Powertrain, vehicle and method of performing a gearshift in the powertrain

1. A powertrain comprising a transmission, a first electric motor and a second electric motor, wherein

the transmission comprises an input shaft to which a source of mechanical power may be connected, an output shaft and a gear assembly providing at least two different gear ratios that may be selected for transfer of mechanical power from the input shaft to the output shaft,

the first electric motor is connected to the input shaft via a first gear, such that torque and rotation may be transferred between the first electric motor and the input shaft, and

the second electric motor is connected to the input shaft via a first clutch and the first gear, such that torque and rotation may be transferred between the second electric motor and the input shaft, and connected to the output shaft via a second clutch a second gear, such that torque and rotation may be transferred between the second electric motor and the output shaft, wherein

the first electric motor is connected to the second electric motor via the first clutch, and the first clutch and the second clutch are friction clutches which may operate with a torque level controllable between zero and a maximum torque level, and the first electric motor, the second electric motor, the first clutch and the second clutch form parts of a torque transfer path bypassing the at least two different gear ratios, the torque transfer path arranged to transfer torque from the input shaft to the output shaft during a gearshift.

2. A powertrain according to claim 1 , wherein the first electric motor is electrically connected to the second electric motor, such that the first electric motor may generate electric power from torque at the input shaft and transfer the generated electric power to the second electric motor.

3. A powertrain according claim 1 , wherein the source of mechanical power is an internal combustion engine or at least one electric motor.

4. A powertrain according to claim 1 , wherein the source of mechanical power is an internal combustion engine connected to the input shaft via a main clutch.

5. A powertrain according to claim 1 , wherein the transmission comprises a layshaft, and any of the first electric motor and the second electric motor is connected to any of the input shaft or the output shaft via the layshaft.

6. A powertrain according to claim 1 , wherein any of the first electric motor and the second electric motor is connected to the input shaft or the output shaft via a gear in the transmission.

7. A vehicle comprising a powertrain according to claim 1 .

8. A method of performing a gearshift from a low gear to a high gear in a powertrain according to claim 4 , comprising the steps of:

a. controlling the torque in the first electric motor and the first clutch to be equal to the torque in the main clutch;

b. transferring torque to the output shaft by engaging the second clutch;

c. disengaging the low gear;

d. reducing a rotational speed of the input shaft by having a higher torque in the first electric motor and the first clutch than in the main clutch; and

e. engaging the high gear when the rotational speed of the input shaft is synchronous with the high gear and the torque in the first electric motor and the first clutch is equal to the torque in the main clutch.

9. A method according to claim 8 , comprising a step of establishing a required torque in the input shaft by any combination of the first electric motor, the second electric motor and an internal combustion engine after the high gear is engaged.

10. A method according to claim 9 , wherein a required torque is obtained by establishing a full torque from the internal combustion engine in the main clutch.

11. A method according to claim 8 , wherein step a, is preceded by a step of running the first and second electric motors rotationally engaged with the input shaft of the transmission, wherein the first clutch is closed and the second clutch is open.

12. A method of performing a gearshift from a low gear to a high gear in a powertrain according to claim 1 , comprising the steps of:

a. controlling the torque in the first electric motor and the first clutch to be equal to the torque in the input shaft;

b. transferring torque to the output shaft by engaging the second clutch;

c. disengaging the low gear;

d. reducing a rotational speed of the input shaft by having a higher torque in the first electric motor and the first clutch than in the input shaft; and

e. engaging the high gear when the rotational speed of the input shaft is synchronous with the high gear and the torque in the first electric motor and the first clutch is equal to the torque in the input shaft.

13. A method according to claim 12 comprising a step of disengaging the second clutch and transferring torque from the second electric motor to the input shaft following the step of engaging the high gear.

14. A method according to claim 12 , wherein step a. is preceded by a step of running the first and second electric motors rotationally engaged with the input shaft of the transmission, wherein the first clutch is closed and the second clutch is open.

15. A method of performing a gearshift from a high gear to a low gear in a powertrain according to claim 4 , comprising the steps of:

a. controlling the torque in the first electric motor and the first clutch to be equal to the torque in the main clutch;

b. transferring torque to the output shaft by engaging the second clutch;

c. disengaging the high gear;

d. increasing a rotational speed of the input shaft by having a higher torque in the first electric motor and the first clutch than in the main clutch; and

e. engaging the low gear when the input shaft speed is synchronous with the low gear and the torque in the first electric motor and the first clutch is controlled to be equal to the torque in the main clutch.

16. A method according to claim 15 , comprising a step of establishing a required torque in the input shaft by any combination of the first electric motor, the second electric motor and an internal combustion engine after the low gear is engaged.

17. A method according to claim 16 , wherein the required torque is obtained by establishing full torque from the internal combustion engine in the main clutch.

18. A method according to claim 15 , wherein step a. is preceded by a step of running the first and second electric motors rotationally engaged with the input shaft of the transmission, wherein the first clutch is closed and the second clutch is open.

19. A method of performing a gearshift from a high gear to a low gear in a powertrain according to claim 1 , comprising the steps of:

a. controlling the torque in the first electric motor and the first clutch to be equal to the torque in the input shaft;

b. transferring torque to the output shaft by engaging the second clutch;

c. disengaging the high gear;

d. increasing a rotational speed of the input shaft by having a higher torque in the first electric motor and the first clutch than in the input shaft; and

e. engaging the low gear when the rotational speed of the input shaft is synchronous with the low gear and the torque in the first electric motor and the first clutch is controlled to be equal to the torque in the input shaft.

20. A method according to claim 19 comprising a step of disengaging the second clutch and transferring torque from the second electric motor to the input shaft following the step of engaging the low gear.

21. A method according to claim 19 , wherein step a. is preceded by a step of running the first and second electric motors rotationally engaged with the input shaft of the transmission, wherein the first clutch is closed and the second clutch is open.