# Patent

## Title
Electromechanical variable transmission

## Abstract

A vehicle drive includes a first gear set and a second gear set both having a sun gear, a ring gear and planetary gears which couple the sun gear to the ring gear. The planetary gears of both sets are rotatably supported by respective planetary gear carriers which are coupled to each other. The vehicle drive also includes an engine, a first clutch which selectively engages the engine to the ring gear of the first gear set, a first motor/generator coupled to the sun gear of the first gear set and a second motor/generator coupled to the sun gear of the second gear set and electrically coupled to the first motor/generator, a second clutch which selectively engages the engine to the second motor/generator, and a third clutch and a third gear set which operate to selectively engage the ring gear of the second gear set to the planetary gear carriers.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation of application Ser. No. 12/820,928, filed Jun. 22, 2010, which is incorporated herein by reference in its entirety.


STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT
The government of the United States has certain rights in this invention pursuant to Contract No. N0014-09-C-0601 awarded by the Office of Naval Research.


BACKGROUND
The present disclosure relates generally to the field of transmissions for vehicles. More specifically, the present disclosure relates to the field of electromechanical infinitely variable transmissions for vehicles.
SUMMARY
One exemplary embodiment relates to a vehicle drive including a first gear set including a sun gear, a ring gear and planetary gears which couple the sun gear to the ring gear. The vehicle drive also includes a second gear set including a sun gear, a ring gear and planetary gears which couple the sun gear to the ring gear. The planetary gears of both sets are rotatably supported by respective planetary gear carriers which are coupled to each other. The vehicle drive further includes an engine and a first clutch which selectively engages the engine to the ring gear of the first gear set. The vehicle drive still further includes a first motor/generator coupled to the sun gear of the first gear set and a second motor/generator coupled to the sun gear of the second gear set and electrically coupled to the first motor/generator. The vehicle drive still further includes a second clutch which selectively engages the engine to the second motor/generator and a third clutch and a third gear set which operate to selectively engage the ring gear of the second gear set to the planetary gear carriers.
Another exemplary embodiment relates to a vehicle transmission including a first planetary gear set having planetary gears and a second planetary gear set having planetary gears directly coupled to the planetary gears of the first planetary gear set. The vehicle transmission also includes an engine rotationally coupled to the first planetary gear set. The vehicle transmission further includes a first electromagnetic device rotationally coupled to the first planetary gear set and a second electromagnetic device rotationally coupled to the second planetary gear set and selectively rotationally engaged with the engine.
Another exemplary embodiment relates to a vehicle having a drive train including a dual-mode transmission having a first gear set and a second gear set. The vehicle also includes an engine coupled to the first gear set. The vehicle further includes a first electromagnetic device coupled to the first gear set and a second electromagnetic device coupled to the second gear set. The vehicle still further includes at least one drive axle coupled to the transmission. During a first mode of operation of the vehicle the second electromagnetic device is selectively coupled to the drive axle via the second gear set and during a second mode of operation of the vehicle the second electromagnetic device is selectively coupled to the engine
Another exemplary embodiment relates to a transmission for a vehicle including a first gear set having a first gear configured to be coupled to an engine, a second gear configured to be coupled to a first electromechanical device, and a third gear configured to be rotationally engaged to a drive axle of the vehicle. The transmission also includes a second gear set having a first gear configured to be coupled to a second electromechanical device, a second gear configured to be coupled to the third gear of the first gear set, and a third gear configured to be selectively rotationally engaged with the drive axle of the vehicle.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of drive train for a vehicle according to an exemplary embodiment.
FIG. 2 is a detailed schematic view of the drive train shown in FIG. 1 according to an exemplary embodiment.
FIG. 3 is a schematic diagram of a control system for the drive train shown in FIG. 1 according to an exemplary embodiment.



