ELECTRIC DRIVE ARRANGEMENT FOR A VEHICLE

Abstract

An electric drive arrangement for a vehicle includes a housing, an electric machine, a transmission, and a hydraulic circuit for circulating a fluid to cool and lubricate the electric machine and the transmission.

Claims

1-14. (canceled)

15. An electric drive arrangement for a vehicle, comprising: a housing; an electric machine with a stator connected to the housing and including stator end-windings, and a rotor with a rotor shaft rotatably supported in the housing; a transmission to transmit a rotary movement from the rotor shaft to drive a driveline of the vehicle; and a hydraulic circuit for circulating a fluid to cool and lubricate the electric machine and the transmission, the hydraulic circuit comprising: an oil sump formed in a lower portion of the housing, a reservoir arranged above the oil sump, wherein the reservoir is configured to temporarily store and feed oil to rotating parts of the transmission, and a bi-directional pump which is hydraulically connected to the oil sump on a suction side, which is further hydraulically connected to the reservoir on a first pressure side and which is hydraulically connected to cooling nozzles of the electric machine on a second pressure side; wherein, operation of the bi-directional pump in a first direction of rotation supplies fluid to the reservoir, and operation of the bi-directional pump in a second direction of rotation supplies fluid to the cooling nozzles for cooling the stator end-windings.

16. The electric drive arrangement according to claim 15, wherein the bi-directional pump is further hydraulically connected via the reservoir to an inner diameter of the driveshaft and/or to the transmission, wherein, operation of the bi-directional pump in the first direction of rotation further supplies fluid to the inner diameter of the driveshaft and/or to the transmission.

17. The electric drive arrangement according to claim 15, wherein the bi-directional pump is hydraulically connected to a heat exchanger on the first pressure side and/or on the second pressure side.

18. The electric drive arrangement according to claim 15, wherein the hydraulic circuit comprises a mode control valve hydraulically connected to the bi-directional pump on the first pressure side and on the second pressure side, a hydraulic stator path connecting the mode control valve with the cooling nozzles and a hydraulic transmission path connecting the mode control valve with the reservoir.

19. The electric drive arrangement according to claim 18, wherein the mode control valve is hydraulically actuated via a pressure line hydraulically connected to the bi-directional pump on the first pressure side.

20. The electric drive arrangement according to claim 15, wherein operation of the bi-directional pump in the first direction of rotation pressurizes the first pressure side to a first pressure level to supply fluid for active cooling of the rotor and active lubrication of the transmission, and wherein supplying fluid to the reservoir reduces a fluid level in a transmission sump.

21. The electric drive arrangement according to claim 15, wherein operation of the bi-directional pump in the second direction of rotation pressurizes the second pressure side to a second pressure level, which is higher than the first pressure level, to supply fluid to the cooling nozzles and increases a fluid level in a transmission sump.

22. The electric drive arrangement according to claim 15, wherein the reservoir is arranged inside the housing.

23. The electric drive arrangement according to claim 22, wherein the reservoir comprises outlets to supply fluid to the inner diameter of the driveshaft and/or to the transmission.

24. The electric drive arrangement according to claim 15, wherein the reservoir is arranged external to the housing.

25. The electric drive arrangement according to claim 24, wherein the reservoir is hydraulically connected to the transmission via conduits to supply fluid to the inner diameter of the driveshaft and/or to the transmission.

26. The electric drive arrangement according to claim 15, wherein the reservoir is hydraulically connected to the oil sump, and wherein operation of the bi-directional pump in a second direction of rotation cause fluid to flow back from the reservoir to the oil sump.

27. The electric drive arrangement according to claim 15, wherein a suction side of the bi-directional pump is connected to a cooling arrangement to cool the fluid.

28. The electric drive arrangement according to claim 15, wherein the cooling arrangement includes: an inner casing portion and an outer casing portion of the housing, the inner casing portion and the outer casing portion forming a casing cooling structure through which a water based coolant is made to flow, and a housing shield arranged radially outside of the outer casing portion and at least partially below a rotary axis of the rotor, thereby forming a shield cooling structure through which fluid can flow towards the oil sump, wherein the casing cooling structure including the coolant is hydraulically separated from the shield cooling structure for the fluid, thereby providing a heat exchange between the coolant and the fluid.

