the input member 16 and the output member 26 B, to a second axis 96 , partially defined by wheel axles 81 A, 81 B, via a sprocket and chain arrangement (drive element 72 , driven element 76 and chain 74 ). In the embodiment of FIG. 1 , the gearing arrangement 78 is positioned axially between the driven element 76 and the differential 80 .

Second Drive Transfer Assembly Embodiment

FIG. 2 shows another embodiment of a drive transfer assembly 127 connected to the output member 26 B of transmission 14 for transferring torque to wheel axles 81 A, 81 B. Components that are the same as those of drive transfer assembly 27 are shown and described with the same reference numbers. Driven member 176 radially surrounds the differential 80 . Chain 174 transfers torque from drive member 72 to driven member 176 and radially surrounds the differential 80 . Both drive member 72 and driven member 176 are sprockets. Because the driven member 176 is radially aligned with the differential 80 , both are on the same side of the gearing arrangement 78 (i.e., input and output to the gearing arrangement 78 are on the same side of the gearing arrangement 78 ).

Third Drive Transfer Assembly Embodiment

FIG. 3 shows another embodiment of a drive transfer assembly 227 connected to the output member 26 B of transmission 14 for transferring torque to wheel axles 81 A, 81 B. Components that are the same as those of drive transfer assembly 27 are shown and described with the same reference numbers. Driven member 276 is radially outward of and partially radially surrounds the gearing arrangement 78 . Chain 274 transfers torque from drive member 72 to driven member 276 and partially radially surrounds the gearing arrangement 78 . Both drive member 72 and driven member 276 are sprockets.

Fourth Drive Transfer Assembly Embodiment

FIG. 4 shows another embodiment of a drive transfer assembly 327 connected to the output member 26 B of transmission 14 for transferring torque to wheel axles 81 A, 81 B. Components that are the same as those of drive transfer assembly 27 are shown and described with the same reference numbers. Chain 374 transfers torque from drive member 72 to driven member 376 . Both drive member 72 and driven member 376 are sprockets. The driven member 376 is positioned axially between the gearing arrangement 78 and the differential 80 .

Fifth Drive Transfer Assembly Embodiment

FIG. 5 shows another embodiment of a drive transfer assembly 427 connected to the output member 26 B of transmission 14 for transferring torque to wheel axles 81 A, 81 B. Components that are the same as those of drive transfer assembly 27 are shown and described with the same reference numbers. Chain 474 transfers torque from drive member 72 to driven member 476 . Both drive member 72 and driven member 476 are sprockets. The gearing arrangement 78 is positioned axially between the driven member 476 and the differential 80 .

Second Transmission Embodiment with Fifth Drive Transfer Assembly Embodiment

Referring to FIG. 6 , powertrain 510 includes an engine 12 and an electrically variable transmission 514 having many of the same components, referred to with the same reference numbers, that function in the same way as shown and described with respect to the transmission 14 and powertrain 10 of FIG. 1 . Although not shown in FIG. 6 , a battery 36 , inverter 38 , and controller 43 are connected with the stators 30 A, 30 B as shown and described in FIG. 1 .

Transmission 514 is configured so that motor/generator 20 is positioned axially between a radially-extending end wall (not shown) of the casing 24 and the planetary gear set 50 . Clutch C 1 is positioned radially outward and aligned with the ring gear 58 of planetary gear set 50 . Clutch C 2 is positioned radially inward of motor/generator 20 , and axially between the end wall and motor/generator 20 . Planetary gear set 50 is positioned axially between motor/generator 20 and the motor/generator 22 . Motor/generator 22 is positioned axially between the planetary gear set 50 and planetary gear set 40 . Planetary gear set 40 is positioned between motor/generator 22 and an opposing radially-extending end wall (not shown) of the casing 24 .

Transmission 514 has an input member 516 axially spaced from and coaxial but not concentric with shaft 560 . Shaft 560 which connects to alternative output members 526 , 526 A. Shaft 562 is coaxial with input member 516 . Output members 526 , 526 A share a common axis of rotation 518 with input member 516 . Input member 516 is connected for common rotation with ring gear 48 . Shaft 562 connects rotor hub 534 A for common rotation with sun gear 42 . The clutch C 2 is nested between axially-extending portion 534 D, hub 534 C and the shaft 562 . Sleeve shaft 560 is concentric with shaft 562 and connects carrier member 54 to carrier member 44 and an output member 526 connected thereto. Sleeve shaft 564 connects rotor hub 534 B with sun gear 52 . Alternate output member 526 A extends from the carrier member 54 .

Drive transfer assembly 427 of FIG. 5 is connected to a drive member 572 mounted to the output member 526 of transmission 514 for transferring torque to wheel axles 81 A, 81 B. Components that are the same as those of drive transfer assembly 27 are shown and described with the same reference numbers. Chain 474 transfers torque from drive member 572 to driven member 476 . Both drive member 572 and driven member 476 are sprockets. Drive member 572 is positioned axially between motor/generator 22 and planetary gear set 40 . The gearing arrangement 78 is positioned axially between the driven member 476 and the differential 80 .

Second Transmission Embodiment with Sixth Drive Transfer Assembly Embodiment

Referring to FIG. 7 , powertrain 610 includes engine 12 and electrically variable transmission 514 of FIG. 6 , with a drive transfer assembly 527 driven by a drive member 672 connected to output member 526 A of transmission 514 . Drive member 672 is positioned axially between planetary gear set 50 and motor/generator 22 , and axially between motor/generators 20 , 22 . Drive transfer assembly 527 transfers torque to wheel axles 81 A, 81 B. Components that are the same as those of drive transfer assembly 27 are shown and described with the same reference numbers. Chain 574 transfers torque from drive member 672 to driven member 576 . Both drive member 672 and driven member 576 are sprockets. The gearing arrangement 78 is positioned axially between the driven member 576 and the differential 80 .

Additional Transmission Embodiments

FIGS. 8-12 show additional embodiments of transmissions 714 , 814 , 914 , 1014 , and 1114 , respectively, each having motor/generators 20 , 22 , planetary gear sets 40 , 50 , and clutches C 1 , C 2 as described herein. Each has a respective input member 716 , 816 , 916 , 1016 , and 1116 for connection with engine 12 of FIG. 1 (engine not shown in FIGS. 8-12 ). As with the transmissions of FIGS. 1 , 6 , and 7 , the sun gear of each of planetary gear sets 40 , 50 is connected for common rotation with the respective rotor of motor/generator 20 , 22 , and multiple possible output member locations are connected for common rotation with carrier members of the planetary gear sets 40 , 50 . For example, transmission 714 has output members 726 and 726 A. Any of the drive transfer assemblies described herein may be driven from either output 726 or 726 A. Transmission 814 has output members 826 , 826 A, and 826 B. Any of the drive transfer assemblies described herein may be driven from either output 826 or 826 B, and drive transfer assembly 527 could be driven from output 826 A. Transmission 914 has output members 926 , 926 A, and 926 B. Any of the drive transfer assemblies described herein may be driven from either output 926 or 926 B, and drive transfer assembly 527 could be driven from output 926 A. Transmission 1014 has output members 1026 , 1026 A, and 1026 B. Any of the drive transfer assemblies described herein may be driven from either output 1026 or 1026 B, and drive transfer assembly 527 could be driven from output 1026 A. Transmission 1114 has output members 1126 and 1126 A. Any of the drive transfer assemblies described herein may be driven from output 1126 . Drive transfer assembly 527 could be driven from output 1126 A.

While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.