DETAILED DESCRIPTION
Referring to FIG. 1, a schematic view of a drive train for a vehicle V1 is shown according to an exemplary embodiment. The vehicle V1 may be a work or commercial vehicle, a military vehicle, or any other type of vehicle.
According to an exemplary embodiment, the drive train includes an engine E1 coupled to a transmission T1. The vehicle V1 also includes a first electromagnetic device EM1 coupled to the transmission T1 and a second electromagnetic device EM2 coupled to the transmission T1. The vehicle V1 also includes at least one drive axle (such as, e.g., rear axle RA1 and/or front axle FA1) coupled to the transmission T1.
According to an exemplary embodiment, the engine E1 is configured to provide rotational mechanical energy to the transmission T1. The engine E1 may be any source of rotational mechanical energy which is derived from a stored energy source such as a liquid or gaseous fuel. Examples are an internal combustion engine (such as a gas, natural gas, or diesel powered engine), turbine, fuel cell, electric motor or any other type of motor capable of providing rotational mechanical energy to the transmission T1. According to one exemplary embodiment, the engine E1 is a twelve liter diesel engine capable of providing approximately 400 to 600 horsepower, 400-1500 ft-lbs of torque, and has a rotational speed of approximately 0 to 2100 rpm. According to one exemplary embodiment, the engine E1 is operated at a relatively constant speed (such as, e.g., 1600 rpm) to maximize fuel efficiency.
According to an exemplary embodiment, the electromagnetic devices EM1, EM2 are electric motor/generator devices that are capable of providing rotational electrical energy (as an electric motor) and/or capable of producing electrical power (as a generator). According to one exemplary embodiment, the electromagnetic devices EM1, EM2 provide electric power to one another, depending on the specific mode of operation of the vehicle V1. For example, the first electromagnetic device EM1 may be operated as a generator to provide electric power to the second electromagnetic device EM2. Alternatively, the second electromagnetic device EM2 may be operated as a generator to provide electric power to the first electromagnetic device EM1.
According to one exemplary embodiment, the first electromagnetic device EM1 and the second electromagnetic device EM2 may be the same (or similar) to one another. However, according to other exemplary embodiments, the first electromagnetic device EM1 and the second electromagnetic device EM2 may be sized differently as required by a particular application. According to one exemplary embodiment, the electromagnetic devices EM1, EM2 are each capable of providing up to approximately 300 horsepower and 1300 ft-lbs of torque and are capable of rotational speeds from approximately −6,000 to 6,000 rpm (i.e., both forward and reverse from 0 to 6,000 rpm).
According to an exemplary embodiment, the transmission T1 is coupled to at least one drive axle of the vehicle V1 (such as, e.g., rear axle RA1 and/or front axle FA1 as shown in FIG. 1). According to one exemplary embodiment, both the rear axle RA1 and the front axle FA1 are driven by the transmission T1. According to other exemplary embodiments, only one of the axles may be driven by the transmission T1. According to yet another exemplary embodiment, additional axles (e.g., such as additional rear axles not shown) may be driven by the transmission T1. According to an exemplary embodiment, each of the axles are coupled to the transmission via a differential gear set (such as, e.g., rear differential RD1 and/or front differential FD1 shown in FIG. 1). Each axle is configured to drive (i.e., provide rotational energy to) one or more wheels/tires to propel (e.g., move, push, drive etc.) the vehicle V1.
Referring now to FIG. 2, a detailed schematic view of the drive train for the vehicle V1 is shown according to exemplary embodiment. As shown in FIG. 2, the transmission T1 includes two planetary gear sets. According to an exemplary embodiment, the transmission T1 includes a first planetary gear set P1 and a second planetary gear set P2. A third planetary gear set P3 is provided as a torque divider (e.g., 30% torque to the front and 70% torque to the rear) if both the front and rear vehicle axles are powered.
