Electric axle
Methods and systems are provided for an electric axle. The electric axle system includes, in one example, an electric machine and a multi-speed transmission that is rotationally coupled to the electric machine and rotationally coupled to two output shafts. The transmission includes a differential rotationally coupled and positioned coaxial to a mode planetary gear set. In the electric axle system, the mode planetary gear set is a meshed planet compound planetary gear set and a mode clutch in the transmission is configured to selectively shift the mode planetary gear set between a first mode and a second mode.
1 . An electric axle system, comprising:
an electric machine; and
a multi-speed transmission rotationally coupled to the electric machine, rotationally coupled to two output shafts, and including:
a differential rotationally coupled to a mode planetary gear set;
a mode clutch configured to selectively shift the mode planetary gear set into:
a first mode where the mode clutch grounds a carrier or a ring gear that are included in the mode planetary gear set; and
a second mode where the mode clutch rotationally couples the carrier to the ring gear; and
an axle disconnect clutch configured to selectively disconnect the differential from the mode planetary gear set;
wherein a rotational axis of the differential is arranged coaxial to a rotational axis of the mode planetary gear set.
2 . The electric axle system of claim 1 , wherein:
the mode planetary gear set is a meshed planet compound planetary gear set; and
the differential is a differential meshed planet compound planetary gear set.
3 . The electric axle system of claim 2 , wherein the ring gear in the mode planetary gear set is directly rotationally coupled to the differential and a sun gear in the mode planetary gear set is rotationally coupled to an upstream component that receives mechanical power from the electric machine.
4 . The electric axle system of claim 3 , wherein a sun gear in the differential meshed planet compound planetary gear set is rotationally coupled to a first output shaft in the two output shafts, and a carrier in the differential meshed planet compound planetary gear set is rotationally coupled to a second output shaft in the two output shafts.
5 . The electric axle system of claim 1 , further comprising a differential locking clutch configured to selectively rotationally couple a ring gear in the differential to a carrier in the differential to lock rotation of the two output shafts.
6 . The electric axle system of claim 1 , wherein the electric machine is positioned coaxial, parallel, or transverse to the mode planetary gear set and the differential.
7 . The electric axle system of claim 1 , wherein the mode clutch is a dog clutch.
8 . A method for operation of an electric axle system, comprising:
operating a mode clutch to:
in a first mode, ground a carrier or a ring gear in a mode planetary gear set;
in a second mode, rotationally couple the carrier and the ring gear in the mode planetary gear set; and
operating an axle disconnect clutch to selectively disconnect the mode planetary gear set from the differential;
wherein the electric axle system includes:
an electric machine;
a multi-speed transmission rotationally coupled to the electric machine, rotationally coupled to two output shafts, and including:
the mode planetary gear set rotationally coupled and positioned coaxial to a differential; and
the mode clutch;
wherein the mode planetary gear set is a meshed planet compound planetary gear set.
9 . The method of claim 8 , wherein:
the differential is a differential meshed planet compound planetary gear set;
the ring gear in the mode planetary gear set is rotationally coupled to a ring gear in the differential meshed planet compound planetary gear set; and
a sun gear and a carrier in the differential meshed planet compound planetary gear set are rotationally coupled to separate output shafts.
10 . The method of claim 8 , further comprising operating a differential locking clutch to rotationally couple a ring gear in the differential to a carrier in the differential to lock rotation of the two output shafts.
11 . An electric axle system, comprising:
an electric machine;
a multi-speed transmission rotationally coupled to the electric machine and including:
a mode planetary gear set rotationally coupled and positioned coaxial to a differential meshed planet compound planetary gear set;
a mode clutch configured to selectively shift the mode planetary gear set into a first mode and a second mode;
a differential locking clutch configured to selectively rotationally couple a ring gear in the differential meshed planet compound planetary gear set to a carrier in the differential meshed planet compound planetary gear set to lock rotation of two output shafts; and
an axle disconnect clutch configured to selectively disconnect the mode planetary gear set from the differential meshed planet compound planetary gear set.
12 . The electric axle system of claim 11 , wherein the mode planetary gear set includes a first ring gear that is rotationally coupled to a second ring gear in the differential meshed planet compound planetary gear set.
13 . The electric axle system of claim 11 , wherein the mode clutch is configured to shift the mode planetary into:
the first mode where the mode clutch grounds a carrier or a ring gear that is included in the mode planetary gear set; and
in the second mode where the mode clutch rotationally couples the carrier to the ring gear in the mode planetary gear set.
14 . The electric axle system of claim 11 , wherein:
a sun gear in the differential meshed planet compound planetary gear set is rotationally coupled to a first output shaft; and
a carrier in the differential meshed planet compound planetary gear set is rotationally coupled to a second output shaft.
15 . The electric axle system of claim 11 , wherein the electric machine and the mode planetary gear set are coaxially arranged.