Electric machine for a vehicle
An electric machine comprising a rotor, a stator, and a fluid-based brake arrangement for said rotor, said fluid-based brake arrangement having a fluid circuit for transporting a brake fluid, said fluid circuit comprising a fluid channel arrangement having at least one radial fluid channel segment extending radially through a part of said rotor so as to allow for directing brake fluid from an inner radial rotor side to an outer radial rotor side, whereby, during rotation of said rotor about an axial centre axis, acceleration of brake fluid in said at least one radial fluid channel segment causes a reaction force exerting a braking torque on the rotor.
1. An electric machine comprising a rotor, a stator, and a fluid-based brake arrangement for said rotor, said fluid-based brake arrangement having a fluid circuit for transporting a brake fluid, said fluid circuit comprising a fluid channel arrangement having at least one radial fluid channel segment extending radially through a part of said rotor so as to allow for directing brake fluid from an inner radial rotor side to an outer radial rotor side, such that, during rotation of said rotor about an axial center axis, acceleration of brake fluid in said at least one radial fluid channel segment causes a reaction force exerting a braking torque on the rotor.
2. The electric machine according to claim 1 , wherein the electric machine is an internal rotor arrangement, in which the stator is an outer stator and the rotor is an inner rotor coaxially arranged inside the outer stator.
3. The electric machine according to claim 2 , wherein the rotor and stator being spaced apart relative each other in the radial direction so as to define a radial space therebetween, wherein the at least one radial fluid channel segment has a radial outlet aligned with the radial space, wherein, during rotation of said rotor, said brake fluid is allowed to flow in said radial space.
4. The electric machine according to claim 1 , wherein said fluid channel arrangement having an entrance for said brake fluid at an axial center of said rotor, said entrance being in fluid connection with said at least one radial fluid channel segment.
5. The electric machine according to claim 1 , wherein said fluid channel arrangement having an outlet arranged proximity to an axial rotor end at the outer radial rotor side, said outlet being in fluid connection with said at least one radial fluid channel segment.
6. The electric machine according to claim 1 , wherein the rotor comprises an inner hollow rotor shaft defining an axial fluid passage for the brake fluid, said axial fluid passage being in fluid communication with the at least one radial fluid channel segment.
7. The electric machine according to claim 1 , further comprising a cooling circuit for said brake fluid, said cooling circuit being arranged in fluid communication with said fluid circuit.
8. The electric machine according to claim 1 , further comprising a reservoir for said brake fluid, said reservoir being arranged in fluid communication with said fluid circuit.
9. The electric machine according to claim 1 , wherein the rotor comprises a lamellar rotor body having a series of radial extending sheets arranged along the axial direction, and wherein each one of the radial extending sheets comprises an axial through hole extending a substantial part in the radial direction, such that the extension of the radial fluid channel segment in the radial and axial direction of the rotor is defined by the series of axial through holes of the radial extending sheets.
10. The electric machine according to claim 9 , wherein axial through holes of consecutive radial extending sheets are arranged with a successive angle increment relative an axial center axis so as to define a continuous part of the radial fluid channel segment in the radial direction and axial direction.
11. The electric machine according to claim 10 , wherein the radial fluid channel segment is a curved radial fluid channel segment.
12. The electric machine according to claim 9 , wherein the radial extension of each one of the axial through holes is shorter than a total radial extension of the radial fluid channel segment.
13. The electric machine according to claim 1 , further comprising a control unit for controlling the flow of brake fluid in said fluid channel arrangement in response to a requested brake power.
14. The electric machine according to claim 1 , wherein the electric machine comprising the brake fluid, said brake fluid being provided in the form of a liquid, such as oil or water.
15. A vehicle comprising an the electric machine according to claim 1 .
16. A method for braking a rotor of an electric machine, comprising receiving a request for braking the rotor of the electric machine in response to a requested brake power; and controlling the flow of brake fluid in a fluid-based brake arrangement having a fluid circuit for transporting the brake fluid, so as to permit transportation of brake fluid through at least one radial fluid channel segment extending radially through a part of said rotor; such that acceleration of the brake fluid in the at least one radial fluid channel segment causes a reaction force exerting a braking torque on the rotor.