According to one exemplary embodiment, the first planetary gear set P1 is configured as a power split device or power splitting planetary gear set, the second planetary gear set P2 is configured as a gear reduction device, and the third planetary gear set P3 is configured as a torque proportioning device. As shown in FIG. 2, the first planetary gear set P1 is coupled to the engine E1, the first electromechanical device EM1, the second electromechanical device EM2 (via the second planetary gear set P2), and to gear G5. The second planetary gear set P2 is also coupled to the gear G5 (via gears G13, G14, G15, clutch C2 and shaft S6).
As shown in FIG. 2, the engine E1 is coupled to a clutch C3 that is configured to selectively rotationally engage/disengage the engine E1 with the transmission T1. The clutch C3 may be any type of clutch capable of rotationally fixing the engine E1 to the transmission T1. When the clutch C3 is engaged, the engine E1 is coupled to a shaft S1. A gear G6 is coupled (e.g., rotationally fixed) to shaft S1 and engages a gear G7 that is coupled (e.g., rotationally fixed) to a shaft S2. The gear G7 in turn is coupled to the first planetary gear set P1 via the shaft S2.
As shown in FIG. 2, the first planetary gear set P1 comprises an annulus or ring gear G1 which is coupled to the shaft S2. As shown, the clutch C3, the gears G6 and G7, and the shaft S2 cooperate to permit engine E1 to drive the ring gear G1. The ring gear G1 is engaged with at least one planetary gear G2 (e.g., one, two, three, four or more planetary gears G2 that are coupled to one another (e.g., rotatably supported) by a planetary gear carrier PGC1). The planetary gear(s) G2 are engaged with a sun gear G3 of the first planetary gear set P1 to couple the ring gear G1 to the sun gear G3.
The sun gear G3 is directly coupled to the first electromagnetic device EM1 by a shaft S3. The first electromagnetic device EM1 may be coupled to an optional brake B1 by a clutch C4. The clutch C4 may be any type of clutch capable of rotationally fixing the first electromagnetic device EM1 to the brake B1. The effect of braking the first electromechanical device EM1 is to fix or hold sun gear G3 without the need to apply electrical energy to the first electromechanical device EM1 to cause the first electromechanical device EM1 to generate enough holding torque to hold the gear G3 from rotating.
According to an exemplary embodiment, the planetary gear carrier PGC1 is coupled to a carrier gear G4. The carrier gear G4 is engaged with a gear G5. In the preferred embodiment of vehicle V1, the gear G5 is part of the third planetary gear set P3 used to divide the power from the transmission T1 to the front and rear axles. In this embodiment, the gear G5 is coupled to the planetary gears of the third planetary gear set P3. If only a single axle is driven by the transmission T1, or a different transfer device is used to drive more than one axle, the third planetary gear set P3 may not be necessary.
The carrier gear G4 is also coupled to the second planetary gear set P2 by a shaft S5 (as will be described in more detail below).
Still referring to FIG. 2, the transmission T1 also includes a clutch C1 that selectively rotationally engages/disengages the engine E1 to the second electromagnetic device EM2. The clutch C1 may be any type of clutch capable of rotationally fixing the engine E1 to the second electromagnetic device EM2, such as a wet clutch.
As shown in FIG. 2, the clutch C1 is coupled to the engine E1 by the shaft S1. When the clutch C1 is engaged, the shaft S1 is coupled to a gear G9. The gear G9 in turn is engaged with a gear G8 that is coupled to the second electromagnetic device EM2. Thus, when the clutch C1 is engaged, the engine is coupled to the second electromagnetic device EM2 to allow the second electromagnetic device EM2 to be driven as a generator (e.g., to provide electrical power to the first electromagnetic device EM1).
