Motor unit with oil cooling passage

1. A motor unit comprising:

a motor including a rotor to rotate about a motor axis extending in a horizontal direction, and a stator radially outside of the rotor;

a gear connected to the rotor;

a housing including a housing space to house the motor and the gear;

oil in a vertically lower region of the housing space; and

an oil passage to lead the oil from the vertically lower region of the housing space to be fed to the motor; wherein

the housing space includes:

a motor chamber to house the motor; and

a gear chamber to house the gear;

the housing includes a partition to divide the motor chamber and the gear chamber;

a bottom portion of the motor chamber is higher than a bottom portion of the gear chamber;

a portion of the oil fed to the motor is in a vertically lower region of the motor chamber;

a vertically lower region of the partition includes a partition opening to bring the gear chamber and the motor chamber into communication with each other;

the partition opening is structured such that a rise in a liquid surface of the oil in the vertically lower region of the motor chamber causes an increase in an amount of transfer of the oil from the motor chamber to the gear chamber through the partition opening;

the housing includes a motor housing portion;

the motor housing portion includes a peripheral wall portion which has a cylindrical shape extending along an outer circumferential surface of the stator;

a recessed portion, which is recessed radially outward, is defined in an inner peripheral surface of the peripheral wall portion;

the recessed portion extends along the horizontal direction; and

a portion of the partition opening is located directly radially opposed to the recessed portion at a same position along the horizontal direction as the recessed portion.

2. The motor unit according to claim 1 , wherein

the partition opening allows the oil to be transferred to the gear chamber through a first region thereof lower than the liquid surface of the oil in the vertically lower region of the motor chamber; and

an increase in an area of the first region is caused by a rise in the liquid surface of the oil in the vertically lower region of the motor chamber.

3. The motor unit according to claim 2 , wherein the area of the first region is structured to increase when the liquid surface of the oil has reached a first liquid level higher than a lower end of the stator and lower than a lower end of the rotor.

4. The motor unit according to claim 3 , wherein

the partition opening includes a first opening and a second opening higher than the first opening; and

the second opening has a greater width along a horizontal direction than the first opening, and a lower end of the second opening is at the first liquid level.

5. The motor unit according to claim 3 , wherein

the partition opening includes an elongated hole extending along an up-down direction, and an expansion portion broader than the elongated hole along a horizontal direction, and joined to the elongated hole on an upper side of the elongated hole; and

a lower end of the expansion portion is at the first liquid level.

6. The motor unit according to claim 1 , wherein the oil passage includes a first oil passage structured such that an amount of transfer of the oil to the motor chamber therethrough varies depending on a vehicle speed, and a second oil passage structured such that an amount of transfer of the oil to the motor chamber therethrough varies regardless of the vehicle speed.

7. The motor unit according to claim 6 , wherein

the first oil passage includes a scraping-up channel along which the oil is transferred to the motor chamber by the gear scraping up the oil; and

the second oil passage is structured to transfer the oil to the motor chamber through an electric pump.

8. The motor unit according to claim 6 , wherein the second oil passage is structured to start the transfer of the oil to the motor chamber therethrough when the motor is started.

9. The motor unit according to claim 1 , wherein

when the motor is in operation, the oil is fed to the motor through the oil passage to lower a level of a liquid surface of the oil in the vertically lower region of the gear chamber, and raise a level of the liquid surface of the oil in the vertically lower region of the motor chamber; and

when the motor is in a stopped state, feeding of the oil to the motor is stopped to raise the level of the liquid surface of the oil in the vertically lower region of the gear chamber, and lower the level of the liquid surface of the oil in the vertically lower region of the motor chamber.

10. The motor unit according to claim 9 , wherein a lower end of the partition opening is lower than a lower end of the stator and is higher than the level of the liquid surface of the oil in the gear chamber when the motor is at rest.