Electric drive system with differential steering

• US 20040069542A1
• Filed: 10/11/2002
• Published: 04/15/2004
• Est. Priority Date: 10/11/2002
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Vanderham, Michael E., Simmons, Gerald P.
• Granted Patent: US 6,892,837 B2
• Time in Patent Office: Days
• US Class Current: 180/6.2
• CPC Class Codes: B62D 11/16 the additional power supply being supplied mechanically

Abstract

An electric drive system is provided. The electric drive system includes a first output member, a second output member, and an electric motor that includes an output shaft having an axis of rotation. The output shaft is operatively engaged with the first and second output members to rotate the first and second output members. A differential steering system is disposed between the electric motor and the first and second output members. The differential steering system includes at least one planetary gear assembly that has an axis of rotation that substantially aligns with the axis of rotation of the output shaft. A steering motor is operatively engaged with the at least one planetary gear assembly and is operable to modify the rotational speed of the at least one planetary gear assembly to thereby adjust the rotational speed of one of the first and second output members relative to the other of the first and second output members.

Claims

1. An electric drive system;

comprising;

a first output member;

a second output member;

an electric motor including an output shaft having an axis of rotation, the output shaft operatively engaged with the first and second output members to rotate the first and second output members;

a differential steering system disposed between the electric motor and the first and second output members, the differential steering system including at least one planetary gear assembly having an axis of rotation that substantially aligns with the axis of rotation of the output shaft; and

a steering motor operatively engaged with the at least one planetary gear assembly and operable to modify the rotational speed of the at least one planetary gear assembly to thereby adjust the rotational speed of one of the first and second output members relative to the other of the first and second output members.

2. The electric drive system of claim 1, further including a first brake engageable with the first output member and a second brake engageable with the second output member.

3. The electric drive system of claim 1, wherein the differential assembly includes a first planetary gear assembly, a second planetary gear assembly, and a third planetary gear assembly, each of the first, second, and third planetary gear assemblies having a sun gear, a planet gear set, a ring gear, and a rotational axis that substantially aligns with the rotational axis of the output shaft.

4. The electric drive system of claim 3, further including a reaction member connecting the sun gears of the first, second, and third planetary gear assemblies.

5. The electric drive system of claim 4, wherein the output shaft of the electric motor is hollow and the reaction member extends therethrough.

6. The electric drive system of claim 3, wherein the output shaft of the electric motor is connected to the planet gear set of the first planetary gear assembly.

7. The electric drive system of claim 3, wherein the differential steering motor operatively engages the ring gear of the second planetary gear assembly.

8. The electric drive system of claim 3, wherein the first output member is connected to the planet gear set of the second planetary gear assembly.

9. The electric drive system of claim 3, wherein the second output member is connected to the planet gear set of the third planetary gear assembly.

10. The electric drive system of claim 9, further including a housing and wherein the ring gear of the third planetary gear assembly is fixed to the housing.

11. The electric drive system of claim 3, wherein the first and second planetary gear assemblies are disposed between the electric motor and the first output member, and the third planetary gear assembly is disposed between the electric motor and the second output member.

12. The electric drive system of claim 3, wherein the ring gear of the first planetary gear assembly is connected to the planet gear set of the second planetary gear assembly.

13. The electric drive system of claim 1, further including a fourth planetary gear assembly disposed between the electric motor and the differential steering system, the fourth planetary gear assembly being configured to reduce the rotational speed of the output shaft.

14. A method of assembling an electric drive system, comprising:

providing an electric motor including an output shaft having an axis of rotation, the electric motor operable to rotate a first output member and a second output member;

disposing a differential steering system having at least one planetary gear assembly between the electric motor and the first and second output members such that an axis of rotation of the planetary gear assembly substantially aligns with the axis of rotation of the output shaft; and

engaging a steering motor with the differential steering system, the steering motor operable to modify the rotational speed of the at least one planetary gear assembly to thereby adjust the rotational speed of one of the first and second output members relative to the other of the first and second output members.

15. The method of claim 14, further including disposing a first brake adjacent the first output member and a second brake adjacent the second output member.

16. The method of claim 15, further including engaging a first sprocket with the first output member and a second sprocket with the second output member.

17. The method of claim 16, wherein the differential steering system includes a first planetary gear assembly, a second planetary gear assembly, and a third planetary gear assembly, and further including providing a housing having a first side configured to receive the first and second planetary gear assemblies, the first output member, the first brake, a first final drive, and the first sprocket, the housing having a second side configured to receive the third planetary gear assembly, the second brake, and a second final drive.

18. A vehicle, comprising:

a first ground engaging device;

a second ground engaging device;

a first output member connected to the first ground engaging device;

a second output member connected to the second ground engaging device;

an electric motor including an output shaft having an axis of rotation, the output shaft operatively engaged with the first and second output members to rotate the first and second output members;

a differential steering system disposed between the electric motor and the first and second output members, the differential steering system including at least one planetary gear assembly having an axis of rotation that substantially aligns with the axis of rotation of the output shaft; and

a differential steering motor operatively engaged with the at least one planetary gear assembly and operable to vary the rotation of the at least one planetary gear assembly to thereby adjust the rotational speed of one of the first and second output members relative to the other of the first and second output members.

19. The vehicle of claim 18, wherein the first and second ground engaging devices are tracks and the first and second ground engaging devices are disposed on opposite sides of the vehicle.

20. The vehicle of claim 19, further including a first sprocket disposed between the first output member and the first ground engaging device and a second sprocket disposed between the second output member and the second ground engaging device.

21. The vehicle of claim 18, further including a first brake engageable with the first output member and a second brake engageable with the second output member.

22. The vehicle of claim 18, wherein the differential assembly includes a first planetary gear assembly, a second planetary gear assembly, and a third planetary gear assembly, each of the first, second, and third planetary gear assemblies having a sun gear, a planet gear set, a ring gear, and a rotational axis that substantially aligns with the rotational axis of the output shaft.

23. The vehicle of claim 22, further including a reaction member connecting the sun gears of the first, second, and third planetary gear assemblies.

24. The vehicle of claim 23, wherein the output shaft of the electric motor is hollow and the reaction member extends therethrough.

25. The vehicle of claim 22, wherein the output shaft of the electric motor is connected to the planet gear set of the first planetary gear assembly.

26. The vehicle of claim 22, wherein the differential steering motor operatively engages the ring gear of the second planetary gear assembly.

27. The vehicle of claim 22, wherein the first output member is connected to the planet gear set of the second planetary gear assembly.

28. The vehicle of claim 22, wherein the second output member is connected to the planet gear set of the third planetary gear assembly.

29. The vehicle of claim 22, further including a housing and wherein the ring gear of the third planetary gear assembly is fixed to the housing.

30. The vehicle of claim 22, wherein the first and second planetary gear assemblies are disposed between the electric motor and the first output member and the third planetary gear assembly is disposed between the electric motor and the second output member.

31. The vehicle of claim 22, wherein the ring gear of the first planetary gear assembly is connected to the planet gear set of the second planetary gear assembly.

32. The vehicle of claim 18, further including a fourth planetary gear assembly disposed between the electric motor and the differential steering system and configured to reduce the rotational speed of the output shaft.