The electromagnetic device EM2 is also coupled to the second planetary gear set P2 by a shaft S4. The shaft S4 is connected to a sun gear G12 of the second planetary gear set P2. The sun gear G12 is engaged with at least one planetary gear G11 (e.g., one, two, three, four or more planetary gears G11 that are coupled to one another (e.g., rotatably supported) by a planetary gear carrier PGC2). The planetary gear(s) G11 in turn are engaged with an annulus or ring gear G10 to couple the sun gear G12 to the ring gear G10.
According to an exemplary embodiment, the planet gear carrier PGC2 of the second planetary gear P2 is coupled to the carrier gear G4 (and the planet gear carrier PGC1) of the first planetary gear set P1 by a shaft S5. Thus, the planet gear carrier PGC1 and the planet gear carrier PGC2 are coupled to one another so that the second electromagnetic device EM2 is coupled to the first planetary gear set P1 via the second planetary gear set P2.
The second electromagnetic device EM2 is also coupled to the third planetary gear set P3 via the second planetary gear set P2. According to an exemplary embodiment, the ring gear G10 of the second planetary gear P2 is coupled to an output gear G13 that is engaged with an idler gear G14. The idler gear G14 in turn is engaged with a gear G15 that is selectively engaged/disengaged to the third planetary gear set P3 by a clutch C2 (via a shaft S6). The clutch C2 may be any type of clutch capable of rotationally fixing the gear G15 to the shaft S6, such as a wet clutch.
According to an exemplary embodiment, the third planetary gear set P3 is a torque proportioning device for the front and rear axles of the vehicle V1. Torque is delivered from the third planetary gear set P3 to the front axle FA1 and/or the rear axle RA1 via shafts S7 and S8. As discussed above, in other exemplary embodiments, the third planetary gear set P3 is not necessary when either the front axle FA1 or rear axle RA1 of the vehicle V1 is not driven by the transmission T1.
According to an exemplary embodiment, the transmission T1 is operated in a low speed mode (e.g., a vehicle speed of approximately 0-10 mph) by having the clutch C2 engaged and the clutch C1 disengaged. According to another exemplary embodiment, the transmission T1 is operated in a high speed mode (e.g., a vehicle speed of approximately 10-65 mph) by having the clutch C1 engaged and the clutch C2 disengaged. According to other various embodiments, the vehicle speeds in the low and high speed modes may vary higher or lower.
According to an exemplary embodiment, an operator (e.g., driver) of vehicle V1 may manually switch the transmission T1 from low speed mode to high speed mode or vice-versa. According to another exemplary embodiment, the transmission T1 is automatically switched from low speed mode to high speed mode (and vice-versa) by a control system (see, e.g., FIG. 3). The control system may include various operator inputs (such as, e.g., desired vehicle speed, torque, traction, terrain, etc.) and also various system inputs (such as, e.g., current vehicle speed, engine speed, power, and torque, electromagnetic device speed, power, and torque, etc.). As shown in FIG. 3, according to one exemplary embodiment, the control system is configured to monitor and/or control the engine, the mode of the transmission, the first electromagnetic device EM1, the second electromagnetic device EM2, the clutch C1, the clutch C2, and/or the clutch C3.
According to an exemplary embodiment, gears within the transmission T1 are sized according to the specific application and desired performance characteristics of the vehicle V1. According to one exemplary embodiment, the gears within the transmission T1 have tooth counts as shown in Table 1. However, according to other exemplary embodiments, the tooth counts of the gears may vary more or less than that shown. According to other exemplary embodiments, the engine E1, the electromagnetic devices EM1 and EM2, the clutches C1-C4, and the shafts S1-S8 may all vary according to the specific application and desired performance characteristics of the vehicle V1.










