ELECTRIC MACHINE

Abstract

The invention relates to an electric machine comprising a stator and a rotor. The rotor is rotatably mounted within the stator and has a rotor shaft which is in the form of a hollow shaft and by means of which a cavity is formed that is provided for receiving a coolant. The rotor shaft has at least two shoulders, and at least one end section, wherein at least three rotor shaft sections with different diameters are formed. A flow element is arranged in the cavity of the rotor shaft in the region of the second rotor shaft section, and at least one radial outlet opening is formed in the casing of the rotor shaft in the region of the second rotor shaft section, said outlet opening fluidically connecting the cavity of the rotor shaft to an outer region of the rotor shaft.

Claims

1. An electrical machine comprising a stator and a rotor, wherein the rotor is rotatably mounted within the stator and has a rotor shaft which is designed as a hollow shaft and by means of which a hollow space is formed, said hollow space being provided for receiving a cooling medium, wherein the rotor shaft has at least two projections at at least one end section, wherein, in this way, at least three rotor shaft sections, specifically a first rotor shaft section, a second rotor shaft section and a third rotor shaft section, with different diameters are formed, wherein a flow element is arranged in the hollow space in the rotor shaft in the region of the second rotor shaft section, and wherein at least one radial outlet opening is formed in the region of the second rotor shaft section in the casing of the rotor shaft, said radial outlet opening fluidically connecting the hollow space in the rotor shaft to an outer region of the rotor shaft.

2. The electrical machine as claimed in claim 1, wherein the flow element is formed in a sleeve-like manner with a central first opening and at least one second opening which is formed in the casing of the flow element, wherein the flow element is arranged in the hollow space in the rotor shaft in such a way that said hollow space is fluidically connected to the radial outlet opening in the casing of the rotor shaft via the second opening in the flow element.

3. The electrical machine as claimed in claim 2, wherein the sleeve-like flow element has a narrow point, wherein the second opening is formed in the region of the narrow point of the flow element.

4. The electrical machine as claimed in claim 1, wherein the electrical machine comprises at least one attachment element, wherein the attachment element is arranged on the rotor shaft in the region of the end section of the rotor shaft in such a way that cooling medium which passes out of the hollow space in the rotor shaft via the radial outlet opening can be routed at least partially over a rotor end face and a stator end face of the stator.

5. The electrical machine as claimed in claim 4, wherein the attachment element is formed in a substantially circular manner with a central third opening and a plurality of radially running tracks and/or channels which are at a uniform distance from one another.

6. The electrical machine as claimed in claim 4 wherein the attachment element is formed with a substantially step-like cross section along a normal plane on a longitudinal axis of the electrical machine and in this way forms a cooling medium collecting section in the region of the radial outlet opening.

7. The electrical machine as claimed in claim 4, wherein the attachment element is composed of plastic.

8. The electrical machine as claimed in 4, wherein the attachment element is integrally formed with a short-circuiting ring of the electrical machine.

Description

DRAWINGS

[0041] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0042] The invention will be described below by way of example with reference to the drawings.

[0043] FIG. 1 shows a plan view of an end face of an electrical machine according to the invention.

[0044] FIG. 2 shows a sectional view of an electrical machine according to the invention along a sectional plane A-A in accordance with FIG. 1 on a longitudinal axis.

[0045] FIG. 3 shows a further sectional view of an electrical machine according to the invention along a sectional plane A-A in accordance with FIG. 1.

[0046] FIG. 4a shows a sectional view of a flow element.

[0047] FIG. 4b shows a plan view of a flow element.

[0048] FIG. 4c shows a perspective view of a flow element.

[0049] FIG. 5 shows an exploded illustration of an electrical machine according to the invention in accordance with FIG. 1.

[0050] FIG. 6 shows a cross-sectional view of an attachment element.

[0051] FIG. 7 shows a sectional view of an electrical machine comprising an attachment element which is integrally formed with a short-circuiting ring.

[0052] FIG. 8 shows an illustration of a detail of an electrical machine in accordance with FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

[0053] The exemplary electrical machine 1, as illustrated in FIG. 1 to FIG. 3, in FIG. 5 and FIG. 7 and FIG. 8, is in the form of an asynchronous machine and comprises a stator 2 and a rotor 3. However, it is also conceivable to form the electrical machine 1 according to the invention as a synchronous machine.

