COOLANT SUPPLY SYSTEM FOR AN ELECTRIC MACHINE

Description

[0001] The invention relates to a coolant supply system for an electric machine in an electrically powered vehicle according to the preamble of claim 1.

[0002] Such an electric machine can be realized as a wet-running electric machine in which the stator, in particular the winding heads of the stator windings, is actively cooled.

[0003] An exemplary electric machine has, viewed in the axial direction, a free electric machine chamber between the rotor / stator arrangement and an electric machine housing wall. This chamber is supplied with coolant to ensure such stator cooling. The electric machine has a rotor shaft bearing arrangement in which the rotor shaft is rotatably mounted in a bearing opening of a hub section of the electric machine housing wall via a pivot bearing. The bearing opening is sealed to the outside of the housing with a sealing element. This creates a free space that extends in the axial direction between the pivot bearing and the sealing element. The free space is bounded radially inward by the rotor shaft and radially outward by the hub section of the electric machine housing wall.

[0004] In the current state of the art, the rotor shaft and thus the rotary bearing can become very hot during electric machine operation. Due to different heat-induced expansions of the inner and outer rings of the rotary bearing, the rotary bearing clearance can be consumed, which is detrimental to the rotary bearing service life and the tendency of the bearing assembly to vibrate.

[0005] DE 10 2019 207 323 A1 discloses an electric motor for a vehicle. US 2015 / 0275715 A1 and DE 11 2012 003 305 T5 disclose further cooling / lubrication systems for an electric motor. DE 10 2010 047 507 A1 discloses a generic, oil-cooled motor / generator for a motor vehicle drive train. EP 0 049 735 B1 discloses an oil-cooled generator.

[0006] The object of the invention is to provide a coolant supply system for an electric machine which, in comparison to the prior art, ensures reliable operation of the rotary bearing of the rotor shaft.

[0007] The object is solved by the features of claim 1. Preferred developments of the invention are disclosed in the subclaims.

[0008] The invention is based on a coolant supply system for an electric machine. In the electric machine, a free electric machine chamber is provided, viewed in the axial direction, between the rotor / stator arrangement and an electric machine housing wall. This chamber is supplied with coolant during electric machine operation in order to effect stator cooling. The coolant can be implemented as oil and / or have a cooling and lubricating function. The electric machine has a rotor shaft bearing arrangement in which the rotor shaft is rotatably mounted in a bearing opening of a hub section of the electric machine housing wall via a pivot bearing. The bearing opening is sealed to the outside of the housing with a sealing element. This creates a free space that extends in the axial direction between the pivot bearing and the sealing element.The free space is limited radially inward by the rotor shaft and radially outward by the hub section of the electric machine housing wall.

[0009] According to claim 1, the following measures are provided for increased cooling of the pivot bearing: The electric machine housing wall has a coolant connection through which coolant can be guided from the electric machine compartment into the free space. According to the invention, the free space is thus additionally supplied with coolant to ensure effective cooling of the pivot bearing. The pivot bearing is therefore cooled on both sides in the axial direction, namely by coolant from the electric machine compartment on the one hand and by coolant from the free space on the other.

[0010] In a technical implementation, the coolant connection can have an inlet and an outlet. In the electric machine design position, the inlet extends above the pivot bearing, while the outlet extends below the pivot bearing. In this case, the coolant can be guided through the inlet into the free space under the effect of gravity. The coolant can then be returned from the free space to the electric machine chamber via the outlet under the effect of gravity.

[0011] The electric machine compartment can be integrated into a coolant hydraulic circuit in which the coolant, particularly pressurized, can be injected into the electric machine compartment via coolant nozzles from the radial outside to the radial inside. Alternatively and / or additionally, the coolant can be guided into the electric machine compartment via stator channels. The coolant collecting at the bottom of the electric machine's housing under the effect of gravity can be guided from the housing interior toward a coolant tank via an extraction system.

[0012] In the coolant-hydraulic circuit described above, a coolant / air mixture can form in the electric machine compartment during electric machine operation, which moves in a vortex flow around the rotor shaft. Similarly, a coolant / air mixture can also move in a vortex flow around the rotor shaft in the free space.

[0013] For adequate cooling of the pivot bearing, an effective coolant supply to the free space is essential. For this purpose, the electric machine housing wall, according to the invention, features a catch contour. Coolant present in the electric machine chamber collects at the catch contour. The coolant collected at the catch contour is guided to the free space via the inlet.

