ELECTRIC MACHINE WITH A RADIAL SHAFT SEALING RING

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 (18) for sealing off the rotor (4) with respect to an interior space (19) of the housing, wherein the sealing device (18) has a radial shaft sealing ring (11) which surrounds the rotor (4) and which delimits a reservoir (12) for coolant leakage. Additionally described are a drivetrain for a vehicle (14) 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 flows 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 the sealing device has a radial shaft sealing ring which surrounds the rotor and which delimits a reservoir for coolant leakage.

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 reservoir is formed between the radial shaft sealing ring and a cover that closes the housing in an axial direction.

4. The electric machine according to claim 3, wherein the cover is produced by way of a casting process.

5. The electric machine according to claim 3, wherein the cover is produced from an aluminium alloy.

6. The electric machine according to claim 1, wherein the radial shaft sealing ring is provided with a grease filling.

7. The electric machine according to claim 1, wherein the radial shaft sealing ring is of dry-running configuration.

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. (canceled)

Description

[0032] The invention will be discussed below on the basis of an exemplary embodiment with reference to the drawings. The drawings are schematic illustrations in which:

[0033] FIG. 1 shows a perspective sectional view of an electric machine according to the invention;

[0034] FIG. 2 shows an enlarged view of the right-hand end of the rotor shaft in FIG. 1;

[0035] FIG. 3 shows a detail of the sealing device; and

[0036] FIG. 4 shows a vehicle according to the invention.

[0037] The electric machine 1 shown in a perspective sectional view in FIG. 1 belongs to the drive of a vehicle. The electric machine 1 may alternatively also have some other function.

[0038] The electric machine 1 comprises a housing 2 with an interior space 19 (see FIG. 2), in which a stator 3 and a rotor 4, which is rotatable relative to the stator 3 and which has a rotor shaft 20, are accommodated. The rotor shaft 20 is enclosed by a cylindrical rotor body 21. 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.

[0039] The inlet 7 and the outlet 6, which may also be interchanged with one another, 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.

[0040] 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 22 (also referred to as a “lance”) into the hollow rotor shaft 20 of the rotor 4. At the end of the cooling pipe 22, the flow direction of the coolant is reversed, following which the coolant flows out of the rotor shaft 20 along an inner wall of the rotor shaft 20 past a sealing device 18 (see FIG. 2) and passes onward to the outlet 6.

[0041] On the outside of the housing 2, there is arranged an inverter 8 that provides the multi-phase AC voltage required for the operation of the electric machine 1.

[0042] FIG. 2 is a sectional view and shows the right-hand end of the rotor shaft 20 illustrated in FIG. 1. The sealing device 18 serves for sealing off the rotor shaft 20 in a radial direction and an axial direction with respect to the housing 2. In particular, the sealing device 18 serves for sealing off the rotor shaft 20 with respect to the interior space 19 of the housing 2, in which the stator 3 is accommodated. The sealing prevents coolant from passing into the interior space 19 and leading, for example, to corrosion of the windings of the stator 3 therein.

[0043] The sealing device 18 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 20 and a section of the housing 2. The slip ring seal 9 seals off the rotor shaft 20 axially.

[0044] The end of the rotor 4 is enclosed by a sleeve 10 composed of hardened high-grade steel. The sleeve 10 is enclosed by a radial shaft sealing ring 11, which seals off the rotor shaft 20 radially with respect to the interior space 19 of the housing 2. The radial shaft sealing ring 11 is provided with a grease filling and is configured as a dry-running radial shaft sealing ring 11.

[0045] The sealing device 18 has the property that, in a particular direction of rotation of the electric machine, which is assigned to reverse travel of the vehicle, the abovementioned technical leakage occurs. Said technical leakage however involves only a small volume of a few millilitres.

[0046] In the sectional view of FIG. 2 and in the enlarged view of FIG. 3, which shows a detail of the sealing device 18, 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 of the housing 2 which surrounds the seals. Said free space, in particular its lower region in the installed state, 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.

[0047] 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 18. The reservoir 12 is thus emptied again if the rotor 4 is rotated in the direction that is opposite to the first direction.

[0048] The housing 2 is closed at its axial side by a cover 13. In the exemplary embodiment illustrated, the cover 13 is composed of an aluminium alloy and is produced by injection moulding.

[0049] In summary, coolant leakage that occurs during 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 by means of the slip ring seal 9 during rotation of the rotor 4 in an opposite, second direction of rotation.

[0050] FIG. 4 shows a vehicle 14 with a drivetrain that comprises the electric machine 1. The electric machine 1 is coupled via a gearbox 15 to a wheel 16 of the vehicle 14. The electric machine 1 is additionally electrically connected to an inverter 8. The battery 17 provides a DC voltage, which is converted by means of the inverter 8 into an AC voltage for the operation of the electric machine 1.

LIST OF REFERENCE DESIGNATIONS

[0051] 1 Electric machine [0052] 2 Housing [0053] 3 Stator [0054] 4 Rotor [0055] 5 Cooling channel [0056] 6 Outlet [0057] 7 Inlet [0058] 8 Inverter [0059] 9 Slip ring seal [0060] 10 Sleeve [0061] 11 Radial shaft sealing ring [0062] 12 Reservoir [0063] 13 Cover [0064] 14 Vehicle [0065] 15 Gearbox [0066] 16 Wheel [0067] 17 Battery [0068] 18 Sealing device [0069] 19 Interior space [0070] 20 Rotor shaft [0071] 21 Rotor body [0072] 22 Cooling pipe