Electric drive device for vehicle

Abstract

1. An electric drive for a vehicle comprising: a housing; an electric machine having a stator connected to the housing and a rotor with a rotor shaft rotatably supported in the housing; a transmission for transmitting rotational motion from the rotor shaft to drive a driveline of the vehicle; and a hydraulic circuit for circulating a fluid for cooling and lubricating the electric machine and the transmission.

Description

Technical Field

[0001] The present invention relates to an electric drive device for a vehicle, which has an electric machine having a housing, a stator connected to the housing, and a rotor having a rotor shaft rotatably supported by the housing, a transmission for transmitting the rotational movement from the rotor shaft to drive the drive line of the vehicle, and a hydraulic circuit for circulating a fluid for cooling and lubricating the electric machine and the transmission.

Background Art

[0002] From US Patent Application Publication No. 2019 / 0229582, a drive device for a vehicle with a lubrication path is known. This lubrication path includes a first oil pump that pumps up the oil stored in the case and supplies the pumped-up oil to the power transmission mechanism to lubricate the power transmission mechanism, and a cooling path that is separated from the lubrication path and provided in the rotating electrical machine. The cooling path includes a second oil pump that pumps up the oil stored in the case and supplies the pumped-up oil exclusively to the rotating electrical machine to cool the rotating electrical machine. The second oil pump is an electric oil pump, and an oil cooler for cooling the oil supplied to the rotating electrical machine is provided in the cooling path.

[0003] From US Patent Application Publication No. 2016 / 0178548, a method for dynamically monitoring the temperature of a fluid in a heat generating device is known, which includes monitoring the temperature of the fluid stored in a fluid sample using a temperature sensor. A first fluid flow rate and a second fluid flow rate are determined. Based on the third fluid flow rate through the active coolant circuit and the temperature of the fluid, the temperature drop of the fluid across the heat exchanger in the active coolant circuit and the third fluid flow rate are determined. Based on the temperature drop of the fluid across the heat exchanger and the third fluid flow rate, the temperature of the fluid supplied to the electric machine via the active coolant circuit is determined. Based on the temperature of the fluid supplied to the electric machine via the active coolant circuit and the temperature of the fluid in the sample, the effective temperature of the fluid is determined.

[0004] U.S. Patent Application Publication No. 2018 / 241288 discloses a cooling structure for a rotating electrical machine that supplies a cooling medium to a stator and a rotor of the rotating electrical machine by a pump to cool the stator and the rotor. The cooling structure includes a first flow path that supplies the cooling medium from the pump to the stator, a second flow path that supplies the cooling medium from the pump to the rotor, and a valve that adjusts the flow rate of the cooling medium in the first flow path and the flow rate of the cooling medium in the second flow path, and controls the cooling state of the stator and the cooling state of the rotor by the valve.

[0005] European Patent Application Publication No. 3517335 discloses an electric vehicle including a first cooling path having a power control unit, a driving motor, and a first pump that flows a first coolant cooled by a first heat exchanger through the power control unit and the second heat exchanger in this order and returns the first coolant to the first heat exchanger, and a second cooling path having a second pump that flows a second coolant cooled by the first coolant in the second heat exchanger through the driving motor and returns the second coolant to the second heat exchanger. The second pump starts or stops the circulation of the second coolant, or increases or decreases the circulation amount of the second coolant based on one or both of the temperature of the power control unit and the temperature of the first coolant.

[0006] The electrical machine and the transmission of a vehicle electrical drive device have different cooling requirements and lubrication requirements, respectively, and these requirements depend on the operating conditions. The performance of the electrical machine is thermally limited during operation. There may be inherent losses in the copper, iron, and magnets of the electric motor, and the temperature of each component and structure is limited by the material properties. Effective cooling is necessary to achieve sufficient torque performance. The passive splash lubrication of the transmission results in agitation losses under high-speed operation. Combining cooling and lubrication for both the electrical machine and the transmission is a compromise regarding efficiency. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Accordingly, an object of the present invention is to propose a vehicle electric drive device provided with a hydraulic circuit for circulating a fluid in order to efficiently cool and lubricate an electric machine and a transmission device.