[0014] According to the invention, the catching contour has an axial web that projects axially from the inside of the electric machine housing wall toward the electric machine chamber. This axial web extends at least partially in the circumferential direction. According to the invention, at least one catching rib is raised radially outward from the axial web. An inner corner region is formed between the axial web and the catching rib, in which coolant drops can collect. The inlet opens directly into the inner corner region via an inlet opening. The inner corner region is designed to be open, particularly against the flow direction of the vortex flow, in order to capture a sufficient amount of coolant.

[0015] In a preferred embodiment, the catch contour can be designed for reversing the direction of rotation of the electric motor. In this case, the catch contour can have two inner corner areas. These can be spaced apart from each other in the circumferential direction. The first inner corner area can be designed to be open in a clockwise direction, viewed in the circumferential direction. In contrast, the second inner corner area can be designed to be open in a counterclockwise direction.

[0016] The free space is bounded radially outward by the inner circumference of the hub section of the electric machine housing wall. A lower inner circumference area forms a free space floor. A coolant reservoir can be formed in the free space floor, in which coolant collects and can be drained via the drain. Preferably, an overflow edge of the drain opening can be spaced from the free space floor by an overflow height. As soon as the coolant level rises to the overflow edge, coolant is drained via the drain toward the electric machine compartment.

[0017] The pivot bearing can be constructed conventionally, consisting of an inner bearing ring mounted on the rotor shaft, an outer bearing ring mounted on the inner circumference of the hub section, and interposed rolling elements. The pivot bearing limits the axial clearance inside the housing. Excessive coolant backflow from the coolant reservoir via the pivot bearing toward the electric machine chamber can lead to increased bearing friction. For this reason, the overflow edge of the drain opening is positioned at a height offset below the inner circumference of the outer bearing ring of the pivot bearing. This inhibits coolant backflow via the pivot bearing into the electric machine chamber.

[0018] In a specific design variant, one end of the rotor shaft can be rotatably supported in the bearing assembly. The electric machine housing wall can also be constructed in two parts, with a radially outer wall section that defines a component access, and a bearing shield that can be used to close the component access. In this case, the bearing assembly is located directly in the bearing shield.

[0019] An embodiment of the invention is described below with reference to the accompanying figures. They show: Fig. 1 shows an enlarged partial sectional view of an electric machine; Fig. 2 shows a catch contour formed on a bearing plate; and Fig. 3 shows a roughly schematic representation of a comparative example of an electric machine not encompassed by the invention.

[0020] For a simpler understanding of the invention, reference is first made to the Figure 3, in which a drive device for a vehicle axle of a two-track vehicle is indicated in a roughly schematic representation. The drive device has an electric machine, which is arranged, for example, in a transverse installation, axially parallel to the flange shafts 3 leading to the vehicle wheels. A stator 4 with a cooperating rotor 5 is arranged in a housing 2 of the electric machine. The rotor shaft 6 is rotatably mounted on axially opposite housing walls 8, 9 of the electric machine housing 2 in bearing openings with pivot bearings 13, 15 interposed.

[0021] The rotor shaft 6 of the electric machine can, for example, be connected in a rotationally fixed manner via a spline to a transmission input shaft 17 of a transmission arrangement 19, which drives onto the two flange shafts 3.

[0022] In the Figure 1 The stator 4 has a plurality of stator windings, of which Figure 1only two stator windings 21 are indicated. Each stator winding 21 has a winding head 23, 25 on each axial side, which projects into an electric machine chamber 27. Each electric machine chamber 27 is integrated into an oil-hydraulic circuit described later, with the aid of which the respective electric machine chamber 27 can be supplied with oil in order to cool the winding heads 23, 25 of the stator 4. In each of the electric machine chambers 27, an oil / air mixture moves in a vortex flow around the rotor shaft 6, which rotates at high speed.

[0023] In the in the Figure 3 In the right-hand bearing arrangement, a shaft end 29 of the rotor shaft 6 is rotatably mounted. The shaft end 29 of the rotor shaft 6 is guided through a hub section 31 of the housing wall 9, with the pivot bearing 15 interposed. The bearing opening delimited by the hub section 31 is sealed to the outside of the housing by a cover-shaped sealing element 33.

[0024] The oil-hydraulic circuit has an oil tank 35, which is connected to a suction pump 37 via a suction line. A pressure line leads from the suction pump 37 to oil supply lines 41, 43. Oil is fed into a radially outer circumferential annular gap 45 via the supply line 41. From there, the oil is guided via radially outer stator channels 47 to another annular gap 49 in the right-hand electric machine chamber 27. The two annular gaps 45, 49 are separated from the respective electric machine chamber 27 by oil spray rings 44. Each of the oil spray rings 44 has nozzles 46 distributed in the circumferential direction, through which oil can be injected into the respective electric machine chamber 27.

