Integrated starter-generator device with power transmission

1. A combination engine starter and power generator device for a work vehicle having an engine, the device comprising:

an electric machine;

a planetary gear set at least having a sun gear, a carrier and a ring gear and configured to receive rotational input from the electric machine and from the engine and to mechanically couple the electric machine and the engine in first and second power flow directions in which in the first power flow direction the planetary gear set effects a first gear ratio and in the second power flow direction the planetary gear set effects a second gear ratio; and

a clutch coupled to the planetary gear set and disposed between the engine and the planetary gear set;

wherein, for engine start up in the first power flow direction, rotational power from the electric machine is input to the planetary gear set through the sun gear and is output from the planetary gear set through the ring gear and the clutch to the engine, and, for power generation in the second power flow direction, rotational power from the engine is input to the planetary gear set through the carrier and is output from the planetary gear set through the sun gear to the electric machine.

2. The device of claim 1 , wherein the first gear ratio is greater than the second gear ratio.

3. The device of claim 2 , wherein the first gear ratio is at least 10 times the second gear ratio.

4. The device of claim 3 , wherein the first gear ratio is about 40-100:1 and the second gear ratio is about 2-10:1.

5. The device of claim 1 , further including a second clutch coupled to the planetary gear set and disposed between the engine and the planetary gear set;

wherein, in the second power flow direction, the second clutch engages the carrier to couple the engine to the carrier.

6. The device of claim 5 , wherein the clutch is disengaged in the second power flow direction and the second clutch is disengaged in the first power flow direction.

7. The device of claim 6 , wherein the clutches are one-way mechanically-actuated clutches.

8. The device of claim 5 , wherein the planetary gear set includes a second ring gear having a different tooth count than the ring gear and coupled to ground.

9. A combination engine starter and electric power generator device for a work vehicle having an engine, the device comprising:

a housing;

an electric machine at least in part contained in the housing; and

a transmission at least in part contained in the housing, the transmission including:

a planetary gear set at least haying a sun gear, a carrier and a ring gear and configured to receive rotational input from the electric machine and from the engine and mechanically couple the electric machine and the engine in first and second power flow directions in which in the first power flow direction the planetary gear set effects a first gear ratio and in the second power flow direction the planetary gear set effects a second gear ratio; and

a clutch assembly mechanically coupled to the planetary gear set, the clutch assembly including:

a first one-way clutch that is engaged when the planetary gear set moves in the first power flow direction and is disengaged when the planetary gear set moves in the second power flow direction; and

a second one-way clutch that is engaged when the planetary gear set moves in the second power flow direction and is disengaged when the planetary gear set moves in the first power flow direction;

wherein, for engine start up in the first power flow direction, rotational power from the electric machine is input to the planetary gear set through the sun gear and is output from the planetary gear set through the ring gear and the first one-way clutch to the engine; and

wherein, for power generation in the second power flow direction, rotational power from the engine is input to the planetary gear set through the second one-way clutch to the carrier and is output from the planetary gear set through the sun gear to the electric machine.

10. The device of claim 9 , wherein the planetary gear set includes a second ring gear having a different tooth

count than the ring gear and coupled to ground.

11. A drivetrain assembly for a work vehicle, comprising:

an engine; and

a combination starter and generator device, the device including:

an electric machine;

a planetary gear set at least haying a sun gear, a carrier and a ring gear and configured to receive rotational input from the electric machine and from the engine and to mechanically couple the electric machine and the engine in first and second power flow directions in which in the first power flow direction the gear set effects a first gear ratio and in the second power flow direction the gear set effects a second gear ratio; and

a first clutch and a second clutch coupled to the gear set and disposed between the engine and the planetary gear set;

wherein, for engine start up in the first power flow direction, rotational power from the electric machine is input to the planetary gear set through the sun gear and is output from the planetary gear set through the ring gear and the first clutch to the engine; and

wherein, for power generation in the second power flow direction, rotational power from the engine is input to the planetary gear set through the second clutch to the carrier and is output from the planetary gear set through the sun gear to the electric machine.

12. The drivetrain assembly of claim 11 , wherein the first clutch is engaged when the planetary gear set moves in the first power flow direction and is disengaged when the planetary gear set moves in the second power flow direction; and

wherein the second clutch is engaged when the planetary gear set moves in the second power flow direction and is disengaged when the planetary gear set moves in the first power flow direction.

13. The drivetrain of claim 12 ,

wherein the first and second clutches are one-way mechanically-actuated clutches.