Means for Solving the Problems

[0008] The above object is achieved by a vehicle electric drive device, the vehicle electric drive device comprising: · a housing; · an electric machine having a stator connected to the housing and a rotor having a rotor shaft rotatably supported by the housing; · a transmission device for transmitting the rotational motion from the rotor shaft for driving the drive line of the vehicle; · a hydraulic circuit for circulating a fluid for cooling and lubricating the electric machine and the transmission device; The hydraulic circuit includes a bidirectional pump whose suction side is hydraulically connected to the oil sump of the housing, a pump-operated switching valve hydraulically connected to the bidirectional pump, a first hydraulic path connecting the switching valve to the cooling nozzles of the electric machine, a second hydraulic path connecting the switching valve to a part of the transmission device, and a heat exchanger for cooling the fluid pumped up by the bidirectional pump via the switching valve. When the bidirectional pump is operated in the first rotational direction, the switching valve is moved to the first position, whereby the fluid is pumped up through the heat exchanger to the first hydraulic path for cooling the electric machine. When the bidirectional pump is operated in the second rotational direction, the switching valve is moved to the second position, whereby the fluid is pumped up through the heat exchanger to the second hydraulic path for cooling and / or lubricating the transmission device, which is achieved by the vehicle electric drive device.

[0009] The advantage of this electric drive device is that, depending on the two rotational directions of the bi-directional pump, by switching between a first rotational direction and a second rotational direction, two modes of the hydraulic circuit are provided for optimizing the cooling and lubrication of the electric machine and the transmission according to the actual cooling and lubrication requirements. The second rotational direction of the bi-directional pump is advantageously applicable when the vehicle is operating at high speed, and thus when the rotational speed of a part of the rotor and the transmission to which the fluid for cooling and lubrication is supplied is high. During high-speed operation, since the torque requirement of the electric machine is relatively low, spray cooling of the electric machine via the cooling nozzles is not required.

[0010] The first rotational direction of the bi-directional pump is advantageously applicable when the vehicle is operating at low speed, and thus when the rotational speed of a part of the rotor and the transmission is relatively low. However, it is common for the torque requirement to be high at low speed, and since high current results in copper losses, advantageously, the stator end windings of the electric machine can be cooled by the fluid supplied to the cooling nozzles, thereby reducing the losses. When the bi-directional pump is operated in the second rotational direction, high-pressure spray cooling of the winding head becomes possible, while the lubrication of the transmission does not require an active fluid supply. In a low-speed situation, passive splash lubrication of the transmission is effective because the agitation losses are relatively small due to the low rotational speed.

[0011] The fluid circulating in the hydraulic circuit is a cooling fluid and a lubricating fluid such as oil, for example. The oil sump may also be referred to as a reservoir arranged to collect the fluid dripping from the electric machine and the transmission by gravity.

[0012] According to one embodiment, the switching valve has a first inlet connected to the first pressure side of the bidirectional pump and a second inlet connected to the second pressure side of the bidirectional pump. The switching valve is driven to a first position by pressurizing the first inlet and to a second position by pressurizing the second inlet. The switching valve can have a first heat exchanger outlet hydraulically connected to the heat exchanger and a second heat exchanger outlet hydraulically connected to the heat exchanger. When the switching valve is in the first position, fluid flows from the first inlet to the heat exchanger, and when the switching valve is in the second position, fluid flows from the second inlet to the heat exchanger. The switching valve can further have a third inlet hydraulically connected to the heat exchanger, a first outlet to a first hydraulic path, and a second outlet to a second hydraulic path. When the switching valve is in the first position, fluid flows from the heat exchanger to the first outlet, and when the switching valve is in the second position, fluid flows from the heat exchanger to the second outlet.

[0013] According to a further embodiment, when the bidirectional pump is operated in a first rotational direction, the first pressure side is pressurized to a first pressure level to supply fluid to a cooling nozzle to cool the stator end winding of the stator, and when the bidirectional pump is operated in a second rotational direction, the second pressure side is pressurized to a second pressure level to supply fluid for active cooling of the rotor and active lubrication of the transmission. The first pressure level may be higher than the second pressure level.

