ELECTRIC MACHINE HAVING A RESERVOIR FOR COOLANT LEAKAGE

Abstract

An electric machine (1), comprising a housing (2), in which a stator (3) and a rotor (4), which is rotatable relative to the stator (3), are accommodated, a cooling device with a cooling channel (5) through which a coolant can flow and which extends from an inlet (7), through the housing (2) and through the rotor (4), to an outlet (6), and a sealing device (21) for sealing off the rotor (4) with respect to an interior space (22) of the housing, wherein a reservoir (12) for coolant leakage that occurs during a rotation of the rotor (4) is formed between the sealing device (21) and the housing (2). Additionally described are a drivetrain and a vehicle (17) having such an electric machine (1), and a method for operating the electric machine (1).

Claims

1. An electric machine, comprising: a housing, in which a stator and a rotor, which is rotatable relative to the stator, are accommodated; a cooling device with a cooling channel through which a coolant can flow and which extends from an inlet, through the housing and through the rotor, to an outlet; and a sealing device for sealing off the rotor with respect to an interior space of the housing, wherein a reservoir for coolant leakage that occurs during a rotation of the rotor is formed between the sealing device and the housing.

2. The electric machine according to claim 1, wherein the sealing device is configured to seal off the rotor in a radial direction and an axial direction.

3. The electric machine according to claim 1, wherein the electric machine is configured such that the coolant leakage occurs during a rotation of the rotor in a first direction of rotation, and said coolant leakage is conveyed out of the reservoir again during a rotation of the rotor in a second direction of rotation that is opposite to the first direction of rotation.

4. The electric machine according to claim 3, wherein the electric machine is configured such that the coolant leakage is returned into the cooling channel during the rotation of the rotor in the second direction of rotation.

5. The electric machine according to claim 3, wherein the rotor, or a component of the sealing device that is rotatable with the rotor, has a surface structure that causes the coolant leakage to be conveyed out of the reservoir.

6. The electric machine according to claim 5, wherein the rotatable component is configured as a ring of a slip ring seal.

7. The electric machine according claim 1, wherein the sealing device comprises a radial shaft sealing ring that delimits the reservoir for the coolant leakage.

8. A drivetrain for a vehicle, which has an electric machine according to claim 1.

9. A vehicle having a drivetrain according to claim 8.

10. A method for operating an electric machine, having a housing, in which a stator and a rotor, which is rotatable relative to the stator, are accommodated, having a cooling device with a cooling channel through which a coolant can flow and which extends from an inlet, through the housing and through the rotor, to an outlet, and having a sealing device for sealing off the rotor with respect to an interior space of the housing, the method comprising: during a rotation of the rotor in a first direction of rotation, forming a reservoir for coolant leakage between the sealing device and the housing; and conveying the coolant leakage out of the reservoir again during a rotation of the rotor in a second direction of rotation that is opposite to the first direction of rotation.

Description

[0028] The invention will be discussed below on the basis of an exemplary embodiment with reference to the figures. The figures are schematic illustrations in which:

[0029] FIG. 1 shows a perspective sectional view of an electric machine according to the invention;

[0030] FIG. 2 shows an enlarged view of the right-hand end of the rotor in FIG. 1;

[0031] FIG. 3 shows a detail of the sealing device; and

[0032] FIG. 4 shows a vehicle according to the invention.

[0033] The electric machine 1 shown in a perspective sectional view in FIG. 1 belongs to the drivetrain of a vehicle.

[0034] The electric machine 1 comprises a housing 2, in which a stator 3 and a rotor 4, which is rotatable relative to the stator 3 and which has a rotor shaft 23, are accommodated. The rotor shaft 23 is enclosed by a cylindrical rotor body 24. The electric machine 1 furthermore comprises a cooling device with a cooling channel 5 through which a coolant can flow and which extends from an inlet 7, through the housing 2, to an outlet 6.

[0035] The inlet 7 and the outlet 6 are connected via coolant lines (not illustrated) to a pump, such that the coolant is conveyed in a circuit. The coolant dissipates heat that is generated during the operation of the electric machine 1.

[0036] It can be seen in FIG. 1 that the cooling channel 5 extends through the housing 2 proceeding from the inlet 7. The coolant flows through a cooling pipe 25 into the hollow rotor shaft 23 of the rotor 4. At the end of the cooling pipe 25, the flow direction of the coolant is reversed, following which the coolant flows out of the rotor shaft 23 past a sealing device 21 (see FIG. 2) and passes onward to the outlet 6.