29. An electric drive arrangement for a vehicle, comprising: a housing; an electric machine with a stator connected to the housing and including stator end-windings, and a rotor with a rotor shaft rotatably supported in the housing; a transmission to transmit a rotary movement from the rotor shaft to drive a driveline of the vehicle; a hydraulic circuit for circulating a fluid to cool and lubricate the electric machine and the transmission, comprising an oil sump formed in a lower portion of the housing, a reservoir arranged above the oil sump, the reservoir configured to temporarily store and feed oil to rotating parts of the transmission, and a bi-directional pump which is hydraulically connected to the oil sump on a suction side, is hydraulically connected to the reservoir on a first pressure side, and is hydraulically connected to cooling nozzles of the electric machine on a second pressure side; wherein operation of the bi-directional pump in a first direction of rotation supplies fluid to the reservoir, and operation of the bi-directional pump in a second direction of rotation supplies fluid to the cooling nozzles for cooling the stator end-windings, wherein the bi-directional pump is further hydraulically connected via the reservoir to an inner diameter of the driveshaft and/or to the transmission, and wherein operation of the bi-directional pump in the first direction of rotation supplies fluid to the inner diameter of the driveshaft and/or to the transmission.

30. An electric drive arrangement for a vehicle, comprising: a housing; an electric machine with a stator connected to the housing and including stator end-windings, and a rotor with a rotor shaft rotatably supported in the housing; a transmission to transmit a rotary movement from the rotor shaft to drive a driveline of the vehicle; and a hydraulic circuit for circulating a fluid to cool and lubricate the electric machine and the transmission, the hydraulic circuit comprising an oil sump formed in a lower portion of the housing, a reservoir arranged above the oil sump, wherein the reservoir is configured to temporarily store and feed oil to rotating parts of the transmission, and a bi-directional pump which is hydraulically connected to the oil sump on a suction side, which is further hydraulically connected to the reservoir on a first pressure side and which is hydraulically connected to cooling nozzles of the electric machine on a second pressure side; wherein operation of the bi-directional pump in a first direction of rotation supplies fluid to the reservoir, and operation of the bi-directional pump in a second direction of rotation supplies fluid to the cooling nozzles for cooling the stator end-windings, and wherein the bi-directional pump is hydraulically connected to a heat exchanger on the first pressure side and/or on the second pressure side.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Exemplary embodiments and further advantages of the electric drive arrangement for a vehicle will be illustrated as follows with reference to the accompanying drawings.

[0036] FIG. 1 shows a schematic illustration of an exemplary embodiment of the electric drive arrangement.

[0037] FIG. 2 shows the embodiment of FIG. 1 with operation of the bi-directional pump in a first direction of rotation.

[0038] FIG. 3 shows the embodiment of FIG. 1 with operation of the bi-directional pump in a second direction of rotation.

[0039] FIG. 4 shows a schematic illustration of a further exemplary embodiment of the electric drive arrangement.

[0040] FIG. 5 shows a schematic illustration of a further exemplary embodiment of the electric drive arrangement.

[0041] FIG. 6 shows a schematic cross-sectional view of the embodiment of FIG. 5.