[0014] According to a further embodiment, the second hydraulic path includes a branch conduit to the inner diameter of the drive shaft. The electromechanical machine can be supplied with fluid from the second hydraulic path via a radial hole in the drive shaft that connects the inner diameter to the rotor.

[0015] According to a further embodiment, the housing has an intermediate wall which separates the oil sump from the motor-side reservoir and the transmission-side reservoir, such that when the bi-directional pump is operated in a first rotational direction, the suction side is hydraulically connected to the motor-side reservoir, and when the bi-directional pump is operated in a second rotational direction, the suction side is hydraulically connected to the transmission-side reservoir. The motor-side reservoir and the transmission-side reservoir may be hydraulically connected via a through-opening in the intermediate wall. A suction filter may be arranged between the oil sump and the bi-directional pump, or between each one of the motor-side reservoir and the transmission-side reservoir and the bi-directional pump. A check valve may be arranged between the oil sump and each one of the first pressure side and the second pressure side of the bi-directional pump in order to block each one of the first pressure side and the second pressure side from their respective suction sides.

[0016] Exemplary embodiments and further advantages of the electric drive unit for a vehicle will be described below with reference to the accompanying drawings.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0018] Figure 1 shows an electric drive device for a vehicle, with a housing 1, an electric machine 2, a transmission 3, and an oil sump 4 shown as a schematic longitudinal sectional view along the axis of rotation A of the rotor 10 of the electric machine 2. A hydraulic circuit 7 for circulating a fluid for cooling and lubricating the electric machine 2 and the transmission 3 is shown partially schematically. Figure 2 shows a detailed schematic view of the switching valve 12 of the hydraulic circuit 7 of Figure 1, with the switching valve 12 set to the second position 26. Figure 3 shows the switching valve 12 of the hydraulic circuit 7 of Figure 1 in its first position 22. Figures 1, 2, and 3 will be described together.

[0019] The electromechanical machine 2 has a stator 9 that is connected to the housing 1 and includes a stator end winding 31, and a rotor 10 that is rotatable relative to the stator 9. A drive shaft 11 is connected to the rotor 10 and is supported by the housing 1 so as to be rotatable about a rotation axis A. The transmission 3 is adapted to transmit the rotational movement from the drive shaft 11 in order to drive a vehicle drive line (not shown). The transmission 3 can include, for example, a reduction gear mechanism, a differential drive, and a coupling (not shown). The fluid of the hydraulic circuit 7 is collected in an oil sump 4 formed in a lower portion of the housing 1. The suction side of the bidirectional pump 24 is hydraulically connected to the oil sump 4 via a fluid supply line 20. A suction filter 25 for filtering the fluid is disposed between the oil sump 4 and the suction side of the bidirectional pump 24. The bidirectional pump 24 is further hydraulically connected to a pump-operated switching valve 12. A first hydraulic path 14 connects the switching valve 12 to the cooling nozzle 33 of the electromechanical machine 2, and a second hydraulic path 15 connects the switching valve 12 to a part of the transmission 3. A heat exchanger 35 is provided for cooling the fluid pumped up by the bidirectional pump 24 via the switching valve 12. When the bidirectional pump 24 is operated in a first rotational direction, the switching valve 12 is moved to a first position 22 as shown in FIG. 3, whereby the fluid is pumped up through the heat exchanger 35 to the first hydraulic path 14 for cooling the electromechanical machine 2. When the bidirectional pump 24 is operated in a second rotational direction, the switching valve 12 is moved to a second position 26 as shown in FIG. 2, whereby the fluid is pumped up through the heat exchanger 35 to the second hydraulic path 15 for cooling and / or lubricating the transmission 3.

