# US 2021/0281148 A1 · Systems and methods for providing direct spray cooling in an electric motor

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- Number: US 2021/0281148 A1
- Document ID: US20210281148A1
- Status: Published application
- Kind: A1
- Application number: 16/807,857
- Filed: 2020-03-03
- Published: 2021-09-09
- Earliest claimed: 2020-03-03
- Assignees: Dana Belgium N.V.
- Applicants: Dana Belgium N.V.
- Inventors: Louis LAMBOURG
- Web page: https://patentgrep.com/patent/US20210281148A1

## CPC

- H02K 9/19: for machines with closed casing and closed-circuit cooling using a liquid cooling medium, e.g. oil
- H02K 1/276: Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
- H02K 1/30: using intermediate parts, e.g. spiders
- H02K 1/32: with channels or ducts for flow of cooling medium
- H02K 2213/03: Machines characterised by numerical values, ranges, mathematical expressions or similar information
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

Methods and systems are provided for providing cooling to an electric motor via direct spray cooling. In one example, a system may include a shaft including an oil conduit extending axially therein and a plurality of openings fluidically coupling the oil conduit to an external surface of the shaft; a rotor positioned coaxial with the shaft, an inner diameter of the rotor greater than an outer diameter of the shaft; and a gas-filled chamber bounded by an inner surface of the rotor and the external surface of the shaft, the gas filled chamber fluidically coupled to the oil conduit via the plurality of openings, and a pressure of a gas in the gas-filled chamber lower than a pressure of oil in the oil conduit.

## Claims

### Claim 1

A rotor assembly of an electric motor, comprising:
a shaft including an oil conduit extending axially therein and a plurality of openings fluidically coupling the oil conduit to an external surface of the shaft;
a rotor positioned coaxial with the shaft, an inner diameter of the rotor greater than an outer diameter of the shaft; and
a gas-filled chamber bounded by an inner surface of the rotor and the external surface of the shaft, the gas filled chamber fluidically coupled to the oil conduit via the plurality of openings, and a pressure of a gas in the gas-filled chamber lower than a pressure of oil in the oil conduit.

### Claim 2 (depends on 1)

The rotor assembly of claim 1, wherein, responsive to the pressure of the gas in the gas-filled chamber lower than the pressure of the oil in the oil conduit, oil sprays from the oil conduit into the gas filled chamber via the plurality of openings, the oil impinging on an internal surface of the rotor, the internal surface of the rotor including a plurality of rotor laminations, the plurality of rotor laminations is in direct contact with the oil sprays.

### Claim 3 (depends on 2)

The rotor assembly of claim 2, wherein the rotor is fixedly coupled to a rotor hub extending axially therein, the rotor hub fixedly coupled to the shaft, and an outer diameter of the rotor hub approximately equal to an inner diameter of the rotor.

### Claim 4 (depends on 3)

The rotor assembly of claim 3, wherein rotating the rotor with a first angular velocity includes rotating the rotor hub with the first angular velocity and rotating the rotor shaft with the first angular velocity.

### Claim 5 (depends on 4)

The rotor assembly of claim 4, wherein the rotor hub comprises a first end cap, a second end cap, and a plurality of supporting rods, each of the supporting rods coupled to the first end cap and the second end cap, such that the rotor hub forms a cylindrical cage.

### Claim 6 (depends on 5)

The rotor assembly of claim 5, wherein the oil impinging on the inner surface of the rotor does not impinge on each of the supporting rods of the rotor hub.

### Claim 7 (depends on 5)

The rotor assembly, of claim 5, wherein each of the first end cap and the second end cap include a plurality of drainage slots, each of the plurality of drainage slots fluidically coupling the gas-filled chamber with an external oil conduit.

### Claim 8 (depends on 7)

The rotor assembly of claim 7, wherein the oil passage is coupled to an external oil sump for collecting and cooling oil from the electric motor.

### Claim 9 (depends on 1)

The rotor assembly of claim 1, wherein the internal surface of the rotor includes a plurality of pin fins.

### Claim 10

A method, comprising:
responsive to a temperature of an electric motor exceeding a threshold temperature of the electric motor, flowing oil to an oil conduit, the oil conduit extending axially within a rotor shaft of the electric motor and having a higher pressure relative to an internal cavity of the electric motor; and
flowing oil from the oil conduit to the internal cavity of the electric motor via a plurality of holes fluidically coupling the oil conduit and the internal cavity.

### Claim 11 (depends on 10)

The method of claim 10, wherein flowing oil from the oil conduit to the internal cavity of the electric motor via the plurality of holes fluidically coupling the oil conduit and the internal cavity includes spraying at least a portion of the oil from the oil conduit on an internal surface of the electric motor.

### Claim 12 (depends on 10)

The method of claim 10, further comprising:
flowing oil out of the internal cavity along an oil flow path to an external oil sump via a plurality of drainage slots, the oil flow path impinging on end windings of a stator of the electric motor.

### Claim 13 (depends on 10)

The method of claim 10, wherein flowing oil to the oil conduit of the electric motor includes increasing an opening of a valve coupled to an oil pump.

### Claim 14 (depends on 10)

The method of claim 10, wherein flowing oil to the oil conduit of the electric motor is responsive to at least one of a motor torque greater than a threshold motor torque, a motor RPM higher than a threshold motor RPM, and a motor temperature higher than a threshold motor temperature.

### Claim 15

A system, comprising:
an electric motor comprising a rotor, a rotor shaft, a rotor hub, and a stator, the rotor shaft mechanically coupled to a load, the rotor hub including a plurality of supporting rods;
a cooling system fluidically coupled to the electric motor, the cooling system including a radiator and a plurality of conduits;
an oil conduit extending axially within the rotor shaft of the electric motor; and
a plurality of holes coupling the oil conduit with an internal chamber of the electric motor.

### Claim 16 (depends on 15)

The system of claim 15, further comprising:
a controller storing executable instructions in non-transitory memory that, when executed, cause the controller to:
flow oil from the oil pump to an oil conduit of the electric motor; and
flow oil from the oil conduit into the internal chamber via the plurality of holes responsive to a pressure of the oil conduit higher than a pressure of the internal chamber of the electric motor.

### Claim 17 (depends on 16)

The system of claim 16, wherein to flow oil from the oil conduit into the internal chamber via the plurality of holes, the controller includes further instructions stored in non-transitory memory that, when executed, cause the controller to:
generate a plurality of oil sprays impinging on an internal surface of the rotor and not impinging on the plurality of supporting rods of the rotor hub.

### Claim 18 (depends on 16)

The system of claim 16, wherein the controller includes further instructions stored in non-transitory memory that, when executed, cause the controller to:
flow oil to end windings of the stator; and
flow oil from the air gap to an external oil sump via a plurality of drainage slots.

### Claim 19 (depends on 18)

The system of claim 18, further including a temperature sensor positioned to measure a temperature of the electric motor; and wherein to flow oil to the oil conduit is responsive to one or a temperature of the motor exceeding a threshold temperature, a motor torque exceeding a threshold motor torque, and a motor RPM exceeding a threshold motor RPM.

### Claim 20 (depends on 15)

The system of claim 15, wherein the internal surface of the rotor includes a plurality of pin fins extending into the internal chamber.