DETAILED DESCRIPTION

[0042] In FIG. 1, an electric drive arrangement for a vehicle is depicted, wherein a housing 1, an electric machine 2, a transmission 3, an oil sump 4 and a reservoir 5 are shown as a schematic representation of a longitudinal cut along a rotary axis A of a rotor 10 of the electric machine 2. The electric machine 2 has a stator 9 connected to the housing 1. The stator 9 includes stator end-windings 31. The rotor 10 is rotatable relative to the stator 9. A driveshaft 11 is connected to the rotor 10 and rotatably supported in the housing 1 about the axis of rotation A. The transmission 3 is adapted to transmit a rotary movement from the driveshaft 11 to drive a driveline of the vehicle, which is not depicted. The transmission 3 may comprise, for example, a reduction gear, a differential drive and a coupling, which are not depicted. A hydraulic circuit 7 for circulating a fluid to cool and lubricate the electric machine 2 and the transmission 3 is in part schematically depicted. The hydraulic circuit 7 comprises the oil sump 4 formed in a lower portion of the housing 1, the reservoir 5 arranged above the oil sump 4, and a bi-directional pump 24 which is hydraulically connected to the oil sump 4 on a suction side via a fluid supply line 20. The reservoir 5 is configured to temporarily store and feed fluid to rotating parts of the transmission 3. The bi-directional pump 24 is further hydraulically connected to the reservoir 5 on a first pressure side 22 and to the cooling nozzles 33 of the electric machine 2 on a second pressure side 26. When the bi-directional pump 24 is operated in a first direction of rotation, fluid is supplied to the reservoir 5, and when the bi-directional pump 24 is operated in a second direction of rotation, fluid is supplied to the cooling nozzles 33 for cooling the stator end-windings 31. The bi-directional pump 24 is further hydraulically connected via the reservoir 5 to an inner diameter 18 of the driveshaft 11 and to the transmission 3. When the bi-directional pump 24 is operated in the first direction of rotation, fluid is further supplied to the inner diameter 18 of the driveshaft 11 and to the transmission 3. In the depicted embodiment, the reservoir 5, which is arranged inside the housing 1 on the transmission side, comprises outlets 8 to supply fluid to bearings and gears of the transmission 3 and to the rotor 9 via the inner diameter 18 of the driveshaft 11. The fluid is administered via radial bores 21 of the driveshaft 11, the radial bores 21 connecting the inner diameter 18 with the rotor 10. The fluid is centrifuged along the rotor 10 towards the stator 9, and flows back into the oil sump 4 due to gravitational force, shown by arrows F.

[0043] The housing 1 includes an intermediate wall 16 separating the oil sump 4 on a motor-side of the housing 1 from a transmission sump 6 on a transmission-side of the housing 1. A passage 37 in the intermediate wall 16 allows fluid dripping off the transmission 3 to flow into the machine-side reservoir 5, as shown by arrow F. The fluid level in the transmission sump 6 can be higher during low speed operation to provide adequate splash lubrication, whereas during high speed operation, the fluid level in the transmission sump 6 is reduced to keep churning losses low.

[0044] A mode control valve 12 is hydraulically connected to both the first and second pressure sides 22, 26 of the bi-directional pump 24. The first and second pressure sides 22, 26 unite at a junction 28 downstream of the bi-directional pump 24. A check valve arrangement 29 prevents fluid flow from the respective active one of the first and second pressure sides 22, 26 to the non-active one. The mode control valve 12 is hydraulically actuated via a pressure line 30, which in this embodiment is hydraulically connected to the bi-directional pump 24 on the first pressure side 22. Thus, depending on the direction of rotation of the bidirectional pump 24 the mode control valve 12 is actuated between a first position and a second position. When the bi-directional pump 24 is operated in the first direction of rotation, the mode control valve 12 is actuated by the pressure in the pressure line 30 into the first position. The downstream check valve of the check valve arrangement 29 on the first pressure side 22 is biased towards its closed position by a check valve spring 39, which is adapted to keep the check valve closed to allow the pressure to build up in the pressure line 30 when the first pressure side 22 becomes the active one. In the first position, a hydraulic transmission path 15 connecting the mode control valve 12 with the reservoir 5 is hydraulically connected to the bi-directional pump 24 on the first pressure side 22. When the bi-directional pump 24 is operated in the second direction of rotation, the mode control valve 12 is not pressurized and thus actuated into the second position by a return spring 32. In the second position, a hydraulic stator path 14 connecting the mode control valve 12 to the cooling nozzles 33 is hydraulically connected to the bi-directional pump 24 on the second pressure side 26.