[0020] According to an exemplary embodiment, the switching valve 12 can have a first inlet 38 connected to the first pressure side 23 of the bidirectional pump 24 and a second inlet 39 connected to the second pressure side 27 of the bidirectional pump 24. Each of the first pressure side 23 and the second pressure side 27 depends on the rotational direction of the bidirectional pump 24. When the bidirectional pump 24 is operated in the first rotational direction, the first pressure side 23 is pressurized, which means that the second pressure side 27 becomes the suction side of the bidirectional pump 24. When the bidirectional pump 24 is operated in the second rotational direction, the second pressure side 27 is pressurized and the first pressure side 23 becomes the suction side of the bidirectional pump 24. The check valves 29 between each of the first pressure side 23 and the second pressure side 27 and the fluid supply line 20 prevent backflow towards the oil sump 4. The switching valve 12 includes a valve housing 30 surrounding a hollow chamber 32, and inside the valve housing 30, the valve spool 17 is driven to the first position 22 by the pressurization of the first inlet 38 and driven to the second position 26 by the pressurization of the second inlet 39. The switching valve 12 also has a first heat exchanger outlet 41 hydraulically connected to the heat exchanger 35 and a second heat exchanger outlet 42 hydraulically connected to the heat exchanger 35. When the switching valve 12 is in the first position, fluid flows from the first inlet 38 to the heat exchanger 35, and when the switching valve 12 is in the second position, fluid flows from the second inlet 39 to the heat exchanger 35. The switching valve 12 has a third inlet 40 hydraulically connected to the heat exchanger 35, a first outlet 43 to the first hydraulic path 14, and a second outlet 44 to the second hydraulic path 15. When the valve spool 17 of the switching valve 12 is in the first position 22, fluid flows from the heat exchanger 35 to the first outlet 43, and when the valve spool 17 of the switching valve 12 is in the second position 26, fluid flows from the heat exchanger 35 to the second outlet 44. Hydraulically connected lines are shown using dots representing connections. Lines that cross but do not have connection dots are hydraulically separated. The flow of fluid through the switching valve 12 is indicated by the arrow F for both the first position 22 in FIG. 3 and the second position 26 in FIG. 2.

[0021] When the two-way pump 24 is operated in the first rotational direction, the first pressure side 23 is pressurized to the first pressure level to supply fluid to the cooling nozzle 33 to spray-cool the stator end winding 31 of the stator 9. The cooling nozzle 33 sprays the fluid under high pressure towards the stator end winding 31, and this fluid flows back from the stator end winding 31 to the oil sump 4. The dotted line 36 represents the fluid level of the oil sump 4. The arrow F indicates the flow of the fluid. The second hydraulic path 15 is not pressurized, and the fluid is not actively conveyed to the transmission 3. The transmission 3 is splash-lubricated from the oil sump 4. The two-way pump 24 is advantageously operated in the first rotational direction when the vehicle is operating at a low speed, and thus when the rotational speeds of the rotor 10 and the rotating parts of the transmission 3 are relatively low.

[0022] When the two-way pump 24 is operated in the second rotational direction, the second pressure side 27 is pressurized to the second pressure level to supply fluid for the active cooling of the rotor 10 and the active lubrication of the transmission 3. The second pressure level may be lower than the first pressure level. The second hydraulic path 15 includes a branch conduit 8 to the inner diameter 18 of the drive shaft 11. The fluid is supplied to the electromechanical machine 2 from the second hydraulic path 15 through the radial hole 21 of the drive shaft 11 that connects the inner diameter 18 to the rotor 10. The fluid is centrifuged along the rotor 10 towards the stator 9 and flows back to the oil sump 4 by gravity as indicated by the arrow F. The fluid returns from the transmission 3 to the oil sump 4. The two-way pump 24 is advantageously operated in the second rotational direction when the vehicle is operating at a high speed, and thus when the rotational speeds of the rotor 10 and the rotating parts of the transmission 3 are high.

[0023] FIG. 4 shows a second exemplary embodiment of the electric drive device in the same schematic view as the first embodiment. The same parts are denoted by the same reference numerals. The electric drive device according to the second embodiment continues to be the same with respect to the housing 1, the electromechanical machine 2, the transmission 3, and the reservoir 4, and these will not be described in detail again. Refer to the above description. The switching valve 12 of the second exemplary embodiment may be the same as the switching valve 12 of the first embodiment, so FIGS. 2 and 3 are continuously referred to as described above.