[0025] By means of the supply line 43, oil is guided through the rotor shaft 6 and via a flow connection 51 in radially inner stator channels 53 into the right electric machine chamber 27. At the housing base of the electric machine housing, in the Figure 3a suction device 54, through which oil collecting at the bottom of the housing can be returned to the oil tank 35 with the aid of a return pump 56.

[0026] As from the Figure 3 As can be seen further, the winding heads 25 projecting into the right-hand electric machine compartment 27 define an inner circumference having a diameter d1. The winding heads 23 projecting into the left-hand electric machine compartment 27 define an inner circumference having a diameter d2 that is smaller than the diameter d1. The winding heads 25 are located on the switching side of the electric machine, to which the power electronics (not shown) are connected, while the winding heads 23 are located on the counter-switching side.

[0027] In order to ensure that the rotor 5 and the rotor shaft 6 are installed without any interference contours during the electrical machine assembly, Figure 3The electric machine housing wall 9 is constructed in two parts, namely a radially outer wall section 55, which defines a component access, and a radially inner bearing plate 57, with which the component access can be closed. The rotor 5 is formed directly in the bearing plate 57. The bearing arrangement for the rotary mounting of the shaft end 29 of the rotor shaft 6 is dimensioned such that the rotor 5 can be inserted into the electric machine housing 2 without any interfering contours. After the setting process has been completed, the bearing plate 57 is mounted on the radially outer wall section 55.

[0028] A core of the invention relates to the geometry of the bearing plate 57, as it is known from Figure 1 and 2 Accordingly, the bearing plate 57 has an oil connection through which oil can be fed from the right electric machine compartment 27 into the free space 59. The free space 59 extends into the Figure 1 or 3in the axial direction between the rotary bearing 15 and the cover-shaped sealing element 33. In addition, the free space 59 is limited radially outwardly by the hub section 31 of the housing wall 9 and radially inwardly by the shaft end 29 of the rotor shaft 6.

[0029] The oil compound has in the Figure 1 an oil inlet 61 and an oil outlet 63. The oil inlet 61 is located in the Figure 1 above the free space 59, while the oil drain 63 is located below the free space 59. During electric machine operation, oil can therefore be guided under the effect of gravity from the electric machine chamber 27 via the oil inlet 61 into the free space 59. Subsequently, the oil can be returned to the electric machine chamber 27 via the oil drain 63 under the effect of gravity from the bottom of the free space 59.

[0030] In the Figure 2An oil reservoir is formed on the free space floor, in which the oil collects and can be drained via the oil drain 63. According to Figure 2, a drain opening of the oil drain 63 has an overflow edge 77, which is spaced from the free space floor by an overflow height h. The overflow edge 77 of the drain opening is positioned by a height offset Δh below an inner circumference of the bearing outer ring 75 of the pivot bearing (15). In this way, a direct backflow of coolant via the pivot bearing 15 into the electric machine chamber 2 is inhibited.

[0031] As from the Figure 1 or 2 As can be seen further, the housing wall 9 has a collecting contour 65 on its inside. Oil drops present in the electric machine chamber 27 collect at the collecting contour 65. The collected oil is led via the oil inlet 61 to the free space 59. In the Figure 1 and 2The catch contour 65 has an axial web 67 projecting axially from the inside of the housing wall in the direction of the electric machine chamber 27. This extends partially in the circumferential direction. From the axial web 67, according to the Figure 1 or 2 Two catch ribs 69 extend radially outward. The two catch ribs 69 are spaced apart from each other in the circumferential direction. An inner corner region 71 is spanned between each of the catch ribs 69 and the axial web 67. The oil collects in the inner corner region 71. Furthermore, the oil inlet 61 opens into the inner corner region 71 via an inlet opening 73.