[0045] The two directions of rotation of the bi-directional pump 24 provide two modes for the hydraulic circuit 7, optimizing cooling and lubrication of the electric machine 2 and the transmission 3, depending on the operating conditions of the electric drive. The bi-directional pump 24 is driven by an electric motor 34. In the fluid supply line 20 upstream of the bi-directional pump 24, a suction filter 25 is arranged. Downstream of the suction filter 25, the fluid supply line 20 is split at a suction side junction 27 into two branches. The branches are connected to the first and second pressure sides 22, 26 of the bi-directional pump 24, respectively. When the suction side of the bi-directional pump 24 is the respective non-active first or second pressure side 22, 26 of the bi-directional pump 24, a backflow of fluid from the respective active first or second pressure sides 22, 26 to the suction side is avoided by the check valves 29 arranged between the bi-directional pump 24 and the suction side junction 27. On the first and second pressure sides 22, 26 of the bi-directional pump 24 the fluid is cooled in a heat exchanger 35 arranged upstream of the mode control valve 12.

[0046] The embodiment of the electric drive arrangement is now further described with regard to FIG. 2, which shows the electric drive arrangement of FIG. 1 with the bi-directional pump 24 being operated in the first direction of rotation. By reversing the pumping direction of the bidirectional pump 24 to the first direction of rotation, the the hydraulic circuit 7 provides lubrication and cooling fluid optimized for high speed operation of the electric machine 2. The downstream check valve 29 on the first pressure side 22 is biased towards its closed position by a check valve spring 39, which is adapted to keep the check valve 29 closed at the moment when the pumping direction is reversed, to build up a pressure in the pressure line 30. By pressurizing the first pressure side 22, the mode control valve 12 is actuated via the pressure line 30 against the biasing force of the return spring 32. The mode control valve 12 directs the fluid flow to the hydraulic transmission path 15. The check valves 29 establish a fluid flow from the supply line 20 through the bi-directional pump 24 towards the first pressure side 22 into the hydraulic transmission path 15, which flow is shown by full lines, whereas the dotted lines show inactive lines. Generally, crossing lines are not connected, unless otherwise stated or depicted by a dot. The first pressure side 22 is pressurized to a first pressure level to supply fluid for active cooling of the rotor 10 and active lubrication of the transmission 3. By supplying fluid to the reservoir 5, depicted by a high fluid level 38 in the reservoir 5, whereas a fluid level 36 in the transmission sump 6 is reduced.

[0047] The embodiment of the electric drive arrangement is now further illustrated with regard to FIG. 3, which shows the electric drive arrangement of FIG. 1 with the bi-directional pump 24 being operated in the second direction of rotation. The second pressure side 26 is pressurized to a second pressure level, which is higher than the first pressure level to supply fluid to the cooling nozzles 33, while a fluid level 36 in the transmission sump 6 is increased, e.g., to the fluid level in the in the oil sump 4. The reservoir 5 is hydraulically connected to the oil sump 4 to allow fluid to flow back from the reservoir 5 to the oil sump 4, resulting in a corresponding fluid level 38 in the reservoir 5. The hydraulic pressure line 30 is not pressurized by the bi-directional pump 24, as the first pressure side 22 now forms the suction side of the bi-directional pump 24. Thus the mode control valve 12 is actuated towards its second position by the return spring 32. The check valves 29 establish a fluid flow from the supply line 20 through the bi-directional pump 24 towards the second pressure side 26 and into the hydraulic stator path 14. The fluid is supplied to the cooling nozzles 33, which spray the fluid onto the winding heads 31 of the stator 9. From the stator 9 the fluid runs down by gravitational force towards the oil sump 4 as shown by arrows F. The hydraulic transmission path 15 is not pressurized and no fluid is actively transported to the transmission 3, which is splash lubricated from the transmission sump 6, which is sufficient for low speed operation of the vehicle and accordingly lower rotation speed of the rotor 10 and rotating parts of the transmission 3.

[0048] In FIG. 4, a further exemplary embodiment of the electric drive arrangement is shown in a similar schematic illustration as the embodiment of FIG. 1. Identical parts are denoted with the same reference numerals. The electric drive arrangement according to this embodiment comprises the housing 1, the electric machine 2, the transmission 3 and the oil sump 4, which are not described in detail again. Reference is made to the description above.

