Drive apparatus

1. A drive apparatus comprising:

a motor including a rotor arranged to rotate about a motor axis;

a transmission system arranged to transfer power of the motor to an axle; and

a housing arranged to house the motor and the transmission system; wherein

the housing includes:

a tubular motor housing arranged to extend from a first axial side to a second axial side along the motor axis; and

a gear housing arranged on the second axial side of the motor housing, and joined to the motor housing;

the transmission system includes a gear system including a combination of a first gear supported by a first bearing and a second gear supported by a second bearing;

the gear housing includes:

a first holding portion arranged to hold the first bearing, and a second holding portion arranged to hold the second bearing; and

surrounding ribs arranged to project to the second axial side from a wall surface of the gear housing, and surround an area that encompasses the first bearing and the second bearing when viewed in an axial direction;

the surrounding ribs include:

a plurality of arc-shaped ribs including an arc-shaped rib arranged to extend along an outer circumferential edge of the first bearing, and an arc-shaped rib arranged to extend along an outer circumferential edge of the second bearing; and

a plurality of straight ribs connected to the plurality of arc-shaped ribs; and

one or more of the straight ribs are each located on a common tangent to the first bearing and the second bearing.

2. The drive apparatus according to claim 1 , wherein

the gear housing includes a third holding portion arranged to hold a third bearing;

the surrounding ribs are arranged to surround an area that encompasses the first bearing, the second bearing, and the third bearing;

one of the plurality of arc-shaped ribs is arranged to extend along an outer circumferential edge of the third bearing; and

one or more of the straight ribs are each located on a common tangent to the second bearing and the third bearing or on a common tangent to the third bearing and the first bearing.

3. The drive apparatus according to claim 1 , wherein

the rotor includes a hollow motor shaft;

the gear system includes a combination of the first gear, the second gear, and a fourth gear arranged to rotate together with the motor shaft and coaxially with the second gear; and

the transmission system includes:

a differential including the second gear; and

an output shaft connected to the differential to rotate in accordance with rotation of the second gear, and including a portion arranged in an interior of the motor shaft.

4. The drive apparatus according to claim 1 , wherein

the gear system includes a planetary gear mechanism including a sun gear, a planetary gear arranged to mesh with the sun gear, an internal gear being in an annular shape and arranged to mesh with the planetary gear, and a carrier connected to the planetary gear; and

one of the first gear and the second gear defines a portion of the planetary gear mechanism.

5. The drive apparatus according to claim 1 , wherein the arc-shaped rib arranged to extend along the outer circumferential edge of the first bearing, and the arc-shaped rib arranged to extend along the outer circumferential edge of the second bearing, are arranged to overlap with the first holding portion and the second holding portion, respectively, when viewed in the axial direction.

6. The drive apparatus according to claim 1 , wherein

the arc-shaped rib arranged to extend along the outer circumferential edge of the first bearing is connected to the straight rib located on the common tangent to the first bearing and the second bearing; and

the arc-shaped rib arranged to extend along the outer circumferential edge of the second bearing is connected to the straight rib located on the common tangent to the first bearing and the second bearing.

7. The drive apparatus according to claim 1 , wherein

the gear housing includes a flow passage member arranged to allow a fluid to flow therein, and arranged to overlap with the first holding portion when viewed in the axial direction;

the plurality of straight ribs include a straight rib arranged to extend toward the first bearing; and

at least one of the arc-shaped rib arranged to extend along the outer circumferential edge of the first bearing and the straight rib arranged to extend toward the first bearing is connected to the flow passage member.

8. The drive apparatus according to claim 1 , wherein the gear housing includes a reinforcing rib arranged to connect two of the arc-shaped ribs to each other inside of an external edge of the surrounding ribs.

9. The drive apparatus according to claim 8 , wherein the reinforcing rib is located on a straight line joining centers of the two arc-shaped ribs to each other.

10. The drive apparatus according to claim 1 , wherein the gear housing includes radial ribs arranged to extend in a radial manner with the first bearing in a center when viewed in the axial direction, and/or radial ribs arranged to extend in a radial manner with the second bearing in a center when viewed in the axial direction.

11. The drive apparatus according to claim 10 , wherein

the gear housing includes at least one of a cylindrical portion coaxial with the first bearing and a cylindrical portion coaxial with the second bearing; and

the radial ribs are arranged to extend from a side surface of the cylindrical portion radially outward with respect to the cylindrical portion.

12. The drive apparatus according to claim 1 , wherein the gear housing includes:

two cylindrical portions coaxial with the first bearing and the second bearing, respectively; and

a cylindrical portion reinforcing rib located on a common tangent to the two cylindrical portions, and connected to side surfaces of the two cylindrical portions.