Electric axle
Methods and systems are provided for an electric axle. The electric axle system includes, in one example, a first electric machine and a planetary reduction differential configured to receive mechanical power from the first electric machine. The planetary reduction differential includes a first planetary gear set directly rotationally coupled to a second planetary gear set. In the electric axle system, a sun gear in the first planetary gear set is directly coupled to an input shaft of the planetary reduction differential.
1 . An electric axle system, comprising:
a first electric machine;
a planetary reduction differential configured to receive mechanical power from the first electric machine;
a Ravigneaux three-speed mode planetary gear set rotationally coupled and positioned coaxial to the planetary reduction differential; and
a mode clutch configured to:
ground a carrier or a ring gear in the Ravigneaux three-speed mode planetary gear set, in a first mode;
ground a second sun gear in the Ravigneaux three-speed mode planetary gear set, in a second mode; and
rotationally couple the carrier or the ring gear to the second sun gear in the Ravigneaux three-speed mode planetary gear set, in a third mode;
wherein a first sun gear in the Ravigneaux three-speed mode planetary gear set is rotationally coupled to the first electric machine;
wherein the planetary reduction differential includes a first planetary gear set directly rotationally coupled to a second planetary gear set;
wherein a sun gear in the first planetary gear set is directly coupled to an input shaft of the planetary reduction differential; and
wherein a carrier in the first planetary gear set is directly coupled to an output shaft.
2 . The electric axle system of claim 1 , wherein:
the first planetary gear set is a simple planetary gear set and the second planetary gear set is a simple planetary gear set; and/or
the first and second planetary gear sets have an identical ring gear to sun gear ratio.
3 . The electric axle system of claim 2 , wherein:
a ring gear in the second planetary gear set is directly coupled to an output shaft;
a ring gear in the first planetary gear set is directly rotationally coupled to a sun gear in the second planetary gear set; and
a carrier in the second simple planetary gear set is grounded.
4 . The electric axle system of claim 1 , wherein:
the first planetary gear set is a simple planetary gear set and the second planetary gear set is a meshed planet compound planetary gear set; and
a ring gear in the second planetary gear set is grounded.
5 . The electric axle system of claim 4 , wherein:
a sun gear in the second planetary gear set is directly coupled to an output shaft; and
a ring gear in the first planetary gear set is directly rotationally coupled to a carrier in the second planetary gear set.
6 . The electric axle system of claim 4 , wherein:
a carrier in the second planetary gear set is directly coupled to an output shaft; and
a ring gear in the first planetary gear set is directly rotationally coupled to a sun gear in the second planetary gear set.
7 . The electric axle system of claim 1 , wherein:
the first planetary gear set is a meshed planet compound planetary gear set and the second planetary gear set is a meshed planet compound planetary gear set; and
a ring gear in the second planetary gear set is grounded.
8 . The electric axle system of claim 7 , wherein:
a sun gear in the second planetary gear set is directly coupled to an output shaft; and
a ring gear in the first planetary gear set is directly rotationally coupled to a carrier in the second planetary gear set.
9 . The electric axle system of claim 7 , wherein:
a carrier in the second planetary gear set is directly coupled to an output shaft; and
a ring gear in the first planetary gear set is directly rotationally coupled to a sun gear in the second planetary gear set.
10 . The electric axle system of claim 1 , wherein the first electric machine is positioned coaxial, parallel, or transverse, to the planetary reduction differential.
11 . The electric axle system of claim 1 , further comprising a second electric machine rotationally coupled to the planetary reduction differential.
12 . A method for operation of an electric axle, comprising:
operating a first electric machine to deliver mechanical power to a planetary reduction differential; and
operating a mode clutch in a Ravigneaux three-speed mode planetary gear set that is rotationally coupled to the planetary reduction differential to shift the Ravigneaux three-speed mode planetary gear set between two operating modes included in a set of three operating modes;
wherein the electric axle includes:
the first electric machine; and
the planetary reduction differential that is configured to receive mechanical power from the first electric machine;
wherein the planetary reduction differential comprises a first planetary gear set directly rotationally coupled to a second planetary gear set;
wherein a sun gear in the first planetary gear set is directly coupled to an input shaft of the planetary reduction differential; and
wherein a carrier in the first planetary gear set is directly coupled to an output shaft.
13 . The method of claim 12 , further comprising operating a second electric machine to deliver mechanical power to the planetary reduction differential.
14 . An electric axle, comprising:
an electric machine;
a planetary reduction differential configured to receive mechanical power from the electric machine;
a Ravigneaux three-speed mode planetary gear set rotationally coupled and positioned coaxial to the planetary reduction differential; and
a mode clutch configured to selectively transition the Ravigneaux three-speed mode planetary gear set between two of three modes;
wherein the mode clutch is configured to:
in a first mode, ground a carrier or a ring gear in the Ravigneaux three-speed mode planetary gear set;
in a second mode, ground a second sun gear in the Ravigneaux three-speed mode planetary gear set; and
in a third mode, rotationally couple the carrier or the ring gear to the second sun gear in the Ravigneaux three-speed mode planetary gear set;
wherein the planetary reduction differential includes a first planetary gear set directly rotationally coupled to a second planetary gear set;
wherein a sun gear in the first planetary gear set is directly coupled to an input shaft of the planetary reduction differential;
wherein a carrier in the first planetary gear set is directly coupled to an output shaft;
wherein a ring gear in the second planetary gear set is directly coupled to an output shaft;
wherein a ring gear in the first planetary gear set is directly rotationally coupled to a sun gear in the second planetary gear set; and
wherein a carrier in the second planetary gear set is grounded.
15 . The electric axle of claim 14 , wherein a ring gear or a carrier in the Ravigneaux three-speed mode planetary gear set is coupled to the planetary reduction differential input shaft.