Electric powertrain with cycloidal mechanism
An electric powertrain for a vehicle includes a cycloidal speed reducer having an input member configured to couple with a traction motor, a cycloidal disc defining a plurality of circumferentially arranged holes, and a plurality of circumferentially arranged pins each disposed in one of the holes. A differential of the vehicle has a case connected to each of the pins. The differential may be a cycloidal differential.
1. An electric powertrain for a vehicle comprising:
a cycloidal speed reducer including an input member configured to couple with a traction motor, a cycloidal disc defining a plurality of circumferentially arranged holes, and a plurality of circumferentially arranged pins each disposed in one of the holes; and
a cycloidal differential including a case connected to each of the pins.
2. The electric powertrain of claim 1 , wherein the input member is an eccentric cam, and the cycloidal disc defines a central hole that receives the eccentric cam and a plurality of lobes circumferentially arranged around an outer surface of the disc.
3. The electric powertrain of claim 1 , wherein the cycloidal speed reducer further includes a ring-pin assembly configured to be rotationally fixed with a stator of the traction motor and encircling the cycloidal disc, the assembly having a plurality of circumferentially arranged ring pins configured to engage with the lobes.
4. The electric powertrain of claim 1 , wherein the cycloidal disc is a pair of discs that have a phase difference between 170 and 200 degrees, inclusive.
5. The electric powertrain of claim 1 , wherein the cycloidal differential includes:
a first cycloidal drive having a first input member rotationally fixed to the case and a first differential output configured to connect with a first half shaft,
a second cycloidal drive having a second input member rotationally fixed to the case and a second output member configured to connect with a second half shaft, and
a coupling element connected between the first and second drives.
6. The electric powertrain of claim 5 , wherein the first and second drives further have first and second cycloidal discs, respectively, that each define lobes and holes.
7. The electric powertrain of claim 6 , wherein the first disc defines m number of lobes, and the second disc defines m+1 number of lobes.
8. The electric powertrain of claim 1 further comprising a traction motor including a stator, a rotor, and an output shaft fixed to the rotor, wherein the input member is coupled to the output shaft.
9. An electric powertrain for a vehicle comprising:
a traction motor including a stator, a rotor, and an output shaft fixed to the rotor; and
a cycloidal speed reducer coupled to the traction motor and including:
a ring-pin assembly rotationally fixed with the stator, encircling the output shaft, and having a plurality of circumferentially arranged ring pins,
an eccentric cam received on the output shaft, and
a cycloidal disc defining a central hole that receives the eccentric cam and a plurality of lobes circumferentially arranged around an outer surface of the disc and configured to engage with the ring pins; and
a cycloidal differential having a case rotationally coupled to the cycloidal disc.
10. The electric powertrain of claim 9 , wherein the cycloidal disc defines a plurality of circumferentially arranged holes, and wherein the cycloidal differential includes a case having a plurality of circumferentially arranged pins that are received in the holes.
11. The electric powertrain of claim 10 , wherein the pins are integrally formed with the case.
12. The electric powertrain of claim 9 , wherein the cycloidal differential includes:
a first cycloidal drive having a first input member rotationally fixed to the case and a first differential output configured to connect with a first half shaft,
a second cycloidal drive having a second input member rotationally fixed to the case and a second output member configured to connect with a second half shaft, and
a coupling element connected between the first and second drives.
13. The electric powertrain of claim 9 , wherein the cycloidal differential further includes first and second cycloidal discs connected to respective first and second differential outputs.
14. The electric powertrain of claim 13 , wherein the traction motor, the cycloidal speed reducer, and the differential are coaxial, and the second differential output extends through a bore of the output shaft.
15. The electric powertrain of claim 13 , wherein the first and second cycloidal discs define a plurality of lobes circumferentially arranged around outer surfaces of the discs, wherein the first disc has m number of lobes, and the second disc has m+1 number of lobes.
16. The electric powertrain of claim 13 , wherein the first cycloidal disc defines a circumferential arrangement of holes, and the cycloidal differential further includes a circumferential array of pins that are disposed in the holes of the first cycloidal disc.
17. An electric axle comprising:
a traction motor including a motor output shaft;
a cycloidal speed reducer coupled to the motor output shaft and including a cycloidal disc configured to have an eccentric, cycloidal motion that rotates slower than the motor output shaft; and
a cycloidal differential including a case connected to the cycloidal disc and first and second differential output shafts.
18. The electric axle of claim 17 further comprising:
a first half shaft connected to the first differential output shaft; and
a second half shaft connected to the second differential output shaft.