[0024] The housing 1 includes an intermediate wall 16, which separates the reservoir 4 into a motor-side reservoir 5 and a transmission-side reservoir 6, and the motor-side reservoir 5 and the transmission-side reservoir 6 are connected via a through-opening 19 in the intermediate wall 16. The motor-side reservoir 5 and the transmission-side reservoir 6 are hydraulically connected to the bidirectional pump 24 via two separate fluid supply lines 20, respectively, and these fluid supply lines 20 are each connected to one possible suction side of the bidirectional pump 24 according to the direction of rotation. Both fluid supply lines 20 have one of two suction filters 25 for filtering the fluid.

[0025] When the bidirectional pump 24 is operated in the first rotational direction, the first pressure side 23 is pressurized and the motor-side reservoir 5 is hydraulically connected to the suction side of the bidirectional pump 24. By moving the switching valve 12 to the first position 22, fluid is supplied to the cooling nozzle 33 via the first hydraulic path 14 to spray-cool the stator end winding 31 of the stator 9. The transmission 3 is splash-lubricated from the transmission-side reservoir 6. The passage 37 provided in the intermediate wall 16 above the through-opening 19 also allows the fluid dripping from the transmission 3 to flow into the machine-side reservoir 5. However, due to the through-opening 19, the fluid level 36 in the machine-side reservoir 5 is adapted to balance with the fluid level in the transmission-side reservoir 6.

[0026] When the two-way pump 24 is operated in the second rotational direction, the second pressure side 27 is pressurized, and the transmission-side reservoir 6 is hydraulically connected to the suction side of the two-way pump 24. By moving the switching valve 12 to the second position 26, fluid is supplied to the second hydraulic path 15 for the active cooling of the rotor 10 and the active lubrication of the transmission 3. A part of the fluid returns from the transmission 3 through the passage 37 provided in the intermediate wall 16 to the machine-side reservoir 5. The fluid supplied to the rotor 10 also flows into the machine-side reservoir 5. Since the fluid from the transmission-side reservoir 6 flows to the suction side of the two-way pump 24, advantageously, the fluid level in the transmission-side reservoir 6 can be reduced. To achieve this, the flow through the through-opening 19 indicated by the arrow F can be adjusted by selecting an appropriate diameter for the through-opening 19. Due to the diameter of the through-opening 19, the fluid level 36 of the machine-side reservoir 5 becomes higher than the fluid level in the transmission-side reservoir 6, and advantageously, the stirring loss during the high-speed operation of the vehicle is kept low.

Explanation of Signs

[0027] 1 Housing 2 Electromechanical 3 Transmission 4 Oil sump 5 Motor-side reservoir 6 Transmission-side reservoir 7 Hydraulic circuit 8 Branch conduit 9 Stator 10 Rotor 11 Drive shaft 12 Switching valve 14 First hydraulic path 15 Second hydraulic path 16 Intermediate wall 17 Spool 18 Inner diameter of the rotor shaft 19 Through-opening 20 Fluid supply line 21 Radial hole 22 First position 23 First suction side 24 Two-way pump 25 Filter 26 Second position 27 Second suction side 28 Connecting part 29 Check valve 30 Valve housing 31 Stator end winding 32 Hollow chamber 33 Spray nozzle 34 Electric motor 35 Heat exchanger 36 Fluid level 37 Passage 38 First inlet 39 Second inlet 40 Third inlet 41 First heat exchanger outlet 42 Second heat exchanger outlet 43 First outlet 44 Second outlet A Axis of rotation F Arrow