[0037] On the outside of the housing 2, there is arranged an inverter 8 that provides the AC voltage required for the operation of the electric machine 1.

[0038] FIG. 2 shows a sectional view of the right-hand end of the rotor shaft 23 shown in FIG. 1. The sealing device 21 serves for sealing off the rotor shaft 23 in a radial direction and an axial direction with respect to the housing 2. In particular, the sealing device 21 serves for sealing off the rotor shaft 23 with respect to an interior space 22 of the housing 2, in which the stator 3 is accommodated. The sealing prevents coolant from passing into the interior space 22 and leading to corrosion of the windings of the stator 3 therein.

[0039] The sealing device 21 comprises a slip ring seal 9 and a radial shaft sealing ring 11. The slip ring seal 9 is arranged in an axial direction between the free end (on the right in FIG. 2) of the rotor shaft 23 and a section of the housing 2. The slip ring seal 9 seals off the rotor shaft 23 axially.

[0040] Said end of the rotor shaft 23 is enclosed by a sleeve 10 composed of hardened high-grade steel. The sleeve 10 is in turn enclosed by the radial shaft sealing ring 11, which seals off the rotor shaft 23 radially with respect to the interior space 22 of the housing 2.

[0041] The sealing device 21 has the property that, in a particular direction of rotation of the electric machine, which is assigned to reverse travel of the electrically driven vehicle, the abovementioned technical leakage occurs. Said technical leakage however involves only a small volume, in the range of a few millilitres.

[0042] In the sectional view of FIG. 2 and in the enlarged view of FIG. 3, which shows a detail of the sealing device 21, it can be seen that an encircling free space is formed between the slip ring seal 9, the radial shaft sealing ring 11 and that section in the interior of the housing 2 which surrounds the seals. Said free space, more specifically its lower region in the installed state of the electric machine 1, serves as a reservoir 12 for the coolant leakage. If the technical leakage occurs as a result of the operation of the electric machine 1, in particular during reverse travel, said leakage collects in the reservoir 12.

[0043] In the event of a reversal of the direction of rotation, said coolant leakage is supplied back to the coolant circuit via the sealing device 21. The reservoir 12 is thus emptied again if the rotor 4 is rotated in the second direction of rotation that is opposite to the first direction of rotation.

[0044] The slip ring seal 9 comprises a static seal 13 and a ring 14 which is rotatable with the rotor shaft 23 and which has a special surface structure. In particular, the slip ring seal 9 may be configured as a mechanical hybrid seal.

[0045] The coolant leakage that has collected in the reservoir 12 is conveyed or conducted back into the coolant circuit again via the sealing device 21 by means of the surface structure of the ring 14.

[0046] Thus, in the method for operating the electric machine 1, coolant leakage that occurs during a rotation of the rotor 4 in the first direction of rotation is collected in the reservoir 12, and said leakage is conveyed out of the reservoir 12 again during a rotation of the rotor 4 in a second direction of rotation that is opposite to the first direction of rotation.

[0047] FIG. 4 shows a vehicle 17 with a drivetrain that comprises the electric machine 1. The electric machine 1 is coupled via a gearbox 18 to a wheel 19 of the vehicle 17. The electric machine 1 is additionally connected to the inverter 8. The energy stored in a battery 20 is converted by the inverter 8 into an AC voltage for the operation of the electric machine 1.

LIST OF REFERENCE DESIGNATIONS

[0048] 1 Electric machine [0049] 2 Housing [0050] 3 Stator [0051] 4 Rotor [0052] 5 Cooling channel [0053] 6 Outlet [0054] 7 Inlet [0055] 8 Inverter [0056] 9 Slip ring seal [0057] 10 Sleeve [0058] 11 Radial shaft sealing ring [0059] 12 Reservoir [0060] 13 Static ring [0061] 14 Rotatable ring [0062] 17 Vehicle [0063] 18 Gearbox [0064] 19 Wheel [0065] 20 Battery [0066] 21 Sealing device [0067] 22 Interior space [0068] 23 Rotor shaft [0069] 24 Rotor body [0070] 25 Cooling pipe