[0049] The reservoir 5, however, is arranged outside the housing 1. The hydraulic circuit 7 for circulating the fluid to cool and lubricate the electric machine 2 and the transmission 3 comprises the oil sump 4 formed in a lower portion of the housing 1 and the external reservoir 5 arranged above the oil sump 4. The external reservoir 5 is configured to temporarily store and feed fluid to rotating parts of the transmission 3. The bi-directional pump 24 is hydraulically connected to the oil sump 4 on the suction side via the fluid supply line 20. The bi-directional pump 24 is further hydraulically connected to the external reservoir 5 on the first pressure side 22 and to the cooling nozzles 33 of the electric machine 2 on a second pressure side 26. When the bi-directional pump 24 is operated in the first direction of rotation, fluid is supplied to the external reservoir 5. When the bi-directional pump 24 is operated in the second direction of rotation, fluid is supplied to the cooling nozzles 33 for cooling the stator end-windings 31. The bi-directional pump 24 is further hydraulically connected via the external reservoir 5 and conduits 17 to the inner diameter 18 of the driveshaft 11 and to the transmission 3. In the depicted embodiment, the fluid is supplied through the conduits 17 from the external reservoir 5 to the bearings and gears of the transmission 3 and to the rotor 9 via the inner diameter 18 of the driveshaft 11. The fluid level 36 in the oil-sump 4 is depicted by two broken lines. The lower fluid level 36 appears when the bi-directional pump 24 is operated in the first direction of rotation and the higher fluid level 36 appears when the bi-directional pump 24 is operated in the second direction of rotation.

[0050] In FIG. 5, a further exemplary embodiment of the electric drive arrangement is shown in a similar schematic illustration as the embodiment of FIG. 4. In FIG. 6, the embodiment of FIG. 5 is shown in a schematic cross section through housing 1 at an axial position of the electric machine 2. Parts of the electric machine 2 are not depicted. FIGS. 5 and 6 are described together. Identical parts are denoted with the same reference numerals. The electric drive arrangement according to this embodiment comprises the housing 1, the electric machine 2, the transmission 3, the oil sump 4, and the external reservoir 5, which are not described in detail again. Reference is made to the description above.

[0051] The hydraulic circuit 7 for circulating a fluid to cool and lubricate the electric machine 2 and the transmission 3 comprises the oil sump 4 formed in a lower portion of the housing 1, the external reservoir 5 configured to temporarily store and feed fluid to rotating parts of the transmission 3, and the bi-directional pump 24 which is hydraulically connected to the oil sump 4 on a suction side via a fluid supply line 20. In this embodiment, the bi-directional pump 24 is directly hydraulically connected to the reservoir 5 on the first pressure side 22 and to the cooling nozzles 33 of the electric machine 2 on the second pressure side 26. Thus, a mode control valve is not necessary to connect the first or second pressure side 22, 26 to the hydraulic transmission path 15 and the hydraulic stator path 14, respectively. A pressure side cooling of the fluid may be provided for one or both of the hydraulic transmission path 15 and the hydraulic stator path 14 by arranging one or two heat exchangers.

[0052] In the depicted embodiment, however, the electric drive arrangement comprises an alternative cooling arrangement 19 to cool the fluid. The cooling arrangement 19 is arranged at a suction side of the bi-directional pump 24. When the suction side is the respective non-active first or second pressure side 22, 26 of the bi-directional pump 24, the first and second pressure sides 22, 26 are connected at the suction side junction 27 upstream of the bi-directional pump 24, which is connected to the cooling arrangement 19. To prevent a fluid backflow from the respective active first or second pressure sides 22, 26 to the suction side, check valves 29 are arranged between the bi-directional pump 24 and the suction side junction 27. The cooling arrangement 19 includes an inner casing portion 41 and an outer casing portion 42 of the housing 1, the inner casing portion 41 and an outer casing portion 42 forming a casing cooling structure 43 through which a water based coolant is made to flow. A housing shield 40 is arranged radially outside of the outer casing portion 42 and at least partially below the rotary axis A of the rotor 10, thereby forming a shield cooling structure 44 through which fluid can flow towards the oil sump 4. The casing cooling structure 43 may similarly be arranged in the housings 1 of the earlier described embodiments. The casing cooling structure 43 including the coolant is hydraulically separated from the shield cooling structure 44 for the fluid, thereby providing a heat exchange between the coolant and the fluid. Advantageously, a suction side heat exchanger for cooling the fluid is thus provided, resulting in a less complicated hydraulic circuit 7, in which the heat exchanger on the pressure side and the mode control valve are omitted.

