WO2020094515A1

WO2020094515A1 - Electric machine with a fluid-type cooling device

Info

Publication number: WO2020094515A1
Application number: PCT/EP2019/079927
Authority: WO
Inventors: Michael Hacklberger; Sebastian KORNEXL; Manfred Geier
Original assignee: Zf Friedrichshafen Ag
Priority date: 2018-11-05
Filing date: 2019-10-31
Publication date: 2020-05-14
Also published as: DE102018218820A1

Abstract

An electric machine (1) having a stator (4), a rotor (7) and having a fluid-type cooling device (15) is described. The rotor (7) is mounted relative to the stator (4) by means of a rotor shaft (10) and a bearing (13) arranged on a bearing bracket (11). The fluid-type cooling device (15) has a cooling pipe (16), which cooling pipe is fixed to a carrier element (17) and which cooling pipe is fluidically connected to a fluid inlet (18) and a fluid outlet (19) and which cooling pipe extends within a recess (10a) of the rotor shaft (10) and so as to form an annular space (10b). Between the rotor shaft (10) and the carrier element (17), a sealing region (20) is provided which has a sealing element (21) which substantially prevents a passage of fluid into a spatial region (22), which is situated outside the sealing region (20), of the electric machine (1). The sealing element (21) comprises a first portion (23a), which is fixed to the carrier element (17), and a second portion (23b), which is fixed to the rotor shaft (10). The second portion (23b) of the sealing element (21) has an outer diameter smaller than an inner diameter of the first bearing (13). The bearing (13) has, on the axial side facing toward the sealing element (21), a seal arrangement (13c) by means of which a bearing interior space (13f) is sealed off against an ingress of cooling fluid.

Description

Electrical machine with a fluid cooling device

The invention relates to an electrical machine with a fluid cooling device according to the preamble of claim 1, as already with the

WO 2016/050534 A1 has become known. To cool the rotor of the electrical machine described there, a cooling tube is axially inserted into a section of the rotor shaft designed as a hollow shaft, through which a cooling fluid can flow into an annular space between the latter and the rotor shaft and can absorb heat loss from the rotor. The coolant can flow in and out on the same end face of the electrical machine, as a result of which only a sealing element between the rotating rotor and the elements of the machine which are fixed for this purpose is required.

The object of the invention is to further improve such a generic electrical machine with a fluid cooling device.

The above object is achieved by an electrical machine with the features specified in claim 1. Advantageous refinements and developments of the invention can be found in the dependent claims and the following description of the figures.

Within the scope of the present invention, an electrical machine with a fluid cooling device is proposed, which initially has a stator with a

Stator laminated core and with a stator winding and a rotor with a rotor laminated core, which is rotatably mounted about an axis to the stator by means of a rotor shaft and a first bearing arranged on a first bearing plate. The fluid cooling device has a cooling tube which is fixed to a stator-fixed support element of the electrical machine and which is connected to a fluid inlet and which extends axially within a central recess in the rotor shaft and forms an annular space to the rotor shaft . The cooling tube is in fluid connection with the annulus and with a fluid outlet at the same time. Next is between the rotor shaft and the Carrier element, a sealing area is provided with a sealing element which, when a cooling fluid flows through from the fluid inlet to the fluid outlet, at least substantially prevents fluid from passing into a space area of the electrical machine outside the sealing area. The sealing element comprises a first section which is fixed to the carrier element and further comprises a second section which is fixed to the rotor shaft and which is in sealing connection with the first section.

According to the invention, it is provided in the electrical machine that the second section of the sealing element has an outer diameter which is smaller than an inner diameter of the first bearing. Furthermore, the first bearing itself has, at least on the axial side facing the mechanical seal, a sealing arrangement acting between a radially inner and a radially outer bearing ring, by means of which a bearing interior is sealed, inter alia, against the ingress of cooling fluid.

The proposed solution has the advantage that, in particular due to the sealing arrangement provided as a component of the first bearing, further sealing elements or corresponding measures can be dispensed with in a space between the sealing element which is directly exposed to the flow of the cooling fluid and the first bearing. This has the further advantage that the electrical machine can be made axially shorter and the installation space gained can be used for other purposes.