[0054] The stator 2 is of substantially hollow-cylindrical shape. The stator 2 comprises a stator core 26, specifically a stator pack, and a plurality of stator windings 27. The stator windings 27 are arranged on the stator core 26 in slots which are provided for this purpose. The stator windings 27 have in each case axially protruding end windings 28 at the two stator end faces 25, 25 of the stator 2. (FIG. 2, FIG. 3 and FIG. 7)

[0055] The term axial corresponds to a direction along or parallel to a longitudinal axis 23 of the electrical machine 1.

[0056] The term radial corresponds to a direction normal to the longitudinal axis 23 of the electrical machine 1.

[0057] The rotor 3 is rotatably mounted within the stator 2 and comprises a rotor core 30, specifically a rotor pack, a rotor cage 31 and a rotor shaft 4. The rotor cage 31 of the rotor 3 has a plurality of conductor bars 32 which, at their ends, are electrically connected via short-circuiting rings 33 at the two rotor end faces 29, 29. (FIG. 2, FIG. 3, FIG. 7)

[0058] The rotor shaft 4 of the rotor 3 of the electrical machine 1 is in the form of a hollow shaft and accordingly has a central hollow space 5. The hollow space 5 in the rotor shaft 4 extends axially over the entire length of the rotor shaft 4. The hollow space 5 in the rotor shaft 4 is designed to guide a cooling medium, that is to say the rotor shaft 4 is designed such that the cooling medium can flow through it. (FIG. 2, FIG. 3, FIG. 7)

[0059] The rotor shaft 4 has two projections in each case at a first end section 6 and at a second end section 7, specifically in each case a first projection 8, 8 and a second projection 9, 9. Owing to the projections 8, 8, 9, 9, the rotor shaft 4 is formed with three rotor shaft sections, specifically with a first rotor shaft section 10, 10, a second rotor shaft section 11, 11 and a third rotor shaft section 12, with respectively different diameters. (FIG. 2, FIG. 3, FIG. 7)

[0060] The diameter of the rotor shaft 4 in the region of the first rotor shaft section 10, 10 is greater than the diameter of the rotor shaft 4 in the region of the second rotor shaft section 11, 11, and the diameter of the rotor shaft 4 in the region of the second rotor shaft section 11, 11 is greater than the diameter of the rotor shaft 4 in the region of the third rotor shaft section 12. (FIG. 2, FIG. 3, FIG. 7)

[0061] With reference to FIG. 2, FIG. 3 or FIG. 7 as viewed from left to right, the rotor shaft 4 is therefore divided into a first rotor shaft section 10, a second rotor shaft section 11, a central third rotor shaft section 12, a further second rotor shaft section 11 and a further first rotor shaft section 10.

[0062] The rotor shaft 4 has an axial inlet opening 34 in the region of the first end section 6, more precisely in the region of the first rotor shaft section 10, and an axial outlet opening 35 in the region of the second end section 7, more precisely of the further first rotor shaft section 10. (FIG. 2, FIG. 3, FIG. 7)

[0063] A flow element 13, 13 is in each case arranged in the hollow space 5 in the rotor shaft 4 in the region of the respective second rotor shaft section 11, 11. (FIG. 3, FIG. 4a to FIG. 4c) Furthermore, a plurality of radial outlet openings 14, 14 are formed at a uniform distance from one another in the casing of the rotor shaft 4 in the region of the second rotor shaft section 11, 11. The radial outlet opening 14, 14 serve to fluidically connect the hollow space 5 in the rotor shaft 4 to an outer region of the rotor shaft 4.

[0064] The flow elements 13, 13 are each formed in a sleeve-like manner and each have a central first opening 15 and also at least a plurality of second openings 16 which are formed in the casing of the respective flow element 13, 13. The respective flow element 13, 13 is arranged in the hollow space 5 in the rotor shaft 4 such that the hollow space 5 in the rotor shaft 4 is fluidically connected to the respective radial outlet openings 14, 14 in the casing of the rotor shaft 4 and therefore to the outer region of the rotor shaft 4 via the second openings 16 in the respective flow element 13, 13. (FIG. 3, FIG. 4a to FIG. 4c; FIG. 7)

[0065] The cooling medium can therefore enter the respective radial outlet openings 14, 14 through the second openings 16 in the casing of the respective flow element 13, 13, and form the secondary volume flow.