Claims

1. An electric drive device for a vehicle, comprising: a housing (1); an electric machine (2) having a stator (9) connected to the housing (1) and a rotor (10) provided with a rotor shaft (11) rotatably supported by the housing (1); a transmission (3) for transmitting the rotational movement from the rotor shaft (11) to drive the drive line of the vehicle; a hydraulic circuit (7) for circulating a fluid for cooling and lubricating the electric machine (2) and the transmission (3); wherein the hydraulic circuit (7) includes: a two-way pump (24) whose suction side is hydraulically connected to an oil sump (4) of the housing (1); a pump-operated switching valve (12) hydraulically connected to the two-way pump (24); a first hydraulic path (14) connecting the switching valve (12) to a cooling nozzle (33) of the electric machine (2); a second hydraulic path (15) connecting the switching valve (12) to a part of the transmission (3); a heat exchanger (35) for cooling the fluid pumped up by the two-way pump (24) via the switching valve (12); wherein the switching valve (12) has: a first inlet (38) connected to a first pressure side (23) of the two-way pump (24), a second inlet (39) connected to a second pressure side (27) of the two-way pump (24), a first heat exchanger outlet (41) hydraulically connected to the heat exchanger (35), a second heat exchanger outlet (42) hydraulically connected to the heat exchanger (35), a third inlet (40) hydraulically connected to the heat exchanger (35), a first outlet (43) to the first hydraulic path (14), and a second outlet (44) to the second hydraulic path (15); when the two-way pump (24) is operated in a first rotational direction, the switching valve (12) is moved to a first position (22), whereby the fluid flows from the first inlet (38), through the first heat exchanger outlet (41), to the heat exchanger (35) for cooling the electric machine (2), then from the heat exchanger (35), through the third inlet (40), to the first outlet (43), and is pumped up to the first hydraulic path (14); When the bidirectional pump (24) is operated in the second rotational direction, the switching valve (12) is moved to the second position (26), whereby fluid flows from the second inlet (39) through the second heat exchanger outlet (42) to the heat exchanger (35) in order to cool and / or lubricate the transmission (3), and from the heat exchanger (35) through the third inlet (40) to the second outlet (44) and is pumped into the second hydraulic path (15). Electric drive device for a vehicle.

2. The electric drive device according to claim 1, wherein the switching valve (12) is driven to the first position (22) by pressurization of the first inlet (38) and is driven to the second position (26) by pressurization of the second inlet (39).

3. The electric drive device according to claim 1 or 2, wherein when the bidirectional pump (24) is operated in the first rotational direction, the first pressure side (23) is pressurized to a first pressure level and fluid is supplied to the cooling nozzle (33) to cool the stator end winding (31) of the stator (9).

4. The electric drive device according to claim 3, wherein when the bidirectional pump (24) is operated in the second rotational direction, the second pressure side (27) is pressurized to a second pressure level and fluid is supplied for active cooling of the rotor (10) and active lubrication of the transmission.

5. The electric drive device according to claim 4, wherein the first pressure level is higher than the second pressure level.

6. The electric drive device according to any one of claims 1 to 5, wherein the second hydraulic path (15) includes a branch conduit (8) to the inner diameter (18) of the rotor shaft (11).

7. The electric drive device according to claim 6, wherein the rotor shaft (11) includes a radial hole (21) connecting the inner diameter (18) to the rotor (10) for supplying fluid from the second hydraulic path (15) to the electromechanical machine (2) in high-speed mode.

8. The housing (1) has an intermediate wall (16), which separates the oil sump (4) into a motor-side reservoir (5) and a transmission-side reservoir (6). When the bidirectional pump (24) is operated in the first rotational direction, the suction side is hydraulically connected to the motor-side reservoir (5). When the bi-directional pump (24) is operated in the second rotational direction, the suction side is hydraulically connected to the transmission-side reservoir (6). The electric drive device according to any one of claims 1 to 7. Claim 9 The electric drive device according to claim 8, wherein the motor-side reservoir (5) and the transmission-side reservoir (6) are hydraulically connected via the through-opening (19) of the intermediate wall (16). Claim 10 The electric drive device according to any one of claims 1 to 9, wherein a suction filter (25) is arranged between the oil sump (4) and the bi-directional pump (24). Claim 11 The electric drive device according to any one of claims 1 to 10, wherein a check valve (29) is arranged between the oil sump (4) and the bi-directional pump (24).

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