A particularly space-saving arrangement can be achieved in that the second section of the sealing element is at least partially axially overlapping to the first bearing. In this way, the axial length of the electrical machine can be shortened again.

To achieve the best possible sealing effect, the sealing element can advantageously be designed as a mechanical seal, in particular as an axial mechanical seal and in particular as a Levitex seal from Carl Freudenberg KG. A le- vitex seal is a gas-lubricated mechanical seal, which is particularly suitable for

Sealing the annular gap between an oil-filled crankcase and a crankshaft of an internal combustion engine is used. An effective diameter of the sealing surfaces involved can thus be kept comparatively small.

An axial overlap of the mechanical seal with the first bearing can also take place within a comparatively small installation space. This means that the first bearing can also be designed with a correspondingly small outside diameter.

In a further embodiment, the first bearing can have a sealing arrangement on both axial sides in order to improve the sealing effect. The interior of the bearing can be filled with a pasty lubricant, in particular with a high-speed grease. Due to the sealing arrangement, a bearing interior can prevent the ingress of cooling fluid and the escape of

Lubricants are protected.

For a noticeable increase in the fluid-cooled inner circumferential surface of the rotor shaft and thus for the purpose of further improving the cooling effect, an inner diameter of the rotor shaft or the central recess there can be made larger in the area of an axial extension of the rotor laminated core than in the area of the first bearing .

The invention is explained below by way of example using an embodiment shown in the figures.

Show it:

1 shows an electrical machine designed as a vehicle axle drive with a fluid cooling device in an axial sectional view;

FIG. 2 shows an enlarged section of the fluid cooling device from FIG. 1 in the region of a bearing plate of the electrical machine;

FIG. 3 shows a perspective illustration of the electrical machine in the region of the end shield from FIG. 3; 4 shows a perspective view of a coolant flange formed on a housing of the electrical machine.

The figures show an electrical machine 1, which is provided and designed in particular for driving an electric or hybrid vehicle. In particular, the electric machine 1 is provided for installation in or on a vehicle axle and thus represents an electric axle drive 2 in connection with further components. The electric machine 1 thus delivers its power to vehicle wheels for moving the vehicle. In this respect, an electric vehicle drive and a vehicle with such an electric machine 1 are also described, going beyond the electric machine 1 explained in detail below.

The electrical machine 1 comprises a stator 4 fixed in a housing 3 with a stator lamination stack 5 and with a stator winding 6 and a rotor 7 with a rotor lamination stack 8 and with a short-circuit cage 9. The electrical machine 1 is thus designed as an asynchronous machine. The rotor 7 is rotatably mounted about an axis A to the stator 4 by means of a rotor shaft 10, a first bearing 13 arranged on a first bearing plate 11 and a second bearing 14 arranged on a second bearing plate 12. The rotor shaft 10 is operatively connected to a gear 36 shown on the left in FIG. 1, which can transmit the engine torque to vehicle wheels via further transmission elements, not shown here in the drawing.

The electrical machine 1 has a fluid cooling device 15 through which a cooling fluid can flow and which can dissipate heat loss to a heat exchanger located outside the electrical machine 1.

The fluid cooling device 15 comprises a cooling tube 16 which is fixed to a stator-fixed support element 17, in particular to the first bearing plate 11 and which is connected to a fluid inlet 18 provided on the bearing plate 11. The cooling tube 16 is axially only on one side through the bearing shield 11 is mounted and extends with its largest section in the axial direction freely within a central recess 10a of the rotor shaft 10 and forms an annular space 10b with the rotor shaft 10. The cooling tube 16 is open axially on both sides and is thus in fluid communication with the annular space 10b and with a fluid outlet 19 which is also provided on the first bearing plate 11. The first bearing plate 11 has a central first through opening 11a for forming the fluid inlet 18 and a second through opening 11b arranged radially to the first through opening for forming the fluid outlet 19. Both through openings 11a, b thus emerge from the end shield 11 on an end-side mounting surface 11c facing away from the rotor 7.