[0066] The two sleeve-like flow elements 13, 13 each have a narrow point 18, wherein the second openings 16 in the respective flow element 13, 13 are formed in the region of the narrow point 18 of the respective flow element 13, 13. (FIG. 4a to FIG. 4c)

[0067] Owing to the design of the electrical machine 1, the cooling medium which is guided through the hollow space 5 in the rotor shaft 4 can be guided in a targeted manner in a simple way, wherein partial volume flows of cooling medium, specifically a main volume flow 36 and a plurality of secondary volume flows 37, 37, the number of which corresponds to the number of radial outlet openings 14, 14, are produced. FIG. 2 and FIG. 3 schematically indicate the main volume flow 36 and the secondary volume flows 37, 37 using arrows.

[0068] The main volume flow 36 leads from the inlet opening 34 in the rotor shaft 4, axially through the hollow space 5 in the rotor shaft 4, to the outlet opening 35 of the rotor shaft 4. The main volume flow 36 therefore substantially takes over dissipation of heat from the rotor 3 of the electrical machine 1. (FIG. 2, FIG. 3)

[0069] The secondary volume flows 37, 37 pass out of the hollow space 5 in the rotor shaft 4 from the respective radial outlet openings 14, 14 in the casing of the rotor shaft 4. (FIG. 2, FIG. 3)

[0070] The outlet velocity of the secondary volume flows 37, 37 from the radial outlet openings 14, 14 depends on the system pressure within the hollow space 5 in the rotor shaft 4 and therefore of the main volume flow 36. However, owing to the arrangement of the respective flow element 13, 13 in the respective region of the second rotor shaft section 11, 11, adequate secondary volume flows 37, 37 can also be formed in pressureless systems.

[0071] If the respective flow element 13, 13 in the respective region of the second rotor shaft section 11, 11 were dispensed with, the quantity/velocity of the secondary volume flows 37, 37 in the case of an increasing throughflow rate of cooling medium at the inlet opening 34 would decrease considerably on account of turbulence phenomena occurring at the division points of the main volume flow 36 and secondary volume flows 37, 37. Conversely, an opposite effect would be observed in the case of a low throughflow rate of cooling mediumthe quantity of secondary volume flows 37, 37 would increase, and this would considerably reduce the cooling efficiency of the main volume flow 36.

[0072] The proportion of the respective secondary volume flows 37, 37 can be set by the width of the second openings 16 in the casing of the respective flow element 13, 13. The larger the second openings 16 are designed to be, the larger the respective secondary volume flows 37, 37conversely, the secondary volume flows 37, 37 are smaller the smaller the second openings 16 are designed to be. (FIG. 4a to FIG. 4c)

[0073] Furthermore, the ratio of main volume flow 36 to secondary volume flows 37, 37 can be set by means of the diameter of the narrow point 18 of the respective flow element 13, 13, wherein the velocity of the secondary volume flows 37, 37 is also determined. (FIG. 4a to FIG. 4c)

[0074] Although the throughflow rate at the inlet opening 34 of the rotor shaft 4 is important for the quantity and/or the velocity of the main volume flow 36 and of the respective secondary volume flows 37, 37, the ratio between the flows, specifically the main volume flow 36 and the respective secondary volume flows 37, 37, is far less sensitive to changes in the throughflow rate at the inlet opening 34 in the rotor shaft 4 owing to the insertion of the respective flow element 13, 13 in the hollow space 5 in the rotor shaft 4. If the throughflow rate is now increased, fewer turbulence phenomena are produced at the respective division points of the main volume flow 36 and the respective secondary volume flows, and the respective secondary volume flows 37, 37 can be diverted more accurately. A reduction in the throughflow rate at the inlet opening 34 in the rotor shaft 4 does not have a disadvantageous effect on the main volume flow 36 on account of the division ratios between the main volume flow 36 and the secondary volume flows 37, 37 remaining constant.

[0075] Therefore, the cooling medium velocity of the main volume flow 36 and of the secondary volume flows 37, 37 can be influenced in a targeted manner owing to the arrangement of the respective flow elements 23, 23 in the region of the respective second rotor shaft section 11, 11.

[0076] The electrical machine 1 further has two attachment elements 19, 19. (FIG. 1 to FIG. 3 and FIG. 5 to FIG. 8)

[0077] An attachment element 19 is arranged fixed to the rotor shaft 4 in the region in the region of the first end section 6 of the rotor shaft 4. The further attachment element 19 is arranged fixed to the rotor shaft 4 in the region of the second end section 7 of the rotor shaft 4. (FIG. 2, FIG. 3, FIG. 5, FIG. 7 and FIG. 8)

[0078] The attachment elements 19, 19 are each designed in such a way that cooling medium passing out of the hollow space 5 in the rotor shaft 4 via the respective radial outlet openings 14, 14 cooling medium which passes out at the respective end sections 6, 7 of the rotor shaft 4 can be routed over the respective rotor end face 29, 29 and the respective stator end face 25, 25.