[0032] The Figure 2The catch contour 65 shown is designed for reversing the direction of rotation of the electric machine. For this purpose, the two inner corner regions 71 are each open in different circumferential directions. This means that a first inner corner region 71 is open against the direction of the eddy flow in the electric machine chamber 27, regardless of the direction of rotation of the electric machine. LIST OF REFERENCE SYMBOLS

[0033] 2Electric machine housing 3Flange shafts 4Stator 5Rotor 6Rotor shaft 8,9Housing wall 11Bearing opening 13, 15Pivot bearing 17Gearbox input shaft 19Gearbox arrangement 21Stator winding 23, 25Winding head 27Electric machine compartment 29Shaft end 31Hub section 33Sealing element 35Coolant tank 37Suction pump 41, 43Supply lines 44Oil splash ring 45Annular gap 46Nozzles 47Radial outer stator channel 49Annular gap 51Flow connection 53Radial inner stator channel 54Suction 55Radial outer wall section 56Return pump 57End shield 59Free space 61Inlet 63Outlet 65Capturing contour 67Axial web 69Catch rib 71Inner corner area 73Inlet opening 75Bearing outer ring 77Overflow edge

Claims

1. Coolant supply system for an electric machine, in which electric machine a free electric machine space (27) is provided between the rotor / stator assembly and an electric machine housing wall (9) in the axial direction and has coolant introduced into it, wherein the electric machine has a rotor shaft bearing assembly in which the rotor shaft (6) is rotationally mounted in a hub portion (31) of the electric machine housing wall (9) by means of a rotary bearing (15), wherein the bearing opening is sealed off with respect to the housing exterior by way of a sealing element (33), specifically so as to form a free space (59) between the rotary bearing (15) and the sealing element (33), wherein the electric machine housing wall (9) has a coolant connection (61, 63), by means of which coolant can be guided from the electric machine space (27) into the free space (59), and wherein the electric machine housing wall (9) has a catching contour (65) at which coolant present in the electric machine space (27) collects and can be guided to the free space (59) via the inlet (61), characterized in that, for providing the inner corner region (71), the catching contour (65) has an axial web (67) which protrudes from the inner side of the electric machine housing wall (9) in the direction of the electric machine space (27) in the axial direction and extends at least partially in the circumferential direction, and in that at least one catching rib (69) is raised radially outwards from the axial web (67).

2. Coolant supply system according to Claim 1, characterized in that the coolant connection has an inlet (61) and an outlet (63), and in that in particular the coolant can be guided into the free space (59) via the inlet (61), in particular under the action of gravity, and / or in that the coolant can be returned from the free space (59) into the electric machine space (27) via the outlet (63), in particular under the action of gravity.

3. Coolant supply system according to Claim 1 or 2, characterized in that the electric machine space (27) is incorporated in a hydraulic circuit, by means of which coolant can be guided into the electric machine space (27), and in that the coolant collecting at the bottom of the housing of the electric machine under the action of gravity can be guided out of the housing interior by means of a suction-extraction means (54).

4. Coolant supply system according to any of the preceding claims, characterized in that the catching contour (65) has at least one inner corner region (71), which is preferably designed to be open counter to the direction of flow of the coolant vortex flow.

5. Coolant supply system according to any of the preceding claims, characterized in that the inner corner region (71), in which the coolant collects, is stretched between the axial web (67) and the catching rib (69), and in that in particular the inlet (61) opens into the inner corner region (71) by way of an inlet opening (73).

6. Coolant supply system according to any of the preceding claims, characterized in that the catching contour (65) acts independently of the direction of rotation of the electric machine, and in that in particular the catching contour (65) has two inner corner regions (71) which are spaced apart from each other in the circumferential direction, and in that the first inner corner region (71) is designed to be open in the clockwise direction, as viewed in the circumferential direction, and the second inner corner region (71) is designed to be open in the anticlockwise direction.

7. Coolant supply system according to any of the preceding claims, characterized in that a coolant reservoir is formed at the bottom of the free space, coolant collecting in the coolant reservoir and being discharged via the outlet (63), and in that in particular an overflow edge (77) of the outlet opening of the outlet (63) is spaced apart from the bottom of the free space by an overflow height (h), and in that in particular the overflow edge (77) of the outlet opening is positioned below a bearing outer ring inner circumference of the rotary bearing (15) by a vertical offset (Δh), so that return of coolant via the rotary bearing (15) into the electric machine space (27) is at least inhibited.

8. Coolant supply system according to any of the preceding claims, characterized in that a shaft end (29) of the rotor shaft (6) is rotatably mounted in the bearing assembly, and / or in that the free space (59) extends between the rotary bearing (15) and the sealing element (33) in the axial direction and is delimited radially to the inside by the rotor shaft (6) and / or is delimited radially to the outside by the hub portion (31) of the electric machine housing wall (9).

9. Coolant supply system according to any of the preceding claims, characterized in that the electric machine housing wall (9) is of two-part construction, specifically with a radially outer wall part (55), which delimits a component access point, and an end plate (57), with which the component access point can be closed, and in that in particular the bearing assembly is arranged in the end plate (57).