A sealing area 20 with a sealing element 21 is provided between the rotor shaft 10 and the bearing plate 11 functioning as a carrier element 17. The sealing element 21 has the task, when flowing through the cooling fluid from the fluid inlet 18 to the fluid outlet 19, to at least substantially prevent a fluid transfer into a spatial region 22 of the electrical machine 1 lying outside the sealing region 20.

In the present case, the sealing element 21 is designed as an axial mechanical seal 23. The mechanical seal 23 comprises a first section 23a, which is fixed on the carrier element 17 and further comprises a second section 23b, which is fixed on the rotor shaft 10 and which is in sealing connection with the first section 23a. As can be seen in FIG. 2, the second section 23b of the sealing element 21 has an outer diameter which is smaller than an inner diameter of the first bearing 13. The second section 23b of the mechanical seal 23 is at least partially axially overlapping with the first bearing 13 arranged.

Furthermore, the first bearing 13 has both on the axial side facing the mechanical seal 23 and on the axial side facing the rotor laminated core 8 a sealing arrangement 13c acting between a radially inner bearing ring 13a and a radially outer bearing ring 13b with two sealing disks 13d, e . The Bearing interior 13f is further sealed with a high-speed grease against the ingress of cooling fluid. On the one hand, this lubricates the bearing 13 and, on the other hand, the penetration of fluid into the inner space 22 of the electrical machine 1 is prevented by the created grease barrier.

For a noticeable increase in the fluid-cooled inner circumferential surface of the rotor shaft 10 and thus for the purpose of further improving the cooling effect, an inner diameter 10c of the rotor shaft 10 or the central recess 10a present there can be made larger than in the area of an axial extension of the rotor laminated core 8 in the area of the first bearing 13.

As can be seen, the rotor shaft 10 is designed as a hollow shaft and is closed in a fluid-tight manner by a closure 24 on the axial side facing away from the fluid inlet 18. Due to the coaxial arrangement of the rotor shaft 10 and the cooling tube 16, the fluid flow undergoes a reversal of direction against the inflow direction and can flow out again on the axial side of the fluid inlet 18, for which purpose a sealing arrangement in the form of the sealing element 21 is only required on this side.

The cooling tube 16, the first bearing 13 and the stator-fixed section 23a of the sealing element 23 are thus received by the first bearing plate 11. The first bearing plate 11 also receives an electrical potential equalization element 25 which interacts with the rotor shaft 10. In the present case, a slip ring arrangement 26 is provided as the potential equalization element 25, which reduces potential differences occurring as shaft voltages between the stator 4 and the rotor 7 by means of an electrical short circuit. The potential equalization element 25 is arranged axially adjacent to the first bearing 13, in particular axially between the bearing 13 and the rotor laminated core 8.

The cooling tube 16 is fixed to a fastening region 11f provided on the end shield 11 or generally on the carrier element 17. In particular, the cooling tube 16 is arranged by means of an interference fit in an axial extension 11e protruding from a base body 11d of the bearing plate 11, which training area 11f. It can be seen in the figures that the fastening area 11f partially overlaps axially with the stator-fixed section 23a of the sealing element 21 or the mechanical seal 23.

Returning to the mounting surface 11 c, a cover element 27 made of a plastic with a web arrangement 27 a is arranged there in a fluid-tight manner. In this case, a fluid inlet channel 28 and a fluid outlet channel 29 are formed by the web arrangement 27a between the bearing plate 11 and the cover element 27 and / or in the cover element 27.

The housing 3 of the electrical machine 1 is designed as a cast part made of a light metal material, in the present case made of an aluminum material. The housing 3 simultaneously forms a fluid cooling jacket 30 surrounding the stator 4 with a fluid channel arrangement 31. On the side facing the first bearing plate 11, the housing 3 has a coolant flange 32 integrally formed therewith with two fluid channel sections 32a, b, which are in fluid communication with the fluid inlet channel 28 and the fluid outlet channel 29 of the cover element 27. The fluid channel section 32a forms an external coolant connection 40. A further external coolant connection, not shown here in the drawing, can be arranged, for example, at another position of the stator cooling jacket or at power electronics for controlling the electrical machine 1, which with its housing and with its cooling circuit with the electrical machine 1 and is connected to the fluid cooling device 15 formed there. The further fluid channel section 32b, on the other hand, forms a connecting channel to the fluid cooling jacket 30 of the stator 4. The fluid cooling device 15 can thus have a cooling section 15a for cooling the rotor 7 and a cooling section 15b for cooling the stator 4, through which the cooling fluid flows in succession, and a fluid connection provided between them is designed as a fixed, tubeless connection channel 32b is.