[0079] The respective attachment element 19, 19 is formed in a substantially circular manner with a central third opening 17. (FIG. 5, FIG. 6)

[0080] The attachment elements 19, 19 are each fastened to the rotor shaft 4 via the central third opening 17.

[0081] The respective attachment elements 19, 19 have a step-like cross section. Furthermore, radially extending tracks 22 are formed starting from the central third opening 17 in the respective attachment element 19, 19. The tracks 22 are formed at a uniform distance from one another with respect to the circumference of the respective attachment element 19, 19. A cooling medium collecting section 24 is formed in the region of the respective radial outlet openings 14, 14 owing to the step-like design of the respective attachment element 19, 19. Cooling medium passing out of the hollow space 5 in the rotor shaft 4 via the respective radial outlet openings 14, 14 is captured in the respective cooling medium collecting section 24 of the respective attachment element 19, 19 and, on account of the centrifugal force which is produced by rotation of the rotor shaft 4 during operation of the electrical machine 1, guided via the respective tracks 14 over the respective rotor end face 29, 29 and the respective stator end face 25, 25. In this way, firstly the two short-circuiting rings 33, 33 at the two rotor end faces 29, 29 of the rotor 3 and the end windings 28 of the stator windings 27 at the two stator end faces 25, 25 of the stator 2 are efficiently cooled. Therefore, a targeted cooling medium flow over the respective rotor end face 29, 29 and the respective stator end face 25, 25 is rendered possible owing to the two attachment elements 19, 19. (FIG. 1 to FIG. 3 and FIG. 5 to FIG. 8)

[0082] In addition, in particular, the rotor core 30 of the rotor 3 is cooled owing to the cooling medium being guided through the rotor shaft 4 which is in the form of a hollow shaft.

[0083] In the first variant embodiment of the electrical machine 1 illustrated in FIG. 1 to FIG. 3 and FIG. 5, the attachment elements 19, 19 are each fastened to the rotor shaft 4 as separate components.

[0084] In the second variant embodiment of the electrical machine 1 illustrated in FIG. 7 and FIG. 8, the attachment elements 19, 19 are each integrally formed with the respective short-circuiting ring 33, 33 of the electrical machine 1. Here, the cooling medium passes out via the respective radial outlet openings 14, 14 in the casing of the rotor shaft 4 and is collected in the cooling medium collecting section 24, which is in the form of a hollow space, formed by the respective short-circuiting ring 33, 33 and the rotor core 30, here, and transported further, through bores 38 in the respective short-circuiting ring 33, 33, in the direction of the respective stator end face 25, 25 where the cooling medium can be freely distributed over all of the end windings 28 of the stator 2 and therefore implements improved heat dissipation at the end windings 28 at the respective stator end face 25, 25. (FIG. 7, FIG. 8)

LIST OF REFERENCE SYMBOLS

[0085] 1 Electrical machine [0086] 2 Stator [0087] 3 Rotor [0088] 4 Rotor shaft [0089] 5 Hollow space [0090] 6 First end section [0091] 7 Second end section [0092] 8, 8 First projection [0093] 9, 9 Second projection [0094] 10, 10 First rotor shaft section [0095] 11, 11 Second rotor shaft section [0096] 12 Third rotor shaft section [0097] 13, 13 Flow element [0098] 14, 14 Radial outlet opening [0099] 15 First opening [0100] 16 Second opening [0101] 17 Third opening [0102] 18 Narrow point [0103] 19 Attachment element [0104] 22 Track [0105] 23 Longitudinal axis [0106] 24 Cooling medium collecting section [0107] 25, 25 Stator end face [0108] 26 Stator core [0109] 27 Stator winding [0110] 28 End winding [0111] 29, 29 Rotor end face [0112] 30 Rotor core [0113] 31 Rotor cage [0114] 32 Conductor bar [0115] 33, 33 Short-circuiting ring [0116] 34 Inlet opening [0117] 35 Outlet opening [0118] 36 Main volume flow [0119] 37, 37 Secondary volume flow [0120] 38 Bore