ELECTRIC MACHINE WITH A SLEEVE ON THE END SECTION OF A ROTOR

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 an end section of the rotor (4) is surrounded by a sleeve (10), which is surrounded by a radial shaft sealing ring (11) of the sealing device (21). Additionally described are a drivetrain for a vehicle (17), a vehicle (17) of said type, 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 (22) of the housing, wherein an end section of the rotor is surrounded by a sleeve, which is surrounded by a radial shaft sealing ring of the sealing device.

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 surface roughness of the sleeve is 0.1 to 0.32 μm.

4. The electric machine according to claim 1, wherein the sleeve is produced from a rust-resistant steel alloy.

5. The electric machine according to claim 4, wherein the sleeve is produced from rust-resistant martensitic chromium steel with the material number 1.4034 or 1.4035.

6. The electric machine according to claim 4, wherein the sleeve is hardened or has a wear-resistant coating.

7. The electric machine according to claim 1, wherein the sleeve is pressed or shrink-fitted onto the rotor or is welded to the rotor.

8. The electric machine according to claim 1, wherein the sleeve projects beyond the end section of the rotor in an axial direction.

9. The drivetrain for a vehicle, which has an electric machine according to claim 1.

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

11. 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 flows 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: as the rotor rotates relative to the stator, a radial shaft sealing ring, which surrounds a sleeve, of the sealing device slides on the sleeve, which surrounds an end section of the rotor.

Description

[0031] 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:

[0032] FIG. 1 shows a perspective sectional view of an electric machine according to the invention;

[0033] FIG. 2 shows an enlarged view of the right-hand end of the rotor in FIG. 1;

[0034] FIG. 3 shows a detail of the sealing device; and

[0035] FIG. 4 shows a vehicle according to the invention.

[0036] 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.

[0037] The electric machine 1 comprises a housing 2 with an interior space 22 (see FIG. 2), in which a stator 3 and a rotatable rotor 4, 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.

[0038] 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.

[0039] 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 (also referred to as a “lance”) 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 along an inner wall of the rotor shaft 23 past a sealing device 21 (see FIG. 2) and passes onward to the outlet 6. As an alternative to this, the coolant may also flow out of the rotor shaft 23 at the opposite end thereof.

[0040] 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.

[0041] FIG. 2 is a sectional view and shows the right-hand end of the rotor 4 or of the rotor shaft 23 from FIG. 1. This may in particular be the end averted from a gearbox. FIG. 3 shows a detail of the sealing device 21, which serves for sealing off the rotor shaft 23 in a radial direction and an axial direction with respect to the interior space 22 of the housing 2 and in which the stator 3 is accommodated. The sealing prevents coolant from passing into the interior space 22 and leading, for example, to corrosion of the windings of the stator 3 therein.

[0042] 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 and functions as a primary seal.

[0043] The end section of the rotor shaft 23 is enclosed by a sleeve 10, which is in turn enclosed by a radial shaft sealing ring 11 of the sealing device 21. The radial shaft sealing ring 11 seals off the rotor shaft 23 radially with respect to the interior space 22 of the housing 2 and functions as a secondary seal. In particular, the radial shaft sealing ring forms a barrier for coolant leakage which has escaped from the cooling circuit at the slip ring seal 9 and which has collected between the radial shaft sealing ring 11 and the housing 2.

[0044] The sleeve 10 has particular properties with regard to roughness and hardness in order to ensure the function of the radial shaft sealing ring 11. The sleeve 10 accordingly has a particularly low surface roughness of 0.2 μm.

[0045] Furthermore, the sleeve 10 is produced from a rust-resistant steel alloy, which in this case is martensitic chromium steel with the material number 1.4034. Through the selection of this material, the sleeve is protected against corrosion. The sleeve is furthermore hardened and ground without any twist.

[0046] It can therefore be assumed that the high surface quality of the sleeve will be maintained over a long service life. The use of a sleeve that is protected against corrosion prevents rust particles from passing into the cooling circuit or into a bearing of the rotor.

[0047] The sleeve 10 is furthermore pressed onto the rotor 4. It can furthermore be seen in FIG. 2 that the sleeve 10 projects beyond the end section of the rotor 4 in an axial direction.

[0048] 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. A region of the free space that is situated at the bottom in the installed state of the electric machine serves as a reservoir 12 for coolant leakage, which is also referred to as technical leakage and can occur in certain operating states of the electric machine. The technical leakage collects in the reservoir 12.

[0049] The slip ring seal 9 comprises a static seal 13 and, as the counterpart thereto, a ring 14 which is rotatable with the rotor 4 and which is composed of a ceramic material. The rotatable ring 14 is fixedly connected to the rotor shaft 23. For this purpose, the rotatable ring 14 is clamped in the protruding section of the sleeve 10, in particular in an intermediate ring 15 which is arranged between the sleeve 10 and the rotatable ring 14 and which is composed of a rubber material, though said intermediate ring may also be omitted. That is to say, the sleeve 10 encloses the intermediate ring 15 along an axially extending contact surface 16, and the intermediate ring 15 encloses the rotatable ring 14, such that the rotatable ring 14 is fastened to the rotor shaft 23.

[0050] As the rotor 4 rotates relative to the stator 3, the radial shaft sealing ring 11, which surrounds the sleeve 10, of the sealing device 21 slides on the sleeve 10, which surrounds an end section of the rotor 4.

[0051] FIG. 4 shows a vehicle 17 with a drivetrain that comprises the electric machine 1 and a gearbox 18. The electric machine 1 is coupled via the gearbox 18 to a wheel 19 of the vehicle 17. The electric machine 1 is additionally connected to the inverter 8. The DC voltage provided by a battery 20 is converted by means of the inverter 8 into a multi-phase AC voltage for the operation of the electric machine 1.

LIST OF REFERENCE DESIGNATIONS

[0052] 1 Electric machine [0053] 2 Housing [0054] 3 Stator [0055] 4 Rotor [0056] 5 Cooling channel [0057] 7 Inlet [0058] 6 Outlet [0059] 8 Inverter [0060] 9 Slip ring seal [0061] 10 Sleeve [0062] 11 Radial shaft sealing ring [0063] 12 Reservoir [0064] 13 Static ring [0065] 14 Rotatable ring [0066] 15 Intermediate ring [0067] 16 Contact surface [0068] 17 Vehicle [0069] 18 Gearbox [0070] 19 Wheel [0071] 20 Battery [0072] 21 Sealing device [0073] 22 Interior space [0074] 23 Rotor shaft [0075] 24 Rotor body [0076] 25 Cooling pipe