TABLE 1







Gear #
Tooth Count









Gear 1
81



Gear 2
24



Gear 3
33



Gear 4
77



Gear 5
77



Gear 6
49



Gear 7
50



Gear 8
55



Gear 9
74



Gear 10
64



Gear 11
19



Gear 12
26



Gear 13
28



Gear 14
47



Gear 15
82










It should be noted that references to “front,” “rear,” “top,” and “base” in this description are merely used to identify various elements as are oriented in the FIGS., with “front” and “rear” being relative to the environment in which the device is provided.
For the purpose of this disclosure, the term “coupled” means the joining of two members directly or indirectly to one another. Such joining may be stationary or moveable in nature. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. Such joining may be permanent in nature or may be removable or releasable in nature.
It is important to note that the construction and arrangement of the electromechanical variable transmission as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (for example, variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present embodiments.

## Claims

1. A drive train for a vehicle, comprising:
a first gear set comprising a sun gear, a ring gear and planetary gears coupling the sun gear to the ring gear;
a second gear set comprising a sun gear, a ring gear and planetary gears coupling the sun gear to the ring gear, wherein the planetary gears of both sets are rotatably supported by respective planetary gear carriers which are coupled to each other;
an engine having an output shaft;
a first clutch which selectively engages the output shaft of the engine with the first gear set;
a first motor/generator coupled to the first gear set;
a second motor/generator coupled to the second gear set and electrically coupled to the first motor/generator;
a second clutch which selectively engages the output shaft of the engine with the second motor/generator; and
a third clutch and a third gear set which operate to selectively engage at least one of the sun gear and the ring gear of the second gear set with the planetary gear carriers of the first and second gear sets.

2. The drive train of claim 1, further comprising a fourth gear set including at least two gears which couple the first clutch to the ring gear of the first gear set.

3. The drive train of claim 1, further comprising a fifth gear set including at least two gears which couple the second clutch to the second motor/generator.

4. The drive train of claim 1, wherein the third gear set includes a first pair of gears which couple the ring gear of the second gear set to the third clutch, and a second pair of gears which couple the third clutch to the planetary gear carriers.

5. The drive train of claim 1, further comprising a brake mechanism for preventing rotation of the first motor/generator.

6. The drive train of claim 1, further comprising a planetary gear set having at least a ring gear, wherein the planetary gear carriers are coupled to the ring gear of the planetary gear set.

7. A drive train for a vehicle, comprising:
a first planetary gear set;
a second planetary gear set directly coupled to the first planetary gear set;
an output shaft selectively coupled to at least one of the first and the second planetary gear sets, wherein the output shaft is radially offset from the first and second planetary gear sets;
an engine rotationally engaged with the first planetary gear set;
a first electromagnetic device rotationally coupled to the first planetary gear set; and
a second electromagnetic device directly coupled to the second planetary gear set and selectively rotationally engaged with the engine.

8. The drive train of claim 7, wherein the first electromagnetic device and the second electromagnetic device are electrically connected to one another to permit the transfer of electrical power between the electromagnetic devices.

9. The drive train of claim 7, wherein at least one of the first electromagnetic device and the second electromagnetic device comprises a motor/generator.

10. The drive train of claim 7, wherein the second planetary gear set includes a ring gear and the first planetary gear set includes a planetary gear that is coupled to the ring gear of the second planetary gear set.

11. The drive train of claim 10, wherein the first planetary gear set is coupled to at least one of a front axle and a rear axle of a vehicle.

12. The drive train of claim 11, wherein the second planetary gear set is selectively rotationally engaged with at least one of the front axle and the rear axle of the vehicle.

13. The drive train of claim 12, wherein when the second planetary gear set is selectively rotationally engaged with at least one of the front axle and the rear axle of the vehicle, the second electromagnetic device is disengaged from the engine.

14. A vehicle, comprising:
a dual-mode transmission comprising a first gear set having a first planetary gear carrier and a second gear set having a second planetary gear carrier, wherein the first planetary gear carrier and the second planetary gear carrier are rotatably coupled;
an engine coupled to the first gear set;
a first motor/generator coupled to the first gear set;
a second motor/generator coupled to the second gear set; and
a drive axle coupled to the dual-mode transmission;
wherein during a first mode of operation of the vehicle the second motor/generator is coupled to the drive axle and decoupled from the engine, and
wherein during a second mode of operation of the vehicle the second motor/generator is selectively coupled to the engine and decoupled from the drive axle.

15. The vehicle of claim 14, wherein the first motor/generator and the second motor/generator are electrically connected to one another so that one of the first and second motor/generators may provide electrical power to the other of the first and second motor/generators.

16. The vehicle of claim 14, wherein the first mode of operation is a low speed mode of operation and the second mode of operation is a high speed mode of operation.

17. The vehicle of claim 14, wherein the dual-mode transmission further comprises a third gear set that is coupled to the drive axle of the vehicle.