Outside the sealing element 21, that is to say on the side of the mechanical seal 23 facing away from the flowing cooling fluid, there is a leakage space 33 with a fluid Collection area 34 is provided, in which a portion of the cooling fluid passing through the sealing area 20 can enter and be collected. The leakage space 33 also has a gas collecting area 35, which is arranged geodetically higher than the fluid collecting area 34 in an operating position of the electrical machine 1. If a cooling fluid with at least one volatile component is used, this can escape via the mechanical seal 23 and collect in the gas collecting area 35.

If the cooling fluid exudes a solid-shaped component when the volatile component escapes, this is likewise taken up by the fluid collecting area 34. To remove the solid-shaped component, a closable engagement opening 34a with a removable closure cover 34b is provided on the fluid collecting area 34.

To remove a cooling fluid present in the fluid collecting area 34, a closable fluid drain opening 34c is provided there with a drain element 34d, in particular a drain screw or a drain plug. In an operating position of the electrical machine 1, the fluid drain opening 34c is oriented essentially geodetically downwards and is arranged geodetically lower than in relation to a gas drain opening 35a of the gas collecting area 35. For easy removal of solid-shaped components, the engagement opening of the closure cover 34b is designed with a larger cross section than the fluid discharge opening 35a.

The fluid drain opening 34c is provided at least approximately at a 6 o'clock position, that is to say between a 5 o'clock and a 7 o'clock position. In contrast, the gas discharge opening 35a is at least approximately provided at a 12 o'clock position, that is to say between an 11 o'clock and a 01 o'clock position. The fluid collecting area 34 and the gas collecting area 35 are provided at least approximately in the same axial position. Furthermore, the mechanical seal 23 can also be located at this axial position or overlap at least axially with the fluid collecting area 34 and / or the gas collecting area 35.

The gas discharge opening 35a of the gas collecting area 35 furthermore has a pressure compensation element 41, as a result of which gases can escape from the gas collecting area 35. The pressure compensation element 41 comprises a semipermeable membrane, which is permeable to air to enable pressure compensation, but is not permeable to fluid.

As already mentioned previously, the second bearing 14 is provided axially spaced apart from the first bearing 13 for mounting the rotor 7, and if necessary it can also be designed axially on one or both sides with sealing rings and with a lubricant filling. The bearing 14 is provided radially between the rotor shaft 10 and the second bearing plate 12, the rotor laminated core 8 extending in an axial space between the first and the second bearings 11, 12. As can be seen, for the purpose of improved cooling, the central recess 10a extends axially through the second bearing 14 within the rotor shaft 10. The cooling tube 16 also extends axially within the rotor shaft 10 beyond the second bearing 12. As can also be seen, the inside diameter of the rotor shaft 10 is larger in the area of the axial extension of the rotor laminated core 8 and in the area of the second bearing 12 than in the area of the first bearing 11.

In the exemplary embodiment explained, the rotor shaft 10 has a shaft section which projects axially beyond the second bearing 12 and leads into the gear 36 with an output element 38 designed as a gearwheel 37. The central recess 10a of the rotor shaft 10 extends axially into the area of the output element 38 and can therefore also be flowed through by the cooling fluid. According to a modification of the arrangement, the cooling tube 16 can also extend axially into the area mentioned. The output element 38 and thus further elements in heat exchange and / or a lubricant or coolant located outside the rotor shaft 10 can thus also come into the effective range of the fluid cooling device 15 and be cooled. As can still be seen in the figures, the output element 38 is arranged on the rotor shaft 10 axially between the second bearing 14 and a third bearing 39. The central recess 10a of the rotor shaft 10 extends axially into the area of the third bearing 39 and is therefore flowed through by the cooling fluid up to this position. The third bearing 39 is therefore also in the effective range of the fluid cooling device 15 described above.