[0053] The shield cooling structure 44 arranged below the rotary axis A of the rotor 10 gathers fluid for cooling the rotor 10 and the winding heads 31. To further enhance the heat exchange of the cooling arrangement 19, the shield cooling structure 44 can comprise channels 45, 47 running generally in parallel in an axial direction. The channels 45, 47 advantageously provide a greater surface and thus improved heat transfer from the fluid to the shield cooling structure 44. Further, the channels 45, 47 allow to use both axial flow directions. Generally, the shield cooling structure 44 may have a downward slope to provide a fluid flow due to gravity force, the fluid flowing for example towards at least one outlet passage 46 from the shield cooling structure 44 into the oil sump 4, which is depicted by arrows F. Each channel 45, 47 may as well have the downward slope. The shield cooling structure 44 may further comprise fins 48 connected to the outer cooling casing portion 42 and/or the housing shield 40. The fins 48 also provide a greater surface and thus improved heat transfer from the fluid to the shield cooling structure 44. The oil flow through the shield cooling structure 44 is illustrated by arrows F. The water based coolant in the casing cooling structure 43 may flow through circumferential channels (not depicted) formed in the inner casing portion 41, thus forming a cross-flow heat exchanger. The shield cooling structure 44 can comprise first and second channels 45, 47 running generally in parallel in the axial direction. The first channel 45 can be separated from the second channel 47 by a wall 49, so that the oil can flow in the first channel 45 in the axial direction opposite to the oil flow in the second channel 47. The shield cooling structure 44 further comprises at least one inlet passage 50 to receive fluid from the rotor 10 inside the inner casing portion 41. The outlet passage 46 and the inlet passage 50 are arranged in the axial direction at opposite ends of the shield cooling structure 44. There can be two inlet passages 50 arranged at opposite ends of the shield cooling structure 44, the fluid flowing either through the first or the second channel 45, 47.

[0054] The fluid level 36 in the oil-sump 4 is depicted by two broken lines, wherein the lower fluid level 36 appears when the bi-directional pump 24 is operated in the first direction of rotation and the higher fluid level 36 appears when the bi-directional pump 24 is operated in the second direction of rotation.

[0055] The depicted parts and features of all the exemplary embodiments of the electric drive are schematic representations, which may deviate from engineering drawing stand-ards. Regarding the function and technical details of the parts and features, the description takes precedence over the drawings.

REFERENCE NUMERALS

[0056] 1 Housing [0057] 2 Electric machine [0058] 3 Transmission [0059] 4 Oil sump [0060] 5 Reservoir [0061] 6 Transmission sump [0062] 7 Hydraulic circuit [0063] 8 Outlet [0064] 9 Stator [0065] 10 Rotor [0066] 11 Driveshaft [0067] 12 Mode control valve [0068] 14 Hydraulic stator path [0069] 15 Hydraulic transmission path [0070] 16 Intermediate wall [0071] 17 Conduits [0072] 18 Inner diameter of the rotor shaft [0073] 19 Cooling arrangement [0074] 20 Fluid supply line [0075] 21 Radial bore [0076] 22 First pressure side [0077] 24 Bi-directional pump [0078] 25 Filter [0079] 26 Second pressure side [0080] 27 Suction side junction [0081] 28 Pressure side junction [0082] 29 Check valve arrangement [0083] 30 Pressure line [0084] 31 Stator end windings [0085] 32 Spring [0086] 33 Cooling nozzles [0087] 34 Electric motor [0088] 35 Heat exchanger [0089] 36 Fluid level [0090] 37 Passage [0091] 38 Fluid level [0092] 39 Check valve spring [0093] 40 Housing shield [0094] 41 Inner casing portion [0095] 42 Outer casing portion [0096] 43 Casing cooling structure [0097] 44 Shield cooling structure [0098] 45 First channels [0099] 46 Outlet passage [0100] 47 Second channels [0101] 48 Fins [0102] 49 Wall [0103] 50 Inlet passage [0104] A Rotary axis [0105] F Arrows