In the above description, designations of functional elements have been chosen in part with reference to a fixed flow direction. In the illustrated electrical machine, the direction of flow of the cooling fluid within the fluid cooling device is basically reversible. When the flow direction is reversed, the functional elements designated with reference to the direction of flow are given the corresponding opposite meaning. This means that, for example, a section or area designated as a fluid inlet now forms the fluid outlet, etc.

Reference number electric machine 15a rotor cooling section

Axle drive 15b stator cooling section

Housing 16 cooling pipe

Stator 17 support element

Stator laminated core 18 fluid inlet

Stator winding 19 fluid outlet

Rotor 20 sealing area

Rotor laminated core 21 sealing element

Short-circuit cage 22 room area

Rotor shaft 23 mechanical seal

a recess 23a first section

b Annulus 23b second section

c Inner diameter 24 closure

End shield 25 potential equalization elements through opening 26 slip ring arrangement b through opening 27 cover element

c Mounting surface 27a bar arrangement

d base body 28 fluid inlet channel

e Axial extension 29 fluid drain channel

f Mounting area 30 fluid cooling jacket

End shield 31 fluid channel arrangement

Bearing 32 coolant flange

a inner bearing ring 32a, b fluid channel section

b outer bearing ring 33 leakage space

c sealing arrangement 34 fluid collecting area d, e sealing disk 34a closable engagement opening f bearing interior 34 b sealing cover

Bearing 34c fluid drain opening

Fluid cooler 34d drain element Gas collection area 39 warehouse

a Gas drain opening 40 external coolant connection gear 41 Pressure compensation element gear A axis of rotation

Output element

Claims

1. Electrical machine (1) with a fluid cooling device (15), comprising

a stator (4) with a stator laminated core (5) and with a stator winding (6),

- A rotor (7) with a rotor laminated core (8) which can be rotated about an axis (A) to the stator (10) by means of a rotor shaft (10) and a first bearing (13) arranged on a first bearing plate (11). 4) is stored and where

- The fluid cooling device (15) has a cooling tube (16) which is fixed to a stator-fixed support element (17) of the electrical machine (1) and is connected to a fluid inlet (18) and which is located axially within a central one Recess (10a) of the rotor shaft (10) and forming an annular space (10b) to the rotor shaft (10), wherein

- The cooling tube (16) with the annular space (10b) and with a fluid outlet (19) is in fluid communication and wherein

- Between the rotor shaft (10) and the carrier element (17), a sealing area (20) with a sealing element (21) is provided, which when a cooling fluid flows through from the fluid inlet (18) to the fluid outlet (19), a fluid transfer into an outside of the sealing area ( 20) at least substantially prevents lying space area (22) of the electrical machine (1),

- The sealing element (21) comprises a first section (23a) which is fixed to the carrier element (17) and further comprises a second section (23b) which is fixed to the rotor shaft (10) and which is connected to the first section. cut (23a) is in sealing connection,

characterized in that

- The second section (23b) of the sealing element (21) has an outer diameter which is smaller than an inner diameter of the first bearing (13), and wherein

- The first bearing (13), at least on the axial side facing the sealing element (21), has a sealing arrangement (13c) acting between a radially inner and a radially outer bearing (13a, 13b), through which a Bearing interior (13f) is sealed against the ingress of cooling fluid.

2. Electrical machine according to claim 1, characterized in that the second

Section (23b) of the sealing element (21) is at least partially axially overlapping to the first bearing (13).

3. Electrical machine according to claim 1 or 2, characterized in that the sealing element (21) as a mechanical seal (23), in particular as an axial mechanical seal and in particular as a Levitex seal, is formed.

4. Electrical machine according to one of claims 1 to 3, characterized in that the first bearing (13) has a sealing arrangement (13c) on both axial sides.

5. Electrical machine according to claim 4, characterized in that the bearing interior (13f) is filled with a pasty lubricant, in particular with a high-speed grease.

6. Electrical machine according to one of claims 1 to 5, characterized in that an inner diameter of the rotor shaft (10) in the region of the first bearing (13) is smaller than in the region of an axial extension of the rotor laminated core (8).